Many people know that there is such a building material as expanded clay. This is common knowledge. But few people can give complete answers to the questions of what it is, what properties it has, how it is produced and where it is used. Let's try to close this gap.
What is expanded clay
Expanded clay is a light porous material produced in the form of gravel or crushed stone. Its production is based on firing in special kilns at a temperature of about 1200 ° C special clay rocks of easy melting. Thanks to firing, the clay structure acquires a finely porous structure with a pronounced hard shell.
This structure of the material determined the diversity of its application. This material is used both in construction work and when planting plants. The unique properties of expanded clay include water and frost resistance, excellent noise-absorbing and heat-insulating parameters. The material is practically not subject to the processes of decay and decomposition, does not attract insects and rodents. In addition, it is durable and fireproof, frost and acid resistant, lightweight and durable, environmentally friendly and economical. Thanks to these qualities, expanded clay is widely used in construction and other sectors of the economy.
Expanded clay as a heat insulator
The ability of expanded clay to be a heat insulator depends on the size of the granules, its strength and bulk density. According to the size of the granules, expanded clay fractions of 5-10, 10-20 and 20-40 mm are distinguished. Each fraction allows 5% of granules of a different size. According to the density of expanded clay, 10 grades are defined, ranging from 250 to 800. This number indicates the number of kilograms in one cubic meter of material. The lower the density, the better the properties of expanded clay as a heat insulator. Expanded clay of large fraction is more durable. It is suitable, for example, for warming the floor in a bathhouse, and the thermal insulation of the attic can also be done with a fine fraction.
Expanded clay production
Only certain clay rocks are suitable for the production of expanded clay. The most suitable are montmorillonite and hydromicaceous clays containing less than 30% quartz. The essence of expanded clay production is the preliminary processing of raw clay, which gives raw granules of a certain size, firing them in special drum ovens to obtain a specific structure and gradual cooling.
There are several technologies for pre-treatment of clay raw materials. This is dry processing, plastic, powder-plastic, as well as wet, or slip. The first (dry) technology - the simplest - provides for a multi-stage crushing of pieces of clay rock with screening of suitable fractions forfurther processing. The second, most common - plastic - consists in kneading raw clay with a clay mixer, molding cylindrical granules and drying them. The powder-plastic technology differs from the previous one only in that the raw materials are converted into powder before kneading. Finally, with wet or slip technology, the so-called slip with a moisture content of about 50 percent is first obtained from raw materials and water using clay mashers, which is then pumped into furnaces, characterized by the presence of curtains of suspended chains. The latter are heated and break the slip into particles, which are then fired.
The rotary kiln in the form of a firing drum is installed at a slight inclination. The initial material in the form of clay granules is poured into its upper end and gradually rolls down to the burning nozzle. Under the influence of hot gases and strong thermal shock, when falling on burning fuel from the nozzle (with a temperature of about 1200 degrees), the clay boils and swells, melting its outer layer.
The entire firing process lasts no more than 45 minutes, forming the familiar lightweight and durable expanded clay gravel. Other fractions of expanded clay production (crushed stone or sand) are obtained by crushing this gravel. Higher quality products can be obtained through technologies based on the use of two and three-drum furnaces, in which the drums rotate at different speeds, creating the optimal mode of heat treatment of raw materials.
The final stage of expanded clay production is cooling in several stages with gradualby lowering the temperature, first in the oven itself, then in drum and layer coolers, and finally in airslides.
Where is expanded clay used
This is just a small list of applications:
- thermal insulation of roofs, ceilings and floors;
- soundproofing of ceilings and floors;
- creating a slope of lawn surfaces; - production of lightweight concrete, expanded clay concrete blocks;
- thermal insulation of foundations and soil;
- drainage in road construction;
- growing plants (hydroponics).
Delivery form of expanded clay
Delivery expanded clay in bags or in bulk on dump trucks. Packed material is much more convenient. It is easier to take into account (20 bags make up one cube of expanded clay), unload, store, and transport to the place of work. Loose expanded clay is cheaper, but it causes more trouble. Therefore, it is better to use expanded clay in bags.
Insulation of the floor with expanded clay
A significant part of the heat energy leaves the house through the floor. To avoid such losses, the floor is insulated. This is especially important in cases where the floor is made of concrete. Among the many thermal insulation materials available on the market, expanded clay is the most affordable. This application of this material (as a heater) is perhaps the most widely used in construction. And this is not surprising. After all, a layer of expanded clay 10 cm thick corresponds in its insulating properties to a meter thick brickwork or 25 cm thick wood. Expanded clay is used for the floor (for itsinsulation) by dry method (bulk method) or by filling with expanded clay concrete screed. The process of warming is quite simple, it can be done on your own. It includes the following steps:
- marking the level of expanded clay backfill (for better insulation, the layer should be at least 10 cm);
- perform waterproofing (high-strength polyethylene film);
- setting beacons to get a flat surface;
- filling and compaction of the insulation layer;
- leveling the surface with the rule;
- pouring a layer of cement-sand screed over expanded clay.
You can start using floors only after the screed has dried. Acceleration of floor insulation can be achieved using the dry method, when Knauf floors are laid over the bulk layer of expanded clay. They can be used immediately after assembling the floor from elements fastened together with PVA glue and self-tapping screws.
