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--estimate the cost of protecting these bridges, and

--develop a plan for repairing these bridge decks as
soon as possible.

AGENCY COMMENTS

In a letter dated November 14, 1978 (see app. II), the Assistant Secretary for Administration, Department of Transportation, stated that the Federal Highway Administration will modify its data retrieval program to better identify bridge decks and their condition on all Federal-aid routes, and thus provide more realistic estimates of the costs of bridge deck restoration to the Congress. This modified data retrieval program should be in operation by 1980. He also said that the funding problem faced by the States should be substantially alleviated by passage of the Surface Transportation Assistance Act of 1978 (P.L. 95-599) which authorizes $4.2 billion of Federal funds for fiscal years 1979 thru 1982 an 80-20 Federal/State ratio for bridge repairs.

CHAPTER 4

COST-EFFECTIVE METHOD NEEDED FOR STOPPING

DETERIORATION OF HEAVILY CONTAMINATED BRIDGES

Many of the existing unprotected bridge decks in 32 States are heavily contaminated. They contain chloride levels above the "corrosion threshold" which will cause the bridge deck to deteriorate and require premature replacement, unless a means is found to halt the deterioration. The Federal Highway Administration has not developed a costeffective solution for stopping the deterioration of chloridecontaminated bridges decks. An effective solution is needed quickly so that currently repairable, chloride-contaminated bridge decks can be protected and their useful life extended, thereby saving billions of dollars.

NEED FOR COST-EFFECTIVE METHOD
OF STOPPING DETERIORATION

The question of whether these physically sound, but chloride-contaminated bridge decks can be protected to achieve their 40-year expected life, has not been resolved by the Federal Highway Administration. In the meantime, the bridge decks continue to deteriorate. A permanent repair procedure of replacing the contaminated portions of the deck is expensive and, as a result, is not being implemented by the States. Numerous techniques have been suggested as possibilities for protecting existing bridge decks from further deterioration. These techniques (which are in various stages of development) include asphalt membranes, concrete overlays, internally sealed concrete, deep polymer impregnation, cathodic protection, and electrochemical removal of chlorides.

The

However, very limited performance data is available on the effectiveness of these potential protective systems. problem now is to develop methods to evaluate these systems that have already been identified. Without performance data, the Federal Highway Administration does not know if any of the alternatives will effectively solve the deterioration problem. Before these potential protective systems can be evaluated, additional laboratory research must be completed

to

--quantify the oxygen level necessary to support corrosion, and

--develop a method to determine the rate of corrosion of reinforcing steel in existing decks.

It is the opinion of various Federal Highway Administration officials, and the consensus of a 1976 project review conference, that this research would provide the capability to more accurately evaluate protective systems for new deck construction, as well as to evaluate rehabilitation methods. Without this research information, there is no sound method of determining which repair technique should be used for a given set of conditions.

Need to quantify other

variables supporting corrosion

The objectives of the research program for bridge deck deterioration have been to investigate methods for controlling or eliminating the corrosion of reinforcing steel in the concrete. The approach has been to explore methods to control or eliminate the effect of chloride--one of the elements, along with oxygen and moisture, required for corrosion to occur.

Some evidence now indicates that controlling oxygen or moisture is also successful. Field evidence is available which shows that membranes/overlays placed over heavily contaminated concrete have reduced the rate of deterioration. Since the chloride level is above that necessary to support corrosion, it is hypothesized that these installations work by limiting the availability of oxygen and moisture. Federal Highway Administration officials told us that there has been no research to quantify the amount of oxygen or moisture necessary to cause corrosion of the reinforcing steel.

Development of evaluation

tools being delayed

Existing evaluation methods cannot measure the rate of deterioration of an existing bridge deck. Therefore, it is extremely difficult to determine if, or to what extent, presently installed protective systems are effective. То provide this capability, the Federal Highway Administration plans to develop a "rate of corrosion" tool. This tool will determine the rate of reinforcing bar corrosion and the amount of stress it induces. A companion tool will measure the permeability of field concrete to chloride.

The importance of these tools--particularly the rate of corrosion tool--was highlighted by one Federal Highway official who stated that the evaluation of membrane/overlay systems is awaiting development of this tool.

The development of these tools is not progressing as rapidly as possible due to the lack of funds, even though they are essential for gathering performance data on the potential methods of controlling bridge deck deterioration. During the period beginning in fiscal year 1974 and continuing until fiscal year 1977, very little research was undertaken to develop these tools. As a result, program officials stated that the development of the rate of corrosion and permeability tools have been delayed by about 3 years. Federal Highway Administration officials are hopeful of fielding these tools within 3 to 5 years.

CONCLUSION

Many decks currently contain chloride beyond the "corrosion threshold." The question of how these chloridecontaminated decks can be salvaged has not been answered by the Federal Highway Administration. Several potential protective systems have been identified for extending the service life of bridge decks. However, very limited performance data on the effectiveness of these protective systems is available. Without this type of performance data, the effectiveness of the various protective systems is unknown.

We believe that it is time for the Federal Highway Administration to emphasize the development of evaluative techniques that will rapidly and accurately determine the effectiveness of the various protective systems for chloridecontaminated decks. Time is important. The sooner these issues can be resolved and applied to existing bridge decks, the fewer the decks that will require complete replacement.

A program to protect existing contaminated bridge decks instead of completely replacing them may save billions of dollars. Expanded and accelerated research is the first step. The second step would be to provide funds for installation of the protective system. Based on the experience in placing protective systems on noncontaminated bridges, the lack of funds could also be a major problem which would prevent installation of effective protective systems on contaminated bridges.

RECOMMENDATION TO THE

SECRETARY OF TRANSPORTATION

We recommend that the Secretary reassess the progress being made in finding proven, cost-effective methods for protecting existing chloride-contaminated bridge decks, and take appropriate action to resolve any problems that are delaying progress.

AGENCY COMMENTS

In a letter dated November 14, 1978 (see app. II), the Assistant Secretary for Administration, Department of Transportation, said that it plans to continue the search for less expensive, more easily applied, permanent rehabilitation procedures which do not involve removal of large quantities of sound concrete. A new federally coordinated research and development project has been formulated and submitted for funding in fiscal year 1980 for this purpose.

With regard to the development of evaluation tools, the Assistant Secretary said that contracts have recently begun, or are about to begin, on the development of what are believed to be the final tools necessary. These are devices to quickly measure the oxygen content at the level of the reinforcing steel, to measure the moisture content at the level of the reinforcing steel, and to determine the rate of corrosion of the reinforcing steel in existing bridge decks. Further, a device for nondestructive measurement of a bridge deck concrete's chloride content at the level of the reinforcing steel is now in the final stages of prototype testing.

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