Expanded clay - loose insulation material. It is light porous balls or burnt fusible clay, therefore it is distinguished by exceptional environmental cleanliness and safety for humans and the environment.
Production
In order for the insulation to be effective, the claydite density should be low. This can be achieved by foaming clay. This happens along the process chain in the factory:
1. In special installations, fusible clay is subjected to powerful thermal shock. This ensures high porosity of the raw material.
2. Next, raw porous granules are melted from the outside - this way they achieve the high strength and tightness necessary for the resistance of balls to moisture and aggressive environmental influences.
Expanded clay technical characteristics directly depend on the accuracy of production processes: deviation from production standards can lead to insufficient porosity and tightness, insulation brittleness.
The properties
Like any building material, expanded clay has a certain set of characteristics that are taken into account when designing objects under construction. These include:
- Bulk and specific gravity.
- Water resistant and humidity.
- Brand strength.
- Thermal conductivity.
- Frost resistance.
Expanded clay density is the primary parameter on which all other values depend. The term refers to the ratio of mass to volume of production.
True and specific gravity
The weight of the granules will tell a lot about the material, first of all, about the thermal insulation and material efficiency.
The density of expanded clay, as well as any bulk material, can be true and specific (bulk). These parameters are interrelated and depend on the method of production of the material - dry, wet, plastic and powder-plastic. Each method has its own raw foaming technology, which is the determining factor in determining the weight value.
The specific gravity of expanded clay is one of the most important characteristics of the material. It shows the ratio of the mass of the selected amount of material to its volume. Since expanded clay is a loose insulation with a porous structure, the shape of the balls is unstable, there are air gaps between them. Therefore, for the same volume of material, the specific (bulk) density will be different.
The true density of expanded clay (another common name is volumetric) is determined in laboratory or factory conditions and shows the weight of the mass of the compacted material without air gaps.
Fractions and weight
The insulation is divided into groups according to the size of the granules. The fraction and density of expanded clay are related by an inverse proportion - the smaller the balls, the higher the ratio of mass to volume:
Granule size (fraction), mm | Expanded clay density, kg / m3 | Weight group |
Up to 5 | Up to 600 | Heavy |
5 ... 10 | Up to 450 | Average |
10 ... 20 | Up to 400 | Easy |
20 ... 40 | Up to 350 | Especially light |
There is another classification that GOST 9757-90 gives. According to the document, expanded clay is divided into grades according to the density of the material. It is indicated by the letter M, followed by a numerical value of the maximum density for the category: M250 weighs 250 kg / m 3 , then in order to M600: M300, M350, M400, M450, M500.
Ratio of characteristics
The bulk density of expanded clay is inextricably linked with other important indicators - humidity and thermal conductivity. This characteristic is always taken into account when choosing a material for insulation of floors, ceilings and walls.
Knowing the normal value of bulk density and expanded clay fraction, we can determine its moisture content. If it is higher than permissible, then the porous granules must be dried before laying in the structure. GOST 9757-90 “Gravel, crushed stone and artificial porous sand” regulates no more than 2% of excess moisture. Accordingly, when weighing expanded clay, the mass of water in it is taken into account, then it is subtracted.
The ratio of density to thermal conductivity is arbitrary, but still holds. As you know from the physics curriculum of the school curriculum, the lower the ratio of mass to volume, the worse the material conducts heat. This rule applies to loose expanded clay. The denser it is, the worse it holds heat. When using such a material, it is necessary to carefully calculate the required layer size so that the structure does not freeze and conduct cold air.
Other specifications
The specific gravity does not affect the other performance, but it is worth talking about them.
The strength of expanded clay granules is achieved at the production stage in the second stage - reflow. Its size is determined by laboratory tests by squeezing granules in a cylinder. It is worth noting that the method has a significant drawback: the result of measuring the strength depends on the shape of the grain and the distribution of pores inside it. To obtain relatively reliable information, I test up to 10 balls from one production batch of material. The strength of expanded clay varies in farts 0.3 ... 6.0 MN / m 2 , which is a good indicator, therefore, the material as a filler is added to concrete.
The thermal conductivity of bulk insulation material is on average 0.08 ... 0.12 W / m * K, which is 8-10 times higher than that of traditional plate heaters. Nevertheless, the use of the material is possible in determining and laying a sufficient thickness of the insulating layer.
The frost resistance of expanded clay should be at least 15 full cycles. For outdoor structures (walls, floors of the first floor) it is advisable to choose up to 50 cycles.
The water absorption of a properly made insulation is almost zero due to the tightness of the granule body due to repeated firing. If water will be absorbed into the granules, the material will cease to fulfill its functions and will begin to collapse. Therefore, GOST 9757-90 sets the maximum permissible threshold of 10-25% by weight depending on the thickness of the layer.
To comply with all technical indicators, they are monitored at the production stage. After transportation, the insulation must be stored in low humidity conditions without additional damaging environmental influences. Closed deposits and hangars should be preferred.
Expanded clay is not afraid of mold, rodents and other biological pests, because its use in closed structures is completely safe.