Mechanical Performance and Durability of Açaí Fibers as Reinforcement in Tropical Clay Soil

This work investigates the use and the durability of natural açaí fibers (Euterpe oleracea) as reinforcement for tropical clayey soil under 6-months of natural environmental exposure. Incorporating 1% and 2% of açaí fibers in relation to soil dry weight, the characterization of soil and fibers was carried out, including XRD, XRF, FTIR, SEM, as well as compaction, direct tensile, and UCS tests. Fibers reduced the dry unit weight and increase the optimum moisture content of the composites due to the low density of vegetal material and the capacity to absorb water. UCS increased significantly at initial conditions – by over 205%—reaching 1059.3 kPa and 1271.3 kPa for 1% and 2% fibers, respectively. FTIR and SEM analyses revealed cellulose degradation over time, which was reflected in reductions of 48.9% in tensile strength, and 44.2% in Young’s modulus of the fibers over the 6-months period. UCS declined with exposure, stabilizing at 4 months for 1% fiber, showing no significant difference from unreinforced soil, as statistically confirmed by ANOVA and Tukey’s test. In contrast, 2% fiber content delayed the degradation durability of the composite, supporting technical feasibility of using açaí fibers as sustainable solution for temporary geotechnical applications in tropical environments.