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Calcium enhanced ambient cured fly Ash based geopolymer binders
Mustafa Shamsah1,2, Robin Kalfat3, Kolluru V L Subramaniam4
1Department of Civil and Construction, School of Engineering, Swinburne University of Technology, Hawthorn, VIC, 3122, Australia.
Scientific Reports
|July 15, 2025
Summary
This study shows that adding a small amount of slag to alkali-activated fly ash mixtures improves compressive strength and setting control. This method offers a systematic way to create high-strength fly ash binders at room temperature.
Area of Science:
- Materials Science
- Geochemistry
- Civil Engineering
Background:
- Alkali-activated fly ash (AAFA) binders are a sustainable alternative to Portland cement.
- Optimizing AAFA properties requires understanding the impact of constituent materials and activation conditions.
- Reactive oxide ratios significantly influence the performance of AAFA systems.
Purpose of the Study:
- To investigate the effects of reactive oxide ratios on the performance of alkali-activated fly ash mixtures.
- To evaluate the influence of slag substitution on flowability, setting time, compressive strength, early kinetics, and reaction products.
- To present a systematic procedure for producing high-strength fly ash binders at room temperature.
Main Methods:
- Preparation of alkali-activated fly ash mixtures with varying slag content.
- Characterization of flowability, setting time, and compressive strength.
- Analysis of early kinetics and reaction products, including sodium alumino-silicate hydrate (NASH) geopolymer formation.
Main Results:
- Alkali-activated fly ash mixtures prepared based on reactive potential exhibit consistent strength under room-temperature curing with low molarity sodium hydroxide.
- A 5% substitution of fly ash with slag enhances compressive strength under room-temperature curing.
- Slag inclusion improves early reactivity, aids setting control, and promotes fly ash dissolution, leading to synergistic strength enhancement through NASH geopolymer formation.
Conclusions:
- Optimizing reactive oxide ratios through strategic slag inclusion is crucial for enhancing the performance of alkali-activated fly ash binders.
- The addition of a small proportion of slag synergistically improves the compressive strength and setting characteristics of AAFA systems.
- A systematic room-temperature curing procedure is presented for producing high-strength fly ash binders activated with alkali, utilizing the benefits of slag incorporation.
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