A kind of 3D printing with light-burned magnesium oxide as base preparation magnesium phosphate cement material and printing method

Abstract

The application relates to the technical field of building 3D printing materials, and discloses a 3D printing magnesium phosphate cement material prepared by taking light-burned magnesium oxide as a base and a printing method, the cement material is composed of the following components in mass fractions: 60-100 parts of magnesium phosphate cement MPC (wherein, magnesium oxide powder MgO is 28-68 parts, potassium dihydrogen phosphate KH2PO4 is 20-53 parts), 0-40 parts of mineral admixture, 3-12 parts of borax, and 20-26 parts of mixed water; wherein, the magnesium oxide is light-burned magnesium oxide (calcination temperature is 600 DEG C-1200 DEG C). The application can be used as the special matching printing material of the 3D printing device which can simultaneously stir and extrude the material and is independently researched and developed by the applicant, the preparation of the device requires reduced calcination temperature and energy consumption, the preparation cost of the magnesium phosphate cement is further reduced, and the setting time of the material is only about 3 minutes (the setting time of the conventional MPC is 20-30 minutes), so that the advantages of the 3D printing technology, the rapid construction, the high strength of the magnesium phosphate cement and the fast setting and hardening of the magnesium phosphate cement can be simultaneously exerted.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of building 3D printing materials, and in particular to a 3D printing magnesium phosphate cement material prepared based on light-burned magnesium oxide and a printing method. BACKGROUND

[0002] 3D printing additive manufacturing technology has been rapidly developed since the late 1990s. This technology has the characteristics of rapidity, automation, effective cost control and improved production efficiency, and can be used for manufacturing complex structures and extreme environments (extreme cold, underground, underwater, moon, etc.). Magnesium phosphate cement (MPC) has the performance characteristics of high early strength, fast setting and hardening, good volume stability and high bonding strength, which is very suitable for 3D printing due to the mutual adaptation with the characteristics of rapid manufacturing of 3D printing. Existing research (such as Qin Jihui, Qian Jiezhi, Song Qing, etc. Research progress and application of magnesium phosphate cement [J]. Journal of Silicate, 2022, 50 (06): 1592-1606.) and Qin Guoxin (Qin Guoxin, Jiao Baohuang. Research progress of magnesium phosphate cement [J]. Bulletin of the Chinese Ceramic Society, 2019, 38 (04): 1075-1079+1085.) show that heavy-burned magnesium oxide (magnesite calcined at a temperature of 1500-1700 DEG C and then ground into particles) has the performance characteristics of low activity, slow magnesium ion dissolution rate, relatively long setting time with less retarder dosage, and sufficient working time, and is one of the main raw materials for existing magnesium phosphate cement. Sun Meishuo (Sun Meishuo, Guan Yan, Bi Wanli, Meng Xianzhang. Influence of boron-doped magnesium oxide at different sintering temperatures on the performance of magnesium phosphate cement [J]. New Building Materials, 2018, 45 (11): 56-58+83.) studied the influence of magnesium oxide powder at different sintering temperatures on the performance of MPC, and considered that the heavy-burned magnesium oxide powder calcined at 1600 DEG C was the best raw material for preparing MPC. Sun Heming et al. (Sun Heming, Guan Yan, Bi Wanli, et al. Influence of crystal characteristics of sintered magnesium oxide powder on the mechanical properties of magnesium phosphate cement [J]. Materials Review, 2022, 36 (19): 91-96.) also pointed out that the magnesium oxide used for preparing MPC at present is heavy-burned magnesium oxide with a calcination temperature of more than 1600 DEG C and a MgO content of more than 88%. The above studies show that the existing MPC basically uses heavy-burned magnesium oxide as one of the raw materials, but the preparation of MPC based on heavy-burned magnesium oxide still has the problems of long raw material production cycle, high energy consumption and high cost, which greatly affects the large-scale engineering application of magnesium phosphate cement at present.

[0003] Unlike the calcined magnesium oxide, the light-burned magnesium oxide can greatly reduce the cost, the required calcination temperature and the energy consumption, and can reduce the cost of raw material preparation and improve the early strength of the test piece. However, the light-burned magnesium oxide has high activity and the magnesium ion dissolution rate is extremely fast, which is not conducive to the control of the setting time of the magnesium phosphate cement, so there is almost no working time, so the magnesium phosphate cement prepared by using the light-burned magnesium oxide as the raw material is currently difficult to apply in engineering, and relevant research has not been reported. In addition, in terms of construction technology, scholars such as Liu Jin et al. (Liu Jin, Ru Runhua, Zhang Zengqi. Research progress of magnesium phosphate cement performance [J]. Materials Review, 2021, 35(23): 23068-23075.) pointed out that the existing traditional construction method may not be suitable for the magnesium phosphate cement with the characteristics of fast setting and fast hardening, because the conventional MPC 3D printing equipment mainly consists of four parts of storage system, pumping system, conveying system and printing system, and the printing process is realized by using the extrusion device of the printing head to extrude the slurry after stirring, and then the slurry is pumped to the printing head of the 3D printing machine through the pipeline. This process requires that the printing material has sufficient working time to ensure that the material does not harden in the pipeline during operation, which makes it difficult to print the rapid-setting cement-based material. If a stirring and molding equipment for the magnesium phosphate cement can be developed, even 3D printing can be realized, which will further promote the application of the magnesium phosphate cement and the development of the modernization of China's construction.

[0004] Therefore, the development of a magnesium phosphate cement material for 3D printing based on light-burned magnesium oxide and a printing method thereof is a means and method for effectively reducing the cost of materials, improving the performance of products, improving the construction efficiency and promoting the development of intelligent construction technology in China. SUMMARY

[0005] In order to solve the technical problems mentioned in the background art, the applicant has independently developed a building 3D printing equipment which can simultaneously mix, stir and extrude materials, and the pumping device in the conventional 3D printing equipment is removed to ensure that the dry material goes out and the wet material goes in, and therefore the unique characteristics enable the 3D printing of the rapid-setting cement-based material, which breaks through the problem that the cement-based material cannot be applied due to the short setting time. The 3D printable magnesium phosphate cement material prepared by the applicant uses light-burned magnesium oxide to replace calcined magnesium oxide, and the setting time is about 3 minutes, which can reduce the preparation cost and energy consumption of the MPC raw material, further improve the early strength of the cement, fully utilize the characteristics of high early strength and fast setting and fast hardening of the magnesium phosphate cement, and meet the performance requirements of 3D printing. By using the above printing equipment, the 3D printing of the material of the application can be successfully realized.

[0006] The technical scheme adopted by the application is as follows:

[0007] A kind of 3D printing with light-burned magnesium oxide as base preparation magnesium phosphate cement material, according to following mass fraction composition: 60~100 portions of magnesium phosphate cement MPC (in which magnesium oxide powder MgO is 28~68 portions, potassium dihydrogen phosphate KH2PO4 is 20~53 portions), mineral admixture 0~40 portions, borax is 3~12 portions, 20~26 portions of mixing water;Wherein, the magnesium oxide adopts light-burned magnesium oxide (magnesium oxide calcination temperature 600 ℃~1200 ℃).

[0008] Preferably, the 3D printing with magnesium phosphate cement material, according to following mass fraction composition: 69 portions of magnesium phosphate cement MPC (41.1 portions of light-burned magnesium oxide MgO, 27.9 portions of potassium dihydrogen phosphate KH2PO4), 31 portions of mineral admixture (fly ash 25 portions, metakaolin 6 portions), 6.2 portions of borax, 24 portions of mixing water.

[0009] Further, the potassium dihydrogen phosphate is selected from industrial grade, purity 98%;The light-burned magnesium oxide powder (MgO), calcination temperature is 850 ℃~950 ℃, particle size 200 mesh;The borax is selected from industrial pure, purity 95%, from Dashiqiao City Juxing Platinum High Temperature Refractory Material Operating Department;Preferably, the mole ratio of light-burned magnesium oxide and potassium dihydrogen phosphate is selected from 5:1 (i.e. mass ratio 1.47:1).

[0010] Further, the mineral admixture fly ash FA, fineness is 11.6%, 45 μm square hole sieve residue I grade fly ash, selected from Dalian Huaneng Power Plant;Metakaolin MK is selected from 325 mesh residue: 0.01% coal-based metakaolin, aluminum silicate content 97-98%, calcination temperature 700-800 ℃, selected from Inner Mongolia Superplate Building Materials.

[0011] Wherein, the main chemical composition of light-burned magnesium oxide powder, fly ash, metakaolin is shown in table 1.

[0012] Table 1 chemical composition of cementitious material

[0013]

[0014] The preparation method of the 3D printing with light-burned magnesium oxide as base magnesium phosphate cement material is that light-burned magnesium oxide, potassium dihydrogen phosphate, borax, fly ash, metakaolin are slowly added into cement mortar mixer and stirred until uniform (low speed stirring 120 s), then the mixing water weighed in advance is poured into the stirring pot and stirred at low speed (62±5 r / min) for 10~30 s, and then stirred at high speed (125±5 r / min) for 60~120 s, to obtain low energy consumption magnesium phosphate cement material.

[0015] Further, the 3D printing light-burned magnesium oxide-based magnesium phosphate cement material can be used as a special matching printing material for the 3D printing device with simultaneous material stirring and extrusion developed by the applicant, and the specific printing steps are as follows:

[0016] (I) ingredient: according to the above method for preparing the 3D printing light-burned magnesium oxide-based magnesium phosphate cement material, dry materials such as light-burned magnesium oxide, potassium dihydrogen phosphate, fly ash, metakaolin and borax are weighed and stirred uniformly, and then loaded into the bunker of the integrated 3D printing device in the form of dry powder;

[0017] (II) printing: the building 3D printing device with integrated material mixing, stirring and extruding functions is used for printing, water is filled in the water tank before printing, and the printing model code is input; during printing, the water flow is controlled to be 80-100 mL per minute, the printing rotation speed is 60 revolutions per minute, the printing speed is 1200 mm / min, the printing magnification is adjusted to 60%-80% according to the printing state, and finally the printing is completed according to the set model.

[0018] The application of the 3D printing light-burned magnesium oxide-based magnesium phosphate cement material can be used for building 3D printing in severe cold regions and special environments such as underground, underwater, moon, and Antarctic, emergency and rapid repair of airport roads, and corrosion and rust prevention coating on the surface of steel bars.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] ① The present application can be used as a special matching printing material for the 3D printing device with simultaneous material stirring and extrusion developed by the applicant. Figure 1The core component in the printing device, a 3D printing nozzle device (with a patent for invention, with a patent number of 109366999B) that simultaneously carries out material stirring and extrusion, mainly includes a motor, an air cylinder, a rotating drum, an upper transmission shaft and a lower transmission shaft arranged on the central axis of the rotating drum. Since the pipeline does not transport mixed slurry, but separates the dry material and liquid material pipelines, it realizes the special-purpose of the dry powder of MPC prepared from light-burned magnesium oxide, that is, the dry powder of MPC is introduced into the rotating drum from the dry material inlet through the material uniformizing device, and water is introduced into the rotating drum from the liquid material inlet I and the liquid material inlet II. Different from the conventional stirring mode, the dry material and water can be contacted and quickly mixed in the air in the drum, so that the light-burned magnesium oxide powder and other materials quickly undergo hydration reaction. At the same time, the stirring blades are installed on the upper transmission shaft of the rotating drum, which can realize the stirring of the dry material and water in the drum, and ensure the uniform mixing of the dry powder and water. At this time, the air cylinder in the printing device drives the downward movement of the upper transmission shaft, the upper transmission shaft is connected with the lower transmission shaft and drives the lower transmission shaft to rotate in the same direction, so that the extrusion blades fixed on the lower transmission shaft rotate in the opposite direction of the rotating drum, which can realize the rapid extrusion of the magnesium phosphate cement slurry after stirring. The main technical feature is that the dry powder and liquid can be mixed and stirred in the printing device through the pipeline, and can be extruded after mixing and stirring, so it has unique advantages for the rapid-setting cement-based material with a setting time of less than 5 minutes. The MPC material prepared based on light-burned magnesium oxide has a short setting time (about 3 minutes) and fast hydration reaction, and its fast-setting and fast-hardening characteristics are very suitable for the characteristics of the 3D printing nozzle that simultaneously carries out material stirring and extrusion. The combination of the two can solve the problem that the existing rapid-setting magnesium phosphate cement is difficult to be used in engineering application due to the short setting time and short construction operation time, and can further expand the practical engineering application of magnesium phosphate cement.

[0021] ②The 3D printing light-burned magnesium oxide-based magnesium phosphate cement-based material developed by the application uses light-burned magnesium oxide and potassium dihydrogen phosphate as main raw materials, and industrial waste such as fly ash and metakaolin as auxiliary cementitious materials to further reduce the preparation cost of MPC; and the setting time of the material is controlled to be about 3 minutes, the compressive strengths of the material at 3h, 3d and 28d are 18.1MPa, 43.77MPa and 45.22MPa respectively, and the bonding strengths of the material at 3h, 3d and 7d are 1.82MPa, 3.89MPa and 4.12MPa respectively; therefore, the material has rapid setting, good mechanical properties and bonding properties, can quickly set and has strength during printing, and can meet the requirements of 3D printing rapid-setting cement-based material and engineering application.

[0022] Compared with the conventional magnesium phosphate cement material prepared by using the calcined magnesium oxide as the base, the low-energy-consumption magnesium phosphate cement base material of the application uses the light calcined magnesium oxide instead of the calcined magnesium oxide as the main raw material, so that the calcination temperature and the energy consumption required for preparing the material can be reduced, the preparation cost of the magnesium phosphate cement can be further reduced, and the cementing material prepared by using the light calcined magnesium oxide as the base can reduce the carbon emission of the building industry. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a 3D printing nozzle device for simultaneously stirring and extruding materials, and the authorized publication number is 109366999B;

[0024] Figure 2 is a mixed-stirring-extruding integrated concrete building 3D printer;

[0025] Figure 3 is the SEM morphology of the MPC test piece of Example 1 and Comparative Example 2 after 28 days (d), (a) the SEM morphology of the MPC prepared by using the calcined magnesium oxide at 1600℃ after 28 days, (b) the SEM morphology of the MPC prepared by using the light calcined magnesium oxide at 850-950℃ after 28 days;

[0026] Figure 4 is a printing process diagram of the application, (a) a 3D printing path diagram, (b) a 3D printing extrusion test physical diagram, (c) a 3D printing construction test physical diagram;

[0027] Figure 5 is a 3D printed entity component diagram of the low-energy-consumption magnesium phosphate cement base material of the application;

[0028] Figure 6 is a 3D printed entity component diagram of the conventional calcined magnesium phosphate cement base material.

[0029] wherein, Figure 1100. motor, 200. cylinder, 300. drum, 400. upper transmission shaft, 500. lower transmission shaft, 600. material mixing device, 700. spatula nozzle, 800. support frame, 201. cylinder coupling, 301. upper end drum, 302. display drum, 303. bottom end drum, 401. transmission gear set, 402. planetary gear set, 403. U-shaped partition, 404. material blocking plate, 405. stirring blade, 406. upper section coupling, 501. lower section coupling, 502. extrusion blade, 503. connecting rod. DETAILED DESCRIPTION

[0030] The technical solutions of the present application are further described in detail below in conjunction with examples. These descriptions are only illustrative of the features and advantages of the present application, and do not limit the protection scope of the present application. Unless otherwise specified, the reagents or raw materials used in the present application can be purchased through conventional channels, and the reagents or raw materials used are used according to conventional methods in the art or according to the product instructions. In addition, any method and material similar or equivalent to those described can be applied to the present application. The preferred implementation methods and materials described herein are only for demonstration.

[0031] In the following examples and comparative examples, the potassium dihydrogen phosphate is an industrial grade with a purity greater than 98%; the borax is an industrial pure with a purity greater than 95%; selected from Daishiqiao City Juge Platinum High Temperature Refractory Materials Operating Department.

[0032] In the following examples and comparative examples, the magnesium oxide powder is respectively heavy-burned magnesium oxide obtained by calcining at 1600°C and grinding, light-burned magnesium oxide obtained by calcining at 850-950°C and grinding, and light-burned magnesium oxide obtained by calcining at 700-800°C and grinding, with a particle size of 200 mesh, and magnesium oxide contents of 92.33%, 85.33%, and 80.78%, respectively, selected from Daishiqiao City Juge Platinum High Temperature Refractory Materials Operating Department.

[0033] In the following examples and comparative examples, the fly ash is Grade I fly ash with a fineness of 11.6%, selected from Dalian Huaneng Power Plant; the metakaolin is coal-based metakaolin with an aluminum silicate content of 97-98%, and a calcination temperature of 700-800°C, selected from Inner Mongolia Chaopai Building Materials.

[0034] Example 1

[0035] A low-energy phosphorus magnesium cement-based material suitable for 3D printing is prepared by the following method:

[0036] Take dry powder material 540g of 850~950℃ light-burned magnesium oxide, 460g of potassium dihydrogen phosphate, 81g of borax, and add them into a JJ-5 type cement mortar stirrer, mix the dry powder material uniformly by low-speed stirring for 2 minutes, then take 240g of mixing water, slowly pour the taken water into the stirring pot by low-speed stirring (62±5r / min) for 10~30s, and then high-speed stirring (125±5r / min) for 60s, to obtain the low-energy consumption condensed magnesium phosphate cement material suitable for 3D printing.

[0037] Comparative Example 1

[0038] The same as Example 1, except that the magnesium oxide powder is 700~800℃ light-burned magnesium oxide.

[0039] Comparative Example 2

[0040] The same as Example 2, except that the magnesium oxide powder is 1600℃ heavy-burned magnesium oxide.

[0041] Example 2

[0042] A preparation method of a low-energy consumption magnesium phosphate cement-based material suitable for 3D printing, comprising the following steps:

[0043] Take dry powder material 446g of 850~950℃ light-burned magnesium oxide, 304g of potassium dihydrogen phosphate, 67g of borax, and 250g of fly ash, and add them into a JJ-5 type cement mortar stirrer, mix the dry powder material uniformly by low-speed stirring for 2 minutes, then take 240g of mixing water, slowly pour the taken water into the stirring pot by low-speed stirring (62±5r / min) for 10~30s, and then high-speed stirring (125±5r / min) for 60~120s, to obtain the low-energy consumption condensed magnesium phosphate cement material suitable for 3D printing.

[0044] Test Example 1

[0045] The same as Example 2, except that the fly ash content is reduced from 25% (of the total amount of light-burned magnesium oxide and potassium dihydrogen phosphate) in Example 2 to 15%, i.e., take 506g of light-burned magnesium oxide, 344g of potassium dihydrogen phosphate, 76g of borax, and 150g of fly ash.

[0046] Test Example 2

[0047] The same as Example 2, except that the fly ash content is reduced from 25% (of the total amount of light-burned magnesium oxide and potassium dihydrogen phosphate) in Example 2 to 20%, i.e., take 476g of light-burned magnesium oxide, 324g of potassium dihydrogen phosphate, 71.4g of borax, and 200g of fly ash.

[0048] Test Example 3

[0049] The same as example 2, except that 4% of metakaolin is additionally added to the total amount of light-burned magnesium oxide and potassium dihydrogen phosphate, i.e. 423 g of light-burned magnesium oxide, 287 g of potassium dihydrogen phosphate, 63.5 g of borax, 250 g of fly ash, and 40 g of metakaolin are weighed respectively.

[0050] Test Example 4

[0051] The same as example 2, except that 6% of metakaolin is additionally added to the total amount of light-burned magnesium oxide and potassium dihydrogen phosphate, i.e. 411 g of light-burned magnesium oxide, 279 g of potassium dihydrogen phosphate, 62 g of borax, 250 g of fly ash, and 60 g of metakaolin are weighed respectively.

[0052] Performance Test

[0053] 1. Setting time test. The setting time of MPC neat paste is determined according to "Cement Standard Consistency Water Content, Setting Time, and Stability Test Method" (GB / T 1346-2001).

[0054] 2. Compressive strength test. The test is performed according to "Cement Mortar Strength Test Method (ISO Method)" (GB / T 17671-1999).

[0055] 3. Bond strength test. The molding is performed according to the provisions in JC / T 2381, and the bond strength is determined by using the method of indirect test of flexural strength. The flexural strength is determined to indirectly represent the bond strength.

[0056] 4. Dry shrinkage test. The volume change of MPC test piece during hardening is tested according to the standard JC / T 603-2004 "Cement Mortar Dry Shrinkage Test Method", and the result calculation is performed according to the provisions in JC / T 603.

[0057] 5. Micro-morphology analysis. The test piece is broken and cut into small pieces of 3-5 mm after reaching the corresponding curing age, and then soaked in anhydrous ethanol to stop hydration, and then placed in an oven for drying (the oven temperature is 52°C); after drying, the test piece is subjected to gold spraying treatment, and the micro-morphology of the sample is observed by using a JSM-6360LV type scanning electron microscope of Japan Electronic, with an acceleration voltage of 0.5KV-30KV.

[0058] The test results of the setting time of neat paste, and the compressive strength, bond strength, and dry shrinkage of test pieces of example 1 and comparative examples 1-2 obtained according to the above method are shown in Table 2.

[0059] Table 2 Test results of magnesium phosphate cement performance with different calcination temperatures of magnesium oxide

[0060]

[0061] The results of the comparison of Example 1 and Comparative Examples 1 and 2 show that the MPC can also be successfully prepared using light-burned magnesium oxide. It can be found from the test results that the setting time of the MPC prepared in Example 1 using light-burned magnesium oxide as the base is shortened from 18 min of the traditional heavy-burned MPC to about 3 min, the compressive strength and the bonding strength are higher than those of Comparative Examples 1 and 2, the 28d dry shrinkage is smaller than that of Comparative Examples 1 and 2, the material has excellent properties of fast setting, fast hardening and high early strength, the printing process is smooth, and the extrusion and construction properties are good. The setting time of the material of Comparative Example 1 is too short, which can easily cause the printing rotary head to be blocked during the printing process, affect the extrusion property of the material, and the printing performance is slightly poor. The setting time of the material of Comparative Example 2 is about 18 min, which is too long, and can affect the construction property after the printing and extrusion, and also reduce the printing efficiency, and the printing effect is not as good as that of Example 1. In summary, compared with Comparative Examples 1 and 2, Example 1 is the preferred scheme, and is most suitable for the rapid-setting magnesium phosphate cement 3D printer (109366999B).

[0062] In addition, from the Figure 3 The 28d SEM morphology of the MPC prepared from magnesium oxide calcined at different temperatures shows that the crystal structure of the MPC is changed by the magnesium oxide calcined at different temperatures. When the heavy-burned magnesium oxide calcined at a temperature of 1600°C in Comparative Example 2 is used ( Figure 3 (a)), the hydration product mainly exists in the form of short columnar and cementitious structures. When the light-burned magnesium oxide calcined at a temperature of 850-950°C in Example 1 is used ( Figure 3 (b)), the hydration product exists in the form of a large number of needle-like structures, the needle-like crystals are interlaced and closely connected, and grow densely, and the struvite plays a good strength role. This also explains from the micro level the reason why the MPC prepared from the light-burned magnesium oxide in Example 1 has relatively excellent mechanical properties.

[0063] In summary of the above tests, the crystal structure of the MPC prepared after the heavy-burned magnesium oxide is replaced by the light-burned magnesium oxide has changed. The use of the light-burned magnesium oxide calcined at a temperature of 850-950°C to prepare the MPC can not only reduce the cost of raw materials, save magnesium ore resources, and reduce the energy consumption in the calcination process, but also further improve the mechanical properties and bonding strength of the material.

[0064] The setting time of the neat paste and the compressive strength test results of the test blocks of Example 2 and Test Examples 1-4 obtained according to the above method are as shown in Table 3.

[0065] Table 3 Test results of different mineral admixtures on the properties of magnesium phosphate cement

[0066]

[0067] The test of example 2 and test examples 1-4 all use light-burned magnesium oxide preparation, so it can be seen that various proportions can be successfully prepared magnesium phosphate cement, and the test results show that the setting time of the prepared MPC is controlled at about 2-3 min, and the early strength is high, which can meet the requirements of 3D printing on the mechanical properties of cement-based materials.

[0068] Example 3

[0069] A preparation of a magnesium phosphate cement-based material suitable for 3D printing, comprising the following method:

[0070] (1) batching: respectively taking 446g of dry material 850-950℃ light-burned magnesium oxide, 304g of potassium dihydrogen phosphate, 250g of fly ash, and 67g of borax, adding them into the stirring pot at one time and stirring uniformly, and loading into the hopper of the integrated 3D printing device as shown in Figures 1-2 ;

[0071] (2) printing: using the material mixing, stirring and extruding function integrated building 3D printing device as shown in Figures 1-2 to print, filling the water tank with water in advance before printing, and inputting the printing model code; adjusting the flow meter and controlling the water flow to be 80-100mL per minute during printing, the printing rotation speed is 60 revolutions per minute, the main shaft speed is 600r / min, the printing speed is 1200mm / min, the printing head outlet is a circular cross section with a diameter of 18.5mm, the printing ratio is adjusted according to the printing state 60%-80%, and finally the printing is completed according to the set model.

[0072] In example 3, the printing design path is a hexagonal printing path as shown in Figure 4 (a), the printing component design height is 10mm per layer, and there are a total of 5 layers, Figure 4 (b), Figure 4 (c), and Figure 5 are the component printing extrusion, printing construction and hexagonal printing component physical map respectively according to the path shown in Figure 4 (a).

[0073] Comparative example 3

[0074] To further verify that the product of the application is a special matching material for the patent equipment (109366999B) of the rapid-setting concrete 3D printer, a conventional magnesium phosphate cement ratio used in engineering (see Zhao Jiangtao, Li Xiangguo, Zhang Yan, Liu Huqing, Yin Xiaopeng. Influence of fly ash on magnesium phosphate cement [J]. Bulletin of the Ceramic Society, 2018, 37(02): 695-700.) is selected to prepare 3D printing materials, and further in Figures 1-2The material was printed using a self-developed rapid-setting concrete 3D printer (109366999B). The specific mix proportions and performance indicators of this material are shown in Table 4. Figure 4 Print the path in (a) and the print result is as follows: Figure 6 As shown.

[0075] Table 4. Mix proportions and performance indicators of conventional reburnt magnesium phosphate cement materials

[0076]

[0077] The comparison printing results between Example 3 and Comparative Example 3 are as follows: Figures 4-6 As shown, from Figure 6 As can be seen, the MPC prepared using traditionally recalcined magnesium oxide exhibits significant water seepage during the printing process, resulting in discontinuous and broken printing strips, and collapse of the printed components, making it impossible to complete the printing of the entire component. In contrast, the low-energy MPC prepared using lightly calcined magnesium oxide in Example 3... Figure 4 (b) It is easy to see that MPC can be successfully pumped and extruded, the printing process is continuous and there is no interruption, and the printing material has good extrudability. Figure 4 (c) Figure 5 The printed hexagonal component has an actual measured height of 45.5mm, which deviates from the theoretical height (50mm) by approximately 5.5mm, within a deviation range of 10%. Due to the short setting time of the low-energy MPC, each layer of the component is sufficient to support the next layer during printing, and no collapse occurred during the entire printing process, demonstrating excellent construction performance. Furthermore, in Example 3, the overall printing time for the 50mm high hexagonal component was less than 10 minutes, demonstrating short printing time and high efficiency.

[0078] The above-described Example 3 and Comparative Example 3 further demonstrate that the material of the present invention is a dedicated matching printing material for the rapid-setting concrete 3D printer (109366999B), which can guarantee the completion of printing related products and components, and the printing effect is good.

[0079] The above description is merely 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 foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A printing method of a magnesium phosphate cement material for 3D printing prepared on the basis of light burned magnesium oxide, characterized in that, The magnesium phosphate cement material is a special matching printing material for a 3D printing device with simultaneous material mixing and extrusion, and is composed of the following mass fractions: 60-100 parts of magnesium phosphate cement MPC, the mass ratio of light-burned magnesium oxide to potassium dihydrogen phosphate in the magnesium phosphate cement MPC being 1.47:1, the MgO being light-burned magnesium oxide with a calcination temperature of 850-950 DEG C, 20-53 parts of potassium dihydrogen phosphate KH2PO4, 0-40 parts of mineral admixtures including fly ash and metakaolin, 3-12 parts of borax, and 20-26 parts of mixing water; the printing method comprises the following steps: (I) batching: the dry materials, i.e., light-burned magnesium oxide, potassium dihydrogen phosphate, fly ash, metakaolin and borax, are weighed and uniformly mixed, and then are loaded into a material bin of an integrated 3D printing device in the form of dry powder; (II) printing: the building 3D printing device with the functions of material mixing, stirring and extrusion is used for printing, water is filled in a water tank before printing, and a printing model code is input; during printing, the water flow is controlled to be 80-100 mL per minute, the printing rotation speed is 60 revolutions per minute, the printing speed is 1200 mm / min, the printing magnification is adjusted to be 60-80% according to the printing state, and finally the printing is completed according to the set model.

2. The printing method according to claim 1, characterized by, The magnesium phosphate cement material is a special matching printing material for a 3D printing device with simultaneous material mixing and extrusion, and is composed of the following mass fractions: 60-100 parts of magnesium phosphate cement MPC, the mass ratio of light-burned magnesium oxide to potassium dihydrogen phosphate in the magnesium phosphate cement MPC being 1.47:1, the MgO being light-burned magnesium oxide with a calcination temperature of 850-950 DEG C, 20-53 parts of potassium dihydrogen phosphate KH2PO4, 0-40 parts of mineral admixtures including fly ash and metakaolin, 3-12 parts of borax, and 20-26 parts of mixing water; the printing method comprises the following steps:

3. The printing method according to claim 1, characterized by, The particle size of the light-burned magnesium oxide is 200 mesh.

4. The printing method according to claim 1, characterized by, The potassium dihydrogen phosphate is of an industrial grade with a purity of 98%, and the borax is of an industrial purity with a purity of 95%.

5. The printing method according to claim 1 or 2, characterized by, The fly ash FA has a fineness of 11.6% and a 45-mesh square hole sieve residue of grade I fly ash.

6. The printing method according to claim 1 or 2, characterized by, The metakaolin MK is selected from a 325-mesh sieve residue: 0.01% of coal-based metakaolin with a silicon aluminum content of 97-98% and a calcination temperature of 700-800 DEG C.

7. Use of a material printed according to the method of any one of claims 1 to 6, characterized in that, The magnesium phosphate cement material is used for building 3D printing in severe cold regions and in special environments such as underground, underwater, moon, and Antarctic.

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