Preparation and characterization of vitrified slag/geopolymers for construction and fire-resistance applications

Abstract

Incinerator ash transforms into vitrified slag through thermal plasma treatment and quenching processes. Thus, the heavy metals contained in the ash can be solidified into the framework structure of the vitrified slag, thus reducing the threat to the environment. This study used vitrified slag as a raw material in preparing geopolymers by applying alkali solutions of predetermined molar ratios at ambient temperature. The influences of alkali solutions at various SiO2/Al2O3 and SiO2/Na2O molar ratios on the properties of the geopolymers were evaluated. A foaming agent was also added during geopolymerization process to increase the porosity of the geopolymers; this could improve the fire resistance characteristics of the geopolymers. The test results indicated that the alkali solution at 57 SiO2/Al2O3 and 0.75 SiO2/Na2O molar ratios can produce geopolymers with optimal mechanical properties and fire resistance characteristics. Adding foaming agent can greatly improve the fire resistance of the geopolymers because of the increased porosity. According to the test results, the geopolymers fabricated using vitrified slag and alkali solutions can be potential materials for construction and fire resistance applications.