FoamConcrete:AState-of-the-Artand State-of-the-PracticeReviewOct 21, 2019 · slag f c A× exp(a×...

Review ArticleFoam Concrete A State-of-the-Art andState-of-the-Practice Review

Yanbin Fu 123 Xiuling Wang 2 Lixin Wang 24 and Yunpeng Li1

1College of Civil and Transportation Engineering Shenzhen University Shenzhen Guangdong 518060 China2Key Laboratory for Special Area Highway Engineering of Ministry of Education Changrsquoan University XirsquoanShaanxi 710064 China3Underground Polis Academy of Shenzhen University Shenzhen Guangdong 518060 China4State Key Laboratory of Rail Transit Engineering Informatization China Railway First Survey and DesignInstitute Group Co Ltd Xirsquoan Shaanxi 710043 China

Correspondence should be addressed to Xiuling Wang wangxiulingchdeducn

Received 21 October 2019 Revised 20 December 2019 Accepted 29 January 2020 Published 26 March 2020

Academic Editor Ivan Giorgio

Copyright copy 2020 Yanbin Fu et al is is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Foam concrete (FC) has the potential of being an alternative to ordinary concrete as it reduces dead loads on the structure andfoundation contributes to energy conservation and lowers the cost of production and labor cost during the construction andtransportation e paper reports a state-of-the-art review of foam concrete in terms of its components manufacturing andmaterial properties like drying shrinkage compressive strength stability and pore structure etc In view of the significance of theFC in engineering construction it also includes a state-of-the-practice review of foam concrete in tunnel and undergroundengineering Some shortcomings and technical limitations as well as emerging direction for performance enhancement of FC arealso discussed Current review concludes that the long-term performance and enhancement-associated properties need to bedeeply investigated is study can help alleviate consumer concerns and further encourage the wider application of FC incivil engineering

1 Introduction

FC is a type of cement mortar containing cement water andstable and homogeneous foam introduced using a suitablefoaming agent [1ndash3] which can be regarded as self-com-pacting materials [4] Other academic terms describing thismaterial are lightweight cellular concrete [5] low-densityfoam concrete or cellular lightweight concrete etc [6ndash8] Inpractice it provides satisfactory solutions to address variouschallenges and problems faced in construction activitiesFewer chemicals containing in this material well meets thesustainable and environmental demands and sometimes itcan be partially or even entirely substituted for normalconcrete [9 10] e textural surface and microstructuralcells make it widely used in the fields of the thermal insu-lation [11 12] sound absorbance [13 14] and fire resistance[15 16] A great number of environmentally friendlybuildings using FC as nonstructural members have been

built in recent years [17 18] It is also used for bridgeabutment filling to eliminate differential settlement [19] Inaddition the applications for prefabricated componentsproduction [20] building foundation [21ndash23] and airportbuffer system are also reported [24] Foam concrete has beencommonly used in construction applications in differentcountries such as Germany USA Brazil UK and Canada[25]

is material has renewed interests in terms of under-ground engineeringis is the requirement of undergroundstructure to control the overlying dead load [26ndash34]whereas the controllable density and low self-weight [35 36]could be effectively used for reducing the dead load Otherproperties such as seismic resistance ideal coordinateddeformation capacity and easy pumping also contribute toenhance the popularity of this material [37 38] Nowadaysthe FC has been quickly promoted as construction materialsfor tunnels and underground works Its excellent self-

HindawiAdvances in Materials Science and EngineeringVolume 2020 Article ID 6153602 25 pageshttpsdoiorg10115520206153602

flowing capacity can be used to fill voids sink holes disusedsewage pipes abandoned subways and so on e low andcontrolled self-weight makes it capable for load reduction orliner elements in tunnel and metro systems [39ndash41]

ough there are limited studies regarding the practicalapplications of FC in civil engineering its properties havebeen deeply studied For example Tan et al [42] performedan investigation on compression deformation properties ofFC used as liner element for the purpose of furtherexplaining stress and strain response e experimentalresults indicated that the compressive strength of FC in-creases with density and confining pressure whereas themodulus of elasticity has a positive correlation only withdensities regardless of confining pressure And no notablecorrelation was observed between peak strain and densitybut peak strain increases with confining pressure Tikalskyet al [43] studied the freeze-thaw durability of cellularconcrete and proposed an improved freeze-thaw testmethod ey reported that depth of absorption was con-sidered as a critical predictor in developing freeze-thaw-resistant concrete which will contribute to promote effec-tiveness in terms of using FC as insulation material fortunnels in cold regions Sun et al [44] explored the influenceof different foaming agents on compressive strength dryingshrinkage and workability of FC which will be helpful todetermine specification and implementation detailsMoreover Amran et al [37] reviewed the compositionpreparation process and properties of FC while the focus ofa review organized by Ramamurthy et al [38] is to classifyliteratures on foaming materials foaming agents cementfillers mix proportion production methods fresh andhardened properties of FC etc Significant progress of FCapplication has been made over the past few decades InCanada cement-based FC has been widely used for tunnelgrouting [45] Zhao et al [46] developed a foam cement-based material as a sacrificial tunnel lining structuralcladding used under the situation of blasting load actionis FC-based sacrificial cladding with the optimizedthickness effectively alleviates the dynamic responses in-duced by blasting loads in tunnel Choi and Ma [47]employed lightweight FC to facilitate tunnel drainagewhereas it was successfully implemented in a two-lanehighway tunnel in South Korea Successful application wasachieved due to the effective formation and distribution ofopen-cell foams with excellent permeability

With the booming development of FC andmanufacturingtechnology FC application in tunnels and undergroundworkshas revealed prominent prospects is review briefly de-scribes the history and development of FC and some forward-looking perspectives are also discussed e FC engineeringproperties and benefits to engineering construction areelaborated e objective of this review is to highlight engi-neering properties material properties and the practicalapplications in tunnel and underground engineering

2 Foam Concrete

21 History and Recent Development ere is a confusionexisted between FC and similar materials in early literatures

ie aerated concrete and air-entrained concrete [48]However one definition (ie FC is defined as a cementingmaterial with the minimum of 20 foams by volume in themixed plastic mortar) introduced by Van Dijk [49] clearlydistinguish the FC from aerated concrete [50 51] and air-entrained concrete [52] e closed air-voids system in FCnotably reduces its density and weight and at the same timeproduces efficient insulation and fire resistance capacity[26 53]

e first Portland cement-based FC was patented byAxel Eriksson in 1923 and then small-scale commercialproduction activities were launched [54] Valora carried outthe first comprehensive investigation in the 1950s [55]Rudnai [56] and Short and Kinniburgh [57] systematicallyreported the composition properties and applications of theFC later FC was initially envisaged as a void filling stabi-lization and insulation material [58] e booming devel-opment of this new constituent material in buildings andconstructions was enhanced in the late 1970s [59] A gov-ernment-oriented assessment on FC could be seen as amilestone event to further widening FC applications

Over the past 30 years FC are widely used for the bulkfilling [38] ditch repair retaining wall [60] bridge abutmentbackfill [17] slab structure of concrete floor [18] andhousing insulation [37] etc (Figure 1) Currently people areincreasingly interested in using it as a nonstructure orsemistructure member for underground engineering suchas grouting works for tunnels damage treatment and linerstructures

22 Material Components and Preparation e basiccomponents of FC consist of (1) water (2) binder (3)foaming agent (4) filler (5) additive and (6) fibere state-of-the-art research and findings on these components to dateare described as follows

Water e water requirement for constituent materialdepends on composition consistency and stability ofthe mortar body [38] e lower water content leads toa hard mixture which easily resulting in bubblebursting [61] e higher water content causes mixturetoo thin to accommodate bubbles thereby causingbubbles separating from the mixture [1] e AmericanConcrete Institute (ACI) recommends that mixedwater should be fresh clean and drinkable [62]Sometimes the mixed water can be replaced byequivalent-performance water received frommunicipalsectors in case the strength FC could reach 90 withinspecified curing time [38]BinderCement is the most commonly used bindereordinary Portland cement rapid hardening Portlandcement calcium sulphoaluminate cement and high-alumina can be used in ranges between 25 and 100of the binder content [59 63]Foaming agent e foaming agent determines FCdensity by controlling generation rate of the bubbles incement paste e resin-based was one of the earliestused foaming agents in FC So far synthetic protein-

2 Advances in Materials Science and Engineering

based composite and synthetic surfactants have beenderived and developed while the most frequently usedare synthetic and protein-based ones [64]Filler Various fillers such as silica fume fly ashlimestone powder granulated blast furnace slag andfly-ash ceramicite [61] have been widely adopted for thepurpose to enrich FC mechanical performances[65ndash67] Addition of these fillers is helpful to improvemix proportion design long-term strength and reducecosts In addition some fine aggregates such as finesand [68] recycled glass powder [69] and surfacemodified chip [70] are commonly used for productionof high-density FCAdditive Commonly used additive includes the waterreducer water-proofing additive retarder coagulationaccelerator etc Plasticizers are always considered toenhance compatibility [43] In fact they are defined aswater reducers to improve performance of fresh con-crete by reducing fluidity and plasticity and there is nonotable impact on concrete segregation was observed[71 72]Fiber A variety of fibers are added into FC so as toimprove strength and reduce shrinkage ey aremainly polypropylene [73 74] glass and polypropylene[75] red ramie [76 77] palm oil steel [78] coconut[79] waste paper cellulose [80] carbon and poly-propylene [81] which usually introduced in rangesbetween 02 and 15 of the mixture volume

FC is commonly prepared by prefoaming method or mix-foaming method [37] e majority of common mixers suchas the inclined drum pan mixer used for concrete or mortaris applicable to FC production e mixer type mix pro-portion and mixing order used for FC depend on adoption ofthe above-mentioned two methods [38] e major proce-dures using these two methods are presented as below

Prefoaming Method (1) e foam and base mixture areprepared independently (2) Totally mix the foam andbase mixture [82]Mix-Foaming Method (1) Surfactants or foaming agentare mixed with base mixture together (especially thecement paste) (2) e foam produces cellular struc-tures in FC

ere are two ways ie dry or wet process used forbubble generation e dry process produces more stable

bubbles with sizes less than 1mm compared to the wetprocess for which the sizes of the generated bubbles arebetween 2mm and 5mm e stable foam helps to resistsmortar pressure until cement solidifies which is advanta-geous to generate reliable pore structure in FC [83]

ough the mixing process and FC quality in these twomethods can be controlled the preforming method isconsidered superior to mix-forming method due to thefollowing [84]

(1) Lower requirements for foaming agents [55](2) e foaming agent content is closely related to air

content in mixture

23 Material Properties Currently weakness and poordurability on FC still exist e discussion on the materialproperties in this section is mainly based on practical ap-plications where there are potential problems such as (1)underground water (2) insufficient structure strength (3)structure crackfailure (4) stabilization issue and (5) cor-rosion e material properties like drying shrinkagecompressive strength and durability are discussed throughliterature review

231 Drying Shrinkage Lack of coarse aggregates leads to4ndash10 times higher shrinkage of the FC than that observed inordinary concrete [15 37]ere aremany factors affecting thedrying shrinkage such as density foaming agent filler ad-ditive andmoisture contents Table 1 presents different dryingshrinkage values observed in some cement-based materials

In general drying shrinkage decreases with the densityreduction [37] e shrinkage differences induced byfoaming agents are bound up with pore structure of FC andthe lower pore connectivity helps to reduce the dryingshrinkage [44] Jones et al [86] observed the decrease ofdrying shrinkage when fine sand was used as fillers instead offly ash because the fine sand provides a superior capacity inresisting shrinkage deformation Many findings demon-strate that fine aggregate such as light ceramsite [87] ex-panded perlite vitrified microsphere [88] and magnesiumexpansive agent [89] together with reduction of foam vol-ume [90] can reduce drying shrinkage Meanwhile re-strictive effects from increase of water and aggregate alsoprovide support for drying shrinkage reduction [91]

It is reported that autoclaving technique reduces 12ndash50drying shrinkage and brings a strength enhancementtherefore autoclaving is an ideal option for maintaining FCproducts within an acceptable strength and shrinkage level[15] To reduce drying shrinkage some aspects like watercontent control selection of binder and foaming agent aswell as mixture modifying with fine aggregate are worthy offurther studies e use of fibers can significantly enhanceresistance capacity on drying shrinkage due to (1) tensilestrength improvement of cement base mixture (2) pre-vention of further cracks development in cement basemixture and (3) capacity improvement of resisting defor-mation Table 2 summarizes and reviews different resultsand findings on the drying shrinkage

Foamconcrete

Trench backfill

Structure fill

Mass void fill

Duct and shaft fill

Sink hole filling

Bridge abutment Tunnel stabilisation

Pavement base

Figure 1 Different applications of FC

Advances in Materials Science and Engineering 3

Some adverse factors such as poor early curing insuf-ficient water conservation measures or harsh productionconditions may cause water evaporation thereby leading toshrinkage or even crack in FC Some technical measuresimproving these situations are illustrated as following

(1) Suitable cement dosage(2) Lower water-cement ratio(3) Strengthen water conservation in early stage(4) Use waterproofing agent(5) Use crack prevention net

232 Compressive Strength ough FC has been deeplystudied some shortcomings such as low strength still restrictits wider applications [100] e strength of FC is deter-mined by different cementitious materials cement dosagemix proportion water-cement ratio foam volume foamingagent curing method additive etc [101] Table 3 illustratessome studies on different factors affecting FC compressivestrength

To a certain extent the density controls the strengthHence it is always to seek a balance between strength anddensity for the purpose tomaximize strength while reducingdensity as much as possible Sometimes this can be achievedthrough optimizing cementitious materials and selectinghigh-quality foaming agents and ultralight aggregatesNambiar et al [1 61] indicated that the filler types determinethe water-solid ratios when FC density is constant and thereduction of sand particle size will help to improve strength

e foam volume exerts a notable impact on the flow be-havior of FC and a reduction in particle size of filler shows apositive effect on strength improvement of FC Park et al[111] added carbon fiber into base mixture so as to producecarbon-fiber-reinforced FC and they reported that thestrength and fracture toughness were obviously improveddue to carbon fiber reinforcement effect e results con-firmed that reasonable water-cement ratios exhibit a notableimpact on enhancing the strength e higher water-cementratio ensures excellent slurry fluidity thereby introducingfoam into cement paste with an even distribution so as toachieve strength growth On the contrary the decrease ofwater cement ratio results in poor fluidity thus reducing thestrength e dominant factor affecting strength is cementquality added into mortar slurry whereas the high strengthcement is considered as an effective way for strength en-hancement However it should be added appropriatelyconsidering the increase of subsequent cost

e investigation indicated that FC strength decreaseswith the voids increase [112ndash114] e impact of foamingagent on strength is mainly manifested in aspects of thebubble size distribution uniformities of bubbles foamstability and foaming capacity Ideally foaming agentsshould be characterized by strong foaming capacity poorwater-carrying capacity per unit and little adverse impactson FC [115ndash118] Attempts and investigations can beconsidered regarding selection of the high-performancefoaming agent so as to prepare the small and uniformbubbles e experimental results showed that the water-cement ratio and air-ash ratio have crucial impacts on FC

Table 1 e drying shrinkage values observed in typical cement-based materials [85]

Material Cement paste Cement mortar Cement concrete FCDrying shrinkage () 015ndash03 008ndash02 006ndash009 015ndash035

Table 2 Review of filler foaming agent and additive used in FC and the resulting density ranges and drying shrinkage

Filler Foaming agent wc ratio Additive Density(kgm3)

Dryingshrinkage

()Reference

Blast-furnaceslag + limestone fine Fatty alcohol-based liquid 029 Magnesium expansive

agent + calcium sulfoaluminate 1611ndash1638 005ndash03228 d [89]

Polymer fiber Foamin C 03 Viscosity enhancing agent 380ndash830 01ndash049 [92]

NAAnimal

based + synthetic + plantbased surfactants

05 NA 600 025ndash0390 d [44]

Crushed sand + FA Hydrogen peroxide 03 Na2SiO3 +NaOH 1889ndash2106 009ndash01180 d [93]

FA+natural sand Protein foaming agent 071ndash222 NA 1000ndash1400 009ndash02365 d [94]

NA Synthetic polymeric latex 045ndash06 NA 260ndash800 018ndash031 [95]

NA Synthetic based 052ndash075 NA 300ndash800 026ndash03590 d [96]

Sand Hydrolyzed protein 05 NA 900ndash1100 07ndash07228 d [97]

Quartz sand PB-2000 NA Microreinforcing additive NA 015ndash03 [98]

FA Organic based 03ndash05 Na2SO4 +Triethanolamine 400ndash800 009ndash01828 d [99]

NA not available FA fly ash


strength [119 120] it also reported that addition of fibers ishelpful to increase strength [73 74 121] e predictionmodels on compressive strength were also investigated bysome researchers ese findings are mainly based on theartificial neural network [122ndash124] extreme learning ma-chine [125] and regression analysis based empirical models[126] Table 4 summarizes the prediction models for com-pressive strength of FC to date

233 Durability e underground members are usuallyfaced with various adverse conditions such as temperaturechange freeze-thaw cycles and acid-base corrosion ese

factors may lead to a poor durability of the FC-basedstructures and members resulting in structural damageswhich seriously affects project safety

(1) Permeability Water absorption of FC is attributed to thecapillary pore infiltration and connected pore infiltration Coxand Van Dijk [134] reported that the water absorption of FCwas higher than that observed in other concrete types due tothe least 20 foam embedded in plastic mortar is capacityis generally twice than that of the normal concrete with thesame water-binder ratio [63] An investigation conducted byNyame [135] found that permeability of concrete mortar

Table 3 Overview on research on factors affecting compressive strength of FC

Composites Factorsinvestigated 28 d CS Main findings and conclusions Reference

OPC

(i) Curingcondition

(ii) Fiber content(iii) Dry density

156ndash1338

(1) Compressive strength increases with dry density increase in nearlylinear while bending strength increases more obviously

(2) e flexural strength was significantly increased when fiber contentincreased to a certain extent but the compressive strength was not

significantly affected

[92]

Cement sand (i) Coconut fibercontent 96ndash146 (1) e volume increase of coconut fiber particle aggregate in FC can

significantly enhance compressive strength with a maximum value of 15 [102]

OPC (i) Water-cementratio 3ndash51 (1) e FC compressive strength varies in an inverted V-shape with the

increase of water cement ratio [103]

OPC (i) Bentonite slurrycontent 3ndash47 (1) e compressive strength decreases with mixing content increase of

bentonite slurry [104]

OPC GBFS FA (i) Foam stabilizer 17ndash23

(1) XG stabilizer performs positively on thermal conductivity andcompressive strength of FC

(2) e compressive strength with mechanical and chemical foamingincreased by 34 and 20 respectively

[105]

OPC(i) Foaming agents(ii) Dry densities(iii) Cement type

020ndash1174

(1)e compressive strength increases more obviously when protein basedfoaming agent is used in mix design as its positive effect on pores

(2) e maximum strength value was recorded in cellophane curing whilethe minimum one was found in air curing

[7]

OPC (i) Aggregatesubstitution 3ndash48

(1) Slag partially substituted for fly ash improves FC strength at roomtemperature but leads to a drying shrinkage and strength loss at high

temperature[19]

Cement naturalsand (i) Additive types 6ndash47

(1) e reinforcement of pore structure and microstructure improvementof cement paste are helpful to improve FC strength

(2) e combination of additives reduces size and connectivity of poresand prevents them from merging as well as produces narrower pores

distribution and achieves higher strength

[106]

OPC (i) Different sandgrading 56ndash70

(1)e samples prepared with 060mm sand have the highest compressivestrength compared to those prepared with coarse sand grade

(2)ewhole water curing provides a better development environment forstrength increase compared to the air curing

[107]

OPC (i) Differentpumice types 05ndash35

(1) e pumice-based FC has the highest compressive strength(2)e density-based empirical model for compressive strength prediction

was proposed[5]

OPC fine sand (i) Different fillertypes 4ndash23

(1) Adding superfine GGBS as a partial substitute for cement can increasestrength slightly without significantly changing mix and workability

(2) e strength with small pore diameter and uniform pore size is higherthan other samples

[108]

OPC (i) Recycled wasteas filler 153ndash1026

(1) Recycled glass-filled FC has higher compressive strength compared tothat filled with plastic

(2) e addition of superplasticizer reduces the amount of macropore andgreatly improves the strength

[109]

OPC sand (i) Recycled wasteas filler 52ndash68

(1) Compared with FC produced with 100 addition of river sand usingrefined mineral powder as filler can improve compressive strength and

strength performance index[110]

OPC ordinary Portland cement FA fly ash CS compressive strength (unit MPa) GBFS granulated blast furnace slag


decreases with porosity decrease after the addition of theaggregate An increase of the aggregate volume in mixtureleads to the increased permeability Meanwhile the in-crease of ashcement quantity in base mixture propor-tionally increases the water vapor permeability especiallyat low densities [114] Kearsley et al [131] studied theinfluence of different fly ash types on the porosity andpermeability e results showed that dry density directlyaffects the porosity but slight impacts of fly ash on porositywere observed In addition an empirical model for per-meability prediction was proposed

kd Gd

ActΔp (1)

where kd vapor flow time rate through unit areaGweight loss thorough t time in hours Ac cross sec-tional-area perpendicular to flow (m2) d thickness ofspecimen in m t time in hour and Δp distance betweendry and moist sides of the specimen

Different methods were employed by Hilal et al [136] toinvestigate effects of pore structure porosity and criticalpore size on permeability and water absorption of FC eresults showed that the critical pore diameter and the porediameter size (gt200 nm) decrease with density increasewhich is closely related to the permeability erefore themanufacture ability to ensure air being contained in stablesmall and uniform bubbles should be highlighted which ishelpful to reduce the permeability of cement paste due totheir integrity and isolation effects

e adsorption of FC mainly depends on filler types porestructure and infiltration mechanism It was reported thatfilling effect from mineral aggregates affects the pore structureand permeability of cement paste [137] Jones and McCarthy[138] compared adsorption differences between sand-based andfly ash-based FC e results indicated that the fly ash-basedmix was endowedwith higher water absorption than thatmixedwith sand e FC adsorption was generally lower than thecorresponding basic mixture and decreases with foam volume

Table 4 Prediction models for compressive strength of FC

No Components Equations Annotations Reference

1OPC andlimestonepowder

fc 00029 times exp(00104c) c dry density (kgm3) [5]

2 OPC fine sandand FA fc A(ln t)B(Sa(mc + mm) + msc)C

A B and C parameter reflecting compressivestrength hydration rate and porosity of mix

t curing time Sa empirical constantmcmm andms cement admixture fine aggregate dosages per

cubic meter

[127]

3 Cement FA andslag fc A times exp(a times p1) + B times exp(b times p2)

a b empirical constants A B fitting constantsp1 p2 porosity [128]

4 Cement FA andslag fc C times (1 minus p1)

c + D times (1 minus p2)d c d empirical constants C D fitting constants [128]

5 OPC and FA fc 00243 times exp(00083c) c dry density (kgm3) [12]

6 Cement and sand fc 034 exp[00022c times (1 + (wcm) + (sc))]c cement content w cmwater to cementitious

material ratio sc sand-to-cement ratio [126]

7 Cement sandand FA fc f[dc(1 + 02ρc + sv)(1 + ks)(1 + sw)ρccw]b

b empirical constant sw filler-cement ratio byweight sv filler-cement ratio by volumef theoretical strength of a paste with zero

porosity ks water-solids ratio by weight cw unitweight of water dc fresh density ρc specific

gravity of cement

[114]

8 Cement sandand FA fc K[206 times α times Vc1 minus Vfl minus Vc(1 minus α)]n

Vc volume of cement Vfl fillers volume percubic meter of concrete α hydration degreeK gel intrinsic strength n empirical constant

[114]

9 Cement and FA fc f(minus0324 + 1325αd)2 αd dry density ratio [129]10 Cement and FA fc 396(ln(t))1174(1 minus p)36 p porosity [129]

11 Cement and ash fc l(ac)2 + m(ac) + nac ashcement ratio by weigth l m and

n constants [130]

12 Cement and FA fc 188[dc(1 + 02ρc)(1 + ks)ρccw]31 dc fresh density ρc specific gravity of cementcw unit weight of water [131]

13 Cement and ash fc 1172fα37b

αb binder ratio by volume f cement pastecompressive strength [63]

14 Cement and sand fc k(cc + w + a)nc w and a absolute volumetric

Proportions of cement water and air k andn constants

[119]

15 Cement fc KS ln(posp)Ks empirical constant pos porosity at zero-

strength [132]

16 Cement fc 245[dc(1 + 02ρc)(1 + Ks)ρccw]27 ρc specific gravity of cement cw unit weight ofwater Ks empirical constant [133]


increase [139] An investigation conducted by Awang andAhmad [78] demonstrated that the water absorption dramat-ically increases owing to the use of steel and polypropylenefibers in the basic mixture Each kind of fiber has a differentsurface morphology that plays an important role in the waterabsorption rate of lightweight FC Another study suggested thatusing pozzolanic admixture and turbulent mixing techniquecan produce water-resistant and durable FC [140]

(2) Frost Resistance Freeze-thaw cycle is one factor thatresponsible for deterioration and failure in concrete[141 142] An investigation carried out by Tsivilis et al [143]revealed that addition of limestone powder reduced frostresistance of FC and limestone cement concretes indicatelower resistance to freezing and thawing compared to the purecement concrete Tikalsky et al [43] performed freeze-thawcycling tests on FCwith differentmix proportions based on animproved method and it is found that the compressivestrength initial penetration depth and water absorption havesignificant effects on the frost resistance but little effects ofdensity and permeability on frost resistance are observed

(3) Carbonization Carbonization increases the risks ofcracking and durability loss of FC [140] Jones and McCarthy[59 138] also reported that a higher incidence of carbon-ization was observed in low-density concrete Compared withfine sand replaced mixture replacing fly ash with cement inmixture notably improved carbonization resistance capacity[86] In addition the foam content increases with decrease offoam density so as to reduce carbonization in FC

(4) Corrosion e resistance capacity of FC to erosive en-vironment depends on its cellular structure However thisstructure does not necessarily reduce resistance capacity forwater penetration whereas voids produced cushioning effectto prevent rapid penetration [139] Sulfate is one of thecorrosive agents that affect the service life of FC while thedamage risk from alkali-silicon reaction on recycled ag-gregate is not significant [144] Sulfate erosion is identified asa complex process and can be influenced by various factorssuch as cement type water-cement ratio exposure timemineral admixture permeability etc [145ndash147] Ranjaniand Ramamurthy [148] carried out 12 months of continuedassessment on FC performance with variable densities of1000 to 1500 kgm3 by immersing FC examples in sodiumsulfate solutions and magnesium sulfate solutions respec-tively e results showed that expansion rate of FC insodium sulfate environment was 28 higher than that inmagnesium sulfate environment leading to a 1 mass lossof specimens in magnesium sulfate environment In addi-tion the corrosion resistance capacity of studied samplesincreases with the decrease of FC density [149]

234 ermal Conductivity Outstanding thermal insulationproperties of FC make it popular in the building insulation Itis widely reported in relevant studies that thermal conductivityis an important parameter influencing thermal insulationperformance FC has excellent thermal insulation properties

due to its porous structure e thermal conductivity valuesare 5ndash30 of those measured on normal concrete and rangefrom 01 to 07WmK for dry density values of 600ndash1600 kgm3 reducing with decreasing densities [150] e thermalconductivity of FC is controlled by the filler density fiber mixratio temperature and pore structure

(1) Influence of Filler Different aggregates and mineraladmixtures have a significant effect on thermal conductivityIt was observed that the addition of the lightweight aggregatein FC reduces the thermal conductivity [151] It is specifiedthat thermal conductivity value for lightweight aggregate FCwith a dry density of 1000 kgm3 is 16 of that measured ontypical cement mortar [152] Artificially introducing poresinto themortar matrix combining with the use of lightweightaggregate with low particle density has been identified to behelpful for reducing thermal conductivity [91] FC with athermal conductivity value of 006ndash016WmK could beproduced by moderately filling polystyrene particles intoporous mortar [153] Giannakou and Jones [154] stated thatthe excellent properties of fly ash such as low density andhollow particles are advantageous to increase the heat flowpaths so as to reduce the thermal conductivity In a study byJones and McCarthy [88] reported that typical thermalconductivity values of FC with dry density of 1000ndash1200 kgm3 range between 023 and 042WmK And 30 re-placement of cement by PFA (pulverized fuel ash) has alsobeen confirmed to lead to a 12ndash38 reduction on thermalconductivity Studies done by Xie et al [104] found that useof bentonite slurry improves the thermal insulation per-formance of FC and observed that with densities of 300 and600 kgm3 the samples with 10 bentonite slurry under-went the largest reduction in thermal conductivity

(2) Influence of Density For FC it was found that the thermalconductivity reacts proportionally with a density Weiglerand Karl [91] observed a 004WmK drop in total thermalinsulation was observed with each 100 kgm3 reduction ofthe densitye thermal insulation performance decreases asthe density volume increases [155 156] In terms of theapplication of FC in wall brick masonry an increase up to23 on thermal insulation was obtained comparing to thenormal concrete when the inner leaf of the wall constructedwith the FC at a density of 800 kgm3 [111]

(3) Influence of Fiber Nagy et al [78] studied the thermalconductivity of several fibers consisting of AR-glass poly-propylene steel kenaf and oil palm fibers e resultsshowed that the thermal conductivity on samples with steelfiber inclusion is higher than those observed in FC withother fibers inclusion while polypropylene fiber presentedthe lowest thermal conductivity is is explained to beexpected because steel fiber itself is a good heat transferconductor Also the higher the fiber inclusion the higherthe thermal conductivity In another study Nagy et al [157]investigated the thermal properties of steel fiber reinforcedconcrete and observed that the addition of steel fiber doesnot necessarily increase the thermal conductivity is isbecause the addition of fiber leads to the increase of porosity


which reduces the density and thermal conductivity edurability properties of FC consisting of five differentsynthetic and natural fibers like polypropylene AR-glasskenaf steel and oil palm fibers were studied by Awang et al[158] ey confirmed that the maximum reduction inshrinkage and the thermal conductivity was obtained fromusing polypropylene fibers

(4) Influence of Mix Ratioe insulation capacities of FC areproven to be sensitive to the change of mortar-foam ratios[49] is difference is more obvious in low-density samplesranging between 200 and 300 kgm3 [159] e denser ce-ment paste with a lower water cement ratio is easier to formpores with lager size than that with a higher water cementratio us the convective heat transfer in the larger poresunder the temperature difference increases the thermalconductivity of the FC with lower water cement ratio [159]

(5) Influence of Temperature It is reported that the thermalinsulation is improved with the decrease of temperatureRichard et al [160] studied the thermal insulation perfor-mance of porous concrete applicated in a low temperatureenvironment and satisfactory results were observed At thesame time Richard et al [161] reviewed the thermal andmechanical properties of FC in the density range of640ndash1440 kgm3 with the ambient temperature ranging be-tween 22 and minus196degC e results indicated that the thermalconductivity value of foam concrete significantly reduced by26 when the temperature falls from 22 to minus196degC

(6) Influence of Pore Structure According to Kumar et al[162] the thermal conductivity was about 50 lower than thatof normal concrete with a thermal conductivity of 143WmKas a result of the uniform pore size in cellular lightweightconcretes (CLCs) FCs with larger size and the wider distri-bution of bubbles were found to have lower thermal con-ductivity at low densities [104] Also it was shown that higherthe porosity the lower the thermal conductivity However theincrease of the joint strength of pore paths was found to oc-casionally increase the thermal conductivity e location andrelative orientation of the pores have a great influence on thethermal conductivity More thermal resistance was observedwhen the pores are arranged at right angles to the heat flowleading to more heat passing through the pores On thecontrary if a layer of pores is parallel to the direction of heatflow a smaller thermal resistance will be produced [163]

235 Pore Structure A critical task in FC production is tocontrol the nature size and distribution of pores becausethe pore characteristic is the key factor to determine thedensity and strength of FC Pores can be generated by (i)mixing a gas releasing agent such as H2O2 or zinc powder inthe pasteur cement mortar or (ii) introducing a large vol-ume of bubbles in mortar Often different foaming methodscomposition of mixture and curing process will produceindividual bubbles with different sizes and distributionswhich further affects performance of the FC

e pore characteristic is an important factor thatcontrols the compressive strength thermal conductivity andpermeability of the FC ese pores are composed of theinterlayer poresspaces gel pores capillary pores and airvoid with pore sizes varying from nanoscale scale to mil-limeter scale [128] Some parameters such as volume sizesize distribution shape and spacing of pores can be used tocharacterize these pores [38] e gel and capillary pores aremainly responsible for the microstructure features [53] euse of additives and the variation of water cement ratio willaffect the pore characteristics For a given density the ad-dition of additive reduces the pore size and connectivity so asto obtain the higher strength e introduction of mineraladmixture such as slag or fly ash in FC results in a reductionon the pore size distribution and total porosity [164] Batoolet al [165] studied the distribution features of pore size incement-based FCe results showed that narrower the poredistribution the greater the conductivity and the smaller thedensity e addition of superplasticizer in combination ofother additives in foam concrete can further benefit im-provement of the pore structure [106]

Researchers found that the pores may be influenced bywater cement ratio owing to the changes in the rheologicalproperties and the ability to resist collapse from the foams Itis observed that the pores were small irregular-shaped andhighly connected at water cement ratios below 08 esepores were determined to be rounded expansive and withwider pore size distribution for water cement ratios over 08because the ability to limit the growth of air bubbles de-creased at high water cement ratios [166] It is reported thatreduction of water cement ratio or the addition of fillersoften brings difficulties in generating an arranged pore area[53] Lower water content helps FC to capture the smallerpore size as well as the increased mass density and com-pressive strength [53] Pore distribution is one of the im-portant microscopic parameters affecting the strength offoam concrete In general foam concrete with narrowerbubble distribution will have the higher strength [118]

A review by Zhang et al [26] summarizes the effects offoaming method on pore properties like size volume andshape as shown in Table 5 It is observed that pore sizes in FCproduced bymechanical foaming are smaller than thosemadeby chemical foaming e connectivity of pores depends onthe density of the mixture not on the foaming method If thedensity reaches a level that allows the adhesive to separateindividual bubbles the pores tend to be closed Otherwise theFC will be dominated by the opening pore structures

Hilal et al [106] used scanning electron microscope(SEM) to characterize pore size and shape parameters andthen studied effects of different additives on strength per-formance e investigation demonstrated that addition ofadditives notably enhanced microstructure and porestructure of FC slurry compared with conventional mixtureough the additives increase the number of pores higherstrength was obtained due to the reduction of pore size andconnectivity which prevents pores from merging andproducing a narrow distribution (see Figure 2) It is con-firmed that FC strength not only depends on pore structure


enhancement but also microstructure improvement of thecement paste

ough many globally sourced literatures on FC havebeen documented it is worth noting that research concerningperformance enhancement from FCmicromechanism shouldnot be neglected whereas microstructure signifies its variousperformance behaviors e macroscopic aspect such asconcrete type filler additive foaming agent and water ce-ment ratio have been widely studied However there are verylimited literatures on FC microstructure so this may be adirection for future efforts to improve FC performance

24 Stability Stability is a major concern in FCe stabilityof FC can be defined as a mixture with small uniform closedpore structure after hardening and no bleeding and segre-gation [167] e stability of the experimental mixture can beevaluated by comparing (i) the calculated and actual quan-tities required to achieve a plastic density within 50 kgm3 ofthe design value and (ii) the calculated and actual watercement ratio [38] e stable foam concrete mix depends onmany factors viz density foaming agent water to cementratio admixture aggregate and admixture

241 Influence of Density e stability characteristics of FCwere studied by Jones et al [168] and they found that con-cretes with a density of less than 500 kgm3 are more likely tobe unstable Also replacement part Portland cement bycompatible calcium sulphoaluminate (CSA) cement canproduce stable low density mixture Another study by JonesandMcCarthy [138] showed that the instability of FC seems toalmost inevitable at a very low density (less than 300 kgm3)

242 Influence of Foaming Agent Lower concentration offoaming agent exerts a positive effect on the stability of FC

[169] e study by Ghorbani et al [170] comparativelyanalyzed the effects of magnetized water on the stability ofthe synthetic-based and protein-based foaming agents eresults showed that magnetic water presents a positive effecton the stability of synthetic foam but has an adverse effecton the stability of protein foam Siva et al [171] developed agreen foaming agent from the natural soap fruit It could beused as a substitute of synthetic foaming agent which meetsthe existing ASTM foaming agent standard e mixturewith high foam content tends to be unstable after pouringwhich hinders the development and use of low density FCExperimental studies showed that severe instability wasobserved in some high foam content mixtures [172] einstability could be easily found in the mixture sample whenthe foam content is over 061m3 showing an increase ininstability with the increase of foam content e results inexperiments by Adams et al [173] confirmed that thefoaming agent with 5wt binder can stabilize the FC at adensity of less than 200 kgm3 Meanwhile the pore struc-ture of protein foam concrete is more uniform than that oftenside-based foam concrete Sun et al [44] studied thestability and workability of FC prepared with syntheticsurfactants animal glueblood based surfactants and plantsurfactants ey stated that as a stable nanoparticle foamsynthetic surfactants foam shows the higher stability and airstrength than those observed in the other two foams whichis advantageous to improve the performance of FC

243 Influence of Mix Ratio e results of the study byGhorbani et al [100] indicated that magnetized water canbenefit the stability of FC For the same mix proportions theFC specimens with magnetized water show the higherstability than the control samples prepared with regular tapwater because of the higher hydration degree It is reportedthat the consistency of the base mixture added to foam

Table 5 Pore features achieved by different foaming methods [26]

Foaming method Diameter ofpores (mm)

Volume ofair voids Shape Density (kgm3)

Chemical foaming gas release 05ndash30 15ndash65 Spherical Typical AAC 300ndash800Mechanical foaming High shear mixing orprefoaming 01ndash10 10ndash50 Less spherical with shape

factor 12ndash14 400ndash1600

(a) (b)

Figure 2 Effect of additives on cement paste microstructure (a) with additive (more homogeneous) and (b) without additive [106]


exhibits a notable influence on the stability of the mixturee spread flow of 45 in workability value is recommendedto produce FC mix in good stability e water to solid ratiorequired for producing stable mixtures increases with theaddition of fly ash [168] e adhesion force between par-ticles and bubbles in the base mixture will enhance thestiffness of the mixturee air foams may affect the stabilityof the mixture during mixing process but this could beprevented by employing the higher water-solid ratio [167]e volume instabilities of cement paste could suffer fromthe large water binder ratio [103] Researchers proposeddifferent methods for evaluating the stability of FC mix (i)density of fresh foamed concrete was compared with itstarget density and (ii) the difference between calculated andactual water cement ratio was checked and keep them closeto 2 [88]

244 Influence of Admixtures and Aggregates For concretewith a density up to 400 kgm3 100 Portland cement canform a stable mixture However for the concrete with adensity less than 400 kgm3 it is required to replace 5 to10 cement with the compatible calcium aluminate ce-ment so as to obtain stable FC [168] Cong and Bing [174]pointed out that the addition of silica fume can improvethe thermal insulation performance and strength andproduce more uniform distribution pores ough the useof quicklime helps in significantly increasing the densityand strength of FC reduction on the foam stability wasobserved

245 Influence of Additive e strength improvement andcollapse prevention on high-performance FC are bothhelped by the addition of superplasticizer and a moderatereduction on water cement ratio [166] In another studythe stability of FC with use of superplasticizer was im-proved by 43 when the water binder ratios were set lessthan 03 [168] Qiao et al [175] studied the applicability ofgemini surfactant as novel air entraining agents for FCe results showed that gemini surfactants have morestable air entraining capacity and higher surface activitycompared to the current standard surfactants used inindustry e gemini surfactants modified with sulfonicgroups have the notable stability air entrainment per-formance surface activity and foaming propertiese useof water reducer to improve the performance of base mix isvery effective for improving the stability of FC mixturee addition of plasticizers increases the workability of thebase mix and prevents mixture with foam content of63ndash80 from collapse e additives in FC produce lessstress on the pores which makes the cement slurry flowmore easily between the neighborly poresis is helpful tolead to a more uniform distribution of cement slurry inpores reducing the coalesce and increasing the size ofpores [172]

Some nano particles such as nano silica or nanotubesare always introduced to modify interface between bubblesand cement paste [176] ese nanoparticles gathering atgas-liquid interface helps to reduce the contact area between

bubbles and forms a dense particle film to restrain thecoalescence and disproportionation of these bubbles At thesame time a three-dimensional network structure will beformed between the foam surface and the continuous phasewhich is advantageous to prolong the drainage time of theliquid membrane [177] A schematic representation of three-phase-foams after foaming reported by Kramer et al [178] isshown in Figure 3

Researchers reported that even though nanoparticles arenot amphiphilic most of them are surface active [179] ehydrophobicity of particles is regarded as a key factor toassess whether the particles could be adsorbed and remainedaround bubbles Binks and Horozov [179] modified the silicasurface with silanol groups and made it to exhibit differentextents of hydrophobicity for the purpose of the investi-gation on foam stability e results suggested that thesurface contents of SiOH varying from 30 to 50 areadvantageous to produce foams with good stability and largefoaming capacity Also an increase of pH value or a re-duction of NaCl concentration caused the foams turningfrom stable three-phase state into unstable two-phase stateGonzenbach et al [180] employed short-chain amphiphilessuch as carboxylic acids alkyl gallates and alkylamines tomodify the surfaces of nano silica and nano alumina In thisway nanoparticles can be adsorbed on the surface of bubblesby chemical bonds so as to produce super stable low-densityfoams [181]

However the foams produced by combining nano-particles with surfactants are not always stable instead theysometimes promote the bubblersquos disappearance e ad-sorption of nanoparticles on the bubble surface will accel-erate the seepage velocity of the liquid film e connectionof the liquid films and bubbles leads to the burst of thebubbles Of course the stability of foam in this situationcould be improved by the use of the suitable nanoparticlesand surfactants [182] Tang et al [183] pointed out that thehydrophilic silica particles combined with sodium dodecylsulfate (SDS) in FC exhibit a positive foam stabilizationeffect whereas the addition of nano silica leads to reduction

Disperse phase

Continuous phase

Nanoparticle

Surface activeagents

Figure 3 Diagrammatic sketch of three-phase-foams after foaming[178]


of bubble size In another study Alargova et al [184] reportedthat the stability of the foams produced by combined use ofthe SDS and bar polymer particles is lower than that observedin single-particle stabilized foams In another study Binkset al [185] revealed that the stability of bubbles formed by themixed system of SiO2 and cetyltrimethylammonium bromide(CTAB) was significantly higher than that in the single CTABsystem but the foaming property was slightly weaker is isbecause some CTAB was adsorbed onto the surface of thenanoparticles which increases the hydrophobicity degree ofthe nano silicae stability of the foam systemwas improvedbut at the same time the foaming capacity was reduced as aresult of the reduction in the concentration of the foamingagent in the solution

25 Enhancement Even though FC has been widely used innonstructural components the applications in structuralmembers are still limited due to its strength issue It isreported that the insufficient strength of FC is mainly be-cause of the uneven distribution of internal pore size It iseasy to lead to stress concentration in small pores underaction of the loads resulting in the destruction of FC einfluence of pore size distribution and pore distributionuniformity on the properties of foam concrete is well known[115 118]us it is essential to minimize the coalescence ofbubbles and improve the numbers of small pores and closedpores in foam concrete

Researchers have made different attempts in order tostrengthen FC Now the addition of fibers is the mostcommonly used method to improve the mechanical prop-erties of FC [73 74] An investigation by Falliano et al [92]stated that 07 fibers mixed in FC did not seem to notablyimprove mechanical strength compared with the referencesample without fibers It is observed that the flexuralstrength was significantly improved when increasing thefiber content to 50 however there is no obvious im-provement in the compressive strength was recorded Es-pecially the improvement of flexural strength mainlydepends on the dry density and is less affected by curingconditions Dawood and Hamad [75] studied reinforcementeffect of glass fibers (GF) polypropylene fiber (PPF) andhybrid fibers (GF +PPF) on the toughness behaviors of high-performance lightweight foam concrete (HPLWFC) eresults showed that the use of glass fiber increases thecompressive strength whereas the addition of polypropyl-ene fiber reduces the compressive strength of the HPLWFCe greatest increment on the compressive strength of theHPLWFC is observed in the experimental species with 04glass fibers and 06 polypropylene fibers Experimentalresults by Hajimohammadi et al [105] confirmed that use ofXanthan gum (XG) as a thickening agent significantly affectsthe viscosity of the foam solution and condensates the liquidfilm around the foams e drainage and collapse of theprefoaming materials can be greatly reduced with the in-crease of XG concentration notably improving the pre-dictability and controllability of the chemical foaming XGmodified samples have smaller and narrower pore sizedistribution compared to the control sample which has a

positive effect on the thermal conductivity and compressivestrength of the specimens

e control of bubble size has an effect on the perfor-mance improvement of FC Xie et al [104] pointed out thatimproving the pore forming method reducing the size ofbubbles and increasing the nanopores in foam concrete havebecome the key issues for FC research For the same densitythe porosity decreased gradually with the increase of ben-tonite slurry content resulting in an increase of wallthickening between pores e pore size decreased with theincrease of bentonite slurry from 0 to 50 the averagepore size decreased significantly and the pore size distri-bution was narrower e gas in the small bubble enters thelarge bubble through the liquid film to balance the pressureso that the bubble is distributed in a large range e thickerwater lubrication film between bubbles restricts the gasexchange of mixture with low precast foam dosage resultingin uniform pore size

Jones et al [168] reported that unstable behavior ofbubbles causes the uneven pore size distribution in FC ecombined action from the buoyancy gravity slurry pres-sure and internal pressure result in instability in bubbleswhen the bubbles are introduced into the cement paste esmaller the bubble the more prominent the instability isunstable state in bubbles leads to the continuous fusion andgrowth of bubbles which makes the bubble size larger ebubble fusion behaviors are more obvious when a largeramount of foams is used Also due to the small amount ofslurry the pressure of the slurry on the bubble becomessmaller and the bubble floats up which leads to surfacesettlement and collapse of FC

Currently a new way to further improve the perfor-mance of FC is introducing the three-phase-foams which ishelpful to weaken the instability by reducing the high in-terfacial energy and free energy of the system [176] A studyby She et al [186] made use of the coupling of organicsurfactant and nanoparticles to change the gas liquid in-terface so as to produce super stable foams for FC pro-duction A separation effect between bubbles and freshcement paste works when the bubbles are added into thecement paste ese bubbles will be balanced under theaction of various forces consisting of bubble limiting force(Fc) the gravity (Fd) the internal bubble pressure (Pi) andsurface tension (Fst) as well as bubble buoyancy (Fb) inducedby surfactant effect as shown in Figure 4

e instability of the bubbles in normal foams is mainlyattributed to the drops of Fst and Fc therefore these bubblesgrow easily and float to the upper region of the slurry underaction of the Fb An undesirable matching between the forcesacting on the bubbles and early strength limits the bubblemotion leading to the stratification and uneven density inthe foam concrete

On the contrary this situation was improved when thebubble surfaces were modified with the addition of nanosilica (NS) particles and the films were enhanced withhydroxypropyl methylcellulose (HPMC) ese NS particlesincrease the surface roughness and the friction drag of thebubbles moving in the cement paste while the free energy onthe bubble surface is absorbed by the NS particles


In addition the use of carbon nanotubes as reinforce-ment components in cement-based materials has attracted alot of attentione structure and performance modificationin FC can be realized by dispersing the multiwalled carbonnanotubes in foam concrete [187] e most significantimprovements in carbon nanotube-based FC are observed inthe mechanical properties [188 189] e addition of carbonnanotubes not only improves the performance of the FC butalso ensures the uniformity of pore size e dispersion ofcarbon nanotubes leads to a fine structure of the cementpaste which results in dense concretes [188 189] A moreuniform and compact cement paste is achieved by the effectof calcium hydroxide crystallization Meanwhile a higheramount of C-S-H in hydration of concrete is observedbecause carbon nanotubes play a role in the formation ofC-S-H phases [190] e strengthening is also provided evenwith a small amount of 01 ww carbon nanotubes relatedto binder content It is also reported that the use of carbonnanotubes with low mass content in nonautoclaved concretereduces its thermal conductivity and improves the me-chanical properties [189]

Kramer et al [176 178 191ndash193] conducted a series ofinvestigations on strengthening of FC by introducingnanoparticles (nano silica carbon nanotubes) for the pur-pose of stabilizing the foams e findings proved that themechanical properties and bubble structures are bothgenerally improved compared to normal foam concrete enanoparticles encapsulating on the foam surface participatein the hydration of the cement thereby increasing hydrationproducts and enhancing the strength of cellular walls of FC

A novel method adding pozzolanic active nanomaterialsinto concrete for reinforcement was put forward recently[193] e produced foam concretes have higher compres-sive strength than those observed in industrial FC withoutneeds of further optimization or other enhancement meansese concretes show possibilities to provide comparableproperties with industrial lightweight concretes in the

future e foam concretes exhibited a specific formation ofhydration products and a shell-like pore structure Also thepore size distribution of the FC was under control due to theuse of three-phase-foams

e findings in [176] confirmed that decrease of pore sizecan be observed bymaking use of the three-phase-foams butthe wider pore size distribution was observed with adoptionof nanotubes It is also reported that the three-phase-foamscombining with other nanomaterials or the obtained ap-proaches can further improve the properties and perfor-mance of FC

3 Practical Application of FC in Tunnels andUnderground Projects

31 Significance and Benefits e FC has been graduallyregarded as a renewed material to address problems faced intunnels and underground projects FC performs well with theexcellent mechanical properties compared to the ordinaryconcrete (OC) and some comparisons are presented inTable 6 It is expected to be partially or completely substitutedfor conventional concrete in underground engineeringproviding with economic social and environmental benefits

311 Excellent Properties e extensive properties varia-tions of FC are applicable for various situations Low density(generally from 300 to 1800 kgm3) helps to reduce dead loadwithout producing lateral load [26 28] A large number ofclosed small pores containing in FC are responsible for itsoutstanding fire resistance [206] low thermal conductivityand sound insulation properties [174 207] which are notavailable in OC e FC with a density varying between 300and 1200 kgm3 usually has a thermal conductivity value of008ndash03WmK [36 208] As a result of light weight and lowmodulus of elasticity the FC-reinforced structures exhibitconsiderable aseismic capability by effectively absorbing and

Cementpaste

Waterinterface

Fd

Fc

Fst

Fc

Fst

Gas

D

Pi

Fb

(a)

Gas

Cementpaste

Nanoparticle

Fd

Fc

Fst

Fc

Fst

DPi

Fb

HPMCliquid

interface

(b)

Figure 4 Forces acting on (a) a normal bubble and (b) a nanoparticle stabilized bubble [186]


diffusing shock energy when subjected to the seismicloading e properties promote the application of FC intunnel and underground engineering can be revealed from(1) low self-weight (2) free flowing and self-leveling (3) loadspreading (4) insulation capacity (5) reliable quality con-trol and (6) freeze and thaw resistance

312 Environment Friendly It is desirable to utilize recycledwaste such as fly ash and recycled glass in FC production soas to protect the environment pollution [209] e main rawmaterials required for FC are cement and foaming agentse majority of the foaming agents are nearly neutralsurfactants with considerable biodegradability in whichbenzene and formaldehyde are usually not containederefore soil water and air are faced with little adverseimpacts [210ndash212] whereas FC can minimize disruption tonatural environment during construction phase

313 Cost and Time Saving It could be an economicallyviable solution particularly in large-volume applicationsExcellent fluidity and self-leveling mean less requirement forenergy consumption and manpower moving by using pipesfor pumping [213] On the premise of ensuring FC strengtha large number of industrial wastes can be used as fillers[214] erefore lower investment for FC application isusually attributable to tailored mix design rapid equipmentinstallation and cost decrease in maintenance

314 Repaid Construction Pumping FC can be realized byequipping with foam mixer power pump and conveyingpipeline in a workload of 200ndash300m3d within the theo-retical vertical height and horizontal distance of 200m and600m respectively [215] A considerable pumping capacityis usually not required as a result of the high fluidity of FCwhile mass production and placement are always based on acontinuous operation so as to notably improve work effi-ciency Also only limited deliveries for raw materials areneeded because the foam acts as the largest volume con-tributor in FC

32 Novel Application in Tunnel Engineering

321 ermal Material In the present years thermalmeasures for cold-region tunnels mainly include electricheat tracing thermal insulation door and antifreeze thermalinsulation layer (ie thermal insulating materials laid on

liner structure) [216ndash218] However the electric heat tracingneeds a lot of energy resources to ensure thermal efficiencywhich slightly deviates from the increasingly demandingrequests from the perspective of energy saving of con-structions e thermal insulation doors are not suitable fortunnels with large traffic volume resulting in sizable heatloss owing to incessant opening and closing [219 220]Hence using FC as liner structure and insulation material ishelpful to simplify construction process and reduce materialcosts

A case study using FC as insulation material in a tunnelin the Tibet the Alpine Region of China was reported byYuan [221] where frozen period with the minimum tem-perature of minus277degC lasts eight months every year Table 7presents the optimum mix proportion of FC used in thestudy e temperature in the measured positions withoutinsulation layer varies significantly compared to locationthat with insulation layer e results indicated that tem-perature change and the minimum temperature in these twolocations are 45degC 2degC and 1degC 3degC respectively efindings regarding impacts of freeze-thaw cycles on FCperformance [44 222] will be helpful to further improve andoptimize the durability of FC used as insulation materials

322 Aseismic Layer e aseismic layer is generally placedbetween rock and tunnel liner in order to transfer some ofrock mass pressure during construction period so as to avoidliner damage when it is subjected to earthquake action[223ndash225] e considerable load-bearing and deformationcapacities promote it to be an ideal aseismic material intunnel engineering As shown in Table 8 Zhao et al [226]developed a new aseismic FC material and then applied it inGonggala tunnel of China e numerical analysis resultsshowed that this new FC-based material significantly re-duced stress and plastic zones in tunnel liner Meanwhile aninvestigation conducted by Huang et al [227] revealed thatusing FC as aseismic material is superior to rubber throughthe durability tests

323 Structure Member Creep deformation in tunnelsespecially for deep ones will continue after completion ofsecondary liner [228ndash231] which easily causes structuredamage or failure Simple increase in secondary linerthickness cannot completely control the creep deformationin rock mass FC-based members embedded between pri-mary support and secondary liner can notably bear defor-mation pressure thereby the high compressibility and

Table 6 Tabulation presents properties comparison between OC and FC [36 107 131 167 194ndash205]

Type

PropertiesPhysical Mechanical Functional

Drydensity(kgm3)

Dryingshrinkage

()

Porosity()

Modulusof

elasticity(GPa)

Compressive strength(MPa)

Tensilestrength(MPa)

Flexuralstrength(MPa)

ermalconductivity(Wm K)

Fluidity(mm)

OC 2000ndash2800 005ndash01 mdash 25ndash38 15ndash80 09ndash25 20ndash90 ca 25 ca190FC 300ndash1800 015ndash035 0ndash84 01ndash10 06ndash430 005ndash055 003ndash09 005ndash03 gt180


ductility of FC can help to eliminate overall damage orfailure e FC with compressive strength of 04ndash07MPaporosity of 68 and density of 800 kgm3 [232] was adoptedin liner system of Tiefengshan No 2 tunnel to resist gypsum-salt-induced swelling pressure Since successful imple-mentation in September 2005 the tunnel has been runningwell and no damages have arisen

Wang et al [233] studied long-term performance of FC-based liner member with a comparison to common large-span soft rock tunnel the findings showed that after creepfor 100 years vault settlement and horizontal convergencereduced by 61 and 45 respectively while plastic zone insecondary liner was obviously decreased Wu et al [234]developed a special yielding support system combined with anew type of FC is newly developed system was embeddedbetween primary support and secondary liner e resultsconfirmed that the plastic zone and deformations at the roofand the sides of the secondary liner were significantly reducedas a result of cushion effect compared to stiff support system

324 Backfill and Reinforcement Table 9 summarizespractical applications of FC used as selective filling materialin road tunnels Specifically the filling cases mainly includespace or cavity fill open-cut and auxiliary tunnel backfillbulk fill such as disused tunnel backfill collapse treatmentetc And some typical applications are described as follows

Kontoe [240] reported a backfill case in the Bolu highwaytwin tunnel repair in Turkey (Figure 5(a)) e tunnelsuffered extensive damages during the 1999 Duzce earth-quake and a large amount of FC was temporarily backfilledto stabilize tunnel face during reconstruction activities eexcellent priorities compared to OC give rise to FC appli-cation in tunnel collapse treatment e controllable densityand strength as well as good liquidity can fill and thensaturate collapsed cavity entirely thus consolidating frac-tured body Figures 5(b) and 5(c) present photos of using FCto reinforce a 20 m long and 96 m deep collapse body inShima tunnel where rockmass was broken and cut obliquely[241] e subsequent feedbacks from construction siteverified the effectiveness of this treatment material

325 Dead Load Reduction Figure 6 illustrates FC appli-cation for load reduction while raising ground to a requiredlevel that commonly used in metro system Recently FCproduction in Europe North America Japan Korea Chinaand Southeast Asia has been the matured technologies

Other forms for the usages of FC include selective fill andreinforcement for safe construction

33 Novel Application in Underground Engineering

331 Underground Coal Mine Roadway e FC applica-tions in coal mines are mainly summarized from three as-pects backfilling materials support system and waterharmful gas blocking which are presented as below

(1) Backfill Material As early as 1992 the United StatesBureau ofMines had released the programmer of using FC ata density of 720 kgm3 to backfill abandoned mines and thetarget used for field construction was No 22 mine in LoganCounty West Virginia [242] And the worldrsquos largest singleuse of FC in mine by far is the stabilization work of CombeDown Stone Mines near Bath of the UK which eventuallyused about 400000m3 FC at density and strength of650 kgm3 and 1MPa respectively (Figure 7) [243]

(2) Support System Tan et al [244] put forward a compositesupport system containing FC damping layer in view of thelarge deformation in soft rock roadway of coal mine eresults showed that shrinkage of U-shaped steel significantlydecreased as the FC absorbs the most of the generateddeformation (Figure 8)

(3) Watergas Blocking e airtight walls in coal mines areconsidered to be an effective method to prevent residual coalfrom spontaneous combustion caused by air leakage In astudy by Wen et al [245] a new type FC was developed foryielding a wall to control potential air leakage e28 d compressive strength of the FC wall reached 5MPa inwhich no remaining fissures were observed therefore iteffectively suppressed air leakage to the gob (Figure 9)

332 Public Pipelines and Facilities Practically utilizing FCmaterials for municipal pipelines backfill helps to controlpostconstruction settlement caused by poor compaction InJapan municipal pipelines such as gas pipelines are alwaysfilled with FC so as to prevent external damage especially inareas where earthquakes occur frequently [246]

FC has been expected to use in hydraulic tunnels to resistdamages during earthquakes struck Dowding and Rozen[247] confirmed a series of seismic damage events on hy-draulic tunnels in USA by statistical analysis on dozens of

Table 7 Optimum proportion for tunnel antifreeze layer (percentage content) [221]

Material Flyash Perlite Foam Polypropylene

fiber WaterWater-proofingadditive

Antifreezeadditive

Waterreducer

Coagulationaccelerator

Ratio 30 18 150 02 40 03 2 1 4

Table 8 Tabulation shows mix proportion of FC used for aseismic isolation layer (unit kgm3) [226]

Material Cement Foam Perlite Water Water-proofing additive Antifreeze additive Water reducer Coagulation accelerator FibreRatio 600 08 108 250 5 13 65 30 1


case tunnels e similar seismic hazards were also bedocumented in Japan during the 1995 OsakandashKobe earth-quake (Ms 72) in which water supply pipelines andsewage drainage systems in Hanshin and adjacent areas wereseverely damaged e water supply systems in Kobe wereeven completely destroyed [248 249] Currently manycontributions have been made to use FC as antiseismicmaterial in hydraulic tunnels e Port Mann Water TunnelProject located in Vancouver Canada was constructed witha total 6000m3 FC to meet a seismic backfill requirement for100-year reliability [250]

4 Thoughts and Future Work forPopularization of FC

41 Emerging Direction for Performance Enhancement of FCough a lot of research has been carried out focusing onmacroscopic properties of FC such as thermal conductivitymechanical properties water absorption etc the studies ondrying shrinkage bubble size control stability and porestructure characterization are still insufficient

Ghorbani et al [110] used scanning electron microscope(SEM) to study FC microstructure e results showed that

New ground

Original ground

Metro tunnel line

Foam concrete

Δh

(a)

Metrosystem

Foam concrete

(b)

Figure 6 FC application in metro system

Table 9 Application examples of selective fill with FC

Reference Tunnel name Country Year Application Brief descriptions

[235] Kent amesidetunnels UK 2010 Reclamation e 50m deep tunnel extends about 90m and FC with density of

400 kgm3 and compressive strength of 05MPa was backfilled

[236] Dakota Project USA 2000 Reinforcementbackfill

e original granular backfill above the tunnel resulted in foundationfoot settlement and finally caused structure deformatione original

filling was removed and replaced by 500 kgm3 FC

[237] Farnworth UK 2015 Auxiliaryconstruction

e 7800m3 FC of 1100 kgm3 and 1MPa was used to backfill the oneof a 300m long double-hole tunnel so as to accept the Tunnelling

Boring Machine (TBM)

[235] ackley UK 2013 Structuralreinforcement

As more distortion was recorded with the crown being forcedupwards into a void A total 2540m3 FC with 1120ndash1130 kgm3 and

1MPa was required for fillers

[238] Huashiya China 2015 Cavity filling Cavities and cracks appeared in secondary liner of tunnel and thenthese defects were filled by FC grouting

[235] Gerrards Crossproject UK 2009 Load reduction

To reduce dead load pile walls were installed on both sides of thetunnel and 26000m3 FCwith 375 kgm3 was used to form horizontal

ground at the top of vault

[239] Wulaofeng China 2009 Seepage watertreatment

e seepage of tunnel side wall was serious and some locations wereeven gushing so FC was used as waterproof material

(a) (b) (c)

Figure 5 (a) Bolu highway twin tunnel [240] (b) collapse and (c) treatment with pumped FC in Shima tunnel [241]


the FC microstructure was notably improved by usingmagnetized water instead of conventional tap water e FCstructure with magnetized water has a lower porosity and isdenser than that with conventional tap water Using mag-netized water in FC increases its stability and compressiveand tensile strengths as well as reduces the water absorption

e FCmicrostructure filled with silica fume was studiedby Reisi et al [251] e SEM and X-ray diffraction testsshowed that the reaction between silica fume and free cal-cium hydroxide in hydrated cement generates the hydratedcalcium silicate Its hardness and durability are higher thancalcium hydroxide so as to reduce the risk of sulfate attack insilica fume FC Consequently the hydrated calcium silicateproduced homogeneous FC with better solid and poredistribution which leads to a higher compressive strengthcompared to FC without silica fume

e X-ray microCT imaging results reported by Chunget al [252] confirmed that the shape and size of pores and

local density of the solids have remarkable impacts onperformance and damage mode of FC which has profoundguiding significance for high-performance FC productionIn addition Zhang andWang [128] confirmed that pore sizenotably affected the compressive strength of glass-fiber-reinforced FC especially at a high porosity e pore shapemaintains relatively constant as a result of the function offoam content and density variation which does not bringabout much effect on mechanical properties of FC

ere are relatively few studies on FC microstructuresuch as shrinkage mechanism shrinkage predictionstrength improvement etc To be sure all of the above-mentioned studies are helpful to deeply understand dura-bility issues therefore linking the microstructure andmacro-performance of FC in order to better enhance itsperformance should be deeply investigated

42 Technical Limitation Dramatically the mix proportionsof FC have always been the technical challenge and one ofthe research hotspots So far there are no clearly definedmethods to determine the mix proportion despite someexperimental-based and error-based methods can be usedRecently Tan et al [8] proposed an equation for mixproportion determination

ρd SaMc

V2 K 1 minus V1( 1113857 K 1 minusMc

ρc

+Mw

ρw

1113888 11138891113890 1113891

My V2ρf

Mp My

α + 1

(2)

where ρd is the dry density of the designed FC (kgm3) Sa isthe empirical coefficient Mc is the mass of cement (kgm3)V1 and V2 are the volume of cement paste and foam re-spectively ρc and ρw are the densities of cement and waterrespectively Mc and Mw are the cement and water re-spectively K is the coefficient My and ρf are the mass anddensity of foam respectively Mp is the mass of foamingagent and α is the dilution ratio

Practically water quality cement lime and other ag-gregates worldwide are characterized by unique features andthe technical level for fiber preparation varies greatly eoptimum mix proportion of FC will also be affected byregional environments [253] Hence it is necessary to de-termine the best mixing proportion under different regionaltests avoiding using existing mix proportion schemes di-rectly is challenge may be one of the important factorsrestricting worldwide applications of FC in tunnel engi-neering [254ndash256]

Develop cheaper foaming agents and generators are alsourgent tasks to promote practicality and wider application ofFC e compatibility between foaming agents and variousadmixtures should be studied to strengthening FC Mean-while to reduce water demand and shrinkage in-deep studyon compatibility of chemical admixtures is required e

(a) (b)

Figure 9 Filling effect of FC wall after (a) 24 hours and (b) 28 days[245]

Figure 8 A composite supporting system containing FC [244]

Figure 7 Combe down stone mines (source httpwwwfoamedconcretecouk)


difficulties encountered in FC production such as mixingtransportation and pumping also need to be solved whereasthey exhibit significant impacts on freshness and hardeningproperties of FC [64]

43 Government Support Regarding as a kind of greenconstruction material FC accords with increasing demandsof sustainable perspective of construction for countriesworldwidee booming development of infrastructures hasincreased the demands for various new environmentalprotection materials in which the FC plays a key role Withthe government support whether the policy or economicaspect the more scientific research outputs from universi-ties research institutes and enterprises will be obtainedwhich is conducive to enhance establishment and reform ofthe relevant industrial systems thereby alleviating consumerconcerns

44 Other Considerations Lack of the complete productiondata and construction experience makes it difficult to formthe complete construction systems erefore establishingthe reliable design and construction procedures for FC usageis helpful to overcome the construction difficulties More-over relevant specifications codes and standards should beimplemented timely so as to standardize the design andconstruction processes of FC

5 Conclusions

Based on the review conducted it was observed that most ofthe studies on FC have been conducted to the evaluation ofits properties rather than on the foam features which hasimpacts on the strength and enhancement of the foammaterial According to the findings provided by researchersthe following conclusions are drawn from extensive litera-ture review

(1) To enhance FC performance and popularization therelevant properties were elaborated and some aspectswere proposed as constraints for wider application ofFC such as drying shrinkage strength issue stabilityenhancement and long-term durability

(2) Foam stability is a significant aspect which signifi-cantly affects the strength of FC Production of thestable FC requires to consider many factors such asthe method of preparation of foam type of foamingagent the accuracy of themixture type of surfactantsand additives used usage of nano particles and mixdesign etc

(3) Very few studies on durability of FC are availableDurability properties of FC mainly influenced by theratio of connected pore to total pore e FC withuniformly distributed closed circular air pores exertsgood thermal and mechanical properties

(4) Current research mainly focuses on the micro-scopical characterization of FC and the impacts ofthe several factors on the physical mechanical andfunctional performance However very limited

literatures have put emphasis on systemic micro-structure characterization of FC

(5) e use of three-phase-foams instead of wet foamsbased on surfactants or proteins and water for im-proving the performance of FC has been renewedinterests because the incorporation of three-phase-foams in cement paste is advantageous to stabilizethe pores and control the pore size distribution

Conflicts of Interest

e authors declare no conflicts of interest

Acknowledgments

e financial support from the National Natural ScienceFoundation of China (No 51678363) Shenzhen Science andTechnology Project (No JCYJ20150525092941052) Under-ground Engineering (Tongji University) (No KLETJGE-B0905) Project on Social Development of Shaanxi ProvincialScience and Technology Department (No 2018SF-382 No2018SF-378) and Fundamental Research Funds for theCentral University CHD (Nos 300102219711 300102219716and 300102219723) is sincerely acknowledged

References

[1] E K K Nambiar and K Ramamurthy ldquoInfluence of fillertype on the properties of foam concreterdquo Cement andConcrete Composites vol 28 no 5 pp 475ndash480 2006

[2] Y Wang S H Zhang D T Niu L Su and D M LuoldquoStrength and chloride ion distribution brought by aggregate ofbasalt fiber reinforced coral aggregate concreterdquo Constructionand Building Materials vol 234 Article ID 117390 2020

[3] J Narayanan and K Ramamurthy ldquoIdentification of set-accelerator for enhancing the productivity of foamed con-crete block manufacturerdquo Construction and Building Ma-terials vol 37 pp 144ndash152 2012

[4] M R Jones K Ozlutas and L Zheng ldquoHigh-volume ultra-low-density fly ash foamed concreterdquo Magazine of ConcreteResearch vol 69 no 22 pp 1146ndash1156 2017

[5] S Kilincarslan M Davraz and M Akccedila ldquoe effect ofpumice as aggregate on the mechanical and thermal prop-erties of foam concreterdquo Arabian Journal of Geosciencesvol 11 no 11 Article ID 289 2018

[6] D T Niu L Zhang F Qiang B Wen and D M LuoldquoCritical conditions and life prediction of reinforcementcorrosion in coral aggregate concreterdquo Construction andBuilding Materials vol 238 Article ID 117685 2020

[7] D Falliano D D Domenico G Ricciardi and E GugliandololdquoExperimental investigation on the compressive strength offoamed concrete effect of curing conditions cement typefoaming agent and dry densityrdquo Construction and BuildingMaterials vol 165 pp 735ndash749 2018

[8] X J Tan W Z Chen J H Wang et al ldquoInfluence of hightemperature on the residual physical and mechanicalproperties of foamed concreterdquo Construction and BuildingMaterials vol 135 pp 203ndash211 2017

[9] T Liu Y J Zhong Z L Han and W Xu ldquoDeformationcharacteristics and countermeasures for a tunnel in difficultgeological environment in NW Chinardquo Advances in CivilEngineering vol 2020 Article ID 1694821 16 pages 2020


[10] Y Wei W Guo and Q Zhang ldquoA model for predictingevaporation from fresh concrete surface during the plasticstagerdquo Drying Technology vol 37 no 11 pp 12ndash23 2019

[11] M A Othuman and Y C Wang ldquoElevated-temperaturethermal properties of lightweight foamed concreterdquo Con-struction and Building Materials vol 25 pp 705ndash716 2011

[12] A A Sayadi J V Tapia T R Neitzert and G C CliftonldquoEffects of expanded polystyrene (EPS) particles on fireresistance thermal conductivity and compressive strength offoamed concreterdquo Construction and Building Materialsvol 11 pp 716ndash724 2016

[13] S Tada ldquoMaterial design of aerated concretendashan optimumperformance designrdquoMaterials and Structures vol 19 no 1pp 21ndash26 1986

[14] H K Kim J H Jeon and H K Lee ldquoWorkability andmechanical acoustic and thermal properties of lightweightaggregate concrete with a high volume of entrained airrdquoConstruction and Building Materials vol 29 pp 193ndash2002012

[15] R C Valore ldquoCellular concrete part 2 physical propertiesrdquoACI Journal Proceedings vol 50 no 6 pp 817ndash836 1954

[16] Z M Huang T S Zhang and Z Y Wen ldquoProportioningand characterization of Portland cement-based ultra-light-weight foam concretesrdquo Construction and Building Mate-rials vol 79 pp 390ndash396 2015

[17] M Decky M Drusa K Zgutova M Blasko M Hajek andW Scherfel ldquoFoam concrete as new material in road con-structionsrdquo Procedia Engineering vol 161 pp 428ndash4332016

[18] M Kadela andM Kozłowski ldquoFoamed concrete layer as sub-structure of industrial concrete floorrdquo Procedia Engineeringvol 161 pp 468ndash476 2016

[19] Z H Zhang J L Provis A Reid andHWang ldquoMechanicalthermal insulation thermal resistance and acoustic ab-sorption properties of geopolymer foam concreterdquo Cementand Concrete Composites vol 62 pp 97ndash105 2015

[20] A S Tarasov E P Kearsley A S Kolomatskiy andH F Mostert ldquoHeat evolution due to cement hydration infoamed concreterdquo Magazine of Concrete Research vol 62no 12 pp 895ndash906 2010

[21] Y Wei J Huang and S Liang ldquoMeasurement and modelingconcrete creep considering relative humidity effectrdquo Me-chanics of Time-dependent Materials vol 24 no 1 pp 1ndash172020

[22] Y Y Li Y M Sun J L Qiu T Liu L Yang and H D SheldquoMoisture absorption characteristics and thermal insulationperformance of thermal insulation materials for cold regiontunnelsrdquo Construction and Building Materials vol 237Article ID 117765 2020

[23] X Z Li C Z Qi and P C Zhang ldquoA micro-macro confinedcompressive fatigue creep failure model in brittle solidsrdquoInternational Journal of Fatigue vol 130 p 14 2020

[24] Z Q Zhang and J L Yang ldquoImproving safety of runwayoverrun through foamed concrete aircraft arresting systeman experimental studyrdquo International Journal of Crash-worthiness vol 20 no 5 pp 448ndash463 2015

[25] P Favaretto G E N Hidalgo C H Sampaio R D A Silvaand R T Lermen ldquoCharacterization and use of constructionand demolition waste from south of Brazil in the productionof foamed concrete blocksrdquo Applied Sciences vol 7 no 10pp 1ndash15 2017

[26] Z H Zhang J L Provis A Reid and H Wang ldquoGeo-polymer foam concrete an emerging material for sustainable

constructionrdquo Construction and Building Materials vol 56pp 113ndash127 2014

[27] P Prabha G S Palani N Lakshmanan and R SenthilldquoBehaviour of steel-foam concrete composite panel under in-plane lateral loadrdquo Journal of Constructional Steel Researchvol 139 pp 437ndash448 2017

[28] J Hulimka R Krzywon and A Jedrzejewska ldquoLaboratorytests of foamed concrete slabs reinforced with compositegridrdquo Procedia Engineering vol 193 pp 337ndash344 2017

[29] J L Qiu Y Q Lu J X Lai C X Guo and KWang ldquoFailurebehavior investigation of loess metro tunnel under local-high-pressure water environmentrdquo Engineering FailureAnalysis vol 112 no 4 2020

[30] J Z Pei B C Zhou and L Lyu ldquoe-Road the largest energysupply of the futurerdquo Applied Energy vol 241 pp 174ndash1832019

[31] L X Wang E L Ma H Li et al ldquoTunnelling inducedsettlement and treament techniques for a Loess Metro inXirsquoanrdquo Advances in Civil Engineering vol 2020 Article ID1854813 16 pages 2020

[32] X G Yu G H Xing and Z Q Chang ldquoFlexural behavior ofreinforced concrete beams strengthened with near-surfacemounted 7075 aluminum alloys barsrdquo Journal of BuildingEngineering vol 28 2020

[33] T Zhang D T Niu and C Rong ldquoGFRP-confined coralaggregate concrete cylinders e experimental and theo-retical analysisrdquo Construction and Building Materialsvol 218 pp 206ndash213 2019

[34] Y C Zheng Y H Zhang L X Wang K Wang and T LiuldquoMechanical reinforcement mechanism of steel fiber rein-forced concrete and its application in tunnelsrdquo Advances inCivil Engineering vol 2020 Article ID 3479475 16 pages2020

[35] K H Yang K H Lee J K Song and M H GongldquoProperties and sustainability of alkali-activated slag foamedconcreterdquo Journal of Cleaner Production vol 68 pp 226ndash233 2014

[36] S Wei Y Q Chen Y S Zhang and M R Jones ldquoChar-acterization and simulation of microstructure and thermalproperties of foamed concreterdquo Construction and BuildingMaterials vol 47 pp 1278ndash1291 2013

[37] Y H M Amran N Farzadnia and A A A AbangldquoProperties and applications of foamed concrete a reviewrdquoConstruction and Building Materials vol 101 pp 990ndash10052015

[38] K Ramamurthy K K K Nambiar and G I S Ranjani ldquoAclassification of studies on properties of foam concreterdquoCement and Concrete Composites vol 31 no 6 pp 388ndash3962009

[39] Y Zheng J Xiong T Liu X Yue and J Qiu ldquoPerformanceof a deep excavation in Lanzhou strong permeable sandygravel stratardquo Arabian Journal of Geosciences vol 13 no 16p 12 2020

[40] H Sun Q P Wang P Zhang Y J Zhong and X B YueldquoSpatiotemporal characteristics of tunnel traffic accidents inChina from 2001 to presentrdquo Advances in Civil Engineeringvol 2019 Article ID 4536414 12 pages 2019

[41] L X Wang C H Li J L Qiu K Wang and T LiuldquoTreatment and Effect of loess metro tunnel under sur-rounding pressure and water immersion environmentrdquoGeofluids vol 2020 Article ID 7868157 15 pages 2020

[42] X J Tan W Z Chen H Y Liu and A H C Chan ldquoStress-strain characteristics of foamed concrete subjected to largedeformation under uniaxial and triaxial compressive


loadingrdquo Journal of Materials in Civil Engineering vol 30no 6 pp 1ndash10 2018

[43] P J Tikalsky J Pospisil and W MacDonald ldquoA method forassessment of the freezendashthaw resistance of preformed foamcellular concreterdquo Cement and Concrete Research vol 34pp 889ndash893 2004

[44] C Sun Y Zhu J Guo Y M Zhang and G X Sun ldquoEffectsof foaming agent type on the workability drying shrinkagefrost resistance and pore distribution of foamed concreterdquoConstruction and Building Materials vol 186 pp 833ndash8392018

[45] S Mindess Developments in the Formulation and Rein-forcement of Concrete Woodhead publishing limitedCambridge UK 2008

[46] H L Zhao H T Yu Y Yuan and H B Zhu ldquoBlastmitigation effect of the foamed cement-base sacrificialcladding for tunnel structuresrdquo Construction and BuildingMaterials vol 94 pp 710ndash718 2015

[47] H Choi and S Ma ldquoAn optimal lightweight foamed mortarmix suitable for tunnel drainage carried out using thecomposite lining methodrdquo Tunnelling and UndergroundSpace Technology vol 47 pp 93ndash105 2015

[48] K C Brady G R A Watts and M R Jones ApplicationGuide AG39 Specification for Foamed Concrete HighwayAgency and Transport Research Laboratory WorkinghamBerks UK 2001

[49] S Van Dijk ldquoFoam concreterdquo Concrete vol 25 pp 49ndash541991

[50] C Karakurt H Kurama and I B Topccedilu ldquoUtilization ofnatural zeolite in aerated concrete productionrdquo Cement andConcrete Composites vol 32 no 1 pp 1ndash8 2010

[51] V Kocı J Madera and R Cerny ldquoComputer aided design ofinterior thermal insulation system suitable for autoclavedaerated concrete structuresrdquo Applied ermal Engineeringvol 58 no 1ndash2 pp 165ndash172 2013

[52] H S Shang and Y P Song ldquoTriaxial compressive strength ofair-entrained concrete after freezendashthaw cyclesrdquo Cold Re-gions Science and Technology vol 90-91 pp 33ndash37 2013

[53] A Just and B Middendorf ldquoMicrostructure of high-strengthfoam concreterdquo Materials Characterization vol 60 no 7pp 741ndash748 2009

[54] R C Valore ldquoCellular concrete part 1 composition andmethods of productionrdquo ACI Journal Proceedings vol 50pp 773ndash796 1954

[55] Sach and H Seifert ldquoFoamed concrete technology possi-bilities for thermal insulation at high temperaturesrdquo CeramicForum International vol 76 pp 23ndash30 Goller 1999

[56] G Rudnai Lightweight Concretes Akademikiado BudapestHungary 1963

[57] A Short and W Kinniburgh Lightweight Concrete AsiaPublishing House Delhi India 1963

[58] K Marcin and K Marta ldquoMechanical characterization oflightweight foamed concreterdquo Advances in Materials Scienceand Engineering vol 2018 pp 1ndash8 2018

[59] M R Jones and A Mccarthy ldquoPreliminary views on thepotential of foamed concrete as a structural materialrdquoMagazine of Concrete Research vol 57 no 1 pp 21ndash31 2005

[60] M A O Mydin and Y C Wang ldquoStructural performance oflightweight steel-foamed concretendashsteel composite wallingsystem under compressionrdquoin-Walled Structures vol 49no 1 pp 66ndash76 2011

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concrete using response surface methodologyrdquo Cement andConcrete Composites vol 28 no 9 pp 752ndash760 2006

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[63] E P Kearsley and P JWainwright ldquoe effect of high fly ashcontent on the compressive strength of foamed concreterdquoCement and Concrete Research vol 31 pp 105ndash112 2001

[64] S S Sahu I S R Gandhi and S Khwairakpam ldquoState-of-the-art review on the characteristics of surfactants and foamfrom foam concrete perspectiverdquo Journal of the Institution ofEngineers (India) Series A vol 99 no 2 pp 391ndash405 2018

[65] C Pickford and S Crompton ldquoFoamed concrete in bridgeconstructionrdquo Concrete vol 30 pp 14-15 1996

[66] M I Norlia R C Amat N L Rahim and S SallehuddinldquoPerformance of lightweight foamed concrete with re-placement of concrete sludge aggregate as coarse aggregaterdquoAdvanced Materials Research vol 689 pp 265ndash268 2013

[67] T H Wee S B Daneti and T Tamilselvan ldquoEffect of wcratio on air-void system of foamed concrete and their in-fluence on mechanical propertiesrdquo Magazine of ConcreteResearch vol 63 no 8 pp 583ndash595 2011

[68] M B Youssef F Lavergne K Sab K Miled and J NejildquoUpscaling the elastic stiffness of foam concrete as a three-phase composite materialrdquo Cement and Concrete Researchvol 110 pp 13ndash23 2018

[69] A Hajimohammadi T Ngo and A Kashani ldquoSustainableone-part geopolymer foams with glass fines versus sand asaggregatesrdquo Construction and Building Materials vol 171pp 223ndash231 2018

[70] A Kashani T D Ngo P Hemachandra andA Hajimohammadi ldquoEffects of surface treatments ofrecycled tyre crumb on cement-rubber bonding inconcrete composite foamrdquo Construction and BuildingMaterials vol 171 pp 467ndash473 2018

[71] S K Agarwal I Masood and S K Malhotra ldquoCompatibilityof superplasticizers with different cementsrdquo Constructionand Building Materials vol 14 pp 253ndash259 2000

[72] A Zingg F Winnefeld L Holzer et al ldquoInteraction ofpolycarboxylate-based superplasticizers with cements con-taining different C3A amountsrdquo Cement and ConcreteComposites vol 31 no 3 pp 153ndash162 2009

[73] C Bing W Zhen and L Ning ldquoExperimental research onproperties of high-strength foamed concreterdquo Journal ofMaterials in Civil Engineering vol 24 no 1 pp 113ndash1182011

[74] O Kayali M N Haque and B Zhu ldquoSome characteristics ofhigh strength fiber reinforced lightweight aggregate con-creterdquo Cement and Concrete Composites vol 25 no 2pp 207ndash213 2003

[75] E T Dawood and A J Hamad ldquoToughness behaviour ofhigh-performance lightweight foamed concrete reinforcedwith hybrid fibresrdquo Structural Concrete vol 16 no 4pp 496ndash507 2015

[76] M S Mahzabin L J Hock M S Hossain and L S Kangldquoe influence of addition of treated kenaf fibre in theproduction and properties of fibre reinforced foamedcompositerdquo Construction and Building Materials vol 178pp 518ndash528 2018

[77] H Awang M H Ahmad and M Almulali ldquoInfluence ofkenaf and polypropylene fibres on mechanical and durabilityproperties of fibre reinforced lightweight foamed concreterdquo


Journal of Engineering Science and Technology vol 10 no 4pp 496ndash508 2015

[78] H Awang and M H Ahmad ldquoDurability properties offoamed concrete with fiber inclusionrdquo International Journalof Civil Structural Construction and Architectural Engi-neering vol 8 pp 273ndash276 2014

[79] M A O Mydin N A Rozlan and S Ganesan ldquoExperi-mental study on the mechanical properties of coconut fibrereinforced lightweight foamed concreterdquo Journal of Mate-rials and Environmental Science vol 6 no 2 pp 407ndash4112015

[80] V Fedorov and A Mestnikov ldquoInfluence of cellulose fiberson structure and properties of fiber reinforced foam con-creterdquo in Proceedings of the 4th International Young Re-searchers Conference on Youth Science Solutions Ideas andProspects YSSIP 2017 vol 143 December 2018

[81] W Abbas E Dawood and Y Mohammad ldquoProperties offoamed concrete reinforced with hybrid fibresrdquo in Pro-ceedings of the 3rd International Conference on BuildingsConstruction and Environmental Engineering BCEE3 2017vol 162 October 2018

[82] R J Pugh ldquoFoaming foam films antifoaming anddefoamingrdquo Advances in Colloid and Interface Sciencevol 64 pp 67ndash142 1996

[83] I T Koudriashoff ldquoManufacture of reinforced foam con-crete roof slabsrdquo ACI Journal Proceedings vol 46 no 9pp 37ndash68 1949

[84] F Zulkarnain and M Ramli ldquoDurability of performancefoamed concrete mix design with silica fume for housingdevelopmentrdquo Journal of Materials Science and Engineeringvol 5 pp 518ndash527 2011

[85] P Chindaprasirt and U Rattanasak ldquoShrinkage behavior ofstructural foam lightweight concrete containing glycolcompounds and fly ashrdquoMaterials and Design vol 32 no 2pp 723ndash727 2011

[86] M R Jones M J McCarthy and A McCarthy ldquoMoving flyash utilisation in concrete forward A UK perspectiverdquo inProceedings of the 2003 International Ash Utilization Sym-posium Center for Applied Energy Research University ofKentucky Lexington KY USA 2003

[87] P E Regan and A R Arasteh ldquoLightweight aggregatefoamed concreterdquo Structural Engineer vol 68 no 9pp 167ndash73 1990

[88] M R Jones and A Mccarthy ldquoHeat of hydration in foamedconcrete effect of mix constituents and plastic densityrdquoCement and Concrete Research vol 36 no 6 pp 1032ndash10412006

[89] K T Wan H G Zhu T Y P Yuen et al ldquoDevelopment oflow drying shrinkage foamed concrete and hygro-me-chanical finite element model for prefabricated buildingfasccedilade applicationsrdquo Construction and Building Materialsvol 165 pp 939ndash957 2018

[90] E K K Nambiar and K Ramamurthy ldquoShrinkage behaviorof foam concreterdquo Journal of Materials in Civil Engineeringvol 21 no 11 pp 631ndash636 2009

[91] H Weigler and S Karl ldquoStructural lightweight aggregateconcrete with reduced density-lightweight aggregate foamedconcreterdquo International Journal of Cement Composites andLightweight Concrete vol 2 no 2 pp 101ndash104 1980

[92] D Falliano D D Domenico G Ricciardi andE Gugliandolo ldquoCompressive and flexural strength of fiber-reinforced foamed concrete Effect of fiber content curingconditions and dry densityrdquo Construction and BuildingMaterials vol 198 pp 479ndash493 2019

[93] C L Hwang and V A Tran ldquoEngineering and durabilityproperties of self-consolidating concrete incorporatingfoamed lightweight aggregaterdquo Journal of Materials in CivilEngineering vol 28 no 9 Article ID 04016075 2016

[94] W She Y Du G T Zhao P Feng Y S Zhang andX Y Cao ldquoInfluence of coarse fly ash on the performance offoam concrete and its application in high-speed railwayroadbedsrdquo Construction and Building Materials vol 170pp 153ndash166 2018

[95] V N Tarasenko ldquoImpact of foamed matrix components onfoamed concrete propertiesrdquo IOP Conference Series Mate-rials Science and Engineering vol 327 Article ID 0320542018

[96] W H Zhao Q Su W B Wang L L Niu and T LiuldquoExperimental study on the effect of water on the propertiesof cast in situ foamed concreterdquo Advances in MaterialsScience and Engineering vol 2018 Article ID 7130465 2018

[97] N Makul and G Sua-Iam ldquoCharacteristics and utilization ofsugarcane filter cake waste in the production of lightweightfoamed concreterdquo Journal of Cleaner Production vol 126pp 118ndash133 2016

[98] A I Kudyakov and A B Steshenko ldquoShrinkage deformationof cement foam concreterdquo IOP Conference Series-MaterialsScience and Engineering vol 71 Article ID 012019 2015

[99] X M Chen Y Yan Y Z Liu and Z H Hu ldquoUtilization ofcirculating fluidized bed fly ash for the preparation of foamconcreterdquo Construction and Building Materials vol 54pp 137ndash146 2014

[100] S Ghorbani S Ghorbani Z Tao J D Brito andM Tavakkolizadeh ldquoEffect of magnetized water on foamstability and compressive strength of foam concreterdquo Con-struction and Building Materials vol 197 pp 280ndash290 2019

[101] D M A Huiskes A Keulen Q L Yu and H J H BrouwersldquoDesign and performance evaluation of ultra-lightweightgeopolymer concreterdquo Materials and Design vol 89pp 516ndash526 2016

[102] Z M Jaini S N Mokhatar A S M Yusof S Zulkiply andM H A Rahman ldquoEffect of pelletized coconut fibre on thecompressive strength of foamed concreterdquo in Proceedings ofthe 3rd International Conference on Civil and EnvironmentalEngineering for Sustainability vol 47 Article ID 01013Malacca Malaysia 2015

[103] Z W Liu K Zhao C Hu and Y F Tang ldquoEffect of water-cement ratio on pore structure and strength of foam con-creterdquo Advances in Materials Science and Engineeringvol 2016 Article ID 9520294 2016

[104] Y Xie J Li Z Y Lu J Jiang and Y H Niu ldquoEffects ofbentonite slurry on air-void structure and properties offoamed concreterdquo Construction and Building Materialsvol 179 pp 207ndash219 2018

[105] A Hajimohammadi T Ngo and P Mendis ldquoEnhancing thestrength of pre-made foams for foam concrete applicationsrdquoCement and Concrete Composites vol 87 pp 164ndash171 2018

[106] A A Hilal N H om and A R Dawson ldquoOn voidstructure and strength of foamed concrete made withoutwith additivesrdquo Construction and Building Materials vol 85pp 157ndash164 2015

[107] S K Lim C S Tan X Zhao and T C Ling ldquoStrength andtoughness of lightweight foamed concrete with differentsand gradingrdquo KSCE Journal of Civil Engineering vol 19no 7 pp 2191ndash2197 2015

[108] R Gowri K B Anand R Gowri and K B Anand ldquoUtili-zation of fly ash and ultrafine GGBS for higher strength foamconcreterdquo in Proceedings of the International Conference on


Advances in Materials and Manufacturing Applications IOPConference Series Materials Science and Engineering vol 310Article ID 012070 Melbourne Australia September 2018

[109] T J Chandni and K B Anand ldquoUtilization of recycled wasteas filler in foam concreterdquo Journal of Building Engineeringvol 19 pp 154ndash160 2018

[110] S K Lim C S Tan B Li T C Ling M U Hossain andC S Poon ldquoUtilizing high volumes quarry wastes in theproduction of lightweight foamed concreterdquo Constructionand Building Materials vol 151 pp 441ndash448 2017

[111] S B Park E S Yoon and B I Lee ldquoEffects of processing andmaterials variations on mechanical properties of lightweightcement compositesrdquo Cement and Concrete Research vol 29pp 193ndash200 1999

[112] X D Chen S XWu and J K Zhou ldquoInfluence of porosity oncompressive and tensile strength of cement mortarrdquo Con-struction and Building Materials vol 40 pp 869ndash874 2013

[113] C Lian Y Zhuge and S Beecham ldquoe relationship be-tween porosity and strength for porous concreterdquo Con-struction and Building Materials vol 25 pp 4294ndash42982011

[114] E K K Nambiar and K Ramamurthy ldquoModels for strengthprediction of foam concreterdquo Materials and Structuresvol 41 pp 247ndash254 2008

[115] E Papa V Medri D Kpogbemabou et al ldquoPorosity andinsulating properties of silica-fume based foamsrdquo Energyand Buildings vol 131 pp 223ndash232 2016

[116] J Feng R F Zhang L L Gong Y Li W Cao andX D Cheng ldquoDevelopment of porous fly ash-based geo-polymer with low thermal conductivityrdquo Materials andDesign vol 65 pp 529ndash533 2015

[117] F S Han G Seiffert Y Y Zhao and B Gibbs ldquoAcousticabsorption behaviour of an open-celled aluminium foamrdquoJournal of Physics D Applied Physics vol 36 p 294 2003

[118] E K K Nambiar and K Ramamurthy ldquoAir-void charac-terisation of foam concreterdquo Cement and Concrete Researchvol 37 no 2 pp 221ndash230 2007

[119] C T Tam T Y Lim R S Ravindrarajah and S L LeeldquoRelationship between strength and volumetric compositionof moist-cured cellular concreterdquo Magazine of ConcreteResearch vol 39 no 138 pp 12ndash18 1987

[120] M H akrele ldquoExperimental study on foam concreterdquoInternational Journal of Civil Structural Environmental andInfrastructure Engineering Research and Development vol 4no 1 pp 145ndash158 2014

[121] J H Lee ldquoInfluence of concrete strength combined withfiber content in the residual flexural strengths of fiberreinforced concreterdquo Composite Structures vol 168pp 216ndash25 2017

[122] M Nehdi Y Djebbar and A Khan ldquoNeural network modelfor preformed-foam cellular concreterdquo ACI MaterialsJournal vol 98 no 5 pp 402ndash409 2001

[123] A Baykasoglu H Gullu H Ccedilanakccedilı and L OzbakırldquoPrediction of compressive and tensile strength of limestonevia genetic programmingrdquo Expert Systems with Applicationsvol 35 no 1ndash2 pp 111ndash123 2008

[124] T Nguyen A Kashani T Ngo and S Bordas ldquoDeep neuralnetwork with high-order neuron for the prediction offoamed concrete strengthrdquo Computer-Aided Civil and In-frastructure Engineering vol 34 pp 316ndash332 2019

[125] Z M Yaseen R C Deo A Hilal et al ldquoPredicting com-pressive strength of lightweight foamed concrete using ex-treme learning machine modelrdquo Advances in EngineeringSoftware vol 115 pp 112ndash125 2018

[126] ACI Committee 523 Guide for Cast-in-Place LowdensityCellular Concrete Farmington Hills MI USA 2006

[127] W H Zhao J J Huang Q Su and T Liu ldquoModels forstrength prediction of high-porosity cast-in-situ foamedconcreterdquo Advances in Materials Science and Engineeringvol 2018 Article ID 3897348 2018

[128] Z H Zhang and H Wang ldquoe pore characteristics ofgeopolymer foam concrete and their impact on the com-pressive strength and modulusrdquo Frontiers in Materialsvol 3 pp 1ndash10 2016

[129] E P Kearsley and P JWainwright ldquoe effect of porosity onthe strength of foamed concreterdquo Cement and ConcreteResearch vol 32 no 2 pp 233ndash239 2002

[130] E P Kearsley and P J Wainwright ldquoAsh content for op-timum strength of foamed concreterdquo Cement and ConcreteResearch vol 32 no 2 pp 241ndash246 2002

[131] E P Kearsley and P J Wainwright ldquoPorosity and perme-ability of foamed concreterdquo Cement and Concrete Researchvol 31 no 5 pp 805ndash812 2001

[132] M Roβler and I Odler ldquoInvestigations on the relationshipbetween porosity structure and strength of hydrated Port-land cement pastes I effect of porosityrdquo Cement and ConcreteResearch vol 15 no 2 pp 320ndash330 1985

[133] G C Hoff ldquoPorosity-strength considerations for cellularconcreterdquo Cement and Concrete Research vol 2 no 1pp 91ndash100 1972

[134] L Cox and S Van Dijk ldquoFoam concrete a different kind ofmixrdquo Concrete vol 36 pp 54-55 2002

[135] B K Nyame ldquoPermeability of normal and lightweightmortarsrdquo Magazine of Concrete Research vol 37 no 130pp 44ndash48 1985

[136] A A Hilal N H om and A R Dawson ldquoPore structureand permeation characteristics of foamed concreterdquo Journalof Advanced Concrete Technology vol 12 no 12 pp 535ndash544 2014

[137] R L Day and B K Marsh ldquoMeasurement of porosity inblended cement pastesrdquo Cement and Concrete Researchvol 18 no 1 pp 63ndash73 1988

[138] M R Jones and A McCarthy ldquoUtilising unprocessed low-lime coal fly ash in foamed concreterdquo Fuel vol 84 no 11pp 1398ndash1409 2005

[139] E K K Nambiar and K Ramamurthy ldquoSorption charac-teristics of foam concreterdquo Cement and Concrete Researchvol 37 no 9 pp 1341ndash1347 2007

[140] E Namsone G Sahmenko and A Korjakins ldquoDurabilityproperties of high-performance foamed concreterdquo ProcediaEngineering vol 172 pp 760ndash767 2017

[141] H S Shang and Y P Song ldquoExperimental study of strengthand deformation of plain concrete under biaxial compres-sion after freezing and thawing cyclesrdquo Cement and ConcreteResearch vol 36 no 10 pp 1857ndash1864 2006

[142] H D Yun S W Kim Y O Lee and K Rokugo ldquoTensilebehavior of synthetic fiber-reinforced strain-hardening ce-ment-based composite (SHCC) after freezing and thawingexposurerdquo Cold Regions Science and Technology vol 67no 1-2 pp 49ndash57 2011

[143] S Tsivilis G Batis E Chaniotakis G Grigoriadis andDeodossis ldquoProperties and behavior of limestone cementconcrete and mortarrdquo Cement and Concrete Researchvol 30 no 10 pp 1679ndash1683 2000

[144] R Jones L Zheng A Yerramala and K S Rao ldquoUse ofrecycled and secondary aggregates in foamed concretesrdquoMagazine of Concrete Research vol 64 no 6 pp 513ndash5252012


[145] H T Cao L Bucea A Ray and S Yozghatlian ldquoe effect ofcement composition and pH of environment on sulfateresistance of Portland cements and blended cementsrdquo Ce-ment and Concrete Composites vol 19 no 2 pp 161ndash1711997

[146] P Brown R D Hooton and B Clark ldquoMicrostructuralchanges in concretes with sulfate exposurerdquo Cement andConcrete Composites vol 26 no 8 pp 993ndash999 2004

[147] M Sahmaran O Kasap K Duru and I O Yaman ldquoEffectsof mix composition and waterndashcement ratio on the sulfateresistance of blended cementsrdquo Cement and ConcreteComposites vol 29 no 3 pp 159ndash167 2007

[148] G I S Ranjani and K Ramamurthy ldquoBehaviour of foamconcrete under sulphate environmentsrdquo Cement and Con-crete Composites vol 34 no 7 pp 825ndash834 2012

[149] P Chindaprasirt S Rukzon and V Sirivivatnanon ldquoRe-sistance to chloride penetration of blended Portland cementmortar containing palm oil fuel ash rice husk ash and flyashrdquo Construction and Building Materials vol 22pp 932ndash938 2008

[150] M R Jones and A McCarthy Behaviour and Assessment ofFoamed Concrete for Construction Applications omasTelford London UK 2005

[151] S Chandra and L Berntsson Lightweight Aggregate Con-crete ASTM Special Technical Publication Philadelphia PAUSA 1994

[152] D Aldridge and T Ansell ldquoFoamed concrete productionand equipment design properties applications and poten-tialrdquo in Proceedings of the One Day Seminar on FoamedConcrete Properties Applications and Latest TechnologicalDevelopments pp 1ndash7 Loughborough University Lough-borough England UK 2001

[153] A Proshin V A Beregovoi A M Beregovoi andI A Eremkin Unautoclaved Foam Concrete and its Con-structions Adapted to the Regional Conditions omasTelford London UK 2005

[154] A Giannakou and M R Jones Potentials of Foamed Con-crete to Enhance the ermal Performance of Low RiseDwellings omas Telford London UK 2002

[155] N Mohd Zahari I Abdul Rahman A Zaidi andA Mujahid ldquoFoamed concrete potential application inthermal insulationrdquo in Proceedings of the Malaysian Tech-nical Universities Conference on Engineering and Technology(MUCEET) MS Garden Kuantan Pahang Malaysia 2009

[156] O P Shrivastava ldquoLightweight aerated concrete-a reviewrdquoIndian Concrete Journal vol 51 pp 10ndash23 1977

[157] B Nagy S G Nehme and D Szagri ldquoermal propertiesand modeling of fiber reinforced concretesrdquo Energy Proce-dia vol 78 pp 2742ndash2747 2015

[158] H Awang A O Mydin andM H Ahmad ldquoMechanical anddurability properties of fiber lightweight foamed concreterdquoAustralian Journal of Basic and Applied Sciences vol 7 no 7pp 14ndash21 2013

[159] F Y Yang ldquoStudy on influence factors of foam concretepropertiesrdquo MS thesis Southwest University of Science andTechnology Mianyang China 2009

[160] T G Richard ldquoLow temperature behaviour of cellularconcreterdquo ACI Journal Proceedings vol 74 no 4 pp 173ndash178 1977

[161] T G Richard J A Dobogai T D Gerhardt andW C Young ldquoCellular concretendasha potential load-bearinginsulation for cryogenic applicationsrdquo IEEE Transactions onMagnetics vol 11 no 2 pp 500ndash503 1975

[162] R Kumar R Lakhani and P Tomar ldquoA simple novel mixdesign method and properties assessment of foamed con-cretes with limestone slurry wasterdquo Journal of CleanerProduction vol 171 pp 1650ndash1663 2018

[163] G Sang Y Zhu G Yang and H B Zhang ldquoPreparation andcharacterization of high porosity cement-based foam ma-terialrdquo Construction and Building Materials vol 91pp 133ndash137 2015

[164] N Gowripalan J G Cabrera A R Cusens andP J Wainwright ldquoEffect of curing on durabilityrdquo ConcreteInternational vol 12 no 12 pp 47ndash54 1990

[165] F Batool and V Bindiganavile ldquoAir-void size distribution ofcement based foam and its effect on thermal conductivityrdquoConstruction and Building Materials vol 149 pp 17ndash282017

[166] J Jiang Z Lu Y Niu J Li and Y Zhang ldquoStudy on thepreparation and properties of high-porosity foamed con-cretes based on ordinary Portland cementrdquo Materials andDesign vol 92 pp 949ndash959 2016

[167] E K K Nambiar and K Ramamurthy ldquoFresh state char-acteristics of foam concreterdquo Journal of Materials in CivilEngineering vol 20 no 2 pp 111ndash117 2008

[168] M R Jones K Ozlutas and L Zheng ldquoStability and in-stability of foamed concreterdquoMagazine of Concrete Researchvol 68 no 11 pp 542ndash549 2016

[169] E Kuzielova L Pach and M Palou ldquoEffect of activatedfoaming agent on the foam concrete propertiesrdquo Con-struction and Building Materials vol 125 pp 998ndash10042016

[170] S Ghorbani S Sharifi J de Brito S Ghorbani M A Jalayerand M Tavakkolizadeh ldquoUsing statistical analysis and lab-oratory testing to evaluate the effect of magnetized water onthe stability of foaming agents and foam concreterdquo Con-struction and Building Materials vol 207 pp 28ndash40 2019

[171] M Siva K Ramamurthy and R Dhamodharan ldquoDevel-opment of a green foaming agent and its performanceevaluationrdquo Cement and Concrete Composites vol 80pp 245ndash257 2017

[172] A Bagheri and S A Samea ldquoParameters influencing thestability of foamed concreterdquo Journal of Materials in CivilEngineering vol 30 no 6 Article ID 04018091 2018

[173] T Adams A Vollpracht J Haufe L Hildebrand andS Brell-Cokcan ldquoUltra-lightweight foamed concrete for anautomated facade applicationrdquo Magazine of Concrete Re-search vol 71 no 8 pp 424ndash436 2019

[174] M Cong and C Bing ldquoProperties of a foamed concrete withsoil as fillerrdquo Construction and Building Materials vol 76pp 61ndash69 2015

[175] M Qiao J Chen C Yu S S Wu N X Gao and Q P RanldquoGemini surfactants as novel air entraining agents forconcreterdquo Cement and Concrete Research vol 100 pp 40ndash46 2017

[176] C Kramer M Schauerte T Muller S Gebhard andR Trettin ldquoApplication of reinforced three-phase-foams inUHPC foam concreterdquo Construction and Building Materialsvol 131 pp 746ndash757 2017

[177] T S Horozov ldquoFoams and foam films stabilised by solidparticlesrdquo Current Opinion in Colloid and Interface Sciencevol 13 no 3 pp 134ndash140 2008

[178] C Kramer T L Kowald and R H F Trettin ldquoPozzolanichardened three-phase-foamsrdquo Cement and Concrete Com-posites vol 62 pp 44ndash51 2015


[179] B P Binks and T S Horozov ldquoAqueous foams stabilizedsolely by silica nanoparticlesrdquo Angewandte Chemie Inter-national Edition vol 44 no 24 pp 3722ndash3725 2005

[180] U T Gonzenbach A R Studart E Tervoort andL J Gauckler ldquoStabilization of foams with inorganic col-loidal particlesrdquo Langmuir the ACS Journal of Surfaces andColloids vol 22 no 26 Article ID 10983 2006

[181] A R Studart U T Gonzenbach I Akartuna E Tervoortand L J Gauckler ldquoMaterials from foams and emulsionsstabilized by colloidal particlesrdquo Journal of MaterialsChemistry vol 17 no 31 pp 3283ndash3289 2007

[182] Y Du Preparation of Nano-Modified Foam Concrete and itsStability and Enhancement Mechanism Southeast Univer-sity pp 9-10 Nanjing China MS thesis 2018

[183] F Q Tang Z Xiao J A Tang and L Jiang ldquoe effect ofSiO2 particles upon stabilization of foamrdquo Journal of Colloidand Interface Science vol 131 no 2 pp 498ndash502 1989

[184] R G Alargova D S Warhadpande V N Paunov andO D Velev ldquoFoam super stabilization by polymer micro-rodsrdquo Langmuir vol 20 no 24 pp 10371ndash10374 2004

[185] B P Binks M Kirkland and J A Rodrigues ldquoOrigin ofstabilisation of aqueous foams in nanoparticle-surfactantmixturesrdquo Soft Matter vol 4 no 12 pp 2373ndash2382 2008

[186] W She Y Du C W Miao et al ldquoApplication of organic-and nanoparticle-modified foams in foamed concrete re-inforcement and stabilization mechanismsrdquo Cement andConcrete Research vol 106 pp 12ndash22 2018

[187] J Keriene M Kligys A Laukaitas G YakolevA Spokauskas and M Aleknevicius ldquoe influence ofmulti-walled carbon nanotubes additive on properties ofnon-autoclaved and autoclaved aerated concretesrdquo Con-struction and Building Materials vol 49 pp 527ndash535 2013

[188] G Yakolev G Pervushin I Maeva et al ldquoModification ofconstruction materials with multi-walled carbon nano-tubesrdquo Procedia Engineering vol 57 pp 407ndash413 2013

[189] G Yakolev J Keriene A Gailius and I Girniene ldquoCementbased foam concrete reinforced by carbon nanotubesrdquoMaterials Science vol 12 no 2 pp 147ndash151 2006

[190] G Y Li P M Wang and X Zhao ldquoMechanical behaviorand microstructure of cement composites incorporatingsurface-treated multi-walled carbon nanotubesrdquo Carbonvol 43 no 6 pp 1239ndash1245 2005

[191] C Kramer O M Azubike and R H F Trettin ldquoReinforcedand hardened three-phase-foamsrdquo Cement and ConcreteComposites vol 73 pp 174ndash184 2016

[192] C Kramer and R H F Trettin ldquoInvestigations of nano-structured three-phase-foams and their application in foamconcretesndasha summaryrdquo Advanced Materials Letters vol 8no 11 pp 1072ndash1079 2017

[193] C Kramer M Schauerte T L Kowald and R H F Trettinldquoree-phase-foams for foam concrete applicationrdquo Mate-rials Characterization vol 102 pp 173ndash179 2015

[194] N Narayanan and K Ramamurthy ldquoStructure and prop-erties of aerated concrete a reviewrdquo Cement and ConcreteComposites vol 22 no 5 pp 321ndash329 2000

[195] H Al-Khaiat and M N Haque ldquoEffect of initial curing onearly strength and physical properties of a lightweightconcreterdquo Cement and Concrete Research vol 28 no 6pp 859ndash866 1998

[196] O Kayali M N Haque and B Zhu ldquoDrying shrinkage offibre-reinforced lightweight aggregate concrete containingfly ashrdquo Cement and Concrete Research vol 29 no 11pp 1835ndash1840 1999

[197] M Gesoglu T Ozturan and E Guneyisi ldquoShrinkagecracking of lightweight concrete made with cold-bonded flyash aggregatesrdquo Cement and Concrete Research vol 34no 7 pp 1121ndash1130 2004

[198] D D Domenico ldquoRC members strengthened with exter-nally bonded FRP plates a FE-based limit analysis ap-proachrdquo Composites Part B Engineering vol 71pp 159ndash174 2015

[199] W Piasta J Gora and W Budzynski ldquoStress-strain rela-tionships and modulus of elasticity of rocks and of ordinaryand high-performance concretesrdquo Construction and Build-ing Materials vol 153 pp 728ndash739 2017

[200] J Xie and J B Yan ldquoExperimental studies and analysis oncompressive strength of normal-weight concrete at lowtemperaturesrdquo Structural Concrete vol 19 pp 1235ndash12442017

[201] D Q Li Z L Li C C Lv G H Zhang and Y M Yin ldquoApredictive model of the effective tensile and compressivestrengths of concrete considering porosity and pore sizerdquoConstruction and Building Materials vol 170 pp 520ndash5262018

[202] K Ding ldquoTechnology research on flexible fining defects oftunnel structurerdquo MS thesis School of Civil EngineeringShandong University Jinan China 2018

[203] C Rudolph and J Valore ldquoCellular concretes part 2 physicalpropertiesrdquo ACI Journal Proceedings vol 50 pp 817ndash8361954

[204] A O Richard and M Ramli ldquoExperimental production ofsustainable lightweight foamed concreterdquo British Journal ofApplied Science and Technology vol 3 no 4 pp 994ndash10052013

[205] A F Roslan H Awang and M Mydin ldquoEffects of variousadditives on drying shrinkage compressive and flexuralstrength of lightweight foamed concrete (LFC)rdquo AdvancedMaterials Research vol 626 pp 594ndash604 2013

[206] M A O Mydin and Y C Wang ldquoMechanical properties offoamed concrete exposed to high temperaturesrdquo Construc-tion and Building Materials vol 26 pp 638ndash654 2012

[207] C Ma and B Chen ldquoExperimental study on the preparationand properties of a novel foamed concrete based on mag-nesium phosphate cementrdquo Construction and BuildingMaterials vol 137 pp 160ndash168 2017

[208] F Gouny F Fouchal P Maillard and S Rossignol ldquoAgeopolymer mortar for wood and earth structuresrdquo Con-struction and Building Materials vol 32 pp 188ndash195 2012

[209] L Z Liu S Miramini and A Hajimohammadi ldquoCharac-terising fundamental properties of foam concrete with anon-destructive techniquerdquo Nondestructive Testing andEvaluation vol 34 no 1 pp 54ndash69 2019

[210] K K B Siram and R K Arjun ldquoConcrete + Green FoamConcreterdquo International Journal of Civil Engineering andTechnology vol 4 pp 179ndash184 2013

[211] A S Moon and V Varghese ldquoSustainable construction withfoam concrete as a green building materialrdquo InternationalJournal of Modern Trends in Engineering and Research vol 2no 2 pp 13ndash16 2014

[212] A S Moon V Varghese and S S Waghmare ldquoFoamconcrete as a green building materialrdquo International Journalof Research in Engineering and Technology vol 2 no 9pp 25ndash32 2015

[213] W She M R Jones Y S Zhang and X Shi ldquoPotential use offoamed mortar (FM) for thermal upgrading of Chinesetraditional Hui-style residencesrdquo International Journal ofArchitectural Heritage vol 9 no 7 pp 775ndash793 2015


[214] K Jitchaiyaphum T Sinsiri C Jaturapitakkul andP Chindaprasirt ldquoCellular lightweight concrete containinghigh-calcium fly ash and natural zeoliterdquo InternationalJournal of Minerals Metallurgy and Materials vol 20 no 5pp 462ndash471 2013

[215] X Yu ldquoResearch on foaming agent for preparation of lightfoam concreterdquo MS thesis College of Science NortheasternUniversity Shenyang China 2015

[216] M N Wang Y C Dong and L Yi ldquoAnalytical solution forloess tunnel based on the bilinear strength criterionrdquo Soilmechanics and Foundation Engineering vol 57 no 3pp 151ndash163 2020

[217] T Liu Y J Zhong Z H Feng W Xu and F T Song ldquoNewconstruction technology of a shallow tunnel in boulder-cobble mixed groundsrdquo Advances in Civil Engineeringvol 2020 Article ID 5686042 14 pages 2020

[218] J X Lai X LWang J L Qiu et al ldquoA state-of-the-art reviewof sustainable energy-based freeze proof technology for cold-region tunnels in Chinardquo Renewable and Sustainable EnergyReviews vol 82 no 3 pp 3554ndash3569 2018

[219] X L Weng Y F Sun B H Yan H S Niu R A Lin andS Q Zhou ldquoCentrifuge testing and numerical modeling oftunnel face stability considering longitudinal slope angle andsteady state seepage in soft clayrdquo Tunnelling and Under-ground Space Technology vol 96 pp 218ndash229 2020

[220] Z Zhou Y Dong P Jiang D Han and T Liu ldquoCalculationof pile side friction by multiparameter statistical analysisrdquoAdvances in Civil Engineering vol 2019 Article ID 263852012 pages 2019

[221] K K Yuan ldquoHigh-strength and heat insulation foam con-crete developing and applying in cold region tunnelrdquoJournal of Glaciology and Geocryology vol 38 pp 438ndash4442016

[222] W Z Chen H M Tian J Q Yuan and J X Tan ldquoDeg-radation characteristics of foamed concrete with lightweightaggregate and polypropylene fibre under freezendashthaw cy-clesrdquo Magazine of Concrete Research vol 65 no 12pp 720ndash730 2013

[223] Y Y Li S S Xu H Q Liu E L Ma and L X WangldquoDisplacement and stress characteristics of tunnel founda-tion in collapsible loess ground reinforced by jet groutingcolumnsrdquo Advances in Civil Engineering vol 2018 ArticleID 2352174 2018

[224] Z CWang Y L Xie H Q Liu and Z H Feng ldquoAnalysis ondeformation and structural safety of a novel concrete-filledsteel tube support system in loess tunnelrdquo European Journalof Environmental and Civil Engineering vol 2018 pp 1ndash212019

[225] S B Zhang S Y He J L Qiu W Xu R Garnes andL X Wang ldquoDisplacement characteristics of a urban tunnelin silty soil by shallow tunnelling methodrdquo Advances in CivilEngineering vol 2020 Article ID 3975745 16 pages 2020

[226] W S Zhao W Z Chen X J Tan and S Huang ldquoStudy onfoamed concrete used as seismic isolation material fortunnels in rockrdquo Materials Research Innovations vol 17no 7 pp 465ndash472 2013

[227] S Huang W Z Chen J P Yang X H Guo and C J QiaoldquoResearch on earthquake-induced dynamic responses andaseismic measures for underground engineeringrdquo ChineseJournal of Rock Mechanics and Engineering vol 28 no 3pp 483ndash490 2009

[228] M Gasc-Barbier S Chanchole and P Berest ldquoCreep be-havior of bure clayey rockrdquo Applied Clay Science vol 26no 1ndash4 pp 449ndash458 2004

[229] M J Heap P Baud P G Meredith S VinciguerraA F Bell and I G Maind ldquoBrittle creep in basalt and itsapplication to time-dependent volcano deformationrdquo Earthand Planetary Science Letters vol 307 no 1-2 pp 71ndash822011

[230] D K Wang J P Wei G Z Yin Y GWang and Z HWenldquoTriaxial creep behavior of coal containing gas in labora-toryrdquo Procedia Engineering vol 26 pp 1001ndash1010 2011

[231] M Naumann U Hunsche and O Schulze ldquoExperimentalinvestigations on anisotropy in dilatancy failure and creep ofopalinus clayrdquo Physics and Chemistry of the Earth Parts ABC vol 32 no 8ndash14 pp 889ndash895 2007

[232] B S Yuan ldquoApplication of corrosion resistant air-tightconcrete in right line of no 2 Tiefengshan tunnelrdquo Highwayvol 7 pp 199ndash201 2006

[233] H Wang W Z Chen X J Tan H M Tian and J J CaoldquoDevelopment of a new type of foam concrete and its ap-plication on stability analysis of large-span soft rock tunnelrdquoJournal of Central South University vol 19 no 11pp 3305ndash3310 2012

[234] G J Wu W Z Chen H M Tian S P Jia J P Yang andX J Tan ldquoNumerical evaluation of a yielding tunnel liningsupport system used in limiting large deformation insqueezing rockrdquo Environmental Earth Sciences vol 77p 439 2018

[235] Foamed Concrete Applications 2018 httpwwwfoamedconcretecouk

[236] M D Jalal A Tanveer K Jagdeesh and F Ahmed ldquoFoamconcreterdquo International Journal of Civil Engineering Re-search vol 8 no 1 pp 1ndash14 2017 httpwwwripublicationcomijcer17ijcerv8n1_01pdf

[237] Case Studies for Foam Concrete 2019 httpwwwgsfoamconcretecouk

[238] K Ding S C Li X Y Zhou et al ldquoEffect of filling for topdefect of secondary lining of tunnel by foam concreterdquoYangtze River vol 48 no 18 pp 73ndash77 2017

[239] J Zhang ldquoLandscape design of tunnel portalndasha case inWulaofeng tunnel of west lake scenic area in HangzhourdquoJournal of Hebei Agricultural Sciences vol 13 no 3pp 87ndash89 2009

[240] S Kontoe L Zdravkovic D M Potts and C O MenkitildquoCase study on seismic tunnel responserdquo Canadian Geo-technical Journal vol 45 no 12 pp 1743ndash1764 2008

[241] K H Cai and T Yu ldquoTreatment scheme and calculationanalysis of Shima tunnel collapserdquo Beifang Jiaotong vol 8pp 61ndash65 2011

[242] H G Deng and C Cheng ldquoClosure of abandonedmine laneswith foam concreterdquo World Mining Express vol 34pp 18-19 1992

[243] F Alan H Mike and A David e stabilisation of CombeDown Stone Mines Combe Down Stone Mines ProjectDulverton UK 2011

[244] X J Tan W Z Chen H Y Liu et al ldquoA combined sup-porting system based on foamed concrete and U-shaped steelfor underground coal mine roadways undergoing largedeformationsrdquo Tunnelling and Underground Space Tech-nology vol 68 pp 196ndash210 2017

[245] H Wen S X Fan D Zhang W F Wang J Guo andQ F Sun ldquoExperimental study and application of a novelfoamed concrete to yield airtight walls in coal minesrdquo Ad-vances in Materials Science and Engineering vol 2018 Ar-ticle ID 9620935 2018

[246] M X Zhang ldquoStudy on filling in natural gas special tunnelrdquoShanghai Gas vol 3 pp 1ndash4 2018


[247] C H Dowding and A Rozen ldquoDamage to rock tunnels fromearthquake shakingrdquo Journal of Geotechnical and Geo-environmental Engineering vol 104 no 2 pp 175ndash191 1978

[248] J Tohda H Yoshimura and L M Li ldquoCharacteristic fea-tures of damage to the public sewerage systems in theHanshin areardquo Soils and Foundations vol 36 pp 335ndash3471996

[249] K Masaru and M Masakatsu ldquoDamage to water supplypipelinesrdquo Soils and Foundations vol 36 pp 325ndash333 1996

[250] Real Foam Cellular Concrete Applications 2018 httpwwwcanadiancellularconcretecom

[251] M Reisi S A Dadvar and A Sharif ldquoMicrostructure andmixture proportioning of non-structural foamed concretewith silica fumerdquo Magazine of Concrete Research vol 69no 23 pp 1218ndash1230 2017

[252] S-Y Chung C Lehmann M A Elrahman and D StephanldquoPore characteristics and their effects on the materialproperties of foamed concrete evaluated using Micro-CTimages and numerical approachesrdquo Applied Sciences vol 7no 6 p 550 2017

[253] B Savija and E Schlangen ldquoUse of phase change materials(PCMs) to mitigate early age thermal cracking in concretetheoretical considerationsrdquo Construction and Building Ma-terials vol 126 pp 332ndash344 2016

[254] C Liu L Xing H W Liu et al ldquoNumerical study of bondslip between section steel and recycled aggregate concretewith full replacement ratiordquo Applied Sciences vol 10 no 3Article ID 887 2020

[255] L X Wang S S Xu J L Qiu et al ldquoAutomatic monitoringsystem in underground engineering construction reviewand prospectrdquo Advances in Civil Engineering Article ID3697253 12 pages 2020

[256] Z P Song G L Shi B Y Zhao K M Zhao and J B WangldquoStudy of the stability of tunnel construction based ondouble-heading advance construction methodrdquo Advances inMechanical Engineering vol 12 no 1 17 pages 2020


flowing capacity can be used to fill voids sink holes disusedsewage pipes abandoned subways and so on e low andcontrolled self-weight makes it capable for load reduction orliner elements in tunnel and metro systems [39ndash41]

ough there are limited studies regarding the practicalapplications of FC in civil engineering its properties havebeen deeply studied For example Tan et al [42] performedan investigation on compression deformation properties ofFC used as liner element for the purpose of furtherexplaining stress and strain response e experimentalresults indicated that the compressive strength of FC in-creases with density and confining pressure whereas themodulus of elasticity has a positive correlation only withdensities regardless of confining pressure And no notablecorrelation was observed between peak strain and densitybut peak strain increases with confining pressure Tikalskyet al [43] studied the freeze-thaw durability of cellularconcrete and proposed an improved freeze-thaw testmethod ey reported that depth of absorption was con-sidered as a critical predictor in developing freeze-thaw-resistant concrete which will contribute to promote effec-tiveness in terms of using FC as insulation material fortunnels in cold regions Sun et al [44] explored the influenceof different foaming agents on compressive strength dryingshrinkage and workability of FC which will be helpful todetermine specification and implementation detailsMoreover Amran et al [37] reviewed the compositionpreparation process and properties of FC while the focus ofa review organized by Ramamurthy et al [38] is to classifyliteratures on foaming materials foaming agents cementfillers mix proportion production methods fresh andhardened properties of FC etc Significant progress of FCapplication has been made over the past few decades InCanada cement-based FC has been widely used for tunnelgrouting [45] Zhao et al [46] developed a foam cement-based material as a sacrificial tunnel lining structuralcladding used under the situation of blasting load actionis FC-based sacrificial cladding with the optimizedthickness effectively alleviates the dynamic responses in-duced by blasting loads in tunnel Choi and Ma [47]employed lightweight FC to facilitate tunnel drainagewhereas it was successfully implemented in a two-lanehighway tunnel in South Korea Successful application wasachieved due to the effective formation and distribution ofopen-cell foams with excellent permeability

With the booming development of FC andmanufacturingtechnology FC application in tunnels and undergroundworkshas revealed prominent prospects is review briefly de-scribes the history and development of FC and some forward-looking perspectives are also discussed e FC engineeringproperties and benefits to engineering construction areelaborated e objective of this review is to highlight engi-neering properties material properties and the practicalapplications in tunnel and underground engineering

2 Foam Concrete

21 History and Recent Development ere is a confusionexisted between FC and similar materials in early literatures

ie aerated concrete and air-entrained concrete [48]However one definition (ie FC is defined as a cementingmaterial with the minimum of 20 foams by volume in themixed plastic mortar) introduced by Van Dijk [49] clearlydistinguish the FC from aerated concrete [50 51] and air-entrained concrete [52] e closed air-voids system in FCnotably reduces its density and weight and at the same timeproduces efficient insulation and fire resistance capacity[26 53]

e first Portland cement-based FC was patented byAxel Eriksson in 1923 and then small-scale commercialproduction activities were launched [54] Valora carried outthe first comprehensive investigation in the 1950s [55]Rudnai [56] and Short and Kinniburgh [57] systematicallyreported the composition properties and applications of theFC later FC was initially envisaged as a void filling stabi-lization and insulation material [58] e booming devel-opment of this new constituent material in buildings andconstructions was enhanced in the late 1970s [59] A gov-ernment-oriented assessment on FC could be seen as amilestone event to further widening FC applications

Over the past 30 years FC are widely used for the bulkfilling [38] ditch repair retaining wall [60] bridge abutmentbackfill [17] slab structure of concrete floor [18] andhousing insulation [37] etc (Figure 1) Currently people areincreasingly interested in using it as a nonstructure orsemistructure member for underground engineering suchas grouting works for tunnels damage treatment and linerstructures

22 Material Components and Preparation e basiccomponents of FC consist of (1) water (2) binder (3)foaming agent (4) filler (5) additive and (6) fibere state-of-the-art research and findings on these components to dateare described as follows

Water e water requirement for constituent materialdepends on composition consistency and stability ofthe mortar body [38] e lower water content leads toa hard mixture which easily resulting in bubblebursting [61] e higher water content causes mixturetoo thin to accommodate bubbles thereby causingbubbles separating from the mixture [1] e AmericanConcrete Institute (ACI) recommends that mixedwater should be fresh clean and drinkable [62]Sometimes the mixed water can be replaced byequivalent-performance water received frommunicipalsectors in case the strength FC could reach 90 withinspecified curing time [38]BinderCement is the most commonly used bindereordinary Portland cement rapid hardening Portlandcement calcium sulphoaluminate cement and high-alumina can be used in ranges between 25 and 100of the binder content [59 63]Foaming agent e foaming agent determines FCdensity by controlling generation rate of the bubbles incement paste e resin-based was one of the earliestused foaming agents in FC So far synthetic protein-









content in mixture





Foamconcrete

Trench backfill

Structure fill

Mass void fill

Duct and shaft fill

Sink hole filling


Pavement base













Dryingshrinkage

()Reference




NAAnimal


05 NA 600 025ndash0390 d [44]
















OPC

(i) Curingcondition


156ndash1338




[92]










[105]


020ndash1174



[7]



temperature[19]





[106]




[107]



was proposed[5]




[108]




[109]







kd Gd

ActΔp (1)











cubic meter

[127]











gravity of cement

[114]



[114]



n constants [130]






[119]


strength [132]



































(a) (b)










Disperse phase

Continuous phase

Nanoparticle






















Cementpaste

Waterinterface

Fd

Fc

Fst

Fc

Fst

Gas

D

Pi

Fb

(a)

Gas

Cementpaste

Nanoparticle

Fd

Fc

Fst

Fc

Fst

DPi

Fb

HPMCliquid

interface

(b)














Type


Drydensity(kgm3)

Dryingshrinkage

()

Porosity()

Modulusof

elasticity(GPa)





Fluidity(mm)



















Antifreezeadditive

Waterreducer


Ratio 30 18 150 02 40 03 2 1 4








New ground

Original ground

Metro tunnel line

Foam concrete

Δh

(a)

Metrosystem

Foam concrete

(b)





















(a) (b) (c)









ρd SaMc


ρc

+Mw

ρw

1113888 11138891113890 1113891

My V2ρf

Mp My

α + 1

(2)




(a) (b)








5 Conclusions










Acknowledgments


References






















































































































































































































































































content in mixture





Foamconcrete

Trench backfill

Structure fill

Mass void fill

Duct and shaft fill

Sink hole filling


Pavement base













Dryingshrinkage

()Reference




NAAnimal


05 NA 600 025ndash0390 d [44]
















OPC

(i) Curingcondition


156ndash1338




[92]










[105]


020ndash1174



[7]



temperature[19]





[106]




[107]



was proposed[5]




[108]




[109]







kd Gd

ActΔp (1)











cubic meter

[127]











gravity of cement

[114]



[114]



n constants [130]






[119]


strength [132]



































(a) (b)










Disperse phase

Continuous phase

Nanoparticle






















Cementpaste

Waterinterface

Fd

Fc

Fst

Fc

Fst

Gas

D

Pi

Fb

(a)

Gas

Cementpaste

Nanoparticle

Fd

Fc

Fst

Fc

Fst

DPi

Fb

HPMCliquid

interface

(b)














Type


Drydensity(kgm3)

Dryingshrinkage

()

Porosity()

Modulusof

elasticity(GPa)





Fluidity(mm)



















Antifreezeadditive

Waterreducer


Ratio 30 18 150 02 40 03 2 1 4








New ground

Original ground

Metro tunnel line

Foam concrete

Δh

(a)

Metrosystem

Foam concrete

(b)





















(a) (b) (c)









ρd SaMc


ρc

+Mw

ρw

1113888 11138891113890 1113891

My V2ρf

Mp My

α + 1

(2)




(a) (b)








5 Conclusions










Acknowledgments


References

























































































































































































































































































Dryingshrinkage

()Reference




NAAnimal


05 NA 600 025ndash0390 d [44]
















OPC

(i) Curingcondition


156ndash1338




[92]










[105]


020ndash1174



[7]



temperature[19]





[106]




[107]



was proposed[5]




[108]




[109]







kd Gd

ActΔp (1)











cubic meter

[127]











gravity of cement

[114]



[114]



n constants [130]






[119]


strength [132]



































(a) (b)










Disperse phase

Continuous phase

Nanoparticle






















Cementpaste

Waterinterface

Fd

Fc

Fst

Fc

Fst

Gas

D

Pi

Fb

(a)

Gas

Cementpaste

Nanoparticle

Fd

Fc

Fst

Fc

Fst

DPi

Fb

HPMCliquid

interface

(b)














Type


Drydensity(kgm3)

Dryingshrinkage

()

Porosity()

Modulusof

elasticity(GPa)





Fluidity(mm)



















Antifreezeadditive

Waterreducer


Ratio 30 18 150 02 40 03 2 1 4








New ground

Original ground

Metro tunnel line

Foam concrete

Δh

(a)

Metrosystem

Foam concrete

(b)





















(a) (b) (c)









ρd SaMc


ρc

+Mw

ρw

1113888 11138891113890 1113891

My V2ρf

Mp My

α + 1

(2)




(a) (b)








5 Conclusions










Acknowledgments


References





















































































































































































































































































OPC

(i) Curingcondition


156ndash1338




[92]










[105]


020ndash1174



[7]



temperature[19]





[106]




[107]



was proposed[5]




[108]




[109]







kd Gd

ActΔp (1)











cubic meter

[127]











gravity of cement

[114]



[114]



n constants [130]






[119]


strength [132]



































(a) (b)










Disperse phase

Continuous phase

Nanoparticle






















Cementpaste

Waterinterface

Fd

Fc

Fst

Fc

Fst

Gas

D

Pi

Fb

(a)

Gas

Cementpaste

Nanoparticle

Fd

Fc

Fst

Fc

Fst

DPi

Fb

HPMCliquid

interface

(b)














Type


Drydensity(kgm3)

Dryingshrinkage

()

Porosity()

Modulusof

elasticity(GPa)





Fluidity(mm)



















Antifreezeadditive

Waterreducer


Ratio 30 18 150 02 40 03 2 1 4








New ground

Original ground

Metro tunnel line

Foam concrete

Δh

(a)

Metrosystem

Foam concrete

(b)





















(a) (b) (c)









ρd SaMc


ρc

+Mw

ρw

1113888 11138891113890 1113891

My V2ρf

Mp My

α + 1

(2)




(a) (b)








5 Conclusions










Acknowledgments


References
















































































































































































































































































kd Gd

ActΔp (1)











cubic meter

[127]











gravity of cement

[114]



[114]



n constants [130]






[119]


strength [132]



































(a) (b)










Disperse phase

Continuous phase

Nanoparticle






















Cementpaste

Waterinterface

Fd

Fc

Fst

Fc

Fst

Gas

D

Pi

Fb

(a)

Gas

Cementpaste

Nanoparticle

Fd

Fc

Fst

Fc

Fst

DPi

Fb

HPMCliquid

interface

(b)














Type


Drydensity(kgm3)

Dryingshrinkage

()

Porosity()

Modulusof

elasticity(GPa)





Fluidity(mm)



















Antifreezeadditive

Waterreducer


Ratio 30 18 150 02 40 03 2 1 4








New ground

Original ground

Metro tunnel line

Foam concrete

Δh

(a)

Metrosystem

Foam concrete

(b)





















(a) (b) (c)









ρd SaMc


ρc

+Mw

ρw

1113888 11138891113890 1113891

My V2ρf

Mp My

α + 1

(2)




(a) (b)








5 Conclusions










Acknowledgments


References















































































































































































































































































































(a) (b)










Disperse phase

Continuous phase

Nanoparticle






















Cementpaste

Waterinterface

Fd

Fc

Fst

Fc

Fst

Gas

D

Pi

Fb

(a)

Gas

Cementpaste

Nanoparticle

Fd

Fc

Fst

Fc

Fst

DPi

Fb

HPMCliquid

interface

(b)














Type


Drydensity(kgm3)

Dryingshrinkage

()

Porosity()

Modulusof

elasticity(GPa)





Fluidity(mm)



















Antifreezeadditive

Waterreducer


Ratio 30 18 150 02 40 03 2 1 4








New ground

Original ground

Metro tunnel line

Foam concrete

Δh

(a)

Metrosystem

Foam concrete

(b)





















(a) (b) (c)









ρd SaMc


ρc

+Mw

ρw

1113888 11138891113890 1113891

My V2ρf

Mp My

α + 1

(2)




(a) (b)








5 Conclusions










Acknowledgments


References






















































































































































































































































































Disperse phase

Continuous phase

Nanoparticle






















Cementpaste

Waterinterface

Fd

Fc

Fst

Fc

Fst

Gas

D

Pi

Fb

(a)

Gas

Cementpaste

Nanoparticle

Fd

Fc

Fst

Fc

Fst

DPi

Fb

HPMCliquid

interface

(b)














Type


Drydensity(kgm3)

Dryingshrinkage

()

Porosity()

Modulusof

elasticity(GPa)





Fluidity(mm)



















Antifreezeadditive

Waterreducer


Ratio 30 18 150 02 40 03 2 1 4








New ground

Original ground

Metro tunnel line

Foam concrete

Δh

(a)

Metrosystem

Foam concrete

(b)





















(a) (b) (c)









ρd SaMc


ρc

+Mw

ρw

1113888 11138891113890 1113891

My V2ρf

Mp My

α + 1

(2)




(a) (b)








5 Conclusions










Acknowledgments


References

































































































































































































































































































Cementpaste

Waterinterface

Fd

Fc

Fst

Fc

Fst

Gas

D

Pi

Fb

(a)

Gas

Cementpaste

Nanoparticle

Fd

Fc

Fst

Fc

Fst

DPi

Fb

HPMCliquid

interface

(b)














Type


Drydensity(kgm3)

Dryingshrinkage

()

Porosity()

Modulusof

elasticity(GPa)





Fluidity(mm)



















Antifreezeadditive

Waterreducer


Ratio 30 18 150 02 40 03 2 1 4








New ground

Original ground

Metro tunnel line

Foam concrete

Δh

(a)

Metrosystem

Foam concrete

(b)





















(a) (b) (c)









ρd SaMc


ρc

+Mw

ρw

1113888 11138891113890 1113891

My V2ρf

Mp My

α + 1

(2)




(a) (b)








5 Conclusions










Acknowledgments


References


























































































































































































































































































Type


Drydensity(kgm3)

Dryingshrinkage

()

Porosity()

Modulusof

elasticity(GPa)





Fluidity(mm)



















Antifreezeadditive

Waterreducer


Ratio 30 18 150 02 40 03 2 1 4








New ground

Original ground

Metro tunnel line

Foam concrete

Δh

(a)

Metrosystem

Foam concrete

(b)





















(a) (b) (c)









ρd SaMc


ρc

+Mw

ρw

1113888 11138891113890 1113891

My V2ρf

Mp My

α + 1

(2)




(a) (b)








5 Conclusions










Acknowledgments


References































































































































































































































































































Antifreezeadditive

Waterreducer


Ratio 30 18 150 02 40 03 2 1 4








New ground

Original ground

Metro tunnel line

Foam concrete

Δh

(a)

Metrosystem

Foam concrete

(b)





















(a) (b) (c)









ρd SaMc


ρc

+Mw

ρw

1113888 11138891113890 1113891

My V2ρf

Mp My

α + 1

(2)




(a) (b)








5 Conclusions










Acknowledgments


References



















































































































































































































































































New ground

Original ground

Metro tunnel line

Foam concrete

Δh

(a)

Metrosystem

Foam concrete

(b)





















(a) (b) (c)









ρd SaMc


ρc

+Mw

ρw

1113888 11138891113890 1113891

My V2ρf

Mp My

α + 1

(2)




(a) (b)








5 Conclusions










Acknowledgments


References





















































































































































































































































































ρd SaMc


ρc

+Mw

ρw

1113888 11138891113890 1113891

My V2ρf

Mp My

α + 1

(2)




(a) (b)








5 Conclusions










Acknowledgments


References


















































































































































































































































































5 Conclusions










Acknowledgments


References















































































































































































































































































FoamConcrete:AState-of-the-Artand State-of-the-PracticeReviewOct 21, 2019 · slag f c A× exp(a×...

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Transcript of FoamConcrete:AState-of-the-Artand State-of-the-PracticeReviewOct 21, 2019 · slag f c A× exp(a×...