Cold-mix asphalt mixture based on compound emulsifier system and preparation method of cold-mix asphalt mixture

Abstract

The invention discloses a cold-mix asphalt mixture based on a composite emulsifier system and a preparation method thereof. The mixture is prepared from the following raw materials: 100 parts of aggregate, 5-10 parts of composite emulsified asphalt, 3-5 parts of cement, 0.01-0.03 part of an anti-stripping agent and 0.09-0.12 part of composite fiber, the preparation method comprises the following steps: dissolving the compound emulsifier in water at 40-65 DEG C, adding the alcohol, and stirring to prepare liquid soap; heating the matrix asphalt, and grinding the soap liquid and the heated matrix asphalt to obtain composite emulsified asphalt; preheating the aggregate; the preparation method comprises the following steps: firstly, carrying out dry mixing on preheated aggregate and mineral powder, then adding composite emulsified asphalt for wet mixing, and finally adding cement and composite fibers for stirring to obtain a cold-mixed asphalt mixture; the cold-mixed asphalt mixture is subjected to three-stage compaction and then covered for moisture preservation, the humidity is kept to be larger than or equal to 80%, and the cold-mixed asphalt mixture is obtained. The problems that in the prior art, emulsified asphalt is poor in storage stability and prone to layering and flocculation, and consequently construction workability is affected are solved.

Description

Technical Field

[0001] This invention belongs to the field of road engineering materials technology, specifically relating to cold-mix asphalt mixtures based on a composite emulsifier system and their preparation method. Background Technology

[0002] Cold-mixed asphalt mixtures are widely used in road maintenance, low-temperature construction, and temporary road construction due to their advantages such as normal temperature construction, energy saving and environmental protection, and convenient construction. However, existing cold-mix asphalt mixtures mostly use a single type of emulsifier or a simple compound of emulsifiers without a scientifically designed mix proportion. Single emulsifiers rely on a single mechanism of action, resulting in poor storage stability of emulsified asphalt, making it prone to stratification and flocculation, severely affecting workability. For example, while traditional anionic emulsifiers have good charge matching with aggregates (such as basalt and limestone), they have weak resistance to salt precipitation and are prone to premature demulsification when exposed to moist aggregates; nonionic emulsifiers, while exhibiting excellent electrolyte resistance, have insufficient adhesion to asphalt, resulting in weak adhesion. Furthermore, existing technologies lack precise control over alcohol-based additives, failing to achieve a balance between the workability required for construction and the demulsification rate, often resulting in problems such as excessively rapid demulsification leading to mixture clumping or excessively slow demulsification affecting early strength formation. Furthermore, existing cold-mix asphalt mixtures generally use single fibers or no fiber reinforcement materials. Single fibers are difficult to form an effective three-dimensional reinforcement network in the asphalt matrix, and their inhibitory effect on crack propagation is limited. Especially under heavy traffic or frequent temperature changes, reflective cracking and fatigue cracking are prone to occur. Traditional cold-mix asphalt mixtures mostly adopt a suspended dense structure with insufficient coarse aggregate and unreasonable porosity control, which makes it easy for moisture to penetrate into the interior and cause peeling damage. At the same time, cement and other cementing materials are not introduced to work synergistically with asphalt, and only emulsified asphalt is relied on for bonding. At high temperatures, the asphalt softens and easily produces rutting, and at low temperatures, the brittleness increases, leading to cracking. Summary of the Invention

[0003] The purpose of this invention is to provide a cold-mix asphalt mixture based on a composite emulsifier system, which solves the problems of poor storage stability, easy stratification and flocculation in existing emulsified asphalt, which affect construction and workability.

[0004] Another object of the present invention is to provide a method for preparing cold-mix asphalt mixtures based on a composite emulsifier system.

[0005] The first technical solution adopted in this invention is a cold-mixed asphalt mixture based on a composite emulsifier system, which is composed of the following raw materials in parts by weight: 100 parts aggregate, 5-10 parts composite emulsified asphalt, 3-5 parts cement, 0.01-0.03 parts anti-stripping agent, and 0.09-0.12 parts composite fiber.

[0006] The first technical solution of the present invention is further characterized in that, Composite emulsified asphalt is made from the following components by weight percentage: 50%~70% base asphalt, 0.1%~7% composite emulsifier, 10%~20% alcohol, and the balance being water; The composite emulsifier is composed of anionic emulsifier, amphoteric emulsifier and nonionic emulsifier, with a weight ratio of (5~55):(3~5):(2~10). Anionic emulsifiers are selected from at least one of sulfate ester salts and sulfonates; The zwitterionic emulsifier is selected from at least one of aminocarboxylic acids and their salts, and betaines; The nonionic emulsifier is selected from at least one of fatty alcohol polyoxyethylene ether and alkylphenol polyoxyethylene ether; The alcohol is selected from at least one of ethanol, tert-butanol, and ethylene glycol, and the weight percentage of the alcohol in the composite emulsified asphalt is 15% to 20%.

[0007] The aggregate is basalt or limestone, and the mud content of the aggregate is ≤3% and the water content is ≤5%. The aggregate has a dense skeleton structure, with coarse aggregate accounting for 50% to 60%, fine aggregate accounting for 20% to 30%, mineral powder accounting for 5% to 10%, and porosity of 15% to 20%.

[0008] The composite fiber is composed of polyester fiber and viscose fiber in a weight ratio of 1:(0.05~0.1).

[0009] The composite emulsified asphalt also contains 3% to 5% by weight of SBR latex or SBS modifier.

[0010] The second technical solution adopted in this invention is a method for preparing cold-mix asphalt mixture based on a composite emulsifier system, comprising the following steps: S1. Dissolve the compound emulsifier in water at 40℃~65℃, add alcohol, and stir evenly to make soap solution; S2. Heat the base asphalt, and simultaneously feed the soap solution and the heated base asphalt to a colloid mill for grinding to obtain composite emulsified asphalt. S3. Preheat the aggregate; S4. First, dry mix the preheated aggregate with mineral powder, then add composite emulsified asphalt and wet mix, and finally add cement and composite fiber and mix to obtain pre-cooled asphalt mixture. S5. The pre-cold-mixed asphalt mixture is compacted in three stages, then covered and kept moist to maintain a humidity of ≥80% to obtain cold-mixed asphalt mixture.

[0011] The second technical solution of the present invention is further characterized in that, The pH value of the soap solution in step S1 is 2~3; In step S2, the penetration of the base asphalt is 60~80, and the temperature of the base asphalt after heating is 110℃~165℃. In step S3, the temperature of the preheated aggregate is 50℃~60℃.

[0012] In step S4, the cement is ordinary Portland cement with a specific surface area ≥300m² / kg.

[0013] The three-stage compaction method in step S5 is as follows: the initial compaction is carried out by static compaction with a 6t light roller for 1 to 2 passes, the secondary compaction is carried out by vibratory compaction with a 12t vibratory roller for 2 to 3 passes, and the final compaction is carried out by static compaction once to eliminate wheel tracks; the compacted cold-mix asphalt mixture is kept moist for more than 7 days.

[0014] The beneficial effects of this invention are: This invention reduces energy consumption and carbon emissions through a cold-mixing process, and reduces organic solvent pollution through the use of alcohols and water, meeting the requirements of green construction. It is also convenient to construct, has a short construction period, and is suitable for emergency repairs and large-area paving. The synergistic effect of composite emulsifiers and fibers reduces material usage and lowers costs. At the same time, the combination of anionic, amphoteric, and nonionic emulsifiers improves the stability of the emulsion through the dual effects of electrostatic repulsion and steric hindrance. Meanwhile, the coarse aggregate forms an interlocking skeleton, which, combined with the fine aggregate, fills the gaps, effectively balancing strength and drainage performance. Attached Figure Description

[0015] Figure 1 This is a schematic flowchart of the preparation method of cold-mix asphalt mixture based on the composite emulsifier system of the present invention; Detailed Implementation The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0016] Example 1 This invention relates to a cold-mix asphalt mixture based on a composite emulsifier system, comprising the following raw materials in parts by weight: 100 parts aggregate, 5-10 parts composite emulsified asphalt, 3-5 parts cement, 0.01-0.03 parts anti-stripping agent, and 0.09-0.12 parts composite fiber. This formulation, through the synergistic effect of its components, can significantly improve the overall performance of the cold-mix asphalt mixture.

[0017] Furthermore, the composite emulsified asphalt is made from the following components by weight percentage: 50%~70% base asphalt, 0.1%~7% composite emulsifier, 10%~20% alcohol, and the balance being water; The composite emulsifier is composed of anionic emulsifier, amphoteric emulsifier, and nonionic emulsifier, with a weight ratio of (5~55):(3~5):(2~10). The three types of emulsifiers have a synergistic effect. The anionic emulsifier can improve the dispersion stability of asphalt particles through charge repulsion. The amphoteric emulsifier can adjust the charge properties under different pH environments and enhance the system's adaptability. The nonionic emulsifier further prevents asphalt particles from agglomerating by means of steric hindrance. The combination of the three makes the composite emulsified asphalt less prone to demulsification during storage and construction, greatly improving its stability and thus ensuring the uniformity of the mixture.

[0018] Furthermore, the anionic emulsifier is selected from at least one of sulfate ester salts and sulfonates; when two are selected, their ratio can be arbitrary. The zwitterionic emulsifier is selected from at least one of aminocarboxylic acids and their salts, and betaine. When two are selected, their ratio can be arbitrary. Nonionic emulsifiers are selected from at least one of fatty alcohol polyoxyethylene ether and alkylphenol polyoxyethylene ether. When two types are selected, their ratio can be arbitrary. The selection of different types of emulsifiers can be flexibly adjusted according to the actual construction environment and raw material characteristics to achieve the best emulsification effect. For example, in a humid environment, the proportion of zwitterionic emulsifier can be appropriately increased to enhance the ability to resist water interference.

[0019] Example 2 Based on Example 1 above, this embodiment of the invention uses a composite emulsifier system in the cold-mix asphalt mixture where the alcohol is selected from at least one of ethanol, tert-butanol, and ethylene glycol, and the weight percentage of the alcohol in the composite emulsified asphalt is 15% to 20%. The alcohol acts as a co-emulsifier, its molecules can insert into the water-asphalt interface, reducing interfacial tension and promoting the adsorption and arrangement of the emulsifier at the interface. Simultaneously, it adjusts the viscosity of the system, making the composite emulsified asphalt easier to combine with aggregates during mixing, thus improving workability and workability.

[0020] Furthermore, the aggregate is basalt or limestone, and the aggregate has a mud content of ≤3% and a water content of ≤5%. The aggregate gradation is a dense skeleton structure, with coarse aggregate accounting for 50%–60%, fine aggregate for 20%–30%, mineral powder for 5%–10%, and a porosity of 15%–20%. Basalt and limestone have high strength and rough surfaces, which facilitates good adhesion with the binder. Low mud and water content prevents soil from adsorbing emulsifiers and water from interfering with the cementing process. In this dense skeleton structure, coarse aggregate forms a robust framework to bear the load, while fine aggregate and mineral powder fill the voids. With an appropriate porosity, both drainage and structural density are ensured, improving the mixture's resistance to deformation and its durability.

[0021] Furthermore, the composite fiber is composed of polyester fiber and viscose fiber in a weight ratio of 1:(0.05~0.1). Polyester fiber has high strength and aging resistance, which can enhance the crack resistance and toughness of the mixture; viscose fiber has good hydrophilicity, can quickly absorb moisture and bond with the binder, improving early strength. The combination of the two in this ratio can synergistically improve the mechanical properties and fatigue resistance of the mixture.

[0022] Example 3 The present invention relates to a cold-mix asphalt mixture based on a composite emulsifier system, which is composed of the following raw materials in parts by weight: 100 parts aggregate, 5-10 parts composite emulsified asphalt, 3-5 parts cement, 0.01-0.03 parts anti-stripping agent, and 0.09-0.12 parts composite fiber.

[0023] Furthermore, the composite emulsified asphalt also contains 3% to 5% by weight of SBR latex or SBS modifier. SBR latex can improve the low-temperature crack resistance and flexibility of the mixture by forming an interpenetrating network structure with the asphalt; SBS modifier can enhance the high-temperature stability and elastic recovery of the asphalt, thus enabling cold-mix asphalt mixtures to maintain good performance under different temperature conditions and broadening their application range.

[0024] Example 4 This invention relates to a method for preparing cold-mix asphalt mixtures based on a composite emulsifier system, used to prepare the aforementioned cold-mix asphalt mixture based on a composite emulsifier system, such as... Figure 1 As shown, it includes the following steps: S1. Dissolve the composite emulsifier in water at 40℃~65℃. This temperature range promotes the full dissolution of emulsifier molecules and maintains their activity. After adding alcohol, stir evenly to prepare a soap solution, controlling the pH value of the soap solution to 2~3. An acidic environment can enhance the emulsifier's adsorption capacity for asphalt, inhibit asphalt particle aggregation, and provide a stable chemical environment for subsequent emulsification reactions.

[0025] S2. Select a base asphalt with a penetration of 60-80 (asphalt in this penetration range has both good fluidity and adhesion, making it suitable for cold-mix processes). Heat it to 110℃-165℃. This temperature reduces the viscosity of the asphalt to facilitate dispersion and avoids the degradation of asphalt performance caused by high temperatures. Simultaneously feed the soap solution and the heated base asphalt to a colloid mill. Through high-speed shearing and grinding, the asphalt is uniformly dispersed in the soap solution as micron-sized particles, forming a stable composite emulsified asphalt.

[0026] S3. Preheat the aggregate to 50℃~60℃. Preheating can remove excess moisture from the surface of the aggregate and improve the temperature compatibility between the aggregate and the composite emulsified asphalt. This prevents the emulsified asphalt from breaking down due to sudden cooling caused by low-temperature aggregate, and ensures that the asphalt can evenly coat the surface of the aggregate during subsequent mixing.

[0027] S4. First, dry-mix the preheated aggregate and mineral powder for 10-15 seconds to ensure the mineral powder adheres evenly to the aggregate surface and enhances interfacial bonding. Then, add the composite emulsified asphalt and wet-mix for 30-40 seconds to fully coat the aggregate with the emulsified asphalt. Finally, add cement and composite fibers and mix for 20-30 seconds. The cement used is ordinary Portland cement with a specific surface area ≥300m² / kg (a high specific surface area can increase the cement hydration reaction rate and enhance the early strength of the mixture). Through multi-stage mixing, the components are ensured to be evenly dispersed to obtain a stable pre-cooled asphalt mixture.

[0028] S5. A three-stage compaction process is adopted for pre-cold-mixed asphalt mixtures: Initial compaction uses a 6t light roller for 1-2 passes of static compaction to stabilize the mixture structure and prevent aggregate displacement caused by heavy rolling; secondary compaction uses a 12t vibratory roller for 2-3 passes to utilize vibration energy to increase the mixture density to the design requirements; final compaction uses one pass of static compaction to eliminate wheel tracks and ensure road surface smoothness. After compaction, the mixture is covered and kept moist for at least 7 days, maintaining an ambient humidity of ≥80% to provide sufficient moisture for cement hydration, promote continuous strength growth, and ultimately form a high-performance cold-mixed asphalt mixture.

[0029] As can be seen from the above, through the synergistic effect of composite emulsifiers, fibers, cement and modifiers, combined with a dense skeleton structure and precise process control, high durability, convenient construction and environmental protection of cold-mix asphalt mixtures are achieved, which has significant engineering application value.

[0030] Example 5 The following raw materials were weighed in this embodiment: 100 parts aggregate, 5 parts composite emulsified asphalt, 5 parts cement, 0.03 parts anti-stripping agent, and 0.12 parts composite fiber.

[0031] The composite emulsified asphalt is made from the following components by weight percentage: 70% base asphalt, 7% composite emulsifier, 15% alcohol, and the balance being water; The composite emulsifier is composed of anionic emulsifier, amphoteric emulsifier and nonionic emulsifier, with a weight ratio of 20:3:8.

[0032] After weighing the raw materials, prepare according to the following steps: S1. Dissolve the compound emulsifier in water at 65°C, add alcohol, and stir well to make soap solution with a pH value of 2. S2. Select a base asphalt with a penetration of 80 and heat it to a temperature of 165°C. Simultaneously feed the soap solution and the heated base asphalt to a colloid mill for grinding to obtain composite emulsified asphalt. S3. Preheat the aggregate to 50°C; S4. First, dry mix the preheated aggregate with mineral powder, then add composite emulsified asphalt and wet mix, and finally add cement and composite fiber and mix. The cement is ordinary Portland cement with a specific surface area ≥300m² / kg to obtain cold-mix asphalt mixture. S5. Three-stage compaction is adopted for cold-mixed asphalt mixture. Specifically, the initial compaction is carried out by static compaction twice with a 6t light roller, the intermediate compaction is carried out by vibratory compaction twice with a 12t vibratory roller, and the final compaction is carried out by static compaction once to eliminate wheel tracks. Cover and moisturize for at least 7 days, maintaining a humidity of ≥80%, to obtain cold-mix asphalt mixture.

[0033] Example 6 This embodiment verifies the differences in road performance between the present technical solution (experimental group) and traditional cold-mixed aggregate (comparison group 1) and commercially available high-performance cold-mixed aggregate (comparison group 2).

[0034] Variable control: Except for core technical parameters (emulsifier system, fiber type, aggregate gradation, modifier), other conditions (aggregate type, curing conditions, test methods) remain consistent.

[0035] The comparison of raw material ratios is shown in Table 1 below: Table 1 Raw Material Comparison Table

[0036] Composition of composite emulsifier (experimental group): Anionic (sodium sulfonate): Amphoteric (betaine): Nonionic (fatty alcohol polyoxyethylene ether) = 30:4:6; The differences in preparation processes are shown in Table 2 below: Table 2 Comparison of Preparation Processes

[0037] Performance tests were conducted, and the test data results are shown in Table 3 below: Table 3 Performance Test Comparison Results

[0038] As shown in Table 3 above, the flexural strain of this experimental group was 3250 με (compared to 2650 με in control group 2). The three-dimensional network formed by the composite fiber (polyester + viscose) effectively inhibited crack propagation, which was superior to single fiber reinforcement. This experimental group exhibited excellent low-temperature crack resistance. The dynamic stability was 5200 cycles / mm (1.7 times higher than the standard). Cement (4%) and SBR latex (4%) synergistically enhanced the stiffness of the asphalt matrix, reducing high-temperature rutting. Furthermore, the loading cycles of this experimental group reached 1.25 million cycles (1.8 times that of control group 1). The multi-component modification improved the fatigue damage resistance of the mixture. Experimental data show that this technical solution, through a composite emulsifier system, multi-component reinforcing materials, and precise process control, significantly outperforms existing conventional technologies in terms of durability, high and low temperature performance, and fatigue life.

[0039] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0040] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A cold-mix asphalt mixture based on a composite emulsifier system, characterized in that, It is composed of the following raw materials in parts by weight: 100 parts aggregate, 5-10 parts composite emulsified asphalt, 3-5 parts cement, 0.01-0.03 parts anti-stripping agent, and 0.09-0.12 parts composite fiber.

2. The cold-mix asphalt mixture based on a composite emulsifier system according to claim 1, characterized in that, The composite emulsified asphalt is made from the following components by weight percentage: 50%~70% base asphalt, 0.1%~7% composite emulsifier, 10%~20% alcohol, and the balance being water; The composite emulsifier is composed of anionic emulsifier, amphoteric emulsifier and nonionic emulsifier, with a weight ratio of (5~55):(3~5):(2~10).

3. The cold-mix asphalt mixture based on a composite emulsifier system according to claim 2, characterized in that, The anionic emulsifier is selected from at least one of sulfate ester salts and sulfonates; The zwitterionic emulsifier is selected from at least one of aminocarboxylic acids and their salts, and betaines; The nonionic emulsifier is selected from at least one of fatty alcohol polyoxyethylene ether and alkylphenol polyoxyethylene ether; The alcohol is selected from at least one of ethanol, tert-butanol, and ethylene glycol, and the weight percentage of the alcohol in the composite emulsified asphalt is 15% to 20%.

4. The cold-mix asphalt mixture based on a composite emulsifier system according to claim 1, characterized in that, The aggregate is basalt or limestone, and the aggregate has a mud content of ≤3% and a water content of ≤5%. The aggregate has a dense skeleton structure, with coarse aggregate accounting for 50% to 60%, fine aggregate accounting for 20% to 30%, mineral powder accounting for 5% to 10%, and porosity of 15% to 20%.

5. The cold-mix asphalt mixture based on a composite emulsifier system according to claim 1, characterized in that, The composite fiber is composed of polyester fiber and viscose fiber in a weight ratio of 1:(0.05~0.1).

6. The cold-mix asphalt mixture based on a composite emulsifier system according to claim 1, characterized in that, The composite emulsified asphalt also contains 3% to 5% by weight of SBR latex or SBS modifier.

7. A method for preparing cold-mix asphalt mixture based on a composite emulsifier system, characterized in that, The method for preparing cold-mix asphalt mixtures based on a composite emulsifier system as described in any one of claims 1 to 6 comprises the following steps: S1. Dissolve the compound emulsifier in water at 40℃~65℃, add alcohol, and stir evenly to make soap solution; S2. Heat the base asphalt, and simultaneously feed the soap solution and the heated base asphalt to a colloid mill for grinding to obtain composite emulsified asphalt. S3. Preheat the aggregate; S4. First, dry mix the preheated aggregate with mineral powder, then add composite emulsified asphalt and wet mix, and finally add cement and composite fiber and mix to obtain pre-cooled asphalt mixture. S5. The pre-cold-mixed asphalt mixture is compacted in three stages, then covered and kept moist to maintain a humidity of ≥80% to obtain cold-mixed asphalt mixture.

8. The method for preparing cold-mix asphalt mixture based on a composite emulsifier system according to claim 7, characterized in that, The pH value of the soap solution in step S1 is 2~3; The penetration of the base asphalt in step S2 is 60~80, and the temperature of the base asphalt after heating is 110℃~165℃; In step S3, the temperature of the preheated aggregate is 50℃~60℃.

9. The method for preparing cold-mix asphalt mixture based on a composite emulsifier system according to claim 7, characterized in that, The cement used in step S4 is ordinary Portland cement with a specific surface area ≥300m² / kg.

10. The method for preparing cold-mix asphalt mixture based on a composite emulsifier system according to claim 7, characterized in that, The three-stage compaction method in step S5 is as follows: the initial compaction is carried out by static compaction with a 6t light roller for 1 to 2 passes, the secondary compaction is carried out by vibratory compaction with a 12t vibratory roller for 2 to 3 passes, and the final compaction is carried out by static compaction once to eliminate wheel tracks; the compacted cold-mix asphalt mixture is kept moist for more than 7 days.

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