China
Africa
Explore chapters and articles related to this topic
Rheological yield stress measurement of paste fill: New technical approaches
Published in Ferri Hassani, Jan Palarski, Violetta Sokoła-Szewioła, Grzegorz Strozik, Minefill 2020-2021, 2021
Maria Silva, Martin Hansson, Matilde Costa e Silva
Yield stress is the critical shear stress that must be exceeded before irreversible deformation and flow can occur. This property is considered by many authors as the most important rheological parameter for the design and operation of a paste system. Physical and chemical/mineralogical properties of paste fill have a significant influence on yield stress, such as: solids content, percentage of cement, particle size distribution (PSD), particle shape, mineralogy, surface properties of tailings, among others.
An introduction to Deep Cone™ thickening technology and its application
Published in Gülhan Özbayoğlu, Çetin Hoşten, M. Ümit Atalay, Cahit Hiçyılmaz, A. İhsan Arol, Mineral Processing on the Verge of the 21st Century, 2017
J.L. Shelley, L. MacNamara, S. Slottee
It is accepted that a minimum quantity of fines (<20μm) is required to form a paste, this is approximately 15–20% in most cases (Slottee & Schreiber 1998). The rheology of that paste will change according to many variables including particle size distribution, liquid viscosity and solid concentration (Klepper et al 1998).
Effect of ultrasonic coupling media and surface roughness on contact transfer loss
Published in Cogent Engineering, 2022
Acoustic contact between probe (probes) and material has to be provided, normally by the application of a coupling medium. A proper coupling media should be used between the probe and the test specimen to achieve the transmission of ultrasonic energy by eliminating air. The coupling media should be selected to suit the surface conditions and the irregularities of the surface to ensure adequate coupling. Contact transfer losses represent the reduction of sound transmission across the interface between a probe and a test object. Different coupling media can be used, but their type shall be compatible with the materials to be examined. Examples include water (possibly containing some agent, e.g., wetting, anti-freeze, corrosion inhibitor), contact paste, oil, cellulose paste (containing water), glycerine, petroleum greases, silicone grease, wallpaper paste, and various commercial paste-like substances. The characteristics of the coupling media shall remain constant throughout the verification, calibration operations, and examination. The coupling media shall be suitable for the temperature range in which it will be used. If the constancy of characteristics cannot be guaranteed during calibration and examination, a transfer correction shall be applied (Bar-Cohn & Mal, 1989, p. 543; Workman et al., 2007, pp. 221–223; International Organization for Standardization, 2014a, p. 5, 2019, p. 3; International Atomic Energy Agency, 2018, pp. 203–204; Kumar, 1996).
Factors influencing the structure build-up of fresh cement asphalt emulsion paste
Published in Road Materials and Pavement Design, 2018
Fresh CA mortar should be highly flowable mortar, which does not require any external vibration during placement for the grouting technology. The high flowability is usually accompanied by separation of constituents (Ozkul & Dogan, 2006). Design of the workability should carefully balance the flowability and segregation resistance. It is reported that the flowability is related to the apparent viscosity under shear (Betancourt, 1988; Cremonesi, Ferrara, Frangi, & Perego, 2010; Ferrara, Cremonesi, & Tregger, 2012). Segregation of course particles can occur under both static (at rest) and dynamic (flowing) conditions. The yield stress is a criterion whether the static segregation of course particles can occur or not (Roussel, 2006a; Saak, Jennings, & Shah, 2001). If the yield stress cannot resist the segregation of course particles at rest, the settling velocity of course particles is governed by the apparent viscosity of paste (Roussel, 2006a; Saak et al., 2001). The dynamic segregation resistance of course particles during placement is related to the apparent viscosity (Saak et al., 2001; Tregger, Gregori, Ferrara, & Shah, 2012). Therefore, the segregation resistance of course particles is dependent on both the yield stress and apparent viscosity of paste. The apparent viscosity and yield stress of paste are related to the thixotropic behaviour. The apparent viscosity of paste decreases with shear time under shear, and it increases with resting time when the shear loading is removed (Roussel, 2005, 2006b). For the thixotropic behaviour, paste can behave as a good fluid during placement, but build up an internal structure to resist the sedimentation of the coarse particles at rest. Therefore, the workability of CA mortar is governed by the rheology and thixotropy of fresh CA paste. It is of great importance to increase the fundamental knowledge about the rheology and thixotropy of fresh CA paste when studying the workability of CA mortar.