Practical experiences in the use of a combination of calcined clay and limestone as clinker substitute in cement

The acceleration of the impact of climate change prompts the cement industry for swift and effective solutions to reduce a large part of the carbon dioxide associated with cement manufacture. The use of Supplementary Cementitious Materials, SCM, such as fly ash and slag have enabled so far, the possibility of partially replacing clinker, the most energy intensive and main responsible component in cement for carbon emissions. However, reserves of both SCM are declining and their price is increasing, and replacing more than 30% clinker with these SCM can compromise early strength. In recent years a global team of scientists from Switzerland, Cuba and India have proven the possibility of dropping clinker content in cement down to 50% or even less through the combined use of calcined kaolinitic clays and limestone, both cheap and abundant materials, to produce a new cement called “LC3”. The resulting cement matches the properties of a CEM I (EN‐197) at all ages, and carbon emission reduction is reportedly around 25‐40%, depending on the cement to compare with. This paper presents the accumulated experience in the investigation of the new cementitious system and the introduction at the industrial level. Issues like the choice of the right clay, calcination technology, product formulation, standardization and economic feasibility will be discussed. The information in this paper is intended to encourage industrial partners to invest in the new technology.