A recycled phosphate cement and its preparation method

Abstract

This invention discloses a recycled phosphate cement and its preparation method. The cement comprises recycled powder, phosphate, and a retarder: wherein, by weight, the recycled powder comprises 45-75 parts, the phosphate comprises 15-50 parts, and the retarder comprises 0-10 parts. This invention utilizes waste magnesium phosphate cement to prepare recycled phosphate cement, solving the problem of high energy consumption when using recycled powder to replace magnesite-prepared reburned magnesium oxide in phosphate cement. It broadens the range of raw material sources for phosphate cement and reduces the high cost of existing magnesium phosphate cement. Furthermore, the struvite monohydrate and novel amorphous seed crystals in the recycled powder can promote early hydration reactions, improving the early strength development of recycled magnesium phosphate cement and compensating for the poor cement performance caused by the low total MgO content in recycled magnesium phosphate cement. Recycled phosphate cement solves the problem of waste magnesium phosphate cement accumulation and achieves the green, sustainable, and circular development of magnesium phosphate cement.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a recycled phosphate cement and its preparation method. Background Technology

[0002] Magnesium phosphate cement is a novel cementitious material formulated in a specific ratio from alkaline components (magnesium oxide), acidic components (soluble phosphates), retarders, and auxiliary components (admixtures, additives, etc.). Its hydration process is an exothermic reaction based on the acid-base neutralization reaction between phosphates and magnesium oxide. It possesses advantages such as rapid setting speed, high early strength, good mechanical properties, good durability, high temperature resistance, and corrosion resistance, making it a promising candidate for rapid repair projects. As a material for repairing and reinforcing concrete structures, magnesium phosphate cement has been widely used in projects such as bridges, airport runways, highways, and sewage treatment plants.

[0003] However, the high cost of raw materials is currently the main factor limiting the widespread application of magnesium phosphate cement. The alkaline component MgO in magnesium phosphate cement is typically obtained by calcining magnesite (MgCO3) at temperatures above 1500℃. MgO usually accounts for 50% to 80% of the mass composition of the powder materials in MPC. Therefore, the production of MgO in MPC is heavily reliant on magnesite resources. Currently, the main magnesite mining areas in my country are located in Liaodong and other areas, with limited sources and reserves. Furthermore, as a non-renewable and irreplaceable resource, the total amount of magnesite mined is currently subject to restrictive limits, resulting in a high price for the magnesium oxide obtained after calcination.

[0004] The large-scale utilization or efficient replacement of various low-activity solid wastes is increasingly becoming a core and hot topic in development. Large quantities of waste magnesium phosphate cement are the main solid waste generated after the service life of magnesium-based repair materials. Disposing of this waste magnesium cement within the building materials industry can effectively alleviate the resource and market pressures on the production of recalcined magnesium oxide raw materials, and is an inevitable trend for achieving the green and sustainable development of magnesium phosphate cement. However, current technologies do not yet offer a solution for the efficient utilization of waste magnesium phosphate cement. Summary of the Invention

[0005] To address the aforementioned shortcomings of existing technologies, the present invention aims to provide a recycled phosphate cement and its preparation method. By heat-treating waste magnesium phosphate cement at a lower temperature to reduce its strength, the cement is then ground and crushed to prepare recycled powder mainly composed of magnesium oxide, struvite monohydrate, and amorphous seed crystals. This aims to solve the problem of high energy consumption when using recycled powder to replace magnesite-prepared recalcined magnesium oxide in phosphate cement, and also to solve the problem of high cost of existing magnesium phosphate cement.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A recycled phosphate cement, the cement comprising recycled powder, phosphate, and a retarder:

[0008] Of these, the recycled powder is 45-75 parts by weight, the phosphate is 15-50 parts, and the retarder is 0-10 parts.

[0009] Preferably, the regenerated powder is obtained by the following method:

[0010] Step 1: Calcine the waste magnesium phosphate cement at 100~400℃ for 15min~2h, then cool it;

[0011] Step 2: The product obtained in Step 1 is crushed to an average particle size of less than 1 mm;

[0012] Step 3: The product obtained in Step 2 is ground until the average particle size is 1~80μm to obtain the regenerated powder.

[0013] Preferably, the phosphate is at least one of potassium dihydrogen phosphate, ammonium dihydrogen phosphate, sodium dihydrogen phosphate, potassium monohydrogen phosphate, or ammonium monohydrogen phosphate.

[0014] Preferably, the retarder is at least one of borax or boric acid.

[0015] Preferably, the main components of the recycled powder include struvite monohydrate and amorphous seed crystals, as well as small amounts of magnesium oxide and struvite. Since the struvite monohydrate and novel amorphous seed crystals in the recycled powder can promote early hydration reactions, they can improve the early strength development of recycled magnesium phosphate cement and compensate for the problem of poor performance caused by the low total MgO content in recycled magnesium phosphate cement.

[0016] This invention also provides a method for preparing recycled phosphate cement. The method involves uniformly mixing 45-75 parts of recycled powder, 15-50 parts of phosphate, and 0-10 parts of retarder. The uniformly mixed mixture can be used according to different water-to-solid ratios as needed for the application scenario.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. This invention prepares recycled powder by calcining waste magnesium phosphate cement at a temperature not exceeding 400℃. In contrast, the recalcined magnesium oxide used in the traditional magnesium phosphate cement preparation process is produced by calcining magnesite at temperatures above 1600℃. Therefore, the recycled powder in this invention can completely replace the recalcined magnesium oxide prepared from magnesite. When formulating the recycled phosphate cement described in this invention, the lower calcination temperature can significantly reduce the energy consumption in the production process of magnesium oxide raw materials in magnesium phosphate cement, greatly reduce the cost of magnesium oxide raw materials in cement, broaden the selection range of magnesium oxide raw materials in magnesium phosphate cement, and has good market prospects.

[0019] 2. This invention calcines waste magnesium phosphate cement rich in magnesium to prepare recycled powder, which is then formulated into recycled magnesium phosphate cement. This reduces the accumulation of waste magnesium phosphate cement and alleviates environmental problems such as dust, soil damage, and groundwater pollution caused by the accumulation of waste magnesium cement. Furthermore, this invention is not difficult to process waste magnesium phosphate cement and has low energy consumption. Recycled magnesium phosphate cement can turn waste magnesium cement into a valuable resource, realizing the recycling and high-value utilization of solid waste resources.

[0020] 3. This invention involves calcining waste magnesium phosphate cement at low temperatures and then grinding it to prepare a recycled powder primarily composed of struvite monohydrate and amorphous materials. Because the struvite monohydrate and novel amorphous seed crystals in the recycled powder can promote early hydration reactions, it can improve the early strength development of the recycled magnesium phosphate cement. This compensates for the problem of low total MgO content in the recycled magnesium phosphate cement leading to poor cement performance, resulting in recycled phosphate cement with superior strength compared to traditional phosphate cement.

[0021] 4. The recycled phosphate cement prepared by this invention fully meets construction requirements, its setting time is easy to control, and its performance is close to that of traditional magnesium phosphate cement. Furthermore, the setting time of recycled magnesium phosphate cement is generally longer than that of traditional magnesium phosphate cement, providing sufficient control time for recycled construction and maintaining high early strength, which will facilitate the engineering application of phosphate cement. Attached Figure Description

[0022] Figure 1 The image shows the XRD pattern of the calcined mixture powder from Example 2.

[0023] In the diagram: 1 is magnesium oxide, 2 is struvite, and 3 is an amorphous product. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the present invention are within the scope of protection of the present invention.

[0025] Unless otherwise specified in the specific circumstances, the numerical ranges listed herein include upper and lower limits, as well as all integers and fractions within that range, but are not limited to the specific values ​​listed when the range is defined.

[0026] I. A type of recycled phosphate cement

[0027] The cement of the present invention comprises recycled powder, phosphate and retarder: wherein, by weight, the recycled powder is 45-75 parts, the phosphate is 15-50 parts, and the retarder is 0-10 parts.

[0028] This invention, after in-depth research on waste magnesium phosphate cement, discovered that the alkaline component MgO accounts for a large proportion of the cement's composition. Only no more than 25% of the total magnesium oxide MgO participates in the hydration reaction of MPC, with the remaining MgO merely serving as a framework. This indicates a high content of reburned MgO in waste phosphate cement. Using waste magnesium phosphate cement as a magnesium-based raw material to prepare recycled magnesium phosphate cement could not only achieve low-cost preparation of the raw material but also significantly reduce the cost of magnesium phosphate cement itself. However, because magnesium phosphate, when used as a repair material, has a dense structure and high strength (typically exceeding 60 MPa at 28 days), directly crushing and grinding waste magnesium cement would be energy-intensive. Furthermore, directly using waste magnesium phosphate cement to replace reburned magnesium oxide in the production of recycled magnesium phosphate cement would reduce the total MgO content, leading to a decrease in the performance of the recycled magnesium phosphate cement, especially its early strength. Therefore, applying magnesium-rich waste magnesium phosphate cement to the preparation of recycled phosphate cement presents a significant challenge.

[0029] During this research process, the present invention unexpectedly discovered that by heat-treating waste magnesium phosphate cement rich in magnesium at 100~400℃ to prepare recycled powder, and then using the recycled powder obtained after heat treatment to prepare recycled magnesium phosphate cement, it is possible not only to reduce the accumulation of waste magnesium phosphate cement and reduce the production cost of magnesium cement, but also to improve the strength development of recycled magnesium phosphate cement, and ultimately achieve the green and sustainable development of phosphate cement.

[0030] In some embodiments, the main components of the recycled powder include struvite monohydrate and amorphous seed crystals, as well as small amounts of magnesium oxide and struvite. The amorphous seed crystals are mainly composed of MgNH4PO4 and Mg3(PO4)2. Since the struvite monohydrate and novel amorphous seed crystals in the recycled powder can promote early hydration reactions, they can improve the early strength development of recycled magnesium phosphate cement and compensate for the problem of poor performance of recycled cement due to low total MgO content. Therefore, the amount of recycled powder is controlled at 45-75 parts, which can be 49 parts, 61 parts, 63 parts, 64 parts, 66 parts, 67 parts, 68 parts, 70 parts, 75 parts, etc., and all ranges and sub-ranges between the above values. It should be understood that, in the embodiments, any of the above ranges can be combined with any other range.

[0031] In some embodiments, the phosphate may be at least one of potassium dihydrogen phosphate, ammonium dihydrogen phosphate, sodium dihydrogen phosphate, potassium monohydrogen phosphate, or ammonium monohydrogen phosphate. A mixture of several phosphates may be used, and the proportion of each phosphate in the mixture is not limited; only the total amount of phosphate needs to be controlled. The amount of phosphate can be adjusted according to the amount of regenerated powder, calculated as a mass percentage. When the amount of regenerated powder decreases, the amount of phosphate can be increased to ensure that the total mass fraction of the mixture of regenerated powder, phosphate, and retarder, or the mixture of regenerated powder and phosphate, meets 100%. Therefore, the amount of phosphate is controlled to be 15-50 parts, and can be 15 parts, 22 parts, 24 parts, 25 parts, 26 parts, 30 parts, 31 parts, 33 parts, 48 ​​parts, 50 parts, etc., as well as all ranges and sub-ranges between the above values. It should be understood that, in the embodiments, any of the above ranges can be combined with any other range.

[0032] In some embodiments, a retarder is an optional component. The retarder is at least one of borax or boric acid, and borax and / or boric acid can be used as the retarder. Whether to add a retarder depends on the specific construction scenario. As mentioned above, the total mass fraction of the mixture of recycled powder and phosphate should be 100% by weight percentage. Therefore, the amount of retarder is controlled to be 0-10 parts, which can be 0 parts, 3 parts, 4 parts, 5 parts, 8 parts, 10 parts, etc., and all ranges and sub-ranges between these values. It should be understood that in the embodiments, any of the above ranges can be combined with any other range.

[0033] In some embodiments, the regenerated powder is obtained by the following method:

[0034] Step 1: Calcine the waste magnesium phosphate cement at 100~400℃ for 15min~2h, then cool it;

[0035] Step 2: The product obtained in Step 1 is crushed to an average particle size of less than 1 mm;

[0036] Step 3: The product obtained in Step 2 is ground until the average particle size is 1~80μm to obtain the regenerated powder.

[0037] In some embodiments, the calcination temperature is controlled between 100 and 400°C, and can be 100°C, 200°C, 250°C, 300°C, 400°C, etc., as well as all ranges and sub-ranges between the above values; the calcination time can be 15 min, 30 min, 45 min, 1.5 h, 1 h, 2 h, etc., as well as all ranges and sub-ranges between the above values. It should be understood that, in the embodiments, any of the above ranges can be combined with any other range.

[0038] II. A method for preparing recycled phosphate cement

[0039] To prepare the recycled phosphate cement of this invention, 45-75 parts of recycled powder, 15-50 parts of phosphate, and 0-10 parts of retarder are mixed evenly. The evenly mixed mixture can be used according to different water-to-solid ratios as needed for the application scenario.

[0040] III. Examples and Comparative Examples

[0041] Example 1

[0042] The method for preparing recycled magnesium phosphate cement powder in this embodiment includes the following steps:

[0043] (1) Calcine the waste magnesium phosphate cement at 100℃ for 2 hours, then remove and allow it to cool naturally;

[0044] (2) The cooled waste magnesium phosphate cement is crushed to less than 1 mm using a crusher;

[0045] (3) Grind the crushed calcined product to 75 μm to obtain the regenerated powder.

[0046] Example 2

[0047] The method for preparing recycled magnesium phosphate cement powder in this embodiment includes the following steps:

[0048] (1) Calcine the waste magnesium phosphate cement at 200℃ for 1 hour, then remove and allow it to cool naturally;

[0049] (2) The cooled waste magnesium phosphate cement is crushed to less than 1 mm using a crusher;

[0050] (3) Grind the crushed calcined product to 25 μm to obtain the regenerated powder.

[0051] Example 3

[0052] The method for preparing recycled magnesium phosphate cement powder in this embodiment includes the following steps:

[0053] (1) Calcine the waste magnesium phosphate cement at 200℃ for 1.5h, remove it and let it cool naturally;

[0054] (2) The cooled waste magnesium phosphate cement is crushed to less than 1 mm using a crusher;

[0055] (3) Grind the crushed calcined product to 50 μm to obtain the regenerated powder.

[0056] Example 4

[0057] The method for preparing recycled magnesium phosphate cement powder in this embodiment includes the following steps:

[0058] (1) Calcine the waste magnesium phosphate cement at 250℃ for 45 min, remove it and let it cool naturally;

[0059] (2) The cooled waste magnesium phosphate cement is crushed to less than 1 mm using a crusher;

[0060] (3) Grind the crushed calcined product to 50 μm to obtain the regenerated powder.

[0061] Example 5

[0062] The method for preparing recycled magnesium phosphate cement powder in this embodiment includes the following steps:

[0063] (1) Calcine the waste magnesium phosphate cement at 300℃ for 30 min, remove it and let it cool naturally;

[0064] (2) The cooled waste magnesium phosphate cement is crushed to less than 1 mm using a crusher;

[0065] (3) Grind the crushed calcined product to 25 μm to obtain the regenerated powder.

[0066] Example 6

[0067] The method for preparing recycled magnesium phosphate cement powder in this embodiment includes the following steps:

[0068] (1) Calcine the waste magnesium phosphate cement at 400℃ for 15 minutes, remove it and let it cool naturally;

[0069] (2) The cooled waste magnesium phosphate cement is crushed to less than 1 mm using a crusher;

[0070] (3) Grind the crushed calcined product to 50 μm to obtain the regenerated powder.

[0071] Comparative Example 1

[0072] A method for preparing reburned magnesium oxide for magnesium phosphate cement using magnesite includes the following steps:

[0073] (1) Crush the magnesite to less than 1 mm using a crusher;

[0074] (2) Calcine the crushed magnesite at 1700℃ for 4 hours, then remove and allow it to cool naturally;

[0075] (3) The cooled calcined product was ground through a 75 μm sieve to obtain recalcined magnesium oxide.

[0076] Comparative Example 2

[0077] The method for preparing recycled magnesium phosphate cement powder in this comparative example includes the following steps:

[0078] (1) Calcine the waste magnesium phosphate cement at 70°C for 1 hour, then remove and allow it to cool naturally;

[0079] (2) The cooled waste magnesium phosphate cement is crushed to less than 1 mm using a crusher;

[0080] (3) Grind the crushed calcined product to 25 μm to obtain the regenerated powder.

[0081] Comparative Example 3

[0082] The method for preparing recycled magnesium phosphate cement powder in this comparative example includes the following steps:

[0083] (1) Calcine the waste magnesium phosphate cement at 500℃ for 1 hour, then remove and allow it to cool naturally;

[0084] (2) The cooled waste magnesium phosphate cement is crushed to less than 1 mm using a crusher;

[0085] (3) Grind the crushed calcined product to 25 μm to obtain the regenerated powder.

[0086] From the appendix Figure 1The phase composition of the recycled magnesium phosphate cement powder prepared in Example 2 shows that the calcined product obtained after low-temperature calcination of waste magnesium phosphate cement mainly consists of magnesium oxide, struvite monohydrate, and amorphous seed crystals. Since the struvite monohydrate and novel amorphous seed crystals in the recycled powder can promote early hydration reactions, they can improve the early strength development of recycled magnesium phosphate cement and compensate for the problem of poor cement performance caused by the low total MgO content in recycled magnesium phosphate cement, resulting in recycled phosphate cement with superior strength compared to traditional phosphate cement. Furthermore, this invention uses a lower calcination temperature for a single calcination, while the recalcined magnesium oxide powder used in the traditional magnesium phosphate cement preparation process is obtained by calcining magnesite at temperatures above 1600℃, and usually requires two calcinations. Therefore, after the calcined mixture powder in this invention completely replaces the recalcined magnesium oxide prepared from magnesite, it can significantly reduce energy consumption in the magnesium oxide raw material production process and has good market prospects.

[0087] IV. Preparation of Phosphate Cement

[0088] 1. Cement that does not contain reheated magnesium oxide

[0089] The recycled powders prepared in Examples 1-6 were used to prepare recycled magnesium phosphate cement samples 1-6, respectively. The recycled powders prepared in Example 2 were used to prepare recycled magnesium phosphate cement samples 7-10 in different proportions. The recalcined magnesium oxide prepared in Comparative Example 1 was used to prepare magnesium phosphate cement control samples. The recycled powders prepared in Comparative Examples 2 and 3 were used to prepare recycled magnesium phosphate cement control samples. The specific proportions and compositions are shown in Table 1. Among them, in cement sample 3, the dihydrogen phosphate mixture was ammonium dihydrogen phosphate and potassium dihydrogen phosphate in a mass ratio of 3:1; in cement sample 2, the borax and boric acid mixture had a borax to boric acid mass ratio of 4:1; and in cement sample 8, the borax and boric acid mixture had a borax to boric acid mass ratio of 3:1.

[0090] Table 1. Composition of recycled magnesium phosphate cement samples (parts by mass)

[0091]

[0092] 2. Cement containing reburned magnesium oxide

[0093] Based on the proportions of cement samples 1-6, partially replace the calcined mixture powder in cement samples 1-6 with the recalcined magnesium oxide prepared in Comparative Example 1, and prepare cement samples 11, 12, 13, 14, 15, and 16 respectively. The mass of recalcined magnesium oxide in each cement sample accounts for 50%, 40%, 35%, 20%, 10%, and 5% of the total mass of recalcined magnesium oxide and recycled powder, respectively, while the proportions of other components remain unchanged.

[0094] V. Performance Comparison

[0095] All the cement samples prepared above were subjected to compressive strength testing in accordance with the "Cement Strength Test Method" (GB / T 17671-1999), with a fixed water-cement ratio of 0.18. The test results are shown in Table 2.

[0096] Table 2 Strength test results of the prepared recycled magnesium phosphate cement samples

[0097]

[0098] As shown in Table 2, cement samples 1-10 are phosphate cements prepared from recycled magnesium phosphate cement powder. Their setting time can be controlled between 27 min and 61 min. Their 3-h, 1-d, and 28-d strengths are close to those of the magnesium phosphate cement prepared entirely from recalcined magnesium oxide in Comparative Example 1, and are all greater than those of Comparative Examples 2 and 3, whose calcination temperatures are outside the recommended range. Among them, the 3-h, 1-d, and 7-d strengths of cement sample 2 are 44.26 MPa, 59.54 MPa, and 80.73 MPa, respectively, which are even higher than the strength of the traditional magnesium phosphate cement in Comparative Example 1. This is related to the fact that struvite and the novel amorphous product seed crystals can promote the hydration reaction. It can be seen that although the preparation process of the recycled powder used in cement samples 1 to 6 is different, their performance can basically meet the construction requirements. Cement samples 7 to 10 are recycled magnesium phosphate cements prepared with the same recycled powder. Although the proportions of recycled powder, dihydrogen phosphate and retarder are different, their setting time and 3-hour and 1-day compressive strength are close to those of the magnesium phosphate cement in Comparative Example 1, and their 28-day compressive strength is better than that of Comparative Group 1.

[0099] Cement samples 11-16 are magnesium phosphate cements prepared by partially replacing recycled powder with recalcined magnesium oxide in Comparative Example 1. Their setting times can be controlled between 21 and 57 minutes, and their 3-hour, 1-day, and 28-day strengths are close to those of the magnesium phosphate cement prepared entirely with recalcined magnesium oxide in Comparative Example 1. It can be seen that although the proportion of recalcined magnesium oxide in the total mass of recalcined magnesium oxide and recycled powder can vary within a wide range, the recycled magnesium phosphate cement prepared by partially replacing recalcined magnesium oxide with recycled powder still meets the performance requirements for construction. Cement sample 12 has a 28-day strength as high as 72.85 MPa, even better than Comparative Example 1, indicating that recycled powder can both partially and completely replace recalcined magnesium oxide, and the resulting recycled magnesium phosphate cement fully meets the performance requirements for construction.

[0100] The firing temperature of different recycled powders also affects the performance of recycled magnesium phosphate cement. Comparing Example 2 and Comparative Examples 2-3, it can be seen that firing temperatures that are too low or too high are detrimental to the strength development of recycled magnesium phosphate cement. The strength of Comparative Examples 2 and 3 is lower than that of Example 2, and also worse than other examples and comparative examples. Furthermore, this also affects the setting rate, leading to setting rates that are too fast or too slow, making it difficult to meet construction requirements. In summary, this invention creatively replaces magnesite with waste magnesium phosphate cement through low-temperature calcination in the production of recycled magnesium phosphate cement. The lower calcination temperature significantly reduces energy consumption in the production process of magnesium oxide raw materials in magnesium phosphate cement, greatly reducing the cost of magnesium oxide raw materials in cement and broadening the selection range of magnesium oxide raw materials in magnesium phosphate cement. Furthermore, recycled powder, mainly composed of magnesium oxide, struvite monohydrate, and amorphous seed crystals, obtained by calcining magnesium-rich waste magnesium phosphate cement as the main raw material, is used to prepare recycled phosphate cement. Struvite monohydrate and amorphous seed crystals can activate the reactivity of recycled magnesium phosphate cement, compensating for the low magnesium oxide content in the recycled powder and improving the strength development of the recycled cement. This will also reduce the accumulation of waste magnesium phosphate cement and alleviate the environmental problems it causes, realizing the recycling and high-value utilization of solid waste resources. Furthermore, the setting time of recycled magnesium phosphate cement is generally longer than that of traditional magnesium phosphate cement, providing sufficient control time for recycled construction and maintaining high early strength, which will help promote the engineering application of phosphate cement.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A recycled phosphate cement, characterized in that, The cement comprises recycled powder, phosphate, and a retarder: Of which, by weight, the recycled powder is 45-75 parts, the phosphate is 15-50 parts, and the retarder is 0-10 parts; The regenerated powder is obtained by the following method: Step 1: Calcine the waste magnesium phosphate cement at 100~400℃ for 15min~2h, then cool it; Step 2: The product obtained in Step 1 is crushed to an average particle size of less than 1 mm; Step 3: The product obtained in Step 2 is ground until the average particle size is 1~80μm to obtain the regenerated powder.

2. The recycled phosphate cement according to claim 1, characterized in that, The phosphate is at least one of potassium dihydrogen phosphate, ammonium dihydrogen phosphate, sodium dihydrogen phosphate, potassium monohydrogen phosphate, or ammonium monohydrogen phosphate.

3. The recycled phosphate cement according to claim 1, characterized in that, The retarder is at least one of borax or boric acid.

4. A method for preparing recycled phosphate cement, characterized in that, The method for preparing the recycled phosphate cement according to any one of claims 1 to 3 is characterized in that 45 to 75 parts of recycled powder, 15 to 50 parts of phosphate, and 0 to 10 parts of retarder are mixed evenly.

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