Evaluation of the effect of heat-adhesive emulsions for tack coats with shear test from the road research laboratory of Barcelona

Abstract

The use of conventional emulsions for tack coats can cause problems as they frequently stick to the tires of construction vehicles. Consequently the bond between the asphalt layers is inadequate. The importance of tack coats in the performance of the pavement means that bituminous emulsions are constantly being improved. Recently, new types of emulsions have been developed from very low penetration bitumen that contains no flux. They are known as “heat-adhesive” emulsions and they are resistant to construction vehicles. The purpose of this study is to analyze the effect of different heat-adhesive emulsions and to verify their performance in service, in comparison with the response of a conventional emulsion. For this reason a new shear test –the LCB test- has been developed in the Road Research Laboratory of the Technical University of Catalonia. This test is carried out at different temperatures, both on laboratory specimens and on cores extracted from recently constructed pavements, where the same emulsions and dosages have been used. The application of the LCB test has shown that the performance of the different heat-adhesive emulsions mainly depends on the characteristics of the base bitumen and the kind of modifier used. At low temperatures, heat-adhesive emulsions reach, in general terms, lower shear resistances than conventional emulsions; however, at intermediate temperatures there are heatadhesives emulsions with both higher and lower strengths than those of the conventional emulsions.