RU2103235C1 - Method for manufacturing articles - Google Patents

Abstract

FIELD: production of building materials; manufacture of custom-made wall panels for low-storey residential and agricultural buildings. SUBSTANCE: lumpy quicklime is ground together with basic blast-furnace slag preliminarily subjected to wet granulation. Slag must have calculated theoretical moisture content sufficient to fully slake lime. Mixture is ground to achieve specific surface area above 2500 sq.cm/g, whereupon quartz sand or low-calcium ash transported hydraulically from ash dumps are added to mixture. The latter is subjected to final grinding up to final specific surface area 3000-3200 sq.cm/g, followed by slaking moulding mixture with aqueous slurry made from wastes of chalk production. Mixture has the following composition, wt. -%: basic blast-furnace slag, 20-30; lumpy quicklime, 5-7.5; quartz sand or ash hydraulically transported from ash dumps, 60-75; wastes of chalk production, 0.1-0.5. EFFECT: simplified manufacturing technology of moulding mixture; higher crack resistance in process of pressing and curing articles under natural conditions and steam treatment; improved decorative and architectural design. 1 tbl

Description

 The invention relates to methods for manufacturing products and can find application in the industry of building materials and products in the preparation of piece wall products (bricks, blocks) for low-rise residential and agricultural buildings.

 A known method of producing products [1], which consists in pre-mixing finely dispersed ash (from burning coal) and slag with a size of less than 4 microns and then mixing this mixture with 6-12% with burnt (quicklime) lime, the ground mixture is moistened with water to 8 -16% and form building elements from it.

Along with the advantages of the method (ash, slag are utilized), there are significant disadvantages:
sophisticated technology for preparing the molding sand, associated with the need to dry the materials before grinding;
low crack resistance of products both during molding by pressing due to the difficult exit of compressed air from a mixture with a high specific surface, and in the process of natural and hydrothermal hardening due to the delayed process of extinguishing burnt lime, including free, contained in the ash;
nondescript architectural appearance, since the color of the products from the mixture is dark gray after natural hardening or steaming.

The closest method to the claimed, both by technical solution and quantitatively-qualitative composition of the molding mixture is given in the description of the invention "Binder" [2] and consists in mixing previously separately ground to a specific surface of 5000-5500 cm ² / g quicklime, taken in an amount of 20-21 wt.% activity of 75-80%, ground to a specific surface of 2300-2500 cm ² / g in an amount of 60.2-64.0% of quartz sand, ground to a specific surface of 3500-3700 cm ² / g the main blast furnace slag in the amount of 12-14%, semi-aquatic gypsum in the amount of 1.5-1.8% and crushing this mixture to a specific surface of 3700-4000 cm ² / g, moistening the mixture and forming building elements from it. Products harden during autoclaving at t = 174 ^o C and P = 0.8 MPa.

Along with the great advantages of preparing the molding sand (slag is utilized and cellular construction products are obtained), there are significant disadvantages:
requires a complex and energy-intensive technology for preparing the mixture associated with the need for preliminary drying of the initial components of the mixture and preliminary separate and secondary grinding to a very high specific surface of 3700-4000 cm ² / g, as well as due to the need for hydrothermal treatment under autoclave hardening conditions;
low crack resistance of the mixture during molding by pressing due to the difficult exit of compressed air from the mixture at a very high specific surface area of 3700-4000 cm ² / g;
low crack resistance of products during hardening both in natural and hydrothermal conditions (steaming) at t = 90-95 ^o C and ambient pressure due to the belated process of extinguishing lime particles;
nondescript architectural appearance of products after steaming and natural hardening conditions, as the color of the products is dark gray.

 The objective of this invention is to simplify the manufacturing technology of the molding mixture and products based on it, as well as to reduce their crack resistance in the process of pressing and hardening under natural conditions and steaming, to increase the architectural appearance.

To achieve the goal in a known method of manufacturing products, including preparing a molding mixture by mixing ground quicklime with an activity of at least 75%, with ground main blast furnace slag, silica-containing filler and calcium-containing salt, mixing the mixture with an aqueous solution, molding and hardening, characterized in that preliminarily they carry out joint grinding of quicklime lump lime with blast-furnace main slag of wet granulation, with calculated-theoretical humidity, enough initial for complete slaking of lime with grinding them to a specific surface of not more than 2500 cm ² / g, then quartz sand or hydraulic dump low-calcium ash is added to the mixture and the mixture is crushed to a specific surface of 3000-3200 cm ² / g, and molding the mixture is carried out an aqueous suspension of calcium salt, which is used as waste chalk production.

When testing the proposed method adopted raw materials and industrial wastes with the following characteristics:
1) lump quicklime containing at least 75% CaO. Meets the requirements of GOST 9179 - 77;
2) blast core slag of wet granulation Tulachermet JSC with a chemical composition, wt. %: SiO ₂ 38.47 - 39.39; Al ₂ O ₃ 7.5 - 9.05; CaO 43.26 - 45.66; MgO 7.27-7.9; FeO 0.31-0.35; MnO 0.23-0.25;
3) dumping low-calcium lignite ash from coal burning near Moscow basin. Meets the requirements of GOST 25818-83 "Fly ash of thermal power plants for concrete". The chemical composition of low-calcium ash from the burning of brown coal of the Moscow Region basin, wt.%: SiO ₂ 49.5 - 64.0; Al ₂ O ₃ 13.2 - 27.29; FeO 5.72-7.82; CaO 1.44 - 2.4; SO ₃ 0.81 - 0.89; Fe ₂ O ₃ 8.18 - 11.18; MgO 0.63 - 0.7; TiO ₂ 0.84 - 1.42; Na ₂ O 0.1 - 0.14; K ₂ O 0.32 - 0.45; p.p.p. 3.28 to 3.6;
4) calcium-containing salt - waste from the production of chalk at a chemical plant in pos. Leninsky, Tula region The chemical composition on a dry mass: Ca (OH) - 48 wt. %; CaCO ₃ - 50 wt.% .; quartz sand - the rest. Humidity - 49%;
5) quartz sand. Adopted ordinary ordinary. Donskoy, Tula region Chemical composition, wt.%: SiO ₂ 88 - 90; Al ₂ O ₃ 2.1-3.6; CaO 1.2-1.8; MgO 0.35-0.4; Fe ₂ O ₃ 1.2 - 2.4.

Example 1. Dosed by gravimetric method by weight: blast-furnace main slag of wet granulation with a maximum particle diameter of 20 mm and a moisture content of 8% in an amount of 4 kg by dry weight (20% of the total weight of the dry mixture) or taking into account a moisture content of 4 kg 348 g (348 g added with water slag), lump quicklime with a maximum particle diameter of 20 mm (dry) in an amount of 1 kg (5% by weight of the dry mixture). Both materials in an amount of 5 kg 348 g were placed in a laboratory ball mill and crushed to a specific surface area of the mixture 2450 cm ² / g Preliminarily, by calculation, the necessary amount of water was established to completely extinguish 1 kg of lime with an activity of 80% (CaO in lime is 80%).

According to the chemical equation
CaO + H ₂ O = Ca (OH) ₂ + Q
56 hours + 18h = 74 V.H.

кг воды (257 г), т.е. введенное количество воды со шлаком (348 г) вполне обеспечит полное гашение извести.56 parts by weight CaO required 18 parts by weight water, and 1 kg with an activity of 80%, i.e., 0.8 kg of CaO is required

kg of water (257 g), i.e. the entered amount of water with slag (348 g) will fully ensure the complete extinguishing of lime.

In the pre-crushed to S = 2450 cm ² / g mixture was added hydraulic waste low-calcium ash TPP from burning brown coal with a moisture content of 10 wt. % in the amount of 14.9 kg by dry weight (74.5% by weight of the dry mixture) or taking into account 10% moisture 16.56 kg, i.e. with ash introduced into the mixture, located in a ball mill, 1.66 kg The ash introduced into the mill contained 3.1% burnt lime particles, which, due to the presence of glass films on their surface, did not go out in the hydraulic dump.

а с золой введено 1,66 кг воды, которой вполне достаточно для гашения 0,5 кг CaO. Второй этап измельчения продолжили до получения удельной поверхности смеси 3000 см²/г. При отборе пробы смеси из мельницы на определение удельной поверхности одновременно определили влажность смеси, которая обладала свойством сыпучести.Therefore, from 16.56 kg, burnt lime particles of 0.51 kg (16.56 x 0.031 = 0.51 kg) were introduced, for the complete extinguishing of which water is required

and 1.66 kg of water was introduced with ash, which is quite enough to extinguish 0.5 kg of CaO. The second grinding step was continued until a specific surface area of the mixture of 3000 cm ² / g was obtained. When sampling the mixture from the mill to determine the specific surface at the same time determined the moisture content of the mixture, which had the property of flowability.

Фактическая же влажность смеси составила 5,3%, т.е. примерно в два раза меньше.Theoretically, the calculated humidity of the mixture should have been:
1) the amount of residual water after the extinguishing of lime in the first stage
348 g - 257 g = 91 g H ₂ O;
2) the amount of residual water after the extinguishing of burnt lime particles made with ash
1.66 kg of H ₂ O - 0.51 kg of H ₂ O = 1.15 g;
total calculation of water in the mixture:
1.150 + 0.91 = 2.06 kg H ₂ O,
and a dry mixture of 19.9 kg, therefore, absolute humidity

The actual humidity of the mixture was 5.3%, i.e. about half as much.

 The latter is explained by the exothermic effect: heat generation during the extinguishing of lime, under the influence of which the excess moisture from the extinguishing evaporates in the form of vapors, is removed from the mill through leaks. Part of the water is spent on the process of partial hydration of minerals of granulated slag (silicates and calcium aluminates).

Thus, at the first and second stage of grinding, there is not only a process of increasing the specific surface of the mixture and slaking lime, but also drying it to a loose state. The dry bulk mixture with a specific surface area of 3000 cm ² / g was moistened with an aqueous suspension obtained by introducing paste into the water - waste chalk production in an amount of 100 g (0.5% by weight of the dry mixture). The prepared mixture was molded by pressing, and prototypes of building products with a diameter and a height of 7 cm were obtained. The samples solidified for one day in humid conditions at a temperature of 20 ± 2 ^o for 28 days. The hardened mixture in the form of prototypes was tested to determine the presence of cracks (visually with a magnifying glass), including after pressing, appearance (color) and strength.

 The test results are shown in the table (mixture and experiment No. 1).

Example 2. The experience of preparing molding mixtures of compositions 2-4 (see table) is carried out according to the methodology described in example 1, but with a different ratio of components and achieving a specific surface area of the mixture equal to 3100 - 3200 cm ² / g.

Example 3 (prototype). The experimental molding mixtures (compositions 5 and 6) were taken with a silica sand and ash filler similar to composition 1, but these mixtures were prepared by the prototype method, i.e. dispensed in an amount of 1 kg, ground quicklime (5% of dry weight) with a specific surface of 5000 cm ² / g, finely ground with a specific surface of 3500 cm ² / g main blast furnace slag 4.0 kg (20% of dry weight), ground with a specific surface of 2500 cm ² / g quartz sand in an amount of 14.9 kg (in experiment 6 the same amount of ash was taken with the same specific surface). All components were placed in a ball mill and finely ground to a specific surface of 3850 cm ² / g, the mixture was slurried with a suspension obtained from 100 g of dry waste from chalk production (0.5% of the dry mixture) and water, then experimental samples were prepared from the mixture by the method Example 1. The test results are shown in the table, example 5 and 6.

 A comparative analysis of the manufacture of the molding sand and products based on it by the proposed and known methods shows the following.

1. The technology of mixture preparation is simplified due to:
excluding the drying process before grinding the starting materials (wet granulation slag, hydraulic ash and quartz sand);
reducing the number of operations and grinding units, since preliminary grinding and secondary milling are carried out in the same grinding apparatus, the apparatus and operation for preliminary extinguishing of lump lime also disappear;
reduction of grinding time and, accordingly, energy consumption by reducing the specific surface of the crushed materials by 1.3-1.5 times;
exceptions in the grinding of semi-aquatic gypsum, because instead of calcium sulfate (CaSO x 0.5 H ₂ O), calcium carbonate is used in a mixture with Ca (OH) ₂ - a paste-like waste of chalk production, which is easily dispersed in water;
exceptions for the use of autoclave processing. The latter is replaced by a steaming process;
2. In the process of pressing the mixture and its hardening with a moist natural process of hardening and steaming, no cracks form;
3. The architectural appearance of the products increases - instead of a dark gray color, the products have a lighter tone, ie light gray color;
4. Almost does not decrease, and even the strength of the products increases.

Achieving this goal (crack resistance in the process of pressing and hardening, as well as giving a light tone to the pressed products) is explained by the following physical and mechanical processes that occur during the preparation of the molding mixture:
1) a decrease in the specific surface of the mixture from 3700-4000 cm ² / g to 3000-3200, which provides a more free exit of compressed air in the process of molding the mixture by pressing and, as a result, contributes to an increase in crack resistance;
2) with the simultaneous grinding of lime and the presence of its contact with moisture, the quenching process is activated (accelerated), which provides a guarantee not only of its complete quenching, but also the quenching of free burnt lime particles in the composition of hydraulic ash. Particles of burnt CaO in the ash are covered with a glassy film that does not allow water to pass through them. When grinding, the film is destroyed and free particles of such lime are quenched. In such a mixture, the process of late quenching of CaO particles during hardening, and, consequently, the formation of cracks in products formed on its basis, disappears;
3) despite the lower content of quicklime in the mixture being prepared in comparison with the composition of the mixture prepared by the method and prototype (two, three times less), the strength of the products not only does not decrease, but also increases slightly. The last effect is due to the following reasons:
during grinding, inactive particles of lime in the ash (burnt) become active, and the increase in Ca (OH) ₂ is due to the introduced waste from the production of chalk, i.e. the increase in active particles of Ca (OH) ₂ contributes to the proposed method;
in the composition of the mixture of the prototype, the leading is mainly calcareous-siliceous substance, and in the inventive slag-calcareous-siliceous substance. The latter is more hydraulically active;
4) the achievement of a lighter tone hardened products is also explained by the application of the proposed method. It is known that during autoclaving from a silicate mixture, light gray products such as the color of silicate brick are formed. This is explained by the formation of calcium hydrosilicates CaO x mSiO ₂ x pH ₂ O, and SiO of ground sand and ash takes an active part in this process. In the process of steaming, the probability of the formation of calcium hydrosilicates is very small, since this mineral is formed only by hydration of low-basic calcium silicates contained in the slag, and therefore the color of the products is dark gray.

In the proposed method, the formation of calcium hydrosilicates in the process of steaming is quantitatively prevailing. This is explained not only by the high content of granular slag in the mixture, but also by the formation of CaO x mSiO ₂ x pH ₂ O in the process of fine grinding in a ball mill in the presence of moisture, because instantaneous high temperature develops during point impacts of balls in places of impacts, which facilitates entry into the reaction of fine sand and silica ash, until the formation of CaO x SiO, i.e. the prepared mass, before molding and steaming, is enriched with calcium hydrosilicates due to SiO silica sand or SiO ash. The hydration process also contributes to the exothermic effect in the volume of the grinding apparatus during the extinguishing of lime.

 The increase in light tone contributes to the waste of chalk production, introduced into the composition of the dry mixture when it is mixed.

The inventive method in comparison with the known has the following technical and economic advantages:
1) reduced energy consumption by 1.5-2.0 times due to the exclusion of drying of materials, reduction of specific surface area;
2) low-activity (low-calcium) brown coal ash and finely dispersed (including finely dispersed substandard grains for concrete) quartz sands with a particle size of less than 1.0-1.5 are utilized;
3) the number of apparatuses (grinding, extinguishing, etc.) is reduced by 1.5-2.0 times;
4) recycled waste production of chalk;
5) to obtain wall products with a brand of 75-1000 products can be molded hollow;
6) the cost of products is reduced due to the positive effects given in paragraphs. 1 - 4, 20-25%.

Claims (1)

A method of preparing products, including preparing a molding mixture by mixing ground quicklime with an activity of at least 75 wt. with ground main blast furnace slag, silica filler and calcium salt, mixing the mixture with an aqueous solution, molding and hardening, characterized in that they preliminarily grind quicklime lump lime with blast primary slag of wet granulation, with theoretical and theoretical humidity sufficient for complete slaking of lime with grinding to a specific surface of not more than 2500 cm ² / g, after which quartz sand or hydraulic dump low-calcium ash is added to the mixture and the house is carried out pouring the mixture to a specific surface of 3000 3200 cm ² / g, and mixing the molding mixture with an aqueous suspension of calcium salt, which is used as waste chalk, in the following ratio of components from the total dry weight of the molding mixture, wt. Blast core slag wet granulation 20 30
Lump quicklime 5 7.5
Quartz sand or hydraulic dump low calcium ash 60 75
Chalk production waste 0.1 0.5
and the hardening of the molding mixture is carried out in the process of natural hardening or steaming.

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