Concrete encasement is generally used for concrete piles that have not deteriorated to the point that the pile is not intact and the steel reinforcing is in good shape. In some cases where the pile is broken, the reinforcing steel may be parallel spliced by welding as directed by engineering.
The general procedures for repairing concrete using concrete encasement are described in Table 5-21. They are essentially the same as for steel piles as described in Section 5.5.1. Planning and estimating data are included in Table 5-22. Some general information is provided below. Refer to the figures in Table 5-21 for an outline of the procedure.
The repair procedure involves:
• Cleaning the pile
• Installing wire reinforcing, spacers, and forms about the pile
• Pouring concrete to fill the space between the pile and the form
Nonmetallic spacers are used to maintain a uniform 4-inch-thick concrete coating and ensure a minimum (2 inches) distance between pile and reinforcing steel and reinforcing and form. Form manufacturer's provide detailed instructions relating to installing their specific designs.
Both flexible and rigid forms are available and manufacturers are listed in Appendix A. Forms may also be fabricated from materials on site. Selecting the form type depends primarily on availability and choice of the designer or construction crew.
• Flexible Forms - These forms are fabricated from a porous fabric and are usually left in place. Both open and closed top models are available. Open top fabric forms are suspended from the piling or overhead structure and are filled to overflowing. The concrete grout fill is topped with an epoxy cap or nonshrinking grout at a 45-degree angle as shown in Figure 5-17.
• Rigid Forms - These forms are open top and bottom. They are removed and reused after the concrete has completely cured. Rigid forms can be fabricated from material found at the construction site. A bottom seal and base plate are required to hold the form in place. A temporary friction clamp and base plate conforming to the pile contour is fabricated and attached to the pile at the bottom of the repair area (Figure 3 of Table 5-21). The rigid form rests on the base plate to form the bottom seal.
The piles and any exposed reinforcing steel must be cleaned of rust, scale, and marine life. Failure to do so would result in poor bond between the concrete and pile. It is also important to ensure that the concrete be poured within 72 hours following cleaning to ensure that new marine growth will not have formed on the pile surface. For warm waters, it may be necessary to further restrict this allowed time period.
Planning and Estimating Data for Steel Sheet Pile Maintenance Using Coating
Description of Task: Coat a steel sheet pile with underwater protective coating in the splash zone and below the low waterline. Unit area to be coated is 1 ft2 below the low waterline.
Size of Crew: Dive station, one laborer.
Special Training Requirements: Familiarity with procedures for removal of marine growth and application techniques for underwater protective coatings.
Equipment Requirements: High-pressure waterblaster, hydraulic grinder with Barnacle Buster attachment, high-pressure pump for waterblaster, hydraulic power unit, protective clothing and gloves for personnel handling the coatings, float stage or work platform.
Productivity of Crew: 30 min/ft2 below water.
Materials: Epoxy-Polyamide Splash Zone Compound - Hand-applied coatings which can be applied underwater or to wet surfaces are commonly called splash zone compounds. Surface preparation by abrasive blasting or high-pressure water jet cleaning is adequate for application of splash zone compounds. The surfaces should be cleaned within 24 hours of coating application. The coating is normally supplied in two-component kits. The components should be mixed at ambient temperatures above 70°F. Although easier to mix when water is added, this practice will result in a coating that will not cure properly, therefore water should never be added when mixing die components. The coating is applied by smearing it over the surface to a thickness of 1/8 inch to 1/4 inch using a gloved hand. Typical coverage is 4.5 to 9 square feet per gallon of coating.
Potential Problems: If the water temperature is less than 50°F, normal formulations of splash zone compounds will not cure properly. Underwater application of the coating may be difficult. Prior to ordering a large quantity of the coating, a test application should be made under conditions identical to those anticipated, including surface preparation and temperature to ensure that good adhesion and proper curing will be achieved. Skin irritation may occur due to contact with the uncured compound if the individual is sensitive to the material. Regarding health, environmental, and safety concerns - the recommendation in the manual to wear gloves when applying splash zone compounds is good. In many cases, local environmental restrictions require that the abrasive blast media and paint be collected and not fall into the water. Abrasive blasting and the application of some paints may also be locally regulated. Particular care should be taken when removing lead-based paint. When removing lead-based paint, the worksite generally needs to be enclosed and all of the paint that is removed needs to be treated as hazardous waste. In addition, special precautions must be taken to prevent contact with or inhaling of the old paint or contaminated blast media.
Planning and Estimating Data for Steel Sheet Pile Maintenance Using Cathodic Protection
Description of Task: Install a sacrificial anode on a steel sheet pile below low water line. A 40-pound anode is attached to the pile with a welded connection.
Size of Crew: Two divers, one laborer.
Special Training Requirements: Familiarity with removal of marine growth, underwater lifting procedures, and light underwater welding.
Equipment Requirements: High-pressure waterblaster, hydraulic grinder with Barnacle Buster attachment, high-pressure pump for waterblaster, hydraulic power unit, welding machine with leads, welding torch, stud driver, lift bags/rigging gear, float stage or work platform.
Procedure: Clean area to bare metal where anode is to be attached. Anode may be attached by bolting, welding, or using a stud driver.
Productivity of Crew: 1 hour per anode.
Anode - The number and spacing of the anodes must be determined by a cathodic protection engineer.
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