Passive corrosion of steel reinforcement in blended cement-based material in the context of nuclear waste disposal

An experimental campaign was carried out to study the passivity of steel embedded in blended cement paste. Mockup samples made of steel coupons (milled or pre-corroded) embedded in cement paste were tested under controlled relative humidity or in a solution simulating clay underground water and under aerated and de-aerated conditions, during up to 3 years. The results of gravimetric measurements show that the average corrosion rates determined on milled coupons are lower than 1 µm/year and vary from 0.2 to 2.7 µm/year for pre-corroded coupons. An apparent passive corrosion state is reached rapidly whatever the environmental conditions. Moreover, solid characterisations (Raman spectroscopy and SEM-EDS) point to a stable state in terms of the nature of the corrosion products and of the composition of the steel/cement paste interface. These results are similar to the ones previously obtained for steel coupons embedded in Portland cement mortar.This paper is part of a supplement on the 6th International Workshop on Long-Term Prediction of Corrosion Damage in Nuclear Waste Systems.