Expansive Concrete
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   When cement cures into concrete, water in the mix combines chemically with the Portland Cement to make Concrete. The process takes about a month, but is mostly done in a week, if you keep the surface moist, and dont let it dry out.

   In the process, the resulting product shrinks slightly. Ordinary 3.5 sack (per cubic yard,) mix is common, but not waterproof. The Navy uses a 7 bag mix to make it waterproof. They use it to coat structures that are in the water, like piers and wharfs. But its rather expensive.

   In many applications, expansive concrete is needed. And this can be made easily, inexpensively, and is mostly waterproof. Youll have to test it for sure.

   Both powered iron and aluminum have been used successfully. This is prepared by grinding (on a bench grinder) a piece of metal, and mixing the metal filings into the wet cement. Over the course of the curing process, the iron filings will rust, or the aluminum filings will become aluminum oxide. The result is slightly larger because of the addition of the oxygen molecule, which makes the metal more stable.

   Since it is larger and mixed throughout the matrix of the concrete, the cured concrete becomes slightly larger, it expands rather than shrinks. The Cement folks dont want to tell you this, because they want you to buy the chemicals from them, and not do it yourself.

   The ratio is about 1 teaspoon per cubic yard, filings to wet cement.

   Test it, and please report to me the results.

    Thanks for your interest.

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