• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1998년도 봄 학술발표회 논문집(I)
• /
• pp.309-314
• /
• 1998

The moisture diffusion and self-desiccation cause the differential drying shrinkage and autogenous shrinkage at early ages, respecitvely. Thus total shrinkage strain includes the differential drying shrinkage and self-desiccation shrinkage. Thus in this study the shrinkage strain was measured at various positions in the exposed concrete and in the sealed concrete the self-desiccation shrinkage was measured. In low-strength concrete, the differential drying shrinkage increases very rapidly, but self-desiccation shrinkage is very small. But high-strength concrete shows the reverse result. And the analytical results for differential drying shrinkage were in good agreement with the test results.

• 한국건축시공학회지
• /
• 제4권4호
• /
• pp.71-77
• /
• 2004

Drying Shrinkage has much complexity as it has relations with both internal elements of concrete and external factors. Therefore, experiments on Concrete Drying Shrinkage are carried out in this study under simplified circumstances applying temperature & Humidity test chamber which enables constant temperature and humidity. Comparative analyses have been made respectively according to the consequences aiming at modelling for prediction of Concrete Drying Shrinkage and making out measures to reduce it. Strain Rate of Drying Shrinkage of concrete under the condition of dry air appears to rise by about 20%-30% in proportion as the temperature rises $5^{\circ}C$ when the humidity was held below 10% compared under the condition of dry temperature & Humidity test chamber. Strain Rate of Drying Shrinkage in pit sand concrete increased 20% higher than measured when in river sand under the condition of 90-day material age. A general formula with two variables is derived as follow ${\varepsilon}={\alpha}_1＋{\beta}_1x_1＋{\beta}_2x_2＋{\beta}_3x_1^2＋{\beta}_5x_2^2$. and also graphed in 3 dimensions, enabling to apply to actual design and predict Strain Rate of Drying Shrinkage in concrete. The results of prediction of Rate of Drying Shrinkage by Response Surface Analysis are as follows. The coefficient of correlation of Drying Shrinkage in Concrete was over 90%.

• Computers and Concrete
• /
• 제3권2_3호
• /
• pp.103-122
• /
• 2006

Drying shrinkage of concrete occurs due to the loss of moisture and thus, it is controlled by moisture diffusion process. On the other hand, the shrinkage causes cracking of concrete and affects its moisture diffusion properties. Therefore, moisture diffusion and drying shrinkage are two coupled processes and their interactive effect is important for the durability of concrete structures. In this paper, the two material parameters in the moisture diffusion equation, i.e., the moisture capacity and humidity diffusivity, are modified by two different methods to include the effect of drying shrinkage on the moisture diffusion. The effect of drying shrinkage on the humidity diffusivity is introduced by the scalar damage parameter. The effect of drying shrinkage on the moisture capacity is evaluated by an analytical model based on non-equilibrium thermodynamics and minimum potential energy principle for a two-phase composite. The mechanical part of drying shrinkage is modeled as an elastoplastic damage problem. The coupled problem of moisture diffusion and drying shrinkage is solved using a finite element method. The present model can predict that the drying shrinkage accelerates the moisture diffusion in concrete, and in turn, the accelerated drying process increases the shrinkage strain. The coupling effects are demonstrated by a numerical example.

• 한국건축시공학회지
• /
• 제6권1호
• /
• pp.73-77
• /
• 2006

Drying Shrinkage has much complexity as it has relations with both internal elements of concrete and external factors. Therefore, experiments on Concrete Drying Shrinkage are carried out in this study under simplified circumstances applying temperature & Humidity test chamber which enables constant temperature and humidify. Comparative analyses have been made respectively according to the consequences aiming at modelling for prediction of Concrete Drying Shrinkage and making out measures to reduce it. As a result Strain Rate of Drying Shrinkage of concrete was measured to increase by average $10{\times}10^{-5}$ in proportion to additional 4% increase in fine aggregate ratio, when water/cement ratio constant. Strain Rate of Drying Shrinkage in pit sand concrete increased 20% higher than measured when in river sand under the condition of 90-day material age. 6. Strain Rate of Drying Shrinkage in sea sand concrete increased $10%{\sim}15%$ higher than measured when in river sand. The results of prediction of Rate of Drying Shrinkage by Response Surface Analysis are as fellows. The coefficient of correlation of Drying Shrinkage in concrete was over 90%.

• 한국산업융합학회 논문집
• /
• 제13권2호
• /
• pp.99-106
• /
• 2010

The effects of additive and shrinkage reducing agent on the drying and autogenous shrinkage of high strength concrete are investigated in this study. As results, when the ratio of W/B(low water to binder ratio) increase, the compressive strength is decreased. Comparing with PC(portland cement) concrete, the strength is 2.8%, 3.2% and 3.8% lower respectively than that of PC when concrete mixing ratio is 0.2%, 0.3% and 0.4% in 28 days curing. Drying shrinkage strain of PC concrete showed $-650{\times}10^{-6}$ in 91 days curing. When SR(shrinkage reducing agent) of 0.2%, 0.3% and 0.4% is mixed, the drying shrinkage strains are 21%, 34% and 41% lower than those of PC in 91 days curing. Autogenous shrinkage strain of PC concrete appeared $-480{\times}10^{-6}$ in 56 days curing. When SR of 0.2%, 0.3% and 0.4% is mixed, the autogenous drying shrinkage strain are 12.5%, 19.8% and 33.3% lower than those of PC in 56 days curing. In cases of using the mineral and shrinkage agent or only using a shrinkage reducing agent also appeared same reducing effects for drying shrinkage and autogenous shrinkage.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2022년도 가을 학술논문 발표대회
• /
• pp.211-212
• /
• 2022

In this study, the cracking control performance of ultra-low shrinkage concrete was investigated by the field application. As a result, drying shrinkage crack occurred in normal concrete wall, but no crack occurred in ultra-low shrinkage concrete wall. It is determined that the drying shrinkage crack control effect of the ultra-low shrinkage concrete is excellent.

• International Journal of Concrete Structures and Materials
• /
• 제9권3호
• /
• pp.337-343
• /
• 2015

Previous studies have shown that the drying shrinkage of recycled aggregate concrete (RAC) is greater than that of natural aggregate concrete (NAC). Drying shrinkage is the fundamental reason for the cracking of concrete, and tensile creep caused by the restraint of drying shrinkage plays a significant role in the cracking because it can relieve the tensile stress and results in the delay of cracking occurrence. However, up till now, all research has been focusing on the compressive creep of RAC. Therefore, in this study, a uniaxial restrained shrinkage cracking test was executed to investigate the tensile creep properties caused by the restraint of drying shrinkage of RAC. The mechanical properties, such as compressive strength, tensile splitting strength, and Young's modulus of RAC were also investigated in this study. The results confirmed that the tensile creep of RAC caused by the restraint of shrinkage was about 20-30 % larger than that of NAC.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
• /
• pp.277-280
• /
• 2003

Material, mix proportion, curing condition, temperature, humidity and wind velocity have an influence on drying shrinkage of concrete. In this paper, to evaluate the effect of curing condition at early age on the drying shrinkage of concrete was investigated varying curing age for different binder. The principal conclusions from this research were as follows: 1) In case of 14 days of water curing, the drying shrinkage of concrete is smaller than 7 days of water curing, independence of type of binder. 2) In case of 4 days of water curing, the ratio of increase of drying shrinkage of concrete using fly-ash and slag powder is more remarkable than using portland cement alone, comparing the drying shrinkage of 7 days of water curing.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
• /
• pp.592-595
• /
• 2004

This Study discusses the properties of drying shrinkage of concrete slab with W/B, water content, fiber and anti-shrinkage agent. According to results, drying shrinkage is reduced with decrease of water content and W/B. Also, compared with plain concrete, drying shrinkage is reduced by using of fiber, anti-shrinkage agent and adding ratio of anti - shrinkage agent. Therefore, in the range of workability if water content and W/B are reduced and using of fiber and anti-shrinkage agent are performed properly, crack by drying shrinkage can be prevented effectively.

• Computers and Concrete
• /
• 제5권5호
• /
• pp.435-448
• /
• 2008

Self-compacting concrete (SCC), characterized by the high flowability and resistance to segregation, is due to the high amount of paste (including cement and mineral admixtures) in contrast with normal concrete (NC). However, the high amount of paste will limit the volume fractions of coarse aggregate,and reduce the tendency of coarse aggregate to suppress drying shrinkage deformations. For this reason, SCC tends to produce higher values of drying shrinkage than NC for the most part. In order to assess the drying shrinkage of SCC quantitatively for application to offshore caisson foundations, the formulas presented in the literatures (ACI 209 and CEB-FIP) are used to predict the values of drying shrinkage in SCC according to the corresponding mix proportions. Additionally, a finite element (FE) model, which assumes concrete to be a homogeneous and isotropic material and follows the actual size and environmental conditions of the caisson, is utilized to simulate stress distribution situations and deformations in the SCC caisson resulting from the drying shrinkage. The probability of cracking and the behavior of drying shrinkage of the SCC caisson are drawn from the analytic results calculated by the FE model proposed in this paper.