Factors affecting the resistance of cementitious materials at high temperatures and medium heating rates

10.1617/14330 ◽  
2005 ◽  
pp. 0-0
Author(s):  
D. Matesova
Keyword(s):  
High Temperatures ◽  
Cementitious Materials ◽  
Heating Rates ◽  
Factors Affecting

Effect of High Temperatures and Heating Rates on High Strength Concrete for Use as Thermal Energy Storage

2010 ◽  
Author(s):  
Emerson E. John ◽  
W. Micah Hale ◽  
R. Panneer Selvam
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Molten Salt ◽  
High Temperatures ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Heat Transfer Fluid ◽  
Heating Rates ◽  
Storage Media ◽  
Concrete Mixtures

In recent years due to rising energy costs as well as an increased interest in the reduction of greenhouse gas emissions, there is great interest in developing alternative sources of energy. One of the most viable alternative energy resources is solar energy. Concentrating solar power (CSP) technologies have been identified as an option for meeting utility needs in the U.S. Southwest. Areas where CSP technologies can be improved are improved heat transfer fluid (HTF) and improved methods of thermal energy storage (TES). One viable option for TES storage media is concrete. The material costs of concrete can be very inexpensive and the costs/ kWhthermal, which is based on the operating temperature, are reported to be approximately $1. Researchers using concrete as a TES storage media have achieved maximum operating temperatures of 400°C. However, there are concerns for using concrete as the TES medium, and these concerns center on the effects and the limitations that the high temperatures may have on the concrete. As the concrete temperature increases, decomposition of the calcium hydroxide (CH) occurs at 500°C, and there is significant strength loss due to degeneration of the calcium silicate hydrates (C-S-H). Additionally concrete exposed to high temperatures has a propensity to spall explosively. This proposed paper examines the effect of heating rates on high performance concrete mixtures. Concrete mixtures with water to cementitious material ratios (w/cm) of 0.15 to 0.30 and compressive strengths of up to 180 MPa (26 ksi) were cast and subjected to heating rates of 3, 5, 7, and 9° C/min. These concrete mixtures are to be used in tests modules where molten salt is used as the heat transfer fluid. Molten salt becomes liquid at temperatures exceeding 220°C and therefore the concrete will be exposed to high initial temperatures and subsequently at controlled heating rates up to desired operating temperatures. Preliminary results consistently show that concrete mixtures without polypropylene fibres (PP) cannot resist temperatures beyond 500° C, regardless of the heating rate employed. These mixtures spall at higher temperatures when heated at a faster rate (7° C/min). Additionally, mixtures which incorporate PP fibres can withstand temperatures up to 600° C without spalling irrespective of the heating rate.

scholarly journals Effects of Heating Rate on Formation of Globular and Acicular Austenite during Reversion from Martensite

Metals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 266 ◽  
Author(s):  
Xianguang Zhang ◽  
Goro Miyamoto ◽  
Yuki Toji ◽  
Tadashi Furuhara
Keyword(s):  
Heating Rate ◽  
High Temperatures ◽  
The Other ◽  
Growth Mode ◽  
High Heating Rate ◽  
Heating Rates ◽  
Other Hand ◽  
High Heating ◽  
Martensite Matrix

The effects of heating rate on the formation of acicular and globular austenite during reversion from martensite in Fe–2Mn–1.5Si–0.3C alloy have been investigated. It was found that a low heating rate enhanced the formation of acicular austenite, while a high heating rate favored the formation of globular austenite. The growth of acicular γ was accompanied by the partitioning of Mn and Si, while the growth of globular γ was partitionless. DICTRA simulation revealed that there was a transition in growth mode from partitioning to partitionless for the globular austenite with an increase in temperature at high heating rate. High heating rates promoted a reversion that occurred at high temperatures, which made the partitionless growth of globular austenite occur more easily. On the other hand, the severer Mn enrichment into austenite at low heating rate caused Mn depletion in the martensite matrix, which decelerated the reversion kinetics in the later stage and suppressed the formation of globular austenite.

scholarly journals Foaming Behavior and Pore Structure Evolution of Foamed Aluminum under the Extrusion Constraint

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Lucai Wang ◽  
Yanli Wang ◽  
Xiaohong You ◽  
Fang Wang
Keyword(s):  
Pore Structure ◽  
Aluminum Foam ◽  
Melting Behavior ◽  
Heating Time ◽  
Structure Evolution ◽  
Heating Rates ◽  
Cross Sectional ◽  
Factors Affecting ◽  
Maximum Expansion ◽  
Foaming Behavior

This study evaluates foaming behavior and pore structure evolution of aluminum foam by cross-sectional image processing, which was prepared by the powder compact melting (PCM) method under the constraint. The results revealed that the heating time and the heating rate are the key factors affecting the foaming behavior and pore structure of aluminum foam. The thermal decomposition of the foaming agent and aluminum melting behavior affect the foam expansion under different heating times and heating rates. The evolution of the pore structure during the foaming process includes pore formation, small-sized spherical pores, large-sized spherical pores, polygonal pores, merging, and collapse. Due to the limitation of the pipe wall, the maximum expansion height and porosity are constrained, and the macrostructure of aluminum foam is improved.

Effect of Polyurethane Viscosity on Self-Healing Efficiency of Cementitious Materials Exposed to High Temperatures from Sun Radiation

2018 ◽  
Vol 30 (7) ◽  
pp. 04018145 ◽  
Author(s):  
B. Van Belleghem ◽  
E. Gruyaert ◽  
K. Van Tittelboom ◽  
W. Moerman ◽  
B. Dekeyser ◽  
...  
Keyword(s):  
High Temperatures ◽  
Cementitious Materials ◽  
Self Healing ◽  
Healing Efficiency

Towards a generic approach to durability: Factors affecting chloride transport in binary and ternary cementitious materials

2019 ◽  
Vol 124 ◽  
pp. 105783 ◽  
Author(s):  
Shiyu Sui ◽  
Fabien Georget ◽  
Hamed Maraghechi ◽  
Wei Sun ◽  
Karen Scrivener
Keyword(s):  
Chloride Transport ◽  
Cementitious Materials ◽  
Factors Affecting
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