Recycled aggregates can cut costs and your carbon footprint |
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Substituting virgin aggregate with recycled aggregate in SuDS installations helps preserve natural resources and can cut costs. However, contractors often go with the ‘safe’ route of virgin aggregates.
The relevant British Standard (BS EN 13242 (+A1:2013)) sets out the properties required for aggregates produced from natural, manufactured and recycled materials. Reputable suppliers will also provide recycled aggregate with a CE mark to show conformity.
However, different below-ground attenuation products may have different requirements for recycled aggregate. In broad terms, ADS StormTech requires a 20/40mm aggregate which is clean, crushed and angular, with less than 5% fines. The amount of fines is limited as the void space between the aggregate allows for additional storage and movement of the storm water. With StormTech, the aggregate has a dual purpose. First, it provides structural support, with the elliptical shape of the arches transferring the loads away from the chambers into the aggregate embedment, whilst the aggregate also provides additional storage volume, increasing the efficiency of the attenuation system in terms of water storage capability. The aggregate also contributes two additional integral water quality treatment stages to the StormTech system, adsorbsion and biodegradation. The first two stages are provided by the patented Isolator Row, sedimentation and filtration. |
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Isolator Row is StormTech’s integral water quality treatment system |
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With recycled aggregate, it’s also important to consider the ground water and whether there are any potentially aggressive substances present. Sulphites, for example, could react with recycled concrete aggregate (and some virgin aggregates) and degrade it over time. Specifications should also set out an average porosity for the aggregate. StormTech’s Technical Note 6.20 provides further information on the use of Recycled Aggregates. |
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Different types of below-ground attenuation systems require different proportions of aggregate. Crates deploy small amounts of aggregate around their perimeter, which can lead to flotation issues in high groundwater, due to lack of dead weight to resist the hydrostatic pressure under the tank. StormTech uses a greater proportion of aggregate. Generally speaking, attenuation products requiring a higher aggregate-to-product ratio tend to have a lower overall carbon footprint per m3 of storage than those requiring less aggregate-to-product. StormTech’s Technical Note 6:50 provides further information on the use of StormTech as a sealed tank system and provisions to manage against flotation. |
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It is important to note that recycled aggregate will not necessarily have lower embodied carbon than virgin aggregate, which tends to be supplied from quarries close to the point of installation. Recycled aggregate can come at a lower cost than its virgin counterpart, again depending largely on transportation distances.
For more information about the use of recycled aggregate, see our recent article in New Civil Engineer. |
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ADVANCED DRAINAGE SYSTEMS |
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StormTech is manufactured by ADS, America's largest manufacturer of thermoplastic corrugated drainage pipes and a specialist in water management systems. StormTech has a long and successful track record with over 50,000 system installations using in excess of 3 million units. |
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To book a CPD seminar or to contact ADS UK call 0203 442 0607 or click here |
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