Baking-free brick prepared from high-content granite tail mud and preparation method

Abstract

The invention discloses a baking-free brick prepared from high-content granite tail mud and a preparation method, the preparation method comprises the following steps: S1, adding 50-70% of granite scrubbing tail mud, 15-25% of pretreated phosphogypsum and 10-20% of a composite curing agent into a stirrer, and mechanically stirring uniformly to prepare a premix; s2, directly adding the premix treated in the step S1 into a mold, vibrating on a vibrating table for 5 minutes, and scraping by using a knife; and S3, putting the mold filled with the mixed material into a plastic film, sealing and storing, and naturally curing a green brick at the room temperature of 20-35 DEG C to obtain the baking-free brick. According to the baking-free brick, the granite scrubbing tail mud and the phosphogypsum are utilized, clay resources are saved, environmental pollution and land occupation caused by tail mud and phosphogypsum storage yards are reduced, meanwhile, the tail mud and the phosphogypsum are subjected to resource utilization, and the national sustainable green development requirement is met.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of building bricks or blocks, and particularly relates to an unburned brick prepared with a high content of granite tailings and a preparation method thereof. Background Art

[0002] In the stone processing process, granite scrubbing tailings are one of the main wastes. Its main components are silicate minerals such as silicon dioxide and aluminum oxide, and it has certain potential application value. However, due to its high moisture content and large accumulation volume, its indiscriminate stacking or discharge will occupy land resources and cause environmental pollution. On the other hand, the large amount of tailings generated during the mining and processing of mineral resources also faces similar environmental problems. Tailings usually contain fine particles and rich mineral components. If left unused, the storage of tailings not only occupies land but also easily causes leachate pollution of water sources. Therefore, how to effectively utilize granite scrubbing sludge and tailings to reduce environmental pressure and develop new building materials has become a focus of attention in academia and industry.

[0003] In recent years, unburned bricks have gradually attracted the attention of researchers as a new type of green and environmentally friendly building material. The production process of unburned bricks does not require high-temperature firing, which avoids the problems of high energy consumption and high carbon dioxide emissions in the production of traditional fired bricks, and is in line with the current concept of low-carbon environmental protection. At the same time, the production of unburned bricks can flexibly utilize various industrial wastes, such as fly ash, slag, etc., and has a high potential for resource utilization. Combining granite sand washing sludge with phosphogypsum tailings resources generated in the phosphoric acid production process to prepare unburned bricks can not only reduce waste emissions and accumulation, but also provide a new type of environmentally friendly material for the construction industry, promoting the diversification and green development of building materials. From the reported preparation of unburned bricks containing tailings, it was found that the amount of tailings used was small and aggregates needed to be added to provide skeleton support.

[0004] Therefore, a kind of unburned brick prepared with high content of granite tailing mud and its preparation method are in urgent need of being proposed. Summary of the Invention

[0005] In order to solve the defects of the prior art, the present invention provides a fire-free brick prepared with a high content of granite tailings and a preparation method thereof.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: The present invention provides an unburned brick prepared with a high content of granite tailings, wherein the unburned brick comprises the following raw materials in terms of mass fraction: Granite scrubbing tailings 50-70% Phosphogypsum 15-25% Composite curing agent 10-20%.

[0007] Preferably, the granite scrubbing tailings are slurries with a particle size of less than 200 meshes obtained by mechanical scrubbing of granite ore, which are sedimented with a flocculant and dried in the sun, and have a moisture content of less than 5%.

[0008] Preferably, the phosphogypsum is flotation phosphogypsum obtained by flotation of phosphogypsum produced in the preparation of phosphoric acid, and its particle size is less than 250 meshes.

[0009] Preferably, the composite curing agent includes silicate cement, quicklime, silica fume and composite water reducer, and the mass ratio thereof is 30-50:70-50:100:5-10.

[0010] Preferably, the composite water reducer is a compound of at least one of a naphthalene-based water reducer, a polycarboxylic acid water reducer and sodium lignin sulfonate.

[0011] The present invention also provides a method for preparing unburned bricks, comprising the following steps: S1. Add 55-70% of granite scrubbing tailings, 15-25% of phosphogypsum, and 20% of composite curing agent into a mixer, add appropriate amount of tap water, and mechanically stir to obtain a premix; S2, filling the premix processed in step S1 into a mold, vibrating it on a vibration table for 5 minutes, and then smoothing it with a knife; S3. Place the mold filled with the mixture in a plastic film and seal it for storage. Naturally cure the bricks at room temperature of 20-35°C. Remove the mold after 7-9 days and continue curing for 28-30 days to obtain unfired bricks.

[0012] Preferably, in step S1, the mass ratio of water to the solids consisting of granite scrubbing tailings, phosphogypsum, and composite curing agent is 0.225 to 0.32.

[0013] Compared with the prior art, the present invention has the following beneficial effects: The composite curing agent used in the present invention contains three substances that can form crystalline gels: one is Portland cement, whose main components are tricalcium silicate 3CaO·SiO2, dicalcium silicate 2CaO·SiO2, tricalcium aluminate 3CaO·Al2O3, and tetracalcium aluminate 4CaO·Al2O3·Fe2O3. These components react with water to form crystalline gels. Furthermore, quicklime and the highly reactive silica particles in silica fume form crystalline gels such as tricalcium silicate and dicalcium silicate. These gels can respectively contain tailings and phosphogypsum particles and gradually harden to form a cementitious solid. The hydrophilic end of the composite water-reducing agent forms hydrogen bonds with tailings and chelates with phosphogypsum, while the hydrophilic end faces outward. Adsorption on the particle surface generates electrostatic repulsion and steric hindrance, dispersing the particles and reducing mixing water consumption. This lowers the water-cement ratio, improving concrete density and enhancing compressive and flexural strength.

[0014] The raw materials used in this invention work synergistically to produce the unfired bricks. Under the action of quicklime, silica fume, a water reducer, and Portland cement, tailings and phosphogypsum are bonded together through a combination of adsorption, chelation, and solidification, resulting in an environmentally friendly, high-compressive-strength unfired brick material. Testing for potentially harmful elements in the finished product revealed that the concentrations of the metal leachates were far below national standards, demonstrating the stability of these metals within the unfired bricks, resulting in low energy consumption, high cost-effectiveness, and environmentally friendly properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The present invention is a flow chart of a method for preparing unburned bricks prepared with a high content of granite tailings. DETAILED DESCRIPTION

[0016] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0017] Example 1

[0018] Reference Figure 1 The process shown in the figure is to prepare unfired bricks, and the specific steps include: (1) Add dried granite scrubbing tailings, pretreated phosphogypsum (particle size less than 140 mesh), and composite curing agent, where the mass percentages of the solid materials are 65%, 15%, and 20% respectively, into a mixer, and then add water (where the mass ratio of water to solid is 0.225), and stir mechanically to obtain a premix.

[0019] (2) The composite curing agent is composed of Portland cement, quicklime, silica fume, and composite water reducer in a mass ratio of 3:7:10:0.5. The composite curing agent formula composition is shown in Table 1#.

[0020] (3) The composite water reducer is prepared by mixing sodium lignin sulfonate and polycarboxylic acid water reducer in a mass ratio of 1:4.

[0021] (4) The premix processed in step (1) is directly filled into the mold, and after vibrating on a vibration table for 5 minutes, it is leveled with a knife.

[0022] (5) The mold filled with the mixture was placed in a plastic film and sealed for storage. The bricks were naturally cured at room temperature of 20-35°C. After 7 days, the molds were removed and continued to be cured for up to 28 days to produce the unfired bricks. The strength and heavy metal leaching of the obtained unfired bricks are shown in Tables 2 and 3, respectively.

[0023] Example 2

[0024] Reference Figure 1 The process shown in the figure is to prepare unfired bricks, and the specific steps include: (1) Add dried granite scrubbing tailings, pretreated phosphogypsum (particle size less than 140 meshes), and composite curing agent, wherein the mass percentages of the solid materials are 55%, 25%, and 20% respectively, into a mixer, and then add water (wherein the mass ratio of water to solid is 0.27), and mechanically stir to obtain a premix.

[0025] (2) The composite curing agent is composed of Portland cement, quicklime, silica fume, and a carboxyl-containing composite water reducer in a mass ratio of 5:5:10:0.5. The composite curing agent formula composition is shown in Table 1, No. 2.

[0026] (3) The composite water reducer is prepared by compounding a naphthalene-based water reducer and a polycarboxylic acid water reducer in a mass ratio of 0.8:1.2.

[0027] (4) The premix processed in step (1) is directly filled into the mold, and after vibrating on a vibration table for 5 minutes, it is leveled with a knife.

[0028] (5) The mold filled with the mixture was placed in a plastic film and sealed for storage. The bricks were naturally cured at room temperature of 20-35°C. After 7 days, the molds were removed and continued to be cured for 28 days to produce the unfired bricks. The strength of the unfired bricks obtained is shown in Table 1. The bricks were divided into two parts and tested for heavy metal leaching. The test results are shown in Table 3.

[0029] Example 3

[0030] Reference Figure 1 The process shown in the figure is to prepare unfired bricks, and the specific steps include: (1) Add dried granite scrubbing tailings, pretreated phosphogypsum (particle size less than 140 meshes), and composite curing agent, wherein the mass percentages of the solid materials are 55%, 25%, and 20% respectively, into a mixer, and then add water (wherein the mass ratio of water to solid is 0.32), and mechanically stir to obtain a premix.

[0031] (2) The composite curing agent is composed of Portland cement, quicklime, silica fume, and composite water reducer in a mass ratio of 5:5:10:1. The composition of the composite curing agent is shown in Table 1, No. 3.

[0032] (3) The composite water reducer is prepared by compounding a naphthalene-based water reducer and a polycarboxylic acid water reducer in a mass ratio of 0.5:1.5.

[0033] (4) The premix processed in step (1) is directly filled into the mold, and after vibrating on a vibration table for 5 minutes, it is leveled with a knife.

[0034] (5) The mold filled with the mixture was placed in a plastic film, sealed, and naturally cured at room temperature of 20-35°C. After 7 days, the mold was removed and cured for 28 days to produce the unfired brick. The strength of the unfired brick is shown in Table 1. The brick was divided into two parts and tested for heavy metal leaching. The test results are shown in Table 3.

[0035] Table 1: Composite curing agent formula composition .

[0036] Table 2: Strength test results of unfired bricks .

[0037] Table 3: Heavy metal leaching test results .

[0038] From the above data, it can be seen that the unfired bricks of the present invention have excellent physical properties and meet the compressive strength requirements of bricks. At the same time, the concentration of each metal leaching solution is much lower than the standard concentration. While the unfired bricks can recycle the granite scrubbing tailings and phosphogypsum, they can also ensure the strength of the bricks, avoid secondary leaching pollution, and have the advantages of energy saving and environmental protection.

[0039] The composite curing agent in the present invention plays an important role in providing strength support during the formation of unfired bricks. First, quicklime (CaO) reacts with added water, crystallization water from phosphogypsum, or water from ambient humidity to form calcium hydroxide, providing an alkaline environment for subsequent reactions. The highly active SiO2 in silica fume reacts with calcium hydroxide to form calcium silicate hydrate (CSH gel), which is a key product of hardening. CSH gel imparts strength and stability to the material. Under curing conditions at a certain humidity, the CaSO4 in the phosphogypsum reacts with Ca(OH)2 to form ettringite or calcium sulfoaluminate. The phosphates contained in the phosphogypsum (such as Ca3(PO4)2) are converted into hydroxyapatite during the curing process, while trace amounts of Al2O3 in the silica fume may participate in the formation of calcium aluminate hydrate (CAH). The relevant reaction formula is as follows: .

[0040] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A fired brick prepared from high-content granite tailings, characterized in that: The unburned bricks include the following raw materials according to mass fraction: Granite scrubbing tailings 50-70% Phosphogypsum 15-25% Composite curing agent 10-20%.

2. The unburned brick prepared from high-content granite tailing mud according to claim 1, characterized in that: The granite scrubbing tailings are obtained by mechanical scrubbing of granite ore, the particle size of which is less than 200 mesh, which is settled with a flocculant and then dried in the sun, and the moisture content of which is less than 5%.

3. The unburned brick prepared from high-content granite tailing mud according to claim 1, characterized in that: The phosphogypsum is flotation phosphogypsum obtained by flotation of the phosphogypsum produced in the preparation of phosphoric acid, and its particle size is less than 250 meshes.

4. The unburned brick prepared from high-content granite tailing mud according to claim 1, characterized in that: The composite curing agent comprises silicate cement, quicklime, silica fume and composite water reducing agent, and the mass ratio thereof is 30-50:70-50:100:5-10.

5. The unburned brick prepared from high-content granite tailing mud according to claim 4, characterized in that: The composite water reducer is prepared by compounding at least one of a naphthalene-based water reducer, a polycarboxylic acid water reducer and sodium lignin sulfonate.

6. A method for preparing unburned bricks according to any one of claims 1 to 5, characterized in that: The steps include: S1. Add 55-70% of granite scrubbing tailings, 15-25% of phosphogypsum, and 20% of composite curing agent into a mixer, add appropriate amount of tap water, and mechanically stir to obtain a premix; S2, filling the premix processed in step S1 into a mold, vibrating it on a vibration table for 5 minutes, and then smoothing it with a knife; S3. Place the mold filled with the mixture in a plastic film and seal it for storage. Naturally cure the bricks at room temperature of 20-35°C. Remove the mold after 7-9 days and continue curing for 28-30 days to obtain unfired bricks.

7. The method for preparing unburned bricks according to claim 6, characterized in that: In step S1, the mass ratio of water to the solids consisting of granite scrubbing tailings, phosphogypsum, and composite curing agent is 0.225-0.32.

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