Jacketing has been employed historically in Florida and elsewhere as a repair and rehabilitation method for corrosion damaged coastal bridge pilings. Such an approach involves either partial or complete encapsulation, most commonly in conjunction with a fiberglass form and mortar fill. Experience has indicated, however, that jacketing for this purpose (corrosion control) is not effective and, in fact~ may accelerate subsequent attack. Consequently, a study was recently performed to evaluate the condition of jacketed coastal bridge pilings in the State. Concurrently, a companion effort addressed development of a method for conducting such inspections non-destructively. The present paper reports data that we~ developed in conjunction with this latter effort and details the inspection protocol that ultimately resulted.
Concrete normally provides a benign environment for embedded reinforcement because of the alkaline nature of the cement paste (pH-13.5) which promotes formation ?l)Formerly, Graduate Research Assistant Florida Atlantic University. of a protective passive film upon the steel. However, such protection is often compromised for bridge pilings and Aated concrete components exposed to marine and coastal waters that contain significant levels of chlorides. Jacketing, which involves encapsulation of either a portion of or the entire piling length, is a methodology which was employed in Florida since 1940until recently in an attempt to rehabilitate and extend the service life of corrosion damaged bridge pilings. Figure 1illustrates schematically the components, materials, and configuration that comprise a jacketed pile.
In 1993, the Bryant Patten Bridges between Saint George Island in Franklin County and the mainland near Panama City were scheduled for repairs and rehabilitation because of concerns regarding deterioration of the pilings, many of which were jacketed. However, upon removing the jackets and loose concrete, it was disclosed that in numerous cases all prestressing tendons were corroded away and concrete cracking and spalling had occurred to such a degree that the piling cross section had been critically reduced. Figures 2 and 3 show example photographs of some of these pilings. This finding raised concerns regarding the integrity of other bridges in the State with jacketed pilings; and a study was initiated for the purpose of investigating and determining the condition of these?. A part of this effort included development of a methodology and protocol for non-destructively characterizing the condition of pilings that are jacketed. This paper reports the findings of the latter undertaking.
The state of bridge and bridge components has historically been represented in terms of a Numerical Condition Rating (NCR), as defined in Table 1. However, the concern in the case of jacketed pilings is that any deterioration of this component maybe concealed from visual inspection. Consequently, assessment of piling condition based upon visual observations alone may be non-conservative and lead to a falsely optimistic conclusion regarding integrity. Figure 4 shows the appearance of a typical jacketed piling, both as observed initially and then subsequent to jacket removal, for the purpose of illustrating this point. On this basis, development of a non-destructive protocol whereby the condition of jacketed pilings can be readily determined was considered to be particularly important.
