Combine technique of conducting materials testing at high pressures

Spalling in Continuously Reinforced Concrete Pavement in Texas

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198120948509 ◽

2020 ◽

Vol 2674 (11) ◽

pp. 731-740

Author(s):

Pangil Choi ◽

Lochana Poudyal ◽

Fouzieh Rouzmehr ◽

Moon Won

Keyword(s):

Finite Element ◽

Reinforced Concrete ◽

Coefficient Of Thermal Expansion ◽

Field Testing ◽

Concrete Pavement ◽

Materials Testing ◽

Finite Element Program ◽

Texas Department ◽

Conducting Materials ◽

Element Program

The performance of continuously reinforced concrete pavement (CRCP) in Texas has been quite satisfactory, primarily thanks to the continuous improvements in design and construction. However, severe spalling has been a major problem, and the Texas Department of Transportation (TxDOT) has sponsored several research projects since 1985 to identify solutions for this serious problem. Even though the research efforts were successful in identifying spalling mechanisms, developing a policy that TxDOT could easily implement has been a challenge. To develop a more practical solution to this problem, TxDOT initiated a research study, and the research efforts consisting of identifying CRCP projects with severe and no spalling, obtaining and conducting materials testing on concrete cores from those projects, analyzing the testing data, and performing theoretical analyses to validate the testing results. Among the material properties evaluated, the coefficient of thermal expansion (CTE) of concrete proved to have the best correlation with spalling. Detailed analyses of mechanistic behavior of concrete conducted with an object-oriented finite element program (OOF2) and commercial finite element program verified the reasonableness of the field-testing results. All concrete cores from CRCP with severe spalling had a CTE larger than 5.5 microstrains/°F, whereas no spalling was observed in concrete with a CTE less than that value. Based on this finding, TxDOT now requires the use of coarse aggregate that will produce concrete with a CTE of less than 5.5 microstrains/°F for CRCP construction. It is expected that this implementation will reduce the spalling in CRCP substantially.

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Flexible Pipes Subjected to SCC CO2: Review and Means to Increase Reliability on Service Life Applied to Brazilian Pre-Salt Fields

10.4043/31135-ms ◽

2021 ◽

Author(s):

Mauricio Brandao ◽

Fabio Pires ◽

Ingrid Poloponsky ◽

Fabio Santos ◽

Diogo Lopes

Keyword(s):

Fracture Mechanics ◽

Service Life ◽

Failure Mode ◽

High Pressures ◽

Small Scale ◽

Materials Testing ◽

Metallic Material ◽

Remaining Service Life ◽

Flexible Pipes ◽

High Concentrations

Abstract Flexible Pipes were widely used in Brazil offshore developments and the challenge on overcoming increasing water depths, high pressures and fluids with high contaminants was always present. In 2017 a new failure mode, called SCC CO2 was disclosed bringing such disruption in the use of this equipment since, at that time, the conditions observed in Brazilian Pre salt were like the "perfect storm" for the failure mode to happen. It had high concentrations of CO2, therefore high permeation in the anulus, high stresses and the possibility to have anulus flooded as result of an outer sheath breach or even due to permeated water. These were the triple conditions needed to have the failure, considering that all metallic material used in the pipe were subjected to this phenomenon. Since the discovery was made, several test campaigns to better understand and replicate the phenomena started. They covered pipe retrieved from field dissection, several small-scale materials testing, and fracture mechanics to create reliable crack propagation calculations. There were 3 mains focus areas; to understand how to deal with the installed fleet, to define the conditions in which a crack would appear and define, using fracture mechanics, how long a crack would take to break the wire. In other words, it was intended to define what is the remaining service life. As a result of this investigation some initial beliefs like that all materials were subjected to the phenomena and that a solution was far away were somehow reduced and reshaped. There was also the initiative to embark on technology for detection of the anulus condition, mainly to define if it is flooded or not. Some ROV inspection means were added to the endfitting and some sensors were added to the interconnected pipe sections that allow conditioning monitoring or inspection from the floating unit, not using a ROV. This paper will cover the improvements done since the disclosure of the phenomena in 2017, reviewing what is known about it so far, what is still to be discovered and how the results achieved to date can contribute for a more reliable and longer service life for the flexible pipes to be applied in a rich CO2 environment.

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Low-voltage field-emission SEM of polymeric membranes for glucose biosensors

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100161862 ◽

1990 ◽

Vol 48 (3) ◽

pp. 860-861

Author(s):

Lorna K. Mayo ◽

Kenneth C. Moore ◽

Mark A. Arnold

Keyword(s):

Glucose Sensor ◽

Low Voltage ◽

Glucose Sensors ◽

Polymeric Membranes ◽

Artificial Endocrine Pancreas ◽

Self Monitoring ◽

Conducting Materials ◽

Insulin Dependent ◽

Living Tissues ◽

Voltage Scanning

An implantable artificial endocrine pancreas consisting of a glucose sensor and a closed-loop insulin delivery system could potentially replace the need for glucose self-monitoring and regulation among insulin dependent diabetics. Achieving such a break through largely depends on the development of an appropriate, biocompatible membrane for the sensor. Biocompatibility is crucial since changes in the glucose sensors membrane resulting from attack by orinter action with living tissues can interfere with sensor reliability and accuracy. If such interactions can be understood, however, compensations can be made for their effects. Current polymer technology offers several possible membranes that meet the unique chemical dynamics required of a glucose sensor. Two of the most promising polymer membranes are polytetrafluoroethylene (PTFE) and silicone (Si). Low-voltage scanning electron microscopy, which is an excellent technique for characterizing a variety of polymeric and non-conducting materials, 27 was applied to the examination of experimental sensor membranes.

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