Abstract
Mortar specimens were exposed to either a 3% NaCl solution or a 3% NaCl+KOH solution for up to 180 days. Exposure to the NaCl solution provoked much more leaching than the NaCl+KOH exposure. Leaching strongly impacted the chloride ingress profiles. The extended leaching led to a maximum total chloride content almost three times higher and a deeper chloride penetration than exposure with limited leaching after 180 days. The higher maximum chloride content seems to be linked to the enhanced binding capacity of the C-S-H and AFm phases upon moderate leaching as determined by SEM-EDS. The total chloride profile appears to be governed by multi-ion transport and the interaction of chloride with the hydration phases. Service life prediction and performance testing both rely on total chloride profiles and therefore ought to take these interactions into account.
Highlights
Reinforced concrete is a commonly used construction material for infrastructure exposed to sea water or de-icing salts, such as harbours, tunnels and bridges
The experimental set-up is simulated by exposing a hydrated cement paste to increasing amounts of exposure solution
It should be noted that, due to a lack of thermodynamic data, the chloride binding by hydrotalcite was not taken into account in the modelling, even though hydrotalcite is able to bind considerable amounts of chlo ride [21]
Summary
Reinforced concrete is a commonly used construction material for infrastructure exposed to sea water or de-icing salts, such as harbours, tunnels and bridges. The design life of these structures is often determined by the time it takes for chlorides to penetrate through the concrete cover and reach a critical chloride content at the steel surface, which enables pitting corrosion of the reinforcement steel. To determine how far chlorides have penetrated into the concrete, chloride ingress profiles are obtained These profiles give the total chloride content in the concrete as a function of depth below the exposed surface. Such total chloride profiles can be obtained from both existing structures to predict their remaining service life, and from laboratoryexposed specimens to predict the durability performance of a given cement or concrete
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