Multiaxial mechanical properties of plain recycled aggregate concrete

Abstract

Multiaxial tests were performed on 150 mm × 150 mm × 150 mm cubic specimens of three strength grades of plain structural recycled aggregate concrete (RAC) at different stress ratios using a large static–dynamic true triaxial machine. Friction-reducing pads (two layers of plastic membrane with lubricants) were placed between the compressive loading plate and the specimens. The tensile loading planes of the concrete samples were processed by an attrition machine and then the samples were glued to the loading plate. The characteristic failure modes of the specimens and the crack directions were observed. The three principal static strengths in the corresponding stress state were measured. The influence of the stress ratios, stress states and strength grade on the triaxial strengths of RAC was also analysed. The experimental results showed that ratio of triaxial failure strength σ_3f to the corresponding uniaxial compressive strength f_c for the three strength grades of RAC was higher than that of conventional concrete (CC), especially under triaxial compression; moreover, it is dependent on the strength grade of RAC, the stress states and stress ratios; however, the differences of tensile–compressive ratios between the RAC and CC are not significant. On this basis, a new failure criterion with the six parameters is proposed for plain RAC under multiaxial stress states. It provides the experimental foundations for strength analysis of RAC structures subject to complex loads.