Effect of beam size on the creep stiffness of asphalt mixtures at low temperatures

Creep stiffness of asphalt mixtures is an essential property used to estimate the susceptibility to low-temperature cracking of asphalt pavements. Currently, creep stiffness is obtained by performing indirect tension creep tests on 150 mm (6 in.) cylindrical asphalt mixture specimens. A simpler test method, in which small mixture specimens are tested, has been recently proposed. The main obstacle in using this test method is the use of small size specimens and that the volume of material tested may not be representative. This paper addresses this critical issue by performing three point bending creep tests on beams of different sizes (6.25 x 12.5 x 100 mm, 12.5 x 25 x 200 mm, and 18.75 x 37.5 x 300 mm). The creep stiffness of 10 asphalt mixtures were determined at three low pavement service temperature levels: high temperature level (PG low limit + 22 degrees C), intermediate temperature level (PG low limit + 10 degrees C), and low temperature level (PG low limit -2 degrees C). Visual inspection and statistical analysis of the experimental results indicate that the creep stiffness of asphalt mixtures can be obtained by testing small beam specimens at test temperatures in the vicinity of the component binder PG low limit.