Controle da retração plástica em lajes de cobertura de concreto armado

Abstract

The plastic shrinkage occurs by the evaporation of water on the newly hardened concrete surface and it is influenced by climatic conditions of the concrete exposition. Its incidence is recurrent in surfaces with an area much larger than the thickness, as slabs. This pathology is harmful for the roof slabs, because they do not receive coating and will be exposed to aggressive agents. In this paper, we propose to predict and solve the plastic shrinkage in precast roof slabs of coverage reinforced concrete, using two lines of research. The prediction was made though Snell (2008) methodology in precast slabs. The results found were compared verifying the efficiency of Snell study, in prevention of the plastic shrinkage occurrence. With the concreting process analysis, the climatic conditions and the temperature of concrete, it was possible to indicate the best solution to solve or reduce the plastic shrinkage, efficiently in the researched precast roof slabs, with different types of cure, each case depending of the slab concreting day. The second stage consisted in laboratory analysis of slabs of small dimensions. The aim was verify the relation between the plastic shrinkage and the healing process.