Pretreated crumb rubber-modified asphalt, and preparation method thereof, and use in emergency pavement repair

Abstract

A rubber crumb is swollen with an edible oil to increase its volume by 12 – 18 %. The rubber crumb may be derrived from waste tires and have a size of 40-80 mesh or 277.96-465.36 microns. The rubber a

Description

TECHNICAL FIELD

[0001] The present disclosure belongs to the technical field of asphalt materials, and particularly relates to a modified crumb rubber and a preparation method thereof, a crumb rubber-modified asphalt and a preparation method and use thereof. BACKGROUND

[0002] Asphalt must maintain consistent quality and performance levels throughout the storage period, as variations in its composition could lead to differences in performance, which in turn affects the durability and effectiveness of asphalt in road construction. By maintaining storage stability, the quality and performance of asphalt could be ensured, resulting in better and more durable road surfaces.

[0003] Rubberized asphalt is a type of asphalt produced by incorporating chloroprene rubber (CR) from waste tires into asphalt. Adding CR could not only enhance the performance of the asphalt, improving high-temperature stability, mechanical properties, and long-term durability of asphalt, but also reduce reflective cracks, ruts, stripping, and noise levels, and provide significant economic and environmental advantages by solving the problem of waste tire disposal. However, rubberized asphalt suffers from problems such as inadequate storage stability.

[0004] Some researchers pre-treat the rubber in the rubberized asphalt with oils, e.g., an aromatic or naphthenic oil, and such activation behavior enhances the compatibility of CR with asphalt. However, a resulting crumb rubber-modified asphalt (CRMA) exhibits poor high-temperature resistance, failing to meet the performance requirements of the material for use in high-temperature areas. SUMMARY

[0005] The present disclosure is intended to provide a modified high-content crumb rubber (HCCR) and a preparation method thereof, a crumb rubber-modified asphalt and a preparation method and use thereof. The modified HCCR provided in the present disclosure enables the crumb rubber-modified asphalt to exhibit excellent storage stability and high-temperature resistance.

[0006] To achieve the objects as described above, the present disclosure provides the following technical solutions.

[0007] The present disclosure provides a modified crumb rubber, including a crumb rubber swollen with an oil, where the oil includes at least one selected from the group consisting of an edible oil and a waste edible oil; and the swelling degree of the crumb rubber swollen with the oil is 12% to 18% increase in volume.

[0008] Preferably, a source of the crumb rubber includes at least one selected from the group consisting of waste truck tires and waste car tires; and the crumb rubber has a particle size of 40 mesh to 80 mesh.

[0009] Preferably, the modified crumb rubber has a particle size of 277.96 pm to 465.36 pm.

[0010] The present disclosure further provides a method for preparing the modified crumb rubber as described in the above solutions, including the steps of:

[0011] mixing the crumb rubber and the oil, and subjecting a resulting mixture to swelling to obtain the modified crumb rubber, where the oil includes at least one selected from the group consisting of the edible oil and the waste edible oil.

[0012] Preferably, a mass ratio of the crumb rubber to the oil is in a range of 1: 0.1 to 1: 0.5.

[0013] Preferably, the swelling is conducted at a temperature of 80 °C to 110 °C for 40 minutes to 75 minutes.

[0014] The present disclosure further provides a crumb rubber-modified asphalt, which includes, in parts by mass, 100 parts of asphalt and 20 parts of a modified crumb rubber, where the modified crumb rubber is the modified crumb rubber as described in the above solutions, or a modified crumb rubber obtained using the method as described in the above solutions;

[0015] under a condition that the crumb rubber-modified asphalt further includes styrenebutadiene-styrene, the crumb rubber-modified asphalt includes, in parts by mass, 100 parts of the asphalt, 20 parts of the modified crumb rubber, and 2 to 4 parts of the styrene-butadiene-styrene;

[0016] under a condition that the crumb rubber-modified asphalt further includes styrene-butadiene-styrene and sulfur, the crumb rubber-modified asphalt includes, in parts by mass, 100 parts of the asphalt, 20 parts of the modified crumb rubber, 4 parts of styrene-butadiene-styrene, and 0.6 parts of the sulfur;

[0017] under a condition that the crumb rubber-modified asphalt further includes a recycled low-density polyethylene and sulfur, the crumb rubber-modified asphalt includes, in parts by mass, 100 parts of the asphalt, 20 parts of the modified crumb rubber, 4 parts of the recycled low-density polyethylene, and 0.6 parts of the sulfur; and

[0018] under a condition that the crumb rubber-modified asphalt further includes styrene-butadiene-styrene, a recycled low-density polyethylene and sulfur, the crumb rubber-modified asphalt includes, in parts by mass, 100 parts of the asphalt, 20 parts of the modified crumb rubber, 2 parts of the styrene-butadiene-styrene, 2 parts of the recycled low-density polyethylene, and 0.6 parts of the sulfur.

[0019] The present disclosure further provides a method for preparing the crumb rubber-modified asphalt as described in the s solutions, including the following steps:

[0020] heating and mixing the asphalt and the modified crumb rubber, and subjecting a first resulting mixture to a first forming to obtain the crumb rubber-modified asphalt;

[0021] under a condition that the crumb rubber-modified asphalt further includes styrenebutadiene-styrene, heating and mixing the asphalt, the modified crumb rubber, and the styrenebutadiene-styrene, and subjecting a second resulting mixture to a second forming to obtain the crumb rubber-modified asphalt;

[0022] under a condition that the crumb rubber-modified asphalt further includes styrenebutadiene-styrene and sulfur, heating and mixing the asphalt, the modified crumb rubber, the styrene-butadiene-styrene, and the sulfur, and subjecting a third resulting mixture to a third forming to obtain the crumb rubber-modified asphalt;

[0023] under a condition that the crumb rubber-modified asphalt further includes a recycled low-density polyethylene and sulfur, heating and mixing the asphalt, the modified crumb rubber, the recycled low-density polyethylene, and the sulfur, and subjecting a fourth resulting mixture to a fourth forming to obtain the crumb rubber-modified asphalt; and

[0024] under a condition that the crumb rubber-modified asphalt further includes styrene-butadiene-styrene, a recycled low-density polyethylene and sulfur, heating and mixing the asphalt, the modified crumb rubber, the styrene-butadiene-styrene, the recycled low-density polyethylene, and the sulfur, subjecting a fifth resulting mixture to a fifth forming to obtain the crumb rubber-modified asphalt.

[0025] Preferably, the first forming, the second forming, the third forming, the fourth forming and the fifth forming each independently include a first stirring and forming, a second stirring and forming, and a third stirring and forming, which are performed sequentially, where the first stirring and forming is conducted at a rotational speed of 500 rpm to 800 rpm for 15 minutes to 30 minutes; the second stirring and forming is conducted at a rotational speed of 4,500 rpm to 5,000 rpm for 60 minutes to 90 minutes; the third stirring and forming is conducted at a rotational speed of 500 rmp to 800 rpm for 15 minutes to 30 minutes; the first forming, the second forming, the third forming, the fourth forming and the fifth forming each are independently conducted at a temperature of 170 °C to 185 °C.

[0026] The present disclosure further provides use of the crumb rubber-modified asphalt as described in the above solutions or a crumb rubber-modified asphalt prepared using the method as described in the above solutions in the field of road engineering.

[0027] The present disclosure provides a modified crumb rubber. The modified crumb rubber according to the present disclosure exhibits good compatibility with asphalt, which could be introduced into asphalt with a high doping amount, and maintains storage stability, thereby overcoming the stability problems of conventional crumb rubbers.

[0028] The present disclosure further provides a method for preparing the modified crumb rubber as described in the above solutions. The method according to the present disclosure involves simple steps with convenient operations, and demonstrates good feasibility.

[0029] The present disclosure further provides a crumb rubber-modified asphalt. The crumb rubber-modified asphalt according to the present disclosure exhibits excellent storage stability and high-temperature resistance, and excellent overall performance. In the present disclosure, a modified crumb rubber is used to significantly improve the storage stability of a crumb rubber-modified asphalt, enabling the crumb rubber-modified asphalt to remain stable in the storage tank for a long period of time without stirring. In the present disclosure, the addition of styrenebutadiene-styrene (SBS) could significantly improve the high-temperature resistance and low-temperature resistance of the crumb rubber-modified asphalt. In the present disclosure, the addition of a recycled low-density polyethylene (RLDPE) could enhance the high-temperature rutting resistance of the crumb rubber-modified asphalt, significantly reduce the temperature sensitivity of the crumb rubber-modified asphalt, and improve the high-temperature resistance of the crumb rubber-modified asphalt. In the present disclosure, the addition of sulfur further effectively improves the storage stability of the crumb rubber-modified asphalt.

[0030] The present disclosure further provides a method for preparing the crumb rubber-modified asphalt as described in the above solutions. The method according to the present disclosure is lowcost and environmentally friendly, with promising potential for industrial application.

[0031] The present disclosure further provides use of the crumb rubber-modified asphalt as described in the above solutions or a crumb rubber-modified asphalt prepared using the preparation method as described in the above solutions in the field of road engineering. The crumb rubber-modified asphalt according to the present disclosure has enhanced properties and achieves high-value utilization of waste rubber materials, is environmentally friendly, and delivers significant economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to illustrate the technical solutions in the embodiments of the present disclosure more clearly, a brief introduction to the drawings required for the embodiments will be provided below. Obviously, the drawings in the following description are merely some of the embodiments of the present disclosure, and those of ordinary skill in the art can also obtain other drawings according to these drawings without involving any inventive effort.

[0033] FIG. 1 shows Flourier transform infrared spectroscopy (FTIR) spectra of the modified crumb rubber prepared in Examples 1-12. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] Definition: The term “low-density polyethylene (LDPE)” as used herein refers to a thermoplastic polymer of ethylene having a density typically in the range of about 0.91 to 0.93 g / cm3, characterized by a branched molecular structure that distinguishes it from high-density polyethylene (HDPE).

[0035] The present disclosure provides a modified crumb rubber, including a crumb rubber swollen with an oil, where the oil includes at least one selected from the group consisting of an edible oil and a waste edible oil; and a swelling degree of the crumb rubber swollen with the oil is 12% to 18% increase in volume.

[0036] In the present disclosure, the crumb rubber may be a high-content untreated crumb rubber (HUCR); a source of the crumb rubber may include at least one selected from the group consisting of waste truck tires and waste car tires; and a particle size of the crumb rubber may be 40 mesh to 80 mesh, and specifically may be 50 mesh, 60 mesh, or 70 mesh.

[0037] In the present disclosure, the swelling degree of the crumb rubber swollen with the oil is 12% to 18% increase in volume (relative to the crumb rubber before oil swelling), and specifically may be 14% or 16%.

[0038] In the present disclosure, a particle size of the modified crumb rubber may be 277.96 pm to 465.36 pm, and specifically may be 250 pm, 280 pm, 320 pm, 350 pm, 380 pm, 420 pm, or 450 pm. Physical and chemical properties of the modified crumb rubber according to the present disclosure are shown in Table 1. Table 1 Physical and chemical properties of modified crumb rubber Indicator Item Numeric value Test criteria Physical properties 60 mesh sieving rate (%) 91 GB / T 19208 Metal content 0.02 GB / T 19208 Fiber content (%) 0.38 GB / T 19208 Relative density 1.0-1.2 JT / T 797 Moisture content 0.6 GB / T 19208 Chemical properties Ash (%) 6 GB / T 4498.1 Acetone extract (%) 15 GB / T 3516 method B Rubber hydrocarbon content (%) 48 GB / T 14837 Carbon black content (%) 32 GB / T 14837

[0039] The present disclosure further provides a method for preparing the modified crumb rubber as described in the above solutions, including the steps of: mixing (referred to as first mixing) a crumb rubber and an oil, and subjecting a resulting mixture to swelling to obtain the modified crumb rubber, where the oil includes at least one selected from the group consisting of an edible oil and a waste edible oil.

[0040] In the present disclosure, the method may further includes subjecting the crumb rubber to pre-drying before use; and the pre-drying may be conducted at a temperature of 40 °C to 60 °C and specifically may be 50 °C, and the pre-drying may be conducted for 30 minutes to 45 minutes, and specifically may be conducted for 35 minutes or 40 minutes.

[0041] In the present disclosure, a mass ratio of the crumb rubber to the oil may be in a range of 1 : 0.1 to 1: 0.5, and specifically may be in a range of 1 : 0.2, 1 : 0.3, or 1 : 0.4.

[0042] In the present disclosure, the first mixing may be conducted for 10 minutes to 15 minutes, and specifically may be conducted for 12 minutes.

[0043] In the present disclosure, the swelling may be conducted at the temperature of 80 °C to 110 °C, and specifically may be 90°C or 100°C; and the swelling may be conducted for 40 minutes to 75 minutes, and specifically may be 50 minutes, 60 minutes, or 70 minutes.

[0044] The present disclosure further provides a crumb rubber-modified asphalt, which includes, in parts by mass, 100 parts of asphalt and 20 parts of a modified crumb rubber, where the modified crumb rubber is the modified crumb rubber as described in the above solutions, or a modified crumb rubber obtained by the method as described in the above solutions;

[0045] under a condition that the crumb rubber-modified asphalt further includes styrenebutadiene-styrene, the crumb rubber-modified asphalt includes, in parts by mass, 100 parts of the asphalt, 20 parts of the modified crumb rubber, and 2-4 parts of the styrene-butadiene-styrene;

[0046] under a condition that the crumb rubber-modified asphalt further includes styrene-butadiene-styrene and sulfur, the crumb rubber-modified asphalt includes, in parts by mass, 100 parts of the asphalt, 20 parts of the modified crumb rubber, 4 parts of the styrene-butadiene-styrene, and 0.6 parts of the sulfur;

[0047] under a condition that the crumb rubber-modified asphalt further includes a recycled low-density polyethylene and sulfur, the crumb rubber-modified asphalt includes, in parts by mass, 100 parts of the asphalt, 20 parts of the modified crumb rubber, 4 parts of the recycled low-density polyethylene, and 0.6 parts of the sulfur; and

[0048] under a condition that the crumb rubber-modified asphalt further includes styrene butadiene-styrene, a recycled low-density polyethylene and sulfur, the crumb rubber-modified asphalt includes, in parts by mass, 100 parts of the asphalt, 20 parts of the modified crumb rubber, 2 parts of the styrene-butadiene-styrene, 2 parts of the recycled low-density polyethylene, and 0.6 parts of the sulfur.

[0049] The crumb rubber-modified asphalt according to the present disclosure includes asphalt; and a penetration (0.1 mm, 25°C) grade of the asphalt may be 60 mm to 80 mm, and specifically may be 65 mm, 70 mm, or 75 mm.

[0050] The crumb rubber-modified asphalt according to the present disclosure includes, in parts by mass, 20 parts of the modified crumb rubber.

[0051] Under a condition that the crumb rubber-modified asphalt further includes styrene-butadiene-styrene, based on the parts by mass of the asphalt, the crumb rubber-modified asphalt according to the present disclosure may include 3 parts of the styrene-butadiene-styrene.

[0052] In the present disclosure, the fundamental properties of the styrene-butadiene-styrene are shown in Table 2. Table 2 Fundamental properties of styrene-butadiene-styrene Property parameter Unit Numeric value Melt index 200 °C 5 kg g / 10 min 0.1 Butadiene / styrene ratio - 70 / 30 Shore A hardness - 76 Tensile strength MPa 20

[0053] Under a condition that the crumb rubber-modified asphalt further includes a recycled low-density polyethylene and sulfur, or under a condition that the crumb rubber-modified asphalt further includes styrene-butadiene-styrene, a recycled low-density polyethylene and sulfur, the fundamental properties of the RLDPE are shown in Table 3. Table 3 Fundamental properties of RLDPE Property parameter Unit Numeric value Melt flow index (MFI) g / 10 min 1.5 Density g / cm3 0.92 Elongation at break % 300 Particle size mm 2-3

[0054] The present disclosure further provides a method for preparing the crumb rubber-modified asphalt as described in the above solutions, including the following steps:

[0055] heating and mixing asphalt and the modified crumb rubber (referred to as a first heating and mixing), and then subjecting a first resulting mixture to forming (referred to as a first forming) to obtain the crumb rubber-modified asphalt;

[0056] under a condition that the crumb rubber-modified asphalt further includes styrene-butadiene-styrene, heating and mixing asphalt, the modified crumb rubber, and styrene-butadiene- styrene (referred to as a second heating and mixing), and then subjecting a second resulting mixture to forming (referred to as a second forming) to obtain the crumb rubber-modified asphalt;

[0057] under a condition that the crumb rubber-modified asphalt further includes styrenebutadiene-styrene and sulfur, heating and mixing asphalt, the modified crumb rubber, styrenebutadiene-styrene, and sulfur (referred to as a third heating and mixing), and then subjecting a third resulting mixture to forming (referred to as a third forming) to obtain the crumb rubber-modified asphalt;

[0058] under a condition that the crumb rubber-modified asphalt further includes a recycled low-density polyethylene and sulfur, heating and mixing asphalt, the modified crumb rubber, the recycled low-density polyethylene, and sulfur (referred to as a fourth heating and mixing), and then subjecting a fourth resulting mixture to forming (referred to as a fourth forming) to obtain the crumb rubber-modified asphalt; and

[0059] under a condition that the crumb rubber-modified asphalt further includes styrenebutadiene-styrene, a recycled low-density polyethylene and sulfur, heating and mixing asphalt, the modified crumb rubber, styrene-butadiene-styrene, the recycled low-density polyethylene, and sulfur (referred to as fifth heating and mixing), and then subjecting a fifth resulting mixture to forming (referred to as fifth forming) to obtain the crumb rubber-modified asphalt.

[0060] In the present disclosure, the second heating and mixing may include the following steps: heating the asphalt to a temperature of 150 °C to 160 °C until the asphalt becomes a fluid state, pre-mixing the modified crumb rubber and the asphalt to obtain a premix, and then mixing styrene-butadiene-styrene and the premix.

[0061] In the present disclosure, the second heating and mixing may be conducted at a temperature of 155 °C.

[0062] In the present disclosure, the third heating and mixing may include the following steps: heating the asphalt to a temperature of 150 °C to 160 °C until the asphalt becomes a fluid state, pre-mixing the modified crumb rubber and the asphalt to obtain a premix, and then mixing styrene-butadiene-styrene, sulfur, and the premix.

[0063] In the present disclosure, the third heating and mixing may be conducted at a temperature of 155 °C.

[0064] In the present disclosure, the fourth heating and mixing may include the following steps: heating the asphalt a temperature of to 150 °C to 160 °C until the asphalt becomes a fluid state, pre-mixing the modified crumb rubber and the asphalt to obtain a premix, and then mixing the recycled low-density polyethylene, sulfur, and the premix.

[0065] In the present disclosure, the fourth heating and mixing may be conducted at a temperature of 155 °C.

[0066] In the present disclosure, the fifth heating and mixing may include the following steps: heating the asphalt to a temperature of 150 °C to 160 °C until the asphalt becomes a fluid state, pre-mixing the modified crumb rubber and the asphalt to obtain a premix, and then mixing SBS, RLDPE, sulfur and the premix.

[0067] In the present disclosure, the fifth heating and mixing may be conducted at a temperature of 155 °C.

[0068] In the present disclosure, the first forming, the second forming, the third forming, the fourth forming and the fifth forming may independently include sequentially performing a first stirring and forming, a second stirring and forming, and a third stirring and forming, where the first stirring and forming may be conducted at a rotational speed of 500 rpm to 800 rpm, and specifically 650 rpm, and the first stirring and forming may be conducted for 15 minutes to 30 minutes, and specifically 22 minutes; the second stirring and forming may be conducted at a rotational speed of 4,500 rpm to 5,000 rpm, and specifically 4,750 rpm, and the second stirring and forming may be conducted for 60 minutes to 90 minutes, and specifically 70 minutes, or 80 minutes; and the third stirring and forming may be conducted at a rotational speed of 500 rpm to 800 rpm, and specifically 650 rpm, and the third stirring and forming may be conducted for 15 minutes to 30 minutes, and specifically 22 minutes.

[0069] In the present disclosure, the temperature for the first forming, second forming, third forming, fourth forming and fifth forming may independently be 170-185°C, and specifically may be 175°C or 180°C.

[0070] The present disclosure further provides the use of the crumb rubber-modified asphalt as described in the above solutions or a crumb rubber-modified asphalt prepared using the preparation method as described in the above solutions in the field of road engineering.

[0071] The crumb rubber-modified asphalt according to the present disclosure exhibits enhanced properties and achieves high-value utilization of waste rubber materials, is environmentally friendly, and delivers significant economic and social benefits.

[0072] To further illustrate the present disclosure, the solutions of the present disclosure will be described in detail below in conjunction with examples, which cannot be construed as limiting the scope of the present disclosure, however. Example 1

[0073] A 60-mesh crumb rubber from waste truck tires was baked in an oven at 60 °C for 30 minutes to remove moisture. Then, a waste edible oil was added to a resulting dried crumb rubber (with a mass being 20% of a mass of asphalt) and mixed at 100 °C for 10 minutes to obtain a mixture, with a mass ratio of the crumb rubber to the waste edible oil being 1: 0.3. The mixture was stored in a container and then baked in an oven at 100 °C for 60 minutes to obtain a modified crumb rubber.

[0074] An asphalt with a penetration (0.1 mm, 25 °C) grade of 60 to 80 was heated in an oven at 160 °C to a fluid state, the modified crumb rubber was slowly poured into a resulting heated asphalt. A resulting mixture was stirred at 185°C at a speed of 500 rpm for 30 minutes, and then transferred to a high-speed shearing machine, stirred at 185 °C at a speed of 5,000 rpm for 60 minutes, and subsequently stirred at 185 °C at a speed of 500 rpm for 30 minutes until the resulting mixture was formed, to obtain a crumb rubber-modified asphalt. Example 2

[0075] A 60-mesh crumb rubber from waste car tires was baked in an oven at 60 °C for 30 minutes to remove moisture. Then, a waste edible oil was added to a resulting dried crumb rubber (with a mass being 20% of a mass of asphalt) and mixed at 100 °C for 10 minutes to obtain a mixture, with a mass ratio of the crumb rubber to the waste edible oil being 1: 0.3. The mixture was stored in a container and then baked in an oven at 100 °C for 60 minutes to obtain a modified crumb rubber.

[0076] An asphalt with a penetration (0.1 mm, 25 °C) grade of 60 to 80 was heated in an oven at 160 °C to a fluid state, the modified crumb rubber was slowly poured into a resulting heated asphalt, SBS (with a mass being 2% of the mass of asphalt) was then added thereto. A resulting mixture was stirred at 185°C at a speed of 500 rpm for 30 minutes, and then transferred to a high-speed shearing machine, stirred at 185 °C at a speed of 5,000 rpm for 60 minutes, and subsequently stirred at 185 °C at a speed of 500 rpm for 30 minutes until the resulting mixture was formed, to obtain the crumb rubber-modified asphalt. Example 3

[0077] A 60-mesh crumb rubber from waste truck tires was baked in an oven at 60 °C for 30 minutes to remove moisture. Then, a waste edible oil was added to a resulting dried crumb rubber (with a mass being 20% of a mass of asphalt) and mixed at 100 °C for 10 minutes to obtain a mixture, with a mass ratio of the crumb rubber to the waste edible oil being 1: 0.3. The mixture was stored in a container and then baked in an oven at 100 °C for 60 minutes to obtain a modified crumb rubber.

[0078] An asphalt with a penetration (0.1 mm, 25 °C) grade of 60 to 80 was heated in an oven at 160 °C to a fluid state, the modified crumb rubber was slowly poured into a resulting heated asphalt, SBS (with a mass being 4% of the mass of asphalt) was then added thereto. A resulting mixture was mixed at 185 °C at a speed of 500 rpm for 30 minutes, and then transferred to a high-speed shearing machine and mixed at 185 °C at a speed of 5,000 rpm for 60 minutes, and subsequently stirred at 185 °C at a speed of 500 rpm for 30 minutes until the resulting mixture was formed, to obtain a crumb rubber-modified asphalt. Example 4

[0079] A 60-mesh crumb rubber from waste truck tires was baked in an oven at 60 °C for 30 minutes to remove moisture. Then, a waste edible oil was added to a resulting dried crumb rubber (with a mass being 20% of a mass of asphalt) and mixed at 100 °C for 10 minutes to obtain a mixture, with a mass ratio of the crumb rubber to the waste edible oil being 1: 0.3. The mixture was stored in a container and then baked in an oven at 100 °C for 60 minutes to obtain a modified crumb rubber.

[0080] An asphalt with a penetration (0.1 mm, 25 °C) grade of 60 to 80 was heated in an oven at 160 °C to a fluid state, the modified crumb rubber was slowly poured into a resulting heated asphalt, SBS (with a mass being 2% of the mass of asphalt) and sulfur (with a mass being 2.5% of a total mass of the modified crumb rubber and SBS) were then added thereto. A resulting mixture was mixed at 185 °C at a speed of 500 rpm for 30 minutes, and then transferred to a high-speed shearing machine and mixed at 185 °C at a speed of 5,000 rpm for 60 minutes, and subsequently stirred at 185 °C at a speed of 500 rpm for 30 minutes until the resulting mixture was formed, to obtain a crumb rubber-modified asphalt. Example 5

[0081] A 60-mesh crumb rubber from waste truck tires was baked in an oven at 60 °C for 30 minutes to remove moisture. Then, a waste edible oil was added to a resulting dried crumb rubber (with a mass being 20% of a mass of asphalt) and mixed at 100 °C for 10 minutes to obtain a mixture, with a mass ratio of the crumb rubber to the waste edible oil being 1: 0.3. The mixture was stored in a container and then baked in an oven at 100 °C for 60 minutes to obtain a modified crumb rubber.

[0082] An asphalt with a penetration (0.1 mm, 25°C) grade of 60 to 80 was heated in an oven at 160°C to the fluid state, the modified crumb rubber was slowly poured into a resulting heated asphalt, SBS (with a mass being 4% of the mass of asphalt) and sulfur (with a mass being 2.5% of a total mass of the modified crumb rubber and SBS) were then added thereto. A resulting mixture was mixed at 185°C at a speed of 500 rpm for 30 minutes, and then transferred to a high-speed shearing machine and mixed at 185 °C at a speed of 5,000 rpm for 60 minutes, and subsequently stirred at 185°C at a speed of 500 rpm for 30 minutes until the resulting mixture was formed, to obtain a crumb rubber-modified asphalt. Example 6

[0083] A 60-mesh crumb rubber from waste truck tires was baked in an oven at 60°C for 30 minutes to remove moisture. Then, a waste edible oil was added to a resulting dried crumb rubber (with a mass being 20% of a mass of asphalt) and mixed at 100 °C for 10 minutes to obtain a mixture, with a mass ratio of the crumb rubber to the waste edible oil being 1: 0.3. The mixture was stored in a container and then baked in an oven at 100°C for 60 minutes to obtain a modified crumb rubber.

[0084] An asphalt with a penetration (0.1 mm, 25°C) grade of 60 to 80 was heated in an oven at 160°C to the fluid state, the modified crumb rubber was slowly poured into a resulting heated asphalt, RLDPE (with a mass being 2% of the mass of asphalt) was then added thereto. A resulting mixture was mixed at 185°C at a speed of 500 rpm for 30 minutes, and then transferred to a highspeed shearing machine and mixed at 185°C at a speed of 5,000 rpm for 60 minutes, and subsequently stirred at 185°C at a speed of 500 rpm for 30 minutes until the resulting mixture was formed, to obtain a crumb rubber-modified asphalt. Example 7

[0085] A 60-mesh crumb rubber from waste truck tires was baked in an oven at 60 °C for 30 minutes to remove moisture. Then, a waste edible oil was added to a resulting dried crumb rubber (with a mass being 20% of a mass of asphalt) and mixed at 100 °C for 10 minutes to obtain a mixture, with a mass ratio of the crumb rubber to the waste edible oil being 1: 0.3. The mixture was stored in a container and then baked in an oven at 100 °C for 60 minutes to obtain a modified crumb rubber.

[0086] An asphalt with a penetration (0.1 mm, 25°C) grade of 60 to 80 was heated in an oven at 160 °C to a fluid state, the modified crumb rubber was slowly poured into a resulting heated asphalt, RLDPE (with a mass being 4% of the mass of asphalt) was then added thereto. A resulting mixture was mixed at 185 °C at a speed of 500 rpm for 30 minutes, and then transferred to a high-speed shearing machine and mixed at 185°C at a speed of 5,000 rpm for 60 minutes, and subsequently stirred at 185 °C at a speed of 500 rpm for 30 minutes until the resulting mixture was formed, to obtain A crumb rubber-modified asphalt. Example 8

[0087] A 60-mesh crumb rubber from waste truck tires was baked in an oven at 60 °C for 30 minutes to remove moisture. Then, a waste edible oil was added to a resulting dried crumb rubber (with a mass being 20% of the mass of asphalt) and mixed at 100 °C for 10 minutes to obtain a mixture, with a mass ratio of the crumb rubber to the waste edible oil being 1: 0.3. The mixture was stored in a container and then baked in an oven at 100 °C for 60 minutes to obtain a modified crumb rubber.

[0088] An asphalt with a penetration (0.1 mm, 25°C) grade of 60 to 80 was heated in an oven at 160 °C to a fluid state, the modified crumb rubber was slowly poured into a resulting heated asphalt, RLDPE (with a mass being 2% of the mass of asphalt) and sulfur (with a mass being 2.5% of a total mass of the modified crumb rubber and RLDPE) were then added thereto. A resulting mixture was mixed at 185 °C at a speed of 500 rpm for 30 minutes, and then transferred to a high-speed shearing machine and mixed at 185°C at a speed of 5,000 rpm for 60 minutes, and subsequently stirred at 185 °C at a speed of 500 rpm for 30 minutes until the resulting mixture was formed, to obtain a crumb rubber-modified asphalt. Example 9

[0089] A 60-mesh crumb rubber from waste truck tires was baked in an oven at 60°C for 30 minutes to remove moisture. Then, a waste edible oil was added to a resulting dried crumb rubber (with a mass being 20% of a mass of asphalt) and mixed at 100 °C for 10 minutes to obtain a mixture, with a mass ratio of the crumb rubber to the waste edible oil being 1: 0.3. The mixture was stored in a container and then baked in an oven at 100 °C for 60 minutes to obtain a modified crumb rubber.

[0090] An asphalt with a penetration (0.1 mm, 25°C) grade of 60 to 80 was heated in an oven at 160 °C to a fluid state, the modified crumb rubber was slowly poured into a resulting heated asphalt, RLDPE (with a mass being 4% of the mass of asphalt) and sulfur (with a mass being 2.5% of a total mass of the modified crumb rubber and RLDPE) were then added thereto. A resulting mixture was mixed at 185 °C at a speed of 500 rpm for 30 minutes, and then transferred to a high-speed shearing machine and mixed at 185°C at a speed of 5,000 rpm for 60 minutes, and subsequently stirred at 185 °C at a speed of 500 rpm for 30 minutes until the resulting mixture was formed, to obtain a crumb rubber-modified asphalt. Example 10

[0091] A 60-mesh crumb rubber from waste truck tires was baked in an oven at 60°C for 30 minutes to remove moisture. Then, a waste edible oil was added to a resulting dried crumb rubber (with a mass being 20% of a mass of asphalt) and mixed at 100 °C for 10 minutes to obtain a mixture, with a mass ratio of the crumb rubber to the waste edible oil being 1: 0.3. The mixture was stored in a container and then baked in an oven at 100 °C for 60 minutes to obtain a modified crumb rubber.

[0092] An asphalt with a penetration (0.1 mm, 25°C) grade of 60 to 80 was heated in an oven at 160 °C to the fluid state, the modified crumb rubber was slowly poured into a resulting heated asphalt, RLDPE (with a mass being 2% of the mass of asphalt) and sulfur (with a mass being 2% of a total mass of the modified crumb rubber and RLDPE) were then added thereto. A resulting mixture was mixed at 185 °C at a speed of 500 rpm for 30 minutes, and then transferred to a highspeed shearing machine and mixed at 185 °C at a speed of 5,000 rpm for 60 minutes, and subsequently stirred at 185 °C at a speed of 500 rpm for 30 minutes until the resulting mixture was formed, to obtain a crumb rubber-modified asphalt. Example 11

[0093] A 60-mesh crumb rubber from waste truck tires was baked in an oven at 60°C for 30 minutes to remove moisture. Then, a waste edible oil was added to a resulting dried crumb rubber (with a mass being 20% of a mass of asphalt) and mixed at 100 °C for 10 minutes to obtain a mixture, with a mass ratio of the crumb rubber to the waste edible oil being 1: 0.3. The mixture was stored in a container and then baked in an oven at 100 °C for 60 minutes to obtain a modified crumb rubber.

[0094] An asphalt with a penetration (0.1 mm, 25°C) grade of 60 to 80 was heated in an oven at 160 °C to a fluid state, the modified crumb rubber was slowly poured into a resulting heated asphalt, SBS (with a mass being 2% of the mass of asphalt), RLDPE (with a mass being 2% of the mass of asphalt), and sulfur (with a mass being 2.5% of a total mass of the modified crumb rubber, SBS and RLDPE) were then added thereto. A resulting mixture was mixed at 185 °C at a speed of 500 rpm for 30 minutes, and then transferred to a high-speed shearing machine and mixed at 185 °C at a speed of 5,000 rpm for 60 minutes, and subsequently stirred at 185°C at a speed of 500 rpm for 30 minutes until the resulting mixture was formed, to obtain a crumb rubber-modified asphalt. Example 12

[0095] A 60-mesh crumb rubber from waste truck tires was taken for later use, and an asphalt with a penetration (0.1 mm, 25°C) grade of 60 to 80 was heated in an oven at 160°C to the fluid state. The crumb rubber from waste truck tires (20% of the mass of asphalt) was slowly poured into a resulting heated asphalt. A resulting mixture was mixed at 185 °C at a speed of 500 rpm for 30 minutes, and then transferred to a high-speed shearing machine and mixed at 185 °C at a speed of 5,000 rpm for 60 minutes, and subsequently stirred at 185 °C at a speed of 500 rpm for 30 minutes until the resulting mixture was formed, to obtain a crumb rubber-modified asphalt. Test Example 1

[0096] The crumb rubber-modified asphalt prepared in Examples 1-12 were subjected to temperature sweep analysis with a TA Discovery HR-20 model dynamic shear rheometer (DSR) using a strain-controlled mode, with a strain of 12%, a frequency of 10 rad / s, and a temperature ranging from 58 °C to 94 °C at intervals of 6 °C. A 25 mm parallel plate geometry with a 1 mm gap was selected. The rutting factor (G* / sin5) for high-temperature performance was tested. The results are shown in Tables 4-5, and the technical performance indexes of the crumb rubber- modified asphalt are shown in Table 6.

[0097] In Tables 4-6, a sulfur content refers to a mass of S relative to a mass of asphalt; the penetration refers to a penetration measured at 25 °C, in 0.1 mm; a ductility refers to a ductility measured at 5 cm / min and 5°C; a rotational viscosity refers to a rotational viscosity at 180 °C; a softening point difference refers to differences between the softening point at the top and the softening point at the bottom of the crumb rubber-modified asphalt at 163 °C for 48 h, which could indicate the storage stability of the crumb rubber-modified asphalt; and the high-temperature performance rutting factor (G* / sin5) refers to the G* / sin5 at 64 °C. Table 4 Physical properties of the crumb rubber-modified asphalts of Examples 1-12 Example Component Penetrati on / mm Softeni ng point / °C Ductil ity / cm Rotation al viscosity / Pas Softenin g point differenc e / °C Example 12 20% HUCR 45.56 59.7 8.9 1.7 8.1 Example 1 20% HCCR 75 56 11.7 0.95 0.5 Example 2 20% HCCR + 2% SBS 67.77 64.5 17.6 1.55 1.4 Example 3 20% HCCR + 4% SBS 59.87 77.4 22.2 2.64 1.0 Example 4 20% HCCR + 2% SBS + 0.55% S 69.9 66.7 29.8 1.37 5.3 Example 5 20% HCCR + 4% SBS + 0.6% S 74.3 88.1 44.9 3.21 1.65 Example 6 20% HCCR + 2% RLDPE 78.8 63.8 9.4 1.48 5.5 Example 7 20% HCCR + 4% RLDPE 74.2 68.7 8.2 2.86 34.2 Example 8 20% HCCR + 2% RLDPE + 0.55% S 84 58.2 11.6 1.0 6.1 Example 9 20% HCCR + 4% RLDPE + 0.6% S 76.75 62.9 11 2.13 0.2 Example 10 20% HCCR + 2% SBS + 2% RLDPE 71.35 65.7 15.1 2.89 5.9 Example 11 20% HCCR + 2% SBS + 2% RLDPE + 0.6% S 78.6 74.2 22.8 2.0 1.1 able 5 High-temperature resistance of the crumb rubber-modified asphalts of Examples 1- 12 Example Component G* / sin5, kPa PG Example 12 20% HUCR 10.89 88 Example 1 20% HCCR 4.6 76 Example 2 20% HCCR + 2% SBS 13.17 88 Example 3 20% HCCR + 4% SBS 21.38 94 Example 4 20% HCCR + 2% SBS + 0.55% S 6.71 88 Example 5 20% HCCR + 4% SBS + 0.6% S 10.25 94 Example 6 20% HCCR + 2% RLDPE 11.16 88 Example 7 20% HCCR + 4% RLDPE 13.35 94 Example 8 20% HCCR + 2% RLDPE + 0.55% S 6.79 82 Example 9 20% HCCR + 4% RLDPE + 0.6% S 8.37 88 Example 10 20% HCCR + 2% SBS + 2% RLDPE 16.66 94 Example 11 20% HCCR + 2% SBS + 2% RLDPE + 0.6% S 10.46 94 Table 6 Technical performance indexes and specifications for the crumb rubber-modified asphalt No. Performance index Unit Specification Standard 1 Penetration mm 60 to 80 T0604 2 Softening point °C >50 T0606 3 Ductility cm > 10 T0605 4 Rotational viscosity Pa s 2.5 ±0.5 T0625 5 Storage stability °C <3 T0661

[0098] As can be seen from Tables 4-6, the crumb rubber-modified asphalts prepared in Example 1, Example 2, Example 3, Example 5, Example 9, and Example 11 all met the storage stability technical requirements for the crumb rubber-modified asphalt (T0661), and the crumb rubber-modified asphalt prepared in Example 5 exhibits the best storage stability and high-temperature resistance. Test Example 2

[0099] The modified crumb rubbers prepared in Examples 1-12 were subjected to Fourier Transform Infrared (FTIR) analysis. The results are shown in FIG. 1.

[0100] As can be seen from FIG. 1, FTIR spectroscopic analysis shows that the crumb rubber-modified asphalt exhibits a distinct peak at 1750 cm'1, which is attributed to the C=O stretching vibration of the ester group. This peak confirms that successive chemical modification by chloroprene rubber was achieved via an esterification reaction during the swelling process of crumb rubber. The chemical modification enhances the compatibility and dispersibility of the modified crumb rubber in asphalt, improving the performance of crumb rubber-modified asphalt.

[0101] As can be seen from the examples above, the modified crumb rubber provided in the present disclosure exhibits good compatibility with asphalt, and could be introduced into asphalt with a high doping amount, and maintains storage stability, thereby enabling the crumb rubber-modified asphalt to overcome stability problems.

[0102] Although the embodiments described above have provided a detailed description of the present disclosure, they are only a part of, rather than all of the embodiments of the present disclosure. All other embodiments that can be obtained according to the examples of the present disclosure without creative efforts shall fall within the scope of the disclosure.

Claims

1. A modified crumb rubber, comprising a crumb rubber swollen with an oil,wherein the oil comprises at least one selected from the group consisting of an edible oil and a waste edible oil; and a swelling degree of the crumb rubber swollen with the oil is 12% to 18% increase in volume.

2. The modified crumb rubber of claim 1, wherein a source of the crumb rubber comprises at least one selected from the group consisting of waste truck tires and waste car tires; and the crumb rubber has a particle size of 40 mesh to 80 mesh.

3. The modified crumb rubber of claim 1 or 2, wherein the modified crumb rubber has a particle size of 277.96 microns (pm) to 465.36 pm.

4. A method for preparing the modified crumb rubber of any one of claims 1-3, comprising the following steps:mixing the crumb rubber and the oil, and subjecting a resulting mixture to swelling to obtain the modified crumb rubber,wherein the oil comprises at least one selected from the group consisting of the edible oil and the waste edible oil.

5. The method of claim 4, wherein a mass ratio of the crumb rubber to the oil is in a range of 1: 0.1 to 1: 0.5.

6. The method of claim 4 or 5, wherein the swelling is conducted at a temperature of 80 °C to 110 °C for 40 minutes to 75 minutes.

7. A crumb rubber-modified asphalt, comprising, in parts by mass, 100 parts of asphalt and 20 parts of the modified crumb rubber of any one of claims 1 to 3, whereinunder a condition that the crumb rubber-modified asphalt further comprises styrenebutadiene-styrene, the crumb rubber-modified asphalt comprises, in parts by mass, 100 parts of the asphalt, 20 parts of the modified crumb rubber, and 2 to 4 parts of the styrene-butadiene-styrene;under a condition that the crumb rubber-modified asphalt further comprises styrene-butadiene-styrene and sulfur, the crumb rubber-modified asphalt comprises, in parts by mass, 100parts of the asphalt, 20 parts of the modified crumb rubber, 4 parts of the styrene-butadiene-styrene, and 0.6 parts of the sulfur;under a condition that the crumb rubber-modified asphalt further comprises a recycled low-density polyethylene and sulfur, the crumb rubber-modified asphalt comprises, in parts by mass, 100 parts of the asphalt, 20 parts of the modified crumb rubber, 4 parts of the recycled low-density polyethylene, and 0.6 parts of the sulfur; andunder a condition that the crumb rubber-modified asphalt further comprises styrene-butadiene-styrene, a recycled low-density polyethylene and sulfur, the crumb rubber-modified asphalt comprises, in parts by mass, 100 parts of the asphalt, 20 parts of the modified crumb rubber, 2 parts of the styrene-butadiene-styrene, 2 parts of the recycled low-density polyethylene, and 0.6 parts of the sulfur.

8. A method for preparing the crumb rubber-modified asphalt of claim 7, comprising the following steps:heating and mixing the asphalt and the modified crumb rubber, and subjecting a first resulting mixture to a first forming to obtain the crumb rubber-modified asphalt;under a condition that the crumb rubber-modified asphalt further comprises styrene-butadiene-styrene, heating and mixing the asphalt, the modified crumb rubber, and the styrene-butadiene-styrene, and subjecting a second resulting mixture to a second forming to obtain the crumb rubber-modified asphalt;under a condition that the crumb rubber-modified asphalt further comprises styrene-butadiene-styrene and sulfur, heating and mixing the asphalt, the modified crumb rubber, the styrene-butadiene-styrene, and the sulfur, and subjecting a third resulting mixture to a third forming to obtain the crumb rubber-modified asphalt;under a condition that the crumb rubber-modified asphalt further comprises a recycled low-density polyethylene and sulfur, heating and mixing the asphalt, the modified crumb rubber, the recycled low-density polyethylene, and the sulfur, and subjecting a fourth resulting mixture to a fourth forming to obtain the crumb rubber-modified asphalt; andunder a condition that the crumb rubber-modified asphalt further comprises styrene-butadiene-styrene, a recycled low-density polyethylene and sulfur, heating and mixing the asphalt, the modified crumb rubber, the styrene-butadiene-styrene, the recycled low-density polyethylene, and the sulfur, and subjecting a fifth resulting mixture to a fifth forming to obtain the crumb rubber-modified asphalt.

9. The method of claim 8, wherein the first forming, the second forming, the third forming, the fourth forming and the fifth forming each independently comprise sequentially performing a first stirring and forming, a second stirring and forming, and a third stirring and forming, wherein the first stirring and forming is conducted at a rotational speed of 500 revolutions per minute (rpm) to 800 rpm for 15 minutes to 30 minutes;the second stirring and forming is conducted at a rotational speed of 4,500 rpm to 5,000 rpm for 60 minutes to 90 minutes;the third stirring and forming is conducted at a rotational speed of 500 rpm to 800 rpm for 15minutes to 30 minutes; andthe first forming, the second forming, the third forming, the fourth forming and the fifth forming each are independently conducted at a temperature of 170 °C to 185 °C.

10. Use of the crumb rubber-modified asphalt of claim 7 in the field of road engineering.

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