Corrosion of reinforcing steel in concrete is a worldwide problem that causes a range of economic, aesthetic and utilization issues. However, if corrosion effects are considered in the design phase and the right decisions are made prior to construction, public-use buildings such as hotels can be built to last and protect against corrosion for 50 and more years.
Regular and planned asset maintenance is vital for reinforced concrete structures. Such maintenance should not be a ‘cosmetic repair’ but rather a proper root cause analysis that must be carried out to identify and understand the actual source of the problem.
Many of the hotels in MENA Region are situated near marine environments that results in rapid occurrence of concrete corrosion.
Usually, the most exposed elements deteriorate first – but the underlying corrosion is unseen. Active corrosion in the steel beneath may take five to 15 years to initiate cracks in the concrete, but much of the corroded reinforcement is not visible.
Corrosion affects all concrete buildings and structures around the world to some extent, with annual costs in the billions to national economies. With hotel assets, corrosion is often an issue of aesthetics and falling concrete where spalling occurs creates public safety risks. Hotel operators do not want scaffolds, cables, and exposed metalwork on display for extended periods of time. The corrosion of steel in concrete is accelerated in harsh environments, especially in coastal, tropical or desert environments where high salt levels or extreme temperatures can accelerate the rate of decay.
Common Causes of Concrete Corrosion
The two most common causes of concrete corrosion are carbonation and chloride (salt attack). In broad terms, when carbonation, chlorides and other aggressive agents penetrate concrete, they initiate corrosion that produces cracking, spalling and weakening of the concrete infrastructure. As reinforcing rods rust the volume of rust product can increase up to six times that of the original steel, thus increasing pressure on the surrounding material, which slowly cracks the concrete. Over the course of many years, the cracks eventually appear on the surface and concrete starts to flake off or spall.
Degradation of reinforcing steel and the subsequent weakening of the concrete occurs from the inside and may be unseen for many years. It is often referred to as “concrete cancer.”
Repair and Prevention
Impressed Current Cathodic Protection
One of the alternative ways to protect assets from corrosion is by deploying a Cathodic Protection System. One type of CP is impressed current cathodic protection (ICCP) which is a technique where a small permanent current is passed through the concrete to the reinforcement in order to virtually stop steel corrosion.
The main benefit of ICCP is that the removal and repair of concrete is vastly reduced, with only the spalled and delaminated concrete requiring repairs.
Once installed, corrosion can be controlled for the long term, eliminating future spalling and deterioration even in severe chloride or carbonation contaminated concrete.
Proper anode system selection is the most vital design consideration for a durable and efficient ICCP system. Incorrect selection and placement of the anode system can result in poor performance and a vastly reduced installation lifetime.