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Calculate specific weight of concrete types

  • Influence specific weight
  • What is the specific weight "> Formula for calculation
    • A simple way to calculate
  • The density of substances
    • What is the density?
    • Convert weight and density
  • Concrete density of concrete types
    • Concrete types by density
    • The density varies

When mixing fresh concrete, it is important to choose the right ratio. For this purpose, the specific weights (= weights) of the concrete types are decisive. It can be a thin mixture with a low concrete density or heavy mixtures. In order to find the ideal conditions for your project, you can use corresponding information in the construction manual or tables. But for this you first need to know how the concrete densities and weights are determined. Read in our guide, which relationships exist to other sizes and how the calculation takes place.

The concrete type (lightweight concrete, normal concrete, heavy concrete) determines the specific weights. On the construction site, this information can be determined with simple means. For this you can fall back on rule of thumb, which allow a very good approximation. When working with tables, always keep in mind the correct units, as they can vary from run to run. You do not have to have a large amount of mathematical skills to do the calculation, and you can use the rule of thumb without the help of a calculator. However, the result is all the more important as it decides on the success of the project. Only if you make the perfect concrete mix, the strength is guaranteed and the desired effect can be set.

Influence specific weight

Fresh concrete is a commonly used material and is characterized by its high strength. It is a mixture of an aggregate and a binder. As a rule cement is used as binder. As an aggregate you can use sand and gravel. The addition of water causes mixing and chemical reaction. Various additives influence the properties of the building material once more. Depending on the exact production one speaks of different types of concrete. Thus fiberglass, steel fibers or synthetic fibers were added to the fiber concrete. Textile concrete is created when you use carbon or AR glass, for example. The compositions of the concrete types decide on the weights and thus on the specific weights.

What is the specific weight ">

Formula for calculation

For the calculation of the weight, the weight is divided by the volume:

Weight = weight (Fg) / volume (V)

Thus, it is necessary to first determine the weight. This is the product of the mass and the gravitational acceleration:

Weight (Fg) = Mass (m) * Fall Acceleration (g)

Example:

You have mixed fresh concrete and now want to determine the specific weight. Then proceed as follows:

Step 1:
Take a vessel whose volume you know. This can be, for example, a 10-liter bucket. Weigh the weight of the empty bucket and note the value.

Calculate concrete weight

Step 2:
Fill the 10 liter bucket with fresh concrete to the mark. As a result, you now know that the concrete has a volume of 10 liters.

Tip: As in the literature and tables often an indication in m³ is required, you can convert the 10 liters in m³ for better comparability. In this case, 1, 000 liters correspond to a volume of 1 m³. Thus, 10 liters correspond to a volume of 0.01 m³.

Step 3:
Now you have to weigh the fresh concrete. Place the bucket on the balance, read the value and remove the size previously measured for the empty bucket. For our example, we assume the concrete weighs 50 kilograms.

Step 4:
Next, calculate the weight. For the case acceleration, an average value of 9.81 m / s² is assumed:

Fg = mass * gravity acceleration
Fg = 50 kg * 9.81 m / s²
Fg = 490.5 newtons

Often the simpler calculation is also calculated with a rule of thumb. To do this, multiply the 50 kilograms by the factor 10. In our example, this results in a value of 500 Newton.

Step 5:
In this step, divide the weight calculated in step 4 by the volume. In our example, a weight of about 500 Newton and a volume of 0.01 m³ were determined. The result of this task is the specific weight.

Weight = weight / volume
Weight = 500 Newton / 0.01 m³
Weight = 500 * 100 Newton / m³
Weight = 50, 000 N / m³

A simple way to calculate

To be able to determine the weight quickly and effectively on the construction site, make use of a special feature. If you use a 10-liter bucket and want to calculate the result in N / L, then that's especially easy.

Example:

The concrete is filled into a 10-liter bucket and weighs 50 kilograms. This results in a weight of rounded 500 Newton. This result is now divided by 10 l volume. The result is again 50, this time in the unit N / l. If the concrete weighed 30 kilograms, then the weight would be 30 N / l.

You want to convert the weight calculated with this method into N / m³ "> The density of substances

In tables you will find not only the specific weights but also the densities. These can easily be converted into the weights or you can calculate the densities from the weights.

What is the density?

Density is defined as the ratio of mass to volume. So there is a bypass of the weight instead, which leads to a simplification.

  1. Step: Fill the concrete into a 10 liter bucket.
  2. Step: Weigh the concrete, removing the empty weight of the bucket.
  3. Step: Divide the weight by the volume. This is in our case 10 liters or 0.01 m³.

Invoice:
If the 10-liter bucket weighs 50 kilograms of concrete, then this results in a density of

50 kg / 10 liters = 5 kg / l

respectively

50 kg / 0.01 m³ = 5, 000 kg / m³

Convert weight and density

If you know the density, then multiply that value by a factor of 10 to get the corresponding weight. If you know the weight, you have to divide it by 10 to get the density.

Tip: You work with the rounded acceleration of 10 m / s² instead of 9.81 m / s².

Concrete density of concrete types

The concrete density depends on the chosen mixture. By varying the materials, a smaller or a larger density can be achieved. This in turn influences the later behavior of the building material. Since each substance has its own density, its properties are also determined. For example, if you dilute the concrete with water, it will not only be thinner, but it will also have a lower density or density. Sand, on the other hand, increases the concrete density.

Concrete types by density

For example, if concrete weighs between 1, 500 and 2, 500 kg / m³, then that means that one cubic meter of the building material weighs around 1, 500 to 2, 500 kilograms. What sounds high at first glance is put into perspective at a second glance, considering that the soil weighs in the same volume ratio of between 1, 300 and 2, 000 kilograms.

lightweight concrete
If the density is below 2, 000 kg / m³, then this is called lightweight concrete. He is often mixed with expanded clay or pumice.

normal concrete
Normal concrete has a density of around 2, 000 to 2, 600 kg / m³.
The weight is therefore 20, 000 to 26, 000 N / m³.

heavy concrete
The concrete density is above 2, 600 kg / m³, ie above 26, 000 N / m³.

prestressing steel

The density varies

On the one hand, you have the opportunity to influence the density by mixing the cement, the aggregate and the water. On the other hand, many additional additives are used. These include:

  • prestressing steel
  • Fibers of plastic, glass or steel

Tip: Note that the density of the building material changes once more during curing. Crystallization of the cement causes crystal needles to form. As a result, a toothing takes place and the volume decreases. Since the weight remains the same, the concrete density and thus the weight is higher.

Tips for quick readers:

  • specific weights are also called weights
    • Weight = weight / volume
    • Density = mass / volume
  • Work with a bucket as a measure
  • at 10-liter bucket:
    • Weight corresponds to the weight in N / l
    • always pay attention to the units
  • Weights and densities differ by a factor of 10
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