Putting cement under the microscope to help improve its performance

By understanding and changing how crystals form in cement, scientists are finding ways to reduce the impact of concrete on the environment.

Cement forms the basis of concrete – the single most widely used material in the world.  

“Manufacture of cement worldwide accounts for approximately eight per cent of all human-produced carbon dioxide,” explains Professor Ian Robinson (UCL Centre for Nanotechnology). 

Professor Robinson’s research aims to adjust the composition of cement so it can act as a carbon sink and offset some of the carbon dioxide produced during its manufacture.  

However, the complexity of cement manufacture and the way critical components of cement react with each other, affect how the concrete performs. If chemical reactions within the cement are suboptimal, the concrete weakens, which can end in disaster. For example, adulterated cement contributed to the widespread collapse of buildings during an earthquake in Izmit, Turkey, in 1999, which killed 17,000 people. 

“This would partially replace cement clinker – an important component of cement manufacture produced at high temperature in a kiln – saving energy and reducing CO2 emissions 

Professor Robinson’s team is using X-ray imaging methods, developed using the UK’s Synchrotron, to understand the performance of cement and concrete materials, working in collaboration with the School of Materials Science and Engineering, Tongji University, Shanghai. 

“One of our goals is to make small changes in cement’s composition, without spoiling its performance,” he explains. “For example, by adding appropriate amounts of industry by-products such as fly ash and granulated blast furnace slag. 

This would partially replace cement clinker – an important component of cement manufacture produced at high temperature in a kiln – saving energy and reducing CO2 emissions during cement production, as well as reducing the impact on the environment for the life of the cement. 

“We are looking at calcite – a compound that forms during cement hydration and can act as a carbon sink,” Professor Robinson explains. 

Using X-ray imaging, the team is closely examining calcite nanocrystal growth in high and low CO2 conditions to check for irregularities and defects in the crystal structure that could affect the concrete’s performance.