As an experimental study, the research in this paper was conducted to illustrate the influence of solids content and composition of cemented paste backfill (CPB) on the material's rheological and mechanical characteristics. A new type of CPB was used in this research, which was composed of waste rock as coarse aggregates, fly ash as fines, lime slag as activator proportions and ordinary Portland cement as binder. The mechanical strength of CPB improved significantly with an increase in the solids content, but the workability decreased because the water content decreased. When the solids content was 75% by weight (wt.%), the slump value was 165 mm, which met the requirement for pumping. At a solids content of 75%, the CPB also had an unconfined compressive strength (UCS) of 1.83 MPa, tensile strength of 0.401 MPa, and Poisson's ratio of 0.136 at a curing time of 28 days. Increasing the fly ash proportion caused the workability and mechanical strength of the CPB to increase until they reached maximum values, at which point subsequent increases caused the values to decrease. The workability of CPB reached its peak when fly ash proportion was 35 wt.%, and the mechanical strength reached its peak at 45 wt.%. The workability of CPB decreased as the lime slag proportion increased. The strength of CPB also increased with an increase in the lime slag proportion, however, only until it reached 12 wt.%, at which point the strength began to decline. The addition of more cement resulted in much better mechanical performance of the CPB samples, especially with longer curing times. However, workability of CPB increased as cement portion increased in the range of 0% to 2.5%, before decreasing over the range of 2.5%-5.0%. (c) 2017 Elsevier B.V. All rights reserved.