Wakota Bridge
I-494 Over the Mississippi River in South St. Paul
PRODUCTS USED:
- Master Builders Degadeck Crack Sealer Plus
OWNER: Minnesota Department of Transportation
CONTRACTOR: Lunda Construction Co.
PROJECT SIZE: 80,000 square feet
Challenge: Seal Transverse hairline cracks on new deck while working with variable temperatures during application while at the same time providing rapid turn over.
Solution: Degadeck Crack Sealer Plus reactive methacrylate resin for sealing cracks in concrete surfaces.
As the much awaited Wakota Bridge moved near opening, transverse cracks were discovered in the concrete overlay. The majority of the cracks were hairline cracks, barely detectable except after rain events. Several options for sealing the cracks were explored, including gravity filling the cracks with low viscosity epoxy. The small size of the cracks made detection difficult and time consuming. Compounding the added cost was the difficulty experienced in attempting to gravity fill cracks as small as 1 mil. After investigation and a trial mock-up on site, it was determined that Degadeck Crack Sealer Plus was the best solution for treating the transverse cracks.
When the overlay was originally installed, it was cured with a white pigmented curing compound. This material was removed by sandblasting. Sandblasting removes bond breakers and contaminants that might inhibit penetration while also exposing additional cracks that were not previously visible.
After sandblasting, the deck is blown clean with oil free compressed air. Degadeck Crack Sealer Plus was supplied in 49 gallon drums. The drums were laid on dollies and fitted with valves for easy mixing and ease of movement on the deck. The material was mixed in five gallon batches using a BPO Hardener in amounts appropriate for the daily temperatures.
Once mixed, the sealer is poured out on concrete and workers move the material along the deck using solvent resistant rollers on extension poles. The material was applied at a rate of approximately 100 square feet per gallon. Coverage rates vary by substrate and should be confirmed with a mock-up on the surface to be treated. Spread the material evenly on the surface, keeping a ribbon of material ahead of the roller, taking care not to allow the material to puddle on the surface.
The very low viscosity of Degadeck Crack Sealer Plus (5-15 cps) allows the material to penetrate even the smallest cracks while minimally altering the surface profile. After spreading the Degadeck Crack Sealer Plus, broadcast silica sand into the wet material to provide slip resistance. This sacrificial layer will wear off over time with abrasion.
This project encompassed 180,000 square feet of bridge deck surface. The application in this area (not including surface preparation time) took approximately five days. Preliminary cores showed crack penetration of a minimum of one inch up to full depth.