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2013SumShotcreteEMag

Technical Tip The nozzle setups shown here are recognized as shotcrete nozzles for wet- and dry-mix applications by ACI. Dry shotcrete nozzles Wet shotcrete nozzles The dry-mix process nozzles are designed to handle All wet shotcrete nozzles have a minimum of a 3/4 in. the high material velocity and produce adequate (20 mm) air line running into them for maximum spray patterns material velocity There are some who will try to convince this the surface or around the bar, producing weaker reading audience that low-volume, low-velocity bond and leaving voids, resulting in fallouts to the mortar spraying is considered shotcrete spraying. ground. ASA is an excellent source for archived Countless trial-and-error attempts have been articles that have useful information on obtaining tried throughout the years, ending up with the the correct nozzles, equipment, and compressors same result: failure. The low-volume sprayed for specific types of shotcrete projects. Many of mixtures would build up on the face of the bar these articles are listed for reference reading at and not wrap behind it, leaving voids behind the the end of this article. reinforcement. Spraying overhead was a bigger Properly shooting the standard ACI Shotcrete disaster because the material did not pack into Nozzleman Certification Test Panel for vertical >100 lbs (45.4 kg) dead weight (to prevent vibration) US #4 steel bars inside panel through the Scaffolding boards side form for support 4 in. x 6 in. x 10 ftACI Certification Panel (see C660 policy) (10.1 cm x 15.2 cm x 3 m) 2.5 ft (0.8 m)(1) 5 ft (1.5 m)(1) Notes: (1) Standard scaffolding dimension: 1. Core diameter 4 in. (nominal) 2. Core locations may be adjusted slightly at the discretion of the examiner, so long as they Standard section: 5 x 5 x 10 ft (1.5 x 1.5 x 3 m) remain along the axis of the reinforcing bars, and at least three bar intersections are covered Half section: 5 x 2.5 x 10 ft (1.5 x 0.8 x 3 m) Typical ACI Shotcrete Nozzleman Certification Test Panel Typical ACI overhead Test Panel setup Shotcrete • Summer 2013 19


2013SumShotcreteEMag
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