Effect of coal gasification slag on the properties of gangue gypsum filling materials

ZHANG Haibo; GUO Zhaoyang; GUO Jinhui; ZHAO Dong; CHEN Yutai; WANG Fei

doi:10.16186/j.cnki.1673-9787.2022080027

Abstract：Objective By utilizing the spherical characteristics of coal gasification slag particles,this study investigates their influence on the flowability and strength of coal mine goaf paste backfilling materials,and analyzes their influencing mechanisms.Methods Used coal gangue aggregate backfill paste with a mass con-centration of 85%as the control group.The backfill paste fine coal gangue aggregate was replaced by the slag by 10%,20%,30%,40%,50%.The bleeding rate,slump,expansion,rheological yield stress,and plastic viscosity of the freshly mixed paste were tested separately.The compressive strength of the paste stone body was tested simultaneously.Results The results showed that with the increased of the slag replacement rate,the bleeding rate of the paste increased,the slump and elongation increased,and the rheological yield stress and plastic viscosity decreased.Compared with the control group,when the slag replacement rate was 10%,the yield stress and plastic viscosity of the paste decreased by 16.7%and 1.6%,respectively.Compared with the 10%substitution group,when the slag substitution rate was 20%,the yield stress and plastic viscosity of the paste are reduced by 47.4%and 15.0%,respectively.The rate of decrease significantly increases.As the slag replacement rate continued to increase,the yield stress and plastic viscosity of the paste gradually rose noe move.The early strength(3,7 d)of the paste stone body slightly decreased with the increased of the slag replacement rate,while there was no significant change in the later strength(28,60 d).Conclusion The coal gangue fine aggregate in the paste filling material was replaced by coal gasification slag,which could improve the flowability of the fresh paste.When the substitution rate reached 20%,the ball shaped slag particles could fully exert the ball lubrication effect between the multi edged coal gangue aggregates,re-duced the mechanical bite of the gangue aggregates,and significantly reduce the yield stress and plastic vis-cosity of the filling paste.And the slag had no significant effect on the later strength of the backfilling paste stone body.