Spotlight on Half Cell Canopy Corrosion Surveys
Building canopy repair involves accessing a variety of different levels of expertise to ensure structural integrity and stability. With many buildings in Hong Kong being high-rise towers, for residential as well as commercial developments, the prevalence of canopies is fairly high. The climate also increases the prevalence, as a canopy is a structure that is usually added to a building to provide protection from the elements, whether rain or shine. In some cases, a canopy is added to a building as an architectural feature, perhaps to add a sense of grandeur to an entrance, or to identify a main lobby area. With so many buildings within the area boasting canopies, canopy assessments and repairs have become a key structural services area.
There are a multitude of different types of testing, from visual examinations to more in-depth and far more destructive variations of investigations. One non-destructive test that can be carried out is a half-cell corrosion survey. This involves a type of mapping which, in essence, assesses the level of corrosive activity within a concrete structure, such as a canopy. It is important to not only identify corrosion but also to get an idea of whether it is active.
Without being too technical, half-cell corrosion surveys to establish the structural integrity of a canopy involve measuring the half-cell potential of reinforcing steel. When corrosion occurs, an electro-chemical process takes place and the higher the potential of the half-cells, the more likely it is that the steel has been corroded in some way.
To begin with, it is important to first work out where the steel bars are located within the concrete. This can be done using a tool called a covermeter. Two separate areas are tested via an electrical connection to ensure that there is a continuous flow, while a digital machine connects the steel to the half-cell measurer to determine its presence.
Within this test, it is also possible for specialists to estimate where areas at greatest risk are located, and with different potential points identified, a full picture of the canopy can be created. This is what leads to the next step, which is either more in-depth analysis and investigation, or repairs. One major advantage of this test is that in the hands of a professional it is straightforward, useful in providing invaluable data, and also highly cost-effective too. This makes it an ideal tool for canopy testing.
