The Highways Agency, Quarry Products Association and Refined Bitumen Association all appreciate the need to maximise the durability of asphalt pavements and overlays. The jointly funded research project at TRL entitled Performance and Durability of Asphalt Roads included two topics, Durability of Asphalt Pavements and Overlaying Concrete, with the principal aim of identifying the techniques and procedures currently considered to be best practice and producing Best Practice Guides based on that knowledge in the form of Road Notes.
Road Note 42, Best Practice Guide for Durability of Asphalt Pavements, concentrates on the durability of the whole pavement rather than that of the asphalt mixtures. For this purpose, pavement durability is
defined as:
the retention over the structure’s expected service-life of a satisfactory level of performance without major maintenance for all properties that are required for the particular road situation in addition to asphalt durability.

The aspects that lead to durability for asphalt pavements are the same when overlaying jointed and continuously reinforced concrete pavements and concrete bridges with asphalt. However, further aspects must be considered when overlaying concrete and these are covered separately in this Road Note. It identifies the different techniques for overlaying concrete, assists in the choice of treatment for a specific situation and gives advice on how to maximise the durability of the treatment.

The aim of both Road Notes is to encourage everyone working in the asphalt industry to contribute to making pavements and overlays as durable as practical. To enable people to fulfil this aim, they need to know not only the actions they can take to enhance or damage durability, but also how their actions may impinge on the efforts of others. An understanding of the intentions and constraints during other phases should help to produce designs that are buildable, materials that have the potential to perform and a pavement that is fit for purpose.

The desire to achieve longer durability for asphalt pavements and overlays is common among those involved in designing, specifying, producing and laying asphalt materials. Therefore, all parties have to work together in a spirit where positive actions are rewarded and negative actions or omissions are discouraged.

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