Mixing of concrete - start with the theory of
Concrete consists of three components, which should be specially prepared and mixed, filling it with a decent amount of water. You will need sand, cement and crushed stone. When using sand it is important that it is clean, washed, especially not desirable presence of even small pieces of clay, because in time it will simply destroy your wall. First, the heterogeneity of the composition of concrete reduces its strength and, consequently, durability, and secondly, with every freeze, pieces of clay will chip the concrete around itself. Therefore, concrete mixing should be provided with quality components.
Thoroughly choose also cement and crushed stone. Cement is a very whimsical material that is demanding for transportation and storage conditions. Therefore, you should buy it from trusted suppliers, best in specialized stores. Because dubious warehouses, where cement could damp, harden, cobble together, rarely guarantee you quality.
At the end of theoretical parting, the main rule of thumb is how to mix concrete: in no case should lumps be allowed, they pose a threat to the integrity of your structure, which will be strengthened by this solution. Therefore, it is better to use mechanized mixing methods, because with your hands it is never good for you to knead even a cube of a solution.
How to mix concrete - prepare the mixture
Concrete can be mixed quickly: mix cement and sand thoroughly, then add crushed stone, mix again well, and then add water and finally bring it to homogeneity. However, the quality of such a solution is not the highest, it is approached more carefully to this process. First sand and gravel are divided into fractions , the ratio of which will depend on the quality of concrete and its suitability for certain jobs.
How to mix concrete of the best quality, now we will understand step by step. First, we break the rubble into factions. This will require several types of screens. The first fraction of crushed stone must contain particles of 11-20 mm in size, for this purpose a sieve with a cell of 10x10 mm is taken and all the crushed stone is sifted, what was left in the sieve is the first fraction. The second fraction remains in a sieve 5x5 mm and has a size of 6-10 mm. The third fraction is what is left in the sieve 3x3 mm, and, accordingly, has dimensions of 4-5 mm.
The same is done with sand, it is also broken up into fractions. Sieves with a cell of 2.5 mm, 1.2 mm, 0.3 mm are needed. The first screen is taken to clean sand from inclusions, but after sieving through the second we get the first fraction. The second fraction remains in the last sieve.
Now we'll figure out how to properly mix concrete using all fractions. Sand is taken in the following proportions: 20-50% - of the first fraction, 50-80% of the second fraction, i.e.the first fraction should be less. There are two compositions for rubble, either from the first( 30-35%) and the second( 65-70%), or from three: 1 - 60%, 2 - 30-35%, 3 - 10-15%.This approach to the preparation of the mortar will make it very dense and strong concrete, and it needs less cement than usual. Water per 1 cu. Of solution will require about 170 liters.
How to properly mix concrete or a few more comments
All these proportions are measured by volume fractions , and not by mass. Mix should only be the amount of concrete that you have enough for an hour, after this time it will already be unsuitable. When choosing cement, take into account that the classes of concrete and cement to be mixed must be distinguished by 2 units, the cement should be higher in class.
We are going to figure out how to knead concrete correctly. If you want to get some specific volume, then remember that when kneading the solution will decrease in volume somewhere by 30-40%, so when calculating, take this into account.
The amount of cement can affect the quality of concrete if it is too small. A lot of cement of special quality will not add, but its lack will lead to low density, looseness and water permeability of the solution, which is undesirable for reinforced concrete structures.
The latest nuance in the manufacture of concrete is its ductility .If your solution is very thick, then it will be difficult to compact, so it must be flowable so that it fills the entire volume itself, and it had to be compacted( trampled) slightly. But the more liquid solution is less strong, since its density is less. Therefore, it is worth to stand the golden mean, and also to focus on the way it is used.