The use of geosynthetic reinforcements placed underneath asphalt overlays, which has been typically used to minimise problems associated with reflective cracking, is evaluated in this study as an approach to improve pavement structural capacity. Whereas geosynthetics have been used to increase the pavement structural performance when used to reinforce the base aggregate, as reported in numerous laboratory and evaluations experiments, such improvement has not been evaluated for the case of geosynthetics within asphalt layers. Accordingly, this paper presents the results of large model tests involving both reinforced and unreinforced hot mix asphalt overlays. Cyclic wheel loads were applied using an accelerated pavement test facility that was specifically developed for this research. A number of pavement sections were constructed using a polyvinyl alcohol geogrid as reinforcement inclusions. The results show a considerable increase in pavements structural performance, as quantified by reduction of strains in the asphalt concrete layers, in the vertical stresses within the pavement layers and in the resilient displacements at the wearing surface. The use of geogrid reinforcements was also found to lead to reduce rutting and permanent lateral movements in the surface layer. Overall, the use of geogrids within asphalt overlays was found to act as a reinforcement element that provide enhanced structural capacity to flexible pavements.

Geosynthetics have been extensively implemented as a pavement maintenance solution to minimize reflective cracking. However, geosynthetics within asphalt overlays can also be used to improve the pavement structural capacity, potentially resulting in reduced permanent displacements and strains in pavement structural layers. Combination of accelerated pavement testing techniques and numerical simulations would be particularly suitable to assess the comparatively new use of geogrids for increased structural capacity of asphalt overlays. Accordingly, this study focuses on two-dimensional finite-element simulations conducted to identify the variables that govern the performance of geogrid-reinforced asphalt overlays and their effect on the response of flexible pavements. The finite-element model is validated by comparing the numerical predictions with the experimental results obtained in large-scale accelerated paved models. A series of finite-element parametric evaluations is conducted by varying the stiffness of both the geogrid and the subgrade materials. The strains mobilized within the geogrid under static loading are also evaluated. The numerical predictions indicate that the presence of the geogrids significantly affects the structural behavior of the pavement, as observed through reduced vertical displacements and strains, although such reductions are not significantly affected by the increases in geogrid stiffness. A reduction in pavement stresses is observed, mainly in the base course layer. The finite-element parametric evaluations show that geogrids placed within the asphalt layers are able to increase the overall bearing capacity of the pavement system, even for cases involving weak subgrades. Finally, the mechanisms of structural enhancement can be associated with numerically predicted geogrid strain distribution, which is found to be particularly consistent with experimental results.

This study aims at evaluating the interface shear strength characteristics of full-scale geosynthetic-reinforced asphalt overlay sections constructed at Salvador International Airport, Brazil. Specifically, 24 experimental sections including 5 different geosynthetic reinforcements and no geosynthetic reinforcement (control) with 4 different tack application rates were considered in the study. Multiple asphalt cores of 150 mm diameter were then extracted and tested in the laboratory using Leutner shear tester. Results demonstrated that the interface shear strength varied depending on the geosynthetic and tack coat rates, and mostly increased with increasing tack application rates. An interaction between tack application rates and geosynthetic characteristics was observed, which was highly influenced by the geosynthetic asphalt retention capacity. Overall, it can be inferred that the geogrid aperture size, mass per unit area of nonwoven geotextile backing, and geosynthetic tensile stiffness influenced the interface shear strength characteristics of geosynthetic-reinforced asphalt overlay.