EXECUTIVE SUMMARY: Novel uses for cement – brief review and outlook
Cement surrounds us every day. As the main ingredient in all forms of concrete – reinforced concrete, building blocks, mortar, roads, paving, roof tiles etc – our entire modern urban lifestyle is completely dependent on this unassuming material. About 2.7 billion tonnes of cement is made around the world each year. The most common cement, Portland cement, is made by burning limestone and clay at over 1400°C to form calcium silicates, but many other types of cement exist based on mixtures of silicates, aluminates, phosphates and sulphates.
Cements have a number of unique properties: e.g., they can easily be mixed with aggregates, formed into any shape and then hardened, all at normal temperatures, and they have an unusual nanostructure that can absorb all sorts of molecules. Although at least 99% of cement is used in construction, these unique properties mean that people are starting to explore cements for a much wider range of uses. Portland cements are used for dealing with nuclear waste and cleaning up contaminated ground. Aluminate cements are used for heat-resistant materials. Various different cements are used by dentists, and cements that mimic the chemistry of bones are used in the reconstruction of damaged skulls and spines. Artists use cement to make Turner Prize-winning sculptures.
Although this demonstrates the versatility of cement, it only scratches the surface of the potential for this unique material. Developing these high-value niche markets for specialised cements could also help offset the increasing production cost for Portland cement. Cement manufacture is energy intensive and also creates extra carbon dioxide by decomposing limestone. As carbon trading prices increase and environmental taxes get tougher, these production costs could double over the next few years.
What is clear is that to fully exploit the capabilities of cement, more communication between cement scientists and new and potential users of cement is required. This will help new users get the most out of cement and showcase the full range of its capabilities to those who have previously mistaken cement to be just a mundane part of the urban landscape.