Effects of Degradation of Vegetal Fibers on the Mechanical Behavior of Reinforced Sand

Abstract

This paper presents the results of an experimental program about the behavior and durability of soils reinforced with randomly distributed vegetal fibers (sisal and curauá) submitted to natural aging by their exposure to environmental conditions, aiming to boost its use in earthworks. The experimental program consisted of triaxial compression tests on sand and sand-fibers samples at zero time (sample control) and in composites exposed to agents from the external environment for up to 8 months. In order to explain the variation in the obtained results, direct tensile tests, scanning electron microscopy and mass loss analysis were performed on the fibers after each exposure period (0, 60, 120 and 240 days). The overall analysis of the results allowed to identify that the effects of natural aging had a significant effect on the mechanical behavior of the vegetable fibers, which consequently affected the mechanical behavior of the sand-fiber composites. Shear strength losses were more relevant and accentuated in composites with curauá fibers, indicating that these fibers, even with higher tensile strength without exposure, are more susceptible to degradation in natural environments than sisal fibers. Even with the loss of mechanical behavior of the fibers, after 8 months of exposure to the climatic agents, they continued to contribute as a reinforcing element in the sandy matrix, since one of the resistance parameters remained higher when compared to the sandy soil without reinforcement.