Colored asphalt concrete and method for producing the same

Abstract

The application relates to the technical field of asphalt concrete, and particularly discloses colored asphalt concrete and a preparation method thereof. The colored asphalt concrete provided by the application comprises the following components in parts by weight: 40-60 parts of 5-10 mm limestone, 5-10 parts of 3-5 mm limestone, 30-35 parts of machine-made sand, 0.5-2 parts of filler, 1.5-4 parts of pigment, 0.5-1 part of a color fixing agent and 2-8 parts of asphalt; the color fixing agent is a mixture of titanium dioxide, octadecyl trimethoxysilane modified bentonite and a coupling agent; further, the weight ratio of the titanium dioxide, the octadecyl trimethoxysilane modified bentonite and the coupling agent is (5-15):(70-85):(0.5-2). The colored asphalt concrete provided by the application has excellent coloring durability, and is not prone to fading, discoloring and other problems after long-term use, and can still maintain good color and luster under long-term external environment.

Description

Technical Field

[0001] This application relates to the field of asphalt concrete technology, specifically to a colored asphalt concrete and its preparation method. Background Technology

[0002] Colored asphalt concrete, as a pavement material that combines decorative and functional properties, is widely used in parks, squares, sidewalks, and scenic roads. Its color is primarily achieved by adding inorganic or organic pigments to the asphalt mixture.

[0003] However, traditional colored asphalt concrete faces serious color durability problems in practical use. On the one hand, asphalt itself contains low-polarity small-molecule components such as aromatic hydrocarbons and a small amount of polar compounds. These components gradually migrate to the road surface during long-term use, covering the pigment particles and causing the road surface to darken, fade, or even discolor. On the other hand, long-term exposure to external environments such as sunlight (ultraviolet rays), rainwater erosion, and vehicle wear accelerates pigment degradation and shedding, seriously affecting the aesthetics and service life of the road surface. Currently, although some literature reports improving the performance of the mixture by adding anti-stripping agents or polymer resins, the effects are not significant.

[0004] Therefore, there is an urgent need to develop a type of colored asphalt concrete with good coloring durability, so that the concrete color can maintain a good luster even under long-term external environmental conditions. Summary of the Invention

[0005] In order to overcome the problems of fading and discoloration and poor coloring durability of existing colored asphalt concrete after long-term use, this application provides a colored asphalt concrete and its preparation method.

[0006] In a first aspect, this application provides a colored asphalt concrete, which adopts the following technical solution: A colored asphalt concrete comprises the following components in parts by weight: 40-60 parts of 5-10mm limestone, 5-10 parts of 3-5mm limestone, 30-35 parts of manufactured sand, 0.5-2 parts of filler, 1.5-4 parts of pigment, 0.5-1 parts of color-fixing agent, and 2-8 parts of asphalt; The fixing agent is a mixture of titanium dioxide, octadecyltrimethoxysilane modified bentonite, and a coupling agent.

[0007] This application provides a colored asphalt concrete that significantly improves the coloring durability of colored asphalt concrete by introducing a ternary composite color-fixing agent composed of titanium dioxide, octadecyltrimethoxysilane modified bentonite and a coupling agent, and combining it with limestone, manufactured sand, filler and asphalt components with specific gradation. This allows the colored asphalt concrete to maintain good color even under external environmental conditions for 3-5 years, fundamentally solving the problem of fading and discoloration of traditional colored asphalt concrete under long-term external exposure.

[0008] In this application, the octadecyltrimethoxysilane-modified bentonite is obtained by organosilane modification of bentonite. This modification increases the interlayer spacing of the bentonite and introduces long-chain alkyl groups onto its surface, thereby improving its specific surface area and organic affinity. This allows for the efficient adsorption and anchoring of low-polarity, easily migrating components such as aromatic hydrocarbons inherent in asphalt. Simultaneously, its layered porous crystal structure physically blocks and confines various small molecules (including some polar components) in the asphalt, inhibiting their migration to the surface and fundamentally preventing color darkening, discoloration, and even fading caused by asphalt migration. Furthermore, the octadecyltrimethoxysilane-modified bentonite itself has a layered porous crystal structure, which can adsorb and bind inorganic pigment particles, effectively preventing pigment migration and precipitation, thus reducing road surface discoloration and fading at the source. Titanium dioxide not only serves as a white base pigment to enhance color saturation but also absorbs ultraviolet light, significantly improving the asphalt's resistance to light and heat aging and extending the color durability of asphalt concrete. The addition of coupling agent can improve the interfacial bonding force between titanium dioxide, octadecyltrimethoxysilane modified bentonite and organic asphalt matrix. On the one hand, it ensures that the fixing agent is uniformly dispersed and firmly anchored in the mixture, and on the other hand, it reduces water penetration and avoids the loss of fixing agent due to mechanical wear or water erosion.

[0009] In some embodiments, the amount of the fixing agent added may be 0.5-0.8 parts or 0.8-1 parts.

[0010] In one specific implementation, the amount of the fixing agent added may be 0.5 parts, 0.8 parts, or 1 part.

[0011] Optionally, the weight ratio of the titanium dioxide, octadecyltrimethoxysilane modified bentonite and coupling agent is (5-15):(70-85):(0.5-2).

[0012] Optionally, the weight ratio of the titanium dioxide, octadecyltrimethoxysilane modified bentonite and coupling agent is (5-10):(80-85):(0.5-1).

[0013] In some embodiments, the weight ratio of the titanium dioxide, octadecyltrimethoxysilane modified bentonite and coupling agent can be (5-10):80:1, (5-15):80:1, (10-15):80:1, 10:(70-80):1, 10:(80-85):1, 10:80:(0.5-1), or 10:80:(1-1.5).

[0014] In one specific implementation, the weight ratio of the titanium dioxide, octadecyltrimethoxysilane modified bentonite, and coupling agent can be 10:80:1, 5:80:1, 15:80:1, 10:70:1, 10:85:1, 10:80:0.5, 10:80:1.5, 1:1:1, or 80:10:1.

[0015] Optionally, the coupling agent is selected from one or more of titanate coupling agents, silane coupling agents, and aluminate coupling agents.

[0016] Optionally, the preparation method of the octadecyltrimethoxysilane modified bentonite includes the following steps: (1) Bentonite pretreatment: Bentonite and water are mixed and dispersed in a weight ratio of 1: (8-12), and after being allowed to stand to remove impurities, centrifuged and purified, dried and pulverized, refined bentonite is obtained. (2) Preparation of silane hydrolysate: Mix ethanol and water in a volume ratio of (3-5):1, add octadecyltrimethoxysilane accounting for 8-15% of the mass of bentonite, adjust the pH of the system to 4-5, stir and hydrolyze to obtain octadecyltrimethoxysilane hydrolysate; (3) Grafting modification reaction: Refined bentonite is added to octadecyltrimethoxysilane hydrolysate, and the solid-liquid ratio is controlled at 1:(4-6). After ultrasonic dispersion, the mixture is heated to 60-70℃ and stirred under reflux for 3-4 hours. Finally, after post-treatment, octadecyltrimethoxysilane modified bentonite is obtained.

[0017] Optionally, the asphalt is No. 70 decolorized asphalt; the manufactured sand is fine aggregate; and the filler is mineral powder.

[0018] Secondly, this application provides a method for preparing colored asphalt concrete, comprising the following steps: First, the pigment and fixing agent are mixed evenly to obtain a premixed pigment; Limestone, manufactured sand and filler are mixed evenly to obtain precast aggregate; Add premixed pigments to precast aggregates and stir for 15-30 seconds; then add heated and molten asphalt and stir for 30-60 seconds to obtain colored asphalt concrete.

[0019] In summary, this application has the following beneficial effects: 1. In the colored asphalt concrete of this application, a ternary composite color-fixing agent consisting of titanium dioxide, octadecyltrimethoxysilane modified bentonite, and coupling agent is used to achieve a synergistic effect on color durability, solving the problem of fading and discoloration caused by asphalt component migration or environmental factors such as ultraviolet light and moisture, so that the concrete color can maintain a good color even under long-term external environment.

[0020] 2. The method for preparing colored asphalt concrete provided in this application first premixes the pigment and fixing agent components, and then mixes them with aggregate and asphalt. This ensures that the fixing agent is evenly dispersed in the mixture and has the characteristics of simple operation and easy large-scale promotion and application. Detailed Implementation

[0021] This application provides a colored asphalt concrete comprising the following components in parts by weight: 40-60 parts of 5-10mm limestone, 5-10 parts of 3-5mm limestone, 30-35 parts of manufactured sand, 0.5-2 parts of filler, 1.5-4 parts of pigment, 0.5-1 parts of fixing agent, and 2-8 parts of asphalt; wherein the fixing agent is a mixture of titanium dioxide, octadecyltrimethoxysilane modified bentonite, and a coupling agent.

[0022] This application also provides a method for preparing the above-mentioned colored asphalt concrete, including the following steps: (1) First, mix the pigment and the fixing agent evenly to obtain a premixed pigment; (2) Mix limestone, manufactured sand and filler evenly to obtain precast aggregate; (3) Add the premixed pigment to the precast aggregate and stir for 15-30 seconds; then add the heated and melted asphalt and stir for 30-60 seconds to obtain colored asphalt concrete.

[0023] The method for preparing octadecyltrimethoxysilane-modified bentonite in this application includes the following steps: (1) Bentonite pretreatment: Sodium-based bentonite and deionized water are placed in a stirring device at a weight ratio of 1:(8-12) and stirred at a speed of 2000-3000 r / min for 20-30 min to form a uniform suspension. The suspension is allowed to stand for 2 h and the upper uniform suspension is taken. Then the upper suspension is placed in a centrifuge and centrifuged at a speed of 3000-4000 r / min for 15-20 min. The supernatant is discarded and the precipitate is dried at 100-110℃ to constant weight. The precipitate is then crushed and passed through a 200-mesh sieve to obtain refined bentonite.

[0024] (2) Preparation of silane hydrolysate: Mix anhydrous ethanol and deionized water in a volume ratio of (3-5):1 in a stirring container and stir at room temperature for 5-10 min; add octadecyltrimethoxysilane accounting for 8-15% of the mass of bentonite to the above mixture and continue stirring at room temperature for 10-15 min; then slowly add glacial acetic acid until the pH value reaches 4-5, and continue stirring at room temperature for 30-40 min to obtain octadecyltrimethoxysilane hydrolysate.

[0025] (3) Grafting modification reaction: The refined bentonite was added to the hydrolysate of octadecyltrimethoxysilane with a solid-liquid ratio of 1:(4-6); then it was placed in an ultrasonic dispersion device and ultrasonically dispersed for 20-30 min at a power of 200-300W; then the above dispersion system was transferred to a stirring container with a reflux device, heated to 60-70℃, and stirred and refluxed at a speed of 150-250 r / min for 3-4 h; finally, the reaction solution was cooled to room temperature, filtered, washed with anhydrous ethanol and deionized water, dried under vacuum at 60-70℃, pulverized, and passed through a 200-mesh sieve to obtain octadecyltrimethoxysilane modified bentonite.

[0026] In the embodiments of this application, No. 70 decolorized asphalt and the pigment gray-blue (batch number 20260320) were both purchased from Sichuan Kelutai Transportation Technology Co., Ltd.; the manufactured sand was fine aggregate with an apparent relative density of 2.766 and a sand equivalent of 74%; the apparent density of the mineral powder was 2.831 t / m³. 3 The water content is 0.5%, the proportion of particles with a size <0.6 mm is 100%, the proportion of particles with a size <0.15 mm is 97.4%, and the proportion of particles with a size <0.075 mm is 90.7%; the particle size of titanium dioxide is 50 nm; the raw materials, reagents, solvents, etc. used in this application are all commercially available.

[0027] The following describes this application in further detail with reference to preparation examples, embodiments, and performance testing. Preparation Example 1

[0028] Preparation Example 1 provides an octadecyltrimethoxysilane modified bentonite.

[0029] The preparation method of the above-mentioned octadecyltrimethoxysilane modified bentonite includes the following steps: (1) Bentonite pretreatment: Sodium-based bentonite and deionized water were placed in a stirring device at a weight ratio of 1:10 and stirred at 2500 r / min for 30 min to form a uniform suspension. The suspension was allowed to stand for 2 h and the upper uniform suspension was taken. The upper suspension was then placed in a centrifuge and centrifuged at 3000 r / min for 20 min. The supernatant was discarded and the precipitate was dried at 105℃ to constant weight. The precipitate was then crushed and passed through a 200-mesh sieve to obtain refined bentonite.

[0030] (2) Preparation of silane hydrolysate: Anhydrous ethanol and deionized water were mixed in a volume ratio of 4:1 and placed in a stirring container. The mixture was stirred at room temperature for 8 min. Octadecyltrimethoxysilane, accounting for 10% of the mass of bentonite, was added to the mixture and stirred at room temperature for 12 min. Then, glacial acetic acid was slowly added dropwise until the pH value reached 4.5. The mixture was stirred at room temperature for 30 min to obtain octadecyltrimethoxysilane hydrolysate.

[0031] (3) Grafting modification reaction: Refined bentonite was added to octadecyltrimethoxysilane hydrolysate with a solid-liquid ratio of 1:5; then it was placed in an ultrasonic dispersion device and ultrasonically dispersed for 20 min at a power of 300 W; then the above dispersion system was transferred to a stirring container with a reflux device, heated to 65 °C, and stirred and refluxed at a speed of 200 r / min for 3.5 h; finally, the reaction solution was cooled to room temperature, filtered, washed with anhydrous ethanol and deionized water, dried under vacuum at 65 °C, pulverized, and passed through a 200 mesh sieve to obtain octadecyltrimethoxysilane modified bentonite. Examples 1-9

[0032] Examples 1-9 each provide a colored asphalt concrete.

[0033] The difference in the above embodiments lies in the weight ratio of titanium dioxide, octadecyltrimethoxysilane modified bentonite, and coupling agent, as shown in Table 1 below.

[0034] The method for preparing the colored asphalt mixture provided in Examples 1-9 includes the following steps: (1) Weigh out titanium dioxide, octadecyltrimethoxysilane modified bentonite (preparation example 1) and titanate coupling agent NDZ-401 according to the proportions shown in Table 1, and mix them to obtain a fixing agent; mix 2 kg of pigment and 0.8 kg of fixing agent evenly to obtain a premixed pigment; (2) Mix 50 kg of 5-10 mm limestone, 8 kg of 3-5 mm limestone, 30 kg of fine aggregate and 1 kg of mineral powder evenly to obtain precast aggregate; (3) Add the premixed pigment to the precast aggregate and stir for 30 seconds; then add 5 kg of heated and melted asphalt and stir for 30-60 seconds to obtain colored asphalt concrete.

[0035] Table 1. Types and proportions of fixing agents used in the colored asphalt concrete provided in Examples 1-9 Example 10

[0036] Example 10 provides a colored asphalt concrete.

[0037] The difference between the above embodiment and Embodiment 2 is that the amount of fixing agent added is 0.5 kg. Example 11

[0038] Example 11 provides a colored asphalt concrete.

[0039] The difference between the above embodiment and Embodiment 2 is that the amount of fixing agent added is 1 kg. Example 12

[0040] Example 12 provides a colored asphalt concrete.

[0041] The difference between the above embodiment and Embodiment 2 is that the titanate coupling agent is replaced with the silane coupling agent KH550. Example 13

[0042] Example 13 provides a colored asphalt concrete.

[0043] The difference between the above embodiment and Embodiment 2 is that the titanate coupling agent is replaced with the aluminate coupling agent LS-62. Comparative Example 1

[0044] Comparative Example 1 provides a colored asphalt concrete.

[0045] The difference between the above comparative example and Example 2 is that the fixing agent is titanium dioxide and coupling agent in a weight ratio of 10:1. Comparative Example 2

[0046] Comparative Example 2 provides a colored asphalt concrete.

[0047] The difference between the above comparative example and Example 2 is that the fixing agent is octadecyltrimethoxysilane modified bentonite and coupling agent in a weight ratio of 80:1. Comparative Example 3

[0048] Comparative Example 3 provides a colored asphalt concrete.

[0049] The difference between the above comparative example and Example 2 is that the fixing agent is titanium dioxide and octadecyltrimethoxysilane modified bentonite in a weight ratio of 10:80. Comparative Example 4

[0050] Comparative Example 4 provides a colored asphalt concrete.

[0051] The difference between the above comparative example and Example 2 is that the fixing agent is titanium dioxide, bentonite and coupling agent in a weight ratio of 10:80:1. Comparative Example 5

[0052] Comparative Example 5 provides a colored asphalt concrete.

[0053] The difference between the above comparative example and Example 2 is that the amount of fixing agent added is 0. Performance testing

[0054] Colored asphalt concrete was prepared according to the methods of Examples 1-13 and Comparative Examples 1-5, and test specimens were prepared according to the standard Marshall mold (inner diameter 101.6 mm, height 87 mm). The following performance tests were performed, and the results are shown in Table 2 below.

[0055] (1) Color difference detection after UV aging test: The test specimens were subjected to accelerated aging test using a QUV UV aging test chamber. The test conditions were: irradiance 0.89 W / m²@340 nm, temperature 60℃, blackboard temperature 65℃, light / condensation cycle of "4h light / 4h condensation", and a total test time of 2000h, which was used to simulate the aging process under outdoor natural light conditions. Before the test, the initial L, a, and b values ​​of the specimen surface color were measured using a colorimeter (based on CIE 1976 CIELAB color space, referring to ASTM D2244 standard). After the test, the L, a, and b values ​​of the same location were measured again, and the color difference ΔE was calculated according to the following formula: ΔE=[(ΔL)] 2 +(Δa) 2 +(Δb) 2 ] 1 / 2 ; In the formula, ΔL represents the difference in brightness, Δa represents the difference in red and green, and Δb represents the difference in yellow and blue.

[0056] (2) Color difference detection after simulated rain cycle test: The specimen was placed under the spray device and sprayed with a solution of pH 6.0±0.2 (simulating rain conditions) at a flow rate of 2L / min for 30min. Then it was dried in an oven at 50℃ for 60min. This is one cycle; a total of 50 cycles were performed. The initial L, a, b values ​​of the surface color of the specimen and the L, a, b values ​​after the test were measured using a colorimeter, and the color difference ΔE was calculated.

[0057] (3) Abrasion resistance: According to the Kentucky fly test method in JTG 3410-2025 "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering", the Los Angeles abrasion tester was used to rotate 300 revolutions without steel balls to determine the mass loss rate of the specimen during the rotational impact process.

[0058] Table 2 Performance test results of colored asphalt concrete obtained in Examples 1-13 and Comparative Examples 1-5

[0059] The test results of Examples 1-9 and Comparative Examples 1-4 show that the fixing agent in Comparative Example 1 is only titanium dioxide and a coupling agent. The resulting colored asphalt concrete has a ΔE value as high as 4.52 before and after UV aging, and a color difference ΔE value as high as 4.21 after the rain test. The fixing agent in Comparative Example 2 is only octadecyltrimethoxysilane-modified bentonite and a coupling agent. The resulting colored asphalt concrete has a ΔE value as high as 5.16 before and after UV aging, and a color difference ΔE value as high as 4.83 after the rain test. The fixing agent in Comparative Example 3 is only titanium dioxide and octadecyltrimethoxysilane-modified bentonite. The resulting colored asphalt concrete has a ΔE value as high as 5.32 before and after UV aging, and a color difference ΔE value as high as 4.95 after the rain test. The fixing agent in Comparative Example 4 is unmodified bentonite. The resulting colored asphalt concrete has a ΔE value as high as 4.78 before and after UV aging, and a color difference ΔE value as high as 4.42 after the rain test. Therefore, this application uses a mixture of titanium dioxide, octadecyltrimethoxysilane modified bentonite, and coupling agent as a color-fixing agent. The three have a synergistic effect, which can significantly improve the color durability of colored asphalt concrete, making it less prone to fading or discoloration under light and rain conditions. Further comparison revealed that the ΔE values ​​of the colored asphalt concrete in Examples 1-7 before and after UV aging were only 1.03-1.46 (<1.50), and the color difference ΔE value after the rain test was only 0.87-1.38 (<1.50); ​​while the ΔE values ​​of the colored asphalt concrete in Examples 8-9 before and after UV aging reached 2.35-2.68, and the color difference ΔE value after the rain test reached 1.98-2.10. This indicates that by further controlling the weight ratio of titanium dioxide, octadecyltrimethoxysilane modified bentonite and coupling agent within the range of (5-15):(70-85):(0.5-2), the colored asphalt concrete obtained in this application has better color durability and is less prone to fading and discoloration.

[0060] The test results of Examples 2, 10-11, and Comparative Example 5 show that the colored asphalt concrete of Comparative Example 5, which did not contain a fixing agent, had a ΔE value as high as 6.85 before and after UV aging and a color difference ΔE value as high as 5.91 after the rain test. In contrast, the colored asphalt concrete of Examples 2 and 10-11 had ΔE values ​​of 1.03-1.36 before and after UV aging and color difference ΔE values ​​of 0.88-1.12 after the rain test. This indicates that by adding a fixing agent to the colored asphalt concrete and controlling its weight part to 0.5-1 part, this application can obtain colored asphalt concrete with good color durability.

[0061] The test results of Examples 2 and 12-13 show that the ΔE value of the colored asphalt concrete in Examples 2 and 12-13 before and after ultraviolet aging is 1.03-1.23, and the color difference ΔE value after the rain test is 0.88-1.05. This indicates that the colored asphalt concrete with good color durability can be obtained by using titanate coupling agent, silane coupling agent or aluminate coupling agent in this application.

[0062] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A type of colored asphalt concrete, characterized in that, It comprises the following components by weight: 40-60 parts of 5-10mm limestone, 5-10 parts of 3-5mm limestone, 30-35 parts of manufactured sand, 0.5-2 parts of filler, 1.5-4 parts of pigment, 0.5-1 part of fixing agent, and 2-8 parts of bitumen; The fixing agent is a mixture of titanium dioxide, octadecyltrimethoxysilane modified bentonite, and a coupling agent.

2. The colored asphalt concrete according to claim 1, characterized in that, The weight ratio of titanium dioxide, octadecyltrimethoxysilane modified bentonite and coupling agent is (5-15):(70-85):(0.5-2).

3. The colored asphalt concrete according to claim 1, characterized in that, The weight ratio of titanium dioxide, octadecyltrimethoxysilane modified bentonite and coupling agent is (5-10):(80-85):(0.5-1).

4. The colored asphalt concrete according to claim 1, characterized in that, The coupling agent is selected from one or more of titanate coupling agents, silane coupling agents, and aluminate coupling agents.

5. The colored asphalt concrete according to claim 1, characterized in that, The preparation method of the octadecyltrimethoxysilane modified bentonite includes the following steps: (1) Bentonite pretreatment: Bentonite and water are mixed and dispersed in a weight ratio of 1: (8-12), and after being allowed to stand to remove impurities, centrifuged and purified, dried and pulverized, refined bentonite is obtained. (2) Preparation of silane hydrolysate: Mix ethanol and water in a volume ratio of (3-5):1, add octadecyltrimethoxysilane accounting for 8-15% of the mass of bentonite, adjust the pH of the system to 4-5, stir and hydrolyze to obtain octadecyltrimethoxysilane hydrolysate; (3) Grafting modification reaction: Refined bentonite is added to octadecyltrimethoxysilane hydrolysate, and the solid-liquid ratio is controlled at 1:(4-6). After ultrasonic dispersion, the mixture is heated to 60-70℃ and stirred under reflux for 3-4 hours. Finally, after post-treatment, octadecyltrimethoxysilane modified bentonite is obtained.

6. The colored asphalt concrete according to any one of claims 1-5, characterized in that, The asphalt is No. 70 decolorized asphalt; the manufactured sand is fine aggregate; and the filler is mineral powder.

7. The method for preparing colored asphalt concrete according to any one of claims 1-6, characterized in that, Includes the following steps: First, the pigment and fixing agent are mixed evenly to obtain a premixed pigment; Limestone, manufactured sand and filler are mixed evenly to obtain precast aggregate; Add premixed pigments to precast aggregates and stir for 15-30 seconds; then add heated and molten asphalt and stir for 30-60 seconds to obtain colored asphalt concrete.

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