Sustainability

Dr Murray Reid, Senior Technical Manager at the Centre for Sustainability (C4S), explains here that using recycled aggregates can add to the sustainability of your project and will generally cost less than primary aggregates.

There is no decrease in performance so long as the aggregates are produced under an appropriate quality control system. WRAP has produced guidance for SME contractors and their clients on the use of recycled aggregates in construction.

Sustainability is one of the current buzz words in construction and has been a feature of Government policy for over a decade. It is generally viewed in terms of three main areas: energy; water; and materials. In the building industry, effort has largely been focused on the first two aspects. However, sustainability can also be boosted by increasing the recycled content of projects, and recycled aggregates provide a simple and cost-effective way to achieve this.

Recycled aggregates are aggregates that have been produced by the processing of inorganic materials previously used in construction, such as construction, demolition and excavation waste. They consist of crushed concrete, brick, building stone, rock, gravel, sand and asphalt with the proportions depending on the materials being processed and the location. They are widely available in urban areas across the UK. Recycled aggregates account for 25 percent of all aggregates used in the UK according to the Quarry Products Association, more than double the quantity 15 years ago.

The sustainability benefits of using recycled aggregates include:

• Preservation of natural resources of rock, sand and gravel
  

• Reduction in transport distances and associated congestion, noise, dust and emissions from lorry movements
  
• Productive use of materials that might otherwise end up in landfill
  
• Reductions in CO2 emissions due to reduced transport distances.
  
  

However, recycled aggregates will only be sustainable if they deliver the same level of performance as primary aggregates. This can be ensured by checking that the recycled aggregates conform to the specification for the relevant application, and that they are produced by a supplier in accordance with an appropriate quality protocol.

(This, of course, applies to all aggregates, not just recycled and secondary ones).

The Waste & Resources Action Programme (WRAP) has produced a Quality Protocol for the production of recycled aggregates from inert waste, which is designed for the specific needs of recycled aggregates. There are versions of the protocol: for England and Wales, Scotland’ and Northern Ireland, and are available at the AggRegain website (www.aggregain.org.uk).

When purchasing recycled aggregates, you should always ensure that the producer is working to a Quality Plan that complies with the WRAP Quality Protocol. WRAP is producing checklists for producers and clients to ensure that the Quality Protocol is being applied properly, and these will be available from the AggRegain
website in the near future.

Recycled aggregates can be used in a variety of applications in building, particularly in the groundworks and infrastructure.

These include:

• Working platforms for piling and ground improvement
• Stone columns
• Earthworks and backfill to structures
• Pipe bedding, drainage, trench backfill
• Capping and sub-base for access roads and car parks
• Coarse aggregate in low strength concrete
• Asphalt can be recycled back into new asphalt in hot or cold mixes.

Many local authorities permit the use of recycled aggregates in their specifications for adopted highways, and some positively encourage their use as part of an overall commitment to sustainable construction. Recycled aggregates have been permitted for a range of applications in the Specification for Highway Works since 2001, subject to the producer using the WRAP Quality Protocol. In addition to the normal requirements for grading, particle strength and durability, this includes strict limits on the amount of foreign material – paper, wood, plasterboard, metal, clay, etc –that are peculiar to recycled aggregates.

In addition to the sustainability benefits, recycled aggregates will generally be cheaper than primary aggregates for the same specification. This is largely due to the reduced transport distances generally required for recycled aggregates; as this also relates directly to the CO2 emissions, price is therefore often a good proxy indication of sustainability; a win-win situation if ever there was one! So take a look at the documents, check you suppliers can deliver quality materials and look for opportunities to increase your sustainability with recycled aggregates.

WRAP has recently produced two short guidance documents, for contractors and clients/specifiers respectively, outlining the benefits of recycled aggregates and how to ensure that you receive quality materials. These can be downloaded from http://www.aggregain.org.uk/publications/index.html.

A number of case studies of the use of recycled aggregates on sites large and small are available in the relevant section of the AggRegain web site, www.aggregain.org.uk. An example is the widening of the M25 between Junctions 12 and 15 and the construction of a spur road to Heathrow Terminal 5, where over 90 percent of the unbound aggregates were recycled aggregates. There is also information on AggRegain about opportunities for their use and the relevant specification requirements.