Introdução à EPT no ensino médio integrado: pílulas de informação em um APP para o processo seletivo do IFBA

Abstract

Utilization of asbestos-containing materials faces a global ban due to their carcinogenic potential, making the treatment of asbestos cement waste (ACW) a priority. Recycling secondary raw materials into cementitious products is a growing research field due to the environmental impact of the concrete industry. This practice helps to save primary raw materials and reduce global CO₂ emissions. While there is a growing interest in waste recycling in the construction sector, the specific influence of thermally treated asbestos cement waste (TCW) on the properties of eco-efficient mortars has not yet been widely investigated, leaving an opportunity to explore its potential as a sustainable and safe material. This study proposes to use and evaluate the efficiency of thermal treatment to inert chrysotile and analyze the partial replacement of Portland Cement (PC) with treated waste, in eco-efficient mortars aiming to reduce CO2 emission and the noble disposal of waste with agglomerating potential. For thermal treatment, the optimal parameters were adopted, which for the type of furnace used, consist of a temperature of 800°C, a calcination time of 1 hour and a waste mass per batch of 5 kg. The mixing design was determined using the Design-Expert software, which optimized the pilot planning resulting in nineteen combinations. These combinations allowed the construction of mathematical models based on experimental data for prediction and optimization. The mortars had their properties evaluated both in the fresh and hardened states. In the fresh state, the consistency index, mass density, incorporated air content and water retention were analyzed. In the hardened state, density, flexural tensile strength, compressive strength, modulus of elasticity, potential tensile adhesion strength to the substrate and surface, and dimensional variation were evaluated. Statistical analysis of the data allowed the evaluation of the effect of each component on the properties of the mortars and the identification of abnormalities in the data. The statistical significance of the factors was established through analysis of variance (ANOVA). The elimination of chrysotile in TCW was confirmed, guaranteeing the safety of the material. Statistical analysis showed that the addition of treated asbestos cement waste (TCW) influences various properties of the mortar. Based on the optimal formulation, it was found that the use of TCW allows a significant reduction in the clinker content of mortars, reducing it by up to 38%. In addition, the high surface area of TCW improves water retention, allowing the elimination of the water-retaining additive. The mechanical properties of mortars, such as compressive and flexural tensile strength, were not negatively influenced by TCW, demonstrating its potential as a sustainable and safe substitute in mortars. The study in question evaluated the replacement of up to 44% of Portland cement with TCW, resulting in an innovative mortar that maintained its mechanical properties, meeting all the classification requirements established by ABNT NBR 13281 for ARV-II type mortars. The results revealed a substantial cost reduction, with the mortar being 37% cheaper. The statistical design of the mixture was shown to be efficient in predicting the evaluated properties, resulting in an eco-efficient coating mortar.