Chemical, mineralogical and thermal characterization of a composite alkali-activated binder based on coal gangue and fly ash

Abstract

In recent years, alkali-activated binders, including materials called “geopolymers” (low calcium alkali-activated materials), have received great attention as a promising green building material while reusing a significant amount of industrial waste byproducts. This study presents preliminary results of an ongoing research project to produce lightweight alkali-activated binder based mortar using two Moroccan locally waste materials coal gangue and fly ash as aluminosilicate sources. The heavy metals (Cd, Cu, Ni, Pb and Zn) included in the coal gangue pose an environmental problem. These harmful heavy metals can be released by leaching coal gangue into water and soil. However, when coal gangue is used in an alkali-activated binder in concrete, these elements can become immobilized in the concrete and subsequently have a potentially positive impact on the environment and health. The raw materials used in the mortar mixture in this study were as follows: coal gangue, fly ash, lime, sand and gypsum. Sodium hydroxide solution (5 M) was used as an alkali activator in the mixture, which was placed into a cylinder mold and cured at room temperature. Then, the product obtained was tested by X-Ray diffraction (XRD), infrared (FTIR) and thermogravimetric analysis (TG-DTA).