Freeze–Thaw Damage Mechanism and Performance of Coal Gangue Concrete

Abstract

To explore the frost damage characteristics of coal gangue and coal gangue concrete in cold regions, and to streamline the validation process of coal gangue applications in engineering fields, this paper conducted freeze–thaw cycle experiments on graded crushed rock (CR), graded coal gangue (CG 1 and CG 2), and coal gangue concrete. The frost damage degree of coal gangue was evaluated using indicators such as mass loss and crushing value. Evaluation criteria including dynamic modulus loss rate and mass loss rate were used to quantify the frost damage of concrete, and the frost damage mechanism of coal gangue concrete was explored through microscopic characterization. Additionally, a frost damage model for coal gangue concrete used in cold regions was established. The research indicates that due to the unique structural characteristics of coal gangue, there is a significant difference in frost resistance compared to CR. Additionally, the content of kaolinite in coal gangue has a profound impact on its frost resistance. Combining characterization analysis with theoretical analysis, the mechanism of frost damage in coal gangue concrete can be inferred. There are numerous capillary pores within the coal gangue concrete, located at the interface of the cement matrix or the coal gangue. Moreover, as coal gangue serves as coarse aggregate in concrete, its inherent laminar structure contains many pores, resulting in a strong water storage capacity within the concrete. Additionally, the expansion of kaolinite further damages the internal structure of the concrete. Subsequently, a frost damage model was established based on the replacement rate of coal gangue within the F100 frost resistance grade and the number of freeze–thaw cycles. This model simplifies the validation process for the frost resistance of coal gangue in engineering applications and provides guidance for coal gangue concrete projects requiring frost resistance within the F100 range.