Context:

• Circularity is important: (add why)

• Built Environment is a big culprit for not using circularity practices: the extraction of minerals used to produce construction materials is responsible for 1/4 of global land use change (

• The production consumes vast amounts of raw materials, with over 3 tonnes of material being required to produce a tonne of OPC, alongside large amounts of heat energy to convert limestone generating high volumes of CO2 emissions and harmful greenhouse gases.(source)

• GGBS has chemical properties similar to clinker

• The Global Cement and Concrete Association (GCCA) Roadmap to Net Zero sets out a seven-point plan to reduce emissions by another 25% over the next decade. The first point in this roadmap is ‘Increased Clinker Substitution’ (source)

  • Increased clinker substitution: The industry will continue to substitute clinker, the main constituent of Portland cement, with supplementary materials such as fly ash (a by-product of the power sector), ground granulated blast-furnace slag (a by-product of the steel manufacturing process), calcined clays, unburnt and ground limestone or recycled concrete fines. Most of these materials have been used in the sector for a long time, already having contributed to lowering the CO2 footprint of both, cement and concrete – for example in the UK market there is 26% clinker substitution [Link]. The roadmap sets out a commitment to further increase clinker substitution and the GCCA will share best practice models from around the world to accelerate its use.

Cement and the Circular Economy

• OPC —> limestone (80%) + clay (20%)
  • Both extracted from the earth
  • Supply of each of these?
• GGBS —> ‘more sustainable’ solution (similar chemical propoerties to clinker)
  • But: requires steel plants which are declining
  • Only enough GGBS globally for 1/12 of total cement production (Institute of Structural Engineers)
  • Not a long-term solution
• Waste-based solution (brief overview of Mevo’s waste-based options)
• Other waste-based materials being experimented with now: calcinated clay, reclaimed xyz
  • Issue: unlikely to ever be a singular waste that can be used to replace all cement
  • Need to find a way to contribute positively to circular economy (e.g. reclaim materials, etc.)

The Efficient Use of GGBS in reducing Global Emissions (Institute of Structural Engineers)