In Situ Assessment of Interlayer Systems to Abate Reflective Cracking in Hot-Mix Asphalt Overlays

Abstract

A method to investigate the effectiveness of interlay systems in hot-mix asphalt (HMA) overlays to retard reflective cracking is introduced. Significant research has been conducted on developing techniques to reduce reflective cracking in HMA overlays. Many interlayer systems have been used in the field; some showed no structural or economical benefits, while others could reduce reflective cracking in the short term. However, long-term and quantitative benefits for many of these techniques have not been realized. Hence, this research fulfills the need to quantify the effectiveness of interlayer systems in delaying or abating reflective cracking–it proposes a systematic approach to identify reflective cracking and a conceptual index to evaluate interlayer systems. Ground-penetrating radar and a video integration system are used to detect surface cracks in overlays as well as joint opening and dowel bars in existing portland cement concrete pavements. Transverse cracks that exist over a joint are classified as joint-associated reflective cracks. Other transverse cracks are categorized as non-joint-associated transverse cracks. These cracks are not considered reflective cracks. A weight function is introduced to incorporate crack severity. Finally, two performance indices are introduced: reflective cracking appearance ratio and transverse cracking appearance ratio. By means of these new indices, the effectiveness of four interlayer system types used in Illinois is quantified: nonwoven reinforcing fabric with asphalt binder, sand antifracture, interlayer stress-absorbing composite, and modified leveling binder.