All civil engineers will be aware of CEM1 concrete. It’s a standard concrete mixture using cement to cure and harden. CEMFree has been created by the David Ball Group to entirely replace the cement requirement in concrete.
What’s wrong with using cement?
Portland cement (OPC) is a mined material. It is therefore a finite resource, and has an environmental impact in its creation. During the curing process of cement / concrete large quantities of carbon dioxide is released into the atmosphere (0.95 tonnes / tonne concrete) which has a knock on effect on global warming and climate change.
What is CEMFree?
CEMFree is high performing cementicious binder that can entirely replace the need for cement. It consists of ground granulated blast-furnace slag (GGBS) and pulverised fuel ash (PFA) plus an admixture (kept very secret!?) so uses a large quantity of waste products in its creation.
CEMFree technical comparison to CEM1
- Better chloride protection
- 0% permeability
- Lower embodied energy (<1.5GJ/tonne vs. 5GJ/tonne)
- 95% less CO2 emissions (0.09tonne/tonne vs. 0.95 tonne/tonne)
- Reduction in thermal expansion so no expansion gap requirements
- No requirement for crack control so reduction in steel usage
- Equal strength at 28 days with a greater strength from then onwards
Publicly available specification is available: PAS 8820:2016
All in all it seems to be a miracle product to help revolutionise the industry into a climate friendly industry. This could presumably also use recycled aggregate to further reduce its environmental impact. It does make you wonder what the admixture is though?