Avalição da possibilidade de substituição parcial do Cimento Portland por cinzas da lama da Estação de Tratamento de Água

Abstract

The proper management of waste generated in Water Treatment Plants (WTPs) is an increasing environmental challenge due to the improper disposal of these residues into water bodies. On the other hand, growing environmental concerns and the pursuit of sustainable solutions in the cement industry have driven research on the use of industrial by-products as partial substitutes for Portland cement. Among these residues, the sludge from Water Treatment Plants stands out. After undergoing drying, grinding, and calcination processes, it exhibits chemical and physical characteristics that may confer pozzolanic properties to the material. This study aimed to evaluate the possibility of partially replacing Portland cement with ash obtained from the calcination of Water Treatment Plant Sludge (WTPS). For this purpose, sludge samples were collected from the Umbeluzi Water Treatment Plant (WTPU), located in Boane district, Maputo province. The sludge was subjected to drying, calcination at 1000 °C, grinding, and subsequently a series of experimental tests to characterize its physicochemical properties and assess its potential as a cement replacement material. The replacement percentages considered in this study were 7%, 10%, and 20%. Among these, the most suitable proportions were found to be 7% and 10% of calcined sludge, as they did not significantly compromise the mechanical performance of the mortar, presenting strength values consistent with the standard’s requirements. Therefore, it is concluded that the sludge analyzed in this study can be used, after calcination, as a partial substitute for Portland cement, thereby contributing to reducing the environmental impact associated with the improper disposal of sludge and minimizing the consumption of raw materials in the cement industry, making the process more economical and sustainable.