Asphalt pavement milling material cold recycling prefabricated part and preparation method

Abstract

The invention relates to the technical field of recycling of renewable resources, in particular to an asphalt pavement milling material cold-recycled prefabricated part and a preparation method, and the asphalt pavement milling material cold-recycled prefabricated part is prepared from the following raw materials in parts by weight: 45 to 53 parts of waste pavement milling material with the particle size of less than 4.75 mm, 19 to 27 parts of waste pavement milling material with the particle size of 4.75 to 9.5 mm, 20 to 28 parts of stone chips, 1 to 1.4 parts of mineral powder, 1.6 to 2.0 parts of silica fume, 4.6 parts of water, 2.3 to 2.7 parts of cement and 2.3 to 2.7 parts of foamed asphalt. According to the invention, the waste asphalt pavement milling material is used as the raw material of the concrete prefabricated component, so that the resource is saved, the utilization rate of the asphalt milling material is increased, and the green development concept is met; the prefabricated parts are manufactured through a cold regeneration process, compared with a traditional hot mix plant regeneration process, energy is saved, environment friendliness is achieved, emission of greenhouse gas is reduced, and therefore the problems that the hot mix plant regeneration mode is high in cost and carbon emission are solved.

Description

Technical Field

[0001] This invention belongs to the field of renewable resource recycling technology in road engineering, and particularly relates to a cold recycled precast component of asphalt pavement milling material and its preparation method. Background Technology

[0002] The maintenance and renovation projects carried out in my country to maintain the service level of asphalt pavements generate tens of millions of tons of waste asphalt mixtures annually. Currently, the mainstream method for utilizing waste asphalt mixtures is to recycle them and then apply them to the pavement structural layers, with a maximum content of up to 30%. However, due to differences in the properties of raw materials, climate, and other factors in different countries and regions, as well as the lack of standardization in the mix design methods for recycled mixtures, there are still obstacles to the recycling technology of waste asphalt mixtures both domestically and internationally, and waste asphalt mixtures cannot be effectively utilized.

[0003] Researchers have proposed a novel method for utilizing waste asphalt mixtures. This method involves using recycled asphalt milling material through a plant-mixed hot recycling and vibration compaction process to create precast components such as curbs, drainage channels, culverts, and slope protection covers. These components exhibit excellent durability and corrosion resistance, significantly improving the performance and aesthetics of highway engineering ancillary facilities. Furthermore, the waste asphalt mixture content in these precast components is as high as 80% or more. However, due to the high energy consumption, high carbon emissions, and relatively high recycling costs associated with plant-mixed hot recycled asphalt mixture precast components, coupled with the complexity of the required equipment system and the stringent requirements for the cleanliness of the milling material, this method is difficult to promote widely. Summary of the Invention

[0004] In view of this, the present invention aims to provide a cold recycled precast component of asphalt milling material and its preparation method, so as to solve the problems of high cost and high carbon emissions of plant-mixed hot recycling method.

[0005] To achieve the above objectives, the technical solution created by this invention is implemented as follows: The first aspect of the present invention provides a precast concrete component made from cold recycled asphalt pavement milling material, comprising the following raw materials in parts by weight: 45-53 parts of waste pavement milling material with a particle size less than 4.75 mm, 19-27 parts of waste pavement milling material with a particle size of 4.75-9.5 mm, 20-28 parts of stone chips, 1-1.4 parts of mineral powder, 1.6-2.0 parts of silica fume, 4.6 parts of water, 2.3-2.7 parts of cement, 2.3-2.7 parts of foamed asphalt, and one selected from 1.3-1.5 parts of silane coupling agent or 0.0125-0.015 parts of asphalt anti-stripping agent.

[0006] Furthermore, the silane coupling agent solution is prepared by mixing silane coupling agent, ethanol and water in a mass ratio of 1:3:10.

[0007] Furthermore, the stone chips are stone chips with a particle size of less than 4.75 mm, and the mud content of the stone chips is ≤3%.

[0008] Furthermore, the base asphalt of the foamed asphalt is selected from one or two of SBS modified asphalt, petroleum asphalt, or rubber modified asphalt.

[0009] Another aspect of the present invention provides a method for preparing a precast concrete component made from asphalt pavement milling material cold recycled concrete, applied to the precast concrete component made from asphalt pavement milling material cold recycled concrete described in the first aspect above, comprising the following steps: S1. The waste asphalt surface layer is crushed to obtain milling material, and the milling material is screened to obtain aggregate for use as precast concrete components. S2. Spray 1.3 to 1.5 parts of silane coupling agent solution evenly onto the surface of the milled material obtained by sieving as aggregate for precast concrete components, and let it stand for 24 hours. S3. Add the milling material obtained in step S2 to the mixing pot, and add 20-28 parts of stone chips, 1-1.4 parts of mineral powder and 1.6-2.0 parts of silica fume and mix evenly to form a dry mixture; S4. Heat and soften the base asphalt. Circulate the heating in the asphalt tank to raise the temperature of the base asphalt to 170°C. Then, transport the heated base asphalt to the foamed asphalt foaming device to obtain foamed asphalt. S5. Add 4.6 parts of water to the mixing pot in step S3 and mix with the dry mix for 70 seconds; then add 2.3 to 2.7 parts of cement and mix for 70 seconds to form mortar. S6. The foamed asphalt foaming device sprays 2.3 to 2.7 parts of foamed asphalt into the mixing pot in step S5, mixes it in the mixing pot for 70 seconds, and obtains foamed asphalt mixture. S7. The foamed asphalt mixture obtained in step S6 is conveyed to the hopper of the brick making machine. The opening and closing of the hopper is controlled to allow the foamed asphalt mixture to enter the mold. The mixture is formed by vibration compaction. After compaction, a precast concrete component blank is obtained. S8. Place the precast concrete component blank in a room temperature environment for natural curing for 72 hours to obtain cold recycled concrete precast components of asphalt pavement milling material.

[0010] Furthermore, in step S1, the particle size of the aggregate is determined according to the required dry mix gradation requirements in step S3, specifically 45-53 parts of waste road milling material with a particle size less than 4.75mm and 19-27 parts of waste road milling material with a particle size of 4.75-9.5mm.

[0011] Furthermore, in step S3, the milling material is a mixture of 45-53 parts of waste road milling material with a particle size of less than 4.75 mm and 19-27 parts of waste road milling material with a particle size of 4.75-9.5 mm.

[0012] Furthermore, in step S5, the technical specifications of the cement are as follows: initial setting time is 99 min, final setting time is 198 min; 3-day compressive strength is 19.3 MPa, 28-day compressive strength is 45.8 MPa; 3-day flexural strength is 4.9 MPa, 28-day flexural strength is 7.9 MPa.

[0013] Furthermore, in step S7, the vibration compaction method specifically involves using a brick-making machine with a power of 7.5KW to vibrate and compact the foamed asphalt mixture in the mold under an impact force of 180KN for a compaction time of 15~20s.

[0014] Another aspect of the present invention provides a method for preparing a precast concrete component made from asphalt pavement milling material cold recycled concrete, applied to the precast concrete component made from asphalt pavement milling material cold recycled concrete described in the first aspect above, comprising the following steps: S1. The waste asphalt surface layer is crushed to obtain milling material, and the milling material is screened to obtain aggregate for use as precast concrete components. S3. Add the milling material obtained in step S1 to the mixing pot, and add 20-28 parts of stone chips, 1-1.4 parts of mineral powder and 1.6-2.0 parts of silica fume and mix evenly to form a dry mixture; S4. Heat and soften the base asphalt. Circulate the heating in the asphalt tank to bring the base asphalt temperature to 170℃. Add 0.0125~0.015 parts of asphalt anti-stripping agent and mix it evenly. Then, transport the heated base asphalt to the foamed asphalt foaming device to obtain foamed asphalt. S5. Add 4.6 parts of water to the mixing pot in step S3 and mix with the dry mix for 70 seconds; then add 2.3 to 2.7 parts of cement and mix for 70 seconds to form mortar. S6. The foamed asphalt foaming device sprays 2.3 to 2.7 parts of foamed asphalt into the mixing pot in step S5, mixes it in the mixing pot for 70 seconds, and obtains foamed asphalt mixture. S7. The foamed asphalt mixture obtained in step S6 is conveyed to the hopper of the brick making machine. The opening and closing of the hopper is controlled to allow the foamed asphalt mixture to enter the mold. The mixture is formed by vibration compaction. After compaction, a precast concrete component blank is obtained. S8. Place the precast concrete component blank in a room temperature environment for natural curing for 72 hours to obtain cold recycled concrete precast components of asphalt pavement milling material.

[0015] Compared with the prior art, the present invention can achieve the following beneficial effects: This invention uses milled waste asphalt pavement as raw material for precast concrete components, saving resources and improving the utilization rate of milled asphalt, which aligns with the concept of green development. By treating the milled material with silane coupling agents and asphalt anti-stripping agents, the aged asphalt on the surface of the milled material is reactivated, and a network structure can be formed on the surface of the milled material, enhancing the adhesion between foamed asphalt and the milled material and improving the performance of foamed asphalt cold recycled mixture. The precast components are produced through cold recycling, which is energy-saving and environmentally friendly compared with the traditional plant-mixed hot recycling process, reducing greenhouse gas emissions and thus solving the problems of high cost and high carbon emissions of plant-mixed hot recycling. Attached Figure Description

[0016] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 A flowchart of a method for preparing a silane coupling agent by selective addition, provided in an embodiment of the present invention; Figure 2 A flowchart of a method for preparing an asphalt anti-stripping agent, provided in an embodiment of the present invention; Figure 3 A production process flow diagram provided for an embodiment of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and do not constitute a limitation thereof. Similar elements in different embodiments are referred to by associated similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of the invention. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, some operations related to the invention are not shown or described in the specification. This is to avoid obscuring the core parts of the invention with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined to form various implementations. Furthermore, the order of the steps or actions in the method description can be changed or adjusted in a manner readily apparent to those skilled in the art. Therefore, the various orders in the specification and drawings are merely for the clear description of a particular embodiment and do not imply a mandatory order, unless otherwise stated that a particular order must be followed.

[0019] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0020] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0021] The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] Example 1 The first aspect of this embodiment provides a precast concrete component made from cold recycled asphalt pavement milling material, comprising the following raw materials in parts by weight: 45-53 parts of waste pavement milling material with a particle size less than 4.75 mm, 19-27 parts of waste pavement milling material with a particle size of 4.75-9.5 mm, 20-28 parts of stone chips, 1-1.4 parts of mineral powder, 1.6-2.0 parts of silica fume, 4.6 parts of water, 2.3-2.7 parts of cement, 2.3-2.7 parts of foamed asphalt, and one selected from 1.3-1.5 parts of silane coupling agent solution or 0.0125-0.015 parts of asphalt anti-stripping agent.

[0023] Specifically, when the precast concrete component is a slope block, the precast concrete component can be composed of the following raw materials: 49 parts of waste road milling material with a particle size of less than 4.75mm, 23 parts of waste road milling material with a particle size of 4.75 to 9.5mm, 24 parts of stone chips, 1.2 parts of mineral powder, 1.8 parts of silica fume, 4.6 parts of water, 2.5 parts of cement, 2.5 parts of foamed asphalt, and 1.5 parts of silane coupling agent.

[0024] Reference Figure 1 and Figure 3 Another aspect of this embodiment provides a method for preparing a precast concrete component made from asphalt pavement milling material cold recycled concrete, applied to the precast concrete component made from asphalt pavement milling material cold recycled concrete described in the first aspect above, comprising the following steps: S1. The waste asphalt surface layer is crushed to obtain milled material, and the milled material is screened to obtain aggregate for use as precast concrete components.

[0025] Specifically, when using a road milling machine to initially crush waste asphalt pavement, the operating speed of the milling machine is controlled to ensure that the initial particle size of the crushed milled material is as uniform as possible and less than or equal to 9.5 mm. The crushed milled material is transported by truck to a screening device, where it is then graded and screened to obtain 45-53 portions of waste road milled material with a particle size of 0.075 mm to 4.75 mm and 19-27 portions of waste road milled material with a particle size of 4.75 mm to 9.5 mm, which will be used as aggregate for precast concrete components. Generally, the particle size of the aggregate is selected based on the required dry mix gradation requirements mentioned below. In this embodiment, it can specifically be 49 portions of waste road milled material with a particle size less than 4.75 mm and 23 portions of waste road milled material with a particle size of 4.75 to 9.5 mm.

[0026] S2. Spray 1.3 to 1.5 parts of silane coupling agent solution evenly onto the surface of the milled aggregate obtained by sieving as precast concrete components, and let it stand for 24 hours.

[0027] Specifically, the milled aggregate, which is crushed and screened and used as aggregate for precast concrete components, is transported by a first belt conveyor. During the transport process, a 1.5-part silane coupling agent solution is evenly sprayed onto the surface of the milled aggregate through a matching spraying device, ensuring that the surface of each milled aggregate particle is covered with the silane coupling agent solution. After spraying, the treated milled aggregate is transported to a silo or designated storage location and left to stand in a natural environment for 24 hours. This allows the silane coupling agent solution to fully react with the aged asphalt on the surface of the milled aggregate, reactivating the aged asphalt and forming a network structure on the surface of the milled aggregate that helps enhance subsequent bonding performance. This lays the foundation for improving the bonding strength between the foamed asphalt and the milled aggregate.

[0028] It should be noted that the silane coupling agent solution is prepared by mixing silane coupling agent, ethanol, and water in a mass ratio of 1:3:10. This preparation ensures that the silane coupling agent is uniformly dispersed in the solution, thereby achieving sufficient and stable coverage when sprayed onto the milled material surface.

[0029] S3. Add the milling material obtained in step S2 to the mixing pot, and add 20-28 parts of stone chips, 1-1.4 parts of mineral powder and 1.6-2.0 parts of silica fume and mix evenly to form a dry mixture.

[0030] Specifically, the milled material treated with the silane coupling agent solution and allowed to stand in step S2 is transported to the mixing pot using a second belt conveyor. The milled material is a mixture of 49 parts of waste road milled material with a particle size less than 4.75 mm and 23 parts of waste road milled material with a particle size of 4.75 mm to 9.5 mm. Simultaneously, 24 parts of stone chips are added to the mixing pot using a third belt conveyor. Then, 1.2 parts of mineral powder and 1.8 parts of silica fume are transported to the mixing pot via a screw conveyor. The mixing pot is then started to thoroughly mix the milled material, stone chips, mineral powder, and silica fume, forming a dry mix that meets the requirements of subsequent processes.

[0031] S4. Heat and soften the base asphalt. Circulate the heating in the asphalt tank until the base asphalt temperature reaches 170℃. Then, transport the heated base asphalt to the foamed asphalt foaming device to obtain foamed asphalt.

[0032] Specifically, the base asphalt needs to be heated and softened to meet the foaming conditions. The temperature of the base asphalt is precisely reached 170℃ through a circulating heating method in the asphalt tank. This temperature is the suitable temperature for base asphalt foaming, ensuring successful foaming in the subsequent foamed asphalt foaming device. The heated base asphalt is then transported through pipelines to the foamed asphalt foaming device, where the foaming process is completed, ultimately yielding foamed asphalt.

[0033] S5. Add 4.6 parts of water to the mixing pot in step S3 and mix with the dry mix for 70 seconds; then add 2.3 to 2.7 parts of cement and mix for 70 seconds to form mortar.

[0034] Specifically, 4.6 parts of water are precisely added to the uniformly mixed dry mix from step S3 via the water pipe connected to the mixing pot. The mixing pot is then turned on and stirred for 70 seconds to ensure the water fully contacts the dry mix and initially wets all solid particles. After stirring, 2.5 parts of cement are added to the mixing pot using a screw conveyor according to the specified ratio. This cement must meet the following technical specifications: initial setting time of 99 minutes, final setting time of 198 minutes, 3-day compressive strength of 19.3 MPa, 28-day compressive strength of 45.8 MPa, 3-day flexural strength of 4.9 MPa, and 28-day flexural strength of 7.9 MPa. Stirring continues for 70 seconds to ensure the cement, water, and dry mix are uniformly mixed, forming a mortar with a certain viscosity and plasticity. Throughout the process, the stirring time is controlled at 70 seconds to ensure uniform mixing of materials and avoid material performance loss due to over-stirring.

[0035] It should be noted that the cement meets the requirements of an initial setting time of 99 minutes and a final setting time of 198 minutes, providing sufficient operating time for processes such as mixing, transportation, and molding, and avoiding the cement from setting too quickly and affecting construction; the compressive strength and flexural strength at 3 days and 28 days ensure that the cement can provide sufficient strength support for precast components at different curing stages, meeting the mechanical performance requirements of road ancillary facilities.

[0036] S6. The foamed asphalt foaming device sprays 2.3 to 2.7 parts of foamed asphalt into the mixing pot in step S5, and mixes it in the mixing pot for 70 seconds to obtain foamed asphalt mixture.

[0037] Specifically, the foamed asphalt foaming device is connected to the mixing pot through a pipeline and precisely sprays 2.5 parts of foamed asphalt into the mortar formed in step S5. After the spraying is completed, the mixing pot continues to run and mix for 70 seconds. During this process, the foamed asphalt, with its high fluidity after foaming, fully contacts and penetrates the solid particles (milling material, stone chips, mineral powder and silica fume) and cement hydration products in the mortar. Through continuous stirring, the foamed asphalt is evenly dispersed and gradually defoamed, forming a continuous and uniform asphalt film on the surface of the solid particles. This achieves full coating and fusion of the foamed asphalt and the mortar, ensuring that the asphalt film is evenly wrapped on the surface of the solid particles, eliminating the phenomenon of local lack of adhesive or asphalt aggregation, and finally forming a foamed asphalt mixture with uniform component distribution and good cohesiveness.

[0038] In this step, the mixing time is set to 70 seconds, which is an optimized design based on material characteristics and process effects. If the mixing time is insufficient, the foamed asphalt and mortar will not fully integrate, resulting in uneven asphalt film coating and localized "dry material" or "clumps" in the mixture, thus affecting the density of the precast concrete component blank. If the mixing time is too long, the bubbles in the foamed asphalt will collapse excessively, losing the fluidity advantage after foaming. This will not only reduce the asphalt's ability to coat solid particles but may also cause segregation of the mixture due to increased asphalt viscosity, weakening its cohesiveness and subsequent molding performance. Therefore, a mixing time of 70 seconds ensures both uniform distribution of the components in the foamed asphalt mixture and maintains the foaming efficiency of the foamed asphalt.

[0039] S7. The foamed asphalt mixture obtained in step S6 is conveyed to the hopper of the brick making machine. The opening and closing of the hopper is controlled to allow the foamed asphalt mixture to enter the mold. The mixture is formed by vibration compaction. After compaction, a precast concrete component blank is obtained.

[0040] Specifically, the foamed asphalt mixture mixed in step S6 is uniformly conveyed to the storage hopper above the brick-making machine via a fourth belt conveyor, ensuring a continuous and stable flow of the foamed asphalt mixture into the hopper. Once the foamed asphalt mixture in the hopper reaches the mold filling requirements, the electric switch valve at the bottom of the hopper is opened, allowing the foamed asphalt mixture to flow evenly into the pre-sized mold cavity under gravity until the mold is full. Then, the vibration compaction system of the brick-making machine is activated, outputting a vibration force of 180KN at a power of 7.5KW, continuously vibrating the foamed asphalt mixture in the mold for 15-20 seconds. This vibration rearranges and compacts the foamed asphalt mixture particles, eliminating internal voids and forming a dense precast concrete component blank. After vibration is complete, the brick-making machine is shut down. Once the blank in the mold has stabilized, the next curing step can begin. During the compaction process, a 7.5KW brick-making machine is used to vibrate and compact the foamed asphalt mixture in the mold under an impact force of 180KN. The compaction time is 15s~20s, which can ensure the molding quality of the green body and its subsequent strength development.

[0041] S8. Place the precast concrete component blank in a room temperature environment for natural curing for 72 hours to obtain cold recycled concrete precast components of asphalt pavement milling material.

[0042] Specifically, a forklift is used to remove the compacted precast concrete component blanks from the mold in step S7, and they are smoothly transported to a room temperature curing area. The precast concrete component blanks are neatly stacked at certain intervals, ensuring air circulation around each blank. During the 72-hour natural curing period, no additional watering or other moisturizing measures are required. The hydration reaction of the cement and the curing process of the foamed asphalt are completed by the moisture carried by the precast concrete component blanks themselves and the ambient humidity. After the 72-hour curing period, the strength of the precast concrete component blanks reaches the design requirements, forming structurally stable and qualified cold recycled asphalt pavement precast concrete components, i.e., slope blocks, which can be used for the construction and installation of road ancillary facilities.

[0043] Through the above technical solution, this invention utilizes milled waste asphalt pavement as raw material for precast concrete components, saving resources, improving the utilization rate of milled asphalt, and conforming to the concept of green development. By treating the milled material with a silane coupling agent, the aged asphalt on the surface of the milled material is reactivated, and a network structure can be formed on the surface of the milled material, enhancing the adhesion between foamed asphalt and the milled material, and improving the performance of the foamed asphalt cold recycled mixture. Precast component production through cold recycling is energy-saving and environmentally friendly compared to traditional plant-mixed hot recycling processes, reducing greenhouse gas emissions and thus solving the problems of high cost and high carbon emissions associated with plant-mixed hot recycling.

[0044] In some embodiments, the aggregate used is aggregate with a particle size of less than 4.75 mm and a mud content of ≤3%. Using aggregate with a particle size of less than 4.75 mm allows for a complementary gradation with milling aggregate (particle size less than 4.75 mm and 4.75~9.5 mm), filling the voids between milling aggregate particles, improving the density of the dry mix, and laying the foundation for uniformity when subsequently mixed with water, cement, and foamed asphalt. A mud content of ≤3% prevents excessive clay from adsorbing cement and foamed asphalt, thus preventing weakening the bonding force between materials. If the mud content is too high, clay will coat the aggregate surface, hindering the cement hydration reaction and the formation of the asphalt film, leading to a decrease in the strength and durability of the mixture.

[0045] In some embodiments, the base asphalt is selected from one or two of SBS modified asphalt, petroleum asphalt, or rubber modified asphalt. This allows for flexible selection of the base asphalt type based on the performance requirements of the precast components. SBS modified asphalt exhibits excellent high and low temperature performance and fatigue resistance; petroleum asphalt is relatively inexpensive and widely available; and rubber modified asphalt excels in elasticity and durability. Selecting one or two of these and combining them can adapt to different climatic environments and application scenarios, ensuring that the subsequently prepared foamed asphalt meets process requirements in terms of foaming performance, stability, and compatibility with other materials, thus providing a foundation for forming high-quality foamed asphalt mixtures.

[0046] Example 2 The first aspect of this embodiment provides a precast concrete component made from cold recycled asphalt pavement milling material, comprising the following raw materials in parts by weight: 45-53 parts of waste pavement milling material with a particle size less than 4.75 mm, 19-27 parts of waste pavement milling material with a particle size of 4.75-9.5 mm, 20-28 parts of stone chips, 1-1.4 parts of mineral powder, 1.6-2.0 parts of silica fume, 4.6 parts of water, 2.3-2.7 parts of cement, 2.3-2.7 parts of foamed asphalt, and one selected from 1.3-1.5 parts of silane coupling agent solution or 0.0125-0.015 parts of asphalt anti-stripping agent.

[0047] Specifically, when the precast concrete component is a shoulder block, the precast concrete component can be composed of the following raw materials: 49 parts of waste road milling material with a particle size of less than 4.75mm, 23 parts of waste road milling material with a particle size of 4.75 to 9.5mm, 24 parts of stone chips, 1.2 parts of mineral powder, 1.8 parts of silica fume, 4.6 parts of water, 2.5 parts of cement, 2.5 parts of foamed asphalt, and 0.013 parts of asphalt anti-stripping agent.

[0048] Reference Figure 2 and Figure 3 Another aspect of this embodiment provides a method for preparing a precast concrete component made from asphalt pavement milling material cold recycled concrete, applied to the precast concrete component made from asphalt pavement milling material cold recycled concrete described in the first aspect above, comprising the following steps: S1. The waste asphalt surface layer is crushed to obtain milled material, and the milled material is screened to obtain aggregate for use as precast concrete components.

[0049] Specifically, when using a road milling machine to initially crush waste asphalt pavement, the operating speed of the milling machine is controlled to ensure that the initial particle size of the crushed milled material is as uniform as possible and less than or equal to 9.5 mm. The crushed milled material is transported by truck to a screening device, where it is then graded and screened to obtain 45-53 portions of waste road milled material with a particle size of 0.075 mm to 4.75 mm and 19-27 portions of waste road milled material with a particle size of 4.75 mm to 9.5 mm, which will be used as aggregate for precast concrete components. Generally, the particle size of the aggregate is selected based on the required dry mix gradation requirements mentioned below. In this embodiment, it can specifically be 49 portions of waste road milled material with a particle size less than 4.75 mm and 23 portions of waste road milled material with a particle size of 4.75 to 9.5 mm.

[0050] S3. Add the milling material obtained in step S1 to the mixing pot, and add 20-28 parts of stone chips, 1-1.4 parts of mineral powder and 1.6-2.0 parts of silica fume and mix evenly to form a dry mixture.

[0051] Specifically, the milled aggregate obtained from screening in step S1, which will serve as aggregate for precast concrete components, is transported to the mixing pot using a second belt conveyor. The milled aggregate is a mixture of 49 parts of milled waste road surface aggregate with a particle size less than 4.75 mm and 23 parts of milled waste road surface aggregate with a particle size between 4.75 mm and 9.5 mm. Simultaneously, 24 parts of stone chips are added to the mixing pot using a third belt conveyor. Then, 1.2 parts of mineral powder and 1.8 parts of silica fume are transported to the mixing pot via a screw conveyor. The mixing pot is then started for thorough mixing, ensuring that the milled aggregate, stone chips, mineral powder, and silica fume obtained from screening are uniformly mixed to form a dry mix that meets the requirements of subsequent processes.

[0052] It should be noted that the stone chips can be stone chips with a particle size of less than 4.75mm, and the mud content of the stone chips is ≤3%.

[0053] S4. Heat and soften the base asphalt. Circulate the heating in the asphalt tank until the base asphalt temperature reaches 170℃. Add 0.0125~0.015 parts of asphalt anti-stripping agent and mix it evenly. Then, transport the heated base asphalt to the foamed asphalt foaming device to obtain foamed asphalt.

[0054] Specifically, the base asphalt is added to an asphalt tank, where it is circulated and heated to 170°C. Then, 0.013 parts of an asphalt anti-stripping agent are added. The base asphalt and anti-stripping agent are then continuously circulated within the tank via a circulating heating and stirring system. After 10 minutes of dynamic circulating stirring to ensure uniform mixing, the heated base asphalt is then transported to a foamed asphalt foaming device for foaming to obtain foamed asphalt.

[0055] It should be noted that the base asphalt can be one or two of SBS modified asphalt, petroleum asphalt, or rubber modified asphalt.

[0056] S5. Add 4.6 parts of water to the mixing pot in step S3 and mix with the dry mix for 70 seconds; then add 2.3 to 2.7 parts of cement and mix for 70 seconds to form mortar.

[0057] Specifically, 4.6 parts of water are precisely added to the uniformly mixed dry mix from step S3 via the water pipe connected to the mixing pot. The mixing pot is then turned on and stirred for 70 seconds to ensure the water fully contacts the dry mix and initially wets all solid particles. After stirring, 2.5 parts of cement are added to the mixing pot using a screw conveyor according to the specified ratio. This cement must meet the following technical specifications: initial setting time of 99 minutes, final setting time of 198 minutes, 3-day compressive strength of 19.3 MPa, 28-day compressive strength of 45.8 MPa, 3-day flexural strength of 4.9 MPa, and 28-day flexural strength of 7.9 MPa. Stirring continues for 70 seconds to ensure the cement, water, and dry mix are uniformly mixed, forming a mortar with a certain viscosity and plasticity. Throughout the process, the stirring time is controlled at 70 seconds to ensure uniform mixing of materials and avoid material performance loss due to over-stirring.

[0058] It should be noted that the cement meets the requirements of an initial setting time of 99 minutes and a final setting time of 198 minutes, providing sufficient operating time for processes such as mixing, transportation, and molding, and avoiding the cement from setting too quickly and affecting construction; the compressive strength and flexural strength at 3 days and 28 days ensure that the cement can provide sufficient strength support for precast components at different curing stages, meeting the mechanical performance requirements of road ancillary facilities.

[0059] S6. The foamed asphalt foaming device sprays 2.3 to 2.7 parts of foamed asphalt into the mixing pot in step S5, and mixes it in the mixing pot for 70 seconds to obtain foamed asphalt mixture.

[0060] Specifically, the foamed asphalt foaming device is connected to the mixing pot through a pipeline and precisely sprays 2.5 parts of foamed asphalt into the mortar formed in step S5. After the spraying is completed, the mixing pot continues to run and mix for 70 seconds. During this process, the foamed asphalt, with its high fluidity after foaming, fully contacts and penetrates the solid particles (milling material, stone chips, mineral powder and silica fume) and cement hydration products in the mortar. Through continuous stirring, the foamed asphalt is evenly dispersed and gradually defoamed, forming a continuous and uniform asphalt film on the surface of the solid particles. This achieves full coating and fusion of the foamed asphalt and the mortar, ensuring that the asphalt film is evenly wrapped on the surface of the solid particles, eliminating the phenomenon of local lack of adhesive or asphalt aggregation, and finally forming a foamed asphalt mixture with uniform component distribution and good cohesiveness.

[0061] In this step, the mixing time is set to 70 seconds, which is an optimized design based on material characteristics and process effects. If the mixing time is insufficient, the foamed asphalt and mortar will not fully integrate, resulting in uneven asphalt film coating and localized "dry material" or "clumps" in the mixture, thus affecting the density of the precast concrete component blank. If the mixing time is too long, the bubbles in the foamed asphalt will collapse excessively, losing the fluidity advantage after foaming. This will not only reduce the asphalt's ability to coat solid particles but may also cause segregation of the mixture due to increased asphalt viscosity, weakening its cohesiveness and subsequent molding performance. Therefore, a mixing time of 70 seconds ensures both uniform distribution of the components in the foamed asphalt mixture and maintains the foaming efficiency of the foamed asphalt.

[0062] S7. The foamed asphalt mixture obtained in step S6 is conveyed to the hopper of the brick making machine. The opening and closing of the hopper is controlled to allow the foamed asphalt mixture to enter the mold. The mixture is formed by vibration compaction. After compaction, a precast concrete component blank is obtained.

[0063] Specifically, the foamed asphalt mixture mixed in step S6 is uniformly conveyed to the storage hopper above the brick-making machine via a fourth belt conveyor, ensuring a continuous and stable flow of the foamed asphalt mixture into the hopper. Once the foamed asphalt mixture in the hopper reaches the mold filling requirements, the electric switch valve at the bottom of the hopper is opened, allowing the foamed asphalt mixture to flow evenly into the pre-sized mold cavity under gravity until the mold is full. Then, the vibration compaction system of the brick-making machine is activated, outputting a vibration force of 180KN at a power of 7.5KW, continuously vibrating the foamed asphalt mixture in the mold for 15-20 seconds. This vibration rearranges and compacts the foamed asphalt mixture particles, eliminating internal voids and forming a dense precast concrete component blank. After vibration is complete, the brick-making machine is shut down. Once the blank in the mold has stabilized, the next curing step can begin. During the compaction process, a 7.5KW brick-making machine is used to vibrate and compact the foamed asphalt mixture in the mold under an impact force of 180KN. The compaction time is 15s~20s, which can ensure the molding quality of the green body and its subsequent strength development.

[0064] S8. Place the precast concrete component blank in a room temperature environment for natural curing for 72 hours to obtain cold recycled concrete precast components of asphalt pavement milling material.

[0065] Specifically, a forklift is used to remove the compacted precast concrete component blanks from the mold in step S7, and they are smoothly transported to a room temperature curing area. The precast concrete component blanks are neatly stacked at certain intervals, ensuring air circulation around each blank. During the 72-hour natural curing period, no additional watering or other moisturizing measures are required. The hydration reaction of the cement and the curing process of the foamed asphalt are completed by the moisture carried by the precast concrete component blanks themselves and the ambient humidity. After the 72-hour curing period, the strength of the precast concrete component blanks reaches the design requirements, forming structurally stable and qualified asphalt pavement milled material cold recycled concrete precast components, i.e., shoulder blocks, which can be used for the construction and installation of road ancillary facilities.

[0066] The test results of unconfined compressive strength, porosity, and edge breakage rate of the precast concrete components based on asphalt pavement milling material prepared in Examples 1 and 2 of this invention are shown in Table 1.

[0067]

[0068] Table 1. Test results of performance indicators of precast concrete components Analysis of the above experimental results revealed that the precast concrete components made from cold recycled asphalt pavement milling material prepared using the method of this invention exhibit good mechanical properties and structural stability. In Example 1, the unconfined compressive strength of the precast component was 3.53 MPa at 3 days, increased to 5.27 MPa at 7 days, and reached 6.64 MPa at 14 days, showing a significant increase with curing time. This indicates that the cement hydration reaction and curing of the foamed asphalt mixture continue, which is beneficial to the steady development of the component's strength. In Example 2, the unconfined compressive strength was 4.43 MPa at 3 days, 4.55 MPa at 7 days, and 5.50 MPa at 14 days, also demonstrating good strength development characteristics.

[0069] Generally, a void ratio of less than 15% and a corner breakage rate of less than 1.5% are considered acceptable for precast concrete components. According to Table 1, the void ratios of the two embodiments are 12.13% and 11.75%, respectively, which are within a reasonable range. This ensures the permeability of the components while avoiding insufficient strength due to excessive voids. The corner breakage rates of the two embodiments are only 0.32% and 0.30%, respectively, also within a reasonable range. This indicates that the components have good resistance to damage during molding and subsequent processing, and high overall structural integrity. These test results verify the rationality of the foamed asphalt cold recycling process and raw material ratio used in this invention. This process can produce precast components that meet the requirements for use in road ancillary facilities, providing reliable technical support for the efficient recycling of asphalt pavement milling materials.

[0070] Although embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

[0071] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A precast component made of cold recycled concrete from asphalt pavement milling material, characterized in that, The raw materials include the following parts by weight: 45-53 parts of waste road milling material with a particle size of less than 4.75 mm, 19-27 parts of waste road milling material with a particle size of 4.75-9.5 mm, 20-28 parts of stone chips, 1-1.4 parts of mineral powder, 1.6-2.0 parts of silica fume, 4.6 parts of water, 2.3-2.7 parts of cement, 2.3-2.7 parts of foamed asphalt, and one of the following: 1.3-1.5 parts of silane coupling agent solution or 0.0125-0.015 parts of asphalt anti-stripping agent.

2. The precast cold recycled concrete component made from asphalt pavement milling material according to claim 1, characterized in that: The silane coupling agent solution is prepared by mixing silane coupling agent, ethanol and water in a mass ratio of 1:3:

10.

3. The precast cold recycled concrete component made from asphalt pavement milling material according to claim 1, characterized in that: The stone chips are stone chips with a particle size of less than 4.75 mm, and the mud content of the stone chips is ≤3%.

4. The precast concrete component made from cold recycled asphalt pavement milling material according to claim 1, characterized in that: The base asphalt of the foamed asphalt is selected from one or two of SBS modified asphalt, petroleum asphalt, or rubber modified asphalt.

5. A method for preparing precast concrete components from cold recycled asphalt pavement milling material, characterized in that: The method applied to a precast concrete component made from cold recycled asphalt pavement milling material according to any one of claims 1-4 includes the following steps: S1. The waste asphalt surface layer is crushed to obtain milling material, and the milling material is screened to obtain aggregate for use as precast concrete components. S2. Spray 1.3 to 1.5 parts of silane coupling agent solution evenly onto the surface of the milled material obtained by sieving as aggregate for precast concrete components, and let it stand for 24 hours. S3. Add the milling material obtained in step S2 to the mixing pot, and add 20-28 parts of stone chips, 1-1.4 parts of mineral powder and 1.6-2.0 parts of silica fume and mix evenly to form a dry mixture; S4. Heat and soften the base asphalt. Circulate the heating in the asphalt tank to raise the temperature of the base asphalt to 170°C. Then, transport the heated base asphalt to the foamed asphalt foaming device to obtain foamed asphalt. S5. Add 4.6 parts of water to the mixing pot in step S3 and mix with the dry mix for 70 seconds; then add 2.3 to 2.7 parts of cement and mix for 70 seconds to form mortar. S6. The foamed asphalt foaming device sprays 2.3 to 2.7 parts of foamed asphalt into the mixing pot in step S5, mixes it in the mixing pot for 70 seconds, and obtains foamed asphalt mixture. S7. The foamed asphalt mixture obtained in step S6 is conveyed to the hopper of the brick making machine. The opening and closing of the hopper is controlled to allow the foamed asphalt mixture to enter the mold. The mixture is formed by vibration compaction. After compaction, a precast concrete component blank is obtained. S8. Place the precast concrete component blank in a room temperature environment for natural curing for 72 hours to obtain cold recycled concrete precast components of asphalt pavement milling material.

6. The method for preparing precast concrete components from asphalt pavement milling material according to claim 5, characterized in that: In step S1, the particle size of the aggregate is determined according to the required dry mix gradation requirements in step S3, specifically 45-53 parts of waste road milling material with a particle size of less than 4.75mm and 19-27 parts of waste road milling material with a particle size of 4.75-9.5mm.

7. The method for preparing precast concrete components from asphalt pavement milling material according to claim 5, characterized in that: In step S3, the milling material is a mixture of 45-53 parts of waste road milling material with a particle size of less than 4.75 mm and 19-27 parts of waste road milling material with a particle size of 4.75-9.5 mm.

8. The method for preparing precast concrete components from asphalt pavement milling material according to claim 5, characterized in that: In step S5, the technical specifications of the cement are as follows: initial setting time is 99 min, final setting time is 198 min; 3-day compressive strength is 19.3 MPa, 28-day compressive strength is 45.8 MPa; 3-day flexural strength is 4.9 MPa, 28-day flexural strength is 7.9 MPa.

9. The method for preparing precast concrete components from asphalt pavement milling material according to claim 5, characterized in that: In step S7, the vibration compaction method specifically involves using a brick-making machine with a power of 7.5KW to vibrate and compact the foamed asphalt mixture in the mold under an impact force of 180KN for a compaction time of 15~20s.

10. A method for preparing precast concrete components from cold recycled asphalt pavement milling material, characterized in that: The method applied to a precast concrete component made from cold recycled asphalt pavement milling material according to any one of claims 1-4 includes the following steps: S1. The waste asphalt surface layer is crushed to obtain milling material, and the milling material is screened to obtain aggregate for use as precast concrete components. S3. Add the milling material obtained in step S1 to the mixing pot, and add 20-28 parts of stone chips, 1-1.4 parts of mineral powder and 1.6-2.0 parts of silica fume and mix evenly to form a dry mixture; S4. Heat and soften the base asphalt. Circulate the heating in the asphalt tank to bring the base asphalt temperature to 170℃. Add 0.0125~0.015 parts of asphalt anti-stripping agent and mix it evenly. Then, transport the heated base asphalt to the foamed asphalt foaming device to obtain foamed asphalt. S5. Add 4.6 parts of water to the mixing pot in step S3 and mix with the dry mix for 70 seconds; then add 2.3 to 2.7 parts of cement and mix for 70 seconds to form mortar. S6. The foamed asphalt foaming device sprays 2.3 to 2.7 parts of foamed asphalt into the mixing pot in step S5, mixes it in the mixing pot for 70 seconds, and obtains foamed asphalt mixture. S7. The foamed asphalt mixture obtained in step S6 is conveyed to the hopper of the brick making machine. The opening and closing of the hopper is controlled to allow the foamed asphalt mixture to enter the mold. The mixture is formed by vibration compaction. After compaction, a precast concrete component blank is obtained. S8. Place the precast concrete component blank in a room temperature environment for natural curing for 72 hours to obtain cold recycled concrete precast components of asphalt pavement milling material.

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