CN110965432B - Method for determining mixing amount of asphalt mixture regenerating agent based on coarse aggregate oil absorption rate - Google Patents
Method for determining mixing amount of asphalt mixture regenerating agent based on coarse aggregate oil absorption rate Download PDFInfo
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- 239000010426 asphalt Substances 0.000 title claims abstract description 293
- 239000000203 mixture Substances 0.000 title claims abstract description 96
- 238000002156 mixing Methods 0.000 title claims abstract description 47
- 238000010521 absorption reaction Methods 0.000 title claims abstract description 29
- 239000003795 chemical substances by application Substances 0.000 title description 17
- 230000001172 regenerating Effects 0.000 title description 6
- 239000012492 regenerant Substances 0.000 claims abstract description 80
- 230000008929 regeneration Effects 0.000 claims abstract description 32
- 238000011069 regeneration method Methods 0.000 claims abstract description 32
- 239000002699 waste material Substances 0.000 claims abstract description 29
- 230000035515 penetration Effects 0.000 claims description 23
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 15
- 229960002415 trichloroethylene Drugs 0.000 claims description 12
- XSTXAVWGXDQKEL-UHFFFAOYSA-N triclene Chemical group ClC=C(Cl)Cl XSTXAVWGXDQKEL-UHFFFAOYSA-N 0.000 claims description 12
- 239000011259 mixed solution Substances 0.000 claims description 11
- 238000000926 separation method Methods 0.000 claims description 11
- 238000004821 distillation Methods 0.000 claims description 6
- 238000007873 sieving Methods 0.000 claims description 5
- 238000010998 test method Methods 0.000 claims description 4
- 230000000875 corresponding Effects 0.000 claims description 3
- 239000000463 material Substances 0.000 abstract description 30
- 238000004064 recycling Methods 0.000 abstract description 13
- 201000010099 disease Diseases 0.000 description 5
- 238000010276 construction Methods 0.000 description 4
- 238000000034 method Methods 0.000 description 4
- 230000003716 rejuvenation Effects 0.000 description 4
- 238000011056 performance test Methods 0.000 description 3
- 238000005452 bending Methods 0.000 description 2
- 239000004566 building material Substances 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000000605 extraction Methods 0.000 description 2
- 229910052500 inorganic mineral Inorganic materials 0.000 description 2
- 239000011707 mineral Substances 0.000 description 2
- 238000002791 soaking Methods 0.000 description 2
- 239000002689 soil Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 235000019738 Limestone Nutrition 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 238000011030 bottleneck Methods 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 239000006028 limestone Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000006011 modification reaction Methods 0.000 description 1
- -1 natural gravels Substances 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000009418 renovation Methods 0.000 description 1
- 239000004575 stone Substances 0.000 description 1
Classifications
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
- E01C19/00—Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving
- E01C19/02—Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving for preparing the materials
- E01C19/10—Apparatus or plants for premixing or precoating aggregate or fillers with non-hydraulic binders, e.g. with bitumen, with resins, i.e. producing mixtures or coating aggregates otherwise than by penetrating or surface dressing; Apparatus for premixing non-hydraulic mixtures prior to placing or for reconditioning salvaged non-hydraulic compositions
-
- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
- E01C19/00—Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving
- E01C19/02—Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving for preparing the materials
- E01C19/10—Apparatus or plants for premixing or precoating aggregate or fillers with non-hydraulic binders, e.g. with bitumen, with resins, i.e. producing mixtures or coating aggregates otherwise than by penetrating or surface dressing; Apparatus for premixing non-hydraulic mixtures prior to placing or for reconditioning salvaged non-hydraulic compositions
- E01C19/1054—Preparing mixtures of which at least part of the solid ingredients has previously been deposited on the surface, excluding penetrating or surface dressing, e.g. in situ mixing, mixing involving lifting of spread or windrowed aggregate
Abstract
The invention relates to a method for determining the mixing amount of a regenerant of an asphalt mixture based on the oil absorption rate of coarse aggregates, which mainly comprises the following steps: screening the recycled aggregate to obtain coarse aggregate in the aggregate, respectively testing the apparent gross volume relative density and the apparent relative density of the coarse aggregate, calculating the content of the absorbed asphalt according to the composition proportion of the coarse aggregate, and then reducing the total old asphalt content on the basis to obtain the reference asphalt dosage for determining the dosage of the regenerant; then carrying out a test on the regeneration performance of the old asphalt, and preliminarily determining the using amount of the regenerant; and finally, comprehensively evaluating the road performance of the regenerated asphalt mixture by preparing the regenerated asphalt mixture, and finally determining the using amount of the regenerant. The method can ensure the excellent performance of the recycled asphalt pavement and realize the recycling level of the waste pavement materials and the improvement of the driving safety of the recycled asphalt pavement.
Description
Technical Field
The invention relates to the technical field of recycling of asphalt pavements in road engineering, in particular to a method for determining the mixing amount of an asphalt mixture regenerating agent based on the oil absorption rate of coarse aggregates.
Background
The asphalt pavement breaks through 130 kilometers in China, lives in the world in the future, and 2 hundred million tons of waste asphalt pavement materials (RAP) are produced by maintenance in large and medium schools every year, which is the most important in the world. RAP materials generated by road maintenance in the operation period are efficiently regenerated, so that road infrastructure provides safe and convenient service for economic and social development, simultaneously reduces resource occupation and environmental damage, better serves for resource conservation and environment-friendly social construction, and has great significance.
At present, the recycling rate of highway pavement materials in China is less than 30 percent and is far lower than the target utilization rate level of more than 90 percent, and the improvement of the mixing proportion of old materials has great significance for solving the problems of resource occupation and environmental pollution caused by the large consumption of new materials and stacked wastes in road engineering. The biggest bottleneck limiting the application of a large proportion of waste asphalt mixture is that the performance of the regenerated asphalt pavement is difficult to guarantee, and technical hidden troubles exist.
Disclosure of Invention
The regeneration of RAP material is mainly the restoration of the properties of the old bitumen therein. In order to restore the properties of the old bitumen to a good level, it is often effective to add to the old bitumen a low viscosity oil with certain light components, such materials being known as rejuvenating agents. With regard to the determination of the amount of RAP material regenerating agent, the current technical specification for road asphalt pavement regeneration (JTG F41) gives the following recommendations: firstly, recovering old asphalt from RAP by an extraction distillation method, and taking trichloroethylene as a solvent, wherein the solvent can completely dissolve the asphalt, so that the total asphalt content in the RAP can be tested; and then, carrying out a regeneration test on the recycled old asphalt by a trial-and-error method, adding the regenerant into the recycled asphalt according to a certain interval arithmetic progression proportion, testing indexes of penetration, softening point, ductility and the like of the asphalt, drawing a change curve, and finally determining the dosage of the regenerant by an interpolation method based on the target regeneration performance of the old asphalt.
In engineering application, the method for determining the using amount of the old asphalt recycling agent can cause the reduction of the high-temperature stability of the recycled asphalt mixture, track diseases are easy to occur at the initial stage of traffic, and even road sections with serious diseases have to be milled and paved again. This has emerged in a number of physical engineering applications, resulting in the loss of a large number of national assets, and at the same time, there are technical concerns over the large scale application of the green paving technology for asphalt pavement recycling. The main reasons for this phenomenon are: the surface of coarse aggregate in the asphalt mixture has a large number of open pores, which can absorb a certain amount of asphalt, the asphalt penetrates into the aggregate to become structural asphalt, and the asphalt outside the thickness of the structural asphalt film is free asphalt, the asphalt is also called effective asphalt, namely the performance of the asphalt mixture is decisively influenced. In the RAP regeneration process, the added regenerant mainly reacts with the free asphalt to regenerate and reduce the aged free asphalt, and asphalt absorbed by the coarse aggregate, namely structural asphalt, does not participate in the reaction.
The current method calculates the regenerant dosage based on the total asphalt content in the RAP, and comprises structural asphalt and free asphalt, but the structural asphalt and the regenerant do not react, so that more free regenerant exists in the mixture. Compared with asphalt, the regenerant has much lower viscosity and is softer, which can cause the high-temperature stability of the mixture to be greatly reduced. Particularly, aiming at the regeneration or on-site regeneration of a large proportion of old materials, the mixing amount of the old materials is higher, the content of the contained structural asphalt is also higher, and if the condition that the coarse aggregates absorb the asphalt is not considered, the content of free regenerants in the regenerated mixture is higher, and the track diseases of the regenerated asphalt pavement are easier to appear. Because of the ruts, the road surface is excessively deformed, the flatness of the road surface is damaged, the driving comfort is greatly reduced, and the rail-shaped ruts seriously endanger the stability of the vehicle in the driving process and seriously threaten the driving safety.
In order to overcome the defects in the prior art, a method for reasonably determining the using amount of the asphalt mixture regenerating agent is needed to ensure the excellent performance of a large proportion of old material regenerated pavements, and the method has remarkable social and economic benefits for improving the regeneration and utilization level of waste pavement materials and the driving safety of the regenerated asphalt pavements.
The invention provides a method for determining the mixing amount of a regenerant of an asphalt mixture based on the oil absorption rate of coarse aggregates and taking the performance of the asphalt mixture as a final evaluation standard, so that the performance of the regenerated asphalt mixture is finally recovered to an excellent level. Therefore, the excellent road performance of the regenerated asphalt pavement is ensured, and the recycling level of the waste asphalt pavement material and the driving safety of the regenerated asphalt pavement are improved.
The main inventive concept of the invention is as follows: when the dosage of the mixture regenerant is determined, the structural asphalt absorbed by the aggregate is reduced. The method mainly comprises the following steps: screening the recycled aggregate to obtain coarse aggregate in the aggregate, respectively testing the apparent gross volume relative density and the apparent relative density of the coarse aggregate, calculating the content of the absorbed asphalt according to the composition proportion of the coarse aggregate, and then reducing the total old asphalt content on the basis to obtain the reference asphalt dosage for determining the dosage of the regenerant; then carrying out a test on the regeneration performance of the old asphalt, and preliminarily determining the using amount of the regenerant; and finally, comprehensively evaluating the road performance of the regenerated asphalt mixture by preparing the regenerated asphalt mixture, and finally determining the using amount of the regenerant.
Means for solving the technical problem
Specifically, in order to achieve the above purpose, the invention adopts the following technical scheme:
a method for determining the mixing amount of a bituminous mixture regenerant based on the oil absorption rate of coarse aggregates is characterized by comprising the following steps:
(1) taking a certain amount of waste asphalt mixture, separating to obtain a mixed solution of asphalt and trichloroethylene and aggregate, and calculating the total asphalt content M in the waste asphalt mixture;
(2) recovering old asphalt in the asphalt and trichloroethylene mixed solution;
(3) testing the relative density rc of the old asphalt at 25 ℃;
(4) according to the regeneration target performance of the old asphalt, preliminarily determining the doping amount x of the regenerant relative to the old asphalt;
(5) testing the proportion h of the coarse aggregate in the aggregate obtained in the step (1), and testing the apparent relative density ra, the gross volume relative density rb and the water absorption w of the coarse aggregate;
(6) calculating the absorption coefficient P of the asphalt and the effective relative density rx of the coarse aggregate according to the apparent relative density ra, the gross volume relative density rb and the water absorption w of the coarse aggregate;
(7) the asphalt content Ma absorbed by the coarse aggregate is calculated as follows: ma ═ (rx-rb) × rc × 100/(rx × rb);
(8) calculating the mixing amount H of the asphalt mixture regenerant according to the following formula: h ═ M-Ma × H) × n × x, wherein n is the blending ratio of the waste asphalt mixture;
in the step (6), the absorption coefficient P of the asphalt is calculated according to the following formula:
P＝0.033w2-0.2936w+0.9339。
further, the total content M of the mixed liquid of asphalt and trichloroethylene, the aggregate and the waste asphalt mixture in the step (1) is obtained according to a centrifugal separation method (T0722-1993) in road engineering asphalt and asphalt mixture test procedures (JTG E20-2011).
Further, the old asphalt in the step (2) is recovered according to the Abelson distillation method (T0726-2011) in the current road engineering asphalt and asphalt mixture test protocol (JTG E20-2011).
Further, the relative density rc of the old asphalt in the step (3) at 25 ℃ is obtained according to an asphalt density and relative density test (T0603-2011) in road engineering asphalt and asphalt mixture sample specification (JTG E20-2011).
Further, the step (4) specifically includes the following steps:
(4-1) testing the penetration degree at 25 ℃, the softening point and the ductility at 15 ℃ of the old asphalt under different regenerant dosages;
(4-2) pointing test results into a graph by taking the dosage of the regenerant as an abscissa and taking the penetration degree, the softening point and the ductility at 25 ℃ as ordinates respectively, and connecting into three curves; according to the regeneration target performance of the old asphalt, the mixing amount x of the regenerant relative to the old asphalt is preliminarily determined.
Further, in the step (4-2), the initial determination of the mixing amount x of the recycling agent relative to the old asphalt is specifically as follows:
selecting a target asphalt label after the regeneration of the old asphalt;
obtaining from the three curves: meanwhile, the blending amount range of the regenerant corresponding to the requirements of penetration, softening point and ductility of a target asphalt label specified in technical Specification for road asphalt pavement regeneration (JTG/T5521-2019) is met;
any value in the regenerant dosage range is selected as a preliminarily determined regenerant dosage x.
Further, the step (5) specifically includes the following steps:
(5-1) sieving the aggregate obtained by the centrifugal separation method by using a standard sieve of 2.36mm, taking the oversize part, and calculating the proportion h of the coarse aggregate in the aggregate;
(5-2) testing the apparent relative density ra, the bulk volume relative density rb and the water absorption w of the coarse aggregate according to the basket method (T0304-2005) of the existing road engineering aggregate test protocol (JTG E42-2005).
Further, in the step (6), the effective relative density rx of the coarse aggregate is calculated according to the following formula: rx ═ P × ra + (1-P) × rb.
Has the advantages that:
according to the invention, based on the oil absorption rate of the coarse aggregate, the asphalt content absorbed by the coarse aggregate is reduced, and the mixing amount of the asphalt mixture regenerant is finally determined through an old asphalt performance test and an overall performance test of the asphalt mixture, so that the excellent performance of the regenerated asphalt pavement is ensured, and the recycling level of the waste pavement material and the driving safety of the regenerated asphalt pavement are improved.
From the perspective of social and economic benefits, the method disclosed by the invention is applied to realize large-scale application of a large proportion of old material regeneration technology. The mileage of newly increased roads in China exceeds 10 kilometers every year, and only pavement engineering consumes more than 5 million tons of building materials such as natural gravels, asphalt, cement and the like, and if 70% of the building materials are replaced by waste materials, the exploitation amount of stone materials can be saved by about 3.5 million tons, so that the consumption of natural resources in road construction is greatly reduced. About 2 million tons of waste pavement materials are generated in road renovation every year in China, the generated waste residue soil is countless, and if 70% of the waste residue soil is recycled, 14000 million tons of waste pavement materials can be digested every year. The social and economic benefits are very obvious.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and, together with the description, serve to explain the disclosed methods of the invention.
FIG. 1 is a graph showing the variation of penetration of old asphalt with the amount of a recycling agent.
FIG. 2 is a graph showing the change of the softening point of old asphalt according to the amount of a regenerant.
FIG. 3 is a graph showing the ductility of old asphalt as a function of the amount of a recycling agent.
Detailed Description
In the following detailed description, numerous specific details are set forth in order to provide a better understanding of the invention. It will be understood by those skilled in the art that the present invention may be practiced without some of these specific details. Methods and means well known to those skilled in the art have not been described in detail so as not to obscure the present invention.
The method for determining the mixing amount of the asphalt mixture regenerant comprises the following steps: taking a certain amount of waste asphalt mixture (RAP), obtaining a mixed solution of asphalt and trichloroethylene and aggregate by using a centrifugal separation method, calculating the total old asphalt content in the RAP on the basis, then recovering the old asphalt from the mixed solution by using an Abson distillation method, adding different amounts of regenerants into the recovered old asphalt, respectively testing the penetration degree, the softening point and the ductility of the regenerated asphalt, and primarily determining the amount of the regenerants according to the test result; sieving the aggregate with a standard sieve of 2.36mm, and taking the part on the sieve as coarse aggregate; testing the apparent relative density and the gross volume relative density of the coarse aggregate by using a basket method, calculating the asphalt absorption coefficient of the coarse aggregate, then calculating the asphalt content absorbed by the coarse aggregate, and reducing the total old asphalt content on the basis to obtain the reference asphalt dosage for determining the dosage of the regenerant; and finally, preparing a regenerated asphalt mixture according to the mixture ratio of the materials, comprehensively evaluating the road performance of the regenerated asphalt mixture, and finally determining the using amount of the regenerant.
The invention provides a method for determining the mixing amount of a regenerant of an asphalt mixture based on the oil absorption rate of coarse aggregates, which comprises the following steps:
1. taking a certain amount of waste asphalt mixture (RAP), and separating asphalt from aggregate according to a centrifugal separation method (T0722-1993) in the current road engineering asphalt and asphalt mixture test procedure (JTG E20-2011) to obtain a mixed solution of asphalt and trichloroethylene and aggregate; on this basis, the total bitumen content M (the percentage of the bitumen mass to the total mass of the mineral aggregate) in the RAP is calculated.
2. According to the existing road engineering asphalt and asphalt mixture test protocol (JTG E20-2011), the method recovers the old asphalt from the asphalt and trichloroethylene mixed solution obtained by the centrifugal separation method, and the old asphalt can be obtained in the process.
3. Selecting recycled old asphalt, and testing the relative density rc of the old asphalt at 25 ℃ according to an asphalt density and relative density test (T0603-2011) in road engineering asphalt and asphalt mixture sample specification (JTG E20-2011); and then adding the regenerant with the known dosage into the old asphalt according to the mass ratio of the old asphalt, slowly stirring uniformly, and testing the penetration, softening point and ductility at 25 ℃ of the old asphalt with different dosages of the regenerant according to an asphalt penetration test (T0604-2011), a softening point test (T0606-2011) and a ductility test (T0605-2011) in road engineering asphalt and asphalt mixture sample specification (JTG E20-2011).
It should be noted that:
there is no particular requirement in the present invention for the known amount of rejuvenating agent, but considering the amount normally used in engineering practice, it is preferred that the initial amount of rejuvenating agent is less than 10% of the mass of the old bitumen.
4. Taking the dosage of the regenerant as a horizontal coordinate, taking the penetration degree at 25 ℃, the softening point and the ductility at 15 ℃ as vertical coordinates respectively, and pointing test results into a graph to form three smooth curves; according to the regeneration target performance of the old asphalt, preliminarily determining the mixing amount x of the regenerant relative to the old asphalt (the mass percentage of the regenerant to the mass of the old asphalt);
it should be noted that:
the initial determination of the mixing amount of the regenerant relative to the old asphalt comprises the following specific steps: selecting a target asphalt label after the regeneration of the old asphalt; obtained from the three curves above: any value in the regenerant doping amount range corresponding to the requirement of penetration, softening point and ductility (that is, the requirement of penetration, softening point and ductility of the target asphalt grade specified in the existing technical specification for road asphalt pavement regeneration (JTG/T5521-2019)) is satisfied as the preliminarily determined regenerant doping amount x in the embodiment.
5. Sieving the aggregate obtained by the centrifugal separation method (preferably, sieving by using a 2.36mm standard sieve), taking the oversize part, and calculating the proportion h of the coarse aggregate in the aggregate; then, the apparent relative density ra, the bulk relative density rb and the water absorption w are tested according to the basket method (T0304-2005) of the existing road engineering aggregate test protocol (JTG E42-2005).
6. The absorption coefficient P of the asphalt and the effective relative density rx of the coarse aggregate were calculated according to the following formulas.
P ═ 0.033w2-0.2936w + 0.9339. Wherein the formula is an asphalt absorption coefficient formula in a dry-method (T0705-2011) of the current road engineering aggregate test regulation (JTG E42-2005).
rx＝P×ra+(1-P)×rb。
7. The asphalt content Ma absorbed by the coarse aggregate (the mass of absorbed asphalt as a percentage of the total mass of the coarse aggregate) was calculated as follows, where rc is the relative density of the asphalt at 25 ℃.
Ma＝(rx-rb)×rc×100/(rx×rb)
8. And calculating to obtain the content of the asphalt absorbed in the old material as Ma multiplied by h according to the proportion h of the coarse aggregate in the aggregate and the content Ma of the asphalt absorbed by the coarse aggregate, so as to obtain the reference old asphalt content M-Ma multiplied by h for determining the doping amount of the regenerant.
9. And then calculating the mixing amount H of the regenerant in the regenerated asphalt mixture (the mass percentage of the regenerant in the total mass of the aggregates in the regenerated mixture) according to the following formula, wherein n is the mixing ratio of the waste asphalt mixture (the mass percentage of the waste asphalt mixture in the total mass of the aggregates in the regenerated mixture).
H＝(M-Ma×h)×n×x
10. According to the design blending proportion of each material of the regenerated asphalt mixture, forming a regenerated asphalt mixture test piece, and inspecting the water stability, high-temperature stability and low-temperature crack resistance of the regenerated asphalt mixture; when the pavement performance of the recycled asphalt mixture meets the standard requirement, taking the mixing amount of the recycling agent as the final mixing amount of the recycling agent of the recycled asphalt mixture; otherwise, adjusting the mixing amount of the regenerant, and re-verifying the performance of the regenerated asphalt mixture until the performance meets the standard requirement.
Examples：
1. Taking 2500g of waste asphalt mixture (RAP), and separating asphalt from aggregate in the RAP according to a centrifugal separation method in the existing road engineering asphalt and asphalt mixture test procedures to obtain a mixed solution of asphalt and trichloroethylene and the aggregate; on the basis of the calculation, the total asphalt content M (the percentage of the asphalt mass to the total mass of the mineral aggregate) in the RAP is 4.2 percent.
2. According to the conventional Abson distillation method in the test regulations of road engineering asphalt and asphalt mixtures, the waste asphalt is recovered from the mixed solution of asphalt and trichloroethylene obtained by a centrifugal separation method, and about 100g of the waste asphalt can be recovered in the process. Then repeating the steps 1-2 approximately 6 times, and collecting about 600g of recycled old asphalt.
3. Selecting recycled old asphalt, and testing the relative density of the old asphalt at 25 ℃ according to an asphalt density and relative density test in road engineering asphalt and asphalt mixture sample regulations to obtain the relative density of the old asphalt of 1.032; the old asphalt was then tested for penetration at 25 c, softening point and ductility at 15 c according to the asphalt penetration, softening point test and ductility test.
4.3 percent of regenerant is added into the old asphalt according to the mass ratio of the old asphalt, and the main technical indexes of the regenerant are shown in the following table 1. And slowly stirring uniformly, and testing the penetration, softening point and ductility at 25 ℃ of the asphalt according to asphalt penetration, softening point and ductility tests in road engineering asphalt and asphalt mixture sample specifications.
TABLE 1 Main technical indices of the regenerants
5. Referring to step 4, 6% and 9% of a rejuvenating agent were added to the recycled old asphalt, and the penetration at 25 ℃, softening point and ductility at 15 ℃ were measured, respectively.
6. The test results are plotted in the figure by using the dosage of the regenerant as the abscissa and the penetration, softening point and ductility at 25 ℃ and 15 ℃ as the ordinate, and are connected into three smooth curves. The test results are shown in FIGS. 1 to 3.
7. In the regeneration test, the target asphalt after the regeneration of the old asphalt is marked as No. 70, and the current technical specification for the regeneration of the asphalt pavement of the highway stipulates No. 70 asphalt: the penetration degree is 60-80 (0.1mm), the softening point is more than 45 ℃, and the ductility is more than 100 cm. Therefore, according to the regeneration target performance, the mixing amount x of the primary regenerant is 9 percent (the mass of the regenerant accounts for the mass of the old asphalt), the penetration degree of the regenerated asphalt is 67.5(0.1mm), the softening point is 53.7 ℃, the ductility is more than 100cm, and the specification requirement of No. 70 asphalt is met.
8. Screening the aggregate obtained by the centrifugal separation method by using a 2.36mm standard sieve, taking the part above the sieve as coarse aggregate, and calculating the proportion of the coarse aggregate in the aggregate to the total mass of the aggregate to be 80%; and then testing the apparent relative density ra, the bulk volume relative density rb and the water absorption w according to the basket method of the current road engineering aggregate test regulation. The test results are shown in table 2 below.
TABLE 2 coarse aggregate Density and Water absorption
9. The absorption coefficient P of the asphalt and the effective relative density rx of the coarse aggregate were calculated according to the following formulas.
P＝0.033w2-0.2936w+0.9339
rx＝P×ra+(1-P)×rb
According to the results of the test of the density and water absorption of the coarse aggregates in the table 1 above, the absorption coefficient P of the asphalt of the coarse aggregates can be calculated to be 0.588, and the effective relative density rx of the coarse aggregates is 2.624.
10. The asphalt content Ma absorbed by the coarse aggregate (the mass of absorbed asphalt as a percentage of the total mass of the coarse aggregate) was calculated as follows, where rc is the relative density of the asphalt at 25 ℃.
Ma＝(rx-rb)×rc×100/(rx×rb)
From the foregoing test results, it was calculated that the asphalt content absorbed by the coarse aggregate (the percentage of the mass of absorbed asphalt to the total mass of the coarse aggregate) was 0.9%.
11. According to the fact that the proportion h of the coarse aggregates in the aggregates is 85% and the asphalt content Ma absorbed by the coarse aggregates is 0.9%, the asphalt content Ma multiplied by h absorbed by the old aggregates is 0.765, and therefore the old asphalt content M-Ma multiplied by h of the standard for determining the doping amount of the recycling agent can be calculated to be 3.4%.
12. And then calculating the mixing amount H of the regenerant in the regenerated asphalt mixture (the mass percentage of the regenerant in the total mass of the aggregates in the regenerated mixture) according to the following formula, wherein the mixing ratio n of the waste asphalt mixture (the mass percentage of the waste asphalt mixture in the total mass of the aggregates in the regenerated mixture) is 70%.
H＝(M-Ma×h)×n×x
Therefore, the mixing amount H of the regenerant is 0.21 percent when the mixing amount of the old material is 70 percent.
13. The blending ratio of each material of the recycled asphalt mixture is designed and shown in the following tables 3-4. The new aggregate is divided into 4 grades of 10-15mm, 5-10mm, 3-5mm and 0-3mm, wherein the aggregate of 10-15mm and 5-10mm is basalt, the aggregate of 3-5mm and 0-3mm is limestone, the crushing value of the coarse aggregate is 14.3 percent, and the abrasion loss of the fine aggregate is 13.5 percent. The newly added asphalt is 70# asphalt, and the technical indexes are shown in the following table 5.
TABLE 3 aggregate mixing ratio of recycled asphalt mixture
TABLE 4 New asphalt and regenerant used in the recycled asphalt mixture
| Amount of new pitch/%) | 2.09 |
| Amount of regenerant/% | 0.21 |
TABLE 5 Main technical indices of newly added asphalt
The water stability, high-temperature stability and low-temperature crack resistance of the regenerated asphalt mixture are tested according to the design blending ratio of various materials of the regenerated asphalt mixture, a mixture test piece is formed according to the existing technical specification for highway asphalt pavement construction, and the test results are shown in the following table 6. Wherein, the water stability is evaluated by the indexes of the soaking Marshall residual stability and the freeze-thaw splitting strength ratio, the high temperature stability is evaluated by the index of the dynamic stability, and the low temperature crack resistance is evaluated by the index of the low temperature bending damage strain.
TABLE 6 test results of recycled asphalt mixture performance
The test result shows that the road performance of the regenerated asphalt mixture obviously meets the standard requirement, namely when the mixing amount of the old material is 70%, the mixing amount of the regenerant of the regenerated asphalt mixture is 0.2%.
Verification example：
In order to verify the validity of the method according to the invention described above, the amount of regenerant is determined by known methods. The test raw materials were the same as in the above examples. Firstly, the extraction distillation method is adopted to recover the old asphalt from RAP, then the trial-and-match method is adopted to carry out the regeneration test of the recovered old asphalt, the regenerant is added into the recovered asphalt according to the arithmetic progression proportion at certain intervals, the indexes of penetration, softening point, ductility and the like of the asphalt are tested, a change curve is drawn, the regeneration test shows that the target asphalt after the regeneration of the old asphalt is marked with a number of 70#, so that the mixing amount of the regenerant is determined to be 9% (the mass of the regenerant accounts for the mass of the old asphalt), and the standard requirement can be met. According to the existing practice, the determination of the mixing amount of the regenerant is finished, and the obtained mixing amount of the regenerant is the percentage of the mass of the regenerant to the mass of the old asphalt.
The final performance of the regeneration of the old asphalt is reflected on the level of the mixture, so for comparison with the invention, the performance test of the regenerated mixture is carried out according to the determined mixing amount of the regenerant.
When the used material content is 70%, the regenerant content H is 4.2% x 70% x 9% 0.26%.
The mix ratio of the reclaimed asphalt and the aggregate is the same as the above example, and the sum of the new asphalt amount and the regenerant amount of the reclaimed asphalt mixture is 2.3% in accordance with the above example, which is shown in Table 7 below.
TABLE 7 New asphalt and regenerant for reclaimed asphalt mixtures
| Amount of new pitch/%) | 2.04 |
| Amount of regenerant/% | 0.26 |
The mixing proportion is designed according to various materials of the regenerated asphalt mixture, a mixture test piece is formed according to the current technical specification for highway asphalt pavement construction, the water stability, the high-temperature stability and the low-temperature crack resistance of the regenerated asphalt mixture are tested and examined, and the test result is shown in the following table 8. Wherein, the water stability is evaluated by the indexes of the soaking Marshall residual stability and the freeze-thaw splitting strength ratio, the high temperature stability is evaluated by the index of the dynamic stability, and the low temperature crack resistance is evaluated by the index of the low temperature bending damage strain.
TABLE 8 test results of recycled asphalt mixture properties
From the above test results, it is understood that the amount of the regenerating agent used is increased irrespective of the oil absorption of the coarse aggregate. Because the viscosity of the regenerant is much lower than that of the asphalt, the regenerant is in a flowing state at normal temperature, so that the mixture is softer and the strength is reduced. The method reflects that the road performance of the recycled asphalt mixture is reduced to different degrees, particularly the dynamic stability is reduced by 62.2 percent compared with the test result of the invention, and the road performance of the recycled asphalt mixture does not meet the standard requirement. When the regenerated asphalt mixture is adopted to pave a regenerated asphalt pavement, track diseases are easy to occur, the service level of the road is reduced, and the driving safety of the road is seriously threatened. Particularly for the regeneration and on-site regeneration of a large proportion of old materials, the higher the mixing amount of the old materials is, the higher the mixing amount demand of the regenerant is, and the situation that the coarse aggregates absorb the asphalt is not considered, the higher the added regenerant is, so that the higher the risk of rutting diseases on the regenerated pavement is.
Embodiments of the present invention have been described above, and the above description is exemplary and not exhaustive. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the illustrated embodiments. The terminology used herein is chosen to best explain the method or practical engineering application of the embodiments, or to enable others of ordinary skill in the art to understand the disclosed embodiments of the present invention.
Claims (8)
1. A method for determining the mixing amount of a bituminous mixture regenerant based on the oil absorption rate of coarse aggregates is characterized by comprising the following steps:
(1) taking a certain amount of waste asphalt mixture, separating to obtain a mixed solution of asphalt and trichloroethylene and aggregate, and calculating the total asphalt content M in the waste asphalt mixture;
(2) recovering old asphalt in the asphalt and trichloroethylene mixed solution;
(3) testing the relative density rc of the old asphalt at 25 ℃;
(4) according to the regeneration target performance of the old asphalt, preliminarily determining the doping amount x of the regenerant relative to the old asphalt;
(5) testing the proportion h of the coarse aggregate in the aggregate obtained in the step (1), and testing the apparent relative density ra, the gross volume relative density rb and the water absorption w of the coarse aggregate;
(6) calculating the absorption coefficient P of the asphalt and the effective relative density rx of the coarse aggregate according to the apparent relative density ra, the gross volume relative density rb and the water absorption w of the coarse aggregate;
(7) the asphalt content Ma absorbed by the coarse aggregate is calculated as follows: ma ═ (rx-rb) × rc × 100/(rx × rb);
(8) calculating the mixing amount H of the asphalt mixture regenerant according to the following formula: h is (M-Ma multiplied by H) multiplied by n multiplied by x, wherein n is the blending ratio of the waste asphalt mixture,
in the step (6), the absorption coefficient P of the asphalt is calculated according to the following formula:
P＝0.033w2-0.2936w+0.9339。
2. the method of claim 1, wherein: the total asphalt content M in the mixed solution of asphalt and trichloroethylene, the aggregate and the waste asphalt mixture in the step (1) is obtained according to a centrifugal separation method (T0722-1993) in road engineering asphalt and asphalt mixture test procedures (JTG E20-2011).
3. The method of claim 1, wherein: the old asphalt in the step (2) is recovered according to an Abelson distillation method (T0726-2011) in the current road engineering asphalt and asphalt mixture test protocol (JTG E20-2011).
4. The method of claim 1, wherein: the relative density rc of the old asphalt in the step (3) at 25 ℃ is obtained according to an asphalt density and relative density test (T0603-2011) in road engineering asphalt and asphalt mixture sample specification (JTG E20-2011).
5. The method of claim 1, wherein: the step (4) specifically comprises the following steps:
(4-1) testing the penetration degree at 25 ℃, the softening point and the ductility at 15 ℃ of the old asphalt under different regenerant dosages;
(4-2) pointing test results into a graph by taking the dosage of the regenerant as an abscissa and taking the penetration degree, the softening point and the ductility at 25 ℃ as ordinates respectively, and connecting into three curves; according to the regeneration target performance of the old asphalt, the mixing amount x of the regenerant relative to the old asphalt is preliminarily determined.
6. The method of claim 5, wherein: in the step (4-2), the initial determination of the mixing amount x of the regenerant relative to the old asphalt is specifically as follows:
selecting a target asphalt label after the regeneration of the old asphalt;
obtaining from the three curves: meanwhile, the blending amount range of the regenerant corresponding to the requirements of penetration, softening point and ductility of a target asphalt label specified in technical Specification for road asphalt pavement regeneration (JTG/T5521-2019) is met;
any value in the regenerant dosage range is selected as a preliminarily determined regenerant dosage x.
7. The method according to claim 5 or 6, characterized in that: the step (5) specifically comprises the following steps:
(5-1) sieving the aggregate obtained by the centrifugal separation method by using a standard sieve of 2.36mm, taking the oversize part, and calculating the proportion h of the coarse aggregate in the aggregate;
(5-2) testing the apparent relative density ra, the bulk volume relative density rb and the water absorption w of the coarse aggregate according to the basket method (T0304-2005) of the existing road engineering aggregate test protocol (JTG E42-2005).
8. The method of claim 1, wherein: in the step (6), the effective relative density rx of the coarse aggregate is calculated according to the following formula:
rx＝P×ra+(1-P)×rb。
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