Good mortar gone bad

[Mike]

A few years ago, I bought a bag of mortar mix to make some small repairs around the house.

After using a small amount, I stored the bag on a shelf in my garage over the winter. The bag never came in contact with my cement garage floor. I used some the next spring, only to discover it went bad. It mixed and applied as usual, but when cured, it just rubbed off with my finger.

So last spring, I bought another bag, and again I used a small amount. But this time time after opening the bag, I poured the remaining mix into a clean and dry 5 gallon plastic bucket with a tight lid. This time I stored it in my basement over the winter (heated).

I just mixed another small batch, only to discover it has gone bad again. It was not clumped together it seemed the same as when it was in the bag It never got hard or anything like that. Is mortar that sensitive? I didn't notice an expiration date. What can I do to make it last longer ?

Please help me to understand about mortar mix.

Thanks Mike

[Doug Miller]

Yep -- absorbed water vapor from the air, reacted with it, and now it won't set. Completely normal.

Use a bucket with an airtight lid next time -- it seems that the lid on your bucket isn't quite as tight as you thought it was.

Or buy it in smaller bags, since you're only using it in small amounts. It's not like the stuff is all that expensive, you know, and it doesn't appear that you use it often enough to be actually saving any money by buying it in bulk.

Mortar, plaster, and concrete cure by chemical reaction with water. This includes water vapor in the air. Once the reaction has taken place, it can't take place a second time -- thus, mortar stored in moist or humid conditions will become unusable, often in a matter of only a few weeks. The key to preserving it is to keep it dry.

[trader4]

You could also put one of those damp remover dessicant widgets in the bucket. That's what I do with grass seed.

[Doug Miller]

That might help, and certainly won't hurt -- but I haven't found it to be necessary, given a truly airtight container.

[readandpostrosie]

another question about mortar.................. i have had my house stoned outside and then mortared in-between each stone, it looks great. HOWEVER........................down on the bottom where the walls meet the sidewalk all the motor is pulling away from the joints in pieces.(2-4 inches) is there a something special added to mortar when using it in this "grout" manner, to make it more "flexible"?

sorry about my lack of proper terminology!

rosie