Each manufacturer of concrete constituents needs to have their products tested by NSF if they want NSF 61 certification. Whether the fibers need NSF 61 certification is an issue with the local authority having jurisdiction for exposure of components to potable water supply systems in your state. Generally, this is the state EPA-type agency, but maybe a federal agency if on a federal project.
We don’t maintain a database of manufacturer products that meet NSF 61. However, you can readily identify contacts for the fiber manufacturers who are ASA corporate members with our Buyers Guide at https://shotcrete.org/products-services-information/buyers-guide/. When entering the Buyers Guide, you can select “Fiber + Reinforcement Sales” and the fiber type subcategory to get a list of our member fiber suppliers.
Membership supports the mission of ASA to provide knowledge, resources, qualification, certification, education, and leadership to increase the acceptance, quality, and safe practices of the shotcrete process.
Annual Dues (Sustaining Corporate Membership includes three Corporate Additional Individual memberships and special recognition in ASA’s Buyers Guide and on the ASA website)
$1500
$1200
$100
$375
$65
Free
Free
Company and specialty information listed in ASA’s online Buyers Guide
X
X
Discount on ACI Shotcreter Certification and Education
X
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Opportunity to be featured as either a Sustaining Corporate or Corporate Member Profile, respectively, in Shotcrete magazine
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Exclusive opportunity to submit items for the Industry News and New Products & Processes columns in Shotcrete magazine
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Discounted ASA member prices on all ASA products
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Contacts to receive bid requests from our Online Project Bid Request Tool
4
1
1
Subscription to quarterly Shotcrete magazine (hard and electronic copy)
X
X
X
X
X*
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X*
Permission to include ASA logo on corporate letterhead and business cards
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Permission to display ASA logo on company website
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Discounted pricing on advertising in Shotcrete magazine
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Complimentary inclusion of advertising company logo from the ASA website to your company website during your advertising quarter
X
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Voting privileges at committee meetings and director/officer elections
4
1
1
1
Fulfills membership requirement for ASA’s annual Outstanding Shotcrete Project Awards Program
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Complimentary annual Onsite Learning Seminars**
2
1
1
Corporate Additional Individual memberships are available for company employees ($200 savings per employee)
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Access to ASA’s “Safety Guidelines for Shotcrete” via ASA’s member Communities portal through “My ASA” at www.shotcrete.org
1
1
Complimentary ASA shotcrete brochure each year
25
25
5
5
5
Complimentary ASA reflective hardhat sticker each year
10
10
1
1
1
*Members outside North America will only receive electronic copies. **Further education for in house, specifiers, or government agencies (1-2 hours)
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About ASA Committees
Committee meetings are open to the public and ASA welcomes and encourages the participation of all interested parties in the shotcrete industry.
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The Board of Directors shall have supervision, control, and direction of the affairs of the Association, shall determine its policies within the limits of the ASA bylaws, shall actively pursue its purpose and shall oversee the disbursement of its funds.
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ACI 506.2-13, “Specification for Shotcrete,” is an excellent resource for answering your questions. ACI 506.2 addresses both preconstruction panels and test panels used for material quality control during construction. ACI 506.2, Section 1.5.1.4, requires that when preconstruction panels are required, the Contractor shall “Construct test panels for each proposed shotcrete mixture, each anticipated orientation, and each proposed nozzleman.” Preconstruction test panels vary in size to adequately represent the embedded reinforcement and section thicknesses in the work to be done.
Test panels shot during construction for evaluation of material properties are covered in ACI 506.2, Section 1.6.3.1, which states: “Construct a test panel for each mixture, each nozzleman, and each work day or for every 50 yd3 (38 m3) placed—whichever results in the most panels. The face dimensions of a test panel shall be a minimum of 16 x 16 in. (406 x 406 mm) with a minimum depth of 5 in. (127 mm). For toughness testing in accordance with ASTM C1550, the face dimension shall be 30.5 in. (775 mm) in diameter and 3 in. (76 mm) thick. Shoot test panels in a vertical orientation only unless otherwise specified.”
ACI 506.2-13 has extensive provisions for the submittals, testing, materials, and execution of shotcrete work by a shotcrete contractor. It cites many of the ASTM testing standards appropriate for shotcrete construction. We recommend you review the document in its entirety to become familiar with current industry standards.
ACI 506.1R-08, “Guide to Fiber-Reinforced Shotcrete,” is a good reference for general use of fibers in shotcrete. If looking at underground applications for shotcrete, ACI 506.5R-09, “Guide to Specifying Underground Shotcrete,” will also offer guidance. The ACI 506 documents are available in hard copy format on our bookstore website with ASA member discounts (shotcrete.org).
Because shotcrete is a method for placing concrete, many, if not most, of the properties of fiber-reinforced concrete, as found in ACI 544 committee documents, are applicable to shotcrete.
Shotcrete is concrete placed at high velocity to achieve compaction. It is dependent on the projection of material with air velocity of 60 to 80 mph (97 to 129 km/h) from the nozzle to consolidate the concrete material in place. It cannot be hand-applied. You may consider hand-applied pre-packaged mortar mixtures to achieve your results, although strength and durability may be less than a similar section with shotcrete because the hand-applied material is not fully compacted. Another alternative is to create an inner cylinder and cast concrete in the space between the box and the form. The concrete could then be vibrated for consolidation.
Recent research into velocity of the material stream shot from the nozzle is approximately 60 to 80 mph (97 to 129 km/h) in the middle of the stream. Outer portions of the stream are slowed and show speeds of about 45 mph (72 km/h). Here’s a link to the Technical Tip published in the Fall 2013 Shotcrete magazine that provides more complete documentation of the research: shotcrete.org/wp-content/uploads/2020/01/2013Fal_TechnicalTip.pd.
ASTM C1140/C1140M-11, “Standard Practice for Preparing and Testing Specimens from Shotcrete Test Panels,” is the appropriate ASTM standard for producing and coring test panels. ASTM C1140 specifies panel size as a minimum of 24 x 24 in. (610 x 610 mm) with a minimum 3.5 in. (89 mm) depth. Without more information on the materials used in the shotcrete and the type of shotcrete, it is impossible to identify what may be causing the lower compressive strength tests.
The compressive strength should increase between 7 and 28 days on a curve equivalent to cast concrete. Strength degradation between 7 and 28 days may be a result of poor shotcrete application or problems with coring or curing of the samples.
In construction of shotcrete dome roofs with inflatable forms, the structural thickness of the dome is built out in layers to prevent overloading the support offered by the inflatable form and foam. Thus, your nozzleman qualification panels should be representative of the dome construction methods. This would include shooting orientation (vertical and varying slopes), shooting procedures (layers), and with the most congested reinforcing. When shotcrete is applied in layers, all you need to do is wait for the first layer to stiffen sufficiently (usually called initial set), before applying the next layer. It is not necessary to wait for days before applying the next lift.
