Cleaner production of one-part white geopolymer cement using pre-treated wood biomass ash and diatomite. (1st February 2019) - Hassan, Hassan Soltan
Abstract: The key point of this investigation is to valorize CaCO3 -rich wood biomass ash (WBA) from brick industry in the preparation of one-part white geopolymer cement (WGPC) using diatomite as main ingredient. The suggested method not only implemented for cleaner production of eco-friendly cement, but also used to WBA disposal. In the present work, WBA was treated with different sodium hydroxide concentrations (at NaOH: CaCO3 molar ratios of 2, 1, 0.5, and 0.25), followed by dying and pulverizing to produce dry activator powder with a fixed fineness. The impact of dry activator content, containing the same NaOH content (3 wt. %), on the performance of one-part WGPC was evaluated by setting times, total porosity, and compressive strength measurements. The results revealed that the compressive strength development enhances with time, associating with the continuation of aluminosilicate (in diatomite) dissolution and formation of strength-giving-phases such as calcium silicate hydrate and calcium aluminosilicate hydrate. The synergistic filling and nucleating effects of CaCO3 were recorded when 21.5 wt., % of pretreated WBA, at NaOH/CaCO3 molar ratio of 0.5, added to diatomite to yield one-part WGPC with optimal 28-days compressive strength (48 MPa) and relatively high whiteness (85%). This qualifies the prepared one-part WGPC to be beneficially used as alternative to white Portland cement in decorative works and prestige construction projects. Graphical abstract: Image 1 Highlights: Wood biomass ash was pretreated by sodium hydroxide to produce dry activator. Diatomite was blended with dry activator to yield white one-part geopolymer cement. The performance of the prepared cement depends on the content of dry activator. The cement containing 21.5% dry activator showed the highest performance.