Influence of built-in thermocouples on temperature field in cement composites exposed to high temperatures

2020 ◽  
Author(s):  
Václav Kočí ◽  
Jiří Maděra ◽  
Jan Kočí ◽  
Robert Černý
Keyword(s):  
Temperature Field ◽  
High Temperatures ◽  
Cement Composites

scholarly journals Behaviour of cement composites with lightweight and heavyweight aggregates at high temperatures

2016 ◽  
Author(s):  
Lenka Bodnarova ◽  
Jitka Hroudova ◽  
Jiri Brozovsky ◽  
Jiri Zach ◽  
Jaroslav Valek
Keyword(s):  
High Temperatures ◽  
Cement Composites

High Temperature Composite of Aluminous Cement with Addition of Metakaolin and Ground Bricks Dust

2013 ◽  
Vol 486 ◽  
pp. 406-411 ◽  
Author(s):  
Ondřej Holčapek ◽  
Pavel Reiterman ◽  
Petr Konvalinka
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
High Temperatures ◽  
Raw Materials ◽  
Cement Composites ◽  
Basalt Fibers ◽  
Aluminous Cement ◽  
The Common ◽  
Temperature Exposure ◽  
Sufficient Strength

The following article deals with the study of mechanical properties of aluminous cement composites exposure to high temperatures. The newly designed mixtures that resist the action of high temperatures 1000 °C find their application in various fields of industrial production or in the form of fire wall for protection bearing structures. All the mechanical properties such as compressive strength and tensile strength in bending were measured on samples 160x40x40 mm. These samples were exposed to temperatures 600 °C and 1000 °C and one group of samples was reference and stayed in laboratory condition. Aluminous cement unlike the common Portland cement keeps sufficient strength even after high temperature exposure. For ensuring required ductility the basalt fibers were added to the mixture. In an effort to use of secondary raw materials as a replacement for cement as well as a suitable binder was used metakaolin and ground brick dust. Very convenient characteristics of these components are their latent hydraulic potential that makes interesting hydration products.

Behavior of Cement Composites Loaded by High Temperature

2015 ◽  
Vol 824 ◽  
pp. 121-125
Author(s):  
Veronika Špedlová ◽  
Dana Koňáková
Keyword(s):  
High Temperature ◽  
Portland Cement ◽  
High Temperatures ◽  
Experimental Program ◽  
Mechanical And Thermal Properties ◽  
Cement Composites ◽  
Basalt Fibers ◽  
Coefficient Of Thermal Conductivity ◽  
Aluminous Cement ◽  
Better Than

In this paper, there are summarized the results of an experimental program focused on basic, mechanical and thermal properties of cement composites according to the high – temperature loading. Four different materials were studied, which differed in used kind of cement and amount of fibers. As a matrix for studied composites the aluminous cement was chosen because of its resistance in high temperature. For a comparison the Portland cement was also tested. The second main ingredient used to provide better resistance in high temperatures - the basalt aggregate, was mixed in every specimen. The basalt fibers were chosen for two of the measured samples, remaining two ones were tested without fibers. The obtained data in this presented analyses show that the application of the aluminous cement leads to increase (depending on temperature) of porosity, which is the cause of decreasing of the coefficient of thermal conductivity. It can seems, that these cement composites will have low mechanical strength in high temperatures, but because of better sintering, the aluminous cement keeps its strength in high temperatures better than Portland cement.

The Possibilities of Application of Cellulose Fibers in Cement Composites, Monitoring the Properties

2014 ◽  
Vol 1054 ◽  
pp. 85-89 ◽  
Author(s):  
Lenka Bodnárová ◽  
Katarína Kostelanská ◽  
Filip Jankech
Keyword(s):  
Mechanical Properties ◽  
Rheological Properties ◽  
High Temperatures ◽  
Heat Load ◽  
Cellulose Fiber ◽  
Cellulose Fibers ◽  
Cement Composites ◽  
Pore System ◽  
Fiber Degradation ◽  
Experimental Works

Application of cellulose fibers in cement composites is one of the possibilities for achieving better utility properties of these composites. This article presents findings of experimental works concerned on increasing the resistance of cement composites to high temperatures. Properties of cement composites with the addition of cellulose fibers Greencel were observed. Rheological properties of fresh composite, mechanical properties and changes of properties after heat load were evaluated. The best mechanical properties showed the samples with technical cellulose, namely with the fiber G-55T and G-700T. The process of cellulose fiber degradation at high temperatures was documented. The process of carbonization of cellulose fibers leads to the creation of pore system, which enables to increase the resistance of cement composites to high temperatures.

Graphite-reinforced Portland cement composites at alternate ultra-high temperatures

2021 ◽  
Vol 378 ◽  
pp. 647-658
Author(s):  
Xingguo Zhang ◽  
Xiayu Zhang ◽  
Yonggang Li ◽  
Kaili Hu ◽  
Desen Mao ◽  
...  
Keyword(s):  
Portland Cement ◽  
High Temperatures ◽  
Cement Composites

scholarly journals Mathematical Modeling of Breast Tumor Destruction Using Fast Heating during Radiofrequency Ablation

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 136 ◽  
Author(s):  
Marek Paruch
Keyword(s):  
Mathematical Modeling ◽  
Temperature Field ◽  
High Temperatures ◽  
Central Area ◽  
Coagulation Necrosis ◽  
Fast Heating ◽  
Thermo Electric ◽  
Immunological Therapy ◽  
Arrhenius Integral ◽  
Pennes Equation

In oncology, hyperthermia is understood as a planned, controlled technique of heating cancerous changes in order to destroy their cells or stop their growth. In clinical practice, hyperthermia is used in combination with radiotherapy, chemotherapy, or immunological therapy. During the hyperthermia, the tissue is typically exposed to a temperature in the range of 40–45 °C, the exception is thermoablation, during which the temperatures reach much higher values. Thermoablation is characterized by the use of high temperatures up to 90 °C. The electrode using the radiofrequency is inserted into the central area of the tumor. Interstitial thermoablation is used to treat, among others, breast and brain cancer. The therapy consists of inducing coagulation necrosis in an area that is heated to very high temperatures. Mathematical modeling is based on the use of a coupled thermo-electric model, in which the electric field is described by means of the Laplace equation, while the temperature field is based on the Pennes equation. Coupling occurs at the level of the additional source function in the Pennes equation. The temperature field obtained in this way makes it possible to calculate the Arrhenius integral as a determinant of the destruction of biological tissue. As a result of numerical calculations regarding the temperature field and the Arrhenius integral, it can be concluded that, with the help of numerical tools and mathematical modeling, one can simulate the process of destroying cancerous tissue.

Polymer-Modified Cement Composites with Increased Resistance to Elevated Temperatures

2013 ◽  
Vol 688 ◽  
pp. 158-164 ◽  
Author(s):  
Jiří Bydžovský ◽  
Ámos Dufka ◽  
Tomáš Melichar
Keyword(s):  
Reinforced Concrete ◽  
High Temperatures ◽  
Elevated Temperatures ◽  
Raw Material ◽  
Cement Composites ◽  
Material Resources ◽  
Laboratory Conditions ◽  
Basic Characteristics

The paper informs on partial results of the research focused on improvement of resistance of cement composites towards actuation of high temperatures invoked by formation of fire. Specifically it is an optimisation of cement composites with use of alternative raw material resources. These cement composites are primarily designed for reconstructions of reinforced concrete constructions. Basic characteristics were tested with specimens exposed in laboratory conditions to an ambient characterized with increased temperatures simulating fire in real construction.

scholarly journals Development of rapid-hardening ultra-high strength cementitious composites using superzeolite and N-C-S-H-PCE alkaline nanomodifier

2021 ◽  
Vol 5 (6 (113)) ◽  
pp. 62-72
Author(s):  
Myroslav Sanytsky ◽  
Tetiana Kropyvnytska ◽  
Iryna Нeviuk ◽  
Pawel Sikora ◽  
Serhii Braichenko
Keyword(s):  
Portland Cement ◽  
High Temperatures ◽  
Elevated Temperatures ◽  
Basalt Fiber ◽  
High Strength ◽  
Operational Reliability ◽  
Cementitious Composites ◽  
Cement Composites ◽  
Repair Work ◽  
Rapid Hardening

It is shown that high operational reliability of structural materials, in particular at high temperatures, is achieved through the use of ultra-high strength cement composites. Studies of various types of Portland cements with mineral additives of the CEM II/A type have established that a stone based on Portland cement with superzeolite is the most resistant to high temperatures. It has been proven that due to the "self-autoclaving" effect, the strength of a stone based on CEM II/A-P 42.5 R is 1.2–1.3 times higher than a stone based on other types of CEM II/A. To obtain fast-hardening cement composites, a nanotechnological approach based on the use of sol-gel technology has been implemented. Using the methods of IR spectroscopy, electron microscopy, the fact of obtaining, by the chemical method of synthesis, an alkaline nanomodifier N-C-S-H-PCE, which is a nano–liquid based on nano-core seeds of sodium/calcium hydrosilicates, has been proved. It has been confirmed that the introduction of the alkaline nanomodifier N-C-S-H-PCE provides a significant intensification of the early structure formation processes in the paste based on Portland cement with superzeolite (after 12 hours, 24 hours and 28 days, the strength is 16.9; 30.5 and 104.1 MPa). It has been established that the complex combination of Portland cement with superzeolite, corundum aggregate, basalt fiber and alkaline nanomodifier provides rapid-hardening of ultra-high strength cement composites (T=400 °C) with improved operational properties. Thus, there is reason to assert the feasibility of developing rapid-hardening ultra-high strength cementitious composites. This solves the problems associated with the need to increase their early strength and performance. As a result, it is possible to carry out repair work to protect equipment from abrasive wear at elevated temperatures

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