Durability, mechanical properties, and fire resistance of wood impregnated with dilute alumino-silicate suspensions at different pH levels

This study evaluates the effects of dilute alumino-silicate suspension (uncured geopolymer dilution) impregnation on Pinus sylvestris sapwood, focusing on pH adjustments. Higher concentrations of the alumino-silicate suspensions (3% and 5%) led to a statistically significant improvement in decay resistance, with all treated samples exhibiting mass losses between 2.2 ± 0.6% and 5.8 ± 1.6%— approximately half of that observed for the untreated controls (9.9 ± 2.4%). In contrast, pH adjustments had only a minor effect. The lowest concentration of dilute alumino-silicate suspensions did not significantly enhance decay resistance, although the mass loss was slightly higher than that of the controls. Mechanical tests showed that intermediate concentrations of alumino-silicate suspensions improved the modulus of elasticity (MOE) and modulus of rupture (MOR), while fire resistance tests indicated an improvement in ignition time of up to 5 s at 5% alumino-silicate suspension. The leaching test revealed challenges with the fixation of the dilute alumino-silicate suspensions, resulting in reduced durability after prolonged water exposure. These findings underscore the potential of dilute alumino-silicate suspensions as sustainable wood treatments. However, further optimization of their formulations is required to enhance adhesion and reduce leachability.