How Brunel Award winners Alexandra Mitchell and Nerissa Patel helped problem-solve the first UK pour of Exegy® ultra-low carbon concrete.
As engineers, learning how things work and how we can make them better is what drives us.
One of the most exciting things for us currently is that we could be shaping the technology of the future through our work on the use of ultra-low carbon concrete (ULCC) in the UK.
Reducing concrete’s CO2 emissions
In 2021 we were successful in gaining a place on Taylor Woodrow’s leadership programme.
Alex was part of a team that was challenged to research how we could reduce the carbon footprint of concrete - a huge piece in the industry’s net zero puzzle.
Concrete contributes towards approximately 8% of global CO2 emissions due to the carbon intensive production of cement.
Taylor Woodrow is part of the global VINCI Construction group, who had worked with Ecocem for over four years to develop a product called Ecocem Ultra.
The product forms part of VINCI Construction’s Exegy® ULCC range and contains 0% ordinary portland cement (OPC).
This reduces the carbon footprint by up to 70% when compared to traditional concrete!
New horizons for ULCC
The product was already in use on the pilot site of the Grand Paris Express and in the construction of the Athletes’ Village in Paris for summer 2024.
However, it hadn’t been used in the UK, and wasn’t yet covered by British standards.
This situation is one that we’ll often be faced with on our journey to net zero – we'll be trying to do things we haven’t done before!
It needs contractors, clients and the supply chain to work together to overcome obstacles and find new ways of working.
Together we can mitigate risk, learn more about the solutions, and then share this knowledge for others in the industry to benefit from lessons learnt.
Given the product’s success in Paris, we wanted to bring it to the UK. Our goal was to learn about it, overcome its challenges in the UK market, and produce a case study for others to learn from.
Our next step was to find the right opportunity for its use.
Finding the right project
At the time we were both project managers at Taylor Woodrow’s EcoPark South project.
This is the first phase in North London Waste Authority’s plans to create a £1.2 billion sustainable waste management hub and energy recovery facility at the existing Edmonton EcoPark.
The project scope included building the following:
- a new flagship resource recovery facility
- a public reuse and recycling centre
- a temporary bulky waste facility
- a new visitor, community, and education facility
After extensive research, development and mix testing of the ULCC, we identified an opportunity for an initial pour on the project.
An ambitious 150m3 pour was undertaken to form a 500mm-thick ground slab for the bulky waste facility.
Pouring this ULCC for the first time in the UK came with a number of challenges to test our problem-solving skills.
The right temperature
A minimum ambient temperature of 15°C was needed to place the ULCC. This would normally set back its use within the UK industry, except during a few summer months.
Unsurprisingly, our programme of works didn’t align with the British summertime – the concrete pours needed to be completed in November.
While it was a huge challenge, we knew that if we could make it work, it would open the doors to being able to use this ULCC in the UK market.
We carried out trial pours using hot water in the concrete mix, temporary encapsulation to retain heat from the warmed concrete, and thermocouples.
A permanent thermometer was placed inside the concrete to monitor the temperature during the curing process.
This combination of measures together worked successfully and enabled us to carry out our 150m3 concrete pour in November as programmed.
Using a concrete pump
ULCC had never previously been placed via a concrete pump, but the logistical constraints of our site, and the size of the concrete pour meant we needed to use one.
We worked with our concrete supplier to develop a pumpable mix design.
We knew that if successful, we’d be unlocking the use of ULCC for large-scale concrete pours and projects in the future.
Sharing knowledge is what we do as an industry – taking lessons learnt and guidance from similar projects.
The absence of similar projects added an extra challenge for us and meant that communications really were the key to success.
Weekly meetings with all stakeholders kept everyone informed on progress and gave us a platform to explain different scenarios and technical data to support our decision making.
The first pour delivered outstanding results.
Concrete performance, both in terms of workability and strength, far exceeded expectations.
Ninety-three percent of the design strength was achieved within 28 days from a mix that was designed to achieve full strength at 56 days.
This resounding success made it the first of several pours on the project and to date, a total of 350m3 of C40/50 compressive strength ULCC has been placed.
Through identifying this opportunity and securing the support of all stakeholders, we’ve been able to deliver a carbon saving of over 48 tonnes, which is something that we’re both immensely proud of.
This work has also provided an example to the industry on how we can reduce our impact on the environment.
We hope the work we’ve done, and our case study can be expanded on and replicated across other projects throughout the UK to help drive down carbon emissions throughout the industry.
Receiving recognition in the form of the Brunel Award is an honour and something that we’ll be talking about for a long time to come.
It’s provided a great platform for knowledge sharing and to meet civil engineers from across the world and learn about their brilliant research and achievements.
The Brunel Award
The Brunel Award is awarded by the ICE each year to recognise excellence in the decarbonisation of civil engineering and the infrastructure sector.
It’s open to teams, individuals or organisations delivering a low carbon solution within the built environment.
Nominations for the 2023 ICE Awards are now open.
The Brunel Award is one of several awards open for nomination each year, so if you know a person or project that is similarly deserving of recognition, please visit the ICE Awards webpage to find out more.