The growing need for new roads may, in many cases, require construction over soft or loose soils that are incapable of supporting additional loads. Designers must identify innovative materials and construction techniques to address the problem of building on soft soils or where sensitive existing utilities or wetlands are present while, at the same time, accelerating project schedules. EPS geofoam can be used to replace compressible soils or in place of heavy fill materials to prevent unacceptable loading on underlying soils and adjacent structures. The high compressive resistance of EPS geofoam makes it able to adequately support traffic loadings associated with secondary and interstate highways. Construction with EPS geofoam also saves time because EPS geofoam is easy to handle without the need for special equipment. Because EPS geofoam is an engineered product it arrives on site already having undergone rigorous Q&A testing, unlike other fill materials that require time consuming QA/QC testing.
A description of a typical road construction, from bottom to top, is as follows: compact a layer of sand at the base of the roadway excavation to provide a level and free draining construction surface. Place the EPS geofoam to the desired height, staggering the vertical joints in each course so as not to create continuous vertical seams.
If required, a separation layer may be placed between the top of the EPS geofoam and the overlying pavement system. A separation layer can have two functions: to enhance the overall performance and life of the pavement system by providing reinforcement, separation and/or filtration and to enhance the durability of the EPS geofoam both during and after construction. Choices for the separation layer include geotextile, hydrocarbon resistant geomembrane, geogrid, geocell with soil fill, soil cement, pozzolanic stabilized materials or a reinforced concrete slab.
For example, if protection against fuel spills is desired, a hydrocarbon resistant geomembrane cover can be placed over the uppermost EPS block course to protect from possible hydrocarbon attack. Alternately, a reinforced concrete load distribution slab can be used to protect the EPS geofoam from hydrocarbon attack and from potential overstressing resulting from heavy traffic loads. Other structural features (i.e., tilt-up panel walls, impact barriers, light and power poles, etc.) can be anchored to the load distribution slab.
The pavement system, which generally consists of select fill, roadbase gravel and an asphalt or concrete pavement driving surface, is subsequently constructed atop the separation layer. Prevention of differential icing is a consideration when using EPS geofoam in roadway construction in cold climates. Differential icing is defined as the formation of ice on the surface of an insulated pavement, when the adjacent, non-insulated pavement remains ice-free. When constructed next to existing roadways, sections of pavement constructed over EPS geofoam can form ice prior to adjoining areas because EPS geofoam is an excellent insulator, which prevents heat from reaching the pavement from the underlying soil. One way to address this concern is to keep the top level of the EPS geofoam at or below the appropriate frost line for the region. For example, for a frost line of 3 feet (0.9 meters), a minimum separation layer and pavement system material thickness of 3 feet (0.9 meters) should be provided over the EPS geofoam.