The absolute bible in the UK for material specification is The Specification for Highway Works. This document is being used extensivley to produce specification documents for many different types of project, which often have no relationship to a 'Highways' project.
The SHW is continually being reviewed, with a major revision due over the next 2 years, with the first ammendments due between Jan and Apr 2004. The big impact of this latest round of revisions, is the adoption of the 'New European' test standards, which will see the dropping of existing tests such as the 10% Fines Value and being replaced by the Los Angeles Coefficient test.
If you are going to use this document, please be aware of these changes and amendments, they WILL have an effect on the use of materials, which are acceptable and which are not.