Análise da incorporação de CO2 em placa cimentícia têxtil

Abstract

The growing concern about the environmental impacts caused by carbon dioxide (CO₂) emissions from the cement industry has driven the development of sustainable and efficient materials. Portland cement, the main binder in concrete and cementitious boards, is responsible for a significant share of global CO₂ emissions. In this context, the present study proposes to investigate alternatives that combine technical performance with a reduced carbon footprint through the use of textile reinforcements in flat cementitious boards subjected to accelerated carbonation. The general objective of this work is to evaluate CO₂ uptake through carbonation under different exposure conditions in flat cementitious boards reinforced with nonwoven fabric and alkali-resistant glass fabric, in comparison with boards reinforced with synthetic PVA fibers, analyzing the differences in physical, mechanical, and microstructural behavior, as well as in eco-efficiency indicators. The experimental methodology consists of material characterization (particle size distribution by laser diffraction, X-Ray Fluorescence, X-Ray Diffraction, specific mass, and Scanning Electron Microscopy), production of samples in batches using molds with internal dimensions of 29.5 × 16 × 1 cm, and natural carbonation (NC) and chamber carbonation (CC), both with controlled relative humidity and temperature, and with the CO₂ concentration set at 5%. The boards feature two layers of fabric interlaid within the cementitious matrix (Nonwoven Fabric Board (NFB) and Alkali-Resistant Glass Fabric Board (ARGB)). The sample groups were produced and subjected to physical tests (porosity, densities, and dimensional variation due to carbonation), mechanical tests (three-point flexural strength), microstructural tests (digital microscopy, thermogravimetry, carbonation depth, and gravimetry by mass loss in a muffle furnace), and eco-efficiency indicators (binder-flexural intensity, carbon-flexural intensity, and equivalent carbon-flexural intensity balance). The results showed that the NFB exhibited higher porosity and water absorption, associated with a greater advance of the carbonation front, reaching 0.79 mm at 14 days under NC and 0.87 mm under CC. CO₂ uptake at 28 days was also higher in the NFB, reaching 1.70% under NC and 0.88% under CC. In contrast, the ARGB showed a lower carbonation depth, associated with its lower porosity, and stood out for its better mechanical performance and lower eco-efficiency across the three proposed indicators. It is concluded that the type of reinforcement exerts a significant influence on the interaction between CO₂ transport, microstructure, and mechanical performance. The NFB showed greater potential for CO₂ mineralization under the conditions evaluated, while the ARGB presented the best balance between structural performance and eco-efficiency. CO₂ uptake was still insufficient to offset the emissions associated with production during the period evaluated, indicating the need for longer exposure times to better assess the carbonation potential of the boards.