Towards a simple and unified modelling of basic creep, shrinckage and drying creep of concrete

A three-dimensional rheological modelling is proposed for the long term concrete mechanical behaviour. Concrete is supposed to have a non-linear visco-elastic behaviour. The non-linearity used first allows conferring a realistic non asymptotic strain to the basic creep, based on a consolidation theory. Moreover, for the non-saturated concrete, a dependence of the capillary pressure effects on the stress state is postulated. It assumed that a damage state exists around microcavities in depression, this damage depends also on the applied stresses whose can led to a closing or opening of the micro-cracking and consequently to a best or to a worst transmission of capillary effects to the solid skeleton. This dependency is highlighted using a simple numerical analysis of a composite material including in an elastic matrix both cavities in depression and rigid inclusions. The linear dependence of capillary effect on the applied stress confers to the model the capability to simulate shrinkage and drying creep strains.