scholarly journals Pecularities of Strength Assessment of Cast-in-Situ Structures in Terms of Siberia

2020 ◽  
Vol 839 ◽  
pp. 43-50
Author(s):  
Irina G. Endzhievskaya ◽  
Iliya G. Kalugin ◽  
Sergey O. Deygraf ◽  
Maksim A. Galkin
Keyword(s):  
Concrete Strength ◽  
Experimental Studies ◽  
Physical And Mechanical Properties ◽  
Design Strength ◽  
Plant Laboratory ◽  
Strength Assessment ◽  
Integrated Research ◽  
Strength Based ◽  
Non Destructive

This article states the results of experimental studies to assess concrete strength in cast-in-situ structures based on a systematic approach, including integrated research methods at all stages of construction of reinforced concrete structures. It was established that the concrete strength of the sample-cubes made on the object simultaneously with the structure and stored under the same conditions was slightly lower than the structures and standard control samples. The decrease in the strength of concrete samples from structures is on average 13,3%. Its value is effected by several factors, one of the main was the maintenance of the structure. The most appropriate is to meet the requirements of achieving 70% of the design strength and higher percentage is required for cast-in-situ construction in terms of winter pouring concrete. At the same time, along with the assessment of the physical and mechanical properties of the structure by non-destructive methods, it is necessary to carry out tests aimed at determining the actual concrete strength based on samples made in the batching plant laboratory and solidified (cured) in permissible humidity conditions (herein after referred as PHC).

scholarly journals IMPACT OF CONCRETE QUALITY WORKS ON CONCRETE STRENGTH OF MONOLITHIC CONSTRUCTIONS

2020 ◽  
pp. 51-58
Author(s):  
I. Zharikov ◽  
A. Laketich ◽  
N. Laketich
Keyword(s):  
Negative Impact ◽  
Concrete Strength ◽  
Experimental Studies ◽  
Control Measures ◽  
Structural Safety ◽  
Destructive Testing ◽  
Design Strength ◽  
Near Surface ◽  
Non Destructive

the production of concrete works in the construction of monolithic frames of buildings and structures is associated with a large number of technological operations and the corresponding dependence of the quality of the products obtained from the culture of construction production and the level of its control. In many cases, concreting is carried out with some deviations from the technical regulations governing the preparation and laying of the concrete mix, which has a negative impact on the consumer characteristics of the structure, first of all, on strength. It is known that the most common methods of industrial control of the quality of concrete work are destructive tests of concrete samples laid in control cubes together with the constructed structure and non-destructive testing of concrete of the strength that has gained strength. However, even qualitatively and timely carried out control measures do not guarantee the achievement of design-controlled design strength throughout the volume, since control cubes are prepared for testing under ideal conditions of laying and concrete set of strength not observed in the design, and non-destructive methods determine the strength of near-surface layers of concrete, which allows judging reliably the strength of the material throughout the volume of the structure. Especially these circumstances relate to the most massive and, at the same time, the most important for the structural safety of the whole building frame structures – monolithic foundation slabs. The difference between the actual strength of the slabs extracted from the slab during the production of the construction and technical expertise of concrete cores depends significantly on the depth of core extraction, while the design of the slab is always carried out on the assumption of an equal strength of the concrete along the depth of the structure, which is obviously the source of the potential limited availability of foundation plates and the cause of the appearance of numerous defects in the construction and operation of structures of the above-foundation part of the frame. The paper presents experimental studies of the authors to determine the actual difference in concrete strength from the depth of foundation slabs and quantifies it.

Weathering conditions of Buddhist caves dug in soft rocks and conservation attempting from the deterioration

2021 ◽  
Author(s):  
Chiaki Oguchi ◽  
Momoko Ogawa ◽  
Kaisei Sakane ◽  
Yasuhiko Tamura
Keyword(s):  
Environmental Monitoring ◽  
Layer Structure ◽  
Physical And Mechanical Properties ◽  
Small Scale ◽  
Central Japan ◽  
Soft Rocks ◽  
Geologic Materials ◽  
Temperature And Humidity ◽  
Non Destructive

<p>The Taya Cave, a sacred Buddhist cave, locates in the precincts of Josenji Temple in Yokohama City, central Japan. The geologic materials of the hills surrounding the cave are soft rocks composed of early Quaternary sedimentary rocks. The cave has a complex three-layer structure with a total length of 570 m. The excavation of the cave is estimated to start in the Kamakura era around A.D. 1200. Since then, the cave became a training place for Buddhists until around 19 C. There are many Buddhist reliefs on the walls and ceiling inside the cave. Because the bedrock is extremely weak, the rocks easily break when they get wet again after drying, namely prone to slaking. Thus, weathering and deterioration have progressed in various parts of the cave. Many valuable Buddhist reliefs have damaged by exfoliation. The walls at several points in the cave have also collapsed on a small scale. Therefore, it is necessary to investigate such deteriorated parts in the cave by simple non-destructive tests of physical and mechanical properties by using Silver Schmidt hammer and ultrasonic velocity test. These measurements clarified the vulnerable points even in the main worship route of the cave. In October 2018, a stainless-steel door installed at the cave entrance to save from deterioration due to slaking. The effect of the door was verified as well by monitoring the environmental conditions inside the cave. Environmental monitoring results revealed that the temperature and humidity near the entrance changed most drastically in this cave. Although the door was closed only at night, the range of maximum and minimum values ​​of temperature and humidity near the entrance became smaller after installation than before. Non-destructive measurements and in situ environmental monitoring are a useful way to assess weathering without damaging geoarchaeological sites. </p>

scholarly journals Experimental research of dependence between informative parameters NDT techniques and steel physical and mechanical properties

2018 ◽  
pp. 44-48
Author(s):  
N. I. Chaban
Keyword(s):  
Mechanical Properties ◽  
Experimental Studies ◽  
Physical And Mechanical Properties ◽  
Ultrasonic Field ◽  
Failure Detectors ◽  
Metal Structures ◽  
New Methods ◽  
Informative Parameters ◽  
Non Destructive

Research of new methods and technologies of non-destructive control of change of long-term metal structures is an actual task of the present. In this article the methodology and results of experimental studies, the main aim of which is to determine the correlation between the intensity of structural noise in the material determined by failure detectors based on ultrasonic field-induced phase grating and the physical and mechanical properties of steels are presented.

scholarly journals The Use of Destructive and non Destructive Testing in Concrete Strength Assessment for a School Building

2019 ◽  
Author(s):  
Vincenzo Minutolo ◽  
Stefania Di Ronza ◽  
Caterina Eramo ◽  
Renato Zona
Keyword(s):  
Concrete Strength ◽  
Calibration Procedure ◽  
Experimental Investigations ◽  
School Building ◽  
Destructive Testing ◽  
Strength Assessment ◽  
Existing Building ◽  
Engineering Department ◽  
The University ◽  
Non Destructive

The present paper aims to increase knowlodge of the methods of resistance estimating of concrete in situ by means of non-destructive tests used to integrate the quantitative results from cylindrical specimens (core). The results of experimental investigations carried out on concrete conglomerate samples of a school building are shown. The experimental campaign then will be presented like a case study, conducted on a series of concrete beams and pillars of an existing building. The distructive tests on cores were conducted at the Civil Structures Laboratory of the Engineering Department of the University of Campania "Luigi Vanvitelli". The expression obtained through the calibration procedure of the values of non-destructive tests with those provided by the core drills allowed to estimate the average values of the compressive strength of the concrete. It is highlighted how this result was achieved with a very limited core number provided that they are extracted in selected points and that there was a proportionality link with the resistances obtained from non distructive tests.

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.

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