RU2472735C1 - Method of producing composite binder, composite binder for producing moulded autoclave hardening articles, moulded article - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to the building industry and can be used to produce silica brick and moulded autoclave hardened wall materials. The method of producing composite binder for producing moulded articles involves pre-slaking highly active lime with water to lime ratio equal to 0.48, in the presence of a gypsum dihydrate additive in amount of 0.05-0.25% of the mass of lime, followed by mixing the obtained lime binder with ground quartz sand in the following ratio, wt %: lime binder 33.3-50, ground quartz sand - the balance. The composite binder is characterised by that it is obtained using the method described above. The moulded article in form of silica brick is characterised by that when using the binder described above, said brick is obtained from a mixture containing the following, wt %: said binder 10-30, non-ground quartz sand 70-90.

EFFECT: wider range of means of producing moulded autoclave hardened articles, having high strength, low cost of production by cutting power consumption when producing the binder and articles based thereon, and controlling lime slaking, dispersity of the binder.

3 cl, 2 tbl, 1 ex, 1 dwg

Description

The invention relates to the construction industry, namely the production of binders, and can be used to produce extruded autoclaved pressed wall materials.

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 that ensures the production of a binder with a specific surface of 4000 cm ² / kg (Vakhnin M.P., Anischenko A.A. Production of silicate brick. - M.: Higher School, 1977. - P. 51 -52) [1]. 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-silica binder, which leads to a decrease in the strength of finished products.

The closest in combination of essential features is a disintegrating method for the production of a silicate mixture. According to this method, lump lime is preliminarily quenched in hydrators in a fluff for a period of extinguishing with loading and unloading of the product up to 40 minutes. In the future, produce simultaneous loading into the disintegrator using batchers of sand and slaked lime powder to obtain a raw material mixture (Khint, I. A. Fundamentals of the production of silicalcite products. - M .: Gosstroyizdat, 1962. - P.26-28) [2]. This method in its technical essence is closest to the claimed. It is also possible to obtain a different fraction of lime slaking products depending on the amount of water used for slaking lime. When extinguishing lime into fluff, heat and water vapor from extinguishing lime go to the transformation of lump lime into the finest powder with a density of 400-450 kg / m ³ (Mikulsky V.G. et al. Building materials. Textbook. Edition. - M.: Publishing House of the Association construction universities, 2004. - P.196) [3]. The disadvantages of this group of inventions are the uncontrollability of the process and not the full consumption of heat from the extinguishing of lime, the duration of the process of extinguishing lime and obtaining building materials of insufficient strength.

The closest technical solution adopted for the prototype is a composite binder consisting of ground quartz sand and quicklime in the ratio 1: 1, which is optimal for the production of pressed products, and the raw mixture obtained on its basis containing 15% binder and 85% quartz sand (Khavkin L.M. Technology of silicate brick. - M.: Stroyizdat, 1982. - P.127) [4]. A disadvantage of the known technical solution is the low strength of the finished product.

The inventive group of inventions is aimed at expanding the arsenal of technical means for the production of composite binder and pressed products based on it, controlling lime extinguishing, dispersion of hydrated binder, increasing the strength of products, reducing costs by reducing energy costs in the production of binder and products based on it.

This problem is achieved by the fact that the method of producing a composite binder for the production of pressed products includes the preliminary extinguishing of highly active lime at a water-lime ratio W / I = 0.48 in the presence of dibasic gypsum additive in the amount of 0.05-0.25% by weight of lime, followed by mixing obtained lime binder with ground quartz sand in the following ratio of components, wt.%:

Lime Binder 33.3-50 Ground quartz sand rest

Composite binder is characterized in that it is obtained by the above method.

A pressed product in the form of silicate brick obtained from this binder and non-ground quartz sand in the following ratio of components, wt.%:

Specified Binder 10-30 Ground Quartz Sand 90-70

The essence of the invention lies in the fact that to obtain a composite binder, highly active lime A = 92% is quenched separately from quartz sand with the addition of two-water gypsum. It has been established that by changing the amount of water to extinguish lime, it is possible to change the temperature and rate of extinguishing lime with a change in the dispersion of the extinguishing products. At a high temperature of lime slaking obtained at a low water consumption in a mixture with the addition of two-water gypsum, gypsum may decompose to its semi-aquatic modification. The dehydration reaction of gypsum to semi-aquatic is an endothermic reaction and begins at a temperature of 107 ° C. The temperature of the lime slaking process in the presence of _two- water gypsum CaSO ₄ · 2H ₂ O, along with a change in the rate of CaO hydration reaction, also affects the dispersion of the products obtained. High quenching temperatures of highly active lime with a water-solid ratio close to theoretical value, and the presence of a mineral additive contribute to a faster reaction rate with temperatures up to 202 ° C and the most dispersed quenching products with a defective structure Ca (OH) ₂ . The solubility of semi-aqueous gypsum is approximately 3.5 times higher than the solubility of two-water gypsum, therefore, the lime mortar is more quickly saturated with semi-aqueous gypsum, which leads to a slowing down of lime quenching.

According to the results of micro studies, the products of lime slaking with the addition of two-water gypsum are highly dispersed (Fig. 1).

Studies of the obtained finely divided lime slaking products with two-water gypsum, carried out by the sedimentation method, allow us to identify the optimal conditions for slaking lime with the maximum amount of ultrafine particles. The optimal condition is the extinguishing of lime at I / O = 0.48 with the addition of 0.25% of two-water gypsum at a process temperature of 153 ° C, where the bulk of the particles is 80.8% in a highly dispersed state up to 63 μm in size (Table 1).

With a change in the amount of water used to extinguish lime and varying the mineral additive, the speed, temperature, and dispersion of the extinguishing products change. In the process of extinguishing pure lime in fluff, small particles of Ca (OH) ₂ in the presence of more water can recrystallize into larger ones, which affects the dispersion of the binder (P. Rebinder, N.V. Mikhailov and others. Structural and mechanical properties of dispersed systems.Materials of the IV conference on cellular concrete, Saratov-Penza, 1969. - P.3-9) [5]. The presence of an additive of two-water gypsum and its transition to a semi-water modification also affects the rate of lime slaking and the process temperature.

Table 1 Change in dispersion of lime slaking products The addition of two-water gypsum,% Maximum lime slaking temperature, ° C The time to reach the maximum quenching temperature, min The number of particles, wt.% up to 63 microns more than 63 microns V / I = 0.32 0.05 190 4,5 73.5 26.5 0.15 191 4,5 73.3 26.7 0.25 191 4,5 79.5 20.5 0.75 196 4,5 76.0 24.0 1,0 192 4.0 74.5 25.5 1.25 198 4.0 69.7 30.3 1,5 202 4.0 69.2 30.8 I / O = 0.48 0.05 170 4,5 78,4 21.6 0.15 163 5,0 78.9 21.1 0.25 153 5,0 80.8 19,2 0.75 182 5,0 76.9 23.1 1,0 194 4,5 75.5 24.5 1.25 173 6.0 73.3 26.7 1,5 168 5.5 71.8 28,2 V / I = 0.64 0.05 168 4,5 78.3 21.7 0.15 158 4,5 77.9 22.1 0.25 158 4,5 78.5 21.5 0.75 159 4,5 74.8 25,2 1,0 170 5,0 75,2 24.8 1.25 184 4,5 76,4 23.6 1,5 173 4,5 73.9 26.1

Using laser granulometry, it was determined that 20% of slaked lime particles with a mineral additive are on a scale from 0 to 5 microns.

Semi-aquatic gypsum obtained by quenching lime at high temperatures lowers the solubility of calcium hydroxide, slowing down the growth of Ca (OH ₂ ) crystals with small amounts of water. As a result, highly dispersed components are formed that are actively involved in the processes of hydration and hardening of the binder. Pre-quenched lime with a mineral additive of two-water gypsum in the composition of the binder is a rather active component and positively affects the course of the hardening processes of the binder.

The possibility of directional modification of two-water gypsum into β-modification of semi-water gypsum in the process of slaking lime in the temperature range 160-190 ° C is thermodynamically justified and established. The temperature increase is achieved by extinguishing highly active lime with a small amount of water with a further increase in the water flow for extinguishing lime up to two times based on the theoretical flow rate according to the hydration reaction (W / I = 0.32): CaO + H ₂ O = Ca (OH) ₂ . The gypsum hemihydrate obtained by quenching lime from two-water gypsum in highly basic mixtures does not hydrate further and, under conditions of heat and humidity treatment, passes into the highly basic calcium sulfate hydrate Ca ₂ (SO ₄ ) ₂ · H ₂ O. This compound is autoclaved in a calcareous sand binder. crystallization of high strength hydrosilicates and calcium hydrosulfosilicates of needle-like morphology. The use of highly active binders and the formation at the early stage of hardening of neoplasms of the highly basic calcium sulfate hydrate Ca ₂ (SO ₄ ) ₂ · H ₂ O contributes to the intensification of the formation of high-strength hydrosilicate binder with less time for hydrothermal hardening, which led to a reduction in time by 30 minutes. Thus, the proposed set of solutions has the criterion of "novelty."

The technical result is the ability to control the speed and temperature of slaking lime, the dispersion of its binder activation with obtaining in the process of autoclave synthesis of a high-strength binder of cementitious material while reducing the energy intensity of the process.

In the technological process, the total exposure time of lime with the addition of two-water gypsum in hydrators is established on the basis of the time that lime is quenched in the presence of a specified amount of water, and is determined by a standard method. Then the extinguished lime is mixed with ground quartz sand to obtain a composite binder, followed by wetting to a molding moisture.

The authors found that in order to obtain high-strength silicate brick, it is recommended to separately extinguish highly active lime in the presence of a mineral additive at V / I = 0.48. The use of a composite binder with pre-quenched lime in the presence of an additive of two-water gypsum at W / I = 0.32 and at W / I = 0.64 is impractical because leads to a change in the processes of structure formation with a decrease in the strength of the finished product.

As one of the options for the practical implementation of the obtained binder, a raw material mixture is proposed, including the proposed binder and non-ground quartz sand in the following ratio of components, wt.%: Composite binder 10-30; silica sand 90-70; water is the rest. Grinding of quartz sand to obtain a binder was carried out in a steel laboratory mill to a specific surface of 250-300 m ² / kg. Pre-slaked lime is mixed in a mixer with ground quartz sand to obtain a lime-sand binder with a ratio of components in the binder lime: sand = 1: 1; 1: 2 and this mass is mixed until completely homogeneous. A filler is introduced into the resulting mass, moistened to a moisture content of 10% and mixed thoroughly. Then a product is pressed from it - tiles, blocks, wall panels and steamed in an autoclave according to the prototype (Khavkin L. M. Technology of silicate brick. - M .: Stroyizdat, 1982. - P. 4) [1].

Example. To obtain 100 g of a composite binder, 50 g (50 wt.%) Of lime was previously extinguished at WI = 0.48 with the addition of 0.075 g of two-water gypsum (0.15 wt.% Of lime). The high temperature from the extinction of highly active lime A = 92% (the extinction temperature was 163 ° C) influenced the dehydration of gypsum into hemihydrate. Subsequently, the lime binder was mixed with pre-ground quartz sand (specific surface 250-300 m ² / kg) at a ratio of 1: 1 (50:50 g). To obtain 100 g of a silicate mixture, 15 g (15 wt.%) Of a previously prepared composite binder was weighed and 85 g (85 wt.%) Of non-ground quartz sand was added (Table 2, mixture No. 9). The components were mixed in a screw mixer until the components were uniformly distributed over the volume of the mixture, and with stirring, they were wetted with water to a moisture content of 8%, taking into account the deduction of water for preliminary slaking of lime. Samples were prepared from the resulting mixture by pressing on a laboratory hydraulic press at a pressure of 20 MPa in the form of cylinders with a height of 30 mm and a diameter of 20 mm.

The obtained samples were subjected to hydrothermal treatment at a vapor pressure of 0.8 MPa, with an isothermal exposure of 5 hours 30 minutes. The exposure time was reduced by 30 minutes. The data are shown in table 2, 3.

table 2 Composition and strength characteristics of silicate wall materials Mix No. The composition of the silicate mixture, wt.% The additive for the extinguishing of lime, wt.% The limit of compressive strength, MPa Astringent Quartz sand 1 (prototype) fifteen 85 0 20.30 2 10 90 0 21.67 3 0.05 23.30 four 0.15 25.05 5 0.25 24.25 6 0.30 22.32 7 fifteen 85 0 22.30 8 0.05 24.70 9 0.15 26,50 10 0.25 23.40 eleven 0.30 20.60 12 twenty 80 0 20.43 13 0.05 23.25 fourteen 0.15 25.45 fifteen 0.25 23.70 16 0.30 21.05 17 thirty 70 0 21.03 eighteen 0.05 22.54 19 0.15 25.74 twenty 0.25 25.04 21 0.30 20.90

The maximum strength of the obtained product when the ratio in the silicate mixture of lime binder (with the addition of 0.15 wt.% Gypsum) and ground quartz sand 1: 1 was 26.5 MPa (table 2, mixture No. 9).

According to the above example, the lime binder was mixed with pre-ground quartz sand at a ratio of 1: 2 (33.3: 66.7 g) and introduced into the raw material mixture to obtain a pressed product. The results of changes in the strength of the autoclaved product are presented in table 3.

Table 3 Composition and strength characteristics of silicate wall materials Mix No. The composition of the silicate mixture, wt.% The additive for the extinguishing of lime, wt.% The limit of compressive strength, MPa Astringent Quartz sand 1 (prototype) fifteen 85 0 20.30 2 10 90 0 21.45 3 0.05 22.14 four 0.15 23.42 5 0.25 23.78 6 0.30 21.89 7 fifteen 85 0 23.35 8 0.05 24.32 9 0.15 24.87 10 0.25 26.12 eleven 0.30 22.87 12 twenty 80 0 21.87 13 0.05 22.93 fourteen 0.15 23.76 fifteen 0.25 25.85 16 0.30 22.34 17 thirty 70 0 22.23 eighteen 0.05 22.89 19 0.15 23.54 twenty 0.25 23.87 21 0.30 22.89

The maximum strength of the obtained product when the ratio in the silicate mixture of lime binder (with the addition of 0.25 wt.% Gypsum) and ground quartz sand 1: 2 was 26.12 MPa (table 3, mixture No. 10).

For boundary compositions, products are accepted whose composite binder contains from 0.05 wt.% To 0.25 wt.%, With these additive ratios, the highest strength values are noted. Reducing or increasing the amount of additive is impractical, because the resulting extruded products acquire a decrease in strength.

The technical result is the expansion of the arsenal of technical means for the production of composite binder and extruded products based on it, an increase in the mechanical strength of products by 25-30% after autoclaving. Achieving a reduction in exposure time at a maximum temperature of autoclave processing by 30 minutes while maintaining physical and mechanical characteristics. Using the proposed technology and recipes will create highly efficient and environmentally friendly pressed products.

Claims (3)

1. A method of obtaining a composite binder for the production of pressed products, comprising pre-extinguishing highly active lime with a water-lime ratio W / I = 0.48 in the presence of an additive of two-water gypsum in an amount of 0.05-0.25% by weight of lime, followed by mixing the resulting lime binder with ground quartz sand in the following ratio of components, wt.%:
Lime Binder 33.3-50 Ground quartz sand Rest 2. Composite binder, characterized in that it is obtained by the method according to claim 1. 3. A pressed product in the form of silicate brick, characterized in that when using the binder according to claim 2, it is obtained from a mixture including, wt.%:
Specified Binder 10-30 Ground Quartz Sand 70-90

Images