Effects of Thermal Conditioning at High Temperatures on the Response of Concrete Elements Confined with a PBO-FRCM Composite System

2022 ◽  
Vol 34 (1) ◽  
Author(s):  
L. Ombres ◽  
P. Mazzuca ◽  
S. Verre
Keyword(s):  
High Temperatures ◽  
Composite System ◽  
Concrete Elements

scholarly journals Insight into the Mechanical Performance of the UHPC Repaired Cementitious Composite System after Exposure to High Temperatures

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4095
Author(s):  
Qing Chen ◽  
Zhiyuan Zhu ◽  
Rui Ma ◽  
Zhengwu Jiang ◽  
Yao Zhang ◽  
...  
Keyword(s):  
Compressive Strength ◽  
High Temperature ◽  
High Temperatures ◽  
Bonding Strength ◽  
Composite System ◽  
Mechanical Performance ◽  
High Performance Concrete ◽  
Interfacial Structure ◽  
Cementitious Composite ◽  
Average Percentage

In this paper, the mechanical performance of an ultra-high-performance concrete (UHPC) repaired cementitious composite system, including the old matrix and the new reinforcement (UHPC), under various high temperature levels (20 °C, 100 °C, 300 °C, and 500 °C) was studied. In this system, UHPC reinforced with different contents of steel fibers and polypropylene (PP) fibers was utilized. Moreover, the physical, compressive, bonding, and flexural behaviors of the UHPC repaired system after being exposed to different high temperatures were investigated. Meanwhile, X-ray diffraction (XRD), baseline evaluation test (BET), and scanning electron microscope (SEM) tests were conducted to analyze the effect of high temperature on the microstructural changes in a UHPC repaired cementitious composite system. Results indicate that the appearance of the bonded system changed, and its mass decreased slightly. The average percentage of residual mass of the system was 99.5%, 96%, and 94–95% at 100 °C, 300 °C, and 500 °C, respectively. The residual compressive strength, bonding strength, and flexural performance improved first and then deteriorated with the increase of temperature. When the temperature reached 500 °C, the compressive strength, bonding strength, and flexural strength decreased by about 20%, 30%, and 15% for the UHPC bonded system, respectively. Under high temperature, the original components of UHPC decreased and the pore structure deteriorated. The cumulative pore volume at 500 °C could reach more than three times that at room temperature (about 20 °C). The bonding showed obvious deterioration, and the interfacial structure became looser after exposure to high temperature.

scholarly journals Design Model Of Bending Reinforced Concrete Elements Under Action Of Transverse Forces Under Conditions Of Increased And High Temperatures

2020 ◽  
Vol 02 (10) ◽  
pp. 17-24
Author(s):  
Mahkamov Y.M. ◽  
Keyword(s):  
Reinforced Concrete ◽  
Crack Resistance ◽  
High Temperatures ◽  
Experimental Studies ◽  
Calculation Model ◽  
Design Model ◽  
Stress Strain ◽  
Concrete Elements

In this article, the calculation of the strength and crack resistance of bending elements operating under conditions of high and high temperatures and transverse forces are proposed to be carried out according to a calculation model developed based on an analysis of experimental studies that takes into account more correctly the physics of the stress-strain phenomenon of the element.

Evaluation of Degradation of Concrete Exposed to High Temperature by Means of Ultrasonic Pulse Method

2013 ◽  
Vol 284-287 ◽  
pp. 1315-1319 ◽  
Author(s):  
Jiří Brožovský ◽  
Lenka Bodnárová ◽  
Rudolf Hela ◽  
Rostislav Drochytka ◽  
Vlastimil Hela
Keyword(s):  
High Temperature ◽  
High Temperatures ◽  
Experimental Work ◽  
Pulse Method ◽  
Ultrasonic Pulse ◽  
Destructive Testing ◽  
Optimization Of Composition ◽  
Concrete Elements ◽  
Non Destructive ◽  
Degree Of Degradation

Ultrasonic pulse method is a non-destructive testing method used for testing materials. For concrete, it is used mostly for determination of dynamic elasticity modulus, compressive strength, homogeneity, to determine depth of cracks or as a supportive method for testing frost resistance. Applicability of using ultrasonic pulse method for evaluation of degradation of concrete exposed to high temperature was proved. This method is unambiguously utilizable for rationalization of experimental work focused on optimization of composition of concrete resistant to high temperatures. Ultrasonic pulse method can be also used for mapping the degree of degradation of concrete elements and structures, which can be measured by means of direct sounding. Appropriateness of the use of ultrasonic pulse method for evaluation of degradation of concrete exposed to high temperature was proved. This method is unambiguously applicable for rationalization of experimental work focused on optimization of composition of concrete resistant to high temperatures. Ultrasonic pulse method can be also used for mapping degree of degradation of concrete elements and structures, which can be measured by means of direct sounding.

scholarly journals To Calculation Of Bended Elements Working Under The Conditions Of Exposure To High And High Temperatures On The Lateral Force By A New Method

2021 ◽  
Vol 03 (05) ◽  
pp. 210-218
Author(s):  
Makhkamov Yuldashali Mamazhonovich ◽  
◽  
Mirzababayeva Sahiba Mirzaakbarovna ◽  
Keyword(s):  
Experimental Data ◽  
Reinforced Concrete ◽  
High Temperatures ◽  
Calculation Method ◽  
Lateral Force ◽  
New Method ◽  
Design Standards ◽  
Current Design ◽  
Calculation Results ◽  
Concrete Elements

The article presents a new method for calculating bending reinforced concrete elements made of conventional and heat-resistant concrete operating under conditions of high and high technological temperatures on the action of transverse forces. The advantage of the proposed calculation method over the method adopted in the current design standards based on a comparison of the calculation results of the experimental data is shown.

In situ REM imaging of surface processes on ceramic bulk crystals from 300 to 1670 K in a conventional TEM

1991 ◽  
Vol 49 ◽  
pp. 660-661
Author(s):  
Z. L. Wang ◽  
J. Bentley
Keyword(s):  
High Temperatures ◽  
Image Resolution ◽  
Atomic Processes ◽  
Crystal Surfaces ◽  
Beam Radiation ◽  
Surface Areas ◽  
Transmission Electron ◽  
Reflection Electron Microscopy ◽  
Gas Reactions

Studying the behavior of surfaces at high temperatures is of great importance for understanding the properties of ceramics and associated surface-gas reactions. Atomic processes occurring on bulk crystal surfaces at high temperatures can be recorded by reflection electron microscopy (REM) in a conventional transmission electron microscope (TEM) with relatively high resolution, because REM is especially sensitive to atomic-height steps.Improved REM image resolution with a FEG: Cleaved surfaces of a-alumina (012) exhibit atomic flatness with steps of height about 5 Å, determined by reference to a screw (or near screw) dislocation with a presumed Burgers vector of b = (1/3)<012> (see Fig. 1). Steps of heights less than about 0.8 Å can be clearly resolved only with a field emission gun (FEG) (Fig. 2). The small steps are formed by the surface oscillating between the closely packed O and Al stacking layers. The bands of dark contrast (Fig. 2b) are the result of beam radiation damage to surface areas initially terminated with O ions.

Processing and characterization of YBa2Cu3O7−x/Ag composites

1990 ◽  
Vol 48 (4) ◽  
pp. 46-47
Author(s):  
Jafar Javadpour ◽  
Bradley L. Thiel ◽  
Sarikaya Mehmet ◽  
Ilhan A. Aksay
Keyword(s):  
Composite System ◽  
Precursor Solution ◽  
Microstructural Development ◽  
Superconducting Properties ◽  
Practical Applications ◽  
Nitrate Precursor ◽  
Cold Pressed ◽  
Tape Cast ◽  
Composite Samples

Practical applications of bulk YBa2Cu3O7−x materials have been limited because of their inadequate critical current density (jc) and poor mechanical properties. Several recent reports have indicated that the addition of Ag to the YBa2Cu3O7−x system is beneficial in improving both mechanical and superconducting properties. However, detailed studies concerning the effect of Ag on the microstructural development of the cermet system have been lacking. Here, we present some observations on the microstructural evolution in the YBa2Cu3O7−x/Ag composite system.The composite samples were prepared by mixing various amounts (2.5 - 50 wt%) AgNO3 in the YBa2Cu3O7−x nitrate precursor solution. These solutions were then spray dried and the resulting powders were either cold pressed or tape cast. The microstructures of the sintered samples were analyzed using SEM (Philips 515) and an analytical TEM (Philips 430T).The SEM micrographs of the compacts with 2.5 and 50 wt% Ag addition sintered at 915°C (below the melting point of Ag) for 1 h in air are displayed in Figs. 1 and 2, respectively.

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