Synergistic enhancement of flame retardancy, mechanical properties, dimensional stability, and mold resistance in bamboo via silica mineralization and hydrophobic treatment

Bamboo is a sustainable structural material with excellent mechanical properties, but its high flammability and hygroscopicity restrict industrial utilization. This study develops a synergistic dual-modification approach using sodium silicate mineralization and hydrophobic treatment to enhance flame retardancy, mechanical strength, dimensional stability, and mold resistance. Compared to untreated bamboo, the modified bamboo exhibited 50.9%, 21.0%, 64.1%, and 16.7% reductions in peak heat release rate, total heat release, peak smoke production rate, and total smoke release, respectively. The Limiting Oxygen Index reached 36.0% with a Fire Performance Index of 1.4. Hydrophobic treatment reduced water absorption by 84.5% and thickness swelling by 52.2% (longitudinal), 52.0% (radial), and 57.6% (tangential), achieving a 147° water contact angle. Mechanical properties improved significantly, with modulus of elasticity and modulus of rupture increasing by 15.3% and 9.2%, respectively. Mold growth was completely inhibited under high humidity conditions. This strategy overcomes key limitations of bamboo in flammability, moisture sensitivity, and mechanical performance while preserving sustainability, thereby demonstrating significant potential for fire-safe construction and engineered biocomposites.