Magnesium phosphate cement suitable for high-temperature condition and preparation method thereof

Abstract

The invention provides magnesium phosphate cement applicable to a high-temperature condition and a preparation method thereof, and relates to the technical field of cement. The magnesium phosphate cement is composed of main components and modified components, wherein the main components are composed of the following raw materials in percentage by mass: 50-80% of a magnesium material, 20-50% of a phosphorus material and the balance of water for mixing; the modified component comprises at least one of a retarding material, an auxiliary cementing material, a fiber material and a weighting material. The invention fills the blank of special cement suitable for high-temperature conditions, and provides an emergency scheme for shielding special environments such as ultrahigh temperature or thermal neutron radiation.

Description

Technical Field

[0001] The invention provides a magnesium phosphate cement suitable for use under high temperature conditions and a preparation method thereof, belonging to the technical field of cement. Background Art

[0002] As a kind of fast-hardening cement, magnesium phosphate cement is now widely used in medical fields such as rapid repair of airport runways, emergency repair of old projects, and bone cement due to its short setting time, high hourly strength, and good biocompatibility. At the same time, due to its small water-cement ratio and high specific gravity, magnesium phosphate cement will produce less pores caused by steam pressure under direct high-temperature curing conditions, and can show strong application potential under different special conditions such as ultra-high temperature fuel consolidation and unmanned construction. However, the performance of magnesium phosphate cement still has limitations, and the further development of magnesium phosphate cement suitable for high-temperature conditions is of great strategic significance. Summary of the invention

[0003] In view of this, the object of the present invention is to provide a magnesium phosphate cement suitable for use under high temperature conditions and a preparation method thereof.

[0004] The present invention is achieved by adopting the following technical solutions:

[0005] A magnesium phosphate cement suitable for use under high temperature conditions, comprising a main component and a modified component, wherein the main component comprises the following raw materials in the following mass percentages:

[0006] 50% to 80% magnesium material, 20% to 50% phosphorus material, and the rest is mixing water;

[0007] The modified component includes at least one of a retarding material, an auxiliary gelling material, a fiber material, and a weighting material; the retarding material includes at least one of borax, boric acid, sodium citrate, citric acid, sodium gluconate, tartaric acid, anhydrous magnesium sulfate, disodium ethylenediaminetetraacetate, sodium tripolyphosphate, and starch ether;

[0008] The auxiliary cementitious material comprises at least one of fly ash, silica fume, metakaolin, granulated blast furnace slag, red mud, bentonite and diatomaceous earth;

[0009] The fiber material includes at least one of steel fiber, glass fiber, graphene nanofiber, polypropylene fiber, and polytetrafluoroethylene fiber;

[0010] The weighting material includes at least one of quartz sand, perlite, iron ore and barite;

[0011] The mass ratio of the main component to the modified component is 100:5-85.

[0012] Preferably, the magnesium material is dead-burned magnesium oxide powder with a magnesium oxide content higher than 80%. Dead-burned magnesium oxide powder is a powdery material obtained by calcining, crushing, grinding and other processes of natural magnesium ore with MgO, Mg(OH)2 and MgCO3 as main chemical components. Preferably, the magnesium ore is natural magnesite ore. The calcination is performed at a high temperature of more than 1500°C for more than one hour.

[0013] Preferably, the phosphorus material is at least one of potassium dihydrogen phosphate and potassium dihydrogen phosphate. The potassium dihydrogen phosphate and potassium dihydrogen phosphate selected in the present invention have a purity higher than 95%.

[0014] Preferably, the auxiliary gelling material is particles or powders with a size of less than 10 meshes; the weighting material has a continuous gradation, and the mesh size range is: 10 mesh-200 mesh.

[0015] In one embodiment, the modified component of the present invention is a mixture of borax and fly ash in a mass ratio of 1:2.

[0016] In one embodiment, the modified component of the present invention is a mixture of borax and silica fume in a mass ratio of 1:2.

[0017] In one embodiment, the modified component of the present invention is a mixture of borax, fly ash and quartz sand in a mass ratio of 1:1:10.

[0018] In one embodiment, the modified component of the present invention is a mixture of borax, fly ash, polypropylene fiber and quartz sand in a mass ratio of 1:1:0.1:10.

[0019] The present invention also provides a method for preparing the magnesium phosphate cement suitable for use under high temperature conditions, comprising the following steps:

[0020] (1) weighing raw materials according to proportion, pouring the weighed magnesium material, phosphorus material, slow-setting material, and auxiliary cementitious material into a planetary mixer and mixing them evenly;

[0021] (2) Then, mixing water is added and stirred slowly for 1 minute, then stirred rapidly for 1 minute, and then fiber materials and weighting materials are added in sequence, and stirring is continued for 2-3 minutes until the mixture is evenly dispersed, thereby obtaining the magnesium phosphate cement suitable for high temperature conditions.

[0022] Preferably, the slow stirring speed is 62±5 r / min; the fast stirring speed is 125±10 r / min.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention is applicable to magnesium phosphate cement under high temperature conditions, wherein the main components are magnesium phosphate inorganic adhesives obtained by mixing magnesium materials and phosphorus materials with water. Magnesium phosphate inorganic adhesives are a kind of refractory materials and have been widely used as fireproof coating materials on the surface of combustible substrates, playing an important role in building fire prevention and fire resistance.

[0025] The present invention greatly delays the chemical bonding process of magnesium phosphate cement by introducing various retarding materials with different chemical mechanisms such as inorganic salts and organic acids, so that the operating time of cement can be regulated, and the application market of magnesium phosphate cement is further broadened. Magnesium phosphate inorganic adhesive has the characteristics of small water-cement ratio. Under high-temperature curing conditions, the steam pressure caused by the evaporation of mixing water is smaller than that of other cements, that is, the pore size and microcracks formed are much less, and the auxiliary cementitious material has a controllable particle size and a spherical shape, which can give full play to the filling effect and morphological effect, further reduce the cement water-cement ratio and prolong its setting time, and increase the mechanical properties of magnesium phosphate cement; in addition, most of the auxiliary cementitious materials can only be used as filling minerals under normal temperature conditions, and high temperature can further enhance the reaction activity of the auxiliary cementitious materials, which helps to generate new adhesive products and improve the working performance of magnesium phosphate cement at high temperatures; at the same time, the auxiliary cementitious materials used as solid waste are applied to cement substrates, which is conducive to the development of environmental protection and accelerates the steady progress of green ecology. Magnesium phosphate inorganic adhesive has high volume stability under high temperature conditions. The fiber material added as a modified component to the magnesium phosphate cement can further improve the anti-cracking performance and bonding performance of the cement, and increase the toughness of the magnesium phosphate cement. Magnesium phosphate cement has a large specific gravity, and the addition of weighting materials such as barite can further increase the specific gravity of the cement, which is suitable for radiation shielding projects under ultra-high temperature conditions.

[0026] The invention fills the blank of special cement suitable for high temperature conditions, and at the same time provides an emergency solution for shielding special environments such as ultra-high temperature or thermal neutron radiation. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the appearance of the magnesium phosphate cement prepared in Example 1-3 after being cured at 800°C for 3 hours. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the present invention clearer, the preferred embodiments of the present invention are further described in detail in conjunction with the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] In the embodiment of the present invention, the magnesia material in the main component is magnesite which is calcined at 1600°C for 2 hours and crushed and ground by a jaw crusher and a ball mill, and the median particle size D50 The particle size is 57.2μm and the MgO content is 92%; the phosphorus material is granular analytical grade potassium dihydrogen phosphate with a chemical purity greater than or equal to 99%; the mixing water is Class III tap water.

[0030] In the embodiment of the present invention, the retarding material in the modified component is analytically pure borax with a chemical purity greater than or equal to 99%; the auxiliary cementitious material is primary fly ash and high-activity silica fume with a median particle size D 50 The fiber material is polypropylene fiber, with a length of 12 mm and a diameter of 18 μm; the weighting material is quartz sand, with a median particle size of D 50 It is 117.63μm.

[0031] The present invention proposes a magnesium phosphate cement suitable for use under high temperature conditions. The following examples are all calculated by mass percentage.

[0032] Example 1

[0033] A magnesium phosphate cement suitable for use under high temperature conditions is prepared from a main component and a modified component in a mass ratio of 100:5, wherein:

[0034] Main components: dead-burned magnesium oxide powder 70%, potassium dihydrogen phosphate 20%, mixing water 10%, the sum of the three is 100%.

[0035] Modifying component: borax.

[0036] (1) weighing raw materials according to proportion, pouring the weighed dead-burned magnesium oxide powder, potassium dihydrogen phosphate, and borax into a planetary mixer and mixing them evenly;

[0037] (2) Then, mixing water is added and stirred slowly for 1 minute, and then stirred quickly for 1 minute to obtain the magnesium phosphate cement M1 suitable for high temperature conditions. The slow stirring speed is 62±5 r / min; the fast stirring speed is 125±10 r / min.

[0038] The magnesium phosphate cement M1 was poured into a 40*40*40mm triple steel mold, and after compaction, it was vibrated on a vibration table for 1 minute. After half an hour of molding, it was quickly demolded and placed in a muffle furnace at 800°C for high temperature curing for 1 hour, 3 hours, 6 hours and 24 hours.

[0039] Example 2

[0040] A magnesium phosphate cement suitable for use under high temperature conditions is prepared from a main component and a modified component in a mass ratio of 100:15, wherein:

[0041] Main components: dead-burned magnesium oxide powder 70%, potassium dihydrogen phosphate 20%, mixing water 10%, the sum of the three is 100%.

[0042] Modified components: Borax and grade fly ash in a mass ratio of 1:2

[0043] (1) First, accurately weigh the dead-burned magnesium oxide powder and potassium dihydrogen phosphate in the main components and the borax and primary fly ash in the modified components, pour them into a planetary mixer and mix them evenly to obtain a mixture A2, and then weigh the mixing water B2 for later use;

[0044] (2) First, pour mixing water B2 into the mixture A2 in the planetary mixer, stir slowly for 1 minute, and then stir quickly for 1 minute until the slurry is evenly dispersed to obtain magnesium phosphate cement M2. The slow stirring speed is 62±5 r / min; the fast stirring speed is 125±10 r / min.

[0045] The magnesium phosphate cement M2 obtained was poured into a 40*40*40mm triple steel mold, and after being compacted, it was vibrated on a vibration table for 1 minute. After half an hour of molding, it was quickly demolded and placed in a muffle furnace at 800°C for high temperature curing for 1 hour, 3 hours, 6 hours and 24 hours.

[0046] Example 3

[0047] A magnesium phosphate cement suitable for use under high temperature conditions is prepared from a main component and a modified component in a mass ratio of 100:15, wherein:

[0048] Main components: dead-burned magnesium oxide powder 70%, potassium dihydrogen phosphate 20%, mixing water 10%, the sum of the three is 100%.

[0049] Modified components: 5% borax and high-activity silica fume in a mass ratio of 1:2.

[0050] (1) First, accurately weigh the dead-burned magnesium oxide powder and potassium dihydrogen phosphate in the main components and the borax and high-activity silica fume in the modified components, pour them into a planetary mixer and mix them evenly to obtain a mixture A3, and then weigh the mixing water B3 for later use;

[0051] (2) First, pour mixing water B3 into the mixture A3 in the planetary mixer, stir slowly for 1 minute, and then stir quickly for 1 minute until the slurry is evenly dispersed to obtain magnesium phosphate cement M3. The slow stirring speed is 62±5 r / min; the fast stirring speed is 125±10 r / min.

[0052] The obtained magnesium phosphate cement M3 was poured into a 40*40*40mm triple steel mold, and after being compacted, it was vibrated on a vibration table for 1 minute. After half an hour of molding, it was quickly demolded and placed in a muffle furnace at 800°C for high temperature curing for 1 hour, 3 hours, 6 hours and 24 hours.

[0053] Example 4

[0054] A magnesium phosphate cement suitable for use under high temperature conditions is prepared from a main component and a modified component in a mass ratio of 100:60, wherein:

[0055] Main components: dead-burned magnesium oxide powder 66.1%, potassium dihydrogen phosphate 18.9%, mixing water 15%, the sum of the three is 100%.

[0056] Modified components: borax, first-grade fly ash and quartz sand in a mass ratio of 1:1:10.

[0057] (1) First, accurately weigh the dead-burned magnesium oxide powder and potassium dihydrogen phosphate in the main components and the borax and primary fly ash in the modified components, pour them into a planetary mixer and mix them evenly to obtain a mixture A4, then weigh the mixing water B4 and quartz sand D4 respectively and set them aside;

[0058] (2) First, pour mixing water B4 into the mixture A4 in the planetary mixer, stir slowly for 1 minute, then stir quickly for 1 minute, and then add quartz sand D4 and stir for 2 minutes until the slurry is evenly dispersed to obtain magnesium phosphate cement M4. The slow stirring speed is 62±5 r / min; the fast stirring speed is 125±10 r / min.

[0059] The obtained magnesium phosphate cement M4 was poured into a 40*40*160mm triple steel mold, and after being compacted, it was vibrated on a vibration table for 1 minute. After half an hour of molding, it was quickly demolded and placed in a muffle furnace at 50°C, 200°C, and 400°C for high temperature curing for 1 hour.

[0060] Example 5

[0061] A magnesium phosphate cement suitable for use under high temperature conditions is prepared from a main component and a modified component in a mass ratio of 100:60, wherein:

[0062] Main components: dead-burned magnesium oxide powder 64.6%, potassium dihydrogen phosphate 18.4%, mixing water 17%, the sum of the three is 100%.

[0063] Modified components: borax, first-grade fly ash and quartz sand in a mass ratio of 1:1:10.

[0064] (1) First, accurately weigh the dead-burned magnesium oxide powder and potassium dihydrogen phosphate in the main components and the borax and primary fly ash in the modified components, pour them into a planetary mixer and mix them evenly to obtain a mixture A5, then weigh the mixing water B5 and quartz sand D5 respectively and set them aside;

[0065] (2) First, pour mixing water B5 into the mixture A5 in the planetary mixer, stir slowly for 1 minute, then stir quickly for 1 minute, and then add quartz sand D5 and stir for 2 minutes until the slurry is evenly dispersed to obtain magnesium phosphate cement M5. The slow stirring speed is 62±5 r / min; the fast stirring speed is 125±10 r / min.

[0066] The obtained magnesium phosphate cement M5 was poured into a 40*40*160mm triple steel mold, and after being compacted, it was vibrated on a vibration table for 1 minute. After half an hour of molding, it was quickly demolded and placed in a muffle furnace at 50°C, 200°C, and 400°C for high temperature curing for 1 hour.

[0067] Example 6

[0068] A magnesium phosphate cement suitable for use under high temperature conditions is prepared from a main component and a modified component in a mass ratio of 100:60.5, wherein:

[0069] Main components: dead-burned magnesium oxide powder 64.6%, potassium dihydrogen phosphate 18.4%, mixing water 17%, the sum of the three is 100%.

[0070] Modified components: borax, first-grade fly ash, polypropylene fiber and quartz sand in a mass ratio of 1:1:0.1:10.

[0071] (1) First, accurately weigh the dead-burned magnesium oxide powder and potassium dihydrogen phosphate in the main components and the borax and primary fly ash in the modified components, pour them into a planetary mixer and mix them evenly to obtain a mixture A6, then weigh the mixing water B6, polypropylene fiber C6 and quartz sand D6 respectively and set them aside;

[0072] (2) First, pour mixing water B6 into the mixture A6 in the planetary mixer, stir slowly for 1 min, then stir quickly for 1 min, then add polypropylene fiber C6 and quartz sand D6 and stir for 2 min until the slurry is evenly dispersed, thereby obtaining magnesium phosphate cement M6.

[0073] The obtained magnesium phosphate cement M6 was poured into a 40*40*160mm triple steel mold, and after compaction, it was vibrated on a vibration table for 1 minute. After half an hour of molding, it was quickly demolded and placed in a muffle furnace at 50°C, 200°C, and 400°C for high temperature curing for 1 hour.

[0074] The compressive strength and flexural strength of each embodiment under different high temperature conditions and curing ages were tested according to GB / T 17671-2021 "Test Method for Cement Mortar Strength". The compressive strength test results of the above-mentioned embodiments 1-3 are shown in Table 1, and the compressive strength and flexural strength test results of embodiments 4-6 are shown in Table 2 and Table 3, respectively. The appearance of embodiments 1-3 after curing at 800℃ for 3 hours is shown in Table 2. Figure 1 shown.

[0075] Table 1 Compressive strength (MPa) test results of Examples 1-3:

[0076] Group / Maintenance time 1h 3h 6h 24h <![CDATA[M1]]> 25.36 24.46 25.53 24.83 <![CDATA[M2]]> 31.52 32.30 33.43 33.77 <![CDATA[M3]]> 37.91 38.56 39.86 42.12

[0077] As can be seen from Table 1, under the high temperature curing condition of 800℃, the compressive strength of the M1 group without auxiliary cementitious materials can reach and stabilize at 24.46MPa-25.53MPa at different ages within 1h-24h. The compressive strength of the M2 and M3 groups at the same age with the addition of primary fly ash and high-activity silica fume reached 31.52MPa-33.77MPa and 37.91MPa-42.12MPa respectively, which is about 28% and 52% higher than that of the M1 group at the same age. This shows that the addition of auxiliary cementitious materials has the effect of optimizing the mechanical properties of magnesium phosphate cement at high temperature. In addition, with the increase of curing age, the optimization effect is more significant.

[0078] from Figure 1 It can be seen that compared with group M1, groups M2 and M3 have darker apparent colors due to the addition of auxiliary cementitious materials. Groups M1 and M2 both have excellent volume stability. In group M3, the active silica fume melts at high temperature and floats to the surface along with steam holes, reacting with MgO to form a MgSiO3 covering layer.

[0079] Table 2 Compressive strength (MPa) test results of Examples 4-6:

[0080]

[0081]

[0082] Table 3 Flexural Strength (MPa) Test Results of Examples 4-6:

[0083] Group / Curing Temperature 50℃ 200℃ 400℃ <![CDATA[M4]]> 3.0 4.0 4.2 <![CDATA[M5]]> 2.5 3.2 3.3 <![CDATA[M6]]> 3.2 2.2 2.8

[0084] It can be seen from Table 2 that as the temperature increases, the compressive strength value also increases. Compared with the M5 group, the compressive strength values ​​of the magnesium phosphate cement in the M4 group under high temperature curing conditions of 50℃, 200℃, and 400℃ increased by 13.2%, 21.9%, and 24.6%, respectively, which shows that reducing the water-cement ratio can significantly improve the mechanical properties of magnesium phosphate cement after high temperature curing. Compared with the M5 group, the compressive strength of the magnesium phosphate cement in the M6 ​​group decreased after the addition of polypropylene fiber. This is because the melting point of polypropylene fiber is around 170℃, and melting at high temperature is not conducive to the development of the strength of magnesium phosphate cement.

[0085] It can be seen from Table 3 that as the temperature increases, the flexural strength value also increases. Compared with the M5 group, the flexural strength values ​​of the magnesium phosphate cement in the M4 group under high temperature curing conditions of 50℃, 200℃, and 400℃ increased by 20%, 25%, and 27.2%, respectively, which indicates that reducing the water-cement ratio can significantly improve the mechanical properties of magnesium phosphate cement after high temperature curing. Compared with the M5 group, the flexural strength of the magnesium phosphate cement in the M6 ​​group increased by 28% at 50℃ after the addition of polypropylene fibers, which indicates that the fiber material can significantly improve the flexural strength of magnesium phosphate cement below the melting point of the fiber material.

[0086] The embodiments described above are part of the embodiments of the present invention, rather than all of the embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A magnesium phosphate cement suitable for use under high temperature conditions, consisting of a main component and a modified component, characterized in that: The main component is composed of the following raw materials in percentage by mass: 50% to 80% magnesium material, 20% to 50% phosphorus material, and the rest is mixing water; The modified component includes at least one of a retarding material, an auxiliary gelling material, a fiber material, and a weighting material; the retarding material includes at least one of borax, boric acid, sodium citrate, citric acid, sodium gluconate, tartaric acid, anhydrous magnesium sulfate, disodium ethylenediaminetetraacetate, sodium tripolyphosphate, and starch ether; The auxiliary cementitious material comprises at least one of fly ash, silica fume, metakaolin, granulated blast furnace slag, red mud, bentonite and diatomaceous earth; The fiber material includes at least one of steel fiber, glass fiber, graphene nanofiber, polypropylene fiber, and polytetrafluoroethylene fiber; The weighting material includes at least one of quartz sand, perlite, iron ore and barite; The mass ratio of the main component to the modified component is 100:5-85.

2. The magnesium phosphate cement suitable for use under high temperature conditions as claimed in claim 1, characterized in that: The magnesia material is dead-burned magnesia powder with a magnesia content higher than 80%.

3. The magnesium phosphate cement suitable for use under high temperature conditions as claimed in claim 1, characterized in that: The phosphorus material is at least one of potassium dihydrogen phosphate and potassium dihydrogen phosphate.

4. The magnesium phosphate cement suitable for use under high temperature conditions as claimed in claim 1, characterized in that: The auxiliary gelling material is particles or powders with a size of less than 10 meshes; the weighting material has a continuous gradation and a mesh size range of 10 meshes to 200 meshes.

5. The magnesium phosphate cement suitable for use under high temperature conditions as claimed in claim 1, characterized in that: The modified component is prepared by mixing borax and fly ash in a mass ratio of 1:

2.

6. The magnesium phosphate cement suitable for use under high temperature conditions according to claim 1, characterized in that: The modified component is prepared by mixing borax and silica fume in a mass ratio of 1:

2.

7. The magnesium phosphate cement suitable for use under high temperature conditions according to claim 1, characterized in that: The modified component is prepared by mixing borax, fly ash and quartz sand in a mass ratio of 1:1:

10.

8. The magnesium phosphate cement suitable for use under high temperature conditions as claimed in claim 1, characterized in that: The modified component is prepared by mixing borax, fly ash, polypropylene fiber and quartz sand in a mass ratio of 1:1:0.1:

10.

9. The method for preparing magnesium phosphate cement suitable for use under high temperature conditions according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) weighing raw materials according to proportion, pouring the weighed magnesium material, phosphorus material, slow-setting material, and auxiliary cementitious material into a planetary mixer and mixing them evenly; (2) Then, mixing water is added and stirred slowly for 1 minute, then stirred rapidly for 1 minute, and then fiber materials and weighting materials are added in sequence, and stirring is continued for 2-3 minutes until the mixture is evenly dispersed, thereby obtaining the magnesium phosphate cement suitable for high temperature conditions.

10. The preparation method according to claim 1, characterized in that: The slow stirring speed is 62±5 r / min; the fast stirring speed is 125±10 r / min.

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