Cellular glass is known as a thermal insulation in two shapes: boards and gravel. It is used in the building industry and for industrial applications. The first sold production was based on a special glass composition and recycled glass was careful introduced with remelting at temperatures around 1500°C. The final high quality product was never adapted to the availability of recycled glass.

At the other side, R&D was performed to find more direct applications of recycled glass and cellular glass gravel was developed. First SiC was used as a foaming agent for gravel but this process involves higher foaming temperature above 900°C and has a tendency to induce open cells (crystallisation) when a too low density was the target. Gravel is continuously foamed on a steel belt which has a short life at 900°C and higher energy consumption. In my opinion, this SiC process will disappear due to the high energy cost and short belt life as a consequence of the high foaming temperature.

A smart (Bulgarian?) individual developed the glycerin / sodium silicate process for gravel, which was already reported in a post. GLAPOR introduced first the large width foaming with this recipe to cut the production cost. Later on the cellular glass market was expanded from floor insulation to road works and other civil engineering work. A Finnish company FOAMIT is showing the way to these alternative applications.

The following files can be downloaded from their site.

• Foamed glass applications
• Foamit brochure
• Innovative use of foamed glass as light weight material of approach embankment

The last file is a paper about an embankment with cellular glass gravel. I give the following citation, which says everything about the advantages and cost saving thanks to cellular glass gravel.

Normal gravel filling was not an option, since it would have caused stability problems, lateral stresses to the piles and increased the strength demands on piles and sheet pile wall anchors. Organizing the temporary traffic over piled structures would have been a costly solution. For these reasons foamed glass was chosen to lighten the embankment load. Foamed glass was also chosen because of its technical and structural qualities, usability and recyclability. Foamed glass’s low unit weight lightened the loads on the subsoil and high friction angle together with low unit weight minimized the lateral stresses against the sheet pile walls. Because of the high friction angle, it was even possible to construct steep embankments without support levels and structures beside foamed glass embankment. Up to 10 000 m3 of foamed glass was delivered to four different embankments on the construction site. The foamed glass will be reused, after the construction of the new bridge abutments, for example in backfills of the market
building and the surrounding roads. Lack of work space near the abutments required a narrower structure, which was achieved by placing the foamed glass between two sheet pile walls.