Asphalt Mixture Specification and Testing

This guide reviews the way asphalt mixture can be specified, with particular emphasis on the test methods used to measure performance. The advantages and limitations of the tests are described for measuring the desired property, and engineers can specify a test according to the material’s use.

The book starts with a resume of specifications and their relative advantages and disadvantages for different situations. Then different properties are discussed in terms of: their specification; the test methods that can be used (primarily the EN 12697 suite of European methods, of which the author has been responsible for drafting); the extent to which the results predict performance; the levels that can be achieved with different asphalt mixes and types; what levels, if any, should be specified in various situations and pavement layers; and which other properties are adversely affected by enhanced performance. The final section covers various aspects of sustainability, with a strong emphasis on durability.

Better understanding should enable clients and consultants who specify pavements to produce durable asphalt pavements more economically, and also help asphalt producers and students trying to understand the black art of asphalt.

Cliff Nicholls‘s experience in civil engineering stretches over 40 years, with over 25 years specialising in highway materials. He is, or has been, a Fellow or Member of five professional institutions and a liveryman of the Worshipful Company of Paviors, and is recently retired as a Principal Research Scientist and Senior Academy Fellow at the UK’s Transport Research Laboratory responsible for research into road pavement materials used for road and airfield pavements.

He assisted the Department of Transport and Highways Agency when it was considering the introduction of thin surfacing systems into the UK and subsequently led the research monitoring their long-term durability for the Highways Agency as well as the potential to incorporate recycled material into these mixtures. He also led the research to produce performance-based tests of high-friction surfacing systems that allowed their specification through a certification scheme. His work has also included the assessment of porous asphalt as a surfacing for trunk roads, updating the design advice for surface dressing, studying the use of recycled and secondary materials in asphalt, and standardising test methods for use on asphalt materials.

He is a member of several European and national standardisation committees including Specialist Groups of the Highway Authorities Products Approval Scheme for the certification of thin surfacing systems, high-friction surfacing systems and polymermodified binders. Until recently he was also the convenor of the Comité Européen de Normalisation task group responsible for test methods for asphalt mixtures.

He has been the author of, or a major contributor to, a number of reports including the last three editions of TRL Road Note 39, Design Guide for road surface dressing, a best practice guide on the durability of asphalt pavements and a report on the service lives of thin surfaces. He edited the book “Asphalt Surfacings”, also published by CRC Press.