Construction of a Precast Prestressed Concrete Pavement Demonstration Project on Interstate 57 Near Sikeston, Missouri
Appendix A: Project Plans and Job Special Provision
instrumentation repaired or replaced as determined by the Engineer. All costs of repairs shall be reimbursed by the contractor. The contractor and the fabricator shall permit the University of Missouri Columbia research team access to the precast panels throughout fabrication and construction.
2.0 The contractor shall notify Dr. Vellore Gopalaratnam at the University of Missouri Columbia at the below address at least four weeks prior to the commencement of panel fabrication. The contractor shall also notify Dr. Gopalaratnam of the shipping and erection schedule of the panels.
Dr. Vellore Gopalaratnam
Department of Civil and Environmental Engineering
E2509 Engineering Building East
Columbia, MO 65211-2200
Phone: (573) 882-2683
Fax: (573) 882-4734
3.0 No direct payment will be made for any expense incurred by the contractor for compliance with any of the specific requirements of this provision, including any delays, inconvenience or extra work, except for those items of work included for payment in the contract.
M. INSTRUMENTATION PLAN
1.0 Plan sheets detailing instrumentation layout and a letter documenting the research team's concerns are attached.
2.0 All cost incurred by the contractor for placement of the 3′x4′ precast box shall be completely covered under item 902-99.02 placement of precast box.
3.0 The costs for all labor, equipment and materials for the installation of the 4″ conduit and 6″ conduit shall be completely covered under item numbers 902-54.00 conduit, 4", trench and 902-99.03 conduit, 6″, trench, respectively.
N. POWER SUPPLY FOR INSTRUMENTATION
1.0 All work necessary for completion of the power supply to the instrumentation, as shown on the plans, shall be completed by June 15, 2005.
2.0 All cost for compliance with this provision shall be considered fully compensated for under the pay items in the contract.
O. PRECAST PRESTRESSED CONCRETE PAVEMENT
1.0 Description. This provision shall cover the fabrication, installation, post-tensioning, and grouting of precast prestressed concrete panels for pavement reconstruction. Herein, the term "panel" shall refer to individual precast concrete panels, including base panels, joint panels, and anchor panels. The term "slab" shall refer to a post-tensioned section of precast panels between expansion joints.
2.0 Materials. Materials shall conform to the requirements of the following Missouri Standard Specifications, except where noted in these Special Provisions.
- Section 205, "Modified Subgrade"
- Section 302, "Stabilized Permeable Base"
- Section 501, "Concrete"
- Section 502, "Portland Cement Concrete Base and Pavement"
- Section 706, "Reinforcing Steel for Concrete Structures"
- Section 717, "Neoprene and Silicone Joint Systems"
- Section 1029, "Fabricating Prestressed Concrete Members for Bridges"
- Section 1036, "Reinforcing Steel for Concrete"
- Section 1039, "Epoxy Resin Material"
- Section 1055, "Concrete Curing Material"
- Section 1057, "Material for Joints"
- Section 1058, "Polyethylene Sheeting"
- Section 1073, "Joint Material for Structures"
3.0 Precast Panel Fabrication.
3.1 Tolerances for precast panels, regardless of type shall be as shown below in Table 1.
|Length (parallel to long axis of panel)||+/- 1/4″|
|Width (normal to long axis of panel)||+/- 1/8″|
|Nominal Thickness||+/- 1/8″|
|Squareness (difference in measurement from corner to corner across top surface, measured diagonally)||+/- 1/8″|
|Horizontal Alignment (upon release of stress)-Deviation from straightness of mating edge of panels||+/- 1/8″|
|Vertical Alignment-Camber (upon release of stress)||+/- 1/8″|
|Deviation of ends (horizontal skew)||+/- 1/8″|
|Deviation of ends (vertical batter)||+/- 1/8″|
|Keyway Dimensional Tolerance||+/- 1/16"|
|Position of Strands||+/- 1/8″ Vertical1
+/- 1/4″ Horizontal
|Position of post-tensioning ducts at mating edges||+/- 1/8″ Vertical1
+/- 1/8″ Horizontal
|Straightness of post-tensioning ducts||+/- 1/4″ Vertical1
+/- 1/4″ Horizontal
|Vertical Dowel Alignment (parallel to bottom of panel)||+/- 1/8″1|
|Horizontal Dowel Alignment (normal to expansion joint)||+/- 1/8″|
|Dowel Location (deviation from shop drawings)||+/- 1/4″ Vertical1
+/- 1/4″ Horizontal
|Dowel Embedment (in either side of expansion joint)||+/- 1″|
|Position of drainage and electrical conduit||+/- 1/2″|
|Straightness of drainage and electrical conduit||+/- 1/2″ Vertical1
+/- 1/2″ Horizontal
|Position of lifting anchors||+/- 3″|
|Position of non-prestressed reinforcement||+/- 1/4″|
|Straightness of expansion joints||+/- 1/8″|
|Initial width of expansion joints||+/- 1/8″|
|Dimensions of blockouts/pockets||+/- 1/8″|
1 Measured from bottom of panel
3.2 Concrete Mix. The concrete mix used will meet the strength requirements set forth in the plans. If minimum strength is not specified in the plans, the mix will be required to reach a compressive strength of 3,500 psi at release of prestress and 5,000 psi at 28 days. The mix will be workable enough to achieve the required surface finish as described below. The installation Contractor must approve the coarse aggregate to be used by the precast fabricator.
3.3 Non-Prestressed Reinforcement. Non-prestressed reinforcement shall be epoxy-coated and shall conform to the requirements of Section 1036.5.
3.4 Pretensioning. Pretensioning materials and procedures shall conform to Section 1029, "Fabricating Prestressed Concrete Members for Bridges." Unless otherwise shown in the plans, all pretensioning material shall be Grade 270, 7-wire low-relaxation strand, as given in Section 1029.6.8.
3.5 Post-tensioning Materials. Post-tensioning ducts shall be rigid galvanized corrugated metal or rigid corrugated polypropylene. The ducts shall have an inside diameter a minimum of 3/8-inch larger than the nominal diameter of the post-tensioning strand.
Grout ports shall be located in the joint panels (Type A) and base panels (Type B), as shown on the panel detail sheets. The grout ports shall have a minimum 1/2-inch inside diameter and shall be compatible with the post-tensioning ducts, providing a watertight seal between the duct and port. Grout ports shall not protrude form the finished surface of the panels, and shall be located at the extreme ends of each tendon, and not more than 50 feet apart between the ends, unless otherwise approved.
3.6 Lifting Anchors. Lifting anchors shall be approved by the Engineer prior to use. Lifting anchors shall be located as shown on the panel detail sheets. The top of the lifting anchors shall be recessed 1/2-inch minimum from the surface of the panel.
3.7 Dowels and Expansion Joints. Shop drawings for the expansion joint detail shall be submitted for approval prior to fabrication of the Joint Panels. The expansion joint shall be able to withstand the expansion and compression and traffic loading requirements specified in the plans. Dowels for the expansion joints will conform to the requirements of Section 1057.3, with the exception that the dowel bars may either be stainless steel clad or epoxy coated. The entire length of the dowel shall be coated with graphite grease or other approved bond breaker, in accordance with Section 1057.3.
Dowels shall remain parallel to the bottom surface of the panel and normal to the expansion joint during casting. Dowel baskets shall not be used to support the dowels in the forms. Unless otherwise shown on the plans, the minimum length of dowel embedment on either side of the expansion joint (in the Joint Panel) shall be one-half the length of the dowel minus the specified initial width of the expansion joint.
Dowel expansion caps specified in the plans shall be approved prior to use. A minimum of 1.5 inches of free movement of the dowel end (within the expansion cap) shall be provided.
3.8 Finishing. Unless otherwise shown in the plans, the top surface of the panels (driving surface) shall receive a carpet drag texture finish, which meets the requirements of Section 502.48. The texture shall be applied in a timely manner after final screening such that the desired texture depth is achieved without disturbing the underlying concrete or turning over aggregate. The surface texture may be applied either parallel or normal to the long axis of the panel, at the discretion of the Engineer.
3.9 Placement in forms. Concrete formwork and placement procedures shall conform to the requirements of Section 1029.62. Concrete shall be placed in a single lift and distributed in such a manner that embedded items such as reinforcement, ducts, dowels, anchors, and lifting devices are not dislodged by the concrete mass. Proper consolidation must be achieved such that honeycombing or segregation of the concrete does not occur and all spaces around embedded items and around the panel forms are filled.
3.10 Curing. Curing of the precast panels shall conform to the requirements of Section 1029.6.11. The Contractor shall submit the proposed curing methods and procedures for approval prior to placing concrete. Curing shall immediately after the surface finishing operation and as soon as marring of the concrete will not occur.
Membrane curing, in accordance with Section 502.6.1, shall be permitted at the discretion of the Engineer. A minimum two applications of the curing membrane, applied immediately after surface texture finishing, shall be required for membrane curing. Membrane curing residue shall be removed from all adjoining surfaces prior to shipment of the panels to the jobsite.
Curing shall be maintained for a minimum of 72 hours from the beginning of curing operations on the sides and top surface of the panels. While in the forms, the forms will be considered to provide adequate curing for the edges (vertical faces) of the panels. If any part of the form is removed, the exposed surface shall receive curing such as that described above. Removal of panels from the forms to a storage area shall be done in such a manner that curing is not interrupted for more than four hours for any member.
3.11 Form Removal and Storage. Panels shall be removed form the forms in such a manner that no damage occurs to the panel. Form removal shall conform to the requirements of Section 1029.6.12. Any materials forming blockouts in the panels shall be removed such that damage does not occur to the panel or the blockout.
Panels shall be stored in such a manner that adequate support is provided to prevent cracking or creep-induced deformation (sagging). Supports beneath the panels shall be located at approximately the same location as the lifting anchors. Panels shall be stacked no higher than five panels per stack, with adequate support between panels. Panels shall be stacked such that individual panels or stacks of panels are not touching one another. Panels stored for long periods of time (longer than one month) shall be checked at least once per month to ensure creep-induced deformation does not occur.
3.12 Unobstructed Ducts and Conduit. After removal from the forms and prior to shipment, the precast fabricator shall check for obstructions in all post-tensioning ducts. The post-tensioning ducts shall be checked by feeding a post-tensioning strand of the same size as that specified for actual post-tensioning completely through each duct. If the strand does not slide freely through the duct, the cause of the obstruction shall be remedied, at the expense of the Contractor, before the panel is shipped.
3.13 Lifting and Handling. Panels shall be handled in such a manner as not to damage the panel during lifting or moving. Lifting anchors cast into the panels shall be sued for lifting and moving the panels at the fabrication plant. The angle between the top surface of the panel and the lifting line shall not be less than sixty degrees (60°), when measured from the top surface of the panel to the lifting line.
Provision shall be made to secure the two halves of each Joint Panel together such that the expansion joint remains closed or at a uniform specified width during handling and transportation. A plan for securing the two halves of the Joint Panel together shall be submitted for approval prior to fabrication of the Joint Panels. The fastening technique shall prevent the expansion joint from opening or closing during lifting and handling and shall not rely upon the dowel bars to resist hinging at the expansion joint. Damage caused to any Joint Panel, including bending of dowel bars, as a result of inadequate bracing shall be repaired at the expense of the Contractor to the satisfaction of the Engineer.
3.14 Transportation. Panels shall be transported in such a manner that the panel will not be damaged during transportation. Panels shall be properly supported during transportation such that cracking or deformation (sagging) does not occur. If more than one panel is transported, proper support and separation must be provided between the individual panels. Panels shall be lying horizontally during transportation, unless otherwise approved.
3.15 Repairs. Repairs of damage caused to the panels during fabrication, lifting and handling, or transportation shall be addressed on a case-by-case basis. Damage within acceptable limits caused to the top surface (driving surface) or to keyed edges of the panels shall be repaired using an approved repair method at the fabrication plant at the expense of the Contractor. Repetitive damage to panels shall be cause for stoppage of fabrication operations until the cause of the damage can be remedied.
3.16 Demonstration of Panel Fit. The precast fabricator shall initially fabricate only three panels and assemble these panels at the fabrication plant to demonstrate the fit of the panels. The panels shall be assembled over a level surface that will not cause damage to the panels during or after assembly. Post-tensioning shall not be required for this trial assembly, and epoxy shall not be required in the joints between panels. Joints between panels should not be more than 1/4-inch wide when assembled. Any problems with fitting the panels caused by imperfections in the panels shall be corrected prior to proceeding with panel fabrication. Panel fabrication may commence following the trial assembly only upon approval.
3.17 Instrumentation. The precast fabricator shall permit the installation of instrumentation in the panel forms prior to placement of concrete. Instrumentation shall be permitted in no fewer than eight (8) precast panels. A schematic layout and instrumentation plan shall be provided to the fabricator and the Engineer for approval prior to beginning panel fabrication. The precast fabricator shall provide at least 7 days advanced notice to the instrumentation installer before casting the instrumented panels. Instrumentation shall include, but is not limited to, temperature sensors, strain gages, and load cells. Instrumentation shall not compromise the integrity of the reinforcing steel, prestressing system, or the precast panel itself. The precast fabricator shall protect the integrity of the instrumentation, including lead wires and connectors at the surface and edges of the precast panels, during fabrication and handling of the instrumented panels.
4.0 Base Preparation. The precast panels shall be placed over a prepared surface as shown on the plans. The surface shall be free from debris and other materials that prevent the panels from fully resting on the base.
4.1 Materials. The base material will be either the existing base material or a new stabilized or asphaltic or cementitious material as shown on the plans. The material will have the drainage characteristics required by the Department.
4.2 Grade Control for Placement. Grade control will be established for placement of the base material to ensure long-wavelength roughness is not built into the base. Grade control will be established using stringlines, laser guidance, or other comparable methods. Grade control methods must be approved prior to base preparation.
4.3 Surface Test. The finished surface of the base material shall be flat and smooth so as to provide full support beneath the panels. The smoothness of the surface of the base material shall be checked by the contractor in accordance with Section 502.8.1, "Straight edging." A 20-ft straightedge shall be used in lieu of a 10-ft straightedge, and the variation of the surface shall be such that a 6-inch diameter circular plate, 1/8 inch thick cannot be passed beneath the straightedge. Any areas of the base surface not conforming to this smoothness requirement shall be corrected at the Contractor's expense in accordance with Section 502.8.1.
5.0 Panel Installation on Site.
5.1 Equipment. The Contractor shall have all equipment required for panel installation, post-tensioning, and grouting on-site prior to beginning panel installation. Lifting and transporting equipment shall not damage the prepared base material prior to or during panel installation. Any damage to the prepared base material will be repaired at the Contractor's expense to the satisfaction of the Engineer.
5.2 Polyethylene Sheeting. A single layer of polyethylene sheeting will be placed over the prepared base material, beneath the precast panels, as shown on the plans. Polyethylene sheeting shall conform to the requirements of Section 1058.3, except that the minimum nominal thickness of the sheeting shall be 6.0 mills unless otherwise specified. Provision shall be made to prevent folds and creases in the sheeting beneath the panels. The surface of the prepared base shall be free from loose debris, which may puncture the polyethylene sheeting prior to placement of the polyethylene sheeting. Any tears or punctures in the polyethylene sheeting shall be repaired to the satisfaction of the Engineer prior to placement of the precast panels over the sheeting. Provision shall be made to prevent the polyethylene sheeting from becoming pinched in the joints between individual precast panels during panel installation.
5.3 Temporary Post-Tensioning. Panels shall be temporarily post-tensioned together during placement to ensure closure of transverse joints prior to final post-tensioning. Unless otherwise specified, temporary post-tensioning shall be completed after placement of no more than two adjacent panels. The anchor access pockets in the joint panels shall be used to feed the temporary post-tensioning strands into the longitudinal (parallel to roadway centerline) ducts. Temporary post-tensioning tendons shall be spaced no more than 20 feet apart and no more than 10 feet from the edge of the panels, as measured across the width of the pavement. Strand use for temporary post-tensioning shall be either 1/2-inch or 0.6-inch nominal diameter, with corresponding temporary anchorage. Any damage to the precast panels during temporary post-tensioning shall be repaired at the Contractor's expense to the satisfaction of the Engineer prior to installation of additional panels. No more than two panels may be placed in sequence between temporary post-tensioning operations.
5.4 Joint Treatment. Unless otherwise shown in the plans, epoxy shall be applied to the adjoining surfaces of the precast panels prior to assembly. The epoxy material shall be suitable for bonding hardened concrete to hardened concrete and shall be approved prior to use. Epoxy shall be proportioned and applied according to the manufacturer's recommendations.
Epoxy shall be applied to both faces of adjoining panels, and shall be kept a minimum of 1/2 inch away from duct openings. The set time of the epoxy shall be such that final post-tensioning is completed before the epoxy hardens. Excess epoxy squeezed out of the joint onto the driving surface of the precast pavement during assembly and/or post-tensioning shall be removed before it hardens.
A compressible foam or neoprene gasket shall be placed around the opening of each post-tensioning duct as shown in the panel details. The seal shall be continuous around each duct opening and shall be compressible such that it will not protrude from the gasket recess shown in the panel details when compressed. The seal shall not cover any part of the opening to the duct and shall not inhibit the flow of grout. Provision shall be made to prevent damage to the gaskets during panel installation.
5.5 Placement Technique. Panels shall be installed one at a time, and shall be installed in such a manner that neither the base material nor the polyethylene sheeting is damaged during installation. The angle between the top surface of the panel and the lifting line attached to each lifting anchor shall not be less than 60 degrees (60°), when measured from the horizontal surface of the panel to the lifting line.
Panels shall be aligned in the longitudinal direction (parallel to the roadway centerline) using the centerline of the panels. The centerline of each panel shall be marked on the top surface of the panel-at the adjoining edges. The location of the centerline on each panel shall be determined from the location of the post-tensioning duct openings at the adjoining edges of the panels.
Panels may be pulled together during placement using approved temporary devices. Any damage to the panels caused by temporary devices shall be repaired at the Contractor's expense to the satisfaction of the Engineer.
The centerline of the panels shall be aligned to a line laid out by a surveyor (provided by the Contractor) on the surface of the base prior to placement of the panels. Shims may be placed in the joints between panels to correct horizontal misalignment of the centerline of the panels. The total thickness of shims used in any joint shall be no more than 1/8 inch. Any damage caused to the panels by shims shall be repaired at the Contractor's expense to the satisfaction of the Engineer.
5.6 Placement Tolerances. Unless otherwise indicated on the plans, the centerline of the panels shall be within 1/4 inch of the pre-surveyed centerline marked on the surface of the base, and the centerline of adjoining panels shall be within 1/8 inch of each other at the adjoining edge.
Vertical alignment of the panels shall be such that the top surface of an individual panel is no more than 3/16 inch higher or lower than the top surface of an adjoining panel at any point along the joint between the panels. The width of the gap between adjoining panels at the top surface of the joint shall be no more than 1/8 inch after completion of temporary post-tensioning.
5.7 Expansion Joints. The expansion joint seal shall conform to the requirements of Sections 1073.2 and 717.10 for a preformed compression seal or Sections 1057.10 and 717.30 for silicon expansion joint seals, as shown in the plans. The header material on either side of the expansion joint shall be approved prior to use and shall be installed at the fabrication plant prior to shipment of the panel, unless otherwise approved for installation at the job site. The header material and joint seal shall be compatible with each other.
The seal for the expansion joints shall be selected by the contractor and approved by the Engineer. The joint seal shall be able to accommodate expansion (stretch) of 1 3/4″ and compression of 1/2″. Groove dimensions ("W" and "D" on plans) and installation width for the joint seal shall be specified by the manufacturer. The width of the expansion joint at the level of the dowels shall be adjusted on-site immediately following completion of post-tensioning based upon the approximate ambient temperature according to:
- T ≤ 50°F: 3/4″
- 50°F < T < 90°F: 1/2″
- T ≥ 90°F: 1/4″
Unless otherwise specified on the plans, expansion joint seals shall be installed following final post-tensioning and prior to opening the pavement to traffic. The width of expansion joints after final post-tensioning will be adjusted to the width specified on the plans. Any debris in the joint shall be removed using compressed air or other approved techniques prior to installing the joint seal.
5.8 Cover Plate/Edge Drain for Expansion Joints. Cover plates and/or edge drains shall be provided at both ends of each expansion joint as shown on the plans. A cover plate with an edge drain shall be installed at each end of the expansion joint where water is expected to drain to. Cover plates shall be installed such that they will not inhibit free movement of the expansion joint. Expansion joints shall be cleared of debris prior to installation of cover plates/edge drains.
5.9 Patching and Repairs. Anchor access pockets (joint panels) shall be "patched" only after completion of post-tensioning but prior to grouting the post-tensioning tendons. The pockets shall be patched with an approved patching material. A fast-setting patching material shall be permitted with the approval of the Engineer. The patching material shall be finished flush with the surface of the surrounding concrete, and shall be suitable for diamond grinding if necessary.
Damage caused to the precast panels during any part of the panel installation process shall be repaired by the contractor at the contractor's expense to the satisfaction of the Engineer. Repairs of damaged areas will be addressed on a case-by-case basis by the Engineer. Damage within acceptable limits caused to the top surface (driving surface) or to keyed edges of the panels shall be repaired using approved repair methods and materials. Repetitive damage to panels shall be cause for stoppage of installation operations until the cause of the damage can be remedied. Patching of post-tensioning anchor access pockets, lifting anchor recesses, and all other recesses shall be completed using approved patching materials and methods.
5.10 Voids Beneath Pavement. The pavement shall be inspected during panel installation for voids beneath the precast panels. At the discretion of the Engineer, the Contractor shall be required to stop panel installation and correct imperfections in the base material causing voids beneath the precast panels.
5.11 Matching Existing Pavement. The precast panels shall be tied into the existing pavement as shown on the plans. The top surface of the precast pavement shall no more than 1/4 inch above or below the surface of the precast pavement. Diamond grinding shall be used bring the top surface of the existing pavement and precast pavement into tolerance if necessary.
5.12 Mid-Slab and End-Slab Anchors. Mid-slab and end-slab anchors shall be provided as shown on the plans to tie the precast pavement slab to the existing subbase. Alternative mid-slab or end-slab anchors shall be approved by the Engineer.
5.13 Instrumentation. The Contractor shall permit access to instrumentation in the precast panels during the panel installation process and shall permit instrumentation of the precast panels and post-tensioning system during the construction process. A schematic layout and an instrumentation plan shall be provided to the Engineer and Contractor for approval at least one month prior to commencement of panel installation on site. Instrumentation shall include, but is not limited to, temperature sensors, strain gages, and load cells. Instrumentation shall not compromise the integrity of the base material, pavement, or the post-tensioning system. The Contractor shall protect the integrity of the instrumentation, including lead wires and connectors extending from the surface of the precast panels, during the panel installation and post-tensioning process.
6.0 Post-Tensioning. Post-tensioning materials, equipment, and procedures shall conform to the prestressing requirements given in Section 1029, "Fabricating Prestressed Concrete Members for Bridges."
The contractor shall use the post-tensioning system shown in the plans, unless a comparable system is approved for use. The dimensions of the anchor access pockets may be adjusted as needed prior to fabrication of the joint panels (Type A) in order to accommodate the stressing ram. The pocket dimensions shall be such that construction traffic can pass over the pockets without damage to the vehicle or disruption to the driver. Dimensions other than those shown in the plans shall be approved by the Engineer prior to fabrication of the joint panels (Type A).
6.1 Materials. Low-relaxation, Grade 270 strands with 0.65-inch nominal diameter, conforming to Section 1029.3.4, shall be used for post-tensioning.
6.2 Strand Insertion. Post-tensioning strands shall be inserted into the ducts at the Joint Panels (Type A), as shown on the plans. Strands shall be either pushed or pulled through the ducts by hand or using an approved mechanical strand pusher. Provision shall be made to prevent separation of the individual wires from the strand during strand insertion.
6.3 Tendon Stressing. Each end of each of the post-tensioning shall be stressed. Post-tensioning strands shall be stressed to 80% of the guaranteed ultimate tensile strength of the strand supplied. The tendon stressing sequence shall be approved prior to the start of post-tensioning. Stressing shall be completed in a single stage unless otherwise specified. Stressing of longitudinal tendons (parallel to the roadway centerline) shall start with a tendon at or near the midpoint of the panels, subsequently alternating between the tendons on either side of the centerline until all tendons have been stressed. Tendons shall be stressed to the magnitude specified in the plans and elongations shall be measured and recorded, in accordance with Section 1029.6.9.
After completion of post-tensioning, the tails of the post-tensioning strands shall be trimmed, and an approved grease cap will be used to cover and seal the end of the strand and post-tensioning anchor.
6.4 Faulty Anchors and Wire Failures. In the event of a faulty post-tensioning anchor, the Contractor shall submit a repair or alternate stressing strategy for approval. No wire failures shall be accepted. The contractor shall provide and install a new strand in the event of a wire failure.
7.0 Tendon Grouting. Unless otherwise shown on the plans, the post-tensioning system shall consist of grouted tendons, in accordance with Section 1029.6.9.
7.1 Materials. The grout mixture shall be a pre-packaged grout specifically manufactured for prestressed tendon grouting, and shall be approved by the Department prior to use. Grout shall be proportioned with water according to the manufacturer's recommendations.
7.2 Equipment. Grouting equipment shall consist of at least the following:
- Equipment for accurately measuring and proportioning by volume or weight the various materials composing the grout,
- A colloidal mixer, capable of operating in a range from 800 rpm to 2,000 rpm and thoroughly mixing the various components of the grout in an approved manner,
- A positive action pump capable of forcing grout into the post-tensioning ducts. The injection pump shall be capable of continuous pumping at rates as low as 1-1/2 gal. per minute,
- The discharge line shall be equipped with a positive cut-off valve at the nozzle end, and a bypass return line for recirculating the grout back into a holding tank or mixer unless otherwise approved, and
- A stop watch and flow cone conforming to the dimensions and other requirements of ASTM C 939, "Standard Method for Flow of Grout for Preplaced-Aggregate Concrete (Flow Cone Method)."
7.3 Procedures. A grouting plan shall be submitted for approval at least 4 weeks before starting grouting operations. Grouting shall be completed within 7 days after stressing of the post-tensioning tendons, unless otherwise approved. Grouting shall not be performed until the anchor access pockets have been patched. Compressible foam shall be injected in each expansion joint to seal the bottom of the joint from grout intrusion. The sides of the pavement slab shall be backfilled to prevent grout leakage from beneath the slab.
The grout fluidity shall be checked according ASTM C 939. Efflux time for fluidity shall be between 10 and 30 seconds after mixing, but no more or less than recommended by the manufacturer. Fluidity shall be adjusted to achieve the necessary flow requirements to achieve fully grouted tendons. If excessive bleeding of the grout is observed, the Engineer may require the Contractor to adjust the grout mixture to reduce bleed. The fluidity of the grout shall be checked at the beginning of each grouting operation and after each time the grout pump and hose is flushed.
Samples for grout compressive strength determination will be collected at least once per day during grouting operations. A minimum of three strength cubes shall be made during each sampling. The average compressive strength of three cubes shall be a minimum of 5,000 psi at 28 days.
Grout shall be pumped into the lowest end of the tendon. Grouting pressure shall not exceed the bursting pressure of the duct/port connection or 145 psi, whichever is less. If grout does not flow from the nearest intermediate port after the maximum grouting pressure has been reached, grout may be pumped into an intermediate port. A diagram of grout flow shall be produced by the contractor to demonstrate full grouting of the tendons.
7.4 Grouting Problems. If grout is observed leaking into an expansion joint, from the end of a joint between panels, from beneath the slab, or out of an adjacent duct, pumping shall be stopped and grout shall be pumped into the nearest intermediate port. Any grout that flows into an expansion joint shall be flushed from the expansion joint immediately. Any grout that hardens in an expansion joint shall be removed at the contractor's expense.
7.5 Cleanup. Upon completion of grouting, recesses in the surface of the panels at the grout ports shall be filled with an approved mortar and finished flush with the surface of the pavement. Any grout that flows onto the finished surface of the pavement during the grouting operation shall be immediately flushed from the surface. Any residual grout which hardens on the pavement surface shall be removed using an approved technique to the satisfaction of the Engineer at the expense of the contractor.
8.0 Underslab Grouting. Underslab grouting shall be used to fill any voids beneath the precast panels that may be present after placing the panels over the prepared base. Underslab grouting shall utilize the underslab grout channels and ports shown in the plans.
8.1 Materials. Grout materials shall consist of a mixture of Type I, II or III Portland cement, a fluidifier, fly ash and water. All materials shall be furnished by the Contractor.
The fluidifier shall be a cement dispersing agent possessing such characteristics that will inhibit early stiffening of the pumpable mortar, tend to hold the solid constituents of the fluid mortar in suspension and prevent completely all setting shrinkage of the grout.
Class C fly ash, meeting the requirements of Section 1018 shall be used. The fly ash shall be selected from an approved source from FS-1018 Table 1.
8.2 Equipment. Equipment for underslab grouting shall consist of the same equipment listed in 7.2.
8.3. Proportioning Grout Mixture. The mixture used in pressure grouting, herein referred to as "Grout Slurry", shall consist of proportions of Portland cement, fly ash, fluidifier and water. The contractor shall furnish the Engineer the proposed mix design meeting the following requirements:
- The grout slurry shall remain fluid and not exhibit a resistance to flow for a minimum of one hour,
- The time of efflux from the flow cone shall be between 10 and 20 seconds. The flow test shall be performed in accordance with ASTM C 939, "Standard Method for Flow of Grout for Preplaced-Aggregate Concrete (Flow Cone Method),"
- The grout slurry shall achieve initial set in less than 4 hours. The grout slurry shall not be allowed to carry traffic until which time it has set to the satisfaction of the Engineer; or until which set time, as determined by ASTM C 266, "Time of Setting of Hydraulic Cement Paste by Gillmore Needles," has been reached, and
- The 7 day compressive strength of the grout slurry shall not be less than 200 psi.
8.4 Procedures. Underslab grouting shall be completed after stressing of the post-tensioning tendons, but not more than 7 days after placement of the precast panels. The Engineer may require grouting to be completed prior to opening the pavement to traffic if significant voids are observed during panel placement. Underslab grouting may be completed prior to tendon grouting only if underslab grouting will not interfere with tendon grouting.
Slab edges shall be backfilled or sealed to prevent grout leakage from beneath the slab during underslab grouting. Likewise, the bottom of all expansion joints shall be sealed prior to underslab grouting to prevent grout leakage into the joints. The sealant material shall be compressible such that it will not inhibit free movement of the expansion joints.
Underslab grouting shall require minimal pressure to force the grout beneath the pavement slab. Under no circumstances should underslab grouting cause the pavement slab to lift. Grout shall be pumped into each underslab grout port of each panel. Grout shall be pumped until it flows out of an adjacent grout port or until the line pressure on the grout pump reaches 5 psi. Grouting pressure of 5 psi may be exceeded if the Contractor can demonstrate the slab lift is not occurring at higher pressures.
The fluidity of the grout shall be checked at the beginning of each grouting operation and after each time the grout pump is flushed .Grout fluidity shall be checked in accordance with ASTM C 939, "Standard Method for Flow of Grout for Preplaced-Aggregate Concrete (Flow Cone Method)." Fluidity shall be adjusted to achieve the necessary flow requirements to achieve full undersealing. If excessive bleeding of the grout is observed, the Engineer may require the Contractor to adjust the grout mixture.
8.5 Grouting Problems. If grout is observed leaking into an expansion joint, from beneath the slab, or out of an adjacent port, grouting shall be stopped and grout will be pumped into the nearest intermediate port. Any grout that flows into an expansion joint shall be flushed from the expansion joint immediately. Any grout that sets up in an expansion joint shall be removed at the Contractor's expense.
8.6 Cleanup. Upon completion of grouting, recesses in the surface of the panels at the grout ports shall be filled with an approved mortar and finished flush with the surface of the surrounding pavement. Any grout that flows onto the finished surface of the pavement during the grouting operation shall be immediately flushed from the surface. Any residual grout which hardens on the pavement surface shall be removed using an approved technique to the satisfaction of the Engineer at the expense of the Contractor.
9.0 Finished Surface. The finished pavement surface shall be tested for smoothness by profilographing in accordance with Section 502.8. Corrective action to improve the profile index shall be accomplished by diamond grinding. Grinding shall be performed with abrasive grinding equipment, designed specifically for grinding pavement surfaces to close tolerances, utilizing diamond cutting blades with a minimum cutting width of 36 inches. Such equipment shall accurately establish slope elevations and profile grade controls. The final ground surface shall not be smooth or polished.
10.0 Method of Measurement.
Measurement will be made by individual units of each panel, complete in place, in the finished pavement. The concrete, reinforcing bars, prestressing and post-tensioning tendons, anchorages and accessories, grout, and other incidentals will be considered a single unit.
11.0 Basis of Payment.
Accepted prestressed post-tensioned panels will be paid for at the contract unit price.