Low-Temperature Emulsion Performance-Graded Specification for Chip Seals

Abstract

Chip seals are applied to existing roadways to slow deterioration and improve pavement surface conditions without increasing the pavement’s structural capacity. Chip seals typically are comprised of asphalt emulsion and aggregate. Although it is well known that the properties of asphalt emulsion are critical to chip seal performance, the current specifications for these binders are empirical in nature and are not based on the properties that relate directly to chip seal performance. This study proposes emulsion performance-graded specifications that are designed to mitigate aggregate loss at low temperatures. To develop the proposed specifications, the research team executed an experimental plan to identify the residual binder properties that relate to chip seal aggregate loss at low temperatures. This research considered both fracture mechanics and rheology-based binder properties. Dynamic shear moduli, evaluated at critical phase angle values, demonstrated the strongest correlation to chip seal aggregate loss at low temperatures. Critical phase angle values were varied as a function of the low-temperature climatic emulsion performance grade of interest. This study also established preliminary specification limits for the dynamic shear modulus values based on critical chip seal performance thresholds.