Smart materials offer a sustainable path to the cities of the future | New Civil Engineer
The world’s urban population has quadrupled since the 1950s. 4bn people live in cities today, but according to the United Nations this could jump to 7bn by 2050. To accommodate roughly 3bn more people, our civil infrastructure needs to grow and keep pace. Amid a climate crisis, the question is how can we do this in a sustainable way?
The biggest challenge to civil infrastructure is degradation. Building degradation is what makes regular building maintenance and upgrades necessary. It creates a vicious cycle – we need more material to maintain and upgrade buildings, but this in turn creates waste. If we are to combat climate change, our civil infrastructure projects of the future must take a leaf out of nature’s book. They need to be able to adapt to the changing environment around them without degradation, and that’s where smart material comes in.
One of the best-known examples of smart materials is self-healing materials. Over the past 15 years, self-healing concrete and asphalt have been developed, and many products have started to enter the market. These materials allow road pavements and concrete elements to repair themselves, albeit on a small scale, much like a tree growing its leaves back.
Whilst self-healing materials are at the forefront of the smart materials revolution, they are only part of the picture. Graphene and the development of other 2D compounds are the stuff of science fiction. These materials can be used to create composites that harvest and store kinetic energy or sunlight, and expel it when needed. This could, to give one example, be used in the construction of our roads – the material would capture sunlight or energy from passing traffic and use it to keep the road warm and free from ice.
Speaking of science fiction, nano-modified materials fit into that category too. We currently rely on extensive and regular inspection routines to check infrastructure is still safe. More work is being done to explore how we could use nano-engineered sensors, which if embedded into concrete, would create composites with their own nervous system. This would allow for the instant and real-time detection of critical events, and could be combined with other responsive systems that jump in to rectify the problem – working in the same way as a living organism.
Nano technology could also be used in building materials to remove CO2 from the air. The CO2 could then be used to promote consistent mineralisation, a useful process that creates compounds that, once stimulated (either by sunlight or temperature), can act as bioreactors. These bioreactors could potentially purify rainwater, cool or heat, or produce energy.
Looking even further into the future, it is possible we could see programmable matter and self-assembly systems. They could revolutionise construction as we know it, paving the way for structures and materials that build themselves, enabling the precise assembly of projects in locations with a shortage of construction skills.
The path towards sustainable civil infrastructure isn’t easy, but such developments could be transformative, both for society and the environment. We cannot stop the growth of our urban environments, but we can certainly build better and smarter.