Modified steel slag aggregate asphalt mixture and preparation method thereof

Abstract

The application belongs to the technical field of asphalt concrete, and particularly relates to a modified steel slag aggregate asphalt mixture and a preparation method thereof. The modified steel slag aggregate asphalt mixture comprises steel slag aggregate, RO fly ash, modified fiber, amino resin modified asphalt and stearate modified limestone powder. The RO fly ash and the modified fiber are uniformly dispersed on the surface of the steel slag aggregate to form modified steel slag aggregate. The amino resin modified asphalt is attached to the modified steel slag aggregate to form steel slag asphalt mixture. The stearate modified limestone powder is filled in the pores of the steel slag asphalt mixture. The modified steel slag aggregate asphalt mixture is innovatively designed with a multi-stage anti-expansion structure, which fundamentally solves the problem that the steel slag asphalt mixture is prone to expansion and causes pavement diseases, effectively enhances the stability of the steel slag, and greatly improves the road performance and service life of the steel slag asphalt mixture.

Description

Technical Field

[0001] This invention belongs to the technical field of asphalt concrete, specifically relating to a modified steel slag aggregate asphalt mixture and its preparation method. Background Technology

[0002] With my country's massive steel production, the amount of steel slag generated is also enormous. However, the low utilization rate of steel slag has led to a series of problems. For example, the long-term accumulation of large quantities of steel slag not only occupies a large amount of land resources but also pollutes the soil, water, and air. On the other hand, during the advancement of infrastructure construction, high-quality stone resources have become scarce and prices remain high. The large-scale mining of rocks also causes ecological damage such as vegetation destruction and soil erosion. Finding effective alternatives to stone has become an urgent problem to be solved.

[0003] In summary, finding effective alternatives to large quantities of unusable steel slag as aggregate is of significant research importance and economic benefit. Steel slag, a bulk industrial waste, possesses excellent mechanical properties and can be used as an aggregate in asphalt mixtures to alleviate aggregate shortages and improve the utilization rate of industrial solid waste. However, steel slag exhibits poor volume stability upon contact with water; direct use in mixtures without treatment can disrupt the volume of the mixture. Currently, the main methods to address this issue are stockpiling or heat treatment of the steel slag aggregate. The former has drawbacks such as large space requirements, long curing and stabilization periods, and low stability assurance rates; the latter requires large equipment, necessitates specialized construction, and demands high operational standards.

[0004] Furthermore, the mixing temperature for steel slag aggregate in asphalt mixtures needs to be 15-20°C higher than that for ordinary aggregate asphalt mixtures. This higher production temperature leads to increased energy consumption and production costs. Currently, the commonly used fiber in asphalt mixtures is lignin fiber. Lignin fiber is extremely susceptible to moisture, and its performance deteriorates rapidly after becoming damp. If damp lignin fiber is used in steel slag asphalt mixtures, it will affect the expansion of this unstable aggregate.

[0005] Yao Liyang's research on the influence of mineral powder A on the stability of asphalt concrete points out that the surface properties of mineral fillers have a significant impact on the aging stability, water stability, and high and low temperature stability of asphalt mixtures. However, the commonly used limestone mineral powder applied to steel slag asphalt mixtures cannot comprehensively improve the high-temperature stability, water stability, aging stability, and workability of these mixtures. Furthermore, the increasing scarcity of limestone fillers has led to a decline in the quality of mineral powder used in engineering projects. Therefore, research on surface modification technology for fillers used in steel slag asphalt mixtures is particularly important. Currently, many methods for modifying mineral powder involve adding quicklime or hydrated lime powder to increase the alkalinity of the mineral powder surface, but this method cannot achieve the long-term stability of steel slag asphalt mixtures. Summary of the Invention

[0006] The purpose of this invention is to provide a modified steel slag aggregate asphalt mixture and its preparation method. This modified steel slag aggregate asphalt mixture innovatively designs a multi-stage anti-expansion structure, which fundamentally solves the problem of steel slag asphalt mixture easily expanding and causing pavement distress. It effectively enhances the stability of steel slag, significantly improves the road performance and service life of steel slag asphalt mixture, and reduces engineering costs while ensuring the overall stability of asphalt pavement.

[0007] The specific technical solution is as follows:

[0008] A modified steel slag aggregate asphalt mixture, the raw materials of which include steel slag aggregate, RO fly ash, modified fiber, amino resin modified asphalt and stearate modified limestone powder;

[0009] Among them, RO fly ash and modified fibers are evenly dispersed on the surface of steel slag aggregate to form modified steel slag aggregate;

[0010] Amino resin modified asphalt is coated with modified steel slag aggregate to form steel slag asphalt mixture;

[0011] Stearate-modified limestone powder is used to fill the pores of steel slag asphalt mixture.

[0012] First, the RO fly ash and modified fibers in the raw materials are evenly dispersed on the surface of the steel slag aggregate, coating the steel slag aggregate and playing a primary stabilizing role, resulting in modified steel slag aggregate with effectively inhibited expansion activity. Then, the amino resin modified asphalt in the raw materials coats the modified steel slag aggregate, playing a secondary stabilizing role, resulting in a steel slag asphalt mixture that can effectively prevent external water intrusion. The mixing temperature is also greatly reduced, from the traditional 170-190℃ mixing temperature of ordinary mixtures to 130-140℃, allowing for warm mixing and greatly reducing energy consumption. Finally, the stearate-modified limestone powder fills the pores of the steel slag asphalt mixture, playing a tertiary stabilizing role, preventing moisture from entering and improving the road performance of the mixture.

[0013] In this invention, the modified steel slag aggregate asphalt mixture comprises the following raw materials in parts by weight: 85-95 parts steel slag aggregate, 8-15 parts RO fly ash, 0.2-0.25 parts modified fiber, 3-5.5 parts amino resin modified asphalt, and 5-11 parts stearate modified limestone powder.

[0014] In this invention, the steel slag aggregate is one of electric furnace steel slag, blast furnace steel slag, or converter steel slag.

[0015] In this invention, the RO fly ash in the modified steel slag aggregate asphalt mixture is composed of the following raw materials in parts by weight: 21-22 parts of iron oxide powder and 78-79 parts of magnesium oxide powder, wherein the weight of fly ash is 10-15 times the total weight of the iron oxide powder and magnesium oxide powder. The average particle size of the iron oxide powder is 180-200 μm; the average particle size of the magnesium oxide powder is 0.2-0.25 μm. The fly ash contains >10% CaO, ≤25.0% fineness, ≤105% water requirement, and ≤8.0% loss on ignition.

[0016] RO fly ash is a mixture of iron oxide powder, magnesium oxide powder and the aforementioned fly ash. RO is defined as a combination of iron oxide powder and magnesium oxide powder.

[0017] After RO fly ash is evenly dispersed and adheres to the surface of steel slag aggregate, it can form a stable film on the surface of steel slag aggregate. When water seeps in from the top or free water precipitates upward from the bottom, the stable film can effectively control the skeleton cracking caused by the reaction between external water and active substances on the surface of steel slag aggregate. This effectively prevents road structure damage caused by instability of the mixture performance and greatly improves the overall stability of steel slag.

[0018] Fly ash contains a large amount of SiO2, which preferentially undergoes hydration reaction, thereby preventing MgO and Fe2O3 from directly hydrating to form Mg(OH)2 and Fe(OH)3. At the same time, the addition of SiO2 reduces the C / S ratio of the system, increasing the content of high-strength calcium silicate in RO fly ash. This allows it to adhere to the surface of steel slag aggregate as a reinforcement, improving the strength and sealing protection of the steel slag aggregate.

[0019] The siliceous components in the fly ash used in this invention can initially inhibit the expansion of steel slag aggregate, and its CaO content is >10%. Under normal temperature and water conditions, it can generate hydrates with hydraulic cementing ability, exhibiting significant cementing (hydraulic) characteristics and high heat of hydration. The fly ash has a fineness ≤25.0%, water requirement ≤105%, and loss on ignition ≤8.0%. When applied to the active aggregate steel slag aggregate described in this invention, it can effectively prevent moisture intrusion and has certain workability.

[0020] In this invention, the preparation method of RO fly ash in the modified steel slag aggregate asphalt mixture includes the following steps:

[0021] (1) Ingredients: Iron oxide powder with a purity of 99.5% and an average particle size of 180-200μm is mixed and ground with magnesium oxide powder with a purity of 99.9% and an average particle size of 0.2-0.25μm to obtain a powder mixture;

[0022] (2) Granulation: The powder mixture obtained in step (1) is pressed into pellets with a diameter of 7-9 mm and a weight of 0.3-0.5 g using a press.

[0023] (3) First sintering: Sinter the pellets obtained in step (2) in a gas-tight electric furnace with a partial pressure of 6-10 atm and a pressure of 1770-1780 K for 24 hours.

[0024] (4) Cooling, grinding and regranulation: The pellets obtained after the first sintering in step (3) are cooled in the furnace at a rate of 300K / h. After cooling, the pellets are taken out, crushed into powder and ground, and then regranulated.

[0025] (5) Secondary sintering: The pellets obtained by re-granulation are sintered again according to the conditions of the first sintering in step (3). After secondary sintering, after cooling to 20-30℃, fly ash is added and mixed evenly for 15-20s.

[0026] In this invention, the amino resin modified asphalt in the modified steel slag aggregate asphalt mixture is composed of the following raw materials in parts by weight: 94-97 parts of base asphalt and 3-6 parts of amino resin.

[0027] Preferably, the base asphalt is No. 90-110 asphalt; the amino resin is one or more of polyphenylene nitrile resin, lignin-based urea-formaldehyde resin, or mixed etherified melamine resin. The selected amino resin can improve the toughness and high-temperature stability of the asphalt mastic.

[0028] The amino resin-modified asphalt of this invention has a lower viscosity than traditional asphalt, which not only allows for uniform coating of steel slag aggregate, resulting in stronger surface cementitious properties, but also reduces the mixing temperature by 25℃-35℃ compared to traditional mixing, achieving warm mixing and effectively reducing energy consumption. Furthermore, this warm-mix asphalt exhibits superior water stability and high-temperature stability compared to steel slag asphalt mixtures made from ordinary modified asphalt. Additionally, the amino resin-modified asphalt demonstrates better storage stability than ordinary asphalt.

[0029] Furthermore, the amino resin modified asphalt of the present invention does not require other processing aids; it only requires the addition of 3-6 parts of amino resin to the base asphalt and preparation according to the described method.

[0030] In this invention, the preparation method of amino resin modified asphalt in the modified steel slag aggregate asphalt mixture includes the following steps:

[0031] (1) Weigh the base asphalt and weigh the required amino resin according to the mixing ratio;

[0032] (2) Heat the base asphalt to 125-140℃, add the amino resin and stir.

[0033] (3) After mixing evenly, the asphalt is sheared. First, shear at 2000 r / min for 10 min, then shear at 5000 r / min for 30 min. During this process, a thermometer with a metal probe is used to control the temperature so that the temperature is always kept at 140-145℃ during the shearing process.

[0034] (4) After shearing, the amino resin modified asphalt should be developed at 130-145℃ for 30 minutes.

[0035] In this invention, the stearate-modified limestone powder in the modified steel slag aggregate asphalt mixture comprises limestone powder, sodium stearate, and a cement-fly ash mixture; wherein the mass ratio of cement to fly ash in the cement-fly ash mixture is 1:1.

[0036] Preferably, the amount of sodium stearate is 1.0-2.0% of the mass of limestone powder; the amount of cement-fly ash mixture is 0.5-0.7% of the mass of limestone powder.

[0037] The stearate-modified limestone powder, through a combination of physical adsorption and chemical reaction, exhibits an oleophilic-hydrophobic surface, thereby improving its adhesion to steel slag asphalt mixtures and significantly enhancing the aging performance, water stability, and high and low temperature stability of the steel slag asphalt mixture. The surface activation of this stearate-modified limestone powder is significantly higher than that of ordinary limestone powder, and the cement-fly ash mixture further improves the workability between the stearate-modified limestone powder and the steel slag asphalt mixture. Taking AC-20 mixture as an example: Marshall stability is increased by approximately 13%, Marshall modulus is increased by 52%, flow value is reduced by 26%, and dynamic stability is 3.36 times that of ordinary AC-20C limestone powder; residual stability is increased by 2.9%, freeze-thaw splitting strength ratio is increased by 11.3%; maximum flexural strain is increased by 28.2%, flowability is good, and the porosity of the formed asphalt mixture is reduced by 18.6%.

[0038] In this invention, the stearate-modified limestone powder in the modified steel slag aggregate asphalt mixture is prepared by the following steps:

[0039] First, stearate is added to limestone ore powder and mechanically ground for 45-60 seconds to obtain a mixed powder.

[0040] Then, cement-fly ash mixture is added to the mixed powder and mixed evenly to obtain stearate-modified limestone mineral powder.

[0041] Preferably, the cement in the cement-fly ash mixture is slag silicate cement P·S·A 32.5.

[0042] In this invention, the modified fiber in the modified steel slag aggregate asphalt mixture is a hydrophobic modified wheat straw fiber. Compared with existing fibers that are easily affected by moisture and thus lose their performance, the modified fiber used in this invention can effectively avoid moisture absorption, and has a high oil absorption rate, thus reducing the amount used.

[0043] The modified fibers described above were prepared by the following method:

[0044] (1) At room temperature, place deionized water in a glass and add NaOH particles to the deionized water by external doping. Stir thoroughly to prepare NaOH solutions with a concentration of 3-8 wt%.

[0045] (2) Immerse the wheat straw fiber in the prepared NaOH solution, stir it thoroughly with a glass rod to ensure that the NaOH solution is in full contact with the straw fiber, and modify the matrix wheat straw fiber by immersion time of 55-60 min under the same concentration conditions.

[0046] (3) Filter out the modified straw fiber, rinse it with deionized water, and dry it at 47-53℃ until constant weight.

[0047] The preparation method of the above-mentioned modified steel slag aggregate asphalt mixture includes the following steps:

[0048] First, steel slag aggregate is mixed with RO fly ash and modified fiber at a mixing temperature of 125℃-140℃ and a mixing time of 80-90s to obtain modified steel slag aggregate.

[0049] Then, the modified steel slag aggregate and the amino resin modified asphalt are mixed at 130℃-140℃ for 90-100s to obtain steel slag asphalt mixture.

[0050] Finally, stearate-modified limestone mineral powder is added to the steel slag asphalt mixture and mixed at 130℃-140℃ for 80-90 seconds to obtain the modified steel slag aggregate asphalt mixture.

[0051] The beneficial effects of this invention are as follows: The modified steel slag aggregate asphalt mixture of this invention fully utilizes the characteristics of steel slag aggregate and the adhesion properties of asphalt. Firstly, it ensures that all admixtures in the mixture can prevent moisture from contacting the steel slag aggregate, and the performance of each material is superior to that of materials currently used in the market. Secondly, the material structure sequence designed in this invention is as follows: first, RO fly ash and modified fibers are attached to the surface of the steel slag aggregate; then, amino resin-modified asphalt is used to coat the initially modified steel slag aggregate; finally, stearate-modified limestone powder is used for filling. After mixing at the mixing temperature designed in this invention for a certain period of time, the prepared steel slag asphalt mixture has high stability, and the acidic and alkaline materials are alternately and evenly distributed, resulting in stronger cohesion after bonding, and the asphalt film adhering to the outside of the steel slag will not peel off.

[0052] This invention addresses both the raw materials and structure of steel slag aggregate asphalt mixtures, thereby completely inhibiting the surface activity of steel slag. The resulting modified steel slag asphalt mixture exhibits significantly enhanced high-temperature stability, asphalt film anti-stripping ability, water damage resistance, and durability.

[0053] Currently, there are several problems with steel slag aggregates used in road construction: firstly, it's impossible to use only steel slag as aggregate; secondly, steel slag asphalt mixtures using coarse steel slag have insufficient resistance to water damage and lack durability. The modified steel slag aggregate asphalt mixture described in this invention significantly improves the performance of asphalt mixtures using only steel slag aggregates, reducing pavement cracking, asphalt film peeling, water damage, and other defects. It also reduces the mining of road aggregates (limestone, basalt, etc.), protects the ecological environment, lowers engineering costs, and enhances pavement durability. This invention solves the current problems of not being able to use only steel slag aggregates and the inability to guarantee post-use quality, significantly promoting the comprehensive application of steel slag aggregates.

[0054] Compared to traditional steel slag asphalt mixtures, the modified steel slag aggregate asphalt mixture of this invention reduces asphalt usage by at least 10%, fuel oil usage by at least 15%, and extends pavement life by 30-35%, which is equivalent to increasing the return on investment by at least 30%. From a full life-cycle (40-year) perspective, the pavement structure per kilometer constructed using the modified steel slag aggregate asphalt mixture of this invention can reduce energy consumption by approximately 212.68 tons of standard coal and CO2 emissions by approximately 602.16 tons compared to traditional pavement structures.

[0055] Taking a four-lane highway as an example, the modified steel slag aggregate asphalt mixture described in this invention can reduce the cost by about 29,800 yuan per kilometer per lane per year compared to ordinary asphalt mixture. Detailed Implementation

[0056] The technical solution of the present invention will be described in detail below through embodiments.

[0057] 1. Freeze-thaw splitting strength: The specimens for the freeze-thaw splitting strength test were formed using the Marshall compaction method, with 50 compactions on each side. The specimens were divided into two groups of four. One group was immersed in water at 25℃ for 2 hours before testing, while the other group underwent water curing, with the following process: immersion in water at room temperature (approximately 25℃) for 20 minutes; immersion in water at 0.09 MPa under vacuum for 15 minutes; storage in a -18℃ refrigerator for 16 hours; constant temperature in a 60℃ water bath for 24 hours; immersion in water at 25℃ for 2 hours. After curing, the pressure value during fracturing was measured, and the freeze-thaw splitting tensile strength ratio (TSR) was calculated. A higher TSR value indicates better water stability of the mixture.

[0058] 2. Water-immersion Marshall test strength: Marshall specimens of asphalt mixtures were molded according to the requirements of the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering". The dimensions of the specimens were then measured. Subsequent tests were conducted only if the specimens met the following requirements: diameter 101.6±0.2 mm, height 63.5±1.3 mm. A batch of qualified specimens was immersed in a standard constant-temperature water bath at 60℃ for 30-45 minutes, followed by ordinary Marshall stability and flow value tests. Another batch of specimens was immersed in a constant-temperature water bath at 60℃ for 48±1 hours, followed by water-immersion Marshall tests. The loading rate for both tests was 50 mm / min. The percentage of water-immersion Marshall stability to ordinary Marshall stability is the residual stability. A higher residual stability indicates better water stability of the mixture.

[0059] 3. Maximum flexural strain at low temperature: In my country's design specifications, the maximum flexural strain of asphalt mixture at low temperature is often used to characterize its low-temperature performance. The larger the maximum flexural strain, the better the asphalt mixture's ability to resist low-temperature cracking.

[0060] 4. Fatigue Bending Test: Fatigue damage is one of the most common forms of failure in asphalt pavement. The fatigue performance of asphalt mixture refers to its ability to resist repeated loads without cracking under specific load environments and climatic conditions. Under repeated vehicle loads, asphalt pavement is subjected to repeated cyclic changes in stress and strain, which gradually reduces the structural strength of the asphalt pavement. When the load is repeated more than a certain number of times, the load stress exceeds the ultimate strength of the pavement material, causing the pavement to crack, i.e., fatigue failure. The early phenomenon of fatigue cracking is the appearance of continuous cracks in the longitudinal direction of the pavement, followed by more deformation, affecting the usability and durability of the asphalt pavement.

[0061] 5. Hamburg Rutting Depth: The Hamburg rutting test, as a method for evaluating the high-temperature rutting resistance and water stability of asphalt mixtures, has a high correlation between its evaluation results and actual road performance, ensuring consistency between the two. Compared with traditional wheel rutting tests, the Hamburg wheel rutting test is one of the most demanding test conditions for testing the water sensitivity and rutting resistance of asphalt mixtures. The basic test procedure involves rolling a steel wheel of a certain specification and weight back and forth over the surface of an asphalt mixture specimen immersed in water at the test temperature a set number of times. The water stability and rutting resistance of the asphalt mixture are judged by measuring the rutting depth and the characteristics of the deformation curve. The main evaluation indicators of the Hamburg wheel rutting test are rutting depth and spalling inflection point. The smaller the rutting depth and the absence of a spalling inflection point, the better the road performance of the mixture.

[0062] Example 1

[0063] The modified steel slag aggregate asphalt mixture comprises 85 parts steel slag aggregate, 10 parts RO fly ash, 0.25 parts modified fiber, 4 parts amino resin modified asphalt, and 11 parts stearate modified limestone mineral powder.

[0064] In this mixture, RO fly ash and modified fibers are evenly dispersed on the surface of steel slag aggregate to form modified steel slag aggregate; amino resin modified asphalt coats the modified steel slag aggregate to form steel slag asphalt mixture; and stearate modified limestone powder fills the pores of the steel slag asphalt mixture.

[0065] The RO fly ash is composed of the following raw materials in parts by weight: 22 parts iron oxide powder, 78 parts magnesium oxide powder, and 1500 parts fly ash.

[0066] The average particle size of the iron oxide powder is 200 μm; the average particle size of the magnesium oxide powder is 0.25 μm. The fly ash is grade C-II.

[0067] The preparation method of the RO fly ash includes the following steps:

[0068] (1) Ingredients: Iron oxide powder with a purity of 99.5% and an average particle size of 200μm is mixed and ground with magnesium oxide powder with a purity of 99.9% and an average particle size of 0.25μm to obtain a powder mixture;

[0069] (2) Granulation: The powder mixture obtained in step (1) is pressed into pellets with a diameter of 9 mm and a weight of 0.5 g using a press.

[0070] (3) First sintering: Sinter the pellets obtained in step (2) in a gas-tight electric furnace with a partial pressure of 10 atm and a gas pressure of 1780 K.

[0071] (4) Cooling, grinding and regranulation: The pellets obtained after the first sintering in step (3) are cooled in the furnace at a rate of 300K / h. After cooling, the pellets are taken out, crushed into powder and ground, and then regranulated.

[0072] (5) Secondary sintering: The pellets obtained by re-granulation are sintered again according to the conditions of the first sintering in step (3). After secondary sintering, after cooling to 30°C, fly ash is added and mixed evenly for 20 seconds.

[0073] The amino resin modified asphalt is composed of the following raw materials in parts by weight: 97 parts of No. 90 asphalt and 3 parts of polystyrene resin.

[0074] The preparation method of the amino resin modified asphalt includes the following steps:

[0075] (1) Weigh the No. 90 asphalt and weigh the required polystyrene resin according to the mixing ratio;

[0076] (2) Heat No. 90 asphalt to 130°C, add the polystyrene resin and stir.

[0077] (3) After mixing evenly, the asphalt is sheared. First, shear at 2000 r / min for 10 min, then shear at 5000 r / min for 30 min. The temperature is kept at 145℃ during the shearing process.

[0078] (4) After shearing, the amino resin modified asphalt should be developed at 130℃ for 30 minutes.

[0079] The raw materials for the stearate-modified limestone powder include limestone powder, sodium stearate, and a cement-fly ash mixture; wherein the mass ratio of cement to fly ash in the cement-fly ash mixture is 1:1.

[0080] The amount of sodium stearate used is 1.3% of the mass of limestone powder; the amount of cement-fly ash mixture used is 0.6% of the mass of limestone powder.

[0081] The method for preparing the stearate-modified limestone ore powder includes the following steps:

[0082] First, stearate is added to limestone ore powder and mechanically ground for 60 seconds to obtain a mixed powder.

[0083] Then, cement-fly ash mixture is added to the mixed powder and mixed evenly to obtain stearate-modified limestone mineral powder;

[0084] The cement used in the cement-fly ash mixture is slag silicate cement P·S·A 32.5.

[0085] The modified fiber is a hydrophobic modified wheat straw fiber.

[0086] The preparation method of the above-mentioned modified steel slag aggregate asphalt mixture includes the following steps:

[0087] First, steel slag aggregate is mixed with RO fly ash and modified fiber at a mixing temperature of 125℃ for 90 seconds to obtain modified steel slag aggregate.

[0088] Then, the modified steel slag aggregate and the amino resin modified asphalt are mixed at 130°C for 100 seconds to obtain steel slag asphalt mixture.

[0089] Finally, stearate-modified limestone mineral powder is added to the steel slag asphalt mixture and mixed at 130°C for 80 seconds to obtain the modified steel slag aggregate asphalt mixture.

[0090] Example 2

[0091] The modified steel slag aggregate asphalt mixture comprises 85 parts steel slag aggregate, 12 parts RO fly ash, 0.20 parts modified fiber, 5 parts amino resin modified asphalt, and 10 parts stearate modified limestone powder.

[0092] In this mixture, RO fly ash and modified fibers are evenly dispersed on the surface of steel slag aggregate to form modified steel slag aggregate; amino resin modified asphalt coats the modified steel slag aggregate to form steel slag asphalt mixture; and stearate modified limestone powder fills the pores of the steel slag asphalt mixture.

[0093] The RO fly ash is composed of the following raw materials in parts by weight: 21 parts iron oxide powder, 79 parts magnesium oxide powder, and 1000 parts fly ash.

[0094] The average particle size of the iron oxide powder is 180 μm; the average particle size of the magnesium oxide powder is 0.2 μm. The fly ash is grade C-II.

[0095] The preparation method of the RO fly ash includes the following steps:

[0096] (1) Ingredients: Iron oxide powder with a purity of 99.5% and an average particle size of 180μm is mixed and ground with magnesium oxide powder with a purity of 99.9% and an average particle size of 0.2μm to obtain a powder mixture;

[0097] (2) Granulation: The powder mixture obtained in step (1) is pressed into pellets with a diameter of 8 mm and a weight of 0.4 g using a press.

[0098] (3) First sintering: Sinter the pellets obtained in step (2) in a gas-tight electric furnace with a partial pressure of 8 atm and a pressure of 1770 K using high-purity argon gas.

[0099] (4) Cooling, grinding and regranulation: The pellets obtained after the first sintering in step (3) are cooled in the furnace at a rate of 300K / h. After cooling, the pellets are taken out, crushed into powder and ground, and then regranulated.

[0100] (5) Secondary sintering: The pellets obtained by re-granulation are sintered again according to the conditions of the first sintering in step (3). After secondary sintering, after cooling to 30°C, fly ash is added and mixed evenly for 20 seconds.

[0101] The amino resin modified asphalt is composed of the following raw materials in parts by weight: 94 parts of No. 110 asphalt and 6 parts of mixed etherified melamine resin.

[0102] The preparation method of the amino resin modified asphalt includes the following steps:

[0103] (1) Weigh the No. 110 asphalt and weigh the required mixed etherified melamine resin according to the proportion;

[0104] (2) Heat No. 110 asphalt to 140°C, add the mixed etherified melamine resin and stir.

[0105] (3) After mixing evenly, the asphalt is sheared. First, shear at 2000 r / min for 10 min, then shear at 5000 r / min for 30 min. The temperature is kept at 145℃ during the shearing process.

[0106] (4) After shearing, the amino resin modified asphalt is developed at 140℃ for 30 minutes.

[0107] The raw materials for the stearate-modified limestone powder include limestone powder, sodium stearate, and a cement-fly ash mixture; wherein the mass ratio of cement to fly ash in the cement-fly ash mixture is 1:1.

[0108] The amount of sodium stearate used is 1.6% of the mass of limestone powder; the amount of cement-fly ash mixture used is 0.5% of the mass of limestone powder.

[0109] The method for preparing the stearate-modified limestone ore powder includes the following steps:

[0110] First, stearate is added to limestone ore powder and mechanically ground for 60 seconds to obtain a mixed powder.

[0111] Then, cement-fly ash mixture is added to the mixed powder and mixed evenly to obtain stearate-modified limestone mineral powder;

[0112] The cement used in the cement-fly ash mixture is slag silicate cement P·S·A 32.5.

[0113] The modified fiber is a hydrophobic modified wheat straw fiber.

[0114] The preparation method of the above-mentioned modified steel slag aggregate asphalt mixture includes the following steps:

[0115] First, steel slag aggregate is mixed with RO fly ash and modified fiber at a mixing temperature of 130℃ for 85 seconds to obtain modified steel slag aggregate.

[0116] Then, the modified steel slag aggregate and the amino resin modified asphalt are mixed at 135°C for 95 seconds to obtain steel slag asphalt mixture.

[0117] Finally, stearate-modified limestone mineral powder was added to the steel slag asphalt mixture and mixed at 135°C for 85 seconds to obtain the modified steel slag aggregate asphalt mixture.

[0118] Example 3

[0119] The modified steel slag aggregate asphalt mixture comprises 92 parts steel slag aggregate, 15 parts RO fly ash, 0.25 parts modified fiber, 3 parts amino resin modified asphalt, and 5 parts stearate modified limestone mineral powder.

[0120] In this mixture, RO fly ash and modified fibers are evenly dispersed on the surface of steel slag aggregate to form modified steel slag aggregate; amino resin modified asphalt coats the modified steel slag aggregate to form steel slag asphalt mixture; and stearate modified limestone powder fills the pores of the steel slag asphalt mixture.

[0121] The RO fly ash is composed of the following raw materials in parts by weight: 22 parts iron oxide powder, 78 parts magnesium oxide powder, and 1300 parts fly ash.

[0122] The average particle size of the iron oxide powder is 200 μm; the average particle size of the magnesium oxide powder is 0.25 μm. The fly ash is grade C-II.

[0123] The preparation method of the RO fly ash includes the following steps:

[0124] (1) Ingredients: Iron oxide powder with a purity of 99.5% and an average particle size of 200μm is mixed and ground with magnesium oxide powder with a purity of 99.9% and an average particle size of 0.25μm to obtain a powder mixture;

[0125] (2) Granulation: The powder mixture obtained in step (1) is pressed into pellets with a diameter of 9 mm and a weight of 0.5 g using a press.

[0126] (3) First sintering: Sinter the pellets obtained in step (2) in a gas-tight electric furnace with a partial pressure of 10 atm and a gas pressure of 1780 K.

[0127] (4) Cooling, grinding and regranulation: The pellets obtained after the first sintering in step (3) are cooled in the furnace at a rate of 300K / h. After cooling, the pellets are taken out, crushed into powder and ground, and then regranulated.

[0128] (5) Secondary sintering: The pellets obtained by re-granulation are sintered again according to the conditions of the first sintering in step (3). After secondary sintering, after cooling to 30°C, fly ash is added and mixed evenly for 20 seconds.

[0129] The amino resin modified asphalt is composed of the following raw materials in parts by weight: 96 parts of No. 90 asphalt and 4 parts of lignin-based urea-formaldehyde resin.

[0130] The preparation method of the amino resin modified asphalt includes the following steps:

[0131] (1) Weigh the No. 90 asphalt and weigh the required lignin-based urea-formaldehyde resin according to the proportion.

[0132] (2) Heat No. 90 asphalt to 130°C and add the lignin-based urea-formaldehyde resin and stir.

[0133] (3) After mixing evenly, the asphalt is sheared. First, shear at 2000 r / min for 10 min, then shear at 5000 r / min for 30 min. The temperature is kept at 145℃ during the shearing process.

[0134] (4) After shearing, the amino resin modified asphalt should be developed at 130℃ for 30 minutes.

[0135] The raw materials for the stearate-modified limestone powder include limestone powder, sodium stearate, and a cement-fly ash mixture; wherein the mass ratio of cement to fly ash in the cement-fly ash mixture is 1:1.

[0136] The amount of sodium stearate used is 1.8% of the mass of limestone powder; the amount of cement-fly ash mixture used is 0.7% of the mass of limestone powder.

[0137] The method for preparing the stearate-modified limestone ore powder includes the following steps:

[0138] First, stearate is added to limestone ore powder and mechanically ground for 60 seconds to obtain a mixed powder.

[0139] Then, cement-fly ash mixture is added to the mixed powder and mixed evenly to obtain stearate-modified limestone mineral powder;

[0140] The cement used in the cement-fly ash mixture is slag silicate cement P·S·A 32.5.

[0141] The modified fiber is a hydrophobic modified wheat straw fiber.

[0142] The preparation method of the above-mentioned modified steel slag aggregate asphalt mixture includes the following steps:

[0143] First, steel slag aggregate is mixed with RO fly ash and modified fiber at a mixing temperature of 125℃ for 90 seconds to obtain modified steel slag aggregate.

[0144] Then, the modified steel slag aggregate and the amino resin modified asphalt are mixed at 130°C for 100 seconds to obtain steel slag asphalt mixture.

[0145] Finally, stearate-modified limestone mineral powder is added to the steel slag asphalt mixture and mixed at 130°C for 80 seconds to obtain the modified steel slag aggregate asphalt mixture.

[0146] Comparative Example 1

[0147] The difference from Example 1 is that the mixing method of the modified steel slag aggregate asphalt mixture preparation method is changed. The order of adding stearate-modified limestone powder is changed to mixing it together with modified fiber and RO fly ash and steel slag aggregate. The specific steps are as follows:

[0148] First, steel slag aggregate is mixed with RO fly ash, modified fiber, and stearate-modified limestone powder at a mixing temperature of 125℃ and a mixing time of 90s to obtain modified steel slag aggregate.

[0149] Then, the modified steel slag aggregate and the amino resin modified asphalt were mixed at 130°C for 100 seconds to obtain the steel slag asphalt mixture of the comparative proportion.

[0150] Everything else is the same as in Example 1.

[0151] Comparative Example 2

[0152] The difference from Example 1 is that the mixing temperature in the modified steel slag aggregate asphalt mixture preparation method is changed to the existing ordinary aggregate mixing temperature of 180°C. Specifically:

[0153] First, steel slag aggregate is mixed with RO fly ash and modified fiber at a mixing temperature of 125℃ for 90 seconds to obtain modified steel slag aggregate.

[0154] Then, the modified steel slag aggregate and the amino resin modified asphalt are mixed at 180°C for 100 seconds to obtain steel slag asphalt mixture.

[0155] Finally, stearate-modified limestone mineral powder is added to the steel slag asphalt mixture and mixed at 180°C for 80 seconds to obtain the modified steel slag aggregate asphalt mixture.

[0156] Everything else is the same as in Example 1.

[0157] Comparative Example 3

[0158] The difference from Example 1 is that the steel slag aggregate asphalt mixture contains 85 parts steel slag aggregate, 10 parts RO fly ash, 0.25 parts ordinary wood fiber, 4 parts amino resin modified asphalt, and 11 parts ordinary limestone mineral powder.

[0159] In this mixture, RO fly ash and ordinary wood fiber are evenly dispersed on the surface of steel slag aggregate to form steel slag aggregate; amino resin modified asphalt is coated with steel slag aggregate to form steel slag asphalt mixture; and ordinary limestone mineral powder is filled in the pores of steel slag asphalt mixture.

[0160] Everything else is the same as in Example 1.

[0161] Comparative Example 4

[0162] The comparative example is a common asphalt mixture, whose raw materials include 88 parts of basalt aggregate, 12 parts of common limestone mineral powder and 0.32 parts of common wood fiber;

[0163] Its preparation method is as follows:

[0164] First, basalt aggregate is added to lignin fiber and dry-mixed at 185°C for 15 seconds.

[0165] Subsequently, basalt aggregate and SBS modified asphalt were mixed at 190°C for 45 seconds to obtain ordinary asphalt mixture.

[0166] Finally, limestone powder is added to the asphalt mixture and mixed at 185°C for 20 seconds to obtain ordinary asphalt mixture.

[0167] Comparative Example 5

[0168] The difference from Example 1 is that the fly ash in the RO fly ash is grade F.

[0169] The relevant indicators for Grade F fly ash are: CaO content 6.5% and free CaO content 0.92%.

[0170] As can be seen from the data in Table 3 below, although both are fly ash, the comparative example uses F-grade fly ash, which will increase the expansion of steel slag.

[0171] Comparative Example 6

[0172] The difference from Example 1 is that the fly ash in the RO fly ash is slag fly ash.

[0173] The relevant indicators of slag and fly ash are shown in Table 1 below:

[0174] Table 1

[0175]

[0176] As can be seen from the data in Table 3 below, although both are fly ash, the slag fly ash used in this comparative example will significantly increase the expansion of steel slag aggregate.

[0177] Comparative Example 7

[0178] The difference from Example 1 is that the structure of the mixture in this comparative example is different. Specifically, stearate-modified limestone powder and modified fiber are uniformly dispersed on the surface of steel slag aggregate to form modified steel slag aggregate; amino resin-modified asphalt is coated with modified steel slag aggregate to form steel slag asphalt mixture; RO fly ash is filled in the pores of steel slag asphalt mixture.

[0179] Comparative Example 8

[0180] The difference from Example 1 is that the steel slag aggregate asphalt mixture in this comparative example includes the following raw materials in parts by weight: 96 parts steel slag aggregate, 4 parts RO fly ash, 0.2 parts modified fiber, 4.3 parts amino resin modified asphalt, and 4 parts stearate modified limestone powder.

[0181] The performance of the steel slag asphalt mixtures described in the following embodiments and comparative examples is tested.

[0182] Table 2. Content of free calcium oxide in various steel slag asphalt mixtures

[0183]

[0184] Table 3. Water stability performance data of various steel slag asphalt mixtures

[0185]

[0186] Conclusion: The biggest problem encountered when applying steel slag aggregate to asphalt pavement surface layers is that steel slag aggregate is prone to expansion and has insufficient adhesion to asphalt, which easily leads to water damage and other defects in the mixture, further damaging the pavement and reducing its service life. Through comparative analysis of various embodiments and comparative examples, it can be seen that the modified steel slag aggregate asphalt mixture described in this invention meets the standard requirements for freeze-thaw splitting strength (standard index: base asphalt ≥70%, modified asphalt ≥75%), water immersion Marshall residual stability (standard index: base asphalt ≥75%, modified asphalt ≥80%), maximum flexural strain at low temperature (standard index: base asphalt ≥2000με, modified asphalt ≥2500με), and Hamburg rutting depth (standard index: ≤12.7mm). The water stability and other road performance of the steel slag asphalt mixture are significantly improved.

[0187] Experimental Example 1

[0188] I. Experimental Objective: To investigate and compare the performance of ordinary No. 90 asphalt and the amino resin modified asphalt described in this invention.

[0189] II. Experimental Materials:

[0190] 1. The relevant indicators of ordinary No. 90 asphalt are shown in Table 4 below:

[0191] Table 4

[0192]

[0193] 2. The amino resin modified asphalt is prepared through the following steps:

[0194] First, heat 96 parts of No. 90 base asphalt to 130℃, then add 4 parts of lignin-based urea-formaldehyde resin and stir. After stirring evenly, shear the asphalt at 2000 r / min for 10 min, then at 5000 r / min for 30 min, keeping the temperature at 145℃ throughout the shearing process. After shearing, develop the sheared amino resin modified asphalt at 140℃ for 30 min to obtain the test sample amino resin modified asphalt.

[0195] III. Experimental Results

[0196] 1. The results of softening point tests at different segregation times are shown in Table 5.

[0197] Table 5

[0198]

[0199] 2. The results of the penetration test at different segregation temperatures are shown in Table 6.

[0200] Table 6

[0201]

[0202] 3. The results of the changes in rheological parameters of ordinary asphalt samples under different storage temperatures are detailed in Table 7.

[0203] Table 7

[0204]

[0205] Continued table

[0206]

[0207] 4. The results of the changes in rheological parameters of amino acid resin modified asphalt samples under different storage temperatures are detailed in Table 8.

[0208] Table 8

[0209]

[0210] Continued table

[0211]

Claims

1. A modified steel slag aggregate asphalt mixture, characterized by, The raw materials include the following weight parts: steel slag aggregate 85-95 parts, RO fly ash 8-15 parts, modified fiber 0.2-0.25 parts, amino resin modified asphalt 3-5.5 parts, and stearate modified limestone powder 5-11 parts; The RO fly ash and the modified fiber are uniformly dispersed on the surface of the steel slag aggregate to form modified steel slag aggregate; The amino resin modified asphalt is attached to the modified steel slag aggregate to form steel slag asphalt mixture; The stearate modified limestone powder is filled in the pores of the steel slag asphalt mixture; The RO fly ash is composed of the following weight parts: iron oxide powder 21-22 parts, magnesium oxide powder 78-79 parts, and fly ash, the weight fraction of which is 10-15 times the total weight fraction of the iron oxide powder and the magnesium oxide powder; The average particle size of the iron oxide powder is 180-200 µm, and the average particle size of the magnesium oxide powder is 0.2-0.25 µm; The CaO content in the fly ash is >10%, the fineness is ≤25.0%, the water requirement is ≤105%, and the loss on ignition is ≤8.0%; The RO fly ash is prepared by the following steps: (1) batching: mixing and grinding the iron oxide powder with a purity of 99.5% and an average particle size of 180-200 µm with the magnesium oxide powder with a purity of 99.9% and an average particle size of 0.2-0.25 µm to obtain a powder mixture; (2) granulation: using a press to press the powder mixture obtained in step (1) into pellets with a diameter of 7-9 mm and a weight of 0.3-0.5 g; (3) first sintering: sintering the pellets obtained in step (2) in a gas-tight electric furnace at a high-purity argon gas pressure of 6-10 atm and a temperature of 1770-1780 K; (4) cooling, grinding, and re-granulation: after the first sintering in step (3), the pellets are cooled in the furnace at a rate of 300 K / h, then taken out, crushed into powder, ground, and re-granulated; (5) second sintering: the re-granulated pellets are sintered again under the same conditions as the first sintering in step (3), and after cooling to 20-30 °C, the fly ash is added and uniformly mixed for 15-20 s.

2. The modified steel slag aggregate asphalt mixture according to claim 1, characterized in that, The amino resin modified asphalt is composed of the following weight parts: base asphalt 94-97 parts and amino resin 3-6 parts.

3. The modified steel slag aggregate asphalt mixture according to claim 2, characterized in that, The base asphalt is 90-110 number asphalt, and the amino resin is one or more of polyphenyl cyanate resin, lignin-based urea-formaldehyde resin, or mixed etherified melamine resin.

4. The modified steel slag aggregate asphalt mixture as claimed in claim 2, wherein, The preparation method of the amino resin modified asphalt includes the following steps: (1) weighing the base asphalt and the required amino resin according to the proportion; (2) heating the base asphalt to 125-140 °C and adding the amino resin for stirring; (3) after uniform stirring, shearing the asphalt at 2000 r / min for 10 min, and then at 5000 r / min for 30 min, with the temperature maintained at 140-145 °C during the shearing process; (4) After shearing, the sheared amino resin modified asphalt is developed at 130-145 DEG C for 30 min.

5. The modified steel slag aggregate asphalt mixture as claimed in claim 1, wherein, The raw materials of the stearate modified limestone mine powder include limestone mine powder, sodium stearate and cement-fly ash mixture; the mass ratio of cement to fly ash in the cement-fly ash mixture is 1:

1.

6. The modified steel slag aggregate asphalt mixture according to claim 5, wherein, The amount of sodium stearate is 1.0-2.0% of the mass of the limestone mine powder; the amount of the cement-fly ash mixture is 0.5-0.7% of the mass of the limestone mine powder.

7. The modified steel slag aggregate asphalt mixture according to claim 5, wherein, The preparation method of the stearate modified limestone mine powder comprises the following steps: First, the stearate is added to the limestone mine powder, and the mixture is mechanically ground for 45-60 s to obtain a mixed powder; Then, the cement-fly ash mixture is added to the mixed powder and mixed uniformly to obtain the stearate modified limestone mine powder.

8. The modified steel slag aggregate asphalt mixture according to claim 7, characterized in that, The cement in the cement-fly ash mixture is slag Portland cement P·S·A 32.

5.

9. The modified steel slag aggregate asphalt mixture as claimed in claim 1, wherein, The modified fiber is hydrophobic modified wheat straw.

10. The method for preparing modified steel slag aggregate asphalt mixture as described in claim 1, characterized in that, The method comprises the following steps: First, the steel slag aggregate is mixed with RO fly ash and modified fiber at a mixing temperature of 125-140 DEG C for 80-90 s to obtain modified steel slag aggregate; Then, the modified steel slag aggregate is mixed with the amino resin modified asphalt at 130-140 DEG C for 90-100 s to obtain steel slag asphalt mixture; Finally, the stearate modified limestone mine powder is added to the steel slag asphalt mixture and mixed at 130-140 DEG C for 80-90 s to obtain modified steel slag aggregate asphalt mixture.

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