Preparation method for preparing magnesium oxysulfate cement by using thermally activated boric sludge

Abstract

The invention relates to a preparation method for preparing magnesium oxysulfate cement by using thermally activated boric sludge, which comprises the following steps: step 1, drying boric sludge, then carrying out ball milling, and sieving with a 200-mesh sieve; 2, activating the activity of magnesium oxide in the boric sludge: thermally activating the boric sludge treated in the step 1 to decompose magnesium carbonate in the boric sludge into magnesium oxide to obtain thermally activated boric sludge containing active magnesium oxide; step 3, respectively grinding an additive and magnesium sulfate heptahydrate; step 4, adding magnesium oxide into the thermally activated boron mud in the step 2, pouring the mixture into a planetary stirrer for multiple times, and mixing and stirring the mixture at the speed of 60-70r / min for 30-60s to obtain uniformly mixed powder; and 5, preparing the boron mud magnesium oxysulfate cement building material. The method has the advantages that a series of problems of boron mud treatment, complex process, low boron mud use amount and the like are effectively solved, meanwhile, the production cost of the magnesium oxysulfate cement is reduced, the boron mud treatment cost is saved, and good economic benefits and ecological benefits can be obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and in particular relates to a method for preparing building materials by utilizing thermally activated boron mud. Background Art

[0002] Boric acid, borax and other products are produced when producing a kind of industrial solid waste residue, the main components of which are calcite and forsterite. With the rapid development of the national economy and society, the total amount of boric acid produced each year has reached more than 2 million tons, and the amount of boric acid produced has reached more than 20 million tons.

[0003] Boron mud is usually treated by natural stacking, and the utilization rate of boron mud is only about 20% of the newly generated boron mud. The long-term accumulation of boron mud occupies a large amount of land resources and causes waste of land resources. Especially in some areas with scarce land resources, the accumulation problem of boron mud is more prominent.

[0004] Impact on land environment: Boric mud contains a large amount of alkaline substances. After these alkaline substances are discharged into the environment, their alkaline liquid can dissolve into groundwater, increasing the pH value of the surrounding farmland soil and causing soil salinization. Salinized soil will inhibit the growth of crops, reduce crop yields, and even cause crop failure in severe cases. Where the boric mud is discharged, due to the serious salinization of the soil, there is often no grass, which damages the ecological environment. Impact on groundwater: Harmful substances in boric mud may enter the groundwater system through infiltration, pollute the groundwater, and affect the drinking water safety of surrounding residents. Impact on the atmosphere: Boric mud particles are relatively fine, and after losing water, they are easily scattered by the wind, forming dust pollution, which pollutes the atmospheric environment. Impact on water bodies: Some chemical plants discharge boric mud directly into rivers, which not only pollutes the river water, but also may block the river and become a hidden danger of floods.

[0005] In recent years, the comprehensive utilization of borax mud mainly includes the recovery of magnesium in borax mud, metallurgical extraction, and the preparation of building materials, concrete, and flocculants for wastewater treatment using borax mud as raw materials. Among them, the recovery and utilization of magnesium in borax mud has attracted great attention. At present, there are building materials applications using borax mud to prepare aerated wall tiles and floor tiles, but these have not been harmlessly treated for borax mud, which may cause environmental pollution. There are also some other applications, such as China's invention patent 202111046142.8, which has a relatively complicated treatment process for borax mud, and its strength is somewhat different from that of existing silicate cement. The resource utilization and industrialization of borax mud have not yet been fully realized, and its actual application is not widespread. Although China's invention patent 202410204303.9 processes a large amount of borax mud, the process is relatively complicated and the final strength is low, and there are few large-scale application scenarios.

[0006] Based on the universality of boron mud application, large dosage, harmlessness and industrial simplification, boron mud building materials currently utilize boron mud to obtain cementitious materials, industrial products or other building products, the final sample effect is poor, the amount of boron mud is small, the process difficulty is large and the intensity is generally not high, but a considerable part of the application scenarios require simple process, good long-term performance, etc., therefore solve the boron mud application problem of this part of demand, become the difficulty in the boron mud resource process. To fundamentally solve the problem of large-scale application of boron mud, or should be based on boron mud building materials, should just meet the requirements of these four aspects. Therefore, the present invention prepares building materials with boron mud as admixture, not only will not produce new solid waste, and can fully realize the resource and harmlessness of boron mud, with extremely high economic benefit and environmental benefit, meet national development needs. Summary of the invention

[0007] Purpose of the Invention

[0008] The purpose of the present invention is to improve the comprehensive utilization rate of industrial waste boron mud, and to provide a large-volume solid waste building material with thermally activated boron mud as the main raw material and a preparation method thereof.

[0009] Technical Solution

[0010] To achieve the above objectives, the present invention is achieved through the following technical solutions:

[0011] A method for preparing magnesium oxysulfate cement by utilizing thermally activated boron mud comprises the following steps:

[0012] Step 1: Dry the boron mud and then ball grind it through a 200-mesh sieve;

[0013] Step 2, activating the activity of magnesium oxide in the boron mud: thermally activating the boron mud treated in step 1, decomposing the magnesium carbonate therein to generate magnesium oxide, and obtaining thermally activated boron mud containing active magnesium oxide;

[0014] Step 3, grinding the admixture and magnesium sulfate heptahydrate separately;

[0015] Step 4: Add the heat-activated boron mud of step 2 to magnesium oxide, pour it into a planetary mixer several times, and mix and stir at a speed of 60 to 70 r / min for 30 to 60 seconds to obtain a uniformly mixed powder;

[0016] Step 5, preparing borax magnesium oxysulfide cement building materials: when borax magnesium oxysulfide cement is prepared by grinding, firstly, the magnesium sulfate heptahydrate and the admixture in step 3 are respectively ground and mixed with the mixed powder, then the prepared water is poured into a planetary mixer, 1 / 3 to 1 / 2 of the mixed powder is continued to be added, and stirred at a speed of 60 to 70 r / min for 30 to 60 s until the slurry is uniform, and the remaining mixed powder is continued to be added, and the mixture is stirred at a speed of 60 to 70 r / min for 5 to 10 minutes to obtain a cementitious material slurry, and finally poured into a mold for molding and curing to obtain magnesium oxysulfide cement.

[0017] As a further description of the above scheme, in step one, the borax mud is first dried at 100-110° C., and after 24 hours, it is placed in a ball mill for the first mechanical ball milling for 15-30 minutes at a rotation speed of 200-300 rpm, and passed through a 100-mesh sieve to obtain borax mud powder. The sieved powder is placed in a ball mill for the second mechanical ball milling for 30-60 minutes at a rotation speed of 300-500 rpm, and passed through a 200-mesh sieve.

[0018] As a further description of the above scheme, in step 2, the thermal activation temperature of the boron mud is 500-900°C, the thermal activation insulation time is 1-3h, the heating rate is ≤5-10°C / min, and the magnesium oxide activity in the boron mud after thermal activation is 20-25%.

[0019] As a further description of the above scheme, in the step 2, the components of the industrial borax mud used are: MgO: 30-55.5%, SiO2: 25-40%, Al2O3: 3.5-5%, CaO: 4-9.5%, Fe2O3: 9-9.44%, Na2O: 1-4%, K2O: 1-2% and other impurities: 1-2%.

[0020] As a further description of the above scheme, in step three, the grinding treatment of the admixture and magnesium sulfate heptahydrate is to put the magnesium sulfate heptahydrate and the admixture into a grinding mill and grind them for 30 to 60 seconds respectively, and the rotation speed of the grinding mill is 28000r / min.

[0021] As a further description of the above scheme, the additive is one or more of citric acid, liquid phosphoric acid, and zinc sulfate, and the additive dosage is 0 to 1.3% of the total mass of the heat-activated boric mud and magnesium oxide.

[0022] As a further description of the above scheme, in the step four, the mass ratio of the magnesium oxide to the heat-activated borax mud is 0.89-1:1, the purity of the magnesium oxide is greater than 85%, and the content of active magnesium oxide in the magnesium oxide is 50-65% by mass; in the step five, the ratio of the mass of magnesium sulfate heptahydrate to the sum of the mass of magnesium oxide and the heat-activated borax mud is 1:2-2.16.

[0023] A building material with a large amount of solid waste prepared by the above-mentioned preparation method.

[0024] Advantages and effects

[0025] (1) Mechanical properties: The magnesium oxysulfate cement prepared by heat-activated boron mud in the present invention has greatly improved mechanical properties compared with the magnesium cement prepared by existing boron mud. The heat-activated boron mud not only has a low requirement for the magnesium oxide content of the boron mud, but also the active magnesium oxide in the boron mud after heat activation participates in the hydration reaction to generate a 5·1·7 phase, which provides a source of strength for the magnesium oxysulfate cement. The modification mechanism of the magnesium oxysulfate cement is as follows: first, the magnesium oxide particles will quickly hydrate after contacting with water, forming a hydration layer on the surface, and releasing OH into the solution. — , then OH — It continues to increase and react with the hydration layer to generate Mg(OH)2, which eventually leads to the destruction of the hydration layer and continuously generates Mg(OH)2 with magnesium oxide. When the homemade admixture is added, the admixture will ionize H + , neutralize part of the OH in the solution — , which reduces the surface energy of the hydration film and reacts with the hydration layer to generate [Ca n— →Mg(OH)(H2O) x-1 ] inhibit the formation of Mg(OH)2, the metal cation Zn in ZnSO4 2+ With OH — The generated Zn(OH)2 further prevents the generation of Mg(OH)2, thus preventing the magnesium oxysulfate cement from expanding and cracking due to the generated Mg(OH)2. 2+ It forms compounds such as magnesium phosphate, which affect the early hardening and impermeability of cement during the hydration process.

[0026] (2) Economic benefits: The present invention uses thermally activated boron mud to replace part of the magnesium oxide, and the required raw materials are few and easy to obtain, which reduces the cost of cement production and provides feasibility for industrialized cement production.

[0027] (3) Environmental protection: The preparation of the present invention requires the addition of boron mud, which is beneficial to solve the problem of excessive stacking of boron mud, reduce environmental pollution, and fully realize the resource utilization and harmlessness of boron mud, with extremely high economic and environmental benefits.

[0028] (4) Scope of application: The present invention can stimulate the activity of magnesium oxide in the boron mud by pre-treating the boron mud, so that it can be flexibly applied to various magnesium building materials, such as foam, building blocks, plates, etc., thereby increasing its universality. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention is further described below in conjunction with the accompanying drawings and specific implementation methods. The protection scope of the present invention is not limited to the following description.

[0030] Figure 1 This is a schematic diagram of the 28d microstructure of Comparative Example 1 of the present invention;

[0031] Figure 2 This is a schematic diagram of the 28d microstructure of Example 1 of the present invention;

[0032] Figure 3 The present invention is a flow chart for preparing the building material. DETAILED DESCRIPTION

[0033] The following embodiments are further descriptions of the content of the present invention as an explanation of the technical content of the present invention, but the essential content of the present invention is not limited to the following embodiments. Ordinary technicians in this field can and should know that any simple changes or replacements based on the essential spirit of the present invention should fall within the scope of protection required by the present invention.

[0034] A method for preparing magnesium oxysulfate cement by utilizing thermally activated boron mud comprises the following steps:

[0035] Step 1: Dry the boron mud, and then ball grind it through a 200-mesh sieve;

[0036] Step 2, activating the activity of magnesium oxide in the boron mud: thermally activating the boron mud treated in step 1, decomposing the magnesium carbonate therein to generate magnesium oxide, and obtaining thermally activated boron mud containing active magnesium oxide;

[0037] Step 3, grinding the admixture and magnesium sulfate heptahydrate separately;

[0038] Step 4: Add the heat-activated boron mud of step 2 to magnesium oxide, pour it into a planetary mixer several times, and mix and stir at a speed of 60 to 70 r / min for 30 to 60 seconds to obtain a uniformly mixed powder;

[0039] Step 5, preparing borax magnesium oxysulfate cement building materials: first, the magnesium sulfate heptahydrate and the admixture in step 3 are respectively ground and mixed with the mixed powder, then the prepared water is poured into a planetary mixer, and 1 / 3 to 1 / 2 of the mixed powder is continued to be added, and stirred at a speed of 60 to 70 r / min for 30 to 60 seconds until the slurry is uniform, and the remaining mixed powder is continued to be added, and the mixture is stirred at a speed of 60 to 70 r / min for 5 to 10 minutes to obtain a cementitious material slurry, and finally poured into a mold for molding and curing to obtain magnesium oxysulfate cement.

[0040] When the borax magnesium oxysulfate cement is prepared by dissolving, magnesium sulfate heptahydrate and an admixture are first dissolved in water to form a magnesium sulfate solution, and then the magnesium sulfate solution is poured into a planetary mixer and 1 / 3 to 1 / 2 of the mixed powder is added and stirred at a speed of 60 to 70 r / min for 30 to 60 seconds until the slurry is uniform, and then the remaining mixed powder is added and mixed and stirred at a speed of 60 to 70 r / min for 5 to 10 minutes to obtain a cementitious material slurry, which is finally poured into a mold for molding and curing to obtain the magnesium oxysulfate cement. Compared with the dissolution preparation method, the grinding preparation process is simple and more convenient to implement; the magnesium oxysulfate cement prepared by the heat-activated boron mud in the present invention has greatly improved mechanical properties compared with the existing magnesium cement prepared by the boron mud, the heat-activated boron mud not only has a low requirement for the content of magnesium oxide in the boron mud, but also the active magnesium oxide in the boron mud after heat activation participates in the hydration reaction to generate a 5·1·7 phase, which provides a source of strength for the magnesium oxysulfate cement. The modification mechanism of the magnesium oxysulfate cement is: first, the magnesium oxide particles will quickly hydrate after contacting with water, a hydration layer will be formed on the surface, and OH will be released into the solution. — , then OH — It continues to increase and react with the hydration layer to generate Mg(OH)2, which eventually leads to the destruction of the hydration layer and continuously generates Mg(OH)2 with magnesium oxide. When the homemade admixture is added, the admixture will ionize H + , neutralize part of the OH in the solution — , which reduces the surface energy of the hydration film and reacts with the hydration layer to generate [Ca n— →Mg(OH)(H2O) x-1 ] inhibit the formation of Mg(OH)2, the metal cation Zn in ZnSO4 2+ With OH — The generated Zn(OH)2 further prevents the generation of Mg(OH)2, thus preventing the magnesium oxysulfate cement from expanding and cracking due to the generated Mg(OH)2. 2+ Compounds such as magnesium phosphate are formed, which affect the early hardening and impermeability of cement during the hydration process; secondly, heat-activated boron mud is used to replace part of the magnesium oxide, and the required raw materials are few and easy to obtain, which reduces the cost of cement production and provides feasibility for industrialized production of cement; in addition, the preparation requires the addition of boron mud, which is conducive to solving the problem of excessive stacking of boron mud, reducing environmental pollution, and fully realizing the resource utilization and harmlessness of boron mud, with extremely high economic and environmental benefits; finally, the present invention can stimulate the activity of magnesium oxide in boron mud by pretreating the boron mud, so that it can be flexibly applied to various magnesium building materials, such as foams, blocks, plates, etc., increasing universality.

[0041] In step 1 of the present invention, the borax is first dried at 100-110°C, and after 24 hours, it is placed in a ball mill for the first mechanical ball milling for 15-30 minutes at a rotation speed of 200-300 revolutions, and passed through a 100-mesh sieve to obtain borax powder, and the sieved powder is placed in a ball mill for the second mechanical ball milling for 30-60 minutes at a rotation speed of 300-500 revolutions, and passed through a 200-mesh sieve. The present invention processes the borax into smaller borax powder, and a smaller particle size means a larger specific surface area, which increases the contact area between the material and the heat. This promotes the heat and mass transfer process and makes the chemical reaction occur more rapidly. Small-particle materials are more likely to achieve uniform temperature distribution during heating, avoiding local over-burning or under-burning caused by excessive internal temperature gradients. This helps to improve the quality and consistency of the product. Impurities or volatile components in small-particle materials are more easily removed during the calcination process, thereby improving the purity of the product.

[0042] In the second step of the present invention, the thermal activation temperature of the boron mud is 500-900° C., the thermal activation holding time is 1-3 hours, the heating rate is ≤5-10° C. / min, and the magnesium oxide activity in the boron mud after thermal activation is 20-25%.

[0043] In step 2 of the present invention, the industrial borax mud used has the following components: MgO: 30-55.5%, SiO2: 25-40%, Al2O3: 3.5-5%, CaO: 4-9.5%, Fe2O3: 9-9.44%, Na2O: 1-4%, K2O: 1-2% and other impurities: 1-2%.

[0044] In step three of the present invention, the grinding treatment of the admixture and magnesium sulfate heptahydrate is to put the magnesium sulfate heptahydrate and the admixture into a grinding mill and grind them for 30 to 60 seconds respectively, and the rotation speed of the grinding mill is 28000 r / min.

[0045] The additive of the invention is one or more of citric acid, liquid phosphoric acid and zinc sulfate, and the additive dosage is 0-1.3% of the total mass of the heat-activated boron mud and magnesium oxide. Advantages of homemade modifiers: First, magnesium oxide particles will quickly hydrate after contact with water, forming a hydration layer on the surface, releasing OH- into the solution, and then OH- will continue to increase and react with the hydration layer to generate Mg(OH)2, finally leading to the destruction of the hydration layer, and continuously generating Mg(OH)2 with magnesium oxide. When homemade admixtures are added, the admixtures will ionize H+, neutralize part of the OH- in the solution, reduce the surface energy of the hydration film, and react with the hydration layer to generate [Can—→Mg(OH)(H2O)x-1] to inhibit the generation of Mg(OH)2. The metal cation Zn2+ in ZnSO4 reacts with OH- to generate Zn(OH)2, further preventing the generation of Mg(OH)2, and preventing magnesium oxysulfate cement from expanding and cracking due to the generation of Mg(OH)2 when soaked in water. Phosphate ions react with Mg2+ to form compounds such as magnesium phosphate, which affect the early hardening and impermeability of cement during the hydration process.

[0046] In step 4 of the present invention, the mass ratio of magnesium oxide to heat-activated boron mud is 0.89-1:1, wherein the purity of magnesium oxide is greater than 85%, and the content of active magnesium oxide in the magnesium oxide is 50-65% by mass; in step 5, the ratio of the mass of magnesium sulfate heptahydrate to the mass sum of magnesium oxide and heat-activated boron mud is 1:2-2.16. A large-volume solid waste building material prepared by the above-mentioned preparation method. The present invention is a large-volume solid waste building material with the following advantages. The present invention uses heat-activated boron mud to replace part of the magnesium oxide, and the required raw materials are less and easy to obtain, which reduces the cost of cement production and provides feasibility for industrialized cement production. Green and environmentally friendly: The preparation of the present invention requires the addition of boron mud, which is conducive to solving the problem of excessive stacking of boron mud, reducing environmental pollution, and fully realizing the resource utilization and harmlessness of boron mud, with extremely high economic and environmental benefits.

[0047] Example 1

[0048] A boric mud magnesium oxysulfate cement, wherein the raw materials used include heat-activated boric mud, magnesium oxide, magnesium sulfate heptahydrate, and an admixture, wherein the mass ratio of magnesium oxide to heat-activated boric mud is 1:1, and the mass ratio of magnesium sulfate heptahydrate to the sum of magnesium oxide and heat-activated boric mud is 1:2.16.

[0049] The thermally activated boron mud in this embodiment has a thermal activation temperature of 700° C. and a thermal activation time of 2 hours. After thermal activation, the activity of magnesium oxide in the boron mud is 21.44%.

[0050] The magnesium oxide in this embodiment has an active MgO content of 50-65%, an optimal active MgO content of 60%±2%, a MgO purity of ≥80%, and an optimal MgO purity of 85%±2%.

[0051] The industrial boron mud composition in this embodiment is as follows:

[0052]

[0053] The magnesium sulfate in this embodiment is magnesium sulfate heptahydrate, the purity of MgSO4·7H2O is ≥99%, and the content of MgSO4 is ≥47%.

[0054] The additives in this embodiment include citric acid, liquid phosphoric acid and zinc sulfate, the purity of citric acid is ≥99.5%, and the impurity is ≤0.5%. The liquid phosphoric acid is liquid, and the effective content is ≥85%; the zinc sulfate is analytically pure ≥99.5%;

[0055] Specifically, the water-cement ratio is 0.25, and the admixtures include 0.5% of citric acid, 0.5% of liquid phosphoric acid, and 0.3% of zinc sulfate, based on the total weight of the heat-activated boric mud and magnesium oxide.

[0056] Example 2

[0057] A boric mud magnesium oxysulfate cement, wherein the raw materials used include heat-activated boric mud, magnesium oxide, magnesium sulfate heptahydrate, and an admixture, wherein the mass ratio of magnesium oxide to heat-activated boric mud is 1:1, and the mass ratio of magnesium sulfate heptahydrate to the sum of magnesium oxide and heat-activated boric mud is 1:2.16.

[0058] The thermally activated boron mud in this embodiment has a thermal activation temperature of 700° C. and a thermal activation time of 2 hours. After thermal activation, the activity of magnesium oxide in the boron mud is 21.44%.

[0059] The magnesium oxide in this embodiment has an active MgO content of 50-65%, an optimal active MgO content of 60%±2%, a MgO purity of ≥80%, and an optimal MgO purity of 85%±2%.

[0060] The industrial boron mud composition in this embodiment is as follows:

[0061]

[0062] The magnesium sulfate in this embodiment is magnesium sulfate heptahydrate, the purity of MgSO4·7H2O is ≥99%, and the content of MgSO4 is ≥47%.

[0063] The additives in this embodiment include citric acid, liquid phosphoric acid and zinc sulfate, the purity of citric acid is ≥99.5%, and the impurities are ≤0.5%. The liquid phosphoric acid is liquid, and the effective content is ≥85%; specifically, the water-cement ratio is 0.25, and the additives include 0.5% of citric acid, 0.5% of liquid phosphoric acid, and 0% of zinc sulfate, accounting for the total weight of boric mud and magnesium oxide.

[0064] Example 3

[0065] A boric mud magnesium oxysulfate cement, wherein the raw materials used include heat-activated boric mud, magnesium oxide, magnesium sulfate heptahydrate, and an admixture, wherein the mass ratio of magnesium oxide to heat-activated boric mud is 1:1, and the mass ratio of magnesium sulfate heptahydrate to the sum of magnesium oxide and heat-activated boric mud is 1:2.16.

[0066] The thermally activated boron mud in this embodiment has a thermal activation temperature of 700° C. and a thermal activation time of 2 hours. After thermal activation, the activity of magnesium oxide in the boron mud is 21.44%.

[0067] The magnesium oxide in this embodiment has an active MgO content of 65%, an optimal active MgO content of 60%±2%, a MgO purity of ≥80%, and an optimal MgO purity of 85%±2%.

[0068] The industrial boron mud composition in this embodiment is as follows:

[0069]

[0070] The magnesium sulfate in the embodiment is magnesium sulfate heptahydrate, the purity of MgSO4·7H2O is ≥99%, and the content of MgSO4 is ≥47%.

[0071] The additives in this embodiment include citric acid, liquid phosphoric acid and zinc sulfate, the purity of citric acid is ≥99.5%, and the impurities are ≤0.5%. The zinc sulfate is analytically pure ≥99.5%;

[0072] Specifically, the water-cement ratio is 0.25, and the admixtures include 0.5% of citric acid, 0% of liquid phosphoric acid, and 0.5% of zinc sulfate based on the total weight of the boric mud and magnesium oxide.

[0073] Comparative Example 1

[0074] A heat-activated boric mud magnesium oxysulfate cement is similar to Example 1, except that the admixture includes 0% citric acid, 0% liquid phosphoric acid, and 0% zinc sulfate based on the total weight of the boric mud and magnesium oxide.

[0075] As shown in Table 1, it can be seen from the examples and comparative examples that the modified samples have high strength, good appearance quality, and good thermally activated boron mud treatment effect, while the unmodified samples have low strength. After adding the self-prepared admixture, the strength of the sample increased significantly in the later stage, and the curing effect of the thermally activated boron mud was good. Compared with the single admixture currently on the market, the sample has good stability after using the self-prepared admixture.

[0076] Comparative Example 1 Example 1 Example 2 Example 3 3d Strength 11.5Mpa 28.8Mpa 34.4Mpa 25.6Mpa 7d Strength 18.7Mpa 52.9Mpa 42.2Mpa 34.5Mpa 28d strength 22.9Mpa 68.1Mpa 54.7Mpa 39.4Mpa

[0077] Table 1

[0078] like Figure 1 and Figure 2As shown in Example 1 and Comparative Example 1, it can be seen that the whiskers in the matrix of the sample with admixture are better developed than those in the blank sample, and a large number of 5·1·7 phases with dense interlaced structures are the important reasons for the high compressive strength of boric mud magnesium oxysulfate cement.

[0079] Obviously, the above-mentioned embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the embodiments of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made on the basis of the above description. It is impossible to list all the embodiments here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing magnesium oxysulfate cement using thermally activated boron mud, characterized in that: The steps include: Step 1: Dry the boron mud and then ball grind it through a 200-mesh sieve; Step 2, activating the activity of magnesium oxide in the boron mud: thermally activating the boron mud treated in step 1, decomposing the magnesium carbonate therein to generate magnesium oxide, and obtaining thermally activated boron mud containing active magnesium oxide; Step 3, grinding the admixture and magnesium sulfate heptahydrate separately; Step 4: Add the heat-activated boron mud of step 2 to magnesium oxide, pour it into a planetary mixer several times, and mix and stir at a speed of 60 to 70 r / min for 30 to 60 seconds to obtain a uniformly mixed powder; Step 5, preparing borax magnesium oxysulfate cement building materials: first, the magnesium sulfate heptahydrate and the admixture in step 3 are respectively ground and mixed with the mixed powder, then the prepared water is poured into a planetary mixer, and 1 / 3 to 1 / 2 of the mixed powder is continued to be added, and stirred at a speed of 60 to 70 r / min for 30 to 60 seconds until the slurry is uniform, and the remaining mixed powder is continued to be added, and the mixture is stirred at a speed of 60 to 70 r / min for 5 to 10 minutes to obtain a cementitious material slurry, and finally poured into a mold for molding and curing to obtain magnesium oxysulfate cement.

2. The preparation method according to claim 1, characterized in that: In the step 1, the boron mud is first dried at 100-110° C., and after 24 hours, it is placed in a ball mill for a first mechanical ball milling for 15-30 minutes at a rotation speed of 200-300 revolutions, and passed through a 100-mesh sieve to obtain boron mud powder, and the sieved powder is placed in a ball mill for a second mechanical ball milling for 30-60 minutes at a rotation speed of 300-500 revolutions, and passed through a 200-mesh sieve.

3. The preparation method according to claim 1, characterized in that: In the step 2, the thermal activation temperature of the boron mud is 500-900° C., the thermal activation holding time is 1-3 hours, the heating rate is ≤5-10° C. / min, and the magnesium oxide activity in the boron mud after thermal activation is 20-25%.

4. The preparation method according to claim 1, characterized in that: In the step 2, the components of the industrial borax mud used are: MgO: 30-55.5%, SiO2: 25-40%, Al2O3: 3.5-5%, CaO: 4-9.5%, Fe2O3: 9-9.44%, Na2O: 1-4%, K2O: 1-2% and other impurities: 1-2%.

5. The preparation method according to claim 1, characterized in that: In the step 3, the grinding treatment of the admixture and magnesium sulfate heptahydrate is to put the magnesium sulfate heptahydrate and the admixture into a grinding mill and grind them for 30 to 60 seconds respectively, and the rotation speed of the grinding mill is 28000 r / min.

6. The preparation method according to claim 1, characterized in that: The additive is one or more of citric acid, liquid phosphoric acid and zinc sulfate, and the additive dosage is 0-1.3% of the total mass of the heat-activated boron mud and magnesium oxide.

7. The preparation method according to any one of claims 1 to 4, characterized in that: In the step 4, the mass ratio of the magnesium oxide to the heat-activated borax mud is 0.89-1:1, the purity of the magnesium oxide is greater than 85%, and the content of active magnesium oxide in the magnesium oxide is 50-65% by mass; in the step 5, the ratio of the mass of magnesium sulfate heptahydrate to the sum of the mass of magnesium oxide and the heat-activated borax mud is 1:2-2.

16.

8. A building material with a large amount of solid waste prepared by the preparation method as claimed in any one of claims 1 to 7.

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