• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.386-391
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• 1998

Recently, high performance concrete developed has a good quality at fresh and hardened state, but high binder contents results in spending much money on manufacturing and many cracks by drying and autogenous shrinkage. Therefore, in this paper, not only prevention of cracks caused by drying and autogenous shrinkage, but improvement of quality and accmplishment of economy by applying F.A(fly ash), S.F(silica fume) and CSA(calcium sulfa aluminate) expansive additives as an inorganic admixtures in W/B 35% are discussed. According to the experimental results, when 5% of CSA Expansive additives and 15:5 (F.A:S.F)are replaced at unit cement content, high performance concrete with both good compensation of drying and autogenous shrinkage at hardened state is accomplished.

• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.5
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• pp.79-85
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• 2004

This study was performed to evalute mechanical and drying shrinkage properties of polypropylene fiber reinforced high flow concrete. The compressive strength and drying shrinkage ratio were increased with increasing the binder volume ratio and decreased with increasing the content of polypropylene fiber. The splitting tensile strength was increased with increasing the binder volume ratio and the content of polypropylene fiber. The flexural strength was increased with increasing the binder volume ratio and increased by the polypropylene fiber content 0.4%, but above the polypropylene fiber content 0.6% was decreased. This concrete can be used for high flow concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.27-30
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• 2003

This study is investigated the various properties and drying shrinkage of concrete according to water content under the condition proper fluidity is adjusted, in order to suggest the method for reduction of crack by drying shrinkage. According to the results, though water content varies, slump and air content are satisfied to the planed values, but shear slump and separation happen at water content of 120 and 140kg/$m^3$ due to the overuse of superplasticizer(SP). As water content is diminished, setting time is retarded by an increase of the using amount of SP, and compressive and tensile strength increase in the range of 160-180kg/㎥ of water content, but decrease significantly at 120 and 140kg/$m^3$. Length change by drying shrinkage decrease with a decrease of water content. Therefore, considering not only drying shrinkage but also fluidity, setting time and strength, it proves that the most appropriate water content of concrete is 160kg/$m^3$ in the condition of this experiment.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.146-152
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• 1996

Polypropylene fiber reinforced mortar and concrete as civil material or architectural material have been used in America and British etc, and have been researched. Polypropylene fibers have many advantages in many points ; in economical costs, chemical stability and durability. It has been reported that polypropylene fiber can control restrained tensile stresses and cracks and increase toughness, resistance to impact, corrosion, fatigue and durability. This study has been performed to obtain the properties of polypropylene fiber reinforced concrete such as compressive strength, flexural strength, toughness, slump, drying shrinkage crack and drying shrinkage characteristics. The test variables are fiber contents, fiber length, fiber types, and so on. From the results of this study, we can expect the effects of the admixtures of polypropylene fiber about strength and drying shrinkage properties in concrete and mortar.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.501-504
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• 2005

This paper discusses the development of drying shrinkage reducing type superplasticizer(DSRS) by varying dosage of polycarboxylic based superplasticizer, liquid type expansive admixture and antifoaming agent. Adequate mixture proportion of each admixture is fixed at 0.3$\%$ of superplasticizer, 0.15$\%$ of liquidtype expansive admixture and 0.0005$\%$ of antifoaming agent to insure the improvement in drying shrinkage as well as comparable to the slump and air content of conventional concrete. With this mixture proportion, compressive strength of concrete using DSRS is comparable to that of conventional concrete. The use of DSRS studied by the authors has a favorable effect on reducing drying shrinkage due to the effect of water content and expansion by expansive admixture.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.533-536
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• 2005

Drying shrinkage and strength of the redispersible SBR and PAE powder-modified mortars were experimentally investigated. Results of the study that the drying shrinkage rapidly increased until 7 days of age and it was then saturated to the value of about $1\~2\times10^{4}$ after 14 days. It turned out that the polymer-cement ratio exerted more influence on the drying shrinkage than the content of powder shrinkage-reducing agent did. Flexural (compressive) strength of the mortar increased (decreased) as the polymer-cement ratio increased and it was 7$\~$11 (23$\~$39) MPa at 7 days of age. The average (maximum) increasing (decreasing) rate turned out to be about 10 (30) $\%$. As in the drying shrinkage case, the polymer-cement ratio exerted more influence on both flexural and compressive strengths than the content of powder shrinkage agent did.

• Journal of the Korea Concrete Institute
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• v.12 no.6
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• pp.109-117
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• 2000

CFRD(Concrete Faced Rockfill Dam) face slab concrete has a much capability to occur crack due to drying shrinkage, plastic shrinkage and bad compaction etc. Because of these cracks of concrete induce structural problem and decrease durability of dam, it is need to reduce crack of face slab concrete. This is an experimental study to analyze the influence factors on crack properties of CFRD face slab concrete. For this purpose, various mix proportion of CFRD face slab concrete and concrete using PPF(polypropylene fiber0 and fly ash was selected. And tests for drying shrinkage, bonding strength, water permeability and plastic shrinkage were performed, and then CFRD D and PPC of those mix proportion were placed in CFRD field. According to test results, it was found that the bonding strength of C1(compact sufficiently) was higher about 10~20% than that of C2(compact insufficiently). And the engineering properties of PPC(concrete using PPF) and FAC(concrete using fly ash) were better than those of the others ; the permeability of PPC and FAC after 8 weeks curing was little lower than that of CFRD D, and plastic shrinkage crack of PPC and FAC was lower 40~60% than crack of CFRD D.

• International Journal of Concrete Structures and Materials
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• v.1 no.1
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• pp.3-9
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• 2007

Fiber-reinforced self-compacting concrete (FRSCC) is a new type of concrete mix that can mitigate two opposing weaknesses: poor workability in fiber-reinforced concrete and cracking resistance in plain SCC concrete. This study focused on early-age cracking of FRSCC due to restrained drying shrinkage, one of the most common causes of cracking. In order to investigate the effect of fiber on shrinkage cracking of FRSCC, ring shrinkage tests were performed for polypropylene and steel fiber-reinforced SCC. In addition, finite element analyses for those specimens were carried out considering drying shrinkage based on moisture diffusion, creep, cracking resistance of concrete, and the effect of fiber. The analysis results were verified via a comparison between the measured and calculated crack width. From the test and analysis results, the effectiveness of fiber with respect to reducing cracking was confirmed and some salient features on the shrinkage cracking of FRSCC were obtained.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.563-566
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• 2000

The study is to examine the drying shrinkage reducing method of mortar using organic shrinkage reducing agent. According to the experiment result, when 2% and 4% of organic shrinkage reducing agent were added, 40% and 50% of the shrinkage rate of mortar were obtained. Also, in the cracking test of plate-shape specimen, the usage of shrinkage agent 2% reduced about 60% of the total cracking length compare to total cracking length the usage of portland cement, the usage of shrinkage agent 4% was not happened crack until 90 days. Accordingly, the usage of shrinkage agent show good effect in prevention of crack.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.473-476
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• 2003

This study discusses the use of anti-shrinkage agent as the method to reduce autogenous and drying shrinkage. According to results, as for the fundamental properties of high performance concrete, fluidity and strength decrease with an increase of the adding ratio of anti-shrinkage agent, but air content increases. Compared with plain concrete, autogenous and drying shrinkage are reduced by 12~52% and 4~22% respectively upto the adding rario of anti-shrinkage agent of 2.0%. When expansive additive is added by 5.0%, they are also reduced by 38~95% and 15~50% respectively. Therefore, as expansive additive of 5.0% and anti-shrinkage agent of 1.0% are added to high performance concrete of around W/B 30%, it is considered that fluidity and strength are hardly influenced, and in addition, crack by shrinkage can be prevented effectively.