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Sample records for high temperature concrete

  1. Experimental needs of high temperature concrete

    Chern, J.C.; Marchertas, A.H.

    1985-01-01

    The needs of experimental data on concrete structures under high temperature, ranging up to about 370 0 C for operating reactor conditions and to about 900 0 C and beyond for hypothetical accident conditions, are described. This information is required to supplement analytical methods which are being implemented into the finite element code TEMP-STRESS to treat reinforced concrete structures. Recommended research ranges from material properties of reinforced/prestressed concrete, direct testing of analytical models used in the computer codes, to investigations of certain aspects of concrete behavior, the phenomenology of which is not well understood. 10 refs

  2. Modeling of concrete response at high temperature

    Pfeiffer, P.; Marchertas, A.

    1984-01-01

    A rate-type creep law is implemented into the computer code TEMP-STRESS for high temperature concrete analysis. The disposition of temperature, pore pressure and moisture for the particular structure in question is provided as input for the thermo-mechanical code. The loss of moisture from concrete also induces material shrinkage which is accounted for in the analytical model. Examples are given to illustrate the numerical results

  3. High temperature polymer concrete compositions

    Fontana, Jack J.; Reams, Walter

    1985-01-01

    This invention is concerned with a polymer concrete composition, which is a two-component composition useful with many bases including metal. Component A, the aggregate composition, is broadly composed of silica, silica flour, portland cement, and acrylamide, whereas Component B, which is primarily vinyl and acrylyl reactive monomers, is a liquid system. A preferred formulation emphasizing the major necessary components is as follows: ______________________________________ Component A: Silica sand 60-77 wt. % Silica flour 5-10 wt. % Portland cement 15-25 wt. % Acrylamide 1-5 wt. % Component B: Styrene 50-60 wt. % Trimethylolpropane 35-40 wt. % trimethacrylate ______________________________________ and necessary initiators, accelerators, and surfactants.

  4. Viscoelastic creep of high-temperature concrete

    Pfeiffer, P.A.; Marchertas, A.H.; Bazant, Z.P.

    1985-01-01

    Presented in this report is the analytical model for analysis of high temperature creep response of concrete. The creep law used is linear (viscoelastic), the temperature and moisture effects on the creep rate and also aging are included. Both constant and transient temperature as well as constant and transient moisture conditions are considered. Examples are presented to correlate experimental data with parameters of the analytical model by the use of a finite element scheme

  5. Structural behavior of reinforced concrete structures at high temperatures

    Yamazaki, N.; Yamazaki, M.; Mochida, T.; Mutoh, A.; Miyashita, T.; Ueda, M.; Hasegawa, T.; Sugiyama, K.; Hirakawa, K.; Kikuchi, R.; Hiramoto, M.; Saito, K.

    1995-01-01

    To establish a method to predict the behavior of reinforced concrete structures subjected simultaneously to high temperatures and external loads, this paper presents the results obtained in several series of tests carried out recently in Japan. This paper reports on the material properties of concrete and steel bars under high temperatures. It also considers the heat transfer properties of thick concrete walls under transient high temperatures, and the structural behavior of reinforced concrete beams subjected to high temperatures. In the tests, data up to 800 C were obtained for use in developing a computational method to estimate the non-linear behavior of reinforced concrete structures exposed to high temperatures. (orig.)

  6. Mechanical properties of concrete for power reactor at high temperatures

    Kawase, Kiyotaka; Tanaka, Hitoshi; Nakano, Masayuki

    1985-01-01

    The purpose of this study is to investigate the mechanical properties of concrete for power reactor at high temperature. This paper presents the creep behavior of concrete at high temperature and the cause by which a specified aggregate is broken at a specified high temperature. The creep coefficient at high temperature is smaller than that at ordinary temperature. (author)

  7. High temperature chemically resistant polymer concrete

    Sugama, T.; Kukacka, L.E.

    High temperature chemically resistant, non-aqueous polymer concrete composites consist of about 12 to 20% by weight of a water-insoluble polymer binder. The binder is polymerized in situ from a liquid vinyl-type monomer or mixture of vinyl containing monomers such as triallylcyanurate, styrene, acrylonitrile, acrylamide, methacrylamide, methyl-methacrylate, trimethylolpropane trimethacrylate and divinyl benzene. About 5 to 40% by weight of a reactive inorganic filler selected from the group consisting of tricalcium silicate and dicalcium silicate and mixtures containing less than 2% free lime, and about 48 to 83% by weight of silica sand/ and a free radical initiator such as di-tert-butyl peroxide, azobisisobutyronitrile, benzoyl peroxide, lauryl peroxide, other orgaic peroxides and combinations to initiate polymerization of the monomer in the presence of the inorganic filers are used.

  8. The effect of high temperatures on concrete incorporating ultrafine ...

    In this work, several concrete formulations have been tested and multi-scale observation of high-temperature behavior of ordinary concrete (compressive strength of 48 MPa) and HPC (compressive strength 75 MPa) were adopted. On the scale of the material, the identification of trends with temperature data such as porosity ...

  9. High temperature behaviour of self-consolidating concrete

    Fares, Hanaa; Remond, Sebastien; Noumowe, Albert; Cousture, Annelise

    2010-01-01

    This paper presents an experimental study on the properties of self-compacting concrete (SCC) subjected to high temperature. Two SCC mixtures and one vibrated concrete mixture were tested. These concrete mixtures come from the French National Project B-P. The specimens of each concrete mixture were heated at a rate of 1 deg. C/min up to different temperatures (150, 300, 450 and 600 deg. C). In order to ensure a uniform temperature throughout the specimens, the temperature was held constant at the maximum temperature for 1 h before cooling. Mechanical properties at ambient temperature and residual mechanical properties after heating have already been determined. In this paper, the physicochemical properties and the microstuctural characteristics are presented. Thermogravimetric analysis, thermodifferential analysis, X-ray diffraction and SEM observations were used. The aim of these studies was in particular to explain the observed residual compressive strength increase between 150 and 300 deg. C.

  10. Short steel and concrete columns under high temperatures

    A. E. P. G. A. Jacintho

    Full Text Available The growing demand for knowledge about the effect of high temperatures on structures has stimulated increasing research worldwide. This article presents experimental results for short composite steel and concrete columns subjected to high temperatures in ovens with or without an axial compression load, numerically analyzes the temperature distribution in these columns after 30 and 60 minutes and compares them with experimental results. The models consist of concrete-filled tubes of three different thicknesses and two different diameters, and the concrete fill has conventional properties that remained constant for all of the models. The stress-strain behavior of the composite columns was altered after exposure to high temperatures relative to the same columns at room temperature, which was most evident in the 60-minute tests due to the higher temperatures reached. The computational analysis adopted temperature rise curves that were obtained experimentally.

  11. Effect of high temperature on integrity of concrete containment structures

    Bhat, P.D.

    1986-01-01

    The effect of high temperature on concrete material properties and structural behavior are studied in order to relate these effects to the performance of concrete containment structures. Salient data obtained from a test program undertaken to study the behavior of a restrained concrete structure under thermal gradient loads up to its ultimate limit are described. The preliminary results indicate that concrete material properties can be considered to remain unaltered up to temperatures of 100 0 C. The presence of thermal gradients did not significantly affect the structures ultimate mechanical load capacity. Relaxation of restraint forces due to creep was found to be an important factor. The test findings are compared with the observations made in available literature. The effect of test findings on the integrity analysis of a containment structure are discussed. The problem is studied from the viewpoint of a CANDU heavy water reactor containment

  12. Improving the high performance concrete (HPC behaviour in high temperatures

    Cattelan Antocheves De Lima, R.

    2003-12-01

    Full Text Available High performance concrete (HPC is an interesting material that has been long attracting the interest from the scientific and technical community, due to the clear advantages obtained in terms of mechanical strength and durability. Given these better characteristics, HFC, in its various forms, has been gradually replacing normal strength concrete, especially in structures exposed to severe environments. However, the veiy dense microstructure and low permeability typical of HPC can result in explosive spalling under certain thermal and mechanical conditions, such as when concrete is subject to rapid temperature rises, during a f¡re. This behaviour is caused by the build-up of internal water pressure, in the pore structure, during heating, and by stresses originating from thermal deformation gradients. Although there are still a limited number of experimental programs in this area, some researchers have reported that the addition of polypropylene fibers to HPC is a suitable way to avoid explosive spalling under f re conditions. This change in behavior is derived from the fact that polypropylene fibers melt in high temperatures and leave a pathway for heated gas to escape the concrete matrix, therefore allowing the outward migration of water vapor and resulting in the reduction of interned pore pressure. The present research investigates the behavior of high performance concrete on high temperatures, especially when polypropylene fibers are added to the mix.

    El hormigón de alta resistencia (HAR es un material de gran interés para la comunidad científica y técnica, debido a las claras ventajas obtenidas en término de resistencia mecánica y durabilidad. A causa de estas características, el HAR, en sus diversas formas, en algunas aplicaciones está reemplazando gradualmente al hormigón de resistencia normal, especialmente en estructuras expuestas a ambientes severos. Sin embargo, la microestructura muy densa y la baja permeabilidad t

  13. Review on fatigue behavior of high-strength concrete after high temperature

    Zhao, Dongfu; Jia, Penghe; Gao, Haijing

    2017-06-01

    The fatigue of high-strength concrete after high temperature has begun to attract attention. But so far the researches work about the fatigue of high-strength concrete after high temperature have not been reported. This article based on a large number of literature. The research work about the fatigue of high-strength concrete after high temperature are reviewed, analysed and expected, which can provide some reference for the experimental study of fatigue damage analysis.

  14. Relationship between permeability and damage in concretes at high temperature

    Dal Pont, St.

    2004-09-01

    Due to its technical and economical advantages, concrete is nowadays the most used building material in civil engineering. Even if its use is known since nearly two centuries, its behavior has not been yet completely explained due to the complexity of its porous microstructure. This fact is quite evident under particular conditions such as, by instance, during an elevation of temperature. This condition can mainly occur in two cases: due to a casualty (e.g. a fire) or in normal use conditions (e.g. storage of nuclear rejects). This work aims at contributing to the study of the phenomena that can be observed in concrete exposed to high temperatures and, in particular, focuses on the study of the evolution of intrinsic permeability. The characterisation of permeability (which is hardly measurable in hot conditions) is necessary for describing and modelling transport phenomena which occur in porous media. An experimental study has been made in collaboration with the CEA. A real-scale hollow cylinder has been instrumented with gauges for studying the evolution of temperature and gas pressure fields inside concrete. Later, the cylinder has been then numerically modelled by means of a thermo-hydro-chemical (THC) and a thermo-hydro-chemo-mechanical (THCM) model. The THC model, implemented by means of the finite volume method, has allowed a first, qualitative study of the behaviour of concrete submitted to high temperature. This model, which, for sake of simplicity, has neglected all mechanical effects, has allowed the description of the main phenomena occurring inside concrete: mass transport, phase changes, microstructure evolution. Later, the modelling has been completed by means of the THCM model using the Hitecosp code, implemented by means of the finite element method at the university of Padua. This code allows a very complete description of the phenomena occurring inside concrete and takes into consideration the mechanical behavior of concrete by means of an

  15. Effect of high temperature or fire on heavy weight concrete properties

    Sakr, K.; EL-Hakim, E.

    2005-01-01

    Temperature plays an important role in the use of concrete for shielding nuclear reactors. In the present work, the effect of different durations (1, 2 and 3 h) of high temperatures (250, 500, 750 and 950 deg. C) on the physical, mechanical and radiation properties of heavy concrete was studied. The effect of fire fitting systems on concrete properties was investigated. Results showed that ilmenite concrete had the highest density, modulus of elasticity and lowest absorption percent, and it had also higher values of compressive, tensile, bending and bonding strengths than gravel or baryte concrete. Ilmenite concrete showed the highest attenuation of transmitted gamma rays. Firing (heating) exposure time was inversely proportional to mechanical properties of all types of concrete. Ilmenite concrete was more resistant to elevated temperature. Foam or air proved to be better than water as a cooling system in concrete structure exposed to high temperature because water leads to a big damage in concrete properties

  16. Prestressed concrete vessels suitable for helium high temperature reactors

    Lockett, G.E.; Kinkead, A.N.

    1967-02-01

    In considering prestressed concrete vessels for use with helium cooled high temperature reactors, a number of new problems arise and projected designs involve new approaches and new solutions. These reactors, having high coolant outlet temperature from the core and relatively high power densities, can be built into compact designs which permit usefully high working pressures. Consequently, steam generators and circulating units tend to be small. Although circuit activity can be kept quite low with coated particle fuels, designs which involve entry for subsequent repair are not favoured, and coupled with the preferred aim of using fully shop fabricated units within the designs with removable steam generators which involve no tube welding inside the vessel. A particular solution uses a number of slim cylindrical assemblies housed in the wall of the pressure vessel and this vessel design concept is presented. The use of helium requires very high sealing standards and one of the important requirements is a vessel design which permits leak testing during construction, so that a repair seal can be made to any faulty part in a liner seam. Very good demountable joint seals can be made without particular difficulty and Dragon experience is used to provide solutions which are suitable for prestressed concrete vessel penetrations. The concept layout is given of a vessel meeting these requirements; the basis of design is outlined and special features of importance discussed. (author)

  17. High temperature concrete composites containing organosiloxane crosslinked copolymers

    Zeldin, A.; Carciello, N.; Kukacka, L.; Fontana, J.

    High temperature polymer concrete composites comprising about 10 to 30% by weight of a liquid monomer mixture is described. It consists essentially of an organosiloxane polymer crosslinked with an olefinically unsaturated monomer selected from the group consisting of styrene, methyl methacrylate, trimethylolpropane trimethacrylate, triallyl cyanurate, n-phenylmalimide, divinyl benzene and mixtures thereof. About 70 to 90% by weight of an inert inorganic filler system containing silica sand and portland cement, Fe/sub 2/O/sub 3/, carbon black or mixtures thereof. Optionally a free radical initiator such as di-tert-butyl peroxide, azobisisobyutyronitrile, benzoyl peroxide, lauryl peroxide and other organic peroxides are used to initiate crosspolymerization of the monomer mixture in the presence of the inorganic filler.

  18. Effect of High Temperature or fire on heavy weight concrete properties used in nuclear facilities

    Sakr, K.

    2003-01-01

    In the present work the effect of different duration (1, 2 and 3 hours) of high temperatures (250 degree C, 500 degree C, 750 degree C and 950 degree C) on the physical and mechanical properties of heavy concrete shields were studied. The effect of fire fitting systems on ordinary concrete was investigated. The work was extended to determine the effect of high temperature or accidental fire on the radiation properties of heavy weight concrete. Results showed that ilmenite concrete had the highest density, absorption, and modulus of elasticity when compared to the other types of studied concrete and it had also higher values of compressive, tensile, bending and bonding strength than ordinary or baryte concrete. Ilmenite concrete had the highest attenuation of transmitted gamma rays in comparing to gravel concrete and baryte concrete. Ilmenite concrete was more resistant to elevated temperature than gravel concrete and baryte concrete. Foam or air as a fire fitting system in concrete structure that exposed to high temperature or accidental fire proved that better than water

  19. Experimental on moisture migration and pore pressure formation of concrete members subjected to high temperature

    Nagao, Kakuhiro; Nakane, Sunao

    1993-01-01

    The experimental studies concerning temperature, moisture migration, and pore pressure of mass concrete mock-up specimens heated up to high temperature at 110degC to 600degC, were performed, so as to correctly estimate the moisture migration behaviour of concrete members subjected to high temperature, which is considered significantly influenced on physical properties of concrete. As a results, it is confirmed that the moisture migration behavior of concrete members can be explained by temperature and pore pressure, and indicate the characteristics both sealed condition (dissipation of moisture is prevented) and unsealed condition (dissipation of moisture occur). (author)

  20. Behaviour of biaxially restrained concretes under high temperature

    Thienel, K.-Ch.; Rostasy, F.S.

    1993-01-01

    Under asymmetric biaxial loading the major restraining stresses of concrete made with expanded shale or quarzite aggregates change between both loading axis. Differences between uniaxial and biaxial restraint vanish, if the restraint is normalized with respect to the ultimate strength at ambient temperature of the same stress ratio K. The type of aggregate and the mix proportions do affect the restraining stresses irrespective of the initial stress ratio K 0 . (author)

  1. Influence of the mix parameters and microstructure on the behaviour of concrete at high temperature

    Kanema, M.; Noumowe, A.; Gallias, J.-L.; Cabrillac, R.

    2005-01-01

    Concrete is used in structures likely to be exposed to high temperature. Data on the behaviour of concrete at high temperature are necessary to design buildings and other civil engineering structures in order to resist under accidental conditions (fire) or particular conditions of service (storage of radioactive waste). The present experimental study was carried out on the behaviour of five concretes containing the same nature and quantity of aggregates and presenting different water/cement ratios. Concrete specimens were submitted to heating-cooling cycles whose maximum temperatures were 150, 300, 450 and 600 degree C. Measurements of compressive and tensile strength, modulus of elasticity and permeability were carried out on cylindrical specimens before and after heating-cooling cycles. The results showed the influence of concrete mix parameters on the residual properties and the dehydration of the cement paste matrix, the evolution of the permeability and thermal stability of concrete when it is subjected to high temperature. (authors)

  2. Prediction of moisture migration and pore pressure build-up in concrete at high temperatures

    Ichikawa, Y.; England, G.L.

    2004-01-01

    Prediction of moisture migration and pore pressure build-up in non-uniformly heated concrete is important for safe operation of concrete containment vessels in nuclear power reactors and for assessing the behaviour of fire-exposed concrete structures. (1) Changes in moisture content distribution in a concrete containment vessel during long-term operation should be investigated, since the durability and radiation shielding ability of concrete are strongly influenced by its moisture content. (2) The pressure build-up in a concrete containment vessel in a postulated accident should be evaluated in order to determine whether a venting system is necessary between liner and concrete to relieve the pore pressure. (3) When concrete is subjected to rapid heating during a fire, the concrete can suffer from spalling due to pressure build-up in the concrete pores. This paper presents a mathematical and computational model for predicting changes in temperature, moisture content and pore pressure in concrete at elevated temperatures. A pair of differential equations for one-dimensional heat and moisture transfer in concrete are derived from the conservation of energy and mass, and take into account the temperature-dependent release of gel water and chemically bound water due to dehydration. These equations are numerically solved by the finite difference method. In the numerical analysis, the pressure, density and dynamic viscosity of water in the concrete pores are calculated explicitly from a set of formulated equations. The numerical analysis results are compared with two different sets of experimental data: (a) long-term (531 days) moisture migration test under a steady-state temperature of 200 deg. C, and (b) short-term (114 min) pressure build-up test under transient heating. These experiments were performed to investigate the moisture migration and pressure build-up in the concrete wall of a reactor containment vessel at high temperatures. The former experiment simulated

  3. The Mechanism of Disintegration of Cement Concrete at High Temperatures

    Jocius Vytautas

    2016-10-01

    Full Text Available Concrete is a composite material composed of a binder, aggregates, water and additives. Mixing of cement with water results in a number of chemical reactions known as cement hydration. Heating of concrete results in dehydration processes of cement minerals and new hydration products, which disintegrate the microstructure of concrete. This article reviews results of research conducted with Portland and alumina cement with conventional and refractory concrete aggregates. In civic buildings such common fillers as gravel, granite, dolomite or expanded clay are usually used. It is important to point out the differences between fillers because they constitute the majority of the concrete volume.

  4. Investigations for determining temperature, pressure and moisture distributions in concrete at high temperatures

    Weber, A.; Kamp, C.L.

    1987-01-01

    The paper gives a report on the test program. The main objective of the tests was the determination of the temperature and moisture fields decisive for the corrosion conditions, which are built up behind the liner in the range of the heated concrete. The determination of transport characteristics of the concrete are another objective. Small concrete specimens are used to determine the following data: Thermal conductivity, heat capacity, diffusion coefficient for liquid water, steam and air, steam sorption therms. The chemical shrinkage of the concrete as a function of moisture and temperature is being evaluated by means of tests and calculations. (orig./HP)

  5. THE EFFECT OF HIGH TEMPERATURES ON CONCRETE INCORPORATING ULTRAFINE SILICA AND POLYPROPYLENE FIBERS

    M. Benkaddour

    2016-05-01

    Full Text Available In recent years, lots of studies have attempted to examine the possible causes for the thermal instability of ordinary concrete and high performance. However, we still do not know the exact terms of phenomena taking place during exposure to high temperature and the technological solutions that exist (polypropylene fibres, thermal reported are not always well controlled.In this work, several concrete formulations have been tested and multi-scale observation of high-temperature behavior of ordinary concrete (compressive strength of 48 MPa and HPC (compressive strength 75 MPa were adopted. On the scale of the material, the identification of trends with temperature data such as porosity and particularly the mechanical properties allow us to better understand the behaviour of concrete at high temperature differential thermal analysis have been also made.

  6. Study of behavior of concrete and cement based composite materials exposed to high temperatures

    Bodnárová, L.; Horák, D.; Válek, J.; Hela, R.; Sitek, L. (Libor)

    2013-01-01

    The paper describes possibilities of observation of behaviour of concrete and cement based composite material exposed to high temperatures. Nowadays, for large-scale tests of behaviour of concrete exposed to high temperatures, testing devices of certified fire testing stations in the Czech Republic and surrounding states are used. These tests are quite expensive. For experimental verification of smaller test specimens, a testing device was built at the Technical University in Brno, wher...

  7. Nonlinear analysis of reinforced concrete structures subjected to high temperature and external load

    Sugawara, Y.; Goto, M.; Saito, K.; Suzuki, N.; Muto, A.; Ueda, M.

    1993-01-01

    A quarter of a century has passed since the finite element method was first applied to nonlinear problems concerning reinforced concrete structures, and the reliability of the analysis at ordinary temperature has been enhanced accordingly. By contrast, few studies have tried to deal with the nonlinear behavior of reinforced concrete structures subjected to high temperature and external loads simultaneously. It is generally known that the mechanical properties of concrete and steel are affected greatly by temperature. Therefore, in order to analyze the nonlinear behavior of reinforced concrete subjected to external loads at high temperature, it is necessary to construct constitutive models of the materials reflecting the influence of temperature. In this study, constitutive models of concrete and reinforcement that can express decreases in strength and stiffness at high temperature have been developed. A two-dimensional nonlinear finite element analysis program has been developed by use of these material models. The behavior of reinforced concrete beams subjected simultaneously to high temperature and shear forces were simulated using the developed analytical method. The results of the simulation agreed well with the experimental results, evidencing the validity of the developed material models and the finite element analysis program

  8. High temperature helium test rig with prestressed concrete pressure vessel

    Schmidl, H.

    1975-10-01

    The report gives a short description of the joint project prestressed concrete vessel-helium test station as there is the building up of the concrete structure, the system of instrumentation, the data processing, the development of the helium components as well as the testing programs. (author)

  9. Properties of Reinforced Concrete Steel Rebars Exposed to High Temperatures

    İlker Bekir Topçu

    2008-01-01

    Full Text Available The deterioration of the mechanical properties of yield strength and modulus of elasticity is considered as the primary element affecting the performance of steel structures under fire. In this study, hot-rolled S220 and S420 reinforcement steel rebars were subjected to high temperatures to investigate the fire performance of these materials. It is aimed to determine the remaining mechanical properties of steel rebars after elevated temperatures. Steels were subjected to 20, 100, 200, 300, 500, 800, and 950∘C temperatures for 3 hours and tensile tests were carried out. Effect of temperature on mechanical behavior of S220 and S420 were determined. All mechanical properties were reduced due to the temperature increase of the steel rebars. It is seen that mechanical properties of S420 steel was influenced more than S220 steel at elevated temperatures.

  10. A contribution to the question of creep and relaxation of concrete under high temperatures

    Schneider, U.

    1979-01-01

    It was initially shown that, in dealing with the high temperature problem, it is expedient to distinguish certain material properties in terms of isothermal and non-isothermal conditions. A general equation of state could be derived to describe the key question complex relating to deformation behaviour of concrete under high temperatures. For the case of an isothermal temperature load under 100 0 C numerous measurement results are available from the literature. The creep behaviour of light and normal concrete up to 450 0 C was investigated and discussed. Pre-storage, concrete utilization, inelastic deformation and the influence of conditions of stress in the heat-up phase on high-temperature creep were treated. It could be shown on the basis of numerous evaluations and computer studies that also under high temperature conditions the creep behaviour of concrete is best described in terms of exponential functions. Preliminary experimental results on creep behaviour under transient temperature conditions have already been published within the framework of the sub-project ''fire properties of components''. These results, together with new measurement values have been subjected to theoretical analysis. The creep functions (phi-functions) for light and normal concrete developed for the transient temperature state constitute an important part of this work. Various suggestions have been made for criteria of failure for concrete at high tempratures. For the transient state a critical concrete temperature can be specified. Investigations on rates of deformation at the time of failure have shown that a so-called high level and low level is possible. The question of high temperature relaxation of conrete was studied both experimentally and theoretically. The constraining force problem was considered in detail in this research for comparison purposes since it offers a number of possibilities for new approaches and solutions particularly from a theoretical viewpoint. (orig

  11. High plastic concrete temperature specifications for paving mixtures.

    2011-08-01

    This report documents a study performed for the Illinois Department of Transportation (IDOT) regarding : concrete roadway construction in hot weather. The main objective in this project is to develop improved : specifications and procedures with resp...

  12. Effect of the type of mineral aggregate on the high-temperature creep of HTR-concrete

    Diederichs, U.; Becker, G.

    1989-01-01

    Within the scope of the research and development work for the prestressed concrete vessel of the HTR 500 High-Temperature Reactor mix design, manufacture as well as mechanical and thermal behavior of the concrete have been comprehensively studied. Of the concrete types analyzed, a basalt concrete showed extremely favorable high-temperature characteristics while a concrete with Rhine gravel was characterized by a good workability. These two types of concrete were subjected to numerous tests, whereby the testing procedures were strongly related to the anticipated combined stress, temperature and moisture conditions in the real structure

  13. Properties of Reinforced Concrete Steel Rebars Exposed to High Temperatures

    Topçu, İlker Bekir; Karakurt, Cenk

    2008-01-01

    The deterioration of the mechanical properties of yield strength and modulus of elasticity is considered as the primary element affecting the performance of steel structures under fire. In this study, hot-rolled S220 and S420 reinforcement steel rebars were subjected to high temperatures to investigate the fire performance of these materials. It is aimed to determine the remaining mechanical properties of steel rebars after elevated temperatures. Steels were subjected to 20, 100, 200, 300, 5...

  14. Artificial neural networks in prediction of mechanical behavior of concrete at high temperature

    Mukherjee, A.; Nag Biswas, S.

    1997-01-01

    The behavior of concrete structures that are exposed to extreme thermo-mechanical loading is an issue of great importance in nuclear engineering. The mechanical behavior of concrete at high temperature is non-linear. The properties that regulate its response are highly temperature dependent and extremely complex. In addition, the constituent materials, e.g. aggregates, influence the response significantly. Attempts have been made to trace the stress-strain curve through mathematical models and rheological models. However, it has been difficult to include all the contributing factors in the mathematical model. This paper examines a new programming paradigm, artificial neural networks, for the problem. Implementing a feedforward network and backpropagation algorithm the stress-strain relationship of the material is captured. The neural networks for the prediction of uniaxial behavior of concrete at high temperature has been presented here. The results of the present investigation are very encouraging. (orig.)

  15. Creep Behavior of High-Strength Concrete Subjected to Elevated Temperatures.

    Yoon, Minho; Kim, Gyuyong; Kim, Youngsun; Lee, Taegyu; Choe, Gyeongcheol; Hwang, Euichul; Nam, Jeongsoo

    2017-07-11

    Strain is generated in concrete subjected to elevated temperatures owing to the influence of factors such as thermal expansion and design load. Such strains resulting from elevated temperatures and load can significantly influence the stability of a structure during and after a fire. In addition, the lower the water-to-binder (W-B) ratio and the smaller the quantity of aggregates in high-strength concrete, the more likely it is for unstable strain to occur. Hence, in this study, the compressive strength, elastic modulus, and creep behavior were evaluated at target temperatures of 100, 200, 300, 500, and 800 °C for high-strength concretes with W-B ratios of 30%, 26%, and 23%. The loading conditions were set as non-loading and 0.33f cu . It was found that as the compressive strength of the concrete increased, the mechanical characteristics deteriorated and transient creep increased. Furthermore, when the point at which creep strain occurred at elevated temperatures after the occurrence of transient creep was considered, greater shrinkage strain occurred as the compressive strength of the concrete increased. At a heating temperature of 800 °C, the 80 and 100 MPa test specimens showed creep failure within a shrinkage strain range similar to the strain at the maximum load.

  16. Creep Behavior of High-Strength Concrete Subjected to Elevated Temperatures

    Minho Yoon

    2017-07-01

    Full Text Available Strain is generated in concrete subjected to elevated temperatures owing to the influence of factors such as thermal expansion and design load. Such strains resulting from elevated temperatures and load can significantly influence the stability of a structure during and after a fire. In addition, the lower the water-to-binder (W–B ratio and the smaller the quantity of aggregates in high-strength concrete, the more likely it is for unstable strain to occur. Hence, in this study, the compressive strength, elastic modulus, and creep behavior were evaluated at target temperatures of 100, 200, 300, 500, and 800 °C for high-strength concretes with W–B ratios of 30%, 26%, and 23%. The loading conditions were set as non-loading and 0.33fcu. It was found that as the compressive strength of the concrete increased, the mechanical characteristics deteriorated and transient creep increased. Furthermore, when the point at which creep strain occurred at elevated temperatures after the occurrence of transient creep was considered, greater shrinkage strain occurred as the compressive strength of the concrete increased. At a heating temperature of 800 °C, the 80 and 100 MPa test specimens showed creep failure within a shrinkage strain range similar to the strain at the maximum load.

  17. High-Temperature Performance and Multiscale Damage Mechanisms of Hollow Cellulose Fiber-Reinforced Concrete

    Liping Guo

    2016-01-01

    Full Text Available Spalling resistance properties and their damage mechanisms under high temperatures are studied in hollow cellulose fiber-reinforced concrete (CFRC used in tunnel structures. Measurements of mass loss, relative dynamic elastic modulus, compressive strength, and splitting tensile strength of CFRC held under high temperatures (300, 600, 800, and 1050°C for periods of 2.5, 4, and 5.5 h were carried out. The damage mechanism was analyzed using scanning electron microscopy, mercury intrusion porosimetry, thermal analysis, and X-ray diffraction phase analysis. The results demonstrate that cellulose fiber can reduce the performance loss of concrete at high temperatures; the effect of holding time on the performance is more noticeable below 600°C. After exposure to high temperatures, the performance of ordinary concrete deteriorates faster and spalls at 700–800°C; in contrast, cellulose fiber melts at a higher temperature, leaving a series of channels in the matrix that facilitate the release of the steam pressure inside the CFRC. Hollow cellulose fibers can thereby slow the damage caused by internal stress and improve the spalling resistance of concrete under high temperatures.

  18. Physical properties of concrete under 3-years exposure to high temperatures up to 110degC

    Nishiuchi, T.; Kanazu, T.; Ishida, H.

    1990-01-01

    Concrete structural members in a storehouse of high level radioactive wastes are designed assuming that they may be subjected to elevated temperature for a long term. So, in this study, concrete properties under temperature conditions (between 65degC-temperature limitation specified in design and 110degC-vaporing temperature of gel water in concrete) and possibility of raising this temperature limitation has been investigated from the view point of long term concrete properties. In this experiment, many properties of concrete were examined, such as compressive strength, tensile strength. Young's modulus, weight loss, pore size distribution under combined conditions (temperature conditions, mix proportions of concrete, moisture conditions). Followings are the main conclusions obtained within the limit of the experiment. 1. Compressive strength of concrete becomes smaller according as temperature becomes high, but there is little difference between the compressive strength at 65degC and 85degC. 2. Young's modulus of concrete decreases linearly according as temperature becomes higher. 3. Weight loss of concrete increases according as temperature becomes higher. 4. Judging from the decreasing rate of physical properties of concrete, it seems possible to raise temperature limitation from 65degC to 85degC. (author)

  19. Creep Behavior of High-Strength Concrete Subjected to Elevated Temperatures

    Minho Yoon; Gyuyong Kim; Youngsun Kim; Taegyu Lee; Gyeongcheol Choe; Euichul Hwang; Jeongsoo Nam

    2017-01-01

    Strain is generated in concrete subjected to elevated temperatures owing to the influence of factors such as thermal expansion and design load. Such strains resulting from elevated temperatures and load can significantly influence the stability of a structure during and after a fire. In addition, the lower the water-to-binder (W?B) ratio and the smaller the quantity of aggregates in high-strength concrete, the more likely it is for unstable strain to occur. Hence, in this study, the compressi...

  20. Influence of Basalt FRP Mesh Reinforcement on High-Performance Concrete Thin Plates at High Temperatures

    Hulin, Thomas; Lauridsen, Dan H.; Hodicky, Kamil

    2015-01-01

    A basalt fiber–reinforced polymer (BFRP) mesh was introduced as reinforcement in high-performance concrete (HPC) thin plates (20–30 mm) for implementation in precast sandwich panels. An experimental program studied the BFRP mesh influence on HPC exposed to high temperature. A set of standard...... furnace tests compared performances of HPC with and without BFRP mesh, assessing material behavior; another set including polypropylene (PP) fibers to avoid spalling compared the performance of BFRP mesh reinforcement to that of regular steel reinforcement, assessing mechanical properties......, requiring the use of steel. Microscope observations highlighted degradation of the HPC-BFRP mesh interface with temperature due to the melting polymer matrix of the mesh. These observations call for caution when using fiber-reinforced polymer (FRP) reinforcement in elements exposed to fire hazard....

  1. Behaviour of a pre-stressed concrete pressure-vessel subjected to a high temperature gradient

    Dubois, F.

    1965-01-01

    After a review of the problems presented by pressure-vessels for atomic reactors (shape of the vessel, pressures, openings, foundations, etc.) the advantages of pre-stressed concrete vessels with respect to steel ones are given. The use of pre-stressed concrete vessels however presents many difficulties connected with the properties of concrete. Thus, because of the absence of an exact knowledge of the material, it is necessary to place a sealed layer of steel against the concrete, to have a thermal insulator or a cooling circuit for limiting the deformations and stresses, etc. It follows that the study of the behaviour of pre-stressed concrete and of the vessel subjected- to a high temperature gradient can yield useful information. A one-tenth scale model of a pre-stressed concrete cylindrical vessel without any side openings and without a base has been built. Before giving a description of the tests the authors consider some theoretical aspects concerning 'scale model-actual structure' similitude conditions and the calculation of the thermal and mechanical effects. The pre-stressed concrete model was heated internally by a 'pyrotenax' element and cooled externally by a very strong air current. The concrete was pre-stressed using horizontal and vertical cables held at 80 kg/cm 2 ; the thermal gradient was 160 deg. C. During the various tests, measurements were made of the overall and local deformations, the changes in water content, the elasticity modulus, the stress and creep of the cables and the depths of the cracks. The overall deformations observed are in line with thermal deformation theories and the creep of the cables attained 20 to 30 per cent according to their position relative to the internal surface. The dynamic elasticity modulus decreased by half but the concrete keeps its good mechanical properties. Finally, cracks 8 to 12 cm deep and 2 to 3 mms wide appeared in that part of the concrete which was not pre-stressed. The results obtained make it

  2. The influence of the scale effect and high temperatures on the strength and strains of high performance concrete

    Korsun Vladimyr Ivanovych

    2014-03-01

    Full Text Available The most effective way to reduce the structure mass, labor input and expenses for its construction is to use modern high-performance concrete of the classes С50/60… С90/105, which possess high physical and mathematic characteristics. One of the constraints for their implementation in mass construction in Ukraine is that in design standards there are no experimental data on the physical and mathematic properties of concrete of the classes more than С50/60. Also there are no exact statements on calculating reinforced concrete structures made of high-performance concretes.The authors present the results of experimental research of the scale effect and short-term and long-term heating up to +200 ° C influence on temperature and shrinkage strain, on strength and strain characteristics under compression and tensioning of high-strength modified concrete of class C70/85. The application of high performance concretes is challenging in the process of constructing buildings aimed at operating in high technological temperatures: smoke pipes, coolers, basins, nuclear power plants' protective shells, etc. Reducing cross-sections can lead to reducing temperature drops and thermal stresses in the structures.

  3. Influence of High Temperatures on the Workability of Fresh Ready-Mixed Concrete

    Victor Sampebulu'

    2012-04-01

    Full Text Available Properties of fresh concrete made in tropical countries, which is mixed, transported (with agitation, placed and initially cured in places where the temperature ranges from about 20oC to 40oC and relative humidity above 60%, are not completely understood. Applicable requirements also differ from country to country and government agencies and private enterprises have their own specifications. Assuming such temperature and relative humidity conditions, the present study is an attempt at evaluating the properties of hot weather concrete in fresh state with using a method of ready–mixed concrete. The fresh concrete was mixed and agitated at varying concrete and ambient temperatures. Three groups of the component materials, each material having such temperature as to bring resulting temperature of the fresh concrete to about 20oC, 30oC, 35oC, were chosen. The temperature of cement was conditioned to about20o, 40oC and 60oC for each of groups respectively. The aggregate was made warm enough to simulate the condition of outdoor pile in ready-mixed concrete plant. The temperature of tap water was always 20oC as it was easily controlled and unlikely affected by outdoor temperature. With the fresh concrete prevented from evaporation, slump loss is caused solely by increased temperature of concrete. During agitation, the slump loss increases rapidly during the first 30 minutes but moderately during the remaining period. Concrete-placing temperature (upon arrival at the work site could be estimated by a proposed formula derived from this study. Besides the freshly mixed concrete temperature, this formula also takes into consideration the ambient temperature, agitating time in transit and hydration heat. The achievement as described in this study may be useful to control concrete quality in terms of strength, shrinkage and other properties of concrete to be placed in hot-humid environment.

  4. Experimental Analysis of Concrete Strength at High Temperatures and after Cooling

    E. Klingsch

    2009-01-01

    Full Text Available In recent years, the cement industry has been criticized for emitting large amounts of carbon dioxide; hence it is developing environment-friendly cement, e.g., blended, supersulfated slag cement (SSC. This paper presents an experimental analysis of the compressive strength development of concrete made from blended cement in comparison to ordinary cement at high temperature. Three different types of cement were used during these tests, an ordinary portland cement (CEM I, a portland limestone cement (CEM II-A-LL and a new, supersulfated slag cement (SSC. The compressive strength development for a full thermal cycle, including cooling down phase, was investigated on concrete cylinders. It is shown that the SSC concrete specimens perform similar to ordinary cement specimens. 

  5. Influence of gas generation on high-temperature melt/concrete interactions

    Powers, D.A.

    1979-01-01

    Accidents involving fuel melting and eventual contact between the high temperature melt and structural concrete may be hypothesized for both light water thermal reactors and liquid metal cooled breeder reactors. Though these hypothesized accidents have a quite low probability of occurring, it is necessary to investigate the probable natures of the accidents if an adequate assessment of the risks associated with the use of nuclear reactors is to be made. A brief description is given of a program addressing the nature of melt/concrete interactions which has been underway for three years at Sandia Laboratories. Emphasis in this program has been toward the behavior of prototypic melts of molten core materials with concrete representative of that found in existing or proposed reactors. The goals of the experimentation have been to identify phenomena particularly pertinent to questions of reactor safety, and phenomena particularly pertinent to questions of reactor safety, and provide quantitative data suitable for the purposes of risk assessment

  6. Effect of Curing Temperature Histories on the Compressive Strength Development of High-Strength Concrete

    Keun-Hyeok Yang

    2015-01-01

    Full Text Available This study examined the relative strength-maturity relationship of high-strength concrete (HSC specifically developed for nuclear facility structures while considering the economic efficiency and durability of the concrete. Two types of mixture proportions with water-to-binder ratios of 0.4 and 0.28 were tested under different temperature histories including (1 isothermal curing conditions of 5°C, 20°C, and 40°C and (2 terraced temperature histories of 20°C for an initial age of individual 1, 3, or 7 days and a constant temperature of 5°C for the subsequent ages. On the basis of the test results, the traditional maturity function of an equivalent age was modified to consider the offset maturity and the insignificance of subsequent curing temperature after an age of 3 days on later strength of concrete. To determine the key parameters in the maturity function, the setting behavior, apparent activation energy, and rate constant of the prepared mixtures were also measured. This study reveals that the compressive strength development of HSC cured at the reference temperature for an early age of 3 days is insignificantly affected by the subsequent curing temperature histories. The proposed maturity approach with the modified equivalent age accurately predicts the strength development of HSC.

  7. Compressive behaviour of hybrid fiber-reinforced reactive powder concrete after high temperature

    Zheng, Wenzhong; Li, Haiyan; Wang, Ying

    2012-01-01

    Highlights: ► We complete the high temperature test and compression test of RPC after 20–900 °C. ► The presence of steel fiber and polypropylene fiber can prevent RPC from spalling. ► Compressive strength increases first and then decreases with elevated temperatures. ► Microstructure deterioration is the root cause of macro-properties recession. ► Equations to express the compressive strength change with temperature are proposed. -- Abstract: This study focuses on the compressive properties and microstructures of reactive powder concrete (RPC) mixed with steel fiber and polypropylene fiber after exposure to 20–900 °C. The volume dosage of steel fiber and polypropylene fiber is (2%, 0.1%), (2%, 0.2%) and (1%, 0.2%). The effects of heating temperature, fiber content and specimen size on the compressive properties are analyzed. The microstructures of RPC exposed to different high temperatures are studied by scanning electron microscope (SEM). The results indicate that the compressive strength of hybrid fiber-reinforced RPC increases at first, then decreases with the increasing temperature, and the basic reason for the degradation of macro-mechanical properties is the deterioration of RPC microstructure. Based on the experimental results, equations to express the relationships of the compressive strength with the heating temperatures are established. Compared with normal-strength and high-strength concrete, the hybrid fiber-reinforced RPC has excellent capacity in resistance to high temperature.

  8. Development and Performance Evaluation of High Temperature Concrete for Thermal Energy Storage for Solar Power Generation

    Selvam, R. Panneer; Hale, Micah; Strasser, Matt

    2013-03-31

    Thermal energy can be stored by the mechanism of sensible or latent heat or heat from chemical reactions. Sensible heat is the means of storing energy by increasing the temperature of the solid or liquid. Since the concrete as media cost per kWhthermal is $1, this seems to be a very economical material to be used as a TES. This research is focused on extending the concrete TES system for higher temperatures (500 °C to 600 °C) and increasing the heat transfer performance using novel construction techniques. To store heat at high temperature special concretes are developed and tested for its performance. The storage capacity costs of the developed concrete is in the range of $0.91-$3.02/kWhthermal. Two different storage methods are investigated. In the first one heat is transported using molten slat through a stainless steel tube and heat is transported into concrete block through diffusion. The cost of the system is higher than the targeted DOE goal of $15/kWhthermal. The increase in cost of the system is due to stainless steel tube to transfer the heat from molten salt to the concrete blocks.The other method is a one-tank thermocline system in which both the hot and cold fluid occupy the same tank resulting in reduced storage tank volume. In this model, heated molten salt enters the top of the tank which contains a packed bed of quartzite rock and silica sand as the thermal energy storage (TES) medium. The single-tank storage system uses about half the salt that is required by the two-tank system for a required storage capacity. This amounts to a significant reduction in the cost of the storage system. The single tank alternative has also been proven to be cheaper than the option which uses large concrete modules with embedded heat exchangers. Using computer models optimum dimensions are determined to have an round trip efficiency of 84%. Additionally, the cost of the structured concrete thermocline configuration provides the TES

  9. Effects of Medium Temperature and Industrial By-Products on the Key Hardened Properties of High Performance Concrete.

    Safiuddin, Md; Raman, Sudharshan N; Zain, Muhammad Fauzi Mohd

    2015-12-10

    The aim of the work reported in this article was to investigate the effects of medium temperature and industrial by-products on the key hardened properties of high performance concrete. Four concrete mixes were prepared based on a water-to-binder ratio of 0.35. Two industrial by-products, silica fume and Class F fly ash, were used separately and together with normal portland cement to produce three concrete mixes in addition to the control mix. The properties of both fresh and hardened concretes were examined in the laboratory. The freshly mixed concrete mixes were tested for slump, slump flow, and V-funnel flow. The hardened concretes were tested for compressive strength and dynamic modulus of elasticity after exposing to 20, 35 and 50 °C. In addition, the initial surface absorption and the rate of moisture movement into the concretes were determined at 20 °C. The performance of the concretes in the fresh state was excellent due to their superior deformability and good segregation resistance. In their hardened state, the highest levels of compressive strength and dynamic modulus of elasticity were produced by silica fume concrete. In addition, silica fume concrete showed the lowest level of initial surface absorption and the lowest rate of moisture movement into the interior of concrete. In comparison, the compressive strength, dynamic modulus of elasticity, initial surface absorption, and moisture movement rate of silica fume-fly ash concrete were close to those of silica fume concrete. Moreover, all concretes provided relatively low compressive strength and dynamic modulus of elasticity when they were exposed to 50 °C. However, the effect of increased temperature was less detrimental for silica fume and silica fume-fly ash concretes in comparison with the control concrete.

  10. Effects of Medium Temperature and Industrial By-Products on the Key Hardened Properties of High Performance Concrete

    Md. Safiuddin

    2015-12-01

    Full Text Available The aim of the work reported in this article was to investigate the effects of medium temperature and industrial by-products on the key hardened properties of high performance concrete. Four concrete mixes were prepared based on a water-to-binder ratio of 0.35. Two industrial by-products, silica fume and Class F fly ash, were used separately and together with normal portland cement to produce three concrete mixes in addition to the control mix. The properties of both fresh and hardened concretes were examined in the laboratory. The freshly mixed concrete mixes were tested for slump, slump flow, and V-funnel flow. The hardened concretes were tested for compressive strength and dynamic modulus of elasticity after exposing to 20, 35 and 50 °C. In addition, the initial surface absorption and the rate of moisture movement into the concretes were determined at 20 °C. The performance of the concretes in the fresh state was excellent due to their superior deformability and good segregation resistance. In their hardened state, the highest levels of compressive strength and dynamic modulus of elasticity were produced by silica fume concrete. In addition, silica fume concrete showed the lowest level of initial surface absorption and the lowest rate of moisture movement into the interior of concrete. In comparison, the compressive strength, dynamic modulus of elasticity, initial surface absorption, and moisture movement rate of silica fume-fly ash concrete were close to those of silica fume concrete. Moreover, all concretes provided relatively low compressive strength and dynamic modulus of elasticity when they were exposed to 50 °C. However, the effect of increased temperature was less detrimental for silica fume and silica fume-fly ash concretes in comparison with the control concrete.

  11. Effects of Medium Temperature and Industrial By-Products on the Key Hardened Properties of High Performance Concrete

    Safiuddin, Md.; Raman, Sudharshan N.; Zain, Muhammad Fauzi Mohd.

    2015-01-01

    The aim of the work reported in this article was to investigate the effects of medium temperature and industrial by-products on the key hardened properties of high performance concrete. Four concrete mixes were prepared based on a water-to-binder ratio of 0.35. Two industrial by-products, silica fume and Class F fly ash, were used separately and together with normal portland cement to produce three concrete mixes in addition to the control mix. The properties of both fresh and hardened concretes were examined in the laboratory. The freshly mixed concrete mixes were tested for slump, slump flow, and V-funnel flow. The hardened concretes were tested for compressive strength and dynamic modulus of elasticity after exposing to 20, 35 and 50 °C. In addition, the initial surface absorption and the rate of moisture movement into the concretes were determined at 20 °C. The performance of the concretes in the fresh state was excellent due to their superior deformability and good segregation resistance. In their hardened state, the highest levels of compressive strength and dynamic modulus of elasticity were produced by silica fume concrete. In addition, silica fume concrete showed the lowest level of initial surface absorption and the lowest rate of moisture movement into the interior of concrete. In comparison, the compressive strength, dynamic modulus of elasticity, initial surface absorption, and moisture movement rate of silica fume-fly ash concrete were close to those of silica fume concrete. Moreover, all concretes provided relatively low compressive strength and dynamic modulus of elasticity when they were exposed to 50 °C. However, the effect of increased temperature was less detrimental for silica fume and silica fume-fly ash concretes in comparison with the control concrete. PMID:28793732

  12. Global weak solutions for coupled transport processes in concrete walls at high temperatures

    Beneš, Michal; Štefan, Radek

    2012-01-01

    We consider an initial-boundary value problem for a fully nonlinear coupled parabolic system with nonlinear boundary conditions modelling hygro-thermal behavior of concrete at high temperatures. We prove a global existence of a weak solution to this system on an arbitrary time interval. The main result is proved by an approximation procedure. This consists in proving the existence of solutions to mollified problems using the Leray-Schauder theorem, for which a priori estimates are obtained. T...

  13. High Performance Concrete

    Traian Oneţ

    2009-01-01

    Full Text Available The paper presents the last studies and researches accomplished in Cluj-Napoca related to high performance concrete, high strength concrete and self compacting concrete. The purpose of this paper is to raid upon the advantages and inconveniences when a particular concrete type is used. Two concrete recipes are presented, namely for the concrete used in rigid pavement for roads and another one for self-compacting concrete.

  14. Influence of Temperature on Workability and Compressive Strength of Ordinary Concrete with High Calcium Fly Ash

    Gołaszewski Jacek

    2017-06-01

    Full Text Available The rheological properties of fresh ordinary concrete are closely affected by temperature and time. The paper presents the study of consistency of fresh concrete mixtures made with Portland cement and cement with calcareous fly ash. Two types of admixtures were used. It was proven that the temperature has a clear effect on workability and compressive strength concrete. Influence on workability can be reduced by selecting the appropriate superplasticizer and cement.

  15. The role of water in the behaviour of concretes at high temperature

    Feraille-Fresnet, A.

    2000-01-01

    Since 1996, three fires have been counted in tunnels in Europe. During each of these accidents. the temperature reached by the structure has been estimated between 800 deg C and 1200 deg C. Beside these spectacular accidental situations, there are many other situations in which concrete structures are submitted to high temperatures during their regular use. Several research work has been undertaken for a better understanding of the behaviour of concrete submitted to high temperatures and the physical phenomena involved. This PhD Thesis takes down as part of this research work and develops, more particularly, the role of water in the material submitted to heating up to high temperatures. At first, we are interested in the role of water inside a material crack, during heating. We have established an original analytical solution giving the liquid-vapour repartition and the stress intensity factor, as functions of crack's length, water molecules contained in the inner of the crack and temperature. Then, we are able to study the crack stability. In the second part, we propose to approach the studied phenomena using the non saturated porous media theory. We present a thermo-hydro-chemical model which permits to describe the concrete behaviour under thermal loading. The material microstructure is defined using a 'porosimetric surface'. Each pore is characterised by two radii: the pore radius and the access radius into the pore. With this description, the zone of pores saturated by liquid is a state variable. We also introduce the concept of kinetic dehydration, clearly lighted by experimental studies. An hypothesis of erosion of the solid phase by dehydration permits to link the evolution of microstructure and of the zone of pores saturated by liquid to the mass of water created by dehydration. (author)

  16. The Effect of High Temperatures on the Effective Thermal Conductivity of Concrete

    Weidenfeld, G.; Aharon, G.; Hochbaum, I.

    2002-01-01

    Concrete thermal conductivity is an important property for thermal analysis of nuclear accidents.Concrete compositions include water,sand,cement and aggregates of various kinds and combinations.Values of concrete's thermal conductivity for some different compositions can be found in the literature[1]but since the material composition and its temperature significantly affect this property,the exact value of a specific composition should be measured

  17. Combined effect of high curing temperature and crack width on chloride migration in reinforced concrete beams

    Elkedrouci, L.; Diao, B.; Pang, S.; Li, Y.

    2018-03-01

    Deterioration of reinforced concrete structures is a serious concern in the construction engineering, largely due to chloride induced corrosion of reinforcement. Chloride penetration is markedly influenced by one or several major factors at the same time such as cuing in combination with different crack widths which have spectacular effect on reinforced concrete structures. This research presents the results of an experimental investigation involving reinforced concrete beams with three different crack widths ranging from 0 to 0.2mm, curing temperatures of 20°C or 40°C and water-to-cement of 0.5. Chloride content profiles were determined under non-steady state diffusion at 20°C. Based on the obtained results, higher chloride content was obtained under condition of high curing temperature in combination with large crack more than 0.1mm and there are no significant differences between narrow crack width (less than 0.1 mm) and beams without crack (0 mm).

  18. Effect of Curing Temperature on the Durability of Concrete under Highly Geothermal Environment

    Yang Tang

    2017-01-01

    Full Text Available To determine the durability of concrete in the actual temperature and humidity of the tunnel environment, this study investigates the mechanical properties, permeability of chloride ion, relative dynamic elastic modulus, and mass loss ratio of concrete specimens cured in the temperature which varied from normal, 40, 60, 75, and 90°C, and the humidity was kept at 90% continuously. Experimental results reveal that the hot temperature curing environment may benefit early stage strength development but reduce the long-term strength. It is proved that 60°C is a critical point. At above 60°C, the strength of the concrete material and its resistance to chloride ion permeability showed a decreasing trend; however, in the appropriate temperature range, the frost resistance properties of the concrete are improved with increasing temperature.

  19. Effect of high temperatures on cement composite materials in concrete structures

    Bodnárová, L.; Válek, J.; Sitek, Libor; Foldyna, Josef

    2013-01-01

    Roč. 10, č. 2 (2013), s. 173-180 ISSN 1214-9705 R&D Projects: GA MŠk ED2.1.00/03.0082; GA ČR GAP104/12/1988 Institutional support: RVO:68145535 Keywords : high temperature * load resistance * concrete * reinforcing of mine works * fiber reinforcement Subject RIV: JJ - Other Materials Impact factor: 0.667, year: 2013 http://www.irsm.cas.cz/materialy/acta_content/2013_02/acta_170_06_Bodnirovi_173-180.pdf

  20. A prestressed concrete pressure vessel for helium high temperature reactor system

    Horner, R.M.W.; Hodzic, A.

    1976-01-01

    A novel prestressed concrete pressure vessel has been developed to provide the primary containment for a fully integrated system comprising a high temperature nuclear reactor, three horizontally mounted helium turbines, associated heat exchangers and inter-connecting ducts. The design and analysis of the pressure vessel is described. Factors affecting the final choice of layout are discussed, and earlier development work seeking to resolve the conflicting requirements of the structural, mechanical, and system engineers outlined. Proposals to increase the present output of about 1000 MW of electrical power to over 3000 MW, by incorporating four turbines in a single pressure vessel are presented. (author)

  1. Influence of Eco-Friendly Mineral Additives on Early Age Compressive Strength and Temperature Development of High-Performance Concrete

    Kaszynska, Maria; Skibicki, Szymon

    2017-12-01

    High-performance concrete (HPC) which contains increased amount of both higher grade cement and pozzolanic additives generates more hydration heat than the ordinary concrete. Prolonged periods of elevated temperature influence the rate of hydration process in result affecting the development of early-age strength and subsequent mechanical properties. The purpose of the presented research is to determine the relationship between the kinetics of the heat generation process and the compressive strength of early-age high performance concrete. All mixes were based on the Portland Cement CEM I 52.5 with between 7.5% to 15% of the cement mass replaced by the silica fume or metakaolin. Two characteristic for HPC water/binder ratios of w/b = 0.2 and w/b = 0.3 were chosen. A superplasticizer was used to maintain a 20-50 mm slump. Compressive strength was determined at 8h, 24h, 3, 7 and 28 days on 10x10x10 cm specimens that were cured in a calorimeter in a constant temperature of T = 20°C. The temperature inside the concrete was monitored continuously for 7 days. The study determined that the early-age strength (t<24h) of concrete with reactive mineral additives is lower than concrete without them. This is clearly visible for concretes with metakaolin which had the lowest compressive strength in early stages of hardening. The amount of the superplasticizer significantly influenced the early-age compressive strength of concrete. Concretes with additives reached the maximum temperature later than the concretes without them.

  2. Development of heat resistant concrete and its application to concrete casks. Improvement of neutron shielding performance of concrete in high temperature environment

    Owaki, Eiji; Hata, Akihito; Sugihara, Yutaka; Shimojo, Jun; Taniuchi, Hiroaki; Mantani, Kenichi

    2003-01-01

    Heat resistant concrete with hydrogen, which is able to shield neutron at more than 100degC, was developed. Using this new type concrete, a safety concrete cask having the same concept of metal casks was designed and produced. The new type cask omitted the inhalation and exhaust vent of the conventional type concrete casks. The new concrete consists of Portland cement added calcium hydroxide, iron powder and iron fiber. It showed 2.17 g/cm 3 density, 10.8 mass% water content, 1.4 W/(m·K) thermal conductivity at 150degC. Increasing of heat resistance made possible to produce the perfect sealing type structure, which had high shielding performance of radiation no consideration for streaming of radiation. Moreover, a monitor of sealing can be set. General view of concrete casks, outer view of 1/3 scaled model, cask storage system in the world, properties of new developed heat resistant concrete, results of shielding calculation are contained. (S.Y.)

  3. High-temperature compatibility between liquid metal as PWR fuel gap filler and stainless steel and high-density concrete

    Wongsawaeng, Doonyapong; Jumpee, Chayanit; Jitpukdee, Manit

    2014-08-01

    In conventional nuclear fuel rods for light-water reactors, a helium-filled as-fabricated gap between the fuel and the cladding inner surface accommodates fuel swelling and cladding creep down. Because helium exhibits a very low thermal conductivity, it results in a large temperature rise in the gap. Liquid metal (LM; 1/3 weight portion each of lead, tin, and bismuth) has been proposed to be a gap filler because of its high thermal conductivity (∼100 times that of He), low melting point (∼100 °C), and lack of chemical reactivity with UO2 and water. With the presence of LM, the temperature drop across the gap is virtually eliminated and the fuel is operated at a lower temperature at the same power output, resulting in safer fuel, delayed fission gas release and prevention of massive secondary hydriding. During normal reactor operation, should an LM-bonded fuel rod failure occurs resulting in a discharge of liquid metal into the bottom of the reactor pressure vessel, it should not corrode stainless steel. An experiment was conducted to confirm that at 315 °C, LM in contact with 304 stainless steel in the PWR water chemistry environment for up to 30 days resulted in no observable corrosion. Moreover, during a hypothetical core-melt accident assuming that the liquid metal with elevated temperature between 1000 and 1600 °C is spread on a high-density concrete basement of the power plant, a small-scale experiment was performed to demonstrate that the LM-concrete interaction at 1000 °C for as long as 12 h resulted in no penetration. At 1200 °C for 5 h, the LM penetrated a distance of ∼1.3 cm, but the penetration appeared to stop. At 1400 °C the penetration rate was ∼0.7 cm/h. At 1600 °C, the penetration rate was ∼17 cm/h. No corrosion based on chemical reactions with high-density concrete occurred, and, hence, the only physical interaction between high-temperature LM and high-density concrete was from tiny cracks generated from thermal stress. Moreover

  4. Spalling behavior and residual resistance of fibre reinforced Ultra-High performance concrete after exposure to high temperatures

    Xiong, Ming-Xiang

    2015-12-01

    Full Text Available Experimental results of spalling and residual mechanical properties of ultra-high performance concrete after exposure to high temperatures are presented in this paper. The compressive strength of the ultra-high performance concrete ranged from 160 MPa~185 MPa. This study aimed to discover the effective way to prevent spalling for the ultra-high performance concrete and gauge its mechanical properties after it was subjected to fire. The effects of fiber type, fiber dosage, heating rate and curing condition were investigated. Test results showed that the compressive strength and elastic modulus of the ultra-high performance concrete declined slower than those of normal strength concrete after elevated temperatures. Polypropylene fiber rather than steel fiber was found effective to prevent spalling but affected workability. The effective fiber type and dosage were recommended to prevent spalling and ensure sufficient workability for casting and pumping of the ultra-high performance concrete.En este trabajo se presentan los resultados más relevantes del trabajo experimental realizado para valorar la laminación y las propiedades mecánicas residuales de hormigón de ultra-altas prestaciones tras su exposición a altas temperaturas. La resistencia a la compresión del hormigón de ultra-altas prestaciones osciló entre 160 MPa~185 MPa. El objetivo de este estudio fue descubrir una manera eficaz de prevenir desprendimientos y/o laminaciones en este hormigón y medir sus propiedades mecánicas después de ser sometido al fuego. Las variables estudiadas fueron la presencia y dosificación de fibras, velocidad de calentamiento y condiciones de curado. Los resultados mostraron, tras la exposición a altas temperaturas, que la resistencia a compresión y el módulo de elasticidad del hormigón de ultra-altas prestaciones disminuían más lento que las de un hormigón con resistencia normal. La fibra de polipropileno resultó más eficaz para prevenir

  5. Research of the Processes of High Temperature Influence on Cementitous Concrete

    Bodnárová, L.; Válek, J.; Sitek, Libor; Foldyna, Josef

    2013-01-01

    Roč. 19, č. 2 (2013), s. 500-503 ISSN 1936-6612 R&D Projects: GA ČR GAP104/12/1988 Grant - others:GA TA ČR(CZ) TA01010948 Institutional support: RVO:68145535 Keywords : cement itous concrete * high temperature influence * physicalmechanical properties Subject RIV: JN - Civil Engineering http://www.ingentaconnect.com/content/asp/asl/2013/00000019/00000002/art00031?token=0052114d07e2a46762c6b635d3e703f252e2e3e5f7a673f7b2f267738703375686f49a0e280f5d6867

  6. Effect of the hydro-thermal load history on the high-temperature creep of HTR-concrete

    Diederichs, U.; Rostasy, F.S.; Becker, G.

    1991-01-01

    In the research and development works for the prestressed concrete vessel for the HTR-500 high temperature reactor, the comprehensive tests concerning mix design, manufacture as well as mechanical and thermal behavior of the concrete have been carried out. The concrete was put to the numerous tests for determining the strength and the creep behavior at elevated temperature. In the real PCRV, the concrete is heated at different heating rate depending on the location of a certain volume element of the concrete in the structure. Furthermore, the heat transport simultaneously causes the moisture transport. For this reason, the test has been planned to investigate the transient creep at various heating rates and in different states of moisture during heating to the accident temperature up to 300 deg C. The cylindrical specimens were used for the high temperature creep test. The test procedure and the test results are reported. It was shown that the thermal history (heating rate, duration of holding at a certain temperature and so on) determines the transient creep deformation to a great extent. (K.I.)

  7. Influence of water and temperature on long term mechanical behaviour of high performance concrete

    Cagnon, H.; Vidal, T.; Sellier, A.; Camps, G.

    2015-01-01

    The experimental program on thermal expansion of concretes presents a dual purpose. The first one is to quantify the differential thermal dilation of the constituents of nuclear containment area. The second is to bring elements of explanation on the damage detected at 80 C. degrees. Between 20 and 80 C. degrees there is an important differential thermal dilation concerning various phases of the concrete. As a comparison cement paste dilates 7 times more than limestone aggregate, mortar 4 times more and concrete 2 times more. This differential thermal deformation can cause a strong microcracking particularly for saturated sample submitted to 80 C. degrees. The value of the coefficient of thermal expansion of concrete and mortar seems to correspond to the value averaged by the coefficients of every phase (cement paste / aggregates) balanced by their volume fraction. Water seems to have an important impact on thermal expansion on saturated samples for a significant rise of temperature (80 C. degrees). To ensure this result, complementary tests will be done. The other experimental program deals with the deformation evolution versus the chronology of temperature/loading cycles and the improvement of understanding of the thermal transient deformation. The thermal transient deformation would be an increase of the kinetics of deformation under load. It seems to be not totally repeatable because of the consolidation of concrete

  8. Pressure and temperature fields and water released by concrete submitted to high heat fluxes

    Andrade Lima, F.R. de

    1982-01-01

    Inovations are introduced in the original program USINT considering thermal conductivity variations with the temperature. A subroutine - PLOTTI - is incorporate to the program aiming to obtain a graphic for results. The new program - USINTG - is used for calculating the field of pressure and temperature and the water released from the concrete structure during a simulation of sodium leak. The theoretical results obtained with USINTG are in good agreement with the experimental results previously obtained. (E.G.) [pt

  9. Effect of temperature on structural quality of the cement paste and high-strength concrete with silica fume

    Janotka, Ivan; Nuernbergerova, Terezia

    2005-01-01

    Experimental investigation conducted to study the thermo-mechanical properties of concrete at Temelin (Czech Republic), Mochovce (Slovakia), and Penly (France) nuclear power plants reveals structural integrity degradation between 100 and 200 deg C due to both a loss of water bound in hydrated cement minerals and subsequently air void formation. Test results indicate changes in strength, average pore radius and calculated permeability coefficients for Mochovce specimens exposed to temperatures up to 400 deg C. It demonstrates that the permeability coefficient measured on the basis of pore sizes using mercury intrusion porosimetry is suitable technique for the evaluation of concrete quality. It confirms that strength and permeability coefficient are equivalent structural quality variables of concrete. At 400 deg C gel-like hydration products are decomposed, at 600 deg C Ca(OH) 2 is dehydroxylated, and CaCO 3 dissociation to CaO and CO 2 accompanied with the re-crystallisation of non-binding phases from hydrated cement under re-combustion are dominant processes between 600 and 800 deg C. This stage of concrete is characterised by the collapse of its structural integrity, revealing residual compressive strength. This paper reports high-strength concrete behaviour subjected to temperatures up to 200 deg C. In accordance with previous results, research studies of structure-property relation show the changes in strength, dynamic modulus of elasticity, strain-stress behaviour, and shrinkage-induced deformations influenced by a hydrate phase decomposition. Volume reduction of the hydrate phase due to the loss of bound water mass is the cause of air void formation, and pore structure coarsening. The main attention is herein devoted to the evaluation of utility property decrease of high-strength concrete and microstructure degradation of the cement paste with the same composition than that in concrete when attacked by elevated temperatures

  10. Possibilities of observation of behaviour of concrete- and cement-based composite materials exposed to high temperatures

    Bodnárová, L.; Horák, D.; Válek, J.; Hela, R.; Sitek, Libor

    2015-01-01

    Roč. 19, č. 5 (2015), s. 936-940 ISSN 1432-8917 Institutional support: RVO:68145535 Keywords : concrete * high temperature * thermal load Subject RIV: JQ - Machines ; Tools Impact factor: 0.830, year: 2014 http://www.tandfonline.com/doi/full/10.1179/1432891714Z.0000000001225?scroll=top&needAccess=true

  11. Effect of High-Temperature Curing Methods on the Compressive Strength Development of Concrete Containing High Volumes of Ground Granulated Blast-Furnace Slag

    Wonsuk Jung

    2017-01-01

    Full Text Available This paper investigates the effect of the high-temperature curing methods on the compressive strength of concrete containing high volumes of ground granulated blast-furnace slag (GGBS. GGBS was used to replace Portland cement at a replacement ratio of 60% by binder mass. The high-temperature curing parameters used in this study were the delay period, temperature rise, peak temperature (PT, peak period, and temperature down. Test results demonstrate that the compressive strength of the samples with PTs of 65°C and 75°C was about 88% higher than that of the samples with a PT of 55°C after 1 day. According to this investigation, there might be optimum high-temperature curing conditions for preparing a concrete containing high volumes of GGBS, and incorporating GGBS into precast concrete mixes can be a very effective tool in increasing the applicability of this by-product.

  12. Real-time measurements of temperature, pressure and moisture profiles in High-Performance Concrete exposed to high temperatures during neutron radiography imaging

    Toropovs, N., E-mail: nikolajs.toropovs@rtu.lv [Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf (Switzerland); Riga Technical University, Institute of Materials and Structures, Riga (Latvia); Lo Monte, F. [Politecnico di Milano, Department of Civil and Environmental Engineering, Milan (Italy); Wyrzykowski, M. [Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf (Switzerland); Lodz University of Technology, Department of Building Physics and Building Materials, Lodz (Poland); Weber, B. [Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf (Switzerland); Sahmenko, G. [Riga Technical University, Institute of Materials and Structures, Riga (Latvia); Vontobel, P. [Paul Scherrer Institute, Laboratory for Neutron Scattering and Imaging, Villigen (Switzerland); Felicetti, R. [Politecnico di Milano, Department of Civil and Environmental Engineering, Milan (Italy); Lura, P. [Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf (Switzerland); ETH Zürich, Institute for Building Materials (IfB), Zürich (Switzerland)

    2015-02-15

    High-Performance Concrete (HPC) is particularly prone to explosive spalling when exposed to high temperature. Although the exact causes that lead to spalling are still being debated, moisture transport during heating plays an important role in all proposed mechanisms. In this study, slabs made of high-performance, low water-to-binder ratio mortars with addition of superabsorbent polymers (SAP) and polypropylene fibers (PP) were heated from one side on a temperature-controlled plate up to 550 °C. A combination of measurements was performed simultaneously on the same sample: moisture profiles via neutron radiography, temperature profiles with embedded thermocouples and pore pressure evolution with embedded pressure sensors. Spalling occurred in the sample with SAP, where sharp profiles of moisture and temperature were observed. No spalling occurred when PP-fibers were introduced in addition to SAP. The experimental procedure described here is essential for developing and verifying numerical models and studying measures against fire spalling risk in HPC.

  13. Danish High Performance Concretes

    Nielsen, M. P.; Christoffersen, J.; Frederiksen, J.

    1994-01-01

    In this paper the main results obtained in the research program High Performance Concretes in the 90's are presented. This program was financed by the Danish government and was carried out in cooperation between The Technical University of Denmark, several private companies, and Aalborg University...... concretes, workability, ductility, and confinement problems....

  14. Design criteria for prestressed concrete pressure vessels for high temperature reactors

    Schimmelpfennig, K.

    1991-01-01

    This paper summarizes the work on design criteria for concrete structures of Prestressed Concrete Reactor Vessels (PCRVs), which has been carried out since 1984 by a couple of competent institutions. After some basic considerations on the safety demands on PCRVs, especially their Prestressed Concrete Structure (PCS), and the consequences for an elevated level of quality to be ensured by the design criteria, an impression is given, first, by what means a higher quality standard is gained with respect to selection of materials and specification of material data in comparison to the usual building industry and what kind of criteria on this behalf should be fixed in a PCRV code. As a further quality increasing feature, the specific demands on design analysis as practised according to the present state of science and as to be treated within a code are discussed. This concerns analyses for steady state and transient temperatures as well as stress and strain analyses for service and ultimate load conditions. It is outlined to what degree calculation models should be detailed, which includes statements about admissible idealizations. As a central topic the question is discussed in what way the ultimate load capacity has to be evaluated, thereby presenting results of some investigations pointing out the conditions under which the design is determined by the different kinds of ultimate load conditions. Finally, some reflections on the demands on monitoring the PCS behaviour during its lifetime and on several questions still to be answered in this field are expressed. (orig.)

  15. Polymer concrete composites for the production of high strength pipe and linings in high temperature corrosive environments

    Zeldin, A.; Carciello, N.; Fontana, J.; Kukacka, L.

    High temperature corrosive resistant, non-aqueous polymer concrete composites are described. They comprise about 12 to 20% by weight of a water-insoluble polymer binder polymerized in situ from a liquid monomer mixture consisting essentially of about 40 to 70% by weight of styrene, about 25 to 45% by weight acrylonitrile and about 2.5 to 7.5% by weight acrylamide or methacrylamide and about 1 to 10% by weight of a crosslinking agent. This agent is selected from the group consisting of trimethylolpropane trimethacrylate and divinyl benzene; and about 80 to 88% by weight of an inert inorganic filler system containing silica sand and portland cement, and optionally Fe/sub 2/O/sub 3/ or carbon black or mica. A free radical initiator such as di-tert-butyl peroxide, azobisisobutyronitrile, benzoyl peroxide, lauryl peroxide, other organic peroxides and combinations thereof to initiate crosspolymerization of the monomer mixture in the presence of said inorganic filler.

  16. Analysis of inner structure changes of concretes exposed to high temperatures using micro X-ray computed tomography

    Sitek, Libor; Bodnárová, L.; Souček, Kamil; Staš, Lubomír; Gurková, Lucie

    2015-01-01

    Roč. 12, č. 1 (2015), s. 78-89 ISSN 1214-9705 R&D Projects: GA ČR GAP104/12/1988 Institutional support: RVO:68145535 Keywords : concrete * cement paste * aggregate * high temperature Subject RIV: JQ - Machines ; Tools Impact factor: 0.561, year: 2015 https://www.irsm.cas.cz/materialy/acta_content/2015_doi/Sitek_AGG_2015_0009.pdf

  17. Durability of lightweight concrete : Phase I : concrete temperature study.

    1968-08-01

    This report describes a study conducted to determine the temperature gradient throughout the depth of a six inch concrete bridge deck. The bridge deck selected for study was constructed using lightweight concrete for the center spans and sand and gra...

  18. Normal and refractory concretes for LMFBR applications. Volume 1. Review of literature on high-temperature behavior of portland cement and refractory concretes. Final report

    Bazant, Z.P.; Chern, J.C.; Abrams, M.S.; Gillen, M.P.

    1982-06-01

    The extensive literature on the properties and behavior at elevated temperature of portland cement concrete and various refractory concretes was reviewed to collect in concise form the physical and chemical properties of castable refractory concretes and of conventional portland cement concretes at elevated temperature. This survey, together with an extensive bibliography of source documents, is presented in Volume 1. A comparison was made of these properties, the relative advantages of the various concretes was evaluated for possible liquid metal fast breeder reactor applications, and a selection was made of several materials of interest for such applications. Volume 2 concludes with a summary of additional knowledge needed to support such uses of these materials together with recommendations on research to provide that knowledge

  19. Mathematical model for creep and thermal shrinkage of concrete at high temperature

    Bazant, Z.P.

    1983-01-01

    Based on the existing limited test data, it is possible to set up an approximate constitutive model for creep and shrinkage at temperatures above 100 0 C, up to about 400 0 C. The model presented here describes the effect of various constant temperatures on the creep rate and the rate of aging, similar effects of the specific water content, the creep increase caused by simultaneous changes in moisture content, the thermal volume changes as well as the volume changes caused by changes in moisture content (drying shrinkage or thermal shrinkage), and the effect of pore pressure produced by heating. Generalizations to time-variable stresses and multiaxial stresses are also given. The model should allow more realistic analysis of reactor vessels and containments for accident situations, of concrete structures subjected to fire, of vessels for coal gasification or liquefaction, etc. (orig.)

  20. High-temperature performance of mortars and concretes based on alkali-activated slag/metakaolin blends

    Bernal, S. A.

    2012-12-01

    Full Text Available This paper assesses the performance of mortars and concretes based on alkali activated granulated blastfurnace slag (GBFS/metakaolin (MK blends when exposed to high temperatures. High stability of mortars with contents of MK up to 60 wt.% when exposed to 600 °C is identified, with residual strengths of 20 MPa following exposure to this temperature. On the other hand, exposure to higher temperatures leads to cracking of the concretes, as a consequence of the high shrinkage of the binder matrix and the restraining effects of the aggregate, especially in those specimens with binders containing high MK content. A significant difference is identified between the water absorption properties of mortars and concretes, and this is able to be correlated with divergences in their performance after exposure to high temperatures. This indicates that the performance at high temperatures of alkali-activated mortars is not completely transferable to concrete, because the systems differ in permeability. The differences in the thermal expansion coefficients between the binder matrix and the coarse aggregates contribute to the macrocracking of the material, and the consequent reduction of mechanical properties.

    Este artículo evalúa el desempeño de morteros y hormigones basados en mezclas de escoria siderúrgica (GBFS/metacaolín (MK, activadas alcalinamente expuestos a temperaturas altas. Se identifica una elevada estabilidad en morteros con contenidos de MK de hasta un 60% cuando se exponen a temperaturas de 600 ºC, con una resistencia residual de 20 MPa posterior a la exposición a esta temperatura. Por otra parte, la exposición a temperaturas más elevadas conduce al agrietamiento de los hormigones como consecuencia de una elevada contracción de la matriz cementante y las restricciones por efecto de los áridos, especialmente en aquellos especímenes con cementantes que contienen altos contenidos de MK. Se identifican diferencias significativas en

  1. Relationship between permeability and damage in concretes at high temperature; Lien entre la permeabilite et l'endommagement dans les betons a haute temperature

    Dal Pont, St

    2004-09-15

    Due to its technical and economical advantages, concrete is nowadays the most used building material in civil engineering. Even if its use is known since nearly two centuries, its behavior has not been yet completely explained due to the complexity of its porous microstructure. This fact is quite evident under particular conditions such as, by instance, during an elevation of temperature. This condition can mainly occur in two cases: due to a casualty (e.g. a fire) or in normal use conditions (e.g. storage of nuclear rejects). This work aims at contributing to the study of the phenomena that can be observed in concrete exposed to high temperatures and, in particular, focuses on the study of the evolution of intrinsic permeability. The characterisation of permeability (which is hardly measurable in hot conditions) is necessary for describing and modelling transport phenomena which occur in porous media. An experimental study has been made in collaboration with the CEA. A real-scale hollow cylinder has been instrumented with gauges for studying the evolution of temperature and gas pressure fields inside concrete. Later, the cylinder has been then numerically modelled by means of a thermo-hydro-chemical (THC) and a thermo-hydro-chemo-mechanical (THCM) model. The THC model, implemented by means of the finite volume method, has allowed a first, qualitative study of the behaviour of concrete submitted to high temperature. This model, which, for sake of simplicity, has neglected all mechanical effects, has allowed the description of the main phenomena occurring inside concrete: mass transport, phase changes, microstructure evolution. Later, the modelling has been completed by means of the THCM model using the Hitecosp code, implemented by means of the finite element method at the university of Padua. This code allows a very complete description of the phenomena occurring inside concrete and takes into consideration the mechanical behavior of concrete by means of an

  2. Relationship between permeability and damage in concretes at high temperature; Lien entre la permeabilite et l'endommagement dans les betons a haute temperature

    Dal Pont, St

    2004-09-15

    Due to its technical and economical advantages, concrete is nowadays the most used building material in civil engineering. Even if its use is known since nearly two centuries, its behavior has not been yet completely explained due to the complexity of its porous microstructure. This fact is quite evident under particular conditions such as, by instance, during an elevation of temperature. This condition can mainly occur in two cases: due to a casualty (e.g. a fire) or in normal use conditions (e.g. storage of nuclear rejects). This work aims at contributing to the study of the phenomena that can be observed in concrete exposed to high temperatures and, in particular, focuses on the study of the evolution of intrinsic permeability. The characterisation of permeability (which is hardly measurable in hot conditions) is necessary for describing and modelling transport phenomena which occur in porous media. An experimental study has been made in collaboration with the CEA. A real-scale hollow cylinder has been instrumented with gauges for studying the evolution of temperature and gas pressure fields inside concrete. Later, the cylinder has been then numerically modelled by means of a thermo-hydro-chemical (THC) and a thermo-hydro-chemo-mechanical (THCM) model. The THC model, implemented by means of the finite volume method, has allowed a first, qualitative study of the behaviour of concrete submitted to high temperature. This model, which, for sake of simplicity, has neglected all mechanical effects, has allowed the description of the main phenomena occurring inside concrete: mass transport, phase changes, microstructure evolution. Later, the modelling has been completed by means of the THCM model using the Hitecosp code, implemented by means of the finite element method at the university of Padua. This code allows a very complete description of the phenomena occurring inside concrete and takes into consideration the mechanical behavior of concrete by means of an

  3. Analysis of Inner Structure Changes of Concretes Exposed to High Temperatures Using Micro X-ray Computed Tomography

    Sitek, Libor; Bodnárová, L.; Souček, Kamil; Staš, Lubomír; Gurková, Lucie

    2015-01-01

    Roč. 12, č. 1 (2015), s. 79-89 ISSN 1214-9705 R&D Projects: GA MŠk(CZ) LO1406; GA ČR GAP104/12/1988; GA MŠk ED2.1.00/03.0082 Institutional support: RVO:68145535 Keywords : concrete * cement paste * aggregate * high temperature Subject RIV: JQ - Machines ; Tools Impact factor: 0.561, year: 2015 https://www.irsm.cas.cz/materialy/acta_content/2015_doi/Sitek_AGG_2015_0009.pdf

  4. Mechanical properties of steel fiber reinforced reactive powder concrete following exposure to high temperature reaching 800 deg. C

    Tai, Yuh-Shiou, E-mail: ystai@cc.cma.edu.tw [Department of Civil Engineering, ROC Military Academy, Kaohsiung, Taiwan (China); Pan, Huang-Hsing; Kung, Ying-Nien [Department of Civil Engineering, Kaohsiung University of Applied Sciences, Kaohsiung, Taiwan (China)

    2011-07-15

    Highlights: > The stress-strain relation of reactive powder concrete after exposure to high temperatures are tested by using displacement control. > Develops regression formulae to estimate the mechanical properties of RPC. > Valuable experimental data have been obtained about RPC with various fiber contents. These data include compressive strength, peak strain and modulus of elasticity. - Abstract: This study investigates the stress-strain relation of RPC in quasi-static loading after an elevated temperature. The cylinder specimens of RPC with {phi} 50 mm x 100 mm are examined at the room temperature and after 200-800 deg. C. Experimental results indicate that the residual compressive strength of RPC after heating from 200-300 deg. C increases more than that at room temperature, but, significantly decreases when the temperature exceeds 300 deg. C. The residual peak strains of RPC also initially increase up to 400-500 deg. C, then decrease gradually beyond 500 deg. C. Meanwhile, Young's modulus diminishes with an increasing temperature. Based on the regression analysis results, this study also develops regression formulae to estimate the mechanical properties of RPC after an elevated temperature, thus providing a valuable reference for industrial applications and design.

  5. Effect of monomer composition on the properties of high temperature polymer concretes

    Zeldin, A.; Kukacka, L.E.; Carciello, N.

    1980-01-01

    The effects of organic monomer composition on the thermomechanical properties of polymer concrete (PC) containing sand-cement mixtures as an agregate filler were investigated. The effects of various monomer mixtures on compressive strength and hydrolytic stability are discussed. Composites were fabricated in the same way as ordinary concrete, with monomer solutions of various compositions and concentrations used to bind the sand-cement mixture. The compressive strengths of th composites before and after exposure to air and to brine solutions at 240/sup 0/C are discussed.

  6. Characterization of High Temperature Modulus of Elasticity of Lightweight Foamed Concrete under Static Flexural and Compression: An Experimental Investigations

    Md Azree Othuman Mydin

    2012-09-01

    Full Text Available This paper focused on an experimental works that have been performed to examine the young’s modulus of foamed concrete at elevated temperatures up to 600°C. Foamed concrete of 650 and 1000 kg/m3 density were cast and tested under compression and bending. The experimental results of this study consistently demonstrated that the loss in stiffness for cement based material like foamed concrete at elevated temperatures occurs predominantly after about 95°C, regardless of density. This indicates that the primary mechanism causing stiffness degradation is microcracking, which occurs as water expands and evaporates from the porous body. As expected, reducing the density of LFC reduces its strength and stiffness. However, for LFC of different densities, the normalised strength-temperature and stiffness-temperature relationships are very similar.

  7. Quantitative study on the effect of high-temperature curing at an early age on strength development of concrete. Experiment with mortar using moderate-heat portland cement

    Sugiyama, Hisashi; Chino, Shigeo

    1999-01-01

    The effect of high-temperature curing at an early age on the strength development of concrete using moderate-heat portland cement was quantitatively studied. High-temperature curing conditions were set so as to give systematic variations in the temperature-time factors. As a result, the integrated value of curing temperature during the period having a significant effect on the strength development was proposed as a parameter that expressed the degree of high-temperature curing. The effect of high-temperature curing on the strength development of concrete using moderate-heat portland cement could be exactly predicted with the integrated value of curing temperature during the period from 0 to 3 days. (author)

  8. Strain measurements at high temperatures in a concrete structure representing a cylindrical section of a PCPV with hot liner

    Schittenhelm, Ch.

    1975-11-01

    In an experimental ring, representing an 1 m high section of the Austrian PCPV-Model with hot liner, different types of strain gauges were installed in the insulating concrete and the prestressed concrete. In this ring the thermal conditions were the same as in the PCPV-Model. In this report the results of measurements of the past two years are brought and comparisons with static calculations is attempted. (author)

  9. Sandwich panels with high performance concrete thin plates at elevated temperatures

    Hulin, Thomas; Hodicky, Kamil; Schmidt, Jacob Wittrup

    2015-01-01

    concerned HMT modelling and elastic stress analysis with nonlinear temperature effects of a full size loaded sandwich wall, qualitatively assessing the location of critically stressed zones. Modelling output was compared to published experimental results. The model reproduced experimental temperature...... recordings satisfactorily, except phase changes of water at low heating rates. It was suggested that the function governing moisture evolution with temperature and pressure should be updated for HPC. Pore pressure was found critical for sandwich structures due their higher temperatures. Adding polypropylene...

  10. Elevated temperature effects on concrete properties

    Grant, P.R.; Gruber, R.S.; Van Katwijk, C.

    1993-08-01

    The design of facilities to process or store radioactive wastes presents many challenging engineering problems. Such facilities must not only provide for safe storage of radioactive wastes but they must also be able to maintain confinement of these materials during and after natural phenomena events. Heat generated by the radioactive decay of the wastes will cause the temperature of the concrete containment structure to increase to a magnitude higher than that found in conventional structures. These elevated temperatures will cause strength-related concrete properties to degrade over time. For concrete temperatures less than 150 degree F, no reduction in strength is taken and the provisions of ACI 349, which states that higher temperatures are allowed if tests are provided to evaluate the reduction in concrete strength properties, apply. Methods proposed in a Pacific Northwest Laboratory (PNL) report, Modeling of Time-Variant Concrete Properties at Elevated Temperatures, can be used to evaluate the effects of elevated temperatures on concrete properties. Using these modified concrete properties the capacity of a concrete structure, subjected to elevated temperatures, to resist natural phenomena hazards can be determined

  11. 3-D Temperature and Stress Simulations of Hardening Concrete

    Jensen, Poul; Buhr, Birit; Thorborg, Jesper

    2003-01-01

    When concrete is cast, heat develops. When the concrete cools down there is a risk that thermal gradients induce cracks in the structure. In the Middle East this is especially important as extensive heat builds up due to the high ambient temperatures. Possible formed cracks will have a detrimenta...

  12. Properties of high-workability concrete with recycled concrete aggregate

    Safiuddin,; Alengaram,Ubagaram Johnson; Salam,Abdus; Jumaat,Mohd Zamin; Jaafar,Fahrol Fadhli; Saad,Hawa Binti

    2011-01-01

    This study presents the effects of recycled concrete aggregate (RCA) on the key fresh and hardened properties of concrete. RCA was used to produce high-workability concrete substituting 0-100% natural coarse aggregate (NCA) by weight. The slump and slump flow of fresh concretes were determined to ensure high workability. In addition, the compressive, flexural and splitting tensile strengths, modulus of elasticity, and permeable voids of hardened concretes were determined. The test results rev...

  13. CONSTITUTIVE MODEL OF STEEL FIBRE REINFORCED CONCRETE SUBJECTED TO HIGH TEMPERATURES

    Lukas Blesak

    2016-12-01

    Full Text Available Research on structural load-bearing systems exposed to elevated temperatures is an active topic in civil engineering. Carrying out a full-size experiment of a specimen exposed to fire is a challenging task considering not only the preparation labour but also the necessary costs. Therefore, such experiments are simulated using various software and computational models in order to predict the structural behaviour as exactly as possible. In this paper such a procedure, focusing on software simulation, is described in detail. The proposed constitutive model is based on the stress-strain curve and allows predicting SFRC material behaviour in bending at ambient and elevated temperature. SFRC material is represented by the initial linear behaviour, an instantaneous drop of stress after the initial crack occurs and its consequent specific ductility, which influences the overall modelled specimen behaviour under subjected loading. The model is calibrated with ATENA FEM software using experimental results.

  14. Experiment and calculation of reinforced concrete at elevated temperatures

    Guo, Zhenhai

    2011-01-01

    Concrete as a construction material goes through both physical and chemical changes under extreme elevated temperatures. As one of the most widely used building materials, it is important that both engineers and architects are able to understand and predict its behavior in under extreme heat conditions. Brief and readable, this book provides the tools and techniques to properly analysis the effects of high temperature of reinforced concrete which will lead to more stable, safer structures. Based on years of the author's research, Reinforced Concrete at Elevated Temperatures four par

  15. Behavior of reinforced concrete at elevated temperatures

    Freskakis, G.N.

    1984-09-01

    A study is presented concerning the behavior of reinforced concrete sections at elevated temperatures. Material properties of concrete and reinforcing steel are discussed. Behavior studies are made by means of moment-curvature-axial force relationships. Particular attention is given to the load carrying capacity, thermal forces and moments, and deformation capacity. The effects on these properties of variations in the strength properties, the temperature level and distribution, the amount of reinforcing steel, and limiting values of strains are considered

  16. Temperature Response in Hardened Concrete Subjected to Tropical Rainforest Environment

    E. I. Egba

    2017-06-01

    Full Text Available The objective of this paper is to characterize concrete micro-environment temperature response to the natural climate of the tropical rainforest. The peculiar warmth, high humidity, and low pressure nature of the tropical rainforest necessitated the present study. Temperature probes were inserted into concrete specimens subjected to the sheltered and unsheltered environment to measure the micro-environment temperature of the concrete, and study the hysteresis characteristics in relation to the climate temperature. Some mathematical relationships for forecasting the internal temperature of concrete in the tropical rainforest environment were proposed and tested. The proposed relationships were found reliable. It was observed that the micro-environment temperature was lower at the crest, and higher at the trough than the climate environment temperature with a temperature difference of 1-3 oC. Also, temperature response in concrete for the unsheltered micro-environment was 1.85 times faster than the response in the sheltered micro-environment. The findings of the study may be used to assist the durability assessment of concrete.

  17. Thermohydraulics in a high-temperature gas-cooled reactor prestressed-concrete reactor vessel during unrestricted core-heatup accidents

    Kroeger, P.G.; Colman, J.; Araj, K.

    1983-01-01

    The hypothetical accident considered for siting considerations in High Temperature Gas-Cooled Reactors (HTGR) is the so called Unrestricted Core Heatup Accident (UCHA), in which all forced circulation is lost at initiation, and none of the auxillary cooling loops can be started. The result is a gradual slow core heatup, extending over days. Whether the liner cooling system (LCS) operates during this time is of crucial importance. If it does not, the resulting concrete decomposition of the prestressed concrete reactor vessel (PCRV) will ultimately cause containment building (CB) failure after about 6 to 10 days. The primary objective of the work described here was to establish for such accident conditions the core temperatures and approximate fuel failure rates, to check for potential thermal barrier failures, and to follow the PCRV concrete temperatures, as well as PCRV gas releases from concrete decomposition. The work was done for the General Atomic Corporation Base Line Zero reactor of 2240 MW(t). Most results apply at least qualitatively also to other large HTGR steam cycle designs

  18. Compilation of three-dimensional coordinates and specific data of the instrumentation of the prestressed concrete pressure vessel/high temperature helium test rig

    Klausinger, D.

    1977-04-01

    The positions of the thermoelements, strain gauges of various types, and of Gloetzl instruments installed by SGAE in the model vessel of the Common Project Prestressed Concrete Pressure Vessel/High Temperature Helium Test Rig are defined in cylindrical coordinates. The specific data of the instruments are given like configuration of multiple instruments; type, group and number of the instrument; number of cable and of channel; calibration factors; resistances of instruments and cables. (author)

  19. Strength properties of concrete at elevated temperatures

    Freskakis, G.N.; Burrow, R.C.; Debbas, E.B.

    1979-01-01

    A study is presented concerning the compressive strength, modulus of elasticity, and stress-strain relationships of concrete at elevated temperatures. A review of published results provides information for the development of upper and lower bound relationships for compressive strength and the modulus of elasticity and establishes exposure conditions for a lower bound thermal response. The relationships developed from the literature review are confirmed by the results of a verification test program. The strength and elasticity relationships provide a basis for the development of design stress-strain curves for concrete exposed to elevated temperatures

  20. The Effect of Elevated Temperature on Concrete Materials and Structures - a Literature Review.

    Naus, Dan J [ORNL

    2006-03-01

    The objective of this limited study was to provide an overview of the effects of elevated temperature on the behavior of concrete materials and structures. In meeting this objective the effects of elevated temperatures on the properties of ordinary Portland cement concrete constituent materials and concretes are summarized. The effects of elevated temperature on high-strength concrete materials are noted and their performance compared to normal strength concretes. A review of concrete materials for elevated-temperature service is presented. Nuclear power plant and general civil engineering design codes are described. Design considerations and analytical techniques for evaluating the response of reinforced concrete structures to elevated-temperature conditions are presented. Pertinent studies in which reinforced concrete structural elements were subjected to elevated temperatures are described.

  1. The Effect of Elevated Temperature on Concrete Materials and Structures - a Literature Review

    Naus, Dan J.

    2006-01-01

    The objective of this limited study was to provide an overview of the effects of elevated temperature on the behavior of concrete materials and structures. In meeting this objective the effects of elevated temperatures on the properties of ordinary Portland cement concrete constituent materials and concretes are summarized. The effects of elevated temperature on high-strength concrete materials are noted and their performance compared to normal strength concretes. A review of concrete materials for elevated-temperature service is presented. Nuclear power plant and general civil engineering design codes are described. Design considerations and analytical techniques for evaluating the response of reinforced concrete structures to elevated-temperature conditions are presented. Pertinent studies in which reinforced concrete structural elements were subjected to elevated temperatures are described.

  2. Effects of Elevated Temperature on Concrete with Recycled Coarse Aggregates

    Salau, M. A.; Oseafiana, O. J.; Oyegoke, T. O.

    2015-11-01

    This paper discusses the effects of heating temperatures of 200°C, 400°C and 600°C each for 2 hours at a heating rate of 2.5°C/min on concrete with the content of Natural Coarse Aggregates (NCA) partially replaced with Recycled Coarse Aggregates (RCA), obtained from demolished building in the ratio of 0%, 15% and 30%.There was an initial drop in strength from 100°C to 200°C which is suspected to be due to the relatively weak interfacial bond between the RCA and the hardened paste within the concrete matrix;a gradual increase in strength continued from 200°C to 450°C and steady drop occurred again as it approached 600°C.With replacement proportion of 0%, 15% and 30% of NCA and exposure to peak temperature of 600°C, a relative concrete strength of 23.6MPa, 25.3MPa and 22.2MPa respectively can be achieved for 28 days curing age. Furthermore, RAC with 15% NCA replacement when exposed to optimum temperature of 450°C yielded high compressive strength comparable to that of control specimen (normal concrete). In addition, for all concrete samples only slight surface hairline cracks were noticed as the temperature approached 400°C. Thus, the RAC demonstrated behavior just like normal concrete and may be considered fit for structural use.

  3. Durability of high performance concrete in seawater

    Amjad Hussain Memon; Salihuddin Radin Sumadi; Rabitah Handan

    2000-01-01

    This paper presents a report on the effects of blended cements on the durability of high performance concrete (HPC) in seawater. In this research the effect of seawater was investigated. The specimens were initially subjected to water curing for seven days inside the laboratory at room temperature, followed by seawater curing exposed to tidal zone until testing. In this study three levels of cement replacement (0%, 30% and 70%) were used. The combined use of chemical and mineral admixtures has resulted in a new generation of concrete called HPC. The HPC has been identified as one of the most important advanced materials necessary in the effort to build a nation's infrastructure. HPC opens new opportunities in the utilization of the industrial by-products (mineral admixtures) in the construction industry. As a matter of fact permeability is considered as one of the fundamental properties governing the durability of concrete in the marine environment. Results of this investigation indicated that the oxygen permeability values for the blended cement concretes at the age of one year are reduced by a factor of about 2 as compared to OPC control mix concrete. Therefore both blended cement concretes are expected to withstand in the seawater exposed to tidal zone without serious deterioration. (Author)

  4. Development study of concrete reinforcement made of aramid fiber-reinforced plastic rods with high radiation resistance. 1. Epoxy resin compounds with a handling at room temperature impregnation

    Udagawa, Akira; Seguchi, Tadao; Moriya, Toshio; Matsubara, Sumiyuki; Hongou, Yoshihiko

    1999-03-01

    Aramid fiber-reinforced plastic (ArFRP) rods were developed in order to avoid from conduction current and/or magnetization of the metallic reinforcement using concrete constructions. For the polymer matrix, new epoxy resin compounds consist of tetraglycidyl diaminodiphenylmethane (30%), diglycidyl ether of bisphenol-A (60%), styrene oxide (10%) and aromatic diamine as a hardner were found to be the best formulation, and which were easily impregnated to the aramid fiber braiding yarn at room temperature. The ArFRP rods has a high radiation resistance, and the tensile strength was maintained to 98% (1.45 GPa) after irradiation dose of 100 MGy (absorbed energy MJ/kg), which is available for the reinforcement of concrete construction for the house of fusion reactor with super conducting magnets. (author)

  5. Analysis of inner structure changes of concretes exposed to high temperatures using micro X-ray computed tomography

    Sitek, L. (Libor); Bodnárová, L.; Souček, K. (Kamil); Staš, L. (Lubomír); Gurková, L. (Lucie)

    2015-01-01

    The X-ray Computed Tomography (X-ray CT) repr esents a progressive non-destructive metho d of analysing the inner structure of materials. The method was used for monitoring changes in inner structure of concrete samples of different composition before and after their exposure to various thermal loads. Eight types of concrete samples were prepared which differed by cement and aggregate types. We intentionally used such composition of concrete mixtures which increased their resist...

  6. The behaviour of concrete at high temperatures and triaxial stress - FE model based on the concrete structure; Betonverhalten bei hohen Temperaturen und triaxialer Beanspruchung - FE-Modell auf der Basis der Betonstruktur

    Ameler, J.

    1997-12-31

    In this work, an analytical material model was developed, based on the finite element (FE) method, with which the material behaviour of a normal quartzite concrete under temperature stress can be described. Starting from natural fires, the short term area and temperatures between the normal temperature and about 800 C are of special interest. Altogether, it was found that important processes reducing the strength, which occur in high temperature stresses of concrete, can be directly traced back to the additive or the mortar phase, while others are due to the interaction between the two partners. In this attempted model, the compound material concrete is therefore regarded as a system consisting of two components, the additive and the mortar matrix. The mortar matrix is defined as the part consisting of the cement, the water and the fine proportion of the additive (diameter{<=}4 mm). (orig./MM) [Deutsch] In der vorliegenden Arbeit wurde ein analytisches Werkstoffmodell auf der Basis der FE-Methode entwickelt, mit dem das Werkstoffverhalten eines quarzitischen Normalbetons unter einer Temperaturbeanspruchung beschrieben werden kann. Ausgehend vom natuerlichen Brandgeschehen, interessieren besonders der Kurzzeitbereich und Temperaturen zwischen Normaltemperatur und ca. 800 C. In der Summe zeichnet sich ab, dass wesentliche festigkeitsmindernde Prozesse, die sich bei einer Hochtemperaturbeanspruchung von Beton abspielen, direkt dem Zuschlag bzw. der Moertelphase zugeordnet werden koennen, waehrend andere auf die Interaktion zwischen den beiden Partnern zurueckzufuehren sind. Im vorliegenden Modellansatz wird der Verbundwerkstoff Beton deshalb als ein aus zwei Komponenten bestehendes System betrachtet, dem Zuschlag und der Moertelmatrix. Die Moertelmatrix wird als der aus dem Zement, dem Wasser und dem Feinanteil des Zuschlags (Durchmesser{<=}4 mm) zusammengesetzte Teil definiert. (orig./MM)

  7. Comparison of winter temperature profiles in asphalt and concrete pavements.

    2014-06-01

    The objectives of this research were to 1) determine which pavement type, asphalt or concrete, has : higher surface temperatures in winter and 2) compare the subsurface temperatures under asphalt and : concrete pavements to determine the pavement typ...

  8. A study on physical properties of concrete and reinforcement at elevated temperatures

    Kanazu, Tsutomu

    2002-01-01

    Reinforced concrete structures such as a containment vessel, a support of the reactor, piping systems and facilities for storing high level radioactive waste in a nuclear power plant are exposed to a high temperature condition. Changes of physical properties of concrete and reinforcement caused by high temperature influence on mechanical behavior of these structures and internal stresses are induced by difference of thermal coefficients between concrete and reinforcement that was reported in the previous paper by the author. These are the special features in high temperature conditions. Temperature dependence of physical properties of concrete and reinforcement are summarized in the paper based on the experimental results. (author)

  9. Thermo-physical properties and transient heat transfer of concrete at elevated temperatures

    Shin, Ki-Yeol; Kim, Sang-Baik; Kim, Jong-Hwan; Chung, Mo; Jung, Pyung-Suk

    2002-01-01

    The objective of this study is to produce our own experimental data of physical properties of domestic concrete used in Korean NPPs, and to study on the thermal behavior of concrete exposed to high temperature conditions. The compressive strength and chemical composition of the concrete used in the Yonggwang NPP units 3 and 4 were analyzed. The chemical composition of Korean concrete is similar to that of US basaltic concrete. The thermal properties of the concrete, such as density, conductivity, diffusivity, and specific heat were also measured with a wide temperature range of 20-1100 deg. C. Most thermo-physical properties of concrete decrease with an increase in temperature except for the specific heat, and particularly the conductivity and the diffusivity are a 50% lower at 900 deg. C as compared with the values at room temperature. The specific heat increases until 500 deg. C, decreases from 700 to 900 deg. C, and then increases again when temperature is above 900 deg. C. In this work, we also have performed CORCON analysis and MCCI experiments to simulate a transient thermal behavior of concrete exposed to high temperature conditions. The measured maximum downward heat flux to the concrete specimen was estimated to be about 2.1 MW m -2 and the maximum erosion rate of the concrete to be 175 cm h -1 with maximum erosion depth of about 2 cm. In the CORCON analysis, it is found that the concrete compositions have an important effect upon concrete erosion

  10. Assessment of Mass Fraction and Melting Temperature for the Application of Limestone Concrete and Siliceous Concrete to Nuclear Reactor Basemat Considering Molten Core–Concrete Interaction

    Hojae Lee

    2016-04-01

    Full Text Available Severe accident scenarios in nuclear reactors, such as nuclear meltdown, reveal that an extremely hot molten core may fall into the nuclear reactor cavity and seriously affect the safety of the nuclear containment vessel due to the chain reaction caused by the reaction between the molten core and concrete. This paper reports on research focused on the type and amount of vapor produced during the reaction between a high-temperature molten core and concrete, as well as on the erosion rate of concrete and the heat transfer characteristics at its vicinity. This study identifies the mass fraction and melting temperature as the most influential properties of concrete necessary for a safety analysis conducted in relation to the thermal interaction between the molten core and the basemat concrete. The types of concrete that are actually used in nuclear reactor cavities were investigated. The H2O content in concrete required for the computation of the relative amount of gases generated by the chemical reaction of the vapor, the quantity of CO2 necessary for computing the cooling speed of the molten core, and the melting temperature of concrete are evaluated experimentally for the molten core–concrete interaction analysis.

  11. Assessment of mass fraction and melting temperature for the application of limestone concrete and siliceous concrete to nuclear reactor basemat considering molten core-concrete interaction

    Lee, Ho Jae; Kim, Do Gyeum [Korea Institute of Civil Engineering and Building Technology, Goyang (Korea, Republic of); Cho, Jae Leon [Korea Hydro and Nuclear Power Co., Ulsan (Korea, Republic of); Yoon, Eui Sik [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of); Cho, Myung Suk [Korea Hydro and Nuclear Power Co., Central Research Institute, Daejeon (Korea, Republic of)

    2016-04-15

    Severe accident scenarios in nuclear reactors, such as nuclear meltdown, reveal that an extremely hot molten core may fall into the nuclear reactor cavity and seriously affect the safety of the nuclear containment vessel due to the chain reaction caused by the reaction between the molten core and concrete. This paper reports on research focused on the type and amount of vapor produced during the reaction between a high-temperature molten core and concrete, as well as on the erosion rate of concrete and the heat transfer characteristics at its vicinity. This study identifies the mass fraction and melting temperature as the most influential properties of concrete necessary for a safety analysis conducted in relation to the thermal interaction between the molten core and the basemat concrete. The types of concrete that are actually used in nuclear reactor cavities were investigated. The H2O content in concrete required for the computation of the relative amount of gases generated by the chemical reaction of the vapor, the quantity of CO2 necessary for computing the cooling speed of the molten core, and the melting temperature of concrete are evaluated experimentally for the molten core-concrete interaction analysis.

  12. Concretes with high mechanical resistance

    Mauny, Pierre.

    1973-01-01

    Description is given of a method for manufacturing concretes with high mechanical resistance in compression, obtained by mixing gravels highly resistant to compression, sand and cement in an aqueous medium. Use is made of sands of porous ceramics, such as terra-cotta, of a grain size from 0,1 to 5mm, the pore diameter of which is from 0.5 to 15 microns, chosen so as to be slighty bigger than the crystals of the cement used. This can be applied to the pre-stressed structures used in the nuclear field [fr

  13. Experimental investigation on temperature distribution of foamed concrete filled steel tube column under standard fire

    Kado, B.; Mohammad, S.; Lee, Y. H.; Shek, P. N.; Kadir, M. A. A.

    2018-04-01

    Standard fire test was carried out on 3 hollow steel tube and 6 foamed concrete filled steel tube columns. Temperature distribution on the columns was investigated. 1500 kg/m3 and 1800 kg/m3 foamed concrete density at 15%, 20% and 25% load level are the parameters considered. The columns investigated were 2400 mm long, 139.7 mm outer diameter and 6 mm steel tube thickness. The result shows that foamed concrete filled steel tube columns has the highest fire resistance of 43 minutes at 15% load level and low critical temperature of 671 ºC at 25% load level using 1500 kg/m3 foamed concrete density. Fire resistance of foamed concrete filled column increases with lower foamed concrete strength. Foamed concrete can be used to provide more fire resistance to hollow steel column or to replace normal weight concrete in concrete filled columns. Since filling hollow steel with foamed concrete produce column with high fire resistance than unfilled hollow steel column. Therefore normal weight concrete can be substituted with foamed concrete in concrete filled column, it will reduces the self-weight of the structure because of its light weight at the same time providing the desired fire resistance.

  14. Effects of temperature on concrete cask in a dry storage facility for spent nuclear fuels

    Huang Weiqing; Wu Ruixian; Zheng Yukuan

    2011-01-01

    In the dry storage of spent nuclear fuels,concrete cask serves both as a shielding and a structural containment. The concrete in the storage facility is expected to endure the decay heat of the spent nuclear fuel during its service life. Thus, effects of the sustaining high temperature on concrete material need be evaluated for safety of the dry storage facility. In this paper, we report an experimental program aimed at investigating possible high temperature effects on properties of concrete, with emphasis on the mechanical stability, porosity,and crack-resisting ability of concrete mixes prepared using various amounts of Portland cement, fly ash, and blast furnace slag. The experimental results obtained from concrete specimens exposed to a temperature of 94 degree C for 90 days indicate that: (1) compressive strength of the concrete remains practically unchanged; (2) the ultrasonic pulse velocity, and dynamic modulus of elasticity of the concrete decrease in early stage of the high-temperature exposure,and gradually become stable with continuing exposure; (3) shrinkage of concrete mixes exhibits an increase in early stage of the exposure and does not decrease further with time; (4) concrete mixes containing pozzolanic materials,including fly ash and blast furnace slag, show better temperature-resisting characteristics than those using only Portland cement. (authors)

  15. Effects of Elevated Temperature on Compressive Strength Of Concrete

    This study presents the results of investigation of the effects of elevated temperatures on the compressive strength of Grade 40 concrete. A total of thirty cube specimens were cast, cured in water at ambient temperature in the laboratory and subjected to various temperature regimes before testing. A concrete mix of 1:1:3 ...

  16. Temperature effects on bond between concrete and reinforcing steel

    Lublóy Éva

    2014-01-01

    Full Text Available Bond behaviour between concrete and reinforcing bars was observed under elevated temperatures. Five different concrete compositions were used. Hundred five pull-out specimens (Ø120 mm, 100 mm were prepared. After removing the specimens from the formwork, they were stored in water for seven days then kept at laboratory conditions until testing. The specimens were 28 days old by testing. After heating up the specimens, they were kept for two hours at these maximum temperatures (20 °C, 150 °C, 300 °C, 400 °C, 500 °C, 800 °C. Specimens were then cooled down in laboratory conditions. Finally the specimens were tested at room temperature. In order to check the compressive strength standard cubes were cast, cured, and heat treated, then tested to compressive strength. The results showed reduction in residual compressive strength and considerable changes in steel-concrete bond under high temperatures. Based on test results, a proposal is presented for the modification of MC2010 bond-ship formula in order to consider temperature effect.

  17. Analysis of coupled transport phenomena in concrete at elevated temperatures

    Beneš, Michal; Štefan, Radek; Zeman, Jan

    2010-01-01

    In this paper, we study a non-linear numerical scheme arising from the implicit time discretization of the Ba\\v{z}ant-Thonguthai model for hygro-thermal behavior of concrete at high temperatures. Existence and uniqueness of the time-discrete solution in two dimensions is established using the theory of pseudomonotone operators in Banach spaces. Next, the spatial discretization is accomplished by the conforming finite element method. An illustrative numerical example shows that the numerical m...

  18. The role of high temperature heterogeneous reaction kinetics in the rate of radionuclide vaporisation during core-concrete interactions

    Raymond, D.P.; Clough, P.N.

    1989-09-01

    Heterogeneous reactions may cause enhanced release of radionuclides during the core-concrete interaction (CCl) stage of a PWR severe accident. The VANESA computer code models these CCI releases using chemical equilibrium assumptions; however, the possibility that chemical kinetics could prevent equilibrium from being achieved is considered in this report. Direct experimental evidence is lacking on these reactions. Therefore, some analogues studies are reviewed, including examples of Eyring's surface reaction rate theory; sequential vaporisation-oxidation processes; iron and steelmaking chemistry; radionuclide evaporation from solid UO 2 . This circumstantial evidence appeared to agree with the current assumptions, in VANESA and some UK modelling studies, that mass transfer, rather than chemical kinetics will limit the rate at which equilibrium is attained. (author)

  19. Interaction between a fluid at high temperature and a concrete: contribution to the modeling of heat and mass transfers

    Introini, C.

    2010-01-01

    In the late phases of some scenario of hypothetical severe accident in Pressurized Water Reactors, a molten mixture of core and vessel structures, called corium, comes to interact with the concrete basemat. The safety numerical tools are lumped parameter codes. They are based on a large averaged description of heat and mass transfers which raises some uncertainties about the multi-scale description of the exchanges but also about the adopted boundary layer structure in the vicinity of the ablation front. In this context, the aim of this work is to tackle the problem of the boundary layer structure by means of direct numerical simulation. This work joins within the more general framework of a multi-scale description and a multi-scale modeling, namely from the local scale associated with the vicinity of the ablation front to the scale associated with the lumped parameter codes. Such a multi-scale description raises not only the problem of the local description of the multiphase multicomponent flow but also the problem of the up-scaling between the local- and the macro-scale which is associated with the convective structures within the pool of corium. Here, we are particularly interested in the building of effective boundary conditions or wall laws for macro-scale models. The difficulty of the multiphase multicomponent problem at the local scale leads us to consider a relatively simplified problem. Effective boundary conditions are built in the frame of a domain decomposition method and numerical experiments are performed for a natural convection problem in a stamp shaped cavity to assess the validity of the proposed wall laws. Even if the treated problem is still far from the target applications, this contribution can be viewed as a first step of a multi-scale modeling of the exchanges for the molten core concrete issue. In the more complicated case of multiphase multicomponent flows, it is necessary to have a direct numerical simulation tool of the flow at the local

  20. Steel fiber reinforced concrete subjected to elevated cyclic temperatures

    Yousif, R. A.; Rasheed, H. M.; Muhammad, H. A.

    1997-01-01

    The results from a series of tests on steel fiber reinforced concrete at elevated cyclic temperature are presented. The residual compressive strength and ultimate splitting tensile strength were nadir's on specimen ts with no fibers and with 0.5% and 1% plain steel fibers over a temperature range of 300-700 C. concrete was subjected to one, two or three cycles of heating and cooling. In general the exposure to temperature decreased the strength of concrete, although the number of heating cycles seems only to have a secondary effect. The results also show that the steel fiber reinforced concrete performs better than plain concrete. Two equations were suggested to predict the strength of concrete and the results show good agreement with the experimental values. . (authors). 10 refs., 1 tabs. 3 figs

  1. Creep of concrete under various temperature, moisture, and loading conditions

    McDonald, J.E.

    1976-01-01

    An investigation was conducted to obtain information on the time-dependent deformation behavior of concrete in the presence of temperature, moisture, and loading conditions similar to those encountered in a prestressed concrete reactor vessel (PCRV). Variables included concrete strength, aggregate types, curing history, temperature, and types of loading (uniaxial, hydrostatic, biaxial, and triaxial). There were 66 test conditions for creep tests and 12 test conditions for unloaded or control specimens. Experimental results are presented and discussed. Comparisons are made concerning the effect of the various test conditions on the behavior of concrete, and general conclusions are formulated

  2. The Effect of Temperature on Moisture Transport in Concrete.

    Wang, Yao; Xi, Yunping

    2017-08-09

    Most concrete structures and buildings are under temperature and moisture variations simultaneously. Thus, the moisture transport in concrete is driven by the moisture gradient as well as the temperature gradient. This paper presents an experimental approach for determining the effect of different temperature gradients on moisture distribution profiles in concrete. The effect of elevated temperatures under isothermal conditions on the moisture transport was also evaluated, and found not to be significant. The non-isothermal tests show that the temperature gradient accelerates the moisture transport in concrete. The part of increased moisture transfer due to the temperature gradient can be quantified by a coupling parameter D HT , which can be determined by the present test data. The test results indicated that D HT is not a constant but increases linearly with the temperature variation. A material model was developed for D HT based on the experimental results obtained in this study.

  3. The assessment of bond strength between heat damaged concrete and high strength fibre reinforced concrete

    Zahid, M. Z. A. Mohd; Muhamad, K.

    2017-09-01

    The aim of this study is to assess the bond strength between heat damaged concrete and high strength fibre reinforced concrete (HPFRC). Firstly, this paper presents the various steps taken to prepare the HPFRC with self-compacting property. The minimum targeted slump flow is 600 mm and minimum targeted compressive strength is 80 MPa. The key mix variables considered are such as type of superplasticizer, water cement ratio and silica fume content. Then, the bond strength between the heat damaged concrete with HPFRC was examined. The experimental parameters are heating temperature, surface treatment technique and curing method and the results show that, all experimental parameters are significantly affected the bond strength between heat damaged concrete and HPFRC.

  4. Microcracking and durability of high strength concretes

    Yssorche, M.P.

    1995-07-01

    Durability of 28 days compressive strength concrete of 20 to 120 MPa has been studied. The ability of concrete to transport aggressive agents has been determined for four properties: the air permeability, the chloride diffusivity, the water absorption and the carbonation. A chloride migration test for high and very high strength concrete (HSC and VHSC) has been built. The relationship between transport properties and the compressive strength after one and 28 days of humid curing has always the same shape: transport decreases when strength increases. However, transport properties often vary in the ordinary concrete field. Beyond, the domain is much more limited. The relationship between transport properties and strength valid for ordinary concrete can not be simply extrapolated for HSC and VHSC. To determine the part of microcracking of HSC and VHSC, concrete behaviour stored in two mediums has been studied: the ones shaming the storing condition of concrete in auto-desiccation, the others reproducing the storing conditions of concrete in desiccation. Auto-desiccation (measuring relative humidity at balance) and desiccation (measuring mass losses) have been showed. Microcracks and shrinkage strains have been measured. It has been showed that auto-desiccation microcracks proving in HSC or VHSC don't question the durability. Microcracks, as for permeability, do not develop between 28 days and one year. On the contrary, desiccation microcracks observed in HSC and VHSC, increase with transport properties between 28 days and 1.5 year. Thus, a bulk concrete is always more durable than a cover concrete. At last, the good influence of increase of curing of 1 to 28 days on the transport of all concretes has been emphasized. (author)

  5. Development of high performance and low radio activation concrete material for concrete cask

    Shirai, Koji; Sonobe, Ryoji

    2005-01-01

    For the realization of the long-term storage of the nuclear spent fuel with the concrete cask technology, a low radio activation high performance concrete was developed, which contains extremely small quantity of Eu and Co and assures enough heat-resistance and durability for degradation. Firstly, the activation analysis was performed to estimate the allowable content limit of their quantities according to the rules issued by Japanese government for determining the classification of the radioactive waste. Secondly, various candidate materials were sampled and irradiated to find out the activation level. As a result, as the optimum concrete mix, the combination of limestone and white fused alumina aggregates with fry-ash was chosen. Moreover, the basic characteristics of the candidate concrete (workability, strength under high temperature, heat conductivity and so on) were evaluated, and the thermal cracking test was executed with hollow cylinders. Finally, the developed concrete material seems to be suitable for the long-term use of concrete cask considering the low activation, high heat resistance and durability during storage. (author)

  6. Effect of elevated temperature on the properties of silica fume and recycled rubber-filled high strength concretes (RHSC

    Magda I. Mousa

    2017-04-01

    The results obtained show high resistance to fire with increasing SF content up to 20% replacement of cement. Additional improvement was obtained with using dolomite and 3% of recycled rubber (2 mm, 5 mm.

  7. Effect of Elevated Temperature on Mechanical Assets of Metakaolin Base Steel Fiber Reinforced Concrete

    Vijay Anand, M.; Ibrahim, Azmi; Patil, Anand A.; Muthu, K. U.

    2017-06-01

    The fact of vast usage of concrete leads to important problems regarding its design and preparation of eco-friendly to obtain an economic cost of the product on varieties of time periods. Conventional ordinary Portland concrete may not able to meet its functional requisites as it found inconsistency in high temperature. The exposing of concrete structure to elevated temperature may be in case of rocket launching space ships, nuclear power plants. In this experiment, to enhance the high temperature resistance, pozzolanic materials and steel fibres are added to preserve the strength characteristics of concrete structure. In this analysis, the pozzolanic admixture MK is used as partial replacement of cementatious materials. The volume fraction of steel fibre is varied 0.25%, 0.5%, 0.75% and 1% by preserving MK as stationary for 10% replacement of cement. The strength parameters of concrete such as compressive strength, split tensile strength and flexural strength are studied.

  8. Testing program for concrete at temperatures to 8940K

    Naus, D.J.; Oland, C.B.; Robinson, G.C.

    1981-01-01

    A test program was conducted to define the variations in mechanical properties of a limestone aggregate concrete and a lightweight insulating concrete exposed to elevated temperatures. Four test series were conducted: (1) unconfined compression; (2) shear; (3) rebar bond; and (4) sustained loading (creep). Tests results are presented

  9. Creep and creep recovery of concrete subjected to triaxial compressive stresses at elevated temperature

    Ohnuma, Hiroshi; Abe, Hirotoshi

    1979-01-01

    In order to design rationally the vessels made of prestressed concrete for nuclear power stations and to improve the accuracy of high temperature creep analysis, the Central Research Institute of Electric Power Industry had carried out the proving experiments with scale models. In order to improve the accuracy of analysis, it is important to grasp the creep behavior of the concrete subjected to triaxial compressive stresses at high temperature as the basic property of concrete, because actual prestressed concrete vessels are in such conditions. In this paper, the triaxial compression creep test at 60 deg. C using the concrete specimens with same mixing ratio as the scale models is reported. The compressive strength of the concrete at the age of 28 days was 406 kg/cm 2 , and the age of the concrete at the time of loading was 63 days. Creep and creep recovery were measured for 5 months and 2 months, respectively. The creep of concrete due to uniaxial compression increased with temperature rise, and the creep strain at 60 deg. C was 2.54 times as much as that at 20 deg. C. The effective Poisson's ratio in triaxial compression creep was 0.15 on the average, based on the creep strain due to uniaxial compression at 60 deg. C. The creep recovery rate in high temperature, triaxial compression creep was 33% on the average. (Kako, I.)

  10. Concrete for PCRV's: Mechanical properties at elevated temperatures and residual mechanical behaviour after triaxial preloading

    Aschl, H.; Moosecker, W.

    1979-01-01

    During the lifetime of reactor vessels stress states will change as a result of changes in loading and heating, shrinkage and creep. For the design of prestressed concrete reactor vessels information is required about the behaviour of concrete under multiaxial short- and long-term loading at elevated temperatures. Therefore, tests were carried out at the Institut fuer Massivbau of the Technical University of Munich to study the properties of mass concrete under uniaxial loading at 353 K. Additionally, biaxial creep of concrete up to 368 K was investigated. Some of the uniaxial test specimens were sealed with a copper foil to avoid drying. The concrete contained calzite gravel. The thermal expansion coefficient of predried concrete was 9.5 x 10 -6 , of sealed concrete 13.6 x 10 -6 and of unsealed concrete 13.2 x 10 -6 . The modulus of elasticity at 353 K (393 K) was reduced by 10 (13)% for sealed and by 15 (22)% for unsealed specimens. Total shrinkage deformations of heated concrete were 190 to 225 microstrains for sealed and 250 to 350 microstrains for unsealed specimens. Creep deformations were highly dependent upon temperature being about 3 times higher at 353 K for sealed and unsealed concrete. (orig.)

  11. Concrete for PCRVs: strength of concrete under triaxial loading and creep at elevated temperatures

    Linse, D.; Aschl, H.; Stoeckl, S.

    1975-01-01

    To provide detailed information for the calculation of prestressed concrete reactor vessels, investigations of the behaviour of concrete under multiaxial loading and on creep at elevated temperatures were made at the Institut fuer Massivbau of the Technical University of Munich. The strength of concrete under triaxial compression is dependent on the stress ratio. The less the stresses differ from hydrostatic compression the more strength increases. Triaxial compression increases very much the deformability of concrete. Plastic deformations of +-10% and more (all stresses compression, but not equal, strains compression or tension) are possible without large cracks. The creep deformations are considerably dependent on the temperature. Creep at 80 0 C is about three to four times higher than at 20 0 C. The Poisson's ratio of creep at elevated temperature seems to be bigger than at normal temperatures at a rate of loading of 35% and 50% of the ultimate strength. (Auth.)

  12. Low velocity impact behaviour of ultra high strength concrete panels

    Ultra high strength concrete; panel; drop weight test; impact analysis;. ABAQUS. 1. Introduction. Ultra high strength concrete ... Knight (2012) investigated the dynamic behaviour of steel fibre reinforced concrete plates under impact loading with ...

  13. Behaviour of a pre-stressed concrete pressure-vessel subjected to a high temperature gradient; Comportement d'un caisson en beton precontraint soumis a un gradient de temperature eleve

    Dubois, F [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Bonvalet, Ch; Dawance, G; Marechal, J C [Centre Experimental de Recherches et d' Etudes du Batiment et des Travaux Publics (CEBTP), 76 - Harfleur (France)

    1965-07-01

    After a review of the problems presented by pressure-vessels for atomic reactors (shape of the vessel, pressures, openings, foundations, etc.) the advantages of pre-stressed concrete vessels with respect to steel ones are given. The use of pre-stressed concrete vessels however presents many difficulties connected with the properties of concrete. Thus, because of the absence of an exact knowledge of the material, it is necessary to place a sealed layer of steel against the concrete, to have a thermal insulator or a cooling circuit for limiting the deformations and stresses, etc. It follows that the study of the behaviour of pre-stressed concrete and of the vessel subjected- to a high temperature gradient can yield useful information. A one-tenth scale model of a pre-stressed concrete cylindrical vessel without any side openings and without a base has been built. Before giving a description of the tests the authors consider some theoretical aspects concerning 'scale model-actual structure' similitude conditions and the calculation of the thermal and mechanical effects. The pre-stressed concrete model was heated internally by a 'pyrotenax' element and cooled externally by a very strong air current. The concrete was pre-stressed using horizontal and vertical cables held at 80 kg/cm{sup 2}; the thermal gradient was 160 deg. C. During the various tests, measurements were made of the overall and local deformations, the changes in water content, the elasticity modulus, the stress and creep of the cables and the depths of the cracks. The overall deformations observed are in line with thermal deformation theories and the creep of the cables attained 20 to 30 per cent according to their position relative to the internal surface. The dynamic elasticity modulus decreased by half but the concrete keeps its good mechanical properties. Finally, cracks 8 to 12 cm deep and 2 to 3 mms wide appeared in that part of the concrete which was not pre-stressed. The results obtained make it

  14. Behaviour of a pre-stressed concrete pressure-vessel subjected to a high temperature gradient; Comportement d'un caisson en beton precontraint soumis a un gradient de temperature eleve

    Dubois, F. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Bonvalet, Ch.; Dawance, G.; Marechal, J.C. [Centre Experimental de Recherches et d' Etudes du Batiment et des Travaux Publics (CEBTP), 76 - Harfleur (France)

    1965-07-01

    After a review of the problems presented by pressure-vessels for atomic reactors (shape of the vessel, pressures, openings, foundations, etc.) the advantages of pre-stressed concrete vessels with respect to steel ones are given. The use of pre-stressed concrete vessels however presents many difficulties connected with the properties of concrete. Thus, because of the absence of an exact knowledge of the material, it is necessary to place a sealed layer of steel against the concrete, to have a thermal insulator or a cooling circuit for limiting the deformations and stresses, etc. It follows that the study of the behaviour of pre-stressed concrete and of the vessel subjected- to a high temperature gradient can yield useful information. A one-tenth scale model of a pre-stressed concrete cylindrical vessel without any side openings and without a base has been built. Before giving a description of the tests the authors consider some theoretical aspects concerning 'scale model-actual structure' similitude conditions and the calculation of the thermal and mechanical effects. The pre-stressed concrete model was heated internally by a 'pyrotenax' element and cooled externally by a very strong air current. The concrete was pre-stressed using horizontal and vertical cables held at 80 kg/cm{sup 2}; the thermal gradient was 160 deg. C. During the various tests, measurements were made of the overall and local deformations, the changes in water content, the elasticity modulus, the stress and creep of the cables and the depths of the cracks. The overall deformations observed are in line with thermal deformation theories and the creep of the cables attained 20 to 30 per cent according to their position relative to the internal surface. The dynamic elasticity modulus decreased by half but the concrete keeps its good mechanical properties. Finally, cracks 8 to 12 cm deep and 2 to 3 mms wide appeared in that part of the concrete which was not pre-stressed. The

  15. Temperature field in concrete when in contact with hot liquids

    Andrade Lima, F.R. de.

    1981-09-01

    In an HCDA (Hypothetical Core Disruptive Accident) it is postulated that liquid metal coolants and core materials come in contact with the retaining concrete structure. A mathematical model and an associated computer program was previously developed to describle the transient heat and mass transfer in the concrete. Implementations on the original program-USINT- are included to consider the variations of the thermal conductivity as a function of the temperature. Also a subroutine - PLOTTI - is incorporated to the program for the plotting of the results. The new program - USINTG - is used to calculate the temperature and pressure fields and the water released from concrete structures during a sodium leak simulation and with the concrete structures in contact with liquid sodium. No consideration about chemical reactions involving the sodium when in contact with concrete is considered. (Author) [pt

  16. Freezing temperature protection admixture for Portland cement concrete

    1996-10-01

    A number of experimental admixtures were compared to Pozzutec 20 admixture for their ability to protect fresh concrete from freezing and for increasing the rate of cement hydration at below-freezing temperatures. The commercial accelerator and low-te...

  17. Ultra high performance concrete dematerialization study

    NONE

    2004-03-01

    Concrete is the most widely used building material in the world and its use is expected to grow. It is well recognized that the production of portland cement results in the release of large amounts of carbon dioxide, a greenhouse gas (GHG). The main challenge facing the industry is to produce concrete in an environmentally sustainable manner. Reclaimed industrial by-proudcts such as fly ash, silica fume and slag can reduce the amount of portland cement needed to make concrete, thereby reducing the amount of GHGs released to the atmosphere. The use of these supplementary cementing materials (SCM) can also enhance the long-term strength and durability of concrete. The intention of the EcoSmart{sup TM} Concrete Project is to develop sustainable concrete through innovation in supply, design and construction. In particular, the project focuses on finding a way to minimize the GHG signature of concrete by maximizing the replacement of portland cement in the concrete mix with SCM while improving the cost, performance and constructability. This paper describes the use of Ductal{sup R} Ultra High Performance Concrete (UHPC) for ramps in a condominium. It examined the relationship between the selection of UHPC and the overall environmental performance, cost, constructability maintenance and operational efficiency as it relates to the EcoSmart Program. The advantages and challenges of using UHPC were outlined. In addition to its very high strength, UHPC has been shown to have very good potential for GHG emission reduction due to the reduced material requirements, reduced transport costs and increased SCM content. refs., tabs., figs.

  18. Microstructure of high-strength foam concrete

    Just, A.; Middendorf, B.

    2009-01-01

    Foam concretes are divided into two groups: on the one hand the physically foamed concrete is mixed in fast rotating pug mill mixers by using foaming agents. This concrete cures under atmospheric conditions. On the other hand the autoclaved aerated concrete is chemically foamed by adding aluminium powder. Afterwards it is cured in a saturated steam atmosphere. New alternatives for the application of foam concretes arise from the combination of chemical foaming and air curing in manufacturing processes. These foam concretes are new and innovative building materials with interesting properties: low mass density and high strength. Responsible for these properties are the macro-, meso- and microporosity. Macropores are created by adding aluminium powder in different volumes and with different particle size distributions. However, the microstructure of the cement matrix is affected by meso- and micropores. In addition, the matrix of the hardened cement paste can be optimized by the specific use of chemical additives for concrete. The influence of aluminium powder and chemical additives on the properties of the microstructure of the hardened cement matrices were investigated by using petrographic microscopy as well as scanning electron microscopy.

  19. Concrete mixtures with high-workability for ballastless slab tracks

    Olga Smirnova

    2017-01-01

    The concrete track-supporting layer and the monolithic concrete slab of ballastless track systems are made in-situ. For this reason the concrete mixtures of high workability should be used. Influence of the sand kind, the quartz microfiller fineness and quantity as well as quantity of superplasticizer on workability of fresh concrete and durability of hardened concrete is shown. The compositions of the high-workability concrete mixtures with lower consumption of superplasticizer are developed...

  20. High performance repairing of reinforced concrete structures

    Iskhakov, I.; Ribakov, Y.; Holschemacher, K.; Mueller, T.

    2013-01-01

    Highlights: ► Steel fibered high strength concrete is effective for repairing concrete elements. ► Changing fibers’ content, required ductility of the repaired element is achieved. ► Experiments prove previously developed design concepts for two layer beams. -- Abstract: Steel fibered high strength concrete (SFHSC) is an effective material that can be used for repairing concrete elements. Design of normal strength concrete (NSC) elements that should be repaired using SFHSC can be based on general concepts for design of two-layer beams, consisting of SFHSC in the compressed zone and NSC without fibers in the tensile zone. It was previously reported that such elements are effective when their section carries rather large bending moments. Steel fibers, added to high strength concrete, increase its ultimate deformations due to the additional energy dissipation potential contributed by fibers. When changing the fibers’ content, a required ductility level of the repaired element can be achieved. Providing proper ductility is important for design of structures to dynamic loadings. The current study discusses experimental results that form a basis for finding optimal fiber content, yielding the highest Poisson coefficient and ductility of the repaired elements’ sections. Some technological issues as well as distribution of fibers in the cross section of two-layer bending elements are investigated. The experimental results, obtained in the frame of this study, form a basis for general technological provisions, related to repairing of NSC beams and slabs, using SFHSC.

  1. A Real-Time Temperature Data Transmission Approach for Intelligent Cooling Control of Mass Concrete

    Peng Lin

    2014-01-01

    Full Text Available The primary aim of the study presented in this paper is to propose a real-time temperature data transmission approach for intelligent cooling control of mass concrete. A mathematical description of a digital temperature control model is introduced in detail. Based on pipe mounted and electrically linked temperature sensors, together with postdata handling hardware and software, a stable, real-time, highly effective temperature data transmission solution technique is developed and utilized within the intelligent mass concrete cooling control system. Once the user has issued the relevant command, the proposed programmable logic controllers (PLC code performs all necessary steps without further interaction. The code can control the hardware, obtain, read, and perform calculations, and display the data accurately. Hardening concrete is an aggregate of complex physicochemical processes including the liberation of heat. The proposed control system prevented unwanted structural change within the massive concrete blocks caused by these exothermic processes based on an application case study analysis. In conclusion, the proposed temperature data transmission approach has proved very useful for the temperature monitoring of a high arch dam and is able to control thermal stresses in mass concrete for similar projects involving mass concrete.

  2. Fibras de polipropileno e sua influência no comportamento de concretos expostos a altas temperaturas: revisão Polypropylene fibers and their influence on the behavior of concretes exposed to high temperatures: review

    A. L. de Castro

    2011-03-01

    Full Text Available A resistência ao fogo de um elemento estrutural de concreto é avaliada pelo intervalo de tempo em que o elemento continua a desempenhar suas funções sob condições de alta temperatura. Normalmente acredita-se que o concreto tem uma excelente durabilidade frente à ação do fogo, entretanto, na prática, a estabilidade desse material é prejudicada pelas altas temperaturas e os elementos de concreto têm apresentado danos excessivos ou mesmo rupturas catastróficas sob tais condições. Quando expostos às altas temperaturas, materiais à base de cimento sofrem mudanças físico-químicas que prejudicam suas propriedades mecânicas e comprometem sua resistência à transferência de calor. Embora as características térmicas de um concreto de alta resistência sejam semelhantes aos de um concreto convencional, este material possui uma maior sensibilidade às altas temperaturas devido à sua porosidade reduzida, apresentando uma maior perda relativa das propriedades mecânicas e a ocorrência do lascamento explosivo na faixa de temperatura entre 100 ºC e 400 ºC. O lascamento pode ser evitado pela introdução de fibras de polipropileno na composição do concreto: quando fundidas e parcialmente absorvidas pela matriz de cimento, as fibras criam uma rede de canais permeável que permite a migração dos gases para o exterior, reduzindo a pressão nos poros do material e, conseqüentemente, eliminando a possibilidade de ocorrência do lascamento explosivo. Assim, no presente artigo, uma revisão sobre o comportamento de concretos expostos às altas temperaturas, bem como a influência da fibra de polipropileno sobre este comportamento foi realizada, direcionando-se para os concretos aplicados na construção civil.The fire resistance of a structural concrete is evaluated by the time length that the element keeps performing its functions under high temperature conditions. It is usually believed that the concrete has an excellent durability

  3. Thermal and Hygric Expansion of High Performance Concrete

    J. Toman; R. Černý

    2001-01-01

    The linear thermal expansion coefficient of two types of high performance concrete was measured in the temperature range from 20 °C to 1000 °C, and the linear hygric expansion coefficient was determined in the moisture range from dry material to saturation water content. Comparative methods were applied for measurements of both coefficients. The experimental results show that both the effect of temperature on the values of linear thermal expansion coefficients and the effect of moisture on th...

  4. Concrete mixtures with high-workability for ballastless slab tracks

    Olga Smirnova

    2017-10-01

    Full Text Available The concrete track-supporting layer and the monolithic concrete slab of ballastless track systems are made in-situ. For this reason the concrete mixtures of high workability should be used. Influence of the sand kind, the quartz microfiller fineness and quantity as well as quantity of superplasticizer on workability of fresh concrete and durability of hardened concrete is shown. The compositions of the high-workability concrete mixtures with lower consumption of superplasticizer are developed. The results of the research can be recommended for high performance concrete of ballastless slab track.

  5. The possibility of using high strength reinforced concrete

    Miura, Nobuaki

    1991-01-01

    There is recently much research about and developments in reinforced concrete using high strength concrete and reinforcement. As a result, some high-rise buildings and nuclear buildings have been constructed with such concrete. Reinforced concrete will be stronger in the future, but there is a limit to its strength defined by the character of the materials and also by the character of the reinforced concrete members made of the concrete and reinforcement. This report describes the merits and demerits of using high strength reinforced concrete. (author)

  6. Initial rheological description of high performance concretes

    Alessandra Lorenzetti de Castro

    2006-12-01

    Full Text Available Concrete is defined as a composite material and, in rheological terms, it can be understood as a concentrated suspension of solid particles (aggregates in a viscous liquid (cement paste. On a macroscopic scale, concrete flows as a liquid. It is known that the rheological behavior of the concrete is close to that of a Bingham fluid and two rheological parameters regarding its description are needed: yield stress and plastic viscosity. The aim of this paper is to present the initial rheological description of high performance concretes using the modified slump test. According to the results, an increase of yield stress was observed over time, while a slight variation in plastic viscosity was noticed. The incorporation of silica fume showed changes in the rheological properties of fresh concrete. The behavior of these materials also varied with the mixing procedure employed in their production. The addition of superplasticizer meant that there was a large reduction in the mixture's yield stress, while plastic viscosity remained practically constant.

  7. High flow concrete 2; Koryudo konkurito 2

    Naruse, Hiroyasu [Mitsubishi Materials Corp., Tokyo (Japan)

    1998-09-10

    Hashimoto et al. compared U-type repletion test that evaluation method of the consistency in design of mix of high workable concrete was proposed as a repletion test with the box test, and it was examined, and it had clarified the difference between the behavior in the test by the analysis of the shearing strain speed by the visualization as the technique, and the important proposal was done, when the evaluation method would be divided in future. Anchors showed that it analyzed it in order to quantitatively evaluate separating resistance-ness of the coarse aggregate, with model and proposes the analysis method on separating resistance-ness of high workable concrete according to the original model, and that the correlation is high. In the future, further examination was carried out on aggregate shapes and lees aggregate amount, etc. and intended to propose the technique which could be analyzed more high-precise. Branch pines examined the effect of the fineness modulus in addition to factors such as real width rate and particle size of a fine aggregate in the technique in which researchers have proposed the setting of class aggregate amount in the top in search of the optimum value. It can be expected that it is future effectively utilized, because it is a proposed equation which sufficiently added characteristics of the Tsumugi aggregate. Temple areas found and proposed that viscosity and of the optimum mortar minute in design of mix in high workable concrete for the dam for the downward flow hour differed from the case in which the 20 mm aggregate was used on the design of mix technique in using the 40 mm aggregate. It is the research which considered the application of high workable concrete to the concrete for the dam, and it seems to be very much useful to future popularization. (translated by NEDO)

  8. Properties of concrete containing different type of waste materials as aggregate replacement exposed to elevated temperature – A review

    Ghadzali, N. S.; Ibrahim, M. H. W.; Sani, M. S. H. Mohd; Jamaludin, N.; Desa, M. S. M.; Misri, Z.

    2018-04-01

    Concrete is the chief material of construction and it is non-combustible in nature. However, the exposure to the high temperature such as fire can lead to change in the concrete properties. Due to the higher temperature, several changes in terms of mechanical properties were observed in concrete such as compressive strength, modulus of elasticity, tensile strength and durability of concrete will decrease significantly at high temperature. The exceptional fire-proof achievement of concrete is might be due to the constituent materials of concrete such as its aggregates. The extensive use of aggregate in concrete will leads to depletion of natural resources. Hence, the use of waste and other recycled and by-product material as aggregates replacements becomes a leading research. This review has been made on the utilization of waste materials in concrete and critically evaluates its effects on the concrete performances during the fire exposure. Therefore, the objective of this paper is to review the previous search work regarding the concrete containing waste material as aggregates replacement when exposed to elevated temperature and come up with different design recommendations to improve the fire resistance of structures.

  9. Behaviour of high-strength concrete incorporating ground ...

    106. Behaviour of high-strength concrete incorporating ground granulated blast furnace slag at high-temperature. Comportement à haute température du béton à haute résistance à base de laitier granulé de haut fourneau. Imene Saadi*1 & Abdelaziz Benmarce2. 1Laboratoire Matériaux Géométraux et Environnement, ...

  10. Behavior of prestressed concrete subjected to low temperatures and cyclic loading

    Berner, D.E.

    1984-01-01

    Concrete has exhibited excellent behavior in cryogenic containment vessels for several decades under essentially static conditions. Tests were conducted to determine the response of prestressed lightweight concrete subjected to high-intensity cyclic loading and simultaneous cryogenic thermal shock, simulating the relatively dynamic conditions encountered offshore or in seismic areas. Lightweight concrete has several attractive properties for cryogenic service including: (1) very low permeability, (2) good strain capacity, (3) relatively low thermal conductivity, and (4) a low modulus of elasticity. Experimental results indicated that the mechanical properties of plain lightweight concrete significantly increase with moisture content at low temperatures, while cyclic loading fatigue effects are reduced at low temperatures. Also, tests on uniaxially and on biaxially prestressed lightweight concrete both indicate that the test specimens performed well under severe cyclic loading and cryogenic thermal shock with only moderate reduction in flexural stiffness. Supplementary tests conducted in this study indicate that conventionally reinforced concrete degrades significantly faster than prestressed concrete when subjected to cyclic loading and thermal shock

  11. effects of temperature levels and concrete cover thickness

    HP USER

    With the knowledge of the temperature of the fire, thickness of concrete cover, residual strength of ... the structural behavior during fires by a careful inspection of the ... visual or physical damage is negligible; and Alonso[9] in the same vein said ...

  12. Behavior of Concrete Cylinders Strengthened with a Basalt-FRP and Subjected to Mechanical Loads and Elevated Temperatures

    Tulendinov, T.; Zesers, A.; Tamužs, V.

    2017-09-01

    Concrete samples were manufactured and strengthened with a basalt FRP (BFRP) using two kinds of winding patterns (spiral and tight). The efficiency of common and temperature-resistant epoxy binders were studied. Some of the samples were encased in an external concrete shell for an additional protection of the FRP reinforcement during heating. Both plain and polypropylene-microfiber-reinforced concretes were used for the external casing. Stress-strain relations of the samples before and after heating were obtained. The effects of high temperatures on the integrity of concrete samples with a BFRP reinforcement was investigated.

  13. A comprehensive investigation into the effect of temperature variation on the mechanical properties of sustainable concrete

    El Mir Abdulkader

    2017-01-01

    Full Text Available Minimizing the production energy and resources consumption are the key principle for engineering sustainability. In the case of concrete structures, this concept can be achieved by the use of materials in the most efficient way considering in the mix design the optimal mechanical and durability properties. The substitution of ordinary Portland cement for other supplementary cementitious materials is assessing the possibility of enhancing the sustainability and decreasing the environmental impact of concrete. Mass concrete is rich in cementitious materials which results in high temperature within the concrete, hence several hazards such as cracking or temperature differences between the interior and the surface of concrete could be prevented. An experimental study evaluated on several one cubic meter sized concrete elements in which during the primary phase of hydration, the temperature variation is recorded in several location offsets with respect to time. Thermal variations results are analyzed in accordance with the cement type, CO2 emission production of cement, compressive strength, water tightness, drying shrinkage and rapid chloride migration coefficient. The results indicate that slag cement CEM III/B 32.5, that incorporates highest amount of slag, ensured improved mechanical, thermal and durability properties in comparison with ordinary Portland cement CEM I 32.5.

  14. Kinetic Hydration Heat Modeling for High-Performance Concrete Containing Limestone Powder

    Xiao-Yong Wang

    2017-01-01

    Full Text Available Limestone powder is increasingly used in producing high-performance concrete in the modern concrete industry. Limestone powder blended concrete has many advantages, such as increasing the early-age strength, reducing the setting time, improving the workability, and reducing the heat of hydration. This study presents a kinetic model for modeling the hydration heat of limestone blended concrete. First, an improved hydration model is proposed which considers the dilution effect and nucleation effect due to limestone powder addition. A degree of hydration is calculated using this improved hydration model. Second, hydration heat is calculated using the degree of hydration. The effects of water to binder ratio and limestone replacement ratio on hydration heat are clarified. Third, the temperature history and temperature distribution of hardening limestone blended concrete are calculated by combining hydration model with finite element method. The analysis results generally agree with experimental results of high-performance concrete with various mixing proportions.

  15. Mechanical properties of high-strength concrete

    Mokhtarzadeh, Alireza

    This report summarizes an experimental program conducted to investigate production techniques and mechanical properties of high strength concrete in general and to provide recommendations for using these concretes in manufacturing precast/prestressed bridge girders. Test variables included total amount and composition of cementitious material (portland cement, fly ash, and silica fume), type and brand of cement, type of silica fume (dry densified and slurry), type and brand of high-range water-reducing admixture, type of aggregate, aggregate gradation, maximum aggregate size, and curing. Tests were conducted to determine the effects of these variables on changes in compressive strength and modulus of elasticity over time, splitting tensile strength, modulus of rupture, creep, shrinkage, and absorption potential (as an indirect indicator of permeability). Also investigated were the effects of test parameters such as mold size, mold material, and end condition. Over 6,300 specimens were cast from approximately 140 mixes over a period of 3 years.

  16. Novel Concrete Temperature Monitoring Method Based on an Embedded Passive RFID Sensor Tag.

    Liu, Yongsheng; Deng, Fangming; He, Yigang; Li, Bing; Liang, Zhen; Zhou, Shuangxi

    2017-06-22

    This paper firstly introduces the importance of temperature control in concrete measurement, then a passive radio frequency identification (RFID) sensor tag embedded for concrete temperature monitoring is presented. In order to reduce the influences of concrete electromagnetic parameters during the drying process, a T-type antenna is proposed to measure the concrete temperature at the required depth. The proposed RFID sensor tag is based on the EPC generation-2 ultra-high frequency (UHF) communication protocol and operates in passive mode. The temperature sensor can convert the sensor signals to corresponding digital signals without an external reference clock due to the adoption of phase-locked loop (PLL)-based architecture. Laboratory experimentation and on-site testing demonstrate that our sensor tag embedded in concrete can provide reliable communication performance in passive mode. The maximum communicating distance between reader and tag is 7 m at the operating frequency of 915 MHz and the tested results show high consistency with the results tested by a thermocouple.

  17. Concrete Waste Recycling Process for High Quality Aggregate

    Ishikura, Takeshi; Fujii, Shin-ichi

    2008-01-01

    Large amount of concrete waste generates during nuclear power plant (NPP) dismantling. Non-contaminated concrete waste is assumed to be disposed in a landfill site, but that will not be the solution especially in the future, because of decreasing tendency of the site availability and natural resources. Concerning concrete recycling, demand for roadbeds and backfill tends to be less than the amount of dismantled concrete generated in a single rural site, and conventional recycled aggregate is limited of its use to non-structural concrete, because of its inferior quality to ordinary natural aggregate. Therefore, it is vital to develop high quality recycled aggregate for general uses of dismantled concrete. If recycled aggregate is available for high structural concrete, the dismantling concrete is recyclable as aggregate for industry including nuclear field. Authors developed techniques on high quality aggregate reclamation for large amount of concrete generated during NPP decommissioning. Concrete of NPP buildings has good features for recycling aggregate; large quantity of high quality aggregate from same origin, record keeping of the aggregate origin, and little impurities in dismantled concrete such as wood and plastics. The target of recycled aggregate in this development is to meet the quality criteria for NPP concrete as prescribed in JASS 5N 'Specification for Nuclear Power Facility Reinforced Concrete' and JASS 5 'Specification for Reinforced Concrete Work'. The target of recycled aggregate concrete is to be comparable performance with ordinary aggregate concrete. The high quality recycled aggregate production techniques are assumed to apply for recycling for large amount of non-contaminated concrete. These techniques can also be applied for slightly contaminated concrete dismantled from radiological control area (RCA), together with free release survey. In conclusion: a technology on dismantled concrete recycling for high quality aggregate was developed

  18. Comparison of Thermal Stability of Dry High-strength Concrete and Wet High-strength Concrete

    Musorina, Tatiana; Katcay, Aleksandr; Selezneva, Anna; Kamskov, Victor

    2018-03-01

    High-strength concrete is a modern material, which occupies it`s own niche on the construction material market. It is applicable in a large-scale high-rise construction, particularly an underground construction is a frequently used solution for a space saving. Usually underground structure is related to a wet usage environment. Though not all properties of the high-strength concrete are investigated to the full extent. Under adverse climatic conditions of the Russian Federation one of the most important properties for constructional materials is a thermal capacity. Therefore, the main purpose of the paper is to compare a thermal capacity of the high-strength concrete in humid conditions and a thermal capacity of the high-strength concrete in dry operational condition. During the study dependency between thermal capacity and design wall thickness and ambient humidity has to be proven with two experiments. As a result the theoretical relation between thermal capacity characteristic - thermal inertia and wall thickness and ambient humidity was confirmed by the experimental data. The thermal capacity of a building is in direct ratio to the construction thickness. It follows from the experiments and calculations that wet high-strength concrete has less thermal stability.

  19. Self-flowing underwater concrete mixtures for high rise structures

    Yousri, K.M.

    2005-01-01

    Placement of conventional concrete mixtures in underwater construction results in a high percentage of material loss due to washout of cement paste. This paper presents the influence of anti washout admixture (AWA) on various properties of concrete. Eleven self-flowing concrete (SFC) mixtures using type II cement were proportioned. A combination of low water cement (w/c), high cement contents, anti washout admixtures, fly ash, and silica fume were used to enhance the resistance of fresh concrete to washout. The concrete mixtures proportioned to be highly flow able, self-leveling and cohesive. The water-cementitious materials ratios ranged between 0.356 and 0.392 which correspond a typical underwater concrete mixture. The concrete mixtures were tested for slump, slump flow, washout resistance and compressive strength. The compressive strength of each concrete mixture cast underwater was determined at 3, 7, 28 days and compared with the compressive strength of the same concrete mixture cast in normal condition (in air). Test results indicated that the use of an AWA facilitates the production of flow able concrete mixtures with the added benefit of lower washout loss. Concrete mixture proportioned using Type II cement and fly ash at level of replacement of 15% was found to develop self flowing concrete with better fresh and hardened properties and more resistant to washout. The self-flowing underwater concretes developed a 28-day compressive strengths ranging from 20 to 28 MPa

  20. EFFECT OF ELEVATED TEMPERATURE ON COMPRESSIVE STRENGTH OF FIBER REINFORCED CONCRETE

    Prashant shinkar*, Prof. Deepak kakade, Dr.A.P.Wadekar

    2017-01-01

    This paper deals with the mechanical properties of concrete with steel fibers subjected to temperatures up to 500°C. Now a day concrete are being used extensively in the construction that might be subjected to elevated temperatures. The behavior of concrete structures at elevated temperatures is of significant importance in predicting the safety of structures in response to certain accidents or particular service conditions. Concrete mixes of M 50 have been designed along with steel fibers fr...

  1. Thermal and Hygric Expansion of High Performance Concrete

    J. Toman

    2001-01-01

    Full Text Available The linear thermal expansion coefficient of two types of high performance concrete was measured in the temperature range from 20 °C to 1000 °C, and the linear hygric expansion coefficient was determined in the moisture range from dry material to saturation water content. Comparative methods were applied for measurements of both coefficients. The experimental results show that both the effect of temperature on the values of linear thermal expansion coefficients and the effect of moisture on the values of linear hygric expansion coefficients are very significant and cannot be neglected in practical applications.

  2. Research on early-warning index of the spatial temperature field in concrete dams.

    Yang, Guang; Gu, Chongshi; Bao, Tengfei; Cui, Zhenming; Kan, Kan

    2016-01-01

    Warning indicators of the dam body's temperature are required for the real-time monitoring of the service conditions of concrete dams to ensure safety and normal operations. Warnings theories are traditionally targeted at a single point which have limitations, and the scientific warning theories on global behavior of the temperature field are non-existent. In this paper, first, in 3D space, the behavior of temperature field has regional dissimilarity. Through the Ward spatial clustering method, the temperature field was divided into regions. Second, the degree of order and degree of disorder of the temperature monitoring points were defined by the probability method. Third, the weight values of monitoring points of each regions were explored via projection pursuit. Forth, a temperature entropy expression that can describe degree of order of the spatial temperature field in concrete dams was established. Fifth, the early-warning index of temperature entropy was set up according to the calculated sequential value of temperature entropy. Finally, project cases verified the feasibility of the proposed theories. The early-warning index of temperature entropy is conducive to the improvement of early-warning ability and safety management levels during the operation of high concrete dams.

  3. Predicting temperature drop rate of mass concrete during an initial cooling period using genetic programming

    Bhattarai, Santosh; Zhou, Yihong; Zhao, Chunju; Zhou, Huawei

    2018-02-01

    Thermal cracking on concrete dams depends upon the rate at which the concrete is cooled (temperature drop rate per day) within an initial cooling period during the construction phase. Thus, in order to control the thermal cracking of such structure, temperature development due to heat of hydration of cement should be dropped at suitable rate. In this study, an attempt have been made to formulate the relation between cooling rate of mass concrete with passage of time (age of concrete) and water cooling parameters: flow rate and inlet temperature of cooling water. Data measured at summer season (April-August from 2009 to 2012) from recently constructed high concrete dam were used to derive a prediction model with the help of Genetic Programming (GP) software “Eureqa”. Coefficient of Determination (R) and Mean Square Error (MSE) were used to evaluate the performance of the model. The value of R and MSE is 0.8855 and 0.002961 respectively. Sensitivity analysis was performed to evaluate the relative impact on the target parameter due to input parameters. Further, testing the proposed model with an independent dataset those not included during analysis, results obtained from the proposed GP model are close enough to the real field data.

  4. Numerical Model of High Strength Concrete

    Wang, R. Z.; Wang, C. Y.; Lin, Y. L.

    2018-03-01

    The purpose of this paper is to present a three-dimensional constitutive model based on the concept of equivalent uniaxial strain. closed Menetrey-Willam (CMW) failure surfaces which combined with Menetrey-Willam meridian and the cap model are introduced in this paper. Saenz stress-strain model is applied and adjusted by the ultimate strength parameters from CMW failure surface to reflect the latest stress or strain condition. The high strength concrete (HSC) under tri-axial non-proportional loading is considered and the model in this paper performed a good prediction.

  5. Analysis of production factors in high performance concrete

    Gilberto Carbonari

    2003-01-01

    Full Text Available The incorporation of silica fume and superplasticizers in high strength and high performance concrete, along with a low water-cement ratio, leads to significant changes in the workability and the energy needed to homogenize and compact the concrete. Moreover, several aspects of concrete production that are not critical for conventional concrete are important for high strength concrete. This paper will discuss the need for controlling the humidity of the aggregates, optimizing the mixing sequence used in the fabrication, and the slump loss. The application of a silica fume concrete in typical building columns will be analyzed considering the required consolidation, the variability of the material strength within the structural element and the relation between core and molded specimen strength. Comparisons will also be made with conventional concrete.

  6. The characteristics of ultra-high performance concrete and cracking behavior of reinforced concrete tensile specimens

    H.A. Rahdar

    2016-09-01

    Full Text Available The tensile behavior of concrete depends on some factors such as member dimensions, reinforcement ratio, diameter of rebar, strength and elasticity modulus of material. In this research the experimental method is used to examine the characteristics and the behavior of ultra-high performance concrete on the tensile behavior of concrete members reinforced by steel rebar. The results show that increasing the rebar cover on diameter rebar ratio (C/d increases the initial stiffening before the cracking stage in concrete. Also, by increasing of reinforcement ratio the cracking space decreased.

  7. Development of Nano technology in High Performance Concrete

    Nima Farzadnia; Abang Abdullah Abang Ali; Ramazan Demirboga; Demirboga, R.

    2011-01-01

    Concrete is the most widely used building material all around the world which has been undergoing many changes aligned with technological advancement. The most recent available type of concrete is high performance concrete which is produced by employing different admixtures both chemical and mineral to enhance mechanical properties and durability. Recently, technology has made it easy for scientist to study nano sized admixtures and their effect on microstructure of concrete. This paper reviews nano particles in cement composites and how they can improve different properties of concrete. (author)

  8. Engineering Performance of High Strength Concrete Containing Steel Fibre Reinforcement

    Md Azree Othuman Mydin

    2013-09-01

    Full Text Available The development and utilization of the high strength concrete in the construction industry have been increasing rapidly. Fiber reinforced concrete is introduced to overcome the weakness of the conventional concrete because concrete normally can crack under a low tensile force and it is known to be brittle. Steel fibre is proved to be the popular and best combination in the high strength concrete to result the best in the mechanical and durability properties of high strength concrete with consideration of curing time, steel fibre geometry, concrete grade and else more. The incorporation of steel fibre in the mortar mixture is known as steel fibre reinforced concrete have the potential to produce improvement in the workability, strength, ductility and the deformation of high strength concrete. Besides that, steel fibre also increases the tensile strength of concrete and improves the mechanical properties of the steel fibre reinforced concrete. The range for any high strength concrete is between 60MPa-100MPa. Steel fibre reinforced concrete which contains straight fibres has poorer physical properties than that containing hooked end stainless steel fibre due to the length and the hooked steel fibre provide a better effective aspects ratio. Normally, steel fibre tensile strength is in the range of 1100MPa-1700MPa. Addition of less steel fibre volumes in the range of 0.5% to 1.0% can produce better increase in the flexural fatigue strength. The strength can be increased with addition of steel fibre up to certain percentage. This paper will review and present some basic properties of steel fibre reinforced concrete such as mechanical, workability and durability properties.

  9. Slippage of steel in high and normal strength concrete

    Ahmed, K.; Siddiqi, Z.A.; Yousaf, M.

    2007-01-01

    Composite action of any reinforced concrete member is only possible if sufficient bond strength exists between steel reinforcing bars and concrete, which can adequately transfer shear stress between them. Bond strength is a function of compressive strength of concrete and hence high strength concrete has higher bond strength (1-2). Therefore required development length can be reduced. In order to investigate the effect of development length on bond stress and slip relationships, experimental investigation was carried out. In this experimentation 24 pull-out samples of high strength concrete and normal strength concrete were casted and tested. The results of this investigation revealed that by increasing the development length from 5db to 10db bond strength increases for both high and normal strength concrete as shown in Figure 11, 12 and 13. However in case of normal strength concrete increase in bond strength is more compared to that in high strength concrete as it is clear from Figure 11 and Figure 13. The increase in bond strength is observed even at 10db development length but the extent is less for 19 mm than 16 mm bars as shown in Figure 12 and Figure 13. This is in agreement with the earlier findings of Chen et al (3) and Harajli et al (1). However in case of HSC the total slippage at 10db is 50% greater than at 5db. This may be due to the fact that more no of concrete keys participate in resisting the slippage. (author)

  10. Testing of High Thermal Cycling Stability of Low Strength Concrete as a Thermal Energy Storage Material

    Chao Wu

    2016-09-01

    Full Text Available Concrete has the potential to become a solution for thermal energy storage (TES integrated in concentrating solar power (CSP systems due to its good thermal and mechanical properties and low cost of material. In this study, a low strength concrete (C20 is tested at high temperatures up to 600 °C. Specimens are thermally cycled at temperatures in the range of 400–300 °C, 500–300 °C, and 600–300 °C, which TES can reach in operation. For comparison, specimens also cycled at temperature in the range of 400–25 °C (room temperature, 500–25 °C, and 600–25 °C. It is found from the test results that cracks are not observed on the surfaces of concrete specimens until the temperature is elevated up to 500 °C. There is mechanical deterioration of concrete after exposure to high temperature, especially to high thermal cycles. The residual compressive strength of concrete after 10 thermal cycles between 600 °C and 300 °C is about 58.3%, but the specimens remain stable without spalling, indicating possible use of low strength concrete as a TES material.

  11. Concrete creep at transient temperature: constitutive law and mechanism

    Chern, J.C.; Bazant, Z.P.; Marchertas, A.H.

    1985-01-01

    A constitutive law which describes the transient thermal creep of concrete is presented. Moisture and temperature are two major parameters in this constitutive law. Aside from load, creep, cracking, and thermal (shrinkage) strains, stress-induced hygrothermal strains are also included in the analysis. The theory agrees with most types of test data which include basic creep, thermal expansion, shrinkage, swelling, creep at cyclic heating or drying, and creep at heating under compression or bending. Examples are given to demonstrate agreement between the theory and the experimental data. 15 refs., 6 figs

  12. Properties, sustainability and elevated temperature behavior of concrete containing Portland limestone cement

    El-Hawary, Moetaz; Ahmed, Mahmoud

    2017-09-01

    The utilization of some type of cheap filler as partial cement replacement is an effective way of improving concrete sustainability. With the recent trends to reduce water to cement ratio and improve compaction, there is no enough space or water for complete hydration of cement. This means that actually, a portion of mixed cement acts as expensive filler. Replacing this portion with cheaper filler that requires less energy to produce is, therefore, beneficial. Crushed limestone is the most promising filler. This work is to investigate the effect of the amount of limestone fillers on the sustainability and the fresh and mechanical properties of the resulting concrete. A rich mix is designed with a low water/cement ratio of 0.4. Lime is introduced as a replacement percentage of cement. Ratios of 0, 10, 20 and 30% were used. Slump, compressive strength, specific gravity and water absorption are evaluated for every mix. In addition, the effect of the amount of lime on the residual strength of concrete subjected to elevated temperatures is also investigated. Samples are subjected to six different temperature stations of 20, 100, 200, 300, 500 and 700°C for six hours before being cooled and subsequently tested for compressive strength and specific gravity. Sustainability of the tested mixes is evaluated through reductions in the emitted carbon dioxide, energy and reduction in cost. Based on the annual use of concrete in Kuwait, the sustainability benefits resulting from the use of limestone filler in Kuwait are evaluated and assessed. The paper is concluded with the recommendation of the use of 15% limestone filler as partial cement replacement where the properties and the behavior under high temperature of the resulting concrete are almost the same as those of conventional concrete with considerable cost and sustainability benefits.

  13. Achieving Mixtures of Ultra-High Performance Concrete

    Mircea POPA

    2013-07-01

    Full Text Available Ultra-High Performance Concrete (UHPC is a relatively new concrete. According to [11] UHPC is that concrete which features compressive strength over C100/115 class. Up to this point standards for this type of concrete were not adopted, although its characteristic strength exceeds those specified in [33]. Its main property is high compressive strength. This provides the possibility of reducing the section of elements (beams or columns made of this type of concrete, while the load capacity remains high. The study consists in blending mixtures of UHPC made of varying proportions of materials. The authors have obtained strengths of up to 160 MPa. The materials used are: Portland cement, silica fume, quartz powder, steel fibers, superplasticiser, sand and crushed aggregate for concrete - andesite.

  14. Equipment and Protocols for Quasi-Static and Dynamic Tests of Very-High-Strength Concrete (VHSC) and High-Strength High-Ductility Concrete (HSHDC)

    2016-08-01

    Concrete (VHSC) and High-Strength High-Ductility Concrete (HSHDC) En gi ne er R es ea rc h an d D ev el op m en t Ce nt er Brett A...Very-High-Strength Concrete (VHSC) and High-Strength High-Ductility Concrete (HSHDC) Brett A. Williams, Robert D. Moser, William F. Heard, Carol F...equipment and protocols for tests of both very-high-strength concrete (VHSC) and high- strength high-ductility concrete (HSHDC) to predict blast

  15. Behavior of hybrid high-strength fiber reinforced concrete slab-column connections under the effect of high tempera

    Reham H. Ahmed

    2016-04-01

    Full Text Available Concrete can be modified to perform in a more ductile form by the addition of randomly distributed discrete fibers in the concrete matrix. The combined effect of the addition of two types of fibers (steel fiber and polypropylene fiber with different percentages to concrete matrix, which is called hybrid effect is currently under investigation worldwide. The current research work presents the conducted experimental program to observe the behavior of hybrid high strength reinforced concrete slab-column connections under the effect of high temperature. For this purpose, ten slab-column connections were casted and tested. The experimental program was designed to investigate the effect of different variables such as concrete mixture, column location and temperature fighting system. All specimens were exposed to a temperature of 500 °C for duration of two hours. To observe the effect of each variable, specimens were divided into four groups according to the studied parameters. The test results revealed that using hybrid high strength concrete HFHSC produced more strength in punching failure compared with high strength concrete HSC when exposed to elevated temperature. Fighting by air had higher initial crack load compared with that for without fighting and fighting by water. On the other hand, fighting by water decreased the ultimate load.

  16. Creep behavior of concrete under multiaxial stress at elevated temperature, 1

    Ohgishi, Sakichi; Kishitani, Koichi; Oshima, Hisaji; Kosaka, Yoshio; Shiire, Toyokazu.

    1977-01-01

    The field of application of concrete structures is extended to that of low and high temperature and dynamic loading. The creep of concrete has been studied under one, two or three axis compression below 80 deg. C, and this is owing to the design standards for PCPVs in Europe and America adopting the design temperature below 80 deg. C. However, the design temperature for PCPVs is expected to rise, and the high temperature, three axis creep of concrete must be studied to examine the physical property and thermodynamics in wide range of temperature, such as free energy gradient, the behavior of adsorbed water molecules, and activating energy, which control the creep. In this study, various problematical points in the development of a testing apparatus which can make three axis compression creep test from 300 to 500 deg. C were pointed out, and the measures to solve them were investigated. The creep testing apparatus was actually manufactured for trial, and the performance was tested. The design conditions for the testing apparatus, the problems in the manufacture, the selection of materials, and the results of trial are described. As for the pressurizing media, oil is used up to 180 deg. C, mercury up to 300 deg. C, and molten anatomical alloy in nitrogen atmosphere up to 500 deg. C. Buried Ailtech gauges can be used for the strain measurement up to 320 deg. C. The leakpreventing method for various penetrations was developed successfully. (Kako, I.)

  17. Reduction of the Early Autogenous Shrinkage of High Strength Concrete

    Drago Saje

    2015-01-01

    Full Text Available The results of a laboratory investigation on the early autogenous shrinkage of high strength concrete, and the possibilities of its reduction, are presented. Such concrete demonstrates significant autogenous shrinkage, which should, however, be limited in the early stages of its development in order to prevent the occurrence of cracks and/or drop in the load-carrying capacity of concrete structures. The following possibilities for reducing autogenous shrinkage were investigated: the use of low-heat cement, a shrinkage-reducing admixture, steel fibres, premoistened polypropylene fibres, and presoaked lightweight aggregate. In the case of the use of presoaked natural lightweight aggregate, with a fraction from 2 to 4 mm, the early autogenous shrinkage of one-day-old high strength concrete decreased by about 90%, with no change to the concrete's compressive strength in comparison with that of the reference concrete.

  18. Shock characterization of an ultra-high strength concrete

    Erzar, B.; Pontiroli, C.; Buzaud, E.

    2016-01-01

    Nowadays, the design of protective structures may imply ultra-high performance concretes. These materials present a compressive strength 5 times higher than standard concretes. However, few reliable data on the shock response of such materials are available in the literature. Thus, a characterization of an ultra-high strength concrete has been conducted by means of hydrostatic and triaxial tests in the quasi-static regime, and plate impact experiments for shock response. Data have been gathered up to 6 GPa and a simple modelling approach has been applied to get a reliable representation of the shock compression of this concrete. (authors)

  19. Feasibility analysis of ultra high performance concrete for prestressed concrete bridge applications.

    2010-07-01

    UHPC is an emerging material technology in which concrete develops very high : compressive strengths and exhibits improved tensile strength and toughness. A : comprehensive literature and historical application review was completed to determine the :...

  20. High filler concrete using fly ash. Chloride penetration and microstructure

    Valcke, S.L.A.; Polder, R.B.; Nijland, T.G.; Leegwater, G.A.; Visser, J.H.M.; Bigaj-van Vliet, A.J.

    2012-01-01

    Most high filler concrete studies are based on relatively high contents of powder (cement + filler) (>400 kg m-3). This paper aims to increase the total fly ash content relative to the clinker content, while simultaneously minimizing the total powder content in the concrete to values lower than 300

  1. High filler concrete using fly ash : Chloride penetration and microstructure

    Valcke, S.L.A.; Polder, R.B.; Nijland, T.G.; Leegwater, G.A.; Visser, J.H.M.; Bigaj-van Vliet, A.J.

    2012-01-01

    Most high filler concrete studies are based on relatively high contents of powder (cement + filler) (>400 kg m-3). This paper aims to increase the total fly ash content relative to the clinker content, while simultaneously minimizing the total powder content in the concrete to values lower than 300

  2. Research on curing behavior of concrete with anti-frost admixtures at subzero temperature

    Ionov, Yulian; Kramar, Ludmila; Kirsanova, Alena; Kolegova, Irina

    2017-01-01

    The purpose of this paper is research on curing behavior of cold-weather concrete with anti-frost admixtures. During the study derivative thermal and X-ray phase analyses were performed and tests were carried out according to the standard GOST technique. The research results obtained reveal the peculiarities of cement hydration and concrete curing at subzero temperatures. The influence of subzero temperatures and anti-frost admixtures on hydrated phases of hardened cement paste and concrete strength formation was studied. It is found that cold-weather concrete does not cure at subzero temperatures, but when defrosting it attains 80 to 85% of its grade strength by the 28th day. Concrete achieves its grade strength when curing in normal conditions in 60 days only. Freezing concrete with anti-frost admixtures results in increase of calcium hydroxide content in hardened cement paste immediately when produced and has increased tendency of concrete to carbonation.

  3. Ground Glass Pozzolan in Conventional, High, and Ultra-High Performance Concrete

    Tagnit-Hamou Arezki; Zidol Ablam; Soliman Nancy; Deschamps Joris; Omran Ahmed

    2018-01-01

    Ground-glass pozzolan (G) obtained by grinding the mixed-waste glass to same fineness of cement can act as a supplementary-cementitious material (SCM), given that it is an amorphous and a pozzolanic material. The G showed promising performances in different concrete types such as conventional concrete (CC), high-performance concrete (HPC), and ultra-high performance concrete (UHPC). The current paper reports on the characteristics and performance of G in these concrete types. The use of G pro...

  4. Effect of Surrogate Aggregates on the Thermal Conductivity of Concrete at Ambient and Elevated Temperatures

    Tae Sup Yun

    2014-01-01

    Full Text Available The accurate assessment of the thermal conductivity of concretes is an important part of building design in terms of thermal efficiency and thermal performance of materials at various temperatures. We present an experimental assessment of the thermal conductivity of five thermally insulated concrete specimens made using lightweight aggregates and glass bubbles in place of normal aggregates. Four different measurement methods are used to assess the reliability of the thermal data and to evaluate the effects of the various sensor types. The concrete specimens are also assessed at every 100°C during heating to ~800°C. Normal concrete is shown to have a thermal conductivity of ~2.25 W m−1 K−1. The surrogate aggregates effectively reduce the conductivity to ~1.25 W m−1 K−1 at room temperature. The aggregate size is shown not to affect thermal conduction: fine and coarse aggregates each lead to similar results. Surface contact methods of assessment tend to underestimate thermal conductivity, presumably owing to high thermal resistance between the transducers and the specimens. Thermogravimetric analysis shows that the stages of mass loss of the cement paste correspond to the evolution of thermal conductivity upon heating.

  5. Temperature measurement and damage detection in concrete beams exposed to fire using PPP-BOTDA based fiber optic sensors

    Bao, Yi; Hoehler, Matthew S.; Smith, Christopher M.; Bundy, Matthew; Chen, Genda

    2017-10-01

    In this study, Brillouin scattering-based distributed fiber optic sensor is implemented to measure temperature distributions and detect cracks in concrete structures subjected to fire for the first time. A telecommunication-grade optical fiber is characterized as a high temperature sensor with pulse pre-pump Brillouin optical time domain analysis (PPP-BODTA), and implemented to measure spatially-distributed temperatures in reinforced concrete beams in fire. Four beams were tested to failure in a natural gas fueled compartment fire, each instrumented with one fused silica, single-mode optical fiber as a distributed sensor and four thermocouples. Prior to concrete cracking, the distributed temperature was validated at locations of the thermocouples by a relative difference of less than 9%. The cracks in concrete can be identified as sharp peaks in the temperature distribution since the cracks are locally filled with hot air. Concrete cracking did not affect the sensitivity of the distributed sensor but concrete spalling broke the optical fiber loop required for PPP-BOTDA measurements.

  6. Influence of bagasse ash and recycled concrete aggregate on hardened properties of high-strength concrete

    P. Rattanachu

    2018-04-01

    Full Text Available This research aimed to use of bagasse ash as a cement replacement in high-strength recycled aggregate concrete (HS-RAC. Crushed limestone was replaced with 100% recycled concrete aggregate (RCA and the ground bagasse ash (GBA was used to partially replace ordinary Portland cement (OPC at 20, 35 and 50%wt of binder to cast HS-RAC. The results indicated that the replacing of crushed limestone with RCA had a negative impact on the properties of the concrete. Increasing the amount of GBA in HS-RAC resulted in a decrease in density and an increase in the volume of permeable pore space. The concrete mixtures prepared with 20%wt GBA replacement of OPC promoted greater the compressive strength than the conventional concrete (CT concrete at 90 days or more. HS-RAC with GBA (up to 50% was more durable in terms of chloride ion penetration resistance, although it had lower compressive strength than the CT concrete.

  7. Temperature and mixing effects on electrical resistivity of carbon fiber enhanced concrete

    Chang, Christiana; Song, Gangbing; Gao, Di; Mo, Y L

    2013-01-01

    In this paper, the effect of temperature and mixing procedure on the electrical resistivity of carbon fiber enhanced concrete is investigated. Different compositions of concrete containing varying concentrations of carbon fiber into normal and self-consolidating concrete (SCC) were tested under DC electrical loading over the temperature range −10 to 20 °C. The electrical resistivity of the bulk samples was calculated and compared against temperature. It was observed that there is an inverse exponential relationship between resistivity and temperature which follows the Arrhenius relationship. The bulk resistivity decreased with increasing fiber concentration, though data from SCC indicates a saturation limit beyond which electrical resistivity begins to drop. The activation energy of the bulk electrically conductive concrete was calculated and compared. While SCC exhibited the lowest observed electrical resistance, the activation energy was similar amongst SCC and surfactant enhanced concrete, both of which were lower than fiber dispersed in normal concrete. (paper)

  8. Time-Dependent Behavior of Shrinkage Strain for Early Age Concrete Affected by Temperature Variation

    Qin, Yu; Yi, Zhijian; Wang, Weina; Wang, Di

    2017-01-01

    Shrinkage has been proven to be an important property of early age concrete. The shrinkage strain leads to inherent engineering problems, such as cracking and loss of prestress. Atmospheric temperature is an important factor in shrinkage strain. However, current research does not provide much attention to the effect of atmospheric temperature on shrinkage of early age concrete. In this paper, a laboratory study was undertaken to present the time-dependent shrinkage of early age concrete under...

  9. Concrete

    2015-01-01

    Concrete is a component of coherent transition between a concrete base and a wooden construction. The structure is based on a quantity of investigations of the design possibilities that arise when combining digital fabrication tools and material capacities. Through tangible experiments the project...... specific for this to happen. And the knowledge and intention behind the drawing becomes specialised through the understanding of the fabrication processes and their affect on the materials.The structure Concrete is a result of a multi-angled kerf series in ash wood and a concrete base. The ash wood is cut...... using a 5-axis CNC router with a thin saw blade attached. The programming of the machining results in variations of kerfs that lets the ash wood twist into unique shapes.The shapes of the revolving ash ribbons continue into the concrete creating a cohesive shape. The form for the concrete itself is made...

  10. Creep and Shrinkage of High Strength Concretes: an Experimental Analysis

    Berenice Martins Toralles carbonari

    2002-01-01

    Full Text Available The creep and shrinkage behaviour of high strength silica fume concretes is significantly different from that of conventional concretes. In order to represent the proper time-dependent response of the material in structural analysis and design, these aspects should be adequately quantified. This paper discusses an experimental setup that is able to determine the creep and shrinkage of concrete from the time of placing. It also compares different gages that can be used for measuring the strains. The method is applied to five different concretes in the laboratory under controlled environmental conditions. The phenomena that are quantified can be classified as basic shrinkage, drying shrinkage, basic creep and drying creep. The relative importance of these mechanisms in high strength concrete will also be presented.

  11. Temperature field in the bottom of concrete reactor vessel; Temperaturno polje u podu betonskog reaktorskog suda

    Jovasevic, V; Tosic, D; Zaric, S; Maksimovic, Lj [Boris Kidric Institute of nuclear sciences, Vinca, Belgrade (Yugoslavia)

    1969-07-01

    This paper contains detailed scheme of reactor bottom vessel made of concrete and the results of calculated relevant temperature distribution. Method applied for calculation is described taking into account all relevant factors and assuming that thermal conductivity of concrete is homogeneous and independent of temperature.

  12. Testing program for determining the mechanical properties of concrete to temperatures of 6210C

    Oland, C.B.; Naus, D.J.; Robinson, G.C.

    1980-01-01

    Concrete temperatures in a Liquid Metal Fast Breeder Reactor (LMFBR) in excess of normal code limits can result from postulated large sodium spills in equipment cells. Elevated temperature concrete property data which may have application for providing a basis for the design and evaluation of such postulated accident conditions is limited. Data thus needed to be developed commensurate with LMFBR plant applications for critical physical and mechanical concrete properties under prototypic thermal accident conditions. A test program was conducted to define the variations in physical and mechanical properties of a limestone aggregate concrete and a lightweight insulating concrete exposed to elevated temperatures. Five test series were conducted: unconfined compression, shear, rebar bond, sustained loading (creep), and thermal properties. Testing procedures for determining the mechanical properties of concrete from ambient to 621 0 C (1150 0 F) are described. Ther thermal properties tests are discussed in a separate paper which is also being presented at this conference

  13. STRENGTH OF NANOMODIFIED HIGH-STRENGTH LIGHTWEIGHT CONCRETES

    NOZEMTСEV Alexandr Sergeevich

    2013-02-01

    Full Text Available The paper presents the results of research aimed at development of nanomodified high-strength lightweight concrete for construction. The developed concretes are of low average density and high ultimate compressive strength. It is shown that to produce this type of concrete one need to use hollow glass and aluminosilicate microspheres. To increase the durability of adhesion between cement stone and fine filler the authors offer to use complex nanodimensinal modifier based on iron hydroxide sol and silica sol as a surface nanomodifier for hollow microspheres. It is hypothesized that the proposed modifier has complex effect on the activity of the cement hydration and, at the same time increases bond strength between filler and cement-mineral matrix. The compositions for energy-efficient nanomodified high-strength lightweight concrete which density is 1300…1500 kg/m³ and compressive strength is 40…65 MPa have been developed. The approaches to the design of high-strength lightweight concrete with density of less than 2000 kg/m³ are formulated. It is noted that the proposed concretes possess dense homogeneous structure and moderate mobility. Thus, they allow processing by vibration during production. The economic and practical implications for realization of high-strength lightweight concrete in industrial production have been justified.

  14. Characterization of High Density Concrete by Ultrasonic Goniometer

    Suhairy Sani; Mohamad Pauzi Ismail; Noor Azreen Masenwat; Nasharuddin Isa; Mohamad Haniza Mahmud

    2014-01-01

    This paper described the results of ultrasonic goniometer measurements on concrete containing hematite. Local hematite stones were used as aggregates to produce high density concrete for application in X-and gamma shielding. Concrete cube samples (150 mm x 150 mm x 150 mm) containing hematite as coarse aggregates were prepared by changing mix ratio, water to cement ratio (w/ c) and types of fine aggregate. All samples were cured in water for 7 days. After 28 days of casting, the concrete cubes were then cut into small size of about 10 mm x 20 mm x 30 mm so that it can be fitted into goniometer specimen holder. From this measurement, longitudinal, shear and surface Rayleigh waves in the concrete can be determined. The measurement results are explained and discussed. (author)

  15. Supersymmetry at high temperatures

    Das, A.; Kaku, M.

    1978-01-01

    We investigate the properties of Green's functions in a spontaneously broken supersymmetric model at high temperatures. We show that, even at high temperatures, we do not get restoration of supersymmetry, at least in the one-loop approximation

  16. Static reliability of concrete structures under extreme temperature, radiation, moisture and force loading

    Stepanek, P.; Stastnik, S.; Salajka, V.; Hradil, P.; Skolar, J.; Chlanda, V.

    2003-01-01

    The contribution presents some aspects of the static reliability of concrete structures under temperature effects and under mechanical loading. The mathematical model of a load-bearing concrete structure was performed using the FEM method. The temperature field and static stress that generated states of stress were taken into account. A brief description of some aspects of evaluation of the reliability within the primary circuit concrete structures is stated. The knowledge of actual physical and mechanical characteristics and chemical composition of concrete were necessary for obtaining correct results of numerical analysis. (author)

  17. Monitoring of temperature fatigue failure mechanism for polyvinyl alcohol fiber concrete using acoustic emission sensors.

    Li, Dongsheng; Cao, Hai

    2012-01-01

    The applicability of acoustic emission (AE) techniques to monitor the mechanism of evolution of polyvinyl alcohol (PVA) fiber concrete damage under temperature fatigue loading is investigated. Using the temperature fatigue test, real-time AE monitoring data of PVA fiber concrete is achieved. Based on the AE signal characteristics of the whole test process and comparison of AE signals of PVA fiber concretes with different fiber contents, the damage evolution process of PVA fiber concrete is analyzed. Finally, a qualitative evaluation of the damage degree is obtained using the kurtosis index and b-value of AE characteristic parameters. The results obtained using both methods are discussed.

  18. A study on the estimation method of internal stresses caused by the difference of thermal expansion coefficients between concrete and reinforcement at elevated temperatures

    Kanazu, Tsutomu

    1998-01-01

    When a reinforced concrete member is exposed to high temperature conditions over 100degC, tensile strain occurs in the concrete and compressive strain occurs in reinforcements due to a difference of thermal expansion coefficients between concrete and reinforcement. Its mechanism is the same as that of restrained stress caused by drying shrinkage of concrete; tensile stress occurs in the concrete because drying shrinkage strain is restrained by reinforcements, but there is a different point that the phenomenon at a high temperature condition includes the change of mechanical properties of concrete and reinforcement. In the study, the phenomenon is measured in the experiments and is clarified quantitatively. Moreover, the estimation method, which is derived from expanding the equation of average strain of reinforcement in the CEB Design Manual, is suggested and is verified by the comparison with the experimental results. (author)

  19. Danish Investigations on Silica Fume Concretes at Elevated Temperatures

    Hertz, Kristian Dahl

    1992-01-01

    Describes fire tests in which the increased risk of explosive spalling of concrete densified by silica fume was first discovered. Further results are discussed from tests to define appropriate limits of silica fume content and to develop a new concrete for slender column units. Observations are m...... are made about circumstances under which superplasticizing additives in concrete gave rise to the development of toxic gases....

  20. Concrete pedestals for high-performance semiconductor production equipment

    Vogen, Wayne; Franklin, Craig L.; Morneault, Joseph

    1999-09-01

    Concrete pedestals have many vibration and stiffness characteristics that make them a superior choice for sensitive semiconductor production equipment including scanners, scanning electron microscopes, focused ion beam millers and optical inspection equipment. Among the advantages of concrete pedestals are high inherent damping, monolithic construction that eliminates low stiffness joints common in steep pedestals, ability to reuse and ease of installation. Steel pedestals that have plates attached to the top of the frame are easily excited by acoustic excitation, especially in the range from 50 Hertz to 400 Hertz. Concrete pedestals do not suffer from this phenomenon because of the high mass and damping of the top surface.

  1. Very high cycle fatigue testing of concrete using ultrasonic cycling

    Karr, Ulrike; Schuller, Reinhard; Fitzka, Michael; Mayer, Herwig [Univ. of Natural Resources and Life Sciences, Vienna (Austria). Inst. of Physics and Materials Science; Denk, Andreas; Strauss, Alfred [Univ. of Natural Resources and Life Sciences, Vienna (Austria)

    2017-06-01

    The ultrasonic fatigue testing method has been further developed to perform cyclic compression tests with concrete. Cylindrical specimens vibrate in resonance at a frequency of approximately 20 kHz with superimposed compressive static loads. The high testing frequency allows time-saving investigations in the very high cycle fatigue regime. Fatigue tests were carried out on ''Concrete 1'' (compressive strength f{sub c} = 80 MPa) and ''Concrete 2'' (f{sub c} = 107 MPa) under purely compressive loading conditions. Experiments at maximum compressive stresses of 0.44 f{sub c} (Concrete 1) and 0.38 f{sub c} (Concrete 2) delivered specimen failures above 109 cycles, indicating that no fatigue limit exists for concrete below one billion load cycles. Resonance frequency, power required to resonate the specimen and second order harmonics of the vibration are used to monitor fatigue damage in situ. Specimens were scanned by X-ray computed tomography prior to and after testing. Fatigue cracks were produced by ultrasonic cycling in the very high cycle fatigue regime at interfaces of grains as well as in cement. The possibilities as well as limitations of ultrasonic fatigue testing of concrete are discussed.

  2. Design and evaluation of high-volume fly ash (HVFA) concrete mixes, report C : shear behavior of HVFA reinforced concrete.

    2012-10-01

    Concrete is the most widely used man-made material on the planet. Unfortunately, producing Portland cement generates carbon dioxide (a greenhouse gas) at roughly a pound for pound ratio. High-volume fly ash (HVFA) concrete concrete with at least ...

  3. Effect of step-wise change of stress and temperature on primary creep of concrete

    Furumura, Fukujiro; Abe, Takeo; Shinohara, Yasuji; Kim, Wha-Jung.

    1991-01-01

    The success of analyzing the behavior of concrete structures at elevated temperature greatly depends on how accurately certain mechanical properties, especially stress-strain curves, creep and thermal expansion, can be determined within wide temperature range. The importance of creep in the design of reinforced and prestressed concrete structures has been more recognized with the advent of the use of concrete at elevated temperature. The creep strain of concrete is affected by stress, time and temperature. The creep law which can predict the creep behavior under varying stress and temperature by using the experimental results of creep strain under constant stress and temperature is indispensable for analyzing the behavior of reinforced concrete structures under varying temperature. Accordingly the main purpose of this study is to clarify the primary creep behavior of concrete under varying stress and temperature. The cylindrical specimens, the testing procedure, the test results and the modified strain hardening law are reported. By using the modified strain hardening law, the primary creep behavior of concrete can be estimated better. (K.I.)

  4. Compressive behavior of steel fiber reinforced recycled aggregate concrete after exposure to elevated temperatures

    Chen, G. M.; He, Y. H.; Yang, H.; Chen, J. F.; Guo, Y.C.

    2014-01-01

    For sustainability considerations, the use of recycled aggregate in concrete has attracted many interests in the research community. One of the main concerns for using such concrete in buildings is its spalling in fire. This may be alleviated by adding steel fibers to form steel fiber reinforced recycled aggregate concrete (SFRAC). This paper presents an experimental investigation into the compressive properties of SFRAC cylinders after exposure to elevated temperatures, including the compres...

  5. Freeze/thaw phenomena in concrete at low temperatures

    Johannesson, Björn

    2007-01-01

    Freeze/thaw damage in concrete is by general practice concluded to be a problem that can be avoided by using air-entraining agents to develop an air bubble structure in the hardened concrete together with the use of a relatively low water to cement ratio in mix. This fact is true for inner damage...

  6. Protective design of critical infrastructure with high performance concretes

    Riedel, W.; Nöldgen, M.; Stolz, A.; Roller, C.

    2012-01-01

    Conclusions: High performance concrete constructions will allow innovative design solutions for critical infrastructures. Validation of engineering methods can reside on large and model scale experiments conducted on conventional concrete structures. New consistent impact experiments show extreme protection potential for UHPC. Modern FEM with concrete models and explicit rebar can model HPC and UHPC penetration resistance. SDOF and TDOF approaches are valuable design tools on local and global level. Combination of at least 2 out of 3 design methods FEM – XDOF- EXP allow reliable prediction and efficient innovative designs

  7. Highly durable and low permeable concrete for LLW facilities

    Yanagibashi, Kunio; Saito, Toshio; Odagawa, Masaro.

    1997-01-01

    Concrete used for LLW facilities is required to be highly durable. The authors evaluated concrete containing glycol ether derivatives and silica fume as admixtures. Compressive strength, diffusion coefficient of water, depth of accelerated carbonation, drying shrinkage, depth of chlorides penetration and resistance to freezing and thawing were investigated using concrete specimens. Compressive strength, depth of accelerated carbonation, diffusion coefficient of 137 Cs were investigated using mortar specimens before and after irradiation of gamma rays. Results showed that using glycol ether derivatives and silica fume was effective in improving the durability. (author)

  8. Fracture Energy of High-Strength Concrete in Compression

    Dahl, Henrik; Brincker, Rune

    is essential for understanding the fracture mechanism of concrete in compression. In this paper a series of tests is reported, carried out for the purpose of studying the fracture mechanical properties of concrete in compression. Including the measurement and study of the descending branch, a new experimental...... method has been used to investigate the influence of boundary conditions, loading rate, size effects and the influence of the strength on the fracture energy of high-strength concrete over the range 70 MPa to 150 MPa, expressed in nominal values....

  9. High performance concrete with blended cement

    Biswas, P.P.; Saraswati, S.; Basu, P.C.

    2012-01-01

    Principal objectives of the proposed project are two folds. Firstly, to develop the HPC mix suitable to NPP structures with blended cement, and secondly to study its durability necessary for desired long-term performance. Three grades of concrete to b considered in the proposed projects are M35, M50 and M60 with two types of blended cements, i.e. Portland slag cement (PSC) and Portland pozzolana cement (PPC). Three types of mineral admixtures - silica fume, fly ash and ground granulated blast furnace slag will be used. Concrete mixes with OPc and without any mineral admixture will be considered as reference case. Durability study of these mixes will be carried out

  10. APPLICATION OF SOFT COMPUTING TECHNIQUES FOR PREDICTING COOLING TIME REQUIRED DROPPING INITIAL TEMPERATURE OF MASS CONCRETE

    Santosh Bhattarai

    2017-07-01

    Full Text Available Minimizing the thermal cracks in mass concrete at an early age can be achieved by removing the hydration heat as quickly as possible within initial cooling period before the next lift is placed. Recognizing the time needed to remove hydration heat within initial cooling period helps to take an effective and efficient decision on temperature control plan in advance. Thermal properties of concrete, water cooling parameters and construction parameter are the most influencing factors involved in the process and the relationship between these parameters are non-linear in a pattern, complicated and not understood well. Some attempts had been made to understand and formulate the relationship taking account of thermal properties of concrete and cooling water parameters. Thus, in this study, an effort have been made to formulate the relationship for the same taking account of thermal properties of concrete, water cooling parameters and construction parameter, with the help of two soft computing techniques namely: Genetic programming (GP software “Eureqa” and Artificial Neural Network (ANN. Relationships were developed from the data available from recently constructed high concrete double curvature arch dam. The value of R for the relationship between the predicted and real cooling time from GP and ANN model is 0.8822 and 0.9146 respectively. Relative impact on target parameter due to input parameters was evaluated through sensitivity analysis and the results reveal that, construction parameter influence the target parameter significantly. Furthermore, during the testing phase of proposed models with an independent set of data, the absolute and relative errors were significantly low, which indicates the prediction power of the employed soft computing techniques deemed satisfactory as compared to the measured data.

  11. Concrete

    Kruse Aagaard, Anders

    2015-01-01

    Concrete is a component of coherent transition between a concrete base and a wooden construction. The structure is based on a quantity of investigations of the design possibilities that arise when combining digital fabrication tools and material capacities.Through tangible experiments the project discusses materiality and digitally controlled fabrications tools as direct expansions of the architect’s digital drawing and workflow. The project sees this expansion as an opportunity to connect th...

  12. Influence of temperature on strain monitoring of degradation in concrete containment buildings

    Ding, Y.; Jaffer, S.; Angell, P.

    2015-01-01

    Concrete containment buildings (CCBs) are important safety structures in a nuclear power plant (NPP). The CCBs can be made of reinforced and post-tensioned (P-T) concrete. Post-tensioning concrete induces compressive stresses, which have to be overcome for the concrete to crack under tensile loads. However, post-tensioned CCBs may undergo pre-stressing losses as they age, which could affect their performance under accident conditions. CANDU 6 reactor buildings contain grouted post-tensioned tendons as the primary reinforcement. The grouting of the tendons makes direct monitoring of pre-stressing losses via lift-off testing impossible. Therefore, instruments have been installed on an existing reactor building to measure and monitor strains and stresses in the concrete and the deformation of the concrete structure to detect aging degradation and indirectly evaluate the pre-stressing losses. However, the instrumentation readings are affected by temporary volume changes in the concrete caused by the influence of environmental factors, particularly temperature, on concrete. In this work, the focus is on developing an understanding of the effect of temperature on the interpretation of instrumentation data from a reactor building. Vibrating Wire Strain Gauge (VWSG) data has been analysed. The influence of concrete coefficient of thermal expansion and temperature distribution within the reactor building walls, on VWSG data, is discussed based on the analysis of the available instrumentation data and available numerical simulation results. The present study demonstrates that temperature distribution within the containment concrete has a significant impact on the VWSG measurements and the coefficient of thermal expansion of concrete is an important factor in the correction of VWSG data for thermal strain. It is recommended that VWSG data obtained over small temperature variations be considered for interpretation to assess pre-stressing losses. (authors)

  13. Effect of temperature on physical and mechanical properties of concrete containing silica fume

    Saad, M.; Hanna, G.B.; Abo-El-Enein, S.A.; Kotkata, M.F.

    1996-01-01

    Heat-resistant materials are usually used for structural purposes. The need for such building materials is particularly important in the chemical and metallurgical industries and for the thermal shieldings of nuclear power plants. Thus the effect of high temperatures on physical and mechanical properties of concrete was investigated. In this study ordinary Portland cement has been partially replaced by ratios of silica fume. The heat treatment temperature varied from 100 to 600 C by increments of 100 C for three hours without any load. Concrete specimens were treated at each temperature level. The specimens were heated under the same condition for each temperature level. Comparison between physical and mechanical properties during heat treatment were investigated. All specimens were moist-cured for 28 days after casting. Tests were carried out on specimens cooled slowly to room temperature after heating. Results of this investigation indicated that the replacement of ordinary Portland cement by 10% silica fume by weight improved the compressive strength by about 64.6%, but replacement of ordinary Portland cement by silica fume by ratios 20 and 30% improved the compressive strength by only 28% at 600 C. This could be attributed to the additional tobermorite gel (CSH phase) which formed due to the reaction of silica fume with Ca(OH) 2

  14. Durability properties of high volume fly ash self compacting concretes

    P. Dinakar; K.G. Babu; Manu Santhanam [Indian Institute of Technology, Chennai (India). Building Technology Division

    2008-11-15

    This paper presents an experimental study on the durability properties of self compacting concretes (SCCs) with high volume replacements of fly ash. Eight fly ash self compacting concretes of various strength grades were designed at desired fly ash percentages of 0, 10, 30, 50, 70 and 85%, in comparison with five different mixtures of normal vibrated concretes (NCs) at equivalent strength grades. The durability properties were studied through the measurement of permeable voids, water absorption, acid attack and chloride permeation. The results indicated that the SCCs showed higher permeable voids and water absorption than the vibrated normal concretes of the same strength grades. However, in acid attack and chloride diffusion studies the high volume fly ash SCCs had significantly lower weight losses and chloride ion diffusion.

  15. Ultra-high performance concrete : a state-of-the-art report for the bridge community.

    2013-06-01

    "The term Ultra-High Performance Concrete (UHPC) refers to a relatively new class of advanced cementitious : composite materials whose mechanical and durability properties far surpass those of conventional concrete. This : class of concrete has been ...

  16. Self compacting concrete incorporating high-volumes of fly ash

    Bouzoubaa, N. [Natural Resources Canada, Ottawa, ON (Canada). International Centre for Sustainable Development of Cement and Concrete; Lachemi, M. [Ryerson Polytechnic Univ., Toronto, ON (Canada). Dept. of Civil Engineering

    2004-07-01

    Self-compacting concrete (SCC) is now widely used in reinforced concrete structures. Fine materials such as fly ash ensure that the concrete has the necessary properties of high fluidity and cohesiveness. An experimental study was conducted in which 9 SCC mixtures and one control concrete were produced in order to evaluate SCC made with high-volumes of fly ash. The content of the cementitious materials remained constant at 400 kg/cubic metre, but the ratio of water to cementitious material ranged from 0.35 to 0.45. The viscosity and stability of the fresh concrete was determined for self-compacting mixtures of 40, 50 and 60 per cent Class F fly ash. The compressive strength and drying shrinkage were also determined for the hardened concretes. Results showed that the SCCs developed a 28-day compressive strength ranging from 26 to 48 MPa. It was concluded that high-volumes of Class F fly ash could offer the following advantages to an SCC: reduced construction time and labour cost; eliminate the need for vibration; reduce noise pollution; improve the filling capacity of highly congested structural members; and, ensure good structural performance. 19 refs., 8 tabs., 2 figs.

  17. A Review of the Effects of Elevated Temperature on Concrete Materials and Structures

    Naus, D.J.; Graves, H.L. III

    2006-01-01

    Concrete's properties are more complex than those of most materials because not only is concrete a composite material whose constituents have different properties, but its properties depend upon moisture and porosity. Exposure of concrete to elevated temperature affects its mechanical and physical properties. Elements could distort and displace, and, under certain conditions, the concrete surfaces could spall due to the buildup of steam pressure. Because thermally-induced dimensional changes, loss of structural integrity, and release of moisture and gases resulting from the migration of free water could adversely affect plant operations and safety, a complete understanding of the behavior of concrete under long-term elevated-temperature exposure as well as both during and after a thermal excursion resulting from a postulated design-basis accident condition is essential for reliable design evaluations and assessments of nuclear power plant structures. As the properties of concrete change with respect to time and the environment to which it is exposed, an assessment of the effects of concrete aging is also important in performing safety evaluations. The effects of elevated temperature on Portland cement concretes and constituent materials are summarized, design codes and standards identified, and considerations for elevated temperature service noted. (authors)

  18. High temperature structural sandwich panels

    Papakonstantinou, Christos G.

    High strength composites are being used for making lightweight structural panels that are being employed in aerospace, naval and automotive structures. Recently, there is renewed interest in use of these panels. The major problem of most commercial available sandwich panels is the fire resistance. A recently developed inorganic matrix is investigated for use in cases where fire and high temperature resistance are necessary. The focus of this dissertation is the development of a fireproof composite structural system. Sandwich panels made with polysialate matrices have an excellent potential for use in applications where exposure to high temperatures or fire is a concern. Commercial available sandwich panels will soften and lose nearly all of their compressive strength temperatures lower than 400°C. This dissertation consists of the state of the art, the experimental investigation and the analytical modeling. The state of the art covers the performance of existing high temperature composites, sandwich panels and reinforced concrete beams strengthened with Fiber Reinforced Polymers (FRP). The experimental part consists of four major components: (i) Development of a fireproof syntactic foam with maximum specific strength, (ii) Development of a lightweight syntactic foam based on polystyrene spheres, (iii) Development of the composite system for the skins. The variables are the skin thickness, modulus of elasticity of skin and high temperature resistance, and (iv) Experimental evaluation of the flexural behavior of sandwich panels. Analytical modeling consists of a model for the flexural behavior of lightweight sandwich panels, and a model for deflection calculations of reinforced concrete beams strengthened with FRP subjected to fatigue loading. The experimental and analytical results show that sandwich panels made with polysialate matrices and ceramic spheres do not lose their load bearing capability during severe fire exposure, where temperatures reach several

  19. Strain measurements of temperatures up to 3000C in a concrete structure

    Schittenhelm, Ch.

    1975-10-01

    Strain measurements in a concrete structure representing a cylindrical section of a Prestressed Concrete Reactor Vessel with hot liner, were made. In order to interpret these values in terms of strain and stress in a three dimensional structure, the gauge characteristics as well as the material date of the concrete have to be known in great detail. The paper deals with the performance of different gauges embedded in small concrete blocks and others of the same type embedded in the test ring. Temperature resistance, long-time performance, electrical drift and hysteresis of the gauges were investigated. (author)

  20. Comparison on Heat of Hydration between Current Concrete for NPP and High Fluidity Concrete including Pozzolan Powders

    Noh, Jea Myoung; Cho, Myung Sug

    2010-01-01

    Nuclear power plant (NPP) concrete structures are exposed to many construction factors that lower the quality of concrete due to densely packed reinforcements and heat of hydration since they are mostly constructed with mass concrete. The concrete currently being used in Korean NPPs is mixed with Type I cement and fly ash. However, there is a demand to improve the performance of concrete with reduced heat of hydration and superior constructability. Many advantages such as improving workability and durability of concrete and decreasing heat of hydration are introduced by replacing cement with pozzolan binders. Therefore, the manufacturing possibility of high fluidity concrete should be investigated through applying multi-component powders blended with pozzolan binders to the concrete structure of NPPs, while the researches on properties, characteristic of hydration, durability and long-term behavior of high fluidity concrete using multi-component cement should be carried out. High fluidity concrete which is made using portland cement and pozzlonan powders such as fly ash and blast furnace slag has better properties on heat of hydration than the concrete currently in use for NPPs

  1. Behaviour of high-strength concrete incorporating ground ...

    of tests were carried out on concrete incorporating Ground Granulated Blast Furnace Slag (GGBFS) of “Mittal ... mechanical properties by using the existing materials on the local market and HSC ..... general shape of the curves whether at 28 days ... Figure.7. Residual compressive strength as a function of temperature.

  2. High temperature refrigerator

    Steyert, W.A. Jr.

    1978-01-01

    A high temperature magnetic refrigerator is described which uses a Stirling-like cycle in which rotating magnetic working material is heated in zero field and adiabatically magnetized, cooled in high field, then adiabatically demagnetized. During this cycle the working material is in heat exchange with a pumped fluid which absorbs heat from a low temperature heat source and deposits heat in a high temperature reservoir. The magnetic refrigeration cycle operates at an efficiency 70% of Carnot

  3. Durability Indicators in High Absorption Recycled Aggregate Concrete

    Luis F. Jiménez

    2015-01-01

    Full Text Available The use of recycled aggregates in structural concrete production has the inconvenience of increasing the fluid transport properties, such as porosity, sorptivity, and permeability, which reduces the resistance against penetration of environmental loads such as carbon dioxide and chloride ion. In this paper, behavior of ten concrete mixtures with different percentages of coarse aggregate replacement was studied. The recycled material was recovered by crushing of concrete rubble and had high absorption values. The results showed that it is possible to achieve good resistance to carbonation and chloride penetration with up to 50% replacement of recycled coarse aggregate for 0.5 water/cement ratio. Finally, new indexes for porosity and sorptivity were proposed to assess the quality of concrete.

  4. The measurement of stresses in prestressed concrete at elevated temperatures

    Dincmen, T.

    1978-03-01

    This report deals with the measurement of stresses in the prestressed concrete vessel at the research center Seibersdorf during the prestressing and the thermal stabilization period. The thermal stabilization was carried out at 120 0 C. (author)

  5. High-temperature superconductivity

    Lynn, J.W.

    1990-01-01

    This book discusses development in oxide materials with high superconducting transition temperature. Systems with Tc well above liquid nitrogen temperature are already a reality and higher Tc's are anticipated. The author discusses how the idea of a room-temperature superconductor appears to be a distinctly possible outcome of materials research

  6. Effects of Elevated Temperatures on the Compressive Strength Capacity of Concrete Cylinders Confined with FRP Sheets: An Experimental Investigation

    Sherif El-Gamal

    2015-01-01

    Full Text Available Due to their high strength, corrosion resistance, and durability, fiber reinforced polymers (FRP are very attractive for civil engineering applications. One of these applications is the strengthening of concrete columns with FRP sheets. The performance of this strengthening technique at elevated temperature is still questionable and needs more investigations. This research investigates the effects of exposure to high temperatures on the compressive strength of concrete cylinders wrapped with glass and carbon FRP sheets. Test specimens consisted of 30 unwrapped and 60 wrapped concrete cylinders. All specimens were exposed to temperatures of 100, 200, and 300°C for periods of 1, 2, and 3 hours. The compressive strengths of the unwrapped concrete cylinders were compared with their counterparts of the wrapped cylinders. For the unwrapped cylinders, test results showed that the elevated temperatures considered in this study had almost no effect on their compressive strength; however, the wrapped specimens were significantly affected, especially those wrapped with GFRP sheets. The compressive strength of the wrapped specimens decreased as the exposure period and the temperature level increased. After three hours of exposure to 300°C, a maximum compressive strength loss of about 25.3% and 37.9%, respectively, was recorded in the wrapped CFRP and GFRP specimens.

  7. Progress of admixtures and quality of concrete. 2. ; Approaches to ultra-high-strength concrete. Konwa zairyo no shinpo to concrete no hinshitsu. 2. ; Chokokyodo concrete eno approach

    Kawai, T. (Shimizu Construction Co. Ltd., Tokyo (Japan)); Abe, M. (Building Research Institute, Tsukuba (Japan))

    1994-02-15

    Ultra-high-strength concrete of 600 kgf/cm[sup 2] or more is reviewed. MDF (macro defect free) cement, spheroidal cement and mechanically stabilized cement have been developed for ultra-high-strength concrete, however, in general, DSP (densified system containing homogeneously arranged ultra-fine particles) technique is now usual in which a water-cement ratio is reduced by use of advanced air entraining and water reducing agents and cured concrete is densified by use of ultra-fine particles as admixture. Four kinds of substances such as naphthalene system and polycarboxylic acid system are used as air entraining and water reducing agents, and silica fume is used as ultra-fine particle admixture which can be effectively replaced with blast furnace slag or fly ash. Various use examples of ultra-high-strength concrete such as an ocean platform are found in the world, however, only some examples such as a PC truss bridge and the main tower of a PC cable stayed bridge in Japan. 22 refs., 10 figs., 2 tabs.

  8. Effect of Temperature and Age of Concrete on Strength – Porosity Relation

    T. Zadražil

    2004-01-01

    Full Text Available The compressive strengths of unsealed samples of concrete at the age of 180 days and have been measured at temperatures 20 °C, 300 °C, 600 °C and 900 °C. All of tests were performed for cold material. We compared our results with those obtained in [10] for the same type of concrete (age 28, resp. 90 days and measured at temperature ranging from 20 °C to 280 °C. Dependencies of compressive strength and porosity were correlated together and compared for the samples of age 28, 90 and 180 days. Behaviour of concrete of the age 90, resp. 180 days confirms generally accepted hypothesis that with increasing porosity strength of the concrete decreases. It has to be stressed out, howerer, that concrete samples of the age 28 days exhibit totally opposite dependency. 

  9. Multiscale imaging and characterization of the effect of mixing temperature on asphalt concrete containing recycled components.

    Cavalli, M C; Griffa, M; Bressi, S; Partl, M N; Tebaldi, G; Poulikakos, L D

    2016-10-01

    When producing asphalt concrete mixture with high amounts of reclaimed asphalt pavement (RAP), the mixing temperature plays a significant role in the resulting spatial distribution of the components as well as on the quality of the resulting mixture, in terms of workability during mixing and compaction as well as in service mechanical properties. Asphalt concrete containing 50% RAP was investigated at mixing temperatures of 140, 160 and 180°C, using a multiscale approach. At the microscale, using energy dispersive X-ray spectroscopy the RAP binder film thickness was visualized and measured. It was shown that at higher mixing temperatures this film thickness was reduced. The reduction in film thickness can be attributed to the loss of volatiles as well as the mixing of RAP binder with virgin binder at higher temperatures. X-ray computer tomography was used to characterize statistically the distribution of the RAP and virgin aggregates geometric features: volume, width and shape anisotropy. In addition using X-ray computer tomography, the packing and spatial distribution of the RAP and virgin aggregates was characterized using the nearest neighbour metric. It was shown that mixing temperature may have a positive effect on the spatial distribution of the aggregates but did not affect the packing. The study shows a tendency for the RAP aggregates to be more likely distributed in clusters at lower mixing temperatures. At higher temperatures, they were more homogeneously distributed. This indicates a higher degree of blending both at microscale (binder film) and macroscale (spatial distribution) between RAP and virgin aggregates as a result of increasing mixing temperatures and the ability to quantify this using various imaging techniques. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.

  10. Highly efficient high temperature electrolysis

    Hauch, Anne; Ebbesen, Sune; Jensen, Søren Højgaard

    2008-01-01

    High temperature electrolysis of water and steam may provide an efficient, cost effective and environmentally friendly production of H-2 Using electricity produced from sustainable, non-fossil energy sources. To achieve cost competitive electrolysis cells that are both high performing i.e. minimum...... internal resistance of the cell, and long-term stable, it is critical to develop electrode materials that are optimal for steam electrolysis. In this article electrolysis cells for electrolysis of water or steam at temperatures above 200 degrees C for production of H-2 are reviewed. High temperature...... electrolysis is favourable from a thermodynamic point of view, because a part of the required energy can be supplied as thermal heat, and the activation barrier is lowered increasing the H-2 production rate. Only two types of cells operating at high temperature (above 200 degrees C) have been described...

  11. Preliminary engineering and economic analysis of the fixation of high-level radioactive wastes in concrete

    Weeren, H.O.; Perona, J.J.

    1979-07-01

    This feasibility study was based on a waste fixation facility that would serve a reprocessing plant with a capacity of 5 metric tons of uranium per day (MTU/day). Postirradiation cooling times of 3 to 10 years prior to waste solidification were assumed. The waste solution would be concentrated, denitrated, mixed with cement, and cast under pressure in cylindrical canisters similar to those envisioned for a glass facility. The solidified waste grout would be vented, to allow the free water to escape, and then sealed. The filled canisters would be shipped to a geologic repository for permanent storage. Recent work with concretes formed under elevated temperatures and pressures (FUETAP) indicates that they are highly leach resistant. The operating costs were estimated for a waste fixation facility under several conditions. Operating costs for a glass fixation facility were also estimated and compared with the operating costs for a concrete fixation facility. The principal conclusion is that concrete could be an alternative to glass as a matrix for fixation of wastes with high heat-generation rates. The operating costs of an optimized concrete fixation process would probably not be greatly higher than the operating costs of a glass plant, and the capital costs would almost surely be lower. In addition, the concrete process is not a high-temperature process and would not have the consequent operating problems

  12. Selected durability studies of geopolymer concrete with respect to carbonation, elevated temperature, and microbial induced corrosion

    Badar, Mohammad Sufian

    This thesis reports a comprehensive study related to the experimental evaluation of carbonation in reinforced geopolymer concrete, the evaluation of geopolymer concretes at elevated temperature, and the resistance of geopolymer concrete to microbial induced corrosion (MIC). Carbonation: Reinforced concretes, made of geopolymer, prepared from two class F fly ashes and one class C fly ash, were subjected to accelerated carbonation treatment for a period of 450 days. Electrochemical, microstructure and pore structure examinations were performed to evaluate the effect of corrosion caused due to carbonation. GPC specimens prepared from class F fly ash exhibited lower corrosion rates by a factor of 21, and higher pH values (pH>12) when compared with concrete specimens prepared from class C Fly ash (GPCMN). Microstructure and pore characterization of GPC prepared using class F fly ash revealed lower porosity by a factor of 2.5 as compared with thier counterparts made using GPC-MN. The superior performace of GPC prepared with the class F fly ash could be attributed to the dense pore structure and formation of the protective layer of calcium and sodium alumino silicate hydrates (C/N-A-S-H) geopolymeric gels around the steel reinforcement. Elevated Temperature: Geopolymers are an emerging class of cementitious binders which possess a potential for high temperature resistance that could possibly be utilized in applications such as nozzles, aspirators and refractory linings. This study reports on the results of an investigation into the performance of a fly ash based geopolymer binder in high temperature environments. Geopolymer concrete (GPC) was prepared using eleven types of fly ashes obtained from four countries. High content alumina and silica sand was used in the mix for preparing GPC. GPC was subjected to thermal shock tests following ASTM C 1100-88. The GPC samples prepared with tabular alumina were kept at 1093° C and immediately quenched in water. GPC specimens

  13. Elastic and strength properties of Hanford concrete mixes at room and elevated temperatures

    Abrams, M.S.; Gillen, M.; Campbell, D.H.

    1979-03-01

    The effects of long-term exposure to elevated temperatures on the physical properties of concrete mixes used in Hanford radioactive waste storage tanks were determined. Temperature had a significant effect on the elastic modulus of concretes. Poisson's ratio determined by the sonic method remained relatively constant. The splitting tensile strength increased rapidly up to 190 days of age. Then strength decreased to about 350 days and either leveled off or increased from that point on. Compressive strength data were erratic

  14. Experimental data of the static behavior of reinforced concrete beams at room and low temperature.

    Mirzazadeh, M Mehdi; Noël, Martin; Green, Mark F

    2016-06-01

    This article provides data on the static behavior of reinforced concrete at room and low temperature including, strength, ductility, and crack widths of the reinforced concrete. The experimental data on the application of digital image correlation (DIC) or particle image velocimetry (PIV) in measuring crack widths and the accuracy and precision of DIC/PIV method with temperature variations when is used for measuring strains is provided as well.

  15. Effect of Elevated Temperature on the Residual Properties of Quartzite, Granite and Basalt Aggregate Concrete

    Masood, A.; Shariq, M.; Alam, M. Masroor; Ahmad, T.; Beg, A.

    2018-05-01

    In the present study, experimental investigations have been carried out to determine the effect of elevated temperature on the residual properties of quartzite, granite and basalt aggregate concrete mixes. Ultrasonic pulse velocity and unstressed residual compressive strength tests on cube specimens have been conducted at ambient and after single heating-cooling cycle of elevated temperature ranging from 200 to 600 °C. The relationship between ultrasonic pulse velocity and residual compressive strength of all concrete mixes have been developed. Scanning electron microscopy was also carried out to study micro structure of quartzite, granite and basalt aggregate concrete subjected to single heating-cooling cycle of elevated temperature. The results show that the residual compressive strength of quartzite aggregate concrete has been found higher than granite and basalt aggregate concrete at ambient and at all temperatures. It has also been found that the loss of strength in concrete is due to the development of micro-cracks result in failure of cement matrix and coarse aggregate bond. Further, the basalt aggregate concrete has been observed lower strength due to low affinity with Portland cements ascribed to its ferro-magnesium rich mineral composition.

  16. Development of high-performance concrete having high resistance to chloride penetration

    Oh, Byung Hwan; Cha, Soo Won; Jang, Bong Seok; Jang, Seung Yup

    2002-01-01

    The resistance to chloride penetration is one of the simplest measures to determine the durability of concrete, e.g. resistance to freezing and thawing, corrosion of steel in concrete and other chemical attacks. Thus, high-performance concrete may be defined as the concrete having high resistance to chloride penetration as well as high strength. The purpose of this paper is to investigate the resistance to chloride penetration of different types of concrete and to develop high-performance concrete that has very high resistance to chloride penetration, and thus, can guarantee high durability. A large number of concrete specimens have been tested by the rapid chloride permeability test method as designated in AASHTO T 277 and ASTM C 1202. The major test variables include water-to-binder ratios, type of cement, type and amount of mineral admixtures (silica fume, fly ash and blast-furnace slag), maximum size of aggregates and air-entrainment. Test results show that concrete containing optimal amount of silica fume shows very high resistance to chloride penetration, and high-performance concrete developed in this study can be efficiently employed to enhance the durability of concrete structures in severe environments such as nuclear power plants, water-retaining structures and other offshore structures

  17. Behavior of Reinforced Concrete Hybrid Trapezoidal Box Girders Using Ordinary and Highly Strength Concrete

    Nameer A. Alawsh

    2018-03-01

    Full Text Available In this paper, the general behavior of reinforced concrete hybrid box girders is studied by experimental and numerical investigation. Experimental work is included casting monolithically five specimens of box girders with trapezoidal cross section and testing it as simply supported under two point loading. Two specimens were cast as homogenous box girders (full normal strength concrete (NSC (about 35 MPa and full high strength concrete (HSC (about 55 MPa and three specimens were cast as hybrid box girders (HSC in upper flange only, HSC in upper flange and half depth of webs, and HSC in bottom flange and total depth of webs. Experimental results showed significant effects of concrete hybridization on the structural behavior of box girders specimens such as: cracking loads, cracking patterns, ultimate strengths, and failure modes. The ultimate strength of Hybrid box girders increased by 23% as average when compared with the homogenous box girder (full NSC and decreased by 9% as average when compared with homogenous box girder (full HSC. In numerical investigation, the tested specimens were modeled and analyzed using three dimensional non-linear finite element analysis. The analysis was carried out by using a computer program (ANSYS V16.1. The numerical results showed an acceptable agreement with the experimental work with difference about (3.12% and 9.588% as average for ultimate load and deflection, respectively.

  18. Study on Real-Time Simulation Analysis and Inverse Analysis System for Temperature and Stress of Concrete Dam

    Lei Zhang

    2015-01-01

    Full Text Available In the concrete dam construction, it is very necessary to strengthen the real-time monitoring and scientific management of concrete temperature control. This paper constructs the analysis and inverse analysis system of temperature stress simulation, which is based on various useful data collected in real time in the process of concrete construction. The system can produce automatically data file of temperature and stress calculation and then achieve the remote real-time simulation calculation of temperature stress by using high performance computing techniques, so the inverse analysis can be carried out based on a basis of monitoring data in the database; it fulfills the automatic feedback calculation according to the error requirement and generates the corresponding curve and chart after the automatic processing and analysis of corresponding results. The system realizes the automation and intellectualization of complex data analysis and preparation work in simulation process and complex data adjustment in the inverse analysis process, which can facilitate the real-time tracking simulation and feedback analysis of concrete temperature stress in construction process and enable you to discover problems timely, take measures timely, and adjust construction scheme and can well instruct you how to ensure project quality.

  19. Analysis of Mechanical Properties of Self Compacted Concrete by Partial Replacement of Cement with Industrial Wastes under Elevated Temperature

    Junaid Mansoor

    2018-03-01

    Full Text Available Self-Compacting Concrete (SCC differs from the normal concrete as it has the basic capacity to consolidate under its own weight. The increased awareness regarding environmental disturbances and its hazardous effects caused by blasting and crushing procedures of stone, it becomes a delicate and obvious issue for construction industry to develop an alternative remedy as material which can reduce the environmental hazards and enable high-performance strength to the concrete, which would make it durable and efficient for work. A growing trend is being established all over the world to use industrial byproducts and domestic wastes as a useful raw material in construction, as it provides an eco-friendly edge to the construction process and especially for concrete. This study aims to enlighten the use and comparative analysis for the performance of concrete with added industrial byproducts such as Ground Granulated Blast Furnace Slag (GGBFS, Silica fumes (SF and Marble Powder (MP in the preparation of SCC. This paper deals with the prediction of mechanical properties (i.e., compressive, tensile and flexural Strength of self-compacting concrete by considering four major factors such as type of additive, percentage additive replaced, curing days and temperature using Artificial Neural Networks (ANNs.

  20. OPTIMIZATION OF THE TEMPERATURE CONTROL SCHEME FOR ROLLER COMPACTED CONCRETE DAMS BASED ON FINITE ELEMENT AND SENSITIVITY ANALYSIS METHODS

    Huawei Zhou

    2016-10-01

    Full Text Available Achieving an effective combination of various temperature control measures is critical for temperature control and crack prevention of concrete dams. This paper presents a procedure for optimizing the temperature control scheme of roller compacted concrete (RCC dams that couples the finite element method (FEM with a sensitivity analysis method. In this study, seven temperature control schemes are defined according to variations in three temperature control measures: concrete placement temperature, water-pipe cooling time, and thermal insulation layer thickness. FEM is employed to simulate the equivalent temperature field and temperature stress field obtained under each of the seven designed temperature control schemes for a typical overflow dam monolith based on the actual characteristics of a RCC dam located in southwestern China. A sensitivity analysis is subsequently conducted to investigate the degree of influence each of the three temperature control measures has on the temperature field and temperature tensile stress field of the dam. Results show that the placement temperature has a substantial influence on the maximum temperature and tensile stress of the dam, and that the placement temperature cannot exceed 15 °C. The water-pipe cooling time and thermal insulation layer thickness have little influence on the maximum temperature, but both demonstrate a substantial influence on the maximum tensile stress of the dam. The thermal insulation thickness is significant for reducing the probability of cracking as a result of high thermal stress, and the maximum tensile stress can be controlled under the specification limit with a thermal insulation layer thickness of 10 cm. Finally, an optimized temperature control scheme for crack prevention is obtained based on the analysis results.

  1. Determination of Temperature Rise and Temperature Differentials of CEMII/B-V Cement for 20MPa Mass Concrete using Adiabatic Temperature Rise Data

    Chee Siang, GO

    2017-07-01

    Experimental test was carried out to determine the temperature rise characteristics of Portland-Fly-Ash Cement (CEM II/B-V, 42.5N) of Blaine fineness 418.6m2/kg and 444.6m2/kg respectively for 20MPa mass concrete under adiabatic condition. The estimation on adiabatic temperature rise by way of CIRIA C660 method (Construction Industry Research & Information Information) was adopted to verify and validate the hot-box test results by simulating the heat generation curve of the concrete under semi-adiabatic condition. Test result found that Portland fly-ash cement has exhibited decrease in the peak value of temperature rise and maximum temperature rise rate. The result showed that the temperature development and distribution profile, which is directly contributed from the heat of hydration of cement with time, is affected by the insulation, initial placing temperature, geometry and size of concrete mass. The mock up data showing the measured temperature differential is significantly lower than the technical specifications 20°C temperature differential requirement and the 27.7°C limiting temperature differential for granite aggregate concrete as stipulated in BS8110-2: 1985. The concrete strength test result revealed that the 28 days cubes compressive strength was above the stipulated 20MPa characteristic strength at 90 days. The test demonstrated that with proper concrete mix design, the use of Portland flyash cement, combination of chilled water and flake ice, and good insulation is effective in reducing peak temperature rise, temperature differential, and lower adiabatic temperature rise for mass concrete pours. As far as the determined adiabatic temperature rise result was concern, the established result could be inferred for in-situ thermal properties of 20MPa mass concrete application, as the result could be repeatable on account of similar type of constituent materials and concrete mix design adopted for permanent works at project site.

  2. Neutron shielding properties of a new high-density concrete

    Lorente, A.; Gallego, E.; Vega Carrillo, H.R.; Mendez, R.

    2008-01-01

    The neutron shielding properties of a new high-density concrete (commercially available under the name Hormirad TM , developed in Spain by the company CT-RAD) have been characterized both experimentally and by Monte Carlo calculations. The shielding properties of this concrete against photons were previously studied and the material is being used to build bunkers, mazes and doors in medical accelerator facilities with good overall results. In this work, the objective was to characterize the material behaviour against neutrons, as well as to test alternative mixings including boron compounds in an effort to improve neutron shielding efficiency. With that purpose, Hormirad TM slabs of different thicknesses were exposed to an 241 Am-Be neutron source under controlled conditions in the neutron measurements laboratory of the Nuclear Engineering Department at UPM. The original mix, which includes a high fraction of magnetite, was then modified by adding different proportions of anhydrous borax (Na 2 B 4 O 7 ). In order to have a reference against common concrete used to shield medical accelerator facilities, the same experiment was repeated with ordinary (HA-25) concrete slabs. In parallel to the experiments, Monte Carlo calculations of the experiments were performed with MCNP5. The experimental results agree reasonably well with the Monte Carlo calculations. Therefore, the first and equilibrium tenth-value layers have been determined for the different types of concrete tested. The results show an advantageous behaviour of the Hormirad TM concrete, in terms of neutron attenuation against real thickness of the shielding. Borated concretes seem less practical since they did not show better neutron attenuation with respect to real thickness and their structural properties are worse. The neutron attenuation properties of Hormirad TM for typical neutron spectra in clinical LINAC accelerators rooms have been also characterized by Monte Carlo calculation. (author)

  3. NANOMODIFIED CONCRETE

    B. M. Khroustalev

    2015-01-01

    Full Text Available One of the main directions in construction material science is the development of  next generation concrete that is ultra-dense, high-strength, ultra-porous, high heat efficient, extra corrosion-resistant. Selection of such direction is caused by extreme operational impacts on the concrete, namely: continuously increasing load on the concrete and various dynamics of such loads; the necessity in operation of concrete products in a wide temperature range and their exposure to various chemical and physical effects.The next generation concrete represents high-tech concrete mixtures with additives that takes on and retain the required properties when hardening and being used under any operational conditions. A differential characteristic of the next generation concrete is its complexity that presumes usage of various mineral dispersed components, two- and three fractional fine and coarse aggregates, complex chemical additives, combinations of polymer and iron reinforcement.Design strength and performance properties level of the next generation concrete is achieved by high-quality selection of the composition, proper selection of manufacturing techniques, concrete curing, bringing the quality of concrete items to the required level of technical condition during the operational phase. However, directed formation of its structure is necessary in order to obtain high-tech concrete.Along with the traditional methods for regulation of the next generation concrete structure, modification of concrete while using silica nanoparticles is also considered as a perspective one because the concrete patterning occurs due to introduction of a binder in a mineral matrix. Due to this it is possible to obtain nano-modified materials with completely new properties.The main problem with the creation of nano-modified concrete is a uniform distribution of nano-materials in the volume of the cement matrix which is particularly important in the cases of adding a modifier in

  4. Element size and other restrictions in finite-element modeling of reinforced concrete at elevated temperatures

    Carstensen, Josephine Voigt; Jomaas, Grunde; Pankaj, Pankaj

    2013-01-01

    to extend this approach for RC at elevated temperatures. Prior to the extension, the approach is investigated for associated modeling issues and a set of limits of application are formulated. The available models of the behavior of plain concrete at elevated temperatures were used to derive inherent......One of the accepted approaches for postpeak finite-element modeling of RC comprises combining plain concrete, reinforcement, and interaction behaviors. In these, the postpeak strain-softening behavior of plain concrete is incorporated by the use of fracture energy concepts. This study attempts...... fracture energy variation with temperature. It is found that the currently used tensile elevated temperature model assumes that the fracture energy decays with temperature. The existing models in compression also show significant decay of fracture energy at higher temperatures (>400°) and a considerable...

  5. Temperature and strain measurements in concrete using micro-structure optical fiber sensors

    Areias, Lou [EURIDICE/SCK - CEN, Mol (Belgium); Vrije Univ. Brussels (Belgium); Geernaert, Thomas; Sulejmani, Sanne [Vrije Univ. Brussels (Belgium); and others

    2015-07-01

    A recent test carried out to evaluate the construction feasibility of the Belgian supercontainer concept incorporated several types of state-of-the-art sensors and innovative monitoring techniques, including the use of different types of optical fiber sensors. One of these is a relatively new type of sensor developed by the Brussels Photonics Team (B-PHOT) of the Vrije Universiteit Brussel. The sensor uses highly birefringent microstructured optical fibers equipped with fiber Bragg gratings (MOFBGs) sensors. They were embedded in a carbon-fiber reinforced composite plate to provide protection against the concrete's highly alkaline environment, facilitate installation in the concrete mould and allow the transfer of strain onto the fiber. The double reflection spectrum of the MOFBGs allows monitoring strain and temperature simultaneously. This paper presents results of temperature and strain measurements obtained with MOFBG sensors during a {sup 1}/{sub 2}-scale test performed in 2013. The results compare well with similar measurements obtained using conventional thermocouples and vibrating wire strain gauges.

  6. High temperature battery. Hochtemperaturbatterie

    Bulling, M.

    1992-06-04

    To prevent heat losses of a high temperature battery, it is proposed to make the incoming current leads in the area of their penetration through the double-walled insulating housing as thermal throttle, particularly spiral ones.

  7. Design criteria for high-temperature-affected, metallic and ceramic components, and for the prestressed concrete reactor pressure vessel of future HTR systems. Final report. Vol. 1-4

    1988-08-01

    This work in five separate volumes reports on the elaboration of basic data for the formulation of design criteria for HTR components and is arranged into the four following subject areas : (1) safety-specific limiting conditions; (2) metallic components; (3) prestressed concrete reactor pressure vessels; (4) graphitic reactor internals. Under item 2, the mechanical and physical characteristics of the materials X20CrMoV 12 1, X10NiCrAlTi 32 20, and NiCr23Co12Mo are examined up to temperatures of 950deg C. Stress-strain rate laws are elaborated for description of the inelastic deformation behavior. The representation of the subject area reactor pressure vessels deals with four main topics: Prestressed concrete support structure, liner, vessel closures, thermal protection system. Quality-assurance classes are defined under item 4 for graphitic components and load levels for load categories. The material evaluation is discussed in detail (e.g. manufacturing monitoring from the raw material to the graphitization and manufacturing testing up to the acceptance test). In addition, the corrosion behavior and irradiation behavior of graphite is examined and rules for computation of stresses in irradiated and unirradiated graphitic components are elaborated. (MM) [de

  8. High temperature structural silicides

    Petrovic, J.J.

    1997-01-01

    Structural silicides have important high temperature applications in oxidizing and aggressive environments. Most prominent are MoSi 2 -based materials, which are borderline ceramic-intermetallic compounds. MoSi 2 single crystals exhibit macroscopic compressive ductility at temperatures below room temperature in some orientations. Polycrystalline MoSi 2 possesses elevated temperature creep behavior which is highly sensitive to grain size. MoSi 2 -Si 3 N 4 composites show an important combination of oxidation resistance, creep resistance, and low temperature fracture toughness. Current potential applications of MoSi 2 -based materials include furnace heating elements, molten metal lances, industrial gas burners, aerospace turbine engine components, diesel engine glow plugs, and materials for glass processing

  9. Fiber Reinforced Concrete (FRC) for High Rise Construction: Case Studies

    Gharehbaghi, Koorosh; Chenery, Rhea

    2017-12-01

    Due to its material element, Fiber Reinforced Concrete (FRC) could be stronger than traditional Concrete. This is due to FRC internal material compounds and elements. Furthermore, FRC can also significantly improve flexural strength when compared to traditional Concrete. This improvement in flexural strength can be varied depending on the actual fibers used. Although not new, FRC is gradually gaining popularity in the construction industry, in particular for high rise structures. This is due to its flexural strength, especially for high seismic zones, as it will provide a better solution then reinforced Concrete. The main aim of this paper is to investigate the structural importance of FRC for the high rise construction. Although there has been numerous studies and literature in justifying the FRC for general construction; this paper will consider its use specifically for high rise construction. Moreover, this paper will closely investigate eight case studies from Australian and United States as a part of the FRC validation for high rise construction. In doing so, this paper will examine their Structural Health Monitoring (SHM) to determine their overall structural performance.

  10. The effects of moisture and temperature variations on the long term durability of polymer concrete

    Barbosa, Ricardo; Hansen, Kurt Kielsgaard; Grelk, Bent

    2013-01-01

    The use of polymer concrete to precast products in construction presents normally many advantages compared to traditional concrete. Higher strength, lower permeability, shorter curing periods, better chemical resistances and a better durability is normally predicated, however this is a research...... and after exposure to different thermal conditions is very important. In this paper, an experimental study concerning the influence of temperature and moisture in cyclic conditions on the durability of polymer concrete based on an unsaturated polyester resin is described and the results are presented...

  11. Digital laminography assessment of the damage in concrete exposed to freezing temperatures

    Wakimoto, Kentaro

    2008-10-01

    The research explores the possibility of using digital laminography as a non-destructive inspection X-ray method to image the damage existing in concrete exposed to low temperatures. Freezing-thawing and scaling tests were performed and digital laminography was used to determine the degree of damage existing inside the concrete samples. First, digital laminography was performed on the concrete sample and then a visual inspection was done by slicing the sample after it was vacuum-impregnated with epoxy in order to compare the differences in crack width. © 2008 Elsevier Ltd. All rights reserved.

  12. Digital laminography assessment of the damage in concrete exposed to freezing temperatures

    Wakimoto, Kentaro; Blunt, Joshua; Carlos, Cruz; Monteiro, Paulo J.M.; Ostertag, Claudia P.; Albert, Richard

    2008-01-01

    The research explores the possibility of using digital laminography as a non-destructive inspection X-ray method to image the damage existing in concrete exposed to low temperatures. Freezing-thawing and scaling tests were performed and digital laminography was used to determine the degree of damage existing inside the concrete samples. First, digital laminography was performed on the concrete sample and then a visual inspection was done by slicing the sample after it was vacuum-impregnated with epoxy in order to compare the differences in crack width. © 2008 Elsevier Ltd. All rights reserved.

  13. Revealing the temperature history in concrete after fire exposure by microscopic analysis

    Annerel, E.; Taerwe, L.

    2009-01-01

    Concrete structures behave in most cases very well during a fire, after which it is often possible to repair or strengthen the structure to a certain level. This could result in important economic benefits, as costs for demolition and rebuilding can be avoided and the building can be reused faster. In this paper three methods for determining the maximum temperature to which a concrete structure was submitted during a fire are studied. Knowledge of the temperature distribution is necessary to assess the overall damage of a concrete structure. First, the physico-chemical transformations of heated concrete are investigated with scanning electron microscopy (SEM). Secondly, the features visible under the polarising and fluorescent microscope (PFM) are discussed. And third, the influence of heat on the colour of the aggregates is analysed.

  14. An Experimental Study of High Strength-High Volume Fly Ash Concrete for Sustainable Construction Industry

    Kate, Gunavant K.; Thakare, Sunil B., Dr.

    2017-08-01

    Concrete is the most widely used building material in the construction of infrastructures such as buildings, bridges, highways, dams, and many other facilities. This paper reports the development, the basic idea, the main properties of high strength-high volume fly ash with application in concrete associated with the development and implementation of Sustainable Properties of High Volume Fly Ash Concrete (HVFAC) Mixtures and Early Age Shrinkage and mechanical properties of concrete for 7,28,56 and 90days. Another alternative to make environment-friendly concrete is the development of high strength-high-volume fly ash concrete which is an synthesized from materials of geological origin or by-product materials such as fly ash which is rich in silicon and aluminum. In this paper 6 concrete mixtures were produced to evaluate the effect of key parameters on the mechanical properties of concrete and its behavior. The study key parameters are; binder material content, cement replacement ratios, and the steel fibers used to High Volume Fly Ash mixtures for increasing performance of concrete.

  15. Modelling of tension stiffening for normal and high strength concrete

    Christiansen, Morten Bo; Nielsen, Mogens Peter

    1998-01-01

    form the model is extended to apply to biaxial stress fields as well. To determine the biaxial stress field, the theorem of minimum complementary elastic energy is used. The theory has been compared with tests on rods, disks, and beams of both normal and high strength concrete, and very good results...

  16. An experimental investigation into the behavior of concrete elements rerofitted with NSM composite strips at elevated temperatures

    Namrou, Abdul Rahman

    Near-surface-mounted (NSM) fiber reinforced polymer (FRP) is another strengthening alternative of externally bonded fiber reinforced polymers. NSM FRP is a promising alternative technology that has emerged for enhancing the strength capacity of concrete structures. Most laboratory researches have focused mainly on the overall member performance and/or the bonding performance of the NSM bars or strips. Limited research has focused on the effect of temperature exposure on NSM FRP performance. The results of an experimental program performed on forty-eight (48) concrete block specimen with NSM carbon-fiber reinforced polymer (CFRP) strengthening systems at elevated temperatures that reaches to 200°C [392°F] to investigate flexural performance. The effect of using two different adhesive systems (epoxy anchoring system) with manufacturer recommendation at ordinary and high temperature exposures is also studied. The adhesive was injected in a NSM groove size (25 mm [1 in] deep x 13 mm [0.5 in] wide) the width and depth of the groove were greater than 3 and 1.5 times the CFRP thickness and width, respectively. Test results show that the interfacial strength of the specimens bonded with the ordinary epoxy is maintained until 75°C [167°F] is reached, while the strength noticeably decreases with an increasing temperature above this limit. The specimens with the high-temperature epoxy preserve interfacial capacity up to 200°C [392°F] despite a trend of strength-decrease being observed. The failure of the test specimens is brittle irrespective of adhesive type. Interfacial damage is localized along the bond-line with the presence of hairline cracks that further develop when interfacial failure is imminent. This thesis also presents an experimental result concerning the bond performance of concrete-adhesive at elevated temperatures that reaches to 200°C [392°F] applied for three hours. Then, the concrete prisms were tested under three point flexural loading. The

  17. Hydric and poro-mechanical behaviour of high performance Andra concrete: effect of microstructure

    Zhang, Yao

    2014-01-01

    This thesis focuses on water retention at high relative humidity (RH) (92-100%) and desiccation shrinkage under moderate temperature (60-80 C) for two high performance concretes CEMI and CEMV (from Andra), in relation with their microstructure.To investigate the origins of the variations in water saturation degree Sw at high RH, both concretes are dried at RH=92, 98 and 100%, from the fully saturated state. For both concretes, sampling affects significantly Sw. For CEMI at 100%RH, sample size also affects Sw, due to surface drying (desorption); at 92 and 98%RH, CEMI is no longer sensitive to surface drying effects; it is sensitive to experimental conditions (RH, T). CEMV is affected by sample size whatever the RH, but not by experimental conditions.From 60 C drying temperature, the relationship between shrinkage and relative mass loss presents four distinct phases. CEMI concrete is dried at 65 C until phase 3 or 4, and then submitted to a coupled poro-mechanical and gas permeability test. For the same sample tested in phase 3 and then 4, a difference in solid skeleton incompressibility modulus Ks is measured, which is significantly lower than the differences in Ks due to sampling.With the Scanning Electron Microscope, the solid phases and morphology of both concretes are quantified. CEM I and CEM V comprise identical phases, even portlandite, yet CEM V concrete has some specific phases, owing to the addition of slag and fly ash. The C-S-H in CEM V have a lower C/S ratio than in CEM I. The (C/S) ratio remains similar when comparing between three different batches. Besides, millimetric pores vary significantly, owing to differences in manufacturing. (author)

  18. Aging mechanisms for concrete components of High-Level Waste storage tanks

    Kassir, M.; Bandyopadhyay, K.; Bush, S.; Mather, B.; Shewmon, P.; Streicher, M.; Thompson, B.; van Rooyen, D.; Weeks, J.

    1995-01-01

    The age-related degradation mechanisms which affect the concrete and the reinforcing steel in the high-level waste (HLW) storage tanks art evaluated with respect to their potential significance to the continued performance of the concrete, and am classified into non-significant and potentially significant. The identified potentially significant degradation mechanisms include the effects of elevated temperature, freezing and thawing, leaching of calcium hydroxide, aggressive chemical attack, and corrosion of the reinforcing steel. To the extent that available knowledge permits, these mechanisms are generically evaluated and quantified so that site-specific plans may be developed to verify whether significant degradation has occurred in the concrete, and, if so, to formulate mitigating measures to avoid further deterioration and possibly repair the degradation or pursue other management options

  19. High temperature reaction kinetics

    Jonah, C.D.; Beno, M.F.; Mulac, W.A.; Bartels, D.

    1985-01-01

    During the last year the dependence of the apparent rate of OD + CO on water pressure was measured at 305, 570, 865 and 1223 K. An explanation was found and tested for the H 2 O dependence of the apparent rate of OH(OD) + CO at high temperatures. The isotope effect for OH(D) with CO was determined over the temperature range 330 K to 1225 K. The reason for the water dependence of the rate of OH(OD) + CO near room temperatures has been investigated but no clear explanation has been found. 1 figure

  20. High-temperature superconductivity

    Ginzburg, V.L.

    1987-07-01

    After a short account of the history of experimental studies on superconductivity, the microscopic theory of superconductivity, the calculation of the control temperature and its possible maximum value are presented. An explanation of the mechanism of superconductivity in recently discovered superconducting metal oxide ceramics and the perspectives for the realization of new high-temperature superconducting materials are discussed. 56 refs, 2 figs, 3 tabs

  1. Experimental Study on Temperature Behavior of SSC (Stiffened Steel Plate Concrete) Structures

    Lee, K. J.; Ham, K. W.; Park, D. S.; Kwon, K. J.

    2008-01-01

    SSC(Stiffened Steel plate Concrete) module method uses steel plate instead of reinforcing bar and mold in existing RC structure. Steel plate modules are fabricated in advance, installed and poured with concrete in construction field, so construction period is remarkably shortened by SC module technique. In case of existence of temperature gap between internal and external structure surface such as containment building, thermal stress is taken place and as a result of it, structural strength is deteriorated. In this study, we designed two test specimens and several tests with temperature heating were conducted to evaluate temperature behavior of SSC structures and RC structure

  2. High temperature pipeline design

    Greenslade, J.G. [Colt Engineering, Calgary, AB (Canada). Pipelines Dept.; Nixon, J.F. [Nixon Geotech Ltd., Calgary, AB (Canada); Dyck, D.W. [Stress Tech Engineering Inc., Calgary, AB (Canada)

    2004-07-01

    It is impractical to transport bitumen and heavy oil by pipelines at ambient temperature unless diluents are added to reduce the viscosity. A diluted bitumen pipeline is commonly referred to as a dilbit pipeline. The diluent routinely used is natural gas condensate. Since natural gas condensate is limited in supply, it must be recovered and reused at high cost. This paper presented an alternative to the use of diluent to reduce the viscosity of heavy oil or bitumen. The following two basic design issues for a hot bitumen (hotbit) pipeline were presented: (1) modelling the restart problem, and, (2) establishing the maximum practical operating temperature. The transient behaviour during restart of a high temperature pipeline carrying viscous fluids was modelled using the concept of flow capacity. Although the design conditions were hypothetical, they could be encountered in the Athabasca oilsands. It was shown that environmental disturbances occur when the fluid is cooled during shut down because the ground temperature near the pipeline rises. This can change growing conditions, even near deeply buried insulated pipelines. Axial thermal loads also constrain the design and operation of a buried pipeline as higher operating temperatures are considered. As such, strain based design provides the opportunity to design for higher operating temperature than allowable stress based design methods. Expansion loops can partially relieve the thermal stress at a given temperature. As the design temperature increase, there is a point at which above grade pipelines become attractive options, although the materials and welding procedures must be suitable for low temperature service. 3 refs., 1 tab., 10 figs.

  3. Durability of concrete materials in high-magnesium brine

    Wakeley, L.D.; Poole, T.S.; Burkes, J.P.

    1994-03-01

    Cement pastes and mortars representing 11 combinations of candidate concrete materials were cast in the laboratory and monitored for susceptibility to chemical deterioration in high-magnesium brine. Mixtures were selected to include materials included in the current leading candidate concrete for seals at the Waste Isolation Pilot Plant (WIPP). Some materials were included in the experimental matrix to answer questions that had arisen during study of the concrete used for construction of the liner of the WIPP waste-handling shaft. Mixture combinations compared Class C and Class F fly ashes, presence or absence of an expansive component, and presence or absence of salt as a mixture component. Experimental conditions exposed the pastes and mortars to extreme conditions, those being very high levels of Mg ion and an effectively unlimited supply of brine. All pastes and mortars showed deterioration with brine exposure. In general, mortars deteriorated more extensively than the corresponding pastes. Two-inch cube specimens of mortar were not uniformly deteriorated, but showed obvious zoning even after a year in the brine, with a relatively unreacted zone remaining at the center of each cube. Loss of calcium from the calcium hydroxide of paste/aggregate interfaces caused measurable strength loss in the reacted zone comprising the outer portion of every mortar specimen. The current candidate mass concrete for WIPP seals includes salt as an initial component, and has a relatively closed initial microstructure. Both of these features contribute to its suitability for use in large placements within the Salado Formation

  4. Investigation on the temperature of the asphalt-concrete facing of embankment dams

    Karel Adam

    2016-01-01

    Full Text Available Asphalt concrete is a traditional material used for the constructions of upstream sealing of reservoir dams, particularly in upper reservoirs of pumped storage hydroelectric plants. The asphalt layer is often exposed to significant fluctuations of temperature caused, for example, by heating the facing from the sun and by its subsequent rapid cooling by water during reservoir periodical filling. To better understand the physical phenomena and behaviour of the facing in terms of vapour diffusion, the state of stress, etc., it is necessary to know temperature phenomena in the asphalt facing. This paper describes the measurement of temperature in the asphalt facing of the Dlouhe Strane pumped storage hydroelectric plant and its evaluation using 1D numerical model of heat flow in the asphalt concrete facing. Numerical simulation for selected load scenarios enabled the temperature phenomena that take place in the construction of the asphalt-concrete facing to be quantified. The analysis shows that during insolation, the asphalt facing is exposed to the significant temperature rise on its surface and also over its whole thickness. Similarly during frost weather the facing becomes frozen in its entire thickness. During the day cycle the temperature in the asphalt layers changes significantly. However, the temperature in the underlying rockfill dam body becomes steady approximately at the depth of 1.0 m. Keywords: Asphalt concrete facing, Temperature distribution analysis, Embankment dam

  5. Temperature Characteristics of Porous Portland Cement Concrete during the Hot Summer Session

    Liqun Hu

    2017-01-01

    Full Text Available Pavement heats the near-surface air and affects the thermal comfort of the human body in hot summer. Because of a large amount of connected porosity of porous Portland cement concrete (PPCC, the thermal parameters of PPCC are much different from those of traditional Portland cement concrete (PCC. The temperature change characteristics of PPCC and the effects on surrounding environment are also different. A continuous 48-hour log of temperature of a PCC and five kinds of PPCC with different porosity were recorded in the open air in the hot summer. The air temperatures at different heights above concrete specimens were tested using self-made enclosed boxes to analyze the characteristics of near-surface air temperature. The output heat flux of different concrete specimens was calculated. The results show that the PPCC has higher temperature in the daytime and lower temperature in the nighttime and larger temperature gradient than the PCC. The air temperature above PPCC is lower than that of PCC after solar radiation going to zero at night. The total output heat flux of PPCC is slightly smaller in the daytime and significantly smaller at night than that of PCC. The results of tests and calculations indicate that PPCC contributes to the mitigation of heating effect of pavement on the near-surface air.

  6. Effects of Outside Air Temperature on Movement of Phosphine Gas in Concrete Elevator Bins

    Studies that measured the movement and concentration of phosphine gas in upright concrete bins over time indicated that fumigant movement was dictated by air currents, which in turn, were a function of the difference between the average grain temperature and the average outside air temperature durin...

  7. Ground Glass Pozzolan in Conventional, High, and Ultra-High Performance Concrete

    Tagnit-Hamou Arezki

    2018-01-01

    Full Text Available Ground-glass pozzolan (G obtained by grinding the mixed-waste glass to same fineness of cement can act as a supplementary-cementitious material (SCM, given that it is an amorphous and a pozzolanic material. The G showed promising performances in different concrete types such as conventional concrete (CC, high-performance concrete (HPC, and ultra-high performance concrete (UHPC. The current paper reports on the characteristics and performance of G in these concrete types. The use of G provides several advantages (technological, economical, and environmental. It reduces the production cost of concrete and decrease the carbon footprint of a traditional concrete structures. The rheology of fresh concrete can be improved due to the replacement of cement by non-absorptive glass particles. Strength and rigidity improvements in the concrete containing G are due to the fact that glass particles act as inclusions having a very high strength and elastic modulus that have a strengthening effect on the overall hardened matrix.

  8. High temperature storage loop :

    Gill, David Dennis; Kolb, William J.

    2013-07-01

    A three year plan for thermal energy storage (TES) research was created at Sandia National Laboratories in the spring of 2012. This plan included a strategic goal of providing test capability for Sandia and for the nation in which to evaluate high temperature storage (>650ÀC) technology. The plan was to scope, design, and build a flow loop that would be compatible with a multitude of high temperature heat transfer/storage fluids. The High Temperature Storage Loop (HTSL) would be reconfigurable so that it was useful for not only storage testing, but also for high temperature receiver testing and high efficiency power cycle testing as well. In that way, HTSL was part of a much larger strategy for Sandia to provide a research and testing platform that would be integral for the evaluation of individual technologies funded under the SunShot program. DOEs SunShot program seeks to reduce the price of solar technologies to 6/kWhr to be cost competitive with carbon-based fuels. The HTSL project sought to provide evaluation capability for these SunShot supported technologies. This report includes the scoping, design, and budgetary costing aspects of this effort

  9. Evaluation of a highway bridge constructed using high strength lightweight concrete bridge girders.

    2011-04-01

    The use of high performance concretes to provide longer bridge spans has been limited due to the capacity of existing infrastructure to handle the load of the girders during transportation. The use of High Strength Lightweight Concrete (HSLW) can pro...

  10. Increased strength of concrete subject to high loading rates

    Curbach, M.

    1987-01-01

    Within the scope of this work various problems are discussed which occur in connection with concrete under high tensile loading rates (e.g. when a plane crashes on a nuclear power plant very high loads occur which act only for a very short time). Particularly the causes for the already frequently noticed increases in strength with increasing loading rates are investigated and also the question whether this increased strength can be taken into account when dimensioning a construction. (MM) [de

  11. High temperature niobium alloys

    Wojcik, C.C.

    1991-01-01

    Niobium alloys are currently being used in various high temperature applications such as rocket propulsion, turbine engines and lighting systems. This paper presents an overview of the various commercial niobium alloys, including basic manufacturing processes, properties and applications. Current activities for new applications include powder metallurgy, coating development and fabrication of advanced porous structures for lithium cooled heat pipes

  12. High Temperature Electrolysis

    Elder, Rachael; Cumming, Denis; Mogensen, Mogens Bjerg

    2015-01-01

    High temperature electrolysis of carbon dioxide, or co-electrolysis of carbon dioxide and steam, has a great potential for carbon dioxide utilisation. A solid oxide electrolysis cell (SOEC), operating between 500 and 900. °C, is used to reduce carbon dioxide to carbon monoxide. If steam is also i...

  13. Influence of Fly Ash on the Compressive Strength of Foamed Concrete at Elevated Temperature

    Ahmad H.

    2014-01-01

    Full Text Available Foamed concrete is a lightweight concrete that is widely used in the construction industry recently. This study was carried out to investigate the influence of fly ash as a cement replacement material to the residual compressive strength of foamed concrete subjected to elevated temperature. For this study, the foamed concrete density was fixed at 1300 kg/m3 and the sand-cement ratio and water-cement was set at 1:2 and 0.45, respectively. The samples were prepared and tested at the age of 28 days. Based on the results, it has been found that with 25% inclusion of fly ash, the percentage of compressive strength loss was decreased by 3 – 50%.

  14. A Study on the Evaluation of Field Application of High-Fluidity Concrete Containing High Volume Fly Ash

    Yun-Wang Choi

    2015-01-01

    Full Text Available In the recent concrete industry, high-fluidity concrete is being widely used for the pouring of dense reinforced concrete. Normally, in the case of high-fluidity concrete, it includes high binder contents, so it is necessary to replace part of the cement through admixtures such as fly ash to procure economic feasibility and durability. This study shows the mechanical properties and field applicability of high-fluidity concrete using mass of fly ash as alternative materials of cement. The high-fluidity concrete mixed with 50% fly ash was measured to manufacture concrete that applies low water/binder ratio to measure the mechanical characteristics as compressive strength and elastic modulus. Also, in order to evaluate the field applicability, high-fluidity concrete containing high volume fly ash was evaluated for fluidity, compressive strength, heat of hydration, and drying shrinkage of concrete.

  15. The suitability of concrete using recycled aggregates (RAs) for high-performance concrete (HPC)

    Torgal, Fernando Pacheco; Ding, Y.; Miraldo, Sérgio; Abdollahnejad, Zahra; Labrincha, J. A.

    2013-01-01

    Most studies related to concrete made with recycled aggregates (RA) use uncontaminated aggregates produced in the laboratory, revealing the potential to re-use as much as 100%. However, industrially produced RA contain a certain level of impurities that can be deleterious for Portland cement concrete, thus making it difficult for the concrete industry to use such investigations unless uncontaminated RA are used. This chapter reviews current knowledge on concrete made with RA, with a focus on ...

  16. High temperature thermometric phosphors

    Allison, Stephen W.; Cates, Michael R.; Boatner, Lynn A.; Gillies, George T.

    1999-03-23

    A high temperature phosphor consists essentially of a material having the general formula LuPO.sub.4 :Dy.sub.(x),Eu.sub.y) wherein: 0.1 wt %.ltoreq.x.ltoreq.20 wt % and 0.1 wt %.ltoreq.y.ltoreq.20 wt %. The high temperature phosphor is in contact with an article whose temperature is to be determined. The article having the phosphor in contact with it is placed in the environment for which the temperature of the article is to be determined. The phosphor is excited by a laser causing the phosphor to fluoresce. The emission from the phosphor is optically focused into a beam-splitting mirror which separates the emission into two separate emissions, the emission caused by the dysprosium dopant and the emission caused by the europium dopent. The separated emissions are optically filtered and the intensities of the emission are detected and measured. The ratio of the intensity of each emission is determined and the temperature of the article is calculated from the ratio of the intensities of the separate emissions.

  17. Deformation of high performance concrete plate under humid tropical weather

    Niken, C.; Elly, T.; Supartono, FX; Laksmi, I.

    2018-03-01

    This paper presents the relationship between surrounding relative humidity and temperature on deformation behavior of one sample concrete plate with compressive strength of 60MPa. This research was done in Indonesia that is in humid tropical weather. A specimens measuring 3000 mm × 1600 mm × 150 mm were used. The behavior was obtained by using four embedded vibrating wire strain gauges (VWESG). As a result there is a very strong relationship between humidity and deformation at the age range of 7 until 21 days. The largest deformation occurs in the corner and the fluctuation of deformation in side position is larger than in the corner and in the middle. The peaks of surrounding relative humidity were fully followed by the deepest valley of deformation on time in the corner, while in another position the range delay time was 8 - 11 hours. There is a strong relationship between surrounding temperature and deformation at the range of 7 until 14 days. The influenced of surrounding relative humidity to concrete behavior is faster and longer than surrounding temperature. The influence of surrounding temperature in humid tropical weather was shorter than in non-humid tropical weather.

  18. Sulfate and Chloride Resistance of High Fluidity Concrete including Fly Ash and GGBS for NPP

    Noh, Jea Myoung; Cho, Myung Sug

    2010-01-01

    Fly ash mixed concrete has been used for NPP concrete structures in Korea in order to prevent aging and improve durability since the Shin.Kori no.1,2 in 2005. Concentrated efforts to develop technology for the streamlining of construction work and to affect labor savings have been conducted in construction. The application of high fluidity concrete for nuclear power plants has been the research subject with the aim of further rationalization of construction works. Since high fluidity concrete can have the characteristics of high density and high strength without compaction. However, high fluidity concrete can cause thermal cracking by heat of hydration. For this reason, the amount of pozzolan binder should be increased in high fluidity concrete for nuclear power plants. In this study, the resistance of high fluidity concrete on sulfate and chloride was compared with that of the concrete currently using for nuclear power plants

  19. Evaluation Of Liner Back-pressure Due To Concrete Pore Pressure At Elevated Temperatures

    James, R.J.; Rashid, Y.R.; Liu, A.S.; Gou, B.

    2006-01-01

    GE's latest evolution of the boiling water reactor, the ESBWR, has innovative passive design features that reduce the number and complexity of active systems, which in turn provide economic advantages while also increasing safety. These passive systems used for emergency cooling also mean that the primary containment system will experience elevated temperatures with longer durations than conventional plants in the event of design basis accidents. During a Loss of Coolant Accident (LOCA), the drywell in the primary containment structure for the ESBWR will be exposed to saturated steam conditions for up to 72 hours following the accident. A containment spray system may be activated that sprays the drywell area with water to condense the steam as part of the recovery operations. The liner back-pressure will build up gradually over the 72 hours as the concrete temperatures increase, and a sudden cool down could cause excessive differential pressure on the liner to develop. For this analysis, it is assumed that the containment spray is activated at the end of the 72-hour period. A back-pressure, acting between the liner and the concrete wall of the containment, can occur as a result of elevated temperatures in the concrete causing steam and saturated vapor pressures to develop from the free water remaining in the pores of the concrete. Additional pore pressure also develops under the elevated temperatures from the non-condensable gases trapped in the concrete pores during the concrete curing process. Any buildup of this pore pressure next to the liner, in excess of the drywell internal pressure, will act to push the liner away from the concrete with a potential for tearing at the liner anchorages. This paper describes the methods and analyses used to quantify this liner back-pressure so that appropriate measures are included in the design of the liner and anchorage system. A pore pressure model is developed that calculates the pressure distribution across the concrete

  20. Heat and moisture flow in concrete as a function of temperature

    Hundt, J.

    1978-01-01

    Due to temperature, reactors in operation cause heat and moisture flows in the thick walled prestressed pressure vessels. These flows were studied in three beams of concrete made with crushed limestone aggregate, and in three beams made of crushed gravel/sand aggregate. The flow phenomena were related to the structural development of the concrete by determining the amount of non-evaporatable water, the total porosity, and the pore size distribution. Local temperature and moisture conditions also influenced the technical properties. Compressive strength, changes in length due to shrinkage and contraction, thermal expansion, and thermal conductivity were determined.

  1. Recent trends in steel fibered high-strength concrete

    Shah, Abid A.; Ribakov, Y.

    2011-01-01

    Highlights: → Recent studies on steel fibred high strength concrete (SFHSC) are reviewed. → Different design provisions for SFHSC are compared. → Applications of SFHSC in new and existing structures and elements are discussed. → Using non-destructive techniques for quality control of SFHSC are reviewed. -- Abstract: Steel fibered high-strength concrete (SFHSC) became in the recent decades a very popular material in structural engineering. High strength attracts designers and architects as it allows improving the durability as well as the esthetics of a construction. As a result of increased application of SFHSC, many experimental studies are conducted to investigate its properties and to develop new rules for proper design. One of the trends in SFHSC structures is to provide their ductile behavior that is desired for proper structural response to dynamic loadings. An additional goal is to limit development and propagation of macro-cracks in the body of SFHSC elements. SFHSC is tough and demonstrates high residual strengths after appearance of the first crack. Experimental studies were carried out to select effective fiber contents as well as suitable fiber types, to study most efficient combination of fiber and regular steel bar reinforcement. Proper selection of other materials like silica fume, fly ash and super plasticizer has also high importance because of the influence on the fresh and hardened concrete properties. Combination of normal-strength concrete with SFHSC composite two-layer beams leads to effective and low cost solutions that may be used in new structures as well as well as for retrofitting existing ones. Using modern nondestructive testing techniques like acoustic emission and nonlinear ultrasound allows verification of most design parameters and control of SFHSC properties during casting and after hardening. This paper presents recent experimental results, obtained in the field SFHSC and non-destructive testing. It reviews the

  2. Mechanical properties of concrete containing a high volume of tire-rubber particles.

    Khaloo, Ali R; Dehestani, M; Rahmatabadi, P

    2008-12-01

    Due to the increasingly serious environmental problems presented by waste tires, the feasibility of using elastic and flexible tire-rubber particles as aggregate in concrete is investigated in this study. Tire-rubber particles composed of tire chips, crumb rubber, and a combination of tire chips and crumb rubber, were used to replace mineral aggregates in concrete. These particles were used to replace 12.5%, 25%, 37.5%, and 50% of the total mineral aggregate's volume in concrete. Cylindrical shape concrete specimens 15 cm in diameter and 30 cm in height were fabricated and cured. The fresh rubberized concrete exhibited lower unit weight and acceptable workability compared to plain concrete. The results of a uniaxial compressive strain control test conducted on hardened concrete specimens indicate large reductions in the strength and tangential modulus of elasticity. A significant decrease in the brittle behavior of concrete with increasing rubber content is also demonstrated using nonlinearity indices. The maximum toughness index, indicating the post failure strength of concrete, occurs in concretes with 25% rubber content. Unlike plain concrete, the failure state in rubberized concrete occurs gently and uniformly, and does not cause any separation in the specimen. Crack width and its propagation velocity in rubberized concrete are lower than those of plain concrete. Ultrasonic analysis reveals large reductions in the ultrasonic modulus and high sound absorption for tire-rubber concrete.

  3. High Early-Age Strength Concrete for Rapid Repair

    Maler, Matthew O.

    The aim of this research was to identify High Early-Age Strength (HES) concrete batch designs, and evaluate their suitability for use in the rapid repair of highways and bridge decks. To this end, two criteria needed to be met; a minimum compressive strength of 20.68 MPa (3000 psi) in no later than 12 hours, and a drying shrinkage of less than 0.06 % at 28 days after curing. The evaluations included both air-entrained, and non-air-entrained concretes. The cement types chosen for this study included Type III and Type V Portland cement and "Rapid Set"--a Calcium Sulfoaluminate (CSA) cement. In addition, two blended concretes containing different ratios of Type V Portland cement and CSA cement were investigated. The evaluation of the studied concretes included mechanical properties and transport properties. Additionally, dimensional stability and durability were investigated. Evaluations were conducted based on cement type and common cement factor. Fresh property tests showed that in order to provide a comparable workability, and still remain within manufactures guideline for plasticizer, the water-to-cement ratio was adjusted for each type of cement utilized. This resulted in the need to increase the water-to-cement ratio as the Blaine Fineness of the cement type increased (0.275 for Type V Portland cement, 0.35 for Type III Portland cement, and 0.4 for Rapid Set cement). It was also observed that negligible changes in setting time occurred with increasing cement content, whereas changes in cement type produced notable differences. The addition of air-entrainment had beneficial effect on workability for the lower cement factors. Increasing trends for peak hydration heat were seen with increases in cement factor, cement Blaine Fineness, and accelerator dosage. Evaluation of hardened properties revealed opening times as low as 5 hours for Type V Portland cement with 2.0 % accelerator per cement weight and further reduction in opening time by an hour when accelerator

  4. Concretization of high level radioactive source in marine sediment

    Weiss, H.V.

    1987-01-01

    A method is described of forming a concretized coating which encapsulates a canister of heat producing materials and provides protection against corrosion by seawater when the canister is placed in an ocean floor-sediment environment. The method comprises: selecting a location on the ocean floor at such a depth that the proximate seawater thereat would be capable of reaching a temperature of at least 110 0 C. when in contact with the canister of heat producing materials. The seawater within the pores of the ocean floor sediment thereat contains sufficient amounts of calcium and sulfate to form, at the temperature, an anhydrite layer around the canister; placing the canister into the ocean floor sediment at the location; and storing the canister at the location for at least one month thereby allowing heat from the canister to raise the temperature of the seawater in the pores of the sediment proximate to the canister to at least 110 0 C. wherein anhydrite precipitates from the proximate seawater and forms a concretized layer on the exterior surfaces of the canister

  5. Optimizing High Performance Self Compacting Concrete

    Raymond A Yonathan

    2017-01-01

    Full Text Available This paper’s objectives are to learn the effect of glass powder, silica fume, Polycarboxylate Ether, and gravel to optimizing composition of each factor in making High Performance SCC. Taguchi method is proposed in this paper as best solution to minimize specimen variable which is more than 80 variations. Taguchi data analysis method is applied to provide composition, optimizing, and the effect of contributing materials for nine variable of specimens. Concrete’s workability was analyzed using Slump flow test, V-funnel test, and L-box test. Compressive and porosity test were performed for the hardened state. With a dimension of 100×200 mm the cylindrical specimens were cast for compressive test with the age of 3, 7, 14, 21, 28 days. Porosity test was conducted at 28 days. It is revealed that silica fume contributes greatly to slump flow and porosity. Coarse aggregate shows the greatest contributing factor to L-box and compressive test. However, all factors show unclear result to V-funnel test.

  6. High temperature materials characterization

    Workman, Gary L.

    1990-01-01

    A lab facility for measuring elastic moduli up to 1700 C was constructed and delivered. It was shown that the ultrasonic method can be used to determine elastic constants of materials from room temperature to their melting points. The ease in coupling high frequency acoustic energy is still a difficult task. Even now, new coupling materials and higher power ultrasonic pulsers are being suggested. The surface was only scratched in terms of showing the full capabilities of either technique used, especially since there is such a large learning curve in developing proper methodologies to take measurements into the high temperature region. The laser acoustic system does not seem to have sufficient precision at this time to replace the normal buffer rod methodology.

  7. High temperature materials

    2003-01-01

    The aim of this workshop is to share the needs of high temperature and nuclear fuel materials for future nuclear systems, to take stock of the status of researches in this domain and to propose some cooperation works between the different research organisations. The future nuclear systems are the very high temperature (850 to 1200 deg. C) gas cooled reactors (GCR) and the molten salt reactors (MSR). These systems include not only the reactor but also the fabrication and reprocessing of the spent fuel. This document brings together the transparencies of 13 communications among the 25 given at the workshop: 1) characteristics and needs of future systems: specifications, materials and fuel needs for fast spectrum GCR and very high temperature GCR; 2) high temperature materials out of neutron flux: thermal barriers: materials, resistance, lifetimes; nickel-base metal alloys: status of knowledge, mechanical behaviour, possible applications; corrosion linked with the gas coolant: knowledge and problems to be solved; super-alloys for turbines: alloys for blades and discs; corrosion linked with MSR: knowledge and problems to be solved; 3) materials for reactor core structure: nuclear graphite and carbon; fuel assembly structure materials of the GCR with fast neutron spectrum: status of knowledge and ceramics and cermets needs; silicon carbide as fuel confinement material, study of irradiation induced defects; migration of fission products, I and Cs in SiC; 4) materials for hydrogen production: status of the knowledge and needs for the thermochemical cycle; 5) technologies: GCR components and the associated material needs: compact exchangers, pumps, turbines; MSR components: valves, exchangers, pumps. (J.S.)

  8. A study on sodium-concrete reaction

    Bae, Jae Heum; Min, Byong Hun [Suwon University, Suwon (Korea, Republic of)

    1997-07-01

    A small sodium-concrete reaction facility was designed, manufactured and installed. this facility has been operated under inert gas(N{sub 2}) with different experimental variables such as sodium injection temperature, injection amount of sodium, aging period of concrete, sodium reservoir temperature. As a result, it was found that sodium injection temperature and injected amount of sodium has little effect on sodium-concrete reaction. However, sodium reservoir temperature and aging period of concrete has relatively high impact on sodium-concrete reaction. Sodium-concrete reaction model has also been developed and compared with experimental results. (Author) 51 refs., 16 tabs., 64 figs.

  9. Production of an economic high-density concrete for shielding megavoltage radiotherapy rooms and nuclear reactors

    Mortazavi, S. M. J.; Mosleh-Shirazi, M. A.; Maheri, M. R.; Haji-pour, A.; Yousefnia, H.; Zolghadri, S.

    2007-01-01

    In megavoltage radiotherapy rooms, ordinary concrete is usually used due to its low construction costs, although higher density concrete are sometimes used, as well. The use of high-density concrete decreases the required thickness of the concrete barrier; hence, its disadvantage is its high cost. In a nuclear reactor, neutron radiation is the most difficult to shield. A method for production of economic high-density concrete witt, appropriate engineering properties would be very useful. Materials and Methods: Galena (Pb S) mineral was used to produce of a high-density concrete. Galena can be found in many parts of Iran. Two types of concrete mixes were produced. The water-to-concrete (w/c) ratios of the reference and galena concrete mixes were 0.53 and 0.25, respectively. To measure the gamma radiation attenuation of Galena concrete samples, they were exposed to a narrow beam of gamma rays emitted from a cobalt-60 therapy unit. Results: The Galena mineral used in this study had a density of 7400 kg/m 3 . The concrete samples had a density of 4800 kg/m 3 . The measured half value layer thickness of the Galena concrete samples for cobalt 60 gamma rays was much less than that of ordinary concrete (2.6 cm compared to 6.0 cm). Furthermore, the galena concrete samples had significantly higher compressive strength (500 kg/cm 2 compared to 300 kg/cm 2 ). Conclusion: The Galena concrete samples made in our laboratories had showed good shielding/engineering properties in comparison with all samples made by using high-density materials other than depleted uranium. Based on the preliminary results, Galena concrete is maybe a suitable option where high-density concrete is required in megavoltage radiotherapy rooms as well as nuclear reactors

  10. Thermal behaviour and water release of concrete heated to temperatures between 300 and 6000C

    L'Homme, A.; Humbert, J.M.; Quillico, J.J.; Lourenco, A.

    1982-06-01

    This paper deals with the description of the experimental device, the study programme and the physical model developed for the final interpretation of the experiments. Some experimental results are given as an example. The experimental device enables one side of a concrete cylinder of 1 m 3 (section 1 m 2 , height 1 m), fitted with temperature and pressure measurement instrument in the mass, to be heated. The water is collected continuously on each of the 2 sides. Several experiments have been carried out on reinforced and non reinforced concrete samples, for hot face maximum temperatures in the 300 to 600 0 C range. The duration of an experiment varies from 2 days to one week. The physical model developed for interpreting the experiments allows for all thermal exchanges and various types of water transport in the porosity of the concrete (gaseous or liquid phase, towards the hot side or the cold side) [fr

  11. High temperature radioisotope capsule

    Bradshaw, G.B.

    1976-01-01

    A high temperature radioisotope capsule made up of three concentric cylinders, with the isotope fuel located within the innermost cylinder is described. The innermost cylinder has hemispherical ends and is constructed of a tantalum alloy. The intermediate cylinder is made of a molybdenum alloy and is capable of withstanding the pressure generated by the alpha particle decay of the fuel. The outer cylinder is made of a platinum alloy of high resistance to corrosion. A gas separates the innermost cylinder from the intermediate cylinder and the intermediate cylinder from the outer cylinder

  12. High-temperature uncertainty

    Timusk, T.

    2005-01-01

    Recent experiments reveal that the mechanism responsible for the superconducting properties of cuprate materials is even more mysterious than we thought. Two decades ago, Georg Bednorz and Alex Mueller of IBM's research laboratory in Zurich rocked the world of physics when they discovered a material that lost all resistance to electrical current at the record temperature of 36 K. Until then, superconductivity was thought to be a strictly low-temperature phenomenon that required costly refrigeration. Moreover, the IBM discovery - for which Bednorz and Mueller were awarded the 1987 Nobel Prize for Physics - was made in a ceramic copper-oxide material that nobody expected to be particularly special. Proposed applications for these 'cuprates' abounded. High-temperature superconductivity, particularly if it could be extended to room temperature, offered the promise of levitating trains, ultra-efficient power cables, and even supercomputers based on superconducting quantum interference devices. But these applications have been slow to materialize. Moreover, almost 20 years on, the physics behind this strange state of matter remains a mystery. (U.K.)

  13. Transport of accelerator produced high energy neutrons though concrete

    Prabhakar Rao, G.; Sarkar, P.K.

    1996-01-01

    Development of a computational system for estimating the production and transport of high energy neutrons in particle accelerators is reported. The energy-angle distribution of neutrons from accelerated ions bombarding thick targets is calculated by a hybrid nuclear reaction model code, ALICE-91, modified to suit the purpose. Subsequent transmission of these neutrons through concrete slabs is treated using the anisotropic source-flux iteration technique (ASFIT) in the framework of a coupled neutron-gamma transport. Several parameters of both the codes have been optimized to obtain the transmitted dose through concrete. The calculations are found to be accurate and at the same time faster compared to the detailed Monte Carlo calculations. (author). 8 refs., 2 figs

  14. High Temperature Piezoelectric Drill

    Bao, Xiaoqi; Bar-Cohen, Yoseph; Sherrit, Stewart; Badescu, Mircea; Shrout, Tom

    2012-01-01

    Venus is one of the planets in the solar systems that are considered for potential future exploration missions. It has extreme environment where the average temperature is 460 deg C and its ambient pressure is about 90 atm. Since the existing actuation technology cannot maintain functionality under the harsh conditions of Venus, it is a challenge to perform sampling and other tasks that require the use of moving parts. Specifically, the currently available electromagnetic actuators are limited in their ability to produce sufficiently high stroke, torque, or force. In contrast, advances in developing electro-mechanical materials (such as piezoelectric and electrostrictive) have enabled potential actuation capabilities that can be used to support such missions. Taking advantage of these materials, we developed a piezoelectric actuated drill that operates at the temperature range up to 500 deg C and the mechanism is based on the Ultrasonic/Sonic Drill/Corer (USDC) configuration. The detailed results of our study are presented in this paper

  15. Analysis of temperature stresses in concrete breakwater elements : Hollow cubes and Tetrapods

    Nooru-Mohamed, M.B.

    1994-01-01

    In this report, the results of a numerical parameter study on temperature stresses caused by hydration of cement in concrete breakwater elements are shown. Two different geometries were analysed namely hollow cubes and tetrapods. The problem encountered in solid cube breakwaters is the undesirable

  16. Numerical modeling of hydration process and temperature evolution in early age concrete

    Caggiano, A.; Pepe, M.; Koenders, E.A.B.; Martinelli, E.; Etse, G.J.

    2012-01-01

    Heat production induced by the hydration reaction and the resulting temperature evolution in the early phases of setting and hardening processes are critical phenomena, often leading to premature cracking of concrete members. However, the interest for simulating such phenomena is also related to the

  17. Early Property Development in Concrete

    Normann, Gitte; Munch-Petersen, Christian

    The Freiesleben Maturity function is widely used for planning of execution. We tested if for concrete with and without fly ash. The test showed surprisingly that the maturity function in general is not valid. We found that curing at high temperature gave a significant decrease in strength. Fly ash...... appears to reduce this decrease somewhat. We also examined the resistance against chloride penetration for the different concrete types. The resistance was reduced at high temperatures for concrete without fly ash. For concrete with fly ash, it was the opposite; concrete with fly ash obtained higher...

  18. High temperature materials and mechanisms

    2014-01-01

    The use of high-temperature materials in current and future applications, including silicone materials for handling hot foods and metal alloys for developing high-speed aircraft and spacecraft systems, has generated a growing interest in high-temperature technologies. High Temperature Materials and Mechanisms explores a broad range of issues related to high-temperature materials and mechanisms that operate in harsh conditions. While some applications involve the use of materials at high temperatures, others require materials processed at high temperatures for use at room temperature. High-temperature materials must also be resistant to related causes of damage, such as oxidation and corrosion, which are accelerated with increased temperatures. This book examines high-temperature materials and mechanisms from many angles. It covers the topics of processes, materials characterization methods, and the nondestructive evaluation and health monitoring of high-temperature materials and structures. It describes the ...

  19. ANALYSIS OF STRESS STATE IN UPPER LAYER OF ROAD CONCRETE PAVEMENT WITH TEMPERATURE ACTION

    M. K. Pshembaev

    2017-01-01

    Full Text Available While being operated auto-road pavements are subjected to intensive mechanical impacts, ultraviolet ray irradiation, freeze-thaw temperatures, freezing and thawing, drying and moistening. Due to these actions various types of pavement distresses appear on the road pavement. The most significant and dangerous type of distresses is micro-cracks on the road surface. One of the main reasons for their formation is an action of weather and climatic factors that initiate large changes in temperature of coating surface and occurrence of large temperature gradients in the upper layer. In this context while designing and operating auto-roads it is rather essential to investigate a stress state in road surface which is caused by temperature action. Purpose of the described investigations is to determine permissible temperature gradients for cement-concrete pavements that exclude formation of micro-cracks on their surface and thickness of damaged surface layer. Calculations of road pavement have been carried out at various laws for temperature distribution in its depth. A finite difference method realized in PARUS software has been used for studying a stress state of cement-concrete auto-roads. Regularities for distribution of stresses in cement-concrete pavement of auto-roads have been obtained at various surface temperatures. Permissible temperature gradients in the upper pavement layer have been determined and thickness of the layer where micro-cracks are formed has been assessed in the paper. Strength criterion based on the process of micro-crack formation and development in the concrete has been used for calculations. Risk of micro-crack formation on the auto-road pavement depends on material strength, conditions of plate fixing and temperature gradients.

  20. High temperature superconductors

    Paranthaman, Parans

    2010-01-01

    This essential reference provides the most comprehensive presentation of the state of the art in the field of high temperature superconductors. This growing field of research and applications is currently being supported by numerous governmental and industrial initiatives in the United States, Asia and Europe to overcome grid energy distribution issues. The technology is particularly intended for densely populated areas. It is now being commercialized for power-delivery devices, such as power transmission lines and cables, motors and generators. Applications in electric utilities include current limiters, long transmission lines and energy-storage devices that will help industries avoid dips in electric power.

  1. Heat generation and temperature-rise in ordinary concrete due to capture of thermal neutrons

    Abdo, E.A.; Amin, E.

    1997-01-01

    The aim of this work is the evaluation of the heat generation and temperature-rise in local ordinary concrete as a biological shield due to capture of total thermal and reactor thermal neutrons. The total thermal neutron fluxes were measured and calculated. The channel number 2 of the ETRR-1 reactor was used in the measurements as a neutron source. Computer code ANISN (VAX version) and neutron multigroup cross-section library EURLiB-4 was used in the calculations. The heat generation and temperature-rise in local ordinary concrete were evaluated and calculated. The results were displayed in curves to show the distribution of thermal neutron fluxes and heat generation as well as temperature-rise with the shield thickness. The results showed that, the heat generation as well as the temperature-rise have their maximum values in the first layers of the shield thickness. 4 figs., 12 refs

  2. Autogenous Deformation of Concrete

    Autogenous deformation of concrete can be defined as the free deformation of sealed concrete at a constant temperature. A number of observed problems with early age cracking of high-performance concretes can be attributed to this phenomenon. During the last 10 years , this has led to an increased...... focus on autogenous deformation both within concrete practice and concrete research. Since 1996 the interest has been significant enough to hold international, yearly conferences entirely devoted to this subject. The papers in this publication were presented at two consecutive half-day sessions...... at the American Concrete Institute’s Fall Convention in Phoenix, Arizona, October 29, 2002. All papers have been reviewed according to ACI rules. This publication, as well as the sessions, was sponsored by ACI committee 236, Material Science of Concrete. The 12 presentations from 8 different countries indicate...

  3. Applications of high-strength concrete to the development of the prestressed concrete reactor vessel (PCRV) design for an HTGR-SC/C plant

    Naus, D.J.

    1984-01-01

    The PCRV research and development program at ORNL consists of generic studies to provide technical support for ongoing PCRV-related studies, to contribute to the technological data base, and to provide independent review and evaluation of the relevant technology. Recent activities under this program have concentrated on the development of high-strength concrete mix designs for the PCRV of a 2240 MW(t) HTGR-SC/C plant, and the testing of models to both evaluate the behavior of high-strength concretes (plain and fibrous) and to develop model testing techniques. A test program to develop and evaluate high-strength (greater than or equal to 63.4 MPa) concretes utilizing materials from four sources which are in close proximity to potential sites for an HTGR plant is currently under way. The program consists of three phases. Phase I involves an evaluation of the cement, fly ash, admixtures and aggregate materials relative to their capability to produce concretes having the desired strength properties. Phase II is concerned with the evaluation of the effects of elevated temperatures (less than or equal to 316 0 C) on the strength properties of mixes selected for detailed evaluation. Phase III involves a determination of the creep characteristics and thermal properties of the selected mixes. An overview of each of these phases is presented as well as results obtained to date under Phase I which is approximately 75% completed

  4. AN EXPERIMENTAL STUDY ON STRENGTH AND PERMEABILITY PROPERTIES OF HIGH STRENGTH CONCRETE

    Yedla Venkatesh * & G. Kalyan

    2017-01-01

    Concrete is the most important engineering material and the addition of some other materials may change the properties of concrete. Mineral additions which are also known as mineral admixtures have been used with cements for many years. There are two types of materials crystalline and non crystalline. High performance concrete (HPC) exceeds the properties and constructability of normal concrete. Micro silica or silica fume is very fine non crystalline material. Silica fume is produced in elec...

  5. Study on the shear transfer of reinforced concrete at elevated temperature

    Ishida, Hiroaki; Kanazu, Tsutomu

    1989-01-01

    Reinforced concrete structures in nuclear power stations, such as a containment vessel and structural members supporting a reactor vessel, are designed assuming that they may be subjected to elevated temperature. In the design code, it is specified that the temperature of concrete must not exceed the limitation, and thermal effect shall be taken into account. In this study, the shearing test using Mattock type specimens was performed to investigate into the shear behavior of the reinforced concrete subjected to elevated temperature. The test parameters studied in this program were the reinforcement ratio in a shear plane, the compressive stress normal to a shear plane and temperature. The maximum shearing load of the specimens heated to 200 degC was about 10-20 % lower than that at normal temperature, but nearly equal to that of the specimens heated to 100 degC. The equation for evaluating the shearing strength ratio was proposed. The cracking width and slip at maximum shearing load increased as temperature rose. Up to 200 degC, the same relation existed between interface shear transfer rigidity and cracking width. (K.I.)

  6. An assessment of temperature history on concrete silo dry storage system for CANDU spent fuel

    Lee, Dong-Gyu; Sung, Nak-Hoon; Park, Jea-Ho; Chung, Sung-Hwan

    2016-01-01

    Highlights: • We performed thermal analysis to predict the temperature distribution in the concrete silo. • Thermal analysis of the concrete silo was based on CFD code. • Temperature distribution and history for storage period was presented. • Thermal analysis results and test results agreed well. • The correlations can predict the maximum fuel temperature over storage period. - Abstract: Concrete silo is a dry storage system for spent fuel generated from CANDU reactors. The silo is designed to remove passively the decay heat from spent fuel, as well as to secure the integrity of spent fuel during storage period. Dominant heat transfer mechanisms must be characterized and validated for the thermal analysis model of the silo, and the temperature history along storage period could be determined by using the validated thermal analysis model. Heat transfer characteristics on the interior and exterior of fuel basket in the silo were assessed to determine the temperature history of silo, which is necessary for evaluating the long-term degradation behavior of CANDU spent fuel stored in the silo. Also a methodology to evaluate the temperature history during dry storage period was proposed in this study. A CFD model of fuel basket including fuel bundles was suggested and temperature difference correlation between fuel bundles and silo’s internal member, as a function of decay heat of fuel basket considering natural convection and radiation heat transfer, was deduced. Temperature difference between silo’s internal cavity and ambient air was determined by using a concept of thermal resistance, which was validated by CFD analysis. Fuel temperature was expressed as a function of ambient temperature and decay heat of fuel basket in the correlation, and fuel temperature along storage period was determined. Therefore, it could be used to assess the degradation behavior of spent fuel by applying the degradation mechanism expressed as a function of spent fuel

  7. Effect of the heating rate on residual thermo-hydro-mechanical properties of a high-strength concrete in the context of nuclear waste storage

    Galle, C.; Pin, M.; Ranc, G.; Rodrigues, S.

    2003-01-01

    Concrete is likely to be used in massive structures for nuclear waste long-term storage facilities in France. In the framework of vitrified waste and spent fuel management, these structures could be submitted to high temperatures. In standard conditions, ambient temperature should not exceed 60 degC but in case of failure of a cooling system, concretes could be temporarily exposed to temperatures up to 250 degC. Depending on the temperature rise kinetics, concretes could be damaged to a greater or lesser extent. In this context, an experimental study on the effect of heating rate on concrete thermo-hydro-mechanical properties exposed to high temperatures (110 - 250 degC) was carried out at the French Atomic Energy Commission (CEA). Data analysis and interpretation provided enough arguments to conclude that, at local scale, the impact of heating rate on residual properties was real though relatively limited. (author)

  8. Design and evaluation of high-volume fly ash (HVFA) concrete mixes, report D : creep, shrinkage, and abrasion resistance of HVFA concrete.

    2012-10-01

    The main objective of this study was to determine the effect on shrinkage, creep, : and abrasion resistance of high-volume fly ash (HVFA) concrete. The HVFA concrete : test program consisted of comparing the shrinkage, creep, and abrasion performance...

  9. Influence of Temperature Upon Permanent Deformation Parameters of Asphalt Concrete Mixes

    Amjad Hamad Albayati

    2017-07-01

    Full Text Available The performance of asphalt concrete pavement has affected by many factors, the temperature is the most important environmental one which has a large effect on the structural behavior of flexible pavement materials. The main cause of premature failure of pavement is the rutting, Due to the viscoelastic nature of the asphalt cement, rutting is more pronounced in hot climate areas because the viscosity of the asphalt binder which is inversely related to rutting is significantly reduced with the increase in temperature resulting in a more rut susceptible paving mixtures. The objective of this study is to determine the effect of temperatures variations on the permanent deformation parameters (permanent strain (p, intercept (a, slope (b, Alpha and Mu as well as resilient strain (r and resilient modulus (Mr. To achieve this objective, one aggregate gradation with 12.5mm nominal maximum size, two grades of asphalt cements (40-50 and 60-70 brought form Al- Daurah refinery, limestone dust filler has been used to prepare the asphalt concrete mixtures. 30 Marshall specimens were prepared to determine the optimum asphalt cement content. Thereafter, 30 cylindrical asphalt concrete specimens (102mm in diameter and 203 mm in height are prepared in optimum asphalt cement and optimum ±0.5 percent. The prepared specimens were used in uniaxial repeated load test to evaluate the permanent deformation parameters of asphalt concrete mixes under the following testing temperature (5, 15, 25, 40 and 60c. The test result analyses appeared that Mr is decrease 51 percent when temperature increased from 5 c to 25 c and then decrease 22 percent with further increase in temperature from 25 c to 60 c. Also, the Alpha value decreases by a factor of 1.25 and 1.13 when temperature increases from 5 c to 25 c and 25 c to 60 c, espectively. Finally, statistical models were developed to predict the Alpha and Mu parameters of permanent deformation.

  10. Effects of temperature, mechanical loading and of their interactions on the permeability of structural concrete

    Choinska, M.

    2006-11-01

    Concrete permeability may influence the durability of structures indirectly by controlling the penetration rate of aggressive agents, but also directly if the structure has a confinement role, like containment vessels of nuclear power plants for instance. In the industrial background on the safety of these structures, the objective of this study is to characterize the evolution of concrete permeability under the effects of temperature and mechanical loading. The permeability tests are performed on hollow concrete cylinders, subjected to temperature up to 150 C and compressive loading up to failure. Experimental results reveal that the effects of temperature and damage may be decoupled for the estimation of permeability and enable us to propose a relation between permeability, damage and temperature. However, this relation may only be applied in the pre-peak phase as concrete remains micro-cracked. In order to overcome this limit to be able to model also permeability increase in the post-peak phase, another parameter, which is crack opening, is introduced in the relation between permeability and damage. This problem, investigated by modelling, is exploited according to two approaches. The first one is based on the definition of a matching law between existing relations of permeability evolution with damage and with crack opening. With this approach the tendencies are similar to the observed ones on the experimental results. The second approach consists in linking from a mechanical point of view damage with crack opening in order to apply the Poiseuille's law for permeability determination. Experimental validation of this approach, emerging towards a continuous model capable to reproduce permeability variations of a concrete structure, constitutes a major perspective of this work. (author)

  11. Qualification of a truly distributed fiber optic technique for strain and temperature measurements in concrete structures

    Henault, J. M.; Salin, J.; Moreau, G.; Delepine-Lesoille, S.; Bertand, J.; Taillade, F.; Quiertant, M.; Benzarti, K.

    2011-04-01

    Structural health monitoring is a key factor in life cycle management of infrastructures. Truly distributed fiber optic sensors are able to provide relevant information on large structures, such as nuclear power plants or nuclear waste disposal facilities. The sensing chain includes an optoelectronic unit and a sensing cable made of one or more optical fibers. A new instrument based on Optical Frequency Domain Reflectometry (OFDR), enables to perform temperature and strain measurements with a centimeter scale spatial resolution over hundred of meters and with a level of precision equal to 1 μ strain and 0.1 °C. Several sensing cables are designed with different materials targeting to last for decades, either embedded in the concrete or attached to the surface of the structure. They must ensure an optimal transfer of temperature and strain from the concrete matrix to the optical fiber. Based on the European guide FD CEN/TR 14748 "Non-destructive testing - Methodology for qualification of non-destructive tests", a qualification method was developed. Tests were carried out using various sensing cables embedded in the volume or fixed to the surface of plain concrete specimens and representative-scale reinforced concrete structural elements. Measurements were performed with an OFDR instrument, while mechanical solicitations were imposed to the concrete element. Preliminary experiments seem very promising since measurements performed with distributed sensing systems are found comparable to values obtained with conventional sensors used in civil engineering and with the Strength of Materials Modelling. Moreover, the distributed sensing system makes it possible to detect and localize cracks appearing in concrete during the mechanical loading.

  12. High temperature interface superconductivity

    Gozar, A.; Bozovic, I.

    2016-01-01

    Highlight: • This review article covers the topic of high temperature interface superconductivity. • New materials and techniques used for achieving interface superconductivity are discussed. • We emphasize the role played by the differences in structure and electronic properties at the interface with respect to the bulk of the constituents. - Abstract: High-T_c superconductivity at interfaces has a history of more than a couple of decades. In this review we focus our attention on copper-oxide based heterostructures and multi-layers. We first discuss the technique, atomic layer-by-layer molecular beam epitaxy (ALL-MBE) engineering, that enabled High-T_c Interface Superconductivity (HT-IS), and the challenges associated with the realization of high quality interfaces. Then we turn our attention to the experiments which shed light on the structure and properties of interfacial layers, allowing comparison to those of single-phase films and bulk crystals. Both ‘passive’ hetero-structures as well as surface-induced effects by external gating are discussed. We conclude by comparing HT-IS in cuprates and in other classes of materials, especially Fe-based superconductors, and by examining the grand challenges currently laying ahead for the field.

  13. Technical Note: Filler and superplasticizer usage on high strength concrete

    Sümer, M.

    2007-08-01

    Full Text Available In this research, the effects of filler (rock-dust usage on high strength concrete have been investigated through lab experiments and some results have been obtained. The experiments involved three series of concrete with different cement proportions of 375 kg/m3, 400 kg/m3, and 425 kg/m3. For each series of concrete, three different groups of samples have been prepared, the first one being the reference concrete which contained 0% chemical admixture and 0% filler, the second one contained 1.5% chemical admixture and 0% filler and finally the last group contained 1.5% chemical admixture and 5% filler to the weight of cement used. The chemical admixture used was a type of Super plasticizer with a brand name of “DARACEM 190”, and the cement used was Ordinary Portland Cement of target compressive strength 42.5 N/mm2, obtained from Nuh Cement Plant. For each batch, Slump Tests and Unit Weight Tests were performed. For each stage and group, two 15 cm cubic samples have been tested for Compressive Strength after being cured in water at 20 ± 2 °C for ages of 3 days, 7 days, 28 and 60 days. The total number of samples was 72. As a result, filler usage was found to reduce the porosity of Concrete, increase the Unit Weight of Concrete, increase the need for water and improve the Compressive Strength Properties of Concrete.En el presente trabajo se estudia la influencia de la utilización de un “filler” (polvo mineral en el comportamiento del hormigón de altas prestaciones. Para ello, se realizan ensayos de laboratorio en los que se emplean tres series de hormigón, cada una con una dosificación de cemento distinta, de 375, 400 y 425 kg/m3. Se preparan tres grupos de probetas de cada serie, el primero o de referencia con 0% de aditivo químico y 0% de “filler”, el segundo con un 1,5% del aditivo químico y 0% de “filler” y el tercero con un 1,5% del aditivo químico y un 5% de “filler” en peso del cemento. Como aditivo se

  14. High temperature metallic recuperator

    Ward, M. E.; Solmon, N. G.; Smeltzer, C. E.

    1981-06-01

    An industrial 4.5 MM Btu/hr axial counterflow recuperator, fabricated to deliver 1600 F combustion air, was designed to handle rapid cyclic loading, a long life, acceptable costs, and a low maintenance requirement. A cost benefit anlysis of a high temperature waste heat recovery system utilizing the recurperator and components capable of 1600 F combustion air preheat shows that this system would have a payback period of less than two years. Fifteen companies and industrial associations were interviewed and expressed great interest in recuperation in large energy consuming industries. Determination of long term environmental effects on candidate recuperator tubing alloys was completed. Alloys found to be acceptable in the 2200 F flue gas environment of a steel billet reheat furnace, were identified.

  15. Design of Ultra High Performance Fiber Reinforced Concrete Shells

    Jepsen, Michael S.; Lambertsen, Søren Heide; Damkilde, Lars

    2013-01-01

    Fiber Reinforced Concrete shell. The major challenge in the design phase has been securing sufficient stiffness of the structure while keeping the weight at a minimum. The weight/stiffness issue has been investigated by means of the finite element method, to optimize the structure regarding overall......The paper treats the redesign of the float structure of the Wavestar wave energy converter. Previously it was designed as a glass fiber structure, but due to cost reduction requirements a redesign has been initiated. The new float structure will be designed as a double curved Ultra High Performance...

  16. High-strength concrete and the design of power plant structures

    Puttonen, J.

    1991-01-01

    Based on the literature, the design of high-strength concrete structures and the suitability of high-strength concrete for the power plant structures have been studied. Concerning the behavior of structures, a basic difference between the high-strength concrete and the traditional one is that the ductility of the high-strength concrete is smaller. In the design, the non-linear stress-strain relationship of the high-strength concrete has to be taken into account. The use of the high-strength concrete is economical if the strength of the material can be utilized. In the long term, the good durability and wear resistance of the high-strength concrete increases the economy of the material. Because of the low permeability of the high-strength concrete, it is a potential material in the safety-related structures of nuclear power plants. The study discovered no particular power plant structure which would always be economical to design of high-strength concrete. However, the high-strength concrete was found to be a competitive material in general

  17. Mechanical properties of concrete mortar at low temperatures

    Arvidson, J.M.; Sparks, L.L.; Steketee, E.

    1984-01-01

    This report includes test results conducted at ambient (295 K), dry-ice and alcohol (195 K), liquid nitrogen (76 K), and liquid helium (4 K) temperatures. The compressive properties reported are Young's modulus, yield (at 0.2% offset) and maximum strengths, and elongation (elastic and plastic). Test specimens (5.1 cm diameter x 10.2 cm) were instrumented with a specially designed, diametrically opposed, cryogenic strain-gaged extensometer that minimizes possible errors due to specimen bending during the test

  18. Effect of elevated temperatures on heavy concrete structural strength in Qinshan phase 3 CANDU 6 reactor buildings

    Alikhan, S.; Khan, A.F.; Chen, S.

    2005-01-01

    Heavy concrete is commonly used inside the Qinshan Phase 3 CANDU 6 reactor buildings for radiation shielding functions in order to provide access to key areas during reactor operation. In some cases, the heavy concrete elements are also structural elements. Concerns have been raised about the functional performance of the heavy concrete structural elements, specifically the primary heat transport pump (PHTS) supporting slabs, surrounding the feeder cabinets when subjected to elevated temperatures between 42 degree C and 121 degree C and their corresponding temperature gradients on a long-term basis during the normal operation of the plant. This paper presents the results of a test investigation on the strength of heavy concrete under elevated temperature conditions being experienced by the heavy concrete structural elements around the feeder cabinet to confirm that these structural elements meet their functional requirements. The loading conditions consist subjecting the specimens to the elevated temperatures and temperature gradient noted during commissioning, including the effect of epoxy coating. The heavy concrete mix proportion and materials of the test samples (ilmenite aggregate and Portland cement) are identical to those used for heavy concrete structural elements surrounding the feeder cabinet. Subsequent to the confirmation of the functional requirements of the heavy concrete structural elements, alarm limits are recommended for these structural elements. (authors)

  19. Highly Conductive Carbon Fiber Reinforced Concrete for Icing Prevention and Curing

    Oscar Galao

    2016-04-01

    Full Text Available This paper aims to study the feasibility of highly conductive carbon fiber reinforced concrete (CFRC as a self-heating material for ice formation prevention and curing in pavements. Tests were carried out in lab ambient conditions at different fixed voltages and then introduced in a freezer at −15 °C. The specimens inside the freezer were exposed to different fixed voltages when reaching +5 °C for prevention of icing and when reaching the temperature inside the freezer, i.e., −15 °C, for curing of icing. Results show that this concrete could act as a heating element in pavements with risk of ice formation, consuming a reasonable amount of energy for both anti-icing (prevention and deicing (curing, which could turn into an environmentally friendly and cost-effective deicing method.

  20. Highly Conductive Carbon Fiber Reinforced Concrete for Icing Prevention and Curing.

    Galao, Oscar; Bañón, Luis; Baeza, Francisco Javier; Carmona, Jesús; Garcés, Pedro

    2016-04-12

    This paper aims to study the feasibility of highly conductive carbon fiber reinforced concrete (CFRC) as a self-heating material for ice formation prevention and curing in pavements. Tests were carried out in lab ambient conditions at different fixed voltages and then introduced in a freezer at -15 °C. The specimens inside the freezer were exposed to different fixed voltages when reaching +5 °C for prevention of icing and when reaching the temperature inside the freezer, i.e. , -15 °C, for curing of icing. Results show that this concrete could act as a heating element in pavements with risk of ice formation, consuming a reasonable amount of energy for both anti-icing (prevention) and deicing (curing), which could turn into an environmentally friendly and cost-effective deicing method.

  1. Physico-mechanical properties of high performance concrete using different aggregates in presence of silica fume

    Salah A. Abo-El-Enein

    2014-04-01

    Full Text Available Heavy weight high performance concrete (HPC can be used when particular properties, such as high strength and good radiation shielding are required. Such concrete, using ilmenite and hematite coarse aggregates can significantly have higher specific gravities than those of concrete made with dolomite and air-cooled slag aggregates. Four different concrete mixes with the same cement content and different w/c ratios were designed using normal dolomite aggregate, air-cooled slag by-product and two different types of iron ore aggregates. High performance concrete (grade-M60 can be achieved using superplasticizer to reduce the water/cement ratio; the effect of SF on the performance of concrete was studied by addition of 10% silica fume to the total cement content. The physico-mechanical properties of coarse aggregates and hardened concrete were studied. The results show that, Ilmenite coarse aggregate gives higher physical and mechanical properties than the other aggregates. Also, addition of 10% silica fume developed a stronger and a denser interfacial transition zone (ITZ between concrete particles and the cement matrix. Crushed air-cooled slag can be used to produce a high-strength concrete with better mechanical properties than corresponding concrete made with crushed hematite and ilmenite. Heavy density concrete made with fine aggregates of ilmenite and air-cooled slag are expected to be suitable as shielding materials to attenuate gamma rays.

  2. Reinforced concrete containment structures in high seismic zones

    Aziz, T.S.

    1977-01-01

    A new structural concept for reinforced concrete containment structures at sites where earthquake ground motions in terms of the Safe Shutdown Earthquake (SSE) exceeds 0.3 g is presented. The structural concept is based on: (1) an inner steel-lined concrete shell which houses the reactor and provides shielding and containment in the event of loss of coolant accident; (2) an outer annular concrete shell structure which houses auxilary reactor equipment and safeguards systems. These shell structures are supported on a common foundation mat which is embeded in the subgrade. Under stipulated earthquake conditions the two shell structures interact to resist lateral inertia forces. Thus the annular structure which is not a pressure boundary acts as a lateral support for the inner containment shell. The concept is practical, economically feasible and new to practice. An integrated configuration which includes the interior shell, the annular structure and the subgrade is analyzed for several static and dynamic loading conditions. The analysis is done using a finite difference solution scheme for the static loading conditions. A semi-analytical three-dimensional finite element scheme combined with a Fast Fourier Transform (FFT) algorithm is used for the dynamic loading conditions. The effects of cracking of the containment structure due to pressurization in conjunction with earthquake loading are discussed. Analytical results for both the finite difference and the finite element schemes are presented and the sensitivity of the results to changes in the input parameters is studied. General recommendations are given for plant configurations where high seismic loading is a major design consideration

  3. Temperature Measurement and Damage Detection in Concrete Beams Exposed to Fire Using PPP-BOTDA Based Fiber Optic Sensors.

    Bao, Yi; Hoehler, Matthew S; Smith, Christopher M; Bundy, Matthew; Chen, Genda

    2017-10-01

    In this study, distributed fiber optic sensors based on pulse pre-pump Brillouin optical time domain analysis (PPP-BODTA) are characterized and deployed to measure spatially-distributed temperatures in reinforced concrete specimens exposed to fire. Four beams were tested to failure in a natural gas fueled compartment fire, each instrumented with one fused silica, single-mode optical fiber as a distributed sensor and four thermocouples. Prior to concrete cracking, the distributed temperature was validated at locations of the thermocouples by a relative difference of less than 9 %. The cracks in concrete can be identified as sharp peaks in the temperature distribution since the cracks are locally filled with hot air. Concrete cracking did not affect the sensitivity of the distributed sensor but concrete spalling broke the optical fiber loop required for PPP-BOTDA measurements.

  4. Laboratory Performance Evaluation of High Modulus Asphalt Concrete Modified with Different Additives

    Peng Li

    2017-01-01

    Full Text Available The objective of this study is to evaluate comprehensive performance of high modulus asphalt concrete (HMAC and propose common values for establishing evaluation system. Three gradations with different modifiers were conducted to study the high and low temperature performance, shearing behavior, and water stability. The laboratory tests for HMAC included static and dynamic modulus tests, rutting test, uniaxial penetration test, bending test, and immersion Marshall test. Dynamic modulus test results showed that modifier can improve the static modulus and the improvements were remarkable at higher temperature. Moreover, modulus of HMAC-20 was better than those of HMAC-16 and HMAC-25. The results of performance test indicated that HMAC has good performance to resist high temperature rutting, and the resistances of the HMAC-20 and HMAC-25 against rutting were better than that of HMAC-16. Then, the common values of dynamic stability were recommended. Furthermore, common values of HMAC performance were established based on pavement performance tests.

  5. Mechanical and Microstructural Evaluations of Lightweight Aggregate Geopolymer Concrete before and after Exposed to Elevated Temperatures.

    Abdulkareem, Omar A; Abdullah, Mohd Mustafa Al Bakri; Hussin, Kamarudin; Ismail, Khairul Nizar; Binhussain, Mohammed

    2013-10-09

    This paper presents the mechanical and microstructural characteristics of a lightweight aggregate geopolymer concrete (LWAGC) synthesized by the alkali-activation of a fly ash source (FA) before and after being exposed to elevated temperatures, ranging from 100 to 800 °C. The results show that the LWAGC unexposed to the elevated temperatures possesses a good strength-to-weight ratio compared with other LWAGCs available in the published literature. The unexposed LWAGC also shows an excellent strength development versus aging times, up to 365 days. For the exposed LWAGC to the elevated temperatures of 100 to 800 °C, the results illustrate that the concretes gain compressive strength after being exposed to elevated temperatures of 100, 200 and 300 °C. Afterward, the strength of the LWAGC started to deteriorate and decrease after being exposed to elevated temperatures of 400 °C, and up to 800 °C. Based on the mechanical strength results of the exposed LWAGCs to elevated temperatures of 100 °C to 800 °C, the relationship between the exposure temperature and the obtained residual compressive strength is statistically analyzed and achieved. In addition, the microstructure investigation of the unexposed LWAGC shows a good bonding between aggregate and mortar at the interface transition zone (ITZ). However, this bonding is subjected to deterioration as the LWAGC is exposed to elevated temperatures of 400, 600 and 800 °C by increasing the microcrack content and swelling of the unreacted silicates.

  6. Dynamic behavior of radiant cooling system based on capillary tubes in walls made of high performance concrete

    Mikeska, Tomás; Svendsen, Svend

    2015-01-01

    elements made of high performance concrete. The influence of the radiant cooling system on the indoor climate of the test room in terms of the air, surface and operative temperatures and velocities was investigated.The results show that the temperature of the room air can be kept in a comfortable range...... using cooling water for the radiant cooling system with a temperature only about 4K lower than the temperature of the room air. The relatively high speed reaction of the designed system is a result of the slim construction of the sandwich wall elements made of high performance concrete. (C) 2015...... the small amount of fresh air required by standards to provide a healthy indoor environment.This paper reports on experimental analyses evaluating the dynamic behavior of a test room equipped with a radiant cooling system composed of plastic capillary tubes integrated into the inner layer of sandwich wall...

  7. Effect of Temperature Variation on Modal Frequency of Reinforced Concrete Slab and Beam in Cold Regions

    Hanbing Liu

    2016-01-01

    Full Text Available Changes of modal frequencies induced by temperature variation can be more obvious than those caused by structural damage, which will lead to the false damage identification results. Therefore, quantifying the temperature effect on modal frequencies is a critical step to eliminate its interference in damage detection. Due to the nonuniform and time-dependent characteristics of temperature distribution, it is insufficient to obtain the reliable relationships between temperatures and modal frequencies using temperatures in air or at surface. In this paper, correlations between measured temperatures (air temperature, surface temperature, mean temperature, etc. and modal frequencies for the slab and beam are comparatively analyzed. And the quantitative models are constructed considering nonuniform temperature distribution. Firstly, the reinforced concrete slab and beam were constructed and placed outside the laboratory to be monitored. Secondly, the correlation coefficients between modal frequencies and three kinds of temperatures are calculated, respectively. Thirdly, simple linear regression models between mean temperature and modal frequencies are established for the slab and beam. Finally, five temperature variables are selected to construct the multiple linear regression models. Prediction results reveal that the proposed multiple linear regression models possess favorable accuracy to quantify the temperature effect on modal frequencies considering nonuniform temperature distribution.

  8. Residual characteristic properties of ternary blended steel fibre reinforced concrete subjected to sustained elevated temperature

    Sinha Deepa A.

    2013-09-01

    Full Text Available To study the behavior of ternary blended steel fibre reinforced concrete when subjected to 800 Deg.C and 1000 Deg.C for 3 hours. It has been found that the ternary blended steel fibre reinforced concrete containing (FA+GGBFS and (FA+MK offer higher resistance to sustained elevated temperatures upto 800 Deg.C, where as the blend containing (FA+SF does not offer any resistance at this temperature. The study reveals that the blend containing (FA+GGBFS and (FA+MK gives highest resistance at replacement levels of (10+20 and (15+15 respectively at sustained exposure to 800 Deg.C.

  9. Prediction of concrete strength in massive structures

    Sakamoto, T.; Makino, H.; Nakane, S.; Kawaguchi, T.; Ohike, T.

    1989-01-01

    Reinforced concrete structures of a nuclear power plant are mostly of mass concrete with cross-sectional dimensions larger than 1.0 m. The temperature of concrete inside after placement rises due to heat of hydration of cement. It is well known that concrete strengths of mass concrete structure subjected to such temperature hysteresis are generally not equal to strengths of cylinders subjected to standard curing. In order to construct a mass concrete structure of high reliability in which the specified concrete strength is satisfied by the specified age, it is necessary to have a thorough understanding of the strength gain property of concrete in the structure and its relationships with the water-cement ratio of the mix, strength of standard-cured cylinders and the internal temperature hysteresis. This report describes the result of studies on methods of controlling concrete strength in actual construction projects

  10. High-performance heavy concrete as a multi-purpose shield

    Mortazavi, S. M. J.; Mosleh-Shirazi, M. A.; Roshan-Shomal, P.; Raadpey, N.; Baradaran-Ghahfarokhi, M.

    2010-01-01

    Concrete has long been used as a shield against high-energy photons and neutrons. In this study, colemanite and galena minerals (CoGa) were used for the production of an economical high-performance heavy concrete. To measure the gamma radiation attenuation of the CoGa concrete samples, they were exposed to a narrow beam of gamma rays emitted from a 60 Co radiotherapy unit. An Am-Be neutron source was used for assessing the shielding properties of the samples against neutrons. The compression strengths of both types of concrete mixes (CoGa and reference concrete) were investigated. The range of the densities of the heavy concrete samples was 4100-4650 kg m -3 , whereas it was 2300-2600 kg m -3 in the ordinary concrete reference samples. The half-value layer of the CoGa concrete samples for 60 Co gamma rays was 2.49 cm; much less than that of ordinary concrete (6.0 cm). Moreover, CoGa concrete samples had a 10% greater neutron absorption compared with reference concrete. (authors)

  11. Fracture toughness of ultra high performance concrete by flexural performance

    Manolova Emanuela

    2016-01-01

    Full Text Available This paper describes the fracture toughness of the innovative structural material - Ultra High Performance Concrete (UHPC, evaluated by flexural performance. For determination the material behaviour by static loading are used adapted standard test methods for flexural performance of fiber-reinforced concrete (ASTM C 1609 and ASTM C 1018. Fracture toughness is estimated by various deformation parameters derived from the load-deflection curve, obtained by testing simple supported beam under third-point loading, using servo-controlled testing system. This method is used to be estimated the contribution of the embedded fiber-reinforcement into improvement of the fractural behaviour of UHPC by changing the crack-resistant capacity, fracture toughness and energy absorption capacity with various mechanisms. The position of the first crack has been formulated based on P-δ (load- deflection response and P-ε (load - longitudinal deformation in the tensile zone response, which are used for calculation of the two toughness indices I5 and I10. The combination of steel fibres with different dimensions leads to a composite, having at the same time increased crack resistance, first crack formation, ductility and post-peak residual strength.

  12. High alkali-resistant basalt fiber for reinforcing concrete

    Lipatov, Ya.V.; Gutnikov, S.I.; Manylov, M.S.; Zhukovskaya, E.S.; Lazoryak, B.I.

    2015-01-01

    Highlights: • Doping of basalt fiber with ZrSiO 4 increased its alkali resistance. • Alkali treatment results in formation of protective surface layer on fibers. • Morphology and chemical composition of surface layer were investigated. • Mechanical properties of fibers were analyzed by a Weibull distribution. • Zirconia doped basalt fibers demonstrate high performance in concrete. - Abstract: Basalt glasses and fibers with zirconia content in the range from 0 to 7 wt% were obtained using ZrSiO 4 as a zirconium source. Weight loss and tensile strength loss of fibers after refluxing in alkali solution were determined. Basalt fiber with 5.7 wt% ZrO 2 had the best alkali resistance properties. Alkali treatment results in formation of protective surface layer on fibers. Morphology and chemical composition of surface layer were investigated. It was shown that alkali resistance of zirconia doped basalt fibers is caused by insoluble compounds of Zr 4+ , Fe 3+ and Mg 2+ in corrosion layer. Mechanical properties of initial and leached fibers were evaluated by a Weibull distribution. The properties of basalt fibers with ZrSiO 4 were compared with AR-glass fibers. The performance of concrete with obtained fibers was investigated

  13. Effect of temperature and moisture on the fracture energy and the thermal properties of concrete

    Kallel, H.; Carre, H.; Laborderie, C.; Masson, B.; Tran, N.C.

    2015-01-01

    In nuclear power plants, during a severe accident the containment building undergoes an increase of pressure, temperature and relative humidity that can reach respectively 5 bars, 140 C. degrees and the saturation of water vapor. Beyond the regulatory calculations, a suitable knowledge of the thermal and mechanical behaviour of the materials and more specifically of the concrete is required to carry out accurate numerical simulations. An experimental apparatus has been designed to assess the fracture energy (G f ) evolutions for concrete under various experimental conditions in terms of temperature and relative humidity of the concrete. Mechanical tests have been performed under different controlled conditions in terms of temperature (T=30 C. degrees ) and liquid water degree of saturation S w (four target values of 50, 70, 90 and 100%). These values of liquid water degree of saturation have been obtained by conditioning the relative humidity of the sealed environment where specimens have been left for the equalisation process by using potassium salt solutions. DCT (Disk-shape Compact Tension) test has been chosen for determining G f . In comparison with three points bending test, the typology of the test, the equipment and all test devices have been validated. Test results show clearly the decreasing of the fracture energy as saturation degree increases. This evolution has a linear trend for S w ranging from 36 % to 97 %

  14. A coupled thermo-hydro-mechanical-damage model for concrete subjected to moderate temperatures

    Bary, B.; Carpentier, O. [CEA Saclay, DEN/DPC/SCCME/LECBA, F-91191 Gif Sur Yvette, (France); Ranc, G. [CEA VALRHO, DEN/DTEC/L2EC/LCEC, F-30207 Bagnols Sur Ceze, (France); Durand, S. [CEA Saclay, DEN/DM2S/SEMT/LM2S, F-91191 Gif Sur Yvette, (France)

    2008-07-01

    This study focuses on the concrete behavior subjected to moderate temperatures, with a particular emphasis on the transient thermo-hydric stage. A simplified coupled thermo-hydro-mechanical model is developed with the assumption that the gaseous phase is composed uniquely of vapor. Estimations of the mechanical parameters, Biot coefficient and permeability as a function of damage and saturation degree are provided by applying effective-medium approximation schemes. The isotherm adsorption curves are supposed to depend upon both temperature and crack-induced porosity. The effects of damage and parameters linked to transfer (in particular the adsorption curves) on the concrete structure response in the transient phase of heating are then investigated and evaluated. To this aim, the model is applied to the simulation of concrete cylinders with height and diameter of 0.80 m subjected to heating rates of 0.1 and 10 degrees C/min up to 160 degrees C. The numerical results are analyzed, commented and compared with experimental ones in terms of water mass loss, temperatures and gas pressures evolutions. A numerical study indicates that some parameters have a greater influence on the results than others, and that certain coupling terms in the mass conservation equation of water may be neglected. (authors)

  15. High Density Radiation Shielding Concretes for Hot Cells of 99mTc Project

    Sakr, K.

    2006-01-01

    High density concrete [more than 3.6 ton/m 3 (3.6x10 3 kg/m 3 )] was prepared to be used as a radiation shielding concrete (RSC) for hot-cells in gel technetium project at inshas to attenuate gamma radiation emitted from radioactive sources. different types of concrete were prepared by mixing local mineral aggregates mainly gravel and ilmenite . iron shots were added to the concrete mixture proportion as partial replacement of heavy aggregates to increase its density. the physical properties of prepared concrete in both plastic and hardened phases were investigated. compressive strength and radiation attenuation of gamma rays were determined. Results showed that ilmenite concrete mixed with iron shots had the highest density suitable to be use as RSC according to the chinese hot cell design requirements. Recommendations to avoid some technical problems of manufacturing radiation shielding concrete were maintained

  16. Properties of High Strength Concrete Applied on Semarang - Bawen Highway

    Setiyawan, Prabowo; Antonius; Wedyowibowo, R. Hawik Jenny

    2018-04-01

    To fulfill the needs of highway construction then a high quality concrete is expected to be produced by a short time and high workability, therefore the addition of additive chemicals needs to be conducted. The objective of the study was to find out the properties of high quality concrete including slump value, compressive strength, flexural strength, elasticity modulus and stress-strain diagrams with the addition of fly ash and superplasticizer. There were five types of mixtures were made in this study with a fas (cement water factor) was 0,41 and an additional 15% of fly ash and a varied superplasticizer of 0%, 0.5%, 1%, 2% towards the weight/volume and cement/water. Test samples of cylinders and prisms or beams were tested in the laboratory at 1, 3, 7, 14, and 28 days. The test results were then compared with the test results made without additional additives. Based on the result of this research, it can be concluded that the increase of slump value due to the addition of 15% fly ash is 0,53 cm of the base slump value. The use of superplasticizer causes the weight of the type to be greater. The optimum dose of superplasticizer is 1,2%, it is still in the usage level according to the F-type admixture brochure (water reducing, high-range admixture) such as 0,6 % -1,5 %. All mixture types which use addition materials for flexural strength (fr'=45kg/cm2) can be achieved at 3 days.

  17. Self-compacting concrete containing different powders at elevated temperatures - Mechanical properties and changes in the phase composition of the paste

    Bakhtiyari, S.; Allahverdi, A.; Rais-Ghasemi, M.; Zarrabi, B.A.; Parhizkar, T.

    2011-01-01

    Fire resistance of self-compacting concretes (SCC) containing limestone and quartz powders, with two different compressive strengths, were evaluated and compared with normal concretes (NC). The residual mechanical strengths of the mixes at different temperatures were measured. The changes in the phase composition of the cement pastes at high temperatures were examined with thermal analysis and X-ray diffractometry methods. The SCC mixes showed a higher susceptibility to spalling at high temperatures but the NC mixes suffered much more from loss of the mechanical strengths. Both the powder types and the compressive strength notably influenced the fire behavior of the SCC. The quartz powder accelerated the hydration of the SCC cement paste at high temperatures, up to 500 o C. However, the quartz-contained SCC showed the highest risk of spalling among all the mixes. The results showed that the thermal analysis could be a useful device for evaluating the fire behavior of building materials.

  18. Self-compacting concrete containing different powders at elevated temperatures - Mechanical properties and changes in the phase composition of the paste

    Bakhtiyari, S., E-mail: bakhtiyari@bhrc.ac.ir [School of Chemical Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Allahverdi, A., E-mail: ali.allahverdi@iust.ac.ir [Cement Research Center, School of Chemical Engineering, Iran University of Science and Technology, Narmak, Tehran 16846-13114 (Iran, Islamic Republic of); Rais-Ghasemi, M., E-mail: raissghasemi@bhrc.ac.ir [Dep. of Concrete Technology, Building and Housing Research Center (BHRC), Tehran (Iran, Islamic Republic of); Zarrabi, B.A., E-mail: zarrabi@chalmers.se [Fire Technology Dep., SP Technical Research Institute of Sweden (Sweden); Parhizkar, T., E-mail: parhizkar@bhrc.ac.ir [Dep. of Concrete Technology, Building and Housing Research Center (BHRC), Tehran (Iran, Islamic Republic of)

    2011-02-20

    Fire resistance of self-compacting concretes (SCC) containing limestone and quartz powders, with two different compressive strengths, were evaluated and compared with normal concretes (NC). The residual mechanical strengths of the mixes at different temperatures were measured. The changes in the phase composition of the cement pastes at high temperatures were examined with thermal analysis and X-ray diffractometry methods. The SCC mixes showed a higher susceptibility to spalling at high temperatures but the NC mixes suffered much more from loss of the mechanical strengths. Both the powder types and the compressive strength notably influenced the fire behavior of the SCC. The quartz powder accelerated the hydration of the SCC cement paste at high temperatures, up to 500 {sup o}C. However, the quartz-contained SCC showed the highest risk of spalling among all the mixes. The results showed that the thermal analysis could be a useful device for evaluating the fire behavior of building materials.

  19. Advances in high temperature chemistry

    Eyring, Leroy

    1969-01-01

    Advances in High Temperature Chemistry, Volume 2 covers the advances in the knowledge of the high temperature behavior of materials and the complex and unfamiliar characteristics of matter at high temperature. The book discusses the dissociation energies and free energy functions of gaseous monoxides; the matrix-isolation technique applied to high temperature molecules; and the main features, the techniques for the production, detection, and diagnosis, and the applications of molecular beams in high temperatures. The text also describes the chemical research in streaming thermal plasmas, as w

  20. Thermal and strength performance of reinforced self-compacting concrete slabs mixed with basalt and PVA fibers in high intensity fire

    Mohd Jani Noraniza

    2017-01-01

    Full Text Available Fibers addition to concrete and the innovation of self-compacting concrete technology lead to the development of high-performance concrete. However, high intensity fire may adversely affect the performance of this type of concrete. A series of fire resistance test experiments to evaluate the performance of fiber reinforced self-compacting concrete (FR-SCC slabs consisting of various mix of basalt and PVA fibers were carried out by subjecting the concrete slabs as an element of construction to high intensity Hydrocarbon fire heating condition. The fire testing condition was in accordance with the standard time-temperature fire curve for 120 minutes up to 1100°C heating temperature. The temperatures on the surface and within the concrete slabs were recorded and the performance of each type of FRSCC slabs were evaluated. The performance of Basalt FR-SCC was found to be more resistant to fire in comparison to PVA FRSCC. There residual compressive strength of core samples were tested and SEM analysis were carried out to determine the effect of high intensity fire on the basalt and PVA FR-SCC slabs.

  1. The Fire Resistance Performance of Recycled Aggregate Concrete Columns with Different Concrete Compressive Strengths

    Dong, Hongying; Cao, Wanlin; Bian, Jianhui; Zhang, Jianwei

    2014-01-01

    In order to ascertain the fire resistance performance of recycled aggregate concrete (RAC) components with different concrete compressive strengths, four full-scaled concrete columns were designed and tested under high temperature. Two of the four specimens were constructed by normal concrete with compressive strength ratings of C20 and C30, respectively, while the others were made from recycled coarse aggregate (RCA) concrete of C30 and C40, respectively. Identical constant axial forces were...

  2. Cast in place temperature 5 influence on fresh concrete made with limestone filler and blended cement

    Soria, E. A.

    2003-12-01

    Full Text Available Properties of fresh concrete play a relevant role on placing and consolidation; and its design strength and durability depends on them. It is well known too that the concrete temperature during placing affects all its properties in different ways and extent. This paper presents the influence of placing temperature of concretes made with portland cement, limestone filer cement and blended cement, commercially available, on slump, slump loss, setting time and bleeding. The results show that generally when concrete temperature rises, the bleeding and slump fall down and the slump loss and setting time are accelerated. However, regardless of the strength class the type of cement affects the value of these variations

    Las propiedades de los hormigones en estado fresco desempeñan un papel fundamental durante las operaciones de colocación y compactación de los mismos y de ellas depende, en gran medida, que se alcance en el estado endurecido la resistencia y la durabilidad de diseño. Es sabido, además, que la temperatura que alcanza un hormigón durante dichas operaciones, afecta en mayor o menor grado a todas sus propiedades, de manera diferente. En el presente trabajo se analizó la influencia de la temperatura de colocación sobre el asentamiento, la pérdida del asentamiento en el tiempo, los tiempos de fraguado y la exudación, en hormigones elaborados con cemento portland normal, fillerizado y compuesto, de procedencia comercial. Los resultados han mostrado, en general, que con el aumento de la temperatura de colocación disminuyen la exudación y el asentamiento; mientras que la pérdida de asentamiento y los tiempos de fraguado se aceleran. Sin embargo, las magnitudes de dichas variaciones resultan a su vez muy influenciadas por el tipo de cemento utilizado, aun siendo de la misma clase resistente.

  3. Chloride Penetration through Cracks in High-Performance Concrete and Surface Treatment System for Crack Healing

    In-Seok Yoon

    2012-01-01

    Full Text Available For enhancing the service life of concrete structures, it is very important to minimize crack at surface. Even if these cracks are very small, the problem is to which extend these cracks may jeopardize the durability of these decks. It was proposed that crack depth corresponding with critical crack width from the surface is a crucial factor in view of durability design of concrete structures. It was necessary to deal with chloride penetration through microcracks characterized with the mixing features of concrete. This study is devoted to examine the effect of high strength concrete and reinforcement of steel fiber on chloride penetration through cracks. High strength concrete is regarded as an excellent barrier to resist chloride penetration. However, durability performance of cracked high strength concrete was reduced seriously up to that of ordinary cracked concrete. Steel fiber reinforcement is effective to reduce chloride penetration through cracks because steel fiber reinforcement can lead to reduce crack depth significantly. Meanwhile, surface treatment systems are put on the surface of the concrete in order to seal the concrete. The key-issue is to which extend a sealing is able to ensure that chloride-induced corrosion can be prevented. As a result, penetrant cannot cure cracks, however, coating and combined treatment can prevent chloride from flowing in concrete with maximum crack width of 0.06 mm and 0.08 mm, respectively.

  4. THE CHANGE IN DEFORMATION CHARACTERISTICS OF CONCRETE MONOLITHIC HIGH-RISE BUILDINGS

    V. V. Punahin

    2009-03-01

    Full Text Available In the article results of studies of deformation features of concrete on actuate cement for monolithic high-altitude buildings are presented. It is shown that in construction of the high-altitude monolithic buildings in a summer period of a year one should take into account the character of changing the concrete elasticity and plasticity in time, which differs from the same indices for the concrete of normal hardening.

  5. Calculation of Prestressed Pressure Vessel Taking into Account the Concrete Temperature Inhomogeneity

    Andreev, Vladimir

    2018-03-01

    The paper deals with the problem of determining the stress state of the pressure vessel (PV) with considering the concrete temperature inhomogeneity. Such structures are widely used in heat power engineering, for example, in nuclear power engineering. The structures of such buildings are quite complex and a comprehensive analysis of the stress state in them can be carried out either by numerical or experimental methods. However, a number of fundamental questions can be solved on the basis of simplified models, in particular, studies of the effect on the stressed state of the inhomogeneity caused by the temperature field.

  6. Elastic-plastic constitutive modeling of concrete

    Takahashi, Y.

    1983-03-01

    The need to understand concrete behavior under high temperatures in the nuclear industry has become rather accute. For this purpose, a constitutive model of concrete especially developed for this severe environment is indispensable. This report reviews the presently available constitutive models of concrete at standard-temperature conditions and considers their advantages and drawbacks. A rather simple but effective approach is selected to treat concrete behavior at high temperatures. Special emphasis is devoted to the modeling of concrete up to and including failure. The derived constitutive model is checked with biaxial and triaxial benchmark experimental results. Very good agreement is obtained

  7. High-impact concrete for fill in US Department of Transportation type shipping containers

    Greenhalgh, W.O.; Cash, R.J.

    1990-01-01

    This report describes the use of light-weight, high-impact concrete in U.S. Department of Transportation-type shipments. The formulations described are substantially lighter in weight (20 to 50 percent) than construction concrete, but product test specimens generally yield superior impact characteristics. The use of this specialty concrete for container fill, encapsulations, or liquid-waste solidification can be advantageous. Use of the material for container or cask construction has the advantage of lighter weight for easier handling, and the container consistently exhibits better performance on drop tests. High-impact concrete does have the disadvantage of less gamma radiation shielding per volume, but some formulation changes discussed in this report can be used to prepare better shielding concrete. Test characteristics of high-impact concrete are included. 3 refs., 6 figs., 7 tabs

  8. Study on creep of fiber reinforced ultra-high strength concrete based on strength

    Peng, Wenjun; Wang, Tao

    2018-04-01

    To complement the creep performance of ultra-high strength concrete, the long creep process of fiber reinforced concrete was studied in this paper. The long-term creep process and regularity of ultra-high strength concrete with 0.5% PVA fiber under the same axial compression were analyzed by using concrete strength (C80/C100/C120) as a variable. The results show that the creep coefficient of ultra-high strength concrete decreases with the increase of concrete strength. Compared with ACI209R (92), GL2000 models, it is found that the predicted value of ACI209R (92) are close to the experimental value, and the creep prediction model suitable for this experiment is proposed based on ACI209R (92).

  9. Self-desiccation mechanism of high-performance concrete.

    Yang, Quan-Bing; Zhang, Shu-Qing

    2004-12-01

    Investigations on the effects of W/C ratio and silica fume on the autogenous shrinkage and internal relative humidity of high performance concrete (HPC), and analysis of the self-desiccation mechanisms of HPC showed that the autogenous shrinkage and internal relative humidity of HPC increases and decreases with the reduction of W/C respectively; and that these phenomena were amplified by the addition of silica fume. Theoretical analyses indicated that the reduction of RH in HPC was not due to shortage of water, but due to the fact that the evaporable water in HPC was not evaporated freely. The reduction of internal relative humidity or the so-called self-desiccation of HPC was chiefly caused by the increase in mole concentration of soluble ions in HPC and the reduction of pore size or the increase in the fraction of micro-pore water in the total evaporable water (T(r)/T(te) ratio).

  10. High-Temperature Piezoelectric Sensing

    Xiaoning Jiang

    2013-12-01

    Full Text Available Piezoelectric sensing is of increasing interest for high-temperature applications in aerospace, automotive, power plants and material processing due to its low cost, compact sensor size and simple signal conditioning, in comparison with other high-temperature sensing techniques. This paper presented an overview of high-temperature piezoelectric sensing techniques. Firstly, different types of high-temperature piezoelectric single crystals, electrode materials, and their pros and cons are discussed. Secondly, recent work on high-temperature piezoelectric sensors including accelerometer, surface acoustic wave sensor, ultrasound transducer, acoustic emission sensor, gas sensor, and pressure sensor for temperatures up to 1,250 °C were reviewed. Finally, discussions of existing challenges and future work for high-temperature piezoelectric sensing are presented.

  11. Characteristics and applications of high-performance fiber reinforced asphalt concrete

    Park, Philip

    Steel fiber reinforced asphalt concrete (SFRAC) is suggested in this research as a multifunctional high performance material that can potentially lead to a breakthrough in developing a sustainable transportation system. The innovative use of steel fibers in asphalt concrete is expected to improve mechanical performance and electrical conductivity of asphalt concrete that is used for paving 94% of U. S. roadways. In an effort to understand the fiber reinforcing mechanisms in SFRAC, the interaction between a single straight steel fiber and the surrounding asphalt matrix is investigated through single fiber pull-out tests and detailed numerical simulations. It is shown that pull-out failure modes can be classified into three types: matrix, interface, and mixed failure modes and that there is a critical shear stress, independent of temperature and loading rate, beyond which interfacial debonding will occur. The reinforcing effects of SFRAC with various fiber sizes and shapes are investigated through indirect tension tests at low temperature. Compared to unreinforced specimens, fiber reinforced specimens exhibit up to 62.5% increase in indirect tensile strength and 895% improvements in toughness. The documented improvements are the highest attributed to fiber reinforcement in asphalt concrete to date. The use of steel fibers and other conductive additives provides an opportunity to make asphalt pavement electrically conductive, which opens up the possibility for multifunctional applications. Various asphalt mixtures and mastics are tested and the results indicate that the electrical resistivity of asphaltic materials can be manipulated over a wide range by replacing a part of traditional fillers with a specific type of graphite powder. Another important achievement of this study is development and validation of a three dimensional nonlinear viscoelastic constitutive model that is capable of simulating both linear and nonlinear viscoelasticity of asphaltic materials. The

  12. Study on Basic Characteristics for the Development of Radiation Shielding High-Weight Concrete

    Mun, Young Bum; Lee, Jea Hyung; Choi, Hyun Kook [Sungshin Cement CO., Sejong (Korea, Republic of); Oh, Jeong Hwan; Choi, Soo Seok [Jeju National University, Jeju (Korea, Republic of)

    2016-05-15

    It is planned to build a power plant more than 6 units. Although the demand of a nuclear power plant is going to increase, the attention for radiation shielding is relatively in a low level. Concrete is one of the excellent and widely used shielding materials. Since the radiation shielding of a given material is proportional to density and thickness, a high-weight concrete with high-weight aggregate which is higher than normal concrete is used for radiation shielding. However, there are a few studies and references about radiation shielding concrete. Therefore, it is required to find a high-weight aggregate. The purpose of this paper is the development of a highweight concrete to improve radiation shielding capability. The radiation shielding rate of high-weight concrete is higher than that of reference concrete. It is confirmed that the density of aggregate and the unit weight of concreate is proportional to the radiation shielding rate. In addition, the chemical composition of aggregate has also has an important effect on γ-ray shielding. Therefore, high weight aggregates of higher density are essentially required to improve radiation shielding capability. The compressive strength of a high weight concrete is better than that of reference concrete. Slump and air contents, however, are slightly increased with by-product aggregates.

  13. New high performance nanoadditives for photocatalytic concrete: synthesis and study

    FALIKMAN Vyacheslav Ruvimovich

    2015-02-01

    Full Text Available Nanotechnologies open up broad prospects for the creation of nanocatalysts, which are being more and more used in solving many problems associated with the protection of environment. Their behavior is directly related to the unique physical and chemical properties that are provided by quantum size effects, as well as the large specific surface area. It is known that the presence of photo catalysts in the construction segment of nanomaterials is becoming more prominent. One of the most significant achievements of the last years are photo catalytic active cement composites, including cements and concretes produced with the use of nanoparticles of titanium dioxide TiO₂ sensibilized through a nanotechnology . Currently they are widely used in practice to produce selfcleaning structures and to make clean an air of megacities. Further research in the field of development of new high-performance photo catalysts based on TiO₂ nanoparticles seems to be very relevant, because such R&D could significantly improve the technical characteristics of photo catalytic cements and concrete. In this paper an improved method to produce photo catalysts has been proposed. New synthesized products are based on TiO₂ nanoparticles applied on different inert carriers, including nanosilica. It was showed that these products can be used as a high performance photo catalyst in cement and cement-gypsum composites suitable for the onversion processes of nitric oxide and volatile organic substances, and air purification. It was determined that performance of the cementitious composites containing synthesized samples is 1,5…3,0 times higher than that for the commercial sample of the nanotitanium dioxide. The use of mechanical mixture of nanotitanium dioxide and inert supports is less effective and subjected to the «dilution law», in general.

  14. High temperature superconductor accelerator magnets

    van Nugteren, J.

    2016-01-01

    For future particle accelerators bending dipoles are considered with magnetic fields exceeding 20T. This can only be achieved using high temperature superconductors (HTS). These exhibit different properties from classical low temperature superconductors and still require significant research and

  15. High-performance hybrid-fibre concrete : Development and utilisation

    Markovic, I.

    2006-01-01

    Although concrete is the most utilised building material nowdays, this material has a large shortcoming: it has a good resistance against compressive stresses, but a very low resistance against tensile stresses. Usual way to solve this problem is the application of steel reinforcement in concrete

  16. Fracture Energy of High-Strength Concrete in Compression

    Dahl, H.; Brincker, Rune

    1989-01-01

    is essential for understanding the fracture mechanism of concrete in compression. In this paper a series of tests is reported, carried out for the purpose of studying the fracture mechanical properties of concrete in compression. Including the measurement and study of the descending branch, a new experimental...

  17. The tunnel sealing experiment: The construction and performance of full scale clay and concrete bulkheads at elevated pressure and temperature

    Martino, J.B.; Dixon, D.A.; Vignal, B.; Fujita, T.

    2006-01-01

    Concepts for deep geologic disposal of radioactive waste, as proposed by many international organizations, include bulkheads or plugs in the shaft, or at the entrances to disposal rooms, or both. The seals are primarily to prevent groundwater transport of radioisotopes along underground openings but also provide a measure of security by restricting tunnel access. The safety of the respective disposal systems relies on the combined performance of the natural barriers (host rock) and engineered barriers (the waste form, the waste container, the buffer barrier, the room, tunnel and shaft backfill and sealing materials). To understand the functionality of these systems it is important to study them in whole or in part at full scale. One such study was the Tunnel Sealing Experiment (TSX), a full-scale tunnel seal component study. The TSX showed it is possible to construct tunnel seals that limit axial flow under high hydraulic gradient and elevated temperature. The clay and concrete bulkheads had seepage rates of 1 mL/min and 10 mL/min at ambient temperature. Elevated temperatures caused a further decrease in seepage past the concrete bulkhead to approximately 2-3 mL/min. (author)

  18. Mechanical behavior of recycled lightweight concrete using EVA waste and CDW under moderate temperature

    E. Q. R. Santiago

    Full Text Available Many benefits can be achieved by using recycled waste as raw material for construction. Some of them are the reduction of the total cost of the construction, the reduction of the consumption of energy and the decrease in the use of natural materials. The construction sector can also incorporate the waste of the other industries, like the waste of the shoes industry, the Ethylene Vinyl Acetate (EVA. EVA aggregate is obtained by cutting off the waste of EVA expanded sheets used to produce insoles and innersoles of the shoes. In this work two types of recycled aggregate were used - construction and demolition waste (CDW and EVA. The aim of this work was to study the influence of the use of these recycled aggregates, as replacement of the natural coarse aggregate, on mechanical behavior of recycled concrete. The experimental program was developed with two w/c ratio: 0.49 and 0.82. Four mixtures with produced with different aggregates substitution rates (0, 50%EVA, 50%CDW and 25%EVA-25%CDW, by volume. Compressive tests were carried out to evaluable the influence of recycled aggregate on strength, elastic modulus and Poisson coefficient. In addition, it was evaluated the effect of the moderate temperatures (50, 70 and 100º C on stress-strain behavior of concretes studied. The results demonstrated that is possible to use the EVA waste and RCD to produces lightweight concrete. The influence of temperature was more significant only on elastic modulus of the recycled concrete with 50%EVA.

  19. Determining the Environmental Benefits of Ultra High Performance Concrete as a Bridge Construction Material

    Lande Larsen, Ingrid; Granseth Aasbakken, Ida; O'Born, Reyn; Vertes, Katalin; Terje Thorstensen, Rein

    2017-10-01

    Ultra High Performance Concrete (UHPC) is a material that is attracting attention in the construction industry due to the high mechanical strength and durability, leading to structures having low maintenance requirements. The production of UHPC, however, has generally higher environmental impact than normal strength concrete due to the increased demand of cement required in the concrete mix. What is still not sufficiently investigated, is if the longer lifetime, slimmer construction and lower maintenance requirements lead to a net environmental benefit compared to standard concrete bridge design. This study utilizes life cycle assessment (LCA) to determine the lifetime impacts of two comparable highway crossing footbridges spanning 40 meters, designed respectively with UHPC and normal strength concrete. The results of the study show that UHPC is an effective material for reducing lifetime emissions from construction and maintenance of long lasting infrastructure, as the UHPC design outperforms the normal strength concrete bridge in most impact categories.

  20. Carbonation Coefficients from Concrete Made with High-Absorption Limestone Aggregate

    Eric I. Moreno

    2013-01-01

    Full Text Available Normal aggregates employed in concrete have absorption levels in the range of 0.2% to 4% for coarse aggregate and 0.2 to 2% for fine aggregate. However, some aggregates have absorption levels above these values. As the porosity of concrete is related to the porosity of both the cement paste and the aggregate and the carbonation rate is a function, among other things, of the porosity of the material, there is concern about the effect of this high porosity material in achieving good quality concrete from the durability point of view. Thus, the objective of this investigation was to study the carbonation rates of concrete specimens made with high-absorption limestone aggregate. Four different water/cement ratios were used, and cylindrical concrete specimens were exposed to accelerated carbonation. High porosity values were obtained for concrete specimens beyond the expected limits for durable concrete. However, carbonation coefficients related to normal quality concrete were obtained for the lowest water/cement ratio employed suggesting that durable concrete may be obtained with this material despite the high porosity.

  1. Dimensional and ice content changes of hardened concrete at different freezing and thawing temperatures

    Johannesson, Björn

    2010-01-01

    Samples of concrete at different water-to-cement ratios and air contents subjected to freeze/thaw cycles with the lowest temperature at about -80 degrees C are investigated. By adopting a novel technique, a scanning calorimeter is used to obtain data from which the ice contents at different freeze...... temperatures can be calculated. The length change caused by temperature and ice content changes during test is measured by a separate experiment using the same types of freeze-thaw cycles as in the calorimetric tests. In this way it was possible to compare the amount of formed ice at different temperatures...... and the corresponding measured length changes. The development of cracks in the material structure was indicated by an ultra-sonic technique by measuring on the samples before and after the freeze-thaw tests. Further the air void structure was investigated using a microscopic technique in which air'bubble' size...

  2. High temperature materials; Materiaux a hautes temperatures

    NONE

    2003-07-01

    The aim of this workshop is to share the needs of high temperature and nuclear fuel materials for future nuclear systems, to take stock of the status of researches in this domain and to propose some cooperation works between the different research organisations. The future nuclear systems are the very high temperature (850 to 1200 deg. C) gas cooled reactors (GCR) and the molten salt reactors (MSR). These systems include not only the reactor but also the fabrication and reprocessing of the spent fuel. This document brings together the transparencies of 13 communications among the 25 given at the workshop: 1) characteristics and needs of future systems: specifications, materials and fuel needs for fast spectrum GCR and very high temperature GCR; 2) high temperature materials out of neutron flux: thermal barriers: materials, resistance, lifetimes; nickel-base metal alloys: status of knowledge, mechanical behaviour, possible applications; corrosion linked with the gas coolant: knowledge and problems to be solved; super-alloys for turbines: alloys for blades and discs; corrosion linked with MSR: knowledge and problems to be solved; 3) materials for reactor core structure: nuclear graphite and carbon; fuel assembly structure materials of the GCR with fast neutron spectrum: status of knowledge and ceramics and cermets needs; silicon carbide as fuel confinement material, study of irradiation induced defects; migration of fission products, I and Cs in SiC; 4) materials for hydrogen production: status of the knowledge and needs for the thermochemical cycle; 5) technologies: GCR components and the associated material needs: compact exchangers, pumps, turbines; MSR components: valves, exchangers, pumps. (J.S.)

  3. Effect of Climate Change on Service Life of High Volume Fly Ash Concrete Subjected to Carbonation—A Korean Case Study

    Ki-Bong Park

    2017-01-01

    Full Text Available The increase in CO2 concentrations and global warming will increase the carbonation depth of concrete. Furthermore, temperature rise will increase the rate of corrosion of steel rebar after carbonation. On the other hand, compared with normal concrete, high volume fly ash (HVFA concrete is more vulnerable to carbonation-induced corrosion. Carbonation durability design with climate change is crucial to the rational use of HVFA concrete. This study presents a probabilistic approach that predicts the service life of HVFA concrete structures subjected to carbonation-induced corrosion resulting from increasing CO2 concentrations and temperatures. First, in the corrosion initiation stage, a hydration-carbonation integration model is used to evaluate the contents of the carbonatable material, porosity, and carbonation depth of HVFA concrete. The Monte Carlo method is adopted to determine the probability of corrosion initiation. Second, in the corrosion propagation stage, an updated model is proposed to evaluate the rate of corrosion, degree of corrosion for cover cracking of concrete, and probability of corrosion cracking. Third, the whole service life is determined considering both corrosion initiation stage and corrosion propagation stage. The analysis results show that climate change creates a significant impact on the service life of durable concrete.

  4. Prediction of concrete compressive strength considering humidity and temperature in the construction of nuclear power plants

    Kwon, Seung Hee; Jang, Kyung Pil [Department of Civil and Environmental Engineering, Myongji University, Yongin (Korea, Republic of); Bang, Jin-Wook [Department of Civil Engineering, Chungnam National University, Daejeon (Korea, Republic of); Lee, Jang Hwa [Structural Engineering Research Division, Korea Institute of Construction Technology (Korea, Republic of); Kim, Yun Yong, E-mail: yunkim@cnu.ac.kr [Structural Engineering Research Division, Korea Institute of Construction Technology (Korea, Republic of)

    2014-08-15

    Highlights: • Compressive strength tests for three concrete mixes were performed. • The parameters of the humidity-adjusted maturity function were determined. • Strength can be predicted considering temperature and relative humidity. - Abstract: This study proposes a method for predicting compressive strength developments in the early ages of concretes used in the construction of nuclear power plants. Three representative mixes with strengths of 6000 psi (41.4 MPa), 4500 psi (31.0 MPa), and 4000 psi (27.6 MPa) were selected and tested under various curing conditions; the temperature ranged from 10 to 40 °C, and the relative humidity from 40 to 100%. In order to consider not only the effect of the temperature but also that of humidity, an existing model, i.e. the humidity-adjusted maturity function, was adopted and the parameters used in the function were determined from the test results. A series of tests were also performed in the curing condition of a variable temperature and constant humidity, and a comparison between the measured and predicted strengths were made for the verification.

  5. Fracture resistance of asphalt concrete modified with crumb rubber at low temperatures

    A. Razmi

    2018-05-01

    Full Text Available The main objective of this study is to obtain fracture toughness of asphalt concrete modified by Crumb Rubber (CR and Sasobit at low temperatures. First, Bending Beam Rheometer (BBR test was performed on unmodified binder (binder 60/70, binder 60/70 + 3%Sasobit and 20%CR + 3%Sasobit modified asphalt binder to find how each modifier affect asphalt binder stiffness and relaxation rate at low temperatures. Mixed mode I/II fracture tests were conducted by cracked Semi-Circular Bending (SCB specimens and the critical stress intensity factors were calculated for pure mode I, mixed mode I/II and pure mode II conditions. Results of BBR tests indicated that 20%CR + 3%Sasobit reduces stiffness and the m-value increase at low temperatures. As a result, 20%CR + 3%Sasobit has positive effect on low temperatures performance by improving thermal cracking resistance. Also, according to the fracture toughness test results, the Warm Mix Asphalt (WMA mixture containing 20% CR, shows higher resistance against crack growth than WMA mixture. It was found that mixed mode I/II can be more detrimental than pure mode I and II conditions. Keywords: Crumb rubber, Asphalt concrete, Bending Beam Rheometer, Fracture resistance, Semi-circular bending test

  6. A p-version embedded model for simulation of concrete temperature fields with cooling pipes

    Sheng Qiang

    2015-07-01

    Full Text Available Pipe cooling is an effective method of mass concrete temperature control, but its accurate and convenient numerical simulation is still a cumbersome problem. An improved embedded model, considering the water temperature variation along the pipe, was proposed for simulating the temperature field of early-age concrete structures containing cooling pipes. The improved model was verified with an engineering example. Then, the p-version self-adaption algorithm for the improved embedded model was deduced, and the initial values and boundary conditions were examined. Comparison of some numerical samples shows that the proposed model can provide satisfying precision and a higher efficiency. The analysis efficiency can be doubled at the same precision, even for a large-scale element. The p-version algorithm can fit grids of different sizes for the temperature field simulation. The convenience of the proposed algorithm lies in the possibility of locating more pipe segments in one element without the need of so regular a shape as in the explicit model.

  7. High Temperature Superconductor Resonator Detectors

    National Aeronautics and Space Administration — High Temperature Superconductor (HTS) infrared detectors were studied for years but never matured sufficiently for infusion into instruments. Several recent...

  8. High Temperature Superconductor Machine Prototype

    Mijatovic, Nenad; Jensen, Bogi Bech; Træholt, Chresten

    2011-01-01

    A versatile testing platform for a High Temperature Superconductor (HTS) machine has been constructed. The stationary HTS field winding can carry up to 10 coils and it is operated at a temperature of 77K. The rotating armature is at room temperature. Test results and performance for the HTS field...

  9. Characterization of Laboratory Prepared Concrete Pastes Exposed to High Alkaline and High Sodium Salt Solutions

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

    2016-06-30

    The objective of this study was to identify potential chemical degradation mechanisms for the Saltstone Disposal Unit (SDU) concretes, which over the performance life of the structures may be exposed to highly alkaline sodium salt solutions containing sulfate, hydroxide, and other potentially corrosive chemicals in salt solution and saltstone flush water, drain water, leachate and / or pore solution. The samples analyzed in this study were cement pastes prepared in the SIMCO Technologies, Inc. concrete laboratory. They were based on the paste fractions of the concretes used to construct the Saltstone Disposal Units (SDUs). SDU 1 and 4 concrete pastes were represented by the PV1 test specimens. The paste in the SDU 2, 3, 5, and 6 concrete was represented by the PV2 test specimens. SIMCO Technologies, Inc. selected the chemicals and proportions in the aggressive solutions to approximate proportions in the saltstone pore solution [2, 3, 5, and 6]. These test specimens were cured for 56 days in curing chamber before being immersed in aggressive solutions. After exposure, the samples were frozen to prevent additional chemical transport and reaction. Selected archived (retrieved from the freezer) samples were sent to the Savannah River National Laboratory (SRNL) for additional characterization using x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive x-ray (EDX) spectroscopy. Characterization results are summarized in this report. In addition, a correlation between the oxide composition of the pastes and their chemical durability in the alkaline salt solutions is provided.

  10. Fatigue behaviour of high performance concretes for wind turbines; Ermuedungsverhalten von Hochleistungsbetonen in Windenergieanlagen

    Lohaus, Ludger; Oneschkow, Nadja; Elsmeier, Kerstin; Huemme, Julian [Hannover Univ. (Germany). Inst. fuer Baustoffe

    2012-08-15

    New developments in the wind energy sector will lead to wind turbines with enormous capacities. As a result, the loads of the supporting structures are also increasing. For some time now, high performance concretes with self-compacting properties have been used in wind turbines for structural connections. Furthermore, slender foundations and prestressed concrete supporting structures made out of high-strength concrete are under development. In future, fatigue design of these high performance concretes is to be done according to the new fib-Model Code 2010. This code includes a new fatigue design model which enables a safe and economic fatigue design, even for high strength concrete. Extensive research with regard to the fatigue behaviour of different types of high performance concrete has been carried out at the Institute of Building Materials Science, Leibniz Universitaet Hannover. As part of these research activities, the influences of steel fibre reinforcement on the fatigue behaviour of high performance concretes are being investigated. In this paper, interim results of these investigations are presented and the potential for the practical applications of high performance concrete is discussed. The results of the conducted investigations are presented in comparison with the new fatigue design model of the fib-Model Code 2010. (orig.)

  11. Recyclability of Concrete Pavement Incorporating High Volume of Fly Ash.

    Yoshitake, Isamu; Ishida, Takeo; Fukumoto, Sunao

    2015-08-21

    Recyclable concrete pavement was made from fly ash and crushed limestone sand and gravel as aggregates so that the concrete pavement could be recycled to raw materials for cement production. With the aim to use as much fly ash as possible for the sustainable development of society, while achieving adequate strength development, pavement concrete having a cement-replacement ratio of 40% by mass was experimentally investigated, focusing on the strength development at an early age. Limestone powder was added to improve the early strength; flexural strength at two days reached 3.5 MPa, the minimum strength for traffic service in Japan. The matured fly ash concrete made with a cement content of 200 kg/m3 achieved a flexural strength almost equal to that of the control concrete without fly ash. Additionally, Portland cement made from the tested fly ash concrete was tested to confirm recyclability, with the cement quality meeting the Japanese classification of ordinary Portland cement. Limestone-based recyclable fly ash concrete pavement is, thus, a preferred material in terms of sustainability.

  12. Innovative process routes for a high-quality concrete recycling.

    Menard, Y; Bru, K; Touze, S; Lemoign, A; Poirier, J E; Ruffie, G; Bonnaudin, F; Von Der Weid, F

    2013-06-01

    This study presents alternative methods for the processing of concrete waste. The mechanical stresses needed for the embrittlement of the mortar matrix and further selective crushing of concrete were generated by either electric impulses or microwaves heating. Tests were carried out on lab-made concrete samples representative of concrete waste from concrete mixer trucks and on concrete waste collected on a French demolition site. The results obtained so far show that both techniques can be used to weaken concrete samples and to enhance aggregate selective liberation (that is the production of cement paste-free aggregates) during crushing and grinding. Electric pulses treatment seems to appear more efficient, more robust and less energy consuming (1-3 kWh t(-1)) than microwave treatment (10-40 kWh t(-1)) but it can only be applied on samples in water leading to a major drawback for recycling aggregates or cement paste in the cement production process. Copyright © 2013 Elsevier Ltd. All rights reserved.

  13. Recyclability of Concrete Pavement Incorporating High Volume of Fly Ash

    Yoshitake, Isamu; Ishida, Takeo; Fukumoto, Sunao

    2015-01-01

    Recyclable concrete pavement was made from fly ash and crushed limestone sand and gravel as aggregates so that the concrete pavement could be recycled to raw materials for cement production. With the aim to use as much fly ash as possible for the sustainable development of society, while achieving adequate strength development, pavement concrete having a cement-replacement ratio of 40% by mass was experimentally investigated, focusing on the strength development at an early age. Limestone powder was added to improve the early strength; flexural strength at two days reached 3.5 MPa, the minimum strength for traffic service in Japan. The matured fly ash concrete made with a cement content of 200 kg/m3 achieved a flexural strength almost equal to that of the control concrete without fly ash. Additionally, Portland cement made from the tested fly ash concrete was tested to confirm recyclability, with the cement quality meeting the Japanese classification of ordinary Portland cement. Limestone-based recyclable fly ash concrete pavement is, thus, a preferred material in terms of sustainability. PMID:28793518

  14. Re-usage of waste foundry sand in high-strength concrete.

    Guney, Yucel; Sari, Yasin Dursun; Yalcin, Muhsin; Tuncan, Ahmet; Donmez, Senayi

    2010-01-01

    In this study, the potential re-use of waste foundry sand in high-strength concrete production was investigated. The natural fine sand is replaced with waste foundry sand (0%, 5%, 10%, and 15%). The findings from a series of test program has shown reduction in compressive and tensile strengths, and the elasticity modulus which is directly related to waste foundry inclusion in concrete. Nevertheless the concrete with 10% waste foundry sand exhibits almost similar results to that of the control one. The slump and the workability of the fresh concrete decreases with the increase of the waste foundry sand ratio. Although the freezing and thawing significantly reduces the mechanical and physical properties of the concrete. The obtained results satisfies the acceptable limits set by the American Concrete Institute (ACI). 2010 Elsevier Ltd. All rights reserved.

  15. Study of measurement method of tritium induced in concrete of high-energy proton accelerator facilities

    Ohtsuka, N.; Ishihama, S.; Kunifuda, T.; Hayasaka, N.; Miura, T.

    2001-01-01

    Various long-loved radionuclides, 3 H, 7 Be, 22 Na, 51 Cr, 54 Mn, 56 Co, 57 Co, 60 Co, 134 Cs, 152 Eu and 154 Eu, have been produced in the shielding concrete of high energy proton accelerator facility through both nuclear spallation reactions and thermal neutron capture reactions of concrete elements, during machine operation. Tritium is the most important nuclide from the radiation protection. There were, however, few measurements of tritium concentration induced in the shielding concrete. In this study, the conditions of measurement method of tritium concentration induced in shielding concrete have been investigated using the activated shielding concrete of the 12 GeV proton beam-line tunnel at KEK and the standard rock (JG-1) irradiated of thermal neutron at the reactor. And the depth profiles of tritium induced in the shielding concrete of slow extracted proton beam line at KEK were determined using this method. (author)

  16. Impact strength and abrasion resistance of high strength concrete with rice husk ash and rubber tires

    M. B. Barbosa

    Full Text Available The paper discusses the application of High Strength Concrete (HSC technology for concrete production with the incorporation of Rice Husk Ash (RHA residues by replacing a bulk of the material caking and rubber tires with partial aggregate volume, assessing their influence on the mechanical properties and durability. For concrete with RHA and rubber, it was possible to reduce the brittleness by increasing the energy absorbing capacity. With respect to abrasion, the RHA and rubber concretes showed lower mass loss than the concrete without residues, indicating that this material is attractive to be used in paving. It is thus hoped that these residues may represent a technological and ecological alternative for the production of concrete in construction works.

  17. Evaluation of capillary pore size characteristics in high-strength concrete at early ages

    Igarashi, Shin-ichi; Watanabe, Akio; Kawamura, Mitsunori

    2005-01-01

    The quantitative scanning electron microscope-backscattered electron (SEM-BSE) image analysis was used to evaluate capillary porosity and pore size distributions in high-strength concretes at early ages. The Powers model for the hydration of cement was applied to the interpretation of the results of image analysis. The image analysis revealed that pore size distributions in concretes with an extremely low water/binder ratio of 0.25 at early ages were discontinuous in the range of finer capillary pores. However, silica-fume-containing concretes with a water/binder ratio of 0.25 had larger amounts of fine pores than did concretes without silica fume. The presence of larger amounts of fine capillary pores in the concretes with silica fume may be responsible for greater autogenous shrinkage in the silica-fume-containing concretes at early ages

  18. Numerical Analysis on Temperature Rise of a Concrete Arch Dam after Sealing Based on Measured Data

    Qingbin Li

    2014-01-01

    Full Text Available The thermal boundary conditions in the construction and operation phases of a concrete arch dam are always complex. After sealing, differences between the arch dam temperature and its sealing temperature can cause compressive or tensile stresses. Based on measured temperature of an arch dam located in China, a temperature rise phenomenon (TRP is found in the after-sealed regions of the arch dam. By mining and analyzing the temperature data of various monitoring apparatus embedded in the arch dam, higher environment temperature is considered to be the main cause for the occurrence of the TRP. Mathematical methods for complex thermal boundary conditions, including external boundary conditions and internal heat source conditions, are proposed in this paper. A finite element model is implemented with the concern of the construction phase and operation phase of the arch dam. Results confirm good agreement with the measured temperature and verify the conjecture that the TRP occurs mainly because the external temperature of the arch dam is higher than its sealing temperature.

  19. Experimental study on infrared radiation temperature field of concrete under uniaxial compression

    Lou, Quan; He, Xueqiu

    2018-05-01

    Infrared thermography, as a nondestructive, non-contact and real-time monitoring method, has great significance in assessing the stability of concrete structure and monitoring its failure. It is necessary to conduct in depth study on the mechanism and application of infrared radiation (IR) of concrete failure under loading. In this paper, the concrete specimens with size of 100 × 100 × 100 mm were adopted to carry out the uniaxial compressions for the IR tests. The distribution of IR temperatures (IRTs), surface topography of IRT field and the reconstructed IR images were studied. The results show that the IRT distribution follows the Gaussian distribution, and the R2 of Gaussian fitting changes along with the loading time. The abnormities of R2 and AE counts display the opposite variation trends. The surface topography of IRT field is similar to the hyperbolic paraboloid, which is related to the stress distribution in the sample. The R2 of hyperbolic paraboloid fitting presents an upward trend prior to the fracture which enables to change the IRT field significantly. This R2 has a sharp drop in response to this large destruction. The normalization images of IRT field, including the row and column normalization images, were proposed as auxiliary means to analyze the IRT field. The row and column normalization images respectively show the transverse and longitudinal distribution of the IRT field, and they have clear responses to the destruction occurring on the sample surface. In this paper, the new methods and quantitative index were proposed for the analysis of IRT field, which have some theoretical and instructive significance for the analysis of the characteristics of IRT field, as well as the monitoring of instability and failure for concrete structure.

  20. Measurement and analysis of temperature, strain and stress of foundation mat concrete in nuclear and thermal power stations

    Haraguchi, Akira; Yamakawa, Hidetsugu; Abe, Hirotoshi

    1981-01-01

    The problems of the thermal stress in concrete structures are roughly divided into the initial stress due to setting heat and the stress due to external temperature after hardening. The initial stress exists in every concrete structure, and it is usually neglected in beams and columns, but it must be taken into account in case of the foundation mat structures in nuclear power stations, for example. In this paper, (1) the results of measurement of temperature, strain and stress in each lift at the time of and after placing concrete in the foundation mat of a nuclear power station and the comparison of them with the results of analysis, (2) the results of measurement of the temperature and stress in a foundation mat, which was carried out to rationalize the design method for the raft type foundation mats in thermal power stations, and (3) the results of examination on the analysis model, external force conditions and boundary conditions used for the design are reported. The analysis method for temperature and thermal stress by finite element method, developed by the Central Research Institute of Electric Power Industry, can take the changes in the heat of hydration in placed concrete, the creep phenomenon of concrete and the restraint at construction joints in consideration. It is necessary to collect the data on the measurement of mat concrete and to develop the accurate analysis method. (Kako, I.)

  1. Effect of High Temperature on the Tensile Behavior of CFRP and Cementitious Composites

    Toutanji, Houssam A.

    1999-01-01

    Concrete and other composite manufacturing processes are continuing to evolve and become more and more suited for use in non-Earth settings such as the Moon and Mars. The fact that structures built in lunar environments would experience a range of effects from temperature extremes to bombardment by micrometeorites and that all the materials for concrete production exist on the Moon means that concrete appears to be the most feasible building material. it can provide adequate shelter from the harshness of the lunar environment and at the same time be a cost effective building material. With a return to the Moon planned by NASA to occur after the turn of the century, it will be necessary to include concrete manufacturing as one of the experiments to be conducted in one of the coming missions. Concrete's many possible uses and possibilities for manufacturing make it ideal for lunar construction. The objectives of this research are summarized as follows: i) study the possibility of concrete production on the Moon or other planets, ii) study the effect of high temperature on the tensile behavior of concrete, and iii) study the effect of high temperature on the tensile behavior of carbon fiber reinforced with inorganic polymer composites. Literature review indicates that production of concrete on the Moon or other planets is feasible using the indigenous materials. Results of this study has shown that both the tensile strength and static elastic modulus of concrete decreased with a rise in temperature from 200 to 500 C. The addition of silica fume to concrete showed higher resistance to high temperatures. Carbon fiber reinforced inorganic polymer (CFRIP) composites seemed to perform well up to 300 C. However, a significant reduction in strength was observed of about 40% at 400 C and up to 80% when the specimens were exposed to 700 C.

  2. Evaluation of microsilica admixture for production of high strength concrete.

    1990-08-01

    This study consisted of a laboratory evaluation of the effect of microsilica on the physical properties of both plastic and hardened portland cement concrete. Microsilica (silica fume) is a by-product of the industrial manufacture of ferro silicon an...

  3. New methods for moisture control of high-performance concrete

    Kovler, Konstantin; Jensen, Ole Mejlhede; Falikman, Vyacheslav

    2005-01-01

    Curing of concrete by both external (conventional) and internal methods is reviewed and analyzed. The focus is given on the mitigation of autogenous shrinkage of low water-to-cementitious materials ratio concrete by means of internal curing. The concepts of internal curing are based on using pre......-soaked lightweight aggregate, super-absorbent polymers or water-soluble chemicals, which reduce water evaporation (so called "internal sealing"). These concepts have been suggested in the 90s, but still are not popular among users, engineers, contractors, concrete suppliers, researchers, and the rest...... of professionals who work for them. The differences between conventional methods of external curing and novel methods of internal curing are described. It is concluded that proper curing is a key factor to achieve durable concrete....

  4. Heavyweight cement concrete with high stability of strength parameters

    Kudyakov, Konstantin; Nevsky, Andrey; Danke, Ilia; Kudyakov, Aleksandr; Kudyakov, Vitaly

    2016-01-01

    The present paper establishes regularities of basalt fibers distribution in movable cement concrete mixes under different conditions of their preparation and their selective introduction into mixer during the mixing process. The optimum content of basalt fibers was defined as 0.5% of the cement weight, which provides a uniform distribution of fibers in the concrete volume. It allows increasing compressive strength up to 51.2% and increasing tensile strength up to 28.8%. Micro-structural analysis identified new formations on the surface of basalt fibers, which indicates the good adhesion of hardened cement paste to the fibers. Stability of concrete strength parameters has significantly increased with introduction of basalt fibers into concrete mix.

  5. Determination of ice content in hardened concrete by low-temperature calorimetry

    Wu, Min; Johannesson, Björn; Geiker, Mette Rica

    2014-01-01

    Low-temperature calorimetry has been used to determine the ice content in concrete at different temperatures when exposed to low-temperature environments. However, the analysis of the ice content from the measured data of heat flow is not straightforward. In this study, two important factors...... influencing the ice content calculation are discussed. The importance of the baseline determination for the calculation of the ice content is realized. Two different methods of generating the baseline are discussed. First, the ‘J-baseline’ is discussed which is a recently proposed extrapolation method based...... the ‘J-baseline’ method and the ‘C-baseline’ method can be used to calculate the approximate baseline. The heat of fusion of the water confined in small pores is another important parameter to be considered in ice content calculation. This property must be carefully analyzed in order to accurately...

  6. Microstructure of ultra high performance concrete containing lithium slag.

    He, Zhi-Hai; Du, Shi-Gui; Chen, Deng

    2018-04-03

    Lithium slag (LS) is discharged as a byproduct in the process of the lithium carbonate, and it is very urgent to explore an efficient way to recycle LS in order to protect the environments and save resources. Many available supplementary cementitious materials for partial replacement of cement and/or silica fume (SF) can be used to prepare ultra high performance concrete (UHPC). The effect of LS to replace SF partially by weight used as a supplementary cementitious material (0%, 5%, 10% and 15% of binder) on the compressive strengths and microstructure evolution of UHPC has experimentally been studied by multi-techniques including mercury intrusion porosimetry, scanning electron microscope and nanoindentation technique. The results show that the use of LS degrades the microstructure of UHPC at early ages, and however, the use of LS with the appropriate content improves microstructure of UHPC at later ages. The hydration products of UHPC are mainly dominated by ultra-high density calcium-silicate-hydrate (UHD C-S-H) and interfacial transition zone (ITZ) in UHPC has similar compact microstructure with the matrix. The use of LS improves the hydration degree of UHPC and increases the elastic modulus of ITZ in UHPC. LS is a promising substitute for SF for preparation UHPC. Copyright © 2018 Elsevier B.V. All rights reserved.

  7. Uncertainty Instability Risk Analysis of High Concrete Arch Dam Abutments

    Xin Cao

    2017-01-01

    Full Text Available The uncertainties associated with concrete arch dams rise with the increased height of dams. Given the uncertainties associated with influencing factors, the stability of high arch dam abutments as a fuzzy random event was studied. In addition, given the randomness and fuzziness of calculation parameters as well as the failure criterion, hazard point and hazard surface uncertainty instability risk ratio models were proposed for high arch dam abutments on the basis of credibility theory. The uncertainty instability failure criterion was derived through the analysis of the progressive instability failure process on the basis of Shannon’s entropy theory. The uncertainties associated with influencing factors were quantized by probability or possibility distribution assignments. Gaussian random theory was used to generate random realizations for influence factors with spatial variability. The uncertainty stability analysis method was proposed by combining the finite element analysis and the limit equilibrium method. The instability risk ratio was calculated using the Monte Carlo simulation method and fuzzy random postprocessing. Results corroborate that the modeling approach is sound and that the calculation method is feasible.

  8. Glazed Concrete

    Bache, Anja Margrethe

    2010-01-01

    Why glazed concrete? Concrete hardens and finds its strength at room temperature whereas clay products must first be fired before they achieve this strength. They are stronger and three times as durable as clay products, which is a weighty reason for choosing concrete.5 Another reason, which....... If this succeeds, it will be possible to manufacture thin, large-scale glazed concrete panels comparable in size to concrete sandwich construction and larger which, with or without back-casting, can work as load-bearing construction elements....

  9. Sustainable normal and high strength recycled aggregate concretes using crushed tested cylinders as coarse aggregates

    Bilal S. Hamad

    2017-12-01

    Full Text Available The paper reports on a research program that was designed at the American University of Beirut (AUB to investigate the fresh and hardened mechanical properties of a high performance concrete mix produced with partial or full substitution of crushed natural lime-stone aggregates with recycled aggregates from crushed tested cylinders in batching plants. Choosing crushed cylinders as source of recycling would result in reusing portion of the waste products of the concrete production industry. An extensive concrete batching and testing program was conducted to achieve two optimum normal and high strength concrete mixes. The variables were the nominal concrete strength (28 or 60 MPa and the percentage replacement of natural coarse aggregates with recycled aggregates from crushed tested cylinders (0, 20, 40, 60, 80, or 100%. Normal strength tested cylinders were used as source of the recycled aggregates for the normal strength concrete (NSC mix and high strength tested cylinders were used for the high strength concrete (HSC mix. Tests on the trial batches included plastic state slump and hardened state mechanical properties including cylinder compressive strength, cylinder splitting tensile strength, modulus of elasticity, and standard beams flexural strength. The results indicated no significant effect on the slump and around 10% average reduction in the hardened mechanical properties for both investigated levels of concrete compressive strength.

  10. The effect of steel slag as a coarse aggregate and Sinabung volcanic ash a filler on high strength concrete

    Karolina, R.; Putra, A. L. A.

    2018-02-01

    The Development of concrete technology is continues to grow. The requisite for efficient constructions that are often viewed in terms of concrete mechanical behavior, application on the field, and cost estimation of implementation increasingly require engineers to optimize construction materials, especially for concrete materials. Various types of concrete have now been developed according to their needs, such as high strength concrete. On high strength concrete design, it is necessary to consider several factors that will affect the reach of the quality strength, Those are cement, water cement ratio (w/c), aggregates, and proper admixture. In the use of natural mineral, it is important for an engineer to keep an eye on the natural conditions that have been explored. So the selection of aggregates as possible is a material that is not causing nature destruction. On this experiment the use of steel slag from PT.Growth Sumatra Industry as a substitute of coarse and fine aggregate, and volcanic ash of mount Sinabung as microsilka in concrete mixture substituted to create high strength concrete that is harmless for the environment. The use of mount sinabung volcanic ash as microsilika coupled with the use of Master Glenium Sky 8614 superplasticizer. This experiment intend to compare high strength concrete based slag steel as the main constituent aggregates and high strength concrete with a conventional mixture. The research result for 28 days old concrete shows that conventional concrete compressive strength is 67.567 MPa, slag concrete 75.958 Mpa, conventional tensile strength 5.435 Mpa while slag concrete 5.053 Mpa, conventional concrete bending strength 44064.96 kgcm while concrete slag 51473.94 kgcm and modulus of conventional concrete fracture 124.978 kg / cm2 while slag concrete 145.956 kg / cm2. Both concrete slump values shows similar results due to the use of superplasticizer.

  11. Development of high shrinkage polyethylene terephthalate (PET) shape memory polymer tendons for concrete crack closure

    Teall, Oliver; Pilegis, Martins; Sweeney, John; Gough, Tim; Thompson, Glen; Jefferson, Anthony; Lark, Robert; Gardner, Diane

    2017-04-01

    The shrinkage force exerted by restrained shape memory polymers (SMPs) can potentially be used to close cracks in structural concrete. This paper describes the physical processing and experimental work undertaken to develop high shrinkage die-drawn polyethylene terephthalate (PET) SMP tendons for use within a crack closure system. The extrusion and die-drawing procedure used to manufacture a series of PET tendon samples is described. The results from a set of restrained shrinkage tests, undertaken at differing activation temperatures, are also presented along with the mechanical properties of the most promising samples. The stress developed within the tendons is found to be related to the activation temperature, the cross-sectional area and to the draw rate used during manufacture. Comparisons with commercially-available PET strip samples used in previous research are made, demonstrating an increase in restrained shrinkage stress by a factor of two for manufactured PET filament samples.

  12. Ultra-High-Performance Concrete And Advanced Manufacturing Methods For Modular Construction

    Sawab, Jamshaid [Univ. of Houston, Houston, TX (United States); Lim, Ing [Univ. of Houston, Houston, TX (United States); Mo, Yi-Lung [Univ. of Houston, Houston, TX (United States); Li, Mo [Univ. of Houston, Houston, TX (United States); Wang, Hong [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Guimaraes, Maria [Electric Power Research Inst. (EPRI), Knoxville, TN (United States)

    2016-04-13

    containment structures to resist lateral forces induced by severe earthquakes and heavy winds. SC modules have good potential for SMR because of their cost-effectiveness and reduced construction time. However, the minimum shear reinforcement (i.e. cross tie) ratio needs to be determined for the steel plate-UHPC (S-UHPC) beams to exhibit a ductile failure mode. In this project, S-UHPC beams were designed and constructed. The beams were tested to evaluate structural capacity and identify the minimum cross ties ratios. In addition, as the bond between UHPC and steel plate is essential for ensuring structural integrity under shear and flexure, it was measured and examined in this project through digital image correlation system and smart piezoelectric aggregate sensors. Large-scale testing and finite element simulation were also performed on S-UHPC wall panels. New bond slip-based constitutive models of steel plate were developed for S-UHPC, which were used in finite element analysis program to predict S-UHPC behavior under shear. The results were well validated through experimental data. The long-term durability of UHPC were established in this project. UHPC specimens were tested under free shrinkage, restrained shrinkage, elevated temperature, water permeation, chloride diffusion, corrosion, and alkali silica reaction. UHPC has demonstrated significantly improved durability compared with control concrete specimens. This research led to a new generation of steel plate-UHPC modules for SMR that can provide large benefits to the electric power industry. Taking advantage of the high strength and durability of UHPC, their modularity and ease of assembly can address the high cost barriers of typical nuclear power plants.

  13. Modeling of Temperature Effect on Modal Frequency of Concrete Beam Based on Field Monitoring Data

    Wenchen Shan

    2018-01-01

    Full Text Available Temperature variation has been widely demonstrated to produce significant effect on modal frequencies that even exceed the effect of actual damage. In order to eliminate the temperature effect on modal frequency, an effective method is to construct quantitative models which accurately predict the modal frequency corresponding to temperature variation. In this paper, principal component analysis (PCA is conducted on the temperatures taken from all embedded thermocouples for extracting input parameters of regression models. Three regression-based numerical models using multiple linear regression (MLR, back-propagation neural network (BPNN, and support vector regression (SVR techniques are constructed to capture the relationships between modal frequencies and temperature distributions from measurements of a concrete beam during a period of forty days of monitoring. A comparison with respect to the performance of various optimally configured regression models has been performed on measurement data. Results indicate that the SVR exhibits a better reproduction and prediction capability than BPNN and MLR models for predicting the modal frequencies with respect to nonuniformly distributed temperatures. It is succeeded that temperature effects on modal frequencies can be effectively eliminated based on the optimally formulated SVR model.

  14. Strength Gain Properties up to five-year age of high-strength mass concrete

    Mitarai, Y.; Shigenobu, M.; Hiramine, T.; Inoue, K.; Nakane, S.; Ohike, T.

    1991-01-01

    Genkai No.3 plant of Kyushu Electric Power Co., Inc. presently under construction is a PWR type nuclear power plant with 1180 MW power output, and a prestressed concrete containment vessel (PCCV) was adopted for the reactor. The concrete used for the construction of the PCCV is the mass concrete with the wall thickness of 1.3 m in the general parts of the cylinder, and about 2 m at buttresses. It is the high strength concrete of the specified strength 420 kgf/cm 2 . As the preliminary study for the construction using such high strength mass concrete, the examination was carried out on the strength gain property of structural concrete using full scale simulated members. The various problems in the quality control were contemplated based on the results of the examination, and were reflected to actual construction, designating 13 weeks as the age for strength control, in order to build the concrete structures with high reliability. In this report, the outline of the study on the strength gain up to 5 year age carried out in the preliminary study is discussed. The experimental method, the method of evaluating structural strength, the mixing proportion of concrete and the results are reported. (K.I.)

  15. Combined Effect of Initial Curing Temperature and Crack Width on Chloride Penetration in Reinforced Concrete Beams

    Elkedrouci Lotfi

    2018-01-01

    Full Text Available Reinforced concrete (RC structures are gradually being degraded all over the world, largely due to corrosion of the embedded steel bars caused by an attack of chloride penetration. Initial curing would be regarded as one factor influencing chloride diffusion in concrete in combination with cover cracking that is also of great attention for reinforced structures. In this study, a non-steady state diffusion test of chloride ion involving RC beam specimens with a water-to-cement ratio of 0.5, initial curing temperatures of 5°C or 20°C and three types of crack widths ranging from 0 to 0.2mm was performed. Chloride content at 5°C or was determined. The results show that the higher chloride content was obtained in condition of crack width large than 0.1mm with low initial curing temperature and there are no obvious differences in chloride content when the crack width was not larger than 0.1mm.

  16. Pervious Concrete

    Torsvik, Øyvind André Hoff

    2012-01-01

    Pervious concrete is a material with a high degree of permeability but generally low strength. The material is primarily used for paving applications but has shown promise in many other areas of usage. This thesis investigates the properties of pervious concrete using normal Norwegian aggregates and practices. An overview of important factors when it comes to designing and producing pervious concrete is the result of this investigation. Several experiments have been performed in the concrete ...

  17. Advanced High Temperature Structural Seals

    Newquist, Charles W.; Verzemnieks, Juris; Keller, Peter C.; Rorabaugh, Michael; Shorey, Mark

    2002-10-01

    This program addresses the development of high temperature structural seals for control surfaces for a new generation of small reusable launch vehicles. Successful development will contribute significantly to the mission goal of reducing launch cost for small, 200 to 300 pound payloads. Development of high temperature seals is mission enabling. For instance, ineffective control surface seals can result in high temperature (3100 F) flows in the elevon area exceeding structural material limits. Longer sealing life will allow use for many missions before replacement, contributing to the reduction of hardware, operation and launch costs.

  18. Resistance to Corrosion of Reinforcement of High Volume Fly Ash Concrete

    Kwon, S. O.; Bae, S. H.; Lee, H. J.; Lee, K. M.; Jung, S. H.

    2014-01-01

    Due to the increasing of interest about the eco-friendly concrete, it is increased to use concretes containing by-products of industry such as fly ash(FA), ground granulated blast furnace slag(GGBFS), silica fume(SF), and etc. Especially, these are well known for improving the resistances to reinforcement corrosion in concrete and decreasing chloride ion penetration. The purpose of this experimental research is to evaluate the resistance against corrosion of reinforcement of high volume fly ash(HVFA) concrete which is replaced with high volume fly ash for cement volume. For this purpose, the concrete test specimens were made for various strength level and replacement ratio of FA, and then the compressive strength and diffusion coefficient for chloride ion of them were measured for 28, 91, and 182 days, respectively. Also, corrosion monitoring by half cell potential method was carried out for the made lollypop concrete test specimens to detect the time of corrosion initiation for reinforcement in concrete. As a result, it was observed from the test results that the compressive strength of HVFA concrete was decreased with increasing replacement ratio of FA but long-term resistances against reinforcement corrosion and chloride ion penetration of that were increased

  19. HIGH TEMPERATURE POLYMER FUEL CELLS

    Jensen, Jens Oluf; Qingfeng, Li; He, Ronghuan

    2003-01-01

    This paper will report recent results from our group on polymer fuel cells (PEMFC) based on the temperature resistant polymer polybenzimidazole (PBI), which allow working temperatures up to 200°C. The membrane has a water drag number near zero and need no water management at all. The high working...

  20. An Experimental Study on Shrinkage Strains of Normal-and High-Strength Concrete-Filled Frp Tubes

    Vincent, Thomas; Ozbakkaloglu, Togay

    2017-09-01

    It is now well established that concrete-filled fiber reinforced polymer (FRP) tubes (CFFTs) are an attractive construction technique for new columns, however studies examining concrete shrinkage in CFFTs remain limited. Concrete shrinkage may pose a concern for CFFTs, as in these members the curing of concrete takes place inside the FRP tube. This paper reports the findings from an experimental study on concrete shrinkage strain measurements for CFFTs manufactured with normal- and high-strength concrete (NSC and HSC). A total of 6 aramid FRP (AFRP)-confined concrete specimens with circular cross-sections were manufactured, with 3 specimens each manufactured using NSC and HSC. The specimens were instrumented with surface and embedded strain gauges to monitor shrinkage development of exposed concrete and concrete sealed inside the CFFTs, respectively. All specimens were cylinders with a 152 mm diameter and 305 mm height, and their unconfined concrete strengths were 44.8 or 83.2 MPa. Analysis of the shrinkage measurements from concrete sealed inside the CFFTs revealed that embedment depth and concrete compressive strength only had minor influences on recorded shrinkage strains. However, an analysis of shrinkage measurements from the exposed concrete surface revealed that higher amounts of shrinkage can occur in HSC. Finally, it was observed that shrinkage strains are significantly higher for concrete exposed at the surface compared to concrete sealed inside the CFFTs.

  1. Materials development and field demonstration of high-recycled-content concrete for energy-efficient building construction; FINAL

    Ostowari, Ken; Nosson, Ali

    2000-01-01

    The project developed high-recycled-content concrete material with balanced structural and thermal attributes for use in energy-efficient building construction. Recycled plastics, tire, wool, steel and concrete were used as replacement for coarse aggregates in concrete and masonry production. With recycled materials the specific heat and thermal conductivity of concrete could be tailored to enhance the energy-efficiency of concrete buildings. A comprehensive field project was implemented which confirmed the benefits of high-recycled-content concrete for energy-efficient building construction

  2. Reinforced concrete containment structures in high seismic zones

    Aziz, T.S.

    1977-01-01

    A new structural concept for reinforced concrete containment structures at sites where earthquake ground motions in terms of the Safe Shutdown Earthquake (SSE) exceeds 0.3 g is presented. The structural concept is based on: (1) an inner steel-lined concrete shell which houses the reactor and provides shielding and containment in the event of loss of coolant accident; (2) an outer annular concrete shell structure which houses auxiliary reactor equipment and safeguards systems. These shell structures are supported on a common foundation mat which is embedded in the subgrade. Under stipulated earthquake conditions the two shell structures interact to resist lateral inertia forces. Thus the annular structure which is not a pressure boundary acts as a lateral support for the inner containment shell. The concept is practical, economically feasible and new to practice. (Auth.)

  3. High Temperature Materials Laboratory (HTML)

    Federal Laboratory Consortium — The six user centers in the High Temperature Materials Laboratory (HTML), a DOE User Facility, are dedicated to solving materials problems that limit the efficiency...

  4. Performance of "Waterless Concrete"

    Toutanji, H. A.; Grugel, R. N.

    2009-01-01

    Waterless concrete consists of molten elementary sulfur and aggregate. The aggregates in a lunar environment will be lunar rocks and soil. Sulfur is present on the Moon in Troilite soil (FeS) and, by oxidation of the soil, iron and sulfur can be produced. Sulfur concrete specimens were cycled between liquid nitrogen (approx.]91 C) and room temperature (^21 C) to simulate exposure to a lunar environment. Cycled and control specimens were subsequently tested in compression at room temperatures (^21 C) and ^-101 C. Test results showed that due to temperature cycling, the compressive strength of cycled specimens was 20% of those non-cycled. This reduction in strength can be attributed to the large differences in thermal coefficients of expansion of the materials constituting the concrete which promoted cracking. Similar sulfur concrete mixtures were strengthened with short and long glass fibres. The lunar regolith simulant was melted in a 25 cc Pt- Rh crucible in a Sybron Thermoline high temperature MoSi2 furnace at melting temperatures of 1450 to 1600 C for times of 30 min to i hour. Glass fibres and small rods were pulled from the melt. The glass fibres were used to reinforce sulfur concrete plated to improve the flexural strength of the sulfur concrete. Beams strengthened with glass fibres showed to exhibit an increase in the flexural strength by as much as 45%.

  5. Strength Development of High-Strength Ductile Concrete Incorporating Metakaolin and PVA Fibers

    Muhammad Fadhil Nuruddin

    2014-01-01

    Full Text Available The mechanical properties of high-strength ductile concrete (HSDC have been investigated using Metakaolin (MK as the cement replacing material and PVA fibers. Total twenty-seven (27 mixes of concrete have been examined with varying content of MK and PVA fibers. It has been found that the coarser type PVA fibers provide strengths competitive to control or higher than control. Concrete with coarser type PVA fibers has also refined microstructure, but the microstructure has been undergone with the increase in aspect ratio of fibers. The microstructure of concrete with MK has also more refined and packing of material is much better with MK. PVA fibers not only give higher stiffness but also showed the deflection hardening response. Toughness Index of HSDC reflects the improvement in flexural toughness over the plain concrete and the maximum toughness indices have been observed with 10% MK and 2% volume fraction of PVA fibers.

  6. Fracture properties of high-strength concrete obtained by direct modification of structure

    Solodkyy Serhiy

    2017-01-01

    Full Text Available High-strength concrete is effectively used worldwide in the last three decades, but it is more brittle in comparison with normal strength concretes. Partial substitution of cement in concrete by active mineral additives and usage of chemical admixture of plasticizing and air-entraining action can considerably change their fracture properties. The obtained results show that the increase of the fracture properties is observed in concretes modified with chemical admixtures incorporating mineral additives such as zeolite and limestone due to consolidation of the concrete microstructure. Densification takes place as a result of limiting the amount of calcium hydroxide (CH due to its reaction with active silica included in the zeolite and the formation of larger amounts of hydrated calcium silicates of tobermorite type as well as calcium hydroaluminate and hydrocarboaluminate with the simultaneous adsorption modification of hydrated products by chemical admixtures.

  7. Strength development of high-strength ductile concrete incorporating Metakaolin and PVA fibers.

    Nuruddin, Muhammad Fadhil; Khan, Sadaqat Ullah; Shafiq, Nasir; Ayub, Tehmina

    2014-01-01

    The mechanical properties of high-strength ductile concrete (HSDC) have been investigated using Metakaolin (MK) as the cement replacing material and PVA fibers. Total twenty-seven (27) mixes of concrete have been examined with varying content of MK and PVA fibers. It has been found that the coarser type PVA fibers provide strengths competitive to control or higher than control. Concrete with coarser type PVA fibers has also refined microstructure, but the microstructure has been undergone with the increase in aspect ratio of fibers. The microstructure of concrete with MK has also more refined and packing of material is much better with MK. PVA fibers not only give higher stiffness but also showed the deflection hardening response. Toughness Index of HSDC reflects the improvement in flexural toughness over the plain concrete and the maximum toughness indices have been observed with 10% MK and 2% volume fraction of PVA fibers.

  8. The influence of calcium nitrate on setting and hardening rate of Portland cement concrete at different temperatures

    Kičaitė, A.; Pundienė, I.; Skripkiūnas, G.

    2017-10-01

    Calcium nitrate in mortars and concrete is used as a multifunctional additive: as set accelerator, plasticizer, long term strength enhancer and as antifreeze admixture. Used binding material and the amount of calcium nitrate, affect the characteristics of the concrete mixture and strength of hardened concrete. The setting time of the initial and the final binding at different temperatures of hardening (+ 20 °C and + 5 °C) of the pastes made of different cements (Portland cement CEM I 42.5 R and Portland limestone cement CEM II/A-LL 42.5 R) and various amounts of calcium nitrate from 1 % until 3 % were investigated. The effect of calcium nitrate on technological characteristics of concrete mixture (the consistency of the mixture, the density, and the amount of air in the mixture), on early concrete strength after 2 and 7 days, as well as on standard concrete strength after 28 days at different temperatures (at + 20 °C and + 5 °C) were analysed.

  9. High temperature divertor plasma operation

    Ohyabu, Nobuyoshi.

    1991-02-01

    High temperature divertor plasma operation has been proposed, which is expected to enhance the core energy confinement and eliminates the heat removal problem. In this approach, the heat flux is guided through divertor channel to a remote area with a large target surface, resulting in low heat load on the target plate. This allows pumping of the particles escaping from the core and hence maintaining of the high divertor temperature, which is comparable to the core temperature. The energy confinement is then determined by the diffusion coefficient of the core plasma, which has been observed to be much lower than the thermal diffusivity. (author)

  10. High temperature high vacuum creep testing facilities

    Matta, M.K.

    1985-01-01

    Creep is the term used to describe time-dependent plastic flow of metals under conditions of constant load or stress at constant high temperature. Creep has an important considerations for materials operating under stresses at high temperatures for long time such as cladding materials, pressure vessels, steam turbines, boilers,...etc. These two creep machines measures the creep of materials and alloys at high temperature under high vacuum at constant stress. By the two chart recorders attached to the system one could register time and temperature versus strain during the test . This report consists of three chapters, chapter I is the introduction, chapter II is the technical description of the creep machines while chapter III discuss some experimental data on the creep behaviour. Of helium implanted stainless steel. 13 fig., 3 tab

  11. Effect of magnetic water on strength and workability of high performance concrete

    Moosa Mazloom

    2016-09-01

    Full Text Available Nowadays, concrete is one of the most important and widely used human product. Improving concrete characteristics have always been one of the fundamental subjects for engineers. Improve the physical properties of water, as one of the main elements of concrete, is one way to improve the characteristics of the concrete. When water passes through the magnetic field, its physical quality has changed, it is called Magnetic water. This study examines the effect of the use of magnetized water (MW with a solenoid current-carrying, on the compressive strength and workability of high performance concrete. The variables of this study were the intensity of magnetic field, the silica fume replacement level and water to cement ratio in different mixes. The results show that using MW increases the workability of concrete about 36% in average.MW in combination with superplasticizer is more effective than MW on workability and compressive strength of concrete. MW had more positive effects on the samples without silica fume. Increasing the intensity of magnetic field improved the workability, 28 and 90 days compressive strength concrete.

  12. Composite Strain Hardening Properties of High Performance Hybrid Fibre Reinforced Concrete

    Vikram Jothi Jayakumar

    2014-01-01

    Full Text Available Hybrid fibres addition in concrete proved to be a promising method to improve the composite mechanical properties of the cementitious system. Fibre combinations involving different fibre lengths and moduli were added in high strength slag based concrete to evaluate the strain hardening properties. Influence of hybrid fibres consisting of steel and polypropylene fibres added in slag based cementitious system (50% CRL was explored. Effects of hybrid fibre addition at optimum volume fraction of 2% of steel fibres and 0.5% of PP fibres (long and short steel fibre combinations were observed in improving the postcrack strength properties of concrete. Test results also indicated that the hybrid steel fibre additions in slag based concrete consisting of short steel and polypropylene (PP fibres exhibited a the highest compressive strength of 48.56 MPa. Comparative analysis on the performance of monofibre concrete consisting of steel and PP fibres had shown lower residual strength compared to hybrid fibre combinations. Hybrid fibres consisting of long steel-PP fibres potentially improved the absolute and residual toughness properties of concrete composite up to a maximum of 94.38% compared to monofibre concrete. In addition, the relative performance levels of different hybrid fibres in improving the matrix strain hardening, postcrack toughness, and residual strength capacity of slag based concretes were evaluated systematically.

  13. A design method for two-layer beams consisting of normal and fibered high strength concrete

    Iskhakov, I.; Ribakov, Y.

    2007-01-01

    Two-layer fibered concrete beams can be analyzed using conventional methods for composite elements. The compressed zone of such beam section is made of high strength concrete (HSC), and the tensile one of normal strength concrete (NSC). The problems related to such type of beams are revealed and studied. An appropriate depth of each layer is prescribed. Compatibility conditions between HSC and NSC layers are found. It is based on the shear deformations equality on the layers border in a section with maximal depth of the compression zone. For the first time a rigorous definition of HSC is given using a comparative analysis of deformability and strength characteristics of different concrete classes. According to this definition, HSC has no download branch in the stress-strain diagram, the stress-strain function has minimum exponent, the ductility parameter is minimal and the concrete tensile strength remains constant with an increase in concrete compression strength. The application fields of two-layer concrete beams based on different static schemes and load conditions make known. It is known that the main disadvantage of HSCs is their low ductility. In order to overcome this problem, fibers are added to the HSC layer. Influence of different fiber volume ratios on structural ductility is discussed. An upper limit of the required fibers volume ratio is found based on compatibility equation of transverse tensile concrete deformations and deformations of fibers

  14. Connections in Precast Buildings using Ultra High-Strength Fibre Reinforced Concrete

    Hansen, Lars Pilegaard

    1995-01-01

    Ultra high-strength concrete adds new dimensions to the design of concrete structures. It is a brittle material but introducing fibres into the matrix changes the material into a highly ductile material. Furthermore, the fibre reinforcement increases the anchorage of traditional reinforcement bar...... and the fire resistance. Such a fibre reinforced ultra high-strength material has been used to develop a simple joint solution between slab elements in a column - slab building system....

  15. Thermal degradation of concrete in the temperature range from ambient to 315 degree C (600 degree F). Revision 10/96

    Kassir, M.K.; Bandyopadhyay, K.K.; Reich, M.

    1996-10-01

    This report is concerned with determining the effect of elevated temperatures on the behavior of concrete. Emphasis is placed on quantifying the degree of potential degradation of the physical properties of concrete in high-level waste storage tanks. The temperature elevation range of interest is from ambient to 315 C (600 F). The literature has been reviewed to examine the applicable experimental data and quantify the degradation in the concrete and reinforcing steel. Since many variables and test conditions control the results in the data base, upper and lower bounds of the degraded properties at temperatures applicable to the environments of the storage tanks are summarized and presented in explicit forms. For properties with large data bases, a normal logarithmic distribution of the data is assumed and a statistical analysis is carried out to find the mean and 84% values of the degraded property in the temperature range of interest. Such results are useful in assessing the effect of elevated temperatures on the structural behavior of the tanks. In addition, the results provide the technical basis for a parametric study that may be necessary to investigate the thermal aspects of the structural integrity of the tanks. 50 refs., 23 figs

  16. Measurement of moisture motion under a temperature gradient in a concrete for SNR-300 using thermal neutrons

    Zelinger, A.

    1975-01-01

    For describing the behavior of the moisture in the concrete of the containment of SNR-300 in a hypothetical accident parameters were determined experimentally. The method is based on transmission of thermal neutrons through a plate of concrete. When a temperature of 170 deg C was applied at one end of the plate migration of moisture and evaporation took place. This could be observed by neutron radiography giving a gross picture of moisture migration. Furthermore the intensity of the transmitted neutron beam was measured with a neutron counter. From these values profiles of the change of moisture concentration could be obtained with a spatial resolution of few millimeters. The method used is entirely different from the conventional moisture meters which use fast neutrons. From the experimental data the mass transfer coefficient of vapour, the diffusion coefficient of vapour in concrete and the porosity of the concrete could be determined

  17. The effect of curing conditions on the durability of high performance concrete

    Bumanis, G.; Bajare, D.

    2017-10-01

    This study researches compressive strength and durability of the high strength self-compacting concrete (SCC) impacted at early stage by the curing conditions. The mixture compositions of metakaolin containing waste and cenospheres as partial cement replacement (15 wt%) were compared to reference SCC with 100% cement. The specimens prepared in advance were demoulded 24h after casting of the SCC and the specific curing conditions were applied for up to 28 days: standard water curing at 20°C (i); indoor curing at 20°C, RH 60% (ii) and low temperature air curing (2°C) at RH 60% (iii). Results indicate that at early stage (14 days) indoor curing conditions increase compressive strength of the SCC whilst no strength loss has been detected even at a low temperature curing. The further strength gain has been substantially reduced for samples cured indoor and at a low temperature with significant variation observed for long term compressive strength (180 days). The metakaolin containing waste has proved to be an effective partial cement replacement and it has improved strength gain even at a low temperature curing. Meanwhile cenospheres have reduced the SCC strength and with no positive effect on strength observed within the standard term. Freeze-thaw durability and resistance to the chloride penetration have been improved for the SCC cured at low temperature. The SCC with metakaolin containing waste has proved to be the most durable thus demonstrating importance of effective micro filler use.

  18. Development of concrete mix proportions for minimizing/eliminating shrinkage cracks in slabs and high performance grouts : final report.

    2017-02-01

    The two focus areas of this research address longstanding problems of (1) cracking of concrete slabs due to creep and shrinkage and (2) high performance compositions for grouting and joining precast concrete structural elements. Cracking of bridge de...

  19. Towards a more common use of Ultra-High Performance Concrete (UHPC) – development of UHPC for ready-mix and prefabrication concrete plants

    Spiesz, P.R.; Hunger, M.; Justnes, Harald; Braarud, Henny

    2017-01-01

    This study addresses the development of ultra-high performance concrete (UHPC) suitable for a mass production in conventional ready-mix and prefabrication concrete plants. In order to facilitate the production process, curing regime and to minimize the costs, no additional treatments (e.g. thermal

  20. High - velocity water jet impact on concrete samples

    Mádr, V.; Uhlář, R.; Hlaváč, L. M.; Sitek, Libor; Foldyna, Josef; Hela, R.; Bodnárová, L.; Kaličinský, J.

    2009-01-01

    Roč. 2, č. 4 (2009), s. 43-48 ISSN 2067-3809 Institutional research plan: CEZ:AV0Z30860518 Keywords : water jet * concrete * depth of penetration * disintegration volume Subject RIV: JM - Building Engineering http://acta.fih.upt.ro/pdf/2009-4/ACTA-2009-4-08.pdf

  1. Shear in high strength concrete bridge girders : technical report.

    2013-04-01

    Prestressed Concrete (PC) I-girders are used extensively as the primary superstructure components in Texas highway bridges. : A simple semi-empirical equation was developed at the University of Houston (UH) to predict the shear strength of PC I-girde...

  2. Investigation of the existence of self compacting properties in high performance concrete through experimental tests

    Heitor H. Yoshida

    2007-03-01

    Full Text Available The self compacting concrete is characterized by its capacity to flow inside the formwork filling it exclusively by the force of the gravity with adequate cohesion and viscosity in such a way that segregation does not occur. One of its characteristic is the presence of fines which provide the necessary cohesion,and grains with maximum diameter of 20 mm. This work presents some procedures and experimental methods that make it possible to evaluate self compacting properties of high performance concrete. First, a bibliographical review on the subject was carried out, and later, the equipment used for the accomplishment of the assays were manufactured, in order to verify the properties related to the self compacting concrete: cohesion, viscosity and segregation. As for the work, two concretes were produced with Portland ARI Cement, thick sand, stone powder, sand 0, superplasticizer made of ether-carboxilate chains that differentiate from each other for the presence of active silica in one of them and fly ash in the other. Based on the results, it was verified whether the high performance concrete had self compacting characteristics. In this case, both were considered positive. It was also analyzed the behavior of these concretes in their hardened state by means of the compressive strength test. The Self Compacting Concrete has many advantages such as: reduction in the number of employees, shorter construction period, the non-use of the vibrator and the filling of formworks with high density of… or of complex geometry.

  3. Effect of mix proportion of high density concrete on compressive strength, density and radiation absorption

    Noor Azreen Masenwat; Mohamad Pauzi Ismail; Suhairy Sani; Ismail Mustapha; Nasharuddin Isa; Mohamad Haniza Mahmud; Mohammad Shahrizan Samsu

    2014-01-01

    To prevent radiation leaks at nuclear reactors, high-density concrete is used as an absorbent material for radiation from spreading into the environment. High-density concrete is a mixture of cement, sand, aggregate (usually high-density minerals) and water. In this research, hematite stone is used because of its mineral density higher than the granite used in conventional concrete mixing. Mix concrete in this study were divided into part 1 and part 2. In part 1, the concrete mixture is designed with the same ratio of 1: 2: 4 but differentiated in terms of water-cement ratio (0.60, 0.65, 0.70, 0.75, 0.80 ). Whereas, in part 2, the concrete mixture is designed to vary the ratio of 1: 1: 2, 1: 1.5: 3, 1: 2: 3, 1: 3: 6, 1: 2: 6 with water-cement ratio (0.7, 0.8, 0.85, 0.9). In each section, the division has also performed in a mixture of sand and fine sand hematite. Then, the physical characteristics of the density and the compressive strength of the mixture of part 1 and part 2 is measured. Comparisons were also made in terms of absorption of radiation by Cs-137 and Co-60 source for each mix. This paper describes and discusses the relationship between the concrete mixture ratio, the relationship with the water-cement ratio, compressive strength, density, different mixture of sand and fine sand hematite. (author)

  4. High temperature corrosion of metals

    Quadakkers, W.J.; Schuster, H.; Ennis, P.J.

    1988-08-01

    This paper covers three main topics: 1. high temperature oxidation of metals and alloys, 2. corrosion in sulfur containing environments and 3. structural changes caused by corrosion. The following 21 subjects are discussed: Influence of implanted yttrium and lanthanum on the oxidation behaviour of beta-NiA1; influence of reactive elements on the adherence and protective properties of alumina scales; problems related to the application of very fine markers in studying the mechanism of thin scale formation; oxidation behaviour of chromia forming Co-Cr-Al alloys with or without reactive element additions; growth and properties of chromia-scales on high-temperature alloys; quantification of the depletion zone in high temperature alloys after oxidation in process gas; effects of HC1 and of N2 in the oxidation of Fe-20Cr; investigation under nuclear safety aspects of Zircaloy-4 oxidation kinetics at high temperatures in air; on the sulfide corrosion of metallic materials; high temperature sulfide corrosion of Mn, Nb and Nb-Si alloys; corrosion behaviour or NiCrAl-based alloys in air and air-SO2 gas mixtures; sulfidation of cobalt at high temperatures; preoxidation for sulfidation protection; fireside corrosion and application of additives in electric utility boilers; transport properties of scales with complex defect structures; observations of whiskers and pyramids during high temperature corrosion of iron in SO2; corrosion and creep of alloy 800H under simulated coal gasification conditions; microstructural changes of HK 40 cast alloy caused by exploitation in tubes in steam reformer installation; microstructural changes during exposure in corrosive environments and their effect on mechanical properties; coatings against carburization; mathematical modeling of carbon diffusion and carbide precipitation in Ni-Cr-based alloys. (MM)

  5. Design and evaluation of a single-span bridge using ultra-high performance concrete.

    2009-09-01

    "Research presented herein describes an application of a newly developed material called Ultra-High Performance Concrete (UHPC) to a : single-span bridge. The two primary objectives of this research were to develop a shear design procedure for possib...

  6. Durability and smart condition assessment of ultra-high performance concrete in cold climates.

    2016-12-31

    The goals of this study were to develop ecological ultra-high performance concrete (UHPC) with local materials and supplementary cementitious materials and to evaluate the long-term performance of UHPC in cold climates using effective mechanical test...

  7. High temperature electronic gain device

    McCormick, J.B.; Depp, S.W.; Hamilton, D.J.; Kerwin, W.J.

    1979-01-01

    An integrated thermionic device suitable for use in high temperature, high radiation environments is described. Cathode and control electrodes are deposited on a first substrate facing an anode on a second substrate. The substrates are sealed to a refractory wall and evacuated to form an integrated triode vacuum tube

  8. RPC operation at high temperature

    Aielli, G; Cardarelli, R; Di Ciaccio, A; Di Stante, L; Liberti, B; Paoloni, A; Pastori, E; Santonico, R

    2003-01-01

    The resistive electrodes of RPCs utilised in several current experiments (ATLAS, CMS, ALICE, BABAR and ARGO) are made of phenolic /melaminic polymers, with room temperature resistivities ranging from 10**1**0 Omega cm, for high rate operation in avalanche mode, to 5 multiplied by 10**1**1 Omega cm, for streamer mode operation at low rate. The resistivity has however a strong temperature dependence, decreasing exponentially with increasing temperature. We have tested several RPCs with different electrode resistivities in avalanche as well as in streamer mode operation. The behaviours of the operating current and of the counting rate have been studied at different temperatures. Long-term operation has also been studied at T = 45 degree C and 35 degree C, respectively, for high and low resistivity electrodes RPCs.

  9. HIgh Temperature Photocatalysis over Semiconductors

    Westrich, Thomas A.

    Due in large part to in prevalence of solar energy, increasing demand of energy production (from all sources), and the uncertain future of petroleum energy feedstocks, solar energy harvesting and other photochemical systems will play a major role in the developing energy market. This dissertation focuses on a novel photochemical reaction process: high temperature photocatalysis (i.e., photocatalysis conducted above ambient temperatures, T ≥ 100°C). The overarching hypothesis of this process is that photo-generated charge carriers are able to constructively participate in thermo-catalytic chemical reactions, thereby increasing catalytic rates at one temperature, or maintaining catalytic rates at lower temperatures. The photocatalytic oxidation of carbon deposits in an operational hydrocarbon reformer is one envisioned application of high temperature photocatalysis. Carbon build-up during hydrocarbon reforming results in catalyst deactivation, in the worst cases, this was shown to happen in a period of minutes with a liquid hydrocarbon. In the presence of steam, oxygen, and above-ambient temperatures, carbonaceous deposits were photocatalytically oxidized over very long periods (t ≥ 24 hours). This initial experiment exemplified the necessity of a fundamental assessment of high temperature photocatalytic activity. Fundamental understanding of the mechanisms that affect photocatalytic activity as a function of temperatures was achieved using an ethylene photocatalytic oxidation probe reaction. Maximum ethylene photocatalytic oxidation rates were observed between 100 °C and 200 °C; the maximum photocatalytic rates were approximately a factor of 2 larger than photocatalytic rates at ambient temperatures. The loss of photocatalytic activity at temperatures above 200 °C is due to a non-radiative multi-phonon recombination mechanism. Further, it was shown that the fundamental rate of recombination (as a function of temperature) can be effectively modeled as a

  10. High temperature thermoelectric energy conversion

    Wood, C.

    1986-01-01

    Considerable advances were made in the late '50's and early early '60's in the theory and development of materials for high-temperature thermoelectric energy conversion. This early work culminated in a variety of materials, spanning a range of temperatures, with the product of the figure of merit, Z, and temperature, T, i.e., the dimensionless figure of merit, ZT, of the order of one. This experimental limitation appeared to be universal and led a number of investigators to explore the possibility that a ZT - also represents a theoretical limitation. It was found not to be so

  11. Properties of Fresh and Hardened High Strength Steel Fibres Reinforced Self-Compacted Concrete

    Saad Ali Al-Ta'an

    2016-10-01

    Full Text Available Fresh and hardened properties of high strength steel fibrous self-compacted concrete were studied in this investigation. One reference high strength self-compacted concrete mix is used, with five percent (by weight of cement silica fume and eight percent of the cement replaced by limestone powder. Three steel fibres percentages by volume of concrete are used (0.4, 0.8, and 1.2. The used steel fibres were a shelled Harex type with irregular cross-section, equivalent diameter of 0.9278 mm, and 32 mm long. Super plasticizer was used to improve the workability and flow ability of the mixes. The test results showed that the presence of steel fibres decrease the flow ability, and increase the time of spreading, segregation, and passing ability of the fresh concrete. For the fibres percentages used, the fresh properties were within the recommended specifications for the self-compacted concrete. The test results showed an early strength development rate more than that for plain normal concrete due to the presence of the fine materials. As for normal concrete, the test results showed also that the increase in the splitting strength is more than the increase in the compressive strength due to the presence of the steel fibres. The brittle mode of failure of the plain unreinforced specimens changed to a ductile one due to the presence of the steel fibres.

  12. Experimental investigations of sandwich panels using high performance concrete thin plates exposed to fire

    Hulin, Thomas; Hodicky, Kamil; Schmidt, Jacob Wittrup

    2015-01-01

    Structural sandwich panels using thin high performance concrete (HPC) plates offer a possibility to address the modern environmental challenges faced by the construction industry. Fire resistance is a major necessity in structures using HPC. This paper presents experimental studies at elevated...... temperatures for panels with 30 mm thick plates stiffened by structural ribs, thick insulation layers, and steel shear connecting systems. Parametric variation assessing the role of each component of the sandwich structure was performed on unloaded specimens of reduced size. Full size walls were tested...... with load. Tests were performed in standard furnaces, following the conditions of REI certification tests. Unloaded specimens successfully passed tests. Loaded specimens met the R and I requirements, failing E due to sustained flaming of the insulation. They exhibited multiple cracking of their exposed...

  13. Prediction of the Chloride Resistance of Concrete Modified with High Calcium Fly Ash Using Machine Learning.

    Marks, Michał; Glinicki, Michał A; Gibas, Karolina

    2015-12-11

    The aim of the study was to generate rules for the prediction of the chloride resistance of concrete modified with high calcium fly ash using machine learning methods. The rapid chloride permeability test, according to the Nordtest Method Build 492, was used for determining the chloride ions' penetration in concrete containing high calcium fly ash (HCFA) for partial replacement of Portland cement. The results of the performed tests were used as the training set to generate rules describing the relation between material composition and the chloride resistance. Multiple methods for rule generation were applied and compared. The rules generated by algorithm J48 from the Weka workbench provided the means for adequate classification of plain concretes and concretes modified with high calcium fly ash as materials of good, acceptable or unacceptable resistance to chloride penetration.

  14. Investigation of water content in primary upper shield of high temperature engineering test reactor (HTTR)

    Sumita, Junya; Sawa, Kazuhiro; Mogi, Haruyoshi; Itahashi, Shuuji; Kitami, Toshiyuki; Akutu, Youichi; Fuchita, Yasuhiro; Kawaguchi, Toru; Moriya, Masahiro

    1999-09-01

    A primary upper shield of the High Temperature Engineering Test Reactor (HTTR) is composed of concrete (grout) which is packed into iron frames. The main function of the primary upper shield is to attenuate neutron and gamma ray from the core, that leads to satisfy dose equivalent rate limit of operating floor and stand-pipe room. Water content in the concrete is one of the most important things because it strongly affects neutron-shielding ability. Then, we carried out out-of-pile experiments to investigate relationship between temperature and water content in the concrete. Based on the experimental results, a hydrolysis-diffusion model was developed to investigate water release behavior from the concrete. The model showed that water content used for shielding design in the primary upper shield of the HTTR will be maintained if temperature during operating life is under 110degC. (author)

  15. Static, Fire and Fatigue Tests of Ultra High-Strength Fibre Reinforced Concrete and Ribbed Bars

    Hansen, Lars Pilegaard; Heshe, Gert

    2001-01-01

    A new building system has been developed during the last 10 years. This new system consists of a column / slab system with 6 x 6 m distance between the columns. The slabs are precast concrete elements of size 2.9 x 5.9 m connected through joints of ultra high strength fibre reinforced concrete...... - Densit Joint Cast ®. Also the connections between the columns and the slabs are made of this very strong concrete material. The paper describes some of the static tests carried out as well as some fire tests. Further, 2 chapters deal with some fatigue tests of the reinforcing bars as well as some fatigue...

  16. Study and application of high-density concrete in radiation-shielding experiment

    Wu Chongming; Ding Dexin; Xiao Xuefu; Wang Shaolin; Lin Xingjun; Shen Yuanyuan

    2008-01-01

    According to the demand for research and construction project, a series of systematic experiments and studies on shielding γ-ray radiation concrete with the density of 4.60 t/m 3 were made in such aspects as mix ratio design, construction technology, uniformly shielding etc. Such issues as uniformity in the construction and compactness were solved. The ray test method for uniformly shielding concrete was presented and some technical steps for this high-density concrete used in the process of test design or construction were summed up. A series of tests and practical applications show that this technology of mix ratio design and construction is feasible. (authors)

  17. High Temperature Transparent Furnace Development

    Bates, Stephen C.

    1997-01-01

    This report describes the use of novel techniques for heat containment that could be used to build a high temperature transparent furnace. The primary objective of the work was to experimentally demonstrate transparent furnace operation at 1200 C. Secondary objectives were to understand furnace operation and furnace component specification to enable the design and construction of a low power prototype furnace for delivery to NASA in a follow-up project. The basic approach of the research was to couple high temperature component design with simple concept demonstration experiments that modify a commercially available transparent furnace rated at lower temperature. A detailed energy balance of the operating transparent furnace was performed, calculating heat losses through the furnace components as a result of conduction, radiation, and convection. The transparent furnace shells and furnace components were redesigned to permit furnace operation at at least 1200 C. Techniques were developed that are expected to lead to significantly improved heat containment compared with current transparent furnaces. The design of a thermal profile in a multizone high temperature transparent furnace design was also addressed. Experiments were performed to verify the energy balance analysis, to demonstrate some of the major furnace improvement techniques developed, and to demonstrate the overall feasibility of a high temperature transparent furnace. The important objective of the research was achieved: to demonstrate the feasibility of operating a transparent furnace at 1200 C.

  18. Construction of precast high performance concrete segmental bridges.

    Ruiz Ripoll, Lidia

    2016-01-01

    The construction of both medium and long span precast concrete segmental bridges is widely spread throughout Spain. Usually, the segments have multiple-keyed epoxy joints, and are assembled by internal prestressing. Yet, there is a more recent type of bridge with dry joints and external prestressing. In these last ones, shear is transferred through physical support between keys and friction between faces of the compressed joint. This shear force is evaluated using friction coefficients from t...

  19. Modeling and Measurement of Sustained Loading and Temperature-Dependent Deformation of Carbon Fiber-Reinforced Polymer Bonded to Concrete.

    Jeong, Yoseok; Lee, Jaeha; Kim, WooSeok

    2015-01-29

    This paper aims at presenting the effects of short-term sustained load and temperature on time-dependent deformation of carbon fiber-reinforced polymer (CFRP) bonded to concrete and pull-off strength at room temperature after the sustained loading period. The approach involves experimental and numerical analysis. Single-lap shear specimens were used to evaluate temperature and short-term sustained loading effects on time-dependent behavior under sustained loading and debonding behavior under pull-off loading after a sustained loading period. The numerical model was parameterized with experiments on the concrete, FRP, and epoxy. Good correlation was seen between the numerical results and single-lap shear experiments. Sensitivity studies shed light on the influence of temperature, epoxy modulus, and epoxy thickness on the redistribution of interfacial shear stress during sustained loading. This investigation confirms the hypothesis that interfacial stress redistribution can occur due to sustained load and elevated temperature and its effect can be significant.

  20. "Green" High-Temperature Polymers

    Meador, Michael A.

    1998-01-01

    PMR-15 is a processable, high-temperature polymer developed at the NASA Lewis Research Center in the 1970's principally for aeropropulsion applications. Use of fiber-reinforced polymer matrix composites in these applications can lead to substantial weight savings, thereby leading to improved fuel economy, increased passenger and payload capacity, and better maneuverability. PMR-15 is used fairly extensively in military and commercial aircraft engines components seeing service temperatures as high as 500 F (260 C), such as the outer bypass duct for the F-404 engine. The current world-wide market for PMR-15 materials (resins, adhesives, and composites) is on the order of $6 to 10 million annually.

  1. High-temperature metallography setup

    Blumenfeld, M.; Shmarjahu, D.; Elfassy, S.

    1979-06-01

    A high-temperature metallography setup is presented. In this setup the observation of processes such as that of copper recrystallization was made possible, and the structure of metals such as uranium could be revealed. A brief historical review of part of the research works that have been done with the help of high temperature metallographical observation technique since the beginning of this century is included. Detailed description of metallographical specimen preparation technique and theoretical criteria based on the rate of evaporation of materials present on the polished surface of the specimens are given

  2. High temperature corrosion in gasifiers

    Bakker Wate

    2004-01-01

    Full Text Available Several commercial scale coal gasification combined cycle power plants have been built and successfully operated during the last 5-10 years. Supporting research on materials of construction has been carried out for the last 20 years by EPRI and others. Emphasis was on metallic alloys for heat exchangers and other components in contact with hot corrosive gases at high temperatures. In this paper major high temperature corrosion mechanisms, materials performance in presently operating gasifiers and future research needs will be discussed.

  3. Determination of the heating temperature of potholes surface on road pavement in the process of repairs using hot asphalt concrete mixes

    Giyasov Botir Iminzhonovich

    2014-12-01

    Full Text Available In the process of roads construction the necessary transport and operational characteristics should be achieved, which depend on the quality of the applied, material and technologies. Under the loads of transport means and the influence of weather conditions on the road pavement deformations and destructions occur, which lead to worsening of transport and operational characteristics, decrease of operational life of the road and they are often the reason of road accidents. According to the data of the Strategic Research Center of "Rosgosstrah" more than 20 % of road accidents in Russia occur due to bad quality of road pavement. One of the main directions in traffic security control and prolongation of operational life for road pavement of non-rigid type is road works, as a result of which defects of pavement are eliminated and in case of timely repairs of high quality the operational life of the road increases for several years. The most widely used material for non-rigid pavement repairs is hot road concrete mixes and in case of adherence to specifications they provide high quality of works. The authors investigate the problems of hot asphalt concrete mixes for repairs of road surfaces of non-rigid type. The results of the study hot asphalt concrete mix’s temperature regimes are offered in case of repair works considering the temperature delivered to the work site and the ambient temperature depending on the type of mix and class of bitumen.

  4. Impact of Steel Fiber Size and Shape on the Mechanical Properties of Ultra-High Performance Concrete

    2015-08-01

    characteristics of steel fiber reinforcement to the mechanical properties of high-strength concretes , this study investigated four commercially available...Standard test method for flexural performance of fiber - reinforced concrete (using beam with third-point loading). Designation: C1609/1609M. West...STEEL FIBERS are low-carbon, drawn w ire for reinforced concrete . NYCON-SF fibers distribute stresses within the concrete and provide improvement

  5. Compression Behavior of Confined Columns with High-Volume Fly Ash Concrete

    Sung-Won Yoo

    2017-01-01

    Full Text Available The use of fly ash in ordinary concrete provides practical benefits to concrete structures, such as a gain in long-term strength, reduced hydration heat, improved resistance to chloride, and enhanced workability. However, few studies with high-volume fly ash (HVFA concrete have been conducted that focus on the structural applications such as a column. Thus, there is a need to promote field applications of HVFA concrete as a sustainable construction material. To this end, this study investigated the compressive behavior of reinforced concrete columns that contain HVFA with a 50 percent replacement rate. Six columns were fabricated for this study. The study variables were the HVFA replacement rate, tied steel ratio, and tie steel spacing. The computed ultimate strength by the American Concrete Institute (ACI code conservatively predicted the measured values, and, thus, the existing equation in the ACI code is feasible for confined RC columns that contain HVFA. In addition, an analysis model was calibrated based on the experimental results and is recommended for predicting the stress-strain relationship of confined reinforced concrete columns that contain HVFA.

  6. High temperature creep of vanadium

    Juhasz, A.; Kovacs, I.

    1978-01-01

    The creep behaviour of polycrystalline vanadium of 99.7% purity has been investigated in the temperature range 790-880 0 C in a high temperature microscope. It was found that the creep properties depend strongly on the history of the sample. To take this fact into account some additional properties such as the dependence of the yield stress and the microhardness on the pre-annealing treatment have also been studied. Samples used in creep measurements were selected on the basis of their microhardness. The activation energy of creep depends on the microhardness and on the creep temperature. In samples annealed at 1250 0 C for one hour (HV=160 kgf mm -2 ) the rate of creep is controlled by vacancy diffusion in the temperature range 820-880 0 C with an activation energy of 78+-8 kcal mol -1 . (Auth.)

  7. Contribution to the explanation of the spalling of small specimen without any mechanical restraint exposed to high temperature

    Morais, Marcus V.G. de; Pliya, Prosper; Noumowe, Albert; Beaucour, Anne-Lise; Ortola, Sophie

    2010-01-01

    The behaviour of concrete subjected to high temperature is studied. The aim of the study is to explain the spalling or bursting phenomenon observed during experimental studies in the laboratory. Mechanical computations are carried out with the finite element code CAST3M developed at the French Atomic Energy Agency (CEA). Heat gradient and water vapour pressure inside the concrete element are determined by using a thermo-hydrous model. Then, the mechanical stresses generated in the studied concrete element are calculated according to two behaviour assumptions: the linear isotropic elastic law and an elastoplastic model. Numerical simulations show that, during the heating cycles, tension stresses are developed in the central part and compression stresses at the surface of the cylindrical concrete element. The highest stresses appear when the surface temperature of the concrete element is about 300 o C. The tension stresses in the specimens then exceed the concrete tensile strength.

  8. Contribution to the explanation of the spalling of small specimen without any mechanical restraint exposed to high temperature

    Morais, Marcus V.G. de, E-mail: mvmorais@unb.b [Cergy-Pontoise University - L2MGC, 5 mail Gay-Lussac Neuville sur Oise, 95031 Cergy-Pontoise Cedex (France); Pliya, Prosper [Cergy-Pontoise University - L2MGC, 5 mail Gay-Lussac Neuville sur Oise, 95031 Cergy-Pontoise Cedex (France); Noumowe, Albert, E-mail: Albert.Noumowe@u-cergy.f [Cergy-Pontoise University - L2MGC, 5 mail Gay-Lussac Neuville sur Oise, 95031 Cergy-Pontoise Cedex (France); Beaucour, Anne-Lise; Ortola, Sophie [Cergy-Pontoise University - L2MGC, 5 mail Gay-Lussac Neuville sur Oise, 95031 Cergy-Pontoise Cedex (France)

    2010-10-15

    The behaviour of concrete subjected to high temperature is studied. The aim of the study is to explain the spalling or bursting phenomenon observed during experimental studies in the laboratory. Mechanical computations are carried out with the finite element code CAST3M developed at the French Atomic Energy Agency (CEA). Heat gradient and water vapour pressure inside the concrete element are determined by using a thermo-hydrous model. Then, the mechanical stresses generated in the studied concrete element are calculated according to two behaviour assumptions: the linear isotropic elastic law and an elastoplastic model. Numerical simulations show that, during the heating cycles, tension stresses are developed in the central part and compression stresses at the surface of the cylindrical concrete element. The highest stresses appear when the surface temperature of the concrete element is about 300 {sup o}C. The tension stresses in the specimens then exceed the concrete tensile strength.

  9. Study of temperature effect on the physical properties of ilmenite-serpentine heat resistant concrete radiation shields

    Kany, A.M.I.; EL-Fouly, M.M.; EL-Gohary, M.I.; Makatious, A.S.; Kamal, S.M.

    1990-01-01

    A series of experimental studies have been carried out to determine the change in unit weigh, compressive strength, water content and neutron macroscopic cross section of a new type of concrete shields made from egyptian ilmenite and serpentine ores when heated for long period at temperatures up to 600 degree C. Results show that the unit weight of the cure concrete has a value of 2.98 Ton/M 3 and decreases with increasing temperature, while the compressive strength reaches a maximum value of 19 Ton/M 2 at 100 degree C. The differential thermal analysis (D.T.A.) of this concrete shows three endothermic peaks at 100 degree C, 48 degree C and 740 degree C. Also, the thermogravimetry analysis (T.G.A.) shows that the cure concrete retains about 11% water content of the total sample weigh and still retains 4.5% of its initial value when heated for long period at 600 degree C. Results also show that the neutron macroscopic cross section (for neutrons of energies < 1 MeV) of the ilmenite-serpentine heat resistant concrete decreases to 18.6% of its initial value after heating to 600 degree C

  10. Laboratory Investigations on Mechanical Properties of High Volume Fly Ash Concrete and Composite Sections

    Aravindkumar B. Harwalkar; S. S. Awanti

    2013-01-01

    Use of fly ash as a supplementary cementing material in large volumes can bring both technological and economic benefits for concrete industry. In this investigation mix proportions for high volume fly ash concrete were determined at cement replacement levels of 50%, 55%, 60% and 65% with low calcium fly ash. Flexural and compressive strengths of different mixes were measured at ages of 7, 28 and 90 days. Flexural strength of composite section prepared from pavement quali...

  11. Fracture toughness and failure mechanism of high performance concrete incorporating carbon nanotubes

    A. Khitab

    2017-10-01

    Full Text Available Cement and concrete composites are inherently brittle and exhibit very less tensile/flexural strength capacity as compared to their compressive strength. Use of thoroughly dispersed carbon nanotubes in the concrete matrix is one of the possible solution for enhancing mechanical properties in tension/flexure. In the present research work, small fractions of multiwall carbon nanotube (MWCNTs i.e. 0.05 and 0.10 wt% of cement have been integrated into the cement concrete to study their effect on the mechanical properties of the resultant concrete mixtures. The enhanced performance of the whole mix lies on a single point that MWCNTs must be thoroughly disperse in the mixture. Hence, special arrangement through usage of high energy sonication along with amended acrylic based polymer (performing as a surfactant was made to have a uniform dispersion of MWCNTs in the concrete mix. The testing of concrete samples includes i.e., flexure, splitting tensile and compressive strengths after 3, 7, 28 and 56 days of curing. After having comparison with the control mix cured for 28 days, it was observed that the addition of 0.05 wt% MWCNTs increased the splitting tensile strength by 20.58%, flexural strength by 26.29% and compressive strength by 15.60%. Through above results, which verify the increase in concrete mix strength after adding MWCNTs, these MWCNTs may be incorporated in the treatment of Nano/micro cracks completed through process of connecting, branching and pinning. Similarly, as proved in threepoint bending tests, MWCNTs also enhances the breaking strains as well as the fracture energy of the concrete mixes, besides, imparting increase to the strength. The investigations have shown that incorporating lesser amounts of MWCNTs i.e., 0.05 and 0.10 wt% of cement to the concrete mixes after insuring there complete dispersion, unusually improve their properties like mechanical strengths and fracture behavior

  12. High-temperature plasma physics

    Furth, H.P.

    1988-03-01

    Both magnetic and inertial confinement research are entering the plasma parameter range of fusion reactor interest. This paper reviews the individual and common technical problems of these two approaches to the generation of thermonuclear plasmas, and describes some related applications of high-temperature plasma physics

  13. High-Temperature Vibration Damper

    Clarke, Alan; Litwin, Joel; Krauss, Harold

    1987-01-01

    Device for damping vibrations functions at temperatures up to 400 degrees F. Dampens vibrational torque loads as high as 1,000 lb-in. but compact enough to be part of helicopter rotor hub. Rotary damper absorbs energy from vibrating rod, dissipating it in turbulent motion of viscous hydraulic fluid forced by moving vanes through small orifices.

  14. Containment of high temperature plasmas

    Bass, R.W.; Ferguson, H.R.P.; Fletcher, H. Jr.; Gardner, J.; Harrison, B.K.; Larsen, K.M.

    1973-01-01

    Apparatus is described for confining a high temperature plasma which comprises: 1) envelope means shaped to form a toroidal hollow chamber containing a plasma, 2) magnetic field line generating means for confining the plasma in a smooth toroidal shape without cusps. (R.L.)

  15. Chemistry of high temperature superconductors

    1991-01-01

    This review volume contains the most up-to-date articles on the chemical aspects of high temperature oxide superconductors. These articles are written by some of the leading scientists in the field and includes a comprehensive list of references. This is an essential volume for researchers working in the fields of ceramics, materials science and chemistry.

  16. Properties of high temperature SQUIDS

    Falco, C.M.; Wu, C.T.

    1978-01-01

    A review is given of the present status of weak links and dc and rf biased SQUIDs made with high temperature superconductors. A method for producing reliable, reproducible devices using Nb 3 Sn is outlined, and comments are made on directions future work should take

  17. High temperature component life assessment

    Webster, G A

    1994-01-01

    The aim of this book is to investigate and explain the rapid advances in the characterization of high temperature crack growth behaviour which have been made in recent years, with reference to industrial applications. Complicated mathematics has been minimized with the emphasis placed instead on finding solutions using simplified procedures without the need for complex numerical analysis.

  18. High rate response of ultra-high-performance fiber-reinforced concretes under direct tension

    Tran, Ngoc Thanh [Department of Civil and Environmental Engineering, Sejong University, 98 Gunja-Dong, Gwangjin-Gu, Seoul 143-747 (Korea, Republic of); Tran, Tuan Kiet [Department of Civil and Environmental Engineering, Sejong University, 98 Gunja-Dong, Gwangjin-Gu, Seoul 143-747 (Korea, Republic of); Department of Civil Engineering and Applied Mechanics, Ho Chi Minh City University of Technology and Education, 01 Vo Van Ngan, Thu Duc District, Ho Chi Minh City (Viet Nam); Kim, Dong Joo, E-mail: djkim75@sejong.ac.kr [Department of Civil and Environmental Engineering, Sejong University, 98 Gunja-Dong, Gwangjin-Gu, Seoul 143-747 (Korea, Republic of)

    2015-03-15

    The tensile response of ultra-high-performance fiber-reinforced concretes (UHPFRCs) at high strain rates (5–24 s{sup −} {sup 1}) was investigated. Three types of steel fibers, including twisted, long and short smooth steel fibers, were added by 1.5% volume content in an ultra high performance concrete (UHPC) with a compressive strength of 180 MPa. Two different cross sections, 25 × 25 and 25 × 50 mm{sup 2}, of tensile specimens were used to investigate the effect of the cross section area on the measured tensile response of UHPFRCs. Although all the three fibers generated strain hardening behavior even at high strain rates, long smooth fibers produced the highest tensile resistance at high rates whereas twisted fiber did at static rate. The breakages of twisted fibers were observed from the specimens tested at high strain rates unlike smooth steel fibers. The tensile behavior of UHPFRCs at high strain rates was clearly influenced by the specimen size, especially in post-cracking strength.

  19. Evaluation of the Chemical and Mechanical Properties of Hardening High-Calcium Fly Ash Blended Concrete.

    Fan, Wei-Jie; Wang, Xiao-Yong; Park, Ki-Bong

    2015-09-07

    High-calcium fly ash (FH) is the combustion residue from electric power plants burning lignite or sub-bituminous coal. As a mineral admixture, FH can be used to produce high-strength concrete and high-performance concrete. The development of chemical and mechanical properties is a crucial factor for appropriately using FH in the concrete industry. To achieve sustainable development in the concrete industry, this paper presents a theoretical model to systematically evaluate the property developments of FH blended concrete. The proposed model analyzes the cement hydration, the reaction of free CaO in FH, and the reaction of phases in FH other than free CaO. The mutual interactions among cement hydration, the reaction of free CaO in FH, and the reaction of other phases in FH are also considered through the calcium hydroxide contents and the capillary water contents. Using the hydration degree of cement, the reaction degree of free CaO in FH, and the reaction degree of other phases in FH, the proposed model evaluates the calcium hydroxide contents, the reaction degree of FH, chemically bound water, porosity, and the compressive strength of hardening concrete with different water to binder ratios and FH replacement ratios. The evaluated results are compared to experimental results, and good consistencies are found.

  20. Behavior and strength of beams cast with ultra high strength concrete containing different types of fibers

    M.M. Kamal

    2014-04-01

    Full Text Available Ultra-high performance concrete (UHPC is a special type of concrete with extraordinary potentials in terms of strength and durability performance. Its production and application implement the most up-to-date knowledge and technology of concrete manufacturing. Sophisticated structural designs in bridges and high-rise buildings, repair works and special structures like nuclear facilities are currently the main fields of applications of UHPC. This paper aimed to evaluate the behavior of ultra-high strength concrete beams. This paper also aimed to determine the effect of adding fibers and explore their effect upon the behavior and strength of the reinforced concrete beams. A total of twelve simple concrete beams with and without shear reinforcements were tested in flexure. The main variables taken into consideration in this research were the type of fibers and the percentage of longitudinal reinforcement as well as the existence or absence of the web reinforcement. Two types of fibers were used including steel and polypropylene fibers. The behavior of the tested beams was investigated with special attention to the deflection under different stages of loading, initial cracking, cracking pattern, and ultimate load. Increased number of cracks was observed at the end of loading due to the use of fibers, which led to the reduced width of cracks. This led to increased stiffness and higher values of maximum loads.

  1. Application of wire sawing method to decommissioning of high level activated concrete

    Hasegawa, Hideki; Nishimura, Youichi; Watanabe, Morishige; Yamashita Yoshitaka

    1999-01-01

    Wire sawing method is proposed as an effective cutting method for the dismantling of high level activated concrete of a nuclear power plant. The cutting test with wire sawing method discussed in this paper was carried out to obtain the data such as the cutting rate, the volume of concrete dust and the time of cutting and related work. The cutting test consisted of two parts; 'Fundamental test' and 'mock-up test.' In the fundamental test, we carried out the cutting test with small concrete blocks simulating the high level activated concrete of Boiling Water Reactor (BWR) and Pressurized Water Reactor (PWR). Through the test, the following data were obtained: the cutting rate of wire sawing, the volume of generated concrete dust and the grading distribution of suspended particulate. We also studied the life of wire and the relations between the wire tension, the wire rotating speed, the steel ratio and the cutting rate. In the mock-up test, we carried out the test with large concrete blocks simulating the part of the reactor shield wall of BWR and the biological shield wall of PWR. Through the mock-up test, we made clear that it is possible that the large test blocks with high re-bar ratio and a steel plate (steel plates) were cut smoothly by the wire sawing method. In the test, the following data were obtained; the cutting rate, the time of the cutting and related work and the remote controllability of cutting machines. (author)

  2. High temperature fusion reactor design

    Harkness, S.D.; dePaz, J.F.; Gohar, M.Y.; Stevens, H.C.

    1979-01-01

    Fusion energy may have unique advantages over other systems as a source for high temperature process heat. A conceptual design of a blanket for a 7 m tokamak reactor has been developed that is capable of producing 1100 0 C process heat at a pressure of approximately 10 atmospheres. The design is based on the use of a falling bed of MgO spheres as the high temperature heat transfer system. By preheating the spheres with energy taken from the low temperature tritium breeding part of the blanket, 1086 MW of energy can be generated at 1100 0 C from a system that produces 3000 MW of total energy while sustaining a tritium breeding ratio of 1.07. The tritium breeding is accomplished using Li 2 O modules both in front of (6 cm thick) and behind (50 cm thick) the high temperature ducts. Steam is used as the first wall and front tritium breeding module coolant while helium is used in the rear tritium breeding region. The system produces 600 MW of net electricity for use on the grid

  3. Development of high-strength concrete mix designs in support of the prestressed concrete reactor vessel design for a HTGR steam cycle/cogeneration plant

    Naus, D.J.; Oland, C.B.

    1985-01-01

    Design optimization studies indicate that a significant reduction in the size of the PCRV for a 2240 MW(t) HTGR plant can be effected through utilization of high-strength concrete in conjunction with large capacity prestressing systems. A three-phase test program to develop and evaluate high-strength concretes (>63.4 MPa) is described. Results obtained under Phase I of the investigation related to materials selection-evaluation and mix design development are presented. 3 refs., 4 figs

  4. High Temperature, High Power Piezoelectric Composite Transducers

    Lee, Hyeong Jae; Zhang, Shujun; Bar-Cohen, Yoseph; Sherrit, StewarT.

    2014-01-01

    Piezoelectric composites are a class of functional materials consisting of piezoelectric active materials and non-piezoelectric passive polymers, mechanically attached together to form different connectivities. These composites have several advantages compared to conventional piezoelectric ceramics and polymers, including improved electromechanical properties, mechanical flexibility and the ability to tailor properties by using several different connectivity patterns. These advantages have led to the improvement of overall transducer performance, such as transducer sensitivity and bandwidth, resulting in rapid implementation of piezoelectric composites in medical imaging ultrasounds and other acoustic transducers. Recently, new piezoelectric composite transducers have been developed with optimized composite components that have improved thermal stability and mechanical quality factors, making them promising candidates for high temperature, high power transducer applications, such as therapeutic ultrasound, high power ultrasonic wirebonding, high temperature non-destructive testing, and downhole energy harvesting. This paper will present recent developments of piezoelectric composite technology for high temperature and high power applications. The concerns and limitations of using piezoelectric composites will also be discussed, and the expected future research directions will be outlined. PMID:25111242

  5. Ultra high performance concrete made with rice husk ash for reduced autogenous shrinkage

    Van Breugel, K.; Van Tuan, N.

    2014-01-01

    Ultra High Strength Concrete (UHPC) is generally made with low w/c mixtures and by adding silica fume. Low w/c mixtures, however, exhibit high autogenous shrinkage, while a high amount of silica fume increases the price of these mixtures. For designing ultra high strength mixtures with low

  6. Large scale high strain-rate tests of concrete

    Kiefer R.

    2012-08-01

    Full Text Available This work presents the stages of development of some innovative equipment, based on Hopkinson bar techniques, for performing large scale dynamic tests of concrete specimens. The activity is centered at the recently upgraded HOPLAB facility, which is basically a split Hopkinson bar with a total length of approximately 200 m and with bar diameters of 72 mm. Through pre-tensioning and suddenly releasing a steel cable, force pulses of up to 2 MN, 250 μs rise time and 40 ms duration can be generated and applied to the specimen tested. The dynamic compression loading has first been treated and several modifications in the basic configuration have been introduced. Twin incident and transmitter bars have been installed with strong steel plates at their ends where large specimens can be accommodated. A series of calibration and qualification tests has been conducted and the first real tests on concrete cylindrical specimens of 20cm diameter and up to 40cm length have commenced. Preliminary results from the analysis of the recorded signals indicate proper Hopkinson bar testing conditions and reliable functioning of the facility.

  7. Calculation of the temperature of asphalt concrete at making the joints of multilane road pavement of non-rigid type

    Giyasov Botir Iminzhonovich

    2015-03-01

    Full Text Available The construction quality of road surface of non-rigid type essentially depend on providing the temperature regimes in the process of laying and packing of hot asphalt concrete mixtures. In order to provide the required characteristics of asphalt concrete due to the surface width it is necessary to provide the temperature regimes of hot asphalt concrete mixture in the zones of lane connection. The hot mixture is promptly cooling right after laying within several minutes, which results, according to the construction technology and the specific conditions of work production, in temperature abuse of the mixture at joints of the lanes at packing. The authors present the analysis of the technology of arranging multilane road surface by one paver with the possibility of heating the surface lane edge with the temperature of the adjacent lane. The results of the studies of the production conditions effect on the temperature of edge heating of the previously laid lanes, and the time required to achieve the maximum heating temperature depending on the relative thickness of coating layers.

  8. Summary: High Temperature Downhole Motor

    Raymond, David W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-10-01

    Directional drilling can be used to enable multi-lateral completions from a single well pad to improve well productivity and decrease environmental impact. Downhole rotation is typically developed with a motor in the Bottom Hole Assembly (BHA) that develops drilling power (speed and torque) necessary to drive rock reduction mechanisms (i.e., the bit) apart from the rotation developed by the surface rig. Historically, wellbore deviation has been introduced by a “bent-sub,” located in the BHA, that introduces a small angular deviation, typically less than 3 degrees, to allow the bit to drill off-axis with orientation of the BHA controlled at the surface. The development of a high temperature downhole motor would allow reliable use of bent subs for geothermal directional drilling. Sandia National Laboratories is pursuing the development of a high temperature motor that will operate on either drilling fluid (water-based mud) or compressed air to enable drilling high temperature, high strength, fractured rock. The project consists of designing a power section based upon geothermal drilling requirements; modeling and analysis of potential solutions; and design, development and testing of prototype hardware to validate the concept. Drilling costs contribute substantially to geothermal electricity production costs. The present development will result in more reliable access to deep, hot geothermal resources and allow preferential wellbore trajectories to be achieved. This will enable development of geothermal wells with multi-lateral completions resulting in improved geothermal resource recovery, decreased environmental impact and enhanced well construction economics.

  9. NSTX High Temperature Sensor Systems

    McCormack, B.; Kugel, H.W.; Goranson, P.; Kaita, R.

    1999-01-01

    The design of the more than 300 in-vessel sensor systems for the National Spherical Torus Experiment (NSTX) has encountered several challenging fusion reactor diagnostic issues involving high temperatures and space constraints. This has resulted in unique miniature, high temperature in-vessel sensor systems mounted in small spaces behind plasma facing armor tiles, and they are prototypical of possible high power reactor first-wall applications. In the Center Stack, Divertor, Passive Plate, and vessel wall regions, the small magnetic sensors, large magnetic sensors, flux loops, Rogowski Coils, thermocouples, and Langmuir Probes are qualified for 600 degrees C operation. This rating will accommodate both peak rear-face graphite tile temperatures during operations and the 350 degrees C bake-out conditions. Similar sensor systems including flux loops, on other vacuum vessel regions are qualified for 350 degrees C operation. Cabling from the sensors embedded in the graphite tiles follows narrow routes to exit the vessel. The detailed sensor design and installation methods of these diagnostic systems developed for high-powered ST operation are discussed

  10. Development of high temperature turbine

    Takahara, Kitao; Nouse, Hiroyuki; Yoshida, Toyoaki; Minoda, Mitsuhiro; Matsusue, Katsutoshi; Yanagi, Ryoji

    1988-07-01

    For the contribution to the development of FJR710, high by-pass ratio turbofan engine, with the study for many years of the development of high efficiency turbine for the jet engine, the first technical prize from the Energy Resource Research Committee was awarded in April, 1988. This report introduced its technical contents. In order to improve the thermal efficiency and enlarge the output, it is very effective to raise the gas temperature at the inlet of gas turbine. For its purpose, by cooling the nozzle and moving blades and having those blades operate at lower temperature than that of the working limitation, they realized, for the first time in Japan, the technique of cooling turbine to heighten the operational gas temperature. By that technique, it was enabled to raise the gas temperature at the inlet of turbine, to 1,350/sup 0/C from 850/sup 0/C. This report explain many important points of study covering the basic test, visualizing flow experiment, material discussion and structural design in the process of development. (9 figs)

  11. Ceramics for high temperature applications

    Mocellin, A.

    1977-01-01

    Problems related to materials, their fabrication, properties, handling, improvements are examined. Silicium nitride and silicium carbide are obtained by vacuum hot-pressing, reaction sintering and chemical vapour deposition. Micrographs are shown. Mechanical properties i.e. room and high temperature strength, creep resistance fracture mechanics and fatigue resistance. Recent developments of pressureless sintered Si C and the Si-Al-O-N quaternary system are mentioned

  12. High-temperature geothermal cableheads

    Coquat, J. A.; Eifert, R. W.

    1981-11-01

    Two high temperature, corrosion resistant logging cable heads which use metal seals and a stable fluid to achieve proper electrical terminations and cable sonde interfacings are described. A tensile bar provides a calibrated yield point, and a cone assembly anchors the cable armor to the head. Electrical problems of the sort generally ascribable to the cable sonde interface were absent during demonstration hostile environment loggings in which these cable heads were used.

  13. Response of concrete exposed to a high heat flux on one surface

    Muir, J.F.

    1977-11-01

    Experiments were performed to investigate the response of concrete to severe thermal environments such as might be encountered during the interaction of molten reactor core materials with the containment substructure following a hypothetical fuel melt accident. The dominant mechanism for erosion of both limestone and basaltic concrete appears to be melting of the cementitious material in the matrix. The erosion proceeded in a quiescent manner with negligible spallation. The erosion rate increased with heat flux, becoming as large as approximately 70 cm/hr for a net surface heat flux of roughly 190 W/cm 2 . Analyses reveal the surface temperature to be the single most significant parameter affecting the net surface heat flux, through its importance to emitted radiation; and that the greatest fraction of the net energy transmitted to the concrete goes into sensible heat

  14. Behaviour of Nano Silica in Tension Zone of High Performance Concrete Beams

    Jaishankar, P.; Vivek, D.

    2017-07-01

    High performance concrete (HPC) is similar to High strength concrete (HSC).It is because of lowering of water to cement ratio, which is needed to attain high strength and generally improves other properties. This concrete contains one or more cementitious materials such as fly ash, Silica fume or ground granulated blast furnace slag and usually a super plasticizer. The term ‘high performance’ is somewhat different because the essential feature of this concrete is that it’s ingredients and proportions are specifically chosen so as to have particularly appropriate properties for the expected use of the structure such as high strength and low permeability. Usage of nano scale properties such as Nano SiO2 can result in dramatically improved properties from conventional grain size materials of same chemical composition. This project is more interested in evaluate the behaviour of nano silica in concrete for 5%, 10%, and 15% volume fraction of cement. Flexural test for beams were conducted with two point loads, at different percentage as mentioned above. From results interpolated, Nano silica with higher order replacement gives optimized results compared to control specimens.

  15. Measurement of the Rheological Properties of High Performance Concrete: State of the Art Report

    Ferraris, Chiara F.

    1999-01-01

    The rheological or flow properties of concrete in general and of high performance concrete (HPC) in particular, are important because many factors such as ease of placement, consolidation, durability, and strength depend on the flow properties. Concrete that is not properly consolidated may have defects, such as honeycombs, air voids, and aggregate segregation. Such an important performance attribute has triggered the design of numerous test methods. Generally, the flow behavior of concrete approximates that of a Bingham fluid. Therefore, at least two parameters, yield stress and viscosity, are necessary to characterize the flow. Nevertheless, most methods measure only one parameter. Predictions of the flow properties of concrete from its composition or from the properties of its components are not easy. No general model exists, although some attempts have been made. This paper gives an overview of the flow properties of a fluid or a suspension, followed by a critical review of the most commonly used concrete rheology tests. Particular attention is given to tests that could be used for HPC. Tentative definitions of terms such as workability, consistency, and rheological parameters are provided. An overview of the most promising tests and models for cement paste is given.

  16. Mock-up experiments for the project of high dose irradiation on the RPV concrete

    Zdarek, J.; Brabec, P.; Frybort, O.; Lahodova, Z.; Vit, J.; Stemberk, P.

    2015-01-01

    Aging of NPP's concrete structures comes into growing interest in connection with solution of life extension programmes of operated units. Securing continued safe operation of NPPs calls for additional proofs of suitable long term behaviour of loaded reinforced concrete structures. An irradiation test of concrete samples was performed in the core of the LVR-15 reactor. The irradiation capsule was hung in the irradiation channel and the cooling of the capsule was ensured through direct contact of the capsule wall with the primary circuit water. Cylindrical, serpentine concrete samples (50 mm in diameter and 100 mm in length), representing composition of WWER RPV cavity, was chosen as a compromise of mechanical properties testing needs and dimension limitations of reactor irradiation channel. Heating during irradiation test was maintained under 93 Celsius degrees by cooling and was controlled by embedded thermocouple. Design of the cooling management was supported by computational analysis. The dependencies of heated concrete samples to the neutron fluence and the gamma heating were obtained by changing the thermal power of the reactor and by changing the vertical position of the sample in the irradiation channel. The irradiation capsule was filled with inert gas (helium) to allow the measurement of generated gas. The determination of concrete samples activity for long-term irradiation was performed on the principles of the Neutron Activation Analysis. Preliminary mock-up tests have proved the ability to fulfill technical needs for planned high dose irradiation experiment

  17. Concrete construction engineering handbook

    Nawy, Edward G

    2008-01-01

    Provides coverage of concrete construction engineering and technology. This work features discussions focusing on: the advances in engineered concrete materials; reinforced concrete construction; specialized construction techniques; and, design recommendations for high performance.

  18. the effect of high temperatures on concrete incorporating ultrafine ...

    Benkaddour M, Senhadji Y, Kazi Aoual F and Semcha A

    1 mai 2016 ... ... CEM II/A 42,5 MPa de la cimenterie LAFARGE de Oggaz (Ouest. Algérien). Ses caractéristiques chimiques, minéralogiques et physiques sont présentées dans les tableaux 1, 2 et 3 respectivement. Tableau 1. Analyse chimique du ciment. Les composants. CaO. SiO2. Al2O3. Fe2O3. MgO SO3. Perte au.

  19. Study of thermal performance of capillary micro tubes integrated into the building sandwich element made of high performance concrete

    Mikeska, Tomas; Svendsen, Svend

    2013-01-01

    The thermal performance of radiant heating and cooling systems (RHCS) composed of capillary micro tubes (CMT) integrated into the inner plate of sandwich elements made of high performance concrete (HPC) was investigated in the article. Temperature distribution in HPC elements around integrated CM...... and cooling purposes of future low energy buildings. The investigations were conceived as a low temperature concept, where the difference between the temperature of circulating fluid and air in the room was kept in range of 1–4 °C.......The thermal performance of radiant heating and cooling systems (RHCS) composed of capillary micro tubes (CMT) integrated into the inner plate of sandwich elements made of high performance concrete (HPC) was investigated in the article. Temperature distribution in HPC elements around integrated CMT...... HPC layer covering the CMT. This paper shows that CMT integrated into the thin plate of sandwich element made of HPC can supply the energy needed for heating (cooling) and at the same time create the comfortable and healthy environment for the occupants. This solution is very suitable for heating...

  20. Computer aided seismic and fire retrofitting analysis of existing high rise reinforced concrete buildings

    Hussain, Raja Rizwan; Hasan, Saeed

    2016-01-01

    This book details the analysis and design of high rise buildings for gravity and seismic analysis. It provides the knowledge structural engineers need to retrofit existing structures in order to meet safety requirements and better prevent potential damage from such disasters as earthquakes and fires. Coverage includes actual case studies of existing buildings, reviews of current knowledge for damages and their mitigation, protective design technologies, and analytical and computational techniques. This monograph also provides an experimental investigation on the properties of fiber reinforced concrete that consists of natural fibres like coconut coir and also steel fibres that are used for comparison in both Normal Strength Concrete (NSC) and High Strength Concrete (HSC). In addition, the authors examine the use of various repair techniques for damaged high rise buildings. The book will help upcoming structural design engineers learn the computer aided analysis and design of real existing high rise buildings ...

  1. Numerical Analysis on the High-Strength Concrete Beams Ultimate Behaviour

    Smarzewski, Piotr; Stolarski, Adam

    2017-10-01

    Development of technologies of high-strength concrete (HSC) beams production, with the aim of creating a secure and durable material, is closely linked with the numerical models of real objects. The three-dimensional nonlinear finite element models of reinforced high-strength concrete beams with a complex geometry has been investigated in this study. The numerical analysis is performed using the ANSYS finite element package. The arc-length (A-L) parameters and the adaptive descent (AD) parameters are used with Newton-Raphson method to trace the complete load-deflection curves. Experimental and finite element modelling results are compared graphically and numerically. Comparison of these results indicates the correctness of failure criteria assumed for the high-strength concrete and the steel reinforcement. The results of numerical simulation are sensitive to the modulus of elasticity and the shear transfer coefficient for an open crack assigned to high-strength concrete. The full nonlinear load-deflection curves at mid-span of the beams, the development of strain in compressive concrete and the development of strain in tensile bar are in good agreement with the experimental results. Numerical results for smeared crack patterns are qualitatively agreeable as to the location, direction, and distribution with the test data. The model was capable of predicting the introduction and propagation of flexural and diagonal cracks. It was concluded that the finite element model captured successfully the inelastic flexural behaviour of the beams to failure.

  2. HIGHLY EFFECTIVE CHEMICAL MODIFIERS FOR PRODUCTION OF CONCRETES WITH PRE-SET PROPERTIES

    Tkach Evgeniya Vladimirovna

    2012-10-01

    Full Text Available The paper demonstrates the application of industrial by-products and recycled materials. Waterproofing admixtures improve the structure and the properties of the cement stone. Development and preparation of highly effective waterproofing modifiers of durable effect, as well as development of the process procedure parameters, including mixing, activation, heat treatment, etc. are to be implemented. The composition of waterproofing modifiers is to be fine-tuned to synergize the behaviour of various ingredients of cement systems to assure the substantial improvement of their strength, freeze- and corrosion resistance. Multi-functional waterproofing admixtures were used to produce highly effective modified concretes. The key idea of the new method of modifying cement-based building materials is that the waterproofing admixture concentration is to exceed 10% of the weight of the binding agent within the per-unit weight of the cement stone, given that its strength does not deteriorate. GKM-type modifier coupled with organo-mineral waterproofing admixture concentration agent GT-M may be recommended for mass use in the manufacturing of hydraulic concrete and reinforced concrete products. Overview of their practical implementation has proven that waterproofing modifier GKM-S, if coupled with waterproofing admixture concentration agent GT-M, improves the corrosion control inside the cement stone and makes it possible to manufacture durable concrete and reinforced concrete products that demonstrate pre-set physical and processing behaviour. Comprehensive concrete modification by modifier GKM-S and waterproofing admixture concentration agent GT-M may be regarded as one of the most ambitious methods of production of highly effective waterproof concretes.

  3. Effects of Silica in Rice Husk Ash (RHA) in producing High Strength Concrete

    Kartini, K; Nurul Nazierah, M.Y; Zaidahtulakmal, M.Z; Siti Aisyah, G

    2012-01-01

    High strength concrete (HSC) are known to have a higher amount of cement binder in the mix design properties with low w/b ratio. The high mass of cement content produced substantial heat liberation in the concrete due to the reaction between cement and water, which can lead to cracking. Additive likes silica fume is too expensive to use in the HSC in order to overcome the problems, however, the initiative of utilizing the rice husk ash (RHA) which have high silica content are apply for the de...

  4. High temperature PEM fuel cells

    Zhang, Jianlu; Xie, Zhong; Zhang, Jiujun; Tang, Yanghua; Song, Chaojie; Navessin, Titichai; Shi, Zhiqing; Song, Datong; Wang, Haijiang; Wilkinson, David P.; Liu, Zhong-Sheng; Holdcroft, Steven [Institute for Fuel Cell Innovation, National Research Council Canada, Vancouver, BC (Canada V6T 1W5)

    2006-10-06

    There are several compelling technological and commercial reasons for operating H{sub 2}/air PEM fuel cells at temperatures above 100{sup o}C. Rates of electrochemical kinetics are enhanced, water management and cooling is simplified, useful waste heat can be recovered, and lower quality reformed hydrogen may be used as the fuel. This review paper provides a concise review of high temperature PEM fuel cells (HT-PEMFCs) from the perspective of HT-specific materials, designs, and testing/diagnostics. The review describes the motivation for HT-PEMFC development, the technology gaps, and recent advances. HT-membrane development accounts for {approx}90% of the published research in the field of HT-PEMFCs. Despite this, the status of membrane development for high temperature/low humidity operation is less than satisfactory. A weakness in the development of HT-PEMFC technology is the deficiency in HT-specific fuel cell architectures, test station designs, and testing protocols, and an understanding of the underlying fundamental principles behind these areas. The development of HT-specific PEMFC designs is of key importance that may help mitigate issues of membrane dehydration and MEA degradation. (author)

  5. Temperature uniformity mapping in a high pressure high temperature reactor using a temperature sensitive indicator

    Grauwet, T.; Plancken, van der I.; Vervoort, L.; Matser, A.M.; Hendrickx, M.; Loey, van A.

    2011-01-01

    Recently, the first prototype ovomucoid-based pressure–temperature–time indicator (pTTI) for high pressure high temperature (HPHT) processing was described. However, for temperature uniformity mapping of high pressure (HP) vessels under HPHT sterilization conditions, this prototype needs to be

  6. Viscosities of corium-concrete mixtures

    Seiler, J.M.; Ganzhorn, J.

    1997-01-01

    Severe accidents on nuclear reactors involve many situations such as pools of molten core material, melt spreading, melt/concrete interactions, etc. The word 'corium' designates mixtures of materials issued from the molten core at high temperature; these mixtures involve mainly: UO2, ZrO2, Zr and, in small amounts, Ni, Cr, Ag, In, Cd. These materials, when flowing out of the reactor vessel, may interact with the concrete of the reactor building thus introducing decomposition products of concrete into the original mixture. These decomposition products are mainly: SiO 2 , FeO, MgO, CaO and Al 2 O 3 in different amounts depending on the nature of the concrete being considered. Siliceous concrete is rich in SiO 2 , limestone concrete contains both SiO 2 and CaO. Liquidus temperatures of such mixtures are generally obove 2300 K whereas solidus temperatures are ∝1400 K. (orig.)

  7. Effect of Hybrid Fibers on the Mechanical Properties of High Strength Concrete

    Hamid H. Hussein, Saeed K. Rejeb Hayder T. Abd

    2014-04-01

    Full Text Available In this study, high strength concrete of 75 MPa compressive strength was investigated. The experimental program was designed to study the effect of fibers and hybrid fibers (steel and polypropylene fibers on the fresh (workability and wet density and hardened properties (compressive strength, splitting strength, flexural strength and dry density of high strength concrete. Results show that decreases in slump flow of all concrete mixtures containing steel, polypropylene and hybrid fibers compared with control mix (0% fiber. Hybrid high strength concrete with steel and polypropylene fibers showed superior compressive, splitting, flexural strengths over the others concrete without or with single fibers content. The test results indicate that the maximum increase in compressive and flexural strengths are obtains with the hybridization ratio (70%steel + 30% polypropylene and were equal to 14.54% and 23.34% respectively, compared with the control mix. While, the maximum increase in splitting tensile strength with (100% steel fiber + 0 polypropylene is 21.19%. 

  8. New potentional of high-speed water jet technology for renovating concrete structures

    Bodnárová, L.; Sitek, L.; Hela, R.; Foldyna, J.

    2011-06-01

    The paper discusses the background and results of research focused on the action of a high-speed water jet on concrete with different qualities. The sufficient and careful removal of degraded concrete layers is very important for the renovation of concrete structures. High-speed water jet technology is one of the most common methods used for removing degraded concrete layers. Different types of high-speed water jets were tested in the experimental part. The classical technology of a single continuous water jet generated with one nozzle was tested as well as the technology of revolving water jets generated by multiple nozzles (used mainly for the renovation of larger areas). A continuous flat water jet and pulsating flat water jet were tested the first time, because the connection of a water jet with the acoustic generator of a pulsating jet offers new possibilities for the use of a water jet (see [1] and [2]). A water jet with such a modification is capable of efficient action and can even be used for cutting solid concrete with a relatively low consumption of energy. A flat pulsating water jet which can be newly used for renovation seems to be a promising technology.

  9. On the performance of circular concrete-filled high strength steel columns under axial loading

    Mohamed Mahmoud El-Heweity

    2012-06-01

    Full Text Available This work presents a numerical study to investigate the performance of circular high-strength steel tubes filled with concrete (CFT under monotonic axial loading. A model is developed to implement the material constitutive relationships and non-linearity. Calibration against previous experimental data shows good agreement. A parametric study is then conducted using the model and compared with codes provisions. Strength and ductility of confined concrete are of primary concern. Variables considered are yield stress of steel tube and column diameter. The assessment of column performance is based on axial load carrying capacities and enhancements of both strength and ductility due to confinement. Two parameters namely strength enhancement factor (Kf and ductility index (μ are clearly defined and introduced for assessment. Results indicate that both concrete strength and ductility of CFT columns are enhanced but to different extents. The ductile behaviors are significantly evident. The increase in yield stress of steel tube has a minimal effect on concrete strength but pronounced effect on concrete ductility. However, reduction in ductility is associated with using high-tensile steel of Grade 70. The overall findings indicate that the use of high-strength tube in CFT columns is not promising. This finding may seriously be considered in seismic design.

  10. Statistical evaluation of the mechanical properties of high-volume class F fly ash concretes

    Yoon, Seyoon

    2014-03-01

    High-Volume Fly Ash (HVFA) concretes are seen by many as a feasible solution for sustainable, low embodied carbon construction. At the moment, fly ash is classified as a waste by-product, primarily of thermal power stations. In this paper the authors experimentally and statistically investigated the effects of mix-design factors on the mechanical properties of high-volume class F fly ash concretes. A total of 240 and 32 samples were produced and tested in the laboratory to measure compressive strength and Young\\'s modulus respectively. Applicability of the CEB-FIP (Comite Euro-international du Béton - Fédération Internationale de la Précontrainte) and ACI (American Concrete Institute) Building Model Code (Thomas, 2010; ACI Committee 209, 1982) [1,2] to the experimentally-derived mechanical property data for HVFA concretes was established. Furthermore, using multiple linear regression analysis, Mean Squared Residuals (MSRs) were obtained to determine whether a weight- or volume-based mix proportion is better to predict the mechanical properties of HVFA concrete. The significance levels of the design factors, which indicate how significantly the factors affect the HVFA concrete\\'s mechanical properties, were determined using analysis of variance (ANOVA) tests. The results show that a weight-based mix proportion is a slightly better predictor of mechanical properties than volume-based one. The significance level of fly ash substitution rate was higher than that of w/b ratio initially but reduced over time. © 2014 Elsevier Ltd. All rights reserved.

  11. Passivation of high temperature superconductors

    Vasquez, Richard P. (Inventor)

    1991-01-01

    The surface of high temperature superconductors such as YBa2Cu3O(7-x) are passivated by reacting the native Y, Ba and Cu metal ions with an anion such as sulfate or oxalate to form a surface film that is impervious to water and has a solubility in water of no more than 10(exp -3) M. The passivating treatment is preferably conducted by immersing the surface in dilute aqueous acid solution since more soluble species dissolve into the solution. The treatment does not degrade the superconducting properties of the bulk material.

  12. CONFINEMENT OF HIGH TEMPERATURE PLASMA

    Koenig, H.R.

    1963-05-01

    The confinement of a high temperature plasma in a stellarator in which the magnetic confinement has tended to shift the plasma from the center of the curved, U-shaped end loops is described. Magnetic means are provided for counteracting this tendency of the plasma to be shifted away from the center of the end loops, and in one embodiment this magnetic means is a longitudinally extending magnetic field such as is provided by two sets of parallel conductors bent to follow the U-shaped curvature of the end loops and energized oppositely on the inside and outside of this curvature. (AEC)

  13. High temperature superconductors and method

    Ruvalds, J.J.

    1977-01-01

    This invention comprises a superconductive compound having the formula: Ni/sub 1-x/M/sub x/Z/sub y/ wherein M is a metal which will destroy the magnetic character of nickel (preferably copper, silver or gold); Z is hydrogen or deuterium; x is 0.1 to 0.9; and y, correspondingly, 0.9 to 0.1, and method of conducting electric current with no resistance at relatively high temperature of T>1 0 K comprising a conductor consisting essentially of the superconducting compound noted above

  14. Bond behavior of reinforcing steel in ultra-high performance concrete.

    2014-10-01

    Ultra-High Performance Concrete (UHPC) is a relatively new class of advanced cementitious composite : materials, which exhibits high compressive [above 21.7 ksi (150 MPa)] and tensile [above 0.72 ksi (5 MPa)] : strengths. The discrete steel fiber rei...

  15. High performance fiber reinforced concrete : Progress in knowledge and design codes

    Walraven, J.C.

    2009-01-01

    High performance fiber reinforced concrete is developing quickly to a modern structural material with a high potential. As for instance testified by the recent symposium on HPFRC in Kassel, Germany (April 2008) the number of structural applications increases. At this moment studies are carried out

  16. The use of nanomodified concrete in construction of high-rise buildings

    Prokhorov, Sergei

    2018-03-01

    Construction is one of the leading economy sectors. Currently, concrete is the basis of most of the structural elements, without which it is impossible to imagine the construction of a single building or facility. Their strength, reinforcement and the period of concrete lifetime are determined at the design stage, taking into account long-term operation. However, in real life, the number of impacts that affects the structural strength is pretty high. In some cases, they are random and do not have standardized values. This is especially true in the construction and exploitation of high-rise buildings and structures. Unlike the multi-storey buildings, they experience significant loads already at the stage of erection, as they support load-lifting mechanisms, formwork systems, workers, etc. The purpose of the presented article is to develop a methodology for estimating the internal fatigue of concrete structures based on changes in their electrical conductivity.

  17. Modern high-temperature superconductivity

    Ching Wu Chu

    1988-01-01

    Ever since the discovery of superconductivity in 1911, its unusual scientific challenge and great technological potential have been recognized. For the past three-quarters of a century, superconductivity has done well on the science front. This is because sueprconductivity is interesting not only just in its own right but also in its ability to act as a probe to many exciting nonsuperconducting phenomena. For instance, it has continued to provide bases for vigorous activities in condensed matter science. Among the more recent examples are heavy-fermion systems and organic superconductors. During this same period of time, superconductivity has also performed admirably in the applied area. Many ideas have been conceived and tested, making use of the unique characteristics of superconductivity - zero resistivity, quantum interference phenomena, and the Meissner effect. In fact, it was not until late January 1987 that it became possible to achieve superconductivity with the mere use of liquid nitrogen - which is plentiful, cheap, efficient, and easy to handle - following the discovery of supercondictivity above 90 K in Y-Ba-Cu-O, the first genuine quaternary superconductor. Superconductivity above 90 K poses scientific and technological challenges not previously encountered: no existing theories can adequately describe superconductivity above 40 K and no known techniques can economically process the materials for full-scale applications. In this paper, therefore, the author recalls a few events leading to the discovery of the new class of quaternary compounds with a superconducting transition temperature T c in the 90 K range, describes the current experimental status of high-temperature superconductivity and, finally, discusses the prospect of very-high-temperature superconductivity, i.e., with a T c substantially higher than 100 K. 97 refs., 7 figs

  18. Studies of high temperature superconductors

    Narlikar, A.

    1989-01-01

    The high temperature superconductors (HTSCs) discovered are from the family of ceramic oxides. Their large scale utilization in electrical utilities and in microelectronic devices are the frontal challenges which can perhaps be effectively met only through consolidated efforts and expertise of a multidisciplinary nature. During the last two years the growth of the new field has occurred on an international scale and perhaps has been more rapid than in most other fields. There has been an extraordinary rush of data and results which are continually being published as short texts dispersed in many excellent journals, some of which were started to ensure rapid publication exclusively in this field. As a result, the literature on HTSCs has indeed become so massive and so diffuse that it is becoming increasingly difficult to keep abreast with the important and reliable facets of this fast-growing field. This provided the motivation to evolve a process whereby both professional investigators and students can have ready access to up-to- date in-depth accounts of major technical advances happening in this field. The present series Studies of High Temperature Superconductors has been launched to, at least in part, fulfill this need

  19. High temperature superconductor current leads

    Zeimetz, B.; Liu, H.K.; Dou, S.X.

    1996-01-01

    Full text: The use of superconductors in high electrical current applications (magnets, transformers, generators etc.) usually requires cooling with liquid Helium, which is very expensive. The superconductor itself produces no heat, and the design of Helium dewars is very advanced. Therefore most of the heat loss, i.e. Helium consumption, comes from the current lead which connects the superconductor with its power source at room temperature. The current lead usually consists of a pair of thick copper wires. The discovery of the High Temperature Superconductors makes it possible to replace a part of the copper with superconducting material. This drastically reduces the heat losses because a) the superconductor generates no resistive heat and b) it is a very poor thermal conductor compared with the copper. In this work silver-sheathed superconducting tapes are used as current lead components. The work comprises both the production of the tapes and the overall design of the leads, in order to a) maximize the current capacity ('critical current') of the superconductor, b) minimize the thermal conductivity of the silver clad, and c) optimize the cooling conditions

  20. Container floor at high temperatures

    Reutler, H.; Klapperich, H.J.; Mueller-Frank, U.

    1978-01-01

    The invention describes a floor for container which is stressed at high, changing temperatures and is intended for use in gas-cooled nuclear reactors. Due to the downward cooling gas flow in these types of reactor, the reactor floor is subjected to considerable dimensional changes during switching on and off. In the heating stage, the whole graphite structure of the reactor core and floor expands. In order to avoid arising constraining forces, sufficiently large expansion spaces must be allowed for furthermore restoring forces must be present to close the gaps again in the cooling phase. These restoring forces must be permanently present to prevent loosening of the core cuits amongst one another and thus uncontrollable relative movement. Spring elements are not suitable due to fast fatigue as a result of high temperatures and radiation exposure. It is suggested to have the floor elements supported on rollers whose rolling planes are downwards inclined to a fixed point for support. The construction is described in detail by means of drawings. (GL) [de