Work

Catalytic heat treatment of wood for enhanced fire and leach resistance

Year: 2026

Type: article

Abstract: Wood is an attractive renewable construction material, but its inherent flammability, hygroscopicity, and poor resistance to leaching limit its broader application in fire-safe structures. This study presents a catalytic heat treatment (CHT) approach combining ammonium dihydrogen phosphate, citric acid, oxalic acid, and glyoxal to achieve durable fire retardancy and moisture resistance in poplar wood. Several formulations were screened based on weight percentage gain (WPG), equilibrium moisture content (EMC), and leach resistance (EN 84), leading to the selection of an optimized formulation (S3) for detailed characterization. Chemical fixation was confirmed by FTIR spectroscopy, revealing esterification, acetal crosslinking, and phosphorus–oxygen bonding, which remained partially intact after leaching. Optical microscopy demonstrated lumen filling and pronounced cell-wall bulking, consistent with reduced hygroscopicity and increased hardness. Thermogravimetric analysis showed enhanced char formation and altered degradation pathways, while cone calorimetry revealed significant reductions in heat release rate (≈60%), smoke production (≈75%), and total heat release (≈40%), alongside increased residue yield. The limiting oxygen index increased from 24% for raw wood to 42% for treated wood. Fire dynamics simulator (FDS) modelling further demonstrated reduced compartment temperatures for treated wood. Neural network models were developed to predict carbon monoxide and smoke production rates, achieving high predictive accuracy for CO production (R2 ≈ 0.96). Overall, the proposed CHT method provides an effective, chemically fixed, and leach-resistant fire-retardant treatment for wood, offering a favourable balance between fire performance, durability, and processing simplicity.

Source: Case Studies in Construction Materials

DOI: 10.1016/j.cscm.2026.e06017