RU2376258C1 - Lime and siliceous binder, method of lime and siliceous binder production and method of moulding sand production for extruded silicate items - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: as disclosed by the invention, the method of lime and siliceous binder production includes separate milling of caustic lime and quartz sand and their further mixing. Quartz sand is milled by wet method and as a result, highly concentrated suspension is produced with 12-20% humidity containing particles less 5 mcm 20-50% and at the following ratio of components, wt %: the above suspension (as dry substance) 15-25, caustic lime 75-85. Lime and siliceous binder is produced using the above described method. Method of moulding sand production is intended for manufacturing extruded silicate items. This method provides for mixing quartz sand with highly-concentrated suspension of 12-20% humidity and containing particles less 5 mcm 20-50%, which is made by wet milling of quartz sand. Next, this mixture is mixed up with caustic lime and further moistened until moulding humidity is achieved. All operation are conducted at the following ratio of components, wt %: quartz sand 70-84, the said lime and suspension at their ratio, wt % to be: lime 75-85 and suspension 15-25, 16-30. The invention is developed in dependant items.

EFFECT: improved quality of items.

6 cl, 2 ex, 6 tbl

Description

The invention relates to the building materials industry and can be used in the manufacture of extruded autoclaved hardened products.

It is known lime-containing binder for the manufacture of silicate brick, consisting of quartz sand and calcined carbonatite, having a composition, wt.%: Sand 50-80%, calcined carbonatite 20-50% (RU 2081861 C1, 6 C04B 28/20). The disadvantage of this analogue is the limited availability of calcined carbonatite in comparison with conventional calcium lime.

A known method of producing a binder, which consists in a joint grinding in tube mills of quartz sand and quicklime. Materials should be fed into the mill continuously, in an amount ensuring the production of a binder with a specific surface of 4000 cm ² / kg (Vakhnin M.P., Anishchenko A.A. Production of silicate brick. M .: Higher school, 1977, 160 p., p. 51-52). The disadvantage of this method is the low intensity of grinding quartz sand as a result of joint grinding of materials (quartz sand and quicklime), which have different hardness and grindability, as well as the inability to activate lime-siliceous binders as a result of wet grinding due to unacceptably high humidity required for storage and transportation under industrial conditions of the obtained binder suspension. The silicate mixture obtained on the basis of such a binder is practically unsuitable for the manufacture of high-quality pressed products based on it.

A known method of preparing a silicate mixture for the production of silicate brick, which consists in the use of intumescent clay rocks as a silica-containing component, this method consists in expanding the specified component as a result of firing, grinding it to a fraction of 0.4-1.2 mm, impregnating with a lime suspension containing up to 10 wt.% solids, subsequent mixing of the obtained material with slaked lime, wetted to the molding moisture (RU 2225378 C1, 6 С04В 28/20). The disadvantage of this analogue is the reduced reactivity of lime and an insufficient increase in the strength of silicate products obtained in this way.

As a prototype, a lime-siliceous binder is selected having the composition, wt.%: Ground quartz sand 10.59-30.51, quicklime 22.00-36.99 and 1.8-8.09% aqueous solution of copper vitriol 46.61-57.63 (RU 2303013 C1, 6 С04В 28/20, С04В 111/20). The disadvantage of this prototype is the high humidity (44-48%) of the binder obtained by the wet method, a low degree of mechanical activation of its components, a short delay in the process of lime hydration (up to 3 hours), and an unfavorable environmental factor.

The closest way to obtain a binder is the method of mixing finely ground quicklime and sand slurry. Quicklime was crushed separately in a ball mill until it passed completely through sieve No. 008. Subsequently, it was mixed with ground sand and extinguished at a water-lime ratio of 0.6. The specific surface area of the resulting product was 1100 m ² / kg. (Yakimechko Y.B. Some features of the use of quicklime in aerated concrete. M.: Building materials. No. 6. 2006. S.26-27). The disadvantage of this prototype is the low degree of mechanical activation of the siliceous component.

As a prototype, a method of preparing a silicate mixture for the production of silicate brick is selected, which consists in preparing a binder from carbide lime and a raw material mixture by grinding lime with an active CaO and MgO content of 60-70% to a specific surface of 9000-10000 cm ² / g or mixed with sand to a specific external surface of 4500-6000 cm ² / g, and the preparation of the raw material mixture is carried out by mixing the obtained binder with sand quarry moisture and a particle size of 0.7-1.1 with simultaneous heating to 70-80 ° C in the following ratio Ponent, wt.%: the specified binder 11-22%; said sand 78-89% (RU 2002120664, 7 С04В 28/20). The disadvantage of this method of preparing a silicate mixture is the use of a binder with a relatively low specific surface area of ground quartz sand in the binder, as well as high energy intensity and complexity of the technological design.

In the inventive method for producing a lime-silica binder, as well as for obtaining a silicate mixture based on it, the tasks were:

- the fullest possible use of the effect of hydration hardening of CaO through the use of separate grinding of the siliceous component and quicklime;

- carry out separate grinding of quicklime to the optimum specific surface, the value of which depends on the type of lime. With separate grinding, directional regulation of the degree of dispersion of the obtained components becomes possible;

- to implement the possibility of mechanochemical activation of the siliceous component due to wet grinding on the principle of obtaining a highly concentrated binder suspension (HCBS);

- receive high-quality products of autoclave type hardening.

The invention is also aimed at increasing the competitiveness of the obtained silicate autoclave products as a result of a 1.8-2 times increase in compression compared to industrial products, improving the technology and expanding the arsenal of means for producing silicate autoclaved products.

These tasks are achieved by a method of producing a lime-siliceous binder, including separate grinding of quicklime and quartz sand, followed by their mixing, in which, according to the proposed solution, the grinding of quartz sand is carried out by the wet method to obtain a highly concentrated suspension with a moisture content of 12-20% and a particle content of less than 5 microns 20-50% and in the following ratio of components, wt.%:

specified suspension (on dry matter) 15-25 quicklime 85-75

In the method for producing a lime-silica binder, said suspension is modified with an organo-mineral additive in an amount of 0.02-0.1 wt.% By weight of the dry matter of the suspension.

The tasks are achieved using a lime-silica binder obtained by separate grinding of quicklime and quartz sand with their subsequent mixing, in which, according to the proposed solution, the grinding of quartz sand is carried out by wet method to obtain a highly concentrated suspension with a moisture content of 12-20% and a particle content of less than 5 microns 20 -50% and in the following ratio of components, wt.%:

specified suspension (on dry matter) 15-25 quicklime 85-75

The lime-silica binder may contain a highly concentrated suspension of silica-containing raw materials, which is modified with an organomineral additive in an amount of 0.02-0.1 wt.% By weight of the dry matter of the suspension.

Tasks are also achieved by the method of obtaining a molding mixture for the production of pressed silicate products, which consists in mixing quartz sand with a highly concentrated suspension of silica-containing raw materials with a moisture content of 12-20% and a particle content of less than 5 microns 20-50% obtained by wet grinding of silica sand, then mixing the resulting mass with ground quicklime and subsequent wetting to molding moisture, in the following ratio of components, wt.%:

quartz sand 70-84

the specified lime and suspension in their ratio, wt.%:

lime 75-85 and suspension 15-25 16-30

In a method for producing a molding mixture for the production of pressed silicate products, a highly concentrated suspension of silica-containing raw materials is modified with an organomineral additive in an amount of 0.02-0.1 wt.% By weight of the dry matter of the suspension.

When using the specified lime-silica binder, it becomes possible to increase the production efficiency of silicate autoclaved pressed materials by optimizing the grain composition of the initial mixture by controlling the content of a certain amount of nanosized particles in the system. To establish the relationship between the method of grinding the binder component, the rate of formation of calcium hydrosilicates and their type in silicate systems. By increasing the degree of dispersion (1.5 times) of the binder components achieved by wet grinding according to the HCBS principle, a higher degree of amorphization and mechanical activation of particles, significantly reduce the temperature and pressure during autoclaving, and increase the physicomechanical characteristics by 40-50% material.

Case Studies

An example of a specific implementation 1.

To obtain a silicate mixture and test its suitability for the production of extruded autoclaved materials, a number of operations were performed in accordance with the claimed method of preparing a lime-siliceous binder and silicate mixture based on it.

Natural and artificial quartz sands can be used as a silica raw material for obtaining a highly concentrated suspension of silica-containing raw materials, in this case, sand of the Ziborovsky deposit with a content of 98.5% SiO ₂ , the chemical composition of which is shown in Table 1, was used.

To obtain a highly concentrated suspension of silica-containing raw materials, wet grinding was carried out in a ball mill with a stepwise loading of the material, observing the basic principles for the preparation of highly concentrated suspensions (Pivinsky, Yu.E. Ceramic binders and ceramic concrete / Yu.E. Pivinsky - M .: Metallurgy, 1990.270 s .).

The choice of the concentration of the system at the first grinding stage was carried out taking into account the packing coefficient of the source material and its other characteristics, as well as the overall dimensions of the mill. In the first grinding stage, usually all of the liquid calculated from the final suspension concentration is introduced. The duration of this stage of the process, depending on many factors, ranges from 1 to 5 hours. In this case, the duration of this stage of the process was 2 hours. The degree of dispersion should be such that the average particle size is at least 10-20 times less than the size of the material introduced during the next loading. Optimal results, as a rule, can be obtained when dispersion is achieved at the first grinding stage, characterized by a significant (up to 20-50%) content of particles of the fraction less than 5 microns. In this case, the suspension is as if compressed, accelerating the process of subsequent grinding after the introduction of the next portion of the material.

With stepwise loading of the material, as the volume concentration increases, the effective density of the grinding media decreases and the humidity increases significantly. Due to a gradual decrease in the volumetric liquid content and an increase in the friction forces, the process temperature increases, which largely determines the rheological properties of the system directly in the grinding process, as well as the properties of a highly concentrated suspension of silica-containing raw materials after grinding. So, with increasing temperature, the overall viscosity of the system decreases significantly, its fluidity increases, as well as dilatant properties, which allows the grinding process to be carried out at elevated concentrations.

After wet grinding, the resulting highly concentrated suspension of silica-containing raw materials had a moisture content of 14.5% with a particle content of less than 5 microns 38%.

Lime was milled dry in a ball mill to a specific surface of 9000 cm ² / g.

To obtain the raw mix (silicate mass) of the required quality, it is necessary to dose them correctly.

The dose of lime in the silicate mass is determined not by the amount of lime in it, but by the content of its active part, which will participate in the hardening reaction, i.e. calcium oxide. Therefore, the rate of lime is established, first of all, depending on its activity.

In production, it is usually installed empirically. The average content of active lime in the silicate mass is 6-8% (Khavkin L.M. Technology of silicate brick / L.M. Khavkin, - M .: Stroyizdat, 1982. 384 p.). When using freshly burnt lime without impurities and underburning, its amount can be reduced; if the lime contains a large amount of unburnt stone and impurities, as well as if the lime was stored for a long time in air, its norm in the mixture should be increased. Both insufficient and excessive amounts of lime in the silicate mass entail undesirable consequences: insufficient lime content reduces the strength of the brick, an increased content increases the cost of production, but at the same time does not have a positive effect on quality. The activity of lime entering production often changes, therefore, to obtain a mass with a given activity, it is often necessary to change the amount of lime in it. At JSC "Building Materials", the city of Belgorod, lime is used with an activity of 70-85% (technological regulations for the production process of silicate brick. TP 002.05307944-2006).

Practically in production, pre-compiled tables are used to determine the dosage of lime in kg per unit of production (1 m ^{3 of} silicate mass or 1000 pieces of brick). Data on the dosage of lime in kg per unit of output are given in Appendix 2 (table 1). In this case, lime with an activity of 70% was used. Silicate mass activity was 7%.

In the process of obtaining a silicate mixture based on the proposed lime-silica binder, stepwise mixing of the obtained HCBS of a siliceous composition with non-ground quartz sand takes place, then the resulting component is mixed with fine ground quicklime with simultaneous wetting of the mixture and subsequent exposure to complete completion of the lime hydration process.

The wetting of the sand mixture was carried out on the basis of the required calculated amount of water for quenching the silicate mixture.

The amount of water required for the quenching process is directly related to the activity of lime, as well as its dispersion.

The total water consumption (Process regulations for the production of silicate brick. TP 002.05307944-2006) to obtain silicate mass of the required quality is about 13% (plumb mass) and is distributed as follows (in%):

- for slaking lime - 2-2.5

- for evaporation during extinction - 3-3.5

- to moisturize the mass - 5.5-6.5

We calculate the amount of water needed to extinguish in this particular case.

The chemical reaction of slaking lime proceeds according to the formula:

CaO + H ₂ O = Ca (OH) ₂

Based on the molecular weight of the reacting substances, we compose the proportion:

56 _CaO → 18 _H2O

7 _CaO → X _H2O ,

Then the amount of water needed to extinguish will be: X = (7 × 18) / 56 = 2.25 (%).

The molding mixture was prepared in mixing runners. Molding mass moisture in this case was 11-12%.

Next, the molding mixture was held in a sealed vessel until the lime hydration process was completed.

The moisture content of the molding silicate mixture after completion of the hydration (quenching) process was 6.0-6.5%.

The amount of water must exactly match the norm. Lack of water leads to incomplete extinguishing of lime; the excess water, although it provides complete quenching, but does not always create the permissible moisture content of the silicate mass. Moisture comes partially from sand, the career moisture of which varies depending on climatic conditions.

In the process of laboratory tests, in this case, dried enriched sand was used, the residual moisture of which can be neglected.

In real production conditions, it is always necessary to make an adjustment for the natural moisture content of raw materials (sand) (Khavkin L.M. Technology of silicate brick / L.M. Khavkin, - M .: Stroyizdat, 1982., p. 95 -97).

The amount of water needed to bring the moisture content of the silicate mass to the desired value can almost also be calculated in advance depending on the career moisture of the sand entering the production and a table can be created to determine the water consumption per unit of production (1000 pieces of brick or 1 m ^{3 of} silicate mass) ( Technological regulations for the production process of silicate brick. TP 002.05307944-2006). The amount of water (in l) needed to re-hydrate the silicate mass (per 1000 pieces of brick), depending on the moisture content of the sand, is given in Appendix 2 (table 2). An example of the calculation is given in Appendix 3.

The required estimated number of constituent components of the molding sand (for laboratory compositions) are shown in table 2.

For all developed compositions, cylinder samples with a diameter and height of 50 mm and a weight of 200 g were molded at a specific pressing pressure of 20 MPa. Then, the samples were autoclaved at OAO Stroimaterialy, Belgorod, at a temperature of 183 ° C and an overpressure of 10 atmospheres according to the following conditions: pressure start-up - 2 hours, isothermal exposure - 6 hours, pressure relief - 2 hours. Next, the cylinder samples tested for strength, density and water absorption. The test results are presented in table 3.

An example of a specific implementation 2.

In this case, the sand of the Razumenskoye deposit with a content of 93.02% SiO ₂ , the chemical composition of which is shown in Table 1, was used as a silica raw material to obtain a highly concentrated suspension of silica-containing raw materials.

To prepare the siliceous component of the lime-silica binder, we used a highly concentrated suspension of silica-containing raw materials with an output moisture content of 16.2% and a particle content of less than 5 μm 45%, with modifying additives introduced into them. The goal of the latter is to improve the technological and rheological properties of molding systems by eliminating their dilatant properties, giving them the necessary plasticity.

As modifying additives, various materials similar to the type of exposure can be introduced into the initial highly concentrated suspensions of silica-containing raw materials. For example, composition: an organic additive based on resorcinol-furfural oligomers (Belgorodsky superplasticizer No. 3 (SB-3)) and sodium tripolyphosphate; composition: (Belgorodsky superplasticizer No. 5 (SB-5) and sodium hydroxide; composition: complex Italian organic diluent with the brand name "reotan" and sodium hydroxide, etc. (Shapovalov NA., Slyusar A.A., Cherevatova A.V. , Ermak Yu.N., Ermak S.N. Pivinsky Yu.E. Integrated modifying organomineral additive for aluminosilicate refractory systems based on highly concentrated ceramic binders. Chemistry and Chemical Technology, 2003, Volume 46, Issue 5. S.137-140).

The effectiveness of a complex additive is due to the summation of various mechanisms of the action of components on the particles of the dispersed phase of HCBS and mixtures. (Shapovalov N.A., Strokova V.V., Cherevatova A.V. Optimization of the structure of the nanosystem based on the example of the All-Russian Military Technical University .// “Building Materials”, No. 9, 2006. P.16-17).

For thinning, increasing the mobility of molding systems, for example, a complex diluting organomineral additive can be used, including 50-90 wt.% Sodium tripolyphosphate and 10-50% resorcinol-containing plasticizer SB-5 (Shapovalov N.A., Slyusar A.A., Cherevatova A.V. et al. Integrated thinning organomineral additive for refractory molding systems and a method of manufacturing materials using it. // RF Patent No. 2238921, publ. 27.10.04, bull. No. 30). A complex additive consisting of 30% sodium tripolyphosphate + 70% SB-3 superplasticizer or a complex additive consisting of 40% sodium hydroxide + 60% SB-5 superplasticizer can also be used. Additives can be introduced in the form of powder or solutions with a density of 1.10-1.30 g / cm ³ at the rate of 0.02-0.1% by weight of dry matter in a highly concentrated suspension of silica-containing raw materials. The fact that the effect of the above additives is similar is confirmed by the experimental data shown in tables 4, 5, 6.

The use of modifying additives in the systems under consideration will improve the basic physical and mechanical characteristics of finished products by 30–40%.

A comparative analysis of the effectiveness of wet sand grinding by the HCBS method showed that even at the initial stage of grinding, the finely ground component obtained by the HCBS method has a higher degree of dispersion of solid particles with a more developed surface morphology and, therefore, a significantly higher reactivity, which ultimately confirmed by a significant improvement in the technical and operational characteristics of silicate material.

In the HCBS system, as a result of mechanochemical activation of the main solid phase, about 1-3% of nanoscale particles are formed already at the grinding stage. The presence of nanoparticles in HCBS has a complex positive effect. The latter concerns both the microstructure and technological aspects of HCBS production, as well as the technical and operational characteristics of the materials obtained on their basis. In addition, when wet grinding, mills consume less electricity, their productivity is 10-15% more.

With the introduction of HCBS instead of the quartz component in the lime-sand binder, the strength increased by 25% compared with the factory composition. In addition, the damping period with this method of administration of HCBS was reduced by almost 2 times - from 40 to 25 minutes.

Based on the studies, it can be concluded that the nanostructured silicate autoclave material is highly technological and promising, since, according to preliminary estimates, the duration of the quenching period is actually reduced by 2 times and, accordingly, a significant reduction in the energy intensity of the autoclave treatment mode is possible, which will give an additional economic effect on existing production .

Table 1.
CHEMICAL COMPOSITION OF SILICA RAW MATERIALS Raw Material Name Chemical composition SiO ₂ Al ₂ O ₃ SO ₃ Fe ₂ O ₃ CaO MgO K ₂ O + Na ₂ O p.p.p. Quartz sand Ziborovsky (Belgorod region) 96.80 0.50 not determined 0.90 0.38 not determined 0.98 0.44 Quartz sand Razumensky (Belgorod region) 93.02 0.92 0.02 0.98 0.62 0.08 0.46 0.86

table 2
Compositions of molding silicate mixtures containing HCBS as part of a lime-silica binder Composition number The composition of the binder,% The composition of the mixture,% Lime HCBS Astringent Sand one 1.1 85 (13.6) 15 (2.4) 16 84 1.2 80 (12.8) 20 (3.2) 1.3 75 (12) 25 (4) 2 2.1 85 (17) 15 (3) twenty 80 2.2 80 (16) 20 (4) 2.3 75 (15). 25 (5) 3 3.1 85 (25.5) 15 (4,5) thirty 70 3.2 80 (24) 20 (6) 3.3 75 (22.5) 25 (7.5)

Calculation Example

For 1 kg of molding sand, the moisture content of the molding system at the time of the start of the hydration process is assumed to be 12%.

For composition 2.2. would need:

704 g of sand, 120 g of water and 176 g of binder, namely: 35.2 g of HCBS and 140.8 g of lime.

Knowing the initial humidity of HCBS (14.5%), we make the necessary adjustment for humidity: with HCBS, 5.1 g of water will enter the molding system.

Therefore, for the composition 2.2. would need:

704 g of sand, 114.9 g of water and 176 g of binder

Table 3. Properties of a Nanostructured Silicate Composite Material Sample No. Indicators Weight kg Volume m Density, kg / m ³ Water absorption,% Strength, MPa CONTROL COMPOSITION one 0.196 0.00011 1781.8 13.44 17.62 2 0.195 0.0001 1957.0 14.45 13.37 3 0.193 0.000104 1855.7 13.02 17.58 Average value 1878.6 13.64 16.19 (17.62) 1 COMPOSITION (15% HCBS) one 0,200 0.000106 1886.8 10.9 21.5 2 0.195 0.000103 1886.8 13.01 19.11 3 0.193 0.000102 1892.2 12.45 25,4 four 0.185 0,000096 1927.1 11.01 21.01 Average value 1895.1 12,99 21,755 (25.4) 2 COMPOSITION (20% HCBS) one 0.185 0.0001 1850.0 12.63 21.70 2 0.197 0.000102 1931.4 12.08 21.66 3 0.195 0.000101 1930,5 12,2 22.22 four 0.194 0.000102 1901.9 12.3 25.48 Average value 1906.8 12.3 23.12 (25.48) 3 COMPOSITION (25% HCBS) one 0.197 0.0001 1970,0 12.41 15,2 2 0.192 0.000102 1882.4 12.45 17.27 3 0.197 0.000102 1931.4 12.07 18.7 four 0.197 0.000104 1894.3 12.47 17.11 Average value 1919.5 12.29 17.06 (18.7)

Claims (6)

1. A method of obtaining a lime-siliceous binder, comprising separate grinding of quicklime and quartz sand, followed by mixing them, characterized in that the grinding of quartz sand is carried out by the wet method to obtain a highly concentrated suspension with a moisture content of 12-20% and a particle content of less than 5 microns 20- 50% and in the following ratio of components, wt.%:
specified suspension (on dry matter) 15-25 quicklime 75-85 2. The method according to claim 2, characterized in that the suspension is modified with an organo-mineral additive in an amount of 0.02-0.1 wt.% By weight of the dry matter of the suspension. 3. Lime-siliceous binder, characterized in that it is obtained by the method according to claim 1. 4. Lime-silica binder according to claim 3, characterized in that the suspension is modified with an organo-mineral additive in an amount of 0.02-0.1 wt.% By weight of the dry matter of the suspension. 5. A method of obtaining a molding mixture for the production of pressed silicate products, characterized in that they mix quartz sand with a highly concentrated suspension of silica-containing raw materials with a moisture content of 12-20% and a particle content of less than 5 microns 20-50%, obtained by wet grinding of silica sand, mixing obtained the mass with ground quicklime and dampening to molding moisture in the following ratio of components, wt.%:
quartz sand 70-84 the specified lime and suspension in their ratio, wt.%: lime 75-85 and a suspension of 15-25, 16-30 6. The method according to claim 5, characterized in that the suspension is modified with an organo-mineral additive, while the organo-mineral additive is introduced in an amount of 0.02-0.1 wt.% By weight of the dry matter of the suspension.