Pozzolanic Potential of Calcined Clays at Medium Temperature as Supplementary Cementitious Material

Valber Domingos Pinheiro, Ramon Fernandes de Abreu, Jonas Alexandre (), Gustavo de Castro Xavier, Markssuel Teixeira Marvila and Afonso Rangel Garcez de Azevedo
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Valber Domingos Pinheiro: Laboratory of Advanced Materials, State University of the Northern Rio de Janeiro, Campos dos Goytacazes 28013-602, Brazil
Ramon Fernandes de Abreu: Laboratory of Advanced Materials, State University of the Northern Rio de Janeiro, Campos dos Goytacazes 28013-602, Brazil
Jonas Alexandre: Civil Engineering Laboratory, State University of the Northern Rio de Janeiro, Campos dos Goytacazes 28013-602, Brazil
Gustavo de Castro Xavier: Civil Engineering Laboratory, State University of the Northern Rio de Janeiro, Campos dos Goytacazes 28013-602, Brazil
Markssuel Teixeira Marvila: CRP-Rio Paranaíba Campus, UFV-Federal University of Viçosa, Rio Paranaíba 38810-000, Brazil
Afonso Rangel Garcez de Azevedo: Civil Engineering Laboratory, State University of the Northern Rio de Janeiro, Campos dos Goytacazes 28013-602, Brazil

Sustainability, 2024, vol. 16, issue 17, 1-19

Abstract: Global warming is intensified by substantial greenhouse gas emissions, with the cement industry contributing significantly by releasing around 0.8 tons of CO 2 per ton of cement produced. To mitigate these impacts, in this study, we investigated the pozzolanic potential of calcined clays, assessing their influence on the properties of Portland cement as sustainable alternatives for partial replacement. Three clays from Campos dos Goytacazes, RJ, were analyzed. After drying and calcining at 600 °C, they underwent physical and chemical analysis. The samples were characterized in terms of grain size, moisture content, grain density and plasticity limit. Chemical analysis by X-ray fluorescence identified the elemental composition of the clays, while X-ray diffraction determined the presence of crystalline and amorphous phases. A mineralogical characterization confirmed the amorphization process and classified the clay as kaolinitic. Scanning electron microscopy provided detailed images of the morphology of the particles. The surface area was measured using the Blaine method, which is essential for understanding the reactivity of calcined clays. A preliminary analysis showed that the calcination at 600 °C led to greater pozzolanic reactivity in the clay samples. A thermal analysis showed a loss of mass, suggesting the dihydroxylation of the kaolinite. The pozzolanic reactivity was extensively evaluated by isothermal calorimetry, which monitored the release of heat during hydration reactions through compressive strength tests on the mortars that showed higher strength than the reference. In addition, modified Chapelle and R 3 tests were carried out, which showed a direct correlation with the compressive strength, also indicating significant pozzolanic reactivity in the material. The results showed that the clays, when calcined, had a highly reactive amorphous structure, resulting from their transformation through the process of dihydroxylation and amorphization. Calorimetry identified the acceleration of the cement hydration reactions, stimulating the formation of calcium silicate hydrates and aluminum compounds, which are essential for mechanical strength. The partial replacement of Portland cement with calcined clays helps to reduce CO 2 emissions without compromising strength and durability, representing a promising strategy for reducing greenhouse gas emissions, with a view to greater environmental sustainability and the efficiency of building materials.

Keywords: portland cement; calcined clay; supplementary cementitious materials; pozzolanic reactivity; sustainability (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2024
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