A method for the production of a recycled asphalt mixture of reclaimed asphalt binder activated and modified with foamed asphalt

Abstract

The application discloses a preparation method of a regenerated asphalt mixture of a rejuvenator-activated and foam-modified asphalt cement, and relates to the technical field of road engineering. Old asphalt pavement is excavated, recycled, crushed and screened to obtain waste asphalt mixture; the waste asphalt mixture is activated by using a rejuvenator; the activated waste asphalt mixture, stone, cement and mineral powder are mixed, and then water is added to obtain compounded aggregate; foam-modified asphalt is added into the compounded aggregate, the foam-modified asphalt cements the compounded aggregate, and a regenerated asphalt mixture is obtained. The application activates the waste asphalt mixture by using a rejuvenator, restores the performance of the waste asphalt mixture, softens part of asphalt on the waste asphalt mixture, helps new and old asphalt cement to be integrated, promotes the penetration and adhesion of the foam-modified asphalt in the waste asphalt mixture, significantly improves the damage tolerance characteristics of the regenerated asphalt mixture, and thus improves the strength performance of the regenerated asphalt mixture.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of road engineering, and discloses a preparation method of regenerated asphalt mixture activated by a regenerating agent and modified by foamed asphalt cement. BACKGROUND

[0002] As a core branch of the asphalt cold recycling technology, the foamed asphalt mixture has significant technical and economic advantages in the field of road engineering due to its unique generation mechanism. The technical system adopts an innovative process of temperature-sensitive cementing material, and forms a structural layer material with semi-flexible characteristics by synergistically mixing foamed modified asphalt and normal-temperature aggregate.

[0003] Compared with the traditional hot-mixed asphalt mixture, the foamed asphalt mixture has good energy-saving and environment-friendly characteristics, and the formed mixture has excellent deformation resistance. The current technology development has formed a complete theoretical framework system, which covers key technical modules such as multi-objective optimization design method of mixture ratio, strength evolution model under water-power coupling, and performance degradation prediction in the whole life cycle.

[0004] The regeneration of waste asphalt mixture faces significant technical bottlenecks in engineering applications, mainly including the following core challenges: significant material heterogeneity, limited regeneration applicability (part of the waste asphalt mixture cannot meet the gradation requirements), and difficulty in activating the cement interface. SUMMARY

[0005] The application activates the waste asphalt mixture by the regenerating agent, restores the performance of the waste asphalt mixture, softens part of the asphalt on the waste asphalt mixture, helps the new and old asphalt cement to be fused, promotes the penetration and adhesion of the foamed modified asphalt in the waste asphalt mixture, significantly improves the damage tolerance characteristics of the regenerated asphalt mixture, and thus improves the strength performance of the regenerated asphalt mixture, thereby solving the technical problem of weak strength of the regenerated asphalt mixture in the prior art.

[0006] According to the purpose of the application, a preparation method of regenerated asphalt mixture activated by a regenerating agent and modified by foamed asphalt cement is provided, which comprises the following steps:

[0007] (1) Old asphalt pavement is excavated, recycled, crushed and sieved to obtain waste and old asphalt mixture; a rejuvenator is sprinkled on the surface of waste and old asphalt of the waste and old asphalt mixture, and then heated to activate the waste and old asphalt on the surface of the waste and old asphalt mixture;

[0008] (2) The waste and old asphalt mixture activated in step (1), stone, cement and mineral powder are mixed, and then water is added to obtain a compound aggregate;

[0009] (3) The base asphalt is heated and then a foaming agent is added, and after being fully mixed, it is put into a shearing machine for shearing, and then poured into a foaming device for foaming to obtain a foamed modified asphalt; the foamed modified asphalt is added to the compound aggregate obtained in step (2), and the foamed modified asphalt cements the compound aggregate to obtain a recycled asphalt mixture.

[0010] Preferably, in step (1), a catalyst is added to the rejuvenator before the rejuvenator is sprinkled on the surface of waste and old asphalt of the waste and old asphalt mixture; the catalyst is used to reduce the activation energy of the reaction of the rejuvenator with the waste and old 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.

[0011] Preferably, the catalyst is oxalic acid.

[0012] Preferably, in step (3), the foamed modified asphalt is added to the compound aggregate obtained in step (2) in batches.

[0013] Preferably, in step (1), the rejuvenator is epoxy soybean oil.

[0014] Preferably, in step (3), the foaming agent is hexadecyl trimethyl ammonium bromide.

[0015] Preferably, in step (3), the temperature of shearing is 155-160°C, the speed of shearing is 2000-3000 r / min, and the time of shearing is 20-25 min.

[0016] Overall, compared with the prior art, the above technical scheme conceived by the present application mainly has the following technical advantages:

[0017] (1) In the present application, the rejuvenator improves the aggregation of asphaltene and supplements the lost light components through physical dispersion; preferably, a catalyst is added, which is used to reduce the activation energy of the reaction of the rejuvenator with the aged asphalt, promote the reaction and colloid reconstruction, accelerate the penetration and neutralize metal ions (such as calcium, magnesium, etc.) to inhibit oxidation, and at the same time, the catalyst can trigger its chemical reaction with asphalt, and synergistically delay secondary aging.

[0018] (2) The gradient mixing process (batch foaming and mixing) of the foamed asphalt mixture of the present application can more accurately control the foaming effect, improve the uniformity of the coating of the mixture, and thus improve the construction adaptability and quality stability.

[0019] (3) The treated recycled asphalt mixture of the present application has significantly improved dry and wet splitting strength and higher water damage resistance by strengthening the interface bonding force between new and old asphalt and the adhesion of asphalt-aggregate.

[0020] (4) The present application has low energy consumption, high safety, simple process and easy operation, and is conducive to large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The strength of the test piece under different processes. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0023] A preparation method of a recycled asphalt mixture activated by a recycling agent and modified by foamed asphalt, comprising the following steps:

[0024] (1) Old asphalt pavement is excavated, recycled, crushed and sieved to obtain waste asphalt mixture; a recycling agent is added to the waste asphalt mixture for mixing, and then heated to activate the waste asphalt mixture by the recycling agent;

[0025] (2) The activated waste asphalt mixture obtained in step (1), stone, cement and mineral powder are mixed, and then water is added to obtain a compounded aggregate;

[0026] (3) The base asphalt is heated and then a foaming agent is added, and after being fully mixed, it is put into a shearing machine for shearing, and then poured into a foaming device for foaming to obtain foamed modified asphalt; the foamed modified asphalt is added to the compounded aggregate obtained in step (2), and the foamed modified asphalt cements the compounded aggregate to obtain a recycled asphalt mixture.

[0027] In some embodiments, in step (1), the activation treatment method is as follows: the regenerating agent is placed in a closed thermostatic oil bath pot and heated to 65±3°C, and kept stirring at 200-300 r / min by a magnetic stirrer, preferably slowly pouring the catalyst (1±0.1% of the mass of the regenerating agent) while keeping the system at 65±3°C and maintaining for 1.5-2 min until the solution shows a flow state; the pre-processed regenerating agent solution is uniformly poured onto the waste asphalt surface of the waste asphalt mixture, and pre-mixing is performed; the pre-mixed system is transferred into a 150±3°C thermostatic curing box, and placed for 1-1.5 h to allow the waste asphalt to undergo sufficient activation reaction.

[0028] In some embodiments, the preparation steps of the foam modified asphalt are as follows: after the base asphalt is preheated to 155-160°C, the foaming agent is added, and after preliminary stirring, it is put into a high-speed shearing machine for shearing for 20-25 min, the shearing temperature is 155-160°C, the shearing rate is 3000±100 r / min, and after completion, it is kept at 150-160°C for 2-2.5 hours; the base asphalt with the foaming agent is preheated to 150-160°C and poured into a foaming device, and after the foaming device is kept at a stable temperature at the set foaming temperature, foaming is performed.

[0029] The following are specific comparative examples and examples

[0030] Comparative Example 1

[0031] The old asphalt pavement is excavated, recycled, crushed and sieved to obtain waste asphalt mixture; the waste asphalt mixture, stone, cement and mineral powder are fed into a mixer according to the mass ratio (80% waste asphalt mixture + 5% coarse stone (9.5-13.2 mm) + 8.5% fine stone (2.36-4.75 mm) + 1.5% cement + 5.0% mineral powder), and dry mixing and wet mixing are performed to form a compound aggregate;

[0032] The preparation steps of the foam modified asphalt are as follows: 500 g of base asphalt is preheated to 155°C, 2.5 g of foaming agent hexadecyl trimethyl ammonium bromide is added, and after preliminary stirring, it is put into a high-speed shearing machine for shearing for 20 min, the shearing temperature is 155°C, the shearing rate is 3000 r / min, and after completion, it is kept at 155°C for 2 hours; the base asphalt with the foaming agent is preheated to 150°C and poured into a foaming device, and after the foaming device is kept at a stable temperature at the set foaming temperature, foaming is performed, and foam modified asphalt with an expansion rate of ≥10 times and a half-life of ≥8 s is obtained;

[0033] The foam modified asphalt is mixed with the above compound aggregate; the interface of the foam asphalt and the compound aggregate is compounded by a stirring process to obtain a regenerated asphalt mixture.

[0034] Example 1

[0035] (1) Old asphalt pavement is excavated, recycled, broken and sieved to obtain waste asphalt mixture;

[0036] 25.6g of the regenerating agent epoxy soybean oil is heated to 65℃ in a closed thermostatic oil bath pot and maintained for 2min until the solution shows a flow state, then uniformly sprinkled on the surface of 3200g of waste asphalt mixture and pre-mixed; the pre-mixed system is transferred into a 150℃ constant temperature curing box and placed for 2h to allow it to undergo sufficient surface activation reaction; the activated waste asphalt mixture, stone, cement and mineral powder are fed into the mixer at a mass ratio of (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) to form a compound aggregate system through dry mixing and wet mixing;

[0037] (2) The preparation steps of the foam modified asphalt are as follows: 500g of base asphalt is preheated to 155℃, then 2.5g of foaming agent hexadecyl trimethyl ammonium bromide is added, and after preliminary stirring, it is put into a high-speed shearing machine for shearing for 20min, the shearing temperature is 155℃, and the shearing rate is 3000r / min; after completion, it is kept at 155℃ for 2h; the base asphalt with the foaming agent is preheated to 150℃ and poured into a foaming device; after the foaming device is kept at the set foaming temperature and the temperature is stable, foaming is carried out to obtain foam modified asphalt with an expansion rate ≥10 times and a half-life period ≥8s;

[0038] The foam modified asphalt is mixed with the above compound aggregate; the interface of the foam asphalt and the compound aggregate is compounded through the stirring process to obtain the recycled asphalt mixture.

[0039] Example 2

[0040] (1) Old asphalt pavement is excavated, recycled, broken and sieved to obtain waste asphalt mixture;

[0041] 25.6g of the regenerating agent epoxy soybean oil is heated to 65℃ in a closed thermostatic oil bath pot and maintained for 2min until the solution shows a flow state, then uniformly sprinkled on the surface of 3200g of waste asphalt mixture and pre-mixed; the pre-mixed system is transferred into a 150℃ constant temperature curing box and placed for 2h to allow it to undergo sufficient surface activation reaction; the activated waste asphalt mixture, stone, cement and mineral powder are fed into the mixer at a mass ratio of (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) to form a compound aggregate system through dry mixing and wet mixing;

[0042] (2) The specific steps for preparing the foamed modified asphalt are: 500 g of base asphalt is preheated to 155°C, 2.5 g of foaming agent cetyltrimethylammonium bromide is added, and after preliminary stirring, it is put into a high-speed shearing machine for shearing for 20 min, the shearing temperature is 155°C, the shearing rate is 3000 r / min, and after completion, it is kept at 155°C for 2 hours for development; the base asphalt with the foaming agent is preheated to 150°C and poured into a foaming device, foaming is carried out after the foaming device keeps the temperature stable at the set foaming temperature, and foamed modified asphalt with an expansion rate of ≥10 times and a half-life of ≥8 s is obtained;

[0043] The gradient compounding process is implemented: first, 56 g of foamed asphalt is initially mixed with the compounded aggregate for 1 min, and then the remaining foamed asphalt is finally mixed for 1 min.

[0044] Example 3

[0045] (1) The old asphalt pavement is excavated, recycled, crushed and sieved to obtain waste asphalt mixture;

[0046] 25.6 g of regenerating agent epoxy soybean oil is placed in a closed constant-temperature oil bath and heated to 65°C, continuously stirred by a magnetic stirrer and slowly poured into a catalyst oxalic acid (1% of the mass of the regenerating agent), the system is kept at 65°C and maintained for 2 min, until the solution shows a flowing state, then uniformly sprinkled on the surface of 3200 g of waste asphalt mixture, and pre-mixed; the pre-mixed system is transferred to a 150°C constant-temperature curing box and placed for 2h to allow it to undergo a full surface activation reaction; the activated waste asphalt mixture, stone, cement and mineral powder are compounded according to the mass ratio (80% waste asphalt mixture + 5% coarse stone (9.5-13.2 mm) + 8.5% fine stone (2.36-4.75 mm) + 1.5% cement + 5.0% mineral powder), and are fed into the mixer in stages, first dry-mixed for 1 min to form a primary framework, then 154.8 g of water (water temperature 25°C) is added, and wet-mixed for 1 min to form a wet system, to obtain a compounded aggregate;

[0047] (2) The specific steps for preparing the foamed modified asphalt are: 500 g of base asphalt is preheated to 155°C, 2.5 g of foaming agent cetyltrimethylammonium bromide is added, and after preliminary stirring, it is put into a high-speed shearing machine for shearing for 20 min, the shearing temperature is 155°C, the shearing rate is 3000 r / min, and after completion, it is kept at 155°C for 2 hours for development; the base asphalt with the foaming agent is preheated to 150°C and poured into a foaming device, foaming is carried out after the foaming device keeps the temperature stable at the set foaming temperature, and foamed modified asphalt with an expansion rate of ≥10 times and a half-life of ≥8 s is obtained;

[0048] The gradient compounding process is implemented: first, 56 g of foamed asphalt is initially mixed with the compounded aggregate for 1 min, and then the remaining foamed asphalt is finally mixed for 1 min.

[0049] Results and analysis

[0050] The following table 1 is the strength data of the reclaimed asphalt mixture obtained by Comparative Example 1 and Examples 1-3;

[0051] .

[0052] Figure 1 The strength of the test piece under different processes. It can be seen that the dry-wet splitting strength and ITS value of the foamed modified reclaimed asphalt mixture prepared by the method of the present application gradually increase with the complication of the mixing process compared with the ordinary foamed asphalt mixture (Comparative Example 1) which is not activated by the reclaiming agent. This is because the reclaiming agent and the catalyst activate part of the aged asphalt on the RAP, which helps the new and old asphalt binders to be integrated, and promotes the penetration and adhesion of the foamed asphalt mortar in the old material. At the same time, the step-by-step addition of foamed asphalt helps to maintain the stability of the quality of foamed asphalt and improve the uniformity of the mixture.

[0053] The wheel rut test is carried out for Example 3. The prepared test piece is placed on the test bed of the wheel rut test machine together with the test mold. The test wheel is in the central part of the test piece, and the walking direction is consistent with the rolling direction of the test piece. The contact pressure of the test wheel and the test piece is controlled at 0.7 MPa at 60℃. According to the test data, the dynamic stability of the foamed asphalt cold recycled mixture reaches 5779 times / mm, which is significantly higher than the standard value of ≥2000 times / mm required by the technical specification.

[0054] Those skilled in the art will readily understand that the above description is only the preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing recycled asphalt mixture activated by a recycling agent and bonded with foam-modified asphalt, characterized in that, Includes the following steps: (1) The old asphalt pavement is excavated, recycled, crushed and screened to obtain waste asphalt mixture; after adding the catalyst to the recycling agent, the catalyst is oxalic acid, and then the recycling agent is sprinkled on the surface of the waste asphalt of the waste asphalt mixture, and then heated to activate the waste asphalt on the surface of the waste asphalt mixture; the catalyst is used to reduce the activation energy of the reaction between the recycling agent and the waste asphalt, promote the reaction and colloidal reconstruction, accelerate the penetration and neutralize metal ions to inhibit oxidation, thereby optimizing the rheological properties of the recycled asphalt; (2) Mix the activated waste asphalt mixture, stone, cement and mineral powder from step (1), and then add water to obtain compound aggregate; (3) After heating the base asphalt, add the foaming agent, mix thoroughly, and then put it into a shearing machine for shearing. The shearing temperature is 155-160℃, the shearing rate is 2000-3000 r / min, and the shearing time is 20-25 min. Then pour it into a foaming device for foaming to obtain foamed modified asphalt. Add the foamed modified asphalt in batches to the compound aggregate obtained in step (2) to control the foaming effect and improve the uniformity of the coating of the mixture. The foamed modified asphalt binds the compound aggregate to obtain recycled asphalt mixture.

2. The method for preparing recycled asphalt mixture with regenerator activation and foam-modified asphalt binder as described in claim 1, characterized in that, In step (1), the regenerator is epoxidized soybean oil.

3. The method for preparing recycled asphalt mixture with regenerator activation and foam-modified asphalt binder as described in claim 1, characterized in that, In step (3), the foaming agent is hexadecyltrimethylammonium bromide.

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