Mixed calcium-increasing hot-activated loess, preparation method and application, modified loess cement-based cementitious material and application, modified loess cement-based cementitious hydration material and application

Abstract

This invention provides a mixed calcium-enriched thermally activated loess and its preparation method and application, modified loess cement-based cementitious materials and their application, and modified loess cement-based cementitious hydration materials and their application, relating to the field of coal mine grouting and water-retaining mining technology. This invention mixes loess with a calcium-enriching agent and calcines it to obtain mixed calcium-enriched thermally activated loess; the calcium-enriching agent includes dolomite and soda ash; the mass ratio of loess to calcium-enriching agent is 1.5–2.5:1; the calcination temperature is 1000–1100℃. This invention utilizes dolomite and soda ash to calcium-enrich and modify loess, and controls the calcination temperature and the amount of calcium-enriching agent, greatly improving the pozzolanic activity of loess, thereby enhancing the hydration reaction activity of modified loess in the preparation of cement-based grouting materials. The mixed calcium-enriched thermally activated loess provided by this invention has excellent application prospects in mine water-retaining grouting.

Description

Technical Field

[0001] This invention relates to the field of coal mine grouting and water-retaining mining technology, specifically to mixed calcium-enriched thermally activated loess and its preparation method and application, modified loess cement-based cementitious materials and their application, and modified loess cement-based cementitious hydration materials and their application. Background Technology

[0002] In regions rich in coal reserves, groundwater resources often coexist with coal resources, posing significant challenges to both coal mining and groundwater protection. While mining coal, it's crucial to prevent water intrusion and subsequent mine flooding accidents, and also to protect groundwater resources as much as possible. This has led to the development of grouting mining technology. Large-scale grouting mining consumes a large amount of cement and other binding materials, significantly increasing mining costs and placing a considerable economic burden on mining companies.

[0003] The oxides in loess are mainly composed of SiO2, CaO, and Al2O3, making it a potential auxiliary cementing material for grouting. However, the low hydration reactivity of the raw loess means that loess alone cannot meet the engineering requirements for the setting performance of grouting materials. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a mixed calcium-enriched thermally activated loess and its preparation method and application, modified loess cement-based cementitious materials and their application, and modified loess cement-based cementitious hydration materials and their application. The mixed calcium-enriched thermally activated loess provided by this invention has high hydration reactivity. When used as an auxiliary cementitious material in the preparation of cement-based grouting materials, it exhibits good performance in terms of setting and cementitious properties, and the mix proportions can be adjusted to meet the needs of different grouting areas.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing mixed calcium-enriched thermally activated loess, comprising the following steps:

[0007] Loess was mixed with a calcium-enhancing agent and then calcined to obtain mixed calcium-enhanced thermally activated loess.

[0008] The calcium-enhancing agent includes dolomite and soda ash;

[0009] The mass ratio of loess to calcium-increasing agent is 1.5–2.5:1;

[0010] The calcination temperature is 1000–1100℃.

[0011] Preferably, the mass ratio of dolomite to soda ash is 1:0.8 to 1.2.

[0012] Preferably, the calcination holding time is 0.8 to 1.2 hours.

[0013] The present invention also provides a mixed calcium-enriched thermally activated loess prepared by the preparation method described in the above technical solution.

[0014] This invention also provides the application of the mixed calcium-enriched thermally activated loess described in the above technical solution as a gel material.

[0015] The present invention also provides a modified loess cement-based cementitious material, comprising a composite gel material and water; the composite gel material comprises cement and the mixed calcium-enriched thermally activated loess described in the above technical solution.

[0016] Preferably, the mass fraction of the calcium-enriched thermally activated loess mixed in the composite gel material is 20-50%.

[0017] The present invention also provides a modified loess cement-based hydration material, which is obtained by curing the modified loess cement-based hydration material described in the above technical solution.

[0018] Preferably, the curing temperature is 18–22°C, the humidity is 90–100%, and the time is 3–28 days; the curing is carried out in a sealed environment.

[0019] The present invention also provides the application of the modified loess cement-based cementitious material or the modified loess cement-based cementitious hydration material described in the above technical solution in grouting and water-retaining mining.

[0020] This invention provides a method for preparing mixed calcium-enriched thermally activated loess, comprising the following steps: mixing loess with a calcium-enriching agent and calcining to obtain mixed calcium-enriched thermally activated loess; the calcium-enriching agent includes dolomite and soda ash; the mass ratio of loess to calcium-enriching agent is 1.5–2.5:1; the calcination temperature is 1000–1100℃. This invention utilizes dolomite and soda ash to calcium-enrich and modify loess, and controls the calcination temperature and the amount of calcium-enriching agent. During high-temperature calcination, the calcium-enriching agent promotes more aluminum to participate in the solid-phase reaction and exists in the calcination product in the form of aluminates and / or metaaluminates. For example, Na captures Al to form NaAlO2, while Ca captures Al to form Ca7AlO12(OH). 4·The addition of 4H₂O increases the concentration of Al ions dissolved in the mixed calcium-enriched thermally activated loess under alkaline conditions. Furthermore, under high-temperature conditions, f-CaO combines with Si in the loess to form hydraulically active calcium silicate products, further increasing Si dissolution in the mixed calcium-enriched thermally activated loess under alkaline conditions. Therefore, the increased active components in the calcined products significantly enhance the hydration reactivity of the modified loess, thereby improving its hydration reactivity in the preparation of cement-based grouting materials and enhancing its cementitious properties. Moreover, this invention utilizes dolomite and soda ash to calcium-enrich the loess, increasing the early hydration rate of the modified loess in the preparation of grouting filling materials, further improving its early cementitious properties. The mixed calcium-enriched thermally activated loess provided by this invention has excellent application prospects in water-retaining grouting mining.

[0021] As shown in the test results of the examples, compared with the single calcium-enriched modified loess obtained by modifying dolomite, the mixed calcium-enriched thermally activated loess modified by dolomite and soda ash of the present invention exhibits a significant increase in the dissolution concentrations of active Si and Al in an alkaline environment. The Si ion dissolution concentration increases by approximately 93.54%, and the Al ion dissolution concentration increases by approximately 33.42%. This indicates that the mixed calcium-enriched thermally activated loess prepared by the present invention has high hydration activity.

[0022] Moreover, the preparation method provided by this invention is simple in process and operation. It uses loess, dolomite and soda ash as raw materials for mixed calcium-enriched thermally activated loess. The raw materials are widely available and easy to obtain. The production cost of mixed calcium-enriched thermally activated loess is low, which has high economic benefits and is suitable for industrial production.

[0023] This invention also provides a modified loess cement-based cementitious material, comprising a composite gel material and water; the composite gel material includes cement and the mixed calcium-enriched thermally activated loess described in the above-mentioned technical solution. This invention uses cement and mixed calcium-enriched thermally activated loess as the composite gel material. In the early stages of hydration, the presence of aluminates and flake aluminates in the mixed calcium-enriched thermally activated loess helps the cementitious system produce more ettringite, shortening the gelation time of the modified loess cement-based cementitious material. It exhibits high gelation performance and has a good effect on sealing fractured rock masses, showing promising application prospects in water-retaining grouting mining, thus achieving the goal of loess resource utilization. As shown in the test results of the examples, compared with single calcium-enriched modified loess obtained by adding dolomite, the final setting time of the modified loess cement-based cementitious material of this invention with added mixed calcium-enriched thermally activated loess is shortened by more than 11.1%. This indicates that the gelation time of the modified loess cement-based cementitious material provided by this invention is [not specified in the original text].

[0024] Moreover, this invention uses mixed calcium-enriched thermally activated loess to replace part of the cement as a gelling material, which can reduce the amount of cement used. At the same time, the calcination temperature for preparing the mixed calcium-enriched thermally activated loess is lower than the calcination temperature in the cement production process, which reduces CO2 emissions and achieves energy conservation and emission reduction.

[0025] This invention also provides a modified loess cement-based hydration material, obtained by curing the modified loess cement-based hydration material described in the above technical solution. The modified loess cement-based hydration material provided by this invention undergoes hydration during curing, producing more ettringite and gel, resulting in a denser micropore structure and a strengthened solid particle skeleton structure. It exhibits high compressive strength and good mechanical properties, and its compressive strength steadily increases with prolonged curing time, meeting the requirements of on-site grouting and showing excellent application prospects in water-retaining grouting mining. As shown in the test results of the examples, compared with the single calcium-enriched modified loess obtained by adding dolomite, the 3-day compressive strength of the modified loess cement-based cementitious hydration material of the present invention with the addition of mixed calcium-enriched thermally activated loess is increased by more than 34.1%, and the 3-day compressive strength can reach 16.24 MPa; the 28-day compressive strength is increased by more than 22.3%, and the 28-day compressive strength can reach 33.98 MPa. This indicates that the modified loess cement-based cementitious hydration material provided by the present invention has high compressive strength. Attached Figure Description

[0026] Figure 1 The graph shows a comparison of the leaching concentrations of active Si and Al between the mixed calcium-enriched thermally activated loess (mixed calcium enrichment) prepared in Example 1 and the dolomite-modified loess (single calcium enrichment) prepared in Comparative Example 1.

[0027] Figure 2 The graph shows the comparison of the final setting time of the gel materials prepared in Examples 2-4 (mixed calcium enrichment) and Comparative Examples 2-4 (single calcium enrichment);

[0028] Figure 3 The figure shows the uniaxial compressive strength test results of the modified loess cement-based grouting cementitious hydration materials prepared in Examples 2-4 (mixed calcium enrichment) and Comparative Examples 2-4 (single calcium enrichment) after 3 days.

[0029] Figure 4 The graph shows the 28-day uniaxial compressive strength test results of the modified loess cement-based grouting hydration materials prepared in Examples 2-4 (mixed calcium enrichment) and Comparative Examples 2-4 (single calcium enrichment). Detailed Implementation

[0030] This invention provides a method for preparing mixed calcium-enriched thermally activated loess, comprising the following steps: mixing loess with the calcium-enriching agent described in the above technical solution, and calcining to obtain mixed calcium-enriched thermally activated loess; the calcium-enriching agent includes dolomite and soda ash.

[0031] Unless otherwise specified, the materials and equipment used in this invention are all commercially available products in the field.

[0032] In this invention, the preferred mass ratio of dolomite to soda ash is 1:0.8 to 1.2, and in specific embodiments it can be 1:0.8, 1:0.85, 1:0.9, 1:0.95, 1:1, 1:1.05, 1:1.1, 1:1.15 or 1:1.2.

[0033] In this invention, the loess is preferably sieved before use, and the particle size of the sieved loess is preferably 0.4–141 μm; the specific surface area of ​​the loess is preferably 368–406 m². 2 / kg.

[0034] In this invention, the mass ratio of loess to calcium-enhancing agent is preferably 1.5 to 2.5:1, and in specific embodiments it can be 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1 or 2.5:1.

[0035] In this invention, the mixing preferably includes sequential stirring and ball milling. In this invention, the stirring speed is preferably 70-90 r / min, more preferably 75-85 r / min, and even more preferably 80 r / min; the stirring time is preferably 5-10 min, more preferably 5-8 min, and even more preferably 5-6 min. In this invention, the ball milling speed is preferably 250-350 r / min, more preferably 280-320 r / min, and even more preferably 300 r / min; the ball-to-material ratio is preferably 0.8-1.2:1, more preferably 0.9-1.1:1, and even more preferably 1:1; the ball milling time is preferably 20-40 min, more preferably 25-35 min, and even more preferably 30 min.

[0036] In this invention, the calcination temperature is preferably 1000-1100℃, more preferably 1050-1100℃, and even more preferably 1080-1100℃; the heating rate from room temperature to the calcination temperature is preferably 10-20℃ / min, more preferably 12-18℃ / min, and even more preferably 15℃ / min; the calcination holding time is preferably 0.8-1.2h, more preferably 0.9-1.1h, and even more preferably 1h.

[0037] The present invention also provides a mixed calcium-enriched thermally activated loess prepared by the preparation method described in the above technical solution.

[0038] This invention also provides the application of the mixed calcium-enriched thermally activated loess described in the above technical solution as a gel material.

[0039] The present invention also provides a modified loess cement-based cementitious material, comprising a composite gel material and water; the gel material comprises cement and the mixed calcium-enriched thermally activated loess described in the above technical solution.

[0040] In this invention, the mass fraction of the mixed calcium-enriched thermally activated loess in the composite gel material is preferably 20-50%, more preferably 20-40%, and even more preferably 20-35%.

[0041] In this invention, the cement preferably comprises silicate cement.

[0042] In this invention, the mass ratio of the composite gel material to water is preferably 1:0.8 to 1.2, and in specific embodiments it can be 1:0.8, 1:0.85, 1:0.9, 1:0.95, 1:1, 1:1.05, 1:1.1, 1:1.15 or 1:1.2.

[0043] In this invention, the preferred method for preparing the modified loess cement-based cementitious material includes the following steps: dry mixing cement and mixed calcium-enriched thermally activated loess, then adding water and mixing again to obtain the modified loess cement-based cementitious material.

[0044] In this invention, the dry mixing preferably includes stirring and mixing, the stirring speed is preferably 70-90 r / min, more preferably 75-85 r / min, and even more preferably 80±2 r / min; the stirring and mixing time is preferably 5-10 min, more preferably 5-8 min, and even more preferably 5-6 min.

[0045] In this invention, the remixing preferably includes stirring, and the stirring speed is preferably 95-105 r / min, more preferably 98-102 r / min, and even more preferably 100 r / min; the stirring time is preferably 4-5 min, more preferably 4.5 min.

[0046] The present invention also provides a modified loess cement-based hydration material, which is obtained by curing the modified loess cement-based hydration material described in the above technical solution.

[0047] In this invention, the modified loess cementitious material is preferably placed in a mold, sealed, and vibrated to compact before curing. In this invention, the compaction time is preferably 1-2 minutes, more preferably 1-1.5 minutes; the compaction is preferably performed on a vibrating table.

[0048] In this invention, the curing process preferably involves placing the modified loess cementitious material in a mold, sealing it, and then curing it. The curing temperature is preferably 18–22°C, more preferably 19–21°C, and even more preferably 20°C; the curing humidity is preferably 90–100%, more preferably 92–98%, and even more preferably 95%; the curing time is preferably 3–28 days; and the curing is preferably carried out in a curing chamber. This invention uses closed conditions for curing, which prevents moisture evaporation during the curing process.

[0049] After completing the curing process, the present invention preferably further includes demolding to obtain the modified loess cement-based gelling hydration material. In the present invention, the demolding preferably includes demolding with a pneumatic gun, which ensures the integrity of the sample.

[0050] In this invention, the 3-day uniaxial compressive strength of the modified loess cement-based cementitious hydration material is preferably >7 MPa, more preferably 7.06-16.3 MPa, and in specific embodiments it can be 7.06 MPa, 11.57 MPa or 16.24 MPa; the 28-day uniaxial compressive strength of the modified loess cement-based cementitious hydration material is preferably >12 MPa, more preferably 12.17-34 MPa, and in specific embodiments it can be 12.17 MPa, 25.01 MPa or 33.98 MPa.

[0051] This invention also provides the application of the modified loess cement-based cementitious material or the modified loess cement-based cementitious hydration material described in the above-mentioned technical solutions in grouting mining. In this invention, the grouting mining preferably includes water-retaining grouting mining in mines, and more preferably includes water-retaining grouting mining in coal mines.

[0052] To further illustrate the present invention, the following detailed descriptions, in conjunction with embodiments, describe the calcium-enhancing agent and its application, the mixed calcium-enhancing thermally activated loess and its preparation method and application, the modified loess cement-based cementitious material and its application, and the modified loess cement-based cementitious hydration material and its application. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0053] In the following examples, the main chemical components of the loess used, by mass percentage, are as follows: CaO 11.663%, SiO2 58.335%, Al2O3 15.555%, MgO 2.454%, Fe2O3 6.047%, Na2O 1.211%, K2O 2.887%, SO3 0.178%, and other substances 1.67%. The loess was sieved before use; the particle size of the sieved loess was 0.4–141 μm, and the specific surface area was 368–406 m². 2 / kg.

[0054] The main chemical components of the dolomite used, by mass percentage, are as follows: CaO 68.132%, SiO2 10.904%, Al2O3 2.022%, MgO 16.818%, Fe2O3 1.369%, Na2O 0.171%, K2O 0.175%, SO3 0.069%, and other substances 0.34%.

[0055] The main chemical components of the silicate cement used, by mass percentage, are as follows: CaO 64.544%, SiO2 17.691%, Al2O3 7.399%, MgO 3.037%, Fe2O3 2.597%, Na2O 0.296%, K2O 0.576%, SO3 3.743%, and other substances 0.117%.

[0056] Example 1

[0057] Dolomite and soda ash were mixed at a mass ratio of 1:1 to obtain a mixed calcium-enhancing agent. The mixed calcium-enhancing agent and loess were then added to a mixer at a mass ratio of 1:2 and stirred at 80 rpm for 5 minutes. The resulting composite powder was then placed in a grinder and ground at 300 rpm for 30 minutes. The ground composite powder was then placed in a muffle furnace and heated from room temperature to 1100℃ at a rate of 15℃ / min, and calcined for 1 hour to obtain mixed calcium-enhanced thermally activated loess. Its mineral composition mainly consists of tricalcium silicate (C3S), dicalcium silicate (C2S), and dodecacalcium heptaaluminate (C6S). 12 A7), calcium aluminate (CA), quartz (SiO2), mullite (AS), lime (CaO), etc. The grinding ball-to-material ratio is 1:1.

[0058] Example 2

[0059] The mixed calcium-enriched thermally activated loess prepared in Example 1 was mixed with silicate cement at a mass ratio of 2:8 and placed in a mixer. The mixture was stirred at a speed of 80±2 r / min for 5 min to obtain grouting cementitious material powder. Water was added and the mixture was stirred at a speed of 100 r / min for 4.5 min. The mixture was then poured into a cylindrical mold with a closed bottom, the top was sealed, and the mixture was compacted on a vibrating table for 1 min to obtain modified loess cement-based grouting cementitious material.

[0060] The modified loess cement-based grouting cementitious material was placed in a curing chamber and cured in a sealed environment at 20°C and 95% humidity for 3–28 days. It was then demolded using a pneumatic gun to obtain the modified loess cement-based grouting cementitious hydration material. The mass ratio of the grouting cementitious material powder to water was 1:1.

[0061] Example 3

[0062] Modified loess cement-based grouting cementitious material and modified loess cement-based grouting cementitious hydration material were prepared according to the method of Example 2. The only difference from Example 2 is that the mass ratio of mixed calcium-enriched thermally activated loess to silicate cement is 3.5:6.5.

[0063] Example 4

[0064] Modified loess cement-based grouting cementitious material and modified loess cement-based grouting cementitious hydration material were prepared according to the method of Example 2. The only difference from Example 2 is that the mass ratio of mixed calcium-enriched thermally activated loess to silicate cement is 5:5.

[0065] Comparative Example 1

[0066] Dolomite and loess were mixed in a mixer at a mass ratio of 1:2 and stirred at 80 rpm for 3 minutes. The resulting composite powder was then ground in a grinder at 300 rpm for 30 minutes. The ground composite powder was then placed in a muffle furnace and heated from room temperature to 825°C at a rate of 15°C / min, and then calcined for 1 hour to obtain dolomite-modified loess. The ball-to-material ratio during grinding was 1:1.

[0067] Comparative Example 2

[0068] The only difference from Example 2 is that the mixed calcium-enriched thermally activated loess is replaced with the dolomite-modified loess prepared in Comparative Example 1.

[0069] Comparative Example 3

[0070] The only difference from Example 3 is that the mixed calcium-enriched thermally activated loess is replaced with the dolomite-modified loess prepared in Comparative Example 1.

[0071] Comparative Example 4

[0072] The only difference from Example 4 is that the mixed calcium-enriched thermally activated loess is replaced with the dolomite-modified loess prepared in Comparative Example 1.

[0073] Test Example 1

[0074] 1. Volcanic ash activity test

[0075] Test method: Take 1g of calcined sample and 100ml of NaOH solution (1mol / L) and put them into a 200ml plastic test tube. Keep the test tube in a constant temperature (20℃) water bath shaker for 7 days. Filter the mixed solution with 0.45μm filter paper to obtain the supernatant. Use inductively coupled plasma optical emission spectrometry (ICP-OES) to test the concentration of Si and Al ions dissolved in the filtrate to evaluate the pozzolanic activity of the material.

[0076] Figure 1This is a comparison chart of the leaching concentrations of active Si and Al in the mixed calcium-enriched thermally activated loess (mixed calcium enrichment) prepared in Example 1 and the dolomite-modified loess (single calcium enrichment) prepared in Comparative Example 1. It can be seen that, compared to the dolomite-modified loess prepared in Comparative Example 1, the leaching concentrations of active Si and Al in the alkaline environment of the mixed calcium-enriched thermally activated loess prepared in this invention are significantly increased. The ion leaching concentration of Si increases by approximately 93.54%, which is due to the combination of f-CaO with more active Si at high temperatures to form calcium silicate products with hydraulic properties; the ion leaching concentration of Al increases by approximately 33.42%, mainly due to Na capturing more Al to form NaAlO2.

[0077] 2. Condensation time test

[0078] Test method: The setting time of the grout is tested using a Vicat apparatus. A ring-shaped attachment is installed on the final setting needle. After the grout has initially set, the mold containing the grout is immediately rotated 180° by translation, with the larger diameter end facing upwards and the smaller end downwards, and placed on the base plate. Then, it is placed in a humidity chamber for further curing. During temporary final setting, measurements are taken every 15 minutes. When the needle penetrates 0.5 mm into the specimen, i.e., when the ring-shaped attachment no longer leaves a mark on the specimen, the cement has reached its final setting state. Upon reaching the final setting state, the measurement should be repeated immediately. When the two results are identical, the grout has reached its final setting state.

[0079] Figure 2 The graph shows a comparison of the final setting times of the gel materials prepared in Examples 2-4 (mixed calcium enrichment) and Comparative Examples 2-4 (single calcium enrichment). It can be seen that, compared with the modified loess cement-based grouting gel materials prepared in Comparative Examples 2-4, the final setting times of the modified loess cement-based gel hydration materials prepared in this invention are shortened by 11.1%, 19.4%, and 31.0%, respectively. The significant reduction in final setting time is mainly due to the fact that during the calcination of the mixed calcium enrichment, more active aluminum participates in the solid-phase reaction, existing in the calcination products in the form of aluminates and metaaluminates. In the initial stage of hydration with cement, this helps the gel system produce more ettringite, thereby shortening the gelation time.

[0080] 3. Uniaxial compressive strength test at 3d and 28d

[0081] Test Method: Cured specimens that had reached the pre-curing time (3 days and 28 days) underwent uniaxial compressive strength testing. A Humboldt HM-5030 uniaxial compression tester (USA) with a maximum loading capacity of 50 kN was used. According to ASTM C39 / C39M-18 standards, the loading rate was 1 mm / min, using a displacement loading method. Before testing, both ends of the specimens were kept as flat as possible, and petroleum jelly was applied to reduce the influence of end friction. At least three specimens were tested, and the average value was taken as the final compressive strength value.

[0082] Figure 3 The graph shows the 3-day uniaxial compressive strength test results of the modified loess cement-based grouting cementitious hydration materials (50mm × 100mm in size) prepared in Examples 2-4 (mixed calcium enrichment) and Comparative Examples 2-4 (single calcium enrichment). Figure 4 The figures show the 28-day uniaxial compressive strength test results of the modified loess cement-based grouting gel hydration materials (50mm × 100mm in size) prepared in Examples 2-4 (mixed calcium enrichment) and Comparative Examples 2-4 (single calcium enrichment). It can be seen that compared with the materials prepared in Comparative Examples 2-4, the 3-day compressive strength of the modified loess cement-based grouting gel hydration materials prepared in this invention increased by 34.1%, 40.2%, and 36.8%, respectively, and the 28-day compressive strength increased by 22.3%, 24.4%, and 24.1%, respectively. The uniaxial compressive strength values ​​at both 3-day and 28-day showed a certain degree of increase. This is mainly because the gel system of the materials prepared in this invention produces more ettringite and gel during hydration, resulting in a denser microporous structure and a strengthened solid particle skeleton structure, thus increasing mechanical properties.

[0083] In summary, the mixed calcium-enriched thermally activated loess prepared by this invention has better hydration activity, and the modified loess cement-based grouting cementitious material prepared with cement and water has a short setting time, which is conducive to rapid construction. It also has high cementitious performance and has a good effect on sealing fractured rock masses. Moreover, the modified loess cement-based grouting cementitious hydration material prepared by this invention has high strength.

[0084] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing mixed calcium-enriched thermally activated loess, comprising the following steps: Loess was mixed with a calcium-enhancing agent and then calcined to obtain mixed calcium-enhanced thermally activated loess. The calcium-enhancing agent includes dolomite and soda ash; The mass ratio of loess to calcium-increasing agent is 1.5–2.5:1; The calcination temperature is 1000–1100℃.

2. The preparation method according to claim 1, characterized in that, The mass ratio of dolomite to soda ash is 1:0.8 to 1.

2.

3. The preparation method according to claim 1 or 2, characterized in that, The calcination holding time is 0.8 to 1.2 hours.

4. The mixed calcium-enriched thermally activated loess prepared by the preparation method according to any one of claims 1 to 3.

5. The application of the mixed calcium-enriched thermally activated loess as described in claim 4 as a gel material.

6. A modified loess cement-based cementitious material, comprising a composite gel material and water; said composite gel material comprising cement and the mixed calcium-enriched thermally activated loess as described in claim 4.

7. The modified loess cementitious material according to claim 6, characterized in that, The mass fraction of the mixed calcium-enriched thermally activated loess in the composite gel material is 20-50%.

8. A modified loess cement-based hydration material, obtained by curing the modified loess cement-based hydration material as described in claim 6 or 7.

9. The modified loess cement-based hydration material according to claim 8, characterized in that, The curing temperature is 18–22℃, the humidity is 90–100%, and the time is 3–28 days; the curing is carried out in a sealed environment.

10. The application of the modified loess cement-based cementitious material according to any one of claims 6 to 7 or the modified loess cement-based cementitious hydration material according to any one of claims 8 to 9 in grouting mining.

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