Somebody recently came and filled this deep hole up with cement. It has been giving off a strong odor.

Does cement typically smell and how long will it take for the smell to go mostly and eventually completely.

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    Depends on ventilation. Next question! :P – isherwood Nov 25 '20 at 13:22
  • Yeah but typically say in a normal ventilated does it happen in a day or two or does it go on for weeks - that’s what I was getting at. – James Wilson Nov 25 '20 at 14:03
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    It is odd that the cement is so smelly that you notice it. I wonder why it's so dark. Is it alpaca poop? – isherwood Nov 25 '20 at 14:11
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    Someone probably used a grout mix – Ed Beal Nov 25 '20 at 14:31
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    @EdBeal or thinset with latex modifier . Very smelly – Kris Nov 25 '20 at 18:29

The odor is a function of the drying process. Some moisture is chemically bound to the cement, but some remains. The dryer and breezier the area is the quicker it'll disperse. We can't really say.

It is odd that the cement is so smelly that you notice it. A new basement slab smells like fresh concrete for weeks or years, but that small patch shouldn't really be noticeable if there's any ventilation at all.

You could coat it with a sealing primer, then paint it to help block the odor.

  • 1
    Wait for 2 weeks prior to sealing it 28 days was the minimum I remember when painting fresh concrete. – Ed Beal Nov 25 '20 at 14:19
  • I don't think that's necessary. Concrete sidewalks are routinely sealed immediately to contain moisture for a better cure. Also, precast.org/2013/10/28-day-myth. – isherwood Nov 25 '20 at 14:20
  • The issue is for the paint in this case outside we do a lot of things we won’t do inside, just stating what the concrete rated paint I use states on the instructions. – Ed Beal Nov 25 '20 at 14:33

I am suspicious that what you smell might not be the cement.

Big question: does it smell like cement? If not, what does it smell like?

What is the thing with the pipe coming out of it? Where does that pipe go?

If you go straight down from the wall opening, what is behind the metal there?

Maybe whatever problem prompted this patch is still a problem and you smell the problem, not the patch.

  • How do you explain to somebody in words what cement smells like, haha. ;) – Craig Nov 27 '20 at 18:10
  • It’s definately what’s been added that smells. The pipe is the exhaust for the gas boiler below. Before the filling it was dust etc coming out no strong smell. Now it’s cleary whatever substance has been added here. – James Wilson Nov 27 '20 at 20:33
  • @Craig - if the spirit moves you, I would read a poem about the smell of cement. – Willk Nov 28 '20 at 17:32
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    @Willk “Ode to a small lump of wet cement I found in my basement one midsummer morning”. – Craig Dec 17 '20 at 21:53

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