How soon can I paint new cement?

mbb

May 25, 2017 at 9:13pm

The chimney of my stucco house was patched with cement 3 days ago. How soon before I can paint it? I assume I have to prime first. If so, would any primer do?

I would much appreciate your help.

Thanks.

mbb

drummerboy

May 27, 2017 at 2:17am

Was the repair replacing the stucco or is it the joints between bricks? Not clear as to what the repair actually is. But then I don't see why you'd paint joints.

Are you hydrating the repaired surfaces daily? This helps to create a strong cure and will increase the life of the repair.

But generally speaking, what's important when applying paint to concrete (cement is the powder you mix with water and an aggregate material like sand to make concrete. My PHD Civil Engineer world-class-expert-on-concrete older-brother tells me this a lot.) is the PH level. This can be tested with a PH pencil available at most paint stores. You should then prime first with an alkali-resistant primer. Use an exterior paint that specifically says it's appropriate for concrete. Most paints like a PH level less than 10, but some paints may specify a higher acceptable PH.

There's no set number of days to wait. You know when it's ready by the PH level. Concrete cures through a chemical process, not through drying, and as such is dependent on many factors, one of which you can control by hydrating the new concrete. The concrete should remain moist for several days for proper curing. This will also help it reach the proper PH faster.

That's pretty much it.

Hydrate the repair for the first week or so.
Test the PH.
Repeat above til PH is below 10.
Prime/Paint with paints appropriate to PH level and suitable for concrete.

Have fun!

fabulouswalls

May 27, 2017 at 11:24am

I would wait up to 30 days depending on the patch. The directions on the paint will also help.

mbb

May 2, 2023 at 7:13pm

drummerboy said:
Was the repair replacing the stucco or is it the joints between bricks? Not clear as to what the repair actually is. But then I don't see why you'd paint joints.
Are you hydrating the repaired surfaces daily? This helps to create a strong cure and will increase the life of the repair.
But generally speaking, what's important when applying paint to concrete (cement is the powder you mix with water and an aggregate material like sand to make concrete. My PHD Civil Engineer world-class-expert-on-concrete older-brother tells me this a lot.) is the PH level. This can be tested with a PH pencil available at most paint stores. You should then prime first with an alkali-resistant primer. Use an exterior paint that specifically says it's appropriate for concrete. Most paints like a PH level less than 10, but some paints may specify a higher acceptable PH.
There's no set number of days to wait. You know when it's ready by the PH level. Concrete cures through a chemical process, not through drying, and as such is dependent on many factors, one of which you can control by hydrating the new concrete. The concrete should remain moist for several days for proper curing. This will also help it reach the proper PH faster.
That's pretty much it.
Hydrate the repair for the first week or so.
Test the PH.
Repeat above til PH is below 10.
Prime/Paint with paints appropriate to PH level and suitable for concrete.
Have fun!