96E06/13/07

S566-96E.doc

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  Use on projects as appropriate.

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**Section 566. - SHOTCRETE**

**Description**

**566.01** This work consists of batching, mixing, transporting,
applying, finishing, testing, and cleaning-up shotcrete materials.

**Material**

**566.02** Material will conform to the following subsections:

> Shotcrete Fine Aggregate 703.01
>
> Shotcrete Coarse Aggregate 703.18
>
> Combined Shotcrete Aggregate Grading 703.18
>
> Chemical Admixtures (Wet mix only) 711.03
>
> Air-Entraining Admixture (Wet mix only) 711.02
>
> Curing Compound 711.01
>
> Portland Cement, Type II, Low Alkali 701.01
>
> Water 725.01
>
> Fly Ash 725.04
>
> Silica Flume 725.04
>
> Reinforcing fibers 725.29

Shotcrete consist of a pneumatically-applied mixture of Portland cement,
aggregate, and water, which is conveyed through a hose and projected at
high velocity onto a surface. The mixture may contain admixtures to
provide quick set, high early strength, and satisfactory adhesion.

**Construction Requirements**

**566.03 General.** Conform to the following:

> ACI 506.2 Specifications for Proportioning and Application of
> Shotcrete.
>
> ACI 506R Guide to Shotcrete
>
> AASHTO T 23 Making and Curing Concrete Test Specimens in the Field.
>
> AASHTO T 24 Obtaining and Testing Drilled Cores and Sawed Beams of
> Concrete.
>
> AASHTO C 311 Method for Sampling and Testing Fly Ash or Natural
> Possolans for
>
> use as a Mineral Admixture in Concrete.
>
> ASTM C 1077 Practice for Laboratories Testing Concrete and Concrete
> Aggregates for use in Construction and Criteria for Laboratory
> Evaluation.

**SUBMITTALS**

Submit the following (**a**, **b**, and **c**) at least 36 calendar days
before placing shotcrete:

**(a) Shotcrete Materials, Preparation, and Application.**

> **(1)** Proposed method of applying shotcrete.
>
> **(2)** Description of proposed equipment for mixing and applying
> shotcrete.
>
> **(3)** Proposed shotcrete mix design according to Subsection 556.06.
>
> **(4)** Provide other information necessary to verify compliance with
> ACI 506.2.

**(b) Reports and Records.** Submit results of all testing of shotcrete
samples to the CO. Submit preconstruction testing reports with the
proposed shotcrete mix design. (See Subsection 556.07 for required
preconstruction testing.) Submit field quality control test reports
within two working days of performing the tests. Include the following
information in the reports:

> **(1)** Sample identification including mix design and test panel
> number and orientation.
>
> **(2)** Date and time of sample preparation including curing
> conditions and sample dimensions.
>
> **(3)** Date, time, and type of test.
>
> **(4)** Complete test results including load and deformation data
> during testing, sketch of sample prior to and after testing, and any
> unusual occurrences observed.
>
> **(5)** Names and signature of person performing the test.
>
> **(6)** Location of steel reinforcement, if used, covered by
> shotcrete.
>
> **(7)** Name of nozzleman.

**(c) Product, Equipment Data, and Samples.**

> **(1)** Applicable manufacturers\' instructions, recommendations,
> literature, performance, and test data for materials and mixing and
> application equipment.
>
> **(2)** Representative samples of shotcrete materials, if request by
> the CO.
>
> **(3)** Certification that shotcrete materials conform to the
> standards specified herein.

**(d)** Prepare and submit a summary of shotcrete production and
application for each shift. Furnish the summary to the CO within 24
hours. Include the following information in the report:

> **(1)** Quantity and location of shotcrete applied including sketches.
>
> **(2)** Observations during production and application.
>
> **(3)** Description of placement equipment.
>
> **(4)** Batch number(s) if applicable.

**566.04 Qualifications.** The Contractor shall submit the following
written documentation at least 20 calendar days prior to placing
shotcrete:

**(a) Project References.** References from at least 3 projects of
comparable nature completed in the last 2 years. References shall
include project name, owner\'s name, and phone numbers.

**(b) Nozzlemen Experience and Training.** Describe the experience of
each nozzleman. Nozzlemen shall have previous experience and training in
the application of shotcrete on at least two projects of comparable
nature. Nozzlemen shall demonstrate their ability to place shotcrete to
meet the requirements of these specifications prior to production
placement.

**(c) Foreman Experience.** Describe the experience of each shotcrete
foreman. Foreman shall have direct shotcrete application experience on
comparable projects.

**(d) Testing Laboratory Certification.** Provide documentation that
testing laboratory complies with the requirement of ASTM C 1077 and has
experience in performing the tests specified in this section. The
testing laboratory shall demonstrate the ability to perform the
requisite tests, or be accredited by AASHTO to meet the requirements of
ASTM C 1077.

**566.05 Equipment.**

For dry mix, provide a water supply system consisting of a job site
storage tank, and a positive displacement pump capable of supplying
water through a regulating valve accurately controllable by the
nozzleman in sufficient amount and at a pressure recommended by the
manufacturer of the delivery machine.

Use equipment for mixing shotcrete materials which is capable of
handling and applying shotcrete containing the specified maximum size
aggregate and admixtures. An air hose and blow pipe shall be available
for use to clear dust and rebound during shotcrete application.

Use an air supply system capable of supplying the delivery machine and
hose with air at the pressures and volumes recommended by the
manufacturer of the machine. No air supply system shall be used that
delivers air contaminated by oil or that is incapable of maintaining
constant pressure.

Use a delivery machine capable of introducing materials to the delivery
hose at a uniform rate with ejection from the nozzle at velocities that
will secure adherence of material to the treated surface with minimum
rebound and maximum density.

**566.06 Shotcrete Mix.**

**(a) Mix Proportions.** Proportion cement, aggregate, and admixtures to
obtain the specified strengths, entrained air content, and set times
specified, and required field performance. Submit mix proportions to the
CO for acceptance. The wet mix process is required when air entrainment
or chemical admixtures are used.

**(b) Compressive Strength.** Test in accordance with AASHTO T 24. The
design mix and the production work, as represented by test cores, shall
develop compressive strength values as required by the contract.

**(c) Water.** Use the amount of water required to produce shotcrete of
suitable strength, consistency, quality, and uniformity with the minimum
amount of rebound.

**(d) Materials.** Unless otherwise approved by the CO, use the same
types and sources of materials as submitted with the mix proportions in
the field trials and production work.

**566.07 Preconstruction Testing.**

**(a) General.** The purpose of preconstruction testing is to ascertain
the compatibility of the proposed ingredients; to verify that the
proposed mix design meets the strength and set time specified; and to
demonstrate the capability of the equipment, workmanship, and materials
to produce acceptable quality shotcrete under field conditions as
determined by inspection and laboratory tests on samples taken from
field trial test panels. Perform preconstruction field trials and
laboratory testing in a manner that will allow demonstration of
achievement of these objectives to be demonstrated.

**(b) Field Trials.** Conduct preconstruction field trials of shotcrete
production and application prior to starting production shotcreting.
Have each proposed nozzleman make the field trials on two vertical test
panels. Construct test panels on wood forms at least 3 feet by 3 feet in
size. Cure test panels in accordance with AASHTO T 23, except do not
immerse the panels. Allow the CO the opportunity to witness all phases
of the field trial work.

**(c) Coring.** Obtain six cores from each test panel to verify the
shotcrete mix design requirements. Take cores from each test panel in
accordance with AASHTO T 24 except that cores shall be 3 inches in
diameter. The ends of the cores shall be trimmed to provide cylinders 3
inches long.

**(d) Testing of Core Samples.** Soak cores in water 40 hours prior to
testing. Identify core specimens by mix designation and test panel
number. Moist cure but do not immerse cores from the time they are taken
until the time they are tested. Perform compressive strength tests on
core samples in accordance with AASHTO T 24. Test three cores after
curing for three days, and test three cores after curing for 28 days.
All specified strength requirements will be satisfied before the
shotcrete mix design will be considered for approval. Allow the CO the
opportunity to witness the tests.

**566.08 Proportioning and Mixing.**

**(a) Mix Design Acceptance.** The CO will accept or reject the
shotcrete mix design based on the results of the preconstruction field
trails and testing. Do not use any shotcrete mix that has not been
approved by the CO. Prior to approving any changes to an approved mix
design, the CO may request additional preconstruction testing at no
additional cost to the government.

**(b) Proportioning Materials.** Use the proportions of ingredients
determined on the basis of the approved mix design.

**566.09 Surface Preparation and Application of Shotcrete.**

**(a) Surface Preparation.** Clean loose material, mud, rebound, and
other foreign matter from all surfaces which are to receive shotcrete,
whether rock or previously shotcreted. Apply shotcrete to moist,
unfrozen surfaces only.

**(b) Shotcrete Application Requirements.**

> **(1)** Use nozzlemen/operators whose qualifications have been
> approved and who have fabricated test panels from which shotcrete test
> results were obtained and found acceptable under these specifications.
>
> **(2)** Hold the nozzle at a distance and position such that the
> stream of flowing material will impinge as nearly as possible at right
> angles to the receiving surface. Apply shotcrete in a circular fashion
> to build up the required layer thickness. Apply mixed material within
> 45 minutes after adding cement.
>
> **(3)** Shotcrete shall flow from the nozzle in a steady uninterrupted
> flow. When flow becomes intermittent, direct the flow away from the
> work area until it becomes steady.
>
> **(4)** Provide equipment which permits application of shotcrete to
> surfaces at an approximate range of 3 to 6 feet from the nozzle. The
> surface of each shotcrete layer shall be uniform and free of sags,
> drips, or runs.
>
> **(5)** The maximum thickness of any individual shotcrete application
> is 2 inches. Build up layers as to achieve the minimum thickness.
> Install approved measuring pins to indicate the thickness of the
> shotcrete layer(s). Install pins on 6-foot centers longitudinally and
> transversely with no less than two pins per increment of surface area
> to receive the shotcrete.
>
> **(6)** Remove laitance, loose material, and rebound. Rebound shall be
> promptly removed from the work areas.
>
> **(7)** Taper construction joints over a distance of at least 1 foot
> to a thin edge. Thoroughly wet the surface of such joints before any
> adjacent section of shotcrete is placed. Do not use square
> construction joints.
>
> **(8)** Construct shotcrete such that a dense and uniform mixture
> without rebound inclusions, segregation, or disassembly weakness to
> bond between layers results.

**566.10 Protection and Curing.**

**(a)** Protect and cure in accordance with ACI 506.2.

**(b)** Keep shotcrete surfaces moist and covered whenever ambient
outside temperature at the exposed shotcrete sections below 32F at any
time during curing.

**(c)** Apply curing compound to exposed shotcrete surfaces. Apply in
accordance with curing compound manufacturer\'s recommendations.

**566.11 Field Quality Control.**

**(a) Weather Limitations.** Do not place shotcrete in cold weather
unless adequately protected when the ambient temperature is below 40F
and falling, or when shotcrete will be subjected to freezing temperature
before obtaining a minimum strength of 750 psi. The temperature of
shotcrete when deposited shall not be less than 50F nor more than 86F.

Do not perform shotcrete operations during high winds and heavy rains.

**(b) Production Test Panels.** Prepare production test panels at the
rate of one for every 6005 square yards of shotcrete applied. Make test
panels 5 feet by 5 feet. Apply the shotcrete 4 inches thick. Obtain six
3-inch diameter core specimens from each panel and determine the
compressive strength of two of the specimens in accordance with AASHTO T
24 at three days, and two specimens at 28 days.

**(c) In-Place Test Cores.** Obtain in-place test cores from completed
work at locations and times determined by the CO. Obtain two test cores
for every 600 square yards of shotcrete placed. Obtain cores in
accordance with AASHTO T 24. Cure core specimens in accordance with
AASHTO T 23 until the specimens are tested. If any core fails to show
adequate bond or shows obvious defects as determined by the CO, two
additional cores shall be taken within 6 feet of the unsatisfactory
core. If either of these additional cores fail to show adequate bond
with the rock or show obvious defects, the shotcrete in the area
surrounding the unsatisfactory cores will be considered to be defective
shotcrete and the CO may require additional thickness of shotcrete, or
may require removal and replacement with new shotcrete, at no additional
cost to the government. Additional core specimens may be required at any
time if, based on field observations, defective shotcrete is suspected.
Determine the compressive strength of cores taken from the completed
work in accordance with AASHTO T 24. Test one core at three days, and
one core at 28 days for each set of two cores taken in every 600 square
yards of shotcrete placed. Fill all core holes with shotcrete so as to
be flush with the surrounding shotcrete surface, and to the satisfaction
of the CO.

**(d) Shotcrete System.** If the CO determines that the Contractor\'s
selected shotcreting system fails to provide satisfactory in-place
shotcrete in accordance with these specifications, the Contractor shall
change to another system.

**566.12 Acceptance.** Shotcrete will be accepted under Subsection
106.04.

**Measurement**

**566.13** Shotcrete will be measured by the square yard of shotcrete
approved.

**Payment**

**566.14** The accepted quantities measured as provided above will be
paid for at the contract price per unit of measurement for the pay item
listed below that is shown in the bid schedule. Payment will be full
compensation for the work prescribed in this section. See Subsection
109.05.

Payment will be made under:

**Pay Item Pay Unit**

56601 Shotcrete Square yard