Crack propagation analysis in bituminous mixtures reinforced by different types of geogrids using digital image correlation

In the rehabilitation of flexible pavements, the use of reinforcement by geogrids has substantially increased recently, aiming to extend the service life of pavements. This work evaluated the effect of fiberglass grid reinforcement on crack propagation of bituminous mixtures. To conduct the research, five different configurations of pre-notched beams constituted of two bituminous mixtures layers, with and without geogrid, were tested. Two different fiberglass geogrids, ultimate tensile strength (UTS) of 100 and 50kN/m, and emulsions as tack coat, made of bitumen pure and modify by polymer (SBS), were combined for the fabrication of three reinforced configurations. In addition, two unreinforced configurations were also fabricated. The first one was a single layer slab and the second one was bi-layered slab composed of two bituminous mixtures layers glued by a tack coat. The specimens were subjected to the four-point bending notched fracture (FPBNF) test, designed at the University of Lyon/ENTPE. A 3D Digital Image Correlation (DIC) technique was used to determine the strain field on specimen central length area during crack propagation. The results showed that the effect of geogrids was clearly noticeable when the specimen is subjected to high strain and the crack starts to propagate into the beams. DIC analysis allowed the observation of grid reinforcement effect on retarding the cracking propagation of bituminous mixtures layers.