Mortar drying time.

tony3619

Filling a couple of holes of missing mortar and the mortar looks quite dry/sandy after 12 hours. Easily rubs away with a finger. 

How long does mortar take to harden. Is 12 hours too short? 

stuart45

12 hours isn't long. You also find with small bits of mortar that it can dry out too quickly, so not achieve a good strength.
Make sure the existing is well damped down first.

grandadgolfer

stuart45 said:

12 hours isn't long. You also find with small bits of mortar that it can dry out too quickly, so not achieve a good strength.
Make sure the existing is well damped down first.

Keep it moist

FreeBear

Spray a bit of water on the area just to dampen it a bit then leave well alone. Whilst the mortar will have dried out, the chemical reaction that makes cement go hard is still taking place. 48 hours will see it going pretty hard with full strength being achieved in around 28 days.

tony3619

FreeBear said:

Spray a bit of water on the area just to dampen it a bit then leave well alone. Whilst the mortar will have dried out, the chemical reaction that makes cement go hard is still taking place. 48 hours will see it going pretty hard with full strength being achieved in around 28 days.

Yea it definitely looks dried out and one section I did touch and it just raked out like normal sand...didn't know if this was nomal after only 12 hours. 

danrv

tony3619 said:

FreeBear said:

Spray a bit of water on the area just to dampen it a bit then leave well alone. Whilst the mortar will have dried out, the chemical reaction that makes cement go hard is still taking place. 48 hours will see it going pretty hard with full strength being achieved in around 28 days.

Yea it definitely looks dried out and one section I did touch and it just raked out like normal sand...didn't know if this was nomal after only 12 hours. 

I found that when I first started repointing my property’s wall. With help here, I’ve got the technique down much better.
Assuming mortar mix is ok (I use 5:1), the key is keeping it damp, I find for as long as possible. Not too much at once though else it will run.
After I’ve done a couple of rows, I give it a mist over with the hose regularly, more so if in direct sunlight.
I also soak the mortar at night before turning in.

tony3619

danrv said:

tony3619 said:

FreeBear said:

Spray a bit of water on the area just to dampen it a bit then leave well alone. Whilst the mortar will have dried out, the chemical reaction that makes cement go hard is still taking place. 48 hours will see it going pretty hard with full strength being achieved in around 28 days.

Yea it definitely looks dried out and one section I did touch and it just raked out like normal sand...didn't know if this was nomal after only 12 hours. 

I found that when I first started repointing my property’s wall. With help here, I’ve got the technique down much better.
Assuming mortar mix is ok (I use 5:1), the key is keeping it damp, I find for as long as possible. Not too much at once though else it will run.
After I’ve done a couple of rows, I give it a mist over with the hose regularly, more so if in direct sunlight.
I also soak the mortar at night before turning in.

Do you think it will be too late now? By the time I get back from work it will of been 24 hours and if it's still brittle will spraying it with water make much difference? Or should I take out where possible and just start again? 

stuart45

Did you finish the joints and compress them with a metal jointer?

tony3619

stuart45 said:

Did you finish the joints and compress them with a metal jointer?

Yea I did, maybe I didn't give it long enough before touching to see how set it was. It just seemed dry and sandy. Parts just fell out 

danrv

tony3619 said:

danrv said:

tony3619 said:

FreeBear said:

Spray a bit of water on the area just to dampen it a bit then leave well alone. Whilst the mortar will have dried out, the chemical reaction that makes cement go hard is still taking place. 48 hours will see it going pretty hard with full strength being achieved in around 28 days.

Yea it definitely looks dried out and one section I did touch and it just raked out like normal sand...didn't know if this was nomal after only 12 hours. 

I found that when I first started repointing my property’s wall. With help here, I’ve got the technique down much better.
Assuming mortar mix is ok (I use 5:1), the key is keeping it damp, I find for as long as possible. Not too much at once though else it will run.
After I’ve done a couple of rows, I give it a mist over with the hose regularly, more so if in direct sunlight.
I also soak the mortar at night before turning in.

Do you think it will be too late now? By the time I get back from work it will of been 24 hours and if it's still brittle will spraying it with water make much difference? Or should I take out where possible and just start again? 

If it’s now dry and still brittle, I don’t think there’s much you can do with it.
I’d rake out and redo.
I didn’t have much luck using just sand and cement. Should be ok, but the mortar in my walls contains hydrated lime so I’m adding this plus a little plasticiser. 
Works well, is very workable and if kept damp, dries quite hard.

stuart45

Damp the wall first, fill with mortar, joint it up and then don't keep sticking your fingers into it. Mist it later to keep it damp. 
If it has gone wrong it's only a 2 minute job to rake it all out and redo it.