Series 600 Specification for Highway Works cl601 paragraph 13 for permitted constituents of recycled aggregates.
The “other” materials referred to as Class X in that paragraph are defined in series 800 Table 8/3.
Don’t get me wrong. That is an appalling job and it shouldn’t, in my opinion, be left like that without an appropriate topping. Unfortunately, the material used quite probably meets the requirements.
Actually, reading that clause again 6f5 can contain up to 50% bituminous materials unless it is “recycled aggregates except recycled asphalt” in which case it is the 1% as stated earlier but with only 5% glass.