Expanded clay is currently the most popular eco-friendly insulation. This building material is distinguished by its small mass and cellular structure. The expanded clay density, as a rule, has relatively low values. But it is noteworthy that one of its most important characteristics is the bulk density of expanded clay. After all, this feature of the material allows you to choose the right fraction in the future. And for the full qualitative characteristics of expanded clay, it is just necessary to take into account the size of the fractions, the volume and specific gravity of this material.
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Getting expanded clay
Expanded clay is obtained in the process of firing specialized clay. Initially, this raw material undergoes all necessary processing, and then it is subjected to a sharp thermal impact. In about 20-40 minutes, the temperature rises from 1050 degrees to 1300 degrees.
Thanks to this, the raw material swells and acquires a new structure - cellular or, in other words, porous. At the same time, the surface of the granules themselves is melted, resulting in an almost perfect airtight shell. That is why granules have such high strength and become much less susceptible to mechanical stress.
Expanded clay fractions
Despite the fact that the density of the material under consideration is quite small, the mechanical strength here is quite high. Due to the special structure of granules, expanded clay is able to withstand high loads and protects numerous types of objects from destruction. And the size of the granules themselves allows us to highlight these types of this raw material:
- Expanded clay gravel;
- Expanded clay sand;
- Expanded clay crushed stone.
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, expanded clay aggregate has a fraction of 5-40 mm. It is obtained by crushing gravel into small particles. The most popular fraction of expanded clay crushed stone is from 0 to 10 mm. The common name for such gravel is crushed expanded clay.
There are several special clay processing modes. It is thanks to these regimes that it is possible to achieve the required density of expanded clay gravel:
- Plastic,
- Wet,
- Dry,
- Powder-plastic.
Bulk Density and Grades
As mentioned above, one of the most important characteristics of expanded clay is density (kg / m3). Moreover, it is bulk density. The quality of expanded clay, as one of the most common heat insulators, also determines the volume of grains, porosity and bulk density. The density of expanded clay gravel varies depending on a particular brand. But in general, it accepts indicators from 250 to 800 kg / m3.
So, if the bulk density of expanded clay gravel has an indicator of less than 250 kg / m3, its brand is M250. Expanded clay with a bulk density of 250-300 kg / m3 has the M300 brand. And expanded clay with a density of 300-350 kg / m3 - M350. Further by analogy. But it is worth considering that after the M450 brand, the bulk density brand increases by 100. For example, the M500, M600 and M700.
The limit values of grades associated with bulk density are also established by GOST 9757-90. The smallest brand of expanded clay gravel and gravel is M250. The maximum brand is M600. Although by agreement with the customer, higher values are acceptable. Expanded clay sand has slightly different indicators - from M500 to M1000. It is worth considering that the minimum characteristics are for reference, but the maximum are required.Thus, it becomes clear that the lighter expanded clay, the better its quality indicators (of course, when comparing the material of the same fraction).
True and specific gravity
When various calculations are made, it is important to keep in mind two types of expanded clay density: specific and true.
The specific gravity of expanded clay, in the first place, is a variable. It depends on the specific type of material under consideration. Thus, this characteristic can take the following values:
- Expanded clay gravel - from 450 to 700 kg / m3,
- Expanded clay dry mix - 800 kg / m3,
- Expanded clay crushed stone - from 600 to 1000 kg / m3.
The true density of expanded clay, a constant value, is the mass of a 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 dry material by the volume of the substance itself, but the pores are not taken into account. It is more obvious to derive the following formula: Pu = m / Va, where Va is the volume, m is the mass.
