Influence of Flame‐Retardant Treatments on the Combustion Behavior and Mechanical Performance of Laminated Bamboo Lumber

ABSTRACT Laminated bamboo lumber (LBL) has emerged as a promising sustainable structural material because of its renewable nature and favorable mechanical properties. However, its inherent combustibility constrains its utilization in environments prone to fire hazards. In this study, the effects of two flame‐retardant treatments, a water‐based formulation and a solid‐phase treatment incorporating amino resin systems, on the combustion behavior and mechanical performance of LBL were investigated. The flame retardants were administered through pressure impregnation before the lamination process. One‐sided fire exposure tests conducted on LBL panels, adhering to the ISO 834 standard curve, revealed that the solid‐phase treatment effectively reduced the charring rate by 28%. This reduction was particularly pronounced in the tangential direction perpendicular to the grain. Notably, the charring rate in the radial direction perpendicular to the grain was nearly double that in the tangential direction, underscoring the substantial anisotropy observed in the thermal degradation process. An analysis of the mechanical properties of LBL materials revealed that flame‐retardant treatments reduced tensile strength and bending strength by 14% and 6%, respectively. Conversely, these treatments increased the compressive strength by 11% to 33% depending on the loading direction. The modulus exhibits variability contingent upon the grain orientation. These findings underscore the inherent trade‐off between enhancing fire resistance and maintaining mechanical performance. They also demonstrated the efficacy of amino resin‐based flame retardants in increasing fire resistance while exerting a minimal effect on mechanical properties. This study highlights the potential of flame‐retarded LBL for structural use in fire‐safe and sustainable construction.