One-part alkali-activated binder produced from inertized asbestos cement waste

Abstract

Owing to its carcinogenic potential and the environmental impacts associated with its disposal, the search for inertization technologies that enable the reuse of asbestos cement waste (ACW) is a priority in several countries. Among the proposed methods, optimized heat treatment is a promising methodology. However, there is a lack of studies aimed at the application of asbestos cement waste, even after proper treatment. Thus, this study investigates the potential use of heat-treated asbestos-cement waste (ACWT) as a precursor of one-part alkali-activated binders. Eleven formulations were established using the I-Optimal algorithm, strategically varying the mass fractions of ACWT, solid sodium metasilicate (SSM) with a molar ratio of SiO2/Na2O equal to 0.98, and water. These formulations served as the basis for the construction of models that relate the properties of pastes with the proportion of materials. The pastes were evaluated by isothermal calorimetry, X-ray diffraction, autogenous shrinkage, drying shrinkage, and compressive strength. The results show that the formulations with an SSM concentration of approximately 5% and molarities close to 1 M presented the best mechanical properties. The addition of SSM had a strong influence on the accumulated heat rate, with the formulations containing the activator showing superior mechanical behavior compared to the mixtures without the activator. Furthermore, the pastes without an activator exhibited lower drying shrinkage and chemical shrinkage. It was possible to verify that ACWT can be applied for the production of alkali-activated binders and that the statistical mixture design is an efficient method for predicting the evaluated properties.