Long-term behaviour of simply supported composite slabs with recycled coarse aggregate

This paper describes an experimental programme and theoretical analysis of the long-term behaviour of composite slabs prepared with recycled aggregate concrete (RAC). The test programme consisted of four full-scale slab samples of thickness 120 mm and 180 mm, with two specimens subjected to sustained loads and two unloaded companion samples. All the specimens were subjected to shrinkage effects and measured in a simply supported static configuration over a period of 268 d. A non-linear numerical model was developed to account for the timedependent behaviour of the composite slabs by including the effects of non-uniform shrinkage, creep and concrete cracking. The model was validated against the test results. A parametric study was then carried out to evaluate the influence of time effects on the long-term deflections of RAC composite slabs. A design approach to be used for routine design of RAC composite slabs was developed and validated through a comparison of calculated values and experimental measurements. Based on the experimental data collected as part of this study, it was found that both the numerical model and the proposed design approach estimated well the time-dependent deflections of RAC composite slabs by considering the influence of the non-uniform shrinkage profile.