Avaliação do uso de geopolímeros para a melhoria de propriedades mecânicas de subcamadas de pavimentos

Abstract

The high demand for natural materials in road construction, combined with the fact that soils from borrow pits near construction sites do not always possess suitable mechanical properties, makes it necessary to stabilize these materials for use in pavement sublayers. Portland cement and lime are the binders commonly used in the chemical stabilization of soils. However, in addition to their high cost, their manufacturing processes cause environmental damage due to the intensive consumption of natural resources and the high emission of greenhouse gases. In this context, geopolymeric materials emerge as a sustainable alternative for chemical stabilization. These materials incorporate industrial waste and by-products in their composition and exhibit cementitious characteristics capable of improving the mechanical properties of soils. Within this framework, the main objective of this study is to investigate, through chemical, physical, and mechanical tests, the feasibility of synthesizing and applying geopolymers in pavement sublayers to improve soil mechanical properties. The main challenge of the research was the synthesis of geopolymers using fly ash (F), BSSF-type steel aggregate (Baosteel Slag Short Flow), and petroleum coke powder (C). To assess the improvement in the soil's mechanical properties, the unconfined compressive strength (UCS) test was used as a preliminary analysis of the technique's viability. The precursors were selected, treated to remove soluble salts, and then binary material combinations were defined, which were subjected to alkaline activation, microstructural characterization, and application to a clayey soil. The stabilization process involved the molding of 600 specimens using miniature equipment, of which 528 were used for UCS analysis with both dry and wet curing at 7, 14, 21, and 28 days, and 72 for investigating shrinkage and expansion effects. The results showed that soils stabilized with geopolymers at different precursor dosages exhibited strength gains. The UCS gain was gradual and showed satisfactory values under air-curing conditions, with the best results obtained using petroleum coke powder. The study developed here highlights the potential of geopolymers produced with alternative materials to improve soil properties for application in pavement sublayers, as well as reduce the environmental impacts associated with road construction.