By: Nick Harvill, Sales Representative
Geofoam is a cellular plastic material that is strong with a very low density, one percent of traditional earth materials. Geofoam has been used in engineering and geotechnical applications worldwide for more than 30 years. Yet many engineers seem to be leery of the load carrying capacity of Geofoam and specify the highest grade to be cautious.
EPS Insulation is specified using ASTM C578. It lists the physical properties of each grade and the insulation value. The compressive strength is listed at 10% deformation. This value is listed for comparison purposes of various insulations and is measured near the failure point. For loading purposes, it has been recommended that 1/3 of this value be used. But for Geofoam use, we have ASTM D6817. It lists the load carrying capacity of each grade of Geofoam at 1% deformation. The compression test is also different from the Insulation compression test to better simulate Geofoam use. This takes the guesswork out of designing for loads.
However, many Engineers do not seem to trust the data. Recently, one engineer specified EPS 46, a material capable of carrying 2680 Lbs./sf, under a 4” retail slab supporting only the store and its occupants. Usually an application like this would require EPS 15 at 520 lbs./sf capacity. EPS 15 is the most commonly specified Geofoam grade; used in stadium and theatre seating, slab on grade fill and other areas where the Geofoam is only needed to provide low load fill. Not only did they specify EPS 46, but they specified 6” steel reinforced knee walls every 5 feet to the existing slab. Under this construction, the Geofoam is not really carrying any load at all and EPS 15 would have been more than sufficient.
Geofoam provides High Strength. It has Predictable Performance with No Settlement. Densities are engineered for applications. If the load approaches the limit of a grade, it is economic to increase to the next grade for safety. Geofoam has Low Water Absorption and is economical, especially when the correct grade is used. Geofoam is:
- Easily Modified on Jobsite
- Variety of Sizes & Shapes
- Termite Resistant
- Environmentally Friendly
Geofoam has been used in engineering and geotechnical applications worldwide for more than 40 years. In a correctly designed application, it will perform for the life of the project.