CATEGORY 400 STRUCTURES SECTION 426 — LATEX MODIFIED CONCRETE OVERLAY FOR BRIDGE DECKS
426.01 Description
Remove the specified amount of the existing bridge deck material mechanically and through hydro-demolition, remove additional areas of deteriorated concrete as directed by the Engineer, clean surface areas to be overlaid. Clean scuppers, downspouts and joint troughs, replace deteriorated reinforcing steel, and place latex modified concrete (LMC). Restrictions. Do not place LMC in Allegany, Garrett, and Washington counties between November 1 and April 30. In all other Counties, do not place LMC between December 1 and April 30. Do not remove any portion of existing bridge deck that will not be overlaid and cured per these restrictions.
426.02 Materials
Fine Aggregate 901.01 Coarse Aggregate 901.01, Size No. 7 Portland Cement Type I 902.03 Concrete for Patching 902.10 Latex Modified Concrete 902.13 Reinforcement Section 908 Water 921.01
426.03 Construction
Dispose of removed material at an approved spoil area.
426.03.01 Collection and Containment of Effluent. Collect and contain all liquid and/or solid
effluent from the high pressure water jet method of concrete removal and ensure that no such effluent reaches any traveled roadway, waterway, or other drainage facilities. The effluent shall be disposed at a site with an MDE approved industrial discharge permit appropriate for the effluent collected. Failure to collect and contain all liquid and/or solid effluent from the high pressure water jet concrete removal will be cause for immediate shut down of high pressure water jet concrete removal operations until corrective actions are taken. Any additional costs associated with a failure to collect and contain the effluent shall be at no additional cost to the Administration 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS and is the sole responsibility of the Contractor. All costs associated with collecting and containing the effluent from the high pressure water jet method of concrete removal shall be incidental to the pertinent removal items in the Contract.
426.03.02 Equipment. Ensure that all proposed equipment meets the requirements specified
herein, and is approved. Deck Removal Equipment
a.Existing Wearing Surface Removal. This equipment is only required when the existing bridge contains an asphalt mix wearing surface. Provide equipment that is capable of removing the wearing surface without damaging armored joints that are to remain or the existing concrete surfaces beyond the specified minimum removal depth. When pavement breakers are proposed, use broad faced chisel blades operated at a slight angle with the horizontal to peel the wearing surface off.
b.Concrete Deck Surface Removal. Power operated mechanical type and high pressure water jet type equipment shall be capable of uniformly removing the specified minimum depth from the existing concrete surface. A minimum of one inch of concrete deck removal shall be completed using the High Pressure Water Jet Type.
1.Mechanical Type. This equipment may be used to remove the concrete deck to a specified depth measured from the top of the concrete deck to provide a roughened surface for the high pressure water jet equipment. Take sufficient pacometer readings to verify the depth to the top layer of deck reinforcement and operate the equipment so as not to damage the reinforcing bars. All additional concrete deck removal shall be completed using high pressure water jet, power driven tools, or hand tools as specified in the Contract.
2.High Pressure Water Jet Type. Hydro-demolition using high pressure water jet type equipment shall be used to remove unsound concrete deck material to the specified depths. This method shall leave roughened, highly bondable deck surface with all the unsound concrete removed. Unsound concrete is defined as existing bridge deck concrete that is deteriorated, de-bonded from the reinforcement, spalled, or determined by the Engineer to be unsound. The high pressure water jet hydro-demolition equipment shall be a computerized, self-propelled machine that utilizes a high pressure water jet stream to provide a rough and bondable surface while removing all unsound concrete and rust and concrete particles from any exposed reinforcement with one pass over the concrete deck surface. Prior to the commencement of the hydro-demolition operations, calibrate the hydro-demolition equipment over a 6 ft x 6 ft area of sound deck concrete as designated by the Engineer to demonstrate proper removal to the minimum specified depth and desired surface finish to bond with the overlay in one pass 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS of the equipment. Move the hydro-demolition equipment to a second 6 ft x 6 ft area of unsound deck concrete as designated by the Engineer to demonstrate proper removal to the minimum specified depth, removal of all unsound concrete, and provide the desired surface finish to bond with the overlay. All construction debris, milling debris, and dust are to be completely removed from the bridge deck surface prior to calibration and commencement of the hydro-demolition operations. If the equipment or end results of the calibration tests are deemed unsatisfactory by the Engineer, remove the hydro-demolition equipment from the project site and provide another high pressure water jet unit for calibration. No additional compensation or Contract time will be provided for this recalibration process if required. Provide verification of the following equipment settings to the Engineer:
a.Water Pressure Gauge. (b) Machine staging control (step). (c) Nozzle size. (d) Nozzle speed (travel). Production hydro-demolition operations may begin after the Engineer has approved the second calibration and has been provided verification of the above equipment settings. Provide the Engineer with the calibration and production settings prior to and during hydro-demolition surface preparation operations. The hydro-demolition operations will be stopped if it is determined that sound concrete is being removed beyond specified limits or unsatisfactory results are being obtained as determined by the Engineer. Perform appropriate recalibration or make the necessary changes in equipment and methods prior to resuming the operation. The specified calibration procedure is required each time the hydro-demolition operation is performed and as required to achieve the specified results. Provide a non-working technical field representative on the project site during the calibration and the hydro-demolition surface preparation operation.
c.Power Driven Hand Tools. Use this equipment for removal of unsound concrete and for removal in areas inaccessible to hydro-demolition. This equipment is permitted with the following restrictions:
1.Do not use pavement breakers heavier than nominal 30 lb class. 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS
2.Do not operate pavement breakers or mechanical chipping tools at an angle greater than 45 degrees measured from the surface of the deck.
3.Do not use chipping hammers heavier than a nominal 15 lb class for concrete removal beneath any reinforcing bars.
d.Hand Tools. Use hand tools such as hammers and chiseled for removal of remaining particles of unsound concrete from beneath any reinforcing bar to achieve the required depth.
e.Abrasive Blasting. Provide equipment capable of removing rust scale and old concrete from reinforcing bars and of removing small chips of concrete partially loosened by the removal operation. LMC Proportioning and Mixing Equipment. Equipment used for mixing shall be self- contained, mobile, continuous mixing, and shall be:
a.Self-propelled and be capable of carrying sufficient unmixed dry bulk cement, sand, coarse aggregate, latex modifier, and water to produce at least 6 yd 3 of concrete. Do not store aggregate in the mixing equipment overnight.
b.Capable of positive measurement of cement being introduced into the mix, have a recording meter visible at all times, and be equipped with a ticket printout that indicates the quantities being mixed.
c.Calibrated to accurately proportion the mix. Certification of the calibration by an approved testing authority will be accepted as evidence of the accuracy if the yield is shown to be true within a tolerance of 1.0 percent in conformance with MSMT 558.
d.Capable of providing positive control of the flow of water and latex emulsion into the mixing chamber. Water flow shall be indicated by flow meter and be readily adjustable to provide for minor variations in aggregate moisture.
e.Capable of being calibrated to automatically proportion and blend all components of indicated composition on a continuous or intermittent basis as required by the finishing operation. It shall discharge mixed material through a conventional chute directly in front of the finishing machine.
f.Capable of spraying water over the entire placement width as it moves ahead to ensure that the surface is wetted to receive the LMC. Placing and Finishing Equipment. The combination of labor and equipment for proportioning, mixing, placing, and finishing LMC shall meet the following minimum requirements except when otherwise specified: 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS TOTAL OVERLAY AREA PER BRIDGE SQUARE YARDS MINIMUM OVERLAY RATE PER HR CUBIC YARDS 0-328 1.0 329-492 1.5 493-656 2.0 over 656 2.5
a.Placing and finishing equipment includes hand tools for placement and for distributing it to approximately the correct level for striking off with the screed.
b.Use an approved finishing machine for finishing all areas of work. The finishing machine shall be self-propelled and capable of forward and reverse movement under positive control. Provisions shall be made for raising all screeds to clear the screeded surface for traveling in reverse. Use a rotating cylinder type finishing machine. It shall span the placement transversely, and be equipped with one or more rotating steel cylinders, augers, and vibratory pans.
c.The finishing machine shall be designed so that when LMC is being mixed and placed under normal operating conditions at the minimum rate, the elapsed time between depositing the LMC on the concrete deck and final screeding does not exceed 10 minutes.
d.Ensure that construction is supervised by the LMC mixture’s representative or as directed by the Engineer.
426.03.03 Deck Removal and Repairs. Remove material to the specified limits as shown on the
Contract plans using mechanical type, high pressure water jet, power driven tools, hand tools, and abrasive blasting as required by the specification. The Engineer will inspect the entire exposed portion of the deck and determine if any repairs are required. The Engineer will specify the type and extent of the repairs. Repair any extraneous damage to the existing bridge that the Engineer deems to have been caused by the removal and cleaning operations, at no additional cost to the Administration. After completion of the initial pass using high pressure water jet, and the deck is dry and frost free, resound the deck to ensure that all unsound material has been removed. Remove unsound concrete as determined by the Engineer using high pressure water jet type method at no additional cost to the Administration. Clean the high pressure water jet and milling debris with a vacuum system equipped with fugitive dust control devices and capable of removing wet debris and water all in the same pass. Blow dry the deck with air to remove excess water. Perform cleaning in a timely manner, before the debris and water are allowed to dry on the deck surface. Provide shielding, as required, to ensure containment of all dislodged concrete within the removal area in order to protect the traveling public from flying debris on, adjacent to, and below the worksite. See 426.03.01 for additional containment requirements. 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS During and after the high pressure water jet type method removal operation (regardless of the depth of concrete deck removal) vehicular traffic, equipment and material storage are strictly prohibited on that portion of bridge deck, whether or not the reinforcement is exposed. These restrictions will be lifted after the LMC has been properly placed and cured as specified in 426.03.07. Ensure that the existing concrete around the reinforcing bars is sound and not debonded especially when more than 1/2 diameter is exposed. Where the bond between existing concrete and reinforcing steel has been destroyed, remove the concrete adjacent to the bar to a depth that will permit concrete bond to the entire periphery of the exposed bar. Ensure that this clearance is at least 1 in. unless lower bar mats make it impractical. Existing reinforcing steel utilized in the finished deck shall meet 421.03.07. Take measures to prevent cutting, stretching, or damaging any exposed reinforcing steel. Regardless of whether it was previously coated, abrasive blast clean and apply epoxy coat touch up system to all exposed reinforcement as specified in Section 465. Use epoxy powder coating touch up material from the Administration’s Approved List. If the Contractor believes that there is not enough time to allow the system to properly cure, request a waiver for this requirement to the Office of Structures prior to the start of removal operations. Replace the reinforcing steel that is damaged or deteriorated with the same diameter bars using epoxy coated bars for all existing reinforcing steel regardless of whether it was previously coated. Refer to 426.03.04 for additional requirements. Keep all areas from which unsound concrete has been removed free of slurry produced by hydro-demolition of concrete in adjacent areas. Remove slurry from prepared areas before proceeding with the surface preparation and properly dispose of at the approved area as specified in 426.03.01. Repair spalled concrete, voids, and other defects that are located within the proposed LMC overlay area according to the methods specified herein. Each repair includes the removal of the additional deck material, all hand-chipping, and filling the repair area voids with LMC overlay while applying the overlay.
a.For cavities less half the deck thickness, no additional work required.
b.For cavities over half the deck thickness but not full depth, furnish and erect temporary protective shields as specified in 405.03.01. If utilized in the original construction of the structure, existing stay in place forms that are in good condition will be sufficient to meet this requirement.
c.For areas where the depth of removal is full depth, meet the following in addition to the requirements of (b):
1.In large areas, supply forms to enable placement of the LMC overlay and support them by blocking from the stringers. If utilized in the original construction of the structure, existing stay in place forms that are in good condition will be sufficient to meet this requirement. 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS
2.In small areas, supply forms to enable placement of the LMC overlay. Forms may be suspended from existing reinforcing bars by wire ties. If utilized in the original construction of the structure, existing stay in place forms that are in good condition will be sufficient to meet this requirement. Clean all bridge scuppers, downspouts, joint troughs, end of bridge inlets, pipes and outfalls of all debris.
426.03.04 Surface Preparation for LMC Overlay. Thoroughly clean the entire milled deck
surface with a high pressure water wash (minimum 7500 psi) within 24 hours before placing the overlay to clean all reinforcement bars of visible rust and clinging concrete detached from the deck and all areas of concrete against which the overlay is to be placed. High pressure water washing may be required on the day the overlay is to be placed so that reinforcing bars are free of visible rust, unless the Engineer determines that a thin coating of flash rust will be acceptable.
426.03.05 Proportioning and Mixing LMC Materials. Mixers shall be clean and the ingredients
accurately proportioned. Mix LMC materials at the site according to the specified requirements for the equipment used. Ensure that the LMC discharged from the mixer is uniform in composition and consistency. Mixing shall enable finishing operations to proceed at a steady pace, with final finishing completed before the formation of the plastic surface film.
426.03.06 Placing and Finishing LMC Overlay. The LMC overlay will be the riding surface of
the bridge. Place the top of the LMC overlay to the true as planned line and grade of the roadways. Produce a finished top of LMC overlay that is smooth riding by placing the LMC overlay in a manner that meets the grade of the proposed adjoining portions of the new bridge decks and adjoining roadways. Place and fasten screed rails in position to ensure finishing the new surface to the required profile. Anchorage for supporting rails shall provide horizontal and vertical stability. Do not treat screed rails with any compound to facilitate their removal. The location of longitudinal joints (if not shown on the Contract Documents) will be determined by the Engineer based on avoiding joints in the vehicular wheel path as much as practical. Review inspection procedures to ensure coordination between contractor, subcontractors, suppliers and the Administration to ensure all understand the procedures to be used. Prior to placement operations, review the equipment, procedures, personnel, and previous results with the Engineer. Revise operations as needed to provide a smooth riding bridge deck meeting 420.03.07(d). Completely clean all surfaces by air blast followed by flushing with water. Prior to placing the LMC overlay, wet the surface and keep it wet for at least one hour. Remove puddles of free water. 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS Place the LMC mixture to approximately 1/4 in. above grade and then screed with an approved power operated finishing machine to the specified line and grade. Use a suitable portable lightweight or wheeled work bridge behind the finishing operation. Hand finishing may be required along the edge. Edge tool joints, except when next to metal expansion dams, curbs, and previously placed lanes. Separate the screed rails and construction bulkheads from the newly placed material by passing a pointing trowel along their inside face. Make the trowel cut for the entire depth and length of screed rails and bulkheads, after the mixture has stiffened sufficiently. Do not separate metal expansion dams from the overlay.
426.03.07 Curing. Cover the surface of the LMC overlay with a single layer of clean, wet burlap
as soon as the surface will support it without deformation. Follow immediately with a layer of 4 mil polyethylene film on the top of burlap and cure the surface for 48 hours. Whenever cold weather protection is required, the polyethylene film shall be covered with R 12 insulating blankets. Provide a sufficient number of maximum/minimum recording thermometers to record temperatures in each LMC placement and ensure that all requirements outlined in 426.03.09 are satisfied. After 48 hours, remove the wet burlap and 4 mil polyethylene film and air cure the LMC for an additional 72 hours. White opaque burlap polyethylene sheeting may be substituted for the polyethylene film with approval of the Engineer, but shall not replace the wet burlap. Plastic shrinkage cracks and cold joints between overlay placements shall be filled with an approved gravity fill polymer such as high molecular weight methacrylate (HMWM), prior to placing traffic on the overlay and in accordance with the manufacturer’s recommendations. Apply sufficient polymer to fill the cracks and once the cracks are filled, excess polymer should be brushed off so that it does not harden in the valleys of the grooves in the finished overlay surface. Apply a light application (approximately 1 lb/yd
2.of an approved sand as needed for improved skid resistance. The polymer must be hard prior to being subjected to traffic. There will be no separate payment for this work. The cost will be incidental to the item for Latex Modified Concrete Overlay.
426.03.08 Grooving. Groove as specified in the applicable portions of 420.03.07(d)(1), but start
after the LMC has been cured as specified in 426.03.07. When a deck is overlaid in staged construction, wait until the whole bridge deck within the stage is overlaid, properly cured, and the minimum compressive strength of 3000 psi has been obtained, and then groove the entire overlay area of the bridge deck prior to allowing traffic to use the area. Additional MOT required for this work will be paid as specified in 426.04.04.
426.03.09 Limitation of Operations. LMC placement includes the applicable deck placement
restrictions specified in 420.03.04. Do not apply loads to the bridge deck overlay until the final section of the overlay placed in the structure’s staged construction has completed its specified air curing period as specified in 426.03.07. No vehicles, including heavy construction equipment, will be permitted on bridge 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS deck overlay until the concrete cylinder breaks have attained a compressive strength of 3000 psi. However, loads such as stored materials, lightweight equipment, and concrete safety parapets, may be placed upon the concrete slab via lifting devices after the air curing period. Do not open the bridge deck overlay to traffic until concrete cylinder breaks have attained a compressive strength of 3000 psi, the air curing period is complete, the cracks are filled with an approved gravity fill polymer as specified in 426.03.07, and the overlay is grooved as specified in 426.03.08. Do not place LMC and concrete adjacent to an LMC surface course less than 96 hours old. This restriction does not apply to a continuation of placement in a lane or strip beyond a joint in the same lane or strip. Do not grind or chip existing concrete pavement within 6 ft of LMC or between the same bridge joint as the LMC placement until the LMC has cured for at least 48 hours. Do not place LMC at temperatures below 45 F. The LMC may be placed at 45 F, if rising temperature is predicted and anticipated for at least 8 hours. Suspend all LMC placements if the surface evaporation rate exceeds 0.10 lb/ft 2/hour as shown in ACI 308, Figure 1. LMC placement may continue at the Contractor’s risk upon approval by the Engineer of measures to be taken to prevent deleterious effect of high surface evaporation rates. At curing temperatures below 55 F, the Engineer will require a longer curing period and conformance with applicable portions of 420.03.13. Any day during which the curing temperature falls below 50 F will not be counted as a curing day. When during the curing period the curing temperature falls below 35 F, the work may be considered as being unsatisfactory and rejected. Remove and replace unsatisfactory LMC at no additional cost to the Administration. During delays up to one hour, several layers of wet burlap may be used to protect the end of the placement from drying. If the delay exceeds one hour, construct a dam or install a bulkhead and wait 12 hours before resuming placement operations. However, placement may continue provided a gap of sufficient length for the finishing machine to clear the previously placed LMC overlay is left in the lane or strip. Protect freshly placed LMC overlays from sudden or unexpected rain. Stop all placing operations when it starts to rain. Remove and replace material damaged by rainfall, as determined by the Engineer, at no additional cost to the Administration. Do not place linseed oil on LMC finished deck surfaces. 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS
426.04 Measurement and Payment
The payment for removal operations and latex modified concrete overlay items will be full compensation for all surveys, removing and cleaning, collection, containment, and disposal of all liquid and/or solid effluent, protective shielding, abrasive blasting, high pressure water washing, air blasting, flushing with water, forming, cleaning scuppers, downspouts, joint troughs, end of bridge inlets, pipes and outfalls, disposal of removed material, and for all material, labor, equipment, tools, and incidentals necessary to complete the work.
426.04.01 Removal and Disposal of Existing Bituminous Wearing Surface from Bridge regardless
of depth will be measured and paid for at the Contract unit price per square yard for the actual surface area removed from the bridge deck.
426.04.02 Removal of Portion of Existing Concrete Deck by mechanical type, high pressure water
jet, power hand tools, or hand tools will be measured and paid for at the Contract unit price per cubic yard for the Removal of Portions of Existing Concrete Deck item. The payment will be full compensation for removing and cleaning existing concrete deck to include the collection, containment, and disposal of all liquid and/or solid effluent from the high pressure water jet method of concrete removal. The estimated cubic yard quantity for this item is based on an estimated removal depth, as specified, measured from the top of the existing concrete deck to the centerline of the top layer of the existing deck reinforcement plus additional removal required as specified in the Contract plans. For structures with a bituminous wearing surface, the estimated removal depth is measured from the top of the existing concrete deck after the entire existing bituminous wearing surface is removed. The minimum price bid for this item shall be as specified in the Schedule of Items.
426.04.03 Additional removal of unsound portions of existing concrete deck regardless of depth
or method will be measured and paid for at the Contract unit price per cubic yard for the Additional Removal of Portions of Existing Concrete Deck. This item is for additional cubic yard quantity of removal in excess of the estimated concrete removal depth specified in 426.04.02. The basis for measurement of this item shall be determined by subtracting the estimated cubic yard quantity of Latex Modified Concrete Overlay, as shown in the Schedule of Items, from the actual cubic yard quantity of Latex Modified Concrete Overlay placed. No payment shall be made under this item if the actual cubic yard quantity of Latex Modified Concrete Overlay placed is less than the estimated quantity as shown in the Schedule of Items. The price of this item shall be fixed at 1.4 times the price bid for Removal of Portions of Existing Concrete Deck.
426.04.04 Latex Modified Concrete Overlay will be measured and paid for at the Contract unit
price per cubic yard for the Latex Modified Concrete Overlay item. Measurement for the volume of concrete will be based on the meter readings on the mixers dispensing the latex modified concrete excluding the calculated volume of any waste. Placing, finishing, curing, sealing, and grooving of the latex modified concrete overlay, and repair of epoxy coating for existing deck reinforcing, and additional maintenance of traffic for grooving operations will not be measured but the cost will be incidental to Latex Modified Concrete Overlay item. 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS
426.04.05 Repair Bar for Deck Reinforcement will be measured and paid for at the Contract unit
price per linear foot. Repair of damaged reinforcement steel, epoxy coating for repair reinforcement steel, and furnishing and placing welded wire fabric for deck repairs will be incidental to the Repair Bar for Deck Reinforcement item.
426.04.06 Furnishing and installing any formwork required for full depth deck repairs will be
measured and paid for at the Contract unit price per square foot for the pertinent Formwork for Full Depth Deck Repairs item. The measurement will be based upon the exposed opening at the bottom of the deck. The cost for form work extending beyond these limits will be incidental to the item. 430 — METAL STRUCTURES CATEGORY 400 STRUCTURES SECTION 430 — METAL STRUCTURES
430.01 Description
Furnish, fabricate, transport, and erect steel beams, plate girders, trusses, grillages, columns and bents, shoes, pedestals, castings, beam retrofit plates and angles, miscellaneous steel, and all incidental structural steel as specified in the Contract Documents or as directed by the Engineer. Refer to Section 432 for bearings and Section 435 and Section 436 for cleaning and painting new and existing structural steel, respectively. Substitutes for Rolled Members. Fabricated shapes may be substituted for the specified rolled shape, provided the substitution is at no additional cost to the Administration and the fabricated shape meets the following requirements:
a.The moment of inertia is equal to or greater than the rolled shape for the full length of the member.
b.The depth is greater than or equal to the rolled shape and does not decrease the designated minimum underclearance.
c.The web or leg thickness is at least 1/2 in.
d.The flange thickness is at least 1 in., the flange width is at least 12 in., and the width to thickness ratio does not exceed 12.
e.It is made of the same material specified for the rolled shape. (f) All normal criteria for creating a welded member are adhered to.
430.02 Materials
Paint Section 435, Section 436, and 912.05 Grout 902.11(c), 902.11(d), 902.11(e) Metals Section 909 Metal Reinforced Epoxy Filler 909.12 Bolts F3125 Grade A325, A490 Nuts A563 Grade C, D, and DH Washers F436 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS
Source: Maryland Standard Specifications for Construction and Materials, 2025 Edition. Pages 470–480 of 1,113.