Various Hydration Reactions of Silica Fume Blended Cement under Different Curing Conditions, and a Hypothesis for the Ultra High Strength Development Mechanism of RPC
Masami UZAWA, Yoshihide SHIMOYAMA@and Shigeo KOSHIKAWA
Abstract:Two-component mortar paste consisting of cement and silica fume was cured in water or steam, and its strength development, cement hydration capacity and silica fume reaction rate were analyzed to identify the role of the admixture, determine the optimum curing condition for RPC containing silica powder and estimate its high strength development mechanism. The total silica fume reaction amount calculated by multiplying the added amount by the reaction rate increased with more silica fume added. Ca/Si ratio of generated C-S-H was about 0.7 at the lowest, suggesting a mixed phase of C-S-H and silica gel. RPC is known that inclusion of silica powder of intermediate sizes increases particle compaction. The low Ca/Si C-S-H with silica gel was considered to further bridge voids between particles firmly, thereby resulting in ultra high strength of RPC. Key Words:Cement, Silica fume, Ca (OH) 2, Combined water, EPMA, RPC, Ultra high strength