660Pneumatically Placed Concrete Mortar

01.01 General. This work consists of constructing reinforced pneumatically placed concrete mortar

surfaces for soil nail retaining walls. P neumatically placed concrete mortar (shotcrete) consists of either dry mixed fine aggregate and Portland cement applied by a suitable mechanism, to which water is added immediately before its expulsion from the nozzle, or mortar premixed by mechanical methods and pneumatically applied through a no zzle onto the prepared surface. P erform shotcrete construction concurrently with soil nail wall construction as specified in Section 644. 660.

01.02 Qualifications. Use workers, including foremen, nozzlemen, and delivery equipment operators,

experienced to perform the work. Shotcrete nozzlemen shall have experience on at least 3 projects in the past 3 years in similar shotcrete application work and demonstrate ability to satisfactorily place the shotcrete. I nitial qualification of nozzlemen will be based either on previous ACI certification or satisfactory completion of qualification test panels. The requirement for nozzlemen to shoot qualification test panels will be waived for nozzlemen who can submit documented proof they have been certified in accordance with the ACI 506.3R Guide to Certification of Shotcrete Nozzlemen. The Certification shall have been done by an ACI recognized shotcrete testing lab and/or recognized shotcreting consultant and have covered the type of shotcrete to be used (plain wet-mix, plain dry -mix). All nozzlemen will be required to periodically shoot production test panels during the course of the work at the frequency specified herein. G ive notification not less than 2 days prior to the shooting of qualification test panels to be used to qualify nozzlemen without previous ACI certification. Use the same shotcrete mix and equipment to make qualification test panels as those to be used for the soil nail wall shotcrete facing. Initial qualification of the nozzlemen will be based on a visual inspection of the shotcrete density and void structure and on achieving the specified 3 day and 28 day compressive strength requirements determined from test specimens extracted from the qualification tes t panels. Conduct qualification test panels, core extraction, and compressive strength testing in accordance with ACI 506.2 and AASHTO T24/ASTM C42, unless otherwise specified herein. 660.

01.03 Submittals. Submit 5 copies of the following information for review and approval at least 15 days

prior to beginning shotcrete placement: 1.D ocumentation of the nozzlemen's qualifications. 2.P roposed methods of shotcrete placement and of controlling and maintaining facing alignment and s hotcrete thickness. 3.S hotcrete mix design in accordance with Subsection 501.02.05, except cores from test panels or production panels will be used instead of cylinders and they will be tested as specified herein. 4.Manuf acturer Certificates of Compliance for drainage geotextile, geocomposite drain strip, drain grate and accessories, and PVC drain piping. 5.F ormwork dimensions and details for casting the CIP facing over the shotcrete construction facing. Include details for formwork connections to the shotcrete facing and/or nails (if applicable), proposed concret e pl acement method and placement rates, and accompanying structural calculations verifying the structural adequacy of the formwork, connections, and shotcrete facing and/or nails to support the loading induced bythe fluid CIP concrete. When anchors embedded into the shotcrete facing will be used to support the 1- sided CIP face form, include calculations illustrating the anchor design load (calculated as the design concrete fluid pressure times the anchor tributary area). The structural calculations shall be prepared and sealed by a Registered Professional Engineer licensed in the State of Nevada. A pproval or rejection of submittals will be given within 10 days after receipt of a complete submission. Do not begin shotcrete construction or incorporate materials into the work until the submittal requirements are satisfied and found acceptable. Changes or deviations from the approved submittals shall be re- submit ted for approval. No adjustments in contract time will be allowed due to incomplete submittals. 660 PNEUMATICALLY PLACED CONCRETE MORTAR A pre -construction meeting will be held prior to the start of wall construction. Attendance is mandatory. The shotcrete Contractor, if different than the soil nail specialty Contractor, shall attend. MATERIALS

660.02.01 General. Materials shall conform to the following Sections:

Portland Cement ................................ .................................................................................................................................... Section 701 Concrete Curing Materials and Admixtures ............................................................................................................................ Section 702 Water ..................................................................................................................................................................................... Section 722 Aggregate for shotcrete shall conform to Section 706 except the following combined gradation requirement shall apply: Sieve Size Percent Passing by Weight 12.5 mm (1/2 in.) ............................................................................ 100 9.50 mm (3/8 in.) ......................................................................... 90-100 4.75 mm (No. 4) .......................................................................... 70-85 2.36 mm (No. 8) .......................................................................... 50-70 1.18 mm (No. 16) ......................................................................... 35-55 600 μm (No. 30) .......................................................................... 20-35 300 μm (No. 50) ........................................................................... 8-20 150 μm (No. 100) .......................................................................... 2-10 Use Type V cement with a minimum of 20% Class F pozzolan by mass in all concrete. In lieu of this requirement, Type II cement with a minimum of 20% Class F pozzolan by mass or Type IP (MS) cement may be substituted therefore. The combined mass of cement and pozzolan will be considered as the mass of the cement when determining compliance with the cement range and maximum water requirements of Table I of Subsection 501.0 2.05. Welded wire fabric shall conform to ASTM A185, A496, or A497. Reinforcing bars shall conform to AASHTO M31/ASTM A615, Grade 420 (60), deformed. PVC pipe shall conform to ASTM D1785 Schedule 40 PVC. Geocomposite drain strips shall conform to the following: GEOTEXTILE PROPERTY TEST METHOD REQUIREMENT Grab Tensile Strength, N (lb) ASTM D4632 ≥ 445 ( ≥ 100) Puncture Strength, N (lb) ASTM D4833 ≥ 226 ( ≥ 60) Elongation, % ASTM D4632 ≥ 50 Apparent Opening Size - AOS, mm (US Sieve) ASTM D4751 0.125 ≤ AOS ≤ 0.25 (120 ≤ AOS ≤ 60) Flow Rate, lpm/m2 (gpm/ft2) ASTM D4491 ≥ 4890 ( ≥ 120) CORE PROPERTY TEST METHOD REQUIREMENT Thickness, mm (in.) ASTM D1777 ≥ 10 ( ≥ 0.40) Compressive Strength, kN/m2 (lb/ft2) ASTM D1621 ≥ 670 ( ≥ 14,000) Flow Rate Per Unit Width, lpm/m gpm/ft ASTM D4716 ≥ 161 ( ≥ 13) Do not begin shotcrete placement until notification is given that the proposed mix design and method of placement are acceptable. Proportion the shotcrete to be pumpable with the concrete pump furnished for the work, with a cementing materials content of at least 390 kg/m 3 (657 lb/yd3) and water/cement ratio not greater than 0.50. Do not use admixtures unless approved. Thoroughly mix admixtures into the shotcrete at the rate specified by the manufacturer. Accelerators, if used, must be compatible with the cement used, be non- corrosive to steel, and not promote other detrimental effects such as cracking or excessive shrinkage. The maximum allowable chloride ion content of all ingredients shall not exceed 0.10% when tested according to AASHTO T260. Air entrainment is not required for temporary shotcrete construction facings. PNEUMATICALLY PLACED CONCRETE MORTAR 660 Provide a shotcrete mix capable of attaining 14 MPa (2,000 psi) compressive strength in 3 days and 28 MPa (4,000 psi) in 28 days. The average compressive strength of each set of three test cores extracted from test panels or wall face must equal or exceed 85% of the specified compressive strength, with no individual core less than 75% of the specified compressive strength, in accordance with ASTM C42. Aggregate and cement may be batched by weight or by volume in accordance with the requirements of ASTM C94 or AASHTO M241/ASTM C685. Use mixing equipment that thoroughly blends the materials in sufficient quantity to maintain placing continuity. Ready mix shotcrete shall comply with AASHTO M157. Batch, deliver, and place shotcrete within 90 minutes of mixing. The use of retarding admixtures may extend application time beyond 90 minutes , if approved. Place t ime limit after mixing as per the manufacturers’ recommendations. CONSTRUCTION

660.03.01 General. Both preconstruction test panels, to verify mix design strengths, and production test panels,

for acceptance, are required. Perform shotcreting and coring of test panels by qualified personnel as directed. Provide equipment, materials, and personnel as necessary to obtain shotcrete cores for testing including construction of test panel boxes, field curing requirements and coring. Shotcrete final acceptance wi ll be based on the 28 day strength. Shotcrete production work may commence upon initial approval of the mix design, nozzlemen, and preconstruction test panels. The shotcrete work by a crew will be suspended if the test results for their work does not satisfy the strength requirements. Before resuming work, the crew shall shoot additional test panels and demonstrate that the shotcrete in the panels satisfies the s pecified strength requirements. Construct at least one preconstruction test panel for each proposed mixture being considered and for each shooting position to be encountered on the job. These test panels may also be used to qualify nozzlemen. Make preconstruction test panels prior to the commencement of production work using the same equipment, mat erials, mixture proportions and procedures proposed for the job. Make preconstruction test panels with minimum dimensions of 750 mm x 750 mm (30 in. x 30 in.) square and at least 100 mm (4 in.) thick. Slope the sides of preconstruction and production test panels at 45 degrees over the full panel thickness to release rebound. Furnish at least one production test panel or, in lieu of production test panels, six 75 mm (3 in.) diameter cores taken from the shotcrete facing, during the first production application of shotcrete and henceforth for every 420 m (500 yd2), or fraction thereof, of shotcrete placed. Construct the production test panels simultaneously with the shotcrete facing installation when directed. Make production test panels with minimum full t hickness dimensions of 450 mm x 450 mm (18 in. x 18 in.) square and at least 125 mm (5 in.) thick. Immediately after shooting, field moist cure the test panels by covering and tightly wrapping with a sheet of material meeting the requirements of ASTM C171 until they are delivered to the testing lab or test specimens are extracted. Do not immerse the test panels in water. Do not further disturb test panels for the first 24 hours after shooting. Provide at least six 75 mm (3 in.) diameter core samples cut from each preconstruction test panel and production test panel. Extract test specimens from test panels in the field or transport to another location for extraction. Keep panels in their forms when transported. Do not take cores from the outer 150 mm (6 in.) of test panels measured in from the top outside edges of the panel form. Trim the ends of the cores to provide test cylinders at least 75 mm (3 in.) long. Take cores from the wall face in lieu of making production test panels, at designated locations. Clearly mark the cores and container to identify the core locations and whether they are for preconstruction or production testing. Mark the section of the wall to correlate with the cores. Immediately wrap cores in wet burlap or material meeting requirem ents of ASTM C171 and seal in a plastic bag. The cores will be delivered to the testing lab within 48 hours of shooting the panels. Dispose of the remainder of the panels. When the test length of a core is less than twice the diameter, the correction factors given in ASTM C42 will be applied to obtain the compressive strength of individual cores. Three cores will be tested at 3 days and three cores will be tested at 28 days in accordance with ASTM C42. Fill core holes in the wall by dry -packing with non- shrink patching mortar after the holes are cleaned and dampened. Do not fill core holes with shotcrete. 660 PNEUMATICALLY PLACED CONCRETE MORTAR

660.03.02 Placing. Clean the face of the excavation and other surfaces to be shotcreted of loose materials,

mud, rebound, overspray , or other foreign mat ter that could prevent or reduce shotcrete bond. Avoid loosening, cracking, or shattering the ground during excavation and cleaning. Remove any surface material which is so loosened or damaged, to a sufficient depth to provide a base that is suitable to receive the shotcrete. Divert water flow and remove standing water so that shotcrete placement will not be detrimentally affected by standing water. Ensure that the thickness of shotcrete satisfies the minimum requirements shown on the plans by using shooting wires, thickness control pins, or other acceptable devices. Install thickness control devices normal to the surface such that they protrude the required shotcrete thickness outside the surface. Ensure that the front face of the shotcrete does not ext end beyond the limits shown on the plans. Do not place shotcrete on frozen surfaces. Protect adjacent surfaces from overspray during shooting. Remove material that loosens as the shotcrete is applied. Maintain a clean, dry, oil -free supply of compress ed air sufficient for maintaining adequate nozzle velocity at all times. Use equipment capable of delivering the premixed material accurately, uniformly, and continuously through the delivery hose. Control shotcrete application thickness, nozzle technique, air pressure, and rate of shotcrete placement to prevent sagging or sloughing of freshly -applied shotcrete. Apply the shotcrete from the lower part of the area upwards to prevent accumulation of rebound. Orient nozzle at a distance and approximately per pendicular to the working face so that rebound will be minimal and compaction will be maximized. Pay special attention to encapsulating reinforcement. Do not work rebound back into the construction. Where shotcrete is used to complete the top ungrouted zone of the nail drill hole near the face, position the nozzle into the mouth of the drillhole to completely fill the void. A clearly defined pattern of continuous horizontal or vertical ridges or depressions at the reinforcing elements after they are covered with shotcrete will be considered an indication of insufficient reinforcement cover or poor nozzle techniques. In this case, immediately suspend the application of shotcrete and implement corrective measures before resuming the shotcrete operations. The shotcreting procedure may be corrected by adjusting the nozzle distance and orientation, by insuring adequate cover over the reinforcement, by adjusting the water content of the shotcrete mix, or by other means. Adjustment in water content of wet -mix requires requalifying the shotcrete mix. Taper construction joints uniformly toward the excavation face over a minimum distance equal to the thickness of the shotcrete layer. Provide a minimum reinforcement overlap at reinforcement splice joints as shown. Clean and wet the surface of a joint before adjacent shotcrete is applied. Where shotcrete is used to complete the top ungrouted zone of the nail drill hole near the face, to the maximum extent practical, clean and dampen the upper grout surface to receive shotcrete, similar to a construction joint. Finish shotcrete as an undisturbed gun finish as applied from the nozzle or a rough screeded finish. Repair shotcrete surface defects as soon as possible after placement. Curing of the shotcrete is not r equired. Construct the shotcrete within the following tolerances: Horizontal location of w ire mesh; rebar; headed s tuds on bearing plates, from p lan location ........................................... ±16 mm (5/8 in.) Headed studs location on b earing plate, from plan location ................................................................................................. 6 mm (1/4 in.) Spacing between reinforcing bars, from plan dimension ....................................................................................................... 25 mm (1 in.) Reinforcing lap, from specified dimension ................................ ........................................................................................... - 25mm (1 in.) Thickness of shotcrete .................................................................................................................................................... - 10 mm (3/8 in.) Nail head bearing plate, deviation from parallel to wall face ................................................................................................................. 10° Remove shotcrete extending into the CIP finish face section beyond the tolerances as shown or specified herein. Remove and replace shotcrete which exhibits segregation, honeycombing, delamination, voids, or sand pockets. In-place shotcrete determined not to meet the speci fied strength requirement will be subject to remediation as determined. PNEUMATICALLY PLACED CONCRETE MORTAR 660

660.03.0 3 Drainage. Install and secure all elements of the wall drainage network as shown, specified herein, or

as required to suit the site conditions. Install all elements of the dr ainage network prior to shotcreting. Install geocomposite drain strips centered between the columns of nails as shown on the plans. The drain strips shall be at least 300 mm (12 in.) wide and placed with the geotextile side against the ground. Secure the strips to the excavation face and prevent shotcrete from contaminating the ground side of the geotextile. Provide continuous drain strips. Make splices with a 300 mm (12 in.) minimum overlap such that the flow of water is not impeded. Repair damage to the geocomposite drain strip, which may interrupt the flow of water. Install connection pipes as shown. Connect pipes to the drain strips using either prefabricated drain grates as shown or using the alternate connection method described below. Install the drain grate per the manufacturer's recommendations. Seal the joint between the drain grate and the drain strip at the discharge end of the connector pipe to prevent shotcrete intrusion. The alternative acceptable method for connection of the connector pipe to the drain strip involves cutting a hole slightly larger than the diameter of the pipe into the strip plastic core but not through the geotextile. Wrap both ends of the connection pipe in geotextile in a manner that prevents migration of fines through the pipe. Tape or seal the inlet end of the pipe where it penetrates the drain strip and the discharge end of the connector pipe in a manner that prevents penetration of shotcrete into the drain strip or pipe. To assure passage of groundwater from the drai n strip into the connector pipe, slot the inlet end of the connector pipe at every 45 degrees around the perimeter of the pipe to a depth of 6 mm (1/4 in.). Provide weepholes through the construction facing to drain water from behind the facing. Install as shown. Use PVC pipe to form the weephole through the shotcrete. Cover the end of the pipe contacting the soil with a drainage geotextile. Prevent shotcrete intrusion into the discharge end of the pipe.

660.03.0 4 Weather Limitations. Protect the shotcrete when the ambient temperature is below 0 ° C (32 °F) and

falling or when it is likely to be subjected to freezing temperatures before gaining sufficient strength. Maintain cold weather protection until the in- place compressive strength of the shotcrete is greater than 5 MPa (750 psi). Cold weather protection includes blankets, heating under tents, or other acceptable means. The temperature of the shotcrete mix, when deposited, shall be not less than 10 ° C (50 ° F) or more than 35 ° C (95 ° F). Suspend shotcrete application during high winds and heavy rain unless suitable protective covers, enclosures, or wind breaks are installed. Remove and replace newly placed shotcrete exposed to rain that washes out cement or otherwise makes the shotcrete unacceptable. Provide a polyethylene film or equivalent for shotcrete protection.

660.03.0 5 Attachment of Nail Head Bearing Plate and Nut. Attach a bearing plate and nut to each nail head

as shown on the plans. While the shotcrete is still plastic and before its initial set, uniformly seat the plate on the shotcrete by hand wrench tightening the nut. Where uniform contact between the plate and the shotcrete cannot be provided, set the plate in a bed of grout. After grout has set for 24 hours, hand wrenc h tighten the nut. Ensure bearing plates with headed studs are in intimate contact with the construction facing and the studs are located within the tolerances as shown or specified herein.

660.03.0 6 CIP Concrete Form Connection to Shotcrete Facing. When mechanical, grouted, or epoxied

anchors embedded into the shotcrete facing are used to support a one- sided CIP face form, perform pullout testing of the embedded anchors in accordance with ASTM C900 and as modified herein. Perform pullout testing of installed anchors prior to attachment of the face form. Select test anchor locations to be representative of the full wall surface area to be covered. For facing areas up to 420 m2 (500 yd2), perform a minimum of three flexure/shear pullout tests with the ancho r located approximately mid- span between two adjacent nail heads and with the nail heads or other reaction points located approximately one- half the nail spacing from the anchor. For facing areas in excess of 420 m2 (500 yd2), perform one additional flexur e/shear pullout test for each additional 210 m2 (250 yd2) of face area. Test these anchors to 1.5 times their required design load (calculated as the design concrete fluid pressure ti mes the anchor tributary area). Perform local punching shear pullout testing on 2% of the installed anchors. Place the load reaction support no closer to the edge of the anchor than the embedment depth of the anchor into the construction facing. Test these anchors to 2.0 times their required design load. Modify the anchor and/or face form support system if the tested anchors do not meet the above test acceptance criteria. Modified anchor installation will require re- testing in accordance w ith the above testing criteria. 660 PNEUMATICALLY PLACED CONCRETE MORTAR METHOD OF MEASUREMENT

660.04.01 Measurement. Pneumati cally placed concrete mortar will be measured by the square meter

(square yard). The area to be measured will be the area lying in a plane of the outside front face of the structure as shown in the plans. BASIS OF PAYMENT

660.05.01 Payment. The accepted quantity, 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 proposal. Payment will be full compensation for the work prescribed in this Section. Payment will be made under: Pay Item Pay Unit Pneumatically Placed Concrete Mortar (depth) ............................................................................................ Square Meter (Square Yard)

Division III

M ATERIALS DETAILS ________ S ECTION 701 P ORTLAND CEMENT SC OPE 701.