Prime coat methods and materials to replace cutback asphalt

Abstract

A prime coat is the application of a suitable bituminous binder applied to a non-bituminous granular base as a preliminary treatment before the application of a bituminous surfacing. The purpose of this research is to establish practical applications of successful prime coats to replace cutback asphalt. An investigation was conducted in order to (1) examine the importance of the bond between the base and various types of surface courses, (2) explore materials and construction techniques to improve prime coat performance, (3) evaluate alternative prime materials in the laboratory, and (4) develop specialized test procedures for prime coats. Laboratory tests were developed to (1) measure the penetration of prime materials in a granular base, (2) measure the shear strength of the different alternatives and evaluate the importance of the prime coat in strengthening the interface between the asphalt layer and the granular base layer, and (3) evaluate the benefits of specific construction methods in providing additional stability to the pavement system. Field evaluations of the different alternatives were performed. End-to-end test pavements were constructed using different prime coat products and construction techniques. Construction and early performance of the different alternatives were monitored.