Over the last 50 years, expanded polystyrene (EPS) has been providing engineers and contractors with an innovative and versatile alternative to traditional fill material. First used in Norway in the early ‘70s followed by Japan and the USA in the mid-‘80s, EPS reduces vertical and horizontal stresses in subsoil and substructures, leading to more stable foundations.
Weighing only 1% the weight of traditional fill, EPS is continuing to prove its capabilities as a modern civil and ground engineering construction material, providing a solution to the UK’s challenging, varied and often unstable ground structure. Applications such as road construction, embankments, noise bunds, retaining walls and landscaping are now commonly using EPS in their construction, ensuring a robust, durable and lightweight solution.
The manufacturing process of EPS has a significant impact on its inherent characteristics. Raw beads are heated with steam causing them to expand and then, following storage for maturation, the beads are fed into a block mould with more steam, causing the bead to expand further and fuse together, forming the rigid block. EPS blocks are literally 98% air, meaning the material is light in weight, yet extremely strong under compression.
Minimal load pressure
In civil engineering fill applications, traditional materials can place unacceptable horizontal and/or vertical stress on the underlying soil or against structures. The use of EPS as a fill material offers a reliable, cost-effective, lightweight solution to these problems, which can simplify construction, as well as reducing the probability of further settlement or unacceptable lateral forces.
Material and labour savings
EPS is easy to handle, store and cut on-site without the need for heavy lifting equipment or safety measures such as protective clothing, masks or goggles. The lightweight nature of EPS means that significantly more blocks can be transported compared to traditional landfill material, ensuring lower carbon emissions and pollution reduction due to the reduced number of loads. Approximately 80m3 of EPS blocks can be loaded onto one single vehicle compared to only 16m3 of traditional landfill, reducing the need for excessive transportation.
The major benefit of EPS over traditional fill material is that it does not add any significant weight to the existing ground, despite any extra load from the structure above, allowing for more straightforward foundation design. Additionally, due to its closed cell structure, EPS is 100 times less dense than traditional fill material, which reduces settlement caused by soil compaction. EPS is manufactured in a wide range of densities from 15kg/m3 up to 43kg/m3 and a range of compressive strengths from 70kPa to 350kPa, ensuring clients the materials’ suitability for a wide range of specifications and applications.
EPS is rot proof making it ideal for direct contact with earth in substructure applications. It does not require indoor storage or become friable or saturated and it will fully maintain its performance characteristics over its expected lifecycle. The durable nature of the material also makes it immune to insect, bacterial and fungal attack, which increases its longevity and maintains its high-performance levels.
Manufactured in a range of compressive strengths and sizes designed specifically for individual applications, EPS has been used in civil engineering applications for over 50 years and because it is lightweight and easy to install, great savings can be made in both installation costs and design complexity.
Proven over a diverse range of products, the versatility of the material is undeniable as it is not only suitable for use in a variety of civil engineering applications, but also for residential housing developments with weak underlying ground structure.
The environmental qualities of EPS make it a sustainable choice and its ability to create stable ground conditions over a long period of time will decrease the need for potentially costly remedial works caused by settlement. The result is a more stable fill material, with none of the associated issues.
Extruded polystyrene (XPS) is also a proven material, being specified as a void fill solution especially for higher load bearing applications. It is important for all projects that civil engineers and contractors work closely with manufacturers to determine the right material, grade and specification for their particular application.