Structural study using 29Si and 27Al Solid State MAS NMR and compressive strength analysis of metakaolin-based geopolymer paste

Funding Sponsor

King Abdullah University of Science and Technology

Author's Department

Construction Engineering Department

Second Author's Department

Construction Engineering Department

Third Author's Department

Construction Engineering Department

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https://doi.org/10.1080/19648189.2025.2523886

All Authors

Heba Fouad Safwan Khedr Tarek Madkour Abdul Hamid Emwas

Document Type

Research Article

Publication Title

European Journal of Environmental and Civil Engineering

Publication Date

1-1-2025

doi

10.1080/19648189.2025.2523886

Abstract

Geopolymers are hardened aluminosilicate gel that develop strength via the crosslinking of tetrahedral silicate and aluminate. Past Research has highlighted a wide range of mechanical properties of geopolymer synthesised from various aluminosilicate materials. This research focuses on studying the effect of variation in the percentages of metakaolin, sodium silicate and sodium hydroxide at a fixed water to solids ratio on the development of geopolymer structure and compressive strength. Kaolin was thermally treated and XRD and FTIR traced the changes in crystalline Kaolin and its transformation into a more disordered structure of metakaolin. Characterisation techniques were used for the study of geopolymer produced. FTIR analysis illustrated the changes in the characteristic bands of metakaolin after being activated with sodium silicate and sodium hydroxide to form geopolymer. The 27Al and 29Si Solid State MAS NMR spectra confirmed the formation of polymerised tetrahedral silicate interconnected to tetrahedral aluminate in the form of Q4(4Al) and Q4(3Al) which are responsible for the attained compressive strength of geopolymer. The produced geopolymers exhibited high early compressive strength and high 28-day compressive strength in the range of 30–81 MPa. This promotes the use of geopolymers as a replacement to Ordinary Portland cement especially in targeted construction applications.

First Page

3477

Last Page

3497

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