Strain distribution in asphalt mixtures during the wheel tracking test at high temperatures

In general rutting in asphalt pavements occurs at high temperatures and cracks occur at cold temperatures. It has been believed that longitudinal cracks mainly arise due to the shear of moving wheels at high temperatures. This research performed wheel tracking tests at 45 degrees C on asphalt samples in holders which at one end consists of transparent glass. The distribution of the tensile and shear strains using the ARAMIS System for gathering data of the exposed end (30 x 5 cm) of the specimens visible through the transparent glass was measured. Thereafter, specimens (5 x 8 x 2.5 cm) cut from large specimen (5 x 30 x 30 cm) for CT scanner. The width of crack was also analyzed by CT scanner in three dimensional. It was found that the rutting depth in all specimens after I h (2400 wheel passes) at 45 degrees C was smaller than 1 mm, but that the tensile strains in all specimens at 1 hour were 25,000 x 10(-6) (2.5%) or larger and a strain of 3.69% which corresponds to a longitudinal crack width of 0.555 mm by CT analysis and ARAMIS system. It was also found that the cracks at the high temperature under the moving wheels were mainly caused by the tensile strain rather than shear strain and the load spreadability in mixtures depends upon the type of mixture and properties of asphalt. It is concluded that both methods are useful to evaluate the damage of mixture (C) 2012 Elsevier Ltd. All rights reserved.