scholarly journals Effect of High Mixing Intensity on Rheological Properties of Cemented Paste Backfill

Minerals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 240 ◽  
Author(s):  
Liuhua Yang ◽  
Hongjiang Wang ◽  
Hong Li ◽  
Xu Zhou
Keyword(s):  
Rheological Properties ◽  
Fine Particles ◽  
Rheological Parameters ◽  
Cemented Paste Backfill ◽  
Mixing Intensity ◽  
Thixotropic Behavior ◽  
Paste Backfill ◽  
Structural Breakdown ◽  
Physical And Chemical ◽  
Insight Into

Cemented paste backfill (CPB) consists of a mixture of fine particles, mainly consisting of tailings and cement dispersed in water. Therefore, it is necessary to introduce an intensive shearing force into the paste during mixing in order to maintain an equilibrium between agglomeration and dispersion. It is influential for the macroscopical fluidity and rheological properties when changes occur in the microstructure of CPB under shear. However, the research on how mixing affects the properties of CPB is still in its infancy. This paper puts an insight into the relation between the mixing intensity and the rheological behavior of the CPB. It can be demonstrated that two threshold mixing intensities exist in this process. After passing the first or lower threshold, the rheological parameters (yield stress and viscosity) of the paste decrease. After passing the second threshold, a continued increase is observed. The changes in rheological properties are connected with physical and chemical changes in the microstructure of the CPB. The results are discussed in light of the three concepts “structural breakdown”, “thixotropic breakdown”, and “thixotropic behavior” of rheological properties of CPB.

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.

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 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 Experimental Study on Mechanical Properties of Cemented Paste Backfill under Temperature-Chemical Coupling Conditions

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Yin Liu ◽  
Hao Li ◽  
Haifeng Wu
Keyword(s):  
Mechanical Properties ◽  
Structural Model ◽  
Sulfate Solution ◽  
Sodium Sulphate ◽  
Effect Of Temperature ◽  
Cemented Paste Backfill ◽  
Chemical Coupling ◽  
Deterioration Mechanism ◽  
Paste Backfill ◽  
Physical And Chemical

To investigate the effect of temperature-chemical coupling on the mechanical properties of cemented paste backfill, three temperatures (20°C, 35°C, and 50°C) and sodium sulfate solution mass concentrations (3%, 5%, and 7%) are applied to simulate the complex environment in a mine. Uniaxial compressive strength and the CPB stress-strain relationship are investigated by applying stress, and the deterioration mechanism was analyzed theoretically according to physical and chemical reactions. At the same time, a structural model of the CPB deterioration mechanism under TC coupling is constructed. Combined with analysis through X-ray diffraction and scanning electron microscopy, it is shown that ettringite and gypsum are the main erosive substances that destroy the structure of CPB and that increased temperatures accelerate the chemical reaction. The concentration change consumes calcium hydroxide, changing the relationship between ettringite and gypsum. Sodium sulphate crystallization is the main form of physical deterioration. The continuous load accelerates the inelastic deformation time of CPB, resulting in a large yield deformation process.

scholarly journals Rheological characterisation of chitosan/sodium lauryl ether sulfate complexes

2019 ◽  
pp. 152-162
Author(s):  
Jelena Milinkovic-Budincic ◽  
Lidija Petrovic ◽  
Jadranka Fraj ◽  
Sandra Bucko ◽  
Jaroslav Katona ◽  
...  
Keyword(s):  
Rheological Properties ◽  
Chemical Properties ◽  
Cationic Polyelectrolyte ◽  
Rheological Parameters ◽  
Mass Ratio ◽  
Sodium Lauryl Ether Sulfate ◽  
Ether Sulfate ◽  
Lauryl Ether ◽  
Pharmaceutical Industries ◽  
Physical And Chemical

Chitosan is a cationic biopolymer, which attracts more and more attention in recent years, due to its exceptional physical and chemical properties, expressive biocompatibility and possibilities of obtaining from renewable sources. Formed polymer/surfactant complexes affect changes in the rheological properties and the final result is the formation of coacervates. The purpose of this study was to investigate the rheological properties of aqueous solutions of cationic polyelectrolyte, chitosan and sodium lauryl ether sulfate (SLES), an anionic surfactant, widely used in the cosmetics industry. Using the Thermo Haake RS600 rheometer, changes in the rheological and elastic properties of chitosan and SLES mixtures have been identified, gained as a result of the interaction of the components. In all examined samples coefficient of thixotropy was increasing with increase SLES concentration and achieves a maximum value at the mass ratio chitosan:SLES 1:2, after which it reduces. The oscillatory measurements in mixtures, performed by amplitude sweep method at low oscillating frequency 1 Hz, show that the linear viscoelastic region increases with increasing SLES concentration up to the same chitosan:SLES mass ratio. By monitoring the changes in the rheological parameters of the mixtures over five days, it was observed that the viscosity, the coefficient of thixotropy and elasticity were increasing, indicating that changes in the system occur over a longer period of time. In that manner, obtained results indicate the possibility of using rheological methods for a more detailed description of the interaction in the chitosan/SLES mixtures, important for their application in cosmetics and pharmaceutical industries.

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