The impact of temperature and pre-wetting of aggregates on rheological properties of coal gangue mortars

Mine filling and tunnel spraying projects pose high requirements on the rheological properties of cement-based materials. The types, conditions of fine sands and the exposed environment have significant effects on the rheological properties. In this light, this paper uses coal gangue sand instead of quartz sand as the fine aggregate of cement-based material and investigates the effect of temperature and aggregate prewetting on the rheological properties of mortar and its mechanism. Results show that the shear stress-shear rate relationship of coal gangue mortar conforms to the characteristics of Herschel-Bulkley (H-B) model, with higher rheological index (higher than 1) and higher consistency than that of quartz sand mortar. The apparent viscosity of coal gangue mortar decreases with increasing temperature, but the effect of aggregate prewetting is not significant. The yield stress of coal gangue mortar at 30 ℃ is 2.99 Pa, 1.45 times higher than that at 10 ℃, and 2.13 times higher after prewetting. The thixotropic ring area of coal gangue mortar is higher than that of quartz sand mortar, and the thixotropic ring area of pre-wetting coal gangue mortar is 398.4 Pa/s, while that of dry coal gangue mortar is 283.3 Pa/s. The obtained results are expected to provide evidence for the rational utilization of coal gangue sand and the design and preparation of rheological materials served in complex environment.