Avaliação do efeito da substituição parcial do cimento por resíduo de calcário nas propriedades mecânicas e térmicas de concretos leves

Abstract

The use of lightweight concrete was first recorded over 3000 years ago. Due to its thermal properties, lower cost and greater production capacity, this type of concrete has been explored in construction that requires lightness and in structures for thermal insulation of exposed concrete. Therefore, this work aimed to evaluate the effects on of the partial replacement of cement by limestone residue on the mechanical and thermal properties of Light Concrete (LC), formulated using expanded clay and expanded vermiculite, as light aggregates. In addition, fine quartz sand was also used as fine aggregate. The mechanical behavior was analyzed by compression strength tests, dynamic elastic modulus and indirect tensile strength by diametrical compression, and the physical behavior by immersion water absorption tests, voids index, porosity, specific mass, and thermal conductivity. In addition, microstructural analysis (XRF and XRD) of the limestone residue was also carried out. For comparison purposes, a reference concrete mix was made without any substitution and, based on it, partial replacement of cement was carried out in 5%, 10%, 15%, 20%, and 25% by lime residue. All concretes had density lower than 1000 kg/m³, with maximum and minimum mix density of 961 kg/m³ and 910 kg/m³, respectively. The thermal conductivity, measured in wet samples, showed values from 0.453 to 0.593 W/(m.K). In the dry samples, the values varied between 0.301 and 0.418 W/(m.K). The compressive strength varied between 11.6 and 6.1 MPa, at 28 days. Another important aspect considered in the study was the consumption of cement, which ranged from 262.5 to 350 kg/m³.