Re: Concrete Mix

Posted by Eugene

In Reply to: Concrete Mix posted by Edwin

Hi Edwin,

The lime is needed in concrete that will see a lot of heat. The base support blocks that hold up the hearth slab will see little to no heat. You should be fine using just the quikrete mix. I did mine using just the fast setting quikrete because it was still cold at night.

I am not sure if it is necessary, but I added some rebar running vertically in the supporting blocks that stuck out at the top so they actually go into the hearth slab.

When you pour the hearth slab, which will get a lot of heat, you should probably mix your own. You can buy all the components (gravel, sand, portland cement and lime) in bags for easy transportation and storage.

One more note, and I may be wrong here, but I believe that Type N masonry cement is actuall made from 1 part portland cement and 1 part lime. If this is true, and I think it is, then you can use that mixed with the sand and gravel. I used some of this when I ran out of lime during the pouring of my concrete cladding.