534Precast Structural Concrete

534.01 Description The Contractor shall design, manufacture, furnish, and install

precast structural concrete arches, box culverts or three sided frames and associated wingwalls, headwalls, toe walls, cut-off walls and appurtenances, in accordance with the Contract Documents.

534.02 Materials Structural precast elements for the arch, box culvert, or three sided

frame and associated precast elements shall meet the requirements of the following Standard Specification Subsection, except as noted otherwise in this specification: Structural Precast Concrete Units 712.061 New concrete mix designs and mix designs not previously approved by the Fabrication Engineer shall be qualified by trial batches prepared in accordance with AASHTO T 126 (ASTM C192). The test results shall demonstrate that the concrete meets the requirements of the Contract Documents. Bedding and backfill material shall conform to the requirements of Standard Specification 703.19, Granular Borrow, Material for Underwater Backfill, with the additional requirement that the maximum particle size shall be limited to 4 inches, or as shown on the Plans.

534.03 Drawings Prepare shop detail, erection and other necessary Working Drawings

in accordance with Standard Specification Section 105.7, Working Drawings. The Department will review the drawings in accordance with the applicable requirements of Section 105.7, Working Drawings. Changes and revisions to the reviewed Working Drawings shall require further review by the Fabrication Engineer. Working Drawings shall include the following minimum details: 5-158

534.04 Design Requirements The Contractor shall design the precast structural

concrete structure in accordance with the AASHTO LRFD Bridge Design Specifications, latest edition. The HL-93 live load specified in the AASHTO LRFD Bridge Design Specifications shall be used for all limit states, except for Strength I. The live load used for the Strength I limit state shall be the Maine Modified live load, which consists of the standard HL-93 Live Load with a 25 percent increase in the Design Truck only. (Wheel loads based on the Design Truck shall be increased 25 percent). Additionally, if the governing load rating factor based on the HL-93 live load is equal to or less than 1.10 and the span is 14 feet, or greater, then a load rating based on the Maine legal truck (Configuration #6) shall also be checked to insure the rating factor is equal to, or greater than, 1.0. The live load deflection check, per AASHTO LRFD Bridge Design Specifications, for the top slab of box culverts and frames with clear spans of 15 feet, or greater, and cover depths of 4 feet, or less, is mandatory. The live load deflection check shall be documented in the design computations submittal. Design calculations that consist of computer program generated output shall be supplemented with at least one hand calculation and graphics demonstrating the design methodology used. The hand calculation shall document, at a minimum, the Strength I load case flexural design check of the top slab positive moment reinforcing steel. Design calculations shall provide thorough documentation of the sources of equations used and material properties. The design shall be load rated in accordance with the AASHTO Manual for Bridge Evaluation, latest edition, by the LRFR method and in accordance with the Department Load Rating Guide. The Contractor shall submit design calculations and load rating, if applicable, for the precast structure to the Department for review. A Professional Engineer, licensed in accordance with State of Maine laws, shall sign and seal all design calculations and drawings. 5-159 The Contractor shall submit the following items for review by the Department, at least forty-five Working Days prior to production:

534.05 Facilities for Inspection Provide a private office at the fabrication plant for the

Department’s inspection personnel, or Quality Assurance Inspectors (QAI’s), in accordance with Section 535.05, Facilities for Inspection. Failure to comply with the above requirements will be considered denial of access to the Work for the purpose of inspection. The Department will reject all Work done when access for inspection is denied.

534.06 Notice of Beginning Work Refer to Section 712.061.

534.07 Quality Control Quality Control (QC) is the responsibility of the Contractor.

Provide a copy of the Quality System Manual (QSM) to the Fabrication Engineer, if requested. Inspect all aspects of the Work in accordance with the Contractor’s QSM. Reject materials and workmanship that do not meet Contract requirements. Record measurements and test results on the appropriate forms from APPENDIX E of Precast/Prestressed Concrete Institute Manual for Quality Control for Plants and Production of Structural Precast Concrete Products (MNL 116), or an equivalent form prepared by the user. Provide copies of measurements and test results to the QAI as follows: Type of Report When Provided to QAI* Aggregate gradations-fine aggregate and coarse aggregate Prior to beginning work and at least once a week thereafter Material certifications /calibration certifications Prior to beginning work (anticipate adequate time for review by QAI) Pre-placement inspection report Prior to the concrete placement Concrete batch slips The morning of the next work day Results of concrete testing The morning of the next work day Concrete temperature records Provide with compressive strength testing Nonconformance reports/repair procedures Within 24 hours of dis covery Results of compressive strength testing (for design strength) Prior to stopping curing / Prior to final acceptance Post-placement inspection report Prior to final acceptance 5-160 * The Contractor and QAI may, by mutual agreement, modify any part of the schedule; however, failure to provide the documentation when required by the Fabrication Engineer will result in the product being deemed unacceptable. The Contractor may perform testing in addition to the minimum required. The results of all testing shall be made available to the Department.

534.08 Quality Assurance Quality Assurance (QA) is the prerogative of the Department.

Refer to Section 712.061.

534.09 Nonconforming Work Refer to Section 712.061.

534.10 Forms Construct forms in accordance with the Working Drawings. The forms

shall be well constructed, carefully aligned and sufficiently tight to prevent leakage of mortar. Reject forms that do not maintain the dimensions shown on the Working Drawings. Seal wooden forms to prevent absorption of water. Apply and cure the sealer in accordance with the manufacturer's product data sheet. Remove all paint, adherent material, foreign matter and debris prior to placing concrete. Apply a non-staining bond-breaking compound to the forms in accordance with the manufacturer's product data sheet. Solvent clean reinforcing steel and welded steel wire fabric contaminated with the bond-breaking compound.

534.11 Reinforcing Steel and Welded Steel Wire Fabric Refer to Sections 712.061 and

503 for fabrication, packaging, handling, storing, placing, splicing and repair of reinforcing steel, welded steel wire fabric and mechanical/welded reinforcing steel splices. The concrete cover over the outside circumferential reinforcement shall be 2 inches, minimum, and the concrete cover over the inside reinforcement shall be 1-½ inches, minimum. The clear distance of the end of circumferential wires shall not be less than 1 inch or more than 2 inches from the end of the units. Use sufficient supports and spacers to maintain the minimum concrete cover. The supports and spacers shall be made of a dielectric material or other material approved by the Fabrication Engineer. Welded steel wire fabric shall meet the spacing requirements and contain sufficient longitudinal wires extending through the unit to maintain the shape and position of the reinforcement. Longitudinal distribution reinforcement may be welded steel wire fabric or deformed steel bars which meet the spacing requirements. The ends of the longitudinal distribution reinforcement shall not be more than 3 inches from the ends of the units. Do not use more than three layers of reinforcing to form a single mat. If reinforcing steel is cut to install lifting devices, install additional reinforcing adjacent to the cut steel, as shown on the Working Drawings. 5-161 Tension splices in the reinforcement will not be permitted. For splices other than tension splices, the overlap shall be a minimum of 12 inches for welded steel wire fabric and as specified in Standard Specification Section 503 for deformed steel bars. The center-to- center wire spacing in wire fabric sheets shall not be less than 2 inches, or more than 4 inches, for the circumferential wires, and shall not be more than eight inches for the longitudinal wires. The center-to-center spacing of the longitudinal distribution steel for either line of reinforcing in the top slab shall not be more than 15 inches.

534.12 Inserts Refer to Section 712.061.

534.13 Concrete Placement Do not batch or place concrete until all the form(s) for any

continuous placement have been inspected and accepted by the Quality Control Inspector (QCI), and the QAI concurs. Test concrete in accordance with the Standards included in Section 712.061. Test the first two loads of concrete for temperature, air entrainment and slump flow for Self-Consolidating Concrete (SCC). If the first load is unacceptable, test the second load as the first. Continue this process until two consecutive loads are acceptable. After two consecutive loads are acceptable, the frequency of testing shall be at the discretion of the QAI. If there is a change in the dosage rate of any admixture or a change of more than 5 F in mix temperature, then test the concrete for temperature, air entrainment and slump flow for SCC. Test every load of 1 cubic yard, or less, from a stationary mixer or 2 cubic yards, or less, from a transit mixer for temperature, air entrainment and slump flow for SCC, prior to placing the concrete in the forms. Perform all testing in the presence of the QAI. The QAI will designate the loads to be tested. Make cylinders used to determine stripping strength during the last 1/3 of the placement. Place the concrete as nearly as possible to its final location. Control the depth of each lift in order to minimize entrapped air voids. The maximum depth of an unconsolidated lift shall be 18 inches. Vibrate the concrete with internal or internal and external vibrators. Do not use external vibrators, only. Insert internal vibrators vertically and penetrate the lower layer of concrete by at least 4 inches. Insert the vibrators in the concrete to assure that the radii of action of the vibrators overlap. Hold the vibrators in position from 5 to 15 seconds; vibration time shall be reduced by 50 percent when placing SCC. Do not use vibrators to move concrete horizontally. Each lift of concrete shall have sufficient plasticity to be consolidated with subsequent lifts. Do not re-temper the concrete with water after discharging has begun. The Contractor may add High Range, Water Reducing, admixture to the concrete after batching if that 5-162 practice conforms to the manufacturer's product data sheet. Discard concrete that becomes unworkable. Do not use water or water-based products to aid in finishing fresh concrete. After the concrete has been placed and finished and before the forms are covered, remove all concrete from projecting reinforcing steel.

534.14 Acceptance and Quality Control Testing of Concrete Refer to Section 712.061.

534.15 Manufacture of Precast Units The units shall be free of fractures. The ends of the

units shall be normal to the walls and centerline of the unit, within the limits of variation provided, except where beveled ends are specified. The surfaces of the units shall be a smooth steel form or troweled surface finish, unless a form liner is specified. The ends and interior of the assembled structure shall make a continuous line of units with a smooth interior surface. Defects which may cause rejection of precast units include, but are not limited to, the following:

534.16 Tolerances Dimensional tolerances shall be in conforma nce with the

following:

534.17 Finishing Concrete Products shall be finished to meet the ordinary finish

requirements of Standard Specification Section 502. Units, or portions of units, that will be exposed to view in their final location shall receive a rubbed finish, per Section 502. The Contractor may use alternative methods of achieving an acceptable finish on exposed units if approved by the Fabrication Engineer. Marking: The date of manufact ure, the production lot number, and the type of unit shall be clearly and indelibly scribed on a rear, unexposed portion of each unit.

534.18 Repairing Defects Defects requiring repair will be considered either non-

structural or structural. Non-Structural Defects: Exposed surfaces shall be of uniform appearance; only minor repairs to remove and blend fins, patch minor spalls and to repair small, entrapped air pockets, shall be permitted. Repair honeycombing, ragged or irregular edges and other non- structural or cosmetic defects using a patching material from the Department Qualified Products List (QPL). The repair, including preparation of the repair area, mixing and application and curing of the patching material, shall be in accordance with the manufacturer's product data sheet. Corners not exposed in the final product may be ground smooth with no further repair necessary, if the depth of the defect does not exceed one-half inch. Remove form ties and other hardware to a depth of not less than one inch from the face of the concrete and patch the holes using a patching material from the Department QPL. Structural Defects: Repair structural defects only with the approval of the Fabrication Engineer. Submit a nonconformance report (NCR) to the Fabrication Engineer with a proposed repair procedure. Do not perform structural repairs without an NCR that has been reviewed by the Fabrication Engineer. Structural defects include, but are not be limited to, exposed reinforcing steel, cracks in bearing areas, through cracks and cracks 0.013 inch in width that extend more than 12 inches in length in any direction. Give the QAI adequate notice prior to beginning any structural repairs.

534.19 Handling, Storage and Transportation Handle, store and transport units in a

manner as to eliminate the danger of chipping, cracks, fracture, and excessive bending stresses. Any units found damaged upon delivery, or damaged after delivery, shall be subject to rejection. 5-164 Do not place precast units in an upright position until a compressive strength of at least 4,000 psi is attained. Precast units may be handled and moved, but not transported, until the 28 day design strength has been attained. Support stored precast units above the ground on dunnage in a manner to prevent twisting or distortion. Protect the units from discoloration and damage. Set precast units on one-half inch thick neoprene pads during shipment to prevent damage to the unit legs. The Contractor shall repair any damage to precast units resulting from shipping or handling; this shall be accomplished by saw cutting a minimum of one-half inch deep around the perimeter of the damaged area, removing any loose concrete out to the saw cut perimeter and installing a polymer-modified cementitious patching material, from the Department’s QPL, per the manufacturer’s product data sheet.

534.20 Installation of Precast Units When footings are required, install the precast units

on concrete footings that have reached a minimum compressive strength of 3,000 psi. Construct the completed footing surface to the lines and grades shown on the Plans. When checked with a 10 foot straightedge, the surface shall not vary more than one-quarter inch in 10 feet. The footing keyway shall be filled with a Department-approved non-shrink flowable cementitious grout with a minimum design compressive strength of 5,000 psi at 28 days, unless otherwise specified in the Contract. Three sided frame and box culvert joints shall be sealed with a Department-approved flexible joint sealant in accordance with ASTM C990. Joints shall be closed tight. Culvert units shall be equipped with joint closure mechanisms to draw units together and close joints to the required opening. Completely fill the exterior face of joints between precast units with a material from the Department QPL and cover with a minimum 12 inch wide joint wrap. Additionally, for box culverts and three sided frames, cover the entire top surface with waterproofing membrane; waterproofing membrane shall extend one foot from the top down the sides of the units. The surfaces shall be free of dirt and deleterious materials before applying the filler material and joint wrap. Install the external wrap in one continuous piece over each unit joint, taking care to keep the joint wrap in place during backfilling. Seal the back of joints between the end unit and attached elements with a non-woven geotextile. Install and tighten the bolts fastening the connection plate(s) between the elements that are designed to be fastened together as designated by the manufacturer. Fill holes that were cast in the units for handling with either Portland cement mortar or with precast plugs secured with Portland cement mortar or other approved adhesive. Place and compact the bedding material as shown on the Plans prior to lifting and setting the culvert units. Backfilling of the structure shall be done in accordance with the manufacturer’s instructions and the Contract Documents. Uniformly distribute backfill material in layers of not more than 8 inches in depth, loose measure, and thoroughly 5-165 compact each layer using approved compactors before successive layers are placed. Compact the Granular Borrow bedding and backfill in accordance with Section 203.12, Construction of Earth Embankment with Moisture and Density Control, except that the minimum required compaction shall be 92 percent of maximum density, as determined by AASHTO T-180, Method C or D. Place and compact the backfill without disturbance or displacement of the structure, keeping the fill at approximately the same elevation on both sides of the structure. Whenever a compaction test fails, the Contractor shall not place additional backfill over the area until the lift is re-compacted and a passing test achieved. Use hand-operated compactors within five feet of the precast structure as well as over the top until it is covered with at least 12 inches of backfill. Take appropriate precautions to protect the top of the culvert from damage during backfilling and/or paving operations. Any damage to the top of the precast structure shall be repaired, or units replaced, at no cost to the Department.

534.21 Method of Measurement Precast Structural Concrete Arches, including three-

sided frames, and Precast Concrete Box Culverts will be measured as one lump sum, complete, in place and accepted.

534.22 Basis of Payment The accepted Precast Structural Concrete Arches, including

three-sided frames, or Precast Concrete Box Culverts will be paid for at the respective Contract lump sum price. The lump sum price shall include associated wingwalls, headwalls, toe walls, cut-off walls and appurtenances, and shall be full compensation for all labor, equipment, materials, professional services, and incidentals necessary for designing, manufacturing, furnishing and installing the precast concrete elements and accessories. Falsework, reinforcing steel, welded steel wire fabric, joint wrap, geotextile, repair material, grout, cast-in-place concrete fill or grout fill for anchorage of precast wings and/or other appurtenances will not be measured and paid for separately, but will be incidental to the lump sum pay item. Cast-in-place concrete, reinforcing steel in cast-in-place elements and waterproofing membrane will be measured and paid for separately, under the provided Contract Pay Items. Pay adjustments for quality level will not be made for precast concrete. Excavation for precast structural concrete structures, including excavation below culverts for bedding and backfilling, will be measured and paid for as provide in Section 206, Structural Excavation. When the minimum cover material extends above the subgrade line, the removal of the cover material necessary to complete the work will not be paid for directly, but shall be considered incidental to the precast structural concrete lump sum pay item. Payment will be made under: P a y I t e m P a y U n i t

534.70 Precast Structural Concrete Arch L u m p S u m

534.71 Precast Concrete Box Culvert Lump Sum

5-166