A double-system composite high-strength non-burning light aggregate, a preparation method and application thereof

Abstract

The application discloses a double-system composite high-strength baking-free light aggregate and a preparation method and application thereof. Thiourea residue, desulfurization gypsum and fly ash are taken as a mixture, the mixture is mixed with water and stirred uniformly, an additive is added and stirred again to obtain a semi-slurry mixture; the semi-slurry mixture is granulated to form an inner core blank; an outer shell mixture layer is uniformly prepared on the surface of the inner core blank to obtain light aggregate spheres; the light aggregate spheres are naturally maintained, pre-dried, and finally pressure carbonization maintained to obtain the double-system composite high-strength baking-free light aggregate. The light aggregate prepared by the application has the advantages of high early strength, low bulk density, small water absorption and the like, can be widely applied to various ranges, and has the characteristics of high solid waste resource utilization degree, energy saving and low consumption, low price and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of building materials, and particularly relates to a double-system composite high-strength non-burning lightweight aggregate as well as a preparation method and application thereof. BACKGROUND

[0002] Lightweight aggregate (also called light aggregate) refers to a general term of light fine aggregate and light coarse aggregate with a bulk density of not more than 1200 kg / m 3 Lightweight aggregate is made of natural raw materials such as shale through sintering at high temperature, which has the disadvantages of great pollution, high energy consumption, and is not conducive to environmental protection and energy saving and emission reduction, greatly limiting the popularization and development of lightweight aggregate. Therefore, in recent years, some scholars have studied the preparation of non-burning lightweight aggregate through natural curing, which has the advantages of energy saving and environmental protection, low price, etc. compared with traditional sintered lightweight aggregate. However, the existing non-burning lightweight aggregate is mostly made of ordinary Portland cement system as cementing material and binder, which has the problems of high pollution and high energy consumption; the product performance is poor, and early strength is often improved by adding early strength agent and fiber, which increases the production cost; and the solid waste raw material is mostly fly ash, which has the problems of single solid waste utilization and low utilization rate.

[0003] Lightweight aggregate is made of natural raw materials such as shale through sintering at high temperature, which has the disadvantages of great pollution, high energy consumption, and is not conducive to environmental protection and energy saving and emission reduction, greatly limiting the popularization and development of lightweight aggregate. Therefore, in recent years, some scholars have studied the preparation of non-burning lightweight aggregate through natural curing, which has the advantages of energy saving and environmental protection, low price, etc. compared with traditional sintered lightweight aggregate. However, the existing non-burning lightweight aggregate is mostly made of ordinary Portland cement system as cementing material and binder, which has the problems of high pollution and high energy consumption; the product performance is poor, and early strength is often improved by adding early strength agent and fiber, which increases the production cost; and the solid waste raw material is mostly fly ash, which has the problems of single solid waste utilization and low utilization rate. SUMMARY

[0004] In view of the problems in the prior art, the purpose of the present application is to provide a double-system composite high-strength non-burning lightweight aggregate as well as a preparation method and application thereof.

[0005] The purpose of the present application is achieved by the following technical solutions.

[0006] A preparation method of a double-system composite high-strength non-burning lightweight aggregate, comprising the following steps:

[0007] (1) Take thiourea slag, desulfurization gypsum and fly ash as a mixture, mix and stir the mixture and water uniformly, add an additive and stir again to obtain a semi-slurry mixture;

[0008] (2) Granulate the semi-slurry mixture in step (1) to form an inner core blank;

[0009] (3) Uniformly prepare an outer shell mixture layer on the surface of the inner core blank in step (2) to obtain a lightweight aggregate sphere; the outer shell mixture is prepared by mixing magnesite tailings calcined magnesia powder, potassium dihydrogen phosphate, borax and water;

[0010] (4) After natural curing, pre-drying the lightweight aggregate sphere in step (3), and finally performing pressure carbonization curing to obtain the double-system composite high-strength non-burning lightweight aggregate.

[0011] Preferably, in step (1), the desulfurized gypsum is activated by grinding before use, and the grinding time is 5-10 min.

[0012] Preferably, in step (1), the mass ratio of thiourea residue, desulfurized gypsum and fly ash is 20-30:20-40:30-40.

[0013] Preferably, in step (1), the mass ratio of water and the mixture is 0.2-0.3:1.

[0014] Preferably, in step (1), the additive is at least one of aluminum hydroxide, water glass and sodium hydroxide.

[0015] Preferably, the additive is prepared by mixing aluminum hydroxide, water glass and sodium hydroxide in a mass ratio of 1-2:1-3:1-3.

[0016] Preferably, the additive is prepared by mixing aluminum hydroxide and water glass in a mass ratio of 1-2:1-2.

[0017] Preferably, in step (1), the mass ratio of the additive and the mixture is 0.05-0.2:1.

[0018] Preferably, in step (2), the granulation is performed by a disc granulator, and the inclination angle of the granulator is 35-70° and the rotation speed is 35-70 rpm. In the granulation process, the material may be too dry to form or too wet to have too much viscosity. At this time, the granulation is completed by adding the mixture or water as described in step (1).

[0019] Preferably, in step (3), the mass ratio of magnesite tailings calcined magnesia powder, potassium dihydrogen phosphate and borax is 70-85:15-30:6-10.

[0020] Preferably, in step (3), the total mass ratio of water, magnesite tailings calcined magnesia powder, potassium dihydrogen phosphate and borax is 0.15-0.18:1.

[0021] Preferably, in step (3), the thickness of the shell mixture layer is 1-2 mm.

[0022] Preferably, in step (4), the natural curing is performed at room temperature for 12-48 h.

[0023] Preferably, in step (4), the pre-drying is performed in an environment with a relative humidity of 40-60% and a temperature of 20-30℃ for 24-48 h.

[0024] Preferably, in step (4), the pressure carbonization curing is performed at a humidity of 50-80%, a CO2 concentration of 50-100% and a pressure of 0.1-0.5 MPa for 24-72 h.

[0025] The double-system composite high-strength baking-free light aggregate is prepared by the preparation method of the double-system composite high-strength baking-free light aggregate.

[0026] The double-system composite high-strength baking-free light aggregate is applied to preparation of light aggregate concrete for bridges, buildings and tunnels.

[0027] Compared with the prior art, the beneficial effects of the application include:

[0028] (1) The application uses thiourea slag-desulfurization gypsum-fly ash as a basic-sulfate-silicate ternary solid waste system, and the active silicon aluminum substances in the fly ash can be quickly dissolved under the synergistic action of OH- and SO4 2- , so that calcium aluminate, amorphous gel and other substances are generated, and therefore the reaction activity in the hydration process of the cementing material is enhanced, the microstructure is improved, and the overall strength of the product is improved.

[0029] (2) Under the action of the additive, the internal active substances of the inner core blank have a series of geopolymer reactions such as polycondensation and depolymerization, and the reaction degree is gradually increased, so that a three-dimensional structure is formed, the internal structure is dense, the porosity is reduced, and the strength and water resistance of the product are improved.

[0030] (3) The shell mixture is in a forming state during the spraying process, and can be quickly bonded to the surface of the inner core blank and tightly combined with the inner core blank, and at the same time, the shell mixture is quickly hardened and obtains high strength, so that the light aggregate can obtain a higher cylinder compressive strength in the early stage, has higher volume crushing resistance and lower water absorption. Secondly, the SiO2 in the fly ash in the inner core blank can react with MgO to generate MgSiO3, which can enhance the solid-phase combination in the system, and the aluminosilicate glass phase can react with phosphate to generate tetrahedral aluminosilicate hydrate, and the structure of the hydration product is stable, and the mechanical properties of the system are enhanced.

[0031] (4) After the light aggregate spherical ball is cured and maintained by CO2, a dense magnesium carbonate layer is formed on the surface, the microstructure of the light aggregate is optimized, the mechanical properties of the light aggregate are improved, and the water absorption of the light aggregate is reduced. At the same time, the carbonation pressure technology can make the carbonation effect more obvious and the carbonation depth higher, so that Ca 2+ in the inner core material reacts with CO3 2- to generate a calcium carbonate layer, so that the performance is improved more obviously.

[0032] (5) The present application solves the problems of high pollution and high energy consumption of the non-burned lightweight aggregate using silicate cement as the cementitious material; early strength agents and fibers are not used to improve the early strength, thereby reducing the production cost; the utilization rate of solid waste is high, which is more than 85%, and the utilization of waste materials is realized while achieving the synergy of solid waste, and the product performance is stable, and the overall performance is superior, and the product cylinder pressure strength is as high as 15.8MPa. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the present application clearer and more apparent, the present application will be further described in detail below with examples. It should be understood that the specific examples described herein are only used to explain the present application and not to limit the present application.

[0034] Example 1

[0035] A double-system composite high-strength non-burned lightweight aggregate, the raw material composition of which is: 100g of thiourea slag, 200g of desulfurization gypsum, 200g of fly ash, 100g of heavy-burned magnesium oxide powder, 25g of potassium dihydrogen phosphate, 10g of borax, and 146g of water (the total of the water required in steps 2 and 4).

[0036] The preparation method of the above-mentioned double-system composite high-strength non-burned lightweight aggregate comprises the following steps:

[0037] (1) Desulfurization gypsum pretreatment: the desulfurization gypsum is subjected to grinding and activation pretreatment, and the grinding time is 8 minutes.

[0038] (2) Pre-wetting and stirring: the thiourea slag, the ground desulfurization gypsum, the fly ash and the water (125g) are weighed according to the weight ratio, then placed in a stirrer with a rotation speed of 75-95 revolutions per minute and stirred for 2 minutes to make them uniformly stirred, then 15g of aluminum hydroxide, 30g of water glass and 30g of sodium hydroxide are added as external agents, and the mixture is rapidly stirred at a rotation speed of 145-160 revolutions per minute for 1 minute to obtain a semi-slurry mixture;

[0039] (3) First granulation: the semi-slurry mixture obtained in step (1) is placed in a disc granulator with an inclination of 35-70° and a rotation speed of 35-70 revolutions per minute, and continuously rolled, and according to the stickiness of the material balls, the mixed thiourea slag, desulfurization gypsum and fly ash powder and water are continuously added for granulation to form the inner core blank;

[0040] (4) Preparation of shell mixture: the heavy-burned magnesium oxide powder, potassium dihydrogen phosphate, borax and water (21g) are weighed according to the weight ratio, then placed in a stir pot and stirred uniformly to form a shell mixture;

[0041] (5) secondary granulation: the inner core blank formed in step (3) is evenly sprayed with the shell mixture for secondary granulation, and a shell mixture with a thickness of 1-2 mm is coated on the surface of the light aggregate ball to obtain a light aggregate ball;

[0042] (6) carbonization curing: the light aggregate ball obtained in step (5) is first cured at room temperature for 24 h, then pre-dried in an environment with a relative humidity of 50% and a temperature of 26°C for 24 h, and finally carbonized and cured in an environment with a CO2 concentration of 100%, a pressure of 0.1 MPa, and a relative humidity of 50% for 24 h to obtain the double-system composite high-strength baking-free light aggregate.

[0043] Example 2

[0044] In this example, the raw material ratio and preparation process are the same as in Example 1, except that the curing conditions are changed as follows:

[0045] The light aggregate ball is first cured at room temperature for 24 h, then pre-dried in an environment with a relative humidity of 50% and a temperature of 26°C for 24 h, and finally carbonized and cured in an environment with a CO2 concentration of 50%, a pressure of 0.5 MPa, and a relative humidity of 80% for 24 h to obtain the double-system composite high-strength baking-free light aggregate.

[0046] Example 3

[0047] In this example, the raw material ratio and preparation process are the same as in Example 1, except that the additive formulation is changed as follows: 40 g of aluminum hydroxide and 40 g of water glass.

[0048] Example 4

[0049] In this example, the raw material ratio and preparation process are the same as in Example 1, except that the grinding pretreatment time of desulfurized gypsum powder and the curing conditions are changed as follows:

[0050] The desulfurized gypsum is ground and activated for pretreatment, and the grinding time is 5 min;

[0051] The light aggregate ball is first cured at room temperature for 48 h, then pre-dried in an environment with a relative humidity of 50% and a temperature of 26°C for 24 h, and finally carbonized and cured in an environment with a CO2 concentration of 100%, a pressure of 0.1 MPa, and a relative humidity of 50% for 24 h to obtain the double-system composite high-strength baking-free light aggregate.

[0052] Example 5

[0053] A double-system composite high-strength baking-free light aggregate, which comprises the following raw materials: 150 g of thiourea slag, 150 g of desulfurized gypsum, 200 g of fly ash, 100 g of heavy-burning magnesium oxide powder, 25 g of potassium dihydrogen phosphate, 10 g of borax, and 146 g of water.

[0054] In this example, the preparation process and curing method are the same as in Example 1.

[0055] Example 6

[0056] A double-system composite high-strength baking-free light aggregate, whose raw material composition is: 150 g of thiourea slag, 200 g of desulfurized gypsum, 150 g of fly ash, 100 g of heavy-burning magnesium oxide powder, 25 g of potassium dihydrogen phosphate, 10 g of borax, and 146 g of water.

[0057] The preparation process and curing method of this example are the same as those of Example 1.

[0058] Comparative Example 1

[0059] The raw material ratio and preparation process of this comparative example are the same as those of Example 1, only the curing conditions are changed, and the curing conditions are as follows:

[0060] The light aggregate spheres are first cured at room temperature for 24 h, then pre-dried in an environment with a relative humidity of 50% and a temperature of 26°C for 24 h, and finally steam-cured at 60°C for 24 h to obtain the light aggregate.

[0061] Comparative Example 2

[0062] The raw material ratio and preparation process of this comparative example are the same as those of Example 1, only the curing conditions are changed, and the curing conditions are as follows:

[0063] The light aggregate spheres are first cured at room temperature for 24 h, then pre-dried in an environment with a relative humidity of 50% and a temperature of 26°C for 24 h, and finally carbonized and cured at a CO2 concentration of 100% and a pressure of 0.1 MPa for 24 h to obtain the light aggregate.

[0064] Comparative Example 3

[0065] The raw material ratio and preparation process of this comparative example are the same as those of Example 1, only the curing conditions are changed, and the curing conditions are as follows:

[0066] The light aggregate spheres are first cured at room temperature for 24 h, then pre-dried in an environment with a relative humidity of 50% and a temperature of 26°C for 24 h, and finally carbonized and cured at a CO2 concentration of 100% and a humidity of 50% for 24 h to obtain the light aggregate.

[0067] Comparative Example 4

[0068] The comparative example is a concrete ceramsite commercially available from Anhui Chanjiu Qu Environmental Science and Technology Co., Ltd.

[0069] The light aggregates obtained in the above examples and comparative examples are tested for performance, and their 28d cylinder compressive strength, 1h water absorption, and bulk density are tested according to GB / T17431.2-2010. The test results are shown in Table 1 below.

[0070] Table 1 Performance Test Overview

[0071]

[0072]

[0073] From the data in the above table, it can be seen that the bulk density and 1h water absorption are related to the cylinder compressive strength, the bulk density and the cylinder compressive strength are positively correlated, and the 1h water absorption and the cylinder compressive strength are negatively correlated. Compared with the comparative example 1, the cylinder compressive strength and the bulk density of the example are higher, and the 1h water absorption is lower. The reason is that, under a certain CO2 concentration and carbonization pressure, Mg 2 + and Ca 2+ react with CO3 2- respectively to generate a dense magnesium carbonate and calcium carbonate layer, optimize the internal pore structure, reduce the porosity, and thus improve the mechanical properties; at the same time, the higher the CO2 concentration, the greater the carbonization pressure within a certain range, the higher the carbonization depth, the more complete the carbonization reaction, and the more superior the lightweight aggregate performance.

[0074] The specific embodiments of the application described above do not constitute a limitation on the protection scope of the application. Any various other corresponding changes and modifications made according to the technical concept of the application shall be included in the protection scope of the claims of the application.

Claims

1. A method for preparing a double-system composite high-strength non-burned lightweight aggregate, characterized by, It comprises the following steps: (1) Take thiourea residue, desulfurization gypsum, fly ash as a mixture, mix the mixture with water and stir uniformly, add an additive and stir again to obtain a semi-slurry mixture; The additive in step (1) is at least one of aluminum hydroxide, water glass and sodium hydroxide; (2) Granulate the semi-slurry mixture in step (1) to form an inner core blank; (3) Uniformly prepare an outer shell mixture layer on the surface of the inner core blank in step (2) to obtain a lightweight aggregate ball; the outer shell mixture is prepared by mixing magnesite tailings heavy-burning magnesia powder, potassium dihydrogen phosphate, borax and water; (4) After natural curing, pre-drying, and finally pressure carbonization curing, the lightweight aggregate ball in step (3) is obtained to obtain the double-system composite high-strength baking-free lightweight aggregate.

2. The method for preparing the dual-system composite high-strength non-fired lightweight aggregate according to claim 1, characterized in that, The mass ratio of the thiourea residue, desulfurization gypsum and fly ash in step (1) is 20-30:20-40:30-40.

3. The method for preparing the dual-system composite high-strength non-fired lightweight aggregate according to claim 1, characterized in that, The additive is prepared by mixing aluminum hydroxide, water glass and sodium hydroxide in a mass ratio of 1-2:1-3:1-3; or The additive is prepared by mixing aluminum hydroxide and water glass in a mass ratio of 1-2:1-2.

4. The preparation method of the double-system composite high-strength baking-free light aggregate according to any one of claims 1-3, characterized in that, The mass ratio of water to the mixture in step (1) is 0.2-0.3:1; The mass ratio of the additive to the mixture in step (1) is 0.05-0.2:

1.

5. The method of claim 1, wherein the method is characterized by: The mass ratio of the magnesite tailings heavy-burning magnesia powder, potassium dihydrogen phosphate and borax in step (3) is 70-85:15-30:6-10; The total mass ratio of water to the magnesite tailings heavy-burning magnesia powder, potassium dihydrogen phosphate and borax in step (3) is 0.15-0.18:

1.

6. The method of claim 5, wherein the method further comprises the step of: The desulfurization gypsum in step (1) is activated and pretreated by grinding before use, and the grinding time is 5-10 min; ​ The thickness of the outer shell mixture layer in step (3) is 1-2 mm.

7. The method according to any one of claims 1 to 3, wherein the method is characterized by, The natural curing method in step (4) is to cure at room temperature for 12-48 h; The pre-drying method in step (4) is to pre-dry in an environment with a relative humidity of 40-60% and a temperature of 20-30℃ for 24-48 h; The pressure carbonization curing method in step (4) is to cure under a humidity of 50-80%, a CO2 concentration of 50-100% and a pressure of 0.1-0.5 MPa for 24-72 h.

8. The double-system composite high-strength baking-free lightweight aggregate prepared by the method of any one of claims 1-7.

9. The application of the double-system composite high-strength baking-free lightweight aggregate of claim 8 in the preparation of lightweight aggregate concrete for bridges, buildings and tunnels.

Images