"Recycled and secondary aggregates have a key role to play in making the construction industry more sustainable and it’s therefore important the industry is able to have full confidence in using these materials"
John Barritt, technical advisor for aggregates at WRAP
Banbury, Oxon, England: New research shows the leaching performance of concrete containing recycled and secondary aggregates to be similar to concrete made using aggregates from primary sources.
The concern is that the leaching of pollutants from this type of concrete could lead to groundwater pollution and threaten drinking water.
The new study, published by WRAP (Waste & Resources Action Programme), is said to provide guidance and reassurance in an area where little information has been available to date and the organisation says that this “enables UK contractors and specifiers to further embrace the use of sustainable aggregates in concrete”.
The research study
The study looked at a variety of secondary and recycled aggregates - including recycled asphalt planings, foundry sand, incinerator bottom ash, crushed concrete and crushed brick – in concrete. Following leaching tests on the various concrete types, the results were analysed to identify the potential for leaching, as this could affect controlled waters.
Waste concrete showing contained aggregate, prior to crushing
The study found that the best method of leach testing the material was in accordance with BS EN 1744-3:2002. This advocates a rapidly stirred tank test on crushed aggregate and is based on the assumption that equilibrium or near-equilibrium is achieved between the liquid and solid phases during the test period.
The nearer to equilibrium a testing system can get, the more likely it is to represent the real or field case and the elements leached from the concrete could be judged to be representative of the longer term situation.
John Barritt, technical advisor for aggregates at WRAP, explained:
“Recycled and secondary aggregates have a key role to play in making the construction industry more sustainable and it’s therefore important the industry is able to have full confidence in using these materials.
“It’s also important the materials are shown not to have an adverse impact on either the properties of concrete or the environment in which they are used. We were pleased to note the study found the performance of both primary aggregate and aggregates that come from recycled and secondary sources to be very similar.
“We also identified a reliable testing method that can be used to determine the likely leaching performance of individual aggregates when used in concrete.”
Further information
To download the full report - Testing of Concrete to Determine the Effects on Groundwater – visit WRAP’s comprehensive AggRegain website – www.aggregain.co.uk.
For further information on WRAP, visit the website www.wrap.org.uk/construction or call the construction team on 0808 100 2040
WRAP works in partnership to encourage and enable businesses and consumers to be more efficient in their use of materials and recycle more things more often. This helps to minimise landfill, reduce carbon emissions and improve our environment.
Established as a not-for-profit company in 2000, WRAP is backed by Government funding from Defra and the devolved administrations in Scotland, Wales and Northern Ireland.