Polystyrene foam boards have been used as a frost protection measure on roads in sweden for about 20 years. Different qualities havebeen tested regarding their long-term function as an insulation. Properties such as bacterial, chemical, and mechanical durability in roads and preserved low-heat conduction have been continuously followed. In the specifications of the national road administration in 1976, the extruded polystyrene skinboard, type hi 50 from the dow chemical company, was recommended for use in an insulated road base. For skid resistance, the depth of insulation was changed from 50 cm, according to the 1976 specifications, to 40 cm below road surface in the specifications of 1984. This change was based on experience from the swedish road and traffic research institute test field. It was observed that a conventional crushed rock roadbase showed the same icing risk potential as a base with 40 cm of sandy gravel above the insulation board. Recommended insulation thicknesses are related to average freezing index at the site. A new procedure is being developed making it possible to calculate the frost heave when the frost penetrates below the base into underlying frost-susceptible soils. The procedure is based on determination of the frost heave properties of soils by a direct freezing test. This makes it possible to optimize the frost-protective base construction in relation to local climatic, geological, and hydrological conditions at the site. This paper appeared in transportation research record no. 1146, Frost protection and insulation for transportation facilities. For covering abstract see IRRD no 817763.
Abstract