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And where land is tight, cities have to expand skywards. The problem is, while high-rise towers of concrete and steel are feats of engineering, they’re bad for the environment.
Concrete is the second most consumed resource after water. The chemical and thermal combustion processes that go into producing four billion tonnes of cement annually is a major reason why concrete is responsible for 8% of total carbon dioxide emissions.
The current situation is unsustainable. Researchers, start-ups and construction companies have been collaborating and researching for a number years now on new, innovative, green materials.
Cement ousted
One such solution is cement-free concrete. Ordinary concrete – known as Portland concrete (OPC) – is a mixture of sand, water and aggregate and the methods of producing it haven’t changed that much since it was patented nearly two centuries ago. Cambridge-based construction materials specialist the DB Group has invented a powder-based, alkaline-activated binder that allows concrete to set.
According to a spokesperson for the DB Group, the binder has “the same structural characteristics of OPC” but “carbon dioxide emissions are up to 80% lower compared to the traditional way of producing concrete”. They add that the material can be produced using a by-product of the iron and steel industry – ground-granulated blast furnace slag – meaning the process is environmentally friendly.
The material has had an onsite trial at a Thames sewer system and a number of small-scale projects. Back in January, it was announced that the cement-free mixture had been successfully applied underneath a viaduct on the M25 as part of repair works.
US firm Solidia Technologies, meanwhile, has invented a similar sustainable cement (in terms of a reduction in carbon dioxide emissions) that can help concrete to cure in less than 24 hours. In comparison, the curing of OPC can take 28 days – and months for it to dry completely.
Solidia is taking the meaning of advanced materials a step further by integrating smart technologies and artificial intelligence into its production. By monitoring the curing process using data science, the start-up can build a picture of what’s going on inside the curing chamber and identify where and how production can be made more efficient.
“The standard curing process can be complex. Machine learning allows us to model, measure and predict and quantify our production,” says chief executive officer Tom Schuler. “Having eyes inside the chamber means we can optimise production, reduce waste and improve quality control.”
Slashing emissions
The case for advanced materials is clear: as populations rise and more buildings and infrastructure are needed, the construction industry needs to find ways to construct sustainably and quickly. It will also drive the cement industry towards achieving its target of reducing emissions by 23 to 24% by 2050, as set out by a 2018 report by the International Energy Agency and Cement Sustainability Initiative.
However, the construction sector has long been known for being traditional and has a reputation for being one of the least digitised sectors. Adoption of advanced materials will depend on a willingness to take risks, while a challenge for those producing the materials will be how to produce them at scale.
The issue of scaleability will be addressed as technology and innovation advances, However, the speed and efficiency by which concrete is produced and cures will need to be matched by efficient processes elsewhere. This includes the development of other advanced materials and the optimisation of processes and ways of working for mechanical engineers, such as the adoption of concrete-printing robots.
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Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.