Need advice on repointing chimney thimble please

[Wildo]

Well when I was disassembling my stovepipe for cleaning I ran into a problem. It was too well secured to the thimble in the block and the thimble pulled part way out of the block along with a fair amount of the mortar around it. I redid the mortar once already and it cracked and came off after a few days. I thought maybe it didn't adhere to the existing stuff since all that came off was exactly what I put on. This time I added more Portland to the mix and got the existing mortar moist before I repointed the joint on the advice of a friend, but after three days it looks like the same thing will happen again in a couple days since a tiny crack on the seam has begun to form.

So... my questions are

1) Is there a better mix to use than regular mud? I am using sakrete mortar mix straight the first time and w/ added Portland cement the second time

2) Should I use stove cement instead due to high heat?

3) How long should I let it cure before firing? minutes, hours, days?

4) Should I use a concrete bonding agent to promote adhesion?

5) Did I forget anything?


All advice is most appreciated thanks

Wildo

 

[pen]

The best advice I can give is to post a couple / bunch of pictures of what you have going on here, then those with experience have the best shot at using what you've already stated to help you out.

pen

 

[begreen]

This doesn't have a simple answer. Here is a short educational video on the topic.


Basically you want polymer resins or fiberglass to strengthen the mortar and you need to provide an expansion joint around the clay tile.

 

[joes169]

This doesn't have a simple answer. Here is a short educational video on the topic.


Basically you want polymer resins or fiberglass to strengthen the mortar and you need to provide an expansion joint around the clay tile.

That looks like a tutorial on a chimney crown/cap??

Pretty sure the OP is asking about patching where the thimble enters the block chimney in the basement.

I would recommend making the hole bigger around the pipe as deep as possible, and fill with a bigger, full depth joint around the pipe. Should have at least 1/2" around the whole pipe to make is last. If you simple put a thin patch over the existing, it likely won't last.

 

[begreen]

Sorry, wires crossed with another thread. You are correct.