Collapsible loess solidification material and preparation method thereof

Abstract

The technical field of soil stabilization specifically relates to a collapsible loess solidification material and its preparation method. Its raw materials are loess, light-burned magnesium oxide, magnesium sulfate heptahydrate, water, and coal gangue. The preparation method involves preparing a mixed solution A (comprising magnesium sulfate heptahydrate and water) and a dry mixture B (comprising light-burned magnesium oxide, coal gangue, and loess), mixing and stirring them uniformly. The material is then formed, demolded, and cured. This method utilizes waste resources, is energy-efficient and environmentally friendly, has a simple production process, and is low-cost. The resulting solidified loess exhibits a 28-day compressive strength of 6.5 to 9.5 MPa.

Description

Technical Field

[0001] The present invention relates to the technical field of soil stabilization, and in particular to a collapsible loess solidification material and a preparation method thereof. Background Art

[0002] The collapsible characteristics of collapsible loess foundations can cause varying degrees of harm to structures, causing them to sink, crack, tilt, and even seriously affect their safety and use. Therefore, when constructing structures such as bridges and culverts in loess areas, it is necessary to have a reliable method for determining collapsible loess foundations and a comprehensive understanding, and to take correct engineering measures to prevent or eliminate their collapsibility. This process is called collapsible loess foundation treatment. At present, lime and cement are the most widely used roadbed reinforcement materials, but in engineering practice, lime soil and cement soil have disadvantages such as low early strength, large shrinkage, easy cracking, and poor fatigue resistance. In addition, their treatment effect is greatly affected by soil quality, and their curing effect on clay, organic soil, and saline soil with a high plasticity index is poor, or sometimes even has no curing effect.

[0003] Magnesium oxysulfate cement, a type of magnesite cement, is a mixture of a certain amount of magnesium oxide, magnesium sulfate, and water to form a ternary system of MgSO4-MgO-H2O, which is then fully hydrated to form an air-hardening cementitious material. Compared with the preparation process of ordinary Portland cement, magnesium oxysulfate cement does not require sintering, steam curing, and other manufacturing processes. In addition, the production process of magnesium oxysulfate cement does not generate dust, waste gas, wastewater, or radioactive products, making it energy-saving and environmentally friendly. In addition, compared with the performance of ordinary Portland cement, magnesium oxysulfate cement has many advantages, such as light weight, low toxicity, fire retardancy, heat preservation, low corrosion, good water resistance, high volume stability, and strong adhesion. Therefore, the development prospects of magnesium oxysulfate cement are very broad.

[0004] Patent application number CN115449374A discloses a collapsible loess roadbed reinforcement material and its preparation method. By adding a roadbed reinforcement material composed primarily of sodium silicate, soil-solidifying enzymes, acrylic ester water-based laminating adhesive, fiber strings, and nano-calcium carbonate, the structure of the collapsible loess particles is altered, causing the original cohesive forces within the soil particles to recombine, resulting in irreversible cohesion, filling internal voids, and improving their compressive strength. This weakens the water absorption capacity of the collapsible loess particles, reducing their hydrophilicity and creating a water-shielding effect, forming a waterproof soil layer. Furthermore, a plurality of staggered reinforcement grid structures are formed within the collapsible loess roadbed, further improving its compressive strength and stability. However, the soil-solidifying enzymes, nano-calcium carbonate, and other additives used in the material are relatively expensive. The present invention is intended to reduce the cost of collapsible loess reinforcement materials. Summary of the Invention

[0005] The purpose of the present invention is to provide a collapsible loess solidification material and a preparation method thereof. Activated coal gangue is doped into the formula to enable high-value and efficient recycling of industrial waste. At the same time, magnesium oxysulfate cement is added to prepare a product with good loess reinforcement effect.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A loess solidification material is characterized in that its raw materials are: light-burned magnesium oxide, magnesium sulfate heptahydrate, water, loess, and coal gangue; the mass ratio of light-burned magnesium oxide to magnesium sulfate heptahydrate is 100:30; the mass ratio of water to loess is 16:100; and the added amount of coal gangue is 6% of the mass of the loess.

[0008] Furthermore, the content of active magnesium oxide in the light-burned magnesium oxide powder is 50% to 69%.

[0009] Furthermore, the coal gangue is activated at 700° C. for 2 hours.

[0010] Furthermore, the compressive strength of the loess solidification material 28d is 6.5~9.5 MPa.

[0011] According to the technical plan, the collapsible nature of collapsible loess foundations can cause varying degrees of damage to structures, causing them to significantly sink, crack, and tilt, and even seriously affecting their safety and usability. Magnesium oxysulfate cement has low alkalinity, low corrosiveness, and good adhesion, so lightly burned magnesium oxide, magnesium sulfate heptahydrate, and coal gangue can be added to the loess. Coal gangue contains active substances such as SiO2 and Al2O3. Furthermore, after being activated at 700°C for two hours, coal gangue exhibits hydration activity and can react with magnesium oxide. The hydrated products generated by the hydration reaction can fill the internal pores and cracks of the loess, changing the microstructure and thus increasing the bond strength between loess particles. This also responds to the current call for "energy conservation and emission reduction," enabling waste recycling and increasing the utilization value of resources.

[0012] At the same time, the present invention also provides a method for preparing the above-mentioned loess solidification material, comprising the following steps:

[0013] (1) Weigh magnesium sulfate heptahydrate and water to prepare a mixed solution A; weigh light-burned magnesium oxide, loess, and coal gangue to prepare a dry mixture B; mix the mixed solution A and the dry mixture B and stir them evenly to prepare a mixture.

[0014] (2) The slurry stirred in step (1) is injected into a mold, molded, and then demoulded. The sample is placed in the air for natural curing.

[0015] Preferably, the mixing time of the mixed solution A and the dry mixture B in step (1) is 5 to 10 minutes.

[0016] Preferably, the molding time in step (2) is 5 minutes; and the natural curing temperature is 20-28°C.

[0017] Preferably, the natural curing humidity in step (2) is 95%.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The raw materials used in the present invention include industrial waste, which reduces the production cost of magnesium oxysulfate cement.

[0020] (2) The manufacturing process of the present invention does not require sintering and steaming, and no waste gas, waste water or radioactive products are generated during the manufacturing process. It is a new type of green cementitious material.

[0021] (3) The present invention prepares loess solidified samples with a 28-day compressive strength of 6.5-9.5 MPa by adding magnesium oxysulfate cement and coal gangue. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a process flow chart for preparing light magnesium oxysulfate cement according to the present invention;

[0023] Figure 2 The appearance of the solidified loess samples prepared in Examples 1 to 3 of the present invention;

[0024] Figure 3 These are scanning electron microscope images of the solidified loess samples prepared in Examples 2 and 3 of the present invention. DETAILED DESCRIPTION

[0025] The embodiments of the present invention will be further described below with reference to the examples.

[0026] In the following examples, the content of active magnesium oxide in the light-burned magnesium oxide powder is 50%~69%. Example

[0027] A collapsible loess solidification material, the preparation method of which comprises the following steps:

[0028] Weigh magnesium sulfate heptahydrate and water to prepare a mixed solution A, in which the mass ratio of light-burned magnesium oxide to magnesium sulfate heptahydrate is 100:30; weigh light-burned magnesium oxide, loess, and coal gangue to prepare a dry mixture B, in which the mass ratio of light-burned magnesium oxide to loess is 7:100, the amount of coal gangue is 6% of the mass of loess, and the mass ratio of water to loess is 16:100; the mixed solution A and the dry mixture B are mixed and stirred for 15 minutes to prepare a mixture, the slurry is injected into a mold and formed for 5 minutes, then demolded, and the sample is placed in air at a temperature of 25±2℃ and a humidity of 95% for curing. Example

[0029] A collapsible loess solidification material, the preparation method of which comprises the following steps:

[0030] Weigh magnesium sulfate heptahydrate and water to prepare a mixed solution A, in which the mass ratio of light-burned magnesium oxide to magnesium sulfate heptahydrate is 100:30; weigh light-burned magnesium oxide, loess, and coal gangue to prepare a dry mixture B, in which the mass ratio of light-burned magnesium oxide to loess is 9:100, the amount of coal gangue is 6% of the mass of loess, and the mass ratio of water to loess is 16:100; the mixed solution A and the dry mixture B are mixed and stirred for 15 minutes to prepare a mixture, the slurry is injected into a mold and formed for 5 minutes, then demolded, and the sample is placed in air at a temperature of 25±2℃ and a humidity of 95% for curing.

[0031] The microscopic morphology of the test block prepared in Example 2 under a scanning electron microscope is as follows: Figure 3 As shown in (b), the larger pores between loess particles are filled with the generated amorphous gel products and flaky Mg(OH)2, which improves the strength of the loess. Example

[0032] A collapsible loess solidification material, the preparation method of which comprises the following steps:

[0033] Weigh magnesium sulfate heptahydrate and water to prepare a mixed solution A, in which the mass ratio of light-burned magnesium oxide to magnesium sulfate heptahydrate is 100:30; weigh light-burned magnesium oxide, loess, and coal gangue to prepare a dry mixture B, in which the mass ratio of light-burned magnesium oxide to loess is 11:100, the amount of coal gangue is 6% of the mass of loess, and the mass ratio of water to loess is 16:100; the mixed solution A and the dry mixture B are mixed and stirred for 15 minutes to prepare a mixture, the slurry is injected into a mold and formed for 5 minutes, then demolded, and the sample is placed in air at a temperature of 25±2℃ and a humidity of 95% for curing.

[0034] Comparative Example

[0035] A collapsible loess solidification material, the preparation method of which comprises the following steps:

[0036] Weigh aqueous solution A; weigh loess B, with the mass ratio of water to loess being 16:100; mix the solutions A and B and stir for 15 minutes to prepare a mixture, inject the slurry into a mold and form for 5 minutes, then demold, and place the sample in air at a temperature of 25±2°C and a humidity of 95% for curing.

[0037] The microscopic morphology of the test piece prepared in the comparative example under the scanning electron microscope is as follows: Figure 3 As shown in (a), it can be seen from the figure that there are large pores between loess particles, which have a great influence on the strength of loess.

[0038] It will be understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the present invention, and the present invention is not limited thereto. Those skilled in the art will appreciate that various modifications and improvements can be made without departing from the spirit and substance of the present invention, and such modifications and improvements are also considered to be within the scope of protection of the present invention.

[0039] The following table compares the general physical and chemical properties of the loess solidified materials prepared in Examples 1 to 3 of the present invention and the comparative example.

[0040] .

Claims

1. A loess solidification material, characterized in that: The raw materials are: light-burned magnesium oxide, magnesium sulfate heptahydrate, water, loess, and coal gangue; the mass ratio of light-burned magnesium oxide to magnesium sulfate heptahydrate is 100:30; the mass ratio of water to loess is 16:100; and the added amount of coal gangue is 6% of the mass of the loess.

2. The loess solidification material according to claim 1, wherein The content of active magnesium oxide in the light-burned magnesium oxide powder is 55% to 69%.

3. The loess solidification material according to claim 1, wherein The coal gangue was activated at 700° C. for 2 hours.

4. The loess solidification material according to claim 1, wherein The compressive strength of the loess solidification material 28d is 6.5~9.5 MPa.

5. A method for preparing the loess solidified material according to claim 1, characterized in that Here are the steps: (1) Weighing magnesium sulfate heptahydrate and water to prepare a mixed solution A; weighing magnesium oxide, loess, and coal gangue to prepare a dry mixture B; mixing the mixed solution A and the dry mixture B and stirring them uniformly to prepare a mixture; (2) The slurry stirred in step (1) is injected into a mold, molded, and then demoulded. The sample is placed in the air for natural curing.

6. The method for preparing the loess solidified material according to claim 5, wherein: The mixing time of the mixed solution A and the dry mixture B in step (1) is 5 to 10 minutes.

7. The method for preparing the loess solidified material according to claim 5, wherein: The mass ratio of water to loess in step (1) is 16:

100.

8. The method for preparing the loess solidified material according to claim 5, wherein: The molding time in step (2) is 5 minutes; the natural curing temperature is 25 ± 2 °C.

9. The method for preparing the loess solidified material according to claim 5, wherein: The natural curing humidity in step (2) is 95%.

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