NZSA 501:Specification for Shotcrete

 NZSA 501:Specification for Shotcrete This specification contains the construction requirements for the application of shotcrete. Wet-­‐mix shotcrete only is specified, and the minimum standards for testing, materials, and execution are provided. This specification is intended to be used by reference or incorporation in its entirety in the Project Specifications. Individual sections, articles, or paragraphs shall not be copied into the Project Specifications, since taking them out of context may change their meaning. Building codes set minimum requirements necessary to protect the public. These Standard Specifications may stipulate requirements more restrictive than the minimum. Adjustments to the needs of a particular project shall be made by the Architect/Engineer by reviewing each of the items in the NZSA 502: Specifications Shotcrete for Checklist and then including the Architect/Engineer's decision on each item as a mandatory requirement in the Project Specifications. CONTENTS ` Section 1—General Section 2—Material Section 3—Execution 1.1—Scope 2.1—Concrete 3.1—Examination 1.2—Definitions 2.2—Cement 3.2—Batching and mixing 1.3—References 2.3—Aggregate 3.3—Surface preparation 1.4—Submittals 2.4—Reinforcement 3.4—Joints 1.5—Quality assurance 2.5—Water 3.5—Alignment control 1.6—Shotcrete core grades 2.6—Admixtures 3.6—Application 1.7—Acceptance 2.7—Curing materials 3.7—Finishing 2.8—Fibers 3.8—Curing 2.9—Delivery, storage, and handling Page1of 2 NZSA 501: Specification for Shotcrete SECTION 1—GENERAL 1.1-­‐Scope This Standard Specification describes the requirements for materials, proportioning, and application of shotcrete parts that are required to be furnished under the Contract Documents. Work is the result of performing services, furnishing labor, and providing and incorporating materials and equipment into the construction, all as required by the Contract Documents. 1.2—Definitions Accepted—Accepted by or acceptable to the Architect/Engineer. Architect/Engineer—The architect, engineer, architectural firm, engineering firm or architectural and engineering firm issuing project drawings and specifications or administering the work under the Contract Documents. Contract Documents—Documents covering the required work and including the project drawings and project specifications. Contractor—The person, firm, or corporation that the owner enters into an agreement with for construction of the work. Core grade—Quality ranking of a shotcrete core. Fiber-­‐reinforced shotcrete (FRS)—Shotcrete mixed with discrete discontinuous fibers commonly made of steel, plastic, or alkali resistant (AR) glass. Formwork—Forms used to establish line and grade for shotcrete work. Gun finish—Undisturbed final layer of shotcrete as applied from nozzle without hand finishing; also known as natural or nozzle finish. Nozzle—Attachment at end of delivery hose from where shotcrete is projected. Nozzleman—Worker on shotcrete crew who manipulates the nozzle shotcrete and controls final disposition of the material. Overspray—Shotcrete material deposited away from the intended receiving surface by air blast. Owner—The corporation, association, partnership, individual, or public body or authority with whom the contractor enters into agreement and for whom the work is provided. Rebound—Shotcrete material that ricochets off the receiving surface. Sand/rock pocket—A porous zone in the shotcrete containing aggregate with reduced mortar content. Shooting—Act of applying shotcrete. Shotcrete—plastic concrete pneumatically projected onto a surface at high velocity. Sloughing—Subsidence of shotcrete, due generally to excessive water in mixture or to vibration of continuous reinforcement or formwork. Submitted—Submitted to the Architect/Engineer for re-­‐ view. Page 2 of 10 NZSA 501: Specification for Shotcrete 1.3—References 1.3.1 Reference standards The following Reference Standards are referred to in this specification and declared to be a part of this Standard Specification: NZS 3101 Concrete Structures Standard NZS 3104 Specification for Concrete Production NZS 3109 Concrete Construction NZS 3121 Specification for Water and Aggregate for Concrete NZS 3122 Portland and Blended Cements NZS 3112.2 Methods of test for concrete AS/NZS 4671 Steel Reinforcing Materials AS 1478 Admixtures for Concrete AS/NZS 3582 Supplementary Cementitious Materials for use with Portland and Blended Cement Part 3: Amorphous Silica AS 3582 Supplementary Cementitious Materials for use with Portland and Blended Cement Part 1:98 Fly Ash Part 2:01 Slag – Ground Granulated Iron Blast-­‐Furnace ASTM C 309 Specification for Liquid Membrane-­‐Forming Compounds for Curing NZSA 503 Specifications for Shotcrete Finish 1.3.2 Reference Organisations and Consultants The material in this specification was contributed from the following organisations and consultants •
Cement & Concrete Association of New Zealand (CCANZ) •
New Zealand Ready Mixed Concrete Association (NZRMCA) •
Aggregate & Quarry Association (AQA)-­‐NZ •
American Concrete Institute (ACI) •
American Shotcrete Association (ASA) •
Sprayed Concrete Association (SCA)-­‐UK •
European Federation of Producers and Applicators of Specialist Products for Structures (EFNARC)-­‐EU •
New Zealand Shotcrete Association (NZAS) •
Beca: Engineering Consultancy-­‐NZ Page 3 of 10 NZSA 501: Specification for Shotcrete •
Holmes Consulting Group: Structural Consulting Engineers-­‐NZ •
Lings Design Consultants-­‐NZ •
Powell Fenwick: Engineering consultants-­‐NZ 1.3.3 Reference Certifications The following Reference Certifications are referred to in this specification and declared to be a part of this Standard Specification: •
NZSA 301: Shotcrete Site Manager •
NZSA 201: Shotcrete Site Foreman •
NZSA 101: Shotcrete Formwork Installer •
NZSA 102: Shotcrete Steel Reinforcing Installer •
NZSA 103: Shotcrete Concrete Technician •
NZSA 104: Shotcrete Nozzleman •
NZSA 105: Shotcrete Vertical Flatwork Finisher 1.4—Submittals Submit proposed mix characteristics including: • Proportions by weights or volumes • Strength • Water-­‐cementitious materials ratio • Aggregate source and grading • Cement type and brand • Water source if other than potable • Proportions • Admixtures data sheets • Test results Submit preconstruction test panel results when required 1.5—Quality assurance 1.5.1 Preconstruction testing 1.5.1.1 Prepare preconstruction test panels for examination by Architect/Engineer prior to job shotcrete placement. Preparation and testing shall comply with NZS 3104. 1.5.1.2 Produce test panels for each proposed mix proportion, each anticipated shooting orientation, and each proposed nozzleman. Mixes shall meet requirements of section 2.1 In half of the test panels provide reinforcement of the same size and spacing required for the work. Obtain six test specimens (minimum50mm diameter) from each panel, three non-­‐ reinforced specimens and three with reinforcing steel. 1.5.1.3 Test the non reinforced specimens for compliance with the specified physical properties in accordance with NZS 3112.2 Page 4 of 10 NZSA 501: Specification for Shotcrete 1.5.1.4 Visually grade the reinforced specimens for compliance with specified core grade (Section 1.6—Shotcrete core grades). 1.5.1.5 Test admixtures for compatibility with cement in accordance with AS 1478. 1.5.1.6 Unless otherwise specified, only nozzlemen with a test panel mean core grade less than or equal to 2.5 (section 1.6) shall be allowed to place job shotcrete. When the prequalification test panel is rejected, a second panel may be shot. When the nozzleman's second mean core grade is greater than 2.5, the nozzleman shall not be permitted to shoot on the project. 1.5.2 Construction testing 1.5.2.1 Produce a material test panel for each mix and each for every 50 cubic meters placed. The panel should be protected immediately against moisture loss using the same method to be used in construction. The samples are marked for later identification (Mix, location, date, operator). The panel should not be moved within 18 hours of being sprayed. Curing should continue thereafter for 7 days or until samples are to be extracted. The test samples should be cored in accordance with NZS 3112.2 or sawn from the panel, but should not include material within 125 mm of the edge (with the exception of the ends of beams for flexural/toughness testing). During transportation to the testing laboratory the panel or sawn samples are packed to protect against mechanical damage and moisture loss. The panel, but should not include material within 125 mm of the edge (with the exception of the ends of beams for flexural/toughness testing). During transportation to the testing laboratory the panel or sawn samples are packed to protect against mechanical damage and moisture loss. 1.5.2.2 Grade cores that include reinforcement in accordance with section 1.6—Shotcrete core grades. 1.5.2.3 Compressive strength tests should be performed in accordance with NZS 3112.2 on drilled cores taken from the Shotcrete structure or from sprayed test panels. Their minimum diameter shall be 50mm and the height/diameter ratio shall be in the range 1.0 to 2.0. 1.6—Shotcrete core grades 1.6.1 Grade 1: Shotcrete specimens are solid; there are no laminations, sandy areas or voids. Small air voids with a maximum diameter of 3mm and maximum length of 6mm are normal and acceptable. Sand pockets, or voids behind continuous reinforcing steel are unacceptable. The surface against the form or ond plane shall be sound, without a sandy texture or voids. Page 5 of 10 NZSA 501: Specification for Shotcrete 1.6.2 Grade 2: Shotcrete specimens shall have no more than two laminations or sandy areas with dimensions not to exceed 3mm thick by 25mm long. The height, width and depth of voids shall not exceed 9mm. Porous areas behind reinforcing steel shall not exceed 12mm in any direction except along the length of the reinforcing steel. The surface against the form or bond plane shall be sound, without a sandy texture or voids. 1.6.3 Grade 3: Shotcrete specimens shall have no more than two laminations or sandy areas with dimensions exceeding 5mm thick by 30mm long, or one major void, sand pocket, or lamination containing loosely bonded sand not to exceed 15mm thick and 30mm in width. The surface against the form or bond plane may be sandy with voids containing overspray to a depth of 1.5 mm. 1.6.4 Grade 4: The core shall meet in general the requirements of Grade 3 cores, but may have two major flaws such as described for Grade 3 or may have one flaw with a maximum dimension of 25 mm perpendicular to the face of the core with a maximum width of 37m. The end of the core that was shot against the form may be sandy and with voids containing overspray to a depth of 3mm. 1.6.5 Grade 5: A core that does not meet the criteria of core grades 1 through 4, by being of poorer quality, shall be classified as Grade 5. 1.6.6 Determination of grade shall be by computing the mean of a minimum of three test specimens. 1.6.7 A mean grade of 2.5 or less is acceptable unless otherwise specified. Individual shotcrete cores with a grade greater than 3 are unacceptable. Page 6 of 10 NZSA 501: Specification for Shotcrete 1.7—Acceptance 1.7.1 Shotcrete work that meets applicable requirements will be accepted. 1.7.2 Shotcrete work that has previously failed to meet one or more requirements, but which has been repaired to bring it into compliance, will be accepted. 1.7.3 Shotcrete work that fails to meet one or more requirements and which cannot be brought into compliance may be accepted or rejected. Modifications may be required to assure that remaining work complies with the requirements. SECTION 2—MATERIALS 2.1-­‐Concrete § A plant possessing a current Certificate of Audit shall supply the concrete. § Unless modified elsewhere all Special concrete shall, as a minimum, meet the requirements of Normal concrete as specified in NZS 3104 2.2—Cement Portland cement: NZS 3122 2.3—Aggregate Aggregates in shall comply with the requirements of NZS 3121 2.4—Reinforcement Reinforcement shall comply with AS/NZS 4671 2.5—Water Mixing water for shotcrete shall meet requirements of NZS 3121 and NZS 3104 Water shall be free of elements that cause stains when used on architectural finishes. 2.6—Admixtures Water-­‐reducing: AS 1478 Retarding: AS 1478 Accelerating: AS 1478 Air-­‐entraining: AS 1478 Fly ash and natural pozzolans: AS 3582 Ground granulated blast-­‐furnace slag AS 3582 Silica fume: AS/NZS 3582 2.7—Curing materials Curing materials that cause stains on architectural finishes shall not be used. Liquid Curing compounds are acceptable and shall comply with ASTM C 309; apply twice the cover-­‐ age (double the application rate) recommended by manufacturers. 2.8—Fibers The fibres used for Shotcrete applications are either steel or high-­‐performance plastic. NZS 3101:2006 sets out design rules for steel-­‐fibre reinforced concrete. Lower modulus plastic fibres can also be used to control plastic shrinkage cracking in Shotcrete Page 7 of 10 NZSA 501: Specification for Shotcrete 2.9—Delivery, storage, and handling Deliver, store, and handle materials to prevent contamination, segregation, corrosion or damage. Store liquid admixtures in order to prevent evaporation and freezing. SECTION 3—EXECUTION The following executions shall be overseen seen by a Certified Shotcrete Site Manger/Foreman (NZSA 301/201) 3.1—Examination 3.1.1-­‐Verify that surfaces are acceptable and are ready to receive work. 3.1.2-­‐Verify that forms are to line and grade, braced against vibration, and constructed to permit escape of air and rebound. Forms to be installed by a Certified Shotcrete Formwork Installer (NZSA 101) 3.1.3-­‐Verify that placement and clearance around reinforcement permits complete encasement. Steel Reinforcement to be installed by a Certified Shotcrete Steel Reinforcing Installer (NZSA 102) 3.1.4-­‐Verify that surfaces to receive shotcrete have been properly prepared according to the Contract Documents. 3.2—Batching and mixing 3.2.1-­‐Batching shall comply with the accuracy specified in NZS 3104. 3.2.2-­‐Use batching and mixing equipment from a plant possessing a current Certificate of Audit 3.2.3-­‐Shoot wet-­‐Ready-­‐mix shotcrete material within 90 min after batching. 3.2.4-­‐Minimum slump of wet-­‐mix shotcrete is 25mm. 3.2.5-­‐ Shotcrete mix and pump operations to be overseen by certified Shotcrete Concrete Technician (NZSA 103) 3.3—Surface preparation 3.3.1 Earth—Prepare surfaces to line and grade. Do not apply shotcrete to frozen surface. Dampen surface immediately prior to shooting. 3.3.2 Concrete, masonry, and shotcrete—When bonding is required, remove all deteriorated, loose unsound material or contaminants that may inhibit bonding. Chip areas to be repaired to remove offsets causing abrupt changes in thickness. Taper edges to eliminate square shoulders at the perimeter of a cavity. Surface shall be saturated surface dry immediately prior to shooting. 3.3.3 Structural/reinforcement—The surface shall be free of deleterious materials that inhibit bonding. For new construction, reinforcement laps shall be separated with a clearance of at least three times the diameter of largest aggregate. Reinforcement shall be secured to prevent movement. Page 8 of 10 NZSA 501: Specification for Shotcrete 3.3.4-­‐Steel Reinforcement to be installed by a Certified Shotcrete Steel Reinforcing Installer (NZSA 102) 3.3.5 Rock—Remove loose material, mud or other foreign material that will prevent bonding. Clean surface. Pre-­‐wet surface immediately prior to shooting. 3.3.6 Forms—Use form-­‐release coating material on re-­‐ movable forms. Secure forms to minimize the effects of vibration. Construct forms to allow escape of placement air and rebound. 3.3.7-­‐ Forms to be installed by a Certified Shotcrete Formwork Installer (NZSA 101) 3.4—Joints 3.4.1 Construction joints—Taper construction joints at a 1 to 1 slope where joint is not subject to compression loads. Surface preparation of joints shall comply with section 3.3.2. Continue reinforcement through construction joint. 3.4.2 Control joints—Place as shown on drawings. Discontinue reinforcement at control joints. 3.5—Alignment control 3.5.1-­‐Install Screed points to establish thick-­‐ness and plane of required surface. Install profiles at corners or off-­‐ sets not established by forms. 3.5.2-­‐Screed points and Profiles to be installed by a Certified Shotcrete Formwork Installer (NZSA 101) 3.6—Application 3.6.1 Placement techniques—Provide a platform that permits nozzleman unobstructed access to the receiving surface. Place shotcrete first in corners, recesses, and other areas where rebound or overspray cannot escape easily. Remove rebound and overspray from previously prepared surfaces prior to shotcrete placement. Place shotcrete with nozzle held approximately perpendicular to the receiving surface. In corners, direct nozzle at approximately 45 degree angle or bisect the corner angle. Apply shotcrete so sags or sloughing do not occur. Discontinue shooting or shield the nozzle stream if wind causes separation of ingredients during shooting. Do not reuse rebound or overspray. Remove laitance from shotcrete surfaces to receive additional shotcrete layers. Surface preparation after final set shall comply with section Do not apply shotcrete on surfaces with standing water or running water. Remove hardened overspray and rebound from adjacent surfaces, including exposed reinforcement. 3.6.2 Encasement of reinforcement—Place shotcrete to completely encase reinforcing steel. Encase reinforcement by shooting with sufficient velocity and plasticity so material flows around and behind the reinforcement. Front face of reinforcement shall remain clean during encasement. 3.6.3-­‐ Shotcrete to be placed by a certified Shotcrete Nozzleman (NZSA 104) 3.7—Finishing 3.7.1-­‐To be in accordance with NZSA 503: Specifications for Shotcrete Finish Page 9 of 10 NZSA 501: Specification for Shotcrete 3.7.2-­‐Shotcrete to be finished by a Certified Shotcrete Vertical Flatwork Finisher (NZSA 105) 3.8—Curing 3.8.1-­‐Immediately after finishing, cure shotcrete continuously by maintaining in a moist condition for seven days or until specified strength is attained or until succeeding shotcrete layers are placed. Cure by one of the following methods: • Ponding or continuous sprinkling • Covering with an absorptive mat or sand that is kept continuously wet • Curing compounds 3.8.2-­‐ Shotcrete to be cured by a Certified Shotcrete Vertical Flatwork Finisher (NZSA 105) 3.9—Hot weather shotcreting Do not place shotcrete when material temperature is above 32 degree Celsius 3.10—Cold weather shotcreting Shooting may proceed when ambient temperature is 4 degrees Celsius and rising. Shooting shall discontinue when ambient temperature is 5 degrees Celsius and falling unless protective measures are taken to protect shotcrete. Shotcrete material temperature, when shot, shall not be less than 10 degrees Celsius or more than 32 degrees Celsius. Shotcrete shall not be placed against frozen surfaces. Applicable procedures used for cold weather concreting may be used for cold weather shotcreting. 3.11—Protection Protect surfaces not intended for shotcrete placement against deposit of rebound and overspray or impact from nozzle stream. Remove rebound and hardened overspray from final shotcrete surfaces and from areas not intended for shotcrete placement. 3.12—Tolerances Tolerances of shotcrete shall comply as specified and in accordance with NZSA 502: Shotcrete Finish Specification Page 10 of 10 NZSA 501: Specification for Shotcrete Page 11 of 10