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Earthen fills, such as soil, crushed rock and sand, have dominated construction for centuries, as they are ubiquitous, familiar, and relatively inexpensive on a per-unit basis. As characteristics vary from one excavation source to another, and can change based on weather, traditional fills can be unpredictable. To address this limitation, project teams must conduct extensive testing—including compacting soil in phases to a percentage of dry density and then sending multiple samples to the lab to confirm results.

Geosynthetics, like EPS geofoam, are produced under controlled conditions and yield predictable and consistent engineered values, which can simplify design and construction and eliminate testing costs. It is a lightweight material alternative to traditional fills that help solve multiple engineering challenges. EPS geofoam is approximately 100 times lighter than soil, and significantly lighter than other lightweight fills like wood chip, cellular concrete, shredded tires & Pumice.

Expanded polystyrene (EPS), also commonly called 'EPS-geofoam', is a generic term which is used to describe expanded polystyrene formed into low-density cellular plastic blocks to be used as lightweight, stable, inert, environmentally safe earth fill material. EPS-geofoam is being successfully used as an alternative to various soil fill applications where a lightweight material is required to reduce stresses on underlying soils or lateral pressure to retaining walls, abutments or foundations.

Expanded polystyrene is created in a two-stage, moulded bead process. EPS geofoam is produced in standard rectangular blocks, but can be custom-cut in the factory to meet various job requirements, including sloped or curved pieces. Additionally, EPS geofoam is easy to trim in the field, as needed, using saws or a hot-wire cutting tool. As an engineered product, it can be produced to obtain the required compressive resistance. EPS geofoam density, only about 1% that of soil and rock, is controlled during the manufacturing process, making it a superior, ultra-lightweight fill material that significantly reduces the stress on underlying subgrades. The lighter load can reduce settlements and can improve stability against bearing and slope failures.

EPS geofoam enables engineers, architects, builders and other industry professionals to design by function, that is, to focus on the key geosynthetic functions they're looking for in a particular project, then select the best combination of products to achieve the goals most cost efficiently.

EPS geofoam provides several unique functions not available with other types of geosynthetic materials. This multi-functionality replaces the need for many different products to achieve the desired results, making EPS geofoam highly cost effective. At the same time, EPS geofoam products work very well as a complementary resource with EPS geofoam-based composites and new synergies enabling end users to design with even greater flexibility and more options, not to mention unique results that would not be otherwise attainable.

EPS geofoam products help reduce and absorb the impacts of naturally occurring forces such as gravity and earthquakes rather than trying to strengthen or stiffen a structure to resist the forces. By working with, rather than against these forces, EPS geofoam gives engineers more flexible solutions to construction challenges.

The two key properties that make EPS geofoam so attractive in design and construction are its low density for stress and deformation-related construction problems, and its thermal insulation properties that help combat frost-heave problems.

The density of EPS geofoam is controlled during the manufacturing process, and ranges from 15 to 22 kg/m3 for lightweight fill applications. This low density is only about 1-2% of the density of soil and rock. Geofoam's ultra-low weight is a common deciding factor in specifying the material for soft soil remediation, as it imparts small dead loads on poor load bearing soils. Additionally, its lightness enables crews to place EPS geofoam blocks by hand, reducing the need for heavy equipment, and simplifying construction on tight jobsites and steep slopes. One truck can carry approximately 92 m3 of geofoam—a volume equal to 12 dump trucks of earthen fill. This helps reduce construction traffic and transportation costs.

Because it is approximately 98% to 99% air by volume, geofoam is a very efficient thermal insulator. EPS geofoam can be produced with higher densities to obtain the higher R-values preferred for insulation purposes, as well as to achieve lower deformation. EPS geofoam has been used in road and airfield pavements and railway track systems, beneath refrigerated storage buildings, sports arenas and storage tanks to prevent ground freezing and heaving, and in below-ground building segments to reduce seasonal heating and cooling requirements.

As with EPS insulation, EPS geofoam has a closed-cell structure that limits water absorption; with proper drainage, weight gain is not expected. The material's water-resistant nature is demonstrated by its frequent use in floating structures, such as piers.

As EPS geofoam is buoyant, it is important to consider uplift forces in applications where the material will be partially or fully submerged. Buoyancy can be minimized by installing geofoam above the water table and ensuring suitable drainage. Additionally, the surcharge from overlying soils or pavements is frequently sufficient to offset uplift forces. Where high water exposure cannot be avoided, supplemental restraints (e.g. screw anchors or restraining straps) might be required.

Other notable geofoam property is its high compressive resistance. Despite its light weight, EPS geofoam is engineered for high strength. The material's compressive resistance ranges from about 15,178 to 128,223 Pa (317 to 2,678 psf) at a one percent strain. Recently identified Westergaard modulus of subgrade reaction, “k” values confirm geofoam has better bearing capacity than most foundation soils. The Westergaard modulus estimates the support of layers below a rigid pavement surface. As long as combined dead/live loads do not exceed one percent strain, EPS geofoam will never creep or experience plastic yield. Geofoam has been successfully used as a sub-base material for pavement sections bearing the live loads of locomotives and jumbo jets.

Correctly specified and installed EPS geofoam is durable and stable, so it is considered permanent, lasting for decades throughout a project's life. It neither decomposes nor is affected by freeze-thaw cycles or road salts, and does not leach toxic chemicals or heavy metals into soil or groundwater.

However, the material can be damaged from exposure to hydrocarbon chemicals, such as some petroleum products that chemically degrade EPS foam. Installation of a compatible geomembrane can protect geofoam from fuel spills or exposure to hydrocarbons in contaminated soils when these conditions might exist.