High mechanical strength porous material used as a foam glass gravel experimentally manufactured from glass waste by an unconventional technique

Abstract

The paper presents a new technique for making foam glass gravel by expanding at high temperature recycled glass waste with a liquid carbonic foaming agent (glycerol) in combination with sodium silicate (also called “water glass”). Unlike the conventional methods known worldwide in similar technological processes, the paper proposes a fast, economical and clean unconventional technique (microwave irradiation), applied to a very small extent in the industrial sector, although in the household it is a widely used process. The experiments carried out by the Daily Sourcing & Research Company on a 0.8 kW-microwave oven aimed at the manufacture of foam glass gravels with physical and mechanical characteristics almost similar to those industrially obtained by conventional methods, simultaneously demonstrating the superior energy efficiency of the technique of using microwave energy as an unconventional source. The products experimentally made had low thermal conductivity (between 0.057-0.063 W/ m·K), high compressive strength for this material type (up to 5.9 MPa) and very low pore size (below 0.9 mm). The specific energy consumption had values between 0.83-0.88 kWh/ kg comparable to those industrially achieved, but it should be considered that the use of a high power microwave equipment could improve the process efficiency by up to 25%.

Keywords

• foam glass gravel
• glass waste
• glycerol
• microwave
• compressive strength