Roadbed mixture and roadbed preparation method

Abstract

The invention discloses a roadbed mixture and a roadbed preparation method, and relates to the technical field of high-leakage roadbeds. The road base mixture is prepared from the following raw materials in parts by mass: 20 to 30 parts of cement, 15 to 20 parts of modified phosphogypsum, 20 to 25 parts of building solid waste filler, 8 to 10 parts of gravel, 10 to 15 parts of modified coal gasification slag, 5 to 10 parts of sodium silicate, 20 to 25 parts of deionized water and 1.8 to 2.2 parts of composite synergist, the preparation method of the roadbed comprises the following steps: filling a roadbed mixture into a mold, vibrating for 2-6 minutes, standing for 24-30 hours, demolding, and maintaining for 28 days to obtain the roadbed. The components such as the modified ardealite, the modified coal gasification slag and the composite synergist are introduced, so that the compressive strength, the shear strength, the water resistance and the durability of the high-leakage roadbed are improved at the same time. Therefore, the method has a wider application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-leakage subgrade, and particularly relates to a road base mixture and a subgrade preparation method. BACKGROUND

[0002] In the subgrade engineering, the building solid waste components such as recycled aggregates, broken bricks and concrete blocks are often processed into the core components of the road base mixture to realize the recycling.

[0003] However, in the actual application process, the subgrade still has many performance short boards: firstly, the water permeability and bearing capacity are unbalanced, if the high water permeability is emphasized, the particles are coarse and the interlocking effect is insufficient, so that the bearing strength and deformation resistance of the subgrade are difficult to meet the driving load requirements; if the bearing stability is pursued, the proportion of fine materials needs to be increased, which is easy to block the internal pores, so that the permeability coefficient is greatly attenuated and the water cannot be quickly drained; secondly, the water resistance is poor, which is easy to soften and disintegrate after encountering water, destroys the overall structural integrity of the mixture, and causes the compressive strength to significantly decrease after soaking; thirdly, the durability is poor, after multiple dry-wet alternation or freeze-thaw cycles, the particles are easy to peel off and the quality is easy to lose, and then the compressive strength continuously attenuates, which is particularly prominent in the rainy and cold regions and other harsh environments. Therefore, the compressive strength, shear strength, water resistance and durability of the existing high-leakage subgrade still need to be improved. SUMMARY

[0004] The present application relates to the technical field of high-leakage subgrade, and particularly relates to a road base mixture and a subgrade preparation method. The existing high-leakage subgrade still has the problems of poor compressive strength, shear strength, water resistance and durability.

[0005] The purpose of the present application can be achieved by the following technical solutions: A road base mixture, comprising the following raw materials in parts by mass: cement 20-30 parts, modified phosphogypsum 15-20 parts, building solid waste filler 20-25 parts, broken stone 8-10 parts, modified coal gasification slag 10-15 parts, sodium silicate 5-10 parts, deionized water 20-25 parts, and composite synergist 1.8-2.2 parts. The modified phosphogypsum is prepared from calcium carbide slag, phosphogypsum, sodium polycarboxylate dispersant and silane coupling agent KH-550. The modified coal gasification slag is a coal gasification slag modified by lauryl betaine and rhamnolipid. The composite synergist is prepared from sodium alginate, sodium tripolyphosphate and nano silicon dioxide.

[0006] Preferably, the preparation method of the modified phosphogypsum is as follows: A1: adjust the pH of deionized water to 5.5-6.5 with glacial acetic acid, then add the silane coupling agent KH-550 and stir uniformly to obtain a coupling agent dispersion liquid; A2: Mix carbide slag and phosphogypsum evenly, then adjust the pH to 6-7 with glacial acetic acid, add sodium polycarboxylate dispersant and stir for 3-5 minutes, then add coupling agent dispersion and stir for 15-20 minutes, and then age at 20-25℃ and 60%-70% relative humidity for 24-32 hours, stirring once every 8 hours to obtain modified phosphogypsum.

[0007] Preferably, the mass ratio of deionized water to silane coupling agent KH-550 in A1 is 40-50:0.5; The mass ratio of the carbide slag, phosphogypsum, sodium polycarboxylate dispersant, and coupling agent dispersion described in A2 is 10-15:80-90:0.3:5-7.

[0008] Preferably, the modified coal gasification slag is prepared as follows: Add lauryl betaine and rhamnolipin to deionized water and stir for 10-15 minutes. Then add coal gasification slag and ultrasonically disperse for 30-50 minutes. Then centrifuge and dry the precipitate at 80-85℃ for 4-6 hours to obtain modified coal gasification slag.

[0009] Preferably, the mass ratio of deionized water, lauryl betaine, rhamnolipid, and coal gasification slag is 140-150:0.1:0.1:20; The particle size of the coal gasification slag is 0.01-10 mm.

[0010] Preferably, the preparation method of the composite synergist is as follows: Sodium alginate and sodium tripolyphosphate are added to deionized water and stirred for 10-15 minutes. Then, nano-silica is added and ultrasonically dispersed for 20-30 minutes. Finally, spray drying is carried out at an inlet air temperature of 160-180℃ and an outlet air temperature of 80-90℃ to obtain the composite synergist.

[0011] Preferably, the mass ratio of the deionized water, sodium alginate, sodium tripolyphosphate, and nano silica is 40-50:2:3:3; The particle size of the composite synergist is 10-50 μm.

[0012] Preferably, the preparation method of the road base mixture is as follows: B1: Add the composite synergist to deionized water and disperse it ultrasonically to obtain a synergist suspension; B2: Mix cement, modified phosphogypsum, construction waste filler, crushed stone, modified coal gasification slag, and sodium silicate evenly, then add synergist suspension and stir for 8-15 minutes to obtain road base mixture.

[0013] Preferably, in the construction solid waste filler described in B2, the mass fraction of particles with a diameter of 0.01-1mm is 5%-10%, the mass fraction of particles with a diameter of 1-5mm is 15%-25%, the mass fraction of particles with a diameter of 5-10mm is 20%-25%, and the mass fraction of particles with a diameter of 10-30mm is 40%-60%. The particle size of the crushed stone described in B2 is 5-20 mm.

[0014] A method for preparing a roadbed includes the following steps: The road base mixture is loaded into a mold and vibrated for 2-6 minutes. Then it is left to stand for 24-30 hours at 20℃ and 95% relative humidity. After demolding, it is cured for 28 days at 20℃ and 95% relative humidity to obtain the roadbed.

[0015] The beneficial effects of this invention are: This invention provides a road base mixture and a method for preparing roadbed. The invention simultaneously improves the compressive strength, shear strength, water resistance, and durability of highly permeable roadbeds through the following methods.

[0016] (1) The modified phosphogypsum of this invention can build an interfacial bridge between phosphogypsum and components such as cement and coal gasification slag, reducing interfacial cracks; at the same time, sodium polycarboxylate salt can make phosphogypsum particles evenly dispersed, avoiding agglomeration and the formation of weak areas. Combined with the acid-base neutralization reaction between carbide slag and phosphogypsum, it can jointly improve the overall structural density and further improve the compressive strength. The amino group of the modified coupling agent can undergo cross-linking reaction with other components, strengthening the chemical bonding force between particles; the evenly dispersed phosphogypsum particles can fill the gaps between aggregates, increase the particle contact area, improve physical adsorption force, and improve cohesion. After modification, the organic long chain of silane coupling agent KH-550 will form a hydrophobic film to reduce water intrusion; carbide slag can neutralize the acidic impurities of phosphogypsum and inhibit the dissolution of hydration products; sodium polycarboxylate salt can also optimize the structure of hydration products and improve their water stability. The three factors work together to effectively improve the softening coefficient. Modified phosphogypsum has a dense structure and low soluble impurity content. Its addition can reduce the erosion, expansion, and contraction damage to the internal structure caused by moisture during alternating wet and dry periods. The tightly bonded interfacial structure can also resist stress changes caused by wet and dry cycles, reducing crack formation and thus reducing mass and strength loss. The densified structure can reduce the internal free water content, weakening the destructive effect of water freezing and expansion during freeze-thaw cycles. The interfacial bonding effect of silane coupling agent KH-550 can inhibit the propagation of microcracks caused by freeze-thaw cycles, preventing overall structural damage, thereby reducing mass and strength loss and improving durability.

[0017] (2) The modified coal gasification slag of this invention has enhanced surface activity, which can tightly bond with the interface of cement hydration products, composite synergists and other components; it can also fill the voids inside the mixture to form a dense skeleton structure, reduce stress concentration and thus improve the overall compressive strength; the active components such as silica and alumina contained in the coal gasification slag can undergo secondary reactions with cement hydration products to generate additional cementitious substances, further strengthening the structural strength. After modification with surfactant, the adsorption of coal gasification slag with components such as sodium alginate and sodium tripolyphosphate is enhanced, and the interparticle bonding force is improved; after the modified coal gasification slag is evenly distributed in the mixture, it can also form a continuous bonding network with cement paste, modified phosphogypsum and other cementitious phases, improving cohesion. When uniformly dispersed modified coal gasification slag particles are subjected to force, they will interlock with each other, hindering relative sliding, which increases the internal friction angle of the mixture and further improves the shear resistance. The interfacial film formed during the surface modification of coal gasification slag can prevent moisture from penetrating into the particle interior and interfacial gaps, reducing the damage of moisture to the bonding structure. The dense skeleton structure and strong interfacial bonding can reduce the risk of particle peeling and structural loosening caused by moisture, improve the softening coefficient, and enhance water resistance. The modified coal gasification slag particles exhibit improved stability, and the interfacial bonding is less prone to cracking and detachment due to alternating wet and dry conditions, thus improving the ability to maintain structural integrity and reducing the loss of mass and compressive strength. The dense structure reduces the internal pore water content, thereby reducing the internal stress caused by freeze-thaw contraction. The strong bonding force between particles can resist freeze-thaw damage, significantly reducing mass loss and compressive strength loss, and improving durability.

[0018] (3) In the composite synergist of this invention, nano-silica can fill the tiny pores of cement, modified phosphogypsum and other components, making the mixture structure more compact; the polymer chains of sodium alginate can form physical entanglement or hydrogen bonds between particles, enhancing the interfacial bonding force of each component and reducing crack propagation under stress; sodium tripolyphosphate can make the composite synergist mix more evenly with other raw materials, avoiding weak points in strength caused by local agglomeration. Sodium alginate can form a continuous adhesive film on the surface of cement hydration products and modified aggregates, improving the adsorption force between particles; the strong interfacial adsorption effect brought by the high specific surface area of ​​nano-silica, combined with the adhesive effect of sodium alginate, further enhances the bonding effect between particles. Sodium tripolyphosphate's chelating effect can bind with calcium ions in cement hydration products, improving the interfacial stability of inorganic components and reducing water erosion. The dense siloxane film formed on the particle surface by nano-silica reduces hydrophilicity. Simultaneously, the composite network structure constructed by sodium alginate, nano-silica, and sodium tripolyphosphate resists water swelling and erosion. These three elements synergistically improve the softening coefficient and enhance water resistance. The densified structure reduces water absorption and precipitation during wet-dry cycles, minimizing damage to the structure caused by salt migration and crystal precipitation, thus reducing mass loss. Reduced porosity decreases internal ice water volume, nano-silica enhances interfacial strength, and the elasticity of sodium alginate alleviates volumetric stress generated by freeze-thaw cycles, reducing compressive strength loss and significantly improving durability.

[0019] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. The embodiments described below are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1: A method for preparing road base mixture and subgrade is as follows: S1: Adjust the pH of 40g of deionized water to 5.5 with glacial acetic acid, then add 0.5g of silane coupling agent KH-550 and stir for 30min to obtain a coupling agent dispersion; S2: Mix 10g of carbide slag and 80g of phosphogypsum and stir for 1 minute. Then adjust the pH to 6 with glacial acetic acid, add 0.3g of sodium polycarboxylate dispersant and stir for 3 minutes. Then add 5g of coupling agent dispersion and stir for 15 minutes. Then age at 20℃ and 60% relative humidity for 24 hours, stirring once every 8 hours to obtain modified phosphogypsum. S3: Add 0.1g lauryl betaine and 0.1g rhamnolipid to 140g deionized water and stir for 10min. Then add 20g coal gasification slag with a particle size of 0.01-10mm and ultrasonically disperse for 30min. Then centrifuge and dry the precipitate at 80℃ for 4h to obtain modified coal gasification slag. S4: Add 2g sodium alginate and 3g sodium tripolyphosphate to 40g deionized water and stir for 10min. Then add 3g nano silica and ultrasonically disperse for 20min. Then spray dry at an inlet air temperature of 160℃ and an outlet air temperature of 80℃ to obtain a composite synergist with a particle size of 10-50μm. S5: Add 1.8g of compound synergist to 20g of deionized water and ultrasonically disperse for 5min to obtain a synergist suspension; S6: Mix 20g cement (P·O 42.5 grade), 15g modified phosphogypsum, 20g construction waste filler, 8g crushed stone with a particle size of 5-20mm, 10g modified coal gasification slag, and 5g sodium silicate and stir for 5 minutes. Then add 21.8g synergist suspension and stir for 8 minutes to obtain road base mixture; wherein, the mass fraction of construction waste filler with a particle size of 0.01-1mm is 5%, the mass fraction of a particle size of 1-5mm is 15%, the mass fraction of a particle size of 5-10mm is 20%, and the mass fraction of a particle size of 10-30mm is 60%. S7: Load the road base mixture into the mold and vibrate for 2 minutes. Then let it stand for 24 hours at 20℃ and 95% relative humidity. After demolding, cure for 28 days at 20℃ and 95% relative humidity to obtain the roadbed.

[0022] Example 2: A method for preparing a road base mixture and subgrade is as follows: S1: Adjust the pH of 45g of deionized water to 6 with glacial acetic acid, then add 0.5g of silane coupling agent KH-550 and stir for 40min to obtain a coupling agent dispersion; S2: Mix 13g of carbide slag and 85g of phosphogypsum and stir for 1.5min. Then adjust the pH to 6.5 with glacial acetic acid. Add 0.3g of sodium polycarboxylate dispersant and stir for 4min. Then add 6g of coupling agent dispersion and stir for 18min. Then age at 23℃ and 65% relative humidity for 24h, stirring once every 8h to obtain modified phosphogypsum. S3: Add 0.1g lauryl betaine and 0.1g rhamnolipid to 145g deionized water and stir for 13min. Then add 20g coal gasification slag with a particle size of 0.01-10mm and ultrasonically disperse for 40min. Then centrifuge and dry the precipitate at 83℃ for 5h to obtain modified coal gasification slag. S4: Add 2g sodium alginate and 3g sodium tripolyphosphate to 45g deionized water and stir for 13min. Then add 3g nano silica and ultrasonically disperse for 25min. Then spray dry at an inlet air temperature of 170℃ and an outlet air temperature of 85℃ to obtain a composite synergist with a particle size of 10-50μm. S5: Add 2g of compound synergist to 23g of deionized water and ultrasonically disperse for 8min to obtain a synergist suspension; S6: Mix 25g cement (P·O 42.5 grade), 17.5g modified phosphogypsum, 22.5g construction waste filler, 9g crushed stone with a particle size of 5-20mm, 12.5g modified coal gasification slag, and 7.5g sodium silicate and stir for 7 minutes. Then add 25g synergist suspension and stir for 11 minutes to obtain road base mixture; wherein, the mass fraction of construction waste filler with a particle size of 0.01-1mm is 8%, the mass fraction of a particle size of 1-5mm is 20%, the mass fraction of a particle size of 5-10mm is 22%, and the mass fraction of a particle size of 10-30mm is 50%. S7: The road base mixture is loaded into the mold and vibrated for 4 minutes. Then it is left to stand for 27 hours at 20℃ and 95% relative humidity. After demolding, it is cured for 28 days at 20℃ and 95% relative humidity to obtain the roadbed.

[0023] Example 3: A method for preparing a road base mixture and subgrade is as follows: S1: Adjust the pH of 50g of deionized water to 6.5 with glacial acetic acid, then add 0.5g of silane coupling agent KH-550 and stir for 50min to obtain a coupling agent dispersion; S2: Mix 15g of carbide slag and 90g of phosphogypsum for 2 minutes, then adjust the pH to 7 with glacial acetic acid, add 0.3g of sodium polycarboxylate dispersant and stir for 5 minutes, then add 7g of coupling agent dispersion and stir for 20 minutes, and then age at 25℃ and 70% relative humidity for 32 hours, stirring once every 8 hours to obtain modified phosphogypsum; S3: Add 0.1g lauryl betaine and 0.1g rhamnolipid to 150g deionized water and stir for 15min. Then add 20g coal gasification slag with a particle size of 0.01-10mm and ultrasonically disperse for 50min. Then centrifuge and dry the precipitate at 85℃ for 6h to obtain modified coal gasification slag. S4: Add 2g sodium alginate and 3g sodium tripolyphosphate to 50g deionized water and stir for 15min. Then add 3g nano silica and ultrasonically disperse for 30min. Then spray dry at an inlet air temperature of 180℃ and an outlet air temperature of 90℃ to obtain a composite synergist with a particle size of 10-50μm. S5: Add 2.2g of compound synergist to 25g of deionized water and ultrasonically disperse for 10min to obtain a synergist suspension; S6: Mix 30g cement (P·O 42.5 grade), 20g modified phosphogypsum, 25g construction waste filler, 10g crushed stone with a particle size of 5-20mm, 15g modified coal gasification slag, and 10g sodium silicate and stir for 10 minutes. Then add 27.2g synergist suspension and stir for 15 minutes to obtain the road base mixture. Among them, the mass fraction of construction waste filler with a particle size of 0.01-1mm is 10%, the mass fraction of a particle size of 1-5mm is 25%, the mass fraction of a particle size of 5-10mm is 25%, and the mass fraction of a particle size of 10-30mm is 40%. S7: The road base mixture is loaded into the mold and vibrated for 6 minutes. Then it is left to stand for 30 hours at 20℃ and 95% relative humidity. After demolding, it is cured for 28 days at 20℃ and 95% relative humidity to obtain the roadbed.

[0024] Comparative Example 1: Compared with Example 1, this comparative example only did not add "modified phosphogypsum" in the preparation process of S6. All other steps and parameters were the same, and will not be repeated here. The final road base mixture and subgrade were obtained.

[0025] Comparative Example 2: Compared with Example 1, this comparative example only did not add "modified coal gasification slag" in the preparation process of S6. All other steps and parameters were the same, and will not be repeated here. The final result was road base mixture and subgrade.

[0026] Comparative Example 3: Compared with Example 1, this comparative example only did not add the "composite synergist" in the preparation process of S6. All other steps and parameters were the same, and will not be repeated here. The final result was road base mixture and subgrade.

[0027] Performance testing: Determination of compressive strength: Referring to the unconfined compressive strength test standard in GB / T 50123-2019 "Standard for Geotechnical Testing Methods", the unconfined compressive strength (MPa) of the roadbeds prepared in Examples 1-3 and Comparative Examples 1-3 of this invention with a curing age of 28 days was determined at a loading rate of 1 mm / min. The test results are shown in Table 1. Determination of cohesion and angle of internal friction: Referring to the direct shear test standard in GB / T 50123-2019 "Standard for Geotechnical Testing Methods", the cohesion (kPa) and internal friction angle (°) of the roadbeds prepared by Examples 1-3 and Comparative Examples 1-3 of this invention with a curing age of 28 days were determined with a vertical stress of 300 kPa. The test results are shown in Table 1. Permeability testing: Referring to GB / T 50123-2019 "Standard for Geotechnical Testing Methods", the permeability coefficients of the roadbeds prepared in Examples 1-3 and Comparative Examples 1-3 of this invention with a curing age of 28 days were determined, and the test results are shown in Table 1. Water resistance test: Referring to GB / T 50123-2019 "Standard for Geotechnical Testing Methods", the softening coefficient of the roadbeds prepared in Examples 1-3 and Comparative Examples 1-3 of this invention with a curing age of 28 days was determined after immersion in water for 28 days (water level 20 mm above the top surface of the sample, water temperature 20℃). The test results are shown in Table 1.

[0028] Table 1: Performance test results of Examples 1-3 and Comparative Examples 1-3

[0029] Durability testing: The mass loss (%) and compressive strength loss (%) of the roadbeds prepared in Examples 1-3 and Comparative Examples 1-3 of the present invention with a curing age of 28 days were measured after 100 wet-dry cycles (one cycle is: soaking in deionized water at 25℃ for 12h + drying at 25℃ for 12h) or 100 freeze-thaw cycles (one cycle is: freezing at -20℃ for 12h + thawing at 20℃ for 12h). The test results are shown in Table 2.

[0030] Table 2: Durability test results of Examples 1-3 and Comparative Examples 1-3

[0031] Data Analysis: As can be seen from Tables 1 and 2, the high permeability roadbed prepared by the embodiments of the present invention has excellent compressive strength, shear strength, permeability, water resistance and durability.

[0032] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A road base course mixture, characterized in that, The raw materials include the following parts by weight: 20-30 parts cement, 15-20 parts modified phosphogypsum, 20-25 parts construction solid waste filler, 8-10 parts crushed stone, 10-15 parts modified coal gasification slag, 5-10 parts sodium silicate, 20-25 parts deionized water, and 1.8-2.2 parts composite synergist. The modified phosphogypsum is prepared from carbide slag, phosphogypsum, sodium polycarboxylate dispersant, and silane coupling agent KH-550. The modified coal gasification slag is coal gasification slag that has been modified by a composite of lauryl betaine and rhamnolipin; The composite synergist is prepared from sodium alginate, sodium tripolyphosphate, and nano-silica.

2. The road base mixture according to claim 1, characterized in that, The modified phosphogypsum is prepared as follows: A1: Adjust the pH of deionized water to 5.5-6.5, then add silane coupling agent KH-550 and stir well to obtain a coupling agent dispersion; A2: Mix carbide slag and phosphogypsum evenly, then adjust the pH to 6-7, add sodium polycarboxylate dispersant and stir for 3-5 minutes, then add coupling agent dispersion and stir for 15-20 minutes, and then age for 24-32 hours to obtain modified phosphogypsum.

3. The road base mixture according to claim 2, characterized in that, The mass ratio of deionized water to silane coupling agent KH-550 in A1 is 40-50:0.5; The mass ratio of the carbide slag, phosphogypsum, sodium polycarboxylate dispersant, and coupling agent dispersion described in A2 is 10-15:80-90:0.3:5-7.

4. The road base mixture according to claim 1, characterized in that, The method for preparing the modified coal gasification slag is as follows: Add lauryl betaine and rhamnolipin to deionized water and stir for 10-15 minutes. Then add coal gasification slag and ultrasonically disperse for 30-50 minutes. Then centrifuge and dry to obtain modified coal gasification slag.

5. The road base mixture according to claim 4, characterized in that, The mass ratio of deionized water, lauryl betaine, rhamnolipin, and coal gasification slag is 140-150:0.1:0.1:

20.

6. The road base mixture according to claim 1, characterized in that, The preparation method of the composite synergist is as follows: Sodium alginate and sodium tripolyphosphate were added to deionized water and stirred for 10-15 minutes. Then, nano-silica was added and ultrasonically dispersed for 20-30 minutes. Finally, the mixture was spray-dried to obtain the composite synergist.

7. The road base mixture according to claim 6, characterized in that, The mass ratio of deionized water, sodium alginate, sodium tripolyphosphate, and nano silica is 40-50:2:3:

3.

8. The road base mixture according to claim 1, characterized in that, The preparation method of the road base mixture is as follows: B1: Add the composite synergist to deionized water and disperse it ultrasonically to obtain a synergist suspension; B2: Mix cement, modified phosphogypsum, construction waste filler, crushed stone, modified coal gasification slag, and sodium silicate evenly, then add synergist suspension and stir for 8-15 minutes to obtain road base mixture.

9. The road base mixture according to claim 8, characterized in that, In the construction solid waste filler described in B2, the mass fraction of particles with a diameter of 0.01-1mm is 5%-10%, the mass fraction of particles with a diameter of 1-5mm is 15%-25%, the mass fraction of particles with a diameter of 5-10mm is 20%-25%, and the mass fraction of particles with a diameter of 10-30mm is 40%-60%. The particle size of the crushed stone described in B2 is 5-20 mm.

10. A method for preparing a roadbed, characterized in that, Includes the following steps: The road base mixture is loaded into the mold and vibrated for 2-6 minutes, then left to stand for 24-30 hours. After demolding, it is cured for 28 days to obtain the roadbed.

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