The current clause in the Specification for Highway Works requires waterproofing systems on concrete bridge decks to be overlaid with a 20 mm thick sand asphalt protection layer and binder and surface courses so that the total thickness of the three layers is 120 mm. However, the total thickness on some bridges has to be reduced and, in such cases, a number of premature failures have occurred. The objective was to develop a specification for surfacings on concrete bridges that will enhance the probability of achieving reasonable durability when they are less than the standard thickness. The research has included a literature search, a questionnaire and a laboratory test programme. The laboratory test programme identified some differences in their properties that have been used to identify the basis for the specification. A secondary test programme was undertaken specifically to look at tests for measuring the flexibility of asphalt materials. Based on the findings and other considerations, various additions and changes to the Design Manual for Roads and Bridges, Specification for Highway Works and Notes for Guidance on the Specification for Highway Works have been proposed. (Author/publisher)
Abstract