Production of sodium silicate from bamboo leaf ash for alkali activation of binders

Abstract

The use of biomass ash for the development of bio-derived activators or precursors of alkali-activated materials has revitalized the search for sustainable source of initial silica materials for alkali-activated cements. In this study, a simple process to produce a one-part sodium silicate activating powder from bamboo leaf ash (BLA) is presented. Bamboo leaves were calcined at 550 ºC and 800 ºC and combined with NaOH pellets to produce a reactive sodium silicate powder. The thermochemical reaction with NaOH converted the amorphous silicates from BLA into a crystalline sodium silicate powder with mineral phases of various Na2O/SiO2 ratios. Na2SiO3 was the main phase identified. The effectiveness of the produced powder was assessed through mechanical compression tests comparing mortars made from commercially available sodium silicate and sodium hydroxide activating solutions. The strength of mortars activated with BLA-based sodium silicate showed lower early strength, but fully comparable 28-day strengths. These initial results confirmed that the reactivity of BLA-silicate powder was similar to that of commercial sodium silicate solutions. The results show the potential valorisation of future biomass renewable energy waste in the production of low carbon, alkali-activated concretes.