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2013SumShotcreteEMag

Panel Affixation Specification Document Shotcrete nozzleman certification for over- head shotcrete requires the use of standardized >100 lbs (45.4 kg) dead weight (to prevent vibration) panels that are affixed overhead. ACI Committee US #4 steel bars inside ment that would include general parameters for (see C660 policy) 4 in. x 6 in. x 10 ftform for supportScaffolding boards-ACI Certification Panelpanel through the side C660 was asked to provide a specification docu an apparatus or structure that would quantify the (10.1 cm x 15.2 cm x 3 m) forces in hanging and shooting a panel to assist and provide guidance with on-site construction. A specification document was developed, accom- 2.5 ft (0.8 m)(1) panied by a sample drawing of a suitable appa- ratus that is typically used for overhead shotcrete nozzleman certification. The proposed apparatus is illustrated in Fig. 1. 5 ft (1.5 m)(1) Shotcrete Core Grades—Standard Certification Panel Core grading shall apply only to cores (1) Standard scaffolding dimension: extracted from the standardized test panel approved by ACI Committee C660. Grading of Half section: 5 x 2.5 x 10 ft (1.5 x 0.8 x 3 m)Standard section: 5 x 5 x 10 ft (1.5 x 1.5 x 3 m) the cores is based on visual examination and measurements of defects. A total of five cores Fig. 1: Overhead standard set-up—ACI Shotcrete Nozzleman Certification are graded using these criteria at specific loca- tions.4,5 Deductions are made for various defects such as (but not limited to) sand lenses; porosity Core Grade No. 1 Core Grade No. 5 pockets; and random voids, especially voids around reinforcing bars. A test panel is declared a failure if any single core exceeds core Grade No. 3 or if more than two of the five cores exceed core Grade No. 3. Averaging core grades is not permitted. Defini- tions of core Grades No. 1 to 5 are provided in the program policy5, and, more recently, in the new document “Shotcrete Core Grades for Use in the Evaluation of Cores during Shotcrete Nozzleman Certification according to CP60 (09).”3 Sample photos of core Grades No. 1 and 5 are presented in Fig. 2. Fig. 2: Core Grades No. 1 and 5 A Message to Shotcrete Specifiers! ACI Shotcrete Nozzleman Certification makes layers of reinforcing), preconstruction qualifica- a difference. Although it does not guarantee per- tion mockups that simulate job-site conditions fection, it provides the specifier with the comfort may be desirable. To assist design professionals, that the nozzleman has demonstrated the basic owners, contractors, and other construction per- knowledge and capabilities to properly apply sonnel in achieving desired quality, ACI 506R-05, shotcrete. However, the ACI-certified nozzleman “Guide to Shotcrete,”6 has procedures for quali- is only one part of the shotcrete construction team. fying shotcrete nozzlemen where project require- A contractor offering to place quality shotcrete ments have features that dictate more than just must have specific knowledge, equipment, ACI nozzleman certification. training, and hands-on experience of an entire Specifier, this ACI Shotcrete Nozzleman Cer- shotcrete construction team—from company tification program has been developed for you. management to the entire field team—to truly be Take advantage of the tool you have been given considered a shotcrete contractor. The identifica- and specify ACI-certified shotcrete nozzlemen on tion and selection of a qualified shotcrete con- your construction projects! tractor is essential for quality shotcrete work on your project. How Do I Get Certified? To ensure a quality shotcrete application on To participate in an ACI Shotcrete Nozzleman specific projects with demanding shotcrete place- Certification program, interested parties should ment (for example, deep sections and multiple first contact ASA. As an LSG, ASA will provide Shotcrete • Summer 2013 15


2013SumShotcreteEMag
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