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Shotcrete FAQs Answer: Stress distribution from external loads through the and corrosive gases shall have a Minimum f´c of 4000 psi (28 tank wall with the shotcrete lining will depend on the geom- MPa)”. Since ACI 350 is more directly applicable to water- etry of the tank and the structural function of sections to be containing structures, the 2001 date is probably the most rel- removed. A professional engineer experienced in shotcrete evant, though ACI 318 introduced the concept in 1991. We do, and concrete tank design should be consulted to ascertain the however, see shotcrete specified at lesser levels for different structural capacity of the completed wall. It would certainly types of uses. be important to create a good bond plane by roughening the surface and removing any loose or fractured materials and Question: We have a unique situation where we need to apply using sufficient drilled dowels to make the existing 12 in. shotcrete around a steel plate that is surrounding a beam sup- (305 mm) wall and new 6 in. (152 mm) overlay work well porting a floor. Can you provide any UL listings for applying together. Also, it might help to specify the use of a shrinkage shotcrete to a steel beam, column, or plate? reducing admixture. Answer: UL designs are typically for the hourly fire proofing Question: When was the 4000 psi (28 MPa) standard set ratings on structural steel members such as I-beams, wide flange for shotcrete? beams, and vessel skirts. The beams and columns are tested for specific fireproofing products, beam sizes, and configura- Answer: ASA has taken the position that structural shotcrete tions. The thickness of the steel and other considerations factor is shotcrete that meets or exceeds a compressive strength of in the evaluation; therefore, there is no blanket UL design 4000 psi (28 MPa). Looking at pertinent ACI Codes related to number that you can use for steel plate. You can get guidance watertight concrete, as we would expect in a pool, we find ACI on the cover needed for different fire ratings in ACI 216.1-97/ 318-95, “Building Code Requirements for Structural Concrete,” TMS 0216.1-97, “Standard Method for Determining Fire introduced a provision in 1995 that required: “Concrete Resistance of Concrete and Masonry, Construction Assemblies.” intended to have low permeability when exposed to water shall Remember that shotcrete is a process for applying concrete. have a Minimum f´c of 4000 psi (28 MPa)”. Similarly, ACI You may also consider looking for a similar concrete UL design 350-01, “Code Requirements for Environmental Concrete and submit it for consideration. Applying the shotcrete at a greater Structures,” first issued in 2001 required: “Concrete intended thickness to compensate for any variances should be proposed to have low permeability when exposed to water, wastewater, and presented to engineer or the owner for consideration. Please note: ASA’s technical team provides the answers to submitted questions as a free service. The information is based on the personal knowledge and experience of the ASA technical team and does not represent the official position of ASA. We assume that the requester has the skills and experience necessary to determine whether the information ASA provided is appropriate for the requester’s purposes. The information provided by ASA is used or implemented by the readers at their OWN RISK. Shotcrete • Spring 2013 59


2013SprShotcreteEMag
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