Creep in High and Very High Performance Concrete
This chapter introduces the results of creep tests that carried out high performance (HP) concretes of the bridges of Joigny and Pertuiset, an HP concrete specially designed to limit cracking in a nuclear reactor containment, as well as on a very HP (VHP) concrete designed for a bridge application. The results are analyzed in terms of present knowledge regarding creep mechanisms. The most important results are kinetics and ageing which are clearly different from current concretes and, for silica-fume HP concretes, the absence of drying creep and hence of a size effect. Creep deformations with and without drying are illustrated in which they are compared with those of the control concrete. The drying creep may be explained by a structural effect related to drying shrinkage: in an unloaded specimen, drying leads to free deformations which are faster and greater at the surface than in depth, and this results in tensions on the surface and cracking.