Lean%20Construction

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(No Transcript)
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By Dr. Attaullah ShahSwedish College of
Engineering and Technology Wah Cantt.

• CE-407
• Lec-01
• Structural Engineering

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Course Outline

• Prestressed concrete.
• Prestressed VS reinforced concrete.
• Types of prestressing.
• Losses in prestressing.
• Analysis and design of simple prestressed
  concrete members.
• Introduction to various prestressing systems.
• Bridge Engineering
• Types of bridges. Site selection. .
• Bridge loadings. Load distribution on bridge
  deck.
• Introduction to design of deck for a simple
  concrete bridge.

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• Advanced Structural Analysis.
• Definition of matrices and determinants.
• Stiffness method.
• Truss element, Beam clement, Plantation of
  stiffness sub matrices of multiple ended
• members.
• Flexibility method.
• Introduction to structural dynamics.

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Assignment No.1

• This is a group presentation assignments which
  will be required to be presented in next class
• Group 1 Define pre-stressing in concrete, the
  rationale and philosophy, types
• Group 2 Explain application of the pre-stressed
  concrete in modern structures.
• Grooup-3 Write a detailed note on the use of
  pre-stressed concrete in Pakistan with examples
  of real life.

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PRESTENSIONING POST- TENSIONING

• METHODS OF PRESTRESSING IN CONCRETE

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What is a pre-stressed concrete

• Prestressed concrete is a particular form of
  reinforced concrete.
• Prestressing involves the application of an
  initial compressive load on a structure to reduce
  or eliminate the internal tensile forces and
  thereby control or eliminate cracking.
• With cracking reduced or eliminated, a
  prestressed section is considerably stiffer than
  the equivalent (usually cracked) reinforced
  section.
• Prestressing may also impose internal forces
  which are of opposite sign to the external loads
  and may therefore significantly reduce or even
  eliminate deflection.

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PRESTRESSED CONCRETE

• PRINCIPLE Using high tensile strength steel
  alloys producing permanent pre-compression in
  areas subjected to Tension.
• A portion of tensile stress is counteracted
  thereby reducing the cross-sectional area of the
  steel reinforcement .
• METHODS - a) Pretensioning
  b)Post-tensioning
• PRETENSIONING - Placing of concrete around
  reinforcing tendons that have been stressed to
  the desired degree.
• POST-TENSIONING - Reinforcing tendons are
  stretched by jacks whilst keeping them inserted
  in voids left pre-hand during curing of concrete.
• These spaces are then pumped full of grout to
  bond steel tightly to the concrete.

STEEL BARS BEING STRETCHED BY JACKS
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POST - TENSIONING

• WHAT IS POST-TENSIONING?
• Post-tensioning- is a method of reinforcing
  (strengthening) concrete or other materials with
  high-strength steel strands called tendons.
• Post-tensioning allows construction that would
  otherwise be impossible due to either site
  constraints or architectural requirements.
• Requires specialized knowledge and expertise to
  fabricate, assemble and install.
• After adequate curing of concrete, reinforcing
  tendons (placed in side the voids of the
  structure) are tensioned/stretched by jacks on
  the sides grouts filled with appropriate mix.
• Applications a) Structural members beams,
  bridge-deck panels, Roof Slabs, Concrete Silos
  Etc.

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BENEFITS

• Concrete is very strong in compression but weak
  in tension
• This deflection will cause the bottom of the beam
  to elongate slightly cause cracking.
• Steel reinforcing bars (rebar) are typically
  embedded in the concrete as tensile
  reinforcement to limit the crack widths.
• Rebar is what is called passive reinforcement
  however it does not carry any force until the
  concrete has already deflected enough to crack.
• Post-tensioning tendons, on the other hand, are
  considered active reinforcing.
• Because it is prestressed, the steel is effective
  as reinforcement even though the concrete may not
  be cracked . Post-tensioned structures can be
  designed to have minimal deflection and
  cracking, even under full load.

Post Tensioned Structure
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ADVANTAGES/APPLICATIONS

• Post-tensioning allows longer clear spans,
  thinner slabs, fewer beams and more slender,
  dramatic elements.
• Thinner slabs mean less concrete is required.
  It means a lower overall building height for the
  same floor-to-floor height.
• Post-tensioning can thus allow a significant
  reduction in building weight versus a
  conventional concrete building with the same
  number of floors reducing the foundation load
  and can be a major advantage in seismic areas.
• A lower building height can also translate to
  considerable savings in mechanical systems and
  façade costs.
• Another advantage of post-tensioning is that
  beams and slabs can be continuous, i.e. a single
  beam can run continuously from one end of the
  building to the other.
• Reduces occurrence of cracks - Freezing thawing
  durability is higher than non pre-stressed
  concrete.

This innovative form is result of post tensioning.
Bridge decks
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• Post-tensioning is the system of choice for
  parking structures since it allows a high degree
  of flexibility in the column layout, span lengths
  and ramp configurations.
• In areas where there are expansive clays or soils
  with low bearing capacity, post-tensioned
  slabs-on-ground and mat foundations reduce
  problems with cracking and differential
  settlement.
• Post-tensioning allows bridges to be built to
  very demanding geometry requirements, including
  complex curves, and significant grade changes.
• Post-tensioning also allows extremely long span
  bridges to be constructed without the use
  of temporary intermediate supports. This
  minimizes the impact on the environment and
  avoids disruption to water or road traffic below.
• In stadiums, post-tensioning allows long clear
  spans and very creative architecture.
  Post-tensioning can also be used to produce
  virtually crack-free concrete for water-tanks.
• The high tensile strength precision of
  placement gives maximum efficiency in size
  weight of structural members.
• Applications of various prestressed techniques
  enable quick assembly of standard units such as
  bridge members, building frames, bridge decks
  providing cost-time savings.

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POST TENSIONING METHOD
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Method of post-tensioning
Wedges tensioned by jacks
Tendons
TENDONS
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PRESTRESSED CONCRETE

• Prestressed concrete, invented by Eugene
  Frevssinet in 1928 is a method for overcoming
  concrete's natural weakness in tension . It can
  be used to produce beams,floors or bridges with a
  longer span than is practical with ordinary
  reinforced concrete. It can be accomplished in
  three ways pre-tensioned concrete, and bonded or
  unbonded.
• Pre-tensioned concrete
• Pre-tensioned concrete is cast around already
  tensioned tendons.
• This method produces a good bond between the
  tendon and concrete, which both protects the
  tendon from corrosion and allows for direct
  transfer of tension.
• The cured concrete adheres and bonds to the bars
  and when the tension is released it is
  transferred to the concrete as compression by
  static friction.
• However, it requires stout anchoring points
  between which the tendon is to be stretched and
  the tendons are usually in a straight line.
• Thus, most pre-tensioned concrete elements are
  prefabricated in a factory and must be
  transported to the construction site, which
  limits their size.
• Pre-tensioned elements may be balcony elements,
  lintels , floor slabs, beams or foundation piles.

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• Bonded post-tensioned concrete
• Bonded post-tensioned concrete is the descriptive
  term for a method of applying compression after
  pouring concrete and the curing process (in
  situ).
• The concrete is cast around a plastic, steel or
  aluminium curved duct, to follow the area where
  otherwise tension would occur in the concrete
  element.
• A set of tendons are fished through the duct and
  the concrete is poured. Once the concrete has
  hardened, the tendons are tensioned by hydraulic
  jacks.
• When the tendons have stretched sufficiently,
  according to the design specifications they are
  wedged in position and maintain tension after
  the jacks are removed, transferring pressure to
  the concrete.
• The duct is then grouted to protect the tendons
  from corrosion. This method is commonly used to
  create monolithic slabs for house construction in
  locations where expansive soils create problems
  for the typical perimeter foundation.
• All stresses from seasonal expansion and
  contraction of the underlying soil are taken into
  the entire tensioned slab, which supports the
  building without significant flexure.
  Post-stressing is also used in the construction
  of various bridges.
• The advantages of this system over unbonded
  post-tensioning are

DECK STEEL LAYING
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• Large reduction in traditional reinforcement
  requirements as tendons cannot destress in
  accidents.
• Tendons can be easily 'weaved' allowing a more
  efficient design approach.
• Higher ultimate strength due to bond generated
  between the strand and concrete.
• No long term issues with maintaining the
  integrity of the anchor/dead end.
• Unbonded post-tensioned concrete
• Unbonded post-tensioned concrete differs from
  bonded post-tensioning by providing each
  individual cable permanent freedom of movement
  relative to the concrete.
• To achieve this, each individual tendon is
  coated with a grease (generally lithium based)
  and covered by a plastic sheathing formed in an
  extrusion process.
• The transfer of tension to the concrete is
  achieved by the steel cable acting against steel
  anchors in the perimeter of the slab.
• The main disadvantage over bonded post-tensioning
  is the fact that a cable can destress itself and
  burst out of the slab if damaged (such as during
  repair on the slab). The advantages of this
  system over bonded post-tensioning are

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External Prestressing

• This refers to the case where prestressing
  tendons are placed outside the concrete section
  and the prestressing force is transferred to a
  structural member through end anchorages or
  deviators. Advantages of external prestressing
  include the possibility of monitoring and
  replacing tendons, ease in concreting and hence
  better concrete quality and the use of narrower
  webs. External prestressing is being increasingly
  used in the construction of new bridges and is a
  primary method for the strengthening and
  rehabilitation of existing structures.
• At NUS, a three-year project on the application
  of external prestressing in structural
  strengthening has been completed, and this has
  resulted in design charts being developed for
  such applications.  Works were also carried out
  on the use of fibre-reinforced polymer (FRP)
  reinforcement as external tendons in both simply
  supported and continuous beams.

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APPLICATIONS
The lower and upper terraces cantilever over the
stream below. The temporary structural steel
shoring was placed beneath the main level terrace.

• Fallingwater is comprised of a series of
  concrete cantilever trays 30-ft. above a
  waterfall. Previous efforts failed to permanently
  address excessive deflections of the cantilever
  and repair the cracks. After a thorough design
  review, the owner and engineer selected an
  external post-tensioning solution for its
  durability, aesthetics and structural
  unobtrusiveness.
• Construction plans called for strengthening of
  three support girders spanning in the north-south
  direction with multistrand post-tensioning
  tendons consisting of multiple 0.5 diameter
  strands.
• Thirteen strand tendons were placed on each side
  of two girders. One 10-strand tendon was placed
  on the western side of the third girder (access
  on the eastern side of this girder was not
  available). Eight monostrand tendons, 0.6
  diameter, were slated for the east-west
  direction.
• The monostrand tendons were stressed in the
  east-west direction and then the multistrand
  tendons were stressed in the north-south
  direction and grouted with a high quality,
  low-bleed cementitious grout mixture.
• VSLs scope of work also included welding steel
  cover plates, attaching structural steel
  channels, injecting epoxy grout, doweling
  reinforced cast in place concrete blocks and the
  installation of near surface mounted carbon fiber
  rods. Challenged with maintaining Fallingwaters
  original setting, furnishings and artwork, the
  project was successfully completed in six months.

Frank Lloyd Wright's Fallingwater Mill Run,
Pennsylvania
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• Cline Avenue Bridge Gary, Indiana
• The Cline Avenue Bridge (SR 912) is a
  predominately cast-in-place post-tensioned
  structure located in Gary, Indiana. The bridge
  mainline is over 6,000 LF, has two adjacent
  segments nearly 35 feet wide each, and contains
  four connecting ramps. An inspection and analysis
  team was assembled to perform a thorough
  investigation of the bridge. The team
  concentrated on the existing post-tensioning
  system and interior and exterior concrete cracks.
  The engineer retained VSL to assist with the
  inspection of the tendons.
• VSL approached the Cline Avenue project with a
  guideline that outlines a statistically sound
  method of sampling the tendons. A statistical
  sample pool (which consisted of the mainline
  structure and the ramps) was defined by
  referencing the American National Standard
  Institutes (ANSI) guideline Sampling Procedures
  and Tables for Inspection by Attributes as
  published by the American Society for Quality
  Control (1993).
• The probable void locations throughout the
  structures mainline segments and ramps were
  initially identified by VSL to appropriately
  distribute the sampling population. Such areas
  consisted of high points, areas approaching and
  leaving the high points, and couplers.
• Using non-destructive Ground Penetrating Radar
  (GPR) and field layout drawings, VSL located
  existing post-tensioning tendons. Once the layout
  was performed, specific tendons throughout the
  bridge and ramp structures were sampled by
  drilling into the duct and exposing the tendon
  for visual inspection. The use of a borescope
  allowed for detailed visual inspection of the
  tendon and also captured video footage to share
  with the owner and the engineer. After review of
  each inspection, VSL placed epoxy in the
  borescope hole to protect the tendons from air
  and moisture intrusion. When voids were
  encountered, the project team observed and
  documented the condition of the strand based on
  the PCI Journal guideline, Evaluation of Degree
  of Rusting on Prestressed Concrete Strand. VSL
  used vacuum grouting technology to fill the void,
  thereby protecting the previously exposed strand.
• The tendon inspection data was analyzed with
  other findings (such as crack survey findings) to
  determine what type of rehabilitation was
  required. VSLs goal to establish a statistically
  sound sample of physically inspected tendons that
  provided valid data as to the current state of
  the existing PT system was accomplished

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Grouting of void using VSLs specialized vacuum grouting equipment
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• 85th Street Bridge Valley Center, Kansas
• The 85th Street North Bridge is a seven span
  post-tensioned haunched slab bridge with a
  typical span of 26 meters for the middle five
  spans, and 20 meters at the ends. This 170 meter
  long bridge accommodates two lanes of traffic
  reaching over the Wichita Valley Center Floodway.
  VSL post-tensioning systems utilized for this
  project include 5-19 longitudinal tendons as well
  as 6-4 transverse tendons.
• Post-tensioned haunched slab bridges are noted
  for ease of construction. Once the geometry of
  the bridge falsework has been obtained,
  prefabricated spacer frames are set into place.
  The spacer frames serve as templates for
  profiling the longitudinal post-tensioning
  tendons and aid in the placement of the remaining
  conventional reinforcement. Transverse tendons
  maintain mid-depth placement along the geometry
  of the haunched slab and provide the minimum
  pre-compression over the length of the structure.
• The fi nished product has several advantages over
  conventionally reinforced concrete. Dead loads
  are balanced by the use of longitudinal
  post-tensioning reducing the sustained loading
  and associated creep. Corrosion resistance is
  increased due to the encapsulation of the
  post-tensioning reinforcement. Through the use of
  transverse post-tensioning, added compression
  improves the longevity of the structure by adding
  resistance to de-icing methods such as salt and
  magnesium chloride. Post-tensioned haunched slab
  bridges allow for a larger span to depth ratio
  than that of conventionally reinforced haunched
  slab bridges. The labor and material savings on
  mild reinforcement is another clear advantage to
  using post-tensioning for this application.

Overlooking the 85th Street Bridge prior to
concrete placement
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• Colorado Convention Center Expansion Denver,
  Colorado
• The Colorado Convention Center Expansion project
  is a 1.4 million square foot expansion of the
  existing facility. This was a multi-level
  project, which included a 1,000-car attached
  parking garage.
• The garage above the street was constructed
  using precast tees and columns with a
  cast-in-place topping slab. In order to maintain
  regular spacing for the columns in the precast
  section of the garage and still maintain an
  unobstructed path for the road and light rail,
  large post-tensioned transfer girders were
  required to support several of the columns above.
  The transfer girders allowed for the placement of
  columns required for the precast design despite
  the restricted column locations at the street
  level.
• Post-tensioning the transfer girders resulted in
  smaller dimensions than a conventional reinforced
  concrete design, an important factor given the
  girders are over 7 feet high and up to 7 feet
  wide and a larger section would not fit within
  the space constraints of the building. The
  girders could not be stressed until after the
  precast garage was fully erected and the topping
  slab poured on the truck dock. Temporary columns
  were placed under the girders to support the load
  until stressing.
• The effective post-tensioning force required for
  the beams ranged from 2176 to 5457 kips. A
  multistrand bonded system was installed

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• The Seward Silo project involved the
  post-tensioning of three interconnected ash silos
  that are part of the Seward Re-Powering Project
  in Seward, Pennsylvania. The overall project
  involved the construction of a new,
  state-of-the-art 208 MW power plant designed to
  burn low-grade coal that can not be burned in
  ordinary coal plants. This is a design-build
  project with Drake-Fluor Daniel as the
  owner/construction manager until the completed
  plant is turned over to Reliant Energy, the
  ultimate owner.
• T.E. Ibberson Company was contracted to build
  three 187-6 tall, interconnected, in-line
  silos two 82-4 diameter fly ash silos and one
  64-8 diameter bed ash silo. The silos were
  built using the slip-form method of construction
  and are believed to be the first interconnected
  silos in the world built using post-tensioning as
  the primary circumferential reinforcement.
• VSLs work was performed from November 2003
  through February 2004, during the second coldest
  winter on record locally. Significant snowfall
  and subzero temperatures made progress
  challenging, yet with a strong focus on safety,
  both cold-related and otherwise, the job was
  completed with no incidents. The job required
  close coordination between the various trades
  working in close proximity and constant
  communication between parties working above and
  below VSLs work locations to phase the work to
  avoid having personnel under an active work zone.
• The strand installation, stressing and grouting
  operations were completed successfully, with
  cold-weather grouting made possible through a
  variety of heating methods.

Seward Silo
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THE BICYCLE WHEEL

• Bicycle wheel as we know it today - each is
  associated with an application of prestressing to
  a structural system.
• The first and most obvious is the tensioned
  spokes - the rider's weight is carried from the
  forks to the ground not by hanging off the top
  spokes, but by reducing the pretension in the
  lower spokes - only a couple of spokes are
  carrying the load at any one time.
• The second is the pneumatic tyre, where the
  compressive load is carried to the ground by
  reducing the tension in the sidewall. The air
  pressure in the tyre does not change when the
  load is applied.
• The final prestressing system is the tyre cord,
  which is shorter than the perimeter of the rim.
  The cord is thus in tension, holding the tyre on
  the rim, which enables the pretension in the
  sidewalls to be reacted

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EQUIPMENTS -

• T6Z-08 Air Powered Grout Pump
• Pumps cement grout only, no sand. 32 Gallon
  Mixing Tank. Mixes up to 2 sacks of material at
  once and allows for grout to be pumped during
  mixing or mixed without pumping.

Approximate size 50" long30.5" high52" wide
Weight 560 lbs.
Production Rate 8 gallons per minuteat 150 psi
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• Colloidal Grout Plant
• The heavy duty, high volume Colloidal Grout Plant
  is favored for precision post-tension grouting.
  The unit features a high speed shear mixer that
  thoroughly wets each particle and discharges the
  mixed material into a 13 cubic foot capacity
  agitating holding tank. A direct coupled
  progressing cavity pump delivers slurries at a
  rate of up to 20 gpm and pressures of up to 261
  psi. The unit easily mixes and pumps slurries of
  Portland cement, fly ash, bentonite, and lime
  flour. All controls are conveniently located on
  the operator platform for easy one-man control.

Pump Pump Type 31.6 progressing cavity
Pump Output/Pressure variable up to 20 gpm, 261 psi
Colloidal Mixer Mix Tank 13.0 CF with bottom clean out
Colloidal Mixer Mixing Pump 2 x 3 x 6 diffuser-type centrifugal
Colloidal Mixer Holding Tank 13.0 paddle agitating
Drive Power Air 300 CFM, 100 psi
Physical Specifications Dimensions 96" L x 60" W x 63" H
Physical Specifications Weight 1800-2800 lbs.
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• T7Z Hydraulic Jacks
• Used for testing and pre-stressing anchor bolts.
  Available with up to 5-1/8" center hole. Unit
  comes with ram, pump, gauge, hoses, jack stand,
  high strength coupling, high strength test rod,
  plate, hex nut and knocker wrench. Calibrations
  are available upon request.
• Note Jack pull rods should have a higher
  capacity than the anchor rod.

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• T80 Post-Tensioning Jacks
• With the T80 series the enclosed bearing housing
  contains a geared socket drive to tighten the
  bolt hex nut during tensioning. Test jack housing
  will accommodate up to a 9 deep pocket.

T80 Post-Tensioning Jacks
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• T8Z-18 Hydraulic Torque Wrench
• The hydraulic torque wrench is used for
  tensioning anchors in tight fitting locations
  where it would be difficult to use an hydraulic
  jack. The wrench is also recommended for use when
  setting the large diameter Spin-Lock anchors. The
  torque wrenches are light weight and can achieve
  a maximum of 8,000 ft-lbs. Torque Tensioning
  charts Williams products can be found here.

MaximumTorque Length Height Weight
5,590 ft./lbs.(773 kg/M) 11.11"(279 mm) 4.49"(114 kg) 16.75 lbs.(7.6 kg)
8,000 ft.lbs.(1,006 kg/M) 12.57"(319 kg) 5.09"(129 kg) 24.95 lbs.(11.3 kg)
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• T8Z Torque Wrench
• For applying torque to the anchor bolt when
  setting the anchor. Torque Tensioning charts
  Williams products can be found here.

BoltDiameter SquareDrive Size Capacity(ft. lbs.)
1/2"-1" 3/4" 0-500
1/2"-1" 3/4" 0-600
1-1/8"-2" 1" 0-1,000
T8Z-04 Torque Multiplier (41) For use with T8Z
Torque Wrench. Other sizes available
Size Square DriveInput Square DriveOutput MaximumTorque
GA 186 1" 1-1/2" 4,000 (ft. lbs.)
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• T1Z T2Z Long Fitting Tool Adapters
• For driving hex nuts and setting tools, typically
  with our Spin-Lock anchor systems. Works with
  torque wrench or impact gun.Available with 1" or
  1-1/2" square drive. Please specify square drive
  for compatability with your equipment.

T1Z Deep Socket
2Z Regular Socket
K3F-26 Long Fitting Wrench Adapter For applying
torque to recessed anchor nuts that are under
tension when using hydraulic jacks. Available in
all anchor sizes.
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Corrosion Protection
Methods of Corrosion Protection
Corrosion Protection Type Abrasion Resistance (4best) Typical Thickness Relative Cost (4highest) Lead Time Can be applied to accessories?
Hot Dip Galvanizing 4 3-4 mils 2 2-4 weeks yes
Epoxy Coating 1 7-12 mils 1 2-3 weeks yes
Pre-Grouted Bars 3 2", 3" or 4"tubing 3 2 weeks no
Extruded Polyethylene Coating 2 23-25 mils 1 2-4 weeks no
Corrosion Inhibiting Compound 2 N.A. 2 2-4 weeks yes
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Methods of Corrosion Protection

• Epoxy Coating
• Fusion bonded epoxy coating of steel bars to
  help prevent corrosion has been successfully
  employed in many applications because of the
  chemical stability of epoxy resins. Epoxy coated
  bars and fasteners should be done in accordance
  with ASTM A-775 or ASTM 934. Coating thickness is
  generally specified between 7 to 12 mils. Epoxy
  coated bars and components are subject to damage
  if dragged on the ground or mishandled. Heavy
  plates and nuts are often galvanized even though
  the bar may be epoxy coated since they are
  difficult to protect against abrasion in the
  field. Epoxy coating patch kits are often used in
  the field for repairing nicked or scratched epoxy
  surfaces.

Cement Grout filled corrugated polyethylene
tubing is often used to provide an additional
barrier against corrosion attack in highly
aggressive soils. These anchors are often
referred to as MCP or Multiple Corrosion
Protection anchors. The steel bars are wrapped
with an internal centralizer then placed inside
of the polyethylene tube where they are then
factory pre-grouted. When specifying couplings
with MCP ground anchors, verify coupling
locations with a Williams representative.
Pre-Grouted Bars
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• Hot Dip Galvanizing
• Zinc serves as a sacrificial metal corroding
  preferentially to the steel. Galvanized bars have
  excellent bond characteristics to grout or
  concrete and do not require as much care in
  handling as epoxy coated bars. However,
  galvanization of anchor rods is more expensive
  than epoxy coating and often has greater lead
  time. Hot dip galvanizing bars and fasteners
  should be done in accordance with ASTM A-153.
  Typical galvanized coating thickness for steel
  bars and components is between 3 and 4 mils. 150
  KSI high strength steel bars should always be
  mechanically cleaned (never acid washed) to avoid
  problems associated with hydrogen embrittlement.

Extruded Polyethylene
Williams strand tendons contain an extruded high
density polyethylene sheathing around each
individual strand in the free-stressing portion
of the anchorage. The sheathing is minimum 60
mils thick and applied once the 7-wire strand has
been coated with a corrosion inhibiting compound.
Extruded polyethylene sheathing provides a
moisture tight barrier for corrosion protection
and allows the strand to elongate freely
throughout the free-stressing length during the
prestressing operation
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Corrosion Inhibiting Wax or Grease with Sheath

• Williams corrosion inhibiting compounds can be
  placed in the free stressing sleeves, in the end
  caps, or in the trumpet areas. Often bars are
  greased/waxed and PVC is slipped over the
  greased/waxed bar prior to shipping. Each are of
  an organic compound with either a grease or wax
  base. They provide the appropriate polar moisture
  displacement and have corrosion inhibiting
  additives with self-healing properties. They can
  be pumped or applied manually. Corrosion
  inhibiting compounds stay permanently viscous,
  chemically stable and non-reactive with the
  prestressing steel, duct materials or grout. Both
  compounds meet PTI standards for Corrosion
  Inhibiting Coating.

Coal Tar Epoxy
Coal tar epoxy has shown to be abrasion resistant, economical and durable. This product when specified should meet or exceed the requirements of (a) Corp of Engineers C-200, C200a and (b) AWWA C-210-92 for exterior. Typically the thickness is between 8 and 24 mils. Make sure that the surfaces of the bar are clean and dry before coating.
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• Heat Shrink Tubing
• Heat Shrink Tubing provides a corrosion protected
  seal when connecting smooth or corrugated
  segments.

Epoxy Coating Patch Kits
Epoxy Coating Patch Kits are available upon
request.
Anchor Head Protection
The most important section of a ground anchor that needs adequate corrosion protection is the portion of the anchor exposed to air/oxygen. This is typically defined as the "anchor head", which generally consists of a steel bearing plate, a hex nut and washer for a bar system, or a wedge plate and wedges for a strand system. For permanent ground anchors it is best to galvanize the hex nut and plates even if the bar is epoxy coated. Galvanized components, if scratched during shipping, are less likely to cause corrosion concerns than scratched epoxy coated components. The end of the steel bar protruding out from the hex nut is often protected by the use of a plastic or steel end cap packed with grease or cement grout. Williams offers several different types of PVC and metal end caps to provide corrosion protection at otherwise exposed anchor ends.
Screw-OnPVC Cap
Fiber Reinforced Nylon Cap
StrandEnd Cap
Steel Tube Welded on Flange with Threaded Screw
Connections
38

• Field Splice for Bars
• Continuous corrosion protection can even be
  accomplished for the MCP Pregrouted anchors
  manufactured from Williams Form Engineering. To
  achieve the equivalent levels of corrosion
  protection the coupled sections of bar anchors
  can be wrapped in a grease impregnated tape that
  is further protected with heat shrink sleeving.
  This scheme is acceptable by most governing
  agencies and is specified in the PTI
  Recommendations for Prestresed Rock and Soil
  Anchors.