Fracture Properties of Multirecycled Asphalt Mixes from Four-Point Bending Test Using Digital Image Correlation and Back Calculation

Six different asphalt mixes were subjected to the four-point bending fracture tests designed at the University of Lyon/Ecole Nationale des Travaux Publics de l’Etat (ENTPE). Among the six tested mixes, three were hot mixes and three were produced according to a warm process with foamed binder. For each of the two processes, the first mix contained 0 % reclaimed asphalt pavement (RAP). The second mix contained 40 % RAP from a milling process. The third mixes contained 40 % of the second mix, aged artificially in the lab and recycled. Two methods were applied to determine the crack propagation during fracture testing. The first one, called the displacement ratio method for predicting crack length, is based on displacements measurements. The second one used digital image correlation and strain field analysis. The two methods gave similar results for crack length values during the tests. The stress intensity factor (KIC) as a function of crack length was calculated. Results showed rather close fracture properties for the six mix types.