Mechanical and Durable Performance of Lime-Steel Slag-Coal Gangue Mixtures Prepared by a Uniform Design Method for Pavement Base Applications

To reduce the accumulation of coal gangue and steel slag, a mixture of lime-steel slag-coal gangue for pavement base was prepared. Six groups of lime-steel slag-coal gangue mixtures were designed using a uniform design method. The 7 d unconfined compressive strength, 180 d compressive resilience modulus and 180 d splitting tensile strength tests, the freeze-thaw cycles, and the wet and dry cycles were carried out to study the mechanical properties, frost resistance and water stability. The expansion effect of f-CaO in steel slag on the mixtures was investigated by water immersion. SEM was used to explore microscopic changes in the mixtures. The field application of coal gangue mixture was carried out for two years. The results show that the regression equations obtained by the uniform test have high accuracy. With the increase of lime in the mixture, the mechanical strength, frost resistance, and water stability of the mixtures were first enhanced and then decreased. With the increase of steel slag, the unconfined compressive strength increased, the compressive resilience modulus increased at first and then decreased, the splitting tensile strength decreased, the BDR value decreased, and the strength loss of water stability increased gradually. The internal structure of the mixtures is stable and has good frost resistance. There is no obvious microscopical difference before and after freeze-thaw cycles. The immersion expansion rate of the mixtures was far less than 1.5 %.