How to calculate the correct dosage of concrete?

The use of concrete is now essential for the construction of resistant structures. So that it meets all the required characteristics, its mixing requires a perfect dosage. Indeed, there are as many types of concrete as there are dosages. We are talking about reinforced concrete and unreinforced concrete. Each of them is intended for a specific function in the field of masonry. Here is everything you need to know about calculating the concrete dosage depending on the result you are looking for.

What are the main components of concrete?

In the preparation of concrete, certain ingredients must necessarily be included. These are cement, aggregates and mixing water.

It is one of the main components of concrete. A finely ground organic material, cement is a hydraulic binder. It is made up of20% clay and of 80% limestone. There are different types of cements.

These are natural, artificial or recycled mineral grains known by several names. They vary in size and are also designated according to their sizes. We then speak of fillers, sands, sands, gravel, gravel, ballast and riprap. They are the source of resistance and durability of concrete.

It is used for the hydration of the cement and gives its fluidity to the concrete. She also plays the lubricant role in that it allows the cohesion of fine grains by transforming them into a paste. However, it must be properly dosed so as not to undermine the strength of the concrete.

What are the optional components for concrete?

The optional components of concrete are adjuvants. These are chemicals added to concrete during its preparation as needed. They modify the property and the rheological behavior of concrete. They are dosed according to the desired properties. There are several types of admixtures that play different roles in concrete.

  • Plasticizers and water reducers

They are made from salts of organic acids, lignosulfonates, melamine sulfonate and naphthalene sulfate. They increase the mechanical strength of concrete by reducing the water content of the grout or mortar.

  • Superplasticizers NF EN 934-2

They are mainly made of melamine or naphthalene. They contribute to a strong increase in the workability of the mortar or the grout.

  • Setting accelerators and hardening accelerators (NF EN 934-2)

They are composed of potash, soda and ammonia. These additives modify the setting and hardening of the mortar. They are used for cold weather concreting.

  • Setting retarders (NF EN 934-2)

Made up of carbohydrates and lignosulphonates, they serve to delay the diffusion of heat by increasing the hydration of the cement.

The main rule of concrete dosage

The dosage of concrete changes depending on the use for which it is intended. Thus, there are concrete dosages indicated for the foundation, for the paving and for a much greater resistance. We speak in this last case of reinforced concrete. These different types of concrete do not contain the same amounts of ingredients. The dosage of the different constituents is therefore the main rule involved in the preparation of concrete.

How to mix manually with a 35 kg bag of cement?

Concrete can be made with a concrete mixer or by hand with suitable tools. To achieve this, a careful dosage of the different constituents must be carried out. Thus, with a bag of 35 kg, it is possible to obtain 100 liters of concrete. To prepare it, you must:

  • 15 liters of mixing water
  • 5 buckets of sand with a capacity of 10 liters
  • 7 buckets of gravel with a capacity of 10 liters
  • 1 bag of cement of 35 kg.

For the manual concrete production, it is necessary :

  • Mix the cement and fine sand using shovels until a homogeneous mixture is obtained
  • Pour the gravel and redo the mixture with the three elements
  • Make a pile with inside, a hollow that can accommodate the 15 liters of water necessary for the constitution of the concrete
  • Finally, gradually pour the water into the hollow of the heap and mix with the shovels

It is important to know that this type of mortar is qualified as reinforced concrete and is suitable for the construction of posts, paving, etc.

Make 3 m³ of concrete with a concrete mixer

For a professional, preparing a 3 m³ mortar with a concrete mixer is very easy. The main factor to be taken care of is the dosage. In fact, to make 3 m³ of concrete, you need:

  • 30 packs of cement of 35 kg
  • 3,600 kg of aggregates
  • 1900 kg of sand
  • 525 l clean water

The first three elements can be poured into the mixer mixer for a perfect mix. As for the water, it is added gradually until a homogeneous mixture is obtained.

Preparation of mixtures

Preparing concrete with a concrete mixer requires a certain know-how. Indeed, to achieve a homogeneous mixture, it is necessary:

  • Fill the top of the concrete mixer to the height of 80% of its capacity
  • Respect the proportions regarding the dosage of the different constituents of the concrete
  • Remove air bubbles to improve the compaction of aggregates using a vibrating needle

By carefully following each of these steps, a good quality concrete is obtained, perfect for durable constructions.

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