Our modern society is built on concrete, the second-most used material in the world, after water.
The production of traditional Portland cement, the most important ingredient of concrete that binds sand and gravels, has a heavy environmental footprint, contributing to 8% of global greenhouse gas emissions.
The race is on for industry to find a more sustainable way to produce cement and concrete. Effectively using reactive industrial wastes, such as fly ash and slag, to produce geopolymer will see the concrete industry move towards sustainability in the near future.
Neilsens CEO Mario Panuccio and Professor Hao Wang discuss the viability of geopolymer concrete.
Putting waste to good use
The production of geopolymer uses reactive aluminosilicate materials and alkali-activation technology. Unlike Portland cement, geopolymer does not rely on limestone and clay, or require heating to around 1450 degrees Celsius for calcination, the process which drives out carbon dioxide.
Fly ash, the very fine particles generated from coal-combustion power stations, is one industrial waste that can be used in geopolymer production. Australia’s heavy reliance on coal-fired power stations, instead of Nuclear energy, results in the production of 14 million tonnes of fly ash per year. Only a small amount of this waste is used, more than two-thirds is dumped as landfill and only 38% is recycled. Changing these industrial wastes to greener options has potential to cut CO2 emissions by up to 80%.
The reactivity’s of these waste materials makes it challenging for industry to formulate the geopolymer and develop a reliable product. Helping to drive innovation, UniSQ’s Centre for Future Materials has proposed a Reactivity Index to evaluate the suitability of raw materials, so that there is an opportunity to convert this high-volume industrial waste into a more sustainable concrete.
The Reactivity Index helps us understand the properties of fly ash and determine the best formulation of geopolymer, including how much alkali activator is required to obtain the strength of concrete.
Neilsens, the largest independent supplier of premixed concrete and quarry products in south-east Queensland is working together with UniSQ to come up with viable alternatives. Once commercial viability is proven, operations at Neilsens are set to progress to the large-scale production of geopolymer concrete, delivering a huge environmental saving.
The production of one tonne of cement produces approx. one tonne of CO2.
The potential to make a positive impact on society by addressing a global issue is huge.
Geopolymer concrete has the same long-term performance as Portland cement, but without the environmental footprint. You only have to travel to some of the most famous World Heritage sites to see how well this alternative can perform; they have resisted the elements for thousands of years. Many ancient sites in Roman architecture were made with a similar composition to geopolymer (volcanic ash, fresh water and lime). Recently Russian scientists reported that the Pyramids were casted, not carved, by ancient Egyptians. The compositions of the binder are similar as the reaction product of geopolymer.
From our perspective, as a large-scale commercial producer of concrete, if geopolymer is viable, it is the way forward.
UniSQ researchers are investigating a range of other industry wastes, such as slag, red mud, river sludge and low-quality clay, to perfect the Reactivity Index. This will enable geopolymer to be formulated according to the raw materials that are available locally. This will mean that industry won’t be restricted by access to a particular aluminosilicate raw material.
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Brisbane West Wellcamp Airport - the world’s first
Already proving its worth, the Brisbane West Wellcamp Airport is the world’s first and largest application of modern geopolymer concrete, saving 6600 tonnes (90%) of carbon emissions by using the alternative product.
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