Approximately 275m tonnes of aggregates are used each year in the UK as raw construction materials. Of this, around 65m tonnes are already derived from recycled or secondary sources. At the moment, recycled and secondary aggregates have the potential to fulfil increased demand, which is estimated at an extra 20m tonnes by 2012. After that, most materials that can be recycled probably will be.
Currently 70% of recycled and secondary aggregates are used as fills, with 18% as sub-base, 7% as concrete and 5% as asphalt. However, Watson believes that there is the potential to change this dramatically so that fills become 33% and use of concrete, asphalt and sub-base treble.
According to Watson, the benefits of using sustainable aggregates are significant, particularly in road building where local authorities can see cost savings. With the National Procurement Strategy for Local Government requiring every council to build sustainability into its procurement strategy, processes and contracts by the end of this year, recycled roads can go a long way to meeting this. Benefits to the community also mean reduced disruption as in-situ recycling can cut time-scales by 50% and reduce lorry movements, he says.
Performance is, of course, paramount and Watson cited the Channel Tunnel Rail Link as a high-profile example of the use of recycled and secondary aggregates. Morgan Vinci was appointed by Union Railways North to construct nearly 13km of the Channel Tunnel Rail Link (CTRL) between the London Tunnel at Dagenham and the Thames Tunnel at Thurrock. The £178m contract involved the provision of all civil works for the line, including three major viaducts, 11 bridges, three major highway divisions, utility equipment diversions and about 10km of piled slab to support the line.
The use of recycled aggregates, in preference to primary aggregates for construction of the piling platform, was explored with a view to reducing costs and maximising environmental benefits. The most appropriate material identified was reject lightweight concrete building blocks Durox which were locally available.
Total potential savings when using recycled blocks compared with using 100% primary aggregate is calculated to be £1,417,904. Transportation costs were less that those predicted for primary aggregates and the material was not subject to the Landfill Tax at £2 per tonne and was granted a waste management licence exemption for use in this context. Avoidance of the Landfill Tax saved the Durox supplier £208,066.
Other indirect benefits included the reduced demand for conventional aggregates, less long-distance haulage and a reduction in landfill space being used.
Watson says that among the lessons taken away from the CTRL project was to ensure that the use of sustainable aggregates was economical, sustainable and technically feasible. It is important to plan for what can be used, he says, and local availability is crucial. Partnering arrangements are key to establishing what solutions can be arrived at.
Barriers to the use of sustainable aggregates are often peoples perceptions rather than specifications, he continued. The new EU Standards do not discriminate against the use of recycled and secondary aggregates, which is a huge boost. The focus is on fitness for purpose rather than on origin.
However, procurement policies may still present problems for green procurement. There are many examples of good practice, says Watson, but this is still an area where tender clau