Calcined clay in cement: Use more clay, less clinker

Reduce the clinker factor down to 50 percent, save money, emit less CO2 – with activated clay

Due to tough market conditions more cement producers want to reduce the clinker factor and to increase the volume of Supplementary Cementitious Materials (SCMs) in their products. Calcined clay offers a sustainable and cost-effective alternative. With its polysius® activated clay technology, thyssenkrupp is providing an innovative solution for the industrial use of clay as an SCM. The technology supports fuel substitution rates of up to 100%. If desired, our solution puts an end to the terracotta-color of calcined clay cement.

One-stop solution for raw material changeover: polysius® activated clay

We offer cement producers comprehensive support in consulting, project development, implementation and operation. This includes

  • Basic analytics & project development including raw material inspection, trial production, mortar tests, and a business case calculation.
  • Planning & execution, ranging from EP to EPCM and EPC projects.
  • Operation & maintenance, from assisted startup to full operation and maintenance.
  • Product portfolio & sales support using high-performance machine technologies and processes, supplemented by warranties regarding substitution rate and/or product performance.
A wealth of geological formations around the world contain potentially usable clay, both from sedimentary deposits and weathered rocks. Often, there are already mining facilities at limestone deposits, aggregate quarries and kaolin mines, which may indicate easy access and a high probability of finding suitable material.

If a promising deposit is found, it must be determined whether it is within a reasonable distance of the processing facility and of an adequate volume to supply a minimum 200 tpd plant. This involves obtaining a representative material sample – no easy task in the case of heterogenous materials.

Once availability is ascertained, the next step is to assess the marketability of the potential end product. Ternary blends, such as Limestone Calcined Clay Cement (LC3), have not yet been standardized in many markets. However, even where no norms have been introduced, it may still be possible to secure a permit.

Finally, a business case must be drawn up as the basis for the investment decision. Project-relevant parameters include the cost of clinker, fuels and electricity, as well as the current supply of other additives.
thyssenkrupp provides comprehensive testing procedures and facilities. Both the clay and resulting cement are put through their paces in our R&D center. So far, we have tested more than 30 different materials for initial feasibility and processing properties and activated them in a muffle furnace, often followed by activation tests in a proprietary pilot (50 kg/hr) or semi-industrial (500 kg/hr) facility. Finally, the activated clay cement undergoes mortar testing in order to determine its composition, workability, water demand, compressive strength and color.

There are two potential plant setups for processing activated clay. Since both variations have their own advantages and disadvantages, we provide detailed advice to interested plant owners. The final decision depends on the individual weighting of a range of criteria.

A strong argument in favor of this type of plant is that it can be retrofitted in a relatively simple way by converting an existing installation. Electrical energy demand is also relatively low, while fuel consumption – by far the most important cost driver – is comparatively high. The choice of feed material and the clay quality require increased attention, with lumpy feed material and pure clays preferred. Compared to option #2, this process configuration has a lower throughput. Controlling the activation temperature and material coloring is challenging, and product quality may be inconsistent.

This process configuration achieves the best possible reactivity, leading to maximum clinker substitution rates and superior product quality. Fuel consumption is lower than with option #1, and a fuel substitution rate of 100% is possible. Color control is also easier to implement. Our machine technology is designed for fine materials and prevents dusting issues. A mill for raw material preparation is required. Overall, the flash dryer, calciner and cooler setup has a smaller floor space, but a greater structural and higher electrical demand.

Benefits of polysius® activated clay

  • Reduce the clinker factor down to 50%
  • Emit 70% less CO2 per ton with clay (180kg CO2 per ton) in comparison to standard cement production with clinker (790 kg CO2 per ton)
  • Improve cement quality and performance due to metakaolinite
  • Lower CAPEX for raw material preparation, pyroprocessing and grinding, and decreased OPEX
  • Reduce energy costs by up to 40% thanks to lower heating temperatures and retention times
  • Substitute increasingly scarce or expensive SCMs
  • Become more self-sufficient in terms of raw materials, particularly in regions where clinker limestone and clinker imports are costly
  • Continue to enjoy a grey product, if desired
  • Benefit from new business opportunities with the refinement of residual materials
  • Substitute fuels up to 100% with coarse and low-quality fuels
  • Spend less on CO2 emission certificates



Leo Fit
Technology Innovation & Sustainability
thyssenkrupp Industrial Solutions AG


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