A method and index for evaluating the permeability of a high-permeability warm recycling agent for in-place thermal recycling technology

Abstract

A kind of high permeability warm recycling agent permeability evaluation method and index for in-place hot recycling technology, comprising the following steps: mixing aged asphalt with new asphalt, adding warm mixing agent to develop warm mixing, to prepare warm asphalt;In the flowing state of warm asphalt, use brass or stainless steel ball with diameter of 15mm to uniformly dip asphalt, and let it cool and solidify naturally;Wrap with recycling agent mixed with tracer, stand at room temperature for 12h to let it penetrate into asphalt layer naturally;Dissolve asphalt layer layer by layer with trichloroethylene, extract the solution, and then test the extract by FTIR, the peak area of tracer gradually decreases with the depth of layer from the infrared spectrum absorption peak, and the penetration concentration attenuation equation of recycling agent is obtained by fitting the data of layer, so that the permeability of warm recycling agent can be evaluated.The present application is simple and easy to operate, can quickly detect the penetration performance of warm recycling agent, and has good application prospect.

Description

Technical Field

[0001] This invention relates to the field of highway pavement material performance testing technology, specifically to a method and index for evaluating the permeability of a high-permeability warm recycling agent used in in-situ thermal recycling technology. Background Technology

[0002] The design life of asphalt pavement is generally 8 to 15 years. Starting now, about 10% of asphalt pavement will enter the maintenance or reconstruction cycle each year, generating millions of tons of waste asphalt pavement materials annually. If these waste asphalt pavement materials could be recycled and reused, at least hundreds of millions of yuan in material costs would be saved each year. Moreover, with the continuous construction of infrastructure, this figure is increasing at a rate of about 15% per year.

[0003] The most common road recycling technology is hot recycling. However, due to the high construction temperature of hot recycling, which affects the performance of asphalt materials and is prone to pollution, warm recycling technology is more suitable for use in road construction. Warm-mix recycling technology combines the cooling technology of warm mixing with the technology of hot recycling. It has the advantages of hot recycling, and saves energy by reducing the mixing and compaction temperature by 20℃-30℃, reduces the aging of asphalt, and thus makes up for the shortcomings of hot recycling technology.

[0004] One of the key aspects of warm-mix recycling technology is the warm recycling of asphalt. When the old asphalt is highly aged or the content of the old asphalt mixture during the recycling process is too high, a recycling agent must be added to restore its performance on the road surface. In this case, warm-recycled asphalt is a composite asphalt material, which is equivalent to adding a certain proportion of warm-mix agent and recycling agent to a mixture of old and new asphalt; that is, it consists of four parts: new asphalt, old asphalt, recycling agent, and warm-mix agent. The added recycling agent and warm-mix agent will change the properties of the asphalt.

[0005] The permeability of recycling agents is one of the most important factors affecting the performance of warm-mix recycled asphalt. Good permeability allows recycling agents to enter the asphalt more quickly and evenly. However, there is currently no unified method or index in the industry to evaluate the permeability of warm-mix recycled asphalt, making it impossible to quickly evaluate the permeability effect of asphalt recycling agents. Summary of the Invention

[0006] Technical problem solved: This invention provides a method and index for evaluating the permeability of a high-permeability warm recycling agent for in-situ thermal recycling technology. This method can determine the permeability effect of asphalt warm recycling agents. The method is simple and easy to operate, and the test cycle is short, so the results can be obtained quickly. This solves the current problem that it is impossible to quickly evaluate the permeability effect of asphalt warm recycling agents.

[0007] Technical solution: A method for evaluating the permeability of a high-permeability thermal regenerator for in-situ thermal regeneration technology, comprising the following steps:

[0008] Step 1. Mix aged asphalt and new asphalt at a mass ratio of (2~4):(6~8) to obtain recycled asphalt;

[0009] Step 2. Add the warm mix additive to the recycled asphalt at a rate of 10-15 wt% of the aged asphalt content. Use a triaxial high-speed shear apparatus at 150°C and a rotation speed of 3000-4000 rpm for 30 min to shear and mix the mixture to obtain a warm mix asphalt sample.

[0010] Step 3. While the warm-mix asphalt sample is in a flowing state, dip a brass or stainless steel ball with a diameter of 15mm connected by a thin metal wire into the asphalt. When dipping, the ball should be completely immersed in the asphalt. Allow it to cool and solidify naturally to obtain a spherical asphalt structure. The allowable error for the diameter of the ball is 0.05mm. The connected wire structure facilitates the dipping of asphalt and hanging for preservation.

[0011] Step 4. Coat the spherical asphalt structure prepared in step 3 with the regenerant containing 5~20 wt% tracer, and let it stand at room temperature for 12 hours to allow it to penetrate into the interior of the asphalt.

[0012] Step 5. Immerse the small balls treated in Step 4 in clear trichloroethylene at 25±0.5℃ for 1 min to dissolve the asphalt and obtain a trichloroethylene asphalt solution.

[0013] Step 6. Place the trichloroethylene asphalt solution into an extractor for extraction to remove the solvent and obtain dissolved asphalt;

[0014] Step 7. Perform FTIR analysis on the dissolved asphalt obtained in Step 6;

[0015] Step 8. Repeat steps 5 to 7 until the asphalt on the surface of the ball is completely dissolved. Use clarified trichloroethylene each time you repeat and dissolve the asphalt to eliminate the influence of impurities on the results.

[0016] Step 9. Encode the number of asphalt dissolution layers from the outside to the inside as 1, 2, 3, 4...n. Observe the characteristic absorption peaks of the tracer in FTIR and calculate their peak areas, labeling them as A1, A2, A3, A4...An respectively. Then, perform data fitting to obtain the concentration decay equation. The penetration performance of the warm recycling agent can be evaluated by the integral value of the dissolution layer sites in the equation or the number of penetration layers under the same conditions. The larger the integral value, the better the penetration performance of the warm recycling agent; the more penetration layers, the better the penetration performance of the warm recycling agent.

[0017] Preferably, in step nine, if the number of permeated layers is less than 50% of the total number of dissolved layers, it is considered medium permeability; 50%-80% is considered high permeability; and more than 80% is considered strong permeability. The integral value of the concentration decay equation is defined as follows: less than 8000 is considered medium permeability; 8000-12000 is considered high permeability; and more than 12000 is considered strong permeability.

[0018] Preferably, in step one, the new asphalt is asphalt made from petroleum products used in road construction, and the aged asphalt is asphalt that has been aged at 163°C for 5 hours.

[0019] Preferably, the new asphalt in step one is SK70# asphalt.

[0020] Preferably, the warm mixing agent in step two is Sasobit™ warm mixing agent.

[0021] Preferably, the thickness of the asphalt in the spherical asphalt structure in step three is 3 mm radially.

[0022] Preferably, in step four, the regenerant coating thickness of adding 5-20 wt% tracer is 1 mm radially.

[0023] Preferably, the tracer is an amino-terminated nitrile rubber, a plasticizer DOP, or a pentasubstituted tetrahydropyrimidine, which should have the characteristics of not reacting with penetrants, warm mix agents, and asphalt and possessing characteristic functional groups, and the regenerator is a bio-oil regenerator, a lightweight regenerator, or a composite regenerator.

[0024] The above-mentioned in-situ thermal regeneration technology uses a high-permeability thermal regenerator permeability evaluation method to evaluate the indicators.

[0025] This invention is based on experiments conducted when trichloroethylene dissolves asphalt at a solubility of 95% and the surface of a small ball is coated with 3mm of asphalt. The results showed that the radial thickness of the dissolved asphalt layer was approximately 0.3-0.6mm per minute of immersion. In practice, the dissolution time should be adjusted appropriately for different solubilities of trichloroethylene and different thicknesses of asphalt coating layers. However, care should be taken not to make the thickness too large to prevent the adhesion from weakening during the suspension process and causing it to drip downwards, thus affecting the test results.

[0026] Beneficial effects: The present invention proposes a method and index for evaluating the permeability of a high-permeability warm recycling agent for in-situ thermal recycling technology. This method can quickly evaluate the permeability of asphalt warm recycling agents, providing convenience for engineering and research, and has good application prospects.

[0027] Under the same conditions, the greater the number of layers where the tracer absorption peak disappears as observed by FTIR and the greater the cumulative interlayer permeation, the better the permeation performance of the warm regenerator. The concentration decay equation and its parameters are defined as evaluation indicators.

[0028] The method and index for evaluating the permeability of warm recycling agents described in this invention refer to the number of asphalt layers of a certain thickness that the warm recycling agent naturally penetrates into under normal temperature conditions, which can be used to evaluate the permeability of warm recycling agents.

[0029] This invention is simple and easy to operate, and can quickly detect the permeation performance of warm regenerators, showing good application prospects. Attached Figure Description

[0030] Figure 1 This is a schematic diagram illustrating the process of the spherical asphalt structure described in this invention, from dipping in and dissolving asphalt to performing FTIR detection.

[0031] Figure 2 This is a flowchart illustrating the operation of the permeability evaluation method for the high-permeability thermal regenerator used in the in-situ thermal regeneration technology described in this invention.

[0032] Figure 3 This is a schematic diagram of the FTIR test results of the present invention, where the horizontal axis represents the infrared spectral wavenumber (cm). -1 The vertical axis represents the absorbance of functional groups (%).

[0033] Figure 4 This is the concentration decay curve fitted in Example 1 of the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0035] Example 1

[0036] A method for evaluating the permeability of a high-permeability thermal regenerator used in in-situ thermal regeneration technology, see [link to relevant documentation]. Figure 2 First, aged asphalt is prepared by aging the base asphalt (new asphalt) in a rotary film oven at 163°C for five hours. The aged asphalt is then removed and set aside. The aged asphalt and new asphalt are then mixed uniformly at a mass ratio of 3:7, with the addition of a glass rod or high-speed mixer if necessary. In this embodiment, the base asphalt used is SK70# asphalt.

[0037] The finished Sasobit™ warm mix additive was added to the asphalt at 12 wt% of the old asphalt content. The mixture was then sheared and stirred at 3000 rpm for 30 minutes at 150°C using a triaxial high-speed shear apparatus to obtain a warm mix asphalt sample.

[0038] See the flow condition of the warm-mix asphalt sample. Figure 1 Dip a small brass or stainless steel ball with a 15mm diameter connecting wire into the asphalt. Immerse the ball completely in the asphalt and remove it after 5 seconds. Repeat this process several times to obtain a uniform and continuous asphalt layer, up to a radial thickness of 3mm. Then suspend the asphalt-coated ball to cool for 15 minutes to ensure the asphalt hardens and sets.

[0039] The cooled asphalt spheres are then coated with a 1mm radial layer of recycling agent containing a tracer. The tracer and recycling agent must be thoroughly mixed, and the mixture is allowed to stand and infiltrate for 12 hours. In this embodiment, the tracer used is DOP, at a dosage of 7.5% of the recycling agent mass. The recycling agent in this embodiment is a commercially available finished composite recycling agent, purchased from Tongsha Asphalt Technology Co., Ltd.

[0040] The pellets were immersed in clarified trichloroethylene at 25°C for 1 minute to dissolve the asphalt, yielding a trichloroethylene asphalt solution. The trichloroethylene asphalt solution was then extracted using an extractor to remove the solvent, obtaining the dissolved asphalt. The dissolved asphalt was analyzed by FTIR. This process was repeated until all the asphalt on the pellet surface was dissolved. Clarified trichloroethylene was used each time to eliminate the influence of impurities on the results. The solvent was placed in the extractor to extract the dissolved asphalt, and the samples were then stored separately. FTIR testing was performed on the extracted samples; the characteristic peak of the plasticizer DOP appeared at 1281 cm⁻¹. -1 Left and right, such as Figure 3 As shown. In this embodiment, the asphalt was dissolved 6 times in total. The number of asphalt dissolution layers from the outside to the inside were 1, 2, 3, 4, 5, and 6, respectively. The characteristic absorption peaks of the tracer in the FTIR were observed and their peak areas were calculated. They were labeled as A1, A2, A3, A4, A5, and A6, respectively. Then, data fitting was performed.

[0041] 1281 cm⁻¹ was measured using Origin 2020 software and FTIR. -1 The peak intensities at the given values ​​were A1=612, A2=574, A3=515, A4=421, A5=387, and A6=262, respectively. The concentration decay equation image fitted using the obtained data is shown below. Figure 4 As shown.

[0042] The fitted concentration decay equation is y = 1.214 + 0.314x 1.759 The total number of permeable layers is 6. Therefore, integrating this equation over the domain (0, 6) yields a value of 15864, indicating that the total permeation of the FTIR peak intensity during the decay process is 15864 cm⁻¹. -1 This is a fairly high concentration value, which shows that the test penetrant has a good penetrating effect.

Claims

1. A method for evaluating the permeability of a high-permeability warm recycling agent for in-place thermal recycling technology, characterized by, The steps are as follows: Step one. Mix the aged asphalt and new asphalt uniformly at a mass ratio of 2-4:6-8 to obtain the recycled asphalt; Step two. Add the warm-mixing agent to the recycled asphalt, the addition amount is 10-15 wt% of the aging asphalt content, and the warm-mixing asphalt sample is obtained after shearing and stirring at 150℃ for 30 min at a speed of 3000-4000 rpm using a triaxial high-speed shearing instrument; Step three. In the flowing state of the warm-mixing asphalt sample, a small brass or stainless steel ball with a diameter of 15 mm connected with a thin metal wire is used to dip the asphalt, the ball is completely immersed in the asphalt during dipping, and the ball asphalt structure is obtained after natural cooling and solidification; Step four. Wrap the recycled agent with 5-20 wt% tracer on the ball asphalt structure prepared in step three, and stand at room temperature for 12 h to allow it to penetrate and immerse into the asphalt; Step five. Dip the ball after step four into clear trichloroethylene at 25±0.5℃ for 1 min to dissolve the asphalt, and obtain the trichloroethylene asphalt solution; Step six. Put the trichloroethylene asphalt solution into an extractor to remove the solvent to obtain the dissolved asphalt; Step seven. Perform FTIR detection on the dissolved asphalt obtained in step six; Step eight. Repeat the operations of steps five to seven until the asphalt on the surface of the ball is completely dissolved; Step nine. Encode the asphalt dissolution layers from outside to inside as 1, 2, 3, 4, …… n, observe the characteristic absorption peak of the tracer in FTIR, and calculate the peak area, which is respectively marked as A1, A2, A3, A4, …… An, then perform data fitting to obtain the concentration attenuation equation, and the penetration performance of the warm recycling agent can be evaluated by the integral value of the equation or the number of penetration layers under the same conditions, the greater the integral value, the better the penetration performance of the warm recycling agent; the more the number of penetration layers, the better the penetration performance of the warm recycling agent, and the specific conditions are as follows: the number of penetration layers accounts for less than 50% of the total number of dissolution layers, which is medium penetration, 50%-80% is high penetration, and more than 80% is strong penetration; the integral value of the concentration attenuation equation is defined as follows: less than 8000 is medium penetration, 8000-12000 is high penetration, and more than 12000 is strong penetration.

2. The method for evaluating the permeability of a high-permeability warm recycling agent for in-place heat recycling technology according to claim 1, characterized in that, The new asphalt in step one is asphalt made of petroleum products for road construction, and the aged asphalt is asphalt after aging treatment of the new asphalt at a temperature of 163℃ for 5 h.

3. The method for evaluating the permeability of a high-permeability warm recycling agent for in-place heat recycling technology according to claim 1, characterized in that, The new asphalt in step one is SK70# asphalt.

4. The method for evaluating the permeability of a high-permeability warm recycling agent for in-place heat recycling technology according to claim 1, characterized in that, The warm-mixing agent in step two is Sasobit™ warm-mixing agent.

5. The method for evaluating the permeability of a high-permeability warm recycling agent for in-place heat recycling technology according to claim 1, characterized in that, The thickness of the asphalt in the ball asphalt structure in step three is 3 mm in radial direction.

6. The method for evaluating the permeability of a high-permeability warm recycling agent for a hot-in-place recycling technology according to claim 1, characterized in that, The wrapping thickness of the recycled agent with 5-20 wt% tracer in step four is 1 mm in radial direction.

7. The method for evaluating the permeability of a high-permeability warm recycling agent for in-place heat recycling technology according to claim 1, characterized in that, The tracer is amino-terminated butylnitrile rubber, plasticizer DOP or five-substituted tetrahydropyrimidine, and the recycled agent is bio-oil recycled agent, light recycled agent or composite recycled agent.

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