TRL was commissioned by the Scottish Road Research Board to investigate the modification of an asphalt mixture known as EME2. The material is used in the main structural part of a road and is required to be durable, water resistant, stiff and deformation resistant. The aim of the study is to determine whether EME2 mixtures require modification to optimise their performance for use on the Scottish road network. The study comprises two phases: Phase I - laboratory investigation; and Phase II – in service performance. This report relates to the first phase of the project. The laboratory research programme required the collaboration of several organisations, including input from the asphalt industry and other material specialists. It includes state of-the–art testing to determine fundamental material characteristics such as stiffness and fatigue properties, low temperature property testing and a microscopy study. The report describes the laboratory testing and results, and discusses the findings to assess the influence of the use of softer grade binders on two EME2 mixtures. The report also discusses the significance of new fatigue data collected as part of the study, and the potential implications of its use in current analytical pavement design.

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