Consumption of materials per 1 m3 of concrete: optimal proportion, calculation features and recommendations

At a construction site of any level, from a skyscraper to a country house, you can not do without concrete. This material is used for pouring foundations, erecting walls in monolithic construction, the installation of ceilings and screeds, in the laying of bricks and other artificial stone. The preparation of concrete in the correct proportion not only ensures the durability and strength of the structures, but also avoids unnecessary material costs.

Concrete composition

In the simplest case, concrete consists of three components:

• Binder.
• Aggregate.
• Water.

The consumption of materials per 1 m3 of concrete is determined by the properties of these materials. Cement grades M100-M600 in strength are used as a binder in the production of the mixture. When mixed with water, a viscous mass forms, when solidified which forms an artificial stone. As a filler, sand or various types of crushed stone are used. This increases the strength of the hardened mortar, since the strength of crushed stone is higher than the strength of cement. In addition, the use of aggregate reduces the shrinkage of the cement mixture.

In addition to the main components, the composition of concrete includes various additives that give the solution additional properties: frost resistance, water resistance, color, etc.

The required consumption of materials per 1m3 of concrete - crushed stone, cement, sand - is determined based on the requirements for the characteristics of the mixture.

Key characteristics of concrete

The most important characteristic of concrete is its compressive strength. Depending on it, a strength class is established. It is indicated by the English letter "B" and the numbers corresponding to the strength of the sample in MPa. Concrete grades from B3.5 to B80 are produced, in civil engineering the most applicable solutions are B15 - B30. In addition to grades, a grade may be used to indicate strength. It is indicated by the Latin letter "M" and the number corresponding to the strength in kg / cm2. Classes and brands are fairly accurately correlated with each other, for example, M200 solution corresponds to class B15, and M300 to class B22.5.

The consumption of materials per 1 m3 of concrete can vary significantly depending on the required class or grade of mortar.

It should be noted that the actual class of concrete is determined only in laboratory conditions for 28 days. Therefore, if you need to know exactly the brand of the mixture, then at the stage of its procurement, several samples should be cast - cubes or cylinders with a height of 100 mm. It is possible to determine the strength of concrete also using the instrument method or Kashkarov’s hammer, but these methods are less accurate.

Selection of the required concrete class

The required concrete grade must be indicated in the design documentation for the construction object. If the construction is carried out independently, it is necessary to determine the brand of the mixture, as this will decisively affect the strength and cost of the building or structure being built.

The purpose of concrete of the most common grades is given below.

• M100 - used for concrete blocking, installation of curbs, small architectural forms;
• M150 - is used when arranging tracks, terminating fence supports;
• M200 - for the erection of walls, porches;
• M250 - production of monolithic foundations, grillages, foundation slabs, lightly loaded floor slabs, stairs, retaining walls;
• M300 - for any loaded structures: walls, floors, foundations;
• M350 - load-bearing walls, columns, ceilings, beams, monolithic foundations.

Sand parameters

To prepare the solution, sand of various origins is used: quarry or river. The second is more preferable, since it has a larger granule size and does not contain impurities. Career sand may vary in particle size distribution. It is preferable to use sand with medium and large granule sizes. Since quarry sand may contain clay or other impurities, it is recommended to sift it.

It is extremely important to pay attention to the humidity of the sand. Depending on this, the amount of water added to the mixture should be adjusted. Given the humidity and particle size distribution, the density of bulk sand can vary from 1.3 to 1.9 t / m3, this must be taken into account when calculating the consumption of materials per 1 m3 of concrete.

Crushed stone selection

Crushed stone in the concrete mix increases the strength of concrete and reduces its shrinkage during solidification. When choosing crushed stone, its fraction and origin are of the greatest importance.

Crushed stone fractions are used in the construction:

• from 5 to 20 mm;
• from 20 to 40 mm;
• from 40 to 70 mm.

Depending on the raw materials, crushed stone is classified into:

• Limestone based on sedimentary rocks.
• Gravel from rounded rock fragments.
• Granite, obtained by crushing granite and granite-gneiss rocks.

Granite crushed stone has the best strength parameters, so if concrete is prepared for critical structures - foundations, columns, ceilings, then it is better to use it. We must not forget that the crushed stone used must not contain impurities, especially clay.

Water-cement ratio

In concrete production, the ratio of cement to water is of prime importance. Water is necessary for the chemical reaction of cement hydration, leading to the formation of cement stone. This ratio decisively determines the class of concrete mix. It is important to consider the brand of cement. The lower the water-cement ratio, the stronger the concrete. The minimum ratio required for cement hydration is 0.2. In practice, concrete is used with a ratio of water to cement of 0.3-0.5. Mixtures with a high water-cement ratio are practically not used.

Determination of proportions of concrete mix

As a rule, for the preparation of concrete, cements of the brands M400 and M500 are used. In practice, to determine the cement consumption per 1m3 of concrete, use the following table.

These data are given for conditions with normal temperature and humidity, as well as for cement, the parameters of which correspond to those indicated on the package. In real life, an excess of cement of 10-15% should be provided.

Then, according to a known amount of cement, the consumption of materials per 1m3 of concrete is calculated, the optimal proportion of cement to sand and gravel is shown in the table.

For example, the consumption of materials per 1 m3 of M200 concrete will be: cement of the M500 brand - 240 kg, sand - 576 kg, crushed stone - 984 kg, water - 120 l.

Concrete production

With large volumes of concrete work, it is advisable to buy ready-made concrete at the nearest factory with delivery by mixer. In industrial production, the norms of material consumption per 1 m3 of concrete are maintained quite strictly. If this is not possible, you can prepare the required amount of the mixture at home. It is important to correctly assess your capabilities - concreting of a separate structure must be carried out in one go.

Before mixing the mixture, the consumption of materials per 1m3 of concrete is determined. Calculation of the consumption rate of the components is not necessary, it is enough to use the table below.

The mixture is prepared in a concrete mixer of the appropriate volume, laying in it measured portions of dry cement, sifted sand and gravel. Water is recommended to be added in portions last.

Additives

In addition to the main components, additives for various purposes are added to the composition of concrete:

• Modifiers . Designed to increase strength and increase frost resistance of concrete.
• Plasticizers . Increase the mobility and water resistance of the mixture.
• Mobility Regulators. They allow to extend the setting time, to maintain mobility during transportation.
• Anti-frost additives. Provide normal setting of the solution at low temperatures, up to minus 20 degrees.
• Set accelerators. Increase setting speed providing the fastest set of strength in the first day.

When using additives, the consumption of materials per 1 m3 of concrete should be determined taking into account the recommendations of the manufacturer. Violation of the instructions for use can have the exact opposite effect.