420 PORTLAND CEMENT CONCRETE STRUCTURES

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420.01 DESCRIPTION.
Furnish, place, finish, and cure concrete bridges, culverts, and miscellaneous structures including cofferdams, forms, and falsework.
420.02 MATERIALS.
Curing Materials       902.07
Form Release Compound       902.08
Concrete Mixes       902.10 and 420.02.04
Grout       902.11
Linseed Oil       902.12
Drains, Downspouts, Weep Holes, and Pipes       905
Reinforcement       908.01
Cast Iron Scuppers       909.04
Anchor Bolts       909.06
Steel Forms Which Remain In Place       909.11
Joint Sealer       911.01
Preformed Joint Fillers       911.02
Preformed Elastomeric Joint Seals       911.04
Water Stops and Flashing       911.08 and 913.05
Production Plants       915
Fusion Bonded Epoxy       917.02
Water       921.01
Epoxy Bonding Compound       921.04
420.02.01 Admixtures. Do not use calcium chloride or other admixtures containing chloride salts in concrete placed on steel bridge deck forms.
420.02.02 Requirements for Accessories. Ensure that accessories such as inserts and ties that will remain in completed superstructures within the top 5 in. of final deck slab concrete are either epoxy coated or made of material other than aluminum that will not rust. These same requirements pertain to accessories that will remain in parapets, sidewalks, or other portions of the structure designated to have epoxy coated reinforcing steel. Do not use inserts in the top half of slabs exposed to vehicular traffic unless specified.
420.02.03 Precast Reinforced Concrete Box Sections. Meet M 259 or M 273 including concrete design strength. All details shall be as specified. Construction joints between the walls and the bottom and top slabs are optional. Certify as specified in 305.03.06.
420.02.04 Composition of Concrete Mixes for Slip Form. For construction of parapets and median barriers on bridges, use Mix No. 6 with a 1 in. maximum slump. Measure the slump at the placement point as the concrete is charged into the slip form machine. Use crushed stone meeting M 43, size No. 7 for the coarse aggregate, proportioned to be 63 percent of the total aggregate in the mix. Other size coarse aggregate may be used provided the slip form results are acceptable.
420.03 CONSTRUCTION.
Produce concrete at the work site or away from the work site by an approved central mixing plant, or by approved truck mixing as specified in Section 915.
When specified, remove portions of existing parapets or end posts as specified in 405.03.
420.03.01 EquipmentAll machinery, tools, and apparatus necessary for the proper construction and acceptable completion of the work, together with the necessary supplies for upkeep and maintenance.. Use equipment of sufficient capacity to complete any unit or section of concrete between construction joints in one continuous operation consistent with approved placement operations. With written approval, hand mixing may be permitted for small volumes of concrete used in isolated portions of the structure where structural integrity is not critical and the volume does not exceed 1 yd3.
420.03.02 Forms.
(a) Design Criteria.
(1) Design Loads. Per AASHTOAmerican Association of State Highway and Transportation Officials LRFD BridgeA structure including supports erected over a depression or an obstruction, such as water, highway, or railway, and having a track or passageway for carrying traffic or other moving loads, and having an opening measured along the center of the roadway of more than 20 feet between undercopings of abutments or spring lines of arches, or extreme ends of openings for multiple boxes; it may also include multiple pipes, where the clear distance between openings is less than half of the smaller contiguous opening. For lengths, all dimensions shall be parallel to the center line of the roadway. The dimensions of handrails will not be taken into account in measuring bridge lengths. Any bridge or highway grade separation structure includes the connecting highways, substructure, superstructure, roadway approaches, entrance plazas, interchanges, overpasses, underpasses, and other structures which the Administration may deem necessary together with all property rights, easements, franchises, and interests acquired by the Administration for the construction and operation of the bridge. Construction Specifications, Temporary Works. Assume the lumber in the forms to weigh 50 lb/ft3.
(2) Design Stresses.
Timber Design. Per ACIAmerican Concrete Institute Standard Recommended Practice for Concrete Formwork (ACIAmerican Concrete Institute 347). Deflections for form members shall not exceed 1/270 of the span or ¼ in. Unit stresses stipulated in AASHTOAmerican Association of State Highway and Transportation Officials for treated timber may be increased by 25 percent, but shall not exceed the values listed below.
Compression Perpendicular to Grain       450 psi
Compression Parallel to Grain       1600 psi
Flexural Stress       1800 psi
Horizontal Shear
   Beams up to 6 in. deep       200 psi
   Beams over 6 in. deep       150 psi
   Axial Tension       1200 psi
Plywood. For plywood without backing, calculate the strength of plywood based on the grain of the face plies running parallel to its span. Install the plywood in this manner.
Steel Members for Forms. Per AASHTOAmerican Association of State Highway and Transportation Officials LRFD Design Specifications and ASHSTO LRFD BridgeA structure including supports erected over a depression or an obstruction, such as water, highway, or railway, and having a track or passageway for carrying traffic or other moving loads, and having an opening measured along the center of the roadway of more than 20 feet between undercopings of abutments or spring lines of arches, or extreme ends of openings for multiple boxes; it may also include multiple pipes, where the clear distance between openings is less than half of the smaller contiguous opening. For lengths, all dimensions shall be parallel to the center line of the roadway. The dimensions of handrails will not be taken into account in measuring bridge lengths. Any bridge or highway grade separation structure includes the connecting highways, substructure, superstructure, roadway approaches, entrance plazas, interchanges, overpasses, underpasses, and other structures which the Administration may deem necessary together with all property rights, easements, franchises, and interests acquired by the Administration for the construction and operation of the bridge. Construction Specifications. For design where no dynamic loading is involved, the AISCAmerican Institute of Steel Construction Standard Manual of Steel Construction, Allowable Stress Design may be used as the accepted design code.
Steel Forms Which Remain in Place. The maximum deflection shall not exceed 1/180 of the span and not in excess of ½ in. Do not use camber to compensate for deflection in excess of these limits. The design spans of the form sheets shall be the clear distance between beam or girder flanges less 2 in.
The unit working stress in the steel sheet and supporting members shall not be more than 0.725 of the specified minimum yield strength of the material furnished but not to exceed 36 000 psi. Compute physical design properties in accordance with the American Iron and Steel Institute SpecificationA written description of functional characteristics, or the nature of a construction item to be procured. It may include a for Design of Cold Formed Steel Structural Members.
(b) Working Drawing Approval. Submit detail, form, falsework, and centering plans and design loads for approval as specified in Section 499. Working drawings for forms shall include all members proposed for use as well as form ties and bracing. Do not submit details for form ties separately; incorporate them in the general working drawings submittal. The rate of placing concrete shall be noted on the working drawings. Approval of the working drawings does not relieve the ContractorAny person having a Contract with a procurement agency. Contractor does not include an employee with an employment Contract, or an employee organization with a collective bargaining agreement. of responsibility as specified in TC-4.01. The provisions of 430.03.28 also apply when working drawings are submitted for falsework and centering.
(c) Forms at Construction Joints and Corners. Provide ties or bolts 3 to 6 in. from each side of construction joints for tightening the forms against the hardened adjacent concrete prior to placing fresh concrete. At joints where forms have been removed and reconstructed, extend the form over the concrete already in place; and draw tightly against the previously placed concrete. Provide fillets at all sharp corners, except when otherwise specified, and provide a bevel or draft in the case of all projections. Chamfer all exposed corners of concrete with 3/4 x 3/4 in. milled chamfer strips, except on unexposed footings or where specified.
(d) Form Scaffolds and Platforms. Build form scaffolds and platforms along the outside of bridge deck fascias during construction of forms for bridge decks. Design and construct them as integral parts of the form supports. Furnish separate design calculations with the working drawing submission. Assume the responsibility of TC-4.01 even after approval of the working drawings.
(e) Forms for Unexposed Surfaces. Ensure that sheathing, studs, and bracing are of sound material, and that studs and wales are straight, true, and surfaced on two edges to a uniform width. Ensure that the inside faces of the forms are constructed sufficiently smooth so that the resulting concrete surfaces are accurately formed.
(f) Forms for Exposed Surfaces. Unless otherwise specified in the Contract DocumentsThe written agreement executed between an Administration and the successful bidder, covering the performance of the work and furnishing of labor, equipment and materials, by which the Contractor is bound to perform the work and furnish the labor, equipment and materials, and by which the Administration is obligated to compensate him therefore at the mutually established and accepted rate or price. The Contract Documents shall include the Invitation for Bids, Notice to Contractors, Instructions to Bidders, Proposal, Contract Forms and Bonds, General Provisions, Specifications, Supplemental Specifications, all Special Provisions, all Technical Provisions, all Plans and Notices to Proceed, also any written Change Orders and Supplemental Agreements that are required to complete the construction of the work in an acceptable manner, including authorized extension thereof, support the bridge deck concrete between stringers with steel forms which remain in place, except in panels where a longitudinal deck construction joint is located between stringers. Ensure that forms used for widening and rehabilitation provide exposed finished concrete surfaces that match the existing structure.
(1) Lined Forms for Exposed Surfaces. Use approved composition board, sanded plywood, or metal for contact surfaces of lined forms for surfaces exposed to weather or view. Ensure that all studs are surfaced two edges to a uniform width. The studs and backing shall be solid, straight, and free of detrimental defects. However, the backing need not be of the quality used for contact forms for unexposed surfaces.
Sheathing for form backing shall be surfaced two sides to a uniform thickness of at least the dimension approved on the working drawings. Ensure that form sheathing is built solidly, securely nailed to studs, and placed to prevent any bulging of the lining.
(2) Unlined Forms for Exposed Surfaces. Use five ply sanded plywood of the specified thickness for surfaces exposed to weather or view. Use plywood manufactured especially for concrete formwork using waterproof glue. All studs and wales shall be surfaced two edges to a uniform width.
Use full size sheets of plywood except where smaller pieces cover an entire area. Solidly back joints to prevent leakage, and nail the edges of abutting sheets to the same stud or blocking with sixpenny nails not more than 8 in. apart. Where rustication occurs, construct horizontal plywood joints behind a rustication strip. Otherwise, place horizontal joints at the same respective elevations in all portions of the structure. Where vertical rustication occurs, construct vertical joints in the lining behind a rustication strip. Otherwise, keep vertical joints to a minimum, butted tightly together and sealed with crack filler as the plywood is nailed in place.
(g) Steel Forms Which Remain in Place.
(1) Installation. The surface in contact with concrete shall be smooth and free of surface irregularities. Ensure that working drawings specify the grade of steel, the physical and sectional properties, and a clear indication of where the forms are supported by steel beam flanges subject to tensile stresses.
Do not weld form supports to flanges of steel that are not considered weldable or to portions of flanges that are subject to tensile stresses.
Welding and welds per AWSAmerican Welding Society BridgeA structure including supports erected over a depression or an obstruction, such as water, highway, or railway, and having a track or passageway for carrying traffic or other moving loads, and having an opening measured along the center of the roadway of more than 20 feet between undercopings of abutments or spring lines of arches, or extreme ends of openings for multiple boxes; it may also include multiple pipes, where the clear distance between openings is less than half of the smaller contiguous opening. For lengths, all dimensions shall be parallel to the center line of the roadway. The dimensions of handrails will not be taken into account in measuring bridge lengths. Any bridge or highway grade separation structure includes the connecting highways, substructure, superstructure, roadway approaches, entrance plazas, interchanges, overpasses, underpasses, and other structures which the Administration may deem necessary together with all property rights, easements, franchises, and interests acquired by the Administration for the construction and operation of the bridge. Welding Code pertaining to fillet welds.
Unless otherwise specified, use steel forms between stringers to support bridge deck concrete, except where a longitudinal deck construction joint is located between stringers.
(2) Procedure Check and Inspection. Remove at least one section of the forms at a location and time selected by the EngineerAny person designated by the Administrator or the procurement officer, acting directly or through his duly authorized representative, such representative acting within the scope of the particular duties assigned to him or of the authority given him. from each span of each bridge in the ContractAny agreement entered into by a procurement agency for the acquisition of supplies, services, construction, construction related services, architectural services or engineering services.Contract does not include: Collective bargaining agreements with employee organizations or agreements creating employer employee relationships, as defined in Article 64A, Section 15A(a)(3), Annotated Code of Maryland, Medicaid, Medicare, Judicare, or similar reimbursement contracts which user eligibility and cost are set by law or regulation.. If the bridge has a longitudinal joint, remove a form on each side of the joint from each span. Do this as soon after placing the concrete as practical to provide visual evidence that the concrete mix and the placement procedures are obtaining the desired results. Remove an additional section if the EngineerAny person designated by the Administrator or the procurement officer, acting directly or through his duly authorized representative, such representative acting within the scope of the particular duties assigned to him or of the authority given him. determines that there have been any changes in the concrete mix or in the placement procedures that warrant additional inspection.
At locations where sections of the forms are removed, replacement of the forms will not be required, but the adjacent metal forms and supports shall be repaired to present a neat appearance and ensure their satisfactory retention. As soon as the form is removed, the concrete surfaces will be examined for cavities, honeycombing, and other defects. If the EngineerAny person designated by the Administrator or the procurement officer, acting directly or through his duly authorized representative, such representative acting within the scope of the particular duties assigned to him or of the authority given him. finds irregularities but determines that the irregularities do not justify rejection of the work, repair the concrete as directed.
Give the concrete an ordinary surface finish as specified in 420.03.07(a). If the concrete where the form is removed is unsatisfactory, remove additional forms, as necessary, to inspect and repair the slab. Modify the method of construction as required to obtain satisfactory concrete. Remove all unsatisfactory concrete and replace or repair as directed.
Provide facilities required for the safe and convenient conduct of the EngineerAny person designated by the Administrator or the procurement officer, acting directly or through his duly authorized representative, such representative acting within the scope of the particular duties assigned to him or of the authority given him.’s inspection procedures.
(h) Steel Forms Which Do Not Remain in Place. The contact surface shall be smooth and free of bolts, bolt heads, nuts, rivet heads, welding seams, and surface irregularities. Forms that produce unacceptable results will be rejected, and shall not be reused.
(1) For Round Columns and Piers. Use steel forms that are at least 10 gauge, have a minimum number of horizontal joints, and are column height.
(2) For Pier Caps and Crash Walls. Prefabricated girder type steel forms may be used for forming pier caps or crash walls. Use one piece where practical for each element of these forms including side, bottom, and end. Arrange splices to provide a symmetrical pattern.
(3) For Reinforced Concrete Box Culverts and Rigid Frames. Use steel forms or forms constructed of wood or composition wood panel sheathing set in metal frames. Steel forms for box culverts and rigid frames shall be at least 10 gauge.
(i) Fiber Column Forms. Fiber column forms shall only be used for round columns. The forms shall produce columns truly round and straight. Protect forms from dampness before concrete is placed. Do not splice fiber forms.
(j) Release Agents. Apply form release compound immediately before placing concrete.
(k) Temporary Supports. Build temporary supports used for centering and falsework on good firm foundations. Unless otherwise provided, ensure that they bear upon strata at or below the frost line unless rock is available. Where required, drive piling for support. Ensure that the strength and bracing of the temporary supports will provide a completed structure having the shape specified. Use jacks or hardwood wedges in connection with the temporary supports to take up settlement either before or during placing of concrete. Set temporary supports to give the structural camber specified, and allowance for shrinkage and settlement. If during construction, any weakness, settlement, or distortion develops, stop the work and remove any masonry affected. Strengthen the temporary structures before resuming. Construct centering to permit gradual and uniform lowering.
(l) Defective Forms. Use an approved device for removing or modifying steel forms which remain in place. Burning is prohibited.
(m) Form Ties. Use approved form ties. Ensure that ties leave no metal closer than 2 in. from the surface. They shall not be fitted with lugs, cones, washers or other devices that act as spreaders within the form or for any purpose that leaves a hole larger than 7/8 in. diameter. When prefabricated steel girder forms are used, use tapered ties no greater than 1-½ in. diameter. Ensure that ties are clean and free of rust. When ties are removed, pressure grout the holes with a nonshrink mortar mixed to match the color and texture of the concrete.
Coat the removable portions of ties with a clear lubricant or other approved material.
During removal of form ties, avoid spalling the concrete on the exposed surface. Do not cut the ties back from the surface.
(n) Form Support Brackets or Devices. Devices attached to previously placed concrete may be used, provided all parts are acceptable. No metal part of an insert, threader, or anchor that remains in the concrete shall be within 2-½ in. of the surface. Do not attach brackets or other devices until the concrete is cured and it has attained a compressive strength of at least 3000 psi. All voids left in the concrete after removal of brackets and other devices shall be no greater than 2 in. diameter. Fill them with mortar and finish the surface as specified in 420.03.07(a).
(o) Form Removal. For determining the time when falsework and forms may be removed, backfill placed, and when loads may be applied to structures, make an adequate number of concrete test specimens in addition to those required to check the quality of the concrete being produced. After meeting all formwork requirements, remove and dispose of all forms except those specified to remain in place.
Do not use methods of form removal likely to cause overstressing of the concrete. Do not remove forms and their support without approval. Remove supports in a manner that permits the concrete to uniformly and gradually take the stresses due to its own weight.
(p) Year Built Marking. Supply the correctly sized forms and molds, and cast the year of completion into each structure, as determined by the EngineerAny person designated by the Administrator or the procurement officer, acting directly or through his duly authorized representative, such representative acting within the scope of the particular duties assigned to him or of the authority given him..
420.03.03 Anchor Bolt Placement. Place anchor bolts as specified in 430.03.31.
420.03.04 Concreting. Clean forms before placing concrete. Ensure that temporary struts, stays, and braces holding the forms in correct shape and alignment are not buried in the concrete. If faces of completed or proposed excavated footing areas are disturbed prior to concreting, extend the footings to bear on acceptable undisturbed faces at no additional cost to the AdministrationShall mean any one of the Administrations within the Maryland Department of Transportation, as listed in GP 1.02..
Place all concrete (except tremie concrete) in the dry.
(a) Foundations. Assume responsibility for any reinforcement fabricated prior to approval of foundations. If bearing material varies more than assumed in design, the EngineerAny person designated by the Administrator or the procurement officer, acting directly or through his duly authorized representative, such representative acting within the scope of the particular duties assigned to him or of the authority given him. may direct the footing be lowered, raised, or deepened; subfoundation placed; piles used; or a combination of these methods used to best obtain bearing. If planned footings are changed vertically, revise reinforcing steel as required. Use plain nonreinforced Concrete Mix No. 1 to construct subfoundation concrete for bridges, retaining walls, and wing walls of box culverts or rigid frames. This concrete need not be vibrated, and the usual curing and cold weather requirements may be reduced to three days. Selected backfill using number 57 aggregate may be used for subfoundation for box culvert barrels, headwalls, and miscellaneous structures.
(b) Concrete Placement. Avoid segregation of the material and the displacement of the reinforcement. The use of troughs, chutes, and pipes for conveying concrete more than 15 ft from the mixer to the forms will be permitted only when approved. Open troughs and chutes shall be metal or metal lined. Where segregation occurs due to steep slopes, equip chutes with baffles.
Where placing operations involve dropping the concrete more than 5 ft, deposit it through a tube made of sheet metal, canvas, or other approved material. Do not use aluminum hoppers or tubes. Keep lower ends as close as possible to the newly placed concrete but not more than 3 ft above the concrete. All tubes shall be at least 6 in. diameter unless otherwise directed. Do not disturb the forms after initial set of the concrete, and do not place any strain on the projecting ends of the reinforcement.
Place concrete in horizontal layers not more than 12 in. high except as provided herein. When less than the complete area of a layer is placed in one operation, terminate it in a vertical bulkhead. Place and vibrate each layer before the preceding layer has taken initial set.
Place concrete in columns and walls in one continuous operation unless otherwise directed. Allow concrete to set at least 12 hours before placing the caps.
Where walls, piers, columns, struts, and posts have horizontal construction joints, do not place succeeding lifts until the lower placement has set for 12 hours.
Prior to subsequent placement, clean all accumulations of mortar splashed upon the reinforcement. Avoid damaging the concrete seal bond near and at the surface of the concrete while cleaning the reinforcing steel.
(c) SuperstructureAll of that part of the structure above bottoms of bearings of simple and continuous spans, skewbacks of arches and tops of footings of rigid frames, except as noted above for substructure. Placement.
(1) Grade Controls for BridgeA structure including supports erected over a depression or an obstruction, such as water, highway, or railway, and having a track or passageway for carrying traffic or other moving loads, and having an opening measured along the center of the roadway of more than 20 feet between undercopings of abutments or spring lines of arches, or extreme ends of openings for multiple boxes; it may also include multiple pipes, where the clear distance between openings is less than half of the smaller contiguous opening. For lengths, all dimensions shall be parallel to the center line of the roadway. The dimensions of handrails will not be taken into account in measuring bridge lengths. Any bridge or highway grade separation structure includes the connecting highways, substructure, superstructure, roadway approaches, entrance plazas, interchanges, overpasses, underpasses, and other structures which the Administration may deem necessary together with all property rights, easements, franchises, and interests acquired by the Administration for the construction and operation of the bridge. Deck Slabs. Place bridge deck slabs supported by new stringers to the specified line and grade. Take all necessary precautions, including a check on all new bridge seat elevations as the last order of work before setting stringers. Complete any adjustments resulting from this check before starting additional work. After the structural steel is set, make a final check of elevations of all the steel stringers at points corresponding to those for dead load deflection and finished roadway elevations. Make computations and have them approved. Set controls at proper elevations to produce finished tops of concrete bridge decks that will be true to the planned line and grade of the roadway.
Perform grade control for bridge deck slab replacements as specified in 405.03.02.
(2) SuperstructureAll of that part of the structure above bottoms of bearings of simple and continuous spans, skewbacks of arches and tops of footings of rigid frames, except as noted above for substructure. Placement Restrictions. Do not erect the superstructure until the substructure forms have been sufficiently stripped to determine the character of the concrete in the entire substructure. In all spans, use plywood forms to cast the concrete bridge deck slabs outside of the stringers.
Unless otherwise specified, pump concrete for deck slabs whenever the volume of concrete in the pour exceeds 50 yd3.
Place all superstructure concrete according to the following schedule:
SUPERSTRUCTURE CONCRETE PLACEMENT SCHEDULE
DATES BEGIN CONCRETE

PLACEMENT AFTER

FINISH BURLAP

PLACEMENT BEFORE

May 15 - June 15 7:00 PM 11:00 AM
June 16 - Aug. 14 9:00 PM 7:00 AM
Aug. 15 - Sept. 15 7:00 PM 11:00 AM
Sept. 16 - May 14 No time restrictions
Do not place or work superstructure concrete in any manner when the temperature in an unshaded location at the placement site is above 80 F. Use floodlighting when existing light is less than 20 average horizontal ft-c over the construction area.
Submit a Situation Plan showing the locations and aiming of floodlights. After reviewing this plan, the EngineerAny person designated by the Administrator or the procurement officer, acting directly or through his duly authorized representative, such representative acting within the scope of the particular duties assigned to him or of the authority given him. will witness a test of the floodlighting system at the proposed construction area. The floodlighting system shall be capable of maintaining 20 ft-c without producing a glare on traffic. Floodlighting systems shall be as approved. When portable generators are used, have an emergency backup system available at all times on the job site.
(3) Rate of Concreting for BridgeA structure including supports erected over a depression or an obstruction, such as water, highway, or railway, and having a track or passageway for carrying traffic or other moving loads, and having an opening measured along the center of the roadway of more than 20 feet between undercopings of abutments or spring lines of arches, or extreme ends of openings for multiple boxes; it may also include multiple pipes, where the clear distance between openings is less than half of the smaller contiguous opening. For lengths, all dimensions shall be parallel to the center line of the roadway. The dimensions of handrails will not be taken into account in measuring bridge lengths. Any bridge or highway grade separation structure includes the connecting highways, substructure, superstructure, roadway approaches, entrance plazas, interchanges, overpasses, underpasses, and other structures which the Administration may deem necessary together with all property rights, easements, franchises, and interests acquired by the Administration for the construction and operation of the bridge. Deck Slabs. Make provisions to ensure that the placement rate of concrete is at least 35 yd3/hour per crew. Under special circumstances, the EngineerAny person designated by the Administrator or the procurement officer, acting directly or through his duly authorized representative, such representative acting within the scope of the particular duties assigned to him or of the authority given him. may give written approval to lower this requirement.
Submit evidence of an adequate source of concrete and placing and finishing equipment capable of meeting the minimum rate of placement while providing the intended quality finish. Submit this evidence at least one week prior to the proposed placement of the bridge deck slab.
Place concrete in slab spans in one continuous operation and in one layer for each span.
Do not mound concrete on forms supported by beams, stringers, or girders. Distribute the concrete to a depth not exceeding the planned slab thickness plus 6 in. before spreading, consolidating, and finishing.
Follow the placing sequence in the numerical order specified without modification. Allow at least 40 hours between the completion of one placement and the start of the next numbered placement.
(d) Box Culverts. If the top slab is the roadway riding surface, place as specified in 420.03.04(c). Construct box culverts by casting in place or use precast reinforced concrete box culvert sections. Whichever method is indicated in the Contract DocumentsThe written agreement executed between an Administration and the successful bidder, covering the performance of the work and furnishing of labor, equipment and materials, by which the Contractor is bound to perform the work and furnish the labor, equipment and materials, and by which the Administration is obligated to compensate him therefore at the mutually established and accepted rate or price. The Contract Documents shall include the Invitation for Bids, Notice to Contractors, Instructions to Bidders, Proposal, Contract Forms and Bonds, General Provisions, Specifications, Supplemental Specifications, all Special Provisions, all Technical Provisions, all Plans and Notices to Proceed, also any written Change Orders and Supplemental Agreements that are required to complete the construction of the work in an acceptable manner, including authorized extension thereof, the alternate method may be used unless otherwise specified. However, all time constraints such as maintenance of traffic, curing, and completion date shall be met.
If precast sections are used, at least 15 ft of all box culvert ends and all footings, wing walls, headwalls, and toe walls shall be cast in place. Additionally, terminate the precast sections at least 1 ft from footings and toe walls. Show lifting devices on the working drawings. Fill lifting holes with nonshrink grout after the precast units are in place. Set the precast reinforced concrete box sections tightly together, and seal the joints per the manufacturer’s recommendations.
Place the bottom slabs of cast in place concrete box culverts for their full depth in one mass or layer and allow to set at least 12 hours before performing any additional work.
Do not place the top slab on single cell box culverts spanning in excess of 10 ft and on multiple cell box culverts until the concrete in the sidewalls has set for at least 12 hours. Construction joints at the top of sidewalls may be omitted in some cases provided the top slabs are placed as follows:
(1) For single cell box culverts spanning 10 ft or less, the sidewall construction joint may be omitted and the top slab placed on the sidewalls, provided the concrete in the sidewalls is allowed to set for approximately two hours before starting to place the top slab.
(2) Regardless of size or number of cells, a written request may be made to place the top slab on the walls of box culverts per (1) above. Submit the proposed plan, including rate and method of placement, and type and size of equipment. With initial approval, the first section of the structure will serve as a demonstration to confirm that there is no excessive cracking or any other detriment, and that satisfactory results will be obtained. After receiving final approval, continue placing the remainder of the box culvert. If at any time the EngineerAny person designated by the Administrator or the procurement officer, acting directly or through his duly authorized representative, such representative acting within the scope of the particular duties assigned to him or of the authority given him. determines that the results are no longer satisfactory, revert to placing the concrete with the 12 hour delay as specified above.
(e) Forming Concrete Parapets and MedianThe portion of a divided highway separating the traveled ways for traffic in opposite directions. Barriers on Bridges. Either the slip form method or conventional fixed form method may be used. However, do not use the slip form method on bridges maintaining traffic or on parapets when railing is specified.
If the slip form method is proposed, demonstrate ability to produce acceptable results. If the demonstration is unacceptable or acceptable results are not maintained during production, stop the slip form operation, remove the unacceptable work, and modify the construction methods. If construction modifications do not produce acceptable results, use the fixed form method. No additional compensation will be made, and no increase will be made in any Contract price. Nor will any revisions be made to the amount of time to complete the Contract as a result of any required removals, modifications, or changes in the method of placing parapets or barriers.
Notify the EngineerAny person designated by the Administrator or the procurement officer, acting directly or through his duly authorized representative, such representative acting within the scope of the particular duties assigned to him or of the authority given him. in writing of the proposed method of constructing the parapets and median barriers prior to beginning superstructure work.
The following shall apply to the consideration of slip forming:
(1) Submit evidence of being capable of producing high quality slip formwork. Prior to beginning any slip form construction, submit a detailed work plan. Include the type of equipment, materials, and procedures to be used, subcontractors involved in the construction, key personnel who will be performing the work (names, training, experience, etc.), as well as detailed information on the proposed process to satisfactorily complete the work.
(2) When possible, include reference in the work plan to at least three other similar projects completed in the State of Maryland or surrounding states. As far as practical, these projects shall have been built using the same equipment, personnel, material, and procedures proposed for the project. The EngineerAny person designated by the Administrator or the procurement officer, acting directly or through his duly authorized representative, such representative acting within the scope of the particular duties assigned to him or of the authority given him. may visit these completed projects to evaluate the acceptability of the finished product.
If the EngineerAny person designated by the Administrator or the procurement officer, acting directly or through his duly authorized representative, such representative acting within the scope of the particular duties assigned to him or of the authority given him. determines that satisfactorily slip formed parapets or median barriers have been demonstrated at the locations submitted in the work plan, the requirements of the off bridge test site specified below may be waived, and the first 50 ft of slip forming on the bridge will be considered the test section for the structure. This test section shall be completed and approved prior to placing the remaining portions of parapet or bridge median barrier.
(3) Do not begin any slip forming operation without written approval of the work plan.
Any proposed revisions or deviations to the approved work plan shall be submitted and approved prior to making the change.
If (2) above is not met, complete an acceptable off bridge test section prior to placing any portion of the parapet or bridge median barrier. Place the appropriate test section of parapet or median barrier using the same equipment, sensor line, support spacing, material, personnel, and procedures described in the work plan. This test section shall match the structure’s horizontal curve as much as practical, be at least 50 ft long, and be placed at a location selected by the ContractorAny person having a Contract with a procurement agency. Contractor does not include an employee with an employment Contract, or an employee organization with a collective bargaining agreement. near the bridge site.
Place the off bridge test section with vertical irregularities varying upward and downward at least ¾ in. Demonstrate that the method of slip forming can compensate for this deviation and provide a top of parapet or median barrier that is true to the proposed line and grade and not necessarily parallel to top of bridge deck. This necessitates that the equipment provide for variations in height of vertical face of parapet where it intersects the top of deck slab.
Position, support, and space the sensor line in the same manner that will be used on the bridge decks, with no stakes, holes, etc., used to support it. Use the sensor support spacing recommended by the slip form machine manufacturer and as necessary to maintain the planned line and grade. Use the same rate of slip forming proposed for the bridge. Saw cut joints in the test section at the same approximate spacing and in the same manner as proposed for the finished bridge. The EngineerAny person designated by the Administrator or the procurement officer, acting directly or through his duly authorized representative, such representative acting within the scope of the particular duties assigned to him or of the authority given him. will evaluate the procedure, material, equipment, and appearance of the test section.
Take three test cores from the test section at directed locations to determine the concrete quality. Honeycombing, sags, tears, or other evidence of poor quality concrete will be cause for rejection of the test section. If the test section is rejected, either place additional test sections until approved, or use the fixed form method.
Do not remove the accepted test section until all parapets or median barriers on the bridges are complete. The slip forming on the bridges will be compared to the approved test section to ensure that similar acceptable structures are being achieved. Following completion and acceptance of all bridge parapets and median barriers, remove and dispose of the off bridge test section.
The entire testing procedure, including removing and disposing of test units, regardless of whether the procedure is approved or rejected, shall be at no additional cost to the AdministrationShall mean any one of the Administrations within the Maryland Department of Transportation, as listed in GP 1.02..
When dual bridges are separated by a joint, construct the two parapets that make up the median barrier in separate operations; not simultaneously. Allow the first median parapet section to cure for at least 40 hours prior to constructing the second section of median parapet. Place additional reinforcing steel to brace the parapet against displacement during the extrusion process. A detail will be included in the Contract DocumentsThe written agreement executed between an Administration and the successful bidder, covering the performance of the work and furnishing of labor, equipment and materials, by which the Contractor is bound to perform the work and furnish the labor, equipment and materials, and by which the Administration is obligated to compensate him therefore at the mutually established and accepted rate or price. The Contract Documents shall include the Invitation for Bids, Notice to Contractors, Instructions to Bidders, Proposal, Contract Forms and Bonds, General Provisions, Specifications, Supplemental Specifications, all Special Provisions, all Technical Provisions, all Plans and Notices to Proceed, also any written Change Orders and Supplemental Agreements that are required to complete the construction of the work in an acceptable manner, including authorized extension thereof. The alignment and rigidity of the reinforcing steel will be strictly enforced to ensure that the minimum clearances specified for concrete cover are maintained.
Ensure that an uninterrupted flow of concrete is provided to the slip form machine. Once the slip form machine is set in motion, keep it advancing until it reaches the proposed stopping point. Organize and schedule the operations in a manner that the next concrete truck will be able to move into position at the slip form machine as soon as the previous truck pulls away without interrupting the machine’s uniform advancement. Under no circumstances may the slip forming be operated in a manner that requires removal of a concrete truck from the bridge before moving another truck into place.
Except for the slip form machine and its concrete supply trucks, do not allow vehicular traffic on the bridge while slip forming operations are in progress.
After setting up the slip form machine and placing the sensor wire, perform a dry run of the equipment in the presence of the EngineerAny person designated by the Administrator or the procurement officer, acting directly or through his duly authorized representative, such representative acting within the scope of the particular duties assigned to him or of the authority given him.. Demonstrate that the parapet or median barrier will envelop preset embedded obstacles and will meet with flush surfaces such as pull boxes, expansion joint plates, etc.
Use concrete of a consistency that the shape of the structure is maintained without support after extrusion. The surface shall be free of surface pits larger than 3/16 in. diameter. Finish the concrete with a light brushing with water only. Finishing with brush applications of grout is prohibited.
If a tear occurs at the top of the parapet or median barrier during the slip forming operation, remove it immediately. Make the repair using acceptable concrete practices. Blend the repair into the barrier to the extent that there is no distinguishable difference in the wall face or top. The rate at which the slip form machine is advanced shall be the same as used on the approved test section.
The shape of the finished parapet or median barrier shall conform to the dimensions specified. The vertical face at the bottom of the concrete safety shaped parapets and median barriers shall not exceed 3-½ in. Ensure that the finished parapet or median barrier does not deviate from the proposed grade and alignment in excess of ¼ in./10 ft.
Use a diamond blade to saw cut joints in the finished parapet or median barrier. Make cuts and space joints as specified. The trapezoidal shaped control joints on the outside of parapets will not be required if slip forming is used. Terminate slip form placements only at a parapet control joint. Saw cut the joints as soon as possible after initial concrete set and after the concrete has set sufficiently to preclude raveling during the sawing. Complete the sawing the same day the concrete is extruded and before any shrinkage cracking occurs. Do not leave concrete overnight without saw cutting the joints.
When portions of the bridge are superelevated, produce the configuration specified, i.e., level top surface, wall normal to deck surface, etc.
(f) Temperature Controls. Ensure concrete temperatures meet 902.10. Heat concrete below these temperatures by one of the following methods:
(1) When the method of heated mixing water is used, do not introduce water above 170 F into the mix.
(2) When the method of heated aggregates is used, heat aggregates containing frozen lumps separately. Do not allow materials containing frozen lumps, ice, or snow to enter the mixer. Heat aggregates by steam coils or other dry heat but do not discharge live steam or hot water into them. Do not use a flamethrower or any direct flame.
When the ambient air temperature is below 40 F, raise the temperature of the air in contact with the reinforcement to 40 F prior to placing concrete. When the ambient air temperature is above 70 F and the reinforcement or steel forms are exposed to the direct rays of the sun, cool the reinforcement and forms to 70 F or less by means of a water spray prior to placing concrete.
When abnormal wind or storms are forecast locally by the National Weather Service, do not place superstructure concrete during the period covered by the forecast.
(g) Pumping. Provide approved equipment that is suitable and adequate in capacity for the work. Arrange the equipment so that no vibrations result that might damage freshly placed concrete. Do not use pumps or discharge lines containing parts made of aluminum.
(h) Use of Conveyors. Concrete may be moved from the mixer to its final position by conveyors. Use conveyors in sections, by which concrete is disposited from one conveyor belt onto the next through a hopper. Limit the maximum rise on any individual section of the conveyor to 30 degrees from the horizontal. For concrete slumps less than 2 in., limit the belt travel speed to 900 ft/minute. Decrease this speed for slumps exceeding 2 in. Conveyers used for placement of decks shall be supported by main load carrying members. Place polyethylene or other acceptable material under the conveyor line to contain any spillage.
420.03.05 Depositing Concrete Under Water. Refer to 402.03.04. Do not deposit concrete in water or expose it to the action of water before setting, unless specified or approved. Use a tremie pipe that is at least 10 in. diameter and equipped with a watertight plug.
Equip the bottom of the pipe with a baffle or deflector plate. The number and location of pipes will be dependent on the size of the pour. Do not disturb the tremie concrete after placement, nor place successive layers on top until the previously placed concrete has developed the necessary strength as determined by the EngineerAny person designated by the Administrator or the procurement officer, acting directly or through his duly authorized representative, such representative acting within the scope of the particular duties assigned to him or of the authority given him.. Do not deposit concrete in water that is less than 35 F. When concrete is deposited in water 36 to 45 F, heat the concrete and place it at a temperature of 60 to 80 F. Do not pump water during concrete placement. Regulate the consistency of the concrete to prevent segregation. Cut down portions of tremie concrete that project more than 6 in. above the top of the as-planned elevation.
(a) Cofferdams. Where cofferdams are used, construct separate forms within the cofferdams except where footing concrete is to be placed against a base of undisturbed material and where the cofferdam is to remain in place and act as the concrete form. In the space between form and cofferdam, keep the water level below the bottom elevation of concrete for at least 12 hours.
(b) Concrete Seals. When feasible, concrete seals for parts of structures under water shall be placed continuously from start to finish to avoid horizontal construction joints. Keep the surface of the concrete as nearly horizontal as practicable at all times to ensure thorough bonding. In these cases, place each succeeding layer of the seal before the preceding layer has taken its initial set. Maintain the slump of tremie concrete between 4 and 8 in. but as close to 4 in. as possible. After dewatering and prior to placing any succeeding layers of concrete, thoroughly clean the top of the foundation seal (tremie concrete).
(c) Concrete Exposed to Saline Water. Do not allow saline water to come in direct contact with the concrete until it conforms to the following table:
CONCRETE IN SALINE WATER
SALINE CONTENT OF WATER BY WEIGHT IN PARTS PER THOUSAND SALINE WATER SHALL NOT CONTACT CONCRETE UNTIL

FOLLOWING MINIMUM TIME IN DAYS HAS ELAPSED AFTER INITIAL SET*

0 to 10 0
10+ to 15 7
15+ to 20 14
20+ to 25 21
Over 25 30
* The EngineerAny person designated by the Administrator or the procurement officer, acting directly or through his duly authorized representative, such representative acting within the scope of the particular duties assigned to him or of the authority given him. may approve a waiver in writing.
Unless otherwise specified, wet cure the concrete for at least seven days while being maintained at 50 F or above.
420.03.06 Consolidation. Except for concrete deposited under water, consolidate concrete by means of internal vibrators. These provisions also apply to precast members or units.
Apply vibration at points uniformly spaced and not further apart than twice the radius over which the vibration is visibly effective.
(a) Internal Vibration. Internal vibrators shall be of an approved type and design. The intensity of application shall visibly affect a mass of concrete of 1 in. slump over a radius of at least 18 in. and have a frequency of vibration of at least 4500 impulses per minute.
(b) External Vibration. External vibrators shall be of an approved type and design. Use external vibration as directed for the following sections: very thin, very heavily reinforced, numerous inserts, or where form surfaces are sharply inclined or battered. For steel grid floors, consolidate filler concrete by applying external vibration to the steel grid.
420.03.07 Finishing Concrete Surfaces. Concrete surfaces shall be finished using one of the following types. However, use an ordinary surface finish as described in (a) below unless otherwise specified.
(a) Ordinary Surface. Immediately following the removal of forms, remove all fins and irregular projections from all surfaces except those that are not to be exposed or not to be waterproofed. On all surfaces, thoroughly clean broken corners or edges and cavities. After having kept them thoroughly moist, point and true them with a mortar of cement and fine aggregate mixed in the proportions used in the grade of the concrete being finished. Remove any excess mortar, and cure the mortar patches as specified in 420.03.09. Carefully tool and clean construction and expansion joints. Ensure that joint filler is exposed for its full length with clean and true edges. Resulting surfaces shall be true and uniform. If the surface cannot be repaired in an acceptable manner, apply a special surface finish as described in (b) below.
(b) Special Surface. Remove fins and projections. Then saturate the surface with water and keep it wet for at least two hours. Thoroughly rub a grout mix of the same proportions as the concrete onto the surface by section using burlap pads or cork floats completely filling all voids, pits, and irregularities. After this grout has dried sufficiently, wipe off the excess using dry, clean burlap. Cure the surface as specified in 420.03.09(f), except use a colorless liquid curing compound. Apply this finish to the exterior faces of cast-in-place superstructures and end posts for bridges over highways, and all interior faces of cast-in-place parapets, bridge median barriers, and end posts. Do not apply this finish to members constructed by the slip form method.
(c) Horizontal Surfaces. Finish all upper horizontal surfaces such as the tops of parapets, copings, and bridge seats by placing an excess of concrete material in the forms and striking off even with a wood template. Apply a steel trowel finish to the tops of handrail (posts and caps), headwalls, parapets, wing walls, and barriers.
Finish the bridge seat bearing areas of the substructure masonry to the elevations specified. Check the elevation of each bearing area prior to finishing to ensure conformance. Ensure that each area is level in all directions, and make adjustments prior to the setting of the concrete. Steel trowel the area. Grind bearing areas that are not flat after final finishing to achieve an acceptable surface.
Bearing areas will be rejected whenever the elevation is below that of the surrounding masonry.
(d) BridgeA structure including supports erected over a depression or an obstruction, such as water, highway, or railway, and having a track or passageway for carrying traffic or other moving loads, and having an opening measured along the center of the roadway of more than 20 feet between undercopings of abutments or spring lines of arches, or extreme ends of openings for multiple boxes; it may also include multiple pipes, where the clear distance between openings is less than half of the smaller contiguous opening. For lengths, all dimensions shall be parallel to the center line of the roadway. The dimensions of handrails will not be taken into account in measuring bridge lengths. Any bridge or highway grade separation structure includes the connecting highways, substructure, superstructure, roadway approaches, entrance plazas, interchanges, overpasses, underpasses, and other structures which the Administration may deem necessary together with all property rights, easements, franchises, and interests acquired by the Administration for the construction and operation of the bridge. Deck Slabs. Use an approved power operated cylinder or roller finishing machine. Set the finishing machine and transverse construction joints parallel to the nearest support lines (abutment or pier). If the skew angle changes at supports, adjust the angle of the screed accordingly as the finishing machine progresses across the deck slab. Place the concrete so that the front edge of the newly placed concrete is as nearly as possible parallel to the skew of the finishing machine. Place the concrete uniformly but not more than 10 ft ahead of the finishing machine, and not more than 6 in. above the top elevation of the finished deck slab.
Do not span the finishing machine greater than the length recommended by the manufacturer. Combine machines or use two machines in which both use a common rail. The proposed method and the location and anchorage of accessories that will remain in the completed superstructures as a result of this requirement are subject to the approval of the EngineerAny person designated by the Administrator or the procurement officer, acting directly or through his duly authorized representative, such representative acting within the scope of the particular duties assigned to him or of the authority given him. and shall meet 420.02.02.
After the concrete has been struck off, check the surface with a long handled 10 ft straightedge operated in a position parallel to the center line of the structure. The straightedge shall be as light weight as possible to avoid distortion of the slab surface, and have a working face no more than 2 in. wide.
Progress longitudinally in overlapping 5 ft increments and transversely in 2 ft increments to locate any irregularities in the surface.
Finish the concrete surface with a full width strip of burlap, mechanically or manually dragged across the surface.
(1) Slab Grooving. Groove all bridge decks including slab bridges and box culverts built to grade. Start the grooving operation after the bridge deck slab has been cured as specified in 420.03.10, and attained a minimum compressive strength as specified in 420.03.15. Groove the bridge deck perpendicular to the center line.
Use a mechanical saw device to cut grooves that are 1/8 in. wide, 3/16 ± 1/16 in. deep, and variably spaced from 5/8 to 7/8 in. apart. Extend the grooves across the slab to within 1 ft of the gutter lines. Do not cut across armored joints or any joint in which an existing joint seal may be damaged; stay clear by 2 ± 1 in. on each side. On joints skewed 70 degrees or less, make one pass parallel to the armored joint unless otherwise directed. Remove the residue resulting from grooving operations from all surfaces in an acceptable manner. Leave all surfaces in a washed, clean condition.
(2) Deck Slab Tolerances. Any slabs found to have deficient thickness may be rejected. Limit surface deviation in a transverse or longitudinal direction to 1/8 in./10 ft from a straight line. For vertical curves, limit deviation (from the curve specified) to 1/8 in./10 ft in a longitudinal direction. Do corrective work prior to grooving.
(e) Sidewalks and Safety Curbs. Use an approved screed to strike off the concrete to the elevation and slope specified. Wood float the concrete to give a gritty surface free from depressions or high spots. Then edge the joints with the appropriate edging tool. Strip curbs and finish as soon as possible.
(f) CulvertAny structure not classified as a bridge which provides an opening under any roadway. Slabs. When the tops of culvert slabs are the roadway riding surface, finish them according to (d) above. If invert slabs and the tops of culvert slabs are not part of the roadway, or when they are to be overlaid with an asphalt mix, screed them by hand or machine and apply a float finish. Maintain the surface within ¼ in. of the grade specified.
Inverts of culverts having a span less than 10 ft need not be straightedged.
420.03.08 Curing. These requirements apply to curing of all concrete surfaces except bridge deck slabs or top surfaces of culverts with integral wearing surfaces, which shall be cured as specified in 420.03.10.
Start curing as soon as the concrete has set sufficiently.
Keep the surfaces wet, even in areas where there is no ready water supply.
(a) Cure culvert invert slabs and all footings for five days using the method specified in 420.03.09(a),(b),(c), or (d).
(b) Cure vertical surfaces in the forms for seven days. However, the forms may be removed after 24 hours for structural elements 6 ft or less in height, or after 48 hours for structural elements greater than 6 ft high, with the provisions specified herein. Cure the surface as specified in 420.03.09(d) for the remainder of the seven day curing period. Do not remove the forms when cold weather protection is required. Forms carrying loads shall remain in place for at least seven days and until the concrete has attained a compressive strength of 3000 psi. Internal bulkheads may be removed after the concrete has been in place for 24 hours, if it is necessary to do so to continue the work without interruption. When a higher strength concrete than specified is used, forms carrying loads shall remain in place for at least three and a half days and until the concrete has attained a compressive strength of 3000 psi.
Fiber column forms may be removed at times specified above, but no later than 10 days after placing concrete.
When parapets or median barriers on structures are formed by the slip form method, begin curing as specified in 420.03.09(f) using a fugitive dye liquid membrane-forming compound immediately after the concrete is finished. Immediately after each joint is saw cut, cure the concrete surfaces for the remainder of the seven days of cure as specified in 420.03.09(d).
(c) Cure tops of end walls, end support walls, headwalls, etc., for three days with burlap or cotton mats as specified in 420.03.09(b) or (d), respectively.
(d) Cure horizontal surfaces for seven days as specified in 420.03.09 (b),(c),(d), or (e).
420.03.09 Curing Methods.
(a) Flooding. Structure units that will be below water in the completed structure may be gradually flooded when approved after the concrete is 12 hours old, provided the curing water meets 921.01. Maintain the water at 35 F or above for the specified curing duration.
(b) Burlap. Use two layers. Overlap successive strips at least 6 in. Place the second layer at least 45 degrees to the first layer, or in lieu of this, the 6 in. overlap of the second layer may be placed midway between the first layer. Thoroughly saturate by immersion in curing water for at least 24 hours prior to placement, and keep it saturated throughout the specified curing duration.
(c) White Opaque Polyethylene Backed Nonwoven Fabric. Use one layer. Overlap successive strips at least 6 in. Thoroughly saturate by immersion in curing water for at least 24 hours prior to placement and keep it saturated throughout the specified curing duration.
(d) Cotton Mats. Use one layer thoroughly saturated with curing water prior to placement and kept saturated throughout the specified curing duration. Keep the material in tight contact with the concrete.
(e) White Opaque Burlap Polyethylene or White Opaque Polyethylene Film. Place white opaque burlap polyethylene sheeting, with the burlap side of the sheeting facing down, on at least one layer of wet burlap. When white opaque polyethylene film is used, place it on at least two layers of wet burlap. Only one layer of cotton mats is required in any usage. These materials may only be used atop the wet burlap or cotton mats on unobstructed flat and reasonably level surfaces.
Lap adjacent mats or sheets at least 1 ft. Bring the ends down around the sides of the concrete being cured and securely fasten to make an airtight seal.
Leave both of these materials in place for the same length of time as required for burlap or cotton mats. These protective coverings need not be wetted down; however, keep the covered burlap or cotton mats wet for the specified duration.
(f) Liquid Membrane. Apply this material according to the manufacturer’s recommendation or as directed. Apply by sprayers and keep it thoroughly agitated before and during use.
420.03.10 BridgeA structure including supports erected over a depression or an obstruction, such as water, highway, or railway, and having a track or passageway for carrying traffic or other moving loads, and having an opening measured along the center of the roadway of more than 20 feet between undercopings of abutments or spring lines of arches, or extreme ends of openings for multiple boxes; it may also include multiple pipes, where the clear distance between openings is less than half of the smaller contiguous opening. For lengths, all dimensions shall be parallel to the center line of the roadway. The dimensions of handrails will not be taken into account in measuring bridge lengths. Any bridge or highway grade separation structure includes the connecting highways, substructure, superstructure, roadway approaches, entrance plazas, interchanges, overpasses, underpasses, and other structures which the Administration may deem necessary together with all property rights, easements, franchises, and interests acquired by the Administration for the construction and operation of the bridge. Deck Slabs. Cure bridge deck slabs and culvert top slabs with integral wearing surfaces, including sidewalks, as specified herein.
Have misting equipment available. Prior to placing concrete, operate the misting equipment for the EngineerAny person designated by the Administrator or the procurement officer, acting directly or through his duly authorized representative, such representative acting within the scope of the particular duties assigned to him or of the authority given him. to verify that the equipment and procedure are capable of misting the entire placement area without damaging the fresh concrete. Do this at the location of proposed use each day that a deck placement is to be made. Keep ample spare parts, water, fuel, etc. readily available. Keep an approved unit available for backup.
Cover the finished concrete with wet burlap as specified in 420.03.09(b). Progress by covering the concrete immediately after the concrete has been finished, but do not leave any portion of the concrete uncovered for more than 45 minutes after placement. Use mist spraying when directed and when the concrete is not covered with wet burlap within 30 minutes after placement. Misting does not relieve the requirement for covering the concrete within the 45 minutes after placement. Once misting is started, continue until wet burlap is complete in place.
After the concrete is covered with wet burlap, cure it as specified in 420.03.09(b) for the remainder of the seven day period. Keep the two layers of burlap continuously and uniformly saturated throughout the curing period. White opaque burlap polyethylene sheeting and white opaque polyethylene film or clear polyethylene film shall not be used over wet burlap except when approved for cold weather protection. Use a sufficient quantity of soaker hoses to meet these requirements. Take immediate action to remedy improper saturation of any area throughout the entire curing period.
Provide a sufficient number of experienced personnel and necessary equipment to ensure proper placement, protection, and curing of the concrete according to these Specifications.
Provide temporary troughs, dams, etc., necessary to keep runoff water from reaching any traveled roadway, shoulder, or sidewalk. Submit the proposed methods of controlling runoff water in these areas. Include locations of all troughs and dams, as well as the proposed methods of attaching them to any portions of the structure. Do not weld or drill holes in any portion of a permanent member of the structure.
The approved procedure will be evaluated after it is underway. If any areas are not functioning in an acceptable manner, modify them to satisfy the requirements for retaining and directing the flow of water.
In rehabilitation construction, where the full use of temporary troughs, dams, etc., is not practical, make approved modifications to the provisions for controlling the runoff water.
420.03.11 Construction Joints. Construction joints are permitted only where specified or authorized in writing.
Clean the surface of the hardened concrete and keep it moist until the additional concrete is placed. Use a grade strip to level the top surface of concrete. At chamfers, steel trowel the top surface of the concrete adjacent to the chamfer.
Where a featheredge might be produced at a construction joint, as in the sloped top surface of a wing wall, use an inset form to produce a blocked in addition to the preceding placement. Ensure that the inset form will produce at least a 6 in. edge thickness of concrete in the succeeding placement.
Place epoxy bonding compound on the surface areas of concrete that existed prior to the beginning of the Contract that will be in contact with new concrete. Apply epoxy bonding compound to the entire face of all deck slab construction joints. Ensure that the surfaces to be coated are clean, sound, and dry. Mix and apply the bonding compound in accordance with the manufacturer’s recommendations.
420.03.12 Linseed Oil Protective Coating. Apply to the integral concrete bridge deck slabs, box culvert wearing surfaces, and sidewalks on bridges and box culverts, when the pertinent Linseed Oil Protective Coating item appears in the Contract DocumentsThe written agreement executed between an Administration and the successful bidder, covering the performance of the work and furnishing of labor, equipment and materials, by which the Contractor is bound to perform the work and furnish the labor, equipment and materials, and by which the Administration is obligated to compensate him therefore at the mutually established and accepted rate or price. The Contract Documents shall include the Invitation for Bids, Notice to Contractors, Instructions to Bidders, Proposal, Contract Forms and Bonds, General Provisions, Specifications, Supplemental Specifications, all Special Provisions, all Technical Provisions, all Plans and Notices to Proceed, also any written Change Orders and Supplemental Agreements that are required to complete the construction of the work in an acceptable manner, including authorized extension thereof.
Prior to the application of the linseed oil protective coating, ensure that the concrete surfaces to be treated are cured, dried, and thoroughly cleaned of all dust, dirt, and deleterious material; and that required permanent paint or tape lane markings have been applied on the structures.
If the concrete is wet, allow it to dry for one to two days at a temperature of at least 60 F. If the concrete surfaces are extremely dry, take the following actions as directed, and at no additional cost to the AdministrationShall mean any one of the Administrations within the Maryland Department of Transportation, as listed in GP 1.02.:
(a) Wet the concrete thoroughly and allow it to dry for one or two days.
(b) Apply a third protective coating at the same rate per gallon as the second coat.
Ensure that the ambient temperature at the time of application is at least 50 F. Ensure that the ambient air temperature following the second application is at least 40 F. Apply two coats on all top surfaces that are not grooved. Apply the first coat at a rate of 40 yd2/gal. Apply the second coat at a rate of 67 yd2/gal. On bridge decks and top slabs of box culverts that are grooved, apply the first coat at a rate of 25 yd2/gal. Apply the second coat at a rate of 45 yd2/gal. Do not apply the second coat until the first coat is dry. If additional coats are required, allow at least 24 hours between them. The drying time may be increased as the ambient temperature falls below 70 F.
420.03.13 Cold Weather Protection. Protect and heat concrete after it has been placed when the air temperature in the shade and away from artificial heat drops to 40 F or lower at the time of placing or at any time within the number of days specified herein. Provide protection and heating as follows:
(a) Protect ordinary concrete and maintain a temperature of at least 50 F for at least seven days following placement.
(b) Do not heat concrete to more than 100 F. At the end of the heating period, cool the concrete surfaces to the temperature of the outside air by slowly reducing the artificial heat at a uniform rate until the temperature of the outside air is reached within a 24 hour period.
Have tarpaulins, insulating devices, and other suitable materials at the site to enclose or protect portions of the concrete requiring protection. Have materials as close as possible before placing the concrete, and install them as rapidly as possible to keep exposure to cold weather to a minimum. Where heating is required, completely enclose the spaces to be heated and use approved heaters to keep the temperature at required levels.
Provide a sufficient number of maximum/minimum thermometers to record temperatures in each concrete placement undergoing cold weather protection.
The curing period for all structure concrete requiring cold weather protection shall meet the cold weather protection period except when the normal curing period is longer.
420.03.14 Underpinning Old Foundations. If underpinning is required, perform the work as directed. Restore or lower the old foundations with Mix No. 6 concrete having a maximum slump of 1-½ in. Perform excavation and underpinning operations in part section, so as not to remove more than 10 percent of the supporting area under the old foundation at one time. When directed, install underpinning by hand, pneumatic, or pumping processes. The usual curing and cold weather requirements will be deleted for the underpinning with other provisions for curing and protection improvised on the job as may be directed.
420.03.15 Loads on Concrete StructuresBridges, culverts, catch basins, drop inlets, retaining walls, cribbing, manholes, end walls, buildings, sewers, service pipes, underdrains, foundation drains, steps, fences, and other features that may be encountered in the work and not otherwise classified.. Refer to GP-5.10, TC-6.13 and .14. Do not erect structural steel or concrete superstructures on concrete substructures until curing is complete, all forms are removed, and substructure concrete has reached a compressive strength of 3000 psi.
Do not apply loads to any new portion of bridge deck or box culvert built to grade until the final section of that unit of the deck has completed its specified curing period. No vehicles, including heavy construction equipment, will be permitted on any new portion of bridge deck or box culvert built to grade until the concrete cylinder breaks for the final section of that unit of the deck has attained a compressive strength of 4500 psi. However, loads such as stored materials, lightweight equipment, concrete safety parapets, sidewalks, and median curbs, may be placed upon the concrete slab via crane or other lifting device when the concrete in the final section of that unit of the deck has attained a compressive strength of 3000 psi.
Do not place backfill on any new portion of box culverts not built to grade until the final section of that unit of the slab has completed its specified curing period and the concrete in that section has attained a compressive strength of 3000 psi.
420.03.16 Prevention and Removal of Stains on Concrete. Prevent rust from structural steel, and staining by asphalt materials or any other substance from discoloring any portion of the concrete. Use construction procedures that prevent staining of any of the concrete. Where unpainted structural steel is specified, protect the pier caps, columns, and abutments with a wrapping of reinforced polyethylene or similar material, and leave it in place to prevent staining until after the structure is completed. If any portion of the concrete is stained, remove the stain and restore the original color without damaging the concrete. Do the work as directed and at no additional cost to the AdministrationShall mean any one of the Administrations within the Maryland Department of Transportation, as listed in GP 1.02.. Do not use chemical solvents without approval.
420.03.17 Safety Hazards. Perform gas detection in and ventilation of confined spaces as specified in TC-3.04.
420.03.18 Defective WorkWork shall be understood to mean the furnishing of all labor, materials, equipment, and other incidentals necessary to the successful completion of the project and the carrying out of all the duties and obligations imposed by the Contract.. Within 24 hours of removing the forms, remove and repair defective work as directed.
(a) At the edges of material remaining in place, make a cut perpendicular to the finished surface to the full depth of the material removed, but not less than 1 in. If the removal of defective concrete affects the structural requirements, remove and replace the member as directed.
(b) Clean defective areas.
(c) Coat defective areas with an epoxy bonding compound.
(d) Patch defective areas with concrete mortar or epoxy matching the color, contour, and texture of surrounding concrete as close as possible.
420.04 MEASUREMENT AND PAYMENT.
Portland cement concrete structures will be measured and paid for as specified. The payment will be full compensation for all forms and form removal, reinforcement steel, curing and misting, scuppers, grooving, 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 all material, labor, equipment (including safety equipment), tools and incidentals necessary to complete the work.
The construction of drainage and weep holes, any pipe necessary, expansion material, flashing, dampproofing, membrane waterproofing, epoxy bonding compound, joints and their placement will not be measured but the cost will be incidental to the concrete item. No deduction in concrete quantities will be made for pipes or conduits having diameters less than 8 in., reinforcement steel, anchors, or any other appurtenances.
420.04.01  Portland cement concrete for Footing Concrete, Subfoundation Concrete, and Tremie Concrete will be measured and paid for at the Contract unit price per cubic yard.
420.04.02  Portland cement concrete for SubstructureAll of that part of the structure below bottoms of bearings of simple and continuous spans, skewbacks of arches and tops of footings of rigid frames, together with the back walls and wing walls. Concrete for BridgeA structure including supports erected over a depression or an obstruction, such as water, highway, or railway, and having a track or passageway for carrying traffic or other moving loads, and having an opening measured along the center of the roadway of more than 20 feet between undercopings of abutments or spring lines of arches, or extreme ends of openings for multiple boxes; it may also include multiple pipes, where the clear distance between openings is less than half of the smaller contiguous opening. For lengths, all dimensions shall be parallel to the center line of the roadway. The dimensions of handrails will not be taken into account in measuring bridge lengths. Any bridge or highway grade separation structure includes the connecting highways, substructure, superstructure, roadway approaches, entrance plazas, interchanges, overpasses, underpasses, and other structures which the Administration may deem necessary together with all property rights, easements, franchises, and interests acquired by the Administration for the construction and operation of the bridge., SuperstructureAll of that part of the structure above bottoms of bearings of simple and continuous spans, skewbacks of arches and tops of footings of rigid frames, except as noted above for substructure. Concrete for BridgeA structure including supports erected over a depression or an obstruction, such as water, highway, or railway, and having a track or passageway for carrying traffic or other moving loads, and having an opening measured along the center of the roadway of more than 20 feet between undercopings of abutments or spring lines of arches, or extreme ends of openings for multiple boxes; it may also include multiple pipes, where the clear distance between openings is less than half of the smaller contiguous opening. For lengths, all dimensions shall be parallel to the center line of the roadway. The dimensions of handrails will not be taken into account in measuring bridge lengths. Any bridge or highway grade separation structure includes the connecting highways, substructure, superstructure, roadway approaches, entrance plazas, interchanges, overpasses, underpasses, and other structures which the Administration may deem necessary together with all property rights, easements, franchises, and interests acquired by the Administration for the construction and operation of the bridge., and Reinforced Concrete Box Culverts will not be measured but will be paid for at the Contract lump sum price. When an Epoxy Coated Reinforcing Steel Bars item for the pertinent structure is included in the Contract DocumentsThe written agreement executed between an Administration and the successful bidder, covering the performance of the work and furnishing of labor, equipment and materials, by which the Contractor is bound to perform the work and furnish the labor, equipment and materials, and by which the Administration is obligated to compensate him therefore at the mutually established and accepted rate or price. The Contract Documents shall include the Invitation for Bids, Notice to Contractors, Instructions to Bidders, Proposal, Contract Forms and Bonds, General Provisions, Specifications, Supplemental Specifications, all Special Provisions, all Technical Provisions, all Plans and Notices to Proceed, also any written Change Orders and Supplemental Agreements that are required to complete the construction of the work in an acceptable manner, including authorized extension thereof, the cost for epoxy protective coated reinforcement steel will be excluded from the Contract lump sum price for SuperstructureAll of that part of the structure above bottoms of bearings of simple and continuous spans, skewbacks of arches and tops of footings of rigid frames, except as noted above for substructure. Concrete for BridgeA structure including supports erected over a depression or an obstruction, such as water, highway, or railway, and having a track or passageway for carrying traffic or other moving loads, and having an opening measured along the center of the roadway of more than 20 feet between undercopings of abutments or spring lines of arches, or extreme ends of openings for multiple boxes; it may also include multiple pipes, where the clear distance between openings is less than half of the smaller contiguous opening. For lengths, all dimensions shall be parallel to the center line of the roadway. The dimensions of handrails will not be taken into account in measuring bridge lengths. Any bridge or highway grade separation structure includes the connecting highways, substructure, superstructure, roadway approaches, entrance plazas, interchanges, overpasses, underpasses, and other structures which the Administration may deem necessary together with all property rights, easements, franchises, and interests acquired by the Administration for the construction and operation of the bridge.. When a bridge deck rehabilitation project, other than bridge widenings, requires modification to the backwalls and wing walls and there is no substructure concrete item, the concrete will be incidental to the SuperstructureAll of that part of the structure above bottoms of bearings of simple and continuous spans, skewbacks of arches and tops of footings of rigid frames, except as noted above for substructure. Concrete item.
420.04.03  Wing walls and footings for reinforced concrete box culverts will not be measured but the cost will be incidental to the Reinforced Concrete Box CulvertAny structure not classified as a bridge which provides an opening under any roadway. item.
420.04.04  Parapets (including end posts) on bridges, wing walls, reinforced concrete box culverts, and retaining walls; or concrete median barriers on bridges and top slabs of reinforced concrete box culverts will not be measured but will be paid for at the Contract lump sum price for the pertinent Concrete Parapet or Concrete MedianThe portion of a divided highway separating the traveled ways for traffic in opposite directions. Barrier items.
420.04.05  Parapet and end post modifications on bridges, wing walls, reinforced concrete box culverts, and retaining walls; or concrete median barriers on bridges and top slabs of reinforced concrete box culverts will not be measured but will be paid for at the Contract lump sum price for the pertinent Parapet Modification item. The payment will also include saw cutting, removal of portions of the existing parapet or end post, drilling, and grouting.
420.04.06 Floodlighting for placement of concrete (including superstructure concrete and concrete overlays) will not be measured but the cost will be incidental to the pertinent Concrete item. The payment will also be full compensation for fuel, backup generator, setup, relocation, and removal.
420.04.07  Linseed oil protective coating will be measured and paid for at the Contract unit price per square yard for the pertinent Linseed Oil Protective Coating item. The payment will be full compensation for all coats including time and cost when a third coat or the application of water is required on dry surfaces.
420.04.08  Cofferdams, temporary supports, or piling will not be measured but the cost will be incidental to the formwork.
420.04.09  Retaining walls will be measured and paid for as specified in 450.04.