Experimental Pavement Structures Insulated with a Polyurethane and Extruded Polystyrene Foam

The purpose of roads in areas of seasonal frost is to attenuate frost penetration and thus permit the design pavement thickness to be reduced. Early indications from actual use are that polystyrene insulation will meet these requirements. Two 100-ft (32.8-m) sections of street were constructed in Sudbury, Ontario, Canada, in September 1964 using 2-by-4-ft by 2-in. (0.610-by l.220-m by 5.08-cm) sheets of extruded polystyrene insulation in the pavement structure at a depth of 16 in. (0.406 m). In the summer of 1965 two additional insulated road sections were constructed in Ottawa, Ontario, Canada. Two types of insulation and methods were used. Extruded polystyrene boards were placed by hand (the same as at Sudbury) at the desired elevation. Polyurethane was foamed in place by spraying the chemicals on the road bed with a specially constructed self-propelled spraying machine. This paper discusses the relative merits of the different methods of roads and, in a broader context, the protection against freezing of underground utilities, such as water mains and sewers.