Anchorage zones behaviour of early age concrete: Application to post-tensioned members

Anchorage zones of post-tensioned (PT) concrete slabs experience concentrated stresses as a result of post-tensioning procedures during the construction. The PT load is applied at two different stages after casting the concrete. This is to prevent shrinkage cracks and to overcome pre-stressing losses. During the early ages, however, concrete undergoes exothermic hydration reaction resulting in volume changes and associated thermal and time-dependent strains. During this time, if the strength development is lagging behind the induced stresses, severe micro-cracking can result. This can be a precursor to anchorage zone failures. To illustrate the case, Finite Element simulation of a rectangular section anchorage specimen is presented. The model consists in two distinct phases: the first phase simulates the hydration and associated thermal effects, and the second phase discusses the mechanical load imposed while the concrete hydration is ongoing. © 2011 Taylor & Francis Group, London