Calcium carbonate hardened body based on microwave heating maintenance as well as preparation method and application thereof

Abstract

The invention discloses a calcium carbonate hardened body based on microwave heating maintenance as well as a preparation method and application thereof. The calcium carbonate hardened body based on microwave heating curing is prepared by curing vaterite and a crystal form regulating agent under a microwave heating condition for 5 minutes to 3 hours. The setting and hardening of the calcium carbonate phase change cementing material are accelerated in a microwave curing manner. Microwaves can penetrate into a calcium carbonate sample, so that the sample can be quickly and uniformly heated, calcium carbonate particles are dissolved and recrystallized, interfaces of the calcium carbonate particles are mutually fused, the structure is densified, and the strength of calcium carbonate cement is improved. The raw materials are wide in source and low in cost, and the hardening method is simple and easy to implement, so that the building material has wide application in the field of building materials, especially the field of low-carbon building materials.

Description

Technical Field

[0001] The invention belongs to the field of inorganic non-metallic materials, and in particular relates to a calcium carbonate hardener based on microwave heating and curing, and a preparation method and application thereof. Background Art

[0002] Anthropogenic carbon dioxide (CO2) is contributing to rising atmospheric CO2 concentrations, which is widely recognized as a major contributor to the greenhouse effect, ocean acidification, and global climate change. Although efforts are underway to reduce CO2 emissions, global anthropogenic CO2 emissions are expected to continue to increase in the coming decades. Carbonate rocks are estimated to contain approximately 39,000,000 Gt of terrestrial CO2, providing a potential pathway for stable, long-term storage of CO2 produced by anthropogenic activities. In addition, carbonate rocks, such as limestone and marble, are primarily composed of calcium carbonate (CaCO3) and have long been widely used by humans as building materials, providing a potential solution for recycling CO2 into value-added materials.

[0003] Calcium carbonate is a very important inorganic non-metallic material and industrial raw material, which has the characteristics of low price, wide source, easy processing, and controllable morphology. Calcium carbonate mainly has the following common crystal forms: aragonite, calcite, vaterite, amorphous calcium carbonate, etc. From the perspective of thermodynamic stability, calcite is the most stable, and it is abundant and widely available. Amorphous calcium carbonate is thermodynamically less stable than calcite. Since there are many types of calcium carbonate crystal forms and the transformation is easy to control, the main method for preparing calcium carbonate block materials is to control the morphological characteristics of calcium carbonate crystals by controlling the transformation of calcium carbonate crystal forms.

[0004] Among the various calcium carbonate crystal forms currently present in calcium carbonate phase change cementitious materials, aragonite has the best effect because aragonite is needle-rod-shaped, and the three-dimensional network structure it forms produces bonding force, which can form a calcium carbonate hardened body with certain mechanical strength. In addition, the main curing method for calcium carbonate phase change cementitious materials is to accelerate the conversion of vaterite to aragonite by steam curing with water. Under the action of water, the free energy of calcium carbonate transformation is reduced, which promotes the crystal transformation of calcium carbonate, and the morphology of calcium carbonate changes by dissolution and recrystallization. However, there are gaps between the particles of the sample obtained by this method, the structure is loose, the degree of bonding is low, the compressive strength is small; the mechanical properties are poor, and the curing time is too long. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a calcium carbonate hardener based on microwave heating and curing, and a preparation method and application thereof.

[0006] The purpose of the present invention is achieved through the following technical solutions: A calcium carbonate hardener based on microwave heating and curing is prepared from vaterite and a crystal form regulator under microwave heating and curing conditions, wherein the microwave heating and curing time is 5 minutes to 3 hours. More preferably, the microwave heating and curing time is 5 minutes to 1 hour.

[0007] The preparation method of the calcium carbonate hardened body based on microwave heating and curing comprises the following steps: mixing vaterite and a crystal modifier in a mass ratio of 1-9:1-7, adding water and stirring to obtain a slurry, and performing microwave heating and curing after the slurry is formed, and the hardened body is obtained after the curing is completed.

[0008] Preferably, the vaterite and the crystal form regulator are mixed in a mass ratio of 5-7:3-5.

[0009] Preferably, the crystal form regulator comprises at least one of aragonite minerals, magnesium-containing phase minerals and strontium-containing phase minerals; The average aspect ratio of the aragonite in the aragonite minerals is 5-40; the magnesium content of the magnesium-containing phase minerals is not less than 45% calculated in the form of magnesium oxide; the strontium content of the strontium-containing phase minerals is not less than 35%.

[0010] Preferably, the average aspect ratio of the aragonite in the aragonite minerals is 8-12; the magnesium content of the magnesium-containing phase minerals is not less than 50% when calculated in the form of magnesium oxide; and the strontium content of the strontium-containing phase minerals is not less than 40%.

[0011] Preferably, the aragonite mineral is at least one of aragonite whiskers, coral powder and shell powder; the magnesium-containing phase mineral is at least one of chlormagnesia ore powder, kieserite ore powder and dolomite ore powder; the strontium-containing phase mineral includes at least one of celestite, strontium ore powder and strontium-rich aragonite ore powder.

[0012] Preferably, in the crystal regulator, the content of aragonite minerals is not less than 40wt%, and the total content of magnesium-containing phase minerals and strontium-containing phase minerals is not less than 20wt%; more preferably, the content of aragonite minerals is not less than 50wt%, and the total content of magnesium-containing phase minerals and strontium-containing phase minerals is not less than 25wt%.

[0013] Preferably, the crystal form regulator further includes a supporting agent, and the supporting agent is at least one of graphene nitride, graphene boride and graphene oxide.

[0014] Preferably, the crystal form regulator is prepared by the following method: grinding and heat treating the components and then mixing them evenly, and the average particle size of the prepared crystal form regulator is 30-80 μm, and the water content is less than 3.00%. More preferably, the average particle size of the prepared crystal form regulator is 30-50 μm, and the water content is less than 2.00%.

[0015] Preferably, the amount of water added is such that the water-to-solid ratio is 0.1-0.5, more preferably 0.25-0.35.

[0016] Preferably, the slurry is formed by extrusion, casting and compression molding, wherein the compression molding pressure is 30-150 MPa, more preferably 75-125 MPa.

[0017] Preferably, the power of the microwave heating curing is 300-800W, more preferably 500-700W.

[0018] The above-mentioned calcium carbonate hardener cured by microwave heating is used as a building material such as coatings, panels, structures and shielding and protection materials.

[0019] The principle involved in the present invention is as follows: the calcium carbonate phase change cementitious material (vaterite and crystal form regulator) of the present invention takes the dissolution and bonding of the calcium carbonate interface as the main source of cementing force. The addition of the crystal form regulator provides crystal seeds for the vaterite crystal form transformation process, reducing the crystal form transformation potential energy. The introduction of magnesium and strontium minerals reduces the occurrence of side reactions of the transformation of vaterite to calcite crystal form through the stabilization of the vaterite crystal form by magnesium and strontium ions. In addition, by introducing a structural support auxiliary agent, the contact structure between the crystal form regulator and the reaction raw materials is optimized, and the regulation effect is promoted. The coagulation and hardening of the calcium carbonate phase change cementitious material is accelerated by microwave curing. Microwaves can penetrate into the calcium carbonate sample, so that the sample can be quickly and evenly heated, so that the calcium carbonate particles dissolve and recrystallize, and the interfaces between the calcium carbonate particles are mutually fused. The microstructure is transformed from rod-like interlacing to spherical particle bonding, so that the structure is densified and the strength of the calcium carbonate cement is improved.

[0020] Compared with the prior art, the beneficial effects of the present invention include: (1) The calcium carbonate phase change cementitious material (vaterite and crystal form regulator) of the present invention has a fast hardening speed and high compressive strength. Compared with the material cured by autoclaving, the present invention has more excellent mechanical properties.

[0021] (2) Microwave heating method has the advantages of fast speed, uniform heating, small temperature gradient, less heat loss, no open flame, no weak joints and weak joints, high repair quality and no pollution. It meets the national requirements of energy conservation, emission reduction and environmental protection, and can meet the needs of rapid entry, rapid operation and rapid evacuation of pavement maintenance. Therefore, it has a wide range of applications in the field of building materials, especially low-carbon building materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the SEM image of the hardened calcium carbonate obtained in Example 1.

[0023] Figure 2This is the SEM image of the hardened calcium carbonate obtained in Example 2.

[0024] Figure 3 This is the SEM image of the hardened calcium carbonate obtained in Example 3.

[0025] Figure 4 This is the SEM image of the hardened calcium carbonate obtained in Example 4.

[0026] Figure 5 This is the SEM image of the hardened calcium carbonate obtained in Example 5.

[0027] Figure 6 This is the SEM image of the hardened calcium carbonate obtained in Comparative Example 1.

[0028] Figure 7 This is the SEM image of the hardened calcium carbonate obtained in Comparative Example 2.

[0029] Figure 8 This is the SEM image of the hardened calcium carbonate obtained in Comparative Example 3. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0031] The vaterite used in the examples and comparative examples of the present invention was prepared by a precipitation method.

[0032] The preparation method of vaterite is as follows: after mixing 1.5 mol / L of equal volume and concentration of calcium chloride dihydrate and anhydrous potassium carbonate, the precipitate is filtered, the filter cake is washed with deionized water and anhydrous ethanol and then dried at 60° C. for 24 hours.

[0033] The vaterite product was characterized by XRD, and the purity of the vaterite was 99.67%.

[0034] The crystal form modifiers used in the embodiments and comparative examples of the present invention are divided into category 1 and category 2, wherein Category 1: The content of coral powder is 57%, and the average aspect ratio of aragonite is 11.43; the content of magnesite powder is 15%, and the mineral magnesium content is 62% calculated in the form of magnesium oxide; the content of celestite powder is 13%, and the mineral strontium content is 44% calculated in the form of strontium sulfate; the structural support component uses graphene oxide aqueous dispersion, the specification is 1mg / ml, and the content is 15%. After the coral powder, magnesite powder, and celestite powder are ground and heat-treated at 220℃ for 10min in air atmosphere, they are mixed with graphene oxide aqueous dispersion and dried at 60℃ for 8h. The average particle size of the obtained crystal form regulator is 47μm and the water content is 1.73%.

[0035] Category 2: The content of coral powder is 41%, and the average aspect ratio of aragonite is 5.77; the content of dolomite is 12%, and the mineral magnesium content is 58% calculated in the form of magnesium oxide; the content of celestite powder is 9%, and the mineral strontium content is 42% calculated in the form of strontium sulfate; the structural support component uses graphene oxide aqueous dispersion, the specification is 1mg / ml, and the content is 38%. After the coral powder, dolomite powder, and celestite powder are ground and heat-treated at 220℃ for 10min in air atmosphere, they are mixed with the graphene oxide aqueous dispersion and dried at 60℃ for 8h. The average particle size of the obtained crystal form regulator is 35μm and the water content is 1.53%.

[0036] Example 1 A method for preparing a calcium carbonate hardener based on microwave heating and curing, the steps are as follows: 40 parts by mass of vaterite and 60 parts by mass of category 1 crystal form regulator were mixed in a stirring pot. After stirring for 5 minutes, water was mixed with the solid raw material at a water-to-solid ratio of 0.35 to obtain a calcium carbonate phase change cementitious material slurry. The slurry was poured into a stainless steel cylindrical mold with a diameter of 20 mm, and pressurized using an automatic press with a molding pressure of 100 MPa. After pressurization for 2 minutes, the mold was demolded to obtain a test block with a height of 20 mm and a diameter of 20 mm. The test block was placed in a microwave environment for curing for 15 minutes. The microwave heating power was 700 W to obtain a calcium carbonate hardened body based on microwave heating curing.

[0037] Example 2 A method for preparing a calcium carbonate hardener based on microwave heating and curing, the steps are as follows: 40 parts by mass of vaterite and 60 parts by mass of category 1 crystal form regulator were mixed in a stirring pot. After stirring for 5 minutes, water was mixed with the solid raw material at a water-to-solid ratio of 0.35 to obtain a calcium carbonate phase change cementitious material slurry. The slurry was poured into a stainless steel cylindrical mold with a diameter of 20 mm, and pressurized using an automatic press with a molding pressure of 100 MPa. After pressurization for 2 minutes, the mold was demolded to obtain a test block with a height of 20 mm and a diameter of 20 mm. The test block was placed in a microwave environment for curing for 30 minutes. The microwave heating power was 700 W to obtain a calcium carbonate hardened body based on microwave heating curing.

[0038] Example 3 A method for preparing a calcium carbonate hardener based on microwave heating and curing, the steps are as follows: 40 parts by mass of vaterite and 60 parts by mass of category 1 crystal form regulator were mixed in a stirring pot. After stirring for 5 minutes, water was mixed with the solid raw material at a water-to-solid ratio of 0.35 to obtain a calcium carbonate phase change cementitious material slurry. The slurry was poured into a stainless steel cylindrical mold with a diameter of 20 mm, and pressurized using an automatic press with a molding pressure of 100 MPa. After pressurization for 2 minutes, the mold was demolded to obtain a test block with a height of 20 mm and a diameter of 20 mm. The test block was placed in a microwave environment for curing for 45 minutes. The microwave heating power was 700 W to obtain a calcium carbonate hardened body based on microwave heating curing.

[0039] Example 4 A method for preparing a calcium carbonate hardener based on microwave heating and curing, the steps are as follows: 50 parts by mass of vaterite and 30 parts by mass of category 2 crystal form regulator were mixed in a stirring pot. After stirring for 5 minutes, water was mixed with the solid raw material at a water-to-solid ratio of 0.20 to obtain a calcium carbonate phase change cementitious material slurry. The slurry was poured into a stainless steel cylindrical mold with a diameter of 20 mm, and pressurized using an automatic press with a molding pressure of 50 MPa. After pressurization for 2 minutes, the mold was demolded to obtain a test block with a height of 20 mm and a diameter of 20 mm. The test block was placed in a microwave environment for curing for 15 minutes. The microwave heating power was 500 W to obtain a calcium carbonate hardened body based on microwave heating curing.

[0040] Example 5 A method for preparing a calcium carbonate hardener based on microwave heating and curing, the steps are as follows: 60 parts by mass of vaterite and 40 parts by mass of category 2 crystal form regulator were mixed in a stirring pot. After stirring for 5 minutes, water was mixed with the solid raw material at a water-to-solid ratio of 0.15 to obtain a calcium carbonate phase change cementitious material slurry. The slurry was poured into a stainless steel cylindrical mold with a diameter of 20 mm, and pressurized using an automatic press with a molding pressure of 30 MPa. After pressurization for 2 minutes, the mold was demolded to obtain a test block with a height of 20 mm and a diameter of 20 mm. The test block was placed in a microwave environment for curing for 30 minutes. The microwave heating power was 600 W to obtain a calcium carbonate hardened body based on microwave heating curing.

[0041] Comparative Example 1 A method for preparing a hardened body of a calcium carbonate phase change cementitious material, comprising the following steps: 40 parts by mass of vaterite and 60 parts by mass of category 1 crystal form regulator were mixed in a stirring pot. After stirring for 5 minutes, water was mixed with the solid raw material at a water-to-solid ratio of 0.35 to obtain a calcium carbonate phase change cementitious material slurry. The slurry was poured into a stainless steel cylindrical mold with a diameter of 20 mm, and pressurized using an automatic press with a molding pressure of 100 MPa. After pressurization for 2 minutes, the mold was demolded to obtain a test block with a height of 20 mm and a diameter of 20 mm. The test block was placed in a steam environment at a temperature of 60°C for curing for 3 days to obtain a hardened calcium carbonate phase change cementitious material.

[0042] Comparative Example 2 A method for preparing a hardened body of a calcium carbonate phase change cementitious material, comprising the following steps: 40 parts by mass of vaterite and 60 parts by mass of category 1 crystal form regulator were mixed in a stirring pot. After stirring for 5 minutes, water was mixed with the solid raw material at a water-to-solid ratio of 0.35 to obtain a calcium carbonate phase change cementitious material slurry. The slurry was poured into a stainless steel cylindrical mold with a diameter of 20 mm, and pressurized using an automatic press with a molding pressure of 100 MPa. After pressurization for 2 minutes, the mold was demolded to obtain a test block with a height of 20 mm and a diameter of 20 mm. The test block was placed in a steam environment at a temperature of 100°C for curing for 3 days to obtain a hardened calcium carbonate phase change cementitious material.

[0043] Comparative Example 3 A method for preparing a hardened body of a calcium carbonate phase change cementitious material, comprising the following steps: 40 parts by mass of vaterite and 60 parts by mass of category 1 crystal form regulator were mixed in a stirring pot. After stirring for 5 minutes, water was mixed with the solid raw material at a water-to-solid ratio of 0.35 to obtain a calcium carbonate phase change cementitious material slurry. The slurry was poured into a stainless steel cylindrical mold with a diameter of 20 mm, and pressurized using an automatic press with a molding pressure of 100 MPa. After pressurization for 2 minutes, the mold was demolded to obtain a test block with a height of 20 mm and a diameter of 20 mm. The test block was placed in a microwave environment for curing for 15 minutes. The microwave heating power was 200 W to obtain a hardened body based on microwave heating curing.

[0044] Performance Testing 1) The compressive strength of the hardened calcium carbonate phase change cementitious materials obtained in Examples 1 to 5 and Comparative Examples 1 to 3 was tested using an electronic universal testing machine at a loading speed of 1 mm / min.

[0045] 2) The aragonite content and the vaterite content of the hardened calcium carbonate phase change cementitious materials obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were tested. The aragonite content and the vaterite content were obtained by quantitative analysis based on XRD.

[0046] The test results are recorded in Table 1.

[0047] Table 1 Test results of Examples 1 to 5 and Comparative Examples 1 to 3

[0048] As shown in Table 1, the compressive strength of the calcium carbonate hardened bodies obtained by Examples 1 to 5 based on microwave heating and curing is higher than that of the comparative example. It can be seen that the microwave energy can significantly improve the compressive strength of the calcium carbonate phase change cementitious material by curing it by microwave heating, compared with steam curing. Specifically, Figure 1 This is a SEM image of the hardened calcium carbonate obtained in Example 1. Figure 2 This is a SEM image of the hardened calcium carbonate obtained in Example 2. Figure 3 This is a SEM image of the hardened calcium carbonate obtained in Example 3. Figure 4 This is a SEM image of the hardened calcium carbonate obtained in Example 4. Figure 5 This is a SEM image of the hardened calcium carbonate obtained in Example 5; Figure 6 This is the SEM image of the hardened body obtained in Comparative Example 1. Figure 7 This is the SEM image of the hardened body obtained in Comparative Example 2. Figure 8 This is the SEM image of the hardened body obtained in Comparative Example 3. Figures 1 to 8 It can be seen that the main components of comparative examples 1 and 2 are needle-shaped aragonite, which forms a hardened body skeleton by interpenetrating and overlapping each other, with high porosity and low compressive strength; comparative example 3 is a hardened body structure under the action of low-power microwaves, with a distinct vaterite interface, poor hardened body adhesion, high porosity and low compressive strength. Compared with the comparative example, the interface between the particles of embodiments 1 to 5 is fused and bonded, thereby making the compressive strength of the hardened body higher.

[0049] The present invention uses microwave heating to dissolve and recrystallize calcium carbonate particles, realizes mutual fusion of interfaces between calcium carbonate spherical particles, densifies the structure, and improves compressive strength. The calcium carbonate phase change gelling material of the present invention has a fast hardening speed and high compressive strength, and can obtain a hardened body with a compressive strength of 49.8 to 68.3 MPa. In addition, the raw material source is wide and the cost is low. The hardening method is also simple and easy, so it has a wide range of applications in the field of building materials, especially in the field of low-carbon building materials.

[0050] The specific implementation of the present invention described above does not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A calcium carbonate hardener based on microwave heating and curing, characterized in that: The method is prepared by curing vaterite and a crystal modifier under microwave heating conditions for 5 minutes to 3 hours.

2. The method for preparing a calcium carbonate hardened body based on microwave heating and curing according to claim 1, characterized in that: The method comprises the following steps: mixing vaterite and a crystal form regulator in a mass ratio of 1-9:1-7, adding water and stirring to obtain slurry, performing microwave heating and curing after the slurry is formed, and obtaining the hardened body after the curing is completed.

3. The method for preparing a calcium carbonate hardened body based on microwave heating and curing according to claim 2, characterized in that: The vaterite and the crystal form regulator are mixed in a mass ratio of 5-7:3-5.

4. The method for preparing a calcium carbonate hardened body based on microwave heating and curing according to claim 2, characterized in that: The crystal form regulator includes at least one of aragonite minerals, magnesium-containing phase minerals and strontium-containing phase minerals; The average aspect ratio of the aragonite in the aragonite minerals is 5-40; the magnesium content of the magnesium-containing phase minerals is not less than 45% calculated in the form of magnesium oxide; the strontium content of the strontium-containing phase minerals is not less than 35%.

5. The method for preparing a calcium carbonate hardened body based on microwave heating and curing according to claim 4, characterized in that: The aragonite mineral is at least one of aragonite whiskers, coral powder and shell powder; the magnesium-containing phase mineral is at least one of chlormagnesia ore powder, kieserite ore powder and dolomite ore powder; the strontium-containing phase mineral includes at least one of celestite, strontium ore powder and strontium-rich aragonite ore powder.

6. The method for preparing a calcium carbonate hardened body based on microwave heating and curing according to claim 4, characterized in that: In the crystal regulator, the content of the aragonite mineral is not less than 40wt%, and the total content of the magnesium-containing phase mineral and the strontium-containing phase mineral is not less than 20wt%.

7. The method for preparing a calcium carbonate hardened body based on microwave heating and curing according to claim 4, characterized in that: The crystal form regulator further includes a supporting auxiliary agent, and the supporting auxiliary agent is at least one of graphene nitride, graphene boride and graphene oxide.

8. The method for preparing a calcium carbonate hardened body based on microwave heating and curing according to claim 4 or 7, characterized in that: The crystal form regulator is prepared according to the following method: grinding and heat treating the components and then mixing them evenly. The average particle size of the prepared crystal form regulator is 30-80 μm and the water content is less than 3.00%.

9. The method for preparing a calcium carbonate hardened body based on microwave heating and curing according to claim 2, characterized in that: The amount of water added is such that the water-to-solid ratio is 0.1-0.5; The slurry is formed by extrusion, casting and pressing. The compression molding pressure is 30-150 MPa; The power of the microwave heating curing is 300-800W.

10. Application of the calcium carbonate hardened body cured by microwave heating as claimed in claim 1 as building materials such as coatings, panels, structures and shielding and protective materials.

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