LC³ or Limestone Calcined Clay Cement is a family of composite cements containing Portland clinker, calcined clay and limestone.  The LC³ technology promises a sustainable growth of economies around the world by reducing up to 40% CO2 emission compared to Ordinary Portland Cement (OPC) at lower investment and production costs.  LC³ uses raw materials and technologies that are already used by the cement industries.  The production process is similar to the way of producing normal cements.  Thus, they provide a practically viable solution to improve sustainability in the cement industry.

MECHANICAL AND OTHER PHYSICAL PROPERTIES OF LC³

LC³ has been seen to develop ultimate strenghts comparable to OPC’s produced using the same clinker.  Strenght development in LC³ has generally been observed to be faster than OPC and Portland Pozzolana Cement (PPC).  LC³ is expected to satisfy all the other requirements of physical characteristics laid down in most of the country standards.  Additionally, calcined clay and limstone improves cohesion of fresh concrete which prevents segregation and bleeding.

RAW MATERIAL FOR LC³

The main raw material in LC³ is kaolinitic clay.  Clays containing 40% to 60% kaolinite are ideal for the production of LC³.  Reddish clay with high iron content are suitable.  Such clays are abundantly available as waste in mines where higher grade white clays are used for high value applications.  The clays are calcined between 700°C to 800°C to make them reactive. Calcination requires almost half the energy required for clinker production.  In LC³ limestone with as little as 75% calcium carbonate content can be used.  These low grade limestone, as well as dolomitic limestone are often rejected in cement plant quarries. Limestone with impurities such as quartz can also be used in LC³ production.  No calcination of the limestone is required.  Apart from calcined clay and limestone, Ordinary Portland clinker is used in the production of LC³.

DURABILITY OF LC³

Under most severe conditions, the performance of LC³ is better than or at par with OPC and PPC. LC³ has a high chloride penetration resistance and produces a dense microstructure with high resistivity, making it ideal for harsh conditions like in marine or desert environment. LC³ concrete blocks placed 2013 at an exposure site offshore in the northern coast of Cuba show no sign of corrosion according to studies carried out.  LC³ is also highly suitable for use with reactive aggregates that are normally rejected for concrete production.

ECONOMY OF LC³

Due to the lower calcination energy requirements, and the lower clinker content, LC³ is more economical to produce than OPC for similar performance. Especially at locations with shortage of high quality fly ash, low limestone quality or excess reserves of waste limestone, LC³ is more economical to produce than PPC. LC³ is also suitable for production where clinker is being imported or the production costs are not competitive. Due to its lower clinker content and lower capital investment required for calcination of clays, LC³ allows higher returns on capital investments. Also, clay and limestone which are otherwise discarded by cement plants can be utilized in LC³ which leads to low raw material cost.

EMISSIONS AND RESOURCE EFFICIENCY FROM LC³

The production of LC³ emits as much as 40% less CO₂ than OPC and 11% less CO₂ than PPC. The production of LC³ implies less energy consumed in comparison with OPC and even PPC in many scenarios. LC³ also offers an interesting solution for the utilization of low grade mine rejects widely available with the cement and ceramic industry. Thus, while it reduces GHG emissions from the cement industry, it also helps in utilization of waste materials, thereby promoting resource efficiency of materials. The production of LC³ implies less energy consumed in comparison with OPC and even PPC in many scenarios.