blauwverkleuring

Blauwverkleuring is a blue discoloration or staining that occurs in lime-based mortars and concrete, particularly in the presence of iron or copper compounds. This phenomenon is also known as "blushing" or "chrome-lime discoloration". The blauwverkleuring effect is often observed on the surface of buildings or structures that have been exposed to the elements for an extended period.

The cause of blauwverkleuring is attributed to the reaction between the lime in the mortar or concrete and the iron or copper ions present in the surrounding environment. The rust or oxidation products of these metals can be absorbed by the lime paste, leading to the formation of chromate ions. When these ions come into contact with the oxygen present in the air, they revert to their original red or brown color. This rapid color change is what gives the blauwverkleuring effect its characteristic blue appearance.

Blauwverkleuring is a relatively common phenomenon in the Netherlands and other regions with high levels of atmospheric pollution. It can have significant aesthetic and structural implications, as the discoloration can be permanent and can compromise the stability of mortar or concrete over time. As a result, many conservation efforts and studies have focused on understanding and mitigating the effects of blauwverkleuring in historical buildings and monuments. By doing so, experts aim to preserve the cultural and architectural heritage of affected regions.