Building the foundation of the house is the most difficult, both in material terms and in terms of labor intensity. In order to ensure reliability and not to spend an excessive amount of money, effort, it is necessary to carefully calculate the amount of cement. This procedure has its own subtleties, taking into account the properties of the soil, the characteristics of supported structures and much more.
When drafting a project, you must immediately enter into it an estimate of the total consumption of bulk building materials, including binders. Buying and transporting even “just” the extra 10 kg can be very expensive; their lack will disrupt the cycle of work at best, at worst - it will not allow them to be performed properly. The role of casting is very large: it helps to quench deformation stresses and to avoid settlement of buildings. In most cases, if there is no good reason to calculate otherwise, the ratio between the components of the mortar (sand, cement and gravel) is assumed to be 3: 1: 5 (in parts).
How is it applied?
For the construction of the foundation of the house, only carefully selected grades of concrete are used. Cooking them requires a certain skill from the builders. In order for the finished mixture to be as durable 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.
The concentration of impurities in this inert material cannot exceed 5%.
For an accurate calculation of the flow rate of the finished cement mixture, it is necessary to take into account the brand of the main binder. M-100 is considered insufficient quality.
Such material is intended primarily for:
- rough screed floors;
- plastering work;
- surface finishes;
- calculations of internal partitions.
Since the bearing capacity of such a material, which is already evident in the fields of its application, is small, per 1 cubic meter. m of the base of the house spend 220 kg of cementitious compound. The M-200 brand is officially recognized as a stucco coating, it is suitable for facial concreting of floors. Compared to the M-100, it is stronger, but costs relatively little. Use this brand of cement is possible only where there is no risk of flooding or severe stress. The specific consumption is 280 kg.
According to professional builders, for the foundation it is better to use cement brand M-300. It is he designed for work of this kind in the best way. Resistance to contact with water, to sulfates, low heat transfer confirm this.
Based on practice, we can assume that for 1 cube. m of foundation should be applied 380 kg of dry binder.
In addition, the M-400 is characterized by excellent resistance to hypothermia , it is recommended for transport construction and for the construction of underground structures. The disadvantage is only the high price (and consumption - 440 kg). M-500 differs from M-400 in increased indicators of elasticity and durability of the stone. On education 1 cube m exactly 0.5 tons of substance is consumed, or 10 bags of 50 kg each.
Important: cheaper types of foundation mortar can be improved by introducing special additives.
But it’s better to nevertheless determine as precisely as possible exactly the necessary type of it, as well as the consumed value.
Not only brand decides
It is not at all necessary to be a professional architect or foreman in order to understand that the exact cost of cement is determined not only by one quality of the binder produced at the plant. It is necessary to take into account the fact that the increase or decrease in the proportion of each component of the mixture changes the time of final aging of concrete. The frame is mainly made of cements of the M-300 group. But brands 600 to 800 are not recommended: they are intended for the construction of only the strongest structures, including high-rise buildings.
What is important - for the construction of small private houses it is not recommended to proceed from calculations on online calculators: the numbers obtained in this way are not always accurate and have significant errors.
Where it is more correct to calculate the volume of the upcoming foundation construction using ready-made formulas:
- for a plate - multiplying the area by height;
- for tape - multiplication of the total length of the created structure 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 breed a mixture without crushed stone, the ratio of water to cement needs to be reduced by 10%. But at the same time, one should not forget about the dependence of the amount of consumed water on the volume of sand and the size of the fraction of rocky materials. In the typical proportions that are given in reference books for non-specialists, such subtleties are omitted. But to ignore this fact in real construction means to face very unpleasant consequences.
Let them 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 cube m. of solution will have 195 kg of water, or 0.195 cubic meters. m. The proportion indicates that you need to choose 368 kg of Portland cement. Knowing the proportion of the most important dry part, it is easy to calculate the required volume of fillers, their percentage, and therefore the total weight.
Although cement of higher grades is consumed more significantly, it is quite correct to take it, because it helps to strengthen the foundation to a reasonable limit.
Tips & Tricks
A logical question arises: "Will the chosen solution have enough strength for building a house?" It is best to check its quality in practice. Having prepared a kind of whetstone from the calculated mixture, it is waiting for it to solidify and, using the average size of the hammer (with a working part weighing 0.5 kg), they try to drive the chisel in one blow. If the blade of the tool has penetrated more than 0.5 cm, this is no good. A more or less suitable artificial stone for the foundation should throw the chisel at such a blow.
There is another nuance - the load exerted on the foundation by the house, its roof, the snow accumulating above and everything that is in the dwelling. Ignoring this indicator, you can never build a good foundation. Because 200 kg per 1 square. cm are considered the minimum bar at which you can at least talk about reliability. Such bearing capacity of concrete is achieved with the correct placement of cement mortar M-400 in a ratio of 1: 3: 5. This requirement fully applies to monolithic supports and tapes under low-rise buildings.
You can approach the solution of the problem and somewhat differently. Let it be required to fill in 1 sq. m solution per 100 mm thick. Such a block can be precisely filled with a standard bag of cement M-400, but if you use M-300, you will need another 1 kg of binder in addition. As a result, in both cases, concrete of category M-150 is obtained, which is suitable only for correcting defects or for holding secondary buildings. Another important fact that is always useful to remember is that 1 cube. m of group 300 concrete is obtained from 600 kg of cement of category M-400.
In order not to make a mistake with the calculation of the necessary building materials, it is worthwhile to focus on the concrete mix recipe specified in SNiP. Strict adherence to the technology will help to eliminate disappointment as a result of their calculations and the mixed solution. According to it, concrete should stand from 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 indicators such as moisture and graininess of the cement: they sometimes have no less effect on the result of construction work than a rigorous calculation of the total consumption of individual components in the mixture.
You can find out how to fill the strip foundation with your own hands from the video below.