scholarly journals Study of Physical and Mechanical Properties of Centrifuged Concrete

2019 ◽  
Vol 18 (4) ◽  
pp. 319-329
Author(s):  
I. I. Palevoda ◽  
S. M. Zhamoidzik ◽  
D. S. Nekhan ◽  
D. S. Batan
Keyword(s):  
Mechanical Properties ◽  
Water Content ◽  
Cross Section ◽  
Outer Layer ◽  
Concrete Strength ◽  
Concrete Structures ◽  
Physical And Mechanical Properties ◽  
Concrete Mixture ◽  
Density Analysis

The paper presents a complex of laboratory and theoretical studies of physical and mechanical properties in centrifuged concrete while using samples of sectoral cross-section which are cut in layers from a finished product. A post made of concrete having B40 grade for compression strength and manufactured while using centrifugation with the help of РТЦ-5 machine. Assessment of heterogeneity across section thickness has been carried out by visual determination of composition changes in cross section, determination of strength, density of the obtained concrete samples, and water content over cross section of concrete mix. According to the results of a visual study on composition of a concrete structure it has been revealed that 1/8 part of the structure (from an inner surface) does not have a large aggregate. Later, as it moves to periphery, there is an increase in coarse aggregate and a decrease in size and number of cells between grains of gravel. An analysis of experimental data has shown that properties of the centrifuged concrete in samples being sawn in layers change significantly: density of concrete in samples of an inner layer is lower by 8 % than in samples of an outer layer, and compressive strength of concrete – by 34 %, water content of concrete mixture of samples of the inner layer has turned out to be by 43 % higher than in samples of the outer layer. Approximating curves showing regularities of changes in density, concrete strength, water content of concrete mixture over thickness have been constructed in the paper. Linear and exponential equations have been obtained that describe changes in physical and mechanical properties of centrifuged concrete over section depending on structure properties as a whole, which, taking into account the obtained correction factors k1 and k2, can be used with an acceptable level of confidence in practical calculations of centrifuged concrete structures. Relationship between strength of centrifuged concrete varying over cross section and action of a centrifugal force of inertia has been revealed in the paper. An equation has been obtained that relates the strength of centrifuged concrete to its density. Analysis of the research results makes it possible to assert that the main source of loading perception in centrifuged concrete structures is outer layers.

scholarly journals DETERMINATION OF CONCRETE PROPERTIES DURING THE ASSESSMENT OF THE CONDITION OF FLAT REINFORCED CONCRETE STRUCTURES

2021 ◽  
pp. 80-87
Author(s):  
V. KOLOKHOV ◽  
V. VOLKOVA ◽  
L. MOROZ ◽  
S. BOGDAN
Keyword(s):  
Mechanical Properties ◽  
Concrete Structure ◽  
Concrete Strength ◽  
Physical And Mechanical Properties ◽  
Concrete Surface ◽  
Core Samples ◽  
Reliable Assessment ◽  
Normalized Parameters ◽  
Non Destructive

 Formulation of the problem. Operation of buildings and structures is based on periodic assessment of the condition of structures. The procedure for determining the strength of concrete by non-destructive methods requires a certain preparation of the concrete surface of the structure and sampling in order to calibrate the devices. During sampling, the samples may be damaged, in addition the surface of the cylinders does not meet the requirements for normalized test conditions. Part of the cores during selection is being destroyed, which reduces the representativeness of the results of determining the physical and mechanical properties of concrete. The purpose of the article is to find out the possibilities to increase the reliability of determining the physical and mechanical properties of concrete. Results. In the conditions of a real object, core samples were taken to study the concrete strength of the damaged area. Samples that did not meet the normalized parameters were prepared for testing using a repair mixture Mapegrout Thixotropic. Testing of the recovered core samples showed that the repair mixture adhered well to the surface of the core. The nature of the destruction in the restored and normalized samples is similar. Conclusions. Studies have shown that: the application of the existing method of determining the strength of concrete for slab structures limits the possibility of using core samples taken from structures; the use of Mapegrout Thixotropic repair mixture allows to carry out tests according to the normative method of damaged concrete samples or samples rejected due to size mismatch; reliable assessment of the deformable properties of concrete cores in many cases is impossible; the existing methodology needs to be improved or replaced by an alternative one; quantitative assessment of the rheological properties of the concrete mixture used for the manufacture of concrete structure is possible on the basis of comparing the deformable and strength characteristics of concrete structure, which requires formalization of the procedure and standardization.

Basic set of experiments for determination of mechanical properties of sand

2014 ◽  
Vol 62 (1) ◽  
pp. 129-137
Author(s):  
A. Sawicki ◽  
J. Mierczyński
Keyword(s):  
Mechanical Properties ◽  
Soil Mechanics ◽  
Physical And Mechanical Properties ◽  
Local Strain ◽  
Initial State ◽  
Laboratory Equipment ◽  
Additional Information ◽  
Basic Set ◽  
Initial Anisotropy

Abstract A basic set of experiments for the determination of mechanical properties of sands is described. This includes the determination of basic physical and mechanical properties, as conventionally applied in soil mechanics, as well as some additional experiments, which provide further information on mechanical properties of granular soils. These additional experiments allow for determination of steady state and instability lines, stress-strain relations for isotropic loading and pure shearing, and simple cyclic shearing tests. Unconventional oedometric experiments are also presented. Necessary laboratory equipment is described, which includes a triaxial apparatus equipped with local strain gauges, an oedometer capable of measuring lateral stresses and a simple cyclic shearing apparatus. The above experiments provide additional information on soil’s properties, which is useful in studying the following phenomena: pre-failure deformations of sand including cyclic loading compaction, pore-pressure generation and liquefaction, both static and caused by cyclic loadings, the effect of sand initial anisotropy and various instabilities. An important feature of the experiments described is that they make it possible to determine the initial state of sand, defined as either contractive or dilative. Experimental results for the “Gdynia” model sand are shown.

scholarly journals DETERMINATION OF THE MECHANISM FOR OPENING QUARTZ PARTICLES WHEN GRINDING QUARTZ-CONTAINING PRODUCTS IN A CENTRIFUGAL MILL

2020 ◽  
Vol 12 (3) ◽  
pp. 454-460
Author(s):  
Yuri KLYKOV ◽  
◽  
Marina KHUDOYAN ◽  
Georgy KIBIZOV ◽  
◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Efficiency ◽  
Test Procedure ◽  
Physical And Mechanical Properties ◽  
High Energy ◽  
Specific Productivity ◽  
Crushed Material ◽  
Centrifugal Mill ◽  
Maximum Productivity

Introduction. Currently used grinding machines, among which drum mills are the most widely used, have a low efficiency, are bulky, are characterized by low specific productivity, significant consumption of steel for grinding bodies and lining, high noise level, and high energy consumption of the grinding process. The most promising devices of a new type that can effectively perform grinding operations at high technological rates are centrifugal mills. The centrifugal mill developed at SKGMI operates on the principle of self-grinding of pieces and particles of crushed mineral raw materials, when they collide and RUB in a mobile toroidal flow formed when the material moves between a rotating Cup-shaped rotor, a fixed body and the overlying layers of the crushed material. Grinding occurs due to the appearance of a gradient of particle velocities over the working body, due to their impact and, to a greater extent, abrasion. The tests of these mills for grinding various materials have shown high efficiency in operation, but until now, the issues of determining the physical and mechanical properties of the crushed material based on the establishment of the particle opening mechanism remain unresolved. The purpose of the tests. Determination of the physical and mechanical properties of the crushed material in a centrifugal mill based on the establishment of the particle opening mechanism. Test procedure. To solve this problem, a vertical centrifugal mill MC-600 with a rotor diameter of 600 mm was used. Tests of the centrifugal mill were carried out according to the following method. The speed of rotation of the rotor was 4.8 and 8.4 s-1, the height of the material column above the rotor was at the level of 250 and 350 mm; 6 radial ribs were installed in the rotor cavity of the mill. The time of each test was 4 hours. The tests were repeated 3–5 times for each mode of operation of the mill. Quartz was used as a reference material for determining the relative pulverizability coefficient. The research was carried out in the production conditions of the Izhevsk machinebuilding plant during the regeneration of spent molding quartz mixtures. Pieces of a liquid-glass mixture based on quartz sand with strength of 1.3 MPa and 4.25 MPa were used as the crushed material. The crushed material was dispersed according to the standard method for each hour of operation of the mill. Samples were taken in the size class -0.200 + 0.074 mm for their fractional analysis by size. Test result. 1. It was Found that the maximum productivity of a centrifugal mill when grinding pieces of material with a strength of 1.3 MPa was achieved with a loading weight of 90–100 kg, and with a strength of 4.25 MPa – 100–110 kg, which indicates the need to create an increased normal pressure of the layers of crushed material located above the mill rotor. It was found that the maximum productivity of a centrifugal mill when grinding pieces of material with a strength of 1.3 MPa and a rotor rotation frequency of 8.4 s-1 was 13.16 t/h, and when grinding pieces of material with a strength of 4.25 MPa – 10.0 t/h. 2. The Dependence of power consumption on the weight of the mill load and the rotor speed increases when the load weight is more than 100 kg. 3. The Highest fraction content of class -0.4 +0.16 mm is 72.14 %, and the content of class -0.074 mm is 3.9 %, i.e. there is no re-grinding of the source material. 4. The specific productivity of the centrifugal mill for the newly formed calculated size classes -0.074 mm and -0.200 mm was 1.28 t/h and 13.0 t/h, respectively. 5. Microscopic study of anshlifov showed that quartz grains in the crushed material mostly have a rounded shape, on average 90–95 % of the grains. In the initial material, about 90% of quartz joints with a binder, and in the crushed material, the number of joints does not exceed 3–5%. Thus, the degree of expansion of quartz reaches to 0.87. Conclusions. The paper presents the results of studies of a centrifugal mill in the conditions of the Izhevsk machinebuilding plant when grinding quartz-containing products. The physical and mechanical properties of the crushed material that significantly affect the efficiency of grinding are determined. The mechanism of the disclosure particles of quartz, which is primarily the mineral content of many ores and defined particle size obtained by grinding. At the same time, it was found that a large yield of thin classes significantly reduces the efficiency of further technology.

scholarly journals Regression analysis and statistical examination of Knoop Hardness on abrasion resistance in Lyca Beige Marbles

Filomat ◽  
2020 ◽  
Vol 34 (2) ◽  
pp. 609-614
Author(s):  
Burcu Aydin ◽  
Fusun Yalcin ◽  
Ozge Ozer ◽  
Gurhan Yalcin
Keyword(s):  
Mechanical Properties ◽  
Regression Analysis ◽  
Physical And Mechanical Properties ◽  
Production Method ◽  
Knoop Hardness ◽  
Decomposition Products ◽  
Marble Quarries ◽  
Selection Of

Marbles are secondary decomposition products formed by metamorphism of limestone. Effective classification of marble quarries in terms of quality enables the selection of a sustainable production method and safety application. This evaluation is based on physico-mechanical properties of the samples. Obtained results of physico-mechanical properties of the marbles were statistically analyzed using Stata 14 and SPSS 21 software. The marbles indicated mostly normal physical and mechanical properties. A strong inverse relationship exists between Abrasion Value and Knoop Hardness Determination that indicates a significant nonlinear relationship. Samples were distinguished into 3 groups of close similarity and related properties. The estimated value of the parameters is in the 95 % confidence interval. The equation obtained by regression analysis was used for the determination of resistance to abrasion.

scholarly journals Determination of Physical and Mechanical Properties of Three-layer Boards of Teak (Tectona grandis), Seike (Cedrelinga catenaeformis) and Mascarey (Hieronima alchorneoides), Company PISMADE S.A., Riobamba Canton, Chimborazo Province

2021 ◽  
Author(s):  
J. Criollo Barahona ◽  
D. Román Robalino ◽  
E. Cabezas ◽  
E. Salazar Castañeda
Keyword(s):  
Mechanical Properties ◽  
Compression Test ◽  
Physical And Mechanical Properties ◽  
Tectona Grandis ◽  
Mechanical Tests ◽  
Hyeronima Alchorneoides ◽  
Commercial Use ◽  
Palabras Clave ◽  
Thickness Measurements

The present investigation aims to determine the physical and mechanical properties in three-layer boards of Teak (Tectona grandis), Seike (Cedrelinga catenaeformis) and Mascarey (Hieronima alchorneoides), from the PISMADE S.A. Company, Canton Riobamba, province of Chimborazo. The three specimens used for each of the species in each of the tests performed were worked on using the ASTM D143-94 standard for the tests of parallel compression, perpendicular compression and flexion, and the DIN-52182 standard, with the main variation in thickness measurements caused by the commercial use established by the company. Mechanical tests showed that Seike had the best results, being superior in two tests: perpendicular compression and flexion. Teak tests gave us results that were superior in the perpendicular compression test. Mascarey, unlike the two species mentioned above, had complications during the trials due to problems with the glue between layers. Keywords: physical and mechanical properties of wood, three-layer boards. Resumen La presente investigación pretende: Determinar las propiedades físicas y mecánicas en tableros tricapa de Teca, Seike (Cedrelinga catenaeformis) y Mascarey (Hyeronima alchorneoides), Empresa PISMADE S.A., cantón Riobamba, provincia de Chimborazo; para lo cual se utilizaron 3 probetas por cada una de las especies en cada uno de los ensayos realizados, las mismas fueron trabajadas con base a la Norma ASTM D143-94 para las pruebas de compresión paralela, compresión perpendicular y flexión y la Norma DIN-52182, teniendo como principal variación en las medidas de espesor debido al uso comercial establecido por la empresa. Las pruebas mecánicas mostraron que Seike tuvo los mejores resultados al ser superior en dos ensayos: Compresión perpendicular y flexión. Los ensayos con Teca nos dieron como resultados que es superior en el ensayo de compresión perpendicular. Mascarey a diferencia de las dos especies mencionadas anteriormente tuvo complicaciones con los ensayos debido a problemas con el pegamento entre capas. Palabras clave: propiedades físicas y mecánicas de la madera, tableros tricapa.

scholarly journals DETERMINATION OF MECHANICAL PROPERTIES OF REPAIR MORTARS USING IN SITU METHODS UNDER DIFFERENT CURINGS

2020 ◽  
Vol 2 ◽  
pp. 3-18
Author(s):  
Ali Saberi Varzaneh ◽  
Mahmoud Naderi
Keyword(s):  
Mechanical Properties ◽  
Concrete Structures ◽  
High Impact ◽  
Physical Factors ◽  
High Confidence ◽  
In Situ Methods ◽  
Repair Mortars ◽  
Friction Transfer

Considering the differences between environmental conditions of concrete structures and laboratory conditions, it is important to determine the parameters of the materials at the site of the structure. One of these materials is cement-based repair mortars due to the damage of concrete structures that may arise due to chemical or physical factors, these structures are required to be repaired. For this reason, in this paper, to determine the strength of repair mortars of different ages and under different Curing, Situ methods "Friction-Transfer" and "Pull-off" were used and the relationships between the Flexural Compressive, Tensile and readings obtained from the above methods on cementations mortars are presented. Experiments were performed on mortars at ages 3, 7, 28, 42 and 90 days under the conditions of "waterlogging", "Curing Agent" and "releasing in the outdoor". The results show the high impact of the process on the Flexural Compressive, Tensile of the repair mortars and the results of the "Friction-Transfer" and "Pull-off" methods. Also, a high correlation coefficient was obtained between the mechanical properties of the mortars and the results of the above tests; it is possible to measure the mechanical properties of repair mortars in situ with high confidence and in situ

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