• 한국농공학회지
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• 제43권5호
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• pp.124-131
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• 2001

The shrinkage properties of high early strength concrete were investigated. One of the method to control microcrack and crack development due to restrained shrinkage is to reinforce concrete with randomly distributed fibers. Regulated-set cement and two different types of fiber were adopted. The experiments for heat of hydration, drying and autogenous shrinkage were conducted. The desirable resistance of high early strength fiber reinforced concrete to restrained shrinkage microcracking was achieved. These results indicate that use of fiber in high early strength concrete plays an important role in control of crack development due to restrained shrinkage.

• Computers and Concrete
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• 제20권2호
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• pp.215-227
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• 2017

A finite element model (FEM) for predicting early-age behavior of reinforced concrete (RC) bridge deck slabs with fiber-reinforced polymer (FRP) bars is presented. In this model, the shrinkage profile of concrete accounted for the effect of surrounding conditions including air flow. The results of the model were verified against the experimental test results, published by the authors. The model was verified for cracking pattern, crack width and spacing, and reinforcement strains in the vicinity of the crack using different types and ratios of longitudinal reinforcement. The FEM was able to predict the experimental results within 6 to 10% error. The verified model was utilized to conduct a parametric study investigating the effect of four key parameters including reinforcement spacing, concrete cover, FRP bar type, and concrete compressive strength on the behavior of FRP-RC bridge deck slabs subjected to restrained shrinkage at early-age. It is concluded that a reinforcement ratio of 0.45% carbon FRP (CFRP) can control the early-age crack width and reinforcement strain in CFRP-RC members subjected to restrained shrinkage. Also, the results indicate that changing the bond-slippage characteristics (sand-coated and ribbed bars) or concrete cover had an insignificant effect on the early-age crack behavior of FRP-RC bridge deck slabs subjected to shrinkage. However, reducing bar spacing and concrete strength resulted in a decrease in crack width and reinforcement strain.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 춘계 학술논문 발표대회
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• pp.82-83
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• 2014

Concrete with self-healing admixture can reduce the crack width by using a compound for chemical reaction with incoming water and carbon dioxide through the crack. Also, concrete with self-healing admixtures can reduce early-age shrinkage crack by using a inorganic expansive agent. In this research, we perform the basic workability test and compressive test. Also, We measure the drying shrinkage of concrete specimen. Finally, we make mock-up (3m X 3m X 0.23m) and monitor the crack width and length for 3 months.

• 한국구조물진단유지관리공학회 논문집
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• 제13권3호통권55호
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• pp.188-196
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• 2009

콘크리트는 초기재령에 있어서 수분의 증발 및 이동으로 소성 및 건조수축 등의 수축현상이 발생한 다. 국내에서는 아령형 구속건조수축몰드를 활용한 콘크리트의 건조수축 균열 평가방법을 KS에서 규격화하여 활용하고 있으나 이는 균열발생시점 및 구속수축응력을 평가하는 방법으로 균열발생량에 관한 정량적 평가는 어려운 실정이다. 이에 본 연구에서는 콘크리트의 수축변형거동 및 균열발생량에 대한 정량적 데이터를 확보하기 위하여 판상-링형 구속시험방법을 개발하고 시험체 치수가 콘크리트의 수축균열에 미치는 영향을 검토하여 판상-링형 구속시험방법의 최적 시험체 치수 도출 및 수축균열특성에 관한 정량적 평가방법을 제안하고 그 적용성을 검증하고자 한다.

• 한국산학기술학회논문지
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• 제17권4호
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• pp.296-302
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• 2016

콘크리트의 내구성 저하로 인한 균열의 보수 및 보강에 소요되는 비용은 콘크리트 구조물의 유지비용 증대로 연결되어 균열발생 저감에 대한 연구가 요구되고 있다. 특히, 전력공급용 시설인 전력구의 경우 지하 매설물이므로 보수 및 보강은 경제적으로 큰 부담이 된다. 그러므로 지하매설 전력구의 경우 효과적인 균열 저감 방안이 설계 초기단계부터 요구되어진다. 본 연구는 전력구용 저수축 콘크리트 제조를 위한 수축저감제 개발의 일환으로 수축저감제 사용 콘크리트의 초기 강도 개선을 위해 TEA를 검토하였다. 검토결과, TEA를 수축저감제의 3% 사용할 경우 조기 강도가 크게 개선되었으며, 수축저감 효과도 우수한 것으로 확인되었다. 또한, TEA 3 %에 수축저감제 2.0 % 혼합하여 적용하였을 경우 압축강도 특성 및 건조수축 길이변화 실험결과에서 가장 우수한 것으로 나타나 수축저감제로서의 가능성을 확인하였다. 추후 수축저감제의 범용적인 적용성 검토를 위하여 수축저감제의 사용재료 변화 등에 대한 다양한 재료변수 요인 검토를 통하여 수축저감제의 성능 검토가 필요할 것으로 사료된다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 추계 학술논문 발표대회
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• pp.44-45
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• 2014

On this study, initial crack index was evaluated by performing FEM analysis to crack propagation from hydration heat for development of precast concrete. On the result, as increased the usage of hardening accelerator, initial compressive strength were improved and setting time also was shortened. Additionally, central temperature of concrete was increased, the reaching time for the highest temperature could be shortened. By the result to assess crack index, there was no problem about crack despite of growth of initial high hydration heating. This result guessed because of small size element when analyzed trough FEM, realization for mass concrete's crack index should be performed.

• 콘크리트학회지
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• 제7권5호
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• pp.164-171
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• 1995

재령 초기에 발생하는 부등건조수축과 시멘트의 수화반응에 의한 수화열은 초기재령 콘크리트 균열의 주요 원인이다. 다라서 재령 초기 콘크리트의 균열 발생 여부를 예측하기 위해서는 수화열과 부등건조수축에 의하여 발생되는 응력의 계산이 필수적이며, 이를 위해서는 초기 재령 콘크리트의 역학적 성질 파악이 매우 중요하다. 이 연구에서는 콘크리트의 동탄성계수와 압축강도, 정탄성계수와 같은 역학적 성질들과의 관계를 구명하기 위하여 공명주기법을 이용한 비파괴 실험을 실시하였으며, 얻어진 실험결과를 기존 예측식과 비교하였다. 또한 기존의 실험치와 이 연구의 실험치를 이용하여 보다 정확한 예측식들을 제안하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.265-268
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• 2004

Plastic shrinkage cracking is a major concern for concrete, especially for flat structures as highway pavement, bridge deck slabs, and bridge deck pavement. LMC(Latex Modified Concrete) be used mainly for bridge deck overlays, so occurrence possibility of plastic shrinkage cracking is very high. But LMC is form a close-packed layer of polymer particles in very early time from the time of adds the latex and water. So plastic shrinkage cracking compare with normal concrete is not occur at final setting time. Results indicates that LMC is advantage to prevent occurrence of plastic shrinkage crack and it's possible co construction for bridge deck overlay effectively.

• KCI Concrete Journal
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• 제14권3호
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• pp.93-101
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• 2002

The details of an approach to account for the factors that have been found to affect the ability and the probability to control cracking due to sawcutting in newly constructed concrete pavements are presented. Several factors such as material strength parameters, method and quality of curing, slab and subbase stiffness, and concrete shrinkage affect the probability of crack initiation. Others are relevant to concrete mixture characteristics that affect development of early aged stresses caused by shrinkage and thermally induced contraction. This paper presents the results of a probabilistic analysis of the factors that affect crack control using sawcut notches. Cost analyses on both conventional and early-entry sawcutting methods are shown to support the results of the probabilistic analysis. From both an operational and cost standpoint, it is evident for the environmental conditions considered that early-entry sawcut methodology holds a significant advantage over conventional methods.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 가을 학술발표회 논문집
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• pp.251-258
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• 2003

The early -age behavior of base restrained reinforced concrete (RC) walls is analyzed using a three-dimensional finite element method in this study. After calculating the temperature and internal relative humidity variations of an RC wall, determination of stresses due to thermal gradients, differential drying shrinkage, and average drying shrinkage is followed, and the relative contribution of these three stress components to the total stress is compared. The mechanical properties of early-age concrete, determined from many experimental studies, are taken into consideration, and a discrete reinforcing steel derived using the equivalent nodal force concept is also used to simulate the cracking behavior of RC walls. In advance, to Predict the crack spacing and maximum crack width in a base restrained RC wall, an analytical model which can simulate the post-cracking behavior of an RC tension member is introduced on the basis of the energy equilibrium before and after cracking of concrete.