Preparation method of warm-mixed regenerated modifier asphalt

Abstract

The invention provides a warm-mixing regenerated modifier asphalt preparation method, and relates to the field of asphalt modifier preparation.The warm-mixing regenerated modifier asphalt preparation method comprises the following steps of raw material preparation, modifier premixing, asphalt mixing modification, high-temperature shearing strengthening and cooling storage. According to the present invention, the problems of low cost and low utilization rate in the prior art are solved, the secondary aging is reduced by reducing the mixing temperature through the mixing temperature, the mixing temperature is reduced by 60-80 DEG C compared with the traditional process, the interface bonding of the old asphalt and the aggregate can be effectively destroyed through the high shear treatment so as to reduce the stripping temperature from 200 DEG C to 140 DEG C or less, and the high wax content natural rubber modifier and the warm mixing agent achieve the synergistic effect according to the ratio; the high-temperature stability of the asphalt is maintained while the viscosity is reduced, and the old material handling capacity is improved by 30% or below.

Description

Technical Field

[0001] The present invention relates to the field of asphalt modifier preparation, and in particular to a method for preparing warm-mix regenerated modifier asphalt. Background Art

[0002] Waste asphalt mixtures refer to discarded asphalt concrete materials generated during road maintenance, renovation, or demolition. These mixtures typically consist of asphalt, aggregates (such as gravel and sand), and other additives. Over long-term use, due to factors such as vehicle loads and the natural environment, asphalt gradually ages and degrades, while aggregates can also wear and break. When roads need to be renovated or rebuilt, the existing asphalt pavement is milled or excavated, creating waste asphalt mixtures. Left untreated, these waste materials not only occupy significant land but also pose a significant environmental risk.

[0003] A large amount of waste asphalt mixture is generated during highway maintenance. Currently, when waste asphalt mixture is mixed with new admixtures in the factory, the waste asphalt mixture needs to be processed first. When mixing the mixture, it needs to be heated to 200°C to remove the sand and gravel in the waste asphalt mixture from the asphalt. However, high-temperature treatment will cause secondary aging of the asphalt, affecting its utilization value and resulting in low utilization rate.

[0004] Therefore, a method for preparing warm mix recycled modifier asphalt is needed. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defects of the existing technology. The present invention proposes a method for preparing warm-mix recycled modifier asphalt, which aims to solve the problem that high-temperature treatment will cause secondary aging of asphalt, affect its utilization value, and have low utilization rate.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing warm mix recycled modifier asphalt, comprising the following steps:

[0007] S1: Raw material preparation: Take the old asphalt obtained by extraction and distillation of old asphalt mixture, and prepare natural rubber modifier, warm mix agent and anti-aging agent;

[0008] S2: Modifier premixing: natural rubber modifier and warm mix agent are mixed in proportion and premixed in the early stage. After the premixing is completed, anti-aging agent is added and the temperature and speed are kept constant for the later stage premixing.

[0009] S3: Asphalt mixing modification: Heat the old asphalt to 120-140℃, stir the old asphalt using an old asphalt mixer, and slowly add the premixed modifier while maintaining the temperature at 120-140℃ and stirring continuously;

[0010] S4: High temperature shear strengthening: the mixed liquid is transferred to the high temperature shear equipment for high temperature shear strengthening;

[0011] S5: Cooling storage: Fill after cooling and control the storage temperature to avoid long-term high-temperature storage.

[0012] Furthermore, the following components are weighed in S1 by mass percentage:

[0013] 10-15% waxy natural rubber modifier, 3-5% warm mix agent, 1-3% anti-aging agent, and the balance is old asphalt.

[0014] Furthermore, the wax-containing natural rubber;

[0015] The wax content of the rubber modifier is 20-30%.

[0016] Furthermore, a twin-shaft shear mixer is used for premixing in S2, pulsed shearing is applied at 60-70°C during the premixing stage, and the rotation speed of the twin-shaft stirring blades is controlled at 1500-2000 r / min.

[0017] Furthermore, the addition rate of slowly adding the premixed modifier is ≤1.5 kg / min.

[0018] Furthermore, the premixing time in the early stage of S2 is 10-15 minutes, and the premixing time in the late stage is 5 minutes.

[0019] Furthermore, the old asphalt mixer stirs the old asphalt at a rotation speed of 2000-3000 r / min, and continues stirring for 30-45 minutes after adding the premixed modifier.

[0020] Furthermore, the specific steps of S4 are as follows:

[0021] S41: The mixed liquid is transferred to a high temperature shearing device;

[0022] S42: Control the heating temperature of the high-temperature shearing device to 150-160° C. and control the shearing rate of the shear blades for 15-20 minutes;

[0023] S43: During the treatment, the temperature is kept constant and nitrogen is introduced for protection.

[0024] Furthermore, the shearing blade has a shearing rate of 5000-8000s-1.

[0025] Furthermore, the cooling temperature is 110-120°C, and the storage temperature is controlled at 100-120°C.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. Mixing temperature reduces secondary aging by lowering the mixing temperature, which is 60-80℃ lower than the traditional process.

[0028] 2. High shear treatment can effectively destroy the interface between old asphalt and aggregate, reducing the stripping temperature from 200°C to below 140°C.

[0029] 3. The high wax content of natural rubber modifier and the proportion of warm mix agent work synergistically to reduce the viscosity while maintaining the high temperature stability of asphalt, increasing the processing capacity of old materials by less than 30%. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The disclosure of the present invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. In the accompanying drawings, the same reference numerals are used to refer to the same components. Among them:

[0031] Figure 1 The figure schematically shows an overall flow chart according to one embodiment of the present invention. DETAILED DESCRIPTION

[0032] It is easy to understand that according to the technical solution of the present invention, without changing the essential spirit of the present invention, a person skilled in the art can propose a variety of interchangeable structural modes and implementation modes. Therefore, the following specific embodiments and drawings are only exemplary descriptions of the technical solution of the present invention and should not be regarded as the entire invention or as a limitation or restriction of the technical solution of the present invention.

[0033] According to one embodiment of the present invention, Figure 1 A method for preparing warm mix recycled modifier asphalt is shown, comprising the following steps:

[0034] Step 1: Prepare the ingredients

[0035] The old asphalt obtained by extraction and distillation of old asphalt mixture (RAP) is tested according to ASTMD5 standard at 25°C with a load of 100g for 5 seconds. The penetration is in the range of 30-50 (0.1mm). The penetration reflects the hardness and aging degree of asphalt. Selecting old asphalt in the range of 30-50 can ensure that it maintains the necessary structural strength in subsequent modification, while avoiding brittleness caused by excessive aging. By controlling the initial hardness of the old asphalt, the basic mechanical properties are provided for subsequent modification, so that the final warm-mix recycled asphalt can still maintain sufficient adhesion when the mixing temperature is lowered.

[0036] Weigh the following ingredients by mass percentage:

[0037] Natural rubber modifier with high wax content of 10-15%. The natural rubber modifier forms a network structure in the asphalt, improving the toughness and fatigue resistance of the asphalt, while reducing the high-temperature viscosity of the asphalt, so that the old asphalt can achieve ideal fluidity at 120-140°C. It also improves the wettability of the asphalt and aggregate, enhances the peeling resistance, and achieves a balance between easy peeling at low temperature and high-temperature stability. The wax component in the natural rubber modifier with high wax content will melt at high temperature, play a lubricating role, reduce the friction between asphalt molecules, thereby reducing the high-temperature viscosity of the asphalt, so that the old asphalt can achieve ideal fluidity at 120-140°C.

[0038] Furthermore, the optimal wax content range is: 20%-30%;

[0039] When the wax content is less than 20%, the viscosity reduction effect of the wax is insufficient, a higher mixing temperature is required, and the risk of secondary aging cannot be effectively reduced;

[0040] When the wax content is greater than 30%, the wax crystal structure will precipitate excessively, causing the high-temperature stability of asphalt to decrease and affecting the anti-rutting performance of the pavement;

[0041] 20%-30% wax content can form a moderate "wax-rubber" network structure, which is easier to disperse in the old asphalt during the shearing process, enhances the adhesion with the aggregate, and reduces the peeling temperature to below 140°C;

[0042] Too high a wax content will increase the low-temperature brittleness of asphalt, but a 20%-30% wax content in a 10-15% modifier (i.e., a wax content of approximately 2%-4.5% in the overall asphalt system) is within a safe range. Combined with an anti-aging agent (1-3%), it can take into account both high and low temperature performance.

[0043] Warm mix agent 3-5%;

[0044] The warm mix agent melts at 120-140°C to form microcrystals, reducing the intermolecular forces of asphalt and reducing the viscosity of asphalt from 2000mPa·s to below 800mPa·s at 120°C. It also reduces secondary aging by lowering the mixing temperature to below 140°C.

[0045] Anti-aging agent 1-3%;

[0046] Anti-aging agents inhibit the oxidation reaction of asphalt caused by high temperature during the processing process, while extending the stability time of asphalt in an environment above 150°C to more than 60 minutes, and increasing the needle penetration ratio of asphalt after aging from 50% to more than 70%. Anti-aging agents reduce the carbonyl index growth rate by 60% in the high-temperature shear stage, significantly reducing secondary aging.

[0047] The balance is old asphalt.

[0048] The purpose of the raw material formula synergy is to form a three-level viscosity control system of old asphalt (high viscosity) + natural rubber modifier (medium viscosity adjustment) + warm mix agent (low viscosity realization), ensuring the feasibility of mixing at 120-140℃. The wax component of high-wax rubber melts at 120-140℃, forming a eutectic system with the warm mix agent, reducing the overall viscosity. The microcrystals of the warm mix agent form physical crosslinking points at high temperatures, compensating for the softening point drop caused by the wax.

[0049] The elastic network of the natural rubber modifier and the microcrystals of the warm mix agent together form an "elastic skeleton-lubricating layer" structure, reducing the peel force from 8.5N to 5.2N;

[0050] The anti-aging agent forms an antioxidant barrier with the double bonds in the natural rubber modifier, reducing the aging rate by 55% when sheared at 150°C.

[0051] Furthermore, the rational combination of raw materials can reduce the mixing temperature from 180-200°C to 120-140°C, reduce fuel consumption by 35%, and increase the utilization rate of waste asphalt from 45% to more than 65%.

[0052] Step 2: Modifier premix

[0053] After the natural rubber modifier with high wax content and the warm mix agent are mixed in proportion, a twin-shaft shear mixer is used to apply pulsed shear at a pulse frequency of 0.5-1 Hz during the premixing stage at 60-70°C, and the speed of the twin-shaft stirring blade is controlled at 1500-2000 r / min. Premix for 10-15 minutes, add the anti-aging agent, continue to maintain the temperature and speed unchanged, and continue stirring for 5 minutes.

[0054] Warm mix agent 60-70℃: In this temperature range, the warm mix agent begins to soften and forms a semi-solid dispersed phase. The natural rubber modifier with a high wax content maintains an elastic state at this temperature. By controlling the softening degree of the warm mix agent, it forms microcrystals under shear force, forming a core-shell structure with the natural rubber modifier particles with a high wax content. The warm mix agent microcrystals act as a shell layer, wrapping the rubber particle core through interfacial interaction. During the subsequent high-temperature shearing, the warm mix agent core can absorb part of the shear energy and reduce the breakage of the natural rubber modifier molecular chain.

[0055] At a rotation speed of 1500-2000r / min and a shear rate of 300-500s-1, the agglomerates of natural rubber modifiers with high wax content can be effectively broken up. The microcrystals of the warm mix agent are oriented along the flow direction in the shear field, thereby forming composite particles of the warm mix agent wrapped with the natural rubber modifier. The interfacial binding energy is increased, and the mixing temperature is reduced. The composite dispersed phase formed by premixing reduces the viscosity of asphalt to below 800mPa·s at 120°C, which is easier to flow than the traditional process (1500mPa·s at 180°C).

[0056] The natural rubber modifier-warm mix agent composite dispersed phase is formed in the first 10-15 minutes, and the anti-aging agent is introduced in the last 5 minutes to avoid it being excessively damaged by shear force, so that the hydrophilicity of the natural rubber modifier with a high wax content and the hydrophobicity of the warm mix agent form an interfacial film, so that the anti-aging agent is evenly adsorbed on the surface of the composite particles.

[0057] The directional adsorption of anti-aging agent on the surface of composite particles during the premixing stage of modifier reduces the oxidation rate by 65% during the high-temperature shearing stage. The warm mix agent microcrystals in the composite particles begin to melt at 135°C, destroying the interface film between the old asphalt and the aggregate, and the stripping temperature drops from 200°C to 138°C.

[0058] Step 3: Asphalt Mix Modification

[0059] Heat the old asphalt to 120-140℃, use an old asphalt mixer to stir the old asphalt at a speed of 2000-3000r / min, and slowly add the premixed modifier at the same time, maintain the temperature at 120-140℃ and continue stirring for 30-45 minutes.

[0060] The purpose of asphalt mixture modification is to reduce the mixing temperature by about 60℃, reduce the mass loss of asphalt after the thin film oven test from 1.8% to 0.6%, and at the same time reduce the adhesion work of modified asphalt from 3.2J / m at 135℃ to 0.6%. 2 Increased to 5.8J / m 2 When the aggregate stripping rate is reduced from 45% to 12% and the old material content is increased from 60% to 75%, the Marshall stability remains ≥8kN.

[0061] Specifically, the asphalt mixing modification steps are as follows:

[0062] First, add the old asphalt into the old asphalt mixer and heat it to 120-140℃;

[0063] Then, start the stirring blade in the old asphalt mixer to make its speed reach 2000-3000r / min, and slowly add the premixed modifier;

[0064] Finally, the temperature was maintained at 120-140°C and stirring was continued for 30-45 minutes.

[0065] The heating temperature of the old asphalt is 120-140℃: the viscosity of the old asphalt is reduced to 1500-2500mPa·s (120℃) or 800-1200mPa·s (140℃), ensuring that the modifier can be effectively dispersed, avoiding the asphalt oxidation caused by the high temperature of 180-200℃ in the traditional process, and then extending the asphalt oxidation induction period from 30 minutes to 90 minutes at 120℃.

[0066] The stirring speed is 2000-3000r / min and the shear rate is 500-800s-1, which can break the agglomerates in the premixed modifier. The turbulent flow field formed makes the natural rubber modifier with high wax content and the microcrystals of the warm mix agent evenly distributed, thereby increasing the dispersion index of the modifier and the interfacial bonding strength.

[0067] Stirring time: 30-45 minutes: The first 15 minutes complete the initial dispersion of the modifier, and the last 15-30 minutes promote molecular-level mixing through Brownian motion, thereby increasing the grafting rate of the high-wax content natural rubber modifier in the asphalt.

[0068] Slowly add the premixed modifier: control the modifier addition rate to ≤1.5kg / min to avoid excessive local concentration and maintain the asphalt temperature fluctuation ≤±3℃, thereby reducing the radial concentration deviation and axial deviation of the modifier in the asphalt.

[0069] Step 4: High temperature shear strengthening

[0070] The mixed liquid is transferred to a high-temperature shearing device and treated at a temperature of 150-160°C and a shear rate of 5000-8000s-1 for 15-20 minutes. During the treatment, a constant temperature is maintained and nitrogen protection is introduced.

[0071] The purpose of high temperature shear strengthening is to reduce the adhesion work between asphalt and aggregate interface from 5.8 J / m 2 Increased to 7.1J / m 2 The 135°C peeling temperature can be further reduced to 130°C, the oxidation induction period in the high-temperature shear stage is extended from 90 minutes to 180 minutes, and when the old material content exceeds 75%, the Marshall modulus of the mixture still remains ≥1200MPa, meeting the needs of heavy-load traffic.

[0072] Specifically, the high temperature shear strengthening steps are as follows:

[0073] First, the mixed liquid is transferred to a high-temperature shear device;

[0074] Then, the heating temperature of the high-temperature shearing device is controlled to be 150-160° C., and the shearing blade is controlled to be at a shear rate of 5000-8000 s-1 for 15-20 minutes;

[0075] Finally, the temperature was kept constant and nitrogen was introduced for protection during the treatment.

[0076] Temperature control at 150-160°C: The warm mix agent is completely melted to form a continuous phase. At this temperature, the viscosity of the old asphalt drops to 300-500 mPa·s, achieving optimal fluidity. This activates the chemical reaction between the high-wax content natural rubber modifier and the asphalt, thereby increasing the solubility of the warm mix agent.

[0077] Shear rate 5000-8000s-1: Generates 100-200MPa shear stress, breaks up natural rubber modifier agglomerates with high wax content, orients the warm mix agent microcrystals along the flow direction, forms a "layered-spherical" composite structure, promotes the breakage and rearrangement of asphalt molecular chains, forms a more uniform network structure, and refines the dispersed phase particle size from 1-5μm to 0.2-1μm, increases the interface area, and improves the shear strength by 45%.

[0078] The processing time is 15-20 minutes: the first 5 minutes complete the initial shear dispersion, the middle 10 minutes promote phase reorganization, and the last 5 minutes stabilize the structure, thereby increasing the complex shear modulus of the modified asphalt.

[0079] Nitrogen protection: oxygen content is controlled to <0.5%, inhibiting asphalt oxidation, reducing double bond oxidative cross-linking of natural rubber modifiers with high wax content, and maintaining the activity of antioxidants.

[0080] Step 5: Cooling and storage

[0081] After cooling to 110-120℃, fill it and control the storage temperature between 100-120℃ to avoid long-term high-temperature storage.

[0082] Example 1:

[0083] Step 1: Prepare the ingredients

[0084] Take the old asphalt obtained by extraction and distillation of old asphalt mixture (RAP). Weigh the following components by mass percentage:

[0085] 10-15% natural rubber modifier with high wax content, 3-5% warm mix agent, 1-3% anti-aging agent, and the balance is old asphalt.

[0086] Step 2: Modifier premix

[0087] After the natural rubber modifier with high wax content and the warm mix agent are mixed in proportion, a twin-shaft shear mixer is used to apply pulsed shear at a pulse frequency of 0.5-1 Hz during the premixing stage at 60-70°C, and the speed of the twin-shaft stirring blade is controlled at 1500-2000 r / min. Premix for 10-15 minutes, add the anti-aging agent, continue to maintain the temperature and speed unchanged, and continue stirring for 5 minutes.

[0088] Step 3: Asphalt Mix Modification

[0089] Heat the old asphalt to 130℃, use an old asphalt mixer to stir the old asphalt at a speed of 2000-3000r / min, and slowly add the premixed modifier at the same time, maintain the temperature at 130℃ and continue stirring for 30-45 minutes.

[0090] Step 4: High temperature shear strengthening

[0091] The mixed liquid is transferred to a high-temperature shearing device and treated at a temperature of 150-160°C and a shear rate of 5000-8000s-1 for 15-20 minutes. During the treatment, a constant temperature is maintained and nitrogen protection is introduced.

[0092] Step 5: Cooling and storage

[0093] After cooling to 110-120℃, fill it and control the storage temperature between 100-120℃ to avoid long-term high-temperature storage.

[0094] Example 2:

[0095] Step 1: Prepare the ingredients

[0096] Take the old asphalt obtained by extraction and distillation of old asphalt mixture (RAP). Weigh the following components by mass percentage:

[0097] 10-15% natural rubber modifier with high wax content, 3-5% warm mix agent, 1-3% anti-aging agent, and the balance is old asphalt.

[0098] Step 2: Modifier premix

[0099] After the natural rubber modifier with high wax content and the warm mix agent are mixed in proportion, a twin-shaft shear mixer is used to apply pulsed shear at a pulse frequency of 0.5-1 Hz during the premixing stage at 60-70°C, and the speed of the twin-shaft stirring blade is controlled at 1500-2000 r / min. Premix for 10-15 minutes, add the anti-aging agent, continue to maintain the temperature and speed unchanged, and continue stirring for 5 minutes.

[0100] Step 3: Asphalt Mix Modification

[0101] Heat the old asphalt to 120℃, use an old asphalt mixer to stir the old asphalt at a speed of 2000-3000r / min, and slowly add the premixed modifier at the same time, maintain the temperature at 120℃ and continue stirring for 30-45 minutes.

[0102] Step 4: High temperature shear strengthening

[0103] The mixed liquid is transferred to a high-temperature shearing device and treated at a temperature of 150-160°C and a shear rate of 5000-8000s-1 for 15-20 minutes. During the treatment, a constant temperature is maintained and nitrogen protection is introduced.

[0104] Step 5: Cooling and storage

[0105] After cooling to 110-120℃, fill it and control the storage temperature between 100-120℃ to avoid long-term high-temperature storage.

[0106] Example 3:

[0107] Step 1: Prepare the ingredients

[0108] Take the old asphalt obtained by extraction and distillation of old asphalt mixture (RAP). Weigh the following components by mass percentage:

[0109] 10-15% natural rubber modifier with high wax content, 3-5% warm mix agent, 1-3% anti-aging agent, and the balance is old asphalt.

[0110] Step 2: Modifier premix

[0111] After the natural rubber modifier with high wax content and the warm mix agent are mixed in proportion, a twin-shaft shear mixer is used to apply pulsed shear at a pulse frequency of 0.5-1 Hz during the premixing stage at 60-70°C, and the speed of the twin-shaft stirring blade is controlled at 1500-2000 r / min. Premix for 10-15 minutes, add the anti-aging agent, continue to maintain the temperature and speed unchanged, and continue stirring for 5 minutes.

[0112] Step 3: Asphalt Mix Modification

[0113] Heat the old asphalt to 140℃, use an old asphalt mixer to stir the old asphalt at a speed of 2000-3000r / min, and slowly add the premixed modifier at the same time, maintain the temperature at 140℃ and continue stirring for 30-45 minutes.

[0114] Step 4: High temperature shear strengthening

[0115] The mixed liquid is transferred to a high-temperature shearing device and treated at a temperature of 150-160°C and a shear rate of 5000-8000s-1 for 15-20 minutes. During the treatment, a constant temperature is maintained and nitrogen protection is introduced.

[0116] Step 5: Cooling and storage

[0117] After cooling to 110-120℃, fill it and control the storage temperature between 100-120℃ to avoid long-term high-temperature storage.

[0118] Example 4:

[0119] Step 1: Prepare the ingredients

[0120] Take the old asphalt obtained by extraction and distillation of old asphalt mixture (RAP). Weigh the following components by mass percentage:

[0121] 10-15% natural rubber modifier with high wax content, 3-5% warm mix agent, 1-3% anti-aging agent, and the balance is old asphalt.

[0122] Step 2: Modifier premix

[0123] After the natural rubber modifier with high wax content and the warm mix agent are mixed in proportion, a twin-shaft shear mixer is used to apply pulsed shear at a pulse frequency of 0.5-1 Hz during the premixing stage at 60-70°C, and the speed of the twin-shaft stirring blade is controlled at 1500-2000 r / min. Premix for 10-15 minutes, add the anti-aging agent, continue to maintain the temperature and speed unchanged, and continue stirring for 5 minutes.

[0124] Step 3: Asphalt Mix Modification

[0125] Heat the old asphalt to 130℃, use an old asphalt mixer to stir the old asphalt at a speed of 2000-3000r / min, and slowly add the premixed modifier at the same time, maintain the temperature at 130℃ and continue stirring for 30-45 minutes.

[0126] Step 4: High temperature shear strengthening

[0127] The mixed liquid was transferred to a high-temperature shearing device and treated at a temperature of 150-160°C and a shear rate of 5000s-1 for 15-20 minutes. During the treatment, the temperature was kept constant and nitrogen was introduced for protection.

[0128] Step 5: Cooling and storage

[0129] After cooling to 110-120℃, fill it and control the storage temperature between 100-120℃ to avoid long-term high-temperature storage.

[0130] Embodiment 5:

[0131] Step 1: Prepare the ingredients

[0132] Take the old asphalt obtained by extraction and distillation of old asphalt mixture (RAP). Weigh the following components by mass percentage:

[0133] 10-15% natural rubber modifier with high wax content, 3-5% warm mix agent, 1-3% anti-aging agent, and the balance is old asphalt.

[0134] Step 2: Modifier premix

[0135] After the natural rubber modifier with high wax content and the warm mix agent are mixed in proportion, a twin-shaft shear mixer is used to apply pulsed shear at a pulse frequency of 0.5-1 Hz during the premixing stage at 60-70°C, and the speed of the twin-shaft stirring blade is controlled at 1500-2000 r / min. Premix for 10-15 minutes, add the anti-aging agent, continue to maintain the temperature and speed unchanged, and continue stirring for 5 minutes.

[0136] Step 3: Asphalt Mix Modification

[0137] Heat the old asphalt to 130℃, use an old asphalt mixer to stir the old asphalt at a speed of 2000-3000r / min, and slowly add the premixed modifier at the same time, maintain the temperature at 130℃ and continue stirring for 30-45 minutes.

[0138] Step 4: High temperature shear strengthening

[0139] The mixed liquid was transferred to a high-temperature shearing device and treated at a temperature of 150-160°C and a shear rate of 6500s-1 for 15-20 minutes. During the treatment, the temperature was kept constant and nitrogen was introduced for protection.

[0140] Step 5: Cooling and storage

[0141] After cooling to 110-120℃, fill it and control the storage temperature between 100-120℃ to avoid long-term high-temperature storage.

[0142] Example 6:

[0143] Step 1: Prepare the ingredients

[0144] Take the old asphalt obtained by extraction and distillation of old asphalt mixture (RAP). Weigh the following components by mass percentage:

[0145] 10-15% natural rubber modifier with high wax content, 3-5% warm mix agent, 1-3% anti-aging agent, and the balance is old asphalt.

[0146] Step 2: Modifier premix

[0147] After the natural rubber modifier with high wax content and the warm mix agent are mixed in proportion, a twin-shaft shear mixer is used to apply pulsed shear at a pulse frequency of 0.5-1 Hz during the premixing stage at 60-70°C, and the speed of the twin-shaft stirring blade is controlled at 1500-2000 r / min. Premix for 10-15 minutes, add the anti-aging agent, continue to maintain the temperature and speed unchanged, and continue stirring for 5 minutes.

[0148] Step 3: Asphalt Mix Modification

[0149] Heat the old asphalt to 130℃, use an old asphalt mixer to stir the old asphalt at a speed of 2000-3000r / min, and slowly add the premixed modifier at the same time, maintain the temperature at 130℃ and continue stirring for 30-45 minutes.

[0150] Step 4: High temperature shear strengthening

[0151] The mixed liquid was transferred to a high-temperature shearing device and treated at a temperature of 150-160°C and a shear rate of 8000s-1 for 15-20 minutes. During the treatment, the temperature was kept constant and nitrogen was introduced for protection.

[0152] Step 5: Cooling and storage

[0153] After cooling to 110-120℃, fill it and control the storage temperature between 100-120℃ to avoid long-term high-temperature storage.

[0154] Comparative Example 1:

[0155] Step 1: Prepare the ingredients

[0156] Take the old asphalt obtained by extraction and distillation of old asphalt mixture (RAP). Weigh the following components by mass percentage:

[0157] 10-15% natural rubber modifier with high wax content, 3-5% warm mix agent, 1-3% anti-aging agent, and the balance is old asphalt.

[0158] Step 2: Modifier premix

[0159] After the natural rubber modifier with high wax content and the warm mix agent are mixed in proportion, a twin-shaft shear mixer is used to apply pulsed shear at a pulse frequency of 0.5-1 Hz during the premixing stage at 60-70°C, and the speed of the twin-shaft stirring blade is controlled at 1500-2000 r / min. Premix for 10-15 minutes, add the anti-aging agent, continue to maintain the temperature and speed unchanged, and continue stirring for 5 minutes.

[0160] Step 3: Asphalt Mix Modification

[0161] Heat the old asphalt to 130℃, use an old asphalt mixer to stir the old asphalt at a speed of 2000-3000r / min, and slowly add the premixed modifier at the same time, maintain the temperature at 130℃ and continue stirring for 30-45 minutes.

[0162] Step 4: Cool and store

[0163] After cooling to 110-120℃, fill it and control the storage temperature between 100-120℃ to avoid long-term high-temperature storage.

[0164] Comparative Example 2:

[0165] Step 1: Prepare the ingredients

[0166] Take the old asphalt obtained by extraction and distillation of old asphalt mixture (RAP). Weigh the following components by mass percentage:

[0167] Warm mix agent 3-5%, the rest is old asphalt.

[0168] Step 2: Asphalt Mix Modification

[0169] Heat the old asphalt to 200℃, use an old asphalt mixer to stir the old asphalt at a speed of 2000-3000r / min, and slowly add the warm mix agent at the same time, maintain the temperature at 200℃ and continue stirring for 30-45 minutes.

[0170] Step 3: High temperature shear strengthening

[0171] The mixed liquid is transferred to a high-temperature shearing device and treated at a temperature of 150-160°C and a shear rate of 5000-8000s-1 for 15-20 minutes. During the treatment, a constant temperature is maintained and nitrogen protection is introduced.

[0172] Step 4: Cool and store

[0173] After cooling to 110-120℃, fill it and control the storage temperature between 100-120℃ to avoid long-term high-temperature storage.

[0174] Comparative Example 3:

[0175] Step 1: Prepare the ingredients

[0176] Take the old asphalt obtained by extraction and distillation of old asphalt mixture (RAP). Weigh the following components by mass percentage:

[0177] Warm mix agent 3-5%, the rest is old asphalt.

[0178] Step 2: Asphalt Mix Modification

[0179] Heat the old asphalt to 200℃, use an old asphalt mixer to stir the old asphalt at a speed of 2000-3000r / min, and slowly add the warm mix agent at the same time, maintain the temperature at 200℃ and continue stirring for 30-45 minutes.

[0180] Step 3: Cool and store

[0181] After cooling to 110-120℃, fill it and control the storage temperature between 100-120℃ to avoid long-term high-temperature storage.

[0182] Modified Asphalt Comparison Table

[0183]

[0184]

[0185] Referring to the table, it can be concluded through Example 1, Example 2 and Example 3 that lowering the mixing temperature (such as Example 2) can reduce asphalt aging (carbonyl index and mass loss decrease), but the amount of old material processed is slightly reduced and the viscosity is slightly increased (possibly due to the decrease in asphalt fluidity at low temperatures). Increasing the mixing temperature (such as Example 3) can increase the amount of old material processed (possibly because high temperature promotes the fusion of old and new materials), but aggravates aging (carbonyl index increases) and reduces viscosity (fluidity increases at high temperatures).

[0186] Referring to the table, it can be obtained through Example 1, Example 4, Example 5, Example 6 and Comparative Example 1 that increasing the shear rate (such as Example 6) can significantly reduce the stripping temperature (improve construction convenience) and viscosity (improve fluidity), while reducing aging (decreased carbonyl index), and the amount of old material processed is equivalent to the benchmark. When there is no shear effect (Comparative Example 1), the stripping temperature is extremely high, the viscosity increases significantly, the amount of old material processed is significantly reduced, and the degree of aging is aggravated (carbonyl index and mass loss double), indicating that shearing is a key process to promote uniform mixing of modifier and asphalt.

[0187] Referring to the table, by implementing Column 1, comparing Column 2, and comparing Column 3, we can see that without a modifier (Comparative Examples 2 and 3), the mixing temperature must be significantly increased (200°C, 70°C higher than the baseline), resulting in a significant increase in peel temperature and viscosity, and a sharp increase in aging indicators (carbonyl index and mass loss) (up to 3-4 times the baseline). Although the amount of recycled material processed did not decrease significantly, the asphalt performance was severely degraded. The presence of a modifier can reduce the application temperature, improve compatibility, and significantly inhibit aging, which is the core factor in ensuring the performance of recycled asphalt.

[0188] In summary: the mixing temperature (120-140℃) can reduce secondary aging by lowering the mixing temperature, which is lower than the traditional process. Low 60-80℃;

[0189] High shear treatment (5000-8000s-1) can effectively destroy the interface between old asphalt and aggregate, reducing the stripping temperature from 200℃ to below 140℃;

[0190] The high wax content of natural rubber modifier (10-15%) and the proportion of warm mix agent (3-5%) work synergistically to reduce the viscosity while maintaining the high temperature stability of asphalt, increasing the processing capacity of old materials by less than 30%.

[0191] The technical scope of the present invention is not limited to the contents of the above description. Those skilled in the art can make various deformations and modifications to the above embodiments without departing from the technical concept of the present invention, and these deformations and modifications should all fall within the protection scope of the present invention.

Claims

1. A method for preparing warm mix recycled modifier asphalt, characterized in that: The steps include: S1: Raw material preparation: Take the old asphalt obtained by extraction and distillation of old asphalt mixture, and prepare natural rubber modifier, warm mix agent and anti-aging agent; S2: Modifier premixing: natural rubber modifier and warm mix agent are mixed in proportion and premixed in the early stage. After the premixing is completed, anti-aging agent is added and the temperature and speed are kept constant for the later stage premixing. S3: Asphalt mixing modification: Heat the old asphalt to 120-140℃, stir the old asphalt using an old asphalt mixer, and slowly add the premixed modifier while maintaining the temperature at 120-140℃ and stirring continuously; S4: High temperature shear strengthening: the mixed liquid is transferred to the high temperature shear equipment for high temperature shear strengthening; S5: Cooling storage: Fill after cooling and control the storage temperature to avoid long-term high-temperature storage.

2. The method for preparing warm mix regenerated modifier asphalt according to claim 1, characterized in that: The following components are weighed in S1 by mass percentage: 10-15% waxy natural rubber modifier, 3-5% warm mix agent, 1-3% anti-aging agent, and the balance is old asphalt.

3. The method for preparing warm mix regenerated modifier asphalt according to claim 1, characterized in that: The wax content of the wax-containing natural rubber modifier is 20-30%.

4. The method for preparing warm mix regenerated modifier asphalt according to claim 1, characterized in that: The premixing in S2 is performed using a twin-shaft shear mixer, pulsed shearing is applied at 60-70° C. during the premixing stage, and the rotation speed of the twin-shaft stirring blades is controlled at 1500-2000 r / min.

5. The method for preparing warm mix regenerated modifier asphalt according to claim 1, characterized in that: The addition rate of the slowly added premixed modifier is ≤1.5 kg / min.

6. The method for preparing warm mix regenerated modifier asphalt according to claim 1, characterized in that: The premixing time in the early stage of S2 is 10-15 minutes, and the premixing time in the late stage is 5 minutes.

7. The method for preparing warm mix regenerated modifier asphalt according to claim 1, characterized in that: The old asphalt mixer stirs the old asphalt at a speed of 2000-3000 r / min, and continues stirring for 30-45 minutes after adding the premixed modifier.

8. The method for preparing warm mix regenerated modifier asphalt according to claim 1, characterized in that: The specific steps of S4 are as follows: S41: The mixed liquid is transferred to a high temperature shearing device; S42: Control the heating temperature of the high-temperature shearing device to 150-160° C. and control the shearing rate of the shear blades for 15-20 minutes; S43: During the treatment, the temperature is kept constant and nitrogen is introduced for protection.

9. The method for preparing warm mix regenerated modifier asphalt according to claim 8, characterized in that: The shearing blade has a shearing rate of 5000-8000s-1.

10. The method for preparing warm mix recycled modifier asphalt according to claim 1, characterized in that: The cooling temperature is 110-120°C, and the storage temperature is controlled at 100-120°C.

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