What type of concrete/cement should I use?

Question

Building a foundation for a greenhouse.

It's about 15' by 11'
it will be 4" thick. (not going to bear much weight at all)

Now, the thing is I am pretty rural and can't have concrete delivered. Plus it's just me and a neighbor doing the job.

The good thing is I own a portable concrete mixer. It can hold 3.5 cubic feet at a time and will take mixing work out of it.

What kind of concrete or cement can I use that has a SLOW curing time so I will have enough time to pour mix it, pour it, and then jump in and help my neighbor smooth it? Needs to be workable probably for several hours.

I don't mind even using cement as I can get the sand and aggregate - plus with the porto mixer, mixing is made easy.

Any other pointers?

Thanks

Answer 1

Use portland cement, at a ratio of 1 shovel cement ,3 sand and 3stone,mix it very wet but not watery.

t

Answer 2

I've been in exactly the same situation. We live on the edge of nowhere and can't get delivered concrete. We poured our greenhouse floor, using Portland premix cement and a mixer. Our mixer is slightly smaller than yours. We used extra water in the mix so it would stay workable longer. Bad idea! The floor did fine until the first winter. It then split, chipped cracked and, well, you get the picture. We ended up redoing it. The second time we divided the floor into three sections. Each section had its own small 3/8" rebar web placed 2" above ground in a 4" floor. We supported the web by driving 10" pieces of 3/8" rebar into the ground and wire to hold the web to them. Lastly, on the sides where the adjoining sections would go, we used 1" x 6" pieces of redwood. We drilled them and ran rebar through to the web – leaving 2' sticking out for attaching the new sections. That piece sticking out was attached to the next section's rebar web. It has been there for several years now, and has no cracks at all. Our temperatures range from 105°F in summer to -40°F in winter.



I put a link in to show how to determine how many cubic yards of concrete you'll need.



Good luck!

Answer 3

Well most of the guys above have explained the the concrete mix technic... 3-2-1 is text book but if its a simple slab non bearing, sure a little extra sand and or gravel will still be ok. Also the wetter the mix the longer the set-up time yet the lower the strenght rating when working with portland cement... You should also consider ground preparation, tamping or packing the ground where your pouring your slab and reinforcing against cracking, throw in some re-bar or at least cheap chicken wire that will make more difference than pondering over you concrete mixing, proper preparation is 75% of the job, good luck.

Answer 4

Use a 3-2-1 mix of Portland Cement, 3/4 inch rock, and sand...

Using your mixer first wet it down inside, then shovel in [3] shovels of rock, [2] shovels of sand, and [1] shovels of Portland cement - do this each time until the mixer is full, but also add water as you go but you want a creamy mix, not too soopy (wet)...Another is to use what is called a "salt and pepper" mix from your local gravel yard...



Typically this is called a "three sack mix" [three sacks of Portland cement for one yard of mixed concrete]



To comlete your project will take aproximately 2.25 yards of concrete and most full size wheelbarrows hold about 4 cubic feet ...A yard of concrete will cover an 8x10 (80sf) area @4 inches thick...

Answer 5

Tj has the mix right and chris has the smoothing down, but you will want more than 4" thick due to settling that may cause cracking. 6" or 8" will be better. I reccomend you rent a tool that will help with shaking the concrete down so you don't have to do it by hand, this will save a lot of work. I had to learn this the hard way.

Answer 6

You might even be able to rent these molds. As far as the concrete mix, you can buy ready mix bags because you need the aggrigate for strength, or you can make your own mix with sand, portland cement, and whatever aggrigate that you want.

Answer 7

pour 1 section at a time you will have time to smooth it out,

at 15 ft long by 11 ft wide you did not state how wide the footing is,

i am assuming your not pouring a floor. just a footer,

3.5 cubic ft will fill a lot on just a footer

don,t add extra water, just make it pancake mix thick

extra water will weaken the mix

Answer 8

Use a sand-mix...you want to mix it to the consistency of peanut butter and dump in wheel barrow loads, spreading with a shovel as you go into your wooden frame...smooth with a trowel roughly as you go...you'll probably have a good hour after you've filled your frame to go back over with a 2x4 spread across the full frame and each of you on a side. Lightly pull and push the 2x4 from one end of your frame to the other(kinda' like 2 guys sawing a log...).As you move down the frame, the excess will push along with you....After the excess has been removed, go over it again, but with extra back and forth motion from one end to the other to create a smooth finish...Let dry and then remove frame...good luck.

Answer 9

1 cement, 3 sand and 3 stone, make it a little sloppy.