Determine the consumption of cement per cube of concrete

Construction of any house begins with a foundation. If you decide to build it yourself, without recruiting specialists, then the question will inevitably arise, what is the consumption of cement for a cube of concrete. There is no unambiguous answer to this question, since both concrete and its main binding component - cement have different characteristics depending on the brand. Let's try to understand these building wisdoms.

What is the grade of concrete

The concrete grade, for example, M200, is an index of its compressive strength. This figure is measured on a cube of concrete with a side of 20 mm after 28 days of drying under normal conditions. For various structures in terms of their operation, concrete of various grades is necessary, for private residential development, as a rule, concrete M100-M300 is used.

Plasticity of concrete

Concrete, as is known, consists not only of cement and water - such a solution is very fragile and it is not suitable for building structures. In addition to cement and water, concrete includes fillers: sand and gravel. They are also subject to certain requirements, both to the size of the particles and to the amount of impurities.

Depending on the amount of fillers and water in the concrete, the consistency of the solution can be different: from cast - liquid, draining from the trowel or shovel, to the non-plastic, standing on the spade, a mound without spreading. To perform the foundation, floor or blind area with a normal amount of reinforcement, medium-plastic concrete is most often used - it slides off the shovel, inclined at an angle of 45 °, without spreading.

Cement, choice and storage conditions

Cement, like concrete, can be of various grades, its binding ability depends on the brand of cement. To produce a solution with the desired characteristics, cement with a brand that is 1.5-2.5 times larger than the concrete grade is required: for example, M400 cement is used for M200 concrete.

Cement loses its properties when stored, even if it looks dry. Therefore, it is better to buy cement shortly before construction starts, and in case of using old cement it is necessary to increase its dose in solution.

Fillers for concrete

Mandatory component in concrete - sand. For the preparation of solutions use sand with a grain size of 1.1 to 3.5 mm. Smaller sand, reminiscent of dust, for concrete preparation is of little use. Also, sands contaminated with silt, clay, organic residues - grass, roots, are not suitable for solution preparation. Sand as a filler creates a grainy structure, facilitating the adhesion of concrete to the reinforcement, which increases the strength of the structure to break.

In addition to sand, concrete contains gravel, crushed stone or expanded clay. Depending on the filler, the solutions can be heavy and light. Granite crushed stone weighted solution, lightweight filler - expanded clay, slag or tuff - used for the preparation of light solutions. The particle size of the rubble in the solution should not exceed ¼ of the thickness of the thinnest part of the structure. For example, for a 10 cm thick slab foundation, gravel is required in concrete with a particle size of not more than 25 mm.

Water is another necessary component of concrete. For the preparation of the solution use a cold or slightly warm in the cold season of clean drinking water. Tap water is suitable for preparing concrete. Water from the river - only if it does not contain the remains of vegetation and other organic matter. Also, it is impossible to use water contaminated with chemical reagents, oils, solvents for the solution.

Composition of solution and calculation of cement per cube of concrete

The composition of the dry mixture is calculated by weight. For foundations and other concrete structures used in low-rise construction, a weight ratio of cement, sand and rubble 1: 4: 4 is usually used. This means that 1 part of cement, 4 parts of sand and 4 parts of crushed stone or gravel are used for the preparation of the solution.

Calculate the water-cement ratio( WC) in accordance with the table. Use the table, based on the desired grade of concrete and the term of solidification, as well as the cement used. This indicator indicates the amount of water attributed to the weight of the required cement. In the table the data for concrete with heavy gravel are given, at use of building rubble to an indicator it is necessary to add 0,05.

For example, you need concrete grade 250, maturation of concrete for construction conditions - 28 days. You use cement grade M400 and building crushed stone. The table finds the V / C for the given conditions: 0.56.Since for concrete using crushed stone, add to the index of 0.05 and get 0.61.

The next indicator - the amount of water in concrete, is calculated on the basis of the necessary plasticity of the solution and the type and size of the particles of the filler used. For example, for medium-plastic concrete with a particle size of 20 mm crushed stone, this figure is 205 liters.

The last step in the calculation is the determination of the amount of concrete components. In order to find the required amount of cement in a cube of concrete, it is necessary to divide the indicator of the amount of water in concrete B into the water-cement ratio of the WC:

C = B / VC = 205 / 0,61 = 336 kg of cement.

The number of remaining components is calculated based on the set ratio of 1: 4: 4.Thus, for a cubic meter of medium-plastic concrete M250, prepared from cement M400 using building gravel with a grain size of 20 mm, it is necessary: ​​

• Cement - 336 kg;
• Sand - 1344 kg;
• Crushed stone - 1344 kg;
• Water - 205 liters.

To make it easier to determine the weight of components, you can use a conventional ten-liter bucket. The bucket contains:

• 13-15 kg of cement;
• 14-17 kg of sand;
• 15-17 kg of rubble.

For the most common brands of concrete with a weight ratio of 1: 4: 4, you can use the table.