This study optimized the binder composition for making 300N/mm2 ultra-high-strength concrete. The use of silica fume with a replacement ratio of 24%, which contained 50% coarse silica flour, attained both high compressive strength and high fluidity. The newly developed chemical admixture showed excellent dispersibility down to 10% water-to-binder ratio, which improved concrete workability, mitigated the delayed setting times, and resulted in 30% less shrinkage and 7% strength gain. For the design strength of 300N/mm2, satisfactory strength and workability can be reached with the specific aggregates and curing scheme reported in our previous study.
