50 PRESTRESSING CONCRETE
50-1.01 General
50-1.01A Summary
50-1.01B Definitions
Reserved
50-1.01C Submittals
50-1.01C(1) General
Submit test sam ples to METS. Notify the Engineer of each submittal. Include in the notification the date and contents of the submittal.
50-1.01C(2) Certifications
Submit the certifications specified in the following to METS:
1.ASTM A416/A416M for uncoated seven -wire steel strand
2.ASTM A722/A722M for uncoated HS -steel bars
3.ASTM A882/A882M for filled epoxy -coated seven -wire prestressing steel strand Include with each certification:
1.Representative load -elongation curve for each size and grade of stran d and for each size of bar
2.Copy of the QC tests performed by the manufacturer
50-1.01C(3) Shop Drawings
Submit shop drawings for the proposed prestressing system electronically to sc.office.associat es@dot.ca.gov . The shop drawings must show complete details and substantiating calculations of the method and materials proposed for use in the prestressing activities, including the addition or rearrangement of reinforc ing steel. The details must outline the method and sequence of stressing and include:
1.Complete specifications and details of the prestressing steel and anchorage system.
2.Jacking stresses.
3.Type of ducts.
4.Proposed arrangement of the prestressing steel in the members.
5.Exact location of anchorage system components, ducts, and other related elements. Show duct location data, including elevations, at least every 1/8th point of the span for each span.
6.Elongation calculations.
7.All other data pertaining to the prestressing. Each shop drawing submittal must consist of drawings for a single bridge or portion of a bridge. For multi - frame bridges, each frame must have a separate shop drawing submittal. Allow 45 days for the review of shop dra wings of structures other than railroad bridges. For railroad bridges, comply with the requirements of the railroad company involved. Include a grouting plan with your shop drawing submittal. If you propose an alternative prestressing system for a CIP PS b ox girder bridge, submit shop drawings, including all details and checked calculations.
50-1.01C(4) Alternative Prestressing Systems for Cast -In-Place Prestressed Box Girder Bridges
The details shown for CIP PS box girder bridges are based on a bonded full -length draped tendon prestressing system. You may submit a VECP for an alternative prestressing system using bonded partial -length tendons. The proposed system and associated details must comply with the following requirements: SECTION 50 PRESTRESSING CONCRETE
1.Moment and sh ear resistances must be at least equal to those used for the design of the structure shown.
2.Concrete strength must be at least that shown.
3.Not less than 35 percent of the total prestressing force at any section must be provided by full -length draped tendons.
4.Anchorage blocks for partial -length tendons must be located such that the blocks will not interfere with the placement of the utility facilities shown or any future utilities to be placed through openings shown.
5.Any temporary prestressing te ndons must be detensioned, and the temporary ducts must be filled with grout before completion of the work. Temporary tendons must be either removed or fully encased in grout before completion of the work. At your request, the Department furnishes you wit h the demand moments and shears used in the design shown.
50-1.01C(5) Test Samples
Submit test samples for the materials to be used in the work as shown in the following table: Material Number of test samples Test sample description Uncoated stranda 1 4-foot-long sample from each reel or pack Epoxy -coated strand: Uncoated stranda 1 4-foot-long sample of uncoated strand removed from each reel or pack before coating Coated stranda 4 5-foot-long sample from each reel or pack of coated strand Epoxy powder 1 8-ounce sample from each batchb Epoxy patching material 1 8-ounce sample from each batchb Bara 1 7-foot-long sample of each size for each heat Bar couplera 1 Coupler from each lot of couplers with two 4 -foot-long barsc Anchorage assembliesa 1 Anchorage assembly from each lot of anchorage assemblies aRandomly selected by the Engineer. bPackaged in an airtight container and identified with the manufacturer's name and batch number. cSubmit coupler and bar samples assembled. The bars must be from the same bar heats to be used in the work. Sampling must comply with the requirements of the ASTM to be used for testing the sample. With each bar or strand test sample, include a certificate from the manufacturer stating the minimum guaranteed ultimate tensile strength of each sample. Identify each test sample by location and Contract number with weatherproof markings. Allow 45 days for the Department's testing. Obtain the Department's authorization of the material before incorporating it into the work.
50-1.01C(6) Grouting Plan
The grouting plan must include:
1.Detailed grouting procedures
2.Type, quantity, and brand of materials to be used
3.Type of equipment to be used and provisi ons for backup equipment
4.Types and locations of grout inlets, outlets, and vents
5.Methods to clean ducts before grouting
6.Methods to control the rate of flow within ducts
7.Theoretical grout volume calculations for each duct
8.Duct repair procedur es for an air pressure test failure
9.Mixing and pumping procedures SECTION 50 PRESTRESSING CONCRETE
10.Direction of grouting
11.Sequence of use of inlets and outlets
12.Procedure for handling blockages
13.Forms for recording grouting information
14.Procedure for secondary grouting
15.Names of people who will perform grouting activities and their relevant experience and certifications
50-1.01C(7) Daily Grouting Report
Submit a daily grouting report for each day grouting is performed. Submit the report within 3 business days after grouting. The report must be signed by the technician supervising the grouting activity. The report must include:
1.Identification of each tendon
2.Date the grouting occurred
3.Time the grouting started and ended
4.Date of placing the prestressing stee l in each duct
5.Date of stressing
6.Type of grout used
7.Injection end and applied grouting pressure
8.Actual and theoretical quantities of grout used to fill each duct
9.Ratio of actual to theoretical grout quantity
10.Records of air, grout, and structure surface temperatures during grouting
11.Summary of tests performed and the results
12.Names of personnel performing the grouting activity
13.Summary of problems encountered and corrective actions taken
14.Summary of void investigation and rep airs made
50-1.01C(8) Post -tensioning Jack Calibration Chart
Submit the post -tensioning jack calibration plot.
50-1.01C(9) Pretensioning Jack Calibration Chart
For any pretensioning jack calibrated by an authorized laboratory, submit a certified calibra tion plot.
50-1.01D Quality Assurance
50-1.01D(1) General
For accurate identification, assign an individual lot number and tag each lot of the following items to be shipped to the job site or casting site:
1.Bars of each size from each heat
2.Strand fr om each reel or pack
3.Anchorage assemblies
4.Bar couplers The Department rejects any unidentified prestressing steel, anchorage assemblies, or bar couplers received at the job site or casting site.
50-1.01D(2) Quality Control
50-1.01D(2)(a) General
Reserved
50-1.01D(2)(b) Equipment and Calibration
50-1.01D(2)(b)(i) General
Each jack body must be permanently marked with the ram area. Each pressure gauge must be fully functional and have an accurately reading, clearly visible dial or display. The dial must be at least 6 inches in diameter and graduated in 100 psi increments or less. Each load cell must be calibrated and have an indicator that can be used to determine the force in the prestressing steel. SECTION 50 PRESTRESSING CONCRETE The range of each load cell must be such that the lower 10 percent of the manufacturer's rated capacity is not used in determining the jacking force. Each jack must be calibrated equipped with its gauges. Mechanically calibrate the gauges with a dead weight tester or other authorized means before cal ibration of the jacking equipment.
50-1.01D(2)(b)(ii) Post -tensioning
Equip each hydraulic jack used to tension prestressing steel with 2 pressure gauges or 1 pressure gauge and a load cell. Only 1 pressure gauge must be connected to the jack during stressing. Each jack used to tension prestressing steel permanently anchored at 25 percent or more of its specified minimum ultimate tensile strength must be calibrated by METS within 1 year of use and after each repair. You must:
1.Schedule the calibrati on of the jacking equipment with METS
2.Verify that the jack and supporting systems are complete, with proper components, and are in good operating condition
3.Provide labor, equipment, and material to (1) install and support the jacking and calibration equipment and (2) remove the equipment after the calibration is complete
4.Plot the calibration results Each jack used to tension prestressing steel permanently anchored at less than 25 percent of its specified minimum ultimate tensile strength must be c alibrated by an authorized laboratory within 180 days of use and after each repair.
50-1.01D(2)(b)(iii) Pretensioning
Each jack used to pretension prestressing steel must be calibrated, equipped with its gauges, by a laboratory on the Authorized Laborator ies List to perform pretensioning calibrations within 1 year of use and after each repair. Calibrate pretensioning jacks:
1.Under ASTM E4 using an authorized laboratory. Certification that the calibration is performed to ASTM accuracy is not required.
2.In the presence of the Engineer. Notify the Engineer at least 2 business days before calibrating the jack.
3.Using 3 test cycles. Average the forces from each test cycle at each increment.
4.To cover the load range used in the work. Gauges for pretensio ning jacks may:
1.Be electronic pressure indicators that display either: 1.1. Pressure in 100 psi increments or less 1.2. Load to 1 percent of the maximum sensor/indicator capacity or 2 percent of the maximum load applied, whichever is smaller
2.Have a dial less than 6 inches in diameter Gauges displaying pressure must have been calibrated within 1 year of the jack calibration. Each hydraulic jack used for pretensioning must be equipped with either 2 gauges or 1 gauge and a load cell or you must have a calibrated standby jack with its gauge present on site during stressing.
50-1.01D(2)(c) Pressure Testing Ducts
For post -tensioned concrete bridges, pressure test each duct with compressed air after stressing. To pressure test the ducts:
1.Seal all inlets , outlets, and grout caps.
2.Open all inlets and outlets on adjacent ducts.
3.Attach an air compressor to an inlet at 1 end of the duct. The attachment must include a valve that separates the duct from the air source. SECTION 50 PRESTRESSING CONCRETE
4.Attach a pressure gauge to the in let at the end of the duct.
5.Pressurize the duct to 50 psi.
6.Lock -off the air source.
7.Record the pressure loss after 1 minute.
8.Repair the leaks with authorized methods and retest if a pressure loss exceeds 25 psi. Compressed air used to clear an d test the ducts must be clean, dry, and free from oil or contaminants.
50-1.01D(2)(d) Duct Demonstrations for Post -Tensioned Members
Before placing forms for deck slabs of box girder bridges, demonstrate that any prestressing steel placed in the ducts is free and unbonded. If no prestressing steel is in the ducts, demonstrate that the ducts are unobstructed. If prestressing steel is installed after the concrete is placed, demonstrate that the ducts are free of water and debris immediately before installin g the steel. Before post -tensioning any member, demonstrate that the prestressing steel is free and unbonded in the duct. Demonstrations must be performed in the presence of the Engineer.
50-1.01D(2)(e) Void Investigation
In the presence of the Engineer, investigate the ducts for voids between 24 and 72 hours after grouting. As a minimum, inspect the inlet and outlet ports at the anchorages and at high points in the tendons for voids after removal of the inlet and outlet pipes. Completely fill any voids fo und with secondary grout.
50-1.01D(2)(f) Personnel Qualifications
Perform post -tensioning field activities, including grouting, under the direct supervision of a technician certified as a Level 2 Bonded PT Field Specialist through the Post -Tensioning Inst itute. Grouting activities may be performed under the direct supervision of a technician certified as a Grouting Technician through the American Segmental Bridge Institute. Perform vacuum grouting under the direct supervision of a person who has been trained and has experience in the use of vacuum grouting equipment and procedures.
50-1.01D(3) Department Acceptance
The Department tests the prestressing steel test samples for compliance with section 50 -1.02B. The Department tests the efflux time of gro ut under California Test 541. The Department may verify the prestressing force using the Department's load cells. The Department determines the reduction of area of each test sample bar with the deformations removed. The deformations are removed by machini ng the bar no more than necessary to remove the deformations over a length of 12 inches. If couplers are used to extend bars, the Department rejects the heat of bars and lot of couplers represented by the assembled unit test sample if the sample does not h ave a tensile strength of at least the manufacturer's minimum guaranteed ultimate tensile strength of the bars. Prestressing steel that sustained physical damage is rejected. Prestressing steel is rejected if surface rust either (1) cannot be removed by ha nd-cleaning with a fine steel wool pad or (2) leaves pits visible to the unaided eye after hand -cleaning. If non -epoxy -coated prestressing steel is installed in the ducts of post -tensioned members after completion of concrete curing and if tensioning and g routing are completed within 10 days after the installation, then (1) rust that may form during this period is not cause for rejection of the steel and (2) the use of a corrosion inhibitor in the duct is not required after installation. SECTION 50 PRESTRESSING CONCRETE
50-1.02 Materials
50-1.02A General
Post-tensioning prestressing systems must be on the Authorized Material List for post -tensioning systems. Organic zinc -rich primer must be on the Authorized Material List for organic zinc rich primer.
50-1.02B Prestressing Steel
Uncoated strand must comply with ASTM A416/A416M. Epoxy -coated strand must comply with ASTM A882/A882M, grit impregnated coating, including annex A1. Bars must comply with ASTM A722/A722M, Type II, including all supplementary requirements, except the maximum weight requirements do not apply. The reduction of area of bars with deformations removed must be at least 20 percent. If couplers are used to extend bars:
1.Assembled units must have a tensile strength of at least the manufacturer's minimum guaranteed ultimate tensile strength of the bars
2.Location of couplers in the member must be authorized Protect the prestressing steel against physical damage and rust or other results of corrosi on at all times, from manufacture to grouting or encasing in concrete. Package the prestressing steel in containers or shipping forms that protect the steel against physical damage and corrosion during shipping and storage. Except for epoxy -coated strand, a corrosion inhibitor that prevents rust or other results of corrosion must be (1) placed in the container or shipping form, (2) incorporated in a corrosion -inhibitor -carrier -type packaging material, or (3) applied directly to the steel if authorized. Corrosion inhibitors must not have a deleterious effect on the steel, concrete, or bond strength of the steel to concrete. Clearly mark each shipping container or form with:
1.Statement that the package contains prestressing steel
2.Type of corrosion inhibitor used
3.Date packaged Immediately replace or restore any damaged container or shipping form to its original condition. Do not store epoxy -coated strand within 1,000 feet of ocean or tidal water for more than 60 days. Patching material for epoxy -coated strand must be:
1.Furnished by the manufacturer of the epoxy powder
2.Applied under the manufacturer's instructions
3.Compatible with the original epoxy powder material
4.Inert in concrete
50-1.02C Grout
Grout must consist of cement and water and may contain an admixture if authorized. Cement must comply with section 90 -1.02B(2). Water must comply with section 90 -1.02D. Admixtures must comply with section 90 -1.02E except admixtures must not contain chloride ions in excess of 0.25 percent by weight. SECTION 50 PRESTRESSING CONCRETE The efflux time of grout immediately after mixing must be at least 11 seconds. Determine the efflux time under California Test 541 . Secondary grout must:
1.Comply with ASTM C1107
2.Not have a deleterious effect on the steel, concrete, or bond strength of the steel to the concrete
50-1.02D Ducts
Ducts for prestressing steel must:
1.Be galvanized rigid ferrous metal.
2.Be fabricated with either welded or interlocked s eams except galvanizing of the welded seams is not required.
3.Be mortar tight.
4.Have sufficient strength to maintain their correct alignment during placing of concrete.
5.Have positive metallic connections at joints between sections that do not result in angle changes at the joints.
6.Have waterproof tape at the connections.
7.Have bends that are not crimped or flattened.
8.Have ferrous metal or polyolefin transition couplings connecting the ducts to anchorage system components. Ferrous metal transition couplings need not be galvanized.
9.Have an inside cross -sectional area of at least 2.5 times the net area of the prestressing steel for multistrand tendons.
10.Have an inside diameter of at least 1/2 inch larger than the diameter of the bar.
11.Have an outside diameter not exceeding 50 percent of the girder web width. Furnish all ducts or anchorage assemblies with pipes or other suitable connections for the injection of grout after prestressing.
50-1.02E Vents
Vent all ducts having a vertic al duct profile change of 6 inches or more. Vents must:
1.Be at least 1/2 -inch-diameter standard pipe or suitable plastic pipe.
2.Be connected to ducts using metallic or plastic structural fasteners. Plastic components must not react with the concrete or enhance corrosion of the prestressing steel and be free from water soluble chlorides.
3.Be mortar tight and taped as necessary.
4.Provide a means for injection of grout through the vents and for sealing the vents.
50-1.02F Permanent Grout Caps
Permanent grout caps for anchorage systems of post -tensioned tendons must:
1.Be glass -fiber-reinforced plastic with antioxidant additives. The environmental stress -cracking failure time must be at least 192 hours under ASTM D1 693, condition C.
2.Completely cover and seal the wedge plate or anchorage head and all exposed metal parts of the anchorage against the bearing plate using neoprene O -ring seals.
3.Have a grout vent at the top of the cap.
4.Be bolted to the anchorage w ith stainless steel fasteners complying with ASTM F593. All fastener components must be alloy 316.
5.Be pressure rated at or above 150 psi.
50-1.02G Debonding Sheathing
Sheathing for debonding prestressing strand must:
1.Be split or un -split flexible p olymer plastic tubing
2.Have a minimum wall thickness of 0.025 inch
3.Have an inside diameter exceeding the maximum outside diameter of the strand by 0.025 to 0.14 inch Split sheathing must overlap at least 3/8 inch. SECTION 50 PRESTRESSING CONCRETE Waterproofing tape used to seal the ends of the sheathing must be flexible adhesive tape. The sheathing and waterproof tape must not react with the concrete, coating, or steel.
50-1.02H Anchorage System
The anchorage system for post -tensioning must:
1.Be capable of holding the prestres sing steel at a force producing a stress of at least 95 percent of the specified ultimate tensile strength of the steel
2.Permanently secure the ends of the prestressing steel
3.Be equipped with permanent grout caps
50-1.03 Construction
50-1.03A Gener al
50-1.03A(1) General
If authorized, you may:
1.Apply a portion of the total prestressing force to a PC member before the member has obtained the concrete strength shown
2.Move the member after applying the portion of prestressing force Except for epo xy-coated strand, prestressing steel installed in members before placing and curing of the concrete must be continuously protected against rust or other results of corrosion until grouted. Protect the steel by using a corrosion inhibitor placed in the duct s or applied to the steel in the duct. After final fabrication of the strand, do not perform any electric welding on the prestressing steel. If electric welding is performed on or near members containing prestressing steel, attach the welding ground direct ly to the steel being welded.
50-1.03A(2) Epoxy -Coated Strand
Cover epoxy -coated strand with an opaque polyethylene sheeting or other suitable protective material to protect the strand from exposure to sunlight, salt spray, and weather. For stacked coils, drape the protective covering around the perimeter of the stack. The covering must be adequately secured and allow for air circulation around the strand to prevent condensation under the covering. Cut epoxy -coated strand using an abrasive saw. Patch all v isible damage to the epoxy coating caused by shipping, job site or casting site handling, installation, or cutting of ends under ASTM A882/A882M.
50-1.03A(3) Ducts
Accurately place prestressing ducts. Securely fasten the ducts in place to prevent movement of the ducts during concrete placement. After installation, cover the duct ends and vents to prevent water or debris from entering. Support ducts vertically and horizontally during concrete placement at a maximum spacing of 4 feet. If prestressing strand is installed using the push -through method, use guide caps at the front end of each strand to protect the duct from damage.
50-1.03A(4) Vents
Place vents at the following locations:
1.Anchorage areas at both ends of the tendon
2.Each high point
3.4 feet upstream and downstream of each crest of a high point
4.Each change in the cross section of duct SECTION 50 PRESTRESSING CONCRETE
50-1.03B Prestressing
50-1.03B(1) General
Tension the prestressing steel using hydraulic jacks. The force in the prestressing steel m ust be the value shown in the shop drawings. After seating, the maximum tensile stress in the prestressing steel must not exceed 75 percent of the minimum ultimate tensile strength shown.
50-1.03B(2) Post -Tensioned Members
50-1.03B(2)(a) General
If reque sted, for verification of the force in the prestressing steel, furnish the resources necessary to install and support the Department's testing equipment at the prestressing steel location and to remove the equipment after the testing is complete. Conduct t he tensioning process such that the force being applied and the elongation of the prestressing steel can be measured at all times. The maximum temporary tensile stress in the prestressing steel of post -tensioned members must not exceed 75 percent of the sp ecified minimum ultimate tensile strength of the prestressing steel. If steam curing is used for PC members, do not install prestressing steel for post -tensioning until the steam curing is completed. Do not tension the prestressing steel of post -tensioned members until (1) at least 10 days after the last concrete has been placed in the member and (2) the concrete has attained the compressive strength described. Distribute the prestressing force of post -tensioned bridge girders with an approximately equal qu antity in each girder and place the force symmetrically about the centerline of the structure. In slabs, distribute the prestressing force uniformly across the slab. Sequence the stressing of post -tensioned bridge girders such that no more than 1/2 of the prestressing force in any girder is applied before an equal force is applied in the adjacent girders. The maximum temporary force variation between girders must not exceed the prestressing force of the largest tendon used in all girders. Do not apply an ec centric force about the centerline of the structure that exceeds 1/6 of the total prestressing force at any time during the prestressing.
50-1.03B(2)(b) Losses
Reserved
50-1.03B(2)(c) Anchorages and Distribution
The ends of post -tensioned prestressing steel must be secured with a permanent type anchoring system. You may omit steel distribution plates or assemblies if you use an anchorage device of a type that is sufficiently large an d that is used in conjunction with a steel grillage embedded in the concrete that effectively distributes the compressive stresses to the concrete. If loop tendon anchorages are used, enclose the anchorages in ducts for their entire length. Where the end o f a post -tensioned assembly is not to be covered by concrete, recess the anchorage system such that the ends of the prestressing steel and all parts of the anchorage system are at least 2 inches inside of the end surface of the members. After post -tensioni ng, fill the recesses with concrete and finish flush. The concrete used to fill the recess must be the same as that used for the structure. The load from the anchorage system must be effectively distributed to the concrete such that:
1.Concrete bearing st ress directly underneath the plate or assembly does not exceed 3,300 psi
2.When the prestressing steel is tensioned to 95 percent of its specified ultimate tensile strength: 2.1. Bending stress in the plate material or assembly material does not exceed th e yield point of the material SECTION 50 PRESTRESSING CONCRETE 2.2. No visible distortion is evident in the anchorage plate
50-1.03B(2)(d) Bonding and Grouting
50-1.03B(2)(d)(i) General
Bond the post -tensioned prestressing steel to the concrete by completely filling the entire void spa ce between the duct and the prestressing steel with grout. Ducts, vents, and grout caps must be clean and free from water and deleterious materials that would impair bonding of the grout or interfere with grouting procedures. Compressed air used for cleani ng must be clean, dry, and free from oil or contaminants. Prevent the leakage of grout through the anchorage assembly by positive mechanical means. Before starting daily grouting activities, drain the pump system to remove any water from the piping system. Break down and thoroughly clean the pump and piping system after each grouting session. After completing duct grouting activities:
1.Abrasive blast clean and expose the aggregate of concrete surfaces where concrete is to be placed to cover and encase the anchorage assemblies
2.Remove the ends of vents 1 inch below the roadway surface
50-1.03B(2)(d)(ii) Grouting Equipment
Grouting equipment must be:
1.Capable of grouting at a pressure of at least 100 psi
2.Equipped with a pressure gauge having a full -scale reading of not more than 300 psi
3.Able to continuously grout the longest tendon on the project in less than 20 minutes Grout must pass through a screen with clear openings of 1/16 inch or less before entering the pump. Fit grout injection pipes, ejection pipes, and vents with positive mechanical shutoff valves capable of withstanding the pumping pressures. If authorized, you may substitute mechanical valves with suitable alternatives after demonstrating their effectiveness. Provide a standb y grout mixer and pump.
50-1.03B(2)(d)(iii) Mixing and Proportioning
Proportion solids by weight to an accuracy of 2 percent. Proportion liquids by weight or volume to an accuracy of 1 percent. Mix the grout as follows:
1.Add water to the mixer followed by the other ingredients.
2.Mix the grout with mechanical mixing equipment that produces a uniform and thoroughly mixed grout without an excessive temperature increase or loss of properties of the mixture.
3.Do not exceed 5 gal of water per 94 lb of ceme nt or the quantity of water in the manufacturer's instructions, whichever is less.
4.Agitate the grout continuously until the grout is pumped. Do not add water after the initial mixing.
50-1.03B(2)(d)(iv) Placing
Pump grout into the duct within 30 minut es of the 1st addition of the mix components. Inject grout from the lowest point of the duct in an uphill direction in one continuous activity maintaining a one-way flow of the grout. You may inject from the lowest anchorage if complete filling is ensured. Before injecting grout, open all vents. Pump the grout at a rate of 16 to 50 feet of duct per minute. SECTION 50 PRESTRESSING CONCRETE Conduct grouting at a pressure range of 10 to 50 psi measured at the grout inlet. Do not exceed maximum pumping pressure of 150 psi at the grout inlet. As grout is injected, continuously discharge grout from the vent to be closed. Do not close any vent until free water, visible slugs of grout and entrapped air have been ejected, and the consistency of the grout flowing from the vent is equivalent to the in jected grout. Close the vents in sequence in the direction of flow starting with the closest vent. Before closing the final vent at the grout cap, discharge at least 2 gal of grout into a clean receptacle. After closing all vents, bleed all high point vent s. Lock a pressure of 5 psi into the duct by closing the grout inlet valve.
50-1.03B(2)(d)(v) Weather Conditions
If hot weather conditions will contribute to quick stiffening of the grout, cool the grout by authorized methods as necessary to prevent block ages during pumping activities. If freezing weather conditions are anticipated during and after the placement of grout, provide adequate means to protect the grout in the ducts from damage by freezing.
50-1.03B(2)(d)(vi) Curing
During grouting and for a p eriod of 24 hours after grouting, eliminate vibration from Contractor -controlled sources within 100 feet of the frame in which grouting is taking place, including from moving vehicles, jackhammers, large compressors or generators, pile driving activities, soil compaction, and falsework removal. Do not vary loads on the span. For PC concrete members, do not move or disturb the members after grouting for 24 hours. If the ambient temperature drops below 50 degrees F, do not move or disturb the members for 48 hours. Do not remove or open valves until grout has set and cured for at least 24 hours.
50-1.03B(2)(d)(vii) Grout Storage
Store grout in a dry environment.
50-1.03B(2)(d)(viii) Blockages
If the grouting pressure reaches 150 psi, close the inlet and pump the grout at the adjacent vent that has just been or is ready to be closed as long as a one -way flow is maintained. Do not pump grout into a succeeding outlet from which grout has not yet flowed. When complete grouting of the tendon cannot be achieved by the steps specified, stop the grouting.
50-1.03B(2)(d)(ix) Secondary Grouting
Perform secondary grouting by vacuum grouting. The vacuum -grouting process must be able to determine the size of the void and measure the volume of grout filling the void. Vacuu m grouting equipment must consist of:
1.Volumeter for the measurement of void volume
2.Vacuum pump with a capacity of at least 10 cfm and equipped with a flow meter capable of measuring the amount of grout being injected
50-1.03B(2)(d)(x) Vertical Tend on Grouting
Provide a standpipe at the upper end of the tendon to collect bleed water and allow it to be removed from the grout. The standpipe must be large enough to prevent the grout elevation from dropping below the highest point of the upper anchorage device. If the grout level drops to the highest point of the upper anchorage device, immediately add grout to the standpipe. Remove the standpipe after the grout has hardened. For vertical tendons in excess of 100 feet high or if grouting pressure exceeds 145 psi, inject grout at a higher vent from which grout has already flowed to maintain one -way flow. SECTION 50 PRESTRESSING CONCRETE
50-1.03B(3) Pretensioned Members
50-1.03B(3)(a) General
Anchor the prestressing steel at stresses that will result in the ultimate retention of jacking f orces at least equal to those shown. If prestressing steel for pretensioning is placed in the stressing bed and is to be exposed to the elements for more than 36 hours before encasing in concrete, protect the steel from contamination and corrosion using au thorized measures. Do not cut or release prestressing steel in pretensioned members until the concrete in the member has attained a compressive strength of at least the value shown or 4,000 psi, whichever is greater. If epoxy - coated strand is used, do not cut or release the steel until the temperature of the concrete surrounding the strand is less than 150 degrees F and falling. If requested, check individually -tensioned strands using authorized methods and equipment for loss of prestress not more than 48 h ours before placing concrete for the members. Strands showing a loss of prestress of more than 3 percent must be retensioned to the original computed jacking force. If prestressing steel in pretensioned members is tensioned at a temperature appreciably low er than the estimated temperature of the concrete and the prestressing steel at the time of initial set of the concrete, the calculated elongation of the prestressing steel must be increased to compensate for the loss in stress. The maximum temporary tensi le stress in the prestressing steel of pretensioned members must not exceed 80 percent of the specified minimum ultimate tensile strength of the prestressing steel. Cut and release the prestressing steel in pretensioned members in such an order that lateral eccentricity of the prestress force is a minimum. Cut off pretensioned prestressing steel flush with the end of the member. After cutting the steel, clean and paint the exposed ends of the steel and a 1 -inch strip of adjoining concrete as follows:
1.Wire brush or abrasive blast clean to remove all dirt and residue on the metal and concrete surfaces.
2.Immediately after cleaning, apply 1 coat of organic zinc -rich primer to the surfaces except apply 2 coats to surfaces that will not be covered by co ncrete or mortar. Do not use aerosol cans. Mix the paint thoroughly when applying and work into any voids in the prestressing steel.
50-1.03B(3)(b) Debonding Prestressing Strands
Where debond prestressing strands are shown, debond the strands by encasing the strands in plastic sheathing along the entire length shown and sealing the ends of the sheathing with waterproof tape. Distribute the debonded strands symmetrically about the vertical centerline of the girder. The debonded lengths of pairs of strands must be equal. Do not end debonding at any one cross section of the member for more than 40 percent of the debonded strands or 4 strands, whichever is greater. Thoroughly seal the ends with waterproof tape to prevent the intrusion of water or cement paste before placing the concrete.
50-1.04 Payment
Not Used
Source: California Standard Specifications, 2024 Edition. Pages 751–762 of 1,372.