What to do with the rubble

Destroyed buildings produce broken concrete, brick, steel, timber, glass and insulation, in quantities that are difficult to hold in the head. What happens to that material is one of the larger decisions in reconstruction and one of the least discussed.

The two paths

As waste: transported to a landfill, occupying land, costing money at both ends and displacing agricultural or urban space permanently.

As material: sorted, crushed, screened and used as sub-base for roads, fill for foundations and aggregate in new concrete. The same reconstruction that produced the rubble needs enormous quantities of exactly this.

Why sorting is the whole problem

Mixed rubble is waste; separated rubble is material. Concrete and brick can be crushed. Steel reinforcement is worth money as scrap and must be removed before crushing. Timber, plastic and insulation contaminate the product.

And war debris carries two hazards ordinary demolition does not: asbestos from older buildings, and unexploded ordnance. Both require the material to be checked before it goes near a crusher, and that check is what makes the whole chain safe or unsafe.

What regulation has to provide

A standard for recycled aggregate, so that a road engineer can specify it with confidence. Without that standard, recycled material has no legal place in a specification and nobody will use it whatever its quality.

A duty to sort at source, because separating on site is cheap and separating at a tip is not.

The economics

Crushing on or near the demolition site removes two long haulage legs — waste out and aggregate in. On a project of any size, that saving alone pays for the plant.

Rubble is a cost for as long as the regulation calls it waste and becomes a material the moment it calls it aggregate; the difference sits in a single document. On the asphalt side I have watched recycled material go into the mix cheaply and soundly for years — the obstacle is never the plant but whether the material can be certified. The cheapest source of aggregate for reconstruction is currently standing as ruins.