Abstract
To investigate the effect of leaching on chloride ingress profiles in concrete and mortar, we exposed concrete and mortar specimens for 90 and 180 days to two different exposure solutions: 3% NaCl, and 3% NaCl with KOH added to limit leaching. The solutions were replaced weekly. After exposure, we determined total chloride profiles to investigate the chloride ingress, and portlandite profiles to assess the extent of leaching. The results showed that leaching during exposure greatly affects the chloride ingress profiles in mortar and concrete. We found that leaching leads to considerably higher maximum total chloride content and deeper chloride penetration into the concrete than in the specimens where leaching was limited. We recommend therefore that leaching should be taken into account in standard laboratory testing and that more mechanistic service life models should be used to take into account the impact of leaching.
Highlights
Today’s society calls for sustainable structures with low carbon footprints, limited use of natural resources, and the resilience to withstand mechanical, chemical and environmental impacts
In the mortar and concrete specimens exposed to the NaCl solution, the depths at which we observed a decrease in the portlandite content correspond to the depths at which we observed chloride ingress after both 90 and 180 days of exposure
In order to investigate the effect of leaching on chloride ingress profiles, concrete and mortar specimens were exposed for 90 and 180 days to two different exposure solutions: 3% NaCl, and 3% NaCl with additional KOH to limit leaching
Summary
Today’s society calls for sustainable structures with low carbon footprints, limited use of natural resources, and the resilience to withstand mechanical, chemical and environmental impacts. Concrete covers must be resistant to chloride penetration and we need to improve our understanding of the mechanisms involved, if we are to design sustainable reinforced concrete structures with a reliable service life. To assess how far chlorides have penetrated the concrete cover, chloride profiles are determined by Service life prediction models are used to assess how long it will take for the chlorides to reach a critical content at the reinforcement. The most commonly used models for chloride ingress prediction are based on Fick’s 2nd law of diffusion, e.g. fib Bulletin 34 [12]. In these models, the error function solution of Fick’s 2nd law is fitted to a measured chloride profile. This approach solely considers the ingress of chlorides; the potential influence of other ions present in sea water, such as sodium, sulphate and magnesium, or of ions leached from the pore solution, such as calcium or potassium, is not considered
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