Pea gravel vs grout for Tilt Up
Pea gravel vs grout for Tilt Up
(OP)
A contractor is requesting to use pea gravel 3000psi concrete underneath the tilt panels instead of the 7000psi non-shrink grout we specify (panel to foundation bearing connection). Can anyone think of any reason why this would be unacceptable? I'm assuming they would dry pack it
The only reasons I would be wary are:
1.) the pea gravel concrete could shrink (more than non-shrink grout)
2.) the pea gravel concrete is lower strength than the panels (4000psi concrete for panels)
However, I believe the degree to which it shrinks would be minimal and the load would have no problem redistributing. Also, the compressive strength of the grout is not a factor as the load typically doesn't go above 50psi.
Anything I am missing?
Thanks!
The only reasons I would be wary are:
1.) the pea gravel concrete could shrink (more than non-shrink grout)
2.) the pea gravel concrete is lower strength than the panels (4000psi concrete for panels)
However, I believe the degree to which it shrinks would be minimal and the load would have no problem redistributing. Also, the compressive strength of the grout is not a factor as the load typically doesn't go above 50psi.
Anything I am missing?
Thanks!






RE: Pea gravel vs grout for Tilt Up
RE: Pea gravel vs grout for Tilt Up
RE: Pea gravel vs grout for Tilt Up
RE: Pea gravel vs grout for Tilt Up
If you don't understand why it was needed when you designed it, then maybe you should re-group a bit before you battle with a contractor trying to subvert your design.
RE: Pea gravel vs grout for Tilt Up
If you are talking about a concrete strength, it is usually done with sample cylinders with a 2:1 aspect ratio. The failure is really a shear failure. This is often interpreted incorrectly as the compressive strength of the basic material.
Grout is normally tested in a square cube with a different failure because of the friction between the platens and the sample.
The application proposed is similar to confined compression. - Very similar to masonry where 2200 psi mortar(3/8" thick) with 8500 psi will test 4800 psi in a 2:1 h/t sample (h/t of 16/8)in a 2 block high hollow ungrouted prism. - Bottom line is you cannot separate materials into separate strength with different test procedures for strength when they act together in an assembly.
The calculated load is 50 psi.
Go at it....
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
RE: Pea gravel vs grout for Tilt Up
Clearly i would prefer the grout as specified, but i want to be able to back up decision to enforce it.
RE: Pea gravel vs grout for Tilt Up
At 2" you need to be careful to specify a 5/8" Max river run to keep from having the contractor's operations getting jammed up.
RE: Pea gravel vs grout for Tilt Up
RE: Pea gravel vs grout for Tilt Up
RE: Pea gravel vs grout for Tilt Up
RE: Pea gravel vs grout for Tilt Up
RE: Pea gravel vs grout for Tilt Up
I am curious as to the repercussions of using "the other animal". I tend to agree with excel that shrinkage and swelling would not be a big deal over such a small height.
RE: Pea gravel vs grout for Tilt Up
If you are flowing grout, you cannot use concrete, unless you are going to modify the concrete so heavily that you've just created a flowable grout from other source materials.
If you are extending grout, now you should be dry-packing in order to ensure a good filling and no inclusions (air in particular).
The question boils down to what ensures the finished product has the properties you need, in this case it is pea gravel extended grout.
At the base of a panel, cracking which will allow water and other materials to penetrate is always an issue, but bear in mind I practice in " super cold throw salt on everything land" and previously in "salt wind land".
RE: Pea gravel vs grout for Tilt Up
This website says a good rule of thumb is 1.5 x concrete strength:
http://www.lmcc.com/concrete_news/0104/astm_c-1107...
But why? Could that be a safety factor due to the different way to determine compressive strength between concrete and grout (cubes vs cylinders?) Have there been problems with compressive grout strength in the past? What does everyone else specify and why?
RE: Pea gravel vs grout for Tilt Up
The definition of a structural engineer: overdesign by a factor of 1.999, instead of the usual 2.