The most common form of sprayed seal is a single/single seal consisting of one layer of conventional bitumen binder covered with a single layer of aggregate. Design of single/single seals forms the basis of the procedures described in this Guide. Choices available to the designer include sizes and combinations of aggregate together with a range of binder options to improve performance through improved temperature susceptibility, enhanced resistance to the stresses from traffic or improved waterproofing of cracked or weak pavements.
There are no quantitative measures available to define the limits of performance of different sizes and types of sprayed seals, or where no sprayed seal can be expected to provide a reasonable level of service and a different type of surfacing is required. This section provides a summary of the selection of surfacing type for a range of traffic, pavement strength and climatic conditions. Additional guidance on selecting pavement surfacings is provided in the Guide to Pavement Technology Part 3: Pavement Surfacings (Austroads 2009a).
The choices involve different costs and risks in performance outcomes. Designers should apply life‑cycle cost analysis, where appropriate, to the selection of surfacing type and use their own experience and judgment in the selection and detailed design of the surfacing. Where that experience is insufficient, designers should seek specialist advice.