SUBSTITUIÇÃO PARCIAL DE BIOCHAR EM RELAÇÃO AO CIMENTO PORTLAND PARA CONFECÇÃO DE CONCRETO E ARGAMASSA COM PROPRIEDADES DE ALTO DESEMPENHO SUSTENTÁVEL

Abstract

The use of traditional mortar and concrete is essential in most construction and public works projects. However, these materials are primarily made from Portland cement, a component that is energy-intensive and generates a significant amount of greenhouse gases, contributing to global warming. This situation represents a considerable challenge for the construction sector, which must find a balance between sustainable development and growing infrastructure needs. Biochar, an organic charcoal produced by organic waste pyrolysis, can be used as an alternative to cement. Therefore, the main objective of this study is to develop a mixture that allows for the partial replacement of cement using rice husk waste products, from which high-performance concrete and mortar with improved properties will be produced, aiming for more efficient and sustainable solutions for the construction industry. The methodology used in this study included two main phases. Firstly, a literature review was conducted using the State of the Art by Systematic Review (StArt) software, with the goal of providing an overview of the current state of the subject, allowing the contents of the substitution to be defined. Next, the experimental phase began, which consisted of the mixing and production of mortars and concretes with partial cement replacement by biochar, specifically 1%, 5%, and 10% by mass. Chemical analyses were performed, notably the pozzolanic reactivity test according to the Chapelle method, in addition to physical characterization (density, porosity, and capillary water absorption) and mechanical testing (compressive strength). The results showed that the performance index for Portland cement at 28 days, expressed as a percentage (%), attained 176% after rounding to the nearest whole number, exceeding the minimum limit of 75% established by ABNT NBR 5752:2014 for evaluating the pozzolanic activity of Portland cement-based materials. The highest compressive strength of the mortars after 28 days of curing was obtained with a 10% replacement rate, that is, 28.24 MPa, while the reference mortar reached 18.17 MPa over the same period. For the concrete, the maximum strength was recorded with a 5% replacement rate at 56 days, reaching an average of 46.65 MPa, in contrast to the reference sample, which showed 35.56 MPa over the same period. The addition of biochar resulted in a reduction in the mortar’s water retention capacity, which decreased from 8.61% (reference) to 5.11% after the addition of 10% biochar. It is concluded that the addition of up to 5% biochar improves the physical-mechanical characteristics, while contributing to the decarbonization and sustainability of cementitious materials.