Partially grouted wall using stretcher blocks

[thoughtofthis]

We've noticed that our partially grouted walls end up containing more grout than we would like. It looks like the stretcher block may be part of the issue.

Issue #1: ACI 530.1 3.3B 3d says, "Vertical cells to be grouted are aligned and unobstructed openings for grout are provided in accordance with the Project Drawings." Webs of stretcher blocks cannot line up.
Issue #2: Masonry Design Guide, NCMA Inspectors Handbook, etc. state, "Where only selected cells are to be grouted, the cross webs adjacent to those cells should be mortared to confine the grout to those selected cells." If the webs don't line up, this isn't possible.

With stretcher blocks in a running bond, you're theoretically left with a 3 in. wide vertical opening for the reinforcing (which is acceptable); however, you're also left with a 1 1/8 in. gap that leads to adjacent cells. If you pump 8 in. - 11 in. slump grout, it's nearly impossible confine grout to only the reinforced cells without additional steps. To confine the grout, you would have to cover every stretcher end with wire mesh in every course? That seems more labor intensive than just laying a standard square end block. Also, how do you make sure the mesh was placed? I doubt an inspector could verify 100% at the bottom of a 48 in. lift.

Is the solution to specify standard blocks for partially grouted walls? What are the benefits of using stretcher blocks anyway?

 

[jayrod12]

Now, except for the self weight of a more than partially grouted wall are there other concerns you have?

 

[thoughtofthis]

Weight is the main issue. Weight impacts seismic. At large openings, it may impact lintels, etc.

 

[msquared48]

Looks like maybe a 10% increase for the wall weight. May not impact the total seismic that much...

Mike McCann, PE, SE (WA)

 

[concretemasonry]

thoughtofthis -

Have you ever considered that your definition of "stretcher" block is really not typical. What thickness walls are you considering and what country are you in?

Block meeting the ASTM C90 spec (specifications for loadbearing concrete masonry units) can have 1 or 2 ends open, can have 1, 2, 3 or more cross webs to form the cores. The ASTM specification give the minimum thicknesses of the elements (face shells and webs) and does have a provision for minimum equivalent web thickness for unique shape. They can be available on different strengths (f'm) from 1500 psi to 4500 psi.

I worked for a concrete products equipment manufacturer that had over 1000 different "standard" mold configuration drawings for just 8x8x16 "standard" block.

In some areas/countries partially reinforced walls are the standard of construction for muti-story (2-22) apartment buildings using 6" thick walls. - They typically design using the ACI 530 standards or a local version.

There wide ranges depending on the local applications/needs and properties.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[thoughtofthis]

msquared48 - Thanks for the feedback. I'm sure we could provide designs that accommodate this issue...but I shouldn't have to assume it's going to be constructed wrong If I only need vertical bars at 32 in. o.c., I shouldn't get a fully grouted wall.

concretemasonry - I provided a sketch in my original post. My definitions of stretcher and standard blocks are as stated in the NCMA TEK manual, but any 2-core block with ears greater than say 3/4 in. on one or both ends will illustrate the point that the webs cannot line up as required in ACI 530.1. I'm in the southeast US and the walls are 8 in. or 12 in.

If you put mesh over the end of the stretcher, do you create a pocket in a reinforced cell beneath that course that may not be consolidated?