According to the World Business Council for Sustainable Development (WBCSD), “Concrete is the most widely used material on earth apart from water, with nearly three tons used annually for each man, woman, and child.” Cement is made by burning fossil fuels when the limestone and clay are heated to over 1300°C and CO2 is liberated from the decomposed limestone according to the following reaction:

The energy intensive calcination step is a necessary key to cement production. Therefore, the focus of reductions in CO2 emissions during cement manufacturing is on energy use. However, energy efficiency is ultimately limited by two factors: (1) the high temperature needed to drive the calcination of limestone, and (2) 60% of CO2 produced in cement manufacture arises from the calcination reaction itself.

The manufacture of cement produces about 0.9 kilograms of CO2 for every kilogram of cement. Around 5 – 8% of global CO2 emissions result from cement manufacture, making this product one of the more polluting activities undertaken by mankind.

So the question is, can we do this better?

One of the primary advantages of geopolymers over traditional cements from an environmental perspective is largely associated with the much lower CO2 emissions from geopolymer manufacture compared to OPC production. This is mainly due to the absence of the high-temperature calcination step in geopolymer synthesis.

While the activators used in geopolymers do reintroduce some Greenhouse cost, the overall CO2 saving due to widespread geopolymer utilisation is in the order of 80-90% when compared with Portland cement. Zeobond Pty Ltd had the ‘green credentials’ of E-Crete put to the test by independent experts who conducted a Life Cycle Analysis and found that E-Crete does indeed produce 80% less CO2 than OPC.

COMPARISON OF GEOPOLYMER CONCRETE AND OPC BINDER SYSTEM GREENHOUSE EMISSIONS

For further information on geopolymers see our research section.