Mortar not hardening in damp weather

[Ford850]

It sounds like it wasn't mixed evenly. What you dumped out had more cement than what you used.

 

[s219]

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.

 

[Egon]

Do a review of your mortar mix and mixing procedures.

 

[Gator6x4]

Replace mortar, it sets through chemical reaction not by drying. You have bad mortar

Agree. :thumbsup:

 

[EddieWalker]

I've never had this happen, so I'm only guessing what it could be. Did you buy Type S or Type N or one of the others? Did you get it from Home Depot or Lowes? or from some other supplier? Any idea of how long it's been sitting? Home Depot and Lowes sells so much that they always have fresh stock. or did you mix your own creation with Portland Cement and sand?

I do not believe your problem is from the temperature or the moisture from the weather.

 

[/pine]

If the blocks are set plumb and level and you can't kick them loose...why not just fill the cells with concrete and move on ?

 

[Gary Fowler]

If the mortar is so weak that you can powder it up after it sets for a couple days then it should be knocked out and replaced. It will only deteriorate with age and cause problems later on. Bite the bullet now and get some new mortar.

One note: If you use cement and sand to make your mortar, it could be something in the sand that is causing the cement not to set. So if you mixed your own, replace the sand also along with the Portland cement.

 

[downsizingnow48]

My guess is the mortar dried too fast, not too slow. Dry concrete block maybe sucked too much water out too fast. Or the footings could have done it too. Or, when you put it on you worked it too much, or waited too long, and it had started to set by the time you set the block on.

In any case I would start over. I would not want known compromised mortar at the bottom of the wall.

 

[drivesitfar]

ALL: i've heard from a few 30+ year masons that HD bagged mortar (and maybe Lowe's too) could get batches with too much sand. i'm far from an expert in mortaring bricks and blocks, but I have done a couple projects. I bought portland cement and i have sandbags full of sand from a flood at a client's shop that weren't used and I use 2-3 parts sand to 1 part Portland on my little brick projects. they seem to hold up.

another issue might be the cold weather so i'm here to see what happened too.

 

[crashz]

Damp conditions would actually allow the cement reaction to cure slower and stronger. But I wonder if the soil and the water around it has a high pH or some chemicals have been used around it that could change the pH?