• Proceedings of the Korea Concrete Institute Conference
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• 1995.10a
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• pp.229-233
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• 1995

In this study we have the properties of drying shrinkage crack of hardened cement mortar using admixtures. The drying shrinkage cracking test process has been examined by the restrained drying shrinkage strain by restraining rate measuring properties of strain-with- restraint by JIS original proposal and keeps a flow value of mortar about 100$\pm$5%. The results show that the usage of shrinkage reducing agent 1.5% was effective on the control of drying shrinkage in OPC and CP by restraining rate 20% and strain-with-restraing 20~30 $\mu$, the usage of expansion agent 0.45% was effective by restraining rate 50~60% and strain-with-restraint 40~80$\mu$, and the effectiveness was increased with shrinkage reducing agent. Also. admixtures such as Flyash, CP and NC reduced restrained shrinkage and drying shrinkage cracking and more with shrinkage reducing agent

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4A
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• pp.787-794
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• 2006

Generally, high performance concrete has characteristics such as low water-cementitious material ratio, lots of unit binder powder, thus the heat of hydration, autogenous shrinkage are tend to be increased. This study is to investigated the effect of the expansive additive and shrinkage reducing agent on the shrinkage properties of high performance concrete as a study to develop the reduction technology of the concrete shrinkage. Test results showed that the expansive additive and shrinkage reducing agent were effective the reduction of shrinkage of high performance concrete. Especially, the using method in combination with expansive additive and shrinkage reducing agent was more effective than the separately using method of that. Also, it analyzed that the combination of expansive additive of 5% and shrinkage reducing agent of 1% was the most suitable mixture, considering to the fluidity, strength and shrinkage properties.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.561-564
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• 2004

In this study, the properties of autogenous shrinkage and dry shrinkage for high performance concrete using Type I and Type IV cement were discussed. According to experimental results, autogenous shrinkage of SN30(the high performance concrete using type I cement) shows values higher than SL30( the high performance concrete using type IV cement). But the dry shrinkage of SN30 is almost the same as SL30. It is observed that the total shrinkage strain of SN30 is higher than that of SL30, because the ratio of autogenous shrinkage of the total shrinkage is relatively large. Therefore, SL30 is more effective to control or minimize the cracking of the high performance concrete, compared with SN30.

• Journal of the Korea Institute of Building Construction
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• v.7 no.3
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• pp.123-130
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• 2007

This study investigated the fundamental properties and shrinkage properties of high performance concrete with water/binder ratio of 0, 30 and with combination of expansive additive and shrinkage reducing agent. According to the results, the fluidity of high performance concrete showed lower the using method in combination with expansive additive and shrinkage reducing agent than the separately using method of that, so the amount of superplasticizer increased when the adding ratio of expansive additive and shrinkage reducing agent increased. However the air content of concrete increased when used in combination with expansive additive and shrinkage reducing agent, so the amount of AE agent decreased. The compressive strength showed the highest at 5% of expansive additive, and decreased with an increase of the amount of shrinkage reducing agent. Furthermore, in order to reduce the shrinkage of high performance concrete, it was found that the using method in combination with expansive additive and shrinkage reducing agent was more effective than separately using method of that. Autogenous shrinkage was predicted using JCI model. Because JCI model is unable to consider the effect of EA and SRA, correction factor should be added to enhance the accuracy.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.17-20
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• 2005

In this study, the properties of autogenous shrinkage stress and dry shrinkage stress for high strength concrete using Type I and Type IV cement were discussed. According to experimental results, autogenous shrinkage stress of SN30(the high strength concrete using type I cement) shows values higher than SL30(the high strength concrete using type IVcement). It is observed that the total shrinkage stress of SN30 is higher than that of SL30, because the ratio of autogenous shrinkage stress of the total shrinkage stress is relatively large. Therefore, SL30 is more effective to control or minimize the cracking of the high strength concrete, compared with SN30.

• Structural Engineering and Mechanics
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• v.5 no.1
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• pp.105-113
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• 1997

This paper proposes a model for simulating concrete shrinkage taking into account aggregate restraint. In the model, concrete is regarded as a two-phase material based on shrinkage property. One is paste phase which undergoes shrinkage. Another is aggregate phase which is much more volumetrically stable. In the concrete, the aggregate phase is considered to restrain the paste shrinkage by particle interaction. Strain compatibility was derived under the assumption that there is no relative macroscopic displacement between both phases. Stresses on both phases were derived based on the shrinking stress of the paste phase and the resisting stress of the aggregate phase. Constitutive relation of paste phase was adopted from the study of Yomeyama, K. et al., and that of the aggregate phase was adopted from the author's particle contact density model. The equation for calculating concrete shrinkage considering aggregate restraint was derived from the equilibrium of the two phases. The concrete shrinkage was found to be affected by the free shrinkage of the paste phase, aggregate content and the stiffness of both phases. The model was then verified to be effective for simulating concrete shrinkage by comparing the predicted results with the autogeneous and drying shrinkage test results on mortar and concrete specimens.

• Journal of the Korea Concrete Institute
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• v.16 no.5 s.83
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• pp.621-626
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• 2004

The use of blast-furnace slag (BFS) in making not only normal concrete but also high-performance concrete has several advantages with respect to workability, long-term strength and durability. However, slag concrete tends to show more shrinkage than normal concrete, especially autogenous shrinkage. High autogenous shrinkage would result in severe cracking if they are not controlled properly. Therefore, in order to minimize the shrinkage stress and to ensure the service life of concrete structures, the autogenous shrinkage behavior of concrete containing BFS should be understood. In this study, small prisms made of concrete with water-binder (cement+BFS) ratio (W/B) ranging from 0.27 to 0.42 and BFS replacement level of $0\%$, $30\%$, and $50\%$, were prepared to measure the autogenous shrinkage. Based on the test results, thereafter, material constants in autogenous shrinkage prediction model were determined. In particular, an effective autogenous shrinkage defined as the shrinkage that contributes to the stress development was introduced. Moreover, an estimation formula of the 28-day effective autogenous shrinkage was proposed by considering various W/B's. Test results showed that autogenous shrinkage increased with replacement level of BFS at the same W/B. Interestingly, the increase of autogenous shrinkage is dependent on the W/B at the same content of BFS; the lower W/B, the smaller increasing rate. In concluding, it is necessary to use the combination of other mineral admixtures such as shrinkage reducing admixture or to perform sufficient moisture curing on the construction site in order to reduce the autogenous shrinkage of BFS concrete.

• 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.

• Advances in materials Research
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• v.11 no.3
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• pp.211-224
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• 2022

The shrinkage and the mechanical properties of polypropylene hybrid fiber reinforced mortar PHFRM were investigated in this study. Mortars were prepared with limestone crushing sand, Portland cement and polypropylene hybrid fibers PHF. Two types of virgin fibers, having the same length (30 mm) were used for reinforcing test mortars, fibers in diameter of 0.45 mm, used by PLAST BROS factory of Bordj Bou Arreridj (Algeria) for the fabrication of brooms (for household cleaning) and fibers in diameter of 0.25 mm, available on the market, having multiple applications. In this investigation, it was aimed to study the total and autogenous shrinkage, the flexural and compressive strength of mortars based on hybrid fibers. As a result, PHF have negatively affected the mortar workability. However, shrinkage risk was reduced and coarser fibers (PF45) were most effective for reducing shrinkage risk. The mechanical performances and the ductility of PHFRM were also enhanced.

• Steel and Composite Structures
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• v.47 no.4
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• pp.539-550
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• 2023

Owing to the obstruction of section steel on the moisture diffusion in concrete, the existing shrinkage prediction models overestimate the time-dependent deformation of steel reinforced concrete (SRC) columns, particularly for the SRC columns with enclosed section steels. To solve this issue, this study deals with analytical and experimental studies on the drying shrinkage for this type of column. First, an effective method for predicting the drying shrinkage of concrete based on finite element model is introduced and two crucial parameters for simulation of humidity field are determined. Then, the drying shrinkage of SRC columns with enclosed section steels is investigated and two modified parameters, which depend on the ambient relative humidity and the ratio of section steel size to column size, are introduced to the B3 model. Finally, an experiment on the shrinkage deformation of SRC columns with enclosed section steels is conducted. Comparing the predicted results with the experimental ones, it demonstrates that the modified B3 model is quite reasonable.