% Increase in Strength for filling in Cement Block Wall with cement and rebar

[GWHH]

For the life of me. I can't remeber the exact number and can't find the info on this subject here. When you take a standard cement block wall of 6 or 8 inch thinkess and its a load bearing wall and fill it up with cement and rebar.

What % does the strength of that wall increase by is it 40% or 60%. I know its one of those numbers, but can't remeber for sure off hand.

Thanks.

[speedy1979]

I don't know the answer to your question but the construction method you describe has been used to build quite a few 6 story apartment buildings here in the Bronx. They seem to be sprouting like Alianthus Altissima in every vacant lot. I sure hope they're strong enough for an earthquake like the one we had here in 1884.

[Kelvin]

Generally speaking - and assuming that the core-fill that you use is of comparable strength to the CMU itself - the increase in load bearing is proportional to the increase in area that becomes solid. So, if your basic block is 8" x 16" w/ two cores of 32 sq.in each, then the solid area of the block is approx. 64 sq.in. If you then filled every other core, then the solid area goes from 64 to 96 sq.in and the basic load carrying capacity increases 50% as well. If you fill every core, then you would effectively double the load bearing capacity. The steel rebar contributes only fractionally to compressive capacity and is more useful in flexural (bending) capacity. Also note, if the wall does have some flexural load on it, then compressive capacity is likely significantly affected (reduced) due to eccentric loading.

[You Need A Thneed]

Sorry to be picky, but when talking about technical things, you have to use the correct technical terms.

They are concrete blocks, not cement blocks. Sidewalks are made of concrete, not cement (though there is cement in the concrete.

[GWHH]

Cement is called cement when in its in dry form or wet form. When it is fully dry it is called concrete. It is called concrete only in its final form! But when speaking in a generic term you can call it any name as most people do.

Originally Posted by You Need A Thneed

Sorry to be picky, but when talking about technical things, you have to use the correct technical terms.

They are concrete blocks, not cement blocks. Sidewalks are made of concrete, not cement (though there is cement in the concrete.

[GWHH]

thanks. I make sure its fully filled up. no use skipping on it at this point. either fill it all up or none at all.

Originally Posted by Kelvin

Generally speaking - and assuming that the core-fill that you use is of comparable strength to the CMU itself - the increase in load bearing is proportional to the increase in area that becomes solid. So, if your basic block is 8" x 16" w/ two cores of 32 sq.in each, then the solid area of the block is approx. 64 sq.in. If you then filled every other core, then the solid area goes from 64 to 96 sq.in and the basic load carrying capacity increases 50% as well. If you fill every core, then you would effectively double the load bearing capacity. The steel rebar contributes only fractionally to compressive capacity and is more useful in flexural (bending) capacity. Also note, if the wall does have some flexural load on it, then compressive capacity is likely significantly affected (reduced) due to eccentric loading.

[GWHH]

Glad you guys found a way to get rid of all those vaccants lots up there. I wonder why they are all 6 story talls, must be some sort of code/cost benefits thing.

Originally Posted by speedy1979

I don't know the answer to your question but the construction method you describe has been used to build quite a few 6 story apartment buildings here in the Bronx. They seem to be sprouting like Alianthus Altissima in every vacant lot. I sure hope they're strong enough for an earthquake like the one we had here in 1884.

[You Need A Thneed]

Originally Posted by GWHH

Cement is called cement when in its in dry form or wet form. When it is fully dry it is called concrete. It is called concrete only in its final form! But when speaking in a generic term you can call it any name as most people do.

Nope. Cement is only one ingredient of concrete. Concrete is a mixture of sand, gravel, cement, and water (and often some other things as well). As soon as it is mixed, it is concrete.

The fact that many people call concrete "cement" doesn't make it correct.