Performance evaluation of modified self-compacting concrete incorporating UFBFS and nano-silica across varying aggregate densities and strength grades

Self-Compacting Concrete (SCC) mixes typically require higher binder content to address segregation that could hinder passing ability and increase the shrinkage probability; therefore, a modified approach is required to address these challenges. Building upon previous findings on M60 grade SCC designed with ultrafine blast-furnace slag (UFBFS) and nano-silica (NS), this study expands the scope of the modified SCC mix design approach to M50 and M70 SCC mixes, using granite-type aggregates as done in the earlier study. The experiment was extended to M50, M60, and M70 SCC mixes with basalt-type aggregates, using the same binder contents of 520 kg/m3, 565 kg/m3, and 610 kg/m3, respectively. Verified for flow properties, all the mixes achieved slump flow values between 650mm and 680mm, T500 less than 6 seconds, a slump to J-ring flow difference less than 50mm, and a V-flow duration of 11 seconds or less. The 28-day compressive strength and flexural strength results for M50, M60, and M70 grade SCC fell in the ranges of 59.0 MPa to 83.4 MPa and 5.5 MPa to 9.20 MPa, respectively. Durability tests at 28 days showed water penetration of less than 10 mm and water absorption of less than 5.5%, and at 56 days, rapid chloride penetration results were less than 800 coulombs. This modified SCC mix design approach could be used across a wider region of India.