Towards Low Carbon Concrete

Kelham Island Concrete at work © Jim Stephenson

The Vision for Low-Carbon Concrete

In our pursuit of more sustainable design practices, we have collaborated with Sheffield-based Kelham Island Concrete, Zero Waste Works, and the University of Sheffield to develop a new low-carbon concrete for interior applications.

Kelham Island Concrete, in partnership with Zero Waste Works, is on a mission to develop sustainable, affordable, and high-quality alternative cement and fibre concrete reinforcement solutions. Using recycled fibres from diverse waste streams as alternative binding solutions, aiming to decarbonise and minimise the environmental impact of their products.

Custom fireplace © Nicholas Worley

Challenges in Developing Low-Carbon Concrete

Creating low-carbon concrete presents several challenges. The primary obstacle is replacing traditional cement, known for its high carbon emissions. KIC is experimenting with various replacements, including fly ash, silica fume, and ground granulated blast furnace slag (GGBS). Integrating these materials requires rigorous testing to ensure the final product meets structural and durability standards.

Another challenge is incorporating recycled fibres. KIC is trialling various fibres, such as steel and polymer fibres, from tyre manufacturing to replace conventional glass fibre. This involves overcoming technical issues related to material compatibility, fibre dispersion, and overall concrete performance.

Benefits of Low-Carbon Concrete

Despite the challenges, the benefits are compelling. The most significant advantage is the reduced carbon footprint. GGBS, a key component in low-carbon concrete, has a CO2 footprint of just 29 kg/tonne compared to 700 kg/tonne for traditional cement. This reduction is achieved through the efficient use of industrial by-products and minimised energy requirements.

Low-carbon concrete also promotes sustainability by using recycled aggregates and reducing manufacturing waste. This conserves natural resources and addresses problematic waste streams, contributing to a circular economy.

Counter at Gail's Earlsfield © Nicholas Worley

What is Regen GGBS?

Regen GGBS (ground granulated blast furnace slag) is a replacement product for some of the normal Portland cement (PC) content in concrete, grout, and mortar. It significantly reduces the environmental impact of a project by cutting CO2 emissions associated with concrete while conserving natural resources. Regen GGBS can replace up to 95% of the PC content in special applications. It is usually supplied as a separate cement component for concrete and is added at the in-mixer stage.

The Sustainability Benefits of Regen GGBS

The production of standard CEM I Portland cement is energy-intensive and CO2-heavy. However, Regen GGBS needs less than one-third of the energy and produces less than 10% of the CO2 emissions compared to PC. This is because GGBS is a by-product of the iron-making industry. Its production involves cooling, drying, and grinding the slag, which uses significantly less energy. Using Regen GGBS in concrete mix reduces embodied CO2 by around 780 kg per tonne replaced, without requiring quarrying of new materials.

Each year, the UK uses over 2 million tonnes of Regen GGBS, which reduces CO2 emissions by almost 1.56 million tonnes, reduces primary energy use by 1.6 million MWh, and saves approximately 2.7 million tonnes of quarrying.

Acknowledging the Shift in Steel Production

While GGBS is a by-product of the steel industry, we recognise the shift from traditional blast furnaces powered by fossil fuels to less energy-intensive electric furnaces. This transition is expected to reduce the availability of GGBS over time, particularly in the UK. As the industry moves towards more sustainable practices, the reliance on GGBS must adapt accordingly, encouraging further innovation in low-carbon concrete solutions.

Applications of Low-Carbon Concrete

The versatility of low-carbon concrete makes it suitable for a wide range of interior applications, including:

Counter-tops
Panelling and cladding
Architectural details
Sinks

Pioneering Sustainable Construction

Kelham Island Concrete, committed to innovation and sustainability, leads in developing this zero-waste, low-carbon concrete. By addressing challenges and leveraging expertise in recycled materials, KIC is reducing the environmental impact of construction and setting new industry standards. The hope is for this product to offer an eco-friendly alternative to traditional materials, paving the way for greener, more responsible construction practices.

Written by Richard Holland with contributions by

Oliver Miller (Founder, Kelham Island Concrete)

Harris Angelakopoulos (Managing Director, Zero Waste Works)

Professor John L Provis (Visiting Professor of Cement Materials Science and Engineering at the University of Sheffield)