scholarly journals Thermal Conductivity of High Performance Concrete in Wide Temperature and Moisture Ranges

10.14311/174 ◽  
2001 ◽  
Vol 41 (1) ◽  
Author(s):  
J. Toman ◽  
R. Černý
Keyword(s):  
Thermal Conductivity ◽  
High Performance ◽  
Room Temperature ◽  
High Performance Concrete ◽  
Measuring Method ◽  
Point Of View ◽  
Temperature Measurements ◽  
Temperature Fields ◽  
Measured Temperature ◽  
Hot Wire

The thermal conductivity of two types of high performance concrete was measured in the temperature range from 100 °C to 800 °C and in the moisture range from dry material to saturation water content. A transient measuring method based on analysis of the measured temperature fields was chosen for the high temperature measurements, and a commercial hot wire device was employed in room temperature measurements of the effect of moisture on thermal conductivity. The measured results reveal that both temperature and moisture exhibit significant effects on the values of thermal conductivity, and these effects are quite comparable from the point of view of the magnitude of the observed variations.

The Possibility of Visualizing Temperature Fields Using Digital Holographic Interferometry

2013 ◽  
Vol 284-287 ◽  
pp. 988-995 ◽  
Author(s):  
Tomáš Vít ◽  
Vít Lédl ◽  
Roman Dolecek ◽  
Pavel Psota
Keyword(s):  
Holographic Interferometry ◽  
Rapid Change ◽  
Optical Methods ◽  
Temperature Fields ◽  
Constant Current ◽  
Special Technique ◽  
Limiting Factor ◽  
Measured Temperature ◽  
Hot Wire ◽  
First Results

The presented paper compares results of measured temperature fields achieved by digital holographic interferometry (DHI) and hot wire anemometry. It shows the possibility of using holographic interferometry for the visualization of temperature fields in periodically moving fluids. The measurement of temperature fields in moving fluids has many inherent difficulties. The usage of point temperature measurement methods, such as Constant Current Anemometry (CCA), is limited to frequencies up to 3000 Hz. This frequency should be the limiting factor for using CCA in fluids when a rapid change of temperature occurs. This shortcoming of CCA measurements could be overcome through the use of optical methods such as digital holographic interferometry. It is necessary to employ a special holographic setup with double sensitivity instead of the commonly used Mach-Zehnder type of holographic interferometer in order to attain parameters sufficient for the studied case. This setup is not as light-efficient as the Mach-Zehnder type but has double sensitivity. The special technique of acquiring and phase averaging the results from holographic interferometry is presented. The paper also shows the first results of an evaluated 3D temperature field.

scholarly journals Graphene-Based Thermal Interface Materials: An Application-Oriented Perspective on Architecture Design

Polymers ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1201 ◽  
Author(s):  
Le Lv ◽  
Wen Dai ◽  
Aijun Li ◽  
Cheng-Te Lin
Keyword(s):  
Thermal Conductivity ◽  
High Performance ◽  
Electronic Devices ◽  
Point Of View ◽  
Future Research ◽  
Thermal Interface Materials ◽  
Research Directions ◽  
Thermal Interface ◽  
Future Research Directions ◽  
Interface Materials

With the increasing power density of electrical and electronic devices, there has been an urgent demand for the development of thermal interface materials (TIMs) with high through-plane thermal conductivity for handling the issue of thermal management. Graphene exhibited significant potential for the development of TIMs, due to its ultra-high intrinsic thermal conductivity. In this perspective, we introduce three state-of-the-art graphene-based TIMs, including dispersed graphene/polymers, graphene framework/polymers and inorganic graphene-based monoliths. The advantages and limitations of them were discussed from an application point of view. In addition, possible strategies and future research directions in the development of high-performance graphene-based TIMs are also discussed.

EXPERIMENTAL STUDY ON DURABILITY OF ROOM TEMPERATURE CURING UFC MORTAR

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Haruka Murakami ◽  
Hiromi Fujiwara ◽  
Masanori Maruoka ◽  
Takahumi Watanabe ◽  
Koji Satori
Keyword(s):  
Experimental Study ◽  
Compressive Strength ◽  
High Performance ◽  
Room Temperature ◽  
Bending Strength ◽  
High Performance Concrete ◽  
Drying Shrinkage ◽  
Concrete Repair ◽  
Repair Materials ◽  
Low Salt

In recent years, as structures become higher, larger, and more durable concrete whose compressive strength of the concrete is 150 N/mm 2 or more have been put to practical use. It is for this reason that it is necessary to develop strengthening materials with equal or better performance. Furthermore, the development of high-performance concrete repair materials is carried out because demand to seismic strengthening and repair increases. In this study, considering these circumstances, it was conducted an experimental study with the aim of developing a repair material using room temperature curing UFC (R-UFC). A binder composition preparation of the R-UFC has excellent fluidity under pressure. It was achieved that high-grade thixotropy, high compressive strength, and high bending strength. It can also be sprayed continuously because of its high thixtoropy. It was confirmed that the sprayed thickness was reached to 20mm by one work. Durability of this R-UFC was investigated and it was confirmed the high sulfate resistance, small drying shrinkage and low salt permeability.

The Influence on High-Temperature Mechanical Properties of Hybrid-Fiber-Reinforced High-Performance Concrete and Microscopic Analysis

2012 ◽  
Vol 226-228 ◽  
pp. 1709-1713
Author(s):  
Lan Yan ◽  
Y.M. Xing ◽  
Ji Jun Li
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Transition Zone ◽  
High Performance ◽  
Room Temperature ◽  
Steel Fiber ◽  
High Performance Concrete ◽  
Interfacial Transition Zone ◽  
Hybrid Fiber ◽  
High Temperature Mechanical Properties

This paper investigated the high temperature mechanical properties of the hybrid fiber reinforced high performance concrete (HFHPC) and normal concrete (NC) .After being subjected to different elevated heating temperatures, two kinds of concretes have been tested for the compressive strength, splitting tensile strength and flexural strength of test specimen at room temperature and 200 °C,400 °C,600 °C,800 °C.Microstructure changes of concrete were also observed by using Scanning Electron Microscopy (SEM) after high temperature. The results show that the hybrid fiber can significantly increase mechanical properties of the concrete at room temperature and high temperature. SEM and XRD analysis shows that there is a permeable diffusion layer in the steel fiber surface because of solid state reaction in the Interfacial Transition Zone of steel fiber and concrete. This permeable diffusion layer is white, bright, serrated and mainly consist of FeSi2 and the complex hydrated calcium silicate. The compounds of this layer change the Interfacial Transition Zone structure, enhance bonding capacity of the steel fiber and matrix, and increase the high temperature mechanical properties of concrete.

Behavior of High Performance Concrete Under High Temperature (60-450°C) for Surface Long-Term Storage: Thermo-Hydro-Mechanical Residual Properties

2000 ◽  
Vol 663 ◽  
Author(s):  
C. Gallé ◽  
J. Sercombe ◽  
M. Pin ◽  
G. Arcier ◽  
P. Bouniol
Keyword(s):  
Thermal Conductivity ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
High Performance ◽  
High Performance Concrete ◽  
Gas Permeability ◽  
Long Term Storage ◽  
Residual Properties ◽  
Term Storage

ABSTRACTAfter various thermal treatments (up to 450°C), residual thermo-hydro-mechanical (T-H-M) properties of two OPC high performance concretes (HPC) were analyzed in the context of surface long-term storage. Materials were prepared with silico-calcareous aggregates (standard HPC) and hematite aggregates (heavy HPC). The initial microstructural (porosity ≈10%) and transport (gas permeability ≈10-19 m2) properties are similar for both concretes. As far as the mechanical aspect is concerned, heavy HPC shows a higher compressive strength and elastic modulus than standard HPC (78 and 63 MPa, 81 and 49 GPa, respectively). Heavy HPC is also characterized by a higher thermal conductivity (7.3 W m-1 K-1 compared to 2.7 W m-1 K-1 for standard concrete). Results analysis show that thermo-hydro-mechanical damages are smaller for heavy HPC. Between 60 and 250°C, the elastic modulus and the compressive strength of standard HPC decrease by 40% and 16%, respectively. For heavy HPC, these parameters respectively decrease by 10% and 4%. A similar trend was observed for thermal conductivity evolution. Gas permeability and porosity data confirm the good behavior of heavy HPC. As a conclusion, hematite HPC seems to provide more interesting T-H-M residual properties than standard HPC. Limited thermal expansion and thermal gradients induced by hematite are probably responsible of this behavior.

Research of High Performance Concrete of C100

2013 ◽  
Vol 838-841 ◽  
pp. 170-174
Author(s):  
Guo Jun Wang
Keyword(s):  
Silicon Content ◽  
High Performance ◽  
High Performance Concrete ◽  
Concrete Strength ◽  
Interface Structure ◽  
Orthogonal Test ◽  
Cementitious Material ◽  
Point Of View ◽  
Aggregate Gradation ◽  
Interface Structures

The effect on concrete strength of various kinds factor was systematically studied by orthogonal test. The amount of cementitious material, slag content, silicon content, water cement ratio, aggregate gradation and other factors was consider. By adjusting the parameters of the experiment, the C100 concrete was preparation successfully, which has high stregth and pumping perfomance. The interface structure of the C100 concrete was analyzed by scanning electron microscope (SEM) and found that C100 has a better interface structures. The concrete is a system and his strength depends on the strength of the suitability of various materials, which is a new point of view was put forward.

Dosage of Metakaolin in High Performance Concrete

2016 ◽  
Vol 722 ◽  
pp. 311-315 ◽  
Author(s):  
Michal Ženíšek ◽  
Tomáš Vlach ◽  
Lenka Laiblová
Keyword(s):  
Compressive Strength ◽  
High Performance ◽  
High Performance Concrete ◽  
Rheological Behaviour ◽  
Economic Benefits ◽  
Point Of View ◽  
Optimal Dosage ◽  
Higher Doses

This article deals with optimal dosage of metakaolin as addition in high performance concrete. The main criteria for assessing the optimal dosage of metakaolin was compressive strength, rheological behaviour and economic benefits. Metakaolin was added to the mixture of high performance concrete in the range from 0 to 25% weight of cement. The comparison of metakaolin and microsilica, which is often used by concrete producers due to its excellent properties, is also performed in this article. The experiments showed that using metakaolin as addition in high performance concrete affects the compressive strength and rheological behaviour positively. While the compressive strength increases especially at lower doses of metakaolin and at higher doses remained unchanged, changes in rheological behaviour were most obvious at the higher doses. From this point of view, it is possible to recommend a higher dose of metakaolin.

Evolution from High Strength Concrete to High Performance Concrete

2014 ◽  
Vol 629-630 ◽  
pp. 49-54
Author(s):  
Vlastimil Bílek ◽  
Vladimíra Tomalová ◽  
Petr Hájek ◽  
Ctislav Fiala
Keyword(s):  
High Strength Concrete ◽  
High Performance ◽  
High Performance Concrete ◽  
High Strength ◽  
Maximum Size ◽  
Point Of View ◽  
Fracture Properties ◽  
Strength Concrete ◽  
Time Period ◽  
Long Term Observation

High strength concrete for the production of concrete railway sleepers was designed more than 20 years ago. The compressive strength of the concrete was very high from the start, but flexure strengths showed some irregular development - a decrease in time. Later, also a significant decrease of fracture properties was recorded. Microcracking was found to be the reason for this; therefore some modifications were performed to avoid this happening (especially the reduction of the maximum size of aggregates from 22 mm to 16 mm or 11 mm). Some problems concerning frost resistance of the concrete with a slag addition were reduced by applying ternary binders. All of the results are discussed from the point of view of a long-term observation of the strengths and fracture properties ́ development during the time period of 5 years or even more.

Mechanical Behavior and Shrinkage of Algerian Very High Performance Concrete Using Local Materials

2017 ◽  
Vol 29 ◽  
pp. 81-89
Author(s):  
Dalila Chiheb ◽  
Mebarek Belaoura ◽  
Mohamed Nadib Oudjit ◽  
Abderrahim Bali
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Point Of View ◽  
Mechanical Mixing ◽  
Alluvial Deposits ◽  
Crushed Aggregate ◽  
Mechanical Performances ◽  
Local Materials ◽  
Crushed Limestone ◽  
Very High

In some parts of Algeria, the alluvial deposits are depleted. Optimizing the use of available resources, has become gradually urgent need and more and more important. Algeria does not remain on the sidelines of this idea, an approach is part of a sustainable development has been developed to make available to the manufacturer a steady stream of material coming from the exploitation of limestone. The importance of this production can be explained by the activity of the carrier ever growing sector. Research programs have been launched in Algeria to focus on aspects, related to the composition of concrete and influence of the nature of the constituents on the mechanical mixing quality, especially compressive strength remains the point of view of the engineer, the most important property of the material, if we exclude the sustainability indicators. Usual concretes were made using local materials. Results showed that the intrinsic properties of the constituents of concrete, and particularly studied the crushed aggregate, provide the concrete characteristics resistors quite satisfactory. To go further and in a growing cares about improving the mechanical strength of these concretes we tried to formulate a very high performance concrete (VHPC) made from local crushed aggregate, in this case the crushed limestone sands as a resource alternative to over-exploited rolled sands. The objective of this study is to enhance the crushed sand in the formulation of VHPC. The referred physical-mechanical performances are related to defer deformations within time (shrinkage) and instantaneous mechanical compressive and flexural strength.

Application of ultra-high performance concrete for thermal resistance materials

2019 ◽  
Author(s):  
Sung-Gul Hong ◽  
Namhee K. Hong ◽  
In-Young Gu
Keyword(s):  
Thermal Conductivity ◽  
Compressive Strength ◽  
Thermal Resistance ◽  
High Performance ◽  
High Performance Concrete ◽  
Curing Temperature ◽  
Core Material ◽  
Ultra High Performance Concrete ◽  
External Temperature ◽  
Low Thermal Conductivity

<p>This paper investigates the thermal resistance of ultra-high performance concrete (UHPC) composites using different fillers of low thermal conductivity. The development of new concrete for energy saving facilities is more demanding for climate change threat to human. The use of UHPC composite with expanded polystyrene (EPS) beads as well as different fillers of low thermal conductivity has shown a viable option of architectural sandwich walls of insulation. The optimum fillers of thermal resistance for UHPC are determined by the tradeoff of compressive strength between heat conductivity. Better thermal properties of some UHPC composites make lower compressive strength of UHPC. To evaluate the varying thermal and mechanical characteristics of UHPC composites with the quantity of fillers, the method of volumetric substitution for UHPC was investigated in this paper. The UHPC composite of thermal resistance with comparable compressive strength can be possibly used for concrete blocks to transfer flexural compression force in efficient thermal breaker systems. Test results show that the strength of the concrete is greatly influenced by the curing method and the most important factors affecting the strength of concrete are curing temperature and curing time. Structural UHPC walls of thermal resistance serve as both load transfer and barrier to external temperature. To investigate the mechanical behavior of composite sandwich panels, the panels for the study are fabricated by new concrete as core and face sheets and the influence of the three components – the mechanical properties of the core material, the strength of the face sheet material, and the bond strength adhesive material – was evaluated. The flexural capacity of the specimens UHPC with EPS core showed high strength in a stable linear behavior before core cracking.</p>

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