A rapid immersion measurement for the diffusion constant of chloride ions in the geopolymer concrete

Accurate measurement of chloride ion diffusion coefficient, without external interference, is essential for obtaining data that closely reflects practical conditions. The diffusion constants of chloride ions within fly ash-based geopolymer concrete (FGPC) with a one-dimension immersion method employed to record the time taken for diffusion to occur over a specific distance were investigated in this work. The results showed a clear relationship between the diffusion constant and the strength of FGPC. Within the same strength of FGPC, the diffusion distance (thickness) is proportional to the square root of diffusion time. The minimum diffusion constant is approximately 8.90 × 10⁻¹¹ m²/s which is close to the result in an immersion test. The method employed in this study is demonstrated to be both feasible and applicable for assessing the diffusion constant of chloride ions in FGPC quickly. It promotes a rapid evaluation method to predict the diffusion process under practical conditions.