concrete question

[gimpy]

A friend is going to help me pour a 8x8 pad to be used as a small patio. We have an electric concrete mixer which holds about a bushel if that matters. I don't want to use quickcrete since it has poor durability. It should work out to about 30 cubic feet or a little lmore than one cubic yard. How much portland cement, sand and gravel? what's the pro's and con's of increasing or decreasing any particular component?

[moopups]

1 cement, 2 sand, 3 gravel is the accepted formula around here, do be prepared to add 25% additional cubic volume due to the compaction factor. Once the mixture gets wet the internal air space no longer exists.

[uncle Will in In.]

You need just over one yard of sand and gravel and six bags of portland cement. Pour a couple gallon of water in the mixer, then put in 5 shovels of gravel and sand mixture. Now add one shovel of cement. Do it all again and slowly add enough water to make it mix well but DO NOT make it sloppy. When it gets close to being wet enough stop adding water and let it mix a couple minutes. It will probably be wetter than you thought.

[farminghandyman]

6 to 7 Bags should do it, pick up 8 or 9 jsut in case your measuring is off, or your not perfectly graded, It is a mess to be a few cubit feet short of mixed concrete on a project, I would rather store for another project or take back a few bags instead of having to run and buy more and leaving a cold joint on one small corner. your sand and gravel should be fairly on but I would prefer some extra cement jsut in case maybe a 1/4 yard or 1/2 yard,

I find unless you measure ever item, (by filling buckets or boxes or some measurement item), it is easily to start to short the size of shovel fill when one starts to tire, and thus you may start to mix it richer as your adding less gravel, over time, and it is easy to run out of cement before you run out of form. Normally you will not short the cement shovel if your using shovel measurements. (do not ask me how I know this).

I find breaking and dumping the sacks of cement into a large tub and then measuring the cement out of the tub instead of trying to pour out of sacks or to work out of the sacks,

I find when mixing by hand the water normally needed is about the same volume as the cement volume, and that is a 1 cement to 5 gravel of mixed size or 1 cement 2 sand and 3 crushed rock,

Actually it take nearly a yard and a quarter of materials to make a yard of cement, as it fills the voids and makes a solid product with little or no voids in the finish product.

One more tip, use rubber or water proof gloves, or coat your hands with vaseline or grease, before you start and mess with the concrete, the concrete dust will suck the moisture out of your skin and will for days after wards, by greasing them it puts a barrier on the skin and keeps it from embedding it self into the skin. If you do get cement on your skin "Bag Balm" will help as much as any thing.

[farminghandyman]

the more you short the concrete or stretch gravel the weaker the mix the poorer the finish you can achieve,

going stronger, no harm stronger cement and better finish, the only draw back is added cost of cement, quicker setting time also,

~~~~~~~~~~~

more than likely you all most need to start to finish the slab before your done pouring it with that small mixer, screed it as you go,

to finish you "float" it that is usually with a bull float or with a hand float, (either wood or magnesium) it pushing the rocks down and brings up the "fat" the cement paste and sand,

you may end up floating it a few times depending on the quickness of the set,

the as it sets, you will use a steel trowel (rectangular) about 3" x 12" to 16" in length, (the knee board should not be sinking any more when you start to trowel),
sighting the edge of the trowel it should be flat or slightly bowed up ward on the out side edges, (up as in Handle),

Drywall trowels are usually wider 4" by about 12" and are usually bowed slightly down to form the seam on dry wall, (DRY WALL TROWELS WILL NOT WORK WELL TO FINISH CONCRETE). They will leave lines in the cement, from the edges of the trowel.

work in a fan pattern, with lightly more pressure on the heel of the trowel with light taper up on the direction of travel, slide it off the concrete do not lift it straight up, or you will take up chunks that will stick to the bottom of the trowel, I work back wards or side ways, use Kneeboards to support you weight on (usually a ply wood square with a cleat on it to grip it to be able to move it), oil the knee boards with diesel, light motor oil kerosene mix, let soak the night before, wet the board before using, slide the knee boards off the concrete,

you can rent or if your friend has, a bull float on a handle that can be worked off the slab and even a Fresno, (a wide trowel on a handle), you will sill probly want to finish it up with a hand trowel, (better finish),

even if you want a broom finish you will want to trowel it out and work it and them broom it when it is the proper hardness,

as the concrete sets, it will shrink and as it sets the rocks and pebbles will show and the surface will become rough, that is why one works the cement with a float and finally with a trowel to keep pushing the rocks down and bringing up the fat, and compacting the surface,

If you have some holes or rough spots, one can use a mixture of fine sand (not gravel)and cement (about 50 /50) and make a cream to fill in little holes and defects as your troweling it out, (if you do not have sand one can screen some gravel to get some).

[mdharris68]

Originally Posted by gimpy

A friend is going to help me pour a 8x8 pad to be used as a small patio. We have an electric concrete mixer which holds about a bushel if that matters. I don't want to use quickcrete since it has poor durability. It should work out to about 30 cubic feet or a little lmore than one cubic yard. How much portland cement, sand and gravel? what's the pro's and con's of increasing or decreasing any particular component?

Quickcrete seems to get poor durability only when it is overmixed with too much water. Have you ever tried to break apart quickcrete thats been poured around a fencepost with no water added? It actually works great when mixed properly. That being said, when mixed properly, it is much easier to use than self mixing and easier to get consistency across the slab. Just my opinion.

[PyroDon]

not sure what the price of ready mix is in your area or what their Min delivery is . around here its just as cheap to have a truck bring out a yard as it would be to try mixing. Cheaper if you factor in your time and sweat .

[artificer]

Another option for the small mixer is to use the bagged mix, and add a bit of cement to each load. Do you mean quickcrete the bagged quick setting mixture, or Sackrete, the pre-mixed concrete? Quickcrete is more expensive, and you'll not be able to mix, pour, finish it before it has set.

The bagged mix we get around here is 3000psi. Its still good stuff for slabs, but adding a bit of cement to each load can bring it up to 5000psi. I typically just put a bag of pre-mix in the mixer, shovel in a scoop of cement, and mix till its done. (scoop size is based on the mix'es bag size)

Remember, if it flows nicely, its probably too wet, and the strength is going to be less than it should be.


Michael

[stanb999]

Originally Posted by gimpy

A friend is going to help me pour a 8x8 pad to be used as a small patio. We have an electric concrete mixer which holds about a bushel if that matters. I don't want to use quickcrete since it has poor durability. It should work out to about 30 cubic feet or a little lmore than one cubic yard. How much portland cement, sand and gravel? what's the pro's and con's of increasing or decreasing any particular component?

You wont get the durabilty out of your "home" mix. Now if cheap is what you want than. You will get what you pay for.

The benefits to Sackcrete. Well perportioned concrete. Fairly easy to manage set times. Easy to follow directions.

Down falls. No one reads the directions......... No add mixtures in the concrete.

Benefits to ReadyMix.
Fresh concrete delivered to site. Total mix consistancy. Company guarantee as the the durability and concrete characteristics. Air entrainment and water reducers added to avoid Freeze thaw issues and increase abrastion resistance.

Pit Falls
Adding water at site. Poor delivery times..... Almost always late....
Cost. Due to small load charges.

[gimpy]

is a "bag" 40 pounds or 80?

Ready mix wanted 850 bucks just to bring it out and pour. They also around here have a terrible history of mixing everything too wet. I'd still have to do everything else. Ten years ago before being disabled I made a similar pad about 1/2 this size and the materials were under 50 dollars. It took me about 8 hours, but I didn't have an electric mixer, and I had to mix it about a 100 feet from the site, and use a wheelbarrow due to other construction. I know there's been some inflation, but that seems way more than reasonable. I already have a pile of gravel, I need to get some sand.

So when I go to sLowes to check prices and add everything up, are you all in agreement that a "bag" of sackcrete (I assume it will list ingredients or say, "just add water") plus water and a "shovel" (I'd probably use a large coffee can) of portland will make a mix to make a pad that should last longer than me? (It will have foot tacffic only, maybe a few large potted plants 30 gal tubs)

I want it to look nice (I'm going to press some leaves into the top as it dries), be durable, no maintenance and not be exhorbitantly expensive. I'm looking for inexpensive but not "cheap".

[Rocky Fields]

Hey.

At $850, I'd mix it myself. Get yourself a helper. One can be loading and working the mixer while the other one wheelbarrows it over and spreads it around with a shovel. After mixing is done, two guys can screed it with a 10 ft. 2x4. Then finish it. Make sure you put water in mixer and keep it running when your done, since you won't have time to scrape it and hose it out until the finishing is complete.

Don't forget the rebar.

Personally, for such a small patio, you might want to try pavers or cast concrete squares.

The premix in the bag is carp. They usually use pea gravel and you need crushed stone for strength.


RF

[stanb999]

Originally Posted by gimpy

is a "bag" 40 pounds or 80?

Ready mix wanted 850 bucks just to bring it out and pour. They also around here have a terrible history of mixing everything too wet. I'd still have to do everything else. Ten years ago before being disabled I made a similar pad about 1/2 this size and the materials were under 50 dollars. It took me about 8 hours, but I didn't have an electric mixer, and I had to mix it about a 100 feet from the site, and use a wheelbarrow due to other construction. I know there's been some inflation, but that seems way more than reasonable. I already have a pile of gravel, I need to get some sand.

So when I go to sLowes to check prices and add everything up, are you all in agreement that a "bag" of sackcrete (I assume it will list ingredients or say, "just add water") plus water and a "shovel" (I'd probably use a large coffee can) of portland will make a mix to make a pad that should last longer than me? (It will have foot tacffic only, maybe a few large potted plants 30 gal tubs)

I want it to look nice (I'm going to press some leaves into the top as it dries), be durable, no maintenance and not be exhorbitantly expensive. I'm looking for inexpensive but not "cheap".

The best thing you can do at those prices is use sackcrete. They are 80lbs.
What you do is mix it as stiff as you can. I'd be carefull adding cement as it could flash set. Then you have little time to finish. Look around they have different types of bagged concrete. Use the one they say for sidewalks and steps. I know this sounds obvious but look at what they say it's for. The post stuff is very boney.

The most critical thing is after finishing. Cover it with plastic for as long as possible. To 28 days if you can. This will do more than anything to add life and wearability.

[PyroDon]

I agree for $850 ready mix wouldnt be worth it cant imagine 850 for a yard and a half its still under 80 a yard here delivered

[highlands]

Mixing concrete from portland cement is the least expensive and gives the most control. It is not hard. The stated 1:2:3 ratio is good. Go for a stiff mix for strength. In cold weather consider adding Calcium Nitrate (available as various admixes for accelerant). Avoid Calcium Chloride to protect the steel. Do use steel - rebar, 661010WWM, etc. I also use PVA fiber for added strength. It's easy to do. Do a 2'x2' tile to practice.

Cheers

-Walter
Sugar Mountain Farm
in the mountains of Vermont
http://SugarMtnFarm.com/blog/
http://HollyGraphicArt.com/
http://NoNAIS.org

[Ed Norman]

We just finished up another 7 yards of concrete with our electric mixer. The ready mix place brought us premixed sand and gravel that we piled on a tarp and kept covered. Then we added cement. Everything looks great.

We did pour a little temporary ramp from a sack of quikrete before we started. A month later, a 2" patch on top had flaked off. I blasted it with the hose and dug a pocket inside about 3" deep. I wasn't impressed. I like mixing our own.

[charles burns]

Don't do it!! (Am I too late?)

Poured concrete patios are butt ugly. Unless you go with a stamped, colored concrete by someone who knows what they are doing. And these only look good because they are made to look like they aren't concrete.

Simple concrete pavers on sand look way better and is very inexpensive. There are some excellent brick sized blocks that you can set on sand that look really good - all easily available.

The thing has to have aesthetic appeal, a concrete slab has none.

If you put a concrete slab patio in I'll call the patio police.

[gimpy]

theres already a sidewalk which creates the forms for two sides, (adding a rectangle into an L) so using a slab shouldn't be an aesthetic problem. I also don't have the energy to be weeding between blocks so a do it once and be done with it slab still has its appeal, and like I said, I'll be pressing leaves into it for some aesthetics. I like the way a different slab turned out 10 years ago. Even my wife says so, and if she's happy then I won't complain.

I called around again to recheck prices and the 850 was apparently a mistake. A different guy from Ready Mix says for 1 and a quarter yard deliverd 15 miles is 200 bucks. I called sLowes again and they couldn't tell me what they carried in terms of any premixed anything but they could tell me a 94 pound bag of portland is 10 bucks, but they couldn't tell me how much volume of concrete that translates to.

At 200 I'm considering it. My friend would end up doing most of the work. My sons tire out to quickly and I don't want to have him working all day. If it's a couple hours, that's fine, but I don't want to feel like I'm taking advantage of him. He's going to help me butcher too (not the same day) and for that I', paying him in food. He gets half of what he butchers, and I get the other half.

[charles burns]

Wait a minute! No one mentioned anything about the wife wanting concrete! That puts a whole new slant on things.

In this case I would go with concrete.

The leaf pattern sounds interesting, I wouldn't mind a look at that when it's done. Are you talking about pressing real leaves into it to make an impression or some kind of leaf block template thing?

[RedneckPete]

I mix concrete regularly with a bell mixer, mine is gas powered, but electric works the same. I can EASILY mix five yards in a day, including placing it. I wouldn't be able to finish it at the same time.

With a small pour like you have, you will likely spend more time waiting for the concrete to set enough to finish it then you will mixing it.

Pete

[hotzcatz]

Sometimes I make big concrete tiles for using around the garden and press leaf shapes into them. I've had good effects by pressing in a large taro leaf then scattering black mortar sand around it. Where the leaf is, the concrete is shiny gray with the outlines of the veins of the leaf and all in it and the surrounding area is darker with a sandy surface.

Adding in some concrete stain could do some artistic things to your concrete. Some folks have been putting a concrete blade on a circular saw and cutting squares or shapes in their slabs then filling the cuts with mortar to make a "tiled" slab. Turns out quite pretty and the tiles definitely won't come loose!