USO DE ADITIVO REDUTOR DE PERMEABILIDADE EM LAJES DE SUBPRESSÃO. CASO HABITAR-DF

The time required for the concrete to maintain its mechanical and physical properties, known as “lifetime”, is an important project parameter. A porous concrete (higher permeability) is more susceptible to the infiltration of water and aggressive substances, which leads to the deterioration of the steel reinforcement and the loss of tightness. For instance, slabs under negative hydrostatic pressure, also known as anti-flotation slabs, are employed in cases where the construction is situated below the water table. There are several advantages in this type of construction: less impact into the construction site due to the lowering of the water table level, preservation of subterranean water and reduction of environmental damages, since it does not required electricity to run water pumps. This work presents a case study concerning the construction of a 30cm thick and 750m3 anti-flotation slabs of reinforced concrete used into the construction of a residential building in Brasília, Brasil. In order to assure the tightness of such structure, a catalyst additive is used. This catalyst is known for its capacity of sealing cracks under 0,4mm by self-healing. The results showed that both the composition of the concrete (containing permeability-reducing admixture) and the adoption of appropriate constructive strategies were essential to ensure a integer and watertight structure.