Why LC3?

For every 20 tonnes of man-made CO2 that enter the atmosphere, one comes from the kilns of cement factories. Emissions in cement production are threefold:

  • From the production of the electrical energy used to grind the raw materials and clinker;
  • From the fuel burned to heat the raw materials in a kiln to 1450°C to form clinker, which is later crushed and blended with gypsum to make cement;
  • Process emissions: as the limestone is heated, it changes into lime and CO2. These emissions represent 60 to 65% of total emissions linked to cement production.

Reducing the amount of clinker in cement, reduces the amount of CO2 in the atmosphere. Now, the amount of clinker is reduced by half in LC3.

LC3 allows growth without abstinence due to resources and CO2 efficiency

With current clinker production facilities, production capacity for cement can be increased twofold without increasing total CO2 emissions. Quarry life can then be considerably extended and costly Carbon capture and storage technologies for emission abatement can be avoided. Emissions of LC3 are estimated to be 20-30% lower than Portland cement because:

  • Reduced clinker content leads to less process emissions from the decarbonation of limestone in clinker and less emissions from heating limestone to form clinker
  • Grinding limestone takes less energy than heating it
  • Calcination of clay takes place at 800°C and uses roughly 55% of the energy needed for clinkerisation at 1450°C.

Existing equipment can be used

LC3 can be produced with existing manufacturing equipment, leading to only marginally increased investments for calcining equipment.

Lower cost of production

Reduced clinker content, decreased fuel consumption for calcination compared to clinker plus the fact that limestone does not need to be heated should contribute to lower production costs. Lower production costs are one of the main drivers for technology uptake.

A well-known technology

Clinker–Limestone systems and Clinker–Calcined Clay systems are well established. In effect, LC3 is optimises the synergy between two already known chemical systems. This leads to a higher degree of confidence that the materials will be durable since the chemical nature of the hydrates and pore structure are similar to other blended cements which have proven durable.

Ressource efficiency

Using low-grade clay and limestone does not require opening new quarries nor deplete agricultural soils.

As a result, LC3 is a very attractive and feasible option to satisfy development and environmental objectives.

Related document: Indian Concrete Journal: Options for the future of cement


Approximately ten tones each of four blends of LC3 -containing 50% clinker, 30% calcined clay, 15% crushed limestone and 5% gypsum – were produced in India using two clays and two limestones of different quality. Details of this production are described in a technical paper published in ICJ. These cements were used to produce micro concrete roofing tiles, solid concrete bricks, hollow concrete blocks, door and window frames and low duty paving blocks. The test of all the blends in actual production scale were consistent with the laboratory results: the strength obtained was equivalent or superior to that products made using the Portland Pozzolanic Cement (PPC). The construction of a two floor reinforced concrete building with hollow concrete blocks infills and micro-concrete roofing tiles made of all four blends produced was also built as a test bed. Further reading…


In Cuba, an industrial trial of 130 tonnes has proven the potential of producing LC3 with a clinker content of approximately 50% even in challenging technical conditions. The trial included the calcination of 110 tonnes of medium grade kaolinitic clay; mixing and homogenising of the calcined material with limestone in a 2:1 ratio; and co-grinding of the materials with clinker and gypsum. Eleven thousand hollow concrete blocks (the most used building materials in Cuba) were produced under standard manufacturing conditions. The experimental blocks met the standard’s requirements for compressive strength and water absorption, indicating that LC3 could replace Portland cement in this kind of industrial application. Several cubic meters of 25 MPa concrete were cast under standard manufacturing conditions, with the new cement.