• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.05b
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• pp.93-96
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• 2009

This study is to examine a change of quality and a material performance of fiber reinforced cement composite for mass production. It is necessary to make Strain-hardening cementitious composite(SHCC) by batcher plant for ready-mixed concrete and use the performance of SHCC which made based on laboratory level. This study makes a comparative performance of press and mechanics that is the property of Strain-hardening by direct tension. In case of making by batcher plant. This experiment has demonstrated that even if it takes long after being mixed small and compared with the one which made based on laboratory, it has a tendency to be dissatisfied with fiver's dispersion and lower its performance of Strain-hardening. The reason why the material performance of SHCC for mass production went down is through SHCC that mixed sometimes matrix's viscosity and fiber's dispersion.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.2
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• pp.95-103
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• 2012

In order to improve the dimensional stability and mechanical performance of cement-based composites, the effect of an expansive admixture based on calcium sulphoaluminate (CSA) on the shrinkage and mechanical properties of strain-hardening cement-based composite (SHCC), which exhibits multiple cracks and pseudo strain-hardening behavior in the direct tension, is investigated. Polyethylene fibers reinforced SHCC mixtures with three levels (30, 70, and 100MPa) of compressive strength were compared through free shrinkage, compressive strength, flexural strength, and direct tensile strength measurements. The SHCC mixtures were cast with and without replacing 10% of Portland cement content with CSA admixture. According to test results, CSA admixture is effective in reducing shrinkage of SHCC material. SHCC mixture with CSA admixture exhibited a little higher strength than companion mixture without CSA admixture.

• Journal of the Korea Concrete Institute
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• v.24 no.4
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• pp.361-368
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• 2012

Required performance for repair materials are strength, ductility, durability and bonding with the substrate concrete. Various kinds of fiber-reinforced cement composites (FRCCs) have been developed and used as repair materials. Strain-hardening cement based composites (SHCC) is one of the effective repair materials that can be used to improve crack-damage tolerance of reinforced concrete (RC) structures. SHCC is a superior FRCC that has multiple cracking characteristic and pseudo strain-hardening behavior. The expansive admixture, which can be used to reduce shrinkage in SHCC materials with less workability by controlling interfacial bonding performance between SHCC and substrate concrete. For the application of SHCC as a repair material to RC structures, this study investigates the flexural performance of expansive SHCC-layered concrete beam. Test variables include the replacement levels of expansive admixture (0 and 10%), repair thickness (30 and 40 mm), and compressive strength of SHCC (30, 70 and 100 MPa). Four point bending tests on concrete beams strengthened with SHCCs were carried out to evaluate the contribution of SHCC on the flexural capacity. The result suggested that expansive SHCC materials can be used for repairing and strengthening of concrete infrastructures.

• Journal of the Korean Institute of Educational Facilities
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• v.19 no.5
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• pp.29-36
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• 2012

The goals of this study are to develop a sprayable strain-hardening cement composite (SHCC) and to investigate the potential of the sprayable SHCC for packing the joint between existing R/C building and seismic retrofit elements. This paper provides the procedure for the development of a sprayable SHCC, test results of fresh properties required to a sprayable SHCC, and mock-up test results of developed sprayable SHCC. Control mixture of polyvinyl alcohol (PVA) fiber-reinforced SHCC (PVA-SHCC) was predetermined based on available research results. The pumpability and sprayability of the SHCC mixture were depended on the fluid property of fresh SHCC mixture. In this study, the effects of admixtures such as AE agent and fly ash on the rheological and rebound properties of control SHCC mixture were investigated to determine a sprayable SHCC mixture. Flow values and air content during shotcreting procedure of sprayable SHCC were also evaluated. The results show that flow or flowability and amount of air of three SHCC mixtures decreased almost linearly according to shotcreting procedure from mixer to nozzle. And the pumpability and sprayability of mixture with AE agent and low amounts of fly ash were superior to the those of SHCC. Mock-up test result show that developed sprayable SHCC indicates much improved workability and shotcrete construction period than conventional method(nonshrinkage mortar).

• Journal of the Korea Concrete Institute
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• v.28 no.1
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• pp.41-48
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• 2016

This research investigates the effects of shrinkage reducing agent (SRA) on the mechanical behavior of strain-hardening cement composite (SHCC). SHCC material with specified compressive strength of 50 MPa was mixed and tested in this study. All SHCC mixes reinforced with volume fraction of 2.2% polyvinyl alcohol (PVA) fiber and test variables are type and dosage of shrinkage reducing agents. The shrinkage reducing materials used in this study are phase change material as the thermal stress reducing materials that have the ability to absorb or release the heat. The effect of SRA was examined based on the change in length caused by shrinkage and hardened mechanical properties, specially compressive, tensile and flexural behaviors, of SHCC material. It was noted that SRA reduces change in length caused by shrinkage at early age. SRA can also improve the tensile and flexural strengths and toughness of SHCC material used in this study.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.25-26
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• 2010

Strain-hardening cementitious composite(SHCC) has been expected excellent reinforcement performance in beam-column joint area. The main variables considered include the type of cement composites(premixed mortar, SHCC with hybrid fiber) and shape and existence of the tie bar. As the result of the tests, existence of the tie bar specimen showed better overall behavior than another.

• Journal of the Korea Concrete Institute
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• v.25 no.4
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• pp.371-379
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• 2013

This paper investigates the cracking and tension-stiffening behavior of 100 MPa shrinkage-compensated strain-hardening cement composite (SHCC) and conventional concrete tie elements in monotonic and cyclic tension. Strain and surface crack formation of tension ties were monitored with two strain displacement transducers and a photo microscope with a lens of magnification 50 times. Three different cement composites such as conventional concrete, shrinkage-compensated SHCC, and normal SHCC were used in the tie specimens to investigate the influence of the cement composite type on the tension stiffening and cracking behavior. Test results indicated that initial shrinkage of the ultra high-strength cement composites is greatly reduced as the 10% replacement of cement by the shrinkage-compensating admixture based on calcium sulfo-aluminate (CSA). The test results on the SHCC tension ties showed that the first cracking load decreases proportionally to the initial shrinkage strain. Reinforced ultra high-strength SHCC ties with the initial shrinkage compensation exhibited improved tension stiffening and smaller crack spacings, i.e. the reduction in crack width. Cyclic loading did not have a significant effect on tension stiffening and cracking behavior of tension ties with normal concrete and SHCC materials.

• Journal of the Korea Concrete Institute
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• v.24 no.3
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• pp.233-240
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• 2012

Hybrid SHCC is being researched actively for its excellent performance in controlling macro and micro cracks using macro and micro fibers, respectively. However, a significant autogenous shrinkage of SHCC is expected since it possesses high unit cement volume in its mix proportion, resulting in autogenous shrinkage cracks. Therefore, this study was performed to evaluate mechanical property of shrinkage-reducing type hybrid SHCC mixed together with steel fiber and PE fiber with excellent micro/macro crack controlling performance. In order to evaluate mechanical property of shrinkage-reducing type hybrid SHCC, replacement ratios of 0% and 10% of expansive admixture and water to binder ratios of 0.45, 0.3, and 0.2 were considered as variables. Then, shrinkage, compressive, flexural, and direct tensile tests were performed. The test results showed that mix proportion with W/B 0.3 significantly improved mechanical performance by using 10% replacement of expansive admixture.

• Journal of the Korea Concrete Institute
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• v.24 no.1
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• pp.3-14
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• 2012

This paper describes experimental results on the seismic performance of SHCC (strain-hardening cement composite) infill wall for improving damage tolerance capacity of non-ductile frame. To investigate the effect of tensile strain capacity and cracking behavior of SHCC materials on the shear behavior of SHCC infill wall, three infill walls were fabricated and tested under cyclic loading. The test parameter in this study is a type of cement composites; concrete and SHCCs. The two types of SHCC materials were prepared for infill walls. In order to induce crack damages into the mid-span of the infill wall, each infill wall had two 100-mm-deep-notches on both sides. Test results indicated that SHCC infill walls showed superior crack control capacities and much larger drift ratios at the peak loads than RC (reinforced concrete) infill wall, as expected. In particular, due to the bridging actions of the reinforcing fibers, SHCC matrix used in this study would delay the stiffness degradation of infill wall after the first inclined cracking. Moreover, from the damage classes based on the cracks' maximum width in the infill walls, it was observed that PIW-SHD specimen possessed nearly threefold seismic capacities compared to PIW-SLD specimen. Also, from the results on the strain of diagonal reinforcements, it can be concluded that the SHCC matrix would resist a part of tensile stresses transferred along steel rebar in the infill wall.

• Journal of the Korea Concrete Institute
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• v.22 no.5
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• pp.727-736
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• 2010

This paper describes results of an preliminary study to produce strain hardening cement-based composites (SHCCs)with consideration of sustainability for infrastructure applications. The aims of this study are to evaluate the influence of recycled materials on the mechanical characteristics of SHCCs, such as compressive, four-point bending, and direct tensile behaviors, and to give basic data for constitutive model for analyzing and designing infra structures with SHCCs. In this study, silica sand, cement, and PVA fibers, were partially replaced with recycled sand, fly-ash, and FET fibers in the mixture of SHCCs, respectively. Test results indicated that fly-ash could improve both bending and direct tensile performance of SHCCs due to increasing chemical bond strength at the interface between PVA fibers and cement matrices. However, SHCCs replaced with PET fibers showed much lower performance in bending and direct tensile tests due to originally low mechanical properties of own fibers, although compressive behavior is similar to PVA2.0 specimen. Also, it was noted that the recycled sand would increase elastic modulus of SHCCs due to larger grain size compared to silica sand. Based on pre-set target value to maintain the performance of SHCCs, it was concluded that the replacement ratio below 20% of fly-ash or below 50% of recycled sands would be desirable for creating sustainable SHCCs.