Market St. Bridge East
Project Description
The Market Street Bridge East in Harrisburg, Pennsylvania, a 16-span reinforced concrete arch bridge across the Susquehanna River, is on the Historic Registry and is owned by PennDOT. The bridge was constructed in 1928 and is in need of rehabilitation due to the severity of concrete deterioration observed along the bridge. As part of the rehabilitation process, Gannett Fleming (GF) led a team to evaluate the bridge and develop an effective rehabilitation strategy and reached out to Vector Corrosion Services (VCS) to provide support by providing concrete materials testing services and support in developing corrosion mitigation rehabilitation strategies.
VCS’s work focused on the bridge elements with a high risk of corrosion deterioration and may need rehabilitation, i.e., the deck, cross-walls, and arches. However, the deck was severely deteriorated, and it was recommended that a full replacement of the deck may be the most cost-effective rehabilitation solution. VCS evaluated the condition of the substructure elements to identify the extent of concrete deterioration, which included visual observations, ground-penetrating radar (GPR) survey for cover-depth analysis, electrical continuity testing, corrosion potential survey, concrete core sampling for tensile testing, petrographic tests, and concrete sampling for chloride concentration measurements. The objective of this evaluation was to determine the extent of damage beyond the visual assessment, identify the root cause of the deterioration, and provide the information necessary to design a lasting and effective rehabilitation strategy.
Project Solution
The results indicated that substructure elements were exposed to the chlorides concentrations well above the corrosion threshold, putting the steel reinforcement at high risk of chloride-induced corrosion. The arch exterior showed limited exposure to chloride contamination and was overall in good condition, but there were localized issues near the construction joint.
VCS provided three recommendations for the rehabilitation of the Bridge.
- The basic repair option consisted of delamination and spall repairs following ICRI Guidelines and installing Type 1 anodes within the patch repairs.
- Targeted corrosion protection to the areas with a high risk of corrosion by installing Type-1 galvanic anodes in and around corrosion hot spots.
- Installation of a global corrosion protection system, i.e., impressed current cathodic protection system to mitigate the effect of reinforcement corrosion.
All these recommendations provide different service life extension at various cost levels. VCS will work with the owner and engineering team to select the most effective strategy and implement it on the Market St Bridge.