An environmental evaluation of geopolymer based concrete production: reviewing current research trends

In this study we carry out a detailed environmental evaluation of geopolymer concrete production using the Life Cycle Assessment methodology. The literature shows that the production of most standard types of geopolymer concrete has a slightly lower impact on global warming than standard Ordinary Portland Cement (OPC) concrete. Whilst our results confirm this they also show that the production of geopolymer concrete has a higher environmental impact regarding other impact categories than global warming. This is due to the heavy effects of the production of the sodium silicate solution. Geopolymer concrete made from fly ashes or granulated blast furnace slags based require less of the sodium silicate solution in order to be activated. They therefore have a lower environmental impact than geopolymer concrete made from pure metakaolin. However, when the production of fly ashes and granulated blast furnace slags is taken into account during the life cycle assessment (using either an economic or a mass allocation procedure), it appears that geopolymer concrete has a similar impact on global warming than standard concrete. This study highlights that future research and development in the field of geopolymer concrete technology should focus on two potential solutions. First of all the use of industrial waste that is not recyclable within other industries and secondly on the production of geopolymer concrete using a mix of blast furnace slag and activated clays. Furthermore geopolymer concrete production would gain from using waste material with a suitable Si/Al molar ratio in order to minimise the amount of sodium silicate solution used. Finally, by taking into account mix-design technology, which has already been developed for OPC concrete, the amount of binder required to produce a geopolymer concrete could be reduced.