Geofoam Frequently Asked Questions

Expanded polystyrene (EPS) block, commonly referred to as geofoam block, is an engineering material with a closed-cell structure. It is a geosynthetic used in geotechnical engineering applications that is approximately 50 to 100 times lighter than conventional fill materials. Its mechanical and physical properties are defined by relevant standards according to product class, and it can be manufactured with a wide range of mechanical properties to suit project-specific service loads.

Geofoam is a well-established geotechnology with mature design and construction practices and is used in a wide range of geotechnical and infrastructure applications. Typical applications include:

• Road and highway embankments
• Bridge approach embankments
• Lane-widening embankments
• Airport runway, apron and taxiway fills
• Railway and light rail embankments
• Retaining wall backfills
• Basement wall backfills
• Slope and landslide stabilization
• Landscape fills
• Grade-raising and platform fills
• Fills over culverts
• Backfills over buried pipes and utility lines
• Sound and noise barriers
• Floating islands
• Seismic isolation and vibration damping applications

These represent some of the most common applications of geofoam technology.

Its main advantages include:

• It is approximately 50 to 100 times lighter than conventional fill materials.
• It substantially reduces design loads acting on supporting systems such as foundation soils or reinforced concrete slabs.
• It does not require heavy construction machinery or equipment for placement.
• It increases construction efficiency, allowing projects to be completed and placed into service more quickly. This can provide advantages in both initial investment cost and overall project cost. As an ultra-lightweight engineering material, geofoam can provide safe solutions on weak soils where bearing capacity, total settlement or differential settlement would otherwise be critical, and on natural or engineered slopes where global stability is a concern, often without requiring conventional ground improvement.
• Because geofoam consists of approximately 98% dry air, it can act as a buffer between the structure and the surrounding ground, helping to reduce seismic loads transmitted to the structure.

In applications constructed over existing infrastructure, geofoam enables fill construction without creating significant additional stress increases on the underlying infrastructure. This can avoid the costs associated with relocation or structural strengthening of buried utilities that might otherwise be required when conventional soil fill is used.

The first stage of a geofoam block fill construction project is block production. All blocks used in geofoam fill construction should consist entirely of EPS, and recycled EPS should not be used in block production. Another important consideration for project stakeholders is that the EPS blocks used in the project should bear CE marking in accordance with TS EN 14933.

Geofoam density typically ranges between 11–45 kg/m³. These values are approximately 1–2% of the density of conventional fills (~1800–2200 kg/m³). For this reason, geofoam is commonly classified as an “ultra-lightweight fill” material.

Because of its closed-cell structure, geofoam has very low water absorption. It can retain its mechanical properties even under long-term exposure to water. Numerous case histories from Türkiye and other countries demonstrate that geofoam blocks can maintain their mechanical performance under service loads over the long term.

Buoyancy stability must always be checked in the design of a geofoam block project. Where required, groundwater levels may be temporarily lowered by pumping during construction. After construction, measures such as increasing the permanent dead load above the geofoam or installing drainage systems that prevent water from rising above the base of the geofoam fill may be implemented.

Geofoam is a proven geotechnology with more than 50 years of documented field performance since its first applications. When geofoam fills are designed for the applicable service loads and in accordance with relevant specifications, both short-term deformation after construction and long-term deformation throughout the service life can be maintained within controlled limits.

Geofoam blocks consist of approximately 98% dry air and therefore exhibit vibration-damping characteristics. This property allows geofoam to be used as a seismic buffer between structures such as retaining walls, basement walls and bridge abutments and adjacent soil fills, significantly reducing the transmission of seismic lateral earth pressures from the soil fill to the structure. However, earthquake-induced lateral forces may exceed the frictional resistance between adjacent geofoam block layers, potentially resulting in relative displacement between the layers. In projects located in areas of high seismicity, site-specific seismic internal stability analyses are therefore performed to evaluate the safety of each interface between adjacent geofoam block layers under earthquake loading. Where necessary, appropriate geometric and mechanical measures are designed to prevent relative displacement between the blocks.

Although EPS-based products are combustible, the EPS raw material used in the production of geofoam blocks contains flame-retardant additives. When the material is exposed directly to a flame source, melting and associated volumetric deformation may occur in the contact area; however, these additives limit continued combustion and flame spread after the flame source is removed. Geofoam blocks should have a Euroclass E reaction-to-fire classification in accordance with EN 13501-1. Where geofoam blocks need to be temporarily stored on site before installation, the storage area should be located away from heat and ignition sources and from construction areas where welding, cutting or other hot works are being performed.

During construction, the vertical and horizontal surfaces of the geofoam fill may not yet be covered by protective layers, making the material’s reaction-to-fire classification and appropriate site fire precautions particularly important. After construction is completed, geofoam blocks used in engineering applications are generally enclosed by reinforced concrete load distribution platforms, soil fill, geomembranes, shotcrete, precast panels or similar protective systems and are not left exposed. Fire performance should therefore be evaluated not only on the basis of the reaction-to-fire classification of the geofoam material itself, but also in the context of the completed system and the protective layers surrounding the geofoam.

Certain organic solvents, including acetone, benzene and paint thinner, can chemically interact with EPS and cause deterioration and material loss in geofoam blocks. Direct contact between geofoam blocks and petroleum-based products should likewise be avoided. In completed geofoam block fills, horizontal surfaces are therefore typically protected with geomembranes or reinforced concrete load distribution platforms, while vertical surfaces are covered with panels, plaster or similar protective systems to prevent direct contact with such chemicals. During construction and temporary storage, care should also be taken to prevent contact between geofoam blocks and organic solvents, petroleum derivatives or other chemicals that may adversely affect EPS.

Yes. Geofoam blocks can be cut to project-specific dimensions on site using portable hot-wire cutting equipment or electric saws. However, the majority of a typical geofoam block fill can generally be constructed by placing factory-produced blocks without requiring additional cutting. Field cutting is usually required along the boundaries of the fill footprint and at final fill elevations to accommodate the project geometry. Although custom-cut blocks generally represent a relatively small proportion of the total fill volume, these cuts are important for constructing the fill in accordance with the design.

When preparing a block layout for a geofoam fill, the longitudinal axes of the blocks in any given layer should be oriented perpendicular to the longitudinal axes of the blocks in the layers immediately above and below, creating a staggered arrangement. Vertical joints between blocks within a layer should not remain continuous throughout the height of the geofoam fill. In addition, the upper surfaces of the blocks in each layer should be arranged parallel to the upper surfaces of the blocks in the adjacent layers above and below.

Geofoam is an inert material and does not release harmful substances into the soil or groundwater. Its low weight can also reduce transportation requirements and excavation volumes, potentially lowering the overall carbon footprint of a project.

The material cost of geofoam blocks is generally higher than that of conventional soil fill. However, the total project cost can often be significantly reduced through advantages such as reduced excavation quantities, elimination of ground improvement where local ground conditions do not satisfy bearing capacity and/or settlement criteria, and faster construction. Numerous case histories in Türkiye and around the world demonstrate that, for embankments constructed over weak soils, geofoam can provide an economically competitive alternative in terms of total project cost despite its higher unit material cost.

No. The suitability of geofoam should be evaluated on a project-specific basis, taking into account project boundary conditions, material logistics and service loads.

Yes. Türkiye’s first large-scale geofoam road embankment application was completed in 2017. Since then, geofoam technology has been increasingly used in bridge approach embankments, highway projects, interchange structures and infrastructure protection applications. In recent years, geofoam has also been selected for major infrastructure projects such as the D-130 Highway Başiskele Interchange Corridor Project in Kocaeli, providing significant advantages in construction duration and total project cost compared with conventional fill solutions.

Geotech Soil and Foundation Engineering provides end-to-end engineering and construction support for geofoam projects:

• Design and engineering optimization
• Supply of CE-marked geofoam blocks
• Site installation supervision
• Turnkey field applications
• Instrumentation and monitoring services
• Performance monitoring and technical reporting

This integrated service structure enables design, construction and performance verification processes to be managed through a single engineering team.