Red mud geopolymerization: The influence of naoh concentration in the synthesis at room temperature

Abstract

The red mud residue of the Bayer process has proved to be adequate in the geopolymerization reaction. The concentration of the activator influences the mechanical performance of the geopolymers. The aim of this research was to evaluate the mechanical performance of Davidovits (SiO2/Al2O3) geopolymers of 2.09, 1.66 and 2.03 ratio synthesized with different NaOH molar concentrations (5, 10, 15, 30 and 40 Molar) on the activator. The mechanical strength test was performed at 24 hours, 7 and 28 days of curing the geopolymers. The geopolymerization reaction was conducted at room temperature of 28°C. Sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) 10 Molar were used as the activator. The geopolymer based on metakaolin of 2.09 showed better mechanical resistance, followed by the material with 10% red mud and 90% metakaolin and 50% metakaolin and 50% red mud. with 2.03 and 1.66 SiO2/Al2O3ratios, respectively. In sequence,the materials were characterized by XRF, XRD, laser particle size analysis, scanning electron microscopy (SEM) and EDS of both raw material and geopolymer fragments. Therefore, the geopolymerization of the red mud presented great potential for the production of geopolymeric materials.