Reinforcing mechanism and calculation method of compressive behavior of hybrid fiber reinforced recycled brick aggregates concrete

The effects of replacement ratio of recycled brick aggregate (RBA), fiber volume content and fiber types on the compressive strength and elastic modulus of steel-polyolefin hybrid fiber reinforced recycled brick aggregates concrete (HF/RBAC) were investigated through compressive strength and modulus test. According to the XRD and X-CT image of RBA, the reaction theory of active components of RBA with cement hydration products and the energy balance, the failure mechanism and fiber reinforced mechanism of HF/RBAC were investigated. The results show that, when all of natural aggregate(NA) was replaced by RBA, the percentage decrements in the cubic compressive strength, prism compressive strength and elastic modulus of HF/RBAC are found to be 36.72%, 24.95% and 43.53%, respectively. When the value of volume content of steel-polyolefin hybrid fiber is 1.5%, the percentage increments in the cubic compressive strength, prism compressive strength and elastic modulus of HF/RBAC are found to be 20.51%, 30.33% and 35.84%, respectively. Finally, the calculation method of compressive strength and elastic modulus of HF/RBAC was proposed. It had taken into account some factors, such as the crushed values, replacement ratio of recycled brick aggregate, the fiber volume content and fiber type.