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.

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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.

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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.