Prediction of time-dependent behaviour of steel–recycled aggregate concrete (RAC) composite slabs via thermo-mechanical finite element modelling

Composite steel-concrete slabs with profiled steel sheeting have been extensively applied in industrial and civil infrastructure, and meanwhile recycled aggregate concrete (RAC) has shown its potential utilisation in reinforced concrete floor systems. To date very limited research efforts have been available on the influence of recycled coarse aggregate (RCA) on the time-dependent behaviour of continuous composite slabs. This study aimed at proposing nonlinear thermo-mechanical FE models to predict the long-term behaviour of composite steel-RAC slabs based on ABAQUS software, to account for the coupled effects of the non-uniform shrinkage and creep deformations caused by the impervious soffit decks, together with concrete cracking. Full-scale experimental data collected from 28 composite slabs with natural aggregate concrete (NAC) and RAC from the literature were used to validate the developed FE models. Using the verified computer models, the influence of RCA incorporation on the time-dependent behaviour of five-span continuous composite slabs were considered to represent typical engineering practice. The results revealed that the composite slabs with 100% RCA exhibited 45.5% and 10.75% increments in the maximum mid-span deflection and support bending moment compared to those with the NAC, respectively. A shrinkage gradient is needed to predict the time-dependent behaviour of continuous steel–RAC composite slabs.