A graded aggregate from certified sources, typically crushed stone, crushed slag, crushed concrete or well-burnt non-plastic shale, but not sand and gravels, used as granular sub base. Its correct name is ‘DTp Type 1 granular sub base’ as defined by the Department of Transport Specification for Highway Works, Clause 803. In order for a material to be defined as Type 1 granular sub base quality it must comply with Clause 803.
Type 1 granular sub base is produced to create a material containing a range of stone particle sizes from 40mm to dust, which naturally interlock when compacted to provide excellent load bearing capacity/ qualities.
Type 1 is a must for high quality paths and is most commonly used granular sub base for building paths.
Type 1 can be produced from pure crushed concrete to make a recycled aggregate which can be used as a alternative to quarry Type 1, where sub base applications require certified material to be used. Like quarried Type 1, recycled Type 1 must be fully certified according to the DTP Specification of Highway Works Clause 803.
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