Cracking of composite fiber-reinforced concrete foundation slabs due to shrinkage

Abstract

Industrial concrete floors made directly on the ground are concrete slabs reinforced with structural reinforcement and often additionally reinforced with dispersed reinforcement in the form of polypropylene or steel fibers. More often than not, these floors are not separated from the reinforced concrete slab; they form a monolithic whole with it. Due to high variable loads and additional pressure of groundwater, in the case of foundation slabs in underground garages, floors ought to be subject to precise static and strength calculations. However, the load from concrete shrinkage is often neglected, as it is considered to appear temporarily in concrete care phase and to disappear gradually when the slab is normally exploited. In the recipe of the concrete mix itself, the composition of aggregate, plasticizing additives, the amount of mixing water and the addition of dispersed reinforcement should be carefully selected in order to minimize concrete shrinkage. The quality of the flooring also has a huge impact upon the course of shrinkage and the distribution of tensile stresses in the floor. The article presents the main errors related to the appearance of excessive cracking caused by shrinkage stress.