LC3 (limestone calcined clay cement)
LC3, or limestone calcined clay cement, is a blended cement combining Portland clinker with calcined clay, limestone and gypsum.
Updated
LC3, short for limestone calcined clay cement, is a blended cement combining Portland clinker with calcined clay, limestone and gypsum. A typical formulation described by the LC3 project uses roughly half clinker, with calcined clay at about twice the proportion of limestone and a small gypsum addition. The clay is kaolinitic and is calcined at a moderate temperature, well below clinkering, which is where much of the claimed energy and carbon benefit originates.
In practice
The synergy in LC3 comes from the reaction between the alumina in the calcined clay and the carbonate in the limestone, which forms carboaluminate phases and refines the pore structure. That refinement is reported to improve resistance to chloride ingress, while early strength is somewhat slower and water demand higher than for ordinary Portland cement. For printing the practical consequences are a stickier, more cohesive paste and a different admixture response, so superplasticiser and accelerator dosages have to be re-established rather than carried over. Clay quality varies by deposit, and consistent supply of suitably kaolinitic clay is the main constraint on wider use.
Related terms
- Supplementary cementitious materials — the broader family of clinker replacements to which calcined clay belongs.
- Geopolymer — an alternative low-clinker route based on alkali activation.
Frequently asked questions
- How much clinker does LC3 actually save?
- The LC3 project describes formulations with roughly half the clinker of ordinary Portland cement, and the associated carbon reduction is usually reported in a similar order. Any figure should be treated as indicative: it depends on the clay quality, the calcination fuel, transport and the cement it is compared against.