Estudo do potencial do pó de concha de marisco como material cimentício suplementar em cimento LC3

Abstract

Faced with increasing global pressure to rationalize the use of finite natural resources and adopt practices aligned with the 2030 Agenda and the Sustainable Development Goals (SDGs), the cement industry has been seeking alternatives that cause less environmental impact, considering its contribution of approximately 8–10% of global carbon dioxide (CO2) emissions associated with cement production. In this context, Limestone Calcined Clay Cement (LC3) stands out as a promising solution, enabling reductions of up to 35% in CO2 emissions through the partial replacement of clinker with calcined clay and limestone filler (LF). However, limestone extraction still entails significant environmental impacts, since it is a non-renewable natural resource. Therefore, it is important to study alternative carbonate sources; among the options, mussel shells (Anomalocardia brasiliana), an abundant residue on the brazilian coast and rich in CaCO3, stand out. Therefore, this work evaluated the technical feasibility of shellfish powder (CMP) as a substitute for LF in LC3 systems, composed of 50% clinker, 30% calcined kaolinitic clay, 5% gypsum, and 15% limestone filler. Formulations with filler substitutions of 25%, 50%, 75%, and 100% by CMP were analyzed. The materials were characterized physically, chemically, and mineralogically, as well as microstructurally. The properties of the mixtures were also evaluated in accordance with the normative requirements. The results indicated that LF and CMP presented similar chemical composition. Regarding microstructure, the formation of ettringite, portlandite, and hemicarboaluminate was observed, as well as the stability of aragonite in the alkaline medium of the paste. It was observed that CMP acted as a heterogeneous nucleation agent, favoring Ca(OH)2 consumption, microstructural refinement, and a 30% increase in mechanical strength for the CMP-treated cement compared to the reference at 91 days. Mixtures with substitutions equal to or greater than 50% met the normative requirements, indicating that the use of CMP is technically feasible when employed in moderate to high levels. It is concluded that CMP can be an alternative material to LF for use in LC3 cements, contributing to the circular economy and minimizing the environmental impact. Furthermore, it aligns with the SDGs.