Preparation method of self-curing material of granite waste powder

Abstract

This invention provides a method for preparing a self-curing material from granite waste powder, belonging to the field of solid waste resource utilization technology. The preparation method includes the following steps A to C: In step A, granite waste powder is placed in a photothermal coupling activation device for activation treatment to obtain activated granite waste powder; in step B, unactivated granite waste powder and activated granite waste powder are mixed, and an alkaline activator solution is added to obtain an alkaline activated slurry; in step C, the alkaline activated slurry is sequentially molded, cured, and maintained to obtain a self-curing material from granite waste powder. This invention utilizes photothermal coupling to activate granite waste powder, breaking the lattice bonds of the granite waste powder and constructing an amorphous silicon-aluminum phase. Self-curing of the granite waste powder is achieved through photothermal and alkaline activation, resulting in a self-cured product with both high compressive strength and water resistance. Furthermore, the preparation method of this invention is relatively simple and environmentally friendly.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a method for preparing a self-curing material from granite waste powder. Background Technology

[0002] Granite is a common building and decorative material. The mining, cutting, and polishing processes of granite generate a significant amount of granite waste powder (GWP). This waste powder consists of fine particles with a complex composition, containing minerals such as silica, feldspar, and mica. It also exhibits uneven particle size distribution and low surface activity, making it difficult to utilize directly.

[0003] In related technologies, granite waste powder is mostly treated by landfilling or stockpiling, which occupies a large amount of land resources and may easily cause dust pollution, water pollution and other problems due to long-term stockpiling, resulting in resource waste and ecological burden.

[0004] Therefore, it is necessary to find a way to realize the resource utilization of granite waste powder. Summary of the Invention

[0005] In view of this, in order to at least partially solve the aforementioned technical problems, the present invention provides a method for preparing a self-curing material from granite waste powder.

[0006] According to one aspect of the present invention, a method for preparing a self-curing material from granite waste powder is provided. The method includes the following steps A to C: In step A, granite waste powder is placed in a photothermal coupling activation device for activation treatment to obtain activated granite waste powder; in step B, unactivated granite waste powder and activated granite waste powder are mixed, and an alkali activator solution is added to obtain an alkali-activated slurry; in step C, the alkali-activated slurry is sequentially molded, cured, and maintained to obtain the self-curing material from granite waste powder.

[0007] According to the preparation method of the self-curing material of granite waste powder according to the embodiments of the present invention, the crystal structure of granite waste powder is destroyed by photothermal coupling activation, generating amorphous silica-alumina phase and active oxides, so that the originally "non-cementing" waste powder is transformed into a precursor with alkali-activated activity, which can react under the action of alkali activator to obtain amorphous silica-alumina phase, and then further form aluminosilicate gel to form strength; the unactivated granite waste powder serves as nucleation sites, playing a role in skeleton support and filling, ensuring the adhesion and mechanical properties of the obtained granite waste powder self-curing material. The introduced photothermal coupling activation device helps to reduce energy consumption, and the self-cementing of granite waste powder is achieved through photothermal-alkali activation synergy, without the need for external cement and polymers.

[0008] According to embodiments of the present invention, the preparation method of the present invention has a simple process flow, is environmentally friendly, and can be operated continuously, and is suitable for the high-value utilization of solid waste resources such as granite cutting mud and stone dust. Attached Figure Description

[0009] The above and other objects, features and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings.

[0010] Figure 1 A flowchart illustrating the preparation method of the self-curing granite waste powder material according to an embodiment of the present invention is shown;

[0011] Figure 2 A schematic diagram of the photothermal coupling activation device according to an embodiment of the present invention is shown;

[0012] Figure 3 A schematic diagram of the photothermal coupling activation system according to an embodiment of the present invention is shown.

[0013] In the above figures, the reference numerals are as follows:

[0014] 1. Pipe body; 11. First end; 12. Second end; 13. Baffle; 14. First section; 15. Second section; 15a. Heat transfer medium outlet;

[0015] 2. Granite waste powder;

[0016] 3. Thermal conductive medium;

[0017] 4. Illumination unit; 41. Light source; 42. Reflective concentrator;

[0018] 5. Transparent protective layer;

[0019] 6. Temperature sensor;

[0020] 7. Circulating pump;

[0021] 8. Waste heat exchange unit; 8a. Heat transfer medium inlet 8a;

[0022] 9. Preheating chamber; 91. Hot air inlet; 92. Preheating raw material layer; 93. Exhaust gas outlet. Detailed Implementation

[0023] The embodiments of the present invention will now be described. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the invention.

[0024] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "comprising" as used herein indicates the presence of features, steps, or operations, but does not exclude the presence or addition of one or more other features.

[0025] Granite is a major building and decoration material. The granite waste powder generated during the processing of granite mainly consists of minerals such as silica, feldspar, and mica. Related technologies often treat granite waste powder through landfilling, which easily leads to resource waste and ecological pollution.

[0026] In related technologies, attempts have been made to form recycled stone bricks or artificial stone from granite waste powder through physical pressing or the addition of external binders. However, this requires the introduction of additional binding materials such as cement and resin, resulting in high costs and the potential introduction of new environmental problems. Alternatively, it can be used as a raw material for glass or ceramics, but the process is complex and requires high purity and particle size of the raw materials, limiting its application. Further attempts have been made to use granite waste powder as an admixture in cement or concrete, but the dosage is limited and negatively impacts the strength and stability of the resulting product.

[0027] In summary, the existing technologies for the treatment and utilization of granite waste powder suffer from low utilization rates, high energy consumption, and negative environmental impacts.

[0028] In the process of realizing the concept of this invention, it was discovered that by using a photothermal coupling activation device to activate granite waste powder, and then combining it with an alkali activator to reconstruct the active phase in the granite waste powder, a green self-curing material with both high strength and high water resistance can be obtained. Moreover, no cement or other materials need to be added, which helps to protect the environment.

[0029] Specifically, according to one embodiment of the present invention, a method for preparing a self-curing material from granite waste powder is provided. Figure 1 A flowchart illustrating the preparation method of the self-curing material made from granite waste powder according to an embodiment of the present invention is shown, as follows: Figure 1 As shown, the preparation method includes the following steps A to C.

[0030] In step A, the granite waste powder is placed in a photothermal coupling activation device for activation treatment to obtain activated granite waste powder.

[0031] In step B, unactivated granite waste powder and activated granite waste powder are mixed, and an alkali activator solution is added to obtain an alkali-activated slurry.

[0032] In step C, the alkali-activated slurry is sequentially molded, cured, and maintained to obtain a self-curing material from granite waste powder.

[0033] According to an embodiment of the present invention, as previously described, granite waste powder is composed of various minerals, containing a large number of stable SiO2 and Al2O3 crystalline phases. The chemical inertness of granite waste powder results in poor direct alkali activation. In step A, after the activation treatment of the present invention, the original lattice bonds of the granite waste powder that cause chemical inertness are first broken, and then an amorphous silicon-aluminum phase is further formed, making it easier for active components such as silicon and aluminum to dissolve, providing more raw materials to participate in the subsequent alkali activation reaction, which helps to significantly improve the reactivity and specific surface area of ​​the granite waste powder, and provides reaction sites for the subsequent alkali activation reaction. In step B, unactivated granite waste powder and activated granite waste powder are mixed. The activated raw material provides the intensity of alkali activation, while the unactivated raw material acts as a buffer, reducing problems such as concentrated exothermic reaction and excessive shrinkage. In addition, the mixing of the two helps to increase the bulk density and improve the fluidity of the alkali-activated slurry. Adding an alkaline activator solution to the mixed granite waste powder helps transform the amorphous silica-alumina phase into silica-alumina gel, for example, generating a NASH-type gel structure, where N represents Na, A represents aluminum, S represents silicon, and H represents water. This means that hydrated sodium aluminosilicate is formed, which is a typical cementing phase and helps to form a strong chemical bond with the surface of the unactivated granite waste powder through silicon-oxygen bonds and silica-aluminosilicate bonds; or generating a (N,C)-ASH-type gel structure, where C represents calcium, which can be understood as calcium-containing hydrated sodium aluminosilicate. Its cementing mechanism is similar to that of the aforementioned hydrated sodium aluminosilicate, and will not be elaborated further.

[0034] It should be noted that this invention, by introducing a photothermal coupling activation device into the activation stage, helps to replace electric heating, saving 30-40% of energy consumption. Furthermore, the self-cementing of granite waste powder is achieved through the synergistic effect of photothermal-alkali activation, eliminating the need for external cement or other adhesive materials, thus saving costs and reducing environmental pollution. The resulting self-curing material from granite waste powder forms a dense silica-alumina network, significantly improving its compressive strength and water resistance. In addition, the process of this invention is simple, environmentally friendly, and can be continuously operated, making it suitable for the high-value utilization of solid waste resources such as granite cutting slurry and stone dust.

[0035] In some embodiments, the activation treatment conditions are as follows: heating from room temperature to 400-800°C at a heating rate of 5-15°C / min, and holding at 400-800°C for 1-3 hours. This setup allows the granite waste powder to lose structural water or hydroxyl groups during the 400-600°C heating stage, disrupting the original crystalline integrity of the minerals. At the 600-800°C stage, the originally well-crystallized minerals such as quartz and feldspar have their crystal lattices destroyed at high temperatures, and their atomic arrangement transforms into short-range disorder, forming an amorphous structure. This structure is easily dissolved in an alkaline environment, and the resulting active oxides can react with the alkaline activator solution to generate additional cementing substances, promoting the dissolution and condensation of silicon and aluminum.

[0036] Optionally, the heating rate may be, for example, 5°C / min, 7°C / min, 9°C / min, 11°C / min, 13°C / min or 15°C / min, or a range consisting of any two of the above values.

[0037] Optionally, the endpoint temperature for heating may be, for example, 400°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, or 800°C, or a range consisting of any two of the above values.

[0038] Alternatively, the heat preservation time may be, for example, 1 hour, 2 hours, or 3 hours, or a range consisting of any two of the above values.

[0039] In some embodiments, the alkaline activator solution comprises a combination of sodium silicate, sodium hydroxide, and water. The aqueous sodium silicate solution (water glass) can be understood as consisting of sodium oxide (Na₂O) and silicon dioxide (SiO₂). The addition of sodium hydroxide provides an alkaline environment that disrupts the silicon-oxygen and aluminum-oxygen bonds in the granite waste powder, while the silicate ions help to provide additional active silicon, thereby regulating the composition of the alkaline-activated slurry and the rate of gelation.

[0040] In some embodiments, the molar ratio of silica to sodium oxide in sodium silicate is 1.1 to 2.7. If the molar ratio is too high, the degree of polymerization of sodium silicate is higher, resulting in higher strength but potentially faster subsequent solidification; if the molar ratio is too low, the alkalinity is higher, the silica and aluminum dissolve more quickly, and the resulting gel structure is looser with limited strength.

[0041] Optionally, the molar ratio of silicon dioxide to sodium oxide can be, for example, 1.1, 1.3, 1.5, 1.7, 1.9, 2.1, 2.3, 2.5 or 2.7, or a ratio composed of any two of the above values.

[0042] In some embodiments, the mass ratio of sodium silicate to sodium hydroxide is (8~12):1. This setting, by adjusting the mass ratio of sodium silicate to sodium hydroxide, determines the modulus and alkali equivalent of the alkali activator solution, significantly impacting the workability and stability of the self-curing granite waste powder material. Adding sodium hydroxide to sodium silicate helps reduce the modulus of sodium silicate, thereby improving the dissolution capacity of silica and aluminum in the activated granite waste powder.

[0043] Optionally, the mass ratio of sodium silicate to sodium hydroxide can be, for example, 8:1, 9:1, 10:1, 11:1 or 12:1, or a range consisting of any two of the above ratios.

[0044] In some embodiments, the mass ratio of the alkali activator solution to the activated granite waste powder is (1~3):1. Adjusting the mass ratio to this range helps improve the workability of the alkali-activated slurry and the density of the formed structure, thereby improving the mechanical properties and durability of the self-curing granite waste powder material.

[0045] Optionally, the mass ratio of the alkali activator solution to the activated granite waste powder can be, for example, 1:1, 2:1, or 3:1, or a range consisting of any two of the above ratios.

[0046] In some embodiments, in step B, the mass ratio of unactivated granite waste powder to activated granite waste powder is 1:(1~3). The addition of unactivated granite waste powder helps to reduce the rate of the alkali-activated reaction, while the activated granite waste powder can directly react with the alkali activator solution to form NASH gel or (N,C)-ASH gel. This synergistic adjustment of the ratio maintains good adhesion and stability while avoiding the negative effects of uneven reaction caused by excessively rapid reaction.

[0047] Optionally, the mass ratio of unactivated granite waste powder to activated granite waste powder may be, for example, 1:1, 1:2 or 1:3, or a range consisting of any two of the above ratios.

[0048] In some embodiments, the mass ratio between water and solids in the alkali-activated slurry is 0.2 to 0.3, which is the mass ratio between water and granite waste powder (including the sum of activated and unactivated powders), thereby ensuring the plasticity of the resulting granite waste powder self-curing material.

[0049] In some embodiments, molding includes: placing the alkali-activated slurry in a mold for compression molding under a pressure of 30-50 MPa, for example, 30 MPa, 40 MPa or 50 MPa, preferably 40 MPa, for a molding time of 8-12 minutes, for example, 8 minutes, 10 minutes or 12 minutes, preferably 10 minutes, for example, molding can be carried out in a cubic mold, so as to solidify the self-curing material of granite waste powder according to the actual application requirements.

[0050] In some embodiments, curing is carried out at 60~140°C, for example, 60°C, 80°C, 100°C, 120°C or 140°C, and the curing time is 6~10h, for example, 6h, 8h or 10h. The curing is carried out under constant temperature conditions, and after curing, an alkali-activated gel is prepared to promote the polymerization of the alkali-activated gel and the densification of the structure.

[0051] In some implementations, curing includes placing the alkali-activated gel in a curing room at room temperature and relative humidity of 95% or higher for 2 to 10 days. This setting helps to further improve the strength and water resistance of the alkali-activated gel, thereby forming a self-curing granite waste powder material that can be formed by self-curing without the addition of cement or other additives.

[0052] In some embodiments, the compressive strength of the granite waste powder self-curing material is 35-40 MPa, and the water absorption rate is 4-6%. The preparation based on the aforementioned steps enables the granite waste powder self-curing material to have both good mechanical properties and high water resistance.

[0053] Figure 2 A schematic diagram of the photothermal coupling activation device according to an embodiment of the present invention is shown, as follows: Figure 2 As shown, the photothermal coupling activation device includes: tube 1 and illumination unit 4.

[0054] The tube body 1 can be made of materials such as transparent quartz or transparent glass. The tube body 1 can be cylindrical and has a first end 11 and a second end 12 opposite each other along its extension direction. The first end 11 is open, and the second end 12 is closed. A partition 13 is provided between the first end 11 and the second end 12 of the tube body 1. The partition 13 can be made of materials such as metal, copper, aluminum, or stainless steel. From the perspective of improving heat conduction, copper is preferred as the material of the partition 13. This partition divides the tube body 1 into a first part 14 with one open side and a second part 15 with one closed side. The open first end 11 is suitable for adding granite waste powder 2 to the first part 14. A tray can be provided on the side of the partition 13 facing the first part 14 to facilitate the holding of the granite waste powder 2. The tray can be made of metal and can be the same material as the partition 13. The side of the first part 14 away from the first end 11 is suitable for containing granite waste powder 2, and the side of the second part 15 near the second end 12 is suitable for containing heat-conducting medium 3, such as heat-conducting oil. The second part 15 can be understood as a cavity for containing heat-conducting medium 3.

[0055] The illumination unit 4 is adjacent to the tube body 1, and the illumination unit 4 is suitable for providing illumination to the heat conduction medium 3. The illumination into the heat conduction medium 3 causes the heat conduction medium 3 to absorb heat and rise in temperature. The heat conduction medium 3 receives the heat from the illumination unit 4 and transfers the heat to the granite waste powder 2 through natural convection, and at the same time transfers it to the partition plate 13.

[0056] According to an embodiment of the present invention, the illumination unit 4 emits light radiation, which directly irradiates the heat-conducting medium 3 (such as heat-conducting oil). The heat-conducting medium 3 has the ability to absorb light of a specific wavelength. After absorbing light energy, the energy of the photons is converted into the thermal kinetic energy of the medium molecules, thereby increasing the temperature of the heat-conducting medium 3 itself. After being heated, the temperature of the heat-conducting medium 3 near the illumination side is higher and the density is lower, so it moves upward; the temperature of the side away from the illumination side is lower and the density is higher, so it sinks downward. This forms natural convection, making the temperature of the second part 15 tend to be uniform. The partition 13 is made of metal and has high thermal conductivity, which efficiently conducts the heat of the heat-conducting medium 3 to the granite waste powder 2 on the other side of the partition 13, thereby realizing indirect heating of the granite waste powder 2, improving heating efficiency and heating uniformity.

[0057] In some embodiments, the tube 1 is inclined, which provides a tendency for the heat transfer medium 3 to flow upward along the inclined direction, thereby enhancing the thermal circulation efficiency in the second part 15, making the temperature distribution of the heat transfer medium 3 more uniform, and thus improving the uniformity of heating the granite waste powder 2.

[0058] In some embodiments, the photothermal coupling activation device further includes a transparent protective layer 5 and a temperature sensor 6. The transparent protective layer 5 is fitted over the tube body 1, creating a vacuum between the transparent protective layer 5 and the tube body 1. The transparent protective layer 5 provides protection for the tube body 1, and the vacuum space helps to effectively reduce heat loss. The temperature sensor 6 is located on the outer side of the first portion 14 of the tube body 1 near the partition 13, and the position of the temperature sensor 6 corresponds to the granite waste powder 2. Figure 3 As shown, this configuration of temperature sensor 6 helps to accurately control the heating rate and the duration of constant temperature, and utilizes the waste heat exchange unit to achieve energy recovery, significantly reducing energy consumption.

[0059] In some embodiments, the illumination unit 4 includes a light source 41 and a reflective concentrator 42. The light source 41 may be a halogen lamp, metal halide lamp, or the like, used as a heat source to provide illumination. The reflective concentrator 42 is fitted over the light source 41 to focus the light emitted by the light source 41 onto the heat-conducting medium 3 of the second part 15, causing the heat-conducting medium 3 to absorb heat and rise in temperature.

[0060] According to yet another embodiment of the present invention, a photothermal coupling activation system is provided.

[0061] Figure 3 A schematic diagram of the photothermal coupling activation system according to an embodiment of the present invention is shown. Figure 3 As shown, the photothermal coupling activation system also includes: a circulating pump 7, a waste heat exchange unit 8, and a preheating chamber 9.

[0062] The waste heat exchange unit 8 is connected to the second part 15 of the pipe body 1 via a pipe, which is suitable for recovering the waste heat of the heat transfer medium 3 and transferring it to the air. The waste heat exchange unit 8 is provided with a heat transfer medium inlet 8a, which is suitable for receiving the heat transfer medium 3 from the second part 15 after it has been heated and completed the heat transfer through the heat transfer medium inlet 8a.

[0063] In some embodiments, the tube body 1 further includes a heat transfer medium outlet 15a, which is located on the side of the second part 15 away from the first end 11, and is suitable for discharging the heat transfer medium 3 that has completed heat transfer after being heated.

[0064] The circulating pump 7 is located on the pipeline between the heat transfer medium outlet 15a of the second part 15 and the heat transfer medium inlet 8a of the waste heat exchange unit 8. The circulating pump 7 is suitable for driving the circulating flow of the heat transfer medium 3.

[0065] In some embodiments, the photothermal coupling activation system further includes a preheating chamber 9, which is connected to the waste heat exchange unit 8 and is adapted to receive preheated air from the waste heat exchange unit 8 and preheat the granite waste powder 2 before it enters the first part 14.

[0066] In some embodiments, the preheating chamber 9 includes a hot air inlet 91 located at the lower part of the preheating chamber 9, and the preheated air from the waste heat exchange unit 8 is continuously introduced into the preheating chamber 9 through the hot air inlet 91.

[0067] In some embodiments, the preheating chamber 9 further includes a preheating raw material layer 92 located inside the preheating chamber 9, the preheating raw material layer 92 being suitable for containing granite waste powder 2.

[0068] In some embodiments, the preheating chamber 9 also includes an exhaust outlet 93 located at the top of the preheating chamber 9, which is suitable for discharging the air after preheating the granite waste powder 2.

[0069] The present invention will be further illustrated below through embodiments and related test experiments and results. In the following detailed description, numerous specific details are set forth for ease of explanation to provide a comprehensive understanding of the embodiments of the present invention. However, it will be apparent that one or more embodiments may be practiced without these specific details. Moreover, the details in the following embodiments can be arbitrarily combined to form other feasible embodiments without conflict.

[0070] It should be noted that the specific embodiments described below are merely illustrative examples, and the scope of protection of this invention is not limited thereto. The chemicals and raw materials used in the following embodiments are all commercially available or prepared using recognized processing methods.

[0071] Example 1:

[0072] Granite waste powder (GWP) obtained from granite sand making tailings or stone cutting slurry through natural settling was placed in a forced-air drying oven and dried at 105℃ for 6 hours to remove free moisture. The dried GWP was then pulverized using a small laboratory pulverizer and passed through a 200-mesh standard sieve to ensure uniform particle size (less than 0.074 mm) and no agglomeration, and was ready for use.

[0073] The dried GWP is then loaded into a photothermal coupling activation device. This device is as follows: Figure 2 The diagram shows a structure consisting of a tube (transparent quartz), a second part (heat-conducting oil chamber), a partition, and a first part (powder-bearing chamber) (including a tray, not shown in the diagram). Heat-conducting oil is injected into the heat-conducting oil chamber until the liquid level is approximately one-third of the height of the second part. The dried GWP is then evenly spread in the metal tray above the partition.

[0074] A halogen photothermal source was activated, and a parabolic reflector was used to concentrate the light, causing the heat transfer oil to heat from room temperature to 600°C at a rate of 10°C / min and maintain the temperature for 2 hours. During the heating process, the heat transfer oil transferred heat to the powder cavity through natural convection and conduction, achieving uniform heating. After observing that the powder color changed from light gray to orange-yellow and its volume slightly expanded, heating was stopped, and the powder was allowed to cool naturally to room temperature, yielding activated granite waste powder.

[0075] Industrial-grade liquid water glass (modulus Ms = 2.2, where modulus is the molar ratio of silicon dioxide to sodium oxide) and sodium hydroxide granules were mixed at a mass ratio of 10:1. NaOH was first dissolved in an appropriate amount of deionized water. After the temperature cooled to room temperature, the water glass solution was slowly added while stirring. After stirring, the mixture was allowed to stand for 24 hours to age, yielding a clear and homogeneous alkali activator solution.

[0076] Take activated GWP and unactivated GWP at a mass ratio of 2:1, and dry mix them in a planetary mixer for 2 minutes to ensure thorough mixing. Then slowly add the alkali activator solution, controlling the water-to-solid ratio at 0.25, and continue mixing for 10 minutes to form a fine, uniform alkali-activated slurry without visible lumps.

[0077] The alkali-activated slurry was injected into a standard 40mm×40mm×40mm cubic mold, vibrated to remove air, and then compacted. After demolding, it was placed in a constant temperature oven and cured at 80℃ for 8 hours to allow the silicon and aluminum species in the system to undergo a condensation reaction and form a stable gel structure, thus obtaining a cured sample.

[0078] After the cured sample was cooled to room temperature, it was transferred to a constant temperature and humidity curing chamber (temperature 20±2℃, relative humidity ≥95%) for 7 days to obtain granite waste powder self-curing material.

[0079] The performance of the obtained self-curing granite waste powder material was tested. Considering that this embodiment used a 40mm×40mm×40mm mold to form the specimens, the compressive strength and water absorption rate were tested according to the relevant principles of GB / T 4111-2013 "Test Methods for Concrete Blocks and Bricks". The compressive strength was obtained by measuring the failure load of the specimen and calculating it in combination with the compressed area; the water absorption rate was calculated by measuring the difference between the mass of the specimen after drying to constant weight and the mass after immersion in water. The test results show that the compressive strength of this self-curing granite waste powder material is 38MPa, and the water absorption rate is 5.8%, exhibiting good self-curing performance and water resistance.

[0080] Example 2:

[0081] This embodiment is basically the same as Embodiment 1, except that the photothermal activation temperature is increased and the holding time is extended to investigate the effect of stronger activation conditions on the densification of the system.

[0082] Granite waste powder from the same batch as in Example 1 was selected, dried at 105°C for 6 hours to remove water, then pulverized and passed through a 200-mesh sieve to obtain dried GWP with uniform particle size.

[0083] The dried GWP was placed in the same photothermal coupling activation device as in Example 1. While maintaining a stable heat transfer oil level, a halogen light source was turned on and focused onto the lower part of the heat transfer oil chamber, causing the oil temperature to rapidly rise from room temperature to 700°C at a rate of 10°C / min and remain at that temperature for 3 hours. During the heating process, the powder gradually changed from light gray to light brown and became loose, indicating that the crystalline structure was partially disrupted and the activity was significantly enhanced. After heating was stopped, the powder was allowed to cool naturally, yielding activated granite waste powder.

[0084] Industrial water glass (modulus Ms=1.8, i.e. the ratio of silicon dioxide to sodium oxide content) and NaOH were mixed at a mass ratio of 9:1. NaOH was first dissolved in deionized water and cooled, and then slowly added to the diluted water glass solution and stirred evenly. The solution was allowed to stand and age for 24 hours to obtain a light and transparent alkali activator solution.

[0085] Mix activated and unactivated GWP at a mass ratio of 1:1 and dry mix in a planetary mixer for 2 minutes. Then slowly add the activator solution, controlling the water-to-solid ratio at 0.25, and continue mixing for 10 minutes to form a homogeneous slurry.

[0086] After the slurry was injected into the same mold as in Example 1 and vibrated to compact it, it was cured at 100°C for 6 hours to allow the alkali-activated reaction to proceed fully and form a dense silica-alumina gel network, thus obtaining a cured sample.

[0087] After the cured sample was cooled to room temperature, it was cured under constant humidity for 7 days to obtain a self-curing material of granite waste powder.

[0088] Using the same testing method as in Example 1, the self-curing material made from granite waste powder was tested. The compressive strength of the self-curing material made from granite waste powder reached 45 MPa, and the water absorption rate was 4.9%, which was significantly improved compared to Example 1. This indicates that the higher activation temperature and sufficient curing promoted the densification of the structure and the improvement of strength.

[0089] Example 3:

[0090] In this embodiment 3, while keeping the photothermal activation conditions unchanged, the main focus is on the effect of increasing the modulus of the alkali activator on the material structure and properties.

[0091] The granite waste powder was dried, dehydrated, crushed, and sieved in the same manner as in Example 1 to obtain dried GWP with uniform particle size.

[0092] The dried GWP was placed in the same photothermal coupling activation device as in Example 1. While maintaining a stable heat transfer oil level, a halogen light source was turned on and focused onto the lower part of the heat transfer oil chamber, causing the heat transfer oil temperature to rapidly rise from room temperature to 600°C at a rate of 10°C / min and remain at that temperature for 2 hours. The dried GWP powder turned a lighter red color, indicating an increase in lattice looseness. Cooling yielded activated granite waste powder.

[0093] The mass ratio of water glass to NaOH was adjusted to 12:1 to increase the modulus of the water glass solution to 2.6. First, a NaOH solution was prepared, cooled, and then diluted water glass was slowly added. The mixture was stirred until homogeneous and allowed to stand for 24 hours to obtain the alkali activator solution.

[0094] Mix activated GWP and unactivated GWP in a mass ratio of 3:1, dry mix in a planetary mixer for 2 minutes, then slowly add high modulus activator solution, control the water-to-solid ratio at 0.28, and continue mixing for 10 minutes until a uniform slurry is formed.

[0095] After the slurry was injected into the same mold as in Example 1 and vibrated to compact it, it was cured at 80°C for 8 hours to form a highly cross-linked gel structure in the high silicon modulus excitation system, thus obtaining a cured sample.

[0096] After the cured sample was cooled to room temperature, it was cured under constant humidity for 7 days to obtain a self-curing material of granite waste powder.

[0097] Using the same testing method as in Example 1, the self-curing material of granite waste powder was tested. The compressive strength of the self-curing material of granite waste powder reached 43 MPa and the water absorption rate was 5.2%, showing that the high modulus activator can significantly improve the adhesion and water resistance of the system. The gel network structure is denser and more stable than that of Example 1.

[0098] Example 4

[0099] This embodiment mainly studies the retention of the self-curing effect of the system when the proportion of activating powder is low.

[0100] Using the same granite waste powder as in Example 1, and drying it sequentially at 105°C for 6 hours in the same manner, then pulverizing and passing it through a 200-mesh sieve, the dried GWP was obtained.

[0101] The dried GWP was placed in the same photothermal coupling activation device as in Example 1. While maintaining a stable heat transfer oil level, a halogen light source was turned on and focused to irradiate the lower part of the heat transfer oil chamber, causing the heat transfer oil temperature to rise rapidly from room temperature to 550°C at a rate of 10°C / min for 2 hours. After activation, the powder color changed from grayish-white to light yellow, and the structure became loose. After cooling, it was removed and ground evenly to obtain activated granite waste powder.

[0102] A water glass activator with a modulus of 2.2 was prepared using the same preparation method as in Example 1. After aging for 24 hours, a clear and homogeneous alkali activator solution was obtained.

[0103] Take activated GWP and unactivated GWP at a mass ratio of 1:3, dry mix for 2 minutes, then slowly add activator solution, control the water-to-solid ratio at 0.30, and continue stirring for 10 minutes to form a fine, uniform alkali-activated slurry without visible dry lumps.

[0104] After the alkali-activated slurry was injected into a mold identical to that in Example 1 and compacted, it was demolded and placed in a constant temperature oven and cured at 90°C for 6 hours. After curing, the gel network of the system was stable and the surface was smooth without cracks, thus obtaining a cured sample.

[0105] After the cured sample was cooled to room temperature, it was transferred to a constant temperature and humidity curing chamber (temperature 20±2℃, relative humidity ≥95%) for 7 days to obtain granite waste powder self-curing material.

[0106] The self-curing material of granite waste powder was tested using the same testing method as in Example 1. The test results showed that the compressive strength of the self-curing material of granite waste powder reached 35 MPa and the water absorption rate was 6.1%. Although it was slightly lower than that in Example 1, it still had good formability, stability and self-curing performance.

[0107] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. 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 method for preparing a self-curing material from granite waste powder, characterized in that, The preparation method includes the following steps A to C: In step A, the granite waste powder is placed in a photothermal coupling activation device for activation treatment to obtain activated granite waste powder; In step B, the unactivated granite waste powder and the activated granite waste powder are mixed, and an alkali activator solution is added to obtain an alkali-activated slurry. In step C, the alkali-activated slurry is sequentially molded, cured, and maintained to obtain the self-curing material of granite waste powder.

2. The preparation method according to claim 1, characterized in that, The conditions for the activation treatment are as follows: The temperature is increased from room temperature to 400-800℃ at a rate of 5-15℃ / min, and then held at 400-800℃ for 1-3 hours.

3. The preparation method according to claim 1, characterized in that, The alkaline activator solution comprises a combination of sodium silicate, sodium hydroxide and water; In the sodium silicate, the molar ratio of silicon dioxide to sodium oxide is 1.1 to 2.7; The mass ratio of sodium silicate to sodium hydroxide is (8~12):1; The mass ratio of the alkaline activator solution to the activated granite waste powder is (1~3):

1.

4. The preparation method according to claim 1, characterized in that, In step B, the mass ratio of the unactivated granite waste powder to the activated granite waste powder is 1:(1~3).

5. The preparation method according to claim 1, characterized in that, The photothermal coupling activation device includes: The tube has a first end and a second end opposite to each other along the extension direction. The first end is open and the second end is closed. A partition is provided between the first end and the second end of the tube to divide the tube into a first part with one side open and a second part with one side closed. The side of the first part away from the first end is adapted to contain the granite waste powder, and the side of the second part near the second end is adapted to contain the heat-conducting medium. An illumination unit is located adjacent to the tube body and is adapted to provide illumination to the heat-conducting medium. The heat-conducting medium receives heat from the illumination unit and transfers the heat to the granite waste powder through natural convection.

6. The preparation method according to claim 5, characterized in that, The tube body is inclined; The photothermal coupling activation device further includes: A transparent protective layer is fitted over the outside of the tube. A temperature sensor is located on the outer side of the first part of the pipe near the partition, and the position of the temperature sensor corresponds to the granite waste powder.

7. The preparation method according to claim 5, characterized in that, The illumination unit includes: Light source; and A reflective focusing cover is fitted over the light source to focus the light emitted by the light source onto the heat-conducting medium.

8. The preparation method according to any one of claims 1 to 7, characterized in that, In the alkali-activated slurry, the mass ratio between water and solids is 0.2 to 0.

3.

9. The preparation method according to any one of claims 1 to 7, characterized in that, The molding process includes: placing the alkali-activated slurry in a mold under a pressure of 30-50 MPa for molding, with a molding time of 8-12 minutes. The curing is carried out at 60~140℃ for 6~10h, and an alkali-activated gel is obtained after curing.

10. The preparation method according to claim 9, characterized in that, The curing process includes: placing the alkali-activated gel in a curing room at room temperature and relative humidity of 95% or higher for 2 to 10 days; The compressive strength of the self-curing granite waste powder material is 35~40MPa, and the water absorption rate is 4~6%.

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