Corrosion of reinforcing steel is a common cause of bridge degradation. The Grove Isle Bridge, which connects a private island in Biscayne Bay to the mainland near Coconut Grove, Fla., suffered from this type of damage. The Grove Island Association hired Fibrwrap Construction, Inc. to repair the bridge using its Tyfo Fibrwrap advanced composite systems for restoration and strengthening. As part of its restoration plan, Fibrwrap Construction used MAPEI concrete restoration products to further strengthen and stabilize the bridge.
The process began with workers removing all delaminated concrete sections from the underside of the bridge slab and pressure washing the exposed concrete areas with water blasts up to 4,000 psi to reach solid concrete. Fibrwrap Construction then installed Tyfo Fibrwrap, a high-strength, fiber-reinforced polymer product, to the bridge's columns, beams and slabs.
Fibrwrap Construction used several MAPEI concrete restoration products throughout the repair process. After cleaning all steel reinforcement bars, crews coated them with Mapefer 1K, an anti-corrosion and bonding mortar. Fibrwrap's crews then formed up the underside areas of the bridge and pumped in Planigrout 712, a non-shrinking cementitious construction grout that contains a corrosion inhibitor and silica fume. Planitop XS was hand applied to repair smaller areas. Planitop FD, a pumpable, full-depth repair mortar ideal for deep repairs that offers a rapid return to service, was applied on the upper sections of the bridge where the sidewalk curbs met the traffic surface.
Once the repair work was complete, the concrete bridge surfaces that were not traffic-bearing were cleaned and waterproofed with Mapelastic cementitious liquid waterproofing membrane, which protects concrete from chemical attack by de-icing salts, sulfates, chlorides and carbon dioxide. This product is designed for application on new or repaired concrete structures, as well as any cementitious surface subject to vibrations and subsequent cracking.
A fast track overlay
Swank Associated Companies, Inc., New Kensington, Pa., performs roadway and bridge repair and maintenance work and is a leader in bridge rehabilitation. Tackling dozens of bridge deck placements annually, its system for bridge overlays is well honed, working with affiliated companies that perform the hydrodemolition of the bridge deck and make the latex modified concrete (LMC) for the overlay. The company also relies on Terex Bid-Well automatic roller pavers from Terex Roadbuilding, owning multiple 3600 bridge and 5000 roadway pavers and older 3200 and 2500 bridge pavers.
For years, the trend in road and bridge rehabilitation has been to complete the repairs during "non-peak" hours. More and more work is taking place at night and over the weekends to reduce construction related congestion on busy roadways and bridges. Strict lane closure time periods are written into contracts with severe disincentives for work that goes beyond the allotted time.
A recent Swank Construction bridge overlay project on the Interstate 376 Parkway Bridge in Pittsburgh was a prime example of working under a tight deadline. The bridge was closed to traffic at 8 p.m. Friday night for a LMC overlay and had to be reopened by 5 a.m. on Monday morning. Not adhering to this time line meant a $30,000 per-hour disincentive.
Swank Construction's entire overlay process - milling, demolition, washing and paving - for the 1,100-foot-long bridge decks had to be completed in less than three days. "We did about three weeks worth of work in a weekend," says Randy Solar, construction superintendent for Swank Associated Companies. There was no room for error.
Swank Construction's process began with milling the existing overlay plus a small portion of the bridge deck. Following closely behind, a hydrodemolition unit then combed the deck with high water pressure between 12,000 to 15,000 psi. "The hydro unit only removes the bad concrete and leaves the good," mentions Solar.
Next, the loose concrete and water was vacuumed away as crews prepped for the final deck wash. After an 8,000 psi power washing, the uneven deck surface was ready for the overlay. "The latex modified concrete bonds to everything, but it does not like heat or wind, so we try to keep it moist and cool," explains Solar.
With time being of the essence, the contractor selected a Rapid Set Mix overlay, which cures to 3,000 psi in three hours. After deck grooving, removing paving equipment and final vacuuming of the bridge deck, the bridge can quickly be opened to traffic, which was the perfect fit for this weekend project.