Heavy Concrete Research Articles

Compatibility of precast heavy and monolithic lightweight concretes deforming

Compatibility of precast heavy and monolithic lightweight concretes deforming

Raw Material Security of Construction in the Far East

The studies of the volcanic rocks of the far Eastern deposits shows the need and the prospect of their wide use as aggregates for the heavy concretes, lightweight concretes for various purposes, insulating materials, mixed binder.

Spectroscopic and thermal analysis of lead-free multipurpose radiation shielding glasses

The genetic algorithm was used to identify glasses, of the composition 50Bi2O3-(50-x) B2O3-xBaO with 25≥x≥5 wt%, that have a similar half-value layer (HVL) and neutron removal cross-section. The structure of these glasses was further explored using a combination of spectroscopic and thermal analysis in order to ascertain whether they possess advantageous physical properties comparable to traditional materials used in nuclear reactor design. Differential scanning calorimetry (DSC) analysis was used to examine the thermal profile of the glass system and to identify glass transition temperature Tg and softening temperature Ts. Glass of the composition 50Bi2O3–30B2O3–20BaO had exhibited the highest thermal stability. Analysis of the Raman spectra of the samples confirmed the presence of BiO6 octahedrons and B-O-B bonds in poly borate chains. A deconvolution of the IR spectra was carried out to determine the relative proportions of BO3 triangles to BO4 tetrahedral units in the glass network that would affect the density and bulk modulus. Optical absorption spectrum of the samples exhibited absorption peaks in the blue region along with a broad band of absorption at longer red wavelengths associated with excitation of bismuth ions. When compared to traditional heavy concretes used in radiation shielding, the bismuth-barium borate glasses exhibited superior performance over conventional barite concrete as a gamma-radiation shield and was comparable to limonite concrete as a neutron radiation shield. The bulk modulus of the glass series was also found to be comparable to that of regular concrete at approximately to 30 GPa.

Identification of principles for calculating composition of heavy magnesia concrete

The article suggests a method for obtaining heavy magnesium concrete on alternative materials, which are magnesium wastes of the mining and refractory industries. The advantages of using a magnesium oxychloride cement as a binder component of a concrete mixture are described. The suitability of the existing methodology for calculating the composition of heavy magnesium concrete has been analyzed and the need for its deep processing has been established. It is established that on the basis of magnesium oxychloride cement and aggregates from dolomite it is possible to obtain heavy concrete in terms of density and strength corresponding to the requirements of the current technical regulations. The need to correct a known method for calculating the composition of heavy concrete, namely the introduction of special correction factors, taking into account the specific features of the materials used, was identified. Based on the calculated formulation, a concrete mixture was obtained and its characteristics were studied.

Microsilica as component of organic-mineral modifier for fine-aggregate concrete

Currently, modern heavy concrete including fine-aggregate ones are systems containing basic and additional components. Their production is not complete without the use of various mineral and organic additives. Such widespread additives include microsilica and various types of polymers. The effective use of additives, based on microsilica with polymers, allows creating heavy concretes with high performance properties. This topic is of a high relevance, so the research works were conducted to study the properties of fine-aggregate concrete, containing microsilica as an active mineral additive in the organic-mineral modifier composition in the Institute of new materials and technologies of Ural Federal University. This paper is devoted to the selection of composition of the organic-mineral modifier, based on the microsilica of OJSC ‘Chelyabinsk Electrometallurgical Works’.

The large helical device vertical neutron camera operating in the MHz counting rate range.

In the currently performed neutral beam (NB) -heated deuterium plasma experiments, neutrons are mainly produced by a beam-plasma reaction. Therefore, time-resolved measurement of the neutron emission profile can enhance the understanding of the classical and/or anomalous transport of beam ions. To measure radial neutron emission profiles as a function of time, the vertical neutron camera (VNC) capable of operation with a counting rate in the MHz range was newly installed on the Large Helical Device (LHD). This is the world's first neutron camera for stellarator/heliotron devices. The VNC consists of a multichannel collimator, eleven fast-neutron detectors, and the digital-signal-processing-based data acquisition system (DAQ). The multichannel collimator having little cross talk was made from hematite-doped heavy concrete, which has a high shielding performance against both neutrons and gamma-rays. A stilbene crystal coupled with a photomultiplier having high-gain-stability in the high-count rate regime was utilized as a fast-neutron scintillation detector because it has a high neutron-gamma discrimination capability at high count rates. The DAQ system equipped with a field programmable logic controller was developed to obtain the waveform acquired with a 1 GHz sampling rate and the shaping parameter of each pulse simultaneously at up to 106 cps (counts per second). Neutron emission profiles were successfully obtained in the first deuterium campaign of LHD in 2017. The neutron emission profile was measured in tangentially co-injected NB-heated plasma with different magnetic axes (R ax). The neutron counts became larger in the inward-shifted configuration, which was consistent with the total neutron rate measured by the neutron flux monitor. The radial peak position of the line-integrated neutron profile which changed according to R ax showed that the VNC worked successfully as designed. The VNC demonstrated the expected performance conducive to extending energetic-particle physics studies in LHD.

Investigation of the Influence of the Initial Composition of Heavy Concrete Designed for the Manufacture of Ring-Section Products on its Properties

The authors conducted the analysis of scientific and technical references relating to the issue of increasing maintenance reliability of pre-stressed reinforced concrete by means of taking into account concrete non-homogeneity in the calculations of strength, deformability and crack resistance of the reinforced concrete products with annular section. The authors stated the opportunity to increase the quality of concrete intended for centrifugation by means of regulating the properties of used materials. It was identified that applying disperse-reinforced fibers resulted in increase in bending tensile strength, decrease in shrinkage, increase in crack resistance and material resistance towards alternate freezing and thawing, drying and humidification cycles. Upon the results of conducted research and comparison of the properties of various fibers, the authors obtained regularities and application rules on fiber use and gave recommendations in terms of applying one of another fiber type. On the basis of the analysis of obtained results the authors made the conclusion that the highest effect in all tests was observed at the application of basalt fibers as they provide for a higher dispersion of cement rock reinforcement while the basalt fiber itself has a higher strength comparing with any other polymer fiber. Further, the authors conducted the research of mechanical properties characteristic for test beams made of heavy concrete to manufacture the annular section products by means of centrifugation. The obtained dependences allow making a conclusion that the percentage ratio of applied crushed stone fractions Fr 5-10 / Fr 5-20 = 50 / 50 under otherwise equal conditions has the highest influence on the heavy concrete ground strength.

Theoretical and Practical Aspects of the Formation of the Variational Structure of Centrifuged Products from Heavy Concrete

Viability of further research of variatropy is justified, as well as its extended use with the purpose of increasing quality of ferroconcrete building constructions. Raw components and equipment used for manufacturing of centrifuged products and variatropic objects are described. Laboratory centrifuge equipped with a direct current engine and thyristor units has been developed and used. Method of applying pressure to a unit mass during centrifuging has been studied. It has been identified that in order for mix particles rising to their most superior position to stick to the mold walls, it is necessary that gravitational force of mg particle and centrifugal force are equal. Effect of hydrodynamic pressure on particles constituting concrete mix has been studied using several formulas and provisions. It has been revealed that centrifugal molding may be used to seal low-viscosity plastic mixes; however, its use causes disintegration of concrete mix. In order to slow down this process, it is necessary to increase viscosity of the entire system and restrict the upper limit of aggregate fineness.

Investigations of Neutron Radiation Shielding Properties for a New Composite Material Based on Heavy Concrete and Basalt Fiber

The paper presents a new composite material for radiation shielding properties. This material is based on super-heavy concrete reinforced with basalt fiber, which could be used in biological protection systems for neutron radiation sources. The simulation of the neutron transport in the presented material was performed using the Monte Carlo Serpent code. Two types of heavy concretes were considered in the present paper: 1) with ordinary rubble coarse aggregate and 2) with barite coarse aggregate. For each type of concrete, the basalt fiber with dosage from 1 kg/m3 to 50 kg/m3 was added. The current transmission rates were obtained as a result of the neutron-physical modelling for neutron transport from source to detector through the proposed concrete samples with different thicknesses. The obtained modelling results were analyzed from the viewpoint of effectiveness of the radiation shielding properties. Also, elastic and capture microscopic cross-sections were considered for some isotopes and as a result, some aspects of the radiation shielding properties were clarified. The concrete with ordinary rubble coarse aggregate has better radiation shielding properties in case of low concrete thicknesses due to better neutron scattering on light nucleuses. In contrast to this, the concrete with barite coarse aggregate has better radiation shielding properties in case of high concrete thicknesses due to better neutron absorption. It is shown that the addition of basalt fiber to concrete not only improves its mechanical properties and reduces the number and size of microcracks, but also increases the ability to protect against neutron flux. The proposed composite material could be recommended for use with the following neutron sources: (D, T) neutron generators, plasma focus devices, fusion reactors and fast reactors. This research was carried out with the financial support of the IAEA, within the terms and conditions of the Research Contract 20638 in the framework of the Coordinated Research Project (CRP) “Accelerator Driven Systems (ADS) Applications and use of Low-Enriched Uranium in ADS (T33002)” within the project ‘The Two-Zone Subcritical Systems with Fast and Thermal Neutron Spectra for Transmutation of Minor Actinides and Long-Lived Fission Products’.

Diagrams of Deformation of Cement Composites Reinforced with Steel Wire Fiber

Modern construction practice acquires such a tendency, at which it is required to use materials with increased physical, mechanical and operational characteristics, and at the same time, do not require significant material, labor and energy costs for their production. One of the most promising building materials that meet the requirements is fiber-reinforced concrete. However, the increase in the volume of its use is limited by the insufficient degree of study of its properties and characteristics. This problem is aggravated by the constantly expanding range of reinforcing fibers, which can give composites produced on their basis, completely different properties and characteristics.
 One of the most important characteristics of fiber-reinforced concrete is crack resistance. The most informative method of research of this characteristic is the construction and analysis of deformation and fracture diagrams of samples obtained during bending tensile strength tests. At the initial stage of the described study, several series of fiber-reinforced concrete samples were tested. During the tests, a standard method for assessing the fracture toughness of heavy and fine-grained concretes, governed by the requirements of GOST 29167, was used. A device specially designed for testing fiber-reinforced concrete was used.
 As a result of the tests, a general view of the deformation diagrams of fiber-reinforced concrete samples was established, strength and energy characteristics of crack resistance, as well as the modulus of elasticity were found, and the labor intensity of the tests was high.
 In this paper we describe a possible way of obtaining fracture patterns for fiber-reinforced concrete by calculation. The resulting diagrams of deformation of fiber-reinforced concrete samples are built on several key points, the determination of which coordinates is made by calculation.
 The paper compares the experimental and calculated fracture toughness characteristics of fiber-reinforced concrete manufactured using steel wire fiber. Comparison of the data presented indicates a satisfactory agreement between the calculated and experimental data, which proves the validity of the proposed method for obtaining fiber-reinforced concrete deformation diagrams.

Experimental and numerical modeling of creep in different types of concrete

Creep in concrete, play a critical role in estimating losses in prestressed concrete structures, such as bridge girders, nuclear containment vessels, etc. The present study aims at investigating the creep under various environmental conditions in different types of concrete made with different ingredients using an experimental and numerical approach. Seven different concrete mixes have been made for this purpose and among the seven mixes, three mixes are self compacted concrete mixes (35 MPa, 55 MPa and 70 MPa), a high volume fly ash concrete mix (45 MPa), two mixes of normally vibrated ordinary Portland cement (OPC) concrete mixes (35 MPa and 45 MPa) and a heavy density concrete (25 MPa). Studies have been carried out at temperature of 25 °C and two relative humidity (RH) conditions (RH of 60% and 70%). An analytical model has been developed to simulate the drying phenomena in concrete based on a poromechanics approach. The hydration effects in blended cements (containing mineral admixture) is considered while developing the model. The proposed model is capable of predicting the degree of hydration, temperature and relative humidity (RH) over the continuum that required for estimating the creep strain. Micro prestress solidification (MPS) is used to estimate the creep strain. It is found that the proposed model is able to predict the drying phenomena and creep strain in various concretes, and which is in good agreement with the corresponding experimental results. It is found that heavy density concrete shows a higher creep strain than the other concretes. This may be due to the lower porosity of hematite aggregate. Further adding fly ash as a mineral admixture to concrete mix reduces the creep. Creep in a reinforced concrete (RCC) beam tested under sustained loading and reported in the literature is simulated using the present model and it is seen that the model predictions are in good agreement with the test data.

Optimization of heavy weight concrete composition and process of prefabrication for prefabricated shielding cladding tiles

The aim of experimental research was to verify the possibility of the prefabrication of the thin shielding cladding tiles from heavy weight concrete with fine. The minimal required density of the concrete was 3800 kg/m3 and the maximal particle size was 2 mm. Because of the though over technology of the complicated locks in the touch of tiles was necessary to achieve consistency around 210 mm flow with the Chryso cone test (modified slum flow test). To obtain this consistency without danger of the heavy weight aggregate segregation the superplasticizer was used. In first step was determined optimal amount of mixing water, in the second step we tested different frequency of vibration to achieve maximal consolidation and as a last step to define composition of mixture we tested 3 types of accelerators of concrete hardening to shorten time of hardening and to facilitate more effective production. As the optimal frequency of vibration for compacting process was determined 75 Hz. The best accelerator of concrete hardening for optimalized mixture was MasterSert XS100 from BASF producer.

Experimental Testing Results of Reinforced Concrete Beams Under Biaxial Bending

The experimental tests data of reinforced concrete beams of a rectangular profile made of heavy concrete on pure biaxial bending are presented. The inclination angle of the external load plane to the vertical axis of inertia of the section varied in the range from 0º to 20º. The tests were conducted to study the work of the biaxial bended elements under load and to verify the developed method for strength analysis of such elements. It has been established that the order of changing the neutral axis position in the section of the biaxial bending beams in the loading process depends primarily on the relative disposition of the external load plane and the resultant in the tensioned reinforcement. It has been confirmed that the ultimate compressed fibrous strains of concrete depend not on the shape of the section, but on the shape of the concrete compressed zone. The results of the tests have good correspondence with theoretical calculations, which proves the expediency of using the developed engineering method for the strength analysis.

INFLUENCE OF TECHNOLOGICAL NON-METALLIC PRODUCTION WASTES ON HEAVY WEIGHT CONCRETE PROPERTIES

Introduction . The following article deals with recycling of non-metallic industrial wastes for the production of heavy weight concretes. Materials and methods . The research uses a set of standard methods. Results. The physical, chemical characteristics and screenings gradation of the quarries Sverdlovsk and Chelyabinsk regions are explored. The compositions of effective heavy weight concretes with strength quality В22, 5-В40 based on stone screening dust and additives MC-Power Flow and Centrament Air 202 have been developed. The structural properties and construction characteristics of concrete mixtures and heavy weight concretes with stone screening dust are studied. The research demonstrates that the addition of MC-Power Flow additive to the concrete mixture in an amount of 0.4 to 0.8 % (by weight of cement) allows to reduce the hardness of the mixture from 26 to 5 seconds and promotes the creation of a tight contact zone at the surface of the aggregate. Moreover, the influence of the complex additive on the pore parameters of heavy weight concrete and on the frost resistance of samples is determined with the use of screening from rocks as a fine aggregate. Samples of heavy concrete frost resistance grade F300 are obtained. Discussion and conclusion . Cost-effectiveness analysis of the screenings use in the composition of heavy weight concrete and the industrial approbation at the precast concrete factory of the Tyumen region are carried out.

INFLUENCE OF SLAGS OF BOILERS WITH CIRCULATING FLUIDIZED BED ON FROST RESISTANCE OF CONCRETE

The results of the study of the influence of slags of boilers with a circulating fluidized bed on the frost resistance of heavy concrete are presented. In the studies was used fallowing materials: Portland cement PC I-500N, sand with a grain size unit Mkr=1,05, crushed granite fraction 5-10 mm, ashes of boilers with circulating fluidized bed, hyperplasticizer "Fluid Premia-196". The research is conducted using mathematical planning of the experiment.It is proved that with the replacement of sand with ashes, frost resistance is somewhat reduced, but the hyperplasticizer contributes to the reduction of frost resistance by reducing the W/C ratio, resulting in the formation of super-fine pore structure of concrete. Fine pores in the structure of concrete compensate for stress from the process of ice formation at low ambient temperatures.The optimal flow of cement has been established in terms of frost resistance, both by full and partial replacement of sand with ash. It was also determined that the optimum should be considered the consumption of a hyperplasticizer in the amount of 1.2-1.4% of the mass of cement.The introduction of ashes in a concrete mixture leads to a decrease in the frost resistance of concrete. This phenomenon is explained by the fact that the slags have water consumption in three times higher than the amount of sand they replace, therefore they contribute to an increase in the W/C ratio. With the increase in W/C increases both the total volume of open pores, and their average size. At the same time, permeability and water absorption increase and in such concrete less reserve pores are formed. In order to increase the frost resistance of concrete, it is customary to restrict W/C depending on the conditions of concrete service. Reducing W/C is possible, as at the expense of reducing water consumption due to the application of plasticizers additives, and by increasing the cost of cement.

Assessing the physical, mechanical properties, and γ-ray attenuation of heavy density concrete for radiation shielding purposes

The main purpose of this research is to improve the shielding of gamma rays by developing special concrete with high physico-mechanical properties using local aggregates. Various concrete mixtures are designed using heavy fine aggregate as a substitute for normal fine aggregate at rates of 20, 40, 60, 80, and 100%, by weight. Other concrete mixtures have been designed by replacing coarse aggregate with 50 and 60% of heavy fine aggregate. The properties such as density, compressive strength, and tensile strength of hardened mixtures were studied. Gamma ray attenuation has been studied on concrete mixtures after exposure to utilized radiation source comprised 137Cs radioactive element with photon energy of 0.662 MeV. From the results, we concluded that the density and compressive strength in addition to the linear attenuation coefficient of hardened mixtures increased with the ratio of replacing normal aggregate with heavy aggregate up to 60%. With an increase of the ratio more than 60%, compressive strength and tensile strength were reduced with the continued increase in density. On the other hand, density and the linear attenuation coefficient increased with the replacement of coarse aggregate by 50 and 60% of the heavy fine aggregate; while both compressive strength and tensile strength decreased.

Fire resistance of concrete walls with light aggregate

Purpose The purpose of this paper is to present the design methods for fire-exposed concrete columns and walls. In addition, it presents analyses and tests showing that the methods are applicable for designing columns and walls of lightweight aggregate concrete based on expanded clay aggregate as well as heavy normal weight concrete and that the methods fit smoothly with cold design, when the fire exposure varies towards no fire. Design/methodology/approach During the 1990s, some of these design methods were included in the Eurocode as “the zone method”. They are still a part of the code. The rest of the methods, which were not included, served in practice, teaching and research. The present paper derives calculation methods proving their connection with common design for load cases without fire exposure. Furthermore, the paper presents full-scale tests proving the validation of the design methods for structural members of light aggregate concrete in addition to the full-scale tests of heavy concrete members. Findings The design methods give correct estimates of the load-bearing capacity of eccentric loaded concrete columns. An extended version of the methods estimates load-bearing capacity for walls with fire exposure on one side with sufficient accuracy for the purpose of design. Originality/value The author developed the main parts of the design methods in the 1980s and 1990s and others have from time to time referred to some parts of them mainly the minor parts published in the Eurocodes. However, owing to work overload, the author has not published the derivation and verification of them before. This paper provides in particular a verification against full-scale tests of light-aggregate concrete walls not published before.

DURABILITY OF HEAVY CONCRETE USING BOILER SLAGS WITH CIRCULATING FLUIDIZED BED

The results of studying the influence of boiler ash slags with a circulating fluidized bed on the freeze-thaw resistance of heavy concretes are presented. The following materials were used in the studies: Portland cement PPC 500 N, sand with the fineness modulus Mf =1.05, crushed granite fraction 5-10 mm, boiler ashes with circulating fluidized bed, hyperplasticizer «Fluid Premia-196». The study was performed using mathematical planning of the experiment. It is proved that with the replacement of sand with ashes, the freeze-thaw resistance is somewhat reduced, but the hyperplasticizer compensates the reduction of freeze-thaw resistance by reducing the W/C ratio, resulting in the formation of super-fine pore structure of concrete. Fine pores in the concrete structure compensate the ice formation stress at low ambient temperatures. The optimal cement consumption has been established in terms of freeze-thaw resistance, both at full and partial replacement of sand with ash. It was also determined that the optimum should be considered the consumption of a hyperplasticizer in the amount of 1.2-1.4% of the cement mass.

Investigation of radiation absorption coefficients of lead-zinc mine waste rock mixed heavy concrete at 662–1460 keV energy range

The objective of this study is to observe the radiation shielding efficiency of concrete produced by using the lead wastes that are stored in lead-zinc mines processing of which is not financially viable in the mines they are extracted from that have negative effects on the environment. Within this scope, concretes were produced to be used as radiation shield concretes. The samples were prepared by altering the amounts of heavy aggregates such as lead–zinc mine waste, Magnetite, Limonite, and Barite at 25%, 50%, and 75% ratios, and concrete samples were prepared in C16/20, C25/30, and C35/45 concrete strength grades to determine the effects of these grades on radiation absorption properties. In order to determine the radiation absorption coefficients, absorption coefficients at 662 keV, 1173 keV, 1332 keV, and 1460 keV energy levels from Cs-137, Co-60 and K-40 sources were determined by concrete slabs with dimensions of 20 × 20 × 5 cm.

Shielding design and analyses of the cold neutron guide hall for the KIPT neutron source facility

Abstract Argonne National Laboratory of the United States and Kharkov Institute of Physics and Technology (KIPT) of Ukraine have cooperated on the development, design, and construction of a neutron source facility. The facility was constructed at Kharkov, Ukraine, and its commissioning process is underway. The facility will be used for researches, producing medical isotopes, and training young nuclear specialists. The neutron source facility is designed with a provision to include a cryogenically cooled moderator system—a cold neutron source (CNS). This CNS provides low-energy neutrons, which will be used in the scattering experiment and material structures analysis. Cold neutron guides, coated with reflective material for the low-energy neutrons, will be used to transport the cold neutrons to the experimental site. The cold neutron guides would keep the cold neutrons within certain energy and angular space concentrated inside, while most of the gamma rays and high-energy neutrons are not affected by the cold neutron guides. For the KIPT design, the cold neutron guides need to extend several meters outside the main shield of the facility, and curved guides will also be used to remove the gamma and high-energy neutron. The neutron guides should be installed inside a shield structure to ensure an acceptable biological dose in the facility hall. Heavy concrete is the selected shielding material because of its acceptable performance and cost. Shield design analysis was carried out for the CNS guide hall. MCNPX was used as the major computation tool for the design analysis, with neutron and gamma dose calculated separately. Weight windows variance reduction technique was also used in the shield design. The goal of the shield design is to keep the total radiation dose below the 5.0 μSv/hr guideline outside the shield boundary. After a series of iterative MCNPX calculations, the shield configuration and parameters of CNS guide hall were determined and presented in this article.