A preparation method for rapid prototyping regenerated water-stable base

Abstract

This invention belongs to the field of road construction, specifically to a method for preparing a rapidly formed regenerated water-stable base. The key technical features are as follows: RAP material, coarse crushed stone, and fine crushed stone are blended to obtain a mixture; the mixture is mixed with cement and a curing agent, then spread on the base, and rolled and cured to obtain the regenerated water-stable base. The amount of RAP material added is calculated according to the following formula: mRAP material / m mixture = (1-Cvi) • PQI; where mRAP material is the total mass of the RAP material, expressed in kg, and m mixture is the total mass of the mixture, expressed in kg; Cvi is the coefficient of variation of the RAP material, which is ≤1 and is a constant; and PQI is the pavement performance index of the RAP material, expressed in a constant. This invention not only conserves resources and enables the application of RAP material in water-stable bases, but also effectively improves the road performance of the water-stable base.

Description

Technical Field

[0001] The present invention relates to the technical field of road construction, and in particular to a method for preparing a rapid-forming regenerated water-stable base. Background Art

[0002] During traditional cement-stabilized gravel construction, the water-stabilized base requires a long curing period, typically 3 to 7 days, before the asphalt surface layer can be applied. Furthermore, the construction section must be closed during the curing period. In areas with high traffic volume and frequent congestion, traditional maintenance methods can cause congestion, reduce traffic efficiency, and impact both transportation and people's mobility. Furthermore, some roads lack traffic diversion facilities, requiring maintenance and renovation and expansion work to proceed while remaining open to traffic. In these circumstances, failure to promptly backfill the asphalt surface layer poses a significant traffic safety hazard.

[0003] Recycled Asphalt Powder (RAP) technology has been widely used in road pavements. With the increasing number of renovation and expansion projects, the total amount of RAP has continued to increase. Application of RAP in the pavement alone can no longer meet the demand for recycled asphalt mixture processing. Applying RAP to cement-stabilized crushed stone by adding an appropriate amount of waste asphalt mixture can not only significantly improve the various road performance properties of the pavement base layer, but also enhance its fatigue resistance, frost resistance, and scour resistance.

[0004] However, due to the uneven performance of RAP materials, the main application layer of waste asphalt material RAP in the base layer is the subbase layer, and it is rarely used in the upper base layer. And like ordinary water-stabilized base layers, the recycled water-stabilized base layer must be cured for 7 days before the next construction process can be carried out, which puts great pressure on the construction period.

[0005] In view of the above-mentioned defects in the prior art, the inventors, based on their rich experience and professional knowledge in engaging in such materials for many years, combined with theoretical analysis, conducted research and innovation, and developed a method for preparing a rapid prototyping regenerated water-stable base layer. Summary of the Invention

[0006] The purpose of the present invention is to develop a method for preparing a rapid-forming regenerated water-stable base, to evaluate the gradation variability and performance of recycled RAP, and to calculate the dosage of RAP material based on the evaluation results, thereby avoiding the degradation of the road performance of the water-stable base caused by excessive differences in the performance of the RAP material.

[0007] The above technical objectives of the present invention are achieved through the following technical solutions:

[0008] The present invention provides a method for preparing a rapid-forming regenerated water-stable base, comprising the steps of: mixing RAP material, coarse crushed stone material, fine crushed stone material, cement and a curing agent to obtain a mixture; spreading the mixture on a base, and rolling and curing the mixture to obtain a regenerated water-stable base;

[0009] The amount of RAP material added is calculated according to the following formula: RAP料 / m 混合料 =(1-C vi )·PQI;

[0010] Among them, m RAP料 is the total mass of RAP material, in kg, m 混合料 is the total mass of the mixture, in kg; C vi is the coefficient of variation of RAP material, ≤1, and the unit is a constant; PQI is the pavement performance index of RAP material, and the unit is a constant.

[0011] The variation of the old material gradation will cause the structural composition of the cement-stabilized RAP mixture to change, resulting in a change in the performance of the cement-stabilized RAP mixture. In order to understand the variation of the old material gradation, the present invention uses the above formula to limit the dosage of the RAP material according to the variation of the RAP material. The larger the coefficient of variation, the more serious the variation. When the variation is serious, the dosage of the RAP material is reduced to avoid the large dosage of the RAP material affecting the road performance of the water-stable base. When the variation is weak, the dosage of the RAP material can be increased. While ensuring the road performance of the water-stable base, the RAP material is used as much as possible to achieve the purpose of saving resources.

[0012] Furthermore, the RAP material was divided into three grades according to the particle size, and each grade was screened three times to calculate the C v i.

[0013] Furthermore, C vi The calculation formula is as follows: Cvi represents the coefficient of variation for the i-th sieve aperture, Pvi represents the mean of the fractional retention for the i-th sieve aperture, and σvi represents the standard deviation of the fractional retention for the i-th sieve aperture. The above formula is based on a limited particle size range for RAP material, with the goal of determining the variation of the RAP material from its particle size distribution.

[0014] Furthermore, the RAP material is divided into three grades according to the particle size, specifically divided into: asphalt milling material 1, with a particle size range of 10 to 20 mm; asphalt milling material 2, with a particle size range of 5 to 10 mm; asphalt milling material 3, with a particle size range of 0 to 5 mm.

[0015] Furthermore, PQI is the pavement performance index of RAP material, which is calculated by the pavement ride quality index RQI, pavement damage condition index PCI, pavement rutting depth index RDI, pavement skid resistance index SRI and pavement structural strength index PSSI.

[0016] The measurement of the above five indicators can not only evaluate the degree of damage of the RAP material during the use of the original pavement, but also determine the degree of damage of the asphalt material in the RAP material and the road performance of the original asphalt through indicators such as the rutting depth index. It helps to judge the asphalt content in the RAP material and then limit the amount of RAP material mixed in the water-stable base.

[0017] If the rutting depth index is low, it means that the penetration of asphalt in the original RAP material is large, and the incorporation degree of RAP material in the water-stable base material should be reduced. If the rutting depth index is high, it means that the performance indicators such as penetration and softening degree of asphalt in the original RAP material are high, and the incorporation amount of RAP material can be increased. The purpose of doing this is to ensure the rigidity of the water-stable base and improve the anti-cracking performance of the water-stable base.

[0018] Furthermore, the calculation formula of PQI is as follows:

[0019] PQI=(RQI+PCI+RDI+SRI+PSSI) / 5.

[0020] Furthermore, the moisture content of the RAP material is ≤3%, and the sand equivalent of the RAP material below 4.75 mm is ≥60%.

[0021] Furthermore, the mass ratio of the coarse crushed stone to the fine crushed stone is (2-3):1.

[0022] Furthermore, the amount of cement used is 3-5% of the total mass of the mixture.

[0023] Furthermore, the grading curve of RAP material adopts an S-type grading curve, and the sieve pass rate of particle size of 4.75mm and below is between the lower limit and the median of the specified range, and the sieve pass rate of particle size of 16mm and above is between the median and the upper limit. The upper and lower limits are determined according to the grading range in the DB32 / T3311-2017 Technical Specifications for Construction of Crack-Resistant Embedded Cement Stabilized Macadam Pavement Base.

[0024] Furthermore, the dosage of the health-preserving agent is 1 to 10% of the total mass of the mixture.

[0025] In summary, the present invention has the following beneficial effects:

[0026] The present invention jointly limits the blending amount of RAP material in the water-stable base mixture through the coefficient of variation of RAP material and the original pavement performance index. While saving resources and enabling the application of RAP material in the water-stable base, it effectively improves the unconfined compressive strength, splitting performance, compressive rebound modulus, shrinkage characteristics and scouring characteristics of the water-stable base. DETAILED DESCRIPTION

[0027] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, a preparation method of a rapid prototyping regenerated water-stable base layer proposed in accordance with the present invention, its specific implementation method, characteristics and effects are described in detail as follows.

[0028] Example 1

[0029] A method for preparing a rapid prototyping regenerated water-stable base. The RAP material in this embodiment was taken from a section of a highway. The road surface test data are as follows:

[0030] project PCI RQI RDI SRI PSSI Performance indicators 88.4 93.5 95.8 89.7 87.5

[0031] The PQI of the RAP material used in this embodiment is 90.98;

[0032] The RAP material in this embodiment is divided into three grades according to the particle size: asphalt milling material 1, with a particle size range of 13.2 to 26.5 mm; asphalt milling material 2, with a particle size range of 4.75 to 9.5 mm; asphalt milling material 3, with a particle size range of 0 to 4.75 mm. The RAP material is divided into three grades according to the particle size, and each grade is screened three times to calculate Cvi.

[0033] C vi The calculation formula is as follows: C vi represents the coefficient of variation of the sieve hole i, P vi represents the average value of the residual rate of the sieve hole i, σ vi represents the standard deviation of the residual rate of the sieve hole i, then C vi =0.45;

[0034] According to the formula m provided by the present invention RAP料 / m 混合料 =(1-C vi )·PQI calculation can be obtained: m RAP料 / m 混合料 =0.5.

[0035] Based on this, the design results of the mix ratio of the recycled water stabilized base in this embodiment are shown in the following table:

[0036]

[0037] The preparation method provided in this embodiment is as follows:

[0038] S1, mixing the above-mentioned asphalt milling materials 1 to 3 with coarse crushed stone and fine crushed stone to obtain a mixture;

[0039] S2. Cement and curing agent are added to the mixture, and a two-step mixing process is adopted with a mixing time of 15 seconds. After mixing, the mixture is relatively uniform, without white material, lumps, or obvious segregation.

[0040] S3. Set up elevation lines on site to ensure that the thickness of the paving and rolling on site meets the requirements (the lower surface has been basically cleaned and moistened with water before paving;

[0041] S4, paving: During the paving process, the paver adopts a tightrope leveling method, and the paving speed is about 2m / min;

[0042] S5. Use a double steel wheel roller for initial compaction, and a single steel wheel roller for secondary compaction using a method of first weak vibration and then strong vibration. Use a rubber wheel for final compaction. After final compaction, the pavement should be smooth, without obvious segregation, and the coarse aggregate should be evenly distributed.

[0043] S6. Immediately after compaction, cover with permeable geotextile for curing, and use a sprinkler truck to spray water to ensure that the surface of the water-stable base is moist during the 7-day curing period.

[0044] Example 2

[0045] A method for preparing a rapid prototyping regenerated water-stable base. The RAP material in this embodiment was taken from a section of a highway. The road surface test data are as follows:

[0046] project PCI RQI RDI SRI PSSI Performance indicators 78.7 36.4 94.6 87.9 88.5

[0047] The PQI of the RAP material used in this embodiment is 77.22;

[0048] The RAP material in this embodiment is divided into three grades according to the particle size: asphalt milling material 1, with a particle size range of 10-20 mm; asphalt milling material 2, with a particle size range of 5-10 mm; asphalt milling material 3, with a particle size range of 0-5 mm. The RAP material is divided into three grades according to the particle size, and each grade is screened three times to calculate C. vi .

[0049] C vi The calculation formula is as follows: Cvi represents the coefficient of variation of the sieve hole i, Pvi represents the average value of the sieve residue rate of the sieve hole i, σvi represents the standard deviation of the sieve residue rate of the sieve hole i, then Cvi = 0.42;

[0050] According to the formula m provided by the present invention RAP料 / m 混合料 =(1-C vi )·PQI calculation can be obtained: m RAP料 / m 混合料 =0.45.

[0051] Based on this, the design results of the mix ratio of the recycled water stabilized base in this embodiment are shown in the following table:

[0052]

[0053] The preparation method provided in this embodiment is as follows:

[0054] S1, mixing the above-mentioned asphalt milling materials 1 to 3 with coarse crushed stone and fine crushed stone to obtain a mixture;

[0055] S2. Cement and curing agent are added to the mixture, and a two-step mixing process is adopted with a mixing time of 15 seconds. After mixing, the mixture is relatively uniform, without white material, lumps, or obvious segregation.

[0056] S3. Set up elevation lines on site to ensure that the thickness of the paving and rolling on site meets the requirements. The lower surface has been basically cleaned and moistened with water before paving.

[0057] S4, paving: During the paving process, the paver adopts a tightrope leveling method, and the paving speed is about 2m / min;

[0058] S5. Use a double steel wheel roller for initial compaction, and a single steel wheel roller for secondary compaction using a method of first weak vibration and then strong vibration. Use a rubber wheel for final compaction. After final compaction, the pavement should be smooth, without obvious segregation, and the coarse aggregate should be evenly distributed.

[0059] S6. Immediately after compaction, cover with permeable geotextile for curing, and use a sprinkler truck to spray water to ensure that the surface of the water-stable base is moist during the 7-day curing period.

[0060] Example 3

[0061] A method for preparing a rapid prototyping regenerated water-stable base. The RAP material in this embodiment was taken from a section of a highway. The road surface test data are as follows:

[0062] project PCI RQI RDI SRI PSSI Performance indicators 88.1 91 90.4 80.5 86.3

[0063] The PQI of the RAP material used in this embodiment is 87.26;

[0064] The RAP material in this embodiment is divided into three grades according to the particle size: asphalt milling material 1, with a particle size range of 10 to 20 mm; asphalt milling material 2, with a particle size range of 5 to 10 mm; asphalt milling material 3, with a particle size range of 0 to 5 mm. The RAP material is divided into three grades according to the particle size, and each grade is screened three times to calculate Cvi.

[0065] C vi The calculation formula is as follows: C vi represents the coefficient of variation of the sieve hole i, P vi represents the average value of the residual rate of the sieve hole i, σvi represents the standard deviation of the residual rate of the sieve hole i, then Cvi=0.36;

[0066] According to the formula m provided by the present invention RAP料 / m 混合料 =(1-Cvi)·PQI calculation: m RAP料 / m 混合料 =0.55.

[0067] Based on this, the design results of the mix ratio of the recycled water stabilized base in this embodiment are shown in the following table:

[0068]

[0069]

[0070] The preparation method provided in this embodiment is as follows:

[0071] S1, mixing the above-mentioned asphalt milling materials 1 to 3 with coarse crushed stone and fine crushed stone to obtain a mixture;

[0072] S2. Cement and curing agent are added to the mixture, and a two-step mixing process is adopted with a mixing time of 15 seconds. After mixing, the mixture is relatively uniform, without white material, lumps, or obvious segregation.

[0073] S3. Set up elevation lines on site to ensure that the thickness of the paving and rolling on site meets the requirements. The lower surface has been basically cleaned and moistened with water before paving.

[0074] S4, paving: During the paving process, the paver adopts a tightrope leveling method, and the paving speed is about 2m / min;

[0075] S5. Use a double steel wheel roller for initial compaction, and a single steel wheel roller for secondary compaction using a method of first weak vibration and then strong vibration. Use a rubber wheel for final compaction. After final compaction, the pavement should be smooth, without obvious segregation, and the coarse aggregate should be evenly distributed.

[0076] S6. Immediately after compaction, cover with permeable geotextile for curing, and use a sprinkler truck to spray water to ensure that the surface of the water-stable base is moist during the 7-day curing period.

[0077] Comparative Example 1

[0078] A method for preparing a rapid prototyping regenerated water-stable base layer, wherein the RAP material in this embodiment is the same as that in Example 1;

[0079] The design results of the mix ratio of the regenerated water stabilized base in this embodiment are shown in the following table:

[0080]

[0081] The preparation method provided in this embodiment is as follows:

[0082] S1, mixing the above-mentioned asphalt milling materials 1 to 3 with coarse crushed stone and fine crushed stone to obtain a mixture;

[0083] S2. Cement and curing agent are added to the mixture, and a two-step mixing process is adopted with a mixing time of 15 seconds. After mixing, the mixture is relatively uniform, without white material, lumps, or obvious segregation.

[0084] S3. Set up elevation lines on site to ensure that the thickness of the paving and rolling on site meets the requirements (the lower surface has been basically cleaned and moistened with water before paving;

[0085] S4, paving: During the paving process, the paver adopts a tightrope leveling method, and the paving speed is about 2m / min;

[0086] S5. Use a double steel wheel roller for initial compaction, and a single steel wheel roller for secondary compaction using a method of first weak vibration and then strong vibration. Use a rubber wheel for final compaction. After final compaction, the pavement should be smooth, without obvious segregation, and the coarse aggregate should be evenly distributed.

[0087] S6. Immediately after compaction, cover with permeable geotextile for curing, and use a sprinkler truck to spray water to ensure that the surface of the water-stable base is moist during the 7-day curing period.

[0088] Comparative Example 2

[0089] A method for preparing a rapid prototyping regenerated water-stable base layer, wherein the RAP material in this embodiment is the same as that in Example 2;

[0090] The design results of the mix ratio of the regenerated water stabilized base in this embodiment are shown in the following table:

[0091]

[0092] The preparation method provided in this embodiment is as follows:

[0093] S1, mixing the above-mentioned asphalt milling materials 1 to 3 with coarse crushed stone and fine crushed stone to obtain a mixture;

[0094] S2. Cement and curing agent are added to the mixture, and a two-step mixing process is adopted with a mixing time of 15 seconds. After mixing, the mixture is relatively uniform, without white material, lumps, or obvious segregation.

[0095] S3. Set up elevation lines on site to ensure that the thickness of the paving and rolling on site meets the requirements. The lower surface has been basically cleaned and moistened with water before paving.

[0096] S4, paving: During the paving process, the paver adopts a tightrope leveling method, and the paving speed is about 2m / min;

[0097] S5. Use a double steel wheel roller for initial compaction, and a single steel wheel roller for secondary compaction using a method of first weak vibration and then strong vibration. Use a rubber wheel for final compaction. After final compaction, the pavement should be smooth, without obvious segregation, and the coarse aggregate should be evenly distributed.

[0098] S6. Immediately after compaction, cover with permeable geotextile for curing, and use a sprinkler truck to spray water to ensure that the surface of the water-stable base is moist during the 7-day curing period.

[0099] Performance Testing

[0100] 1. The strength of the water-stable base of Examples 1 to 3 and Comparative Examples 1 to 2 was tested using the unconfined compressive strength test method T0805-1994 of the "Test Procedure for Inorganic Binder Stabilized Materials for Highway Engineering" (JTG E51-2009). The results are as follows:

[0101] project 1d strength / MPa 3d strength / MPa 7d strength / MPa Example 1 2.9 3.5 4.6 Example 2 3.1 3.7 4.8 Example 3 2.8 3.8 4.5 Comparative Example 1 1.6 2.4 3.1 Comparative Example 2 1.7 2.6 3.3

[0102] According to the data comparison between Comparative Example 1 and Example 1 and the data comparison between Comparative Example 2 and Example 2, it can be seen that if the formula provided by the present invention is not used to limit the amount of RAP material added, the strength of the water-stable base layer will be reduced.

[0103] 2. The water-stable bases of Examples 1 to 3 and Comparative Examples 1 to 2 were cored. The results are shown in the following table:

[0104] project Coring results Example 1 Dense appearance and well-formed bottom Example 2 Dense appearance and well-formed bottom Example 3 Dense appearance and well-formed bottom Comparative Example 1 The appearance is dense, the bottom is well formed, and there are holes Comparative Example 2 The appearance is dense, the bottom is well formed, and there are holes

[0105] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been presented as a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with the present profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a rapid prototyping regenerated water-stable base layer, characterized in that: The RAP material, crushed stone coarse material and crushed stone fine material are mixed to obtain a mixture; the mixture is mixed with cement and curing agent and then spread on the base layer, and after rolling and curing, a regenerated water-stable base layer is obtained; The amount of RAP material added is calculated according to the following formula: RAP料 / m 混合料 =(1-C vi ) PQI; Among them, m RAP料 is the total mass of RAP material, in kg, m 混合料 is the total mass of the mixture, in kg; C vi is the coefficient of variation of RAP material, ≤1, and the unit is a constant; PQI is the pavement performance index of RAP material, and the unit is a constant; The RAP material is divided into three grades according to the particle size, and each grade is screened three times to calculate the C vi ; The C vi The calculation formula is as follows: ; C vi represents the coefficient of variation of the sieve hole i, P vi represents the average value of the residual rate of the sieve hole i, σ vi It represents the standard deviation of the residual rate of the sieve hole at the i-th level; The PQI is the pavement performance index of RAP material, which is calculated by the pavement ride quality index RQI, pavement damage index PCI, pavement rutting depth index RDI, pavement skid resistance index SRI and pavement structural strength index PSSI.

2. The method for preparing a rapid prototyping regenerated water-stable base according to claim 1, characterized in that: The RAP material is divided into three grades according to the particle size, specifically divided into: asphalt milling material 1, with a particle size range of 10~20mm; asphalt milling material 2, with a particle size range of 5~10mm; asphalt milling material 3, with a particle size range of 0~5mm.

3. The method for preparing a rapid prototyping regenerated water-stable base according to claim 1, characterized in that: The calculation formula of the PQI is as follows: PQI=(RQI+PCI+RDI+SRI+PSSI) / 5.

4. The method for preparing a rapid prototyping regenerated water-stable base according to claim 1, characterized in that: The moisture content of the RAP material is ≤3%, and the sand equivalent of the RAP material below 4.75 mm is ≥60%.

5. The method for preparing a rapid prototyping regenerated water-stable base according to claim 1, characterized in that: The amount of cement used is 3-5% of the total mass of the mixture.

6. The method for preparing a rapid prototyping regenerated water-stable base according to claim 1, characterized in that: The gradation curve of the RAP material adopts an S-type gradation curve.

7. The method for preparing a rapid prototyping regenerated water-stable base according to claim 1, characterized in that: The dosage of the health-free agent is 0.1-10% of the total mass of the mixture.

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