Nano/microcharacterization on mechanical properties and structures of geopolymeric matrices and interfacial transition zones

Luo, Zhiyu

Nano/microcharacterization on mechanical properties and structures of geopolymeric matrices and interfacial transition zones

Luo, Zhiyu

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Publication Type:: Thesis
Issue Date:: 2021

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Field	Value	Language
dc.contributor.author	Luo, Zhiyu
dc.date.accessioned	2021-10-07T23:02:41Z
dc.date.available	2021-10-07T23:02:41Z
dc.date.issued	2021
dc.identifier.uri	http://hdl.handle.net/10453/150909
dc.description	University of Technology Sydney. Faculty of Engineering and Information Technology.	en_US.UTF-8
dc.description.abstract	This study aims to promote the fundamental understanding of fly ash-based geopolymer through micro and nanoscale mechanical and structural characterization. Geopolymer concrete is studied from two aspects of paste and interfacial transition zone (ITZ). In addition to properties investigation and related mechanism analysis, new insights and methods are provided for the nano/micromechanical testing and analysis of highly heterogeneous materials. Prior to research, several typical nanomechanical testing techniques are introduced and compared. The review provides the current research trend, advantages/disadvantages and suitable application of these techniques in cement-based materials. Then, based on the study of geopolymer paste, some critical questions of the statistical nanoindentation technique (SNT) are discussed. The study reveals the disadvantages of using the least-square estimation (LSE) for deconvolution of data in some highly heterogeneous materials such as geopolymers and proposes a "compromise approach" using maximum likelihood estimation (MLE) for deconvolution. Correlation and difference of different statistical techniques are analyzed to clarify the rationality of the proposed method. Thereafter, the effects of the general design parameters such as silica modulus, alkali concentration, and curing condition on the properties of N-A-S-H gel and its association with the performance of geopolymer are investigated and discussed. The properties of geopolymer are further modified by nano-SiO₂ and nano-TiO₂. The effects of different nanoparticles on microstructure, gel proportion and gel micromechanical properties are discussed to reveal the macro-strength reinforcement mechanism. For ITZ research, a method based on modelled ITZ samples is proposed to facilitate comparison research and nanomechanical testing. This part starts with the comparison of ITZ in geopolymer concrete and Portland cement (PC) concrete. The mechanism of the better ITZ performance in geopolymer than PC is revealed. Afterwards, scratch technique coupled with Gaussian mixture model (GMM) is introduced on the modelled ITZ samples as a quick method for interfacial properties evaluation. The statistical results indicate that silica modulus is an important factor governing the interfacial properties of geopolymer. In the last section of ITZ research, the heterogeneity of ITZ in section concrete is categorized into three levels. The study promotes the heterogeneity of the investigated ITZ to the second level for a deeper understanding of ITZ in geopolymer. Echoing the beginning of the thesis, scratch and indentation techniques are combined used, which clearly shows some of their different advantages for nanomechanical properties investigation. Strategies are proposed to overcome the higher level of heterogeneity to realize ITZ properties investigation with feasible workload and accuracy.	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/10453/150909/2/02whole.pdf
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	au.edu.uts.lib/ppc
dc.rights	info:eu-repo/semantics/openAccess
dc.rights	info:eu-repo/semantics/openAccess
dc.title	Nano/microcharacterization on mechanical properties and structures of geopolymeric matrices and interfacial transition zones	en_US.UTF-8
dc.type	Thesis
utslib.copyright.status	open_access	*
utslib.copyright.embargo	2022-10-03T00:00:00+1000

Abstract:

This study aims to promote the fundamental understanding of fly ash-based geopolymer through micro and nanoscale mechanical and structural characterization. Geopolymer concrete is studied from two aspects of paste and interfacial transition zone (ITZ). In addition to properties investigation and related mechanism analysis, new insights and methods are provided for the nano/micromechanical testing and analysis of highly heterogeneous materials. Prior to research, several typical nanomechanical testing techniques are introduced and compared. The review provides the current research trend, advantages/disadvantages and suitable application of these techniques in cement-based materials. Then, based on the study of geopolymer paste, some critical questions of the statistical nanoindentation technique (SNT) are discussed. The study reveals the disadvantages of using the least-square estimation (LSE) for deconvolution of data in some highly heterogeneous materials such as geopolymers and proposes a "compromise approach" using maximum likelihood estimation (MLE) for deconvolution. Correlation and difference of different statistical techniques are analyzed to clarify the rationality of the proposed method. Thereafter, the effects of the general design parameters such as silica modulus, alkali concentration, and curing condition on the properties of N-A-S-H gel and its association with the performance of geopolymer are investigated and discussed. The properties of geopolymer are further modified by nano-SiO₂ and nano-TiO₂. The effects of different nanoparticles on microstructure, gel proportion and gel micromechanical properties are discussed to reveal the macro-strength reinforcement mechanism. For ITZ research, a method based on modelled ITZ samples is proposed to facilitate comparison research and nanomechanical testing. This part starts with the comparison of ITZ in geopolymer concrete and Portland cement (PC) concrete. The mechanism of the better ITZ performance in geopolymer than PC is revealed. Afterwards, scratch technique coupled with Gaussian mixture model (GMM) is introduced on the modelled ITZ samples as a quick method for interfacial properties evaluation. The statistical results indicate that silica modulus is an important factor governing the interfacial properties of geopolymer. In the last section of ITZ research, the heterogeneity of ITZ in section concrete is categorized into three levels. The study promotes the heterogeneity of the investigated ITZ to the second level for a deeper understanding of ITZ in geopolymer. Echoing the beginning of the thesis, scratch and indentation techniques are combined used, which clearly shows some of their different advantages for nanomechanical properties investigation. Strategies are proposed to overcome the higher level of heterogeneity to realize ITZ properties investigation with feasible workload and accuracy.

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