Low carbon concrete for the London Olympic Park, UK
The Olympic Delivery Authority (ODA) set a number of sustainability targets to be met for all construction activities, including:
- Construction materials (by value) comprise at least 20% recycled content;
- 25% of aggregate used will be recycled;
- 50% of materials (by weight) will be transported to site by sustainable means (e.g. rail);
- Energy-efficient, low emission vehicles will be used on-site.
For the Olympic park the ODA initially estimated that 500,000m 3 of ready-mixed concrete with an associated 1 million tonnes of aggregate would be required. The pre-qualification questionnaire and subsequent Invitation to Tender (ITT) for concrete supply used a balanced score-card approach to evaluate tenders. The tender questions were worded to encourage the supply chain to identify opportunities within the marketplace and to deliver innovative solutions to meet the ODA‘s sustainability targets listed above.
In total 20% of the weighting of the technical assessment in the tender evaluation was applied to meeting sustainability requirements. The concrete supplier proposed a number of mix designs that met the ODA sustainability requirements, in particular considering alternatives to cement and the use of secondary aggregate. The concrete supplier demonstrated a clear commitment to meeting and exceeding the ODA sustainability targets. The ODA determined that the best approach to meeting sustainability requirements was to establish a single ready-mix concrete batching plant on site to supply all the park concrete needs. This greatly reduced the number of deliveries to site and ensured continuity of supply for all contractors.
The ODA Sustainability team led numerous workshops for contractors at different project stages. An initial meeting was held with project teams and the concrete supplier technical team prior to the specification of ready-mix concrete and contract award. The aim of the workshop was to introduce project teams to the potential contribution sustainable concrete mix designs could make to project sustainability targets such as recycled aggregate content and total recycled content.
In total almost 22% (170,000 tonnes) of recycled and secondary aggregate were used in approximately 450,000m3 of ready-mix concrete poured during construction of the park. An average cement substitute of 32% and transportation of aggregates by rail contributed to a reduction of 24% in the embodied energy of the concrete (30,000 tonnes CO2e) and eliminated over 70,000 vehicle movements.
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