SHOTCRETE
PART 1 GENERAL
1.1SECTION INCLUDES
A.Shotcrete mix design, application and curing
1.2RELATED SECTIONS
A.Section 03055: Portland Cement Concrete
1.3REFERENCES
A.AASHTO T 152: Air Content of Freshly Mixed Concrete by the Pressure
Method
B.ASTM C 309: Liquid Membrane-Forming Compounds for Curing Concrete
C.ASTM C 1604: Obtaining and Testing Drilled Cores of Shotcrete
1.4DEFINITIONS
A.Dry Mix Process – Shotcrete production process in which most of the
water is added at the nozzle.
B.Nozzle Operator – Worker on shotcrete crew who manipulates the nozzle,
controls consistency of dry mix shotcrete, and controls final disposition of the material.
C.Rebound – Shotcrete that fails to adhere to the surface on which the
shotcrete is being applied.
D.Wet Mix Process – Shotcrete production process in which cement,
aggregate, water and admixtures are first mixed together before introduction into the delivery hose.
Shotcrete
1.5SUBMITTALS
A.Shotcrete mix design with mix proportions and test results for approval.
1.The Department approves shotcrete mix designs based on
preconstruction test panel results.
2.Include at least the following:
a.Aggregate source and grading
b.Cement type and brand
c.Water source
d.Type and dosage of hydration stabilizing/extended-set
admixtures, if used
e.Discharge time limit for wet mix shotcrete
f.Preconstruction test panel test results including at least the
following: 1) Sample identification, including mix design and test panel number and orientation. 2) Date and time of core sample preparation including sample dimensions. 3) Date and time of compression test. 4) 28 day compressive strength. 5) Names and signatures of people performing the compression test. 6) Name of nozzle operator who produced test panel. 7) Air content measured at the time of test panel creation (wet mix only).
B.Written documentation of the shotcrete supervisor’s and nozzleman’s
qualifications including proof of ACI Shotcrete Nozzleman certification for review.
1.ACI Shotcrete Nozzleman Certification
2.Experience on at least three comparable projects.
a.Include project names, locations and owners' contact
information
C.Production summary reports for each shift
1.Submit for information within 24 hours of completing shift.
2.Include at least the following:
a.Observations of success or problems of equipment
operation, application, final product conditions, and any other relevant issues during production and application. 1) Include sketches for locations as necessary.
b.Shotcrete batch number(s) if applicable
Shotcrete
1.6ACCEPTANCE
A.The Department will perform testing according to Table 1.
Table 1 Sampling and Testing Schedule Property or Test Methods or Frequency Sampling Point Characteristic Specifications Air Content Prior to AASHTO T 152 1 per load1 (Wet Mix Only) placement 1 set per 50 cy; 28 day Compressive Production test ASTM C 1604 at least one set Strength panels2 per day When continuous mixing is used, sample every 10 cy. A single compressive strength test result is the average result from three 3-inch diameter core specimens from the same test panel tested according to ASTM C 1604 at 28 days.
B.Shotcrete that fails to meet the strength requirements based on the
following will be cause for rejection.
1.Specified 28 day minimum compressive strength test result less
than 0.85 times the minimum 28 day compressive strength.
2.A single core compressive strength test result less than 0.75 times
the minimum 28 day compressive strength.
3.The engineer may accept a 'reject' lot based on engineering
analysis. The Department will apply a price reduction on rejected shotcrete allowed to stay in place.
C.Shotcrete that has been damaged by frost, or which lacks uniformity,
exhibits segregation, honeycombing, lamination with a shotcrete stage, or shows excessive cracking will be cause for rejection.
PART 2 PRODUCTS
2.1SHOTCRETE
A.Refer to Section 03055 for material requirements.
B.Conform to the requirements in Table 2.
Shotcrete
Table 2 Shotcrete Air Content 28 day Minimum Process Range Compressive Strength2 (psi) Dry Mix N/A 4,000 8% - 10% at the Wet Mix 4,000 pump According to ASTM C 1604
C.Use the amount of water required to produce shotcrete of suitable
strength, consistency, quality, and uniformity with the minimum amount of rebound.
2.2MIX DESIGN
A.Design mixes to meet the requirements of this Section and project specific
criteria.
B.Preconstruction Test Panels
1.Refer to this Section, Article 3.1.
2.3CURING COMPOUND
A.Use a curing compound that complies with ASTM C 309 Type 1-D or Type
2, Class A.
PART 3 EXECUTION
3.1TEST PANELS
A.Forms and Construction
1.Construct wood forms for preconstruction and production test
panels at least 3.5 inch thick by 2 ft by 2 ft in size.
2.Construct wood forms with plywood back 0.75 inch thick minimum.
3.Do not include reinforcing steel bars in the test panels
B.Preconstruction Test Panels
1.Produce test panels for each proposed mix design.
a.Include a separate test panel for each anticipated shooting
orientation (slab, slopes, vertical, and overhead), and each proposed nozzle operator.
Shotcrete
b.Assign a test panel number and record specific information
about the panel required for submittal.
2.Notify the Engineer of the time and location of preconstruction test
panel production so that the Engineer may witness the production.
C.Production Test Panels
1.Produce separate panels for each nozzle operator applying
shotcrete.
a.Produce production test panels for every 50 cubic yards of
material placed, but not less than one panel per day.
b.Shoot test panels in the same manner as that being used on
the project, including distance from nozzle, angle and orientation.
c.Include a separate test panel for each mix design used by
the nozzle operator and each shooting orientation that mix design was used in (slab, slopes, vertical, and overhead).
2.Cure test panels in similar conditions to what is anticipated in the
field and until test specimens are sampled.
D.Compressive Strength Test
1.Use a core drill to remove three, 3 inch diameter samples from the
center of the test panel, at least 5 inch clear of the edges.
2.Remove the test specimens at least 21 calendar days and no more
than 26 calendar days age.
a.Coordinate timing of specimen removal, delivery and testing
with the Engineer.
3.Store cores in watertight plastic bags and label with the project
number, test panel number, date of placement, and name of nozzle operator.
4.Deliver cores to the Department for testing immediately after
removal.
3.2SURFACE PREPARATION
A.Prepare shotcrete application surface according to the following:
1.Remove loose material, mud, rebound, and other foreign matter.
2.Clear any vegetation or organic material from the surface.
3.Remove curing compound on previously placed shotcrete surfaces
by sandblasting.
4.Install depth gages on 4 ft centers longitudinally and vertically to
indicate the thickness of shotcrete layers.
5.Dampen natural excavated surfaces immediately before shooting.
a.Remove standing water before shooting.
6.Achieve saturated surface dry condition on shotcrete surfaces.
Shotcrete
3.3APPLICATION
A.Limitations
1.Do not apply shotcrete during adverse weather including rain,
snow, and high winds without adequate protection authorized by the Engineer.
2.Cease placement operations when the ambient temperature drops
below 50 degrees F.
B.Use authorized nozzle operators and approved mix designs.
C.Apply shotcrete in one or more layers.
1.Apply shotcrete within discharge time limit indicated in the
approved mix design.
2.Make the surface of each shotcrete layer uniform and free of sags,
drips, or runs.
3.Limit the layer thickness to 3 inch per application with no sloughing
or sagging.
4.Broom or scarify the applied surface and allow the layer to harden if
additional thickness is required.
5.Remove laitance, loose material, and rebound.
a.Promptly remove rebound from the work area.
6.Construction Joints
a.Taper construction joints at an approximately 45 degree
angle from the receiving surface.
b.Form joints by cutting plastic shotcrete. Roughen shotcrete
in the joint face while it is still plastic.
3.4CURING
A.Apply curing compound to shotcrete surfaces which are exposed in their
final condition.
1.Apply at twice the rate indicated for formed surfaces recommended
by the manufacturer.
B.Cure for at least 7 consecutive days or the time necessary to attain 70
percent of the specified 28 day minimum compressive strength, whichever period is less.
1.Immediately repair damage to the curing compound film during the
specified curing period by re-spraying.
END OF SECTION
Shotcrete
Shotcrete in other states
Utah revises spec sections through supplementals and new editions. We check this one every week and email you the day it changes. Free, no account.
Source: Utah Standard Specifications for Road and Bridge Construction, 2026 Edition. Pages 303–308 of 1,331.
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