MIX PROPORTION OPTIMIZATION OF HIGH FLUIDITY CONCRETE AND ITS MICROSTRUCTURE CHARACTERIZATION

According to the actual conditions of construction projects in Africa, the properties and microstructure of two kinds of high fluidity concrete were compared. Compared with Portland slag cement concrete mixed with silica fumes used now, the optimized ordinary Portland cement concrete had been appropriately reduced the water-binder ratio, increased the paste-aggregate ratio, and adjusted the type and amounts of admixture. Slump flow of fresh concrete and compressive strength of hardened concrete were measured, early hydration exothermic characteristics of paste were studied, and microstructure and pore characteristics of harden paste were analyzed by SEM and MIP. The results showed that the performances of flow, slump retention, and compressive strength at each age of ordinary Portland cement concrete were better than that of slag Portland cement concrete mixed with silica fumes. The early hydration degree of ordinary Portland cement paste was higher than that of slag Portland cement paste mixed with silica fume, and the pore structure of ordinary Portland cement paste was denser.