Compositions and Microstructures of Carbonated Geopolymers with Different Precursors
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View abstract on PubMed
Summary
This summary is machine-generated.Geopolymers made from fly ash and slag readily carbonate. Carbonation forms nahcolite or calcite, with blend-based geopolymers showing unique pore-plugging structures, revealing gel composition and changes.
Area Of Science
- Materials Science
- Geochemistry
- Construction Materials
Background
- Geopolymers (GPs) are susceptible to carbonation, particularly when cured at ambient temperatures.
- Understanding the impact of carbonation on geopolymer matrix gel composition and microstructure is crucial.
Purpose Of The Study
- To investigate the composition and microstructure of geopolymer matrix gels.
- To identify the carbonation products formed in geopolymers derived from fly ash (FA) and ground granulated blast-furnace slag (GGBS).
- To analyze compositional changes in geopolymers after carbonation using advanced analytical techniques.
Main Methods
- Preparation of geopolymers using low-lime FA and GGBS precursors, alone or blended.
- Specimen curing at 20 °C with alkali activator solution, followed by sealed or accelerated carbonation.
- Analysis using X-ray Diffraction (XRD), Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDS), and ternary diagram analysis.
Main Results
- Carbonation products identified as nahcolite (FA-based GPs) and calcite (GGBS-based GPs).
- SEM-EDS revealed cube-shaped and small calcite particles in GGBS-based GPs, and unique hail-like particles in FA/GGBS blend-based GPs.
- Ternary diagram analysis confirmed hail-like particles as calcite and C-A-S-H gel complexes that plug pores in spongy C-A-S-H gels.
Conclusions
- Combined ternary diagram analysis of S-(C+M+N)-A and A-(C+M)-N effectively determines geopolymer gel type and carbonation products.
- C-A-S-H gels exhibit linear distribution along the (C+M+N)-albite join, while N-A-S-H gels show scattered distribution in S-(C+M+N)-A diagrams.
- Distinct zoning for N-A-S-H and C-A-S-H gels is observed in A-(C+M)-N diagrams, aiding in understanding compositional changes post-carbonation.
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