Doctor of Philosophy (PhD)
Engineering Science (Interdepartmental Program)
Durability of reinforced concrete structures depends highly on the integrity of the concrete which protects the structure from the environment. However, concrete is a brittle material and as such it is prone to cracking which allows for detrimental agents to penetrate the structure and produce early deterioration. Embedding microcapsules with chemical healing agents in concrete materials for self-healing applications as well as implementing SMAs as reinforcement of concrete structures for self-closing of cracks are both state-of-the-art techniques with enormous potential for enhancement of concrete infrastructure durability. In this work, both techniques are combined as an alternative for superior self-healing of cracks in concrete materials to prevent early deterioration of structures. The objective of this study was to evaluate the mechanism and effectiveness of microcapsules with encapsulated calcium nitrate on self-healing of unreinforced and reinforced (Steel and SMA) cement mortar. To fulfill this objective, short term healing efficiency (up to 28 days) of unreinforced and reinforced (Steel and SMA) mortar beam specimens with calcium nitrate containing microcapsules were evaluated under different environmental conditions (dry, water submerged, and wet and dry cycles) at different microcapsule dosages. Specimens were cracked by three-point bending test and evaluated during the healing period by light microscopy and Ultrasonic Pulse Velocity (UPV) test. Cracks analyzed ranged from 13 to 387 μm. Water submerged healing conditions yielded the best self-healing results followed by wet and dry cycles. Dry healing conditions did not enable appreciable healing, thereby suggesting the need of external moisture conditions for proper functioning of the self-healing mechanism proposed. Moreover, SMA reinforced specimens (with and without microcapsules) presented an enhanced healing performance at early stages of the healing process likely due to the self-closing effect. Furthermore, the general tendency of healing results suggested that the combination of microcapsules and SMA favored self-healing. Lastly, the healing products generated in cracks were investigated under ESEM-EDS to assess their chemical nature. The overwhelming majority of healing products were identified as likely calcium carbonate in the form of calcite crystals, and a limited quantity of gel-like healing products of possibly CSH chemical nature were also identified.
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Arce Amador, Gabriel Andres, "Healing Mechanism Investigation of Self-Healing Concrete by Microencapsulated Calcium Nitrate" (2017). LSU Doctoral Dissertations. 4311.
Available for download on Saturday, February 23, 2019