Common low-grade clay enhances low-carbon concrete
The combined clay mix after being heat treated, ready for use as a cement supplement (Photo: RMIT)
June 5, 2025 – Scientists at RMIT University in Melbourne, Australia, have successfully transformed low-grade clay into a high-performance cement supplement, potentially opening up a new market for sustainable building materials.
Global cement production – an essential component of concrete – is responsible for 8 percent of the world’s CO₂ emissions.
Replacing a portion of cement with clay can help reduce this environmental impact. However, high-quality kaolin clay, which is best suited for this purpose, is increasingly in demand for ceramics, paint, cosmetics, and paper.
The RMIT team has now demonstrated that cheaper and more abundant illite clay can be mixed with lower-grade kaolin clay to produce stronger concrete. The researchers developed a new process in which low-grade illite and kaolin clays are combined in equal parts and heated to 600 degrees Celsius.
According to the RMIT researchers, this method could replace up to 20 percent of cement content with these lower-quality clay combinations.
The study was published in Construction and Building Materials under the title ‘A combination technique to improve natural low-grade illite as supplementary cementitious material for concrete.’
