1043SHOTCRETE

1043.1DESCRIPTION—This work is the production, application, and construction of pneumatically applied

shotcrete according to ACI 506. Shotcrete may be produced by either dry-mix or a wet-mix process.

1043.2MATERIAL—

10%, by weight of the total cementitious material. For pre-packaged dry mix shotcrete, use silica fume that is pre-blended by the manufacturer.

evaluate aggregate for reactivity and if using aggregates that are deemed potentially reactive use according to Section 704.1(g). Conform to the composite gradation envelope in Table A. Other gradations according to ACI 506, Table 2.1 may be approved by the Representative.

TABLE A Aggregate Gradation Sieve Size Total Percent Passing 1/2-inch 100 3/8-inch 90 - 100 No. 4 70 - 85 No. 8 50 - 70 No. 16 35 - 55 No. 30 20 - 35 No. 50 8 - 20 No. 100 2 - 10

Use a migrating corrosion inhibitor according to AASHTO M 194, from a manufacturer listed in Bulletin

fibers that are a minimum of 1/2-inch length, monofilament or collated-fibrillated microfibers.

in Table B.

TABLE B Shotcrete Mix Design Requirements Test Description Test Method Age (Days) Specified Requirements Maximum Water/Cementitious Materials Ratio - - 0.40 Air Content - As Shot (%)* AASHTO T 152 - 4 ± 1.5 Slump at Discharge into Pump (inches) AASHTO T 119 - 3 1/2 ± 1 1/2 Minimum Compressive Strength (psi) PTM No. 611 7

3,600 4,500 *compensate for air entrainment loss during shooting according to ACI 506

or volume according to AASHTO M 157 or AASHTO M 241. For pre -packaged dry-mixes, provide mixes according to ASTM C1480, and from a manufacturer listed in Bulletin 15.

1043.3CONSTRUCTION—

Assign a shotcrete crew supervisor that has at least 5 years’ experience in shotcrete repair work on projects of similar size and character. Provide nozzlemen who are certified by the ACI for application of the proposed shotcrete process for bot h vertical and overhead surface and who have successfully completed three projects, of similar size and character. Submit written documentation to the Structure Control Engineer at least 10 working days before start of shotcrete work, which provides the following:

• Proof of experience for shotcrete crew supervisor and nozzlemen. Submit three references for crew supervisor and nozzlemen from persons who were responsible for supervision of these projects.

• Mix designs and test records, showing all material sources and indicating conformance to project specifications for all shotcrete materials.

• Details of proposed forming, bracing, falsework, or temporary support systems.

• A field QC plan

Provide in the field QC plan at a minimum, the following:

• A list of the proposed shotcreting equipment, including water supply pumps, valves and mixing equipment. Provide brand name, model and capacity of proposed pump or gun and air compressor.

• Details of proposed means of preparing existing concrete substrate in areas to receive shotcrete.

• Details of proposed means of controlling line, grade, and reinforcement cover.

• Details of proposed methods for control and disposal of waste materials, including demolition slurries, blasting grits, concrete debris, waste shotcrete, rebound, and overspray.

• Details of the proposed curing procedures

Do not start shotcreting work until the Structure Control Engineer has reviewed and approved all submittals.

and disintegrated particles, and material that might impair the bond between the surfaces to be covered and the shotcrete mixture. Remove unsound concrete and mortar, as directed. After removal of unsound material, clean sound surface. Clean existing reinforcement to SSPC-SP6 cleaning standards. Saturate the prepared concrete substrate w ith clean water the day befores hotcrete application. Bring wetted surfaces to a saturated surface dry (SSD) condition before application of shotcrete. Do not applys hotcrete to a dry

surface, or to a surface with free surface water.

storage requirements of Sections 1002.3(a) and 1002.3(b). Lap adjacent sheets of wire fabric a minimum length of 4 inches for 2 -inch mesh and a minimum length of 6 inches for 3 -inch mesh. Fasten wire fabric together with wire ties at intervals of not more than 18 inches.

unless otherwise indicated or directed, place a layer of wire fabric for each 3 -inch layer of shotcrete or fraction thereof. More than one layer of fabric may be attached to an expansion anchor, provided the anchor is long enough. Hold the wire fabric in place by means of wedge expansion anchors, either 1/4-inch diameter by 3 to 3 1/4 inches in length, or 3/8 -inch diameter by 3 3/4 to 4 inches in length. Use longer 3/8-inch diameter anchors where necessary , unless otherwise indicated . Space 1/4-inch diameter anchors approximately 20 inches center-to-center in each direction, starting 3 inches from the outside edges of the areas to be shotcreted. Space 3/8 -inch diameter anchors approximately 30 inches center -to-center in each direction, starting 6 inches from the outside edges of the areas to be shotcreted. Fasten the fabric to the wedge expansion anchors away from the prepared surface, with 1 inch clear below the finished surface of the repair. Where existing reinforcement is exposed due to removal of deteriorated concrete, wire fabric may be tied to this reinforcement at 18-inch intervals, to form a cage to position and support the fabric within 1 inch of the finished surface of repair. Avoid excessive wire fabric layers, which may create planes of weakness or internal stresses.

descending air temperature, away from artificial heat, falls to 40F or less. Do not resume operations until the air temperature, away from artificial heat, rises above 40F. For mix proportioning in cold weather, d o not let water with a temperature above 90F come in direct contact with the cement, until the cement has been mixed with the aggregates. Place shotcrete when the mix temperature is between 50F and 100F. Do not use materials containing frost, lumps, or crusts of hardened materials. Do not place shotcrete on surfaces which are less than 40F.

above, take thermometer readings of the plastic concrete at 1/2-hour intervals and at the conclusion of the mixing cycles. Discontinue shotcrete operations if the plastic concrete temperature exceeds 90F for wet mix or 100F for dry mix. Lower the temperature of reinforcement and receiving surfaces below 100F before shooting.

due to environmental conditions such as wind and rain.

Section 704.3. For plant or truck mixed material, produce according to Section 704.2. Apply all shotcrete within 90 minutes after addition of mix water to the batch. Do not use shotcrete that has exceeded 45 minutes without agitation. Utilize shotcrete delivery equipment capable of delivering a steady stream of uniformly mixed material to the discharge nozzle at the proper velocity and rate of discharge.

shotcrete within 45 minutes of the first contact of cement with water. Discard aged materials and do not apply them in the work.

Provide shotcrete delivery equipment capable of delivering an uninterrupted flow of pre-dampened material to the discharge nozzl e at sufficient velocity. Use a rotary gun or pressure vessel with pre- dampening equipment.

shotcrete mixture, equipment, and crew to produces hotcrete conforming to the project specifications. Acceptance of the pre-construction trial results is required before application of any shotcrete on the project. Perform the pre-construction trial with the certified nozzlemen proposed for use on the project. Nozzlemen who have not been pre -qualified may not applys hotcrete on the project. Use the same materials, shotcrete mixture and equipment proposed for use on the project and approximate working conditions, reinforcement and shooting positions (vertical and overhead). Obtain 5 cores from each mock-up at locations selected by the Representative. At least two of the cores must contain reinforcement when the work represented by the panels contains reinforcement. The Representative will visually examine the cores for defects. If defects are evident, the Representative will grade the cores according to the requirements of ACI 506 . A test mock -up with any single core grade exceeding Core Grade 3 or with more than two of the 5 cores having a Core Grade 3 will be considered a failure. In addition to the mock -up, pre-qualify the s hotcrete mixture by shooting a plain (non -reinforced) test panel, minimum 24 inches x 24 inches, according to ASTM C1140. Perform compressive strength testing on 3 cores from the test panel, according to PTM No. 606. Mixture will be approved for application on the project if all 3 cores meet the 7-day minimum compressive strength of 3,600 pounds per square inch. If the pre -construction test specimens fail to meet the project performance requirements, mak e the necessary adjustments in shotcrete materials, mixture design, or application, and re-shoot test panels. Do not start shotcrete work on the project until the pre -construction performance testing requirements have been met.

Establish new lots daily. A lot is each 25 cubic yards of shotcrete production, or portion thereof. Shoot the test panel in the same position as the work being done. Produce, store, handle, and field cure construction lot test panels in the same manner as the permanent work. Extract 3 cores from each test panel according to ASTM C1140 for compressive strength testing. Perform 28-day acceptance testing on the extracted cores according to ASTM C1140 and PTM No. 606. Acceptance of the lot represented will be based on the compressive strength testing of the 28 -day acceptance cores. If the results of the average, (N=3) fails to meet a minimum 28-day compressive strength of 4,500 pounds per square inch , adjustments to payment will be made according to Section 110.10(d) using the minimum compressive strength requirements of Class AAA concrete.

approved by the Representative before the application of any shotcrete. For restoration and repair work, finish shotcrete to match existing surfaces. For finishing on bridge piers, caps, soffit, and abutments, t rim shotcrete with a cutting rod or other suitable device to the specified line and grade. Unless otherwise specified, finish shotcrete to a sandy texture as approved by the Representative using a rubber float or other suitable finishing tools. Tolerance of finished surface must not exceed 1/4-inch under a 10-foot straightedge in any direction. Abrupt surface irregularities must not exceed 1/8-inch. Continuously remove accumulations of rebound and overspray using blowpipe, or other suitable devices in advance of deposition of new s hotcrete. Protect all fixtures and adjacent concrete surfaces from buil d- up of rebound, overspray and shotcrete trimmings. Remove all such materials on a daily basis. Construct construction joints to a 45 -degree tapered edge. Cut plastics hotcrete with a trow el or other suitable tool to form a construction joint. Do not featheredge construction joints. For large applications requiring multiple layers, remove curing compound on previously placed shotcrete surfaces by sandblasting. Install approved depth gauges to indicate the thickness of the shotcrete layers. Install depth gauges on 6 -foot centers longitudinally and transversely with no less than two gauges per increment of surface area to receive shotcrete. Moisten all surfaces.

thickness burlap and/or fogging for 7 days . Keeps hotcrete and burlap fully saturated during the entire

curing period. Assure 100% contact between the burlap application and shotcrete material. As an alternate, two applications of liquid membrane-forming curing compounds may be used only when water curing is not feasible and approved by the Representative.

of the shotcrete surfaces at 50F or greater for the first 4 days after application of shotcrete and above 40F for the last 3 days of the curing period. Do not count a day on which the minimum curing temperatures are not maintained as a curing day . Do not utilize cold weather curing until the Representative reviews the proposed means of maintaining the curing temperature. Do not use unvented heaters that may cause carbonation. If at any time during the curing period, the curing temperature falls below 35F, the Department will consider the work unsatisfactory and will reject it.

Deficiencies during the shotcrete application process, such as, but not limited to the following, constitute a cause for shotcrete rejection:

• Failure to properly control and remove build-up of overspray and rebound

• Incomplete consolidation of shotcrete around reinforcing steel

• Incorporation of sand lenses, excessive voids, delaminations, sags or sloughing

• Failure to apply shotcrete to the required line, grade and tolerance

Perform remedial work to correct deficiencies while shotcrete is still plastic. The hardened shotcrete will be examined by the Representative for any evidence of excessive plastic or drying shrinkage cracking, tears, featheredging, slou ghs, or other deficiencies. The Representative will sound the material to check for delaminations. If delaminations are discovered during sounding , or if directed by the R epresentative, conduct bond pull -off tests according to ASTM C900 at locations a nd a frequency selected by the R epresentative. The average of a set of three bond pull -off strengths must exceed 145 pounds per square inch, with no individual result less than 100 p ounds per square inch. If the bond pull-off strength results fail to meet the specified requirement, the work will be rejected. When test results or the assessment of plastic or hardened shotcrete indicate deficiencies or non- conformance to the specifications, the Representative will implement a program to evaluate the in -place shotcrete. Provide all labor, materials, and equipment necessary to perform the evaluation at no cost to the Department. Correct deficiencies to the satisfaction of the Representative. Remove and replace deficient or non-conforming shotcrete at no cost to the Department.

1043.4MEASUREMENT AND PAYMENT—Square Foot