A fully generalised, coupled, multi-phase, hygro-thermo-mechanical model for concrete

A detailed and fully generalised (3D) hygro-thermo-mechanical model for concrete is presented. The model captures the complex behaviour of this composite material through the adoption of a multi-phase material description which captures the strong coupling between the separately considered solid, liquid and gas fields. Heat and mass transport of the fluid phases are modelled in a coupled manner such that an accurate description of the fluid transport processes in concrete is possible, illustrating in particular the redistribution of liquid and the increases in vapour content and pore pressure associated with the application of elevated temperatures. The mechanical behaviour of the solid skeleton is modelled by way of an isotropic thermo-mechanical damage model in which the degradation of the material due to both mechanical and thermal loading is taken into account. Coupling with the hygro-thermal components of the model allows for the effects of material degradation on mass transport to be captured. The model is validated over a wide range of capability through the reproduction of two sets of separate and differing experimental results concerning isothermal drying and high temperature problems. For these two problems, the model is shown to reproduce accurately values for total moisture mass losses, moisture distributions, temperatures and pore pressures developed in both time and space in various types of both ordinary and high performance concrete materials. A further parametric study is then presented where the model is used to investigate the roles of various mechanical behaviours in the overall hygro-thermo-mechanical response of the concrete under high temperature conditions. The implications of the results are discussed in detail