cementconcretewater
I am using forms to build a decorative wall. The instructions say I need 38 liters total per form. The form ends up producing a wall section 200 centimeters long x 50 centimeters high.
How do I calculate how much sand, cement and water will produce 38 liters of concrete?
Sloping the soil would never be a bad idea, but more important is supporting the perimeter with a proper foundation. Why do you need a slab at all? Assuming you have a reason for using a slab I would normally recommend a "floating slab" setup, but that is probably not feasible because you are placing a pre-built structure there. A floating slab would require the perimeter foundation to extend above grade in order for your floor to be level with grade. Not possible because your walls and floor are already built. An alternative would be one like shown below (dimensions shown could be reduced appropriate to your structure size). It is critical that the soil and gravel below be compacted.
I think you can assume the cement mix is about the same density as sand. It won't be exact, but since the cement is the smaller proportion the error won't be great.
According to this site, 1 cubic meter of beach sand weighs 1,529.20 kg.
Best Answer
http://www.everything-about-concrete.com/concrete-mixing-ratios.html
In your case:
38l / 7 = 5.42l. This is one "part" of your total volume.
5.42l * 1 = 5.42l cement
5.42l * 3 = 16.26l sand
5.42l * 3 = 16.26l aggregate (gravel)
Obviously it's not common to mix concrete in such precise quantities. You'll probably use larger, round volumes such as shovels-full or 60 lb. bags as your "parts". For example, add 1 shovel of cement, 3 shovels of sand, and 3 of gravel to a mixing bin. Repeat this until you have the desired quantity of concrete.
Regarding water volume, that depends on the "slump", or flow quality, of the mix desired. Typically you slowly mix in water until the concrete is workable. Too much water weakens the resulting concrete and makes finishing more difficult.