chapter 3 rigid pavement - DOT On-Line Publications - Department ...

practice, chloride contents above 1.5-2.0 lbs./cu. yd. indicate a high
potential for corrosion.
The corrosion surveys conducted on these sections show there is a high
probability that steel corrosion is widespread throughout the three
sections, and a high potential exists for cracking of the pavement due to
corrosion. The current ASTM CB76-80 specification indicates the following
regarding the significance of the numerical value of the potentials
measured:
1) Less than 0.2 volts, there is a greater than 90 percent probability
that no reinforcing steel corrosion is occurring.
2) Between 0.2 and 0.35 volts, corrosion activity is uncertain.
3) Over 0.35 volts, there is a greater than 90 percent probability that
corrosion is occurring.
Also, in laboratory tests where potentials were greater than 0.5 volts,
approximately half of the specimens cracked due to corrosion activity.
The delamination survey data for the three sections indicates substantial
areas of delaminated concrete in the medium and high distress areas.
The Pachometer survey data for these three sections indicates a range of
concrete cover from 1.5 inches to 3.75 inches in the overlay areas. The
plans specified a tolerance of 2 l/2 - i: 11/16 inches in the overlay area.
Based on our field observations of the cracks and distresses in the
pavement and the above distress survey information, we believe there is a
significant amount of corrosion of the reinforcing steel in each of the
three test sections. There may be a somewhat lower level of corrosion
activity in the low distress area as compared to the medium and high areas,
nevertheless, extensive corrosion is likely occurring.
In reviewing the cores from the three test sections, it is apparent that
the corrosion activity is predominately in the transverse bars. Nearly
without exception, vertical and horizontal cracks were present where
transverse bars were experiencing even minor corrosion. See Attachments 1
and 2 for illustrations. The vertical crack above the bars likely
contributed to creating an environment that allowed corrosion to begin.
The Team also observed there had been a significant amount of full-depth
patching within the project. We understand patching operations have been
ongoing the last several years. As stated above, the outer lanes,
particularly the EB outer lanes, experienced early distress, and extensive
patching was already done in these lanes. Generally, the patches appeared
to be performing s: . sfactorily. Data showing the rate of deterioration on
this project was noi available.
3.7.8