A green production method of asphalt concrete for carbon emission reduction

Abstract

The present application relates to the technical field of road construction materials, and particularly relates to a carbon emission reduction asphalt concrete green production method, which comprises the following steps: placing high-proportion recycled asphalt mixture in a preheating and drying system to perform low-temperature drying and infrared preheating; introducing supercritical carbon dioxide into an asphalt modification tank to prepare carbon sequestration foamed asphalt; mixing the carbon sequestration foamed asphalt binder and the mixed preheated aggregate system, and adding a warm mix agent and a recycling agent to obtain asphalt concrete mixture; collecting monitoring parameters of emitted carbon dioxide in real time, and dynamically adjusting process parameters based on the monitoring parameters to correct mixing speed and heating power; performing dust removal and heat exchange treatment on flue gas generated by a mixing tower, and recycling condensate water for drying cylinder heating, mixing water or dust suppression spraying. The present application is used to overcome the problem of RAP aging caused by heating in the prior art.

Description

Technical Field

[0001] This invention relates to the field of road construction materials technology, and in particular to a green production method for carbon-reducing asphalt concrete. Background Technology

[0002] With the continuous expansion of highway construction and maintenance, traditional hot-mix asphalt mixtures consume large amounts of fossil fuels and emit huge amounts of carbon dioxide, nitrogen oxides, and dust during production, making it a typical high-energy-consuming and high-carbon-emission industry. Increasing the content of recycled asphalt mixtures, reducing mixing temperature, and reducing carbon emissions have become core pain points that the industry urgently needs to address.

[0003] Chinese invention patent, publication number CN116462449A, discloses a RAP-steel slag hot recycled asphalt mixture, its preparation method, and its application. This method involves a primary recycling process: mixing RAP fine aggregate with an asphalt recycling agent and regenerating at a temperature not exceeding 60°C, reducing the softening point of the aged asphalt in the RAP fine aggregate by more than 15%, thus obtaining recycled RAP fine aggregate; and a secondary hot recycling process: heating the recycled RAP fine aggregate to 130°C–150°C and the steel slag coarse aggregate to 200°C–220°C, while adding new asphalt and mineral powder while still hot, resulting in the RAP-steel slag hot recycled asphalt mixture. Although this method reduces the production temperature to some extent, the following technical problems still exist: RAP heating and aging problems are prominent: Traditionally, high-temperature drum drying of RAP is used directly, which easily leads to secondary severe aging of the old asphalt attached to the RAP surface. This not only results in the loss of the effective adhesion of the old asphalt, but also releases a large amount of asphalt fumes. Lack of proactive carbon sequestration methods: Existing technologies are mostly focused on passive energy conservation, failing to actively capture and utilize CO2 in industrial waste gas, thus limiting carbon reduction potential; It is difficult to balance the uniformity and performance of the mixture: When the RAP content exceeds 40%, the old asphalt and the new asphalt are difficult to fully integrate at low temperatures, resulting in a sharp decline in the fatigue resistance and low-temperature crack resistance of the recycled pavement. Summary of the Invention

[0004] Therefore, this invention provides a green production method for carbon-reducing asphalt concrete to overcome the problem of easy aging of RAP during heating in the prior art.

[0005] To achieve the above objectives, the present invention provides a green production method for carbon-reducing asphalt concrete, comprising: Step S1: The high-proportion recycled asphalt mixture is placed in a preheating drying system and dried at a low temperature of 90℃~110℃ and preheated with infrared to control the moisture content of the recycled asphalt mixture within the range of 0.2%~0.5%. At the same time, the industrial waste solid aggregate is heated to 100℃~120℃ through a waste heat recovery system to obtain a mixed preheated aggregate system. Step S2: Introduce supercritical carbon dioxide with a pressure of 8.5MPa to 12.0MPa into the asphalt modification tank to prepare carbon-fixed foamed asphalt with an expansion rate of 15 to 25 times, so that the carbon fixation content reaches 850mg / kg, and obtain carbon-fixed foamed asphalt binder. Step S3: At 130℃~145℃, a staged shear mixing process is adopted to mix the carbon-fixed foamed asphalt binder with the mixed preheated aggregate system, and add 1.2%~2.5% of warm mix agent and 5.0%~9.0% of old asphalt by weight of warm mix agent to control the porosity of the mixture within the range of 3.0%~5.0% to ensure the uniformity of the mixture and obtain asphalt concrete mixture; Step S4: Real-time monitoring parameters of carbon dioxide emissions are collected, and process parameters are dynamically adjusted based on the monitoring parameters to correct the mixing speed and heating power.

[0006] Furthermore, in step S1, the amount of the high-proportion recycled asphalt mixture is 45% to 60% of the total mass of the asphalt concrete; The industrial waste solid aggregates include one or more of steel slag, blast furnace slag, tailings sand, and construction waste crushed stone.

[0007] Furthermore, in step S1, the combined processing time of low-temperature drying and infrared preheating is 20 min to 40 min; The waste heat recovery system utilizes the waste heat from the exhaust gas after heat exchange in step S5 to preheat the industrial waste solid aggregate to 100℃~120℃ in a fluidized bed.

[0008] Furthermore, in step S2, the temperature of the supercritical carbon dioxide is controlled at 35°C to 50°C, and the pressure is controlled at 8.5 MPa to 12.0 MPa. The amount of supercritical carbon dioxide injected is 1.8% to 3.2% of the mass of the base asphalt, and the half-life of the carbon-fixed foam asphalt is stably controlled between 12s and 18s.

[0009] Further, in step S3, the staged shearing and mixing process includes the following steps: Step S31: The preheated aggregate system and the recycling agent are added to the mixer and pre-sheared and mixed at a speed of 35 r / min to 45 r / min for 30 s to 50 s; Step S32: The carbon-fixed foam asphalt binder is continuously sprayed into the mixing plant, and the rotation speed is increased to 55 r / min to 70 r / min for high shear mixing for 20 s to 35 s. Step S33: Add the warm mixing agent and mineral powder into the mixer, and complete the final mixing at a speed of 40 r / min to 50 r / min for a mixing time of 25 s to 40 s.

[0010] Further, in step S3, the warm mix agent is an organic wax-based warm mix agent or a surfactant-based warm mix agent, and its addition amount is 1.2% to 2.5% of the mass of the base asphalt; The regenerator is a high aromatic hydrocarbon regenerator or a naphthenic vegetable oil regenerator, and its addition amount is 5.0% to 9.0% of the mass of old asphalt in the recycled asphalt mixture.

[0011] Furthermore, in step S4, the parameter deviation state is determined based on the real-time collected monitoring parameters and historical production parameters, wherein the production parameters are determined by the production parameters with the highest degree of fusion between new and old asphalt in the historical production data. The first parameter deviation state is determined based on the positive deviation and is corrected by adjusting the mixing speed; The second parameter, the deviation state, is determined based on a negative deviation and is corrected by adjusting the heating power.

[0012] Furthermore, under the first parameter deviation state, a mixing speed compensation coefficient is determined based on the difference of the positive deviation, and a mixing speed correction value is determined based on the mixing speed compensation coefficient and the original mixing speed; When the second parameter deviates, a heating power compensation coefficient is determined based on the difference in the positive deviation, and a heating power correction value is determined based on the heating power compensation coefficient and the original heating power.

[0013] Furthermore, the green production method also includes: Step S5: The flue gas generated by the mixing plant is introduced into a multi-stage dust removal and heat exchange system for dust removal and heat exchange treatment. The hot air after heat exchange treatment is reused for heating the drying drum. At the same time, the generated condensate is recovered and reused for mixing water or dust suppression spraying.

[0014] Specifically, the multi-stage dust removal and heat exchange system includes a cyclone dust collector, a bag filter dust collector, and a shell-and-tube heat exchanger connected sequentially by pipes. The dust-laden flue gas generated in the mixing plant first enters the cyclone dust collector for coarse dust removal to remove large dust particles with a diameter greater than or equal to 10 μm. Then, it enters the bag filter dust collector for fine dust removal. The clean flue gas after dust removal enters the tube side of the shell-and-tube heat exchanger and exchanges heat with the cold air entering counter-currently in the shell side. The temperature of the hot air after heat exchange is controlled at 80℃~120℃ and sent to the drying cylinder as an auxiliary heating heat source through the return air duct. The condensate precipitated at the shell side outlet of the shell-and-tube heat exchanger is collected in a water collection pan and sent back to the mixing plant water tank through a water delivery pipe for reuse in mixing or dust suppression spraying in the stockyard.

[0015] Furthermore, the components of the carbon-reducing asphalt concrete include: Carbon-fixed foamed asphalt binder, high-proportion recycled asphalt mixture, industrial waste solid aggregate, warm mix additive, recycling agent and mineral powder; The mass fractions of each component are: The mixture consists of 100 parts of high-proportion recycled asphalt mixture and industrial waste solid aggregate, 4.0 to 5.5 parts of carbon-fixed foamed asphalt binder, 0.06 to 0.15 parts of warm mix agent, 0.12 to 0.32 parts of recycling agent, and 3.5 to 6.5 parts of mineral powder.

[0016] Compared with the prior art, the beneficial effects of the present invention are that by strictly controlling the preheating temperature of RAP at 90℃~110℃ and combining it with infrared preheating technology, the moisture content of RAP is precisely reduced to 0.2%~0.5%, which effectively avoids secondary aging of old asphalt and large-scale volatilization of VOCs while thoroughly removing moisture. Furthermore, this invention innovatively introduces supercritical carbon dioxide foaming technology, controlling the supercritical CO2 injection amount to 1.8% to 3.2%, which not only achieves in-situ mineralization and fixation of more than 850mg of CO2 per ton of asphalt, but also the micro-foamed structure formed significantly reduces the high-temperature viscosity of asphalt, reducing the mixing temperature to 130℃ to 145℃. Furthermore, this invention completely breaks the black rock effect of high-content RAP through a staged shearing and mixing process, stabilizing the porosity of the mixture at 3.0% to 5.0%, and significantly improving the integration of new and old asphalt and its road performance. Furthermore, relying on multi-stage heat recovery, a dynamic closed loop of combustion power and shear frequency is achieved, reducing overall carbon emissions by more than 30% compared to traditional hot-mix asphalt mixtures. Attached Figure Description

[0017] Figure 1 This is a schematic flowchart of the green production method for carbon-reducing asphalt concrete according to the present invention. Figure 2The infrared preheating temperature, treatment time and moisture content curves are for the carbon emission reduction green production method of asphalt concrete of the present invention. Figure 3 This is one of the graphs showing the relationship between preheating temperature and moisture content in the carbon-reducing green production method of asphalt concrete of the present invention. Figure 4 This is the second diagram showing the relationship between preheating temperature and moisture content in the carbon-reducing green production method of asphalt concrete of the present invention. Figure 5 This diagram illustrates the relationship between the amount of carbon dioxide injected and the foaming process in the green production method of asphalt concrete for carbon emission reduction according to the present invention. Detailed Implementation

[0018] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0019] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0020] Please see Figure 1 As shown, this invention provides a green production method for asphalt concrete that reduces carbon emissions, comprising the following steps: Step S1: The high-proportion recycled asphalt mixture is placed in a preheating drying system and dried at a low temperature of 90℃~110℃ and preheated with infrared to control the moisture content of the recycled asphalt mixture within the range of 0.2%~0.5%. At the same time, the industrial waste solid aggregate is heated to 100℃~120℃ through a waste heat recovery system to obtain a mixed preheated aggregate system. Please see Figure 2 As shown, the infrared preheating temperature, processing time, and moisture content curves of the carbon-reducing green production method for asphalt concrete of this invention demonstrate the relationship between moisture content of recycled material and processing time at different preheating temperatures. The higher the temperature, the faster the moisture content decreases. At 90℃, it takes 40 minutes to reduce the moisture content to 0.48%; while at 110℃, it only takes 20 minutes to reach 0.22%. The target range in the figure is our core control range, i.e., a moisture content between 0.2% and 0.5%. Below 90℃, the moisture content is too high, posing a risk of water damage; while above 110℃, although drying is fast, it leads to severe aging of the old asphalt, affecting its performance. Therefore, 90–110℃ is determined to be the optimal preheating temperature window.

[0021] Step S2: Supercritical carbon dioxide with a pressure of 8.5MPa to 12.0MPa is introduced into the connection of the asphalt modification tank to prepare carbon-fixed foam asphalt. The expansion rate of the carbon-fixed foam asphalt is 15 to 25 times so that the carbon fixation content reaches 850mg / kg, and carbon-fixed foam asphalt binder is obtained. The carbon fixation content reached 850 mg / kg. This value was obtained by taking about 10 g of carbon-fixed foamed asphalt binder sample, placing it in a tube furnace, heating it to 550 °C at 10 °C / min under a nitrogen atmosphere, and pyrolyzing it at a constant temperature for 30 min. The gas released by pyrolysis was passed into a gas absorption bottle containing 0.1 mol / L sodium hydroxide standard absorbent solution, and the carbon dioxide content in the absorbent solution was determined by acid-base titration. The ideal carbon fixation content was then calculated.

[0022] Please see Figure 5 As shown, it is a graph showing the relationship between the amount of carbon dioxide injected and the foaming of the green production method of asphalt concrete for carbon emission reduction of the present invention. Specifically, in step S2, the amount of supercritical CO2 injected is 1.8% to 3.2%, the temperature is 35℃ to 50℃, the pressure is 8.5 to 12.0 MPa, the expansion rate is controlled at 15 to 25 times, and the half-life is 12s to 18s.

[0023] Supercritical CO2 has extremely high solubility in asphalt. Upon pressure relief, it rapidly vaporizes to form microbubbles, significantly reducing asphalt viscosity. Insufficient injection volume results in inadequate foaming volume, failing to encapsulate high proportions of RAP aggregate; excessive injection volume causes bubbles to easily coalesce and burst, leading to a drastically shortened half-life and loss of warm-mix effect. Experimental results are shown in Table 1. Table 1. Effects of different supercritical CO2 injection rates on foaming properties.

[0024] As shown in Table 1, when the CO2 injection amount is between 1.8% and 3.2%, the expansion rate and half-life fall within the target range, ensuring sufficient mixing time. The expansion rate of control group 1-1 is only 8 times, which cannot meet the requirements for warm mixing; the half-life of control group 1-2 is only 6.5s, which is less than 12s, and the foam breaks down in the early stage of mixing, losing its encapsulation ability.

[0025] Step S3: At 130℃~145℃, a staged shear mixing process is adopted to mix the carbon-fixed foamed asphalt binder with the mixed preheated aggregate system, and add 1.2%~2.5% of warm mix agent and 5.0%~9.0% of old asphalt by weight of warm mix agent to control the porosity of the mixture within the range of 3.0%~5.0% to ensure the uniformity of the mixture and obtain asphalt concrete mixture; Step S4: Real-time monitoring parameters of carbon dioxide emissions are collected, and process parameters are dynamically adjusted based on the monitoring parameters to correct the mixing speed and heating power.

[0026] Specifically, in step S1, the amount of the high-proportion recycled asphalt mixture is 45% to 60% of the total mass of the asphalt concrete; The industrial waste solid aggregates include one or more of steel slag, blast furnace slag, tailings sand, and construction waste crushed stone.

[0027] Specifically, in step S1, the combined processing time of low-temperature drying and infrared preheating is 20 min to 40 min; The waste heat recovery system utilizes the waste heat from the exhaust gas after heat exchange in step S5 to preheat the industrial waste solid aggregate to 100℃~120℃ in a fluidized bed.

[0028] Specifically, in step S2, the temperature of the supercritical carbon dioxide is controlled at 35°C to 50°C, and the pressure is controlled at 8.5 MPa to 12.0 MPa. The amount of supercritical carbon dioxide injected is 1.8% to 3.2% of the mass of the base asphalt, and the half-life of the carbon-fixed foam asphalt is stably controlled between 12s and 18s.

[0029] Understandably, heating temperature and moisture content are key factors in determining the effectiveness of RAP recycling. Excessive temperature leads to severe volatilization of lightweight components in the old asphalt, causing it to age and harden rapidly; insufficient temperature prevents the removal of residual moisture from the aggregate, which can cause asphalt foaming and cracking during subsequent mixing, resulting in water damage.

[0030] To demonstrate the beneficial effects of parameter S1, different preheating temperature test groups were set up while keeping other conditions constant. The experimental data are shown in Table 2.

[0031] Table 2. Data on the effects of different RAP preheating temperatures on moisture content and aging of old asphalt.

[0032] As shown in Table 2, when the preheating temperature of implementation groups 2-1 to 2-3 was controlled between 90℃ and 110℃, the moisture content met the standard, and the asphalt aging index was greater than 89%, with extremely low VOC emissions. In contrast, the temperature of control group 1-1 was too low, resulting in a moisture content as high as 0.85%, which did not meet the standard and was prone to subsequent spalling. In control group 1-2, the temperature was too high; although the moisture content was extremely low, the old asphalt was severely aged, the penetration retention rate plummeted to 72.1%, and VOC emissions surged, demonstrating that exceeding the parameter range degraded the technical effect.

[0033] In this embodiment, the RAP content reaches 45%–60%, far exceeding the industry standard upper limit of 30%, significantly reducing the consumption of new asphalt and natural aggregates, and lowering raw material costs and resource extraction pressure. Industrial waste solid aggregates, such as steel slag, mine slag, tailings sand, and construction waste crushed stone, replace natural aggregates, solving the problem of solid waste accumulation pollution, while improving the mechanical properties of the mixture.

[0034] Specifically, in step S3, the staged shearing and mixing process includes the following steps: Step S31: The preheated aggregate system and the recycling agent are added to the mixer and pre-sheared and mixed at a speed of 35 r / min to 45 r / min for 30 s to 50 s; Step S32: The carbon-fixed foam asphalt binder is continuously sprayed into the mixing plant, and the rotation speed is increased to 55 r / min to 70 r / min for high shear mixing for 20 s to 35 s. Step S33: Add the warm mixing agent and mineral powder into the mixer, and complete the final mixing at a speed of 40 r / min to 50 r / min for a mixing time of 25 s to 40 s.

[0035] Understandably, the combined processing time ensures that the RAP moisture content remains stable and meets the standard, avoiding insufficient dehydration due to too short a time or aging due to too long a time. Utilizing the waste heat from the S5 exhaust gas to preheat the waste solid aggregate to 100℃~120℃ in the fluidized bed reduces the heating load on the drying drum, further reducing fuel consumption and carbon emissions.

[0036] Specifically, in step S3, the warm mix agent is an organic wax-based warm mix agent or a surfactant-based warm mix agent, and its addition amount is 1.2% to 2.5% of the mass of the base asphalt; The regenerator is a high aromatic hydrocarbon regenerator or a naphthenic vegetable oil regenerator, and its addition amount is 5.0% to 9.0% of the mass of old asphalt in the recycled asphalt mixture.

[0037] Understandably, step S3 employs a staged shear mixing process, with a rotation speed of 35–45 r / min for pre-mixing the recycling agent, a rotation speed of 55–70 r / min for high-shear mixing of foamed asphalt, and a rotation speed of 40–50 r / min for final mixing of mineral powder.

[0038] If traditional one-pot simultaneous mixing is used, the recycling agent cannot preferentially penetrate and soften the old RAP asphalt, and the high shear force will break up the mineral powder agglomerates, leading to an abnormal increase in oil absorption. The experimental results are shown in Table 3: Table 3. Data on the Influence of Mixing Process on the Porosity and Blending Degree of the Mixture

[0039] As shown in Table 3, the porosity of implementation group 3-1 remained stable at 4.2%, and the TSR was as high as 89.5% (far exceeding the standard requirement of 80%), indicating extremely high integration between the new and old asphalt. In contrast, due to one-pot mixing, a large amount of foamed asphalt in control group 3-1 was adsorbed by cold mineral powder, resulting in uneven coating of RAP, a porosity as high as 6.8% (not up to standard), and poor water stability.

[0040] Specifically, in step S4, the parameter deviation state is determined based on the real-time collected monitoring parameters and historical production parameters. The production parameters are determined by the production parameters with the highest degree of fusion between new and old asphalt in the historical production data. The first parameter deviation state is determined based on the positive deviation and is corrected by adjusting the mixing speed; The second parameter, the deviation state, is determined based on a negative deviation and is corrected by adjusting the heating power.

[0041] Specifically, in step S4, under the first parameter deviation state, the ratio of the difference of the positive deviation to the historical production parameter is calculated to obtain the mixing speed compensation coefficient, and the product of the mixing speed compensation coefficient and the original mixing speed is calculated to obtain the mixing speed correction value. Under the second parameter deviation state, the ratio of the difference in positive deviation to the historical production parameter is calculated to determine the heating power compensation coefficient, and the product of the heating power compensation coefficient and the original heating power is calculated to determine the heating power correction value.

[0042] Understandably, when the first parameter deviates from the state of a positive surge in instantaneous power or local temperature difference, it indicates, on a microscopic level, that the multiphase materials in the mixing pot have undergone microscopic agglomeration or a sharp increase in viscosity. The mixing speed compensation coefficient is dynamically increased according to the proportion of the positive deviation difference, and a speed-up command is output to break up the rheological agglomeration using strong mechanical energy. After the mixture is homogeneous, the speed drops back down.

[0043] The second parameter deviation occurs when the aggregate temperature rise rate or discharge temperature drops negatively. Microscopically, this indicates that the waste aggregate contains latent water, which absorbs a large amount of heat, leading to a system enthalpy deficit. The algorithm dynamically increases the heating power compensation coefficient according to the proportion of the negative deviation difference, precisely fine-tunes the burner valves, and replenishes the missing latent heat of vaporization.

[0044] When introducing recycled asphalt mixtures with a proportion as high as 45% to 60%, the surface of the old aggregate is dry and easily clumps together with mineral powder and new asphalt. Upon detecting a surge in power, the mixing speed is immediately increased. Strong mechanical shear force instantly breaks up the clumps before they solidify, allowing the carbon-fixed foamed asphalt to evenly coat each aggregate. Furthermore, timely speed reduction after correction avoids material segregation caused by excessive shearing, ensuring that the porosity of the final product is stably controlled within the optimal range of 3.0% to 5.0%, significantly improving the integration of new and old asphalt.

[0045] Through precise temperature control correction in the second deviation state, the latent moisture in the waste aggregate is completely squeezed out, preventing the steam boiling generated when free water comes into contact with hot asphalt from damaging the microscopic stable structure of copper dioxide foam. This ensures that the foam has a high expansion rate of 15 to 25 times and a healthy half-life of 12 to 18 seconds, providing the necessary fluidity compensation and lubrication for mixing at low temperature and high RAP content.

[0046] Specifically, the green production method of the present invention further includes: Step S5: The flue gas generated by the mixing plant is introduced into a multi-stage dust removal and heat exchange system for dust removal and heat exchange treatment. The hot air after heat exchange treatment is reused for heating the drying drum. At the same time, the generated condensate is recovered and reused for mixing water or dust suppression spraying.

[0047] Specifically, the components of the carbon-reducing asphalt concrete include: Carbon-fixed foamed asphalt binder, high-proportion recycled asphalt mixture, industrial waste solid aggregate, warm mix additive, recycling agent and mineral powder; The amount of mineralized carbon dioxide in the carbon-fixing foamed asphalt binder is not less than 850 mg / kg.

[0048] The mass fractions of each component are: The mixture consists of 100 parts of high-proportion recycled asphalt mixture and industrial waste solid aggregate, 4.0 to 5.5 parts of carbon-fixed foamed asphalt binder, 0.06 to 0.15 parts of warm mix agent, 0.12 to 0.32 parts of recycling agent, and 3.5 to 6.5 parts of mineral powder.

[0049] It is understandable that a carbon fixation content greater than or equal to 850 mg / kg is a direct material manifestation of the supercritical foaming mineralization effect in step S2; and the narrow mass fraction range of each admixture ensures that the new and old asphalt can not only be fully integrated under warm mixing conditions of 130℃~145℃, but also meet the stringent standards for resistance to rutting and water damage.

[0050] The process synergy effect of this invention is reflected in: The low-temperature constant water control in step S1 provides a prerequisite for the long-term foaming in step S2. If too much free water remains in step S1, uncontrollable water vapor boiling will occur when the CO2 foam comes into contact with hot asphalt in step S2, destroying the microscopic stable structure of the CO2 foam.

[0051] The high expansion rate microbubbles in step S2 provide fluidity compensation for the low-temperature, high RAP content mixing in step S3. High RAP itself is extremely dry and relies entirely on the huge volume of foam formed in step S2 for instantaneous encapsulation, while the stepped rotation speed in step S3 is perfectly matched with the 12-18s half-life of foamed asphalt.

[0052] Example 1 Step S1: Place 50% RAP in a preheating drying system and dry it at 100°C for 30 minutes with infrared preheating until the moisture content drops to 0.35%; preheat the waste solid aggregate to 110°C using residual heat, wherein the waste solid aggregate is steel slag. In step S2, the supercritical CO2 injection amount is controlled at 2.6% of the base asphalt, the pressure is 10.0 MPa, and the prepared foamed asphalt has an expansion rate of 20 times and a half-life of 15 s. Step S3: Perform a three-stage variable frequency shear mixing process at 135℃, adding 1.8% warm mixing agent and 7.0% regenerator; Step S4: Start real-time monitoring and feedback adjustment. Determine the parameter deviation state based on the comparison results between real-time parameters and production parameters. When the first parameter deviation state or the second parameter deviation state occurs, dynamically correct the mixing speed and heating power through the compensation coefficient. Step S5: Start the exhaust gas dust removal and heat exchange cycle.

[0053] Example 2 In this embodiment, the parameters are taken as the maximum values ​​of the process parameters in order to verify the effectiveness of the parameter boundary conditions.

[0054] Step S1: RAP dosage is increased to the limit of 60%, preheating temperature is 120℃, time is 20min, and moisture content is 0.22%.

[0055] Step S2: Supercritical CO2 injection amount 3.2%, expansion rate 25 times, half-life 16.5s.

[0056] Step S3: Mixing temperature 145℃, add 2.5% warm mixing agent and 9.0% regenerator, and perform three-stage shear mixing.

[0057] Steps S4 and S5 are the same as in Example 1.

[0058] Example 3 Step S1: Place 45% RAP in a preheating drying system and dry it at 100°C for 30 minutes with infrared preheating until the moisture content drops to 0.35%; preheat the waste solid aggregate to 90°C using residual heat.

[0059] In step S2, the supercritical CO2 injection amount is controlled at 1.8% of the base asphalt, the pressure is 8.5 MPa, and the prepared foamed asphalt has an expansion rate of 15 times and a half-life of 13 s.

[0060] Step S3: Mix at 135℃, perform a three-stage variable frequency shear mixing process, and add 1.8% warm mixing agent and 7.0% regenerator.

[0061] Steps S4 and S5 are the same as in Example 1.

[0062] Comparative Example 1 In this comparative example, low-temperature infrared preheating and staged mixing were omitted. RAP and waste aggregate were directly heated to 140°C in a conventional drum using an open flame. During mixing, all aggregates, recycling agent, and foamed asphalt were simultaneously added to the mixing pot, and the mixture was mixed at a constant speed of 50 r / min for 45 seconds per batch. Steps S2, S4, and S5 remained consistent with those in Example 1.

[0063] Comparative Example 2 In this comparative example, the supercritical CO2 injection process in step S2 is omitted, and carbon-fixed foamed asphalt is not prepared. Cooling and mixing are achieved solely using conventional organic chemical warm mix agents. The remaining steps S1, S3, S4, and S5 are exactly the same as in Example 1.

[0064] Comparative Example 3 In this comparative example, the process optimization dynamic feedback mechanism in step S4 is disabled. During production, the burner air-fuel ratio and valve opening are set manually based on experience, and the stirring variable frequency motor is always maintained at a constant full load without adaptive correction for instantaneous power and local temperature differences. The remaining processes are the same as in Example 1.

[0065] The product was tested, and the test results are shown in the table below: Table 4 Product Testing Results

[0066] The depth test data in Table 4 clearly demonstrates the absolute superiority of the synergistic effect of the various technical steps in this invention: Examples 1-3 demonstrate that the present invention establishes robust parameter boundaries. Whether using the median parameters in Example 1, the upper limit of the maximum parameters in Example 2, or the lower limit of the minimum parameters in Example 3, the porosity of the final product consistently falls within the range of 3.0% to 5.0%. Furthermore, all three examples successfully achieved active mineralization and carbon sequestration of 855–920 mg / kg, with a carbon emission reduction rate of 31.2%–38.2% per ton. In Example 3, due to the use of an extremely low preheating temperature of 90°C, the old asphalt penetration retention rate reached 94.8%, exhibiting near-zero aging at the microscopic level. This strongly demonstrates that the overall parameter range defined by the present invention possesses extremely high universality and scientific tolerance.

[0067] The deterioration of Comparative Example 1 demonstrates the irreplaceable nature of low-temperature infrared and staged shearing in step S1. Comparative Example 1, which uses traditional high-temperature open flame heating and one-pot mixing, resulted in severe secondary thermal oxidation of the old asphalt, causing the penetration retention rate to plummet to 61.2%. Simultaneously, due to the lack of staged flexible penetration and high-frequency shearing, the integration degree of the new and old asphalt was only 58.4%, and the porosity of the mixture was as high as 6.5%, severely failing to meet standards and making the road surface highly susceptible to water seepage and damage.

[0068] Comparative Example 2 demonstrates the core lubricating effect of supercritical carbon dioxide foaming. In Comparative Example 2, only a chemical warm-mix agent was used to mix 50% high-proportion RAP at 135°C. Due to the loss of the bearing lubrication effect brought about by microbubble expansion, the dynamic viscosity of the asphalt was too high, resulting in an increase in porosity to 5.8% and limited blending. More importantly, the carbon fixation amount was reduced to zero, causing the overall carbon emission reduction rate to plummet to 12.4%, completely losing the core emission reduction potential of the active carbon fixation of this invention.

[0069] Comparative Example 3 demonstrates the supporting role of the dynamic deviation feedback correction mechanism in achieving extreme carbon reduction. Comparative Example 3 disabled the parameter deviation-based feedback adjustment mechanism of S4, employing fixed-power heating and constant full-load stirring. Although the product quality was barely acceptable, the significant waste of energy due to the large amount of useless mechanical and thermal work output in the initial stage of heat conduction and the later stage of low viscosity resulted in a sharp drop in carbon emission reduction rate from 34.5% in Example 1 to 22.1%. This proves that the dynamic compensation and correction mechanism based on positive / negative deviation depth can accurately avoid overheating and ineffective shearing.

[0070] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A green production method for carbon-reducing asphalt concrete, characterized in that, Includes the following steps: Step S1: The high-proportion recycled asphalt mixture is placed in a preheating drying system and dried at a low temperature of 90℃~110℃ and preheated with infrared to control the moisture content of the recycled asphalt mixture within the range of 0.2%~0.5%. At the same time, the industrial waste solid aggregate is heated to 100℃~120℃ through a waste heat recovery system to obtain a mixed preheated aggregate system. Step S2: Introduce supercritical carbon dioxide with a pressure of 8.5MPa to 12.0MPa into the asphalt modification tank to prepare carbon-fixed foamed asphalt with an expansion rate of 15 to 25 times, so that the carbon fixation content reaches 850mg / kg, and obtain carbon-fixed foamed asphalt binder. Step S3: At 130℃~145℃, a staged shear mixing process is adopted to mix the carbon-fixed foamed asphalt binder with the mixed preheated aggregate system, and add 1.2%~2.5% of warm mix agent and 5.0%~9.0% of old asphalt by weight of warm mix agent to control the porosity of the mixture within the range of 3.0%~5.0% to ensure the uniformity of the mixture and obtain asphalt concrete mixture; Step S4: Real-time monitoring parameters of carbon dioxide emissions are collected, and process parameters are dynamically adjusted based on the monitoring parameters to correct the mixing speed and heating power.

2. The green production method for carbon-reducing asphalt concrete according to claim 1, characterized in that, In step S1, the amount of the high-proportion recycled asphalt mixture is 45% to 60% of the total mass of the asphalt concrete; The industrial waste solid aggregates include one or more of steel slag, blast furnace slag, tailings sand, and construction waste crushed stone.

3. The green production method for carbon-reducing asphalt concrete according to claim 2, characterized in that, In step S1, the combined processing time of low-temperature drying and infrared preheating is 20 min to 40 min; The waste heat recovery system utilizes the waste heat from the exhaust gas after heat exchange in step S5 to preheat the industrial waste solid aggregate to 100℃~120℃ in a fluidized bed.

4. The green production method for carbon-reducing asphalt concrete according to claim 3, characterized in that, In step S2, the temperature of the supercritical carbon dioxide is controlled at 35℃~50℃, and the pressure is controlled at 8.5MPa~12.0MPa. The amount of supercritical carbon dioxide injected is 1.8% to 3.2% of the mass of the base asphalt, and the half-life of the carbon-fixed foam asphalt is stably controlled between 12s and 18s.

5. The green production method for carbon-reducing asphalt concrete according to claim 4, characterized in that, In step S3, the staged shearing and mixing process includes the following steps: Step S31: The preheated aggregate system and the recycling agent are added to the mixer and pre-sheared and mixed at a speed of 35 r / min to 45 r / min for 30 s to 50 s; Step S32: The carbon-fixed foam asphalt binder is continuously sprayed into the mixing plant, and the rotation speed is increased to 55 r / min to 70 r / min for high shear mixing for 20 s to 35 s. Step S33: Add the warm mixing agent and mineral powder into the mixer, and complete the final mixing at a speed of 40 r / min to 50 r / min for a mixing time of 25 s to 40 s.

6. The green production method for carbon-reducing asphalt concrete according to claim 5, characterized in that, In step S3, the warm mix agent is an organic wax-based warm mix agent or a surfactant-based warm mix agent, and its addition amount is 1.2% to 2.5% of the mass of the base asphalt; The regenerator is a high aromatic hydrocarbon regenerator or a naphthenic vegetable oil regenerator, and its addition amount is 5.0% to 9.0% of the mass of old asphalt in the recycled asphalt mixture.

7. The green production method for carbon-reducing asphalt concrete according to claim 6, characterized in that, In step S4, the parameter deviation state is determined based on the real-time collected monitoring parameters and historical production parameters. The production parameters are determined according to the production parameters with the highest degree of fusion between new and old asphalt in the historical production data. The first parameter deviation state is determined based on the positive deviation and is corrected by adjusting the mixing speed; The second parameter, the deviation state, is determined based on a negative deviation and is corrected by adjusting the heating power.

8. The green production method for carbon-reducing asphalt concrete according to claim 7, characterized in that, Under the first parameter deviation state, a mixing speed compensation coefficient is determined based on the difference of the positive deviation, and a mixing speed correction value is determined based on the mixing speed compensation coefficient and the original mixing speed; When the second parameter deviates, a heating power compensation coefficient is determined based on the difference in the positive deviation, and a heating power correction value is determined based on the heating power compensation coefficient and the original heating power.

9. The green production method for carbon-reducing asphalt concrete according to claim 8, characterized in that, The green production method also includes: Step S5: The flue gas generated by the mixing plant is introduced into a multi-stage dust removal and heat exchange system for dust removal and heat exchange treatment. The hot air after heat exchange treatment is reused for heating the drying drum. At the same time, the generated condensate is recovered and reused for mixing water or dust suppression spraying.

10. Carbon-reducing asphalt concrete prepared by the green production method according to any one of claims 1-9, characterized in that, The components of the carbon-reducing asphalt concrete include: Carbon-fixed foamed asphalt binder, high-proportion recycled asphalt mixture, industrial waste solid aggregate, warm mix additive, recycling agent and mineral powder; The mass fractions of each component are: The mixture consists of 100 parts of high-proportion recycled asphalt mixture and industrial waste solid aggregate, 4.0 to 5.5 parts of carbon-fixed foamed asphalt binder, 0.06 to 0.15 parts of warm mix agent, 0.12 to 0.32 parts of recycling agent, and 3.5 to 6.5 parts of mineral powder.

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