Performance evaluation of cement mortar incorporating alkali-treated natural fibers of varying lengths and volume fractions

Purpose This study investigates the influence of alkali-treated Phragmites australis (PA) biofibers with varying lengths and contents on the mechanical and shrinkage properties of cement mortar composites, contributing to the development of sustainable and durable construction materials. Design/methodology/approach Mortar specimens were prepared by incorporating PA fibers at three lengths (2 cm, 3 cm, and 4 cm) and four volume fractions (0.5%, 1%, 1.5%, and 2%). The samples were cured for 90 days. Key properties evaluated included compressive strength, flexural strength, density, ultrasonic pulse velocity (UPV), autogenous shrinkage, drying shrinkage, and expansion. A comparative analysis was performed to identify the optimal fiber configuration. Findings The results demonstrated that fiber length and content significantly affect mortar performance. Specifically, 2 cm fibers enhanced flexural strength and drying shrinkage resistance. It achieved an increase of 16% and a decrease of 20.16% compared to the control mix, respectively. However, 4 cm fibers were most effective in controlling autogenous shrinkage and expansion, where they recorded a decrease of 25.2 and 24.5%, respectively, compared to the control mix. The 3 cm fibers contributed positively to compressive strength, density, and UPV. An optimal fiber content of 1% was identified, offering the best balance between strength and durability. Excessive fiber content negatively impacted performance due to weak fiber-matrix bonding. Originality/value This research highlights the feasibility of using alkali-treated biofibers as reinforcement in cementitious composites, offering insights into fiber-matrix interactions and long-term performance, which are critical for advancing eco-friendly construction technologies.