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Tack Coat Rate and Geotextile Coverage Influence on Interlayer Bonding and Rutting Resistance in Flexible Pavements Cover

Tack Coat Rate and Geotextile Coverage Influence on Interlayer Bonding and Rutting Resistance in Flexible Pavements

Open Access
|Aug 2026

Abstract

Interlayer bonding in flexible pavements has an essential influence on their structural strength and performance. In this study, the combined outcome of application rate of tack coat and the condition of geotextile coverage on the interlayer shear strength (ISS) and the rutting resistance of double-layer asphalt systems is investigated. Specimens of binder and wearing courses were prepared with CSS-1H (cationic slow-setting asphalt emulsion, low-viscosity grade, with harder asphalt residue) emulsified tack coat at amounts of 0, 0.3, 0.6, 0.9 and 1.2 L/m2. Three interface patterns of geotextile coverage were tested; unreinforced, 50% and 100%. The bonding between layers was assessed by direct shear bond test, and the rutting resistance was evaluated by wheel tracking test.

Results revealed that the optimal amount of tack coat was highly dependent on the interface condition. Unreinforced specimens achieved the maximum ISS of approximately 1083.89 kPa at 0.3 L/m2, while the geotextile-reinforced mixes required higher tack coat rates to develop sufficient bonding due to emulsion absorption by the geotextile. In general, control specimens showed higher ISS values compared to specimens compromising geotextile between layers, but there is a significant enhancement in resistance to permanent deformation for specimens modified with geotextile with a sufficient amount of tack coat. The full geotextile coverage with 1.2 L/m2 tack coat resulted in the best rutting performance, reducing the rut depth by approximately 28% when compared with the optimum unreinforced condition. At its optimum tack coat application rate of 0.9 L/m2, partial geotextile coverage achieved a 17.4% reduction in rut depth relative to the optimum unreinforced condition, indicating a potentially economical alternative. The results emphasize the need to optimize the application rate of tack coat and geotextile coverage to provide balanced interlayer bonding and rutting resistance of asphalt pavements.

DOI: https://doi.org/10.2478/cee-2027-0015 | Journal eISSN: 2199-6512 (formerly 1336-5835) | Journal ISSN: 1336-5835
Language: English
Submitted on: Jun 26, 2026
Accepted on: Jul 22, 2026
Published on: Aug 19, 2026
Published by: University of Žilina
In partnership with: Paradigm Publishing Services
Publication frequency: 4 issues per year

© 2026 Hassan H. Al-Abodi, Ahmed F. Al-Tameemi, published by University of Žilina
This work is licensed under the Creative Commons Attribution 4.0 License.