USE OF VERMICULITE ROCK IN THE PRODUCTION OF BUILDING MATERIALS

E. A. Guber, A. V. Petrov

(Presented by the scientific seminar of the Department of Silicate Technology)

The ever-increasing rates of industrial and housing construction dictate the need to search for lightweight aggregates possessing thermal-insulation and acoustic properties. The use of such materials in construction makes it possible to reduce the weight of building structures, saves basic building materials, and helps reduce fuel consumption in the operation of residential buildings and industrial enterprises, which leads to cheaper construction and lower operating costs. The quantity and range of the various thermal-insulation materials currently being produced are far from sufficient.

The increased technical level of construction requires the creation of ever new thermal-insulation materials, making effective use of local raw materials for this purpose.

Among new heat- and sound-insulating materials, expanded vermiculite—thermovermiculite—and products based on it have recently been gaining increasing recognition. Vermiculite deposits have been developed mainly in the European part of the Union, on the Kola Peninsula, and in the Urals.

Vermiculite products are not produced at all in Siberia, and transporting them from the European part is too expensive because of the bulkiness of the products. In addition, long-distance transport worsens the valuable properties of the material (it is fragile and, under shaking, becomes crushed, losing its shape).

We have studied a new deposit of vermiculite rock—the Tebinskoye deposit, located in Kemerovo Oblast, in Western Siberia. The material composition of the rock has been studied in detail, the production regime for obtaining thermovermiculite has been worked out, recommendations have been given for using it to manufacture certain types of products, and the principal properties of these products have been described.

According to the results of petrographic analysis, the rock under investigation consists of vermiculite—57%—and hornblende—43%. The vermiculite is yellowish-brown in color, with perfect cleavage in one direction, and forms platy aggregates.

The pleochroism of the mineral is distinct: along \(N_g\) the color is orange-brown, along \(N_p\)—orange-yellow; \(N_g = 1.581\), \(N_p = 1.561\). Hornblende is represented by prismatic crystals and irregular grains having a dark-green color and distinct pleochroism. The index of ref—

refractive indices \(N_g' = 1.654\), \(N_p' = 1.640\). Individual grains of quartz are present. The chemical analysis was performed on two samples: the rock in its natural state and the fraction coarser than 1 mm, represented mainly by lamellar aggregates.

The results of the chemical analysis are given in Table 1.

Table 1

Judging by the increase in the amount of MgO and ignition loss in the fraction \(> 1\) mm, there is more vermiculite in it. The elevated content of Fe₂O₃ in the samples confirms the presence in the rock of the ferruginous variety of vermiculite—jefferisite, in which magnesium is isomorphously replaced by iron.

X-ray and thermal analysis also confirm the presence of vermiculite. The weight-loss curve and the differential-thermal curve of the investigated rock in its natural state are shown in Fig. 1.

Fig. 1. Thermal curves: 1 — weight-loss curve, 2 — DT curve

Thus, all research methods establish the presence of vermiculite.

The expanding capacity of the vermiculite rock upon heating was established as a function of the temperature and firing regime. The optimum expansion temperature is 650–700°C; the maximum expansion time at these temperatures is 1.5–2 min. The bulk weight of the investigated rock in the expanded state is 270 kg/m³. The obtained thermovermiculite may be characterized by the grade “300.”

The possibility was established of using thermovermiculite as an aggregate for lightweight concretes; for this purpose the grain-size composition of the vermiculite was investigated, and the water-cement ratio (w/c) was determined under specified conditions of compaction and hardening for three batches. The specimens were prepared by the method of the “Teploproekt” Institute [1]. The test results are presented in Table 2.

The thermal-conductivity coefficient of the vermiculite-concrete batches investigated ranges from 0.12 to 0.139 kcal/m·h·deg. On the basis of thermovermiculite, specimens in the form of bricks and tiles were made under laboratory conditions. As the binder, clays from two deposits of Tomsk Oblast were used: Voronovskoe—a white, refractory clay, and Kargasokskoe—a red, low-melting clay. The raw mix was prepa—

was carried out in the ratio: 3 parts thermovermiculite and 1 part clay. Products with a binder of low-melting clay were fired at 900°, and with refractory clay at 1000, 1050, and 1100°.

Table 2

The results for the physicomechanical properties of the fired products are given in Table 3.

Table 3

As can be seen from the table, vermiculite products made with a binder from the indicated clays fully satisfy the requirements imposed on products of this kind.

Thermovermiculite is also suitable for loose-fill insulation according to all the indices required for this purpose [2]: the bulk weight does not exceed 350 kg/m³. The grain composition ensures minimum settlement of the fill; the thermal-conductivity coefficient of thermovermiculite is 0.042 kcal/m·h·deg.; refractoriness is 1320°C.

Thermovermiculite can be used for plaster possessing heat- and sound-insulating properties, where it is used instead of sand.

The data of laboratory investigations, carried out thus far on only one representative sample from the Tebin deposit, made it possible to draw the following conclusions:

1. The rock of the Tebin deposit contains 60% ferruginous vermiculite and 40% hornblende.

2. On firing the rock, thermovermiculite is obtained with a bulk weight of 300 kg/m³ and a thermal-conductivity coefficient of 0.042 kcal/m·h·deg.

3. Thermovermiculite can be used:

a) for the production of lightweight concrete with a bulk density of 700–1000 kg/m³ and \(\sigma_{\text{comp}}\) of 15–27.5 kg/cm²;

b) in the production of heat- and sound-insulating slabs on a clay binder, with a bulk density of 700 kg/m³, \(\sigma_{\text{comp}} = 29\) kg/cm², \(\sigma_{\text{bend}} = 13\) kg/cm², at a firing temperature of 900–1000°C;

c) for bulk high-temperature insulation.

1. Development of the Tebinsk deposit in Kemerovo Oblast promises the future development of a number of new production facilities within Siberia.

REFERENCES

1. N. N. Kalyanov, A. N. Merzlyak. Vermiculite and Perlite-Porous Aggregates for Concrete. Moscow, 1964.

2. F. S. Podolyak. Experience in the Use of Vermiculite in Large-Panel Construction. Chelyabinsk, South Ural Book Publishing House, 1965.

3. Production and Use of Vermiculite. Collection of articles, Publishing House of the USSR Academy of Sciences, Moscow, 1963.

4. Problems of Clay Mineralogy. Collection of articles, IL Publishing House, Moscow, 1962.