THE EFFECT OF ADDING ALUMINA AS AN ALUMINUM SOURCE TO THE DIATOMACEOUS EARTH-BASED GEOPOLYMER

Significant attention has been directed toward the cement industry to combat escalating CO₂ emissions globally. Portland Cement (PC) production is recognized as an important contributing factor. Researchers have actively investigated geopolymers as a sustainable alternative to traditional PC production and application. Geopolymers are inorganic polymers formed by aluminosilicate precursors with an alkaline solution. This study delves into the novel approach of fabricating geopolymers by harnessing Diatomaceous Earth, a silica-rich solid waste material from the wine industry. The primary objective of this research was to examine the impact of incorporating aluminum powder as an aluminum source, aiming to attain Si/Al ratios of 2.5 and 3.5. The alkaline solution consisted of sodium hydroxide (10M and 12M) and sodium silicate (Na₂O:10.6% and SiO₂:26.5%). These materials were thoroughly blended to form a fresh geopolymer mixture, which underwent a 28-day curing process, the first four days of which were spent in a 40 ºC oven before being moved to room temperature (25 ºC). The results unveiled a crystalline aluminum oxide phase in the X-ray diffraction analysis, indicating that a portion of the alumina remained unreacted, particularly evident in samples with a Si/Al ratio of 2.5. This observation was further supported by the Scanning Electron Microscopy analysis, which revealed a spherical morphology, signifying the existence of unreacted alumina particles with a final Si/Al ratio of 3.3 These findings suggest that the alumina powder did not actively partake in the geopolymerization, preventing the desired Si/Al ratios from being achieved and, consequently, compromising the properties of the geopolymer.