Geopolymer technology as a replacement for Portland cement is here to stay. In countries such as Australia, geopolymers are already being marketed. The geopolymers marketed by these companies are composed of fly ash, the by-product of burning coal in a power plant, and slag, the by-product of steel making, E-Crete™. This reduces the resulting CO2 in concrete by at least 60% compared to concrete based on ordinary Portland cement (OPC).
The main process difference between OPC and geopolymer cement is that OPC is based on a high-energy manufacturing process that imparts high potential energy to the material through calcination. This means that the activated material will readily react with a low energy material such as water. In contrast, geopolymer cement uses very low energy materials, such as fly ash, slag and other industrial wastes, and a small amount of high chemical energy materials (alkaline activators) to react only on the surface of the particles and act as a glue.
At the Construction Technology Centre, we have been committed to this technology for several years and have developed various projects of our own and in collaboration with other companies and other technology centres. The aim is to develop new materials that produce a minimum amount of industrial by-products and CO2 during their production.
Ordinary Portland Cement (OPC) is a binder or hydraulic cement which, when mixed with aggregates, water and steel fibres, creates what we know as concrete and is the most widely used commodity in the world with over 3 billion tonnes produced annually. It is also the third largest source of CO2 emissions of human origin, representing approximately 7 to 8% of all emissions. In Spain alone it accounts for 5% of the CO2 generated annually, given that one of its main ingredients, clinker, needs to be fired at temperatures of 1,400 degrees Celsius.
OPC is the dominant source of CO2 emissions from concrete (over 70%) and the main source of emissions in road, infrastructure and construction projects.
The use of geopolymers instead of traditional Portland cement provides two significant environmental benefits: the first is the reduction of CO2, which is unparalleled in the construction industry, and the second is the use of recycled industrial waste, which means less extraction of raw materials.
At present, there are already projects in which the use of geopolymer concrete is already a reality, such as the Global Change Institute building at the University of Queensland in Australia, or the New Delhi metro in India.
