Factors Influencing the Carbonation Kinetics of Calcium Silicate-Based Binders—An Overview

The production of hydraulic binders, representing the essential constituent part of concrete and mortar, can be associated with high energy consumption and huge CO2 emissions (at least 2.4 billion tons in 2022). Without appropriate measures, the situation will only worsen. The global annual output of cement stood at 4.4 billion tons of cement, whereas the annual production has been increasing at a rate of ca 5%. In order to significantly reduce CO2 emissions, the following solutions are most widely used in the world: clinker additives; unconventional fuels; decreased energy-related expenses; and technological innovations. However, these are not sufficient to cut down on greenhouse gas emissions and bring them close to zero. Therefore, the utilization and development of alternative binders denoted by a reduced CO2 footprint in comparison to that of conventional cement are among the main objectives of building materials manufacturers as well as researchers. This paper reviews obstacles, solutions and alternatives for the fabrication of hydraulic cementitious materials, along with the general principles of the carbonization of binders, such as natural processes and intensified processes, the impact of various parameters on the chemical and physical transformations, as well as the mechanism of interaction of OPC, belite, and blended cement with CO2. The production of low-lime binders, along with time-optimized carbonation, can significantly improve carbon footprint values. However, due to the huge variety of blended cements, their hardening process by mineral carbonation needs to be investigated extensively and systematically, as it is emphatically dependent on many numerical values and criteria. Environmentally and economically acceptable production can only be achieved on the grounds of the optimized parameters of the entire process.