Study on key micromechanics of recycled concrete based on compound random aggregate model

Abstract A compound random aggregate program of recycled concrete is developed based on the concrete damage plasticity constitutive mode using computer language. Bifacial mesoscopic models of the recycled concrete are studied with ABAQUS finite element analysis software. The mesoscopic performance of the recycled concrete are studied as follows: uniaxial compression strength, strain change, damage process, stress state, and so on. The influence factors of the mesoscopic mechanical properties of recycled concrete are analyzed. The analysis results show that there are concentration problems of tensile and shear stress in the internal and external interface area of the recycled concrete under the action of uniaxial compression load. The concentration of the tensile stress and shear stress may result in the damage failure of recycled concrete. The initial damage appears the first in weaker interfacial area, after that the damage is developed towards the mortar area. The recycled concrete compressive strength is greatly influenced by the new hardened mortar strength and old hardened mortar strength, and the influence of the interfacial area and the outer surface area is small. The mechanical properties of the recycled concrete are weakened due to the old hardened mortar.