CALIPSO™ - Calcined Clay for the Cement Industry

With an increasing global population and vast regions of the world experiencing unprecedented levels of growth and prosperity (ie Asia), it is evident that the world will require record levels of urbanisation now and into the future.

According to UNIDO (United nations industrial development organization) a specialised agency of the United Nations, the world is expected to build a New York City equivalent every month for the next 40 years. This level of infrastructure demand will inevitably place a significant strain on the raw material supply chain and lead to more direct and indirect carbon emissions of businesses involved in processing and supplying the raw materials for this infrastructure boom.

Cement is one key ingredient that will be used to satisfy this insatiable demand, but with global carbon emissions of 8% directly related to its processing and production, there is an immediate need to begin decarbonising this process now and introduce new technologies to reduce intense carbon emissions.

Calix has been working with industry to reduce these carbon emissions by developing clinker substitutes that have characteristics on-par with OPC (Original Portland Cement) when utilised as a supplementary cement material (SCM).

The use of calcined clay blends as an SCM is an emerging technology showing promise as a sustainable substitute (e.g. LC3 technology or Limestone Calcined Clay Cement). When calcined clay is manufactured using Calix technology, it is activated so it can be used successfully as an SCM in cement and/or concrete production.

In the Calix Flash indirect heating process, a patented design, the clay particles do not come into direct contact with the heat source. This ensures the following:

1. High conversion of clay
2. Highly stable clay product
3. High process energy efficiency
4. High Yields and throughputs
5. 100% off-gas capture

The resulting calcined clay product, when used in blends such as LC3 cements (30% clay, 15% lime, 5% gypsum and 50% clinker), exhibits characteristics that are on-par with OPC. In Europe, new building codes incorporate the use of 50% clinker blends and in the US, the ASTM standards for 50% clinker blends are starting to be incorporated.

The use of SCM’s in cement and concrete are crucial in decarbonising the economy and unlocking between US $800 billion to US $1.9 trillion in the green built environment value pool (McKinsey and Company, 2022). Fly ash is one such SCM that has shown to be used satisfactorily in limited clinker substitution but with the shutting down of coal fired power plants across the globe due to increased regulatory pressures and emissions intensiveness, means output will be significantly reduced.

The US Energy and Information Administration (EIA, 2022) has reported that a significant reduction in fly ash production in the US by 30 million short tons (27.7 metric tonnes) is to be expected in 2023 from 2022 alone, which drastically reduces output of this SCM based cement.

Silica fume being another SCM used in cement production has great properties with regards to corrosion resistance to chemicals and high salty environments as experienced in marine environments, but requires specialist attention during construction phases of a project and its clinker substitution content (percentile) is significantly lower than that of clay. By using Calix’s patented electric calciner design for the calcination of clay for SCM based cement, the industry is well on the way to achieving the following goals.

1. Improved energy efficiency
2. Switching to low carbon intensive fuels
3. Reducing clinker content in cement
4. Formulations for use in batching plants

These are important goals if the world is to meet 2050 global emissions targets and to keep the temperature increases to below 2˚C as outlined by the Paris Climate Agreement.