Preparation method of recycled asphalt mixture activated by regenerant and cemented by foam modified asphalt

Abstract

The invention discloses a preparation method of a recycled asphalt mixture activated by a regenerant and cemented by foam modified asphalt, and relates to the technical field of road engineering. Digging, recycling, crushing and screening the old asphalt pavement to obtain a waste asphalt mixture; activating the waste asphalt mixture by using a regenerant; mixing the activated waste asphalt mixture, stone, cement and mineral powder, and then adding water to obtain compound aggregate; and adding the foam modified asphalt into the compound aggregate, and cementing the compound aggregate with the foam modified asphalt to obtain the recycled asphalt mixture. According to the method, the waste asphalt mixture is activated through the regenerant, the performance of the waste asphalt mixture is recovered, part of asphalt on the waste asphalt mixture is softened, new and old fusion of the asphalt cement is facilitated, and permeation and adhesion of foam modified asphalt in the waste asphalt mixture are promoted; the damage tolerance characteristic of the recycled asphalt mixture is obviously improved, so that the strength performance of the recycled asphalt mixture is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of road engineering, and specifically discloses a preparation method of a recycled asphalt mixture activated by a regenerant and cemented with foamed modified asphalt. Background Art

[0003] As a core branch of asphalt cold recycling technology, foamed asphalt mixture exhibits significant technical and economic advantages in the field of road engineering due to its unique generation mechanism. This technical system adopts an innovative process of temperature-sensitive binder materials, and forms a semi-flexible structural layer material by synergistically mixing foamed modified asphalt and normal-temperature aggregates. Compared with traditional hot-mix asphalt mixtures, it not only has good energy-saving and environmental protection characteristics, but also the formed mixture has excellent anti-deformation ability. The current technological development has formed a complete theoretical framework system, covering key technical modules such as multi-objective optimization design method for mix proportion, strength evolution model under water-hydraulic coupling action, and prediction of performance decay in the whole life cycle.

[0004] The recycling of waste asphalt mixture faces significant technical bottlenecks in engineering applications, mainly manifested as significant material heterogeneity, limited recycling applicability (some waste asphalt mixtures cannot meet the grading requirements), and difficulty in activating the cemented interface. For the foamed asphalt cold recycling system, its mechanical response mechanism presents a typical layered composite characteristic: the macroscopic strength is jointly composed of the geometric interlocking effect of the aggregate skeleton and the viscoelastic coupling effect of the cemented phase, among which the "spot welding" type cemented system formed by cement-foamed asphalt has a decisive influence on the performance of the interfacial transition zone (ITZ). Although the current process can achieve the primary recycling of waste asphalt mixture, there are still significant defects in key indicators such as the fusion degree of new and old asphalt and the penetration depth of the mortar, resulting in weak strength and forming a short board in structural performance. Summary of the Invention

[0005] The present invention activates waste asphalt mixture with a regenerant to restore the performance of the waste asphalt mixture, softens part of the asphalt on the waste asphalt mixture, helps the asphalt binder to achieve new and old fusion, promotes the penetration and adhesion of foamed modified asphalt inside the waste asphalt mixture, significantly improves the damage tolerance characteristics of the recycled asphalt mixture, thereby improving the strength performance of the recycled asphalt mixture, and thus solving the technical problem of weak strength existing in the recycled asphalt mixture in the prior art.

[0006] According to the purpose of the present invention, a preparation method of a recycled asphalt mixture activated by a regenerant and cemented with foamed modified asphalt is provided, including the following steps: (1) Excavate, recycle, crush and screen the old asphalt pavement to obtain waste asphalt mixture; sprinkle the rejuvenator on the surface of the waste asphalt in the waste asphalt mixture, and then heat it to activate the waste asphalt on the surface of the waste asphalt mixture by the rejuvenator. (2) Mix the activated waste asphalt mixture, stone materials, cement and mineral powder in step (1), and then add water to obtain a compound aggregate. (3) After heating the base asphalt and adding a foaming agent, fully mix them, then put them into a shearing machine for shearing, and then pour them into a foaming device for foaming to obtain foamed modified asphalt; add the foamed modified asphalt to the compound aggregate obtained in step (2), and the foamed modified asphalt cements the compound aggregate to obtain a recycled asphalt mixture.

[0007] Preferably, in step (1), after adding the catalyst to the rejuvenator, sprinkle the rejuvenator on the surface of the waste asphalt in the waste asphalt mixture; the catalyst is used to reduce the activation energy of the reaction between the rejuvenator and the waste asphalt, promote the reaction and colloid reconstruction, accelerate the penetration and neutralize metal ions to inhibit oxidation, so as to optimize the rheological properties of the recycled asphalt.

[0008] Preferably, the catalyst is oxalic acid.

[0009] Preferably, in step (3), add the foamed modified asphalt to the compound aggregate obtained in step (2) in batches.

[0010] Preferably, in step (1), the rejuvenator is epoxy soybean oil.

[0011] Preferably, in step (3), the foaming agent is cetyltrimethylammonium bromide.

[0012] Preferably, in step (3), the temperature of the shearing is 155 - 160 °C, the rate of the shearing is 2000 - 3000 r / min, and the time of the shearing is 20 - 25 min.

[0013] Generally speaking, compared with the prior art by the above technical solutions conceived by the present invention, the following technical advantages are mainly possessed: (1) In the present invention, the rejuvenator improves the asphaltene aggregation by physical dispersion and replenishes the lost light components; preferably, a catalyst is added, and the catalyst is used to reduce the activation energy of the reaction between the rejuvenator and the aged asphalt, promote the reaction and colloid reconstruction, accelerate the penetration and neutralize metal ions (such as calcium, magnesium, etc.) to inhibit oxidation. At the same time, the catalyst can trigger its chemical reaction with the asphalt, and cooperate with the antioxidant property to delay the secondary aging.

[0014] (2)The gradient remixing process of the foamed asphalt mixture of the present invention (foaming in batches and mixing in) can more precisely control the foaming effect, improve the coating uniformity of the mixture, thereby enhancing the construction adaptability and quality stability.

[0015] (3)For the recycled asphalt mixture treated by the present invention, by strengthening the bonding force at the interface between the new and old asphalt and the adhesion between asphalt and aggregates, the dry and wet splitting strength is significantly improved and it has higher water damage resistance performance.

[0016] (4)The present invention has low energy consumption, high safety, simple process, easy to operate, and is conducive to large-scale production. Description of the Drawings

[0017] Figure 1 Strength of specimens under different processes. Detailed Embodiments

[0018] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0019] A preparation method of a recycled asphalt mixture with regenerant activation and foam-modified asphalt cementing, comprising the following steps: (1)Dig, recycle, crush and screen the old asphalt pavement to obtain waste asphalt mixture; add the regenerant to the waste asphalt mixture for mixing, and then heat it to activate the waste asphalt mixture with the regenerant; (2)Mix the activated waste asphalt mixture, stone materials, cement and mineral powder obtained in step (1), and then add water to obtain a compound aggregate; (3)Heat the base asphalt, add a foaming agent, mix well, put it into a shearing machine for shearing, and then pour it into a foaming device for foaming to obtain foamed modified asphalt; add the foamed modified asphalt to the compound aggregate obtained in step (2), and the foamed modified asphalt cements the compound aggregate to obtain a recycled asphalt mixture.

[0020] In some embodiments, in step (1), the activation treatment method is as follows: Place the regenerant in a closed constant-temperature oil bath and heat it to 65 ± 3°C. Keep stirring continuously at 200 - 300 r / min with a magnetic stirrer. Preferably, slowly pour in the catalyst (1 ± 0.1% of the mass of the regenerant), and simultaneously maintain the system at 65 ± 3°C for 1.5 - 2 min until the solution shows a flowing state; evenly sprinkle the pretreated regenerant solution on the surface of the waste asphalt of the waste asphalt mixture and perform pre-mixing; transfer the pre-mixed system to a constant-temperature curing box at 150 ± 3°C and place it for 1 - 1.5 h to allow sufficient activation reaction of the waste asphalt.

[0021] In some embodiments, the specific steps for preparing the foamed modified asphalt are as follows: Preheat the base asphalt to 155 - 160°C, then add the foaming agent. After preliminary stirring, put it into a high-speed shearing machine and shear for 20 - 25 min. The shearing temperature is 155 - 160°C, and the shearing rate is 3000 ± 100 r / min. After completion, keep it warm and develop at 150 - 160°C for 2 - 2.5 hours; Preheat the base asphalt added with the foaming agent to 150 - 160°C and then pour it into the foaming device. After the foaming device maintains a stable temperature at the set foaming temperature, start foaming.

[0022] The following are specific comparative examples and examples Comparative Example 1 Dig, recycle, crush and screen the old asphalt pavement to obtain waste asphalt mixture; Feed the waste asphalt mixture, stone materials, cement, and mineral powder into the mixer according to the mass ratio (80% waste asphalt mixture + 5% coarse aggregate (9.5 - 13.2 mm) + 8.5% fine aggregate (2.36 - 4.75 mm) + 1.5% cement + 5.0% mineral powder), and form a compound aggregate through dry mixing and wet mixing; The specific steps for preparing the foamed modified asphalt are as follows: Preheat 500 g of base asphalt to 155°C, then add 2.5 g of the foaming agent cetyltrimethylammonium bromide. After preliminary stirring, put it into a high-speed shearing machine and shear for 20 min. The shearing temperature is 155°C, and the shearing rate is 3000 r / min. After completion, keep it warm and develop at 155°C for 2 hours; Preheat the base asphalt added with the foaming agent to 150°C and then pour it into the foaming device. After the foaming device maintains a stable temperature at the set foaming temperature, start foaming to obtain a foamed modified asphalt with an expansion ratio ≥ 10 times and a half-life ≥ 8 s; Mix the foamed modified asphalt with the above compound aggregate; Achieve the interfacial compounding of the foamed asphalt and the compound aggregate through the stirring process to obtain the recycled asphalt mixture.

[0023] Example 1 (1) Dig, recycle, crush and screen the old asphalt pavement to obtain waste asphalt mixture; 25.6g of regeneration agent epoxidized soybean oil was placed in a closed constant temperature oil bath pot and heated to 65℃ and maintained for 2min until the solution was in a flowing state, and then evenly sprinkled on the surface of 3200g of waste asphalt mixture and pre-mixed; the pre-mixed system was transferred to a 150℃ constant temperature curing box and placed for 2h to allow it to undergo a sufficient surface activation reaction; the activated waste asphalt mixture, stone, cement, and mineral powder were added to the mixer according to the mass ratio (80% waste asphalt mixture + 5% coarse stone (9.5-13.2mm) + 8.5% fine stone (2.36-4.75mm) + 1.5% cement + 5.0% mineral powder), and a composite aggregate system was formed through dry mixing and wet mixing; (2) The specific steps for preparing foamed modified asphalt are as follows: 500g of base asphalt is preheated to 155°C, 2.5g of foaming agent hexadecyltrimethylammonium bromide is added, and after preliminary stirring, it is placed in a high-speed shearing machine for shearing for 20 minutes, the shearing temperature is 155°C, and the shear rate is 3000r / min. After completion, it is kept at 155°C for 2 hours; the base asphalt with the foaming agent added is preheated to 150°C and poured into a foaming device. After the foaming device maintains a stable temperature at the set foaming temperature, foaming is carried out to obtain a foamed modified asphalt with an expansion ratio ≥10 times and a half-life ≥8s; The foamed modified asphalt is mixed with the above-mentioned compound aggregate; the interface compounding of the foamed asphalt and the compound aggregate is achieved through a stirring process to obtain a recycled asphalt mixture.

[0024] Example 2 (1) Excavating, recycling, crushing and screening the old asphalt pavement to obtain waste asphalt mixture; 25.6g of regeneration agent epoxidized soybean oil was placed in a closed constant temperature oil bath pot and heated to 65℃ and maintained for 2min until the solution was in a flowing state, and then evenly sprinkled on the surface of 3200g of waste asphalt mixture and pre-mixed; the pre-mixed system was transferred to a 150℃ constant temperature curing box and placed for 2h to allow it to undergo a sufficient surface activation reaction; the activated waste asphalt mixture, stone, cement, and mineral powder were compounded as aggregates according to the mass ratio (80% waste asphalt mixture + 5% coarse stone (9.5-13.2mm) + 8.5% fine stone (2.36-4.75mm) + 1.5% cement + 5.0% mineral powder), and the materials were added to the mixer in stages, first dry mixed for 1min to form a primary skeleton, and then 154.8g (water temperature 25℃) was added and wet mixed for 1min to form a wet system to obtain a compounded aggregate; (2)The specific steps for preparing the foamed modified asphalt are as follows: Preheat 500 g of base asphalt to 155 °C, add 2.5 g of foaming agent cetyltrimethylammonium bromide, after preliminary stirring, put it into a high-speed shearing machine and shear for 20 min, the shearing temperature is 155 °C, the shearing rate is 3000 r / min, and after completion, keep it at 155 °C for heat development for 2 hours; Preheat the base asphalt added with the foaming agent to 150 °C and pour it into the foaming device, and carry out foaming after the temperature of the foaming device is stable at the set foaming temperature to obtain foamed modified asphalt with an expansion ratio ≥ 10 times and a half-life ≥ 8 s; Implement the gradient remixing process: First, initially mix 56 g of foamed asphalt with the compounded aggregate for 1 min, and then add the remaining foamed asphalt for final mixing for 1 min.

[0025] Example 3 (1)Excavate, recycle, crush and screen the old asphalt pavement to obtain waste asphalt mixture; Place 25.6 g of regenerant epoxidized soybean oil in a closed constant-temperature oil bath and heat it to 65 °C, keep stirring continuously through a magnetic stirrer and slowly pour in the catalyst oxalic acid (1% of the mass of the regenerant), keep the system at 65 °C and maintain for 2 min until the solution shows a flowing state, then evenly sprinkle it on the surface of 3200 g of waste asphalt mixture and carry out pre-mixing; Transfer the pre-mixed system to a 150 °C constant-temperature curing box and place it for 2 h to allow it to carry out a sufficient surface activation reaction; According to the mass ratio (80% waste asphalt mixture + 5% coarse aggregate (9.5 - 13.2 mm) + 8.5% fine aggregate (2.36 - 4.75 mm) + 1.5% cement + 5.0% mineral powder), compound the activated waste asphalt mixture, aggregate, cement and mineral powder, and feed them into the mixer in stages. First, dry mix for 1 min to form a primary framework, then add 154.8 g of water (water temperature 25 °C) and wet mix for 1 min to form a wet system to obtain the compounded aggregate; (2)The specific steps for preparing the foamed modified asphalt are as follows: Preheat 500 g of base asphalt to 155 °C, add 5.005 g of foaming agent cetyltrimethylammonium bromide, after preliminary stirring, put it into a high-speed shearing machine and shear for 20 min, the shearing temperature is 155 °C, the shearing rate is 3000 r / min, and after completion, keep it at 150 °C for heat development for 2 hours; Preheat the base asphalt added with the foaming agent to 150 °C and pour it into the foaming device, and carry out foaming after the temperature of the foaming device is stable at the set foaming temperature to obtain foamed modified asphalt with an expansion ratio ≥ 10 times and a half-life ≥ 8 s; Implement the gradient remixing process: First, initially mix 56 g of foamed asphalt with the compounded aggregate for 1 min, and then add the remaining foamed asphalt for final mixing for 1 min.

[0026] Results and Analysis Table 1 below shows the strength data of the recycled asphalt mixtures obtained in Comparative Example 1 and Examples 1-3; 。

[0027] Figure 1 They are the strengths of specimens under different processes. It can be seen that compared with the ordinary foamed asphalt mixture without being activated by a regenerant (Comparative Example 1), for the foamed modified recycled asphalt mixture prepared by the method of the present invention, with the complication of the mixing process, the dry and wet splitting strengths and ITS values of the mixed and formed specimens are gradually increasing. This is because the regenerant and the catalyst activate some of the aged asphalt on the RAP, which helps the asphalt binder to achieve new-old fusion, promotes the penetration and adhesion of the foamed asphalt mortar inside the old materials. At the same time, adding foamed asphalt in gradients helps to maintain the stability of the quality of the foamed asphalt and improve the uniformity of coating of the mixture.

[0028] For Example 3, a rutting test was carried out. The prepared specimen together with the test mold was placed on the test bench of the rutting tester. The test wheel was in the central part of the specimen, and its traveling direction was the same as the rolling direction of the specimen. The contact pressure between the test wheel and the specimen was controlled to be 0.7 MPa at 60°C. It can be seen from the test data that the dynamic stability of the foamed asphalt cold recycled mixture reached 5779 times / mm, which is significantly higher than the standard value of ≥2000 times / mm required by the technical specification.

[0029] It is easy for those skilled in the art to understand that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included within the protection scope of the present invention.

Claims

1. A preparation method of a regenerated asphalt mixture with regenerant activation and foam-modified asphalt cementation, characterized in that, It includes the following steps: (1) Dig, recycle, crush, and screen the old asphalt pavement to obtain waste asphalt mixture; sprinkle the rejuvenator on the waste asphalt surface of the waste asphalt mixture, and then heat it to activate the waste asphalt on the surface of the waste asphalt mixture with the rejuvenator; (2) Mix the waste asphalt mixture activated in step (1), stone materials, cement, and mineral powder, and then add water to obtain a compound aggregate; (3) Heat the base asphalt, add a foaming agent, mix well, put it into a shearing machine for shearing, and then pour it into a foaming device for foaming to obtain foamed modified asphalt; add the foamed modified asphalt to the compound aggregate obtained in step (2), and the foamed modified asphalt cements the compound aggregate to obtain a recycled asphalt mixture.

2. The preparation method of the recycled asphalt mixture regenerated by regenerant activation and foam-modified asphalt cementing, characterized in that, In step (1), after adding the catalyst to the rejuvenator, sprinkle the rejuvenator on the waste asphalt surface of the waste asphalt mixture; the catalyst is used to reduce the activation energy of the reaction between the rejuvenator and the waste asphalt, promote the reaction and colloid reconstruction, accelerate the penetration and neutralize metal ions to inhibit oxidation, thereby optimizing the rheological properties of the recycled asphalt.

3. The preparation method of the regenerated asphalt mixture with regenerant activation and foam-modified asphalt binder as claimed in claim 1, wherein, In step (1), after adding the catalyst to the rejuvenator, sprinkle the rejuvenator on the waste asphalt surface of the waste asphalt mixture; the catalyst is used to reduce the activation energy of the reaction between the rejuvenator and the waste asphalt, promote the reaction and colloid reconstruction, accelerate the penetration and neutralize metal ions to inhibit oxidation, thereby optimizing the rheological properties of the recycled asphalt.

4. The preparation method of the regenerated asphalt mixture with regenerant activation and foam-modified asphalt binder as claimed in claim 1, characterized in that, In step (3), add the foamed modified asphalt to the compound aggregate obtained in step (2) in batches.

5. The preparation method of the regenerated asphalt mixture activated by a regenerant and foam-modified with asphalt binder according to claim 1, characterized in that In step (1), the rejuvenator is epoxy soybean oil.

6. The preparation method of the recycled asphalt mixture with regenerant activation and foam-modified asphalt binder as described in claim 1, characterized in that, In step (3), the foaming agent is cetyltrimethylammonium bromide.

7. The preparation method of the regenerated asphalt mixture with regenerant activation and foam-modified asphalt binder according to claim 1, characterized in that, In step (3), the temperature of the shearing is 155 - 160 °C, the shearing rate is 2000 - 3000 r / min, and the shearing time is 20 - 25 min.

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