Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 24
24
CHAPTER FOUR
CATHODIC PROTECTION USE: POLICIES AND PRACTICES
To obtain a more complete understanding of the use and the The perception of the magnitude of the corrosion prob-
application of cathodic protection technology, the corrosiv- lem correlates reasonably well with their deicing salt use.
ity of the environment, the decision-making process, and the From the four agencies that indicated that corrosion was a
application and use of cathodic protection systems need to minor problem, two have salt use in the range of 0 to 5 tons
be analyzed. As cathodic protection technology is relatively and two in the range of 6 to 10 tons per lane-mile per year.
more expensive than the other alternatives, with the excep- Eight of the respondents that indicated that corrosion is a
tion of electrochemical chloride extraction, the perception of moderate problem use 0 to 5 tons per lane-mile per year. Of
corrosivity of the environment is very important in justifying the remaining, 4 agencies use 6 to 10, 4 agencies use 11 to
its use. Similarly, if the decision-making processes for repair 15, and 2 agencies use 16 to 20 tons per lane-mile per year
and rehabilitation either are not sophisticated enough or do of deicing salts. Four respondents did not provide their
not include cathodic protection as an alternative, then the use deicing salt usage and one only has marine exposure. Three
of the technology would be limited. The design, installation of the eight respondents that consider corrosion to be a
and quality control, and monitoring and maintenance prac- major problem, Connecticut, Oklahoma, and Oregon, have
tices have a significant impact on the experience of use of this salt use in the range of 0 to 5 tons per lane-mile per year.
technology. The survey conducted in this effort focused sev- Oregon's primary exposure condition is the marine envi-
eral questions in these areas. A summary of the responses is ronment along the Pacific Coast. Of the agencies that indi-
presented here. cated it was a major problem, the state of Virginia uses 6
to 10, Utah and Vermont use 11 to 15, and New York and
MAGNITUDE OF THE PROBLEM
Pennsylvania use more than 20 tons per lane-mile per year
of deicing salt.
A summary of responses to the question regarding the mag-
nitude of the corrosion problem faced by the agency is pre- A summary of salt usage agencies is presented in Table 5.
sented in Table 4. Mississippi is the only state among the The majority of the respondents, 17 of the 32 agencies that
respondents that does not have a corrosion problem on its provided salt usage information, have average salt usage in
reinforced concrete bridge structures. Four respondents (Ari- excess of 5 tons per lane-mile. The manner in which the
zona, Indiana, New Jersey, and Wyoming) indicated that it SHRP Methods Application Manual (47) categorizes salt
was a minor problem. A majority of respondents consider it use implies that salt use of more than 5 tons per lane-mile is
to be a moderate problem. Eight respondents, Connecticut, the highest category of use. Based on the SHRP Manual, a
New York, Oklahoma, Oregon, Pennsylvania, Utah, Vermont, majority of the respondents are in the high usage category.
and Virginia, consider it to be a major problem.
The relationship between deicing salt use and the mag-
Table 4 indicates that corrosion is at least a moderate nitude of the problem can be a simple one. However, the
problem for 30 of 36 respondents. Considering that many analysis is difficult to perform because (1) deicing salt data
states and several Canadian provinces that experience severe available from various sources are often incomplete; (2) data
winters did not respond to this survey, the actual corrosion are often not compiled in a uniform manner; (3) deicing salt
problem must be much more severe than that suggested by the use varies from one part of the state to another; (4) the num-
responses received in this effort. ber of bridges vary from one part of the state to another;
(5) the exposure is a combination of deicing salts and marine
Interestingly, the top five users of the cathodic protection environment; and (6) some of the states or portions of the
technology, Missouri, New Brunswick, Florida, Ontario, and states may be using non-chloride-bearing deicing salts. The
Alberta have classified their corrosion problem as moderate. climatic conditions can also have a significant impact on
Thus, it is reasonable to conclude that cathodic protection the rate of corrosion and the diffusion of chloride ions into
could be an applicable tool for a majority of the agencies, the concrete and thereby influence the relationship between
based on the magnitude of their corrosion problem. How- deicing salts and magnitude of the problem. For example, in
ever, many agencies now use epoxy-coated rebar and at least every cold environment, although salt usage is much higher,
one state has questioned the applicability of cathodic protec- the colder temperatures maintain corrosion at much lower
tion on the rebars. levels.
