Abstract: Coal paste backfilling material (CPBM) is composed of coal gangue, flyash, ordinary portland cement and tap water. In order to identify the properties of each raw material, the mineral composition, chemical composition of coal gangue flyash have been analyzed; the compressive strength, porosity and electrical resistivity have been studied at different curing times. The samples taken from curing time of 7 d, 14 d and 28 d, have been evaluated for their mineral composition and microstructure. The law of CPBM property with increasing curing time has been analyzed, and the correlation among the compressive strength, porosity, resistivity and hydrating process has also been deeply discussed. The results indicate that firstly, with the curing time increasing, compressive strength and electrical resistivity are increasing, while porosity and small pore content are reducing. Secondly, hydrated and pozzolanic reaction occur in the change of CPBM property, with calcium hydroxide, C-S-H gel and ettringite being the reaction products. The calcium hydroxide crystal is only found at the curing time of 7 d, not at 14 d and 28 d, and the types and quantities of ettringite crystal at 28 d are more than at 7 d and 14 d. The crystal structure of 28 d presented more slender with the curing time increasing. Thirdly, the hydrated and pozzolanic reaction are the two primary reasons causing the change of performance of CPBM strength with the change of curing time. Moreover，there is some interrelation between the performances.

Key words: paste backfilling material, compressive strength, porosity, electrical resistivity, hydrated and pozzolanic reaction