The influence of carboxylated styrene butadiene rubber coating on the mechanical performance of vegetable fibers and on their interface with a cement matrix

Abstract Carboxylated styrene butadiene rubber (XSBR) coating was applied on several vegetable fibers and its effect on physical–chemical and mechanical performance were evaluated. Curaua, jute and sisal fibers were used in this study. The influence of coating treatment was evaluated by water absorption capacity test, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetry (TGA). Pullout tests were performed in order to evaluate the fiber–matrix bonding. Fiber embedment lengths of 25 mm was used. A free calcium hydroxide cement mortar was used as matrix. Furthermore, direct tensile tests were performed in the treated and virgin natural fibers. The treatment creates a polymer layer surrounding the fiber, reducing the water absorption capability. The results indicate an increase of the tensile strength of all studied fibers. The interaction between the polymer and natural fibers may be ruled by the cellulose amount of fibers and their crystallinity. An increase in maximum load was observed during fiber pullout, as a consequence of the increase of chemical bonding between treated fibers and the cementitious matrix.