• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.11a
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• pp.175-176
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• 2011

Applying previous studies performed in the moisture transportation characteristics and shrinkage of lightweight concrete application of shrinkage reduction is to discuss. Applicability of shrinkage reduction effect of lightweight concrete applies for the analysis of PSC girder bridge beam placed on the construction site. Stress of the concrete bridge deck, rebar quantity is calculated by effective elastic modulus method and crack risk is assessed by moisture transport and differential shrinkage analysis. After approximately 10 days maximum tensile stress occurs 6MPa, similar to the case of normal concrete, a maximum tensile stress occurs 3MPa in lightweight concrete and comparing to normal concrete stress was reduced to approximately 50%. Normal and lightweight concrete crack index, respectively, is reduced 1.6 to 1.2, 1.2 to 0.9 in surface and boundary region. Therefore, reduction in shrinkage of concrete were able to confirm reduction of crack risk.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.209-210
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• 2021

This study aims to develop ultra-low-shrinkage high-quality concrete. Therefore, the concrete drying shrinkage characteristics according to the type and amount of the shrinkage reducing agent were reviewed. As a result, the performance of Hexylene Glycol(HG) and Polyol was superior to that of PolyEthylene Glycol(PEG), which is most widely used in Korea. In addition, the shrinkage reduction effect was improved as the amount of PEG was increased, but the disadvantage of the strength reduction when excessive use was confirmed.

• Journal of the Korea Institute of Building Construction
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• v.10 no.4
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• pp.113-122
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• 2010

In this study, 150MPa ultra-high-strength concrete was manufactured, and its performance was reviewed. As technically meaningful autogenous shrinkage reportedly occurs at a W/B ratio of 40% or less, although it occurs in all concrete regardless of the W/B ratio, the effects of the use of expansive admixture and shrinkage reducer, or of the friction and restraint of forms that may result in the effective reduction of autogenous shrinkage, were reviewed. As a result, considering the flow and strength characteristics, it was found that the slump flow time was shorter with expansive admixture, and shortest with shrinkage reducer. All specimens with $30kg/m^3$ expansive admixture showed high strength at early material age. Their strength decreased due to the expansion cracks when there was excessive use of expansive admixture, and the use of shrinkage reducer did not influence the change in the strength according to the material age. The expansive admixture had a shrinkage reduction effect of 80%, while the shrinkage reducer had a shrinkage reduction effect of 30%, indicating that the expansive admixture had a stronger effect. It seems that mixing the two will have a synergistic effect. The shrinkage reduction rate was highest when the W/B ratio was 20%. The form suppressed the expansion and shrinkage at the early period, and the demolding time did not significantly influence the shrinkage. The results of the study showed that the excessive addition of expansive admixture leads to expansion cracks, and the expansive admixture and shrinkage reducer have the highest shrinkage reduction effect when they are mixed.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.285-288
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• 2004

Generally, the autogenous shrinkage of high performance concrete is important in that it can lead the early cracks in concrete structures. In the previous study, The. autogenous shrinakge of HPC was found to decrease with incresing expansive additive and shrinakge reduction agent. In case of combined use, the autogenous shrinakge was more reduction than in case separate use. The purpose of this study is to derive a realistic equation to estimate the autogenous shrinakge model of high performance concrete with exapnsive agent and shrinakge reduction agent. investigated the durability of high performance concrete using expansive additive and shrinkage reducing agent. The proposed equation showed reasonably good correlation with test data on autogenous shrinakge of high performance concrete with material for shrinkage reduction.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.05b
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• pp.69-72
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• 2009

This study reviewed the reduction effect of autogenous shrinkage of high strength mortar by plant edible oils based on existing studies, in an effort to find the method of reducing autogenous shrinkage of high strength concrete. To summarize the results, first as characteristics of fresh mortar, substitution of plant edible oil showed slight reduction in liquidity. Compressive strength was reduce at age of 28 days compared to plain mix regardless of type and substitution ratio. Ratio of change in the length of autogenous shrinkage of high strength mortar by plant oils was found to reduce compared to the plain, and the reduction effect was most satisfactorγ in bean oil.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.05a
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• pp.81-82
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• 2011

This paper is to compare and analyze WOE created by emulsifying waste oil & WOES added by stimulant with the existing SR in order to solve the problem of strength and reduction in fluidity occurring in time of the use of waste oil to reduce the autogenous shrinkage of high strength mortar. As experimental results, in case of WOE, there almost never happened a drop in fluidity at 1% replacement and compressive strength also showed the strength value similar to Plain. On the other hand, the effect of strength improvement consequent upon the use of stimulant was found to be insufficient. The change of autogenous shrinkage generally showed a better reduction effect in shrinkage comparing to Plain. In case of WOE1, reduction effect in autogenous shrinkage was found to be more excellent than the existing SR. Accordingly, WOE1 is analyzed to be desirable if reduction in autogenous shrinkage, strength & up to the aspect of fluidity are taken into consideration.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.313-314
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• 2009

With the purpose of reducing autogenous shrinkage of high strength mortar, shrinkage reduction effect was examined in this study using plant oils as the compound for shrinkage reduction. As a result of examination, satisfactory reduction effect was shown using plant oils in comparison to plain mixture. Most excellent effect was shown by soybean oil.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.11a
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• pp.101-105
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• 2009

The purpose of this study is to reduce autogenous shrinkage of high-strength concrete. Previous studies were investigated to measure the effects of reductions to autogenous shrinkage when applying bean oil to concrete. The results of the study showed that as the mixture rate of BO increased, fluidity decreased and air quantity decreased slightly. In early age, compressed strength increased compared to Plain while decreased in long-term age. As an autogenous shrinkage characteristic, reduction effect increased according to increase in mixture rate. When mixture rate is 1%, approximately 30% decreased compared to Plain in BO. At 2%, BO decreased by about 32%. In addition, in the case of BO, autogenous shrinkage was shown to decrease compared to expansive additive and shrinkage-reducing agent.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.549-552
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• 2004

This paper investigated the drying and autogenous shrinkage of high performance concrete(HPC) with mixture adjustment under various specimen size. For fresh concrete properties, HPC with mixture adjustment need a higher dosage of SP agent due to fluidity reduction, and a larger dosage of AE agent due to the reduction of air content. HPC with mixture adjustment exhibited a smaller strength development than control HPC. For drying shrinkage, an increase in specimen size occurred with small expansion during water curing and at air curing, less drying shrinkage was observed. Autogenous shrinkage was not affected by specimen size. Autogenous shrinkage of HPC with mixture adjustment exhibited less than half of control HPC.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.575-578
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• 2005

Recently, various concrete reinforcing fibers have been used to reduce the plastic shrinkage cracking which occurs before the concrete hardens. In this study, the physical properties of nylon fiber reinforced concrete such as slump, air content, compressive strength and tensile strength were investigated. In addition, the performance of nylon fiber in the plastic shrinkage cracking reduction of mortar has been estimated in comparison with polypropylene fiber and cellulose fiber. Nylon fiber showed considerable advantages in terms of the workability of concrete and the plastic shrinkage cracking reduction of mortar compared with polypropylene fiber and cellulose fiber.