Theses and Dissertations from UMD

Permanent URI for this communityhttp://hdl.handle.net/1903/2

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM

More information is available at Theses and Dissertations at University of Maryland Libraries.

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2004 - 200912010 - 20121

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    Damage Detection in Fiber Reinforced Concrete with Ultrasonic Pulse Velocity Testing
    (2012) Hong, Rongjin; Goulias, Dimitrios G; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    In concrete, fatigue and freeze-thaw are associated with the progressive growth of internal microcracks. The Ultrasonic Pulse Velocity (UPV) technique, one of the most widely used Nondestructive Testing (NDT) methods, is promising in evaluating internal microcracks and eventually detecting damage. The primary objective of this research was to determine the effectiveness of using UPV to detect damage development in polypropylene fiber reinforced concrete under fatigue and freeze-thaw conditions. In order to realize this, i) several experiments were conducted on control samples to assess the response and limitations of UPV, and ii) fatigue and freeze-thaw samples were tested with UPV to evaluate its ability to detect crack development. In terms of modeling, three alternative models were examined and presented relating UPV with porosity and damage.
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    Characterization of Pore Structure and Crack Propagation in Concrete Using X-Ray Computed Tomography
    (2004-12-13) Hunter, Opio Konata; Amde, Amde M; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    This thesis utilized the method of computed tomography to quantify the pore structure and the development of cracks in concrete specimens due to delayed ettringite formation. The pore structure is responsible for the passage of harmful substances through the concrete matrix, while delayed ettringite formation causes expansion and internal cracking in concrete structures; particularly in prestressed and precast concrete elements. Computed tomography is a relatively new technique that can be utilized to determine the pore structure and crack propagation in concrete specimens within the mm to micrometer range. The experiment was successful in quantifying the pore structure in the specimens. The pore sizes and total porosity of each specimen were determined along with the pore size distribution on diameter and volume. A comparison was then made with the mercury intrusion porosimetry technique. However, the second objective of analyzing internal cracking due to delayed ettringite formation was not met.