CN114216819A - Method for determining mixing amount of old materials in recycled asphalt mixture - Google Patents
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- 239000010426 asphalt Substances 0.000 title claims abstract description 261
- 239000000203 mixture Substances 0.000 title claims abstract description 106
- 239000000463 material Substances 0.000 title claims abstract description 79
- 238000002156 mixing Methods 0.000 title claims abstract description 76
- 238000000034 method Methods 0.000 title claims abstract description 73
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- 239000011521 glass Substances 0.000 claims description 31
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- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 claims description 15
- 235000019738 Limestone Nutrition 0.000 claims description 13
- 239000006028 limestone Substances 0.000 claims description 13
- 238000003756 stirring Methods 0.000 claims description 13
- ZHNUHDYFZUAESO-UHFFFAOYSA-N Formamide Chemical compound NC=O ZHNUHDYFZUAESO-UHFFFAOYSA-N 0.000 claims description 10
- 238000001816 cooling Methods 0.000 claims description 10
- 238000010438 heat treatment Methods 0.000 claims description 10
- 238000004519 manufacturing process Methods 0.000 claims description 9
- 239000012153 distilled water Substances 0.000 claims description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical group O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 8
- 239000003153 chemical reaction reagent Substances 0.000 claims description 7
- 238000012935 Averaging Methods 0.000 claims description 5
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- 238000002474 experimental method Methods 0.000 claims description 5
- 238000001514 detection method Methods 0.000 abstract description 7
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- 239000002699 waste material Substances 0.000 description 8
- 238000011056 performance test Methods 0.000 description 7
- 239000011384 asphalt concrete Substances 0.000 description 6
- 238000005452 bending Methods 0.000 description 6
- 239000007788 liquid Substances 0.000 description 6
- 230000003287 optical effect Effects 0.000 description 6
- 238000004064 recycling Methods 0.000 description 6
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- 239000012492 regenerant Substances 0.000 description 5
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- 238000010276 construction Methods 0.000 description 4
- 235000009161 Espostoa lanata Nutrition 0.000 description 3
- 240000001624 Espostoa lanata Species 0.000 description 3
- 238000004140 cleaning Methods 0.000 description 3
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- 230000007547 defect Effects 0.000 description 3
- 238000005238 degreasing Methods 0.000 description 3
- 238000013461 design Methods 0.000 description 3
- 238000007598 dipping method Methods 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
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- 238000011160 research Methods 0.000 description 3
- 238000007790 scraping Methods 0.000 description 3
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- 239000003795 chemical substances by application Substances 0.000 description 2
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- G01N13/02—Investigating surface tension of liquids
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N13/00—Investigating surface or boundary effects, e.g. wetting power; Investigating diffusion effects; Analysing materials by determining surface, boundary, or diffusion effects
- G01N13/02—Investigating surface tension of liquids
- G01N2013/0208—Investigating surface tension of liquids by measuring contact angle
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Abstract
The invention relates to the technical field of asphalt regeneration, in particular to a method for determining the mixing amount of old materials in a regenerated asphalt mixture. The method comprises the steps of firstly respectively obtaining the surface energy of a new asphalt test specimen and the surface energy of an old asphalt test specimen, then presetting the surface energy of the needed reclaimed asphalt, and finally substituting the surface energy into a calculation formula to obtain the mixing amount of the old material in the needed reclaimed asphalt, wherein the calculation formula is as follows: x ═ S (SFE)1‑SFE3)/(SFE2‑SFE3) 100%, wherein: SFE1Presetting the surface energy of the needed regenerated asphalt; SFE2Is the surface energy of the old asphalt; SFE3Surface energy of the new asphalt; x is the old material mixing amount (%). The method for determining the mixing amount of the old material in the recycled asphalt mixture is simple to operate, can accurately determine the mixing amount of the old material, saves the detection time and saves the raw materials. Meanwhile, the regenerated asphalt mixture obtained by the method for determining the doping amount has good road performance and valueCan be widely popularized and applied.
Description
Technical Field
The invention relates to the technical field of asphalt regeneration, in particular to a method for determining the mixing amount of old materials in a regenerated asphalt mixture.
Background
Road traffic, as an important sign for measuring national economic strength and modernization level, is an infrastructure for people's life, social development and national economy. Under the working policy of 'overall planning, combination of bars and blocks, layered responsibility and combined construction', the development of the road traffic industry in China is rarely met, the cross-over development occurs, and the traffic construction really becomes the key item day of economic construction in various regions. With the rapid development of the economy of China, the highway construction of China also obtains remarkable achievement in a short time.
Although the highway traffic mileage is the first in the world in China, under the action of environmental conditions and traffic loads, the asphalt pavement does not reach the designed service life, so that the defects of rutting, asphalt film peeling, loosening, particle dropping, net cracking, pit and the like are commonly caused, and the research on the regeneration of the asphalt pavement is very important. As is well known, the problem of waste Asphalt resources and the problem of pollution of waste materials can be solved by using a recycled Asphalt mixture (RAP) to produce and prepare a recycled Asphalt mixture. Meanwhile, the application of the RAP material can reduce the use of fresh aggregate and the production amount of new asphalt. Meanwhile, the dynamic modulus of the asphalt mixture can be improved by adding the RAP material, so that the regenerated asphalt pavement has better anti-rutting performance.
At present, the preparation method of the recycled asphalt mixture mainly comprises the following four steps: hot plant mix regeneration, hot in-place regeneration, cold emulsified asphalt regeneration and cold foamed asphalt regeneration. At present, hot mix plant recycling is the most widely applied method, but the existing method for determining the mixing amount of old materials in the recycled asphalt mixture is relatively complicated, and the Marshall design method is a volume design method and is the most widely applied method for designing the mixing ratio of the asphalt mixture at present. The disadvantages of this method are that marshall impact compaction does not simulate well the actual road compaction and marshall stability does not fully evaluate the shear strength of asphalt mixes. For old asphalt pavement materials which are seriously aged and brittle, if the old asphalt pavement materials are directly mixed into an asphalt mixture by high-viscosity asphalt without softening by using a regenerant, the Marshall stability is high, and the stability is higher when the mixing ratio of the old asphalt materials is higher, but the regenerated asphalt mixture has good quality. In contrast, paving a pavement surface with such asphalt mixtures can lead to premature cracking. Therefore, the Marshall test method is used to determine that the amount of the reclaimed asphalt mixture is not satisfactory.
Patent CN 107545125B discloses a method for calculating the mixing amount of old materials in a reclaimed asphalt mixture. The calculation method of the invention judges the size relationship of a and b according to the optimum asphalt content setting value b and the asphalt content a in the old material, further calculates the maximum doping amount p of the old material in the regenerated asphalt mixture, further calculates the amounts m and n of the old asphalt and the old aggregate which still need to be doped according to the maximum doping amount p of the old material, and finally calculates the doping amounts g and f of the new aggregate and the new asphalt.
Patent CN 102785291B discloses a method for determining the blending amount of asphalt mixture recycling agent, which comprises: 1) milling old materials and extracting; 2) testing the performance of the old asphalt; 3) determining the type and the mixing amount of a regenerant; wherein the old asphalt performance test comprises the following steps: 1) measuring the macroscopic viscosity of the waste asphalt; 2) and (4) measuring the micro components of the waste asphalt. The method is characterized in that the asphalt aging index C and the colloid instability index I are calculated by measuring the macroscopic viscosity index and the microscopic components of the waste asphalt. And aging gradient M, drawing a relation curve of the aging gradient M and aging time T, determining asphalt aging critical point T, and further determining the type and the mixing amount of the regenerant according to the waste asphalt with different aging grades.
Patent CN 110261587B discloses a method for determining a hot in-place recycling mix proportion, which comprises: sampling an old asphalt pavement to obtain an old asphalt mixture sample, wherein the old asphalt mixture sample comprises: a performance test sample for testing the performance of the old asphalt pavement and a test sample for manufacturing a test article; performing performance test on the performance test sample to obtain a performance test result, and determining the optimal mixing ratio and the target mixing ratio of the regenerant of the regenerated mixture according to the performance test result; and determining the proportion of the optimal new asphalt to the new aggregate in the new asphalt mixture and the proportion of the optimal new asphalt mixture to the old asphalt pavement by using the test sample. By the method for determining the mix proportion of the hot in-place recycling re-mixing, the quality of the recycling agent to be added, the quality of the new asphalt mixture and the proportion of new asphalt and new aggregate in the new asphalt mixture can be rapidly determined in the re-mixing process, and the efficiency of hot in-place recycling re-mixing is improved.
The patent CN 105601176B discloses a plant-mixed hot recycled asphalt concrete production method, which comprises a plant-mixed hot recycled asphalt concrete grading determination method, a plant-mixed hot recycled asphalt concrete oil-stone ratio determination method and a plant-mixed hot recycled asphalt concrete preparation process. The method has the advantages that the old materials are divided into three grades, the influence of the variability of the old materials on the road performance of the plant-mixed hot recycled asphalt concrete is avoided, and meanwhile, the plant-mixed hot recycled asphalt concrete with different road performance can be obtained by controlling the passing rate of the key sieve pores; the method greatly reduces the test amount for determining the optimal asphalt addition amount; in the preparation process, the new material and the new asphalt are uniformly mixed and then added into the heated old material, so that the thickness difference of the asphalt films of the new and old asphalt mixtures is reduced, the asphalt dosage is effectively reduced, and the occurrence of white materials is avoided.
The above patent technology provides technical support for calculating the mixing amount of new and old asphalt and new and old aggregates, and greatly promotes the technical development of the research and research of the asphalt mixture mixing amount determining method. Second, the marshall design method was used to determine the mix ratio, since marshall impact compaction does not simulate the actual road compaction well and marshall stability does not fully evaluate the shear strength of the mix. Therefore, if the old asphalt pavement material which is seriously aged and brittle is directly mixed with high-viscosity asphalt to form an asphalt mixture without softening the old asphalt pavement material by using a regenerant, the Marshall stability is high, and the stability is higher when the mixing ratio of the old asphalt pavement material is higher, but the good quality of the regenerated asphalt mixture is not shown. In contrast, paving a pavement surface with such asphalt mixtures can lead to premature cracking. Therefore, it is necessary to provide a method for accurately determining the mixing amount of the old asphalt mixture, which is simple and convenient to operate, saves the detection time, saves the raw materials, and can ensure the mixing amount of the old asphalt mixture with easy quality.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to solve the technical problem of providing the method for determining the mixing amount of the old material in the regenerated asphalt mixture, which is simple to operate, can accurately determine the mixing amount of the old material, saves the detection time and saves the raw materials.
The technical scheme adopted by the invention for realizing the purpose is as follows: a method for determining the mixing amount of old materials in a reclaimed asphalt mixture comprises the steps of firstly respectively obtaining the surface energy of a new asphalt test specimen and the surface energy of an old asphalt test specimen, then presetting the surface energy of needed reclaimed asphalt, and finally substituting into a calculation formula to obtain the mixing amount of the old materials in the needed reclaimed asphalt, wherein the calculation formula is as follows:
wherein: SFE1Presetting the surface energy of the needed regenerated asphalt; SFE2Is the surface energy of the old asphalt; SFE3Surface energy of the new asphalt; x is the old material mixing amount (%).
The method for determining the mixing amount of the old materials in the recycled asphalt mixture comprises the following specific steps:
(1) heating new asphalt, dripping the heated new asphalt on a glass slide, manufacturing a glass slide new asphalt test piece, and cooling to room temperature for later use;
(2) pouring the old asphalt mixture and the stone into a mixing machine for stirring, controlling the temperature of the mixing machine to be 160 ℃ for 200s, taking out the old asphalt test specimen after stirring, and cooling to room temperature for later use;
(3) controlling the test temperature to be 20-25 ℃, selecting a contact angle reagent, detecting 6 groups of contact angles, removing data with larger errors, and averaging the rest data;
(4) inputting the contact angle, the surface tension, the polar component and the dispersion component obtained in the step (3) into surface energy calculation software, and respectively obtaining the surface energy of the new asphalt and the surface energy of the old asphalt through a fitted equation;
(5) and finally, measuring the surface energy of the required regenerated asphalt according to a plurality of experiments, and calculating the mixing amount of the old material in the required regenerated asphalt according to a calculation formula of the mixing amount of the old material.
In the method for determining the mixing amount of the old materials in the recycled asphalt mixture, in the step (1), the heating temperature of the new asphalt is 130-160 ℃, and the thickness of the new asphalt test specimen is 1.5-2 mm.
In the step (2), the old asphalt mixture is firstly heated in the oven for 2-3h, and the temperature of the oven is set to 110-.
In the method for determining the doping amount of the old material in the regenerated asphalt mixture, the stone block in the step (2) is a limestone block, the limestone block is cut into cubes before the stone block and the old asphalt mixture are put into a mixer, then the cubes are put into an oven, the temperature of the oven is adjusted to be 150 ℃ plus 170 ℃, and the stone block is dried to be constant weight.
In the method for determining the mixing amount of the old materials in the recycled asphalt mixture, in the step (3), the contact angle reagent is distilled water, glycerol or formamide.
The method for determining the mixing amount of the old materials in the recycled asphalt mixture has the beneficial effects that: compared with the traditional method of determining the mixing amount of the old materials by manufacturing a Marshall test piece, the method can greatly save detection time and raw materials by applying a surface energy method; through the calculation of the surface energy, the mixing amount of the old material can be accurately determined, the material waste caused by manufacturing a Marshall test piece is reduced, the resources are saved, the time and the energy spent on detecting the performance of the mixture are saved, and the mixing amount of the old material of the regenerated material can be determined only through the surface energy. The method for determining the mixing amount of the old material in the recycled asphalt mixture is simple to operate, can accurately determine the mixing amount of the old material, saves the detection time and saves the raw materials. Meanwhile, the regenerated asphalt mixture obtained by the method for determining the doping amount has good road performance and is worthy of wide popularization and application.
Drawings
FIG. 1 is a diagram of a new asphalt test specimen;
FIG. 2 is a diagram of a sample for an old asphalt test;
FIG. 3 is a test result of the surface energy of an old asphalt test specimen calculated by software;
FIG. 4 is a comparison graph of dynamic stability test data of a fresh asphalt mixture (A), a recycled asphalt mixture (B) prepared by a common method and a recycled asphalt mixture (C) prepared by the method of the invention;
FIG. 5 is a comparison chart of the low-temperature bending test data of the fresh asphalt mixture (A), the recycled asphalt mixture (B) prepared by the common method and the recycled asphalt mixture (C) prepared by the method of the invention.
Detailed Description
The invention is further explained in detail with reference to the drawings and the specific embodiments;
example 1
As shown in fig. 1, 2 and 3, a method for determining the mixing amount of an old material in a reclaimed asphalt mixture comprises the following steps of firstly respectively obtaining the surface energy of a new asphalt test specimen and the surface energy of an old asphalt test specimen, then presetting the surface energy of required reclaimed asphalt, and finally substituting the preset surface energy into a calculation formula to obtain the mixing amount of the old material in the required reclaimed asphalt:
(1) cleaning a glass slide with distilled water, removing impurities such as dust on the surface, wiping the surface of the glass slide with a degreasing cotton ball, baking the glass slide close to a hot electric furnace, covering the glass slide with a dust separation device for 30min, cooling to room temperature, heating new asphalt to 150 ℃, dipping a small amount of asphalt on the glass slide with a brush, slightly inclining the glass slide to enable the asphalt to slowly flow on the surface of the glass slide until the glass slide is smooth and free of bubbles, covering the prepared new asphalt test piece on the glass slide with the asphalt thickness of 1.5mm, and cooling the prepared new asphalt test piece to room temperature.
(2) Preparing limestone stone blocks, cutting the limestone stone blocks into cubes of 8 blocks, wherein the side length standard is 2cm, putting the cubes in an oven, adjusting the temperature of the oven to 150 ℃, and drying the limestone stone blocks to constant weight.
(3) Taking 2kg of old asphalt mixture, putting the old asphalt mixture into an oven, setting the temperature of the oven at 120 ℃, and heating for 3 h. Adjusting the temperature of the mixer to 150 ℃, pouring the old asphalt mixture and the cubic stone into the mixer, starting stirring, and stirring for 180 s. And taking out the old asphalt test specimen after stirring, scraping off non-asphalt residues on the surface, putting the old asphalt test specimen into a dust separation device to cover the old asphalt test specimen until the old asphalt test specimen is cooled to room temperature.
(4) Controlling the temperature of a laboratory at 20 ℃, respectively placing a new asphalt test piece and an old asphalt test piece on an optical contact angle instrument, starting the optical contact angle instrument, selecting distilled water, glycerol and formamide as contact angle reagents, detecting 6 groups of contact angles by using each liquid, removing data with large errors, and averaging the rest data.
(5) The contact angle, surface tension, polar component and dispersion component of the three liquids at 20 ℃ are input into surface energy calculation software. The surface energy of the new asphalt test piece is 21.33mJ/m through the fitted equation2The surface energy of the old asphalt test piece is 24.61mJ/m2。
(6) According to the conclusion of multiple experiments, when the surface energy of the reclaimed asphalt mixture is 1.1 times that of the new asphalt, the pavement performance meets the specification requirement, and the SFE1 is 23.46mJ/m2According toThe formula for calculating the mixing amount of the old materials is as follows:
wherein: SFE1Presetting the surface energy of the needed regenerated asphalt; SFE2Is the surface energy of the old asphalt; SFE3Surface energy of the new asphalt; x is the old material mixing amount (%).
The above values are substituted into a calculation formula to calculate that x is 65.0%.
Therefore, the mixing amount of the old asphalt is 65.0 percent under the condition of selecting the new asphalt and the old asphalt mixture, and the pavement performance of the asphalt meets the standard requirement.
The method for determining the mixing amount of the old materials in the recycled asphalt mixture can be used for determining the reasonable mixing amount of the old materials in the recycled asphalt mixture. Aiming at the defects of long experimental period, material waste and complicated steps of the existing Marshall test piece manufacturing method for determining the mixing amount of the old material, the method can greatly save detection time and raw materials by using a surface energy method, and can accurately determine the mixing amount of the old material. The method comprises the specific steps of respectively manufacturing surface energy test specimens of the new asphalt and the old asphalt mixture, measuring a contact angle by using a lying-drop method, calculating the surface energy, and substituting the surface energy of the preset regenerated asphalt into a calculation formula to obtain the proper amount of the old asphalt. That is, the invention can greatly improve the detection efficiency and save raw materials by applying the surface energy method, and can accurately determine the mixing amount of the old materials, and the determined surface energy has high representativeness and can fully represent the anti-rutting property of the regenerated asphalt. It is known that the surface energy of asphalt can represent the level of adhesion property of asphalt, and the surface energy of asphalt gradually increases as the aging degree of asphalt increases. Therefore, the present invention can be realized by evaluating the properties of asphalt using surface energy.
Example 2
A method for determining the mixing amount of old materials in a reclaimed asphalt mixture comprises the following steps of firstly respectively obtaining the surface energy of a new asphalt test specimen and the surface energy of an old asphalt test specimen, then presetting the surface energy of needed reclaimed asphalt, and finally substituting the surface energy into a calculation formula to obtain the mixing amount of the old materials in the needed reclaimed asphalt, wherein the method comprises the following specific steps:
(1) cleaning a glass slide with distilled water, removing impurities such as dust on the surface, wiping the surface of the glass slide with a degreasing cotton ball, baking the glass slide close to a hot electric furnace, covering the glass slide with a dust separation device for 30min, cooling to room temperature, heating new asphalt to 150 ℃, dipping a small amount of asphalt on the glass slide with a brush, slightly inclining the glass slide to enable the asphalt to slowly flow on the surface of the glass slide until the glass slide is smooth and free of bubbles, covering the prepared new asphalt test piece on the glass slide with the asphalt thickness of 1.5mm, and cooling the prepared new asphalt test piece to room temperature.
(2) Preparing limestone stone blocks, cutting the limestone stone blocks into cubes of 8 blocks, wherein the side length standard is 2cm, putting the cubes in an oven, adjusting the temperature of the oven to 150 ℃, and drying the limestone stone blocks to constant weight.
(3) Taking 2kg of old asphalt mixture, putting the old asphalt mixture into an oven, setting the temperature of the oven at 120 ℃, and heating for 3 h. Adjusting the temperature of the mixer to 150 ℃, pouring the old asphalt mixture and the cubic stone into the mixer, starting stirring, and stirring for 180 s. And taking out the old asphalt test specimen after stirring, scraping off non-asphalt residues on the surface, putting the old asphalt test specimen into a dust separation device to cover the old asphalt test specimen until the old asphalt test specimen is cooled to room temperature.
(4) Controlling the temperature of a laboratory at 20 ℃, respectively placing a new asphalt test piece and an old asphalt test piece on an optical contact angle instrument, starting the optical contact angle instrument, selecting distilled water, glycerol and formamide as contact angle reagents, detecting 6 groups of contact angles by using each liquid, removing data with large errors, and averaging the rest data.
(5) The contact angle, surface tension, polar component and dispersion component of the three liquids at 20 ℃ are input into surface energy calculation software. The surface energy of the new asphalt test piece obtained by the fitted equation is 17.25mJ/m2The surface energy of the old asphalt test piece is 21.75mJ/m2。
(6) According to the conclusion of multiple experiments, when the surface energy of the regenerated asphalt mixture is 1.2 times of that of the new asphalt, the pavement performance of the regenerated asphalt mixture meets the standard requirement,then SFE1 is 20.70mJ/m2According to a calculation formula of the mixing amount of the old materials:
wherein: SFE1Presetting the surface energy of the needed regenerated asphalt; SFE2Is the surface energy of the old asphalt; SFE3Surface energy of the new asphalt; x is the old material mixing amount (%).
The above values are substituted into the calculation formula to calculate that x is 76.67%.
Example 3
A method for determining the mixing amount of old materials in a reclaimed asphalt mixture comprises the following steps of firstly respectively obtaining the surface energy of a new asphalt test specimen and the surface energy of an old asphalt test specimen, then presetting the surface energy of needed reclaimed asphalt, and finally substituting the surface energy into a calculation formula to obtain the mixing amount of the old materials in the needed reclaimed asphalt, wherein the method comprises the following specific steps:
(1) cleaning a glass slide with distilled water, removing impurities such as dust on the surface, wiping the surface of the glass slide with a degreasing cotton ball, baking the glass slide close to a hot electric furnace, covering the glass slide with a dust separation device for 30min, cooling to room temperature, heating new asphalt to 150 ℃, dipping a small amount of asphalt on the glass slide with a brush, slightly inclining the glass slide to enable the asphalt to slowly flow on the surface of the glass slide until the glass slide is smooth and free of bubbles, covering the prepared new asphalt test piece on the glass slide with the asphalt thickness of 1.5mm, and cooling the prepared new asphalt test piece to room temperature.
(2) Preparing limestone stone blocks, cutting the limestone stone blocks into cubes of 8 blocks, wherein the side length standard is 2cm, putting the cubes in an oven, adjusting the temperature of the oven to 150 ℃, and drying the limestone stone blocks to constant weight.
(3) Taking 2kg of old asphalt mixture, putting the old asphalt mixture into an oven, setting the temperature of the oven at 120 ℃, and heating for 3 h. Adjusting the temperature of the mixer to 150 ℃, pouring the old asphalt mixture and the cubic stone into the mixer, starting stirring, and stirring for 180 s. And taking out the old asphalt test specimen after stirring, scraping off non-asphalt residues on the surface, putting the old asphalt test specimen into a dust separation device to cover the old asphalt test specimen until the old asphalt test specimen is cooled to room temperature.
(4) Controlling the temperature of a laboratory at 20 ℃, respectively placing a new asphalt test piece and an old asphalt test piece on an optical contact angle instrument, starting the optical contact angle instrument, selecting distilled water, glycerol and formamide as contact angle reagents, detecting 6 groups of contact angles by using each liquid, removing data with large errors, and averaging the rest data.
(5) The contact angle, surface tension, polar component and dispersion component of the three liquids at 20 ℃ are input into surface energy calculation software. The surface energy of the new asphalt test piece is 16.39mJ/m through the fitted equation2The surface energy of the old asphalt test piece is 18.67mJ/m2。
(6) According to the conclusion of multiple experiments, when the surface energy of the reclaimed asphalt mixture is 1.05 times that of the new asphalt, the pavement performance meets the specification requirement, and the SFE1 is 17.21mJ/m2According to a calculation formula of the mixing amount of the old materials:
wherein: SFE1Presetting the surface energy of the needed regenerated asphalt; SFE2Is the surface energy of the old asphalt; SFE3Surface energy of the new asphalt; x is the old material mixing amount (%).
The above values are substituted into a calculation formula to calculate that x is 36.0%.
The performance test is carried out on the recycled asphalt mixture prepared by the method for determining the doping amount of the old material in the recycled asphalt mixture, the fresh-mixed asphalt mixture (A), the recycled asphalt mixture (B) prepared by the common method and the recycled asphalt mixture (C) prepared by the method are respectively prepared according to the standard AC-13 grading median, the high-temperature performance is determined by a rutting test, wherein the dynamic stability of the fresh-mixed asphalt mixture (A) is 6089 times/mm, the dynamic stability of the recycled mixture (B) prepared by the common method is 6530 times/mm, the dynamic stability of the recycled asphalt mixture (C) prepared by the method is 6190 times/mm, as shown in figure 4, the dynamic stability of the recycled asphalt mixture prepared by the common method is closer to that of the fresh-mixed asphalt mixture compared with the method for determining the doping amount of the common old material, and the dynamic stability of the mixture determined by the common method is much higher than that of the old material, this is because the ordinary old asphalt is not accurately mixed, which results in higher mixing amount of old asphalt, and the old asphalt becomes brittle due to aging and hardening, and the dynamic stability becomes higher. Respectively preparing a fresh asphalt mixture (A), a recycled mixture (B) by a common method and a recycled asphalt mixture (C) prepared by the method according to a standard AC-13 grading median, and determining low-temperature performance by a low-temperature trabecular bending test, wherein the bending strain of the fresh asphalt mixture (A) is 3259u epsilon, the bending strain of the recycled mixture (B) by the common method is 2600u epsilon, and the bending strain of the recycled asphalt mixture (C) prepared by the method is 3029u epsilon, as shown in figure 5, as can be seen from the attached drawings and test data, compared with a common old material mixing amount determining method, the low-temperature bending strain of the invention is close to that of the fresh asphalt mixture, which shows that the old material mixing amount determining method adopted by the invention is more reasonable, and the performance of the prepared asphalt mixture is more excellent.
The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention accordingly, and not to limit the protection scope of the present invention accordingly. All equivalent changes or modifications made according to the spirit of the present disclosure should be covered within the scope of the present disclosure.
Claims (6)
1. A method for determining the mixing amount of old materials in a recycled asphalt mixture is characterized by comprising the following steps: respectively obtaining the surface energy of a new asphalt test specimen and the surface energy of an old asphalt test specimen, presetting the surface energy of the needed reclaimed asphalt, and finally substituting into a calculation formula to obtain the mixing amount of the old material in the needed reclaimed asphalt, wherein the calculation formula is as follows:
wherein: SFE1Presetting the surface energy of the needed regenerated asphalt; SFE2Of old bitumenSurface energy; SFE3Surface energy of the new asphalt; x is the old material mixing amount (%).
2. The method for determining the mixing amount of the old materials in the reclaimed asphalt mixture according to claim 1, which is characterized by comprising the following steps:
(1) heating new asphalt, dripping the heated new asphalt on a glass slide, manufacturing a glass slide new asphalt test piece, and cooling to room temperature for later use;
(2) pouring the old asphalt mixture and the stone into a mixing machine for stirring, controlling the temperature of the mixing machine to be 160 ℃ for 200s, taking out the old asphalt test specimen after stirring, and cooling to room temperature for later use;
(3) controlling the test temperature to be 20-25 ℃, selecting a contact angle reagent, detecting 6 groups of contact angles, removing data with larger errors, and averaging the rest data;
(4) inputting the contact angle, the surface tension, the polar component and the dispersion component obtained in the step (3) into surface energy calculation software, and respectively obtaining the surface energy of the new asphalt and the surface energy of the old asphalt through a fitted equation;
(5) and finally, measuring the surface energy of the required regenerated asphalt according to a plurality of experiments, and calculating the mixing amount of the old material in the required regenerated asphalt according to a calculation formula of the mixing amount of the old material.
3. The method for determining the mixing amount of the old materials in the reclaimed asphalt mixture according to claim 2, which is characterized in that: in the step (1), the heating temperature of the new asphalt is 130-.
4. The method for determining the mixing amount of the old materials in the reclaimed asphalt mixture according to claim 2, which is characterized in that: in the step (2), the old asphalt mixture is firstly heated in an oven for 2-3h, and the temperature of the oven is set to be 110-.
5. The method for determining the mixing amount of the old materials in the reclaimed asphalt mixture according to claim 2, which is characterized in that: the stone in the step (2) is limestone stone, the limestone stone is cut into cubes before the stone and the old asphalt mixture are put into a mixer, then the cubes are put into an oven, the temperature of the oven is adjusted to 150-.
6. The method for determining the mixing amount of the old materials in the reclaimed asphalt mixture according to claim 2, which is characterized in that: in the step (3), the contact angle reagent is selected from distilled water, glycerol and formamide.
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