Where does the fireclay powder come from?
Kaolin, or white refractory clay, is formed in nature with the erosion of granite and other rocks, in which feldspars are present. It is the latter that are the natural basis of kaolin. This name comes from the place where white clay with high refractory indices was first discovered - in China, in Jiangxi Province, there is the Kaolin area, which translates as "high hill".Possessing an extraordinarily finely dispersed structure that provides an ideal chamotte powder, the material is very in demand in many spheres of production, including in the manufacture of paints, varnishes, adhesives. But it represents the greatest value in the manufacture of refractory compounds.
Fireclay aggregate is divided into three granulometric parameters: crushed stone( coarse-grained), sand( fine-grained) and powder, which is a fine-milled additive.
First, kaolin must be cleaned of foreign impurities, which include rock particles, as well as quartz sand, which, during firing, can turn into glass sags. Then at a temperature of 1300 to 1500 degrees in special furnaces, kaolin is burned to a complete loss of plasticity, meaning that the only 1% moisture contained in the clay is vaporized. The sintered briquettes are then ground to obtain chamotte sand of different fractions, which are then sieved to obtain the same particle diameter. You can also get chamotte by grinding a fight of refractory bricks made from white kaolin clay.
Fireclay or firebrick
When the furnace burns a fire, the temperature inside can reach 1200 degrees, and not every brick can withstand such heat. In addition, the masonry must withstand temperature changes. That is why most of the stove makers choose fireclay stone for the construction of fireplaces and stoves. In fact, it is nothing like refractory bricks, although they are made from kaolin and decorative tiles. It is noteworthy that white clay retains its natural color when roasting up to 1200 degrees. Further, when the temperature rises to 1300, "ruddy" color appears, but at 1350 degrees and above, along with a steady brown color, the geometry of the product begins to change, due to warping. The brick can even turn with a screw or bend an arc.
In the manufacture of building blocks and slabs, fireclay clay with similar sand is used. Quartz or river filler can not replace fractions of burnt chopped kaolin for the reason that at high temperatures quartz has the property of expanding, which will lead to the destruction of bricks. As for river sand, its adhesion to chamotte clay will be inadequate due to the smoothed shape of the particles. Plastic white clay, along with which enters the mixture of chamotte crumbs - is the optimal combination that allows you to get a building stone that withstands repeated heating and cooling without losing quality indicators. The brick is made of any shape, including wedge-shaped, so necessary for laying the vaults of furnace chambers.
Chamotte mortar for masonry - there is always a choice
To get the right solution for work, you can use far from any shredded chaff, you need to choose the right brand. The fact is that in addition to the size of fractions, sand or crumb from white burnt clay is also classified by the degree of refractoriness. So, the mark ZSHA should have a maximum heat resistance not lower than 1690 degrees, and the chamotte filler ZSBB - not less than 1630. In addition, this material is obtained either by crushing specially prepared and burnt briquettes, or by grinding the used crushed kaolin brick. In the latter case, a "y" marking may be placed on the bag, otherwise - "recycled", fireclay mortar with such filler can not be used in responsible works.
Various mixtures with kaolin as the main component are used both for laying fireplaces and stoves, and for their internal coating. In this case, the compositions may be different. For example, 1 part white clay and 2 parts chamotte sand with a particle diameter of not more than 0.5 millimeters - this solution is perfect for masonry. Another option - kaolin clay - 1 part, blue Cambrian clay - 1 part, chamotte sand( up to 0.5 mm) - 4 parts. In some cases portland cement is added to the composition to obtain high-strength products, although, the fireclay concrete will have a relatively low maximum refractoriness, about 1550 degrees.