Deformation characterisation of asphalt concrete behaviour

This paper investigates the deformation behaviour of two generic UK asphaltic materials, a gap graded asphalt and a continuously graded macadam. Uniaxial testing has been carried out in both tension and compression. The testing has encompassed uniaxial creep over a range of temperatures and stress levels. Constant strain rate tests over a range of strain rates and test temperatures were also undertaken. A number of creep recovery tests have been conducted to investigate the recoverable component of the behaviour. Repeated creep recovery tests in compression show that the total and permanent strains decrease after an initially high first cycle and then remain fairly constant until increasing as damage occurs. Triaxial creep tests have been carried out in compression over a range of axial and confining stress levels. Results from these tests have been used to examine the effect of confinement and changes in volume during the deformation process. It has been found that confinement has a stiffening effect on the steady-state deformation behaviour which is found to be higher for the continuously graded mixture.