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2014WinShotcreteEMag

and beyond 2000 ft (600 m); and make it to the nozzle without plugs despite being fiber-rein- forced. Especially in overhead areas, the shotcrete material needed to have an accelerated set once sprayed, yet retain some plasticity for shaping or rough finishing. Each nozzleman could see first- hand how important angle, velocity, mixture design, and equipment manipulation (such as man lifts) were to the overall success of the job. The job was always made more difficult by the requirement to add reinforcement to some of the rock substrate (refer to Fig. 5). Welded wire was attached to the rock bolts, and, on occasion, a metal mine strap was adhered to potentially loose rock material. These reinforce- ment requirements (overly reinforced in our humble opinion) likely reduced the bond of the fresh shotcrete to the rock substrate. Nozzle movements had to be perfect in and around a Fig. 5 mine strap and where welded wire sheets over- lapped, but there was virtually no access to the the program took effect, was 40 yd3 (31 m3) rock substrate behind the reinforcing material. of shotcrete placement per day, spread over three In those few areas where the mesh overlapped, 8-hour shifts. By project completion, we were the crew adeptly cut out the overlapping layer capable of applying over 200 yd3 (150 m3) in a to allow proper shotcrete application and a good 24-hour period, per heading, with rebound hov- bond to the rock facing. ering between 5 and 10%. For a project of this magnitude, it wouldn’t have been possible to get Current Status those numbers without a comprehensive training According to Sean Clevenstine, General and evaluation program in place. What I believe Superintendent of Concrete at Schiavone Con- made our program effective was the fact that it struction, who oversaw the shotcrete applications was “graduated”—each individual was walked on the project: through the application process step by step, “Simple mathematics can be used to show the under a qualified supervisor. The end result was effectiveness of the program. In early 2011, our a highly productive, exceptional quality product. It production goal based on past performance before also validated the craft members of Local #147 Shotcrete • Winter 2014 35


2014WinShotcreteEMag
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