TheInfluenceofNano-SiO andRecycledPolypropylene ...

Research ArticleThe Influence of Nano-SiO2 and Recycled PolypropylenePlastic Content on Physical Mechanical and ShrinkageProperties of Mortar

Haiming Chen12 Yangchen Xu 12 Donglei Zhang 12 Lingxia Huang 12

Yuntao Zhu 12 and Le Huang 12

1School of Civil Engineering and Architecture Anhui University of Science and Technology Huainan 232001 China2Engineering Research Center of Underground Mine Construction Ministry of EducationAnhui University of Science and Technology Huainan 232001 China

Correspondence should be addressed to Yangchen Xu 775546912qqcom

Received 6 June 2019 Revised 24 August 2019 Accepted 13 September 2019 Published 20 October 2019

Academic Editor Behzad Nematollahi

Copyright copy 2019Haiming Chen et alis 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

is work is aimed to study the possibility of recycling plastic waste (polypropylene (PP)) as aggregate instead of sand in themanufacturing of mortar or concrete For this an experimental study was carried out to evaluate the influence of nano-SiO2 andrecycled PP plastic particlesrsquo content on physical mechanical and shrinkage properties and microstructure of the mortars withrecycled PP plastic particles e sand is substituted with the recycled PP plastic particles at dosages (0 20 40 and 60 byvolume of the sand) e nano-SiO2 content is 5 by weight of cement e physical (porosity water absorption and density)mechanical (compressive and flexural strength) and shrinkage properties of the mortars were evaluated and a complementarystudy on microstructure of the interface between cementitious matrix and PP plastic particles was made e measurements ofphysical and mechanical properties showed that PP-filled mortar had lower density and better toughness (higher ratio of flexuralstrength to compressive strength) However the compressive strength and flexural strength of PP-filled mortar is reduced and theporosity water absorption autogenous shrinkage and dry shrinkage increased as compared to normal cement mortar eaddition of nano-SiO2 reduced the porosity water absorption and drying shrinkage of PP-filled mortar and effectively improvedthe mechanical properties but increased its autogenous shrinkage Amicroscopic study of the interfacial zone (plastic-binder) hasshown that there is poor adhesion between PP plastic particles and cement paste From this work it is found that recycled PPplastic waste has a great potential to be a construction material It can be used as partial replacement of natural aggregates instead

1 Introduction

Plastic a common macromolecule compound is widelyused in all walks of life for its excellent properties of lowdensity high durability high impact resistance and easyprocessing [1] According to statistics the global plasticproduction in 2017 is nearly 350 million tons [2] and theannual output is growing steadily China is not only a bigproducer of plastics but also a big consumer of plastics Itstotal plastic consumption accounts for about a quarter of theworld and has become the largest plastic consumer in theworld [3] Plastics offer many benefits to the society butunfortunately also drawbacks For a long time the main

treatment methods of plastic waste in various countries arelandfill incineration and transportation to other countriesDue to the very low biodegradability of plastic waste [4ndash6]landfill will make it exist in the soil for a long time increasingthe burden of land resources while incineration of plasticwaste will produce polycyclic aromatic hydrocarbons car-bon monoxide and other harmful substances thereby se-riously contaminating the environment Under thebackground of global resource shortage recycling plasticwaste can reduce resource waste avoid environmentalpollution and achieve sustainable development Howeverthe status of recycling plastic waste is not satisfactory Evenin the developed countries it is difficult to have a high

HindawiAdvances in Civil EngineeringVolume 2019 Article ID 6960216 12 pageshttpsdoiorg10115520196960216

recycling rate of plastic waste in the areas where in-frastructure construction is relatively perfect For instancethe recycling rate of plastic waste is below 40 in almost allEuropean countries [7] In 2012 the total amount of plasticwaste in municipal solid waste was 317 million tons in theUnited States only 88 of which was recycled [8]erefore how to treat plastic waste efficiently and improvethe recycling rate is a difficult problem to be solved urgently

At present a promisingmethod of recycling plastic wasteis to grind it into recycled plastic particles and mix them intoconcrete or mortar instead of original building materials[5ndash7 9 10] In this way not only plastic waste can be ef-fectively utilized but also the environment can be protectedand thus good economic and social benefits can be achieved

In the past ten years many researchers have studied theapplication of plastic waste particles in concrete or mortarAlbano et al [11] mixed recycled polyethylene terephthalate(PET) into concrete instead of original fine aggregates tostudy its mechanical behavior e results indicated thatPET-filled concrete showed a decrease in compressivestrength splitting tensile strength modulus of elasticity andultrasonic pulse velocity however the water absorptionincreased when volume proportion and particle size of PETincreased Ismail and Al-Hashmi [12] used plastic waste offabriform shapes as a partial replacement for sand and foundthat the results showed a tendency for compressive strengthand flexural strength values of plastic waste concrete mix-tures to decrease below the plain mixtures by increasing theplastic waste ratio When plastic waste ratio in concrete was20 the flexural strength at 28 days curing age was 305lower than that of the reference concrete Liang et al [13] putrecycled PP plastic powder into concrete substituting part offine aggregates and the results showed that the higher thesubstitution rate of PP plastic powder the lower the com-pressive strength and the cube compressive strength of PP-filled concrete was 262 lower than reference concrete at20 of substitution of PP plastic particles Frigione [14]substituted the 5 by weight of fine aggregate (natural sand)in concrete with an equal weight of PET aggregates man-ufactured from the waste unwashed PET bottles (WPET) Itwas found that the WPET concrete displayed similarworkability characteristics compressive strength andsplitting tensile strength slightly lower than the referenceconcrete It can be seen that the addition of plastic wasteparticles has a negative impact on the mechanical propertiesof concrete or mortar However it can improve the ductilityof concrete or mortar because plastic has certain elasticityFor example Rebeiz and Craft [15] incorporated plasticwaste particles into asphalt concrete and found that theincorporation of plastic waste particles can increase thetoughness of asphalt concrete and reduce the occurrence ofcracks Liu et al [16] put recycled ABSPC plastic particlesinto normal concrete to make a plastic modified concreteand found that the ductility of the modified concrete wasimproved Foti [17] made PET bottles into fibers and mixedthem into concrete e results showed that the averagetensile strength of the fiber-reinforced concrete is very highindicating that the ductility of concrete can be improved byadding PET fibers Hannawi et al [18] replaced partial

natural aggregates by polycarbonate (PC) and PET waste inmortar and found that the calculated flexural toughnessfactors increased significantly with increasing volumefraction of PET and PC aggregates Kou et al [19] replacedriver sand with polyvinyl chloride (PVC) plastic wastegranules in percentages of 0 5 15 and 30 by volumein concrete It was found that the concrete prepared withpartial replacement by PVC was lighter more ductile andhad lower drying shrinkage and higher resistance to chlorideion penetration

e plastic-filled concrete or mortar shows a decrease incompressive strength compared to normal concrete whichlimits the application of plastic waste in concrete or mortarAs one of the three emerging technologies in the 21stcentury nanotechnology has developed rapidly and is widelyused in various industries including construction industryPrevious studies have shown that the unique size effect ofnanomaterials can improve the microstructure of the in-terfacial transition zone (ITZ) between hardened cementpaste and aggregates and the strength of concrete is in-creased [20ndash24] erefore the mechanical properties ofplastic-filled concrete can be improved by adding nano-materials Hasan-Nattaj andNematzadeh [25] found that theintroduction of nano-SiO2 in the fiber-reinforced concreteimproved the elastic modulus due to an increase in thecompactness of the cement paste bond with aggregates eexperiments of Nazari and Riahi [26] showed that thestrength and water permeability of the specimens have beenimproved by adding SiO2 nanoparticles in the cement pasteup to 40 wt Zhao and Liu [27] found that the in-troduction of nano-SiO2 in rubber-recycled concreteamazingly improved the microstructure of rubber-recycledconcrete and the mechanical properties of rubber-recycledconcrete are significantly improved Jo et al [28] experi-mentally studied the properties of cement mortars withnano-SiO2 e results showed that nanoscale SiO2 behavednot only as filler to improve mortar cement microstructurebut also as a promoter of pozzolanic reaction

Polypropylene (PP) plastic is one of the most commonlyused consumer plastics which is widely used in food pack-aging industry e PP plastic waste can be ground intoparticles and applied in concrete ormortar which can preventthe environmental contamination caused by plastic waste andrealize recycling plastic waste Based on the above researchresults the purpose of this paper is to study the possibility ofrecycling plastic waste as aggregate partially instead of sand inthe mortar or concrete the effects of recycled PP plasticparticles content and nano-SiO2 on physical mechanical andshrinkage properties of mortar and to analyze the micro-characteristics of PP-filled mortar with nano-SiO2 by scan-ning electron microscopy (SEM) e research results canprovide references for the application of plastic waste andnanotechnology in concrete or mortar

2 Materials and Methods

21 Materials Used e materials used in this work werePortland cement sand a polycarboxylate-based super-plasticizer nano-SiO2 and recycled PP plastic particles e

2 Advances in Civil Engineering

Portland cement was purchased from Huainan ShunyueCement Co Ltd (China) whose strength grade was425MPa density was 3120 kgm3 and specific surface areawas 1447m2g e chemical composition of the cement isshown in Table 1 e sand was obtained from local sourceswith fineness modulus of 26 and apparent density of2650 kgm3 e superplasticizer was produced by ShanxiQinfen Building Materials Co Ltd (China) whose waterreduction rate was 30 e nano-SiO2 (content ge995powder particle size asymp 30plusmn 5 nm and specific surface area is200m2g) was produced by Shanghai Keyan Industrial CoLtd e recycled PP plastic particles were purchased fromZhejiang Yuyao Fengli Plastic Co Ltd (China) which wereshort columns with lengths from 2mm to 35mm elasticmodulus of 097GPa water capacity of less than 04 andrelative density of 089sim092 gcm3 as shown in Figure 1

22 Mix Design and Processing of Mortars e mix pro-portions of mortars are shown in Table 2 e content of thesuperplasticizer was the percentage of the weight of thecementitious materials e dosage of superplasticizer wascontrolled in order to avoid the floating phenomenon ofrecycled PP plastic particles due to its light density eplastic particles were added into mortars replacing 0 2040 and 60 sand by volume e nano-SiO2 content wasthe 5 by weight of cement Brief procedure for mortarprocessing was as follows (1) put the nanoparticles cementand sand in the mixing pot and mix for 2min (2) add waterand superplasticizer into the mixing pot slowly and mix foradditional 3min and (3) add the recycled PP plastic particlesinto the mixing pot and mix for additional 3min During themixing process the flowability and workability of the mortarmixtures were kept consistent by adjusting the dosage of thesuperplasticizer When this mixing process was finished therecycled PP plastic particles and nano-SiO2 were homoge-neously distributed throughout the mortar

23 Physical Properties Test of Mortar Specimens e dryweight D suspended weight S and saturated weight W oftest mortar specimens at day 28 were measured according toASTM C20-00 [29] Brief procedure for physical propertiestest of mortar specimens was as follows (1) dry the testmortar specimens in an oven at 105degC to constant weightand weigh the dry weight D (2) place the test mortarspecimens in distilled water boil for 2 hours and weigh thesuspended weight S of each test specimen after boiling andcooling for a minimum of 12 hours and while suspended inwater and (3) blot each specimen lightly with a moistenedsmooth linen or cotton cloth to remove all drops of waterfrom the surface and determine the saturated weightW eapparent porosity P the water absorption A apparentspecific gravity T and bulk density B are respectivelycalculated according to formulas (1)sim(4)

(1) Apparent porosity

P W minus D

W minus Stimes 100 (1)

(2) Water absorption

A W minus D

Dtimes 100 (2)

(3) Apparent specific gravity

T D

D minus S (3)

(4) Bulk density

B D

W minus S (4)

24 Flexural andCompressive Strength Test e flexural andcompressive strength of mortar specimens were determinedaccording to ASTM C348-18 [30] and ASTM C349-18 [31]by molding 24 prism specimens with 40 by 40 by 160mm asshown in Figure 2 e mortar specimens were removedfrom the molds after curing for 24 h in a standard curing boxat a temperature of (23plusmn 1)degC and a relative humidity ofmore than 95 en immerse the specimens in saturatedlime water for 3 d 7 d or 28 d

25 Autogenous Shrinkage According to ASTM C1698-09[32] the autogenous shrinkage strain of mortar specimenswere measured e fresh mixture was slowly poured intothe corrugated mold during vibration and then placed onthe corrugated plastic support rack During the testsmaintain the surrounding air temperature at 230plusmn 10degC Atthe time of final setting tfs the first length L(tfs) wasmeasured e autogenous strain of the specimen at time texpressed as μmm is calculated with the following formula

εautogenous L(t) minus L tfs( 1113857

L tfs( 1113857times 106 μmm (5)

where L(t) is the length of the specimen at time t

Table 1 e main chemical composition of the cement

Compounds CaO SiO2 Al2O3 SO3 MgO Fe2O3

Percentage () 638 2065 452 270 216 228

Figure 1 Recycled PP plastic particles with lengths from 2mm to35mm

Advances in Civil Engineering 3

26 Dry Shrinkage According to ASTM C596-18 [33] thedry shrinkage of mortar specimens with 20 by 20 by 280mmwas determined Moist cure the specimens in the molds inthe standard curing box for 24 h en remove the speci-mens from the molds and cure in lime-saturated water for48 h At the age of 72 h remove the specimens from waterwipe with damp cloth and immediately obtain a lengthcomparator reading for each specimen en place thespecimens in air storage with temperature of (23plusmn 1)degC andrelative humidity of (50plusmn 3) Obtain a length comparatorreading for each specimen after 1 2 3 4 5 6 7 14 21 and28 days of air storage Drying shrinkage is calculated byequation

εdry l(t) minus l t0( 1113857

l t0( 1113857times 106 μmm (6)

where l(t) is the length of the sample at the measuring timeand l(t0) is the initial length of the sample at the age of 72 h

27Microscopic Test When curing time up to 28 days crushthe PP-filled mortar specimens into small pieces with a size ofabout 8 by 8 by 5mm and polish them by a polishing ma-chine and then dry them in a vacuum drying oven for 48hours Fix the dried mortar pieces on a circular platform witha diameter of about 5 cm with double-sided adhesive tape andapply a proper amount of conductive tape to both sides of themortar pieces and then remove their surface debris with the

ear wash balls en spray the mortar pieces containing pasteand plastic with metal coating by magnetron sputtering inmagnetron ion diffractometer (MSP-2S) 120 seconds on thefront and 30 seconds on the sides Finally the microstructureswere studied by scanning electron microscopy (HITACHIS3400) In this experiment the specimens were placed in thecenter of the scanning electron microscope and the bondinginterface between the recycled PP plastic particles and thecement paste was observed

All parameters above are explained with mean andstandard deviation (SD) values

3 Results and Discussion

31 Physical Properties e effect of the recycled PP plasticparticlesrsquo content on physical properties (apparent porositywater absorption apparent specific gravity and bulk density)of the PP-filled mortar after 28 d curing age is shown inFigure 3 e apparent porosity and water absorption haveincreased considerably for all mortar specimens with theincrease of the content of replacement of sand by recycled PPplastic particles e apparent specific gravity and bulkdensity have decreased with the increase of recycled PP plasticratio For example compared to PP0 the apparent porosityand water absorption of PP6 increased by 7202 and11702 respectively while the apparent specific gravity andbulk density decreased by 1571 and 2052 respectivelye decrease in density of mortars can be attributed to the fact

(a) (b)

Figure 2 Flexural and compressive strength test of PP-filled mortar specimens

Table 2 Mix proportions of the mortar

Experimental conditions Water-to-cement (WC) ratio SP ()Mix proportion (gkg)

Cement Sand Water PP plastic Nano-SiO2

PP0 03 065 3846 500 1154 0 0PP2 03 04 3846 400 1154 347 0PP4 03 035 3846 300 1154 694 0PP6 03 03 3846 200 1154 1042 0PN0 03 08 3846 500 1154 0 192PN2 03 05 3846 400 1154 347 192PN4 03 045 3846 300 1154 694 192PN6 03 04 3846 200 1154 1042 192


that the density of recycled plastic is lower than that of sand[34] e images shown in Figure 4 clearly show the gooddistribution of recycled PP plastic particles in the mortarmixes and there is no phenomenon that PP plastic particlesare floating due to their light weight It should also be notedthis distribution has favored to obtain a lightweight mortar[5] Comparing the curves of PP and PN in Figure 3 it isfound that the physical properties of mortar specimens wereimproved after adding nano-SiO2 For example compared toPP6 the apparent porosity and water absorption of PN6 werereduced by 2461 and 2467 respectively and the apparentspecific gravity increased by 438 while the bulk densityonly increased by 017is shows that the addition of nano-SiO2 can improve the pore structure of plastic mortars reduce

the porosity and water absorption [35 36] make them morecompact and thus improve the bulk density of plastic mortar

32 Mechanical Properties

321 Compressive Strength Test compressive strength re-sults are shown in Figure 5 e compressive strength of PP-filled mortars decreased with increase in plastic wastecontent at all curing times Compared to control mixes PP0the compressive strength of PP2 PP4 and PP6 decreased by1519 3898 and 5353 respectively at day 28 whichshows that the compressive strength of PP-filled mortars hasan approximate linear reduction relationship with the

4

6

8

10

12

14

16

App

aren

t por

osity

()

PP plastic particles content ()

378

2601

32643162

1971

7202

2461

PP0 2 4 6PN0 2 4 6

0 20 40 60

(a)

PP0 2 4 6PN0 2 4 6

2

3

4

5

6

7

8

9

Wat

er ab

sorp

tion

()


1233

4622

33143133

1966

11702

2467

0 20 40 60

(b)

PP0 2 4 6PN0 2 4 6

19

20

21

22

23

24

App

aren

t spe

cific

gra

vity

(gc

m3 )


305

368

261

438

781

1116

1571

0 20 40 60

(c)

PP0 2 4 6PN0 2 4 6

17

18

19

20

21

22Bu

lk d

ensit

y (g

cm

3 )


771

1364

2052017

011

039

028

0 20 40 60

(d)

Figure 3 Effect of the recycled PP plastic particles content on physical properties of the PP-filled mortar (a) apparent porosity (b) waterabsorption (c) apparent specific gravity and (d) bulk density


dosage e reduction in the compressive strength of PP-filled mortars might be due to either a very poor bondstrength between the cement paste and the surface of therecycled PP plastic particles or the low strength of thisrecycled PP plastic particles and or the hydrophobic natureof plastic waste which can inhibit cement hydration reactionby restricting water movement e plastic has smallerelastic modulus [37] and its ability to transfer stresses ispoor playing the role of lsquoporosityrsquo e fracture section afterthe compression test is shown in Figure 6e grooves left bythe recycled PP plastic particles peeling off from cement

paste can be clearly seen in Figure 6 which shows the lowbond strength between the surface of the recycled PP plasticparticles and the cement paste

erefore improving the compressive strength ofplastic mortar or concrete is the key to the application ofplastic waste in mortar or concrete When 5 nano-SiO2was added to the mortars the compressive strength of themortars was obviously improvede compressive strengthof PN0 PN2 PN4 and PN6 increased by 2038 15873636 and 1066 respectively compared to PP0 PP2PP4 and PP6 at day 7 is is due to the physical properties

(a) (b) (c) (d)

Figure 4 e photographs of mortar specimensrsquo section with different recycled PP plastic particlesrsquo content (a) PP0 (b) PN2 (c) PP4 and(d) PN6

80

70

60

50

40

30

20

10

06040200


Com

pres

sive s

tren

gth

(MPa

)

2036

2038

1170

613

1587

1234

2214

36361566

576

1066257

3d (PP)3d (PN)7d (PP)

7d (PN)28d (PP)28d (PN)

Figure 5 Evolution of the compressive strength of mortars as function of curing time (3 7 and 28 d) e error bars represent the standarddeviation of six test specimens


of nano-SiO2 e nano-SiO2 particle size is very smallwhich can be used as a physical filler to make the interfacebetween the aggregates and cement paste more compact Atthe same time the nano-SiO2 has high activity Nano-SiO2can react with Ca(OH)2 in the interfacial transition zonebetween the aggregates and cement paste to form C-S-H gel[26] which can enhance the structure of the interfacialtransition zone and thus increase the compressive strengthof plastic mortar

322 Flexural Strength e results of the flexural strengthof mortar specimens have been given in Figure 7 Accordingto these results the flexural strength of mortar specimensdecreased with the increase in PP plastic particles contentCompared to control mixes PP0 the flexural strength of PP2PP4 and PP6 decreased by 970 3108 and 4304respectively at the age of day 28 is is due to the lowresistance of the plastic waste [5] When nano-SiO2 wasadded the flexural strength of mortar specimens was biggerthan that of mortar specimens without nano-SiO2 Forexample compared to PP0 PP2 PP4 and PP6 the flexuralstrength of PN0 PN2 PN4 and PN6 increased by 12381277 1693 and 396 respectively at day 28 ere-fore the addition of nano-SiO2 can compensate for thenegative impact on the flexural strength of mortar specimensto a certain extent because of the use of plastic waste as sand-substitution aggregate which will promote the application ofplastic waste in mortar or concrete

323 Flexural-Compressive Ratio e flexural-compres-sive ratio of mortar specimens as function of the recycledPP plastic particles content is shown in Figure 8 Accordingthese results the flexural-compressive ratio of plasticmortar increased with the increase in recycled PP plasticparticles content Compared to the control mixes PP0 theflexural-compressive ratio of PP2 PP4 and PP6 increasedby 647 1295 and 2257 respectively at day 28 isshows that recycled PP plastic particles can effectivelyimprove the toughness of mortar because the flexural-compressive ratio can reflect the toughness of concrete or

mortar and the greater the flexural-compressive ratio thebetter the toughness of concrete [38] e results of PNadding nano-SiO2 are consistent with and are slightlyhigher than those of PP without nano-SiO2 is is due tothat adding nano-SiO2 can improve mortar structure andincrease its strength e strength of PP-filled mortar is lessthan that of the control normal mortar however PP-filledmortar has better toughness which has potential appli-cation in construction and buildings with toughnessrequirements

For the mortar specimens with 20ndash60 of substitution ofrecycled PP plastic particles by volume of the sand thecompressive strength at day 28 decreased by between 1519and 5353 and the flexural strength decreased by between970 and 4304 erefore if there is a requirement for thestrength of the concrete or mortar it is suggested that thesubstitution ratio of plastic waste should be controlled within20 by volume of the sandWhen conditions permit a certainamount of nano-SiO2 can be added into the concrete ormortar to increase its strength and toughness For non-load-bearing structures without too high strength requirements orbuildings with toughness requirements the amount of recy-cled PP plastic particles can be increased appropriately

33 Autogenous Shrinkage e results of the autogenousshrinkage of mortar specimens as function of curing time areshown in Figure 9

According to the results the autogenous shrinkage ofmortar specimens increased slightly with increase in therecycled PP plastic particles content Compared to PP0 theautogenous shrinkage of PP2 PP4 and PP6 increased by739 1875 and 2708 respectively at day 28 is canbe attributed to the facts that the addition of PP plasticparticles results in the mortar specimens less compact andthe elastic modulus of plastic particles is smaller than that ofnatural aggregates [37] while the autogenous shrinkage ofmortar increases with the decrease of elastic modulus ofaggregates [39] Moreover with the increase of recycled PPplastic particles content the porosity of PP-filled mortarincreases gradually and its stiffness decreases graduallywhich will result in the increase of deformation and au-togenous shrinkage

It can also be seen from Figure 9 that the incorporationof nano-SiO2 had a great influence on the autogenousshrinkage deformation of plastic mortar At day 28 com-pared to PP0 PP2 PP4 and PP6 the autogenous shrinkageof PN0 PN2 PN4 and PN6 groups increased by 46597443 7321 and 11535 respectively is observationwas already verified by Guo et al [40] Nano-SiO2 can refinethe pore size distribution in the plastic mortar [41] whichleads to an increase of capillary tension and a correspondingincrease of autogenous shrinkage At the same time thelarger specific surface area of nano-SiO2 [25 42] leads to therapid combination of nano-SiO2 and the mixed water in themortar which further aggravates the water shortage betweenthe pores of the cement paste reduces the relative humidityinside the cement paste and increases the autogenousshrinkage

Plastic particles peel offfrom the cement slurry

Figure 6 e photograph of the mortarrsquos fracture section


34DryingShrinkage e drying shrinkage curves of plasticmortar are shown in Figure 10

Similar to autogenous shrinkage the drying shrinkage ofmortars increased with the increase in recycled PP plastic

particlesrsquo content Compared to PP0 the drying shrinkage ofPP2 PP4 and PP6 increased by 1206 2206 and3449 respectively at day 28 e reason is that with the

10

8

6

4

2

06040200



7d (PN)28d (PP)28d (PN)

1660

1154

1238

591

1193

1277

2691

27101693

632

543396

Flex

ural

stre

ngth

(MPa

)

Figure 7 Evolution of the flexural strength of mortars as function of curing time (3 7 and 28 d) e error bars represent the standarddeviation of three test specimens

0 20 40 600115

0120

0125

0130

0135

0140

0145

0150

0155

Flex

ural

-com

pres

sive s

tren

gth

ratio


PN0 2 4 6 (28d)PP0 2 4 6 (28d)

647

6231295

22571350

2347

Figure 8 Evolution of the flexural-compression ratio of mortars asfunction of plastic waste content

2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

100200300400500600700800900

100011001200

Aut

ogen

ous s

hrin

kage

10ndash6

PN6PN4PN2PN0

Agedays

PP6PP4PP2PP0

00

Figure 9 e autogenous shrinkage strain of plastic mortar vscuring time


increase of recycled PP plastic particlesrsquo content the internalporosity of mortars increases gradually and free water andcapillary water in mortar are easier to evaporate [43] and thedrying shrinkage deformation is greater It can also be seenfrom Figure 10 that the drying shrinkage deformation ofplastic mortar can be decreased by adding nano-SiO2Compared to PP0 PP2 PP4 and PP6 the drying shrinkageof PN0 PN2 PN4 and PN6 decreased by 606 6111148 and 548 respectively at day 28 is may bebecause the microfilling effect of nano-SiO2 can reduce thecontent of capillary pores in plastic mortar and the

shrinkage of plastic mortar is usually caused by water loss ofcapillary pores e refinement pore size of nano-SiO2 canincrease the difficulty of moisture migration and reduce theshrinkage of plastic mortar [44] In addition in cementhydration process nano-SiO2 consumes a large amount ofCH to form dense C-S-H resulting the plastic mortarrsquosmicrostructure more compact and firm and more resistantto shrinkage deformation due to water dispersion loss [45]e results of this study are consistent with the results ofstudies by Li and Yao [45] Guneyisi et al [46] and Du andPang [47] Furthermore the drying shrinkage of plastic

0 42 6 8 10 12 14 16 18 20 22 24 26 28 300

100200300400500600700800900

1000110012001300140015001600

Dry

ing

shrin

kage

10ndash6

Agedays

PN0PN2PN4PN6

PP0PP2PP4PP6

Figure 10 e drying shrinkage of the plastic mortar vs curing time

(a) (b)

(c) (d)

PPPP

Sand

Sand Cement pasteCement paste

Cement pasteVoids Cement paste

Figure 11 SEM pictures of the mortar specimens at day 28 (a) PP0 (b) PN0 (c) PP6 and (d) PN6


mortar was larger than its autogenous shrinkage whethernano-SiO2 was added or not which is related to the dryingshrinkage mechanism Drying shrinkage is the result of thecombined action of volume shrinkage and internal autog-enous shrinkage caused by the loss or migration of porewater in concrete in the air

35 Microstructural Study e SEM of PP0 PN0 PP6 andPN6 at curing age of 28 days is shown in Figure 11 whichmagnifies the microstructure 350 times and 3000 times It isobserved in Figure 11(a) that there are some obvious cracksand voids at the interface between sand and cement pasteCompared to PN0 the structure of PP0 is less dense andPP0 has more porosity and wider cracks By contrast it isobserved in Figure 11(b) that the structure of PN0 is morecompact with fewer cracksis is due to the size effect of thenano-SiO2 which can fill into the pores between sand andcement paste make the structure denser and improve thestrength of mortar e poor adhesion between the plasticand the cement paste is clearly observed in Figure 11(c)Compared to PP0 PP6 has more porosity and wider cracksand the structure of PP0 is less dense And it is noticeablethat the recycled PP plastic particles can be manually andeasily pulled out from the matrix at the fracture section ofthe mortar specimens which is consistent with the results ofSEM Figure 11(d) shows that the structure of PP-filledmortar with nano-SiO2 is denser with relatively good ad-hesion between the plastic and cement paste Compared toPP0 and PP6 the PN0 and PN6 become more compact anduniform due to the filling effect of the nano-SiO2 and thenimproved strength can be achieved

4 Conclusions

is paper has presented the results of a systematic study onthe influence of nano-SiO2 and recycled PP plastic particlesrsquocontent on physical mechanical and shrinkage properties ofmortar From the results obtained from this study thefollowing conclusions can be drawn

(i) is plastic waste type can be used successfully asaggregate instead of sand in mortar

(ii) With the increase in the replacement ratio of sandby recycled PP plastic particles

(1) e apparent porosity and water absorption ofplastic mortar increase

(2) e apparent specific gravity bulk densitycompressive strength and flexural strengthdecrease

(3) e toughness is improved because the flexural-compressive ratio increases and

(4) e autogenous shrinkage and dry shrinkageincrease

(iii) e addition of nano-SiO2 reduces the porositywater absorption and drying shrinkage of plasticmortar increases its density and flexural-com-pressive ratio and effectively improves the com-pressive and flexural strength of plastic mortar

However the addition of nano-SiO2 also increasesthe autogenous shrinkage of plastic mortarerefore when using nano-SiO2 to enhance themechanical properties of plastic mortar the adverseeffect on autogenous shrinkage strain of plasticmortar should be considered

(iv) e results of SEM show that there is a poor ad-hesion between recycled PP plastic particles andcement paste Nano-SiO2 can make the interfacestructure between cement paste and aggregates(natural aggregate and PP plastic aggregate) morecompact thus improving the mechanical propertiesof plastic mortar

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare no conflicts of interest

Acknowledgments

is work was funded by the National Natural ScienceFoundation of China (Project No 41440018 41977236 and41672278) and the National Natural Science Foundation ofChina Overseas and Hong Kong-Macao Scholar Co-operative Research Foundation (Project No 51728201)

References

[1] D Lithner A Larsson and G Dave ldquoEnvironmental andhealth hazard ranking and assessment of plastic polymersbased on chemical compositionrdquo Science of the Total Envi-ronment vol 409 no 18 pp 3309ndash3324 2011

[2] PlasticsEurope Plasticsmdashthe Facts 2018 an Analysis of Eu-ropean Plastics Production Demand and Waste Data Asso-ciation of Plastic Manufacturers Brussels Bruxelles Belgium2018

[3] D Chen X Huang P Wang X Liang and X ZhouldquoRecycling effective ways of waste plasticsrdquo EngineeringPlastics Application vol 40 pp 92ndash94 2012

[4] A Poonyakan M Rachakornkij M Wecharatana andW Smittakorn ldquoPotential use of plastic wastes for lowthermal conductivity concreterdquo Materials vol 11 no 10p 1938 2018

[5] B Safi M Saidi D Aboutaleb and M Maallem ldquoe use ofplastic waste as fine aggregate in the self-compacting mortarseffect on physical and mechanical propertiesrdquo Constructionand Building Materials vol 43 pp 436ndash442 2013

[6] S Yang X Yue X Liu and Y Tong ldquoProperties of self-compacting lightweight concrete containing recycled plasticparticlesrdquo Construction and Building Materials vol 84pp 444ndash453 2015

[7] C Jacob-Vaillancourt and L Sorelli ldquoCharacterization ofconcrete composites with recycled plastic aggregates frompostconsumer material streamsrdquo Construction and BuildingMaterials vol 182 pp 561ndash572 2018


[8] L Gu and T Ozbakkaloglu ldquoUse of recycled plastics inconcrete a critical reviewrdquo Waste Management vol 51pp 19ndash42 2016

[9] N Saikia and J de Brito ldquoUse of plastic waste as aggregate incement mortar and concrete preparation a reviewrdquo Con-struction and Building Materials vol 34 pp 385ndash401 2012

[10] R Siddique J Khatib and I Kaur ldquoUse of recycled plastic inconcrete a reviewrdquo Waste Management vol 28 no 10pp 1835ndash1852 2008

[11] C Albano N Camacho M Hernandez A Matheus andA Gutierrez ldquoInfluence of content and particle size of wastepet bottles on concrete behavior at different wc ratiosrdquoWasteManag vol 29 pp 2707ndash2716 2009

[12] Z Z Ismail and E A Al-Hashmi ldquoUse of waste plastic inconcrete mixture as aggregate replacementrdquo Waste Man-agement vol 28 no 11 pp 2041ndash2047 2008

[13] J Liang H Chen Y Xiao L Guo and T Jiang ldquoResearch onof compressive performance modified concrete with recycledPP powderrdquo Concrete vol 331 pp 79ndash81 2017

[14] M Frigione ldquoRecycling of PET bottles as fine aggregate inconcreterdquo Waste Management vol 30 no 6 pp 1101ndash11062010

[15] K S Rebeiz and A P Craft ldquoPlastic waste management inconstruction technological and institutional issuesrdquo Re-sources Conservation and Recycling vol 15 no 3-4pp 245ndash257 1995

[16] F Liu H Huang X Xia L Li G Zhong and Y GuoldquoMechanical test on modified concrete with recycled plasticparticles and its numerical simulationrdquo Journal of BuildingMaterials vol 14 no 2 pp 173ndash179 2011

[17] D Foti ldquoPreliminary analysis of concrete reinforced withwaste bottles PET fibersrdquo Construction and Building Mate-rials vol 25 no 4 pp 1906ndash1915 2011

[18] K Hannawi S Kamali-Bernard andW Prince ldquoPhysical andmechanical properties of mortars containing PET and PCwaste aggregatesrdquo Waste Management vol 30 no 11pp 2312ndash2320 2010

[19] S C Kou G Lee C S Poon and W L Lai ldquoProperties oflightweight aggregate concrete prepared with PVC granulesderived from scraped PVC pipesrdquo Waste Managementvol 29 no 2 pp 621ndash628 2009

[20] J Gaitero ldquoMulti-scale study of the fibre matrix interface andcalcium leaching in high performance concreterdquo Ph D thesisUniversity of the Bask Country (UPV-EHU) Bilbao Spain2008

[21] A Porro J S Dolado I Campillo E Erkizia Y D Migueland Y S D Ibarra ldquoEffects of nanosilica additions on cementpastesrdquo in Proceedings of the International Conference Held atthe University of Dundee Applications of Nanotechnology inConcrete Design pp 87ndash96 omas Telford PublishingScotland UK July 2005

[22] K Sobolev I Flores R Hermosillo and L M Torres-Martınez ldquoNanomaterials and nanotechnology for high-performance cement compositesrdquo in Proceedings of the ACISession on Nanotechnology of Concrete Recent Developmentsand Future Perspectives pp 91ndash118 Denver CO USANovember 2006

[23] T Ji ldquoPreliminary study on the water permeability and mi-crostructure of concrete incorporating nano-SiO2rdquo Cementand Concrete Research vol 35 no 10 pp 1943ndash1947 2005

[24] H Li H-g Xiao J Yuan and J Ou ldquoMicrostructure ofcement mortar with nano-particlesrdquo Composites Part BEngineering vol 35 no 2 pp 185ndash189 2004

[25] F Hasan-Nattaj andM Nematzadeh ldquoe effect of forta-ferroand steel fibers on mechanical properties of high-strengthconcrete with and without silica fume and nano-silicardquoConstruction and Building Materials vol 137 pp 557ndash5722017

[26] A Nazari and S Riahi ldquoe effects of SiO2 nanoparticles onphysical and mechanical properties of high strength com-pacting concreterdquo Composites Part B Engineering vol 42no 3 pp 570ndash578 2011

[27] Q Zhao and Y Liu ldquoResearch on mechanical properties ofconcrete with nano-silica rubber and recycled concreterdquoJournal of Henan University (Natural Science) vol 46pp 111ndash115 2016

[28] B-W Jo C-H Kim G-H Tae and J-B Park ldquoCharacter-istics of cement mortar with nano-SiO2 particlesrdquo Con-struction and Building Materials vol 21 no 6 pp 1351ndash13552007

[29] ASTM Standard Test Method for Apparent Porosity WaterAbsorption Apparent Specific Gravity and Bulk Density ofBurned Refractory Brick and Shapes by Boiling Water ASTMC20-00 ASTM International West Conshohocken PA USA2015

[30] ASTM Standard Test Method for Flexural Strength of Hy-draulic-Cement Mortars ASTM C348-18 ASTM In-ternational West Conshohocken PA USA 2018

[31] ASTM Standard Test Method for Compressive Strength ofHydraulic-Cement Mortars Using Portions of Prisms Broken inFlexure ASTM C349-18 ASTM International West Con-shohocken PA USA 2018

[32] ASTM Standard Test Method for Autogenous Strain of Ce-ment Paste andMortar ASTMC1698-09 ASTM InternationalWest Conshohocken PA USA 2014

[33] ASTM Standard Test Method for Drying Shrinkage of MortarContaining Hydraulic Cement ASTM C596-18 ASTM In-ternational West Conshohocken PA USA 2018

[34] N Saikia and J de Brito ldquoMechanical properties and abrasionbehaviour of concrete containing shredded PET bottle wasteas a partial substitution of natural aggregaterdquo Constructionand Building Materials vol 52 pp 236ndash244 2014

[35] L Chen and D F Lin ldquoApplications of sewage sludge ash andnano-SiO2 to manufacture tile as construction materialrdquoConstruction and Building Materials vol 23 no 11pp 3312ndash3320 2009

[36] A Heidari and D Tavakoli ldquoA study of the mechanicalproperties of ground ceramic powder concrete incorporatingnano-SiO2 particlesrdquo Construction and Building Materialsvol 38 pp 255ndash264 2013

[37] Z Dong K Zhao and Y Wang ldquoResearch status of recycledPET concreterdquo Concrete vol 329 pp 100ndash104 2017

[38] J Yang Z Feng and X Jiang ldquoToughness and rigidity ofcomposite additives modified concreterdquo Science Technologyand Engineering vol 15 pp 279ndash283 2015

[39] L Wu N Farzadnia C Shi Z Zhang and H Wang ldquoAu-togenous shrinkage of high performance concrete a reviewrdquoConstruction and BuildingMaterials vol 149 pp 62ndash75 2017

[40] B Guo R Sun and F Zheng ldquoExperimental study of concreteautogenous shrinkage with superfine active silicardquo Ready-Mixed Concrete vol 1 pp 24ndash28 2007

[41] Z Wu C Shi K H Khayat and S Wan ldquoEffects of differentnanomaterials on hardening and performance of ultra-highstrength concrete (UHSC)rdquo Cement and Concrete Compositesvol 70 pp 24ndash34 2016

[42] A Pourjavadi S M Fakoorpoor A Khaloo and P HosseinildquoImproving the performance of cement-based composites


containing superabsorbent polymers by utilization of nano-SiO2 particlesrdquo Materials amp Design vol 42 pp 94ndash101 2012

[43] X Wang W Xu J Feng and P Zhu ldquoExperimental researchon the influence of recycled coarse aggregate on the shrinkageof concreterdquo Concrete vol 310 pp 59ndash62 2015

[44] J Zeng Z Fan and S Wang ldquoComparative research on effectof metakaolin and silica fume on mortar drying shrinkagerdquoJournal of Wuhan University of Technology vol 36 pp 115ndash120 2014

[45] J Li and Y Yao ldquoA study on creep and drying shrinkage ofhigh performance concreterdquo Cement and Concrete Researchvol 31 no 8 pp 1203ndash1206 2001

[46] E Guneyisi M Gesoglu S Karaoglu and K MermerdasldquoStrength permeability and shrinkage cracking of silica fumeand metakaolin concretesrdquo Construction and Building Ma-terials vol 34 pp 120ndash130 2012

[47] H Du and S D Pang ldquoHigh performance cement compositeswith colloidal nano-silicardquo Construction and Building Ma-terials vol 224 pp 317ndash325 2019


International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

Hindawiwwwhindawicom Volume 2018


Active and Passive Electronic Components

VLSI Design



Shock and Vibration


Civil EngineeringAdvances in

Acoustics and VibrationAdvances in



Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Control Scienceand Engineering

Journal of



Journal ofEngineeringVolume 2018

SensorsJournal of



RotatingMachinery


Modelling ampSimulationin EngineeringHindawiwwwhindawicom Volume 2018


Chemical EngineeringInternational Journal of Antennas and

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Navigation and Observation


Hindawi

wwwhindawicom Volume 2018

Advances in

Multimedia

Submit your manuscripts atwwwhindawicom

recycling rate of plastic waste in the areas where in-frastructure construction is relatively perfect For instancethe recycling rate of plastic waste is below 40 in almost allEuropean countries [7] In 2012 the total amount of plasticwaste in municipal solid waste was 317 million tons in theUnited States only 88 of which was recycled [8]erefore how to treat plastic waste efficiently and improvethe recycling rate is a difficult problem to be solved urgently

At present a promisingmethod of recycling plastic wasteis to grind it into recycled plastic particles and mix them intoconcrete or mortar instead of original building materials[5ndash7 9 10] In this way not only plastic waste can be ef-fectively utilized but also the environment can be protectedand thus good economic and social benefits can be achieved

In the past ten years many researchers have studied theapplication of plastic waste particles in concrete or mortarAlbano et al [11] mixed recycled polyethylene terephthalate(PET) into concrete instead of original fine aggregates tostudy its mechanical behavior e results indicated thatPET-filled concrete showed a decrease in compressivestrength splitting tensile strength modulus of elasticity andultrasonic pulse velocity however the water absorptionincreased when volume proportion and particle size of PETincreased Ismail and Al-Hashmi [12] used plastic waste offabriform shapes as a partial replacement for sand and foundthat the results showed a tendency for compressive strengthand flexural strength values of plastic waste concrete mix-tures to decrease below the plain mixtures by increasing theplastic waste ratio When plastic waste ratio in concrete was20 the flexural strength at 28 days curing age was 305lower than that of the reference concrete Liang et al [13] putrecycled PP plastic powder into concrete substituting part offine aggregates and the results showed that the higher thesubstitution rate of PP plastic powder the lower the com-pressive strength and the cube compressive strength of PP-filled concrete was 262 lower than reference concrete at20 of substitution of PP plastic particles Frigione [14]substituted the 5 by weight of fine aggregate (natural sand)in concrete with an equal weight of PET aggregates man-ufactured from the waste unwashed PET bottles (WPET) Itwas found that the WPET concrete displayed similarworkability characteristics compressive strength andsplitting tensile strength slightly lower than the referenceconcrete It can be seen that the addition of plastic wasteparticles has a negative impact on the mechanical propertiesof concrete or mortar However it can improve the ductilityof concrete or mortar because plastic has certain elasticityFor example Rebeiz and Craft [15] incorporated plasticwaste particles into asphalt concrete and found that theincorporation of plastic waste particles can increase thetoughness of asphalt concrete and reduce the occurrence ofcracks Liu et al [16] put recycled ABSPC plastic particlesinto normal concrete to make a plastic modified concreteand found that the ductility of the modified concrete wasimproved Foti [17] made PET bottles into fibers and mixedthem into concrete e results showed that the averagetensile strength of the fiber-reinforced concrete is very highindicating that the ductility of concrete can be improved byadding PET fibers Hannawi et al [18] replaced partial

natural aggregates by polycarbonate (PC) and PET waste inmortar and found that the calculated flexural toughnessfactors increased significantly with increasing volumefraction of PET and PC aggregates Kou et al [19] replacedriver sand with polyvinyl chloride (PVC) plastic wastegranules in percentages of 0 5 15 and 30 by volumein concrete It was found that the concrete prepared withpartial replacement by PVC was lighter more ductile andhad lower drying shrinkage and higher resistance to chlorideion penetration

e plastic-filled concrete or mortar shows a decrease incompressive strength compared to normal concrete whichlimits the application of plastic waste in concrete or mortarAs one of the three emerging technologies in the 21stcentury nanotechnology has developed rapidly and is widelyused in various industries including construction industryPrevious studies have shown that the unique size effect ofnanomaterials can improve the microstructure of the in-terfacial transition zone (ITZ) between hardened cementpaste and aggregates and the strength of concrete is in-creased [20ndash24] erefore the mechanical properties ofplastic-filled concrete can be improved by adding nano-materials Hasan-Nattaj andNematzadeh [25] found that theintroduction of nano-SiO2 in the fiber-reinforced concreteimproved the elastic modulus due to an increase in thecompactness of the cement paste bond with aggregates eexperiments of Nazari and Riahi [26] showed that thestrength and water permeability of the specimens have beenimproved by adding SiO2 nanoparticles in the cement pasteup to 40 wt Zhao and Liu [27] found that the in-troduction of nano-SiO2 in rubber-recycled concreteamazingly improved the microstructure of rubber-recycledconcrete and the mechanical properties of rubber-recycledconcrete are significantly improved Jo et al [28] experi-mentally studied the properties of cement mortars withnano-SiO2 e results showed that nanoscale SiO2 behavednot only as filler to improve mortar cement microstructurebut also as a promoter of pozzolanic reaction

Polypropylene (PP) plastic is one of the most commonlyused consumer plastics which is widely used in food pack-aging industry e PP plastic waste can be ground intoparticles and applied in concrete ormortar which can preventthe environmental contamination caused by plastic waste andrealize recycling plastic waste Based on the above researchresults the purpose of this paper is to study the possibility ofrecycling plastic waste as aggregate partially instead of sand inthe mortar or concrete the effects of recycled PP plasticparticles content and nano-SiO2 on physical mechanical andshrinkage properties of mortar and to analyze the micro-characteristics of PP-filled mortar with nano-SiO2 by scan-ning electron microscopy (SEM) e research results canprovide references for the application of plastic waste andnanotechnology in concrete or mortar

2 Materials and Methods

21 Materials Used e materials used in this work werePortland cement sand a polycarboxylate-based super-plasticizer nano-SiO2 and recycled PP plastic particles e






P W minus D



A W minus D

Dtimes 100 (2)


T D

D minus S (3)

(4) Bulk density

B D

W minus S (4)




L tfs( 1113857times 106 μmm (5)




Percentage () 638 2065 452 270 216 228





l t0( 1113857times 106 μmm (6)







(a) (b)











4

6

8

10

12

14

16

App

aren

t por

osity

()


378

2601

32643162

1971

7202

2461

PP0 2 4 6PN0 2 4 6

0 20 40 60

(a)

PP0 2 4 6PN0 2 4 6

2

3

4

5

6

7

8

9

Wat

er ab

sorp

tion

()


1233

4622

33143133

1966

11702

2467

0 20 40 60

(b)

PP0 2 4 6PN0 2 4 6

19

20

21

22

23

24

App

aren

t spe

cific

gra

vity

(gc

m3 )


305

368

261

438

781

1116

1571

0 20 40 60

(c)

PP0 2 4 6PN0 2 4 6

17

18

19

20

21

22Bu

lk d

ensit

y (g

cm

3 )


771

1364

2052017

011

039

028

0 20 40 60

(d)






(a) (b) (c) (d)


80

70

60

50

40

30

20

10

06040200


Com

pres

sive s

tren

gth

(MPa

)

2036

2038

1170

613

1587

1234

2214

36361566

576

1066257


7d (PN)28d (PP)28d (PN)

















10

8

6

4

2

06040200



7d (PN)28d (PP)28d (PN)

1660

1154

1238

591

1193

1277

2691

27101693

632

543396

Flex

ural

stre

ngth

(MPa

)


0 20 40 600115

0120

0125

0130

0135

0140

0145

0150

0155

Flex

ural

-com

pres

sive s

tren

gth

ratio


PN0 2 4 6 (28d)PP0 2 4 6 (28d)

647

6231295

22571350

2347


2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

100200300400500600700800900

100011001200

Aut

ogen

ous s

hrin

kage

10ndash6

PN6PN4PN2PN0

Agedays

PP6PP4PP2PP0

00





0 42 6 8 10 12 14 16 18 20 22 24 26 28 300

100200300400500600700800900

1000110012001300140015001600

Dry

ing

shrin

kage

10ndash6

Agedays

PN0PN2PN4PN6

PP0PP2PP4PP6


(a) (b)

(c) (d)

PPPP

Sand







4 Conclusions











Data Availability




Acknowledgments


References






















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia






P W minus D



A W minus D

Dtimes 100 (2)


T D

D minus S (3)

(4) Bulk density

B D

W minus S (4)




L tfs( 1113857times 106 μmm (5)




Percentage () 638 2065 452 270 216 228





l t0( 1113857times 106 μmm (6)







(a) (b)











4

6

8

10

12

14

16

App

aren

t por

osity

()


378

2601

32643162

1971

7202

2461

PP0 2 4 6PN0 2 4 6

0 20 40 60

(a)

PP0 2 4 6PN0 2 4 6

2

3

4

5

6

7

8

9

Wat

er ab

sorp

tion

()


1233

4622

33143133

1966

11702

2467

0 20 40 60

(b)

PP0 2 4 6PN0 2 4 6

19

20

21

22

23

24

App

aren

t spe

cific

gra

vity

(gc

m3 )


305

368

261

438

781

1116

1571

0 20 40 60

(c)

PP0 2 4 6PN0 2 4 6

17

18

19

20

21

22Bu

lk d

ensit

y (g

cm

3 )


771

1364

2052017

011

039

028

0 20 40 60

(d)






(a) (b) (c) (d)


80

70

60

50

40

30

20

10

06040200


Com

pres

sive s

tren

gth

(MPa

)

2036

2038

1170

613

1587

1234

2214

36361566

576

1066257


7d (PN)28d (PP)28d (PN)

















10

8

6

4

2

06040200



7d (PN)28d (PP)28d (PN)

1660

1154

1238

591

1193

1277

2691

27101693

632

543396

Flex

ural

stre

ngth

(MPa

)


0 20 40 600115

0120

0125

0130

0135

0140

0145

0150

0155

Flex

ural

-com

pres

sive s

tren

gth

ratio


PN0 2 4 6 (28d)PP0 2 4 6 (28d)

647

6231295

22571350

2347


2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

100200300400500600700800900

100011001200

Aut

ogen

ous s

hrin

kage

10ndash6

PN6PN4PN2PN0

Agedays

PP6PP4PP2PP0

00





0 42 6 8 10 12 14 16 18 20 22 24 26 28 300

100200300400500600700800900

1000110012001300140015001600

Dry

ing

shrin

kage

10ndash6

Agedays

PN0PN2PN4PN6

PP0PP2PP4PP6


(a) (b)

(c) (d)

PPPP

Sand







4 Conclusions











Data Availability




Acknowledgments


References






















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia




l t0( 1113857times 106 μmm (6)







(a) (b)











4

6

8

10

12

14

16

App

aren

t por

osity

()


378

2601

32643162

1971

7202

2461

PP0 2 4 6PN0 2 4 6

0 20 40 60

(a)

PP0 2 4 6PN0 2 4 6

2

3

4

5

6

7

8

9

Wat

er ab

sorp

tion

()


1233

4622

33143133

1966

11702

2467

0 20 40 60

(b)

PP0 2 4 6PN0 2 4 6

19

20

21

22

23

24

App

aren

t spe

cific

gra

vity

(gc

m3 )


305

368

261

438

781

1116

1571

0 20 40 60

(c)

PP0 2 4 6PN0 2 4 6

17

18

19

20

21

22Bu

lk d

ensit

y (g

cm

3 )


771

1364

2052017

011

039

028

0 20 40 60

(d)






(a) (b) (c) (d)


80

70

60

50

40

30

20

10

06040200


Com

pres

sive s

tren

gth

(MPa

)

2036

2038

1170

613

1587

1234

2214

36361566

576

1066257


7d (PN)28d (PP)28d (PN)

















10

8

6

4

2

06040200



7d (PN)28d (PP)28d (PN)

1660

1154

1238

591

1193

1277

2691

27101693

632

543396

Flex

ural

stre

ngth

(MPa

)


0 20 40 600115

0120

0125

0130

0135

0140

0145

0150

0155

Flex

ural

-com

pres

sive s

tren

gth

ratio


PN0 2 4 6 (28d)PP0 2 4 6 (28d)

647

6231295

22571350

2347


2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

100200300400500600700800900

100011001200

Aut

ogen

ous s

hrin

kage

10ndash6

PN6PN4PN2PN0

Agedays

PP6PP4PP2PP0

00





0 42 6 8 10 12 14 16 18 20 22 24 26 28 300

100200300400500600700800900

1000110012001300140015001600

Dry

ing

shrin

kage

10ndash6

Agedays

PN0PN2PN4PN6

PP0PP2PP4PP6


(a) (b)

(c) (d)

PPPP

Sand







4 Conclusions











Data Availability




Acknowledgments


References






















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia






4

6

8

10

12

14

16

App

aren

t por

osity

()


378

2601

32643162

1971

7202

2461

PP0 2 4 6PN0 2 4 6

0 20 40 60

(a)

PP0 2 4 6PN0 2 4 6

2

3

4

5

6

7

8

9

Wat

er ab

sorp

tion

()


1233

4622

33143133

1966

11702

2467

0 20 40 60

(b)

PP0 2 4 6PN0 2 4 6

19

20

21

22

23

24

App

aren

t spe

cific

gra

vity

(gc

m3 )


305

368

261

438

781

1116

1571

0 20 40 60

(c)

PP0 2 4 6PN0 2 4 6

17

18

19

20

21

22Bu

lk d

ensit

y (g

cm

3 )


771

1364

2052017

011

039

028

0 20 40 60

(d)






(a) (b) (c) (d)


80

70

60

50

40

30

20

10

06040200


Com

pres

sive s

tren

gth

(MPa

)

2036

2038

1170

613

1587

1234

2214

36361566

576

1066257


7d (PN)28d (PP)28d (PN)

















10

8

6

4

2

06040200



7d (PN)28d (PP)28d (PN)

1660

1154

1238

591

1193

1277

2691

27101693

632

543396

Flex

ural

stre

ngth

(MPa

)


0 20 40 600115

0120

0125

0130

0135

0140

0145

0150

0155

Flex

ural

-com

pres

sive s

tren

gth

ratio


PN0 2 4 6 (28d)PP0 2 4 6 (28d)

647

6231295

22571350

2347


2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

100200300400500600700800900

100011001200

Aut

ogen

ous s

hrin

kage

10ndash6

PN6PN4PN2PN0

Agedays

PP6PP4PP2PP0

00





0 42 6 8 10 12 14 16 18 20 22 24 26 28 300

100200300400500600700800900

1000110012001300140015001600

Dry

ing

shrin

kage

10ndash6

Agedays

PN0PN2PN4PN6

PP0PP2PP4PP6


(a) (b)

(c) (d)

PPPP

Sand







4 Conclusions











Data Availability




Acknowledgments


References






















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia





(a) (b) (c) (d)


80

70

60

50

40

30

20

10

06040200


Com

pres

sive s

tren

gth

(MPa

)

2036

2038

1170

613

1587

1234

2214

36361566

576

1066257


7d (PN)28d (PP)28d (PN)

















10

8

6

4

2

06040200



7d (PN)28d (PP)28d (PN)

1660

1154

1238

591

1193

1277

2691

27101693

632

543396

Flex

ural

stre

ngth

(MPa

)


0 20 40 600115

0120

0125

0130

0135

0140

0145

0150

0155

Flex

ural

-com

pres

sive s

tren

gth

ratio


PN0 2 4 6 (28d)PP0 2 4 6 (28d)

647

6231295

22571350

2347


2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

100200300400500600700800900

100011001200

Aut

ogen

ous s

hrin

kage

10ndash6

PN6PN4PN2PN0

Agedays

PP6PP4PP2PP0

00





0 42 6 8 10 12 14 16 18 20 22 24 26 28 300

100200300400500600700800900

1000110012001300140015001600

Dry

ing

shrin

kage

10ndash6

Agedays

PN0PN2PN4PN6

PP0PP2PP4PP6


(a) (b)

(c) (d)

PPPP

Sand







4 Conclusions











Data Availability




Acknowledgments


References






















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia
















10

8

6

4

2

06040200



7d (PN)28d (PP)28d (PN)

1660

1154

1238

591

1193

1277

2691

27101693

632

543396

Flex

ural

stre

ngth

(MPa

)


0 20 40 600115

0120

0125

0130

0135

0140

0145

0150

0155

Flex

ural

-com

pres

sive s

tren

gth

ratio


PN0 2 4 6 (28d)PP0 2 4 6 (28d)

647

6231295

22571350

2347


2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

100200300400500600700800900

100011001200

Aut

ogen

ous s

hrin

kage

10ndash6

PN6PN4PN2PN0

Agedays

PP6PP4PP2PP0

00





0 42 6 8 10 12 14 16 18 20 22 24 26 28 300

100200300400500600700800900

1000110012001300140015001600

Dry

ing

shrin

kage

10ndash6

Agedays

PN0PN2PN4PN6

PP0PP2PP4PP6


(a) (b)

(c) (d)

PPPP

Sand







4 Conclusions











Data Availability




Acknowledgments


References






















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia




0 42 6 8 10 12 14 16 18 20 22 24 26 28 300

100200300400500600700800900

1000110012001300140015001600

Dry

ing

shrin

kage

10ndash6

Agedays

PN0PN2PN4PN6

PP0PP2PP4PP6


(a) (b)

(c) (d)

PPPP

Sand







4 Conclusions











Data Availability




Acknowledgments


References






















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia




4 Conclusions











Data Availability




Acknowledgments


References






















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia


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