Watch this high-density polyurethane foam raise concrete slabs thanks to the magic of physics. The foam, called PolyLEVEL, is applied through a hole drilled in the concrete, expanding under the concrete and pushing it up.
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Polyurethane is awesome :) I make mine from vegetable oils (non epoxydisation methods employed in it's creation). They had a novel use for pu foam in conjunction with tanks and boggy land/ landmine covered areas.