Study of cure conditions effect on the properties of wood biomass fly ash geopolymers

This work investigated the influence of processing parameters on properties of geopolymers based on wood biomass fly ash. Five curing methods were applied, with and without moisture and temperature control, associated with 2 concentrations of alkali activators, sodium silicate and sodium hydroxide (1.0 and 1.5 weight ratios), and a fixed composition (75 wt.% wood biomass fly ash and 25 wt.% metakaolin). Cured geopolymers were characterized by compressive strength tests after 28 days and by analytical techniques to evaluate morphology and internal structure. The results showed different physical and chemical properties tailored by the processing parameters variation, suggesting several applications. For instance, the samples obtained with hydrothermal conditions and SS:SH = 1.0 might be used for adsorption of pollutants, and those produced at room condition with SS:SH=1.5 may be employed as dense mortars. Most importantly, a low-energy curing method at room temperature enabled to produce geopolymers with mechanical properties in the order of magnitude of those obtained at higher times or temperatures. (C) 2020 The Authors. Published by Elsevier B.V.