2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS CATEGORY 400 STRUCTURES SECTION 423 — REPAIRS 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. 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
423.02.03 Concrete for Bridge Deck Repairs.
Mix No. 6 Concrete Rapid Hardening Cementitious Material for Concrete Pavement Repairs 902.10 902.14, 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:
a.More than 6 in. beyond the original finish surface.
b.More than 3 in. beyond the reinforcing steel.
c.More than 1 in. beneath the bearing. Do not resume work until after obtaining approval from the Office of Structures. The Engineer and Office of Structures will determine any extraneous damage to the existing bridge caused by the Contractor’s operations, which the Contractor shall repair at no additional cost to the Administration.
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. 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS 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 thatisnotheavier 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 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. 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS 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:
a.Type I Deck Repairs. This repair includes cavities less than 1 in. deep. The cavity may require hand chipping that does not extend below the existing reinforcement. Fill the void with the asphalt mix wearing surface while the final surface is being placed.
b.Type II Deck Repairs. This repair includes areas where the depth of deck removal is over 1 in. deep but not full depth. Make sure that the limits of concrete removal extend below the reinforcement as specified in 423.03.04. Fill the cavity with rapid hardening cementitious material.
c.Type III Deck Repairs. This repair includes areas where the depth of deck removal is full depth. Fill the cavity with rapid hardening cementitious material for deck repairs up to 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS 9 ft2. For repair areas larger than 9 ft2, use Mix No. 6 concrete or as otherwise directed by the Engineer. In large areas, supply formwork, which may be suspended from or supported by the stringers, to enable the placement of the concrete. In small areas, supply formwork, which may be suspended from existing reinforcing bars by wire ties, to enable the placement of the concrete. The Engineer will determine the method used. Ensure that the top surface of all deck repairs is even with the top surface of the existing concrete deck. Take all necessary precautions to produce smooth riding bridge deck by placing the concrete in a manner that meets the grade of the proposed adjoining portions of the existing bridge deck. The location of longitudinal joints will be determined by the Engineer based on avoiding joints in the vehicular wheel path as much as practical. For concrete patches over 6 ft in any direction, give the top surface of all patch areas a final textured finish consisting of 1/8 in. wide by 1/8 in. deep transverse corrugations spaced approximately 1/4 in. apart. For concrete patches less than 6 ft in any direction, provide a roughened broom finish on the top surface. The method of texturing shall be approved by the Engineer prior to placing the material in the patch. Mix, place, and cure the rapid hardening cementitious material according to the manufacturer’s recommendations.
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 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
2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS 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. 425 — LIGHTWEIGHT SUPERSTRUCTURE CONCRETE CATEGORY 400 STRUCTURES SECTION 425 — LIGHTWEIGHT SUPERSTRUCTURE CONCRETE
425.01 Description
Furnish and install lightweight concrete.
425.02 Materials
Lightweight Concrete 902.10, Mix 10
425.03 Construction
Conform to 420.03 and as specified herein. Handle lightweight aggregates in a manner that provides a thorough sprinkling of the aggregates during the stockpiling to produce damp aggregate. Sprinkle to obtain uniform distribution of moisture. Then permit the aggregates to drain as long as necessary to produce a uniform moisture content. Maintain the moisture content as much as practical until the aggregate is used. Add the admixtures to the mix according to the manufacturer’s recommendations.
425.03.01 Existing Structures. Remove existing bridge decks as specified in 405.03.02. Note
that the deck replacement material may be lighter than the existing deck and the deflection caused by the lighter material will be less than the material removed. Therefore, compute modified rebound figures to be used in lieu of dead load deflections to establish grade controls to produce finished tops of concrete bridge decks that will be true to as planned line and grade.
425.04 Measurement and Payment
Lightweight concrete structures will be measured and paid for as specified. The payment will be full compensation for all forms and form removal, reinforcing steel, curing and misting, scuppers, mechanical and electrical work, all cost incidental to the conducting of tests for oxygen content and presence of gases and applying mechanical ventilation to confined spaces, year built markings, and for all material, labor, equipment (including safety equipment), tools, and incidentals necessary to complete the work. 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS
Source: Maryland Standard Specifications for Construction and Materials, 2025 Edition. Pages 462–467 of 1,113.