Effect of Microwave Radiation Temperature and Content of Different Solid Waste on the Microstructure and Physicomechanical Properties of Lightweight Aggregates

Microwave radiation in the production of lightweight aggregates, it has not yet been thoroughly explored. Therefore, the main goal of the research is to analyze the possibility of using various types of waste, such as waste rock (0-30 %) and glass cullet (10 %), fly ash (50-80 %) and waste solution using different microwave tem-perature (1000, 1050, 1100 degrees C) in order to obtain lightweight aggregates. Above factors and, chemical and mineral composition of the waste materials, affect the microstructure and physico-mechanical parameters of the aggregates.). The thermophysical behavior (DTG/TG), grain composition, chemical composition (XRF), phase composition (XRD) and microstructure (SEM, mu-CT) were analyzed. The microstructure, as well as the related characteristics of aggregates, i.e. water absorption, density, and compressive strength, depend on the sintering temperature, chemical composition and mineral waste raw material. The best properties were obtained for a raw material mixture containing 80 % coal fly ash, 10 % glass cullet, 10 % clay and 48 g of the waste solution (per 100 g of raw mixture), sintered in the microwave at 1100 degrees C. The aggregates were characterized by water ab-sorption of 6.96 %, bulk of 1.70 g/cm3, loose bulk density 0.60 g/cm3, and compressive strength 5.95 MPa. Closed porosity determined by micro-CT was 8.41 %, open -0.24 %, sphericity 0.62. The total porosity depends on the loose bulk density and particle density of lightweight aggregates.Furthermore, washout tests meet environmental requirements. The proposed technology, moreover, enables a short time of thermal processing of raw materials, and thus energy savings and a sustainable approach to the production of green pellets. Thanks to the high strength, the obtained aggregates can replace commercial aggregates.