MICROWAVE HEAT TREATMENT OF WASTES (CLAY, GLASS AND COAL ASH) TO MANUFACTURE A HIGH MECHANICAL STRENGTH CELLULAR AGGREGATE

Abstract

The paper presents experimental results obtained in the manufacturing process of a lightweight aggregate using a finely ground mixture of wastes (clay, glass and coal ash) expanded with silicon carbide as a foaming agent. The originality of the work consists in the use of microwave radiation in a direct heating process, the energy efficiency being remarkable (0.58-0.85 kWh/kg), unlike all the manufacturing processes known in the world, industrial or experimental on a small scale. Given that glass alone is not suitable for foaming by direct microwave heating, but the favorable effect of adding glass to clay on the physical and mechanical characteristics of lightweight (expanded) clay aggregate is known, the experiments aimed to determine the maximum allowable proportion of glass in clay without affecting the microstructure of the material. The characteristics of the experimental samples were almost similar to those of industrially manufactured products by conventional methods (0.60-0.69 g/cm³ the apparent density, 0.100-0.116 W/m·K the thermal conductivity, 7.8-8.3 MPa the compression strength, 9.3-17.5% the water absorption).