Comparison of Mechanical and Microstructural Properties of Fly Ash Geopolymer in Water and Chloride Environment
In cement industry, the emissions of greenhouse gases specifically CO2 from the clinker production led to the need of alternative binders. Geopolymer binder whose precursors are sourced from industrial by-products such as fly ash that are rich is silica and alumina has been studied extensively in...
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| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Trans Tech Publications Ltd, Switzerland
2021
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| Subjects: | |
| Online Access: | http://ir.unimas.my/id/eprint/36399/1/chloride1.pdf http://ir.unimas.my/id/eprint/36399/ https://www.scientific.net/DDF.411 http://10.4028/www.scientific.net/DDF.411.143 |
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| Summary: | In cement industry, the emissions of greenhouse gases specifically CO2 from the clinker
production led to the need of alternative binders. Geopolymer binder whose precursors are sourced
from industrial by-products such as fly ash that are rich is silica and alumina has been studied
extensively in the past decades. Chloride attack is one of the threats to concrete structures. Analysis
at microstructural level needs to be studied carefully before this binder can be used with confidence.
This study attempts to compare the properties of fly ash geopolymer binder when exposed in water
and chloride solution. Fly ash geopolymer pastes were prepared using 12M sodium hydroxide
(NaOH) as activator. The pastes were tested under two separate curing conditions, i.e in ambient and
in distilled water. Compressive strength test along with microstructure properties of samples cured at
7, 14 and 28 days were conducted via Universal testing machine, Fourier Transform Infra-Red (FTIR)
spectroscopy and Scanning Electron Microscope with Energy-dispersive X-ray (SEM-EDX). After
28 days of curing, these samples were immersed in 10% sodium chloride (NaCl) solution for another
56 days. Samples cured in ambient condition showed better mechanical performance than those in
distilled water. Their differences in compressive strength were also seen consistent with the FTIR
results. Samples exposed to NaCl and distilled water showed similar mechanical performance and
microstructural properties. Based on SEM-EDX analysis, samples cured in ambient were rich in silica
and alumina while the intensity of these compounds were observed to reduce when exposed to
distilled water. Samples cured in ambient showed stronger intensity of Si/Al gel as compared to
samples exposed to chloride environment and distilled water and these were consistent with the
compressive strength results obtained. When immersed in water, concentration gradient changes in
the liquid phases, leading to ions diffusion and causing decrement in strength and durability of the
solids in fly ash geopolymer. |
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