Areia descartada de fundição como matéria-prima para produção de fibrocimento extrudado

Abstract

The generation of solid waste in the industrial sector is growing at an accelerated pace, increasing the volume of discarded materials and posing a significant challenge to environmental sustainability, which requires innovative strategies for its management and reuse. Among the most impactful industrial wastes, discarded foundry sand (DFS) stands out due to its high volume of usage and disposal. This study evaluated the influence of using discarded foundry sand on the physical (bulk density, apparent porosity, water absorption), mechanical (modulus of rupture, modulus of elasticity, and toughness), thermal (thermal conductivity), microstructural, and durability properties of fiber cement, considering the substitution of agricultural limestone with DFS at levels of 25%, 50%, 75%, and 100%. A control treatment, without substitution, was also produced for comparison. The discarded foundry sand was characterized in terms of granulometry, real density, pozzolanic activity, structure, and compatibility with cement (via X-ray fluorescence, X-ray diffraction, and inhibition testing). The limestone was analyzed for granulometry and real density, and the eucalyptus cellulose fiber for its structure. Subsequently, fiber cement composites were formed using a laboratory-scale extrusion process. The control formulation consisted of 65% CPV-ARI cement, 30% limestone, and 5% eucalyptus cellulose reinforcement, along with additives at 1% HPMC (hydroxypropyl methylcellulose) and 1% carboxylic polyester additive, both relative to the cement mass. After extrusion, the samples underwent 28 days of curing and 25 to 50 cycles of accelerated aging. The physical, mechanical, thermal, microstructural, and durability properties were then evaluated. The results indicate that DFS can effectively replace limestone in fiber cement. The experimental findings demonstrate that 100% DFS substitution not only maintained but also improved the properties of fiber cement. Moreover, all treatments complied with applicable standards, enabling the total replacement of limestone in fiber cement production. This substitution facilitates the proper disposal of DFS waste and contributes to the development of more sustainable construction materials.