RU2305666C1 - Lime binder, method of preparation of lime binder and method of preparation of silicate mixture on base of lime binder for production of molded articles of autoclave hardening - Google Patents

Abstract

FIELD: manufacture of building materials; manufacture of lime-and-sand brick and wall materials.

SUBSTANCE: proposed method includes mixing of nonground quartz sand and lime binder followed by holding the silicate mixture for slaking lime for at least 3 h without subsequent additional humidification at the following ratio of components, mass-%: nonground quartz sand, 74.40-86.61; lime binder, 13.39-25.60; lime binder contains the following components, mass-%: unslaked lime, 38.84-43.05 and 2.81-9.26-5 aqueous solution of copper vitriol, 56.95-61.16. Solution for production of binder is introduced at temperature of from 0 to 55C during grinding of lime. Binder may contain additive CB-3 in the amount of 0.27-0.32% of its mass. Lime binder may be stores and transported during several hours due to delay of hydration terms.

EFFECT: wide range of means for production of molded articles of autoclave hardening; enhanced compressive strength of articles due to activation of lime binder; avoidance of adhering of lime on mill walls and on milling bodies.

6 cl, 4 tbl, 3 ex

Description

The invention relates to the construction materials industry and can be used in the manufacture of silicate brick and wall materials.

It is known lime-containing binder for the manufacture of silicate brick, consisting of quartz sand and calcined carbonatite (RU 2081861 C1, 6 C04B 28/20). The disadvantage of this analogue is the relative inaccessibility of calcined carbonatite in comparison with conventional calcium lime obtained by calcining limestone or chalk.

A known method of producing a lime-silica binder, consisting in the joint grinding of lime and sand, taken in certain proportions (Technology of products from silicate concrete / A.V. Satalkin. M .: Publishing house of construction literature, 1972. - 335 S.).

The disadvantage of the above two analogues is the use of quartz sand as a component of the binder, because quartz sand is an abrasive material and when grinding a binder it quickly abrades grinding media and the lining of the mill.

A known method of producing a silicate mixture for silicate brick, which consists in processing the mixture in one unit - a rod mill, into the neck of which directly feed all the raw materials, as well as water with a temperature of 120 ° C, or hot steam, or water and steam together in an amount sufficient to completely extinguish the desired molding moisture content of the mixture ready for pressing (RU 2188177 C3 С04В 28/20). The disadvantage of this analogue is the reduced reactivity of lime in the absence of additives.

The closest is a binder in the form of crushed pure quicklime (Vakhnin M.P. Anishchenko A.A. Production of silicate brick. M.: Higher school, 1977. - 160 p. - S. 51-52).

The closest way to obtain a binder is the method of grinding pure quicklime in tube mills. (Vakhnin M.P. Anishchenko A.A. Production of silicate brick. M .: Higher school, 1977. - 160 p. - p. 51-52).

A common disadvantage of the two prototypes listed above is that lime adheres to the walls of the mill and grinding media during grinding, as well as the inability to activate the lime binder as a result of wet grinding due to the unacceptably high humidity required for storage and transportation under industrial conditions of the obtained binder suspension, in which based on such a binder, the silicate mixture is unsuitable for pressing raw material based on it.

The closest is a method of preparing a silicate mixture for the production of silicate brick, which consists in thoroughly mixing the two main components - ground quicklime and natural quartz sand and quenching in silos for 1.5 to 4 hours, after which the raw mixture is additionally moistened to the molding moisture (Mukhina TG Production of silicate brick. A textbook for the training of workers in production. M: Higher school, 1971. - 232 pp. - pp. 96-99).

The disadvantage of this prototype is the low compressive strength obtained on the basis of this silicate mixture of autoclaved products.

In the inventive method for producing a lime binder, as well as for obtaining a silicate mixture based on it, the following tasks are set:

- to delay the hydration of lime for a period that allows you to store and transport the resulting lime binder in an industrial environment, while reducing the moisture of the lime binder obtained by co-grinding water with quicklime;

- activate lime binder as a result of wet grinding and, as a result, increase the compressive strength of the resulting products;

- avoid sticking lime on the walls of the mill and grinding media when grinding it.

The invention is also aimed at increasing the competitiveness of the obtained silicate autoclave products as a result of increasing the compressive strength of up to 30% compared with products based on the silicate mixture of the prototype for a method for preparing a silicate mixture, as well as increasing the arsenal of means for producing silicate autoclaved products.

This task is achieved using a lime binder, including quicklime, which according to the proposed solution additionally contains 2.81-9.26% aqueous solution of copper sulfate, in the following ratio, wt.%:

Quicklime 38.84-43.05 Aqueous solution of copper sulfate 56.95-61.16

The lime binder may additionally contain an additive SB-3 in an amount of 0.27-0.32% by weight of the lime binder.

The objective is achieved by a method of producing a lime binder, including grinding lime, in which according to the proposed solution in the grinding process, an additional 2.81-9.26% aqueous solution of copper sulfate is added, having a temperature of 0-55 ° C, in the following ratio of components, wt.% :

Quicklime 38.84-43.05 Aqueous solution of copper sulfate 56.95-61.16

In the method for producing a lime binder into a binder in the process of grinding the components, an additive SB-3 can be added in an amount of 0.27-0.32% by weight of the lime binder.

The objective is also achieved by a method of producing a silicate mixture for the production of extruded autoclaved products, including mixing non-ground quartz sand and lime binder and subsequent exposure of the mixture to extinguish lime, in which, according to the proposed solution, the obtained silicate mixture is kept for at least 3 hours without subsequent wetting, in the following ratio components, wt.%:

Ground Quartz Sand 74.40-86.61 Lime Binder 13.39-25.60,

while the binder has a composition, wt.%:

Quicklime 38.84-43.05 2.81-9.26% aqueous solution of copper sulfate 56.95-61.16

In the method for producing a silicate mixture for the production of extruded autoclaved hardening products, the lime binder may additionally contain SB-3 additive in an amount of 0.27-0.32% by weight of the lime binder.

The invention consists in delaying the hydration of lime in a lime binder for several hours. Upon receipt of a lime binder as a result of wet grinding of the components (lime, aqueous solution of copper sulfate) in the mill, a moisture content of 53.89 to 55.35% is achieved. As a result of wet grinding of lime with an aqueous solution of copper sulfate, the mobility of the lime binder is preserved. For a suspension of lime binder, a minimum spreadability of more than 60 mm was adopted for the MKHTI TN-2 flowmeter (Butt Yu.M., Timashev V.V. Workshop on the chemical technology of binders. Textbook for chemical and technological specialties of universities. M: Higher school, 1773. 504 p. S. 134), sufficient for its transportation by hydraulic transport and storage under industrial conditions for several hours (at least 3). When using the specified lime binder, it becomes possible to prepare a silicate mixture by dosing and mixing the obtained lime binder with non-ground quartz sand with a sufficiently low humidity of the silicate mixture (after preliminary exposure to complete hydration of lime in the mixture) and obtaining pressed autoclaved hardened products. The obtained calcareous binder retains its flowing properties for several hours, necessary for carrying out the corresponding technological processes in the preparation of the finished silicate mixture. This technical result is achieved as a result of the action of an aqueous solution of copper sulphate on lime with wet grinding of a lime binder, which allows to reduce the amount of water (by 12-16%) in the composition of the lime binder while maintaining the necessary rheological properties. The aqueous solution of copper sulphate, in addition, allows the mechanical activation of the resulting lime binder as a result of wet grinding, which leads to increased compressive strength of the resulting autoclaved products, and also prevents the negative effect of lime sticking to the mill walls and grinding media during grinding.

The bulk of the lime in the resulting lime binder is in an unhydrated state. Lime hydration occurs after a few hours, when the lime binder should be mixed with ground sand, binding part of the water to calcium hydroxide, which further reduces the moisture content of the entire silicate mixture and brings it to condition. The above effect of an aqueous solution of copper sulfate on quicklime is not mentioned in the scientific and technical literature. It is impossible to assume such an effect of copper sulfate on quicklime during wet grinding, relying on the properties of lime and an aqueous solution of copper sulfate already studied, which proves compliance with the criterion of "inventive step". The achievement of this criterion is confirmed by the receipt of a flowing lime binder with a moisture content of 53.89-55.35% while maintaining unhydrated lime in the mixture for more than 3 hours, which allows to reduce the final moisture content of the inventive silicate mixture to the required limit. If there is no mixing of copper sulfate in the water, the required fluidity of the suspension of lime binder is achieved when the moisture of the lime binder is in the range of 67-70% (without taking into account the loss of water for hydration). The use of such a calcareous binder leads to a finished silicate mixture with a moisture content of 16-20%, which is unacceptable, because causes the release of water when pressing raw. The use of wet grinding allows you to activate the lime binder, which leads to increased compressive strength obtained on the basis of the inventive lime binder autoclaved products.

The authors found that the temperature of the used solution of copper sulfate should be from 0 ° C to 55 ° C. When the temperature of the solution rises above 55 ° C, hydration and thickening of the lime binder occurs in the mill or within a few minutes after unloading, which will not allow carrying out technological processes of storage and transportation of the lime binder in a fluid state. When the concentration of an aqueous solution of copper sulfate is greater than 9.26%, or when the amount of an aqueous solution of copper sulfate is less than 56.95%, the lime binder loses fluidity, which will not allow such technological operations as transportation by hydrotransport, storage in sludge pools and mixing of the binder with ground sand. When using an aqueous solution of a lower concentration than 2.81% within the established limits of its quantity, a delay in the hydration of lime in the lime binder does not occur, which also leads to thickening of the lime binder in the mill or after unloading.

If it is necessary to further increase the retention time of the flowing properties of the proposed lime binder, SB-3 additive (GOST 10534-78. Sulfonate additive SB-3) is used, which increases the delay in hydration of lime in a lime binder by a factor of 1.5-2, caused by an aqueous solution of copper vitriol. SB-3 additive is introduced together with the other components of the lime binder (lime, aqueous solution of copper sulfate) in the mill during grinding. The specified additive in an amount below the established limit does not delay the hydration of lime in a lime binder, obtained in accordance with the claimed method. The more SB-3 additives in the lime binder, the longer the hydration of lime in the lime binder is delayed. The maximum content of SB-3 in a lime binder is limited by economic considerations and is determined by the technologically necessary delay time for lime hydration and maintaining the fluidity of the suspension of lime binder.

In contrast to the prototype for a method of preparing a silicate mixture, the inventive silicate mixture, in the process of its preparation does not need additional moisture. The moisture content of the obtained silicate mixture after lime hydration is reduced, because part of the water reacts with lime. The loss of moisture by the silicate mixture during production processes does not adversely affect the quality of the products obtained, since the moisture content of the silicate mixture remains within the permissible limits and allows the raw material to be molded from it by pressing.

The following are examples of the use of the proposed method for producing silicate mixtures for producing silicate extruded articles of autoclave hardening. The experiments were carried out in laboratory conditions using a 0.7 L laboratory ball mill, a hydraulic press and a laboratory autoclave. The results of the experiments are aimed at proving the industrial applicability of the proposed method of preparing a silicate mixture on the example of extruded autoclaved products. Data on the strength characteristics of samples obtained from a silicate mixture prepared in accordance with the inventive method for producing a silicate mixture, are compared with the data of silicate products obtained from a silicate mixture prepared in accordance with the prototype for a method for preparing a silicate mixture.

It is not possible to use lime binder prepared by grinding lime and water for comparison, because with the joint grinding of water and lime without the content of copper sulphate dissolved in the prescribed limits within the water, the effect of delayed hydration of lime is observed only for a period of up to 20-21 minutes. Thus, when unloading the resulting lime suspension, it continues to hydrate and lose flowing properties. This effect does not allow to keep the flowing lime binder in production. Even when a lime binder is obtained without copper sulfate dissolved in water as a result of a longer grinding (up to 20-21 minutes), the moisture of the lime binder does not allow the silicate mixture to be prepared on its basis, which will not give water separation during pressing.

The compositions of the starting components are shown in tables 1 and 2.

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 calcareous binder and silicate mixture.

35 g (43.05%) of quicklime and 46.3 g (56.95%) of a previously prepared 2.81% aqueous solution (solution temperature was 25 ° C) of copper sulfate were loaded into a laboratory mill, and grinding was performed for 10 minutes. The obtained lime binder was unloaded from the mill and stored for 1 hour. Then, a silicate mixture was obtained by dosing and mixing 73 g (79.44%) of non-ground quartz sand with 18.9 g (20.56%) of lime binder, the resulting silicate mixture was aged until the lime hydration was completely completed in the mixture (5 hours) without subsequent wetting. The moisture content of the obtained silicate mixture is 9.11% (taking into account moisture loss on hydration).

Samples were prepared from the obtained silicate mixture by pressing on a laboratory hydraulic press at a pressure of 20 MPa in the form of cylinders 30 mm high and 20 mm in diameter.

The obtained samples were subjected to hydrothermal treatment at a vapor pressure of 0.8 MPa with an isothermal exposure of 6 hours. The data are shown in table 4, example 1.2.

The strength of the obtained sample was 13.6 MPa.

To assess the effectiveness of the use of the proposed method for the preparation of silicate mixtures, a series of experiments was carried out, during which mixtures with different ratios of components were prepared to assess the possible boundary values of the content of components. The data are shown in table 3, compositions 1-4. By experience, the maximum and minimum possible ratios of non-ground quartz sand and lime binder were established, at which it is possible to obtain raw material by pressing, suitable for further autoclave processing. Such ratios of quartz sand and calcareous binder are limited by the maximum allowable final moisture content of the mixture of 8-12%. The data corresponding to the compressive strengths of the obtained samples are summarized in table 4, compositions 1.1-2.3.

An example of a specific implementation 2.

This example shows the possibility of using additives SB-3 for the preparation of calcareous binder and silicate mixtures based on it.

35 g (43.05%) of quicklime and 46.3 g (56.95%) of a pre-prepared 2.81% aqueous solution (solution temperature was 25 ° C) of copper sulfate, 0.26 g (0.26 g) were loaded into a laboratory mill 0.32% of the mass of lime binder) additives SB-3, and grinding was performed within 10 minutes. The obtained lime binder was unloaded from the mill and stored for the required 5 hours (Table 3, example 5). Next, a silicate mixture was obtained by dosing and mixing 76 g (75.10%) of non-ground quartz sand with 24.2 g (24.9%) of lime binder, the resulting silicate mixture was kept in a silicate mixture silo until the hydration of lime in the silicate mixture was complete (24 hours) without subsequent wetting. Samples from the obtained silicate mixture were prepared in a known manner in accordance with example 1. The moisture content of the obtained silicate mixture is 10.66% (taking into account moisture loss on hydration).

The data are shown in table 4, example 5.2.

The strength of the obtained sample was 11.73 MPa.

To assess the effectiveness of the use of the proposed method of preparing a silicate mixture, a series of experiments was carried out, during which a number of mixtures with different ratios of components were prepared to assess the possible boundary values of the content of components together with SB-3 additive. The data are shown in table 3, compositions 5-6.

The compressive strength data of the obtained samples are summarized in table 4, compositions 5.1-6.2.

An example of a specific implementation 3 is given to compare the characteristics of the mixtures proposed by the authors and the products prepared on their basis with the mixture and product obtained in accordance with the prototype for a method for producing a silicate mixture (dry method).

The dry method for producing a silicate mixture consisted of the following operations. 35 g (100%) of quicklime ground in a laboratory ball mill until a specific binder surface of about 400-420 m ² / kg (10 minutes) is reached (Table 3, composition 10). Next, 10 g (10%) of the obtained binder was mixed with 90 g (90%) of non-ground sand and the resulting mixture was wetted to a molding moisture of 6.5-7% (taking into account the loss of water due to hydration and evaporation). Next, the silicate mixture was kept under airtight conditions until hydration of lime in the mixture occurred.

Samples were made from the obtained silicate mixture and subjected to hydrothermal treatment in accordance with Example 1. The compressive strength of such samples was 7.55 MPa. The data are shown in table 4, example 10.1.

Table 4 Compositions of silicate mixtures and strength characteristics of autoclaved products obtained on their basis Silicate composition No. The composition of the silicate mixture, wt.% SB-3,% by weight of the binder Compressive strength, MPa Mixture endurance, hour Press water separation Sand quartz ground Lime Binder 1.1 * 86.61 13.39 0 6.5 24 No 1.2 79.44 20.56 0 13.6 5 No 1.3 75,10 24.9 0 16,0 8 No 1.4 86.61 13.39 0 no 2.5 No 2.1 79.00 21 0 12.9 3 No 2.2 74.40 25.6 0 15.0 5 No 2.3 73.5 26.5 0 no 5 there is 5.1 86.61 13.39 0.32 6.13 5 No 5.2 75,10 24.9 0.32 11.73 24 No 5.3 73.5 26.5 0.32 no 24 there is 6.1 79.00 21 0.27 9.98 24 No 6.2 74.40 25.6 0.27 13.83 24 No 10.1 90 10 0 7.55 3 No * The first number to the point in the composition number of the silicate mixture corresponds to the composition number of the binder used in table 3.

The required amount of copper sulfate added to the composition of the inventive calcareous binder aqueous solution, its concentration, the amount of SB-3 additive added depend on the amount and activity used in the preparation of quicklime and was determined empirically for each composition.

As can be seen from tables 3 and 4, the amount of 2.81-9.26% aqueous solution of copper sulfate (as well as its concentration) should be within the established limits and make up 56.95-61.16% of the mass of lime binder (Table 3 , compositions 1, 2, 5, 6), below which the lime binder cannot be stored for a long time in a fluid state (Table 3, compositions 3, 4, 7, 8). When using an aqueous solution of copper sulfate during wet grinding, it became possible to reduce the moisture of the lime binder from 60-70%, which would be necessary until the fluid state of the lime binder without an aqueous solution of copper sulfate, to 53.89-55.35% (without loss of moisture) for hydration) with the preservation of lime binder necessary fluidity and the possibility of storage in this state for 3-10 hours. From table 3 it follows that the effect of the aqueous solution of copper sulfate in the composition of the calcareous binder is manifested in the amount of not less than the established limits (Table 3, composition 1). Below this limit, the hydration time of lime is significantly reduced (Table 3, composition 3). The maximum limit of the content of copper sulfate in the aqueous solution is limited by the fact that at high concentrations relative to the mass of the lime binder, its fluid properties are lost and it becomes impossible to transport the lime binder by hydraulic transport in industrial conditions (Table 3, compositions 3, 7). An increase in the amount of an aqueous solution of copper sulfate above the limit set in the application causes an increase in the moisture content of the silicate mixture to the limits at which water separation is observed when pressing raw, which is defective.

When using the SB-3 additive, it is possible to extend the fluid state of the lime binder for up to 8-10 hours. The minimum amount of SB-3, which makes sense to add to extend the flowing state of the lime binder, is 0.27% by weight of the lime binder (Table 3, formulations 6). The minimum limit of the content of SB-3 additive is due to the fact that with a decrease in its amount, an extension of the delay in the hydration of lime is not observed (not shown in the table).

The maximum content of SB-3 in a lime binder is limited by technological and economic considerations and is determined by the specified required time for delaying the hydration of lime and maintaining the fluidity of the suspension of lime binder (Table 3, composition 5). When the concentration of SB-3 additive is within the established limits, the hydration delay time increases by 1.5–2 times.

When using an aqueous solution of copper sulfate with a temperature of more than 55 ° C, the fluid properties of the resulting lime binder are lost as a result of hydration of lime in the mill during joint grinding (Table 3, composition 9).

When the silicate mass is kept for less than 3 hours, cracks and bulges appear on the raw surface, which leads to a decrease in the strength of the samples obtained after hydrothermal treatment to unacceptably low values or their complete destruction. Exposure to a silicate mixture longer than the specified amount of time does not entail a negative effect on the strength of the resulting extruded autoclaved products. The exposure time of the silicate mixture until complete hydration of lime in the silicate mixture is determined empirically and depends on the activity of the lime binder and the ratio of the amount of lime in the lime binder, the amount of SB-3 added to the composition of the lime binder and copper sulfate dissolved in water. The exposure time of the silicate mixture depends on the time required for the complete hydration of lime in the lime binder minus the storage time of the lime binder before it is introduced into the silicate mixture. The time of complete hydration of lime is determined empirically. For example, if the time for the complete hydration of lime in a lime binder is 5 hours, and 2 hours have passed from the time the lime binder was obtained, then the mixture must be aged for at least 3 hours. For example: a lime binder of composition 1 from table 3 was prepared. This lime binder was aged 2.5 hours, after which it was introduced into the silicate mixture. Samples were pressed from the obtained silicate mixture (in accordance with Example 1). After 1.5 hours, the samples were covered with cracks and bulges, i.e. turned out to be completely unsuitable for their further use. A similar situation is observed with the rest of the compositions in the case when the exposure time of the silicate mixture is less than the time for which the lime in the lime binder does not completely hydrate. The authors found that for the lime binder proposed in the claimed solution, the minimum exposure time is 3 hours. The maximum exposure time of the lime binder is not more than 10 hours.

When using a larger amount of lime binder than 25.60% by weight of the silicate mixture, water separation occurs when pressing raw material, which is unacceptable and is a defect (Table 4, compositions 2.3 and 5.3). With a smaller amount of calcareous binder than 13.39%, the formability of the silicate mixture is significantly reduced by pressing raw (not shown in the table).

Claims (6)

1. Lime binder, including quicklime, characterized in that the lime binder further comprises a 2.81-9.26% aqueous solution of copper sulfate in the following ratio, wt.%: Quicklime 38.84-43.05 Aqueous solution of copper sulfate 56.95-61.16 2. Lime binder according to claim 1, characterized in that it further comprises an additive SB-3 in an amount of 0.27-0.32% by weight of the binder. 3. A method of obtaining a lime binder, including grinding quicklime, characterized in that during the grinding process, an additional 2.81-9.26% aqueous solution of copper sulfate is added, having a temperature of 0-55 ° C, in the following ratio of components, wt.% : Quicklime 38.84-43.05 Aqueous solution of copper sulfate 56.95-61.16 4. The method of producing a lime binder according to claim 3, characterized in that in the process of grinding the components, an SB-3 additive is additionally added to the lime binder in an amount of 0.27-0.32% by weight of the lime binder. 5. A method of producing a silicate mixture for the production of extruded autoclaved hardened products, comprising mixing non-ground quartz sand and lime binder and subsequent exposure of the mixture to extinguish lime, characterized in that the resulting silicate mixture is held for at least 3 hours without subsequent wetting in the following ratio of components, wt .%: Ground Quartz Sand 74.40-86.61 Lime Binder 13.39-25.60 while the lime binder has a composition, wt.%: Quicklime 38.84-43.05 2.81-9.26% aqueous solution copper sulfate 56.95-61.16 6. A method of producing a silicate mixture for the production of extruded autoclaved hardened products according to claim 5, characterized in that the lime binder further comprises SB-3 additive in an amount of 0.27-0.32% by weight of the lime binder.