Concrete is the most widely used construction material in the world. While cement is the key ingredient, its manufacturing process remains a major contributor to climate change.


s a building material concrete cannot be matched, to the extent that it is the most widely used building material across the globe. Although its impact on the earth is severe, the issue is not strictly concrete itself, rather the key ingredient that goes into it, namely cement.

According to Chatham House in its 2018 report, Making Concrete Change, each year more than four billion tonnes of cement are produced, with the manufacturing process a major contributor to carbon dioxide emissions. In fact, each year cement accounts for around eight per cent of global CO2 emissions.

In the long run this is unsustainable and, what’s more, the regulatory and societal pressures are closing in. The Paris Agreement on Climate Change is forcing cement companies to address their environmental impact and consumers are increasingly asking difficult questions of companies who are perceived to be contributing to, or slow in addressing, the impact of their product or services on the climate crisis. Michael Roddy, managing director at CCP (a Sigmaroc plc company) says: “And yet, concrete continues to be a building staple, used across the built environment from major infrastructure projects to housebuilding. The cement industry has responded to these conflicting pressures with a range of initiatives – from carbon capture through to the replacement


of fossil fuels used in the manufacturing process – in order to reduce its carbon footprint. Similarly, the construction industry has responded by using new materials and embracing new non-concrete designs.” Roddy points out that the mountain left to climb remains steep. Take housebuilding for example. Traditional concrete blocks made with ordinary Portland cement (OPC) account for over 2.7 tonnes of CO2 for an average three-bed semi-detached house.

Workable solutions

“There is clearly a need for action but finding a solution that works as well as concrete is a big task, because any substitute will need to have excellent loadbearing properties and be capable of being used in a wide variety of applications.,” he says.

One solution is to use what are being termed ‘novel’ cements that use new ingredients, but so far very few have become commercially viable. That, Roddy believes, is about to change with a new product called Greenbloc, a cement-free ultra-low carbon dense concrete block that is being manufactured by CCP. Greenbloc uses Cemfree, a low carbon alternative to traditional cement that is made from industrial by-products. It has the same loadbearing capacities as traditional OPC concrete blocks and, most importantly, it complies with HSE guidelines

and is manufactured to BS EN 771 – 3: (2011). In use, it can be stored and placed in the same way as an OPC block and it complies with Part E of the Building Regulations for Walls and Floors, making it suitable for a wide range of applications, including foundations, load bearing walls, internal leaves of cavity walls and partition walls.

Using the example of the same three- bedroom detached house, the cement-free binder, Cemfree, used to manufacture Greenbloc results in 73% lower embodied carbon: a saving of 2.7 tonnes of CO2 per dwelling. In fact, figures from the National Energy Foundation suggest that switching to Greenbloc for a housebuilding project can offset electricity emissions on an average three- bedroom house for almost four years. Roddy says: “That is the sort of CO2 performance that concrete manufacturers and concrete users in the construction industry are under pressure to deliver. There is no doubt that, as a building material, cement cannot be matched, however it remains the source of too much CO2 to be viable as a long-term solution. “Products like Greenbloc will not replace OPC overnight, but they do offer a clear route forward for the construction industry as it moves towards a more sustainable future, decreasing the carbon footprint of one of its core building products and the projects it is used in.” BMJ April 2021

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