Estabilização de solo com sílica fume: influência da ativação por cal e do reforço com fibras de polipropileno

Abstract

The soils of the Guabirotuba Formation present high expansion potential and low natural strength, which compromises the stability of geotechnical structures such as embankments and slopes. Faced with this problem, this research aims to evaluate the mechanical behavior of a low plasticity silt (ML) from the aforementioned formation, chemically stabilized with lime-activated silica fume and reinforced with polypropylene fibers, aiming at its application in embankments. The experimental program was conducted with mixtures containing different contents of silica fume (6%, 9%, and 12%), a fixed lime content (9%), and the addition of 0.5% fibers. The methodology encompassed compaction tests, unconfined compressive strength, and split tensile strength at 7, 14, and 28 days of curing, in addition to consolidated undrained (CU) triaxial tests and microstructural analyses via scanning electron microscopy (SEM). It was found that lime is the essential activator for the pozzolanic reactions; while mixtures containing only silica fume exhibited a decrease in strength, those activated with lime formed a dense cementing matrix that increased strength in a statistically significant manner (gains of up to 58% in unconfined compression and 117% in split tension). The inclusion of fibers fulfilled the purpose of transforming the failure mode from brittle to ductile, controlling crack propagation. The triaxial tests and SEM images confirmed the expressive gain in effective cohesion provided by the composite. Finally, the stability analysis revealed that the natural soil presented instability (safety factor <1.5) in simulations under saturated conditions, while the stabilized mixtures guaranteed structural integrity (safety factor > 1.5) in all scenarios evaluated by the Spencer method. It is concluded that the developed material is a viable and safe technical alternative for direct application in earthworks.