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.

Variation of Concrete Strength with the Insertion of Carbon Nanotubes

2013 ◽  
Vol 818 ◽  
pp. 124-131
Author(s):  
Assed N. Haddad ◽  
Jorge F. de Morais ◽  
Ana Catarina J. Evangelista
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotubes ◽  
Construction Industry ◽  
Concrete Strength ◽  
Cement Composites ◽  
Deformation Properties ◽  
The Face ◽  
Non Destructive ◽  
Technological Community

Nanomaterials could change the face of modern construction because they are more resistant, more durable and have notable features. Concrete is a material widely used in construction industry worldwide. Carbon nanotube has been considered a new and outstanding material in nanoscience field with great potential application in the construction industry. The study presented in this paper, aims at assessing how carbon nanotubes can affect cement composites and so the concrete, in terms of microstructure and physical-mechanical properties. Three different ratios of carbon nanotubes have been searched: 0.20%, 0.40% and 0.60%. To evaluate the mechanical properties of the samples, destructive and non-destructive tests were carried out to obtain compressive strength, tensile strength by diametrical compression, dynamic modulus of elasticity as well as the determination of their deformation properties. This work also aims to motivate entrepreneurs and professionals in the sector of civil engineering on the advantages of the application of nanotechnology in construction, as well as providing information to the scientific and technological community in general.

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.

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.

Control of properties and structure of steel vessels by cooling in various media at the outlet of rolling and pressing lines

2021 ◽  
pp. 34-38
Author(s):  
R. L. Shatalov ◽  
V. A. Medvedev
Keyword(s):  
Mechanical Properties ◽  
Physical And Mechanical Properties ◽  
Metal Structure ◽  
Machine Building ◽  
Regression Equations ◽  
Wide Range ◽  
Industrial Mineral ◽  
Cooling Media ◽  
Technological Limitations ◽  
Non Destructive

When controlling the mechanical properties and structure of vessels made of carbon structural steels manufactured by hot deformation on rolling and pressing lines (PPL) of machine-building enterprises of Russia, such cooling media as water, I20 industrial mineral oil, air are used. The applied cooling media are able to provide the workpieces with a given structure with a wide range of mechanical properties. However, the cooling media have a number of technological limitations and conditions of the use, non-compliance with which leads to reject. When cooled in oil, the probability of ignition is high; when cooled in water, hardening cracks may form, and air is not always able to provide the required rate and uniformity of heat transfer to the environment. The efficiency of control of physical and mechanical properties and structure of deformed vessels made of 50 steel by cooling in TERMAT polymer aqueous solutions in different concentrations on PPL of the plant of JSC NPO Pribor was studied. The effect of varying the concentration from 2 to 9% of TERMAT polymer on the formation of metal structure, as well as physical and mechanical properties of hot-deformed vessels was studied. The results of testing the strength and plastic characteristics of vessels by destructive and non-destructive control methods are presented. According to the results of physical and mechanical properties, regression equations were obtained with at least 95% reliability of R2, which establish the relationship between the controlled plastic and strength parameters of the vessel metal`s properties. The conducted researches allowed to compare the indicators of the main physical and mechanical properties of steel vessels at the PPL outlet and to propose methods of inhomogeneity control that reduce time and material costs by 5–10% during the tests.

A Review of Ultrasonic Application on Non-destructive Testing Method for Concrete Structure

2014 ◽  
Vol 70 (3) ◽  
Author(s):  
Nasarudin Ahmad ◽  
Ruzairi Abdul Rahim ◽  
Herlina Abdul Rahim ◽  
Mohd Hafiz Fazlul Rahiman
Keyword(s):  
Concrete Structure ◽  
High Speed ◽  
Structural Integrity ◽  
Surface Hardness ◽  
Concrete Surface ◽  
Non Destructive Testing ◽  
Destructive Testing ◽  
Surface Absorption ◽  
Processing Techniques ◽  
Non Destructive

Although the technique of using ultrasound has reached maturity by given the extent of the development of sensors, but the use of the various areas still can be explore. Many types of ultrasonic sensors are still at conventional in use especially for measurement equipment in the industry. With the advancement of signal processing techniques, high-speed computing, and the latest techniques in image formation based Non-destructive testing (NDT) methods, the usage of ultrasound in concrete NDT testing is very extensive because the technique is very simple and should not damage the concrete structure to be investigated. Many of the parameters need to be tested using ultrasound techniques to concrete can be realized. Starting with the initial process for of concrete mixing until the concrete matured to the age of century old. Various tests are available to test a variety of non-destructive of concrete completely, in which there is no damage to the concrete, through those where the concrete surface is damaged a bit, to partially destructive testing, such as core tests and insertion and pull-off test, which surface to be repaired after the test. Testing parameter features that can be evaluated using non-destructive testing and destructive testing of some rather large and include basic parameters such as density, elastic modulus and strength and surface hardness and surface absorption, and reinforcement location, size and distance from the surface. In some cases it is also possible to check the quality of the workmanship and structural integrity of the ability to detect voids, cracks and delamination. A review of NDT using ultrasound on concrete are presented in this paper to highlight the important aspect to consider when one to consider the application and development of ultrasound testing on concrete by considering ultrasound signal capturing, processing and presenting.

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