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Post-Tensioning Manual
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This Chapter addresses grouting topics generally in the sequence in which operations occur on site. Beginning with a grouting plan, this guidance is provided with regard to equipment, on-site tests of production grout, injection of horizontal and vertical tendons, post-grouting inspection, vacuum grouting to fill any voids and grouting reports to accompany tendon stressing reports. An overview of a few grouting problems and their solutions is provided. Finally, a set of examples for grouting procedures of various types of tendons is offered for information and guidance.
A Grouting Plan should be developed and implemented for construction. In general, project responsibilities regarding the Grouting Plan are:
A Grouting Plan typically addresses the following:
* Note: Provisions for grouting of a group of tendons is only necessary in the event of potential cross-over flow between internal tendons at a defect, splice or joint. Group grouting may be needed for efficiency and quality control of operations in some cases. However, normally, internal draped tendons in a cast-in-place superstructure or spliced I-girder are usually grouted one at a time. Prior to group grouting, it is essential to make sure that there is sufficient supply of materials and back-up equipment in case of breakdown. Simultaneous grouting of a group of internal tendons should combine operations for all tendons in that group, recognizing that injection will be done at several injection ports, in sequence or in parallel, with multiple outlets requiring closing in sequence after evacuation of grout of the required consistency.
For information and guidance, examples of procedures to be addressed in a grouting plan or shown on shop drawings for grouting various types of tendons refer to 4.5 below.
All materials for grouting should be qualified by appropriate laboratory testing or certification prior to use in the project (Chapter 2).
Grouting should proceed as soon as possible after installation and stressing of the tendons. Depending upon environmental conditions, temporary protection may be necessary and temporary protection of the ends of the strands will be necessary. For example, grout inlets and outlets may be closed drains opened and ends of tendons fitted with temporary caps.
Prior to grouting, tendon ducts, grout inlets and outlets, and anchors, should be examined and debris and water should be removed to avoid blockages or dilution and grout.
Prior to installing post-tensioning (strand) tendons, it is recommended that ducts be proven for clearance and absence of blockages by passing through a suitably sized torpedo. When proving is done depends upon the particular type of construction - see Chapter 3.
Connections from grout hose to inlets and outlets should be airtight and free from dirt. Inlets and outlets should be provided with positive shut-offs capable of withstanding the maximum grouting pressure. The required grouting pressure should take into account the pressure head for vertical changes in profile.
Appropriate repairs should be made to any damaged inlets and outlets prior to grouting.
Prior to grouting, it is recommended that the post-tensioning ducts be tested using compressed air to verify if any duct connections, joints or fittings require sealing or repair. Compressed air should be clean, dry and free from any oil or contaminants.
A possible test would be to consider the duct system satisfactory if, after pressurizing to an initial pressure (e.g. 0.7MPa (100 psi)) the pressure loss over five minutes is less than 10% (e.g. 0.07MPa (10psi).
Depending upon the type of construction, this test could be run:
Normally, only one such test would be made as appropriate for the project.
In any case, it would be necessary to temporarily seal the ends of ducts. This could be done with anchor grout caps. Testing to 0.7MPa (100 psi) before concrete placement (1) would be a severe test of a duct system. A lower pressure may be appropriate, according to recommendations of the manufacturer of the ducts and fittings. Testing of a girder before shipping from the yard (2) is suitable only for tendons that begin and end in within the girder and need no splices on site. If a girder has to be spliced to others, then the test should be made on site for the fully continuous duct (3). Longitudinal ducts in precast segments should be tested after erection (4). External tendons can only be tested on site after fabrication of the duct system (4). Temporarily sealing a tendon with long strand tails projecting from anchors is very difficult and is not recommended (5).
Leaks should be sealed in an appropriate manner - such as tightening or re-seating connections and fittings or using a suitable sealant approved by the manufacturer of the PT duct system and acceptable to the Engineer. Leaks at match-cast joints could be sealed by epoxy injection or other acceptable means. In no case should duct tape be used as a seal; however, it may be used to provide temporary support or restraint.
Mixer
The mixer should be capable of continuous mechanical mixing to produce a homogeneous, stable, grout free of lumps or un-dispersed material that it supplies continuously to the pump.
Mixers are of two main types: vane (or paddle) mixers with a speed of about 1,000 rpm or high-speed shear (colloidal) mixers with a speed of about 1,500 rpm. The high speed mixer distributes cement more uniformly, improves bleed characteristics and minimizes cement lumps.
A high-speed mixer is recommended for pre-bagged grouts.
Storage Hopper and Screen
Most grouting equipment has a mixing (blending) tank which discharges through a screen into a storage hopper or tank mounted over the grout pump (Figure 4.1). The storage hopper should also have a mixing rotor to keep the grout agitated for continuous use and should be kept partially full at all times. The screen should contain openings of 3mm (1/8in) maximum size to screen lumps from the mix. The screen should be inspected periodically. If lumps of cement remain on the screen, then the mix is not suitable.
 Figure 4.1 - Grout Mixing And Pumping Equipment |
For thixotropic grouts, two identical mixing/storage tanks are needed that alternate between blending and storage, so that a new mix can be started while that in storage is pumped. A high-speed (colloidal) mixer is needed for each tank. For thixotropic grouts, the screen between the tank and pump may have openings of 5mm (3/16 in). The grout pump should have precise pressure control and be fed from each holding tank in turn.
Grout Pump
Grout pumps should be of the positive displacement type and able to maintain an outlet pressure of at least 1MPa (145psi) with little variation. The pump, hoses and connections should be able to maintain pressure on completely grouted ducts. A shut-off valve should be installed in the line so that it can be closed off under pressure, as necessary (Figure 4.1).
Pumps with a variable output capability are adaptable to delivery demands of different duct diameters or to group grouting. However, the grouting pressure should be limited to help prevent blow-outs in the equipment, protect operators, prevent excessive segregation or bleed and prevent possible splitting of concrete by over-pressurizing the ducts.
Pumps should have a system for re-circulating the grout when pumping is not in progress and should have seals to prevent oil, air or other foreign substance entering the grout or prevent loss of grout or water. At the pump, grout piping should incorporate a sampling tee with a stop valve. The number of bends and changes in size should be minimized.
Pressure Gauge
A pressure gage with a full scale reading of not more than 2MPa (300 psi) should be attached between the pump outlet and duct inlet. For short lengths (say less than about 10M (30 feet) of grout hose, the gauge may be placed near the pump - for long lengths, at the inlet. For hose lengths over 30M (100 ft), a gage near the pump and one at the inlet may help identify whether sudden pressure build-ups are in the hoses or the ducts.
Hoses
The diameter and pressure rating of hoses should be compatible with the pump and anticipated maximum pressures. All hoses should be firmly connected to pump outlets, pipes and inlets. It is recommended that grout hoses be at least 20mm (¾ in) inside diameter for lengths up to about 30M (100 ft) and that a reduction in size at connectors be avoided. Also, narrow openings should be avoided. Both can lead to pressure build-up and possible risk of blockage.
For sampling and testing daily production of fluid grout the following equipment should be available:
Specification requirements for field testing may vary by project and not all of the listed equipment may be necessary.
When project contract documents require vacuum grouting, equipment should be provided at the job-site concurrently with all pressure grouting operations (Figure 4.2). Vacuum grouting equipment should be of the volumetric measuring type with the ability to measure the volume of a void and supply a measured volume of grout to fill that void.
Provisions for vacuum grouting are usually not necessary for projects containing only transverse (deck slab) tendons with a length of less than 30M (100 ft).
Figure 4.2 -Vacuum Grouting Equipment |
A standby grout mixer and pump should be available during grouting operations.
An air-compressor is needed for a supply of oil-free compressed air for checking ducts for integrity and leaks or help blow out any water. Lengths of air hose should be sufficient to insert and reach along ducts to blow debris or water out as necessary.
Adequate flushing equipment and potable water supply should be available in the event it is necessary to completely remove grout from a duct. However, although flushing has been required in the past, it is no longer recommended. As remedial action, removal of grout should be done only with the concurrence of the Engineer when necessary. Vacuum grouting is a preferred method for grouting partially filled ducts in most situations.
All grouting equipment should be thoroughly cleaned after grouting.
The proportions in the mix should be based upon the mix approved prior to grouting is begun whether for a mix to be blended on site or for a pre-qualified, pre-bagged grout (Chapter 4). Dry powder and pre-bagged grout materials should be batched by weight to an accuracy of +2%. Water and liquid admixtures may be batched by weight or volume to an accuracy of +1%. Any water content in any liquid admixtures should be counted toward the quantity of water.
The materials should be mixed to produce a homogeneous grout without excessive temperature rise or loss of fluid properties (flow cone). The mix should be continuously agitated until it is pumped. Water must not be added to increase fluidity if it has decreased by delayed use of the grout. Typically, the mix time for grout should be in accordance with the qualification trials and generally not more than 4 minutes for a vane mixer or 2 minutes for a high-speed shear mixer.
Unless otherwise specified by the manufacturer, the constituents may be added as follows:
Condensed, dry compacted silica fume should not be added to a mix as it agglomerates and does not blend well, leading to a poor mix.
In order to ensure the correct consistency and density of daily production grout, fluidity and density should be within acceptable limits according to the following requirements. Additional water must never be added to a mix to meet fluidity test requirements and surplus, discharged and tested grout should be properly discarded.
It is recommended that daily production grout be monitored before and after injection according to the tests in the following Sections.
For normal (non-thixotropic grouts) it is recommended that at the beginning of each day's production grouting, either a wick induced bleed test (Figure 2.2) be performed on the mix for that day or a Schupack Pressure Bleed Test (Figure 2.3).
Because the wick induced bleed test takes at least three hours, discretion must be exercised to avoid unnecessary delay when starting new (daily) grouting operations. Consequently, it is suggested that this test be performed regularly on currently stored materials intended for use in the near term so that acceptable results can be routinely maintained to facilitate continued production grouting.
As an alternative, the Schupack Pressure Bleed Test should require less time and should be suitable for most manufactured (pre-bagged) grouts. Reference should be made to the manufacturer. Information on the test may be found in Appendix C of the PTI "Specification for Grouting of Post-Tensioned Structures", (latest edition).
The consistency of non-thixotropic grouts should be tested according to ASTM C939 "Standard Test Method for Flow of Grout". The efflux time should be between 11 and 30 seconds immediately after mixing. After allowing the grout to stand for 30 minutes without further agitation, the efflux time should be less than 30 seconds.
For thixotropic grouts, the modified ASTM C939 test should be used where the flow cone is filled to the top, i.e. above the standard level, and the time to fill a one-liter container is measured. The efflux time should be between 5 and 30 seconds immediately after mixing. After allowing the grout to stand for 30 minutes without agitation and then remixing for 30 seconds, the efflux time should be less than 30 seconds.
[Note: The modified flow-cone may not be suitable for some types of thixotropic grout. It is understood to give different results for different grout manufacturers. An alternative test that measures the spread diameter of a collapsed cylinder of grout is under consideration by industry. It was developed for off-shore projects in Norway and Sweden.]
The density of a thixotropic grout may be sampled and checked at the inlet using the "mud-balance" test of the American Petroleum Institute (API) (ASTM C185).
Immediately after a uniform flow of uncontaminated grout is obtained at the last outlet, a fluidity test should be performed on the grout discharged from the outlet using the standard ASTM C 939 flow cone test (Figure 2.1). The efflux time should not be less than that measured at the pump / inlet. If the efflux time is too short, then more grout should be discharged and test again. This should be repeated until the grout has an acceptable uniform consistency: i.e. a minimum acceptable efflux time of 11 seconds providing that the maximum efflux time is less than 30 seconds.
Alternatively, the fluidity and density of the discharged grout may be checked using the Wet Density Method for field samples (ASTM C 138). The measured density should fall within acceptable values.
Immediately after a uniform flow of uncontaminated grout is obtained at the last outlet, a fluidity test should be performed on the grout discharged from the outlet using the modified ASTM C 939 flow cone test (Figure 2.1). The maximum efflux time should be less than 30 seconds. Alternatively, the density of the discharge grout may be checked using the API mud-balance. [Note: This may be a more suitable method for certain commercial, thixotropic and highly fluid grouts with very short efflux times of a few seconds. The density at the outlet should not be less than that measured at the pump / inlet. ]
Prior to grouting, all grout outlets should be opened and checked to ensure they are free and clear of any debris and water. Grouting should proceed according to an approved Grouting Plan (4.1).
Grout pumping methods should ensure complete filling of the ducts and encasement of post-tensioning steel. Grout should be pumped in a continuous operation and be ejected from the first, and subsequent outlets, until all visible slugs of water or entrapped air have been removed prior to closing each outlet in turn. At each outlet and final grout cap, pumping should continue until the consistency of the discharged grout is equivalent to that being injected at the inlet. At least 7.5 liters (2 gallons) of good, consistent, quality grout should be discharged through the final anchor and cap before closing them.
For normal operations grout should be injected at a pressure of less than 0.52 MPa (75psi) at the inlet. Pumping pressures should not exceed 1MPa (145 psi).
Although higher pressures than this might be sustained by internal ducts of HDPE or steel or external ducts of steel pipe, higher pressures are not recommended for grouting. Sometimes an initial temporary higher pressure may be needed to mobilize a thixotropic grout, but, once flowing, pumping pressures should be the same as for normal grouts.
Unless otherwise approved by the Engineer, grout should be injected at a rate of 16 feet [5M] to 50 feet [15M] of duct per minute under normal pumping pressures.
For information and guidance, refer to examples of recommended locations of grout inlets and outlets in 4.5 below.
For generally horizontal or draped tendons, grouting should proceed from an inlet at the lowest point of the tendon profile. This may be at an initial anchor or at an intermediate low point in the tendon profile.
Grout should be injected steadily and consistently at the designated inlet. When grout flow through the first intermediate outlet is of a consistency of that being injected and is free of all slugs of air or water, the first outlet may be closed. Injection should continue until the same flow is obtained from the next outlet in turn, whereupon it should be closed. Grouting injection should continue until all intermediate outlets have been closed and grout flows from the last anchor outlet. Grouting should continue until at least 2 gallons of grout have been discharged through the last anchor and its grout cap in order to ensure that the anchor and cap are fully filled.
If during injection, the actual grouting pressure exceeds the maximum allowed at the inlet, then the inlet should be closed and the grout pumped in at the next available vent, providing that grout has already flowed from that vent - so that one-way grout flow is maintained.
For further information and guidance, see 4.5 below.
Checking a grouted tendon should primarily be in accordance with AASHTO LRFD Construction Specifications. Reference may also be made to the PTI Grouting Specification.
The following alternative method has been adopted by FDOT and is included for information only:
"After all outlets have been bled and closed, the pressure should be raised to approximately 0.52MPa (75psi) and held for two minutes while the tendon is examined for any evidence of leaks and avoid the unintended loss of grout. A drop in pressure during the two minute period would indicate leaks. In order to check pressure loss, a pressure gage should be placed in the line between the exit valve at the pump, which is closed off under pressure, and the tendon inlet, which is left open. Alternatively, a pressure gage could be installed at any convenient outlet. Leaks should be sealed using methods approved by the Engineer and the pressure test repeated."
Checking a grouted tendon should primarily be in accordance with AASHTO LRFD Construction Specifications. Reference may also be made to the PTI Grouting Specification.
The following alternative method has been adopted by FDOT and is included for information only:
"When there are no leaks or when they have been properly sealed, the 0.52MPa (75 psi) pressure should be released to 0.03MPa (5psi) for ten minutes to allow any entrapped air to flow to high points. After ten minutes, the grouting pressure should be increased as necessary in order to release any entrapped air or water and discharge grout at each of the tendon high point outlets in turn. The system should then be locked off at a pressure of 0.21MPa (30psi)."
When complete grouting by the above methods cannot be achieved, then the grouting operation should be terminated. After 24 hours (i.e. after the grout has set), the tendon should be inspected, if necessary, by drilling and using an endoscope or probe (4.3.8). Voids should be measured and filled using volumetric measuring vacuum grouting or other methods approved by the Engineer. The disposition of a blocked tendon will be a project specific determination.
This Section addresses the grouting of conventional post-tensioning systems in vertical applications. Grouting of Cable-Stays is not addressed in this document.
Grout for relatively short vertical tendons such as vertical PT bars in webs or diaphragms of a superstructure may be the same as that used in longitudinal tendons. However, for applications in tall piers or towers, a grout with very low bleed characteristics is essential and it may be necessary to inject the grout in intermediate lifts.
For vertical tendons, a standpipe should be provided at each upper end to store bleed water and grout and to maintain the grout level above the level of the prestressing anchorage and grout cap. The pipe should be designed and installed so to ensure that bleed will at no time cause the level of the grout to drop below a point established on the standpipe at least 0.3M (1 foot) above the highest point of the anchorage and cap and so that all bleed water rises into the standpipe and does not accumulate in the anchorage and cap. Clear plastic pipe is suitable for a standpipe.
Grout should be injected at the lowest point and discharged through the standpipe. The fluidity and density of the grout before and after injection should be checked. The standpipe should be filled so that the level does not drop below the anchorage and cap. If, after ceasing active pumping, the level drops below the level established on the standpipe, grout should be immediately added to the standpipe.
For vertical tendons in excess of 30M (100 ft) high, or if the grouting pressure exceeds 1MPa (145 psi), then grout should be injected at higher outlets from which grout has already flowed, so that one-way flow of grout is maintained. Grout should be allowed to flow from an outlet until all air and water has been purged prior to using that outlet for injection
When complete grouting by the above methods cannot be achieved, then the grouting operation should be terminated. After 24 hours (i.e. after the grout has set), the standpipe should be removed and the anchorage and cap examined to make sure that they are completely full; if necessary by drilling and using an endoscope or probe (4.3.8). Voids should be measured and filled using volumetric measuring vacuum grouting.
It is preferred that partially complete grout not be flushed out with water - this is not only difficult but it is impossible to remove all excess water. This will lead to excessive bleed upon re-grouting - especially if flushing is only partially successful. Grout should only be flushed out when given the approval of the Engineer. In extreme cases, removal of grout may require high pressure hydro-demolition. If removal in this fashion is required, all the grout and tendon should be removed.
It is recommended that all inspections be performed in the presence of the Inspector (CEI).
Valves, caps and pipes at inlets and outlets should not be removed or opened until the grout has set and cured for a minimum of 24 hours after grouting. However, within 72 hours of grouting, all inlets and outlets should be opened to facilitate inspection. Inspection of the grout should be performed within one hour of opening.
All inlets and outlets should be inspected to ensure complete filling with grout. All inlets and outlets should be capped and sealed (below) within four (4) hours of the completion of inspection, completion of vacuum grouting or removal of non-inspected inlets and outlets.
Vacuum-grouting, when necessary, should be completed within 72 hours of inspection.
At anchorages, sometimes, depending upon geometry, it is possible that an inlet or outlet may appear to be filled, but a void may exist inside the anchor trumpet or duct. Consequently, the grout inlet or outlet at the anchorage should be drilled just sufficient to penetrate the inner surface of the trumpet or duct. Drilling equipment should have an automatic shut-off when steel is encountered so that the tendon is not damaged. Grout caps over anchorages should not be drilled unless voids are suspected by sounding.
Grout outlets (pipes) or inlets in the duct between anchorages should be installed in such a way that they can be drilled just sufficient to penetrate the inner surface of the duct and then be inspected in the same way as at an anchorage.
When a void is found, it should be examined to determine its extent. All voids should be completely filled using the volumetric measuring vacuum grouting process.
For longitudinal superstructure tendons, the following frequency of inspection is suggested:
For relatively short vertical tendons in superstructure webs or diaphragms, the top (anchor) outlet of each tendon should be inspected. All inlets and outlets should be inspected for vertical tendons in substructures.
Drilled inspection holes that do not encounter voids should be filled with an approved cementitious grout or epoxy using an injection tube extending to the bottom of the drilled hole.
In general, when any tendon grouting operations have been prematurely terminated before the ducts could be completely filled with grout, ducts should be drilled into and explored for voided areas using an endoscope in order to determine the extent and volume of voids. Grout inlets and outlets should be installed and the voids filled using volumetric measuring vacuum grouting equipment.
Vacuum grouting is a method of withdrawing air from voids to create as complete a vacuum as possible and then using this vacuum to draw grout in to fill the voids. The efficiency of the method depends significantly upon the degree to which all leaks can be effectively sealed. Since it is impossible to create a complete vacuum, most operations are done under a partial vacuum. Also, grout is normally injected under pressure - so the method may be referred to as "vacuum assisted pressure grouting".
Leaks at anchorages, grout inlets or outlets can usually be sealed by tightening grout caps. However, it is difficult to seal a leak somewhere along the length of a tendon at a breach in the duct wall, at a poorly made duct splice or if there is cross-communication between ducts through incompletely sealed epoxy joints or defects in concrete. A positive air pressure test should reveal the presence of such leaks. As far as possible, such leaks should be sealed with epoxy or epoxy injection.
Vacuum grouting equipment should include a device for measuring the volume of the voids so that the amount of grout injected can be checked against that anticipated to give some assurance that the voids have been filled. Most devices function on the basis of measuring pressure changes when voids are connected to an evacuated pressurized vessel of known volume or vice-versa.
If a void has a constriction, say somewhere along a tendon, it may not be possible to inject grout beyond it. Consequently, the volume of vacuum injected grout will be less than the measured volume. An attempt should then be made to complete the vacuum grouting from the other end, if possible. If the location of a constriction is known, or if a void exists somewhere in the center of the tendon and dos not connect with the ends, it may be possible to carefully drill into the duct and install intermediate grout inlets and outlets for vacuum grouting.
When vacuum grouting is necessary, it is should be completed within 72 hours of the inspection of the inlets and outlets by drilling and probing. Caps and seals should be completed within four (4) hours of the completion of vacuum grouting.
Unless otherwise approved by the Engineer, grout for vacuum grouting should be the same as that used to grout the tendons.
Mixer
Because vacuum grouting usually involves relatively small quantities of grout, the grout mixer and storage hopper need not necessarily be the same as that for main grouting operations. However, mixer must be capable of thoroughly mixing the constituents to meet fluidity and other requirements for normal or thixotropic grouts.
Volumeter
A device referred to as a "volumeter" is needed to measure the volume of the grout voids. This device may use either a vacuum or air pressure method. It may be an analog or digital device.
Grout Hopper and Pump
A grout pump should be a positive displacement (piston and cylinder) device with a suitable sized hopper and attachments for hoses.
Hoses and Valves
Hoses and valves are needed to connect an air compressor or vacuum pump with the volumeter, grout pump and duct inlet. Valves should be installed as necessary to facilitate evacuation of the air from the voids, measurement of the volume of void and switching over to inject grout under pressure.
Vacuum grouting generally involves the following activities:
It is recommended that threaded plastic caps be used to seal all grout inlet and outlet pipes and that threaded plugs be installed in anchorages and grout caps once the grout pipe and shut-off valve have been removed (Figure 2.9).
Where an inlet or outlet is permanently recessed within the concrete, provision should be made to accommodate the threaded plastic cap at clear depth of at least 25mm (1in) by means of a formed recess. The recess should be cleaned and completely filled with an approved epoxy material. The surface of the recess should be prepared to receive the epoxy material in accordance with the recommendations of the manufacturer of the epoxy (Appendix D).
After grouting, all post-tensioning anchorages should be properly prepared and protected as necessary. For further information, refer to Appendix D.
A report on tendon grouting, inspection, vacuum grouting and sealing should be provided from the Contractor to the Engineer within 72 hours of the completion of sealing. The tendon grouting report should include, but need not necessarily be limited to:
The "Grouting Report" should be coordinated with the "Stressing Report".
If there is a breakdown, then use the available standby equipment. Standby equipment should be periodically checked to make sure it is in working order. Standby equipment may be a second set of production grouting equipment in operation nearby. In any event, standby equipment should be mobilized as soon as possible.
Standby equipment should be brought into operation within 15 to 30 minutes or else grout may begin to solidify and it will be too difficult to mobilize the grout, especially on long tendons.
If standby equipment cannot be brought into operation, then the grouting should be terminated.
The grout should be inspected (4.3.8) and completed using vacuum grouting (4.3.9) or other approved methods and procedures proposed by the Contractor and approved by the Inspector (CEI).
If it requires excessive pressure to inject grout, there may be a blockage. Excessive pressure would be any pressure about 50% more than the limiting pressure in 4.3.5.2. In no circumstances should attempts be made to force grout through. Excessive pressure can lead to failure of ducts or cracking of concrete, depending upon circumstances and details.
If grout cannot be injected at an intermediate outlet from which it has already flowed, grouting should cease. The grout should be inspected (4.3.8) and completed using vacuum grouting (4.3.9) or other approved methods and procedures proposed by the Contractor and approved by the Inspector (CEI) (See also 4.3.6.2 and 4.3.7.3).
It is preferred that flushing of incomplete grout not be used (4.3.6.5 and 4.3.7.4) unless it is unavoidable under some very special circumstance - in which case it should only be done with the approval of the Inspector (CEI).
The risk of cross-grouting should be detected by the duct pressure test (4.3.1.3) and action taken to accommodate grouting of the tendons as a group (see requirements for the Grouting Plan (4.1).
If, however, cross grouting is discovered only during production grouting, then if the other affected tendons have already been satisfactorily stressed, grouting should continue until all tendons affected by cross-grouting have been fully grouted. If cross grouting is into empty ducts or ducts containing tendons that have not yet been stressed, then grouting should stop and the affected ducts or tendons should be flushed. After the incomplete grout has set in the leaking tendon, leaks should be sealed using appropriate and approved techniques (e.g. epoxy injection). Grouting should be inspected (4.3.8) and completed using vacuum grouting (4.3.9).
Prior to grouting, if the flow-cone time exceeds the allowable limits, perform another test. If the flow time still exceeds allowable limits, check the source, date, storage and mixing of grout materials.
Do not add water or any high-range water reducer to improve fluidity. If necessary, abandon the batch and begin again with new material.
The following are offered for guidance. This is not an exhaustive set of examples for all conceivable circumstances and should be considered only for information and guidance.
 Figure 4.3 - Grouting details for a 2-span spliced girder duct system |
 Figure 4.4 - Grouting details for a 4-span spliced girder duct system |
 Figure 4.5 -Grouting details for a 3-span, drop-in and spliced girder duct system |
This example applies to any type of structure cast-in-place on falsework such as boxes, solid slabs and voided slabs.
 Figure 4.6 - Grouting details for cellular box, voided or solid slab duct system |
For a typical cantilever tendon, where the cantilever is on a rising longitudinal gradient, the following procedure would. It would also apply to a similar top slab continuity tendon.
 Figure 4.7 - Grouting of cantilever (at top continuity) tendons |
 Figure 4.8 - Grouting bottom continuity tendons in variable depth box girders |
Figure 4.9 shows a typical external tendon in the end span of a span-by-span segmental bridge.
 Figure 4.8 - Grouting details for end span, external tendon |
Depending upon the details at the pier segments, the tendon may exit horizontally or may curve over and head down to the anchor as shown in Figure 4.10. This requires two different arrangements for the grout outlet vents.
 Figure 4.10 - Grouting vent locations at pier segments in span-by-span bridges |
External tendons typically run along the top of the bottom slab with a small clearance. When it is necessary to provide a drain as well as a grout inlet at the low point of the profile, then the grout tube connections should be located so as to allow the duct to drain. A possible concept is illustrated in Figure 4.11.
 Figure 4.11 - Possible grout and drainage connections for bottom external tendons |
 Figure 4.12 - Grouting details for lateral tendons in hammerhead piercap |
Vertical post-tensioning tendons in a pier are illustrated in Figure 4.13.Intermediate grout inlets and outlets are necessary at intervals of no more than approximately 6M (20 ft). This is to facilitate proper filling and, if necessary, staged injection at intervals.
 Figure 4.13 - Grouting and anchor details for vertical tendons in piers |
 Figure 4.14 - Grouting details details and anchor protection for vertical and lateral tendons in C-pier |
