Low-carbon high-performance magnesium phosphate cement prepared from serpentine and preparation method of low-carbon high-performance magnesium phosphate cement

Abstract

The invention relates to the technical field of magnesium phosphate cement preparation, and particularly discloses low-carbon high-performance magnesium phosphate cement prepared from serpentine and a preparation method of the low-carbon high-performance magnesium phosphate cement. The magnesium phosphate cement comprises the following components in parts by weight: 50-75 parts of active powder obtained by co-calcining serpentine and calcareous components, 20-40 parts of phosphate and 2-10 parts of a retarder. The active powder is prepared by the following method: uniformly mixing serpentine powder and calcareous component powder, and then calcining. And grinding the calcined product to obtain the product. The method not only overcomes the problems of high carbon emission and high cost caused by preparation of magnesium phosphate cement from magnesite, but also solves the problem that low-activity serpentine cannot directly replace magnesite for preparation of magnesium phosphate cement.

Description

Technical Field

[0001] The invention relates to the technical field of magnesium phosphate cement preparation, and in particular to low-carbon and high-performance magnesium phosphate cement prepared by using serpentine and a preparation method thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Magnesium phosphate cement is a special cementitious material based on acid-base neutralization reaction. Compared with ordinary Portland cement, magnesium phosphate cement has the characteristics of fast hardening and early strength, good fluidity, high bonding strength, and small volume shrinkage. It has been widely used in the fields of rapid repair of concrete such as roads and bridges and solidification of hazardous waste. The excellent performance of magnesium phosphate cement also makes it show broad application prospects in the rapid repair of housing construction, factory facilities, highways and other projects.

[0004] Dead-burned magnesium oxide is the main component of magnesium phosphate cement (usually accounting for 50-80% by mass), and dead-burned magnesium oxide is usually obtained by calcining magnesite at above 1600°C. Its quality determines the performance of magnesium phosphate cement. However, my country's magnesite resources are unevenly distributed and have limited reserves. There are only large magnesite deposits in Liaoning and Shandong. Therefore, the price of magnesium oxide on the market is generally high, which limits the promotion and application of magnesium phosphate cement.

[0005] In addition, as the cement industry actively promotes the research and development of low-carbon cementitious materials, the carbon emissions of producing magnesium oxide by calcining magnesite have also been controversial. This is because magnesite decomposes and releases CO during the calcination process. 2 The average carbon emission for every ton of magnesium oxide produced is 1.3 to 1.5 tons, which results in the carbon emission of magnesium phosphate cement being even higher than that of silicate cement, which further restricts the development and promotion of magnesium phosphate cement. Summary of the invention

[0006] The present invention provides a low-carbon, high-performance magnesium phosphate cement prepared using serpentine and a preparation method thereof, which not only overcomes the high carbon emission and high cost problems caused by preparing magnesium phosphate cement using magnesite, but also solves the problem that low-activity serpentine cannot directly replace magnesite for the preparation of magnesium phosphate cement. Specifically, the technical solution of the present invention is as follows.

[0007] Firstly, the present invention discloses a low-carbon, high-performance magnesium phosphate cement prepared by using serpentine, comprising components in the following proportions: 50-75 parts by weight of active powder obtained by calcining serpentine and a calcareous component together, 20-40 parts by weight of phosphate, and 2-10 parts by weight of a retarder.

[0008] Furthermore, the phosphate includes at least one of ammonium dihydrogen phosphate, potassium dihydrogen phosphate, ammonium monohydrogen phosphate, potassium monohydrogen phosphate, etc.

[0009] Furthermore, the retarder includes at least one of borax, boric acid, triethanolamine and the like.

[0010] Furthermore, the particle size of the active powder is 1-75 μm.

[0011] Secondly, the present invention discloses a method for preparing the active powder, comprising the following steps: uniformly mixing serpentine powder and calcareous component powder, and then calcining the mixture. After the mixture is calcined, the calcined product is ground to obtain the active powder.

[0012] Furthermore, the mass ratio of the serpentine powder to the calcareous component powder is 40-55:45-55.

[0013] Furthermore, the calcareous component includes at least one of quicklime, slaked lime and carbide slag.

[0014] Furthermore, the particle size of the serpentine powder and the calcareous component powder is not less than 100 μm.

[0015] Furthermore, the calcination temperature is 900-1300° C., and the calcination time is 30-180 min.

[0016] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects: Serpentine is a magnesium silicate mineral [Mg 6 Si 4 O 10 (OH 8 )] as the main magnesium-containing substance. Compared with magnesite, serpentine has more abundant reserves and is more widely distributed throughout the country. If serpentine is used to replace magnesite to prepare magnesium phosphate cement, it is expected to solve the problems of high price and large carbon emissions of magnesium phosphate cement. However, since the magnesium silicate phase in serpentine is very stable at room temperature and has no reaction activity. To this end, the present invention calcined serpentine. However, the inventor found that: since the product formed after serpentine dehydration is [Mg 2 SiO 4] This inert mineral has no reaction activity and cannot form a gelling component, resulting in that the calcined struvite cannot be used to make magnesium phosphate cement. To this end, the present invention finds that when serpentine is mixed with a calcareous component and calcined together, not only the required calcination temperature (900-1300°C) is much lower than the temperature (above 1600°C) for calcining magnesia to prepare dead-burned magnesium oxide, which can greatly reduce fuel consumption and reduce costs. In addition, the calcareous component can be used to convert the mineral phase in serpentine into dicalcium silicate, while fully retaining the MgO in the serpentine, thereby forming the active powder of the MgO-dicalcium silicate-magnesium struvite system. When this active powder is used to prepare magnesium phosphate cement, the MgO, as an alkaline component in magnesium phosphate cement, reacts with phosphate to form a high-strength gelling hydration product struvite. The hydration rate of the dicalcium silicate is accelerated under the action of phosphate, and the formed hydrated dicalcium silicate forms an amorphous phosphosilicate product with phosphate, thereby being able to continuously contribute to the strength development of magnesium phosphate cement, so that the strength of magnesium phosphate cement, especially the strength in a humid environment, is continuously developed, which can effectively improve the problem of slow strength development rate or even shrinkage of traditional magnesium phosphate cement in a water environment, and improve the performance of magnesium phosphate cement while effectively expanding its application field. The magnesium silicate is filled in the pores of the hydration product of magnesium phosphate cement as a micro-aggregate, which helps to improve its density and mechanical properties. In summary, the present invention not only achieves the purpose of preparing magnesium phosphate cement by using serpentine instead of magnesite, but also, compared with the method of preparing dead-burned magnesium oxide by calcining magnesite, the present invention does not generate CO when calcining serpentine and calcareous components to prepare active components containing magnesium oxide. 2 , significantly reducing the carbon emissions of magnesium phosphate cement. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] 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.

[0018] Figure 1 This is a picture of the active powder sample prepared in the following Example 1.

[0019] Figure 2 This is a fluidity test chart of the magnesium phosphate cement prepared in the following Example 1.

[0020] Figure 3 This is a compressive strength test diagram of the magnesium phosphate cement prepared in the following Example 1. DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or under conditions recommended by the manufacturer.

[0022] Unless otherwise defined, all professional and scientific terms used in the present invention have the same meanings as those familiar to those skilled in the art. The reagents or raw materials used in the present invention can be purchased through conventional channels. Unless otherwise specified, the reagents or raw materials used in the present invention are used in a conventional manner in the art or in accordance with the product instructions.

[0023] In addition, any method and material similar or equivalent to the described content can be applied to the method of the present invention. The technical solution of the present invention is further described in conjunction with the accompanying drawings and specific embodiments.

[0024] Example 1 A method for preparing low-carbon, high-performance magnesium phosphate cement using serpentine, comprising the following steps: (1) Serpentine and quicklime are crushed and ground to a particle size of less than 100 μm. The obtained serpentine powder and quicklime powder are set aside.

[0025] (2) The serpentine powder and quicklime powder are mixed in a ratio of 55 parts by weight to 45 parts by weight and stirred evenly. The obtained mixture is then heated to 900°C at a heating rate of 10°C / min and calcined for 3 hours. After completion, the calcined product is naturally cooled, and then ground and passed through a square hole sieve with an aperture of 75 μm to obtain an active powder. The sample is as follows: Figure 1 shown.

[0026] (3) Weigh 68 parts by weight of the active powder of this embodiment, 22 parts by weight of potassium monohydrogen phosphate, and 10 parts by weight of boric acid according to the following proportions. Mix the above components evenly, add clean water at a water-binder ratio of 0.2, and stir evenly to obtain magnesium phosphate cement.

[0027] Performance test: 1. According to the "Concrete admixture homogeneity test method" (GB / T 8077-2023), the fluidity of the acid magnesium cement prepared in this embodiment was tested (such as Figure 2 2. According to the "Test Method for Cement Mortar Strength" (GB / T17671-2021), the early (3h) compressive strength and late (28d) compressive strength of the acid magnesium cement prepared in this embodiment were tested (as shown in Figure 33. Referring to the softening coefficient test method in JC / T 698-2010 "Gypsum Blocks", the test blocks prepared by the magnesium phosphate cement that were air-cured for 28 days were immersed in water for 24 hours, and the compressive strength before and after immersion was tested. The ratio of the strength after immersion in water to the strength before immersion in water was taken as the strength retention rate. The results are shown in the following table. It can be seen that the active powder enables the magnesium phosphate cement to maintain good strength in a water environment. This is because the active powder composed of magnesium oxide, dicalcium silicate and magnesia calcium silicate avoids the problem of strength shrinkage of magnesium phosphate cement in a water environment: .

[0028] Example 2 A method for preparing low-carbon, high-performance magnesium phosphate cement using serpentine, comprising the following steps: (1) The serpentine and slaked lime are crushed and ground to a particle size of less than 100 μm. The obtained serpentine powder and slaked lime powder are set aside.

[0029] (2) The serpentine powder and slaked lime powder are mixed in a ratio of 45 parts by weight: 55 parts by weight and stirred evenly. The obtained mixture is then heated to 1100°C at a heating rate of 10°C / min and calcined for 1 hour. After completion, the calcined product is naturally cooled, and then ground and passed through a square hole sieve with an aperture of 50 μm to obtain an active powder for standby use.

[0030] (3) Weigh 75 parts by weight of the active powder of this embodiment, 40 parts by weight of ammonium dihydrogen phosphate, and 8 parts by weight of boric acid according to the following proportions. Mix the above components evenly, add clean water at a water-binder ratio of 0.2, and stir evenly to obtain magnesium phosphate cement.

[0031] Performance test: 1. According to the "Test Method for Homogeneity of Concrete Admixtures" (GB / T 8077-2023), the fluidity of the acid magnesium cement prepared in this embodiment was tested. 2. According to the "Test Method for Strength of Cement Mortar" (GB / T17671-2021), the early (3h) compressive strength and late (28d) compressive strength of the acid magnesium cement prepared in this embodiment were tested. 3. Referring to the softening coefficient test method in JC / T 698-2010 "Gypsum Block", the test blocks prepared with the magnesium phosphate cement that had been air-cured for 28 days were immersed in water for 24 hours, and the compressive strength before and after immersion was tested. The ratio of the strength after immersion in water to the strength before immersion in water was used as the strength retention rate. The results are shown in the following table: .

[0032] Example 3 A method for preparing low-carbon, high-performance magnesium phosphate cement using serpentine, comprising the following steps: (1) Serpentine and carbide slag are crushed and ground to a particle size of less than 100 μm. The obtained serpentine powder and carbide slag powder are set aside.

[0033] (2) The serpentine powder and carbide slag powder are mixed in a ratio of 40 parts by weight to 50 parts by weight and stirred evenly. The obtained mixture is then heated to 1300°C at a heating rate of 15°C / min and calcined for 30 minutes. After completion, the calcined product is naturally cooled, and then ground and passed through a square hole sieve with a pore size of 1 μm to obtain an active powder for standby use.

[0034] (3) Weigh 50 parts by weight of the active powder of this embodiment, 20 parts by weight of potassium dihydrogen phosphate, and 2 parts by weight of borax according to the following proportions. Mix the above components evenly, add clean water at a water-binder ratio of 0.2, and stir evenly to obtain magnesium phosphate cement.

[0035] Performance test: 1. According to the "Test Method for Homogeneity of Concrete Admixtures" (GB / T 8077-2023), the fluidity of the acid magnesium cement prepared in this embodiment was tested. 2. According to the "Test Method for Strength of Cement Mortar" (GB / T17671-2021), the early (3h) compressive strength and late (28d) compressive strength of the acid magnesium cement prepared in this embodiment were tested. 3. Referring to the softening coefficient test method in JC / T 698-2010 "Gypsum Block", the test blocks prepared with the magnesium phosphate cement that had been air-cured for 28 days were immersed in water for 24 hours, and the compressive strength before and after immersion was tested. The ratio of the strength after immersion in water to the strength before immersion in water was used as the strength retention rate. The results are shown in the following table: .

[0036] Example 4 A method for preparing magnesium phosphate cement using magnesite, comprising the following steps: (1) The magnesite is crushed and ground to a particle size of less than 100 μm to obtain magnesite powder for later use.

[0037] (2) The magnesite powder is heated to 1600°C at a heating rate of 10°C / min and calcined for 3 hours, then taken out and naturally cooled; after completion, the calcined product is naturally cooled, and then ground and passed through a square hole sieve with an aperture of 75 μm to obtain dead-burned magnesium oxide, which is set aside.

[0038] (3) Weigh 68 parts by weight of the dead-burned magnesium oxide, 22 parts by weight of potassium monohydrogen phosphate, and 10 parts by weight of boric acid according to the following proportions. Mix the above components evenly, add clean water at a water-binder ratio of 0.2, and stir evenly to obtain magnesium phosphate cement.

[0039] Performance test: 1. According to the "Test Method for Homogeneity of Concrete Admixtures" (GB / T 8077-2023), the fluidity of the acid magnesium cement prepared in this embodiment was tested. 2. According to the "Test Method for Strength of Cement Mortar" (GB / T17671-2021), the early (3h) compressive strength and late (28d) compressive strength of the acid magnesium cement prepared in this embodiment were tested. 3. Referring to the softening coefficient test method in JC / T 698-2010 "Gypsum Block", the test blocks prepared with the magnesium phosphate cement that had been air-cured for 28 days were immersed in water for 24 hours, and the compressive strength before and after immersion was tested. The ratio of the strength after immersion in water to the strength before immersion in water was used as the strength retention rate. The results are shown in the following table: .

[0040] Example 5 A method for preparing low-carbon, high-performance magnesium phosphate cement using serpentine, comprising the following steps: (1) The serpentine is crushed and ground to a particle size of less than 100 μm to obtain serpentine powder for later use.

[0041] (2) The serpentine powder is heated to 1100° C. at a heating rate of 10° C. / min and calcined for 1 h. After completion, the calcined product is naturally cooled, and then ground and passed through a square hole sieve with a pore size of 50 μm to obtain calcined serpentine powder for later use.

[0042] (3) Weigh 75 parts by weight of the calcined serpentine powder, 40 parts by weight of ammonium dihydrogen phosphate, and 8 parts by weight of boric acid according to the following proportions. Mix the above components evenly, add clean water at a water-binder ratio of 0.2, and stir evenly to obtain magnesium phosphate cement.

[0043] Performance test: The fluidity of the acid magnesium cement prepared in this embodiment was tested according to the "Test Method for Homogeneity of Concrete Admixtures" (GB / T 8077-2023). The test results show that the fluidity is 128 mm. In addition, since only calcining serpentine results in inactive magnesium silicate formed by dehydration, it cannot react with phosphate to form a gelling component, and a test block cannot be obtained for testing, so the strength cannot be formed.

[0044] Example 6 A method for preparing low-carbon, high-performance magnesium phosphate cement using serpentine, comprising the following steps: (1) The magnesite and carbide slag are crushed and ground to a particle size of less than 100 μm, and the obtained magnesite powder and carbide slag powder are set aside.

[0045] (2) The magnesite powder and carbide slag powder are mixed in a ratio of 40 parts by weight to 50 parts by weight and stirred evenly. The obtained mixture is then heated to 1300°C at a heating rate of 15°C / min and calcined for 30 minutes. After completion, the calcined product is naturally cooled, and then ground and passed through a square hole sieve with an aperture of 1 μm to obtain an active powder for standby use.

[0046] (3) Weigh 50 parts by weight of the active powder of this embodiment, 20 parts by weight of potassium dihydrogen phosphate, and 2 parts by weight of borax according to the following proportions. Mix the above components evenly, add clean water at a water-binder ratio of 0.2, and stir evenly to obtain magnesium phosphate cement.

[0047] Performance test: 1. According to the "Test Method for Homogeneity of Concrete Admixtures" (GB / T 8077-2023), the fluidity of the acid magnesium cement prepared in this embodiment was tested. 2. According to the "Test Method for Strength of Cement Mortar" (GB / T17671-2021), the early (3h) compressive strength and late (28d) compressive strength of the acid magnesium cement prepared in this embodiment were tested. 3. Referring to the softening coefficient test method in JC / T 698-2010 "Gypsum Block", the test block prepared by the magnesium phosphate cement that was air-cured for 28 days was immersed in water for 24 hours, and its compressive strength before and after immersion was tested. The ratio of the strength after immersion in water to the strength before immersion in water was used as the strength retention rate. The results are shown in the following table. This is because: the components of the active powder are MgO and CaO, which react very quickly with phosphates, resulting in a rapid loss of fluidity of the magnesium phosphate cement, and due to the intense heat release during the reaction, the concrete becomes porous inside, resulting in a decrease in strength: .

[0048] The above description is only a preferred embodiment of the present invention and is 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 can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. 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 low-carbon, high-performance magnesium phosphate cement prepared using serpentine, characterized in that: The invention comprises the following components in the following proportions: 50-75 parts by weight of active powder obtained by calcining serpentine and calcareous components together, 20-40 parts by weight of phosphate, and 2-10 parts by weight of retarder.

2. The low-carbon, high-performance magnesium phosphate cement prepared using serpentine according to claim 1, characterized in that: The phosphate includes at least one of ammonium dihydrogen phosphate, potassium dihydrogen phosphate, ammonium monohydrogen phosphate, and potassium monohydrogen phosphate.

3. The low-carbon, high-performance magnesium phosphate cement prepared using serpentine according to claim 1, characterized in that: The retarder comprises at least one of borax, boric acid and triethanolamine.

4. The low-carbon, high-performance magnesium phosphate cement prepared using serpentine according to claim 1, characterized in that: The particle size of the active powder is 1-75 μm.

5. The low-carbon, high-performance magnesium phosphate cement prepared using serpentine according to any one of claims 1 to 4, characterized in that: The active powder is prepared by the following method: serpentine powder and calcareous component powder are mixed evenly, and then calcined; after completion, the calcined product is ground to obtain the active powder.

6. The low-carbon, high-performance magnesium phosphate cement prepared using serpentine according to claim 5, characterized in that: The mass ratio of the serpentine powder to the calcareous component powder is 40-55:45-55.

7. The low-carbon, high-performance magnesium phosphate cement prepared using serpentine according to claim 5, characterized in that: The calcareous component includes at least one of quicklime, slaked lime and carbide slag.

8. The low-carbon, high-performance magnesium phosphate cement prepared using serpentine according to claim 5, characterized in that: The particle size of the serpentine powder is not less than 100 μm.

9. The low-carbon, high-performance magnesium phosphate cement prepared using serpentine according to claim 5, characterized in that: The particle size of the calcareous component powder is not less than 100 μm.

10. The low-carbon, high-performance magnesium phosphate cement prepared using serpentine according to any one of claims 5 to 9, characterized in that: The calcination temperature is 900-1300° C., and the calcination time is 30-180 minutes.

Images