Bermuda
Hot-dip galvanized reinforcing
steel in concrete has been used extensively
since the early 1950s. One of the first installations
occurred in the construction of the Longbird
Bridge in Bermuda by the US Navy in 1953.
Galvanized steel was used to reinforce the
bridge deck in the construction of an 18-foot
long, single approach span concrete bridge.
The Bermuda marine environment is highly
corrosive as exhibited in a 1978 inspection
of bridges and quays conducted by Construction
Technology Labs. This inspection included
the Longbird Bridge and showed chloride levels
in the concrete up to 4.3 kg/m3 (7.3lb/yd3).
During this inspection, a low chloride ion
gradient across the concrete cores indicated
that significant chlorides were already in
the
concrete at the time of placing (most likely
from salt water used to mix the concrete).
The internal
chloride concentration, combined with salt
spray from the nearby ocean, produce an extremely
corrosive environment.
According to this inspection, the galvanized
coating had only been slightly affected by
corrosion, as 98% of the initial zinc (galvanized)
coating remained intact. A later inspection
of the galvanized reinforcement in the Longbird
Bridge was conducted in response to the Bermuda
Ministry of Works and Engineering’s unilateral
specification of hot-dip galvanized reinforcement. In
this report, evidence of zinc coating integrity
was found on exposed sections of rebar during
repairs made in 1984, after 30 years of exposure
to extremely high chloride levels.
