Cracks in Concrete Tanks
FPrimeC was engaged by the client to perform a digital inspection and nondestructive testing of concrete tanks in Sarnia ON. Two underground concrete tanks at an oil refinery in Sarnia exhibited sign of vertical cracking on the crown and interior faces. The cracks resulted in chemicals leaking through.
The structures were generally buried underground, with only top 1 ft. of the walls accessible above the ground. The cooling water tank had to be examined while it was in operation, making the inspection and testing particularly a challenging task.
Condition Assessment of Concrete Tank
FPrimeC’s approach to this challenging investigation involved underwater digital inspection using borescope video, and advanced non-destructive evaluation of concrete walls to identify the location, severity and extent of concrete cracks. An advanced procedure based on the propagation of surface waves in concrete elements was adapted for this study.
Digital Inspection
Underwater visual inspection was conducted using borescope video, and waterproof 360 Cameras. Carrying out a digital inspection was necessary so that all further testing and data could easily be referenced, especially for future repairs. However, the visual inspection was challenging, particularly due to presence of algae and vegetation inside the water tank, which blocked the clear view of the exiting cracks.
Nondestructive Testing of Concrete Tank
An advanced nondestructive testing method was customized to investigate the potential location and depth of cracks. The Rayleigh Wave Method was selected for this project. The method uses the attenuation characteristics of Rayleigh waves (a type of surface wave) to test the depth of cracks in concrete structures.
The concept behind The Rayleigh wave method is similar to those used in the Spectral Analysis of Surface Waves (SASW). Using this method, an accurate estimation of the depth of each crack was able to be determined with minimum intervention and no interruption in the operation of the asset.
Repair Solutions for Cracks
Afterwards FPrimeC was able to provide the client with a report, which provided the location of each crack (in proximity to a reference point) as well as the depth of each crack. Based on this information, a repair procedure was designed and customized. FPrimeC engineers worked closely with the client and prime consultant to fine tune a repair program that can be implemented while the asset is under operation. FPrimeC was able to provide the client with a detailed repair plan, excavation parameters and recommended ideal grouting materials to be used.