A modified kaolin, its method of preparation and use in the preparation of a waste rock-based cementitious material
Modified kaolin was prepared by microwave heating and combined with high-silica waste rock to prepare waste rock-based cementitious materials. This solved the problem of high energy consumption and incompatibility in kaolin modification, achieving efficient utilization and performance improvement, and is suitable for corrosion-resistant flooring materials.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- UNIV OF SCI & TECH LIAONING
- Filing Date
- 2026-05-21
- Publication Date
- 2026-07-14
AI Technical Summary
Existing methods for modifying kaolin consume a lot of energy and cannot simultaneously improve its activity. Furthermore, the comprehensive utilization rate of high-silica waste rock is low, which limits its application in cementitious materials.
Modified kaolin was prepared by microwave heating, which broke the hydrogen bonds and silicon-oxygen bonds in the layered structure of kaolin, improving its surface energy and reactivity. It was then used as a reinforcing component in waste rock-based cementitious materials and combined with high-silica waste rock to prepare corrosion-resistant flooring materials.
It improves the comprehensive utilization rate of high-silica waste rock, enhances the mechanical properties and corrosion resistance of cementitious materials, reduces costs, and is suitable for ground materials in acid rain and industrial wastewater environments.
Smart Images
Figure FT_1 
Figure FT_2 
Figure FT_3
Abstract
Description
Technical Field
[0001] This invention belongs to the field of mineral material modification and solid waste utilization technology, specifically relating to a modified kaolin, its preparation method, and its application in the preparation of waste rock-based cementitious materials. Background Technology
[0002] Kaolin is an important layered silicate clay mineral, widely used in the ceramics, papermaking, coatings, and building materials industries due to its chemical stability, high whiteness, and abundant resources. In the construction materials field, kaolin is often used as a mineral admixture to improve the performance of concrete. However, natural kaolin typically has a high degree of crystallinity and a dense internal structure, resulting in low pozzolanic activity at room temperature, making it difficult to fully react with cement hydration products. This low activity limits the effectiveness of kaolin in cementitious materials, leading to slow later-stage strength gain in concrete and limited improvement in durability.
[0003] To date, methods for improving the activity of kaolin mainly focus on thermal activation (calcination) and mechanical activation (ultrafine grinding). While the traditional high-temperature calcination method can disrupt the ordered crystal structure of kaolin, producing metakaolin with higher volcanic ash activity, this method is energy-intensive and easily leads to mineral particle sintering, reducing specific surface area and affecting its dispersibility and reactivity in materials. Mechanical activation primarily breaks down particles through physical force, but the improvement in activity is limited.
[0004] Currently, although methods exist for modifying kaolin, they generally suffer from the problem of high energy consumption and a lack of simultaneous improvement in activity. Simple mechanical crushing is insufficient to disrupt its stable crystal structure; while traditional heat treatment, if not properly controlled at the temperature, can easily lead to overheating of the mineral, forming inert crystals. Therefore, it is necessary to develop a modified kaolin preparation method that balances low energy consumption and high activity, and its specific application in the preparation of waste rock-based cementitious materials, to achieve efficient utilization of solid waste resources. Summary of the Invention
[0005] To address the technical problems of high energy consumption and incompatibility in existing kaolin modification methods, as well as the low comprehensive utilization rate of high-silica waste rock, this invention provides a modified kaolin, its preparation method, and its application in the preparation of waste rock-based cementitious materials. This invention uses a green, efficient, and low-energy-consumption microwave heating method to prepare modified kaolin, which can improve the crystallization defects and surface activity of kaolin. Then, this modified kaolin is used as a reinforcing component in high-silica waste rock-based cementitious materials, which can further improve the mechanical properties and corrosion resistance of the cementitious materials.
[0006] In a first aspect, the present invention provides modified kaolin, wherein the modified kaolin is a modified material with a flaky microstructure obtained by microwave heating of raw kaolin ore; and the modified kaolin comprises 20% to 30% kaolin and 70% to 80% metakaolin by mass fraction.
[0007] Furthermore, the modified kaolinite has a large number of active sites and exhibits high pozzolanic activity.
[0008] In a second aspect, the present invention provides a method for preparing the above-mentioned modified kaolin, comprising the following steps: crushing and dry screening the raw kaolin ore to obtain pretreated kaolin powder; taking the pretreated kaolin powder and heating it with microwave to obtain modified kaolin.
[0009] Furthermore, in the pretreated kaolin powder, particles with a size of -0.074 mm +0.045 mm account for 95% of the total mass.
[0010] Furthermore, the particle size of -0.074 mm +0.045 mm refers to a particle size less than 0.074 mm and greater than 0.045 mm.
[0011] Furthermore, the microwave power of the microwave heating is 1.5~2.5 KW, and the time is 15~18 min.
[0012] The basic principle of this invention is to utilize the "internal heating" mechanism of microwave heating to directly act on the interior of kaolin molecules, causing the molecules to vibrate violently and generate heat. This uniform heating method can rapidly break the hydrogen bonds and silicon-oxygen bonds in the layered structure of kaolin, significantly improving the surface energy and reactivity of kaolin without causing severe particle sintering.
[0013] Thirdly, the present invention provides a waste rock-based cementitious material, wherein the raw materials of the waste rock-based cementitious material include the above-mentioned modified kaolin as a reinforcing material, as well as high silica waste rock, cementitious material and water.
[0014] Furthermore, the amount of modified kaolin added is 8% to 12% of the cementitious material.
[0015] Furthermore, the water-cement ratio of the waste rock-based cementitious material is 0.40~0.55, where the water-cement ratio is the ratio of the mass of water to the mass of the cementitious material.
[0016] Furthermore, the ratio of the high-silica waste rock to the cementing material is a conventional ratio.
[0017] Furthermore, the cementing material is cement.
[0018] Furthermore, the particle size composition of the high-silica waste rock, by mass fraction, is as follows: particles with a size of -4.75 mm + 2.80 mm account for 0.5%~2.5%, particles with a size of -2.80 mm + 1.70 mm account for 25%~30%, particles with a size of -1.70 mm + 0.27 mm account for 45%~55%, particles with a size of -0.27 mm + 0.074 mm account for 15%~25%, and particles with a size of -0.074 mm account for 1%~3%.
[0019] Fourthly, the present invention provides a method for preparing the above-mentioned waste rock-based cementitious material, comprising the following steps: taking high-silica waste rock with different particle size compositions, cementitious material and modified kaolin, mixing them, adding water and stirring evenly to obtain mortar; then pouring the mortar into a mold, vibrating it, molding and curing it to obtain the final product.
[0020] Furthermore, it is molded in a mold, cured for 24 hours, then demolded, and cured for 28 days under standard conditions.
[0021] Fifthly, this invention provides the application of the aforementioned waste rock-based cementitious material in the preparation of corrosion-resistant flooring materials.
[0022] The waste rock cementitious material described in this invention has good corrosion resistance and is suitable for the preparation of ground materials in acid rain environments or industrial wastewater environments.
[0023] The beneficial effects of this invention are:
[0024] 1. The modified kaolin of this invention, combined with high-silica waste rock, can improve the comprehensive utilization rate of high-silica waste rock and reduce the stockpiling of bulk solid waste, environmental pollution, and the occurrence of natural disasters.
[0025] 2. This invention can effectively remove impurities from minerals and improve the activity of kaolin volcanic ash by using suitable microwave conditions. It can also be used as a reinforcing material for waste rock-based cementitious materials, which can reduce costs and increase efficiency compared to metakaolin.
[0026] 3. The modified kaolin of this invention is a green and environmentally friendly material that can be widely used in catalysis, adsorption, concrete materials and other fields.
[0027] 4. After 28 days of curing, the flexural strength of the concrete reinforced with the modified kaolin of this invention is about 12±0.5 MPa and the compressive strength is about 65±0.5 MPa. Compared with the kaolin-high silica waste rock cementitious material (Comparative Example 1) and the high silica waste rock cementitious material (Comparative Example 2) prepared under the same conditions, the flexural strength of the modified kaolin-high silica waste rock cementitious material (Example 1) is increased by 17.6%±5% and 20%±5%, respectively, and the compressive strength is increased by 30%±5% and 38%±5%, respectively.
[0028] 5. Concrete reinforced with the modified kaolin of this invention exhibits good corrosion resistance after 28 days of curing. Compared to kaolin-high silica waste rock cementitious materials and high silica waste rock cementitious materials, the modified kaolin-high silica waste rock cementitious material prepared by adding modified kaolin shows a more stable mechanical property retention ability in sulfuric acid and sodium hydroxide solutions. The waste rock-based cementitious material with 10% modified kaolin content, after being soaked in sulfuric acid solution with a pH of 3 for 28 days, has a flexural strength of approximately 11.4 ± 0.5 MPa and a compressive strength of approximately 55.3 ± 0.5 MPa; after being soaked in sodium hydroxide solution with a pH of 12 for 28 days, the flexural strength is approximately 11.6 ± 0.5 MPa and the compressive strength is approximately 56.2 ± 0.5 MPa. Attached Figure Description
[0029] Figure 1 The XRD pattern (left) and SEM morphology image (right) of the modified kaolin obtained in Example 1 are shown.
[0030] Figure 2 The image shows the SEM morphology of the modified kaolin-high silica waste rock cementitious material obtained in Example 2.
[0031] Figure 3 The image shows the SEM morphology of the kaolin-high silica waste rock cementitious material obtained in Comparative Example 1.
[0032] Figure 4 The image shows the SEM morphology of the high-silica waste rock cementitious material obtained in Comparative Example 2.
[0033] Figure 5 The image shows the SEM morphology of the modified kaolin-high silica waste rock cementitious material obtained in Example 2 after immersion in an acidic solution.
[0034] Figure 6 The image shows the SEM morphology of the modified kaolin-high silica waste rock cementitious material obtained in Example 2 after immersion in an alkaline solution. Detailed Implementation
[0035] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the invention, but do not limit the invention in any way.
[0036] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials described are commercially available unless otherwise specified.
[0037] Example 1 A method for preparing modified kaolin includes the following steps: (1) Take the raw kaolin ore, crush it, dry screen it, and obtain a sample with a particle size of 0.045~0.074 mm and a particle mass ratio of more than 95%, which is pretreated kaolin powder.
[0038] (2) Take 50 g of pretreated kaolin powder and spread it evenly in a ceramic crucible. Place it in a microwave heating device, adjust the microwave power to 2 KW, heat for 15 min, and take it out after natural cooling to obtain modified kaolin.
[0039] The modified kaolin obtained in this embodiment was analyzed by XRD and SEM. The obtained XRD patterns and SEM morphology are shown in the figure. Figure 1 XRD analysis revealed a decrease in the intensity of characteristic peaks in kaolinite, indicating significant disorder in its crystal structure; the mass ratio of kaolinite to metakaolinite was approximately 1:4. SEM analysis showed that the kaolinite exhibited increasingly pronounced lamellae.
[0040] Example 2 A method for preparing waste rock-based cementitious materials based on the modified kaolin obtained in Example 1 includes the following steps: (1) Take 450 g of cement (cementing material), 45 g of modified kaolin (accounting for 10% of the total cementing material), 225 mL of water (water-cement ratio of about 0.5), and 1350 g of high-silica waste rock; wherein, the particle size range and mass percentage of the high-silica waste rock are as follows: -4.75 mm +2.80 mm accounts for 1.8%, -2.80 mm +1.70 mm accounts for 28.2%, -1.70 mm +0.27 mm accounts for 49.0%, -0.27 mm +0.074 mm accounts for 19.0% and -0.074 mm accounts for 2.0%; (2) The above materials are first placed in a cement mortar mixer and mixed evenly to obtain cementitious mortar. The mixed mortar is then poured into a mold and shaped. It is then placed in a cement mortar vibrating table for compaction. After curing for 24 hours, it is demolded and cured for 28 days to obtain modified kaolin-high silica waste stone cementitious material.
[0041] Comparative Example 1 The difference between this comparative example and Example 2 is that the modified kaolin is replaced with kaolin, while the other operation steps are the same as in Example 2, and the kaolin-high silica waste rock cementitious material under the same conditions is obtained.
[0042] Comparative Example 2 The difference between this comparative example and Example 2 is that no reinforcing material was added to modify the kaolin, while the remaining operation steps were the same as in Example 2, and high silica waste rock cementitious material was obtained under the same conditions.
[0043] 1. The flexural strength and compressive strength of the modified kaolin-high silica waste rock cementitious material obtained in Example 2, the kaolin-high silica waste rock cementitious material obtained in Comparative Example 1, and the high silica waste rock cementitious material obtained in Comparative Example 2 were tested respectively. The results showed that the flexural strength of the modified kaolin-high silica waste rock cementitious material obtained in Example 2 was about 12±0.5 MPa and the compressive strength was about 65±0.5 MPa; the flexural strength of the kaolin-high silica waste rock cementitious material obtained in Comparative Example 1 was about 10.2±0.5 MPa and the compressive strength was about 50±0.5 MPa. Compared with Comparative Example 1, the flexural strength of Example 2 increased by 17.6%±5% and the compressive strength increased by 30%±5%; the flexural strength of the high silica waste rock cementitious material obtained in Comparative Example 2 was about 10±0.5 MPa and the compressive strength was about 47±0.5 MPa. Compared with Comparative Example 2, the flexural strength of Example 2 increased by 20%±5% and the compressive strength increased by 38%±5%.
[0044] 2. The modified kaolin-high silica waste rock cementitious material obtained in Example 2, the kaolin-high silica waste rock cementitious material obtained in Comparative Example 1, and the high silica waste rock cementitious material obtained in Comparative Example 2 were examined by scanning electron microscopy. The results are as follows: Figure 2 , Figure 3 , Figure 4 As shown in the figure. The results indicate that the pozzolanic activity of modified kaolin is enhanced due to the hydration reaction between cement and water, which produces products such as calcium hydroxide. The reaction with calcium hydroxide and other substances is more vigorous, resulting in the production of more substances similar to CSH gel and ettringite (AFt). The addition of modified kaolin can enhance the mutual bonding force between different particle sizes of waste rock, thereby improving the mechanical properties of the cementitious material.
[0045] 3. The modified kaolin-high silica waste rock cementitious material obtained after 28 days of curing in Example 2, the kaolin-high silica waste rock cementitious material obtained in Comparative Example 1, and the high silica waste rock cementitious material obtained in Comparative Example 2 were respectively immersed in a sulfuric acid solution with a pH of 3 for 28 days. After acid immersion, their mass loss rate, flexural strength, and compressive strength were tested. The test results showed that after 28 days of acid immersion, the mass loss rate of the material obtained in Example 2 was approximately 1.2% ± 0.5%, the flexural strength was approximately 11.4 ± 0.5 MPa, and the compressive strength was approximately 55.3 ± 0.5 MPa. The material obtained in Comparative Example 1 had a mass loss rate of approximately 1.8% ± 0.5%, a flexural strength of approximately 10.2 ± 0.5 MPa, and a compressive strength of approximately 43.8 ± 0.5 MPa. After 28 days of acid immersion, Example 2, compared to Comparative Example 1, showed a lower mass loss rate of 0.6 ± 0.5%, an increased flexural strength of 11.8% ± 0.5%, and an increased compressive strength of 26.3% ± 0.5%. The material obtained in Comparative Example 2 had a mass loss rate of approximately 2.1% ± 0.5%, a flexural strength of approximately 9.3 ± 0.5 MPa, and a compressive strength of approximately 39.3 ± 0.5 MPa. After 28 days of acid immersion, Example 2, compared to Comparative Example 2, showed a lower mass loss rate of 0.9 ± 0.5%, an increased flexural strength of 22.6% ± 0.5%, and an increased compressive strength of 40.7% ± 0.5%. Subsequently, the acid-immersed samples (Example 2) were examined using a scanning electron microscope, and the results are as follows: Figure 5 As shown in the figure. The results indicate that sulfuric acid etching preferentially reacts with the CSH gel on its surface, but because the solution remains acidic, aluminum mainly reacts as Al. 3+ It exists in the form of sulfuric acid, which then forms gypsum. Gypsum has a small expansion force and forms a relatively dense surface structure; however, due to the high concentration of sulfuric acid, it can cause some erosion on the surface of cementitious materials.
[0046] 4. The modified kaolin-high silica waste rock cementitious material obtained after 28 days of curing in Example 2, the kaolin-high silica waste rock cementitious material obtained in Comparative Example 1, and the high silica waste rock cementitious material obtained in Comparative Example 2 were respectively immersed in a sodium hydroxide solution with a pH of 12 for 28 days. After the alkali immersion was completed, their mass loss rate, flexural strength, and compressive strength were tested. The test results showed that after 28 days of alkali immersion, the mass loss rate of the material obtained in Example 2 was approximately 0.9±0.5%, the flexural strength was approximately 11.6±0.5 MPa, and the compressive strength was approximately 56.2±0.5 MPa. The material obtained in Comparative Example 1 had a mass loss rate of approximately 1.2% ± 0.5%, a flexural strength of approximately 10.3 ± 0.5 MPa, and a compressive strength of approximately 45.8 ± 0.5 MPa. After alkali immersion for 28 days, Example 2, compared to Comparative Example 1, had a lower mass loss rate of 0.3 ± 0.5%, a higher flexural strength of 12.6% ± 0.5%, and a higher compressive strength of 22.7% ± 0.5%. The material obtained in Comparative Example 2 had a mass loss rate of approximately 1.4 ± 0.5%, a flexural strength of approximately 9.6 ± 0.5 MPa, and a compressive strength of approximately 40.3 ± 0.5 MPa. After alkali immersion for 28 days, Example 2, compared to Comparative Example 2, had a lower mass loss rate of 0.5 ± 0.5%, a higher flexural strength of 20.8% ± 0.5%, and a higher compressive strength of 39.5% ± 0.5%. Subsequently, the alkali-immersed sample (Example 2) was examined using a scanning electron microscope, and the results are as follows. Figure 6 As shown. The results indicate that, due to the initial stage of erosion, Na... + With Ca 2+ NASH gel is generated through displacement; at the same time, due to the high concentration of the eroding solution and the external pressure, the surface of the gel material shows signs of erosion and becomes porous.
[0047] In summary, the modified kaolin-high silica waste rock cementitious material provided by this invention has good corrosion resistance and is suitable for the preparation of ground materials in acid rain environments or industrial wastewater environments.
Claims
1. A modified kaolin, characterized in that: The modified kaolin is a modified material with a flaky microstructure obtained by microwave heating of raw kaolin ore; by mass fraction, the modified kaolin includes 20%~30% kaolin and 70%~80% metakaolin.
2. The method for preparing modified kaolin according to claim 1, characterized in that: The raw kaolin ore is crushed and dry-screened to obtain pretreated kaolin powder; the pretreated kaolin powder is then heated by microwave to obtain modified kaolin.
3. The method for preparing modified kaolin according to claim 2, characterized in that: In the pretreated kaolin powder, particles with a size of -0.074 mm to +0.045 mm account for more than 95% of the total mass.
4. The method for preparing modified kaolin according to claim 2, characterized in that: The microwave heating process uses a microwave power of 1.5~2.5 KW and a duration of 15~18 min.
5. A waste rock-based cementitious material, characterized in that: The raw materials for the waste rock-based cementitious material include the modified kaolin as described in claim 1 as a reinforcing material, as well as high-silica waste rock, cementitious material, and water.
6. The waste rock-based cementitious material according to claim 5, characterized in that: The amount of modified kaolin added is 8% to 12% of the cementitious material.
7. The waste rock-based cementitious material according to claim 5, characterized in that: The water-cement ratio of the waste rock-based cementitious material is 0.40~0.55, where the water-cement ratio is the ratio of the mass of water to the mass of the cementitious material.
8. The waste rock-based cementitious material according to claim 5, characterized in that: The cementing material is cement.
9. The waste rock-based cementitious material according to claim 5, characterized in that: The particle size composition of the high-silica waste rock, by mass fraction, is as follows: particles with a size of -4.75 mm +2.80 mm account for 0.5%~2.5%, particles with a size of -2.80 mm +1.70 mm account for 25%~30%, particles with a size of -1.70 mm +0.27 mm account for 45%~55%, particles with a size of -0.27 mm +0.074 mm account for 15%~25%, and particles with a size of -0.074 mm account for 1%~3%.
10. The method for preparing the waste rock-based cementitious material according to claim 5, characterized in that: Take high-silica waste rock with different particle sizes, cementing materials and modified kaolin, mix them, add water and stir evenly to obtain mortar; then pour the mortar into a mold, vibrate it, and cure it to obtain the final product.