Interface Adhesion in Geosynthetic-Reinforced Asphalt Mixtures under Variable Temperature Conditions

Abstract

Interface adhesion plays a critical role in the structural performance and durability of asphalt overlays reinforced with geosynthetics. Insufficient bonding between layers may lead to slippage, premature cracking, and reduced service life, particularly under elevated temperatures. This study investigates the interface shear strength (ISS) of asphalt–asphalt and asphalt–geosynthetic–asphalt systems, focusing on the influence of testing temperature, tack coat application rate, and binder type. Three geocomposite reinforcements commonly used in pavement rehabilitation were evaluated in combination with a conventional asphalt binder and polymer-modified binder applied as tack coats at different rates. Monotonic interlayer shear tests were performed using the Louisiana Interlayer Shear Strength Tester (LISST) at temperatures of 10 °C, 25 °C, and 40 °C. The results demonstrate a pronounced reduction in ISS with increasing temperature, confirming the strong thermal sensitivity of the interface. Specifically, the reduction in ISS for control specimens were observed up to 90%, when the temperature increased from 10°C to 40°C. In addition, tack coat application rate exhibited non-linear behavior, with intermediate rates generally providing more reliable adhesion. Furthermore, polymer-modified binder showed slightly better performance than conventional asphalt binder under critical temperature conditions. Overall, the findings provide practical insights for the construction of geosynthetic-reinforced asphalt overlays, particularly in regions with thermal variations.