Materials Performance

OCT 2018

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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Page 128 of 138

OCTOBER 2018 WWW.MATERIALSPERFORMANCE.COM 40 person on the planet per year, resulting in more than twice as much concrete being used than the entire quantity of steel, aluminum, glass, plastic, and wood. Much of this concrete is reinforced with steel to improve its tensile properties. Thermodynamically, steel is going to corrode at some point, but the high alkalinity of the concrete embedment passivates the steel from cor- rosion until either the pH falls below about 9, deleterious ions ingress into concrete (such as chlorides), or the electrical potential of the steel is influ- enced such as from stray current leakage. Corrosion of reinforcing steel in concrete is considered to be the primary cause of concrete deterioration. Two universal rules of concrete construction are that concrete cracks and steel rusts. Increased Use of Monitoring Technology As technology improves and infrastructure deteriorates, monitoring of fac- tors related to corrosion will increase. The objective of monitoring should change from monitoring of the initiation time of corrosion or the rate of cor- rosion propagation to indications of when preventative maintenance should occur. In other words, monitoring will be used to indicate when protective actions should occur for the greatest effect on the life cycle cost of the structure. Monitoring systems will evolve to be durable for the long life of concrete and be wirelessly connected without requiring external power (such as through radio frequency identification [RFID] technology) and to also be less consuming of power as battery technology improves. Increased Usage of Robotic Inspection Investigation of corrosion is time consuming and often involves difficult location access, which is costly and potentially hazardous. Drones are already in common use for improved visual inspection as they can locate a camera in areas that would otherwise only be accessible with scaffolding or rope work. Experimentation with drones using contact sensors is beginning where the positioning of the drone will allow contact of a probe to the con- crete surface such as for crack identification, resistivity testing, or reinforc- ing steel location (pachometer or ground-penetrating radar). Positioning and control will continue to improve and allow better and longer access, with eventual development of additional monitoring technologies such as open circuit potential, or even linear polarization resistance. Further development of drone technology will allow improved underwater inspection through miniaturization, perhaps small robots that can crawl to provide up-close inspections. Preventative and Proactive Maintenance It has been stated that the most successful concrete repair is the one that is never done. Studies of concrete repairs indicate that the durability of the repairs is usually less than the durability of the remaining structure. This is caused by dissimilarities of the repair material to the host concrete (such as restrained shrinkage occurring in the fresh repair material bonded to con- crete that has long ago stopped shrinking, resulting in cracking and disbond- ment), failure to address the repair holistically (repairing only locally visible damage rather than addressing the causes of deterioration in the entire structure), and deferring repairs until corrosion damage becomes visible. When one purchases an automobile, it comes with a manual that includes scheduled maintenance to extend the vehicle service life. If one ignores changing the oil, then in a few years one will replace the engine. On the other hand, if one were to change the oil every 1,000 miles (1,609 km), the service life will be greatly extended but the maintenance cost will also be quite high. For a concrete structure a maintenance plan needs to be developed and implemented to determine the "sweet spot" for concrete maintenance to maximize the service life and minimize the maintenance cost, just like the car service manual does for the vehicle owner. Since each structure is different,

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