Accelerated Latex Concrete Overlays and Hydro-demolition used to Preserve the SR 376 Parkway Bridges in Pittsburgh, PA
The SR 376 Parkway in Pittsburgh, PA is an Urban Interstate that carries over 123,000 vehicles per day. After years of service in the hot summers and cold winters of Pittsburgh, repairs were needed to preserve the Parkway. Heavy traffic volumes and chlorides from deicing salts had taken their toll on the concrete pavement and bridges.
Faced with the challenge of maintaining heavy volumes of traffic and the need to get the repairs done quickly, the Pennsylvania Department of Transportation made the decision to perform the work only during “non-peak” traffic hours – weekends and nights. Lane restrictions would only be permitted between the hours of 9pm and 5am during the week and during the weekends from 9pm Friday to 5am Monday. Only 21 weekends would be allowed to perform the work. If the contractor failed to have all lanes open during “peak” hours, they would face liquidated damages of $30,000 / hour.
In order for Hydro-Technologies to repair the 21 bridge decks on the project (over 30,000 sy of bridge deck area) in the allotted time frames, a 2” Rapid Set Latex Modified Concrete was selected as the overlay material. RSLMC will achieve 3000 psi of compressive strength in just 3 hours and resists shrinkage cracking because of the fast setting nature of the concrete product. RSLMC has been successfully used since the early 1990’s to repair and preserve thousands of bridge decks throughout the United States. A minimum service life of over 20 years is expected of the RSLMC Overlays when they are placed on hydr-demolition prepared surfaces. RSLMC is used throughout the United States to repair bridge decks when the bridge work must be performed over weekends and during “non-peak” traffic hours.
Prior to placement of the RSLMC Overlays, the existing Latex Modified Concrete Overlays (which were 23 years old – placed in 1984 on new decks) were removed by mechanical scarification. Fast Track Hydro-demolition Surface Preparation was then used over the total surface of the bridge decks to provide a highly bondable surface, to reduce chloride ion concentrations in the existing decks and to locate and remove partial depth repair areas of unsound concrete. Only sound and uniform strength concrete remained in the decks after the hydro-demolition operations were complete. The decks were cleaned by vacuuming and power-washing prior to the RSLMC installations.
The bridge overlay work began on March 23, 2007 and was completed on July 22, 2007. Only 14 of the 21 allotted weekends were required to complete the work. With superior construction scheduling and great weather during the Spring/Summer 2007 construction season, the contractor was able to complete the bridge deck overlay work well ahead of schedule.