Selected granular fill is used in more specialised applications than general fill and has more specific requirements of fill performance. The principal use is for capping; other fills include for reinforced soil and anchored earth structures, and the fill surrounding corrugated steel buried structures.
Many types of recycled and secondary aggregates can be used; in capping. Design Manual for Roads and Bridges (DMRB) Vol. 7 Section 1 Part 2 HD35/04 shows that the only material specifically prohibited is unburnt colliery spoil.
Some RSAs that can be used in selected granular fill applications are listed below.
Blast furnace slag, phosphoric slag and Recycled asphalt are permitted but not generally used due to the relative high value of these materials. Recycled glass is unlikely to be used. Spent oil shale/ blaise, unburnt colliery spoil and steel slag cannot be used as selected granular fill.
Specifier gives detailed information for grades of selected granular fill, including Classes 6A to 6R. These are covered in the Specification for Highway Works (SHW) Series 600 'Earthworks'.
Capping is constructed from Class 6F1, 6F2, 6F3, 6F4, 6F5, and 6S, granular materials or Class 9A, 9B, 9C, 9D, 9E, or 9F stabilised materials.
Categories of selected granular fill include: