Resíduo de caulim primário como material pozolânico em concreto seco: propriedades físico-mecânicas e durabilidade.

Abstract

The accumulation of waste beneficiation of kaolin the producing region of the state of Paraíba is worrying environmentalists and motivating research that will propose solutions for reuse of waste as alternative raw material in various industries. Previous research has demonstrated the potential of kaolin waste for to be used as pozzolanic material, and this study aimed to evaluate the influence of its use in physical and mechanical properties of concrete dried, also evaluating the durability tests through degradation by exposure to sulfates and rainfall simulation driven. Initially it was performed the physical, chemical and mineralogical residue, which was performed after grinding and calcination temperature of study to obtain a material with pozzolanic reactivity, this reactivity assessed by determining the activity index with Portland cement at 28 days. For definition of the traits to be evaluated was used statistical experimental design Central Composite Rotational Design (CCRD) being used for the analysis of Response Surface Methodology (RSM) whose results indicated traces 1:5,56, and 1:6,67 1:8,33. The use of metakaolin, the residue obtained was evaluated as a replacement to the mass of cement in said trace in the levels 10%, 15%, 20% and 25%. The physical and mechanical properties evaluated were compressive strength, tensile strength by diametral compression, elastic modulus, density, water absorption and voids. Analysis by thermogravimetry and X-ray diffraction were also performed to confirm the pozzolanic reaction. The residue calcined at 800 ° C showed characteristics suitable for the use as a pozzolanic material. Replacement of 10% and 15% of the mass of cement by the same percentage of kaolin waste in concrete and 1:8,33 factor A dash / (C + M) = 0.57 promoted, respectively, increases of 12% and 6% in compressive strength of concrete reference without mineral addition. For other traits and levels of substitution was no reduction in compressive strength and indirect tension. For the remaining traits and levels of substitution was reduction in compressive strength and indirect tension. Was observed, compared to the reference test bodies, a reduction in dimensional expansion of concrete containing 10% of cement replaced by the residue, however, for all traits and all substitution levels there was an increase in the rate of water absorption, the which, although higher than the reference concrete, had values that meet the ceilings of ABNT. After the rainfall simulation driven tests, the samples was used in which the residue showed higher weight loss and they tend to increase with increasing levels of substitution and the results of chemical analysis indicated of the leached indicated that the decomposition occurred in concrete is connected with the low reactivity of pozzolanic waste.