Effect of air-cooled blast furnace slag aggregate on mechanical properties of ultra-high-performance concrete

This research is mainly focusing on making UHPFRC lightweight, cost-effective, and environment friendly with the application of waste material. Air-cooled blast furnace slag aggregate (ACBFSA) was chosen as coarse aggregate with 30%, 50%, and 100% replacement by volume of regular limestone coarse aggregate in this study. Both straight and hooked fibers were used in mixtures of UHPFRC. The impact of coarse aggregates and dual fibers on the mechanical characteristics and fracture parameters was investigated. Fracture analysis has been widely considered as an effective way to analyze the stability of cracks, crack propagation, and safety evaluation. Compressive strength, splitting tensile strength, elastic modulus, fracture toughness, and fracture energy were all examined experimentally. Experimental results determined that concrete workability decreased with every increase in the replacement ratio of natural aggregate. The compression and splitting tensile strength was first increased at 30% replacement and then decreased at 50% and 100% replacement of NA. Flexural and fracture properties show a uniform decrease as the replacement percentage increases. It indicates that ACBFSA has low resistance against cracking which is closer to the UHPFRC without coarse aggregates. Results also prove that the low-cost and eco-friendly waste material ACBFSA can be used in UHPFRC as partially and somehow fully replacement while retaining the main properties.