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Sample records for cementitious composites ecc

  1. Nanoscale characterization of engineered cementitious composites (ECC)

    International Nuclear Information System (INIS)

    Engineered cementitious composites (ECC) are ultra-ductile fiber-reinforced cementitious composites. The nanoscale chemical and mechanical properties of three ECC formulae (one standard formula, and two containing nanomaterial additives) were studied using nanoindentation, electron microscopy, and energy dispersive spectroscopy. Nanoindentation results highlight the difference in modulus between bulk matrix (∼ 30 GPa) and matrix/fiber interfacial transition zones as well as between matrix and unreacted fly ash (∼ 20 GPa). The addition of carbon black or carbon nanotubes produced little variation in moduli when compared to standard M45-ECC. The indents were observed by electron microscopy; no trace of the carbon black particles could be found, but nanotubes, including nanotubes bridging cracks, were easily located in ultrafine cracks near PVA fibers. Elemental analysis failed to show a correlation between modulus and chemical composition, implying that factors such as porosity have more of an effect on mechanical properties than elemental composition.

  2. Shear behavior of reinforced Engineered Cementitious Composites (ECC) beams

    DEFF Research Database (Denmark)

    Paegle, Ieva; Fischer, Gregor

    2010-01-01

    This paper describes an experimental investigation of the shear behavior of beams consisting of steel reinforced Engineered Cementitious Composites (ECC). Based on the strain hardening and multiple cracking behavior of ECC, this study investigates the extent to which ECC can improve the shear...... capacity of beams loaded primarily in shear and if ECC can partially or fully replace the conventional transverse steel reinforcement in beams. However, there is a lack of understanding of how the fibers affect the shear carrying capacity and deformation behavior of structural members if used either in...... randomly distributed PVA (polyvinyl alcohol) fiber beams with different stirrup spacing and reinforced concrete (RC) beams for comparison. Displacement and strain measurements taken using the ARAMIS photogrammetric data acquisition system by means of processing at high frame rate captured images of applied...

  3. Self-Healing of Microcracks in Engineered Cementitious Composites (ECC) Under a Natural Environment

    OpenAIRE

    Li, Victor C.; Emily N. Herbert

    2013-01-01

    This paper builds on previous self-healing engineered cementitious composites (ECC) research by allowing ECC to heal outdoors, in the natural environment, under random and sometimes extreme environmental conditions. Development of an ECC material that can heal itself in the natural environment could lower infrastructure maintenance costs and allow for more sustainable development in the future by increasing service life and decreasing the amount of resources and energy needed for repairs. Det...

  4. Application of Engineered Cementitious Composites (ECC) in modular floor panels

    DEFF Research Database (Denmark)

    Lárusson, Lárus Helgi; Fischer, Gregor; Jönsson, Jeppe

    2008-01-01

    adaptability to various loading requirements, and the efficient utilization of material resources and industrial byproducts. The work described in this paper is a continuation of previous activities on composite floor panels in which light gage steel joists were integrally cast with the ECC slab. The modular...... concept introduced in this paper aims at improvements in the manufacturing process of the panels by casting the ECC slab separately and subsequently joining it with the steel trusses. The focus of this paper is on design and manufacturing of a prototype modular panel and on its structural behavior under...... service conditions and at ultimate. The modular floor panel concept is introduced, modeled, and verified with experimental tests of various configurations....

  5. Shear behavior of reinforced Engineered Cementitious Composites (ECC) beams

    DEFF Research Database (Denmark)

    Paegle, Ieva; Fischer, Gregor

    capacity of beams loaded primarily in shear and if ECC can partially or fully replace the conventional transverse steel reinforcement in beams. However, there is a lack of understanding of how the fibers affect the shear carrying capacity and deformation behavior of structural members if used either in...... the Eurocode and ACI Code are found to be over-conservative but can be modified by utilizing the tensile strength of ECC. An expression for the load carrying capacity is proposed by expressing the ECC shear strength in terms of the crack angle....... combination with conventional transverse reinforcement or exclusively to provide shear resistance. The experimental investigation focuses on the influence of fibers on the shear caring capacity and the crack development in ECC beams subjected to shear. The experimental program consists of ECC with short...

  6. Mechanical interaction of Engineered Cementitious Composite (ECC) reinforced with Fiber Reinforced Polymer (FRP) rebar in tensile loading

    DEFF Research Database (Denmark)

    Lárusson, Lárus Helgi; Fischer, Gregor; Jönsson, Jeppe

    This paper introduces a preliminary study of the composite interaction of Engineered Cementitious Composite (ECC), reinforced with Glass Fiber Reinforced Polymer (GFRP) rebar. The main topic of this paper will focus on the interaction of the two materials (ECC and GFRP) during axial loading...... as well as crack widths and crack distributions in the ECC. Results indicate that the interaction of the ductile ECC together with the elastic brittle behavior of the GFRP make a highly compatible ductile composite. The combination of multiple cracking and limited crack width of ECC insures good...

  7. Self-Healing of Microcracks in Engineered Cementitious Composites (ECC Under a Natural Environment

    Directory of Open Access Journals (Sweden)

    Victor C. Li

    2013-07-01

    Full Text Available This paper builds on previous self-healing engineered cementitious composites (ECC research by allowing ECC to heal outdoors, in the natural environment, under random and sometimes extreme environmental conditions. Development of an ECC material that can heal itself in the natural environment could lower infrastructure maintenance costs and allow for more sustainable development in the future by increasing service life and decreasing the amount of resources and energy needed for repairs. Determining to what extent current ECC materials self-heal in the natural environment is the first step in the development of an ECC that can completely heal itself when exposed to everyday environmental conditions. This study monitored outdoor ECC specimens for one year using resonant frequency (RF and mechanical reloading to determine the rate and extent of self-healing in the natural environment. It was found that the level of RF, stiffness, and first cracking strength recovery increased as the duration of natural environment exposure increased. For specimens that underwent multiple damage cycles, it was found that the level of recovery was highly dependent on the average temperature and amount of precipitation between each damage event. However, RF, stiffness, and first cracking strength recovery data for specimens that underwent multiple loading cycles suggest that self-healing functionality can be maintained under multiple damage events.

  8. Shrinkage Reducing Measures for Engineering Cementitious Composites

    Institute of Scientific and Technical Information of China (English)

    YANG Yingzi; YAO Yan; GAO Xiaojian; DENG Hongwei; YU Pengzhan

    2008-01-01

    Inhibition measurement of shrinkage of engineering cementitious composites(ECC) was investigated due to typical ECC with higher free drying shrinkage.The effects of expanded admixture (EA),shrinkage reducing admixture (SRA),coarse sand+stone powder (CS+SP)and superabsorbent polymer (SAP) on drying shrinkage and mechanical properties were studied.The experimental results show that ECC incorporating EA,SRA and coarse sand can retain around 60% of the typical ECC's free drying shrinkage.Superabsorbent polymerl(SAP) can delay the development of free drying shrinkage of ECC at different ages,and the effect of SAP is not distinct like the actions of EA,superabsorbent polymer(SRA) and coarse sand.Significantly,SAP may act as artificial flaw to form a more homogeneous defect system that increases the potential of saturated multiple cracking,hence the ductility of ECC will be improved greatly.

  9. A Plastic Damage Mechanics Model for Engineered Cementitious Composites

    DEFF Research Database (Denmark)

    Dick-Nielsen, Lars; Stang, Henrik; Poulsen, Peter Noe; Kabele, Petr

    This paper discusses the establishment of a plasticity-based damage mechanics model for Engineered Cementitious Composites (ECC). The present model differs from existing models by combining a matrix and fiber description in order to describe the behavior of the ECC material. The model provides...

  10. A Plastic Damage Mechanics Model for Engineered Cementitious Composites

    DEFF Research Database (Denmark)

    Dick-Nielsen, Lars; Stang, Henrik; Poulsen, Peter Noe;

    2007-01-01

    This paper discusses the establishment of a plasticity-based damage mechanics model for Engineered Cementitious Composites (ECC). The present model differs from existing models by combining a matrix and fiber description in order to describe the behavior of the ECC material. The model provides...... information about crack opening and spacing, which makes it possible to assess the condition of a structure in the serviceability state. A simulation of a four point bending beam is performed to demonstrate the capability of the model....

  11. Engineered cementitious composites for strengthening masonry infilled reinforced concrete frames

    DEFF Research Database (Denmark)

    Dehghani, Ayoub; Nateghi-Alahi, Fariborz; Fischer, Gregor

    2015-01-01

    The results of the second part of a comprehensive experimental program, aimed at investigating the behavior of masonry infilled reinforced concrete (RC) frames strengthened with fiber reinforced engineered cementitious composites (ECC) used as an overlay on the masonry wall, are presented in this...

  12. Strengthening masonry infill panels using engineered cementitious composites

    DEFF Research Database (Denmark)

    Dehghani, Ayoub; Fischer, Gregor; Nateghi Alahi, Fariborz

    2015-01-01

    ECC in order to assess its distinctive mechanical properties such as tensile stress–strain behavior and multiple cracking. To investigate the influence of a thin layer of ECC on plain masonry in terms of changes in stiffness, strength, and deformability, small scale tests have been conducted on......This comprehensive experimental study aims at investigating the behavior of masonry infill panels strengthened by fiber reinforced engineered cementitious composites (ECC). The experimental program included testing of materials, masonry elements and panels. Material tests were carried out first for...

  13. Mechanical Behavior of Rectangular Steel-Reinforced ECC/Concrete Composite Column under Eccentric Compression

    Institute of Scientific and Technical Information of China (English)

    潘金龙; 鲁冰; 顾大伟; 夏正昊; 夏天阳

    2015-01-01

    In order to improve the seismic performance, deformation ability and ultimate load-carrying capacity of columns with rectangular cross section, engineered cementitious composite (ECC) is introduced to partially substitute concrete in the edge zone of reinforced concrete columns and form reinforced ECC/concrete composite columns. Firstly, based on the assumption of plane remaining plane and the simplified constitutive models, the calculation method of the load-carrying capacity of reinforced ECC/concrete columns is proposed. The stress and strain distribu-tions and crack propagation of the composite columns in different states of eccentric compressive loading are ana-lyzed. Then, nonlinear finite element analysis is conducted to study the mechanical performance of reinforced ECC/concrete composite columns with rectangular cross section. It is found that the simulation results are in good agreement with the theoretical results, indicating that the proposed method for calculating the load-carrying capacity of concrete/ECC composite columns is valid. Finally, based on the proposed method, the effects of ECC thickness, com-pressive strength of concrete and longitudinal reinforcement ratio on the mechanical performance of reinforced ECC/concrete composite columns are analyzed. Calculation results indicate that increasing the thickness of ECC layer or longitudinal reinforcement ratio can effectively increase the ultimate load-carrying capacity of the composite column with both small and large eccentricity, but increasing the strength of concrete can only increase the ultimate load-carrying capacity of the composite column with small eccentricity.

  14. Designing added functions in engineered cementitious composites

    Science.gov (United States)

    Yang, En-Hua

    In this dissertation, a new and systematic material design approach is developed for ECC with added functions through material microstructures linkage to composite macroscopic behavior. The thesis research embodies theoretical development by building on previous ECC micromechanical models, and experimental investigations into three specific new versions of ECC with added functions aimed at addressing societal demands of our built infrastructure. Specifically, the theoretical study includes three important ECC modeling elements: Steady-state crack propagation analyses and simulation, predictive accuracy of the fiber bridging constitutive model, and development of the rate-dependent strain-hardening criteria. The first element establishes the steady-state cracking criterion as a fundamental requirement for multiple cracking behavior in brittle matrix composites. The second element improves the accuracy of crack-width prediction in ECC. The third element establishes the micromechanics basis for impact-resistant ECC design. Three new ECCs with added functions were developed and experimentally verified in this thesis research through the enhanced theoretical framework. A green ECC incorporating a large volume of industrial waste was demonstrated to possess reduced crack width and drying shrinkage. The self-healing ECC designed with tight crack width was demonstrated to recover transport and mechanical properties after microcrack damage when exposed to wet and dry cycles. The impact-resistant ECC was demonstrated to retain tensile ductility with increased strength under moderately high strain-rate loading. These new versions of ECC with added functions are expected to contribute greatly to enhancing the sustainability, durability, and safety of civil infrastructure built with ECC. This research establishes the effectiveness of micromechanics-based design and material ingredient tailoring for ECC with added new attributes but without losing its basic tensile ductile

  15. Service life prediction and cementitious composites

    DEFF Research Database (Denmark)

    Stoklund Larsen, E.

    The present Ph.D.thesis describes and discusses the applicability of a systematic methodology recommended by CIB W80/RILEM-PSL for sevice life prediction. The report describes the most important inherent and environmental factors affecting the service life of structures of cementitious composites....... On the basis of this discription of factors and experience from a test programme described in SBI Report 222, Service life prediction and fibre reinforced cementitious composites, the applicabillity of the CIB/RILEM methodology is discussed....

  16. Energy-dissipating and self-repairing SMA-ECC composite material system

    International Nuclear Information System (INIS)

    Structural component ductility and energy dissipation capacity are crucial factors for achieving reinforced concrete structures more resistant to dynamic loading such as earthquakes. Furthermore, limiting post-event residual damage and deformation allows for immediate re-operation or minimal repairs. These desirable characteristics for structural ‘resilience’, however, present significant challenges due to the brittle nature of concrete, its deformation incompatibility with ductile steel, and the plastic yielding of steel reinforcement. Here, we developed a new composite material system that integrates the unique ductile feature of engineered cementitious composites (ECC) with superelastic shape memory alloy (SMA). In contrast to steel reinforced concrete (RC) and SMA reinforced concrete (SMA-RC), the SMA-ECC beams studied in this research exhibited extraordinary energy dissipation capacity, minimal residual deformation, and full self-recovery of damage under cyclic flexural loading. We found that the tensile strain capacity of ECC, tailored up to 5.5% in this study, allows it to work compatibly with superelastic SMA. Furthermore, the distributed microcracking damage mechanism in ECC is critical for sufficient and reliable recovery of damage upon unloading. This research demonstrates the potential of SMA-ECC for improving resilience of concrete structures under extreme hazard events. (paper)

  17. Energy-dissipating and self-repairing SMA-ECC composite material system

    Science.gov (United States)

    Li, Xiaopeng; Li, Mo; Song, Gangbing

    2015-02-01

    Structural component ductility and energy dissipation capacity are crucial factors for achieving reinforced concrete structures more resistant to dynamic loading such as earthquakes. Furthermore, limiting post-event residual damage and deformation allows for immediate re-operation or minimal repairs. These desirable characteristics for structural ‘resilience’, however, present significant challenges due to the brittle nature of concrete, its deformation incompatibility with ductile steel, and the plastic yielding of steel reinforcement. Here, we developed a new composite material system that integrates the unique ductile feature of engineered cementitious composites (ECC) with superelastic shape memory alloy (SMA). In contrast to steel reinforced concrete (RC) and SMA reinforced concrete (SMA-RC), the SMA-ECC beams studied in this research exhibited extraordinary energy dissipation capacity, minimal residual deformation, and full self-recovery of damage under cyclic flexural loading. We found that the tensile strain capacity of ECC, tailored up to 5.5% in this study, allows it to work compatibly with superelastic SMA. Furthermore, the distributed microcracking damage mechanism in ECC is critical for sufficient and reliable recovery of damage upon unloading. This research demonstrates the potential of SMA-ECC for improving resilience of concrete structures under extreme hazard events.

  18. Use of flexible engineered cementitious composite in buildings

    International Nuclear Information System (INIS)

    This article describes the applications and benefits of a recently developed smart building material namely Engineered cementitious composite (ECC), also known as flexible or bendable concrete. Conventional concretes have a strain capacity of only 0.1 percent and are highly brittle and rigid. This lack of bend ability is a major cause of failure under strain and has been a pushing factor in the development of an elegant material which is capable to exhibit an enhanced flexibility. An ECC has a strain capacity of more than 3 percent and thus acts more like a ductile metal rather than like a brittle glass. The aim of this paper is to highlight a probable success of ECC in terms of industrial and commercial use in Pakistan. With the introduction of flexible concrete in building technology, it is likely to have safer and more durable construction. The material is expected to display reduced detrimental impacts on the natural environment. A bendable concrete is composed of all the ingredients of a traditional concrete minus coarse aggregates or crushed stones and is reinforced with micro mechanically designed polymer fibers. The mechanism of action of the micro-polymeric fibers in concrete has also been emphasized. The principles of mix designs of the mortar incorporating fibers to make an ECC have also been explained. It has also been mentioned in detail as how this technology can be used to enhance the flexibility of some modern concrete types like flowing concrete, self-compacting concrete, and lightweight concrete. ECC is a green construction material. The possible benefits like environment friendliness, cost effectiveness, and durability have been also been elucidated in the paper. (author)

  19. Nano-modification to improve the ductility of cementitious composites

    International Nuclear Information System (INIS)

    Effect of nano-sized mineral additions on ductility of engineered cementitious composites (ECC) containing high volumes of fly ash was investigated at different hydration degrees. Various properties of ECC mixtures with different mineral additions were compared in terms of microstructural properties of matrix, fiber-matrix interface, and fiber surface to assess improvements in ductility. Microstructural characterization was made by measuring pore size distributions through mercury intrusion porosimetry (MIP). Hydration characteristics were assessed using thermogravimetric analysis/differential thermal analysis (TGA/DTA), and fiber-matrix interface and fiber surface characteristics were assessed using scanning electron microscopy (SEM) through a period of 90 days. Moreover, compressive and flexural strength developments were monitored for the same period. Test results confirmed that mineral additions could significantly improve both flexural strength and ductility of ECC, especially at early ages. Cheaper Nano-CaCO3 was more effective compared to nano-silica. However, the crystal structure of CaCO3 played a very important role in the range of expected improvements

  20. Nano-modification to improve the ductility of cementitious composites

    Energy Technology Data Exchange (ETDEWEB)

    Yeşilmen, Seda [Department of Civil Engineering, Çankaya University, Ankara (Turkey); Al-Najjar, Yazin [Department of Civil Engineering, Gaziantep University, Gaziantep (Turkey); Balav, Mohammad Hatam [Department of Civil Engineering, Gazi University, Ankara (Turkey); Şahmaran, Mustafa, E-mail: sahmaran@gazi.edu.tr [Department of Civil Engineering, Gazi University, Ankara (Turkey); Yıldırım, Gürkan [Department of Civil Engineering, Gazi University, Ankara (Turkey); Lachemi, Mohamed [Department of Civil Engineering, Ryerson University, Toronto, ON (Canada)

    2015-10-15

    Effect of nano-sized mineral additions on ductility of engineered cementitious composites (ECC) containing high volumes of fly ash was investigated at different hydration degrees. Various properties of ECC mixtures with different mineral additions were compared in terms of microstructural properties of matrix, fiber-matrix interface, and fiber surface to assess improvements in ductility. Microstructural characterization was made by measuring pore size distributions through mercury intrusion porosimetry (MIP). Hydration characteristics were assessed using thermogravimetric analysis/differential thermal analysis (TGA/DTA), and fiber-matrix interface and fiber surface characteristics were assessed using scanning electron microscopy (SEM) through a period of 90 days. Moreover, compressive and flexural strength developments were monitored for the same period. Test results confirmed that mineral additions could significantly improve both flexural strength and ductility of ECC, especially at early ages. Cheaper Nano-CaCO{sub 3} was more effective compared to nano-silica. However, the crystal structure of CaCO{sub 3} played a very important role in the range of expected improvements.

  1. Self-healing of Micro-cracks in Engineered Cementitious Composites

    OpenAIRE

    Suryanto B.; Wilson S.A.; McCarter W.J.

    2015-01-01

    The performance of an Engineered Cementitious Composite (ECC) to self-heal micro-cracks under a controlled laboratory environment is presented. Ten dog-bone shaped samples were prepared; five of them were preloaded to known strains and then left to heal in water in a temperature-controlled laboratory. Ultrasonic pulse velocity (UPV) measurements were undertaken to monitor the crack-healing process. It was found that all samples exhibited recoveries in UPV and were able to recover to betwee...

  2. Extrusion of ECC-Material

    DEFF Research Database (Denmark)

    Stang, Henrik; Li, Victor C.

    1999-01-01

    An extrusion process especially designed for extrusion of pipes made from fiber reinforced cementitious materials has been developed at Department of Structural Engineering and Materials at the Technical University of DenmarkEngineered Cementitious Composite (ECC) materials have been developed in...... recent years at Department of Civil and Envirionmetal Engineering, University of Michigan. These materials have been developed with the special aim of producing high performance , strain hardening materials with low volume concentrations of short fibers in a cementitious material.ECC material spcimens...... have until now been produced by traditional casting processes. In the present paper results from a recent collaborative reserach project are documented - demonstrating that ECC materials can be extruded in the process referred to above....

  3. Extrusion of ECC-Material

    DEFF Research Database (Denmark)

    Stang, Henrik; Li, Victor C.

    An extrusion process especially designed for extrusion of pipes made from fiber reinforced cementitious materials has been developed at Department of Structural Engineering and Materials at the Technical University of DenmarkEngineered Cementitious Composite (ECC) materials have been developed in...... recent years at Department of Civil and Envirionmetal Engineering, University of Michigan. These materials have been developed with the special aim of producing high performance , strain hardening materials with low volume concentrations of short fibers in a cementitious material.ECC material spcimens...... have until now been produced by traditional casting processes. In the present paper results from a recent collaborative reserach project are documented - demonstrating that ECC materials can be extruded in the process referred to above....

  4. Analysis of Graphite-Reinforced Cementitious Composites

    Science.gov (United States)

    Vaughan, R. E.

    2002-01-01

    Strategically embedding graphite meshes in a compliant cementitious matrix produces a composite material with relatively high tension and compressive properties as compared to steel-reinforced structures fabricated from a standard concrete mix. Although these composite systems are somewhat similar, the methods used to analyze steel-reinforced composites often fail to characterize the behavior of their more advanced graphite-reinforced counterparts. This Technical Memorandum describes some of the analytical methods being developed to determine the deflections and stresses in graphite-reinforced cementitious composites. It is initially demonstrated that the standard transform section method fails to provide accurate results when the elastic moduli ratio exceeds 20. An alternate approach is formulated by using the rule of mixtures to determine a set of effective material properties for the composite. Tensile tests are conducted on composite samples to verify this approach. When the effective material properties are used to characterize the deflections of composite beams subjected to pure bending, an excellent agreement is obtained. Laminated composite plate theory is investigated as a means for analyzing even more complex composites, consisting of multiple graphite layers oriented in different directions. In this case, composite beams are analyzed using the laminated composite plate theory with material properties established from tensile tests. Then, finite element modeling is used to verify the results. Considering the complexity of the samples, a very good agreement is obtained.

  5. 钢筋增强 ECC/混凝土组合柱压弯性能分析%Mechanical behaviors of steel reinforced ECC/concrete composite columns under combined vertical and horizontal loading

    Institute of Scientific and Technical Information of China (English)

    单奇峰; 潘金龙; 陈俊涵

    2015-01-01

    In order to improve the load capacity,seismic performance and performance-cost ratio of the columns,the concrete at the base of reinforced concrete (RC)columns is substituted with engineered cementitious composites (ECC)to form ECC /RC composite columns.Based on the existing material properties,the mechanical behaviors of the ECC columns,ECC /RC composite columns and RC columns were numerically studied under combined vertical and horizontal loading with the software of ATENA.Then,the failure mechanism of ECC columns and ECC /RC composite columns were comprehensively studied and compared with that of the RC columns.Then,the effects of the height of the ECC,the axial compression ratio,and the transverse reinforcement ratio on the mechanical behaviors of the composite or the ECC column are studied.The calculation results show that the ultimate load capacity,ductility and crack resistance of the ECC or ECC /RC composite columns are superior to those of the RC columns.The ECC /RC composite column with a height of the ECC layer of 1.2h (h is the height of the cross section)can achieve similar mechanical properties of a full ECC column.With high shear strength,ECC can undertake the shear force and significantly reduce the amount of stirrups, avoiding construction issues and promoting its engineering application.%为了提高柱的承载力、抗震性能和性价比,采用工程水泥基复合材料(ECC)材料替代钢筋混凝土(RC)柱柱根区域的混凝土形成 ECC /RC 组合柱.基于已有的材料性能试验数据,采用 ATENA 有限元软件对 ECC 柱、ECC /RC 组合柱及 RC 柱的压弯性能进行数值分析.研究了 ECC 柱和 ECC /RC 组合柱的破坏机理,并与 RC 柱进行对比,进而探究 ECC 高度、轴压比和体积配箍率3个参数对 ECC /RC 组合柱或 ECC 柱压弯性能的影响.结果表明:ECC 柱和 ECC /RC 组合柱较 RC 柱具有更高的承载力、延性和抗裂能力;ECC高度在1.2h

  6. X-ray computed microtomography of three-dimensional microcracks and self-healing in engineered cementitious composites

    International Nuclear Information System (INIS)

    Concrete cracking and deterioration can potentially be addressed by innovative self-healing cementitious materials, which can autogenously regain transport properties and mechanical characteristics after the damage self-healing process. For the development of such materials, it is crucial, but challenging, to precisely characterize the extent and quality of self-healing due to a variety of factors. This study adopted x-ray computed microtomography (μCT) to derive three-dimensional morphological data on microcracks before and after healing in engineered cementitious composite (ECC). Scanning electron microscope and energy dispersive x-ray spectroscopy were also used to morphologically and chemically analyze the healing products. This work showed that the evolution of the microcrack 3D structure due to self-healing in cementitious materials can be directly and quantitatively characterized by μCT. A detailed description of the μCT image analysis method applied to ECC self-healing was presented. The results revealed that the self-healing extent and rate strongly depended on initial surface crack width, with smaller crack width favoring fast and robust self-healing. We also found that the self-healing mechanism in cementitious materials is dependent on crack depth. The region of a crack close to the surface (from 0 to around 50–150 μm below the surface) can be sealed quickly with crystalline precipitates. However, at greater depths the healing process inside the crack takes a significantly longer time to occur, with healing products more likely resulting from continued hydration and pozzolanic reactions. Finally, the μCT method was compared with other self-healing characterization methods, with discussions on its importance in generating new scientific knowledge for the development of robust self-healing cementitious materials. (paper)

  7. Service life prediction and fibre reinforced cementitious composites

    DEFF Research Database (Denmark)

    Stoklund Larsen, E.

    , the factors affecting the pure cementitious composite are described. Different sizes and types of fibre reinforced crmentitious composites have been chosen to illustrate different ageing and deterioration mechanisms. Some ageing mechanisms can be accelerated and others cannot which is demonstrated in...

  8. Self-healing of Micro-cracks in Engineered Cementitious Composites

    Directory of Open Access Journals (Sweden)

    Suryanto B.

    2015-12-01

    Full Text Available The performance of an Engineered Cementitious Composite (ECC to self-heal micro-cracks under a controlled laboratory environment is presented. Ten dog-bone shaped samples were prepared; five of them were preloaded to known strains and then left to heal in water in a temperature-controlled laboratory. Ultrasonic pulse velocity (UPV measurements were undertaken to monitor the crack-healing process. It was found that all samples exhibited recoveries in UPV and were able to recover to between 96.6% and 98% of their pre-test UPV values over a period of four weeks. An accelerated rate of healing was observed in the initial two-day period immediately following the preloading test.

  9. Fatigue enhancement of concrete beam with ECC layer

    International Nuclear Information System (INIS)

    The pseudo strain-hardening behavior of Engineered Cementitious Composites (ECC) is a desirable characteristic for it to replace concrete to suppress brittle failure. This widespread use of ECC in the industry is, however, limited by its high cost. To achieve higher performance/cost, ECC can be strategically applied in parts of a structure that is under relatively high stress and strain. In this paper, layered ECC-concrete beams subjected to static and fatigue flexural loads were investigated by experiments. The static test results showed that the application of a layer of ECC on the tensile side of a flexural beam increased its flexural strength and the degree of improvement increased with the thickness of ECC applied. In addition, the layer of ECC enhanced the ductility of the beam and the failure mode changed from brittle to ductile. Under four-point cyclic loading, the ECC layer significantly improved the fatigue life of the beam. Moreover, in comparison to plain concrete beams, layered ECC beams could sustain fatigue loading at a larger deflection without failure. The great improvement in fatigue performance was attributed to the effectiveness of ECC in controlling the growth of small cracks. The experimental findings reflect the feasibility of using ECC strategically in critical locations for the control of fatigue crack growth

  10. Progress in Research on Carbon Nanotubes Reinforced Cementitious Composites

    Directory of Open Access Journals (Sweden)

    Qinghua Li

    2015-01-01

    Full Text Available As one-dimensional (1D nanofiber, carbon nanotubes (CNTs have been widely used to improve the performance of nanocomposites due to their high strength, small dimensions, and remarkable physical properties. Progress in the field of CNTs presents a potential opportunity to enhance cementitious composites at the nanoscale. In this review, current research activities and key advances on multiwalled carbon nanotubes (MWCNTs reinforced cementitious composites are summarized, including the effect of MWCNTs on modulus of elasticity, porosity, fracture, and mechanical and microstructure properties of cement-based composites. The issues about the improvement mechanisms, MWCNTs dispersion methods, and the major factors affecting the mechanical properties of composites are discussed. In addition, large-scale production methods of MWCNTs and the effects of CNTs on environment and health are also summarized.

  11. Shape optimization of small span textile reinforced cementitious composite shells

    OpenAIRE

    TYSMANS, Tine; ADRIAENSSENS, Sigrid; Wastiels, Jan

    2009-01-01

    p. 1755-1766 The property of concrete to be poured into any shape and harden at ambient temperatures makes it the most widely-used material for shells. Using this traditionally brittle material in shells restricts their forms to mostly compression shapes. Often steel reinforcement is still necessary to carry tensile forces occurring under different load combinations and to limit crack formation. A new composite material, textile reinforced cementitious composite (TRC), eliminates this rest...

  12. The microstructure of self-healed PVA ECC under wet and dry cycles

    Directory of Open Access Journals (Sweden)

    Jia Huan Yu

    2010-06-01

    Full Text Available Self-healing of ECC (Engineered Cementitious Composites subjected to cyclic wetting and drying regimes is investigated in this paper. ECC structures subjected to outdoor environmental conditions such as wind and rain runoff can be simulated by accelerated test method of wetting and drying cycles. Uniaxial tensile tests of ECC M45 and ECC 2.8FA specimen are conducted respectively. It is found that crack width of ECC 2.8FA is around 10 μm with increased amount of fly ash, while the crack width of ECC M45 is around 100 μm. New insights about the microstructure and chemical composition analysis of ECC specimens initially cracked to 2% strain and then self-healed under wet-dry cycles are presented.

  13. Hybrid fiber reinforcement and crack formation in Cementitious Composite Materials

    DEFF Research Database (Denmark)

    Pereira, E.B.; Fischer, Gregor; Barros, J.A.O.

    2011-01-01

    The use of different types of fibers simultaneously for reinforcing cementitious matrices is motivated by the concept of a multi-scale nature of the crack propagation process. Fibers with different geometrical and mechanical properties are used to bridge cracks of different sizes from the micro- to...... the macroscale. In this study, the performance of different fiber reinforced cementitious composites is assessed in terms of their tensile stress-crack opening behavior. The results obtained from this investigation allow a direct quantitative comparison of the behavior obtained from the different...... fiber reinforcement systems. The research described in this paper shows that the multi-scale conception of cracking and the use of hybrid fiber reinforcements do not necessarily result in an improved tensile behavior of the composite. Particular material design requirements may nevertheless justify the...

  14. Hybrid fiber reinforcement and crack formation in Cementitious Composite Materials

    DEFF Research Database (Denmark)

    Pereira, E.B.; Fischer, Gregor; Barros, J.A.O.

    2011-01-01

    the macroscale. In this study, the performance of different fiber reinforced cementitious composites is assessed in terms of their tensile stress-crack opening behavior. The results obtained from this investigation allow a direct quantitative comparison of the behavior obtained from the different......The use of different types of fibers simultaneously for reinforcing cementitious matrices is motivated by the concept of a multi-scale nature of the crack propagation process. Fibers with different geometrical and mechanical properties are used to bridge cracks of different sizes from the micro- to...... fiber reinforcement systems. The research described in this paper shows that the multi-scale conception of cracking and the use of hybrid fiber reinforcements do not necessarily result in an improved tensile behavior of the composite. Particular material design requirements may nevertheless justify the...

  15. Meso-mechanical analysis of steel fiber reinforced cementitious composites

    OpenAIRE

    Caggiano, Antonio

    2013-01-01

    2010 - 2011 The mechanical behavior of cement-based materials is greatly affected by crack propagation under general stress states. The presence of one or more dominant cracks in structural members modifies its response, possibly leading to brittle failure modes. The random dispersion of short steel fibers in cement materials is a new methodology used for enhancing the response in the post-cracking regime. The behavior of Fiber-Reinforced Cementitious Composite (FRCC), compared...

  16. Conductivity-based strain monitoring and damage characterization of fiber reinforced cementitious structural components

    Science.gov (United States)

    Hou, Tsung-Chin; Lynch, Jerome P.

    2005-05-01

    In recent years, a new class of cementitious composite has been proposed for the design and construction of durable civil structures. Termed engineered cementitious composites (ECC), ECC utilizes a low volume fraction of short fibers (polymer, steel, carbon) within a cementitious matrix resulting in a composite that strain hardens when loaded in tension. By refining the mechanical properties of the fiber-cement interface, the material exhibits high tolerance to damage. This study explores the electrical properties of ECC materials to monitor their performance and health when employed in the construction of civil structures. In particular, the conductivity of ECC changes in proportion to strain indicating that the material is piezoresistive. In this paper, the piezoresistive properties of various ECC composites are thoroughly explored. To measure the electrical resistance of ECC structures in the field, a low-cost wireless active sensing unit is proposed. The wireless active sensing unit is capable of applying DC and AC voltage signals to ECC elements while simultaneously measuring their corresponding voltages away from the signal input. By locally processing the corresponding input-output electrical signals recorded by the wireless active sensing units, the magnitude of strain in ECC elements can be calculated. In addition to measuring strain, the study seeks to correlate changes in ECC electrical properties to the magnitude of crack damage witnessed in tested specimens. A large number of ECC specimens are tested in the laboratory including a large-scale ECC bridge pier laterally loaded under cyclically repeated drift reversals. The novel self-sensing properties of ECC exploited by a wireless monitoring system hold tremendous promise for the advancement of structural health monitoring of ECC structures.

  17. Innovative Structural Materials and Sections with Strain Hardening Cementitious Composites

    Science.gov (United States)

    Dey, Vikram

    The motivation of this work is based on development of new construction products with strain hardening cementitious composites (SHCC) geared towards sustainable residential applications. The proposed research has three main objectives: automation of existing manufacturing systems for SHCC laminates; multi-level characterization of mechanical properties of fiber, matrix, interface and composites phases using servo-hydraulic and digital image correlation techniques. Structural behavior of these systems were predicted using ductility based design procedures using classical laminate theory and structural mechanics. SHCC sections are made up of thin sections of matrix with Portland cement based binder and fine aggregates impregnating continuous one-dimensional fibers in individual or bundle form or two/three dimensional woven, bonded or knitted textiles. Traditional fiber reinforced concrete (FRC) use random dispersed chopped fibers in the matrix at a low volume fractions, typically 1-2% to avoid to avoid fiber agglomeration and balling. In conventional FRC, fracture localization occurs immediately after the first crack, resulting in only minor improvement in toughness and tensile strength. However in SHCC systems, distribution of cracking throughout the specimen is facilitated by the fiber bridging mechanism. Influence of material properties of yarn, composition, geometry and weave patterns of textile in the behavior of laminated SHCC skin composites were investigated. Contribution of the cementitious matrix in the early age and long-term performance of laminated composites was studied with supplementary cementitious materials such as fly ash, silica fume, and wollastonite. A closed form model with classical laminate theory and ply discount method, coupled with a damage evolution model was utilized to simulate the non-linear tensile response of these composite materials. A constitutive material model developed earlier in the group was utilized to characterize and

  18. Experimental Study on Cementitious Composites Embedded with Organic Microcapsules

    Directory of Open Access Journals (Sweden)

    Zhiwei Qian

    2013-09-01

    Full Text Available The recovery behavior for strength and impermeability of cementitious composites embedded with organic microcapsules was investigated in this study. Mortar specimens were formed by mixing the organic microcapsules and a catalyst with cement and sand. The mechanical behaviors of flexural and compression strength were tested. The results showed that strength could increase by up to nine percent with the addition of a small amount of microcapsules and then decrease with an increasing amount of microcapsules. An orthogonal test for investigating the strength recovery rate was designed and implemented for bending and compression using the factors of water/cement ratio, amount of microcapsules, and preloading rate. It is shown that the amount of microcapsules plays a key role in the strength recovery rate. Chloride ion permeability tests were also carried out to investigate the recovery rate and healing effect. The initial damage was obtained by subjecting the specimens to compression. Both the recovery rate and the healing effect were nearly proportional to the amount of microcapsules. The obtained cementitious composites can be seen as self-healing owing to their recovery behavior for both strength and permeability.

  19. Dynamic fracture behaviour in fibre-reinforced cementitious composites

    Science.gov (United States)

    Yu, Rena C.; Cifuentes, Héctor; Rivero, Ignacio; Ruiz, Gonzalo; Zhang, Xiaoxin

    2016-08-01

    The object of this work is to simulate the dynamic fracture propagation in fibre-reinforced cementitious composites, in particular, in steel fibre reinforced concrete (SFRC). Beams loaded in a three-point bend configuration through a drop-weight impact device are considered. A single cohesive crack is assumed to propagate at the middle section; the opening of this crack is governed by a rate-dependent cohesive law; the fibres around the fracture plane are explicitly represented through truss elements. The fibre pull-out behaviour is depicted by an equivalent constitutive law, which is obtained from an analytical load-slip curve. The obtained load-displacement curves and crack propagation velocities are compared with their experimental counterparts. The good agreement with experimental data testifies to the feasibility of the proposed methodology and paves the way to its application in a multi-scale framework.

  20. An experimental investigation of innovative bridge columns with engineered cementitious composites and Cu-Al-Mn super-elastic alloys

    Science.gov (United States)

    Hosseini, F.; Gencturk, B.; Lahpour, S.; Ibague Gil, D.

    2015-08-01

    Recent strong earthquakes have shown that reinforced concrete (RC) bridge columns constructed using conventional materials and techniques suffer from major damage and permanent deformations. The yielding of the longitudinal reinforcement as the main source of energy absorption, and cracking and spalling of concrete results in a dysfunctional bridge structure that does not support the post-disaster recovery efforts. This paper investigates the use of engineered cementitious composites (ECCs) and Cu-Al-Mn super-elastic alloys (SEAs) to improve the performance of bridge columns under seismic loads. A new column design is proposed, which is composed of a pre-fabricated ECC tube that encompasses the longitudinal and transverse steel reinforcement (rebar). The rebar in the plastic hinge region of the cantilever columns was totally or partially replaced with Cu-Al-Mn SEA bars. The tube was filled with conventional concrete after it was placed inside the rebar cage of the foundation. ECC exhibits superior tensile ductility, bonding with steel, energy absorption and shear resistance, in addition to lower permeability and reduced crack widths compared to conventional concrete. Cu-Al-Mn SEA bars are capable of recovering large inelastic deformations exceeding 12% strain. The proposed approach capitalizes on the deformability of ECC with reduced damage, and the energy absorption capacity of Cu-Al-Mn SEA bars without permanent deformation. A total of six column specimens were constructed and tested under simulated seismic loading. The number of rebars replaced with Cu-Al-Mn SEA bars, ECC mixture design, and the ratio of the concrete core area to total column cross-sectional area were the variables investigated in the test program. A comparison of the results indicated that the proposed concept with no Cu-Al-Mn SEA bars provides higher lateral strength, similar energy absorption and reduced damage compared to conventional RC columns; however, similar to a conventional column, it

  1. Shear crack formation and propagation in reinforced Engineered Cementitious Composites

    DEFF Research Database (Denmark)

    Paegle, Ieva; Fischer, Gregor

    2011-01-01

    capacity of beams loaded primarily in shear. The experimental program consists of ECC with short randomly distributed polyvinyl alcohol (PVA) fiber beams with different stirrup arrangements and conventional reinforced concrete (R/C) counterparts for comparison. The shear crack formation mechanism of ECC is...

  2. Triboluminesence multifunctional cementitious composites with in situ damage sensing capability

    Science.gov (United States)

    Olawale, David O.; Dickens, Tarik; Uddin, Mohammed J.; Okoli, Okenwa O.

    2012-04-01

    Structural health monitoring of civil infrastructure systems like concrete bridges and dams has become critical because of the aging and overloading of these CIS. Most of the available SHM methods are not in-situ and can be very expensive. The triboluminescence multifunctional cementitious composites (TMCC) have in-built crack detection mechanism that can enable bridge engineers to monitor and detect abnormal crack formation in concrete structures so that timely corrective action can be taken to prevent costly or catastrophic failures. This article reports the fabrication process and test result of the flexural characterization of the TMCC. Accelerated durability test indicated that the 0.5 ZnS:Mn/Epoxy weight fraction ITOF sensor configuration to be more desirable in terms of durability. The alkaline environment at the highest temperature investigated (45 °C) resulted in significant reduction in the mean glass transition and storage moduli of the tested ITOF thin films. Further work is ongoing to correlate the TL response of the TMCC with damage, particularly crack opening.

  3. Uniaxial Compressive Properties of Ultra High Toughness Cementitious Composite

    Institute of Scientific and Technical Information of China (English)

    CAI Xiangrong; XU Shilang

    2011-01-01

    Uniaxial compression tests were conducted to characterize the main compressive performance of ultra high toughness cementitious composite(UHTCC)in terms of strength and toughness and to obtain its stress-strain relationships.The compressive strength investigated ranges from 30 MPa to 60 MPa.Complete stress-strain curves were directly obtained,and the strength indexes,including uniaxial compressive strength,compressive strain at peak stress,elastic modulus and Poisson's ratio,were calculated.The comparisons between UHTCC and matrix were also carried out to understand the fiber effect on the compressive strength indexes.Three dimensionless toughness indexes were calculated,which either represent its relative improvement in energy absorption capacity because of fiber addition or provide an indication of its behavior relative to a rigid-plastic material.Moreover,two new toughness indexes,which were named as post-crack deformation energy and equivalent compressive strength,were proposed and calculated with the aim at linking up the compressive toughness of UHTCC with the existing design concept of concrete.The failure mode was also given.The study production provides material characteristics for the practical engineering application of UHTCC.

  4. Microstructural analysis and characterization of the ECCS steel composite with PET co-laminated sheets

    International Nuclear Information System (INIS)

    The production of thin metal-polymer laminates aims to combine good mechanical properties and resistance to degradation from external aggressive means. But to achieve this surface and interphase structural aspects of the metallic substrates, like the protective polymer substrate, have to be satisfied. Using SEM, TEM, SFET electronic microscopy and EDAX microanalysis, this work characterizes the different substrates that are contained in a metal-polymer laminate made of a steel veneer covered with ECCS electrolytic chrome and superficially protected with a co-laminated polyethylene terephthalate (PET). The morphology and composition of these substrates that allow good adherence of the metal-polymer laminate is studied at the interphase level (CW)

  5. Micro-mechanical Analysis of Fiber Reinforced Cementitious Composites using Cohesive Crack Modeling

    DEFF Research Database (Denmark)

    Dick-Nielsen, Lars; Stang, Henrik; Poulsen, Peter Noe

    2006-01-01

    This paper discusses the mechanism appearing during fiber debonding in fiber reinforced cementitious composite. The investigation is performed on the micro scale by use of a Finite Element Model. The model is 3 dimensional and the fictitious crack model and a mixed mode stress formulation are...... implemented. It is shown that the cohesive law for a unidirectional fiber reinforced cementitious composite can be found through superposition of the cohesive law for mortar and the fiber bridging curve. A comparison between the numerical and an analytical model for fiber pull-out is performed....

  6. Numerical framework for modeling of cementitious composites at the meso-scale

    OpenAIRE

    Jerábek, Jakub

    2011-01-01

    The application of composite materials as a building material has been constantly growing in popularity during the last decades. Composite materials combine several material components to allow for an optimal utilization of their favorable properties. The focus of this work is the modeling of the cementitious composites at the extit{meso-scale}. In particular, the motivation of the thesis is to model textile reinforced concrete, a new composite material combining a high-strength textile reinf...

  7. Self-healing behavior of strain hardening cementitious composites incorporating local waste materials

    NARCIS (Netherlands)

    Qian, S.; Zhou, J.; Rooij, M.R. de; Schlangen, E.; Ye, G.; Breugel, K. van

    2009-01-01

    The self-healing behavior of a series of pre-cracked fiber reinforced strain hardening cementitious composites incorporating blast furnace slag (BFS) and limestone powder (LP) with relatively high water/binder ratio is investigated in this paper, focusing on the recovery of its deflection capacity.

  8. Cementitious Composites Engineered with Embedded Carbon Nanotube Thin Films for Enhanced Sensing Performance

    Science.gov (United States)

    Loh, Kenneth J.; Gonzalez, Jesus

    2015-07-01

    Cementitious composites such as concrete pavements are susceptible to different damage modes, which are primarily caused by repeated loading and long-term deterioration. There is even greater concern that damage could worsen and occur more frequently with the use of heavier vehicles or new aircraft carrying greater payloads. Thus, the objective of this research is to engineer cementitious composites with capabilities of self-sensing or detecting damage. The approach was to enhance the damage sensitivity of cementitious composites by incorporating multi-walled carbon nanotubes (MWNT) as part of the mix design and during casting. However, as opposed to directly dispersing MWNTs in the cement matrix, which is the current state-of-art, MWNT-based thin films were airbrushed and coated onto sand particles. The film-coated sand was then used as part of the mix design for casting mortar specimens. Mortar specimens were subjected to compressive cyclic loading tests while their electrical properties were recorded simultaneously. The results showed that the electrical properties of these cementitious composites designed with film-coated sand exhibited extremely high strain sensitivities. The electrical response was also stable and consistent between specimens.

  9. Effect of hybrid fiber reinforcement on the cracking process in fiber reinforced cementitious composites

    DEFF Research Database (Denmark)

    Pereira, Eduardo B.; Fischer, Gregor; Barros, Joaquim A.O.

    2012-01-01

    tensile deformations in the composite, the fibers with different geometrical and mechanical properties restrain the propagation and further development of cracking at different scales from the micro- to the macro-scale. The optimized design of the fiber reinforcing systems requires the objective......The simultaneous use of different types of fibers as reinforcement in cementitious matrix composites is typically motivated by the underlying principle of a multi-scale nature of the cracking processes in fiber reinforced cementitious composites. It has been hypothesized that while undergoing...... materials is carried out by assessing directly their tensile stress-crack opening behavior. The efficiency of hybrid fiber reinforcements and the multi-scale nature of cracking processes are discussed based on the experimental results obtained, as well as the micro-mechanisms underlying the contribution of...

  10. Transition from Multiple Macro-Cracking to Multiple Micro-Cracking in Cementitious Composites

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jun; LENG Bing

    2008-01-01

    This paper presents an experimental study of the possibility of transition from multiple macro-cracking to multiple micro-cracking in cementitious composites.Conventional polyvinyl alcohol fiber reinforced cementitious composites normally exhibit macroscopic strain-hardening and multiple cracking after the first cracks appear.However,the individual crack width at the saturated stage is normally 60 to 80 μm.In the current study,the effect of fine aggregate size on the cracking performance,especially the individual crack width in the strain-hardening stage was studied by bending tests.The results show that the individual crack widths can be reduced from 60-80 μm to 10-30 μm by modifying the particle size of the fine aggregates used in the composites.

  11. About microcracking due to leaching in cementitious composites: X-ray microtomography description and numerical approach

    International Nuclear Information System (INIS)

    Chemical shock of cement based materials leads to significant degradation of their physical properties. A typical scenario is a calcium leaching due to water (water with very low pH compared with that of pore fluid). The main objective of this paper is to evaluate the evolution of microstructure induced by leaching of a cementitious composite using synchrotron X-ray micro tomography, mainly from an experimental point of view. In this particular case, it was possible to identify cracking induced by leaching. After a description of the degradation mechanism and the X-ray synchrotron microtomographic analysis, numerical simulations are performed in order to show that cracking is induced by an initial pre-stressing of the composite, coupled with decalcification shrinkage and dramatic decrease in tensile strength during leaching. X-ray microtomography analysis allowed to make evidence of an induced microcracking in cementitious material submitted to leaching.

  12. Modeling of ECC materials using numerical formulations based on plasticity

    DEFF Research Database (Denmark)

    Dick-Nielsen, Lars; Stang, Henrik; Poulsen, Peter Noe

    2006-01-01

    scale it is shown that the cohesive law for a unidirectional fiber reinforced cementitious composite can be found through superposition of the cohesive law for mortar and the fiber bridging curve. On the meso scale I it is shown that the maximum crack opening observed during crack propagation in ECC is...... small, 20 ¹m and also small compared to typical deformations at peak bridging stress. On the meso scale II interaction between initial flaws and micro cracks was observed. A framework is presented for the formulation of a damage mechanics model comprising the damage mechanisms on the micro and meso......This paper discusses the considerations for the establishment of a damage model for ECC. Three different length scales are used in the approach for deriving the damage model. On each length scale important phenomena are investigated by use of numerical and analytical calculations. On the micro...

  13. Direct assessment of tensile stress-crack opening behavior of Strain Hardening Cementitious Composites (SHCC)

    OpenAIRE

    Pereira, E. N. B.; Fischer, G.; Barros, Joaquim A. O.

    2012-01-01

    The process of designing Strain Hardening Cementitious Composites (SHCC) is driven by the need to achieve certain performance parameters in tension. These are typically the pseudo-strain hardening behavior and the ability to develop multiple cracks. The assessment of the tensile load-deformation of these materials is therefore of great importance and is frequently carried out by characterizing the material tensile stress-strain behavior. In this paper an alternative approach...

  14. Characterization of cracking in strain hardening cementitious composites using the compact tension test

    OpenAIRE

    Pereira, E. N. B.; Fischer, G.; Barros, Joaquim A. O.

    2012-01-01

    The characterization of the tensile behavior of strain hardening cementitious composites (SHCC) is of significant importance to the material design. In a previous work the tensile stress-crack opening response of different types of SHCC was characterized using notched specimens tested in direct tension, where a single crack was obtained and mechanically characterized by performing Single Crack Tension Test (SCTT). In this study the tensile behavior of SHCC materials is charact...

  15. Bond Characteristics of Macro Polypropylene Fiber in Cementitious Composites Containing Nanosilica and Styrene Butadiene Latex Polymer

    Directory of Open Access Journals (Sweden)

    Jae-Woong Han

    2015-01-01

    Full Text Available This study evaluated the bond properties of polypropylene (PP fiber in plain cementitious composites (PCCs and styrene butadiene latex polymer cementitious composites (LCCs at different nanosilica contents. The bond tests were evaluated according to JCI SF-8, in which the contents of nanosilica in the cement were 0, 2, 4, 6, 8, and 10 wt%, based on cement weight. The addition of nanosilica significantly affected the bond properties between macro PP fiber and cementitious composites. For PCCs, the addition of 0–2 wt% nanosilica enhanced bond strength and interface toughness, whereas the addition of 4 wt% or more reduced bond strength and interface toughness. The bond strength and interfacial toughness of LCCs also increased with the addition of up to 6% nanosilica. The analysis of the relative bond strength showed that the addition of nanosilica affects the bond properties of both PCC and LCC. This result was confirmed via microstructural analysis of the macro PP fiber surface after the bond tests, which revealed an increase in scratches due to frictional forces and fiber tearing.

  16. A review: Self-healing in cementitious materials and engineered cementitious composite as a self-healing material

    DEFF Research Database (Denmark)

    Wu, Min; Johannesson, Björn; Geiker, Mette

    2012-01-01

    Cementitious materials are the most widely used building materials all over the word. However, deterioration is inevitable even since the very beginning of the service life, then maintenance and repair work, which are often labor- and capital-intensive, would be followed. Thus, self-healing of th...

  17. Evaluation of test methods used to characterize fiber reinforced cementitious composites

    DEFF Research Database (Denmark)

    Paegle, Ieva; Fischer, Gregor

    2013-01-01

    tensile properties of Fiber Reinforced Cement Composites (FRCC) over the direct measurement of the tensile behavior because of the more convenient test setup and ease of specimen preparation. Three and four-point bending tests and round determinate panel test were carried out to evaluate the flexural......This paper describes an investigation of fiber reinforced cementitious composites in terms of their behavior under tensile and flexural loading. Flexural testing and subsequent derivation of the tensile stress-deformation response from the flexural test data are preferred in the assessment of the...

  18. A Review on Nanomaterial Dispersion, Microstructure, and Mechanical Properties of Carbon Nanotube and Nanofiber Reinforced Cementitious Composites

    Directory of Open Access Journals (Sweden)

    Shama Parveen

    2013-01-01

    Full Text Available Excellent mechanical, thermal, and electrical properties of carbon nanotubes (CNTs and nanofibers (CNFs have motivated the development of advanced nanocomposites with outstanding and multifunctional properties. After achieving a considerable success in utilizing these unique materials in various polymeric matrices, recently tremendous interest is also being noticed on developing CNT and CNF reinforced cement-based composites. However, the problems related to nanomaterial dispersion also exist in case of cementitious composites, impairing successful transfer of nanomaterials' properties into the composites. Performance of cementitious composites also depends on their microstructure which is again strongly influenced by the presence of nanomaterials. In this context, the present paper reports a critical review of recent literature on the various strategies for dispersing CNTs and CNFs within cementitious matrices and the microstructure and mechanical properties of resulting nanocomposites.

  19. Cementitious Composites for Immobilization of Radioactive Waste into Final Wasteform

    International Nuclear Information System (INIS)

    Research and development works are important on universal cementation technological processes to achieve maximal conditioning efficiency for various type wastes such as saline liquid radioactive waste (LRW), where the variants of cement composition formulations, modes of cement compounds preparation and types of equipment are minimised. This work presents the results of development of multi-component cement compositions for the complex of technological processes of different types of radioactive waste (RAW) cementation: concentrated saline LRW, concentrated boron-containing saline LRW, LRW with high surface active substances content, with residues, liquid organic radioactive waste, spent ion-exchange resins and filter-perlite powder, ash residues from solid radioactive waste (SRW) combustion, mixed closely packed and large-fragmented SRW. The research has found technological parameters of equipment and cement compositions providing reliable RAW cementation. Continuous and periodic cycle plants were developed for LRW cementation by mixing. Pouring and penetration methods were developed for SRW cementation. Based on compliance with equipment parameters, methods and cement grouts were selected for most effective technological processes of cementation. Formulations of cement compositions were developed to provide reliable preparation of cement compounds with maximal waste loading at required cement compound quality. The complex of technological processes of cementation using multi-component cement compositions allows highly efficient treatment of the wide range of RAW including problematic waste streams and wastes generated in small amounts. Rational reduction of cementation variants significantly increases economical efficiency of immobilisation. (author)

  20. Photocatalytic Cementitious Composites containing Mesoporous Titanium Dioxide Nanoparticles

    Directory of Open Access Journals (Sweden)

    FALIKMAN Vyacheslav Ruvimovich

    2014-02-01

    Full Text Available The advanced method to produce nanoparticles of anatase mesoporous TiO₂ with high specific surface 300 m²/g has been developed. It was shown that titanium nanodioxide can be used in cement and gypsum composites as a highly efficient photocatalyst in the conversion processes of nitric oxide and volatile organic substances. Influence of radiation intensity, relative humidity, and concentration of contaminant and its stream speed on photocatalysis was studied. It was determined that efficiency of the composites with synthesized samples is 1,5–1,7 times higher than that of the commercial sample of the titanium nanodioxide.

  1. Property investigation of calcium–silicate–hydrate (C–S–H) gel in cementitious composites

    International Nuclear Information System (INIS)

    Calcium–silicate–hydrate (C–S–H) gel, the main product of cement hydration, contributes the most to engineering properties of concrete. Hence, the microstructural physical and mechanical properties of C–S–H gel present in cementitious composites were investigated by the coupled nanoindentation and scanning electron microscope analysis. The physical and mechanical properties were linked through the micro-poromechanical approach. Through this study, an insight was provided into the microstructural features of C–S–H gel present in cementitious composites. It is found that C–S–H gel is a multi-scale composite composed of C–S–H solid, pore and intermixtures at the scale of nanoindentation on C–S–H gel, and the physical and mechanical properties of C–S–H gel can be influenced by the porosity and volume fraction of the intermixtures. - Highlights: • A coupled nanoindentation and scanning electron microscope technique was applied. • The physical and mechanical properties were linked by the proposed model. • The porosity and poroelastic parameters were reported for the first time. • The influence of water to cement ratio was studied

  2. RC beams shear-strengthened with fabric-reinforced-cementitious-matrix (FRCM) composite

    Science.gov (United States)

    Loreto, Giovanni; Babaeidarabad, Saman; Leardini, Lorenzo; Nanni, Antonio

    2015-12-01

    The interest in retrofit/rehabilitation of existing concrete structures has increased due to degradation and/or introduction of more stringent design requirements. Among the externally-bonded strengthening systems fiber-reinforced polymers is the most widely known technology. Despite its effectiveness as a material system, the presence of an organic binder has some drawbacks that could be addressed by using in its place a cementitious binder as in fabric-reinforced cementitious matrix (FRCM) systems. The purpose of this paper is to evaluate the behavior of reinforced concrete (RC) beams strengthened in shear with U-wraps made of FRCM. An extensive experimental program was undertaken in order to understand and characterize this composite when used as a strengthening system. The laboratory results demonstrate the technical viability of FRCM for shear strengthening of RC beams. Based on the experimental and analytical results, FRCM increases shear strength but not proportionally to the number of fabric plies installed. On the other hand, FRCM failure modes are related with a high consistency to the amount of external reinforcement applied. Design considerations based on the algorithms proposed by ACI guidelines are also provided.

  3. Significance of Shrinkage Induced Clamping Pressure in Fiber-Matrix Bonding in Cementitious Composite Materials

    DEFF Research Database (Denmark)

    Stang, Henrik

    1996-01-01

    The present paper accesses the significance of shrinkage inducedclamping pressure in fiber/matrix bonding mechanisms incementitious composite materials. The paper contains a description of an experimental setup whichallows mbox{measurement} of the clamping pressure which develops on anelastic...... inhomogeneity embedded in a matrix consisting of acementitious material undergoing shrinkage during hydration(autogenous shrinkage). Furthermore, the paperpresents the analysis necessary to perform an interpretation of the experimental results and which allows for thedetermination of the clamping pressure...... used in high performance cementitious composite materials.Assuming a Coulomb type of friction on the fiber/matrix interface andusing typical values for the frictional coefficient it is shownthat the shrinkage induced clamping pressure could be one of the mostimportant factors determining the frictional...

  4. Excellent bonding behaviour of novel surface-tailored fibre composite rods with cementitious matrix

    Indian Academy of Sciences (India)

    Fernando Cunha; Sohel Rana; Raul Fangueiro; Graça Vasconcelos

    2014-08-01

    Novel composite rods were produced by a special braiding technique that involves braiding of polyester yarns around a core of resin-impregnated carbon fibres and subsequent curing. The surface roughness of these braided rods was tailored by replacing one or two simple yarns in the outer-braided layer with braided yarns (produced from 8 simple yarns) and adjusting the take-up velocity. Pull-out tests were carried out to characterize the bond behaviour of these composite rods with cementitious matrix. It was observed that the rod produced with two braided yarns in the outer cover and highest take-up speed was ruptured completely before pull-out, leading to full utilization of its tensile strength, and exhibited 134% higher pull-out force as compared to the rods produced using only simple braiding yarns.

  5. Direct assessment of tensile stress-crack opening behavior of Strain Hardening Cementitious Composites (SHCC)

    DEFF Research Database (Denmark)

    Pereira, Eduardo B.; Fischer, Gregor; Barros, Joaquim A.O.

    2012-01-01

    -deformation behavior of these materials is therefore of great importance and is frequently carried out by characterizing the material tensile stress–strain behavior. In this paper an alternative approach to evaluate the tensile performance of SHCC is investigated. The behavior of the material in tension is studied at......The process of designing Strain Hardening Cementitious Composites (SHCC) is driven by the need to achieve certain performance parameters in tension. These are typically the pseudo-strain hardening behavior and the ability to develop multiple cracks. The assessment of the tensile load...... the level of a single crack. The derived tensile stress-crack opening behavior is utilized to analyze and compare the influence of various composite parameters on the resulting tensile behavior. The deformations occurring during tensile loading are furthermore examined using a digital image...

  6. Characterization of cracking in Strain-Hardening Cementitious Composites using the compact tension test

    DEFF Research Database (Denmark)

    Pereira, Eduardo B.; Fischer, Gregor; Barros, Joaquim A. O.

    The characterization of the tensile behavior of strain hardening cementitious composites (SHCC) is of significant importance to the material design. In a previous work the tensile stress-crack opening response of different types of SHCC was characterized using notched specimens tested in direct...... tension, where a single crack was obtained and mechanically characterized by performing Single Crack Tension Test (SCTT). In this study the tensile behavior of SHCC materials is characterized under eccentric tensile load using the Compact Tension Test (CTT). The long edge notch placed in the rectangular...... results are discussed and compared to the numerically derived responses. The tensile load-displacement responses observed in the CTTs were simulated using the cohesive crack model. The tensile stress-crack opening behaviors previously obtained with the SCTT tests were utilized to derive the traction...

  7. FUNDAMENTAL PROPERTIES OF ULTRA HIGH PERFORMANCE-STRAIN HARDENING CEMENTITIOUS COMPOSITES AND USAGE FOR REPAIR

    Science.gov (United States)

    Kunieda, Minoru; Shimizu, Kosuke; Eguchi, Teruyuki; Ueda, Naoshi; Nakamura, Hikaru

    This paper presents the fundamental properties of Ultra High Performance-Strain Hardening Cementitious Composites (UHP-SHCC), which were depeloped for repair applications. In particular, mechanical properties such as tensile response, shrinkage and bond strength were investigated experimentally. Protective performance of the material such as air permeability, water permeability and penetration of chloride ion was also confirmed comparing to that of ordinary concrete. This paper also introduces the usage of the material in repair of concrete st ructures. Laboratory tests concerining the deterioration induced by corrosion were conducted. The UHP-SHCC that coverd the RC beam resisted not only crack opening along the rebar due to corrosion but also crack opening due to loading tests.

  8. 氯盐环境对PVA纤维增强水泥基复合材料抗冻性的影响%Influence of Chloride Environment on Frost Resistance of PVA Fiber Reinforced Engineered Cementitious Composite

    Institute of Scientific and Technical Information of China (English)

    张菊; 刘曙光; 闫长旺; 白建文; 闫敏

    2013-01-01

    在氯盐环境和淡水环境中进行聚乙烯醇纤维增强水泥基复合材料(polyvinyl alcohol fiber reinforced engineered cementitious composite,PVA-ECC)快速冻融试验,研究了氯盐环境对试件外观形貌、质量损失率、相对动弹性模量和耐久性指数的影响.结果表明:氯盐环境中,PVA-ECC试件质量在冻融循环初期呈增大趋势,在冻融循环后期因表层严重剥落,导致质量下降,质量损失率显著增大,整个冻融循环过程中试件的耐久性指数较小,相对动弹性模量明显下降;淡水环境中PVA-ECC试件经历冻融循环后基本保持原有形状和尺寸,质量损失率变化幅度较小,相对动弹性模量下降趋势平缓,耐久性指数较大.与淡水环境相比,氯盐环境中PVA-ECC试件的抗冻性显著下降,表明氯盐环境对PVA-ECC抗冻性有重要影响.%The frost resistance of polyvinyl alcohol fiber reinforced engineered cementitious composite (PVA-ECC) in chloride and freshwater environments was investigated via an accelerated freeze-thaw test.Influence of chloride environment on the appearance morphology,mass loss ratio,relative dynamic elastic modulus (Erd) and durability indices was analyzed.The results show that the mass of specimen in chloride environment increases during first freeze-thaw cycles,but the mass and Erd both decrease,the mass loss rate increases during later freeze-thaw cycles because the surface layer of specimen flakes away seriously.The durability indices of specimen in chloride environment are less during whole freeze-thaw cycles.However,the original shape and size unchange,the mass loss rate changes slightly,Erd decreases and the durability indices are more for the specimen in freshwater environment during the freeze-thaw cycles.The frost resistance of specimen can decrease readily in chloride environment rather than in freshwater environment,illustrating that the chloride environment has a significant effect on the frost resistance of

  9. Tailoring of fiber-reinforced cementitious composites (FRCC) for flexural strength and reliability

    Science.gov (United States)

    Obla, Karthikeyan Hariya

    Bending is the most common form of loading for many construction elements. The bending strength or Modulus of Rupture (MOR) and flexural ductility are therefore critical properties particularly for those elements which are not reinforced by rebars. Such elements include highway barriers, certain wall panels, thin sheet elements and small diameter pipes. The tensile and bending strengths of concrete are very low. In addition, as a brittle material, concrete also demonstrates a large variability in bending strength. A large variability in MOR leads to inefficient use of the material since the design strength has to be close to the lower bound of the material's strength distribution. The potential of fiber in improving MOR is well recognized in fiber reinforced concrete. The use of fiber to enhance material reliability is much less studied. This thesis addresses both aspects employing a combination of theoretical and experimental treatments. Research findings are reported as Part I and Part II of this thesis. Carbon fibers are increasingly attractive for reinforcing cementitious composites. They can be manufactured to yield a wide range in modulus and strength. Carbon fibers are non-corrosive, and fire and alkali. In addition, the price of pitch based carbon fibers are dropping rapidly to make them economically viable for the building and construction industries. In Part I of the thesis, a study on the optimization of the bending strength of carbon FRCC using a fracture based flexural model that links the fiber, interface, and matrix micro-parameters to composite bending strength is presented. Carbon fiber, interface and matrix parameters were tailored to yield optimal properties such as high MOR and ductility. Four point bend tests were conducted on CFRCCs to confirm the findings. Some problems specially affecting carbon FRCCs such as fiber breakage during mixing were also studied and its effects on composite uniaxial tensile properties analyzed by developing new

  10. The Influence of Nano-Fe3O4 on the Microstructure and Mechanical Properties of Cementitious Composites.

    Science.gov (United States)

    Sikora, Pawel; Horszczaruk, Elzbieta; Cendrowski, Krzysztof; Mijowska, Ewa

    2016-12-01

    In the last decade, nanotechnology has been gathering a spectacular amount of attention in the field of building materials. The incorporation of nanosized particles in a small amount to the building materials can influence their properties significantly. And it can contribute to the creation of novel and sustainable structures. In this work, the effect of nano-Fe3O4 as an admixture (from 1 to 5 wt.% in mass of the cement) on the mechanical and microstructural properties of cementitious composites has been characterised. The study showed that Fe3O4 nanoparticles acted as a filler which improved the microstructure of a cementitious composite and reduced its total porosity, thus increasing the density of the composite. The presence of nanomagnetite did not affect the main hydration products and the rate of cement hydration. In addition, the samples containing nanomagnetite exhibited compressive strength improvement (up to 20 %). The study showed that 3 wt.% of nano-Fe3O4 in the cementitious composite was the optimal amount to improve both its mechanical and microstructural properties. PMID:27067730

  11. The Influence of Nano-Fe3O4 on the Microstructure and Mechanical Properties of Cementitious Composites

    Science.gov (United States)

    Sikora, Pawel; Horszczaruk, Elzbieta; Cendrowski, Krzysztof; Mijowska, Ewa

    2016-04-01

    In the last decade, nanotechnology has been gathering a spectacular amount of attention in the field of building materials. The incorporation of nanosized particles in a small amount to the building materials can influence their properties significantly. And it can contribute to the creation of novel and sustainable structures. In this work, the effect of nano-Fe3O4 as an admixture (from 1 to 5 wt.% in mass of the cement) on the mechanical and microstructural properties of cementitious composites has been characterised. The study showed that Fe3O4 nanoparticles acted as a filler which improved the microstructure of a cementitious composite and reduced its total porosity, thus increasing the density of the composite. The presence of nanomagnetite did not affect the main hydration products and the rate of cement hydration. In addition, the samples containing nanomagnetite exhibited compressive strength improvement (up to 20 %). The study showed that 3 wt.% of nano-Fe3O4 in the cementitious composite was the optimal amount to improve both its mechanical and microstructural properties.

  12. Micro-mechanical damage and rough crack closure in cementitious composite materials

    Science.gov (United States)

    Jefferson, A. D.; Bennett, T.

    2007-02-01

    A micro-mechanics based damage model is presented which uses the solution of an elastic body with penny-shaped cracks. The major new aspect of the work is the inclusion of a rough crack closure component in the model. The model uses a damage-surface, described in terms of transformed strain components. Inelastic strain components in each direction are computed by considering the total directional strains on an equivalent band of elastic material and then removing the elastic component. Details of the model implementation in a Mathcad sheet are given. The results from a series of single point simulations are given for uniaxial and biaxial tension and compression stress/strain paths. Each path is computed with the full model and with a damage only version of the model which does not simulate crack closure effects. It is shown that the incorporation of the rough contact component allows the model to reproduce dilatant post-peak behaviour in compression and to simulate, with reasonable accuracy, the shape of the biaxial strength envelope for cementitious composite materials. Copyright

  13. Restrained Shrinkage-Induced Cracking of Light Weight High Performance Fiber Reinforced Cementitious Composites

    Directory of Open Access Journals (Sweden)

    Shaikh F.U Ahmed

    2009-01-01

    Full Text Available Problem statement: Shrinkage induced cracking cause damage to reinforced concrete structures. An experimental study was conducted on restrained shrinkage test of cement mortar and light weight High Performance Fiber Reinforced Cementitious Composites (HPFRCC. Approach: Two types of light weight HPFRCC and a premix mortar containing small amount of fiber were included in the experiment. Results: Results showed the multiple cracks, as many as 49, in light weight HPFRCC specimens compared to few cracks (about six cracks in the premix mortar specimen. At the end of shrinkage test, the width of the cracks in the mortar specimen was more than 250 μm with the largest crack width of about 400 μm. However, the scenario was quite different in light weight HPFRCC specimens, where the width of almost all cracks was less than 100 μm. Conclusion: The higher number of multiple cracks with small cracks width in light weight HPFRCC specimens due to drying shrinkage was due to their strain hardening and ductile behavior compared to quasi brittle behavior of premix mortar where less number of wide cracks was observed.

  14. Theoretical analysis on bending behavior of function-ally graded composite beam crack-controlled by ultrahigh toughness cementitious composites

    Institute of Scientific and Technical Information of China (English)

    XU ShiLang; LI QingHua

    2009-01-01

    Ultrahigh toughness cementitious composites (UHTCC) obviously show strain hardening property under tensile or bending loading. The failure pattern of the UHTCC components exhibits multiple fine cracks under uniaxial tensile loading with prominent tensile strain capacity in excess of 3%, with merely 60 μm average crack width even corresponding to the ultimate tensile strain state. The approach adopted is based on the concept of functionally-graded concrete, where part of the concrete, which surrounds the main longitudinal reinforcement in a RC (reinforced concrete) member, is strategically replaced with UHTCC with excellent crack-controlling ability. Investigations on bending behavior of functionally-graded composite beam crack controlled by UHTCC has been carried out, including theo-retical analysis, experimental research on long composite beams without web reinforcement, validation and comparison between experimental and theoretical results, and analysis on crack control. In addi-tion to improving bearing capacity, the results indicate that functionally-graded composite beams using UHTCC has been found to be very effective in preventing corrosion-induced damage compared with RC beams. Therefore, durability and service life of the structure could be enhanced. This paper discusses the development of internal force and crack propagation during loading process, and presents analysis of the internal force in different stages, moment-curvature relationship from loading to damage and calculation of mid-span deflection and ductility index. In the end, the theoretical formulae have been validated by experimental results.

  15. Theoretical analysis on bending behavior of functionally graded composite beam crack-controlled by ultrahigh toughness cementitious composites

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Ultrahigh toughness cementitious composites (UHTCC) obviously show strain hardening property under tensile or bending loading. The failure pattern of the UHTCC components exhibits multiple fine cracks under uniaxial tensile loading with prominent tensile strain capacity in excess of 3%, with merely 60 μm average crack width even corresponding to the ultimate tensile strain state. The approach adopted is based on the concept of functionally-graded concrete, where part of the concrete, which surrounds the main longitudinal reinforcement in a RC (reinforced concrete) member, is strategically replaced with UHTCC with excellent crack-controlling ability. Investigations on bending behavior of functionally-graded composite beam crack controlled by UHTCC has been carried out, including theo- retical analysis, experimental research on long composite beams without web reinforcement, validation and comparison between experimental and theoretical results, and analysis on crack control. In addition to improving bearing capacity, the results indicate that functionally-graded composite beams using UHTCC has been found to be very effective in preventing corrosion-induced damage compared with RC beams. Therefore, durability and service life of the structure could be enhanced. This paper discusses the development of internal force and crack propagation during loading process, and presents analysis of the internal force in different stages, moment-curvature relationship from loading to damage and calculation of mid-span deflection and ductility index. In the end, the theoretical formulae have been validated by experimental results.

  16. Experimental investigation and analysis on flexural performance of functionally graded composite beam crack-controlled by ultrahigh toughness cementitious composites

    Institute of Scientific and Technical Information of China (English)

    LI QingHua; XU ShiLang

    2009-01-01

    Based on the concept of functionally graded concrete, UHTCC (ultrahigh toughness cementitious composites) material with excellent crack-controlling ability is strategically substituted for part of the concrete, which surrounds the main longitudinal reinforcement in a reinforced concrete member. In-vestigations on bending behavior of such a functionally graded composite beam crack-controlled by UHTCC (abbreviated as UHTCC-FGC beam) have been carried out. After establishing a theoretical cal-culation model, the paper discusses the results of four-point bending experiment on long composite beams without web reinforcement, and validates the theoretical formulae through experimental results of UHTCC-FGC beams with different thicknesses of UHTCC layer. Besides improving bearing capacity and saving steel reinforcements, the results indicate that UHTCC-FGC beams can also effectively con-trol the deformation and enhance the ductility of members. At last, the optimal thickness of UHTCC layer in UHTCC-FGC beams has been confirmed, which can not only save materials and improve me-chanical performance of members, but also be very effective in preventing corrosion-induced damage and enhancing the durability of members by controlling crack width below 0.05 mm under service con-ditions.

  17. Experimental investigation and analysis on flexural performance of functionally graded composite beam crack-controlled by ultrahigh toughness cementitious composites

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Based on the concept of functionally graded concrete,UHTCC(ultrahigh toughness cementitious composites)material with excellent crack-controlling ability is strategically substituted for part of the concrete,which surrounds the main longitudinal reinforcement in a reinforced concrete member.Investigations on bending behavior of such a functionally graded composite beam crack-controlled by UHTCC(abbreviated as UHTCC-FGC beam)have been carried out.After establishing a theoretical cal-culation model,the paper discusses the results of four-point bending experiment on long composite beams without web reinforcement,and validates the theoretical formulae through experimental results of UHTCC-FGC beams with different thicknesses of UHTCC layer.Besides improving bearing capacity and saving steel reinforcements,the results indicate that UHTCC-FGC beams can also effectively control the deformation and enhance the ductility of members.At last,the optimal thickness of UHTCC layer in UHTCC-FGC beams has been confirmed,which can not only save materials and improve mechanical performance of members,but also be very effective in preventing corrosion-induced damage and enhancing the durability of members by controlling crack width below 0.05mm under service conditions.

  18. Simulation of strain-hardening in ECC uniaxial test specimen by use of a damage mechanics formulation

    DEFF Research Database (Denmark)

    Dick-Nielsen, Lars; Stang, Henrik; Poulsen, Peter Noe

    scale it is shown that the cohesive law for a unidirectional fiber reinforced cementitious composite can be found through superposition of the cohesive law for mortar and the fiber bridging curve. On the meso scale I it is shown that the maximum crack opening observed during crack propagation in ECC is...... small, 20 ¹m and also small compared to typical deformations at peak bridging stress. On the meso scale II interaction between initial flaws and micro cracks was observed. A framework is presented for the formulation of a damage mechanics model comprising the damage mechanisms on the micro and meso......This paper discusses the considerations for the establishment of a damage model for ECC. Three different length scales are used in the approach for deriving the damage model. On each length scale important phenomena are investigated by use of numerical and analytical calculations. On the micro...

  19. Dynamic damage and stress-strain relations of ultra-high performance cementitious composites subjected to repeated impact

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Ultra-high performance cementitious composites (UHPCC) were prepared by replacing 60% of cement with ultra-fine industrial waste powders.The dynamic damage and compressive stress-strain relations of UHPCC were studied using split Hopkinson pressure bar (SHPB).The damage of UHPCC subjected to repeated impact was measured by the ultrasonic pulse velocity method.Results show that the dynamic damage of UHPCC increases linearly with impact times and the abilities of repeated impact resistance of UHPCC are improved with increasing fiber volume fraction.The stress waves on impact were recorded and the average stress,strain and strain rate of UHPCC were calculated based on the wave propagation theory.The effects of strain rate,fibers volume fraction and impact times on the stress-strain relations of UHPCC were studied.Results show that the peak stress and elastic modulus decrease while the strain rate and peak strain increase gradually with increasing impact times.

  20. Low Frequency Electrical and Magnetic Methods for Non-Destructive Analysis of Fiber Dispersion in Fiber Reinforced Cementitious Composites: An Overview

    OpenAIRE

    Sergio Toscani; Liberato Ferrara; Roberto Ottoboni; Marco Faifer

    2013-01-01

    Non-destructive analysis of fiber dispersion in structural elements made of Fiber Reinforced Concrete (FRC) and Fiber Reinforced Cementitious Composites (FRCCs) plays a significant role in the framework of quality control and performance prediction. In this paper, the research activity of the authors in the aforementioned field all over the last lustrum will be reviewed. A method based on the measurement of the inductance of a probe to be placed on the specimen will be presented and its progr...

  1. Description of near-tip fracture processes in strain hardening cementitious composites using image-based analysis and the compact tension test

    DEFF Research Database (Denmark)

    Pereira, Eduardo B.; Fischer, Gregor; Barros, Joaquim A.O.

    2013-01-01

    characterized under eccentric tensile loading using the Compact Tension Test (CTT). The present research further extends this investigation, with particular emphasis on cementitious composites reinforced with multiple types of fibers. The experimental tensile load-displacement results are discussed and compared...... to the numerically derived responses. Furthermore, the crack initiation and propagation at the early stages of the loading sequence are analyzed. The size of the specimens and the resolution of the digital images acquired allow the detection of relatively small displacements and crack openings. The...

  2. Characterization and immobilization of white slag from secondary metallurgical processes in cementitious composites

    OpenAIRE

    Zalar Serjun, Vesna

    2015-01-01

    The fundamental objective of this study was to define such a cement composite with the addition of white (ladle) slag, which will provide functionality for selected purposes and furthermore, prevent the leaching of toxic elements into the environment. The recovery (recycling) of secondary metallurgical slags from stainless steel production has an important synergistic impact on the environment. In this study, detailed characterization of slag derived from two different ladle refin...

  3. Post-cracking characteristics of high performance fiber reinforced cementitious composites

    Science.gov (United States)

    Suwannakarn, Supat W.

    The application of high performance fiber reinforced cement composites (HPFRCC) in structural systems depends primarily on the material's tensile response, which is a direct function of fiber and matrix characteristics, the bond between them, and the fiber content or volume fraction. The objective of this dissertation is to evaluate and model the post-cracking behavior of HPFRCC. In particular, it focused on the influential parameters controlling tensile behavior and the variability associated with them. The key parameters considered include: the stress and strain at first cracking, the stress and strain at maximum post-cracking, the shape of the stress-strain or stress-elongation response, the multiple cracking process, the shape of the resistance curve after crack localization, the energy associated with the multiple cracking process, and the stress versus crack opening response of a single crack. Both steel fibers and polymeric fibers, perceived to have the greatest potential for current commercial applications, are considered. The main variables covered include fiber type (Torex, Hooked, PVA, and Spectra) and fiber volume fraction (ranging from 0.75% to 2.0%). An extensive experimental program is carried out using direct tensile tests and stress-versus crack opening displacement tests on notched tensile prisms. The key experimental results were analysed and modeled using simple prediction equations which, combined with a composite mechanics approach, allowed for predicting schematic simplified stress-strain and stress-displacement response curves for use in structural modeling. The experimental data show that specimens reinforced with Torex fibers performs best, follows by Hooked and Spectra fibers, then PVA fibers. Significant variability in key parameters was observed througout suggesting that variability must be studied further. The new information obtained can be used as input for material models for finite element analysis and can provide greater

  4. Low Frequency Electrical and Magnetic Methods for Non-Destructive Analysis of Fiber Dispersion in Fiber Reinforced Cementitious Composites: An Overview

    Directory of Open Access Journals (Sweden)

    Sergio Toscani

    2013-01-01

    Full Text Available Non-destructive analysis of fiber dispersion in structural elements made of Fiber Reinforced Concrete (FRC and Fiber Reinforced Cementitious Composites (FRCCs plays a significant role in the framework of quality control and performance prediction. In this paper, the research activity of the authors in the aforementioned field all over the last lustrum will be reviewed. A method based on the measurement of the inductance of a probe to be placed on the specimen will be presented and its progressive development will be described. Obtained correlation with actual fiber dispersion, as checked by means of destructive methods, as well as with the mechanical performance of the composite will also be presented, in an attempt to address the significance of the method from an engineering application perspective.

  5. Low frequency electrical and magnetic methods for non-destructive analysis of fiber dispersion in fiber reinforced cementitious composites: an overview.

    Science.gov (United States)

    Faifer, Marco; Ferrara, Liberato; Ottoboni, Roberto; Toscani, Sergio

    2013-01-01

    Non-destructive analysis of fiber dispersion in structural elements made of Fiber Reinforced Concrete (FRC) and Fiber Reinforced Cementitious Composites (FRCCs) plays a significant role in the framework of quality control and performance prediction. In this paper, the research activity of the authors in the aforementioned field all over the last lustrum will be reviewed. A method based on the measurement of the inductance of a probe to be placed on the specimen will be presented and its progressive development will be described. Obtained correlation with actual fiber dispersion, as checked by means of destructive methods, as well as with the mechanical performance of the composite will also be presented, in an attempt to address the significance of the method from an engineering application perspective. PMID:23337334

  6. Using Converter Dust to Produce Low Cost Cementitious Composites by in situ Carbon Nanotube and Nanofiber Synthesis

    Directory of Open Access Journals (Sweden)

    Péter Ludvig

    2011-03-01

    Full Text Available Carbon nanotubes (CNTs and nanofibers (CNFs were synthesized on clinker and silica fume particles in order to create a low cost cementitious nanostructured material. The synthesis was carried out by an in situ chemical vapor deposition (CVD process using converter dust, an industrial byproduct, as iron precursor. The use of these materials reduces the cost, with the objective of application in large-scale nanostructured cement production. The resulting products were analyzed by scanning electron microscopy (SEM, transmission electron microscopy (TEM and thermogravimetric analysis (TGA and were found to be polydisperse in size and to have defective microstructure. Some enhancement in the mechanical behavior of cement mortars was observed due to the addition of these nano-size materials. The contribution of these CNTs/CNFs to the mechanical strength of mortar specimens is similar to that of high quality CNTs incorporated in mortars by physical mixture.

  7. Review of durability of cementitious engineered barriers in repository environments

    International Nuclear Information System (INIS)

    This report is concerned with the durability of cementitious engineered barriers in a repository for low and intermediate level nuclear waste. Following the introduction the second section of the review identifies the environmental conditions associated with a deep, hard rock repository for ILW and LLW that are relevant to the durability of cementitious barriers. Section three examines the microstructure and macrostructure of cementitious materials and considers the physical and chemical processes of radionuclide immobilization. Potential repository applications and compositions of cementitious materials are reviewed in Section four. The main analysis of durability is dealt with in Section five. The different types of cementitious barrier are considered separately and their most probable modes of degradation are analysed. Concluding remarks that highlight critical technical matters are given in Section six. (author)

  8. Chloride diffusion in partially saturated cementitious material

    DEFF Research Database (Denmark)

    Nielsen, Erik Pram; Geiker, Mette Rica

    2003-01-01

    The paper proposes a combined application of composite theory and Powers' model for microstructural development for the estimation of the diffusion coefficient as a function of the moisture content of a defect-free cementitious material. Measurements of chloride diffusion in mortar samples (440 kg...

  9. Combined meso-scale modeling and experimental investigation of the effect of mechanical damage on the transport properties of cementitious composites

    Science.gov (United States)

    Raghavan, Balaji; Niknezhad, Davood; Bernard, Fabrice; Kamali-Bernard, Siham

    2016-09-01

    The transport properties of cementitious composites such as concrete are important indicators of their durability, and are known to be heavily influenced by mechanical loading. In the current work, we use meso-scale hygro-mechanical modeling with a morphological 3D two phase mortar-aggregate model, in conjunction with experimentally obtained properties, to investigate the coupling between mechanical loading and damage and the permeability of the composite. The increase in permeability of a cylindrical test specimen at 28% aggregate fraction during a uniaxial displacement-controlled compression test at 85% of the peak load was measured using a gas permeameter. The mortar's mechanical behavior is assumed to follow the well-known compression damaged plasticity (CDP) model with isotropic damage, at varying thresholds, and obtained from different envelope curves. The damaged intrinsic permeability of the mortar evolves according to a logarithmic matching law with progressive loading. We fit the matching law parameters to the experimental result for the test specimen by inverse identification using our meso-scale model. We then subject a series of virtual composite specimens to quasi-static uniaxial compressive loading with varying boundary conditions to obtain the simulated damage and strain evolutions, and use the damage data and the previously identified parameters to determine the evolution of the macroscopic permeability tensor for the specimens, using a network model. We conduct a full parameter study by varying aggregate volume fraction, granulometric distribution, loading/boundary conditions and "matching law" parameters, as well as for different strain-damage thresholds and uniaxial loading envelope curves. Based on this study, we propose Avrami equation-based upper and lower bounds for the evolution of the damaged permeability of the composite.

  10. Converting from ECCE to SICS

    Directory of Open Access Journals (Sweden)

    Nick Astbury

    2009-03-01

    Full Text Available Cataract continues to be the cause of almost half the cases of blindness worldwide and the challenge to meet the needs and develop the required resources is as great as ever.Cataract surgery has evolved from couching, first practised several thousand years ago, through intra- and extracapsular extraction (ECCE, to phacoemulsification. However, whatever the technique, the most important aspect is the outcome for patients. Today, the focus is more and more on excellence, which was one of the central themes of the 8th General Assembly.

  11. Microstructure characterization of multi-phase composites and utilization of phase change materials and recycled rubbers in cementitious materials

    Science.gov (United States)

    Meshgin, Pania

    2011-12-01

    This research focuses on two important subjects: (1) Characterization of heterogeneous microstructure of multi-phase composites and the effect of microstructural features on effective properties of the material. (2) Utilizations of phase change materials and recycled rubber particles from waste tires to improve thermal properties of insulation materials used in building envelopes. Spatial pattern of multi-phase and multidimensional internal structures of most composite materials are highly random. Quantitative description of the spatial distribution should be developed based on proper statistical models, which characterize the morphological features. For a composite material with multi-phases, the volume fraction of the phases as well as the morphological parameters of the phases have very strong influences on the effective property of the composite. These morphological parameters depend on the microstructure of each phase. This study intends to include the effect of higher order morphological details of the microstructure in the composite models. The higher order statistics, called two-point correlation functions characterize various behaviors of the composite at any two points in a stochastic field. Specifically, correlation functions of mosaic patterns are used in the study for characterizing transport properties of composite materials. One of the most effective methods to improve energy efficiency of buildings is to enhance thermal properties of insulation materials. The idea of using phase change materials and recycled rubber particles such as scrap tires in insulation materials for building envelopes has been studied.

  12. Pulse Velocity Measurements in Fly Ash Blended Cementitious Systems Containing 43 Grade Cement

    OpenAIRE

    V.M. Sounthararajan; Mr. A. Sivakumar

    2013-01-01

    Investigations on the different supplementary cementitious materials based on the hardening properties and the optimized dosage in cementitious systems find the right choice of pozzolanic material. It is essential to combine various additive/admixtures in concrete in proper proportions to maximize the benefits resulting in cost savings in construction. In the recent years, production technology and composition of hydraulic cements affect the setting and early age behavior of cementitious mate...

  13. Attacks and countermeasures on AES and ECC

    DEFF Research Database (Denmark)

    Tange, Henrik; Andersen, Birger

    foreseeable while the rounds are performed. ECC (Elliptic Curve Cryptography) is used as a public key crypto system with the key purpose of creating a private shared between two participants in a communication network. Attacks on ECC include the Pohlig-Hellman attack and the Pollard's rho attack. Furthermore...

  14. Application of headed studs in steel fiber reinforced cementitious composite slab of steel beam-column connection

    Science.gov (United States)

    Yao, Cui; Nakashima, Masayoshi

    2012-03-01

    Steel fiber reinforced cementitous composites (SFRCC) is a promising material with high strength in both compression and tension compared with normal concrete. The ductility is also greatly improved because of 6% volume portion of straight steel fibers. A steel beam-column connection with Steel fiber reinforced cementitous composites (SFRCC) slab diaphragms is proposed to overcome the damage caused by the weld. The push-out test results suggested that the application of SFRCC promises larger shear forces transferred through headed studs allocated in a small area in the slab. Finite element models were developed to simulate the behavior of headed studs. The failure mechanism of the grouped arrangement is further discussed based on a series of parametric analysis. In the proposed connection, the SFRCC slab is designed as an exterior diaphragm to transfer the beam flange load to the column face. The headed studs are densely arranged on the beam flange to connect the SFRCC slab diaphragms and steel beams. The seismic performance and failure mechanism of the SFRCC slab diaphragm beam-column connection were investigated based on the cyclic loading test. Beam hinge mechanism was achieved at the end of the SFRCC slab diaphragm by using sufficient studs and appropriate rebars in the SFRCC slab.

  15. Potential Use of Strain Hardening ECC in Permanent Formwork with Small Scale Flexural Beams

    Institute of Scientific and Technical Information of China (English)

    LI Hedong; Christopher K Y Leung; XU Shilang; CAO Qian

    2009-01-01

    Utilizing pre-cast ECC panels as participating permanent formwork of concrete members,and the validity of using ECC to disperse the single crack in concrete into multiple ones in ECC were studied.In the process,totally two kinds of ECC with different tensile properties,7 series of flat panels with different top surface figures and 3 U-shape panels with different inner surface forms were investigated.To evaluate the performance of the permanent formworks,small ECC-concrete composite beams were cast and tested mechanically.The 4-point bending test results show that the use of pre-cast ECC panels as permanent formwork can significantly improve the load capacity and toughness of a concrete member,effectively dispersing single widely opened crack in concrete into multiple ones in ECC.Most permanent formworks show perfect bond with the concrete cast on them, while the ones with partially debonded zone achieve the best mechanical performance.The U-shape permanent formworks show better performances than the flat ones,achieving much betler improvements in both the load capacity and toughness,together with better crack width control.

  16. Extrusion of ECC: Recent Developments and Applications

    DEFF Research Database (Denmark)

    Stang, Henrik; Fredslund-Hansen, Helge; Puclin, Tony;

    2008-01-01

    Extrusion of particulate pastes and suspensions in general is difficult and the rheological parameters play a central role in the process when using conventional extruders. More important – the rheological properties of the paste or suspension are subjected to conflicting demands in an extrusion...... process. Extrusion of cementitious (fiber reinforced) materials has proven particularly difficult due to the high inter-particle friction combined with the disastrous effect of static zones in the flow pattern, and to the ease of phase migration or separation. In order to deal with these conflicting...... demands on the rheological properties of cementitious particulate materials, various methods have been suggested to dewater the particle suspension during extrusion, however practical extrusion of thin-walled cementitious large-scale elements has not been possible until the discovery of the “dewatering...

  17. Absorbency of Superabsorbent Polymers in Cementitious Environments

    DEFF Research Database (Denmark)

    Esteves, Luis Pedro; Jensen, Ole Mejlhede

    2012-01-01

    Optimal use of superabsorbent polymers (SAP) in cement-based materials relies on knowledge on how SAP absorbency is influenced by different physical and chemical parameters. These parameters include salt concentration in the pore fluid, temperature of the system and SAP particle size. The present...... composition of the exposure liquid is investigated with atomic absorption spectroscopy. The paper provides the reader with knowledge about the absorption capacity of SAP in a cementitious environment, and how the absorption process may influence the cement pore fluid....

  18. Thermodynamics of Autogenous Self-healing in Cementitious Materials

    NARCIS (Netherlands)

    Huang, H.

    2014-01-01

    Concrete is a brittle composite cementitious material that easily fractures under tensile loading. Microcracks can appear throughout the concrete prior to application of any load because of temperature-induced strain and autogenous and drying shrinkage. There is no doubt that these cracks provide pr

  19. Fracture propagation in cementitious materials

    DEFF Research Database (Denmark)

    Skocek, Jan

    Mechanical behavior of structures made from cementitious materials has been successfully modeled using non-linear fracture mechanics in recent decades. On the structural scale, an assumption of homogeneity of the material is valid and well established theories can be applied. However, if focus is...... materials needs to be able to take this complexity into account. In this thesis, two frameworks for prediction of strengths of cementitious materials are developed. The rst one relates the strength of materials with aggregates with the properties of the matrix and distribution of aggregates. The second one...

  20. Spillage of ECC Water Jet by Cross Flow

    International Nuclear Information System (INIS)

    The force ratio between cross flow drag and injection moment is governing the ECC intake fraction in the ECBD duct system. To quantify the ECC bypass fraction with spillage, a CFD model of 1/1-scale downcomer annulus with DVI+ECBD is considered. In this numerical study, the applicability and feasibility of a commercial CFD code for the simulation of the ECC water column are tested. The spillage of ECC water jet in the DVI+ ECBD system is estimated by CFD calculation and analogy. The CFD results show that the ECC water jet is bounded in the intake hole of the ECBD. The ECC water jet does not shift to the outside of the intake hole of the ECBD at the given condition. The analogy also shows the similar results. From the present study, it can be concluded that the displacement of the ECC water jet is bounded on the maximum displacement due to the gravitational force (buoyancy force)

  1. Spillage of ECC Water Jet by Cross Flow

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Taesoon; Park, Choonkyung [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2013-05-15

    The force ratio between cross flow drag and injection moment is governing the ECC intake fraction in the ECBD duct system. To quantify the ECC bypass fraction with spillage, a CFD model of 1/1-scale downcomer annulus with DVI+ECBD is considered. In this numerical study, the applicability and feasibility of a commercial CFD code for the simulation of the ECC water column are tested. The spillage of ECC water jet in the DVI+ ECBD system is estimated by CFD calculation and analogy. The CFD results show that the ECC water jet is bounded in the intake hole of the ECBD. The ECC water jet does not shift to the outside of the intake hole of the ECBD at the given condition. The analogy also shows the similar results. From the present study, it can be concluded that the displacement of the ECC water jet is bounded on the maximum displacement due to the gravitational force (buoyancy force)

  2. Setup of Extruded Cementitious Hollow Tubes as Containing/Releasing Devices in Self-Healing Systems

    OpenAIRE

    Alessandra Formia; Salvatore Terranova; Paola Antonaci; Nicola Maria Pugno; Jean Marc Tulliani

    2015-01-01

    The aim of this research is to produce self-healing cementitious composites based on the use of cylindrical capsules containing a repairing agent. Cementitious hollow tubes (CHT) having two different internal diameters (of 2 mm and 7.5 mm) were produced by extrusion and used as containers and releasing devices for cement paste/mortar healing agents. Based on the results of preliminary mechanical tests, sodium silicate was selected as the healing agent. The morphological features of several mi...

  3. Strontium Uptake by Cementitious Materials

    Energy Technology Data Exchange (ETDEWEB)

    Wieland,E.; Tits, J.; Kunz, D.; Dahn, R.

    2008-01-01

    Wet chemistry experiments and X-ray absorption fine structure (XAFS) measurements were carried out to investigate the immobilization of nonradioactive Sr and 85Sr in calcite-free and calcite-containing Portland cement. The partitioning of pristine Sr between hardened cement paste (HCP) and pore solution, and the uptake of 85Sr and nonradioactive Sr were investigated in batch-type sorption/desorption experiments. Sr uptake by HCP was found to be fast and nearly linear for both cements, indicating that differences in the compositions of the two cements have no influence on Sr binding. The partitioning of pristine Sr bound in the cement matrix and 85Sr between HCP and pore solution could be modeled in terms of a reversible sorption process using similar Kd values. These findings allow 85Sr uptake to be interpreted in terms of an isotopic exchange process with pristine Sr. Sr K-edge EXAFS measurements on Sr doped HCP and calcium silicate hydrate (C-S-H) samples reveal no significant differences in the local coordination environments of pristine Sr and Sr bound to the cement matrix upon sorption. The first coordination sphere consists of five to six oxygen atoms located at a distance of about 2.6 Angstroms, which corresponds to Sr-O distances in the hydration sphere of Sr2+ in alkaline solution. Sr binds to the cement matrix via two bridging oxygen atoms located at a distance of about 3.6 Angstroms. No further neighboring atoms could be detected, indicating that Sr is taken up as a partially hydrated species by HCP. Wet chemistry and spectroscopic data further indicate that Sr binding to C-S-H phases is likely to be the controlling uptake mechanism in the cement matrix, which allows Sr uptake by HCP to be predicted based on a Ca-Sr ion exchange model previously developed for Sr binding to C-S-H phases. The latter finding suggests that long-term predictions of Sr immobilization in the cementitious near field of repositories for radioactive waste can be based on a

  4. Effect of Limestone Powder on Microstructure of Ternary Cementitious System

    OpenAIRE

    Zhang, Y.; Ye, G.

    2012-01-01

    The pressure to reach sustainability favours the development of ternary composite cement. The synergistic effect on mechanical behaviour at 28 days between limestone powder (LP) and pozzolanic additives, i.e. fly ash (FA) and blast furnace slag (BFS), has been documented. In order to better understand the synergistic effect, this article investigated the effect of LP on the microstructure of PC-FA and PC-BFS cementitious system. The mineralogy and pore structure were determined after 28 days ...

  5. Thermodynamics of Autogenous Self-healing in Cementitious Materials

    OpenAIRE

    Huang, H

    2014-01-01

    Concrete is a brittle composite cementitious material that easily fractures under tensile loading. Microcracks can appear throughout the concrete prior to application of any load because of temperature-induced strain and autogenous and drying shrinkage. There is no doubt that these cracks provide preferential access for aggressive agents to penetrate into the concrete, probably causing corrosion of reinforcement steel and degradation of concrete. As a result, the service life of reinforced co...

  6. Two-phase flow dynamics in ECC

    International Nuclear Information System (INIS)

    The present report summarizes the achievements within the project ''Two-phase Systems and ECC''. The results during 1978 - 1980 are accounted for in brief as they have been documented in earlier reports. The results during the first half of 1981 are accounted for in greater detail. They contain a new model for the Basset force and test runs with this model using the test code RISQUE. Furthermore, test runs have been performed with TRAC-PD2 MOD 1. This code was implemented on Edwards Pipe Blowdown experiment (a standard test case) and UC-Berkeley Reflooding experiment (a non-standard test case.) (Auth.)

  7. Noise-based Stego-ECC

    OpenAIRE

    Rahardjo Budi; Muchtadi-Alamsyah Intan; Paryasto Marisa

    2014-01-01

    A novel method of inserting noise into stream of ciphered text is proposed. The goal of inserting noise is to increase the level of uncertainty, thus making it harder for an attacker to detect data and noise. This form of steganography is implemented using Elliptic Curve Cryptography (ECC). The process of embedding the noise to the message in the encryption process and removing the noise from the message in the decryption process is proposed in this work by modifying ElGamal to allow auto det...

  8. Noise-based Stego-ECC

    Science.gov (United States)

    Rahardjo, Budi; Muchtadi-Alamsyah, Intan; Paryasto, Marisa

    2014-03-01

    A novel method of inserting noise into stream of ciphered text is proposed. The goal of inserting noise is to increase the level of uncertainty, thus making it harder for an attacker to detect data and noise. This form of steganography is implemented using Elliptic Curve Cryptography (ECC). The process of embedding the noise to the message in the encryption process and removing the noise from the message in the decryption process is proposed in this work by modifying ElGamal to allow auto detection of data and noise.

  9. Injection transition analysis of PLGS MP/LP ECC system

    International Nuclear Information System (INIS)

    To analyze the transition from MP ECC to LP ECC injection, a RELAP5 model has been developed for the Point Lepreau Generating Station (PLGS) MP/LP ECC system. By using this model, some transition analyses have been performed with emphasis on stroke times of the dousing tank suction test isolating valves and the recovery sump isolating valves. The results indicate that if either in-line valve pair of the dousing tank isolation valves fails to close, air could be ingested by the ECC pumps shortly after the dousing tank is empty. (author)

  10. ECC over RSA for Asymmetric Encryption-A Review

    Directory of Open Access Journals (Sweden)

    Kamlesh Gupta

    2011-05-01

    Full Text Available Cryptography is used to transmit the data securely in open network. This paper gives the survey of Elliptic Curve Cryptosystem (ECC used in many applications. ECC is a when compared to RSA and discrete logarithm systems, is a better option for the future. For this reason ECC is such an excellent choice for doing asymmetric cryptography in portable devices right now. The smaller ECC keys it turn makes the cryptographic operations that must be performed by the communicating devices to be embedded into considerably smaller hardware, so that software applications may complete cryptographic operations with fewer processor cycles, and operations can be performed much faster, while still retaining equivalent security. This means, in turn, reduced power consumption, less space consumed on the printed circuit board, and software applications that run more rapidly make lower memory demands. In brief, for communication using smaller devices and asymmetric cryptosystem we need ECC.

  11. An ECC-Based Blind Signature Scheme

    Directory of Open Access Journals (Sweden)

    Fuh-Gwo Jeng

    2010-08-01

    Full Text Available Cryptography is increasingly applied to the E-commerce world, especially to the untraceable payment system and the electronic voting system. Protocols for these systems strongly require the anonymous digital signature property, and thus a blind signature strategy is the answer to it. Chaum stated that every blind signature protocol should hold two fundamental properties, blindness and intractableness. All blind signature schemes proposed previously almost are based on the integer factorization problems, discrete logarithm problems, or the quadratic residues, which are shown by Lee et al. that none of the schemes is able to meet the two fundamental properties above. Therefore, an ECC-based blind signature scheme that possesses both the above properties is proposed in this paper.

  12. Quality assurance of ECCS in nuclear reactors

    International Nuclear Information System (INIS)

    Size and shape of split or rupture in clad increases the whole body radiation exposure to the staff of the nuclear reactors. Suggests that a plant operating with 0.125 percent pin-hole fuel cladding defects showed a general five-fold increase in whole-body radiation exposure rates in some areas of the plant when compared to a sister plant with high-integrity fuel. Therefore Quality Assurance (QA) checks on Emergency Core Cooling System (ECCS) in Nuclear Reactors are very important to ensure minimum radiation hazard during Loss of Coolant Accident (LOCA). These checks will protect environment and public from radiation to great extent. The rate of rise of fuel temperature subsequent to LOCA should be lower than 5.5℃/s

  13. Concrete compositions and methods

    Science.gov (United States)

    Chen, Irvin; Lee, Patricia Tung; Patterson, Joshua

    2015-06-23

    Provided herein are compositions, methods, and systems for cementitious compositions containing calcium carbonate compositions and aggregate. The compositions find use in a variety of applications, including use in a variety of building materials and building applications.

  14. Preparation of Cementitious Material Using Smelting Slag and Tailings and the Solidification and Leaching of Pb2+

    OpenAIRE

    Dan Zhang; Shiliu Shi; Chengbiao Wang; Xiaocong Yang; Lijie Guo; Shanshan Xue

    2015-01-01

    The composite cementitious materials were prepared with lead-zinc tailings, lead-zinc smelting slag, and cement clinker. The effect of material ratio on the mechanical properties, the phase analysis, and microstructures were investigated. The effect of the pH and stripping time on the leaching amount of lead ion was discussed. The results show that the additive amount of the tailings should be minimized for the cementitious materials meeting the strength requirements, controlled within 10%. T...

  15. Condensation during gravity driven ECC: Experiments with PACTEL

    Energy Technology Data Exchange (ETDEWEB)

    Munther, R.; Kalli, H. [Lappeenranta Univ. of Technology (Finland); Kouhia, J. [Technical Research Centre of Finland, Lappeenranta (Finland)

    1995-09-01

    This paper provides the results of the second series of gravity driven emergency core cooling (ECC) experiments with PACTEL (Parallel Channel Test Loop). The simulated accident was a small break loss-of-coolant accident (SBLOCA) with a break in a cold leg. The ECC flow was provided from a core makeup tank (CMT) located at a higher elevation than the main part of the primary system. The CMT was pressurized with pipings from the pressurizer and a cold leg. The tests indicated that steam condensation in the CMT can prevent ECC and lead to core uncovery.

  16. ECC water spreading width for flat plate

    International Nuclear Information System (INIS)

    To investigate the characteristics of water jet spreading width induced by Direct Vessel Injection(DVI), a steady state and separate effect test focusing on the effect of the downcomer curvature was performed using a rectangular flat-plate air-water open channel test facility. Comparative tests using various scaled diameter(D) of water jet nozzle, channel gap(W), water jet velocity(VJET), and forced cross air-flow(Vc) on the water film are performed for the Korean Next Generation Reactor(KNGR) during the late reflood phase of LBLOCA. A simplified and visible thin acryl plates were used. The air-water channel has a nearly full height in height between DVI and coldleg. The channel gap and the diameter of water injection nozzle have scaled ratios of 1/50 ∼ 1/10 by volume scaling method. The cross flow is introduced in the airwater channel to investigate the cross flow effects on the ECC water jet spreading width. The major parameters measured in the experiments are the film width of ECC water, the shifted degree of water film boundary by the cross air flow, and the attachment liquid fraction to total injected water in the region of front plate against water injected wall plate. It was found out that (1) If the test scale is increased, for the typical film spreading width without any cross flow, the film width is linearly increased at the bottom of air-water channel except at the top of film. (2) If the cross flow is induced on the liquid film for the test scale of 1:51.68, the highly shifted film shape is formed (3) If the test scale and the water injection velocity are increased, the attachment ratio of liquid on the front plate is sharply increased. (4) The attachment ratio of liquid on the front plate is strongly increased by cross flow. In the case of 9.52 scaled test, the attachment ratio of liquid is affected by both the cross flow and the water injection velocity

  17. Study on cementitious properties of steel slag

    Directory of Open Access Journals (Sweden)

    Zhu G.

    2013-01-01

    Full Text Available The converter steel slag chemical and mineral components in China’s main steel plants have been analysed in the present paper. The electronic microscope, energy spectrum analysis, X-ray diffraction analysis confirmed the main mineral compositions in the converter slag. Converter slag of different components were grounded to obtain a powder with specific surface area over 400m2/kg, making them to take place some part of the cement in the concrete as the admixture and carry out the standard tests. The results indicate that the converter slag can be used as cementitious materials for construction. Furthermore, physical mechanic and durability tests on the concrete that certain amount of cement be substituted by converter steel slag powder from different steel plants are carried out, the results show that the concrete with partial substitution of steel slag powder has the advantages of higher later period strength, better frost resistance, good wear resistance and lower hydration heat, etc. This study can be used as the technical basis for “Steel Slag Powder Used For Cement And Concrete”, “Steel Slag Portland Cement”, “Low Heat Portland Steel Slag Cement”, “Steel Slag Road Cement” in China, as well as a driving force to the works of steel slag utilization with high-value addition, circular economy, energy conservation and discharge reduction in the iron and steel industry.

  18. ECCS Operability With One or More Subsystem(s) Inoperable

    International Nuclear Information System (INIS)

    Plant Technical Specifications are issued by the US NRC to ensure that safe nuclear power plant operation is maintained within the assumptions for parameters and Structures, Systems, and Components (SSCs) made in the plant safety analysis reports. The Technical Specifications are made up of Limiting Conditions for Operation (LCOs), which are the minimum set of requirements that must be met based on the assumptions of the safety analysis, Actions, which are the remedial or compensatory actions that must be taken if the LCO is not met, and Surveillance Requirements, that demonstrate that the LCO is met. The Technical Specification Actions contain Completion Times (CTs) which are the time within which remedial actions must be taken, in the event that the LCO is not met. The Improved Standard Technical Specifications (ISTS) for Westinghouse plants are contained in NUREG-1431, Revision 2. Condition A of Technical Specification 3.5.2 (ECCS- Operating) in NUREG-1431, Revision 2, allows components to be taken out of service for up to 72 hours, as long as 100% of the ECCS flow equivalent to a single Operable ECCS train exists. Condition A would allow, for example, the A train low head safety injection (LHSI) and the B train high head safety injection (HHSI) pumps to be taken out of service (for 72 hours) as long as it could be demonstrated that the remaining components could provide 100% train equivalent flow capacity. The 'cross-training' allowed by this Condition in the ISTS provides flexibility when performing routine pre-planned preventive maintenance and testing, as well as during emergent corrective maintenance and testing associated with random component inoperabilities. Without this flexibility, a unit would have to initiate a plant shutdown within 1 hour, if component(s) were inoperable in different trains. In order to implement this flexibility, the various combinations of components in opposite trains must be evaluated to determine whether 100% of the ECCS flow

  19. Glass science tutorial: Lecture No. 8, introduction cementitious systems for Low-Level Waste immobilization

    International Nuclear Information System (INIS)

    This report presents details about cementitious systems for low-level waste immobilization. Topics discussed include: composition and properties of portland cement; hydration properties; microstructure of concrete; pozzolans; slags; zeolites; transport properties; and geological aspects of long-term durability of concrete

  20. Glass science tutorial: Lecture No. 8, introduction cementitious systems for Low-Level Waste immobilization

    Energy Technology Data Exchange (ETDEWEB)

    Young, J.F.; Kirkpatrick, R.J.; Mason, T.O.; Brough, A.

    1995-07-01

    This report presents details about cementitious systems for low-level waste immobilization. Topics discussed include: composition and properties of portland cement; hydration properties; microstructure of concrete; pozzolans; slags; zeolites; transport properties; and geological aspects of long-term durability of concrete.

  1. Impact of ECCS design of VVER reactors on PTS issue

    International Nuclear Information System (INIS)

    In 1996, a study of Pressurized Thermal Shock (PTS) was started in the Nuclear Research Institute Rez (UJV) covering the NPPs operated in the Czech Republic. PTS analyses for NPP Dukovany (VVER-440/213) have been performed first and later a similar study was initiated for NPP Temelin (VVER-1000/320). Our PTS analyses produced many interesting interim results concerning design of Emergency Core Cooling System (ECCS). The presented paper deals with these findings and summarizes possible improvements of ECCS from the point of view of PTS issue. In general, it can be said that design of ECCS system of VVER (or PWR) was previously focused, more or less, only to emergency core cooling and containment spraying, and no (or minimal) attention was paid to PTS issue. However, the injection of cold water from the ECCS system (during an accident with ECCS actuation) is potentially a major contributor to rapid cooldown of reactor coolant system (RCS), where especially the fast and unsymmetrical temperature drop in reactor downcomer (DC) could challenge the reactor pressure vessel (RPV) integrity. The fast decrease of coolant temperature in DC would lead to a significant increase of thermal stresses in the thick wall of embrittled RPV. Consequently, these thermal stresses together with stresses from inner pressure could in conditions of relatively cold RPV material initiate a fast fracture from a flaw potentially existing in the RPV wall. Nowadays it is obvious that the ECCS design should take into account not only the needs of emergency cooling of the reactor core (and containment spraying), but also the PTS issue. The ECCS design should be optimized from all these points of view. This is however not an easy task, because requirements of core cooling and minimization of PTS risks are usually contradictory. Naturally, this challenging task would be easier to fulfill while designing a new NPP (VVER or PWR in general). However, it is possible to improve the ECCS design and thus

  2. Innovative mix design of cementitious materials for enhancing strength and ductility

    OpenAIRE

    Ahmad, Sajjad

    2015-01-01

    Cement based composites i.e. paste, mortar and concrete are the most utilized materials in the construction industry all over the world. Cement composites are quasi-brittle in nature and possess extremely low tensile strength as compared to their compressive strength. Due to their low tensile strength capacity, cracks develop in cementitious composites due to the drying shrinkage, plastic settlements and/or stress concentrations (due to external restrains and/or applied stresses) etc. These c...

  3. The immobilisation of clinoptilolite within cementitious systems

    International Nuclear Information System (INIS)

    The zeolitic ion exchanger clinoptilolite was encapsulated within various cementitious systems in order to assess their suitability for the retention of the radioelements, Cs and Sr. The pozzolanic reaction of clinoptilolite is reduced in composites containing BFS and PFA and appears not to continue after 7 days of hydration. Ca(OH)2 persists up to 360 days of hydration in a 9:1BFS:OPC system with 10% clinoptilolite added, despite the presence of unreacted pozzolana. This may be due to low pH of the pore solution, if Na and K act as counter cations in the aluminous C-S-H, a product of pozzolanic hydration or are exchanged onto the clinoptilolite. Saturation of the pore solution with Ca may prevent further dissolution of Ca(OH)2. Cs leaching occurs in all samples during accelerated tests due to breakdown of the clinoptilolite structure. The alternative cement system calcium sulfo-aluminate cement (CSA) has a different hydration chemistry and properties to OPC and OPC composites with a lower pore solution pH. Clinoptilolite appears to react in a hydrating CSA system with significant reaction continuing between 28 and 90 days of hydration. Leaching of Cs from CSA is higher than from an OPC system, in which almost all of the clinoptilolite crystallinity is lost. The major product of CSA hydration is ettringite. Cs may be adsorbed within cation sites of the C-S-H in an OPC system but not by ettringite which does not retain Cs so Cs has high mobility and leachability through the CSA matrix. (authors)

  4. Damage detection in concrete and cementitious composites

    Science.gov (United States)

    Wu, Hwai-Chung; Pai, P. Frank

    2008-03-01

    Traditionally ultrasonic testing is used to estimate the extent of damage in a concrete structure. However Pulse-velocity and amplitude attenuation methods are not very reliable, and are difficult to reveal early damage of concrete. In a previous study, a new active modulation approach, Nonlinear Active Wave Modulation Spectroscopy, was developed and found promising for early detection of damage in concrete. In this procedure, a probe wave is passed through the system in a fashion similar to regular acoustic methods for inspection. Simultaneously, a second, low-frequency modulating wave is applied to the system to effectively change the size and stiffness of flaws microscopically and cyclically, thereby causing the frequency modulation to change cyclically as well. It has been also shown that it is advantageous to apply the Hilbert-Huang transform to decompose nonlinear non-stationary time-domain responses of plain concrete. Such procedure leads to improving the damage detection sensitivity of this modulation method in concrete. In this paper, further investigation on mortar and fiber reinforced concrete will be presented and discussed.

  5. Long-term alteration of cementitious materials

    International Nuclear Information System (INIS)

    Long-term alteration of cementitious materials in the geological condition has been discussed for the safety assessment of radioactive waste disposal. This paper describes the status of understanding long-term chemical alteration of cement, by reviewing some of our investigations on this issue in which we developed a thermodynamic incongruent C-S-H dissolution/precipitation model and a reactive transport calculation code. Alteration of C-S-H gel in a saline groundwater and the change of chemical barrier performance of cementitious materials due to the alteration are also discussed. Some key issues to be discussed further are given and suggested for the future studies on the long-term alteration of cementitious materials in the repository environment. (author)

  6. 曲げ試験によるPVA-ECCの引張性能評価

    OpenAIRE

    清水, 克将; 金久保, 利之; 閑田, 徹志; 永井, 覚

    2006-01-01

    ECC (Engineered Cementitious Composites), which is grouped in one of the fiber reinforced cementitious composites, shows pseudostiain hardening behavior with several percent tensile strain and multiple cracks. Evaluation method for tensile properties (tensile strength and ultimate strain) of ECC is proposed by using bending test results. In this research, uniaxial tension test and bending test of PVA-ECC (ECC with Polyvinyl alcohol fiber) is conducted to obtain correlation between tensile pro...

  7. Monitoring system of ECCS injection system upon periodical inspection

    International Nuclear Information System (INIS)

    An ECCS reactor injection system is automatically monitored upon periodical inspection. That is, a memory device stores information of the stand-by state of the ECCS reactor injection system upon periodical inspection. A data input means inputs monitoring item data in the present state. A required monitoring target is designated by the input means. A judging means compares the data of the monitoring target with the stand-by state information successively, to judge whether or not the monitoring target is in a predetermined stand-by state. A display means displays the result of the judgment. In the present system thus constituted, since it can be automatically judged whether or not the ECCS reactor injection system, as a monitoring target, is in the predetermined stand-by state, it is possible to reduce the operator's burden and improve the safety. (I.S.)

  8. On the Application of Inertial Microfluidics for the Size-Based Separation of Polydisperse Cementitious Particulates

    Science.gov (United States)

    Kumar, Aditya; Lewis, Peter; Balonis, Magdalena; Di Carlo, Dino; Sant, Gaurav

    2015-06-01

    The early-age performance of concrete is determined by the properties of the cementitious binder and the evolution of its chemical reactions. The chemical reactivity, and to some extent, the composition of cementitious particles can depend on particle size. Therefore, it is valuable to physically separate cementing minerals into well-defined size classes so that the influences of both particle size and composition on reaction progress can be studied without the confounding effects of a broad particle size distribution. However, conventional particle separation methods (e.g., density fractionation, wet sieving, field-flow extraction, ultrasonification-sedimentation) are time-consuming and cumbersome and result in poor particle yields and size-selectivity, thus, making them unsuitable for processing larger volumes of cementitious powders (on the order of grams). This study applies a novel inertial microfluidics (IMF) based procedure to separate cementitious powders on the basis of their size. Special attention is paid to optimizing operating variables to ensure that particles in a fluid streamline achieve unique equilibrium positions within the device. From such positions, particles can be retrieved as per their size using symmetrical outlet configurations with tuned fluidic resistances. The approach is critically assessed in terms of: (1) its ability to separate cementitious powders into narrow size bins, and therefore its feasibility as a fractionation procedure, and (2) quantitatively relating the operating parameters to the particle yield and size selectivity. The study establishes metrics for assessing the ability of IMF methods to classify minerals and other polydisperse particles on the basis of their size.

  9. Development of Calculation Algorithm for ECCS Kinematic Shock

    International Nuclear Information System (INIS)

    The void fraction of inverted U-pipes in front of SI(Safety Injection) pumps impact on the pipe system of ECCS(Emergency Core Cooling Systems). This phenomena is called as 'Kinematic Shock'. The purpose of this paper is to achieve the more exactly calculation when the kinematic shock is calculated by simplified equation. The behavior of the void packet of the ECCS pipes is illustrated by the simplified (other name is kinematic shock equation).. The kinematic shock is defined as the depth of total length of void clusters in the pipes of ECCS when the void cluster is continually reached along the part of pipes in vertical direction. In this paper, the simplified equation is evaluated by comparing calculation error each other.]. The more exact methods of calculating the depth of the kinematic shock in ECCS is achieved. The error of kinematic shock calculation is strongly depended on the calculation search gap and the order of Taylor's expansion. From this study, to select the suitable search gap and the suitable calculation order, differential root method, secant method, and Taylor's expansion form are compared one another

  10. Early Childhood Caries (ECC): an infectious transmissible oral disease

    NARCIS (Netherlands)

    H.R. Poureslami; W.E. van Amerongen

    2009-01-01

    Dental caries in babies and toddlers is called Early Childhood Caries (ECC). It is an infectious and transmissible die-to-bacterial disease. Detailed knowledge regarding the acquisition and transmission of infectious agents facilitates a more comprehensive approach toward prevention. Mutans streptoc

  11. Effect of the yaw injection angle on the ECC bypass in comparison with the horizontal DVI

    International Nuclear Information System (INIS)

    The comparison tests for the direct emergency core cooling (ECC) bypass fraction were experimentally performed with a typical direct vessel injection (DVI) nozzle and an ECC column nozzle having a yaw injection angle to the gravity axis. The ECC yaw injection nozzle is newly introduced to make an ECC water column in the downcomer region. The yaw injection angle of the ECC water relative to the gravity axis is varied from 0 to (±)90 deg. stepped by 45 deg. . The tests are performed in the air-water separate effect test facility (direct injection visualization and analysis (DIVA)), which is a 1/7.07 linearly scaled-down model of the APR1400 nuclear reactor. The test results show that (1) if the ECC water column is injected into the wake region which is induced by the hot leg blunt body in the downcomer annulus, the ECC bypass fraction is greatly reduced compared with the typical horizontal ECC injection which makes ECC film on the downcomer wall. At the same time, the ECC penetration toward the lower downcomer region becomes larger than those of a typical horizontal type of direct vessel injection on the downcomer wall vertically. (2) If the ECC water column is injected near the broken cold leg, the ECC water is directly bypassed. Thus, the ECC penetration fraction is greatly reduced compared with a typical film type of the horizontal ECC injection. (3) In order to minimize the ECC bypass fraction, the ECC water should be injected toward the wake region of the hot leg blunt bodies

  12. The JAERI code system for evaluation of BWR ECCS performance

    International Nuclear Information System (INIS)

    Development of respective computer code system of BWR and PWR for evaluation of ECCS has been conducted since 1973 considering the differences of the reactor cooling system, core structure and ECCS. The first version of the BWR code system, of which developmental work started earlier than that of the PWR, has been completed. The BWR code system is designed to provide computational tools to analyze all phases of LOCAs and to evaluate the performance of the ECCS including an ''Evaluation Model (EM)'' feature in compliance with the requirements of the current Japanese Evaluation Guideline of ECCS. The BWR code system could be used for licensing purpose, i.e. for ECCS performance evaluation or audit calculations to cross-examine the methods and results of applicants or vendors. The BWR code system presented in this report comprises several computer codes, each of which analyzes a particular phase of a LOCA or a system blowdown depending on a range of LOCAs, i.e. large and small breaks in a variety of locations in the reactor system. The system includes ALARM-B1, HYDY-B1 and THYDE-B1 for analysis of the system blowdown for various break sizes, THYDE-B-REFLOOD for analysis of the reflood phase and SCORCH-B2 for the calculation of the fuel assembl hot plane temperature. When the multiple codes are used to analyze a broad range of LOCA as stated above, it is very important to evaluate the adequacy and consistency between the codes used to cover an entire break spectrum. The system consistency together with the system performance are discussed for a large commercial BWR. (author)

  13. VARIABILITY OF KD VALUES IN CEMENTITIOUS MATERIALS AND SEDIMENTS

    Energy Technology Data Exchange (ETDEWEB)

    Almond, P.; Kaplan, D.; Shine, E.

    2012-02-02

    Measured distribution coefficients (K{sub d} values) for environmental contaminants provide input data for performance assessments (PA) that evaluate physical and chemical phenomena for release of radionuclides from wasteforms, degradation of engineered components and subsequent transport of radionuclides through environmental media. Research efforts at SRNL to study the effects of formulation and curing variability on the physiochemical properties of the saltstone wasteform produced at the Saltstone Disposal Facility (SDF) are ongoing and provide information for the PA and Saltstone Operations. Furthermore, the range and distribution of plutonium K{sub d} values in soils is not known. Knowledge of these parameters is needed to provide guidance for stochastic modeling in the PA. Under the current SRS liquid waste processing system, supernate from F & H Tank Farm tanks is processed to remove actinides and fission products, resulting in a low-curie Decontaminated Salt Solution (DSS). At the Saltstone Production Facility (SPF), DSS is mixed with premix, comprised of blast furnace slag (BFS), Class F fly ash (FA), and portland cement (OPC) to form a grout mixture. The fresh grout is subsequently placed in SDF vaults where it cures through hydration reactions to produce saltstone, a hardened monolithic waste form. Variation in saltstone composition and cure conditions of grout can affect the saltstone's physiochemical properties. Variations in properties may originate from variables in DSS, premix, and water to premix ratio, grout mixing, placing, and curing conditions including time and temperature (Harbour et al. 2007; Harbour et al. 2009). There are no previous studies reported in the literature regarding the range and distribution of K{sub d} values in cementitious materials. Presently, the Savannah River Site (SRS) estimate ranges and distributions of K{sub d} values based on measurements of K{sub d} values made in sandy SRS sediments (Kaplan 2010). The actual

  14. Variability Of KD Values In Cementitious Materials And Sediments

    International Nuclear Information System (INIS)

    Measured distribution coefficients (Kd values) for environmental contaminants provide input data for performance assessments (PA) that evaluate physical and chemical phenomena for release of radionuclides from wasteforms, degradation of engineered components and subsequent transport of radionuclides through environmental media. Research efforts at SRNL to study the effects of formulation and curing variability on the physiochemical properties of the saltstone wasteform produced at the Saltstone Disposal Facility (SDF) are ongoing and provide information for the PA and Saltstone Operations. Furthermore, the range and distribution of plutonium Kd values in soils is not known. Knowledge of these parameters is needed to provide guidance for stochastic modeling in the PA. Under the current SRS liquid waste processing system, supernate from F and H Tank Farm tanks is processed to remove actinides and fission products, resulting in a low-curie Decontaminated Salt Solution (DSS). At the Saltstone Production Facility (SPF), DSS is mixed with premix, comprised of blast furnace slag (BFS), Class F fly ash (FA), and portland cement (OPC) to form a grout mixture. The fresh grout is subsequently placed in SDF vaults where it cures through hydration reactions to produce saltstone, a hardened monolithic waste form. Variation in saltstone composition and cure conditions of grout can affect the saltstone's physiochemical properties. Variations in properties may originate from variables in DSS, premix, and water to premix ratio, grout mixing, placing, and curing conditions including time and temperature (Harbour et al. 2007; Harbour et al. 2009). There are no previous studies reported in the literature regarding the range and distribution of Kd values in cementitious materials. Presently, the Savannah River Site (SRS) estimate ranges and distributions of Kd values based on measurements of Kd values made in sandy SRS sediments (Kaplan 2010). The actual cementitious material Kd values

  15. Method for characterization of the redox condition of cementitious materials

    Energy Technology Data Exchange (ETDEWEB)

    Almond, Philip M.; Langton, Christine A.; Stefanko, David B.

    2015-12-22

    Disclosed are methods for determining the redox condition of cementitious materials. The methods are leaching methods that utilize an in situ redox indicator that is present in the cementitious materials as formed. The in situ redox indicator leaches from cementitious material and, when the leaching process is carried out under anaerobic conditions can be utilized to determine the redox condition of the material. The in situ redox indicator can exhibit distinct characteristics in the leachate depending upon the redox condition of the indicator.

  16. Microfibres and hydrogels to promote autogenous healing in cementitious materials

    OpenAIRE

    Snoeck, Didier; Dubruel, Peter; De Belie, Nele

    2013-01-01

    Cementitious materials are sensitive to crack formation and it would be beneficial if the material could stop the crack propagation, repair the damage and reach again the original liquid-tightness and/or strength. Therefore, a cementitious material with synthetic microfibres and superabsorbent polymers (SAPs) is proposed. Upon crack formation, the microfibres will become active and due to the bridging action, they will stop the opening of a crack, forcing the cementitious material to crack so...

  17. Study on rich alumina alkali-activated slag clay minerals cementitious materials for immobilization of radioactive waste

    International Nuclear Information System (INIS)

    The composition and some properties of its pastes of rich alumina alkali-activated slag clay minerals (RAAASCM) cementitious materials for immobilization of radioactive waste are studied. Experimental results show that heat activated kaolinite, Xingjiang zeolite, modified attapulgite clay are better constituents of RAAASCM. RAAASCM cementitious materials pastes exhibit high strength, low porosity, fewer harmful pore, and high resistance to sulphate corrosion as well as gamma irradiation. The Sr2+, Cs+ leaching portion of the simulated radioactive waste forms based on RAAASCM, is low

  18. Preparation of Cementitious Material Using Smelting Slag and Tailings and the Solidification and Leaching of Pb2+

    Directory of Open Access Journals (Sweden)

    Dan Zhang

    2015-01-01

    Full Text Available The composite cementitious materials were prepared with lead-zinc tailings, lead-zinc smelting slag, and cement clinker. The effect of material ratio on the mechanical properties, the phase analysis, and microstructures were investigated. The effect of the pH and stripping time on the leaching amount of lead ion was discussed. The results show that the additive amount of the tailings should be minimized for the cementitious materials meeting the strength requirements, controlled within 10%. The leaching amount of cementitious materials remains low in a larger range of pH, which can effectively reduce the leaching of heavy metal lead. The leaching kinetics of lead ions in the three kinds of samples could be better described by the pseudo-second-model.

  19. Durability based life cycle assessment of concrete with supplementary cementitious materials exposed to carbonation

    OpenAIRE

    Van den Heede, Philip; De Belie, Nele

    2015-01-01

    Until now, it remains unclear how "green" concrete compositions with high volumes of supplementary cementitious materials really are, especially when subject to carbonation-induced steel corrosion. This paper results from accelerated carbonation tests for high-volume fly ash (HVFA) and fly ash + silica fume (FA+SF) concrete. They served as input for a probabilistic service life prediction on fib Bulletin 34, and a subsequent life cycle assessment. the inverse effective carbonation resistance ...

  20. Overview of recent work on self-healing in cementitious materials

    OpenAIRE

    Lv, Z; Chen, D

    2014-01-01

    Cracks, especially microcracks, in concrete are of paramount importance to the durability and the service life of cementitious composite. However, the self-healing technology, including autogenous healing and autonomous healing, is expected to be one of effective tools to overcome this boring problem. In this paper, we focus on the autogenous healing of concrete material and a few of recent works of autonomous healing are also mentioned. The durability and the mechanical properties improved b...

  1. Evaluation of a microcapsule based self-healing system for cementitious materials

    OpenAIRE

    Zhang, M.; Han, N; F. Xing; Wang, X.; Schlangen, H.E.J.G.

    2013-01-01

    An international cooperation research project has been financially supported by China Nature Science Foundation, which consists of three relatively independent, but strategically integrated research sub-programs, aiming at the formation of a selfhealing system based on the microcapsule principle for the cementitious composites. In this paper, a self-healing system triggered by physical process (cracking) is introduced. The healing material mainly consists of epoxy like materials. The discussi...

  2. Non-destructive testing techniques for the observation of healing effects in cementitious materials: an introduction

    OpenAIRE

    GROSSE, CU; Van Tittelboom, Kim; De Belie, Nele

    2013-01-01

    To develop an appropriate method of self-healing for cementitious materials including the right composition and amount of suitable healing agents it is required to investigate the healing efficiency for certain material mixtures. While some researchers evaluate the regain in compressive strength by means of destructive load tests, this method is obviously second best in particular for field applications. In a large EU project the best candidates among the non-destructive testing methods are i...

  3. Physical characterization methods for supplementary cementitious materials

    OpenAIRE

    Arvaniti, Eleni; Juenger, Maria; Bernal, Susan; Duchesne, Josée; Courard, Luc; Leroy, Sophie; Provis, John; Klemm, Agnieska; De Belie, Nele

    2015-01-01

    The main supplementary cementitious materials (SCMs) that are used today are industrial by-products. In most cases the quality of these materials cannot be controlled during their production, resulting in materials with varied characteristics. The adequate physical characterization of SCMs is important to better predict their performance and optimize their use in concretes production. There are standardized methods used to determine the particle characteristics for Portland cements that are u...

  4. Secure Cluster Based Routing Using SAT/ILP Techniques and ECC EL-Gamal Threshold Cryptography in MANET

    Directory of Open Access Journals (Sweden)

    Mr. P. Kanagaraju. Me, (Ph. D

    2014-03-01

    Full Text Available The Elliptic curve cryptography ( ECC a promising and important because it requires less computing power, bandwidth, and also the memory when comparing to other cryptosystems The clustering algorithm using the Integer Linear Programming (ILP and Boolean Satisfiability (SAT solvers. These improvements will secure the application of SAT and ILP techniques in modeling composite engineering problem that is the Clustering Problem in Mobile Ad-Hoc Networks (MANETs. The Clustering Problem in MANETs consists of selecting the most appropriate nodes of a given MANET topology as clusterheads, and ensuring that regular nodes are related to clusterheads such that the lifetime of the network is maximized. In which, discussing SAT/ILP techniques for clustering techniques and ECC El Gamal Threshold Cryptography for the security. Through our implementation, explored the possibility of using ECCEG-TC in MANETs.

  5. Experimental determination of lower plenum ECC injection effectiveness

    International Nuclear Information System (INIS)

    The effectiveness of lower plenum emergency core coolant (ECC) injection during a double ended offset shear cold leg break loss-of-coolant accident (LOCA) was investigated experimentally in a small-scale model of a pressurized water reactor (PWR). In order to determine relative merit of the lower plenum injection concept to mitigate the severity of a large break LOCA, data from lower plenum injection experiments were compared to data from an experiment in the Semiscale Mod-3 sytem in which cold leg ECC injection was utilized. The results indicated that lower plenum injection was extremely effective in initiating early reflooding of the core and earlier rod quenching than was observed in the cold leg injection experiment

  6. An overview of the BWR ECCS strainer blockage issues

    Energy Technology Data Exchange (ETDEWEB)

    Serkiz, A.W.; Marshall, M.L. Jr.; Elliott, R. [Nuclear Regulatory Commission, Washington, DC (United States)

    1996-03-01

    This Paper provides a brief overview of actions taken in the mid 1980s to resolve Unresolved Safety Issue (USI) A-43, {open_quotes}Containment Emergency Sump Performance,{close_quotes} and their relationship to the BWR strainer blockage issue; the importance of insights gained from the Barseback-2 (a Swedish BWR) incident in 1992 and from ECCS strainer testing and inspections at the Perry nuclear power plant in 1992 and 1993; an analysis of an US BWR/4 with a Mark I containment; an international community sharing of knowledge relevant to ECCS strainer blockage, additional experimental programs; and identification of actions needed to resolve the strainer blockage issue and the status of such efforts.

  7. Considerations for realistic ECCS evaluation methodology for LWRs

    International Nuclear Information System (INIS)

    This paper identifies the various phenomena which govern the course of large and small break LOCAs in LWRs, and affect the key parameters such as Peak Clad Temperature (PCT) and timing of the end of blowdown, beginning of reflood, PCT, and complete quench. A review of the best-estimate models and correlations for these phenomena in the current literature has been presented. Finally, a set of models have been recommended which may be incorporated in a present best-estimate code such as TRAC or RELAP5 in order to develop a realistic ECCS evaluation methodology for future LWRs and have also been compared with the requirements of current ECCS evaluation methodology as outlined in Appendix K of 10CFR50. 58 refs

  8. HIGH SPEED POINT ARITHMETIC ARCHITECTURE FOR ECC ON FPGA

    Directory of Open Access Journals (Sweden)

    Rahila Bilal,

    2010-09-01

    Full Text Available Elliptic curve cryptography plays a crucial role in networking and communication security. ECC have evolved in the recent past as an important alternative to established systems like RSA. This paper describes the implementation of an elliptic curve coprocessor based on the FPGA , which can provide a significant speedup for these cryptosystems. The FPGA configuration file is synthesized from VHDL code applying different hardware synthesis products. The implementation of ECC lies in three levels: scalar multiplication, point addition/doubling and finite field modular arithmetic. In this paper, we present a novel fast architecture for the point addition/doubling level in the projective coordinate. The proposed Architecture is based on Binary Field. The Design performs multiplication using Polynomial Basis. Analysis shows that, with reasonable hardware overhead, our architecture can achieve a high speedup for the point addition operation and point Doubling operation.Furthermore, the architecture is parameterized for different data widths to evaluate the optimal resource utilization.

  9. Cementitious Barriers Partnership Scm Paste Samples Exposed To Aggressive Solutions

    Energy Technology Data Exchange (ETDEWEB)

    Foster, T. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2014-12-01

    The Cementitious Barriers Partnership (CBP) Project is a multi-disciplinary, multi-institutional collaboration supported by the United States Department of Energy (US DOE) Office of Waste Processing. The objective of the CBP project is to develop a set of tools to improve understanding and prediction of the long-term structural, hydraulic, and chemical performance of cementitious barriers used in nuclear applications.

  10. Cementitious barriers partnership transport properties of damaged materials

    Energy Technology Data Exchange (ETDEWEB)

    Langton, C. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2014-11-01

    The Cementitious Barriers Partnership (CBP) Project is a multi-disciplinary, multi-institutional collaboration supported by the United States Department of Energy (US DOE) Office of Waste Processing. The objective of the CBP project is to develop a set of tools to improve understanding and prediction of the long-term structural, hydraulic, and chemical performance of cementitious barriers used in nuclear applications.

  11. Characteristics of Cast Stone cementitious waste form for immobilization of secondary wastes from vitrification process

    Science.gov (United States)

    Chung, Chul-Woo; Um, Wooyong; Valenta, Michelle M.; Sundaram, S. K.; Chun, Jaehun; Parker, Kent E.; Kimura, Marcia L.; Westsik, Joseph H.

    2012-01-01

    The high-temperature in vitrification process of radioactive wastes could cause radioactive technetium ( 99Tc) in secondary liquid wastes to become volatile. Solidified cementitious waste forms at low temperature were developed to immobilize radioactive secondary waste. This research focuses on the characterization of a cementitious waste form called Cast Stone. Properties including compressive strength, surface area, phase composition, and technetium leaching were measured. The results indicate that technetium diffusivity is affected by simulant type. Additionally, ettringite and AFm (Al 2O 3-Fe 2O 3-mono) main crystalline phases were formed during hydration. The Cast Stone waste form passed the qualification requirements for a secondary waste form, which are compressive strength of 3.45 MPa and technetium diffusivity of 10 -9 cm 2/s. Cast Stone was found to be a good candidate for immobilizing secondary waste streams.

  12. Use of polypropylene fibers coated with nano-silica particles into a cementitious mortar

    International Nuclear Information System (INIS)

    Fiber reinforced cementitious composite (FRCC) materials have been widely used during last decades in order to overcome some of traditional cementitious materials issues: brittle behaviour, fire resistance, cover spalling, impact strength. For composite materials, fiber/matrix bond plays an important role because by increasing fiber/matrix interactions is possible to increase the behaviour of the entire material. In this study, in order to improve fiber to matrix adhesion, two chemical treatments of polypropylene fibers were investigated: alkaline hydrolysis and nano-silica sol-gel particles deposition. Treatmtents effect on fibers morphology and mechanical properties was investigated by scanning electron microscopy (SEM) and tensile tests. SEM investigations report the presence of spherical nano-silica particles on fiber surface, in the case of sol-gel process, while alkaline hydrolysis leads to an increase of fibers roughness. Both treatments have negligible influence on fibers mechanical properties confirming the possibility of their use in a cementitious mortar. Pullout tests were carried out considering three embedded length of fibers in mortar samples (10, 20 and 30 mm, respectively) showing an increase of pullout energy for treated fibers. The influence on fiber reinforced mortar mechanical properties was investigated by three-point flexural tests on prismatic specimens considering two fibers length (15 and 30 mm) and two fibers volume fractions (0.50 and 1.00 %). A general increase of flexural strength over the reference mix was achieved and an overall better behaviour is recognizable for mortars containing treated fibers

  13. Use of polypropylene fibers coated with nano-silica particles into a cementitious mortar

    Science.gov (United States)

    Coppola, B.; Di Maio, L.; Scarfato, P.; Incarnato, L.

    2015-12-01

    Fiber reinforced cementitious composite (FRCC) materials have been widely used during last decades in order to overcome some of traditional cementitious materials issues: brittle behaviour, fire resistance, cover spalling, impact strength. For composite materials, fiber/matrix bond plays an important role because by increasing fiber/matrix interactions is possible to increase the behaviour of the entire material. In this study, in order to improve fiber to matrix adhesion, two chemical treatments of polypropylene fibers were investigated: alkaline hydrolysis and nano-silica sol-gel particles deposition. Treatmtents effect on fibers morphology and mechanical properties was investigated by scanning electron microscopy (SEM) and tensile tests. SEM investigations report the presence of spherical nano-silica particles on fiber surface, in the case of sol-gel process, while alkaline hydrolysis leads to an increase of fibers roughness. Both treatments have negligible influence on fibers mechanical properties confirming the possibility of their use in a cementitious mortar. Pullout tests were carried out considering three embedded length of fibers in mortar samples (10, 20 and 30 mm, respectively) showing an increase of pullout energy for treated fibers. The influence on fiber reinforced mortar mechanical properties was investigated by three-point flexural tests on prismatic specimens considering two fibers length (15 and 30 mm) and two fibers volume fractions (0.50 and 1.00 %). A general increase of flexural strength over the reference mix was achieved and an overall better behaviour is recognizable for mortars containing treated fibers.

  14. Self-degradable Cementitious Sealing Materials

    Energy Technology Data Exchange (ETDEWEB)

    Sugama, T.; Butcher, T., Lance Brothers, Bour, D.

    2010-10-01

    A self-degradable alkali-activated cementitious material consisting of a sodium silicate activator, slag, Class C fly ash, and sodium carboxymethyl cellulose (CMC) additive was formulated as one dry mix component, and we evaluated its potential in laboratory for use as a temporary sealing material for Enhanced Geothermal System (EGS) wells. The self-degradation of alkali-activated cementitious material (AACM) occurred, when AACM heated at temperatures of {ge}200 C came in contact with water. We interpreted the mechanism of this water-initiated self-degradation as resulting from the in-situ exothermic reactions between the reactants yielded from the dissolution of the non-reacted or partially reacted sodium silicate activator and the thermal degradation of the CMC. The magnitude of self-degradation depended on the CMC content; its effective content in promoting degradation was {ge}0.7%. In contrast, no self-degradation was observed from CMC-modified Class G well cement. For 200 C-autoclaved AACMs without CMC, followed by heating at temperatures up to 300 C, they had a compressive strength ranging from 5982 to 4945 psi, which is {approx}3.5-fold higher than that of the commercial Class G well cement; the initial- and final-setting times of this AACM slurry at 85 C were {approx}60 and {approx}90 min. Two well-formed crystalline hydration phases, 1.1 nm tobermorite and calcium silicate hydrate (I), were responsible for developing this excellent high compressive strength. Although CMC is an attractive, as a degradation-promoting additive, its addition to both the AACM and the Class G well cement altered some properties of original cementitious materials; among those were an extending their setting times, an increasing their porosity, and lowering their compressive strength. Nevertheless, a 0.7% CMC-modified AACM as self-degradable cementitious material displayed the following properties before its breakdown by water; {approx}120 min initial- and {approx}180 min final

  15. Feeding pattern a dual risk? otitis media (OM and early childhood caries (ECC

    Directory of Open Access Journals (Sweden)

    P. Sangeetha

    2014-04-01

    Full Text Available Purpose: To determine the prevalence of Otitis media (OM and Early childhood caries (ECC and their coexistence in children with a history of faulty feeding patterns. Method: Children aged 5 years and below were recruited at random from dental and medical hospitals. Parents of these children were posed with questions about the feeding methods, feeding patterns such as duration, frequency, position, burping, specific childhood illness etc. Children (120 were examined for ECC by a Paedodontist and OM by an Otolaryngologist and were segregated into three groups i.e. Control group, ECC group and OM group respectively. The ECC group was sub grouped into ECC only and ECC&OM group. The OM group was also similarly sub grouped into OM group and OM&ECC group. Collected data were tabulated and subjected for statistical analysis using Pearson Chi – square test. Results: Prevalence of ECC, OM, and their coexistence increased with age P < 0.001, whereas gender difference was not statistically significant. Overall Prevalence of their coexistence in children was 51.25%. Significant percentages (25% of children in the OM group were fed in supine position. Children fed on demand (47.5% experienced ECC. overall 85% (p=.017 of children had coexistence of ECC&OM fed on demand and during bed time. Significant numbers of children who were burped occasionally after feeding (35% or were not burped at all (12.5% were affected with both ECC and OM. Conclusion: Prevalence of their coexistence was higher in children with OM. Significant association existed between on demand feeding and ECC; supine feeding position and OM. Risk factors in common for both the disease were combined feeding position, on demand, bed time feeding and occasionally burping.

  16. The Cementitious Barriers Partnership (CBP) Software Toolbox Capabilities In Assessing The Degradation Of Cementitious Barriers

    International Nuclear Information System (INIS)

    The Cementitious Barriers Partnership (CBP) Project is a multi-disciplinary, multi-institutional collaboration supported by the U.S. Department of Energy (US DOE) Office of Tank Waste and Nuclear Materials Management. The CBP program has developed a set of integrated tools (based on state-of-the-art models and leaching test methods) that help improve understanding and predictions of the long-term structural, hydraulic and chemical performance of cementitious barriers used in nuclear applications. Tools selected for and developed under this program have been used to evaluate and predict the behavior of cementitious barriers used in near-surface engineered waste disposal systems for periods of performance up to 100 years and longer for operating facilities and longer than 1000 years for waste disposal. The CBP Software Toolbox has produced tangible benefits to the DOE Performance Assessment (PA) community. A review of prior DOE PAs has provided a list of potential opportunities for improving cementitious barrier performance predictions through the use of the CBP software tools. These opportunities include: 1) impact of atmospheric exposure to concrete and grout before closure, such as accelerated slag and Tc-99 oxidation, 2) prediction of changes in Kd/mobility as a function of time that result from changing pH and redox conditions, 3) concrete degradation from rebar corrosion due to carbonation, 4) early age cracking from drying and/or thermal shrinkage and 5) degradation due to sulfate attack. The CBP has already had opportunity to provide near-term, tangible support to ongoing DOE-EM PAs such as the Savannah River Saltstone Disposal Facility (SDF) by providing a sulfate attack analysis that predicts the extent and damage that sulfate ingress will have on the concrete vaults over extended time (i.e., > 1000 years). This analysis is one of the many technical opportunities in cementitious barrier performance that can be addressed by the DOE-EM sponsored CBP software

  17. The Cementitious Barriers Partnership (CBP) Software Toolbox Capabilities in Assessing the Degradation of Cementitious Barriers - 13487

    International Nuclear Information System (INIS)

    The Cementitious Barriers Partnership (CBP) Project is a multi-disciplinary, multi-institutional collaboration supported by the U.S. Department of Energy (US DOE) Office of Tank Waste and Nuclear Materials Management. The CBP program has developed a set of integrated tools (based on state-of-the-art models and leaching test methods) that help improve understanding and predictions of the long-term structural, hydraulic and chemical performance of cementitious barriers used in nuclear applications. Tools selected for and developed under this program have been used to evaluate and predict the behavior of cementitious barriers used in near-surface engineered waste disposal systems for periods of performance up to 100 years and longer for operating facilities and longer than 1000 years for waste disposal. The CBP Software Toolbox has produced tangible benefits to the DOE Performance Assessment (PA) community. A review of prior DOE PAs has provided a list of potential opportunities for improving cementitious barrier performance predictions through the use of the CBP software tools. These opportunities include: 1) impact of atmospheric exposure to concrete and grout before closure, such as accelerated slag and Tc-99 oxidation, 2) prediction of changes in Kd/mobility as a function of time that result from changing pH and redox conditions, 3) concrete degradation from rebar corrosion due to carbonation, 4) early age cracking from drying and/or thermal shrinkage and 5) degradation due to sulfate attack. The CBP has already had opportunity to provide near-term, tangible support to ongoing DOE-EM PAs such as the Savannah River Saltstone Disposal Facility (SDF) by providing a sulfate attack analysis that predicts the extent and damage that sulfate ingress will have on the concrete vaults over extended time (i.e., > 1000 years). This analysis is one of the many technical opportunities in cementitious barrier performance that can be addressed by the DOE-EM sponsored CBP software

  18. The Cementitious Barriers Partnership (CBP) Software Toolbox Capabilities In Assessing The Degradation Of Cementitious Barriers

    Energy Technology Data Exchange (ETDEWEB)

    Flach, G. P. [Savannah River Site (SRS), Aiken, SC (United States); Burns, H. H. [Savannah River Site (SRS), Aiken, SC (United States); Langton, C. [Savannah River Site (SRS), Aiken, SC (United States); Smith, F. G. III [Savannah River Site (SRS), Aiken, SC (United States); Brown, K. G. [Vanderbilt University, Nashville, TN (United States); Kosson, D. S. [Vanderbilt University, Nashville, TN (United States); Garrabrants, A. C. [Vanderbilt University, Nashville, TN (United States); Sarkar, S. [Vanderbilt University, Nashville, TN (United States); van der Sloot, H. [Hans van der Sloot Consultancy (The Netherlands); Meeussen, J. C.L. [Nuclear Research and Consultancy Group, Petten (The Netherlands); Samson, E. [SIMCO Technologies Inc. , 1400, boul. du Parc - Technologique , Suite 203, Quebec (Canada); Mallick, P. [United States Department of Energy, 1000 Independence Ave. SW , Washington, DC (United States); Suttora, L. [United States Department of Energy, 1000 Independence Ave. SW , Washington, DC (United States); Esh, D. W. [U .S. Nuclear Regulatory Commission , Washington, DC (United States); Fuhrmann, M. J. [U .S. Nuclear Regulatory Commission , Washington, DC (United States); Philip, J. [U .S. Nuclear Regulatory Commission , Washington, DC (United States)

    2013-01-11

    The Cementitious Barriers Partnership (CBP) Project is a multi-disciplinary, multi-institutional collaboration supported by the U.S. Department of Energy (US DOE) Office of Tank Waste and Nuclear Materials Management. The CBP program has developed a set of integrated tools (based on state-of-the-art models and leaching test methods) that help improve understanding and predictions of the long-term structural, hydraulic and chemical performance of cementitious barriers used in nuclear applications. Tools selected for and developed under this program have been used to evaluate and predict the behavior of cementitious barriers used in near-surface engineered waste disposal systems for periods of performance up to 100 years and longer for operating facilities and longer than 1000 years for waste disposal. The CBP Software Toolbox has produced tangible benefits to the DOE Performance Assessment (PA) community. A review of prior DOE PAs has provided a list of potential opportunities for improving cementitious barrier performance predictions through the use of the CBP software tools. These opportunities include: 1) impact of atmospheric exposure to concrete and grout before closure, such as accelerated slag and Tc-99 oxidation, 2) prediction of changes in Kd/mobility as a function of time that result from changing pH and redox conditions, 3) concrete degradation from rebar corrosion due to carbonation, 4) early age cracking from drying and/or thermal shrinkage and 5) degradation due to sulfate attack. The CBP has already had opportunity to provide near-term, tangible support to ongoing DOE-EM PAs such as the Savannah River Saltstone Disposal Facility (SDF) by providing a sulfate attack analysis that predicts the extent and damage that sulfate ingress will have on the concrete vaults over extended time (i.e., > 1000 years). This analysis is one of the many technical opportunities in cementitious barrier performance that can be addressed by the DOE-EM sponsored CBP software

  19. The Cementitious Barriers Partnership (CBP) Software Toolbox Capabilities in Assessing the Degradation of Cementitious Barriers - 13487

    Energy Technology Data Exchange (ETDEWEB)

    Flach, G.P.; Burns, H.H.; Langton, C.; Smith, F.G. III [Savannah River National Laboratory, Savannah River Site, Aiken SC 29808 (United States); Brown, K.G.; Kosson, D.S.; Garrabrants, A.C.; Sarkar, S. [Vanderbilt University, Nashville, TN (United States); Van der Sloot, H. [Hans Van der Sloot Consultancy (Netherlands); Meeussen, J.C.L. [Nuclear Research and Consultancy Group, Petten (Netherlands); Samson, E. [SIMCO Technologies Inc., 1400, boul. du Parc-Technologique, Suite 203, Quebec (Canada); Mallick, P.; Suttora, L. [United States Department of Energy, 1000 Independence Ave. SW, Washington, DC (United States); Esh, D.W.; Fuhrmann, M.J.; Philip, J. [U.S. Nuclear Regulatory Commission, Washington, DC (United States)

    2013-07-01

    The Cementitious Barriers Partnership (CBP) Project is a multi-disciplinary, multi-institutional collaboration supported by the U.S. Department of Energy (US DOE) Office of Tank Waste and Nuclear Materials Management. The CBP program has developed a set of integrated tools (based on state-of-the-art models and leaching test methods) that help improve understanding and predictions of the long-term structural, hydraulic and chemical performance of cementitious barriers used in nuclear applications. Tools selected for and developed under this program have been used to evaluate and predict the behavior of cementitious barriers used in near-surface engineered waste disposal systems for periods of performance up to 100 years and longer for operating facilities and longer than 1000 years for waste disposal. The CBP Software Toolbox has produced tangible benefits to the DOE Performance Assessment (PA) community. A review of prior DOE PAs has provided a list of potential opportunities for improving cementitious barrier performance predictions through the use of the CBP software tools. These opportunities include: 1) impact of atmospheric exposure to concrete and grout before closure, such as accelerated slag and Tc-99 oxidation, 2) prediction of changes in K{sub d}/mobility as a function of time that result from changing pH and redox conditions, 3) concrete degradation from rebar corrosion due to carbonation, 4) early age cracking from drying and/or thermal shrinkage and 5) degradation due to sulfate attack. The CBP has already had opportunity to provide near-term, tangible support to ongoing DOE-EM PAs such as the Savannah River Saltstone Disposal Facility (SDF) by providing a sulfate attack analysis that predicts the extent and damage that sulfate ingress will have on the concrete vaults over extended time (i.e., > 1000 years). This analysis is one of the many technical opportunities in cementitious barrier performance that can be addressed by the DOE-EM sponsored CBP

  20. Setup of Extruded Cementitious Hollow Tubes as Containing/Releasing Devices in Self-Healing Systems

    Directory of Open Access Journals (Sweden)

    Alessandra Formia

    2015-04-01

    Full Text Available The aim of this research is to produce self-healing cementitious composites based on the use of cylindrical capsules containing a repairing agent. Cementitious hollow tubes (CHT having two different internal diameters (of 2 mm and 7.5 mm were produced by extrusion and used as containers and releasing devices for cement paste/mortar healing agents. Based on the results of preliminary mechanical tests, sodium silicate was selected as the healing agent. The morphological features of several mix designs used to manufacture the extruded hollow tubes, as well as the coatings applied to increase the durability of both core and shell materials are discussed. Three-point bending tests were performed on samples produced with the addition of the above-mentioned cementitious hollow tubes to verify the self-healing effectiveness of the proposed solution. Promising results were achieved, in particular when tubes with a bigger diameter were used. In this case, a substantial strength and stiffness recovery was observed, even in specimens presenting large cracks (>1 mm. The method is inexpensive and simple to scale up; however, further research is needed in view of a final optimization.

  1. Evaluation of natural colonisation of cementitious materials: effect of bioreceptivity and environmental conditions.

    Science.gov (United States)

    Manso, Sandra; Calvo-Torras, María Ángeles; De Belie, Nele; Segura, Ignacio; Aguado, Antonio

    2015-04-15

    Incorporation of living organisms, such as photosynthetic organisms, on the structure envelope has become a priority in the area of architecture and construction due to aesthetical, economic and ecological advantages. Important research efforts are made to achieve further improvements, such as for the development of cementitious materials with an enhanced bioreceptivity to stimulate biological growth. Previously, the study of the bioreceptivity of cementitious materials has been carried out mainly under laboratory conditions although field-scale experiments may present different results. This work aims at analysing the colonisation of cementitious materials with different levels of bioreceptivity by placing them in three different environmental conditions. Specimens did not present visual colonisation, which indicates that environmental conditions have a greater impact than intrinsic properties of the material at this stage. Therefore, it appears that in addition to an optimized bioreceptivity of the concrete (i.e., composition, porosity and roughness), extra measures are indispensable for a rapid development of biological growth on concrete surfaces. An analysis of the colonisation in terms of genus and quantity of the most representative microorganisms found on the specimens for each location was carried out and related to weather conditions, such as monthly average temperature and total precipitation, and air quality in terms of NOx, SO2, CO and O3. OPC-based specimens presented a higher colonisation regarding both biodiversity and quantity. However, results obtained in a previous experimental programme under laboratory conditions suggested a higher suitability of Magnesium Phosphate Cement-based (MPC-based) specimens for algal growth. Consequently, carefully considering the environment and the relationships between the different organisms present in an environment is vital for successfully using a cementitious material as a substrate for biological growth. PMID

  2. Disease Management of Early Childhood Caries: ECC Collaborative Project

    Directory of Open Access Journals (Sweden)

    Man Wai Ng

    2014-01-01

    Full Text Available Until recently, the standard of care for early childhood caries (ECC has been primarily surgical and restorative treatment with little emphasis on preventing and managing the disease itself. It is now recognized that surgical treatment alone does not address the underlying etiology of the disease. Despite costly surgeries and reparative treatment, the onset and progression of caries are likely to continue. A successful rebalance of risk and protective factors may prevent, slow down, or even arrest dental caries and its progression. An 18-month risk-based chronic disease management (DM approach to address ECC in preschool children was implemented as a quality improvement (QI collaborative by seven teams of oral health care providers across the United States. In the aggregate, fewer DM children experienced new cavitation, pain, and referrals to the operating room (OR for restorative treatment compared to baseline historical controls. The teams found that QI methods facilitated adoption of the DM approach and resulted in improved care to patients and better outcomes overall. Despite these successes, the wide scale adoption and spread of the DM approach may be limited unless health policy and payment reforms are enacted to compensate providers for implementing DM protocols in their practice.

  3. DESIGN AND IMPLEMENTATION OF HIGH PERFORMANCE ECC COPROCESSOR

    Directory of Open Access Journals (Sweden)

    RAHILA BILAL,

    2010-11-01

    Full Text Available This article presents the Design of a crypto processor to implement the Elliptic curve point multiplication .We investigate the potential of the hardware/software co -design to realize a flexible – low resource Elliptic Curve Cryptography (ECC processor over binary fields GF(2163 on FPGA platforms. The proposed design is for m=163, recommended by ECC standards. The arithmetic operations are carried out using polynomial basis. The Elliptic curve point multiplication kP is based on Montgomery algorithm. The Architecture is parameterizedfor different data widths (4,8,16,163 bits to evaluate the optimal resource utilization.. The processor is implemented on the FPGA 2vp4fg256-7 and works at a frequency clock of 368.793MHz; the performance is 4.660ns per point multiplication over GF(2 163 uses 294 slices, 510 4 input LUT’S .The processor implemented presents a good performance, which is very suitable for applications that require high speed .

  4. Architecture for gas transport through cementitious materials

    Science.gov (United States)

    Vu, Thai Hoa; Frizon, Fabien; Lorente, Sylvie

    2009-05-01

    This paper documents the transport of gaseous species through porous media, with application to cementitious materials. An artificial pore network was created based on mercury intrusion porometry results obtained with samples of cement paste. The flow architecture model consists of parallel channels made of assemblies of truncated cones. Gas diffusion is described as a function of the saturation degree of the material. The model accounts for the effects of the liquid curtains, and the impact of tortuosity on gas diffusion. The results show that constructing an artificial architecture based on Hg porometry allows us to describe with a good accuracy the material porous network. The liquid curtains operate as an obstacle to H2 diffusion. They are determined as a function of the water saturation level and the pore channels geometry. Furthermore, the role of tortuosity as an indicator of gas diffusion accessibility is captured. The sudden drop in the effective diffusion coefficient around a saturation degree of 70% is predicted accurately.

  5. The synthesis of cementitious compounds in molten salts

    OpenAIRE

    Sheikh, R. A.

    2016-01-01

    This thesis describes an investigation into the synthesis of cementitious compounds in molten salts. These compounds are produced in energy-intensive industries (EIIs), such as the cement process, and are responsible for emitting significant quantities of carbon dioxide (CO2) emissions. Molten salt synthesis (MSS) involves dissolving compounds in a molten salt and reacting in solution. If the MSS of cementitious compounds can occur at lower temperatures than EIIs, this could lead to fewer qua...

  6. Evaluation of ECC related phenomena during semiscale MOD-1 isothermal tests

    International Nuclear Information System (INIS)

    Selected experimental data from tests performed during the Semiscale Mod-1 isothermal test series are analyzed. The analysis is confined to data that describe phenomena related to the injection of emergency core coolant (ECC). The analysis is directed at the ECC related phenomena in the intact loop cold leg, inlet annulus, downcomer, and lower plenum because, depending on injection location, some or all of these components will be in contact with the ECC as it flows to a position where cooling of an active core could result. Specifically, the condensation phenomena that occur in the intact loop cold leg, inlet annulus, and downcomer are analyzed along with dowmcomer heat transfer counter-current flow phenomena to determine their effects on ECC delivery. The effectiveness of injecting ECC at various locations in the Semiscale Mod-1 system is evaluated

  7. Combined group ECC protection and subgroup parity protection

    Energy Technology Data Exchange (ETDEWEB)

    Gara, Alan; Cheng, Dong; Heidelberger, Philip; Ohmacht, Martin

    2016-02-02

    A method and system are disclosed for providing combined error code protection and subgroup parity protection for a given group of n bits. The method comprises the steps of identifying a number, m, of redundant bits for said error protection; and constructing a matrix P, wherein multiplying said given group of n bits with P produces m redundant error correction code (ECC) protection bits, and two columns of P provide parity protection for subgroups of said given group of n bits. In the preferred embodiment of the invention, the matrix P is constructed by generating permutations of m bit wide vectors with three or more, but an odd number of, elements with value one and the other elements with value zero; and assigning said vectors to rows of the matrix P.

  8. Challenges and Benefits of Utilizing Carbon Nanofilaments in Cementitious Materials

    Directory of Open Access Journals (Sweden)

    Ardavan Yazdanbakhsh

    2012-01-01

    Full Text Available Carbon nanofibers/tubes (CNF/Ts are very strong and stiff and as a result, are expected to be capable of enhancing the mechanical properties of cementitious materials significantly. Yet there are practical issues concerning the utilization of CNF/Ts in cementitious materials. This study summarizes some of the past efforts made by different investigators for utilizing carbon nanofilaments in cementitious materials and also reports recent experimental research performed by the authors on the mechanical properties of CNF-reinforced hardened cement paste. The major difficulties concerning the utilization of CNF/Ts in cementitious materials are introduced and discussed. Most of these difficulties are related to the poor dispersibility of CNF/Ts. However, the findings from the research presented in this work indicate that, despite these difficulties, carbon nanofilaments can significantly improve the mechanical properties of cementitious materials. The results show that CNFs, even when poorly dispersed within the cementitious matrix, can remarkably increase the flexural strength and cracking resistance of concrete subjected to drying conditions.

  9. Entombment Using Cementitious Materials: Design Considerations and International Experience

    Energy Technology Data Exchange (ETDEWEB)

    Seitz, Roger Ray

    2002-08-01

    Cementitious materials have physical and chemical properties that are well suited for the requirements of radioactive waste management. Namely, the materials have low permeability and durability that is consistent with the time frame required for short-lived radionuclides to decay. Furthermore, cementitious materials can provide a long-term chemical environment that substantially reduces the mobility of some long-lived radionuclides of concern for decommissioning (e.g., C-14, Ni-63, Ni-59). Because of these properties, cementitious materials are common in low-level radioactive waste disposal facilities throughout the world and are an attractive option for entombment of nuclear facilities. This paper describes design considerations for cementitious barriers in the context of performance over time frames of a few hundreds of years (directed toward short-lived radionuclides) and time frames of thousands of years (directed towards longer-lived radionuclides). The emphasis is on providing an overview of concepts for entombment that take advantage of the properties of cementitious materials and experience from the design of low-level radioactive waste disposal facilities. A few examples of the previous use of cementitious materials for entombment of decommissioned nuclear facilities and proposals for the use in future decommissioning of nuclear reactors in a few countries are also included to provide global perspective.

  10. Entombment Using Cementitious Materials: Design Considerations and International Experience

    Energy Technology Data Exchange (ETDEWEB)

    Seitz, R.R.

    2002-05-15

    Cementitious materials have physical and chemical properties that are well suited for the requirements of radioactive waste management. Namely, the materials have low permeability and durability that is consistent with the time frame required for short-lived radionuclides to decay. Furthermore, cementitious materials can provide a long-term chemical environment that substantially reduces the mobility of some long-lived radionuclides of concern for decommissioning (e.g., C-14, Ni-63, Ni-59). Because of these properties, cementitious materials are common in low-level radioactive waste disposal facilities throughout the world and are an attractive option for entombment of nuclear facilities. This paper describes design considerations for cementitious barriers in the context of performance over time frames of a few hundreds of years (directed toward short-lived radionuclides) and time frames of thousands of years (directed towards longer-lived radionuclides). The emphasis is on providing a n overview of concepts for entombment that take advantage of the properties of cementitious materials and experience from the design of low-level radioactive waste disposal facilities. A few examples of the previous use of cementitious materials for entombment of decommissioned nuclear facilities and proposals for the use in future decommissioning of nuclear reactors in a few countries are also included to provide global perspective.

  11. Entombment Using Cementitious Materials: Design Considerations and International Experience

    International Nuclear Information System (INIS)

    Cementitious materials have physical and chemical properties that are well suited for the requirements of radioactive waste management. Namely, the materials have low permeability and durability that is consistent with the time frame required for short-lived radionuclides to decay. Furthermore, cementitious materials can provide a long-term chemical environment that substantially reduces the mobility of some long-lived radionuclides of concern for decommissioning (e.g., C-14, Ni-63, Ni-59). Because of these properties, cementitious materials are common in low-level radioactive waste disposal facilities throughout the world and are an attractive option for entombment of nuclear facilities. This paper describes design considerations for cementitious barriers in the context of performance over time frames of a few hundreds of years (directed toward short-lived radionuclides) and time frames of thousands of years (directed towards longer-lived radionuclides). The emphasis is on providing a n overview of concepts for entombment that take advantage of the properties of cementitious materials and experience from the design of low-level radioactive waste disposal facilities. A few examples of the previous use of cementitious materials for entombment of decommissioned nuclear facilities and proposals for the use in future decommissioning of nuclear reactors in a few countries are also included to provide global perspective

  12. Chemical modeling of cementitious grout materials alteration in HLW repositories

    International Nuclear Information System (INIS)

    This paper reports on an investigation initiated into the nature of the chemical alteration of cementitious grout in HLW repository seals, and the implications for long-term seal performance. The equilibrium chemical reaction of two simplified portland cement-based grout models with natural Canadian Shield groundwater compositions was modeled with the computer codes PHREEQE and EQ3NR/EQ6. Increases in porosity and permeability of the grout resulting from dissolution of grout phases and precipitation of secondary phases were estimated. Two bounding hydrologic scenarios were evaluated, one approximating a high gradient, high flow regime, the other a low-gradient, sluggish flow regime. Seal longevity depends in part upon the amount of groundwater coming into intimate contact with, and dissolving, the grout per unit time. Results of the analyses indicate that, given the assumptions and simplifications inherent in the models, acceptable seal performance (i.e., acceptable increases in hydraulic conductivity of the seals) may be expected for at least thousands of years in the worst cases analyzed, and possibly much longer

  13. Temporary Cementitious Sealers in Enhanced Geothermal Systems

    Energy Technology Data Exchange (ETDEWEB)

    Sugama T.; Pyatina, T.; Butcher, T.; Brothers, L.; Bour, D.

    2011-12-31

    Unlike conventional hydrothennal geothermal technology that utilizes hot water as the energy conversion resources tapped from natural hydrothermal reservoir located at {approx}10 km below the ground surface, Enhanced Geothermal System (EGS) must create a hydrothermal reservoir in a hot rock stratum at temperatures {ge}200 C, present in {approx}5 km deep underground by employing hydraulic fracturing. This is the process of initiating and propagating a fracture as well as opening pre-existing fractures in a rock layer. In this operation, a considerable attention is paid to the pre-existing fractures and pressure-generated ones made in the underground foundation during drilling and logging. These fractures in terms of lost circulation zones often cause the wastage of a substantial amount of the circulated water-based drilling fluid or mud. Thus, such lost circulation zones must be plugged by sealing materials, so that the drilling operation can resume and continue. Next, one important consideration is the fact that the sealers must be disintegrated by highly pressured water to reopen the plugged fractures and to promote the propagation of reopened fractures. In response to this need, the objective of this phase I project in FYs 2009-2011 was to develop temporary cementitious fracture sealing materials possessing self-degradable properties generating when {ge} 200 C-heated scalers came in contact with water. At BNL, we formulated two types of non-Portland cementitious systems using inexpensive industrial by-products with pozzolanic properties, such as granulated blast-furnace slag from the steel industries, and fly ashes from coal-combustion power plants. These byproducts were activated by sodium silicate to initiate their pozzolanic reactions, and to create a cemetitious structure. One developed system was sodium silicate alkali-activated slag/Class C fly ash (AASC); the other was sodium silicate alkali-activated slag/Class F fly ash (AASF) as the binder of temper

  14. Effects of cementitious leachates on the EBS

    Energy Technology Data Exchange (ETDEWEB)

    Koskinen, K.

    2014-01-15

    This report describes the method using which the effects of cement based materials on the engineering barrier system in the repository for spent nuclear fuel planned to Olkiluoto has been assessed. The phenomena considered are degradation of cement based materials due to interaction with groundwater, release of degradation products to groundwater, migration of degradation products in fracture network, interaction of degradation products with rock, and interaction of degradation products with buffer and backfill. Assessment of degradation of cement based materials is based on theories presented in the literature, measurements, and on numerical simulations. Migration of degradation products from the porewater for cementitious materials to the groundwater passing by gives rise to formation of a plume downstream of the material. This plume is comprised of degradation products. The ability of the plume to transport degradation products is assessed using the concept of concentration boundary layers. In the assessment of plume migration in hydraulically active fracture network it has been assumed that the plume does not get mixed with the surrounding groundwater such that the concentrations of the degradation products in the plume remain unaltered. In addition to this, only the transmissivities of various parts of the fracture network limit the migration of the plume. The migration of the plumes is assessed by using the values of known transmissivities in the potential flowpaths. The reactions of the plume with fracture minerals has been assessed, but due to the uncertainties in the parameters used in these assessments the mechanisms potentially decreasing the amounts of degradation products and their concentrations in the plume are not accounted for. Interactions with engineering barrier system are limited to the interactions of the plume with buffers and deposition tunnel backfills. These reactions are not considered in details due to insufficient understanding, but on

  15. Early-age characteristics of red mud-coal gangue cementitious material.

    Science.gov (United States)

    Zhang, Na; Sun, Henghu; Liu, Xiaoming; Zhang, Jixiu

    2009-08-15

    This experimental research was to investigate the possibility of incorporating red mud and coal gangue as raw materials for the production of red mud-coal gangue cementitious material, abbreviated as RGC, including analyses of its chemical composition, physical properties, mechanical properties and hydration products. The red mud and coal gangue (at a ratio of 3:2) were mixed together and shaped in small spheres with a water to solid ratio of 0.30 and then calcined at 600 degrees C for 2h. Subsequently, the RGC was prepared by blending 50% the resultant red mud-coal gangue mixtures, 24% blast-furnace slag, 20% clinker and 6% gypsum. The hydration products of RGC were characterized by XRD, TG-DTA and SEM-EDS. The results showed that it is feasible to use red mud and coal gangue to replace up to 50% of the raw materials to produce cementitious material, which can be called as silica-alumina based cementitious material. The hydration products of RGC are mostly ettringite, calcium hydroxide and C-S-H gel. As the dominant products, C-S-H gel and ettringite are principally responsible for the strength development of RGC in early hydration process. The content of Ca(OH)(2) initially increased but later was depleted after reaching the peak value at 21 days. Moreover, it is found that the composition of the C-S-H gel shifted towards higher Si, Al and Na contents with the increase of hydration age, whereas that of Ca shifted towards lower content. PMID:19237241

  16. Cementitious Materials in Safety Cases for Geological Repositories for Radioactive Waste: Role, Evolution and Interactions. A Workshop organised by the OECD/NEA Integration Group for the Safety Case and hosted by ONDRAF/NIRAS. Cementitious materials in safety cases for radioactive waste: role, evolution and interactions

    International Nuclear Information System (INIS)

    The OECD Nuclear Energy Agency (NEA) Integration Group for the Safety Case (IGSC) organised a workshop to assess current understanding on the use of cementitious materials in radioactive waste disposal. The workshop was hosted by the Belgian Agency for Radioactive Waste and Enriched Fissile Materials (Ondraf/Niras), in Brussels, Belgium on 17-19 November 2009. The workshop brought together a wide range of people involved in supporting safety case development and having an interest in cementitious materials: namely, cement and concrete experts, repository designers, scientists, safety assessors, disposal programme managers and regulators. The workshop was designed primarily to consider issues relevant to the post-closure safety of radioactive waste disposal, but also addressed some related operational issues, such as cementitious barrier emplacement. Where relevant, information on cementitious materials from analogous natural and anthropogenic systems was also considered. This report provides a synthesis of the workshop, and summarises its main results and findings. The structure of this report follows the workshop agenda: - Section 2 summarises plenary and working group discussions on the uses, functions and evolution of cementitious materials in geological disposal, and highlights key aspects and discussions points. - Section 3 summarises plenary and working group discussions on interactions of cementitious materials with other disposal system components, and highlights key aspects and discussions points. - Section 4 summarises the workshop session on the integration of issues related to cementitious materials using the safety case. - Section 5 presents the main conclusions from the workshop. - Section 6 contains a list of references. - Appendix A presents the workshop agenda. - Appendix B contains the abstracts and, where provided, technical papers supporting oral presentations at the workshop. - Appendix C contains the abstracts and, where provided, technical

  17. Acoustic Emission Monitoring of Cementitious Wasteforms

    International Nuclear Information System (INIS)

    A summary is presented of the potential of non-destructive acoustic emission (AE) method to be applied for structures immobilising nuclear wastes. The use and limitations of the method are discussed with given examples of experimental configurations and results obtained from AE monitoring and data analysis of two different processes addressing particular issues related to the nuclear waste immobilisation. These are (a) corrosion of aluminium, classified as intermediate level waste (ILW) in the UK, encapsulated in cementitious structures and (b) partial melting and solidification during cooling of granite at a pressure of 0.15 GPa which simulates the conditions in a deep borehole disposal of canisters of vitrified high level waste (HLW). Methodology for analysis of the collected data and characterisation of the potential AE sources is performed at different steps including simple signals count and more complex signal parameter-based approach and advanced signal processing. The AE method has been shown as a potential tool for monitoring and inspection of structures immobilising nuclear wastes in relation to the time progress of different interactions of the waste with the encapsulating matrix or the wasteform with the hosting environment for permanent disposal. (author)

  18. Cementitious waste option scoping study report

    International Nuclear Information System (INIS)

    A Settlement Agreement between the Department of Energy (DOE) and the State of Idaho mandates that all high-level radioactive waste (HLW) now stored at the Idaho Chemical Processing Plant (ICPP) on the Idaho National Engineering and Environmental Laboratory (INEEL) will be treated so that it is ready to be moved out of Idaho for disposal by a target date of 2035. This study investigates the nonseparations Cementitious Waste Option (CWO) as a means to achieve this goal. Under this option all liquid sodium-bearing waste (SBW) and existing HLW calcine would be recalcined with sucrose, grouted, canisterized, and interim stored as a mixed-HLW for eventual preparation and shipment off-Site for disposal. The CWO waste would be transported to a Greater Confinement Disposal Facility (GCDF) located in the southwestern desert of the US on the Nevada Test Site (NTS). All transport preparation, shipment, and disposal facility activities are beyond the scope of this study. CWO waste processing, packaging, and interim storage would occur over a 5-year period between 2013 and 2017. Waste transport and disposal would occur during the same time period

  19. Cementitious waste option scoping study report

    Energy Technology Data Exchange (ETDEWEB)

    Lee, A.E.; Taylor, D.D.

    1998-02-01

    A Settlement Agreement between the Department of Energy (DOE) and the State of Idaho mandates that all high-level radioactive waste (HLW) now stored at the Idaho Chemical Processing Plant (ICPP) on the Idaho National Engineering and Environmental Laboratory (INEEL) will be treated so that it is ready to be moved out of Idaho for disposal by a target date of 2035. This study investigates the nonseparations Cementitious Waste Option (CWO) as a means to achieve this goal. Under this option all liquid sodium-bearing waste (SBW) and existing HLW calcine would be recalcined with sucrose, grouted, canisterized, and interim stored as a mixed-HLW for eventual preparation and shipment off-Site for disposal. The CWO waste would be transported to a Greater Confinement Disposal Facility (GCDF) located in the southwestern desert of the US on the Nevada Test Site (NTS). All transport preparation, shipment, and disposal facility activities are beyond the scope of this study. CWO waste processing, packaging, and interim storage would occur over a 5-year period between 2013 and 2017. Waste transport and disposal would occur during the same time period.

  20. Modal analysis of an ECC duct for APR+ reactor barrel

    International Nuclear Information System (INIS)

    Advanced Power Reactor Plus (APR+) provides four Direct Vessel Injection (DVI) ducts on the reactor barrel to enhance the performance of Emergency Core Cooling System (ECCS). Several studies on safety analysis have verified the excellent performance of the DVI duct. In this study, from the viewpoint of mechanical integrity, modal analyses of two full-scaled DVI ducts have been presented; both numerical analysis and modal tests have been performed in air and water. It was found that the numerical simulation and modal test coincide with each other. The DVI duct is a thin shell of 5 mm thickness, so that harmonic responses to RCP blade passing frequencies should be checked. The dominant passing frequencies are known to be 20, 40, 60, 120 and 240 Hz. In addition, an interesting thing in this study is that added mass effect by coolant seems to be so significant that the natural frequency of the ducts under water could be considerably low as compared with those in air; the natural frequency under water is 60 % lower than that in air. (author)

  1. Short term hydrogen generation following LOCA and loss of ECCS

    International Nuclear Information System (INIS)

    The purpose of the present study is to estimate the amount of hydrogen that can be generated due to metal water reaction following LOCA and loss of ECCS in a 500 MWe PHWR. A computer code HYGEN (Hydrogen Generation) written in FORTRAN calculates time-dependent fuel temperature during the post blowdown period and the amount of hydrogen generated as a result of metal water reaction. It is seen from the analyses that metal water reaction depends on fuel bundle power, its initial temperature and steam flow conditions. At present, four groups of channels have been analysed for different steam flow conditions, and it is found that, for an about 5 gm/sec steam flow condition, the maximum of amount of hydrogen is generated (5.76 x 104 gm-mole) due to the zircaloy - steam reaction. This amount of hydrogen, when considered mixed in volume V1 (drywell) of the reactor building, means that the global concentration reaches about 2.76% by volume. So, it is seen that in the short term, the global hydrogen concentration in the reactor building is well below the flammability limit of 4% by volume. (author) 4 refs., 1 tab., 10 figs

  2. Preestrita pihtimus : Friedrich Nietzsche ja tema substantsiaalne mina (Ecce homo) / Jaan Undusk

    Index Scriptorium Estoniae

    Undusk, Jaan, 1958-

    1998-01-01

    Varem ilmunud raamatu järelsõnana: Nietzsche, Friedrich. Ecce homo : kuidas saadakse selleks, mis ollakse / tlk. Jaan Undusk. Tallinn : Vagabund, 1996. Sisu: Poeetiline, filosoofiline, dionüüsiline kaanon ; Künism contra hulluskahtlus ; Antikristlik pihtimus ; Egoretoorika

  3. Determination of required delay time following reactor shutdown prior to actuation of LOFT ECCS Bypass

    Energy Technology Data Exchange (ETDEWEB)

    Carmichael, C.F.

    1977-04-22

    The results of calculations are presented for the decay time required prior to LOFT ECCS shutdown bypass actuation following a reactor shutdown. These calculations are based on a LOCA occurring during hot shutdown which would void the core. Based on an operator response time of 20 minutes to manually establish ECC flow, the reactor decay time was calculated to prevent the fuel cladding temperature from exceeding 1100/sup 0/F. Results show that 211 hours are required following normal reactor shutdown from 55 MW reactor power before ECCS shutdown bypass actuation can be allowed if the reactor is not in cold shutdown condition. One hundred (100) seconds are required following a LOCE before ECCS shutdown bypass actuation can be allowed.

  4. Thermal conductivity and other properties of cementitious grouts

    Energy Technology Data Exchange (ETDEWEB)

    Allan, M.

    1998-08-01

    The thermal conductivity and other properties cementitious grouts have been investigated in order to determine suitability of these materials for grouting vertical boreholes used with geothermal heat pumps. The roles of mix variables such as water/cement ratio, sand/cement ratio and superplasticizer dosage were measured. In addition to thermal conductivity, the cementitious grouts were also tested for bleeding, permeability, bond to HDPE pipe, shrinkage, coefficient of thermal expansion, exotherm, durability and environmental impact. This paper summarizes the results for selected grout mixes. Relatively high thermal conductivities were obtained and this leads to reduction in predicted bore length and installation costs. Improvements in shrinkage resistance and bonding were achieved.

  5. THERMAL CONDUCTIVITY AND OTHER PROPERTIES OF CEMENTITIOUS GROUTS

    Energy Technology Data Exchange (ETDEWEB)

    ALLAN,M.

    1998-05-01

    The thermal conductivity and other properties cementitious grouts have been investigated in order to determine suitability of these materials for grouting vertical boreholes used with geothermal heat pumps. The roles of mix variables such as water/cement ratio, sand/cement ratio and superplasticizer dosage were measured. In addition to thermal conductivity, the cementitious grouts were also tested for bleeding, permeability, bond to HDPE pipe, shrinkage, coefficient of thermal expansion, exotherm, durability and environmental impact. This paper summarizes the results for selected grout mixes. Relatively high thermal conductivities were obtained and this leads to reduction in predicted bore length and installation costs. Improvements in shrinkage resistance and bonding were achieved.

  6. Cementitious Barriers Partnership Accomplishments And Relevance To The DOE Complex

    International Nuclear Information System (INIS)

    The Cementitious Barriers Partnership (CBP) was initiated to reduce risk and uncertainties in the performance assessments that directly impact U.S. Department of Energy (DOE) environmental cleanup and closure programs. The CBP is supported by the DOE Office of Environmental Management (DOE-EM) and has been specifically addressing the following critical EM program needs: (i) the long-term performance of cementitious barriers and materials in nuclear waste disposal facilities and (ii) increased understanding of contaminant transport behavior within cementitious barrier systems to support the development and deployment of adequate closure technologies. To accomplish this, the CBP has two initiatives: (1) an experimental initiative to increase understanding of changes in cementitious materials over long times (> 1000 years) over changing conditions and (2) a modeling initiative to enhance and integrate a set of computational tools validated by laboratory and field experimental data to improve understanding and prediction of the long-term performance of cementitious barriers and waste forms used in nuclear applications. In FY10, the CBP developed the initial phase of an integrated modeling tool that would serve as a screening tool which could help in making decisions concerning disposal and tank closure. The CBP experimental programs are underway to validate this tool and provide increased understanding of how CM changes over time and under changing conditions. These initial CBP products that will eventually be enhanced are anticipated to reduce the uncertainties of current methodologies for assessing cementitious barrier performance and increase the consistency and transparency of the DOE assessment process. These tools have application to low activity waste forms, high level waste tank closure, D and D and entombment of major nuclear facilities, landfill waste acceptance criteria, and in-situ grouting and immobilization of vadose zone contamination. This paper

  7. Obtaining cementitious material from municipal solid waste

    Directory of Open Access Journals (Sweden)

    Macías, A.

    2007-06-01

    Full Text Available The primary purpose of the present study was to determine the viability of using incinerator ash and slag from municipal solid waste as a secondary source of cementitious materials. The combustion products used were taken from two types of Spanish MSW incinerators, one located at Valdemingómez, in Madrid, and the other in Melilla, with different incineration systems: one with fluidised bed combustion and other with mass burn waterwall. The effect of temperature (from 800 to 1,200 ºC on washed and unwashed incinerator residue was studied, in particular with regard to phase formation in washed products with a high NaCl and KCl content. The solid phases obtained were characterized by X-ray diffraction and BET-N2 specific surface procedures.El principal objetivo del trabajo ha sido determinar la viabilidad del uso de las cenizas y escorias procedentes de la incineración de residuos sólidos urbanos, como materia prima secundaria para la obtención de fases cementantes. Para ello se han empleado los residuos generados en dos tipos de incineradoras españolas de residuos sólidos urbanos: la incineradora de Valdemingómez y la incineradora de Melilla. Se ha estudiado la transformación de los residuos, sin tratamiento previo, en función de la temperatura de calentamiento (desde 800 ºC hasta 1.200 ºC, así como la influencia del lavado de los residuos con alto contenido en NaCl y KCl en la formación de fases obtenidas a las diferentes temperaturas de calcinación. Las fases obtenidas fueron caracterizadas por difracción de rayos X y área superficial por el método BET-N2.

  8. A new and superior ultrafine cementitious grout

    International Nuclear Information System (INIS)

    Sealing fractures in nuclear waste repositories concerns all programs investigating deep burial as a means of disposal. Because the most likely mechanism for contaminant migration is by dissolution and movement through groundwater, sealing programs are seeking low-viscosity sealants that are chemically, mineralogically, and physically compatible with the host rock. This paper presents the results of collaborative work directed by Sandia National Laboratories (SNL) and supported by Whiteshell Laboratories, operated by Atomic Energy of Canada, Ltd. The work was undertaken in support of the Waste Isolation Pilot Plant (WIPP), an underground nuclear waste repository located in a salt formation east of Carlsbad, NM. This effort addresses the technology associated with long-term isolation of nuclear waste in a natural salt medium. The work presented is part of the WIPP plugging and sealing program, specifically the development and optimization of an ultrafine cementitious grout that can be injected to lower excessive, strain-induced hydraulic conductivity in the fractured rock termed the Disturbed Rock Zone (DRZ) surrounding underground excavations. Innovative equipment and procedures employed in the laboratory produced a usable cement-based grout; 90% of the particles were smaller than 8 microns and the average particle size was 4 microns. The process involved simultaneous wet pulverization and mixing. The grout was used for a successful in situ test underground at the WIPP. Injection of grout sealed microfractures as small as 6 microns (and in one rare instance, 3 microns) and lowered the gas transmissivity of the DRZ by up to three orders of magnitude. Following the WIPP test, additional work produced an improved version of the grout containing particles 90% smaller than 5 microns and averaging 2 microns. This grout will be produced in dry form, ready for the mixer

  9. The effect of nitrates on the alteration of the cementitious material

    International Nuclear Information System (INIS)

    TRU waste includes various chemical compounds such as nitrates. The influence of the chemical compounds on the performance of the barrier system should be estimated. Since the temperature of the deep-underground is higher than that of the near surface and a part of the TRU waste generates the heat accompanied with the decay of the radioactive nuclides, the influences of the heat to the barrier material also should be taken into account. In this study, we estimated the influence of sodium nitrate and also that of the leachate from the ROBE-waste (borate-solidified body of concentrated low-level waste) to the degradation of the cementitious material. We also obtained the mineralogical data of cementitious mineral after alteration in elevated temperature conditions. Results in this year are described below. 1) Alteration of characteristics of cementitious material in nitrate solution were evaluated by the water permeation test using sodium nitrate solution. The enhancement of the alteration of cementitious material due to sodium nitrate was observed. The dissolution quantity of the calcium of sodium nitrate solution permeated sample was larger than that of deionized water permeated sample (denoted as 'blank' in following). Hydraulic conductivity of sodium nitrate solution permeated sample was lower than blank, but after changing permeation liquid from sodium nitrate solution to deionized water, hydraulic conductivity rose quickly. The increase of porosity and the decrease of compressive strength were observed in the case of sodium nitrate solution compared with blank. In the nitrate solution, sulfate type and carbonate type of AFm changed into the nitrate type AFm. The nitrate type AFm altered to the carbonate type AFm when the nitrate concentration was lowered. 2) The influence of the leachate from the two types of ROBE-waste on the dissolution of the cementitious material was evaluated by the leaching experiments. Dissolution of the calcium from the cementitious

  10. Indications for Self-Sealing of a Cementitious L and ILW Repository

    International Nuclear Information System (INIS)

    Repositories for low and intermediate level nuclear waste contain large amounts of cementitious material. As a consequence of the interaction with formation waters, the cement will be degraded forming secondary minerals. The amount of precipitating secondary minerals depends on the chemical composition of the formation water. Furthermore, in the vicinity of the repository the hydraulic conditions and the parameters describing mass (radionuclide) transport will change with time during the cement degradation phase. As a result, porosity changes due to mineral and cement reactions will influence permeability and diffusivity: formation water rich in CO2 will lead to calcite precipitation in the water conducting zones surrounding the cementitious waste repository and, therefore, will have an impact on the radionuclide release from the cementitious repository into the host rock environment. Laboratory column experiments showed concurrent porosity and permeability changes during degradation of porous cement discs. However, very different quantitative results have been observed when CO2-rich or pure water were used. The sequentially coupled flow, transport and chemical reaction code, MCOTAC, is used to include such observations in the modelling. A porosity-permeability and a porosity-diffusivity relation are used for describing cement degradation and related secondary mineral precipitation. For these complex coupled processes one-dimensional modelling has reached its limits of applicability. Therefore, two-dimensional model calculations are used to predict the temporal evolution of transport parameters for radionuclides within a 'small scale' near-field of a cementitious waste repository. Mineral reactions influence hydraulic and transport parameters within such a near-field, causing reduced solute transport in the vicinity of the repository due to porosity and permeability changes at the rock-repository-interface. Also, the transport of radionuclides from the repository

  11. Quantifying moisture transport in cementitious materials using neutron radiography

    Science.gov (United States)

    Lucero, Catherine L.

    A portion of the concrete pavements in the US have recently been observed to have premature joint deterioration. This damage is caused in part by the ingress of fluids, like water, salt water, or deicing salts. The ingress of these fluids can damage concrete when they freeze and expand or can react with the cementitious matrix causing damage. To determine the quality of concrete for assessing potential service life it is often necessary to measure the rate of fluid ingress, or sorptivity. Neutron imaging is a powerful method for quantifying fluid penetration since it can describe where water has penetrated, how quickly it has penetrated and the volume of water in the concrete or mortar. Neutrons are sensitive to light atoms such as hydrogen and thus clearly detect water at high spatial and temporal resolution. It can be used to detect small changes in moisture content and is ideal for monitoring wetting and drying in mortar exposed to various fluids. This study aimed at developing a method to accurately estimate moisture content in mortar. The common practice is to image the material dry as a reference before exposing to fluid and normalizing subsequent images to the reference. The volume of water can then be computed using the Beer-Lambert law. This method can be limiting because it requires exact image alignment between the reference image and all subsequent images. A model of neutron attenuation in a multi-phase cementitious composite was developed to be used in cases where a reference image is not available. The attenuation coefficients for water, un-hydrated cement, and sand were directly calculated from the neutron images. The attenuation coefficient for the hydration products was then back-calculated. The model can estimate the degree of saturation in a mortar with known mixture proportions without using a reference image for calculation. Absorption in mortars exposed to various fluids (i.e., deionized water and calcium chloride solutions) were investigated

  12. The Heat Exchanger for Passive Part ECCS of WWER-1000 on Base of the Thermo siphons

    International Nuclear Information System (INIS)

    One of NPP's systems providing safe operation is the system of emergency core cooling system (ECCS), which primary function in accidents is to flood the nuclear reactor core and to assure the sub critical condition and core cooling. At injection of cold water in reactor thermal stresses and thermal fatigue in the vessel cladding and constructional materials are arise. Low temperature of the water injected in reactor is a reason of occurrence of these undesirable consequences. Some variants of the water heating in accumulators of ECCS are considered. Now at Ukrainian NPPs the electrical heating in accumulators is used. Electrical heaters create the essential additional loading to diesel generators at imposing of two accidents - the large break and losses of power supplies on own needs. It is offered to use a heater in accumulators that working by a principle two-phase thermal siphon which advantages is: small dimensions, small delay and design reliability. In such heat exchanger the heating medium is a direct steam and the heated up medium is water with boric acid from accumulators of ECCS. Under requirements of the service regulations of ECCS accumulators it is necessary to guarantee injected water heating up to 90 ?? in case of a small break and to 150 ?? in case of the large break. Results of calculations for different external diameters of a tube of thermal siphon which have allowed to define the constructive sizes of heat exchanger, providing necessary conditions for required functioning of passive part ECCS are submitted The calculation and analysis of operating modes of the changed circuit of passive part ECCS for various accidents is carried out. The calculated pressure drop indicates that changes do not have essential influence on system work as a whole. Thus, the submitted decision provides the increase of reliability of ECCS at small and large breaks accidents, i.e. in all modes stipulated by the project.(author)

  13. REFERENCE CASES FOR USE IN THE CEMENTITIOUS BARRIERS PARTNERSHIP

    International Nuclear Information System (INIS)

    The Cementitious Barriers Project (CBP) is a multidisciplinary cross cutting project initiated by the US Department of Energy (DOE) to develop a reasonable and credible set of tools to improve understanding and prediction of the structural, hydraulic and chemical performance of cementitious barriers used in nuclear applications. The period of performance is >100 years for operating facilities and > 1000 years for waste management. The CBP has defined a set of reference cases to provide the following functions: (1) a common set of system configurations to illustrate the methods and tools developed by the CBP, (2) a common basis for evaluating methodology for uncertainty characterization, (3) a common set of cases to develop a complete set of parameter and changes in parameters as a function of time and changing conditions, and (4) a basis for experiments and model validation, and (5) a basis for improving conceptual models and reducing model uncertainties. These reference cases include the following two reference disposal units and a reference storage unit: (1) a cementitious low activity waste form in a reinforced concrete disposal vault, (2) a concrete vault containing a steel high-level waste tank filled with grout (closed high-level waste tank), and (3) a spent nuclear fuel basin during operation. Each case provides a different set of desired performance characteristics and interfaces between materials and with the environment. Examples of concretes, grout fills and a cementitious waste form are identified for the relevant reference case configurations

  14. Ancient analogues concerning stability and durability of cementitious wasteform

    International Nuclear Information System (INIS)

    The history of cementitious materials goes back to ancient times. The Greeks and Romans used calcined limestone and later developed pozzolanic cement by grinding together lime and volcanic ash called open-quotes pozzolanclose quotes which was first found near Port Pozzuoli, Italy. The ancient Chinese used lime-pozzolanic mixes to build the Great Wall. The ancient Egyptians used calcined impure gypsum to build the Great Pyramid of Cheops. The extraordinary stability and durability of these materials has impressed us, when so much dramatically damaged infrastructure restored by using modern portland cement now requires rebuilding. Stability and durability of cementitious materials have attracted intensive research interest and contractors' concerns, as does immobilization of radioactive and hazardous industrial waste in cementitious materials. Nuclear waste pollution of the environment and an acceptable solution for waste management and disposal constitute among the most important public concerns. The analogy of ancient cementitious materials to modern Portland cement could give us some clues to study their stability and durability. This present study examines selected results of studies of ancient building materials from France, Italy, China, and Egypt, combined with knowledge obtained from the behavior of modern portland cement to evaluate the potential for stability and durability of such materials in nuclear waste forms

  15. REFERENCE CASES FOR USE IN THE CEMENTITIOUS BARRIERS PARTNERSHIP

    Energy Technology Data Exchange (ETDEWEB)

    Langton, C

    2009-01-06

    The Cementitious Barriers Project (CBP) is a multidisciplinary cross cutting project initiated by the US Department of Energy (DOE) to develop a reasonable and credible set of tools to improve understanding and prediction of the structural, hydraulic and chemical performance of cementitious barriers used in nuclear applications. The period of performance is >100 years for operating facilities and > 1000 years for waste management. The CBP has defined a set of reference cases to provide the following functions: (1) a common set of system configurations to illustrate the methods and tools developed by the CBP, (2) a common basis for evaluating methodology for uncertainty characterization, (3) a common set of cases to develop a complete set of parameter and changes in parameters as a function of time and changing conditions, and (4) a basis for experiments and model validation, and (5) a basis for improving conceptual models and reducing model uncertainties. These reference cases include the following two reference disposal units and a reference storage unit: (1) a cementitious low activity waste form in a reinforced concrete disposal vault, (2) a concrete vault containing a steel high-level waste tank filled with grout (closed high-level waste tank), and (3) a spent nuclear fuel basin during operation. Each case provides a different set of desired performance characteristics and interfaces between materials and with the environment. Examples of concretes, grout fills and a cementitious waste form are identified for the relevant reference case configurations.

  16. Prediction of Flexural Capacity of RC Beams Strengthened in Flexure with FRP Fabric and Cementitious Matrix

    Directory of Open Access Journals (Sweden)

    Kyusan Jung

    2015-01-01

    Full Text Available This paper presents both experimental and analytical research results for predicting the flexural capacity of reinforced concrete (RC beams strengthened in flexure with fabric reinforced cementitious matrix (FRCM. In order to assess the efficiency of the FRCM-strengthening method, six beams were strengthened in flexure with FRCM composite having different amounts and layers of FRP fabric and were tested under four-point loading. From test results, it was confirmed that the slippage between the FRP fabric and matrix occurs at a high strain level, and all of the FRCM-strengthened beams failed by the debonding of the FRCM. Additionally, a new bond strength model for FRCM considering the slippage between fabric and matrix was proposed, using a test database to predict the strengthening performance of the FRCM composite. The prediction of the proposed bond strength model agreed well with the debonding loads of the test database.

  17. Electro-decontamination of cementitious materials

    International Nuclear Information System (INIS)

    The end of operations in nuclear facilities is followed by various decontamination and decommissioning operations. Similar to other electrochemical techniques such as re-alkalinisation and chloride extraction, an electrokinetic remediation process is being developed as a specific method for deeply contaminated concrete structures. Two cements, an ordinary Portland and a 30% slag cement, have been chosen for the conducted work.Mortars and concretes are contaminated by adding non-radioactive cesium in the batch water, cesium being a representative specie of deep encountered contaminants. The conducted experimental and numerical work have focused on three main aspects: characterizing and understanding the cesium transport mechanisms, assessing the electro-remediation process at lab-scale and evaluating the real scale constraints. Using existing knowledge of chloride transport mechanisms, experiments have been conducted to characterize the cesium interactions with cementitious phase and ionic transport in saturated materials. A numerical model have then been developed to describe the cesium transport, taking into account the ionic activity coefficients and interactions with solid phases. Indeed, lab-scale experiments have demonstrated that electro-remediation reduced to 20-50% the initially contained cesium after a three weeks treatment. Treated samples analysis confirmed that deeply diffused cesium is migrating to the surface. Moreover, conducted experiments showed the consistency between the different materials properties, applied currents and decontamination efficiency. A comparative analysis of experiments carried on samples with different shapes, formulations and contamination modes helped assessing and optimizing the process efficiency for various continuous and variable applied currents. Finally, electro-remediation experiments have also been carried on 1m2 concrete slabs. Liquid catholyte and anolyte solutions are replaced by alumina gels and cellulose pastes

  18. Hubungan Perilaku Diet Anak Dengan Early Childhood Caries (ECC) Pada Anak Usia 12-36 Bulan Di Kecamatan Medan Barat

    OpenAIRE

    Wahab, Mohd Khairul Izwan Bin Abdul

    2014-01-01

    Early Childhood Caries (ECC) merupakan istilah yang digunakan untuk menjelaskan tentang suatu pola karies yang unik pada anak usia pra-sekolah. Etiologi ECC sama seperti karies umum yang lainnya yaitu multifaktorial dengan perilaku diet menjadi faktor predisposisi. Penelitian ini bertujuan untuk melihat hubungan antara kategori perilaku diet dengan pengalaman ECC pada anak usia 12-36 bulan di Kecamatan Medan Barat. Kategori perilaku diet tersebut terdiri atas pola makan utama, pola makan seli...

  19. Direct ECC bypass phenomena in the MIDAS test facility during LBLOCA reflood phase

    International Nuclear Information System (INIS)

    This paper describes the experimental results of ECC Direct Bypass Phenomena in the downcomer during the late reflood phase of LBLOCA of the reactor that adopts Direct Vessel Injection as a ECC system. The experiments have been performed in MIDAS test facility using superheated steam and water. The test condition was determined, based on the preliminary analysis of TRAC code, from modified linear scaling method of 1/4.93 length scale. To measure the direct bypass fraction according to the nozzle location, separate effect tests have been performed in case of DVI-4(farthest from broken cold leg) injection, DVI-2(closest to broken cold leg) injection, and DVI-2 and 4 injection, respectively. Also the test was carried out varying the steam flow rate greatly to investigate the effect of steam flow rate on the direct bypass fraction of ECC water. Test results show that the direct bypass fraction of ECC water depends significantly on the injected steam mass flow rate. DVI-4 tests show that the direct bypass fraction increases drastically as the steam flow rate increases. However, in DVI-2 test most of the injected ECC water penetrates into lower downcomer. The direct bypass characteristic in each of DVI-2 and DVI-4 tests is reflected into the direct bypass characteristic curve of DVI-2 and 4 test. The steam condensation reaches to the theoretically allowable maximum value

  20. Direct ECC bypass phenomena in the MIDAS test facility during LBLOCA reflood phase

    Energy Technology Data Exchange (ETDEWEB)

    Yun, B. J.; Kweon, T. S.; Ah, D. J.; Ju, I. C.; Song, C. H.; Park, J. K. [KAERI, Taejon (Korea, Republic of)

    2001-10-01

    This paper describes the experimental results of ECC Direct Bypass Phenomena in the downcomer during the late reflood phase of LBLOCA of the reactor that adopts Direct Vessel Injection as a ECC system. The experiments have been performed in MIDAS test facility using superheated steam and water. The test condition was determined, based on the preliminary analysis of TRAC code, from modified linear scaling method of 1/4.93 length scale. To measure the direct bypass fraction according to the nozzle location, separate effect tests have been performed in case of DVI-4(farthest from broken cold leg) injection, DVI-2(closest to broken cold leg) injection, and DVI-2 and 4 injection, respectively. Also the test was carried out varying the steam flow rate greatly to investigate the effect of steam flow rate on the direct bypass fraction of ECC water. Test results show that the direct bypass fraction of ECC water depends significantly on the injected steam mass flow rate. DVI-4 tests show that the direct bypass fraction increases drastically as the steam flow rate increases. However, in DVI-2 test most of the injected ECC water penetrates into lower downcomer. The direct bypass characteristic in each of DVI-2 and DVI-4 tests is reflected into the direct bypass characteristic curve of DVI-2 and 4 test. The steam condensation reaches to the theoretically allowable maximum value.

  1. ROSA-II experimental program for PWR LOCA/ECCS integral tests

    International Nuclear Information System (INIS)

    This paper is the final report of the ROSA-II experimental program, in which summary of the integral test results on thermal hydraulic behavior in a loss-of-coolant accident (LOCA) of pressurized water reactor (PWR) and on the effect of emergency core cooling system (ECCS) is presented. The ROSA-II test facility has a volume scaling factor of approximately 1/400 and core heating power of 2.4 MW. Specific feature of the facility is the versatility of the break conditions, the ECCS injection conditions and the secondary system conditions. After numbers of integral tests under various test conditions, (1) condensation-depressurization effect due to ECC water, (2) stored heat release from the structural materials and (3) counter current flow limitation (CCFL) at the specific locations were found to be important phenomena for the core cooling. To supply cooling water as soon as possible to the core was indicated to be very important for successful core cooling. Based on these results, more effective ECCS was proposed and the effectiveness of the proposed ECCS was experimentally verified. On the other hand, part of the experimental data was utilized to evaluate the predictability of RELAP-3 and RELAP-4J computer codes. (author)

  2. Experimental studies on in-bundle ECCS injection for Advanced Heavy Water Reactor

    International Nuclear Information System (INIS)

    The Advanced Heavy Water Reactor (AHWR) being designed at BARC is an innovative reactor with Thorium utilization as its major objective. It has many advanced passive safety features. One such feature is passive injection of emergency coolant after postulated Loss of Coolant Accident (LOCA). A novel feature of this injection scheme is that the injection does not take place in the header/plenum as in other reactors, but directly in to the bundle. For this purpose, the fuel cluster incorporates a central water rod which communicates with the ECCS header. The water rod extends along full length of the fuel cluster. In event of LOCA in the Main Heat Transport (MHT) system, ECC water flows from the accumulator to the water rod through ECCS header. The water flows into the bundle through holes in the water rod. The AHWR fuel cluster has fuel pins arranged in three concentric rings (of 12, 18 and 24 pins) around the central rod. While it is ensured that water does reach the fuel cluster, whether it reaches the outer ring of pins is needs investigation as the pins are closely spaced (1-3 mm gap between adjacent rods). The objective of the present experiments is to determine under what conditions (ECC flow and decay heat), the ECC water is able to rewet and cool all the fuel pins. The experiments have been done in a short, instrumented fuel bundle simulating the geometry of the AHWR fuel cluster

  3. Cementitious Barriers Partnership FY2013 End-Year Report

    Energy Technology Data Exchange (ETDEWEB)

    Flach, G. P. [Savannah River Site (SRS), Aiken, SC (United States); Langton, C. A. [Savannah River Site (SRS), Aiken, SC (United States); Burns, H. H. [Savannah River Site (SRS), Aiken, SC (United States); Smith, F. G. [Savannah River Site (SRS), Aiken, SC (United States); Kosson, D. S. [Vanderbilt University, School of Engineering, Nashville, TN (United States); Brown, K. G. [Vanderbilt University, School of Engineering, Nashville, TN (United States); Samson, E. [SIMCO Technologies, Inc., Quebec (Canada); Meeussen, J. C.L. [Nuclear Research and Consultancy Group (NRG), Petten (The Netherlands); van der Sloot, H. A. [Hans van der Sloot Consultancy, Langedijk (The Netherlands); Garboczi, E. J. [Materials & Construction Research Division, National Institute of Standards and Technology, Gaithersburg, MD (United States)

    2013-11-01

    In FY2013, the Cementitious Barriers Partnership (CBP) demonstrated continued tangible progress toward fulfilling the objective of developing a set of software tools to improve understanding and prediction of the long-term structural, hydraulic and chemical performance of cementitious barriers used in nuclear applications. In November 2012, the CBP released “Version 1.0” of the CBP Software Toolbox, a suite of software for simulating reactive transport in cementitious materials and important degradation phenomena. In addition, the CBP completed development of new software for the “Version 2.0” Toolbox to be released in early FY2014 and demonstrated use of the Version 1.0 Toolbox on DOE applications. The current primary software components in both Versions 1.0 and 2.0 are LeachXS/ORCHESTRA, STADIUM, and a GoldSim interface for probabilistic analysis of selected degradation scenarios. The CBP Software Toolbox Version 1.0 supports analysis of external sulfate attack (including damage mechanics), carbonation, and primary constituent leaching. Version 2.0 includes the additional analysis of chloride attack and dual regime flow and contaminant migration in fractured and non-fractured cementitious material. The LeachXS component embodies an extensive material property measurements database along with chemical speciation and reactive mass transport simulation cases with emphasis on leaching of major, trace and radionuclide constituents from cementitious materials used in DOE facilities, such as Saltstone (Savannah River) and Cast Stone (Hanford), tank closure grouts, and barrier concretes. STADIUM focuses on the physical and structural service life of materials and components based on chemical speciation and reactive mass transport of major cement constituents and aggressive species (e.g., chloride, sulfate, etc.). THAMES is a planned future CBP Toolbox component focused on simulation of the microstructure of cementitious materials and calculation of resultant

  4. Effects of solution mass transport on the ECC ozonesonde background current. [Electrochemical Concentration Cell

    Science.gov (United States)

    Thornton, D. C.; Niazy, N.

    1983-01-01

    A technique is developed to measure the effective mass transport parameter for the electrochemical concentration cell (ECC) ozonesonde in order to determine the mass transport rate constant for the ECC as a function of pressure. It is shown that a pressure dependent factor in the background current originates in a convective mass transport parameter. It is determined that for atmospheric pressures greater than 100 mb the mass transport parameter is a constant, while at pressures less than 100 mb it decreases logarithmically with pressure. It is suggested that the background current correction is directly correlated to the mass transport parameter pressure dependence. The presently used background current correction, which is based on the partial pressure of oxygen, is found to lead to an overestimation of the integrated ozone value in the troposphere for the ECC ozonesonde data.

  5. Upper plenum energency core coolant (ECC) injection in the semiscale Mod-1 system

    International Nuclear Information System (INIS)

    Two different PWR plant configurations were simulated in the Semiscale Mod-1 system. The first system configuration represented a double-ended cold leg break in one loop of a four-loop PWR plant. Accumulators injected ECC into both the upper plenum and the cold legs, and two different upper plenum ECC injection rates were evaluated. For the second simulation, the Semiscale Mod-1 system was configured to represent a double-ended cold leg break in one loop of a two-loop PWR system. In this case, ECC was injected by the low pressure injection system (LPIS) into the upper plenum, and accumulator water was injected into the intact and broken loop cold legs. This injection technique is similar to that used in several American-made two-loop PWRs

  6. Performance of Engineered Cementitious Composites for Concrete Repairs

    OpenAIRE

    Zhou, J.

    2011-01-01

    Background and goals of this thesis The concrete repair, rehabilitation and retrofitting industry grows rapidly, driven by deterioration of, damage to and defects in concrete structures. However, it is well known that to achieve durable concrete repairs is very difficult. The failure of concrete repairs causes high economical, social and environmental impacts. The main reason of failures is that most repair materials and the repair-substrate interface cannot withstand the high stresses induce...

  7. Electromagnetic Shielding and Absorption Properties of Fiber Reinforced Cementitious Composites

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xiuzhi; SUN Wei

    2012-01-01

    In order to investigate the electromagnetic shielding effectiveness (SE) and absorbing properties of fiber reinforced concrete,steel fiber,carbon fiber and synthetic polyvinyl alcohol (PVA) fiber reinforced concrete were researched.The results show that with the increase of fiber volume fraction,the SE and trend of frequency change of corresponding fiber reinforced concrete are enhanced.When the volume content of steel fiber is 3%,the SE of concrete is above 50 dB and its frequency is above 1.8 GHz.Moreover,in the range of 8-18 GHz,steel fiber,carbon fiber and PVA fiber all can improve the microwave absorption properties of concrete.The concrete with 0.5% carbon fiber can achieve the best absorbing property,the minimum reflectivity is about -7 dB; while steel fiber optimal volume fraction is 2%.The reflectivity curve of PVA fiber reinforced concrete fluctuates with the frequency,and the minimum value of the reflectivity is below -10 dB.The results show that fiber reinforced concrete could be used as EMI(electromagnetic interference) prevention buildings by attenuating and reflecting electromagnetic wave energy.

  8. BREASTFEEDING AND EARLY CHILDHOOD CARIES (ECC SEVERITY OF CHILDREN UNDER THREE YEARS OLD IN DKI JAKARTA

    Directory of Open Access Journals (Sweden)

    Risqa Rina Darwita

    2008-12-01

    Full Text Available The prevalence and severity of caries in children under three years old are constantly increasing. One of the cause is the increase consumption of cariogenic carbohydrate. Breast milk have buffer capacity that eventually able to prevent caries. The aims of this research are to discover the correlation between breastfeeding with the severity of Early Childhood Caries (ECC in children under three years old, to provide information on prevalence and severity of caries in children under three years, and to explain factors influencing the incidence of ECC. This research designed cross sectionally and conducted upon 565 children aged 12-38 months, selected using multistage cluster random sampling. The ECC prevalence of children under three years in DKI Jakarta is 52.7%, with average score of def-t 2.85. Bivariate analysis showed that, variables which correlate with the level of ECC are; the way to deliver (p=0,012, frequency (p=0,002, duration (p=0,002, salivary buffer capacity (p=0.013, habitual consumption of sugary diet (p=0.005, child’s dental hygiene behavior (p=0.002, and mother’s education (p=0.001. Multivariate analysis showed that ECC can be explained by these variables: age, mother’s education, the way to deliver and frequency of breast milk complements/replacement of consumtions, child’s brushing habit, plaque pH, and salivary buffer capacity. Resulting determination coefficient 32.1%. There is no significant correlation between breastfeeding and the level of Early Childhood Caries (ECC. The role of protective qualities of breastfeeding are not shown because of bias in obtaining data influence the incidence of caries.

  9. Advances in microstructural investigation using the REM-ECC-imaging technique; Fortschritte in der Gefuegeuntersuchung mit Hilfe des REM-ECC-Abbildungsverfahrens

    Energy Technology Data Exchange (ETDEWEB)

    Stickler, C.; Melisova, D.; Weiss, B.; Stickler, R. [Vienna Univ. (Austria). Inst. fuer Physikalische Chemie; Mingler, B. [Vienna Univ. (Austria). Inst. fuer Materialphysik

    2001-01-01

    With the improvements made in scanning electron microscopy (SEM) it is now possible, using the electron-channelling-contrast-imaging (ECCI) technique, to image the global arrangement of dislocations in metallic materials. This type of investigation is complementary to imaging by diffraction contrast in the transmission electron microscope (TEM) and in comparison requires less specimen preparation. Using the ECCI-technique, it is possible to examine almost the whole of the electro-polished surface of a solid specimen at magnifications of up to 10,000 times. In addition, using selected-area-channelling-diagrams (SACP), the orientation of areas of the specimen less than 30 {mu}m in diameter can be determined. In doing this, there is no requirement to tilt the specimen, the orientation being related directly to the ECC-image. Following a short description of the SEM-ECC imaging process, its possible uses are illustrated with reference to actual practical examples. (orig.)

  10. TOPFLOW-PTS air-water experiments on the phase separation in the ECC nozzle and the ECC water mixing during PTS scenarios

    International Nuclear Information System (INIS)

    In two-phase Pressurized Thermal Shock scenarios several thermal hydraulic phenomena, such as direct contact condensation, entrainment of steam bubbles and multi-scale momentum transfer are involved. The TOPFLOW-PTS experimental assembly represents a 1:2.5 scaled model of a PWR downcomer, cold leg with emergency core cooling injection and a pump simulator. It is build up for the development and validation of CFD models. The setup is highly instrumented - a large number of thermocouples, an infrared and a high-speed camera as well as wire mesh sensors are used to obtain CFD-grade data. As a first step air-water experiments were done with the special aim to investigate the behaviour of the liquid jet from the ECC injection into the cold leg. They indicated that the jet momentum at the impact position is very important for the mixing process and stratification inside the ECC nozzle needs to be considered in CFD calculations. (author)

  11. ECCS strainer clogging due to corrosion of hot-dip galvanized steel containment internals

    International Nuclear Information System (INIS)

    Damage to fibrous insulation materials located near to a LWR primary circuit coolant leak may compromise the operation of the emergency core cooling system (ECCS), if insulation fibers are transported to the containment sump strainers, where they may block or penetrate the strainers. Beside insulation material, other forms of debris may influence the sump strainer clogging behavior as well as the cooling water chemistry. Especially, the long-term contact of the water jet from the leak with hot-dip galvanized (zinc coated) steel grating treads installed in the containment may cause corrosion of the corresponding materials. Subsequently, the formation of particulate corrosion products may occur by spalling of solid corrosion products from the metallic surfaces or precipitation of solids from the liquid phase. In the event of a LOCA, such processes may lead to an accelerated clogging of the fiber-laden sump strainers. This is especially important in PWRs, where post-LOCA corrosion is accelerated due to the specific primary coolant water chemistry (boric acid, lithium hydroxide). Experimental investigations, performed by AREVA-NP GmbH Erlangen, have shown that corrosion of hot-dip galvanized steel gratings can lead to significant head loss increases across the fiber-laden sump strainers, especially in the presence of boric acid. During several integral tests, steep head loss rises have been observed after approx. 10 hours of exposure to the break flow. Additionally, detailed experimental investigations regarding the influence of corrosion processes on the chemical composition of the coolant as well as on the strainer clogging behavior were established within a research project funded by the BMWi. While previous experiments were focused on the influence of the zinc corrosion on the water chemistry, the priority of the present investigations is given to the mechanisms that cause sump strainer clogging. (orig.)

  12. A pedoprosthetic rehabilitation in patients with severe early childhood caries (S-ECC).

    Science.gov (United States)

    Mishra, Apurva; Pandey, Ramesh; Pandey, Neelisha; Jain, Eesha

    2013-01-01

    Early childhood caries (ECC) is a rapid form of dental caries. ECC is the most common chronic childhood disease that can compromise a child's self-esteem, nutritional intake, oral development and quality of life, subsequently leading to malocclusion and psychological problems. The restoration of severely decayed primary teeth is often a difficult procedure that offers a great challenge to paediatric dentists. The present case series document the clinical management of patients suffering from severe early childhood caries using removable partial prosthesis restoring their masticatory function and aesthestics. The ultimate aim of the treatment was to improve psychological and physiological development leading to better functioning of the stomatognathic system. PMID:23843409

  13. Crypto-processeur ECC en RNS sur FPGA avec inversion modulaire rapide

    OpenAIRE

    Bigou, Karim; Tisserand, Arnaud

    2013-01-01

    Nous développons un crypto-processeur RNS pour ECC sur Fp à la fois très rapide et robuste face à certaines SCA. Dans ce article court, nous décrivons l'utilisation de RNS pour ECC, l'architecture générale de notre crypto-processeur et son implantation sur FPGA. Nous présentons un nouvel algorithme d'inversion modulaire RNS basé sur l'algorithme d'Euclide binaire étendu qui permet une accélération d'un facteur 6.

  14. Influence of Cementitious Materials and Aggregates Content on Compressive Strength of Palm Kernel Shell Concrete

    OpenAIRE

    U.J. Alengaram; Jumaat, M. Z.; H. Mahmud

    2008-01-01

    This study reports the effect of cementitious materials, fine and coarse aggregates content on workability and compressive strength of palm kernel shell concrete. Palm kernel shells a by product of the production of palm oil, were used as lightweight aggregates. The following cementitious materials were added: 10% silica fume as additional cementitious material and 5% fly ash as cement replacement on weight of cement. The influence of varying fine aggregate and palm kernel shell content...

  15. Wet-Treated MSWI Fly Ash Used as Supplementary Cementitious Material

    Directory of Open Access Journals (Sweden)

    Martin Keppert

    2015-01-01

    Full Text Available Municipal solid waste incineration (MSWI is a common technique in treatment of domestic waste. This technique annually produces approximately 25 Mt solid residues (i.e., bottom and fly ash worldwide which is also a major issue in current research. In this research we are concerned with reusing the fly ash (FA as supplementary cementitious material (SCM in concrete. Such application solves the problem with heavy metal immobilization as well. To remove the high content of undesired soluble salts, number of washing treatments has been applied. Chemical composition of FA has been examined before and after treatments. The impact of cement substitution by FA in concrete was evaluated by measurement of its compressive strength and durability.

  16. Talc as raw material for cementitious products formulation

    Directory of Open Access Journals (Sweden)

    C.J. Ngally Sabouang

    2014-09-01

    Full Text Available This study reports the characterization of a talc from Cameroon as a possible source material for cement formulation. To that end, the talc sample was characterized and mixed with a solution of sodium polyphosphate to formulate the cementitious products. Addition of magnesia (MgO was done to analyze the effect of available MgO on the products. Fourier transform infrared, X-rays diffraction, linear shrinkage, compressive strength and scanning electron microscopy were used to analyze the products. The compressive strength increased with addition of MgO and the linear shrinkage decreased. All the analyses indicate that talc is a raw material of interest in cementitious products formulation; however, the inclusion of the MgO is a key factor for a better performance of the products.

  17. Leaching from cementitious waste forms in belowground vaults

    International Nuclear Information System (INIS)

    Solidification and/or stabilization with cementitious materials prior to burial is one option for disposal of liquid hazardous and radioactive wastes. A common design for disposal of cementitious waste forms is to pour the material into large belowground vaults. The leaching performance of partially degraded monolithic vaults is examined quantitatively for facilities located in humid to semiarid climates. Development of perched water on the vault roof leading to fracture flow through the structure is predicted for a wide range of climate and design conditions. Leaching controlled by diffusion in matrix blocks out to fractures is examined parametrically in relation to water flux rate and crack spacing. Depending upon the parameters examined, release rate may be controlled by water flux rate or diffusion. Under some circumstances, contaminant release rates and exit concentrations are predicted to be inversely related. In this situation, minimization of release does not result in the lowest predicted groundwater concentrations below the vault

  18. Self-Healing Efficiency of Cementitious Materials Containing Microcapsules Filled with Healing Adhesive: Mechanical Restoration and Healing Process Monitored by Water Absorption

    OpenAIRE

    Li, Wenting; Jiang, Zhengwu; Yang, Zhenghong; Zhao, Nan; Yuan, Weizhong

    2013-01-01

    Autonomous crack healing of cementitious composite, a construction material that is susceptible to cracking, is of great significance to improve the serviceability and to prolong the longevity of concrete structures. In this study, the St-DVB microcapsules enclosing epoxy resins as the adhesive agent were embedded in cement paste to achieve self-healing capability. The self-healing efficiency was firstly assessed by mechanical restoration of the damaging specimens after being matured. The fle...

  19. Electrochemical migration technique to accelerate ageing of cementitious materials

    OpenAIRE

    Abbas Z.; Tang L; Babaahmadi A.

    2013-01-01

    Durability assessment of concrete structures for constructions in nuclear waste repositories requires long term service life predictions. As deposition of low and intermediate level radioactive waste (LILW) takes up to 100 000 years, it is necessary to analyze the service life of cementitious materials in this time perspective. Using acceleration methods producing aged specimens would decrease the need of extrapolating short term data sets. Laboratory methods are therefore, needed for acceler...

  20. Corrosion of cementitious materials under geological disposal conditions

    International Nuclear Information System (INIS)

    The long-term behavior of cementitious materials in high saline brines has been investigated by means of a time accelerating leaching experiment and by the geochemical modeling. The investigated materials, salt cement and oxychloride cement, were leached with a saturated NaCl solution and an 1P21 solution, likely to occur in salt and potash mines, used in Germany as repositories for radioactive and hazardous chemical wastes. The employed leaching experiment was developed at GRS specifically for boundary conditions of underground repositories. The experimentally observed reaction path was modeled using the computer code EQ3/6 and compared with results of a full-scale experiment in the Asse salt mine. A good agreement between experimental data and the modelling results was obtained. The employed experimental and modelling tools have proved to be suitable for the evaluation of the long-term stability of cementitious materials in repositories in salt formations. Considering the good agreement between the long lasting full-scale in-situ experiment and the time accelerating laboratory scale cascade experiments we conclude, that it is possible to predict the chemical behavior of cementitious materials in salt solutions. The cascade experiment is a fast method, that enables the prediction of the chemical changes in solution during the cement corrosion processes. For the investigated materials in contact to brines a good agreement between the experimental data and the modeling results was obtained. The existing thermodynamic database for the geochemical modeling however is still incomplete. Solubility data and dissolution models for CSH phases are incomplete or missing. The Pitzer coefficients of Si and Al still need to be determined more accurately. However the present state of the geochemical modeling with the existing database allows a valuable insight into the processes taking place along the reaction path in the extremely complex system. The employed experimental and

  1. Cementitious artificial aggregate particles for high-skid resistance pavements

    OpenAIRE

    De Larrard, François; MARTINEZ CASTILLO, Rafael; Sedran, Thierry; HAUZA, Philippe; Poirier, Jean Eric

    2012-01-01

    For some critical road sections, a high skid resistance of wearing course is required to minimise the risk of traffic accidents. Nowadays this skid resistance is mainly brought by the use of special aggregates as calcined bauxite, a scarce and expensive material. The paper presents a patented technology, where a special high-performance mortar is produced and crushed at early age. These cementitious artificial aggregates (CAA) can display aggregate properties close to those of calcined bauxit...

  2. Atmospheric carbonation of low portlandite content cementitious materials

    OpenAIRE

    Morandeau, Antoine

    2013-01-01

    Reaction of gaseous atmospheric CO2 with calcium-bearing phases in concrete infrastructure components is known to cause a lowering of alkalinity, leading to depassivation and corrosion of rebars. Carbonation mechanism is quite well understood from a physico-chemical point of view, especially in the case of materials made of OPC. Nonetheless the impact of supplementary cementitious materials (SCM), such as fly-ash, on carbonation is still an active research field. The pozzolanic reaction betwe...

  3. Computer Modeling of Leaching of Heavy Metal from Cementitious Waste

    OpenAIRE

    Peng Hu; Wei Dai

    2013-01-01

    Thermodynamic equilibrium model was used to simulate the results of leaching heavy metal from cementitious wastes. Modeling results of the leached major element concentrations for samples agreed well with the leaching test using the set of pure minerals and solid solutions present in the database. The model revealed Pb and Cd were predominantly incorporated within the calcium silicate hydrate matrix while a greater portion of Cd exist as discrete particles in the cement pores. Precipitation w...

  4. Mechanical properties of structures 3D printed with cementitious powders

    OpenAIRE

    Feng, Peng; Meng, Xinmiao; Chen, Jian Fei; Ye, Lieping

    2015-01-01

    The three dimensional (3D) printing technology has undergone rapid development in the last few years and it is now possible to print engineering structures. This paper presents a study of the mechanical behavior of 3D printed structures using cementitious powder. Microscopic observation reveals that the 3D printed products have a layered orthotropic microstructure, in which each layer consists of parallel strips. Compression and flexural tests were conducted to determine the mechanical proper...

  5. Rheology and Reactivity of Cementitious Binders with Plasticizers

    OpenAIRE

    Vikan, Hedda Vestøl

    2005-01-01

    The rheological behaviour of cementitious pastes has been studied by various means. Six different cements have been studied in main parts of the work and all of them have been characterized according to the Rietveld method in order to determine the exact content of minerals. Easily soluble alkalis were measured by plasma-emission- spectroscopy of the fluid filtered from paste. Three types of plasticizers namely naphthalene sulfonate formaldehyde condensate (SNF), lignosulphonate and polyacryl...

  6. Magnetic properties of soft layer/FePt-MgO exchange coupled composite Perpendicular recording media

    Institute of Scientific and Technical Information of China (English)

    Yin Jin-Hua; Takao Suzuki; Pan Li-Qing

    2008-01-01

    The magnetic properties of exchange coupled composite(ECC)media that are composed of perpendicular magnetic recording media FePt-MgO and two kinds of soft layers have been studied by using an x-ray diffractometer,a polar Kerr magneto-optical system(PMOKE)and a vibrating sample magnetometer(VSM).The results show that ECC media can reduce the coercivities of perpendicular magnetic recording media FePt-MgO.The ECC media with granular-type soft layers have weaker exchange couplings between magnetic grains and the magnetization process,for ECC media of this kind mainly follow the Stoner-Wohlfarth model.

  7. Electrochemical migration technique to accelerate ageing of cementitious materials

    International Nuclear Information System (INIS)

    Durability assessment of concrete structures for constructions in nuclear waste repositories requires long term service life predictions. As deposition of low and intermediate level radioactive waste (LILW) takes up to 100 000 years, it is necessary to analyze the service life of cementitious materials in this time perspective. Using acceleration methods producing aged specimens would decrease the need of extrapolating short term data sets. Laboratory methods are therefore, needed for accelerating the ageing process without making any influencing distortion in the properties of the materials. This paper presents an electro-chemical migration method to increase the rate of calcium leaching from cementitious specimens. This method is developed based on the fact that major long term deterioration process of hardened cement paste in concrete structures for deposition of LILW is due to slow diffusion of calcium ions. In this method the cementitious specimen is placed in an electrochemical cell as a porous path way through which ions can migrate at a rate far higher than diffusion process. The electrical field is applied to the cell in a way to accelerate the ion migration without making destructions in the specimen's micro and macroscopic properties. The anolyte and catholyte solutions are designed favoring dissolution of calcium hydroxide and compensating for the leached calcium ions with another ion like lithium. (authors)

  8. Electrochemical migration technique to accelerate ageing of cementitious materials

    Science.gov (United States)

    Babaahmadi, A.; Tang, L.; Abbas, Z.

    2013-07-01

    Durability assessment of concrete structures for constructions in nuclear waste repositories requires long term service life predictions. As deposition of low and intermediate level radioactive waste (LILW) takes up to 100 000 years, it is necessary to analyze the service life of cementitious materials in this time perspective. Using acceleration methods producing aged specimens would decrease the need of extrapolating short term data sets. Laboratory methods are therefore, needed for accelerating the ageing process without making any influencing distortion in the properties of the materials. This paper presents an electro-chemical migration method to increase the rate of calcium leaching from cementitious specimens. This method is developed based on the fact that major long term deterioration process of hardened cement paste in concrete structures for deposition of LILW is due to slow diffusion of calcium ions. In this method the cementitious specimen is placed in an electrochemical cell as a porous path way through which ions can migrate at a rate far higher than diffusion process. The electrical field is applied to the cell in a way to accelerate the ion migration without making destructions in the specimen's micro and macroscopic properties. The anolyte and catholyte solutions are designed favoring dissolution of calcium hydroxide and compensating for the leached calcium ions with another ion like lithium.

  9. Electrochemical migration technique to accelerate ageing of cementitious materials

    Directory of Open Access Journals (Sweden)

    Abbas Z.

    2013-07-01

    Full Text Available Durability assessment of concrete structures for constructions in nuclear waste repositories requires long term service life predictions. As deposition of low and intermediate level radioactive waste (LILW takes up to 100 000 years, it is necessary to analyze the service life of cementitious materials in this time perspective. Using acceleration methods producing aged specimens would decrease the need of extrapolating short term data sets. Laboratory methods are therefore, needed for accelerating the ageing process without making any influencing distortion in the properties of the materials. This paper presents an electro-chemical migration method to increase the rate of calcium leaching from cementitious specimens. This method is developed based on the fact that major long term deterioration process of hardened cement paste in concrete structures for deposition of LILW is due to slow diffusion of calcium ions. In this method the cementitious specimen is placed in an electrochemical cell as a porous path way through which ions can migrate at a rate far higher than diffusion process. The electrical field is applied to the cell in a way to accelerate the ion migration without making destructions in the specimen’s micro and macroscopic properties. The anolyte and catholyte solutions are designed favoring dissolution of calcium hydroxide and compensating for the leached calcium ions with another ion like lithium.

  10. Mechanical properties of gangue-containing aluminosilicate based cementitious materials

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    High performance aluminosilicate based cementitious materials were produced using calcined gangue as one of the major raw materials.The gangue was calcined at 500℃.The main constituent was calcined gangue, fly ash and slag, while alkali-silicate solutions were used as the diagenetic agent.The structure of gangue-containing aluminosilicate based cementitious materials was studied by the methods of IR, NMR and SEM.The results show that the mechanical properties are affected by the mass ratio between the gangue, slag and fly ash, the kind of activator and additional salt.For 28-day curing time, the compressive strength of the sample with a mass proportion of 2:1:1 (gangue: slag: fly ash) is 58.9 MPa, while the compressive strength of the sample containing 80wt%gangue can still be up to 52.3 MPa.The larger K+ favors the formation of large silicate oligomers with which Al(OH)4- prefers to bind.Therefore, in Na-K compounding activator solutions more oligomers exist which result in a stronger compressive strength of aluminosilicate-based cementitious materials than in the case of Na-containing activator.The reasons for this were found through IR and NMR analysis.Glauber's salt reduces the 3-day compressive strength of the paste, but increases its 7-day and 28-day compressive strengths.

  11. The Sequence Modeling Method Based on ECC in Developing Program Specifications

    Institute of Scientific and Technical Information of China (English)

    CAI Jiamei

    1999-01-01

    This article discusses the developing process of theversion sequences of specifications and the formal expressions ofvarious reconstructions including the expansion and revision of theversion at each stage. The author suggests using ECC (Extended Calculusof Construction) to describe the specifications of formal system andusing functional language ML to implement this developing process.

  12. Preparation and evaluation of 68Ga-ECC as a PET renal imaging agent

    International Nuclear Information System (INIS)

    Development of a gallium-68-labeled renal tracer can be a good substitute for Tc-99m, a known SPECT tracer. In this study, effort was made to develop 68Ga-ethylenecysteamine cysteine (68Ga-ECC). Ga-ECC was prepared using generator-based 68GaCl3 and ethylenecysteamine cysteine (ECC) at optimized conditions. Stability of the complex was checked in human serum followed by partition coefficient determination of the tracer. The biodistribution of the tracer in rats was studied using tissue counting and PET/CT imaging up to 120 min. Ga-ECC was prepared at optimized conditions in 15 min at 90 °C (radiochemical purity ≈97 ± 0.88 % ITLC, >99 % HPLC, specific activity: 210 ± 5 GBq/mM). 68Ga-ECC was a water-soluble complex based on partition coefficient data (log P; −1.378) and was stable in the presence of human serum for 2 h at 37 °C. The biodistribution of the tracer demonstrated high kidney excretion of the tracer in 10–20 min. The SUVmax ratios of the liver to left kidney were 0.38 and 0.39 for 30 and 90 min, respectively, indicating high kidney uptake. Initial biodistribution results showed significant kidney and urinary excretion of the tracer comparable to that of the homologous 99mTc compound. The complex could be a possible PET kidney imaging agent with a fast imaging time

  13. Preparation and evaluation of {sup 68}Ga-ECC as a PET renal imaging agent

    Energy Technology Data Exchange (ETDEWEB)

    Mizaei, Alireza; Jaililan, Amir Reza; Mazidi, Mohammad; Aghanejad, Ayuob; Yousefnia, Hassan; Shabani, Gholamli; Ardaneh, Khosro [Radiation Application Research School, Nuclear Science and Technology Research Institute, Tehran (Iran, Islamic Republic of); Geramifar, Patham; Beiki, Davood [Research Center for Nuclear Medicine, Shariati Hospital, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of)

    2015-09-15

    Development of a gallium-68-labeled renal tracer can be a good substitute for Tc-99m, a known SPECT tracer. In this study, effort was made to develop {sup 68}Ga-ethylenecysteamine cysteine ({sup 68}Ga-ECC). Ga-ECC was prepared using generator-based {sup 68}GaCl3 and ethylenecysteamine cysteine (ECC) at optimized conditions. Stability of the complex was checked in human serum followed by partition coefficient determination of the tracer. The biodistribution of the tracer in rats was studied using tissue counting and PET/CT imaging up to 120 min. Ga-ECC was prepared at optimized conditions in 15 min at 90 °C (radiochemical purity ≈97 ± 0.88 % ITLC, >99 % HPLC, specific activity: 210 ± 5 GBq/mM). {sup 68}Ga-ECC was a water-soluble complex based on partition coefficient data (log P; −1.378) and was stable in the presence of human serum for 2 h at 37 °C. The biodistribution of the tracer demonstrated high kidney excretion of the tracer in 10–20 min. The SUV{sub max} ratios of the liver to left kidney were 0.38 and 0.39 for 30 and 90 min, respectively, indicating high kidney uptake. Initial biodistribution results showed significant kidney and urinary excretion of the tracer comparable to that of the homologous {sup 99m}Tc compound. The complex could be a possible PET kidney imaging agent with a fast imaging time.

  14. Experimental study on long-term stability of bentonite. Influence of hyperalkaline pore water generated by the chemical reaction of cementitious material and saline groundwater

    International Nuclear Information System (INIS)

    The engineered barrier system (EBS) in the geological disposal of TRU waste is composed of bentonite and cementitious materials. The montmorillonite component of bentonite is, however, not chemically compatible with the high pH leachates derived from cementitious materials and may alter to a more stable secondary mineral assemblage. Previous research for TRU waste disposal has focused on the alteration behavior of bentonite in leachates from cementitious materials exposed to fresh groundwater. If the EBS is located in the coastal region, then the leachates will instead be derived from the interaction of cementitious materials and saline groundwater. This has important implications for the alteration of bentonite because the likely difference in the chemical composition of the leachate will influence the dissolution rate of montmorillonite and the composition of the secondary mineral assemblage. At present, these processes are not well understood. The focus of the present study was to examine the alteration of bentonite in high pH saline groundwaters. Two solutions were used in batch immersion experiments of bentonite. The first solution was prepared using a mixture of NaOH and NaCl (NN), and the second solution was prepared using synthetic Region 1 water (high K and Na content) and synthetic seawater (SR). Analysis showed that bentonite altered to analcime in the NN solution and to analcime and phillipsite-K in the SR solution. Moreover, the generation of calcium silicate hydrate and calcium aluminosilicate hydrate were extrapolated in the SR solution based on the concentrations of dissolved species. These alteration products were in accord with Oda et al.(2005), who summarized the possible relationships between the secondary mineral assemblage of bentonite under high pH conditions and the influence of solution composition. (author)

  15. Microbiological activities in a shallow-ground repository with cementitious wasteform

    International Nuclear Information System (INIS)

    Cementitious wasteform with immobilised nuclear power plant operational radioactive waste disposed in a near surface testing repository for about 20 years have been analysed for microbiological activities. Clean cultures were selected from the main metabolic groups expected within repository environment e.g. anaerobic de-nitrifying, fermenting, sulphur-reducing, iron-reducing, and oxidizing, thio-bacterium and mushrooms. Microbiological species were identified within cementitious wasteform, in the clayey soil near the wasteform and in the contacting water. The most populated medium was the soil with microbial populations Bacillus, Pseudomonas and Micrococcus, and densities of populations up to 3.6*105 colony/g. Microbial populations of generic type Bacillus, Pseudomonas, Rhodococcus, Alcaligenes, Micrococcus, Mycobacterium, and Arthrobacter were identified within cementitious wasteform. Populations of Arthrobacter, Pseudomonas, Alcaligenes, Rhodococcus, Bacillus and Flavobacterium were identified in the water samples contacting the cementitious wasteform. Microbiological species identified are potential destructors of cementitious wasteform and containers. (authors)

  16. CEMENTITIOUS BARRIERS PARTNERSHIP FY13 MID-YEAR REPORT

    Energy Technology Data Exchange (ETDEWEB)

    Burns, H.; Flach, G.; Langton, C.; KOSSON, D.; BROWN, K.; SAMSON, E.; MEEUSSEN, J.; SLOOT, H.; GARBOCZI, E.

    2013-05-01

    In FY2013, the Cementitious Barriers Partnership (CBP) is continuing in its effort to develop and enhance software tools demonstrating tangible progress toward fulfilling the objective of developing a set of tools to improve understanding and prediction of the long‐term structural, hydraulic and chemical performance of cementitious barriers used in nuclear applications. In FY2012, the CBP released the initial inhouse “Beta‐version” of the CBP Software Toolbox, a suite of software for simulating reactive transport in cementitious materials and important degradation phenomena. The current primary software components are LeachXS/ORCHESTRA, STADIUM, and a GoldSim interface for probabilistic analysis of selected degradation scenarios. THAMES is a planned future CBP Toolbox component (FY13/14) focused on simulation of the microstructure of cementitious materials and calculation of resultant hydraulic and constituent mass transfer parameters needed in modeling. This past November, the CBP Software Toolbox Version 1.0 was released that supports analysis of external sulfate attack (including damage mechanics), carbonation, and primary constituent leaching. The LeachXS component embodies an extensive material property measurements database along with chemical speciation and reactive mass transport simulation cases with emphasis on leaching of major, trace and radionuclide constituents from cementitious materials used in DOE facilities, such as Saltstone (Savannah River) and Cast Stone (Hanford), tank closure grouts, and barrier concretes. STADIUM focuses on the physical and structural service life of materials and components based on chemical speciation and reactive mass transport of major cement constituents and aggressive species (e.g., chloride, sulfate, etc.). The CBP issued numerous reports and other documentation that accompanied the “Version 1.0” release including a CBP Software Toolbox User Guide and Installation Guide. These documents, as well as, the

  17. Engineering Properties and Correlation Analysis of Fiber Cementitious Materials

    OpenAIRE

    Wei-Ting Lin; Yuan-Chieh Wu; An Cheng; Sao-Jeng Chao; Hui-Mi Hsu

    2014-01-01

    This study focuses on the effect of the amount of silica fume addition and volume fraction of steel fiber on the engineering properties of cementitious materials. Test variables include dosage of silica fume (5% and 10%), water/cement ratio (0.35 and 0.55) and steel fiber dosage (0.5%, 1.0% and 2.0%). The experimental results included: compressive strength, direct tensile strength, splitting tensile strength, surface abrasion and drop-weight test, which were collected to carry out the analysi...

  18. Impact of carbonation on water transport properties of cementitious materials

    International Nuclear Information System (INIS)

    Carbonation is a very well-known cementitious materials pathology. It is the major cause of reinforced concrete structures degradation. It leads to rebar corrosion and consequent concrete cover cracking. In the framework of radioactive waste management, cement-based materials used as building materials for structures or containers would be simultaneously submitted to drying and atmospheric carbonation. Although scientific literature regarding carbonating is vast, it is clearly lacking information about the influence of carbonation on water transport properties. This work then aimed at studying and understanding the change in water transport properties induced by carbonation. Simultaneously, the representativeness of accelerated carbonation (in the laboratory) was also studied. (author)

  19. Modelling for the mechanical behavior of cementitious granular materials

    Science.gov (United States)

    Zhong, Xiaoxiong

    Crack damages due to load application are commonly observed in cementitious granular materials such as concrete, cemented sand, and ceramic materials. Previous analytical models for these types of materials have been developed based on continuum mechanics using a phenomenological approach. However, the theories of continuum mechanics have limitations when used for analyzing fracture mechanism and localized damages at a micro-scale level. Therefore, a microstructural approach is desirable for the analysis of these types of materials. In this dissertation, a contact law was derived for the inter-particle behavior of two particles connected by a cement binder. Microcracking process within binder was fully taken into account by regarding crack length as a basic damage factor. The binder initially contains small-size cracks which propagate and grow under external loading. As a result the binder is weakened with lower strength in shear and tension. Theory of fracture mechanics was employed to model the propagation and growth of these microcracks for both the shear fracture mode and normal fracture mode. The contact law was then incorporated in the analysis for the overall damage behaviors of cementitious granular material using the statistical micromechanics approach and the distinct element method. These overall damage behaviors include the stress-strain relationship, fracture strength, development of damage zone, and fatigue deformation. The micro-parameters affecting these behaviors are mainly the microcrack length and density, binder toughness, and binder elastic constants. In the numerical simulations, the cementitious granular materials were represented by 2-D random assemblies of rods bonded by cement binders with preexisting microcracks. Stress-strain relationships were modeled and validated for the uniaxial tension and compression tests, biaxial tension and compression tests, and double cantilever beam test. Force-deflection relationship and fatigue deformation

  20. Scaling and design report of ECC performance test facility (SWAT) of SMART

    International Nuclear Information System (INIS)

    SWAT (SMART ECC Water Asymmetric Two-phase choking test facility) was designed by 1/5 scaling ratio using the modified linear scaling method. The design characteristics of the SMART such that the elevation of RCP suction nozzles is the same with that of the ECC injection nozzles are maintained to reduce a distortion caused by the gravitational effect. Thermal hydraulic phenomena in a test facility designed by the modified linear scaling method can be simulated more accurately than those by the full-height and reduced area scaling method. The main part of the test section is SG-side upper down-comer. The boundary conditions are saturated steam and water flow condition and drain flow rate to control the collapsed water level in the down-comer. The test data of the SWAT can produce the well-defined boundary condition to validate the thermal hydraulic analysis code for the SMART

  1. Dynamics of electron-capture-to-continuum (ECC) formation in slow ion-atom collisions

    Energy Technology Data Exchange (ETDEWEB)

    Afaneh, F [Physics Department, The Hashemite University, PO Box 150459, Zarqa 13115 (Jordan); Schmidt, L Ph H [Institut fuer Kernphysik, Max-von-Laue-Str. 1, 60438 Frankfurt (Germany); Schoeffler, M [Institut fuer Kernphysik, Max-von-Laue-Str. 1, 60438 Frankfurt (Germany); Stiebing, K E [Institut fuer Kernphysik, Max-von-Laue-Str. 1, 60438 Frankfurt (Germany); Al-Jundi, J [Physics Department, The Hashemite University, PO Box 150459, Zarqa 13115 (Jordan); Schmidt-Boecking, H [Institut fuer Kernphysik, Max-von-Laue-Str. 1, 60438 Frankfurt (Germany); Doerner, R [Institut fuer Kernphysik, Max-von-Laue-Str. 1, 60438 Frankfurt (Germany)

    2007-05-28

    The zero-degree ejected-electron spectrum for protons incident on He at 25 keV is examined experimentally using the COLTRIMS technique. The momentum distribution of the emitted electrons for the transfer ionization (TI) reaction channel is measured in coincidence with the momentum vectors of the recoil ion and the scattered projectile. The momentum distribution of the electrons emitted around zero degree in the forward direction for the TI reaction channel shows two prominent structures: the electron-capture-to-the-continuum (ECC) peak and the saddle-point peak. From the measured fully differential electron emission cross sections with respect to the scattering plane we can deduce that the main ECC formation mechanism is electron promotion via quasimolecular orbitals.

  2. Study on Secret Key Management Project of WSN Based on ECC

    Directory of Open Access Journals (Sweden)

    Ming Lu

    2012-04-01

    Full Text Available In order to solve the symmetrical encryption method of key management project for Wireless Sensor Network (WSN existing the deficiencies problem, the problem as follows: the WSN is not secure enough; there is no authentication mechanism among nodes. According to this circumstance, firstly elliptic curve cryptosystem (ECC is used in this paper, and then it makes analysis of the principle of TinyOS. The calculation speed of elliptic curve has been improved based on optimal extended field by selecting suitable big prime number and other ways. We proposed a key management scheme for WSN based on ECC and clustering. At last, we make simulation with TinyOS. The simulation shows that proposed scheme is more secure, including forth security and back security, stronger Anti-DDos capacity and supporting dynamic structure of WSN comparing other traditional schemes. Furthermore, the computational complexity and energy cost of proposed scheme are feasible.

  3. BREASTFEEDING AND EARLY CHILDHOOD CARIES (ECC) SEVERITY OF CHILDREN UNDER THREE YEARS OLD IN DKI JAKARTA

    OpenAIRE

    Risqa Rina Darwita; Herwati Djoharnas; Febriana Setiawati Sugito

    2008-01-01

    The prevalence and severity of caries in children under three years old are constantly increasing. One of the cause is the increase consumption of cariogenic carbohydrate. Breast milk have buffer capacity that eventually able to prevent caries. The aims of this research are to discover the correlation between breastfeeding with the severity of Early Childhood Caries (ECC) in children under three years old, to provide information on prevalence and severity of caries in children under three yea...

  4. Interference of sulphur dioxide to balloon-borne ECC ozone sensors over the Valley of Mexico

    OpenAIRE

    I. Kanda; Basaldud, R.; Horikoshi, N.; Okazaki, Y.; S. E. Benítez Garcia; Ortínez, A.; Ramos Benítez, V. R.; B. Cárdenas; Wakamatsu, S.

    2014-01-01

    Abnormal decrease in the ozonesonde sensor signal occurred during air-pollution study campaigns in November 2011 and March 2012 in Mexico City. Sharp drops around 5 km a.s.l. and above were observed in November 2011, and a broad deficit in the convective boundary layer in March 2012. Various circumstantial evidence indicates that the decrease was due to interference of SO2 gas to Electrochemical Concentration Cell (ECC) ozone sensors. The sharp drops in ...

  5. Caregiver knowledge and attitudes of preschool oral health and early childhood caries (ECC)

    OpenAIRE

    Schroth, Robert J; Brothwell, Douglas J.; Moffatt, Michael E. K.

    2007-01-01

    OBJECTIVES: Prevention strategies are integral to improving the oral health for young Aboriginal children. For such to be effective, it is important to understand the social value that parents and caregivers ascribe to primary teeth. The purpose of this paper is to report caregiver knowledge and attitudes toward preschool oral health and early childhood caries (ECC) from 4 communities in Manitoba. STUDY DESIGN: Cross-sectional study, including a retrospective interview with caregivers. METH...

  6. A Privacy-Preserving Grouping Proof Protocol Based on ECC with Untraceability for RFID

    OpenAIRE

    Henry Ker-Chang Chang; Erl-Huei Lu; Shin-Yan Chiou; Wen-Tsai Ko

    2012-01-01

    An RFID (Radio-Frequency IDentification) system provides the mechanism to identify tags to readers and then to execute specific RFID-enabled applications. In those applications, secure protocols using lightweight cryptography need to be developed and the privacy of tags must be ensured. In 2010, Batina et al. proposed a privacy-preserving grouping proof protocol for RFID based on ECC (Elliptic Curve Cryptography) in public-key cryptosystem. In the next year, Lv et al. had shown that Batina et...

  7. Reconstruction of the Emergency Core Cooling System (ECCS), Confinement Spray System (SSK) and Pressurizer Safety Valves and Relief Line (PVKO)

    International Nuclear Information System (INIS)

    The paper deals with the results of reconstruction of the ECCS, SSK, and PVKO systems as implemented during the Gradual Upgrading with safety upgrading of the Bohunice V1 nuclear power plant 1997 to 2000. (author)

  8. Direct ECC bypass phenomena in the MIDAS test facility during LBLOCA reflood phase

    International Nuclear Information System (INIS)

    As one of the advanced design features of the APR1400, Direct Vessel Injection(DVI) system is being considered instead of conventional Cold Leg Injection(CLI) system. It is known that the DVI system greatly enhances the reliability of the Emergency Core Cooling (ECC) system. However, there is still a dispute on its performance in terms of water delivery to the reactor core during the reflood phase of a large-break Loss-Of-Coolant Accident (LOCA). Thus, experimental validation is under progress. In this paper, test results of direct ECC bypass performed in the steam-water test facility called MIDAS (Multi-dimensional Investigation in Downcomer Annulus Simulation) are presented. The test condition is determined, based on the preliminary analysis of TRAC code, by applying the 'modified linear scaling method' with the 1/4.93 length scale. From the tests, ECC direct bypass fraction, steam condensation rate and information on the flow distribution in the upper annulus downcomer region are obtained

  9. Direct ECC Bypass Phenomena During LBLOCA Reflood Phase Observed in the MIDAS Test: Facility

    International Nuclear Information System (INIS)

    One of the advanced design features of the APR-1400, direct vessel injection (DVI) system is being considered instead of conventional cold leg injection (CLI) system. It is known that the DVI system greatly enhances the reliability of the emergency core cooling (ECC) system. However, there is still a dispute on its performance in terms of water delivery to the reactor core during the reflood phase of a large-break loss-of-coolant accident (LOCA). Thus, experimental validation is in progress. In this paper, test results of a direct ECC bypass performed in the steam-water test facility called MIDAS (Multi-dimensional Investigation in Downcomer Annulus Simulation) is presented. The test condition is determined, based on the preliminary analysis of TRAC code, by applying the 'modified linear scaling method' with the 1/4.93 length scale. From the tests, ECC direct bypass fraction, steam condensation rate and information on the flow distribution in the upper annulus downcomer region is obtained. (authors)

  10. Direct ECC bypass phenomena in the MIDAS test facility during LBLOCA reflood phase

    Energy Technology Data Exchange (ETDEWEB)

    Yun, B. J.; Kwon, T. S.; Euh, D. J.; Chu, I. C.; Park, W. M.; Song, C. H.; Park, J. K. [KAERI, Taejon (Korea, Republic of)

    2002-10-01

    As one of the advanced design features of the APR1400, Direct Vessel Injection(DVI) system is being considered instead of conventional Cold Leg Injection(CLI) system. It is known that the DVI system greatly enhances the reliability of the Emergency Core Cooling (ECC) system. However, there is still a dispute on its performance in terms of water delivery to the reactor core during the reflood phase of a large-break Loss-Of-Coolant Accident (LOCA). Thus, experimental validation is under progress. In this paper, test results of direct ECC bypass performed in the steam-water test facility called MIDAS (Multi-dimensional Investigation in Downcomer Annulus Simulation) are presented. The test condition is determined, based on the preliminary analysis of TRAC code, by applying the 'modified linear scaling method' with the 1/4.93 length scale. From the tests, ECC direct bypass fraction, steam condensation rate and information on the flow distribution in the upper annulus downcomer region are obtained.

  11. Evaluation of ECC bypass data with a nonlinear constrained MLE technique

    International Nuclear Information System (INIS)

    Recently, Battelle's Columbus Laboratories have been involved in scale-model tests of emergency core cooling (ECC) systems for hypothesized loss-of-coolant accidents in pressurized water reactors (PWR). These tests are intended to increase our understanding of ECC bypass, which can occur when steam flow from the reactor core causes the emergency coolant to bypass the core and flow directly to the break. One objective of these experiments is the development of a correlation which relates the flow rate of water penetrating to the core to the steam flow rate. This correlation is derived from data obtained from a 2/15 scale model PWR at various ECC water injection rates, subcoolings, pressures, and steam flows. The general form of the correlation being studied is a modification of the correlation first proposed by Wallis. The correlation model is inherently nonlinear and implicit in form, and the model variables are all subject to error. Therefore, the usual nonlinear analysis techniques are inappropriate. A nonlinear constrained maximum-likelihood-estimation technique has been used to obtain estimates of the model parameters, and a Battelle-developed code, NLINMLE, has been used to analyze the data. The application of this technique is illustrated by sample calculations of estimates of the model parameters and their associated confidence intervals for selected experimental data sets. 5 figures, 7 tables

  12. A Secure-Enhanced Data Aggregation Based on ECC in Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Qiang Zhou

    2014-04-01

    Full Text Available Data aggregation is an important technique for reducing the energy consumption of sensor nodes in wireless sensor networks (WSNs. However, compromised aggregators may forge false values as the aggregated results of their child nodes in order to conduct stealthy attacks or steal other nodes’ privacy. This paper proposes a Secure-Enhanced Data Aggregation based on Elliptic Curve Cryptography (SEDA-ECC. The design of SEDA-ECC is based on the principles of privacy homomorphic encryption (PH and divide-and-conquer. An aggregation tree disjoint method is first adopted to divide the tree into three subtrees of similar sizes, and a PH-based aggregation is performed in each subtree to generate an aggregated subtree result. Then the forged result can be identified by the base station (BS by comparing the aggregated count value. Finally, the aggregated result can be calculated by the BS according to the remaining results that have not been forged. Extensive analysis and simulations show that SEDA-ECC can achieve the highest security level on the aggregated result with appropriate energy consumption compared with other asymmetric schemes.

  13. Quorum sensing in the plant pathogen Erwinia carotovora subsp. carotovora: the role of expR(Ecc).

    Science.gov (United States)

    Andersson, R A; Eriksson, A R; Heikinheimo, R; Mäe, A; Pirhonen, M; Kõiv, V; Hyytiäinen, H; Tuikkala, A; Palva, E T

    2000-04-01

    The production of the main virulence determinants of the plant pathogen Erwinia carotovora subsp. carotovora, the extracellular cell wall-degrading enzymes, is partly controlled by the diffusible signal molecule N-(3-oxohexanoyl)-L-homoserine lactone (OHHL). OHHL is synthesized by the product of the expI/carI gene. Linked to expI we found a gene encoding a putative transcriptional regulator of the LuxR-family. This gene, expR(Ecc), is transcribed convergently to the expI gene and the two open reading frames are partially overlapping. The ExpR(Ecc) protein showed extensive amino acid sequence similarity to the repressor EsaR from Pantoea stewartii subsp. stewartii (formerly Erwinia stewartii subsp. stewartii) and to the ExpR(Ech) protein of Erwinia chrysanthemi. Inactivation of the E. carotovora subsp. carotovora expR(Ecc) gene caused no decrease in virulence or production of virulence determinants in vitro. In contrast, there was a slight increase in the maceration capacity of the mutant strain. The effects of ExpR(Ecc) were probably mediated by changes in OHHL levels. Inactivation of expR(Ecc) resulted in increased OHHL levels during early logarithmic growth. In addition, overexpression of expR(Ecc) caused a clear decrease in the production of virulence determinants and part of this effect was likely to be caused by OHHL binding to ExpR(Ecc). ExpR(Ecc) did not appear to exhibit transcriptional regulation of expI, but the effect on OHHL was apparently due to other mechanisms. PMID:10755301

  14. Interaction of low pH cementitious concretes with groundwaters

    International Nuclear Information System (INIS)

    Some engineering construction concepts for high level radioactive waste underground repositories consider the use of a bentonite barrier in contact with cementitious materials with a pore fluid pH value inferior or equal to 11 (based on low-pH cements) to maintain the bentonite stability. The research on low-pH cementitious materials is mainly addressed from two different approaches, one with Calcium Silicate Cements (OPC, Ordinary Portland Cement based), the other with Calcium Aluminates Cements (CAC based). The use of these both types of cements (OPC based or CAC based) implies the use of high mineral additions contents in the binder that should significantly modify most of the concrete 'standard' properties. Taking into account the long life expected in this type of repositories, parameters related to the durability of the low-pH concretes must be analyzed. This work shows some recent studies that deal with the evaluation of the resistance of low-pH concretes to long term groundwater aggression. After a presentation of the accelerated leaching test (based on a percolation method), results are given for the characterization of the leaching solution evolution and the evaluation of the modifications generated in the solid phases. Results show that the low-pH concretes evaluated have good resistance against groundwater interaction, although an altered front can be observed from the surface in all the tested samples

  15. Engineering Properties and Correlation Analysis of Fiber Cementitious Materials

    Directory of Open Access Journals (Sweden)

    Wei-Ting Lin

    2014-11-01

    Full Text Available This study focuses on the effect of the amount of silica fume addition and volume fraction of steel fiber on the engineering properties of cementitious materials. Test variables include dosage of silica fume (5% and 10%, water/cement ratio (0.35 and 0.55 and steel fiber dosage (0.5%, 1.0% and 2.0%. The experimental results included: compressive strength, direct tensile strength, splitting tensile strength, surface abrasion and drop-weight test, which were collected to carry out the analysis of variance to realize the relevancy and significance between material parameters and those mechanical properties. Test results illustrate that the splitting tensile strength, direct tensile strength, strain capacity and ability of crack-arresting increase with increasing steel fiber and silica fume dosages, as well as the optimum mixture of the fiber cementitious materials is 5% replacement silica fume and 2% fiber dosage. In addition, the Pearson correlation coefficient was conducted to evaluate the influence of the material variables and corresponds to the experiment result.

  16. Technetium Sorption By Cementitious Materials Under Reducing Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Kaplan, Daniel I. [Savannah River National Lab., Aiken, SC (United States); Estes, Shanna L. [Clemson Univ., SC (United States). Environmental Engineering and Earth Sciences; Arai, Yuji [Clemson Univ., SC (United States). College of Agriculture, Forestry and Life Sciences; Powell, Brian A. [Clemson Univ., SC (United States). Environmental Engineering and Earth Sciences

    2013-07-18

    The objective of this study was to measure Tc sorption to cementitious materials under reducing conditions to simulate Saltstone Disposal Facility conditions. Earlier studies were conducted and the experimental conditions were found not to simulate those of the facility. Through a five month subcontract with Clemson University, sorption of {sup 99}Tc to four cementitious materials was examined within an anaerobic glovebag targeting a 0.1% H{sub 2}(g)/ 99.9% N{sub 2}(g) atmosphere. Early experiments based on Tc sorption and Eh indicated that 0.1% H{sub 2}(g) (a reductant) was necessary to preclude experimental impacts from O{sub 2}(g) diffusion into the glovebag. Preliminary data to date (up to 56 days) indicates that sorption of {sup 99}Tc to cementitious materials increased with increasing slag content for simulated saltstone samples. This is consistent with the conceptual model that redox active sulfide groups within the reducing slag facilitate reduction of Tc(VII) to Tc(IV). These experiments differ from previous experiments where a 2% H{sub 2}(g) atmosphere was maintained (Kaplan et al., 2011 (SRNL-STI-2010-00668)). The impact of the 2% H{sub 2}(g) reducing atmosphere on this data was examined and determined to cause the reduction of Tc in experimental samples without slag. In the present ongoing study, after 56 days, Tc sorption by the 50-year old cement samples (no slag) was undetectable, whereas Tc sorption in the cementitious materials containing slag continues to increase with contact time (measured after 1, 4, 8, 19 and 56 days). Sorption was not consistent with spike concentrations and steady state has not been demonstrated after 56 days. The average conditional K{sub d} value for the Vault 2 cementitious material was 873 mL/g (17% slag), for the TR547 Saltstone (45% slag) the conditional K{sub d} was 168 mL/g, and for TR545 (90% slag) the conditional K{sub d} was 1,619 mL/g. It is anticipated that additional samples will be collected until steady state

  17. Degradation Of Cementitious Materials Associated With Saltstone Disposal Units

    Energy Technology Data Exchange (ETDEWEB)

    Flach, G. P; Smith, F. G. III

    2013-03-19

    The Saltstone facilities at the DOE Savannah River Site (SRS) stabilize and dispose of low-level radioactive salt solution originating from liquid waste storage tanks at the site. The Saltstone Production Facility (SPF) receives treated salt solution and mixes the aqueous waste with dry cement, blast furnace slag, and fly ash to form a grout slurry which is mechanically pumped into concrete disposal cells that compose the Saltstone Disposal Facility (SDF). The solidified grout is termed “saltstone”. Cementitious materials play a prominent role in the design and long-term performance of the SDF. The saltstone grout exhibits low permeability and diffusivity, and thus represents a physical barrier to waste release. The waste form is also reducing, which creates a chemical barrier to waste release for certain key radionuclides, notably Tc-99. Similarly, the concrete shell of an SDF disposal unit (SDU) represents an additional physical and chemical barrier to radionuclide release to the environment. Together the waste form and the SDU compose a robust containment structure at the time of facility closure. However, the physical and chemical state of cementitious materials will evolve over time through a variety of phenomena, leading to degraded barrier performance over Performance Assessment (PA) timescales of thousands to tens of thousands of years. Previous studies of cementitious material degradation in the context of low-level waste disposal have identified sulfate attack, carbonation influenced steel corrosion, and decalcification (primary constituent leaching) as the primary chemical degradation phenomena of most relevance to SRS exposure conditions. In this study, degradation time scales for each of these three degradation phenomena are estimated for saltstone and concrete associated with each SDU type under conservative, nominal, and best estimate assumptions. The nominal value (NV) is an intermediate result that is more probable than the conservative

  18. Overview of recent work on self-healing in cementitious materials

    Directory of Open Access Journals (Sweden)

    Lv, Z.

    2014-12-01

    Full Text Available Cracks, especially microcracks, in concrete are of paramount importance to the durability and the service life of cementitious composite. However, the self-healing technology, including autogenous healing and autonomous healing, is expected to be one of effective tools to overcome this boring problem. In this paper, we focus on the autogenous healing of concrete material and a few of recent works of autonomous healing are also mentioned. The durability and the mechanical properties improved by the self-healing phenomenon are reviewed from experimental investigation and practical experience. Several aspects of researches, such as autogenous healing capability of an innovative concrete incorporated geo-materials, self-healing of engineered cementitious composite and fire-damaged concrete, effect of mineral and admixtures on mechanism and efficiency of self-healing concrete are summarized to evaluate the presented progresses in the past several years and to outline the perspective for the further developments. Moreover, a special emphasis is given on the analytical models and computer simulation method of the researches of self-healing in cementitious materials.Las fisuras, y sobre todo las microfisuras, tienen una gran repercusión en la durabilidad y en la vida útil de los materiales cementantes. Ante este problema, la tecnología de la autorreparación, tanto autógena como autónoma, se presenta como una solución eficaz. El artículo se centra en la reparación autógena del hormigón, así como en algunos trabajos recientes sobre la reparación autónoma. Se describen las mejoras de las propiedades de durabilidad y de resistencia que proporciona la técnica del hormigón autorreparable, tanto desde el punto de vista de la investigación experimental como del de la experiencia práctica. A fin de evaluar los avances logrados en los últimos años y de trazar las grandes líneas de desarrollo futuro, se resumen varios de los aspectos

  19. Talc-based cementitious products: Effect of talc calcination

    Directory of Open Access Journals (Sweden)

    C.J. Ngally Sabouang

    2015-09-01

    Full Text Available This study reports the use of calcined talc for cementitious products making. The calcination is used to enhance the availability of magnesium from talc to react with phosphate for cement phase formation. It is shown that previous calcination of talc leads to products having enhanced mechanical performance due to the formation of more cement phase than in products based on raw talc. Talc fired at 900 °C was found to be the one in which magnesium release was maximal. Firing at temperature higher than 900 °C leads to the stabilization of enstatite, which decreased the magnesium availability. The cement phase is struvite, which was better detected on the X-ray patterns of the products involving fired talc. All the products have very rapid setting time and low shrinkage.

  20. Innovation in use and research on cementitious material

    International Nuclear Information System (INIS)

    In this paper we discuss innovations in concrete technology which are currently being applied in the field-namely high and ultra high performance (strength), and self consolidating concrete. We discuss the factors which have enabled these developments and ongoing needs in these areas. The importance of sustainability as the major driver for future innovations and prospects for development of new cementitious materials with lower environmental impact is briefly discussed. Finally the importance of innovation in research is examined. The dramatic development in experimental and computational techniques over recent years opens up wide-ranging possibilities for understanding the micro- and nano- scale chemical and physical processes which underlie performance at a macroscopic level. The example of computational approaches at the atomic and molecular scale is presented in detail. In order to exploit the opportunities presented by such new techniques, there needs to be greater efforts to structure interdisciplinary, multi-group research

  1. Towards a mechanistic understanding of actinide retention by cementitious materials

    International Nuclear Information System (INIS)

    Full text of publication follows. Calcium silicate hydrate (C-S-H) are considered to be the most important constituent of hardened cement paste (HCP) with respect to their abundance and the diversity of structural sites exposed for cation and anion binding. Furthermore, C-S-H phases may control the long term release of radionuclides due to their stability during the evolution of the cementitious near field. The retention of Nd (III) by crystalline C-S-H phases has been studied by combined use of wet chemical methods, synchrotron based spectroscopic, laboratory-based X-ray diffraction techniques and an appropriate theoretical approach. The investigations enable us to propose a mechanistic model for the immobilisation of trivalent lanthanides and actinides in crystalline C-S-H phases. (authors)

  2. Computer Modeling of Leaching of Heavy Metal from Cementitious Waste

    Directory of Open Access Journals (Sweden)

    Peng Hu

    2013-07-01

    Full Text Available Thermodynamic equilibrium model was used to simulate the results of leaching heavy metal from cementitious wastes. Modeling results of the leached major element concentrations for samples agreed well with the leaching test using the set of pure minerals and solid solutions present in the database. The model revealed Pb and Cd were predominantly incorporated within the calcium silicate hydrate matrix while a greater portion of Cd exist as discrete particles in the cement pores. Precipitation was found to be the dominant mechanism controlling heavy metal solubility with carbonate and silicate species governing the solubility of Pb and carbonate, silicate and hydroxide species governing the solubility of Cd. In the presence of acetic acid, at low pH values Pb and Cd acetate complexes were predominant whereas, at high pH values, hydroxide species dominated. In the presence of municipal landfill leachate, Pb and Cd organic complexes dominated the heavy metal species in solution.

  3. Evaluation of natural colonisation of cementitious materials: Effect of bioreceptivity and environmental conditions

    OpenAIRE

    Manso Blanco, Sandra; Calvo-Torrás, María Angeles; De Belie, Nele; Segura Pérez, Ignacio; Aguado de Cea, Antonio

    2015-01-01

    Incorporation of living organisms, such as photosynthetic organisms, on the structure envelope has become a priority in the area of architecture and construction due to aesthetical, economic and ecological advantages. Important research efforts are made to achieve further improvements, such as for the development of cementitious materials with an enhanced bioreceptivity to stimulate biological growth. Previously, the study of the bioreceptivity of cementitious materials has been carried out m...

  4. Predicting the Probability of Failure of Cementitious Sewer Pipes Using Stochastic Finite Element Method

    OpenAIRE

    Alani, Amir M.; Asaad Faramarzi

    2015-01-01

    In this paper, a stochastic finite element method (SFEM) is employed to investigate the probability of failure of cementitious buried sewer pipes subjected to combined effect of corrosion and stresses. A non-linear time-dependant model is used to determine the extent of concrete corrosion. Using the SFEM, the effects of different random variables, including loads, pipe material, and corrosion on the remaining safe life of the cementitious sewer pipes are explored. A numerical example is prese...

  5. 3D morphological and micromechanical modeling of cementitious materials

    International Nuclear Information System (INIS)

    The goal of this thesis is to develop morphological models of cementitious materials and use these models to study their local and effective response. To this aim, 3D images of cementitious materials (mortar and concrete), obtained by micro-tomography, are studied. First, the mortar image is segmented in order to obtain an image of a real microstructure, to be used for linear elasticity computations. The image of concrete is used, after being processed, to determine various morphological characteristics of the material. A random model of concrete is then developed and validated by means of morphological data. This model is made up of three phases, corresponding to the matrix, aggregates and voids. The aggregates phase is modelled by implantation of Poisson polyhedra without overlap. For this purpose, an algorithm suited to the vector generation of Poisson polyhedra is introduced and validated with morphological measurements. Finally, the effective linear elastic properties of the mortar and other simulated microstructures are estimated with the FFT (Fast-Fourier Transform) method, for various contrasts between the aggregates and matrix' Young moduli. To complete this work, focused on effective properties, an analysis of the local elastic response in the matrix phase is undertaken, in order to determine the spatial arrangement between stress concentration zones in the matrix and the phases of the microstructure (aggregates and voids). Moreover, a statistical fields characterization, in the matrix, is achieved, including the determination of the Representative Volume Element (RVE) size. Furthermore, a comparison between effective and local elastic properties obtained from microstructures containing polyhedra and spheres is carried out. (author)

  6. The CSNI/PWG-1 international task group on ECCS reliability

    Energy Technology Data Exchange (ETDEWEB)

    Sandervag, O.; Riekert, T.; Serkiz, A.; Hyvarinen, J.

    1996-03-01

    A steam line loss-of-coolant accident (LOCA) occurred when a safety relief valve inadvertently opened in the Barseback-2 nuclear power plant. The steam jet stripped fibrous insulation from adjacent pipework. Part of that insulation debris was transported to the wetwell pool and clogged the intake strainers for the drywell spray system after about one hour. Although the incident in itself was not very serious, it revealed a weakness in the defense-in-depth concept which under other circumstances could have led to failure of the emergency core cooling system (ECCS) to provide water to the core. Before the Barseback-2 LOCA, international regulators of nuclear power plants and the nuclear power plant industry had considered safety questions related to strainer clogging as resolved. Many European countries had followed the guidance for strainers in pressurized water reactors (PWRs) contained in United States Nuclear Regulatory Commission`s (USNRC) Regulatory Guide 1.82, Water Sources for Long Term Recirculation Cooling Following a Loss-of-Coolant Accident, 1974. However, data obtained from European experimental programs carried out in the late seventies to determine the performance of strainers indicated that this guide was not adequate. In addition, Swedish plant owners had used this guidance to judge performance of emergency core cooling systems (ECCS) in their plants. Analyses at that time had indicated that strainer clogging, if occurring at all, would at least not occur during the first ten hours after a LOCA. Since operation of the ECCS would be needed for a long time, backflushing capabilities and monitors of pressure drop across the strainers were installed in older Swedish BWR plants with small strainer areas. These actions were judged to be adequate compliance with the revised USNRC Regulatory Guide 1.82, Rev. 1, issued in 1985. Safety questions related to strainer clogging were considered to have been resolved until the incident happened in Barseback-2.

  7. The CSNI/PWG-1 international task group on ECCS reliability

    International Nuclear Information System (INIS)

    A steam line loss-of-coolant accident (LOCA) occurred when a safety relief valve inadvertently opened in the Barseback-2 nuclear power plant. The steam jet stripped fibrous insulation from adjacent pipework. Part of that insulation debris was transported to the wetwell pool and clogged the intake strainers for the drywell spray system after about one hour. Although the incident in itself was not very serious, it revealed a weakness in the defense-in-depth concept which under other circumstances could have led to failure of the emergency core cooling system (ECCS) to provide water to the core. Before the Barseback-2 LOCA, international regulators of nuclear power plants and the nuclear power plant industry had considered safety questions related to strainer clogging as resolved. Many European countries had followed the guidance for strainers in pressurized water reactors (PWRs) contained in United States Nuclear Regulatory Commission's (USNRC) Regulatory Guide 1.82, Water Sources for Long Term Recirculation Cooling Following a Loss-of-Coolant Accident, 1974. However, data obtained from European experimental programs carried out in the late seventies to determine the performance of strainers indicated that this guide was not adequate. In addition, Swedish plant owners had used this guidance to judge performance of emergency core cooling systems (ECCS) in their plants. Analyses at that time had indicated that strainer clogging, if occurring at all, would at least not occur during the first ten hours after a LOCA. Since operation of the ECCS would be needed for a long time, backflushing capabilities and monitors of pressure drop across the strainers were installed in older Swedish BWR plants with small strainer areas. These actions were judged to be adequate compliance with the revised USNRC Regulatory Guide 1.82, Rev. 1, issued in 1985. Safety questions related to strainer clogging were considered to have been resolved until the incident happened in Barseback-2

  8. Chemical effects and the impact to insulation debris filter cakes at ECCS upstream and downstream components

    International Nuclear Information System (INIS)

    Investigations regarding release, solution, transportation and deposit of corrosion products become important to reactor safety research for PWR, when considering the long-term behaviour of emergency core cooling systems (ECCS) during loss of coolant accidents (LOCA). The knowledge of corrosion processes in boric acid is necessary to evaluate the impact on insulation debris filter cakes in upstream (sump strainers) and downstream (reactor core) components and their influence on head loss and heat removal out of the core. Generic complex experiments determined the quantity of flow-induced, released corrosion products and their influences on head losses at filter cakes. (author)

  9. Compendium of ECCS [Emergency Core Cooling Systems] research for realistic LOCA [loss-of-coolant accidents] analysis: Final report

    International Nuclear Information System (INIS)

    In the United States, Emergency Core Cooling Systems (ECCS) are required for light water reactors (LWRs) to provide cooling of the reactor core in the event of a break or leak in the reactor piping or an inadvertent opening of a valve. These accidents are called loss-of-coolant accidents (LOCA), and they range from small leaks up to a postulated full break of the largest pipe in the reactor cooling system. Federal government regulations provide that LOCA analysis be performed to show that the ECCS will maintain fuel rod cladding temperatures, cladding oxidation, and hydrogen production within certain limits. The NRC and others have completed a large body of research which investigated fuel rod behavior and LOCA/ECCS performance. It is now possible to make a realistic estimate of the ECCS performance during a LOCA and to quantify the uncertainty of this calculation. The purpose of this report is to summarize this research and to serve as a general reference for the extensive research effort that has been performed. The report: (1) summarizes the understanding of LOCA phenomena in 1974; (2) reviews experimental and analytical programs developed to address the phenomena; (3) describes the best-estimate computer codes developed by the NRC; (4) discusses the salient technical aspects of the physical phenomena and our current understanding of them; (5) discusses probabilistic risk assessment results and perspectives, and (6) evaluates the impact of research results on the ECCS regulations. 736 refs., 412 figs., 66 tabs

  10. ROSA-III tests on BWR pump suction-line 200% break LOCAs with partial and total ECCS failure

    International Nuclear Information System (INIS)

    This report presents experiment data for three recirculation-pump suction-line 200% (double-ended) break tests, RUNs 902, 905 and 924, conducted in the ROSA-III test facility, a 1/424 volumetrically-scaled simulator of a boiling water reactor (BWR). These three tests, together with two other tests that have been already reported elsewhere (RUNs 926 and 901), make a set of five tests which addressed the effects of ECCS failure modes on core cooling performance for this break geometry. Results from these five tests are compared in this report. RUNs 902, 924 and 926 simulated three different single-failure modes of emergency core cooling system (ECCS) associated with failure of one out of the three emergency diesel generators (DGs) in the BWR. RUN 926 simulated DG failure disabling the high pressure core spray (HPCS) pump; RUN 924 the low pressure core spray (LPCS) pump and one out of the three low pressure coolant injection (LPCI) pumps; and RUN 902 two out of the three LPCI pumps. RUN 905 simulated hypothetical total failure of ECCS, and RUN 901 a fully-functional ECCS. For all the ECCS DG single-failure tests (RUNs 902, 924 and 926), the measured peak cladding temperatures (PCTs) were considerably lower than the licensing criterion of 1473 K. The HPCS failure (RUN 926) resulted in the severest core heatup among these three tests. (author)

  11. Leaching of radionuclides from cementitious wasteform in laboratory and field conditions

    International Nuclear Information System (INIS)

    Both real and simulated radioactive cementitious wasteform were tested to compare leaching rates in field and laboratory conditions. High leaching rates were found for sodium and nitrate for initial period of leaching in laboratory test. Cs137 leaching rates in the first 6-month period were on average by an order of magnitude lower compared those of Na+ and NO3-. However the average annual Cs137 leaching rate in the deionized water was about 35 times higher compared with the measured average value for the first year of the field test. Cumulative leached fraction of Cs137 for the first year of tests (3.74%) was close to values reported in literature however they were more than two orders of magnitude higher than leached fraction of Cs137 after the first year of repository test (0.01%). To compare field and laboratory test results, a scaling factor is required which aims to account for surface to volume factor, temperature and contacting water composition differences. (authors)

  12. Use of X-ray diffraction to quantify amorphous supplementary cementitious materials in anhydrous and hydrated blended cements

    International Nuclear Information System (INIS)

    The content of individual amorphous supplementary cementitious materials (SCMs) in anhydrous and hydrated blended cements was quantified by the PONKCS [1] X-ray diffraction (XRD) method. The analytical precision and accuracy of the method were assessed through comparison to a series of mixes of known phase composition and of increasing complexity. A 2σ precision smaller than 2–3 wt.% and an accuracy better than 2 wt.% were achieved for SCMs in mixes with quartz, anhydrous Portland cement, and hydrated Portland cement. The extent of reaction of SCMs in hydrating binders measured by XRD was 1) internally consistent as confirmed through the standard addition method and 2) showed a linear correlation to the cumulative heat release as measured independently by isothermal conduction calorimetry. The advantages, limitations and applicability of the method are discussed with reference to existing methods that measure the degree of reaction of SCMs in blended cements

  13. Influence of ECCS Core Barrel Duct on Reflood Behavior Predicted by MARS Code

    International Nuclear Information System (INIS)

    The present study is to discuss the influence of ECBD on the thermal-hydraulic behavior during the reflood phase of LBLOCA using the MARS-KS code and the related modeling consistent with the one previously developed. Influence of ECBD adopted in APR+ Standard Design on LBLOCA reflood behavior was discussed based on the MARS-KS code prediction. The ECBD was modeled as close as to its physical configuration. The prediction result shows a reduction of ECCS bypass due to ECBD but not significant impact on PCT during reflood phase. Aside from the PCT impact, further code assessment is needed using the applicable experiment simulating a LBLOCA with ECBD to confirm the expected ECBD related phenomena and to get an information of the uncertainty of the phenomena. A device, ECBD (Emergency Core Cooling System Core Barrel Duct), has been proposed at APR+ Standard Design, which was to provide a direct flow path from the elevation of Direct Vessel Injection (DVI) nozzle to the one of active core within the reactor vessel downcomer. It's main function is to reduce the amount of the bypassed ECCS water especially during the reflood phase of large break loss-of-coolant accident (LBLOCA). Since the ECBD design was based on the DVI of APR1400 which was approved through licensing process, the impact of ECBD needs to be assessed in comparison with APR1400 DVI and also the case without ECBD

  14. Study on ECC injection modes in reflood tests with SCTF core II

    International Nuclear Information System (INIS)

    In Slab Core Test Facility (SCTF) tests, a forced feed reflooding mode is adopted as ECC water injection method to investigate parameter effects in detail on thermal-hydraulic behaviors in pressure vessel under the same boundary conditions at core inlet. This is because a gravity feed mode with cold leg injection, which is considered to be better simulation for PWR, has an uncertainty against the boundary conditions of core due to the parameter change. However, it is necessary to justify the validity of forced feed mode because the solid system of that mode might change two-dimensional thermal-hydraulic behaviors in pressure vessel to be investigated in SCTF. This report makes clear the effects of difference in ECC water injection mode (Gravity Feed/Forced Feed) on the thermal-hydraulic behaviors in the pressure vessel using the comparison between the data in the gravity feed test and in the forced feed one and the comparison between the data and the predictions with REFLA code. Major conclusion is that the difference in feed mode does not affect the thermal-hydraulic behaviors in the pressure vessel including the two-dimensional behaviors as far as the boundary conditions of the core are similar. (author)

  15. ROSA-III experimental program for BWR LOCA/ECCS integral simulation tests

    International Nuclear Information System (INIS)

    This is the final report of the ROSA-III experimental program, in which the summary of integral simulation test results is described on thermal-hydraulic behavior during a loss-of-coolant accident (LOCA) of a boiling water reactor (BWR) and on the effectiveness of the emergency core cooling system (ECCS). Also presented in the report are the assessment results of computer codes for the BWR LOCA analysis and of the similarity between ROSA-III test results and thermal-hydraulic phenomena during a BWR LOCA by using ROSA-III test data and code analysis results. The ROSA-III facility is a volumetrically scaled (1/424) BWR system with an electrically heated core consisting of four half-length bundles. Many test series were conducted between April 1978 and March 1983. The similarity between a ROSA-III test and a BWR LOCA concerning the fundamental thermal-hydraulic phenomena has been confirmed for major ROSA-III tests. The accident scenario has been well understood and defined for various break locations and break sizes. The effectiveness of the current BWR ECCS design has been well demonstrated. (author)

  16. A Provably-Secure ECC-Based Authentication Scheme for Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Junghyun Nam

    2014-11-01

    Full Text Available A smart-card-based user authentication scheme for wireless sensor networks (in short, a SUA-WSN scheme is designed to restrict access to the sensor data only to users who are in possession of both a smart card and the corresponding password. While a significant number of SUA-WSN schemes have been suggested in recent years, their intended security properties lack formal definitions and proofs in a widely-accepted model. One consequence is that SUA-WSN schemes insecure against various attacks have proliferated. In this paper, we devise a security model for the analysis of SUA-WSN schemes by extending the widely-accepted model of Bellare, Pointcheval and Rogaway (2000. Our model provides formal definitions of authenticated key exchange and user anonymity while capturing side-channel attacks, as well as other common attacks. We also propose a new SUA-WSN scheme based on elliptic curve cryptography (ECC, and prove its security properties in our extended model. To the best of our knowledge, our proposed scheme is the first SUA-WSN scheme that provably achieves both authenticated key exchange and user anonymity. Our scheme is also computationally competitive with other ECC-based (non-provably secure schemes.

  17. Prosthetic Oral Rehabilitation of a Child With S-ECC: A Case Report with Histopathologic Analysis.

    Science.gov (United States)

    Tannure, P N; Moraes, G G; Borba, McU; Abrahão, A; Andrade, Mtrc; Fidalgo, Tks

    2015-01-01

    The aim of this case report is to describe the treatment planning of a young child with severe early childhood caries (S-ECC) as well as the prosthetic rehabilitation technique. A 3-year-old female child was referred to the pediatric dentistry clinic with the chief complaint of tooth pain, difficulty in eating and recurrent hospitalizations caused by dental infections. The mother reported intermittent episodes of fever and recurrent swelling of child's face. The girl presented angular cheilitis and was referred to a dietitian. The treatment plain consisted on a behavior changes in oral hygiene habits, exodontias of all primary teeth and oral rehabilitation with a prosthesis. The extracted teeth with periapical lesions were submitted to histopathologic analysis (hematoxilin and eosin staining) and revealed an inflammatory infiltrate. The aesthetic requirement of children with S-ECC has been a challenge to pediatric dentists. In the present case, the oral rehabilitation provided for the children better aesthetic, nutrition, phonation, and functional conditions. PMID:26551361

  18. Condensation in the cold leg as results of ECC water injection during A LOCA: modeling and validation

    International Nuclear Information System (INIS)

    During postulated LOCA events in pressurized water reactors, cold water is injected into cold legs by emergency core cooling system (ECCS). As the ECC water comes into contact with steam, the amount of condensation in the cold legs which results from mixing of the two phases is expected to have an effect on the thermal hydraulic behavior of the system. During boil off period and recovery period of a small break LOCA, the condensation in the cold leg is enhanced by the impingement of the ECC jet on the layer of liquid, when the flow in the cold leg is expected to be horizontal stratified. Consequently, the reactor coolant system (RCS) depressurization is accelerated, which in turn increases ECC flow rate and promotes accumulator injection. For a large break LOCA, the condensation process in the cold leg during refill period helps to reduce bypass flow at the top of downcomer, promoting ECC penetration. The condensation in the cold leg during reflood period is an important factor in determining the ECC bypass, the break flow rate, the downcomer and core water inventory, and the liquid subcooling in the downcomer, which in turn impacts the peak cladding temperature during reflood. A cold leg condensation model was considered for the new release of WCOBRA/TRAC-TF2 safety analysis code and presented in an authors' previous work. The model was further improved to better capture relevant data and a revised model was found to be in better agreement with such experimental data. The intent of this paper is to present the validation for the cold leg condensation model. The improved cold leg condensation model is assessed against various small break and large break LOCA separate effects tests such as COSI experiments, ROSA experiments and UPTF experiments. Those experiments cover a wide range of cold leg dimensions, system pressures, mass flow rates, and fluid properties. All the predicted condensation results match reasonably well with the experimental data. (author)

  19. REVIEW OF MECHANISTIC UNDERSTANDING AND MODELING AND UNCERTAINTY ANALYSIS METHODS FOR PREDICTING CEMENTITIOUS BARRIER PERFORMANCE

    Energy Technology Data Exchange (ETDEWEB)

    Langton, C.; Kosson, D.

    2009-11-30

    Cementitious barriers for nuclear applications are one of the primary controls for preventing or limiting radionuclide release into the environment. At the present time, performance and risk assessments do not fully incorporate the effectiveness of engineered barriers because the processes that influence performance are coupled and complicated. Better understanding the behavior of cementitious barriers is necessary to evaluate and improve the design of materials and structures used for radioactive waste containment, life extension of current nuclear facilities, and design of future nuclear facilities, including those needed for nuclear fuel storage and processing, nuclear power production and waste management. The focus of the Cementitious Barriers Partnership (CBP) literature review is to document the current level of knowledge with respect to: (1) mechanisms and processes that directly influence the performance of cementitious materials (2) methodologies for modeling the performance of these mechanisms and processes and (3) approaches to addressing and quantifying uncertainties associated with performance predictions. This will serve as an important reference document for the professional community responsible for the design and performance assessment of cementitious materials in nuclear applications. This review also provides a multi-disciplinary foundation for identification, research, development and demonstration of improvements in conceptual understanding, measurements and performance modeling that would be lead to significant reductions in the uncertainties and improved confidence in the estimating the long-term performance of cementitious materials in nuclear applications. This report identifies: (1) technology gaps that may be filled by the CBP project and also (2) information and computational methods that are in currently being applied in related fields but have not yet been incorporated into performance assessments of cementitious barriers. The various

  20. Factors Predisposing to Early Childhood Caries (ECC) in Children of Pre-School Age in the City of Zagreb, Croatia

    OpenAIRE

    Lulić-Dukić, O.; Jurić, H.; Dukić, W.; Glavina, D.

    2001-01-01

    The aim of this study was to investigate factors predisposing to early childhood caries (ECC) in pre-school children in the city of Zagreb, Croatia. The investigation was carried out on the sample of 145 children (77 boys and 68 girls) aged between 2 and 5 years, including clinical examination of dental status and survey on the habits among the parents. The overall prevalence of ECC was 30%: in girls it was 25%, and in boys 48%. The study on the risk factors was designed as a c...

  1. CEMENTITIOUS GROUT FOR CLOSING SRS HIGH LEVEL WASTE TANKS - #12315

    Energy Technology Data Exchange (ETDEWEB)

    Langton, C.; Burns, H.; Stefanko, D.

    2012-01-10

    In 1997, the first two United States Department of Energy (US DOE) high level waste tanks (Tanks 17-F and 20-F: Type IV, single shell tanks) were taken out of service (permanently closed) at the Savannah River Site (SRS). In 2012, the DOE plans to remove from service two additional Savannah River Site (SRS) Type IV high-level waste tanks, Tanks 18-F and 19-F. These tanks were constructed in the late 1950's and received low-heat waste and do not contain cooling coils. Operational closure of Tanks 18-F and 19-F is intended to be consistent with the applicable requirements of the Resource Conservation and Recovery Act (RCRA) and the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) and will be performed in accordance with South Carolina Department of Health and Environmental Control (SCDHEC). The closure will physically stabilize two 4.92E+04 cubic meter (1.3 E+06 gallon) carbon steel tanks and isolate and stabilize any residual contaminants left in the tanks. The closure will also fill, physically stabilize and isolate ancillary equipment abandoned in the tanks. A Performance Assessment (PA) has been developed to assess the long-term fate and transport of residual contamination in the environment resulting from the operational closure of the F-Area Tank Farm (FTF) waste tanks. Next generation flowable, zero-bleed cementitious grouts were designed, tested, and specified for closing Tanks 18-F and 19-F and for filling the abandoned equipment. Fill requirements were developed for both the tank and equipment grouts. All grout formulations were required to be alkaline with a pH of 12.4 and chemically reduction potential (Eh) of -200 to -400 to stabilize selected potential contaminants of concern. This was achieved by including Portland cement and Grade 100 slag in the mixes, respectively. Ingredients and proportions of cementitious reagents were selected and adjusted, respectively, to support the mass placement strategy developed by

  2. DEMONSTRATION OF LEACHXS/ORCHESTRA CAPABILITIES BY SIMULATING CONSTITUENT RELEASE FROM A CEMENTITIOUS WASTE FORM IN A REINFORCED CONCRETE VAULT

    Energy Technology Data Exchange (ETDEWEB)

    Langton, C.; Meeussen, J.; Sloot, H.

    2010-03-31

    The objective of the work described in this report is to demonstrate the capabilities of the current version of LeachXS{trademark}/ORCHESTRA for simulating chemical behavior and constituent release processes in a range of applications that are relevant to the CBP. This report illustrates the use of LeachXS{trademark}/ORCHESTRA for the following applications: (1) Comparing model and experimental results for leaching tests for a range of cementitious materials including cement mortars, grout, stabilized waste, and concrete. The leaching test data includes liquid-solid partitioning as a function of pH and release rates based on laboratory column, monolith, and field testing. (2) Modeling chemical speciation of constituents in cementitious materials, including liquid-solid partitioning and release rates. (3) Evaluating uncertainty in model predictions based on uncertainty in underlying composition, thermodynamic, and transport characteristics. (4) Generating predominance diagrams to evaluate predicted chemical changes as a result of material aging using the example of exposure to atmospheric conditions. (5) Modeling coupled geochemical speciation and diffusion in a three layer system consisting of a layer of Saltstone, a concrete barrier, and a layer of soil in contact with air. The simulations show developing concentration fronts over a time period of 1000 years. (6) Modeling sulfate attack and cracking due to ettringite formation. A detailed example for this case is provided in a separate article by the authors (Sarkar et al. 2010). Finally, based on the computed results, the sensitive input parameters for this type of modeling are identified and discussed. The chemical speciation behavior of substances is calculated for a batch system and also in combination with transport and within a three layer system. This includes release from a barrier to the surrounding soil as a function of time. As input for the simulations, the physical and chemical properties of the

  3. Modified ECC ozone sonde for long-duration flights aboard isopicnic drifting balloons

    Science.gov (United States)

    Gheusi, Francois; Durand, Pierre; Verdier, Nicolas; Dulac, François; Attié, Jean-Luc; Commun, Philippe; Barret, Brice; Basdevant, Claude; Clénet, Antoine; Fontaine, Alain; Jambert, Corinne; Meyerfeld, Yves; Roblou, Laurent; Tocquer, Flore

    2015-04-01

    Since few years, the French space agency CNES has developed boundary-layer pressurized balloons (BLPB) with the capability to transport scientific payloads at isopicnic level over very long distances and durations (up to several weeks in absence of navigation limits). However, the autonomy of conventional electrochemical concentration cell (ECC) ozone sondes, that are widely used for tropospheric and stratospheric soundings, is limited to few hours due to power consumption and electrolyte evaporation (owing to air bubbling in the cathode solution). In collaboration with the French research community, CNES has developed a new ozone payload suited for long duration flights aboard BLPB. The mechanical elements (Teflon pump and motor) and the electrochemical cell of conventional ECC sondes have been kept but the electronic implementation is entirely new. The main feature is the possibility of programming periodic measurement sequences -- with possible remote control during the flight. To increase the ozone sonde autonomy, a strategy has been adopted of short measurement sequences (typically 2-3 min) regularly spaced in time (e.g. every 15 min, which is usually sufficient for air quality studies). The rest of the time, the sonde is at rest (pump motor off). The response time of an ECC sonde to an ozone concentration step is below one minute. Consequently, the measurement sequence is typically composed of a one-minute spin-up period after the pump has been turned on, followed by a one- to two-minute acquisition period. All time intervals can be adjusted before and during the flight. Results of a preliminary ground-based test in spring 2012 are first presented. The sonde provided correct ozone concentrations against a reference UV analyzer every 15 minutes during 4 days. Then we illustrate results from 16 BLBP flights launched in the low troposphere over the Mediterranean during summer field campaings in 2012 and 2013 (TRAQA and ChArMEx programmes). BLPB drifting

  4. Bioreceptivity evaluation of cementitious materials designed to stimulate biological growth.

    Science.gov (United States)

    Manso, Sandra; De Muynck, Willem; Segura, Ignacio; Aguado, Antonio; Steppe, Kathy; Boon, Nico; De Belie, Nele

    2014-05-15

    Ordinary Portland cement (OPC), the most used binder in construction, presents some disadvantages in terms of pollution (CO2 emissions) and visual impact. For this reason, green roofs and façades have gain considerable attention in the last decade as a way to integrate nature in cities. These systems, however, suffer from high initial and maintenance costs. An alternative strategy to obtain green facades is the direct natural colonisation of the cementitious construction materials constituting the wall, a phenomenon governed by the bioreceptivity of such material. This work aims at assessing the suitability of magnesium phosphate cement (MPC) materials to allow a rapid natural colonisation taking carbonated OPC samples as a reference material. For that, the aggregate size, the w/c ratio and the amount of cement paste of mortars made of both binders were modified. The assessment of the different bioreceptivities was conducted by means of an accelerated algal fouling test. MPC samples exhibited a faster fouling compared to OPC samples, which could be mainly attributed to the lower pH of the MPC binder. In addition to the binder, the fouling rate was governed by the roughness and the porosity of the material. MPC mortar with moderate porosity and roughness appears to be the most feasible material to be used for the development of green concrete walls. PMID:24602907

  5. Implementation and verification of different ECC mitigation designs for BRAMs in flash-based FPGAs

    CERN Document Server

    Yang, Zhenlei; Zhang, Zhangang; Liu, Jie; Su, Hong

    2015-01-01

    Embedded RAM blocks (BRAMs) in field programmable gate arrays (FPGAs) are susceptible to single event effects (SEEs) induced by environmental factors such as cosmic rays, heavy ions, alpha particles and so on. As technology scales, the issue will be more serious. In order to tackle this issue, two different error correcting codes (ECCs), the shortened Hamming codes and shortened BCH codes, are investigated in this paper. The concrete design methods of the codes are presented. Also, the codes are both implemented in flash-based FPGAs. Finally, the synthesis report and simulation results are presented in the paper. Moreover, the heavy-ion experiments are performed, the experimental results indicate that the error cross-section using the shortened Hamming codes can be reduced by two orders of magnitude compared with the device without mitigation, and no errors are discovered in the experiments for the device using the shortened BCH codes.

  6. A Secure ECC-based RFID Mutual Authentication Protocol to Enhance Patient Medication Safety.

    Science.gov (United States)

    Jin, Chunhua; Xu, Chunxiang; Zhang, Xiaojun; Li, Fagen

    2016-01-01

    Patient medication safety is an important issue in patient medication systems. In order to prevent medication errors, integrating Radio Frequency Identification (RFID) technology into automated patient medication systems is required in hospitals. Based on RFID technology, such systems can provide medical evidence for patients' prescriptions and medicine doses, etc. Due to the mutual authentication between the medication server and the tag, RFID authentication scheme is the best choice for automated patient medication systems. In this paper, we present a RFID mutual authentication scheme based on elliptic curve cryptography (ECC) to enhance patient medication safety. Our scheme can achieve security requirements and overcome various attacks existing in other schemes. In addition, our scheme has better performance in terms of computational cost and communication overhead. Therefore, the proposed scheme is well suitable for patient medication systems. PMID:26573649

  7. Quick Look Report of the SMART ECC injection performance test I3

    International Nuclear Information System (INIS)

    The objective of this report is to describe test results of the Test I3 simulating the 2 inch SBLOCA of the SMART using the SWAT test facility. The Test I3 was performed to produce experimental data for the validation of the TASS/SMR-S thermal hydraulic analysis code, and to investigate the related thermal hydraulic phenomena in the down-comer region during the 2 inch SBLOCA of the safety inject line. The particular phenomena for the observation are ECC bypass and multi-dimensional flow characteristics to verify the effectiveness and performance of the safety injection system. In this report, the corresponding steady state test conditions, including initial and boundary conditions along with major measuring parameters, and related experimental results were described

  8. Probabilistic evaluation of mispositioned ECCS motor operated valves in Westinghouse NSSS

    International Nuclear Information System (INIS)

    During the past few years the definition of single active failure has been expanded to include the spurious action of a powered component. The main emphasis for this expansion in the definition of active failure came from the NRC Staff. Their concern is documented in Branch Technical Positions which require electrical power lockout of certain motor operated valves which if spuriously moved during an accident could defeat safety system response. These positions further require fluid system design changes instead of power lockout for certain other valves. This paper is a summary of the methodology and results of the evaluation performed to address the NRC positions. This evaluation provides technical justification for the reliable operation of certain Emergency Core Cooling System (ECCS) motor operated valves. It is intended that this treatment of a single failure issue will increase the awareness of the industry to the potential role of quantitative probabilistic analysis in determining failure criteria for Nuclear Power Generating Stations

  9. Large break LOCA analysis for retrofitted ECCS at MAPS using modified computer code ATMIKA

    International Nuclear Information System (INIS)

    Full text: Computer code ATMIKA which has been used for thermal hydraulic analysis is based on unequal velocity equal temperature (UVET) model. Thermal hydraulic transient was predicted using three conservation equations and drift flux model. The modified drift flux model is now able to predict counter current flow and the relative velocity in vertical channel more accurately. Apart from this, stratification model is also introduced to predict the fuel behaviour under stratified condition. Many more improvements were carried out with respect to solution of conservation equation, heat transfer package and frictional pressure drop model. All these modifications have been well validated with published data on RD-12/RD-14 experiments. This paper describes the code modifications and also deals with the application of the code for the large break LOCA analysis for retrofitted emergency core cooling system (ECCS) being implemented at Madras Atomic Power Station (MAPS). This paper also brings out the effect of accumulator on stratification and fuel behaviour

  10. Interference of sulphur dioxide to balloon-borne ECC ozone sensors over the Valley of Mexico

    Directory of Open Access Journals (Sweden)

    I. Kanda

    2014-01-01

    Full Text Available Abnormal decrease in the ozonesonde sensor signal occurred during air-pollution study campaigns in November 2011 and March 2012 in Mexico City. Sharp drops around 5 km a.s.l. and above were observed in November 2011, and a broad deficit in the convective boundary layer in March 2012. Various circumstantial evidence indicates that the decrease was due to interference of SO2 gas to Electrochemical Concentration Cell (ECC ozone sensors. The sharp drops in November 2011 are considered to be caused by the SO2 plume from the Popocatépetl volcano to the south-east of Mexico City. Response experiments of the ECC sensor to representative atmospheric trace gases showed that only SO2 could generate the observed abrupt drops. The vertical structure of the plume reproduced by a Lagrangian particle diffusion simulation also supported this assumption. The near-ground deficit in March 2012 is considered to be generated by the SO2 plume from the Tula industrial complex to the north-west of Mexico City. Sporadic large SO2 emission is known to occur from this region, and before and at the ozonesonde launching time, large intermittent peaks of SO2 concentration were recorded at the ground-level monitoring stations. The difference between the O3 concentration obtained by ozonesonde and that by UV-based O3 monitor was consistent with the SO2 concentration measured by a UV-based monitor on the ground. The plume vertical profiles estimated by the Lagrangian particle diffusion simulation agreed fairly well with the observed profile. Statistical analysis of the wind field in Mexico City revealed that the Popocatépetl effect is most likely to occur from June to October, and the Tula effect all the year.

  11. Guideline on in-service testing (IST) of ECCS for nuclear power stations in Japan

    International Nuclear Information System (INIS)

    In Japan, METI (Ministry of Economy, Trade and Industry) periodic inspections are conducted every 13 months in accordance with the EUIL (Electric Utility Industry Law) for light water reactors. On the other hand, during operation, many kinds of function tests are conducted in accordance with Technical Specifications or utilities voluntary test procedures. However, these maintenance activities during outages are in other respects considered too costly and more than necessary because of its predetermined maintenance interval and its old-fashioned full scope maintenance menu. In these circumstances, the ASME O and M Codes and Standards, which are applied to nuclear power plants in the United States, came to be one of the issues to be considered among Japanese utilities. This is because the ASME O and M Codes and Standards, which are developed to verify the operational readiness of equipment or systems by condition based maintenance or performance testing without overhauls, will be considered to suggest a rational alternative to our existing maintenance activities. Because there had been no standard for function tests other than the METI inspection procedures in Japan, activities started for the development of Japanese Operation and Maintenance Guideline (hereinafter called the Japanese OM Guideline or the Guideline) for function tests and condition monitoring. The Japanese OM Guideline is not proclaimed for regulatory use, but the long-term objective is to provide a substantial basis to change the current maintenance activities including regulatory inspection. The Guideline is composed of five parts, which are general requirements, pumps, valves, snubbers and ECCS systems. This paper gives a summary of the ECCS part of the Japanese OM Guideline, in particular, focusing on the differences between the Guideline and the ASME O and M Standards, and topics or discussion during their establishment. (author)

  12. Experiments of ECCS strainer blockage and debris settling in suppression pools

    Energy Technology Data Exchange (ETDEWEB)

    Hecker, G.E.; Johnson, A.B.; Murthy, P.; Padmanabhan

    1996-03-01

    If a rupture occurs in a nuclear power station pipe that leads to or from the reactor pressure vessel, the resultant Loss of Coolant Accident (LOCA) would initiate a chain of events involving complex flow phenomena. In a Boiling Water Reactor (BWR), the steam or liquid pipe break pressurizes the dry well, forcing the inert containment gases and steam through downcomers into the suppression pool, thoroughly mixing any particulates and pipe insulation debris carried with the gas flow to the pool. As the steam flow decreases, its unsteady condensation at the end of the downcomers (Condensation Oscillation and Chugging) produces continued water motion in the suppression pool and downcomers. During the blowdown event, high pressure and then low pressure pumps automatically start injecting water from the suppression pool into the reactor to keep its temperature under control. Proper functioning of this Emergency Core Cooling System (ECCS) is critical for the first 30 minutes or so, before operators have time to consider and align alternative sources of cooling water. A major concern for proper operation of the ECCS is the effect of fragmented insulation and plant particulates on the head loss at pump suction strainers. Sufficient loss could exceed the NPSH margin, causing cavitation with a resultant loss of pump capacity and longevity. The bead loss increases with the mass of debris accumulated on the pump strainers, which in turn is dependent on the debris concentration versus time in the suppression pool. This paper describes two sets of experiments that quantified the strainer head loss. One set of experiments considered the mixing and settling of fibrous insulation debris and fine iron oxide particles in the suppression pool during and after chugging. These tests used a reduced scale facility which duplicated the kinetic energy per unit water volume to define the concentration of the actual materials in the pool versus time.

  13. Prevalence of candida albicans in dental plaque and caries lesion of early childhood caries (ECC) according to sampling site

    OpenAIRE

    Ghasempour, Maryam; Sefidgar, Seyed Ali Asghar; Eyzadian, Haniyeh; Gharakhani, Samaneh

    2011-01-01

    Background: Candida albicans may have cariogenic potential but its role in caries etiology has not been established. The aim of this study was to determine candida albicans in supragingival dental plaque and infected dentine of cervical and proximal in early childhood caries (ECC).

  14. Incorporating Indigenous Knowledge and Practice into ECCE: A Comparison of Programs in The Gambia, Senegal and Mali

    Science.gov (United States)

    Soudee, Alicia Ranck

    2009-01-01

    Early Childhood Development (ECD) has emerged as a theme in international and African dialogue on education in recent years. UNESCO's Division of Basic Education Early Childhood promotes an integrated approach to Early Childhood Care and Education (ECCE) policy development and review. The study examines how this is implemented in three West…

  15. Appraisal of a cementitious material for waste disposal: Neutron imaging studies of pore structure and sorptivity

    International Nuclear Information System (INIS)

    Cementitious materials are conventionally used in conditioning intermediate and low level radioactive waste. In this study a candidate cement-based wasteform has been investigated using neutron imaging to characterise the wasteform for disposal in a repository for radioactive materials. Imaging showed both the pore size distribution and the extent of the cracking that had occurred in the samples. The rate of the water penetration measured both by conventional sorptivity measurements and neutron imaging was greater than in pastes made from Ordinary Portland Cement. The ability of the cracks to distribute the water through the sample in a very short time was also evident. The study highlights the significant potential of neutron imaging in the investigation of cementitious materials. The technique has the advantage of visualising and measuring, non-destructively, material distribution within macroscopic samples and is particularly useful in defining movement of water through the cementitious materials.

  16. Iron ore tailings used for the preparation of cementitious material by compound thermal activation

    Institute of Scientific and Technical Information of China (English)

    Zhong-lai Yi; Heng-hu Sun; Xiu-quan Wei; Chao Li

    2009-01-01

    In the background of little reuse and large stockpile for iron ore railings, iron ore tailing from Chinese Tonghua were used as raw material to prepare cementitious materials. Cementitious properties of the iron ore tailings activated by compound thermal ac-tivation were studied. Testing methods, such as XRD, TG-DTA, and IR were used for researching the phase and structure variety of the iron ore tailings in the process of compound thermal activation. The results reveal that a new cementitious material that contains 30wt% of the iron ore tailings can be obtained by compounded thermal activation, whose mortar strength can come up to the stan-dard of 42.5 cement of China.

  17. Parametric study of the potential for BWR ECCS strainer blockage due to LOCA generated debris. Final report

    International Nuclear Information System (INIS)

    This report documents a plant-specific study for a BWR/4 with a Mark I containment that evaluated the potential for LOCA generated debris and the probability of losing long term recirculation capability due ECCS pump suction strainer blockage. The major elements of this study were: (1) acquisition of detailed piping layouts and installed insulation details for a reference BWR; (2) analysis of plant specific piping weld failure probabilities to estimate the LOCA frequency; (3) development of an insulation and other debris generation and drywell transport models for the reference BWR; (4) modeling of debris transport in the suppression pool; (5) development of strainer blockage head loss models for estimating loss of NPSH margin; (6) estimation of core damage frequency attributable to loss of ECCS recirculation capability following a LOCA. Elements 2 through 5 were combined into a computer code, BLOCKAGE 2.3. A point estimate of overall DEGB pipe break frequency (per Rx-year) of 1.59E-04 was calculated for the reference plant, with a corresponding overall ECCS loss of NPSH frequency (per Rx-year) of 1.58E-04. The calculated point estimate of core damage frequency (per Rx-year) due to blockage related accident sequences for the reference BWR ranged from 4.2E-06 to 2.5E-05. The results of this study show that unacceptable strainer blockage and loss of NPSH margin can occur within the first few minutes after ECCS pumps achieve maximum flows when the ECCS strainers are exposed to LOCA generated fibrous debris in the presence of particulates (sludge, paint chips, concrete dust). Generic or unconditional extrapolation of these reference plant calculated results should not be undertaken

  18. Parametric study of the potential for BWR ECCS strainer blockage due to LOCA generated debris. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Zigler, G.; Brideau, J.; Rao, D.V.; Shaffer, C.; Souto, F.; Thomas, W. [Science and Engineering Associates, Inc., Albuquerque, NM (United States)

    1995-10-01

    This report documents a plant-specific study for a BWR/4 with a Mark I containment that evaluated the potential for LOCA generated debris and the probability of losing long term recirculation capability due ECCS pump suction strainer blockage. The major elements of this study were: (1) acquisition of detailed piping layouts and installed insulation details for a reference BWR; (2) analysis of plant specific piping weld failure probabilities to estimate the LOCA frequency; (3) development of an insulation and other debris generation and drywell transport models for the reference BWR; (4) modeling of debris transport in the suppression pool; (5) development of strainer blockage head loss models for estimating loss of NPSH margin; (6) estimation of core damage frequency attributable to loss of ECCS recirculation capability following a LOCA. Elements 2 through 5 were combined into a computer code, BLOCKAGE 2.3. A point estimate of overall DEGB pipe break frequency (per Rx-year) of 1.59E-04 was calculated for the reference plant, with a corresponding overall ECCS loss of NPSH frequency (per Rx-year) of 1.58E-04. The calculated point estimate of core damage frequency (per Rx-year) due to blockage related accident sequences for the reference BWR ranged from 4.2E-06 to 2.5E-05. The results of this study show that unacceptable strainer blockage and loss of NPSH margin can occur within the first few minutes after ECCS pumps achieve maximum flows when the ECCS strainers are exposed to LOCA generated fibrous debris in the presence of particulates (sludge, paint chips, concrete dust). Generic or unconditional extrapolation of these reference plant calculated results should not be undertaken.

  19. Influence of electrified surface of cementitious materials on structure formation of hardened cement paste

    Science.gov (United States)

    Alekseev, A.; Gusakov, A.

    2015-01-01

    To provide high strength and durability of concrete it is necessary to study the influence of physical and chemical and mechanical principles of dispersed cementitious systems. The experimental bench was developed to study the influence of electrified surface of cementitious materials on structure formation of hardened cement paste. The test bench allows accelerating the processes of dissolution of cementing materials in water due to influence of electric discharge on their surface. Cement activation with high-voltage corona discharge when AC current is applied allows increasing the ultimate compressive strength of hardened cement paste by 46% at the age of one day and by 20% at the age of 28 days.

  20. Hydration reactions and ettringite formation in selected cementitious coal conversion by-products

    International Nuclear Information System (INIS)

    Cementitious reactions and ettringite formation, which occur when water is added to high-calcium fly ash, to many dry flue gas desulfurization solids, and to two of the residues from the emerging clean coal technologies, fluidized bed combustion and limestone injection multiphase burner, have been studied. The parameters varied included water to solid ratio and curing time. Crystalline reactants and products were monitored by X-ray powder diffraction. The amount of ettringite, the principal crystalline cementitious reaction product, was determined after three months of curing. In this paper results are discussed in terms of available Ca, Al and S in each by-product and w/s ratio

  1. Method for characterization of the rate of movement of an oxidation front in cementitious materials

    Energy Technology Data Exchange (ETDEWEB)

    Almond, Philip M.; Langton, Christine A.; Stefanko, David B.

    2016-03-01

    Disclosed are methods for determining the redox condition of cementitious materials. The methods are leaching methods that utilize a redox active transition metal indicator that is present in the cementitious material and exhibits variable solubility depending upon the oxidation state of the indicator. When the leaching process is carried out under anaerobic conditions, the presence or absence of the indicator in the leachate can be utilized to determine the redox condition of and location of the oxidation front in the material that has been subjected to the leaching process.

  2. Weathering Effect on 99Tc Leachability from Cementitious Waste Form

    International Nuclear Information System (INIS)

    The mass transfer of contaminants from the solid phase to the waste form pore water, and subsequently out of the solid waste form, is directly related to the number and size distribution of pores as well as the microstructure of the waste form. Because permeability and porosity are controlled by pore aperture size, pore volume, and pore distribution, it is important to have some indication of how these characteristics change in the waste form during weathering. Knowledge of changes in these key parameters can be used to develop predictive models that estimate diffusivity or permeability of radioactive contaminants can be used to develop predictive models that estimate diffusivity or permeability of radioactive contaminants from waste forms for long-term performance assessment. It is known that dissolution or precipitation of amorphous/crystalline phases within waste forms alters their pore structure and controls the transport of contaminants our of waste forms. One very important precipitate is calcite, which is formed as a result of carbonation reactions in cement and other high-alkalinity waste forms. Enhanced oxidation can also increase Tc leachability from the waste form. To account for these changes, weathering experiments were conducted in advance to increase our understating of the long-term Tc leachability, especially out of the cementitious waste form. Pore structure analysis was characterized using both N2 absorption analysis and XMT techniques, and the results show that cementitious waste form is a relatively highly-porous material compared to other waste forms studied in this task, Detailed characterization of Cast Stone chunks and monolith specimens indicate that carbonation reactions can change the Cast Stone pore structure, which in turn may correlate with Tc leachability. Short carbonation reaction times for the Cast Stone causes pore volume and surface area increases, while the average pore diameter decreases. Based on the changes in pore volumes

  3. Mechanical resilience and cementitious processes in Imperial Roman architectural mortar.

    Science.gov (United States)

    Jackson, Marie D; Landis, Eric N; Brune, Philip F; Vitti, Massimo; Chen, Heng; Li, Qinfei; Kunz, Martin; Wenk, Hans-Rudolf; Monteiro, Paulo J M; Ingraffea, Anthony R

    2014-12-30

    The pyroclastic aggregate concrete of Trajan's Markets (110 CE), now Museo Fori Imperiali in Rome, has absorbed energy from seismic ground shaking and long-term foundation settlement for nearly two millenia while remaining largely intact at the structural scale. The scientific basis of this exceptional service record is explored through computed tomography of fracture surfaces and synchroton X-ray microdiffraction analyses of a reproduction of the standardized hydrated lime-volcanic ash mortar that binds decimeter-sized tuff and brick aggregate in the conglomeratic concrete. The mortar reproduction gains fracture toughness over 180 d through progressive coalescence of calcium-aluminum-silicate-hydrate (C-A-S-H) cementing binder with Ca/(Si+Al) ≈ 0.8-0.9 and crystallization of strätlingite and siliceous hydrogarnet (katoite) at ≥ 90 d, after pozzolanic consumption of hydrated lime was complete. Platey strätlingite crystals toughen interfacial zones along scoria perimeters and impede macroscale propagation of crack segments. In the 1,900-y-old mortar, C-A-S-H has low Ca/(Si+Al) ≈ 0.45-0.75. Dense clusters of 2- to 30-µm strätlingite plates further reinforce interfacial zones, the weakest link of modern cement-based concrete, and the cementitious matrix. These crystals formed during long-term autogeneous reaction of dissolved calcite from lime and the alkali-rich scoriae groundmass, clay mineral (halloysite), and zeolite (phillipsite and chabazite) surface textures from the Pozzolane Rosse pyroclastic flow, erupted from the nearby Alban Hills volcano. The clast-supported conglomeratic fabric of the concrete presents further resistance to fracture propagation at the structural scale. PMID:25512521

  4. Mechanical resilience and cementitious processes in Imperial Roman architectural mortar

    Science.gov (United States)

    Landis, Eric N.; Brune, Philip F.; Vitti, Massimo; Chen, Heng; Li, Qinfei; Kunz, Martin; Wenk, Hans-Rudolf; Monteiro, Paulo J. M.; Ingraffea, Anthony R.

    2014-01-01

    The pyroclastic aggregate concrete of Trajan’s Markets (110 CE), now Museo Fori Imperiali in Rome, has absorbed energy from seismic ground shaking and long-term foundation settlement for nearly two millenia while remaining largely intact at the structural scale. The scientific basis of this exceptional service record is explored through computed tomography of fracture surfaces and synchroton X-ray microdiffraction analyses of a reproduction of the standardized hydrated lime–volcanic ash mortar that binds decimeter-sized tuff and brick aggregate in the conglomeratic concrete. The mortar reproduction gains fracture toughness over 180 d through progressive coalescence of calcium–aluminum-silicate–hydrate (C-A-S-H) cementing binder with Ca/(Si+Al) ≈ 0.8–0.9 and crystallization of strätlingite and siliceous hydrogarnet (katoite) at ≥90 d, after pozzolanic consumption of hydrated lime was complete. Platey strätlingite crystals toughen interfacial zones along scoria perimeters and impede macroscale propagation of crack segments. In the 1,900-y-old mortar, C-A-S-H has low Ca/(Si+Al) ≈ 0.45–0.75. Dense clusters of 2- to 30-µm strätlingite plates further reinforce interfacial zones, the weakest link of modern cement-based concrete, and the cementitious matrix. These crystals formed during long-term autogeneous reaction of dissolved calcite from lime and the alkali-rich scoriae groundmass, clay mineral (halloysite), and zeolite (phillipsite and chabazite) surface textures from the Pozzolane Rosse pyroclastic flow, erupted from the nearby Alban Hills volcano. The clast-supported conglomeratic fabric of the concrete presents further resistance to fracture propagation at the structural scale. PMID:25512521

  5. Characterizing saturated mass transport in fractured cementitious materials

    Science.gov (United States)

    Akhavan, Alireza

    Concrete, when designed and constructed properly, is a durable material. However in aggressive environments concrete is prone to gradual deterioration which is due to penetration of water and aggressive agents (e.g., chloride ions) into concrete. As such, the rate of mass transport is the primary factor, controlling the durability of cementitious materials. Some level of cracking is inevitable in concrete due to brittle nature of the material. While mass transport can occur through concrete’s porous matrix, cracks can significantly accelerate the rate of mass transport and effectively influence the service life of concrete structures. To allow concrete service life prediction models to correctly account for the effect of cracks on concrete durability, mass transport thru cracks must be characterized. In this study, transport properties of cracks are measured to quantify the saturated hydraulic permeability and diffusion coefficient of cracks as a function of crack geometry (i.e.; crack width, crack tortuosity and crack wall roughness). Saturated permeability and diffusion coefficient of cracks are measured by constant head permeability test, electrical migration test, and electrical impedance spectroscopy. Plain and fiber reinforced cement paste and mortar as well as simulated crack samples are tested. The results of permeability test showed that the permeability of a crack is a function of crack width squared and can be predicted using Louis formula when crack tortuosity and surface roughness of the crack walls are accounted for. The results of the migration and impedance tests showed that the diffusion coefficient of the crack is not dependent on the crack width, but is primarily a function of volume fraction of cracks. The only parameter that is changing with the crack width is the crack connectivity. Crack connectivity was found to be linearly dependent on crack width for small crack and constant for large cracks (i.e.; approximately larger than 80 µm). The

  6. Mechanisms of cementitious material deterioration in biogas digester.

    Science.gov (United States)

    Voegel, C; Bertron, A; Erable, B

    2016-11-15

    Digesters produce biogas from organic wastes through anaerobic digestion processes. These digesters, often made of concrete, suffer severe premature deterioration caused mainly by the presence of fermentative microorganisms producing metabolites that are aggressive towards cementitious materials. To clarify the degradation mechanisms in an anaerobic digestion medium, ordinary Portland cement paste specimens were immersed in the liquid fraction of a running, lab-scale digester for 4weeks. The anaerobic digestion medium was a mixture of a biowaste substrate and sludge from municipal wastewater treatment plant used as a source of anaerobic bacteria. The chemical characteristics of the anaerobic digestion liquid phase were monitored over time using a pH metre, high performance liquid chromatography (HPLC) and ion chromatography (HPIC). An initial critical period of low pH in the bioreactors was observed before the pH stabilized around 8. Acetic, propionic and butyric acids were produced during the digestion with a maximum total organic acid concentration of 50mmolL(-1). The maximum ammonium content of the liquid phase was 40mmolL(-1), which was about seven times the upper limit of the highly aggressive chemical environment class (XA3) as defined by the European standard for the specification of concrete design in chemically aggressive environments (EN 206). The changes in the mineralogical, microstructural and chemical characteristics of the cement pastes exposed to the solid and liquid phase of the digesters were analysed at the end of the immersion period by X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectrometry (EDS) and electron-probe micro-analysis (EPMA). A 700-μm thick altered layer was identified in the cement paste specimens. The main biodeterioration patterns in the bioreactors' solid/liquid phase were calcium leaching and carbonation of the cement matrix. PMID:27432729

  7. Bond strength of cementitious borehole plugs in welded tuff

    International Nuclear Information System (INIS)

    Axial loads on plugs or seals in an underground repository due to gas, water pressures and temperature changes induced subsequent to waste and plug emplacement lead to shear stresses at the plug/rock contact. Therefore, the bond between the plug and rock is a critical element for the design and effectiveness of plugs in boreholes, shafts or tunnels. This study includes a systematic investigation of the bond strength of cementitious borehole plugs in welded tuff. Analytical and numerical analysis of borehole plug-rock stress transfer mechanics is performed. The interface strength and deformation are studied as a function of Young's modulus ratio of plug and rock, plug length and rock cylinder outside-to-inside radius ratio. The tensile stresses in and near an axially loaded plug are analyzed. The frictional interface strength of an axially loaded borehole plug, the effect of axial stress and lateral external stress, and thermal effects are also analyzed. Implications for plug design are discussed. The main conclusion is a strong recommendation to design friction plugs in shafts, drifts, tunnels or boreholes with a minimum length to diameter ratio of four. Such a geometrical design will reduce tensile stresses in the plug and in the host rock to a level which should minimize the risk of long-term deterioration caused by excessive tensile stresses. Push-out tests have been used to determine the bond strength by applying an axial load to cement plugs emplaced in boreholes in welded tuff cylinders. A total of 130 push-out tests have been performed as a function of borehole size, plug length, temperature, and degree of saturation of the host tuff. The use of four different borehole radii enables evaluation of size effects. 119 refs., 42 figs., 20 tabs

  8. Long-Term Technetium Interactions With Reducing Cementitious Materials

    International Nuclear Information System (INIS)

    Technetium is among the key risk drivers at the Saltstone Facility. The way that it is immobilized in this cementitious waste form is by converting its highly mobile Tc(VII) form to a much less mobile Tc(IV) form through reduction by the cement's blast furnace slag. This report includes a review of published data and experimental results dealing with Tc leaching from Portland cement waste forms. The objectives for the literature study were to document previous reports of Tc interactions with slag-containing cementitious materials. The objectives for the laboratory study were to measure Tc-saltstone Kd values under reducing conditions. From the literature it was concluded: (1) Spectroscopic evidence showed that when Tc(IV) in a slag-cement was exposed to an oxidizing environment, it will convert to the more mobile Tc(VII) species within a short time frame, 2.5 years. (2) SRS saltstone will reduce Tc(VII) in the absence of NaS or sodium dithionite in a reducing atmosphere. (3) Only trace concentrations of atmospheric oxygen (30 to 60 ppm O2; Eh 120 mV) at the high pH levels of cementitious systems is required to maintain Tc as Tc(VII). (4) Experimental conditions must be responsible for wide variability of measured Kd values, such that they are either very low, ∼1 mL/g, or they are very high ∼1000 mL/g, suggesting that Tc(VII) or Tc(IV) dominate the systems. Much of this variability appears to be the result of experimental conditions, especially direct controls of oxygen contact with the sample. (5) A field study conducted at SRS in the 1980s indicated that a slag-saltstone immobilized Tc for 2.5 years. Below background concentrations of Tc leached out of the slag-containing saltstone, whereas Tc leached out of the slag-free saltstone at the rate of nitrate loss. One possible explanation for the immobilization of Tc in this study was that the slag-saltstone maintained reducing conditions within the core of the 55-gallon sample, whereas in the small-scale lab

  9. Cementitious Grout for Closing SRS High Level Waste Tanks - 12315

    International Nuclear Information System (INIS)

    In 1997, the first two United States Department of Energy (US DOE) high level waste tanks (Tanks 17-F and 20-F: Type IV, single shell tanks) were taken out of service (permanently closed) at the Savannah River Site (SRS). In 2012, the DOE plans to remove from service two additional Savannah River Site (SRS) Type IV high-level waste tanks, Tanks 18-F and 19-F. These tanks were constructed in the late 1950's and received low-heat waste and do not contain cooling coils. Operational closure of Tanks 18-F and 19-F is intended to be consistent with the applicable requirements of the Resource Conservation and Recovery Act (RCRA) and the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) and will be performed in accordance with South Carolina Department of Health and Environmental Control (SCDHEC). The closure will physically stabilize two 4.92E+04 cubic meter (1.3 E+06 gallon) carbon steel tanks and isolate and stabilize any residual contaminants left in the tanks. Ancillary equipment abandoned in the tanks will also be filled to the extent practical. A Performance Assessment (PA) has been developed to assess the long-term fate and transport of residual contamination in the environment resulting from the operational closure of the F-Area Tank Farm (FTF) waste tanks. Next generation flowable, zero-bleed cementitious grouts were designed, tested, and specified for closing Tanks 18-F and 19-F and for filling the abandoned equipment. Fill requirements were developed for both the tank and equipment grouts. All grout formulations were required to be alkaline with a pH of 12.4 and to be chemically reducing with a reduction potential (Eh) of -200 to -400. Grouts with this chemistry stabilize potential contaminants of concern. This was achieved by including Portland cement and Grade 100 slag in the mixes, respectively. Ingredients and proportions of cementitious reagents were selected and adjusted to support the mass placement strategy developed by

  10. Synthesis of a Cementitious Material Nanocement Using Bottom-Up Nanotechnology Concept: An Alternative Approach to Avoid CO2 Emission during Production of Cement

    Directory of Open Access Journals (Sweden)

    Byung Wan Jo

    2014-01-01

    Full Text Available The world’s increasing need is to develop smart and sustainable construction material, which will generate minimal climate changing gas during their production. The bottom-up nanotechnology has established itself as a promising alternative technique for the production of the cementitious material. The present investigation deals with the chemical synthesis of cementitious material using nanosilica, sodium aluminate, sodium hydroxide, and calcium nitrate as reacting phases. The characteristic properties of the chemically synthesized nanocement were verified by the chemical composition analysis, setting time measurement, particle size distribution, fineness analysis, and SEM and XRD analyses. Finally, the performance of the nanocement was ensured by the fabrication and characterization of the nanocement based mortar. Comparing the results with the commercially available cement product, it is demonstrated that the chemically synthesized nanocement not only shows better physical and mechanical performance, but also brings several encouraging impacts to the society, including the reduction of CO2 emission and the development of sustainable construction material. A plausible reaction scheme has been proposed to explain the synthesis and the overall performances of the nanocement.

  11. Geochemical performance evaluation and characterization of a potential cementitious repository sealing material for application in the Topopah Spring tuff NNWSI investigations

    International Nuclear Information System (INIS)

    Preliminary geochemical evaluations of some portland cement based materials have been made in Nevada Nuclear Waste Storage Investigations (NNWSI), for possible nuclear waste repository sealing applications in welded tuff focused in the Yucca Mountain area. Portland cement based sealing materials have been evaluated in the NNWSI for possible sealing applications in a nuclear waste repository in the Topopah Spring tuff member. Cementitious sealing materials developed for long-term stability should be as nearly as possible in thermodynamic equilibrium with the host rock, or any disequilibrium should not have negative impact upon the integrity of the host rock. A primary step in achieving this equilibrium condition is to minimize the chemical potential between the sealant and the host rock. Two different approaches were evaluated to achieve this compatibility. The one approach utilized indigenous materials for the formulation of the concrete and the other utilized reactive admixtures to adjust the bulk chemical composition of the concrete formulation to approximate the local rock bulk chemistry. Testing of both formulations at conditions that represented the maximum credible temperature and pressure conditions of a repository were completed and show that the use of an indigenous tuff in the formulation without adjusting the matrix chemistry caused alterations which might compromise the performance of the concrete. In contrast, the chemically adjusted cementitious formulation exhibited minimal alteration in the J-13 groundwater of the designed test. 3 refs., 2 figs., 4 tabs

  12. THERMALLY CONDUCTIVE CEMENTITIOUS GROUTS FOR GEOTHERMAL HEAT PUMPS. PROGRESS REPORT BY 1998

    Energy Technology Data Exchange (ETDEWEB)

    ALLAN,M.L.; PHILIPPACOPOULOS,A.J.

    1998-11-01

    Research commenced in FY 97 to determine the suitability of superplasticized cement-sand grouts for backfilling vertical boreholes used with geothermal heat pump (GHP) systems. The overall objectives were to develop, evaluate and demonstrate cementitious grouts that could reduce the required bore length and improve the performance of GHPs. This report summarizes the accomplishments in FY 98.

  13. Design of microcapsule system used for self-healing cementitious material

    NARCIS (Netherlands)

    Zhang, M.; Han, N.; Xing, F.; Schlangen, H.E.J.G.

    2013-01-01

    For a microcapsule based self-healing system in the cementitious material, a fundamental issue is to find and facilitate a suitable microcapsule system, concerning either the material selection or design and manufacture process. In this study, urea formaldehyde resin is used for the shell of microca

  14. Predicting the Probability of Failure of Cementitious Sewer Pipes Using Stochastic Finite Element Method

    Directory of Open Access Journals (Sweden)

    Amir M. Alani

    2015-06-01

    Full Text Available In this paper, a stochastic finite element method (SFEM is employed to investigate the probability of failure of cementitious buried sewer pipes subjected to combined effect of corrosion and stresses. A non-linear time-dependant model is used to determine the extent of concrete corrosion. Using the SFEM, the effects of different random variables, including loads, pipe material, and corrosion on the remaining safe life of the cementitious sewer pipes are explored. A numerical example is presented to demonstrate the merit of the proposed SFEM in evaluating the effects of the contributing parameters upon the probability of failure of cementitious sewer pipes. The developed SFEM offers many advantages over traditional probabilistic techniques since it does not use any empirical equations in order to determine failure of pipes. The results of the SFEM can help the concerning industry (e.g., water companies to better plan their resources by providing accurate prediction for the remaining safe life of cementitious sewer pipes.

  15. Predicting the Probability of Failure of Cementitious Sewer Pipes Using Stochastic Finite Element Method.

    Science.gov (United States)

    Alani, Amir M; Faramarzi, Asaad

    2015-06-01

    In this paper, a stochastic finite element method (SFEM) is employed to investigate the probability of failure of cementitious buried sewer pipes subjected to combined effect of corrosion and stresses. A non-linear time-dependant model is used to determine the extent of concrete corrosion. Using the SFEM, the effects of different random variables, including loads, pipe material, and corrosion on the remaining safe life of the cementitious sewer pipes are explored. A numerical example is presented to demonstrate the merit of the proposed SFEM in evaluating the effects of the contributing parameters upon the probability of failure of cementitious sewer pipes. The developed SFEM offers many advantages over traditional probabilistic techniques since it does not use any empirical equations in order to determine failure of pipes. The results of the SFEM can help the concerning industry (e.g., water companies) to better plan their resources by providing accurate prediction for the remaining safe life of cementitious sewer pipes. PMID:26068092

  16. Research Progresses of New Type Alkali-activated Cementitious Material Catalyst

    Directory of Open Access Journals (Sweden)

    ZHANG Yao-Jun, YANG Meng-Yang, KANG Le, ZHANG Li, ZHANG Ke

    2016-03-01

    Full Text Available Alkali-activated solid aluminosilicate-based cementitious material is one of prospective research fields of advanced inorganic non-metallic materials. Its classification, preparation process, formation mechanism, and potential applications are reviewed in this paper. It is considered that its microstructure and chemical characteristics intensively depend on the raw materials and synthesis conditions. Geopolymers derive from alkali-activated metakaolin or fly ash with low calcium content, while the amorphous calcium silicate hydrate (C-S-H gels root in the chemical-activated solid wastes of granular blast furnace slag, steel slag and other solid aluminosilicate wastes with high calcium contents. Even though durability of alkali-activated cementitious materials as the building structure materials has been widely studied in the past decades, the intrinsic brittleness still restricts their applications in the field of civil and building engineering. Therefore, exploration of a new applied approach is by far the best option. In recent years, many researches report that the alkali-activated cementitious materials are used as novel precursors and catalysts for some kinds of heterogeneous reactions. The latest research progresses on alkali-activated cementitious material-based catalysts are discussed.

  17. Behaviour of cementitious materials: sulfates and temperature actions

    International Nuclear Information System (INIS)

    The research work presented in this Ph.D. thesis is related to the nuclear waste underground repository concept. Concrete could be used in such a repository, and would be subjected to variations of temperature in presence of sulfate, a situation that could induce expansion of concrete. The research was lead in three parts: an experimental study of the possibility of an internal sulfate attack on mortars; an experimental study and modeling of the chemical equilibriums of the CaO-SiO2-Al2O3-SO3-H2O system; and a modeling of the mechanisms of internal and external sulfate attacks, and the effect of temperature. The results show that mortars can develop expansions after a steam-cure during hydration, but also when a long steam-cure is applied to one-year-old mortars, which is a new point. Ettringite precipitation can be considered as responsible for these expansions. The experimental study of the CaO-SiO2-Al2O3-SO3-H2O system clarified the role of Calcium Silicate Hydrates (C-S-H) on chemical equilibriums of cementitious materials. Sulfate sorption on C-S-H has been studied in detail. The quantity of sulfate bound to the C-S-H mainly depends on the sulfate concentration in solution, on the Ca/Si ratio of the C-S-H and is not significantly influenced by temperature. Aluminium inclusion in the C-S-H seems to be a significant phenomenon. Temperature increases the calcium sulfo-aluminate solubilities and thus increases sulfates concentration in solution. A modeling of the chemical system is proposed. Simulations of external sulfate attack (15 mmol/L of Na2SO4) predict ettringite precipitation at 20 and 85±C. Simulation of internal sulfate attack was performed at a local scale (a hydrated cement grain). An initial inhomogeneity can lead, after a thermal curing at 85±C, to ettringite precipitation in zones originally free from ettringite. This new-formed ettringite could be the origin of the expansions. (author)

  18. Evolution of 99Tc Species in Cementitious Nuclear Waste Form

    International Nuclear Information System (INIS)

    Technetium (Tc) is produced in large quantities as a fission product during the irradiation of 235U-enriched fuel for commercial power production and plutonium genesis for nuclear weapons. The most abundant isotope of Tc present in the wastes is 99Tc because of its high fission yield (∼6%) and long half-life (2.13x105 years). During the Cold War era, generation of fissile 239Pu for use in America's atomic weapons arsenal yielded nearly 1900 kg of 99Tc at the U.S. Department of Energy's (DOE) Hanford Site in southeastern Washington State. Most of this 99Tc is present in fuel reprocessing wastes temporarily stored in underground tanks awaiting retrieval and permanent disposal. After the wastes are retrieved from the storage tanks, the bulk of the high-level waste (HLW) and lowactivity waste (LAW) stream is scheduled to be converted into a borosilicate glass waste form that will be disposed of in a shallow burial facility called the Integrated Disposal Facility (IDF) at the Hanford Site. Even with careful engineering controls, volatilization of a fraction of Tc during the vitrification of both radioactive waste streams is expected. Although this volatilized Tc can be captured in melter off-gas scrubbers and returned to the melter, some of the Tc is expected to become part of the secondary waste stream from the vitrification process. The off-gas scrubbers downstream from the melters will generate a high pH, sodium-ammonium carbonate solution containing the volatilized Tc and other fugitive species. Effective and cost-efficient disposal of Tc found in the off-gas scrubber solution remains difficult. A cementitious waste form (Cast Stone) is one of the nuclear waste form candidates being considered to solidify the secondary radioactive liquid waste that will be generated by the operation of the waste treatment plant (WTP) at the Hanford Site. Because Tc leachability from the waste form is closely related with Tc speciation or oxidation state in both the simulant and

  19. Safety evaluation report on Westinghouse Electric Company ECCS evaluation model for plants equipped with upper head injection

    International Nuclear Information System (INIS)

    For plants which include an ice condenser containment concept, Westinghouse has planned an additional safety system known as the upper head injection (UHI) system to augment the emergency core cooling system. This system is comprised of additional accumulator tanks and piping arranged to supply cooling water to the top of the core during the blowdown period following a postulated large-break loss-of-coolant accident (LOCA). The objective of UHI is to add to the core cooling provided by the conventional emergency core cooling system (ECCS) and so permit operation at linear heat rates comparable to those permitted in plants utilizing the dry containment concept. In this way, plants which include the UHI system would have greater operating flexibility while still meeting the acceptance criteria as defined in paragraph 50.46 of 10 CFR Part 50. This review is concerned with those changes to the Westinghouse ECCS evaluation model that have been proposed for the UHI-LOCA model

  20. Comparison of Long Term Tropospheric Ozone Trends Measured by Lidar and ECC Ozonesondes from 1991 to 2010 in Southern France

    Science.gov (United States)

    Ancellet, G.; Gaudel, A.; Godin-Beekmann, S.

    2016-06-01

    ECC (Electrochemical Concentration Cell) ozonesondes and UV DIAL (Differential Absorption Lidar) measurements have been carried out simultaneously at OHP (Observatoire de Haute Provence, 44°N, 6.7°E, 690 m) since 1991. A unique long-term trend assessment by two different instruments operated routinely at the same location is possible. Air mass trajectories have been calculated for all the ozone observations available at OHP. The bias between the seasonal mean calculated with lidar and ECC ozone vertical profiles for 4 timeperiods of 5 years is 0.6 ppbv in the free troposphere (4-8 km). Larger differences (> 10 ppbv) are explained by the need for clear sky conditions during lidar observations. The measurements of both instruments have been combined to decrease the impact of short-term atmospheric variability on the trend estimate.

  1. Experiment data report for semiscale Mod-1 test S-04-1 (baseline ECC test)

    International Nuclear Information System (INIS)

    Recorded test data are presented for Test S-04-1 of the Semiscale Mod-1 Baseline ECC Test Series. This test is among several Semiscale Mod-1 experiments conducted to investigate the thermal and hydraulic phenomena accompanying a hypothesized loss-of-coolant accident in a pressurized water reactor system. Test S-04-1 was conducted from an initial cold leg fluid temperature of 5420F and an initial pressure of 2,263 psia. A simulated double-ended offset shear cold leg break was used to investigate the system response to a depressurization and reflood transient using system volume scaled coolant injection parameters. System flow was set to achieve a core fluid temperature differential of 660F at a full core power of 1.6 MW. The flow resistance of the intact loop was based on core area scaling. An electrically heated core with a flat radial power profile was used in the pressure vessel to simulate the effects of a nuclear core. During system depressurization, core power was reduced from the initial level of 1.6 MW in such a manner as to simulate the surface heat flux response of nuclear fuel rods until such time that departure from nucleate boiling might occur. Blowdown to the pressure suppression system was accompanied by simulated emergency core cooling injection into both the intact and broken loops. Coolant injection was continued until test termination at 200 seconds after initiation of blowdown

  2. Estimated net value and uncertainty for automating ECCS switchover at PWRs

    Energy Technology Data Exchange (ETDEWEB)

    Walsh, B.; Brideau, J.; Comes, L.; Darby, J.; Guttmann, H.; Sciacca, F.; Souto, F.; Thomas, W.; Zigler, G. [Science and Engineering Associates, Inc., Albuquerque, NM (United States)

    1996-02-01

    Question for resolution of Generic Safety Issue No. 24 is whether or not PWRs that currently rely on a manual system for ECCS switchover to recirculation should be required to install an automatic system. Risk estimates are obtained by reevaluating the contributions to core damage frequencies (CDFs) associated with failures of manual and semiautomatic switchover at a representative PWR. This study considers each separate instruction of the corresponding emergency operating procedures (EOPs), the mechanism for each control, and the relation of each control to its neighbors. Important contributions to CDF include human errors that result in completely coupled failure of both trains and failure to enter the required EOP. It is found that changeover to a semiautomatic system is not justified on the basis of cost-benefit analysis: going from a manual to a semiautomatic system reduces the CDF by 1.7 {times} 10{sup {minus}5} per reactor-year, but the probability that the net cost of the modification being less than $1, 000 per person-rem is about 20% without license renewal. Scoping analyses, using optimist assumptions, were performed for a changeover to a semiautomatic system with automatic actuation and to a fully automatic system; in these cases the probability of a net cost being less than $1,000/person-rem is about 50% without license renewal and over 95% with license renewal.

  3. Implementation and verification of different ECC mitigation designs for BRAMs in flash-based FPGAs

    Science.gov (United States)

    Yang, Zhen-Lei; Wang, Xiao-Hui; Zhang, Zhan-Gang; Liu, Jie; Su, Hong

    2016-04-01

    Embedded RAM blocks (BRAMs) in field programmable gate arrays (FPGAs) are susceptible to single event effects (SEEs) induced by environmental factors such as cosmic rays, heavy ions, alpha particles and so on. As technology scales, the issue will be more serious. In order to tackle this issue, two different error correcting codes (ECCs), the shortened Hamming codes and shortened BCH codes, are investigated in this paper. The concrete design methods of the codes are presented. Also, the codes are both implemented in flash-based FPGAs. Finally, the synthesis report and simulation results are presented in the paper. Moreover, heavy-ion experiments are performed, and the experimental results indicate that the error cross-section of the device using the shortened Hamming codes can be reduced by two orders of magnitude compared with the device without mitigation, and no errors are discovered in the experiments for the device using the shortened BCH codes. Supported by National Natural Science Foundation of China (11079045, 11179003 and 11305233)

  4. Estimated net value and uncertainty for automating ECCS switchover at PWRs

    International Nuclear Information System (INIS)

    Question for resolution of Generic Safety Issue No. 24 is whether or not PWRs that currently rely on a manual system for ECCS switchover to recirculation should be required to install an automatic system. Risk estimates are obtained by reevaluating the contributions to core damage frequencies (CDFs) associated with failures of manual and semiautomatic switchover at a representative PWR. This study considers each separate instruction of the corresponding emergency operating procedures (EOPs), the mechanism for each control, and the relation of each control to its neighbors. Important contributions to CDF include human errors that result in completely coupled failure of both trains and failure to enter the required EOP. It is found that changeover to a semiautomatic system is not justified on the basis of cost-benefit analysis: going from a manual to a semiautomatic system reduces the CDF by 1.7 x 10-5 per reactor-year, but the probability that the net cost of the modification being less than $1, 000 per person-rem is about 20% without license renewal. Scoping analyses, using optimist assumptions, were performed for a changeover to a semiautomatic system with automatic actuation and to a fully automatic system; in these cases the probability of a net cost being less than $1,000/person-rem is about 50% without license renewal and over 95% with license renewal

  5. The latitudinal distribution of ozone to 35 km altitude from ECC ozonesonde observations, 1982-1990

    Science.gov (United States)

    Komhyr, W. D.; Oltmans, S. J.; Lathrop, J. A.; Kerr, J. B.; Matthews, W. A.

    1994-01-01

    Electrochemical concentration cell (ECC) ozone-sonde observations, made in recent years at ten stations whose locations range from the Arctic to Antarctica, have yielded a self-consistent ozone data base from which mean seasonal and annual latitudinal ozone vertical distributions to 35 km have been derived. Ozone measurement uncertainties are estimated, and results are presented in the Bass-Paur (1985) ozone absorption coefficient scale adopted for use with Dobson ozone spectrophotometers January 1, 1992. The data should be useful for comparison with model calculations of the global distribution of atmospheric ozone, for serving as apriori statistical information in deriving ozone vertical distributions from satellite and Umkehr observations, and for improving the satellite and Umkehr ozone inversion algorithms. Attention is drawn to similar results based on a less comprehensive data set published in Ozone in the Atmosphere, Proceedings of the 1988 Quadrennial Ozone Symposium where errors in data tabulations occurred for three of the stations due to inadvertent transposition of ozone partial pressure and air temperature values.

  6. Xilinx and Modelsim Habitat for Design of ECC Co-Processor Architecture

    Directory of Open Access Journals (Sweden)

    B.MuthuKumar

    2012-04-01

    Full Text Available Xilinx is a most significant synthesizing tool for controller design in various engineering field specifically industrial engineering, instrumentation engineering, robotics, telecommunication, computer science engineering etc. To verify the working functionality of devices in these engineering fields, Modelsim simulator is preferred, where the other synthesizing tools are Lattice, Altera, Actel etc. ALDEC simulator and ISE simulators are competitors of Modelsim. Uncomplicated implementation of the device, dynamic powercalculation, trouble-free verification of functionality and energetic area calculation can be achieved charmingly in Xilinx and Modelsim compared to their competitors. Architecture of any very large scale integration (VLSI design, the Xilinx and Modelsim play an imperative role to achieve the hardware efficiency of the design andfunctionality verification of the design. This paper establishes how these tools create a habitat for designing architecture, by explaining the typical steps involved in elliptic curve cryptography (ECC processor using Modelsim 5.7 and Xilinx 9.2i. The performance measure options viz. the hardware efficiency, functionalityefficiency, area and power calculations are also explored.

  7. Status and direction of safety evaluation on ECCS recirculation sump clogging issue

    International Nuclear Information System (INIS)

    Debris clogging of containment recirculation sump can be a significant challenge on long term cooling following the design basis accidents such as Loss-of-Coolant Accident (LOCA) requiring a long term recirculation operation of Emergency Core Cooling System (ECCS) and Containment Spray System (CSS). In the present study, aiming at the development of regulatory capability to evaluate the safety related to the sump clogging issue in the domestic Nuclear Power Plants (NPP), the status and trend in the regulation and research on the issue in foreign countries were reviewed and investigated and the status of Korean NPP was also evaluated. The direction and the basic framework to develop the regulatory guidance and demonstrative analysis method as part of safety evaluation were proposed. The obtained conclusions are as follows: First, the sump clogging is an issue with high potential for the domestic operating NPP, thus, it required the proper plant capability which can be achieved by design change and procedural change. Such a capability should be developed by the conservative evaluation considering the plant-specific design features and using the proven technology. Second, the regulatory guidance and the demonstrative analysis method should be developed with a basis of the proposed framework for through the effort in the next step. The output would be guidance for the licensee's effort in resolving the issue including the issue evaluation and identification of the improvements

  8. Robust ECC-based authenticated key agreement scheme with privacy protection for Telecare medicine information systems.

    Science.gov (United States)

    Zhang, Liping; Zhu, Shaohui

    2015-05-01

    To protect the transmission of the sensitive medical data, a secure and efficient authenticated key agreement scheme should be deployed when the healthcare delivery session is established via Telecare Medicine Information Systems (TMIS) over the unsecure public network. Recently, Islam and Khan proposed an authenticated key agreement scheme using elliptic curve cryptography for TMIS. They claimed that their proposed scheme is provably secure against various attacks in random oracle model and enjoys some good properties such as user anonymity. In this paper, however, we point out that any legal but malicious patient can reveal other user's identity. Consequently, their scheme suffers from server spoofing attack and off-line password guessing attack. Moreover, if the malicious patient performs the same time of the registration as other users, she can further launch the impersonation attack, man-in-the-middle attack, modification attack, replay attack, and strong replay attack successfully. To eliminate these weaknesses, we propose an improved ECC-based authenticated key agreement scheme. Security analysis demonstrates that the proposed scheme can resist various attacks and enables the patient to enjoy the remote healthcare services with privacy protection. Through the performance evaluation, we show that the proposed scheme achieves a desired balance between security and performance in comparisons with other related schemes. PMID:25732081

  9. Study on the alteration of hydrogeological and mechanical properties of the cementitious Material. 3

    International Nuclear Information System (INIS)

    We experimentally investigated the influence of several phenomena at the disposal environment, to evaluate the long-term alteration of cementitious material. The results are shown below. 1. Hardened cement paste specimens were altered and characterized after artificial seawater permeation. The calcium dissolution was accelerated, and secondary minerals containing magnesium were deposited. The permeability became one to three orders of magnitude smaller than data from specimens altered by deionized water permeation. It was estimated that secondary mineral formations reduced the permeability. These results meant that seawater and pure water differ remarkably from each other in influence to alteration of cementitious material. 2. Two type mixture proportions concrete, two type mixture proportions mortar and a cement paste under same W/C ratio 55% were characterized, to apply the accumulated data of paste to concrete or mortar. Compressive strength of paste was lower than that of concrete and mortar. It was contrary to the previous report. The behavior of Young's modulus and Poisson's ratio could be explained well using amount of aggregate. The data of permeability meant that boundary between aggregate and cement paste didn't become path of water flow, and that aggregate disturbed permeation. 3. Self-sealing property of cracked specimen of cementitious material were investigated by the water permeation test using sodium bicarbonate solution. The permeability decreased in two orders of magnitude, and possibility of sealing was suggested. By the morphology, the deposits in the cracks might be portlandite and C-S-H, and be not calcium carbonate. 4. Alteration of characteristics of cementitious material in sodium-nitrate and ammonia solution was evaluated by the water permeation test. Alteration degree of the nitrate and ammonia solution case showed similar trend to that of the sodium nitrate solution case. This result meant that ammonia solution would not influence the

  10. UPTF-TRAM test A3. Turn-over of the hot-leg injected ECC in the steam generator direction

    International Nuclear Information System (INIS)

    The UPTF TRAM test A3 was a separate effects test to investigate the interaction between the hot leg-injected ECC and the single-phase or two-phase natural circulation in the hot leg in the case of an SBLOCA in a PWR. The experimental investigation of 7 runs was mainly concentrated on the following phenomena: - Transport of hot leg injected ECC water to the upper plenum or in the direction of steam generator, depending on the loop mass flow, -Utilization of the condensation potential of ECC water, - Mixing of the saturated water with the ECC water, - Effect of hot leg injection on the flow phenomena in the hot leg, - Effect of pressure (3 and 15 bar) on the scaling and hence the verification of the scaling concept applied. A preliminary evaluation of the test is presented in the Quick Look Report. (orig.)

  11. Performance Verification of the Lattice-type ECCS Sump Strainer to Prevent the Thin-bed effect

    International Nuclear Information System (INIS)

    In the event of a Loss of Coolant Accident (LOCA), a variety of debris could be generated under the post-LOCA conditions. The debris could block the Emergency Core Cooling System (ECCS) sump strainer, leading to a considerable head loss which in turn causes an abnormal ECCS and/or CS pump performance. The determination of strainer capacity is very important through the optimization of the head loss due to debris blockage. Especially, the thin-bed effect is a dominant factor to the design of the strainer. This paper presents experimental head loss data to confirm an advantage of an advanced lattice-type strainer for the thin-bed effect and is compared to the results of NUREG/CR-6224 head loss correlation. The thin-bed effect is a dominant design factor because the head loss could increase drastically by the lack of available voids in the debris bed for coolant to pass through it. Though this study, the lattice-type strainer to reduce or prevent the thin-bed effect has been designed. As the experimental data shows, there is no thin-bed effect in the present lattice-type strainer. It is expected that the required capacity of the strainer to maintain the function of ECCS will be significantly reduced by the lattice-type strainer of the present study

  12. Effects of high temperature ECC injection on small and large break BWR LOCA simulation tests in ROSA-III program (RUNs 940 and 941)

    International Nuclear Information System (INIS)

    The ROSA-III program, of which principal results are summarized in a report of JAERI 1307, conducted small and large-break loss-of-coolant experiments (RUNs 940 and 941) with high water temperature of the emergency core cooling system (ECCS) are one of the parametric study with respect to the ECCS effect on core cooling. This report presents all the experiment results of these two tests and describes additional finding with respect to the hot ECC effects on core cooling phenomena. By comparing these two tests (water temperature of 393 K) with the standard ECC tests of RUNs 922 and 926 (water temperature of 313 K), it was found that the ECC subcooling variation had a small influence on the core cooling phenomena in 5 % small break tests but had larger influence on them in 200 % break tests. The ECC subcooling effects described in the previous report are reviewed and the temperature distribution in the pressure vessel is investigated for these four tests. (author)

  13. Experimental and theoretical study for the multidimensional phenomena of the ECC bypass in the DVI system downcomer during reflood phase of the LBLOCA

    Energy Technology Data Exchange (ETDEWEB)

    Song, Chul Hwa; Cho, Hyoung Kyu; Yun, Byong Jo; Euh, Dong Jin; Kwon, Tae Soon

    2005-02-01

    In the present study, a new scaling methodology, 'Modified Linear Scaling', was developed which can reproduce the multidimensional ECC behaviors in the DVI system downcomer and its applicability was experimentally and analytically evaluated. An exploratory test was performed to identify the mechanism and flow patterns of the ECC bypass and to investigate the effect of the downcomer geometry on the ECC bypass. Based on the observation results, an analysis for the two-dimensional film flow was conducted, which was found to the dominant flow regime in the DVI system downcomer and it introduced the Wallis parameters as the major scaling parameters of the direct ECC bypass. From the experiments and analysis, scaling requirements of the multidimensional phenomena were derived that the aspect ratio of the test facility and the film spreading width of the ECC should be preserved in the proto and reduced model. The modified linear scaling was developed which can satisfy the scaling requirements from the two-dimensional two-fluid equations and some important phenomena, which may not be fully represented by the equations, were additionally analyzed as a local phenomena scaling. The applicability of the scaling methodology is experimentally and analytically evaluated from the separate effect tests for the direct ECC bypass and sweep-out in various scales of the test sections and the developed analytical models.

  14. Flexural strengthening of masonry members using advanced cementitious materials

    OpenAIRE

    Barros, Joaquim A. O.; Esmaeeli, Esmaeel; Manning, Elizabeth; Häßler, D.

    2011-01-01

    Two different cement based fiber reinforced composites for the flexural strengthening of masonry beams under monotonic loading are studied. Steel Fiber Reinforced Self- Compacting Concrete (SFRSCC) with tensile strain-softening behavior, and PVA fiber reinforced cement based mortar (SHCC) with tensile Strain-Hardening were the developed composites. Both composites were applied on the tensile surface of masonry beams and the effectiveness of this technique for the flexural stren...

  15. Development and Demonstration of Material Properties Database and Software for the Simulation of Flow Properties in Cementitious Materials

    Energy Technology Data Exchange (ETDEWEB)

    Smith, F. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Flach, G. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-03-30

    This report describes work performed by the Savannah River National Laboratory (SRNL) in fiscal year 2014 to develop a new Cementitious Barriers Project (CBP) software module designated as FLOExcel. FLOExcel incorporates a uniform database to capture material characterization data and a GoldSim model to define flow properties for both intact and fractured cementitious materials and estimate Darcy velocity based on specified hydraulic head gradient and matric tension. The software module includes hydraulic parameters for intact cementitious and granular materials in the database and a standalone GoldSim framework to manipulate the data. The database will be updated with new data as it comes available. The software module will later be integrated into the next release of the CBP Toolbox, Version 3.0. This report documents the development efforts for this software module. The FY14 activities described in this report focused on the following two items that form the FLOExcel package; 1) Development of a uniform database to capture CBP data for cementitious materials. In particular, the inclusion and use of hydraulic properties of the materials are emphasized; and 2) Development of algorithms and a GoldSim User Interface to calculate hydraulic flow properties of degraded and fractured cementitious materials. Hydraulic properties are required in a simulation of flow through cementitious materials such as Saltstone, waste tank fill grout, and concrete barriers. At SRNL these simulations have been performed using the PORFLOW code as part of Performance Assessments for salt waste disposal and waste tank closure.

  16. Photovoltaic's silica-rich waste sludge as supplementary cementitious material (SCM)

    International Nuclear Information System (INIS)

    Waste sludge, a solid recovered from wastewater of photovoltaic-industries, composes of agglomerates of nano-particles like SiO2 and CaCO3. This sludge deflocculates in aqueous solutions into nano-particles smaller than 1 μm. Thus, this sludge constitutes a potentially hazardous waste when it is improperly disposed. Due to its high content of amorphous SiO2, this sludge has a potential use as supplementary cementitious material (SCM) in concrete. In this study the main properties of three different samples of photovoltaic's silica-rich waste sludge (nSS) were physically and chemically characterized. The characterization techniques included: scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), nitrogen physical adsorption isotherm (BET method), density by Helium pycnometry, particle size distribution determined by laser light scattering (LLS) and zeta-potential measurements by dynamic light scattering (DLS). In addition, a dispersability study was performed to design stable slurries to be used as liquid additives for the concrete production on site. The effects on the hydration kinetics of cement pastes by the incorporation of nSS in the designed slurries were determined using an isothermal calorimeter. A compressive strength test of standard mortars with 7% of cement replacement was performed to determine the pozzolanic activity of the waste nano-silica sludge. Finally, the hardened system was fully characterized to determine the phase composition. The results demonstrate that the nSS can be utilized as SCM to replace portion of cement in mortars, thereby decreasing the CO2 footprint and the environmental impact of concrete. -- Highlights: •Three different samples of PV nano-silica sludge (nSS) were fully characterized. •nSS is composed of agglomerates of nano-particles like SiO2 and CaCO3. •Dispersability studies demonstrated that nSS agglomerates are broken to nano-size. •nSS can be classified as a

  17. Reaction and Diffusion of Cementitious Water in Bentonite: Results of `Blind' Modelling

    Science.gov (United States)

    Watson, C.; Hane, K.; Savage, D.; Benbow, S.; Cuevas, J.; Fernandez, R.

    2009-04-01

    The potential deleterious geochemical interactions of clay with cement/concrete may provide a constraint on the use of the latter material in deep geological disposal facilities for radioactive wastes. Consequently, it is important to have a fundamental understanding of these interactions to be able to assess their likely impact over the long timescales appropriate to the isolation of radioactive wastes from the human environment. Here, a laboratory experiment investigating the effects of cementitious water diffusing through bentonite has been simulated using a coupled reactive-transport geochemical modelling code. The modelling study was carried out before the results of the experiments were available, as an exercise in ‘blind' modelling. A sensitivity study was carried out to investigate uncertainties associated with a number of input parameters, such as the precise nature of kinetic and ion-exchange reactions, diffusion coefficients, pore water composition, and montmorillonite dissolution models. The experiments used two types of fluid; one saturated with calcium hydroxide showed little mineralogical alteration, which was predicted by the computer simulations. A high pH K-Na-OH-based water however, caused alteration (pore blocking by hydrotalcite, gibbsite and brucite growth) to a depth of 2 mm in the bentonite after a period of 1 year. Experimental evidence showed that ion exchange of Mg-montmorillonite to K-montmorillonite was not confined to this thin region however, and was found to extend throughout the whole of the bentonite sample. The pore blocking by mineral precipitation and movement of ion exchange fronts through the bentonite were accurately simulated by the model. The choice of dissolution model for montmorillonite played an important role in the outcome of the simulations. Of the cases considered in the sensitivity study, that employing the so-called ‘Yamaguchi model' was clearly the best match, exhibiting all the main characteristics of the

  18. Bond slip and crack development in FRC and regular concrete specimens longitudinally reinforced with FRP or steel under tension loading

    DEFF Research Database (Denmark)

    Lárusson, Lárus Helgi; Fischer, Gregor

    tensile loading using high definition image analysis in two unique test setups. Two different types of cementitious materials, conventional concrete and highly ductile Engineered Cementitious Composite (ECC), and two types of reinforcement bars, regular steel and Glass Fiber Reinforcement Polymer (GFRP......), were tested. It was found that the ductile ECC in contrast to regular brittle concrete decreases crack widths significantly which effectively results in decreased bond slip between the reinforcement and surrounding matrix. Furthermore the use of elastic GFRP in comparison to elastic/plastic steel...

  19. Methyl methacrylate as a healing agent for self-healing cementitious materials

    International Nuclear Information System (INIS)

    Different types of healing agents have already been tested on their efficiency for use in self-healing cementitious materials. Generally, commercial healing agents are used while their properties are adjusted for manual crack repair and not for autonomous crack healing. Consequently, the amount of regain in properties due to self-healing of cracks is limited. In this research, a methyl methacrylate (MMA)-based healing agent was developed specifically for use in self-healing cementitious materials. Various parameters were optimized including the viscosity, curing time, strength, etc. After the desired properties were obtained, the healing agent was encapsulated and screened for its self-healing efficiency. The decrease in water permeability due to autonomous crack healing using MMA as a healing agent was similar to the results obtained for manually healed cracks. First results seem promising: however, further research needs to be undertaken in order to obtain an optimal healing agent ready for use in practice

  20. Penetration of corrosion products and corrosion-induced cracking in reinforced cementitious materials

    DEFF Research Database (Denmark)

    Michel, Alexander; Pease, Brad J.; Peterova, Adela;

    2014-01-01

    -induced corrosion (10, 50, and 100 mu A/cm(2)). X-ray attenuation measurements and visual investigations provided both qualitative and quantitative information on the penetration of solid corrosion products into the surrounding cementitious matrix. X-ray attenuation measurements provided time- and location-dependent...... concentrations of corrosion products averaged through the specimen thickness. Digital image correlation (DIC) was used to measure corrosion-induced deformations including deformations between steel and cementitious matrix as well as formation and propagation of corrosion-induced cracks. Based on experimental...... corrosion products. The conceptual model was implemented into a FEM based cracking model and compared to experimental results provided in the literature and obtained from DIC measurements. (C) 2013 Elsevier Ltd. All rights reserved....

  1. Effect of phase separation structure on cementitious reactivity of blast furnace slag

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Blast furnace slag samples with phase separation structure were prepared by re-melting and then water quenching process. By use of XRD,DTA and SEM technologies in combination with mechanical property experiment,the structure characteristics of samples were determined and their effects on cementitious reactivity were investigated. The results show that the samples with phase separation have better cementitious reactivity than sample with homogenous glass and sample with crystalline phases,which mainly contributes to its glass structure with coexistence of Ca-O rich phase and Si-O rich phase. Moreover,the amorphous samples possess hydrability which is affected by their formation process,since phase separation extends the range of possible Ca-rich crystalline phases.

  2. Setting and Strength Characteristics of Alkali-activated Carbonatite Cementitious Materials with Ground Slag Replacement

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The effect of the ground granulated blast-furnace slag (GGBFS) addition, the modulus n (mole ratio of SiO2 to Na2 O ) and the concentration of sodium silicate solution on the compressive strength of the ma terial, i e alkali-activated carbonatite cementitious material (AACCMfor short ) was investigated.In addition, it is found that barium chloride has a satisfactory retarding effect on the setting of AACCM in which more than 20% ( by mass ) groud carbonatite was replaced by GGBFS.As a result, a cementitious material, inwhich ground carbona tite rock served as dominative starting material, with 3-day and 28-da y compressive strength greater than 30 MPa and 60 MPa and with continuous strength gain beyond 90 days was obtained.

  3. Ion Transport and Microstructure of Sandwich Cementitious Materials Exposed to Chloride Environment

    Institute of Scientific and Technical Information of China (English)

    WANG Xingang; WANG Kai; WANG Rui; XIE Tao; HUANG Jie

    2015-01-01

    Ion transport of sandwich cementitious materials (SCM) exposed to chloride environment was investigated by accelerated diffusion method and natural diffusion method. Pore structure and micromorphology of SCM were investigated by MIP and SEM-EDS. In comparison with the monolayer structural high performance concrete (HPC), conductive charge for 6 hours, chloride diffusion coefficient, and apparent chloride diffusion coefifcient of SCM were decreased by 30%-40%, two orders of magnitude and 40%-50%, respectively. Pore structure of ultra low ion permeability cementitious materials (ULIPCM) prepared for the facesheet is superior to that of HPC prepared for the core. As for porosity, the most probable pore radius, the content of pores with radius 50 nm and the surface area of pores, the order is ULIPCM

  4. Effect of phase separation structure on cementitious reactivity of blast furnace slag

    Institute of Scientific and Technical Information of China (English)

    LI Yu; SUN HengHu; LIU XiaoMing; CUI ZengDi

    2009-01-01

    Blast furnace slag samples with phase separation structure were prepared by re-melting and then water quenching process. By use of XRD, DTA and SEM technologies in combination with mechanical prop-erty experiment, the structure characteristics of samples were determined and their effects on cemen-titious reactivity were investigated. The results show that the samples with phase separation have better cementitious reactivity than sample with homogenous glass and sample with crystalline phases, which mainly contributes to its grass structure with coexistence of Ca-O rich phase and Si-O rich phase. Moreover, the amorphous samples possess hydrability which is affected by their formation process, since phase separation extends the range of possible Ca-rich crystalline phases.

  5. Leaching experiment of alkali-activated cementitious materials solidified forms of radioactive incineration ash

    International Nuclear Information System (INIS)

    In order to solidify safely radioactive incineration ash, the alkali-activated cementitious materials were prepared with slag, fly ash, cement and zeolite, with water glass or sodium silicate (sulfate) as the activator. The recommended formulation of solidification matrix is 65% (mass fraction, the same below) slag, 10% fly ash, 20% zeolite, 2% cement, 3% Ca (OH)2. Adding quantity of water glass is 5%, when addition of 30% radioactive incineration ash, with 0.34-0.35 of the ratio of water and ash, the mechanical property of solidification forms performs well. The leaching rate of U for the cement wastes forms is 6.0 x 10-6 cm/d in 35 d, and the long time leaching rate is very low. The results of diffusion coefficient of U in the solidification forms indicate that retention capability about U of alkali-activated cementitious materials si good. The leaching mechanisms of solidification forms are discussed. (authors)

  6. Prevalence and socio-behavioral influence of early childhood caries, ECC, and feeding habits among 6 – 36 months old children in Uganda and Tanzania

    Directory of Open Access Journals (Sweden)

    Masumo Ray

    2012-07-01

    Full Text Available Abstract Background Early childhood caries (ECC is a serious problem that has remained unexplored in sub-Saharan Africa. This study aimed to identify possible socio-behavioral correlates of ECC focusing 6–36 months old children and their caretakers. Methods Cross sectional studies were conducted in a high fluoride rural area, Manyara, Tanzania and a low fluoride urban area, Kampala, Uganda. Totals of 1221 and 816 child - caretaker pairs attending health care facilities for growth monitoring were recruited in Manyara and Kampala, respectively. All caretakers completed face to face interviews at the health care facility. Children underwent oral clinical examination whereby ECC and Enamel hypoplasia were recorded using the dmft (WHO 1997 and the DDE index (FDI 1992. Results The prevalence of ECC was 3.7% in Manyara and 17.6% in Kampala. According to multiple logistic regression analyses, received oral health information from health worker was the strongest determinant of ECC in Manyara, adjusted OR 0.3, 95% CI 0.09 – 0.93. In Kampala, visible plaque, high sugar intake and presence of enamel hypoplasia associated with ECC, adjusted ORs 2.8 (95% CI 1.61- 4.95, 3.0 (95% CI 1.39 – 6.34 and 2.3 (95% CI 1.36 - 3.95. Conclusion Oral health education aimed at caretakers of 6–36 months, including health care workers’ information regarding the detrimental consequences for oral health of frequent sugar consumption and poor oral hygiene is important for prevention of ECC in Tanzania and Uganda.

  7. Research on side-channel attack methods of ECC%一种椭圆曲线密码算法ECC旁路攻击方法研究

    Institute of Scientific and Technical Information of China (English)

    李浪; 杨柳; 李肯立; 王奕; 徐雨明; 焦铬; 邹祎

    2013-01-01

    针对椭圆曲线密码算法ECC的旁路安全性进行研究,分析了ECC算法的旁路攻击脆弱点.对点乘和点加进行了研究,在此基础上,研究ECC密码算法差分功耗攻击过程,给出了未加防护和加入一位固定值掩码的ECC算法差分功耗攻击方法;并进行了相应的攻击实验,对两种旁路攻击实验结果进行了比较分析,表明未加防护的ECC算法不能防御旁路攻击.同时实验结果显示,相对于对称密码算法,ECC密码算法攻击的难度较大.%This paper studied side-channel attacks of ECC algorithm, and analyzed side-channel attacks weak point of the ECC algorithm. It researched point multiplication and point addition of ECC. On the basis,researched it differential power analysis attacks process of ECC, and proposed differential power analysis attack methods for unprotected and added a fixed value mask ECC algorithm. It carried out the side-channel attack experiments, analyzed the experimental results of two kinds of side-channel attacks. The results show that unprotected ECC algorithm does not resist side-channel attacks. Meanwhile, the experimental results show that side-channel attacks of ECC cryptographic algorithms are more difficult than the symmetric ciphers.

  8. Final Report - Assessment of Potential Phosphate Ion-Cementitious Materials Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Naus, Dan J [ORNL; Mattus, Catherine H [ORNL; Dole, Leslie Robert [ORNL

    2007-06-01

    The objectives of this limited study were to: (1) review the potential for degradation of cementitious materials due to exposure to high concentrations of phosphate ions; (2) provide an improved understanding of any significant factors that may lead to a requirement to establish exposure limits for concrete structures exposed to soils or ground waters containing high levels of phosphate ions; (3) recommend, as appropriate, whether a limitation on phosphate ion concentration in soils or ground water is required to avoid degradation of concrete structures; and (4) provide a "primer" on factors that can affect the durability of concrete materials and structures in nuclear power plants. An assessment of the potential effects of phosphate ions on cementitious materials was made through a review of the literature, contacts with concrete research personnel, and conduct of a "bench-scale" laboratory investigation. Results of these activities indicate that: no harmful interactions occur between phosphates and cementitious materials unless phosphates are present in the form of phosphoric acid; phosphates have been incorporated into concrete as set retarders, and phosphate cements have been used for infrastructure repair; no standards or guidelines exist pertaining to applications of reinforced concrete structures in high-phosphate environments; interactions of phosphate ions and cementitious materials has not been a concern of the research community; and laboratory results indicate similar performance of specimens cured in phosphate solutions and those cured in a calcium hydroxide solution after exposure periods of up to eighteen months. Relative to the "primer," a separate NUREG report has been prepared that provides a review of pertinent factors that can affect the durability of nuclear power plant reinforced concrete structures.

  9. Final Report - Assessment of Potential Phosphate Ion-Cementitious Materials Interactions

    International Nuclear Information System (INIS)

    The objectives of this limited study were to: (1) review the potential for degradation of cementitious materials due to exposure to high concentrations of phosphate ions; (2) provide an improved understanding of any significant factors that may lead to a requirement to establish exposure limits for concrete structures exposed to soils or ground waters containing high levels of phosphate ions; (3) recommend, as appropriate, whether a limitation on phosphate ion concentration in soils or ground water is required to avoid degradation of concrete structures; and (4) provide a 'primer' on factors that can affect the durability of concrete materials and structures in nuclear power plants. An assessment of the potential effects of phosphate ions on cementitious materials was made through a review of the literature, contacts with concrete research personnel, and conduct of a 'bench-scale' laboratory investigation. Results of these activities indicate that: no harmful interactions occur between phosphates and cementitious materials unless phosphates are present in the form of phosphoric acid; phosphates have been incorporated into concrete as set retarders, and phosphate cements have been used for infrastructure repair; no standards or guidelines exist pertaining to applications of reinforced concrete structures in high-phosphate environments; interactions of phosphate ions and cementitious materials has not been a concern of the research community; and laboratory results indicate similar performance of specimens cured in phosphate solutions and those cured in a calcium hydroxide solution after exposure periods of up to eighteen months. Relative to the 'primer,' a separate NUREG report has been prepared that provides a review of pertinent factors that can affect the durability of nuclear power plant reinforced concrete structures

  10. Design of microcapsule system used for self-healing cementitious material

    OpenAIRE

    Zhang, M.; Han, N.; Xing, F.; Schlangen, H.E.J.G.

    2013-01-01

    For a microcapsule based self-healing system in the cementitious material, a fundamental issue is to find and facilitate a suitable microcapsule system, concerning either the material selection or design and manufacture process. In this study, urea formaldehyde resin is used for the shell of microcapsule, and bisphenol – an epoxy resin E-51 diluted by n-butyl glycidy ether (BGE) is adopted as the heal-agent inside the microcapsule. The production process mainly includes pre-polymerization pre...

  11. Various durability aspects of cement pastes and concretes with supplementary cementitious materials

    OpenAIRE

    SAILLIO, Mickael; BAROGHEL BOUNY, Véronique; PRADELLE, Sylvain

    2016-01-01

    The use of supplementary cementitious materials (SCMs) as a constituent for concrete receives considerable attention, due to the lower CO2 emission of these materials compared to the production of classic Portland cement. Furthermore, concretes incorporating SCMs show some improved durability properties. SCMs are mainly pozzolanic materials (Fly Ash or Metakaolin) or alkali-activated materials such as ground granulated blast slag (GGBS). In this paper, the durability of concretes and cement p...

  12. Long Term Behaviour of Cementitious Materials in the Korean Repository Environment

    International Nuclear Information System (INIS)

    The safe management of radioactive waste is a national task required for sustainable generation of nuclear power and for energy self-reliance in Korea. After the selection of the final candidate site for low- and intermediate-level waste (LILW) disposal in Korea, a construction and operation license was issued for the Wolsong LILW Disposal Center (WLDC) for the first stage of disposal. Underground silo type disposal has been determined for the initial phase. The engineered barrier system of the disposal silo consists of waste packages, disposal containers, backfills, and a concrete lining. Main objective of our study in this IAEA-CRP is to investigate closure concepts and cementitious backfill materials for the closure of silos. For this purpose, characterisation of cementitious materials, development of silo closure concept, and evaluation of long-term behaviour of cementitious materials, including concrete degradation in repository environment, have been carried out. The overall implementation plan for the CRP comprises performance testing for the physic-chemical properties of cementitious materials, degradation modelling of concrete structures, comparisons of performance for silo closure options, radionuclide transport modelling (considering concrete degradation in repository conditions), and the implementation of an input parameter database and quality assurance for safety/performance assessment. In particular, the concrete degradation modelling study has been focused on the corrosion of reinforcement steel induced by chloride attack, which was of primary concern in the safety assessment of the WLDC. A series of electrochemical experiments were conducted to investigate the effect of dissolved oxygen, pH, and Cl on the corrosion rate of reinforcing steel in a concrete structure saturated with groundwater. Laboratory-scale experiments and a thermodynamic modelling were performed to understand the porosity change of cement pastes, which were prepared using

  13. Quantitative methods used to characterize the impregnation of a glass multifilament yarn by a cementitious matrix

    OpenAIRE

    Aljewifi, Hana; Fiorio, Bruno; Gallias, Jean-Louis.

    2009-01-01

    International audience This paper presents two experimental methods that allow to quantify the impregnation level of the yarn / matrix interface, in the case of Textile Reinforced Concrete (TRC). These methods have been tested on three different glass yarns laid in a cementitious matrix, with three different impregnation levels resulting from the manufacturing process. The first method (comparative mercury intrusion porosity test) is based on the evaluation by mercury intrusion porosity of...

  14. Quantitative methods to characterize the impregnation of a glass multifilament yarn by a cementitious matrix

    OpenAIRE

    Aljewifi, Hana; Fiorio, Bruno; Gallias, Jean-Louis.

    2009-01-01

    This paper focuses on two experimental methods that give indicators linked to the impregnation level of the yarn / matrix interface, in the case of Textile Reinforced Concrete (TRC). These methods have been tested on three different glass yarns laid in a cementitious matrix, with three different impregnation levels resulting from the manufacturing process. The first method (comparative mercury intrusion porosity test) is based on the evaluation by mercury intrusion porosity of the pores volum...

  15. Composites

    OpenAIRE

    Zhao, Hanqing; Guo, Yuanzheng

    2014-01-01

    This thesis was a literature study concerning composites. With composites becoming increasingly popular in various areas such as aerospace industry and construction, the research about composites has a significant meaning accordingly. This thesis was aim at introducing some basic information of polymer matrix composites including raw mate-rial, processing, testing, applications and recycling to make a rough understanding of this kind of material for readers. Polymeric matrices, fillers,...

  16. Leaching characteristics of steel slag components and their application in cementitious property prediction.

    Science.gov (United States)

    Li, Zaibo; Zhao, Sanyin; Zhao, Xuguang; He, Tusheng

    2012-01-15

    High-efficiency recovery and utilization of steel slag are important concerns for environmental protection and sustainable development. To establish a rapid method to evaluate the cementitious properties of steel slag, leaching tests were carried out on steel slag components via an evaporation-condensation method; the leaching characteristics and mechanism of the slag were also investigated. The relationship between leaching characteristics and cementitious properties, which were represented by mortar compressive strength, was analyzed. Results show that there exist significant differences among the amounts of chemically active leached components. The leaching process can be described by the shrinking unreacted core model controlled by intra-particle diffusion, and is in accordance with Kondo R hydration kinetics equation. The leaching process showed a good linear relationship between the amounts of components leached from steel slag and the mortar compressive strength of cementitious materials prepared from reference cement and steel slag with mass ratios of 50:50 and 70:30. The compressive strengths of mortars subjected to 7, 28, and 90 days of curing can be accurately predicted by the sum of leached (CaO+Al(2)O(3)) obtained after a certain length of leaching time. PMID:22088502

  17. Hydration characteristics and environmental friendly performance of a cementitious material composed of calcium silicate slag.

    Science.gov (United States)

    Zhang, Na; Li, Hongxu; Zhao, Yazhao; Liu, Xiaoming

    2016-04-01

    Calcium silicate slag is an alkali leaching waste generated during the process of extracting Al2O3 from high-alumina fly ash. In this research, a cementitious material composed of calcium silicate slag was developed, and its mechanical and physical properties, hydration characteristics and environmental friendly performance were investigated. The results show that an optimal design for the cementitious material composed of calcium silicate slag was determined by the specimen CFSC7 containing 30% calcium silicate slag, 5% high-alumina fly ash, 24% blast furnace slag, 35% clinker and 6% FGD gypsum. This blended system yields excellent physical and mechanical properties, confirming the usefulness of CFSC7. The hydration products of CFSC7 are mostly amorphous C-A-S-H gel, rod-like ettringite and hexagonal-sheet Ca(OH)2 with small amount of zeolite-like minerals such as CaAl2Si2O8·4H2O and Na2Al2Si2O8·H2O. As the predominant hydration products, rod-like ettringite and amorphous C-A-S-H gel play a positive role in promoting densification of the paste structure, resulting in strength development of CFSC7 in the early hydration process. The leaching toxicity and radioactivity tests results indicate that the developed cementitious material composed of calcium silicate slag is environmentally acceptable. This study points out a promising direction for the proper utilization of calcium silicate slag in large quantities. PMID:26691955

  18. Low-alkaline cementitious grout for high-level nuclear waste disposal

    International Nuclear Information System (INIS)

    The stratum disposal system for high-level nuclear waste mainly involves the use of natural bedrock, called the natural barrier, and over pack and the buffer, those are designated as the artificial barrier. Grouting technology is indispensable for the environment that the crack and the underground water flow of the bedrock bring about mass transport, also ratio active component. However, typical cementitious grout material is strongly alkaline and the alkalinity that it imparts to the barrier material, especially to mineral substances in the bedrock or buffer, is suspected to compromise the performance of the barrier system over the long term. In order to avoid this undesirable alkaline influence, we have developed a procedure for reducing the alkaline state in cementitious materials by employing high volumes of additives such as pozzolanic materials. In this paper, we discuss the basic properties of low-alkaline cementitious grout, and explain how to select and mix appropriate proportions of grout to accomplish the end-objective, i.e., develop an efficient stratum disposal system. We also elaborate on progress achieved in research on this topic over the last two years. (author)

  19. Composition

    DEFF Research Database (Denmark)

    2014-01-01

    Memory Pieces are open compositions to be realised solo by an improvising musicians. See more about my composition practise in the entry "Composition - General Introduction". Caution: streaming the sound files will in some cases only provide a few minutes' sample. Please DOWNLOAD them to hear them...

  20. Composition

    DEFF Research Database (Denmark)

    Bergstrøm-Nielsen, Carl

    2010-01-01

    New Year is an open composition to be realised by improvising musicians. It is included in "From the Danish Seasons" (see under this title). See more about my composition practise in the entry "Composition - General Introduction". This work is licensed under a Creative Commons "by-nc" License. You...

  1. Composition

    DEFF Research Database (Denmark)

    Bergstrøm-Nielsen, Carl

    2011-01-01

    Strategies are open compositions to be realised by improvising musicians. See more about my composition practise in the entry "Composition - General Introduction". Caution: streaming the sound files will in some cases only provide a few minutes' sample. Please DOWNLOAD them to hear them in full...

  2. Composition

    DEFF Research Database (Denmark)

    Bergstrøm-Nielsen, Carl

    2014-01-01

    Cue Rondo is an open composition to be realised by improvising musicians. See more about my composition practise in the entry "Composition - General Introduction". Caution: streaming the sound/video files will in some cases only provide a few minutes' sample, or the visuals will not appear at all...

  3. R&D Plan for RISMC Industry Application #1: ECCS/LOCA Cladding Acceptance Criteria

    Energy Technology Data Exchange (ETDEWEB)

    Szilard, Ronaldo Henriques [Idaho National Lab. (INL), Idaho Falls, ID (United States); Zhang, Hongbin [Idaho National Lab. (INL), Idaho Falls, ID (United States); Epiney, Aaron Simon [Idaho National Lab. (INL), Idaho Falls, ID (United States); Tu, Lei [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2016-04-01

    The Nuclear Regulatory Commission (NRC) is finalizing a rulemaking change that would revise the requirements in 10 CFR 50.46. In the proposed new rulemaking, designated as 10 CFR 50.46c, the NRC proposes a fuel performance-based equivalent cladding reacted (ECR) criterion as a function of cladding hydrogen content before the accident (pre-transient) in order to include the effects of higher burnup on cladding performance as well as to address other technical issues. A loss of operational margin may result due to the more restrictive cladding embrittlement criteria. Initial and future compliance with the rule may significantly increase vendor workload and licensee costs as a spectrum of fuel rod initial burnup states may need to be analyzed to demonstrate compliance. The Idaho National Laboratory (INL) has initiated a project, as part of the DOE Light Water Reactor Sustainability Program (LWRS), to develop analytical capabilities to support the industry in the transition to the new rule. This project is called the Industry Application 1 (IA1) within the Risk-Informed Safety Margin Characterization (RISMC) Pathway of LWRS. The general idea behind the initiative is the development of an Integrated Evaluation Model (IEM). The motivation is to develop a multiphysics framework to analyze how uncertainties are propagated across the stream of physical disciplines and data involved, as well as how risks are evaluated in a LOCA safety analysis as regulated under 10 CFR 50.46c. This IEM is called LOTUS which stands for LOCA Toolkit for US and it represents the LWRS Program’s response to the proposed new rule making. The focus of this report is to complete an R&D plan to describe the demonstration of the LOCA/ECCS RISMC Industry Application # 1 using the advanced RISMC Toolkit and methodologies. This report includes the description and development plan for a RISMC LOCA tool that fully couples advanced MOOSE tools already in development in order to characterize and optimize

  4. Cementitious Barriers Partnership (CBP): Training and Release of CBP Toolbox Software, Version 1.0 - 13480

    International Nuclear Information System (INIS)

    The Cementitious Barriers Partnership (CBP) Project is a multi-disciplinary, multi-institutional collaboration supported by the Office of Tank Waste Management within the Office of Environmental Management of U.S. Department of Energy (US DOE). The CBP program has developed a set of integrated tools (based on state-of-the-art models and leaching test methods) that improve understanding and predictions of the long-term hydraulic and chemical performance of cementitious barriers used in nuclear applications. Tools selected for and developed under this program are intended to evaluate and predict the behavior of cementitious barriers used in near-surface engineered waste disposal systems for periods of performance up to or longer than 100 years for operating facilities and longer than 1,000 years for waste management purposes. CBP software tools were made available to selected DOE Office of Environmental Management and field site users for training and evaluation based on a set of important degradation scenarios, including sulfate ingress/attack and carbonation of cementitious materials. The tools were presented at two-day training workshops held at U.S. National Institute of Standards and Technology (NIST), Savannah River, and Hanford included LeachXSTM/ORCHESTRA, STADIUMR, and a CBP-developed GoldSim Dashboard interface. Collectively, these components form the CBP Software Toolbox. The new U.S. Environmental Protection Agency leaching test methods based on the Leaching Environmental Assessment Framework (LEAF) were also presented. The CBP Dashboard uses a custom Dynamic-link library developed by CBP to couple to the LeachXSTM/ORCHESTRA and STADIUMR codes to simulate reactive transport and degradation in cementitious materials for selected performance assessment scenarios. The first day of the workshop introduced participants to the software components via presentation materials, and the second day included hands-on tutorial exercises followed by discussions of

  5. Cementitious Barriers Partnership (CBP): Training and Release of CBP Toolbox Software, Version 1.0 - 13480

    Energy Technology Data Exchange (ETDEWEB)

    Brown, K.G.; Kosson, D.S.; Garrabrants, A.C.; Sarkar, S. [Vanderbilt University, School of Engineering, CRESP, Nashville, TN 37235 (United States); Flach, G.; Langton, C.; Smith, F.G. III; Burns, H. [Savannah River National Laboratory, Aiken, SC 29808 (United States); Van der Sloot, H. [Hans Van der Sloot Consultancy, Dorpsstraat 216, 1721BV Langedijk (Netherlands); Meeussen, J.C.L. [Nuclear Research and Consultancy Group, Westerduinweg 3, Petten (Netherlands); Samson, E. [SIMCO Technologies, Inc., Quebec (Canada); Mallick, P.; Suttora, L. [U.S. Department of Energy, Washington, DC (United States); Esh, D.; Fuhrmann, M.; Philip, J. [U.S. Nuclear Regulatory Commission, Washington, DC (United States)

    2013-07-01

    The Cementitious Barriers Partnership (CBP) Project is a multi-disciplinary, multi-institutional collaboration supported by the Office of Tank Waste Management within the Office of Environmental Management of U.S. Department of Energy (US DOE). The CBP program has developed a set of integrated tools (based on state-of-the-art models and leaching test methods) that improve understanding and predictions of the long-term hydraulic and chemical performance of cementitious barriers used in nuclear applications. Tools selected for and developed under this program are intended to evaluate and predict the behavior of cementitious barriers used in near-surface engineered waste disposal systems for periods of performance up to or longer than 100 years for operating facilities and longer than 1,000 years for waste management purposes. CBP software tools were made available to selected DOE Office of Environmental Management and field site users for training and evaluation based on a set of important degradation scenarios, including sulfate ingress/attack and carbonation of cementitious materials. The tools were presented at two-day training workshops held at U.S. National Institute of Standards and Technology (NIST), Savannah River, and Hanford included LeachXS{sup TM}/ORCHESTRA, STADIUM{sup R}, and a CBP-developed GoldSim Dashboard interface. Collectively, these components form the CBP Software Toolbox. The new U.S. Environmental Protection Agency leaching test methods based on the Leaching Environmental Assessment Framework (LEAF) were also presented. The CBP Dashboard uses a custom Dynamic-link library developed by CBP to couple to the LeachXS{sup TM}/ORCHESTRA and STADIUM{sup R} codes to simulate reactive transport and degradation in cementitious materials for selected performance assessment scenarios. The first day of the workshop introduced participants to the software components via presentation materials, and the second day included hands-on tutorial exercises followed

  6. Effect of Limestone Powder on Microstructure of Ternary Cementitious System

    NARCIS (Netherlands)

    Zhang, Y.; Ye, G.

    2012-01-01

    The pressure to reach sustainability favours the development of ternary composite cement. The synergistic effect on mechanical behaviour at 28 days between limestone powder (LP) and pozzolanic additives, i.e. fly ash (FA) and blast furnace slag (BFS), has been documented. In order to better understa

  7. 1D modelling of alteration of compacted bentonite due to cementitious leachate

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. The interaction between the bentonite buffer and alkaline fluids deriving from cementitious materials used in the construction and operation of a KBS-3 spent-fuel repository is considered as a risk to the long-term chemical stability of bentonite. The associated long-term safety concerns include a loss of bentonite swelling pressure, increased hydraulic conductivity, and possibly fracturing of bentonite due to cementation. Consequently, it is important to identify and quantify the mechanisms controlling the degradation of the buffer by a cement leachate. This would subsequently help take adequate measures to mitigate the risk posed by alkaline attack. In this work, 1D reactive transport model (TOUGHREACT v. 1.0) calculations have been carried out to shed light on the possible extent of MX-80 bentonite alteration due to three leachates envisaged to represent different stages of cement degradation and subsequent mixing with the ground water. The reaction time for the calculations was set at 10,000 years or until the porosity was clogged in the compacted bentonite, whichever occurred earlier. A common feature of the model outcome for each leachate is the total consumption of gypsum and calcite in the bentonite and the clogging of the pore space by secondary mineral phases at the interface between the buffer and the rock fracture. Depending on the pH (12.17, 11.60 or 9.70), this clogging was calculated to occur after 10, 18 and 5,900 years of interaction, respectively. For each case, the heavily altered zone in bentonite is typically located within 1 cm from the interface, although for the lowest pH, the alteration extends slightly further into the bentonite due to the longer time it takes to clog the porosity. Overall, the model results are found sensitive to the chemical composition of the leachate interacting with the buffer. Regardless of the case studied, there is a significant smectite fraction left at the end of

  8. Safe and durable storage of waste from reprocessing in E-EV-SE and ECC facilities

    International Nuclear Information System (INIS)

    managed, the main parameter impacting the design being the heat released. E-EV-SE and ECC facilities were initially designed for a lifetime in the order of 50 years. Assessment has been performed to study their ability for lifetime extension. Phenomenon involved have been identified and mainly relates to atmospheric corrosion risk of metallic components and potentially concrete evolution, which remain however very slow evolving parameters, that can be monitored. The main result of these studies is that these two facilities are liable to be safely operated up to 100 years or more. Some modifications in the operation, monitoring and maintenance procedures, in the next decades, could allow meeting such a goal, if needed. In this line, these storage concepts could be, after a possible additional improvement, part of a French strategy encompassing the use of long term storage. The decision is now in the Parliament's hands

  9. Effect of Sucrose Concentration on Sucrose-Dependent Adhesion and Glucosyltransferase Expression of S. mutans in Children with Severe Early-Childhood Caries (S-ECC

    Directory of Open Access Journals (Sweden)

    Wei Zhao

    2014-09-01

    Full Text Available Sucrose, extracellular polysaccharide, and glucosyltransferases (GTFs are key factors in sucrose-dependent adhesion and play important roles in the process of severe early-childhood caries (S-ECC. However, whether sucrose concentration regulates gtf expression, extracellular polysaccharide synthesis, and sucrose-dependent adhesion is related to the different genotypes of S. mutans isolated from ECC in children and still needs to be investigated. In this study, 52 strains of S. mutans were isolated from children with S-ECC and caries-free (CF children. Water-insoluble glucan (WIG synthesis was detected by the anthrone method, adhesion capacity by the turbidimetric method, and expression of gtf by RT-PCR in an in vitro model containing 1%–20% sucrose. The genotypes of S. mutans were analyzed by AP-PCR. The results showed that WIG synthesis, adhesion capacity, and gtf expression increased significantly when the sucrose concentration was from 1% to 10%. WIG synthesis and gtfB as well as gtfC expression of the 1% and 5% groups were significantly lower than those of the 10% and 20% groups (p < 0.05. There were no significant differences between the 10% and 20% groups. The fingerprints of S. mutans detected from individuals in the S-ECC group exhibited a significant difference in diversity compared with those from CF individuals (p < 0.05. Further, the expression of gtfB and gtfC in the S-ECC group was significantly different among the 1- to 5-genotype groups (p < 0.05. It can be concluded that sucrose-dependent adhesion might be related to the diversity of genotypes of S. mutans, and the 10% sucrose level can be seen as a “turning point” and essential factor for the prevention of S-ECC.

  10. Mechanical interaction between concrete and structural reinforcement in the tension stiffening process

    DEFF Research Database (Denmark)

    Lárusson, Lárus Helgi; Fischer, Gregor; Jönsson, Jeppe

    2011-01-01

    Engineered Cementitious Composite (ECC), have been combined with steel and glass fiber reinforced polymer (GFRP) reinforcement to contrast the effects of brittle and ductile cement matrices as well as elastic/plastic and elastic reinforcement on the tension stiffening process. Particular focus was on the...

  11. OVERVIEW OF THE U.S. DEPARTMENT OF ENERGY AND NUCLEAR REGULATORY COMMISSION PERFORMANCE ASSESSMENT APPROACHES: CEMENTITIOUS BARRIERS PARTNERSHIP

    Energy Technology Data Exchange (ETDEWEB)

    Langton, C.; Burns, H.

    2009-05-29

    Engineered barriers including cementitious barriers are used at sites disposing or contaminated with low-level radioactive waste to enhance performance of the natural environment with respect to controlling the potential spread of contaminants. Drivers for using cementitious barriers include: high radionuclide inventory, radionuclide characteristics (e.g., long half-live, high mobility due to chemical form/speciation, waste matrix properties, shallow water table, and humid climate that provides water for leaching the waste). This document comprises the first in a series of reports being prepared for the Cementitious Barriers Partnership. The document is divided into two parts which provide a summary of: (1) existing experience in the assessment of performance of cementitious materials used for radioactive waste management and disposal and (2) sensitivity and uncertainty analysis approaches that have been applied for assessments. Each chapter is organized into five parts: Introduction, Regulatory Considerations, Specific Examples, Summary of Modeling Approaches and Conclusions and Needs. The objective of the report is to provide perspective on the state of the practice for conducting assessments for facilities involving cementitious barriers and to identify opportunities for improvements to the existing approaches. Examples are provided in two contexts: (1) performance assessments conducted for waste disposal facilities and (2) performance assessment-like analyses (e.g., risk assessments) conducted under other regulatory regimes. The introductory sections of each section provide a perspective on the purpose of performance assessments and different roles of cementitious materials for radioactive waste management. Significant experience with assessments of cementitious materials associated with radioactive waste disposal concepts exists in the US Department of Energy Complex and the commercial nuclear sector. Recently, the desire to close legacy facilities has created

  12. Analysis on the safety verification tests of the ECCS driven by the electrically 4 trains during LBLOCA

    International Nuclear Information System (INIS)

    The design change of the safety injection pump as the electrically 4 trains resulted in a shorter quenching time than that of the two train case. There was no significant difference owing to the different SIP combinations. The nitrogen gas injected into the system affected on the higher water level in the RPV and the shorter quenching time than those of the other cases, which were performed without the nitrogen gas injection. Thus, the nitrogen gas injection into the RPV has a positive effect from the view point of safety. From these series of experiments, we can conclude that the design change of the safety injection pump as the electrically 4 train improves the safety during the LBLOCA reflood phase. The APR1400 design has been changed such that the safety injection pumps are driven by four emergency diesel generators in the design certification process from the U. S. NRC. Owing to the design change, the total amount of water injected from three SIPs to the reactor pressure vessel is expected to increase compared with the case of a two train ECC system. The bypass ratio will also be different depending on the different combinations of three available SIPs, and might have different influences on the thermal hydraulic characteristics during the reflood phase of the LBLOCA. After the SIT injection is terminated, the nitrogen gas remaining in the SITs can flow into the reactor coolant system (RCS). It can be expected that the nitrogen gas injection has a positive effect from the view point of the core cooling performance. However, there is no available experimental data to confirm this expectation at the moment. Thus, the verification experiments of the reflood phase during a large break LOCA were performed to evaluate the core cooling performance of the four trains ECCS with the assumption of a single failure. Verification experiments of the reflood phase during a large break LOCA were performed to evaluate the core cooling performance of the four train ECCS with

  13. Impact of cementitious materials decalcification on transfer properties: application to radioactive waste deep repository

    International Nuclear Information System (INIS)

    Cementitious materials have been selected to compose the engineering barrier system (EBS) of the French radioactive waste deep repository, because of concrete physico-chemical properties: the hydrates of the cementitious matrix and the pH of the pore solution contribute to radionuclides retention; furthermore the compactness of these materials limits elements transport. The confinement capacity of the system has to be assessed while a period at least equivalent to waste activity (up to 100.000 years). His durability was sustained by the evolution of transfer properties in accordance with cementitious materials decalcification, alteration that expresses structure long-term behavior. Then, two degradation modes were carried out, taking into account the different physical and chemical solicitations imposed by the host formation. The first mode, a static one, was an accelerated decalcification test using nitrate ammonium solution. It replicates the EBS alteration dues to underground water. Degradation kinetic was estimated by the amount of calcium leached and the measurement of the calcium hydroxide dissolution front. To evaluate the decalcification impact, samples were characterized before and after degradation in term of microstructure (porosity, pores size distribution) and of transfer properties (diffusivity, gas and water permeability). The influence of cement nature (ordinary Portland cement, blended cement) and aggregates type (lime or siliceous) was observed: experiments were repeated on different mortars mixes. On this occasion, an essential reflection on this test metrology was led. The second mode, a dynamical degradation, was performed with an environmental permeameter. It recreates the EBS solicitations ensured during the re-saturation period, distinguished by the hydraulic pressure imposed by the geologic layer and the waste exothermicity. This apparatus, based on triaxial cell functioning, allows applying on samples pressure drop between 2 and 10 MPa and

  14. The Expanded Capabilities Of The Cementitious Barriers Partnership Software Toolbox Version 2.0 - 14331

    Energy Technology Data Exchange (ETDEWEB)

    Burns, Heather; Flach, Greg; Smith, Frank; Langton, Christine; Brown, Kevin; Kosson, David; Samson, Eric; Mallick, Pramod

    2014-01-10

    The Cementitious Barriers Partnership (CBP) Project is a multi-disciplinary, multi-institutional collaboration supported by the U.S. Department of Energy (US DOE) Office of Tank Waste Management. The CBP program has developed a set of integrated tools (based on state-of-the-art models and leaching test methods) that help improve understanding and predictions of the long-term structural, hydraulic and chemical performance of cementitious barriers used in nuclear applications. The CBP Software Toolbox – “Version 1.0” was released early in FY2013 and was used to support DOE-EM performance assessments in evaluating various degradation mechanisms that included sulfate attack, carbonation and constituent leaching. The sulfate attack analysis predicted the extent and damage that sulfate ingress will have on concrete vaults over extended time (i.e., > 1000 years) and the carbonation analysis provided concrete degradation predictions from rebar corrosion. The new release “Version 2.0” includes upgraded carbonation software and a new software module to evaluate degradation due to chloride attack. Also included in the newer version are a dual regime module allowing evaluation of contaminant release in two regimes – both fractured and un-fractured. The integrated software package has also been upgraded with new plotting capabilities and many other features that increase the “user-friendliness” of the package. Experimental work has been generated to provide data to calibrate the models to improve the credibility of the analysis and reduce the uncertainty. Tools selected for and developed under this program have been used to evaluate and predict the behavior of cementitious barriers used in near-surface engineered waste disposal systems for periods of performance up to or longer than 100 years for operating facilities and longer than 1000 years for waste disposal. The CBP Software Toolbox is and will continue to produce tangible benefits to the working DOE

  15. The influence of superabsorbent polymers on the autogenous shrinkage properties of cement pastes with supplementary cementitious materials

    DEFF Research Database (Denmark)

    Snoeck, D.; Jensen, Ole Mejlhede; De Belie, N.

    2015-01-01

    Fly ash and blast-furnace slag containing binders are frequently used in the construction industry and it is important to know the extent of autogenous shrinkage and its (ideal) mitigation by superabsorbent polymers in these systems as a function of their age. In this paper, the autogenous...... shrinkage was determined by manual and automated shrinkage measurements. Autogenous shrinkage was reduced in cement pastes with the supplementary cementitious materials versus Portland cement pastes. At later ages, the rate of autogenous shrinkage is higher due to the pozzolanic activity. Internal curing by...... means of superabsorbent polymers is successful, independent of this long term higher rate of shrinkage in mixtures with supplementary cementitious materials....

  16. Development of evaluation methodology for effects of cementitious grouting materials on groundwater and rock in fractured media

    International Nuclear Information System (INIS)

    Leachates from cementitious grouting materials used for reducing water inflow are hyperalkaline and chemically reactive with the engineered barriers and host rock for geological disposal of high-level radioactive waste. Evaluation methods for long-term alteration of the fractured rock have been developed since the extent of chemical modification may influence the transport and retardation properties of radionuclides in the far field. The present study shows the current status of the development of the methodology (i.e., procedure, models, and simulation codes) for evaluating the effects of cementitious grouting materials on groundwater and rock. (author)

  17. Solution of the nonlinear Poisson–Boltzmann equation: Application to ionic diffusion in cementitious materials

    International Nuclear Information System (INIS)

    A robust numerical solution of the nonlinear Poisson–Boltzmann equation for asymmetric polyelectrolyte solutions in discrete pore geometries is presented. Comparisons to the linearized approximation of the Poisson–Boltzmann equation reveal that the assumptions leading to linearization may not be appropriate for the electrochemical regime in many cementitious materials. Implications of the electric double layer on both partitioning of species and on diffusive release are discussed. The influence of the electric double layer on anion diffusion relative to cation diffusion is examined.

  18. The microbiology of the Maqarin site, Jordan -- A natural analogue for cementitious radioactive waste repositories

    International Nuclear Information System (INIS)

    The Maqarin site, Jordan is being studied as a natural analogue of a cementitious radioactive waste repository. The microbiology has been studied and diverse microbial populations capable of tolerating alkaline pH were detected at all sampling localities. Dissolved organic carbon was identified as the potentially most important reductant with sulfate identified as the main oxidant, both supply energy for microbial life. Calculations on upper limits of microbial numbers were made with a microbiology code (MGSE) using existing information but the results are overestimates when compared with field observations. This indicates that the model is very conservative and that more information on, for example, carbon sources is required

  19. Utilization of copper slag as a cementitious material in reactive powder concrete

    OpenAIRE

    Edwin, Romy Suryaningrat; De Schepper, Mieke; Gruyaert, Elke; De Belie, Nele

    2015-01-01

    This research studies the use of copper slag from a plant in Belgium as a cementitious material in reactive powder concrete (RPC). The quickly cooled granulated copper slag (QCS) was ground intensively using a planetary ball mill. A lower water-to-binder ratio of 0.18 was chosen for the RPC in this study. Various concrete and cement paste samples were produced with increasing copper slag contents from 0 to 20 wt% in steps of 5 wt%. Particle size distribution (PSD) and specific surface area (S...

  20. Effect of total cementitious content on shear strength of high-volume fly ash concrete beams

    International Nuclear Information System (INIS)

    Highlights: ► Existing design standards conservatively predicted the capacity of the HVFAC beams. ► In general, the HVFAC beams exceeded the code predicted shear strengths. ► The cementitious content did not have effect on the shear behavior of the HVFAC beams. - Abstract: The production of portland cement – the key ingredient in concrete – generates a significant amount of carbon dioxide. However, due to its incredible versatility, availability, and relatively low cost, concrete is the most consumed manmade material on the planet. One method of reducing concrete’s contribution to greenhouse gas emissions is the use of fly ash to replace a significant amount of the cement. This paper compares two experimental studies that were conducted to investigate the shear strength of full-scale beams constructed with high-volume fly ash concrete (HVFAC) – concrete with at least 50% of the cement replaced with fly ash. The primary difference between the two studies involved the amount of cementitious material, with one mix having a relatively high total cementitious content (502 kg/m3) and the other mix having a relatively low total cementitious content (337 kg/m3). Both mixes utilized a 70% replacement of portland cement with a Class C fly ash. Each of these experimental programs consisted of eight beams (six without shear reinforcing and two with shear reinforcing in the form of stirrups) with three different longitudinal reinforcement ratios. The beams were tested under a simply supported four-point loading condition. The experimental shear strengths of the beams were compared with both the shear provisions of selected standards (US, Australia, Canada, Europe, and Japan) and a shear database of conventional concrete (CC) specimens. Furthermore, statistical data analyses (both parametric and nonparametric) were performed to evaluate whether or not there is any statistically significant difference between the shear strength of both mixes. Results of these

  1. Mechanisms of Nd(III) and Eu(III) uptake by cementitious materials

    International Nuclear Information System (INIS)

    Cement is an important component of the multi-barrier system in repositories for low-level and intermediate level radioactive waste. The waste loading potential of cementitious materials is well established but their long-term ability to delay the release of radionuclides from waste repositories and the chemical mechanisms governing radionuclide immobilization are poorly understood at the molecular level. This knowledge, however, is essential for detailed long-term predictions of the environmental impact of cement-stabilized waste forms. The present doctoral study aims at developing mechanistic models of the retention mechanism of lanthanides, in particular Nd(III) and Eu(III), in cementitious materials, using synchrotron- and laser-light-based spectroscopic and laboratory-based X-ray diffraction techniques in combination with wet chemistry experiments. Macro- and micro-scale investigations on Nd(III) and Eu(III) doped crystalline and amorphous calcium silicate hydrates (C-S-H) provide fundamental information on uptake mechanisms at the atomic/molecular level. This information was used for the development of the retention model. Spectroscopic studies on Nd(III) doped cementitious matrices were performed to discern the coordination environment of these elements in cement matrices. In the first phase of the doctoral study a mechanistic model was developed for two Nd(III) doped crystalline C-S-H phases, 11 Å tobermorite (Ca5Si6O16(OH)2∙7H2O) and xonotlite (Ca6Si6O17(OH)2). In the second phase the model was tested on Nd(III) doped amorphous C-S-H phases with calcium-to-silica molar ratios varying between 0.56 and 1.54 and in complex cement systems. In the last phase, studies on Eu(III) doped crystalline C-S-H phases were carried out to test whether or not the model developed for Nd(III) can be used to interpret the Eu(III) retention by cementitious materials at very low metal loadings. Trivalent lanthanides e.g., Nd(III) and Eu(III), were regarded as suitable

  2. Development of porosity of cement paste blended with supplementary cementitious materials after carbonation

    OpenAIRE

    Wu, B.; YE, guang

    2015-01-01

    Supplementary cementitious materials (SCMs) like fly ash (FA) and blast furnace slag (BFS) are normally used to replace parts of Ordinary Portland cement (OPC) to reduce the cost and CO2 emission. Some consequences are the reduction of portlandite (CH) content and the formation of C-S-H with low Ca/Si ratio, due to pozzolanic reactions. It is known that carbonation of portlandite leads to a reduction in the porosity which is ascribed to the positive difference of molar volumes between CH and ...

  3. Accelerated leaching of cementitious materials using ammonium nitrate (6 M): influence of test conditions

    International Nuclear Information System (INIS)

    We have focused on the test conditions influence on accelerated degradation of cementitious materials using ammonium nitrate. PH-buffering and renewal of the leaching solution were studied. PH-buffering appeared not to be very important when the renewal pH remains under eight. Renewal appeared to be the most influential feature. Its absence leads to calcium accumulation in the leaching solution inducing aggressiveness fall. Degradation is then less marked in terms of depth, flux and mineralogy. The resulting porosity increase is also smaller. (authors)

  4. Cost-Effective Cementitious Material Compatible with Yucca Mountain Repository Geochemistry

    Energy Technology Data Exchange (ETDEWEB)

    Dole, LR

    2004-12-17

    The current plans for the Yucca Mountain (YM) repository project (YMP) use steel structures to stabilize the disposal drifts and connecting tunnels that are collectively over 100 kilometers in length. The potential exist to reduce the underground construction cost by 100s of millions of dollars and improve the repository's performance. These economic and engineering goals can be achieved by using the appropriate cementitious materials to build out these tunnels. This report describes the required properties of YM compatible cements and reviews the literature that proves the efficacy of this approach. This report also describes a comprehensive program to develop and test materials for a suite of underground construction technologies.

  5. Influence of supplementary cementitious materials on hydration, microstructure development, and durability of concrete

    OpenAIRE

    Simcic, Tina

    2015-01-01

    In recent years the use of supplementary cementitious materials in the production of concrete has become an ever more frequent trend, since such use contributes to a sustainable concrete industry. The main reason for this lies in the reduction of the specific energy requirement and of carbon dioxide emissions in the production of cement (OPC). One such environmentally friendly product is fly ash (FA), which occurs as a by-product of coal-fired thermal power plants. In the first part of the...

  6. Development of engineered cementitious composites with limestone powder and blast furnace slag

    NARCIS (Netherlands)

    Zhou, J.; Qian, S.; Sierra Beltran, M.G.; Ye, G.; Van Breugel, K.; Li, V.C.

    2009-01-01

    Nowadays limestone powder and blast furnace slag (BFS) are widely used in concrete as blended materials in cement. The replacement of Portland cement by limestone powder and BFS can lower the cost and enhance the greenness of concrete, since the production of these two materials needs less energy an

  7. STUDY ON DUCTILITY AND CRACK BEHAVIOUR OF ENGINEERED CEMENTITIOUS COMPOSITES BASED FERROCEMENT

    OpenAIRE

    Mr. S. Ramesh; B.Jose Ravundraraj; Ram Kumar, R.; G.Ashok

    2016-01-01

    The Reinforced cement concrete structure shows good behaviour at all loading conditions but it is bulky and has increased cost. In order to reduce the self weight the ferrocement panels can be used in place of reinforced cement concrete. As ferrocement panels are thin elements consisting of cement mortar and reinforced with closely spaced galvanised steel wire mesh it shows improved ductile behaviour. The cost of manufacture of ferrocement panel can be brought down by using engineered cementi...

  8. Electrical resistivity and ultrasonic measurements during sequential fracture test of cementitious composite

    Directory of Open Access Journals (Sweden)

    V. Veselý

    2014-10-01

    Full Text Available Cracks in cover of reinforced and pre-stressed concrete structures significantly influence the ingress of deleterious species causing decrease in durability of these structures. The paper is focused on the effect of fracture process on two selected physical parameters of concrete – the electrical resistivity and the ultrasonic pulse passing time – which might be employed as the quality indicator of concrete cover within (nondestructive procedure(s of assessment of the structural durability. The concrete electrical resistivity and ultrasonic passing time were investigated here with respect to two variants of treatment of the test specimens’ surface (the pre-dried surface and the wet surface. Test configuration of three-point bending of notched beam was utilized to control the crack propagation; the fracture process passed through several loading–unloading sequences between which the electrical resistivity and ultrasonic passing time readings over the fractured region were performed. Equivalent elastic crack model was used for estimation of the fracture advance (described via the effective crack length at the loading stages corresponding to the resistivity and ultrasonic measurements. Relationships between changes of both the concrete resistivity and ultrasonic pulse passing time and the effective crack length is determined and discussed.

  9. Modelling the influence of steel fibres on the electrical resistivity of cementitious composites

    DEFF Research Database (Denmark)

    Solgaard, Anders Ole Stubbe; Michel, Alexander; Stang, Henrik; Geiker, Mette Rica; Küter, André; Edvardsen, Carola

    2009-01-01

    One of the governing factors on the corrosion of embedded reinforcement is the electrical resistivity of the concrete. The combination of steel fibres and conventional reinforcement bars has been used in a number of structures. However, the addition of electrical con-ductive fibres might influence...... resistivity of steel fibre reinforced concrete (SFRC). The parameters investigated in the following are the fibre geometry, the fibre volume and the transitional resistance. On basis of the experimental results, a model, taking the resistivity of the fibres and the concrete matrix into account is proposed....

  10. Image-based detection and analysis of crack propagation in cementitious composites

    DEFF Research Database (Denmark)

    Pereira, E.B.; Fischer, Gregor; Barros, J.A.O.

    2011-01-01

    after the cracking process has occurred. The alternative nondestructive methods are often either not precise enough or experimentally too demanding. In this study, the use of an image analysis procedure to capture the crack initiation and propagation process is described, which utilizes digital images...... small crack openings, allowing a thorough investigation and analysis of the cracking processes in concrete....

  11. Shear crack formation and propagation in fiber reinforced cementitious composites (FRCC)

    DEFF Research Database (Denmark)

    Paegle, Ieva; Fischer, Gregor

    2011-01-01

    strain hardening of both FRCC materials was observed under shear loading. The influence of fibers, fiber type, including polyvinyl alcohol (PVA) and polypropylene (PP) fibers, and shear crack angle were investigated. Based upon photogrammetric results, fundamental descriptions of shear crack opening...

  12. Shear crack formation and propagation in fiber reinforced cementitious composites (FRCC)

    DEFF Research Database (Denmark)

    Paegle, Ieva; Fischer, Gregor

    2012-01-01

    strain hardening of both FRCC materials was observed under shear loading. The influence of fibers, fiber type, including polyvinyl alcohol (PVA) and polypropylene (PP) fibers, and shear crack angle were investigated. Based upon photogrammetric results, fundamental descriptions of shear crack opening...

  13. Crack path and fracture surface modifications in cement composites

    Directory of Open Access Journals (Sweden)

    Sajjad Ahmad

    2015-10-01

    Full Text Available There is a tremendous increase in the use of high strength and high performance self-consolidating cementitious composites due to their superior workability and mechanical strengths. Cement composites are quasi-brittle in nature and possess extremely low tensile strength as compared to their compressive strength. Due to the low tensile strength capacity, cracks develop in cementitious composites due to the drying shrinkage, plastic settlements and/or stress concentrations (due to external restrains and/or applied stresses etc. These cracks developed at the nanoscale may grow rapidly due to the applied stresses and join together to form micro and macro cracks. The growth of cracks from nanoscale to micro and macro scale is very rapid and may lead to sudden failure of the cement composites. The present paper reports the modifications in the crack growth pattern of the high performance cement composites to achieve enhanced ductility and toughness. The objective was accomplished by the incorporation of the micro sized inert particulates in the cement composite matrix. The results indicate that the incorporation of micro sized inert particles acted as the obstacles in the growth of the cracks thus improving the ductility and the energy absorption capacity of the self-consolidating cementitious composites.

  14. Safety verification for the ECCS driven by the electrically 4 trains during LBLOCA reflood phase using ATLAS

    Energy Technology Data Exchange (ETDEWEB)

    Park, Yusun; Park, Hyun-sik; Kang, Kyoung-ho; Choi, Nam-hyun; Min, Kyoung-ho; Choi, Ki-yong, E-mail: kychoi@kaeri.re.kr

    2014-10-01

    Highlights: • Safety improvement by adopting 4 train emergency core cooling system was validated experimentally. • General thermal hydraulic behaviors of the system during LBLOCA reflood phase were successfully demonstrated. • Key parameters such as the liquid levels, the PCTs, the quenching time, and the ECC bypass ratios were investigated. • Asymmetric effects of the different combination of safety injection were negligible during the reflood period. - Abstract: The APR1400 is equipped with four safety injection pumps driven by two emergency diesel generators. However, the design has been changed so that the four safety injection pumps are driven by 4 emergency diesel generators during the design certification process from the U.S. NRC. Thus, 4 safety injection pumps (SIPs) are completely independent electrically and mechanically and three safety injection pumps are available in a single failure condition. This design change could have a certain effects on the thermal-hydraulic phenomenon occurring in the downcomer region during the late reflood phase of a large break loss of coolant accident (LBLOCA). Thus, in this study, a verification experiment for the reflood phase of a LBLOCA was performed to evaluate the core cooling performance of the 4 train emergency core cooling system (ECCS) with an assumption of a single failure. And the different combinations of three SIPs positions were tested to investigate the asymmetric effects on the reactor core cooling performance. The overall experimental results revealed the typical thermal–hydraulic trends expected to occur during the reflood phase of a large-break LOCA scenario for the APR1400. Experiment with the injection of three SIPs showed a faster core quenching time and lower bypass ratio than that of the case in which two SIPs were injected. The RPV wall temperature distributions showed the similar trend in spite of the different SIP combinations.

  15. Safety verification for the ECCS driven by the electrically 4 trains during LBLOCA reflood phase using ATLAS

    International Nuclear Information System (INIS)

    Highlights: • Safety improvement by adopting 4 train emergency core cooling system was validated experimentally. • General thermal hydraulic behaviors of the system during LBLOCA reflood phase were successfully demonstrated. • Key parameters such as the liquid levels, the PCTs, the quenching time, and the ECC bypass ratios were investigated. • Asymmetric effects of the different combination of safety injection were negligible during the reflood period. - Abstract: The APR1400 is equipped with four safety injection pumps driven by two emergency diesel generators. However, the design has been changed so that the four safety injection pumps are driven by 4 emergency diesel generators during the design certification process from the U.S. NRC. Thus, 4 safety injection pumps (SIPs) are completely independent electrically and mechanically and three safety injection pumps are available in a single failure condition. This design change could have a certain effects on the thermal-hydraulic phenomenon occurring in the downcomer region during the late reflood phase of a large break loss of coolant accident (LBLOCA). Thus, in this study, a verification experiment for the reflood phase of a LBLOCA was performed to evaluate the core cooling performance of the 4 train emergency core cooling system (ECCS) with an assumption of a single failure. And the different combinations of three SIPs positions were tested to investigate the asymmetric effects on the reactor core cooling performance. The overall experimental results revealed the typical thermal–hydraulic trends expected to occur during the reflood phase of a large-break LOCA scenario for the APR1400. Experiment with the injection of three SIPs showed a faster core quenching time and lower bypass ratio than that of the case in which two SIPs were injected. The RPV wall temperature distributions showed the similar trend in spite of the different SIP combinations

  16. Alteration of the cementitious material under the saline environment

    International Nuclear Information System (INIS)

    Leaching experiment of ordinary and fly ash mixed cement were carried out by using the artificial sea water and deionized water as leachates. The pH values of saline leachates were decreased at the lower solid/liquid ratio in comparison with the case of deionized leachates. Mg(OH)2 and ettringite were observed only in the case of saline water. The results of the geochemical calculation with inputs of Mg(OH)2, ettringite and hydrotalcite well represented in the change of pH value and the mineral-composition with those of the experiment. However, in the latter stage of the fly ash mixed cement case, calculated concentrations of Si and Al of the leachate weren't consistent with the observed values. These results showed that substitution of Mg for Ca and influences of sulfate ion should be considered in the modeling of the cement alteration in the saline water case, and Al-substituted C-S-H might be considered in the alteration of fly ash mixed cement. (author)

  17. Desorption isotherms of cementitious materials: study of an accelerated protocol and estimation of RVE

    International Nuclear Information System (INIS)

    In the framework of French radioactive waste management and storage, the durability evaluation and prediction of concrete structures requires the knowledge of desorption isotherm of concrete. The aim of the present study is to develop an accelerated experimental method to obtain desorption isotherm of cementitious materials more quickly and to estimate the Representative Volume Element (RVE) size related to the desorption isotherm of concrete. In order to ensure that experimental results can be statistically considered representative, a great amount of sliced samples of cementitious materials with three different thicknesses (1 mm, 2 mm and 3 mm) have been de-saturated. The effect of slice thickness and the saturation condition on the mass variation kinetics and the desorption isotherms is analyzed. The influence of the aggregate distribution on the water content and the water saturation degree is also analyzed. A method based on statistical analysis of water content and water saturation degree is proposed to estimate the RVE for water desorption experiment of concrete. The evolution of shrinkage with relative humidity is also followed for each material during the water desorption experiment. A protocol of cycle of rapid desaturation-re-saturation is applied and shows the existence of hysteresis between desorption and adsorption. (author)

  18. Studies of ancient concrete as analogs of cementitious sealing materials for a repository in tuff

    Energy Technology Data Exchange (ETDEWEB)

    Roy, D.M.; Langton, C.A.

    1989-03-01

    The durability of ancient cementitious materials has been investigated to provide data applicable to determining the resistance to weathering of concrete materials for sealing a repository for storage of high-level radioactive waste. Because tuff and volcanic ash are used in the concretes in the vicinity of Rome, the results are especially applicable to a waste repository in tuff. Ancient mortars, plasters, and concretes collected from Rome, Ostia, and Cosa dating to the third century BC show remarkable durability. The aggregates used in the mortars, plasters, and concretes included basic volcanic and pyroclastic rocks (including tuff), terra-cotta, carbonates, sands, and volcanic ash. The matrices of ancient cementitious materials have been characterized and classified into four categories: (1) hydraulic hydrated lime and hydrated lime cements, (2) hydraulic aluminous and ferruginous hydrated lime cements ({plus_minus} siliceous components), (3) pozzolana/hydrated lime cements, and (4) gypsum cements. Most of the materials investigated are in category (3). The materials were characterized to elucidate aspects of the technology that produced them and their response to the environmental exposure throughout their centuries of existence. Their remarkable properties are the result of a combination of chemical, mineralogical, and microstructural factors. Their durability was found to be affected by the matrix mineralogy, particle size, and porosity; aggregate type, grading and proportioning; and the methodology of placement. 30 refs.

  19. Cementitious stabilization of chromium, arsenic, and selenium in a cooling tower sludge

    International Nuclear Information System (INIS)

    The Federal Facility Compliance Agreement (FFCA) establishes an aggressive schedule for conducting studies and treatment method development under the treatability exclusion of RCRA for those mixed wastes for which treatment methods and capabilities have yet to be defined. One of these wastes is a radioactive cooling tower sludge. This paper presents some results of a treatability study of the stabilization of this cooling tower sludge in cementitious waste forms. The sample of the cooling tower sludge obtained for this study was found to be not characteristically hazardous in regard to arsenic, barium, chromium, lead, and selenium, despite the waste codes associated with this waste. However, the scope of this study included spiking three RCRA metals to two orders of magnitude above the initial concentration to test the limits of cementitious stabilization. Chromium and arsenic were spiked at concentrations of 200, 2,000, and 20,000 mg/kg, and selenium was spiked at 100, 1,000, and 10,000 mg/kg (concentrations based on the metal in the sludge solids). Portland cement, Class F fly ash, and slag were selected as stabilizing agents in the present study. Perlite, a fine, porous volcanic rock commonly used as a filter aid, was used as a water-sorptive agent in this study in order to control bleed water for high water contents. The highly porous perlite dust absorbs large amounts of water by capillary action and does not present the handling and processing problems exhibited by clays used for bleed water control

  20. Micro-mechanics based representative volume element modeling of heterogeneous cementitious materials

    Science.gov (United States)

    Shahzamanian Sichani, Mohammadmehdi

    The current work focuses on evaluation of the effective elastic properties of cementitious materials through a voxel based FEA approach. Voxels are generated for a heterogeneous cementitious material (Type-I cement) consisting of typical volume fractions of various constituent phases from digital microstructures. The microstructure is modeled as a micro-scale representative volume element (RVE) in ABAQUS to generate cubes several tens of microns in dimension and subjected to various prescribed deformation modes to generate the effective elastic tensor of the material. The RVE-calculated elastic properties such as moduli and Poisson's ratio are validated through an asymptotic expansion homogenization (AEH) and compared with rule of mixtures. Both Periodic (PBC) and Kinematic boundary conditions (KBC) are investigated to determine if the elastic properties are invariant due to boundary conditions. In addition the method of "Windowing" was used to assess the randomness of the constituents and to validate how the isotropic elastic properties were determined. The average elastic properties obtained from the displacement based FEA of various locally anisotropic micro-size cubes extracted from an RVE of size 100x100x100 microns showed that the overall RVE response was fully isotropic. The effects of domain size, degree of hydration, kinematic and periodic boundary conditions, domain sampling techniques, local anisotropy, particle size distribution (PSD), and random microstructure on elastic properties are studied.

  1. The Influence of Calcium Chloride Salt Solution on the Transport Properties of Cementitious Materials

    Directory of Open Access Journals (Sweden)

    Yaghoob Farnam

    2015-01-01

    Full Text Available The chemical interaction between calcium chloride (CaCl2 and cementitious binder may alter the transport properties of concrete which are important in predicting the service life of infrastructure elements. This paper presents a series of fluid and gas transport measurements made on cementitious mortars before and after exposure to various solutions with concentrations ranging from 0% to 29.8% CaCl2 by mass. Fluid absorption, oxygen diffusivity, and oxygen permeability were measured on mortar samples prepared using Type I and Type V cements. Three primary factors influence the transport properties of mortar exposed to CaCl2: (1 changes in the degree of saturation, (2 calcium hydroxide leaching, and (3 formation of chemical reaction products (i.e., Friedel’s salt, Kuzel’s salt, and calcium oxychloride. It is shown that an increase in the degree of saturation decreases oxygen permeability. At lower concentrations (~12%, the formation of chemical reaction products (mainly calcium oxychloride is a dominant factor decreasing the fluid and gas transport in concrete.

  2. COMBS: open source python library for RVE generation - Application to microscale diffusion simulations in cementitious materials

    International Nuclear Information System (INIS)

    In the context of radioactive waste storage and disposal, the knowledge of the concrete diffusivity is primordial in the numerical simulations of the long term behavior of these materials. COMBS is an open source python library, it is used to define the shapes of the inclusions, to insert them in the box featuring the representative volume element (RVE) of the cementitious medium, and to assess their diffusive properties. The algorithms developed in COMBS target a fast placement of the inclusions and a fast generation of the RVE shape and mesh. Two application cases are considered: the unaltered material diffusivity and the degraded material diffusivity. The first case of application focuses on the description of the capillary porosity. The second application case focuses on the description of the degradation of cementitious material (mineral and porosity) and the diffusive properties associated. The reliability of the analytical effective medium approximations (MT and SC) is confirmed from 3D finite elements (FE) calculations performed on a matrix-inclusions microstructure obtained by RVE generation with Combs. The results also show the need to take into account the percolation behavior

  3. Thermal conductivity of cementitious grouts for geothermal heat pumps. Progress report FY 1997

    Energy Technology Data Exchange (ETDEWEB)

    Allan, M.L.

    1997-11-01

    Grout is used to seal the annulus between the borehole and heat exchanger loops in vertical geothermal (ground coupled, ground source, GeoExchange) heat pump systems. The grout provides a heat transfer medium between the heat exchanger and surrounding formation, controls groundwater movement and prevents contamination of water supply. Enhanced heat pump coefficient of performance (COP) and reduced up-front loop installation costs can be achieved through optimization of the grout thermal conductivity. The objective of the work reported was to characterize thermal conductivity and other pertinent properties of conventional and filled cementitious grouts. Cost analysis and calculations of the reduction in heat exchanger length that could be achieved with such grouts were performed by the University of Alabama. Two strategies to enhance the thermal conductivity of cementitious grouts were used simultaneously. The first of these was to incorporate high thermal conductivity filler in the grout formulations. Based on previous tests (Allan and Kavanaugh, in preparation), silica sand was selected as a suitable filler. The second strategy was to reduce the water content of the grout mix. By lowering the water/cement ratio, the porosity of the hardened grout is decreased. This results in higher thermal conductivity. Lowering the water/cement ratio also improves such properties as permeability, strength, and durability. The addition of a liquid superplasticizer (high range water reducer) to the grout mixes enabled reduction of water/cement ratio while retaining pumpability. Superplasticizers are commonly used in the concrete and grouting industry to improve rheological properties.

  4. 改进的ECC算法在网络信息安全中的研究%Research on Improved ECC Algorithm in Network and Information Security

    Institute of Scientific and Technical Information of China (English)

    魏先民

    2013-01-01

    目前网络信息安全遭受许多网络威胁,现有的加密算法已经无法满足网络信息安全的需求.提出了一种基于网络信息安全的改进ECC算法,该算法基于原有的ECC算法,对其进行点积运算的优化和平方剩余判定的优化,并对私钥更新变换进行了优化,以提高原有ECC算法的运算效率和安全性能.实验表明,基于网络信息安全的改进ECC算法在安全性能上比常用的RSA算法以及原有的ECC算法都有显著提高,该方案切实有效.%Network information security suffers many network threats, the existing encryption algorithm has been unable to meet the needs of network and information security problems. This paper proposed an improved ECC algorithm based on network information security, and the algorithm is based on the original ECC algorithm and makes its dot product operation optimization and square residual determination,optimization and transformation of the private key update to improve the original operational efficiency and safety performance of the ECC algorithm. The experiments show that the ECC algorithm based on network information security has significant improvements in safety performance than the RSA algorithm as well as the original ECC algorithms,and the program is effective.

  5. Hydration mechanism and leaching behavior of bauxite-calcination-method red mud-coal gangue based cementitious materials.

    Science.gov (United States)

    Zhang, Na; Li, Hongxu; Liu, Xiaoming

    2016-08-15

    A deep investigation on the hydration mechanism of bauxite-calcination-method red mud-coal gangue based cementitious materials was conducted from viewpoints of hydration products and hydration heat analysis. As a main hydration product, the microstructure of C-A-S-H gel was observed using high resolution transmission electron microscopy. It was found that the C-A-S-H gel is composed of amorphous regions and nanocrystalline regions. Most of regions in the C-A-S-H gel are amorphous with continuous distribution, and the nanocrystalline regions on scale of ∼5nm are dispersed irregularly within the amorphous regions. The hydration heat of red mud-coal gangue based cementitious materials is much lower than that of the ordinary Portland cement. A hydration model was proposed for this kind of cementitious materials, and the hydration process mainly consists of four stages which are dissolution of materials, formation of C-A-S-H gels and ettringite, cementation of hydration products, and polycondensation of C-A-S-H gels. There are no strict boundaries among these four basic stages, and they proceed crossing each other. Moreover, the leaching toxicity tests were also performed to prove that the developed red mud-coal gangue based cementitious materials are environmentally acceptable. PMID:27131457

  6. Corrosion of cementitious materials under geological disposal conditions with resulting effects on the geochemical stability of clay minerals

    International Nuclear Information System (INIS)

    The long-term behaviour of cemented fly ashes and bentonite (MX80) has been investigated in high saline solutions by means of a cascade experiment, batch experiment and by the geochemical modelling of the observed reactions. In contact to IP21 the degradation of CSH phases in the cementitious material could be proposed indicated by the accumulation of Ca in solution. In contact to NaCl brine only a small amount of Ca in solution could be detected indicating a slight dissolution of CSH phases in the cementitious material. Considering the good agreement between the time accelerating laboratory scale cascade experiment and the modelled reaction path using the computer code EQ3/6 we conclude, that it is possible to predict the chemical behaviour of cementitious materials in salt solutions. The degradation experiments with MX80 and cementitious material in NaCl and IP21 solution showed an accumulation of Si and Al in solution and then a remove possibly indicating the formation of new phases. In contact to high saline solutions a reduction of swelling pressure of MX80 at various reduced initial dry densities could be observed in comparison to pure water. Moreover a reduced water-uptake of MX80 in contact to high saline and alkaline solution was obtained. (authors)

  7. Composites

    Science.gov (United States)

    Taylor, John G.

    The Composites market is arguably the most challenging and profitable market for phenolic resins aside from electronics. The variety of products and processes encountered creates the challenges, and the demand for high performance in critical operations brings value. Phenolic composite materials are rendered into a wide range of components to supply a diverse and fragmented commercial base that includes customers in aerospace (Space Shuttle), aircraft (interiors and brakes), mass transit (interiors), defense (blast protection), marine, mine ducting, off-shore (ducts and grating) and infrastructure (architectural) to name a few. For example, phenolic resin is a critical adhesive in the manufacture of honeycomb sandwich panels. Various solvent and water based resins are described along with resin characteristics and the role of metal ions for enhanced thermal stability of the resin used to coat the honeycomb. Featured new developments include pultrusion of phenolic grating, success in RTM/VARTM fabricated parts, new ballistic developments for military vehicles and high char yield carbon-carbon composites along with many others. Additionally, global regional market resin volumes and sales are presented and compared with other thermosetting resin systems.

  8. Design and Micromagnetic Simulation of Fe/L10-FePt/Fe Trilayer for Exchange Coupled Composite Bit Patterned Media at Ultrahigh Areal Density

    Directory of Open Access Journals (Sweden)

    Warunee Tipcharoen

    2015-01-01

    Full Text Available Exchange coupled composite bit patterned media (ECC-BPM are one candidate to solve the trilemma issues, overcome superparamagnetic limitations, and obtain ultrahigh areal density. In this work, the ECC continuous media and ECC-BPM of Fe/L10-FePt/Fe trilayer schemes are proposed and investigated based on the Landau-Lifshitz-Gilbert equation. The switching field, Hsw, of the hard phase in the proposed continuous ECC trilayer media structure is reduced below the maximum write head field at interlayer exchange coupling between hard and soft phases, Aex, higher than 20 pJ/m and its value is lower than that for continuous L10-FePt single layer media and L10-FePt/Fe bilayer. Furthermore, the Hsw of the proposed ECC-BPM is lower than the maximum write head field with exchange coupling coefficient between neighboring dots of 5 pJ/m and Aex over 10 pJ/m. Therefore, the proposed ECC-BPM trilayer has the highest potential and is suitable for ultrahigh areal density magnetic recording technology at ultrahigh areal density. The results of this work may be gainful idea for nanopatterning in magnetic media nanotechnology.

  9. Fluid flow separation in a reactor pressure vessel during an ECC injection. Single phase flow and two phase flow (air-water) experimental results

    International Nuclear Information System (INIS)

    Full text of publication follows: Within the framework of the nuclear power plant lifetime issue, the assessment of the French 900 MWe (3-loops) series reactor pressure vessel (RPV) integrity has been performed. A simplified analysis has shown that the most severe loading conditions are given by the small break loss of coolant accidents due to the pressurized injection of cold water (9 deg. C) into the cold leg and down comer of the RPV. During these transient scenarios, single or two-phase (uncovered cold leg) flows have been shown in the cold leg, depending on the crack size and RPV model (900 MWe or 1300 MWe). An experimental study has been carried out, on the one hand, to consolidate the numerical results obtained with CFD home code (Code-Saturne) which mainly showed the stratified flow in the cold leg and the fluid flow separation and its oscillations in the down comer during a single phase scenario. These physical phenomena are important for the thermal RPV loading assessment. On the other hand, the absence of experimental two-phase data necessitated to carry out an experimental study around the mixing area behavior (free surface, stratified flow) during an ECC injection with an uncovered cold leg. The new EDF R and D mock up, called HYBISCUS, is a facility which is made out of Plexiglas (atmosphere pressure) and represents a half scale CP0 geometry with one cold leg and part of the down comer. The mock up modularity allows us to insert representative ECC nozzles and a thermal shield. In reference to the reactor scenarios, the experimental operating conditions are derived from the conservation of the density effects (Froude number). For that, a heated salted water flow is used to represent the ECC injection whereas water represents the cold leg fluid. This mock up has been defined in order to represent single phase flow (cold leg and down comer full of water) or two-phase flow (uncovered cold leg) ECC scenarios. This paper reports experimental results

  10. Flexural strengthening of RC beams using hybrid composite plate (HCP): experimental and analytical study

    OpenAIRE

    Esmaeeli, Esmaeel; Barros, Joaquim A. O.

    2015-01-01

    Hybrid Composite Plate (HCP) is a reliable recently proposed retrofitting solution for concrete structures, which is composed of a strain hardening cementitious composite (SHCC) plate reinforced with Carbon Fibre Reinforced Polymer (CFRP). This system benefits from the synergetic advantages of these two composites, namely the high ductility of SHCC and the high tensile strength of CFRPs. In the materialstructural of HCP, the ultra-ductile SHCC plate acts as a suitable medium for s...

  11. Development of New Cementitious Caterials by Alkaline Activating Industrial by-Products

    Science.gov (United States)

    Fernández-Jimenez, A.; García-Lodeiro, I.; Palomo, A.

    2015-11-01

    The alkaline activation of aluminosiliceous industrial by-products such as blast furnace slag and fly ash is widely known to yield binders whose properties make them comparable to or even stronger and more durable than ordinary Portland cement. The present paper discusses activation fundamentals (such as the type and concentration of alkaline activator and curing conditions) as well as the structure of the cementitious gels formed (C-A-S-H, N-A-S-H). The durability and strength of these systems make these materials apt for use in many industrial applications, such as precast concrete elements (masonery blocks, railroad sleepers), protective coatings for materials with low fire ratings and lightweight elements.

  12. MORTAR INCORPORATING SUPPLEMENTARY CEMENTITIOUS MATERIALS: STRENGTH, ISOTHERMAL CALORIMETRY AND ACIDS ATTACK

    Directory of Open Access Journals (Sweden)

    Y. Senhadji

    2016-05-01

    Full Text Available Supplementary cementitious materials (SCMs prove to be effective to meet most of the requirements of durable concrete and leads to a significant reduction in CO2 emissions. This research studies the effect different SCMs (natural pozzolan (PN/ limestone fine (FC at various remplacement levels on the physical and mechano-chemical resistance of blended mortar. The paper primarily deals with the characteristics of these materials, including heat of hydration, strength and effects of aggressive chemical environments (using sulphuric acid and nitric acid. Over 6 mixes were made and compared to the control mix. Tests were conducted at different ages up to 360 days. The experimental results in general showed that Algerian mineral admixtures (PN/FC were less vulnerable to nitric and sulphuric acid attack and improved the properties of mortars, but at different rates depending on the quantity of binder.

  13. Multiscale characterization of chemical–mechanical interactions between polymer fibers and cementitious matrix

    Energy Technology Data Exchange (ETDEWEB)

    Hernández-Cruz, Daniel; Hargis, Craig W.; Bae, Sungchul; Itty, Pierre A.; Meral, Cagla; Dominowski, Jolee; Radler, Michael J.; Kilcoyne, David A.; Monteiro, Paulo J. M.

    2014-04-01

    Together with a series of mechanical tests, the interactions and potential bonding between polymeric fibers and cementitious materials were studied using scanning transmission X-ray microscopy (STXM) and microtomography (lCT). Experimental results showed that these techniques have great potential to characterize the polymer fiber-hydrated cement-paste matrix interface, as well as differentiating the chemistry of the two components of a bi-polymer (hybrid) fiber the polypropylene core and the ethylene acrylic acid copolymer sheath. Similarly, chemical interactions between the hybrid fiber and the cement hydration products were observed, indicating the chemical bonding between the sheath and the hardened cement paste matrix. Microtomography allowed visualization of the performance of the samples, and the distribution and orientation of the two types of fiber in mortar. Beam flexure tests confirmed improved tensile strength of mixes containing hybrid fibers, and expansion bar tests showed similar reductions in expansion for the polypropylene and hybrid fiber mortar bars.

  14. Influence of cementitious additions on rheological and mechanical properties of reactive powder concretes

    Science.gov (United States)

    Zenati, A.; Arroudj, K.; Lanez, M.; Oudjit, M. N.

    2009-11-01

    Following needs of concrete market and the economic and ecological needs, several researchers, all over the world, studied the beneficial effect which the incorporation of the mineral additions in Portland cement industry can bring. It was shown that the incorporation of local mineral additions can decrease the consumption of crushing energy of cements, and reduce the CO2 emission. Siliceous additions, moreover their physical role of filling, play a chemical role pozzolanic. They contribute to improving concrete performances and thus their durability. The abundance of dunes sand and blast furnace slag in Algeria led us to study their effect like cementitious additions. The objective of this paper is to study the effect of the incorporation of dunes sand and slag, finely ground on rheological and mechanical properties of reactive powder concretes containing ternary binders.

  15. Hydration mechanism of a cementitious material prepared with Si-Mn slag

    Science.gov (United States)

    Zhang, Xu-Fang; Ni, Wen; Wu, Jun-Yu; Zhu, Li-Ping

    2011-04-01

    A cementitious material was prepared by mixing 80wt% Si-Mn slag powder, 10wt% lime, and 10wt% anhydrite. The compressive strength of mortar samples reaches 51.48 MPa after 28 d curing. The analyses of X-ray diffraction (XRD) and scanning electron microscopy (SEM) show that much ettringite is formed in the sample cured for 3 d, and C-S-H gel increases rapidly during subsequent curing. Nuclear magnetic resonance (NMR) analysis of 29Si and 27Al and infrared spectroscopy (IR) analysis show that aluminum decomposition from tetrahedral network of the slag glass and its subsequent migration and re-combination play an important role in the process of hydration and strength development of the samples.

  16. Contribution to the study of multi-physical phenomena in cementitious materials

    International Nuclear Information System (INIS)

    This document is a synthesis of the applied research studies undertaken by the author during ten years, first at the University of Marne-La-Vallee during the period 1999-2002, then at the CEA. These studies concern the modeling and the numerical simulations of the cementitious materials behavior subjected on the one hand to moderate thermomechanical and hydric loadings, and on the other hand to chemical attacks due to the migration of calcium, carbonate and sulfate ions. The developed approaches may be viewed as multi-physical in the sense that the models used for describing the behavior couple various fields and phenomena such as mechanics, thermal, hydric and ionic transfers, and chemistry. In addition, analytical up-scaling techniques are applied to estimate the physical properties associated with these phenomena (mechanical, hydraulic and diffusive parameters) as a function of the microstructure and the hydric state of the material. (author)

  17. Electrokinetic decontamination of porous media. Experimental study and modeling of the cesium transport through cementitious materials

    International Nuclear Information System (INIS)

    The aim of this work is to study the nuclear decontamination of cementitious materials by an electrokinetic method. Special attention is given to the understanding of the mechanisms leading to the removal of radioelements from the material. First, a bibliographic research allowed us to reduce the study to a normalized mortar and to cesium ions. This choice was confirmed by the experimental study of interactions between the contaminant and the material. Next, the efficiency of the electrokinetic decontamination was experimentally shown in laboratory conditions and electromigration was identified as the main transport phenomenon. Then, a numerical model was implemented in order to describe the ionic transport by electromigration. The results obtained were compared to experiments. Finally, some applications and developments of the electrokinetic process were proposed. (author)

  18. Synthesis of a Cementitious Material Nanocement Using Bottom-Up Nanotechnology Concept: An Alternative Approach to Avoid CO2 Emission during Production of Cement

    OpenAIRE

    Byung Wan Jo; Sumit Chakraborty; Kwang Won Yoon

    2014-01-01

    The world’s increasing need is to develop smart and sustainable construction material, which will generate minimal climate changing gas during their production. The bottom-up nanotechnology has established itself as a promising alternative technique for the production of the cementitious material. The present investigation deals with the chemical synthesis of cementitious material using nanosilica, sodium aluminate, sodium hydroxide, and calcium nitrate as reacting phases. The characteristic ...

  19. Methods to assess radioisotope migration in cementitious media using radial diffusion and advection

    International Nuclear Information System (INIS)

    One of the primary aims of this project is to understand how a range of isotopes associated with radioactive wastes, move through the cementitious media potentially present in a geological disposal facility (GDF). This paper describes the development of experimental methods that use radial flow from intact cylinders of cementitious material to evaluate the potential for diffusion and advection of relevant isotopes through Nirex reference vault backfill (NRVB). The small scale and cost effectiveness of the approach means that multiple experiments can be undertaken encompassing the full range of physical (and chemical) variations. The radial flow experimental method uses small pre-cast cylinders of the matrix under investigation. For diffusion an appropriate concentration of the isotope of interest (90Sr in the present experiments) is introduced into a cavity in the centre of the cylinder, which is then sealed, and placed in a solution previously equilibrated with the matrix. The increase in concentration of the isotope in the external solution is then determined at defined time intervals. For advection 90Sr is similarly introduced into the central core of the cylinder and then equilibrated water is forced under nitrogen pressure, from the central core to the outside of the cylinder where it is collected in a tray prior to analysis. Both experimental set ups and results have been modelled using conventional numerical solutions and the simulation package GoldSim. Concerning diffusion experiments the modelled data reproduces the observed data effectively with a right diffusivity value of 9*10-11 m2/s. Concerning advection results are more mitigated and need further investigation

  20. Implications of the use of low-pH cementitious materials in high activity radioactive waste repositories

    International Nuclear Information System (INIS)

    One of the most accepted engineering construction concepts for high radioactive nuclear waste of underground repositories considers the use of low pH cementitious materials, in order to avoid the formation of an alkaline plume fluid which perturbs one of the engineered barriers of the repository, the bentonite. The accepted solution to maintain the bentonite stability, which is function of the pH, is to develop cementitious materials that generate pore waters with pH ≤ 11, because the corrosion velocity of the clay is significantly reduced below this value. The IETcc-CSIC has focused the research activity on low-pH cementitious materials using two cements: Ordinary Portland Cements (OPC) and Calcium Aluminates Cements (CAC). In both cases, the achievement of a low-pH environment implies the use of high content of mineral admixtures to prepare the binder. Obviously, the inclusion of high contents of mineral admixtures in the cement formulation modifies most of the concrete 'standard' properties and the microstructure of the obtained cement products. When designing a concrete based on low-pH binders, not only the functional requirements have to be reached but also the modifications of the basic properties of the concrete must be taken into account. Besides, due to the location and the long service life of this type of products, their durability properties must be also guaranteed. This paper deals with the procedure followed in the design of a specific application of low pH cements; for instance, the shotcrete plug fabrication. The challenge of this type of use (shotcreting) is more complex taking into account that requires the employment of additives that must be compatible with the concrete mixture. Furthermore, their effectiveness must be assured without increase the pH above the admissible levels. Therefore, their compatibility with admixtures is tested in the present work. The compliance of the requirements for a shotcrete plug was evaluated at laboratory scale

  1. Investigation of the methodology for selecting cementitious materials for the different components in the underground facility. Deriving component requirements and investigation of the weighting methodology

    International Nuclear Information System (INIS)

    For conceptual facility design, it is necessary to select appropriate cementitious materials to meet the requirements for each component of the underground disposal facility before detailed investigations are carried out for site selection. Cementitious materials will be used for constructing major components of the underground facility and suitable materials for each component are selected tentatively by comparing the selection methodology with relevant information about the component for which the cementitious material will be used. The objective of this study is to list and sort the required characteristics of cementitious materials for each component in the facility, in order to provide input for determining the material selection methodology. When deriving the required characteristics of the cementitious materials for each component, physico-chemical properties that will fulfil required operational functions and minimize effects on the safety function of the disposal system due to alteration or degradation were investigated. Based on these investigations, step changes in the state of the disposal system are identified, including the bedrock around the drifts, by considering alteration or degradation of the cementitious material. Significant components for ensuring the safety function can be identified by specifying the step changes in the state of the disposal system. (author)

  2. 基于 ECC算法的TLS协议设计与优化%Design and optimization of TLS protocol based on ECC

    Institute of Scientific and Technical Information of China (English)

    王魁; 李立新; 余文涛; 王冠众; 王振

    2014-01-01

    为解决TLS协议存在的握手交互次数多、密钥计算开销大等诸多性能问题,在对TLS协议进行分析的基础上,设计了一种基于ECC算法的TLS协议,用ECC算法代替原协议中的RSA算法,充分发挥ECC算法的优越性,提高协议的性能。使用缓存握手参数的方法对协议交互过程进行优化,通过SVO逻辑对优化后的协议进行形式化证明,证明协议是安全的。通过实验将改进后的协议与原协议进行了比较分析,结果表明,随着协议安全等级的提高,改进后的协议在性能上具有明显的优越性。%In order to improve efficiency flaws of TLS protocol such as frequent interaction times and high computation over-load,through the analysis and research on the protocol,this paper proposed a new ECC-based protocol in which RSA was sub-stituted by ECC.It improved the new protocol performance.Through cache handshake parameters,the number of shake hands interaction was less.It used SVO logic to analyze ECC-based protocol,and the result shows that it is secure.The simulation experiment and comparison with original protocol show that with the increased level of security,the new ECC-based protocol is more predominant.

  3. Conductivity probes for two-phase flow pattern determination during emergency core cooling (ECC) injection experiments at the COCO facility (PHDR)

    International Nuclear Information System (INIS)

    The paper describes the use of needle-shaped conductivity probes for two-phase flow pattern determination during simulated ECC. The first results appear promising and the use of such probes as additional instrumentation can be envisaged in the future on power reactors, e.g. for the control of water level, once some improvements have been achieved, in particular regarding the stability of the probe. (orig.)

  4. Cementitious Near-Field Sorption Data Base for Performance Assessment of an ILW Repository in Opalinus Clay

    Energy Technology Data Exchange (ETDEWEB)

    Wieland, E.; Van Loon, L. R

    2003-08-01

    The present report describes a cement sorption database (SDB) for the safety-relevant radionuclides to be disposed of in the planned Swiss repository for long-lived intermediate-level radioactive wastes (ILW). This report is an update on earlier SDBs, which were compiled for the cementitious near field of a repository for low- and intermediate-level radioactive wastes (L/ILW) by BRADBURY + SAROTT (1995) and BRADBURY + VAN LOON (1998). The radionuclide inventories are determined by the waste streams to be disposed of in the ILW repository. A list of the safety-relevant radionuclides was provided based on the currently available information on ILW inventories. The compositions of the cement porewaters in the near fields of the L/ILW and ILW repositories, which had been calculated using well-established codes for modelling cement degradation, were compared to identify any differences in the near-field conditions and to assess their influence on radionuclide sorption. Sorption values were selected based on the previously reported SDBs for the near field of the L/ILW repository. Sorption values were revised if new information and/or data were available which allowed changes to or re-appraisals of the data to be made. The sorption values recommended in this report were either selected on the basis of data from in-house experimental studies or from literature data. For some key radioelements, i.e., Cs(l), Sr(II), Ni(II), Eu(lll), Th(IV) and Sn(IV), new data were available from in-house measurements. These elements had been selected for experimental studies due to their relevance to safety assessment and/or their importance as appropriate chemical analogues. Degradation products of bitumen and cellulose, concrete admixtures and cement-derived near-field colloids were taken into account as the main potential perturbations, which could reduce radionuclide sorption in the near field. Possible impacts of the perturbing factors on radionuclide mobility were considered and

  5. Cementitious Near-Field Sorption Data Base for Performance Assessment of an ILW Repository in Opalinus Clay

    International Nuclear Information System (INIS)

    The present report describes a cement sorption database (SDB) for the safety-relevant radionuclides to be disposed of in the planned Swiss repository for long-lived intermediate-level radioactive wastes (ILW). This report is an update on earlier SDBs, which were compiled for the cementitious near field of a repository for low- and intermediate-level radioactive wastes (L/ILW) by BRADBURY + SAROTT (1995) and BRADBURY + VAN LOON (1998). The radionuclide inventories are determined by the waste streams to be disposed of in the ILW repository. A list of the safety-relevant radionuclides was provided based on the currently available information on ILW inventories. The compositions of the cement porewaters in the near fields of the L/ILW and ILW repositories, which had been calculated using well-established codes for modelling cement degradation, were compared to identify any differences in the near-field conditions and to assess their influence on radionuclide sorption. Sorption values were selected based on the previously reported SDBs for the near field of the L/ILW repository. Sorption values were revised if new information and/or data were available which allowed changes to or re-appraisals of the data to be made. The sorption values recommended in this report were either selected on the basis of data from in-house experimental studies or from literature data. For some key radioelements, i.e., Cs(l), Sr(II), Ni(II), Eu(lll), Th(IV) and Sn(IV), new data were available from in-house measurements. These elements had been selected for experimental studies due to their relevance to safety assessment and/or their importance as appropriate chemical analogues. Degradation products of bitumen and cellulose, concrete admixtures and cement-derived near-field colloids were taken into account as the main potential perturbations, which could reduce radionuclide sorption in the near field. Possible impacts of the perturbing factors on radionuclide mobility were considered and

  6. An ElGamal_type(t,n)Threshold Digital Signature Scheme Based on ECC%一个基于ECC的ElGamal型(t,n)门限数字签名方案

    Institute of Scientific and Technical Information of China (English)

    张险峰; 秦志光; 刘锦德

    2003-01-01

    This paper comprehensively introduces and analyzes Shamir Secret Sharing, Pedersen's Verifiable SecretSharing based on ECC, verifiable secret sharing without a trusted center based on ECC and an ElGamal digital signa-ture scheme based on ECC. Based on the theoretical introduction, an ElGamal_type(t, n) threshold digital signaturescheme Based on ECC is designed. The performance of the scheme is analyzed. And an application based on thescheme is described. In the scheme, a trusted center to deal with the sharing secret is eliminated. No secret communi-cation is required in the signature issuing phase. The scheme is characterized by excellent security as well as high effi-ciency.

  7. The Behaviours of Cementitious Materials in Long Term Storage and Disposal of Radioactive Waste. Results of a Coordinated Research Project

    International Nuclear Information System (INIS)

    Radioactive waste with widely varying characteristics is generated from the operation and maintenance of nuclear power plants, nuclear fuel cycle facilities, research laboratories and medical facilities. This waste must be treated and conditioned, as necessary, to provide waste forms acceptable for safe storage and disposal. Many countries use cementitious materials (concrete, mortar, etc.) as a containment matrix for immobilization, as well as for engineered structures of disposal facilities. Radionuclide release is dependent on the physicochemical properties of the waste forms and packages, and on environmental conditions. In the use of cement, the diffusion process and metallic corrosion can induce radionuclide release. The advantage of cementitious materials is the added stability and mechanical support during storage and disposal of waste. Long interim storage is becoming an important issue in countries where it is difficult to implement low level waste and intermediate level waste disposal facilities, and in countries where cement is used in the packaging of waste that is not suitable for shallow land disposal. This coordinated research project (CRP), involving 24 research organizations from 21 Member States, investigated the behaviour and performance of cementitious materials used in an overall waste conditioning system based on the use of cement - including waste packaging (containers), waste immobilization (waste form) and waste backfilling - during long term storage and disposal. It also considered the interactions and interdependencies of these individual elements (containers, waste, form, backfill) to understand the processes that may result in degradation of their physical and chemical properties. The main research outcomes of the CRP are summarized in this report under four topical sections: (i) conventional cementitious systems; (ii) novel cementitious materials and technologies; (iii) testing and waste acceptance criteria; and (iv) modelling long

  8. Experimental Research on Steel Reinforced PP ECC Long Columns%钢筋增强PP ECC长柱试验

    Institute of Scientific and Technical Information of China (English)

    俞家欢; 吴琼; 赵同峰

    2012-01-01

    目的 研究钢筋增强PP ECC长柱力学性能,以期满足工程设计的抗震要求.方法 对6根钢筋增强PPECC柱和1根混凝土长柱进行轴压试验研究,分析不同长细比、龄期、配筋率等参数对柱子的破坏形态、变形特点和力学性能的影响.结果 试验参数范围内,轴压长柱的承载力随着长细比的增加缓慢下降,PP ECC柱的破坏形态与普通混凝土明显不同.极限状态时,PP ECC的裂纹宽度控制在0.05 mm以内,并且未出现PP ECC的压溃崩碎现象.PP ECC的承载力随着配筋率的增加而增加,但延性呈缓慢下降趋势.随着龄期的增长,PPECC延性有所下降,承载力虽然呈上升趋势,但变化不明显.结论 轴压PP ECC柱的破坏形态未出现普通混凝土的压溃崩碎现象,其延性优于普通混凝土,抗震性能优异.%This paper is aimed at studying the mechanical properties of steel reinforced PP ECC columns,in the hope of meeting seismic requirements of the engineering design. Axial compression test was performed for 6 steel reinforced PP ECC and 1 concrete long columns, analyzing the effect of different slenderness rati-o,age,reinforcement ratio and other parameters on the columns of failure forms,deformation characteristics and mechanical properties. Within the scope of test parameters, the bearing capacity of long columns under axial compression declines slowly with the slenderness ratio increases. Failure forms of PP ECC columns are apparently different from that of common concrete columns. In the limit state, PP ECC crack width is controlled within 0.05 mm and crushing phenomenon does not appear. The bearing capacity of PP ECC long columns is increased with reinforcement ratio increases, but the ductility decreased slowly. With the growth of age,ductility of PP ECC declines, the bearing capacity rises,but not significantly. Failure form of PP ECC columns does not present the crushing phenomenon of common concrete columns, ductility is

  9. The solubility of nickel and its migration through the cementitious backfill of a geological disposal facility for nuclear waste.

    Science.gov (United States)

    Felipe-Sotelo, M; Hinchliff, J; Field, L P; Milodowski, A E; Holt, J D; Taylor, S E; Read, D

    2016-08-15

    This work describes the solubility of nickel under the alkaline conditions anticipated in the near field of a cementitious repository for intermediate level nuclear waste. The measured solubility of Ni in 95%-saturated Ca(OH)2 solution is similar to values obtained in water equilibrated with a bespoke cementitious backfill material, on the order of 5×10(-7)M. Solubility in 0.02M NaOH is one order of magnitude lower. For all solutions, the solubility limiting phase is Ni(OH)2; powder X-ray diffraction and scanning transmission electron microscopy indicate that differences in crystallinity are the likely cause of the lower solubility observed in NaOH. The presence of cellulose degradation products causes an increase in the solubility of Ni by approximately one order of magnitude. The organic compounds significantly increase the rate of Ni transport under advective conditions and show measurable diffusive transport through intact monoliths of the cementitious backfill material. PMID:27198634

  10. Potential of Carbon Nanotube Reinforced Cement Composites as Concrete Repair Material

    OpenAIRE

    Tanvir Manzur; Nur Yazdani; Md. Abul Bashar Emon

    2016-01-01

    Carbon nanotubes (CNTs) are a virtually ideal reinforcing agent due to extremely high aspect ratios and ultra high strengths. It is evident from contemporary research that utilization of CNT in producing new cement-based composite materials has a great potential. Consequently, possible practical application of CNT reinforced cementitious composites has immense prospect in the field of applied nanotechnology within construction industry. Several repair, retrofit, and strengthening techniques a...

  11. Shear strengthening of damaged reinforced concrete beams with hybrid composite plates

    OpenAIRE

    Baghi, Hadi; Barros, Joaquim A. O.; Rezazadeh, Mohammadali; Laranjeira, João Pedro Santos

    2015-01-01

    This paper aims to evaluate experimentally the potentialities of Hybrid Composite Plates (HCPs) technique for the shear strengthening of reinforced concrete (RC) beams that were previously subjected to intense damage in shear. HCP is a thin plate of Strain Hardening Cementitious Composite (SHCC) reinforced with Carbon Fiber Reinforced Polymer (CFRP) laminates. For this purpose, an experimental program composed of two series of beams (rectangular and T cross section) was executed t...

  12. Project Opalinus Clay: Radionuclide Concentration Limits in the Cementitious Near-Field of an ILW Repository

    Energy Technology Data Exchange (ETDEWEB)

    Berner, U

    2003-05-01

    The disposal feasibility study currently performed by Nagra includes a succession of quantitative models, aiming at describing the fate of radionuclides potentially escaping from the repository system. In this chain of models the present report provides the so called 'solubility limits' (maximum expected concentrations) for safety relevant radionuclides from ILW wastes, disposed of in a chemically reducing, cementitious environment. From a chemical point of view, the pore waters of hydrated cement matrices provide an exceptional environment. Compared with usual ground waters exhibiting pH-values of around 8, cement pore waters are strongly alkaline with pH-values from 12.5 to 13.5 and contain nearly no carbonate and only little sulfate. Oxides and hydroxides mainly determine solubility and speciation of the elements. Solubility and speciation calculations in cementitious pore waters were performed using the very recently updated Nagra/PSI Chemical Thermodynamic Data Base (TDB) for the majority of the 36 elements addressed as potentially relevant. Wherever possible, maximum concentrations compiled in this report were based on geochemical calculations. In order to ensure full traceability, all thermodynamic data not included in the TDB are explicitly specified in the document. For similar reasons the compilation of results (Table 1) clearly distinguishes between calculated and recommended items. The heading 'CALCULATED' lists maximum concentrations based on data fully documented in the TDB; results under the heading 'RECOMMENDED' include data from other sources. The pH sensitivity of the results was examined by performing calculations at pH 13.4, in accordance with the pH of non-altered cement pore water. Solubility increases predominantly for elements that tend to form anionic hydroxide complexes (Sn, Pd, Zr, Ni, Eu, Cd, Mo, Co). Oxidizing conditions around +350 mV might be expected in the environment of nitrate-containing wastes. In

  13. Use of Cementitious Materials for SRS Reactor Facility In-Situ Decommissioning

    International Nuclear Information System (INIS)

    The United States Department of Energy (US DOE) concept for facility in-situ decommissioning (ISD) is to physically stabilize and isolate intact, structurally sound facilities that are no longer needed for their original purpose of producing (reactor facilities), processing (isotope separation facilities) or storing radioactive materials. The Savannah River Site 105-P and 105-R Reactor Facility ISD project requires approximately 250000 cubic yards of cementitious materials to fill the below-grade structure. The fills are designed to prevent subsidence, reduce water infiltration, and isolate contaminated materials. This work is being performed as a Comprehensive Environmental Response, Compensations and Liability Act (CERCLA) action and is part of the overall soil and groundwater completion projects for P- and R-Areas. Funding is being provided under the American Recovery and Reinvestment Act (ARRA). Cementitious materials were designed for the following applications: (A) Below-grade massive voids / rooms: Portland cement-based structural flowable fills for: (A.1) Bulk filling; (A.2) Restricted placement and (A.3) Underwater placement. (B) Special below-grade applications for reduced load bearing capacity needs: (B.1) Cellular portland cement lightweight fill. (C) Reactor vessel fills that are compatible with reactive metal (aluminum metal) components in the reactor vessels (C.1) Blended calcium aluminate - calcium sulfate based flowable fill; (C.2) Magnesium potassium phosphate flowable fill. (D) Caps to prevent water infiltration and intrusion into areas with the highest levels of radionuclides: (D.1) Portland cement based shrinkage compensating concrete. A system engineering approach was used to identify functions and requirements of the fill and capping materials. Laboratory testing was performed to identify candidate formulations and develop final design mixes. Scale-up testing was performed to verify material production and placement as well as fresh and cured

  14. Project Opalinus Clay: Radionuclide Concentration Limits in the Cementitious Near-Field of an ILW Repository

    International Nuclear Information System (INIS)

    The disposal feasibility study currently performed by Nagra includes a succession of quantitative models, aiming at describing the fate of radionuclides potentially escaping from the repository system. In this chain of models the present report provides the so called 'solubility limits' (maximum expected concentrations) for safety relevant radionuclides from ILW wastes, disposed of in a chemically reducing, cementitious environment. From a chemical point of view, the pore waters of hydrated cement matrices provide an exceptional environment. Compared with usual ground waters exhibiting pH-values of around 8, cement pore waters are strongly alkaline with pH-values from 12.5 to 13.5 and contain nearly no carbonate and only little sulfate. Oxides and hydroxides mainly determine solubility and speciation of the elements. Solubility and speciation calculations in cementitious pore waters were performed using the very recently updated Nagra/PSI Chemical Thermodynamic Data Base (TDB) for the majority of the 36 elements addressed as potentially relevant. Wherever possible, maximum concentrations compiled in this report were based on geochemical calculations. In order to ensure full traceability, all thermodynamic data not included in the TDB are explicitly specified in the document. For similar reasons the compilation of results (Table 1) clearly distinguishes between calculated and recommended items. The heading 'CALCULATED' lists maximum concentrations based on data fully documented in the TDB; results under the heading 'RECOMMENDED' include data from other sources. The pH sensitivity of the results was examined by performing calculations at pH 13.4, in accordance with the pH of non-altered cement pore water. Solubility increases predominantly for elements that tend to form anionic hydroxide complexes (Sn, Pd, Zr, Ni, Eu, Cd, Mo, Co). Oxidizing conditions around +350 mV might be expected in the environment of nitrate-containing wastes. In this case, significant

  15. Cementitious Barriers Partnership (CBP): Using the CBP Software Toolbox to Simulate Sulfate Attack and Carbonation of Concrete Structures - 13481

    International Nuclear Information System (INIS)

    The Cementitious Barriers Partnership (CBP) Project is a multi-disciplinary, multi-institutional collaboration supported by the U.S. Department of Energy Office of Tank Waste Management. The CBP project has developed a set of integrated modeling tools and leaching test methods to help improve understanding and prediction of the long-term hydraulic and chemical performance of cementitious materials used in nuclear applications. State-of-the-art modeling tools, including LeachXSTM/ORCHESTRA and STADIUMR, were selected for their demonstrated abilities to simulate reactive transport and degradation in cementitious materials. The new U.S. Environmental Protection Agency leaching test methods based on the Leaching Environmental Assessment Framework (LEAF), now adopted as part of the SW-846 RCRA methods, have been used to help make the link between modeling and experiment. Although each of the CBP tools has demonstrated utility as a standalone product, coupling the models over relevant spatial and temporal solution domains can provide more accurate predictions of cementitious materials behavior over relevant periods of performance. The LeachXSTM/ORCHESTRA and STADIUMR models were first linked to the GoldSim Monte Carlo simulator to better and more easily characterize model uncertainties and as a means to coupling the models allowing linking to broader performance assessment evaluations that use CBP results for a source term. Two important degradation scenarios were selected for initial demonstration: sulfate ingress / attack and carbonation of cementitious materials. When sufficient sulfate is present in the pore solution external to a concrete barrier, sulfate can diffuse into the concrete, react with the concrete solid phases, and cause cracking that significantly changes the transport and structural properties of the concrete. The penetration of gaseous carbon dioxide within partially saturated concrete usually initiates a series of carbonation reactions with both

  16. Cementitious Barriers Partnership (CBP): Using the CBP Software Toolbox to Simulate Sulfate Attack and Carbonation of Concrete Structures - 13481

    Energy Technology Data Exchange (ETDEWEB)

    Brown, K.G.; Kosson, D.S.; Garrabrants, A.C.; Sarkar, S. [Vanderbilt University, School of Engineering, CRESP, Nashville, TN 37235 (United States); Flach, G.; Langton, C.; Smith, F.G.III; Burns, H. [Savannah River National Laboratory, Aiken, SC 29808 (United States); Van der Sloot, H. [Hans Van der Sloot Consultancy, Dorpsstraat 216, 1721BV Langedijk (Netherlands); Meeussen, J.C.L. [Nuclear Research and Consultancy Group, Westerduinweg 3, Petten (Netherlands); Seignette, P.F.A.B. [Energy Research Center of The Netherlands, Petten (Netherlands); Samson, E. [SIMCO Technologies, Inc., Quebec (Canada); Mallick, P.; Suttora, L. [U.S. Department of Energy, Washington, DC (United States); Esh, D.; Fuhrmann, M.; Philip, J. [U.S. Nuclear Regulatory Commission, Washington, DC (United States)

    2013-07-01

    The Cementitious Barriers Partnership (CBP) Project is a multi-disciplinary, multi-institutional collaboration supported by the U.S. Department of Energy Office of Tank Waste Management. The CBP project has developed a set of integrated modeling tools and leaching test methods to help improve understanding and prediction of the long-term hydraulic and chemical performance of cementitious materials used in nuclear applications. State-of-the-art modeling tools, including LeachXS{sup TM}/ORCHESTRA and STADIUM{sup R}, were selected for their demonstrated abilities to simulate reactive transport and degradation in cementitious materials. The new U.S. Environmental Protection Agency leaching test methods based on the Leaching Environmental Assessment Framework (LEAF), now adopted as part of the SW-846 RCRA methods, have been used to help make the link between modeling and experiment. Although each of the CBP tools has demonstrated utility as a standalone product, coupling the models over relevant spatial and temporal solution domains can provide more accurate predictions of cementitious materials behavior over relevant periods of performance. The LeachXS{sup TM}/ORCHESTRA and STADIUM{sup R} models were first linked to the GoldSim Monte Carlo simulator to better and more easily characterize model uncertainties and as a means to coupling the models allowing linking to broader performance assessment evaluations that use CBP results for a source term. Two important degradation scenarios were selected for initial demonstration: sulfate ingress / attack and carbonation of cementitious materials. When sufficient sulfate is present in the pore solution external to a concrete barrier, sulfate can diffuse into the concrete, react with the concrete solid phases, and cause cracking that significantly changes the transport and structural properties of the concrete. The penetration of gaseous carbon dioxide within partially saturated concrete usually initiates a series of carbonation

  17. Prefabricated floor panels composed of fiber reinforced concrete and a steel substructure

    DEFF Research Database (Denmark)

    Lárusson, Lárus H.; Fischer, Gregor; Jönsson, Jeppe

    2013-01-01

    element.The activities described in this paper are an extension of previous work where composite floor panels composed of light gauge steel joists were integrally cast with a thin-walled Engineered Cementitious Composite (ECC) slab. The main focus of the present study was to revise and improve the design...... detailing of these integrally cast deck panels and to modify them by providing individually cast anchor points in the precast ECC slab, which are subsequently used to attach a steel truss substructure.Full-scale experiments were carried out to verify the structural behavior of the integrally cast panels and...

  18. ANDRA - Referential Materials. Volume 1: Context and scope; Volume 2: Argillaceous materials; Volume 3: Cementitious materials; Volume 4: The corrosion of metallic materials

    International Nuclear Information System (INIS)

    This huge document gathers four volumes. The first volume presents some generalities about materials used in the storage of radioactive materials (definition, design principle, current choices and corresponding storage components, general properties of materials and functions of the corresponding storage components, physical and chemical solicitations experienced by materials in a storage), and the structure and content of the other documents. The second volume addresses argillaceous materials. It presents some generalities about these materials in the context of a deep geological storage, and about their design. It presents and comments the crystalline and chemical, and physical and chemical characteristics of swelling argillaceous materials and minerals, describes how these swelling argillaceous materials are shaped and set up, presents and comments physical properties (hydraulic, mechanical and thermal properties) of these materials, comments and discusses the modelling of the geo-chemical behaviour, and their behaviour in terms of containment and transport of radionuclides. The third volume addresses cementitious materials. It presents some generalities about these materials in the context of a deep geological storage, and about their definition and specifications. It presents some more detailed generalities (cement definition and composition, hydration, microstructure of hydrated cements, adjuvants), presents and comments their physical properties (fresh concrete structure and influence of composition, main aimed properties in the hardened status, transfer, mechanical, and thermal properties, shaping and setting up of these materials, technical solutions for hydraulic works). The fourth volume addresses the corrosion of metallic materials. It presents some generalities about these materials in the context of a deep geological storage of radioactive materials. It presents metallic materials and discusses their corrosion behaviour. It describes the peculiarities

  19. Modelling Long-Term Evolution of Cementitious Materials Used in Waste Disposal

    International Nuclear Information System (INIS)

    This report summarizes the latest developments at SCK-CEN in modelling long-term evolution of cementitious materials used as engineered barriers in waste disposal. In a first section chemical degradation of concrete during leaching with rain and soil water types is discussed. The geochemical evolution of concrete thus obtained forms the basis for all further modelling. Next we show how the leaching model is coupled with a reactive transport module to determine leaching of cement minerals under diffusive or advective boundary conditions. The module also contains a simplified microstructural model from which hydraulic and transport properties of concrete may be calculated dynamically. This coupled model is simplified, i.e. abstracted prior to being applied to large-scale concrete structures typical of a near-surface repository. Both the original and simplified models are then used to calculate the evolution of hydraulic, transport, and chemical properties of concrete. Characteristic degradation states of concrete are further linked to distribution ratios that describe sorption onto hardened cement via a linear and reversible sorption process. As concrete degrades and pH drops the distribution ratios are continuously updated. We have thus integrated all major chemical and physical concrete degradation processes into one simulator for a particular scale of interest. Two simulators are used: one that can operate at relatively small spatial scales using all process details and another one which simulates concrete degradation at the scale of the repository but with a simplified cement model representation. (author)

  20. Long-term degradation (or improvement?) of cementitious grout/concrete for waste disposal at Hanford

    Energy Technology Data Exchange (ETDEWEB)

    Piepho, M.G. [Daniel B. Stephens & Associates, Inc., Richland, WA (United States)

    1997-12-31

    If grout and/or concrete barriers and containments are considered for long-term (500 yrs to 100,000 ) waste disposal, then long-term degradation of grout/cement materials (and others) need to be studied. Long-term degradations of a cementitious grout monolith (15.4mW x 10.4mH x 37.6mL) and its containment concrete shell and asphalt shell (each 1-m thick) were analyzed. The main degradation process of the concrete shell was believed to be fractures due to construction joints, shrinkage, thermal stress, settlement, and seismic events. A scenario with fractures was modeled (flow and transport model) for long-term risk performance (out to a million yrs). Even though the concrete/grout is expected to fracture, the concrete/grout chemistry, which has high Ph value, is very beneficial in causing calcite deposits from calcium in the water precipitating in the fractures. These calcite deposits will tend to plug the fracture and keep water from entering. The effectiveness of such plugging needs to be studied more. It`s possible that the plugged fractures are more impermeable than the original concrete/grout. The long-term performance of concrete/grout barriers will be determined by its chemistry, not its mechanical properties.

  1. Thermally conductive cementitious grouts for geothermal heat pumps. Progress report FY 1998

    Energy Technology Data Exchange (ETDEWEB)

    Allan, M.L.; Philippacopoulos, A.J.

    1998-11-01

    Research commenced in FY 97 to determine the suitability of superplasticized cement-sand grouts for backfilling vertical boreholes used with geothermal heat pump (GHP) systems. The overall objectives were to develop, evaluate and demonstrate cementitious grouts that could reduce the required bore length and improve the performance of GHPs. This report summarizes the accomplishments in FY 98. The developed thermally conductive grout consists of cement, water, a particular grade of silica sand, superplasticizer and a small amount of bentonite. While the primary function of the grout is to facilitate heat transfer between the U-loop and surrounding formation, it is also essential that the grout act as an effective borehole sealant. Two types of permeability (hydraulic conductivity) tests was conducted to evaluate the sealing performance of the cement-sand grout. Additional properties of the proposed grout that were investigated include bleeding, shrinkage, bond strength, freeze-thaw durability, compressive, flexural and tensile strengths, elastic modulus, Poisson`s ratio and ultrasonic pulse velocity.

  2. Preparation of New Cementitious System using Fly Ash and Dehydrated Autoclaved Aerated Concrete

    Institute of Scientific and Technical Information of China (English)

    SHUI Zhonghe; LU Jianxin; TIAN Sufang; SHEN Peiliang; DING Sha

    2014-01-01

    We experimentally studied the interaction between pozzolanic material (fly ash) and dehydrated autoclaved aerated concrete (DAAC). The DAAC powder was obtained by grinding aerated concrete waste to particles finer than 75μm and was then heated to temperatures up to 900℃. New cementitious material was prepared by proportioning fly ash and DAAC, named as AF. X-ray diffraction (XRD) was employed to identify the crystalline phases of DAAC before and after rehydration. The hydration process of AF was analyzed by the heat of hydration and non-evaporable water content (Wn). The experimental results show that the highest reactivity of DAAC can be obtained by calcining the powder at 700℃and the dehydrated products are mainlyβ-C2S and CaO. The cumulative heat of hydration and Wn was found to be strongly dependent on the replacement level of fly ash, increasing the replacement level of fly ash lowered them in AF. The strength contribution rates on pozzolanic effect of fly ash in AF are always negative, showing a contrary tendency of that of cement-fly ash system.

  3. Monitoring the cementitious materials subjected to sulfate attack with optical fiber excitation Raman spectroscopy

    Science.gov (United States)

    Yue, Yanfei; Bai, Yun; Muhammed Basheer, P. A.; Boland, John J.; Wang, Jing Jing

    2013-10-01

    Formation of ettringite and gypsum from sulfate attack together with carbonation and chloride ingress have been considered as the most serious deterioration mechanisms of concrete structures. Although electrical resistance sensors and fiber optic chemical sensors could be used to monitor the latter two mechanisms on site, currently there is no system for monitoring the deterioration mechanisms of sulfate attack. In this paper, a preliminary study was carried out to investigate the feasibility of monitoring sulfate attack with optical fiber excitation Raman spectroscopy through characterizing the ettringite and gypsum formed in deteriorated cementitious materials under an optical fiber excitation + objective collection configuration. Bench-mounted Raman spectroscopy analysis was also conducted to validate the spectrum obtained from the fiber-objective configuration. The results showed that the expected Raman bands of ettringite and gypsum in the sulfate-attacked cement paste can be clearly identified by the optical fiber excitation Raman spectrometer and are in good agreement with those identified from bench-mounted Raman spectrometer. Therefore, based on these preliminary results, it is considered that there is a good potential for developing an optical fiber-based Raman system to monitor the deterioration mechanisms of concrete subjected to sulfate attack in the future.

  4. Preparation of Silica Nanoparticles and Its Beneficial Role in Cementitious Materials

    Directory of Open Access Journals (Sweden)

    S. Ahalawat

    2011-07-01

    Full Text Available Spherical silica nanoparticles (n‐SiO2 with controllable size have been synthesized using tetraethoxysilane as starting material and ethanol as solvent by sol‐gel method. Morphology and size of the particles was controlled through surfactants. Sorbitan monolaurate, sorbitain monopalmitate and sorbitain monostearate produced silica nanoparticles of varying sizes (80‐150 nm, indicating the effect of chain length of the surfactant. Increase in chain length of non‐ionic surfactant resulted in decreasing particle size of silica nanoparticles. Further, the size of silica particles was also controlled using NH3 as base catalyst. These silica nanoparticles were incorporated into cement paste and their role in accelerating the cementitious reactions was investigated. Addition of silica nanoparticles into cement paste improved the microstructure of the paste and calcium leaching is significantly reduced as n‐SiO2 reacts with calcium hydroxide and form additional calcium‐ silicate‐hydrate (C‐S‐H gel. It was found that calcium hydroxide content in silica nanoparticles incorporated cement paste reduced ~89% at 1 day and up to ~60% at 28 days of hydration process. Synthesized silica particles and cement paste samples were characterized using scanning electron microscopy (SEM, powder X‐ray diffraction (XRD, infrared spectroscopy (IR and thermogravimetric analysis (TGA.

  5. Development of leachate test for delayed ettringite formation potential in cementitious materials

    Science.gov (United States)

    France-Mensah, Jojo

    Delayed Ettringite Formation (DEF) has been known to be the cause of expansion and cracking at latter ages in concrete that has been heat cured at temperatures around 70 degree Celsius or above. Currently, the only method available for measuring DEF-related physical expansion in concrete can sometimes take over a year to yield relevant results. A leachate method was proposed as a means of taking advantage of the release and solubility of the adsorbed ions (e.g., calcium, sulfates and aluminates) and alkali ions (e.g., sodium and potassium) in the pore solution after heat curing of the cement paste matrix. These ions, known to contribute to DEF, were leached out of concrete into the leaching solution. The results of the leachate test were correlated to physical expansion data of similar samples from an earlier study. The aim of this research is to apply this knowledge to develop an accelerated leachate test method for identifying the potential for DEF in cementitious materials in a shorter time than the existing method. The objectives of this research are: (1) to identify the ion(s) through leaching that is/are the controlling factors in predicting the rate of expansion and overall expansion of mortar; (2) to identify the ion(s) that is/are responsible for the lag time or age of deleterious expansion through DEF; and (3) to investigate the effect of heat curing on the overall, rate of, and age (time) of expansion.

  6. Data on plutonium sorption onto cementitious materials under conditions of reducing and of presence of nitrate

    International Nuclear Information System (INIS)

    In terms of safety assessment of TRU waste disposal, data on plutonium sorption of cementitious materials have been obtained by means of a static batch-type experiment. Because the repository condition will be reducing and be affected by considerable amount of nitrate, the authors carried out the experiments using ordinary portland cement (OPC) under the reducing (Na2S2O4 as added as reductant) and anoxic condition (O2 ≤ 1 ppm) and solution of 0 to 0.5 M NaNo3. Other experimental conditions are: liquid/solid (L/S) ratios; 100 and 1000 mLg-1, Initially added plutonium; 2.84x10-10 M, Temperature; 25±5degC and Reaction times; 7, 14 and 28 days. the experimental results suggest that distribution coefficient (Kd) ranges 50 to 1000 mLg-1 in case of L/S = 100 mL g-1. Similarly the Kd ranges, 100 to 10000 mLg-1 at L/S = 1000 mLg-1. These Kd values tend to increase with lapsing reaction time. On the basis of these results, we recommend 50 mLg-1 as a conservative Kd value of plutonium on OPC in a TRU waste repository condition. (author)

  7. Observing the setting and hardening of cementitious materials by X-ray dark-field radiography

    International Nuclear Information System (INIS)

    Novel X-ray imaging methods expand conventional attenuation-based X-ray radiography by the phase- and the dark-field contrasts. While weakly absorbing structures in the specimen can be better visualized in phase contrast, the dark-field contrast provides information about morphological sub-pixel microstructures. Here we report an application of dark-field X-ray radiography for imaging the time-resolved setting process in fresh cement. Our results demonstrate that the microstructural changes within the cement result in a decreasing dark-field signal. We quantify this imaging signal with a time-dependent dark-field scatter coefficient and show its good correlation with the compressional wave velocity. We further present images based on a pixel-wise analysis of the scattering signal and a corresponding logistic fit. These images emphasize the benefit of dark-field imaging of cementitious materials as it provides two dimensional spatial information on the processes within the sample while other established testing techniques only provide information on the bulk average

  8. PHREEQC modelling of leaching of major elements and heavy metals from cementitious waste forms

    International Nuclear Information System (INIS)

    In this study, Ca, Mg, Al, and Pb concentrations leached from un-carbonated and carbonated ordinary Portland cement - dried waste incinerator bottom ash samples during single extraction tests (EN12457 test) at a pH from 1 to 12, were modelled using the geochemical code PHREEQC. A good agreement was found between modelling results and experiments in terms of leached concentrations for Ca, Mg, and Al by defining a single set of pure mineralogical phases for both the un-carbonated and carbonated (three levels) samples. The model also predicted well the observed decrease in Ca leaching with increasing carbonation. Modelling results further revealed that leaching of Pb is not controlled by dissolution/precipitation of pure Pb containing minerals only (carbonates and (hydr)oxides). The addition of solid solutions (calcite-cerrusite and gibbsite-ferri-hydrite-litharge solid solutions) and adsorption reactions on amorphous Fe- and Al-oxides improved the model representation of the experimentally observed amphoteric leaching profile of Pb from the cementitious material. (authors)

  9. Study of 225 deg C thermoluminescent of quartz inclusions extracted from cementitious building materials

    International Nuclear Information System (INIS)

    Incidents of excessive exposure of the population to ionizing radiation could result from a nuclear explosion, the direct exposure to a source theft or loss or an accidental exposure to a source without shielding, for example. During these incidents the victims seldom are using individual protection equipment used in the measurement and control of the doses that were exposed. One of the ways found to the doses assessment due to exposure to this type of accident is the retrospective dosimetry, which determines the excessive doses of radiation exposure, whether chronological or acute, using common materials available in the public domain. The methodology for the application of retrospective dosimetry for thermoluminescence in buildings previously burned, as bricks, it is already well established. Interest is now turning to the use of cementitious building materials such as mortar and concrete to enlarge the scope of application. This study aimed to examine some of these materials and techniques for their possible application in the doses assessment from an accidental irradiation by thermoluminescence. For this the peak about 225 deg C of natural quartz and it extracted of mortar and concrete was certain your stability for the plateau and storage tests, and also the dependence of your luminescent intensity with radiation dose. Presenting a life relatively tans compared enough to that of the accumulation of natural and long radiation sign for dosimetric applications, besides other favorable characteristics, the mortar presented evidence that is possible for retrospective dosimetry through thermoluminescence. (author)

  10. Effect of alkali-activation on aluminosilicate-based cementitious materials

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    High-performance aluminosilieate-based eementitious materials were produced with fly ash from a coal power plant as one of the major raw materials.The structures of fly ash containing aluminosilicate-based cementitious materials were compared before and after treatment by the methods of nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM).During the 28 d curing time,the compressive strength of water glass and fly ash samples increased from 9.08 MPa to 26.75 MPa.The results show that most of the stiff shells are destroyed after mechanical grinding and chemical activation.Magic angle spinning (MAS)NMR of 27Al shows that the wide peak becomes narrow and the main peak shifts to the direction of low field,indicating the decrease of polymerization degree,the enhancing of activity,the decrease of six-coordination structure,and the increase of small and symmetrical four-coordination polyhedron structure within the aluminum-oxygen polyhedron network.Comparisons between MAS NMR of 29Si with different treatments suggest that Q0 disappears,the quantity of Q2 increases,and the quantity of Q4 decreases.The polym

  11. Microstructural changes in a cementitious membrane due to the application of a DC electric field.

    Science.gov (United States)

    Covelo, Alba; Diaz, Belen; Freire, Lorena; Novoa, X Ramon; Perez, M Consuelo

    2008-07-01

    The use of electromigration techniques to accelerate chloride ions motion is commonly employed to characterise the permeability of cementitious samples to chlorides, a relevant parameter in reinforced concrete corrosion. This paper is devoted to the study of microstructure's changes occurring in mortar samples when submitted to natural diffusion and migration experiments. The application of an electric field reduces testing time in about one order of magnitude with respect to natural diffusion experiments. Nevertheless, the final sample's microstructure differs in both tests. Impedance Spectroscopy is employed for real time monitoring of microstructural changes. During migration experiments the global impedance undergoes important increase in shorter period of time compared to natural diffusion tests. So, the forced motion of ions through the concrete membrane induces significant variations in the porous structure, as confirmed by Mercury Intrusion Porosimetry. After migration experiments, an important increase in the capillary pore size (10-100 nm) was detected. Conversely, no relevant variations are found after natural diffusion tests. Results presented in this work cast doubt on the significance of diffusion coefficient values obtained under accelerated conditions. PMID:18569312

  12. Observing the setting and hardening of cementitious materials by X-ray dark-field radiography

    Energy Technology Data Exchange (ETDEWEB)

    Prade, F., E-mail: friedrich.prade@ph.tum.de [Lehrstuhl für Biomedizinische Physik, Physik-Department and Institut für Medizintechnik, Technische Universität München, 85748 Garching (Germany); Chabior, M., E-mail: michael.chabior@tum.de [Lehrstuhl für Biomedizinische Physik, Physik-Department and Institut für Medizintechnik, Technische Universität München, 85748 Garching (Germany); Malm, F., E-mail: fabian.malm@tum.de [Lehrstuhl für Zerstörungsfreie Prüfung, Centrum Baustoffe und Materialprufung, Technische Universität München, 81245 München (Germany); Grosse, C.U., E-mail: Grosse@tum.de [Lehrstuhl für Zerstörungsfreie Prüfung, Centrum Baustoffe und Materialprufung, Technische Universität München, 81245 München (Germany); Pfeiffer, F., E-mail: franz.pfeiffer@tum.de [Lehrstuhl für Biomedizinische Physik, Physik-Department and Institut für Medizintechnik, Technische Universität München, 85748 Garching (Germany)

    2015-08-15

    Novel X-ray imaging methods expand conventional attenuation-based X-ray radiography by the phase- and the dark-field contrasts. While weakly absorbing structures in the specimen can be better visualized in phase contrast, the dark-field contrast provides information about morphological sub-pixel microstructures. Here we report an application of dark-field X-ray radiography for imaging the time-resolved setting process in fresh cement. Our results demonstrate that the microstructural changes within the cement result in a decreasing dark-field signal. We quantify this imaging signal with a time-dependent dark-field scatter coefficient and show its good correlation with the compressional wave velocity. We further present images based on a pixel-wise analysis of the scattering signal and a corresponding logistic fit. These images emphasize the benefit of dark-field imaging of cementitious materials as it provides two dimensional spatial information on the processes within the sample while other established testing techniques only provide information on the bulk average.

  13. Cementitious binders from activated stainless steel refining slag and the effect of alkali solutions.

    Science.gov (United States)

    Salman, Muhammad; Cizer, Özlem; Pontikes, Yiannis; Snellings, Ruben; Vandewalle, Lucie; Blanpain, Bart; Van Balen, Koen

    2015-04-01

    With an aim of producing high value cementitious binder, stainless steel refining slag containing a high amount of CaO in γ-dicalcium silicate form was activated with NaOH and Na-silicate as well as KOH and K-silicate solutions, followed by steam curing at 80 °C. Higher levels of alkali-silicate in the activating solution resulted in higher cumulative heat suggesting accelerated reaction kinetics. With respect to compressive strength, higher levels of alkali silicate resulted in higher strength and the mortars with Na activator were found to have higher early strength than the ones with K activator. The long term strength was found to be similar, regardless of the alkali metal. Thermogravimetric, QXRD and FTIR analyses showed an increase in the amount of reaction products (C-S-H type) over time, further confirming the reactivity of the crystalline slag. Batch leaching results showed lower leaching of heavy metals and metalloids with K activator compared to the Na activator. These results demonstrate that the alkali type and the ratio of hydroxide to silicates have a significant impact on the hydration and mechanical strength development of the stainless steel slag. The above findings can aid in the recycling and valorization of these type of slags which otherwise end up landfilled. PMID:25577317

  14. PVA-ECCのひび割れ面でのせん断伝達機構と部材のせん断耐力評価

    OpenAIRE

    清水, 克将; 金久保, 利之; 閑田, 徹志; 永井, 覚

    2007-01-01

    In this research, PVA-ECC (Engineered Cementitious Composites with Polyvinyl alcohol fiber), which is one of the composites showing pseudostrain hardening behavior in uniaxial tension, is focused. Method of single plane shear test under tensile stress as normal stress on crack surface is conducted to clarify shear transfer mechanism on crack surface. From the test results, tensile shear strength on crack surface is about half of uniaxial tensile strength. This means that normal stress for cra...

  15. Considerations for Probabilistic Analyses to Assess Potential Changes to Large-Break LOCA Definition for ECCS Requirements

    International Nuclear Information System (INIS)

    The U.S.NRC has undertaken a study to explore changes to the body of Part 50 of the U.S. Federal Code of Regulations, to incorporate risk-informed attributes. One of the regulations selected for this study is 10 CFR 50.46, Acceptance Criteria for Emergency Core Cooling Systems for Light-Water Nuclear Power Reactors. These changes will potentially enhance safety and reduce unnecessary burden on utilities. Specific attention is being paid to redefining the maximum pipe break size for LB-LOCA by determining the spectrum of pipe diameter (or equivalent opening area) versus failure probabilities. In this regard, it is necessary to ensure that all contributors to probabilistic failures are accounted for when redefining ECCS requirements. This paper describes initial efforts being conducted for the U.S.NRC on redefining the LB-LOCA requirements. Consideration of the major contributors to probabilistic failure, and deterministic aspects for modeling them, are being addressed. At this time three major contributors to probabilistic failures are being considered. These include: (1) Analyses of the failure probability from cracking mechanisms that could involve rupture or large opening areas from either through-wall or surface flaws, whether the pipe system was approved for leak-before-break (LBB) or not. (2) Future degradation mechanisms, such as recent occurrence of PWSCC in PWR piping need to be included. This degradation mechanism was not recognized as being an issue when LBB was approved for many plants or when the initial risk-informed inspection plans were developed. (3) Other indirect causes of loss of pressure-boundary integrity than from cracks in the pipe system also should be included. The failure probability from probabilistic fracture mechanics will not account for these other indirect causes that could result in a large opening in the pressure boundary: i.e., failure of bolts on a steam generator manway, flanges, and valves; outside force damage from the

  16. 基于ECC的认证协议及动态密钥管理方案%The Authentication Protocol and Dynamic Key Management Based on ECC

    Institute of Scientific and Technical Information of China (English)

    曹阳

    2009-01-01

    针对当前无线网络中认证和密钥管理存在的安全缺陷,通过对椭圆曲线密码体制(ECC)的研究,结合ECMOV密钥协商协议和IEEE 802.1X扩展认证协议EAP-TLS及X.509证书,提出了一种在无线局域网中基于ECC的双向认证协议及密钥管理方案.

  17. Preliminary analysis of modeling of Pars and steam injectors to support long-term operation of LWR passive ECCS using a best estimate thermal-hydraulics code

    International Nuclear Information System (INIS)

    In order to control the amount of hydrogen produced, during the chemical reaction of steam and strongly overheated zirconium in a LWR severe accident, several control methos have been proposed. In a considerable number of nuclear power plants the initial preferred solution was either the use of an inert containment atmosphere or the use of igniters. However, the use of Pars (Passive autocatalytic recombiners) has been considered an important addition to this set of H2 controls. Pars have appealing features such as, low maintenance, do not require active components to start operation, and can initiate the H2 and O2 recombination at low concentrations. However, under certain conditions these Pars may trigger H2 ignition leading to deflagration s with possible containment damages. Combustions, poisons and liquid may inhibit or reduce the Pars operation. Advanced LWR designs (generation III + and IV) are also considering the use of Pars as a supporting system to the long term operation of their passive ECCS (Emergency Core Cooling Systems) because they may transport the energy of containment H2 and O2 gases to external sinks. Even when the ECCS of modern nuclear power plants are designed to maintain containment conditions under established limits, there are small amounts of O2 and H2 produced mainly by H2O radiolysis, and after several days of containment isolation, these gases may accumulate in places where the possibility of a H2 deflagration increases. Therefore, the use of Pars looks initially as an interesting solution to long-term H2 control during a Dba. However, the H2 and O2 recombination is an exothermic process resulting in additional steam and energy releases to the containment. In order to avoid a direct deposition of the steam and energy (Pars produced) into the containment atmosphere, we propose to use them to operate steam injectors that can bring cold water to replenish ECCS pools. This work presents Pars and steam injectors models, simulations and

  18. Fibrous and textile materials for composite applications

    CERN Document Server

    Fangueiro, Raul

    2016-01-01

    This book focuses on the fibers and textiles used in composite materials. It presents both existing technologies currently used in commercial applications and the latest advanced research and developments. It also discusses the different fiber forms and architectures, such as short fibers, unidirectional tows, directionally oriented structures or advanced 2D- and 3D-textile structures that are used in composite materials. In addition, it examines various synthetic, natural and metallic fibers that are used to reinforce polymeric, cementitious and metallic matrices, as well as fiber properties, special functionalities, manufacturing processes, and composite processing and properties. Two entire chapters are dedicated to advanced nanofiber and nanotube reinforced composite materials. The book goes on to highlight different surface treatments and finishes that are applied to improve fiber/matrix interfaces and other essential composite properties. Although a great deal of information about fibers and textile str...

  19. Development of an accurate pH measurement methodology for the pore fluids of low pH cementitious materials

    Energy Technology Data Exchange (ETDEWEB)

    Alonso, M. C.; Garcia Calvo, J. L. [The Spanish National Research Council (CSIC), Madrid (Spain); Walker, C. [Japan Atomic Energy Agency (JAEA), Ibaraki (Japan)] [and others

    2012-08-15

    The main objective of this project has been the development of an agreed set of protocols for the pH measurement of the pore fluid of a low pH cementitious material. Three protocols have been developed (Chapter 2), a reference method, based on pore fluid expression (PFE), and two routine methods with and without filtering, based on Ex Situ Leaching (ESL) procedures. Templates have been designed on which to record details of the pH measurement for the reference (PFE) method (Appendix C) and the routine (ESL) methods without and with filtering (Appendix D). Preliminary protocols were based on a broad review of the literature (Appendix A) and refined through a series of test experiments of the more critical parameters (Appendix B). After definition of the preliminary protocols, two phases of interlaboratory tests were performed. The first phase (Chapter 3) used the same low pH cement paste and enabled the nine participating laboratories to use, become familiar with and to identify any problems/uncertainties in the preliminary protocols. The reported pH values were subjected to a statistical analysis of the (within laboratory) repeatability and (between-laboratory) reproducibility and so provided a reliability test of the preliminary protocols. The second phase (Chapter 4) of interlaboratory tests used four different candidate low pH cementitious materials in the same nine laboratories, which allowed testing, validation and comparison of the reported pH values, which were obtained using the final protocols for the reference (PFE) and routine (ESL) methods by statistical analysis. The proposed final protocols (Chapter 2) have resulted in the reported pH values having low deviation and high reproducibility and repeatability. This will allow confidence in the pH value when selecting a candidate low pH cementitious material to be used in the engineered component of a high-level nuclear waste repository.

  20. Development of an accurate pH measurement methodology for the pore fluids of low pH cementitious materials

    International Nuclear Information System (INIS)

    The main objective of this project has been the development of an agreed set of protocols for the pH measurement of the pore fluid of a low pH cementitious material. Three protocols have been developed (Chapter 2), a reference method, based on pore fluid expression (PFE), and two routine methods with and without filtering, based on Ex Situ Leaching (ESL) procedures. Templates have been designed on which to record details of the pH measurement for the reference (PFE) method (Appendix C) and the routine (ESL) methods without and with filtering (Appendix D). Preliminary protocols were based on a broad review of the literature (Appendix A) and refined through a series of test experiments of the more critical parameters (Appendix B). After definition of the preliminary protocols, two phases of interlaboratory tests were performed. The first phase (Chapter 3) used the same low pH cement paste and enabled the nine participating laboratories to use, become familiar with and to identify any problems/uncertainties in the preliminary protocols. The reported pH values were subjected to a statistical analysis of the (within laboratory) repeatability and (between-laboratory) reproducibility and so provided a reliability test of the preliminary protocols. The second phase (Chapter 4) of interlaboratory tests used four different candidate low pH cementitious materials in the same nine laboratories, which allowed testing, validation and comparison of the reported pH values, which were obtained using the final protocols for the reference (PFE) and routine (ESL) methods by statistical analysis. The proposed final protocols (Chapter 2) have resulted in the reported pH values having low deviation and high reproducibility and repeatability. This will allow confidence in the pH value when selecting a candidate low pH cementitious material to be used in the engineered component of a high-level nuclear waste repository

  1. Theoretical analysis of a novel electricity–cooling cogeneration system (ECCS) based on cascade use of waste heat of marine engine

    International Nuclear Information System (INIS)

    Highlights: • A cascade use of waste heat aboard ships base on RC–ARS system was investigated. • Better performance can be achieved at a lower temperature of RC for the cogeneration system. • The exergy efficiency of cogeneration system can increase by 84%. - Abstract: This study presents a performance analysis of a novel electricity–cooling cogeneration system (ECCS) which combines a Rankine cycle (RC) with an absorption refrigeration cycle (ARC) to recover the exhaust heat of marine engine aboard ships. The RC is to provide electricity using water as the working fluid and the ARC is to provide cooling capacity needed aboard ships using a binary solution of ammonia–water as the working pair. Several performance parameters, including electricity output of Rankine cycle, cooling capacity, coefficient of performance (COP) of absorption refrigeration cycle and exergy efficiency, are analyzed and optimized. The simulation results indicate that compared with basic Rankine cycle, higher exergy efficiency can be realized by ECCS due to the extra cooling energy generated by the ARC, especially at a low condensing temperature of Rankine cycle. When the condensing temperature is 323 K and the superheat is 100 K, the exergy efficiency of the cogeneration system increases by 84%

  2. Bias in peak clad temperature predictions due to uncertainties in modeling of ECC bypass and dissolved non-condensable gas phenomena

    International Nuclear Information System (INIS)

    This report describes a general method for estimating the effect on the Reflood Phase PCT from systematic errors (biases) associated with the modelling of the ECCS and dissolved nitrogen, and the application of this method in estimating biases in the Reflood Phase PCT (second PCT) predicted by the TRAC/PF1/MOD1, Version 14.3. The bias in the second PCT due to the uncertainty in the existing code models for ECCS related phenomena is -19 degree K (-34 degree F). The negative bias implies that the code models for this phenomena are conservative. The bias in the second PCT due to the lack of modelling of dissolved N2 in the code is estimated to be 9.9 degree K (17.8 degree F). The positive bias implies that the absence of dissolved N2 model makes the code prediction of PCT non-conservative. The bias estimation in this report is a major exception among all other uncertainty and bias assessments performed in conjunction with the CSAU methodology demonstration, because this bias estimation benefitted from using full-scale test data from the full-scale Upper Plenum Test Facility (UPTF). Thus, the bias estimates presented here are unaffected by scale distortions in test facilities. Data from small size facilities were also available and an estimate of bias based on these data will be conservative. 35 refs., 18 figs., 5 tabs

  3. Bias in peak clad temperature predictions due to uncertainties in modeling of ECC bypass and dissolved non-condensable gas phenomena

    Energy Technology Data Exchange (ETDEWEB)

    Rohatgi, U.S.; Neymotin, L.Y.; Jo, J.; Wulff, W. (Brookhaven National Lab., Upton, NY (USA))

    1990-09-01

    This report describes a general method for estimating the effect on the Reflood Phase PCT from systematic errors (biases) associated with the modelling of the ECCS and dissolved nitrogen, and the application of this method in estimating biases in the Reflood Phase PCT (second PCT) predicted by the TRAC/PF1/MOD1, Version 14.3. The bias in the second PCT due to the uncertainty in the existing code models for ECCS related phenomena is {minus}19{degree}K ({minus}34{degree}F). The negative bias implies that the code models for this phenomena are conservative. The bias in the second PCT due to the lack of modelling of dissolved N{sub 2} in the code is estimated to be 9.9{degree}K (17.8{degree}F). The positive bias implies that the absence of dissolved N{sub 2} model makes the code prediction of PCT non-conservative. The bias estimation in this report is a major exception among all other uncertainty and bias assessments performed in conjunction with the CSAU methodology demonstration, because this bias estimation benefitted from using full-scale test data from the full-scale Upper Plenum Test Facility (UPTF). Thus, the bias estimates presented here are unaffected by scale distortions in test facilities. Data from small size facilities were also available and an estimate of bias based on these data will be conservative. 35 refs., 18 figs., 5 tabs.

  4. BWR LOCA simulation test (RUN 992) in ROSA-III program for a 10% main steam line break with ECCS double failures

    International Nuclear Information System (INIS)

    A loss-of-coolant accident (LOCA) caused by pipe rupture at the high pressure core spray (HPCS) line is equivalent to a LOCA with double failures on the emergency core cooling systems (ECCSs) in a boiling water reactor (BWR) system by assuming single failure on another ECCS. This report presents the ROSA-III experimental results of RUN 992, which simulates a 10% main steam line break (MSLB) LOCA with double failure assumption on the HPCS and the low pressure core spray (LPCS) systems. The ROSA-III test facility simulates a BWR system with volumetric scale of 1/424 and has the principal systems, i.e., four half-length electrically-heated fuel bundles, two active recirculation loops, four types of ECCSs, and steam and feedwater systems. The report clarifies effectiveness of ECCS even for this double failure assumption in a 10% MSLB LOCA and also clarifies effects of the automatic depressurization system (ADS) on core cooling. In addition to these, mass balance and mass distribution in the system were investigated to clarify the core cooling condition in the small MSLB LOCA test. (author)

  5. Results of ECCS analysis and expedient based on them relevant to pressurizer level gauges in (2 or 3 loop) PWR nuclear power plants

    International Nuclear Information System (INIS)

    The Nuclear Safety Commission investigated the report dated July 17, 1979, submitted by the Special Committee on Examination of Reactor Safety on the results of ECCS analysis and the expedient based on them, relevant to pressurizer level gauges in (2 or 3 loop) PWR nuclear power plants other than Ohii power plant, concerning the problem of the pressurizer level gauges pointed out relating to the accident of the Three Mile Island No. 2 nuclear power plant in the United States. The Commission judged the above report reasonable. The contents of investigation include the propriety of determining the representative plant by selecting Ikata No. 1 or Takahama No. 1 plant, the propriety of the preconditions for safety analysis and analysis codes (use of MARVEL and SATAN codes), the results of safety analysis investigations and others. The propriety of maintaining the circuit of generating safe injection signal by the coincidence of the decrease of reactor pressure with the decrease of pressurizer level, the influence of adding the circuit for safe injection signal (P' circuit) which operates due to the abnormal decrease of reactor pressure on the past analysis for ECCS evaluation, and the effect of the block circuit added to the P' circuit are specifically reported in detail. (Wakatsuki, Y.)

  6. Assessment of the efficiency of prefabricated hybrid composite plates (HCPs) for retrofitting of damaged interior RC beam–column joints

    OpenAIRE

    Esmaeeli, Esmaeel; Barros, Joaquim A. O.; Sena-Cruz, José; Varum, H.; Melo, J.

    2015-01-01

    The effectiveness of prefabricated hybrid composite plates (HCPs) as a seismic retrofitting solution for damaged interior RC beam-column joints is experimentally studied. HCP is composed of a thin plate made of strain hardening cementitious composite (SHCC) reinforced with CFRP sheets/laminates. Two full-scale severely damaged interior beam-column joints are retrofitted using two different configurations of HCPs. The effectiveness of these retrofitting solutions mainly in terms of hysteretic ...

  7. Self-Healing Efficiency of Cementitious Materials Containing Microcapsules Filled with Healing Adhesive: Mechanical Restoration and Healing Process Monitored by Water Absorption

    Science.gov (United States)

    Li, Wenting; Jiang, Zhengwu; Yang, Zhenghong; Zhao, Nan; Yuan, Weizhong

    2013-01-01

    Autonomous crack healing of cementitious composite, a construction material that is susceptible to cracking, is of great significance to improve the serviceability and to prolong the longevity of concrete structures. In this study, the St-DVB microcapsules enclosing epoxy resins as the adhesive agent were embedded in cement paste to achieve self-healing capability. The self-healing efficiency was firstly assessed by mechanical restoration of the damaging specimens after being matured. The flexural and compressive configurations were both used to stimulate the localized and distributed cracks respectively. The effects of some factors, including the content of microcapsules, the curing conditions and the degree of damage on the healing efficiency were investigated. Water absorption was innovatively proposed to monitor and characterize the evolution of crack networks during the healing process. The healing cracks were observed by SEM-EDS following. The results demonstrated that the capsule-containing cement paste can achieve the various mechanical restorations depending on the curing condition and the degree of damage. But the voids generated by the surfactants compromised the strength. Though no noticeable improved stiffness obtained, the increasing fracture energy was seen particularly for the specimen acquiring 60% pre-damage. The sorptivity and amount of water decreased with cracks healing by the adhesive, which contributed to cut off and block ingress of water. The micrographs by SEM-EDS also validated that the cracks were bridged by the hardened epoxy as the dominated elements of C and O accounted for 95% by mass in the nearby cracks. PMID:24312328

  8. Self-healing efficiency of cementitious materials containing microcapsules filled with healing adhesive: mechanical restoration and healing process monitored by water absorption.

    Directory of Open Access Journals (Sweden)

    Wenting Li

    Full Text Available Autonomous crack healing of cementitious composite, a construction material that is susceptible to cracking, is of great significance to improve the serviceability and to prolong the longevity of concrete structures. In this study, the St-DVB microcapsules enclosing epoxy resins as the adhesive agent were embedded in cement paste to achieve self-healing capability. The self-healing efficiency was firstly assessed by mechanical restoration of the damaging specimens after being matured. The flexural and compressive configurations were both used to stimulate the localized and distributed cracks respectively. The effects of some factors, including the content of microcapsules, the curing conditions and the degree of damage on the healing efficiency were investigated. Water absorption was innovatively proposed to monitor and characterize the evolution of crack networks during the healing process. The healing cracks were observed by SEM-EDS following. The results demonstrated that the capsule-containing cement paste can achieve the various mechanical restorations depending on the curing condition and the degree of damage. But the voids generated by the surfactants compromised the strength. Though no noticeable improved stiffness obtained, the increasing fracture energy was seen particularly for the specimen acquiring 60% pre-damage. The sorptivity and amount of water decreased with cracks healing by the adhesive, which contributed to cut off and block ingress of water. The micrographs by SEM-EDS also validated that the cracks were bridged by the hardened epoxy as the dominated elements of C and O accounted for 95% by mass in the nearby cracks.

  9. Multiple determinations of isotope diffusion in cementitious backfills and Ordinary Portland Cement (OPC) monoliths

    International Nuclear Information System (INIS)

    The full text of publication follows: The UK concept for geological disposal of intermediate level (ILW) and low level waste (LLW) includes backfill materials based on admixtures of Ordinary Portland Cement (OPC). It is expected that the evolution of these backfill materials will generate high pH conditions and the corrosion of the metal canisters used for disposal will promote a low Eh environment. This combination of conditions within the near field of the Geological Disposal Facility (GDF) will reduce the solubility of many radionuclides and retard migration. In addition, sorption to some of the cementitious phases may contribute significantly to the retardation of many radionuclides. It is clearly important to understand how diffusion of radionuclides contributes to the overall migration from the repository. However, it remains practically difficult to isolate the effect of diffusion from other processes such as sorption and advection which may also occur in the near field and far fields of the GDF. This presentation describes a series of experiments undertaken to evaluate the diffusion of a selection of relevant radionuclides in saturated backfills (including the NIREX reference vault backfill, NRVB) and OPC matrices. The experiments build upon a significant number of related sorption studies previously undertaken by the radiochemistry group at Loughborough University and complement a series of small scale advection experiments also being undertaken. The experimental technique uses small pre-cast blocks (monoliths) of the matrix under investigation. An appropriate concentration of the isotope of interest is introduced in a cavity in the centre of the block, which is then sealed, and finally, placed in a solution previously equilibrated with the matrix. The increase in concentration of the isotope in the external solution is then determined at defined time intervals. The interpretation of the results is undertaken with methods conventionally used for geological

  10. DURABILITY OF GREEN CONCRETE WITH TERNARY CEMENTITIOUS SYSTEM CONTAINING RECYCLED AGGREGATE CONCRETE AND TIRE RUBBER WASTES

    Directory of Open Access Journals (Sweden)

    MAJID MATOUQ ASSAS

    2016-06-01

    Full Text Available All over the world billions of tires are being discarded and buried representing a serious ecological threat. Up to now a small part is recycled and millions of tires are just stockpiled, landfilled or buried. This paper presents results about the properties and the durability of green concrete contains recycled concrete as a coarse aggregate with partial replacement of sand by tire rubber wastes for pavement use. Ternary cementious system, Silica fume, Fly ash and Cement Kiln Dust are used as partial replacement of cement by weight. Each one replaced 10% of cement weight to give a total replacement of 30%. The durability performance was assessed by means of water absorption, chloride ion permeability at 28 and 90 days, and resistance to sulphuric acid attack at 1, 7, 14 and 28 days. Also to the compression behaviors for the tested specimens at 7, 14, 28 and 90 days were detected. The results show the existence of ternary cementitious system, silica fly ash and Cement Kiln Dust minimizes the strength loss associated to the use of rubber waste. In this way, up to 10% rubber content and 30% ternary cementious system an adequate strength class value (30 MPa, as required for a wide range of common structural uses, can be reached both through natural aggregate concrete and recycled aggregate concrete. Results also show that, it is possible to use rubber waste up to 15% and still maintain a high resistance to acid attack. The mixes with 10%silica fume, 10% fly ash and 10% Cement Kiln Dust show a higher resistance to sulphuric acid attack than the reference mix independently of the rubber waste content. The mixes with rubber waste and ternary cementious system was a lower resistance to sulphuric acid attack than the reference mix.

  11. Modelling study of the distribution of activation products in a cementitious repository

    International Nuclear Information System (INIS)

    Thermodynamic modelling has been used to study the behaviour of the activation products Ni-59, Nb-94 and Zr-93 in the cementitious/bentonite/crushed-rock near field of a radioactive waste repository. The work had two main aims: (a) to obtain estimates of the most realistic solubilities for the three radioelements present in decommissioning waste under the near-field conditions, (b) to calculate the rate of migration of the radionuclides through the near-field barriers. The calculated solubilities at pH 12.4 and 25 deg C are approximately 1*10-7 M, 4*10-9 M and 6*10-8 M for Ni, Zr and Nb respectively. These values correspond to solubilities measured for amorphous-type solids where very efficient solid-liquid separation is achieved. Uncertainties in the data values are discussed. Calculations to investigate the effect of a lower host-rock temperature on these solubilities suggest that the solubilities will rise to about 1*10-5 M, 8*10-9 M for Ni, Zr and Nb respectively, but there is less certainty in the input data. Modelling has been performed using the CHEQMATE computer code to calculate the rate of migration of the radioelements through the concrete and bentonite/crushed-rock barriers, assuming solubility control and control by corrosion of the source metals. The results demonstrated that the assumption of solubility control of corrosion control made little difference to the model, because in the corrosion control case the metals reached their solubility limits rapidly. The inclusion of groundwater flow increased the metal ion concentration by less than a factor of 2 in each case. The fluxes out of the TVO repository after a given time were predicted to be significantly less than those from the IVO repository due to the greater thickness of concrete in the TVO repository. (orig.). (16 refs., 9 figs., 23 tabs.)

  12. Modelling the leaching of Pb, Cd, As, and Cr from cementitious waste using PHREEQC

    International Nuclear Information System (INIS)

    A leaching model was developed using the United States Geological Survey public domain PHREEQC geochemical package to simulate the leaching of Pb, Cd, As, and Cr from cementitious wastes. The model utilises both kinetic terms and equilibrium thermodynamics of key compounds and provides information on leachate and precipitate speciation. The model was able to predict the leaching of Pb, Cd, As, and Cr from cement in the presence of both simple (0.1 and 0.6 M acetic acid) and complex municipal landfill leachates. Heavy metal complexation by the municipal landfill leachate was accounted for by the introduction of a monoprotic organic species into the model. The model indicated Pb and As were predominantly incorporated within the calcium silicate hydrate matrix while a greater portion of Cd was seen to exist as discrete particles in the cement pores and Cr (VI) existed mostly as free CrO42- ions. Precipitation was found to be the dominant mechanism controlling heavy metal solubility with carbonate and silicate species governing the solubility of Pb and carbonate, silicate and hydroxide species governing the solubility of Cd. In the presence of acetic acid, at low pH values Pb and Cd acetate complexes were predominant whereas, at high pH values, hydroxide species dominated. At high pH values, the concentration of As in the leachate was governed by the solubility of Ca3(AsO4)2 with the presence of carbonate alkalinity competing with arsenate for Ca ions. In the presence of municipal landfill leachate, Pb and Cd organic complexes dominated the heavy metal species in solution. The reduction of As and Cr in municipal landfill leachate was crucial for determining aqueous speciation, with typical municipal landfill conditions providing the reduced forms of As and Cr

  13. Modelling the leaching of Pb, Cd, As, and Cr from cementitious waste using PHREEQC.

    Science.gov (United States)

    Halim, Cheryl E; Short, Stephen A; Scott, Jason A; Amal, Rose; Low, Gary

    2005-10-17

    A leaching model was developed using the United States Geological Survey public domain PHREEQC geochemical package to simulate the leaching of Pb, Cd, As, and Cr from cementitious wastes. The model utilises both kinetic terms and equilibrium thermodynamics of key compounds and provides information on leachate and precipitate speciation. The model was able to predict the leaching of Pb, Cd, As, and Cr from cement in the presence of both simple (0.1 and 0.6M acetic acid) and complex municipal landfill leachates. Heavy metal complexation by the municipal landfill leachate was accounted for by the introduction of a monoprotic organic species into the model. The model indicated Pb and As were predominantly incorporated within the calcium silicate hydrate matrix while a greater portion of Cd was seen to exist as discrete particles in the cement pores and Cr (VI) existed mostly as free CrO4(2-) ions. Precipitation was found to be the dominant mechanism controlling heavy metal solubility with carbonate and silicate species governing the solubility of Pb and carbonate, silicate and hydroxide species governing the solubility of Cd. In the presence of acetic acid, at low pH values Pb and Cd acetate complexes were predominant whereas, at high pH values, hydroxide species dominated. At high pH values, the concentration of As in the leachate was governed by the solubility of Ca3(AsO4)2 with the presence of carbonate alkalinity competing with arsenate for Ca ions. In the presence of municipal landfill leachate, Pb and Cd organic complexes dominated the heavy metal species in solution. The reduction of As and Cr in municipal landfill leachate was crucial for determining aqueous speciation, with typical municipal landfill conditions providing the reduced forms of As and Cr. PMID:16043281

  14. Nietzsche como destino da filosofia e da humanidade? interpretação contextual do § 1 do capítulo "por que sou um destino", de ecce homo

    Directory of Open Access Journals (Sweden)

    Werner Stegmaier

    2010-01-01

    Full Text Available The following translation is a reduced and revised version of the paper Schicksal Nietzsche? Zu Nietzsches Selbsteinschätzung als Schicksal der Philosophie und der Menschheit (Ecce Homo, Warum ich ein Schicksal bin §1" - originally published in Nietzsche-Studien 37 (2008 - which was specially prepared to be presented in lecture organized by the Grupo de Pesquisa Spinoza & Nietzsche (Spinoza & Nietzsche research group - SpiN, in the Universidade Federal do Rio de Janeiro (Rio de Janeiro's Federal University, on September 14, 2009. In the text, the autor employs his own philological-hermeneutical methodology, which is called contextual interpretation, in the purpose to clarify the concepts of the first aphorism from "Why I am a destiny", from Ecce Homo, in its own context, in the context of Ecce Homo and in the context of the entire work from Nietzsche.

  15. Influence of bending test configuration on cracking behavior of FRC

    DEFF Research Database (Denmark)

    Finazzi, Silvia; Paegle, Ieva; Fischer, Gregor;

    2014-01-01

    (SFRC) and Engineered Cementitious Composites (ECC), were tested and are described in this study. The materials were chosen so that one of them would be strain hardening (ECC) and the other tension softening (SFRC). Notched and un-notched three- and four-point bending tests were carried out to determine......This paper describes an investigation of the influence of the testing configuration for Fiber Reinforced Concrete in bending and aims at evaluating the influence of the test configuration details on the characterization of the material. Two different types of FRC, Steel Fiber Reinforced Concrete...

  16. Evaluation of long-term interaction between cement and bentonite for geological disposal (2) XAFS analysis of calcium silicate hydrate precipitates at cementitious and bentonite material interface

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. Numerical analyses of the long-term alteration of the engineered barriers used for the disposal of TRU waste predicted precipitation of C-S-H minerals at the interface between the cementitious materials and the bentonite-based buffer. When the C-S-H precipitates at this interface, the diffusion coefficient in the engineered barriers will decrease, resulting in reduced mass transport, which feeds back to reduce the rate of subsequent alteration. The C-S-H predicted to form at the cement-bentonite interface could not be identified directly using conventional analytical tools, including XRD, due to its low crystallinity. The authors propose that XAFS analysis, which provides spectra sensitive to the valency and coordination of the element of interest regardless of its crystallinity, would be capable of characterizing the C-S-H. The presence of the C-S-H precipitated as a secondary mineral has already been confirmed by applying chemical and XAFS analyses to bentonite specimens collected from the compacted bentonite-cement interface. However, because of the limitations on the width of specimens that can be collected by cutting from block samples, i.e. approximately 1 mm, detailed concentration profiles could not be obtained for this secondary C-S-H. In this study, XAFS spectra of thin specimens were measured using an X-ray detector in order to obtain detailed concentration profiles for the C-S-H formed at the interface between the cementitious material and the bentonite-based buffer. The X-ray detector used in the XAFS analysis consists of 1024 photodiodes arranged in line with a 0.025 mm pitch (photodiode array; PDA). Ca-K-edge XAFS measurements were conducted at the Photon Factory of the KEK. The synchrotron was operated in top-up mode with 450 mA during the measurements. Specimens were taken from a contact sample of compacted bentonite (Kunigel V1; dry density of 1.6 g/cm3) and hardened OPC (w/c = 0.6) immersed in

  17. The Cementitious Barriers Partnership Experimental Programs and Software Advancing DOE@@@s Waste Disposal/Tank Closure Efforts @@@ 15436

    International Nuclear Information System (INIS)

    The U.S. Department of Energy Environmental Management (DOE-EM) Office of Tank Waste Management-sponsored Cementitious Barriers Partnership (CBP) is chartered with providing the technical basis for implementing cement-based waste forms and radioactive waste containment structures for long-term disposal. DOE needs in this area include the following to support progress in final treatment and disposal of legacy waste and closure of High-Level Waste (HLW) tanks in the DOE complex: long-term performance predictions, flow sheet development and flow sheet enhancements, and conceptual designs for new disposal facilities. The DOE-EM Cementitious Barriers Partnership is producing software and experimental programs resulting in new methods and data needed for end-users involved with environmental cleanup and waste disposal. Both the modeling tools and the experimental data have already benefited the DOE sites in the areas of performance assessments by increasing confidence backed up with modeling support, leaching methods, and transport properties developed for actual DOE materials. In 2014, the CBP Partnership released the CBP Software Toolbox @@ @@Version 2.0@@@ which provides concrete degradation models for 1) sulfate attack, 2) carbonation, and 3) chloride initiated rebar corrosion, and includes constituent leaching. These models are applicable and can be used by both DOE and the Nuclear Regulatory Commission (NRC) for service life and long-term performance evaluations and predictions of nuclear and radioactive waste containment structures across the DOE complex, including future SRS Saltstone and HLW tank performance assessments and special analyses, Hanford site HLW tank closure projects and other projects in which cementitious barriers are required, the Advanced Simulation Capability for Environmental Management (ASCEM) project which requires source terms from cementitious containment structures as input to their flow simulations, regulatory reviews of DOE performance

  18. The Cementitious Barriers Partnership Experimental Programs and Software Advancing DOE’s Waste Disposal/Tank Closure Efforts – 15436

    Energy Technology Data Exchange (ETDEWEB)

    Burns, Heather [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Flach, Greg [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Smith, Frank [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Langton, Christine [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Brown, Kevin [Vanderbilt Univ./CRESP, Nashville, TN (United States); Kosson, David [Vanderbilt Univ./CRESP, Nashville, TN (United States); Samson, Eric [SIMCO Technologies, Inc. (United States); Mallick, Pramod [US DOE, Washington, DC (United States)

    2015-01-27

    The U.S. Department of Energy Environmental Management (DOE-EM) Office of Tank Waste Management-sponsored Cementitious Barriers Partnership (CBP) is chartered with providing the technical basis for implementing cement-based waste forms and radioactive waste containment structures for long-term disposal. DOE needs in this area include the following to support progress in final treatment and disposal of legacy waste and closure of High-Level Waste (HLW) tanks in the DOE complex: long-term performance predictions, flow sheet development and flow sheet enhancements, and conceptual designs for new disposal facilities. The DOE-EM Cementitious Barriers Partnership is producing software and experimental programs resulting in new methods and data needed for end-users involved with environmental cleanup and waste disposal. Both the modeling tools and the experimental data have already benefited the DOE sites in the areas of performance assessments by increasing confidence backed up with modeling support, leaching methods, and transport properties developed for actual DOE materials. In 2014, the CBP Partnership released the CBP Software Toolbox –“Version 2.0” which provides concrete degradation models for 1) sulfate attack, 2) carbonation, and 3) chloride initiated rebar corrosion, and includes constituent leaching. These models are applicable and can be used by both DOE and the Nuclear Regulatory Commission (NRC) for service life and long-term performance evaluations and predictions of nuclear and radioactive waste containment structures across the DOE complex, including future SRS Saltstone and HLW tank performance assessments and special analyses, Hanford site HLW tank closure projects and other projects in which cementitious barriers are required, the Advanced Simulation Capability for Environmental Management (ASCEM) project which requires source terms from cementitious containment structures as input to their flow simulations, regulatory reviews of DOE performance

  19. Strain hardening fiber reinforced cement composites for the flexural strengthening of masonry elements of ancient structures

    OpenAIRE

    Esmaeeli, Esmaeel; Manning, Elizabeth; Barros, Joaquim A. O.

    2013-01-01

    To assess the strengthening ability of a strain hardening cementitious composite (SHCC), a layer of SHCC was applied to masonry beams subjected to bending. When compared to the strengthening performance of steel fibre reinforced self-compacting concrete (SFRSCC) layer for this type of brittle beams, the SHCC presented better workability in fresh state, and provided a higher load carrying capacity and deflection ductility even with a smaller layer thickness. By using the data...

  20. Wedge-Splitting Test – Determination of Minimal Starting Notch Length for Various Cement Based Composites

    Czech Academy of Sciences Publication Activity Database

    Seitl, Stanislav; Klusák, Jan; Veselý, V.; Řoutil, L.

    452-453, - (2011), s. 81-84. ISSN 1013-9826 R&D Projects: GA AV ČR KJB200410901; GA ČR GA103/08/0963 Institutional research plan: CEZ:AV0Z20410507 Keywords : wedge-splitting test, cementitious composites, quasi-brittle fracture, brittle fracture Subject RIV: JL - Materials Fatigue, Friction Mechanics www.scientific.net

  1. Testing the model of the rings of cement composites in the blast

    OpenAIRE

    Doležel, Vladimír; Pokorný, Jiří; Suchánek, Vladimír

    2013-01-01

    This paper deals with the description and evaluation of experimental results obtained by testing rings of underground structures under extreme loads – blast. Models rings were made at a scale of 1/20 of cementitious composites in the shape of a circular tunnel. The materials used were plain concrete, synthetic fiber reinforced concrete, and steel fiber reinforced concrete. Test specimens were made of rings, joined together and placed into the made groove. In each group, were placed 2 senso...

  2. Development of Design Procedures for Flexural Applications of Textile Composite Systems Based on Tension Stiffening Models

    OpenAIRE

    Mobasher, Barzin

    2011-01-01

    The Aveston Copper and Kelly (ACK) Method has been routinely used in estimating the efficiency of the bond between the textile and cementitious matrix. This method however has a limited applicability due to the simplifying assumptions such as perfect bond. A numerical model for simulation of tensile behavior of reinforced cement-based composites is presented to capture the inefficiency of the bond mechanisms. In this approach the role of interface properties which are instrumental in the simu...

  3. Self-decomposable Fibrous Bridging Additives for Temporary Cementitious Fracture Sealers in EGS Wells

    Energy Technology Data Exchange (ETDEWEB)

    Sugama T.; Pyatina, T.; Gill, S.; Kisslinger, K.; Iverson, B.; Bour, D.

    2012-11-01

    This study evaluates compatibility of a self-degradable temporary fracture sealer with the drilling mud and plugging and self-degrading performance of different fibers to be used in combination with the sealer. The sodium silicate-activated slag/Class C fly ash (SSASC) cementitious sealer must plug fractures at 85oC to allow continuous well drilling and it must degrade and leave the fractures open for water at later times when exposed to temperatures above 200oC. The sealer showed good compatibility with the mud. Even the blend of 80/20 vol.% of sealer/mud reached a compressive strength of more than 2000 psi set as one of the material criteria, mostly due to the additional activation of the slag and Class C fly ash by the alkaline ingredient present in the drilling fluid. In contrast, the drilling fluid was detrimental to the compressive strength development in conventional Class G well cement, so that it failed to meet this criterion. Among several organic fibers tested both polyvinyl alcohol (PVA)-and nylon-based fibers showed adequate plugging of the sealer in slot nozzles of 1-in. wide x 6-in. long x 0.08 in. and 0.24 in. high under pressures up to 700 psi. PVA fibers displayed better compressive toughness and self-degrading properties than nylon. The compressive toughness of sealers made by adding 1.0 wt% 6 mm-length PVA and 0.5 wt% 19 mm-length PVA was 9.5-fold higher than that of a non-bridged sealer. One factor governing the development of such high toughness was an excellent adherence of PVA to the SSASC cement. The alkali-catalyzed self-decomposition of PVA at 200°C led to the morphological transformation of the material from a fibrous structure to a microscale flake-like structure that helped the desirable conversion of the sealer into small fragments. In contrast, nylon’s decomposition provided a reticular network structure in the self-degraded sealer resulting in bigger fragments compared against the sealer with PVA. The PVA fiber has a high

  4. USE OF CEMENTITIOUS MATERIALS FOR SRS REACTOR FACILITY IN-SITU DECOMMISSIONING - 11620

    Energy Technology Data Exchange (ETDEWEB)

    Langton, C.; Stefanko, D.; Serrato, M.; Blankenship, J.; Griffin, W.; Waymer, J.; Matheny, D.; Singh, D.

    2010-12-07

    The United States Department of Energy (US DOE) concept for facility in-situ decommissioning (ISD) is to physically stabilize and isolate in tact, structurally sound facilities that are no longer needed for their original purpose of, i.e., producing (reactor facilities), processing (isotope separation facilities) or storing radioactive materials. The Savannah River Site 105-P and 105-R Reactor Facility ISD requires about 250,000 cubic yards of grout to fill the below grade structure. The fills are designed to prevent subsidence, reduce water infiltration, and isolate contaminated materials. This work is being performed as a Comprehensive Environmental Response, Compensations and Liability Act (CERCLA) action and is part of the overall soil and groundwater completion projects for P- and R-Areas. Cementitious materials were designed for the following applications: (1) Below grade massive voids/rooms: Portland cement-based structural flowable fills for - Bulk filling, Restricted placement and Underwater placement. (2) Special below grade applications for reduced load bearing capacity needs: Cellular portland cement lightweight fill (3) Reactor vessel fills that are compatible with reactive metal (aluminum metal) components in the reactor vessels: Calcium sulfoaluminate flowable fill, and Magnesium potassium phosphate flowable fill. (4) Caps to prevent water infiltration and intrusion into areas with the highest levels of radionuclides: Portland cement based shrinkage compensating concrete. A system engineering approach was used to identify functions and requirements of the fill and capping materials. Laboratory testing was performed to identify candidate formulations and develop final design mixes. Scale-up testing was performed to verify material production and placement as well as fresh and cured properties. The 105-P and 105-R ISD projects are currently in progress and are expected to be complete in 2012. The focus of this paper is to describe the (1) grout mixes

  5. ECC ALGORITHM FOR PREVENTING SIDE-CHANNEL ATTACK%抗侧信道攻击的椭圆曲线密码算法

    Institute of Scientific and Technical Information of China (English)

    姚剑波; 张涛

    2013-01-01

    Having high safety and effective computational property,the elliptic curve cryptosystem (ECC) is very suitable for embedded mobile environment with resource constraints.Side-channel attack (SCA) is a powerful cipher attack method,it uses leaking information of cipher-chip in its operation process to attack chip cryptographic algorithms.In view of the situation that the SCA on ECC mainly concentrates on scalar multiplication operation,an improved algorithm FWNAF (Fractional Width-w NAF) based on RWNAF (Refined Width-w NAF) is proposed.This algorithm utilise the fragments window technology,further improves the utilisation ratio of the storage resource and reduces the "jitter phenomenon " in system computing performance caused by the sharp change in system resources.%椭圆曲线密码系统具有较高的安全性和有效的计算性,非常适合于资源受限的嵌入式移动环境.侧信道攻击是一种强有力的密码攻击方法,利用密码芯片在运算过程中泄露的信息对芯片的密码算法进行攻击.针对侧信道攻击椭圆曲线密码系统主要集中在对标量乘运算的攻击,提出一种基于RWNAF(Refined Width-w NAF)的改进算法FWNAF (Fractional Width-w NAF)算法.该算法利用碎片窗口技术,进一步提高存储资源的利用效率,同时也减少由于系统资源急剧变化而引发的系统计算性能的“抖动现象”.

  6. Damage development, phase changes, transport properties, and freeze-thaw performance of cementitious materials exposed to chloride based salts

    Science.gov (United States)

    Farnam, Yaghoob

    Recently, there has been a dramatic increase in premature deterioration in concrete pavements and flat works that are exposed to chloride based salts. Chloride based salts can cause damage and deterioration in concrete due to the combination of factors which include: increased saturation, ice formation, salt crystallization, osmotic pressure, corrosion in steel reinforcement, and/or deleterious chemical reactions. This thesis discusses how chloride based salts interact with cementitious materials to (1) develop damage in concrete, (2) create new chemical phases in concrete, (3) alter transport properties of concrete, and (4) change the concrete freeze-thaw performance. A longitudinal guarded comparative calorimeter (LGCC) was developed to simultaneously measure heat flow, damage development, and phase changes in mortar samples exposed to sodium chloride (NaCl), calcium chloride (CaCl 2), and magnesium chloride (MgCl2) under thermal cycling. Acoustic emission and electrical resistivity measurements were used in conjunction with the LGCC to assess damage development and electrical response of mortar samples during cooling and heating. A low-temperature differential scanning calorimetry (LT-DSC) was used to evaluate the chemical interaction that occurs between the constituents of cementitious materials (i.e., pore solution, calcium hydroxide, and hydrated cement paste) and salts. Salts were observed to alter the classical phase diagram for a salt-water system which has been conventionally used to interpret the freeze-thaw behavior in concrete. An additional chemical phase change was observed for a concrete-salt-water system resulting in severe damage in cementitious materials. In a cementitious system exposed to NaCl, the chemical phase change occurs at a temperature range between -6 °C and 8 °C due to the presence of calcium sulfoaluminate phases in concrete. As a result, concrete exposed to NaCl can experience additional freeze-thaw cycles due to the chemical

  7. Selecting a suitable specimen shape with low constraint value for determination of fracture parameters of cementitious composites

    Czech Academy of Sciences Publication Activity Database

    Seitl, Stanislav; Korte, S.; De Corte, W.; Boel, V.; Sobek, J.; Veselý, V.

    Zurich: Trans Tech Publications, 2014 - (Milazzo, A.; Aliabadi, M.), s. 481-484. (Key Engineering Materials. 577-578). ISBN 978-3-03785-830-1. ISSN 1013-9826. [FDM 2013 - International Conference on Fracture and Damage Mechanics /12./. Sardinia (IT), 17.09.2013-19.09.2013] R&D Projects: GA ČR(CZ) GAP104/11/0833 Institutional support: RVO:68081723 Keywords : fracture mechanics * boundary conditions * crack tip fields * stress intensity factor * Tstress Subject RIV: JL - Materials Fatigue, Friction Mechanics

  8. Effects of CuO Nanoparticles on Microstructure, Physical, Mechanical and Thermal Properties of Self-Compacting Cementitious Composites

    Institute of Scientific and Technical Information of China (English)

    Ali Nazari; Shadi Riahi

    2011-01-01

    In the present study, split tensile strength of self-compacting concrete with different amount of CuO nanoparticles has been investigated. CuO nanoparticles with the average particle size of 15 nm were added partially to self compacting concrete and split tensile strength of the specimens has been measured. The results indicate that CuO nanoparticles are able to improve the split tensile strength of self compacting concrete and recover the negative effects of polycarboxylate superplasticizer on split tensile strength. CuO nanoparticle as a partial replacement of cement up to 4 wt% could accelerate C-S-H gel formation as a result of increased crystalline Ca(OH)2 amount at the early ages of hydration. The increase of the CuO nanoparticles more than 4 wt% causes the decrease of the split tensile strength because of unsuitable dispersion of nanoparticles in the concrete matrix. Accelerated peak appearance in conduction calorimetry tests, more weight loss in thermogravimetric analysis and more rapid appearance of related peaks to hydrated products in X-ray diffraction (XRD) results all also indicate that CuO nanoparticles up to 4 wt% could improve the mechanical and physical properties of the specimens. Finally, CuO nanoparticles could improve the pore structure of concrete and shift the distributed pores to harmless and few-harm pores.

  9. PARTNERSHIP FOR THE DEVELOPMENT OF NEXT GENERATION SIMULATION TOOLS TO EVALUATE CEMENTITIOUS BARRIERS AND MATERIALS USED IN NUCLEAR APPLICATION - 8388

    International Nuclear Information System (INIS)

    The US DOE has initiated a multidisciplinary cross cutting project to develop a reasonable and credible set of tools to predict the structural, hydraulic and chemical performance of cement barriers used in nuclear applications over extended time frames (e.g., > 100 years for operating facilities and > 1000 years for waste management). A partnership that combines DOE, NRC, academia, private sector, and international expertise has been formed to accomplish the project objectives by integrating existing information and realizing advancements where necessary. The set of simulation tools and data developed under this project will be used to evaluate and predict the behavior of cementitious barriers used in near surface engineered waste disposal systems, e.g., waste forms, containment structures, entombments and environmental remediation, including decontamination and decommissioning (D and D) activities. The simulation tools will also support analysis of structural concrete components of nuclear facilities (spent fuel pools, dry spent fuel storage units, and recycling facilities, e.g., fuel fabrication, separations processes). Simulation parameters will be obtained from prior literature and will be experimentally measured under this project, as necessary, to demonstrate application of the simulation tools for three prototype applications (waste form in concrete vault, high level waste tank grouting, and spent fuel pool). Test methods and data needs to support use of the simulation tools for future applications will be defined. This is a national issue that affects all waste disposal sites that use cementitious waste forms and structures, decontamination and decommissioning activities, service life determination of existing structures, and design of future public and private nuclear facilities. The problem is difficult because it requires projecting conditions and responses over extremely long times. Current performance assessment analyses show that engineered barriers

  10. Equilibrium and kinetic models on the adsorption of Reactive Black 5 from aqueous solution using Eichhornia crassipes/chitosan composite.

    Science.gov (United States)

    El-Zawahry, Manal M; Abdelghaffar, Fatma; Abdelghaffar, Rehab A; Hassabo, Ahmed G

    2016-01-20

    New natural biopolymer composite was prepared using extracted cellulose from an environmentally problematic water hyacinth Eichhornia crassipes (EC). The extracted cellulose was functionalized by chitosan and TiO2 nanoparticles to form EC/Chitosan (EC/Cs) composite network. Surface characterization of EC/Cs natural biopolymer composite was examined by spectrum analysis FT-IR, specific surface area, micropore volume, pore width and SEM. Furthermore, the sorption experiments were carried out as a function of pH, various initial dye concentration and contact time. Experiment results showed that the EC/Cs composite have high ability to remove C.I. Reactive Black 5 from its dye-bath effluent. The equilibrium sorption evaluation of RB5 conformed and fitted well to Langmuir adsorption isotherm models and the maximum sorption capacity was 0.606 mg/g. The kinetic adsorption models followed pseudo-second order model and the dye intra-particle diffusion may suggesting a chemical reaction mechanism. Further, it was obvious from the investigation that this composite could be applied as a promising low cost adsorbent for anionic dye removal from aqueous solutions. PMID:26572382

  11. Development of a sorption data base for the cementitious near-field of a repository for radioactive waste

    International Nuclear Information System (INIS)

    The migration of radionuclides within a repository for radioactive waste is retarded due to interaction with the engineered barrier system. Sorption processes play a decisive role in the retardation of radionuclides in the repository environment, and thus, the development of sorption data bases (SDBs) is an important task and an integral part of performance assessment. The methodology applied in the development of a SDB for the cementitious near-field of a repository for long-lived intermediate-level waste is presented in this study. The development of such a SDB requires knowledge of the chemical conditions of the near-field and information on the uptake process of radionuclides by hardened cement paste. The principles upon which the selection of the 'best available' laboratory sorption values is based are outlined. The influence of cellulose degradation products, cement additives and cement-derived colloids on the sorption behaviour of radionuclides is addressed in conjunction with the development of the SDB. (author)

  12. A multi-scale approach of mechanical and transport properties of cementitious materials under rises of temperature

    International Nuclear Information System (INIS)

    The modern industrial activities (storage of nuclear waste, geothermal wells, nuclear power plants,...) can submit cementitious materials to some extreme conditions, for example at temperatures above 200 C. This level of temperature will induce phenomena of dehydration in the cement paste, particularly impacting the CSH hydrates which led to the mechanical cohesion. The effects of these temperatures on the mechanical and transport properties have been the subject of this thesis.To understand these effects, we need to take into account the heterogeneous, porous, multi-scale aspects of these materials. To do this, micro-mechanics and homogenization tools based on the Eshelby problem's solution were used. Moreover, to support this multi-scale modeling, mechanical testing based on the theory of porous media were conducted. The measurements of modulus compressibility, permeability and porosity under confining pressure were used to investigate the mechanisms of degradation of these materials during thermal loads up to 400 C. (author)

  13. An investigation of magnox sludge and alumino-ferric floc waste simulate, immobilised by a cementitious matrix

    International Nuclear Information System (INIS)

    Magnox sludge and alumino ferric floc simulates, prepared using non-radioactive tracers were immobilised by a cementitious system. Formulation design aimed at optimising pollutant leaching with permeability and compressive strength as secondary considerations. The behaviour of the products under accelerated weathering conditions was investigated. The study was divided into two parts: Formulation design in Phase I and the systematic testing of the optimum formulations under freeze-thaw, and hydration -dehydration conditions in Phase 2. Analytical method development for leachate analysis continued through both Phases. The Barnwood method of leach testing was used. The immobilised waste had good physical properties (i.e. high strength and low permeability) and a significant improvement was achieved during the course of the work in the leach rates of the tracers, particularly of caesium and strontium. (author)

  14. Significance of steel electrical resistance method in the evaluation of reinforcement corrosion in cementitious systems

    Directory of Open Access Journals (Sweden)

    Krajci, L.

    2004-06-01

    Full Text Available The suitable detection system of steel reinforcement corrosion in concrete structures contributes to the reduction of their maintenance costs. Method of steel electrical resistance represents non-destructive monitoring of steel in cementitious systems. Specially prepared and arranged test specimen of steel as a corrosion sensor is embedded in mortar specimen. Verification tests of this method based on chloride corrosion of steel in mortars as well as its visual inspection are introduced. Significance of steel electrical resistance method lies in the expression of steel corrosion by these quantitative parameters: reduction of cross-section of steel, thickness of corroded layer and loss of weight of steel material. This method is an integral method that allows the indirect determination of mentioned corrosion characteristics. The comparison of verified method with gravimetric evaluation of steel corrosion gives a good correspondence. Test results on mortars with calcium chloride dosages between 0.5% and 4.0% by weight of cement prove high sensitiveness and reliability of steel electrical resistance method.

    La utilización de un sistema de detección de la corrosión de las armaduras en estructuras de hormigón puede contribuir a la reducción de sus costes de mantenimiento. El método de la resistencia eléctrica del acero consiste en la monitorización no-destructiva realizada sobre el acero en sistemas cementantes. Dentro de la muestra de mortero se coloca el sistema de detección, especialmente preparado y fijado, actuando como un sensor de la corrosión. En este trabajo se presentan ensayos de verificación de este método, junto con inspecciones visuales, en morteros sometidos a corrosión de armaduras por efecto de los cloruros. La efectividad de este método de la resistencia eléctrica del acero se expresa, en la corrosión de armaduras, de acuerdo a los siguientes parámetros cuantitativos: reducción de la sección transversal del

  15. Reactive transport modeling of the interaction between water and a cementitious grout in a fractured rock. Application to ONKALO (Finland)

    International Nuclear Information System (INIS)

    Highlights: → It is planned to seal conductive fractures near a repository with cementitious grout. → Modeling includes simultaneous hydration and leaching of the grout. → Modeling results show a very limited formation of the high-pH plume. → Results are in qualitative agreement with borehole monitoring data. - Abstract: Grouting of water-conducting fractures with low-alkali cement is foreseen for the potential future repository for spent nuclear fuel in Finland (ONKALO). A possible consequence of the interaction between groundwater and grout is the formation of high-pH solutions which will be able to react with the host rock (gneisses) and alter its mineralogy and porosity. A reactive transport modeling study of this possible alteration has been conducted. First, the hydration of the low-alkali cementitious grout has been modeled, using results from the literature as a guide. The hydrated cement is characterized by the absence of portlandite and the presence of a C-S-H gel with a Ca/Si ratio about 0.8 after tens of years (Ca/Si is about 1.7 in Ordinary Portland Cement). Second, calculations have simulated the interaction between flowing water and grout and the formation of an alkalinity plume, which flows beyond the grouted section of the fracture. The calculations include the hydration and simultaneous leaching of the grout through diffusive exchange between the porewater in the grout and the flowing water in the fracture. The formation of an alkaline plume is extremely limited when the low-pH grout is used. Even when using a grout with a lower silica fume content, the extent and magnitude of the alkaline plume is quite minor. These results are in qualitative agreement with monitoring at ONKALO.

  16. On a morphological approach of the meso-structure for the multi-scale analysis of the thermo-hydro-mechanical behaviour of cementitious materials

    International Nuclear Information System (INIS)

    The investigation of the behavior of heated concrete is a major research topic which concerns the assessment of safety level of structures when exposed to high temperatures, for instance during a fire. For this purpose, several modeling approaches were developed within thermo-hydro-mechanical (THM) frameworks in order to take into account the involved physic-chemical and mechanical processes that affect stability of heated concrete. However, existing models often do note account explicitly for the heterogeneity of the material: concrete is composite material that may be schematized as an assembly of inclusions (aggregates) embedded in a cementitious matrix (cement paste). This latter may be described as a partially saturated open porous medium. The aggregates are characterized by their mineralogical nature together with their morphology and size distribution. The material heterogeneity bring an additional complexity: the need to take into account the microstructure in order to quantify the effect of matrix-inclusion thermal, hygral and mechanical incompatibilities on the THM behavior of concrete. This work is a first step in this direction. For this purpose, a three-dimensional (3D) multi-scale finite element model is developed. It allows affecting specific behaviors to matrix and inclusions. For the former, where mass transports occur within the connected porous network, a three-fluids approach (liquid water, vapor and dry air) is adopted and is coupled to a poro-mechanical damage based approach. For inclusions (aggregates) no hygral component arises a pure thermo-mechanical model is considered. The developed model is then used to investigate, either by 2D or 3D numerical simulations, effects of mineralogical nature, morphology and distribution of aggregates. Studied effects have mainly concerned the influence of these parameters on local fluctuations of simulated temperature, gas pressure and damage fields with regard to experimentally observed dispersion. The

  17. Un ejemplo de constitución genérica en la literatura espiritual: el «paso» del Ecce Homo

    Directory of Open Access Journals (Sweden)

    Pego Puigbó, Armando

    2001-12-01

    Full Text Available Spiritual Literature represents a very special branch within the literary system. In this article the genre of the «paso», which is completely different from the dramatic one, will be discussed beyond the traditional approches, based on thematic, formal and discoursive features. In this way, in the «paso» a possible connection of a literary kind with a kind of knowledge and experience is proposed. The Renaissance Genre-Theory can provide a view which allows us to surpass the narrow frame of mimesis. The literary kind is opened to the world, which is represented through the communicative powers of rhetoric devices. The «paso» belongs to the epidictic genre. The praise of Christ adopts the narration of a passage taken out from the Passion, according to figurae sententiae waiting for affective answers. But its spiritual condition is produced by cultural implications which warrant the correct interpretation of its meanings. Examples of Ecce homo by Francisco de Osuna, Juan de Ávila and fray Luis de Granada are analysed according to this purpose.La literatura espiritual representa una rama muy especial dentro del sistema literario. En este artículo, se discutirá el género del «paso», en nada parecido a su homónimo dramático, más allá de los criterios temático, formal y discursivo. En el «paso» puede proponerse una posible conexión entre una clase literaria y una clase de conocimiento y experiencia. La teoría renacentista de los géneros es capaz de ofrecer una perspectiva que supera el estrecho marco de la mímesis. La clase literaria se abre al mundo real, representado por medio de la fuerza comunicativa de los procedimientos retóricos. En este sentido el «paso» pertenece al género epidíctico en cuanto que la alabanza de Cristo adopta la forma de una narración extraída del relato de la Pasión. Las figuras de pensamiento buscan una respuesta afectiva, cuyo empleo y sentido son correctamente interpretados a través de

  18. Development of a new test method for Mineral Based Composites

    DEFF Research Database (Denmark)

    Täljsten, Björn; Orosz, Katalin

    2008-01-01

    The well-known wedge splitting test, often used for characterizing brittle materials has been modified and adapted to testing MBC-reinforced concrete under splitting load. MBC (Mineral Based Composites) is a newly developed strengthening system for existing concrete structures where FRPs, mainly...... CFRP grids are externally bonded to the concrete surface by means of cementitious bonding agents. Crack development, crack patterns, crack opening displacement (COD) versus splitting load and fracture energy are investigated and evaluated. Development of a suitable test specimen and test setup has been...

  19. Contribution to the French program dedicated to cementitious and clayey materials behavior in the context of Intermediate Level Waste management - Hydrogen transfer and materials durability

    Science.gov (United States)

    Bary, B.; Bouniol, P.; Chomat, L.; Dridi, W.; Gatabin, C.; Imbert, C.; L´Hostis, V.; Le Bescop, P.; Muzeau, B.; Poyet, S.

    2013-07-01

    This article illustrates a contribution of the CEA Laboratory of Concrete and Clay Behavior (“LECBA”s) for the assessment and modeling of the Long-Term behavior of cementitious and clayey materials in the context of nuclear ILW (Intermediate Level Waste) management. In particular, we aim at presenting two main topics that are studied at the Lab. The first one is linked to safety aspects and concern hydrogen transfer within cementitious as well as clayey materials (host rock for French nuclear waste disposal). The second point concerns the assessment of durability properties of reinforced concrete structures in the disposal (pre-closure and post-closure) conditions. Experimental specific tests and phenomenological modelling are presented.

  20. Micro-structural characterization of the hydration products of bauxite-calcination-method red mud-coal gangue based cementitious materials

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xiaoming [State Key Laboratory of Advanced Metallurgy, School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Zhang, Na [Green Construction Materials and Circulation Economy Center, Architectural Design and Research Institute of Tsinghua University Co., Ltd., Beijing 100084 (China); Yao, Yuan, E-mail: yuanyaocas@163.com [School of Engineering and Computer Science, University of the Pacific, Stockton, CA 95211 (United States); Sun, Henghu; Feng, Huan [School of Engineering and Computer Science, University of the Pacific, Stockton, CA 95211 (United States)

    2013-11-15

    Highlights: • Al{sup IV} and Al{sup VI} both exist in the hydration products. • Increase of Ca/Si ratio promotes the conversion from [AlO{sub 4}] to [AlO{sub 6}]. • Polymerization degree of [SiO{sub 4}] in the hydration products declines. -- Abstract: In this research, the micro-structural characterization of the hydration products of red mud-coal gangue based cementitious materials has been investigated through SEM-EDS, {sup 27}Al MAS NMR and {sup 29}Si MAS NMR techniques, in which the used red mud was derived from the bauxite calcination method. The results show that the red mud-coal gangue based cementitious materials mainly form fibrous C-A-S-H gel, needle-shaped/rod-like AFt in the early hydration period. With increasing of the hydration period, densification of the pastes were promoted resulting in the development of strength. EDS analysis shows that with the Ca/Si of red mud-coal gangue based cementitious materials increases, the average Ca/Si and Ca/(Si + Al) atomic ratio of C-A-S-H gel increases, while the average Al/Si atomic ratio of C-A-S-H gel decreases. MAS NMR analysis reveals that Al in the hydration products of red mud-coal gangue based cementitious materials exists in the forms of Al{sup IV} and Al{sup VI}, but mainly in the form of Al{sup VI}. Increasing the Ca/Si ratio of raw material promotes the conversion of [AlO{sub 4}] to [AlO{sub 6}] and inhibits the combination between [AlO{sub 4}] and [SiO{sub 4}] to form C-A-S-H gel. Meanwhile, the polymerization degree of [SiO{sub 4}] in the hydration products declines.