423Repairs to Concrete Structures

423.01 Description

Furnish all materials, labor, and equipment necessary to perform the repair of the existing concrete bridge elements. Remove existing unsound concrete; clean and apply protective coating to existing reinforcing steel, replace reinforcing steel; place, finish and cure concrete, grout, and mortar. All requirements of Section 405, Section 420, and Section 421 shall apply except as stated herein.

423.02 Materials

Aggregates Section 901 Curing Materials 902.07 Reinforcing Steel 908.01, 908.02, 908.05 and 908.07 Epoxy Protective Coating 917.01, Match Existing Color Epoxy Bonding Compound 921.04 Anchor Bolts 909.06 Water 921.01

423.02.01 Trowel Grade Mortar.

Synthetic Fibers 902.06.06 Mortar for Grout 902.11(a) or (b), 4500 psi Trowel grade mortar for concrete repairs shall be fiber reinforced, trowel-able, patching mortar designed for overhead use. Color shall match existing.

423.02.02 Concrete for Structural Repairs (Not Including Bridge Decks).

Mix No. 5 Concrete 902.10 Non-shrink Grout 902.11(c), QPL The non-shrink grout may contain pea gravel (No. 8 Stone) conforming to the gradation of the following table. The quality and laboratory test methods shall conform to 901.01 except that the plasticity index shall not exceed 9. 423 — REPAIRS TO CONCRETE STRUCTURES 2026 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS SIEVE SIZE PERCENT PASSING 3/4 in. 100 1/2 in. 85-100 3/8 in. 70-100 No. 4 0-55 No. 8 0-15 No. 16 0-8 If the quantity of concrete to be used in a single day is low (less than 2 cubic yards) or in areas where concrete delivery is impractical, the contractor has the option to mix the concrete on site in lieu of receiving it from a ready-mix plant. Mix No. 5 concrete can be replaced with a mixture of non-shrink grout and pea gravel proportioned and mixed in accordance with the manufacturer’s recommendations. This substitution is subject to the approval of the Engineer and is at no additional cost to the Administration.

423.02.03 Concrete for Bridge Deck Repairs.

Mix No. 6 Concrete 902.10 Rapid Hardening Cementitious Material for Concrete Pavement Repairs 902.14, QPL

423.03 Construction

Submit the proposed methods of protecting the public against injury and damage from demolition operations. When required, protective shields shall meet 405.03.01. Provide safe access to all areas of the existing structure to be repaired. Prior to the start of any repair work, conduct a thorough inspection in the presence of the Engineer. The purpose of this inspection will be to identify the location and extent of concrete deterioration and repair. The Engineer will establish the extent of removal and determine when sound concrete is encountered. Restrictions. Wait at least 72 hours after the placement of concrete, grout, or mortar before chipping on any section that has a common side or point. Except for bridge deck sections that are not directly over beams or stringers, immediately stop concrete removal and notify the Engineer and the Office of Structures, if at any time an area is identified as having deteriorated concrete beyond the following limits:

423.03.01 Equipment. Ensure that all equipment is calibrated and capable of thoroughly mixing

all material. Use only approved mixing and placing equipment in the preparation and handling of the concrete. This includes the use of on-site batch plants, volumetric mix trucks, or portable tilt drum mixers. Use a self-cleaning mixer capable of discharging all mixed material without any carryover from one batch to the next. Remove oil and other rust inhibitors from all equipment in contact with the concrete before the mixes are used. Clean the mixing equipment at least once a day. When applicable, submit to the Engineer a drawing showing details of forms and support system(s) with appropriate dimensions prior to placing concrete. Do not drop concrete or grout from a height which could result in the separation of the mix. Refer to 420.03.04 (b).

423.03.02 Storage. Store and handle cement as specified in 902.01. Store sand to prevent

segregation or contamination of the material. Store all reinforcing bundles at the site on suitable blocking or platforms at least 4 in. above all type of surfaces and vegetation. Keep the reinforcing free of dirt, oil, grease, paint, and other foreign matter.

423.03.03 Surface Preparation. Provide a vertical or horizontal perimeter having a shoulder

perpendicular to the surface of the structure for a depth of at least 1 in. Feathered edges are not permitted. Remove deteriorated areas of concrete to sound concrete with a chipping hammer that is not heavier than a nominal 65 lb. class on bridge decks and a 30 lb. class on all other areas. For bridge superstructures, do not use chipping hammers heavier than a nominal 15 lb. class for concrete removal beneath any reinforcing bars. Do not operate mechanical chipping tools at an angle greater than 45 degrees measured from the surface of the concrete. Continue chipping to at least 1 in. behind the reinforcing steel and until there is no sudden change in the depth of the cavity. After the Engineer has determined that all concrete is sound, abrasive blast the cavity surface. Just prior to applying the concrete, grout, or mortar, thoroughly clean all surfaces by air blast or vacuum as determined by the Engineer followed by wetting and damp drying. Mix and apply an epoxy bonding compound on the sound concrete repair areas per the manufacturer’s recommendations. Contain all blast waste and loose concrete, and promptly remove it to an approved disposal site. Keep blast waste and loose concrete out of waterways.

423.03.04 Reinforcement. If sound concrete is encountered before the reinforcing steel is

exposed, remove sound concrete to a depth of 1 in. behind the reinforcing steel. Exercise care to prevent cutting, stretching, or damaging any exposed reinforcing steel. If sound concrete is found beyond 3-1/2 in. of the proposed finished surface but no reinforcing is encountered, dowel 423 — REPAIRS TO CONCRETE STRUCTURES 2026 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS additional No. 4 reinforcing bars installed at 12 in. center to center horizontally and vertically, 2 in. clear of proposed finished surface. Dowel as specified in Section 406 except use any type of grout specified in 902.11. Ensure that existing reinforcing steel to be incorporated into any repair work meets 421.03.07. Abrasive blast all exposed existing reinforcing steel that will be incorporated in the new work to a near white finish to remove all rust, dirt, scale, and loose concrete. The Engineer will establish if reinforcing steel is to be reused or replaced. Regardless of whether the reinforcement was previously coated, coat all exposed existing reinforcement steel with epoxy touch-up system in conformance with Section 465. The Engineer may waive this requirement if there is not enough time for the system to properly cure. For anchoring additional reinforcing to masonry surfaces, set at least 3/8 in. diameter expansion bolts in drilled holes, or set plain round No. 4 bars in approved dry packed grout tightly driven in drilled holes. Ensure that the drilled holes are at least 3 in. deep. All bolts and bars shall be set in solid masonry (not in mortar, joints, or cracks) and have heads or hooks on their outer ends. Where formwork is not being installed, reinforce vertical repair areas with additional welded wire reinforcement in addition to the refurbished reinforcing steel. The fabric may be wired to existing reinforcement without the use of expansion bolts, etc., where approved by the Engineer. Cut welded wire reinforcement into sheets of proper size. Bend the separate sheets over templates to follow the outlines of the member or surface to be covered. Securely hold in a uniform position by tying to the bolts or bars with 14 gauge black annealed wire. Space ties at no more than 12 in. Overlap adjacent sheets of welded wire reinforcement at least two squares. Tie them together with a 14 gauge black annealed wire at intervals not exceeding 18 in.

423.03.05 Guides. In areas where there is no formwork, use sufficient guides to obtain the full

thickness of mortar specified and to ensure uniform and straight lines.

423.03.06 Repairs to Bearing Areas. In areas where beams or girders are directly bearing on

the deteriorated concrete, jack the beams as specified in Section 478 prior to concrete removal. Unless otherwise specified, epoxy coat the repaired bearing area as specified in Section 464.

423.03.07 Bridge Deck Repairs. Do not remove any portion of the existing bridge deck that

cannot be patched, cured, and open to traffic within the timeframe specified in specified maintenance of traffic restrictions. If required, remove any asphalt wearing surface as specified in Section 475. Remove deteriorated areas of the existing concrete bridge deck down to sound concrete by use of power-driven hand tools. After removal of deteriorated concrete is complete, remove all rust, oil, or other foreign materials detrimental to achieving bond followed by abrasive blasting and air blast or vacuum as determined by the Engineer. Repairs shall be Type I, Type II, or Type III as noted below: 423 — REPAIRS TO CONCRETE STRUCTURES 2026 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS

423.03.08 Curing and Cold Weather Protection. Refer to Section 420. Except for rapid

hardening cementitious material, keep concrete and grout repairs continuously wet for at least seven days after application. Liquid membrane forming compound will be permitted with prior approval.

423.03.09 Finishing. Finish the area of repair to match the existing structure.

423.04 Measurement and Payment

The payment for Repairs to Concrete will be full compensation for all completed repair areas, and will include scaffolding, installing and removing debris shields, removal of existing deteriorated concrete, inspections, cleaning and epoxy touch up of existing reinforcement steel, furnishing and placing new reinforcement steel as required, drilling and grouting holes, furnishing and installing welded steel wire fabric, surface preparation, furnishing and placing epoxy bonding compound, forming, furnishing and placing mortar, grout, or concrete, making and transporting test cubes or 423 — REPAIRS TO CONCRETE STRUCTURES 2026 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS cylinders, curing, removing formwork, applying epoxy protective coating, and any other material, labor, equipment, tools, and incidentals necessary to repair the concrete.

423.04.01 Trowel Grade Mortar for Structure Repairs will be measured and paid at the Contract

unit price per cubic foot.

423.04.02 Rehabilitation of Concrete Structures will be measured and paid for at the Contract

unit price per cubic foot of concrete in place.

423.04.03 Type II and Type III Bridge Deck repairs will be measured and paid for at the Contract

unit price per cubic foot for the pertinent Type Deck Repair.

423.04.04 If removal of debris is needed for Type 1 Deck Repairs, it will be measured and paid

for at the Contract unit price per square foot for the Type I Deck Repair. Any asphalt used for Type 1 Deck Repair areas will be measured and paid for at the Contract unit price per ton for the pertinent Asphalt Mix for Bridge Deck item as specified in Section 475.