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2014WinShotcreteEMag

Shotcrete FAQs As a service to our readers, each issue of Shotcrete will include selected questions and provide answers by the American Shotcrete Association (ASA). Questions can be submitted to info@shotcrete.org. Selected FAQs can also be found on the ASA website, http://shotcrete.org/pages/products-services/technical-questions.htm. Question: We are in the process of building a shotcrete pool temperatures, but only with proper planning, procedures, and and are required to wet-test the pool before set, waterproofing, likely at some cost. and tile. What is the expected water-loss percentage? We are required to achieve 1%. Question: What is the fire rating information for shotcrete? Answer: We are not aware of a specific standard for pools. Answer: Shotcrete is concrete, pneumatically applied. So the same However, ACI 350.1-10, “Specification for Tightness Testing fire ratings for concrete would apply to shotcrete. The standard of Environmental Engineering Concrete Containment Struc- is ACI 216.1, “Code Requirements for Determining Fire Resis- tures,” specifies a volume loss of 0.05% of volume per day tance of Concrete and Masonry Construction Assemblies.” conducted over a 72-hour test period for “hydrostatic tightness testing of open liquid containment structures. Specifics of Question: I am doing an owner/builder pool. The shotcrete conducting the test can be found in the ACI 350.1-10 document. company I hired left an approximately 4 x 4 in. (102 x 102 mm) It should be noted that the pool should be filled and allowed hole in the deep end of the pool on the side wall. What is the to saturate for 3 days before beginning the measurements. proper way to patch this hole prior to plastering? (The shotcrete was applied a month ago.) Question: We are working on a project with a wall that requires additional capacity due to increased loading requirements. We Answer: The normal repair is to pressure wash with at least are contemplating shotcrete with additional reinforcing to 3000 psi (21 MPa) of water pressure to remove any dirt and provide additional thickness for the wall. laitance on the surface of the concrete. Given the rather small Is it possible to achieve a composite wall to design for a size of the hole, it can be hand-patched with a nonshrink thicker section for bending, using the bond of the existing hydraulic cement with at least 4000 psi (28 MPa) 28-day com- concrete and shotcrete along with a reinforcing bar hook pressive strength to plug the hole. After the patch is completed, anchor epoxied into the existing wall? Any information you roughen the surface that will receive the plaster. can provide would be appreciated. Question: The Los Angeles City Bulletin states that no bars Answer: Shotcrete is often used in similar applications. The over No. 8 (No. 25) shall be used. The structural engineer has question of bending is a structural engineering question. No. 10 (No. 32) bars in the columns. I am being told the test Shotcrete is a method of placing concrete and the properties panel will get this approved but my City Inspector is balking of shotcrete are similar if not the same as cast concrete. To a little. Is there a publication or code somewhere that allows achieve a composite wall, you must ensure that the existing the test panel to supersede the LADBS Bulletin? surface is properly prepared to maximize the potential bond between the overlay shotcrete and the existing wall. Shotcrete Answer: The International Building Code (IBC), Section 1913, placed against a properly prepared existing wall should achieve allows for larger bars as long as it is demonstrated in a Precon- great bonding strength without the use of bonding agents. struction Test Panel. However, the Local Building Code likely Drilled and grouted dowels also contribute to the system, takes precedence over the IBC. You may want to present IBC working as a composite wall. Section 1913, which requires anything over a No. 5 (No. 16) bar to be proven in a Preconstruction Test Panel. Question: I am looking for some technical assistance con- There have been many projects shot in Los Angeles County cerning temperature guidelines for shooting gunite pools. Is subject to the LADBS with bar sizes larger than No. 8 bars. there a suggested range of air temperature and humidity that ASA is not in a position to give you project references, but is recommended? Thanks for your help! perhaps our local members can. Properly encasing No. 10 (No. 32) bars can be challenging, Answer: Shotcrete is a method of placing concrete. The basic and should only be attempted by qualified contractors using guidelines for placing concrete or shotcrete can be found in ACI Certified Nozzlemen who have previous successful expe- documents ACI 305R-10, “Guide to Hot Weather Concreting,” rience doing this type of work. and ACI 306R-10, “Guide to Cold Weather Concreting.” There are some basic “rules of thumb,” such as 40°F (4°C) Question: What are the common standard test methods to and rising for starting concrete/shotcrete operations and 40°F measure or assess the permeability of shotcrete? (4°C) and falling for stopping concrete/shotcrete operations. With proper planning and procedures, concrete or shotcrete Answer: Boiled absorption and volume of permeable voids can be placed at below-freezing temperatures and at very hot testing (ASTM C642) may be required for structures that need 70 Shotcrete • Winter 2014


2014WinShotcreteEMag
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