thermal stresses in bituminous flexible pavements

this report describes the calculation of thermal stresses within a bituminous flexible pavement when it is subjected to the range of temperature variations that occur in the british climate. the pavement is considered to be composed of a single slab of linear visco-elastic material which is thermorheologically simple, superimposed on a semi-infinite solid. transient thermal stresses are calculated using a simple mathematical model of the pavement for time dependent temperature distributions. the material behaviour was characterised by uniaxial stress relaxation tests on a gap-graded hot-rolled asphalt (to bs 594), which is extensively used in the basecourse layer of flexible pavements. the thermal stresses induced in the top of the basecourse in this model by a severe winter's day are shown to reach maximum tensile values of the order of 50 kn/m.sq. the induced stresses during the rest of the year are very much smaller. if an exceptionally cold climate is considered the temperature induced stresses can attain very large tensile values, but these are extremely unlikely in the british isles. thermal stresses of the order of 100 kn/m.sq. may be reached in the surface of the wearing course when conditions of rain cool the surface rapidly during winter conditions (a).