Prediction Of Mechanical Performance Of Cemented Paste Backfill By The Electrical Resistivity Measurement
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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.
Fatigue Mechanical Behaviors Of Rock Backfill Composites Laboratory Study
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Author : Yu Wang
language : en
Publisher: Scientific Research Publishing, Inc. USA
Release Date : 2024-07-18
Fatigue Mechanical Behaviors Of Rock Backfill Composites Laboratory Study written by Yu Wang and has been published by Scientific Research Publishing, Inc. USA this book supported file pdf, txt, epub, kindle and other format this book has been release on 2024-07-18 with Antiques & Collectibles categories.
This book is intended as a reference book for advanced graduate students and re-search engineers in rock mechanics related to mining engineering. The cemented tailings backfill (CTB) technique is widely used in deep underground mining, since this tech-nique is effective to support surrounding rock, control rockburst, reduce ground sub-sistence, and reduce surface disposal of tailings. Plenty of investigations have been attempted to experimentally or numerically evaluate the strength of CTB with different components (e.g., mixture of cement, tailings, fly ash, blast furnace slag, etc.) to ensure the geological stability when extracting adjacent stopes. After extracting ore from stopes, CTB is filled in the gob, stress redistribution occurs in the backfill stope and surrounding rocks. Due to the elasticity mismatch of these two kinds of material, differential de-formation occurs and they both resist the overburden pressure and deformation. As a result, the interactions between the surrounding rock and tailing backfill material have significant role in maintaining the long-term stability of mine stopes. Apart from the investigations on the static mechanical behaviors of rock- backfill composited backfill (RBCS) material, the RBCS in the stope are also exposed to disturbed stress (e.g., blast vibration, excavation, earthquake, etc.), and the disturbed stress is usually equivalent to cyclic or fatigue loads. As a result, investigations on rock-backfill interactions subjected to the disturbed stress are critical and significant to maintain the long- term stability of mine stopes.
Concrete International
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Author :
language : en
Publisher:
Release Date : 1990
Concrete International written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1990 with Concrete categories.
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
Mechanical Properties Of Cemented Paste Backfill Under Low Confining Stress
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Author : Andrew Ning Pan
language : en
Publisher:
Release Date : 2019
Mechanical Properties Of Cemented Paste Backfill Under Low Confining Stress written by Andrew Ning Pan and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019 with categories.
Cemented paste backfill (CPB) plays an increasingly important role in the mining industry due to rapid delivery rate, tight-filling characteristics, relatively insignificant water management issues during filling, and generally uniform as-placed mechanical properties. The most common basis for assessing backfill strength is Unconfined Compressive Strength (UCS), and some of the most commonly used design methods have UCS as a fundamental design parameter. However, actual CPB properties and behavior under the range of confining stresses relevant to these design methods has been studied very little. This work uses UCS tests and a novel direct tensile test method and compares test results with strengths obtained from direct shear tests. A form of punching shear was also investigated, but the results were found unsatisfactory for design purposes. For materials with UCS up to about 1 MPa, the UCS and tensile strengths are consistent with the Mohr-Coulomb failure envelope obtained from direct shear tests.
Electrical Resistivity And Temperature Of Fresh Cement Paste As Indicators For Setting Time
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Author : Ahmad Shahroodi
language : en
Publisher:
Release Date : 2021
Electrical Resistivity And Temperature Of Fresh Cement Paste As Indicators For Setting Time written by Ahmad Shahroodi 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.
The process, rate, and quality of cement hydration (a complex physical-chemical process) affect the properties development of concrete, such as its compressive strength, penetrability, and setting. Among all, setting time is one of the important properties for the concrete industry, as it is the factor in determining the consolidation, finishing, and curing time of a concrete pour. Inadequate determination of concrete setting time will result in improper finishing, formation of cold joints between layers of concrete, and curing time delay. Therefore, short- and long-term performance of concrete, concrete durability, and its life span will be affected. Concrete setting time proceeds from an initial stage (end of concrete pouring and consolidation) to a final stage (end of finishing process and beginning of curing) with the hydration of cement particles in the matrix of concrete. The accurate determination of the setting time in concrete projects has always been a question. Setting time is measured in laboratory setups by the traditional method of the Vicat needle (as standardized in ASTM C191). However, the field condition of a concrete pour is different from a lab set up, so the importance of replacing a lab-based setting time test with a field applicable method is out of question. This research project studies the feasibility of using a practical and non-destructive technique to detect the actual concrete setting time and its development in a reasonable amount of time. In this research, the electrical properties and internal temperature of cementing-based mixtures are monitored over the first 24 hours of hydration. The electrical properties of concrete and cement-based materials and corresponding internal temperature are influenced by many factors affected by cement hydration, similar to the setting time. The main goal of this research project is to establish a predicting method for the fresh cement paste setting time by monitoring either the electrical properties or the internal temperature of the mixture. To isolate the effect of the specimen geometry, electrical resistivity has been chosen as the electrical properties' representative in this study. It is measured by a novel resistivity-meter setup. However, to develop a time-saving and accurate method, microstructure factors affecting the electrical resistivity development of fresh cement paste need to be studied. These factors are (1) the ionic concentration and ionic variation in the pore solution (in the liquid phase of the cement paste microstructure), and (2) the hydration products formation and crystallization (or the physical characteristics of the cement paste microstructure). Since formation of hydration products and crystallization are exothermic, the changes in the internal temperature of the materials are also monitored. Finally, reliable predicting indicators, electrical resistivity and internal temperature values, which are influenced by not only the fresh stage ionic concentration, but also by the development and changes in the physical characteristics of microstructure are proposed to the industry.
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.
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.
Autogenous Shrinkage Of Cement Paste Interpreted By Electrical Resistivity And Capillary Stress At Early Age
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Author : Jiayin Tao
language : en
Publisher:
Release Date : 2018
Autogenous Shrinkage Of Cement Paste Interpreted By Electrical Resistivity And Capillary Stress At Early Age written by Jiayin Tao 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.
Autogenous shrinkage caused by the self-desiccation of cement-based materials at early age requires more attention from researchers because it can increase the risk of cracking in concrete. This article presents the relationships among autogenous shrinkage after final setting, the estimated effective capillary stress, and electrical resistivity of cement pastes. Autogenous shrinkage, internal relative humidity, chemical shrinkage, and electrical resistivity were measured for the plain cement paste that had water to cement ratios (W/C) of 0.3, 0.35, and 0.4 at early age. Electrical resistivity and its rate curve were presented to analyze the influence of W/C on the hydration process. A fitting function containing W/C, electrical resistivity, and three constant parameters was put forward to quantify the relationship between autogenous shrinkage and electrical resistivity. The autogenous shrinkage of cement paste at different ages can be predicted by the resistivity at 24 h; the relationship between electrical resistivity at 24 h and the effective capillary stress S.?cap at 24 h, 48 h, 72 h, and 96 h was also established to support the effectiveness of relating the self-desiccation development trend and electrical property of cement paste. This study introduces innovative and quick methods to estimate the autogenous shrinkage of cement paste by electrical resistivity.
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.