The Rheological Properties and Strength Characteristics of Cemented Paste Backfill with Air-Entraining Agent

Abstract

Clogging pipelines is one of the most common and urgent problems in paste backfill mining. The aim of the present study was to solve the problem of pipe blockage in paste backfill mining. In this paper, paste mixed with coal gangue, fly ash, cement, and additives is used to investigate the influence of three air-entraining agents (AEAs) (including sodium dodecyl sulfate (SDS), triterpene saponin (SJ), and sodium abietate (SA)) on the flow characteristics and strength characteristics of the paste. A series of relevant tests was conducted on the paste, such as air content experiments, slump and expansion experiments, viscosity and yield stress tests, and the uniaxial compressive strength (UCS) test. The results show that the air content of the paste increases with increasing AEA content, but the increase is limited and reaches a maximum at 0.9 AEA. The slump of the paste increased by up to 10–13 mm, and expansion increased by up to 66–130 mm compared to the paste without AEA. The viscosity of the paste decreased by up to 0.13–0.20 Pa·s, and the yield stress decreased by 81.47%–93.7% of the original. The strength of the paste was also reduced, and after 28 days of curing, the strength was reduced by up to 1–1.2 MPa. Taking into account the strength requirement of 3 MPa for the paste from the Linxi mine, it was considered that the dosage of 0.9 B was a good choice, as it could better change the flowability of the paste and reduce the pipeline transportation resistance and transportation energy consumption. At the same time, the strength was also acceptable. The study in this paper can provide a reference for performance studies of pastes mixed with coal gangue, fly ash, cement, and additives as materials.

Experimental Study on the Cross-Scale Relationship of Cemented Backfill under the Action of an Air-Entraining Agent

“…It can be observed in the figure that strength decreases as the fractal dimension increases, which is consistent with the research results of other scholars [15,17]. Their relationships are as follows: y = −0.007e (66.667×(x−2.711)) + 0.890 (6) y = −7.981x + 23.488 (7) y = −13.144x + 39.417 (8) where x represents the fractal dimension, and y represents strength (MPa). It can be observed in the formulas that the relationships differ within the different pore size ranges.…”

“…However, mines also have certain requirements for backfill materials, with the basic requirement being to achieve a certain level of fluidity and strength [4,5]. Adding an air-entraining agent (AEA) can improve the flowability of the filling slurry, but it also has a certain impact on the strength [6,7]. The AEA mainly changes the pore structure of the backfill material, and it also has a certain impact on the hydration reactions, thereby affecting the strength.…”

Preparation of Paste Filling Body and Study on Supported Transportation Laws Using Flac3D Simulation

“…Five different experimental groups of coal mine paste proportions were carried out. It was known that the flow characteristics of the GFB in the pipeline had less relative misalignment in the pipeline conveying process [30]. A time gradient was set to comprehensively compare the fluidity after the storage time from the beginning of mixing completion to the pipeline conveying process.…”

Investigation of Viscoelastic-Plastic Properties of Fresh Cemented Gangue Fly Ash Backfill Slurries

“…As one of the most significant fossil energy sources in industry, coal is crucial to the social and economic advancement of people in the majority of the world's nations [1]. With the development of the economy, the energy consumption of human beings has increased, and more and more coal needs to be mined [2].…”