Influence of lightweight aggregates on the physical and mechanical residual properties of concrete subjected to high temperatures

Abstract This research studies the high temperature behavior of lightweight aggregate concretes (LWAC) by providing a comprehensive study that regroups the physical, thermo-mechanical and mechanical properties of three different LWACs. Then these properties are compared to the properties of a normal-weight concrete (NWC) as well as to those of the mortar phase of these concretes, thus, enabling us to isolate and identify specific behaviors of the lightweight aggregates (LWA). Contrary to the normal weight aggregates, the LWAs showed a compatibility in thermal strain with the mortar phase, which led to fewer cracks in the interfacial transition zone (ITZ) and thus, it resulted in a divergence in behavior between LWACs and NWC, particularly for the residual permeability and tensile strength values. While LWACs generally exhibited lower decrease of failure strengths, and Young Modulus with temperature than NWCs, its Poisson’s ratio was greatly decreased after 300 °C.