Sustainability in Construction Materials (R. Alfani)

Cement’s carbon problem is severe, contributing almost 8% of total carbon emissions globally. Key stakeholders including governments, policy makers, investors and the development and construction sectors as well as  thee cement industry are increasingly focussed on reducing cement emissions to meet the EU’s targets for 2030 and beyond. 

Representing 75% of Europe’s average cement by weight, clinker is responsible for c.95% of cement’s carbon footprint. Any discussion on the decarbonisation of cement and concrete must focus on Portland cement clinker. Only one third of the CO2 emitted during the manufacturing process for clinker comes from the energy to heat the kiln and other energy intensive processes. Even if clinker was produced using entirely green energy, the carbon footprint of clinker would only reduce by one third. The remaining two thirds comes from the chemical reaction when the limestone breaks down inside the kiln from CaCO3 to CaO (quicklime) and CO2. These are known as process emissions. 

There are only two ways  of decarbonising cement production– capture the emissions once produced using carbon capture technology  or avoiding producing CO2 during the manufacturing process. 

To date much of the focus in the cement industry has been on delivering energy efficiencies and developing carbon capture solutions. Energy efficiencies have delivered some impressive gains in the last decade; however, these gains are now becoming incremental. Carbon Capture technology, an essential part in the industry’s journey to net zero, is, not yet fully developed, or proven, and is unlikely to be commercially available and operational before 2035 at the earliest. 

Reducing the clinker content of cement will automatically reduce emissions. Low carbon, low clinker cements have the potential to deliver a step change in terms of carbon reduction by 2030 and recent research and development work has accelerated both the availability and scalability of low carbon alternatives. Received wisdom in the industry has been that while low carbon cements are available, they will never be sufficiently scalable to meet demand. This is no longer the case. 

Historically, low-carbon blended cements have relied on large volumes of GGBS and fly ash (by-products of the energy and steel industries). These are excellent solutions; however, availability is limited and  will only reduce over time. As the energy and steel industries  reduce their own carbon footprint, the supply of fly ash and GGBS will diminish, making it impossible for the construction industry to rely on these materials in the long term.

Low clinker high efficiency blended cements hold the key. These cements use available materials extremely efficiently and the concrete they are used to produce performs at least as well as traditional cement in terms of durability, workability and strength. They use the reactive elements of their composition extremely efficiently and use  significantly more limestone fillers when compared with current standards, and well beyond the typical amounts used in the industry today. This results in an immediate reduction in CO2 emissions by 60-75% by significantly reducing the amount of clinker produced and its associated carbon footprint.  Ecocem has developed a new generation of scalable low clinker highly efficient cements and concrete. 

The results are stark. Concrete as strong, durable and workable as conventional concrete, but with a fraction of the carbon footprint. And ready to deploy today at existing plants and with minimal additional cost to the industry.