Investigating the microstructure of alkali activated fly ash, ground granulated blast furnace slag (GGBS), or their mixtures by depth sensing nanoindentation and structure dependence of their composition by Magic Angle Spinning (MAS) NMR

Micromechanical properties from nano-indentation investigation are useful for relating macro properties. The micromechanical strength of alkali activation of fly ash (P₁), GGBS (P₂) as a sole binder and in the combination of 1:1 (P₃) is correlated with their respective microstructure by using TEM micrograph, MAS-NMR, FTIR, and Powder XRD. TEM /SAD pattern showed the clusters of the NASH gel in P₁ and P₃. Elastic modulus distribution lies in the range of ≤ 20, and 22–55 GPa corresponding to the low to high-density of geopolymer gels and the value above 60 GPa to unreacted particles of the precursors like fly ash or GGBS. The conceptual framework of nanocrystal formation and distribution of the structural features of gels in each binder is related through the histogram of the Elasticity (E) value. These results endorse the micromechanical properties of fly ash, and GGBS blended geopolymers that fairly and strongly support for the degree of reaction.