Properties of interfacial transition zones in recycled aggregate/ waste glass concrete and its influence on the mechanical properties under complicated stress states

Zhao, Hanbing

Properties of interfacial transition zones in recycled aggregate/ waste glass concrete and its influence on the mechanical properties under complicated stress states

Zhao, Hanbing

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Publication Type:: Thesis
Issue Date:: 2024

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Field	Value	Language
dc.contributor.author	Zhao, Hanbing
dc.date.accessioned	2024-06-19T01:03:48Z
dc.date.available	2024-06-19T01:03:48Z
dc.date.issued	2024
dc.identifier.uri	http://hdl.handle.net/10453/179563
dc.description	University of Technology Sydney. Faculty of Engineering and Information Technology.	en_US.UTF-8
dc.description.abstract	To alleviate the burden on natural resources, waste concrete and glass are recycled as aggregate in concrete production. The performance of concrete with recycled aggregate is normally lower than the concrete with natural aggregate. Due to the high content of amorphous silicon and alkali metal oxides in waste glass, alkali-silica reaction (ASR) is prone to occur when waste glass is recycled as aggregate in concrete. If the waste glass is further ground to powder and used to replace cement, the ASR expansion will be greatly weakened, and the glass powder possesses pozzolanic activity, which can improve the performance of concrete. This study fully explored the influence of old mortar, glass particles and glass powder on the cohesion strength of the interfacial transition zones (ITZs) from micro-levels. The ITZ is considered to be the weakest area in concrete, and it is the key to explaining the mechanism of concrete mechanical properties and water permeability. Therefore, a variety of testing techniques were used to evaluated the microstructure, chemical composition distribution and micromechanical properties of ITZs in recycled aggregate concrete (RAC). Meanwhile, the role of glass powder and glass particles in the ITZ and adjacent matrix was also investigated. The study reveals that the new ITZ between the old and new mortars in the RAC has the largest ITZ width. Within 28 days, the microstructure and micromechanical properties of the new ITZ were weaker than those of the old ITZ bonded to natural coarse aggregate (NCA). However, as time goes by, when the curing time reached one year, the incompletely reacted cement particles in the old mortar continued to hydrate, which contributed to strengthen the bond strength between the new and old cement paste. In addition, the pozzolanic effect of glass powder can effectively improve the bonding performance between cement paste, NCA and old mortar. For the study of macroscopic mechanical properties, concrete cylindrical specimens containing recycled coarse aggregate (RCA) and recycled glass sand (RGS) were fabricated. RCA was used to replace NCA, and RGS was used to replace natural fine aggregate (NFA), with replacement ratio of 0%, 50% and 100%. The stress-strain curves of concrete samples under confining pressure and pore water pressure were measured. The results show that the pore water pressure accelerates the expansion of micro-cracks in the concrete specimens. On the other hand, the supporting effect of pore water pressure improved the resistance to compressive deformation of concrete specimens.	en_US.UTF-8
dc.format	Thesis (PhD)
dc.language.iso	en_US	en_US.UTF-8
dc.relation	https://opus.lib.uts.edu.au/bitstream/10453/179563/1/thesis.pdf
dc.rights	info:eu-repo/semantics/openAccess
dc.rights	The author owns the copyright in this thesis including all reproduction and reuse rights for the work. The work may not be altered without the permission of the copyright owner. Attribution is essential when quoting or paraphrasing from this thesis.
dc.rights	© 2024 Hanbing Zhao
dc.rights	au.edu.uts.lib/nph
dc.title	Properties of interfacial transition zones in recycled aggregate/ waste glass concrete and its influence on the mechanical properties under complicated stress states	en_US.UTF-8
dc.type	Thesis
utslib.copyright.status	open_access	*

Abstract:

To alleviate the burden on natural resources, waste concrete and glass are recycled as aggregate in concrete production. The performance of concrete with recycled aggregate is normally lower than the concrete with natural aggregate. Due to the high content of amorphous silicon and alkali metal oxides in waste glass, alkali-silica reaction (ASR) is prone to occur when waste glass is recycled as aggregate in concrete. If the waste glass is further ground to powder and used to replace cement, the ASR expansion will be greatly weakened, and the glass powder possesses pozzolanic activity, which can improve the performance of concrete. This study fully explored the influence of old mortar, glass particles and glass powder on the cohesion strength of the interfacial transition zones (ITZs) from micro-levels. The ITZ is considered to be the weakest area in concrete, and it is the key to explaining the mechanism of concrete mechanical properties and water permeability. Therefore, a variety of testing techniques were used to evaluated the microstructure, chemical composition distribution and micromechanical properties of ITZs in recycled aggregate concrete (RAC). Meanwhile, the role of glass powder and glass particles in the ITZ and adjacent matrix was also investigated. The study reveals that the new ITZ between the old and new mortars in the RAC has the largest ITZ width. Within 28 days, the microstructure and micromechanical properties of the new ITZ were weaker than those of the old ITZ bonded to natural coarse aggregate (NCA). However, as time goes by, when the curing time reached one year, the incompletely reacted cement particles in the old mortar continued to hydrate, which contributed to strengthen the bond strength between the new and old cement paste. In addition, the pozzolanic effect of glass powder can effectively improve the bonding performance between cement paste, NCA and old mortar. For the study of macroscopic mechanical properties, concrete cylindrical specimens containing recycled coarse aggregate (RCA) and recycled glass sand (RGS) were fabricated. RCA was used to replace NCA, and RGS was used to replace natural fine aggregate (NFA), with replacement ratio of 0%, 50% and 100%. The stress-strain curves of concrete samples under confining pressure and pore water pressure were measured. The results show that the pore water pressure accelerates the expansion of micro-cracks in the concrete specimens. On the other hand, the supporting effect of pore water pressure improved the resistance to compressive deformation of concrete specimens.

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