Section 2426. Structural Concrete Repair.

2426.01 DESCRIPTION.
This work is repairing spalled or deteriorated structural concrete as specified in the contract documents. This work may or may not include the installation of concrete anchors, reinforcing bars or wire mesh.

Concrete repair shall be one of two types:

A. Shallow Repair.
Shallow repair shall be 3/4 inch to 1 1/2 inch (20 mm to 40 mm) in depth, be placed against sound concrete, require a bonding grout, and not use forms to support the patching material. Forms may be needed in areas of shallow repair where the patching material can not support itself. In these areas bonding grout will not be required.

B. Regular Repair.
Regular repair shall have a minimum depth of 1 1/2 inch or 3/4 inch (40 mm to 20 mm) behind an unbonded reinforcing bar, whichever is greater, and be placed against sound concrete. Forms shall be used but no bonding grout will be required. When repairing a vertical face, the patch shall be placed in heights not to exceed 4 feet (1.2 m). Access ports shall be provided at 4 foot (1.2 m) intervals in the forms for placement and vibration. Forms shall be removed in accordance with Article 2403.18.

The Engineer will outline the areas to be repaired.

2426.02 MATERIALS.
Materials shall meet the appropriate requirements of Division 41.

Mix proportions are as follows:

A. Bonding Grout.
Bonding grout shall contain equal parts by weight (mass) of Type I cement and sand with enough water to form a slurry. The consistency shall be such that the slurry can be applied with a stiff brush in a thin even coating that will not run or puddle.

B. Concrete.

1. Shallow Repair.

PROPORTIONS
Materials

(by weight (mass))
Type I Portland cement
Concrete sand (Section 4110)
Coarse aggregate (Article 4115.05)

4 parts
5 parts
5 parts

The mixture shall contain enough water to form a consistency that will permit placement and consolidation by hand compaction without slumping.

2. Regular Repair.
Class O concrete shall be furnished. The slump shall be targeted at 3 inches (75 mm) with a variation not to exceed ± 1 inch (25 mm).

2426.03 EQUIPMENT.
Equipment for preparation of the repair areas shall meet the requirements of Article 2413.03, A.

2426.04 SURFACE PREPARATION.
All loose, disintegrated and unsound concrete shall be removed from the repair areas. All repairs shall be outlined with a 3/4 inch (20 mm) deep saw cut. Concrete anchors and wire mesh may be required, as shown in the contract documents. Overhead repairs may require special procedures, as proposed by the Contractor and approved by the Engineer. After removal of loose, unsound concrete, the repair area shall be sandblasted and followed by an air blast with oil free air so the substratum is sound, clean and free of all contaminants. Extreme care must be exercised in concrete removal so that prestressed strands are not damaged. The substrate must be dry prior to the placement of concrete or the application of the bonding grout, if required.

Exposed reinforcement shall be sandblasted to remove all rust. Damaged or badly corroded reinforcing bars shall be removed and replaced, as directed by the Engineer.

2426.05 PLACEMENT PROCEDURE.

A. Shallow Repair.

1. Bonding Grout.
The bonding grout shall be applied to the properly cleaned, dry surface of the old concrete with a stiff bristle brush. The old concrete surface must not be prewetted prior to grout placement.

2. Repair Concrete.
The repair concrete shall be placed and compacted before the grout dries. If the grout dries prior to concrete placement, the grout shall be removed by sandblasting and reapplied. The Contractor shall strike off and finish the repair concrete to the correct lines.

B. Regular Repair.
Concrete shall be placed in accordance with Article 2403.08.

2426.06 CURING.
White pigmented curing compound shall be applied to the concrete immediately following concrete finishing or immediately after forms are removed. This shall be done in accordance with Article 2403.10, except that the rate of application shall be 100 square feet per gallon (2.5 m2/L).

2426.07 METHOD OF MEASUREMENT.
The Engineer will compute the square feet (square meters) of Concrete Repair from measurements of the surface area repaired measured to the nearest 0.1 foot (0.1 m). Distinction shall not be made between shallow repair and regular repair.

2426.08 BASIS OF PAYMENT.
For the number of square feet (square meters) of Concrete Repair completed, measured as provided above, the Contractor will be paid the contract unit price per square foot (square meters). This payment shall be full compensation for removal from the project of excess concrete, for furnishing all material, equipment, sandblasting exposed reinforcement, removing and replacing damaged reinforcing bars, forms, and labor necessary to complete the work in accordance with the contract documents.

The payment for Concrete Repair will include the cost of all concrete anchors and wire mesh required. If replacement is needed, the payment for concrete repair will also include the cost of reinforcing bars.