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Concrete Pile Damage

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Our firm is the CM on the reconstruction of the commercial port
here that suffered major damage in the 1993 earthquake.  Part of
the work is driving 24" sq precast pretensioned concrete piles of
lengths varying from 40 ft to 120 ft 

We have encountered a problem with some of the piles.  On a 40 ft
pile that has apparently been subject to normal handling stresses
only, the corner of the pile has spalled or peeled off in a
remarkably straight line resulting in the pile having a 6"
"chamfer" along one corner over part of the length of the pile. The piece 
apparently fell off when the pile was being lifted. The in-place testing 
indicates that this may have occurred on some of the driven piles also.

The pile prestressing is 16 - 0.6" dia strands arranged in a
circle with 1/2" dia spirals with 3" minimum cover to the
spirals.

I am investigating 4 areas as follows:

1. The stress distribution over the pile section may not be
uniform.  The compressive stress at the corners, being further
from the prestressing, is probably less than that in the center
of the section.  This would result in shear stresses being
induced parallel to the pile length

2. Steam curing was specified but not done.  "Conventional"
(compounds, water...) curing was.

3. Could the heat from the concrete be significant?  No special
measures were taken to dissipate the heat.  Members with a
maximum dimension of 24" are reasonbly common here and no special
measures are normally taken.

4. Is the detensioning sequencing critical?  I went and looked
over the contractor's stressing and casting operation.  The piles
are cast and stressed in a 400 ft length which is broken up with
rigid spacers at the appropriate locations for the various pile
lengths.

Has anyone encountered this phenomenon before?  I would welcome
any comments and suggestions.

Bruce Swanney, P.E.
Winzler & Kelly, Guam