A mechanistic test to evaluate effects of interface condition characteristics on hot-mix asphalt overlay reflective cracking performance

Reflective cracking is a distress mode that is of particular concern for pavements with thin hot-mix asphalt (HMA) overlay as a maintenance and/or rehabilitation method. Traditionally, efforts have been made to mitigate reflective cracking by increasing overlay thickness, using anti-reflective cracking interlayer systems and special treatments on existing pavements and cracks. A new way to improve HMA overlay reflective cracking resistance is to use highly polymer-modified asphalt emulsion (PMAE) interface. Tests currently available are not appropriate to evaluate the effects of interface conditions on reflective cracking. This paper presents the second phase of a study devoted to develop a mechanistic test to study effects of interface conditions on pavement cracking performance. A new approach to represent reflective cracking (a teflon spacer introduced in an existing pavement layer) instead of the traditional notch method was introduced to the composite specimen interface cracking test developed for top-down cracking. In this study, effects of two types of interface conditions, conventional tack coat and PMAE, on reflective cracking were evaluated. HMA fracture mechanics was employed to identify the reflective cracking mechanism when the teflon spacer was installed in the composite specimen. Test results clearly indicated that the proposed test method with the teflon spacer was able to simulate reflective cracking mechanism and evaluate effects of interface conditions on reflective cracking.