Post-cracking behaviour and toughness enhancement of concrete made with wooden ash and nylon fibres

Abstract

This study investigates the flexural behaviour of concrete made with wooden ash (WA) as a partial cement replacement and the addition of nylon fibres (NF) as a fiber reinforcement. Four concrete mixes containing 0%, 5%, 10%, and 15% WA replacement and 1% constant NF were casted. Beam specimens (150 × 100 × 500 mm) were tested under four-point bending to evaluate comprehensive flexural behaviour, including strength, crack resistance, stiffness degradation, ductility, deformation capacity, energy absorption, toughness, and flexural performance (FP) factor. The results indicate that mix-10% achieved the highest flexural strength of 4.8 MPa with a 50% improvement compared to the control mix (3.19 MPa). Furthermore, it also shows the highest crack resistance ratio (0.644), indicating improved resistance to crack initiation. Also, mix-15% shows the highest peak load (23.30 kN), post-cracking SR (1.9), total toughness (30.60 kN·mm), and FP factor (89.79 kN·mm). Furthermore, the stiffness response showed a reduction in initial stiffness from 32.22 kN·mm−1 to 3.65 kN·mm−1, suggesting a transition from brittle to ductile structural behaviour. The improved performance is attributed to the pozzolanic reactivity of WA, combined with the crack-bridging mechanism of NF. The findings concluded that concrete made with 10%–15% WA with NF provides an optimal balance between strength, toughness, and deformation capacity. Therefore, it can be used for structural applications requiring enhanced durability, impact resistance, and damage tolerance.