Mechanical properties and frost resistance of recycled brick aggregate concrete modified by nano-SiO 2

Abstract In this work, brick aggregates were immersed in nano-SiO 2 solution for 2 days, and the effects of nano-SiO 2 on the brick aggregate properties, mechanical properties (compressive strength, flexural strength, and splitting tensile strength), frost resistance (apparent phenomenon, mass loss, relative dynamic modulus of elasticity, and compressive strength) of recycled brick aggregate concrete and the microstructure of recycled brick aggregate concrete were investigated. The results show that nano-SiO 2 can effectively improve the performance of recycled brick aggregate and the mechanical properties of recycled brick aggregate concrete, mainly by reducing the water absorption and crushing index and improving the compressive strength, flexural strength, and splitting tensile strength. With increasing nano-SiO 2 solution concentration, the compressive strength, flexural strength, and splitting tensile strength of recycled brick aggregate concrete first increase and then decrease. The frost resistance of recycled brick aggregate concrete is superior to that of ordinary aggregate concrete, while the frost resistance of nano-SiO 2 -modified recycled brick aggregate concrete is inferior to that of recycled brick aggregate concrete. In addition, the freeze‒thaw damage mechanism of recycled brick aggregate concrete is analyzed, and a freeze‒thaw damage life prediction model of nano-SiO 2 -modified recycled brick aggregate concrete based on the Weibull distribution is proposed.