Effect of particle-size gradation on cyclic shear properties of recycled concrete aggregate

Abstract

Recycled concrete aggregate (RCA) materials have been used as recyclable resources. To study the effect of particle-size gradation on the cyclic shear behaviour of RCA, direct shear tests (monotonic, cyclic, and post-cyclic monotonic) were performed. The RCA had friction angles of 51.41–55.5° and California bearing ratios (CBR) of 95–137%. The shear displacement rate was determined to be 1 mm/min, and the normal stress values were determined to be 30, 60, and 90 kPa. The shear characteristics of the RCA before and after cyclic shear were compared. The shear strength of well-graded RCA was larger than those of poorly-graded and discontinuously-graded. Under different normal stresses and cyclic displacement amplitudes, the vertical displacement of the well-graded RCA increased considerably. The shear stiffness and damping of well-graded RCA were larger than those of the other RCA types. The value of shear stiffness of the poorly graded RCA was between that of the well-graded and discontinuously-graded, and the damping ratio of the discontinuously graded RCA was between that of the poorly-graded and well-graded. Further, the friction angle obtained in the post-cyclic monotonic direct shear (PCDS) tests was higher than that obtained in the monotonic direct shear (MDS) tests. The shear strength of RCA was enhanced after cyclic shearing, and the well-graded RCA showed the best performance in friction characteristics.