• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2013년도 추계 학술논문 발표대회
• /
• pp.156-157
• /
• 2013

As the chemical shrinkage and autogenous shrinkage of paste constitutes a large part of the shrinkage of high strength concrete, a good understanding of characteristics of chemical shrinkage and autogenous shrinkage is essential in order to understand chemical shrinkage and autogenous shrinkage of concrete. In this study, a preliminary study on effect of mineral admixture on chemical shrinkage and autogenous shrinkage of paste was compared.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
• /
• pp.687-692
• /
• 2002

The chemical shrinkage and the autogenous shrinkage have been determined experimentally for cement pastes incorporating different W/C ratio and different amount of the following addition: silica fume, fly ash and sand. The measurement method of the chemical shrinkage and autogenous shrinkage both were the volumetric technique. The silica fume has a effect of increasing the autogenous shrinkage while have a minor effect on the chemical shrinkage. The addition of fly-ash and sand both decreased the amount of chemical shrinkage and autogenous shrinkage.

• 한국주조공학회지
• /
• 제37권6호
• /
• pp.193-198
• /
• 2017

In this study, volumes of shrinkage and porosity of A356.2 alloys during casting were analyzed as a function of melt temperature, pouring diameter, mold temperature, and Sr content. The temperature of the melt barely affected the shrinkage and porosity formation. The pouring diameter determined the pouring rate, and it was proportional to the shrinkage, yet no relationships with the density of porosity were observed. When the mold was heated at $400^{\circ}C$, shrinkage and porosity in the alloy increased above the one in the mold without heating. However, the mold without heating experienced interior shrinkage and the porosity was mainly distributed near interior shrinkage. The addition of Sr to the melt resulted in more shrinkage and less porosity.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2009년도 추계 학술논문 발표대회
• /
• pp.73-76
• /
• 2009

In ultra-high-strength concrete, chemical shrinkage is larger than drying shrinkage due to using a large amount of cement and admixtures, and this is a factor deteriorating the quality of structures. Thus, we need a new technology for minimizing the shrinkage strain of ultra-high-strength concrete. So, this study have prepared super-high-strength concrete with specified mixing design strength of over 100MPa and have evaluated a method of reducing chemical shrinkage by using expander and shrinkage-reducing agent. According to the results of this study, with regard to the change in length by chemical shrinkage, an expansion effect was observed until the age of seven days. The expansion effect was higher than previous research that used only expander or shrinkage reducing agent. In addition, ultra-high-strength concrete showed a shrinkage rate that slowed down with time, and the effect of the addition of expander material on compressive strength was insignificant. That is shown that required more database to be accumulated through experimental research for the shrinkage strain of members.

• 한국건축시공학회지
• /
• 제4권2호
• /
• pp.81-88
• /
• 2004

The purpose of this study is to investigate the chemical shrinkage and autogenous shrinkage of high strength cement paste and silica fume and fly ash and sand to cement ratio by the method of volumetric tests, and also investigate the autogenous shrinkage of high measurement method, and compare the results of volumetric test and linear length measurement test. A series of cement paste which have W/C ratio of 25%, 35%, 45% respectively were planed to study the effect of the W/C ratio to the shrinkages, and a series of cement paste which were replaced the cement by the silica fume and fly ash with 5%, 10%, 15% as the mass of cement respectively were planed to investigate the effects of poazolana to the shrinkages. A series of mortar which have a C/S ratio of 1:1, 1:1.5, 1:2 respectively were planed to investigate the shrinkage resistant effect of aggregate.

• 콘크리트학회논문집
• /
• 제23권4호
• /
• pp.441-448
• /
• 2011

이 연구에서는 실리카퓸 및 수축 저감제, 팽창재, 고성능 감수제의 혼입을 변수로 한 초고성능 시멘트 복합체(UHPCC)의 초기 수축 거동을 평가하기 위하여 화학수축 및 자기수축 실험을 수행하고, 응결 측정 결과와 비교하여 UHPCC의 자기건조 시작 시점에 대하여 분석하였다. 실험 결과, 실리카퓸 및 수축 저감제는 초기 화학수축을 증가시키는 경향을 보였으며, 고성능 감수제는 시멘트와 배합수의 수화 반응을 지연시키고 화학수축을 저감시키는 것으로 나타났다. 수축 저감제와 팽창재를 조합하여 적용한 경우 약 49%의 자기수축 저감 효과를 보였으며, 팽창재는 경화를 촉진 시키는 것으로 나타났다. 또한 UHPCC는 다수의 섬유 혼입과 낮은 물-결합재비에 의해 초결 이전부터 자기건조 현상이 발생하는 것으로 나타났다.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2012년도 추계학술대회 논문집
• /
• pp.751-752
• /
• 2012

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
• /
• pp.429-432
• /
• 2006

The shrinkage mechanism of high strength concrete is different from that of normal concrete. The shrinkage of normal concrete is subjected to evaporate moisture in concrete, but most shrinkage in high strength concrete is caused by chemical reaction. To analyze shrinkage of concrete exactly, it is necessary to divide drying shrinkage with autogenous shrinkage in terms of degree of hydration, especially in concrete with low W/C ratio. The proposed method can provide a rational basis for prediction of shrinkage in high strength concrete structure.

• Elastomers and Composites
• /
• 제55권2호
• /
• pp.120-127
• /
• 2020

In this study, molding shrinkage of PPS resin was investigated. Two types of PPS resins with differing glass fiber and calcium carbonate content were used for this purpose. To observe mold shrinkage, molding conditions based on injection temperature, injection speed, and the position of the cushion were selected. Circular and rectangular specimens were used for the study model. Injection molding simulation was performed to predict the filling pattern and mold shrinkage, and the simulation results were compared with the experimental conclusions. It was observed that the mold shrinkage showed the highest shrinkage (distributed from 0.05% to 0.32%) dependence on the injection temperature, and the lowest shrinkage (distributed from 0.05% to 0.31%) dependence on the injection speed. The role of the position of the cushion in mold shrinkage was difficult to observe. The results of the simulation mostly agreed with the experimental results; however, for some molding conditions, the mold shrinkage in the simulation was overestimated as compared to that in the experiment.

• 펄프종이기술
• /
• 제43권5호
• /
• pp.17-26
• /
• 2011

Drying behavior and physical properties of HwBKP, SwBKP, and OCC handsheets depending on kneading, refining and wet pressing were analyzed. The maximum drying shrinkage velocity was newly adopted to verify the effect of mechanical treatment of pulps by evaluating drying behavior according to varying the kneading, refining and wet pressing treatments. Those various treatments were changed to evaluate the relationship between the maximum drying shrinkage velocity and handsheets properties. When the drying shrinkage and the maximum drying velocity increased by refining and wet-pressing, handsheets strength was increased. The maximum drying shrinkage velocity showed higher correlation with physical properties of paper than WRV at different refining loads at SwBKP and mixed pulp. At high wet-web dryness, drying shrinkage, the maximum drying shrinkage velocity and strength properties of handsheet were increased. It meant that drying shrinkage behavior was highly affected by not only fibers' shrinkage but also fiber bonding. Kneading pre-treatment for KOCC and SwBKP effectively modified fiber properties and increasing paper strength and drying shrinkage. The effect of kneading pre-treatment was also confirmed by the maximum drying shrinkage velocity. Strength properties of mixed pulp handsheets were not increased by the kneading pre-treatment, although the maximum drying shrinkage velocity and WRV was increased. It meant that fibers network bonding of HwBKP was limited because of ves sels and ray cells' interference for bonding. Therefore in order to improve paper strengths containing HwBKP by mechanical treatments, interference of vessels and ray cells for fiber bondings should be carefully controlled.