Avaliação das propriedades mecânicas, reológicas e ambientais de pastas de LC3 produzidas com argilas da região Oeste do estado do Paraná

Abstract

The reduction of CO2 emissions associated with the cement industry depends on the development of materials capable of partially replacing clinkers while maintaining adequate mechanical and rheological performance. In this context, LC3 cement emerges as a promising alternative, combining calcined clay and limestone filler to reduce environmental impact and optimize the microstructure of cementitious matrices. This study evaluated the potential of clays collected in the western region of the state of Paraná to produce LC3 pastes, investigating their chemical, physical, and mineralogical properties, as well as their effects on the mechanical, rheological, and environmental behavior of the mixtures. Six clays were collected, beneficiated, and calcined at 850 °C, and characterized by XRF, XRD, TGA, zeta potential, SEM, laser granulometry, and specific gravity. The results showed kaolinite content ranging from 39.8% to 79.16%. Calcination promoted kaolinite amorphization, an increase in mean particle size, and an intensification of surface charge. LC3 pastes were prepared with different clays and compared to a reference produced solely with Portland cement. The LC3 mixtures exhibited pseudoplastic rheological behavior, with an increase in yield stress proportional to the kaolinite content, evidenced by a strong Pearson correlation (r = 0.93). Mechanical results indicated strength gains between 7 and 28 days exceeding 37% for matrices containing clays from Santa Helena. Environmental analysis showed an average reduction of 29.6% in CO2 emissions per m3 of paste compared to the reference, as well as a lower CO2/MPa ratio after 28 days for all LC3-containing cementitious matrices. These results demonstrate the technical and environmental feasibility of using these regional clays in LC3 cement formulations, contributing to the advancement of low-carbon cementitious systems aligned with sustainability demands in the construction industry.