Development of construction and demolition waste-based engineered geopolymer composites with self-healing capability

2021-9
Ulugöl, Hüseyin
Construction and demolition waste (CDW) has been a popular alternative to mainstream precursors (fly-ash, slag, metakaolin, etc.) for geopolymerization. Its chemical content also has a promising future for self-healing behavior, which is strikingly important for sustainability. Engineered Geopolymer Composites (EGCs) meet one of the important requirements of self-healing with its limited crack width. In this thesis study, CDW-based materials were evaluated in the context of both geopolymer production and EGC development. Besides, the self-healing performance of EGCs has also been assessed. The first stage of this study was the development of the geopolymer paste with a single CDW content. Thus, the usability of each CDW material in geopolymer production was determined. After determining the optimum conditions for CDW-based materials, geopolymer pastes with multi CDW based materials were developed as the second stage of this dissertation study. In the third stage, concrete waste was also utilized as recycled concrete aggregate in the production of geopolymer mortar. In the last part of the study, EGCs with fiber addition were developed. Optimum fiber content was set to obtain a deflection hardening behavior. Preloading EGCs were exposed to wetting-drying cycles to perform a self-healing process in laboratory conditions. Electrical impedance and water absorption measurements and optical observations were used to assess the selfhealing process. In addition, mechanical recoveries were determined at the end of the healing period. Optical observations and microstructural investigations were carried out to justify the findings. All results showed that EGCs generated with CDW-based materials have the capability of self-healing. Optical observations and microstructural investigations exhibit that many cracks were filled with CaCO3, Na2CO3 and geopolymerization reaction products. Line mapping analyses show that recycled concrete aggregate can participate in geopolymerization reactions and relatively higher interfacial transition zone characteristics can be obtained. According to the water absorption results, the pore volume of geopolymers may be increased with raising maturity, unlike cementitious systems. On the other hand, it was also found out that parameters that raise the rate of early geopolymerization may limit the self-healing performance.

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Citation Formats
H. Ulugöl, “Development of construction and demolition waste-based engineered geopolymer composites with self-healing capability,” Ph.D. - Doctoral Program, Middle East Technical University, 2021.