A belite-aluminate mineral additive and its preparation method and application

Abstract

The present invention belongs to the technical field of solid waste resource utilization, and discloses a belite - aluminate mineral additive, its preparation method and application. The raw materials are composed of the following components by mass: 25 - 40 parts of bauxite tailings slag, 60 - 65 parts of carbide slag, 1 - 8 parts of coal gangue, 0.1 - 0.5 parts of CaF2, 2 - 8 parts of fluorogypsum, and 0.1 - 0.5 parts of borax. The main components of the prepared belite - aluminate mineral additive are: monocalcium aluminate, dodecacalcium heptaaluminate, dicalcium silicate and tetracalcium aluminoferrite. When modifying portland cement with an incorporation amount of about 10%, it can effectively shorten the setting time of the cement and improve the early strength, with excellent performance, achieving low - temperature calcination and saving energy.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste resource utilization, and specifically relates to a belite-aluminate mineral additive and a preparation method and application thereof. Background Art

[0002] The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Calcium carbide slag is the waste residue with calcium hydroxide as the main component after acetylene gas is obtained by hydrolyzing calcium carbide (CaC2). Calcium carbide slag can replace limestone to produce building materials and be used for environmental governance.

[0004] The low- and medium-grade bauxite used in the Al2O3 industry produces tailings accounting for about 20% of the original ore during the beneficiation process. These tailings piles not only bring about a series of problems such as environmental pollution and land occupation, but also because the tailings have fine particles, they are easy to form dust and cause air pollution, which is harmful to people's health and life.

[0005] Coal gangue is one of the industrial solid wastes with the largest emission in my country. my country's "coal-based" energy utilization structure makes coal gangue have high intensity, large stockpile, wide coverage and many hazards, causing huge social and environmental pressure, which has seriously restricted the sustainable development of the coal industry.

[0006] Portland cement is an important building material, mainly used to make concrete and mortar. Because of its good fire resistance and high temperature resistance, it is also used to make fireproof materials and high temperature resistant materials. Portland cement has low early strength and long setting time, which makes it difficult to meet the occasions that require rapid hardening and high early strength. Summary of the invention

[0007] In view of the deficiencies in the prior art, the object of the present invention is to provide a belite-aluminate mineral additive and a preparation method and application thereof.

[0008] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0009] In a first aspect, the present invention provides a belite-aluminate mineral additive, wherein the raw materials thereof are composed of the following components by weight: 25-40 parts of alumina tailings, 60-65 parts of carbide slag, 1-8 parts of coal gangue, 0.1-0.5 parts of CaF2, 2-8 parts of fluorgypsum, and 0.1-0.5 parts of borax.

[0010] Bauxite tailings mainly contain mineral components such as Al2O3, SiO2, Fe2O3, CaO, etc., most of which are layered silicate minerals. They can replace part of the clay and aluminum-iron correction raw materials in the production of mineral additives. Because the particle size of bauxite tailings is low, the 0.08mm sieve residue is less than 8.5%, which can meet the fineness requirements of raw materials in the production of mineral additives. Therefore, the tailings can be directly used in the preparation of mineral additive raw materials without fine grinding by a grinder.

[0011] In the present invention, the functions of each raw material are as follows:

[0012] The content of SiO2 in alumina tailings is about 32%, and the content of Al2O3 is 40.05%;

[0013] Carbide slag: Carbide slag is a cheap industrial solid waste, which contains rich Ca(OH)2 and provides a calcium source for the preparation of mineral additives;

[0014] Coal Gangue: Coal Gangue is rich in silicon and aluminum, providing calcium for the preparation of mineral additives;

[0015] CaF2: As a mineralizer, it is used to reduce the temperature of mineral phase formation;

[0016] Fluorogypsum: Fluorogypsum is also an industrial solid waste. Its main component is anhydrous calcium sulfate, which is different from the dihydrate calcium sulfate in desulfurized gypsum. It is used to provide calcium sulfate for mineral formation.

[0017] Borax acts as a retarder.

[0018] Based on the physicochemical properties of each raw material, the optimal matching calculation is carried out, and the target minerals and mineral composition contents in the belite-aluminate mineral additive are directional matched and designed to finally optimize the best raw material ratio and plan.

[0019] During the calcination stage, the CaO-SiO2-Al2O3-Fe2O3-SO3-TiO2-MgO-Na2O multi-component system composed of the raw materials undergoes a solid phase chemical reaction to produce dicalcium silicate C2S, monocalcium aluminate CA and dodecalycium heptahedronate C 12 A7 is the main mineral component of the mineral additive, CA is the main fast-hardening mineral in the belite-aluminate mineral additive, which is characterized by normal coagulation and rapid hardening, and is the main source of additive strength. 12 The coordination of aluminum and calcium in A7 crystal is very irregular, and there are a lot of cavities in its structure, which water can easily enter. 12 A7 hydrates and solidifies very quickly, but its strength is not as high as CA. Dicalcium silicate - C2S provides later strength. After adding calcium fluoride (CaF2), the firing temperature drops by 50~100℃. Calcium fluorosilicate and calcium fluoroaluminate (C 11A7·CaF2) and other intermediate compounds. The prepared belite-aluminate mineral additive has excellent quality. When modifying silicate cement, it can effectively shorten the setting time of cement and improve its early strength.

[0020] Since carbide slag and alumina tailings have a high moisture content, they need to be dried before use.

[0021] In some embodiments, the raw materials of the belite-aluminate mineral additive are composed of the following components by weight: 25-40 parts of alumina tailings, 60-65 parts of carbide slag, 3-5 parts of coal gangue, 0.1-0.3 parts of CaF2, 4-6 parts of fluorgypsum, and 0.2-0.4 parts of borax.

[0022] Preferably, the raw materials of the belite-aluminate mineral additive are composed of the following components by mass: 25-40 parts of alumina tailings, 60-65 parts of carbide slag, 3-5 parts of coal gangue, 0.2 parts of CaF2, 5 parts of fluorgypsum, and 0.3 parts of borax.

[0023] In a second aspect, the present invention provides a method for preparing the belite-aluminate mineral additive, comprising the following steps:

[0024] After grinding and drying the bauxite tailings, carbide slag, coal gangue and CaF2, they are mixed and calcined in proportion. The calcination temperature is 1200-1500°C and the calcination time is 50-70min. After calcination, they are rapidly cooled to room temperature.

[0025] After the fired clinker is crushed, fluorgypsum and borax are added in proportion, mixed and ground to obtain the belite-aluminate mineral additive.

[0026] Rapid cooling can reduce the destructive effect of MgO and avoid the precipitation of MgO crystals, thereby improving the stability of mineral additives and preventing volume changes of water mineral additives during the hardening process; rapid cooling can avoid the transformation of β-C2S (dicalcium silicate) into γ-C2S, which will cause volume expansion and cause clinker pulverization, affecting the strength and performance of the clinker.

[0027] In some embodiments, the rapid cooling method is to use a grate cooler to cool the high-temperature clinker, rapidly reducing the temperature from above 1100°C to below 200°C.

[0028] In some embodiments, the specific surface area after grinding is 350-450 kg / m 2 , preferably 400kg / m 2 The residue percentage of 0.08mm square hole sieve is controlled below 3%.

[0029] After the material is ground, the specific surface area of ​​the material is increased and the hydration activity of the material is increased.

[0030] In a third aspect, the present invention provides the use of the belite-aluminate mineral additive in modifying cement.

[0031] In some embodiments, when the belite-aluminate mineral additive is used to modify cement, the belite-aluminate mineral additive, fluorgypsum and silicate cement are uniformly mixed in a mass ratio of 9-15:0.2-0.8:85-95 to obtain the product.

[0032] Preferably, the mass ratio of belite-aluminate mineral additive, fluorgypsum and silicate cement is 9-12:0.4-0.6:88-92.

[0033] The beneficial effects achieved by one or more embodiments of the present invention are as follows:

[0034] Compared with the production of ordinary sulphoaluminate mineral additives, the advantage of the present invention is that the raw materials make use of a large amount of solid waste bauxite tailings generated during the beneficiation of the alumina industry and solid waste carbide slag generated by the chemical industry, replacing the high-grade natural resources required for the production of traditional sulphoaluminate mineral additives, greatly reducing the cost of raw materials. At the same time, since the main component of the carbide slag that replaces limestone is Ca(OH)2, it produces H2O but not any CO2 during calcination and decomposition, which saves energy and reduces emissions and has important environmental significance.

[0035] The main components of the Belite-aluminate mineral additive prepared by the reasonable proportion of bauxite tailings, carbide slag and other siliceous materials are: monocalcium aluminate (CA), dodecaluminum heptaaluminate (C 12 A7), dicalcium silicate (C2S) and tetracalcium aluminoferrate (C4AF), the proportion of each mineral is 55-70%, 25-40%, 5% and 5% respectively. When the silicate cement is modified with an addition amount of about 10%, it can effectively shorten the setting time of cement and improve the early strength, with excellent performance, low temperature calcination and energy saving.

[0036] The belite-aluminate mineral additive prepared by the present invention has the characteristics of lower clinker calcination temperature and free CaO content, higher early strength and later strength gain rate, lower hydration heat, corrosion resistance, excellent stability and the like. It can not only meet the multifunctional and high-performance requirements of modern construction projects for mineral additives, but also improve the utilization rate of tailings resources, achieve the purpose of saving resources and protecting the environment, and is a feasible way to achieve sustainable production of mineral additives, which is of great significance to the national economy and social development. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0038] Figure 1 The XRD spectrum of the belite-aluminate mineral additive clinker obtained by firing in Example 1;

[0039] Figure 2 This is a SEM photo of the belite-aluminate mineral additive obtained by firing in Example 1, wherein a is spherical granular C2S; b is needle-rod-shaped CA and amorphous C 12 A7;

[0040] Figure 3 The XRD pattern of the belite-aluminate mineral additive obtained by firing in Example 2;

[0041] Figure 4 This is a SEM photo of the belite-aluminate mineral additive obtained by firing in Example 2, wherein a is spherical granular C2S; b is needle-shaped CA and amorphous C 12 A7;

[0042] Figure 5 The XRD pattern of the belite-aluminate mineral additive obtained by firing in Example 3;

[0043] Figure 6 This is a SEM photo of the belite-aluminate mineral additive obtained by firing in Example 3, where a is spherical granular C2S; b is needle-shaped CA and amorphous C 12 A7. DETAILED DESCRIPTION

[0044] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0045] The present invention will be further described below in conjunction with the embodiments.

[0046] The raw materials required in the following examples and comparative examples include alumina tailings, carbide slag, coal gangue and analytically pure chemical reagent CaF2, and the main chemical components are shown in Table 1.

[0047] Table 1 Chemical analysis of raw materials / %

[0048]

[0049] The detection and experimental methods of the obtained products are as follows:

[0050] 1. The free calcium oxide content shall be determined according to GB 176 “Chemical Analysis Methods for Cement”;

[0051] 2. The specific surface area is determined according to GB / T 8074 “Determination of specific surface area of ​​cement”;

[0052] 3. The setting time shall be measured in accordance with GB / T 1346 "Test Methods for Water Consumption, Setting Time and Stability of Cement Standard Consistency";

[0053] 4. The fluidity of cement mortar shall be determined according to GB / T 2419 method;

[0054] 5. The strength shall be measured in accordance with GB / T 17671-1999 "Test method for strength of mineral additive mortar".

[0055] Example 1

[0056] Alumina tailings, carbide slag, coal gangue and analytical pure chemical reagent CaF2 are used for mixing, among which alumina tailings account for 36.72%, carbide slag accounts for 62.3%, coal gangue accounts for 0.98%, and 0.2% CaF2 is added.

[0057] Put the prepared raw material into the horizontal drum ball mill, mix and grind for 30 minutes, take it out and pass it through a 0.08mm square hole sieve, control the raw material fineness to 0.08mm, and the square hole sieve residue percentage ≤3%;

[0058] After the raw materials are ground and mixed evenly, add 15% of the raw materials weight of water and mix evenly until there is no obvious agglomeration, beat it into a corrugated cake of φ60×8mm, and dry it at 105℃ for 2h;

[0059] The dried material was moved to a high-temperature resistance furnace for calcination at a temperature of 1200°C for 50 minutes. After calcination, it was rapidly cooled to room temperature.

[0060] The fired belite-aluminate clinker was crushed, 5% by mass of fluorgypsum and 0.3% by mass of borax were added, mixed thoroughly, and ground to a specific surface area of ​​400 kg / m 2 , control the sieve residue of 0.08mm fineness to ≤3%, and obtain the belite-aluminate mineral additive.

[0061] The XRD spectrum of the fired belite-aluminate mineral additive is as follows: Figure 1 As shown, the main mineral phases in the product are: C2S (d=4.90, 2.74, 2.75, 2.19Ǻ), CA (d=3.70, 2.85, 2.75Ǻ), C 12 A7 (d=4.89, 2.68, 2.19Ǻ), C4AF (d=2.77, 2.69, 2.19Ǻ).

[0062] SEM images, such as Figure 2 As shown, calcium aluminate CA usually appears as fine plate-like or needle-like crystals (such as Figure 2 b). Its crystal structure is relatively complex and usually plays a role in accelerating the reaction during cement hydration. 12 The microscopic morphology of A7 is usually an irregular polyhedron. It is a fast-reacting mineral phase that has an important influence on the early strength development of cement. The microscopic morphology of dicalcium silicate C2S is mostly large elliptical crystals, which are round particles (such as Figure 2 It reacts slowly during cement hydration, but plays a major role in the long-term strength development of cement.

[0063] The prepared belite-aluminate mineral additive is added to 90% of 42.5R silicate cement in a ratio of 9.5% and 0.5% fluorgypsum, and the mixture is put into a mill and mixed evenly to prepare modified silicate cement for use, where % is the mass percentage.

[0064] The modified cement product was tested by the cement mortar strength test method (GB / T 17671-1999), and the compressive strength after 3 days and 28 days was 46.2MPa and 75.9MPa respectively. The initial setting time was 102min, and the final setting time was 178min.

[0065] The blank 42.5R cement sample without belite-aluminate mineral additives (3-day and 28-day compressive strengths are 33.5MPa and 61.2MPa, respectively. Initial setting time is 213min, and final setting time is 321min) has its early strength increased by 37.9% and its initial setting time shortened by 52.1%.

[0066] Example 2

[0067] Alumina tailings, carbide slag, coal gangue and analytical pure chemical reagent CaF2 are used for mixing, among which alumina tailings account for 31.4%, carbide slag accounts for 64.51%, coal gangue accounts for 4.09%, and 0.2% CaF2 is added.

[0068] The prepared raw materials were ground, pressed into cakes, and dried (same as in Example 1) and then moved to a high-temperature resistance furnace for calcination at a temperature of 1200° C. for 60 minutes.

[0069] The fired belite-aluminate clinker was crushed, 5% by mass of fluorgypsum and 0.3% by mass of borax were added into a mill and ground, and the sieve residue of 0.08 mm was controlled to be ≤3%, and the belite-aluminate mineral additive was obtained. Its XRD spectrum is as follows: Figure 3As shown in the figure, the main minerals of additive clinker are C2S (d=4.90, 2.74, 2.75, 2.19Ǻ), CA (d=3.70, 2.85, 2.75Ǻ), C 12 A7 (d=4.89, 2.68, 2.19Ǻ), C4AF (d=2.77, 2.69, 2.19Ǻ).

[0070] SEM photos of additive clinker, such as Figure 4 As shown, the main minerals are round-grained C2S ( Figure 4 a), needle-shaped CA and amorphous C 12 A7( Figure 4 (b)

[0071] The prepared belite-aluminate mineral additive is added to 90% of 42.5R silicate cement in a ratio of 9.5% and 0.5% fluorgypsum, and the mixture is put into a mill and mixed evenly to prepare modified silicate cement for use, where % is the mass percentage.

[0072] The modified cement product was tested by the cement mortar strength test method (GB / T 17671-1999), and the compressive strength after 3 days and 28 days was 43.8MPa and 73.4MPa respectively. The initial setting time was 107min, and the final setting time was 195min.

[0073] The blank 42.5R cement sample without belite-aluminate mineral additives (3-day and 28-day compressive strengths are 33.5MPa and 61.2MPa, respectively. Initial setting time is 213min, and final setting time is 321min) has its early strength increased by 30.7% and its initial setting time shortened by 49.8%.

[0074] Example 3

[0075] Alumina tailings, carbide slag, coal gangue and analytical pure chemical reagent CaF2 are used for mixing, among which alumina tailings account for 26.05%, carbide slag accounts for 66.60%, coal gangue accounts for 7.35%, and 0.2% CaF2 is added.

[0076] The prepared raw materials were ground, pressed into cakes, and dried (same as in Example 1) and then moved to a high-temperature resistance furnace for calcination at a temperature of 1200° C. for 60 minutes.

[0077] The fired belite-aluminate clinker was added with 5% fluorgypsum and 0.3% borax and ground into a mill, and the sieve residue of 0.08mm was controlled to be ≤3% to obtain a belite-aluminate mineral additive. Its XRD spectrum is as follows: Figure 5 As shown in the figure, the main minerals of additive clinker are C2S (d=4.90, 2.74, 2.75, 2.19Ǻ), CA (d=3.70, 2.85, 2.75Ǻ), C12 A7 (d=4.89, 2.68, 2.19Ǻ), C4AF (d=2.77, 2.69, 2.19Ǻ).

[0078] SEM photos of additive clinker, such as Figure 6 As shown, the main mineral is round-grained C2S (such as Figure 6 a), needle-shaped CA and amorphous C 12 A7 (such as Figure 6 (b)

[0079] The prepared belite-aluminate mineral additive is added to 90% of 42.5R silicate cement in a ratio of 9.5% and 0.5% fluorgypsum, and the mixture is put into a mill and mixed evenly to prepare modified silicate cement for use, where % is the mass percentage.

[0080] The modified cement product was tested by the cement mortar strength test method (GB / T 17671-1999), and the compressive strength after 3 days and 28 days was 43.1MPa and 71.3MPa respectively. The initial setting time was 111min, and the final setting time was 203min.

[0081] The blank 42.5R cement sample without belite-aluminate mineral additives (3-day and 28-day compressive strengths are 33.5MPa and 61.2MPa, respectively. Initial setting time is 213min, and final setting time is 321min) has its early strength increased by 28.8% and its initial setting time shortened by 47.9%.

[0082] Comparative Example 1

[0083] The difference from Example 1 is that the coal gangue is omitted, and the rest is the same as Example 1.

[0084] The modified cement product was tested by cement mortar strength test method (GB / T 17671-1999), and the compressive strength after 3 days and 28 days was 36.5 MPa and 65.3 MPa respectively, the initial setting time was 185 min, and the final setting time was 275 min.

[0085] Compared with the blank 42.5R cement sample (the compressive strength at 3 days and 28 days was 33.5MPa and 61.2MPa respectively. The initial setting time was 213min and the final setting time was 321min), the compressive strength at 3 days and 28 days increased by 8.9% and 6.5% respectively, and the initial setting time and final setting time were shortened by 13.1% and 14.3% respectively.

[0086] Comparative Example 2

[0087] The difference from Example 1 is that CaF2 is omitted, and the rest is the same as Example 1.

[0088] The modified cement product was tested by the cement mortar strength test method (GB / T 17671-1999), and the compressive strength after 3 days and 28 days was 35.6MPa and 63.3MPa respectively. The initial setting time was 192min, and the final setting time was 286min.

[0089] Compared with the blank 42.5R cement sample (the compressive strength at 3 days and 28 days was 33.5MPa and 61.2MPa respectively. The initial setting time was 213min and the final setting time was 321min), the compressive strength at 3 days and 28 days increased by 6.3% and 3.4% respectively; the initial setting time and final setting time were shortened by 9.8% and 10.9% respectively.

[0090] Comparative Example 3

[0091] The difference from Example 1 is that 5% of fluorgypsum is omitted, and the rest is the same as Example 1.

[0092] The modified cement product was tested by cement mortar strength test method (GB / T 17671-1999), and the compressive strength after 3 days and 28 days was 37.4 MPa and 67.3 MPa respectively, the initial setting time was 171 min, and the final setting time was 265 min.

[0093] Compared with the blank 42.5R cement sample (the compressive strength at 3 days and 28 days was 33.5MPa and 61.2MPa respectively. The initial setting time was 213min and the final setting time was 321min), the compressive strength at 3 days and 28 days increased by 11.6% and 9.9% respectively; the initial setting time and final setting time were shortened by 19.7% and 17.4% respectively.

[0094] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A belite-aluminate mineral additive, characterized in that: The raw materials are composed of the following components by weight: 25-40 parts of alumina tailings, 60-65 parts of carbide slag, 1-8 parts of coal gangue, 0.1-0.5 parts of CaF2, 2-8 parts of fluorgypsum, and 0.1-0.5 parts of borax; After grinding and drying the bauxite tailings, carbide slag, coal gangue and CaF2, they are mixed and calcined in proportion. The calcination temperature is 1200-1500°C and the calcination time is 50-70min. After calcination, they are rapidly cooled to room temperature. After the fired clinker is crushed, fluorgypsum and borax are added in proportion, mixed and ground to obtain the belite-aluminate mineral additive; The rapid cooling method is to use a grate cooler to cool the high-temperature clinker, rapidly reducing the temperature from above 1100° C. to below 200° C.

2. The belite-aluminate mineral additive according to claim 1, characterized in that: The raw materials are composed of the following components by weight: 25-40 parts of alumina tailings, 60-65 parts of carbide slag, 3-5 parts of coal gangue, 0.1-0.3 parts of CaF2, 4-6 parts of fluorgypsum, and 0.2-0.4 parts of borax.

3. The belite-aluminate mineral additive according to claim 2, characterized in that: The raw materials are composed of the following components by weight: 25-40 parts of alumina tailings, 60-65 parts of carbide slag, 3-5 parts of coal gangue, 0.2 parts of CaF2, 5 parts of fluorgypsum and 0.3 parts of borax.

4. The method for preparing the belite-aluminate mineral additive according to any one of claims 1 to 3, characterized in that: The steps include: After grinding and drying the bauxite tailings, carbide slag, coal gangue and CaF2, they are mixed and calcined in proportion. The calcination temperature is 1200-1500°C and the calcination time is 50-70min. After calcination, they are rapidly cooled to room temperature. After the fired clinker is crushed, fluorgypsum and borax are added in proportion, mixed and ground to obtain the belite-aluminate mineral additive.

5. The method for preparing the belite-aluminate mineral additive according to claim 4, characterized in that: The specific surface area after grinding is 350-450 kg / m 2 .

6. The method for preparing the belite-aluminate mineral additive according to claim 5, characterized in that: The specific surface area after grinding is 400kg / m 2 .

7. Use of the belite-aluminate mineral additive according to any one of claims 1 to 3, or the belite-aluminate mineral additive prepared by the preparation method of the belite-aluminate mineral additive according to any one of claims 4 to 6 in modifying cement.

8. The use according to claim 7, characterized in that: When the belite-aluminate mineral additive is used to modify cement, the belite-aluminate mineral additive, fluorgypsum and silicate cement are uniformly mixed in a mass ratio of 9-15:0.2-0.8:85-95 to obtain the product.

9. The use according to claim 8, characterized in that: The mass ratio of belite-aluminate mineral additive, fluorgypsum and silicate cement is 9-12:0.4-0.6:88-92.

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