Experimental study on durability of red mud-blast furnace slag geopolymer mortar

Red mud (RM) is an industrial solid waste with high alkalinity. The preparation of RM as a geopolymer for construction is an effective means of recovery and treatment of RM. However, the durability of the geopolymer containing red mud is an important reason for restricting its promotion. In this paper, chloride ion permeability of geopolymer mortar and cement mortar was measured by two types of electric flux methods. Besides, corrosion potential and corrosion current of steel bars in geopolymer mortar and cement mortar conditioned in artificial climate and natural environment were studied, respectively. The results showed that the chloride ion resistance of the geopolymer was better than that of the cement mortar. The improved ASTM C1202 method was suitable for the evaluation of chloride ion permeability of geopolymer mortar since it could effectively solve the problem of long immersion time. The ASTM C876 Standard was not suitable for judging the corrosion state of steel bars in geopolymer mortar since the corrosion current method can better reflect the corrosion of steel bars in geopolymer than the corrosion potential method. The critical content of chloride ion in the geopolymer mortar (0.5 wt%) that causes the steel to passivate is significantly higher than that of cement mortar (0.3 wt%). Geopolymer mortar exhibited a stronger ability to protect steel bars from corrosion than cement mortar due to its density and resistance to ion penetration.