Curling Deformations and Stresses of Insulated Rigid Pavements

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The problems associated with freezing and thawing of the subgrade soil underneath highway and airfield pavements in countries with cold winters like Canada are well known. In the southern parts of Canada, the subgrade can be protected from freezing by a thick layer of granular material or a thin insulating layer. In northern regions, layers of granular materials or insulation can maintain the subgrade in a frozen condition.Previous studies have shown that extruded polystyrene foam is effective as an insulating material. However, the effect of this material on the physical behavior of pavements has not previously been investigated.To study the effect of a thin insulating layer on the curling deformation and thermal properties of rigid pavements two concrete slabs were cast in the field. One slab was laid over a 1½ in (4 cm) thick layer of styrofoam, while the second slab was cast over a 1½ in. (4 cm) thick layer of sand without insulation. A 10 in. (25 cm) subbase layer of compacted gravel was used underneath both slabs.Both slabs were instrumented from surface through foundation to determine the temperature distribution and to establish the curling behavior of the slabs. Periodic readings were taken during one warm and one cold weather period. The results derived from these readings have indicated that insulation reduces curling deformation of pavement slabs and does not significantly effect temperature gradients across their thickness.