Estudo do concreto laterítico dosado com aditivo plastificante à base de lignosulfonato.

Abstract

In order to attend the population increase, the construction sector needs more inputs for the implementation of construction of buildings, roads, airports, industries, bridges, dams, tunnels etc. Concrete is a construction material of great use in the whole planet. The coarse aggregates in concrete are commonly used from igneous rocks, scarce in some regions of the planet and also in Northern Brazil. Lateritic concretions which today have no economic value are present in lateritic soils of the tropics and in Brazil, covering 65% of its territory. In this research analysis the physical and mechanical properties of concrete were made in fresh and hardened state, made with lateritic concretions using a first generation plasticizer additive based on lignosulfonates. It was produced a reference concrete, CR, with slum of 80 ± 20 mm and three comparative admixtures with additive variations of 0.4%, 0.6% and 0.8% on the cement mass, keeping a constant water/cement factor. It was investigated in this research: setting time and paste flow; slump test and spread the table Graff in fresh concrete. The unconfined compressive strength, splitting tensile strength and bending tensile strength were determined at 3, 7 and 28 days and the modulus of elasticity of charged cycles and by test ultrasonography were compared with theoretical expressions from Brazilian standards (ABNT), Comite Euro-International du Beton (CEB) and American Concrete Institute (ACI). The Poisson's ratio and the stress-strain curve were determined. The analysis of the microstructure by scanning electron microscope (SEM), showed the process of cracking of the samples at 3 and 28 days in hardened concrete. The results indicated that the addition of the additive plasticizer increased the unconfined compressive strength and modulus of elasticity at 28 days compared to the reference concrete. Tensile strength by splitting tensile strength and bending tensile strength showed no significant differences compared to the reference concrete. For mixes with 0.8% additive plasticizer, a value above the level of saturation, the unconfined compressive strength and elasticity modulus at 3 days and 7 days were lower compared to other mixes, however higher than the same at 28 days. This is probably due to the delay in the setting time of cement, common additions in excess of the ideal content of organic additives from the first generation. All the concrete had achieved satisfactory levels of workability, strength and deformation.