Abstract: Coal gasification slag (CGS) is a by-product of the coal gasification process,and the mineral phase containing amorphous silica-aluminate gives it the potential to be used as a cementitious material. In this study,the activation pretreatment of CGS was carried out by mechanical milling to explore the applicability of CGS in cementitious materials,and the hydration reaction process was analyzed by a series of characterization means,such as XRD,SEM,TG-DTG,and FTIR,to elucidate the mechanism of the milling time on the particle properties of CGS and the activity of volcanic ash. The results showed that the particle size of CGS showed a decreasing and then increasing trend with the increase of grinding time,and the characteristic particle size of CGS reached the minimum value when grinding for 80 min,and the D10 ,D50 and D90 were 1. 0 μm,4. 7 μm, and 23. 6 μm,respectively. The mechanically milled CGS for 80 min showed optimal cementing performance,and the 28 d activity index of cementitious sand was 91. 5%. The 28 d compressive strength was up to 46. 5 MPa,which was 120. 4% higher than the compressive strength of the unactivated cementitious sand,and met the requirements for the use of volcanic ash mixes. In addition,the mechanical grinding process destroys the crystal structure of CGS,which is conducive to the release of active substances,and generates a large number of hydration products dominated by calcite,Ca(OH)2 and C-(A) -S-H gel,which has a significant enhancement effect on the activity of volcanic ash. From the microscopic morphology,it can be seen that with the increase of activation time,the microstructure of the hydration products is gradually uniform and dense. This study provides a green and low-carbon solution for the resourceful,large-scale and high-value utilization of coal gasification slag,which is of great significance for achieving carbon peak and carbon neutrality. 

Key words: coal gasification slag,mechanical grinding,particle characterization,volcanic ash activity