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<p>In the pursuit of sustainable infrastructure, the development of eco-friendly cement is vital. Geopolymers of the N–(C)–A–S–H network performed better, but there is a significant variation in microstructural changes. This study examines the effect of a fly ash and GGBS blend (1:1) geopolymers, activated by either NaOH (SH) or sodium silicate (SS), on their acid durability through the mechanical and microstructural properties of geopolymers FG<sub>SH</sub> and FG<sub>SS</sub>. The surface and core parts of the samples were analysed using multiple techniques. FG<sub>SH</sub> retained 70% compressive strength after 90&#xa0;days in 10% H₂SO₄, while FG<sub>SS</sub> retained 55%, with the control maintaining strength of 30 ≤ 40&#xa0;MPa. The FTIR band of (Si–O–Si/Al) from control samples showed a blue shift from 975 to 1080–1090&#xa0;cm<sup>–1</sup> in the acid-corroded surface of FG<sub>SS</sub>″ and FG<sub>SH</sub>″, which is attributed to the highly polymerised silica gel. The sharp peak around 667&#xa0;cm<sup>−1</sup> is the evident presence of the acid corrosion by-product of calcium sulphate. The dissolution of calcium-based gel affects the Al–O linkages at the Al<sup>IV</sup> site in the zeolitic framework, which was evident from the disappearance of the Q<sup>1</sup> to Q<sup>3</sup> environment from <sup>29</sup>Si NMR. δ<sub>27Al</sub> −8.6&#xa0;ppm, indicating the presence of aluminium sulphate, which confirms the needle form of ettringite in SEM analysis. A shift in δ<sub>27Al</sub> from 62 to 42&#xa0;ppm confirmed poorly crystalline C–(N)–A–S–H or amorphous N–A–S–H gel in FG<sub>SS</sub>″. An ion exchange reaction mechanism was proposed to explain corrosion behaviour.</p>

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Acid resistance of alkali-activated fly ash–GGBS: role of NaOH and Na2SiO3

  • 期刊论文

  • 发表日期：

    2025年11月7日

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  • G. Sharmila,
  • M. Manivannan,
  • R. Jeyalakshmi

摘要

In the pursuit of sustainable infrastructure, the development of eco-friendly cement is vital. Geopolymers of the N–(C)–A–S–H network performed better, but there is a significant variation in microstructural changes. This study examines the effect of a fly ash and GGBS blend (1:1) geopolymers, activated by either NaOH (SH) or sodium silicate (SS), on their acid durability through the mechanical and microstructural properties of geopolymers FGSH and FGSS. The surface and core parts of the samples were analysed using multiple techniques. FGSH retained 70% compressive strength after 90 days in 10% H₂SO₄, while FGSS retained 55%, with the control maintaining strength of 30 ≤ 40 MPa. The FTIR band of (Si–O–Si/Al) from control samples showed a blue shift from 975 to 1080–1090 cm–1 in the acid-corroded surface of FGSS″ and FGSH″, which is attributed to the highly polymerised silica gel. The sharp peak around 667 cm−1 is the evident presence of the acid corrosion by-product of calcium sulphate. The dissolution of calcium-based gel affects the Al–O linkages at the AlIV site in the zeolitic framework, which was evident from the disappearance of the Q1 to Q3 environment from 29Si NMR. δ27Al −8.6 ppm, indicating the presence of aluminium sulphate, which confirms the needle form of ettringite in SEM analysis. A shift in δ27Al from 62 to 42 ppm confirmed poorly crystalline C–(N)–A–S–H or amorphous N–A–S–H gel in FGSS″. An ion exchange reaction mechanism was proposed to explain corrosion behaviour.