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Investigation of Mechanical Properties and Durability of Alkali-activated Slag Concrete Lightened with Scoria and Its Microstructural Study

Mahmoudzadeh Vaziri, Nima | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54699 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Khaloo, Alireza
  7. Abstract:
  8. Concrete has long been one of the most widely used materials in the world. Cement, as a major component of concrete, due to the use of fossil fuels in its production process, emitting greenhouse gases such as carbon dioxide, which cause air pollution and environmental issues such as climate change. On the other hand, the wastes of industrial factories such as slag of the Blast furnace, due to their large volume and lack of sufficient space for storage of these wastes, lead to the release of these wastes that have alkaline structures into enviroment, causing environmental pollution Such as embankment pollution. Alkali-activated concrete has prevented the release of these pollutant into the environment by removing cement from the concrete structure and also using industrial waste materials as binder. In this research, Grand Granulated Blast slag was used to make Alkali-activated concrete. Various tests such as uniaxial compressive strength, elastic modulus, density, water absorption, ultrasonic pulse velocity, electrical resistance to different parameters such as slag content, sodium hydroxide solution concentration and replacement of conventional aggregates with different percentages of lightweight aggregate, are studied. By replacing lightweight aggregates with conventional aggregates, we saw slight changes in the amount of compressive strength for replacement of 50 and 100, and at the same time, we saw an increase in water absorption for these replacements, respectively. In the next part of this study, the effect of temperature increase parameters of 0, 150, 450 ° C on the tests of compressive strength, density, elastic modulus and ultrasonic wave velocity were investigated. Concrete with ordinary aggregates showed a greater reduction in compressive strength than concretes with Scoria Lightweight Aggregtes infront of incremental heat. Then, in order to verify and more accurately study the structure of Alkali-activated concrete at ambient temperature and at increasing temperature, the microstructure of concrete was examined by scanning electron microscopy, which in the resulting images showed an increase in microcracks both in the geopolymer matrix and in the Interfacial Transition Zone (ITZ). Also, by examining the SEM images, the complete formation of CSH, CASH and NASH gels was observed, which caused more compaction of the concrete structure and also showed the desired geopolymerization process in the process of Alkali-activated concrete
  9. Keywords:
  10. Alkali-Activated Concrete ; Scanning Electron Microscopy (SEM) ; Scoria Lightweigth Aggregate ; Industrial Wastes ; Geopolymer Concrete ; Grand Granulated Blast Slag

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