Floor tiles made from Belolgorsk clays
Abstract Generated abstract
This paper evaluates the suitability of white and gray semi-acid clays from the Belogorsk deposit for manufacturing floor tiles, including mixtures with fusible blue and brown clays and with chamotte. Experimental bodies were formed by the semi-dry method at varied pressures and 9 percent water content, then assessed for compaction, drying behavior, firing shrinkage, water absorption, and tile performance after firing. The results indicate that white and gray clays behave similarly, show no drying shrinkage under the tested conditions, and can produce regular, crack-free tiles meeting key standard requirements after firing. Additions of 30 percent blue and brown clays improved some properties, especially water absorption and abrasion resistance, supporting fuller use of the deposit.
Full Text
Floor Tiles Made from Belogorsk Clays
P. G. Usov
White clays and gray clays with various shades from the Belogorsk deposit, in composition, constitute one group of semi-acid clays. They have no noticeable difference in their properties. The different intensity of the gray coloration of these clays is due to the presence in them of varying amounts of carbonaceous matter, which does not exert a noticeable influence on their technological properties.
In the manufacture of floor tiles, the white and gray clays were considered as one variety and were tested in a mixture in proportion to the thickness of their beds. At the same time, a batch with additions of fusible brown and blue clays occurring in the upper horizon was tested.
Such an approach is expedient from the point of view of a more complete use of the clays of the deposit.
A characteristic feature of the white and gray clays is that they contain small quantities of particles of colloidal size, and products made from them by the plastic method of forming have low shrinkage during drying and very high shrinkage during firing. With high firing shrinkage, warping of the products is sometimes observed.
In the semi-dry method of forming, we sought to obtain, as far as possible, a denser structure of the products in the dry state, so as to reduce their shrinkage during firing. For the same purpose, batches of white and gray clays with additions of chamotte were tested. The possibility of increasing the degree of densification of the structure during forming by applying higher pressures was indicated in the work of G. V. Kukolev, L. Ya. Mishulovich, and Ya. M. Syrkin [1].
Using their data, we formed experimental specimens with the greatest amount of water for semi-dry forming, equal to 9%, at pressures from 200 to 1000 kg/cm². In all cases the batch had the same fineness of grinding and was checked by screening through a sieve of 250 openings/cm². The forming capacity of the bodies is given in Table 1.
Table 1
| Forming pressure, kg/cm² | White + gray clay | Clay + 20% chamotte | Clay + 40% chamotte | Clay + 30% blue and brown clays |
|---|---|---|---|---|
| 200 | 2.0 | 1.90 | 1.76 | 2.00 |
| 400 | 2.40 | 2.30 | 2.10 | 2.41 |
| 600 | 2.35 | 2.30 | 2.20 | 2.40 |
| 800 | 2.42 | 2.35 | 2.37 | 2.42 |
| 1000 | 2.35 | 2.45 | 2.40 | 2.40 |
Batches consisting only of white and gray clays, as well as with additions of blue and brown clays, with 9% water, reach their final structural density ...
ture at a pressure of 400 kg/cm². The presence of chamotte in the body composition increases the internal friction of the mass during forming. In these bodies, unlike clays, the degree of compaction increases with increasing forming pressure up to 1000 kg/cm².
No drying shrinkage is observed in products made from clays alone and from clays with chamotte additions, formed with 9% water.
The behavior during firing of products made from a mixture of white clays and gray clays of various shades, as well as from white and gray clays with an addition of 30% fusible blue and brown clays, is given in Table 2.
Table 2
| Body compositions | Water absorption of specimens, %, after firing at a temperature of °C | Water absorption of specimens, %, after firing at a temperature of °C | Water absorption of specimens, %, after firing at a temperature of °C | Water absorption of specimens, %, after firing at a temperature of °C | Water absorption of specimens, %, after firing at a temperature of °C | Water absorption of specimens, %, after firing at a temperature of °C |
|---|---|---|---|---|---|---|
| 800 | 900 | 1000 | 1050 | 1100 | 1150 | |
| 1. Mixture of white and gray clays | 16.00 | 16.2 | 14.10 | 11.8 | 4.0 | 2.0 |
| 2. Mixture of white and gray clays with an addition of 30% fusible clays | 15.6 | 15.8 | 14.6 | 6.3 | 0.5 | 0.5 |
The value of firing shrinkage after firing at the sintering temperature of the clay is given in Table 3.
The shrinkage of specimens made from clays, when fired at the sintering temperature, has a large absolute value compared with bodies containing chamotte additions, and the densification of the structure during firing in these bodies proceeds faster than in bodies with chamotte.
Table 3
| Forming pressure, kg/cm² | From a mixture of white and gray clays: shrinkage | From a mixture of white and gray clays: water absorption | From clays with 20% chamotte: shrinkage | From clays with 20% chamotte: water absorption | From clays with 40% chamotte: shrinkage | From clays with 40% chamotte: water absorption | From clays with 30% blue and brown clays: shrinkage | From clays with 30% blue and brown clays: water absorption |
|---|---|---|---|---|---|---|---|---|
| 200 | 11.0 | 0.15 | 5.25 | 7.2 | 6.0 | 3.93 | 10.6 | 0.10 |
| 400 | 9.25 | 0.10 | 6.50 | 3.46 | 5.5 | 2.29 | 9.2 | 0.10 |
| 600 | 8.75 | 0.10 | 6.50 | 1.60 | 5.75 | 2.10 | 8.7 | 0.10 |
| 800 | 8.50 | 0.11 | 6.75 | 1.08 | 5.25 | 2.00 | 8.7 | 0.15 |
| 1000 | 8.25 | 0.11 | 6.25 | 1.10 | 7.25 | 2.00 | 8.68 | 0.10 |
In bodies with chamotte, under identical firing conditions, the density of the product structure is directly dependent on the magnitude of the forming pressure, while the shrinkage remains a constant value.
Floor tiles of normal size were prepared from bodies of two compositions:
- From a mixture of white clays and gray clays of various shades.
- The first body with an addition of 30% blue and brown clays.
Before forming, the bodies were thoroughly mixed on laboratory edge runners, first in the dry state and then with the addition of 9% water. The tiles were formed at a pressure of 300 kg/cm². After drying, the tiles were fired in a kerosene furnace at a temperature of 1160°, with a soaking time at this temperature of 30 minutes. The fired tiles had the correct shape and had no cracks.
The appearance of the tiles is shown in Fig. 1, and the physicomechanical characteristics are given in Table 4.
Fig. 1
Table 4
| No. | Property | From batch No. 1 | From batch No. 2 | Requirement according to OST 10556—40 |
|---|---|---|---|---|
| 1 | Shape | regular | regular | regular |
| 2 | Color | gray | red | — |
| 3 | Water absorption, % | 2,01; 2,42; 2,05 | 1,0; 0,75; 0,55 | not more than 4 |
| 4 | Impact strength | 7; 9; 8 | 10; 10; 8 | not less than 3 |
| 5 | Hardness | between 6 and 7 | 7; 7 | not less than 7 |
| 6 | Abrasion | 0,30; 0,35 | 0,10; 0,09 | not above 0,2 |
Conclusion
The white and gray clays of the Belogorsk deposit, both in pure form and with an addition of 30% blue and brown clays, are suitable for the production of floor tiles.
References
- Kukolev G. V., Mishulovich L. Ya. and Syrkin Ya. M. On the use of high pressure in pressing ceramic tiles. Journal “Glass and Ceramics,” pp. 8–10, 1952.