CN113668328B

CN113668328B - High-quality recycling treatment method when RAP bulk blending amount is more than 40%

Info

Publication number: CN113668328B
Application number: CN202111010498.6A
Authority: CN
Inventors: 刘光东; 张超; 魏必成; 贾晓娟; 高信春
Original assignee: Fujian Provincial Expressway Datong Detection Co ltd; Fujian Provincial Expressway Technology Consulting Co ltd
Current assignee: Fujian Provincial Expressway Datong Detection Co ltd; Fujian Provincial Expressway Technology Consulting Co ltd
Priority date: 2021-08-31
Filing date: 2021-08-31
Publication date: 2023-06-02
Anticipated expiration: 2041-08-31
Also published as: CN113668328A

Abstract

The invention discloses a processing method for realizing high-dosage and high-quality cyclic recycling of RAP, which comprises the following steps: s1, setting a control standard of RAP in a reclaimed asphalt utilization mixture; s2, milling and recycling old pavement, and uniformly performing primary screening on the RAP recovered by milling; s3, crushing and shaping the primarily screened RAP; s4, grading and screening the crushed and shaped RAP, and grading and selecting the RAP meeting the index standard in the step S1; s5, performing plant-mixed thermal recycling on the selected RAP. The invention provides a treatment method for realizing high-doping amount and high-quality recycling of RAP, which optimizes the pretreatment process of the RAP, firstly performs primary screening on the RAP, and then performs crushing, re-grading and screening on the RAP on a screen until the treated RAP meets the controllable use requirement of the high-doping amount, thereby remarkably improving the efficiency and quality of standardized treatment and reducing the variability of the RAP.

Description

High-quality recycling treatment method when RAP bulk blending amount is more than 40%

Technical Field

The invention relates to the technical field of road engineering materials, in particular to a processing method for realizing high-dosage and high-quality cyclic recycling of RAP.

Background

In recent years, the development of national expressways is rapid, the total mileage of national expressways is over 16 ten thousand kilometers, the built-up driving mileage of expressways in Fujian province is over 6000 kilometers, the expressways enter a large-area maintenance period in the next few years, and asphalt pavement maintenance projects generate huge amounts of old asphalt mixtures each year, if the old asphalt mixtures are not recycled, the stacking of the huge amounts of old asphalt mixtures can cause huge pressure on occupied land and environment. In the plant-mixed regenerated asphalt mixture with performance meeting the requirements at the current state of the art, the utilization rate of RAP is generally only 20-40%, and the economy of RAP regeneration and utilization is limited, so that the enthusiasm of technical popularization and application is low. In 8 months 2019, a new edition of Highway asphalt pavement regeneration technical Specification (JTG/T5521-2019) is issued, the plant-mix thermal regeneration doping amount of an asphalt pavement is not more than 30% of a recommended value, the technical index requirement of the old asphalt penetration is reduced to be not less than 20 (0.01 mm), but a practical and feasible process method for truly realizing large doping amount (more than 40%) and high-quality utilization of the old asphalt mixture is still not available, related technical results are still under exploration, and the high-value and high-performance regeneration utilization of the old asphalt mixture can reduce waste and protect environment, has considerable economic benefits and is a necessary way for sustainable development in the future asphalt pavement maintenance field.

At present, regarding the utilization of the recycled asphalt mixture, most students consider that variability of the RAP in the use process can be effectively reduced by strictly controlling the RAP milling process and enhancing the fine management of the RAP, so that the recycled asphalt mixture with stable performance is obtained, and the expected goal can be realized through theoretical analysis in the mode, but in the actual process, the strictly controlling the RAP milling process and enhancing the fine management of the RAP can increase workload of construction parties, has higher requirements on the area of a mixing station, and is not easy to realize large-scale popularization and use of the RAP.

Disclosure of Invention

The invention provides a treatment method for realizing high-dosage and high-quality cyclic recycling of RAP, which optimizes the pretreatment process of the RAP, firstly performs primary screening on the RAP, and then performs crushing, re-grading and screening on the RAP on a screen until the treated RAP meets the controllable use requirement of the high dosage, thereby remarkably improving the efficiency and quality of standardized treatment.

In order to achieve the above purpose, the present invention adopts the following technical scheme:

a processing method for realizing high-dosage and high-quality cyclic recycling of RAP comprises the following steps:

s1, setting a control standard of RAP in a reclaimed asphalt utilization mixture;

s2, milling and recycling old pavement, and uniformly performing primary screening on the RAP recovered by milling;

s3, crushing and shaping the primarily screened RAP;

s4, grading and screening the crushed and shaped RAP, and grading and selecting the RAP meeting the index standard in the step S1;

s5, performing plant-mixed thermal recycling on the selected RAP.

Preferably, the index criteria in step S1 include RAP bitumen content, rapson diameter proportion, RAP mineral aggregate grading fluctuation value.

Preferably, the control standard of the RAP asphalt content is set to be not more than 3.0% of the RAP asphalt content with the particle size of 4.75mm or more.

Preferably, after the RAPS diameter material proportion is treated by a combustion method or a extraction method, the ratio of the obtained real mineral aggregate to pass through the sieve holes is set to be not more than 20 percent.

Preferably, the grading fluctuation value of the RAP mineral aggregate is the fluctuation value of the passing rate of the RAP mineral aggregate under different sieve pores, the specific setting comprises that the fluctuation value of the passing rate of the RAP mineral aggregate under the sieve pores with the size of 0.075mm is +/-2%, the fluctuation value of the passing rate of the RAP mineral aggregate under the sieve pores with the size of not more than 2.36mm is +/-4%, and the fluctuation value of the passing rate of the RAP mineral aggregate under the sieve pores with the size of not less than 4.75mm is +/-5%.

Preferably, the primary screening in step S2 is specifically to select RAP with a diameter of more than 10mm by using a 10mm vibrating screen.

Preferably, the water content of the RAP is not more than 3% in the primary screening, crushing and shaping and re-screening processes.

After the technical scheme is adopted, compared with the background technology, the invention has the following advantages:

1. the invention relates to a treatment method for realizing high-dosage and high-quality cyclic recycling of RAP, which optimizes the pretreatment process of RAP, firstly performs primary screening on the RAP, and then performs crushing, re-grading and screening on the RAP on a screen until the treated RAP meets the controllable use requirement of high dosage, thereby remarkably improving the efficiency and quality of standardized treatment and reducing the variability of the RAP.

2. According to the treatment method for realizing high-dosage and high-quality cyclic recycling of RAP, after the milled and recovered RAP is uniformly stacked and subjected to primary screening, RAP unified materials are directly classified and applied, so that the management difficulty in the milling and recovering process of old materials is greatly reduced, and the site construction is facilitated.

3. The invention relates to a treatment method for realizing high-quality recycling of large-dosage of RAP, which is characterized in that a command standard of RAP in a regenerated asphalt utilization mixture is set through experiments, the RAP asphalt content, the RAP-less diameter material proportion and the RAP mineral aggregate grading fluctuation value are innovatively set, the quality control requirement is set for the RAP, the RAP dosage is improved, and meanwhile, the regenerated asphalt utilization mixture with stable performance is prepared, so that a theoretical basis is provided for large-scale popularization and application of the RAP.

Drawings

FIG. 1 is a flow chart of the method steps of the present invention;

FIG. 2 is a graph of 4.75mm mesh passage of mineral aggregate after burning RAP of different particle sizes in example 2 of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.

It should be noted that, in the present invention, terms "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are all based on the orientation or positional relationship shown in the drawings, and are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the apparatus or element of the present invention must have a specific orientation, and thus should not be construed as limiting the present invention.

Examples

Referring to FIG. 1, the invention discloses a processing method for realizing high-dosage and high-quality cyclic recycling of RAP, which comprises the following steps:

s2, milling and recycling old pavement, uniformly stacking milled and recycled RAPs, uniformly performing primary screening by using a 10mm vibrating screen, and selecting RAPs with the diameter of more than 10 mm;

s3, crushing and shaping the primarily screened RAP, reducing the aggregation of coarse RAP aggregates, playing a role in factory treatment, and promoting the consistency of the properties of old road materials;

according to the RAP type and the practical engineering application situation in the classified screening, the screening classification sieve holes can be adjusted and set as required; and in the step of grading utilization, the optimal grading sieve pore size is selected, and the RAP larger than the optimal grading sieve pore size is only recycled, so that the influence of RAP fine aggregate on grading fluctuation of the reclaimed asphalt mixture is reduced, and the stability of the performance of the reclaimed asphalt mixture is further controlled.

S5, performing plant-mixed thermal recycling on the selected RAP.

Wherein the water content of the RAP is not more than 3% in the process of primary screening, crushing, shaping and rescreening.

The index standard in the step S1 comprises the RAP asphalt content, the RAPS diameter material proportion and the RAP mineral aggregate grading fluctuation value.

The control standard of the RAP asphalt content is set to be not more than 3.0% of the RAP asphalt with the particle size of more than 4.75 mm.

After the RAP with the proportion of the RAPS diameter material being above the sieve holes is treated by a combustion method or a extraction method, the proportion of the obtained real mineral aggregate passing through the sieve holes is set to be not more than 20 percent according to the control standard of the proportion of the RAPS diameter material.

The fluctuation value of the grading of the RAP mineral aggregate is the fluctuation value of the passing rate of the RAP mineral aggregate under different sieve holes, the fluctuation value of the passing rate of the RAP mineral aggregate under the sieve holes with the size of 0.075mm is specifically set to be +/-2%, the fluctuation value of the passing rate of the RAP mineral aggregate under the sieve holes with the size of not more than 2.36mm is set to be +/-4%, and the fluctuation value of the passing rate of the RAP mineral aggregate under the sieve holes with the size of not less than 4.75mm is specifically set to be +/-5%.

Example 1

Asphalt content, water content and grading change detection are carried out by sampling typical AC-20 asphalt mixture milling materials of a surface layer in an old highway, and each index data is obtained by taking an average value from 5 groups of detection data as shown in the following table:

in the table, "+" indicates that the passing rate of the screen holes for extracting the true grading is larger than the passing rate of the corresponding screen holes of the RAP.

The RAP test data of the upper table section show that:

the RAP coarse aggregate (with the particle size larger than 5 mm) after screening treatment is mainly large-particle-size mineral aggregate and an asphalt mortar adhering ' aggregate ' structure in various asphalt mixtures of the original pavement, and the small proportion of the RAP coarse aggregate is full-fine aggregate ' aggregate; the RAP coarse aggregate has the characteristics of large total proportion content, stone as a main component, low old asphalt content and easiness in air drying to reduce the water content.

The RAP fine aggregate (particle size is smaller than 5 mm) after screening treatment comprises all small-particle-size mineral aggregates in various asphalt mixtures of the original pavement and all asphalt cement and asphalt mortar bonded with each other in a 'particle-group' structure; the method has the advantages that the influence on the accurate evaluation of the RAP screening grading is large, the method comprises a higher proportion of aged asphalt, the moisture absorption and water retention capacity is high, and the quality control and improvement difficulty of the reclaimed asphalt mixture are increased.

Example 2

Selecting RAP system materials milled on a certain base, dividing the RAP into particle size specifications of 0-5mm, 5-6mm, 6-7mm, 7-8mm, 8-9mm, 9-10mm, 10-12mm, 12-16mm, and > 16mm by adopting a non-standard sieve, testing asphalt content of RAP with different particle size specifications by a combustion method, screening the mineral materials after the combustion of the RAP, and testing the results shown in Table 3. As shown in Table 3, the old asphalt content in the coarse RAP aggregate with the thickness of more than 5mm is obviously lower than the asphalt content of 0-5mm RAP, and the proportion of the old asphalt in the reclaimed asphalt mixture prepared by adopting the RAP with the thickness of more than 5mm is not more than 30% based on the total asphalt, so that the recycling difficulty of the aged old asphalt is greatly reduced, the binder in the reclaimed asphalt mixture is mainly added new asphalt, the performance of the reclaimed asphalt mixture is mainly added new asphalt, and the influence of the old asphalt on the performance of the reclaimed asphalt mixture is reduced. The RAP bitumen content and the mineral aggregate passing rate after combustion with different particle sizes are shown in the following table:

according to the table, the proportion of RAP with different particle sizes is shown in the table, the proportion of 12-16mm RAP in the stacked RAP reaches 32.9%, the proportion of 7-8mm RAP is minimum, the proportion of the RAP is only 0.6%, the proportion of the RAP is more than 7mm RAP is 65.6%, the coarse aggregate of RAP is mainly made of stone materials, the requirement of performance satisfaction can be realized through proper bias grading design, and the number requirement of single-grade large-mixing recycling can be met.

In addition, the specific surface area of the RAP coarse aggregate is large, the rapid air drying is easy to reduce the water content, the adverse effect of the water with the largest specific heat in the RAP on the temperature control in the mixing process of the reclaimed asphalt mixture can be naturally reduced, the heating consumption of the RAP is reduced, and the heating temperature of the new aggregate is reduced to a certain extent.

In conclusion, the technical characteristics of the RAP coarse aggregate have a relatively positive effect on plant-mixed heat recycling, and compared with the RAP fine aggregate, the stable and accurate control on asphalt, grading and temperature is easier to realize.

Example 3

As the instability of the performance of the reclaimed asphalt mixture mainly comes from the difficulty in controlling the variation of the RAP performance, particularly the grading variation of the RAP is larger, in order to further understand the condition that the RAP with different particle size specifications is coated with fine aggregates, the 4.75mm passing rate of mineral aggregate after the combustion of the RAP with different particle size specifications of the base is researched, and the research result is shown in a graph in figure 2, the passing rate of sieve pores with the particle size of more than 7mm and the RAP with the particle size of 4.75mm is within 30 percent, and as the particle size of the RAP is increased, the sieve pore passing rate of each grade of RAP with 4.75mm basically shows a tendency of decreasing, and the larger the particle size of the RAP is, the less the coated fine aggregates are coated, but the sieve pore passing rate of 4.75mm appears in the cases that the RAP with the particle size of 10-12mm and the RAP with the particle size of 12-16mm are larger than 9-10mm and the RAP are shown.

In order to obtain the regenerated asphalt mixture with stable performance, the grading variability of the RAP needs to be controlled, and in the embodiment, a diameter-less material proportion parameter is innovatively provided, wherein the diameter-less material proportion parameter is defined as that after the RAP above a certain sieve pore is subjected to combustion or extraction, the material of the obtained real mineral aggregate passing through the sieve pore of the grading sieve is the diameter-less material of the grade, the proportion of the real mineral aggregate is the diameter-less material proportion, and the index control standard of the diameter-less material proportion of the RAP is set to be not more than 20%.

Example 4

If the fluctuation of the RAP mineral aggregate is too large, the fluctuation of the mineral aggregate gradation of the reclaimed asphalt mixture is not satisfactory, and the variation coefficient of the RAP mineral aggregate gradation fluctuation values with different particle diameters of the base is calculated, so that the results are shown in the following table:

as shown in the table above, the passing rate variation coefficient of the mineral aggregate with 12-16mm and > 16mmRAP in the sieve pores with 0.075-0.3mm and 0.3-13.2mm is more than 10%, and the passing rate variation coefficient of the mineral aggregate with other particle size RAP in each sieve pore is less than 10%.

Therefore, variability of the RAP mineral aggregate gradation is reduced through a pretreatment process, and a control standard is determined for the standardized RAP mineral aggregate fluctuation value. The specific setting of the command standard comprises that the fluctuation value of the passing rate of the RAP at a sieve aperture of 0.075mm is +/-2%, the fluctuation value of the passing rate of the RAP at a sieve aperture of not more than 2.36mm is +/-4%, and the fluctuation value of the passing rate of the RAP at a sieve aperture of not less than 4.75mm is +/-5%.

In summary, in order to obtain the high-doping amount RAP regenerated asphalt mixture with stable performance, the standard index is provided for the RAP asphalt content, the proportion of the minor diameter materials and the grading fluctuation value of the RAP mineral aggregate after standardized treatment, and is shown in the following table:

the present invention is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present invention are intended to be included in the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

The high-quality recycling treatment method for the RAP system material when the doping amount is more than 40 percent is characterized by comprising the following steps of:

s1, setting a control standard of RAP system materials in a reclaimed asphalt utilization mixture;

s2, milling and recycling old pavement, and uniformly and primarily screening RAP unified materials recycled by milling;

s3, crushing and shaping the RAP system materials subjected to primary screening;

s4, grading and screening the crushed and shaped RAP aggregate, and grading and selecting the RAP aggregate meeting the index standard in the step S1;

s5, performing plant-mixed heat recycling on the selected RAP system materials;

in step S1, the index control criteria of the RAP aggregate include RAP aggregate asphalt content, RAP aggregate minor-diameter material proportion, and RAP aggregate mineral aggregate grading fluctuation value, where:

the control standard of the RAP bulk asphalt content is set to be not more than 3.0% of the RAP bulk asphalt with the grain diameter of more than 4.75 mm;

after the RAP aggregate with the proportion of the RAP aggregate-less diameter material being above the sieve holes is treated by a combustion method or a extraction method, the proportion of the obtained real mineral aggregate passing through the sieve holes is set to be not more than 20% by weight according to the control standard of the proportion of the RAP aggregate-less diameter material;

the RAP aggregate mineral aggregate grading fluctuation value is a fluctuation value of the passing rate of the RAP aggregate under different sieve holes, and the variability of the RAP aggregate mineral aggregate grading is controlled by the RAP aggregate mineral aggregate grading fluctuation value, and the method comprises the following steps: fluctuation value of passing rate of RAP aggregate in 0.075mm sieve mesh is + -2%; fluctuation value of passing rate of RAP aggregate in sieve holes with the diameter of not more than 2.36mm is +/-4%; the fluctuation value of the passing rate of RAP bulk materials in sieve holes with the diameter not smaller than 4.75mm is +/-5%.
2. The method for recycling and treating the high quality of the RAP system material when the doping amount is more than 40 percent according to claim 1, which is characterized in that: in the step S2, a 10mm vibrating screen is adopted to select RAP system materials with the diameter of more than 10 mm.
3. The method for recycling and treating the high quality of the RAP system material when the doping amount is more than 40 percent according to claim 1, which is characterized in that: the water content of the RAP aggregate is not more than 3% during primary screening, crushing, shaping and re-screening.