Glued-laminated bamboo with different adhesive options for a more sustainable construction

Despite the growing demand for sustainable construction materials, limited research has evaluated the performance of bio-based adhesives, such as castor-oil-based polyurethane (PU), compared with conventional polyvinyl acetate (PVA) in glued-laminated bamboo (GLB) for structural use. This study assessed the physical, mechanical, and microstructural properties of GLB bonded with PU and PVA. PU-bonded samples showed higher mechanical performance (18% improved modulus of rupture and 37% improved shear strength); however, these differences were not statistically significant (p > 0.05). In terms of moisture-related properties, PVA exhibited higher water absorption (72% vs. 65%) and slightly lower thickness swelling (9.1% vs. 9.9%) after 168 h of immersion, indicating comparable dimensional stability between the two adhesives. Scanning electron microscopy (SEM) and image analysis confirmed PU’s deeper penetration and stronger inter-fiber cohesion, whereas PVA showed limited penetration and more interfacial failure. These findings indicate that PU is more suitable for load-bearing applications, while PVA is more appropriate for non-structural uses, emphasizing the critical role of adhesive penetration in GLB structural integrity.