Production of porous geopolymers using ash and slag waste of power plants in the Russian Arctic

Abstract

Coal combustion at thermal power plants generates much ash and slag waste which amass at waste sites and have a dramatic adverse effect on the environment. In the meanwhile, ash and slag is a valuable source for the production of silicate materials for road making and civil construction. The most promising technology for the synthesis of silicate materials is selected from the viewpoint of energy and resource efficiency—the low-temperature alkaline activation and production of porous geopolymers. A range of mix formulations is developed on the basis of ash and slag from Severodvinsk PP-1, with addition of an alkaline activator (mixture of sodium hydroxide solution and liquid glass), various sponging agents and a foam stabilizer. The increase in the amount of an alkaline activator noticeably decreases the foam stability. The aluminum powder is a less active sponging agent as compared with the hydrogen peroxide solution. The introduction of a foam stabilizer essentially increases the number of pores and decreases the foam density. The synthesis of geopolymeric materials using ash and slag from Apatity PP produced a material with the density of 456 kg/m3 and with the pores 300–600 μm in size upon average. Addition of a surfactant greatly decreases the average size of pores at insignificant reduction in the density of the test samples. On the evidence of the research, the optimal composition of the activation mixture is selected for manufacturing porous geopolymeric materials with a density less than 500 kg/m3, including an alkaline activator, hydrogen peroxide as a sponging agent and a surfactant as a foam stabilizer. The study was supported by the Russian Science Foundation in the framework of Agreement No. 21-19-00203 Effective Heat-Curable Eco-Geopolymers for Road Construction in the Russian Arctic Using Combustion Waste of Solid Fuels at Local Power Pants under guidance by E. A. Yatsenko.