scholarly journals Hydration Heat of Nonshrinkage Concrete in Large-Diameter CFST Arch Ribs Cured at Low Temperatures

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Tuo Shi ◽  
Nianchun Deng ◽  
Dong Pan ◽  
Shi Wang
Keyword(s):  
Temperature Field ◽  
Low Temperature ◽  
Low Temperatures ◽  
Research Method ◽  
Large Diameter ◽  
Hydration Heat ◽  
Experimental Results ◽  
Element Simulation ◽  
Temperature Environment ◽  
Arch Bridges

To study the construction of concrete-filled steel tubular (CFST) arch bridges in Tibet, China, the hydration-temperature field of nonshrinkage concrete in large-diameter CFST arch ribs was evaluated in a temperature-testing box to simulate a low-temperature environment. A finite element simulation was then conducted to replicate the experimental results. Finally, an improved formula with the parameters related to the diameter, the position, and the retarding time of concrete for predicting the hydration heat generated by non-shrinkage concrete in large-diameter CFST arch ribs cured at low temperatures was proposed. The formula results were shown to be consistent with the experimental results for low-temperature conditions and large diameters. This research method can be extended to predict the hydration heat at all locations in different-diameter CFSTs with different concrete mixes cured at various temperatures.

scholarly journals Experimental Study on Deformation Behavior and Compressive Strength of Concrete Cast in Steel Tube Arches under Low-Temperature Conditions

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Tuo Shi ◽  
Nianchun Deng ◽  
Xiao Guo ◽  
Wen Xu ◽  
Shi Wang
Keyword(s):  
Compressive Strength ◽  
Low Temperature ◽  
Performance Test ◽  
Large Diameter ◽  
Test Site ◽  
Steel Tube ◽  
Design Strength ◽  
Curing Conditions ◽  
Expansive Agent ◽  
Arch Bridges

Taking the construction of a concrete-filled steel tube (CFST) arch bridge (part of the Sichuan-Tibet Railway) in low temperatures as the test site, firstly the deformation performance test of concrete was carried out. Following this initial testing, measurement of compressive strength and shrinkage performance was conducted in large-diameter CFSTs under a variety of curing conditions. Experimental results showed that the expansion effect of Ca-Mg composite expansive agent in concrete was better than that of other expansive agents at any stage. Under low-temperature curing (0°C), the sampling strength of the large-diameter CFSTs reached 73.5% of the design strength at 28 d in the presence of a nonthermal curing system. The design strength itself was reached, when a curing system involving a thermal insulation film was applied, and use of this film also led to improvements in concrete shrinkage. The results suggested that a Ca-Mg composite expansive agent, combined with an insulation film curing system, should be the technique selected for concrete pumping construction of CFST arch bridges in Tibet.

Magnon drag and the low temperature thermopower of GeMnTe

1978 ◽  
Vol 56 (5) ◽  
pp. 497-500
Author(s):  
A. Cafaro ◽  
F. T. Hedgcock ◽  
W. B. Muir
Keyword(s):  
Low Temperature ◽  
Experimental Evidence ◽  
Thermoelectric Power ◽  
Low Temperatures ◽  
Impurity Scattering ◽  
Experimental Results ◽  
Phonon Drag ◽  
Degenerate Semiconductors ◽  
Upper Limit

The thermoelectric power of pure GeTe and GeMnTe containing 1 and 5at.% Mn has been measured between 25 and 2.5 K. The manganese doped Ge–Te alloys ferromagnetically order at low temperatures and theoretical estimates of the magnon drag contribution to the thermopower in these degenerate semiconductors is 60 μV/K. When appropriate allowance is made for the effects of impurity scattering on the phonon drag thermopower there appears to be no experimental evidence for a magnon drag contribution to the thermopower of this magnitude. An upper limit for the magnon drag contribution to the thermopower estimated from the experimental results for these materials is 0.5 μV/K.

scholarly journals Low Temperature Experiments on Gas-Phase Chemical Processes

2000 ◽  
Vol 197 ◽  
pp. 237-250 ◽  
Author(s):  
B. R. Rowe ◽  
C. Rebrion Rowe ◽  
A. Canosa
Keyword(s):  
Low Temperature ◽  
Reaction Kinetics ◽  
Gas Phase ◽  
Low Temperatures ◽  
Chemical Processes ◽  
Experimental Results ◽  
Phase Chemical

A review of the most recent experimental results concerning reaction kinetics at low temperatures is presented, most of them having been obtained using the CRESU technique. Some astrochemical consequences are also highlighted.

Experimental Research on Hydration Heat Temperature of Concrete Box Girder in Low-Temperature Environment

2013 ◽  
Vol 470 ◽  
pp. 1045-1050
Author(s):  
Wei Gang Sun ◽  
Lai Jun Liu ◽  
Qun Hu Wu ◽  
Jian Ping Feng
Keyword(s):  
Low Temperature ◽  
Cross Section ◽  
Hydration Heat ◽  
Early Age ◽  
Box Girder ◽  
Heat Temperature ◽  
Cracking Control ◽  
Concrete Temperature ◽  
Temperature Environment ◽  
Concrete Box Girder

The temperature stress is one of the main reasons for early age cracking of concrete under low temperatures,it has the actual value of reference for the design and construction of concrete structures to study the regularities of hydration heat temperature of concrete box girder in low-temperature environment. Therefore, through the test of concrete box girder hydration heat temperature, this paper analyses the temp-time curves of temperature of the concrete box-bridge cross section. The results can be used for concrete temperature control and/or cracking control of box girder in similar environmental area.

An Experimental Study on the Heat Transfer of Traveling Airborne Water Droplets in Cold Environment

2015 ◽  
Vol 32 (2) ◽  
pp. 219-225 ◽  
Author(s):  
Y.-K. Chuah ◽  
J.-T. Lin ◽  
K.-H. Yu
Keyword(s):  
Heat Transfer ◽  
Low Temperature ◽  
Size Distribution ◽  
Droplet Size ◽  
Heat Balance ◽  
Droplet Size Distribution ◽  
Experimental Results ◽  
Rapid Freezing ◽  
Water Droplets ◽  
Temperature Environment

AbstractThis paper presents experimental results on rapid freezing of water droplets injected into a low temperature environment. A heat balance method was applied to determine the ratio of the water droplets frozen at the collection after the airborne time. The experimental results show that rapid freezing of water droplets could be achieved within three seconds of airborne time. Droplet size distribution of the frozen water droplets after collection was estimated. Heat transfer during the airborne time was calculated with consideration of the droplet size distribution. At attempt was taken to compare the heat transfer obtained with some previous studies on heat transfer of spherical objects in air. The research results show that droplet size distribution is important for the prediction of heat transfer of water droplets traveling in air. The results presented in this study contribute to the understanding of heat transfer of water droplets injected into a low temperature air.

Damage of Basement and Foundation under Low-Temperature Environment and its Analysis

2014 ◽  
Vol 578-579 ◽  
pp. 1233-1239
Author(s):  
Guang Yi Liu ◽  
Qi Wang ◽  
Hong Xing Wang
Keyword(s):  
Low Temperature ◽  
Low Temperatures ◽  
Building Structures ◽  
Frost Heaving ◽  
Protective Measures ◽  
Cold Regions ◽  
Foundation Slab ◽  
Building Element ◽  
Temperature Environment ◽  
Punching Failure

Due to inappropriate protective measures during construction, building structures in cold regions can easily suffer from frost heaving damage during the wintering period. Such damage is relatively invisible and can hardly be detected. According to the actual engineering conditions, this paper comprehensively analyzes the destructional form of each building element at low temperatures as well as discusses the methods to detect and evaluate damage of buildings at low temperatures. The author finds that: Under low-temperature environment, punching failure often occurs between the foundation slab and bearing platform and the anchor connection between the pile and bearing platform can easily become ineffective.

In situ Tensile Experiments at Low Temperatures on Niobium Single Crystals by H.V.E.M.

1975 ◽  
Vol 33 ◽  
pp. 58-59
Author(s):  
F. H. Louchet ◽  
L. P. Kubin
Keyword(s):  
Electron Microscope ◽  
Transition Temperature ◽  
Low Temperature ◽  
Slip System ◽  
Low Temperatures ◽  
Tensile Axis ◽  
Image Intensifier ◽  
Screw Dislocations ◽  
Source Operation

Experiments have been carried out on the 3 MeV electron microscope in Toulouse. The low temperature straining holder has been previously described Images given by an image intensifier are recorded on magnetic tape.The microtensile niobium samples are cut in a plane with the two operative slip directions [111] and lying in the foil plane. The tensile axis is near [011].Our results concern:- The transition temperature of niobium near 220 K: at this temperature and below an increasing difference appears between the mobilities of the screw and edge portions of dislocations loops. Source operation and interactions between screw dislocations of different slip system have been recorded.

Multiple-fracturing and viewing of the same frozen sample at different depths using a low temperature FESEM

1996 ◽  
Vol 54 ◽  
pp. 820-821
Author(s):  
M.V. Parthasarathy ◽  
C. Daugherty
Keyword(s):  
Temperature Field ◽  
Low Temperature ◽  
Field Emission ◽  
Multiple Fracture ◽  
Precise Control ◽  
Cold Stage ◽  
Different Depths ◽  
Transfer Device

The versatility of Low Temperature Field Emission SEM (LTFESEM) for viewing frozen-hydrated biological specimens, and the high resolutions that can be obtained with such instruments have been well documented. Studies done with LTFESEM have been usually limited to the viewing of small organisms, organs, cells, and organelles, or viewing such specimens after fracturing them.We use a Hitachi 4500 FESEM equipped with a recently developed BAL-TEC SCE 020 cryopreparation/transfer device for our LTFESEM studies. The SCE 020 is similar in design to the older SCU 020 except that instead of having a dedicated stage, the SCE 020 has a detachable cold stage that mounts on to the FESEM stage when needed. Since the SCE 020 has a precisely controlled lock manipulator for transferring the specimen table from the cryopreparation chamber to the cold stage in the FESEM, and also has a motor driven microtome for precise control of specimen fracture, we have explored the feasibility of using the LTFESEM for multiple-fracture studies of the same sample.

INVAR M93

Alloy Digest ◽  
2008 ◽  
Vol 57 (1) ◽  
Keyword(s):  
Fracture Toughness ◽  
Low Temperature ◽  
Physical Properties ◽  
Tensile Properties ◽  
Low Temperatures ◽  
Bend Strength ◽  
Temperature Performance ◽  
Ni Content ◽  
Precision Alloys ◽  
Ni Alloy

Abstract Invar is an Fe-Ni alloy with 36% Ni content that exhibits the lowest expansion of known metals from very low temperatures up to approximately 230 deg C (445 deg F). Invar M93 is a cryogenic Invar with improved weldability. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and shear and bend strength as well as fracture toughness and fatigue. It also includes information on low temperature performance as well as forming and joining. Filing Code: FE-143. Producer or source: Metalimphy Precision Alloys.

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