Influence of shell ash on pore structure and mechanical characteristics of cemented tailings backfill

Aiming to investigate the impact of different shell ash (SA) dosages and particle sizes on the pore structure, mechanical properties, and microstructure of the cemented tailings backfill, NMR tests, the uniaxial compression tests, AE tests, and SEM tests were carried out in this paper. The following conclusions were reached: (1) As the dosage of SA increases, macro pores gradually transform into secondary pores and micro pores, the pore structure distribution is rationalized. The 1250 mesh cemented tailings backfill (SACTB) exhibits the highest degree of hydration reaction, followed by the 3000 mesh SACTB. Thus, adding SA to the filling material significantly increases macroscopic mechanical properties of SACTB. (2) SACTB is primarily dominated by tensile damage, with a small proportion being shear damage or accompanied by shear damage. (3) AE cumulative ringing counts in the time range through the rapidly growing, stabilizing, and continuing rising in three phases. The AE process can be summarized as a rising, stable, and active period. (4) For the improvement of the microstructure and macroscopic mechanical properties of SACTB, it is recommended to use 1250 mesh SA when the dosage is be-tween 3 % and 5 %. Similarly, when the dosage is between 8 % and 10 %, it is advisable to use 3000 mesh SA.