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What is the likely construction/material of the basement floor shown below? It's not very flat, and the surface appears sandy. It's almost as if some kind of skim-coat was applied to the dirt floor. I've seen this type of basement floor frequently in old New England homes. What's it called? What's it made of? Is this technique still used today?

Note: answers such as "this floor appears to be partly made of water" are certainly accurate, but don't really get at what I'm looking for.

image of concrete floor

  • I have very similar floor in parts of my basement. I think it might be dry packed cement? But would be interesting to know what it actually is. – Vitaliy Nov 21 '12 at 1:11
  • Darn, you took my line! How's old is the house? – GdD Nov 21 '12 at 13:02
  • @GdG: I'd guess originally 1920s-40s, recent renovation. – mac Nov 22 '12 at 3:55
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For sure it is a cementious material utilizing portland cement as binding agent. Anything more specific is speculative. If the uneven, raised surface in the background is covered with similar material, this is almost certainly "shotcrete" or "gunite". Pneumatically placed concrete, cement, or mortar. Based on the sandy surface, it was probably a dry mix placement, where dry material and water come out of the gun separately and are essentially "mixed" on impact with the supporting surface. Proper mixing of this method is largely dependent on the applicator's skill.

The other method is wet mix, where pre-mixed material is shot out of the gun. The quality of wet mix placement is more predictable. When done properly over rebar to proper thickness, shotcrete is just as strong as poured in place concrete. Therefore, the technique is still used, often to install tunnel liners and similar roadway works.

P.S. I actually lol'd at you floor of water comment :)

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