Structural and Service Performance of Composite Slabs with High Recycled Aggregate Concrete Contents

This study investigates the structural and serviceability performance of composite slabs cast with recycled aggregate concrete (RAC). Fifteen slabs (2.0m by 1.0m and 0.15m thick) were tested: five in four-point bending up to failure, five to examine vertical deflections after 90 days of sustained loading, and five to examine human-induced vibrations. Different contents of coarse and fine recycled concrete aggregates (RCA) were examined (0%, 25%, 50%, 75% or 100%). The results from the four-point bending tests indicate that the use of RCA reduced the flexural capacity only marginally (by 7% for slabs with 100% RCA), but it reduced the energy absorption of the slabs more significantly (by up to 22%). The vertical deflections of the slabs after 90 days of sustained loading was similar, regardless of the level of RCA replacement. The results from the human-induced vibration tests show that all the slabs met the serviceability limits in current Eurocode 5, which indicates that RAC with high 100% of RCA is suitable for the construction of composite slabs. Finite element analyses (FEA) using Abaqus® provided further insight into the serviceability performance of the slabs. The FEA results show that the vibration performance of the slabs was mainly affected by their span length. The vibration frequencies of the slabs decreased (by up to 29.2%) as the span increased from 6m to 12m. This article presents new experimental data and insights into the structural and serviceability behaviour of composite slabs cast with 100% RCA, which are scarce in the existing literature. Hence, it contributes towards a better understanding on the behaviour of composite slabs cast with RAC. This in turn can encourage a more efficient use of resources in construction.