Impact of aminosilane and colloidal nano-silica modification on the properties of ambient-cured geopolymer-bonded lignocellulosic composites

This study investigates the effect of modifying ambient-cured geopolymer-bonded composites of coir fibre and wood particles with γ-aminopropyltriethoxysilane (APTES, 0.10 wt%) and colloidal nano-silica (CNS, 1.45 wt%). APTES-modified binders had lower workability (200.7 ± 11.5 mm spread diameter) than unmodified (255.3 ± 12.5 mm) and CNS (248.5 ± 8.9 mm) counterparts. Setting times were similar, with the APTES variant setting faster. CNS-modified binders showed the highest reactivity, reaching peak temperature at 39.5 min. Physicochemical, mechanical, and microstructural analyses were conducted on the composites. CNS-modified composites had the highest internal bond strength (1.52 ± 0.11 N mm−2), flexural modulus (5416.3 ± 222.8 N mm−2), flexural strength (10.2 ± 0.7 N mm−2), and work to maximum force (670.4 ± 23.3 Nmm). APTES-modified composites exhibited superior water resistance, with the lowest water absorption (18.1 ± 0.5 %) and thickness swelling (0.10 ± 0.03 %) after three 24 h-cycles of water soaking. The pH value remained at 11 over 28 days. Microstructural analysis revealed improved adhesion and reduced voids and cracks in modified composites, which increased performance and water resistance. Coir fibre-reinforced composites exhibited higher strength than those with wood particles. These findings highlight the feasibility of producing ambient-cured geopolymer-bonded lignocellulosic composites for building applications.