Abstract
The purpose of this study is to develop the precast concrete without steam curing. Generally, it is necessary that the precast concrete must cure in steam condition. If we make a precast concrete without steam curing, we could save the manufacturing energy and $CO_2$ emission. In this experiment, the high early strength cement containing massive $C_3S$ quantity was used to enhance the early strength of cement mortar using admixtures which can accelerate $C_3S$ hydration reaction in the condition of room temperature. The measuring items are zero flow, setting times, compressive strength and analysis of MIP & SEM. From the results of this experiment, hardening catalyst is very effective to increase the high early strength of cement mortar according to the early formation of C-S-H hydrate. The compressive strength of mortar is increased that it increases in the amount of consumption of hardening catalyst. The increasing cause of the compressive strength of mortar is decrease in a pore ratio and pore size of mortar due to the acceleration of $C_3S$ hydration with hardening catalyst. Also, the generation of C-S-H was confirmed by use of a hardening catalyst according to an SEM analysis. When the strength and workability of mortar are considered, the appropriate amount of hardening catalyst dosage is about 1.0%.
