A comprehensive study on the physico-mechanical properties of a sustainable mortar reinforced by waste wood fiber

The present research promotes the use of eco-friendly cementitious composites by investigating a sustainable mortar reinforced with waste wood fibers (WWF), which has not been widely studied in the construction materials area. A major challenge in WWF application is their hydrophilic nature, which can weaken the fiber-matrix interfaces and lead to poor composite performance. To address this issue, alkali-treatment and silica fume (SF) were applied, and their effects on the properties of waste wood fiber reinforced mortar (WWFM) were assessed. WWF were treated with sodium hydroxide (NaOH) solutions at varying concentrations and durations, and silica fume (SF) was incorporated to enhance interfacial bonding. For the assessment of properties, flowability, compressive strength, water capillary absorption, and scanning electron microscopy (SEM) tests were performed. Flexural performance and fracture behavior were examined using three-point bending tests coupled with the digital image correlation (DIC) technology. Results showed that appropriate alkali-treatment notably improved the WWF-matrix bonding. The incorporation of the treated WWF significantly enhanced the tensile strength and fracture properties of the mortar. When 0.9 % WWF treated with 2.5 wt% NaOH solution for 2 hours were used, the flexural strength of the WWFM reached 8 MPa, a 50.9 % increase over the reference samples. This sample also achieved a 95.6 % improvement in the unstable fracture toughness, reaching 1.573 MPa·m 1/2 . Additionally, the coupled effect of alkali treatment and SF significantly improved the water absorption resistance of WWFM. Compared to matrix enhancement, alkali treatment is more effective for improving the interfacial bonding, considering the adverse effects of matrix enhancement on the fracture performance of composites. • Suitable alkali treatment improves the roughness of waste wood fiber (WWF) surface. • Alkali treatment efficiently improves the mechanical properties of mortar. • Incorporation of the treated WWF enhances the fracture properties of mortar. • Coupled effect of NaOH treatment and SF is beneficial for durability. • Enhanced bonding performance due to WWF allows cracks to fully develop.