This paper describes the development and use of a direct tension test for measuring the strength and failure strain of asphalt binders. This test, which is used to determine the strain at failure (strain tolerance) of asphalt binders, was selected by the Strategic Highway Research Program (SHRP) as a specification test for asphalt binders. Test methods available prior to the development of this test were found inadequate for accurately measuring the strain tolerance of asphalt binders. Therefore, these methods were judged unsuitable for specification purposes. The dog bone geometry used in the direct tension test method described in this paper is widely used for other materials. Each specimen requires slightly more than three grams of asphalt binder. The specimen is gripped using plastic inserts cast as an integral part of the test specimen. The specimen is loaded through holes in the inserts using specially designed pins that automatically align the test specimen. Specimen elongation is measured using a noncontact laser-based extensometer which provides accurate and repeatable measurements. The method is easy to use and is designed to provide the strain-at-failure-data needed for specification purposes.

The aim of the studies presented in this report is the implementation of rational concepts and testing procedures for the design and manufacture of bituminous materials for applications in pavement construction. Practical test procedures are recommended for binder evaluation, mix design and performance assessment of bituminous materials. The three main topics addressed are binder testing, mix design and mechanical testing of mixtures. Each is examined through interlaboratory tests and there is a literary review of existing practices and methods for the production of polymer modified binders, mixture design and the mechanical properties of mixtures.