ᐅ Building a wall: how much is 7 cubic meters...?

toxicmolotow schrieb:
Is the rule of three already too difficult? When is it taught? 4th grade? 5th grade? It used to be called word problems.

Necessary information can be found on every bag of cement or online.

That’s very kind of you. Bulk density and all that stuff were not covered in 4th or 5th grade.

toxicmolotow schrieb:
The original poster realized that they need to convert one unit into another. The concept of bulk density is irrelevant for solving the problem. There is a factor that needs to be applied (multiplication), and that’s it.

In Step 1, the density of concrete is needed. Step 2 then involves using a rule of three to calculate the actual amount of each ingredient.


Copy and paste from a website:

"You can find the density of concrete in standard reference books or online tables. Depending on the composition, the value for concrete is d = 2.1 - 2.6 t/m³ (2.1 - 2.6 tons per cubic meter). For calculation purposes, an average value of d = 2.4 t/m³ = 2400 kg/m³ (149.9 lb/ft³) is suitable, which should be safe for most applications."

No guarantee is given by me regarding accuracy.

That means 7 cubic meters (cbm) equals 16.8 tons of concrete. According to Bauexperte’s mix ratio, that’s 1,527 kilograms (liters) of water, 3,054 kilograms of cement, and 12,218 kilograms of gravel.
A few kilos won’t get you very far. I wouldn’t want to mix these quantities myself either—just think about how many times you’d have to run a small concrete mixer to reach that amount. A delivery is probably more practical...

The cost for 1 cubic meter of ready-mix concrete is approximately 90–140 euros, depending on the type and chemical additives of the concrete. Just last week, I needed C25/30 for 95 euros plus VAT.

I definitely wouldn’t want to mix it by hand for that price.

Then try getting 12,218 kg (26,925 lbs) of gravel from the building materials supplier—they will want to know the volume, that is, the cubic meters (cbm). For that, the bulk density is required.

The building materials supplier can handle that by simply consulting their tables.