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Position Statement #5 ASA Pool and Recreational Shotcrete Committee after initial set, as well as the cleaning and SSD conditions provided for in 3.4.2.2. Thus, shotcrete placed in layers does not produce a “cold joint” as defined by ACI because it produces excellent bond between the layers. This has been confirmed by visual inspection of numerous cores taken through multiple layers of shotcrete, where it is often impossible to identify where one layer stops and the other starts, unlike cold joints in cast-in-place work where the difference between lifts is readily apparent. The connection point between two or more layers of shotcrete or between days of placement is considered to be a “construction joint.” This joint is still considered to be monolithic based on the shotcrete application methods. Swimming pool shotcrete performance, durability, watertightness, and compressive values depend greatly on the proper application and preparation of the construction joint. Preparation includes shaping the joint to a 45-degree angle, cleaning overspray from adjacent reinforcement not yet embedded, and roughening the surface of the joint with a stiff broom, brush, or tool. The joint can then stand for as long as needed before the next placement. When it is time to complete the area, the joint must be cleaned and predampened to a saturated surface-dry damp condition. When properly shooting and curing the subsequently placed shotcrete, the concrete will act as a monolithic section, just as if there were never a joint there to begin with. The secret in making this a joint that acts monolithically with perfect bond is the combination of the proper surface preparation of the joint and high-impact velocity of the shotcrete stream. Shotcrete is a paste-rich concrete that is pneumatically driven by impact into the rough surface left by the joint preparation. No bonding agents are needed, and indeed no bonding agents should be used because they may interfere with the bond of the fresh paste to the rough substrate. To reiterate, shotcrete swimming pool construction using quality materials, proper equipment, surface preparation, and placement techniques will not have cold joints and will behave monolithically. Also, with high-velocity impact on a receiving surface, the cement paste penetrates the existing threedimensional bond plane and requires no bonding agents for proper adhesion between shotcrete layers or applications. Contributing authors: Bill Drakeley, Charles Hanskat, Chris Zynda References ACI Committee 309, 2005, “Guide for Consolidation of Concrete (ACI 309R-05),” American Concrete Institute, Farmington Hills, MI, 36 pp. ACI Committee 318, 2011, “Building Code Requirements for Structural Concrete and Commentary (ACI 318-11),” American Concrete Institute, Farmington Hills, MI, 503 pp. ACI Committee 506, 2013, “Specification for Shotcrete (ACI 506.2-13),” American Concrete Institute, Farmington Hills, MI, 12 pp. ACI Committee E703, 2008, “Shotcrete for the Craftsman (CCS-4(08)),” American Concrete Institute, Farmington Hills, MI, 85 pp. ACI CT-13, 2013, ACI Concrete Terminology, American Concrete Institute, Farmington Hills, MI, http://www.concrete.org/portals/0/files/pdf/ACI_ Concrete_Terminology.pdf. ASA Pool & Recreational Shotcrete Committee, “Position Statement #1, Compressive (Strength) Values of Pool Shotcrete,” American Shotcrete Association, Farmington Hills, MI, http://www.shotcrete.org/media/pdf/ASA PositionPaper_PoolRec_1.pdf. ASA Pool & Recreational Shotcrete Committee, 2012, “Position Statement #2, Definitions of Key Shotcrete Terminology,” Shotcrete, V. 15, No. 3, Summer, p. 27-29. Beaupré, D., 1999, “Bond Strength of Shotcrete Repair,” Shotcrete, V. 1, No. 2, Spring, pp. 12-15. Hanskat, C., 2014, “Shotcrete Placed in Multiple Layers does NOT Create Cold Joints,” Shotcrete, Spring, pp. 40-41. Zhang, L.; Morgan, R.; and Mindness S., 2016, “Comparative Evaluation of Transport Properties of Shotcrete Compared to Cast-in-Place Concrete,” ACI Materials Journal, V. 113, No. 3, May-June, pp. 373-384. Position Statements ASA has produced position statements on the best practices for proper shotcrete placement. To date, five position statements from our Pool & Recreational Shotcrete Committee and one from our Board of Direction have been issued. These statements have also been published in Shotcrete magazine. Visit http://www.shotcrete.org/pages/products-services/shotcrete-resources.htm. Shotcrete • Fall 2016 45


2016FallShotcreteEMag
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