Volume 40, Issue 5 (September 2012)
Nonlinear Response Characterization of Bituminous Mortar
In mesomechanics performance studies of porous asphalt concrete (PA), one of the crucial component materials influencing the raveling performance of the mixture is bituminous mortar. In relation fatigue performance, the viscoelastic response of the mortar for loads corresponding to the magnitude and frequency of the truck loading is important. In this paper, the mechanical response of a bituminous mortar material is investigated at various shear stress levels and loading frequencies. A dynamic shear rheometer setup with a specimen geometry specially developed for mortar testing is utilized. The mortar, which consists of bitumen, filler, and fine fractions of sand, is produced with a composition similar to that of a standard PA mixture. The tests were conducted at various temperatures in the frequency domain. The results show that the selected mortar test setup produces results with good repeatability. The results of high shear measurements show the presence of nonlinear behavior at shear stress levels in the range of 10 kPa for temperatures of 30°C and above. At temperatures of 0°C and below, the mortar exhibits linear viscoelastic behavior at shear stress levels of up to 1 MPa. The observed nonlinear viscoelastic behavior is described using Schapery nonlinear theory. The paper discusses the testing methods and the interpretation and description of results with the nonlinear theory. It also discusses the implications of the results for mechanistic based PA performance models.