Determining Methods for Evaluating Corrosion Damage in Piles Encapsulated in Protective Jackets

The primary purpose of this study was to determine methods to evaluate the condition of piles that had been encapsulated in fiberglass and mortar jackets. The secondary goal of the study was to use the evaluation methods to perform a condition assessment of the HRBT piles. To accomplish the goals of this study, fifty-three bridge piles were carefully selected on the Hampton Roads Bridge and Tunnel (HRBT) in Hampton Virginia. Each pile studied represented a variety of conditions. ages, types, and locations.

The methods used to evaluate the jacketed piles were both destructive and non­destructive. Methods that would be considered destructive were chloride analysis. and jacket autopsy. Non-destructive methods included, cross-hole sonic logging, ground penetrating radar, sonic echo, impulse response, electrochemical half-cell, electromagnetic cover meter. electrical resistivity. ultrasonic pulse velocity, and visual assessment.

No individual test method was able to completely indicate the condition of the jacketed piles, but a combination of the methods did provide valuable information about the condition of the piles. A combination of half-cell measurements, sonic echo, impulse response, ground penetrating radar, and chloride analysis was useful to evaluate the condition of jacketed piles. Ultrasonic pulse velocity was used to deten11ine the velocity of sound through the piles. Cross-hole sonic logging was not effective on the piles due to the difficulty of placing the transducers on the piles. The cover meter was not an effective evaluation method due its limited depth of penetration and inability to detect minor section loss in the reinforcement. Resistivity measurements were made to evaluate the concrete and mortar's susceptibility to corrosion.

The HRBT piles were discovered to be subject to a wide range of corrosion activity from severe section loss of a vertical tendon to no corrosion at all. A majority of the piles exhibited active corrosion, but only a small portion of the piles were suffering from substantial corrosion damage. The jackets hid damage, causing the severity of the actual condition of the piles to be underestimated when assessed visually.

From the results of this study, researchers recommend that jackets with mortar fill not be installed on piles with prior corrosion damage, as the jacket will obscure future damage and may accelerate corrosion.