Loose spikes and bolts; worn, cracked or broken rails, and deteriorated ties.

Deterioration of service lines, terminal boxes, outlets, broken brackets, loose insulation, corroded piping, andbroken seals.

CONCEALED DAMAGES are often overlooked in a visual inspection. It is often necessary to resort to special methods or tests. When underwater damage is suspected, divers are generally required. Some of the methods used to discover concealed damages are tapping with a hammer and probing with a chisel, a screwdriver, or a sharp-pointed instrument to detect deterioration or decay. This type of inspection will usually indicate whether further examination is necessary. Any evidence of damage or deterioration affecting the structural stability of any structure should be the subject of an immediate engineering study.

Waterfront structures, for the most part, contain one or more of the following materials: concrete, metal, wood, stone, earth, or masonry units. Therefore, the following sections describe the maintenance and repair procedures unique to each of these materials, in general, with specific procedures when they apply to certain types of structures.

CONCRETE STRUCTURES

Concrete is a fairly permanent construction material, but local conditions can produce defects that require corrective measures. You should be familiar with common types of defects that occur in concrete and know what measures to take to correct these defects.

Repairing Concrete

When concrete that covers reinforcing steel is deteriorated, spalled, or cracked, the reinforcing steel begins to rust and repairs should be made promptly to avoid excessive damage. All loosened materials must be removed and the concrete cut back to sound material. Cut the areas to be patched a minimum of 1 inch and at right angles to the surface. If the reinforcing steel is seriously damaged by rust, cut the concrete back far enough to replace the damaged steel with new reinforcing. New reinforcing bars should match the original bars in size and grade of steel and should be lapped at each end for a length of not less than 30 diameters of the original bars or as directed by higher authority. The new bars must be securely wired or welded to the old before patching. Exposed reinforcing steel that is not seriously damaged by rust should be cleaned by brushing or sandblasting to make a firm bond with the new concrete. Reinforcing steel should be covered by a minimum of 3 inches of concrete if at all possible.

Superstructure Repairs

Repairs to superstructures will include filling surface cracks, replacing structural members, cutting and filling expansion joints, and resurfacing decks.

SURFACE CRACKS that are not structural defects must be promptly filled to avoid the entrance of water. Thoroughly clean the crack with a high-pressure water jet to remove all foreign matter. Edges of the crack should be moistened, but not wet. Fill the crack with a thin grout of cement and water or a epoxy-based material, using a brush, if necessary, to push the grout in the crack. For wider cracks, use a mortar of cement, sand, and water instead of cement grout. If such cracks are of insufficient width to permit placement of filler material, they should be cut out before cleaning. After filling the crack, cover with burlap or sand and keep the covering moist for at least 3 days. Asphalt, tar, and certain other materials may also be used with satisfactory results for sealing random cracks in concrete decks and curbs.

PATCHING AND REPLACEMENT forms are usually required except for minor patches on top of a slab and for pressure-applied concrete or epoxy-based material. Forms may be of pipe, sheet metal, or wood and either left in place or stripped. They should be strong, well-braced and, if they are to be stripped, designed so they can be removed without damaging the concrete. Pressure-applied concrete is generally used to repair spalling on the underside of a deck or beam. Cut back the spalled area to sound concrete, and replace reinforcement as described earlier. Then repair or rebuild to the original section with pressure-applied concrete. Slabs or other structural members that are broken or severely damaged must be replaced. The assistance of qualified engineers should be obtained to analyze such cases to determine the cause of failure and to furnish an adequate design of replacement members. Methods of patching deck slabs of reinforced concrete piers are shown in figures 7-12 and 7-13. Slabs may be broken through by overloading. If this is a relatively small area and near the center of a span, it can be repaired by cutting out the deck and reconcreting, as shown in figure 7-13. To repair a hole, you can bevel the concrete as shown