On the importance of initial stresses in concrete and of the resulting mechanical effects

Abstract From various results of tests of crack propagation in mortars and concretes in different uniform hygral conditions and at different imposed displacement rates, the roles and importance of the various physical causes that might explain the nonlinearities observed during unloading are analyzed : overall viscoelasticity, confined viscoelasticity, initial stresses. Various approaches reveal the importance of the initial stresses. If their role is confirmed, fruitful lines of investigation will be opened up in the field of the laws governing the mechanical behaviour and fatigue of concrete.