Determination of coefficient of thermal contraction of asphalt concrete using indirect tensile test hardware

Accurate values of coefficient of thermal contraction of asphalt concrete can be determined using the hardware in the Superpave indirect tension (IDT) test, a method for determining the creep compliance and strength of asphalt concrete mixtures in tension. Even though the IDT hardware has slightly higher variability than strain gages in determining the coefficient of thermal contraction values, results are more reliable than using estimated volumetric relationships used in the Superpave. This hardware can also be used to determine the coefficient of thermal contraction values of asphalt concrete. Coefficient measurements of thermal contraction coefficient should be carried out when evaluating the possible thermal tracking of such mixtures because the Superpave equation for measuring the coefficient of thermal contraction is not accurate. The coefficient of thermal contraction of the linear variable differential transformers should be determined using a material of insignificant coefficient of thermal contraction value, and then calibrated using a reference material. At least three specimens should be evaluated or three independent replicate measurements should be carried out.