Mechanical and Durability Performance of Sisal, Jute, and Hemp Fiber-Reinforced Concrete: Effects of Chemical Treatment and Fiber Geometry

This study investigates the influence of three natural fibers – sisal, jute, and hemp – on the mechanical and durability properties of concrete, using a Taguchi L9 orthogonal array to systematically vary fiber type, content (5–15% by weight), length (5–15 mm), and chemical treatment (untreated, NaOH, silane). Five key properties were evaluated: tensile strength, compressive strength, flexural strength, water absorption, and thermal conductivity. The best-performing mix was S105ST (sisal, 10%, 5 mm, silane-treated), which achieved the highest tensile strength (3.6 MPa), compressive strength (32.0 MPa), and flexural strength (6.3 MPa), alongside lowest water absorption (5.1%) and lowest thermal conductivity (0.65 W/m·K). In contrast, the worst-performing mix, J55UT (jute, 5%, 5 mm, untreated), showed only 2.3 MPa tensile strength, 25.9 MPa compressive strength, 3.8 MPa flexural strength, 9.3% water absorption, and 0.79 W/m·K thermal conductivity. ANOVA revealed that chemical treatment had the highest influence across all properties, contributing over 75% of the variance in water absorption and thermal conductivity. Microstructural validation through SEM and XRD confirmed superior fiber–matrix bonding and reduced porosity in the best sample. These findings highlight the critical role of optimized fiber treatment and dosage in enhancing both mechanical strength and durability, offering a sustainable path toward high-performance green concrete.