Compounding effect between influences of fine and coarse recycled aggregates on non-uniform shrinkage behavior of steel-concrete composite slab section

Abstract

The steel-recycled aggregate concrete (RAC) composite slab is a practical structural member for applying RAC with the fine recycled aggregate (FRA). Despite its advantages, the non-uniform shrinkage (NUS) of composite slabs makes its long-term behaviour the critical factor controlling its design. The use of recycled aggregates would further enlarge the influence of the NUS, while no study has focused on the influence of FRA. Therefore, this paper aims to investigate the influence of FRA on the RAC NUS with different coarse recycled aggregate (CRA) contents. Fifteen RAC slab specimens were fabricated to monitor the shrinkage strain development, considering the replacement ratios of CRA and FRA (rCRA and rFRA), slab thickness, and moisture-transferring boundary conditions. Experimental results showed that 1) the FRA significantly increased both the shrinkage strain value and its gradient through slab thickness, 2) the FRA and CRA had a significant compounding effect (i.e. the influence of FRA varied with rCRA) on the NUS of RAC, and the compounding effect varied with slab thickness. The test results were used to develop a model for the NUS of RAC made with both FRA and CRA. The predicted results well matched the test data from the literature and this study. Finally, a parametric analysis was conducted based on the proposed model.