Asphalt mixture containing steel slag powder and preparation method thereof

Abstract

The invention discloses an asphalt mixture containing steel slag powder and a preparation method thereof, and belongs to the technical field of asphalt mixtures. By comparing the physicochemical properties of different steel slag powder, namely particle size distribution conditions, thermal stability analysis, phase composition and microwave thermal induction performance test, and analyzing the physicochemical property difference between the electric furnace steel slag powder and the converter steel slag powder, the steel slag powder replacing mineral powder is selected and doped into the asphalt mixture; and the temperature rise characteristic and the self-healing characteristic of the steel slag asphalt mixture are researched.

Description

Technical Field

[0001] This invention belongs to the field of asphalt mixture technology, specifically relating to an asphalt mixture containing steel slag powder and its preparation method. Background Technology

[0002] Statistics show that over 95% of highway pavements are paved with asphalt mixtures, which consist of aggregates, asphalt, and fillers, with aggregates accounting for as much as 90%. Annual stone consumption reaches 22 billion tons, with approximately 25% used for road construction. This crushed stone is often obtained through quarrying, and large-scale mining severely damages the ecological environment and hinders sustainable development. Therefore, there is an urgent need to find alternative resources to alleviate the pressure of excessive stone consumption.

[0003] With the rapid development of the steel industry, the annual output of steel slag continues to increase. Steel slag is a waste product generated during steelmaking, and its composition is complex, including various oxides, metallic impurities, sulfides, and materials for adjusting properties. However, due to technological limitations and insufficient environmental awareness, the utilization rate of steel slag was low in the early stages, resulting in a large amount of steel slag being buried or piled up every year, causing serious environmental pollution. Although steel slag is considered waste, it is a reusable resource in many fields, leading to increased efforts in its resource utilization. The main application is in road construction, where the current utilization rate is close to 90%. The application of coarse steel slag in road engineering is mainly due to its high alkalinity, high density, large specific surface area, rough and porous surface. The CH bonds it contains combine with the acidic components in asphalt to form a large amount of structural asphalt on the aggregate surface, generating strong chemical adsorption and thus enhancing the adhesion between the asphalt and the aggregate. Currently, the utilization rate of steel slag is low, with an effective utilization rate of less than 30%. Furthermore, with the advancement of ironmaking technology, steel slag has changed from coarse steel slag with larger particles to steel slag with finer particle size, or even steel slag powder. Research in this area is still somewhat insufficient.

[0004] 1. Study on the characteristics of steel slag powder: As early as the 1960s, numerous researchers both domestically and internationally began extensively studying the recycling and utilization of steel slag. Steel slag was initially used as an aggregate for paving road base layers, and a relatively mature industrial system has been established, providing strong technical support for the application of steel slag powder in asphalt mixtures.

[0005] Zghair et al. added nano- and micro-sized steel slag powder to modified asphalt, stirred and mixed it at 145℃, and then tested the physical properties of the asphalt mortar. The results showed that the addition of nano- and steel slag powder increased the viscosity and softening point temperature of the steel slag powder asphalt mortar, while decreasing its ductility and permeability. However, the asphalt mortar with 3% nano-sized steel slag showed a higher permeability index and a better effect on resisting rutting damage.

[0006] Meng et al. treated rubber particles with a silane coupling modifier, incorporated steel slag powder and rubber powder into asphalt, and studied and analyzed the high-temperature performance of the asphalt mastic. The results showed that the coupling modifier promoted the swelling of the SBS-modified asphalt and rubber particle polymer, forming a well-developed cross-linked network structure in the asphalt mastic, thereby improving its high-temperature performance.

[0007] Waligora et al. analyzed the chemical composition and mineralogical characteristics of steel slag and found that it contained calcium silicate, iron oxide, and lime. The results indicated that CaO exists in steel slag as both 1-3 μm particles and aggregated into larger particles, and that free CaO may be the main factor contributing to the instability of the steel slag.

[0008] Zhao Gang studied the surface morphology, chemical composition, and particle size distribution of steel slag powder and limestone powder, and prepared asphalt mixtures using these two fillers. The effects of the two fillers on the crack resistance of the mixtures were evaluated using indirect tensile tests. The results showed that steel slag powder, being a high-alkalinity filler, exhibited superior crack resistance compared to limestone powder.

[0009] Tao G et al. investigated the effect of steel slag filler on the rheological properties of asphalt mastic by analyzing the surface characteristics, chemical composition, and crystal structure of steel slag filler and limestone filler. The results showed that partially replacing mineral powder in asphalt enhanced its deformation resistance, but reduced its low-temperature crack resistance.

[0010] Liu Jinzhou et al. established a molecular model of steel slag minerals to evaluate and analyze the influence of mineral composition on the interaction between asphalt and steel slag. The results showed that the colloids and aromatics in the strongly alkaline mineral phase are beneficial to improving the bonding ability between asphalt and steel slag.

[0011] Wu Fahong et al. analyzed the intrinsic relationship between the macroscopic characteristics and microstructure of steel slag using X-ray diffraction, scanning electron microscopy, and other testing methods. They found that adding a single or multiple activator can improve the activity of steel slag, promote the secondary hydration of Ca(OH)2, generate ettringite and CSH gel, and thus improve its strength.

[0012] Hao et al. used thermodynamic calculation software and scanning electron microscopy to analyze the phase composition and morphology of steel slag, and studied the effect of basicity on the chemical composition and phase precipitation of steel slag. The results showed that when the basicity of steel slag is 2.0, it can promote the formation of cementitious mineral C2S, thereby improving the adhesion performance of the mortar.

[0013] Imashuku et al. used X-ray excitation optics to form images and determined the CaO content in steel slag powder. High-temperature heat treatment of industrial steel slag caused f-CaO to produce strong light at 600 nm, which could be used to distinguish its phase composition. This method is of great significance for the practical application and production of steel slag powder.

[0014] Shen AQ et al. evaluated the adhesion between different aggregates and rubber asphalt using pull-out and net adsorption tests. Their study showed that the porous nature of steel slag aggregate and the chemical reaction between it and asphalt resulted in superior adhesion between steel slag aggregate and rubber asphalt compared to diabase.

[0015] Liu W et al. analyzed the adhesion, interfacial microstructure, and adsorption characteristics of asphalt and steel slag aggregate from both physical adsorption and chemical reaction perspectives using scanning electron microscopy, infrared spectroscopy, and dynamic shear rheology. The results showed that steel slag exhibits greater adhesion and better bonding performance with asphalt. This is because the pits and textures on the surface of steel slag create a skeletal effect between the aggregates, enhancing the strength of the asphalt-steel slag aggregate interface and thus improving adhesion.

[0016] Kong et al. analyzed the chemical composition and microstructure of steel slag powder filler, and studied the softening point and viscosity of asphalt mastic. The results showed that the microstructure of steel slag powder filler is more abundant, and its angularity index is about 15% higher than that of mineral powder filler, which leads to improved performance indicators such as softening point and viscosity of steel slag powder asphalt mastic, and it has good application prospects.

[0017] Zheng et al. used the Rigden principle to test the microscopic voids per unit mass of filler and the fixed asphalt-free ratio in asphalt mastic samples, and determined the low-temperature cohesive strength and low-temperature flexural creep stiffness change rate of asphalt mastic as critical failure control indicators. The results showed that the content and microstructure of mineral fillers significantly affect the filler-asphalt interaction, and the dosage of mineral powder fillers can be determined through reasonable calculation.

[0018] Zhou et al. studied the adhesion properties and interfacial failure mechanisms of asphalt mortar with basalt and steel slag using molecular dynamics simulations. The results showed that the surface roughness and bonding ability of steel slag were greater than those of basalt, and both steel slag and basalt aggregates exhibited bonding failure and cohesive failure.

[0019] Li Qiushi et al. used two different modified asphalt binders to study the low-strain rheological and high-strain toughness fracture properties of the asphalt binders. The results showed that steel slag powder contains a large amount of CaO and has a large specific surface area, which can absorb more polar components and improve the adhesion of asphalt mortar. Under higher loading temperatures and slower loading rates, the crack tip opening displacement of steel slag powder is higher than that of lime powder mortar system.

[0020] Sabapathy et al. conducted surface modification experiments on steel slag to replace coarse aggregate, and found the optimal dosage ratio for surface modification of steel slag aggregate. They found that the mixture prepared under the optimal ratio had a 25% higher compressive strength than natural stone, and the splitting tensile strength reached its peak at a substitution amount of 25%.

[0021] Zhu Yaming et al. quantitatively analyzed the thermal conversion process of coal tar pitch using Fourier transform infrared spectroscopy (FTIR) peak fitting. The results showed that coal tar pitch is converted into an aliphatic aromatic form upon heating, during which oxygen-containing functional groups undergo deoxygenation reactions and some heteroatoms are removed.

[0022] Ma Xiaoyan et al. prepared asphalt mastics with four different filler volume fractions and established a fatigue life prediction model for asphalt mastics using linear amplitude scanning (LAS) tests based on viscoelastic continuous damage theory and fatigue failure criteria. They investigated and analyzed the relationship between stress-strain, material integrity coefficient, and strength damage evolution of the asphalt mastics. The results showed that the addition of filler reduced the peak width of the LAS stress-strain curve of the asphalt mastics, and the fatigue life of the mastics gradually decreased with increasing filler volume fraction. Furthermore, the interaction coefficient between asphalt and filler was positively correlated with the fatigue performance of the asphalt mastics.

[0023] Cosme RL et al. conducted rheological property tests on steel slag powder asphalt mastic and compared rheological parameters such as phase angle and complex shear modulus. The results showed that the use of steel slag powder improved the rheological properties of the mastic, increasing its elastic recovery ability and reducing its sensitivity.

[0024] Wei M et al. tested the chemical functional groups, self-healing properties, and rheological properties of steel slag powder asphalt mortar under different aging methods using Fourier transform infrared spectroscopy and DSR experiments. The results showed that after the addition of steel slag filler, no new functional groups were generated in the asphalt mortar, and physical adsorption was the main process, which improved its compressive strength and self-healing properties.

[0025] 2. Research on steel slag asphalt mixture: Bessa IS et al. used digital image processing technology to evaluate the angularity, surface texture, sphericity and flatness of three aggregates (granite, limestone and steel slag) before polishing and before and after degradation, and concluded that steel slag aggregate has better wear resistance than ordinary stone.

[0026] Shu Z et al. [studied the effects of steel slag content on the road performance, thermal conductivity, and outdoor temperature distribution of rubber asphalt mixtures, and found that the deformation resistance was best when the steel slag content was 40%; the low-temperature cracking resistance was best when the steel slag content was 60%. Steel slag increased the thermal conductivity of the mixture and also increased the cumulative temperature difference between the top and bottom layers. The temperature stress ratio was lowest when the content was 40%.]

[0027] Niu Yonghong et al. tested and analyzed the road performance of steel slag asphalt mixtures with different admixture contents, including high-temperature rutting tests, low-temperature beam tests, and fatigue tests. The study found that the high-temperature performance was best when the steel slag content was 50%; the low-temperature failure strain reached its maximum when the steel slag content was 75%; the fatigue performance showed a trend of first increasing and then decreasing, but reached its peak at an admixture content of 25%. This indicates that partially replacing coarse aggregate with steel slag can improve the road performance of the mixture and has significant economic benefits.

[0028] Asi IM et al. studied the properties of AC asphalt mixtures with steel slag at different substitution rates, using indirect tensile strength, creep modulus, rutting resistance, fatigue life, and spalling resistance tests to evaluate the effectiveness of steel slag aggregate. The results showed that the performance improvement of AC asphalt mixtures was best when the steel slag aggregate content was 75%.

[0029] Skaf M et al. studied the mechanical properties of electric arc furnace steel slag and its main properties as an aggregate in asphalt mixtures. The results showed that when electric arc furnace steel slag partially replaces coarse aggregate, it can improve the mechanical properties, fatigue performance, and durability of the mixture.

[0030] Chen JS et al. studied the road performance of SMA asphalt mixtures and found that steel slag asphalt mixtures have high resistance to permanent deformation and wet damage. Steel slag, as a coarse aggregate, partially replaces natural aggregates in asphalt mixtures, which can improve their rutting resistance.

[0031] Kavussi et al. partially replaced limestone coarse aggregate with electric arc furnace steel slag in asphalt mixtures and evaluated the fatigue performance of the steel slag asphalt mixture by conducting bending beam fatigue tests under controlled stress mode. The results showed that the incorporation of steel slag aggregate increased the adhesion between asphalt and aggregate, thereby improving the fatigue performance of the asphalt mixture.

[0032] Oluwasola EA et al. investigated the feasibility of using electric arc furnace steel slag and copper tailings as substitutes for asphalt pavements. The results showed that asphalt mixtures containing electric arc furnace steel slag and copper tailings exhibited better high-temperature rutting performance and were less prone to permanent deformation, making them suitable as alternative aggregates in asphalt mixtures.

[0033] Yang Yongli et al. analyzed the slag-forming process, physical and mechanical properties, and chemical composition of steel slag, and prepared and analyzed the road performance of basalt steel slag SMA-13 ​​asphalt mixtures with different admixture amounts. The results showed that after aging, all indicators of the steel slag met the specifications. The addition of steel slag improved the stability and shear strength of the asphalt mixture, but reduced its low-temperature crack resistance.

[0034] Xiao et al. prepared asphalt mixtures by replacing limestone powder with steel slag powder at different proportions and studied its effect on water sensitivity. The results showed that the aggregate asphalt coating rate was the highest and the water damage resistance was the best when the steel slag powder replacement rate was 25%. Excessive addition of steel slag powder led to a decrease in the adhesion between asphalt and aggregate and a deterioration in water damage resistance. Therefore, the optimal dosage of steel slag powder was 25%.

[0035] Quantao et al. investigated the effects of incorporating steel slag or steel fibers on the mechanical, thermal, and healing properties of asphalt mixtures. The results showed that adding steel slag or steel fibers improved the water stability, resistance to particle loss, and fracture energy of asphalt mixtures, resulting in better mechanical properties and induced healing performance.

[0036] Liu Liping et al. conducted mix design studies on conventional AC-13 asphalt mixtures and asphalt mixtures containing steel slag, and compared and analyzed their road performance, including high-temperature, low-temperature, water stability, and fatigue properties. The results showed that the AC-13 asphalt mixture containing steel slag did not have problems with volume stability, and its road performance was superior to that of conventional asphalt mixtures.

[0037] Fu Z et al. evaluated basic asphalt mixtures and asphalt mixtures with added anti-rutting agents or lignin fibers. Their study showed that adding 0.4% anti-rutting agent and 0.3% lignin fibers significantly improved the high-temperature performance, low-temperature performance, and water stability of the asphalt mixtures.

[0038] In summary, although the use of coarse steel slag in asphalt mixtures has been studied to a certain extent and supported by reliable experimental data, with many researchers proposing optimal dosages in experiments, current research on the application of steel slag powder is still somewhat insufficient. On the one hand, the production processes and physicochemical properties of different types of steel slag powder vary, leading to differences in experimental results. On the other hand, the impact of different steel slag powder dosages on the performance of the binder and mixture also varies, especially regarding the long-term stability of the mixture under moisture conditions. Therefore, further research is needed to promote the wider application of steel slag powder in asphalt mixtures. Summary of the Invention

[0039] To address the issues in existing technologies where different steel slag powders have varying production processes and physicochemical properties, resulting in inconsistent test results and varying effects of different steel slag powder dosages on asphalt mixture performance, this invention provides an asphalt mixture containing electric furnace steel slag powder and its preparation method. This invention compares the physicochemical properties of different steel slag powders, including particle size distribution, thermal stability analysis, phase composition, and microwave thermal induction performance testing. By analyzing the differences in physicochemical properties between electric furnace steel slag powder and converter steel slag powder, this invention selects steel slag powder to replace mineral powder for incorporation into the asphalt mixture. Furthermore, the asphalt mixture gradation design is performed, and the optimal asphalt-aggregate ratio is determined under different steel slag powder dosages.

[0040] The technical solution of the present invention is as follows: This study addresses the shortcomings in existing research on steel slag by replacing mineral powder with steel slag powder in asphalt mastic and mixtures at different dosages. The relevant performance indicators were tested and compared with those of conventional asphalt mastic and mixtures to explore the impact of steel slag powder replacing mineral powder on the performance of asphalt mastic and mixtures. This is significant for realizing the resource utilization of steel slag and improving the performance of road surfaces.

[0041] The objective of this invention is achieved through the following technical solution: A method for preparing an asphalt mixture containing steel slag powder includes the following steps: S1: Mix coarse aggregate and fine aggregate at a mass ratio of 1:2, stir and dry to obtain mixture A; S2: Add electric arc furnace slag and converter slag to mixture A respectively. Mix the electric arc furnace slag, converter slag and mixture A in a mass ratio of 2:2:8 to obtain mixture B. S3: Heat the asphalt and stir continuously, then add mixture B to the asphalt and stir until evenly mixed to obtain an asphalt mixture.

[0042] Furthermore, the coarse aggregate mentioned in S1 refers to aggregate with a particle size greater than 4.75 mm, usually composed of crushed stone, which plays a skeletal role in the mixture; the main technical indicators include: It should be clean, dry, and have a rough surface, and have good adhesion to asphalt; The content of needle-like and flaky particles is ≤15%; Crushing value: ≤26% when used for surface layers of urban expressways and main roads; Water absorption rate ≤2.0%.

[0043] The fine aggregate mentioned in S1 refers to aggregate with a particle size < 4.75 mm, usually composed of natural sand or manufactured sand, used to fill the voids between coarse aggregates; the main technical indicators include: It should be clean, dry, free from weathering and impurities; Mud content <3%~5%; The particle size distribution should be medium sand or higher; In hot-mix dense-graded asphalt mixtures, the amount of natural sand should not exceed 20% of the total aggregate.

[0044] Furthermore, the stirring described in S1 is performed at a speed of 300-500 rpm for 30 minutes. The drying process lasted 60 minutes, with the drying temperature controlled at 110℃. 120℃, for 1 hour 1.5h.

[0045] Furthermore, the main components of the electric arc furnace slag described in S2 are: calcium oxide (CaO) content of 35.66%, silicon oxide (SiO2) content of 19.20%, iron oxide (Fe2O3+FeO) content of 29.83%, aluminum oxide (Al2O3) content of 6.23%, magnesium oxide (MgO) content of 7.48%, with the balance being free calcium oxide (f-CaO) and free magnesium oxide (f-MgO).

[0046] The main components of the converter steel slag are: high calcium oxide (CaO) content, generally 38.10%; iron oxide (Fe2O3) content, 33.40%; silicon oxide (SiO2) content, 9.55%; aluminum oxide (Al2O3) content, 2.63%; magnesium oxide (MgO) content, 3.92%; and the balance being f-CaO and f-MgO.

[0047] Furthermore, the stirring described in S2 is performed at a speed of 300-500 rpm for 30 minutes. 60 minutes.

[0048] Furthermore, in S3, heating the asphalt means heating the asphalt to 130°C. 180℃; the asphalt and mixture B are mixed at a mass ratio of 1:2; the stirring speed is 300rpm-500rpm for 30min. 60 minutes.

[0049] This invention also relates to an asphalt mixture containing steel slag powder, obtained according to the above-mentioned method for preparing an asphalt mixture containing steel slag powder. The typical properties of the prepared asphalt mixture containing steel slag powder are as follows: The study investigated the temperature rise characteristics of asphalt mixtures containing steel slag powder. Three sets of experiments were conducted to study the effects of different heating methods on the temperature rise of asphalt mixtures containing steel slag powder. The results showed that a heating cycle of 40s-2min rest-heating-2min rest-40s-heating resulted in a more uniform temperature distribution in the asphalt mixture. With the total heating time remaining constant, increasing the number of heating cycles reduced the temperature range of the asphalt mixture specimens. The self-healing characteristics of asphalt mixtures containing steel slag powder are influenced by multiple factors, with temperature being a key factor and positively correlated with self-healing ability. Semi-circular bending specimens were prepared, and experiments were conducted using the strength ratio before and after healing as the healing rate index. The study found that increasing the steel slag powder content increased the peak load of the asphalt mixture and improved the healing rate; however, excessively high content weakened the overall material integrity. Considering all factors, a content of 60% was deemed appropriate. Simultaneously, increasing the heating time improved the healing effect, but excessively long heating times caused asphalt aging; approximately 120s yielded the best results.

[0050] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention discloses an asphalt mixture containing steel slag powder. The invention selects electric furnace steel slag powder and converter steel slag powder as research objects. The physicochemical properties of the steel slag powder are analyzed from the perspectives of particle size distribution, phase analysis, and thermal stability. The microwave thermal induction performance of the steel slag powder is analyzed from the perspectives of microwave heating principle, microwave absorption performance, electromagnetic parameters, and battery loss. Based on the comparison, the selected steel slag powder is used as an admixture to replace mineral powder, thereby enabling the gradation design of the asphalt mixture and the determination of the optimal asphalt-aggregate ratio. Compared with existing asphalt mixtures, the asphalt mixture of this invention has better self-healing properties; the microwave thermal induction of steel slag powder can accelerate the healing of the asphalt.

[0051] 2. The preparation method of asphalt mixture containing steel slag powder according to the present invention, compared with the existing asphalt mixture preparation method, the preparation method of the present invention has the advantage that steel slag powder can conduct heat during the mixture preparation process, which accelerates the synthesis of the mixture, and thus selects steel slag powder to replace mineral powder and incorporate it into the asphalt mixture. Attached Figure Description

[0052] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0053] Figure 1 This is a diagram showing the temperature rise characteristics of the aggregate in Example 1; Figure 2This is a temperature distribution diagram for group A in Example 1; Figure 3 This is a temperature distribution diagram for group B in Example 1; Figure 4 This is a temperature distribution diagram for group C in Example 1; Figure 5 This is a diagram of the semi-circular specimen in Embodiment 1 of the present invention; Figure 6 This is a graph showing the relationship between the amount of steel slag powder and the healing rate in Example 1 of the present invention. Figure 7 This is a graph showing the effect of microwave heating time on the healing rate of asphalt mixture in Example 1 of the present invention; Figure 8 This is a gradation design curve diagram in Embodiment 1 of the present invention. Detailed Implementation

[0054] The following embodiments are provided to describe the present invention in detail and comprehensively, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more explicit definition of the scope of protection of the present invention, but are not intended to limit the scope of the present invention.

[0055] All raw materials used in the following examples are commercially available: Example 1: A method for preparing an asphalt mixture containing steel slag powder includes the following steps: S1: Mix coarse aggregate and fine aggregate at a mass ratio of 1:2, stir and dry at 300 rpm for 60 min, and control the drying temperature at 110℃ for 1.5 h to obtain mixture A; S2: Add electric furnace slag and converter slag to mixture A respectively. Mix electric furnace slag, converter slag and mixture A in a mass ratio of 2:2:8 to obtain mixture B. The stirring speed is 300 rpm and the time is 60 min. S3: Heat the asphalt to 130℃ and stir continuously. Add mixture B to the asphalt. Mix the asphalt and mixture B at a mass ratio of 1:2. Stir until uniform, at a speed of 300 rpm for 60 minutes to obtain the asphalt mixture.

[0056] Example 2: A method for preparing an asphalt mixture containing steel slag powder includes the following steps: S1: Mix coarse aggregate and fine aggregate at a mass ratio of 1:2, stir and dry at a speed of 500 rpm for 30 min, and control the drying temperature at 120℃ for 1 h to obtain mixture A; S2: Add electric furnace slag and converter slag to mixture A respectively. Mix electric furnace slag, converter slag and mixture A in a mass ratio of 2:2:8 to obtain mixture B. The stirring speed is 500 rpm and the time is 30 min. S3: Heat the asphalt to 180℃ and stir continuously. Add mixture B to the asphalt. Mix the asphalt and mixture B at a mass ratio of 1:2. Stir until uniform, at a speed of 500 rpm for 30 minutes to obtain the asphalt mixture.

[0057] Comparative Example 1: The difference between Comparative Example 1 and Example 1 lies in the type of steel slag powder added to mixture A. Specifically, the steel slag powder added to mixture A is converter steel slag powder; otherwise, it is the same as in Example 1. The prepared asphalt mixture has the following properties: The microwave thermal induction properties of steel slag powder are analyzed from the perspectives of microwave heating principle, microwave absorption performance of steel slag powder, electromagnetic parameters, and battery loss.

[0058] Results and Discussion: Electric arc furnace (EAF) steel slag powder reacts more readily with matter. The microwave absorption effect of EAF steel slag powder is superior to that of converter steel slag powder; the heating rate of EAF steel slag powder is 0.99℃ / s, while that of converter steel slag powder is 0.94℃ / s. Based on the electromagnetic parameters of the two powders, it is evident that EAF steel slag powder possesses superior electromagnetic wave absorption and heat transfer properties.

[0059] Experimental example: 1. Experiments were conducted using Example 1. 2. Materials and Methods 2.1 Raw materials 2.1.1 Steel slag materials Electric arc furnace slag powder and converter slag powder 2.1.2 Asphalt Mixture Materials AC-13 asphalt mixture was used. 2.2 Study on the temperature rise characteristics of asphalt mixtures: 2.2.1 Heating characteristics of aggregates: The designed basalt aggregate was placed in a microwave oven and heated for 2 minutes. The aggregate was removed every 20 seconds, and the temperature distribution of the aggregate was captured by an infrared thermal imager. The results are as follows. Figure 1 As shown; Figure 1 The graph shows the heating characteristics of the aggregate in Example 1. As can be seen from the temperature distribution image, there is a significant temperature difference on the surface of the aggregate when the heating process continues to the critical point of two minutes.

[0060] 2.2.2 Temperature rise characteristics of asphalt mixtures containing steel slag powder: To investigate the change in thermal efficiency of steel slag powder after incorporation into asphalt mixtures, and to analyze the thermophysical properties of steel slag powder asphalt concrete mixtures by heating them using different methods, three different heating methods were employed to heat samples of steel slag powder asphalt concrete mixtures, and the temperature changes were measured. This experiment used a steel slag powder content of 60% as an example. Three microwave heating test groups were used to study the influence of different heating modes on the temperature changes of the steel slag powder asphalt concrete mixture. Thermocouples were used to measure the internal temperature of the samples to obtain the internal temperature distribution. The temperature changes of the specimens after microwave heating are shown in the figure.

[0061] Figure 2 This is a temperature distribution diagram of Group A in Example 1. It can be seen that Group A is a temperature distribution diagram obtained through continuous heating. Figure 3 The temperature distribution diagram of Group B in Example 1 shows that Group B was obtained by heating for 60 seconds, resting for 4 minutes, and then heating for another 60 seconds. Figure 4 The temperature distribution diagram for Group C in Example 1 shows that Group C was obtained by heating for 40 seconds, resting for 2 minutes, then heating for 40 seconds, resting for 2 minutes, and finally heating for 40 seconds.

[0062] 2.3 Study on the self-healing properties of asphalt mixtures containing steel slag powder: 2.3.1 Factor analysis of self-healing test: In studying the self-healing properties of asphalt mixtures, steel slag powder was initially used to replace mineral powder in the asphalt mixture. Therefore, the amount of steel slag powder added during microwave heating also affects the self-healing performance of the asphalt mixture. Most studies on the effect of heating time on the self-healing properties of asphalt mixtures found that microwave heating for approximately 120 seconds resulted in the best self-healing effect. 2.3.2 Preparation of semi-circular bending specimens: To better analyze the self-healing characteristics of asphalt mixtures, this paper uses a rotary compactor (Superpave) to prepare asphalt mixture specimens containing steel slag powder. The rotary compactor can ensure that the specimens have high density and uniformity. The prepared cylindrical asphalt mixture specimens are cut into semi-circular samples with a diameter of 150 mm and a height of 50 mm. A small incision with a depth of 10 mm and a width of 2 mm is cut at the center of the bottom of the semi-circular sample. Figure 5 The image shows a semi-circular specimen from Example 1. It can be seen that the cut specimen allows for easy cracking along the cut to form a fissure. 2.3.3 Effect of steel slag powder content on self-healing performance: According to the test plan, steel slag powder content of 30% to 80% was designed at 10% intervals. Fracture healing test was carried out on semi-circular specimens of asphalt mixture containing steel slag powder to determine the healing rate of asphalt mixtures with different steel slag powder contents under microwave heating. Figure 6 The graph showing the relationship between the steel slag powder content and the healing rate in Example 1 shows that as the steel slag powder content increases, the peak load of the semi-circular bending of the asphalt mixture also increases with the increase of the steel slag powder content, thus obtaining the graph showing the relationship between the steel slag powder content and the healing rate. 2.3.4 Effect of heating time on self-healing properties: The experiment used asphalt mixtures with steel slag powder content of 50%, 60%, and 70% to verify the effect of four different heating times (60s, 80s, 100s, and 120s) on the healing effect of asphalt mixtures containing steel slag powder. Figure 7 The graph shows the effect of microwave heating time on the healing rate of asphalt mixture in Example 1. It can be seen that the healing rate of asphalt mixture with three steel slag powder contents changes with the heating time. 2.4 Asphalt Mixture Proportion Design: 2.4.1 The asphalt mixture type used is AC-13. The asphalt mixture is prepared by determining the upper limit, lower limit and median of the gradation based on the sieving results of the aggregate. Figure 8 The gradation design curve diagram in Example 1 shows its gradation curve; 2.4.2 Set 0%, 30%, 40%, 50%, 60%, and 70% of electric furnace steel slag powder to replace mineral powder and incorporate them into asphalt mixtures to design the optimal asphalt-aggregate ratio.

[0063] 3. Conclusion: This application focuses on the self-healing properties of asphalt mixtures, combining microwave heating technology with electric furnace steel slag powder to explore the temperature rise characteristics of aggregates and asphalt mixtures containing steel slag powder. It also investigates the factors influencing the self-healing properties of asphalt mixtures and analyzes the impact of different factors on the properties of asphalt mixtures. The main conclusions are as follows: 1. Design AC-13 asphalt mixture, determine the gradation of asphalt mixture, select 0%, 30%, 40%, 50%, 60%, 70%, and 80% of electric furnace steel slag powder to replace mineral powder and add it to the asphalt mixture, and determine the Marshall volume parameters of the asphalt mixture specimens to obtain the optimal asphalt-aggregate ratio of 4.8%.

[0064] 2. Heating basalt aggregate revealed a significant temperature difference between the center and periphery of the aggregate surface, primarily due to the varying sizes and shapes of the aggregate affecting microwave absorption and reflection. In investigating the effects of different heating methods on the temperature rise of asphalt mixtures containing steel slag powder, three sets of experiments were conducted. The results showed that a heating-rest-40s-2min-heat-2min-heat-40s-rest-40s pattern resulted in a more uniform temperature distribution in the asphalt mixture. Furthermore, while maintaining the total heating time, appropriately increasing the number of heating cycles reduced the temperature range of the asphalt mixture specimens.

[0065] 3. The self-healing ability of asphalt and asphalt mixtures is influenced by various factors, with temperature being a key factor and positively correlated with self-healing capacity. Experiments were conducted using semi-circular bending specimens and the ratio of strength before and after healing as the healing rate index. The study found that increasing the steel slag powder content increased the peak load of the asphalt mixture and improved the healing rate; however, excessively high content weakened the overall material integrity. Considering all factors, a content of 60% was deemed appropriate. Simultaneously, increasing the heating time improved the healing effect, but excessively long heating times caused asphalt aging; approximately 120 seconds yielded the best results.

[0066] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing asphalt mixture containing steel slag powder, characterized in that, Includes the following steps: S1: Mix coarse aggregate and fine aggregate at a mass ratio of 1:2, stir and dry to obtain mixture A; S2: Add electric arc furnace slag and converter slag to mixture A respectively. Mix the electric arc furnace slag, converter slag and mixture A in a mass ratio of 2:2:8 to obtain mixture B. S3: Heat the asphalt and stir continuously, then add mixture B to the asphalt and stir until evenly mixed to obtain an asphalt mixture.

2. The method for preparing an asphalt mixture containing steel slag powder according to claim 1, characterized in that, The coarse aggregate mentioned in S1 is aggregate with a particle size greater than 4.75 mm, composed of crushed stone, and its main technical specifications include: Clean, dry, with a rough surface, it has good adhesion to asphalt; The content of needle-like and flaky particles is ≤15%; Crushing value: ≤26% when used for surface layers of urban expressways and main roads; Water absorption rate ≤2.0%.

3. The method for preparing an asphalt mixture containing steel slag powder according to claim 1, characterized in that, The fine aggregate mentioned in S1 refers to aggregate with a particle size < 4.75 mm, composed of natural sand or manufactured sand, and its main technical indicators include: Clean, dry, unweathered, and free of impurities; Mud content <3%~5%; The particle size distribution is medium sand or larger.

4. The method for preparing an asphalt mixture containing steel slag powder according to claim 1, characterized in that, The stirring described in S1 is performed at a speed of 300-500 rpm for 30 minutes. The drying process lasted 60 minutes, with the drying temperature controlled at 110℃. 120℃, for 1 hour 1.5h.

5. The method for preparing an asphalt mixture containing steel slag powder according to claim 1, characterized in that, The composition of the electric arc furnace slag described in S2 is as follows: calcium oxide content is 35.66%, silicon oxide content is 19.20%, iron oxide content is 29.83%, aluminum oxide content is 6.23%, magnesium oxide content is 7.48%, and the balance is free calcium oxide and free magnesium oxide; The composition of the converter steel slag is as follows: calcium oxide content is 38.10%, iron oxide content is 33.40%, silicon oxide content is 9.55%, aluminum oxide content is 2.63%, magnesium oxide content is 3.92%, and the balance is f-CaO and f-MgO.

6. The method for preparing an asphalt mixture containing steel slag powder according to claim 1, characterized in that, The stirring described in S2 is performed at a speed of 300-500 rpm for 30 minutes. 60 minutes.

7. The method for preparing an asphalt mixture containing steel slag powder according to claim 1, characterized in that, In S3, heating the asphalt means heating the asphalt to 130°C. 180℃; the asphalt and mixture B are mixed at a mass ratio of 1:2; the stirring speed is 300rpm-500rpm for 30min. 60 minutes.

8. An asphalt mixture containing steel slag powder, characterized in that, The asphalt mixture containing steel slag powder prepared according to any one of claims 1-7 has self-healing properties.

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