What sand is needed for concrete: the quality standards of
The sand that is used for the production of concrete is a loose mixture of grains that are formed by the gradual weathering of rock. It consists mainly of igneous and less often sedimentary rocks. If such natural sand is absent, then a mixture obtained by artificial rock crushing is used. For the production of concrete, sand must comply with the standards set by GOST.According to it, there should not be more than ten percent of grains passing through a sieve of 0.14 millimeters, and no more than three percent of the total mass of clay, pulverized and silty impurities.
Note! The most harmful is the admixture of clay, as it envelops the particles of sand and reduces the adhesion to other materials. Organic substances should be the minimum possible amount, because they make the strength less and even can destroy cement. In the sand, there should be no grains larger than ten millimeters, and grains measuring 5-10 millimeters are allowed not more than five percent.
Begin to sift the sand through a sieve with the largest mesh. The residues after each sieving serve as a basis for its distribution in size( it is large, small, medium and very small).For the production of concrete, a composition is used with large grains, with a sufficient number of medium and small grains. Its density also plays an important role. So, for cement grade M200 the density of sand should be about 1550 kilograms per cubic meter.
Sand for the production of aerated concrete
A variety of concrete is aerated concrete. For its production, sand is also needed. Portland cement acts as an cementitious cement. There are different production technologies, but sand is always used. The strongest strength of aerated concrete is obtained when it is prepared with the following ratio: 20 percent Portland cement, 40 percent lime and 40 percent sand. As you can see, sand occupies almost half of this composition, which makes the material durable.
Note! The norms for the choice of sand for aerated concrete are the same as for simple concrete.
Sand for aerated concrete must be cleaned of all foreign objects, such as organic matter, stones, large clods of clay and lime. It is necessary to pass it through the same system as the mixture for ordinary concrete. The main role in the quality of the mixture will be sand purity, its dryness and thoroughness of sifting.
Calculation of the quantity of
To obtain high-quality material, it is necessary to make the correct ratio of cement and sand. For example, the consumption of sand per cube of concrete using cement grade M200 will be 667 kilograms. The calculation is as follows: one cubic meter of sand weighs 1500 kilograms, crushed stone - 1700 kilograms and cement - 1400 kilograms. The finished volume of concrete will be much heavier. This happens because all voids when mixed will be filled with small grains. Therefore, only 0.65 m3 of the finished mixture will leave the cubic meter of the dry mix.
Note! Mix concrete in a ratio of 1: 3: 5.That is, a bucket of cement needs three buckets of sand and five buckets of rubble.
Therefore, to prepare a cubic meter of concrete, much more dry components will have to be used. So, to prepare mixtures for 0.2 cubic meters of cement, you need to take 0.9 m3 of gravel, 185 liters of water and 0.4 m3 of sand. Thus, knowing these proportions, you can independently calculate the ratio of sand in cement.