Efeito da substituição parcial da cal hidratada por lama de cal na resistência á compressão e durabilidade de um solo residual de Lavras/MG

Abstract

Rural roads, also known as unpaved roads, play a fundamental role in the socioeconomic integration of rural areas. However, these roads are frequently affected by degradation processes, mainly due to water action and the low mechanical capacity of local soils, resulting in high maintenance costs. In this context, the use of industrial waste as an alternative material for soil stabilization has emerged as a technically promising and environmentally sustainable strategy. This study aimed to evaluate the effect of partially replacing hydrated lime with lime sludge at replacement levels of 25%, 50%, 75%, and 100% on the compressive strength and durability of a residual soil from the municipality of Lavras, Minas Gerais, Brazil, for application in rural roads. The soil, hydrated lime, and lime sludge were characterized regarding their physical, chemical, and morphological properties. The mixtures were evaluated through compaction tests, unconfined compressive strength (UCS) tests after curing periods of 7 and 28 days, and durability tests under wetting–drying cycles. Additionally, the Material Circularity Indicator (MCI) was calculated to integrate mechanical performance and waste utilization into a single circularity metric. Chemical analyses by X-ray fluorescence and morphological analyses by scanning electron microscopy were also performed. The results indicated that the partial replacement of hydrated lime significantly altered the mechanical behavior of the stabilized soil. The T25 mixture, corresponding to 25% replacement of lime by lime sludge, showed the best balance between mechanical strength, durability, and circularity. This treatment achieved an average UCS of approximately 649 kPa after 28 days of curing, associated with lower mass losses and lower volumetric variations compared to mixtures with higher replacement levels. Furthermore, it was the only treatment to present a positive MCI value. The reference mixture composed exclusively of hydrated lime showed the highest absolute UCS values, reaching approximately 1033 kPa after 28 days of curing. Chemical analyses indicated that the calcium content in the T25 mixture was sufficient to promote soil stabilization mechanisms, while morphological analyses revealed a denser and more homogeneous microstructure, with greater particle agglomeration and reduced apparent porosity. These findings corroborate the observed mechanical performance and indicate that, at this replacement level, lime sludge acted efficiently as a complementary material to hydrated lime without compromising compressive strength or durability of the soil-binder system. It can be concluded that the partial replacement of hydrated lime with lime sludge presents technical and environmental feasibility for soil stabilization under the laboratory conditions evaluated, providing support for applications in rural roads. The T25 treatment showed the best balance between mechanical performance, durability, and environmental benefit, contributing to the valorization of industrial waste and to the reduction of conventional material consumption.