Estabilização de solos lateríticos: uma alternativa para os resíduos de cinza da casca de arroz

Abstract

Highway constructions involve large amounts of materials and earthworks that it could be avoided with a better use of residual material from the same place of the highway construction. In order to better understand and use the lateritic soils, which are the predominant soils in Brazil, this study aimed to characterize and improve the properties of a laterite soil from a deposit located in southern Brazil, through the addition of rice husk ash, seeking its application in base and sub-base layers of pavements. The materials used in the development of the study were: a latosol from a deposit located in Cândido Godoi - RS; Hydrated lime dolomitic class CH-II; Rice husk ash (RHA) and distilled water. The materials were subjected to characterization tests, Physical-chemical test proposed by Casanova to determinate the dosages, and Mini-Proctor compaction tests to determine the density and optimum moisture molding. It was cast specimens of soil, soil+lime, soil+lime+RHA, and soil+RHA in cylinders with dimensions of 5 x 10 cm that remained healing, in a place with controlled temperature, during 7, 28, and 56 days. The resistance of the specimens was verified by the compression test. The soil was classified as a lateritic clay by the MCT methodology, a MH material by the Unified Soil Classification System, and an A 7-5 by the AASHTO Soil Classification System. The proportion of 94% of soil and 6% of lime, and 94% of soil, 2.4% of lime, and 3.6% of RHA were the recommended alternatives to stabilize the analyzed samples. Although there was no substantial gain in strength in the proposed mixtures for all curing times, the additions of lime and lime combined with RHA considerably increased the soil modulus of elasticity. This fact appears as the biggest gain of this study because as rigidity increases, it can be assumed that the deflections in the final layer will be reduced. It can be concluded that the soil properties were really improved for all mixes, except for the mixture of soil+RHA, because such dosages conferred greater rigidity to the material. Furthermore, although the average of the resistances of the natural soil are higher, some samples of soil+lime and soil+lime+RHA are in the same resistance range because of the dispersion of the results.