Study on mechanical properties and freeze-thaw damage law of steel fiber coal gangue concrete

The massive accumulation of coal gangue (Waste from coal mining) harmed the environment and occupied the land. Replacing aggregate with coal gangue (CG) is an effective way to solve the accumulation problem. The purpose of this paper is to expand the utilization of CG in construction in cold area. Steel fiber (SF) is used as enhancement method to improve the performance of coal gangue aggregate concrete (CGC). In addition, there are few researches on the relationship between frost resistance and the age of SFCGC materials, and they mainly focus on the material level. Therefore, the optimal mixture of SFCGC is studied by orthogonal test. On this basis, the frost resistance and bearing capacity damage of SFCGC and SFCGC columns at different ages during freeze-thaw cycle (FTC) were investigated. Indicate that the optimal mixture is determined as 35 % coal gangue ceramsite (CGc), 35 % coal gangue ceramic sand (CGs), and 0.9 % SF. The ranking of factors affecting mechanical properties is analyzed as SF content > CGc substitution rate > CGs substitution rate. And the GM (1,4) strength prediction grey model of SFCGC is established. SFCGC can reach 125 FTCs, and the material freeze-resistance diminishes as the curing age shortens, and the loss rate of compressive strength boosts with the increase of FTCs (reached 61.9 % in 125 FTC). Under identical conditions, the SFCGC column with steel reinforcement exhibited more severe deterioration, culminating in failure after 100 FTCs. The damage laws and failure patterns of SFCGC reinforced columns under FTCs are obtained. The established model can provide effective support for the application of SFCGC in engineering.