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Harbor
Crane Rail Removal
The outboard crane rail (the rail nearest the curb) was removed
to accommodate sufficient anchorage length for the transverse composite
reinforcement in the curb slab. Details of the rail connection to
the deck were unknown prior to the project (as-built drawings did
not exist). As the contractor removed asphalt and uncovered the
rails, we found 1-inch (2.5 cm) diameter anchor bolts at 30 inches
on center holding the rail between Bents 177 and 189 (west end)
and 18 inches on center between Bents 216 and 225 (east end). The
contractor cut the anchor bolts and removed the rail section. Below
the rail was a continuous bearing plate on the east end and 6-inch
by 12-inch (15 cm by 30 cm) plates at 30 inches (75 cm) on center
on the west end. The steel plates and anchor bolts were left in
place. The plates were set on a 2-inch deep bedding of concrete
mortar containing ¾-inch (2 cm) aggregate. The bedding was
disbonded from the substrate and had to be removed over the length
of the east end. A 1-inch (3 cm) deep cut was made in the concrete
1 inch (3 cm) back from the edge of the rail slot. The walls of
the slot were then “chiseled” out with a jackhammer
to provide a rough surface to bond with the repair material (Figures
13 and 14).
An additional 112 ft2 (10.5 m2) of delaminated concrete was removed
from the deck adjacent to the rail.
Figure 13. Removing unsound concrete adjacent
to outside rail slot (removed).
Figure 14. Typical concrete removal from
edge walls of rail slot.
Several concrete repairs that had been completed 3 years earlier
(1996) did not securely bond to the substrate and had to be removed.
Disbonding of these repairs was discovered while removing adjacent
concrete. Although the 15-pound (7.3 kgm) jackhammers disclosed
additional areas of delaminated concrete, they are too small to
cause the delaminations. The jackhammer size was specifically limited
to preclude damage to sound concrete and their use was appropriate.
Almost 40 percent additional unsound concrete was removed from
the top of the deck than originally estimated by condition assessment,
which resulted in additional expense to the Government and delays
in the project. NFESC extensive site investigations prior to the
project were unable to disclose all the unsound concrete. This experience
emphasizes the common complaint in the Navy and industry that existing
non-destructive methods are not adequate to predict the extent of
unsound concrete.
Concrete removal on the underside proceeded similarly to that on
the top of the deck using saw cut perimeters and 15-pound (7.3 kgm)
pneumatic hammers. Repairs made in 1996 used a “form and pump”
method that extended the surface outward by about 2 inches (5 cm)
(Figure 7). Several protruding patches that interfered with the
installation of cathodic protection and external reinforcement were
removed. In addition, previous “flush” repairs were
disbonded from the concrete substrate. Built-up repair patches totaling
56 ft2 (5.2 m2) were chipped approximately 1/2 inch (1 cm) below
flush with the prevailing surface with a jackhammer. The contractor
removed 24 ft2 (2.2 m2) of previous “flush” repair areas
that were disbonded.
Abandoned pipes and other utility lines were removed in preparing
the underside of Bravo 25. The contractor encountered no asbestos.
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