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Effect of Compressive Loading on Transport Properties of Cement-Based Materials
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- Author / Creator
- Hoseini,Meghdad
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The durability of concrete is one of its most important properties and has been an attractive subject for research in recent years. One of the criteria that affect concrete durability is permeability. Transport processes in concrete have been investigated for several decades. However, the correlation between transport coefficients and applied stress has received only little attention. On the other hand, measuring permeability involves a time-consuming test, with attendant concerns about system equilibrium and load control. Non Destructive Testing (NDT) of concrete makes it possible to obtain many test results from a single specimen and thus gives the opportunity to follow the changes in the properties of the specimen with time and under external influences. The scope of this study encompasses two major points of research focus. The first involves developing an experimental model for relating the permeability of cement-based materials under stress through non-destructive means, by measuring the Ultrasonic Pulse Velocity. The second part of this study examines the change in microstructure in cement-based materials under stress by employing x-ray tomography. A new parameter, pore connectivity, is introduced and was found to relate better to the permeability and damage caused by compressive stress. In all cases, the effect of fibre inclusion in mix designs is examined.
The results show that both permeability and ultrasonic pulse velocity are stress-dependent and there is a correlation between the change of permeability and ultrasonic pulse velocity in cement-based materials under stress. The proposed permeability-UPV model has shown to have a good accuracy in predicting the permeability of concrete via a Non-Destructive Test method.
On the other hand, the presented method for determining the pore connectivity of cement-based materials, has shown a good agreement with the permeability results (which also depend on the interconnectivity of the voids and pores). This study showed that more than the creation of new voids, it is the forging of connectivity between existing pores and microcracks that leads to increases in permeability. Moreover, by introducing a damage value parameter, the onset of damage was found to occur around the same stress level that the sharp increase in permeability, UPV and pore connectivity happen. These findings support a design approach which limits service load stresses to 60% of peak capacity. The defined damage value parameter was also found to be a good criterion for examining the concrete structures under service conditions. -
- Graduation date
- Spring 2013
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.