CMU wall reinforcing and grouting height
CMU wall reinforcing and grouting height
(OP)
I talked to someone at SMI rebar who said that walls 24' high or so are being specified with continuous rebar more often (no splices allowed).
I am somewhat perplexed as to how this will work. Where I am, usually low lift grouting and 48 bar diameter splices for the wall reinforcing is what I have seen used.
I know that nobody is going to thread the blocks over the top of the reinforcing as the wall is built. Therefore, the only option I see is to pour from 24', which would seem to cause a lot of voids in the grout as you go down the wall.
1)Is this actually being done? And if so, wouldn't
cleanouts be required going up the wall
vertically?
2)How can the bottom lifts be effectively consolidated from
20' above?
3)How could you possibly tell what the final position of
the rebar would be in the wall towards the bottom of the
pour?
I am somewhat perplexed as to how this will work. Where I am, usually low lift grouting and 48 bar diameter splices for the wall reinforcing is what I have seen used.
I know that nobody is going to thread the blocks over the top of the reinforcing as the wall is built. Therefore, the only option I see is to pour from 24', which would seem to cause a lot of voids in the grout as you go down the wall.
1)Is this actually being done? And if so, wouldn't
cleanouts be required going up the wall
vertically?
2)How can the bottom lifts be effectively consolidated from
20' above?
3)How could you possibly tell what the final position of
the rebar would be in the wall towards the bottom of the
pour?






RE: CMU wall reinforcing and grouting height
The easy one first:
There are patented devices for holding rebar in place in the cells of the cmu - not cheap though. Also, if you use "Ivany" block, the horizontal reinforcing effectively holds the vertical rebar in place, but not in the centre of the cell.
Certainly, the Code requires cleanouts for high lift grouting. The Code allows a maximum grout pour height of 24 feet assuming a minimum 3inch width of grout space. See Table 7 in the ACI 530 Specs. However, the maximum lift height is limited to 5 feet. It is unclear from the Spec, if cleanouts are required at the bottom of each successive lift.
Hope this helps.
RE: CMU wall reinforcing and grouting height
It just seems to me like it would be difficult handling a 24' piece of rebar and placing it down into each cell. But I guess some engineers are worried that splicing is not being done properly so continuous bars are being specified.
RE: CMU wall reinforcing and grouting height
RE: CMU wall reinforcing and grouting height
RE: CMU wall reinforcing and grouting height
The code allows rebar to be spliced and even installing rebar in adjacent grouted cells untied can be used as an approved "splice"!
If the rebar spacers are installed to hold the bars in the center of the cell, how do you get the grout past the spacer and insure continous grouting?
We have to make these designs practical and buildable. Using short lengths of rebar, splicing and grouting as you go up the wall is the way to go IMHO.
Talk to some good mason contractors, they have to put this stuff in the wall, they should have some good ideas on what works and what doesn't. Of course, all of their thoughts on the subject may not be printable, but the good contractors know how to do it economically, if the designers would only listen.
RE: CMU wall reinforcing and grouting height
He said even large bars #7,#8 can be placed this manner without a problem. I also asked if voids in the grout would be a problem and he said they would not be as long as the grout meets Code requirements for the pour height.
He suggested doing it this way because it separates groups completely, block layers, reinforcement placers, grouters.
The whole thing is somewhat fascinating to me. I would like to get a mason contractor's opinion on it.
RE: CMU wall reinforcing and grouting height
42 feet...wow!
http://www.masonrymagazine.com/7-02/grouting.html
RE: CMU wall reinforcing and grouting height
http://www.masonrymagazine.com/12-03/grout.html
RE: CMU wall reinforcing and grouting height