Evaluation of shear bonding and reflective crack propagation in a geocomposite reinforced overlay

Abstract

Geocomposites can be employed with an asphalt overlay to improve the service life of pavements and reduce reflective cracks. However, similar to other geosynthetic solutions, geocomposites can cause de-bonding between asphalt layers, thus reducing pavement longevity. This research focuses on factors that influence the initiation and propagation of shear bonding and reflective cracks in an asphalt overlay. Laboratory double-shear and pull-out tests are conducted, and the shear bonding and pull-out strength of geocomposites in asphalt specimens are calculated. The performance of each specimen in terms of reflective crack initiation and propagation are investigated. A power law model that relates crack propagation to the number of loadings is developed and verified. Observations of geocomposite sliding on the asphalt layer reveal that this phenomenon contributes less than 40% to the overall shear bonding. Analyses reveal that the number of required loading cycles to initiate reflective cracking and crack propagation varies exponentially with the shear bonding between the overlay and the existing layer. Therefore, overlay longevity declines rapidly with decreasing shear bond strength. The exponential relationship is valid irrespective of whether or not the normal load is applied on the interlayer surface. Moreover, the results indicate that temperature is the parameter with most influence on the shear bonding between the layers and the initiation and propagation of reflective cracks, while the tack-coat application rate and geocomposite grid size are less critical. Finally, this study reveals that the decrease in shear bonding between layers both increases the stress relief ability in the interlayer zone and decreases the reinforcement capacity of geocomposite grids. Increased shear bonding between the overlay and existing pavement increases the resistance to reflective cracking.