Wst 02 – Recycled Aggregates

Apportioning foundations where not all floors are assessed - KBCN0643

Where a development does not include all the storeys of a building, not all of the aggregates used in the building foundations need to be included in the assessment.  Any apportioning must be justified and calculated by a structural engineer, and it is the responsibility of the assessor to ensure that the process used is appropriate, robust and meets the aim of the credit issue.

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Considering Sand and Cement Replacements - KBCN0181

Neither sand or cement replacements should be taken into account when assessing the percentage of recycled or secondary aggregate used in a project. The recycled aggregates issue only assesses the use of coarse aggregates.  

29/03/2017 Title amended and additional reference to cement substitutes added

 

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Excluding applications from assessment - KBCN0875

Where a structural engineer has determined that recycled or secondary aggregate cannot be used in line with the criteria for a particular application, or where they will not allow the minimum BREEAM level to be used, that application can be excluded from the assessment. Where the engineer allows some content to be used, this percentage must still be specified in the excluded application. The engineer's decision must be suitably justified (for example following the BS8500 series and associated standards) and must be provided as evidence for the BREEAM assessment.

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Existing materials recycled on site - KBCN0813

When existing elements are recycled (ie crushed and used as aggregate) on site, they can contribute to awarding credits as recycled aggregates. This issue aims to recognise and encourage the use of recycled and secondary aggregates and addresses waste rather than materials. It refers to recycled aggregate obtained on-site or off-site, based on materials identified as waste and removed during construction works. 

Previous incorrect KBCN text amended. CN 'Aggregates in existing applications' to be amended accordingly in next reissue of the RFO Technical manuals.

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Granular fill and capping - KBCN1378

Granular fill and capping only refers to roadworks and not building foundations.

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Recycled aggregate evidence prior to contractor’s appointment - KBCN0231

If the contractor has not been appointed at the time of submitting the Design Stage assessment, whilst it is imperative for the design team to demonstrate a firm commitment to meet the criteria and award the credit at this stage, a letter from the design team or developer to confirm that no contractor has been appointed should be submitted in lieu of the stated letter of confirmation. This should also be clarified in the Assessment Report. BREEAM recognises that it may not be desirable to confirm the specification, source and availability of a particular recycled aggregate for a project where the contractor has not been appointed yet. This would restrict the contractor's ability to source the most economically viable recycled aggregate to meet the BREEAM criteria.

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Recycled aggregates requirements - KBCN0343

The amount of recycled and/or secondary aggregate must be greater than 25% of the total amount of high-grade aggregate specified for the development. In order for the recycled/ secondary aggregate in each high-grade application to be included in the calculation of the 25% amount, the minimum percentages in the relevant table must first be met. Note: not all high-grade applications must meet the percentages in the table in order to award a credit, however all high-grade aggregate must be included in the total.   The following example is taking figures from UK NC 2014. The applications and percentages vary with each scheme version. If only Structural Frame, Building foundations and Granular fill/capping are present. The following calculation would be carried out to confirm compliance:

Structural Frame = 50 tonnes of aggregate; of which 5 tonnes is recycled/ secondary aggregate

Building foundations = 50 tonnes of aggregate; of which 8 tonnes is recycled/ secondary aggregate

Granular fill/capping = 80 tonnes of aggregate; of which 80 tonnes is recycled/ secondary aggregate

  Table 54 minimum percentages are:

Structural Frame must have 15% recycled/ secondary aggregate for 1 credit, i.e. at least 15% of 50 = 7.5 tonnes. In our example we have 5 tonnes, therefore this amount cannot be included in the total calculation, and all 50 tonnes must be considered as primary aggregate.

Building foundations must have 20% recycled/ secondary aggregate for 1 credit, i.e. at least 10 tonnes. We have 8 tonnes, so again, this must all be considered as primary aggregate.

Granular fill/capping must have 100% recycled/ secondary aggregate for 1 credit. In our example all 80 tonnes is, therefore this amount can be considered as recycled/ secondary aggregate.

  To determine if a credit can be awarded, the following calculation is then carried out:

Total aggregate; 50 + 50 + 80 = 180 tonnes Aggregate to be included in calculating % = 80 tonnes (Granular fill/capping only) % therefore is 80/180 = 44% which exceeds the 25% minimum

This shows that despite two high-grade applications not meeting the minimum threshold percentages, the overall % is sufficient to award the credit. The same principle applies to the calculation of the Exemplary level criteria.

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