Pea Gravel Coming to Surface when Troweling
#1
09-15-14, 11:30 AM
Pea Gravel Coming to Surface when Troweling
No big deal as I'm only working on a slab for a workshop, but was curious. I have to work some of the concrete with a trowel as I poured around some 6 X 6 posts. As I'm working some of the concrete around the posts, pea gravel is working its way up to the surface (doesn't make for a very smooth surface). Perhaps it's all a matter of practice.
Thank you
Thank you
#2
09-15-14, 01:03 PM
For future reference, part of the troweling process is pushing the aggregate down so you can work the top to be nice and smooth. I'm not a pro at this, just have had some experience and watched one job go from soup to solid faster than 4 amateurs could do much with it. Fortunately it didn't matter, a stoop basement floor, but I will never sit back and relax as we did that time.
Hope your job came out all right.
Bud
Hope your job came out all right.
Bud
#3
09-15-14, 01:12 PM
Thank you, Bud. Just before reading your post, I looked up the difference between float and trowel and what each is supposed to be used for. I didn't float my slab, but it looks pretty good for a first time (I think so at least). I have one more section to do. I think I'll skip floating it too so it's all consistent. However, I wouldn't mind giving it a try to see the difference. I've already mixed and poured 78 80lbs bags of concrete. I won't be doing another project like this just to see if I can float. 
#5
09-15-14, 02:48 PM
LOL, "I've already mixed and poured 78 80lbs bags of concrete. I won't be doing another project like this just to see if I can float." It always looks easy on paper. I yield and mix only when I can't get a truck to deliver. I even pay the short load extra fee when I only need a yard.
I didn't see the size of your project, but a tool you would love is a bull float. I own one, but rarely see it as it moves from family to friend and so on. Always seem to be able to find it when needed, maybe just lucky. Short of putting a power trowel up there a bull float will give you a pretty good looking job. Of course mixing slows the whole process down.
Best,
Bud
I didn't see the size of your project, but a tool you would love is a bull float. I own one, but rarely see it as it moves from family to friend and so on. Always seem to be able to find it when needed, maybe just lucky. Short of putting a power trowel up there a bull float will give you a pretty good looking job. Of course mixing slows the whole process down.
Best,
Bud
#6
09-15-14, 07:00 PM
Member
Most pea gravel mixes aren't the best for providing a decent strength concrete, for several reasons. Round aggregate particles lack the ability to interlock with each other and larger fine aggregate pieces, but rather roll over and against each other. If coarse aggregate particles tend to float, it usually means their density is lacking. And such mixes are often a bit weak in their Portland cement content, too, making them adequate for low-strength situations but lacking where higher strength or greater durability are required. As has already been mentioned, working concrete mixes with steel trowels is usually required to bring the fines to the surface, where they can do the most good.
As an aside, Bud, you'll be lucky if you recognize your bull float if/when it ever returns home. Most loaner tools I allowed out of sight too long weren't usable when they finally returned home--I learned that lesson the hard way.
As an aside, Bud, you'll be lucky if you recognize your bull float if/when it ever returns home. Most loaner tools I allowed out of sight too long weren't usable when they finally returned home--I learned that lesson the hard way.
#7
09-16-14, 10:54 AM
Frost Heaving
As I get closer to getting this slab completed, I hear more of what I missed. A neighbor across the street came over to see what I was working on when he saw my old pickup loaded down with 2400 pounds of concrete. When he looked at my slab, he asked if I had connected the sections at the joints with rebar to keep them even if/when they heave from frost. What is the likelihood of that happening? I planned on attaching my base plates to the slab when I frame the workshop. If the slab heaves, that's going to mess up everything sitting on it. I read something about frost heaving being a concern with "small footings". What size would be a small footing? My smallest slab section is 4 X 8.
Here's what the slab(s) look like. https://slab.shutterfly.com/pictures/8. This is my first slab, so keep that in mind. I didn't put down any gravel as the ground here is VERY hard/dense. The slab in places, particularly the back 2 quarters, are nearly 5 inches thick in a good percentage of the middle.
Here's what the slab(s) look like. https://slab.shutterfly.com/pictures/8. This is my first slab, so keep that in mind. I didn't put down any gravel as the ground here is VERY hard/dense. The slab in places, particularly the back 2 quarters, are nearly 5 inches thick in a good percentage of the middle.
#8
09-16-14, 11:09 AM
Regarding the uneven ground, I didn't want to disturb what was very tightly packed ground only to try and make it even. I didn't think it would matter that the slab was a little thicker in places.
#9
09-16-14, 11:43 AM
Perhaps I should try and look some of this up before asking here. My question regarding frost heave, from what I gathered, depends on many factors. I live near Indianapolis, IN. The soil where I poured the slab packs tight and sticks to your shoes like crazy. It's even difficult to spray it off. I would assume there's a lot of clay in it (although not like I remember when in Georgia. It was all red). From what I've read, clay can be a good thing as the water doesn't absorb as easily. But, the scale I was looking at put the frost heaving at medium for clay (soil being only 1 factor). I suppose I should still put the base plates on the slab. Otherwise, I could lift them up an inch or so toenailing into the 6 X 6 posts. The 6 X 6 posts are well below the frost line. They could certainly take all the load. I'll only have siding on the walls. Any thoughts would be appreciated.
My question regarding frost heave, from what I gathered, depends on many factors. I live near Indianapolis, IN. The soil where I poured the slab packs tight and sticks to your shoes like crazy. It's even difficult to spray it off. I would assume there's a lot of clay in it (although not like I remember when in Georgia. It was all red). From what I've read, clay can be a good thing as the water doesn't absorb as easily. But, the scale I was looking at put the frost heaving at medium for clay (soil being only 1 factor). I suppose I should still put the base plates on the slab. Otherwise, I could lift them up an inch or so toenailing into the 6 X 6 posts. The 6 X 6 posts are well below the frost line. They could certainly take all the load. I'll only have siding on the walls. Any thoughts would be appreciated.
#10
09-16-14, 01:09 PM
Member
Clay will absorb water, and can result in significant frost heave. Depends on the clay, how hard the freeze is, and how much water has been absorbed before freezing. If the frost heave is uniform, your building shouldn't suffer any. I don't think I'd worry about not having rebar in between slab sections of concrete, as that's not something that's done very often (if ever, not counting your neighbor's experience). I think your bigger problem will be when the slab heaves but the timber columns don't, since you said they extend below the frost line. You might experience some localized concrete spalling at the column interfaces when/where that occurs.
The photos show that you batched/poured too wet, evidenced by the cream/slurry in the foreground (where the front slab hasn't been poured yet). There's also a hint of honey-combing along visible form line, which can be eliminated in the future by more vigorous spading of the fluid concrete along the forms. The finished slabs also have a few bird baths, indicating you didn't strike-off while keeping a roll of mud moving against the screed.
The photos show that you batched/poured too wet, evidenced by the cream/slurry in the foreground (where the front slab hasn't been poured yet). There's also a hint of honey-combing along visible form line, which can be eliminated in the future by more vigorous spading of the fluid concrete along the forms. The finished slabs also have a few bird baths, indicating you didn't strike-off while keeping a roll of mud moving against the screed.
#11
09-16-14, 02:07 PM
Thanks, BridgeMan45. I put way too much water in the last bag of concrete where you see all the slurry. I was used to mixing 2 bags at a time and mixed only 1 to fill in some low spots. I was in too much of a hurry to mix another. The 2 sections in the back came out much better, IMO than the one in the front, but I didn't dump a sloppy batch in either of those.
#12
09-17-14, 02:10 PM
Think I'll lift the bottom plates for walls off the slab. Maybe lift it 2 inches. I can still run the siding down to the slab. There are pavers I installed several years ago in my backyard, over a thick layer of gravel, that have moved. I assume that's from frost heaving. I don't mind the slabs heaving in the workshop, but I don't want my walls compromised if there's significant heaving. With the strength of the 6 X 6 posts and a beam across the top, there should be no problem with hanging everything instead of resting on slab. I should be able to install framing and siding in such a way I can transfer most of the weight to the posts. Can anyone think of a reason this won't work?
Thank you
Thank you
