Preparation method of elastic additive for recycled asphalt mortar

Abstract

The application discloses a preparation method of an elastic additive for recycled asphalt mortar, and comprises the following specific steps: S1, preparing a porous SiO2 carrier by taking rice husk ash as raw material; S2, dissolving linear SBS particles in an organic solvent, and then compounding the linear SBS particles with the porous SiO2 carrier after adding a compatilizer to form a SiO2 / SBS compound; S3, immersing the SiO2 / SBS compound in an ionic liquid functionalized carbon quantum dot dispersion liquid to perform modification treatment, and obtaining a modified compound; and S4, performing interface modification on the surface of the modified compound by using a silane coupling agent to obtain a modified elastic additive. The application aims to provide a preparation method of an elastic additive for recycled asphalt mortar, macroscopic network structure and elastic support are provided by SBS modification, and interface activity and filling effect are enhanced at a microscopic level by IL-CQDs modification, the two synergistically form a multi-level reinforcing system, and the modification effect is more remarkable.

Description

Technical Field

[0001] This invention belongs to the field of asphalt technology, and specifically relates to a method for preparing an elastic additive for recycled asphalt mortar. Background Technology

[0002] Asphalt pavements are widely known for their excellent road performance, but they gradually age over time, requiring regular maintenance and repair. To achieve the concept of green maintenance, environmental pollution and resource waste should be reduced at every stage of asphalt pavement development. Traditional milling and repaving methods consume large amounts of non-renewable resources and generate emissions, while recycling technologies reuse waste asphalt pavement materials for new pavement, saving resources, reducing costs, and improving efficiency.

[0003] After being subjected to repeated loading, the formation and propagation of internal cracks in asphalt pavements are the root cause of fatigue damage. If these cracks or damages are not repaired in a timely and effective manner, they will gradually evolve into macroscopic cracks, eventually leading to structural brittle fracture. Recycled asphalt mixtures, whose raw materials are derived from aged asphalt in old asphalt pavement materials, often have lower fatigue cracking resistance than virgin asphalt mixtures due to insufficient fusion between new and old asphalt. During use, recycled asphalt mixtures inevitably develop cracks or damage, which adversely affects the 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 between new and old asphalt, promoting rapid fusion and diffusion of the two. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing an elastic additive for recycled asphalt mortar. This method utilizes SBS modification to provide a macroscopic network structure and elastic support, while IL-CQDs modification enhances interfacial activity and filling effect at the microscopic level. The synergistic effect of these two methods forms a multi-layered reinforcement system. Furthermore, IL-CQDs, through their surface charge and π-π interactions, further optimize the interfacial bonding between SBS and asphalt, while simultaneously accelerating the fusion and diffusion of new and old asphalt, resulting in a more significant modification effect.

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

[0006] A method for preparing an elastic additive for recycled asphalt mortar includes the following specific steps:

[0007] S1. Porous SiO2 support was prepared using rice husk ash as raw material;

[0008] S2. Linear SBS particles are dissolved in an organic solvent, and after adding a compatibilizer, they are combined with a porous SiO2 support to form a SiO2 / SBS composite.

[0009] S3. The SiO2 / SBS composite is immersed in an ionic liquid functionalized carbon quantum dot dispersion for modification treatment to obtain the modified composite.

[0010] S4. The modified elastic additive is obtained by interfacial modification of the surface of the modified composite with a silane coupling agent.

[0011] Preferably, in step S1 above, the method for preparing the porous SiO2 support includes the following steps:

[0012] (1) Rice husk ash is mixed with alkaline substances and calcined to produce silicates;

[0013] (2) Add silicate to deionized water, add acid to adjust the pH value, so that silica gel precipitates and ages, wash and dry to obtain porous SiO2 support.

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

[0015] Preferably, in step S2, the styrene content in the linear SBS particles is 20% to 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% to 10% of the mass of SBS; the solid-liquid ratio of the porous SiO2 support to the SBS solution is 1 to 2: 4 to 6.

[0016] Preferably, in step S3 above, 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(trifluoromethanesulfonyl)imide salt.

[0017] Preferably, the aforementioned method for preparing ionic liquid functionalized carbon quantum dots is as follows:

[0018] (1) Precursor preparation: Pine wood chips are mixed with ionic liquid, deionized water is added, and stirred to form a uniform suspension;

[0019] (2) Hydrothermal carbonization: The mixture is transferred to a high-pressure reactor, reacted, centrifuged, and freeze-dried for 24 hours to obtain powdered ionic liquid functionalized carbon quantum dots.

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

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

[0022] A modified recycled asphalt mortar, comprising an elastic additive prepared by the above-described preparation method, wherein the addition amount is 3% to 15% of the mass of asphalt.

[0023] The advantages of this invention are:

[0024] (1) This invention dissolves linear SBS particles in an organic solvent and combines them with rice husk ash-based porous SiO2 carrier, which can achieve uniform dispersion and fixation of SBS on the porous SiO2 surface. 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) used in this invention have excellent dispersibility and functionality. Their imidazole ring structure can be embedded into the carbon skeleton through π-π interaction. At the same time, anions induce the enrichment of negative charges on the surface of carbon quantum dots, which enhances 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, and forms a more uniform and stable asphalt system, thereby improving the fatigue resistance of recycled asphalt mortar. As a nanoscale 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 asphalt.

[0026] (3) The high-elasticity recycled asphalt mortar based on oil-rich RAP fine aggregate of the present invention can quickly and efficiently promote the fusion of aged asphalt in RAP with new asphalt and modified materials, thereby improving the road performance of recycled asphalt mixture to a high extent. Detailed Implementation

[0027] The present invention will be described in detail below with reference to specific embodiments.

[0028] Example 1: A method for preparing an elastic additive for recycled asphalt mortar, comprising the following specific steps:

[0029] (1) Rice husk ash (SiO2 content ≥90%, particle size <100μm) was mixed with NaOH at a mass ratio of 1:2 and calcined in a muffle furnace at 600℃ for 2 hours to allow amorphous SiO2 to react with NaOH to generate sodium silicate (Na2SiO3); after cooling, deionized water (solid-liquid ratio 1:10) was added, stirred for 30 minutes and unreacted impurities were filtered out; HCl (concentration 36%) was added dropwise to the filtrate until pH=2, and silicic acid (H2SiO3) gel was precipitated and allowed to stand for aging for 12 hours; it was washed with deionized water until neutral and vacuum filtered to obtain wet gel; the wet gel was placed in a supercritical CO2 drying device (temperature 40℃, pressure 10MPa) and dried for 24 hours to obtain a porous SiO2 support.

[0030] (2) Linear SBS particles (SBS 791-H, styrene content 30%) were dissolved in toluene (concentration 20wt%) and stirred at 60℃ for 4 hours until completely dissolved; 5wt% maleic anhydride (MAH) was added as a compatibilizer and stirred for another hour; porous SiO2 carrier powder was impregnated in the SBS solution (solid-liquid ratio 1:5) and ultrasonically treated (40kHz, 200W) for 30 minutes to promote solution penetration into the pores; the mixture was transferred to a rotary evaporator (temperature 50℃, speed 60rpm) and the toluene was evaporated under reduced pressure until the solution volume decreased by 80%, so that the SBS molecular chains were entangled and fixed inside the pores; the impregnated material was placed in a vacuum drying oven (80℃, -0.1MPa) and dried for 12 hours to completely remove residual solvent, thus obtaining the SiO2 / SBS composite.

[0031] (3) Mix 10g of pretreated pine sawdust with 50mL of [BMIM][BF4] ionic liquid, add 100mL of deionized water, and magnetically stir for 2 hours to form a uniform suspension. Transfer the mixture to a high-pressure reactor and react at 180℃ for 8 hours. The ionic liquid serves as the reaction medium, and its imidazole ring structure is embedded into the carbon skeleton through π-π interactions. At the same time, BF4... - Anions induce the enrichment of negative charges on the surface of carbon quantum dots; after cooling, centrifuge (12000 rpm, 20 min), collect the supernatant, filter it with a 0.22 μm filter membrane to remove large particulate impurities, and then put it into a dialysis bag for purification for 48 hours (replacing deionized water every 6 hours) to completely remove unreacted ionic liquid; freeze-dry the purified black solution for 24 hours to obtain dark brown powdery IL-CQDs.

[0032] 0.1 g of IL-CQDs powder was added to 100 mL of 3% ethanol solution and sonicated (40 kHz, 30 min) to form a uniform dispersion. The SiO2 / SBS composite was then immersed in the dispersion and soaked at room temperature for 2 hours. After filtration, it was dried at 120 °C for 1 hour to obtain the modified SiO2 / SBS composite.

[0033] (4) The modified SiO2 / SBS composite was immersed in an ethanol solution of silane coupling agent (KH550) (concentration 3%), soaked at room temperature for 2 hours, filtered, and dried at 120°C for 1 hour to obtain the modified elastic additive.

[0034] Example 2: A method for preparing an elastic additive for recycled asphalt mortar, comprising the following specific steps:

[0035] (1) Rice husk ash (SiO2 content ≥90%, particle size <100μm) was mixed with KOH at a mass ratio of 1:2.5 and calcined in a muffle furnace at 550℃ for 2.5 hours to generate potassium silicate (K2SiO3); after cooling, deionized water (solid-liquid ratio 1:12) was added, stirred for 40 minutes and impurities were filtered out; H2SO4 (concentration 30%) was added dropwise to the filtrate until pH=1.5, precipitating silica gel, and allowed to stand for aging for 10 hours; washed with deionized water until neutral, and vacuum filtered to obtain wet gel; the wet gel was placed in a supercritical CO2 drying device (temperature 45℃, pressure 12MPa) and dried for 20 hours to obtain porous SiO2 support.

[0036] (2) SBS particles (25% styrene content) were dissolved in xylene (18 wt%) and stirred at 65°C for 5 hours until completely dissolved; 6 wt% epoxy resin was added as a compatibilizer and stirring was continued for 1.5 hours; porous SiO2 support was impregnated in SBS solution (solid-liquid ratio 1:4) and ultrasonically treated (50 kHz, 250 W) for 40 minutes; transferred to a rotary evaporator (temperature 55°C, speed 70 rpm) and the solvent was evaporated under reduced pressure until the volume decreased by 85%; the impregnated material was dried in a vacuum drying oven (75°C, -0.1 MPa) for 10 hours to obtain SiO2 / SBS composite.

[0037] (3) 15g of pretreated pine sawdust was mixed with 60mL of [BMIM][TFSI] ionic liquid, and 120mL of deionized water was added. The mixture was magnetically stirred for 3 hours to form a suspension. The suspension was then transferred to a high-pressure reactor and reacted at 190℃ for 7 hours. After cooling, the suspension was centrifuged (10000rpm, 25min), filtered, and purified by dialyzing for 50 hours. The suspension was then freeze-dried to obtain IL-CQDs. 0.15g of IL-CQDs was dispersed in 100mL of 2.5% KH560 ethanol solution and sonicated (45kHz, 35min). The SiO2 / SBS complex was immersed in the dispersion and soaked at room temperature for 2.5 hours. After filtration, the mixture was dried at 110℃ for 1.5 hours.

[0038] (4) The modified composite was immersed in KH570 ethanol solution (concentration 4%), soaked at room temperature for 1.5 hours, filtered, and dried at 130°C for 0.5 hours to obtain the elastic additive.

[0039] Comparative Example 1

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

[0041] Comparative Example 2

[0042] The specific difference between this comparative example and Example 1 is that it was not modified with IL-CQDs.

[0043] Comparative Example 3

[0044] The specific difference between this comparative example and Example 1 is that it did not undergo SBS modification and IL-CQDs modification.

[0045] The elastic additives prepared in Examples 1, 2, and Comparative Examples 1-3 were used to prepare recycled asphalt mortar. The specific steps were as follows: 5 kg of elastic additive and 8 kg of compatibilizer were added to a high-speed shear mill and sheared at 3500 r / min for 30 minutes at 180°C. Then, the temperature was raised to 200°C for swelling for 30 minutes. The compatibilizer used was naphthenic oil. Next, 65 kg of oil-rich RAP fines heated to 130°C and 12 kg of... A mixture of 70# base asphalt, 3 kg of dibutyl phthalate and dioctyl phthalate as a regenerator, 1.5 kg of amino-terminated restoring agent as a crosslinking agent, and 2 kg of isooctyl alcohol polyoxyethylene ether as a penetrant were added to a mixing pot. The mixture was stirred at 1000 r / min for 4 minutes at 160℃, and then at 500 r / min for 16 minutes to obtain a high-elasticity recycled asphalt mortar based on oil-rich RAP fine aggregate. The oil-rich RAP fine aggregate was RAP with a particle size of 0-3 mm after fine separation, and its asphalt-aggregate ratio was 8%. The mass ratio of each component was as follows: elastic additive 5%, compatibilizer 8%, oil-rich RAP fine aggregate 65%, base asphalt 12%, regenerator 3%, crosslinking agent 1.5%, and penetrant 2%.

[0046] Performance testing

[0047] The performance of the recycled asphalt mortars prepared with the elastic additives in Examples 1, 2, 1, and 2 was tested.

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

[0049] The recycled asphalt mixture adopted the SMA-13 ​​gradation. The RAP (recycled asphalt mixture) was sourced from the SMA-13 ​​surface layer of a highway in Jiangsu Province. High-elasticity recycled asphalt mortar was added during the asphalt mixture mixing process, with the addition amount referring to the total content of new asphalt and RAP fine aggregate in the mix design. The RAP 0-3mm content was 20%. According to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011), recycled asphalt mixture slab specimens were formed by wheel rolling and cut into small beam specimens with a length of 380mm±5mm, a thickness of 50mm±5mm, and a width of 63.5mm±5mm. Four-point bending tests with strain control (400με) were conducted to determine the fatigue life of the recycled asphalt mixture.

[0050] Table 1 Fatigue life of recycled asphalt mixtures

[0051] Specimen type Fatigue life (times) Example 1 95215 Example 2 82212 Comparative Example 1 62235 Comparative Example 2 63754 Comparative Example 3 43754 Conventional process recycled asphalt mixture 54317

[0052] As shown in Table 1, the fatigue life of Examples 1 and 2 was significantly higher than that of Comparative Examples 1-3 and the recycled asphalt mixture produced by conventional processes, indicating that the synergistic effect of SBS modification and IL-CQDs modification can significantly improve the fatigue resistance of recycled asphalt mixtures. The fatigue life of Comparative Example 1 (SBS only) and Comparative Example 2 (IL-CQDs only) was slightly higher than that of Comparative Example 3 (no modification), but much lower than that of Examples 1 and 2, indicating that the effect of single modification is limited. Example 1 had the highest fatigue life, reaching 95,215 cycles, which was about 75.3% higher than that of conventional processes, proving that the effect of SBS modification followed by IL-CQDs modification on rice husk ash-based porous SiO2 was optimal.

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

[0054] The rutting test (T0719-2011) in the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011) was conducted. The recycled asphalt mixture was compacted into standard-sized slab specimens (300mm×300mm×50mm) using a wheel-rolling method. These specimens were then cut into strip specimens (300mm×300mm×50mm) for the rutting test. The test procedure was as follows: the specimens were placed in the rutting tester, preheated to 60℃ and kept at that temperature for 5 hours; a standard tire load (0.7MPa) was applied, and the specimens were rolled repeatedly at a frequency of 42 times / min; the rutting depth of the specimens was recorded at different rolling cycles (e.g., every 1000 cycles); and the dynamic stability (DS) was calculated.

[0055] Table 2 Dynamic stability of recycled asphalt mixtures

[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 Conventional process recycled asphalt mixture 5140

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

[0058] The foregoing has shown and described 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 way, and all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A method for producing an elastic aid for recycling asphalt mortar, characterized by, The preparation method comprises the following specific steps: S1, preparing a porous SiO2 carrier with rice husk ash as raw material; S2, dissolving linear SBS particles in an organic solvent, adding a compatibilizer, and then compounding with the porous SiO2 carrier to form a SiO2 / SBS composite; S3, immersing the SiO2 / SBS composite in an ionic liquid functionalized carbon quantum dot dispersion liquid for modification treatment to obtain a modified composite; The ionic liquid functionalized carbon quantum dots are carbon quantum dots modified with imidazole-based ionic liquids; S4, performing interface modification on the surface of the modified composite by using a silane coupling agent to obtain a modified elastic auxiliary agent.

2. A method of preparing an elastic aid for recycled asphalt mortar according to claim 1, characterized in that, In the step S1, the preparation method of the porous SiO2 carrier comprises the following steps: (1) mixing rice husk ash with an alkaline substance and calcining to generate silicate; (2) adding the silicate into deionized water, adding an acid liquid to adjust the pH value, allowing the silica gel to precipitate and age, and then performing washing and drying treatment to obtain the porous SiO2 carrier.

3. A method of preparing an elastic additive for recycled asphalt mortar according to claim 2, characterized in that, The alkaline substance is NaOH or KOH, the mass ratio of the rice husk ash to NaOH is 1:1.5-1:3, the calcination temperature is 500-700 DEG C, and the calcination time is 1-3 hours; the acid liquid is HCl with a concentration of 36%, and the pH value is adjusted to 2-3.

4. The method of claim 1, wherein the elastic extender for recycling asphalt mortar is prepared by mixing 100 parts by weight of the base material, 10 to 30 parts by weight of the reinforcing material, 10 to 30 parts by weight of the softening material, and 10 to 30 parts by weight of the plasticizer. In the 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.

5. The method for preparing an elastic additive for recycled asphalt mortar according to claim 1, characterized in that, In the step S3, the imidazole-based ionic liquid is 1-butyl-3-methylimidazolium tetrafluoroborate or 1-ethyl-3-methylimidazolium bis-trifluoromethanesulfonimide.

6. A method of preparing an elastic additive for recycled asphalt mortar according to claim 5, characterized in that, The preparation method of the ionic liquid functionalized carbon quantum dots is as follows: (1) precursor preparation: mixing pine sawdust with an ionic liquid, adding deionized water, and stirring to form a uniform suspension; (2) hydrothermal carbonization: transferring the mixed liquid into a high-pressure reaction kettle, reacting, centrifuging, and freeze-drying for 24 hours to obtain powder-shaped ionic liquid functionalized carbon quantum dots.

7. A method of preparing an elastic additive for recycled asphalt mortar according to claim 6, characterized in that, The use amount ratio of the pine sawdust to the ionic liquid is 5-15 g:40-60 mL.

8. The method of claim 1, wherein the elastic extender for recycled asphalt mortar is prepared by mixing 100 parts by weight of the base material, 10 to 30 parts by weight of the reinforcing material, 10 to 30 parts by weight of the filler, and 0.1 to 1 part by weight of the dispersant. In the step S4, the silane coupling agent is KH550, KH560 or KH570, and the ethanol solution concentration is 1%-5%.

9. A modified recycled asphalt mortar, characterized in that, The elastic auxiliary agent prepared by the preparation method of claim 1 is added in an amount of 3%-15% of the mass of the asphalt.