CharacteristicsThe main bitumen characteristics of interest are its viscosity and its ability to be handled safely.
Viscosity: the degree of fluidity of the bitumen at a standard test temperature. The viscosity of bitumen varies according to its temperature; therefore when comparing grades of bitumen, it is essential to carry out tests at standard temperature.
Safety: to ensure that bitumen may be used safely, it is critical that its flash point occurs at a much greater temperature than that at which road construction work is carried out. The flash point is the temperature at which the heated bitumen will release fumes that will ignite (flash) in the presence of a naked flame or a spark.
Test DevelopmentExperience in using bitumen in engineering projects has led to the adoption of certain test procedures that are indicative of the characteristics that identify adequate performance. However, there are two important points to be taken into account when considering these test procedures.
1. Strict adherance to the specified test procedures.
2. Different specifying authorities use different standard test procedures.
Some of the tests have evolved with the development of the industry and are empirical methods. Consequently it is essential that they are carried out in strict compliance with the recommended procedures if they are to be accurate measurements of the bitumen’s properties.
Modern technology is continually being employed by major bitumen manufacturers at their research centres and in industry sponsored university research projects to find new ways of measuring the physical properties of bitumen, and translating these into specifications relating to road performance.
Specifying AuthoritiesVarious organisations representing bitumen manufacturers and users have laid down standard test procedures. Major test methods specifiers are:
SA Standards Australia
Austroads The association of Australian and New Zealand road transport and traffic authorities
AusSpec Joint Venture between Standards Australia and the Institute of Public Works Engineering Australia (IPWEA)
ASTM American Society for Testing and Materials (USA)
AASHTO American Association of State Highway and Transportation Officials (USA)
DIN Deutsche Industrie Norm (Germany)
IP Institute of Petroleum (UK)
LCPC Laboratoire Central des Ponts et Chaussées (France)