Evaluation of Stripping in Virginia’s Pavements

Virginia has struggled with stripping of asphalt mixes since the 1970s. Initially, chemical antistripping additives were used; eventually, hydrated lime was required, under certain conditions, when it proved to be effective in a limited set of field tests. The specifications were then changed to require hydrated lime or a chemical additive that could produce a tensile strength ratio (TSR) equivalent to that obtained with hydrated lime. Because of this change, it was believed that chemical additive manufacturers made improvements to produce a new generation of additives that were superior to those previously available. In 1991, a small field study was initiated in Virginia to determine the performance of the new-generation additives and hydrated lime. The pavements still showed significant stripping. A follow-up survey including 74 sites scattered throughout the state verified this finding. No significant difference in the amount of stripping was detected between the mix types or between mixes that used chemical additives and those that used hydrated lime. In the initial study, the TSR test did not indicate accurately the stripping performance of the mixes. Because of this work, the Virginia Department of Transportation is considering changing its density specification and additional research is being conducted.