Material selection and traffic opening guidance for chip or scrub seals

Chip and scrub seal material selection is a long-standing challenge to favourable pavement performance and, historically, is based on empirical methods. This paper’s primary objective is to provide guidance for a seal treatment system (i.e. emulsion and aggregates) at high and low temperatures in the context of rejuvenation and aggregate retention. In contrast, commonly used methodologies are less comprehensive, focusing, for example, on only one performance aspect (e.g. aggregate retention) or one material (e.g. emulsion). Temperature is a major consideration of this paper since commonly used specifications call for test temperatures opposite of what may be optimal (e.g. viscosity testing at 135°C is commonly used to characterise rejuvenation, though rejuvenation seeks to address distresses typically associated with lower temperatures, such as cracking). Recommendations, which better align test temperatures, are to use bending beam rheometer mixture beam testing to evaluate rejuvenation and sweep testing to evaluate aggregate retention and traffic opening.