Effect of the incorporation ratio of recycled concrete aggregate on the properties of self-compacting mortar

Abstract

This paper investigates the effect of the addition of recycled concrete aggregate (RCA) on the properties of self-compacting cement-based materials at the mortar scale, at the incorporation ratios of 0, 25, 50, and 100 %. The results showed that the yield stress and the plastic viscosity of the mortar increased with the incorporation ratio of RCA. Slump flow and V-funnel time were used to assess these properties. The mechanical strength of the mix also increases with the RCA incorporation ratio. A quantitative analysis of the data demonstrated that the effect of the addition of RCA on the mortar's rheological properties can be attributed to a decrease of the aggregate's packing density (morphology effect), a decrease of the effective water-to-cement ratio of the mix (water-to-cement ratio effect), and an increase of the aggregate's effective volume fraction (volume fraction effect). The latter two effects are caused by the aggregate's high water absorption, whose impact on mechanical strength is stronger than that caused by the morphology effect. In addition, the increase of the mix's strength can also be attributed to the increase of the effective water-to-cement ratio of the mix and to the bonding quality between the aggregate and the cementitious matrix. The increment in the incorporation ratio of RCA causes a reduction of the effective water-cement ratio of the mix and an increase of the bonding quality.