Low-carbon concrete can sustainably protect our coastlines
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Published
28 March 2022
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A newly designed low-carbon concrete mix from the University of East London (UEL) can reduce CO₂ emissions by 40 per cent compared to traditional concrete.
The low-carbon concrete designs replaces cement with recycled materials including granulated slag from steelworks and pulverised ash from coal power plants – residue which can be scraped from the bottom of furnaces.
The designs show that it is possible to use up to 60 per cent steel furnace waste in the mixes without the concrete losing its compressive strength.
The research was conducted by Dr Ali Abbas, associate professor from UEL, in collaboration with Arup, a world-leading firm in providing sustainable engineering solutions. It is published in a paper titled 'Reducing embodied carbon dioxide of structural concrete with lightweight aggregate,' in the Proceedings of the Institution of Civil Engineers – Engineering Sustainability.
Dr Ravindra Jayaratne, reader in coastal engineering from UEL who has conducted post tsunami field work across the world, proposes that this low-carbon concrete can be manufactured to build cheaper, more sustainable and equally durable coastal defences.
Concrete is the most common material for making breakwaters – a collection of hard materials which stretch out to sea to protect coasts from incoming waves.
Cement, the main binder in a concrete mix, is primarily made of clinker – a residue produced by firing limestone and clay in a furnace heated to 1,450°C.
Producing that much heat is typically done by burning fossil fuels, emitting greenhouse gases in the process, which rise into the atmosphere and heats our planet, melting ice caps which increase ocean surface levels. Current construction involving cement is responsible for about 7 per cent of annual CO₂ emissions.
"The concrete seawalls and breakwater which are designed to protect our coasts and people from the consequences of global heating are indirectly contributing to it," said Dr Jayaratne.
"By using recycled materials we can cut construction reliance on concrete and defend our coasts in a more sustainable way," he continued.
Concrete contributes to climate change
The new low-carbon concrete designed by Dr Abbas and the proposed model to use it to manufacture coastal defences, led by Dr Jayaratne, helps reduce concrete’s carbon footprint and build equally as strong defences.
Steel fibres akin to hairpins are also added to the mix, eliminating the need to assemble vast steel mesh grids. The process requires less materials and therefore less heat, which produces less CO₂ emissions.
"Without concrete, many of the world's most impressive buildings and structures – such as Australia’s Sydney Opera House and the Hoover Dam in Las Vegas – wouldn't exist", said Dr Abbas.
"However, the impact it has on our planet is telling and the construction industry must find a way to reduce concrete's carbon footprint while keeping the benefits of a cheap and durable building material," he continued.
The low-carbon concrete mix, produced a 40 per cent smaller carbon footprint compared to traditional concrete. The costs and emissions of construction are lower as a result, and the final product is just as strong as a traditional breakwater.
"Using less to build more may worry coastal communities which live in fear of tsunamis, as sustainable breakwaters are likely to be thinner, smaller and curved instead of straight," said Dr Jayaratne.
"However just because something is bigger, it does not always mean it is stronger. We have a responsibility to ensure that our defences against climate change are not indirectly causing it.
"Our low-carbon structures are just as strong and show that the world can adapt to the effects of climate change without making it worse," he concluded.
Read the full paper, 'Reducing embodied carbon dioxide of structural concrete with lightweight aggregate,' published in the Proceedings of the Institution of Civil Engineers – Engineering Sustainability.
Read Dr Jayaratne’s paper proposing to manufacture breakwaters with the low-carbon concrete in, 'Stability of Breakwater Armor Units against Tsunami Attacks,' published Journal of Waterway, Port, Coastal, and Ocean Engineering (available here).
