Thermal treatment optimization of asbestos cement waste (ACW) potentializing its use as alternative binder

Abstract

This study aims to optimize the thermal treatment of asbestos cement waste (ACW) to make it suitable for use as an alternative binder. The optimization was performed using a 2k factorial design with the central point having temperature (600 and 800 °C), time (1 and 3 h), and mass (1 and 5 kg) as factors. The percentages of chrysotile, belite (C2S), and calcite in the treated ACW were the main experimental responses obtained through thermogravimetric analysis (TGA/DTG) and X-ray diffraction (XRD). Eleven experiments were conducted to develop models correlating the experimental responses with the factors and their interactions. The results show that chrysotile underwent complete dehydroxylation in treatments in which the temperature is 700 °C or higher. With an increase in the calcination temperature, the belite content increased in the treated ACW; however, a higher amount of CO2 was emitted to the atmosphere during treatment. The optimal treatment was performed by calcining 5 kg of ACW heated in a furnace for 1 h at 800 °C. Under these conditions, chrysotile was completely removed with an estimated CO2 emission of 175.60 gCO2/kg of treated waste. Moreover, the treated residue was found to have 40.42% belite, providing the material with binding capacity.