Mechanical, microstructural, and chloride ion penetration data of metakaolin specimens

Within this window, an optimal concentration of 14 M facilitates a synergistic regime in which geopolymerization produces a gel that is both dense (enhancing physical protection) and chemically active for chloride binding.

This results in a significantly reduced chloride diffusion coefficient of 4.19 × 10⁻¹² m²/s. Deviations from this window lead to a decoupling of the synergistic effect: lower alkalinity yields a porous microstructure, whereas higher alkalinity inhibits effective chemical binding despite ongoing pore refinement.