Avaliação do potencial da cinza de folha de bambu como material cimentício suplementar na produção de concretos e seus efeitos sob a ação de íons cloreto

Abstract

Cement is a widely used construction material worldwide. However, its production has significant environmental impacts, characterized by high energy consumption, unbridled extraction of natural resources, and considerable carbon dioxide emissions. Given this reality, researchers have been dedicated to analyzing alternatives that can partially replace cement in concrete production. Considering the worldwide practice of incorporating waste with pozzolanic properties in concrete production, the evaluation of the pozzolanic activity of supplementary cementitious materials becomes crucial for the search for more sustainable solutions. In this context, this study explores the potential of bamboo leaf ash (BLA), derived from the disposal of bamboo leaves, as a partial substitute for cement. The research focused on the production of BLA, varying the calcination temperatures (500, 600, 700, 900, and 1000 °C). The ash was characterized through chemical, physical, thermal, and pozzolanic activity analyses, aiming to identify the best condition for production. The BLA with the best properties was then used as a partial substitute for cement (5%, 10% and 15%) in the production of concrete, which was subjected to analyses of compressive strength, water absorption by capillarity and chloride diffusion coefficient, according to the methodologies of NT Build 492 and UNE 83987. The analysis of the chemical composition of the BLAs showed that, at all calcination temperatures, it is a pozzolanic material. However, the highest temperatures (900 and 1000 °C) showed a crystalline structure, while the ashes calcined at 500, 600 and 700 °C exhibited high amorphism and pozzolanic activity index in accordance with the requirements of NBR 12653, in addition to presenting high reactivity by the Modified Chapelle method. The BLA calcined at 600 °C stood out as the most efficient, exhibiting a reactive pozzolanic characteristic of amorphous structure and a high silica content in its composition. When partially replacing cement with BLA in concrete, a decrease in water absorption by capillarity and in the chloride diffusion coefficient was observed as the substitution content increased. In addition, there was an increase in compressive strength. With the substitution of 15%, an increase of more than 18% in compressive strength was recorded, in addition to reductions of more than 35% in water absorption by capillarity and 71% in the chloride diffusion coefficient, indicating the viability of using this agricultural residue as a supplementary cementitious material.