Old powder not hardening right

[dawndusk01]

I just spent time laying a bunch solid blocks in my damp basement using a Type N masonry cement mix that may be as old as two years and I am confused about the result. I mixed it pretty strong, like a 2 to 5 ratio, but when I checked the excess mortar the next day, it was surprisingly soft and crumbly.

But here is the thing I always thought bad cement looks like a solid lump in the bag and I've seen that many times before. This powder was still totally fine and flowable with no clumps at all and I had no clue it was going to fail like this. This is just plain Type N masonry cement, not a pre-mixed mortar product. It seems like the cement can lose its strength without physically hardening in the bag first and that goes against what some people at places like the Portland Cement Association told me years ago. And is there an easy test to check old cement powder for strength before you waste time mixing up a whole batch?

 

[speed fighter]

Reason is that cement is a very hygroscopic material, meaning it slowly absorbs atmospheric moisture, even through paper bags and even in a seemingly dry storage area like a basement, and this absorption is just enough to cause a slow, partial hydration of the tiny cement particles. For easy field test next time, just grab a handful of the old cement powder and squeeze it tightly. If it retains its compacted shape and does not crumble back into a loose powder when you gently poke it. That is a sign the material has absorbed too much moisture and its strength is already compromised.

 

[install4you]

Even after 28 years in an installation trade, I'm still a stubborn DIY'er for everything else. I know how frustrating it can be to work so hard to do everything right & be caught off guard with something like old cement. A couple years ago I had to start over with a small landscape project because of old mortar mix.
Is there a test for mortar premix? I had over half a bag left at the end of that project. From purchase to done was less than a week. I stored it in a 5-gal bucket with a tight lid. Should that mix be ok? I'm about to use it.
Eddie

 

[El VMX]

I don;t think there is a way to test it but as long as it was stored properly, not hardened and still a fine powder.

I hope this helps!

 

[install4you]

I think I came out OK on the stored mortar mix because it was sealed up. However, I forgot to wet the surface before starting so I'm hoping the stucco repair lasts.
There's another thread where I asked about that problem.
Oh well...