Preparation method of elastic additive for recycled asphalt mortar

Abstract

The invention discloses a preparation method of an elastic aid for recycled asphalt mortar. The preparation method comprises the following specific steps: S1, preparing a porous SiO2 carrier by taking rice hull ash as a raw material; s2, dissolving the linear SBS particles in an organic solvent, adding a compatilizer, and compounding with the porous SiO2 carrier to form a SiO2 / SBS compound; s3, immersing the SiO2 / SBS compound into the ionic liquid functionalized carbon quantum dot dispersion liquid, and carrying out modification treatment to obtain a modified compound; s4, performing interface modification on the surface of the modified compound through a silane coupling agent to obtain the modified elastic aid. According to the preparation method of the elastic auxiliary agent for the recycled asphalt mortar, a macroscopic network structure and elastic support are provided through SBS modification, the interfacial activity and the filling effect are enhanced on the microscopic level through IL-CQDs modification, a multi-layer enhancing system is formed through the synergistic effect of the SBS modification and the IL-CQDs modification, and the modification effect is more remarkable.

Description

Technical Field

[0001] The present invention belongs to the technical field of asphalt, and particularly relates to a preparation method of an elastic auxiliary agent for recycled asphalt mortar. Background Art

[0002] Asphalt pavements are well-known for their excellent road performance. However, over time, they gradually age and require regular maintenance and repair. To achieve the concept of green maintenance, environmental pollution and resource waste should be reduced at all stages of asphalt pavements. The traditional milling and resurfacing method consumes a large amount of non-renewable resources and generates emissions. By using recycling technology to reuse waste asphalt pavement materials for laying new pavements, resources can be saved, costs can be reduced, and efficiency can be improved.

[0003] After asphalt pavements are subjected to repeated loadings, the generation and propagation of internal cracks are the fundamental causes of fatigue damage. If these cracks or damages are not repaired in a timely and effective manner, they will gradually evolve into macroscopic cracks, ultimately leading to structural brittle fractures. Recycled asphalt mixtures are made from the aged asphalt in old asphalt pavement materials. However, due to the insufficient fusion of new and old asphalt, their fatigue cracking resistance is often inferior to that of brand-new asphalt mixtures. During use, cracks or damages will inevitably occur in recycled asphalt mixtures, which will have an adverse impact on the service performance and lifespan of asphalt pavements. Therefore, there is an urgent need for a method or technology that can quickly and effectively solve the problem of insufficient fusion of new and old asphalt, and promote the rapid fusion and diffusion of new and old asphalt. Summary of the Invention

[0004] To solve the deficiencies of the prior art, the purpose of the present invention is to provide a preparation method of an elastic auxiliary agent for recycled asphalt mortar. Through SBS modification, a macroscopic network structure and elastic support are provided, while IL-CQDs modification enhances the interfacial activity and filling effect at the microscopic level. The two act synergistically to form a multi-level reinforcement system; IL-CQDs further optimize the interfacial bonding force between SBS and asphalt through its surface charge and π-π interaction, and at the same time accelerate the fusion and diffusion of new and old asphalt, making the modification effect more significant.

[0005] To achieve the above objectives, the present invention adopts the following technical solutions:

[0006] A preparation method of an elastic auxiliary agent for recycled asphalt mortar, comprising the following specific steps:

[0007] S1. Prepare a porous SiO2 carrier using rice husk ash as the raw material;

[0008] S2. Dissolve linear SBS particles in an organic solvent, add a compatibilizer, and then compound with the porous SiO2 carrier to form a SiO2 / SBS composite;

[0009] S3. Immerse the SiO2 / SBS composite in an ionic liquid-functionalized carbon quantum dot dispersion for modification to obtain a modified composite;

[0010] S4. Perform interfacial modification on the surface of the modified composite with a silane coupling agent to obtain a modified elastic auxiliary agent.

[0011] Preferably, in the aforementioned step S1, the preparation method of the porous SiO2 carrier includes the following steps:

[0012] (1) Mix rice husk ash with an alkaline substance and calcine to generate silicate;

[0013] (2) Add the silicate to deionized water, add an acid solution to adjust the pH value to precipitate and age the silica gel, wash and dry to obtain a porous SiO2 carrier.

[0014] Preferably, the aforementioned alkaline substance is NaOH or KOH, the mass ratio of rice husk ash to NaOH is 1:1.5 - 1:3, the calcination temperature is 500 - 700 °C, and the calcination time is 1 - 3 hours; the acid solution is 36% HCl, and the pH is adjusted to 2 - 3.

[0015] Preferably, in the aforementioned step S2, the content of styrene in the linear SBS particles is 20% - 40%, the organic solvent is toluene, xylene or tetrahydrofuran, the compatibilizer is one of maleic anhydride, epoxy resin or titanate coupling agent, and the addition amount is 1% - 10% of the mass of SBS; the solid-liquid ratio of the porous SiO2 carrier to the SBS solution is 1 - 2:4 - 6.

[0016] Preferably, in the aforementioned step S3, the ionic liquid-functionalized carbon quantum dots are carbon quantum dots modified with imidazole-based ionic liquids, and the imidazole-based ionic liquids are 1-butyl-3-methylimidazolium tetrafluoroborate or 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide.

[0017] Preferably, the preparation method of the aforementioned ionic liquid-functionalized carbon quantum dots is:

[0018] (1) Preparation of the precursor: Mix pine sawdust with an ionic liquid, add deionized water, and stir to form a uniform suspension;

[0019] (2) Hydrothermal carbonization: Transfer the mixed solution to a high-pressure reaction kettle, react, centrifuge, and freeze-dry for 24 hours to obtain powdery ionic liquid-functionalized carbon quantum dots.

[0020] Preferably, the dosage ratio of the aforementioned pine sawdust to the ionic liquid is 5 - 15 g:40 - 60 mL.

[0021] Preferably, in the aforementioned step S4, the silane coupling agent is KH550, KH560 or KH570, and the concentration of its ethanol solution is 1% to 5%.

[0022] A modified recycled asphalt mortar contains the elastic aid prepared by the above preparation method, and the addition amount is 3% to 15% of the mass of the asphalt.

[0023] The beneficial effects of the present invention are as follows:

[0024] (1) By dissolving linear SBS particles in an organic solvent and compounding them with a rice husk ash-based porous SiO2 carrier, the present invention can achieve uniform dispersion and fixation of SBS on the surface of porous SiO2. Adding a compatibilizer can enhance the interfacial bonding force between SBS and SiO2, thereby improving the modification effect;

[0025] (2) The ionic liquid-functionalized carbon quantum dots (IL-CQDs) adopted in the present invention have excellent dispersibility and functionality. Its imidazole ring structure can be embedded in the carbon skeleton through π-π interaction. At the same time, the anion induces the surface of the carbon quantum dots to be enriched with negative charges, enhancing the interaction between IL-CQDs and asphalt; the introduction of IL-CQDs significantly improves the interfacial activity of the composite material, promotes the fusion and diffusion between new and old asphalt, forms a more uniform and stable asphalt system, thereby enhancing the anti-fatigue performance of the recycled asphalt mortar; as a nano-scale filler, IL-CQDs can fill the tiny voids inside the asphalt, reduce defects and improve the overall density, thereby enhancing the high-temperature deformation resistance of the asphalt;

[0026] (3) The high-elastic recycled asphalt mortar based on rich-oil RAP fines of the present invention can quickly and efficiently promote the rapid fusion of the aged asphalt in RAP with new asphalt and modification materials, and improve the road performance of the recycled asphalt mixture to a high degree; Specific Embodiments

[0027] The present invention will be specifically introduced below in combination with specific embodiments.

[0028] Example 1. A preparation method of an elastic aid for recycled asphalt mortar includes the following specific steps:

[0029] (1) Mix rice husk ash (SiO2 content ≥ 90%, particle size < 100 μm) with NaOH at a mass ratio of 1:2, place it in a muffle furnace at 600 °C and calcine for 2 hours to react amorphous SiO2 with NaOH to form sodium silicate (Na2SiO3); after cooling, add deionized water (solid-liquid ratio 1:10), stir for 30 minutes and filter unreacted impurities; gradually add HCl (concentration 36%) to the filtrate until pH = 2, and precipitate silica acid (H2SiO3) gel, then let it stand and age for 12 hours; wash with deionized water until neutral, and vacuum filter to obtain wet gel; place the wet gel in a supercritical CO2 drying equipment (temperature 40 °C, pressure 10 MPa), dry for 24 hours to obtain a porous SiO2 support.

[0030] (2) Dissolve linear SBS particles (SBS 791-H, styrene content 30%) in toluene (concentration 20 wt%), stir at 60 °C for 4 hours until completely dissolved; add 5 wt% maleic anhydride (MAH) as a compatibilizer and continue stirring for 1 hour; immerse the porous SiO2 support powder in the SBS solution (solid-liquid ratio 1:5), and ultrasonically treat (40 kHz, 200 W) for 30 minutes to promote the infiltration of the solution into the pores; transfer to a rotary evaporator (temperature 50 °C, rotation speed 60 rpm), reduce the pressure to evaporate toluene until the volume of the solution decreases by 80%, so that part of the molecular chains of SBS are entangled and fixed in the pores; place the impregnated material in a vacuum drying oven (80 °C, -0.1 MPa), dry for 12 hours to completely remove the residual solvent, and obtain a SiO2 / SBS composite.

[0031] (3) Mix 10 g of pretreated pine sawdust with 50 mL of [BMIM][BF4] ionic liquid, add 100 mL of deionized water, and magnetically stir for 2 hours to form a homogeneous suspension. Transfer the mixture to a high-pressure reactor and react at 180 °C for 8 hours. The ionic liquid serves as both a reaction medium, and its imidazole ring structure is embedded in the carbon skeleton through π-π interaction. At the same time, the BF4 - anion induces the surface of the carbon quantum dots to enrich negative charges; after cooling, centrifuge (12000 rpm, 20 minutes), take the supernatant, filter with a 0.22 μm filter membrane to remove large particle impurities, and then load it into a dialysis bag for purification for 48 hours (replace deionized water every 6 hours) to completely remove the unreacted ionic liquid; freeze-dry the purified black solution for 24 hours to obtain dark brown powdered IL-CQDs.

[0032] Add 0.1 g of IL-CQDs powder to 100 mL of 3% ethanol solution, ultrasonically treat (40 kHz, 30 minutes) to form a homogeneous dispersion, immerse the SiO2 / SBS composite in the above dispersion, soak at room temperature for 2 hours, filter and dry at 120 °C for 1 hour to obtain a modified SiO2 / SBS composite.

[0033] (4) Immerse the modified SiO2 / SBS composite in an ethanol solution (concentration 3%) of silane coupling agent (KH550), soak at room temperature for 2 hours, filter and dry at 120 °C for 1 hour to obtain a modified elastic auxiliary agent.

[0034] Example 2. A preparation method of an elastic auxiliary agent for recycled asphalt mortar, comprising the following specific steps:

[0035] (1) Mix rice husk ash (SiO2 content ≥ 90%, particle size < 100 μm) and KOH in a mass ratio of 1:2.5, place in a muffle furnace at 550 °C and calcine for 2.5 hours to generate potassium silicate (K2SiO3); after cooling, add deionized water (solid-liquid ratio 1:12), stir for 40 minutes and filter impurities; gradually add H2SO4 (concentration 30%) to the filtrate until pH = 1.5 to precipitate silica gel, and let it stand and age for 10 hours; wash with deionized water until neutral, and vacuum filter to obtain wet gel; place the wet gel in a supercritical CO2 drying equipment (temperature 45 °C, pressure 12 MPa) and dry for 20 hours to obtain a porous SiO2 carrier.

[0036] (2) Dissolve SBS particles (styrene content 25%) in xylene (concentration 18 wt%), stir at 65 °C for 5 hours until completely dissolved; add 6 wt% of epoxy resin as a compatibilizer and continue to stir for 1.5 hours; immerse the porous SiO2 carrier in the SBS solution (solid-liquid ratio 1:4), and perform ultrasonic treatment (50 kHz, 250 W) for 40 minutes; transfer to a rotary evaporator (temperature 55 °C, rotation speed 70 rpm), and reduce the volume of the solvent by decompression evaporation by 85%; dry the impregnated material in a vacuum drying oven (75 °C, -0.1 MPa) for 10 hours to obtain a SiO2 / SBS composite.

[0037] (3) Mix 15 g of pretreated pine sawdust with 60 mL of [BMIM][TFSI] ionic liquid, add 120 mL of deionized water, and stir magnetically for 3 hours to form a suspension; transfer to a high-pressure reaction kettle and react at 190 °C for 7 hours; after cooling, centrifuge (10000 rpm, 25 minutes), filter and dialyze and purify for 50 hours, and obtain IL-CQDs after freeze-drying. Disperse 0.15 g of IL-CQDs in 100 mL of 2.5% KH560 ethanol solution and perform ultrasonic treatment (45 kHz, 35 minutes); immerse the SiO2 / SBS composite in the dispersion, soak at room temperature for 2.5 hours, filter and dry at 110 °C for 1.5 hours.

[0038] (4) Immerse the modified composite in a KH570 ethanol solution (concentration 4%), soak at room temperature for 1.5 hours, filter and dry at 130 °C for 0.5 hours to obtain an elastic auxiliary agent.

[0039] Comparative Example 1

[0040] The specific difference between this comparative example and Example 1 is that SBS modification was not carried out.

[0041] Comparative Example 2

[0042] The specific difference between this comparative example and Example 1 is that IL-CQDs modification was not carried out.

[0043] Comparative Example 3

[0044] The specific difference between this comparative example and Example 1 is that neither SBS modification nor IL-CQDs modification was carried out.

[0045] The elastic aids prepared in Example 1, Example 2 and Comparative Examples 1 to 3 were used to prepare recycled asphalt mortar. The specific steps were as follows: 5 kg of elastic aid and 8 kg of compatibilizer were added to a high-speed shearing machine and sheared at a speed of 3500 r / min at 180 °C for 30 minutes, and then the temperature was raised to 200 °C for swelling for 30 minutes, where the compatibilizer was selected as naphthenic oil; then 65 kg of rich-oil RAP fine material heated to 130 °C, 12 kg of 70# base asphalt, 3 kg of a mixture of dibutyl phthalate and dioctyl phthalate as a regenerant, 1.5 kg of an end-amino restoring agent as a crosslinking agent, and 2 kg of isooctyl polyoxyethylene ether as a penetrant were added to the mixing pot and stirred at 1000 r / min for 4 minutes under the condition of 160 °C, and then stirred at 500 r / min for 16 minutes to obtain a high-elastic recycled asphalt mortar based on rich-oil RAP fine material, where the rich-oil RAP fine material was RAP with a particle size of 0-3 mm after fine separation, and its asphalt-aggregate ratio was 8%, and the mass ratio of each component was 5% of elastic aid, 8% of compatibilizer, 65% of rich-oil RAP fine material, 12% of base asphalt, 3% of regenerant, 1.5% of crosslinking agent, and 2% of penetrant.

[0046] Performance detection test

[0047] Performance tests were carried out on the recycled asphalt mortar prepared from the elastic aids in Example 1, Example 2, Comparative Example 1 and Comparative Example 2.

[0048] (1) Fatigue life detection of recycled asphalt mortar:

[0049] The recycled asphalt mixture adopts the SMA-13 gradation. Among them, the RAP (recycled asphalt mixture) is sourced from the SMA-13 surface course of a certain expressway in Jiangsu. The high-elastic recycled asphalt mortar is added during the mixing of the asphalt mixture. The addition amount refers to the total admixture content of the new asphalt and the RAP fine material in the mix design. The RAP 0-3mm admixture is 20%. According to the standard of "Test Procedures for Bitumen and Bituminous Mixtures for Highway Engineering" (JTG E20-2011), the wheel rolling method is used to form the recycled asphalt mixture slab specimens, and they are cut into beam specimens with a length of 380mm ± 5mm, a thickness of 50mm ± 5mm, and a width of 63.5mm ± 5mm. A four-point bending test with strain control (400με) is carried out to determine the fatigue life of the recycled asphalt mixture.

[0050] Table 1 Fatigue life of recycled asphalt mixture

[0051] Specimen type Fatigue life (cycles) Example 1 95215 Example 2 82212 Comparative Example 1 62235 Comparative Example 2 63754 Comparative Example 3 43754 Recycled asphalt mixture with conventional process 54317

[0052] As can be seen from Table 1, the fatigue lives of Example 1 and Example 2 are significantly higher than those of Comparative Example 1-3 and the recycled asphalt mixture with conventional technology, indicating that the synergistic effect of SBS modification and IL-CQDs modification can significantly improve the fatigue resistance of the recycled asphalt mixture. The fatigue lives of Comparative Example 1 (only SBS) and Comparative Example 2 (only IL-CQDs) are slightly higher than that of Comparative Example 3 (no modification), but much lower than those of Example 1 and Example 2, indicating that the single modification effect is limited. The fatigue life of Example 1 is the highest, reaching 95,215 times, which is about 75.3% higher than that of the conventional process, proving that the effect is the best after the rice husk ash-based porous SiO2 is loaded with SBS and then modified by IL-CQDs.

[0053] (2) High-temperature stability detection of recycled asphalt mortar

[0054] The test is carried out according to the rutting test (T0719-2011) in the "Test Procedures for Bitumen and Bituminous Mixtures for Highway Engineering" (JTG E20-2011). The wheel rolling method is adopted to compact the mixed recycled asphalt mixture into standard-sized slab specimens (300mm×300mm×50mm); cut into strip specimens (300mm×300mm×50mm) required for the rutting test. The test steps are as follows: put the specimens into the rutting tester, preheat to 60°C and keep warm for 5 hours; apply the standard tire load (0.7MPa), and carry out reciprocating rolling at a frequency of 42 times / min; record the change of rut depth of the specimens at different rolling times (such as every 1000 times); calculate the dynamic stability (DS).

[0055] Table 2 Dynamic stability of recycled asphalt mixture

[0056] Specimen type Dynamic stability (cycles / mm) Example 1 8250 Example 2 7860 Comparative Example 1 6120 Comparative Example 2 5980 Comparative Example 3 4320 Recycled asphalt mixture with conventional process 5140

[0057] As can be seen from Table 2, the dynamic stability of Example 1 and Example 2 is significantly higher than that of Comparative Examples 1-3 and the recycled asphalt mixture of the conventional process. This shows that the synergistic effect of SBS modification and IL-CQDs modification can significantly improve the high-temperature stability of the recycled asphalt mortar. The dynamic stability of Example 1 is the highest, reaching 8250 times / mm, which is about 60.7% higher than that of the conventional process, fully demonstrating the superiority of the present invention in terms of high-temperature stability.

[0058] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any form. Any technical solutions obtained by means of equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims

1. The preparation method of an elastic auxiliary agent for recycled asphalt mortar according to claim 1, characterized in that, It includes the following specific steps: S1. Prepare a porous SiO2 carrier using rice husk ash as a raw material; S2. Dissolve linear SBS particles in an organic solvent, add a compatibilizer, and then compound with the porous SiO2 carrier to form a SiO2 / SBS composite; S3. Immerse the SiO2 / SBS composite in an ionic liquid-functionalized carbon quantum dot dispersion for modification treatment to obtain a modified composite; S4. Perform interfacial modification on the surface of the modified composite using a silane coupling agent to obtain a modified elastic auxiliary agent.

2. The preparation method of an elastic auxiliary agent for recycled asphalt mortar according to claim 1, characterized in that, In the step S1, the preparation method of the porous SiO2 carrier includes the following steps: (1) Mix rice husk ash with an alkaline substance and calcine to generate silicate; (2) Add the silicate to deionized water, add an acid solution to adjust the pH value to precipitate and age the silica gel, and perform washing and drying treatments to obtain a porous SiO2 carrier.

3. The preparation method of an elastic auxiliary agent for recycled asphalt mortar according to claim 2, characterized in that, The alkaline substance is NaOH or KOH, the mass ratio of rice husk ash to NaOH is 1:1.5 - 1:3, the calcination temperature is 500 - 700 °C, and the calcination time is 1 - 3 hours; the acid solution is 36% HCl, and the pH is adjusted to 2 - 3.

4. The preparation method of an elastic auxiliary agent for recycled asphalt mortar according to claim 1, characterized in that, In the step S2, the styrene content in the linear SBS particles is 20% - 40%, the organic solvent is toluene, xylene or tetrahydrofuran, the compatibilizer is one of maleic anhydride, epoxy resin or titanate coupling agent, and the addition amount is 1% - 10% of the mass of SBS; the solid-liquid ratio of the porous SiO2 carrier to the SBS solution is 1 - 2:4 - 6.

5. The preparation method of an elastic additive for recycled asphalt mortar according to claim 1, characterized in that In the step S3, the ionic liquid-functionalized carbon quantum dot is a carbon quantum dot modified with an imidazole-based ionic liquid, and the imidazole-based ionic liquid is 1-butyl-3-methylimidazolium tetrafluoroborate or 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide.

6. The preparation method of an elastic auxiliary agent for recycled asphalt mortar according to claim 5, characterized in that, The preparation method of the ionic liquid-functionalized carbon quantum dot is: (1) Preparation of the precursor: Mix pine sawdust with an ionic liquid, add deionized water, and stir to form a uniform suspension; (2) Hydrothermal carbonization: Transfer the mixed solution to a high-pressure reaction kettle, react, centrifuge, and freeze-dry for 24 hours to obtain a powdery ionic liquid-functionalized carbon quantum dot.

7. The preparation method of an elastic auxiliary agent for recycled asphalt mortar according to claim 6, characterized in that, The dosage ratio of the pine sawdust to the ionic liquid is 5 - 15 g:40 - 60 mL.

8. The preparation method of an elastic auxiliary agent for recycled asphalt mortar according to claim 1, characterized in that, In the step S4, the silane coupling agent is KH550, KH560 or KH570, and the concentration of its ethanol solution is 1% - 5%.

9. A modified recycled asphalt mortar, characterized in that, An elastic auxiliary agent prepared by the preparation method described in claim 1 is included, and its addition amount is 3% - 15% of the mass of asphalt.