About Geopolymers

What and how?

Geopolymer is an alternative cementitious material made by combining materials that are rich in silica and alumina, such as fly and bio ash, slags and tailings. When the right type of raw materials are mixed under correct pH conditions, a geopolymerization process is triggered. Here, the materials form a 3D aluminosilicate network with a similar or even higher strength compared to conventional OPC (Ordinary Portland cement) based concrete.

Geopolymers vrs OPC-based concrete

Low carbon
footprint

Because most of the raw materials used in geopolymers originate from industrial waste streams, the carbon footprint of the end product can be up to 90% smaller compared to a OPC-based product. Another reason for having a low carbon footprint is the fact that geopolymer-based concrete does not include the production of clinker that is highly energy intensive and releases CO2 in the chemical process itself.

Technical
benefits

Geopolymer based concrete is also known to have higher flexural strength, lower drying shrinkage and higher resistance to chemical attack compared to conventional, cement-based concrete. Geopolymers also have a high freeze-thaw as well as high thermal resistance.

Origin

Using geopolymers is not a new invention. In fact, a similar mechanism behind geopolymers has been already used in the construction of the Egyptian pyramids (Barsoum et al. 2006). Many ancient buildings in the Roman architecture were also made with a similar composition to geopolymer with a mixture of volcanic ash, water and lime.

Commercialization

In addition to being a researched topic, there has also been early stage commercialization of geopolymers. For example, since 2014 there has been already a fully operating airport in Brisbane, Australia. Geopolymers were used in the turning node, taxiway areas as well as the foundations and wall panels used in the terminal building and all civil works on the site including the entry bridge.

Geopolymers are especially suitable for ground engineering because of the lower standards compared to e.g. load-bearing buildings. The building codes are also now being reworked to become more performance-based, enabling new materials such as geopolymers to be used.

Another reason driving the commercialization of geopolymers is the urgent need to find low CO2 building materials. As there has been more focus on the operational energy of buildings, the CO2 emissions arising from the construction phase and materials (also called embodied carbon) have received less attention. Fortunately there are promising policy initiatives to reduce the environmental impact associated with the construction materials.

Sources

Barsoum, M. W., Ganguly, A., & Hug, G. (2006). Microstructural evidence of reconstituted limestone blocks in the Great Pyramids of Egypt. Journal of the American Ceramic Society, 89(12), 3788-3796. Link