rubbing up new concrete

[mnemonix]

Got my concrete in yesterday. Today it's reasonably firm and no ponding water. Can I rub it up with a steel trowel to smooth out the tamping marks? I tried a test patch which seemed to bring some water and sand to the surface as it smoothed, but I don't want to cause any damage to the concrete surface if this isn't the right thing to be doing!

 

[Alastairreid]

You can trowel it up using your steel float, let the surface water evaporate then use a wooden or nylon float to give it a final rub.

 

[mnemonix]

Thanks for the quick reply.

So this isn't going to make the concrete surface more fragile? Where it's dried already it's almost glossy, whereas rubbing it up gives it a grainy appearance and leaves some loose sand on the surface.

The firmness of the concrete after 18 hours is such that if I press my finger into it, it leaves only a feint impression.

 

[Alastairreid]

All you are doing is ironing out the trowel lines indentations etc, it will have no adverse effect on the strength or stability of the finished surface once cured.

 

[Norcon]

Must have been a weak mix. Normally after 18 hours steel trowelling is not possible and it shouldn't be.

 

[mnemonix]

I was able to rub out the tamping marks with the trowel with a bit of effort, which worked up a sort of slurry on the surface which I smoothed off. Should I be concerned? If it's hard by tomorrow will it be ok? It's pretty cool and damp here, though it's indoors.

(edit) I can easily push the sharp edge of my trowel into the concrete still - 30 hours after it was laid.