Thermomechanical and mechanical behaviour of asphalt mixtures at cold temperature. Road and laboratory investigations

Temperature variations are particularly harmful to wearing courses with asphalt mixture. During wintertime, and especially, at very low temperatures, a surface cracking may appear and propagate more or less rapidly. An experimental investigation has been carried out on specimens of bituminous mixtures cored in the wearing course of 16 test sections of a motorway in Switzerland. These 16 wearing courses are composed with 16 different bitumen as pure bitumen, polymer modified bitumen and bitumen with additives. Those selected bitumen give a representation of the bitumen market in the 80's in Switzerland. 8 years after construction, bituminous mixtures specimens were cored in the driving carriageway and in the "emergency lane", which is not driving Their thermomechanical behaviour through the Tensile Stress Restrained Specimens Test (TSRST), and their mechanical behaviour when subjected to mechanical load through a new highly precise Direct Tensile Test (DTT) were assessed. Significative behaviour, which was depending on the origin of the specimens (carriageway or emergency lane) were observed through the TSRST. In addition, this paper provides a relevant approach procedure for investigating thermal cracking at low temperature with a highly precise DTT.