Modelling the Swelling due to Delayed Ettringite Formation - Application to a Real Bridge

2016 ◽  
Vol 711 ◽  
pp. 722-729
Author(s):  
Othman Omikrine-Metalssi ◽  
Badreddine Kchakech ◽  
Stéphane Lavaud ◽  
Bruno Godart
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Cement Paste ◽  
Early Age ◽  
High Humidity ◽  
Delayed Ettringite Formation ◽  
Precise Control ◽  
Ettringite Formation ◽  
Structural Disorders

Delayed ettringite formation (DEF) can affect the long-term durability of concrete structures by causing cracking and expansion of the material. Consequently, mechanical properties decrease which may cause large structural disorders due to unexpected deformations and additional stresses in concrete and reinforcement. This reaction consists in ettringite crystallization within concrete after hardening is substantially complete, and in which no sulphates come from outside the cement paste. It may occur in materials that have been subjected to temperature above about 65 °C at early age and to high humidity. At this high temperature, the ettringite turns unstable while the concrete is still plastic and forms again after cooling in the hardened material, thus generating swelling due to crystallisation pressure.This article aims to present a new model for the calculation of structures affected by DEF and to study the effect of the prefabrication temperature on the development of this reaction. In this context, the elaborated model was applied to the 3D simulations of a real bridge affected by this phenomenon. The results highlight that the temperature reached in the precast beams of the studied bridge during prefabrication has a significant effect on the displacements and stresses. Therefore, more precise control of the prefabrication temperature has to be applied in order to prevent the swelling and damage to structures.

Polyimide Copolymers Containing Various Levels Of The 6F Moiety For High Temperature And Microelectronic Applications

1991 ◽  
Vol 227 ◽  
Author(s):  
M. Haider ◽  
E. Chenevey ◽  
R. H. Vora ◽  
W. Cooper ◽  
M. Glick ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Electrical Properties ◽  
Oxidative Stability ◽  
Trifluoromethyl Group ◽  
Thermal And Mechanical Properties

ABSTRACTTrifluoromethyl group-containing polyimides not only show extraordinary electrical properties, but they also exhibit excellent long-term thermo-oxidative stability. Among the most thermomechanically stable structural polyimides are those from 6F dianhydride (6FDA) and 6F diamines. The effects of substituting non-fluorine containing monomers such as BTDA, mPDA and 4,4′-DADPS for the hexafluoroisopropylidene monomers on the dielectric, thermo-oxidative, thermal and mechanical properties of the copolymers were studied.

Research on Barite Concrete Mixed with Fly Ash

2013 ◽  
Vol 275-277 ◽  
pp. 2107-2111
Author(s):  
Qiu Lin Zou ◽  
Jun Li ◽  
Zhen Yu Lai
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Compressive Strength ◽  
High Temperature ◽  
Fly Ash ◽  
Apparent Density ◽  
Cycle Times ◽  
Residual Compressive Strength ◽  
Temperature Performance

Barite concrete with density grade of 3 and strength grade of C30 was prepared by mixing with different fineness of fly ash. The workability, mechanical properties and long-term high temperature performance of the prepared barite concrete were researched. Results show that the workability of barite concrete is improved by mixing with fly ash, and no segregation of mixture has been observed. The apparent density and 3d, 28d compressive strength of barite concrete are decreased obviously after mixing with fly ash. But with the increasing of the fineness of fly ash, the apparent density and 3d, 28d compressive strength of barite concrete have a slight increase. High temperature residual compressive strength is decreased with the increasing of temperature. The cycle times of heat treatment at 400°C only has a little effect on residual compressive strength of barite concrete.

scholarly journals Characterization of Titanium Nanotube Reinforced Cementitious Composites: Mechanical Properties, Microstructure, and Hydration

Materials ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1617 ◽  
Author(s):  
Hyeonseok Jee ◽  
Jaeyeon Park ◽  
Erfan Zalnezhad ◽  
Keunhong Jeong ◽  
Seung Min Woo ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Cement Paste ◽  
Cementitious Materials ◽  
Cement Clinker ◽  
Early Age ◽  
Potential Candidate ◽  
Hydration Kinetics ◽  
Cement Pastes ◽  
Viable Solution ◽  
First Time

In recent years, nano-reinforcing technologies for cementitious materials have attracted considerable interest as a viable solution for compensating the poor cracking resistance of these materials. In this study, for the first time, titanium nanotubes (TNTs) were incorporated in cement pastes and their effect on the mechanical properties, microstructure, and early-age hydration kinetics was investigated. Experimental results showed that both compressive (~12%) and flexural strength (~23%) were enhanced with the addition of 0.5 wt.% of TNTs relative to plain cement paste at 28 days of curing. Moreover, it was found that, while TNTs accelerated the hydration kinetics of the pure cement clinker phase (C3S) in the early age of the reaction (within 24 h), there was no significant effect from adding TNTs on the hydration of ordinary Portland cement. TNTs appeared to compress the microstructure by filling the cement paste pore of sizes ranging from 10 to 100 nm. Furthermore, it could be clearly observed that the TNTs bridged the microcracks of cement paste. These results suggested that TNTs could be a great potential candidate since nano-reinforcing agents complement the shortcomings of cementitious materials.

scholarly journals Pore size analyses of cement paste exposed to external sulfate attack and delayed ettringite formation

2019 ◽  
Vol 123 ◽  
pp. 105766 ◽  
Author(s):  
Yushan Gu ◽  
Renaud-Pierre Martin ◽  
Othman Omikrine Metalssi ◽  
Teddy Fen-Chong ◽  
Patrick Dangla
Keyword(s):  
Pore Size ◽  
Cement Paste ◽  
Sulfate Attack ◽  
Delayed Ettringite Formation ◽  
Ettringite Formation

Flip-Chip Ball Grid Array Lead-Free Solder Joint Under Reliability Test

2005 ◽  
Vol 127 (4) ◽  
pp. 446-451 ◽  
Author(s):  
Ming-Hwa R. Jen ◽  
Lee-Cheng Liu ◽  
Jenq-Dah Wu
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Service Time ◽  
Flip Chip ◽  
Failure Modes ◽  
Mechanical Responses ◽  
Operational Life ◽  
Different Temperatures ◽  
Free Solder

The work is aimed to investigate the mechanical responses of bare dies of the combination of pure tin∕Al–NiV–Cu Under bump metallization (UBM) and packages of pure tin∕Al–NiV–Cu UBM/substrate of standard thickness of aurum. The mechanical properties under multiple reflow and long term high temperature storage test (HTST) tests at different temperatures and the operational life were obtained. A scanning electron microscope was used to observe the growth of IMC and the failure modes in order to realize their reaction and connection. From the empirical results of bare dies, the delamination between IMC and die was observed due to the tests at 260 °C multiple reflow. However, their mechanical properties were not affected. Nevertheless, the bump shear strength of bare dies were decreased by HTST tests. In package, all the results of mechanical properties by multiple reflow test and HTST test were significantly lowered. It was shown that the adhesion between bump and die reduced obviously as tests going on. As for high temperature operational life test in the conditions of 150 °C and 320 mA (5040A∕cm2), the average stable service time of the package was 892 h, and the average ultimate service time of the package was 1053 h.

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