Expansion of glass waste by the double effect of liquid and solid foaming agents for manufacturing the foam glass gravel (FGG) in a 10 kW-microwave oven

Abstract

An industrially manufacturing recipe of foam glass gravel (FGG) from glass waste by an unconventional heating technique, using simultaneously a liquid foaming agent (glycerol) and a solid one (calcium carbonate) was tested on a 10 kW-microwave oven. Using a ceramic crucible based on silicon carbide with large dimensions, placed in a horizontal position, inside which a metal mold containing the finely ground pressed raw material mixture was inserted, the conditions were created to experiment the manufacture of a much higher quantity and on a significantly extended surface of 725 cm2 of foamed product compared to previous tests performed on a 0.8 kW-microwave oven. In terms of quality, the results were appropriate, the characteristics of FGG samples manufactured by sintering at 834-840 ºC using the conversion of microwave power to heat being within the limits of values required for this type of thermal insulation material (bulk density of 0.20-0.25 g/cm3, thermal conductivity of 0.062-0.070 W/m•K, compressive strength of 7.1-7.4 MPa, water absorption below 3% and pore size between 0.10-0.65 mm).

Keywords

• foam glass gravel
• microwave heating
• glass waste
• glycerol
• calcium carbonate