Sand-lime brick made from beneficiated sands
Abstract Generated abstract
This paper examines the use of clay-rich fine sands from the Kopylovo plant and similar deposits for sand-lime brick production, focusing on whether beneficiation can improve product quality. Laboratory and semi-industrial tests evaluated washing and hydrocyclone separation to remove clay, followed by comparison of grain-size composition, mineral and chemical characteristics, mix parameters, and brick performance for natural and beneficiated sands. The results indicate that beneficiation produced a quartz-rich sand with much lower clay content, reduced water demand, higher raw mix density, increased compressive and bending strength, and improved frost resistance. The authors recommend hydromechanical extraction with hydrocyclone separation for deposits where clay content varies widely.
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SAND-LIME BRICK MADE FROM BENEFICIATED SANDS
P. G. USOV, S. A. BABENKO, V. M. VITYUGIN, N. S. DUBOVSKAYA
(Presented by the scientific seminar of the Department of General Chemical Technology)
The sand used at the Kopylovo plant in its natural state contains about 23% clay, and its grain-size composition is characterized by the content of grains (Table 1). As can be seen from the table, this is a fine sand, with a predominant grain size of less than 0.15 mm; their content in the sand is about 60%. Beneficiation of sands by washing out the clay significantly improves all, without exception, the quality characteristics of sand-lime brick.
Table 1
Grain-size composition of the sand
| Type of sand | Partial residues, %, on sieves with openings, mm | Partial residues, %, on sieves with openings, mm | Partial residues, %, on sieves with openings, mm | Partial residues, %, on sieves with openings, mm | Partial residues, %, on sieves with openings, mm | Partial residues, %, on sieves with openings, mm | Passed through 0.15 mm sieve, % | Fineness modulus |
|---|---|---|---|---|---|---|---|---|
| Type of sand | 5 | 25 | 1.2 | 0.6 | 0.3 | 0.15 | Passed through 0.15 mm sieve, % | Fineness modulus |
| Natural | 0.0 | 0.58 | 0.86 | 4.25 | 26.22 | 7.42 | 60.60 | 0.79 |
| Beneficiated | 0.0 | 0.0 | 1.35 | 7.50 | 40.18 | 8.31 | 42.58 | 1.17 |
Separation of sand from clay can be carried out effectively in hydrocyclones, which have recently found wide application in the mining industry. The results of laboratory studies on the washability of sands are given in Table 2. From the initial sand, containing 23% clay, a high-purity quartz product of favorable chemical composition was obtained, characterized by a basic oxide content within the range of 97–98%.
Mineralogical analysis of the beneficiated sands showed a quartz content of about 95%, ore minerals—0.5%, and others—4.5%. The data from the laboratory studies formed the basis for the construction of an industrial seasonal beneficiation installation. The flow diagram of the installation’s equipment train is shown in Fig. 1.
The initial sand is delivered by dump trucks to bunker 1; by feeder 2 it is fed onto belt conveyor 3. The latter feeds the sand into scrubber 4; water is also supplied here at a solid-to-liquid ratio of S:L = 1:3.
Large lumps of clay and pebbles 3 mm in size are directed automatically from the scrubber to the dump. For their transportation, hydrocyclone drain 7 is used. The sand and clay that have passed through the scrubber are collected in sump 5, from which, by sand pump 6 under a pressure of 1.5–2
Table 3
Characteristics of products separated during sand beneficiation
| Product name | Partial residues, % on sieves, mm: 2.5 | Partial residues, % on sieves, mm: 1.6 | Partial residues, % on sieves, mm: 1.0 | Partial residues, % on sieves, mm: 0.63 | Partial residues, % on sieves, mm: 0.4 | Partial residues, % on sieves, mm: 0.315 | Partial residues, % on sieves, mm: 0.20 | Partial residues, % on sieves, mm: 0.16 | Partial residues, % on sieves, mm: 0.10 | Partial residues, % on sieves, mm: 0.05 | Partial residues, % on sieves, mm: pan | Clay component, % |
|---|---:|---:|---:|---:|---:|---:|---:|---:|---:|---:|---:|---:|---:|
| Original sand | 0.25 | 0.00 | 0.07 | 0.06 | 0.17 | 0.97 | 22.24 | 18.74 | 21.65 | 8.46 | 2.53 | 1.83 | 23 |
| Quarry product | — | — | 0.03 | 0.05 | 0.17 | 1.37 | 29.7 | 21.0 | 26.0 | 13.2 | 2.85 | 3.21 | 2.42 |
| Clay product | — | — | — | 0.01 | 0.02 | 0.05 | 0.95 | 1.75 | 3.97 | 5.43 | 3.02 | 8.02 | 76.78 |
| Quarry product | — | — | — | 0.05 | 0.17 | 1.84 | 33.0 | 23.45 | 26.17 | 11.24 | 1.59 | 0.96 | 1.18 |
| Clay product | — | 0.32 | 0.07 | 0.07 | 0.08 | 0.20 | 2.8 | 3.5 | 6.3 | 6.77 | 3.00 | 3.56 | 73.33 |
Fig. 1. Diagram of an industrial installation for sand beneficiation (explanation in the text).
...are fed into the hydrocyclone. Here the sand is separated from the clay. The beneficiated sand is collected on a specially prepared site, where it is dewatered by natural drainage.
The sand thus beneficiated underwent semi-industrial tests at the Kopylovo sand-lime brick plant in parallel with natural sand. The test results are given in Table 3.
All batches of products made with beneficiated sand withstand the frost-resistance test. Most batches of products made with natural sand have unsatisfactory frost-resistance results.
Table 3
Technological parameters of lime-sand mixes and physicomechanical characteristics of products
| Type of sand and its specific surface, cm² | Mix parameters: active lime, % | Mix parameters: slaking water, % | Mix parameters: molding moisture, % | Total weight of raw mix, kg/l | Product characteristics: bulk density, kg/dm³ | Product characteristics: strength, kg/cm², compression | Product characteristics: strength, kg/cm², bending | Product characteristics: water absorption, % |
|---|---|---|---|---|---|---|---|---|
| Natural, 420 | 9.5 | 18.0 | 9.5 | 1.80 | 1.91 | 127 | 22 | 16.8 |
| Beneficiated, 380 | 9.5 | 14.0 | 7.0 | 1.95 | 1.97 | 196 | 32 | 15.5 |
Thus, when using sands from the Tugan and other similar deposits in the production of wall silicate materials, their beneficiation is necessary in order to wash out the clay.
Because of the lens-like occurrence of sands in the deposit, the clay content in the sand samples studied varies within the range of 5–45%. This circumstance makes the need for sand beneficiation even more acute, since the use of such sands will be difficult. A method of extracting sands with simultaneous washing to remove clay should be recommended. For this purpose, the most suitable method will be a hydromechanical one, with mandatory separation of the sand from the clay in hydrocyclones.