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BENDABLE CONCRETE: A REVIEWSagar Gadhiya1*, T N Patel2 and Dinesh Shah3

1 PG Student, Civil Engineering Department, Sardar Vallabhbhai Institute of Technology, Vasad, Gujarat 388306.2 Associate Professor, Civil Engineering Department, Sardar Vallabhbhai Institute of Technology, Vasad, Gujarat 388306.3 Associate Professor, Architecture Department, Sardar Vallabhbhai Institute of Technology, Vasad, Gujarat 388306.

*Corresponding author:Sagar Gadhiya sgrgadhia@gmail.com

ISSN 2319 – 6009 www.ijscer.comVol. 4, No. 1, February 2015

© 2015 IJSCER. All Rights Reserved

Int. J. Struct. & Civil Engg. Res. 2015

Review Article

INTRODUCTIONConventional concretes are almost un-bendable and have a strain capacity of only0.1% making them highly brittle and rigid. Thislack of bendability is a major cause of failureunder strain and has been a pushing factor inthe development of an elegant material namely,bendable concrete also known as EngineeredCementitious Composites abbreviated asECC. This material is capable to exhibitconsiderably enhanced flexibility. A bendableconcrete is reinforced with micromechanicallydesigned polymer fibres.

ECC is made from the same basicingredients as conventional concrete but with

Bendable concrete also known as Engineered Cementitious Composites abbreviated as ECCis class of ultra-ductile fiber reinforced cementitious composites, characterized by high ductilityand tight crack width control. This material is capable to exhibit considerably enhanced flexibility.An ECC has a strain capacity of more than 3% and thus acts more like a ductile metal ratherthan like a brittle glass. A bendable concrete is reinforced with micromechanically designedpolymer fibres. In this paper literature survey of fresh and mechanical properties of differentECC mixtures are evaluated by incorporating supplementary cementitious material, i.e., fly ashand different aggregate type considering various parameters, i.e., types of fibers, compressivestrength, flexural strength and deflection.

Keywords: Bendable Concrete, ECC-Engineered Cementitious Composites, Deflection,Compressive strength, Flexural strength

the addition of High-Range Water Reducing(HRWR) agent is required to impart goodworkability. However, coarse aggregates arenot used in ECCs (hence it is a mortar ratherthan concrete). The powder content of ECC isrelatively high. Cementitious materials, suchas fly ash, silica fume, blast furnace slag, silicafume, etc., may be used in addition to cementto increase the paste content. Additionally,ECC uses low amounts, typically 2% byvolume, of short, discontinuous fibres. ECCincorporates super fine silica sand and tinyPolyvinyl Alcohol-fibres covered with a very thin(nanometer thick), slick coating. This surface

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coating allows the fibre to begin slipping whenthey are over loaded so they are not fracturing.

curing conditions, including air curing, 3% CO2

concentration curing, cyclic wet/dry (dry under3% CO2 concentration) curing and watercuring. For all curing conditions, deflectioncapacity after self-healing can recover or evenexceed that from virgin samples with almostall precracking ages. After self-healing, flexuralstiffness was also retained significantlycompared with that from virgin samples, eventhough the level of retaining decreases withthe increase of precracking time. The flexuralstrength increases for samples pre-crackedat the age of 14 days and 28 days, presumablydue to continuous hydration of cementitiousmaterials afterwards. Furthermore, it waspromising to utilize nanoclay as distributedinternal water reservoirs to promote self-healing behavior within ECC without relying onexternal water supply.

Victor C Li et al. (2012) carried outexperimental study to improve the fibredistribution by adjusting the mixing sequence.With the standard mixing sequence, fibres areadded after all solid and liquid materials aremixed. The undesirable plastic viscositybefore the fibre addition may cause poor fibredistribution and results in poor hardenedproperties. With the adjusted mixingsequence, the mix of solid materials with theliquid material is divided into two steps andthe addition of fibres is between the two steps.In this paper, the influence of different watermixing sequences was investigated bycomparing the experimental results of theuniaxial tensile test and the fibre distributionanalysis.

The result was concluded that comparedwith the standard mixing sequence, theadjusted mixing sequence increases the

Figure 1: Response of ECCunder Flexural Loading

It prevents the fibre from rupturing whichwould lead to large cracking. Thus an ECCdeforms much more than a normal concretebut without fracturing. Figure 1 represents thebehavior of ECC under flexural loading and itcan be seen that the beam can deform wellwithout direct failure. The different ingredientsof ECC work together to share the appliedload. ECC has proved to be 50 times moreflexible than traditional concrete, and 40 timeslighter, which could even influence designchoices in skyscrapers. Additionally, theexcellent energy absorbing properties of ECCmake it especially suitable for critical elementsin seismic zones.

LITERATURE REVIEWQian et al. (2010) carried out experimentalstudy to investigate the self-healing behaviorof ECC with focus on the influence of curingcondition and precracking time. Four-pointbending tests was used to pre crack ECCbeams at different age, followed by different

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tensile strain capacity and ultimate tensilestrength of ECC and improves the fibredistribution.

Yu Zhu et al. (2012) carried out anexperimental study to develop a kind of greenECC with high tensile ductility and strongenough matrix strength, especially at early age.A series of investigations was carried out toevaluate mechanical properties and dryingshrinkage of ECC with 70% combinationmineral admixtures of FA and groundgranulated blast furnace slag (SL). Four ECCmixtures with constant W/B of 0.25 areprepared with combined inclusion of FA andSL as constant cement replacement level of70%. The laboratory measurements arecarried out, including direct tensile test, four-point bending test, and compressive strengthand drying shrinkage.

The experimental results show that ECCwith combination mineral admixtures canachieve strain hardening behavior, tensilecapacity of ECC can be more than 2.5% at 90days. Meanwhile, compared to ECC only withfly ash, slag and fly ash can effectively increasecompressive strength of ECC, especially atearly age. Incorporating SL into matrix canslightly increase drying shrinkage of ECC.However, among four ECC mixtures, ECC with30% SL and 40% FA presents the lowestdrying shrinkage at later ages.

Jun Zhang et al. (2013) carried out anexperimental study on the potentialapplications of the fibre reinforced engineeredcementitious composite with characteristic oflow drying shrinkage (LSECC) in concretepavements for the purpose of eliminating jointsthat are normally used to accommodate

temperature and shrinkage deformation. It wasfound that a composite slab containing bothplain concrete and LSECC, with steel bars atthe LSECC/concrete interface, and designedconstruction procedures, it is possible tolocalize the tensile cracks into the LSECCstrip instead of cracking in adjacent concreteslab. The crucial problem that interfacial failurein composite slab was prevented by usingreinforcing bars across the interfaces. Due tothe strain-hardening and high strain capacityof the LSECC, the overall strain capacity andthe integrity of the composite slab can besignificantly improved. The temperature andshrinkage deformations can beaccommodated by adequate selection on thelength ratio of LSECC strip and concrete slab.

Mustafa Sahmaran et al. (2013) carried outexperimental work for 36 different ECCmixtures to evaluate the combined effects ofthe following factors on workability andrheological properties: water-binder (w/b),sand-binder (s/b), superplasticizer-binder (SP/b) ratios and maximum aggregate size(Dmax). A mini-slump cone, a Marsh cone anda rotational viscometer was used to evaluatethe workability and rheological properties ofECC mixtures. Compressive strength and fourpoint bending tests was used for mechanicalcharacteristics of ECC mixtures at 28 days.The effects of studied parameters (w/b, s/b,SP/b and Dmax) was characterized andanalyzed using regression models, which canidentify the primary factors and theirinteractions on the measured properties.Statistically significant regression models wasdeveloped for all tested parameters as functionof w/b, s/b, SP/b and Dmax. To find out thebest possible ECC mixture under the range of

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parameters investigated for the desiredworkability and mechanical characteristics, amulti-objective optimization problem wasdefined and solved based on the developedregression models.

Experimental results indicate that w/b, s/band SP/b parameters affect the rheologicaland workability properties. On the other hand,for the range of studied aggregate sizes, Dmaxis found to be statistically insignificant on therheological and workability properties of ECC,also in addition to that the mid-span beamdeflection capacities, which reflect materialductility, of ECC mixtures varied noticeably withthe change of s/b and Dmax designparameters. Both of these two parametersnegatively affect the deflection capacity of theECC mixtures. The other parameters havealmost no effect on the mid-span beamdeflection capacities of ECC mixtures.

Yu Zhu et al. (2014) carried outexperimental study to investigate themechanical properties of ECC produced byhigh volume mineral admixtures which are flyash, slag and silica fume. Emphasis of thisstudy is placed on building the correlationbetween compressive strength and theparameters obtained in load–deflection curvesof 12 different ECC mixtures in binary andternary system of binder materials withdifferent mineral admixtures (FA, SL and silicafume) and to build the correlation betweencompressive strength and durability of ECC.The water-binder materials ratio (W/B) is keptat 0.25 for various ECC mixtures. Thereplacement levels of different mineraladmixtures in all ECCs in binary systems ofbinder materials are 50%, 60%, 70% and 80%,respectively (FA + cement and SL + cement).

In ternary system (FA + SL + cement and FA +SF + cement), the total replacement of mineraladmixtures is 70%, the ratios of FA/SL andFA/SF are different in ECC mixtureproportions. The toughness behavior andcompressive strength of 12 different ECCmixtures are firstly measured by fourpointbending test and compressive strength test,respectively.

The results indicate that the compressivestrength has an inverse relationship withdeflection, toughness index and fractureenergy, respectively; but the compressivestrength have an direct proportional relationwith flexural strength, first cracking load, andpeaking load, respectively.

Additionally, in the binary system of bindermaterials, the ductility of ECC can be obviouslyimproved by introducing high volume fly ashand slag replacing the cement, respectively.However, the compressive strength of ECCwith fly ash and slag can reduce 40% and 14%,respectively. For the ternary system of bindermaterials with replacement 70% of cement, thecombination of fly ash and slag can keep notonly the excellent ductility of ECC, but alsoenough stronger matrix strength. Meanwhile,the combination of fly ash and silica fume onlyincrease the compressive strength, butweaken the toughness of ECC.

Tahir Kemal Erdem (2014) carried outexperimental work to study size effect on theresidual properties of ECC was investigatedon the specimens exposed to hightemperatures up to 800°C. Cylindricalspecimens having different sizes wereproduced with a standard ECC mixture.Changes in pore structure, residual

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compressive strength and stress–strain curvesdue to high temperatures were determinedafter air cooling. Standard ECC mixture (M45)with a fly ash-cement ratio (FA/C) of 1.2 bymass was used in this investigation which wasprepared in a standard mortar mixer at waterto cementitious material ratio of 0.27.

Experimental results indicate that despitethe increase of specimen size, no explosivespalling occurred in any of the specimensduring the high temperature exposure.Increasing the specimen size and exposuretemperature decreased the compressivestrength and stiffness. Percent reduction incompressive strength and stiffness due to hightemperature was similar for all specimen sizes.

Bensaid Boulekbache et al. (2012) carriedout experimental study to examining theinfluence of the paste yield stress andcompressive strength on the behavior of Fibre-Reinforced Concrete (FRC) versus directshear. The parameters studied are the steelfibre contents, the aspect ratio of fibres andthe concrete strength. Prismatic specimens ofdimensions 10 * 10 * 35 cm made of concreteof various yield stress reinforced with steelfibres hooked at the ends with three fibrevolume fractions (i.e., 0%, 0.5% and 1%) andtwo aspects ratio (65 and 80) were tested todirect shear. Three types of concretes withvarious compressive strength and yield stresswere tested, an Ordinary Concrete (OC), aSelf-Compacting Concrete (SCC) and a HighStrength Concrete (HSC). The concretestrengths investigated include 30 MPa for OC,60 MPa for SCC and 80 MPa for HSC.

The results show that the shear strength andductility are affected and have been improved

very significantly by the fibre contents, fibreaspect ratio and concrete strength. As thecompressive strength and the volume fractionof fibres increase, the shear strengthincreases. The ductility was much higher forordinary and self-compacting.

Soutsos et al. (2012) carried outexperimental study on commercially availablesteel and synthetic fibres. Flexural stress –deflection relationships have been used todetermine: flexural strength, flexural toughness,equivalent flexural strength, and equivalentflexural strength ratio.

The flexural toughness of concrete wasfound to increase considerably when steel andsynthetic fibres were used. However, equaldosages of different fibres did not result inspecimens with the same flexural toughness.

Pajak and Ponikiewski (2013) carried outexperimental study to investigate the flexuralbehavior of self-compacting concretereinforced with straight and hooked end steelfibres at levels of 0.5%, 1.0% and 1.5% andcompare it to Normally Vibrated Concrete(NVC). The laboratory tests were determinedaccording to RILEM TC 162-TDFrecommendation.

The flexural behavior of SCC appeared tobe comparable to NCV, where the increase offibres volume ratio cause the increase in prepeak and postpeak parameters of SCC.Nevertheless, the type of steel fibres influencesmuch this dependency. However, the SCCachieves the maximum crack mouthdisplacement for lower deflections than NVC.

Albert et al. (2014) carried out experimentalstudy on Polyolefin fibre-reinforced concreteenhanced with steel-hooked fibres in low

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proportions. Four types of conventionalfibrereinforced concrete with steel andpolyolefin fibres were produced on the basisof the same self-compacting concrete alsomanufactured as reference. These concretemixtures were manufactured separately withthe same fibre contents being subsequentlyused for two more hybrid mixtures. Fractureproperties, in addition to fresh and mechanicalproperties, were assessed.

The result revealed that it is possible toproduce a hybrid fibre reinforced self-compacting concrete with a combination ofhooked steel fibres and macro polyolefinfibres, preserving the high performance freshproperties within the most common self-compacting requirements. It should also benoted that the addition of Fibres did notnoticeably change the compressive strength,indirect tensile strength or modulus of elasticityof the reference SCC for any of the amounts,types or combination of fibres used.

LITERATURE SUMMARY• Compressive strength is directly related to

the Flexural strength and inversely relatedto deflection but if the compressive strengthis kept in limited ranges, the desirable valueof related parameters can be obtained.

• Compressive strength decreases with theincrease in the cementitious material i.e. flyash, silica fume, LP etc.

• Incorporation SL into matrix can effectivelyincrease compressive strength at all ages,especially at early age

• The water to cementitious material (w/c)ratio 0.27 gives the best result.

• Compared with the standard mixingsequence, by adjusting mixing sequenceincreases the tensile strain capacity andultimate tensile strength of ECC andimproves the fibre distribution.

• Increasing the specimen size and exposuretemperature decreased the compressivestrength and stiffness.

• In Hybrid fibres mixture the compressivestrength decreases with decreasing flexuralstrength.

• The ductility in direct shear depends on thefibre orientation and is significantlyimproved when the fibres are perpendicularto the shear plane.

• The Polycarboxylate based superplasticizermortar mixes give more workability andhigher compressive strength at all agescompare with sulphonated melamineformaldehyde based SP.

REFERENCES1. Alberti M G, Enfedaque A, Galvez J C,

Canovas M F and Osorio I R (2014),“Polyolefin fibrereinforced concreteenhanced with steel-hooked fibres in lowproportions”, Journal of Materials andDesign, Vol. 60, pp. 57–65.

2. Bensaid Boulekbache, Mostefa Hamrat,Mohamed Chemrouk and SofianeAmziane (2012), “Influence of yield stressand compressive strength on direct shearbehaviour of steel fibrereinforcedconcrete”, Journal of Construction andBuilding Materials, Vol. 27, pp. 6–14.

3. Jian Zhou, Shunzhi Qian, Guang Ye,Oguzhan Copuroglu, Klaas van Breugel

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and Victor C Li (2012), “Improved fibredistribution and mechanical properties ofengineered cementitious composites byadjusting the mixing sequence”, Journalof Cement & Concrete Composites, Vol.34, pp. 342–348.

4. Jun Zhang, Zhenbo Wang and XiancunJu (2013), “Application of ductile fibrereinforced cementitious composite in jointless concrete pavements”, journal ofComposites, Part B, Vol. 50, pp. 224–231.

5. Maulin Bipinchandra Mavani M E (2012),Thesis, “Fresh/Mechanical/ DurabilityProperties and Structural Performance ofEngineered Cementitious Composite(ECC)”, Ryerson University.

6. Mustafa Sahmaran, Zafer Bilici, ErdoganOzbay, Tahir K. Erdem, Hasan E Yuceland Mohamed Lachemi (2013),“Improving the workability and rheologicalproperties of Engineered CementitiousComposites using factorial experimentaldesign”, Journal of Composites: Part B,Vol. 45, pp. 356-368.

7. Pajak M and Ponikiewski T (2013),“Flexural behaviour of self-compactingconcrete reinforced with different typesof steel fibres”, Journal of Constructionand Building Materials, Vol. 47, pp. 397-408.

8. Qian S Z, Zhou J and Schlangen E(2010), “Influence of curing condition and

precracking time on the self-healingbehaviour of Engineered CementitiousComposites”, Journal of Cement &Concrete Composites, Vol. 32, pp. 686–693.

9. Soutsos M T, Le T T and LampropoulosA P (2012), “Flexural performance of fibrereinforced concrete made with steel andsynthetic fibres”, Journal of Constructionand Building Materials, Vol. 36, pp. 704-710.

10. Tahir Kemal Erdem (2014), “Specimensize effect on the residual properties ofengineered cementitious compositessubjected to high temperatures”, Journalof Cement & Concrete Composites, Vol.45, pp. 1–8.

11. Yu Zhu, Yingzi Yang and Yan Yao (2012),“Use of slag to improve mechanicalproperties of engineered cementitiouscomposites (ECCs) with high volumes offly ash”, Journal of Construction andBuilding Materials, Vol. 36, pp. 1076-1081.

12. Yu Zhu, Zhaocai Zhang, Yingzi Yang andYan Yao (2014), “Measurement andcorrelation of ductility and compressivestrength for engineered cementitiouscomposites (ECC) produced by binaryand ternary systems of binder materials:Fly ash, slag, silica fume and cement”,Journal of Construction and BuildingMaterials, Vol. 68, pp. 192-198.