Unlocking durability enhancement in intact cylindrical Moso bamboo (Phyllostachys edulis) via pilot-scale steam heat treatment

Bamboo is a sustainable material with rapid growth and excellent mechanical properties; however, its susceptibility to biological degradation and surface deterioration under outdoor conditions limits its applications. Although steam heat treatment has been widely studied to improve bamboo durability, most previous studies have relied on strip and small-sized specimens, limiting their industrial applicability. In this study, steam heat treatment was applied to full-length cylindrical Moso bamboo ( Phyllostachys edulis ) using a large-scale industrial facility (1.8 × 1.8 × 8 m³), highlighting the feasibility of the process under practical manufacturing conditions at 120–180 °C. This approach enabled direct evaluation of circumferential and diameter changes in intact bamboo under realistic processing conditions. With increasing temperature, moisture content decreased while specific gravity increased, accompanied by progressive shrinkage and densification. However, at 180 °C, pronounced cracking and splitting were observed, associated with significant hemicellulose degradation. In terms of mechanical performance, the modulus of rupture (MOR) increased with temperature and reached its maximum at 140 °C, showing a 38.9% improvement compared to the untreated control, followed by a decline at higher temperatures. At ≥ 160 °C, durability against fungal decay and termite attack was markedly improved. These results indicate that heat treatment at 140–160 °C provides an optimal balance between mechanical performance, dimensional stability, and durability for cylindrical bamboo, highlighting its distinction from conventional studies using processed specimens. • Pilot-scale steam treatment of full-length intact cylindrical bamboo enabled direct evaluation of dimensional changes. • Optimal range (140–160 °C) balanced structural integrity and durability, while 180 °C induced structural damage. • The modulus of rupture (MOR) increased by up to 38.9% at 140 °C compared to the untreated condition. • Heat treatment generated lignin-derived compounds associated with enhanced biological resistance. • The findings provide practical guidance for industrial applications of cylindrical bamboo