603Prestressed Concrete Members

603.1-DESCRIPTION: This work consists of the construction of precast/prestressed concrete members, pretensioned in accordance with these specifications and in conformity with the plan details and notes. This work shall include manufacturing, inspection, handling, storing, tr ansporting and erecting of structural members of precast/prestressed concrete, and, when specified, shall also include precast concrete members which do not contain pretensioning steel components. Concrete floors, curbs, parapets, curtain walls, and diaphragms shall be cast in place on the project unless otherwise provided for on the plans. When the above elements are specified as precast members, they shall be manufactured in accordance with this specification. 603.2-MATERIALS: Materials shall meet the requirements specified in the following Sections/Subsections: Precast/Prestressed Concrete Materials Sections/Subsections +Admixtures Air Entraining Admixtures 707.1 Retarding Admixtures 707.2 Water Reducing Admixtures 707.3 Supplementary Cementitious Materials (SCMs)** 707.4 Specific Performance Admixtures 707.17 Cement ASTM C150, 701.3 Coarse Aggregates* 703.1, 703.2, & 703.3 Concrete Sealant 707.12 Elastomeric Bearing Pads 715.14 Fine Aggregates # 702.1 Hot-Poured Elastic Type Concrete Joint Sealer 708.3 Mixing Water 715.7 Preformed Expansion Joint Filler 708.1 Prestressing Steel 709.2 Reinforcing Steel 709.1 Shear-Key Grout 715.5 Steel Bolts and Nuts 709.23 Welded Wire Fabric 709.4 # When the top surface of a prestressed member is designed as the bridge wearing surface * The maximum size of coarse aggregate shall not exceed the minimum horizontal or vertical clear spacing between pretensioned or reinforcing steel elements divided by 1.33. Lightweight aggregates shall not be used unless their use is permitted by the Engineer in writing. For Class S -P concrete, a blend of two AASHTO gradations of coarse aggregates can be used. The maximum aggregate size permitted is ¾ inches (19 mm). A coarse aggregate gradation using a #67 aggregate is allowed only if 100% of the material passes the ¾ inch (19 mm) sieve ** The use of a SCM is not permitted when a blen ded hydraulic cement is used. For the purposes of cement material substitution with SCMs, Type IL cement shall not be treated as a blended cement, and a SCM may be used with Type IL cement. For Class S -P concrete, a combination of up to two SCMs are perm itted, as shown in Table 603.6.3.1. The maximum percent of total cementitious materials permitted in Class S -P concrete mix designs is shown in Table 603.6.3.1. + Calcium chloride or any admixture containing chloride ion in excess of 0.1 percent by weigh t shall not be used in prestressed concrete members. 603.2.1-Inspection and Testing: A representative of the Engineer shall have free entry at all times, while the work on the Contract is being performed, to all parts of the manufacturer’s works which concern the manufacture of the materials ordered. The manufacturer shall afford the representative of the Engineer, without charge, all reasonable facilities to satisfy themselves that the material is being furnished in accordanc e with these specifications. Inspection and acceptance procedures for prestressed concrete bridge members shall be in accordance with MP 603.10.40. The Fabricator’s QC Personnel, as a minimum, shall be a certified ACI Grade I Concrete Field Testing Technician and/or a WVDOH PCC Inspector. In addition, if Self-Consolidating Concrete (SCC) is used, Fabrication Plant QC Personnel shall be a certified ACI SCC Testing Technician. Component materials used in the fabrication of precast and prestressed concrete members, and any ship loose materials pertaining to precast and prestressed concrete items, shall be approved in accordance with MP 603.02.10. 603.3-PLANT REQUIREMENTS AND APPROVAL: 603.3.1-Plant Approval: All fabricators of prestressed concrete members shall be certified in the appropriate Group and Category in accordance with the Precast/Prestressed Concrete Institute (PCI) Plant Certification Program. Fabricators shall be certified in Group B3 or B4 for manufacture of prestressed straight strand bridge members. For prestressed draped strand bridge members, the fabricator shall be certified in Group B4. The En gineer or his authorized representative shall approve all plants manufacturing prestressed and precast reinforced concrete bridge members before manufacture of the members may be started. Requests for such approvals shall be submitted to the Engineer at least three weeks prior to the date of manufacture of the members. Requests shall include details of the plant facilities, materials, and the production methods the manufacturer intends to use. The manufacturer shall have an established quality control program in effective operation at the plant. This program shall be submitted to the Engineer for approval at least 30 days prior to the start of the production. If a contractor/fabricator is found to consistently deviate from PCI guidelines, the contractor/fabricator will be required to use independent laboratory quality control testing and inspection until it can be shown that conformity with PCI guidelines has been reestablished. The laboratory used is subject to the approval by the Engineer. The cost of the independent laboratory is to be borne by the contractor/fabricator. 603.3.2-Supervision: The contractor/fabricator shall provide a PCI Level II certified technician, skilled in the use of the system of prestressing to be used, who shall supervise the work and give the Engineer or his representative such assistance as may be considered necessary. 603.3.3-Equipment and Tools: 603.3.3.1-General: All equipment, tools and machinery used in the work shall be adequate for the purpose for which it is to be used and shall be maintained in a satisfactory working condition. The use of portable prete nsioning beds for the manufacture of prestressed concrete members is not acceptable. The contractor/fabricator shall provide all other equipment and tools necessary for the construction and the prestressing. 603.3.3.2-Equipment: The jacks shall be eq uipped with instruments for monitoring the hydraulic pressure. Electronic pressure transducers with digital indicators may be used. All pressure gauges or electronic pressure indicators shall indicate the load directly to one percent (1%) of the maximum gauge or sensor/indicator capacity or two percent (2%) of the maximum load applied, whichever is smaller. Each jack and its gauge shall be calibrated as a unit with the cylinder extension in the approximate position that it will be at final jacking force. The calibration of the jack and gauge shall be done while the jack is in the identical configuration as will be used on the site, e.g., same length hydraulic lines. An independent laboratory shall furnish certified calibration charts with each jack and gauge used in the work. Certified calibration of each ram shall be made prior to the start of stressing operations and every six (6) months thereafter, or as requested by the Engineer. Any repair of the rams, such as replacing seals, changing length of hydraulic lines, changing type of pump or using gauges which have not been calibrated with the ram, shall be cause for recalibration of the jack and gauge with a load cell. No extra compensation will be allowed for the initial or subsequent ram calibrations. 603.3.3.3-Forms and Casting Beds: Forms and casting beds shall be subject to the approval of the Engineer. Unless otherwise approved, only metal forms on concrete founded casting beds shall be used. The forms and casting beds shall be well constructed, carefully aligned, substantial and firm, securely braced and fastened together, sufficiently tight to prevent leakage of mortar and strong enough to withstand the action of mechanical vibrators. The forms shall be constructed to permit movement of the member s without damage during release of the prestressing force or movement caused by thermal expansion during curing. The casting beds and all form work will be approved before any concrete is placed, but such approval shall not relieve the contractor/fabricator of responsibility for the results obtained. 603.4-WORKING DRAWINGS: 603.4.1-General: The contractor/fabricator shall expressly understand that the Engineer’s approval of the working drawings submitted by the contractor/fabricator covers the requirements for "strength and detail," and that the Engineer assumes no responsibility for errors in dimensions. Working drawings must be approved prior to performance of the work involved and such approval shall not relieve the contractor/fabricator of any responsibility under the contract for the successful completion of the work. All working drawings shall be in English units. Use of dual (metric and English) units is not allowed. 603.4.2-Shop Drawings: The contractor/fabricator shall submit copies of the detailed shop drawings to the Engineer for approval. Shop drawings shall be submitted sufficiently in advance of the start of the work to allow time for review by the Engineer and correct ions by the contractor/fabricator without delaying the work. The size of the original drawings shall be twenty-two (22) inches x thirty-four (34) inches including margins, unless otherwise permitted. The shop drawings submitted for approval may be reduced. Shop drawings for concrete structures shall give full detailed dimensions and sizes of component parts of the structure and details of all miscellaneous parts. Design camber for all members shall be shown on the shop drawings. 603.4.3-Erection Drawings: The contractor shall submit drawings illustrating fully their proposed method of erection. The drawings shall show details of all falsework bents, bracing, guys, dead-men, lifting devices, and attachments to the bridge members: sequence of erection, location of cranes and barges, crane capacities, location of lifting points on the bridge members, and weights of the members. The plan and drawings shall be complete in detail for all anticipated phases and conditions during erection. Design calculations , sealed by a Registered Professional Engineer, shall be submitted by the contractor/fabricator to the Engineer for approval which will demonstrate that allowable stresses for falsework and concrete members being erected are not exceeded and that member ca pacities and final geometry shall be correct. When the designated concrete deck overhang exceeds thirty ( 30) inches, the erection drawings submitted by the contractor/fabricator shall include complete details of the forming and bracing for the overhang and shall transmit the concrete deck dead load to an area of the beam or stringer which will prevent distortion. All forming and bracing procedures are subject to approval of the Engineer. 603.5-REINFORCEMENT: All reinforcing bars and welded wire fabric shall meet all requirements of Section 602 and shall be free of frost, loose rust, grease, dirt, oil, paint, mill scale, corrosion or other deleterious substances. Any steel which cannot be satisfactorily cleaned shall not be used. When splicing is required, all reinforcing bars shall be lapped for a length of at least 30 bar diameters. Reinforcing bars, welded wire fabric and other embedded fixtures shall be accurately placed as indicated on the Plans and shall be maintained in their correct position during the manufacture of the unit. Reinforcement shall not be held in position by tack welding. The minimum concrete cover for reinforcing steel shall be as follows, unless otherwise shown on the Plans: Main Reinforcement......................................1½ inches Slab Reinforcement, top of slab ....................1½ inches Slab Reinforcement, bottom of slab ..............1 inch Stirrups and Ties............................................1 inch The longitudinal or main wires of welded wire fabric shall be placed transverse to the longitudinal axis of the unit. Laps of welded wire fabric shall be a minimum of six (6) inches unless otherwise approved by the Engineer. 603.6-CONCRETE: 603.6.1-General: The composition, proportioning, and mixing of concrete shall be such so as to produce a homogeneous concrete mixture of a quality that will conform to the test and design requirements specified and as noted on the Plans. Concrete for all prestressed members shall have a minimum compressive strength as may be specified on the plans or in the special provisions. Materials used to form voids in the members shall be fabricated from form material acceptable to the Engineer or from cardboard, which has been treated with a waterproofing agent. Any void made from more than one piece of material shall be glued and banded to prevent separation during concreting operations. Any evidence of separation will be cause for rejection. All concrete materials including admixtures shall meet requirements specified in subsection 603.2 and/or as indicated in the plans. 603.6.1.1-Class S-P Concrete: Class S-P concrete shall be self-consolidating concrete for precast/prestressed applications and may be used for the fabrication of prestressed concrete box beams. If Class S -P concrete is to be used in the fabrication of prestressed concrete I-Beams or Bulb Tee Beams, additional testing, as outlined in Section 603.6.1.1.1, shall be required. Class S-P concrete shall meet the requirements of this Section. Class S-P concrete shall consist of a homogeneous, flowable mixture of cement, fine aggregate, coarse aggregate, chemical admixtures and water. Class S-P concrete may also contain fly ash, slag cement, and silica fume. The mixture proportions shall be such that the Class S-P concrete will resist segregation, bleeding, and the generation of foam during placement, and will need no external compaction or vibration, unless the mix is qualified as outlined in Section 603.6.1.1.1. While the properties of fresh SCC differ significantly from that of conventional fresh concrete, the quality in terms of strength, durability, an d performance of the hardened SCC shall be equal to or better than that of a similar specified conventional concrete mix. Establishment of the mixture proportions shall be coordinated with the manufacturer of the admixtures which will be used in the Class S-P concrete. SCC exhibits self -leveling capabilities. Creating a successful SCC mix requires combining ingredients to achieve a highly-flowable product that also has the capability to resist dynamic segregation and foaming during placement while resisting static segregation and bleeding once in place. SCC mix designs are often achieved using high -range water reducing (HRWR) admixtures, and by carefully selecting a proper aggregate gradation, incorporating high volumes of powder in the mix, through the u se of viscosity-modifying admixtures (VMAs), or a combination of the previously mentioned. For Class S -P concrete, a combination of admixtures which may be used includes water-reducing admixtures, air -entraining agents, water -reducing and retarding admixtures, VMAs, shrinkage -reducing admixtures (SRAs), and other specific performance admixtures, provided they are on the WVDOH approved list of admixtures. These admixtures used shall all come from the same manufacturer, and measures should be taken to ensu re that no adverse reactions occur. Also, for Class S -P concrete, it is permitted to use a combination of up to two AASHTO gradations of coarse aggregate to obtain an optimal combination of strength, self -consolidating ability, and passing ability. Likewise, a combination of up to two SCMs may be used in combination with Portland cement for Class S-P concrete in order to achieve ideal characteristics for the mix. 603.6.1.1.1-Pre-Qualification of Class S -P Concrete Construction Methods: If Class S -P is to be used in the fabrication of prestressed concrete I -Beams or Bulb Tee Beams, or if vibration is to be used during fabrication, the Class S -P concrete mix and proposed method of construction must be pre-qualified prior to fabrication. A full-size test me mber, at least ten (10) feet in length shall be constructed with the Class S- P concrete mix which will be used during fabrication. The full -size test member shall represent the “worst-case” member which the Fabricator shall be allowed to fabricate, using Class S-P concrete. This “worst-case” member shall consist of the tallest I-beam or Bulb Tee shape and shall contain the maximum amount of prestressing strand and reinforcing steel which would be encountered in such a member. The type and maximum duration of vibration, which will be used during fabrication, shall also be used during construction of this test member. All other aspects of construction of this test member, including the free fall height of concrete above the beam, shall be identical to those which will be used during fabrication of members during production. After the completion of curing of this test member, three four (4) inch diameter cores shall be taken from the member at mid-length. One core shall be taken from the top flange of the member, one core shall be taken from the web of the member at mid-height, and one core shall be taken from the bottom flange or bulb of the member. A point count, in accordance with MP 700.03.50 or other equivalent test method approved by the Engineer, shall be performed on each of these cores in order to determine if segregation is occurring due to the vibration. If the results of the point counts show that the percentages of coarse aggregate, fine aggregate, air content, and paste vary by more than 15% between any of these three cores, that type of member shall not be permitted to be constructed with Class S-P concrete. If, at some time after the above mentioned “worst-case” test member is fabricated and tested, the Fabricator needs to fabricate a me mber larger than this “worst -case” member (which would now be a new “worst-case” member), the Engineer shall determine, based on the test results from the previous “worst-case” member, whether or not the testing required in this section will again be requi red for this new “worst -case” member. If the test results from the previous “worst-case” member are within an acceptable margin below the allowable test criteria, and if the new “worst -case” member is not significantly larger than the previous “worst-case” member, then the Engineer may allow this new “worst - case” member to be constructed with Class S -P concrete without additional pre - qualification testing required in this section. 603.6.2-Mix Design: Concrete mixtures shall be established initially by methods in accordance with ACI 301, Chapter 4. Class S -P concrete mixtures shall be developed in accordance with MP 711.03.23 and the requirements of this Section, not the ACI methods. Mixes may be designed either by a commercial laboratory or by PCI certified concrete plant personnel. Prior to adoption of a mix design as a plant standard, it shall be field tested by use of the production plant batching and mixing equipment, construction methods, and curing to be used in production of the members. All design mixes shall be developed using the type of cement, the type and gradation of aggregates, and admixtures proposed for use in plant mixes. The mix design shall also include either compressive strength tests or a penetration resistance test (in accordance with ASTM C403) that verify the amount of time it takes to achieve a compressive strength of 500 psi. The Engineer shall approve the mix design. When any of these variables are changed, or after a three-year time period, the mix shall be re-evaluated and submitted to the Engineer for approval. Any design mix with an aggregate(s) that has a reactivity class R1, R2, or R3, as shown as in Approved Aggregates Source List, shall be developed in accordance with subsection 601.3.1.1. If an aggregate Source is not listed on the Approved Aggregates Source List, the Division will test the fine and coarse aggregate from the Source, in accordance with AASHTO T 303, to determine the reactivity class of the aggregate prior to its use on a ny WVDOH project. The Division will inform the Fabricator of the reactivity class of aggregates that they are proposing to use. If a cement Source and/or a SCM Source are not listed on the Approved Source List, the Division will test cement and/or SCM from that Source prior to its use on any WVDOH project. 603.6.2.1-Class S -P Concrete Mix Design Testing: To ensure repeatability of production, two batches of concrete with the same mix proportions shall be created for mix qualification testing. The results of this testing shall be submitted to the Division for approval at least 45 days prior to the use of the mix in construction. Personnel performing testing on Class S -P concrete shall be certified by ACI as a Self -Consolidating Concrete Testing Technician. The two trial batches at the target cement factor plus one bag (see Section 3.3 of MP 711.03.23), are not required for Class S-P concrete mixes. Batching equipment and curing procedures for test specimens fabricated from these test batches should be as close as possible to the techniques that will be used by the Fabricator during production. The minimum batch size for these trial batches shall be 2.0 yd 3, or the largest possible batch when using the mixer that will be used for production, if approved by the Division. The fresh properties measured at the proposed time of casting for each trial batch shall include air content, consistency, Visual Stability Index (VSI), T 50, J -Ring Value, Unit Weight, Yield, Rapid Assessment of Static Segregation Resistan ce, and Segregation Resistance. Target values and their tolerances for the fresh properties of the trial batches shall conform to the requirements in the following table: TABLE 603.6.2.1A Fresh Property Mix Design Batch Acceptance Criteria Air Content ***Target minus 0.5% ≤ Air Content ≤ ***Target plus 1.5% Slump Flow (ASTM C1611) Target ≤ Spread ≤ Target plus 1.5 inches 2 seconds ≤ T50 ≤ 7 seconds Visual Stability Index ≤ 1.0 Passing Ability (ASTM C1621) J-Ring Value ≤ 1 inch Rapid Assessment of Static Segregation Resistance (ASTM C1712) Penetration Depth (PD) ≤ 0.5 inch Segregations Resistance (ASTM C1610) Segregation ≤ 12% Unit Weight and Yield ± 2% of Theoretical *** The target air content of Class S-P concrete shall be determined in accordance with Table 603.6.2.1B TABLE 603.6.2.1B Nominal Maximum Aggregate Size in the Class S-P Mix Target Air Content of Class S-P Concrete 3/8 inch (9.5 mm) 7.5% ½ inch (12.5 mm) 7.0% ¾ inch (19 mm) 6.0% After the properties of the trial batches of fresh concrete have been established to be within the specification limits in Table 603.6.2.1A, specimens will be cast for compressive strength, modulus of elasticity, creep, length change (total shrinkage), rapid chlorid e permeability and freeze -thaw testing. Casting of all Class S -P specimens to be used for hardened property testing shall be done in one lift without rodding. Compressive strength testing shall be conducted on both trial batches, but modulus of elasticity , creep, length change (total shrinkage), rapid chloride permeability and freeze -thaw testing is only required on one of the trial batches. If steam curing is to be used during the production, the same curing procedure (time, temperature, etc.) shall be used on all of the above test specimens except for the shrinkage specimens. After discontinuation of steam curing, all specimens shall be cured as noted in the footnotes in the table below. Target values and their tolerances for the hardened properties of the trial batches shall conform to the requirements in Table 603.6.2.1C: TABLE 603.6.2.1C Hardened Property Test Total # Specimens Specimen Size Age at Testing Magnitude of Loading Approval Condition Compressive 7 4”x8” 1 @ 24 ± 2 hrs. Load Until per Design Strength or 6”x12” 1 @ 3days ± 2 hrs. Failure (AASHTO T 22) cylinders 1 @ 7days ± 2 hrs. 1 @ 14days ± 2 hrs. 3 @ 28days ± 4 hrs. Modulus of 7 6”x12” 1 @ 3days ± 2 hrs. 40% of a≥ 57,000√f ' c Elasticityb cylinders 1 @ 7days ± 2 hrs. compressive (ASTM C469) 1 @ 14days ± 2 hrs. strength 3 @ 28days ± 4 hrs. (obtained above) Creepb (ASTM C512) 8 total (3 loaded, 6”x12” cylinders 72 ± 2 hours at age of initial loading 40% of compressive Creep Coefficient c 3 remain unloaded, strength at time of ≤ 1.19 at 90 days a 2 tested for loading compressive strength) Length Change 3 3”x3”x11” 56 days 28-day cure ≤ 0.0002 at 28 (ASTM C157) prisms per ASTM C157 then days of Air Storage a Air Storage for 28-days Rapid Chlorideb 3 4”x2” 56 days 60.0 ± 0.1 V ≤ 1500 Permeability disc or coulombs (AASHTO T specimen 28 days (56 days) or 277) ≤ 2000 coulombs (28 days) Freeze-Thaw 3 3”x4”x16” 28 day cure prior to 300 cycles Durability Resistance prisms testing (0oF to 40oF) Factor ≥ 80 (ASTM C666- Procedure A)b