Flexural and Shear Characterization of Geosynthetic Reinforced Asphalt Overlays

In the current study, the flexural and shear characteristics of geosynthetic-reinforced asphalt overlays placed on a pre-cracked old pavement layer are evaluated in two different stages. The unreinforced and geosynthetic reinforced two-layered asphalt beam specimens with 40 mm deep notch (crack) in the bottom layer are tested under repeated four-point bending test and interface shear strength test equipments to understand the flexural and shear characteristics, respectively. The two-layered asphalt specimen consists of a 45 mm thick old pavement layer extruded from an existing highway as a bottom layer, a binder tack coat, an interlayer and finally a hot mix asphalt (HMA) overlay. Two different types of geosynthetic-interlayers, namely, biaxial polyester grid coated with polymer modified binder having a square aperture of 18 mm (PET) and a glass-grid composite (GGC) are used in the study.

The flexural fatigue and interface shear strength test results indicate that the reinforced specimens improved the fatigue life of overlays and among them, the performance of GGC specimens are superior. However, the inclusion of geosynthetic-interlayers at the interface of old and new layers reduce the interface shear strength, resulting in a possible delamination of the pavement layers. A reduction of 17% and 36% in interface shear strength was witnessed in PE, and GGC reinforced specimens, respectively. Overall, the geosynthetic-interlayers improved the performance life of asphalt overlays invariably, before failure.