Date of Award

2019

Document Type

Campus Access Dissertation

Degree Name

Doctor of Philosophy in Civil Engineering (PhD)

Administrative Home Department

Department of Civil and Environmental Engineering

Advisor 1

Qingli Dai

Committee Member 1

Zhanping You

Committee Member 2

Jacob Hiller

Committee Member 3

Ibrahim Miskioglu

Abstract

This study aims to investigate the effects of added calcium or glass powder on the phase formation, development of micro/atomic structure and mechanical/durability performance of metakaolin-based geopolymer. The correlation between the calcium contents and the formation process of the geopolymeric gel was studied with the in-situ X-ray Pair Distribution Function (PDF) and X-ray Diffraction (XRD) tests. The results showed that the calcium-contained phases can serve as nucleation sites for the precipitation of sodium aluminosilicate gel to accelerate the alkali-activated reaction.

Based on the obtained correlation between the chemical compositions of starting materials and the phase formation of geopolymer, further tests on glass powder modified metakaolin-based geopolymer were conducted. The atomic-structure, nanopore structure, and microstructure of the metakaolin-based geopolymer with different contents of glass powder (0%, 5%, 10%, and 20% by the weight of the precursor) were characterized by the PDF technique, SEM/EDX analysis, and nitrogen sorption test. The results showed that the geopolymer mixtures with added glass powder had higher Si/Al ratio, more strong Si-O-Si linkages, and finer nanopore structure.

The fresh properties and mechanical properties of glass powder modified metakaolin-based geopolymer were further investigated. The added glass powder improved workability and prolonged setting time of the synthesized geopolymer samples. The gel phase of the geopolymer samples with 10% of glass powder achieved the highest elastic modulus and contact creep modulus due to the reduced gel porosity and improved atomic structure of the gel.

Lastly, the shrinkage behavior of metakaolin-based geopolymer with/without glass powder modification was investigated. The results showed that glass powder replacement can reduce the drying shrinkage of metakaolin-based geopolymer under different drying conditions. The reduction of drying shrinkage in glass powder modified metakaolin-based geopolymer was due to the reduced water evaporation at the early stage and the enhanced creep modulus of the gel phase. The test results indicated the added glass powder can potentially improve both mechanical and durability performance of the metakaolin based geopolymer with the adequate replacement level.

Available for download on Saturday, August 01, 2020

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