How Much Cement Needed?

[fiftyplusfive]

I need to cement an area of approximately 5 metres by 5 metres. I am told I will need 5 tons of concrete. If I mix it myself (not buy readymixed) how many bags of cement and sand will I need?

[Mamyalynne]

Try here...


http://www.diydoctor.org.uk/projects/mixing_concrete.htm

[Captain2]

To start off ..... how thick is the concrete bed then we can work out the cubic content?

[fiftyplusfive]

approximately 5 cm

[Clanad]

The rule of thumb standard is the 1-2-3 concrete mix (1 part Cement plus 2 Parts Sand plus 3 Parts Gravel). Works about all the time. Determining how many bags of cement will require knowing the volume of your cement mixer. Most smaller ones used for home DIY projects will only handle about 2 times the above volumes... so 2 volumes of cement, 2 volumes of sand and 3 volumes of gravel.

I usually use a standard garden spade for loading the mixer and 3 spades full of cement is roughly 1 cubic foot (12X12X12 inches) more or less. I find that I can get about .6 cubic feet out of one 80 pound bag of cement.

The easier method (still requires mixing) is to order a product called Quickcrete (here in the U.S.). As the name implies, it is bags of already mixed cement, sand and gravel at the correct mixture for a given project. Simply add water and mix... about 2/3 cubic feet per 80 pound bag of this product... (sorry, we don't do meters).

[Captain2]

Using mamya's link, the quantities are here:
http://www.diydoctor.org.uk/projects/mixing_concrete.htm

If you are sure it is 5cm (2") thick I would suggest this is more of a screed than a bed of concrete and would be inclined to use just a cement and sand mix.

[Mamyalynne]

I thought the calculator looked simple - there are lots of others to try.

[Captain2]

Ooops I put fiftyplusfive's dimensions into the link and copied and pasted - thought it would transfer with my figures in but obviously not :(

[Davemano]

Depending on what the base is for, with it only being about 2 inches thick it could be likely to crack or even distort unless there is a suitable hardcore underlay.

[Baldric]

///If you are sure it is 5cm (2") thick I would suggest this is more of a screed than a bed of concrete and would be inclined to use just a cement and sand mix.///

That's what the OP said, it was Clanad that turned it into Concrete!

[Captain2]

Balders
From the OP 'i need to cement...' 'need 5 tons of concrete' so a bit open to debate. I was just trying to cover both angles.

(And without being derogatory, a lot of people, not in construction, will call it a cement floor instead of a concrete floor).

[Baldric]

///how many bags of cement and sand will I need? ///

[Mamyalynne]

Well, one does one's best.

[fiftyplusfive]

Thank you all for your help. I am probably at fault mixing concrete and cement up. I have an area in the garden which was covered in gravel but after about 30 years has become weed infested. Husband has dug up the gravel and laid some black weed suppresant material. I don't really want him to put gravel down again and thought cement/concrete might be a cheaper alternative to paving slabs. Its not a much used area,only where my washing line goes,not used for sitting or anything else.

[The Builder]

If there are weeds springing up, then it suggests that there is an amount of topsoil to be cleared first. Concrete is only as good as its base underneath.

50mm is rather thin for concrete, but you could get away with it if you lay at least 100mm of rammed hardcore down first (after removing the topsoil.)

Anything less than that is liable to settle differentially ....... in other words ........ crack :o(

[fiftyplusfive]

Decided to have a rethink.Thank you all for your replies.