Page 252 - Challenges in Corrosion Costs Causes Consequences and Control(2015)

230 CORROSION CONTROL AND PREVENTION

TABLE 4.16 Summary of Costs and Life Expectancy for Rehabilitation Methods
Average Range Average Range of
Type of Cost of Cost Life Expected
2
2
Maintenance ($/m ) ($/m ) (Years) Life (Years)
Impressed current (CO) (deck) 114 92–137 35 15–35
Impressed current CP 143 76–211 20 5–35
(substructure)
Sacrificial anode CP 118 108–129 15 10–20
(substructure)
Electrochemical removal (deck) 91 53–129 15 10–20
Electrochemical removal 161 107–215 15 10–20
(substructure)

the prestressing steel and concrete and possible hydrogen embrittlement (from
overprotection of the prestressing steel) have been alleviated by the establishment of
criteria for the qualification of prestressed concrete bridge components for CP.
The costs of electrochemical rehabilitation alternatives for bridge structures are
given in Table 4.16.
In general, electrochemical methods are in competition with rehabilitation utiliz-
ing an overlay such as low-slump, high-performance, or latex-modified concrete. The
deck condition is often the controlling factor in the selection of the rehabilitation
method. In some instances, a combination of these methods is selected. For example,
electrochemical removal of chloride followed by an overlay or an overlay in conjunc-
tion with CP to mitigate any further corrosion.
Salt-induced reinforcing steel corrosion in concrete bridges is a serious problem
and an economic burden. Although the positive effect of corrosion protection mea-
sures can be seen on individual cases, there are many bridges (thousands) without
corrosion control.
It is useful to note that even the latest corrosion control methods are not likely to
prevent all corrosion for the life of the bridge structure. Therefore, there is a need for
repair/rehabilitation of bridge structures, and the mitigation of existing corrosion will
draw the attention of bridge engineers for years to come.
There are several methods for the rehabilitation of concrete structures that have
deteriorated because of chloride-induced corrosion of the reinforcing steel. The
problems in concrete structure are generally found after significant deterioration
has resulted in the cracking and spalling of the concrete, and the majority of the
remedial measures are applied after removal and patching of the damaged concrete.
The available methods are based on one of the following principles (16).

1. Provision of a barrier on the surface of the concrete to prevent future ingress of
chloride (overlays, membranes, etc.).
2. Control of the electrochemical reactions at the steel surface to mitigate the cor-
rosion reactions by imposing proper voltage field on the rebar CP.