Thermo-chemo-hygro-mechanical simulation of the restrained shrinkage ring test for cement-based materials under distinct drying conditions

Abstract

A thermo-chemo-hygro-mechanical (TCHM) simulation approach for modelling the concrete behaviour during restrained shrinkage ring tests under two distinct drying conditions, namely, top and bottom as well as circumferential drying, is presented herein. The models were calibrated using data from an extensive round robin testing programme, which involved measurements on the time dependent properties of a specific concrete mix. Experiments and simulations accounted for the evolution of cement hydration, moisture diffusion, mechanical and viscoelastic properties and concrete fracture. The modelling approach was validated using results from an unrestrained shrinkage prism test and a restrained shrinkage ring test under top and bottom drying, and insights are obtained for the behaviour of restrained concrete rings under the two distinct drying conditions. It was observed that drying develops faster in rings under top and bottom drying compared to those under circumferential drying and so develops microcracking which is initiated at the steel–concrete interface. Conversely for circumferential drying, microcracking firstly occurs at the outer circumference due to the self-restraining effects arising from moisture gradients and is eventually induced in the steel–concrete interface. The top and bottom drying condition may be adopted for shorter testing duration; however, it does not encapsulate the self-restraining effects well.