Geofoam

Geofoam is expanded polystyrene (EPS) or extruded polystyrene (XPS) manufactured into large lightweight blocks. The blocks vary in size but are often 2 m × 0.75 m × 0.75 m (6.6 ft × 2.5 ft × 2.5 ft). The primary function of geofoam is to provide a lightweight void fill below a highway, bridge approach, embankment or parking lot. EPS Geofoam minimizes settlement on underground utilities. Geofoam is also used in much broader applications, including lightweight fill, green roof fill, compressible inclusions, thermal insulation, and (when appropriately formed) drainage.

Geofoam shares principles with geocombs (previously called ultralight cellular structures) which has been defined as "any manufactured material created by an extrusion process that results in a final product that consists of numerous open-ended tubes that are glued, bonded, fused or otherwise bundled together." The cross-sectional geometry of an individual tube typically has a simple geometric shape (circle, ellipse, hexagon, octagon, etc.) and is on the order of 25 mm (0.98 in) across. The overall cross-section of the assemblage of bundled tubes resembles a honeycomb that gives it its name. Presently, only rigid polymers (polypropylene and PVC) have been used as geocomb material.

The first use of EPS Geofoam was in Oslo, Norway in 1972. Geofoam was used in the embankments around the Flom Bridge in an effort to reduce settlements. Prior to installing geofoam, this area experienced 20–30 centimeters of settlement annually causing extreme roadway damage.

Due to the success of the Oslo geofoam project, the first International Geofoam Conference was held in Oslo, Norway in 1985 for engineers to exchange knowledge, research results, share new applications, and discuss case histories. Since then, two more conferences were held in Tokyo, Japan and Salt Lake City, US, in 1996 and 2001, respectively. The most recent conference was held in June 2011 in Lillestrom, Norway.

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