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  1. #1
    Join Date
    Feb 2010

    Default powdering concrete in basement crawlspace

    I have a crawl space in an addition where the concrete was poured right before a downpour and was flooded prior to setting. The addition was built over and the water evaporated, but the the concrete floor in the crawl space is powdery - worse than a dirt floor. Solid concrete, no cracks but can be sc****d 1/4 inch or more before reaching solid concrete. Tearing out the concrete is not an option. Is there a product that will seal it enough for light storage and occasional entry such as a concrete leveler, or will that flake off? Or should I put in sleepers and a plywood floor? I have moisture/mildew problems in the basement but the attached crawl space is dry. Its approximately 500 sq feet.

  2. #2
    Join Date
    Jan 2015

    Default Re: powdering concrete in basement crawlspace

    Seems this is a common problem. Concrete dusting is very common, a nuisance, and can be unhealthy under regular exposure. The causes of this are plentiful. In your case it was long term excess surface water preventing a proper cure. In homes it is often due to concrete being cured with heavy expose to carbon monoxide. This prevents the top from curing out properly and it disintegrates over time. In most other cases it is due to overworking and over watering the slab. Again the top layer is not very sound and breaks down. This happens outdoors just as often except it is really unknown as the dust just goes on its merry way.
    Concrete densifiers-like sodium tru hard- are typically a remedy as they will help to lock up the surface and prevent future degredation. They are simple to apply and are not issues with toxicity or fumes. In this case, if the surface is bad down a quarter inch I would be inclined to grind off that surface before applying a densifier treatment. If it is that powdery, a densifier will not make the correction. Just applying a sealer is a tough call as it will not penetrate far enough to reach solid concrete and will likely peel away.
    Last edited by creteguru; 01-07-2015 at 03:55 PM.

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