Evaluation on recycled clinker production and properties from regeneration of completely recycle concrete

Abstract In this study, a completely recyclable concrete (CRC) was prepared based on the composition of raw cement meal. 97.78 wt% waste CRC produced after demolition was incorporated in raw cement meal with minor correction admixtures. Recycled cement clinker was produced at four different temperatures (1300 °C, 1350 °C, 1400 °C, and 1450 °C). The burnability, X-ray diffraction (XRD) patterns, and properties of the hydration products were compared with those of classical clinker. The results show that the introduction of trace elements and impurities in waste CRC can effectively reduce the temperature and viscosity of the liquid phase. Compared to the reference raw cement meal, the temperature at which a large amount of liquid phase recycled raw meal appears is reduced by approximately 28 °C, and the temperature at which the sintering reaction of recycled raw meal occurs is reduced by approximately 200 °C. Therefore, the apparent activation energy of C3S formation is reduced by 33.4%. The optimum calcination temperature reduced by about 50℃ compared to that of classical raw meal. The recycled cement obtained from CRC has slower hydration activity and lower strength in the early stage, but exhibits a strong hydration capacity in the later stage. The 3-day and 28-day strength of the recycled cement is decreased by 22.28% and 24.20%, respectively, compared to that of the reference cement.