Performance of RC slabs under the combined effect of applied loads and restrained shrinkage

One of the key factors towards a proper service life behaviour of reinforced concrete (RC) structures is the adequate control of crack widths by the reinforcement, as to ensure adequate durability. However, currently existing methodologies for reinforcement design are not satisfactory in providing instructions for adequate control of crack widths when RC members are subjected to high restraints to deformation (e.g. due to shrinkage), in combination with vertical loads (both dead and live). This is a typical situation in RC slabs applied in buildings. The reason of the unsatisfactory character of current design provisions and recommendations is related to the very high complexity of phenomena at interplay, particularly the non-uniform distribution of moisture in concrete that inherently brings non-uniform distribution of stresses (in space and time) due to drying shrinkage, which in turn have important influence in the process of crack development. This paper intends to contribute for deepening knowledge on these processes by deploying a thermo-hygro-mechanical simulation framework, which is described and validated, to the analysis of a highly restrained slab in service load conditions.Funding provided by the Portuguese Foundation for Science and Technology (FCT) to the Research Projects PTDC/ECM/099250/2008, EXPL/ECMEST/1323/2013 and PTDC/ECM-EST/1056/2014 (POCI-01-0145-FEDER-016841), as well to the Research Units ISISE (POCI-01-0145-FEDER007633) and CONSTRUCT (POCI-01-0145-FEDER007457) is gratefully acknowledged. A word of acknowledgment is also given to the help provided by Margarida Vieira, who assisted the experimental work in the course of her MSc thesis. The authors would also like to acknowledge the benefits of crosslinking research through the network of COST Action TU1404 “Towards the next generation of standards for service life of cement-based materials and structures” (www.tu1404.eu).