Standard Specifications for Road, Bridge, and Municipal Construction 2020 (M 41-10)

Permanent Ground Anchors

6-17

3. Unbonded length corrosion protection system, including the permanent rubber seal

between the trumpet and the tendon unbonded length corrosion protection and
the transition between the tendon bond length and the unbonded tendon length
corrosion protection.

4.  Bond length corrosion protection system
5.  Anchorage and trumpet
6.  Anchorage corrosion protection system
7.  Anchors using non-restressable anchorage devices

The Contractor shall submit Type 2 Working Drawings consisting of shop plans as
specified in

Section 6-03.3(7)

for all structural steel, including the permanent ground

anchors.

The Contractor shall submit Type 1 Working Drawings consisting of the mix design for
the grout conforming to

Section 9-20.3(4)

and the procedures for placing the grout. The

Contractor shall also submit the methods and materials used in filling the annulus over
the unbonded length of the anchor.

The Contractor shall submit Type 2 Working Drawings consisting of the method proposed
to be followed for the permanent ground anchor testing. This shall include all necessary
drawings and details to clearly describe the method proposed.

The Contractor shall submit Type 2 Working Drawings consisting of calibration data
for each load cell, test jack, pressure gauge and master pressure gauge to be used. The
calibration tests shall have been performed by an independent testing Laboratory and
tests shall have been performed within 60 calendar days of the date submitted.

6-17.3(4) Preconstruction Conference

A permanent ground anchor preconstruction conference shall be held at least 5 working
days prior to the Contractor beginning any permanent ground anchor Work at the site
to discuss construction procedures, personnel, and equipment to be used. The list of
materials specified on the Record of Materials Form (ROM) for this item of Work will also
be discussed. Those attending shall include:
1. (representing the Contractor) The superintendent, on site supervisors, and all

foremen in charge of drilling the ground anchor hole, placing the permanent ground
anchor and grout, and tensioning and testing the permanent ground anchor.

2. (representing the Contracting Agency) The Engineer, key inspection personnel, and

representatives from the WSDOT Construction Office and Materials Laboratory
Geotechnical Services Branch.

If the Contractor’s key personnel change, or if the Contractor proposes a significant
revision of the approved permanent ground anchor installation plan, an additional
conference shall be held before any additional permanent ground anchor operations
are performed.

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Permanent Ground Anchors

6-17.3(5) Tendon Fabrication

The tendons can be either shop or field fabricated. The tendon shall be fabricated as
shown in the shop plans.

The Contractor shall select the type of tendon to be used. The tendon shall be sized so
the factored design load does not exceed 80 percent of the minimum guaranteed ultimate
tensile strength of the tendon. In addition, the tendon shall be sized so the maximum test
load does not exceed 80 percent of the minimum guaranteed ultimate tensile strength of
the tendon.

The Contractor shall be responsible for determining the bond length and tendon bond
length necessary to develop the factored design load indicated in the Plans in accordance
with Sections

. The minimum bond length shall be

10 feet in rock and 15 feet in soil.

When the Plans require the tendon bond length to be encapsulated, the tendon bond
length portion of the tendon shall be corrosion protected by encapsulating the tendon
in a grout-filled PE or PVC tube as specified in

Section 6-17.2

as supplemented in the

Special Provisions. The tendons can be grouted inside the encapsulation prior to inserting
the tendon in the drill hole or after the tendon has been placed in the drill hole. Expansive
admixtures can be mixed with the encapsulation grout if the tendon is grouted inside the
encapsulation while outside the drill hole. The tendon shall be centralized within the bond
length encapsulation with a minimum of 0.20 inches of grout cover. Spacers shall be used
along the tendon bond length of multi-element tendons to separate the elements of the
tendon so the prestressing steel will bond to the encapsulation grout.

Centralizers shall be used to provide a minimum of 0.5 inches of grout cover over
the tendon bond length encapsulation. Centralizers shall be securely attached to the
encapsulation and the center-to-center spacing shall not exceed 10 feet. In addition, the
upper centralizer shall be located a maximum of 5 feet from the top of the tendon bond
length and the lower centralizer shall be located a maximum of 1 foot from the bottom of
the tendon bond length.

The centralizer shall be able to support the tendon in the drill hole and position the
tendon so a minimum of 0.5 inches of grout cover is provided and shall permit free flow
of grout.

Centralizers are not required on encapsulated, pressure-injected ground anchor tendons
if the ground anchor is installed in coarse grained soils (more than 50 percent of the soil
larger than the number 200 sieve) using grouting pressures greater than 150 psi.

Centralizers are not required on encapsulated, hollow-stem-augered ground anchor
tendons if the ground anchor is grouted through and the hole is maintained full of a stiff
grout (8-inch slump or less) during extraction of the auger.

The minimum unbonded length of the tendon shall be the greater of 15 feet or that
indicated in the Plans.

Permanent Ground Anchors

6-17

Corrosion protection of the unbonded length shall be provided by a sheath completely
filled with corrosion inhibiting grease or grout. If grease is used under the sheath,
provisions shall be made to prevent the grease from escaping at the ends of the sheath.
The grease shall completely coat the tendon and fill the voids between the tendon and
the sheath.

If the sheath is not fabricated from a smooth tube, a separate bond breaker shall be
provided. The bond breaker shall prevent the tendon from bonding to the anchor grout
surrounding the tendon unbonded length.

The total anchor length shall not be less than that indicated in the Plans or the approved
Working Drawing submittal.

Anchorage devices shall be capable of developing 95 percent of the minimum guaranteed
ultimate tensile strength of the prestressing steel tendon. The anchorage devices shall
conform to the static strength requirements of Section 3.1 of the Post Tensioning Institute
Specification for Unbonded Single Strand Tendons, First Edition – 1993.

Non-restressable anchorage devices may be used except where indicated in the Plans.

Restressable anchorages shall be provided on those ground anchors that require
reloading. The post-tensioning supplier shall provide a restressable anchorage compatible
with the post-tensioning system provided.

The bearing plates shall be sized so the bending stresses in the plate do not exceed the
yield strength of the steel when a load equal to 95 percent of the minimum guaranteed
ultimate tensile strength of the tendon is applied, and the average bearing stress on the
concrete does not exceed that recommended in Section 3.1.3 of the Post Tensioning
Institute Specification for Unbonded Single Strand Tendons, First Edition – 1993.

The trumpet shall have an inside diameter equal to or larger than the hole in the bearing
plate. The trumpet shall be long enough to accommodate movements of the Structure
during testing and stressing. For strand tendons with encapsulation over the unbonded
length, the trumpet shall be long enough to enable the tendon to make a transition from
the diameter or the tendon in the unbonded length to the diameter of the tendon at
the anchor head without damaging the encapsulation. Trumpets filled with corrosion-
inhibiting grease shall have a permanent rubber seal provided between the trumpet and
the tendon unbonded length corrosion protection. Trumpets filled with grout shall have a
temporary seal provided between the trumpet and the tendon unbonded length corrosion
protection or the trumpet shall overlap the tendon unbonded length corrosion protection.

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Permanent Ground Anchors

6-17.3(6) Tendon Storage and Handling

Tendons shall be handled and stored in such a manner as to avoid damage or corrosion.
Damage to the prestressing steel as a result of abrasions, cut, nicks, welds and weld
splatter will be cause for rejection by the Engineer. The prestressing steel shall be
protected if welding is to be performed in the vicinity. Grounding of welding leads to
the prestressing steel is forbidden. Prestressing steel shall be protected from dirt, rust,
and deleterious substances. A light coating of rust on the steel is acceptable. If heavy
corrosion or pitting is noted, the Engineer will reject the affected tendons.

The Contractor shall use care in handling and storing the tendons at the site. Prior to
inserting a tendon in the drill hole, the Contractor and the Engineer will examine the
tendon for damage to the encapsulation and the sheathing. If, in the opinion of the
Engineer, the encapsulation is damaged, the Contractor shall repair the encapsulation
in accordance with the tendon supplier’s recommendations and as approved by the
Engineer. If, in the opinion of the Engineer, the smooth sheathing has been damaged, the
Contractor shall repair it with ultra high molecular weight polyethylene (PE) tape. The tape
shall be spiral wound around the tendon so as to completely seal the damaged area. The
pitch of the spiral shall ensure a double thickness at all points.

6-17.3(7) Installing Permanent Ground Anchors

The Contractor shall select the drilling method, the grouting procedure, and the grouting
pressure used for the installation of the ground anchor.

When caving conditions are encountered, no further drilling will be allowed until the
Contractor selects a method to prevent ground movement. The Contractor may use
a temporary casing. The Contractor’s method to prevent ground movement shall be
submitted as a Type 2 Working Drawing. The casings for the anchor holes, if used, shall
be removed. The drill hole shall be located so the longitudinal axis of the drill hole and
the longitudinal axis of the tendon are parallel. The ground anchor shall not be drilled in
a location that requires the tendon to be bent in order to enable the bearing plate to be
connected to the supported Structure. At the point of entry the ground anchor shall be
installed within plus or minus 3 degrees of the inclination from horizontal shown in the
Plans or the Working Drawing submittal. The ground anchors shall not extend beyond the
Right of Way limits.

The tendon shall be inserted into the drill hole to the desired depth. When the tendon
cannot be completely inserted without difficulty, the Contractor shall remove the tendon
from the drill hole and clean or redrill the hole to permit insertion. Partially inserted
tendons shall not be driven or forced into the hole.

The Contractor shall use a grout conforming to

Section 6-17.2

as supplemented in the

Special Provisions.

Permanent Ground Anchors

6-17

The grout equipment shall produce a grout free of lumps and undispersed cement. A
positive displacement grout pump shall be used. The pump shall be equipped with a
pressure gauge near the discharge end to monitor grout pressures. The pressure gauge
shall be capable of measuring pressures of at least 150 psi or twice the actual grout
pressures used by the Contractor, whichever is greater. The grouting equipment shall be
sized to enable the grout to be pumped in one continuous operation. The mixer shall be
capable of continuously agitating the grout.

The grout shall be injected from the lowest point of the drill hole. The grout may be
pumped through grout tubes, casing, or drill rods. The grout can be placed before or
after insertion of the tendon. The quantity of the grout and the grout pressures shall be
recorded. The grout pressures and grout takes shall be controlled to prevent excessive
heave in soils or fracturing of rock formations.

The Contractor shall make and cure grout cubes once per day in accordance with WSDOT

T 813

. These samples shall be retained by the Contractor until all associated verification,

performance and proof testing of the permanent ground anchors has been successfully
completed. If the Contractor elects to test the grout cubes for compressive strength,
testing shall be conducted by an independent laboratory and shall be in accordance with
the FOP for AASHTO T 106.

After grouting, the tendon shall not be loaded for a minimum of 3 days.

No grout shall be placed above the top of the bond length during the time the bond
length grout is placed. The grout at the top of the drill hole shall not contact the back of
the Structure or the bottom of the trumpet. Except as otherwise noted, only nonstructural
filler shall be placed above the bond length grout prior to testing and acceptance of the
anchor. The Contractor may place structural grout above the bond length grout prior to
testing and acceptance of the anchor subject to the following conditions:
1. The anchor unbonded length shall be increased by 8 feet minimum.
2. The grout in the unbonded zone shall not be placed by pressure grouting methods.

The corrosion protection surrounding the unbonded length of the tendon shall extend
up beyond the bottom seal of the trumpet or 1 foot into the trumpet if no trumpet seal
is provided. If the protection does not extend beyond the seal or sufficiently far enough
into the trumpet, the Contractor shall extend the corrosion protection or lengthen the
trumpet.

The corrosion protection surrounding the no load zone length of the tendon shown
in the Plans shall not contact the bearing plate or the anchor head during testing and
stressing. If the protection is too long, the Contractor shall trim the corrosion protection
to prevent contact.

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Permanent Ground Anchors

The bearing plate and anchor head shall be placed so the axis of the tendon and the drill
hole are both perpendicular to the bearing plate within plus or minus 3 degrees and the
axis of the tendon passes through the center of the bearing plate at the intersection of
the trumpet and the bearing plate when fully seated with the alignment load.

The trumpet shall be completely filled with corrosion inhibiting grease or grout. Trumpet
grease can be placed anytime during construction. Trumpet grout shall be placed after
the ground anchor has been tested. The Contractor shall demonstrate to the Engineer
that the procedure selected by the Contractor for placement of either grease or grout
produces a completely filled trumpet.

All anchorages permanently exposed to the atmosphere shall be covered with a corrosion
inhibiting grease-filled or grout-filled cover. The Contractor shall demonstrate to the
Engineer that the procedures selected by the Contractor for placement of either grease
or grout produces a completely filled cover. If the Plans require restressable anchorages,
corrosion inhibiting grease shall be used to fill the anchorage cover and trumpet.

6-17.3(8) Testing and Stressing

Each ground anchor shall be tested. The test load shall be simultaneously applied to
the entire tendon. Stressing of single elements of multi-element tendons will not be
permitted. The Engineer will record test data.

The testing equipment shall consist of a dial gauge or vernier scale capable of measuring
to 0.001 inch and shall be used to measure the ground anchor movement. The
movement-measuring device shall have a minimum travel equal to the theoretical elastic
elongation of the total anchor length plus 1 inch. The dial gauge or vernier scale shall
be aligned so that its axis is within 5 degrees from the axis of the tieback. A hydraulic
jack and pump shall be used to apply the test load. The jack and pressure gauge shall be
calibrated by an independent testing Laboratory as a unit. Each load cell, test jack and
pressure gauge, and master pressure gauge, shall be calibrated as specified in

Section

6-17.3(3)

. Additionally, the Contractor shall not use load cells, test jacks and pressure

gauges, and master pressure gauges, greater than 60 calendar days past their most recent
calibration date, until such items are re-calibrated by an independent testing Laboratory.

The pressure gauge shall be graduated in increments of either 100 psi or 2 percent of the
maximum test load, whichever is less. The pressure gauge will be used to measure the
applied load. The pressure gauge shall be selected to place the maximum test load within

the middle ⅔ of the range of the gauge. The ram travel of the jack shall not be less than

the theoretical elastic elongation of the total anchor length at the maximum test load
plus 1 inch. The jack shall be independently supported and centered over the tendon
so that the tendon does not carry the weight of the jack. The Contractor shall have a
second calibrated jack pressure gauge at the site. Calibration data shall provide a specific
reference to the jack and the pressure gauge.

The loads on the tiebacks during the performance and verification tests shall be
monitored to verify consistency of load as defined in

Section 6-17.3(1)

. Performance test

loads, and verification test loads when specified in the Special Provisions, sustained for

Permanent Ground Anchors

6-17

5 minutes or less, and all proof test leads, shall be monitored by the jack pressure gauge
alone. Performance test loads, and verification test loads when specified in the Special
Provisions, sustained for longer than 5 minutes shall be monitored with the assistance of
an electric or hydraulic load cell. The Contractor shall provide the load cell and a readout
device. The load cell shall be mounted between the jack and the anchor plate. The load

cell shall be selected to place the maximum test load within the middle ⅔ of the range

of the load cell. The stressing equipment shall be placed over the ground anchor tendon
in such a manner that the jack, bearing plates, load cell and stressing anchorage are
in alignment.

The permanent ground anchor load monitoring procedure for performance test loads, and
verification test loads when specified in the Special Provisions, sustained for longer than
5 minutes shall be as follows:
1. For each increment of load, attainment of the load shall be initially established and

confirmed by the reading taken from the jack gauge.

2. Once the permanent ground anchor load has been stabilized, based on the jack

gauge reading, the load cell readout device shall immediately be read and recorded
to establish the load cell reading to be used at this load. The load cell reading is
intended only as a confirmation of a stable permanent ground anchor load, and shall
not be taken as the actual load on the permanent ground anchor.

3. During the time period that the load on the permanent ground anchor is held at this

load increment, the Contractor shall monitor the load cell reading. The Contractor
shall adjust the jack pressure as necessary to maintain the initial load cell reading.
Jack pressure adjustment for any other reason will not be allowed.

4. Permanent ground anchor elongation measurements shall be taken at each load

increment as specified in Sections

6-17.3(8)A

and

6-17.3(8)B

5. Steps 1 through 4 shall be repeated at each increment of load, in accordance with

the load sequence specified in Sections

6-17.3(8)A

and

6-17.3(8)B

6-17.3(8)A

Verification Testing

Verification tests will be required only when specified in the Special Provisions.

6-17.3(8)B

Performance Testing

Performance tests shall be done in accordance with the following procedures.
Five percent of the ground anchors or a minimum of three ground anchors, whichever is
greater, shall be performance tested. The Engineer shall select the ground anchors to be
performance tested. The first production anchor shall be performance tested.

The performance test shall be made by incrementally loading and unloading the ground
anchor in accordance with the following schedule, consistent with the Load Resistance
Factor Design (LRFD) design method. The load shall be raised from one increment to
another immediately after a deflection reading.

Page 6-326

Permanent Ground Anchors

Performance Test Schedule

Load

0.25FDL

0.25FDL
0.50FDL

0.25FDL
0.50FDL
0.75FDL

0.25FDL
0.50FDL
0.75FDL
1.00FDL

Jack to lock-off load

Where:

AL is the alignment load
FDL is the factored design load.

The maximum test load in a performance test shall be held for 10 minutes. The load-hold
period shall start as soon as the maximum test load is applied and the anchor movement,
with respect to a fixed reference, shall be measured and recorded at 1, 2, 3, 4, 5, 6, and
10 minutes. If the anchor movement between 1 and 10 minutes exceeds 0.04 inches, the
maximum test load shall be held for an additional 50 minutes. If the load-hold is extended,
the anchor movement shall be recorded at 20, 30, 40, 50, and 60 minutes. If an anchor
fails in creep, retesting will not be allowed. All anchors not performance tested shall be
proof tested.

6-17.3(8)C

Proof Testing

Proof tests shall be performed by incrementally loading the ground anchor in accordance
with the following schedule, consistent with the LRFD design method. The load shall
be raised from one increment to another immediately after a deflection reading. The
anchor movement shall be measured and recorded to the nearest 0.001 inches with
respect to an independent fixed reference point at the alignment load and at each
increment of load. The load shall be monitored with a pressure gauge. At load increments
other than the maximum test load, the load shall be held just long enough to obtain the
movement reading.

Permanent Ground Anchors

6-17

Proof Test Schedule

Load

0.25FDL
0.50FDL
0.75FDL
1.00FDL

Jack to lock-off load

Where:

AL is the alignment load
FDL is the factored design load

The maximum test load in a proof test shall be held for 10 minutes. The load-hold
period shall start as soon as the maximum test load is applied and the anchor movement
with respect to a fixed reference shall be measured and recorded at 1, 2, 3, 4, 5, 6, and
10 minutes. If the anchor movement between 1 and 10 minutes exceeds 0.04 inches, the
maximum test load shall be held of an additional 50 minutes. If the load-hold is extended,
the anchor movements shall be recorded at 20, 30, 40, 50, and 60 minutes. If an anchor
fails in creep, retesting will not be allowed.

6-17.3(9) Permanent Ground Anchor Acceptance Criteria

A performance or proof tested ground anchor with a 10 minute load hold is acceptable
if the:
1. Ground anchor carries the maximum test load with less than 0.04 inches of

movement between 1 and 10 minutes; and

2. Total movement at the maximum test load exceeds 80 percent of the theoretical

elastic elongation of the tendon unbonded length.

A verification, performance or proof tested ground anchor with a 60-minute load hold is
acceptable if the:
1. Ground anchor carries the maximum test load with a creep rate that does not exceed

0.08 inches/log cycle of time and is a linear or decreasing creep rate.

2. Total movement at the maximum test load exceeds 80 percent of the theoretical

elastic elongation of the tendon unbonded length.

If the total movement of the ground anchors at the maximum test load does not exceed
80 percent of the theoretical elastic elongation of the tendon unbonded length, the
Contractor shall replace the ground anchor at no additional cost to the Contracting
Agency. Retesting of a ground anchor will not be allowed.

When a ground anchor fails, the Contractor shall modify the design, the construction
procedures, or both. These modifications may include, but are not limited to, installing
replacement ground anchors, modifying the installation methods, increasing the bond
length or changing the ground anchor type. Any modification that requires changes to

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Permanent Ground Anchors

the Structure shall have prior approval of the Engineer. Any modifications of design or
construction procedures shall be at the Contractor’s expense.

Upon completion of the test, the load shall be adjusted to the lock-off load indicated in
the Plans and transferred to the anchorage device. The ground anchor may be completely
unloaded prior to lock-off. After transferring the load and prior to removing the jack a lift-
off reading shall be made. The lift-off reading shall be within 10 percent of the specified
lock-off load.

If the load is not within 10 percent of the specified lock-off load, the anchorage shall be
reset and another lift-off reading shall be made. This process shall be repeated until the
desired lock-off load is obtained.

6-17.4 Measurement

Permanent ground anchors will be measured per each for each permanent ground anchor
installed and accepted.

Permanent ground anchor performance tests will be measured per each for each anchor
performance tested.

The permanent ground anchor verification testing program will not be measured but will
be paid for on a lump sum basis.

6-17.5 Payment

Payment will be made for each of the following Bid items when they are included in the
Proposal:

“Permanent Ground Anchor”, per each.
All costs in connection with furnishing and installing permanent ground anchors
shall be included in the unit Contract price per each for “Permanent Ground Anchor”,
including proof testing of the installed anchor as specified
“Permanent Ground Anchor Performance Test”, per each.
“Permanent Ground Anchor Verification Test”, lump sum.

Shotcrete Facing

6-18

Shotcrete Facing

6-18.1 Description

This Work consists of constructing shotcrete facing as shown on the Plans. Shotcrete
constructed as concrete slope protection shall be constructed in accordance with

Section 8-16

6-18.2 Materials

Materials shall meet the requirements of the following sections:
Cement

9-01

Aggregates for Portland Cement Concrete

9-03.1

Premolded Joint Filler

9-04.1(2)

Steel Reinforcing Bar

9-07.2

Epoxy-Coated Steel Reinforcing Bar

9-07.3

Concrete Curing Materials and Admixtures

9-23

Fly Ash

9-23.9

Ground Granulated Blast Furnace Slag

9-23.10

Microsilica Fume

9-23.11

Water

9-25

Other materials required, including materials for shotcrete, shall be as specified in the
Special Provisions.

6-18.3

Construction Requirements

6-18.3(1) Submittals

The Contractor shall submit Type 2 Working Drawings consisting of the following:
1.  The shotcrete mix design with compressive strength test results.
2.  Method and equipment used to apply, finish and cure the shotcrete facing.
3.  Documentation of the experience of the nozzle operators in applying shotcrete.

6-18.3(2) Mix Design

Shotcrete shall be proportioned to produce a 4,000 psi compressive strength at 28 days.

Admixture shall be used only after receiving permission from the Engineer. If admixtures
are used to entrain air, to reduce water-cement ratio, to retard or accelerate setting time,
or to accelerate the development of strength, the admixtures shall be used at the rate
specified by the manufacturer.

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Shotcrete Facing

6-18.3(3) Testing

The Contractor shall make shotcrete test panels for evaluation of shotcrete quality,
strength, and aesthetics. Both preproduction and production test panels shall be
prepared. The Contractor shall remove at least three cores from shotcrete test panels in
accordance with ASTM C1604, except all cores obtained for the purpose of shotcrete
strength testing shall meet the following:
1. The core diameter shall be at least 3.0 times the maximum aggregate size, but not

less than 4 inches.

2. The core length shall be a minimum of 2.0 times the core diameter.
3. Cores shall be taken at a minimum distance of 1 inch from edge of core to edge of

test panel and a minimum clear distance of 1 inch between them.

4. Test panels shall be sized to meet the core spacing specified above, but in no case

shall be smaller than 12 by 12 inch.

Cores removed from the panels shall be wiped off to remove surface drill water and
immediately wrapped in wet burlap and sealed in a plastic bag. Cores shall be clearly
marked to identify from where they were taken and whether they are for preproduction
or production testing. If for production testing, the section of the wall represented by
the cores shall be clearly marked on the cores. Cores shall be delivered to the Engineer
within 2 hours of coring. The remainder of the panels shall remain the property of the
Contractor.

6-18.3(3)A

Preproduction Testing

At least three cores for each mix design shall be prepared for evaluation and testing of the
shotcrete quality and strength. One 48 by 48-inch qualification panel shall be prepared
for evaluation and approval of the proposed method for shotcrete installation, finishing,
and curing. Both the test panel and the 48-inch qualification panels shall be constructed
using the same methods and initial curing proposed to construct the shotcrete facing,
except that the test panel shall not include wire reinforcement. The test panel shall be
constructed to the minimum thickness necessary to obtain the required core samples. The
48-inch qualification panel shall be constructed to the same thickness as proposed for the
production facing. Production shotcrete Work shall not begin until satisfactory test results
are obtained and the panels are accepted by the Engineer.

6-18.3(3)B

Production Testing

The Contractor shall provide three cores for each section of facing shot. The production
panels shall be constructed using the same methods and initial curing used to construct
the shotcrete wall, but without wire reinforcement. The panels shall be constructed to
the minimum thickness necessary to obtain the required core samples. If the production
shotcrete is found to be unsuitable based on the results of the test panels, the section(s)
of the wall represented by the test panel(s) shall be repaired or replaced to the satisfaction
of the Engineer at no additional cost to the Contracting Agency. Core acceptance testing
for the 28-day compressive strength will be performed in accordance with ASTM C1604.

Shotcrete Facing

6-18

6-18.3(4) Qualifications of Contractor’s Personnel

All nozzle operators shall have had at least 1 year of experience in the application of
shotcrete. Each nozzle operator will be qualified, by the Engineer, to place shotcrete, after
successfully completing one test panel for each shooting position and surface type which
will be encountered.

Qualification will be based on a visual inspection of the shotcrete density, void structure,
and finished appearance along with a minimum 7-day compressive strength of 2,500 psi
determined from the average test results from two cores taken from each test panel. The
7-day core compressive strength shall be tested by the Contractor in accordance with
ASTM C1604.

The Contractor shall notify the Engineer not less than 2 days prior to the shooting of a
qualification panel. The mix design for the shotcrete shall be the same as that slated for
the wall being shot.

Shotcrete shall be placed only by personnel qualified by the Engineer.

If shotcrete finish Alternative B or C is specified, evidence shall be provided that all
shotcrete crew members have completed at least three projects in the last 5 years where
such finishing, or sculpturing and texturing of shotcrete was performed.

6-18.3(5) Placing Wire Reinforcement

Reinforcement of the shotcrete shall be placed as shown in the Plans. The wire
reinforcement shall be securely fastened to the steel reinforcing bars so that it will be 1 to
1.5 inches from the face of the shotcrete at all locations, unless otherwise shown in the
Plans. Wire reinforcement shall be lapped 1.5 squares in all directions, unless otherwise
shown in the Plans.

6-18.3(6) Alignment Control

The Contractor shall install non-corroding alignment wires and thickness control pins
to establish thickness and plane surface. The Contractor shall install alignment wires
at corners and offsets not established by formwork. The Contractor shall ensure that
the alignment wires are tight, true to line, and placed to allow further tightening. The
Contractor shall remove the alignment wires after facing construction is complete.

6-18.3(7) Shotcrete Application

A clean, dry supply of compressed air sufficient for maintaining adequate nozzle velocity
for all parts for the Work and for simultaneous operation of a blow pipe for cleaning away
rebound shall be maintained at all times. Thickness, method of support, air pressure, and
rate of placement of shotcrete shall be controlled to prevent sagging or sloughing of
freshly applied shotcrete.

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Shotcrete Facing

The shotcrete shall be applied from the lower part of the area upwards. Surfaces to be
shot shall be damp, but free of standing water.
The nozzles shall be held at an angle approximately perpendicular to the working face
and at a distance that will keep rebound at a minimum and compaction will be maximized.
Shotcrete shall emerge from the nozzle in a steady uninterrupted flow. If, for any reason,
the flow becomes intermittent, the nozzle shall be diverted from the Work until a steady
flow resumes.
Surface defects shall be repaired as soon as possible after initial placement of
the shotcrete. All shotcrete which lacks uniformity; which exhibits segregation,
honeycombing, or lamination; or which contains any dry patches, slugs, voids, or sand
pockets, shall be removed and replaced with fresh shotcrete by the Contractor, to the
satisfaction of the Engineer at no cost to the Contracting Agency.
Construction joints in the shotcrete shall be uniformly tapered over a minimum distance
of twice the thickness of the shotcrete layer. The surface of the joints shall be cleaned
and thoroughly wetted before adjacent shotcrete is placed. Shotcrete shall be placed in a
manner that provides a finish with uniform texture and color across the construction joint.
The shotcrete shall be cured by applying a clear curing compound in accordance with

Section 9-23.2

. The curing compound shall be applied immediately after final gunning.

Two coats of curing compound shall be applied to the shotcrete surface immediately after
finishing. When shotcrete is specified in the Plans as the final fascia finish, the curing
requirements specified in

Section 6-02.3(11)

shall apply.

If field inspection or testing, by the Engineer, indicates that any shotcrete produced,
fails to meet the requirements, the Contractor shall immediately modify procedures,
equipment, or system, as necessary to produce Specification Material. All substandard
shotcrete already placed shall be repaired by the Contractor, to the satisfaction of the
Engineer, at no additional cost to the Contracting Agency. Such repairs may include
removal and replacement of all affected materials.

6-18.3(8) Shotcrete Finishing

When the shotcrete facing is an interim coating to be covered by a subsequent shotcrete
coating or a cast-in-place concrete fascia later under the same Contract, the Contractor
shall strike off the surface of the shotcrete facing with a roughened surface as specified
in

Section 6-02.3(12)

. The grooves of the roughened surface shall be either vertical

or horizontal.

When the shotcrete facing provides the finished exposed final surface, the shotcrete
face shall be finished using the alternative aesthetic treatment shown in the Plans. The
alternatives are as follows:

•

Alternative A – After the surface has taken its initial set (crumbling slightly when cut),
the surface shall be broom finished to secure a uniform surface texture.

•

Alternative B – Shotcrete shall be applied in a thickness a fraction beyond the
alignment wires and forms. The shotcrete shall stiffen to the point where the surface
does not pull or crack when screeded with a rod or trowel. Excess material shall be
trimmed, sliced, or scraped to true lines and grade. Alignment wires shall be removed

Shotcrete Facing

6-18

and the surface shall receive a steel trowel finish, leaving a smooth uniform texture
and color. Once the shotcrete has cured, pigmented sealer shall be applied to the
shotcrete face. The shotcrete surface shall be completed to within a tolerance of
½ inch of true line and grade.

•

Alternative C – Shotcrete shall be hand-sculptured, colored, and textured to simulate
the relief, jointing, and texture of the natural backdrop surrounding the facing. The
ends and base of the facing shall transition in appearance as appropriate to more
nearly match the color and texture of the adjoining Roadway fill slopes. This may
be achieved by broadcasting fine and coarse aggregates, rocks, and other native
materials into the final surface of the shotcrete while it is still wet, allowing sufficient
embedment into the shotcrete to become a permanent part of the surface.

6-18.4 Measurement

Shotcrete facing will be measured by the square foot surface area of the completed facing
measured to the neat lines of the facing as shown in the Plans.

6-18.5 Payment

Payment will be made for each of the following Bid items when they are included in the
Proposal:

“Shotcrete Facing”, per square foot.
All costs in connection with constructing shotcrete facing as specified shall be
included in the unit Contract price per square foot for “Shotcrete Facing” including
all steel reinforcing bars, premolded joint filler, polyethylene bond breaker strip,
joint sealant, PVC pipe for weep holes, exterior surface finish, and pigmented sealer
(when specified).

Page 6-334

6-19 Shafts

6-19.1 Description

This work consists of constructing the shafts in accordance with the Plans, these
Specifications, and as designated by the Engineer.

6-19.2 Materials

Materials shall meet the requirements of the following sections:
Cement

9-01

Aggregates for Concrete

9-03.1

Steel Reinforcing Bar

9-07.2

Epoxy-Coated Steel Reinforcing Bar