Water Preventing Concrete From Hardening

Discussion in 'The Water Cooler' started by whoosh, Apr 2, 2011.

  1. whoosh

    whoosh Cooler King
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    TOKYO, April 3 (Reuters) - Japanese officials grappling on Sunday to end the world's worst nuclear crisis since Chernobyl were focusing on a crack in a concrete pit that was leaking radiation into the ocean from a crippled reactor.

    Tokyo Electric Power Co (TEPCO) said it had found a crack in the pit at its No.2 reactor in Fukushima, generating readings 1,000 millisieverts of radiation per hour in the air inside the pit. [ID:nL3E7F2039]

    "With radiation levels rising in the seawater near the plant, we have been trying to confirm the reason why, and in that context, this could be one source," said Hidehiko Nishiyama, deputy head of the Nuclear and Industrial Safety Agency (NISA), said on Saturday.

    He cautioned, however: "We can't really say for certain until we've studied the results."


    TEPCO has begun pouring concrete into the pit to stop the leak, he said.

    Public broadcaster NHK said late on Saturday that water was preventing the concrete from hardening and the pit was still leaking.

    Officials from the utility said checks of the other five reactors found no cracks.

    Nishiyama said that to cool the damaged reactor, NISA was looking at alternatives to pumping in water, including an improvised air conditioning system, spraying the reactor fuel rods with vaporized water or using the plant's cleaning system.
    WRAPUP 1-Japan nuclear struggle focuses on cracked reactor pit | Reuters
     
  2. whoosh

    whoosh Cooler King
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    How can concrete set up under water?

    How does the concrete get hard in a situation like that? The answer is that the mixture does not actually 'dry out' when it hardens. Rather, the water in the mixture undergoes a chemical reaction with the cement, which forms hard crystals which bind the sand and pebbles together - no water has to escape. In fact, if the mix dries out before it is cured, it turns back into the loose dry ingredients (sort of). That is why you have to cover up a freshly poured concrete sidewalk with plastic here in dry Santa Fe, to prevent the surface from drying out.

    This knowledge has been around a long time:""There is also a kind of powder from which natural causes produces astonishing results. This substance, when mixed with lime and rubble, not only lends strength to buildings of other kinds, but even when piers are constructed of it in the sea, they set hard under water.":
    http://askville.amazon.com/concrete-set-harder-underwater/AnswerViewer.do?requestId=10288742
     

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