Roadbed filler based on engineering residue soil and preparation method thereof

Abstract

The invention discloses a roadbed filler based on engineering muck and a preparation method thereof, and belongs to the technical field of building materials, and the roadbed filler based on the engineering muck is characterized by comprising the following raw materials in parts by weight: 100 parts of engineering muck, 5-12 parts of cement, 5-7 parts of slag powder and 2-5 parts of an exciting agent; the engineering muck comprises fine aggregate with the particle size of 0-4.75 mm and coarse aggregate with the particle size of 4.75-53 mm, and the weight ratio of the fine aggregate to the coarse aggregate is (2-3): (7-8). According to the application, the modified material is added into the engineering muck, and meanwhile, the ratio of the coarse aggregate to the fine aggregate in the engineering muck is adjusted, so that the bearing capacity and the stability of the engineering muck serving as the roadbed material are effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and in particular to a subgrade filler based on construction waste soil and a preparation method thereof. Background Art

[0002] Construction waste soil includes construction waste, excavated soil, etc. With the acceleration of the urbanization process, the amount of construction waste soil generated during urban construction is astonishing. On the one hand, a large amount of waste occupies urban land and affects the urban landscape. On the other hand, the waste soil is blown by the wind and the dust fills the sky, and it flows everywhere after being washed by heavy rain, bringing serious pollution to the surrounding environment.

[0003] With the rapid development of road construction projects in China, the demand for subgrade fillers is increasing day by day. Applying construction waste soil to the fillers of subgrade projects can not only effectively alleviate the problem of tight filler supply, but also promote the reuse of construction waste. However, when directly using construction waste soil, there are problems such as low bearing capacity, easy cracking, and poor durability. Based on this, it is necessary to improve the properties of construction waste soil by adding modified materials. Commonly used existing inorganic modified materials include cement, lime, etc., which can be used alone or in combination. However, the recycled aggregates in construction waste soil have a wide grading range and low strength, and there are many cracks on the surface of the aggregates, resulting in relatively poor bearing capacity and stability of the construction waste soil even after adding modified materials, and the service life of the subgrade is short. Summary of the Invention

[0004] In order to solve the problems in the prior art, the present invention provides a subgrade filler based on construction waste soil and a preparation method thereof. By adding modified materials to the construction waste soil and adjusting the ratio of fine and coarse aggregates in the construction waste soil at the same time, the bearing capacity and stability of the construction waste soil as a subgrade material are effectively improved.

[0005] A subgrade filler based on construction waste soil provided by the present invention adopts the following technical scheme: A subgrade filler based on construction waste soil, the subgrade filler comprises the following raw materials in parts by weight: 100 parts of construction waste soil, 5 - 12 parts of cement, 5 - 7 parts of slag powder, and 2 - 5 parts of activator; The construction waste soil includes fine aggregates with a particle size of 0 - 4.75 mm and coarse aggregates with a particle size of 4.75 - 53 mm, and the weight ratio of the fine aggregates to the coarse aggregates is (2 - 3):(7 - 8).

[0006] By adopting the above technical solutions, the construction muck is reasonably classified into fine aggregate and coarse aggregate, and by controlling the weight ratio of the two to be (2 - 3):(7 - 8), the grading characteristics of the construction muck can be effectively improved. At the same time, adding materials such as cement, slag powder and activator can significantly improve the strength and stability of the subgrade filler. Specifically, the synergistic effect of cement and slag powder can enhance the cementing performance of the subgrade filler, and the addition of the activator further promotes the reaction of mineral active components, improving the overall bearing capacity and durability. This ratio design not only makes full use of the construction muck resources, but also solves the problems such as low bearing capacity and easy cracking when it is directly used, thus extending the service life of the subgrade.

[0007] Preferably, the coarse aggregate includes aggregates with particle sizes of 4.75 - 19 mm, 19 - 37.5 mm and 37.5 - 53 mm with a weight ratio of (2.8 - 3.8):(2.2 - 3.2):(1.1 - 2.1).

[0008] By adopting the above technical solutions, the proportion of aggregates in each particle size range in the coarse aggregate is reasonably optimized, making the grading of the coarse aggregate more uniform. Specifically, the combination of aggregates with particle sizes of 4.75 - 19 mm, 19 - 37.5 mm and 37.5 - 53 mm with a weight ratio of (2.8 - 3.8):(2.2 - 3.2):(1.1 - 2.1) can effectively reduce the void ratio, improve the compactness of the subgrade filler, thereby enhancing the overall stability and bearing capacity of the subgrade. This grading optimization can also improve the stress distribution inside the construction muck, reduce the cracking risk, and extend the service life of the subgrade.

[0009] Preferably, the coarse aggregate is subjected to a modification treatment before use, and the modification treatment method includes the following steps: (1) Prepare an aqueous sodium silicate solution with a concentration of 6 - 10 wt%, and soak the coarse aggregate in the aqueous sodium silicate solution for 20 - 24 h; (2) After completely drying the coarse aggregate soaked in step (1), spray a slurry composed of cement, diatomite and water, and naturally cure and dry to obtain the modified coarse aggregate.

[0010] By adopting the above technical solutions, the modification treatment of coarse aggregates can significantly improve the performance of subgrade fillers based on construction waste soil. Specifically, by soaking the coarse aggregates in an aqueous sodium silicate solution with a concentration of 6-10 wt% for 20-24 h, the microcracks and pores on the surface of the coarse aggregates can be effectively sealed, and the surface denseness can be enhanced, thereby improving the strength and water erosion resistance of the coarse aggregates. Further, by spraying a slurry composed of cement, diatomite and water and naturally curing and drying, a stable protective film can be formed on the surface of the coarse aggregates, which not only enhances the adhesion between the coarse aggregates and the fine aggregates, but also further improves the bearing capacity and stability of the entire subgrade filler, and extends the service life of the subgrade.

[0011] Preferably, the weight ratio of the cement to the diatomite is (1-2):1, and the water-cement ratio of the slurry is 0.4-0.5.

[0012] By adopting the above technical solutions, adjusting the weight ratio of the cement to the diatomite to (1-2):1 can optimize the bonding performance and filling effect of the slurry, and further enhance the strength and durability of the surface of the coarse aggregates. At the same time, controlling the water-cement ratio of the slurry within the range of 0.4-0.5 can effectively reduce the shrinkage cracks of the slurry, improve its density, thereby enhancing the adhesion between the modified coarse aggregates and the fine aggregates, and improving the overall stability and bearing capacity of the subgrade filler.

[0013] Preferably, the slurry in step S3 further includes a water reducing agent accounting for 0.1% of the total weight of the cement and the diatomite.

[0014] By adopting the above technical solutions, the addition of the water reducing agent can effectively reduce the water consumption of the slurry, improve the fluidity of the slurry, and make the slurry cover the surface of the coarse aggregates more evenly during the spraying process. At the same time, the use of the water reducing agent can enhance the adhesion between the slurry and the coarse aggregates, further improve the strength and durability of the modified coarse aggregates, and thus improve the overall performance of the subgrade filler based on construction waste soil.

[0015] Preferably, the amount of the slurry is 0.1-0.3 of the weight of the coarse aggregates.

[0016] By adopting the above technical solutions, controlling the amount of the slurry to be 0.1-0.3 of the weight of the coarse aggregates can ensure that a uniform coating layer is formed on the surface of the coarse aggregates, which will neither lead to poor modification effect due to too little slurry nor cause waste of resources or affect the overall performance of the subgrade filler due to too much slurry. The slurry within this dosage range can effectively fill the cracks and pores on the surface of the coarse aggregates, improve the strength and durability of the coarse aggregates, and thus further enhance the bearing capacity and stability of the subgrade filler based on construction waste soil.

[0017] Preferably, a silane aqueous solution with a concentration of 10-12 wt is sprayed on the coarse aggregates before spraying the slurry.

[0018] By adopting the above technical solution, the coarse aggregate is sprayed with an aqueous solution of silane with a concentration of 10-12wt% before spraying the slurry, which can effectively improve the hydrophobic property of the surface of the coarse aggregate, reduce the erosion of water on the coarse aggregate, and thus enhance the durability of the coarse aggregate. Generally speaking, the modified coarse aggregate acts synergistically with engineering soil, cement, slag powder and activator to further improve the overall stability and bearing capacity of the subgrade filler. Specifically, the effects of spraying the aqueous solution of silane include: improving the surface characteristics of the coarse aggregate, reducing the water absorption rate, improving the freeze-thaw resistance, and extending the service life of the subgrade.

[0019] Preferably, the activator is composed of sodium sulfate and sodium hydroxide in a weight ratio of 1:1.

[0020] By adopting the above technical solution, the activator is set to be composed of sodium sulfate and sodium hydroxide in a weight ratio of 1:1, which can effectively improve the activity of the mineral components in the engineering soil, promote the hydration reaction of cement and slag powder, and enhance the overall strength and stability of the subgrade filler. The specific effects include: improving the bearing capacity of the engineering soil, reducing the cracking phenomenon, and extending the service life of the subgrade.

[0021] The second aspect of the present application is to provide a preparation method of a subgrade filler based on engineering soil as described above, including the following steps: mixing engineering soil, cement, slag powder, and activator in proportion to form a mixture, and turning and curing the mixture for 5 days to obtain the subgrade filler.

[0022] In summary, the present invention has the following beneficial effects: By adjusting the proportion of aggregates with different particle sizes in the engineering soil and the modification treatment of the coarse aggregate, the present application effectively improves the bearing capacity, service stability and durability of the subgrade when using engineering soil. Specific Embodiments

[0023] The following further describes the present invention in detail with reference to embodiments. All reagents not indicating the manufacturer are conventional reagent products that can be obtained through commercial purchase.

[0024] Preparation Example 1 A method for modifying coarse aggregate, including the following steps: (1) Prepare an aqueous solution of sodium silicate with a concentration of 6wt%, and soak the coarse aggregate in the aqueous solution of sodium silicate for 20h; (2) After completely drying the coarse aggregate soaked in step (1), spray a slurry composed of cement, diatomite and water, where the water-cement ratio of the slurry is 0.4, the weight ratio of cement to diatomite is 1:1, and the weight ratio of the coarse aggregate to the slurry during spraying is 1:0.1. After spraying, the coarse aggregate is naturally cured and dried to obtain the modified coarse aggregate.

[0025] Preparation Example 2 A method for modifying coarse aggregate, comprising the following steps: (1) Prepare an aqueous sodium silicate solution with a concentration of 10 wt%, and soak the coarse aggregate in the aqueous sodium silicate solution for 24 h; (2) After completely drying the coarse aggregate soaked in step (1), spray a slurry composed of cement, diatomaceous earth and water, wherein the water-cement ratio of the slurry is 0.5, the weight ratio of cement to diatomaceous earth is 2:1, and during the spraying process, the weight ratio of the coarse aggregate to the slurry is 1:0.3. The sprayed coarse aggregate is naturally cured and dried to obtain the modified coarse aggregate.

[0026] Preparation Example 3 A method for modifying coarse aggregate, comprising the following steps: (1) Prepare an aqueous sodium silicate solution with a concentration of 10 wt%, and soak the coarse aggregate in the aqueous sodium silicate solution for 24 h; (2) After completely drying the coarse aggregate soaked in step (1), spray an aqueous silane solution with a concentration of 10 wt%, and then spray a slurry composed of cement, diatomaceous earth and water, wherein the water-cement ratio of the slurry is 0.5, the weight ratio of cement to diatomaceous earth is 2:1, and during the spraying process, the weight ratio of the coarse aggregate to the slurry is 1:0.3. The sprayed coarse aggregate is naturally cured and dried to obtain the modified coarse aggregate.

[0027] Preparation Example 4 A method for modifying coarse aggregate, comprising the following steps: (1) Prepare an aqueous sodium silicate solution with a concentration of 10 wt%, and soak the coarse aggregate in the aqueous sodium silicate solution for 24 h; (2) After completely drying the coarse aggregate soaked in step (1), spray an aqueous silane solution with a concentration of 12 wt%, and then spray a slurry composed of cement, diatomaceous earth and water, wherein the water-cement ratio of the slurry is 0.5, the weight ratio of cement to diatomaceous earth is 2:1, and during the spraying process, the weight ratio of the coarse aggregate to the slurry is 1:0.3. The sprayed coarse aggregate is naturally cured and dried to obtain the modified coarse aggregate.

[0028] Preparation Example 5 A method for modifying coarse aggregate, comprising the following steps: (1) Prepare an aqueous sodium silicate solution with a concentration of 10 wt%, and soak the coarse aggregate in the aqueous sodium silicate solution for 24 h; (2) After completely drying the coarse aggregate soaked in step (1), spray an aqueous solution of silane with a concentration of 12 wt%, and then spray a slurry composed of cement, diatomaceous earth, water reducer and water. The water-cement ratio of the slurry is 0.5, the weight ratio of cement to diatomaceous earth is 2:1, and the amount of water reducer is 0.1% of the total amount of cement and diatomaceous earth. During the spraying process, the weight ratio of the coarse aggregate to the slurry is 1:0.3. After spraying, the coarse aggregate is naturally cured and dried to obtain the modified coarse aggregate.

[0029] Preparation Example 6 A method for modifying coarse aggregate, which is different from Preparation Example 1 in that the slurry in step (2) does not contain diatomaceous earth, and the others are the same as Preparation Example 1.

[0030] Example 1 A method for preparing a subgrade filler based on construction waste soil, comprising the following steps: mixing 10 kg of construction waste soil, 0.5 kg of cement, 0.5 kg of slag powder and 0.2 kg of activator to form a mixture, and performing turning and curing on the mixture for 5 days to obtain the subgrade filler; Wherein the construction waste soil includes fine aggregate with a particle size of 0 - 4.75 mm and coarse aggregate with a particle size of 4.75 - 53 mm. The weight ratio of the fine aggregate to the coarse aggregate is 2:8, that is, the fine aggregate is 2 kg and the coarse aggregate is 8 kg; The coarse aggregate includes aggregates with a particle size of 4.75 - 19 mm, aggregates with a particle size of 19 - 37.5 mm and aggregates with a particle size of 37.5 - 53 mm in a weight ratio of 2.8:2.2:1.1, that is, the amount of aggregates with a particle size of 4.75 - 19 mm is 3.67 kg, the amount of aggregates with a particle size of 19 - 37.5 mm is 2.89 kg, and the amount of aggregates with a particle size of 37.5 - 53 mm is 1.44 kg; The coarse aggregate is modified by the modification method of Preparation Example 1 before use; The activator is composed of sodium sulfate and sodium hydroxide in a weight ratio of 1:1.

[0031] Example 2 A method for preparing a subgrade filler based on construction waste soil, comprising the following steps: mixing 10 kg of construction waste soil, 0.9 kg of cement, 0.6 kg of slag powder and 0.4 kg of activator to form a mixture, and performing turning and curing on the mixture for 5 days to obtain the subgrade filler; Wherein the construction waste soil includes fine aggregate with a particle size of 0 - 4.75 mm and coarse aggregate with a particle size of 4.75 - 53 mm. The weight ratio of the fine aggregate to the coarse aggregate is 2:8, that is, the fine aggregate is 2 kg and the coarse aggregate is 8 kg; The coarse aggregate includes aggregates with a particle size of 4.75 - 19 mm, aggregates with a particle size of 19 - 37.5 mm, and aggregates with a particle size of 37.5 - 53 mm in a weight ratio of 2.8:2.2:1.1, that is, the amount of aggregates with a particle size of 4.75 - 19 mm is 3.67 kg, the amount of aggregates with a particle size of 19 - 37.5 mm is 2.89 kg, and the amount of aggregates with a particle size of 37.5 - 53 mm is 1.44 kg; The coarse aggregate is modified by the modification method of Preparation Example 1 before use; The activator is composed of sodium sulfate and sodium hydroxide in a weight ratio of 1:1.

[0032] Example 3 A preparation method of a subgrade filler based on construction waste soil includes the following steps: 10 kg of construction waste soil, 1.2 kg of cement, 0.7 kg of slag powder, and 0.5 kg of activator are stirred and mixed to form a mixture, and the mixture is turned and cured for 5 days to obtain the subgrade filler, that is, the fine aggregate is 2 kg and the coarse aggregate is 9 kg; Among them, the construction waste soil includes fine aggregates with a particle size of 0 - 4.75 mm and coarse aggregates with a particle size of 4.75 - 53 mm, and the weight ratio of the fine aggregate to the coarse aggregate is 2:8, that is, the fine aggregate is 2 kg and the coarse aggregate is 8 kg; The coarse aggregate includes aggregates with a particle size of 4.75 - 19 mm, aggregates with a particle size of 19 - 37.5 mm, and aggregates with a particle size of 37.5 - 53 mm in a weight ratio of 2.8:2.2:1.1, that is, the amount of aggregates with a particle size of 4.75 - 19 mm is 3.67 kg, the amount of aggregates with a particle size of 19 - 37.5 mm is 2.89 kg, and the amount of aggregates with a particle size of 37.5 - 53 mm is 1.44 kg; The coarse aggregate is modified by the modification method of Preparation Example 1 before use; The activator is composed of sodium sulfate and sodium hydroxide in a weight ratio of 1:1.

[0033] Example 4 A preparation method of a subgrade filler based on construction waste soil, which is different from Example 2 in that the weight ratio of the fine aggregate to the coarse aggregate in the construction waste soil is 3:7, that is, the fine aggregate is 3 kg and the coarse aggregate is 7 kg, and the dosages and proportions of other components are the same as those in Example 1.

[0034] Example 5 A preparation method of subgrade filler based on construction waste soil, different from Example 2 in that the coarse aggregate is 8 kg, and the coarse aggregate includes aggregates with a particle size of 4.75 - 19 mm, aggregates with a particle size of 19 - 37.5 mm, and aggregates with a particle size of 37.5 - 53 mm in a weight ratio of 3.3:2.8:1.6, that is, the amount of aggregates with a particle size of 4.75 - 19 mm is 3.43 kg, the amount of aggregates with a particle size of 19 - 37.5 mm is 2.91 kg, and the amount of aggregates with a particle size of 37.5 - 53 mm is 1.66 kg, and the others are the same as Example 2.

[0035] Example 6 A preparation method of subgrade filler based on construction waste soil, different from Example 2 in that the coarse aggregate is 8 kg, and the coarse aggregate includes aggregates with a particle size of 4.75 - 19 mm, aggregates with a particle size of 19 - 37.5 mm, and aggregates with a particle size of 37.5 - 53 mm in a weight ratio of 3.8:3.2:2.1, that is, the amount of aggregates with a particle size of 4.75 - 19 mm is 3.34 kg, the amount of aggregates with a particle size of 19 - 37.5 mm is 2.81 kg, and the amount of aggregates with a particle size of 37.5 - 53 mm is 1.85 kg, and the others are the same as Example 2.

[0036] Example 7 A preparation method of subgrade filler based on construction waste soil, different from Example 5 in that the coarse aggregate is modified by the modification method of Preparation Example 2, and the others are the same as Example 5.

[0037] Example 8 A preparation method of subgrade filler based on construction waste soil, different from Example 5 in that the coarse aggregate is modified by the modification method of Preparation Example 3, and the others are the same as Example 5.

[0038] Example 9 A preparation method of subgrade filler based on construction waste soil, different from Example 5 in that the coarse aggregate is modified by the modification method of Preparation Example 4, and the others are the same as Example 5.

[0039] Example 10 A preparation method of subgrade filler based on construction waste soil, different from Example 5 in that the coarse aggregate is modified by the modification method of Preparation Example 5, and the others are the same as Example 5.

[0040] Comparative Example 1 A preparation method of subgrade filler based on construction waste soil, different from Example 1 in that the activator is missing in the subgrade raw materials, and the others are the same as Example 1.

[0041] Comparative Example 2 A preparation method of subgrade filler based on construction waste soil, which is different from Example 1 in that the addition amount of activator in the subgrade raw materials is 0.8 kg, and the others are the same as those in Example 1.

[0042] Comparative Example 3 A preparation method of subgrade filler based on construction waste soil, which is different from Example 1 in that the coarse aggregate is obtained by the modification method of Preparation Example 6, and the others are the same as those in Example 1.

[0043] Comparative Example 4 A preparation method of subgrade filler based on construction waste soil, which is different from Example 1 in that the coarse aggregate is directly used without modification treatment, and the others are the same as those in Example 1.

[0044] Performance testing After paving and compacting the subgrade fillers obtained in the above examples and preparation examples, the compactness, CBR value, and resilient modulus of the road surface are detected, and the test results are shown in Table 1.

[0045] Table 1 Performance test results of subgrade fillers Project Compaction Degree % CBR % Resilient Modulus MPa Example 1 98 43.5 52.6 Example 2 98 45.4 54.8 Example 3 98 44.9 54.5 Example 4 98 45.2 54.7 Example 5 98 51.6 59.4 Example 6 98 49.2 56.6 Example 7 98 52.3 59.1 Example 8 98 59.6 65.4 Example 9 98 60.3 67.6 Example 10 98 61.5 69.2 Comparative Example 1 81 28.6 37.3 Comparative Example 2 83 38.3 48.6 Comparative Example 3 90 38.7 44.8 Comparative Example 4 87 32.6 39.4 As can be seen from Table 1 above: In Examples 1-3 of the present application, by adjusting the contents of cement, slag powder, and activator, the CBR value and resilient modulus of the subgrade filler are effectively guaranteed, so that the construction waste soil can be well applied to the subgrade filler, saving costs.

[0046] Compared with Example 2, in Examples 4-6, when the particle size ratios of the three kinds of aggregates in the coarse aggregate of the construction waste soil remain unchanged, by increasing the fine aggregate, the performance of the subgrade filler in Example 4 is basically the same as that of the filler in Example 2. However, by adjusting the particle size ratios of the three kinds of aggregates in the coarse aggregate, the performance of the subgrade fillers obtained in Examples 5-6 is significantly increased compared with that in Example 2. It can be seen that the particle size ratios of the three kinds of aggregates in the coarse aggregate have a relatively large impact on the performance of the subgrade filler.

[0047] Compared with Example 5, in Examples 8-9, when the modification method of the coarse aggregate is changed, it also has a very large impact on the performance of the subgrade filler. Specifically, compared with Example 5, in Examples 8-9, when spraying an aqueous silane solution on the coarse aggregate during the modification process of the coarse aggregate, and in Example 10, the modification of the coarse aggregate is after spraying an aqueous silane solution and adding a water reducing agent to the slurry, the CBR value and resilient modulus of the coarse aggregates obtained in Examples 8-10 are significantly increased compared with those in Example 5. Thus, it can be seen that when modifying the coarse aggregate, spraying an aqueous silane solution before spraying the slurry can effectively improve the performance of the coarse aggregate, thereby significantly improving the performance of the construction waste soil in the subgrade filler.

[0048] Compared with Example 1, in Comparative Examples 1-2, when the activator was missing or excessively added in the raw materials, the compaction degree, CBR value and resilient modulus of the subgrade filler obtained in Comparative Examples 1-2 were much lower than the performance in Example 1. The reason may be that the activator can activate the active components in engineering soil and slag powder, and can synergistically react with cement to generate cementitious substances such as calcium silicate hydrate. These products can fill the particle gaps and improve the compaction density. However, when the dosage of the activator is too much, it may lead to too fast early reaction and the mixture becoming brittle, resulting in a decrease in compaction degree. Moreover, the excessive activator may cause uneven distribution of the products or generate expansive substances, leading to a decrease in the bearing capacity (CBR) of the subgrade filler.

[0049] Compared with Example 1, in Comparative Examples 3-4, when only sodium silicate was used to modify the coarse aggregate or the coarse aggregate was not modified, the various performances obtained in Comparative Examples 3-4 were lower than those in Example 1, especially the performances in Comparative Example 4 were even lower. Thus, it can be seen that the modification treatment of the coarse aggregate can effectively improve the performance of engineering soil as a subgrade filler.

[0050] The examples of this specific embodiment are all preferred embodiments of the present invention, and do not limit the protection scope of the present invention accordingly. Therefore, all equivalent changes made according to the structure, shape and principle of the present invention should be covered within the protection scope of the present invention.

Claims

1. A subgrade filler based on construction muck, characterized in that: The subgrade filler comprises raw materials in the following weight parts: 100 parts of engineering muck, 5 - 12 parts of cement, 5 - 7 parts of slag powder, and 2 - 5 parts of activator; The engineering muck comprises fine aggregate with a particle size of 0 - 4.75 mm and coarse aggregate with a particle size of 4.75 - 53 mm, and the weight ratio of the fine aggregate to the coarse aggregate is (2 - 3):(7 - 8).

2. The subgrade filler based on construction waste soil according to claim 1, characterized in that: The coarse aggregate comprises aggregates with a particle size of 4.75 - 19 mm, aggregates with a particle size of 19 - 37.5 mm, and aggregates with a particle size of 37.5 - 53 mm in a weight ratio of (2.8 - 3.8):(2.2 - 3.2):(1.1 - 2.1).

3. The subgrade filler based on construction waste soil according to claim 1, characterized in that: The coarse aggregate is subjected to modification treatment before use, and the modification treatment method comprises the following steps: (1) Prepare an aqueous sodium silicate solution with a concentration of 6 - 10 wt%, and soak the coarse aggregate in the aqueous sodium silicate solution for 20 - 24 h; (2) After completely drying the coarse aggregate soaked in step (1), spray a slurry composed of cement, diatomite and water, and naturally cure and dry to obtain the modified coarse aggregate.

4. The subgrade filler based on construction waste soil according to claim 3, characterized in that: The weight ratio of the cement to the diatomite is (1 - 2):1, and the water - cement ratio of the slurry is 0.4 - 0.

5.

5. A subgrade filler based on construction waste soil according to claim 3, characterized in that: The slurry in step S3 further comprises a water - reducing agent accounting for 0.1% of the total weight of the cement and the diatomite.

6. The subgrade filler based on construction waste soil according to claim 3, characterized in that: The amount of the slurry is 0.1 - 0.3 of the weight of the coarse aggregate.

7. The subgrade filler based on construction waste soil according to claim 3, characterized in that: Before spraying the slurry, the coarse aggregate is first sprayed with an aqueous silane solution with a concentration of 10 - 12 wt.

8. The subgrade filler based on construction waste soil according to claim 1, characterized in that: The activator is composed of sodium sulfate and sodium hydroxide in a weight ratio of 1:

1.

9. A preparation method of a subgrade filler based on construction waste soil as described in any one of claims 1-8, characterized in that: It comprises the following steps: stirring and mixing the engineering muck, cement, slag powder, and activator in proportion to form a mixture, and performing turning and curing on the mixture for 5 days to obtain the subgrade filler.