Very Small Concrete Slab Patch - Hand Mix?

[smyrna5]

Hello all. Great forum here. I had a problem with a concrete step that abuts my house and caused it to rot the wood. It required me to break out a piece 8.5'x1.5' from the slab they poured on the top of a concrete block wall about 4" thick to replace the wood. Altogether, this is only about 4.2 cubic feet (about half a yard) of concrete.

I cut the slab as deep as I could (about 2") with a masonry blade on an old circular saw before breaking it out, so the break is pretty clean at the top. Now, I want to repair the damage to the slab by re-pouring the section I broke out. I don't really care if it ties in perfectly the old slab, since I intend to put an expansion joint there to assist with drainage anyway. Although the original had no steel in it, I intend to put some mesh or rebar in the replacement piece just to be safe.

I have never done much concrete work, so I am not sure how fast I have to pour it for it to set up as one 8.5'x1.5' x 4" piece. I'd like to mix the 7-80# bags by hand to pour this, if I have enough time. Can I do this an still have the small part I am pouring be one monolithic sheet?

Here's a picture of it:

http://www.flickr.com/photos/smyrna5/10406572894/

 

[Garage Coffee Roaster]

It can be done......but it depends on how in shape you and your arms are.

To hand mix concrete right will take a good amount of energy. I have mixed a few bags by hand to pour a slab and I vowed to buy a mixer next time.

I now have a electric mixer that makes things much easier. I have used it to pour a 60 foot x 3 foot sidewalk and a 10x21' garage slab.

Can you buy, rent or borrow a small mixer?

 

[gpflepsen]

Just a few things...

There's 27 cubic feet in a (cubic) yard.

I'd plan on using eight 80 lb bags of premix.

I loathe hand mixing concrete, especially multiple bags. Rent a mixer and save both time and effort. Home Depot should have one like this:

You should find that the typical 3000 psi mix will give you plenty of time to get the whole thing placed before you need to finish it. Be skimpy with the water added, just a bit too much will have you waiting to finish and produce weaker concrete.

 

[smyrna5]

Thanks guys. Renting a mixer is a good idea. I really wanted to make sure I would have time to pour it all before set up. The mixer would definitely speed up the time needed to mix and pour.

 

[1/2 Cup]

I would grab a couple of your buddies to help as well.

 

[gmt]

Rent a mixer for sure! I mixed 5 60 pound bags by hand and will never do that again.

 

[Zeke]

Mixing 2-3 sacks at a time in a contractor's wheelbarrow is child's work if you have a concrete hoe. You will have plenty of time to do this. Concrete doesn't start to set until you quit agitating it. I'd give it at least 45 min after floating it before troweling and edging. You will know when it's ready as the glossy surface turns to a soft matte look. When you trowel it and bring up the cream, it will again appear wet. Leave it alone until it looks flat again.

Tip: use a bag of mortar mix in the last batch as you fill up the form. Or add a shovel of cement to each 3 bags to richen the mixture. Bag crete is notoriously short on cement and hard to finish. Straight out of the bag it's good for fence posts and that's about all.

If you talk to a pro, all you're doing is making your own 6 sack mix out of what is maybe a 4 sack mix. Just buy a small sack of cement and keep any left over in a sealed pail high and dry and you'll have cement for the next project.

 

[ford33]

Rent the mixer. I mixed two 80 lb bags this weekend and my arms and shoulder were tired and sore from just that little quantity. Add water per the bag instructions.

 

[holdover]

I agree with Zeke about adding some portland so it will finish nicely, Quickcrete has an awful lot of gravel in it which makes it hard to float/finish. You might consider placing some short pieces of rebar into the side of your existing slab to keep the new piece from settling, using a 1/2' masonary bit drill about 2-3" in the side, then place the rebar into the hole leaving a few inches outside. New concrete does not bond well to existing concrete.. buy a few six-packs to enjoy After your friends come over to help

 

[smyrna5]

Good tip on adding a few short pieces of rebar into the existing slab to keep the new one from settling. Also thanks for the portland cement advice on the top layers of the fill. I was surprised when I broke off the piece that not only was there no rebar or mesh in it, but whatever fill dirt they may have put under the slab was gone. I guess it compacted quite a bit in the 40 years since they built it.

I'm not sure what genius thought it was a good idea to **** it up to my house right where the 2x10 band that the floor rafters are nailed to are, without any flashing or other way for the water to get off the wood. It was even sloped into my house slightly so the water was sure to pour onto the wood below my door. To be fair, the slab could have settled that way over the years, but I don't think so. Fortunately it only rotted about 5 feet of the 2x10 outer band. I would have never known it, if I hadn't been replacing some siding and saw the damage underneath my door. I had great fun jacking up my house enough to get a section of that 2x10 out to replace it. I'm going to try to put a slight slope away from the house on the replacement.

 

[smyrna5]

Good tip on adding a few short pieces of rebar into the existing slab to keep the new one from settling. I was surprised when I broke off the piece that not only was there no rebar or mesh in it, but whatever fill dirt they may have put under the slab was gone. I guess it compacted quite a bit in the 40 years since they built it.

I'm not sure what genius thought it was a good idea to **** it up to my house right where the 2x10 band that the floor rafters are nailed to are, without any flashing or other way for the water to get off the wood. It was even sloped into my house slightly so the water was sure to pour onto the wood below my door. To be fair, the slab could have settled that way over the years, but I don't think so. Fortunately it only rotted about 5 feet of the 2x10 outer band. I would have never known it, if I hadn't been replacing some siding and saw the damage underneath my door. I had great fun jacking up my house enough to get a section of that 2x10 out to replace it. I'm going to try to put a slight slope away from the house on the replacement.

http://www.flickr.com/photos/smyrna5/10409374343/

You can see the lights in my crawl space where I had to put the jacks in this picture. Floor joists are resting on the new 2x4 before I put on the new header band on the outside.

 

[PugetDude]

With a mixer this job will be a easy job. Two friends and I did an 80 bag pour on a dock anchor once that was inacessable by truck, so we staged the mixer and the concrete with a 12' aluminum rowboat.. it took several trips... Took longer to get the materials in place than it did to mix and pour the concrete. We did add a shovelfull of portland to each mixer load, as Zeke suggested. Hasn't cracked or spalled yet.
Good luck with your repair.

 

[signcrafter]

I like to think I'm a fairly in shape guy and I'm not afraid of physical work at all, but mixing concrete by hand just plain *****!

I was doing some fence posts this summer and after the first 6 or so bags I printed out a HF 20% off coupon and went to harbor freight and bought this concrete mixer for 160 bucks, http://www.harborfreight.com/3-1-2-half-cubic-ft-cement-mixer-67536.html. It will take you an hour or two to put it together but once it's together it mixes cement great two bags at a time. I would mix a batch and dump in wheel barrow and start another batch mixing and go dump the wheel barrow. When I got back the next load was mixed. Best 160 I spent. Personally I don't care if I ever use the mixer again, it paid for itself already. But I'm sure I'll use it again down the road and there isn't to many complicated parts to go wrong so should last.

 

[Buckgnarly]

If mixing a few bags by hand wears you out, you probably should be doing more mixing by hand!

 

[gpflepsen]

Does walking 5 miles for groceries wear you out? Can you use a tool to do it much faster and with less effort? The same applies to mixing concrete. If you enjoy it by hand, knock yourself out. I'll use a mixer, and drive to the store.

 

[NUTTSGT]

It's entirely possible to mix by hand but I think you will get a more consistent mix if you buy, rent or borrow a mixer. I'd agree with Zeke about getting a bag of portland cement to add some extra to the mix.

 

[monkeybar]

FWIW, my wife & I mixed (in our 3 cu. ft. electric mixer) around 55,000lbs of concrete, pouring using a wheelbarrow, in the winter, (temperature works against hand-pouring, due to the time involved) and have sidewalk and a large slab 15' X 30' between the house & garage, in pieces we felt the limit of our ability, realistically, 30 square feet at a time. All forming was by 3-1/2" wide 2X4 forming. This took almost 3 months of working almost daily. I hand-finished each section, able to "reach" without standing in the mix. Most squarish sections were 6X5 ft. Sidewalk was 30" wide, so longer sections were done, 10 or 12 feet long. Of course, rebar was tossed in as a matter of course, as "insurance", if you will. Results were Most Gratifying!

If anyone cares, ask, please, I'll post pics. monkey

Edit: I am 71 years old. If I can do it, a young guy surely ought to be MORE able to do it. In years past, I had sand & aggregate brought out. This time we bought concrete mix in bags. In the middle of this job, my old Sears mixer broke it's support frame, the yoke which swivels the drum. Dumped that load into the form, dragged out my "buzz" box, welded the frame back together, it held OK for the rest of the job I regard EVERYTHING as a challenge not insurmountable. If there's a way, find it, do it!