Straight-dipping asphalt mixture based on light-weight SBS modifier and preparation method thereof

Abstract

The application discloses a kind of direct mixing asphalt mixture based on light SBS modifier and preparation method thereof, including matrix asphalt, light SBS modifier, aggregate and fiber;Aggregate includes steel slag, limestone and mineral powder, and the aggregate is according to SMA grading, and 10-15mm and 5-10mm in this grading are carbonized steel slag, 0-3mm is limestone, and the rest is mineral powder;Light SBS modifier includes cosolvent, crosslinking agent and foaming SBS;When preparing, aggregate is dry mixed with light SBS modifier, fiber, then matrix asphalt is wet mixed, and asphalt mixture is prepared.The application is based on foaming SBS, and light SBS modifier is obtained;And at the same time, based on the addition of carbonized steel slag as aggregate, not only the problem of expansion involved in subsequent hydration reaction caused by steel slag is avoided, but also the strength of the asphalt mixture is enhanced, the mechanical properties are improved, and the steel slag is fully utilized, green and environmentally friendly.

Description

Technical Field

[0001] This invention belongs to the field of asphalt mixture preparation, and particularly relates to a direct-mix asphalt mixture based on a lightweight SBS modifier and its preparation method. Background Technology

[0002] Lightweight materials are a key focus of new materials development, and foaming is the most direct means of achieving polymer lightweighting. Foaming technology generally refers to microcellular foaming molding technology. In injection molding, extrusion, and blow molding processes, supercritical carbon dioxide or nitrogen gas is first injected into a special plasticizing device, allowing the gas to fully and uniformly mix / diffuse with the molten raw material to form a single-phase mixed sol. This sol is then introduced into a mold cavity or die, causing a huge pressure drop in the mixed sol, resulting in the precipitation and formation of numerous bubble nuclei within it. During the subsequent cooling and molding process, the bubble nuclei inside the sol continuously grow and solidify, ultimately obtaining microcellular foamed plastic products – this is the process of foaming technology. In road surface materials, foaming technology has both advantages and disadvantages. While achieving lightweighting through foaming technology reduces material usage, it also lowers strength. Therefore, achieving a balance between lightweight materials and strength is crucial.

[0003] Steel slag is the molten slag discharged during the steelmaking process. It is formed by the reaction of the furnace charge (primarily pig iron, carbon, silicon, manganese, phosphorus, etc.) with limestone at high temperatures using air or oxygen. With the development of the steel industry, the amount of steel slag has increased significantly, and its disposal without utilization leads to increasingly severe environmental pollution. In the past, the long-term neglect and accumulation of steel slag on slag heaps not only occupied large amounts of land but also caused serious environmental pollution. Therefore, effectively utilizing this steel slag can bring both good economic benefits and significant environmental protection.

[0004] The application of steel slag as a substitute for traditional mineral aggregates in asphalt concrete has begun to be studied in depth. However, steel slag contains free calcium oxide and free magnesium oxide, which will generate calcium hydroxide and magnesium hydroxide in the later hydration reaction, causing gas expansion and leading to potential instability issues in steel slag-containing building materials. Solving the problem of poor stability of steel slag is key to the large-scale resource development and utilization of steel slag. Steel slag has high carbonation reactivity in carbon dioxide-rich environments, and accelerating the preparation of building materials from carbonized steel slag is one way to utilize steel slag resources. When steel slag reacts with carbon dioxide, it can not only absorb and solidify greenhouse gases, but also form carbonate products with stable microstructures, which can be used to prepare building materials.

[0005] Based on this, we continue with an asphalt mixture that achieves lightweighting while avoiding impact on properties such as strength. Summary of the Invention

[0006] Purpose of the invention: The technical problem to be solved by the present invention is to provide a direct-mix asphalt mixture based on a lightweight SBS modifier and its preparation method. This asphalt mixture achieves material lightweighting while avoiding the impact on strength, and makes full use of steel slag waste, making it green and environmentally friendly.

[0007] Technical solution: The present invention is a direct-mix asphalt mixture based on a lightweight SBS modifier, comprising base asphalt, lightweight SBS modifier, aggregates and fibers. The amount of base asphalt added is 4-6% of the asphalt mixture, the amount of lightweight SBS modifier added is 3-5% of the base asphalt, and the amount of fibers added is 0.2-0.3% of the asphalt mixture.

[0008] The aggregate includes steel slag, limestone, and mineral powder, and is graded according to SMA gradation. In this gradation, the 10-15mm and 5-10mm portions are carbonized steel slag, the 0-3mm portion is limestone, and the remainder is mineral powder. The carbonized steel slag is produced by carbonizing steel slag, sodium gluconate, and water in a weight ratio of 1:(0.05-0.1):(0.08-0.1).

[0009] The lightweight SBS modifier comprises a cosolvent, a crosslinking agent, and foaming SBS in a weight ratio of (0.5-1):(0.01-0.08):1.

[0010] This invention, based on foamed SBS and combined with carbonized steel slag, not only achieves material lightweighting but also avoids weakening of strength and other properties, thus improving mechanical properties. The specific surface area of ​​the foamed SBS facilitates SBS dispersion, and its larger porosity allows for the adsorption of various additives, ensuring complete integration with the SBS and increasing the melt flow index of the modifiers, enabling rapid melting and dispersion to achieve the desired modification effect. Secondly, sodium gluconate is used as a carbonization additive to carbonize the steel slag. The addition of gluconate, on the one hand, makes the slurry alkaline after dissolving in water, promoting the synergistic hydration and carbonization reaction of the steel slag-nickel slag; on the other hand, sodium gluconate, after dissolving in water, adheres to the surface of the steel slag, inducing complexation of metal cations within the steel slag matrix. This, in turn, triggers the diffusion of alkali metal cations from the steel slag matrix to the surface, increasing the leaching of metal cations and promoting the combination reaction of metal cations with carbonate ions in the coarse pores, capillaries, and gel pores of the steel slag. This results in a more complete carbonization reaction of the steel slag, generating more carbonate products and improving the strength of the resulting asphalt mixture.

[0011] Furthermore, in the SMA gradation of the asphalt mixture of the present invention, the proportion of 10-15mm steel slag is 40%, the proportion of 5-10mm steel slag is 38%, the proportion of 0-3mm limestone is 12%, and the proportion of mineral powder is 10%.

[0012] Furthermore, the base asphalt in the asphalt mixture of the present invention can be petroleum asphalt, tar asphalt, or natural asphalt.

[0013] Furthermore, the carbonized steel slag in the asphalt mixture of the present invention can be obtained by the following steps: the steel slag is mixed evenly with sodium gluconate and water, and the resulting cake sample is placed in a carbonization kettle. CO2 with a concentration of 80-100 wt.% is introduced, and the carbonization reaction is carried out for 1.5-3 hours under the conditions of pressure 0.5-1 MPa and temperature 65-80℃. Then, the mixture is ground for 20-30 minutes.

[0014] This invention performs a carbonization reaction on steel slag. During carbonization, water molecules diffuse into the coarse pores, capillary pores, and gel pores of the steel slag and diffuse into the interior of the steel slag. The surrounding carbon dioxide diffuses to the surface of the steel slag and dissolves in the water to form carbonate ions. The alkali metal cations in the steel slag are fully leached out and react with carbonate ions to form carbonates. This avoids the potential for gas expansion caused by free calcium oxide and magnesium oxide in the steel slag during the later hydration reaction, which could lead to poor stability.

[0015] Furthermore, the solvent oil in the asphalt mixture of the present invention can be white oil, and the crosslinking agent can be sulfur, DTDM vulcanizing agent, DTDC vulcanizing agent, or polysulfide alkylphenol.

[0016] Furthermore, the foamed SBS in the asphalt mixture of the present invention can be prepared by the following steps: placing SBS in a sealed high-pressure autoclave, maintaining pressure at 150-180℃ and 10-30MPa CO2 pressure for 20-30 minutes, then cooling to 100-120℃ within 5 minutes, and then releasing the gas to obtain foamed SBS.

[0017] Furthermore, the density of steel slag in the asphalt mixture of this invention is ≥2.9 kg / m³. 3 Moisture content ≤0.5%, CaO+MgO ≥40.0wt%.

[0018] Furthermore, the asphalt mixture of the present invention contains basalt fiber, glass fiber, lignin fiber or bamboo fiber.

[0019] The method for preparing the above-mentioned direct-mix asphalt mixture according to the present invention includes the following steps: dry mixing aggregates with lightweight SBS modifier and fiber at 180-195℃, and then adding base asphalt and wet mixing at 165-175℃ to obtain asphalt mixture.

[0020] Beneficial effects: Compared with the prior art, the significant advantages of the present invention are: the asphalt mixture is based on foamed SBS and obtains a lightweight SBS modifier, which reduces the amount of SBS modifier used; at the same time, the addition of carbonized steel slag as aggregate not only avoids the problem of expansion caused by steel slag during subsequent hydration reaction, but also enhances the strength of the asphalt mixture, improves mechanical properties, and makes full use of steel slag waste, which is green and environmentally friendly. Detailed Implementation

[0021] The technical solution of the present invention will be further described in detail below with reference to the embodiments.

[0022] It should be noted that all raw materials used in this invention are commercially available. Specifically, the steel slag used is directly waste steel slag from steel plants, with a density ≥2.9 kg / m³. 3 Moisture content ≤0.5%, CaO+MgO ≥40.0wt%.

[0023] The aggregates used in this invention include steel slag and limestone, and their gradation is designed according to SMA, as shown in Table 1 below.

[0024] Table 1. Aggregate Gradation Table

[0025] Graded 10-15mm 5-10mm 0-3mm raw material Carbide steel slag Carbide steel slag limestone Mineral powder Percentage / % 40 38 12 10

[0026] Example 1

[0027] The raw material composition of the asphalt mixture in this embodiment is shown in Table 1 below.

[0028] Table 1. Raw material composition of asphalt mixture in Example 1

[0029]

[0030] The method for preparing asphalt mixture in this embodiment includes the following steps:

[0031] (1) Preparation of carbonized steel slag: The steel slag is mixed with sodium gluconate and water evenly, and the sample is made into a cake and placed in a carbonization kettle. CO2 with a concentration of 90 wt% is introduced and carbonized for 2.5 h under the conditions of 0.8 MPa pressure and 70℃ temperature. Then it is ground.

[0032] (2) Preparation of foamed SBS: SBS was placed in a sealed high-pressure autoclave and held at 170°C for 25 minutes under a supercritical CO2 pressure of 20 MPa. Then, the temperature was lowered to 110°C within 5 minutes and the gas was released to obtain foamed SBS.

[0033] (3) Preparation of asphalt mixture: The aggregate, lightweight SBS modifier, and fiber are first dry-mixed at 190°C, and then the base asphalt is added and wet-mixed at 170°C to obtain the asphalt mixture.

[0034] Example 2

[0035] The raw material composition of the asphalt mixture in this embodiment is shown in Table 2 below.

[0036] Table 2. Asphalt mixture raw material composition of Example 2

[0037]

[0038]

[0039] The method for preparing asphalt mixture in this embodiment includes the following steps:

[0040] (1) Preparation of carbonized steel slag: The steel slag is mixed with sodium gluconate and water evenly, and the sample is made into a cake. The cake is placed in a carbonization kettle, and CO2 with a concentration of 95 wt% is introduced. The carbonization reaction is carried out for 2 hours under the conditions of 0.7 MPa pressure and 75℃ temperature. Then it is ground.

[0041] (2) Preparation of foamed SBS: SBS is placed in a sealed high-pressure autoclave and held at 160°C for 25 min under supercritical CO2 pressure of 25 MPa. Then, the temperature is reduced to 110°C within 5 min and the gas is released to obtain foamed SBS.

[0042] (3) Preparation of asphalt mixture: The aggregate, lightweight SBS modifier, and fiber are first dry-mixed at 190°C, and then the base asphalt is added and wet-mixed at 170°C to obtain the asphalt mixture.

[0043] Example 3

[0044] The raw material composition of the asphalt mixture in this embodiment is shown in Table 3 below.

[0045] Table 3. Raw material composition of asphalt mixture in Example 3

[0046]

[0047] The method for preparing asphalt mixture in this embodiment includes the following steps:

[0048] (1) Preparation of carbonized steel slag: The steel slag is mixed with sodium gluconate and water evenly, and the sample is made into a cake and placed in a carbonization kettle. CO2 with a concentration of 80 wt.% is introduced and carbonized for 3 hours under the conditions of 0.5 MPa pressure and 65℃ temperature. Then it is ground.

[0049] (2) Preparation of foamed SBS: SBS is placed in a sealed high-pressure autoclave and held at 150°C for 30 minutes under a supercritical CO2 pressure of 10 MPa. Then, the temperature is lowered to 100°C within 5 minutes and the gas is released to obtain foamed SBS.

[0050] (3) Preparation of asphalt mixture: The aggregate, lightweight SBS modifier, and fiber are first dry-mixed at 180°C, and then the base asphalt is added and wet-mixed at 165°C to obtain the asphalt mixture.

[0051] Example 4

[0052] The raw material composition of the asphalt mixture in this embodiment is shown in Table 4 below.

[0053] Table 4. Raw material composition of asphalt mixture in Example 4

[0054]

[0055] The method for preparing asphalt mixture in this embodiment includes the following steps:

[0056] (1) Preparation of carbonized steel slag: Mix steel slag with sodium gluconate and water evenly, make a cake sample block and place it in a carbonization kettle, introduce CO2 with a concentration of 100vt.%, and carbonize for 1.5h under the conditions of 1MPa pressure and 80℃ temperature, then grind for 30min.

[0057] (2) Preparation of foamed SBS: SBS is placed in a sealed high-pressure autoclave and held at 180°C for 20 minutes under a supercritical CO2 pressure of 30 MPa. Then, the temperature is lowered to 120°C within 5 minutes and the gas is released to obtain foamed SBS.

[0058] (3) Preparation of asphalt mixture: The aggregate, lightweight SBS modifier, and fiber are first dry-mixed at 195°C, and then the base asphalt is added and wet-mixed at 175°C to obtain the asphalt mixture.

[0059] Comparative Example 1

[0060] The basic steps are the same as in Example 1, except that steel slag is used directly to prepare the asphalt mixture instead of carbonized steel slag. The raw material composition and content are shown in Table 5 below.

[0061] The raw material composition of the asphalt mixture in this comparative example is shown in Table 5 below.

[0062] Table 5. Raw material composition of asphalt mixture in Comparative Example 1

[0063]

[0064] The method for preparing asphalt mixture in this embodiment includes the following steps:

[0065] (1) Preparation of foamed SBS: SBS was placed in a sealed high-pressure autoclave and held at 170°C for 25 min under supercritical CO2 pressure of 20 MPa. Then, the temperature was lowered to 110°C within 5 min and the gas was released to obtain foamed SBS.

[0066] (2) Preparation of asphalt mixture: The aggregate, lightweight SBS modifier, and fiber are first dry-mixed at 190°C, and then the base asphalt is added and wet-mixed at 170°C to obtain the asphalt mixture.

[0067] Comparative Example 2

[0068] The basic steps are the same as in Example 1, except that sodium gluconate, a carbonization aid, is not added to the carbonized steel slag. The raw material composition and content are shown in Table 6 below.

[0069] The raw material composition of the asphalt mixture in Comparative Example 2 is shown in Table 6 below.

[0070] Table 6. Raw material composition of asphalt mixture in Comparative Example 2

[0071]

[0072]

[0073] The method for preparing asphalt mixture in this embodiment includes the following steps:

[0074] (1) Preparation of carbonized steel slag: Mix steel slag and water evenly, make a cake sample block and place it in a carbonization kettle, introduce CO2 with a concentration of 90 vt.%, and carbonize for 2.5 h under the conditions of 0.8 MPa pressure and 70℃ temperature, then grind for 25 min.

[0075] (2) Preparation of foamed SBS: SBS was placed in a sealed high-pressure autoclave and held at 170°C for 25 minutes under a supercritical CO2 pressure of 20 MPa. Then, the temperature was lowered to 110°C within 5 minutes and the gas was released to obtain foamed SBS.

[0076] (3) Preparation of asphalt mixture: The aggregate, lightweight SBS modifier, and fiber are first dry-mixed at 190°C, and then the base asphalt is added and wet-mixed at 170°C to obtain the asphalt mixture.

[0077] According to the testing standards for asphalt mixtures, the asphalt mixtures prepared in Examples 1-4 and Comparative Examples 1-2 were made into sample blocks for performance testing, and the results are shown in Table 7 below.

[0078] Table 7. Asphalt mixture performance test results for Examples 1-4 and Comparative Examples 1-2

[0079]

[0080] As shown in Table 7, the asphalt mixture prepared by this invention is lightweight, and its thermal stability and rutting resistance meet or exceed the requirements.

Claims

1. A direct-mix asphalt mixture based on a lightweight SBS modifier, characterized in that, The mixture includes the following raw materials: base asphalt, lightweight SBS modifier, aggregates, and fibers. The amount of base asphalt added is 4-6% of the mass of the asphalt mixture, the amount of lightweight SBS modifier added is 3-5% of the mass of the base asphalt, and the amount of fibers added is 0.2-0.3% of the mass of the asphalt mixture. The aggregate includes carbide steel slag, limestone, and mineral powder, and the aggregate is graded according to SMA gradation. In this gradation, the 10-15mm and 5-10mm portions are carbide steel slag, the 0-3mm portion is limestone, and the remainder is mineral powder. The carbide steel slag is produced by carbonizing steel slag, sodium gluconate, and water in a weight ratio of 1:(0.05-0.1):(0.08-0.1). The lightweight SBS modifier comprises a cosolvent, a crosslinking agent, and foaming SBS in a weight ratio of (0.5-1):(0.01-0.08):

1.

2. The direct-mix asphalt mixture based on lightweight SBS modifier according to claim 1, characterized in that: In the SMA gradation, 10-15mm carbide steel slag accounts for 40% of the mass, 5-10mm carbide steel slag accounts for 38%, 0-3mm limestone accounts for 12%, and mineral powder accounts for 10%.

3. The direct-mix asphalt mixture based on lightweight SBS modifier according to claim 1, characterized in that, The base asphalt is petroleum asphalt, tar asphalt, or natural asphalt.

4. The direct-mix asphalt mixture based on lightweight SBS modifier according to claim 1, characterized in that, The solvent oil is white oil, and the crosslinking agent is sulfur, DTDM, DTDC, or polysulfide alkylphenol.

5. The direct-mix asphalt mixture based on lightweight SBS modifier according to claim 1, characterized in that, The carbonized steel slag is prepared by the following steps: steel slag is mixed evenly with sodium gluconate and water, and a cake sample is made and placed in a carbonization kettle. CO2 with a concentration of 80-100 wt.% is introduced, and the carbonization reaction is carried out for 1.5-3 hours under the conditions of pressure 0.5-1 MPa and temperature 65-80℃. After that, it is crushed and sieved.

6. The direct-mix asphalt mixture based on lightweight SBS modifier according to claim 1, characterized in that, The foamed SBS is prepared by the following steps: SBS is placed in a sealed autoclave and held at 150-180℃ under a CO2 pressure of 10-30MPa for 20-30 minutes. Then, the temperature is lowered to 100-120℃ within 5 minutes, and the gas is released to obtain foamed SBS.

7. The direct-mix asphalt mixture based on lightweight SBS modifier according to claim 1, characterized in that, The steel slag density is ≥2.9 kg / m³. 3 Moisture content ≤0.5%, CaO+MgO ≥40.0wt%.

8. The direct-mix asphalt mixture based on lightweight SBS modifier according to claim 1, characterized in that, The fiber is basalt fiber, glass fiber, lignin fiber or bamboo fiber.

9. A method for preparing the direct-mix asphalt mixture according to claim 1, characterized in that, The process includes the following steps: dry mixing aggregates with lightweight SBS modifier and fibers at 180-195℃, then adding base asphalt and wet mixing at 165-175℃ to obtain asphalt mixture.

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