Concrete sealers

MikeAmann

I'm looking for opinions as to what works.... and what doesn't.
Based on this https://concretesealerreviews.com/best-concrete-sealers-for-2017/ , I am liking their pick for Siloxa-Tek 8500 concentrate. The top of Mom's chimney has some damage. The mortar is gone in places and some of the bricks have spalled. The neighbors have similar damage. Repair work is planned soon. I am going to have to power wash the chimney first. Suggestions for what to use for a cleaner please. When the work is complete, I plan to seal the brick/concrete/mortar. And it will get a new stainless steel cap https://www.homedepot.com/p/The-Forever-Cap-17-in-x-45-in-Fixed-Stainless-Steel-Chimney-Cap-FSCC1745/203764803

Also, there are 3 flues - one for the boiler and HWH, one for the fireplace, and one for the former wood-burning stove. The WB stove is gone and I will never use the fireplace. How can I seal off the two unused flues to keep the cold air out? One is square, the other round.
One last thing.... IF I ever decide to move the HWH, can I move it to the flue that was used for the WB stove? Thanks.

Jamie Hall

Go easy on the power washer. Old brick has a hard surface glaze which you isn't obvious, but you don't want to damage it. If you doon't hurt it, the brick will last centuries. Damage it, and you're looking at decades at most.

On closing a flue -- if you close it at the top, close it at the bottom as well. That way no one will accidentally connect something to it.

MikeAmann

Yes, but what to use? In the basement, for the WB stove flue I made a round plug from 2" rigid foam board insulation and sealed it with adhesive caulk. At the top of the chimney I could use stainless steel covering similar plugs.

MikeAmann

TTT for @Bob Harper