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Photo:   Deck sealer test specimen
Photo 1. Deck sealer test specimen.
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Effectiveness and Life Performance of Concrete Bridge Deck and Crack Sealers
Research by
Melissa Dorshorst / Prof. Jose Pincheira
Dept of Civil & Environmental Engineering

The primary objective of this project was to complete a systematic assessment of concrete bridge deck and crack sealers based on their effectiveness and life performance. Deck sealers are commonly applied during the final stages of construction to protect the deck against chloride ion intrusion. Crack sealers are used to penetrate, fill, and bond existing cracks back together. While both types of products are commonly used by Departments of Transportation around the country, little is known about the effectiveness of the products over time.

The deck sealer portion of the project focused on measuring the ability of 14 different deck sealers to resist chloride ion intrusion from a deicer solution typically used on Wisconsin bridges. Several batches of concrete were cast, each containing 10 concrete prisms measuring 3"x11"x11." Twenty-one days after casting the concrete, the top 11"x11" surface of six specimens from each batch were sealed with a concrete bridge deck sealer currently available to and possibly in use by the Wisconsin DOT. The remaining four specimens from each batch were left with their top surfaces unsealed to serve as controls. A week after sealing, the top surface of each specimen was sandblasted, removing approximately 1/8" of the top concrete surface to simulate abrasion that would occur on bridge decks due to vehicular traffic. The specimens were then allowed to dry out for 14 days, during which time a foam dam was built around the outside perimeter of the top of the specimens.

After the drying period, all six of the sealed specimens and three of the unsealed specimens from each batch began 90 days of continuous ponding of a deicer solution, 3% sodium chloride. While some specimens were left to be ponded at ambient conditions in the Wisconsin Structures and Materials Testing Laboratory, companion specimens for each sealer were ponded while subjected to freezing and thawing cycles. The cycles, intended to simulate Wisconsin winters, were performed in a temperature controlled room at the University of Wisconsin Biotron, where one cycle of freezing at -4°F alternating with thawing at 86°F was performed each day.

At the conclusion of ponding, all specimens were rinsed of the remaining deicer solution and allowed to air dry. Three samples were drilled from each specimen, taken from a depth of 0.5" to 1" below the top surface. These samples were tested using a titration procedure to determine the percent of chloride they contained. The sealed samples were compared to the unsealed samples from each batch to measure the relative performance of the sealers, where the lower percent chloride ion indicated a sealer was better able to penetrate and protect the concrete. In addition, chloride ion tests from the specimens subjected to freezing and thawing cycles were used to gauge the decreased ability of the sealer to protect the concrete due to freezing and thawing.

The second area of this project focused on testing concrete crack sealers on their depth of penetration and bond strength and durability. Concrete prisms measuring 3"x4"x16" were cast, cut in half lengthwise, and cracked lengthwise through the center. The cracked pieces were then repositioned using aluminum foil as a shim to create a crack of a desired width. Crack sealers Photo:  Crack sealer specimen were then applied to the cracked pieces to rebond them. After applying the sealers, some specimens underwent a depth of penetration test, in which the sealed specimens were sliced through their thickness, and the maximum depth of penetration of the sealer was measured. Another set of specimens were tested to determine the bond strength of the sealer to the concrete. A companion set of specimens were subjected to 300 freezing

Photo 2. Crack sealer specimen ready to be sealed

and thawing cycles, where the temperature of the specimens was alternately lowered to 0°F and raised to 50°C in a period of five hours. At the conclusion of the freeze thaw cycles these specimens were also tested for bond strength to determine the durability of the sealer to remain bonded to the concrete while experiencing freezing and thawing cycles.

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