How to calculate the amount of cement for a foundation?

Building the foundation of a house is the most difficult both in material terms and in terms of labor intensity. To ensure reliability and not spend an excessive amount of money and effort, you need to carefully calculate the amount of cement. This procedure has its own subtleties, taking into account the properties of the soil, the characteristics of the supporting structures and much more.

When drawing up a project, you must immediately enter into it an estimate of the total consumption of bulk building materials, including binders. Buying and transporting even "only" an extra 10 kg can be very expensive; a lack of them will disrupt the cycle of work at best, and at worst, will not allow them to be completed properly. The role of filling is very important: it helps to damp deformation stresses and avoid settlement of buildings. In most cases, unless there are compelling reasons to count otherwise, the ratio between the components of the mortar (sand, cement and gravel) is assumed to be 3: 1: 5 (in fractions).

Only carefully selected types of concrete are used to build the foundation of the house. Making them requires a certain skill from the builders. In order for the finished mixture to be as strong as possible, granite crushed stone is used in the form of fractions of 1-4 cm. To obtain a foundation solution, alluvial grades of quarry sand with a grain size of 0.12-0.35 cm are used.

For an accurate calculation of the consumption of the finished cement mixture, it is necessary to take into account the brand of the main binder. M-100 is considered to be of insufficient quality.

Such material is intended primarily for:

• rough floor screeds;
• plastering works;
• surface finishes;
• laying out internal partitions.

Since the bearing capacity of such a material, which can be seen already in the areas of its application, is small, by 1 cubic meter. m of the base of the house consume 220 kg of a binder. The M-200 brand is officially recognized as a plaster and masonry coating, it is suitable for front concreting of floors. Compared to the M-100, it is stronger, but it costs relatively little. Use this grade of cement only where there is no risk of flooding or severe stress. The specific consumption is 280 kg.

According to professional builders, it is better to use M-300 cement for the foundation. It is he who is designed for this kind of work in the best possible way. Resistance to contact with water, sulfates, low heat transmission confirm this.

M-400 is distinguished in addition by excellent resistance to hypothermia., recommended for the field of transport construction and for the construction of underground structures. The only drawback is the high price (and consumption - 440 kg). M-500 differs from M-400 in increased indicators of elasticity and durability of the stone. For education 1 cubic meter. m already consumed exactly 0.5 tons of substance, or 10 bags of 50 kg.

Important: cheaper varieties of foundation mortar can be improved by introducing special additives.

It is not at all necessary to be a professional architect or foreman to understand that the exact cost of cement is determined not only by the quality of the binder produced at the plant.It is also necessary to take into account the fact that the time of the final ripening of concrete changes from an increase or decrease in the proportion of each component of the mixture. The frame is mainly made of cements of the M-300 group. But it is not recommended to use grades from 600 to 800: they are intended for the construction of only the most robust structures, including multi-storey buildings.

What is important - for the construction of small private houses, it is not recommended to start from calculations on online calculators: the numbers obtained in this way are not always accurate and have significant errors.

It is much more correct to calculate the volume of the upcoming foundation construction using ready-made formulas:

• for a slab - multiplying area by height;
• for a tape - multiplying the total length of the structure being created and the area across;
• for piles, the cross-section of one support is multiplied by the total number of support blocks.

Important: when planning to dilute the mixture without crushed stone, the ratio of water and cement must be reduced by 10%. But at the same time, we must not forget about the dependence of the amount of consumed water on the volume of sand and the size of the fraction of stony materials. In typical proportions, which are given in reference books for non-specialists, such subtleties are omitted. But to ignore this circumstance in real construction means to face very unpleasant consequences.

Let's take for work:

• crushed stone 2.5 cm with a density of 2700 kg;
• sand mass with fine grain with a density of 2500 kg;
• Portland cement M-400 with a density of 3 tons.

To obtain a solution of the M-300 group from these components, a coefficient of 0.53 is required. For 1 cubic meter m. solution will have 195 kg of water, or 0.195 cubic meters. m. The proportion indicates that 368 kg of Portland cement should be selected. Knowing the fraction of the most important dry part, it is easy to calculate the required volume of fillers, their percentages, and, consequently, the total weight.

A natural question arises: "Will the chosen solution have enough strength for building a house?" It is best to test its quality in practice. Having prepared a kind of bar from the calculated mixture, they wait for it to solidify and, using a medium-sized hammer (with a weight of the working part of 0.5 kg), they try to drive the chisel in with one blow. If the blade of the tool is embedded more than 0.5 cm, this is no good. An artificial stone, more or less suitable for a foundation, should throw off the chisel with such an impact.

There is another nuance - the load exerted on the foundation by the house, its roof, snow accumulating at the top and everything that is in the dwelling. By ignoring this indicator, you can never build a good foundation. Therefore, 200 kg per 1 sq. cm are considered the minimum bar at which one can at least talk about reliability. Such bearing capacity of concrete is achieved with the correct laying of cement mortar M-400 in a ratio of 1: 3: 5. This requirement fully applies to both monolithic supports and tapes under low-rise buildings.

You can approach the solution of the problem in a slightly different way. Suppose you want to fill in 1 sq. m with a solution of 100 mm thick. Such a block can be accurately filled with a standard bag of M-400 cement, but if you use M-300, you will need an additional 1 kg of binder. As a result, in both cases, concrete of the M-150 category is obtained, suitable only for correcting defects or for retaining secondary buildings. Another important fact that is always useful to remember is that 1 cube. m of concrete of the 300th group is obtained from 600 kg of cement of the M-400 category.

In order not to be mistaken with the calculation of the necessary building materials, it is worth focusing on the formulation of the concrete mixture specified in the SNiP. Strict adherence to technology will help eliminate disappointment as a result of your calculations and the mixed solution.According to her, concrete must stand for 28 to 30 days at a temperature of about 20 degrees. In addition to the exact observance of quantitative proportions, it is worth thinking about such indicators as moisture, grain size of cement: they sometimes have no less effect on the result of construction work than a strict calculation of the total consumption of individual components in the mixture.

You can learn how to fill the strip foundation with your own hands from the video below.