Mechanical Strength and Water Absorption of Natural Fiber-Reinforced Cement Mortars: A Comparative Experimental Study

This study examined the use of five natural fibers (cotton, coconut coir, jute, sisal, and sheep wool) as reinforcements for cement mortars with a standard mix design. Sixteen fiber-reinforced mixtures were prepared with a constant fiber length of 10 mm. The mixtures were tested after 28 days for Water Absorption (WA) and mechanical performance. Fracture sections were visually assessed to evaluate dispersion quality, with some fiber additions improving flexural behavior. The highest flexural strength was obtained with sisal at 5% by volume (5.53 MPa versus 3.90 MPa for the control), and compressive strength was better at low dosages. Jute and coconut fibre of 1% reached 19.59 MPa and 19.50 MPa, respectively, while the initial mixture reached 14.62 MPa. WA generally increased with fiber content, reaching 30.44% for sheep wool at 4%, which led to severe strength reductions and visibly non-uniform fiber distribution. Overall, when the dosage remains within a dispersion-stable window, untreated natural fibers can improve mortar performance. Low contents of jute and coconut coir provided the most consistent compressive gains. However, excessive sheep wool led to connected porosity, high water uptake, and severe strength loss.