Because of the drying time, concrete work requires good planning and preparation. This also includes the calculation of the material requirements. Find out here how much concrete a 25 or 40 kilogram sack of cement.
In a nutshell
- Mixing ratio of concrete: 1 part cement to 4 parts gravel
- Dimensions rather uncommon
- Volume matters
- 0.052m³ (52L) concrete from 25kg cement
- 0.083m³ (83L) concrete from 40kg cement
Table of contents
- mix concrete
- determine material requirements
- frequently asked Questions
mix concrete
Concrete is a mixture of
- 1 part cement
- 4 parts sand/gravel
- 0.5 to 0.7 parts water
The cement content determines the hardness of the concrete, the sand ensures its strength.
Going from this mixing ratio out, it's easy to get how much concrete a sack of cement makes. So A 25kg sack of cement produces 125kg of concrete. A 40kg bag accordingly for 200kg of concrete.
Tip: Mix only as much concrete as you can use in 30 minutes. After this time, the surface of the concrete begins to tighten and is then more difficult to work with.
determine material requirements
Due to the high density, mass specifications are rather misleading when calculating the material requirements. It is better to determine the required volume.
Concrete is primarily used to fill voids, create structural components, and hold objects such as fence posts in place. The material requirement therefore corresponds to the volume of the cavity or component to be filled. This is calculated from the well-known mathematical formulas for basic bodies:
- Block: length x width x height (plates, rectangular holes for setting in concrete)
- Cylinder: base x height; Base area = 3.14 x r² (holes for setting in concrete, round components)
- Cone/ pyramid: 1/3 x base x height (pointed components)
For a 10cm thick floor slab with an area of 1m x 1m you need 0.1m³ of concrete. That corresponds to 240kg and thus a material requirement of almost 2 sacks of cement at 25kg each.
Tip: To determine the volume of bulky bodies such as components or decorative elements, fill the corresponding shape with water. You can then pour this into a measuring cup and read off the volume.
frequently asked Questions
Mortar is used for masonry. However, this differs from concrete only in the smaller grain size of the sand. The mixing ratio and thus the amount of cement remain the same.
With a density of 2.4g/cm³ 1 m³ of concrete weighs approx. 2400kg. If you divide this by 5 according to the rule of thumb, you get 480kg of cement, i.e. 12 bags of 40kg each.
To make decorations, you can use special creative or craft concrete or make it yourself. To do this, mix the known ingredients in the following ratio:
– 1 part cement
– 2 parts of sand
– Water as needed
Unbound cement dust is highly hydrophilic and can irritate the skin and mucous membranes. Therefore, protect yourself when handling work gloves and wearing a mask. A damp cloth in front of the mouth and nose also effectively protects against irritation of the mucous membranes, as water binds the cement dust.