Technically yes. It absorbs moisture from the air like a dessicant. The
moisture allows the chemical reaction to begin. Depending on the humidity,
time and exposure (a plastic bag will help) this can be negligable to almost
completely hardened.

Yours is the first example I have heard of the actual consequences of this
process though.

I probably would have done just like you did. Tonight I will put that bag
of spare grout in a sealed 5 gal bucket.



"Mike" wrote in message
...
I have a 60 lb bag of mortar that I bought for a small project.
I used a few scoops, and stored the opened bag in my garage
for a year or 2. The bag feels somewhat hardened (not rock hard)
I needed to patch some drill holes in my cement block basementt wall.
I took a few scoops from the bag, It was't too difficult to get it out.
Then I mixed up a batch (not too much water & not too little)
I moistened the cement block (to slow the mortar cure a little)
all seemed to go ok, but a day later the mortar is dry looking,
but I can rub it off with my finger (it just crumbles away with ease)
If I spray water on it (from a water spray bottle with a pump trigger)
It washes out with ease.Can a bag of unused mortar go bad ?
Or is it beacuse it is still winter, and I am working in a heated
basement that is very dry ?

Thanks for your comments - advice