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2017SummerShotcreteEMag

Fig. 5: Large highway tunnel project in Seattle, WA, with over 750,000 ft2 (69,677.28 m2) of structural shotcrete, completely done with a post-injected hydrophilic membrane/textile composite system for blindside waterproofing Ross King is Vice President of Business Development for Torrent Shotcrete Group in Toronto, ON, and Vancouver, BC, Canada. He has more than 40 years of experience as a Principal in the heavy concrete construction business. • Shotcrete is placed in short, visible lifts, with overspray blown off the blindside waterproofing continuously until the end of placement. There is no additional risk for both mechanical and chemically bonded waterproofing degradation due to a buildup of dry concrete paste, which typically happens in form-and-pour. • Shotcrete reinforcing bar stabilization requires far fewer anchorage penetrations than most one-sided formwork systems, therefore requiring less detailing, and reduces the risk of leakage. • Structural shotcrete now creates the opportunity to use a post-grouted hydrophilic curtain wall fabric, which accommodates shrinkage cracking, and other irregularities that can occur in any concrete placement (refer to Fig. 5). This system cannot be used with form-and-pour because the fabric grid would be crushed by the form pressure, vibration would force cement paste into the fabric, and the injection tubes would be knocked off by the concrete drop placement and vibration. Also, no concrete contractor would approve several holes drilled through expensive formwork, let alone trying to fish the pipes through the holes in the form while closing the form panel. CONCLUSIONS My opinion, after many years of experience in the form-andpour industry and more recently in the rapidly growing structural shotcrete sector, is that structural shotcrete is THE solution to improving blindside waterproofing. We need to toss aside all the silly misconceptions and incorrect details that have been presented for blindside waterproofing projects and objectively consider the total performance of the completed concrete walls when using shotcrete placement. SUMMER’S NOT OVER YET! Get your ASA baseball cap today! ASA’s new logo adds a sharp look to this exclusive baseball cap, available online now only from the ASA Bookstore. www.shotcrete.org/bookstorenet www.shotcrete.org Summer 2017 | Shotcrete 51


2017SummerShotcreteEMag
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