Yesterday's mortar

[geraldthehamster]

This is probably a stupid question, but we had best part of a barrow of mortar left, mixed yesterday afternoon, on a job rebuilding one of my outbuildings. Friend suggested we cover it up tightly with plastic, and see if it could be rescued this morning. Today it's solid but still damp and easy to separate and crumble. Would it be daft to put it back in the mixer for a while and then use it? Would it have gone off already to the extent that it will be weakened? I've rescued mortar on the same day before, but overnight seems slightly daft to me.

Cheers
Richard

 

[geraldthehamster]

...I've chucked it. Still interested in opinions, though

 

[^woody^]

Cement sets by a chemical reaction and once it starts it can't be stopped

 

[wessex101]

I think you can do it with lime mortar but as Woody said portland cement will have started to set so by re-wetting it you've lost a lot of its strength.

 

[theprinceofdarkness]

Brick laying mortar does not have to be very strong - lime mortar for instance. I would compromise and use it in new mortar batches, say 10%.
Frank

 

[tomfe]

You may find it makes the rest of the mortar go off quicker like with plaster, for £3 i don't really think it's worth it.

 

[geraldthehamster]

It struck me as a daft idea but my friend seemed convinced so I thought there was nothing to be lost by giving it a try Fortunately it was still wet enough to break easily out of the barrow, before chucking it away.

 

[JohnD]

you would have to add fresh cement to it. I've known builders to the same, but spreading it out so it dries too fast to gain strength so it crumbles when put in the mixer.

Because of the way cement works, in particles that harden from the outside of each, depending how long it was kept wet while curing, if you grind down old hard concrete and re-wet it, it will harden again. I wouldn't trust the strength, though.

 

[geraldthehamster]

you would have to add fresh cement to it.

That makes sense; I suppose also you've done is turn what used to be mortar into slightly sharper sand.

Cheers
Richard