Making cement is the third largest source of carbon emissions in the world after the burning of fossil fuels and deforestation—but the Australian roads of the future could be paved with cement that is made in a process that generates less than half the carbon emissions of traditional methods.
Each year, the world produces about 12 billion tonnes of concrete and about 1.6 billion tonnes of its key ingredient, Portland cement, which is generated by breaking calcium carbonate into carbon dioxide and calcium oxide.
This produces some 2 billion tons of carbon dioxide—so the Geopolymer and Mineral Processing Group (GMPG) at the University of Melbourne, now led by Dr John Provis, went looking for a lower carbon way of making cement.
They have now developed binders and concretes based on a low-CO2 aluminosilicate compounds called geopolymers.
The former head of GMPG, Prof Jannie van Deventer, founded Zeobond Pty Ltd to turn these geopolymers into a product called E-Crete™.
Consisting of fly ash, a coal-fired power station by-product, and slag from steel manufacturing, E-Crete™ reduces the embedded carbon dioxide of concrete by at least 60% compared to ordinary Portland cement (OPC)-based concrete.
The researchers used the Australian Synchrotron to look at the shapes of the materials that make up the cement at the nanometre scale and see how those shapes affect how they pack together. This allows them to experiment with different proportions of materials to see which will be the most stable and long-lasting.
Now, in collaboration with the state of Victoria’s road authority, VicRoads, Zeobond has been able to demonstrate that E-Crete™ is every part the equal to OPC-based concrete. E-Crete™ is now used in VicRoads concrete applications including pavement and pre-cast. And VicRoads has changed its building standards to allow green cement paving. John is now hoping to have the international standards changed.