The most important use of cement is in the production of concrete. It acts as the binder that ‘glues’ the other key ingredients of concrete – sand and gravel. Cement typically makes up about 12% of the concrete mix.
Clinker, the main component of cement, is obtained during the calcination of limestone. The clinker is then ground and blended with other materials into a powder (cement). Most CO2 emissions from cement manufacturing result from the production of clinker. Reducing the clinker content therefore reduces the energy and carbon intensity of the cement produced.
Cement production generates CO2 emissions from two sources: combustion (38%) and calcination (62%). Combustion-generated CO2 emissions are related to fuel use while emissions due to calcination are generated when the raw materials (mostly limestone and clay) are heated and CO2 is liberated from the decomposed limestone.