Semi-bound surfaces

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Semi-bound surfaces are generally spread and levelled using an asphalt mini paving machine. However, where access may be more difficult for larger plant, a drag box could be used instead. A drag box will lay the material reasonably well.

Where hand laying is necessary, take care not to over rake the material as the coarser and finer materials will separate, with the larger material coming to the top.

For best results, lay materials whilst damp and then compact using a heavy vibrating roller (120 type roller is recommended) to ensure adequate compaction. This material does not harden quickly after delivery, allowing time to get the material into difficult work sites (it can be stockpiled for a few days on site before laying).

The recommended laying depth for semi-bound surfaces range from 50mm to 100mm.

Always specify the tolerance of surface eveness for semi-bound surfaces - less than 5mm gap under a 3m straight edge placed along the path surface provides a smooth and even surface which will prevent puddles forming, and pleasant surface for all path users to enjoy safely.

Materials

Semi-bound surface materials available in Scotland tend to be composites from one or more recycled or secondary aggregates such as screened road planings, blaes, crushed concrete.

In central Scotland, Toptrec is available to purchase as a 100% recycled material made of well graded aggregate products including shale waste and screened road planings. This material is generally graded as 20mm to dust and has reasonably good binding properties from the road planing content. It is proprietary product produced by Tarmac, and is best laid by surfacing contractor with experience and knowledge of how to lay it properly. The main limiting factor for using Toptrec is the cost of haulage from Tarmac’s quarry in West Lothian.

toptrec surface

To find out more about path construction using Toptrec have a look here.

Specification
icon Toptrec Path - Standard Detail Drawing & Specification Details

 

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