Development of a viscosity specification for hot-poured bituminous sealants

Current crack sealant specifications focus on using simple empirical tests such as penetration, resilience, flow, and bonding to cement concrete briquettes (ASTM D 6690) [1] to measure the ability of the material to resist cohesive and adhesive failures. There is, however, no indication of the pertinence of these standard tests to predict the success of field installation and sealant performance. In an effort to bridge the gap between sealant fundamental properties and field performance, performance-based guidelines for the selection of hot-poured crack sealants are currently being developed. This paper proposes a new viscosity test procedure to help assess the propensity of sealants to wet the crack surface during installation. The proposed procedure calls for the use of a Brookfield rotational viscometer equipped with a modified spindle rod and an SC4-27 spindle at a speed of 60 r/min. Sealants are heated 20 min at the recommended installation temperature and the viscosity is measured after 30 s of spindle rotation in the hot sealant. These experimental conditions provide viscosities representative of sealant viscosity at shear rates during field application. The repeatability for within laboratory and between laboratories was found to be 5.4 and 17%, respectively. This repeatability is comparable with the corresponding variability of the SuperPave viscosity test for asphalt binders.