Re: Concrete Block



Its a factor of volume and the atomic weights of the elements that make the components of concrete. I dont think they have much choice in the matter. ;)
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Because they make them with two types of concrete, regular at 145 pcf or light weight around 100 pcf (not sure exactly of lightweight concrete, can't get it easily in Pacific NW). That's why they call them concrete block.
CID...

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> "skroob"> wrote >>> Why do they make them so heavy? >> >> Its a factor of volume and the atomic weights of the elements that make >> the components of concrete. I dont think they have much choice in the >> matter. ;) > > Someone told me that the builders fill the hollow portions of the blocks > with concrete after they have been stacked in the shape of a wall.
> If the blocks are going to be filled with concrete anyway, why can't they be > made of a less heavy substance? > Seems like it would be easier and faster to build walls if the blocks were > lighter than they presently are. > There must be a flaw in my thinking, otherwise someone would have thought of > this already. > >
Don? you need to get out more LOL
CMU do not need to be filled with concrete when the wall is built, however they can be at times. Sometime we add rebar and grout solid to give additional strength at certain vertical elements, sometimes horizonatal courses are grouted solid (bond beams) some times just a small area is grouts solid.....around lintel bearing. The open cells are often filled with insulation if it is only a single wythe wall. Also note that CMU comes in different weights based on its composition, which can also affect it's fire rating.
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Don wrote:

It's called "a desk job." <g>
Notan
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Since I (and all detailers I know) really dislike detailing masonry fill cells, I would be all for the elimination of CMU walls. PIP or Tilt-Up panels should be mandatory.
:-)
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>> > "skroob"> wrote >> >>> Why do they make them so heavy? >> >> >> >> Its a factor of volume and the atomic weights of the elements that >> make >> >> the components of concrete. I dont think they have much choice in the >> >> matter. ;) >> > >> > Someone told me that the builders fill the hollow portions of the >> blocks >> > with concrete after they have been stacked in the shape of a wall. >> >> > If the blocks are going to be filled with concrete anyway, why can't >> they be >> > made of a less heavy substance? >> > Seems like it would be easier and faster to build walls if the blocks >> were >> > lighter than they presently are. >> > There must be a flaw in my thinking, otherwise someone would have >> thought of >> > this already. >> > >> > >> >> Don? you need to get out more LOL >> >> CMU do not need to be filled with concrete when the wall is built, >> however they can be at times. >> Sometime we add rebar and grout solid to give additional strength at >> certain vertical elements, sometimes horizonatal courses are grouted solid >> (bond beams) some times just a small area is grouts solid.....around >> lintel bearing. The open cells are often filled with insulation if it is >> only a single wythe wall. Also note that CMU comes in different weights >> based on its composition, which can also affect it's fire rating. >> > > Since I (and all detailers I know) really dislike detailing masonry fill > cells, I would be all for the elimination of CMU walls. PIP or Tilt-Up > panels should be mandatory. > > :-)
Nope.......we use intergral color ground face more than any other material :-)
> >
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You can't use ungrouted concrete block walls on the west coast if you are using the IBC code. All CMU walls are to be fully grouted and reinforced. You can use partial grouted walls where seismic areas are not high but never complete hollow walls.
CID...
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In a previous post Don says...

Don:
What you've described is overkill. Here's my recommendation:
#5 vert @ 32" o/c. Fill the other cells with insulation: Perlite, Zonelite, or something similar.
Horizontal reinforcing = Bond beams w/ (2) #4 @ 48 o/c
No joint reinforcing (Dur-o-wal). Most masons hate the stuff because it slows down their production.
You might look at using ICF for the house, including foundations. The better types have places to attached siding on the outside and drywall on the inside.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
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Bob Morrison wrote:

AAC...lightweight and you can cut it with regular tools...
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Dayymn, I had said earlier how much I dislike CMU reinf. detailing, but with your design I'll make an exception. Detailing the bars as you mentioned above you are looking at btwn 60&65lbs/lf of rebar for a 10'0h wall, not including ftgs and piers. At that rate it'd would be almost worthwhile to detail.
When you say you want to tie the verts to the beam bars, will they be tied to bars on the face of the beam or to the center run of bars? I need to know so I can figure if they need to be offset bent or not. Do I need to hook the verts @ top/beam. Masons love it when we put a standard hook (12" for #6) on the verts, so they have to "snake" the bar through the cell. Talking about slowing down production...
Let me know when you're ready to get started, I need a new boat.
:-)
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In a previous post Don says...

Geez, where you building this thing? On the surface of Mars?
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
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lighten
Then they'd carry more of them.
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be
of
An alternernate system I have seen is EPS blocks, with R.C. cores and bond beams, for stucco finish. Seems to be structurally limited, but perhaps engineered R.C. makes this more effective than one might think.
R'zenboom
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Heavy block is a good sound blocker.
As others have mentioned, they make them in a "normal" weight and lightweight version. There are actually several different lightweight versions. You also can get a variation in the overall weight of a block due to the amount of open area. A three cell block will be typcially heavier than a two cell block.
From my perspective, I really like heavy block because that weight helps block sound especially the low frequency sounds that are difficult to block with light constructions. A lighter block can be used with the cavities filled with mortar so the overall weight is about the same as a heavier block to give comparable performance to a heavier block.
Beware of claims of lightweight fillers for the core that say they improve acoustical performance. One claims to perform as well as filling a block with sand. However, if you look at their test, you find they filled lightweight block with sand and heavyweight block with their product, so the overall weight was the same.

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Just to make sure I am not misinterpreted, PIP or tilt-up concrete can be good for sound blockage also. I was not trying to advocate block over these options.

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Usually not all of them.

be
There is a system that uses styrofoam, I believe.
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