Influence Of Self Healıng On The Mechanıcal Propertıes Of Geopolymer Bınder Composıtes
Özet
Engineered geopolymer composites (EGC), is emerged through a combination of the geopolymer material developed as an alternative to Portland cement (PC), whose usage is increasing day by day with the growing population around the world and which is responsible for 8% of human-induced carbon dioxide (CO2) emission, together with the engineered cementitious composite (ECC) technology that is hundreds of times more ductile than conventional concrete by exhibiting strain hardening response and multiple micro-crack formation. As the rate of usage of Portland cement increases with each day, the harm to the environment also increases. For this reason, new generation environmentally friendly materials developed as an alternative to PC, obtained by activating aluminosilicate-based industrial by-products such as fly ash and metakaolin, with alkaline solutions are called geopolymers. Although the geopolymer material stands out with its high strength, thermal resistance, and environmental friendliness, it is a brittle material by nature, just like concrete. For this reason, the ductility problem must be eliminated to ensure the applicability of the geopolymer material, which is currently not very suitable for large-scale field applications. In addition, ECC, which can able to make high levels of deflection thanks to its micro-mechanical based design approach, has been used for years in dams, bridge-deck slabs, and large-scale field applications with various special requirements through its high strength and durability features and its applicability have been proven. For this reason, it is very important to develop engineered geopolymer composites due to the sustainability, protection of natural resources, and to meet the requirement for high strength and durability with the developing industry and technology.
Construction demolition wastes (CDW) is one of the growing problems with the effect of the increasing population worldwide. Construction demolition wastes that emerged with the development of infrastructural systems, urban transformation, construction/demolition, and repair processes, constitute a serious problem due to the storage, pollution of natural resources, mixing with lean drinking water and soil. Therefore, rational solutions are required to eliminate this problem. In this thesis study, it is planned to recycle and reuse of CDW, which constitutes the majority of the wastes currently available worldwide, with the geopolymerization technique. Since it is an aluminosilicate source and easy to obtain, it is thought that CDWs are very suitable for geopolymerization.
Cracks may occur in concrete due to infrastructure problems, difficulties in applications, and harsh environmental factors, and sometimes the properties of the material cannot be recovered as these cracks negatively affect both strength and durability. In this case, it is necessary to intervene as quickly as possible and begin the maintenance and repair processes. However, traditional maintenance and repair processes do not eliminate the problems, and in some cases, no maintenance and repair can be made due to structural constraints. Fast repair mortars and other repair materials produced by the developing technology also cause the result to be ineffective in terms of the high cost. For this reason, the self-repairing of the material without any external intervention eliminates cost/labor and increases the service life of the material. Although self-healing is observed in almost all types of Portland cement, it becomes very effective with the ECC material that can form multiple micro-cracks. Thanks to the researches in the literature, the effect of self-healing on the properties of concrete has been proven. However, a comprehensive study has not been performed in geopolymer systems yet, and therefore the functioning of the self-healing mechanism in geopolymer material is not fully known.
The main purpose of this master's thesis study is to produce environmentally friendly engineered geopolymer composites that are obtained from 100% construction demolition wastes, exhibit high mechanical performance, can make high deflection by demonstrating strain hardening, can create multiple micro-crack damages, and to examine the effects of the self-healing behavior that have not found a chance to be studied much in the literature, on the mechanical properties of engineered geopolymer composites. To examine the composite development and autogenous self-healing behavior, which are the main points of the thesis, it is aimed to investigate the microstructure of the composites obtained by chemical analysis such as SEM-EDX, XRD, and FTIR, as well as comprehensive laboratory studies.
