Burenichevskaya Rock as a Raw Material for Floor Tiles
Abstract Generated abstract
This paper evaluates rock from the Burenichevskoye deposit near Kemerovo as a single-component raw material for ceramic floor tiles. Using mineralogical, granulometric, chemical, and standard ceramic testing, the authors characterize its hydromica-rich composition, firing behavior, molding properties, shrinkage, strength, and water absorption. Laboratory semi-dry forming experiments indicate that the rock can be ground, moistened, pressed, and fired at about 1200 degrees to produce gray tiles with regular shape, low water absorption, and abrasion resistance above the standard, while addition of 20 percent brick clay yields red tiles fired at 1100 to 1150 degrees with similarly favorable properties.
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Burenichevskaya Rock—Raw Material for Floor Tiles
P. G. Usov, E. M. Aristova
(Presented by the scientific-methodological seminar of the Faculty of Chemical Technology)
The distinctive mineralogical composition of the rock of the Burenichevskoye deposit makes it possible to recommend it as a raw material for the production of floor tiles without batching with other materials. In its natural composition it contains all the necessary components of a tile body, which at the plants of the Union is usually prepared by batching various natural materials: clays, feldspar, pegmatite, quartz, and others. By macroscopic characteristics the rock is analogous to clay of loose structure. It has the following grain composition.
Table 1
| Content of fraction, % | Content of fraction, % | Content of fraction, % | Content of fraction, % | Content of fraction, % | Content of fraction, % | Content of fraction, % | Content of fraction, % |
|---|---|---|---|---|---|---|---|
| Coarser than 1.0 mm | 1.0–0.5 mm | 0.5–0.25 mm | 0.25–0.05 mm | 0.05–0.01 mm | 0.01–0.005 mm | 0.001–0.005 mm | Finer than 0.001 mm |
| 0.19 | 3.58 | 2.65 | 10.95 | 32.33 | 11.13 | 16.16 | 23.25 |
Fractions coarser than five microns are composed of unrounded fragments of quartz-mica rocks, quartz, individual fragments of weathered sericite schists, limestones, and limonite. The quartz-mica rocks are represented by angular fragments of light-gray and rarely greenish color, up to 3 mm in size, which are easily destroyed under mechanical action.
The surface of the fragments is uneven and porous. The pore depressions are filled with a grayish, silky micaceous mass. In places the rock is penetrated by brown iron oxides. When ground into powder, by means of immersion one identifies in it hydrated mica, quartz, feldspar, vermiculite-like kaolinite, and isolated grains of calcite, zircon, tourmaline, limonite, rutile, and the finest dust-like particles not determinable with a microscope.
Hydromica occurs in the form of irregular lamellae and flakes ranging in size from 0.005–0.05 mm.
Quartz is observed more often in the form of micrograins up to 0.005 mm in size, and more rarely in the form of larger, semi-rounded and angular grains up to 0.15 mm in size.
Feldspars form angular fragments up to 0.018 mm in size, sometimes with well-pronounced polysynthetic twinning.
Vermiculite-like kaolinite occurs in the form of elongated, more rarely worm-like intergrowths.
Quartz of fractions coarser than five microns is represented by angular fragments of light-gray color.
Greenish sericitic schists are observed in the form of fragments up to 5 mm in size with a smooth silky surface.
Limestone occurs in the form of medium-grained fragments, with grain sizes up to 4 mm, white and grayish in color.
Limonite is represented by fragments up to 4 mm in size, dark brown and almost black in color.
In the dispersed fractions there is a higher content of hydromicas, vermiculite-like kaolinite, and limonite; moreover, their content increases as the dispersity of the rock increases.
In the fine fractions, individual grains of zircon, tourmaline, feldspars, and dusty material with a refractive index higher than that of quartz are observed.
The chemical composition of the rock and of the fractions with particle size finer than five microns is given in Table 2.
Table 2
| Sample | H₂O | l.o.i. | SiO₂ | TiO₂ | A₂O₃ | Fe₂O₃ | CaO | MgO | R₂O | Sum |
|---|---|---|---|---|---|---|---|---|---|---|
| Rock | 1.57 | 5.76 | 65.0 | 0.32 | 18.85 | 1.68 | 0.49 | 1.88 | 4.28 | 99.84 |
| Fractions < 5 µ | 1.76 | 7.54 | 56.0 | 0.33 | 26.86 | 1.91 | 0.52 | 2.71 | 2.30 | 99.93 |
Oriented aggregates of fractions finer than one micron, when deposited from suspensions, form a scale-like, parallel-fibrous form with refractive indices: \(Ng = 1.578 \pm 0.003\), \(Np = 1.557 \pm 0.003\), and birefringence \(= 0.021\).
The form of the aggregates and the refractive indices of the fine fractions correspond to hydromicas.
The ceramic properties of the rock were investigated by standard methods.
In this case the rock, in an air-dry state, was ground on edge runners until it passed completely through a sieve with 0.5 mm openings.
The molding properties of the ground rock and the characteristics of specimens in the dry state are given in Table 3, and their behavior during firing is shown in Fig. 1.
The rock has a refractoriness of 1550°, a sintering temperature of 1200°, and a melting interval of 350°. It sinters calmly, over a long temperature interval. A very favorable property of the rock is its ability to form the complete structure of products during molding, both from a plastic body and from a semi-dry one. In both cases, firing shrinkage during firing of the products to complete sintering does not exceed seven percent. Articles made from it retain their shape very well during firing.
Floor tiles of standard size were prepared in the laboratory by a semi-dry forming method according to the simplest scheme. The rock in the dry state is ground until it passes completely through a sieve with 0.5 mm openings, and after moistening to 8–9 percent, tiles are formed from it. The tiles are formed normally at a pressure of 150 kg/cm² and, in the freshly formed state, have a sufficiently high mechanical
Fig. 1. Behavior of articles made from the rock during firing: 1—water absorption, in %, 2—shrinkage, in %, 3—flexural breaking strength, kg/cm², 4—compressive breaking strength, kg/cm².
strength, which fully ensures their further technological processing. The low content of colloids in the rock greatly facilitates drying of articles made from it.
Table 3
| Forming moisture content, % | Shrinkage on drying, % | Cohesion, kg/cm² | Coefficient of sensitivity to drying | Temporary resistance of dry specimens, kg/cm² — compression | Temporary resistance of dry specimens, kg/cm² — bending |
|---|---|---|---|---|---|
| 25.0 | 3.7 | 7.0 | 0.31 | 38 | 10 |
The forming water from the semi-dry mass is released rapidly, without shrinkage of the articles. Under industrial conditions, when firing in a tunnel kiln, it will probably be possible to send the tiles for firing in the freshly formed state, thereby completely eliminating the drying stage. From Burenichevo rock alone, after firing at a temperature of 1200°, the floor tiles have an even gray color, a regular shape, water absorption of not more than 2.5%, and abrasion strength considerably above the standard.
With an addition of ordinary brick clay in an amount of 20%, Burenichevo rock yields floor tiles with an even red coloration, more attractive than those made from the pure rock. The technology for producing red tiles remains practically just as simple as from the rock alone.
The red clay and the rock are proportioned in the dry state; then the mixture is ground, moistened, and formed into tiles under the same conditions as the pure rock. No noticeable differences in the behavior and properties of freshly-
formed tiles made from the batch has not been established. The optimum firing temperature for tiles made from the batch lies within the range of 1100–1150°.
The tiles have water absorption of up to 2% and abrasion resistance above the standard.
Conclusions
- Burenichevskaya rock is an excellent raw material for floor tiles, without batching with other materials. In a mixture with brick clay, colored floor tiles can be obtained on its basis.
The rock deposit is located 12 km from the city of Kemerovo, in the area of Burenchevo Station, on the Kemerovo–Topki railway line.