Diffusion of selenate in disc-shaped samples of hardened concrete and mortar pastes was studied using the through-diffusion technique. Experiments were performed under atmospheric conditions for periods of up to several months. Samples had a water to cement ratio (w/c) of 0.4. All tests showed considerable decrease in diffusion rates with time due to CaCO3, Ca(OH)2, and ettringite precipitation, identified by scanning electron microscopy–energy-dispersive X-ray analyses. Effective diffusion coefficients, De, were calculated for selenate anion in the linear region with values of 2.4×10−12 and 7.2×10−12 m2/s for mortar and concrete, respectively.
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