Creating A Future With Concrete
It is hard to fully comprehend just how much concrete is used worldwide. Its strength and durability have led it to become the most widely used material in the world, with global production hitting 4.1 billion tonnes in 2015.
With such vast quantities being used around the globe, it is hardly surprising that concrete has a sizeable carbon footprint. Estimates of its contribution to man-made greenhouse gas emissions range from around five per cent to nine per cent – well over double the two per cent released by the global aviation industry – with most of these emissions coming from cement, a key component used as a binder in conventional concrete and made largely from limestone which uses huge amounts of energy to heat.
While concrete is often overlooked in discussions of emissions cuts, demand is unlikely to be quelled in the short or mid-term. China in particular is now consuming concrete in vast quantities using more cement between 2011 and 2013 than the US used in the entire 20th Century. As a result, the country emitted 1.5 Gt of CO2 from concrete production in 2012, 84 per cent more than any other country or region.
As demand for infrastructure from the world’s quickly urbanising population continues to grow, the expansion of concrete use is unlikely to be curbed, making it critical for businesses and policymakers to address how emissions from its production and deployment can be reduced. While there are many options which could be used to reduce emissions ranging from the development of cement-free concretes to the recycling of existing concrete or use of carbon capture and storage, research has shown big emissions cuts could also be made without the need for new technologies, changes in production, or novel material use.
In a paper published in July in the journal Environmental Research Letters, researchers estimated annual CO2 emissions from concrete could be cut by 24 per cent simply by implementing currently used strategies more widely. The research looked at the impact on concrete emissions of expanding several currently used methods more widely, including lowering the proportion of clinker – the limestone-based material in cement responsible for much of its emissions – while increasing the amount of common lower carbon components. Meanwhile, the amount of carbon-intensive binder needed in the first place could be reduced if the construction industry allows more time for concrete to reach optimum strength.
“If a higher age can be specified, more strength development will be allowed to occur and typically less binder would be required,” Sabbie Miller, assistant professor at the University of California, Davis and lead author of the paper, told BusinessGreen.
With the main barriers to implementing these sorts of methods education, local norms and cost rather than technical constraints, there are clearly opportunities for regulations and incentives to help curb emissions from concrete. Meanwhile, many companies around the world are already taking action to replace concrete-related equipment to increase efficiency or using alternative fuels to reduce emissions.
But such measures are always only going to trim emissions from concrete when full decarbonisation will eventually be needed. Consequently, there are a number of more technically ambitious developments happening in the world of concrete designed to slash emissions from the sector.
One example is Cemfree, a low-carbon alternative to cement made from a by-product of the blast furnaces used in the iron industry. In January, water supplier Anglian Water announced an initial trial using Cemfree instead of cement as a base for one its kiosks had resulted in a 60 per cent reduction in the concrete’s embodied carbon compared to the firm’s 2010 baseline level. As well as offering these significant emission cuts, Cemfree has a lower water footprint than conventional Portland cement, while also being more resistant to chemicals, meaning it could prove more durable if used in waste water or water recycling plants exposed to hydrogen sulphide gas.
However, while Anglian Water has already used Cemfree in a second kiosk, the material’s novelty in some ways works against it. For obvious reasons, explains Fionn Boyle, innovation project manager for Anglian Water, it can only be used in low risk applications at first, and the British standards for concrete are currently based around conventional cement. “For doing things that are structural, so for any of our water retaining structures or any of our sewer pipes that are made out of concrete or anything like that, it would have to meet a certain standard, and the testing just hasn’t been done yet to do that with CemFree [or] for other low carbon concretes that are out there,” Boyle tells BusinessGreen.
Original article from Business Green, September 8, 2016