Mortar not hardening in damp weather

[Deere Dude]

So the sample pieces I brought in last night hardened up overnight, but I can squeeze them between my thumb and finger and they crumble into dust. Definitely not right. I can't kick the blocks loose from the footing, but I am going to give the mortar a scrape with a chisel or trowel and I suspect it will crumble loose. If that's the case, I will tear it apart, clean off the footings, try to dry out the area a bit (mud pit now), and re-set all the blocks. I bought a brand new bag of mortar this morning and we have a small window of mild weather left (59F today, 49F tonight, 61F tomorrow) before winter returns tomorrow evening. That should be plenty enough time for the new mortar to set up before I have to worry about cold weather. What a way to derail progress, but could have been worse.

I take it this is premixed mortar and sand. If it is I would pick a different supplied for the redo. Or was this just a bag of mortar then you add sand?

I have mixed S or N, I don't recall which is for what, but mixed with mason sand and had great results in very hot and even cold weather. I question the sand quality.

Either way it seems like some bad stuff.

 

[s219]

I ended up chiseling out the old mortar which basically fell apart and crumbled. Even though the blocks felt solid, I just didn't trust the mortar to bear weight. Seeing how crumbly it was as I loosened it up, I think it was right to be suspicious.

After scraping the mortar off the footings, I hit them with a wire brush, then wiped with water, let them dry, and cleaned off with a shop vac. I re-set the blocks with a new batch of mortar and hope it turns out better this time.

The new bag of mortar mix (pre-mixed type S) that I bought this morning had a manufacture date of January 2019. The old mortar, which I bought last week, had a date of February 2017! I don't know if that was a contributing factor -- I know mortar mix can go bad -- but I will check the date on these things more carefully. I have been using mortar for decades with very little attention paid to the product or process, and it's always just worked and been idiot proof.

 

[repete]

When I buy the bagged stuff I usually add some portland cement to the mixture just to be sure.

 

[lilranch2001]

Lime mortar has a shelf life, it loses potency after some time, 6 months is what we always used as a time frame.

 

[s219]

New mortar worked like a champ!

 

[EddieWalker]

The new bag of mortar mix (pre-mixed type S) that I bought this morning had a manufacture date of January 2019. The old mortar, which I bought last week, had a date of February 2017!

Are you buying from Home Depot or Lowes? I'm struggling with the concept that either store has mortar on hand that's a year old, or with the sack from 2017, over 2 years old. Where I live, they rotate their stock and sell so much of it that there is always new stuff coming in. Just guessing, I don't think any of it sits for more then a month or two.

 

[lilranch2001]

I took it that he had it as a leftover

 

[drivesitfar]

S219: congrats and guessing old mix didn't have enough Portland in it. if you have more bags of the old stuff laying around maybe buying a 60 or 94 bag of Portland cement would maybe be a good purchase and add a portion to each batch. i'm not 100% on this working, but thinking it should.

in any case you are back in business.

 

[lilranch2001]

I do not think it was a matter of lack of portland, I believe it was a fact that the mix had lost its potency since it had gone past its usable shelf life.

I think it would be silly to try to fix it for the price, so much labor in a project and still potentially have a faulty wall who knows what the end results would be.

 

[CADplans]

It might be best to "lime" the lawn with the old stuff that is left over,,,

(NOTE: I tried putting left over mortar on grass one time,, I did not see the effect that putting lime down has,, You would think that anything that changes the pH would have the same effect? Maybe the mortar is slower acting than lime?)