Replacement Reconstruction

Deterioration that affects the structural integrity of the concrete structure, such as missing lengths of reinforcing steel, should be repaired by replacement or reconstruction of sections of the structure. A method using pumped or tremied concrete is used when holes extend through the concrete section, or are larger than 1 ft2 in area and over 4 inches deep, or are more than 1/2 ft2 in area and deeper than the reinforcing steel. A description of the repair technique is provided in Table 5-27.

• All questionable quality concrete should be removed by hand or power tools.

• The edges of the hole should be square and the top rim should be sloped in the direction of the pour.

• Surfaces of the hole that are above water should be kept continually wet for several hours to allow partial saturation of the old concrete to take place to ensure proper curing of the new concrete.

• Just prior to placement of the new concrete, the holes should be thoroughly cleaned of marine growth.

• Form work should be mortar tight and attached to the existing structure with form ties. Use cotton caulking or similar materials to make tight seal.

Table 5-24

Planning and Estimating Data for Concrete Pile Repair Using Epoxy Patching

Description of Task: Repair a deteriorated concrete pile by patching with hand-applied'epoxy. Unit area to be repaired is 1 ft2 underwater.

Size of Crew: Dive station, one laborer.

Special Training Requirements: Familiarity with procedures for removing marine growth and application of epoxy patching compounds underwater.

Equipment Requirements: High-pressure waterblaster, hydraulic grinder with Barnacle Buster attachment, high-pressure pump for waterblaster, hydraulic power unit, protective clothing for personnel handling the epoxy patching compound, float stage or work platform.

Productivity of Crew: 30 min/ft2 underwater.

Materials:

Epoxy Patching Compound - Epoxy patching compounds are usually purchased in two-component kits, with an aggregate additive. A 1-gallon kit might include 1 gallon of each component plus aggregate, resulting in more than a 2-gallon yield. Patching coverage is measured in square feet per gallon. The required patching yield is obtained by taking the square footage to be covered and dividing by the square foot per gallon coverage rate.

Potential Problems: If water temperature is less than 60°F, proper adhesion to the pile may not occur. Skin irritation may occur if individual is sensitive to the epoxy material. Use protective gloves while mixing and applying epoxy materials.

Table 5-25

Planning and Estimating Data for Concrete Pile Repair Using Epoxy Injection

Description of Task: Repair a 6-inch-deep crack in a concrete pile by injecting low-viscosity neat epoxy grout into the crack. Total length of crack to be repaired is 10 feet.

Size of Crew: Dive station, one laborer.

Special Training Requirements: Familiarity with procedures for removing marine growth, the use of epoxy grout pump, and the use of injectable epoxy.

Equipment Requirements: High-pressure waterblaster, hydraulic grinder with Barnacle Buster attachment, hydraulic impact wrench with masonry bits, high-pressure pump for waterblaster, hydraulic power unit, protective clothing for personnel handling the epoxy compound, epoxy pump, float stage or work platform.

Productivity of Crew: 10 to 20 min/linear foot of crack.

Materials:

Low-Viscosity Epoxy Grout - Commercially available injectable epoxy grouts are usually purchased in two-component kits. Mixing proportions will vary, so manufacturers' instructions should be followed. The volume of the crack must be estimated by taking its length, average width, and average depth. An additional 25 percent should be added to allow for overfilling of the cracks and inaccuracies in estimating the size of the cracks.

Potential Problems: If water temperature is less than 60 °F, proper adhesion to the pile may not occur. Skin irritation may occur if individual is sensitive to the epoxy material. Use protective gloves when mixing or applying epoxy materials.

Table 5-26

Planning and Estimating Data for Concrete Pile Maintenance Using Wrapping

Description of Task: Wrap a concrete pile with commercially available polyvinyl chloride (PVC) wrapping sheets from 1 foot above the high waterline to 2 feet below the low waterline. Total length to be wrapped is 10 to 20 feet.

Size of Crew: Dive station, one laborer.

Special Training Requirements: Familiarity with procedures for removal of marine growth and with installation procedure for the PVC pile wrap to be used.

Equipment Requirements: High-pressure waterblaster, hydraulic grinder with Barnacle Buster attachment, high-pressure pump for waterblaster, hydraulic power unit, special fastener tools for pile wrapping (dependent on manufacturer), float stage or work platform.

Productivity of Crew: 3 hours per pile.

Materials:

Polyvinyl Chloride Pile Wrap Unit - Commercially available PVC pile wraps are available in many prefabricated sizes to fit various pile sizes and lengths. Some have separate units for splash zone and underwater use, while others are a single unit. Manufacturers' literature should be consulted before ordering.

Strap and Special Fittings - Each pile wrap manufacturer has particular fasteners and special fittings. Manufacturers' literature should be consulted before ordering.

Potential Problems: Projections or sharp edges on the pile may puncture or tear the pile wrap, so care should be taken to remove such problems.

Table 5-27 Typical Concrete Wall Repair

Problem: Severely deteriorated areas require replacement with cast-in-piace concrete.

Description of Repairs: Defective section of wall is removed, surfaces and reinforcing steel are prepared, fonnwork constructed, and wall is restored with cast-in-place concrete.

Materials: Sand-cement mortar and poitland cement concrete as designed by engineer, anti-washout admixture may be added for underwater repairs. Equipment used includes sandblasting and air-water jet cleaning equipment, concrete saw, air chipping hammer, air-suction gun for mortar if available, power vibrator and tamper, and conventional concrete placement tools.

Preparation:

• Use air hammer to remove unsound concrete to 3/4-inch minimum depth.

• Cut the top edge of the hole to slope as shown in Figure 1. If necessary to fill the hole from both sides, the slope of the cut should be modified accordingly.

• Cut the bottom and sides of the hole approximately square with the face of the wall. Spalling and featheredges can be avoided by having chippers work from both faces. All interior corners should be rounded to a minimum radius of 1 inch.

• Ensure a minimum of 1 inch clearance around all exposed reinforcing. Remove unnecessary tie wires.

• Clean all surfaces to bond to new concrete with wet sandblasting and water jet. Clean exposed steel with abrasive blasting. Epoxy coat steel where possible. Parallel splice-weld new steel where 25 percent or more of original diameter is lost.

Repair Procedures:

• Construct front forms for patches so the concrete can be placed in lifts not more than 12 inches high. The back form can be built in one piece. Fabricate and fit all forms before concrete placement is started.

• Chimneys (accesses) may be required at more than one level. In some cases, a chimney may be necessary on both sides of the wall or beam. In all cases, the chimney should extend the full width of the hole.

• Ensure forms are substantially constructed so that pressure can be applied.

• Ensure forms are mortar tight at all joints between adjacent sections, between the forms and concrete, and at the tie-bolt holes to prevent the loss of mortar. Twisted or stranded caulking cotton, folded canvas strips, or similar material should be placed between the joints as the forms are assembled.

• Surfaces to receive new concrete should be kept wet for several hours prior to placement.

• Immediately before placing the front section of form for each lift, coat the surface of the old concrete with a 1/8-inch-thick layer of mortar. This mortar should have the same sand and cement content and the same water-cement ratio as the new concrete. The surface should be damp, but not wet. The mortar can be applied with an air-suction gun, by brushing, or being rubbed into the surface by hand encased in a rubber glove.

• Place concrete immediately. Ensure thorough compaction by vibration/tamping.

• Forms may be removed the day after placement. If chimneys were used, remove the remaining projections the second day working up from the bottom.

• Thoroughly moist-cure the new concrete.

• Finish with a wood float finish. Tool or chamfer edges and corners as required.

Face from which concrete ii being placed

Sloped rim

Rounded corners

Sharp edgea

Sloped rim

Rounded corners

Sharp edgea

Front form is made up in sections for ■uccetaive 12-inch lifti

Formwork for Typical Wall Repair

Preparation of Irregular Area for Typical Wall Repair

Front form is made up in sections for ■uccetaive 12-inch lifti

Existing wall

Repair . concrete

Existing wall

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