Strain field distribution of asphalt mortar using digital image processing

The difference between the modulus of asphalt mixture components leads to the complex deformation phenomenon that the strain primarily accumulates in asphalt mortar. Conventional deformation testing methods cannot easily capture the local deformation, limiting the usage of isotropic deformation measurement of asphalt mixture. This study aimed (1) to propose a method to extract stain field of asphalt mortar by digital image correlation (DIC) and digital image process method, as well as (2) to delve into the strain field in the asphalt mortar position at various temperatures and loading rates. In the present study, DIC was first applied to calculate the full strain field of asphalt mixture; subsequently, the aggregate, asphalt mortar as well as void were obtained using digital image process method. Based on digital image processing method, the strain at asphalt mortar position was achieved. According to the results of the strain field distribution of asphalt mortar in indirect tensile test, probability density of low strain region decreased, while that of medium and high strain region increased in the loading process. The results illustrated that asphalt mixture with low filling factor (the area ratio of mortar to the whole mixture) had higher strain in a smaller area. In the meantime, at low temperature, the mean strain of high strain zone was lower, and the area of that became smaller.