A Fundamental Test of Temperature Crack Reduction Method Application by Setting Time Control of Large-Scaled Mat Foundation Mass Concrete

Constructing large-scale mat foundation mass concrete is increasing for the stability of building structure, because a lot of high rise building are being built in order to make full use of limited space. However, It is of increasing concerns that because limited placing equipments, available job-site and systems for mass concete placement in construction field do not allow to place great quantity of concrete at the same time in large scale mat foundation, consistency between placement lift can not be secured. And also, it is likely to crack due to stress caused by the difference of hydration heat generation time. To find out the solution against above problems, this study is to reconfirm the performance of normal concrete designed by mix proportion and super retarding concrete. The Fundamental test shows what happens if low heat proportioning and control method of setting time are applied at the job-site of newly constructed high rise building. The test result show that slump flow of concrete has been somewhat increased as the target retarding time gets longer, while the air content has been slightly decreased but this is no great difference from normal concrete. The setting time shows to be retarded as target retarding time gets longer, the range of retarding time increases. It is necessary to increase the amount of mix of super retarding agent in the proportion ration by setting curing temperature high since outdoor curing is about 6 hours faster than standard curing, which means the temperature of the concrete will be higher than the temperature of the surrounding environment, due to its high hydration heat when applying in a construction site. The compressive strength of super retarding concrete appears to be lower than normal concrete due to the retarding action in the early stage. However, as the time goes by, the compressive strength gets higher, and by the 28th day the strength becomes the same or higher than normal concrete.

초대형 매트기초 매스 콘크리트의 응결시간조정에 의한 온도균열저감 공법적용의 기초적 실험