Concrete project: will this work?

Sodo · Nov 30, 2014

FTG-05 said:
No matter what, I still have to move the bag, cut the bag, drop the bag contents and then add water.

Sorry FTG but it kinda looks like you missed the most important feature of this method ,,,,the entire reason it works!

--- water goes in the FEL first ---- 3 qts per 80 lb bag

Lets say you are doing 7 of 14 bags. Almost ALL of the the pre-measured water goes in the FEL first (5 gallons?). Then you dump 5 bags into the water, which mixes very easily, because it's like soup. 5 of your 7 bags are done, with very little effort. Only the last 2 bags are hard work. You set your final mixture once per batch, at the end with the remaining measured water.

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OK have at it, forms are lookin' good. 6x6 is not a big deal it will go quick even one at a time. I understand asking on the forum first - I do it too.

s219 · Nov 30, 2014

I think you'll do fine. But it will be work! One of my hardest days this summer was mixing, pouring, and finishing concrete for the apron on my barn. Didn't help that it was super hot and humid, and I was sweating like a pig. Anyhow, I learned to setup as many shortcuts as possible! One was to subdivide the apron into smaller sections, so that I could work on smaller sections and finish each one separately, but that's probably not feasible for a 6x6 square like you're pouring (mine was a long rectangle).

To me, the hardest physical part was moving the sacks, mixing, and then dumping the mix (did it all by hand with 80# sacks, mixing 5-6 sacks at a time in the plastic dump wagon for my lawn tractor). Used about 24 sacks total. Troweling was fun and went well -- I liked seeing the results unfold right in front of my eyes. The only tricky part was knowing when to apply the broom finish -- it's all about timing but it was the first time I ever did a broom finish so I had to guess. I got it perfect on the first section, but the other two sections didn't broom as well (probably still too wet). When everything dried, it was hard to tell the difference, so perhaps it's somewhat forgiving.

ultrarunner · Nov 30, 2014

FredH said:
Rarely use pre mix bags , I always get sand / gravel mix from a local rock place and mix it 4 shovel fulls of that with 1 cement shovel . Add water accordingly . Most of the time I mix 16 to 4 , which when dumped into a double tire wheelbarrow is about all you want to push around . Last slab I did was 14' x 8' x 5.5" . Wife helped scree it off but the mixing , dumping was all me . That shed still stands this day without a crack any were .

For that amount , I think you will be fine . Don't mix to wet or to dry . The way you talk about dumping it into your bucket will work since you will have some settling of the mix . but no water loss . So before you dump into your form , just use a garden hoe to stir it a little before dumping .

Images below are similar to the type mixer I have

Fred H.

View attachment 400776 View attachment 400777

I had/have the same mixer as your white one... did a good job until I loaned it out and it came back with a cracked yoke... did not notice it until I started to use it... thankfully, a neighbor had a Harbor Frieght he was long done with and it's been a trouper as long as I mix no more than 2 60# sacks at a time.

FTG-05 · Nov 30, 2014

Sodo said:
Sorry FTG but it kinda looks like you missed the most important feature of this method ,,,,the entire reason it works!

--- water goes in the FEL first ---- 3 qts per 80 lb bag

Lets say you are doing 7 of 14 bags. Almost ALL of the the pre-measured water goes in the FEL first (5 gallons?). Then you dump 5 bags into the water, which mixes very easily, because it's like soup. 5 of your 7 bags are done, with very little effort. Only the last 2 bags are hard work. You set your final mixture once per batch, at the end with the remaining measured water.

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OK have at it, forms are lookin' good. 6x6 is not a big deal it will go quick even one at a time. I understand asking on the forum first - I do it too.

What do you use to mix it with? I don't have a hoe, another reason I don't want to mix it by hand. Oh, I also planned to use the FEL to hold all the bags of concrete so I don't have to bend over or drive my truck into my back yard..

Either way, I think I pretty much decided to pour right at the pad site, rather than mix one place, then transport and pour all at once.

Put plastic down first - Yes/No?

CurlyDave · Dec 1, 2014

I wouldn't put plastic down. I would put enough gravel, 1" -2", under it to make what an engineer would call a "capillary break", just so that the slab isn't constantly in a puddle.

Raise the forms a little bit so the concrete thickness is not reduced by the gravel.

I would not use bricks to hold up the rebar. They swell up more than concrete when they are soaked in water and may crack the concrete after it has cured. Get some dobes (pronounced dough-bees) which are small concrete cubes intended for this purpose. They are really inexpensive.

Even pieces of a broken-up cinder block are better than the bricks.

Don't make the pad exactly level. About 1/4" per 12" of slope will let rainwater drain off.

FTG-05 · Dec 1, 2014

Ha! Learn something new every day! Didn't know that about bricks. Fortunately, I have plenty of both old bricks and concrete blocks. In fact, I was wondering what to do with one that I was tripping over the other day. it looks like I now have a use for it.

Ok, no plastic, one less thing to worry about. I do have gravel to put down, but not a lot.

The pad is not exactly level, it generally follows the original slope albeit not quite as steep, obviously. Not sure about the 1/4" per 12" but it definitely slopes down a bit.

And now it looks like the rainy season has hit central TN: NOAA is predicting rain all week. The good news is that this will quiet the woods down for still hunting.

BuilderML · Dec 1, 2014

What was i ever thinking???? You don't want to use plastic under your slab.

You don't want to have the slab in water or have the concrete stay wet. It will only last about a month before it all falls apart thanks to the plastic under it. I wonder how the Hoover **** has lasted so long???

Did the engineer forget that it was going to hold back just a little water? Or is every bridge around the world on the brink of failure due to the concrete holding it up happens to be sitting in water? Forget the plastic its going to hold back gallons and gallons of water. Maybe you should have a tap built into your slab so you could have a drink just in case your thirsty while your out having some fun. Funny thing is concrete will only take on so much water and that is it. So if you place your slab on the ground it will wick up the moisture out of the ground. Looks like your slab will fail both ways. What is one to do???? I think concrete is out of the question. Sorry i tried to give you an idea on how you could get some more "open time" on your pour. Looks like i'll keep my comments to myself next time. Good luck with your project.

FTG-05 · Dec 1, 2014

About the only thing I got done today was a trip to HD for more concrete and some concrete tools (I lost all mine in the last move - or they're still packed which is essentially the same thing, but I digress). Don't tell Sodo but I also got a hoe with those holes in it; it's designed to mix mortar etc.

Removed the rebar assemblies and added some gravel, and then tamped it down until it started raining. There's about an inch of water in the pad right now. I'll tamp it again tomorrow until it feels right. Sorry, no pics.

Got the tabletop out of it's form; the lifting eye worked perfectly, although it's not near the COG. Weight was right at 310 lbs, see pic.

FTG-05 · Dec 3, 2014

Well, not much to do around here with all the rain we've had plus some more on the way.

So I decided to install a 24/7 tamping project! Basically, the 12 concrete blocks that will form the columns for the tabletop, plus some wood and my tractor ballast weight on top.

Pics:

In this pic, you can see the location of my shooting bench with my 110 yard range and the corner of my shop/orgy bar/Skeeter Pee Production Center/reloading room:

And I am not happy with the way the top of the tabletop turned out!!! I had made a concerted effort to ensure the tabletop concrete form was a smooth as possible, using a visqueen/plastic sheet between some (formerly) very smooth plywood surface. Not Happy!

Sodo · Dec 3, 2014

Plastic squirmed under the mud. Dang thats disappointing.

Heres an idea. Level it up deadnuts flat and float it with some concrete driveway resurfacer.

Maybe you can make a little dam all the way around with a strong tape like 2 thicknesses of Duct tape. Try that & see if it sticks to your concrete. You may have to let it cure further or warm the whole slab up inside a heated garage? Then pour it 1/4" thick or less, being very careful to just let it flow to the tape dam on its own. Remove the tape dam after it sets then sand (while surfacer is still green) until the edge is round and comfy.

CurlyDave · Dec 3, 2014

I would pour a new one. This gives you a chance to put the lifting eye in a better location.

The traditional way to prevent concrete from sticking to wood is to spray a coat of diesel fuel on the wood before placing the concrete. The concrete will have the grain of the wood on it if you do this. For small jobs like this one, WD-40 works a little bit better than diesel but is a lot more expensive. For only a few square feet, the convenience may outweigh the cost.

Otherwise make the the top side of the bench the top side of the pour and give it a smooth steel trowel finish. Round the corners with the concrete tool you said you have. If you can do it in a shop, so much the better.

How are you going to attach the top to the legs? Gravity and friction is not a good answer. If you are sitting at this bench when your buddy somehow slides it into your lap, it could hurt your privates more than you would like, and it would screw up the finish on your rifle.

SPIKER · Dec 3, 2014

the plastic was a bad choice it stretched under the crete pouring into the form. To make them for counter tops use either Melamine (MDF with a smooth stick free coating of plastic) OR use standard MDF/Plywood and then melt wax to fill all the voids and grains of the wood. Then take a flat SS metal scraper to remove JUST THE TOP of the wax smoothing it out then hit it with a propane hand torch to level out the little imperfections of the wax. BEES wax or some old candles are OK to use and both can be had cheap enough however the Melamine is the quickest and easiest (not to mention can be had as cheap or cheaper than regular plywood.)

Once ya have sides screwed into it ya go back and use caulk or wax to seal up the corners and make a rounded over corner. There are some moldings that can also be had to put into the corners (still need to wax / caulk) the crack seems for the rounded over look.)

I also agree about having an attachment point to the base legs.

You can ALSO grind that flat (one ya made already) using same methods as making a counter top. Be sure to SEAL the heck out of the TOP SIDE of the thing once ya got it in place to keep water from seeping into it.

Mark

FTG-05 · Dec 3, 2014

I'm done with the lifting eye, it served it's purpose. Movement now will be done with my forks.

It will be set onto concrete blocks, final positioned, then I plan to lift it about 2", lay some concrete adhesive onto the tops of the block, then carefully lower the tabletop into final position. Concrete adhesive plus the 310 lbs weight should do all I need it to do.

As bad as it is, the tabletop is really really smooth except for where the plastic deformed it. Oh well. I had always planned on using some left over carpet for the table top anyway. I was just expecting a better surface.

And I misspoke earlier: it wasn't a plywood that the tabletop was formed on, it was some sort of very smooth wood panel that my stone work came in on. I just re purposed it due to it's very smooth surface.

More rain tomorrow, Friday and Saturday. The tamp project weighs about 46% more than the concrete pad does so it will continue to condense the pad subsurface while I'm there or not. Gotta get ready for a wedding this weekend, the wifey unit is already getting crazy about it, like that's a big surprise!

Prolly won't pour until Monday or so, depending on weather and what not. That's ok, the tabletop could use some more curing anyway.

FTG-05 · Dec 7, 2014

CurlyDave said:
I would pour a new one. This gives you a chance to put the lifting eye in a better location.

The traditional way to prevent concrete from sticking to wood is to spray a coat of diesel fuel on the wood before placing the concrete. The concrete will have the grain of the wood on it if you do this. For small jobs like this one, WD-40 works a little bit better than diesel but is a lot more expensive. For only a few square feet, the convenience may outweigh the cost.

Otherwise make the the top side of the bench the top side of the pour and give it a smooth steel trowel finish. Round the corners with the concrete tool you said you have. If you can do it in a shop, so much the better.

How are you going to attach the top to the legs? Gravity and friction is not a good answer. If you are sitting at this bench when your buddy somehow slides it into your lap, it could hurt your privates more than you would like, and it would screw up the finish on your rifle.

Oops! I forgot to do this. Thankfully, it came out easy enough anyway.

Last Thursday, I poured my #1 concrete wheel weight. Recalling this thread, I spread grease over my mold and then sprayed it with a diesel fuel/ATF mix. Hopefully, it will come out OK, but that's for another thread.

It's stopped raining today and will be clear for the next week or so. I'll finalize tamp the pad surface tomorrow and then plan to pour it on Tuesday. I'll let it sit one day, then set the first course of 4 concrete blocks, half fill them with concrete and let that sit one day (that should be this Wednesday). The next day, I'll lay the other three courses and fill those blocks with concrete. After one day, I'll glue the 4" solid blocks to the tops of those. So, a total four 8x8x16 concrete blocks plus one 4x8x16 sold block for a total height of 36" for the columns. With the 3.5" tabletop, the bench will be just under 40" high.

Thanks,

FTG-05 · Dec 15, 2014

Ok, between the rain and freezing temps, I finally got the pad done yesterday. I used 16 and 1/2 bags of concrete. I first started mixing two bags at a time, but after almost a disaster (the mixer tipped over with two bags in it), I started mixing at a rate of 1 and 1/2 bags at a time. That worked out much better. I felt I had plenty of time to let the mixer work while I spread and worked the concrete into the rebar and into every little nook and cranny.

Pics:

Pad cleaned of leaves, tamped down and rebar emplaced and ready to go:

16 bags in the truck and 8 in the tractor. You can see the tabletop in the right center.

About halfway done. I used the home made tool at the bottom to spread the concrete and work it into the rebar.

And just before dark, I was finally able to get a rough broom finish on the surface. After this pic was taken, I did use my edger tool to put an edge on the pad surface, but I got too tired to take a pic of it.

Thanks for looking!

EddieWalker · Dec 15, 2014

What did I miss? Why are the pieces of rebar and wood sticking up from the pad?

Eddie

FTG-05 · Dec 15, 2014

Look to the right of the third/halfway done pic. Those are some of the concrete blocks I'll use for the columns to hold the tabletop. I welded the column rebar to the pad rebar frame so it would be precisely placed and be fully embedded once the pad was done. The wood blocks are nothing more than a safety pad to prevent a fall or trip from turning into an impalement injury.

Today, I placed and filled the concrete block columns. It started raining just as I was mixing the last bag, so I didn't get any pics. Depending on how much it rains tomorrow, I should not only get pics but also finish the job and my shooting bench will be ready!.

Thanks,

Indygunworks · Dec 15, 2014

Looks like you did a pretty good job. Make sure you seal the concrete though.

EddieWalker · Dec 15, 2014

I'm still lost. Are you going to put a table and chair on top of those pieces of rebar? and sit on it?

How are you going to keep it from wobbling around?

Eddie