How do I mix the concrete? Casting of chimney crown.

[Ockeponken]

Hello,
I'm planning to cast a new chimney cap. The linked thread has given me a good understanding of the work itself, https://www.byggahus.se/forum/threads/tillverka-skorstenskrona.59426/, but I'm wondering if anyone has a good understanding of the recipe and what proportions to mix?
Best regards

 

[Larsa]

Get a metal hood instead. When I installed a new fireplace, the mason swore over our existing crown and said it would be hell when someone has to repair the chimney.

But those were his words. I have less knowledge...

 

[Oldboy]

Isn't a concrete chimney crown a recent invention that started when oil burners were introduced? The oil contained sulfur that caused corrosion at the top where the smoke condensed. Those problems don't occur with wood burning as I understand it? Then lead sheeting was also used as a lining since the concrete did not completely withstand the sulfuric acid either.

So, if I remember correctly, this leads to the question of whether a concrete crown is needed or not.

 

[Plupp 405730]

The concrete is needed to protect the masonry from rain and wetness, alternatively a sheet metal-clad top.

 

[valter53]

Buy ready-mixed concrete in a bag. Available in both coarse and fine.
Just mix with water. The amount is specified on the bag.

 

[Ockeponken]

Concrete is needed to protect the masonry from rain and wet conditions, alternatively a metal-clad top..

Thank you for starting to steer the thread in the right direction! A metal cap will be placed on top, but for the "right," i.e., desired appearance, a cast crown is what is needed. Only recipes are being sought. If no good tips come in, a couple of bags of ready-mix without any other ballast will have to do the job.

 

[Plupp 405730]

Thank you for someone starting to turn the thread in the right direction! On top, there will be a metal hood, but for the "right," i.e., desired appearance, it is a cast crown that's required. It's only the recipe that's being sought. If no good tips come in, it will be a couple of bags of premix without any other aggregate that will do the job.

How thick will it be?