Sealing concrete, cabin sole

[B.Hart]

  Just a reminder to always grind any area you are planing to bond to, then clean with acetone.  my 0.02

[Craig Weis]

I use to manufacture a cement lined, black iron [11 ga steel] water heating tank with a 25 year warranty.

The cement is a  TYPE K expanding cement.
Expanding cement does not really expand but actually shrinks less then regular cement. Typically this type K is used in bridge work and road work.

Additionally for high heat floors/roofs and walls and burner tubes for bake-off ovens, where paint is baked off at 750 deg F. [Burn-off ovens]. The smoke from the burned off paint is directed through a afterburned lined with cerafelt [space shuttle tiles] at 1550 deg F for 15 seconds to destruct the voc's and smoke. Exhausting nothing but hot air. Anyway...

The ratio of sand to cement in our dry mixer was 4~100 pound bags of cement and 2~100 pound bags of sand mixed for 25 minutes.

Two metered squirts of water, about 14 pound each each squirt, was added to 2~50 pounds of dry in the wet mixer and mixed for about 5 minutes.

Poured into small pails the cement was then banged through a funnel and into the tank where it was spun horizontally at 550 rpm for 20 minutes in any of our five spinners and the excess water vacuumed out with a shop vac and long piece of 3/4 inch dia pvc pipe.

Next day the top head was poured, and the following day the bottom head was poured. Poured heads do not achieve the hardness of the side wall as one can imagine. Head cement is a little wetter, just to get it to move and lay down in the tank with out cracking.

TANKS ARE WATERED AT EVERY STEP TO KEEP CEMENT FROM CRACKING DURING THE CURE PROCESS. At time the cement drys under water as it turns into concrete. Tanks are always spray-misted to keep them hydrated.

On the fourth day day tanks are scoped and visually checked for cracks. Before being painted.

Cracked cement in tanks are banged out, cement pulverized with a hammer and bar manually, vacuumed and re poured. A rare occasion. But the tanks look like they have been through a hail storm.

Finished lined tanks weigh about 78 pounds for the small tanks and 117 pounds for the large tanks. All moved by grunt work.

All the materials I have seen at my local Door County lumber yard for anyone to purchase.

The Portland Cement chemists who were kind enough to visit us ['cause we used 80,000 pounds of type K a mounth] and help with crack abatement. They tell us that the full cure that is 100% occurs in about 88 years!!! Really. But actual use-to-good cure is in about 21 days. skip is amazed.

Bottom line is don't seal the cement. Mine on Comfort and Joy is 'Alla natural' as I noticed when I installed a bilge pump in the lowest part of the keel, which in the 19 is hollow and under the portapotty. Rich at Com-Pac told me they chuck in some pig iron with the cement once in a while. Weight is weight. skip.