A «carbon footprint» of low water demand cements and cement-based concrete

Due to the fact, that the contribution of the global cement industry to CO2 emissions achieves as 6-7%, the Cement Sustainability Initiative, in collaboration with International Energy Agency, has set up the target value of 370 kg of carbon dioxide emission to 1 t of Portland cement by 2050. Currently, these indicators are at the level of 835 kg (535 kg of CO2 from decarbonization of limestone, 330 kg for fuel combustion). The well-known and newly developed technologies for CO2 capture, storage and utilization (CCS, CCU) are being also analyzed for the binders with a low carbon footprint. However, to date, all of them are not ready for commercialization because they are costly and cannot fully achieve the target value of CO2 emissions by 2050. The most productive and widely used approach, which does not require reconstruction of cement plants, is to reduce the clinker capacity in cement during the grinding of clinker with substitutional hydraulic, pozzolanic, "inert") additives. Nevertheless, such a dilution affects the performance of cement and reduces the' strength, especially when using limestone-the most available cement filler; carbon dioxide emissions per standard cement strength are not reduced. The "carbonate" types of cement of low water demand (CLWD-CB) have been developed, which possess low content of clinker (no more than 30%) combined with low energy consumption for grinding, high technological and strength parameters. According to the environment ranking, these types of cement are superior to all standard European types of cement. At all the stages of the life cycle, which includes clinker-cement-concrete-concrete structure-concrete scrap (dismantling of the structure), the replacement of standard types of cement with CLWD-CB will make it possible to reduce the carbon footprint from the binder by two times, and from CLWD-CB-based concrete-by four times.