Evaluation of the Relationship between Asphalt Binder Properties and Non-Load Related Cracking

A laboratory study was conducted to evaluate if there was any potential relationship between asphalt binder properties and non-load related cracking, as part of a research project involving airfield asphalt pavements. The objective of the research was to identify one or more parameters that could be easily determined by testing that would allow an airport manager to monitor the loss of durability experienced with aging and to use the information to evaluate when the airfield asphalt pavement would need preventative maintenance to minimize the effects of non-load associated cracking. Three asphalt binders were selected representing different expected aging characteristics, in the laboratory study. Testing was conducted on asphalt binders in their unaged condition, as well as on asphalt binders that had undergone long-term aging in the Pressure Aging Vessel (PAV) at 100C and 2.1 MPa pressure for 20, 40, and 80 hours. The purpose of the longer PAV aging times was not to correlate with any expected service life, but simply to create a more highly-aged sample. Past research suggested some relationship between ductility (conducted at an intermediate temperature) and the durability of an asphalt pavement. Using ductility as the hypothesized property related to flexibility, two parameters were identified that related well to ductility and the expected loss of flexibility with aging. The first is a parameter suggested by other researchers—G′/(η′/G′)—as determined using the Dynamic Shear Rheometer (DSR). The second is a parameter that quantifies the difference in continuous grade temperature for stiffness and relaxation properties—referred to in the paper as ΔTc. In both cases, the parameters appear to quantify the loss of relaxation properties as an asphalt binder ages. Limited field testing from three general aviation airports generally confirmed the findings from the lab study, with the newer pavements having values of G′/(η′/G′) and ΔTc that displayed more flexibility and less aging than the older pavements. Based on the study results, values were determined for both parameters that could provide an indication of a loss of durability that could result in a greater risk of non-load associated cracking.