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Thread: Shotcrete rebound question

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    Join Date
    Jul 2013
    Saint Louis, MO

    Shotcrete rebound question

    In almost every picture I see of pool construction, whether it is shotcrete or gunite being shot, I see the walls shot first. The workers are standing on the rebar in the pool floor, and there is always some concrete running down the wall, under the rebar & onto the floor. It is still there when the floor is shot. They just blast the shotcrete floor right on top of it. Is this the "rebound" I always hear about? Should it not be present? If it's so important, why aren't floors shot first so that whatever slides off the walls can just be scraped off? If the walls are shot first (like most builders seem to do), how much of this "run down" should I ask that they pick out from in between rebar & remove?
    18x40 ft shotcrete, 4-8 ft deep. Pebble Sheen finish. Coverstar auto cover. Hayward c4030 filter. Hayward H series 300k BTU. Intelliflo pump. Intellichlor IC40. Pentair Easytouch controls. Dolphin Nautilus robot.

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    nuklhed's Avatar
    Join Date
    Jul 2013
    Las Vegas, NV

    Re: Shotcrete rebound question

    This is an excellent question. Most experienced gunite crews understand the mandatory objective of the process is to encapsulate the steel in crete. Yes, it's customary for rebound to simply fall to the bottom of the hole but those guys understand their job is to ensure it accumulates no deeper than the bottom of the bar cage, and the blast when they get there knocks it back and compacts it. That compacting action is part of the process that causes the particles to bond together monolithically, so in this sense rebound is not waste, it becomes part of the cross-section. And you'll probably see the guys lift the cage here and there to raise it up into the fresh product they're applying. In fact, watch to see if they indeed do that. If they're not, and if you see them walking around on enough accumulation to cover the bars, especially if they're just shooting over it, point out what they're doing is not the required practice, and take photos because you may need them. You're getting a substandard job.
    While it's true that the least structural stress is on the bottom of a pool, that's no excuse to simply let the steel down there revert back to oxide over the years.
    23,000g IG plaster, slate tile and masonry cascades. Three levels, two pumps: (upper wading 12" dp, with 3.5-ft slate cascade); secondary (double 2-ft waterfall cascades); lower main swimming, two skimmers. New Ultraflex II. Hayward: 3hp pump, 4-cartridge filter. Las Vegas, NV (desert enviro). Water temp: winter avg. 45f, summer avg. 86f. Water service: private well, TDS hard @ 250+ppm but NO Ca+ !! Persistent mustard algae.

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    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: Shotcrete rebound question

    I have often seen gunite crews shovel out rebound and place it in some portion of the pool that needs filling but is not structural, typically areas that have been over dug.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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