As a practical and effective tool for quantitative in-plane deformation measurement of a planar surface, two-dimensional digital image correlation (2D DIC) is now widely accepted and commonly used in the field of experimental mechanics. This paper presents an overview of the use of DIC-based techniques for asphalt mixture characterisation reported in the literature. 2D DIC is well suited to analyse asphalt materials mechanical properties because of their anisotropic and heterogeneous nature. Fundamentals of DIC are first briefly described. Specific advantages of using these techniques in a context of asphalt material characterisation are then highlighted. Critical issues that require further research and development are finally examined.

A laboratory investigation was performed to evaluate the influence of filler type and Rigden fractional voids on fundamental fracture limits of asphalt mixtures and mastics. Fracture properties of 14 different asphalt mixtures and mastics composed by the combination of 7 different fillers and 2 asphalt binders were evaluated using: a visco-elastic fracture mechanics-based crack growth law for mixtures; the Bending Beam rheometer for mastics at low temperatures and a Modified Direct Tension Test for mastics at intermediate temperatures. A Digital Image Correlation System was employed to detect strain distribution and damage evolution in mastics. Experimental results indicate that the filler type and Rigden fractional voids affect the fracture limits and the definition of strain distribution and damage evolution of both mixtures and mastics, while other properties result more dependent on the physio-chemical interaction between filler and asphalt binder.

The use of a three-point bending beam (3PB) test was investigated to characterise hot mix asphalt (HMA) cracking behaviour. Fundamental HMA fracture properties, identified as tensile strength and fracture energy density at first fracture, were determined for six different asphalt mixtures (two natural and four SBS polymer modified) applying the HMA Fracture Mechanics framework. Full-field strain maps obtained from an in-house developed digital image correlation-based method were observed to better understand the crack initiation and propagation mechanisms in the 3PB specimen. The resulting fracture behaviour was predicted using a displacement discontinuity boundary element method to model the microstructure of the six asphalt mixtures and to predict their fracture properties. Both numerical and experimental results indicate that the fracture mechanism of asphalt mixtures can be properly described from 3PB test results when appropriate interpretation models are used.