Pavement base mixture and preparation method thereof

Abstract

The invention relates to the technical field of building materials, and discloses a pavement base mixture and a preparation method thereof. The pavement base mixture is prepared from the following components in parts by weight: 50 to 65 parts of building solid waste reclaimed materials, 12 to 15 parts of modified iron tailings, 8 to 10 parts of cement, 7 to 9 parts of modified asphalt, 2.5 to 3.5 parts of auxiliaries and 25 to 30 parts of water. According to the prepared pavement base mixture, the building solid waste reclaimed material, the modified iron tailings and the modified asphalt are added, so that a mixed structure with high strength, good stability and durability is obtained, and the pavement base mixture has good freezing resistance, anti-permeability and mechanical property. And the building solid waste regenerated material and the iron tailing solid waste are recycled, so that the construction cost is effectively reduced, the excessive development of resources is reduced, low-carbon economy is formed, and the method is suitable for base construction of municipal roads and expressways.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and in particular to a road base mixture and a preparation method thereof. Background Art

[0002] Cement-stabilized crushed stone (crushed stone is natural aggregate, natural sand and gravel) mixture is the most widely used base material in road construction. Although it has many advantages, this base material is prone to non-load cracks, which lead to early damage. With the rapid advancement of industrialization and urbanization, the construction industry has developed rapidly, and new projects such as infrastructure construction can be seen everywhere. A large number of existing buildings have reached their service life or cannot meet the use requirements and have been demolished. This phenomenon will not only cause a huge waste of construction resources, but also lead to the problem of construction waste. If a large amount of construction waste cannot be effectively utilized or reasonably disposed of, it will cause a serious waste of resources and will also aggravate serious damage to the natural environment. Therefore, it is extremely important and urgent to realize the resource utilization of construction waste and steadily improve its utilization level.

[0003] Road construction is an important part of my country's infrastructure construction. The project volume is large and a large amount of natural sand and gravel materials are consumed every year. At present, recycled aggregates made from construction waste as raw materials have been widely used in various types of buildings. However, compared with natural aggregates, recycled aggregates have disadvantages in terms of macroscopic properties, such as low density, low strength, and high water and oil absorption. When using recycled aggregates, it is necessary to fully consider the impact of recycled aggregates on the strength, frost resistance, and crack resistance of the mixture. In order to ensure the crack resistance of the base layer, studies have been conducted to add rubber powder to cement-stabilized gravel mixtures. By modifying the rubber powder, while ensuring its bonding ability with cement-based materials, the high elasticity of the rubber powder is used to improve the toughness and shrinkage crack resistance of the mixture, effectively preventing and controlling reflective cracks in semi-rigid base asphalt pavements and promoting resource conservation and utilization. However, existing research is based on the incorporation of rubber powder into cement-stabilized gravel mixtures with natural aggregates, and research on the incorporation of rubber powder into cement-stabilized construction waste mixtures with recycled aggregates has not yet been recorded.

[0004] In the existing technology, crushed stone and other materials are often used in water-stable base layers in road engineering construction, which still has the following shortcomings: the soaring prices of natural resources have led to a substantial increase in construction costs; the excessive exploitation of natural resources is not conducive to environmental protection and the sustainable development of engineering construction, and also increases environmental governance costs.

[0005] Therefore, as the scale of construction expands, there is an urgent need to find a new material for road construction to reduce construction costs, reduce over-exploitation of resources, respond to the country's low-carbon economy, and at the same time improve road surface strength and reduce cracking problems. Summary of the Invention

[0006] The present invention provides a pavement base mixture and a preparation method thereof. The prepared pavement base mixture is obtained by adding construction solid waste recycled materials, modified iron tailings and modified asphalt to obtain a mixed structure with high strength, good stability and durability. The pavement base mixture has good frost resistance, impermeability and mechanical properties, is suitable for the base construction of municipal roads and highways, and solves the problems of high road construction costs, over-exploitation of resources, low road strength and easy cracking proposed in the above-mentioned background technology.

[0007] In a first aspect, the present invention provides a pavement base mixture, consisting of the following components in parts by weight: 50 to 65 parts of recycled construction solid waste, 12 to 15 parts of modified iron tailings, 8 to 10 parts of cement, 7 to 9 parts of modified asphalt, 2.5 to 3.5 parts of additives, and 25 to 30 parts of water.

[0008] As a preferred technical solution of the present invention, the modified iron tailings are prepared by mixing iron tailings and modified rubber powder in a mass ratio of 3 to 4:1.

[0009] As a preferred technical solution of the present invention, the modified asphalt is prepared by stirring and mixing the following components in parts by weight: 50-60 parts of asphalt, 8-12 parts of straw powder, 5-8 parts of hydroxypropyl methylcellulose, and 2-3 parts of sodium lauryl sulfate.

[0010] As a preferred technical solution of the present invention, the recycled construction solid waste material includes concrete aggregate, ceramics, gypsum and glass, and the mass ratio of the concrete aggregate, ceramics, gypsum and glass is 1-2:2-3:1-2:0.5-1.

[0011] As a preferred technical solution of the present invention, the modified rubber powder is prepared by adding 2.0-2.5% NaOH and 1.5-2.0% KMnO4 by weight of the rubber powder, mixing and stirring for 20-25 minutes, and then adding 1.8-2.5% silane coupling agent by weight of the rubber powder and performing silane grafting treatment for 30-35 minutes.

[0012] As a preferred technical solution of the present invention, the mass concentration of the NaOH is 80-85%, and the mass concentration of the KMnO4 is 85-90%.

[0013] As a preferred technical solution of the present invention, the silane coupling agent is composed of γ-aminopropyltriethoxysilane (KH-550) and γ-glycidyloxypropyltrimethoxysilane (KH-560) in a mass ratio of 1.2 to 1.5:1.

[0014] As a preferred technical solution of the present invention, the cement is PO 32.5 ordinary Portland cement.

[0015] As a preferred technical solution of the present invention, the auxiliary agent is any one of cellulose, resin glue, and lignin, or a mixture of two of them.

[0016] In a second aspect, the present invention provides a method for preparing a road base mixture, comprising the following steps:

[0017] S1. Weigh construction solid waste recycled materials, modified iron tailings, cement, and modified asphalt in proportion, place them in a first mixing bin, stir and mix them, and then take out to obtain mixture A.

[0018] S2. Mixture A, additives and water are placed in a second mixing bin and stirred to obtain a pavement base mixture.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. In the present invention, modified iron tailings are prepared by adding modified rubber powder to iron tailings. The modified rubber powder is surface treated with NaOH and KMnO4, and then subjected to silane grafting treatment. This can significantly improve the compatibility and bonding effect of the rubber powder with the concrete interface, reduce the generation of micro cracks in the matrix, and improve the utilization rate of the iron tailings while improving the compressive strength of the mixture. Among them, the NaOH solution makes the rubber surface hydrophilic by removing substances such as zinc stearate on the rubber surface, thereby improving the bonding performance of the rubber and the concrete matrix. KMnO4 oxidizes the double bonds on the rubber surface through its strong oxidizing properties, introduces polar groups such as hydroxyl (-OH), thereby enhancing the hydrophilicity and roughness of the rubber surface, and improving the bonding ability of the rubber and the mixture. Silane grafting treatment is a method for effectively improving the performance of rubber powder. The dispersibility, compatibility and comprehensive performance of the rubber powder can be significantly improved by silane grafting treatment. The high silicon content of the iron tailings can be used as an active filler, which complements the elasticity of the rubber and broadens its application in green building materials.

[0021] 2. The present invention adds modified asphalt during the preparation of the pavement base mixture. The modified asphalt can significantly improve the stability, durability and shear resistance of the asphalt, and slow down the formation of pavement cracks. Hydroxypropyl methylcellulose optimizes its compaction performance and mechanical properties by changing the viscosity and volume characteristics of asphalt, making it an effective modifier that helps improve the overall quality and durability of the mixture. Hydroxypropyl methylcellulose plays a role in modified asphalt mainly by thickening, improving rutting resistance and optimizing mechanical properties. The role of sodium dodecyl sulfate in modified asphalt is mainly reflected in its emulsification, anti-aging, improved compatibility and promotion of pore structure formation. Straw fiber significantly improves the high-temperature performance and shear resistance of asphalt by enhancing the adhesion and stability of asphalt. The addition of straw powder can improve the water stability of asphalt mixtures, thereby adapting to the needs of rainy areas and extending the service life of pavement. In addition, the three-dimensional network structure of straw powder helps to disperse stress, slow down the formation and development of cracks, and further improve the durability of modified asphalt. Sodium dodecyl sulfate, hydroxypropyl methylcellulose, and straw powder act synergistically in modified asphalt, not only increasing the gelation temperature of hydroxypropyl methylcellulose but also altering its gelation process, thereby improving asphalt performance. Furthermore, the association process between sodium dodecyl sulfate and hydroxypropyl methylcellulose reduces free energy, thereby altering the critical association concentration and saturation point of the polymers. Straw powder improves asphalt adhesion and durability by enhancing interfacial properties and providing physical support, further enhancing its compatibility with asphalt.

[0022] 3. The modified rubber powder in the present invention is susceptible to desulfurization and degradation reactions at high temperatures. These chemical reactions alter the colloidal structure and properties of the asphalt. The rubber particles swell and partially degrade, forming an interpenetrating network structure with the asphaltene in the asphalt. This structure significantly enhances the overall strength and temperature adaptability of the material. After the modified rubber powder is treated with silane grafting, chemical modification with a silane coupling agent improves the compatibility and adhesion of the rubber powder with the interface. Silane grafting significantly improves the surface chemical properties of the rubber powder, thereby enhancing its interfacial interaction with the sodium lauryl sulfate surfactant. The chemical bonding of the hydroxyl groups in the hydroxypropyl methylcellulose with the silane coupling agent in the modified rubber powder significantly enhances the material's performance.

[0023] 4. The pavement base mixture prepared by the present invention, by adding construction solid waste recycled materials, modified iron tailings, and modified asphalt, obtains a mixed structure with strength, stability, and durability. This gives the pavement base mixture excellent frost resistance, impermeability, and mechanical properties, making it suitable for base construction of municipal roads and highways. Furthermore, since construction solid waste recycled materials and iron tailings are both solid wastes, their solid waste recycling can effectively reduce construction costs, reduce overexploitation of resources, and contribute to a low-carbon economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a flow chart for preparing the pavement base mixture. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] like Figure 1 As shown, the present invention provides a method for preparing a pavement base mixture, comprising the following preparation steps: Step 1, preparation of modified iron tailings: weighing rubber powder, adding NaOH and KMnO4, mixing and stirring for 20 minutes, and then adding a silane coupling agent for silane grafting treatment for 30 minutes to obtain modified rubber powder; mixing the iron tailings and modified rubber powder in proportion to obtain modified iron tailings. Step 2, preparation of modified asphalt: stirring and mixing asphalt, straw powder, hydroxypropyl methylcellulose, and sodium lauryl sulfate to obtain modified asphalt. Step 3, weighing construction solid waste recycled materials, modified iron tailings, cement, and modified asphalt in proportion, and placing them in a first mixing bin, stirring and mixing, and then taking out to obtain mixture A. Step 4, placing mixture A, additives, and water in a second mixing bin, stirring and mixing to obtain a pavement base mixture.

[0027] The raw materials used in the present invention are all commercially available raw materials.

[0028] Example 1:

[0029] A pavement base mixture is composed of the following components in parts by weight: 50 parts of recycled construction solid waste (composed of concrete aggregate, ceramics, gypsum and glass in a mass ratio of 1:2:1:0.5), 12 parts of modified iron tailings, 8 parts of cement (P.O32.5 ordinary Portland cement), 7 parts of modified asphalt, 2.5 parts of auxiliary resin glue, and 25 parts of water.

[0030] Preparation of modified iron tailings: (1) Preparation of modified rubber powder: Weigh the rubber powder, add 2.0% NaOH (NaOH mass concentration is 80%) and 1.5% KMnO4 (KMnO4 mass concentration is 85%) based on the weight of the rubber powder, mix and stir for 20 minutes, then add 1.8% silane coupling agent (KH-550 and KH-560 in a mass ratio of 1.2:1) based on the weight of the rubber powder and carry out silane grafting treatment for 30 minutes to obtain the product; (2) Preparation of modified iron tailings: Mix the iron tailings and modified rubber powder in a mass ratio of 3:1 to obtain the product.

[0031] Preparation of modified asphalt: 50 parts of asphalt, 8 parts of straw powder, 5 parts of hydroxypropyl methylcellulose and 2 parts of sodium lauryl sulfate were weighed and mixed.

[0032] A method for preparing a road base mixture comprises the following steps:

[0033] S1 weighed construction solid waste recycled materials, modified iron tailings, cement and modified asphalt in proportion, and placed in the first mixing bin and stirred, and then removed to obtain a mixture A;

[0034] S2. Mixture A, additives and water are placed in a second mixing bin and stirred to obtain a pavement base mixture.

[0035] Example 2:

[0036] A pavement base mixture is composed of the following components in parts by weight: 65 parts of recycled construction solid waste (composed of concrete aggregate, ceramic, gypsum and glass in a mass ratio of 2:3:2:1), 15 parts of modified iron tailings, 10 parts of cement (PO 32.5 ordinary Portland cement), 9 parts of modified asphalt, 3.5 parts of auxiliary cellulose and 30 parts of water.

[0037] Preparation of modified iron tailings: (1) Preparation of modified rubber powder: Weigh the rubber powder, add 2.5% NaOH (NaOH mass concentration is 85%) and 2.0% KMnO4 (KMnO4 mass concentration is 90%) based on the weight of the rubber powder, mix and stir for 25 minutes, then add 2.5% silane coupling agent (KH-550 and KH-560 in a mass ratio of 1.5:1) based on the weight of the rubber powder and carry out silane grafting treatment for 35 minutes to obtain the product; (2) Preparation of modified iron tailings: Mix the iron tailings and modified rubber powder in a mass ratio of 4:1 to obtain the product.

[0038] Preparation of modified asphalt: 60 parts of asphalt, 12 parts of straw powder, 8 parts of hydroxypropyl methylcellulose and 3 parts of sodium lauryl sulfate were weighed and mixed.

[0039] A method for preparing a road base mixture comprises the following steps:

[0040] S1 weighed construction solid waste recycled materials, modified iron tailings, cement and modified asphalt in proportion, and placed in the first mixing bin and stirred, and then removed to obtain a mixture A;

[0041] S2. Mixture A, additives and water are placed in a second mixing bin and stirred to obtain a pavement base mixture.

[0042] Example 3:

[0043] A pavement base mixture is composed of the following components in parts by weight: 60 parts of recycled construction solid waste (composed of concrete aggregate, ceramic, gypsum and glass in a mass ratio of 1:2:1:1), 13 parts of modified iron tailings, 9 parts of cement (PO 32.5 ordinary Portland cement), 8 parts of modified asphalt, 3.0 parts of additives (composed of resin glue and lignin in a mass ratio of 1:1), and 28 parts of water.

[0044] Preparation of modified iron tailings: (1) Preparation of modified rubber powder: Weigh the rubber powder, add 2.2% NaOH (NaOH mass concentration is 85%) based on the weight of the rubber powder and 1.8% KMnO4 (KMnO4 mass concentration is 85%) based on the weight of the rubber powder, mix and stir for 22 minutes, then add 2.0% silane coupling agent (KH-550 and KH-560 in a mass ratio of 1.3:1) based on the weight of the rubber powder and carry out silane grafting treatment for 32 minutes to obtain the product; (2) Preparation of modified iron tailings: Mix the iron tailings and modified rubber powder in a mass ratio of 3.5:1 to obtain the product.

[0045] Preparation of modified asphalt: 55 parts of asphalt, 10 parts of straw powder, 6 parts of hydroxypropyl methylcellulose, and 2.5 parts of sodium lauryl sulfate were weighed and mixed.

[0046] A method for preparing a road base mixture comprises the following steps:

[0047] S1 weighed construction solid waste recycled materials, modified iron tailings, cement and modified asphalt in proportion, and placed in the first mixing bin and stirred, and then removed to obtain a mixture A;

[0048] S2. Mixture A, additives and water are placed in a second mixing bin and stirred to obtain a pavement base mixture.

[0049] Comparative Example 1:

[0050] The difference from the first embodiment is that the construction solid waste recycled materials are removed.

[0051] Comparative Example 2:

[0052] The difference from the first embodiment is that the modified iron tailings are removed.

[0053] Comparative Example 3:

[0054] The difference from Example 1 is that the modified asphalt is removed.

[0055] Comparative Example 4:

[0056] The difference from Example 1 is that the modified asphalt is replaced with No. 70 ordinary asphalt.

[0057] The pavement base mixtures prepared in Examples 1, 2, and 3 and Comparative Examples 1, 2, 3, and 4 were molded into unconfined compressive strength specimens at a compaction degree of 96%. After curing for 6 days under standard conditions and immersion in water for 1 day, unconfined compressive strength testing, shrinkage testing, and compressive rebound modulus testing were performed. The test results are shown in Table 1.

[0058] Table 1

[0059]

[0060] As shown in Table 1, the pavement base mixtures prepared in Examples 1, 2, and 3 all exhibited significant 7d unconfined compressive strength, shrinkage change, and 7d compressive rebound modulus tests. The pavement base mixtures prepared in Examples 1, 2, and 3 exhibited excellent compressive strength and shrinkage, demonstrating that the addition of recycled construction solid waste, modified iron tailings, and modified asphalt to the pavement base mixture resulted in a high-strength, stable, and durable hybrid structure. This resulted in the pavement base mixture exhibiting excellent frost resistance, impermeability, and mechanical properties, making it suitable for base construction on municipal roads and highways.

[0061] According to JTG E51-2009 "Test Procedure for Inorganic Binder Stabilized Materials for Highway Engineering", the pavement base mixtures prepared in Examples 1, 2, and 3 and Comparative Examples 1, 2, 3, and 4 were subjected to compaction tests and road performance tests. The test results are shown in Table 2.

[0062] Table 2

[0063]

[0064] As can be seen from Table 2, the pavement base mixtures prepared in Examples 1, 2, and 3 have relatively high maximum dry density, 7d splitting tensile strength, and 7d flexural strength. Modified rubber powder, after surface treatment with NaOH and KMnO4 and subsequent silane grafting, significantly improves the compatibility and bonding between the rubber powder and the concrete interface, reducing the generation of microcracks in the matrix. Rubber powder can form a flexible matrix that absorbs energy during crack propagation and slows the rate of crack expansion. Modified rubber powder can reduce the shrinkage of the cementitious material in the base material, reduce internal stress, and help reduce the generation and expansion of cracks. Incorporating an appropriate amount of recycled construction solid waste can increase the toughness and tensile strength of the base material, thereby improving crack resistance. Pavement base mixtures with higher 7-day splitting tensile strength have better crack resistance because high strength indicates a tighter internal structure and greater resistance to crack propagation. The increase in 7-day splitting tensile strength indicates an increase in the tensile strength and flexural strength of the pavement base mixture, which will make the pavement base mixture more capable of withstanding external loads and stresses, reduce the width and depth of cracks, and reduce the possibility of crack generation, thereby improving the durability and stability of the base material and thus improving the crack resistance.

[0065] The following tests were conducted on the pavement base mixtures prepared in Examples 1, 2, 3 and Comparative Examples 1, 2, 3 and 4:

[0066] Improved vacuum saturated Marshall test, the test standard refers to T0709-2000 "Marshall stability test for asphalt mixture" and GB / T2050123-2019 "Standard for geotechnical test methods".

[0067] Flexible wall test; test standards refer to ASTM D5887 and ASTM D5084.

[0068] Wet-dry cycle test: the test standard refers to ASTM D4843.

[0069] The test results are shown in Table 3.

[0070] Table 3

[0071]

[0072] As shown in Table 3, the pavement base mixtures prepared in Examples 1, 2, and 3 exhibited minimal mass loss and high unconfined compressive strength after 10 cycles. By incorporating recycled construction solid waste, modified iron tailings, and modified asphalt into the pavement base mixture, a high-strength, stable, and durable hybrid structure was achieved, resulting in excellent frost resistance, impermeability, and mechanical properties for municipal roads and highways.

[0073] In summary, the present invention obtains a mixed structure with high strength, good stability and durability by adding construction solid waste recycled materials, modified iron tailings and modified asphalt to the pavement base mixture, so that the pavement base mixture has good frost resistance, impermeability and mechanical properties, and reuses construction solid waste recycled materials and iron tailings solid waste, effectively reducing construction costs, reducing excessive resource development, forming a low-carbon economy, and is suitable for the base construction of municipal roads and highways.

[0074] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications based on the present invention to solve substantially the same technical problems and achieve substantially the same technical effects are all included in the scope of protection of the present invention.

Claims

1. A road base mixture, characterized in that: The invention is composed of the following components in parts by weight: 50 to 65 parts of construction solid waste recycled materials, 12 to 15 parts of modified iron tailings, 8 to 10 parts of cement, 7 to 9 parts of modified asphalt, 2.5 to 3.5 parts of additives, and 25 to 30 parts of water; The modified iron tailings are prepared by mixing iron tailings and modified rubber powder in a mass ratio of 3 to 4:1; The modified asphalt is prepared by stirring and mixing the following components in parts by weight: 50-60 parts of asphalt, 8-12 parts of straw powder, 5-8 parts of hydroxypropyl methylcellulose, and 2-3 parts of sodium lauryl sulfate.

2. The pavement base mixture according to claim 1, characterized in that: The construction solid waste recycled material includes concrete aggregate, ceramics, gypsum and glass, and the mass ratio of the concrete aggregate, ceramics, gypsum and glass is 1-2:2-3:1-2:0.5-1.

3. The pavement base mixture according to claim 1, characterized in that: The modified rubber powder is prepared by adding 2.0-2.5% NaOH and 1.5-2.0% KMnO4 based on the weight of the rubber powder, mixing and stirring for 20-25 minutes, and then adding 1.8-2.5% silane coupling agent based on the weight of the rubber powder and performing silane grafting treatment for 30-35 minutes.

4. The pavement base mixture according to claim 3, characterized in that: The mass concentration of the NaOH is 80-85%, and the mass concentration of the KMnO4 is 85-90%.

5. The road base mixture according to claim 3, characterized in that: The silane coupling agent is composed of gamma-aminopropyltriethoxysilane and gamma-glycidyloxypropyltrimethoxysilane in a mass ratio of 1.2 to 1.5:

1.

6. The road base mixture according to claim 1, characterized in that: The cement is PO 32.5 ordinary Portland cement.

7. The pavement base mixture according to claim 1, characterized in that: The auxiliary agent is any one of cellulose, resin glue and lignin or a mixture of two of them.

8. The method for preparing a road base mixture according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1 weighed construction solid waste recycled materials, modified iron tailings, cement and modified asphalt in proportion, and placed in the first mixing bin and stirred, and then removed to obtain a mixture A; S2. Mixture A, additives and water are placed in a second mixing bin and stirred to obtain a pavement base mixture.

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