Effect of alkali treatment on physical–chemical properties of sisal fibers and adhesion towards cement-based matrices

Abstract

This work aims to evaluate the effect of alkali treatment on sisal fibers to improve the fiber properties and the effectiveness of their use as reinforcement in cement-based matrices. Alkaline solution concentration (1, 5 and 10 wt% NaOH) and post-treatment protocol (use of distilled water or acetic acid) influence were evaluated. The physical, chemical, thermal, wettability and surface characteristics were analyzed. Also, single-fiber direct tensile and pullout tests were performed. Results showed an increase in cellulose proportion with a reduction in hemicellulose and lignin content upon alkali treatment. Consequently, enhanced thermal stability and a decrease on the water uptake tendency were reached. Additionally, improved tensile properties, as well as an enhanced bond with the cementitious matrix, were found for alkali-treated fibers. Also, fibers became more stable when subjected to alkaline aggressive conditions. Thus, the alkali-treated sisal fiber seems to be an adequate and sustainable alternative as reinforcement for cement-based matrices.