Semi-flexible pavement grouting material and preparation method thereof

Abstract

The invention relates to the technical field of engineering materials, and particularly discloses a semi-flexible pavement grouting material and a preparation method thereof. The semi-flexible pavement grouting material provided by the invention is prepared from cement, nano calcium carbonate modified microbeads, styrene-acrylic emulsion modified calcined diatomite, composite fine aggregate, an early strength agent, a water reducing agent, a water retaining agent, a defoaming agent and water, the composite fine aggregate comprises silica fume, calcined shell powder and coal gangue micro powder. According to the semi-flexible pavement grouting material disclosed by the invention, the components of the semi-flexible pavement grouting material are reasonably designed, and the composite fine aggregate, the nano calcium carbonate modified microbeads and the styrene-acrylic emulsion modified calcined diatomite are used as core reinforcing components; the strength, the stability and the fatigue resistance of the semi-flexible pavement grouting material are remarkably improved through the multi-dimensional synergistic effect with the cement, the early strength agent, the water reducing agent and other components, and a new thought is provided for preparation of the semi-flexible pavement grouting material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of engineering materials, in particular to a semi-flexible pavement grouting material and a preparation method thereof. BACKGROUND

[0002] As a composite structure with both the bearing capacity of rigid pavement and the crack resistance of flexible pavement, the semi-flexible pavement is increasingly widely applied in heavy-load traffic, airport runway and other projects in recent years, and its core performance depends on the filling and reinforcement of the grouting material to the base and the interfacial adhesion. In the prior art, the semi-flexible pavement grouting material is mostly prepared based on ordinary Portland cement, fine sand, mineral admixtures and other components, which can meet the basic filling requirements, but has the following defects in complex working conditions: first, the water retention performance is weak, and the water is easily lost due to evaporation or siphonage of the base pores in the early stage of cement hydration, resulting in insufficient early hydration and thus reducing the early strength and prolonging the construction period; second, the late strength and stability are insufficient, the late cementitious activity of the single cement-based cementitious system is attenuated, and the aggregate gradation matching is poor, which easily causes volume shrinkage cracking, reduces the overall modulus of the base and shortens the service life of the pavement; third, the fatigue resistance is weak, and the internal micro-cracks of the material are easily expanded and penetrated to the asphalt surface layer under the repeated load of heavy vehicles, forming reflection cracks and accelerating the damage of the pavement structure. The above defects seriously restrict the popularization and application of the semi-flexible pavement in high-frequency heavy-load, dry-hot / large temperature difference and other environments. Therefore, developing a grouting material with early strength, excellent late strength and fatigue resistance has become a key technical bottleneck to improve the engineering quality of the semi-flexible pavement. SUMMARY

[0003] In view of this, the present application provides a semi-flexible pavement grouting material and a preparation method thereof.

[0004] To solve the above technical problems, the technical scheme provided by the present application is as follows: The present application provides a semi-flexible pavement grouting material, which comprises the following raw material components in mass fraction: cement 50-60 parts, nano-calcium carbonate modified microbeads 15-20 parts, benzene-polypropylene emulsion modified calcined diatomite 10-15 parts, composite fine aggregate 15-20 parts, early strength agent 0.1-0.3 parts, water reducing agent 0.2-0.6 parts, water retaining agent 0.1-0.2 parts, defoaming agent 0.05-0.1 parts and water 20-30 parts. The composite fine aggregate comprises silica fume, calcined shell powder and coal gangue micro powder.

[0005] Compared to existing technologies, the semi-flexible pavement grout provided by this invention features microspheres modified with nano-calcium carbonate, resulting in increased surface roughness and specific surface area. This accelerates the hydration of the C3S phase to form CSH gel. Furthermore, the nano-calcium carbonate in the modified microspheres exhibits high reactivity, reacting with the aluminum phase components in cement to form ettringite, replenishing early expansion components, reducing shrinkage microcracks, and comprehensively improving the early and later strength of the grout. Silica fume further fills the surface micropores of the nano-calcium carbonate modified microspheres, strengthening the compactness of the grout structure and thus improving its early and later strength. The inventors have discovered that the nano-calcium carbonate modified microspheres can also reduce crystal defects in cement hydration products, thereby improving the crack resistance and toughness of the grout. Moreover, the nano-calcium carbonate modified microspheres possess a specific morphology that reduces interparticle friction, optimizes slurry flowability, and ensures more uniform dispersion of cement particles and more complete hydration reactions, thereby enhancing the early strength, later strength, stability, and fatigue resistance of the grout.

[0006] In styrene-acrylic emulsion-modified calcined diatomaceous earth, the calcined diatomaceous earth not only possesses a rich porous structure, but calcination also activates active sites on the diatomaceous earth surface, allowing it to fully participate in cement hydration. However, simply adding calcined diatomaceous earth may result in excessive water absorption due to its porous structure, thus affecting the bleeding rate and later strength of the concrete. Through extensive experimentation, the inventors discovered that when styrene-acrylic emulsion is further modified into calcined diatomaceous earth, the polymer film of the emulsion can seal some of the excessively water-absorbing micropores, reducing the bleeding rate of the later grouting material. The membrane can also form a hydrophobic barrier, reducing the rapid evaporation of water in the water-storing micropores of calcined diatomaceous earth, thereby improving the early and later strength of the grout. At the same time, the surface polymer membrane of styrene-acrylic emulsion modified calcined diatomaceous earth further improves the interfacial transition zone between components, reduces interfacial defects, and enhances the bond between cement and aggregate, thereby improving the strength of the grout. In addition, the styrene-acrylic emulsion polymer membrane in styrene-acrylic emulsion modified calcined diatomaceous earth has good flexibility, forming an elastic network inside the grout, thereby improving the stability and fatigue resistance of the grout.

[0007] The silica fume in the composite fine aggregate is rich in active silica, which further reacts with cement to form dense CSH gel, improving the later strength of the grout. The calcium oxide from calcined shell powder participates in the hydration reaction, accelerating the formation of ettringite and CSH gel, thereby improving the early strength of the grout. At the same time, its porous structure can also adsorb free water, helping to retain water and improving the later strength of the grout. Coal gangue powder reacts in an alkaline environment to form hydrated calcium aluminate, providing cementing substances and further improving the strength of the grout. In the composite fine aggregate provided by this invention, the three elements work synergistically to refine the pores inside the grout system, ensuring the hydration environment required for early strength, providing a continuous reaction source for later strength growth, and improving the stability and fatigue resistance of the grout.

[0008] Preferably, the preparation method of the nano-calcium carbonate modified microspheres includes the following steps: Step a: Add the microbeads to an ethanol-water solution to obtain a microbead dispersion; Step b: Disperse nano-calcium carbonate in an aqueous ethanol solution to obtain a nano-calcium carbonate dispersion. Step c: Add the silane coupling agent to the microbead dispersion, then add the nano-calcium carbonate dispersion for impregnation, perform solid-liquid separation, wash, and dry to obtain the nano-calcium carbonate modified microbeads.

[0009] In the preparation method of modified calcium carbonate nanospheres provided by this invention, an ethanol-water solution is used as the dispersion medium. This not only facilitates the stable dispersion of the nanospheres and the calcium carbonate nanospheres but also promotes the uniform grafting of silane coupling agents onto the surface of the nanospheres. This allows the calcium carbonate nanospheres to achieve directional coating through silane coupling agent bridging, improving coating uniformity and interfacial bonding. Furthermore, the preparation method provided by this invention is simple, efficient, and highly controllable. It also reduces reagent consumption and operational steps, lowers production costs, and the post-processing steps are simple and easy to perform, making it suitable for industrial-scale mass production.

[0010] It should be further noted that in step a, the microbeads also need to be pretreated in hydrochloric acid solution.

[0011] For example, the pretreatment specifically includes the following steps: adding microbeads to hydrochloric acid solution, stirring, filtering, washing until neutral, and drying.

[0012] Pretreatment of microspheres can also improve their stability in coating nano-calcium carbonate, thereby improving the performance of the grouting material.

[0013] For example, the mass-to-volume ratio of the microbeads to the hydrochloric acid solution is 1 g: (5~6) mL, and the mass concentration of the hydrochloric acid solution is 1%~2%.

[0014] For example, the stirring conditions are: stirring at a speed of 300~320 rpm for 30~35 minutes.

[0015] For example, the drying conditions are drying at 75~80°C to constant weight.

[0016] Preferably, in step a, the microspheres are fly ash microspheres with a particle size of 10~15μm.

[0017] Preferably, in step a, the ratio of the amount of microbeads to the ethanol aqueous solution is 1g:(3~3.2)mL, and the volume ratio of ethanol to water in the ethanol aqueous solution is 1:(0.9~1.2).

[0018] Preferably, in step b, the particle size of the nano-calcium carbonate is 80~120nm.

[0019] Preferably, the mass ratio of the nano-calcium carbonate to the microbeads is (10~15):100.

[0020] Preferably, in step b, the ratio of the amount of nano-calcium carbonate to the ethanol aqueous solution is 1g:(20~30)mL, and the volume ratio of ethanol to water in the ethanol aqueous solution is 1:(0.9~1.2).

[0021] Preferably, in step c, the silane coupling agent is silane coupling agent KH-560.

[0022] Preferably, in step c, the mass ratio of the silane coupling agent to the microspheres is (3~5):100.

[0023] Preferably, in step c, the immersion temperature is 60~65℃ and the immersion time is 1.5~2.5h.

[0024] For example, in step c, stirring is required during impregnation, and the stirring rate is 300~350 rpm.

[0025] The preparation method of the styrene-acrylic emulsion modified calcined diatomaceous earth includes the following steps: S1. Calcine diatomaceous earth at 550~600℃ to obtain calcined diatomaceous earth; S2. Add the calcined diatomaceous earth and dispersant to water to obtain a calcined diatomaceous earth dispersion; S3. Add styrene-acrylic emulsion to water to obtain a diluted styrene-acrylic emulsion solution; S4. At 50~60℃, the diluted styrene-acrylic emulsion is added to the calcined diatomaceous earth dispersion, impregnated, filtered, washed, and dried to obtain the styrene-acrylic emulsion modified calcined diatomaceous earth.

[0026] In the preparation method of styrene-acrylic emulsion modified calcined diatomaceous earth provided by the present invention, calcination not only removes impurities such as organic matter from the diatomaceous earth, but also optimizes the porous structure of the diatomaceous earth and increases the active sites on the surface of the diatomaceous earth, providing a good foundation for subsequent modification; further, in S4, the styrene-acrylic emulsion dilution is added to the calcined diatomaceous earth dispersion for impregnation treatment, and the polymer in the styrene-acrylic emulsion is adsorbed onto the pores and surface of the diatomaceous earth to form a polymer film, thereby improving the performance of the grouting material.

[0027] Preferably, in S1, the particle size of the diatomaceous earth is 80~100μm.

[0028] More preferably, in S1, the calcination time is 2~2.5h.

[0029] Preferably, in S2, the ratio of calcined diatomaceous earth to water is 100g:(300~320)mL.

[0030] It should be further noted that in S2, when the calcined diatomaceous earth and dispersant are added to the water, they need to be stirred. The stirring speed can be 400~450 rpm, and the stirring time is not limited, until the calcined diatomaceous earth is dispersed.

[0031] Preferably, in S2, the dispersant is polyvinylpyrrolidone.

[0032] Preferably, in S2, the mass ratio of the dispersant to the calcined diatomaceous earth is (0.3~0.5):100.

[0033] Preferably, in S3, the grade of the styrene-acrylic emulsion is 455, which is purchased from Jinan Yuchuan New Materials Co., Ltd.

[0034] Preferably, in S3, the mass-to-volume ratio of the styrene-acrylic emulsion to water is 1 g: (4~5) mL.

[0035] Preferably, the mass ratio of the styrene-acrylic emulsion to the calcined diatomaceous earth is (12~18):100.

[0036] It should be further noted that in S3, after adding water to the styrene-acrylic emulsion, it is necessary to stir at a speed of 600~650 rpm for 5~10 minutes to ensure that the styrene-acrylic emulsion is diluted evenly.

[0037] For example, in S4, the styrene-acrylic emulsion diluent is added to the calcined diatomaceous earth dispersion in a dropwise manner.

[0038] Preferably, in step S4, the immersion temperature is 50~60℃ and the immersion time is 2~2.5h.

[0039] Preferably, the calcined shell powder is obtained by calcining shell powder at 850~900℃.

[0040] Through extensive experiments, the inventors have demonstrated that when shell powder is calcined at a specific temperature, it forms a large number of microporous structures. On the one hand, these structures can absorb some of the moisture in the grout, thus playing a water-retaining role and reducing the amount of water-retaining agent required to a certain extent. On the other hand, the microporous structures can also be filled by other aggregates, reducing the porosity inside the grout and thereby improving the performance of the grouting material. In addition, experiments have shown that compared with the direct application of shell powder, the stability and fatigue resistance of the grouting material made from calcined shell powder are significantly improved.

[0041] When shell powder is calcined at a specific temperature, the calcium carbonate in it decomposes into calcium oxide, which rapidly hydrates in water to form calcium hydroxide, accelerating the formation of ettringite and CSH gel, thereby improving the early strength of the grout.

[0042] More preferably, the calcination temperature is 1.5~2.5h.

[0043] More preferably, the particle size of the calcined seashell powder is 0.15~0.3mm.

[0044] Preferably, the mass ratio of silica fume, calcined shell powder and coal gangue powder is (2~3):(1~2):(2~3).

[0045] Preferably, the particle size of the silica fume is 15~40μm.

[0046] Preferably, the particle size of the coal gangue powder is 60~80μm.

[0047] Preferably, the cement is 42.5 rapid-hardening sulfoaluminate cement.

[0048] Preferably, the early strength agent includes at least one of lithium carbonate or lithium chloride.

[0049] Preferably, the water-reducing agent is a polycarboxylate water-reducing agent.

[0050] Preferably, the water-reducing agent is purchased from Jinan Quanchi New Materials Co., Ltd.

[0051] Preferably, the water-retaining agent is hydroxypropyl methylcellulose.

[0052] Preferably, the water-retaining agent is purchased from Jinan Qingtian Chemical Technology Co., Ltd.

[0053] Preferably, the defoamer is an organosilicon defoamer.

[0054] More preferably, the defoamer is Zhubao PD-2000E, purchased from Beijing Zhubao New Technology Co., Ltd.

[0055] This invention provides a method for preparing the above-mentioned semi-flexible pavement grout, comprising the following steps: Mix all raw material components of the semi-flexible pavement grout, except for water, until homogeneous. Then add water and continue mixing until homogeneous to obtain the semi-flexible pavement grout.

[0056] This invention, through the rational design of the composition of semi-flexible pavement grout, uses composite fine aggregate, nano-calcium carbonate modified microspheres, and styrene-acrylic emulsion modified calcined diatomaceous earth as core reinforcing components. Through multi-dimensional synergistic effects with cement, early strength agent, and water-reducing agent, it significantly improves the strength, stability, and fatigue resistance of semi-flexible pavement grout, providing a new approach to the preparation of semi-flexible pavement grout. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0058] In this embodiment of the invention, the early strength agent is lithium carbonate, the dispersant is polyvinylpyrrolidone; the grade of styrene-acrylic emulsion is 455, purchased from Jinan Yuchuan New Materials Co., Ltd.; the cement is 42.5 rapid-hardening sulfoaluminate cement; the water-reducing agent is polycarboxylate water-reducing agent, purchased from Jinan Quanchi New Materials Co., Ltd.; the water-retaining agent is purchased from Jinan Qingtian Chemical Technology Co., Ltd.; and the defoamer is Zhubao PD-2000E, purchased from Beijing Zhubao New Technology Co., Ltd.

[0059] To better illustrate the present invention, further examples are provided below.

[0060] Example 1 This embodiment provides a semi-flexible pavement grouting material, comprising the following raw material components in parts by weight: 60 parts cement, 15 parts nano-calcium carbonate modified microspheres, 15 parts styrene-acrylic emulsion modified calcined diatomaceous earth, 20 parts composite fine aggregate, 0.1 parts early strength agent, 0.5 parts water-reducing agent, 0.2 parts water-retaining agent, 0.1 parts defoamer, and 20 parts water. The composite fine aggregate comprises a mixture of silica fume with a particle size of 15-20 μm, calcined shell powder with a particle size of 0.15-0.2 mm, and coal gangue powder with a particle size of 60-70 μm, in a mass ratio of 2:1:2. The preparation method of nano-calcium carbonate modified microspheres includes the following steps: Step a: Add fly ash microspheres with a particle size of 10~15μm to hydrochloric acid solution at a mass-volume ratio of 1g:5mL. Stir at 300rpm for 30min, filter, wash until neutral, and dry at 75℃ to constant weight. Add the pretreated fly ash microspheres to an ethanol aqueous solution (ethanol and water volume ratio of 1:1) at a dosage ratio of 1g:3mL to obtain a microsphere dispersion. Step b: Disperse nano-calcium carbonate with a particle size of 80~100nm in an ethanol aqueous solution (volume ratio of ethanol to water is 1:1) to obtain a nano-calcium carbonate dispersion with a concentration of 1g / 30mL. Step c: Add silane coupling agent KH-560 to the microbead dispersion at a mass ratio of 5:100, then add nano-calcium carbonate dispersion at a mass ratio of 10:100, and impregnate at 60℃ for 2.5h. During the impregnation process, stir at a rate of 300rpm, separate the solid and liquid, wash, and dry to obtain nano-calcium carbonate modified microbeads. The preparation method of styrene-acrylic emulsion modified calcined diatomaceous earth includes the following steps: S1. Calcined diatomaceous earth with a particle size of 80~90μm is calcined at 600℃ for 2.5h to obtain calcined diatomaceous earth; S2. Add calcined diatomaceous earth and dispersant to water, and then stir at 450 rpm until the calcined diatomaceous earth is dispersed to obtain a calcined diatomaceous earth dispersion; the ratio of calcined diatomaceous earth to water is 100g:300mL, and the mass ratio of dispersant to calcined diatomaceous earth is 0.3:100. S3. According to the mass-volume ratio of styrene-acrylic emulsion to water of 1g:4mL, add styrene-acrylic emulsion to water and stir at 650rpm for 5min to obtain styrene-acrylic emulsion dilution. S4. At 50℃, the diluted styrene-acrylic emulsion was added dropwise to the calcined diatomaceous earth dispersion at a mass ratio of 12:100. The mixture was then soaked at 50℃ for 2 hours, filtered, washed, and dried to obtain styrene-acrylic emulsion modified calcined diatomaceous earth. Calcined shell powder is obtained by calcining shell powder at 850℃ for 2 hours.

[0061] This embodiment provides a method for preparing the above-mentioned semi-flexible pavement grout, including the following steps: Mix all raw material components of the semi-flexible pavement grout, except for water, until homogeneous. Then add water and continue mixing until homogeneous to obtain the semi-flexible pavement grout.

[0062] Example 2 This embodiment provides a semi-flexible pavement grouting material, comprising the following raw material components in parts by weight: 50 parts cement, 18 parts nano-calcium carbonate modified microspheres, 10 parts styrene-acrylic emulsion modified calcined diatomaceous earth, 15 parts composite fine aggregate, 0.3 parts early strength agent, 0.6 parts water-reducing agent, 0.1 parts water-retaining agent, 0.05 parts defoamer, and 25 parts water. The composite fine aggregate comprises a mixture of silica fume with a particle size of 20-30 μm, calcined shell powder with a particle size of 0.2-0.3 mm, and coal gangue powder with a particle size of 70-80 μm in a mass ratio of 3:1:3. The preparation method of nano-calcium carbonate modified microspheres includes the following steps: Step a: Add fly ash microspheres with a particle size of 10~15μm to hydrochloric acid solution at a mass-to-volume ratio of 1g:6mL. Stir at 320rpm for 35min, filter, wash until neutral, and dry at 80℃ to constant weight. Add the pretreated fly ash microspheres to an ethanol-water solution (ethanol and water volume ratio of 1:1) at a volume ratio of 1g:3.2mL to obtain a microsphere dispersion. Step b: Disperse nano-calcium carbonate with a particle size of 100~120nm in an ethanol aqueous solution (volume ratio of ethanol to water is 1:1) to obtain a nano-calcium carbonate dispersion with a concentration of 1g / 20mL. Step c: Add silane coupling agent KH-560 to the microbead dispersion at a mass ratio of 3:100, then add nano-calcium carbonate dispersion at a mass ratio of 15:100, and impregnate at 65°C for 1.5 hours. During the impregnation process, stir at a rate of 350 rpm, separate the solid and liquid, wash, and dry to obtain nano-calcium carbonate modified microbeads. The preparation method of styrene-acrylic emulsion modified calcined diatomaceous earth includes the following steps: S1. Calcined diatomaceous earth with a particle size of 90~100μm is calcined at 550℃ for 2h to obtain calcined diatomaceous earth; S2. Add calcined diatomaceous earth and dispersant to water, and then stir at 400 rpm until the calcined diatomaceous earth is dispersed to obtain a calcined diatomaceous earth dispersion; the ratio of calcined diatomaceous earth to water is 100g:320mL, and the mass ratio of dispersant to calcined diatomaceous earth is 0.5:100. S3. According to the mass-volume ratio of styrene-acrylic emulsion to water of 1g:5mL, add styrene-acrylic emulsion to water and stir at 600rpm for 10min to obtain styrene-acrylic emulsion dilution. S4. At 60℃, the diluted styrene-acrylic emulsion was added dropwise to the calcined diatomaceous earth dispersion at a mass ratio of 18:100. The mixture was then soaked at 50℃ for 2 hours, filtered, washed, and dried to obtain styrene-acrylic emulsion modified calcined diatomaceous earth. Calcined shell powder is obtained by calcining shell powder at 900℃ for 2.5 hours.

[0063] This embodiment provides a method for preparing the above-mentioned semi-flexible pavement grout, including the following steps: Mix all raw material components of the semi-flexible pavement grout, except for water, until homogeneous. Then add water and continue mixing until homogeneous to obtain the semi-flexible pavement grout.

[0064] Example 3 This embodiment provides a semi-flexible pavement grouting material, comprising the following raw material components in parts by weight: 55 parts cement, 20 parts nano-calcium carbonate modified microspheres, 12 parts styrene-acrylic emulsion modified calcined diatomaceous earth, 18 parts composite fine aggregate, 0.2 parts early strength agent, 0.2 parts water-reducing agent, 0.2 parts water-retaining agent, 0.08 parts defoamer, and 30 parts water. The composite fine aggregate comprises a mixture of silica fume with a particle size of 30-40 μm, calcined shell powder with a particle size of 0.2-0.3 mm, and coal gangue powder with a particle size of 70-80 μm, in a mass ratio of 2:2:3. The preparation method of nano-calcium carbonate modified microspheres includes the following steps: Step a: Add fly ash microspheres with a particle size of 10~15μm to hydrochloric acid solution at a mass-volume ratio of 1g:5mL. Stir at 320rpm for 30min, filter, wash until neutral, and dry at 80℃ to constant weight. Add the pretreated fly ash microspheres to an ethanol-water solution (ethanol and water volume ratio of 1:1) at a dosage ratio of 1g:3mL to obtain a microsphere dispersion. Step b: Disperse nano-calcium carbonate with a particle size of 80~90nm in an ethanol aqueous solution (volume ratio of ethanol to water is 1:1) to obtain a nano-calcium carbonate dispersion with a concentration of 1g / 25mL. Step c: Add silane coupling agent KH-560 to the microbead dispersion at a mass ratio of 4:100. Then add nano-calcium carbonate dispersion at a mass ratio of 15:100. Impregnate at 60°C for 2 hours. Stir at 300 rpm during impregnation. Separate solid and liquid, wash, and dry to obtain nano-calcium carbonate modified microbeads. The preparation method of styrene-acrylic emulsion modified calcined diatomaceous earth includes the following steps: S1. Calcined diatomaceous earth with a particle size of 90~100μm is calcined at 600℃ for 2h to obtain calcined diatomaceous earth; S2. Add calcined diatomaceous earth and dispersant to water, and then stir at 400 rpm until the calcined diatomaceous earth is dispersed to obtain a calcined diatomaceous earth dispersion; the ratio of calcined diatomaceous earth to water is 100g:300mL, and the mass ratio of dispersant to calcined diatomaceous earth is 0.5:100. S3. According to the mass-volume ratio of styrene-acrylic emulsion to water of 1g:5mL, add styrene-acrylic emulsion to water and stir at 600rpm for 5min to obtain styrene-acrylic emulsion dilution. S4. At 55℃, the diluted styrene-acrylic emulsion was added dropwise to the calcined diatomaceous earth dispersion at a mass ratio of 15:100. The mixture was then soaked at 55℃ for 2.5 hours, filtered, washed, and dried to obtain styrene-acrylic emulsion modified calcined diatomaceous earth. Calcined shell powder is obtained by calcining shell powder at 850℃ for 2 hours.

[0065] This embodiment provides a method for preparing the above-mentioned semi-flexible pavement grout, including the following steps: Mix all raw material components of the semi-flexible pavement grout, except for water, until homogeneous. Then add water and continue mixing until homogeneous to obtain the semi-flexible pavement grout.

[0066] Comparative Example 1 This comparative example provides a semi-flexible pavement grout, which differs from Example 1 in that: the nano-calcium carbonate modified microspheres are replaced with an equal amount of nano-silica modified microspheres, and the preparation method includes the following steps: Step a: Add fly ash microspheres with a particle size of 10~15μm to hydrochloric acid solution at a mass-volume ratio of 1g:5mL. Stir at 300rpm for 30min, filter, wash until neutral, and dry at 75℃ to constant weight. Add the pretreated fly ash microspheres to an ethanol aqueous solution (ethanol and water volume ratio of 1:1) at a dosage ratio of 1g:3mL to obtain a microsphere dispersion. Step b: Disperse nano-silica with a particle size of 80~100nm in an ethanol aqueous solution (volume ratio of ethanol to water is 1:1) to obtain a nano-silica dispersion with a concentration of 1g / 30mL. Step c: Add silane coupling agent KH-560 to the microbead dispersion at a mass ratio of 5:100, then add nano silica dispersion at a mass ratio of 10:100, and impregnate at 60°C for 2.5 hours. During the impregnation process, stir at a rate of 300 rpm, separate the solid and liquid, wash, and dry to obtain modified microbeads. The other steps and ingredients are the same as in Example 1.

[0067] Comparative Example 2 This comparative example provides a semi-flexible pavement grout, which differs from Example 1 in that: the styrene-acrylic emulsion modified calcined diatomaceous earth is replaced with an equal amount of ethylene-vinyl acetate copolymer modified calcined diatomaceous earth. The ethylene-vinyl acetate copolymer, CAS number 24937-78-8, was purchased from Wuhan Kemike Biomedical Technology Co., Ltd. The specific preparation method includes the following steps: S1. Calcined diatomaceous earth with a particle size of 80~90μm is calcined at 600℃ for 2.5h to obtain calcined diatomaceous earth; S2. Add calcined diatomaceous earth and dispersant to water, and then stir at 450 rpm until the calcined diatomaceous earth is dispersed to obtain a calcined diatomaceous earth dispersion; the ratio of calcined diatomaceous earth to water is 100g:300mL, and the mass ratio of dispersant to calcined diatomaceous earth is 0.3:100. S3. According to the mass-volume ratio of ethylene-vinyl acetate copolymer to water of 1g:4mL, add ethylene-vinyl acetate copolymer to water and stir at 650rpm for 5min to obtain ethylene-vinyl acetate copolymer mixture. S4. At 50°C, the ethylene-vinyl acetate copolymer mixture was added dropwise to the calcined diatomaceous earth dispersion at a mass ratio of 12:100. The mixture was then soaked at 50°C for 2 hours, filtered, washed, and dried to obtain modified calcined diatomaceous earth. The other steps and ingredients are the same as in Example 1.

[0068] Comparative Example 3 This comparative example provides a semi-flexible pavement grouting material, which differs from Example 1 in that: calcined shell powder is replaced with an equal amount of shell powder; The other steps and ingredients are the same as in Example 1.

[0069] Example of effect The semi-flexible pavement grouting materials prepared in Examples 1-3 and Comparative Examples 1-3 were tested. The specific testing standards and indicators are as follows: The 2-hour compressive strength and 28-day compressive strength were tested according to JTT / 1238-2019 "Cement-based Grouting Materials for Semi-flexible Mixtures". The Marshall stability and dynamic stability were tested according to the technical indicators of JTG 3410-2025 "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering". The specific test results are shown in Table 1: Table 1

[0070] As shown in Table 1, the semi-flexible pavement grout provided in this embodiment of the invention exhibits excellent early and late strength. Its compressive strength at 2 hours reaches 21.9 MPa, and its compressive strength at 28 days reaches 53.6 MPa. Furthermore, the semi-flexible pavement grout provided in this embodiment of the invention has a Marshall stability of 21.6 kN and a dynamic stability ≥18000 cycles / mm, demonstrating excellent stability and fatigue resistance. In contrast, the semi-flexible pavement grouts prepared in Comparative Examples 1-3 of this invention show significantly lower compressive strength, stability, and fatigue resistance than the semi-flexible pavement grout prepared in Example 1. This invention optimizes the composition of each raw material in the semi-flexible pavement grout, resulting in a semi-flexible pavement grout with excellent compressive strength, stability, and fatigue resistance, providing a new approach to the preparation of semi-flexible pavement grouts.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A semi-flexible pavement grouting material, characterized in that, The raw material components include the following parts by weight: 50-60 parts cement, 15-20 parts nano-calcium carbonate modified microspheres, 10-15 parts styrene-acrylic emulsion modified calcined diatomaceous earth, 15-20 parts composite fine aggregate, 0.1-0.3 parts early strength agent, 0.2-0.6 parts water-reducing agent, 0.1-0.2 parts water-retaining agent, 0.05-0.1 parts defoamer, and 20-30 parts water; The composite fine aggregate includes silica fume, calcined shell powder, and coal gangue powder.

2. The semi-flexible pavement grouting material as described in claim 1, characterized in that, The preparation method of the nano-calcium carbonate modified microbeads includes the following steps: Step a: Add the microbeads to an ethanol-water solution to obtain a microbead dispersion; Step b: Disperse nano-calcium carbonate in an aqueous ethanol solution to obtain a nano-calcium carbonate dispersion. Step c: Add the silane coupling agent to the microbead dispersion, then add the nano-calcium carbonate dispersion for impregnation, perform solid-liquid separation, wash, and dry to obtain the nano-calcium carbonate modified microbeads.

3. The semi-flexible pavement grouting material as described in claim 2, characterized in that, In step a, the microspheres are fly ash microspheres with a particle size of 10~15μm; In step b, the particle size of the nano-calcium carbonate is 80~120nm; The mass ratio of the nano-calcium carbonate to the microbeads is (10~15):100; In step c, the mass ratio of the silane coupling agent to the microspheres is (3~5):

100.

4. The semi-flexible pavement grouting material as described in claim 1, characterized in that, The preparation method of the styrene-acrylic emulsion modified calcined diatomaceous earth includes the following steps: S1. Calcine diatomaceous earth at 550~600℃ to obtain calcined diatomaceous earth; S2. Add the calcined diatomaceous earth and dispersant to water to obtain a calcined diatomaceous earth dispersion; S3. Add styrene-acrylic emulsion to water to obtain a diluted styrene-acrylic emulsion solution; S4. At 50~60℃, the diluted styrene-acrylic emulsion is added to the calcined diatomaceous earth dispersion, impregnated, filtered, washed, and dried to obtain the styrene-acrylic emulsion modified calcined diatomaceous earth.

5. The semi-flexible pavement grouting material as described in claim 4, characterized in that, In S1, the particle size of the diatomaceous earth is 80~100μm; In S1, the calcination time is 2~2.5h; The mass ratio of the styrene-acrylic emulsion to the calcined diatomaceous earth is (12~18):100; In S4, the immersion temperature is 50~60℃ and the immersion time is 2~2.5h.

6. The semi-flexible pavement grouting material as described in claim 1, characterized in that, The calcined shell powder is obtained by calcining shell powder at 850~900℃.

7. The semi-flexible pavement grouting material as described in claim 6, characterized in that, The calcination temperature is 1.5~2.5h.

8. The semi-flexible pavement grouting material as described in claim 1, characterized in that, The particle size of the calcined seashell powder is 0.15~0.3mm; The particle size of the silica fume is 15~40μm; The particle size of the coal gangue powder is 60~80μm.

9. The semi-flexible pavement grouting material as described in claim 1 or 8, characterized in that, The mass ratio of silica fume, calcined shell powder and coal gangue powder is (2~3):(1~2):(2~3).

10. A method for preparing a semi-flexible pavement grouting material according to any one of claims 1 to 9, characterized in that, Includes the following steps: Mix all raw material components of the semi-flexible pavement grout, except for water, until homogeneous. Then add water and continue mixing until homogeneous to obtain the semi-flexible pavement grout.

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