SECTION SHOTCRETE Cast-In-Place Concrete Precast Prestressed Concrete Joists and Beams.

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1 SECTION SHOTCRETE PART 1 GENERAL 1.01 SUMMARY A. Related Sections: Cast-In-Place Concrete Precast Prestressed Concrete Joists and Beams REFERENCES A. American Society for Testing and Materials (ASTM): 1. C Specification for Portland Cement. 2. C Specification for Chemical Admixtures for Concrete SUBMITTALS A. Submit proposed mix proportions before starting work REFERENCES A. American Concrete Institute (ACI): 1. ACI 506R-90 Guide to Shotcrete. 2. ACI Specifications for Materials, Proportioning and Application of Shotcrete QUALITY ASSURANCE A. Perform shotcrete work according to ACI 506 and unless otherwise specified TESTING A. Testing will be performed by the Board Testing Laboratory. 1. Provide one 18" x 18" x 3" deep plywood panel for each day's (or fraction thereof) shotcreting operation for testing purposes. Project No. SPECIFICATION GUIDELINES

2 a. Shotcrete each panel under direction of testing laboratory. B. Panels will be tested according to ACI C. Pre-construction testing is not required ENVIRONMENTAL REQUIREMENTS A. Suspend exterior shotcrete operations during high winds or rainy weather when work cannot be protected. B. Protect adjacent areas from shotcrete and shotcreting operation products. PART 2 PRODUCTS 2.01 MATERIALS A. Cement: ASTM C150 Type I or II. B. Aggregates and Water: Proportioned to achieve mix design SHOTCRETE MIX A. Comply with the following requirements: 1. Compressive strength (28 day minimum): 3,000 psi. 2. Contractor's Option: Retarding admixtures meeting ASTM C494 may be used. B. Ensure thorough mixing of concrete. C. Ensure mix stands no more than 15 minutes. D. Maintain quality control records during production of shotcrete and make records available to A/E. E. Provide mix, plastic enough to give good compaction and low percentage of rebound, with adequate stiffness to prevent sagging EQUIPMENT A. Mixing Equipment: Capable of thoroughly mixing aggregate, cement and water in sufficient quantity to maintain Project No. SPECIFICATION GUIDELINES

3 continuous placement. B. Air Supply: Clean air adequate for maintaining sufficient nozzle velocity for parts of work and for simultaneous operation of blow pipe for cleaning any rebound. C. Delivery Equipment: Capable of discharging aggregatecement-water mixture accurately, uniformly, and continuously through delivery hose. PART 3 EXECUTION 3.01 PREPARATION OF SURFACE A. Remove, by chipping, existing unsound concrete. 1. Minimize abrupt changes in thickness of repair. 2. Remove square shoulders. 3. Taper edges. B. Where existing reinforcing is rusted, remove concrete from behind reinforcing to allow rust removal and subsequent shotcreting behind reinforcing. C. Sandblast surface to receive shotcrete. 1. Sandblasting operation shall remove all loose rust or other undesirable materials from exposed reinforcing steel. D. Tie into place additional reinforcing bars as directed by A/E. E. Thoroughly clean and wet cementitious surfaces before receiving shotcrete. 1. Keep porous surfaces damp for several hours before shotcreting ALIGNMENT CONTROL A. Provide ground wires to establish thickness and plane surface where required. B. Install ground wires at corners and offsets not established by form work where required. Project No. SPECIFICATION GUIDELINES

4 C. Ensure alignment wires are right, true to line, and placed to allow further tightening APPLICATION AND WORK QUALITY STANDARDS A. Allow easy access to shotcrete surfaces for screeding and finishing to allow uninterrupted application. B. Determine operating procedures for placement in close quarters, extended distances, or around unusual obstructions where placement velocities and mix consistency must be adjusted. C. Begin wall applications at bottom, and ensure work does not sag. D. Hold nozzle as perpendicular to surface as work will permit to secure maximum compaction with minimum rebound. E. Follow routine to fill and encase reinforcement, using maximum layer thickness. Encase reinforcement with first layer. F. Build up layers by making several passes of the nozzle over work area. G. After initial set, remove excess material outside ground lines. H. Allow each layer of shotcrete to take initial set before applying succeeding layers. I. Remove laitance that has taken final set by sandblasting, and clean with air-water jet. J. Sound work with hammer for voids. Cut out and replace with succeeding layers. K. Keep rebound and other loose or porous material out of new construction. L. Remove rebound which does not fall clear of work. Discard salvaged rebound. M. Finishes: Project No. SPECIFICATION GUIDELINES

5 1. Where shotcrete work will be concealed by ceilings, finish with natural gun finish. 2. Where shotcrete surface is to receive a separate finish such as stucco, cut back shotcrete surface with a sharp edge trowel to allow for a separate application of stucco. 3. Where shotcrete work forms the finish for exposed concrete joist construction, steel trowel and rub surface to match adjacent surrounding surfaces. N. Keep completed surfaces wet for minimum of 7 days. 1. Membrane curing allowed only where drying conditions are not severe BASIS OF PAYMENT ****** ***** **** *** ** * ** *** **** ***** ****** NOTE TO SPECIFIER: Provide the following information if it is applicable to the Base Bid forms. ****** ***** **** *** ** * ** *** **** ***** ****** A. Include cost of shotcrete work for the entire project as a part of the lump sum Base Bid form. 1. Shotcrete work shall include chipping, sandblasting, providing required reinforcing bars, shotcrete, surface finishing, profit, overhead, insurance, taxes, and bond required to complete the work. 2. The cost of shotcrete work for the entire project to be included in the Base Bid shall be based upon an estimated quantity of bags of cement, each weighing pounds, to be used in required shotcrete work. END OF SECTION Project No. SPECIFICATION GUIDELINES