Highly variable by deposit

Excavation material occurs as a by-product of nearly all construction projects, generated through site preparation, landscaping, substructure and basement construction. It can comprise of rock, sand, gravel, clay and soil. The composition of the material depends on the underlying site geology and depth of excavation. Excavation material is considered waste only when it exceeds the amount that can be re-utilised onsite.

Excavation waste reflects parent geology and given the diverse geology across the UK, the waste material cannot be characterised by a single set of mineralogical characteristics.

Large scale construction and infrastructure projects provide the most straightforward logistics for re-use, since they offer significant volumes of material from a consistent source. This can be evidenced in the case of the Crossrail project in London, which between 2012-2015 resulted in 6 million tonnes of excavation waste removed from tunnelling operations in Central London, the majority of which was London Clay (Davis and Mellings, 2015).

Beyond extraction from a single source, having a limited geographic focus and careful material selection can also increase the chance of obtaining consistent raw materials. BC Materials, based in Brussels, produce rammed earth, plasters and unfired bricks all derived from excavation waste collected in the city region (circulareconomy.europa.eu, 2019).