Polypropylene fiber modified expanded rock soil roadbed modifier, and preparation method and application thereof

Abstract

The application relates to the technical field of building engineering materials, and particularly discloses a polypropylene fiber modified expanded rock-soil roadbed modifier and a preparation method and application thereof. The polypropylene fiber modified expanded rock-soil roadbed modifier disclosed by the application comprises the following components: a non-metallic oxide, a metallic oxide, a nucleating agent and polypropylene fibers. The non-metallic oxide is composed of the following components: 65-69 parts of SiO2 and 2-4 parts of SeO2. The metallic oxide is composed of the following components: 21-25 parts of Al2O3, 9-13 parts of CaO, 7-9 parts of CuO, 2.5-3.5 parts of Fe2O3 and 1.5-2.5 parts of MgO. The nucleating agent is composed of talcum powder and sorbitol. The modifier disclosed by the application effectively reduces the expansion force and free expansion rate of the modified expanded rock-soil body, and enables the modified expanded rock-soil body to maintain the radial linear shrinkage rate in multiple dry-wet cycles.

Description

Technical Field

[0001] This application relates to the technical field of building materials, specifically to a polypropylene fiber-modified expandable soil and rock subgrade modifier, its preparation method, and its application. Background Technology

[0002] Expansive rock (soil) is a special type of soil and rock mass that is extremely sensitive to moisture. It expands and softens when exposed to water, and shrinks and disintegrates when it loses water. Due to its significant expansion and contraction characteristics, it is prone to cracking under alternating wet and dry conditions, which seriously affects the long-term stability and safety of engineering structures. Therefore, effective protective measures must be taken for roadbeds composed of this type of soil and rock.

[0003] For the protection of excavated expansive rock (soil) subgrades, conventional treatment methods mainly include the following: The protection of excavated expansive rock (soil) subgrades focuses on "waterproofing and moisture retention, improvement and reinforcement, and structural resistance." The core is to construct a waterproof system by quickly sealing the road surface, setting up drainage ditches, and laying a waterproof layer to isolate moisture changes. For soils with strong expansibility, replacement or lime and cement improvement are used to weaken their expansibility. Simultaneously, structural measures such as gentle slopes, retaining walls, and other structural measures are used to resist the remaining expansibility. All measures must be used comprehensively and implemented promptly to ensure the long-term stability of the subgrade.

[0004] In addition, in terms of improvement, the traditional way to treat expansive soil and rock is to use lime, cement and other methods. However, the water stability of expansive soil and rock treated by these methods is poor, and the properties of the modified expansive soil and rock are unstable. The hydrophysical and mechanical properties often do not achieve the expected modification effect.

[0005] Therefore, a novel method is needed to modify expansive soils. Summary of the Invention

[0006] To address the aforementioned technical problems, this application provides a polypropylene fiber-modified expandable soil and rock subgrade modifier, its preparation method, and its application.

[0007] In one aspect, this application provides a polypropylene fiber modified expansive soil and rock subgrade modifier, specifically comprising the following components in parts by weight: 67-73 parts of non-metallic oxide, 44-50 parts of metallic oxide, 6-10 parts of nucleating agent, and 0.2-0.6 parts of polypropylene fiber; The non-metallic oxide is composed of the following components in parts by weight: SiO2: 65-69 parts, SeO2: 2-4 parts; The metal oxide is composed of the following components in parts by weight: Al2O3: 21-25 parts, CaO: 9-13 parts, CuO: 7-9 parts, Fe2O3: 2.5-3.5 parts, MgO: 1.5-2.5 parts; The nucleating agent is composed of talc and sorbitol in a weight ratio of 6-7.5:0.5-2.

[0008] The purpose of this application is to overcome the significant swelling and shrinkage characteristics of expansive rock (soil) and prevent it from forming cracks under alternating wet and dry conditions, which could seriously affect the long-term stability and safety of engineering structures. Therefore, a modifier for expansive rock and soil subgrade, prepared from polypropylene fibers and non-metallic oxides, metal oxides, and nucleating agents, is provided. This material not only has good affinity with expansive rock (soil), good setting properties, and high bond strength, but more importantly, through the incorporation of polypropylene fibers, it greatly improves the crack resistance and resistance to swelling and shrinkage deformation caused by wet and dry cycles in expansive rock and soil, achieving rapid, efficient, durable, and economical protection.

[0009] The modifiers in this application work synergistically through the following mechanisms: active metal oxides and non-metal oxides undergo ion exchange and cementation reactions with expansive clay minerals (such as montmorillonite and illite) to generate a stable silicate mixed crystal structure, fundamentally reducing its water absorption and swelling potential. The nucleating agent acts as a crystal nucleus to adsorb clay particles, guiding the clay crystal layers to stack along a fixed direction (rather than randomly expanding). The directional stacking of crystal layers results in more uniform spacing and controllable swelling, thereby reducing overall swelling force and free swelling rate; it can also induce the growth of hydration products on the crystal nucleus surface, enhancing shrinkage resistance. Polypropylene fiber, as a high-performance synthetic fiber, is lightweight, wear-resistant, corrosion-resistant, and has good dispersibility. Introducing it into expansive rock and soil subgrade amendments can significantly improve the comprehensive performance of the material. Through the reinforcing effect of the fiber, it effectively improves the tensile and shear strength of the soil, inhibits crack propagation, improves the ductility of the soil, and enhances its crack resistance and durability, thus meeting the crack resistance and anti-swelling-shrinkage cycle requirements of expansive rock and soil subgrades in rapid protection.

[0010] Preferably, the polypropylene fiber modified expansive soil and rock subgrade modifier specifically comprises the following components in parts by weight: 69-71 parts of non-metallic oxide, 46-48 parts of metal oxide, 7-9 parts of nucleating agent, and 0.3-0.5 parts of polypropylene fiber.

[0011] Preferably, the non-metallic oxide is composed of the following components in parts by weight: SiO2: 66-68 parts, SeO2: 2.5-3.5 parts.

[0012] Preferably, the metal oxide comprises the following components in parts by weight: Al2O3: 22-24 parts, CaO: 10-12 parts, CuO: 7.5-8.5 parts, Fe2O3: 2.8-3.2 parts, and MgO: 1.8-2.2 parts.

[0013] Preferably, the nucleating agent is composed of talc and sorbitol in a weight ratio of 6.5-7:1-1.5.

[0014] In one specific implementation, the nucleating agent contains talc and sorbitol in weight ratios of 6:0.5, 6:1, 6:1.5, 6:2, 6.5:0.5, 6.5:1, 6.5:1.5, 6.5:2, 7:0.5, 7:1, 7:1.5, 7:2, 7.5:0.5, 7.5:1, 7.5:1.5, and 7.5:2.

[0015] Experimental analysis shows that using talc and sorbitol in the above weight ratio as nucleating agents can further improve the application effect of the modifier in modified expansive soil and rock.

[0016] Preferably, the polypropylene fiber has the following specifications: length of 6-20 mm, diameter of 20-50 μm, aspect ratio of 200-500, elastic modulus ≥3.5 GPa, and density of 0.85-0.95 g / cm³.

[0017] Secondly, this application provides a method for preparing the polypropylene fiber-modified expansive soil and rock subgrade modifier, comprising the following steps: A non-metallic oxide, a metallic oxide, and a nucleating agent are mixed and calcined at 950-1450℃ for 3-6 hours to obtain the calcined product. The calcined material was mixed with polypropylene fibers and ground until the specific surface area was ≥400 m². 2 / kg yields the finished product.

[0018] Preferably, the roasting process parameters are: roasting at 950-1100℃ for 60-100 min, roasting at 1150-1300℃ for 60-100 min, and roasting at 1350-1450℃ for 100-200 min in sequence.

[0019] Thirdly, this application provides the application of the polypropylene fiber-modified expansive soil and rock subgrade modifier in the method of modifying expansive soil and rock.

[0020] Fourthly, this application provides a method for modifying expansive soil and rock, which uses the polypropylene fiber modified expansive soil and rock roadbed modifier to modify the expansive soil, with a dosage of 3-7%.

[0021] In summary, the technical solution of this application has the following effects: The expansive soil and rock subgrade modifier of this application achieves significant breakthroughs in both physical reinforcement and chemical modification by introducing the synergistic effect between polypropylene fibers, active oxides, and nucleating agent components. The polypropylene fibers form a three-dimensional network structure in the soil, effectively binding soil particle displacement and inhibiting the development of shrinkage cracks during wet-dry cycles, while simultaneously improving the soil's toughness and crack resistance. Meanwhile, the active metal oxides and non-metal oxides undergo ion exchange and cementation reactions with expansive clay minerals (such as montmorillonite and illite) to generate a stable silicate mixed crystal structure, fundamentally reducing its water absorption and swelling potential.

[0022] The expansive soil subgrade modifier of this application not only reduces the expansive force of the modified soil to below 32 kPa and controls the free expansion rate to within 15%, but also maintains the radial shrinkage rate below 5.2% in multiple wet-dry cycles, which is significantly better than single modification methods.

[0023] The expansive rock and soil subgrade modifier of this application combines environmental friendliness, strong construction adaptability, and long-term stability. It can be widely used in the treatment of expansive rock and soil subgrades in highway, railway, water conservancy and other projects, effectively extending the service life of the project and reducing maintenance costs. It has important engineering application value and economic significance. Detailed Implementation

[0024] The present application will be further described in detail below with reference to embodiments, comparative examples and performance test results. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0025] Example

[0026] Example 1

[0027] Example 1 provides a polypropylene fiber-modified expandable soil and rock roadbed modifier.

[0028] The preparation method of the polypropylene fiber modified expansive soil and rock subgrade modifier in Example 1 is as follows: The non-metallic oxide is obtained by mixing the following components: SiO2: 67g, SeO2: 3g.

[0029] The metal oxide is obtained by mixing the following components: Al2O3: 23g, CaO: 11g, CuO: 8g, Fe2O3: 3g, MgO: 2g.

[0030] The nucleating agent is obtained by mixing the following components: talc: 7g, sorbitol: 1g.

[0031] The specifications of polypropylene fiber are as follows: length 10-18mm, diameter 30-40μm, aspect ratio 300-400, and density 0.91g / cm³.

[0032] 70g of non-metallic oxide and 47g of metallic oxide were mixed and calcined sequentially at 1000℃ for 80min, 1200℃ for 80min, and 1400℃ for 150min to obtain the calcined product.

[0033] The calcined material was mixed with 7g of nucleating agent and 0.4g of polypropylene fiber, and then ground until the specific surface area was ≥400m². 2 / kg yields the finished product.

[0034] Examples 2-5 Examples 2-5 provide a polypropylene fiber-modified expandable soil and rock roadbed modifier.

[0035] The difference between the above embodiments and Embodiment 1 is that the amount of each raw material component is different, as shown in Table 1.

[0036] Table 1. Amounts of each raw material component in Examples 1-5 and Comparative Examples 2-3

[0037] All other process parameters in the above embodiments are the same as those in Embodiment 1.

[0038] Examples 6-9 Examples 6-9 provide a polypropylene fiber-modified expandable soil and rock roadbed modifier.

[0039] The specific difference between the above embodiments and Embodiment 1 is that the compositions of the non-metallic oxides or metallic oxides are different, as shown below.

[0040] In Example 6: The non-metallic oxide was obtained by mixing the following components: SiO2: 65g, SeO2: 4g.

[0041] In Example 7: The non-metallic oxide was obtained by mixing the following components: SiO2: 69g, SeO2: 2g.

[0042] In Example 8, the metal oxide was obtained by mixing the following components: Al2O3: 21g, CaO: 13g, CuO: 7g, Fe2O3: 3.5g, MgO: 1.5g.

[0043] In Example 9, the metal oxide was obtained by mixing the following components: Al2O3: 25g, CaO: 9g, CuO: 9g, Fe2O3: 2.5g, MgO: 2.5g.

[0044] All other process parameters in the above embodiments are the same as those in Embodiment 1.

[0045] Examples 10-12 Examples 10-12 provide a polypropylene fiber-modified expandable soil and rock roadbed modifier.

[0046] The difference between the above embodiments and Embodiment 1 is that the composition of the nucleating agent is different, as shown below.

[0047] In Example 10: The nucleating agent was obtained by mixing the following components: talc: 6.5g, sorbitol: 1.5g.

[0048] In Example 11: The nucleating agent was obtained by mixing the following components: talc: 6g, sorbitol: 2g.

[0049] In Example 12: The nucleating agent was obtained by mixing the following components: talc: 7.5g, sorbitol: 0.5g.

[0050] All other process parameters in the above embodiments are the same as those in Embodiment 1.

[0051] Comparative Example Comparative Example 1 Comparative Example 1 provides a modified expansive soil-rock subgrade modifier.

[0052] This comparative example uses polypropylene fiber as a modifier for modified expansive soil and rock subgrade.

[0053] Comparative Examples 2-3 Comparative Examples 2 and 3 each provide a modified expansive soil-rock subgrade modifier.

[0054] The difference between the above comparative example and Example 1 is that the amount of each raw material component is different, as shown in Table 1.

[0055] All other process parameters in the above comparative examples are the same as those in Example 1.

[0056] Comparative Examples 4-6 Comparative Examples 4-6 each provide a modified expansive soil-rock subgrade modifier.

[0057] The difference between the above comparative example and Example 1 is as follows:

[0058] In Comparative Example 4, the non-metallic oxide was obtained by mixing the following components: SiO2: 63g, SeO2: 7g.

[0059] In Comparative Example 5, the metal oxide was obtained by mixing the following components: Al2O3: 11g, CaO: 23g, CuO: 6g, Fe2O3: 4g, MgO: 3g.

[0060] In Comparative Example 6: The nucleating agent was obtained by mixing the following components: talc: 5g, sorbitol: 3g.

[0061] All other process parameters in the above comparative examples are the same as those in Example 1.

[0062] Performance testing The polypropylene fiber-modified expansive soil and rock roadbed modifier prepared in the examples or comparative examples was mixed with expansive soil and rock with a water content of 25.3% at a dosage of 5%.

[0063] Then, molded specimens were obtained according to the specifications in JTG 3441-2024. The expansion force, expansion rate, and radial shrinkage rate of the molded specimens were tested. Unmodified expansive soil was used as a control example.

[0064] Test results are shown in Table 2.

[0065] Table 2. Performance test results of polypropylene fiber-modified expansive soil and rock subgrade modifier in the examples and comparative examples.

[0066] As can be seen from the test results in Table 2 above, the expansive soil subgrade modifier prepared by the technical solution provided in this application not only reduces the expansive force of the modified soil to below 32 kPa and controls the free expansion rate to within 15%, but also maintains the radial shrinkage rate below 5.2% in multiple wet and dry cycles.

[0067] By comparing the test results of Example 1 and Comparative Examples 1-2, it can be seen that Comparative Example 1, which directly uses polypropylene fiber as a modifier for expanding soil and rock subgrade, and Comparative Example 2, which directly uses active oxides and nucleating agents after calcination as a modifier for expanding soil and rock subgrade, have poor modification effects on expanding soil and rock. In contrast, the modifier prepared by calcining active oxides and nucleating agents and then introducing polypropylene fibers in this application has excellent modification effects on expanding soil and rock.

[0068] By comparing the test results of Examples 1-5 and Comparative Example 3, it can be seen that the amount of non-metallic oxide in Comparative Example 3 is low, while the amount of metal oxide is high, resulting in a poor modification effect of the prepared modifier on expansive soil. In contrast, the modifier prepared in this application, by designing and matching the amount of non-metallic oxide to 67-73 parts and the amount of metal oxide to 44-50 parts, exhibits excellent modification effect on expansive soil.

[0069] By comparing the test results of Examples 1, 6-9, and Comparative Examples 4-5, it can be seen that the amount of raw material components in non-metallic oxides and metal oxides has a significant impact on the performance of the modifier. In Comparative Example 4, the amount of raw material components in the non-metallic oxides was mismatched, and in Comparative Example 5, the amount of raw material components in the metal oxides was mismatched, resulting in a poor modification effect on expansive soils. In contrast, the modifier prepared in this application, composed of the following components by weight: SiO2: 65-69 parts, SeO2: 2-4 parts; and the following components by weight: Al2O3: 21-25 parts, CaO: 9-13 parts, CuO: 7-9 parts, Fe2O3: 2.5-3.5 parts, MgO: 1.5-2.5 parts, exhibits excellent modification effects on expansive soils.

[0070] By comparing the test results of Examples 1, 10-12, and Comparative Example 6, it can be seen that the modifier prepared in Comparative Example 6, using 5g of talc and 3g of sorbitol as nucleating agents, has a poor modification effect on expansive soil. In contrast, the modifier prepared in this application, using talc and sorbitol in a weight ratio of 6-7.5:0.5-2 as nucleating agents, exhibits excellent modification effects on expansive soil.

[0071] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A polypropylene fiber-modified expandable soil and rock subgrade modifier, characterized in that, Specifically, it includes the following components in parts by weight: 67-73 parts non-metallic oxide, 44-50 parts metallic oxide, 6-10 parts nucleating agent, and 0.2-0.6 parts polypropylene fiber; The non-metallic oxide is composed of the following components in parts by weight: SiO2: 65-69 parts, SeO2: 2-4 parts; The metal oxide is composed of the following components in parts by weight: Al2O3: 21-25 parts, CaO: 9-13 parts, CuO: 7-9 parts, Fe2O3: 2.5-3.5 parts, MgO: 1.5-2.5 parts; The nucleating agent is composed of talc and sorbitol in a weight ratio of 6-7.5:0.5-2.

2. The polypropylene fiber-modified expansive soil and rock subgrade modifier according to claim 1, characterized in that, Specifically, it includes the following components in parts by weight: 69-71 parts non-metallic oxide, 46-48 parts metallic oxide, 7-9 parts nucleating agent, and 0.3-0.5 parts polypropylene fiber.

3. The polypropylene fiber-modified expansive soil and rock subgrade modifier according to claim 1, characterized in that, The non-metallic oxide is composed of the following components in parts by weight: SiO2: 66-68 parts, SeO2: 2.5-3.5 parts.

4. The polypropylene fiber-modified expansive soil and rock subgrade modifier according to claim 1, characterized in that, The metal oxide comprises the following components in parts by weight: Al2O3: 22-24 parts, CaO: 10-12 parts, CuO: 7.5-8.5 parts, Fe2O3: 2.8-3.2 parts, MgO: 1.8-2.2 parts.

5. The polypropylene fiber-modified expansive soil and rock subgrade modifier according to claim 1, characterized in that, The nucleating agent is composed of talc and sorbitol in a weight ratio of 6.5-7:1-1.

5.

6. The polypropylene fiber-modified expansive soil and rock subgrade modifier according to claim 1, characterized in that, The specifications of the polypropylene fiber are as follows: length 6-20mm, diameter 20-50μm, aspect ratio 200-500, elastic modulus ≥3.5Gpa, and density 0.85-0.95g / cm³.

7. The preparation method of the polypropylene fiber-modified expansive soil and rock subgrade modifier according to any one of claims 1-6, characterized in that, Includes the following steps: Non-metallic oxides and metallic oxides are mixed and calcined at 950-1450℃ for 3-6 hours to obtain the calcined product. The calcined material was mixed with a nucleating agent and polypropylene fiber, and then ground until the specific surface area was ≥400 m². 2 / kg yields the finished product.

8. The preparation method of the polypropylene fiber modified expansive soil and rock subgrade modifier according to claim 1, characterized in that, The roasting process parameters are as follows: roasting at 950-1100℃ for 60-100 min, roasting at 1150-1300℃ for 60-100 min, and roasting at 1350-1450℃ for 100-200 min in sequence.

9. The application of the polypropylene fiber modified expansive soil and rock subgrade modifier as described in any one of claims 1-6 in the method of modifying expansive soil and rock.

10. A method for modifying expansive soil and rock, characterized in that, The expansive soil is modified using the polypropylene fiber modified expansive soil subgrade modifier according to any one of claims 1-6, with a dosage of 3-7%.

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