Oklahoma D.O.T. Bridges Case Study
PROBLEM: Demonstration of Surtreat products on bridges with visible spalling of the decks and bent caps
STRUCTURE: Structural concrete bridge decks along I-40 in Oklahoma
PROBLEM:
Surtreat personnel, at the suggestion of Oklahoma Department of Transportation staff, performed a visual inspection of several bridges on I-40 near the Oklahoma-Texas border in May, 2002. The purpose was to identify several locations for demonstration of Surtreat formulations under field conditions and to experiment with the delivery of Surtreat formulations through an asphalt overlay. Ultimately, three bridges were selected; two located 4.3 miles east of US 283 and one bridge with concrete deck overlaid with asphalt, located 11.7 miles east of the Texas line. The bridges with exposed concrete decks were selected because of visible spalling of the decks and bent caps. The bridge with asphalt overlay was selected to test the potential for Surtreat to penetrate through the asphalt in concentration to migrate into the concrete. This bridge deck did not have a membrane under the asphalt. The test and demonstration protocol is described later. The goal was to demonstrate abatement of corrosion and reduce permeability of the concrete on the first two bridges under field conditions. The purpose of the third bridge test was to field test penetration of Surtreat through an asphalt overlay to reduce porosity and provide corrosion abatement on the underlying concrete deck.
SITE DESCRIPTIONS:
The test bridges are located on I-40 west of Oklahoma City. The climate is arid and the bridges have been exposed to both sodium chlorides and magnesium chlorides. The bridge with asphalt overlay is located just east of Erick, 11 miles east of the Texas line The two bridges with concrete decks, (eastbound and westbound) are just east of Sayre.
The Erick bridge was built in 1972. It has a length of 599′, width curb to curb 38′, (26’ treatable) 22,762 sq ft (curb to curb) underside 23,840 sq ft (outside to outside). The concrete deck is 8″ thick, with steel beams spanning 34′ and concrete bents and columns. The bridge is experiencing corrosion, spalling and delamination. The underside of this bridge was accessed by the ODOT Snooper truck. The asphalt overlay was milled off three years ago, destroying the original membrane. It was then re-topped with asphalt. Core tests performed July 11, 2002 found that the shoulders were not milled and therefore have a membrane in place, limiting the treatable area to the two 13” traffic lanes The asphalt cores, 4” diameter, were tested for penetration rates with good results, using SURTREAT TPS 2 under laboratory conditions. A test panel was located on the Erick westbound bridge starting 140’ west of the east abutment. One 19’ panel spanning the two traffic lanes between expansion joints was delineated for treatment.
The eastbound Sayre bridge was built in 1970, with a length of 178′ and curb to curb width of 38′. The deck is supposed to have 2″ cover over the rebar, however rebar exposed in the traffic lanes varied in depth from 3⁄4” to 2”. The deck had numerous spalls, concrete and asphalt patches. The deck is 6764 sq ft curb to curb and the underside is 7369 outside to outside. Three test panels were delineated on this eastbound Sayre bridge measured 99’ west of the east end of the parapet wall to an expansion joint. Three 10’ curb to curb test panels were delineated for treatment and control. The westbound Sayre bridge appears to be similar to the eastbound bridge but built in 1980. Dimensions are the same with exception of some difference in steel beam length. The problems are the similar. Three test panels were delineated on the westbound Sayre bridge measured 30’ west of the east end of the parapet wall to an expansion joint. Three 10’ curb to curb test panels were delineated for treatment and control.
TESTING:
Several field test methodologies were utilized to develop our data.
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- Capo-Test for strength estimation of compressive strength near to surface
- GWT for measurement of water permeation at a constant pressure
- GalvaPulse to measure corrosion rate in rebar
- Acid reactivity using 20% HCl
- Rainbow Dye spray indicator for pH and carbonation indicator
CONCLUSION:
The demonstration and test results show that limited application of Surtreat formulations have cut corrosion rates in half, doubling the service life of the structure,(where treated). Higher application rates and more thorough surface preparation can provide even greater service life extensions. The porosity reductions achieved are important in reducing future penetration of water, chlorides and other elements essential to the corrosion cycle.
WANT TO SEE HOW SURTREAT® CUT THE CORROSION RATES ON THESE BRIDGES IN HALF?
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