Nov 15 2007
New research published by WRAP (Waste & Resources Action Programme) has shown the leaching performance of concrete containing recycled and secondary aggregates to be similar to concrete made using aggregates from primary sources.
The study provides guidance and reassurance in an area where little information has been available to date and enables UK contractors and specifiers to further embrace the use of sustainable aggregates in concrete.
Using a variety of secondary and recycled aggregates - including recycled asphalt planings, foundry sand, incinerator bottom ash, crushed concrete and crushed brick - the report analysed the potential for elements within the aggregates to be leached from concrete into controlled waters such as groundwater and drinking water.
The study also determined that the best method of evaluating the suitability of recycled and secondary aggregates for use in concrete (in relation to their release of undesirable substances) was testing the material in accordance with BS EN 1744-3:2002. This refers to a rapidly stirred tank test carried out on crushed aggregate material and is based on the assumption that equilibrium or near-equilibrium is achieved between the liquid and solid phases during the test period.
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.”
To download the full report - Testing of Concrete to Determine the Effects on Groundwater – visit WRAP’s comprehensive AggRegain website – www.aggregain.co.uk.