Effect of Natural and Artificial Silicon Additives on the Physicomechanical Performance of Dolomite-based Alkaline-Activated Mortar

Abstract

Dolomite, an abundant mineral worldwide, was employed as a precursor to enhance alkaline-activated mortar (AAM) applications. Due to limited literature, the study explored the effects of natural and artificial silicon additives on the physical and mechanical properties of dolomite-based AAM. Artificial silicon, in the form of micro-silica (SiO2), and natural silicon, represented by kaolin, were employed. AAM samples were produced by incorporating 5%, 10%, and 15% micro SiO2 or kaolin by weight. Activators such as potassium hydroxide (KOH) and barium carbonate (BaCO3) were used. The resulting AAM specimens were subjected to tests measuring various physical and mechanical properties. The outcomes exhibited an increase in unit weight, compressive strength, flexural strength, and ultrasonic pulse velocity with an increase in micro-silica, kaolin, and BaCO3 content. This can be attributed to their filler effect, which yields a denser structure with reduced porosity and water absorption. Fourier transform infrared spectroscopy (FTIR) revealed no significant differences among the AAM specimens. X-ray diffraction (XRD) analysis confirmed the presence of quartz and witherite mineral phases, substantiating the improved behavior of AAM samples after using micro-silica, kaolin, and BaCO3 owing to the filler effect. Furthermore, AAM specimens incorporating micro-silica, kaolin, and BaCO3 exhibited superior microstructure compared to other specimens. Scanning electron microscopy images supported the observed physical and mechanical properties. Energy dispersive spectroscopy analysis identified calcium silicate hydrate and potassium aluminosilicate as the primary hydration products in all examined AAM samples. Overall, the addition of micro-silica, kaolin, and BaCO3 in dolomite-based AAM resulted in enhanced physicomechanical performance.