Temperature Gradient of Concrete Pavement Slab Overlaid with Asphalt Surface Course

2000 ◽  
Vol 1730 (1) ◽  
pp. 25-33 ◽  
Author(s):  
Tatsuo Nishizawa ◽  
Shigeru Shimeno ◽  
Akinori Komatsubara ◽  
Masashi Koyanagawa
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Stress ◽  
Temperature Gradient ◽  
Numerical Simulations ◽  
Structural Design ◽  
Concrete Slab ◽  
Concrete Pavement ◽  
Reduction Effect ◽  
The Relationship

In the structural design of composite pavement with a concrete pavement slab overlaid with an asphalt surface course, it is very important to estimate the temperature gradient in the concrete slab. An asphalt surface course reduces the temperature gradient in an underlaid concrete slab, resulting in the reduction of thermal stress of the concrete slab. This effect was investigated by temperature measurement in model pavements and by thermal conductivity analysis. Thermal properties were estimated by a backanalysis by using measured temperatures over 1 year. From the numerical simulations varying the thickness of asphalt surface and concrete slab, the relationship between the reduction effect and the asphalt thickness was derived as a function of the thickness of asphalt surface course, which can be used in the structural design of the composite pavement.

scholarly journals Analysis of temperature gradient in concrete pavement

2018 ◽  
Vol 67 (4) ◽  
pp. 59-70
Author(s):  
Grzegorz Rogojsz
Keyword(s):  
Thermal Stress ◽  
Temperature Distribution ◽  
Temperature Gradient ◽  
Air Temperature ◽  
Experimental Research ◽  
Analytical Methods ◽  
Concrete Slab ◽  
Climatic Conditions ◽  
Concrete Pavement

The paper presents the results of experimental research that is the continuation of the research conducted as a part of a Ph.D. dissertation. The experimental research consisted in measuring the temperature at various depths inside a concrete slab, including its surface, and measuring the air temperature. The temperature distribution was measured on a concrete slab with dimensions similar to real road slab dimensions. The aim of the research was to determine the temperature gradient in the concrete slab in Polish climatic conditions and to verify the available analytical methods. Keywords: temperature gradient, concrete pavement, thermal stress in concrete pavement.

Research of Zero Stress Temperature Gradient in Cement Concrete Pavement

2013 ◽  
Vol 723 ◽  
pp. 163-170 ◽  
Author(s):  
Xiang Shen Hou ◽  
Xin Kai Li ◽  
Bo Peng ◽  
Guang Hui Deng
Keyword(s):  
Temperature Gradient ◽  
Concrete Beam ◽  
Concrete Slab ◽  
Strain Sensor ◽  
Concrete Pavement ◽  
Early Age ◽  
Cement Concrete ◽  
Setting Process ◽  
Cement Concrete Pavement ◽  
Design Guidance

There is no temperature stress and temperature curling according to the present cement concrete pavement design, when the temperature gradient of cement concrete pavement in service is zero, and it does not consider the effect of Built-in curling caused in early-age setting process of cement concrete to cement concrete pavement in service. In fact, there is Built-in curling in cement concrete slab when it is after the completion of the cement concrete slab is poured, and the curling is mainly upward. It is in the setting process, when cement concrete is on the final set, the cement concrete is at the critical moment when is just able to bear load, and it exists temperature gradient but no strain in the pavement slab, the temperature gradient is known as "Built-in construction temperature gradient" in AASHTO2002 design guidance, and it is the important part of the Built-in curling. In this paper, cement concrete beam specimens were poured in outdoor and temperature sensor and strain sensor were buried in the cement concrete specimens to detect early-age internal temperature field and strain field, and then the study of Built-in curling and Built-in construction temperature gradient were carried out.

Research on the Relationship between Thermal Conductivity and Porosity during Carbonation of Cement Materials

2014 ◽  
Vol 1065-1069 ◽  
pp. 1838-1841
Author(s):  
Son Tung Pham
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Cement Mortar ◽  
Total Porosity ◽  
Accelerated Carbonation ◽  
Experimental Campaign ◽  
Hydrostatic Weighing ◽  
Specific Material ◽  
The Relationship ◽  
Microstructural Studies

The objective of this work was to examine the relationships that may exist between porosity and thermal conductivity with particular reference to normalized cement mortar which is most commonly found in civil engineering. Samples were prepared and subjected to accelerated carbonation at 20°C, 65% relative humidity and 20% CO2 concentration. We investigated the evolution of the total porosity measured by hydrostatic weighing and of the thermal properties measured by Hotdisk method. This experimental campaign allowed relating the total porosity and the thermal conductivity before and during carbonation. These results can be used for further studies which can propose models predicting the thermal conductivity if changes in porosity are known. Moreover, the results indicated that the thermal conductivity of a cement material is directly related to the density and inversely related to porosity. Finally, this study showed that a characteristic coefficient can be deduced for two states of material: non-carbonated and carbonated. This coefficient is therefore proper to a specific material and can be used not only for modeling the relationship between porosity and thermal properties but also for other microstructural studies of cement materials.

scholarly journals Metamorphism and thermal properties of fresh snow (study in the Moscow region)

2016 ◽  
Vol 56 (2) ◽  
pp. 199-206 ◽  
Author(s):  
R. A. Chernov
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Temperature Gradient ◽  
Negative Temperature ◽  
Average Temperature ◽  
The North ◽  
Coefficient Of Thermal Conductivity ◽  
European Part Of Russia ◽  
Snow Conditions

As a result of laboratory tests were obtained values of the coefficient thermal conductivity (Keff) of new snow for different types of the solid precipitation: plates, needles, stellars, graupels. Snow samples were collected during a snowfall and placed in the freezer. For all types of sediment thermal conductivity of snow is equal to 0.03–0.04 W/m·°C. Transformation of new snow occurs within 10 days at average temperature −10 °C and the gradient temperature of 50–60 °C/m. Under these conditions, the metamorphism leads to an increase the density of snow, size of grains and rounded snow particles. At the beginning of the experiment, the thermal conductivity of snow is linearly increased in proportion to the density of the snow. However, after 3–5 days Keff stabilized at about 0.08–0.09 W/m·°C, although the density of the snow and size of grains continued to increase. This effect occurs with the appearance of faceted crystals and loosening of snow. In the future, while maintaining a negative temperature coefficient of thermal conductivity remained unchanged. Thus, the temperature gradient metamorphism affect to the thermal conductivity snow, which plays an important role in maintaining the thermal insulation properties of snow cover. The article describes the formula to calculate the thermal conductivity of the snow conditions in the temperature gradient metamorphism. Such conditions are characteristic of the vast expanses of the north and northeast of the European part of Russia. On the basis of long-term observations in Moscow shows the average minimum and maximum values for the density of the snow woods and fields on the basis of which can be calculated for the thermal properties of the snow.

The Effect of β-SiC Nanowires on the Properties of Al2O3 Composites

2016 ◽  
Vol 690 ◽  
pp. 240-245
Author(s):  
Wasana Khongwong ◽  
Chumphol Busabok
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Flexural Strength ◽  
Bending Test ◽  
Matrix Composites ◽  
Sic Nanowires ◽  
Four Point Bending ◽  
Four Point Bending Test ◽  
Cold Pressed ◽  
The Relationship

To investigate the effect of adding b-SiC nanowires on the properties of the Al2O3 matrix composites, four different amounts of SiC nanowires, 0.05, 0.1, 0.2 and 0.25 wt% were mixed with Al2O3 powder. All mixtures were ball-milled and dried in an oven at a temperature of 120°C. The Al2O3-SiC mixtures were uniaxially pressed into pellets under 5 MPa and were then isostatically cold-pressed (CIP) under a pressure of 200 MPa. Specimens (13 mm in diameter and 2.5 mm in thickness) were sintered in a tube furnace at the temperature of 1400°C for 1 h in Ar atmosphere. Physical and thermal properties of pellet composites were characterized. The bar shape specimens with dimension of 3 mm x 4 mm x 35 mm were prepared for four-point bending test. The relationship between thermal conductivity and flexural strength versus grain connection of composites have been investigated. The results showed that the composites with adding SiC nanowires at 0.05-0.2 wt% possessed lower thermal conductivity than those monolithic Al2O3 specimens. However, the thermal conductivity of the composite specimens with 0.25 wt% SiC nanowires became higher than those of monolithic Al2O3 specimens. The flexural strengths of the composites gradually decreased with the increasing amount of SiC nanowires.

Effect of transverse temperature gradient on the migration of a deformable droplet in a Poiseuille flow

2018 ◽  
Vol 850 ◽  
pp. 1142-1171 ◽  
Author(s):  
Sayan Das ◽  
Shubhadeep Mandal ◽  
Suman Chakraborty
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Temperature Gradient ◽  
Numerical Simulations ◽  
Thermal Convection ◽  
Shape Deformation ◽  
Droplet Radius ◽  
Channel Height ◽  
State Position ◽  
Transverse Position

Intricate manipulation of droplets in fluidic confinements may turn out to be critically important for achieving their controlled transverse distributions. Here, we study the migration characteristics of a suspended deformable droplet in a parallel plate channel under the combined influence of a constant temperature gradient in the transverse direction and an imposed pressure driven flow. An outstanding question concerning the resultant non-trivial dynamical features that we address here pertains to the nonlinearity that results as a consequence of the shape deformation, which does not permit us to analyse the combined transport as a mere linear superposition of the results for the thermocapillary and imposed flow driven droplet migration in an effort to obtain the final solution. For the analytical solution, an asymptotic approach is used, where we neglect any effect of inertia or thermal convection of the fluid in either of the phases. To obtain a numerical solution, we use the conservative level set method. We perform numerical simulations over a wide range of governing parameters and obtain the dependence of the transverse steady position of the droplet on different parameters. In order to address practical microfluidic set-ups, the influence of a bounding wall as well as the effect of thermal convection and finite shape deformation on the cross-stream migration of the droplet is investigated through numerical simulations. Increase in the thermal Marangoni stress shifts the steady-state transverse position of the droplet further away from the channel centreline, for any particular value of the capillary number (which signifies the ratio of the viscous force to the surface tension force). The confinement ratio, which is the ratio of the droplet radius to the channel height, plays an important role in predicting the transverse position of the droplet and thus has immense consequences for the design of droplet-based microfluidic devices with enhanced functionalities. A large confinement ratio drives the droplet towards the channel centre, whereas a smaller confinement ratio causes the droplet to move towards the wall. Moreover, for a fixed droplet radius and constant imposed temperature gradient, an increase in the channel height results in an increase in the time required for the droplet to reach the steady-state position. However, the final steady-state position of the droplet is independent of its initial position but at the same time dependent on the droplet phase thermal conductivity. A larger droplet thermal conductivity compared with the carrier phase results in a steady-state droplet position closer to the channel centreline. A higher fluid inertia, on the other hand, shifts the steady-state position towards the channel wall.

Measurements of Thermal Properties of Gaskets for the Design of Bolted Flange Joints Under Thermal Conduction Conditions

2006 ◽  
Author(s):  
Takahiro Ohmura ◽  
Kanji Hanashima ◽  
Junichi Nyumura ◽  
Toshiyuki Sawa
Keyword(s):  
Thermal Conductivity ◽  
Thermal Expansion ◽  
Thermal Properties ◽  
Effective Thermal Conductivity ◽  
Linear Thermal Expansion ◽  
Absolute Temperature ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients ◽  
Bolted Flange ◽  
The Relationship

In this study, the thermal properties of the gaskets, which were used for designing the bolted flange joints, such as effective thermal conductivity, specific heat, linear thermal expansion coefficient and so on were measured. Especially, the effective thermal conductivities were measured by using the heat flow method. The relationship between the gasket structure and the thickness was shown by using an equivalent thermal resistance, and an empirical equation of effective thermal conductivity, which was related to the bulk density and absolute temperature, was proposed by deriving the heat conduction in solid, radiation and gas. Also, in the measurement of the linear thermal expansion coefficients of the gaskets, the measured values were shown to change substantially below 150 °C, and to depend on the heating rate and the load applied on the gasket sample.

Influence of Cracked Size of Old Concrete Pavement on Asphalt Overlay Stress

2012 ◽  
Vol 446-449 ◽  
pp. 2405-2411 ◽  
Author(s):  
Yong Hong Wang ◽  
Xiong Jun He ◽  
Hong Sheng Qiu ◽  
Xi Ming Tan
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Thermal Stress ◽  
Concrete Slab ◽  
Relational Theory ◽  
Concrete Pavement ◽  
Base Surface ◽  
Asphalt Overlay ◽  
Paving Asphalt ◽  
Pressure Stress

For the old concrete pavement with large proportion damage, it can be reconstructed by paving asphalt surface after cracked and stabilized with punching technique. But there is great difference in adopting the cracked size of pavement slab in every place and there is no relational theory basis. So the authors use 3-D finite element method to analyze the relationships of cracked size of concrete slab and load stress, thermal stress, coupling stress in asphalt overlay and pressure stress on the base surface. The results show that the influence of cracked size on thermal stress and coupling stress is much greater than load stress. With the decrease of cracked size, the thermal stress and coupling stress in asphalt overlay decrease rapidly, the stress centralization at joints and cracks lessens evidently, while the pressure stress on base surface increases. Considering the factors synthetically, it is reasonable for the cracked size from 80cm to 100cm.

scholarly journals The Thermal Parameters of Mortars Based on Different Cement Type and W/C Ratios

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4258
Author(s):  
Agata Stolarska ◽  
Jarosław Strzałkowski
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Specific Surface ◽  
Surface Area ◽  
Point Of View ◽  
Thermal Parameters ◽  
Cement Type ◽  
Water Absorbability ◽  
The Relationship ◽  
Total Specific Surface Area

This study examines the thermal parameters of mortars based on different cement type and water-cement W/C ratios. The presented relationships are important from the point of view of thermal insulation of the entire building component, of which the mortar is a part. The thermal properties of the mortar, and in particular its dependence on the degree of moisture, is important information from the point of view of hygrothermal simulations of building components. The moisture effect on the thermal properties was tested using nine mortar types. The study consisted of producing nine types of mortar on the basis of three cements (CEM I 42.5R, CEM II A-S 52.5N, CEM III A 42.5N). For each cement type, three variants of specimens were prepared which differed according to their water/cement ratio (0.50, 0.55 and 0.60). The main research of thermal parameters was carried out using a non-stationary method based on the analysis of changing heat flux readings. The thermal conductivity, volume-specific heat and thermal diffusivity values were analyzed. The tests performed allowed for determination of the density of specimens, water absorbability and thermal parameters in three water saturation states: dry, natural and wet. Additional microstructural tests were performed using mercury intrusion porosimetry. The obtained parameters were used to determine the relationship between the measured properties. An adverse effect of dampness on the thermal insulation of the studied materials was confirmed. In extreme cases, the increase in thermal conductivity due to material high moisture was 93%. The cement used affects the relationship between the total specific surface area and the W/C ratio. As expected, the total porosity of specimens was higher for mortars with higher W/C ratios. A strong correlation has been demonstrated between the total surface area and thermal conductivity. The opposite results were obtained when assessing the relationship between the total specific surface area and water absorbability. In case of specimens CEM II A-S 52.5N, the relation was the proportional, and in specimens CEM III A 42.5N, the relationship was inversely proportional to the W/C ratio.

Effect of Refractory᾽s Thermal Conductivity on the Thermal Stress Field of the COREX Gasifier Top

2011 ◽  
Vol 418-420 ◽  
pp. 800-803
Author(s):  
Wen Dong Xue ◽  
Xiao Xiao Huang ◽  
Jing Xie ◽  
Xing Da Cui
Keyword(s):  
Thermal Conductivity ◽  
Thermal Stress ◽  
Stress Field ◽  
Change Rate ◽  
Thermal Stress Field ◽  
The Relationship

The top of COREX-3000 gasifier was numerical simulated and investigated the relationship between thermal conductivity and the thermal-stress field. It is concluded that when the thermal conductivity of the working lining and permanent lining is respectively 0.95W / (m•K) and 0.5 W / (m•K), the change rate of the top stress along radical direction is minimum.

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