A cold-mixed and cold-laid emulsified asphalt mixture and its preparation method

Abstract

The present invention relates to the technical field of road construction materials, and particularly relates to an emulsified asphalt mixture for cold mixing and cold paving and a preparation method thereof. Compared with the prior art, the present invention not only maintains the long-term storage stability of the emulsified asphalt, but also enables the mixture to break emulsion as soon as possible after being paved on the road surface, so as to achieve early opening to traffic. The aggregate has a wide application range and is suitable for any cold construction process of the road surface, such as micro-surfacing, sand-containing fog seal layer, "white to black" of cement pavement, energy conservation and environmental protection. It breaks through the limitation of the heat preservation conditions during the transportation of traditional hot-mixed mixtures and the strict temperature conditions during the compaction process, and is convenient for construction.

Description

Technical Field

[0001] The present invention relates to the technical field of road construction materials, and particularly relates to an emulsified asphalt mixture for cold mixing and cold paving and a preparation method thereof. Background Art

[0002] Basically, asphalt mixtures for roads are all traditional hot mixing and hot paving. During the production and construction process, the pollution of the environment by dust and asphalt fumes is inevitable. Although people have taken many measures and invested a large amount of funds in recent years, the pollution problem has not been fundamentally solved. The key to studying cold mixing and cold paving of asphalt mixtures is the development of modified emulsified asphalt for cold mixing. Modified emulsified asphalt has been widely used in road surfaces, such as slurry seal, microsurfacing, sand-containing fog seal, cold patch materials, etc. However, it has not yet been realized for the cold mixing and cold paving of asphalt mixtures, especially for large-scale batch production. At present, the existing emulsified asphalt generally has the deficiency of poor permeability, mainly because: the large viscosity of emulsified asphalt hinders the penetration of asphalt droplets; the demulsification speed of emulsified asphalt is fast, and the emulsified asphalt demulsifies before it can fully penetrate, forming an oil skin on the surface of the base layer that can be picked up by the transport vehicle and paver; after the concrete is formed, the emulsified asphalt still contains water, and sufficient bonding force can only be generated after the water is completely evaporated, which results in low early strength of emulsified asphalt concrete. How to invent an emulsified asphalt mixture for cold mixing and cold paving is a technical problem to be solved. Summary of the Invention

[0003] Aiming at the deficiencies of the existing technology, the present invention provides an emulsified asphalt mixture for cold mixing and cold paving and a preparation method thereof. A special emulsified asphalt that is stable at normal temperature is used, which does not demulsify during storage and transportation, and also does not demulsify during the mixing process and paving process of the mixture, and can achieve the purpose of uniform mixing with aggregates; after the emulsified asphalt mixture is mixed well, it is paved at normal temperature, and then subjected to double compaction and final compaction to achieve densification, and finally an emulsified asphalt concrete pavement material with high early strength is obtained.

[0004] The technical solution adopted by the present invention is as follows: An emulsified asphalt mixture for cold mixing and cold paving, by mass fraction, comprises the following components: 8-12 parts of emulsified asphalt, 1-4 parts of SBR latex, 1-3 parts of C9 resin, 65-70 parts of aggregates; the emulsified asphalt is a matrix asphalt, a non-ionic emulsifier, a cationic emulsifier, a stabilizer, and water with a mass ratio of (60-70):(0.8-1.2):(0.1-0.5):(0.1-0.5):(30-35).

[0005] The aggregates adopt an intermittent dense gradation, and its gradation conforms to the following table:

[0006] Particle size, mm 19 16 13.2 9.5 4.75 2.36 Sieve opening passing rate, % 100 95 75 55 22-24 17-19 Particle size, mm 1.18 0.6 0.3 0.15 0.075 Sieve opening passing rate, % 18 13-15 12-12.5 11-11.5 10

[0007] By compounding cationic emulsifiers and non-ionic emulsifiers, the non-ionic components are embedded in the micelles of the cationic emulsifiers, reducing the repulsive force between charge groups, improving the electrostatic stability of the mixed system, and achieving the purpose of not breaking emulsion during most of the aggregate mixing process and paving process, and achieving uniform mixing with the aggregate; by using C9 resin and SBR latex in combination to modify emulsified asphalt together, by adjusting the effective content of the asphalt emulsion and the aggregate dense ratio, the contradictions of the total liquid volume required to meet mixing and compaction and the contradiction between the optimal mortar dosage and voids after emulsion breaking in the case of continuous dense grading are avoided, so as to achieve the purpose of easy drainage and compaction during the rolling process.

[0008] Preferably, the non-ionic emulsifier is alkylnaphthol polyoxyethylene ether. Compared with alkylphenol polyoxyethylene ether, naphthalene ring compounds can be biodegraded, are non-toxic, harmless and environmentally friendly, and have better emulsifying effects.

[0009] Preferably, the cationic emulsifier is a slow-cracking asphalt emulsifier. It is used to extend the demulsification time of emulsified asphalt. Emulsified asphalt is very easy to demulsify during cold mixing, improving storage stability and controlling the mixing demulsification time.

[0010] Preferably, the cationic emulsifier is prepared by the following method: N,N-dimethyloctadecylamine and epichlorohydrin with a molar ratio of 1:(1 - 1.2) are put into a reactor and reacted at 50 - 60 °C for 5 - 8 h to obtain 2,3-epoxypropyl dimethyloctadecyl ammonium chloride; after chitosan is dispersed in a solvent, sodium hydroxide is added and alkalized at 70 - 75 °C for 2 - 4 h, and then the 2,3-epoxypropyl dimethyloctadecyl ammonium chloride solution is slowly dropped and subjected to ring-opening reaction for 6 - 8 h to obtain the finished product. As a chitosan derivative, it can form a protective film on the surface of asphalt droplets to increase the interfacial strength. The ring structure in its molecule can provide steric hindrance for the emulsion, increasing the difficulty of contact between the asphalt emulsion and the aggregate to achieve the purpose of slow cracking; at the same time, there are a large number of amino groups in the molecule that are converted into nitrogen positive ions after protonation, and the positive charge of the quaternary ammonium salt intermediate enhances the electrostatic attraction with the negative charge on the surface of the aggregate, accelerating the adsorption process of the aggregate to the emulsified asphalt after mixing to achieve the purpose of quick setting; and multiple positive charge groups in the molecule increase the ζ potential of the micelles in the emulsion, enhancing the mutual repulsive force, and ultimately enhancing the storage stability of the emulsified asphalt. With a dosage of only 0.5 - 1% of the emulsion quality, excellent surface activity can be achieved.

[0011] Preferably, the stabilizer is an inorganic stabilizer and an organic stabilizer with a mass ratio of 1:1. For the compound emulsifier of cationic and non-ionic, the inorganic stabilizer and the organic stabilizer are selected for compounding to improve the emulsion stability.

[0012] Preferably, the inorganic stabilizer is one or a mixture of more than one of calcium chloride, magnesium chloride, sodium chloride, and ammonium chloride. It can increase the potential difference between interfacial films, increase the repulsive force between asphalt particles, thereby reducing the sedimentation of particles and preventing delamination.

[0013] Preferably, the organic stabilizer is one or a mixture of more than one of polyacrylic acid, polyvinyl alcohol, and methyl cellulose. It can increase the viscosity of the solution, strengthen the interfacial film, reduce the flocculation and aggregation between particles, thereby improving the stability.

[0014] Preferably, the matrix asphalt is one of SK-90, Zhonghai-90, and Jingbo-90.

[0015] On the other hand, the present invention provides a preparation method for a cold-mixed and cold-laid emulsified asphalt mixture, which is characterized by including the following steps:

[0016] S1. Mix the formulated amount of non-ionic emulsifier, cationic emulsifier, stabilizer, and water evenly to prepare a soap solution, and store it at a constant temperature of 60-70 °C;

[0017] S2. Add the soap solution, preheated asphalt, and SBR latex to a colloid mill for grinding in sequence to obtain SBR-modified emulsified asphalt;

[0018] S3. Add the preheated C9 resin to a colloid mill and carry out modification treatment with the SBR-modified emulsified asphalt to obtain modified emulsified asphalt;

[0019] S4. Add the modified emulsified asphalt to the aggregate and stir it fully at normal temperature for 30-50 s to prepare a cold-mixed and cold-laid emulsified asphalt mixture, which can be paved and used at normal temperature. By adopting the process of modifying and emulsifying simultaneously, the operation is simple and the performance of the emulsified asphalt is stable.

[0020] Preferably, the shear speed of the colloid mill is maintained at 1800 r / min to 2000 r / min, and the preheating temperature of the asphalt and C9 resin is 110-120 °C.

[0021] Beneficial effects: Compared with the prior art, the present invention not only maintains the long-term storage stability of the emulsified asphalt, but also enables the mixture to break emulsify as soon as possible after being paved on the road surface, so as to open to traffic as early as possible. The aggregate has a wide range of applications and is suitable for any cold construction process on the road surface, such as micro-surfacing, sand-containing fog seal layer, "white to black" of cement pavement, energy-saving and environmental protection. It breaks through the insulation condition limitation during the transportation of traditional hot-mixed mixtures and the strict temperature condition limitation during the compaction process, and is convenient for construction. Specific embodiments

[0022] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0023] It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the relative positional relationship and movement conditions between components in a specific posture. If the specific posture changes, the directional indications will also change accordingly. In addition, the descriptions involving "first", "second", etc. in the present invention are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0024] Example 1 Preparation of Cationic Emulsifier

[0025] N,N-dimethyloctadecylamine and epichlorohydrin with a molar ratio of 1:1 were put into a reactor and reacted at 50°C for 5 - 8 h to obtain 2,3-epoxypropyl dimethyloctadecyl ammonium chloride. After chitosan was dispersed in isopropanol, when the system temperature rose to 50°C, 30% wt of NaOH solution was added to swell chitosan for 3 h. 2,3-epoxypropyl dimethyloctadecyl ammonium chloride was dissolved in isopropanol to form an intermediate solution. After the system temperature was raised to 70°C, the intermediate solution was slowly dropped in and the ring-opening reaction was carried out at a constant temperature for 8 h. After the reaction, the filter cake obtained by vacuum filtration was washed three times with absolute ethanol, and then vacuum-dried and ground to obtain the finished product. The surface tension value of the emulsifier aqueous solution with a concentration of 1 g / L was measured to be 20.2 mN / m at 30°C by the Wilhelmy method; the Zeta potential of the emulsifier aqueous solution with a concentration of 1 g / L reached +60.1 mV.

[0026] Example 2 Preparation of Cationic Emulsifier

[0027] N,N-dimethyloctadecylamine and epichlorohydrin with a molar ratio of 1:1.1 were put into a reactor and reacted at 60 °C for 8 h to obtain 2,3-epoxypropyl dimethyloctadecyl ammonium chloride; chitosan was dispersed in isopropanol, and after the system temperature rose to 50 °C, 30% wt of NaOH alcohol solution was added to swell chitosan for 3 h. 2,3-epoxypropyl dimethyloctadecyl ammonium chloride was dissolved in isopropanol to prepare an intermediate solution. After the system temperature rose to 70 °C, the intermediate solution was slowly dropped in and reacted at a constant temperature for 6 h for ring-opening reaction. After the reaction, the filter cake obtained by vacuum filtration was washed three times with absolute ethanol, and then dried in vacuum and ground to obtain the finished product. The surface tension value of the aqueous solution of the emulsifier measured by the Wilhelmy method was 19.7 mN / m at room temperature, and the Zeta potential of the aqueous solution of the emulsifier with a concentration of 1 g / L reached +59.3 mV.

[0028] Example 3 Preparation of Cationic Emulsifier

[0029] N,N-dimethyloctadecylamine and epichlorohydrin with a molar ratio of 1:1.2 were put into a reactor and reacted at 55 °C for 6 h to obtain 2,3-epoxypropyl dimethyloctadecyl ammonium chloride; chitosan was dispersed in isopropanol, and after the system temperature rose to 50 °C, 30% wt of NaOH solution was added to swell chitosan for 3 h. 2,3-epoxypropyl dimethyloctadecyl ammonium chloride was dissolved in isopropanol to prepare an intermediate solution. After the system temperature rose to 70 °C, the intermediate solution was slowly dropped in and reacted at a constant temperature for 7 h for ring-opening reaction. After the reaction, the filter cake obtained by vacuum filtration was washed three times with absolute ethanol, and then dried in vacuum and ground to obtain the finished product. The surface tension value of the aqueous solution of the emulsifier measured by the Wilhelmy method was 19.1 mN / m at room temperature, and the Zeta potential of the aqueous solution of the emulsifier with a concentration of 1 g / L reached +58.1 mV.

[0030] Example 3-8 Preparation of Modified Emulsified Asphalt

[0031] Heat the formulated base asphalt to a fluid state; prepare soap solution: put the formulated cationic emulsifier into 60-70℃ water, stir continuously, wait until the emulsifier is completely melted, then add the formulated non-ionic emulsifier and stabilizer in sequence and mix evenly to obtain soap solution, adjust the pH value, and store at a constant temperature of 60-70℃; after filling the colloid mill with boiling water and preheating, add soap solution for circulation, adjust the shear speed of the colloid mill at 1800r / min~2000r / min, slowly add the asphalt preheated to 110-120℃ into the colloid mill, after the asphalt is completely poured in, add SBR latex, stabilize shear grinding for 4-6min to obtain SBR modified emulsified asphalt; then slowly add C9 resin preheated to 110-120℃, stabilize shear grinding for 12-16min to obtain brown modified emulsified asphalt with uniform particles. The raw materials and mass proportions of Examples 3 to 8 are shown in Table 2 below. The performance of the emulsified asphalt was tested in accordance with the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering", as shown in Table 3.

[0032] Table 2 Raw material ratio table

[0033]

[0034]

[0035] Table 3 Emulsified asphalt performance table

[0036] Storage stability Evaporation residue, % Oversize residue, % Initial setting time, min Example 3 > 7 days 62.6 0.03 70 Example 4 > 7 days 62.4 0.03 68 Example 5 > 7 days 63.9 0.02 62 Example 6 > 7 days 62.5 0.03 63 Example 7 > 7 days 62.7 0.03 68 Example 8 > 7 days 64.3 0.02 57

[0037] It can be seen from the above table that emulsified asphalt can be stable for more than 7 days and has good storage stability. After mixing with type I graded limestone aggregate, the mixture is in a paste state with an initial setting time of 55-70 minutes. The amount of emulsifier used only accounts for 0.5-1% of the asphalt emulsion, which meets the needs of slurry seal and micro-surface rapid repair construction.

[0038] Examples 9-16

[0039] The modified emulsified asphalt (Example 8) and aggregate in the formula are fully stirred at room temperature to prepare a cold-mixed and cold-laid emulsified asphalt mixture; the emulsified asphalt mixture is pre-pressed, placed at 110°C for curing for 24 hours, and then re-pressed and finally pressed to finally prepare a road performance test specimen. The raw materials, mass mix ratios and grading tables of Examples 9 to 16 are shown in Table 4 below.

[0040] Table 4 shows the proportion of modified emulsified asphalt mixture

[0041] Emulsified asphalt Aggregate Gradation Example 9 15 65 J1 Example 10 17 65 J2 Example 11 12 65 J3 Example 12 17 68 J4 Example 13 15 68 J5 Example 14 12 68 J6 Example 15 17 70 J7 Example 16 15 70 J8

[0042] Based on (SMA-16 grading median value) design the following J1-J8, see Table 5 below

[0043]

[0044] For the formed emulsified asphalt mixture specimens, referring to the "Test Procedures for Bitumen and Bituminous Mixtures in Highway Engineering" (JTJ052 - 2000), the road - using performance tests were carried out, and the results are shown in Table 6.

[0045] Table 6 Road - using Performance Test

[0046]

[0047]

[0048] It can be seen from Tables 4 - 6 that the mixture prepared in this application has excellent road - using performance. By optimizing the gap - graded aggregate, taking the aggregate with a particle size of 9.5 - 4.75 mm as the main - skeleton particles and the aggregate with a particle size of 4.75 - 1.18 mm as the interfering particles, on the premise that the content of the aggregate with a particle size greater than 9.5 mm remains unchanged, increasing the main - skeleton particles and reducing the interfering particles equally can weaken the influence of the internal interference effect of the mixture, help to form drainage channels, enhance the drainage capacity during the compaction process and accelerate the drainage rate during the curing stage. The weakening of the interference effect also makes the mixture relatively easy to compact, which is conducive to obtaining a smaller void ratio (as shown in Examples 9 - 12). However, when increasing the main - skeleton particles and reducing the interfering particles equally for the aggregate with a particle size of 1.18 - 0.075 mm, it is difficult to reduce the void ratio (as shown in Examples 13 - 16); while optimizing the gap - graded aggregate can make the emulsion fully wrap the aggregate and combine with the coarse - aggregate skeleton interlock structure, increase the contact area between the aggregates, and then increase the internal frictional resistance, which improves both the shear resistance at high temperature and the low - temperature performance of the mixture.

[0049] Finally, it should be noted that the above description is only the preferred embodiment of the present invention. Under the inspiration of the present invention and without violating the purpose and claims of the present invention, those skilled in the art can make various similar representations, and such transformations all fall within the protection scope of the present invention.

Claims

1. An emulsified asphalt mixture for cold mixing and cold paving, characterized in that, By mass fraction, it includes the following components: 8 - 12 parts of emulsified asphalt, 1 - 4 parts of SBR latex, 1 - 3 parts of C9 resin, and 65 - 70 parts of aggregate; The emulsified asphalt is composed of matrix asphalt, non - ionic emulsifier, cationic emulsifier, stabilizer, and water with a mass ratio of (60 - 70):(0.3 - 0.7):(0.2 - 0.5):(0.1 - 0.5):(30 - 35); The cationic emulsifier is prepared by the following method: Put N, N - dimethyloctadecylamine and epichlorohydrin with a molar ratio of 1:(1 - 1.2) into a reactor, react at 50 - 60 °C for 5 - 8 h to obtain 2, 3 - epoxypropyl dimethyloctadecyl ammonium chloride; After dispersing chitosan in a solvent, add sodium hydroxide, alkalize at 70 - 75 °C for 2 - 4 h, and then slowly drop the 2, 3 - epoxypropyl dimethyloctadecyl ammonium chloride solution, and carry out ring - opening reaction for 6 - 8 h to obtain the finished product; The matrix asphalt is one of SK - 90, Zhonghai - 90, and Jingbo - 90; The aggregate adopts discontinuous dense gradation, and its gradation conforms to the following table: 。 2. The emulsified asphalt mixture for cold mixing and cold paving according to claim 1, characterized in that: The non - ionic emulsifier is alkylnaphthol polyoxyethylene ether.

3. The emulsified asphalt mixture for cold mixing and cold paving according to claim 1, characterized in that: The cationic emulsifier is a slow - cracking asphalt emulsifier.

4. The emulsified asphalt mixture for cold mixing and cold paving according to claim 1, wherein: The stabilizer is an inorganic stabilizer and an organic stabilizer with a mass ratio of 1:

1.

5. A cold mix and cold lay emulsified asphalt mixture according to claim 1, characterized in that: The inorganic stabilizer is one or a mixture of calcium chloride, magnesium chloride, sodium chloride, and ammonium chloride.

6. The emulsified asphalt mixture for cold mixing and cold paving according to claim 1, characterized in that: The organic stabilizer is one or a mixture of polyacrylic acid, polyvinyl alcohol, and methyl cellulose.

7. A preparation method of the cold-mixed and cold-laid emulsified asphalt mixture as described in claims 1-6, characterized in that It includes the following steps: S1. Mix the formula amount of non - ionic emulsifier, cationic emulsifier, stabilizer, and water evenly to prepare a soap solution, and store it at a constant temperature of 60 - 70 °C; S2. Add the soap solution, pre - heated asphalt, and SBR latex into a colloid mill for grinding in sequence to prepare SBR - modified emulsified asphalt; S3. Add the pre - heated C9 resin into the colloid mill and carry out modification treatment with SBR - modified emulsified asphalt to obtain modified emulsified asphalt; S4. Add the modified emulsified asphalt into the aggregate and stir well at room temperature for 30 - 50 s to prepare a cold - mix and cold - lay emulsified asphalt mixture, which can be paved and used under normal temperature conditions.

8. The preparation method according to claim 7, characterized in that: The shear speed of the colloid mill is maintained at 1800 r / min - 2000 r / min, and the pre - heating temperature of asphalt and C9 resin is 110 - 120 °C.

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