Investigation on steel fiber strengthening of waste brick aggregate cementitious composites

The waste red brick aggregate substituted with natural coarse aggregate can effectively alleviate environmental pollution in engineering concrete constructions. However, its mechanical performance lags far behind natural coarse aggregate due to micro-pore voids and micro-cracks. Three types of steel fiber contents (0, 1%, and 2%) are selected to improve the mechanical behavior of recycled concrete in this study. Cubic compression test, splitting tensile test, prism compression test, and static compressive elastic modulus test are carried out to study the influence of steel fiber content and replacement rate of recycled coarse aggregate. In addition, the stress-strain behavior and failure mechanism of steel fiber recycled brick aggregate concrete are discussed, and microscopic crack development is also analyzed. Test results show that the specimens without steel fiber are prone to aggregate destruction under loading. The cubic and prismatic compressive strength decreased by 48% and 34%, while the splitting tensile strength reduced by 40%. The mechanical properties substantially improve when the steel fiber content is 1%. The finite element model of steel fiber recycled brick aggregate concrete under uniaxial compression is established. The constitutive model for predicting uniaxial compression of steel fiber recycled brick aggregate concrete is also proposed.