A creep testing investigation is described, in which different creep tests were employed under various testing conditions on continuously graded asphalt mixtures (dense asphalt concrete, unmodified and polymer modified), and a discontinuously graded asphalt mixture (stone mastic asphalt). The tests used are the simple creep test, and the cyclic creep test in which both block-pulse loading and sinusoidal loading were applied. Besides hydraulic, also pneumatic control of loading was used to investigate the influence of the rise-time of the load. This study was performed to see if the unconfined creep test is suitable for the purpose of asphalt mixture design, and for the purpose of specification of the resistance to permanent deformation, or rutting, of asphalt mixtures. For fundamental reasons the cumulative (permanent) deformation as a mixture "property" as obtained from the unconfined creep test does not provide a basis for performance related (i.e. non-empirical) specification of resistance to rutting, nor for quantitative prediction of rutting of pavement layers. (A)
Abstract