Effect of fibre treatment duration in enhancing the mechanical properties of treated kenaf fibre lightweight foamed composite

The drive towards sustainable, lightweight building materials has accelerated interest in natural fibre-reinforced composites, yet challenges in strength performance remain a major limitation. This study investigates the influence of alkali treatment duration on the reinforcing efficiency of Treated Kenaf Fibre (TKF) in Lightweight Foamed Composites (LFCs) with a target density of 1200 ± 50 kg/m³. The experimental programme optimised the water-to-cement (W/C) ratio, characterised fibre surface modification using Scanning Electron Microscopy (SEM) and Energy-dispersive X-Ray spectroscopy (EDX), and evaluated fresh and mechanical properties, including compressive, residual, splitting tensile and flexural strengths. An optimum W/C ratio of 0.60 provided adequate workability without compromising strength development. SEM and EDX analyses indicated progressive fibre surface modification with increasing treatment duration, with the 12-h TKF exhibiting the most pronounced surface contaminants removal and surface roughness. Proceed to composite incorporation, LFC-TKF-12H showed slightly reduced flowability while maintaining improved density consistency and mix stability. Additionally, LFC-TKF-12H exhibited the highest overall mechanical performance among all mixes. Relative to the control mix, the compressive strength increased by 19%, splitting tensile strength by 38%, flexural strength by 34% and residual strength by 36%, corresponding to a strength retention factor of 76%. The results highlight alkali treatment duration as a key parameter governing fibre surface modification and reinforcing effectiveness in LFCs.