Effect of crushed air-cooled blast furnace slag on mechanical properties of concrete

Morphology characteristics of mix aggregates with crushed air-cooled blast furnace slag (SCR) and crushed limestone (LCR) with 5-20 mm and 20-40 mm gradation were represented by numerical parameters including angularity number (AN) and index of aggregate particle shape and texture (IAPST). The effect of mix aggregates containing SCR on compressive strength and splitting tensile strength of concrete was investigated. Fracture characteristics of concrete, interfacial structure between aggregates and matrix were analyzed. The experimental results show that porous and rough SCR increases contact area with matrix in concrete, concave holes and micro-pores on the surface of SCR are filled by mortar and hydrated cement paste, which may increase interlocking and mechanical bond between aggregate and matrix in concrete. SCR can be used to produce a high-strength concrete with better mechanical properties than corresponding concrete made with LCR. The increase of AN and IAPST of aggregate may enhance mechanical properties of concrete.