scholarly journals Specific Mixing Energy of Cemented Paste Backfill, Part II: Influence on the Rheological and Mechanical Properties and Practical Applications

Minerals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1159
Author(s):  
Reagan Kabanga Dikonda ◽  
Mamert Mbonimpa ◽  
Tikou Belem
Keyword(s):  
Mechanical Properties ◽  
Rheological Properties ◽  
Yield Stress ◽  
Specific Energy ◽  
Distribution System ◽  
Flow Index ◽  
Cemented Paste Backfill ◽  
Practical Applications ◽  
Mixing Energy ◽  
Paste Backfill

The rheological properties (yield stress, flow index and infinite dynamic viscosity) and mechanical properties (unconfined compressive strength, UCS) of different cemented paste backfill (CPB) recipes must be determined during the laboratory optimization phase. However, the influence of the mixing procedure on these properties has scarcely been studied so far. The objective of this paper is to assess to what extent these properties depend on the specific mixing energy (SME) for a given type of mixer. CPB recipes were prepared based on two types of tailing (CPB-T1 and CPB-T2, also referred to as T1 and T2) at a fixed solid percentage for each type of tailing using the Omcan laboratory mixer. A mixture of 80% slag and 20% GU was used as a binder. The mixing time and the rotation speed of the mixer were successively varied. For each recipe prepared, we determined the SME, the rheological properties of fresh CPB (at the end of mixing) and the UCS at 7, 28 and 90 days of curing. The results show that yield stress and infinite viscosity decreased when SME increased in an interval going from 0.3 to 3.8 Wh/kg and 0.6 to 6 Wh/kg for CPB-T1 and CPB-T2, respectively. An increasing trend in UCS with increasing SME was also observed. Empirical equations describing the change of the rheological properties with the SME are used to estimate the change in rheological properties of CPB along the distribution system, considering the specific energy dissipation during CPB transportation. A mixing procedure for obtaining CPB mixtures that are representative of CPB deposited in underground mine stopes is suggested for laboratories who currently use a same mixing procedure, irrespective of the variable field specific energy.

scholarly journals Shear thinning and thickening of cemented paste backfill

2019 ◽  
Vol 29 (1) ◽  
pp. 80-93 ◽  
Author(s):  
Liuhua Yang ◽  
Hongjiang Wang ◽  
Aixiang Wu ◽  
Hong Li ◽  
Arlin Bruno Tchamba ◽  
...  
Keyword(s):  
Shear Rate ◽  
Rheological Properties ◽  
Yield Stress ◽  
Shear Thinning ◽  
High Shear ◽  
Cemented Paste Backfill ◽  
Concentrated Suspension ◽  
History Effects ◽  
Paste Backfill ◽  
Shear History

Abstract Cemented paste backfill (CPB) is considered to be a concentrated suspension in which tailings are bonded together by the hydraulic binder and water, and it has a high solid volume concentration (≥50 vol.%). Although the shear thinning and thickening of CPB has been extensively reported in literature, the shear history effects have been ignored in previous studies. In this paper, by using rheometer and Focused Beam Reflectance Measurement, the relationship between the rheological properties and microstructure of the paste under different shear histories was studied. The results have shown that at a low shear rate, CPB revealed shear thinning, low yield stress and low index parameters; while exhibited shear thickening, high yield stress and high consistency index when at high shear rates of shear history. This agreed with the general trends shown in the FBRM analysis. It was proposed that the action of shear is beneficial to particle dispersion, whereas a high shear rate history tends to promote the aggregation of particles. It was revealed that both shear thinning and thickening of paste are related to the situation of particles (flocculation, dispersion and aggregation), and shear history effects play an important role in rheological properties of CPB.

scholarly journals Rheological Properties of Ultra-Fine Tailings Cemented Paste Backfill under Ultrasonic Wave Action

Minerals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 718
Author(s):  
Weicheng Ren ◽  
Rugao Gao ◽  
Youzhi Zhang ◽  
Maoxin Hou
Keyword(s):  
Rheological Properties ◽  
Yield Stress ◽  
Ultrasonic Wave ◽  
Mass Concentration ◽  
Wave Action ◽  
Cemented Paste Backfill ◽  
Fine Tailings ◽  
Paste Backfill ◽  
Rheological Test ◽  
Positive Effect

Ultra-fine tailings cemented paste backfill (UCPB) exhibits special rheological characteristics with the effect of an ultrasonic sound field. In this study, in order to explore the thickening effect of slurry under ultrasonic wave action, we examined the rheological properties with ultrasonic wave tests of UCPB and the rheological properties after ultrasonic wave tests of UCPB. We found that the rheological curve of the slurry changed; the Herschel–Bulkley (HB) model in the initial state transformed into the Bingham model under the action of ultrasound. Ultrasonic waves have a positive effect on reducing slurry viscosity and yield stress. The rheological test of the slurry with ultrasonic wave action had a positive effect on significantly reducing the apparent viscosity and initial yield stress of slurry with a 62% mass concentration. The rheological test of slurry with ultrasonic wave action and the rheological test after ultrasonic wave action both have positive effects on reducing the viscosity and yield stress of the slurry with a 64% to 68% mass concentration; the overall effect of reducing the viscosity and yield stress of UCPB is greater after ultrasonic wave action of UCPB.

scholarly journals Using Coupled Rheometer-FBRM to Study Rheological Properties and Microstructure of Cemented Paste Backfill

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Hongjiang Wang ◽  
Liuhua Yang ◽  
Hong Li ◽  
Xu Zhou ◽  
Xiaotian Wang
Keyword(s):  
Shear Rate ◽  
Rheological Properties ◽  
Yield Stress ◽  
Rheological Behavior ◽  
Shear Thickening ◽  
Threshold Value ◽  
Rheological Parameters ◽  
Cemented Paste Backfill ◽  
Reflectance Measurement ◽  
Paste Backfill

Rheological properties, such as the yield stress, viscosity, and thixotropy, are related to the microstructure of cemented paste backfill (CPB). To highlight the relationship, two instruments were combined to measure the changes in the microstructure and the rheological properties of CPB simultaneously. In this way, the particle/agglomerate size distribution characterized by the focused beam reflectance measurement (FBRM) and the rheological factors measured by the rheometers could be directly linked. The results show that when under shearing, the intrinsic network structure of CPB responds to the shear-induced stresses with the interference of interparticle forces, leading to changes in the rheological behavior. Shear thinning can be found in CPB suspensions with a microstructure that is either loose interconnection or random. With an increase in the shear rate, random collisions among particles become organized in the flow, lowering the yield stress and viscosity. However, when the shear rate exceeds a certain threshold value, the rheological parameters change as a result of shear thickening. The results of this study contribute to better understanding of the complex rheological behavior of CPB.

scholarly journals Specific Mixing Energy of Cemented Paste Backfill, Part I: Laboratory Determination and Influence on the Consistency

Minerals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1165
Author(s):  
Reagan Kabanga Dikonda ◽  
Mamert Mbonimpa ◽  
Tikou Belem
Keyword(s):  
Mixing Time ◽  
Companion Paper ◽  
Cemented Paste Backfill ◽  
Practical Applications ◽  
Power Meter ◽  
Mixing Energy ◽  
Mixing Parameters ◽  
Paste Backfill ◽  
Semi Empirical ◽  
Load Mass

Slump determination is widely used to assess the consistency and transportability of fresh cemented paste backfill (CPB). CPB consistency can depend on the mixing procedure for CPB preparation. In this paper, a method was developed to determine the specific mixing energy (SME) that is dissipated during the preparation of CPB mixtures and to analyze its effect on CPB consistency. For this purpose, CPB recipes were prepared using two tailings and the mixing parameters (mixing time and speed and load mass) were successively varied. SME was determined for each mixture using a power meter equipped with an energy recording system mounted on a laboratory Omcan mixer. Slump was also determined for each mixture. A semi-empirical model was then developed to predict SME as a function of the mixing parameters. Results showed that predicted SME compared well with measured SME during CPB preparation. Results also showed that slump increased with increasing SME. The influence of SME on the rheological and mechanical properties of CPB and practical applications are presented in a companion paper.

Effects of temperatures and pH values on rheological properties of cemented paste backfill

2021 ◽  
Vol 28 (6) ◽  
pp. 1707-1723
Author(s):  
Qin-li Zhang ◽  
Yi-teng Li ◽  
Qiu-song Chen ◽  
Yi-kai Liu ◽  
Yan Feng ◽  
...  
Keyword(s):  
Rheological Properties ◽  
Cemented Paste Backfill ◽  
Ph Values ◽  
Paste Backfill

scholarly journals Investigating the Effect of Solid Components on Yield Stress for Cemented Paste Backfill via Uniform Design

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Yong Wang ◽  
Aixiang Wu ◽  
Lianfu Zhang ◽  
Fei Jin ◽  
Xiaohui Liu
Keyword(s):  
Yield Stress ◽  
Mass Fraction ◽  
Cement Content ◽  
Uniform Design ◽  
Free Water ◽  
Experimental Program ◽  
Cemented Paste Backfill ◽  
Free Water Content ◽  
Key Factor ◽  
Paste Backfill

Cemented paste backfill (CPB) technology has been applied quite popular around the world. Yield stress is a key factor determining whether CPB could be transported. In order to reveal the effect of solid components on yield stress of CPB, a uniform design experimental program (four factors and six levels) was conducted to test the rheological property of a mine’s CPB. The tested four factors including mass fraction, cement versus other solids ratio, coarse tailings, and gravel contents were considered during the experiment design. Likewise, six experimental levels were given to each factor. Results of the test show that yield stress increased with the mass fraction and cement content. However, the trend reversed for the content of coarse tailings and gravel. Contribution of the four factors to yield stress in descending order is mass fraction > content of gravel > content of coarse tailings > cement versus other tailings ration. Effect of solid components on the yield stress of CPB is mainly due to the different flocculation structure inside the CPB. These various flow structures result in the different free-water content of CPB, leading to a different yield stress value.

scholarly journals Experimental Investigation on Mechanical Properties of In Situ Cemented Paste Backfill Containing Coal Gangue and Fly Ash

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Xinguo Zhang ◽  
Shichuan Zhang
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Fly Ash ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Friction Angle ◽  
Coal Gangue ◽  
Cemented Paste Backfill ◽  
Paste Backfill

Cemented paste backfill containing coal gangue and fly ash (CGFACPB) is an emerging backfill technique for coal mines that allows environmentally hazardous coal gangue and fly ash to be reused in the underground goaf. Meanwhile, CGFACPB can provide an efficient ground support and reduce the surface subsidence. Due to the difference of consolidation environment between the laboratory and the field, the mechanical properties of the cemented paste backfill vary significantly. In this paper, the core specimens were collected from an underground coal mine where the CGFACPB was used for coal mining, and the mechanical properties of the collected specimens were investigated. The cores were obtained from the underground coal mine, and then the standard cylinders or discs were prepared in laboratory. The uniaxial compressive strength (UCS), Young’s modulus, and Poisson’s ratio were determined by the compression tests, and the tensile strength was achieved by the Brazilian test. Then the internal friction angle and cohesion were calculated using the improved Mohr–Coulomb strength criterion. The results showed the development of UCS can be divided into four stages, and the final long-term stable value was about 5.1 MPa. The development of Young’s modulus had similar trend. Young’s modulus had a range from 550 MPa to 750 MPa and the mean value of 675 MPa. Poisson’s ratio gradually increased with the underground curing duration and eventually approached the stable value of 0.18. The failure type of compression samples was mainly single-sided shear failure. The development of tensile strength can be divided into two stages, and the stable value of the tensile strength was about 1.05 MPa. The development of cohesion can be divided into four stages, and the stable value was about 1.75 MPa. The stable value of the internal friction angle was about 25°. This study can provide significant references for not only the long-term stability evaluation of CGFACPB in the field but also the design of optimal recipe of the cemented paste backfill (CPB).

Relevance of SEM to Long-Term Mechanical Properties of Cemented Paste Backfill

2018 ◽  
Vol 36 (4) ◽  
pp. 2171-2187 ◽  
Author(s):  
Naguleswaran Niroshan ◽  
Ling Yin ◽  
Nagaratnam Sivakugan ◽  
Ryan Llewellyn Veenstra
Keyword(s):  
Mechanical Properties ◽  
Cemented Paste Backfill ◽  
Paste Backfill
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