A kind of high-strength slag unburned ceramsite and preparation method thereof

Abstract

The present invention discloses a high-strength slag unfired ceramsite and a preparation method thereof, and belongs to the technical field of building materials. The high-strength slag unfired ceramsite of the present invention is composed of an internal core and a wrapping shell, wherein the internal core is an oblate structure obtained by extrusion granulation, and the wrapping shell is wrapped on the surface of the internal core, and its outer shape is an equiaxial structure, and a plurality of pits are formed on the surface of the wrapping shell. The present invention effectively improves the structural strength of the unfired ceramsite through structural optimization without adding more cementitious materials, which is conducive to improving the utilization rate of slag and plays a role in absorbing a large amount of slag.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and particularly relates to a high-strength and high-binding-strength slag unfired ceramsite and a preparation method thereof. Background Art

[0002] Engineering waste is a component of construction waste, mainly from real estate construction projects, underground pipeline corridor projects and subway projects. Most of the engineering waste is usually transported to waste disposal sites for storage. If the engineering waste is not effectively utilized, the amount of waste will increase. In addition, the waste disposal site requires personnel management and occupies a large amount of land. If it is not properly handled, it will cause environmental and economic problems. At present, the method of resource utilization of engineering waste is usually to use fly ash and garbage incineration ash as cementing materials, solidify the engineering waste, and then sinter it in a rotary kiln to prepare ceramsite, or sinter it in a tunnel kiln to make porous sintered bricks.

[0003] For example, Chinese patent 201110241100.X discloses a ceramsite and a method for preparing it, and Chinese patent 201710204695.9 discloses a method for preparing lightweight ceramsite using slag, but the energy consumption, carbon emissions and processing costs of the above-mentioned methods for preparing sintered ceramsite and sintered bricks are relatively high. In addition, some researchers have also tried to use slag as a raw material to process it into unfired ceramsite, but the proportion of cementitious materials and mineral admixtures in the ingredients of unfired ceramsite is relatively large. For example, Chinese patent CN111170710A discloses a high-strength unfired ceramsite and a method for preparing it. The cylinder compressive strength of the high-strength unfired ceramsite is as high as 5 to 10 MPa, but the proportion of slag is only 50 to 70%.

[0004] Therefore, reducing the proportion of cementitious materials in unfired expanded clay and increasing the amount of slag added are of great significance for large-scale disposal of slag and protection of sand and gravel resources. Summary of the invention

[0005] 1. Problem to be solved

[0006] The purpose of the present invention is to provide a high-strength slag unfired ceramsite and a preparation method thereof, so as to solve the problem that a high proportion of cementitious materials need to be added to the existing unfired ceramsite and the utilization rate of slag is low.

[0007] 2. Technical solution

[0008] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0009] The invention discloses a high-strength slag unfired ceramsite, which consists of an inner core and a wrapping shell, wherein the inner core is an oblate structure obtained by extrusion granulation, the wrapping shell is wrapped around the surface of the inner core, and its outer shape is an equiaxial structure, and a plurality of pits are formed on the surface of the wrapping shell.

[0010] At present, there have been studies on the application of slag to unfired ceramsite, thereby realizing the resource utilization of slag. However, in the prior art, due to the limitation of the slag's own strength, it is usually necessary to add more cementitious materials, and the utilization rate of slag is relatively low. Based on this situation, the present invention optimizes the structure of slag unfired ceramsite and designs it into a double-layer structure, wherein the internal core is an oblate structure obtained by extrusion granulation molding, and the external part of the internal core is wrapped to form an equiaxial outer shell, so that the structural strength of unfired ceramsite can be effectively guaranteed, so that the amount of cementitious materials can be reduced, the amount of slag in unfired ceramsite can be increased, and the utilization rate of slag can be improved. At the same time, the surface of the wrapped shell is formed with a number of pits, so that the contact area with the cement paste can be increased, the fluidity of the concrete is formed to remain unchanged, and the concrete grade and durability are enhanced due to the enhanced aggregate bond strength.

[0011] Specifically, the cylinder compressive strength of the unfired ceramsite after curing for 28 days in a humid environment with a relative humidity of more than 90% is 8 to 15 MPa, or the cylinder compressive strength of the unfired ceramsite after curing for 5 to 10 hours under hydrothermal conditions with a water vapor pressure of 5 to 10 atm is 10 to 20 MPa.

[0012] Furthermore, the ingredients of the inner core and the outer shell both contain soil solidifier and slag, wherein the slag accounts for 90-94% of the ingredients of the inner core and the soil solidifier accounts for 6-10%, the slag accounts for 85-90% of the ingredients of the outer shell and the soil solidifier accounts for 10-15%, and the mass of the inner core accounts for 30%-70% of the total weight of the unfired expanded clay.

[0013] The present application further optimizes the material composition and mass ratio of the inner core and the outer shell of the unfired expanded clay, thereby maximizing the amount of slag added and the utilization rate while simultaneously meeting the different strength requirements of the inner and outer layers of the unfired expanded clay.

[0014] Furthermore, adhesive solution is added to the ingredients of the inner core and the outer shell, wherein the ratio of the adhesive solution in the inner core is 16-20% of the total weight of the soil solidifier and the slag, and the ratio of the adhesive solution in the outer shell is 12-16% of the total weight of the soil solidifier and the slag.

[0015] Furthermore, the soil solidifier in the present application is preferably a composite cementitious material composed of ordinary Portland cement and persulfate cement, wherein the Portland cement is at least one of Portland cement, ordinary Portland cement, fly ash Portland cement, slag Portland cement, steel slag slag Portland cement, and composite Portland cement, the cement grade is ≥ 42.5, and the mass proportion of Portland cement is 20-50%, and the mass proportion of persulfate cement is 50-80%. The adhesive in the present application is preferably polyvinyl alcohol, sodium carboxymethyl cellulose or methyl cellulose, and the concentration of the adhesive solution is 1% to 1 / 1000. However, it should be noted that the soil solidifier and adhesive are not limited to the above-mentioned specific substances, and other existing soil solidifiers and adhesives can also be used.

[0016] The present invention also provides a method for preparing the high-strength slag unfired ceramsite, comprising:

[0017] S1, a step of preparing an oblate inner core by using an extrusion granulation molding process;

[0018] S2, a step of granulating and molding the surface of the inner core to obtain a wrapping shell with an equiaxial shape; and

[0019] S3, a step of forming a plurality of pits on the surface of the wrapping shell.

[0020] The existing unfired ceramsite is prepared by roller pressing granulation or extrusion granulation, or rolling granulation in a balling disk. The former two will result in a smooth surface of the ceramsite, and the gripping force is lower than that of natural aggregates. The latter takes a long time to form, and the cylinder pressure strength of the unfired ceramsite is low. Based on the above situation, the present application first prepares an oblate internal core through an extrusion granulation forming process, thereby effectively improving the structural strength of the internal core. Therefore, on the one hand, the amount of slag can be increased, and on the other hand, it is convenient for subsequent rapid granulation to obtain an equiaxial outer shell, and the ceramsite forming speed is accelerated.

[0021] Furthermore, in step S1, the ingredients of the inner core are mixed evenly and then added together into a roller granulator for extrusion granulation; in step S2, a disc granulator is used for molding, the inner core is fed into an inclined disc, and at the same time, the mixture of slag and soil curing agent in the outer shell ingredients is fed into the disc, and the adhesive solution is continuously sprayed on the surface of the above mixture in the form of a spray during the rotation of the disc. Under the action of the friction between the powder and the disc, the core material rises with the rotation of the disc, and rolls downward under the action of gravity, and is thrown to the edge of the disc due to the centrifugal force, so that the mixture of slag and soil curing agent in the outer shell ingredients wraps the inner core into an equiaxed ceramsite body with increased size due to the capillary force.

[0022] Furthermore, in step S2, the rotation speed of the disc is controlled to be 10 to 20 rpm, preferably 15 to 20 rpm, and the molding time of the wrapped shell is 3 to 5 minutes, which greatly shortens the molding time.

[0023] Furthermore, in step S3, a rotating drum is used for processing, and the inner wall of the rotating drum is provided with a plurality of needle puncture protrusions. When the ceramsite body reaches the designed size, it exits the disc granulator and enters the rotating drum. The pointed needle puncture protrusions on the inner surface of the drum modify the surface of the ceramsite body into a surface with multiple pits, and the equiaxial shape of the ceramsite body does not change. The density of the outer layer of the dense core is further improved under the centrifugal force of the ball-forming disk and the rotating drum, so that the density of the entire ceramsite body is improved, thereby obtaining improved mechanical properties. The unfired ceramsite body exiting the drum has a cylinder pressure strength of 8 to 15 MPa after curing for 28 days in a humid environment with a relative humidity of more than 90%, or curing for 5 to 10 hours under the hydrothermal conditions of a water vapor pressure of 5 to 10 atm to become an unfired ceramsite finished product with a cylinder pressure strength of 10 to 20 MPa.

[0024] Furthermore, the height of the needle protrusions is 2 to 3 mm, and each needle protrusion is arranged in a field shape or a triangle shape with a distance of 10 to 20 mm from the surrounding needle protrusions (the field shape means that adjacent needles are arranged at the four vertices of a square, and the triangle shape means that adjacent needles are arranged at the three vertices of a triangle).

[0025] In summary, compared with the prior art, the present invention can achieve the following beneficial effects:

[0026] (1) The present invention adopts an extrusion granulation molding process to prepare an oblate inner core, and then wraps the inner core to form an equiaxial outer shell, so that the structural strength of the unfired expanded clay can be effectively improved through structural optimization without adding more cementitious materials, which is beneficial to improving the utilization rate of the slag and playing a role in absorbing a large amount of slag.

[0027] (2) In the present invention, a plurality of pits are formed on the outer shell surface of the unfired expanded clay aggregate, thereby increasing the contact area with the cement paste, resulting in the fluidity of the concrete being unchanged, thereby enhancing the concrete grade and durability due to the enhanced aggregate bonding strength; at the same time, the present invention further preferably adopts a rotating drum with needle-pierced protrusions on the inner surface to shape the pits on the outer shell surface, which is also beneficial to further improve the density of the entire unfired expanded clay aggregate.

[0028] (3) The present invention first adopts an extrusion granulation molding process to prepare an oblate inner core, so that an equiaxial outer shell can be quickly wrapped on the surface of the inner core by a ball-forming disk, and the desired particle size can be formed in the molding disk within 5 minutes, which significantly improves the molding speed and molding efficiency of the expanded clay.

[0029] (4) The cylinder compressive strength of the unfired expanded clay obtained by the present invention is relatively high, which can reach 20 MPa. In addition, the silicon and aluminum components in the unfired expanded clay will precipitate and react with the calcium hydroxide in the cement paste when cracks appear in the concrete. The reaction products can fill the cracks and have the function of self-repairing the concrete structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The process flow chart of the method for preparing high-strength slag unburned ceramsite of the present invention;

[0031] Figure 2 It is a schematic diagram of the structure of the rotating drum used in the present invention.

[0032] In the figure: 1. drum body; 2. lining plate; 3. needle-punched protrusions. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with specific embodiments.

[0034] Example 1

[0035] The preparation method of the high-strength slag unburned ceramsite of this embodiment is as follows Figure 1 As shown, the process steps include:

[0036] (1) Ingredients

[0037] The slag unburned ceramsite is composed of two parts tightly combined, namely the inner core A and the wrapping shell B, the inner core A accounts for 30% of the mass of the whole ceramsite, and the rest is the wrapping shell B. Among them, the ingredients of the inner core A and the wrapping shell B are composed of soil curing agent, slag and adhesive solution. The mass proportions of each component in the ingredients of the inner core A are: soil curing agent is 6%, slag is 94%, and adhesive solution accounts for 16% of the sum of the mass of the first two. The mass proportions of each component in the ingredients of the wrapping shell B are: soil curing agent is 10%, slag is 90%, and adhesive solution accounts for 12% of the sum of the mass of the first two.

[0038] In this embodiment, the soil solidifying agent in ingredients A and B is a composite cementitious material composed of silicate cement and persulfate cement, wherein silicate cement accounts for 20% and persulfate cement accounts for 80%, and the silicate cement is 52.5 silicate cement. The adhesive solution adopts a polyvinyl alcohol solution, and the mass concentration of polyethylene is 1%.

[0039] (2) Forming of ceramsite body

[0040] The A ingredient is added into a mixer and mixed evenly, and then fed into a roller granulator for extrusion granulation into an oblate core. After the surface of the core material is sprayed and moistened, it is fed into the inclined disc of the disc granulator, and the mixture of the slag and the soil curing agent in the B ingredient is fed at the same time. The mixing time is 3 minutes. During the rotation of the disc, the polymer solution is sprayed onto the surface of the mixture of the slag and the soil curing agent in the B ingredient in the disc in the form of a spray. The rotation speed of the disc is 15 rpm. The amount of the adhesive solution continuously sprayed accounts for 12% of the feed amount of the mixture of the slag and the soil curing agent in the B ingredient. Under the friction between the powder and the disc, the core material rises with the rotation of the disc, and rolls downward under the action of gravity. At the same time, it is thrown to the edge of the disc due to the centrifugal force, so that the mixture of the B ingredient wraps the core material into an equiaxed ceramsite body with an increased size due to the capillary force.

[0041] (3) Forming of pits on the surface of ceramsite

[0042] When the required size is reached, the ceramsite body exits the disc granulator and enters a drum. Under the action of the pointed needle puncture protrusions on the inner surface of the drum, the surface of the ceramsite body is modified into a surface with many pits, while the equiaxial shape of the ceramsite body does not change. The cylinder pressure strength of the unfired ceramsite body exiting the drum is 15MPa after curing in a humid environment with a relative humidity of more than 90% for 28 days, and the particle size of the unfired ceramsite is 6mm.

[0043] like Figure 2 As shown, the drum includes a drum body 1, a lining plate 2 is arranged inside the drum body 1, and a plurality of needle-punctured protrusions 3 are arranged on the inner surface of the lining plate 2. The height of the needle-punctured protrusions 3 is 3 mm, and each needle-punctured protrusion is distributed in a field shape with a distance of 15 mm from the surrounding needle-punctured protrusions. Under the action of the centrifugal force formed by the rotation of the drum, the closely arranged needle-punctured protrusions 3 on the lining plate 2 press the surface of the ceramsite blank passing through into multiple pits, and make the outer shell of the ceramsite blank further dense.

[0044] Example 2

[0045] The method for preparing high-strength slag unburned ceramsite of this embodiment comprises the following process steps:

[0046] (1) Ingredients

[0047] In the high-strength slag-free ceramsite of this embodiment, the inner core A accounts for 70% of the mass of the whole ceramsite, and the outer shell B accounts for 30% of the mass of the whole ceramsite. The soil curing agent accounts for 10% of the ingredients of the inner core A, the slag accounts for 90%, and the adhesive solution accounts for 20% of the sum of the mass of the first two. The mass of the soil curing agent accounts for 15% of the ingredients of the outer shell B, and the slag accounts for 85%.

[0048] The soil solidifying agent of this embodiment is a composite cementitious material composed of ordinary Portland cement and persulfate cement, wherein the proportion of Portland cement is 50%, the proportion of persulfate cement is 50%, and the Portland cement is 42.5 ordinary Portland cement. The adhesive solution adopts a methylcellulose solution, and the mass concentration of methylcellulose is 1 / 1000.

[0049] (2) Forming of ceramsite body

[0050] The A ingredient is added to a mixer and stirred evenly, and then fed into a roller granulator to be extruded and granulated into an oblate core. After the surface of the core material is sprayed and moistened, it is fed into the inclined disc of a disc granulator to form a wrapped shell. The specific molding process is the same as that in Example 1. In this embodiment, the rotation speed of the disc is 20 rpm, and the amount of adhesive solution continuously sprayed accounts for 15% of the feed amount of the mixture of the B ingredient slag and soil solidifier, and the molding time of the wrapped shell is 5 minutes.

[0051] (3) Forming of pits on the surface of ceramsite

[0052] When the required size is reached, the ceramsite body exits the disc granulator and enters the drum, and the surface of the ceramsite body is modified into a surface with multiple pits. In this embodiment, the height of the acupuncture protrusions is 2 mm, and each acupuncture is distributed in a triangle with a distance of 10 mm from the surrounding acupunctures. The unfired ceramsite body exiting the drum is cured for 10 hours under the hydrothermal condition of a water vapor pressure of 10 atm to become an unfired ceramsite finished product with a drum pressure strength of 20 MPa, and the particle size of the unfired ceramsite is 5 mm.

[0053] Example 3

[0054] The method for preparing high-strength slag unburned ceramsite of this embodiment comprises the following process steps:

[0055] (1) Ingredients

[0056] In the high-strength slag-free ceramsite of this embodiment, the inner core A accounts for 60% of the mass of the whole ceramsite, and the outer shell B accounts for 40% of the mass of the whole ceramsite. The soil curing agent accounts for 8% of the ingredients of the inner core A, the slag accounts for 92%, and the adhesive solution accounts for 18% of the sum of the masses of the former two. The soil curing agent accounts for 10% of the mass of the ingredients of the outer shell B, and the slag accounts for 90%.

[0057] In the soil solidifier of this embodiment, silicate cement accounts for 40%, persulfate cement accounts for 60%, and the silicate cement is 42.5 ordinary silicate cement. The adhesive solution adopts methyl cellulose solution, and the mass concentration of methyl cellulose is 0.2%.

[0058] (2) Forming of ceramsite body

[0059] The A ingredient is added to a mixer and stirred evenly, and then fed into a roller granulator to be extruded and granulated into an oblate core. After the surface of the core material is sprayed and moistened, it is fed into the inclined disc of a disc granulator to form a wrapped shell. The specific molding process is the same as that in Example 1. In this embodiment, the rotation speed of the disc is 18 rpm, and the amount of adhesive solution continuously sprayed accounts for 16% of the feed amount of the mixture of the B ingredient slag and soil solidifier, and the molding time of the wrapped shell is 4 minutes.

[0060] (3) Forming of pits on the surface of ceramsite

[0061] When the required size is reached, the ceramsite body exits the disc granulator and enters the drum, and the surface of the ceramsite body is modified into a surface with multiple pits. In this embodiment, the height of the needle puncture protrusions 3 is 3 mm, and each needle puncture is distributed in a triangle with a distance of 20 mm from the surrounding needle punctures. The unfired ceramsite body exiting the drum is cured for 5 hours under the hydrothermal condition of a water vapor pressure of 5 atm to become an unfired ceramsite finished product with a drum pressure strength of 12 MPa, and the particle size of the unfired ceramsite is 8 mm.

[0062] Example 4

[0063] The method for preparing high-strength slag unburned ceramsite of this embodiment comprises the following process steps:

[0064] (1) Ingredients

[0065] In the high-strength slag unfired ceramsite of this embodiment, the inner core A accounts for 50% of the mass of the whole ceramsite, and the outer shell B accounts for 50% of the mass of the whole ceramsite. The soil curing agent accounts for 9% of the ingredients of the inner core A, the slag accounts for 91%, and the adhesive solution accounts for 20% of the sum of the masses of the first two. The soil curing agent accounts for 12% of the mass of the ingredients of the outer shell B, and the slag accounts for 88%.

[0066] In the soil solidifier of this embodiment, silicate cement accounts for 40%, persulfate cement accounts for 60%, and the silicate cement is 42.5 ordinary silicate cement. The adhesive solution uses sodium carboxymethyl cellulose solution, and the mass concentration of sodium carboxymethyl cellulose is 1 / 1000.

[0067] (2) Forming of ceramsite body

[0068] The A ingredient is added to a mixer and stirred evenly, and then fed into a roller granulator to be extruded and granulated into an oblate core. After the surface of the core material is sprayed and moistened, it is fed into the inclined disc of a disc granulator to form a wrapped shell. The specific molding process is the same as that in Example 1. In this embodiment, the rotation speed of the disc is 20 rpm, and the amount of adhesive solution continuously sprayed accounts for 16% of the feed amount of the mixture of the B ingredient slag and soil solidifier, and the molding time of the wrapped shell is 3 minutes.

[0069] (3) Forming of pits on the surface of ceramsite

[0070] When the required size is reached, the ceramsite body exits the disc granulator and enters the drum, and the surface of the ceramsite body is modified into a surface with multiple pits. In this embodiment, the height of the acupuncture protrusions is 2 mm, and each acupuncture is distributed in a triangle with a distance of 10 mm from the surrounding acupunctures. The unfired ceramsite body exiting the drum is cured for 10 hours under the hydrothermal condition of a water vapor pressure of 10 atm to become an unfired ceramsite finished product with a drum pressure strength of 18 MPa, and the particle size of the unfired ceramsite is 10 mm.

Claims

1. A high-strength slag unburned ceramsite, characterized in that: The unfired ceramsite is composed of an inner core and a wrapping shell, wherein the inner core is an oblate structure obtained by extrusion granulation, the wrapping shell is wrapped around the surface of the inner core, and its outer shape is an equiaxial structure, and a plurality of pits are formed on the surface of the wrapping shell; The ingredients of the inner core and the outer shell both contain soil solidifier and slag, wherein the slag accounts for 90-94% of the ingredients of the inner core and the soil solidifier accounts for 6-10%, the slag accounts for 85-90% of the ingredients of the outer shell and the soil solidifier accounts for 10-15%, and the mass of the inner core accounts for 30%-70% of the total weight of the unfired ceramsite.

2. The high-strength slag unburned ceramsite according to claim 1, characterized in that: The cylinder compressive strength of the unfired ceramsite after curing for 28 days in a humid environment with a relative humidity of more than 90% is 8-15 MPa, or the cylinder compressive strength after curing for 5-10 hours under hydrothermal conditions with a water vapor pressure of 5-10 atm is 10-20 MPa.

3. The high-strength slag unburned ceramsite according to claim 2, characterized in that: Adhesive solution is added to the ingredients of the inner core and the outer shell, wherein the ratio of the adhesive solution in the inner core is 16-20% of the total weight of the soil solidifier and the slag, and the ratio of the adhesive solution in the outer shell is 12-16% of the total weight of the soil solidifier and the slag.

4. The high-strength slag unburned ceramsite according to claim 3, characterized in that: The soil solidifying agent is a composite cementitious material composed of ordinary Portland cement and persulfate cement, wherein the Portland cement accounts for 20-50% and the persulfate cement accounts for 50-80%.

5. A method for preparing high-strength slag unburned ceramsite according to any one of claims 1 to 4, characterized in that: include: S1, a step of preparing an oblate inner core by using an extrusion granulation molding process; S2, a step of granulating and molding the surface of the inner core to obtain a wrapping shell with an equiaxial shape; and S3, a step of forming a plurality of pits on the surface of the wrapping shell.

6. The method for preparing high-strength slag unburned ceramsite according to claim 5, characterized in that: In step S1, the ingredients of the inner core are mixed evenly and then added together into a roller granulator for extrusion granulation; in step S2, a disc granulator is used for molding, the inner core is fed into an inclined disc, and at the same time, a mixture of slag and soil curing agent in the outer shell ingredients is fed into the disc, and an adhesive solution is continuously sprayed on the surface of the above mixture in the form of a spray during the rotation of the disc, so that the inner core is wrapped into an equiaxed ceramsite body with an increased size.

7. The method for preparing high-strength slag unburned ceramsite according to claim 6, characterized in that: In step S2, the rotation speed of the disc is controlled to be 10 to 20 revolutions per minute, and the molding time of the wrapped shell is 3 to 5 minutes.

8. The method for preparing high-strength slag unburned ceramsite according to any one of claims 5 to 7, characterized in that: In step S3, a rotating drum is used for processing, and the inner wall of the rotating drum is provided with a plurality of needle-punched protrusions.

9. The method for preparing high-strength slag unburned ceramsite according to claim 8, characterized in that: The height of the needle puncture protrusions is 2 to 3 mm, and each needle puncture protrusion is distributed in a field shape or a triangle shape with a distance of 10 to 20 mm from the surrounding needle puncture protrusions.

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