Interface shear strength and shear fatigue resistance of fibreglass grid-reinforced asphalt concrete test specimens

This research was undertaken to study the effects of grid opening size and tack coat type on both the shear strength and shear fatigue resistance at the interface of fibreglass grid-reinforced asphalt concrete specimens and, more importantly, to correlate these effects with the interfacial fatigue performance under four-point bending beam fatigue loading. The specimens were fabricated using a 12.5-mm nominal maximum aggregate size surface mixture. Two types of fibreglass grid, differing only in the grid opening size, and two tack coats, a PG 64-22 asphalt binder and a slow-setting anionic asphalt emulsion with low viscosity, were used to reinforce the specimen interfaces. The digital image correlation technique was utilised to measure displacements, strains, and crack lengths. The test results indicate that a strong tack coat and a grid with large openings can potentially improve the shear resistance of a grid-reinforced interface but the effects of these two parameters might differ under monotonic and cyclic loading conditions. The cyclic shear, beam fatigue, and monotonic displacement-controlled shear test results suggest that the grid opening size plays a key role in the interface shear fatigue performance, however tack coat quality plays a more important role on the interface shear strength of the specimens.