Cement is the major component of concrete which has been the main strength bearing building material for more than a century. However, its production is accountable for a considerable percentage of the global CO2 emissions and is very energy-intensive. The possibility of using Hydrated Cement Powder (HCP) to replace parts of Ordinary Portland Cement (OPC) in concrete has been considered to reduce the energy cost. The partial replacement of OPC for making new concrete intends to decrease the CO2 emissions associated with OPC production. However, it was reported that the HCP needs treatment to produce new concrete of the required mechanical strength. The thermal treatment method has proven to be successful in improving the properties of HCP before its reuse. Previous research has stated that for using HCP in concrete; the optimum strength is achieved by heating the HCP in the range of 400°C to 800°C. Among other factors, the type of cement used influences the optimum heating temperature and attainable strength. This paper confirms that 600°C is the best heating temperature when using the OPC type CEM I 52.5R. X-ray diffraction (XRD), differential scanning calorimetry (DSC), and thermogravimetry (TG) measurements were used to identify the crystalline phase transitions resulting from the thermal treatment. Scanning electron microscopy (SEM) was used to display the microstructure evolution. Furthermore, this research investigates how the OPC could be partially replaced by thermally treated HCP in mortar without affecting the mechanical strength.
.jpg "Gustave Semugaza, Masters photo")