From the ancient world to the present day, Kim Barton of IMS Consulting (Europe) explains why concrete is the most commonly used material in construction, and how it can be made more sustainable in future.
Cementing materials have been used widely, from as far back as the ancient world. The Romans were probably the first to master cement, which helps to explain why many of their buildings have survived for so long. In the first century BC, the Roman architect and engineer, Pollio, wrote the ‘Ten books of Architecture’ that discusses ‘pozzolanic’ cement made from volcanic ash and lime from the village of Pozzuoili near Vesuvius. The cement was used in breakwaters at Pozzuoili Bay that still stand today, despite being eroded by the sea for over 2000 years.
When the Roman Empire fell, concrete expertise was all but lost, not being rediscovered until two centuries later. Joseph Aspidin was granted the first patent for Portland cement and the process of roasting limestone and clay before grinding into a powder to make artificial stone. His son William refined the process, creating a material that is very similar to the cement still used today. The process requires limestone and clay to be heated at temperatures approaching 1000◦C, where they break down to provide the element of cement called ‘clinker’, which is then ground into a powder and gypsum added. Water and aggregate is then used to convert the cement mixture into concrete. Although cement and concrete are often used interchangeably, cement is actually only one of the ingredients of concrete, making up only 7-15 per cent by weight of concrete’s total mass.
Today, concrete is the single most widely used construction material; besides water it is thought to be the most commonly used material on earth. As populations increase, with city populations estimated to double by the middle of the century, it is anticipated that demand for cement can only grow. However, this growth presents a problem; cement production contributes five per cent of global annual carbon dioxide emissions. The reason that it has such a big carbon footprint is because of the sheer quantity used. In fact, concrete manufacturing uses very little energy compared to other materials, with recycled steel requiring up to ten times more energy. Despite its carbon footprint, concrete has some core sustainability attributes that are often overlooked.
As we can see from the Romans’ use of the material, concrete is incredibly durable – withstanding 2000 years of sea erosion can safely be described as sustainable. Concrete’s resilience can make sure that buildings are able to last for hundreds of years, with limited maintenance costs. Its durability means that fewer resources are required for construction over time. Minimal maintenance is also a great sustainability asset. Materials such as timber may require treatment over time for woodworm or termite, requiring the use of harmful chemicals. In addition, concrete does not melt or burn.
Concrete is a great insulator and can make sure that a building is energy efficient and maintains a stable temperature. Concrete will also absorb heat and release it over several hours, usually at night. Also, using concrete minimises the loss of energy from a building due to the minimal amount of joints or connections.
The resources necessary to make concrete are sand, aggregates and limestone; all naturally abundant. Producing concrete locally means that transport is limited and local communities benefit from the economic growth.
The cement industry is coming together, companies beginning to look at how they can work together to reduce emissions. At last year’s climate summit in Paris, the cement industry released its Low Carbon Technology Partnerships initiative (LCTPi). The LCTPi is led by the World Business Council for Sustainable Development and looks across nine sectors to develop unique, action-oriented programmes. These bring together companies and partners to accelerate the development of low-carbon technology solutions to stay below the agreed 2°C rise in average temperatures. The initiative has gathered over 150 global businesses with 70 partners to work collaboratively on the climate challenge. The programme for cement is looking at how it can reduce emissions through the identification of existing and new technologies, and promoting cross-industry collaboration.
The Cement LCTPi was led by the Cement Sustainability Initiative (CSI), a global effort by 24 major cement producers with operations in more than 100 countries who believe there is a strong business case for the pursuit of sustainable development. Collectively these companies account for around 30 per cent of the world’s cement production and range in size from very large multinationals to smaller local producers.
Concrete can also be beautiful. It has of course had its ugly moments and its association with ‘Brutalism’ could be misinterpreted as it being ‘brutal’. However, it’s actually raw and mouldable, creating buildings unlike any others. In a book called ‘The Brutal World’, released this year, Peter Chadwick brings together impressive concrete structures from around the world, demonstrating concrete’s versatility and beauty. Among the impressive buildings featured are the Centro de Exposições do Centro Administrativo, Bahia, Brazil, 1974 by João Filgueiras Lima and the TWA terminal at JFK Airport in New York.
Cement and concrete are undoubtedly fascinating materials that have shaped architecture and our built environment. The Roman structures that pioneered the material, and still stand today, may hold the key to reducing concrete’s carbon footprint and increasing its sustainability. Researchers analysed the Pozzuloli Bay breakwaters and believe they have uncovered its secrets. Analysis pinpointed why Roman concrete was superior to most modern concrete in durability, why its manufacture was less environmentally damaging and how these improvements could be adopted in the modern world. Ongoing research, collaboration, new technology and initiatives are all helping to reduce the carbon footprint of cement.
With its many sustainability attributes and our dependence on it, cement is undoubtedly helping to build our future. We need to recognise that there is no single solution to climate change, no perfect material or building. But, we do need to understand the whole life-cycle of materials, their benefits and their flaws.