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Hot rolled asphalt (HRA) mixtures (NGA2.1)
- HRA design mixtures give better resistance to deformation where queuing of heavy traffic is likely to occur, and may also be more economical to lay.
- Type C mixtures use fine aggregate of a coarser grading than Type F mixtures – usually associated with the use of crushed rock fines. Such mixtures tend to be stiffer and are less well suited to the reinstatement of small openings.
Surface course mixtures
- The advantage of using chipped HRA 30/10F 40/60 is that the mixture can be used in footways, footpaths, cycle tracks and the carriageway. The other HRA options are limited in application.
- Special care should be taken when using high stone content HRA (HRA 55/14 and HRA 50/10) to comply with texture depths.
- The use of HRA 30/10 F surf is especially convenient when the reinstatement extends into road types 3 or 4, as the same material can be used for the whole surface.
- Figure NGA2.1 shows examples of good/bad rate of chippings.