LOCAL RAW MATERIALS FOR CONSTRUCTION MATERIALS IN THE OIL- AND GAS-BEARING REGION OF TOMSK OBLAST

P. G. Usov, N. F. Voronova

(Presented by the scientific-methodological seminar of the CTF)

In the north of Tomsk Oblast there are deposits of low-melting clays suitable for the manufacture of red building brick and lightweight concrete aggregate—expanded clay. These deposits are the Aleksandrovskoye deposit, located near the village of Aleksandrovo, and the Vasyuganskoye deposit, located 3 km southwest of the village of Novyi Vasyugan.

In terms of macroscopic characteristics, these rocks are gray clay and yellow-brown loam, lying beneath a small vegetation layer 0.3–1.0 m thick. The bed thickness is 2.9–3.25 m.

The grain-size composition of the rocks is given in Table 1. The predominant mineralogical components of the coarse-dispersed fractions are feldspars: plagioclase, orthoclase, and microcline.

Table 1

Grain-size composition of the rocks

In chemical composition (Table 2), the rocks belong to the group of semi-acidic rocks; in refractoriness, to low-melting clays. Table 3 gives the chemical compositions of fractions smaller than 1 micron.

Table 2

Chemical composition of the rocks

Table 3

Chemical composition of fractions smaller than 1 micron

The chemical-composition data, especially the ratio of SiO₂ to Al₂O₃, give an approximate idea of the mineralogical composition of the rocks studied. The molecular ratio SiO₂:Al₂O₃ shows that the composition of the clayey component of these rocks is represented by the beidellite group.

The quantitative content of iron, magnesium, and potassium oxides also indicates the presence of the beidellite group (1).

Technological studies established the molding moisture content, shrinkage during drying, coefficient of sensitivity to drying, and bonding capacity. These data are given in Table 4.

Table 4

Technological properties of clays

Table 5

Characteristics of the sintering behavior of the rocks

During firing, owing to their sandiness, the rocks give little shrinkage. Water absorption decreases only slightly with increasing temperature (Table 5). The rocks sinter at temperatures above 1100°C. Table 6 gives data on the change in the mechanical strength of products during firing.

On the basis of chemical and mineralogical studies, it may be concluded that these rocks are typical raw materials for the manufacture of red building brick. These clays are processed into brick at a molding moisture content of 22–25%. The optimum firing temperature of the brick is 950–1000°C; under these conditions brick grades “75” and “100” are obtained.

Raw materials for the production of expanded clay are clayey rocks of various chemical and mineralogical compositions that are capable of swelling in a neutral medium at a temperature of 1050–1250°C.

The literature (2) indicates that the determining criteria for the suitability of clays for the production of expanded clay are mineralogi-

the mineralogical composition, the degree of dispersion, and the amount of clayey matter in the rock. Under equal conditions, hydromicaceous and montmorillonite clays bloat better during firing than kaolinitic clays. This is explained by the special composition and structural character of the crystal lattice of montmorillonite and hydromicas, by their ability to replace certain ions with others, and by the strength of the bonds of hydroxyl groups in the lattice. The chemical composition also provides some indication of the suitability of clay for expanded clay aggregate. A low-melting clay containing 4–10% Fe₂O₃, 3–5% alkali oxides, and 3–6% alkaline-earth oxides will be suitable for this purpose (3).

From the chemical-composition data given in Table 2 it is evident that the content of fluxing oxides in the clays ensures the formation of the necessary amount of melt at a temperature of 1100–1200°C. Iron oxides, being reduced to the ferrous form, impart to the resulting melt a high wetting ability, and the ferrosilicates formed in this process impart long-melting behavior, i.e., properties needed by the melt for the satisfactory course of the bloating process of the mass.

Table 6

Mechanical strength

Table 7

Properties of expanded clay aggregate

Firing of the rocks under study is carried out in a silite furnace in the form of granules 3–4 cm in diameter, with a molding moisture content of 22–25%, at a temperature of 1170–1180°C for 10 minutes. After this treatment regime, expanded clay aggregate with a bulk density of 0.66–0.50 g/cm³ was obtained. Data on the properties of the expanded clay aggregate are given in Table 7.

Conclusions

1. In terms of technological properties, the rocks under study are typical low-melting raw materials, widely distributed within Tomsk Oblast and used in the production of red building brick.

2. In terms of chemical composition, the rocks belong to the semacid, low-melting rocks.

3. A clayey-matter content of more than 11% in the rocks ensures high cohesion, as a result of which products dried after molding have sufficient mechanical strength, which is very important in the production of building brick and expanded clay aggregate.

4. The sensitivity of the rocks to drying indicates the absence of a tendency to explode when introduced into a heated furnace.

References

1. Methods for Studying Sedimentary Rocks, edited by N. M. Strakhov, vol. I. Gosgeoltekhizdat, Moscow, 1957.

2. S. P. Onatskii. Selection and Evaluation of Clay Raw Materials for the Production of Expanded Clay. Gosstroiizdat, Moscow, 1957.

3. E. V. Kostyrko, P. Pshenichin. “Expanded Clay.” Construction Materials, No. 2, 1951.