Secondary and Recycled Aggregates

BRMCA Guidance for Use of Secondary and/or Recycled Aggregate within Concrete.

BRMCA Ready-Mixed Concrete Member Companies have the technical expertise to produce and supply concrete containing a range of secondary and/or recycled aggregate, and at a range of percentage replacement levels (i.e. replacing primary aggregate).

BRMCA advice to specifiers would be to engage with Ready-Mixed Concrete Companies to ensure the availability, best and most effective use of secondary and recycled aggregate prior to specification. The Area/Regional, or in some cases National Technical Manager/Director should be contacted in this regard.

In general terms, recycled aggregates should only be introduced as a replacement for the coarse aggregate element of fresh concrete and at percentages that do not adversely affect (i.e. increase) the overall cementitious content of the concrete.

Further information and exceptions can be found within BS8500-2.

Consideration should be given as to whether or not the introduction of secondary and/or recycled aggregate into concrete will in fact provide a more sustainable and environmentally sound project, as their introduction into other forms of construction material and applications may provide more viable options in both economic and 'eco-friendly' terms.

This is as a consequence of a number of factors given below, all of which generate additional CO2 emissions, which may counterbalance the perceived benefits of introducing recycled aggregate into concrete:

• Availability and subsequent transportation distance
• Increase in cement/combination content of concrete when secondary or recycled aggregate is introduced as a result of the inherent variation in material quality.
• Production, processing, screening, washing and grading of recycled materials to improve their consistency and quality to a level that they may be considered suitable for introduction into concrete.
  Note - Alternative uses may require significantly less processing.

Other technical considerations include:

• Recycled concrete aggregate may not be suitable for aggressive ground or severe freeze-thaw conditions (see BS 8500).
• Recycled concrete aggregate may increase the creep of concrete.
• Recycled aggregates (excluding recycled concrete aggregate) require the specifier to include source specific requirements with respect to ASR and sulfate limits (see BS 8500).