PEMB guys do it without grout all the time (but I really don't like it).
If you have large loads the grout should give you a better feeling about the load being applied evenly to the top of foundation or pier. By sloping out from the base plate you can get a little more bearing area on your pier. The grout allows a little play in the as-cast foundation height as gives you space for leveling. On exterior base plates the grout keeps water from sitting in the plate/pier joint.
Not really compelling arguments for sure. I'd need to scour AISC to see if grout is actually required.
In addition if the anchor bolts were cast with sleeves to allow some movement the grouting of the sleeves can be carried out at the same time as the underside of the baseplate. Some corrosion reistance is provided for the bolts.
Theoretically, there is no reason for grout under a baseplate.
Theoretically, the concrete would be perfectly flat, dead-nuts level left and right and fore-and-aft (or north-south-east-west for you civil-type readers out there), and the concrete would be clean and dust free machined to a perfectly flat match with the bottom of the plate - which would of course - also be perfectly falt and dead-nuts level north-south and east-west.
Theoretically, the bolts would be perfectly vertical and always at the right length and exactly at the right spacing ....
Ain't gonna happen. Heck perfect baseplates on perfect concrete surfaces don't even happen underneath the highly machined baseplates of turbine and generator casings.
So, in the real world, you gotta play some games and use some approximations. Over the years, people have found that getting everything as close as possible in making the column and then welding on baseplates; then pouring and leveling the concrete pads, floors, and foundations; then allowing the bolts/studs to protrude "too far" above the top of the baseplate allows room for grout to be jammed in under the baseplate above and around the bolts. The column is leveled using the bolts and a set of nuts under and over the plate, NOT by bolting the baseplate tightly down to the uneven floor or concrete pad.
Hopefully - and usually it really does happens - the grout is stuffed far enough under the plate and with enough pressure so enough grout connects top-of-concrete and bottom-of-baseplate to carry the load. If it doesn't carry the load, you find out when the column collapses years later. Or hours later.
[My opinion? There's got to be a better and cheaper way than having a guy push grout around to a 45 degree slope with a trowel and a piece of cardboard and plywood. And there for sure has to be a better and faster and cheaper way of pouring grout in pump baseplates (other than through too-little-pour holes!) ]
racookpe,
Try building a form around the column and pouring premixed pourable grout from one side. When it builds up to the same level on the other side, it's full.
I still prefer setting 1/4" leveling plates and grouting those in place ahead of steel erection. I usually provide the leveling plates to the contractor to use as a template in setting the bolts. If coordinated properly and installed properly, this makes column erection extremely fast.
You have mentioned that before on another thread. I have never seen that technique used. Is it common in your area? Do you use leveling nuts under the 1/4" plate?
BA-
I honestly do not know if it is used commonly in my area.
And, yes, I use leveling nuts under the plate. The field guys love it. They set and level the plate to the correct elevation and, if they choose and are careful enough, they can lift the plate to place the grout and set the plate back into the grout and let it spread under the plate.
All I know is it has provided nearly 100% mistake free foundation construction for me and has helped eliminate excessively large base plate holes (that drives me nuts). I tend to think the base plate hole sizes given by AISC are ridiculous.
Once the column is in place, that's it, she's done.
The only concern I have ever had with the method was compressive loads on the anchor rods b/c of the leveling nuts.
I suppose you could actually remove the 1/4" plate before setting the column directly on the grout, but maybe that would not be a very smart idea as the column base-plate might gouge the grout. So, in effect, the 1/4" plate acts like armour for the grout.
When you do that, do you consider the baseplate to be bearing uniformly on the grout or do you consider the leveling nuts to be "hard" points. Toad expressed a concern about that.
And I have another question: What is the importance of non-metallic grout (which I have always seen to be non-shrink too). What do they mean by non-metallic?
It all depends on the baseplate design. A base designed to sit on lets say 4 points - ie, the hold-down points doesn't need grout under the rest of the base, just levelling provision under the base at these points - you can / could grout at these points. A baseplate designed to be fully grouted, usually a much lighter construction should be levelled and then fully grouted under the side rails of the baseplate (again, depends on design). The practice in the paper industry in Australia and New Zealand was to fill the open style baseplate completely with grout after positioning and levelling the base, this was to make it non-moveable and to ensure pulp etc didn't lodge in and around the baseplate causing corrosion problems and ensured that everything was much cleaner, a good wash-down every few days was much easier resulting in a much cleaner environment.
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
