At the moment, expanded clay is the most popular eco-friendly insulation. This building material is distinguished by its small mass and honeycomb structure. The density of expanded clay, as a rule, has relatively low values. But it is noteworthy that one of its main characteristics is precisely the bulk density of expanded clay. After all, this feature of the material allows you to select the right fractions in the future. And for full qualitative characteristics of expanded clay it is necessary to take into account the size of fractions, volume and specific gravity of this material.
The production of expanded clay occurs in the process of firing specialized clay. Initially, this raw material passes all necessary processing, and then it undergoes a sharp thermal impact. Approximately 20-40 minutes the temperature from 1050 degrees rises to 1,300 degrees.
Due to this, the raw material is swollen and acquires a new structure - cellular or, in other words, porous. In this case, the surface of the granules themselves melts, resulting in an almost perfect hermetic shell. That is why pellets have such high strength and become much less susceptible to mechanical influences.
Despite the fact that the density of the material in question is rather small, the mechanical strength here is quite high. Due to the special structure of the granules, the claydite is able to withstand high loads and protects numerous types of objects from destruction. And the size of the pellets themselves allows us to distinguish these types of this raw material:
- Expanded clay gravel;
- Expanded clay sand;
- Expanded clay aggregate.
Expanded clay sand is characterized by a fraction size of 0-5 mm. Gravel, as a rule, has the following fractions: from 5 to 10, from 10 to 20 mm, from 20 to 40 mm.
As for the last point, the expanded clay rubble has a fraction of 5-40 mm. It is produced by crushing gravel into small particles. The most popular fraction of expanded clay aggregate is from 0 to 10 mm. The common name of such rubble is claydite crushed.
There are several special treatment modes for clay. It is thanks to these modes and it is possible to achieve the necessary density of expanded clay gravel:
Bulk density and brands
As already mentioned above, one of the most important characteristics of expanded clay is the density (kg / m3). And it is the bulk density. The quality of expanded clay, as one of the most common thermal insulators, also determines the volume of grains, porosity and bulk bulk density. The density of expanded clay gravel varies depending on the specific brand. But in general, it takes values from 250 to 800 kg / m3.
So, if the bulk density of expanded clay gravel is less than 250 kg / m3, its grade is M250. Claydite with a bulk density of 250-300 kg / m3 has the M300 grade. A claydite with a density of 300-350 kg / m3 - M350. Further by analogy. But it is worth considering that after the mark M450, the brand of bulk density increases by 100. For example, the M500, M600 and M700.
The limiting values of grades associated with bulk density are established by GOST 9757-90. The most minimal brand of expanded clay gravel and crushed stone is M250. The maximum mark is M600. Although with the agreement with the customer, higher values are permissible. Keramzit sand has slightly different indicators - from M500 to M1000. It should be borne in mind that the minimum characteristics are reference, but the maximum are mandatory for compliance. Thus, it becomes clear that the lighter the expanded clay, the better its quality indicators (of course, when comparing the material of the same fraction).
The true and specific gravity
When different calculations are made, it is important to keep in mind two types of density of expanded clay: specific and true.
The specific density of expanded clay is, in the first place, a variable. It depends on the specific type of material in question. Thus, this characteristic can take the following values:
- Expanded gravel - from 450 to 700 kg / m3,
- Claydite-concrete dry mixture - 800 kg / m3,
- Expanded clay aggregate - from 600 to 1000 kg / m3.
The true density of expanded clay, a constant value, is the mass per unit volume of a given material in a dense state (Pu). This indicator is necessary in order to determine the specific gravity. So, for its calculation, it is required to divide the weight of the dry material by the volume of the substance itself, but the pores are not taken into account. More clearly derive the following formula: Pu = m / Va, where Va - volume, m - mass.