EXPERIMENTAL MEASUREMENTS OF CHLORIDE-ION DIFFUSION RATES USING A 2-COMPARTMENT DIFFUSION CELL - EFFECTS OF MATERIAL AND TEST VARIABLES

Chloride ion diffusion rates in cementitious paste have been determine d using a modification to the ''standard'' two-compartment diffusion c ell. Ordinary Portland cement samples of varying water/cement ratios w ere investigated together with similar materials to which varying amou nts of pyrolysed scrap automotive polymer (Sheet Moulding Compound - S MC) had been added. The effects of changes in the experimental conditi ons (sample thickness, chloride ion concentration in first compartment ) were also investigated. The chloride ion diffusivity was reduced by either reducing the water/cement ratio or by the incorporation of pyro lysed SMC into the mix. There was a small decrease in effective chlori de ion diffusivity with increase in sample thickness. The concentratio n of chloride ion in Cell 1 had no significant effect on the measured diffusivity. However, by increasing the concentration, the time requir ed to make the diffusivity measurements can be significantly reduced.