Class 1A is a well graded granular material that is typically used as general fill.
The grading requirements are detailed in Series 600 of the Specification for Highway Works.
It can be produced using both quarried & recycled materials.
The materials that can be used are described as ‘Any material, or combination of materials, other than material designated as Class 3 in the Contract. Recycled Aggregates’
If the material is to be used within the construction of a highway then it must meet the specifications detailed in the Series 600 Earthworks of the Specification for Highway Works.
Table 6/2: Grading Requirements for Acceptable Earthworks Materials Other than 6F4, 6F5 and 6S.
Sources