EXEGY ®ULTRA ultra-low-carbon concrete slabs  for the Edmonton EcoPark waste management centre in London

In January 2021, Taylor Woodrow, a subsidiary of VINCI Construction, began work on the expansion of the facility called EcoPark South, which will provide a flagship Resource Recovery Facility with capacity to manage 135,000 tonnes of recyclable material every year. In addition to the Resource Recovery Facility, the site will provide the first ever public Reuse and Recycling Centre and EcoPark House will open up the site to the public, providing a knowledge-sharing hub for waste prevention and recycling.

In November 2021, Taylor Woodrow’s team poured 450^m3 of EXEGY®_ULTRA concrete  to make three concrete slabs measuring 30 x 10 m and 0.5 m thick for the temporary bulky waste recycling facility.

The ECOCEM ULTRA binder, which forms the basis of this concrete, is a clinker-free binder, composed of 95% alkali blast furnace slag activated by sodium carbonate. As British Standards (BS) do not currently cover concretes with such high percentages of blast furnace slag, Taylor Woodrow had to obtain a derogation from the BS and acceptance from the client and designer. Given the temporary nature of these slabs (18 to 24 months), it was possible to obtain this derogation for the first time in the United Kingdom.

Indeed, there is currently no test data in the United Kingdom to validate the qualities of this concrete such as durability, service life, adhesion strength to the reinforcement, oxidation. Tests were therefore carried out to implement this concrete on this site.

But the EXEGY®_ULTRA solution  has been proven in France. It was used for the first time in 2019 in the construction of six structural columns for VINCI’s headquarters, the archipelago located in Nanterre, and was then used for deep foundations and around thirty segments of line 18 of the Grand Paris Express, in partnership with the Société du Grand Paris.

This EXEGY® solution  was then deployed throughout 2022, with nearly 20,000 m3 on several large-scale projects such as the Athletes’ Village project in the heart of Universeine for  VINCI Immobilier and a set of two buildings with 71 housing units for I3F, built by Sicra Île-de-France in La Celle-Saint-Cloud (78).

The concrete mix was produced by the concrete distributor CEMEX, partner Exegy®. It is a C40/50 concrete for which it was possible to remove the formwork between 24 and 48 hours after the concrete was poured, thanks to a few adaptations made on site.

Indeed, the temperature of such concrete must be at least 15°C, and ideally above 20°C, whereas throughout the duration of the project, the ambient temperature varied between 6 and 10°C.

In order to meet the formwork release times and reach the desired temperatures, hot water was used at the concrete plant. In addition, a temporary “tent” was installed on the first slab, to insulate the concrete and allow the hydration process to begin, but this process was not necessary for the second slab. The tent could be replaced by one of the antifreeze blankets with sufficient insulation. Thermocouples were used to monitor the temperature of the concrete throughout the process.

In addition to ECOCEM ULTRA; An additional 13,000 m3 of low-carbon concrete was poured to build the piles, foundations, basements, floor slabs, walls and elevator shaft. It is a mixture of CEMIII/A and CEM III/B.