A warm mix agent for recycled asphalt and a warm mix recycled asphalt mixture and a method of manufacture

Abstract

The present application relates to a kind of recycled asphalt warm mix agent and its warm mix recycled asphalt mixture and preparation method, recycled asphalt warm mix agent, including two components of warm mix agent and reagent;The raw material of warm mix agent includes solvent, viscosity reducer and surfactant with mass ratio of 100:(13-20):(3.5-5), wherein the solvent is the mixture of elaidic acid and tung oil acid;Reagent is the powder obtained by calcining treatment of calcium carbonate.Warm mix recycled asphalt mixture includes mixture A, 0.65-1% of warm mix agent in the mass of mixture A, 1-2% of reagent in the mass of mixture A, and 1.5%-4.0% of asphalt in the mass of mixture A;Mixture A includes aggregate, RAP and mineral powder with mass ratio of 100:(40-150):(1-10).The present application can reduce construction temperature by more than 50 DEG C.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of road engineering materials, in particular to a warm-mixing agent for recycled asphalt, warm-mixing recycled asphalt mixture and a preparation method thereof. BACKGROUND

[0002] A large amount of recycled asphalt concrete (RAP) is produced in the process of maintenance and reconstruction of asphalt pavement, and the current development trend is to utilize RAP by using plant-mixing hot recycling technology. Since RAP contains a large amount of aged asphalt, the heating equipment for aggregate cannot be used in the asphalt mixing station, and a special heating cylinder is needed to preheat RAP. At the same time, considering that RAP contains a large amount of aged asphalt, the preheating temperature of RAP cannot be too high, which results in a low delivery temperature of the produced recycled asphalt mixture, which is more significant when the RAP content is increased. In addition, from the perspective of the durability of recycled asphalt mixture, RAP also needs to be added at a lower temperature, because a higher preheating temperature of RAP will accelerate the further aging of the aged asphalt in RAP, which will further reduce the delivery temperature of the recycled asphalt mixture. The low delivery temperature of the recycled asphalt mixture not only leads to poor uniformity in the mixing process of RAP, new aggregate and new asphalt, but also affects the compaction degree in the subsequent paving and rolling process, and reduces the performance of the recycled asphalt pavement.

[0003] Therefore, the use of warm-mixing technology enables the recycled asphalt mixture to be compacted at a lower temperature, which is an important technical means to ensure the construction quality of high RAP content. The existing warm-mixing technology can reduce the construction temperature of asphalt mixture by about 30℃, which can solve this problem to a certain extent. However, under the conditions of high RAP content and low preheating temperature of RAP, the existing technology cannot meet the requirements. SUMMARY

[0004] The present application aims to overcome the above technical deficiencies and provide a warm-mixing agent for recycled asphalt, a warm-mixing recycled asphalt mixture and a preparation method thereof, which solve the technical problem of high construction temperature of the warm-mixing recycled asphalt mixture in the prior art.

[0005] To achieve the above technical purposes, the technical solution provided by the present application is as follows:

[0006] In a first aspect, the present application provides a warm-mixing agent for recycled asphalt, which comprises two components of a warm-mixing agent and a reaction agent. The raw materials of the warm-mixing agent include solvent, viscosity reducer and surfactant in a mass ratio of 100:(13-20):(3.5-5), wherein the solvent is a mixture of elaidic acid and tung oil acid; and the reaction agent is a powder obtained by calcining calcium carbonate.

[0007] This invention uses low-melting-point organic compounds with acid radicals, oleic acid and tung acid, as diluents, which can significantly reduce the viscosity of asphalt, thereby enabling construction at lower temperatures. Furthermore, it employs high-temperature calcined calcium carbonate powder as a reactant, designed to react with the diluents and achieve a suitable reaction, thereby increasing the viscosity of oleic acid and tung acid after the recycled asphalt mixture is constructed, resulting in better road performance of the recycled asphalt mixture.

[0008] Preferably, the mass ratio of the warming agent to the reactant is (0.65-1):(1-2).

[0009] Preferably, the solvent is a mixture of oleic acid and tung acid in a mass ratio of 1:1.

[0010] Preferably, the viscosity reducer is microcrystalline wax with a melting point of 85–90°C.

[0011] The warm mix additive of this invention uses microcrystalline wax as a viscosity reducer. It is liquid at the construction temperature of asphalt, which can reduce the construction viscosity of asphalt to a certain extent. At the same time, during the service of asphalt mixture, microcrystalline wax is solid, which can solidify asphalt and improve the strength of asphalt mixture.

[0012] Preferably, the surfactant is a mixture of alkylphenol polyoxyethylene ether and sodium dodecyl diphenyl ether disulfonate; more preferably, the surfactant is a mixture of alkylphenol polyoxyethylene ether and sodium dodecyl diphenyl ether disulfonate in a mass ratio of 1:0.5.

[0013] This invention's warm mix admixture uses nonionic alkylphenol polyoxyethylene ether and anionic sodium dodecyl diphenyl ether disulfonate as a composite surfactant. Since the diluents oleic acid and tung oil acid are generally negatively charged, their fusion with asphalt results in the asphalt also becoming negatively charged. The nonionic and anionic surfactants used in this invention can remain stable under negatively charged conditions, preventing charge neutralization and agglomeration. Through these combined effects, the warm mix admixture prepared by this invention can reduce construction temperatures while ensuring the road performance of recycled asphalt mixtures.

[0014] Secondly, the present invention provides a method for preparing a recycled asphalt warm mix admixture, comprising the following steps: mixing a solvent, a viscosity reducer and a surfactant in proportion, heating to 100-120°C and mixing evenly, and cooling to room temperature to obtain the warm mix admixture;

[0015] Calcium carbonate is heated to 1050–1150°C and held at that temperature for 1–2 hours, then cooled to room temperature to obtain calcined material; the calcined material is then ground into powder to obtain a reactant.

[0016] Preferably, the specific conditions for uniform mixing during the preparation of the warm mixing agent are: high-speed shearing is used for stirring and mixing for 5 to 10 minutes; the shearing rate used for high-speed shearing is 3000 to 3500 r / min.

[0017] During the preparation of the reactants, calcium carbonate was heated at a rate of 15–20 °C / min; the calcined material was ground to a specific surface area of ​​250–350 m². 2 / kg of powder.

[0018] Preferably, the purity of the calcium carbonate is greater than 85%.

[0019] Thirdly, the present invention provides a warm-mix recycled asphalt mixture, comprising mixture A, a warm-mix agent comprising 0.65 to 1% of the mass of mixture A, a reactant comprising 1 to 2% of the mass of mixture A, and asphalt comprising 1.5% to 4.0% of the mass of mixture A;

[0020] Mixture A comprises aggregates, RAP and mineral powder in a mass ratio of 100:(40-150):(1-10).

[0021] Preferably, the aggregate is one of limestone, diabase or basalt, with a particle size of 2 to 30 mm; the gradation specification is a mixture of two or more of the following in any proportion: 2.36 to 4.75 mm, 4.75 to 9.5 mm, 9.5 to 13.2 mm, 9.5 to 16 mm, 9.5 to 19 mm, and 19 to 26.5 mm.

[0022] Preferably, the RAP is a waste asphalt mixture with a particle size of less than 10mm obtained after all the recycled asphalt pavement has been crushed by a crusher, and the asphalt content is 3.6% to 7.0%.

[0023] Preferably, the mineral powder is limestone mineral powder, and the passing rate of the 0.075mm sieve is 85-95%.

[0024] Preferably, the asphalt is Grade 70 A asphalt or ID modified asphalt.

[0025] Fourthly, the present invention provides a method for preparing warm-mix recycled asphalt mixture, comprising the following steps:

[0026] Aggregates, RAP and mineral powder are mixed in a certain mass ratio to obtain mixture A. Then, a warm mix agent preheated to 100-120°C is added. Finally, reactants and asphalt are added simultaneously and stirred evenly to obtain a warm mix recycled asphalt mixture.

[0027] Preferably, the aggregate is added at a temperature of 170–200°C; the RAP is added after being preheated to 100–120°C; the mineral powder is added at room temperature; the reactant is added at room temperature; and the asphalt is added at a temperature of 160–165°C.

[0028] Preferably, after adding the warm mix agent, stir for 30-60 seconds; after adding the asphalt and reactant, stir for 60-90 seconds.

[0029] Preferably, after the mixture A is mixed in a certain proportion, the synthesized gradation is required to meet the requirements of Table 5.3.2-2 in JTG F40-2004.

[0030] Compared with the prior art, the beneficial effects of the present invention include:

[0031] This invention provides a recycled asphalt warm mix agent, its warm mix recycled asphalt mixture, and a preparation method thereof. Unlike traditional asphalt warm mix agents, the warm mix agent of this invention has good compatibility with waste asphalt mixtures, lower construction temperature, and minimal impact on the road performance of asphalt mixtures. This invention can reduce the construction temperature by more than 50°C, and can provide certain technical support for plant-mixed hot recycling technology. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0033] To avoid redundancy, some of the raw materials and processes used in the following embodiments and comparative examples will be described here:

[0034] The solvent in step (1) is a mixture of oleic acid and tung acid in a mass ratio of 1:1.

[0035] The viscosity reducer in step (1) is microcrystalline wax with a melting point of 88-89℃.

[0036] The surfactant in step (1) is a mixture of alkylphenol polyoxyethylene ether and sodium dodecyl diphenyl ether disulfonate in a mass ratio of 1:0.5.

[0037] The addition temperature of each raw material in step (3) refers to the temperature of the raw material itself when it is added. For example, if the addition temperature of the aggregate is 170-200℃, the aggregate is preheated to 170-200℃ before being added. The same applies to other raw materials (no preheating is required if it is added at room temperature).

[0038] Example 1

[0039] The present invention provides a method for preparing warm-mix recycled asphalt mixture, comprising the following steps:

[0040] (1) Preparation of warm mixing agent

[0041] The solvent, viscosity reducer, and surfactant were mixed in a mass ratio of 100:15:4, heated to 105°C, and stirred using high-speed shearing (shear rate of 3200 r / min). After stirring for 10 min, the mixture was cooled to room temperature to obtain a warm-mixing agent.

[0042] (2) Preparation of reactants

[0043] Calcium carbonate (87% purity) was heated to 1100℃ at a rate of 20℃ / min, held at that temperature for 2 hours, cooled to room temperature, and then the calcined material was ground to a specific surface area of ​​300 m². 2 / kg of powder yields the reactant.

[0044] (3) Preparation of warm-mix recycled asphalt mixture

[0045] Mixture A is made by combining aggregate, RAP and mineral powder in a mass ratio of 100:43:6. Then, the warm mix agent prepared in step (1) is added and stirred for 30 seconds. At the same time, asphalt and the reactant prepared in step (2) are added and stirred for 90 seconds.

[0046] The aggregate in step (3) is limestone with a gradation of 2.36-4.75mm, 4.75-9.5mm, and 9.5-13.2mm, and is added at a temperature of 180℃.

[0047] The RAP mentioned in step (3) is a waste asphalt mixture with a particle size range of 0-10mm obtained after all the recycled asphalt pavement has been crushed by a crusher. The asphalt content is 5.0%, and the addition temperature is 110℃.

[0048] The mineral powder mentioned in step (3) is limestone mineral powder with a 0.075mm sieve aperture of 95% and is added at room temperature.

[0049] The amount of warm mixing agent in step (3) is 0.7% of the mass of mixture A, and the addition temperature is 110℃.

[0050] The asphalt in step (3) is No. 70 Grade A asphalt, with an admixture amount of 3.3% of the mass of mixture A, and an addition temperature of 160℃.

[0051] The reactant in step (3) is 1% of the mass of mixture A and is added at room temperature.

[0052] The mixture A described in step (3) is mixed according to the mass ratio of aggregate:RAP:mineral powder of 100:43:6. The resulting gradation is shown in Table 1.

[0053] Table 1 Synthetic Gradients

[0054] Mesh / mm 16 13.2 9.5 4.75 2.36 1.18 0.6 0.3 0.15 0.075 Pass rate / % 100.0 96.9 72.4 40.9 31.2 19.4 13.6 10.0 8.0 6.8

[0055] The performance of the warm-mix recycled asphalt mixture obtained in Example 1 was tested, and the test results are shown in Table 2. The test results show that the porosity, Marshall stability, and water immersion residual stability of the specimens are similar under molding conditions of 100℃ and 155℃, indicating that the construction temperature can be reduced by more than 50℃.

[0056] Table 2 Performance Test Results

[0057]

[0058] The testing methods for void ratio, Marshall stability, and water immersion residual stability shall be in accordance with T0705 and T0709 of the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" JTG E20-2011.

[0059] Example 2

[0060] The method for preparing warm-mix recycled asphalt mixture of the present invention includes the following steps:

[0061] (1) Preparation of warm mixing agent

[0062] The solvent, viscosity reducer, and surfactant were mixed in a mass ratio of 100:14:4.5, heated to 105°C, and stirred using high-speed shearing (shear rate of 3200 r / min). After stirring for 8 minutes, the mixture was cooled to room temperature to obtain a warm-mixing agent.

[0063] (2) Preparation of reactants

[0064] Calcium carbonate (92% purity) was heated to 1080℃ at a heating rate of 18℃ / min, held at that temperature for 2 hours, cooled to room temperature, and then the calcined material was ground to a specific surface area of ​​320 m². 2 / kg of powder yields the reactant.

[0065] (3) Preparation of warm-mix recycled asphalt mixture

[0066] Mixture A is made by combining aggregate, RAP and mineral powder in a mass ratio of 100:49.2:6.8. Then, the warm mix agent prepared in step (1) is added and stirred for 40 seconds. At the same time, asphalt and the reactant prepared in step (2) are added and stirred for 90 seconds.

[0067] The aggregate in step (3) is basalt with a gradation of 2.36-4.75mm, 4.75-9.5mm, and 9.5-13.2mm, and is added at a temperature of 190℃.

[0068] The RAP mentioned in step (3) is a waste asphalt mixture with a particle size range of 0-10mm obtained after all the recycled asphalt pavement has been crushed by a crusher. The asphalt content is 5.3%, and the addition temperature is 120℃.

[0069] The mineral powder mentioned in step (3) is limestone mineral powder with a 0.075mm sieve aperture of 95% and is added at room temperature.

[0070] The amount of warm mixing agent in step (3) is 0.9% of the mass of mixture A, and the addition temperature is 110℃.

[0071] The asphalt in step (3) is ID modified asphalt, with an admixture amount of 3.1% of the mass of mixture A, and an addition temperature of 165℃.

[0072] The reactant in step (3) is 2% of the mass of mixture A and is added at room temperature.

[0073] The mixture A described in step (3) is mixed according to the mass ratio of aggregate:RAP:mineral powder of 100:49.2:6.8. The resulting gradation is shown in Table 3.

[0074] Table 3 Synthetic Gradients

[0075] Mesh / mm 16 13.2 9.5 4.75 2.36 1.18 0.6 0.3 0.15 0.075 Pass rate / % 100.0 97.0 73.3 44.8 32.7 20.8 14.3 10.5 7.8 6.9

[0076] The performance of the warm-mix recycled asphalt mixture obtained in Example 2 was tested, and the test results are shown in Table 4. The test results show that the porosity, Marshall stability, and water immersion residual stability of the specimens are similar under molding conditions of 110℃ and 165℃, indicating that the construction temperature can be reduced by more than 50℃.

[0077] Table 4 Performance Test Results

[0078]

[0079] Example 3

[0080] The method for preparing warm-mix recycled asphalt mixture of the present invention includes the following steps:

[0081] (1) Preparation of warm mixing agent

[0082] The solvent, viscosity reducer, and surfactant were mixed in a mass ratio of 100:17:4.8, heated to 120°C, and stirred using high-speed shearing (shear rate of 3500 r / min). After stirring for 10 min, the mixture was cooled to room temperature to obtain a warm-mixing agent.

[0083] (2) Preparation of reactants

[0084] Calcium carbonate (90% purity) was heated to 1150℃ at a rate of 20℃ / min, held at that temperature for 1.5 hours, cooled to room temperature, and then the calcined material was ground to a specific surface area of ​​290 m². 2 / kg of powder yields the reactant.

[0085] (3) Preparation of warm-mix recycled asphalt mixture

[0086] Mixture A is made by combining aggregate, RAP and mineral powder in a mass ratio of 100:51.8:7.1. Then, add the warm mix agent prepared in step (1), stir for 30 seconds, and then add asphalt and the reactant prepared in step (2) and stir for 90 seconds.

[0087] The aggregate in step (3) is basalt with a gradation of 2.36-4.75mm, 4.75-9.5mm, and 9.5-13.2mm, and is added at a temperature of 185℃.

[0088] The RAP mentioned in step (3) is a waste asphalt mixture with a particle size range of 0-10mm obtained after all the recycled asphalt pavement has been crushed by a crusher. The asphalt content is 5.1%, and the addition temperature is 120℃.

[0089] The mineral powder mentioned in step (3) is limestone mineral powder with a 0.075mm sieve aperture of 86% and is added at room temperature.

[0090] The amount of warm mixing agent in step (3) is 0.8% of the mass of mixture A, and the addition temperature is 110℃.

[0091] The asphalt in step (3) is ID modified asphalt, with an admixture amount of 3.7% of the mass of mixture A, and an addition temperature of 165℃.

[0092] The reactant in step (3) is 2% of the mass of mixture A and is added at room temperature.

[0093] The mixture A described in step (3) is prepared by mixing aggregate:RAP:mineral powder in a mass ratio of 100:51.8:7.1. The resulting gradation is shown in Table 5.

[0094] Table 5 Synthetic Gradients

[0095] Mesh / mm 16 13.2 9.5 4.75 2.36 1.18 0.6 0.3 0.15 0.075 Pass rate / % Mesh / mm Pass rate / % 100.0 97.1 72.5 44.4 32.3 22.0 15.9 11.0 9.0 6.7

[0096] Comparative Example 1

[0097] A warm-mix recycled asphalt mixture is prepared in a manner largely similar to that of Example 3, except that no reactant is used; the warm-mix agent is a surfactant-type warm-mix agent, erucamide (molecular weight 337.58, density 0.94 g / cm³). 3 The dosage is 1% of the amount of ID modified asphalt, and it is added after premixing with asphalt. Other conditions are the same as in Example 3.

[0098] Comparative Example 2

[0099] A warm-mix recycled asphalt mixture is prepared in a manner similar to that of Example 3, except that no reactant is used.

[0100] Comparative Example 3

[0101] Compared to Example 3, only oleic acid was used as the solvent, while the other steps and conditions were the same as in Example 3.

[0102] The performance of the warm-mix recycled asphalt mixtures obtained in Example 3 and Comparative Examples 1-3 was tested, and the test results are shown in Table 6.

[0103] Table 6 Performance test results of Example 3 and Comparative Examples 1-3

[0104]

[0105]

[0106] As shown in Table 6, the test results indicate that in Comparative Example 1, the porosity of the specimen molded at 110℃ was significantly higher than that at 165℃, while the Marshall stability and water-immersion residual stability were significantly lower. In Comparative Example 2, the porosity, Marshall stability, and water-immersion residual stability of the specimen molded at 110℃ were not significantly different from those of Example 3, but the Marshall stability and water-immersion residual stability were significantly lower than those of Example 3. In Comparative Example 3, the porosity, Marshall stability, and water-immersion residual stability of the specimen molded at 110℃ were not significantly different from those of Example 165℃, but the Marshall stability and water-immersion residual stability were somewhat lower than those of Example 3. In Example 3, the porosity, Marshall stability, and water-immersion residual stability of the specimen molded at 110℃ were similar to those of Example 165℃, indicating that the construction temperature can be reduced by more than 50℃, and good road performance can be maintained after the construction temperature is reduced.

[0107] In summary, this invention provides a recycled asphalt warm mix agent, its warm mix recycled asphalt mixture, and a preparation method thereof. Unlike traditional asphalt warm mix agents, the recycled asphalt warm mix agent of this invention has good compatibility with waste asphalt mixtures, lower construction temperature, and minimal impact on the road performance of asphalt mixtures. This invention can reduce the construction temperature by more than 50°C, and can provide certain technical support for plant-mixed hot recycling technology.

[0108] 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 recycled asphalt warm mix admixture, characterized in that, It includes two components: a warm mixing agent and a reactant; the raw materials of the warm mixing agent include a solvent, a viscosity reducer and a surfactant in a mass ratio of 100:(13-20):(3.5-5), wherein the solvent is a mixture of oleic acid and tung oil acid; The reactant is obtained by heating calcium carbonate to 1050-1150℃, holding it at that temperature for 1-2 hours, and then cooling it to room temperature to obtain a calcined product; the calcined product is then ground into powder. The viscosity reducer is microcrystalline wax; The surfactant is a mixture of alkylphenol polyoxyethylene ether and sodium dodecyl diphenyl ether disulfonate.

2. The recycled asphalt warm mix admixture according to claim 1, characterized in that, The mass ratio of the warm-mixing agent to the reactant is (0.65~1):(1~2); The solvent is a mixture of oleic acid and tung acid in a mass ratio of 1:

1.

3. The method for preparing the recycled asphalt warm mix admixture according to any one of claims 1-2, characterized in that, The process includes the following steps: mixing solvent, viscosity reducer and surfactant in a certain proportion, heating to 100-120°C and mixing evenly, and cooling to room temperature to obtain a warm mix agent; Calcium carbonate is heated to 1050–1150°C and held at that temperature for 1–2 hours, then cooled to room temperature to obtain calcined material; the calcined material is then ground into powder to obtain a reactant.

4. The method for preparing the recycled asphalt warm mix admixture according to claim 3, characterized in that, During the preparation of the warm mixing agent, the specific conditions for uniform mixing are: high-speed shearing is used for stirring and mixing for 5 to 10 minutes; the shearing rate used for high-speed shearing is 3000 to 3500 r / min. During the preparation of the reactants, calcium carbonate was heated at a rate of 15–20 °C / min; the calcined material was ground to a specific surface area of ​​250–350 m². 2 / kg of powder.

5. A warm-mix recycled asphalt mixture prepared based on the recycled asphalt warm-mix agent according to any one of claims 1-2, characterized in that, It includes mixture A, the warm mix agent comprising 0.65 to 1% of the mass of mixture A, the reactant comprising 1 to 2% of the mass of mixture A, and asphalt comprising 1.5% to 4.0% of the mass of mixture A; Mixture A comprises aggregates, RAP and mineral powder in a mass ratio of 100:(40-150):(1-10).

6. The warm-mix recycled asphalt mixture according to claim 5, characterized in that, The aggregate is one of limestone, diabase, or basalt, with a particle size of 2-30mm; the RAP is a waste asphalt mixture with a particle size of less than 10mm obtained by crushing all recycled asphalt pavement, with an asphalt content of 3.6-7.0%; the mineral powder is limestone mineral powder; and the asphalt is No. 70 Grade A asphalt or ID modified asphalt.

7. The method for preparing warm-mix recycled asphalt mixture as described in claim 5, characterized in that, Includes the following steps: Aggregates, RAP and mineral powder are mixed in a certain mass ratio to obtain mixture A. Then, a warm mix agent preheated to 100-120°C is added. Finally, reactants and asphalt are added simultaneously and stirred evenly to obtain a warm mix recycled asphalt mixture.

8. The method for preparing warm-mix recycled asphalt mixture according to claim 7, characterized in that, Aggregates, RAP, and asphalt need to be preheated before being added; the addition temperature of aggregates is 170-200℃; the addition temperature of RAP is 100-120℃; and the addition temperature of asphalt is 160-165℃.

9. The method for preparing warm-mix recycled asphalt mixture according to claim 7, characterized in that, After adding the warm mix agent, stir for 30–60 seconds; after adding the asphalt and reactant, stir for 60–90 seconds.

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