Abundant and cheap low-grade clay has been converted into a high-performance cement supplement by researchers in Victoria, opening up a new market for sustainable construction materials.
The team from RMIT University’s School of Engineering has demonstrated that illite clay can be mixed with low-grade kaolinite clay, to make stronger concrete. Equal amounts of the two ingredients can be processed together, rather than separately, and heated at 600 Celsius; this led to several improvements in concrete performance.
Project lead Dr Chamila Gunasekara, said low-grade illite clay does not normally bind well with cement and water, but that the joint heating, or co-calcination, process greatly enhances illite clay’s pozzolanic reactivity.
“Based on this approach, we are able to replace 20% of cement usage using low-grade illite and kaolin combinations, while achieving even better performance of the yield product.”
There was an 18% increase in the amount of disordered material in the new clays, which is beneficial for strength and durability. The material also holds more water in a chemically stable form, pointing to better long-term reactions that help the structure stay strong.
“Porosity is reduced significantly by 41%, with its compressive strength increased by 15%, where changes in the way iron compounds formed help create a tighter and more compact internal structure,” Dr Gunasekara said.
Study lead author Dr Roshan Jayathilakage said the technique was also more energy efficient as it streamlines industrial operations and lowers fuel use, making it economically and environmentally scalable.
The study was published in Construction and Building Materials.
Image: The team (L-R): Dr Roshan Jayathilakage, Dr Chamila Gunasekara, Dr David Law,
A/Prof. Dilan Robert, Prof. Sujeeva Setunge, Dr Yuguo Yu.
About the author
Desi Corbett
Desi is the Editor of Concrete in Australia, at the helm since December 2013, and our weekly news writer since 2016. Focused on concrete and construction for more than 11 years, her expertise in this field forms part of a journalism career spanning three decades. To get in touch please email desi@corbettcomms.com