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This chapter investigates the nano/micromechanical properties of sodium aluminosilicate hydrate (N-A-S-H) gel in alkali-activated fly ash (AAFA) geopolymers using grid nanoindentation and maximum likelihood estimation (MLE). The study explores the challenges in accurately identifying pure N-A-S-H gel due to the presence of mixed phases and the influence of crystals and unreacted particles. The MLE method is shown to be advantageous over the least-square estimation (LSE) method, providing a more reliable separation of the N-A-S-H phase. The results indicate that the proportion of pure N-A-S-H gel is relatively low (6.28–10.67%) due to interactions with other phases. The mechanical properties of N-A-S-H gel are found to be slightly lower than those of low-density C-S-H in Portland cement paste, with elastic modulus ranging from 12.70 to 15.46 GPa and hardness from 0.59 to 0.73 GPa. The study concludes that the presence of crystals and the heterogeneous nature of AAFA significantly affect the detection and properties of N-A-S-H gel, highlighting the need for further research to understand the intrinsic mechanical properties of this phase.

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Applying Grid Nanoindentation and Maximum Likelihood Estimation for N–A–S–H Gel in Geopolymer Paste

  • 章节

  • 发表日期：

    2025年

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  • Wengui Li,
  • Hanbing Zhao,
  • Kejin Wang

摘要

This chapter investigates the nano/micromechanical properties of sodium aluminosilicate hydrate (N-A-S-H) gel in alkali-activated fly ash (AAFA) geopolymers using grid nanoindentation and maximum likelihood estimation (MLE). The study explores the challenges in accurately identifying pure N-A-S-H gel due to the presence of mixed phases and the influence of crystals and unreacted particles. The MLE method is shown to be advantageous over the least-square estimation (LSE) method, providing a more reliable separation of the N-A-S-H phase. The results indicate that the proportion of pure N-A-S-H gel is relatively low (6.28–10.67%) due to interactions with other phases. The mechanical properties of N-A-S-H gel are found to be slightly lower than those of low-density C-S-H in Portland cement paste, with elastic modulus ranging from 12.70 to 15.46 GPa and hardness from 0.59 to 0.73 GPa. The study concludes that the presence of crystals and the heterogeneous nature of AAFA significantly affect the detection and properties of N-A-S-H gel, highlighting the need for further research to understand the intrinsic mechanical properties of this phase.