Foaming agent for rubber modified asphalt as well as preparation method and application of foaming agent

Abstract

The invention discloses a foaming agent for rubber modified asphalt as well as a preparation method and application of the foaming agent. The foaming agent is composed of 40%-60% of a friction resistance reducing agent, 20%-35% of a foam stabilizer and 5%-15% of an auxiliary agent. Wherein the friction resistance reducing agent is white oil; the foam stabilizer is polyacrylic acid and a salt compound thereof; the auxiliary agent is sodium carbonate. A part A (white oil phase and sodium carbonate emulsification) and a part B (polyacrylic acid and salt compounds thereof) of the foaming agent are prepared step by step, so that reduction of internal friction resistance in the foaming process and a synergistic effect of saponification reaction and double-electric-layer stable foam are realized. The foaming agent can significantly improve the expansion rate and half-life period of rubber modified foamed asphalt, optimizes the rubber dispersibility and pavement durability, and is suitable for preparation of foamed asphalt in road engineering.

Description

Technical Field

[0001] The present invention relates to the technical field of road engineering materials, and particularly relates to a foaming agent for rubber-modified asphalt, its preparation method and application. The aim is to optimize the foaming characteristics of rubber-modified asphalt from different stages of foam asphalt preparation (foam formation stage, foam stability maintenance stage) through the effective compound application of white oil, sodium carbonate, polyacrylic acid and its salt compounds, and finally improve the application effect of foam asphalt in road paving and maintenance. Background Art

[0002] Foam asphalt is widely used in the field of road engineering, and its foaming characteristics directly affect the uniformity of the mixture of asphalt and aggregates, the coating effect, and the construction quality and durability of the final road surface. Excellent foaming characteristics can make the asphalt disperse evenly when mixed with aggregates, ensure that the aggregates are well "spot-welded" by the asphalt, and thus improve the strength and stability of the road surface. However, in the process of preparing rubber-modified foam asphalt at present, there are many challenges in improving its foaming characteristics.

[0003] Traditional asphalt foaming methods mostly rely on single components (such as surfactants) to adjust the foaming performance, and there are often problems such as poor foam stability and low expansion ratio. The high viscosity of ordinary rubber asphalt makes it difficult for water to evaporate and bubbles to form, and the formed bubbles are easy to break in a short time, which is difficult to meet the requirements of actual engineering for the performance of foam asphalt, affects the overall performance of the road surface, and limits the application layer and scope of foam asphalt. At the same time, the compatibility between rubber and asphalt is poor, resulting in uneven dispersion of rubber in asphalt, which affects the enhancement effect of rubber on foam stability. At present, there is no research and application on effectively compounding white oil, sodium carbonate, polyacrylic acid and its salt compounds to improve the foaming characteristics of modified foam asphalt, and the internal friction resistance reduction effect and double-layer electric layer stable foam mechanism in the foaming process of rubber-modified asphalt have not been optimized. Therefore, in order to solve these problems, developing a new composite foaming agent to optimize the foaming characteristics of rubber-modified asphalt has important practical significance for improving the quality of road engineering. Summary of the Invention

[0004] Object of the Invention

[0005] The present invention relates to the technical field of road engineering materials, and particularly relates to a foaming agent for rubber-modified asphalt, its preparation method and application. The aim is to optimize the foaming characteristics of rubber-modified asphalt from different stages of foam asphalt preparation (foam formation stage, foam stability maintenance stage) through the effective compound application of white oil, sodium carbonate, polyacrylic acid and its salt compounds, and finally improve the application effect of foam asphalt in road paving and maintenance.

[0006] Technical Solution

[0007] A foaming agent for rubber - modified asphalt according to the present invention, calculated by mass percentage, comprises the following components: friction reducer 40% - 60%, foam stabilizer 20% - 35%, auxiliary agent 5% - 15%.

[0008] Furthermore, the friction reducer is white oil.

[0009] Furthermore, the foam stabilizer is polyacrylic acid and its salt compounds, selected from one or more combinations of polyacrylic acid, sodium polyacrylate, potassium polyacrylate, and ammonium polyacrylate.

[0010] Furthermore, the auxiliary agent is sodium carbonate.

[0011] A preparation method of a foaming agent for rubber - modified asphalt according to the present invention is carried out according to the following steps:

[0012] S1. The preparation method separately prepares part A of the foaming agent for rubber - modified asphalt and part B of the foaming agent for rubber - modified asphalt;

[0013] S2. The preparation method of part A of the foaming agent is as follows: First, based on the type of polyacrylic acid and its salt compounds, determine the matching dosage of sodium carbonate according to its optimal hydrolysis pH range. Secondly, premix white oil with sodium carbonate solution, heat to 80°C, and carry out preliminary emulsification by mechanical stirring for 10 min. Then, slowly increase the temperature to 110°C to remove water. Finally, carry out high - speed shear emulsification at 4500 r / min for 45 min and then cool to room temperature to obtain part A of the foaming agent;

[0014] S3. Use one or more combinations of polyacrylic acid, sodium polyacrylate, potassium polyacrylate, and ammonium polyacrylate as part B of the asphalt foaming agent;

[0015] S4. Under normal temperature and light - proof conditions, separately and hermetically store part A and part B of the foaming agent for rubber - modified asphalt.

[0016] An application method of a foaming agent for rubber - modified foamed asphalt according to the present invention has the following application steps:

[0017] S1. Heat the rubber - modified asphalt to a molten - flow state;

[0018] S2. Slowly add part A of the foaming agent according to 3% - 7% of the mass of the matrix asphalt in the rubber - modified asphalt, raise the temperature of the rubber - modified asphalt to 180°C, and carry out high - speed shear dispersion at 5000 r / min for 30 min;

[0019] S3. Put the above - prepared asphalt into an asphalt foaming machine to make it in a heating - cycle state at the foaming temperature;

[0020] S4. Slowly drop part B of the foaming agent into the rubber-modified asphalt at a rate of 1% - 2% of the mass of the base asphalt in the asphalt, and circulate and stir in the asphalt circulation device for 35 minutes.

[0021] S5. Start the foaming machine to prepare foamed asphalt, and conduct foaming treatment according to the conventional water-based foaming process.

[0022] S6. Conduct performance tests on the foamed asphalt, such as expansion ratio, half-life, stability, and uniformity.

[0023] Principle of the Invention

[0024] 1. White oil: As a key component for reducing the internal frictional resistance (abbreviation: internal frictional resistance) of the rubber-modified asphalt system, it mainly acts in the foaming stage of rubber-modified foamed asphalt. From the perspective of molecular interactions, white oil with a low molecular weight can penetrate into the gaps between asphalt molecules, weaken the intermolecular forces (van der Waals forces, hydrogen bonds, and other secondary bonds) between asphalt molecules, reduce the internal frictional resistance of the asphalt system, and thus improve the kinetic conditions for water evaporation and bubble formation. During the foaming process, an asphalt environment with lower internal frictional resistance is conducive to the rapid formation and stable growth of bubbles, thereby increasing the expansion ratio of foamed asphalt. At the same time, based on the interfacial chemistry theory, there are complex interfacial chemical interactions between white oil, asphalt, and water. White oil molecules can adsorb on the "asphalt-water" interface to form an oriented arrangement layer, reduce the interfacial tension, and promote the foaming and growth of bubbles. In addition, according to the dispersion theory, white oil with a high affinity for rubber can regulate the balance relationship between the surface adsorption energy and volume exclusion effect of rubber, keep the rubber spacing stable at a certain length, reduce the aggregation tendency between rubber particles, reduce the entanglement between molecular chains, improve its dispersion uniformity in the asphalt matrix, and effectively inhibit the formation of uneven droplets at the bottom of the asphalt foam film caused by rubber particle agglomeration (Note: According to the foam dynamics principle, the existence of such uneven droplets will damage the original foam structure, making the substances in the foam film show an uneven situation with less at the top and more at the bottom, exacerbating the rupture of the bubble film), which also plays an important role in maintaining the stability stage (abbreviation: "stability maintenance stage") of rubber-modified foamed asphalt.

[0025] 2. Sodium carbonate: Its main function is to transform the neutral or weakly acidic rubber-modified asphalt system into a weakly alkaline environment and undergo a saponification reaction with the asphalt system. Under alkaline conditions, fatty acids or other organic acids in the asphalt will react with sodium carbonate in a saponification reaction to produce by-products such as soap (fatty acid salts) and glycerol. The reaction products can act as emulsifiers, which can significantly reduce the surface tension at the gas-liquid interface, making it easier for water vapor to enter and disperse in the asphalt, promoting the formation of bubbles; moreover, this emulsifier can reduce the viscosity of the asphalt, thereby improving the rheology of the asphalt to increase the expansion ratio of rubber foamed asphalt.

[0026] 3. Polyacrylic acid and its salts: Based on the DLVO theory and charge effect, this material is selected and mainly acts on the "stabilization stage" of foamed asphalt. In a weakly alkaline modified asphalt system, the carboxylate ions (-COO - ) hydrolyzed from polyacrylic acid and its salts carry negative charges. After adsorbing on the surface of the bubble film, they can attract counterions (such as sodium ions, potassium ions, etc.) to form a stable double electric layer, and the absolute value of the Zeta potential of the double electric layer > 40 mV. According to Coulomb's law, there will be a repulsive force between two objects with the same charge. The existence of this double electric layer makes an electrostatic repulsive force generated between adjacent bubble films, preventing the contact and merger of bubble films, thereby prolonging the lifespan of the foam. In addition, the double electric layer can also change the surface properties of the bubble film and reduce the influence of capillary action. Capillary action will cause the liquid to flow from thick places to thin places, eventually making the bubble film thinner and rupturing. The existence of the double electric layer can slow down this process: (1) Increase the adhesion energy: The double electric layer increases the adhesion energy between the bubble film and the liquid, making the liquid not easy to lose; (2) Improve the elastic modulus: The bubble film with a charged layer has a higher elastic modulus and can better resist external pressure and deformation. In addition, under weak alkaline conditions, the hydrolysis product of polyacrylic acid and its salts is carboxylate ions, and the hydrolysis efficiency ≥ 90% within the pH range of 8 - 10. Therefore, the molar ratio of it to sodium carbonate is required to be controlled between 1:1 and 1:2.

[0027] 4. Synergistic starting effect for promoting the foaming reaction: White oil enhances the fluidity of the system by reducing the internal frictional resistance of the rubber-modified foamed asphalt system, providing a more favorable molecular motion environment for the saponification reaction between sodium carbonate and organic acids in asphalt and the hydrolysis reaction of polyacrylic acid and its salts. Sodium carbonate undergoes a saponification reaction in an alkaline environment to generate an emulsifier, which further changes the viscosity and rheology of asphalt. The emulsifier can more quickly promote the dispersion of water in asphalt, creating conditions for foaming. At the same time, the hydrolysis reaction of polyacrylic acid and its salts is also smoother in the low-viscosity environment created by white oil and the weakly alkaline environment provided by sodium carbonate. The carboxylate ions (-COO - ) hydrolyzed can be adsorbed on the surface of potential bubble films more timely, preparing in advance for stabilizing the bubble film.

[0028] 5. Synergistic mechanism for stabilizing bubble growth and maintenance: At the initial stage of bubble formation, white oil reduces the internal frictional resistance of the rubber-modified asphalt system, enabling the bubbles to expand rapidly. At this time, the emulsifier generated by sodium carbonate adsorbs on the surface of the bubbles, reducing the surface tension of the "gas-liquid" interface and further promoting the growth of the bubbles. The double electric layer generated by the hydrolysis of polyacrylic acid and its salts begins to play a role. As the bubbles expand, the negatively charged carboxylate ions (-COO -) It accumulates on the surface of the bubble film, attracts counterions to form an electric double layer, and the electrostatic repulsion generated synergizes with the role of the emulsifier in reducing the surface tension to prevent the bubble film from breaking due to excessive stretching, ensuring that the bubbles can stably grow to a larger size. During the bubble stability stage, the emulsifier generated by sodium carbonate continues to stabilize the "gas-liquid" interface, while the electric double layer formed by polyacrylic acid and its salts prevents the merger and fusion of bubble films from the charge aspect. There are differences in the charge density, hydrolysis rate, and pH adaptability of different polyacrylic acids and their salts, and it is necessary to optimize their effects by synergistically using friction reducer and auxiliary agents. The three act synergistically, greatly prolonging the lifespan of the foam and significantly enhancing the stability of the foam.

[0029] Beneficial effects

[0030] 1. By effectively compounding white oil, sodium carbonate, and polyacrylic acid and its salts, the present invention fully exerts the targeted effects and synergistic effects of the three substances. The addition of white oil significantly reduces the internal frictional resistance of the rubber-modified asphalt system. Sodium carbonate undergoes a saponification reaction to generate an emulsifier, and polyacrylic acid and its salts hydrolyze to form an electric double layer to stabilize the bubble film, thereby greatly increasing the expansion ratio and half-life of the rubber-modified foamed asphalt and optimizing the foaming characteristics of the rubber-modified foamed asphalt.

[0031] 2. The rubber-modified foamed asphalt prepared by using the composite foaming agent of the present invention can better wrap the aggregates in road engineering applications, improve the strength and durability of the asphalt mixture, effectively extend the service life of the road surface, and reduce the road maintenance cost.

[0032] 3. The preparation and use methods of the composite foaming agent of the present invention are simple in operation and low in cost, suitable for industrial production, and have application prospects. Specific embodiments

[0033] To better understand the present invention, the following further elaborates on the present invention in detail with reference to specific embodiments, but the protection scope of the present invention is not limited to these embodiments.

[0034] Example 1

[0035] Take 100 g of white oil and a saturated solution of sodium carbonate with a solid mass of 25 g. After premixing the white oil and the sodium carbonate solution, heat it to 80 °C and perform preliminary emulsification by mechanical stirring for 10 min. Then, slowly increase the temperature to 110 °C to remove water. Finally, perform high-speed shear emulsification at 4500 r / min for 45 min and then cool it to room temperature to obtain part A of the foaming agent;

[0036] Take 20 g of polyacrylic acid as part B of the foaming agent;

[0037] Take 2 kg of rubber powder modified asphalt (the mass ratio of rubber powder to asphalt is 4:100), heat it to a flowing state at 160 °C, slowly add part A of 50 g of foaming agent, then raise the temperature of the rubber modified asphalt to 180 °C, and perform high-speed shear dispersion at 5000 r / min for 30 min;

[0038] Pour the above-prepared foamed asphalt into a foamed asphalt foaming machine, turn on the heating cycle, make it circulate and stir at the foaming temperature of 150 °C, slowly drop part B of 10 g of foaming agent at a rate of 1 g / min, perform circulatory agitation and development for 35 min, then start the foaming machine, and prepare foamed asphalt according to the conventional water-based foaming process. Test the expansion ratio and half-life performance of the foamed asphalt. The technical performance indicators are shown in Table 1.

[0039] Table 1 Technical indicators of the foamed asphalt prepared in Example 1

[0040]

[0041] Example 2

[0042] Take 60 g of white oil and a saturated sodium carbonate solution with a solid mass of 15 g. After premixing the white oil and the sodium carbonate solution, heat it to 80 °C, perform mechanical stirring for 10 min for preliminary emulsification, then slowly increase the temperature to 110 °C to remove water, and finally perform high-speed shear emulsification at 4500 r / min for 45 min, and then cool it to room temperature to obtain part A of the foaming agent;

[0043] Take 20 g of sodium polyacrylate and 35 g of polyacrylic acid, stir evenly to obtain part B of the foaming agent;

[0044] Take 2 kg of rubber powder modified asphalt (the mass ratio of rubber powder to asphalt is 6:100), heat it to a flowing state at 160 °C, add 40 g of part A of the foaming agent for rubber modified asphalt, then raise the temperature of the rubber modified asphalt to 180 °C, and perform high-speed shear dispersion at 5000 r / min for 30 min;

[0045] Pour the above-prepared foamed asphalt into a foamed asphalt foaming machine, turn on the heating cycle, make it circulate and stir at the foaming temperature of 170 °C, slowly drop part B of 20 g of foaming agent at a rate of 1 g / min, perform circulatory agitation and development for 35 min, then start the foaming machine, and prepare foamed asphalt according to the conventional water-based foaming process. Test the expansion ratio and half-life performance of the foamed asphalt. The technical performance indicators are shown in Table 2.

[0046] Table 2 Technical indicators of the foamed asphalt prepared in Example 2

[0047]

[0048] Comparative Example 1

[0049] Without adding the composite foaming agent of the present invention, rubber-modified foamed asphalt was prepared according to the conventional water machine foaming process. After testing, the expansion ratio of the rubber-modified foamed asphalt was 12 to 13 times, and the foam half-life was 11 to 15 s.

[0050] By comparing the results of Example 1, Example 2 and Comparative Example 1, it can be clearly seen that the composite foaming agent of the present invention can significantly improve the foaming characteristics of rubber-modified foamed asphalt and has good application effects.

[0051] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A foaming agent for rubber-modified asphalt, characterized in that, Calculated by mass percentage, the foaming agent comprises the following components: 40% - 60% of friction reducer, 20% - 35% of foam stabilizer, and 5% - 15% of auxiliary agent.

2. The preparation method of a foaming agent for rubber modified asphalt according to claim 1, characterized in that: The friction reducer is white oil.

3. The preparation method of a foaming agent for rubber modified asphalt according to claim 1, characterized in that: The foam stabilizer is polyacrylic acid and its salt compounds, selected from one or more combinations of polyacrylic acid, sodium polyacrylate, potassium polyacrylate, and ammonium polyacrylate.

4. The preparation method of a foaming agent for rubber modified asphalt according to claim 1, characterized in that: The auxiliary agent is sodium carbonate.

5. A method for preparing a foaming agent for rubber modified asphalt according to claim 1, characterized in that, The preparation method is carried out according to the following steps: S1. The preparation method separately prepares part A of the foaming agent for rubber-modified asphalt and part B of the foaming agent for rubber-modified asphalt. S2. The preparation method of part A of the foaming agent is as follows: First, based on the type of polyacrylic acid and its salt compounds, determine the matching dosage of sodium carbonate according to its optimal hydrolysis pH range. Second, premix white oil with sodium carbonate solution, heat it to 80°C, and perform preliminary emulsification by mechanical stirring for 10 min. Then, slowly increase the temperature to 110°C to remove water. Finally, perform high-speed shear emulsification at 4500 r / min for 45 min and then cool it to room temperature to obtain part A of the foaming agent. S3. Use one or more combinations of polyacrylic acid, sodium polyacrylate, potassium polyacrylate, and ammonium polyacrylate as part B of the asphalt foaming agent. S4. Under normal temperature and light-proof conditions, separately store part A and part B of the foaming agent for rubber-modified asphalt in sealed containers.

6. A foaming agent for rubber-modified asphalt prepared by the method according to any one of claims 1 - 5.

7. The application method of the foaming agent for rubber modified asphalt according to claim 6, characterized in that, Comprises the following steps: S1. Heat the rubber-modified asphalt to a molten flow state. S2. Slowly add part A of the foaming agent according to 3% - 7% of the mass of the matrix asphalt in the rubber-modified asphalt, raise the temperature of the rubber-modified asphalt to 180°C, and perform high-speed shear dispersion at 5000 r / min for 30 min. S3. Put the above-prepared asphalt into an asphalt foaming machine and keep it in a heating cycle state at the foaming temperature. S4. Slowly drop part B of the foaming agent according to 1% - 2% of the mass of the matrix asphalt in the rubber-modified asphalt and perform cyclic stirring in the asphalt circulation device for 35 min. S5. Start the foaming machine to prepare foamed asphalt and perform foaming treatment according to the conventional water-based foaming process. S6. Test the properties of the foamed asphalt such as expansion ratio, half-life, stability, and uniformity.

Images