EPS Geofoam Specifications

Designing to the 1 percent strain value

The single most important number on a geofoam submittal is the compressive resistance at 1 percent strain. EPS behaves elastically up to roughly 1 percent deformation; beyond that, sustained stress produces creep, meaning slow, permanent deformation over the life of the fill. Standard practice, reflected in NCHRP guidance for geofoam embankments, is therefore to keep long-term dead load stress at or below the 1 percent strain value, with total dead plus live load checked against the elastic limit as well.

In practice the designer computes the vertical stress at the top of the geofoam mass from the pavement section, cover soil, and traffic loading, then selects the lightest D6817 class whose 1 percent strain resistance exceeds that stress with the required margin. Where stresses vary through the fill, projects commonly zone the block layout, placing a higher class such as EPS29 in the top course under the load distribution slab and a lighter class such as EPS19 or EPS15 in the body of the fill. The 5 and 10 percent strain values in the class table are index properties for quality control rather than design allowables.

InsulFoam GF manufacturer data

EC Applications supplies and installs InsulFoam GF, an EPS geofoam product line manufactured to meet or exceed ASTM D6817 across the standard density classes. Per the manufacturer's published data, InsulFoam GF is produced in multiple densities and block sizes to match the job specification, is resistant to moisture, insects, and mold, contains no HCFCs or formaldehyde, and is 100 percent recyclable. Because blocks are molded and cut to order, the shop drawing set, not a stock catalog, determines the block dimensions delivered to site.

A typical submittal package for an InsulFoam GF project includes the D6817 class certification with density and compressive resistance test results, block layout drawings, and the manufacturer's product data sheet. ECA assembles that package as part of the installation scope.

Block dimensions, placement, and layout

Geofoam blocks are molded in large billets and cut to project dimensions at the plant. Common block faces are on the order of 4 by 8 feet with thicknesses from roughly 8 to 40 inches, though sizes vary by molder and are set by the approved layout drawings. Blocks are placed by hand or with light equipment on a prepared, leveled bedding layer of sand or fine granular material, laid in running-bond courses with vertical joints staggered between layers, and interlocked with barbed mechanical connector plates to resist shifting during construction.

Field adjustments are made with hot-wire cutters or saws so blocks fit tightly around utilities, structures, and grade breaks. Because the material is buoyant, designs below the water table or in flood-prone sections must check hydrostatic uplift; standard mitigations include drainage layers that keep water off the fill mass, adequate overburden, and in some cases anchorage detailed by the engineer of record.

Protection layers over the fill

EPS is degraded by prolonged UV exposure and dissolved by petroleum hydrocarbons, so the specification always pairs the fill mass with a protection system. Under pavements, a reinforced concrete load distribution slab or a well-graded granular layer spreads concentrated wheel loads before they reach the blocks. Where fuel spills are a credible exposure, such as roadway and bridge approach fills, a geomembrane separation layer over the geofoam is standard practice, and ECA self-performs that lining work alongside the block placement. Buried placement with soil cover handles the UV concern; blocks stored on site should be covered until placed.