In recent years, it has been pointed out that many concrete structures are likely to accrue the initial defects in construction work because of the massive and complicated configuration and function of concrete structures. The service life of concrete structures and the structural performance will be lowered due to loading and environmental attack such as carbonation, frost action, and drying shrinkage. In the last few decades, various types of chemical admixtures have been developed, with emphasis on making highly durable concrete and on producing highly flowable concrete for self-compacting. In this paper, a new cement dispersing agent for retempering, denoted as CDA was examined to confirm its effect on fundamental properties of concrete. This chemical agent is used not only to improve the performance on vibrating consolidation of fresh concrete, but also to increase the resistance to segregation of concrete. The addition of agent will promise the dispersion of cement particles and the reduction of bleeding of concrete. The CDA is a negative ion type cement dispersing agent having a main component of Polyester fiber. The benefit of CDA is given in the dosage of a small amount of agent (0.5~1.0g/m3). The improvement in vibrating consolidation of fresh concrete was depended on late addition for retmpering. It was observed by the vibrating table-type consistency meter. From the tests for bleeding, setting, mechanical properties, durability, and micro structures of concrete such as Vickers hardness and pore size distribution, the benefit of CDA was also confirmed.
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