So, the preparation of concrete will require the presence of sand, the particles of which have sizes from 1.2 millimeters up to 3.5 millimeters. The use of sand with a smaller fraction is not allowed. Ideally, sand should differ in cleanliness, that is, it is not allowed to have particles of silt or clay. The content of clay or silty particles should not exceed 5 percent, because greater value has a very negative effect on the strength of concrete strength.
Checking the presence of contaminants in the sand is performed as follows: sand is poured into the sand, water is added, after which the mixture is shaken. If the water manages to remain transparent or only a little clouded, then we can talk about the purity of the sand. If the water is very cloudy and acquires a clay tint, then sand cannot be used in concrete solution.
The purity of gravel is also a prerequisite. Gravel particles can vary from 1 to 8 centimeters. It is quite allowed to replace gravel gravel with similar dimensions.
In total, several varieties of cement are distinguished: slag -portland cement, Portland cement, pocolane Portland cement, as well as many fast -hard -harding options.
In many ways, the composition of concrete for the foundation is the same, but there are some subtleties. The most common option is Portland cement, the use of which is allowed for any structures, including a monolithic foundation.
Slag portland cement is characterized by increased resistance to moisture, but lower resistance to low temperatures, it gains maximum strength much longer.
Potzzolan cement is ideal if the operational conditions involve a high level of humidity, that is, it is great for the construction of underground or even underwater structures. In the air, this type of cement can give a strong shrinkage and lose a certain percentage of strength.
The use of rapidly hardening varieties of cement makes it possible to reduce the duration of concrete to a couple of weeks, but it is also necessary to fill and stir such a solution much faster. If you arrange a monolithic foundation with your own hands, then you should give preference to Portland cement.