Regenerated SMA-13 asphalt mixture with high RAP doping amount and processing method of regenerated SMA-13 asphalt mixture

Abstract

The invention discloses a regenerated SMA-13 asphalt mixture with high RAP doping amount and a processing method of the regenerated SMA-13 asphalt mixture, and belongs to the technical field of asphalt materials. The regenerated SMA-13 asphalt mixture with the high RAP doping amount comprises the following raw materials in parts by weight: 5-15 parts of small-particle-size RAP; the preparation method comprises the following steps: preparing the following components in parts by weight: 35-50 parts of RAP with large particle size, 40-60 parts of basalt with particle size of 0-15mm, 5-10 parts of mineral powder and 0.2-0.5 part of lignocellulose; the regenerated SMA-13 asphalt mixture with the high RAP doping amount comprises new asphalt which accounts for 4 to 6 percent of the regenerated SMA-13 asphalt mixture with the high RAP doping amount; the small-particle-size RAP is RAP with the particle size smaller than 3 mm, and the large-particle-size RAP is RAP with the particle size of 5-10 mm or RAP with the particle size of 10-15 mm. According to the regenerated SMA-13 asphalt mixture with the high RAP mixing amount, a regenerant is not used, the RAP mixing amount is high, and the obtained regenerated SMA-13 asphalt mixture is superior to the standard requirement.

Description

Technical Field

[0001] This invention belongs to the field of asphalt material technology, specifically relating to a high RAP content recycled SMA-13 ​​asphalt mixture and its processing method. Background Technology

[0002] With the rapid development of highway construction, the surface layer of most high-grade highways is made of SMA asphalt pavement. Every year, a large number of asphalt concrete pavements face medium or even major repairs. Given resource scarcity and increasing environmental awareness, the effective reuse of recycled asphalt mixtures (RAP) to alleviate the pressure of scarce road construction materials has gradually gained attention. Research on recycled asphalt mixtures allows for the recycling of asphalt, a non-renewable resource.

[0003] Reclaimed asphalt pavement (RAP) is widely used in new construction and repair projects due to its economic and environmental benefits. Using RAP not only reduces reliance on natural asphalt and mineral aggregates but also lowers energy consumption. For high-grade asphalt pavements, especially the surface layer, hot recycling technology is often employed, which is further divided into plant-mixed hot recycling and in-situ hot recycling. Plant-mixed hot recycling involves crushing and grading the milled RAP, determining the appropriate blending ratio, and then mixing it with new asphalt, new aggregates, recycling agents, and fibers in a designed mix proportion. The resulting recycled mixture is then transported to the construction site for paving and compaction. However, recycled mixtures prepared using this method are easily affected by the properties of the old material. RAP differs from SBS modified asphalt in that, under long-term environmental conditions, the lightweight components volatilize, leading to hardening and brittleness, and poor crack resistance. Therefore, a certain amount of recycling agent needs to be added to replenish the lightweight components; the amount of recycling agent added is generally around 5%. While recycling agents can soften old asphalt and restore its original properties, they also have a negative impact on the old asphalt's resistance to high-temperature flow deformation. Therefore, it is not recommended to use too much recycling agent.

[0004] In addition, the disadvantage of plant-mixed hot recycling technology is that the utilization rate of old materials is low. In order to avoid secondary aging of the recycled asphalt pavement material (RAP) obtained by milling during the production process, the heating temperature is often relatively low. Therefore, the heating temperature of the new material can only be increased before the two are mixed. This results in the content of old material usually being less than 30%. Heating the new material to a higher temperature will also increase energy consumption and does not meet the standards for energy conservation and emission reduction. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a high-RAP-content recycled SMA-13 ​​asphalt mixture and its processing method. This method does not use recycling agents and has a high RAP content, resulting in a recycled SMA-13 ​​asphalt mixture that exceeds standard requirements.

[0006] This invention is achieved through the following technical solutions. In this invention, the first aspect provides a high RAP content recycled SMA-13 ​​asphalt mixture, comprising the following raw materials in parts by weight: 5-15 parts small-diameter RAP; 35-50 parts large-diameter RAP; 40-60 parts basalt with a particle size less than 15 mm; 5-10 parts mineral powder; and 0.2-0.5 parts lignocellulose. The high RAP content recycled SMA-13 ​​asphalt mixture includes 4-6 wt% asphalt, which accounts for 4-6 wt% of the high RAP content recycled SMA-13 ​​asphalt mixture. The small-diameter RAP refers to RAP with a particle size of less than 3 mm, and the large-diameter RAP refers to RAP with a particle size of 5-10 mm or RAP with a particle size of 10-15 mm.

[0007] Furthermore, the composition of the high RAP content asphalt mixture is as follows: The following components are used in high-RAP recycled SMA-13 ​​asphalt mixtures: 5-15 parts RAP with a particle size of less than 3mm, 35-45 parts RAP with a particle size of 5-10mm, 8-15 parts basalt with a particle size of less than 3mm, 38-45 parts basalt with a particle size of 10-15mm, 5-10 parts mineral powder, and 0.2-0.5 parts lignocellulose, comprising 4-6 wt% of the asphalt; or The high-RAP content recycled SMA-13 ​​asphalt mixture contains 5-15 parts RAP with a particle size of less than 3mm, 40-50 parts RAP with a particle size of 10-15mm, 8-15 parts basalt with a particle size of less than 3mm, 30-40 parts basalt with a particle size of 5-10mm, 5-10 parts mineral powder, and 0.2-0.5 parts lignocellulose, accounting for 4-6 wt% of the asphalt.

[0008] Furthermore, the high RAP content asphalt mixture comprises: 10 parts RAP with a particle size less than 3mm, 40 parts RAP with a particle size of 5-10mm, 11 parts basalt with a particle size less than 3mm, 40 parts basalt with a particle size of 10-15mm, 9 parts mineral powder, and 0.3 parts lignocellulose, comprising 4-6 wt% of the high-RAP content recycled SMA-13 ​​asphalt mixture; or The mixture consists of 10 parts RAP with a particle size of less than 3 mm, 45 parts RAP with a particle size of 10-15 mm, 11 parts basalt with a particle size of less than 3 mm, 35 parts basalt with a particle size of 5-10 mm, 9 parts mineral powder, and 0.3 parts lignocellulose, accounting for 4-6 wt% of the high RAP content recycled SMA-13 ​​asphalt mixture.

[0009] Furthermore, the length of the lignin fibers is 2-5 mm.

[0010] Furthermore, the asphalt content of the small-particle-size RAP is greater than 7%; the asphalt content of the large-particle-size RAP is less than 2%.

[0011] In this invention, a second aspect provides a method for processing the high RAP content recycled SMA-13 ​​asphalt mixture, comprising the following steps: (1) RAP is crushed, ground and sieved to obtain small-diameter RAP and large-diameter RAP respectively; (2) Heat the large-diameter RAP and basalt to 200~220℃ and add them to the mixing pot. Then add the small-diameter RAP and lignocellulose to the mixing pot for dry mixing. After dry mixing, add the remaining asphalt and mineral powder for wet mixing, and then discharge the material.

[0012] Furthermore, the remaining asphalt mentioned in step (2) is SBS modified asphalt.

[0013] Furthermore, in step (2), the dry mixing time is 25~30s, the wet mixing time is 40~45s, and the discharge temperature is 175~190℃.

[0014] Furthermore, the RAP described in step (1) has a moisture content of less than 3% before screening.

[0015] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: This invention obtains RAP with different particle sizes by sieving RAP, and controls the RAP content by adding RAP aggregates with different particle sizes at different temperatures and stages, thereby increasing the RAP content and utilization rate of RAP material. Moreover, without using recycling agents, the performance of the high RAP content asphalt mixture is higher than the standard. Detailed Implementation

[0016] The present invention is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods not specifically described in the following examples are generally performed under conventional conditions or as recommended by the manufacturer.

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of skill in the art. All reagents and materials used in this invention are readily available through conventional means, and unless otherwise specified, they shall be used in accordance with conventional methods in the art or as per the product instructions.

[0018] The raw materials used in the embodiments and comparative examples of this invention were subjected to sieving and density tests. All sieving tests were conducted using the water sieving method. The results are shown in Tables 1 and 2 below: Table 1 Summary of Screening Results Table 2 Summary of Density Results In the following examples and comparative examples, the lignin fibers had a length of 2-5 mm, an ash content of 17.5%, a pH value of 8.2, and an oil absorption rate of 6.5 times. All the parts mentioned are parts by weight.

[0019] Example 1 A high-RAP-content recycled SMA-13 ​​asphalt mixture is composed of the following raw materials in parts by weight: 10 parts of RAP with a particle size of less than 3 mm, 40 parts of RAP with a particle size of 5-10 mm, 11 parts of basalt with a particle size of less than 3 mm, 40 parts of basalt with a particle size of 10-15 mm, 9 parts of mineral powder, and 0.3 parts of lignocellulose. Processing method for recycled SMA-13 ​​asphalt mixture with high RAP content: (1) RAP is crushed, ground and sieved to obtain small-diameter RAP (particle size less than 3 mm) and large-diameter RAP (particle size 5~10 mm) respectively, and the moisture content during sieving is controlled to be less than 3%; (2) Heat the large-particle RAP and basalt to 210°C and add them to the mixing pot. Then add the small-particle RAP and lignocellulose to the mixing pot and dry mix for 30 seconds. After dry mixing, add SBS modified bitumen ID (to make the total bitumen content account for 6%) and mineral powder and wet mix for 45 seconds. Then discharge the material at a temperature of 175°C.

[0020] The performance test data of the high RAP content asphalt mixture prepared in Example 1 are shown in Table 3 below: Table 3 Performance test data of the high RAP content asphalt mixture prepared in Example 1 .

[0021] Example 2 A high-RAP-content recycled SMA-13 ​​asphalt mixture is composed of the following raw materials in parts by weight: 10 parts of RAP with a particle size of less than 3 mm, 45 parts of RAP with a particle size of 10-15 mm, 11 parts of basalt with a particle size of less than 3 mm, 35 parts of basalt with a particle size of 5-10 mm, 9 parts of mineral powder, and 0.3 parts of lignocellulose. Processing method for recycled SMA-13 ​​asphalt mixture with high RAP content: Preparation method of asphalt mixture with high RAP content: (1) RAP is crushed, ground and sieved to obtain small-diameter RAP (particle size less than 3 mm) and large-diameter RAP (particle size 10~15 mm) respectively, and the moisture content during sieving is controlled to be less than 3%; (2) Heat the large-particle RAP and basalt to 210°C and add them to the mixing pot. Then add the small-particle RAP and lignocellulose to the mixing pot and dry mix for 30 seconds. After dry mixing, add SBS modified bitumen ID (to make the total bitumen content account for 6%) and mineral powder and wet mix for 45 seconds. Then discharge the material at a temperature of 175°C.

[0022] The performance test data of the high RAP content asphalt mixture prepared in Example 2 are shown in Table 4 below: Table 4 Performance test data of the high RAP content asphalt mixture prepared in Example 2 .

[0023] Comparative Example 1 Unlike Example 1, Comparative Example 1 is an SMA-13 ​​asphalt mixture without added RAP material, composed of the following raw materials in parts by weight: 35 parts of basalt with a particle size of 10-15 mm, 41 parts of basalt with a particle size of 5-10 mm, 15 parts of basalt with a particle size of less than 3 mm, 9 parts of mineral powder, and 0.3 parts of lignocellulose.

[0024] Basalt with a particle size of 10-15mm, 5-10mm, or less than 3mm is heated to 200℃ and dry-mixed with lignocellulose for 15s. Then, SBS modified bitumen ID (to make the total bitumen content 6%) and mineral powder are added and wet-mixed for 40s. The discharge temperature is 175℃.

[0025] The performance test data of the asphalt mixture with high RAP content prepared in Comparative Example 1 are shown in Table 5 below: Table 5 Performance test data of the asphalt mixture with high RAP content prepared in Comparative Example 1 .

Claims

1. A high RAP content recycled SMA-13 asphalt mixture, characterized in that, The raw materials include the following weight parts: small particle size RAP 5-15 parts; large particle size RAP 35-50 parts, basalt with particle size less than 15 mm 40-60 parts, mineral powder 5-10 parts, and lignocellulose 0.2-0.5 parts; The high-RAP-content regenerated SMA-13 asphalt mixture includes 4-6 wt% asphalt of the high-RAP-content regenerated SMA-13 asphalt mixture. The small particle size RAP is RAP with particle size less than 3 mm, and the large particle size RAP is RAP with particle size 5-10 mm or RAP with particle size 10-15 mm.

2. The high RAP content recycled SMA-13 asphalt mixture according to claim 1, characterized in that, The high-RAP-content asphalt mixture includes: Small particle size RAP 5-15 parts, large particle size RAP 35-45 parts, basalt with particle size less than 3 mm 8-15 parts, basalt with particle size 10-15 mm 38-45 parts, mineral powder 5-10 parts, and lignocellulose 0.2-0.5 parts, and 4-6 wt% asphalt of the high-RAP-content regenerated SMA-13 asphalt mixture; or Small particle size RAP 5-15 parts, large particle size RAP 35-45 parts, basalt with particle size less than 3 mm 8-15 parts, basalt with particle size 10-15 mm 38-45 parts, mineral powder 5-10 parts, and lignocellulose 0.2-0.5 parts, and 4-6 wt% asphalt of the high-RAP-content regenerated SMA-13 asphalt mixture.

3. The high RAP content recycled SMA-13 asphalt mixture as claimed in claim 2, characterized in that The high-RAP-content asphalt mixture includes: Small particle size RAP 5-15 parts, large particle size RAP 35-45 parts, basalt with particle size less than 3 mm 8-15 parts, basalt with particle size 10-15 mm 38-45 parts, mineral powder 5-10 parts, and lignocellulose 0.2-0.5 parts, and 4-6 wt% asphalt of the high-RAP-content regenerated SMA-13 asphalt mixture; or Small particle size RAP 5-15 parts, large particle size RAP 35-45 parts, basalt with particle size less than 3 mm 8-15 parts, basalt with particle size 10-15 mm 38-45 parts, mineral powder 5-10 parts, and lignocellulose 0.2-0.5 parts, and 4-6 wt% asphalt of the high-RAP-content regenerated SMA-13 asphalt mixture.

4. The high RAP content recycled SMA-13 asphalt mixture as claimed in claim 2, wherein, The lignocellulose has a length of 2-5 mm.

5. The high RAP content recycled SMA-13 asphalt mixture as claimed in claim 1 wherein, The small particle size RAP has an asphalt content greater than 7%, and the large particle size RAP has an asphalt content less than 2%.

6. A process for producing the high RAP content recycled SMA-13 asphalt mixture as claimed in any one of claims 1 to 5, characterized in that, The method includes the following steps: (1) crushing, grinding and screening the RAP to obtain small particle size RAP and large particle size RAP; (2) heating the large particle size RAP and basalt to 200-220℃, adding them into a mixing pot, then adding the small particle size RAP and lignocellulose into the mixing pot for dry mixing, adding the remaining asphalt and mineral powder into the mixing pot for wet mixing, and then discharging.

7. The method of claim 6, wherein the recycled SMA-13 asphalt mixture has a high RAP content. The remaining asphalt in step (2) is SBS modified asphalt.

8. The process for high RAP content recycled SMA-13 asphalt mixture as claimed in claim 6 wherein, The dry mixing time in step (2) is 25-30 s, the wet mixing time is 40-45 s, and the discharging temperature is 175-190℃.

9. The method of claim 6, wherein the recycled SMA-13 asphalt mixture is a high RAP content SMA-13 asphalt mixture. The RAP in step (1) has a water content less than 3% before screening.

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