How much concrete needed for 35 sq ft?

Question

i was looking at the back of a bag of quikcrete and it says i need 25 60# bags. that seems like a lot, but is that right. is there a better way to make a 35 sq ft slab 4 inches, thick

Answer 1

I use this when I need it... http://www.concretenetwork.com/concrete/...

Answer 2

Sorry, hunny, but your math is wrong.  35 sq. ft. at 4" thick is 11.67 cu. ft. (35/3=11.67).  A 60 lb. bag of Quikrete equals approximately 1/2 cu. ft., so 23-25 bags is correct.  It's less than 1/2 yard (27 cu. ft. is a yard), so it definitely would cost you a lot to have a redi-mix truck deliver it.  If you can rent a mixer, it makes things easy, but mixing 25 bags in a wheelbarrow isn't the worst job in the world.  Good luck.  Hope this helps.

Answer 3

A 35 sq. ft. slab 4" thick will take approximately 4 cubic feet of concrete.  A commercial firm will not likely deliver that small a quantity.  According to the Quickcrete website, a 40 lb bag yields approximately 0.3 cu.ft. .  Therefore you will in theory require about 13, 40-lb bags of Quickcrete.  In practice, you will likely need 15-16 bags.

While this is a very small project, it is just about big enough to warrant buying Portland cement, sand and crushed rock and mixing your own concrete.  The proper mix is 1 spade of cement, 2 spades of sand, and 3 spades of crushed rock (max 3/4").  Mix with as little water as possible to make everything grey.

Be sure to overfill your form and "jounce" the mix thoroughly with your spade to settle it into the form.  Bang on the form with a heavy hammer also.  Screet across the top of the form with a long 2x4 to get it smooth.  Wait 'til the water sheen goes off the concrete, then do any edge finishing you intend with a trowel or broom lightly across the top to make a slip-free finish.

Cover your work with plastic sheeting and keep your concrete wet for at least a week before removing the forms.

Good luck

Answer 4

The easiest way would be to call a concrete company and have a load of concrete delivered.  Otherwise rent a cement mixer and use that.  You could always do it the hard way, mix it by hand, but you're going to be there a long, long time.