Mechanical performance, hydration characteristics and microstructures of high volume blast furnace ferronickel slag cement mortar by wet grinding activation.

• Wet grinding was used to improve the activity of BFFS for high volume BFFS cement mortar. • The 28 d compressive strength of specimens with 50% and 70% BFFS (D50 = 2.5 μm) reach 109% and 97% of that of control cement specimens respectively. • The pozzolanic behavior and filling effect of superfine BFFS particles improve the microstructure and strength greatly. Replacement of cement clinker by industrial wastes has been verified as an effective way to reduce carbon emissions. To realize the application of blast furnace ferronickel slag (BFFS) in high volume in cement mortar, wet grinding was used to improve the activity of BFFS. Three fineness (D50 = 13 μm, 5 μm and 2.5 μm) and three contents (30%, 50% and 70%) of BFFS were investigated comparatively. Isothermal calorimetry, X-ray diffractometer(XRD), Thermal analyzer (TG), Fourier Transform Infrared (FTIR), Mercury injection apparatus (MIP) and Scanning Electron Microscope (SEM) were employed to examine the hydration process and microstructures. The results showed that the pozzolanic behavior and filling effect of BFFS could be improved remarkably by wet-grinding method. The compressive strength of specimens with 50mirc% and 70% BFFS (D50 = 2.5 μm) after curing 28 days could reach 109% and 97% of that of control cement specimens respectively. The results of XRD, TG and FTIR revealed that refined BFFS was involved in pozzolanic reaction at age of 3 days, the effect was more significant with the grinding duration extending. Furthermore, the pore size distribution and the porosity were optimized obviously. Results highlight that wet-grinding treatment of BFFS provided an effective way to improve the early and late age strength of high-volume BFFS cement mortar. [ABSTRACT FROM AUTHOR]