1. Introduction

Expanded Polystyrene, EPS, geofoam is a super-lightweight, closed cell, rigid, plastic foam. Its unit weight puts it in a separate category compared to other types of engineering lightweight materials as shown in table 2-1. In 1950, expanded polysty-rene was invented (BASF, 1997). Geofoam has now been successfully utilized in a number of countries all over the world. Some of these countries are Norway, The Netherlands, the United States, Japan, Germany and Malaysia.

In Norway the first road insulation project with EPS geofoam was performed in 1965 (Aab?e, 2000) and the first road embankment project utilizing EPS geofoam was completed in 1972 (Frydenlund, 1991) when the National Road 159 Flom Bridges project involved replacing one meter of ordinary fill material with blocks of EPS in embankments adjoining a bridge founded on piles to firm ground. The em-bankments were resting on a 3m thick layer of peat above 10m of soft, sensitive clay. Before using EPS geofoam, settlement rates were of the order of 20-30 cm annually and accelerating due to frequent adjustments of the road level. Settlement was suc-cessfully halted after using EPS geofoam. In the Netherlands the first EPS geofoam projects start early seventies (van Dorp, 1996)

Table 2-1 Types of Lightweight Materials (after Miki, H., 1996)

Even though EPS geofoam was used in the United States much earlier than in most countries, subsequent progress was slow. Recently, EPS geofoam is used in a growing trend in a number of applications in the States. The largest volume of EPS geofoam in one project is about 100,000 cubic meters in Salt Lake City in the recon-struction of interstate I-15.

The first EPS geofoam application in Japan was an embankment fill in 1985 (Miki, H., 1996) where 470 cubic meters were utilized in the project. EPS geofoam fill as high as 15m was constructed (Yamanaka, et al., 1996)

In Germany, although EPS was used for the first time in the 1960s as frost protection layers in pavement, it was first used in highway construction in March of 1995 (Hillmann, 1996) where EPS was utilized to minimize the differential settlement of a bridge approach. EPS geofoam as a lightweight fill material was first introduced in 1992 in Malaysia (Mohamad, 1996).

EPS geofoam structures performed well under static loading as will be seen in the example applications in this chapter. Experience in Japan with EPS geofoam showed that EPS geofoam structures also performed well under seismic loading. During the years of 1993 to 1995 strong earthquakes occurred in various parts in Ja-pan. Hotta, et al., (1996) reported 5 earthquakes of magnitude range 6.6 to 8.1. Al-though some damage occurred to EPS sites, Hotta et al., considered that EPS em-bankments are highly stable during earthquakes

This chapter presents a background about this lightweight material. First the chemical composition is described together with the manufacturing process of both the raw material and the final product, the geofoam blocks. The main manufacturing steps that control the characteristic of the final product is highlighted.

Selected properties of EPS geofoam are presented with a literature survey about the implication of these properties. Density, compression behavior, interface friction, time-dependent behavior, tension behavior and other engineering properties are presented. Previous laboratory work that is of importance to engineering applica-tions is shown. Important design and construction concerns are identified.

Standards that control the material testing or the design in a number of coun-tries is shown. Finally, examples of the various engineering applications are shown with related details for some of them.