Expanded clay is a loose insulating material. It is light porous balls or fired 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 density of expanded clay should be small. This can be achieved by foaming clay. This happens along the technological chain at the plant:
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 high strength and tightness, which is necessary for the resistance of the balls to moisture and aggressive environmental influences.
The technical characteristics of expanded clay directly depend on the accuracy of production processes: deviation from manufacturing standards can lead to insufficient porosity and tightness, and fragility of the insulation.
Properties
Like any building material, expanded clay has a certain set of characteristics that take into accountwhen designing objects under construction. These include:
- Bulk and specific gravity.
- Waterproof and moisture resistant.
- Strength grade.
- Thermal conductivity.
- Frost resistance.
The density of expanded clay is the primary parameter on which all other values depend. The concept means the ratio of mass to volume of products.
True and specific gravity
The weight of the granules tells a lot about the material, primarily about the thermal insulation and efficiency of the material.
The density of expanded clay, like 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 technology for foaming raw materials, which is the determining factor in determining the weight value.
The specific density 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 compacted material without airgaps.
Fractions and weights
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 value of 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 | Medium |
| 10…20 | Up to 400 | Easy |
| 20…40 | Up to 350 | Extremely light |
There is another classification given by GOST 9757-90. According to the document, expanded clay is divided into grades according to the density of the material. It is denoted by the letter M, followed by the numerical value of the maximum density for the category: M250 weighs 250 kg/m3, then in order up to M600: M300, M350, M400, M450, M500.
Performance ratio
The bulk density of expanded clay is inextricably linked with other important indicators - with humidity and thermal conductivity. This characteristic is always taken into account when choosing a material for insulating 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 acceptable, then the porous granules must be dried before being placed in the structure. GOST9757-90 "Gravel, crushed stone and artificial porous sand" regulates no more than 2% 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 conditional, but still takes place. As is known from the physics course of the school curriculum, the lower the value of the ratio of mass to volume, the worse the material conducts heat. This rule also applies to loose expanded clay. The denser it is, the worse it retains heat. When using such a material, it is necessary to carefully calculate the required layer size so that the structure does not freeze and does not conduct cold air.
Other specifications
Specific Gravity has no effect on other performance, but worth talking about.
The strength of expanded clay granules is achieved at the production stage during the second stage - fusion. Its size is determined by laboratory tests by squeezing the granules in a cylinder. It should be noted that the method has a significant drawback: the result of strength measurement 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. Expanded clay strength ranges from 0.3…6.0 MN/m2, which is a good indicator, so the material is added as a filler to concrete.
The thermal conductivity of bulk insulating material averages 0.08…0.12 W/mK, which8-10 times higher than traditional slab heaters. However, the application of the material is possible when determining and laying a sufficient thickness of the insulating layer.
Frost resistance of expanded clay should be at least 15 full cycles. For external structures (walls, floors of the first floor), it is advisable to choose up to 50 cycles.
Water absorption of a properly made insulation is almost zero due to the tightness of the pellet body due to repeated firing. If water is absorbed into the granules, the material will cease to perform its functions and begin to break down. Therefore, GOST 9757-90 sets a maximum allowable threshold of 10-25% by weight, depending on the thickness of the layer.
To comply with all technical indicators, they are controlled at the production stage. After transportation, the insulation must be stored in conditions of low humidity without additional damaging effects of the environment. Preference should be given to closed deposits and hangars.
Expanded clay is not afraid of mold, rodents and other biological pests, therefore its use in closed structures is completely safe.
