There are around 2,300 bridges connecting different highways in New Zealand, and many of them are prone to corrosion mainly caused by carbonation and chloride.
While new bridges have the latest technology and materials that extend their lifespan, corrosion is bound to occur at some point. For this reason, bridge infrastructure requires constant upkeep such as using a sandblaster to remove rust.
Construction companies can reduce the chances of corrosion for reinforced concrete bridges by applying a protective layer of coating, or cathodic protection that acts as a barrier for corrosive elements. Electrochemical chloride extraction and electrochemical re-alkalisation also serve as other options, yet there only a handful of contractors who are adept in these procedures. Some experts believe that cathodic protection remains the best choice for reversing the effects of corrosion.
Engineers and commercial builders should be particular about the choice of materials for a certain location as well. For instance, weathering steel isn’t ideal for bridges that are exposed to high salinity level and other pollutants. Choosing the right materials are just as important since corrosion leads to around $9 billion of infrastructure damages every year.
While carbonation and chloride are the most common causes of corrosion, inefficient bridge designs could be a significant factor in certain situations, particularly for structures constantly in contact with water.
Some are just unavoidable like buildings and structures near coastal areas. The salinity level in these places tends to be higher than inland regions. Aside from sandblasting, patch repairs are the usual technique in New Zealand for the removal of damaged concrete with results lasting up to 10 years.
There’s no permanent way to eliminate corrosion, so the end goal of bridge infrastructure developers always centres on prolonging the structure’s good condition. Routine maintenance will be the key to achieve this feat.