By decreasing the w/b ratio (from 0.35 to 0.25), the coarser pyrogenic nanosilica (NS200) at smaller percentage (0.75%) showed better performance in enhancing compressive strength than finer type (NS380). This result was more noticeable at the w/b ratio of 0.25. Moreover, at each w/b ratio (0.25, 0.30, and 0.35), the utilization of coarser pyrogenic nanosilica (NS200) at higher replacement ratio (1.5%) caused the highest splitting tensile strength among different HPC mixtures. In addition, at w/b ratio of 0.25, control mixture exhibited higher splitting tensile strength than HPC mixtures containing different percentages of NS380 at middle ages (28 and 91 days).