13-9000-0001 - DESIGN-BUILD PRECAST REINFORCED CONCRETE STRUCTURE.pdf

ITEM 9000-0001 – DESIGN-BUILD PRECAST REINFORCED CONCRETE

STRUCTURE

1. Description

1.1. Type - This work shall consist of the design, manufacture, storage, delivery and constructing a CON/SPAN® bridge system in accordance with these specifications and in reasonably close conformity with the lines, grades, design and dimensions shown on the plans or as established by the Engineer. In situations where two or more specifications apply to this work, the most stringent requirements shall govern.

1.2. Designation Precast reinforced concrete CON/SPAN® bridge units manufactured in accordance with this specification shall be designated by span and rise. Precast reinforced concrete wingwalls and headwalls manufactured in accordance with this specification shall be designated by length, height, and deflection angle. Precast Reinforced Concrete EXPRESS® foundation units manufactured in accordance with this specification shall be designated by length, height and width.

1.3. Alternates Precast reinforced concrete CON/SPAN® Bridge System as supplied by CONTECH Engineered Solutions is the basis of this design.

Proposed alternates must be of equal or greater span and must provide the documentation listed below at least 20 days prior to bid. Any approved alternate shall be designated via addenda 10 days prior to bid.

Alternates will not be evaluated after the bid.

- Bridge drawings including a plan view showing total bridge length and end treatment wall length and angles, upstream and downstream end elevations showing precast span, clear span, precast rise, clear rise, headwall height and wall thickness dimensions of bridge members and bridge end treatments.

- Product specific foundation design detailing foundation width, thickness, required reinforcement and concrete compressive strength.

- Design calculations for precast concrete elements and foundations sealed by a registered professional engineer in the State of Pennsylvania. The Professional engineer signing the shop drawings and calculations MUST have at least 5 years’ experience designing Soil Interactive structures utilizing PUBLIC domain software.

- Hydraulic analysis demonstrating no increase in headwater elevation, tailwater elevation or velocity. Contact engineer for acceptable hydraulic software list.

2. Design

2.1. Specifications The precast elements are designed in accordance with the "AASHTO LRFD Bridge Design Specifications" 9th Edition, adopted by the American Association of State Highway and Transportation Officials, 2020. A minimum of one foot of cover above the crown of the bridge units is required in the installed condition. (Unless noted otherwise on the shop drawings and designed accordingly.)

3. Materials

3.1. Concrete The concrete for the precast elements shall be air-entrained when installed in areas subject to freeze-thaw conditions, composed of Portland cement, fine and coarse aggregates, admixtures and water.

Air-entrained concrete shall contain 6 ± 2 percent air. The air-entraining admixture shall conform to AASHT0 M154. The minimum concrete compressive strength shall be as shown on the shop drawings.

3.1.1. Portland Cement - Shall conform to the requirements of ASTM Specifications C150-Type I, Type II, or Type lIl cement.

3.1.2. Coarse Aggregate - Shall consist of stone having a maximum size of 1 inch. Aggregate shall meet requirements for ASTM C33.

3.1.3. Water Reducing Admixture - The manufacturer may submit, for approval by the Engineer, a water-reducing admixture for the purpose of increasing workability and reducing the water requirement for the concrete.

3.1.4. Calcium Chloride - The addition to the mix of calcium chloride or admixtures containing calcium chloride will not be permitted.

3.1.5. Mixture The aggregates, cement and water shall be

proportioned and mixed in a batch mixer to produce homogeneous concrete meeting the strength requirements of this specification. The proportion of Portland cement in the mixture shall not be less than 564 pounds (6 sacks) per cubic yard of concrete.

3.2. Steel Reinforcement

3.2.1. The minimum steel yield strength shall be 60,000 psi, unless otherwise noted on the shop drawings.

3.2.2. All reinforcing steel for the precast elements shall be fabricated and placed in accordance with the detailed shop drawings submitted by the manufacturer.

3.2.3. Reinforcement shall consist of welded wire reinforcing conforming to ASTM Specification A 1064, or deformed steel bars conforming to ASTM Specification A 615, Grade 60.

Longitudinal distribution reinforcement may consist of welded wire fabric or deformed billet-steel bars.

3.3. Steel Hardware

3.3.1. Bolts and threaded rods for wingwall connections shall conform to ASTM A 307. Nuts shall conform to AASHTO M292 (ASTM A194) Grade 2H. All bolts, threaded rods and nuts used in wingwall connections shall be mechanically zinc coated in accordance with ASTM B695 Class 50.

3.3.2. Structural Steel for wingwall connection plates and plate washers shall conform to AASHTO M 270 (ASTM A 709) Grade 36 and shall be hot dip galvanized as per AASHTO

M111 (ASTM A123).

3.3.3. Inserts for wingwalls shall be 1" diameter Two-Bolt Preset Wingwall Anchors as manufactured by Dayton Superior Concrete Accessories, Miamisburg, Ohio, (800) 745-3700 and shall be electro zinc coated in accordance with ASTM

B633 SC-1.

3.3.4. Ferrule Loop Inserts shall be F-64 Ferrule Loop Inserts as manufactured by Dayton Superior Concrete Accessories, Miamisburg, Ohio, (800) 745-3700.

3.3.5. Hook Bolts used in attached headwall connections shall be

ASTM A307.

3.3.6. Inserts for detached headwall connections shall be AISI Type 304 stainless steel, Expanded Coil inserts manufactured by Dayton Superior Concrete Accessories, Miamisburg, Ohio,

(800) 745-3700. Coil rods and nuts used in headwall connections shall be AISI Type 304 stainless steel. Washers used in headwall connections shall be either AISI Type 304 stainless steel plate washers or AASHTO M270 (ASTM A709) Grade 36 plate washers hot dip galvanized as per AASHTO

M111 (ASTM A123).

3.3.7. Mechanical splices of reinforcing bars shall be made using the Dowel Bar Splicer System as manufactured by Dayton Superior Concrete Accessories, Miamisburg, Ohio, (800) 745- 3700, and shall consist of the Dowel Bar Splicer (DB-SAE) and Dowel-In (DI) or as manufactured by Barsplice Products Inc, Dayton, Ohio, (937) -275-8700, and shall consist of Barsplice XP Type 2 System.

4. Manufacture of Precast Elements Subject to the provisions of Section 5, below, the precast element dimension and reinforcement details shall be as prescribed in the plan and shop drawings provided by the manufacturer.

4.1. Forms The forms used in manufacture shall be sufficiently rigid and accurate to maintain the required precast element dimensions within the permissible variations given in Section 5 of these specifications. All casting surfaces shall be of a smooth material.

4.2. Placement of Reinforcement

4.2.1. Placement of Reinforcement in Precast Bridge Units - The cover of concrete over the outside circumferential reinforcement shall be 2 inches minimum. The cover of concrete over the inside circumferential reinforcement shall be 1 1/2 inches minimum, unless otherwise noted on the shop drawings. The clear distance of the end circumferential wires shall not be less than one inch nor more than two inches from the ends of each section. Reinforcement shall be assembled utilizing single or multiple layers of welded wire fabric (not to exceed 3 layers), supplemented with a single layer of deformed billet-steel bars, when necessary. Welded wire fabric shall be composed of circumferential and longitudinal wires meeting the spacing requirements of 4.3, below, and shall contain sufficient longitudinal wires extending through the bridge unit to maintain the shape and position of the reinforcement. Longitudinal distribution reinforcement may be welded wire fabric or deformed billet-steel bars and shall meet the spacing requirements of 4.3, below. The ends of the longitudinal distribution reinforcement shall be not more than 3 inches and not less than 1 1/2 inches from the ends of the bridge unit.

4.2.2. Bending of Reinforcement for Precast Bridge Units – The outside and inside circumferential reinforcing steel for the corners of the bridge shall be bent to such an angle that is approximately equal to the configuration of the bridge’s outside corner.

4.2.3. Placement of Reinforcement for Precast Wingwalls and

Headwalls - The cover of concrete over the longitudinal and transverse reinforcement shall be 2 inches minimum. The clear distance from the end of each precast element to the end of reinforcing steel shall not be less than ½ inch nor more than 3 inches. Reinforcement shall be assembled utilizing a single layer of welded wire fabric, or a single layer of deformed billet-steel bars. Welded wire fabric shall be composed of transverse and longitudinal wires meeting the spacing requirements of 4.3, below, and shall contain sufficient longitudinal wires extending through the element to maintain the shape and position of the reinforcement. Longitudinal reinforcement may be welded wire fabric or deformed billet-steel bars and shall meet the spacing requirements of 4.3, below.

4.2.4. Placement of Reinforcement for Precast Foundation Units – The cover of concrete over the bottom reinforcement shall be 3 inches minimum. The cover of concrete for all other reinforcement shall be 2 inches minimum. The clear distance from the end of each precast element to the end of reinforcing steel shall not be less than 2 inches nor more than 3 inches.

Reinforcement shall be assembled utilizing a single layer of welded wire fabric or a single layer of deformed billet-steel bars. Welded wire fabric shall be composed of transverse and longitudinal wires meeting the spacing requirements of 4.3, below, and shall contain sufficient longitudinal wires extending through the element to maintain the shape and position of the reinforcement. Longitudinal reinforcement may be welded wire fabric or deformed billet-steel bars and shall meet the spacing requirements of 4.3, below.

4.3. Laps, Welds, Spacing

4.3.1. Laps, Welds, and Spacing for Precast Bridge Units - Tension splices in the circumferential reinforcement shall be made by lapping. Laps may be tack welded together for assembly purposes. For smooth welded wire fabric, the overlap shall meet the requirements of AASHTO 8.30.2 and 8.32.6. For deformed welded wire fabric, the overlap shall meet the requirements of AASHTO 8.30.1 and 8.32.5. The overlap of welded wire fabric shall be measured between the outer-most longitudinal wires of each fabric sheet. For deformed billet-steel bars, the overlap shall meet the requirements of AASHTO 8.25. For splices other than tension splices, the overlap shall be a minimum of 12" for welded wire fabric or deformed billet-steel bars. The spacing center to center of the circumferential wires in a wire fabric sheet shall be not less than 2 inches nor more than 4 inches. The spacing center to center of the longitudinal wires shall not be more than 8 inches. The spacing center to center of the longitudinal distribution steel for either line of reinforcing in the top slab shall be not more than 1 foot 4 inches.

4.3.2. Laps, Welds, and Spacing for Precast Wingwalls, Headwalls and Foundations - Splices in the reinforcement shall be made by lapping. Laps may be tack welded together for assembly purposes. For smooth welded wire fabric, the overlap shall meet the requirements of AASHTO 8.30.2 and 8.32.6. For deformed welded wire fabric, the overlap shall meet the requirements of AASHTO 8.30.1 and 8.32.5. For deformed billet-steel bars, the overlap shall meet the requirements of AASHTO 8.25. The spacing center-to-center of the wires in a wire fabric sheet shall be not less than 2 inches nor more than 8 inches.

4.4. Curing The precast concrete elements shall be cured for a sufficient length of time so that the concrete will develop the specified compressive strength in 28 days or less. Anyone of the following methods of curing or combinations thereof shall be used:

4.4.1. Steam Curing - The precast elements may be low-pressure steam cured by a system that will maintain a moist atmosphere.

4.4.2. Water Curing - The precast elements may be water cured by any method that will keep the sections moist.

4.4.3. Membrane Curing - A sealing membrane conforming to the requirements of ASTM Specification C309 may be applied and shall be left intact until the required concrete compressive strength is attained. The concrete temperature at the time of application shall be within +/- 10 degrees F of the atmospheric temperature. All surfaces shall be kept moist prior to the application of the compounds and shall be damp when the compound is applied.

4.5. Storage, Handling & Delivery

4.5.1. Storage

Precast concrete bridge elements shall be lifted and stored in “as-cast” position.

Precast concrete headwall and wingwall units are cast, stored and shipped in a flat position.

The precast elements shall be stored in such a manner to prevent cracking or damage. Store elements using timber supports as appropriate. The units shall not be moved until the concrete compressive strength has reached a minimum of 2500 psi, and they shall not be stored in an upright position.

4.5.2. Handling

Handling devices shall be permitted in each precast element for the purpose of handling and setting.

Spreader beams may be required for the lifting of precast concrete bridge elements to preclude damage from bending or torsion forces.

4.5.3. Delivery

Precast concrete elements must not be shipped until the concrete has attained the specified design compressive strength, or as directed by the design Engineer.

Precast concrete elements may be unloaded and placed on the ground at the site until installed. Store elements using timber supports as appropriate.

4.6. Quality Assurance - The Precaster shall demonstrate adherence to the standards set forth in the NPCA Quality Control Manual. The Precaster shall meet either Section 4.6.1 or 4.6.2

4.6.1. Certification: The Precaster shall be certified by the Precast/Prestressed Concrete Institute Plant Certification Program or the National Precast Concrete Association's Plant Certification Program prior to and during production of the products covered by this specification.

4.6.2. Qualifications, Testing and Inspection

4.6.2.1. The Precaster shall have been in the business

of producing precast concrete products like those specified for a minimum of three years. He shall maintain a permanent quality control department or retain an independent testing agency on a continuing basis. The agency shall issue a report, certified by a licensed engineer, detailing the ability of the Precaster to produce quality products consistent with industry standards.

4.6.2.2. The Precaster shall show that the following tests

are performed in accordance with the ASTM standards indicated. Tests shall be performed as indicated in Section 6 of these specifications.

4.6.2.2.1. Air Content: C231 or C173

4.6.2.2.2. Compressive Strength: C31, C39, C497

4.6.2.3. The Precaster shall provide documentation

demonstrating compliance with this section to CONTECH® Engineered Solutions at regular intervals or upon request.

4.6.2.4. The Owner may place an inspector in the plant

when the products covered by this specification are being manufactured.

4.6.3. Documentation - The Precaster shall submit Precast

Production Reports to CONTECH® Engineered Solutions as required.

5. Permissible Variations

5.1. Bridge Units

5.1.1. Internal Dimensions - The internal dimension shall vary not more than 1% from the design dimensions nor more than 1- 1/2 inches whichever is less.

5.1.2. Slab and Wall Thickness - The slab and wall thickness shall not be less than that shown in the design by more than 1/4 inch. A thickness more than that required in the design shall not be cause for rejection.

5.1.3. Length of Opposite Surfaces - Variations in laying lengths of two opposite surfaces of the bridge unit shall not be more than 1/2 inch in any section, except where beveled ends for laying of curves are specified by the purchaser.

5.1.4. Length of Section - The underrun in length of a section shall not be more than 1/2 inch in any bridge unit.

5.1.5. Position of Reinforcement - The maximum variation in position of the reinforcement shall be ± 1/2 inch. In no case shall the cover over the reinforcement be less than 1 1/2 inches for the outside circumferential steel or be less than 1 inch for the inside circumferential steel as measured to the external or internal surface of the bridge. These tolerances or cover requirements do not apply to mating surfaces of the joints.

5.1.6. Area of Reinforcement - The areas of steel reinforcement shall be the design steel areas as shown in the manufacturer's shop drawings. Steel areas greater than those required shall not be cause for rejection. The permissible variation in diameter of any reinforcement shall conform to the tolerances prescribed in the ASTM Specification for that type of reinforcement.

5.2. Wingwalls & Headwalls

5.2.1. Wall Thickness - The wall thickness shall not vary from that shown in the design by more than 1/2 inch.

5.2.2. Length/ Height of Wall sections - The length and height of the wall shall not vary from that shown in the design by more than 1/2 inch.

5.2.3. Position of Reinforcement - The maximum variation in the position of the reinforcement shall be ± 1/2 inch. In no case shall the cover over the reinforcement be less than 1 1/2 inches.

5.2.4. Size of Reinforcement - The permissible variation in diameter of any reinforcing shall conform to the tolerances prescribed in the ASTM Specification for that type of reinforcing. Steel area greater than that required shall not be cause for rejection.

5.3. Foundation Units

5.3.1. Wall Thickness - The wall thickness shall not vary from that shown in the design by more than 1/2 inch.

5.3.2. Length/ Height/Width of Foundation sections - The length, height and width of the foundation units shall not vary from that shown in the design by more than 1/2 inch.

5.3.3. Position of Reinforcement - The maximum variation in the position of the reinforcement shall be ± 1/2 inch. In no case shall the cover over the reinforcement be less than 1 1/2 inches.

5.3.4. Size of Reinforcement - The permissible variation in diameter of any reinforcing shall conform to the tolerances prescribed in the ASTM Specification for that type of reinforcing. Steel area greater than that required shall not be cause for rejection.

6. Testing/ Inspection

6.1. Testing

6.1.1. Type of Test Specimen - Concrete compressive strength shall be determined from compression tests made on cylinders or cores. For cylinder testing, a minimum of 4 cylinders shall be taken for each bridge element. For core testing, a minimum of 2 cores shall be taken for each bridge element. Each element shall be considered separately for the purpose of testing and acceptance.

6.1.2. Compression Testing - Cylinders shall be made and tested as prescribed by the ASTM C 39 Specification. Cylinders shall be cured in the same environment as the bridge elements.

Cores shall be obtained and tested for compressive strength from each element in accordance with the provisions of the ASTM C42 specification.

6.1.3. Acceptability of Cylinder Tests - When the average

compressive strength of all cylinders tested of the same age is equal to or greater than the design compressive strength, and no cylinder tested has a compressive strength less than 90% of required concrete strength, then the element shall be accepted. When the compressive strength of the cylinders tested does not conform to these acceptance criteria, the acceptability of the element may be determined as described in section 6.1.4, below.

6.1.4. Acceptability of Core Tests - The compressive strength of the concrete in a bridge element is acceptable when each core test strength is equal to or greater than the design concrete strength. When the compressive strength of a core tested is less than the design concrete strength, the precast element from which that core was taken may be re-cored. When the compressive strength of the re-core is equal to or greater than the design concrete strength, the compressive strength of the concrete in that bridge element is acceptable.

6.1.4.1. When the compressive strength of any recore is

less than the design concrete strength, the precast element from which that core was taken shall be rejected.

6.1.4.2. Plugging Core Holes - The core holes shall be

plugged and sealed by the manufacturer in a manner that the elements will meet all the test requirements of this specification. Precast elements so sealed shall be considered satisfactory for use.

6.1.4.3. Test Equipment - Every manufacturer furnishing

precast elements under this specification shall furnish all facilities and personnel necessary to carry out the test required.

6.2. Inspection The quality of materials, the process of manufacture, and the finished precast elements shall be subject to inspection by the purchaser.

7. Joints The bridge units shall be produced with flat butt ends. The ends of the bridge units shall be such that when the sections are laid together, they will make a continuous line with a smooth interior free of appreciable irregularities, all compatible with the permissible variations in section 5, above. The joint width between adjacent precast units shall not exceed 3/4 inches.

8. Workmanship/ Finish The bridge units, wingwalls, headwalls and foundation units shall be substantially free of fractures. The ends of the bridge units shall be normal to the walls and centerline of the bridge section, within the limits of the variations given in section 5 above, except where beveled ends are specified. The faces of the wingwalls and headwalls shall be parallel to each other, within the limits of variations given in section 5, above. The surface of the precast elements shall be a smooth steel form or troweled surface. Trapped air pockets causing surface defects shall be considered as part of a smooth, steel form finish.

9. Repairs Precast elements may be repaired, if necessary, because of imperfections in manufacture or handling damage and will be acceptable if, in the opinion of the purchaser, the repairs are sound, properly finished and cured, and the repaired section conforms to the requirements of this specification.

10. Rejection The precast elements shall be subject to rejection on account of any of the specification requirements. Individual precast elements may be rejected because of any of the following:

10.1. Fractures or cracks passing through the wall, except for a single end crack that does not exceed one half the thickness of the wall.

10.2. Defects that indicate proportioning, mixing, and molding not in compliance with section 4 of these specifications.

10.3. Honeycombed or open texture.

10.4. Damaged ends, where such damage would prevent making a

satisfactory joint.

11. Marking Each bridge unit shall be clearly marked by waterproof paint. The following shall be shown on the inside of the vertical leg of the bridge section:

Bridge Span X Bridge Rise Date of Manufacture Name or trademark of the manufacturer

12. Installation Preparation To ensure correct installation of the precast concrete bridge system, care and caution must be exercised in forming the support areas for bridge units, headwall, and wingwall elements. Exercising special care will facilitate the rapid installation of the precast components.

12.1. Footings

Do not over excavate foundations unless directed by site soil engineer to remove unsuitable soil.

The site soils engineer shall certify that the bearing capacity meets or exceeds the footing design requirements, prior to the contractor pouring of the footings. The bridge units and wingwalls shall be installed on either precast or cast-in-place concrete footings. The size and elevation of the footings shall be as designed by the Engineer. A keyway shall be formed in the top surface of the bridge footing as specified on the plans. No keyway is required in the wingwall footings, unless otherwise specified on the plans.

The footings shall be given a smooth float finish and shall reach a compressive strength of 2,000 psi before placement of the bridge and wingwall elements. Backfilling shall not begin until the footing has reached the full design compressive strength.

The footing surface shall be constructed in accordance with grades shown on the plans. When tested with a 10-foot straight edge, the surface shall not vary more than 1/4 inch in 10 feet.

If a precast concrete footing is used, the contractor shall prepare a 4-inch-thick base layer of compacted granular material the full width of the footing prior to placing the precast footing.

The foundations for precast concrete bridge elements and wingwalls must be connected by reinforcement to form one monolithic body.

Expansion joints shall not be used.

The contractor shall be responsible for the construction of the foundations per the plans and specifications.

13. Installation

13.1. General The installation of the precast concrete elements shall be as explained in the publication CON/SPAN Bridge Systems Installation Handbook.

13.1.1. Lifting It is the responsibility of the contractor to ensure that a crane of the correct lifting capacity is available to handle the precast concrete units. This can be accomplished by using the weights given for the precast concrete components and by determining the lifting reach for each crane unit. Site conditions must be checked well in advance of shipping to ensure proper crane location and to avoid any lifting restrictions. The lift anchors or holes provided in each unit are the only means to be used to lift the elements. The precast concrete elements must not be supported or raised by other means than those given in the manuals and drawings without written approval from CONTECH® Engineered Solutions.

13.1.2. Construction equipment weight restrictions: In no case shall equipment operating in excess of the design load (HL93) be permitted over the bridge units unless approved by CONTECH® Engineered Solutions.

13.1.2.1. In the immediate area of the bridge units, the

following restrictions for the use of heavy construction machinery during backfilling operations apply:

• No construction equipment shall cross the bare precast concrete bridge unit.

• After the compacted fill level has reached a minimum of 4 inches over the crown of the bridge, construction equipment with a weight of less than 10 tons may cross the bridge.

• After the compacted fill level has reached a minimum of 1 foot over the crown of the bridge, construction equipment with a weight of less than 30 tons may cross the bridge.

• After the compacted fill level has reached the design cover, or 2 feet minimum, over the crown of the precast concrete bridge, construction equipment within the design load limits for the road may cross the precast concrete bridge.

13.2. Leveling Pad/ Shims The bridge units and wingwalls shall be set on hardboard shims conforming to ASTM D1037 or plastic shims (Dayton Superior P-80, P-81 or approved equal) measuring 5" x 5", minimum, unless shown otherwise on the plans. A minimum gap of 1/2 inch shall be provided between the footing and the bottom of the bridge's vertical legs or the bottom of the wingwall. Also, a supply of 1/4 inch, 1/2 inch & 1/8-inch-thick hardboard or plastic shims for various shimming purposes shall be on site.

13.3. Placement of Bridge Units

The bridge units shall be placed as shown on the Engineer's plan drawings. Special care shall be taken in setting the elements to the true line and grade. The joint width between adjacent precast units shall not exceed 3/4 inches.

13.4. It is the contractor’s responsibility to maintain the structure span during all phases of installation. Due to the arch shape, bridge elements will tend to spread under self-weight. It is imperative that any lateral spreading of the bridge elements be avoided during and after their placement. Generally, horizontal cable ties or tie rods are shipped in the larger bridge elements to assist in preventing this spreading.

Cable ties/tie rods shall not be removed until bridge units are grouted and grout has cured. It is recommended that temporary hardwood blocks be used in conjunction with the cable/tie rods to maintain span.

If, however, due to site restrictions, these cable ties/tie rods must be removed prior to placement of the bridge elements, the contractor must notify CONTECH (manufacturer) and request a suggested installation procedure.

In addition, if the cable ties/tie rods must be removed prior to setting arch units, the following quality control procedure must be followed:

1) Find “measured span” upon arch unit’s delivery to site, prior to lifting from truck and removing cable ties/tie rods. “Measured span” shall be the average of (3) span measurements along the lay length of the arch unit.

2) After setting of bridge unit on the foundation, verify the span. This “installed span measurement” shall not exceed the maximum of

A) The nominal span + ½” OR

B) The “measured span”.

If the “installed span measurement” exceeds this amount, the arch unit shall be lifted and re-set until the “installed span measurement” meets the limits.

13.5. Placement of Wingwalls, Headwalls & Foundation Units

The wing walls, headwalls and foundations shall be placed as shown on the plan drawings. Special care shall be taken in setting the elements to the true line and grade.

13.6. Waterproofing/ Joint protection and Subsurface Drainage

13.6.1. External Protection of Joints - The butt joint made by two adjoining bridge units shall be covered with a 7/8" x 1 3/8" preformed bituminous joint sealant and a minimum of a 9-inch-wide joint wrap. The surface shall be free of dirt before applying the joint material. A primer compatible with the joint wrap to be used shall be applied for a minimum width of nine inches on each side of the joint. The external wrap shall be CS-212 by CONRETE SEALANTS INC., EZ-WRAP RUBBER by PRESS-SEAL GASKET CORPORATION, SEAL WRAP by MAR MAC MANUFACTURING CO. INC. or approved equal.

The joint shall be covered continuously from the bottom of one bridge section leg, across the top of the bridge and to the opposite bridge section leg. Any laps that result in the joint wrap shall be a minimum of six inches long with the overlap running downhill.

13.6.2. In addition to the joints between bridge units, the joint between the end bridge unit and the headwall shall also be sealed as described above. If precast wingwalls are used, the joint between the end bridge unit and the wingwall shall be sealed with a 2'-0" strip of filter fabric. Also, if lift holes are formed in the bridge units, they shall be primed and covered with a 9" x 9" square of joint wrap.

13.6.3. During the backfilling operation, care shall be taken to keep the joint wrap in its proper location over the joint.

13.6.4. Subsoil drainage shall be as directed by the engineer.

13.7. Grouting

13.7.1. Grouting shall not be performed when temperatures

are expected to go below 35° for a period of 72 hours.

Grouting should be completed as soon as practical after precast arches have been installed.

Fill the bridge-foundation keyway with cement grout (Portland cement and water or cement mortar composed of Portland cement, sand and water) with a minimum 28-day compressive strength of 3000 psi. Vibrate as required to ensure that the entire key around the bridge element is completely filled. If bridge elements have been set with temporary ties (cables, bars, etc.) grout must attain a minimum compressive strength of 1500 psi before ties may be removed.

13.7.2. All grout shall have a maximum aggregate size of ¼

inch.

13.7.3. Lifting and erection anchor recesses shall be filled with grout.

13.7.4. After grout has reached its design strength the

temporary hardwood wedges shall be removed and their holes filled with grout.

13.8. Backfill

13.8.1. Do not perform backfilling during wet or freezing

weather.

13.8.2. No backfill shall be placed against any structural

elements until they have been approved by the Engineer.

13.8.3. Backfill shall be considered as all replaced excavation and new embankment adjacent to the precast concrete elements. The project construction and material specifications, which include the specifications for excavation for structures and roadway excavation and embankment construction, shall apply except as modified in this section.

13.8.4. Backfill Zones

• In-situ soil

• Zone A: constructed embankment or overfill.

• Zone B: fill that is directly associated with precast concrete bridge installation.

• Zone C: road structure.

13.8.5. Required Backfill Properties

13.8.5.1. In-situ soil

Natural ground is to be sufficiently stable to allow effective support to the precast concrete bridge units.

As a guide, the existing natural ground should be of similar quality and density to Zone B material for minimum lateral dimension of one bridge span outside of the bridge footing.

13.8.5.2. Zone A

Zone A requires fill material with specifications and compacting procedures equal to that for normal road embankments.

4'-0" min

F ill

H e ig h t

SPAN FILL HEIGHT

ACCEPTABLE MATERIAL

INSIDE ZONE B

≤ 24'-0" ≥ 12'-0" A1, A3

≤ 24'-0" < 12'-0" A1, A2, A3, A4

> 24'-0" all A1, A3

13.8.5.3. Zone B

Generally, soils shall be reasonably free of organic matter, and, near concrete surfaces, free of stones larger than 3 inches in diameter. See charts for detailed descriptions of acceptable soils.

13.8.5.4. Zone C

Zone C is the road section of gravel, asphalt or concrete built in compliance with local engineering practices.

13.8.5.5. Geotechnical engineer shall review gradations of all interfacing materials and, if necessary, recommend geotextile filter fabric (provided by contractor).

13.8.6. Placing and Compacting Backfill

Dumping for backfilling is not allowed any nearer than 3 ft from the bridge leg.

The fill must be placed and compacted in layers not exceeding 8 inches. The maximum difference in the surface levels of the fill on opposite sides of the bridge must not exceed 2 feet.

The fill behind wingwalls must be placed at the same time as that of the bridge fill. It must be placed in progressively placed horizontal layers not exceeding 8 inches per layer.

The backfill of Zone B shall be compacted to a minimum density of 95% of the Standard Proctor, as required by

AASHTO T-99.

Soil within 1 foot of concrete surfaces shall be hand compacted. Elsewhere, use of rollers is acceptable. If

#10 #40 #200 Liquid

Limit

Plasticity

Index

GW, GP, SP A-1a 50 max 30 max 15 max 6 max Largely gravel but can include sand and fines

GM, SW, SP,

SM

A-1b 50 max 25 max 6 max

Gravelly sand or graded sand, may include fines

GM, SM, ML,

SP, GP

A-2 A-2-4 35 max 40 max 10 max

Sands, gravels with low-plasticity silt fines

SC, GC, GM A-2-5 35 max 41 min 10 max Sands, gravels with plastic silt fines

SP, SM, SW A-3 51 min 10 max non-plastic Fine sands

ML, SM, SC A-4 36 min 40 max 10 max Low-compressibility silts

A-1

Acceptable Soils for use in Zone B Backfill

Soil Description

AASHTO

Subgroup

Percent passing US Sieve No.

Typical USCS

Materials

AASHTO

Group

Character of Fraction passing No. 40 Sieve vibrating roller-compactors are used, they shall not be started or stopped within Zone B and the vibration frequency should be at least 30 revolutions per second.

The backfill material and compacting behind wingwalls shall satisfy the criteria for the bridge backfill, Zone B.

Backfill against a waterproofed surface shall be placed carefully to avoid damage to the waterproofing material.

13.8.7. Bridge Units

For fill heights over 12 feet (as measured from top crown of bridge to finished grade), no backfilling may begin until a backfill compaction testing plan has been coordinated with and approved by CONTECH® Engineered Solutions.

13.8.8. Wingwalls

Backfill in front of wingwalls shall be carried to ground lines shown in the plans.

13.8.9. Monitoring

The contractor shall check settlements and horizontal displacement of foundation to ensure that they are within the allowable limit provided by the engineer. These measurements should give an indication of the settlements and deformations along the length of the foundations.

The first measurement should take place after the erection of all precast bridge system elements, a second after completion of backfilling, and a third before opening of the bridge to traffic. Further measurements may be made according to local conditions.

14. MEASUREMENT AND PAYMENT – Lump Sum