Calcined Clay Cement: The New Fly Ash for Low Carbon Concrete?

The dominance of coal as the power source for electricity is reducing worldwide and in some countries has been fully phased out, particularly in western Europe. Over the next 20 years or so most countries will fully adopt renewable energy. This will mean that, other then recovered material, the availability of run-of-station fly ash will be significant reduced.
In the UK, the Low Carbon Concrete Group of The Green Construction Board has published the Low Carbon Concrete Routemap, which describes the path to net zero by 2050. This has identified that calcined clay could be a large volume raw material to produce low carbon cement (and an embodied CO2 around a third that of Portland cement clinker).
This paper will report on the performance of a range of calcined clay cements produced at industrial-scale rotary and flash calciners using overburden and interburden waste clays from existing Portland cement plants.
A wide range of structural concretes were assessed and it will be demonstrated that calcined clays of this type are highly pozzolanically-reactive and can produce very high compressive strengths and exceptional chloride resistance. The paper will also consider carbonation, which given pozzolanicity of Calcined Clays, can be higher than ‘conventional normal concrete’.