AME completed a Design Level Waterfront Facility Inspection (WFI) at Station Provincetown in February 2019. This investigation included above water and underwater inspections of the waterfront assets at this facility. The inspection was completed to validate the findings from the 2018 Routine Waterfront Inspection and to collect detailed defect information to support the design of repairs.
The 2018 inspection documented widespread cracking and failed repairs on the concrete piles supporting the pier access trestle. In order to determine the root cause of the deterioration, this inspection included in depth concrete testing consisting of on-site voltage potential and half-cell surveys as well as laboratory analyses on concrete core samples.
A half-call corrosion potential survey was completed on discrete piles to identify the probability of active corrosion. This was completed by drilling holes in the piles, connecting leads to the reinforcing steel and measuring the electrical potential between the steel reinforcing and a reference electrode.
A total of eight concrete cores were extracted from the piles for further examination in the laboratory. To better define the observed deterioration, two cores were taken from two piles with visible deterioration, and two cores from two piles with no apparent deterioration, to be used as a baseline. The cores were 2.75 inches in diameter and averaged in 7.56 inches in length.
The laboratory testing included sulfate profiles, petrographic analysis, and chloride profiles. The petrographic analysis was completed on three of the pile cores to better define the cause of observed deterioration.
The laboratory testing completed on the concrete core samples and half-cell corrosion survey indicate the concrete cover is saturated with sufficient levels of chlorides to initiate corrosion in the steel reinforcement. Corrosion of the reinforcing steel is caused by chloride ion intrusion a common mode of deterioration of reinforced concrete exposed to seawater and salt spray. Over time chloride levels penetrate into the concrete cover, once chloride penetration reaches the reinforcing steel and reaches a certain threshold corrosion of the reinforcing steel has initiated. However, visual deterioration, such as corrosion spalling, may not be evident for four to ten years from the time the concentration of chlorides at the reinforcement level reaches a critical point, applying stress to the exterior concrete cover.
The findings of the laboratory testing concluded the cracking is not a result of an expansive chemical reaction. It is likely the initial cracking of the piles occurred during the original installation of the piles or shortly after initial construction. Coring operations found jetting tubes located at the center of the piles. After construction it is possible the jetting remained full of water, froze, and expanded, causing cracking from pressure developed within the tube. This cracking was further “opened up” from the exterior as a result of sea water exposure and freeze/thaw deterioration.
Waterfront Facilities Inspection and Condition Assessment – US Naval Station Washington
Inspection and asset inventory of the waterfront structures including deck components, mooring/berthing system elements, appurtenances, slope protection, civil/mechanical and electrical utilities.
Design-Level Inspection and Assessment at US Navy Air Station in Alaska
Assessment of the facilities’ general structural condition and provide recommendations for short-term repairs to stabilize the Fuel Pier from damage.