Influence du vent sur le comportement des bétons au très jeune âge

An experimental study is made in our laboratory in order to explain the concrete behavior at very early age. Three concretes having the same paste volume, gravel/sand ratio (G/S), an identical workability and three different effective water/cement ratios (Weff/C) were studied. The tests were realized in a ventilated tunnel allowing to impose an uniform wind speed during the experiment, while maintaining a constant temperature and a constant hygrometry. The tests showed that when these concretes are not protected, they cracked very early (before the beginning of set) in severe conditions (restrained shrinkage) whether it is with or without wind. The cracking risk of concrete surface at the very early age is linked to the migration of a part of the excess water outside the concrete which generates very important dimensional variations. To study the phenomenon, measurements of evaporation, capillary depression and horizontal longitudinal deformations were made for the three concretes with or without wind. MOTS-CLES. Retrait plastique, fissuration au jeune âge, sechage.