Understanding Concrete Carbonation
A major building material, ensuring the quality and performance of concrete is actually about checking the condition of buildings and structures. A structural survey may include a test to assess the strength of concrete. A more detailed investigation, with HOKLAS concrete testing Hong Kong focused, is to test concrete carbonation depth.
On a basic level, carbonation occurs when the calcium hydroxide in cement reacts with carbon dioxide in the air. The impact is to decrease how porous the concrete is which has a hardening effect which can make the material stronger and more tensile. However, while this may not be an issue in non-reinforced concrete, and actually a positive, it can be destructive and dangerous with reinforced concrete.
Carbonation reduces the pH level of concrete and this greater acidity has a negative effect whereby the protective layer that stops the steel reinforcements from being corroded is not effective. Rusted metal expands the concrete and the result is instability, less durability and crumbling concrete. For the environment and in terms of safety, carbonation needs to be discovered and dealt with as early as possible.
Drilling and using a special indicator is one way in which the depth of carbonation can be detected, with colour changes happening where there are issues. By testing for this problem and also guarding against potential future issues, it’s worth investing in checking the health of concrete and of a building or structure as a whole. This can save time, money and pain-points in the future which can become far greater if a problem is not discovered until real damage is done.
In Hong Kong and other tropical climates, this test is particularly important as humidity acts like a catalyst on cement carbonation. The heat doesn’t help matters either. Building facades exposed to the elements are often the first parts of buildings to suffer from corrosion. When cracks appear this exacerbates the problem with more carbon dioxide leaking in a lowering alkalinity. The result can be a structure that becomes in a state of major decline.
Concrete issues can equate to structural problems that need immediate action at some point, albeit that the process of carbonation is relatively slow, at a rate of 1 mm per year on average. Once the depth of the carbonation is identified steps can be taken to repair the damage such as removing the corrosion and any loose concrete plus protective measures.