COMPARISON OF CALCULATED AND MEASURED THERMAL STRESSES IN ASPHALT CONCRETE

The paper presents the comparison of calculated and measured thermal stresses induced in restrained asphalt concrete specimens by cooling. Thermal stresses were measured in the Thermal Stress Restrained Specimen Test. The calculations of thermal stresses were performed with the use of a theoretical formula based on the temperature dependent stiffness modulus. The novel approach applied in this paper was that the stiffness modulus of asphalt concrete which was used in calculations was measured in a creep test at low temperatures on the same material which was used in the Thermal Stress Restrained Specimen Test. Realistic values of stiffness moduli resulted in a good compatibility between calculated and measured thermal stresses. The creep test at low temperatures was performed in bending according to the method developed at the Gdansk University of Technology. Three types of bitumen were used to produce asphalt concrete. The lowest thermal stresses were induced in the Thermal Stress Restrained Specimen Test in asphalt concrete with 50/70 multigrade bitumen, next with DE 80B SBS polymer modified bitumen and the highest with 50/70 plain bitumen.