Concrete questions

[csmeutah]

So I've placed my block just looking for a little clarification. the manual says "Block the cores that you have not filled with your empty concrete bag to stop your hearth concrete from spilling into the holes." Later it mentions leaving space on the edge of the hardibacker so the concrete fills all the cores when pouring the hearth.

Do all cores get filled?
Rebar in everyother core/block?
how much concrete will I need to fill everyother core?

Any clarification would be appreciated.

[david s]

Re: Concrete questions

It means fill every second core and block off the all but the top brick core for the others.
Rebar only in the cores that are totally filled.
You need more concrete than you would think it will take. Fill the core of one block, measure its volume, then multiply by how many you have to fill.

[csmeutah]

Re: Concrete questions

thx, that helps. any guesses on the concrete? I'm wondering if it would be easier to bring in a full yard of concrete in a trailer.

[david s]

Re: Concrete questions

thx, that helps. any guesses on the concrete? I'm wondering if it would be easier to bring in a full yard of concrete in a trailer.

I don't know what kind of blocks you are using. The 8" blocks I use take 3 litres/core, but the 6" blocks only take 2 litres, part of the reason I prefer to use 6" blocks.

[Tscarborough]

Re: Concrete questions

.26 cubic foot for 8" block, .66 cubic foot per 80# bag of regular concrete mix. If you are in an earthquake zone or wear both belt and suspenders, then fill the corners and every 3rd core, otherwise don't worry about grouting any cores.

[JRPizza]

I just pored my cores today. I didn't think the .26 cubic foot sounded right, so I measured the cores in my 8X8X16 blocks. 5"X6" times the height of four blocks (30.5) gives 915 cubic inches, which rounds to about .53 cubic feet. I filled 14 cores so I figured I needed (14X.53) about 7.4 ft^3 of concrete. At 2/3 ft^ per 80 pound bag I should have needed a little more than 11 bags, but it only took slightly more than 10 bags. First couple of bags were mixed a little dry so probably didn't pack into the cores as much as the later, wetter mixed bags, and I didn't account for the small volume of the rebar (about 16 in^3 per core). If you figure about 900 in^3 for a four block high stack with .5 in rebar you will probably be pretty close.

[Wozza]

A 20kg bag of concrete will apparently fill 0.1 cubic metres. After doing my base and my hearth I used the exact volume plus 10% in each case.

[RandyJ]

I guess I went a little over board on the filling. I did all the corners and every core on my short walls and every other on the long walls. I went through 18 60# bags for that. I was a little worried about the short walls moving during the poor of my front arch and support slab. It I am sure was all in my head but now my base is bomb proof now. It is frightening just how heave these things get if you are not attention . I think I am at around 16000# if I did my addition right.

Randy