Contractor Resource Center

Introduction
Until the early 1970’s, West Virginia along with most other states used black steel for reinforcement in nearly all reinforced concrete structures. In slab structures such as bridge decks it had long been noted that deterioration of the deck surface was directly related to oxidation of the top mat of the steel reinforcement. As the reinforcement oxidizes the tensile stresses produced are often higher than the strength of the concrete. This eventually produces cracking and spalling of the structure.
Although uncoated steel was being used, it was not considered unprotected steel. Normal concrete s high-alkali environment passivates the steel effectively preventing corrosion. Problems occur when either of two occurrences happens - Carbonation of the concrete or the presence of chloride ions. If either or both of these conditions are met the steel will spontaneously begin to corrode or rust at localized areas.⁽¹⁾
During this period in time a widely held belief was that if the steel could be more permanently protected from exposure, oxidation could be practically eliminated. This led to the development and use of epoxy coatings. The use of these coatings has been the chief and in most cases the only form of protection of steel reinforcement in West Virginia and many other states. Since that time nearly all cast in place deck structures in West Virginia have used epoxy coated steel reinforcement.
In 1992 reports began to surface that the epoxy coating practice was not providing the protection for which it was intended. ⁽²⁾ Previous studies involving the use of epoxy coated steel in Florida also produced unfavorable conclusions and resulted in the cessation of specifying the use of epoxy coated reinforcement by the Florida Department of Transportation in 1988. ⁽³⁾
Due to these and reviews of other reports, the Materials Control, Soil and Testing Division of the West Virginia Department of Highways instituted a study of the present condition of older bridge decks using epoxy coated reinforcing steel.
The purpose as defined in the approved work plan for this investigation was to evaluate the in-service performance of the referenced bridge decks. The evaluation procedure included a thorough visual survey on each deck with particular attention given to surface and subsurface deck cracking. Evidence of rust staining would also be of particular interest. In addition a complete delamination survey was performed using the chain drag technique in accordance with ASTM D4580. The delamination survey was used to identify only areas that were the result of reinforcement corrosion. Areas indicating delamination, which could be definitely associated with non-epoxy coated expansion devices or with scaling, were not considered in this investigation. After these processes were completed, areas exhibiting evidence of corrosion would be further investigated by coring. It has long been a policy in West Virginia to avoid coring bridge decks when there is no cause for concern.

Investigation
All decks were surveyed between May and August of 1993. In order to maintain uniformity the same personnel were used for all investigations.
This paper documents the investigation of fourteen individual bridge decks that were identified as among the first using epoxy coated steel reinforcement in West Virginia. These decks are identified in Table 1. The bridges in this investigation served a wide range of traffic both in numbers and type. The lowest average daily traffic (ADT) count was on bridge numbers 2768 and 2776 with an ADT of forty. The highest count was an ADT of 15,000 on bridge 2953. The type of traffic varied from bridge 2673 which had virtually no truck travel to bridge 2655 which had 62% truck travel. The functional classification ranged from expressway sites (2672 and 2668) down to rural sites (2776 and 2768).

Bridge #2975 WV 37 East Lynn Bridge
Year constructed - 1976
Initial Investigation June 29, 1993
This is a two-lane deck with a pedestrian walkway separated by a parapet. The deck is 172 feet long and 30 feet wide. The area of the deck is 5160 square feet. No steel associated delamination. There is what could be considered normal transverse cracking the full width of the deck. These cracks are very light and are not associated with any delamination. The only ’defects’ observable on the deck three small circular spalled areas. The first two areas are approximately 8 to 10 inches in diameter and approximately 1/2 to 3/4 inches in depth. These two areas are located at the center of the northbound lane 51 feet from the southern end of the structure. The third area is located in the southbound lane approximately 30 feet from the south end of the deck and approximately 2 feet from the centerline. The depth of this spall is approximately 1/2 inch. No delaminations were detected at these spalled areas.

Bridge #2655 US 52 Kermit
Year constructed - 1976
Initial Investigation July 21, 1993
The deck consists of two fifteen-foot lanes with a four-foot shoulder on either side. The length of this deck is approximately 445 feet. The area is 17000 square feet. The interesting aspect of the visual investigation was the lack of defects. No patching, spalling or cracking was evident. The bottom of the deck showed no signs of cracking. No delaminations other than scaling associated with the expansion dams were detected.

Bridge #2665 Rt. 2 Huntington Bridge
Year constructed - 1976
Initial Investigation July 28, 1993
This deck is a two-lane structure with an attached pedestrian walkway opened to traffic in 1976. The deck is 584 feet in length with two 15-foot lanes and a 6-foot walkway separated from the traffic lanes by a 1-foot parapet. This comprises approximately 21,000 square feet. The deck is slightly arched with the high point of the arch being approximately 200 feet from the south end of the deck. Visual investigation found no spalling or patches. Transverse cracking was evident in much of the deck. No cracking was found in the deck north of the north-end expansion device. In the immediate vicinity of the highest portion of the slight arch, the transverse cracking was more frequent occurring at approximately 2-foot intervals. In the remaining area of the deck the cracking appeared approximately on 4-foot centers. Nearly all the area of the wheelpaths had completely exposed aggregate. No popouts were observed. The underside of the deck was not visible due to corrugated metal (possibly forms) completely covering the bottom of the deck. The delamination survey found no rebar-associated delaminations. Delamination associated with the expansion dams occurred only on the northern expansion dam in the southbound lane.

Bridge #2768 Co. 37 Buffalo Creek
Year constructed - 1976
Initial Investigation June 14, 1993
The deck measured 116 feet in length with two 12-foot wide traffic lanes and two eleven foot shoulders. The area of this deck is 5300 feet. No spalling, patching, or cracking were observed on either the deck surface or the underside. No delaminations were found in either of the two traffic lanes or in much of the shoulders. Approximately 25% of the shoulders could not be examined for delamination due to the large buildup of rubble adjacent to the parapets.

Bridge #2847 US 52 McDowell County
Year constructed - 1976
Initial Investigation August 3, 1993
This deck consisted of two 12-foot lanes and two 4-foot shoulder. The length of the deck is approximately 130 feet and the area approximately 4100 square feet. Visually, there were no apparent deficiencies found. The delamination survey found 1 area of approximately 1 square foot in the Westbound lane. This delamination is located in the right wheelpath approximately 138 feet from the Eastern end of the deck. The underside of the deck exhibited no defects of any kind.

Bridge #2673 I-79 Overhead Bridge
Year constructed - 1975
Initial Investigation June 9, 1993
This deck is not part of mainline I-79 but an overpass carrying a County route over the interstate. Shoulder markings are not visible. The dimensions of the deck are 42 feet by approximately 400 feet. The two-lane deck encompasses approximately 17,000 square feet. An extremely low number of cracks (approximately 12) were noted on the surface of the deck. No delaminations were noted other than those associated with the expansion dam devices located at either end of the deck and at the first construction joint in from either end. The underside exhibited very light cracking with some light efflorescence.

Bridge #2672 I-79 Mainline Bridge
Year constructed - 1976
Initial Investigation June 8, 1993
Two decks are involved in this site. Both decks consist of two 12-foot lanes, 1 twelve-foot shoulder and 1 four-foot shoulder. Each deck is approximately 7000 square feet in area. No re-bar-associated delaminations were noted in any portion of the two decks. A normal amount of transverse cracking was observed with one exception. Each deck was divided into 5 sections by construction joints. There was noticeably more of the transverse cracking in the second and fourth section from the southern end of the Southbound deck and the second section, again from the southern end, of the Northbound deck. Again, this cracking did not appear to be severe or out of the ordinary for decks of this age. It is somewhat more unusual that the remaining section exhibited so little cracking. The underside of the deck exhibited some light cracking and associated efflorescence.

Bridge #2776 Co. 37 Buffalo Creek
Year constructed - 1975
Initial Investigation June 14, 1993
The deck measured 136 feet in length with two 12-foot wide traffic lanes and two eleven foot shoulders. The area of this deck is 6200 feet. No spalling, patching, or cracking were observed on the deck surface. No delaminations were found in either of the two traffic lanes or in much of the shoulders. Approximately 25% of the shoulders could not be examined for delamination due to the large buildup of rubble adjacent to the parapets. The underside of the deck was not accessible.

Bridge #2668 I-79 Big Sandy Bridge
Year constructed - 1976
Initial Investigation June 7,8, 1993
This is a 2-deck bridge with each deck approximately 980 feet long by 40 feet in width. The area of each deck is 39,200 square feet. In both decks there was a noticeably higher number or transverse cracks in the traffic lanes only. These cracks are four to six feet in length on approximately four-foot centers. There are no delaminations associated with this cracking pattern. The Southbound deck exhibited no delamination. The Northbound deck contained one area of approximately one square foot of delamination. This occurs 92 feet from the Southern expansion dam almost directly on passing lane/left shoulder stripe. There is also a popout approximately two inches deep associated with this delamination. The underside of both decks was typical in that they exhibited typical light cracking and some efflorescence.

Bridge # 2771 WV 20 Hinton Bridge
Year constructed - 1976
Initial Investigation June 14, 1993
This two-lane deck with a separated pedestrian walkway is 1300 feet long and approximately 32 feet wide. The area of the deck is 41600 square feet. This deck visually was in very good condition. The typical light transverse cracking was evident in only six of the fourteen panels separated by construction joints in the deck. No delaminations were encountered. One unusual feature was a large number of pop-outs, about the size of an individual coarse aggregate particle, in the panel beginning at approximately 327 feet from the Southern expansion dam. As was stated, no delaminations occurred in this area and the depth of these pop-outs was not sufficient to reach the top mat of the re-inforcing steel. The underside of the deck was not accessible.

Bridge # 2953 US 19 Adamson St. Bridge
Year constructed - 1975
Initial Investigation August 10, 1993
This is a two-lane deck with a separated pedestrian walkway. The dimensions of the deck are 300 feet in length and 30 feet in width for a total surface area of 9000 square feet. With the exception of one full width transverse crack 175 feet from the Southern expansion dam, there were no defects observable on the surface of the deck. This crack occurs approximately mid-way between the two piers of the bridge. No delaminations and no other cracks were found. There was a uniform exposure of the aggregate on the entire surface of the deck, not just in the wheelpaths. The underside of the deck was not accessible.

Bridge # 2930 Industrial Bridge
Year constructed - 1974
Initial Investigation August 10, 1993
This deck consisted of two lanes and two separated pedestrian walkways. The length of the deck is 557 feet and the width was measured to be 32 feet. The surface area is 17800 square feet. Delaminations were observed in a number of areas on this deck. All linear measurements were taken from the Southern end of the deck. At 37 feet, a delamination approximately 2 feet wide extends for the width of both lanes. This delamination is centered on a construction joint. At approximately 62 feet a one square foot delamination was present in the left wheelpath of the Northbound lane. At 82 feet, a delaminated area was detected approximately 1 foot wide and 6 feet in length. The area begins at the pedestrian walkway parapet and extends into the Northbound lane approximately two feet. At 250 feet, an area of approximately one square foot in the right wheelpath of the Northbound lane. At 320 feet, an area of approximately one square foot in the center of the Southbound lane. The total area of all these delaminations is approximately forty square feet. Some light, full-width and partial- width, transverse cracking was observed. No delaminations were associated with any of the cracks.

Table 2 presents the results of the delamination surveys performed on each deck.

Conclusions
Any conclusions made from this investigations must be based on the evidence gathered. From this evidence several conclusions are apparent. First, the bridges surveyed could be considered typical. The traffic count data and wheelpath wear noted in the visual survey illustrates that the bridges have and are carrying varying amounts of traffic.
Nearly all the decks exhibited transverse cracking on the deck surface. This cracking was uniformly light and in no case was there any delamination associated with the cracking. Prior experience would indicate that most if not all the noted cracking could have been shrinkage related. It is also important to note that none of the cracking observed on the underside of the deck exhibited any signs of rust staining. This would lead one to conclude that either no corrosion was taking place in the deck or that no water was permeating out the bottoms of the decks.
Another conclusion that can easily be drawn is that it is apparent that for practical purposes there are virtually no delaminations present in these decks. Ten of the fourteen decks physically had zero delamination. Of the remaining four decks the percent delamination ranged from 0.002 percent to 1.0 percent. These percentages are from experience considered insignificant. Again it should be repeated that these decks have had nearly twenty years of service.
One factor that is not readily apparent from the data is to what extent the decks have been subjected to chloride ions in the form of de-icing salts. In West Virginia, the climate is such that there is normally no extremely long periods of heat or cold. Located at the latitude that we are and with the higher than average elevations, we do experience very large numbers of freeze thaw cycles each year. In many ways this produces greater problems for pavements and bridge decks that long periods of one extreme. One of the problems associated with this type of climate is the use of often-large amounts of de-icing salts deposited each winter season.
The normal method of determining the chloride content present in concrete is AASHTO test method T260. This involves drilling a test core into the concrete to obtain specimens for laboratory analysis. As was previously mentioned, it is not the normal policy of the West Virginia Department of Transportation to core what are apparently sound concrete structures. In this case, to positively determine the presence of chlorides, four of these decks were tested in accordance with AASHTO T260. The results of that testing is presented in Table 3.

Finally to illustrate the difference between decks that have epoxy coated reinforcement and decks that do not, data was analyzed on decks of approximately the same age, usage and maintenance that did not contain epoxy coated reinforcement. This data is presented in Table 4. As can be readily seen by comparing the data taken from bridges with similar ages, chloride contents and usage, there is a dramatic difference in the percentage of delaminations. Of particular interest is in comparing bridge numbers 2668 and 2672 from the epoxy coated group with 2669 and 2670 from the non-epoxy group. The reason for this particular interest is that all eight of these decks are located on the same route within a four-mile section. In fact the four non-epoxy decks are located between the four epoxy decks. These decks must have been subjected to the same traffic, weather, and maintenance conditions. The four deck employing epoxy coated reinforcement exhibited a total of one square foot of reinforcement associated delamination in a total area of 92,400 square feet. The four decks not employ the coated reinforcement averaged 8.5 percent delamination. Visually, the major difference between the two groups was the transverse cracking in the non-coated group was more easily detected. No indications of rust staining were apparent on any of the decks.
From the data collected in this investigation, it can be concluded that the use of epoxy coated reinforcement in bridge deck in West Virginia has resulted in a dramatic decrease in delaminated areas and therefore an increase in the useful service life of these structures.

Footnotes
⁽¹⁾- R.E. Weyers, B.D Prowell, M.M. Sprinkel and M. Vorster, Concrete Bridge Protection, Repair, and Rehabilitation Relative to Reinforcement Corrosion: A Method Application Manual, Strategic Highway Research Program, SHRP-S-360, 1993
⁽²⁾- K. Clear, Effectiveness of Epoxy Coated Reinforcing Steel, Canadian Strategic Highway Research Program, March 1992
⁽³⁾ - L. L. Smith, R. J. Kessler and R. G. Powers, Corrosion of Epoxy-Coated Rebar in a Marine Environment, Transportation Research Circular No. 403, March 1993