scholarly journals Influence of Sulphate Attack on Properties of Modified Cement Composites

2021 ◽  
Vol 11 (18) ◽  
pp. 8509
Author(s):  
Grigoriy Yakovlev ◽  
Irina Polyanskikh ◽  
Anastasiya Gordina ◽  
Igor Pudov ◽  
Vít Černý ◽  
...  
Keyword(s):  
Composite Materials ◽  
Sodium Sulphate ◽  
Design Stage ◽  
Specific Electrical Conductivity ◽  
Cement Matrix ◽  
Cement Composites ◽  
Building Structures ◽  
Sample Structure ◽  
Physical And Chemical ◽  
Quantitative Indicators

Monitoring the condition of building structures based on composite materials in aggressive environments shows that the deterioration of basic properties occurs under the influence of various factors such as temperature and humidity changes,in addition to changes in the chemical composition of air environment. In addition, the composite materials during the operation must retain not only the mechanical properties laid down at the design stage, but also the electro-physical characteristics, regardless of the type of destructive effects. In the current study, the quantitative assessment of the result of the interaction of an aggressive sulphate-containing medium with composites modified with conductive and dielectric additives was carried out. The effect of sulphateattack on the specific electrical conductivity of cement composites was studied. The nature of the interaction was evaluated by changing the properties of the samples of the developed compositions under the influence of a single-normal solution of sodium sulphate. The analysis was carried out by means of potentiometric titration using the exchange interaction method by fixing the degree of absorption of sulphate ions and determining the concentration of calcium ions in the solution. The measurement of the solution potential allowed determination of the quantitative indicators of the rate of calcium hydroxide leaching from the sample structure,which is necessary to assess the intensity of the destruction process and determine the nature of the change in strength properties.Measurements of the electrical resistivity of samples under the constant influence of sulphate aggression were taken during 28 days of observation. A method for quantifying the effect of a sulphate medium on a cement matrix was proposed that enables the material durability to be predicted. The features of changes in the morphology of structural components after exposure to aggressive solution were determined by physical and chemical methods.

scholarly journals Properties of cement composites based on limestone depending on their granulometric composition

Vestnik MGSU ◽  
2020 ◽  
pp. 999-1006
Author(s):  
Svetlana V. Samchenko ◽  
Olga V. Alexandrova ◽  
Anton Yu. Gurkin
Keyword(s):  
Composite Materials ◽  
Portland Cement ◽  
Granulometric Composition ◽  
Coarse Grained ◽  
Cement Matrix ◽  
Cement Composites ◽  
Construction Costs ◽  
Initial Strength ◽  
Fine Grained ◽  
Additional Formation

Introduction. The use of limestone in cement compositions as an additional cementing agent solves both environmental and economic problems, namely, reduction of construction costs. In this regard, the study of the properties of the granulometric composition and volumetric content of cement composites, containing limestone, becomes increasingly important. The mission of this research is to optimize the properties of composite materials containing Portland cement and limestone by changing the granulometric composition of flour limestone. Materials and methods. Limestone, having three different Blaine milling fineness values of 250, 300 and 450 m2/kg, was used; its content reached 10, 15, 25 and 35 %. Cement and sand mortars were applied for testing purposes. The influence of the granulometric composition of limestone on the workability and compressive strength of composite cement was determined. Results. The effect of limestone on the limit shear stress becomes more pronounced when the amount of limestone increases to 25 and 35 %. This is most noticeable for limestone with a high content of fine fractions of 5–20 µm. The use of finely milled limestone increases the initial strength of the composite material. By adding 10 and 15 % of such limestone we can increase the strength by 16–20 %, and supplementary 25–35 % of limestone increases strength by 5–8 %. Strength enhancement is due to the reactivity of limestone and formation of calcium hydrocarbon aluminate 3CaO∙Al2O3∙СаСО3∙12H2O, which promotes formation of the crystal framework of the cement matrix. Additional formation of crystalline hydrates in the initial coagulation structure deteriorates the mortar workability, but increases its strength. Conclusions. The use of coarse-grained limestone significantly improves mortar workability, while the use of fine-grained limestone increases its content without reducing its strength. The granulometric composition of ground limestone shall be as close as possible to the granulometric composition of cement for the properties of composite materials containing Portland cement and limestone to be optimized.

scholarly journals Waste Tire Particles and Gamma Radiation as Modifiers of the Mechanical Properties of Concrete

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Eduardo Sadot Herrera-Sosa ◽  
Gonzalo Martínez-Barrera ◽  
Carlos Barrera-Díaz ◽  
Epifanio Cruz-Zaragoza
Keyword(s):  
Mechanical Properties ◽  
Gamma Radiation ◽  
Chemical Properties ◽  
Plain Concrete ◽  
Cement Matrix ◽  
Portland Cement Concrete ◽  
High Concentration ◽  
Good Tool ◽  
Waste Tire ◽  
Physical And Chemical

In polymer reinforced concrete, the Young’s modulus of both polymers and cement matrix is responsible for the detrimental properties of the concrete, including compressive and tensile strength, as well as stiffness. A novel methodology for solving such problems is based on use of ionizing radiation, which has proven to be a good tool for improvement on physical and chemical properties of several materials including polymers, ceramics, and composites. In this work, particles of 0.85 mm and 2.80 mm obtained from waste tire were submitted at 250 kGy of gamma radiation in order to modify their physicochemical properties and then used as reinforcement in Portland cement concrete for improving mechanical properties. The results show diminution on mechanical properties in both kinds of concrete without (or with) irradiated tire particles with respect to plain concrete. Nevertheless such diminutions (from 2 to 16%) are compensated with the use of high concentration of waste tire particles (30%), which ensures that the concrete will not significantly increase the cost.

scholarly journals Preparation and Mechanical Properties of Graphene Oxide: Cement Nanocomposites

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Fakhim Babak ◽  
Hassani Abolfazl ◽  
Rashidi Alimorad ◽  
Ghodousi Parviz
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Graphene Oxide ◽  
Cement Mortar ◽  
Cement Matrix ◽  
Cement Composites ◽  
Xrd Diffraction ◽  
Calcium Silicate Hydrates ◽  
The Matrix ◽  
Scanning Electron

We investigate the performance of graphene oxide (GO) in improving mechanical properties of cement composites. A polycarboxylate superplasticizer was used to improve the dispersion of GO flakes in the cement. The mechanical strength of graphene-cement nanocomposites containing 0.1–2 wt% GO and 0.5 wt% superplasticizer was measured and compared with that of cement prepared without GO. We found that the tensile strength of the cement mortar increased with GO content, reaching 1.5%, a 48% increase in tensile strength. Ultra high-resolution field emission scanning electron microscopy (FE-SEM) used to observe the fracture surface of samples containing 1.5 wt% GO indicated that the nano-GO flakes were well dispersed in the matrix, and no aggregates were observed. FE-SEM observation also revealed good bonding between the GO surfaces and the surrounding cement matrix. In addition, XRD diffraction data showed growth of the calcium silicate hydrates (C-S-H) gels in GO cement mortar compared with the normal cement mortar.

Study of Whiskers to be Used in Composite Materials

2021 ◽  
Vol 316 ◽  
pp. 51-55
Author(s):  
Tamara I. Shishelova ◽  
Vadim V. Fedchishin ◽  
Mikhail A. Khramovskih
Keyword(s):  
Mechanical Properties ◽  
Composite Materials ◽  
Chemical Properties ◽  
High Strength ◽  
Rapid Expansion ◽  
Physical And Chemical Properties ◽  
Reinforcement Fiber ◽  
Object Of Study ◽  
Physical And Chemical ◽  
And Chemical Properties

Rapid expansion of technologies poses higher requirements to structural materials and items made of them. Conventional materials are being replaced by composite materials (composites). Different additives enhancing the properties of initial materials are used as reinforcement fibers of composites. Utilization of micro-and nanosize particles for production of present-day materials is paid much attention to. Whiskers are among such materials. These crystals have high strength, high chemical and temperature resistance. But for rational utilization of whickers of different chemical composition in composite materials one should know their physical and chemical properties. Objectives of the paper: to study physical and chemical properties of whiskers in different compounds, their composition and structure; to prove experimentally the feasibility of utilizing whiskers as a reinforcement fiber of composite materials. Object of study: specimens of whiskers of silicon nitride (Si3N4), aluminum oxide (Al2O3), aluminum nitride (AlN), and mullite (Al6Si2O13). Methods of investigation: thermal study of specimens, study of mechanical properties and chemical strength, and IR-spectroscopy. Results of study: specimens of whiskers have been studied and their mechanical properties have been tabulated for comparison. Extensive thermal investigation was followed by deduction of regularities and identification of chemical properties of whiskers. IR-spectra of whiskers have been studied and conclusions on molecular composition and on presence of impurities in some whiskers have been made.

scholarly journals Application of the nanoindentation method in assessing of properties of cement composites modified with silica-magnetite nanostructures

2018 ◽  
Vol 163 ◽  
pp. 02002 ◽  
Author(s):  
Elzbieta Horszczaruk ◽  
Roman Jedrzejewski ◽  
Jolanta Baranowska ◽  
Ewa Mijowska
Keyword(s):  
Mechanical Properties ◽  
Magnetite Nanoparticles ◽  
Positive Influence ◽  
Cement Matrix ◽  
Core Shell ◽  
Indentation Modulus ◽  
Cement Composites ◽  
Interfacial Zone ◽  
Berkovich Indenter ◽  
The Core

The results of investigation of the cement composites modified with 5% of silica-magnetite nanostructures of the core-shell type are presented in the paper. The nanoindentation method employing three-sided pyramidal Berkovich indenter was used in the research. The mechanical properties and microstructure of the modified cement composites were evaluated on the basis of the values of hardness and indentation modulus measured inside the cement matrix and in the aggregate-paste interfacial zone. The results were compared with those obtained for the reference composites without nanostructures. The positive influence of the presence of silica-magnetite nanoparticles on the tested properties was found out.

scholarly journals DESIGN OF CEMENT COMPOSITES WITH INCREASED IMPERMEABILITY

Vestnik MGSU ◽  
2016 ◽  
pp. 72-81
Author(s):  
Roman Sergeevich Fedyuk
Keyword(s):  
Composite Materials ◽  
Cement Composite ◽  
Vapor Permeability ◽  
Cement Stone ◽  
Cement Composites ◽  
Hydrated Cement ◽  
Body Density ◽  
Scale Levels ◽  
Positive Effect ◽  
Improved Characteristics

The paper deals with the development of composite binders for producing concrete with improved characteristics of gas, water and vapor permeability. The authors investigate the processes of composite materials formation in order of decreasing scale levels from macro to nanostructures. The criteria for optimization of the volume of dispersed additives in concrete are offered. The authors theoretically studied the technological features of the formation of hydrated cement stone structure. A positive effect of nanodispersed additives on the structure and physico-mechanical properties of cement composite materials are predicted. Thanks to its improved features, such as good ratio of strength and body density, high density and lifetime, the modified concrete may be used when solving various practical tasks of the construction branch.

scholarly journals CONCEPTUAL DESIGN OF THE WING OR FUSELAGE STRUCTURE OF A MAINLINE AIRCRAFT MADE OF METAL-POLYMER COMPOSITE MATERIALS

2021 ◽  
pp. 74-82
Author(s):  
Valery Pechenyuk ◽  
◽  
Yuri Popov ◽  
Keyword(s):  
Composite Material ◽  
Composite Materials ◽  
Polymer Composite ◽  
Polymer Composite Material ◽  
Polymer Composite Materials ◽  
Design Stage ◽  
Aluminum Sheets ◽  
Preliminary Design Stage ◽  
Modified Formula ◽  
Metal Polymer

The analysis of existing aircraft structures made of metal-polymer composite materials is carried out, and a list of them with passport characteristics is compiled. The Fokker F-27 Friendship, Boeing-777 and Airbus A380, which use ARALL and GLARE materials, were selected as the aircraft under study. Formulas are determined and the distribution of normal force flows between metal and composite elements in the composition of MPCM based on aluminum sheets (aluminum-fiberglass – SIAL- 1-1, SIAL-3-1 and SIAL-1441 (9/8)) and titanium alloys (samples of titanium-carbon fiber from the patent-Example 1 and Example 3). To determine these parameters, the formulas used for a composite structure made of different materials are used. On the basis of the specification known MPCM the modified formula mixture rule for calculating the strength of new materials with a given set of orientation angles of PCM and the presence of layers of sheet metal, a comparison with standard mechanical characteristics and to show the efficiency of these formulas. Using these formulas, you can determine the strength characteristics for an arbitrary composition of the MPCM package. The features of the choice of design permissible stresses for the design of the airframe of a mainline aircraft made of metal-polymer composite material are highlighted. The concept of designing aircraft airframe elements using MPCM is considered. The results of this work will allow us to determine the rational components of the metal-polymer composite material and the structure of their distribution in the airframe design at the preliminary design stage.

scholarly journals Options for solving the problem of parts of the Shelter object located outside the New Safe Confinement

2020 ◽  
Vol 19 (4) ◽  
pp. 57-65
Author(s):  
O. V. Balan ◽  
◽  
S. Gh. Brylka ◽  
V. V. Derengovskyi ◽  
V. V. Yehorov ◽  
...  
Keyword(s):  
Cost Effective ◽  
Radiation Condition ◽  
Design Stage ◽  
Final Decision ◽  
Building Structures ◽  
Short Term ◽  
Design Studies ◽  
Financial Costs ◽  
Work Area ◽  
Goals And Objectives

The parts of the Shelter object structures remained outside the New Safe Confinement (protruding parts) are considered in the article. The analysis of the building structures condition of the turbine hall and the deaerator stack protruding parts on the east and west sides is carried out and the necessity of works on strengthening and/or dismantling of bearing structures is confirmed. Possible variants of reconstruction of the Shelter object protruding parts are stated and the technological sequence of works is provided. The analysis of the possibilities of performing works in the conditions of functioning of the New Safe Confinement — Shelter object system proved that such activity is rather difficult task, which can cause significant physical and financial costs. As there is no guarantee of trouble-free operation of the building structures of the protruding parts during the entire service life of the New Safe Confinement, it is necessary to make every effort to solve this problem in the short term. The results of the analysis allow to choose the most advantageous solution to the goals and objectives for the safest and most cost/effective dismantling and/or strengthening of structures of protruding parts, taking into account a number of different criteria. These criteria may be different in nature, which allowed to build a generalized efficiency indicator for individual criteria with certain weights that determine the importance of each of the criteria for decision making. Based on the results of the analysis, these options can be considered equivalent. The final decision on the choice of the optimal variant for the Shelter object protruding parts reconstruction can be made after detailing the technological decisions at the design stage of protruding parts reconstruction and before the design studies of the radiation condition in the work area. The obtained information can be used as input data during the design of the reconstruction of the deaerator stack and the turbine hall parts of the Shelter object, which protrude beyond the New Safe Confinement.

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