Caracterização de argilas da região Sudeste do estado do Paraná para utilização como material cimentício suplementar

Abstract

To reduce the cement industry's environmental impact, recent studies have focused on decreasing clinker usage by incorporating supplementary cementitious materials (SCMs). The use of calcined clays in combination with limestone fillers as SCMs in ternary cements has gained momentum. This study aimed to characterize clayey material samples from the southeastern region of Paraná, Brazil, and evaluate their feasibility as SCMs. Seven ceramic clay samples were collected from the region, processed through grinding, and thermally activated at 850 °C. The clays were characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), and particle size distribution analysis. Subsequently, the incorporation of the clays into cement pastes was evaluated by preparing a reference matrix composed solely of Portland cement (PC), mixtures with 20% clay and 80% PC, as well as ternary cement formulations containing 30% calcined clay, 55% PC, and 15% filler. Rotational rheometry, isothermal calorimetry, compressive strength tests (at 3, 7, and 28 days), and XRD were conducted on the cement pastes. Additionally, a simplified analysis of carbon dioxide (CO₂) emissions from the evaluated compositions was performed. The study identified locally available clays with potential for use as SCMs in Portland cement matrices and ternary cements, with compressive strengths at 28 days equivalent to the reference mix, corroborated by the intensified formation of carboaluminate (AFm) phases identified through XRD. Moreover, CO₂ emission reductions of up to 38.0% were observed compared to the PC-only mix, demonstrating both the technical and environmental feasibility of using these clays in ternary cements and as SCMs.