Microscale Analysis Of Cemented Paste Backfill Microform
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Microscale Analysis Of Cemented Paste Backfill Microform
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Author : Dragana Simon
language : en
Publisher: Library and Archives Canada = Bibliothèque et Archives Canada
Release Date : 2005
Microscale Analysis Of Cemented Paste Backfill Microform written by Dragana Simon and has been published by Library and Archives Canada = Bibliothèque et Archives Canada this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with categories.
This study shows that wave-based techniques provide insight into some of the factors that affect the behaviour of CPB. Electromagnetic wave-based measurements are sensitive to changes in structure, free water content, bound water content, and ion availability and/or mobility. This research shows that the effective conductivity is a useful parameter to monitor the hydration process, even in low cement content pastes. Shear wave-based measurements are a useful tool to monitor the stiffness evolution in CPB. Apparent yield stress measurements are sensitive to particle-particle interactions and reflect changes in the material's composition, including water content, binder content and type, and chemical additives. All tests show that during the early stages, Portland cement hydration has little effect on the microstructure development, stiffness and flow characteristics of cement-containing pastes. The macroscopic properties of cemented paste backfill (CPB), including fluidity and strength, depend on particle-particle and particle-fluid interactions; thus, it is important to determine the fundamental interactions between the paste constituents to optimize paste design. Specific topics of interest in this study include the effects of paste composition (e.g., binder content and type, and pore fluid chemistry) on the microstructure development, and electromagnetic, rheological and mechanical properties (e.g., setting time, unconfined compressive strength and stiffness) with time. The effect of the pore fluid chemistry on the properties of the CPB depends on the type and amount of the additive. In CPB, calcium chloride and sodium chloride accelerate cement hydration and improve the UCS during the first six months of hydration. Conversely, ferric chloride and hydrochloric acid retard the hydration and setting of CPB. The tested superplasticizers retard cement hydration, increase the UCS and lower the apparent yield stress of CPB. A drawback to using the superplasticizers tested in this study is that a high shear stress is required to re-initiate flow in the pastes.
In Situ Properties And Liquefaction Potential Of Cemented Paste Backfill Microform
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Author : Kim-Anne Le Roux
language : en
Publisher: National Library of Canada = Bibliothèque nationale du Canada
Release Date : 2004
In Situ Properties And Liquefaction Potential Of Cemented Paste Backfill Microform written by Kim-Anne Le Roux and has been published by National Library of Canada = Bibliothèque nationale du Canada this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004 with categories.
Mercury intrusion porosimetry as well as semi-qualitative image analysis techniques such as scanning electron microscopy, microCT and visual analysis software were used to develop an understanding of the structure developed in field CPB in both the macro and micro scale. Standard oedometer consolidation testing with a modified loading rate was used to investigate the interrelationship of loading rate, which simulates rate of paste accumulation in a stope and the hydration of binder of the paste. The results show that the structure that develops is sensitive to both the binder content of the CPB and the rate of paste accumulation. Cemented paste backfill (CPB) has gained increasing popularity in the last 5 to 10 years and is used routinely in several mines. However, most of the CPB designs are based on laboratory prepared CPB material properties and there is growing awareness that the field CPB may be different from the laboratory prepared material. A field based investigation quantified the extent to which the field material differs from laboratory material. Not only is the field material more heterogeneous than expected, but on average it has a higher void ratio and a lower degree of saturation. These differences impact the performance of the field material. Numerical analysis using FLAC 3D was undertaken to show the influence of the field condition on the stability of the CPB. This research provides practical recommendations for industrial application and provides a framework for further investigation of CPB. Several research projects arising from this initial work are already underway through the Lassonde Institute at the University of Toronto, and several more are at the proposal stage. Static and dynamic liquefaction testing of early age CPB showed that liquefaction due to self-weight alone is unlikely but that blasting too close to the CPB can mobilize the material. Practical recommendations such as limiting blasting in proximity to early age CPB and cordoning off vulnerable areas during the critical initial 24 hr period that the paste is vulnerable to dynamic liquefaction. The cyclic liquefaction results are believed to be the first reported for cemented paste backfill.
Cemented Paste Backfill
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Author : Yong Wang
language : en
Publisher: Elsevier
Release Date : 2024-05-19
Cemented Paste Backfill written by Yong Wang and has been published by Elsevier this book supported file pdf, txt, epub, kindle and other format this book has been release on 2024-05-19 with Science categories.
In view of the demand for the research on the transport resistance characteristics and mechanical properties of CPB under the influence of temperature effect, the book comprehensively describes the studies on rheological and mechanical properties of CPB materials used in underground metal mines. This book covers a wide range of topics, including a new definition of CPB, past participation and flow-induced corrosion of pipeline under the constant temperature condition, multiphysics processes in CPB and the associated consolidation process, the variation of rheological parameters and transport resistance, prediction model for rheological properties, mechanical behavior and properties of CPB and fiber-reinforced CPB, and control technology to reduce the adverse effect of temperature. Therefore, an academic framework for the transport resistance characteristics and mechanical properties under the temperature effect was established in this book. - Investigates rheological properties and multiphysics processes in CPB materials around the world - Looks into systematic studies on pipe transport and mechanical properties of CPB under temperature effects - Focuses mainly on the effect of temperature on paste transport and mechanical properties under the temperature effect, which provides a theoretical basis for safe and efficient filling operation and associated future research in this field - Offer in-depth insights into the evolution of the rheological and mechanical properties of CPB under the effect of temperatures
Liquefaction Of Early Age Cemented Paste Backfill
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Author : Abdolreza Saebimoghaddam
language : en
Publisher:
Release Date : 2010
Liquefaction Of Early Age Cemented Paste Backfill written by Abdolreza Saebimoghaddam and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
Modern mines require systems that quickly deliver backfill to support the rock mass surrounding underground openings. Cemented Paste Backfill (CPB) is one such backfilling method, but concerns have been raised about CPB's liquefaction susceptibility especially when the material has just been placed, and if it is exposed to earthquakes or large mining induced seismic events. Conventional geotechnical earthquake engineering for surface structures is now relatively advanced and well accepted, and so the objective of this thesis is to consider how that framework might be extended to assess the liquefaction potential of CPB. Seismic records were analyzed for earthquakes and for large mining induced events. Important seismological trends were consistent for rockbursts and earthquakes when the signals were recorded at distances as proximate as one kilometre, suggesting that the conventional earthquake engineering approach might plausibly be adapted for such design situations. For production blasts and for more proximate locations to rockbursts, much higher frequencies dominate and therefore new design methods may be required. Monotonic triaxial tests conducted on normally consolidated uncemented mine tailings demonstrated that the material is initially contractive up to a phase transition point, beyond which dilation occurs. Most importantly the material never exhibits unstable strain softening behaviour in compression, and only temporary or limited liquefaction in extension. The addition of 3% binder results in initial sample void ratios that are even higher than their uncemented counterparts, and yet the material friction is slightly enhanced when tested at 4 hours cure. These results suggest that the flow liquefaction phenomenon commonly associate with undrained loose sand fills will not occur with paste backfill. Cyclic triaxial test results analyzed in terms of number of cycles to failure for a given cyclic stress ratio exhibited a trend consistent with previous tests on similar materials. However, the addition of 3% binder and testing at 4 hours cure resulted in an order of magnitude larger number of cycles to failure - a surprising and dramatic increase, suggesting good resistance of the material to cyclic mobility. Future research is recommended to build on these results and develop more robust methods for liquefaction assessment of CPB.
Using Thermal Profiles Of Cemented Paste Backfill To Predict Strength
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Author : Mahsa Mozaffaridana
language : en
Publisher:
Release Date : 2011
Using Thermal Profiles Of Cemented Paste Backfill To Predict Strength written by Mahsa Mozaffaridana and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
Measurement of the strength development of Cemented Paste Backfill in laboratory cast cylinders does not replicate the in situ strengths of CPB in mine stopes. The mass of CPB in a filled stope is large and temperature rises due to the heat of hydration of the cementing materials, thus accelerating the gain in strength, relative to laboratory specimens stored at ambient temperature. The purpose of this study was to determine the impact on strength development when CPB test cylinders were subjected to a temperature profile mimicking that in a large mass, such as a mine stope. Also, maturity (the integral of time and temperature during hydration of the CPB) was compared to actual strengths, and the maturity -- strength concept used in concrete technology was applied. It was found that the strength- maturity relationship was applicable to CPB once the base line or datum temperature was adjusted.
Modeling Of Coupled Processes In Hydrating Cemented Paste Backfill Structures And Application To The Analysis Of Their Performance
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Author : Othman Nasir
language : en
Publisher:
Release Date : 2008
Modeling Of Coupled Processes In Hydrating Cemented Paste Backfill Structures And Application To The Analysis Of Their Performance written by Othman Nasir and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with Cement categories.
Prediction Of Mechanical Performance Of Cemented Paste Backfill By The Electrical Resistivity Measurement
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Author : Wenbin Xu
language : en
Publisher:
Release Date : 2018
Prediction Of Mechanical Performance Of Cemented Paste Backfill By The Electrical Resistivity Measurement written by Wenbin Xu and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with Concrete categories.
Cemented Paste Backfill (CPB) has become a useful practice in many modern operations around the world. This method is an innovative tailings disposal and underground mine backfilling scheme that returns much of this material to the underground stope field. Thus, it is of great interest for financial and security reasons to fully comprehend the mechanical performance of such underground CPB. Uniaxial compressive strength (UCS) is one of the most commonly used parameters for evaluating the mechanical performance of CPB. Electrical resistivity (ER) measurement, which is a method of nondestructive testing, can also be used to determine the mechanical properties of CPB. This study was undertaken to suggest a nondestructive testing method that would permit prediction of the UCS of a CPB within 90 days. Five CPB samples were prepared at different cement-to-tailing ratios (1/4, 1/6, and 1/8 by weight) and solid content (65 and 70 wt. %), and a curing period of 3-90 days was used for ER measurement. Seventy-five CPB samples were prepared with the same cement content as those used in the pastes for UCS tests cured for 3, 7, 28, 56, and 90 days. The results of the ER measurement show that the ER versus curing periods of 3-90 days first drop to a minimum value and then gradually increase with time. The greater ER values of CPB are reached when the greater cement-to-tailing ratio and solid content is used. A logarithmic relationship is established between the UCS and the ER of CPB at 90 days. It is possible that a nondestructive method could be developed to evaluate the strength of underground CPB based on the obtained logarithmic relationship with ER at 90 days.
A Study Of The Geotechnical Characteristics And Liquefaction Potential Of Paste Backfill
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Author : Khosrow Aref
language : en
Publisher:
Release Date : 1988
A Study Of The Geotechnical Characteristics And Liquefaction Potential Of Paste Backfill written by Khosrow Aref and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1988 with categories.
"The Tailspinner system was developed to produce paste backfill. This system dewaters the full stream tailing material from approximately 55% to 24% water content. These densified tailings are mixed with cement prior to placement in a stope." --
Strength And Deformation Behaviour Of Cemented Paste Backfill In Sub Zero Environment
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Author : Shuang Chang
language : en
Publisher:
Release Date : 2016
Strength And Deformation Behaviour Of Cemented Paste Backfill In Sub Zero Environment written by Shuang Chang and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
Temperature Dependency Of The Rheological Properties And Strength Of Cemented Paste Backfill That Contains Sodium Silicate
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Author : Ghada Abdulbaqi Ali
language : en
Publisher:
Release Date : 2021
Temperature Dependency Of The Rheological Properties And Strength Of Cemented Paste Backfill That Contains Sodium Silicate written by Ghada Abdulbaqi Ali and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021 with categories.
Over the past decades, cemented paste backfill (CPB) has become a common, environmentally friendly method of managing mine wastes (such as tailings). This technology allows up to 60% of the total amount of tailings to be reused and filled in the mine stopes after converting them into cemented material. Beside reducing the environmental risks associated with the traditional disposal of these materials, turning them into cemented material and placing them in the underground mine stopes can also provide secondary support for these stopes in addition to minimizing the risk of ground subsidence in the mine area. CPB is an engineered mixture of tailings, water, and hydraulic binder (such as cement, blast furnace slag, and fly ash) that is mixed in the paste plant and delivered into the mine stopes through a gravity or pumping based transportation system. During the transportation of CPB through the delivery system pipelines, the flowability of CPB depends on the rheology of the transported CPB, which is affected by different factors, such as the transportation time, temperature variation, binder type, and chemical composition of these mixtures. In addition, the performance of CPB, after placing the CPB mixture into the mine stopes, is mainly dependent on the role of the hydraulic binder, as it increases the mechanical strength of the mixture through the process of cement hydration. The mechanical strength is also influenced by different factors, such as time progress, temperature variation, and presence of chemical additives. It has previously been found that fresh CPB transported and/or placed in the mine stopes can be susceptible to temperature variation of different sources, such as the climatic effects, heat generated from the surrounding rocks, and heat generated during the process of cement hydration. Unsuitable flowability of CPB through the delivery system might lead to significant financial losses due to clogging of pipelines with unexpected hardening of CPB during transportation, which will cause delay in work and possible damages to the pipelines. Also, failure of CPB structure in the mine stopes due to inappropriate mechanical strength may cause casualties to the mine workers as well as significant environmental and economic damages. Many researchers studied the rheological properties and/or strength development of CPB under the individual effect of any of the aforementioned factors. Additionally, many researchers have evaluated the coupled effect of some of these factors on the rheology and mechanical strength of CPB material. Hitherto, there are currently no studies that addressed the combined effect of all these conditions on the rheological properties and strength development of CPB. At the first stage of this M.A.Sc. study, a series of experimental tests was conducted on fresh CPB in order to determine the combined effect of time, temperature, binder content, and chemical additives on the rheological properties of CPB. These experiments include rheological properties test (yield stress and viscosity), microstructural analysis (thermal analysis and XRD), chemical analysis (pH and Zeta potential), and monitoring tests (electrical conductivity), which were conducted on 125 CPB samples that were mixed and prepared at different temperatures (2oC, 20oC, 35oC) and cured for different curing time (0 hrs., 0.25 hrs., 1 hr., 2hrs, and 4 hrs.). These samples were prepared with different blends of hydraulic binders (PCI, PCI/Slag, and PCI/FA) and contained different dosages of sodium silicate (0%, 0.1%, 0.3%, and 0.5%). The results obtained show that rheology of CPB increases with the progress of curing time. It also increases with the increase in the initial (mixing and curing) temperature and content of sodium silicate. It was also found that the partial usage of slag and FA reduces the rheological properties. However, CPBs containing PCI/FA as binder have lower rheological properties, and thus better flowability, than those that contain PCI/Slag as binder. At the second stage of this M.A.Sc. study, in order to understand the combined effect of time, temperature and sodium silicate content on the strength development of slag-CPB, unconfined compression (UCS) test, microstructural analysis (thermal analysis and MIP), and monitoring tests (electrical conductivity, suction, and volumetric water content) were conducted on 72 CPB samples that were prepared with PCI-Slag as a binder, cured for different times (1 day, 3 days, 7 days, and 28 days) under different curing temperatures of (2oC, 20oC, 35oC), and contained different dosages of sodium silicate (0%, 0.3% and 0.5%). The results obtained at this stage showed that the strength development of slag-CPB increases with the progress of curing time and temperature. It also increases with the increase in the sodium silicate content. Also, the combined effect of high temperature, high dosage of sodium silicate and longer curing time showed significant enhancement in the mechanical strength of slag-CPB. The findings of this M.A.Sc. research will contribute to cost effective, efficient, and safer design of CPB structures in the mine areas. It will also help in minimizing financial loss associated with unsuitable flowability of CPB transported in the CPB delivery system besides reducing the risks of human loss, and the environmental and economic damages associated with the failure of CPB structures.