We’ve talked a lot about the various uses for Geofoam, or Expanded Polystyrene on our blog the past few months. In commercial construction, specifically large, road or embankment type structures, Geofoam has been pretty well documented here.
What we have yet to mention is that the formal name Geosynthetics, or the class of fill for which is used, come in multiple varieties. Geofoam and Geocomb. For the purposes of this article, we’ll focus only on Geofoam. As taken from the 1999 report of:
John S. Horvath, Ph.D., P.E. Professor of Civil Engineering Manhattan College School of Engineering Civil Engineering Department Bronx, New York 10 471-4098
“For example, it is necessary to specify a specific polymer, product thickness, surface texture and other properties to completely describe a geomembrane. The term geocomb, also coined by the author, is of more recent (1999) vintage and is used to define open-cell extruded materials that, in cross-section, have a honeycomb appearance. Such products were formerly called “ultra-light cellular structures” (ULCS)……….
Functions and Their Applications Thermal Insulation ………. EPS and XPS were both used initially to provide thermal insulation, first above ground (1950s) and then below (1960s). Foams in general are very efficient thermal insulators because they are approximately 98% to 99% gas by volume (as noted previously, the gas trapped in the cells of most foams is air, at least in the long term) and gases are typically very efficient thermal insulators. Therefore, it is perhaps not surprising that the first known application of what we now call geofoam was as thermal insulation of:
- Road and airfield pavements, and railway track systems to prevent or at least reduce seasonal frost heaving and thawing or retard thawing in permafrost areas;
- The below-ground portions of buildings to reduce seasonal heating and/or cooling requirements;
- Beneath refrigerated storage buildings and sports arenas to prevent freezing and heaving of the underlying ground and
- Beneath on-grade storage tanks containing cold liquids, also to prevent freezing and heaving of the underlying ground (one of the relatively few applications where glass foam was and is used almost exclusively). Known examples of these applications date back to the mid-1960s.1
Early users of Geofoam experienced unexpected problems associated with cold weather known as “differential icing.” The insulated layer in roadways (Geofoam) created a cooling effect on the surface above. This condition led to wet, slippery roads, and end up creating spot icing. Traditionally constructed roadways (structural steel and Portland cement) were more susceptible to temperature fluctuations. The freeze-thaw effects (differential icing) of cold temperatures creates problems and expense for city, county and national DOT administrations. Potholing, heaving and cracking of roadways became a common problem in most climate areas. The use of Geofoam as an underlayment and membrane material was intended to prevent differential icing, but most of the time it did not.
This caused the US Department of Transportation outlawing, or limiting the use of Geofoam in road, rail and pavement construction. The limited knowledge of the time in the ‘50’s and ‘60’s stunted an otherwise stellar performing material that is not only cost-saving, ultra-light to handle and durability.
Figure 1: Effect of asphalt concrete thickness on pavement surface temperature for a model with no base and 30.5 cm of geofoam.2
As you can see from the diagram above, Figure 1, because there is no granulated base between the pavement and Geofoam, the air temperature is much warmer than the pavement, causing it to ice over in spots or sections. Granulated road base used as a membrane and separator between the upper level of the pavement and the Geofoam material.
From studies performed in Scandinavia, especially at the Norwegian Road Research Laboratory (NRRL), strategies were formulated that either completely eliminated differential icing, or at least minimized it. For the short version, adding a specified layer of granulated protection layer, which is calculated by a specific formula dependent upon location of use.
Figure 2: Effect of base thickness on pavement surface temperature for a model with 2.5 cm asphalt concrete and 30.5 cm of geofoam. Base thermal conductivity of 22.3 cal/cm-hr- ˚C and heat capacity of 0.17 cal/g-˚C.2
With a granulated base separating the Geofoam from the pavement materials, air and surface temperature are nearly identical, minimizing or eliminating icing over of the pavement area.
Although Geofoam has yet to reach its full potential, many road, railway, levee and airport runway construction projects are now incorporating Geofoam.
Geofoam is a lightweight (some call it ultra-lightweight) material that is 1%-2% the weight of traditional soils as fill. Using Geofoam in earthworks has benefits that no other product known at this time. Some of them are due to the fact that this ultra-lightweight material significantly minimizes stress on subgrades. This benefit aids in soil settlements, stability against slope and load-bearing failures, with the most effective being EPS Block Geofoam.
The results of the Scandinavian study mentioned earlier helped catapult Geofoam in construction in minimizing ground vibrations, such as railways as they pass by, as well as ground tremors of a low variety.
Science engineers took the Scandinavian studies and duplicated the research, certifying the process to be used as per the Department of Transportation.
Polymolding LLC produces EPS Geofoam in block form and is ready and available to discuss your construction needs. Feel free to contact us for a no obligation consultation.