Characterization of the stiffness of asphalt surfacing materials on orthotropic steel bridge decks using dynamic modulus test and flexural beam test

A laboratory study was conducted to determine the dynamic modulus and the flexural stiffness of three typical surfacing materials on orthotropic steel bridge decks, including polymer-modified asphalt concrete, gussasphalt concrete and epoxy asphalt concrete. Master curves of the measured dynamic modulus and flexural stiffness were obtained and compared to investigate the differences in stiffness property of the three materials. The results show that both the dynamic modulus test and the flexural stiffness test can be used in the material classification. The epoxy asphalt concrete exhibits the highest dynamic modulus and flexural stiffness. The dynamic modulus master curves are higher than those of the flexural stiffness for all the surfacing materials especially at low frequency and/or high temperature, which is probably due to the major differences in state of stress, specimen fabrication and aggregate interlock effect between the two test methods. The flexural beam test which loads the specimens in flexural tension is better at reproducing the stress state of surfacings on orthotropic steel bridge decks. Furthermore, the size requirement of specimen in the dynamic modulus test makes it impossible to obtain the specimens directly from actual surfacings. Therefore, the flexural beam test is more appropriate for the characterization of surfacing materials on orthotropic steel bridge decks.