Steel slag cement stone phase change material and preparation method thereof

Abstract

This invention discloses a steel slag cement stone phase change material and its preparation method. The steel slag cement stone phase change material comprises the following components by weight: 50-65 parts cement matrix; 15-25 parts phase change temperature-regulating steel slag filler; 15-25 parts phase change temperature-regulating mineral filler; the phase change temperature-regulating steel slag filler comprises the following components by weight: 10-15 parts steel slag powder, 3-6 parts first phase change material, and 2-4 parts graphene powder; the phase change temperature-regulating mineral filler comprises the following components by weight: 8-12 parts metakaolin, 3-6 parts second phase change material, and 2-4 parts hexagonal boron nitride. The phase change composite material of this invention can absorb and release heat in different phase change temperature zones to delay road surface heating and reduce peak temperature; the phase change material has high encapsulation efficiency and is not prone to leakage during the melting period; at the same time, it maintains or improves the mechanical strength, wear resistance, and thermal conductivity of the cement matrix, thereby meeting the requirements of road engineering construction and service.

Description

Technical Field

[0001] This invention belongs to the field of road construction materials, and in particular relates to a road phase change material and its preparation method. Background Technology

[0002] With increasing demands for urban thermal environment and road durability, improving the near-surface temperature field and reducing peak road surface temperature through material-based methods has become a hot topic in pavement material research. Phase change materials (PCMs) absorb and release a large amount of latent heat through solid-liquid phase transitions, enabling them to buffer temperature rises or release heat within a certain temperature range, thereby regulating pavement temperature. However, directly adding PCMs to pavement mixtures or road materials typically has the following drawbacks: PCMs are prone to leakage during melting, causing performance loss and pollution; mechanical wear of the PCM itself or its encapsulation shell during mixing and construction can lead to failure; direct addition reduces the overall mechanical strength and wear resistance of the material; and the temperature regulation range of a single PCM system is limited, making it difficult to adapt to environments with large daytime temperature fluctuations.

[0003] While existing technologies employing resin microcapsules or single cement-based encapsulation methods reduce leakage to some extent, they still suffer from insufficient wear resistance and thermal conductivity, narrow phase change temperature ranges, or poor thermal cycling stability, limiting their widespread application in road engineering. Therefore, there is an urgent need to provide a composite material system that can efficiently encapsulate phase change materials, prevent leakage, and simultaneously maintain thermal conductivity, mechanical strength, and durability, while also achieving a wide temperature range or graded temperature regulation to adapt to the complex thermal environment requirements of roads. Summary of the Invention

[0004] The technical problem to be solved by this invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a steel slag cement stone phase change material and its preparation method. This invention provides a phase change composite material with a wide temperature range or graded temperature regulation capability, which can absorb and release heat in different phase change temperature zones to delay the road surface temperature rise and reduce the peak temperature; the phase change material has high encapsulation efficiency and is not easy to leak during the melting period; at the same time, it maintains or improves the mechanical strength, wear resistance and thermal conductivity of the cement matrix, thereby meeting the requirements of road engineering construction and service.

[0005] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0006] A steel slag cementitious phase change material, comprising the following components in parts by weight:

[0007] 50-65 parts cementitious matrix;

[0008] 15-25 parts of phase change temperature regulating steel slag filler;

[0009] 15-25 parts of phase change temperature-regulating mineral filler;

[0010] The phase change temperature-regulating steel slag filler comprises the following components in parts by weight: 10-15 parts steel slag powder, 3-6 parts first phase change material, and 2-4 parts graphene powder. The above-mentioned amounts of each component can ensure the mechanical properties of the material, achieve good phase change thermal energy regulation effect, and at the same time, without sacrificing the structural integrity and service life of the material.

[0011] The phase change temperature-regulating mineral filler comprises the following components in parts by weight: 8-12 parts metakaolin, 3-6 parts second phase change material, and 2-4 parts hexagonal boron nitride. Through a reasonable combination of metakaolin, second phase change material, and hexagonal boron nitride, thermal energy regulation and improved heat transfer efficiency can be achieved over a wider temperature range. In this formulation, metakaolin provides sufficient structural stability and durability, while an appropriate amount of second phase change material adds thermal energy regulation capability to the material in another temperature range.

[0012] The solid-liquid phase transition temperature ranges of the first phase change material and the second phase change material do not overlap or are at least partially offset.

[0013] In the aforementioned steel slag cement stone phase change material, preferably, the cement matrix comprises the following raw materials in parts by weight: 10-30 parts sand, 23-27 parts cement, 11-17 parts mixing water, 0.2-1.0 parts quick-setting agent, 1-2 parts stabilizer, and 1-2 parts water-reducing agent; the cement comprises one or more silicate cements, and its strength grade is not lower than 42.5, and the specific surface area of ​​the cement is not less than 300 m² / kg; the sand comprises one or more quartz sands or manufactured sands; the quick-setting agent comprises one or more of chlorate, silicate, and alkali-free liquid quick-setting agents; and the stabilizer comprises hydroxypropyl methylcellulose or its derivatives.

[0014] In the aforementioned steel slag cement stone phase change materials, preferably, the first phase change material includes one or more of polyethylene glycol 2000, myristic acid, n-hexadecyl alcohol and capric acid, and its phase change temperature is 40-50℃, and its latent heat of phase change is ≥150J / g.

[0015] In the aforementioned steel slag cement stone phase change materials, preferably, the second phase change material includes one or more of polyethylene glycol 4000, polyethylene glycol 6000, stearic acid, and ethylene glycol stearate, and its phase change temperature is 50-60℃, and its latent heat of phase change is ≥150J / g.

[0016] In the aforementioned steel slag cement stone phase change material, preferably, the graphene powder has 1-10 layers, an average sheet diameter of 0.5-10μm, and a specific surface area of ​​50-1000m² / g, so as to form an efficient heat conduction network in the filler and enhance mechanical properties.

[0017] In the aforementioned steel slag cement stone phase change material, preferably, the hexagonal boron nitride is used to improve the thermal conductivity and thermal stability of the filler and the composite, and preferably the particle size and packing morphology are adapted to the kaolin pores to achieve complementary thermal conduction networks.

[0018] The encapsulation rate (the ratio of the actual adsorption / encapsulation mass of the phase change material to the mass of the added phase change material) of the phase change temperature regulating steel slag filler and phase change temperature regulating mineral filler of the present invention is preferably ≥80%. The thermal conductivity of the final material is preferably ≥0.8W / (m·K), and the compressive strength is ≥30MPa after standard curing for 28 days.

[0019] As a general technical concept, the present invention also provides a method for preparing the above-mentioned steel slag cement stone phase change material, comprising the following steps:

[0020] (1) Steel slag is pretreated to obtain steel slag powder; the steel slag powder is activated by alkali, and then mixed with the first phase change material and graphene powder by vacuum impregnation to prepare a phase change temperature-regulating steel slag filler precursor. Finally, the phase change temperature-regulating steel slag filler precursor is dried to obtain phase change temperature-regulating steel slag filler.

[0021] (2) A phase change temperature-regulating mineral filler precursor was prepared by mixing metakaolin, second phase change material and hexagonal boron nitride using a vacuum impregnation method. Finally, the phase change temperature-regulating mineral filler precursor was dried to obtain the phase change temperature-regulating mineral filler.

[0022] (3) Mix the cement matrix, phase change temperature regulating steel slag filler and phase change temperature regulating mineral filler, pour into a mold, and cure to obtain steel slag cement stone phase change material.

[0023] In the above preparation method, preferably, the pretreatment of steel slag includes the following steps: the steel slag is finely pulverized using a high-energy ball mill, and then the particle size distribution is optimized by sieving and magnetic separation to obtain steel slag powder with a particle size D50 of 5-50 μm. Then, heavy and light impurities are separated. An organic alcohol amine grinding aid is added during ball milling. The organic alcohol amine includes one or more of monoethanolamine, diethanolamine, triethanolamine, isopropanolamine, diisopropanolamine, and triisopropanolamine. The amount of the grinding aid added is 0.1-2.0 wt% of the mass of the steel slag. The activator for alkaline activation of the steel slag powder includes one or more of potassium aluminosilicate, sodium aluminosilicate, and aluminum hydroxide. The amount of the activator is 1-10 wt% of the mass of the steel slag powder. The activation treatment is carried out at 20-90℃ for 0.5-6 h. The particle size D50 of steel slag powder is 5-50μm, which can provide sufficient specific surface area and pore structure to support phase change materials; after alkali activation, its pozzolanic activity is improved, which is conducive to the synergistic formation of a dense matrix with cement hydration products.

[0024] In the above preparation method, preferably, alkali-activated steel slag powder, the first phase change material, and graphene powder are vacuum impregnated and stirred in a water bath at 60-80℃, allowing the phase change material to penetrate into the pores of the steel slag powder and fully disperse with the graphene powder. The phase change temperature-regulating steel slag filler precursor is dried in a vacuum oven at a vacuum degree of 0.02-0.08 MPa, a temperature of 80-90℃, and a drying time of 18-24 hours. The alkali-activated steel slag powder, the first phase change material, and the graphene powder are all fine, dry, and thoroughly mixed. After mixing, the solution is transferred to a vacuum impregnation container to begin the vacuum impregnation process. The 60-80℃ water bath environment promotes interaction and reaction, ensuring uniform diffusion distribution. During vacuum drying, the vacuum pump is adjusted to set the vacuum degree in the container within the range of 0.02-0.08 MPa. The lower vacuum degree helps remove air and moisture from the mixture, preventing the formation of bubbles during drying, and simultaneously promoting better penetration of the first phase change material into the steel slag powder.

[0025] In the above preparation method, preferably, metakaolin, the second phase change material, and hexagonal boron nitride are vacuum impregnated and stirred in a water bath at 60-80℃ to obtain a phase change temperature-regulating mineral filler precursor. The precursor is then dried in a vacuum oven at a vacuum degree of 0.02-0.08 MPa, a temperature of 80-90℃, and a drying time of 18-24 hours. The metakaolin, the second phase change material, and the hexagonal boron nitride are all finely and thoroughly mixed. After mixing, the solution is transferred to a vacuum impregnation container to begin the vacuum impregnation process. The 60-80℃ water bath environment promotes interaction and reaction, ensuring uniform diffusion distribution. During vacuum drying, the vacuum pump is adjusted to set the vacuum degree in the container within the range of 0.02-0.08 MPa. A lower vacuum degree helps remove air and moisture from the mixture, preventing bubble formation during drying, and simultaneously promoting better penetration of the second phase change material and hexagonal boron nitride into the metakaolin.

[0026] In the above preparation method, preferably, the metakaolin is first dried in a high-temperature oven at a temperature ≥150℃, and the surface of the metakaolin is modified using a silane coupling agent. The metakaolin is preferably selected from varieties with medium to high specific surface area and controllable pore structure. The pretreatment includes drying at ≥150℃ for 6 hours and optional surface modification with a silane coupling agent to improve compatibility and encapsulation efficiency with phase change materials. Drying the metakaolin first removes moisture and impurities, increases specific surface area and porosity, and promotes the subsequent silane coupling agent modification effect. Modification using a silane coupling agent may include the following steps: adding the pretreated metakaolin to a coupling agent solution and stirring thoroughly to ensure the coupling agent is uniformly coated on the metakaolin surface. This process is usually carried out at room temperature, but may require appropriate heating depending on the specific coupling agent and target reaction. Under stirring conditions, the siloxane groups of the coupling agent react with the hydroxyl groups on the metakaolin surface to form stable chemical bonds, thereby modifying the metakaolin surface. After the modification reaction is completed, unreacted coupling agent and other residues are removed by filtration and washing, and then dried again to obtain the modified metakaolin. Metakaolin modified with silane coupling agent is used to prepare phase change temperature-regulating mineral fillers, which can enhance the interfacial bonding between the phase change temperature-regulating mineral fillers, phase change temperature-regulating steel slag fillers, and cement hydration products, thereby improving the stability of the double-network interpenetrating structure and reducing phase change material leakage.

[0027] In the above preparation method, preferably, before adding the phase change temperature regulating steel slag filler and the phase change temperature regulating mineral filler to the cement matrix, the phase change temperature regulating steel slag filler and the phase change temperature regulating mineral filler are pre-dispersed with a portion of mixing water to form a slurry, and then added to the cement matrix in steps, so that the two types of fillers are uniformly dispersed in the cement matrix and form a mutually interconnected double network structure.

[0028] In the above preparation method, preferably, after pouring into the mold and before the slurry initially sets, a magnetic field of 0.01-0.30T is applied to the slurry in the mold for 30-300s to regulate the uniformity of distribution and spatial configuration of phase change temperature-regulating steel slag filler in the cement stone matrix.

[0029] More specifically, the preparation method of the above-mentioned steel slag cement stone phase change material includes the following steps:

[0030] (1) The steel slag is pretreated by high-energy ball milling to refine the steel slag and by screening and magnetic separation to remove light impurities and optimize particle size distribution. The resulting steel slag powder is treated with alkaline activator (one or more of potassium aluminosilicate, sodium aluminosilicate, and aluminum hydroxide) to improve activity. Organic alcohol amine grinding aids (one or more of monoethanolamine, diethanolamine, triethanolamine, isopropanolamine, diisopropanolamine, and triisopropanolamine) can be added to the ball milling process to improve dispersibility and particle size distribution. The preferred amount of grinding aid is 0.1-2.0 wt% of the steel slag mass.

[0031] (2) Prepare phase change temperature-regulating steel slag filler. After mixing the steel slag powder obtained in step (1) with the first phase change material and graphene powder according to the ratio, the first phase change material and graphene are fully penetrated into the pores of the steel slag and uniformly dispersed under the water bath condition of 60-80℃ by vacuum impregnation method. Then, the obtained precursor is placed in a vacuum oven for drying (temperature 80-90℃, vacuum degree 0.02-0.08MPa, drying for 18-24h) to obtain phase change temperature-regulating steel slag filler.

[0032] (3) Prepare phase change temperature-regulating mineral filler. Preheat and dry metakaolin (≥150℃, 6h) and modify its surface with silane coupling agent. Mix the treated metakaolin with the second phase change material and hexagonal boron nitride at 60-80℃ using vacuum impregnation method to allow the phase change material to enter the pores of metakaolin. Place the precursor in a vacuum oven with the same parameter range for drying (temperature 80-90℃, vacuum degree 0.02-0.08MPa, drying for 18-24h) to obtain phase change temperature-regulating mineral filler.

[0033] (4) Weigh the following raw materials by mass percentage: 10-30% sand, 23-27% cement, 15-25% phase change temperature regulating steel slag filler obtained in step (2), 15-25% phase change temperature regulating mineral filler obtained in step (3), 11-17% mixing water, 0.2-1% quick-setting agent, 1-2% stabilizer and 1-2% water-reducing agent. The sum of the above components is 100%.

[0034] (5) Weigh out the sand, stabilizer, water-reducing agent and cement according to the proportion and put them into the mixing pot and mix for 1-2 minutes. Then add water and stir for 1-2 minutes to form a uniform slurry.

[0035] (6) Add the phase change temperature-regulating steel slag filler obtained in step (2) and the phase change temperature-regulating mineral filler obtained in step (3) to the slurry and continue stirring at low speed for 30-45 seconds. Finally, add the quick-setting agent and stir at high speed for 45-60 seconds. More preferably, it may include:

[0036] (6-1) Pre-dispersion slurry preparation: A portion of the mixing water (preferably 10-30% of the total mixing water) is added to the phase change temperature-regulating mineral filler, along with a corresponding proportion of water-reducing agent and stabilizer. The mixture is then stirred at high speed for 20-60 seconds to obtain a pre-dispersion slurry of the phase change temperature-regulating mineral filler. Similarly, a portion of the mixing water (preferably 10-30% of the total mixing water) is added to the phase change temperature-regulating steel slag filler, and the mixture is stirred at high speed for 20-60 seconds to obtain a pre-dispersion slurry of the phase change temperature-regulating steel slag filler. Pre-dispersion slurry preparation can break up filler agglomeration and reduce the tendency for sedimentation and segregation.

[0037] (6-2) Sequential multi-step mixing: After forming a uniform slurry in step (5), it is preferable to first add the phase change temperature-regulating mineral filler pre-dispersed slurry and stir at low speed for 20-40s to allow it to preferentially enter the slurry pores and form a stable bond with the cement hydration system; then add the phase change temperature-regulating steel slag filler pre-dispersed slurry and stir at low speed for 20-40s, followed by medium speed stirring for 10-30s to further homogenize it; finally add the quick-setting agent and stir at high speed for 45-60s.

[0038] (7) After mixing, the cement slurry is poured into a prefabricated mold and cured for 10-28 days. The steel slag cement stone phase change material is then prepared. Preferably, the cement stone has a particle size of 4.5-13.2 mm, with multi-faceted and irregularly shaped particles and a sphericity of no more than 0.6. More preferably, the slurry, after mixing and being poured into the mold, is placed in a magnetic field environment before initial setting. A magnetic field of 0.01-0.30T is applied for 30-300 seconds. The steel slag is magnetically separated / contains iron, giving it a magnetic response. The magnetic field acts on the micro-rearrangement of the steel slag filler skeleton network, inhibiting local enrichment and sedimentation segregation, and promoting the formation of a more uniform and continuous double-network interpenetrating structure with the phase change temperature-regulating mineral filler.

[0039] This invention utilizes the difference in phase change temperature to enhance the temperature control effect and applicability of artificial aggregates through graded temperature regulation, expanding the temperature control range, improving the thermal response speed and thermal dispersion rate of the aggregates, and realizing the multi-functional application of artificial aggregates. Specifically, this invention first optimizes phase change temperature-regulating steel slag fillers and phase change temperature-regulating mineral fillers. For the phase change temperature-regulating steel slag filler, an efficient mechanochemical method is adopted, using multi-stage grinding and sieving magnetic separation processes, combined with selectively optimized organic alcohol amine grinding aids, to improve the physical stability and chemical activity of steel slag powder, thereby enhancing its performance as a carrier. Graphene is then used in the composite process. Graphene's two-dimensional planar structure and high specific surface area allow it to form an efficient heat conduction network within the filler, improving the thermal response rate of the phase change material. Furthermore, graphene possesses excellent mechanical properties, enhancing the strength, mechanical stability, and wear resistance of artificial aggregates. Simultaneously, due to its excellent surface properties, graphene can act as a "bridge" to improve the compatibility between steel slag and phase change materials. For phase change temperature-regulating mineral fillers, liquid phase change materials are filled into the voids of porous minerals (metakaolin) in a vacuum environment, providing a stable carrier for the phase change material. The macroporous structure of the minerals provides the space required for solid-liquid conversion during use, thereby improving the volume stability of the phase change material in artificial aggregates. Adding hexagonal boron nitride to the metakaolin composite significantly improves the thermal conductivity of the composite material, overcoming the low thermal conductivity of metakaolin. Simultaneously, hexagonal boron nitride exhibits high chemical and thermal stability, remaining stable at high temperatures, thus improving the service life and reliability of the phase change aggregate at high temperatures.

[0040] This invention optimizes both phase change temperature-regulating steel slag filler and phase change temperature-regulating mineral filler, revealing a significant synergistic effect between them. Specifically, the melting or solidification hysteresis effects of the two composite materials are not entirely the same. The combined use of phase change temperature-regulating steel slag filler and phase change temperature-regulating mineral filler can prolong the overall phase change process, increase the system's thermal inertia, and achieve graded temperature control. By using different phase change materials, a multifunctional and wide-range dual temperature regulation function is achieved. The thermal conductivity characteristics of graphene and hexagonal boron nitride enable rapid temperature distribution and uniform control. The combined use of the two fillers, through energy absorption and release during their phase change process, complements each other, increasing the system's thermal inertia and more effectively balancing the impact of external temperature changes on the internal environment, thus achieving long-term temperature stability. Meanwhile, the phase change temperature-regulating steel slag filler and the phase change temperature-regulating mineral filler use steel slag and metakaolin as matrices, respectively. In the cement system, metakaolin and steel slag promote the formation of hydrated calcium silicate with low Ca / Si ratio and high Al / Ca ratio. These hydration products help improve the compressive strength and durability of the materials. Metakaolin and steel slag can undergo a pozzolanic reaction in the cement system. The SiO2 in metakaolin and the Al2O3 in steel slag react in the cement matrix, optimizing the pore structure and improving the microstructure of the cement, reducing capillary volume, improving its resistance to harmful solutions and ion diffusion, and enhancing its freeze-thaw resistance.

[0041] The preparation process employed in this invention involves adding the phase change temperature-regulating filler during the cement slurry stage, thereby minimizing early losses during mixing and other processing steps. In subsequent curing, the products formed by the hydration of the cement matrix tightly encapsulate the dispersed phase change material, ultimately providing robust encapsulation and durable strength support. Furthermore, by introducing multi-faceted and irregularly shaped particles into the mold design, not only are the internal friction requirements for road materials met, but the compatibility of different gradations is also optimized, enhancing the product's practical application value. Precast cement stone units with multi-faceted and irregular shapes are produced by casting using specially designed molds. When these units are assembled, their irregular surfaces and edges interlock, generating multi-dimensional mechanical interference, thus forming an efficient force chain network and interlocking structure between the units. This structure provides excellent internal friction resistance, giving the structure superior overall stability and deformation resistance.

[0042] Compared with the prior art, the advantages of the present invention are as follows:

[0043] 1. The steel slag cement stone phase change material of the present invention achieves the function of "graded temperature regulation" or "wide temperature range temperature regulation" by using different phase change materials in two carriers, steel slag and metakaolin, and staggering their phase change ranges. It can effectively prolong the phase change process, improve the thermal inertia of the system, and better adapt to the day and night temperature difference and instantaneous high temperature of the road.

[0044] 2. The steel slag cement stone phase change material of the present invention utilizes the porous structure of highly active steel slag powder and metakaolin as a carrier, combined with vacuum impregnation and drying processes, to achieve efficient encapsulation of the phase change material, significantly reducing the risk of leakage and improving cycle stability. Furthermore, the resource utilization of steel slag as a carrier can reduce material costs.

[0045] 3. The steel slag cement stone phase change material of this invention introduces graphene and hexagonal boron nitride to construct a thermally conductive network, significantly improving the thermal conductivity and phase change response rate of the composite material. Simultaneously, graphene, with its optimized two-dimensional sheet structure and high specific surface area, not only imparts excellent thermal conductivity to the material but also enhances the wear resistance and compressive strength of the composite through its own mechanical reinforcement effect, thereby meeting the mechanical requirements for road construction and use. The steel slag cement stone phase change material of this invention optimizes the composition of the phase change temperature-regulating steel slag filler and the phase change temperature-regulating mineral filler. By introducing graphene and hexagonal boron nitride, it achieves high thermal conductivity, excellent mechanical strength, and strengthens the thermal and chemical stability of the product.

[0046] 4. The steel slag cement stone phase change material of the present invention exhibits a significant synergistic effect in the cement system as a composite of metakaolin and steel slag, serving as a phase change temperature-regulating mineral filler. The active components, such as metakaolin and steel slag, can undergo secondary reactions with the hydration products in the cement matrix, forming more stable hydration products. The composite system can participate in the pozzolanic reaction, promoting the formation of low Ca / Si ratio, partially Al-doped C-(A)-SH gel, thereby improving the structural density and early-to-late-stage mechanical properties of the cement stone. Furthermore, the synergistic reaction can significantly refine the pore structure, reduce the volume of harmful capillaries, decrease solution erosion and ion diffusion rates, and effectively improve the material's freeze-thaw resistance and durability.

[0047] 5. More preferably, the steel slag cement stone phase change material of the present invention, by regulating the uniformity of distribution, relative position, spatial configuration and interface bonding state of phase change temperature-regulating steel slag filler and phase change temperature-regulating mineral filler in the cement stone matrix, the components work synergistically to construct a three-dimensional interconnected "double network interpenetrating structure". The phase change temperature-regulating steel slag filler particles and phase change temperature-regulating mineral filler particles are uniformly dispersed and interpenetrating in the cement stone matrix, and form a more stable bond at the interface, thereby synergistically improving thermal conductivity response, effective utilization of latent heat of phase change, anti-leakage durability and mechanical load-bearing performance. The specific solution involves using "pre-dispersion slurry preparation + sequential multi-step mixing" to suppress the agglomeration and segregation of the two types of fillers during the mixing process; furthermore, a weak magnetic field is applied before the initial setting of the slurry to regulate the microscale distribution of the phase change temperature-regulating steel slag filler, thereby improving its uniformity and continuity within the matrix; at the same time, the silane coupling agent is combined with kaolin modified to improve the interfacial interaction between the phase change temperature-regulating mineral filler, the phase change temperature-regulating steel slag filler, and cement hydration products, thereby enhancing the stability of the double-network interpenetrating structure.

[0048] Overall, the steel slag cement stone phase change material of the present invention has advantages such as dual temperature regulation function, wide temperature regulation range, good wear resistance, good thermal conductivity, timely temperature regulation, low leakage, high strength and stability, which further improves the applicability of steel slag cement stone phase change material in road surface and can be widely used in asphalt mixtures of different gradations. Detailed Implementation

[0049] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0050] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0051] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0052] Example 1:

[0053] A phase change temperature-regulating steel slag filler comprises the following raw materials in parts by weight: 12 parts steel slag powder, 4.5 parts PEG2000 (first phase change material), and 3 parts graphene powder. Its preparation method is as follows:

[0054] Step S1: Place 1 kg of steel slag in a high-energy ball mill, add 0.5 wt% triethanolamine as a grinding aid, and ball mill until the particle size D50 is approximately 20 μm. Then, perform sieving and magnetic separation to remove light impurities and residual iron. Next, mix the above steel slag powder with 5 wt% sodium aluminosilicate powder, and perform dry alkaline activation to obtain activated steel slag powder for later use.

[0055] Step S2: Weigh the raw materials according to the ratio of 12 parts activated steel slag powder, 4.5 parts PEG2000 (first phase change material), and 3 parts graphene powder. Place the three materials in a beaker, heat in a 70°C water bath and stir until the PEG2000 is completely melted. Then transfer the beaker to a vacuum drying oven and maintain it at 0.05MPa vacuum and 70°C for 2 hours for vacuum impregnation.

[0056] Step S3: After impregnation, the mixture is transferred to a vacuum oven and dried at 85°C and 0.05MPa vacuum for 20 hours. After cooling, it is crushed and sieved to obtain phase change temperature-regulating steel slag filler.

[0057] A phase change temperature-regulating mineral filler comprises the following raw materials in parts by weight: 10 parts metakaolin, 4.5 parts PEG6000 (second phase change material), and 3 parts hexagonal boron nitride. Its preparation method is as follows:

[0058] Step S1: Dry the metakaolin in an oven at 160°C for 6 hours to remove moisture and activate the pores.

[0059] Step S2: Weigh the raw materials according to the ratio of 10 parts metakaolin, 4.5 parts PEG6000 (second phase change material), and 3 parts hexagonal boron nitride. Place the three materials in a beaker, heat in a 70°C water bath and stir until the PEG6000 is completely melted. Then transfer the beaker to a vacuum drying oven and maintain it at 0.05MPa vacuum and 70°C for 2 hours for vacuum impregnation.

[0060] Step S3: After impregnation, the mixture is transferred to a vacuum oven and dried at 85°C and 0.05MPa vacuum for 20 hours. After cooling, it is crushed and sieved to obtain phase change temperature-regulating mineral filler.

[0061] The steel slag cement stone phase change material of this embodiment includes a cement matrix, the aforementioned phase change temperature-regulating steel slag filler, and the aforementioned phase change temperature-regulating mineral filler. The specific proportions and preparation methods are as follows:

[0062] (1) Weigh each component according to the following mass percentages: cement matrix raw materials: sand 20.7%, cement 25.7%, mixing water 14%, quick-setting agent 0.6%, stabilizer 1.5%, water-reducing agent 1.5%; functional fillers: the phase change temperature regulating steel slag filler prepared above 18%, and the phase change temperature regulating mineral filler 18%.

[0063] (2) Add sand, stabilizer, water-reducing agent and cement into the paste mixer in proportion, dry mix for 90 seconds, then add mixing water and continue mixing for 90 seconds to form a uniform paste. Then add phase change temperature regulating steel slag filler and phase change temperature regulating mineral filler to the paste in sequence, mix at low speed for 40 seconds, and finally add quick-setting agent and switch to high speed mixing for 50 seconds.

[0064] (3) The mixed slurry is injected into the precast mold. The mold cavity is designed as an irregular polyhedron, which is intended to form a cement stone precast unit with multiple edges and irregular shape after demolding. After vibration and compaction, the mold is placed in a standard curing box (temperature 20±1℃, relative humidity ≥95%) for 24 hours before demolding. Then, standard curing is continued for 28 days to obtain the steel slag cement stone phase change material unit specimen of this embodiment.

[0065] Example 2:

[0066] A phase change temperature-regulating steel slag filler comprises the following raw materials in parts by weight: 10 parts steel slag powder, 6 parts myristic acid (first phase change material), and 2 parts graphene powder. Its preparation method is as follows:

[0067] Step S1: Place 1 kg of steel slag in a high-energy ball mill, add 0.5 wt% triethanolamine as a grinding aid, and ball mill until the particle size D50 is approximately 20 μm. Then, perform sieving and magnetic separation to remove light impurities and residual iron. Next, mix the above steel slag powder with 5 wt% sodium aluminosilicate powder, and perform dry alkaline activation to obtain activated steel slag powder for later use.

[0068] Step S2: Weigh the raw materials according to the ratio of 10 parts activated steel slag powder, 6 parts myristic acid (first phase change material), and 2 parts graphene powder. Place the three materials in a beaker, heat in a 70°C water bath and stir until the myristic acid is completely melted. Then transfer the beaker to a vacuum drying oven and maintain it at 0.05 MPa vacuum and 70°C for 2 hours for vacuum impregnation.

[0069] Step S3: After impregnation, the mixture is transferred to a vacuum oven and dried at 85°C and 0.05MPa vacuum for 20 hours. After cooling, it is crushed and sieved to obtain phase change temperature-regulating steel slag filler.

[0070] A phase change temperature-regulating mineral filler comprises the following raw materials in parts by weight: 8 parts metakaolin, 6 parts stearic acid (second phase change material), and 2 parts hexagonal boron nitride; its preparation method is as follows:

[0071] Step S1: Dry the metakaolin in an oven at 160°C for 6 hours to remove moisture and activate the pores.

[0072] Step S2: Weigh the raw materials according to the ratio of 8 parts metakaolin, 6 parts stearic acid (second phase change material), and 2 parts hexagonal boron nitride. Place the three materials in a beaker, heat in a 70°C water bath and stir until the stearic acid is completely melted. Then transfer the beaker to a vacuum drying oven and maintain it at 0.05 MPa vacuum and 70°C for 2 hours for vacuum impregnation.

[0073] Step S3: After impregnation, the mixture is transferred to a vacuum oven and dried at 85°C and 0.05MPa vacuum for 20 hours. After cooling, it is crushed and sieved to obtain phase change temperature-regulating mineral filler.

[0074] The steel slag cement stone phase change material of this embodiment includes a cement matrix, the aforementioned phase change temperature-regulating steel slag filler, and the aforementioned phase change temperature-regulating mineral filler. The specific proportions and preparation methods are as follows:

[0075] (1) Weigh each component according to the following mass percentages: cement matrix raw materials: sand 16.2%, cement 27%, mixing water 16%, quick-setting agent 0.8%, stabilizer 1.2%, water-reducing agent 1.8%; functional fillers: the phase change temperature regulating steel slag filler prepared above 15%, and phase change temperature regulating mineral filler 22%.

[0076] (2) Add sand, stabilizer, water-reducing agent and cement into the paste mixer in proportion, dry mix for 90 seconds, then add mixing water and continue mixing for 90 seconds to form a uniform paste. Then add phase change temperature regulating steel slag filler and phase change temperature regulating mineral filler to the paste in sequence, mix at low speed for 40 seconds, and finally add quick-setting agent and switch to high speed mixing for 50 seconds.

[0077] (3) The mixed slurry is injected into the precast mold. The mold cavity is designed as an irregular polyhedron, which is intended to form a cement stone precast unit with multiple edges and irregular shape after demolding. After vibration and compaction, the mold is placed in a standard curing box (temperature 20±1℃, relative humidity ≥95%) for 24 hours before demolding. Then, standard curing is continued for 28 days to obtain the steel slag cement stone phase change material unit specimen of this embodiment.

[0078] Example 3:

[0079] A phase change temperature-regulating steel slag filler comprises the following raw materials in parts by weight: 15 parts steel slag powder, 3 parts n-hexadecyl alcohol (first phase change material), and 4 parts graphene powder. Its preparation method is as follows:

[0080] Step S1: Place 1 kg of steel slag in a high-energy ball mill, add 0.5 wt% triethanolamine as a grinding aid, and ball mill until the particle size D50 is approximately 20 μm. Then, perform sieving and magnetic separation to remove light impurities and residual iron. Next, mix the above steel slag powder with 5 wt% sodium aluminosilicate powder, and perform dry alkaline activation to obtain activated steel slag powder for later use.

[0081] Step S2: Weigh the raw materials according to the ratio of 15 parts activated steel slag powder, 3 parts n-hexadecyl alcohol (first phase change material), and 4 parts graphene powder. Place the three materials in a beaker, heat in a 70°C water bath and stir until the n-hexadecyl alcohol is completely melted. Then transfer the beaker to a vacuum drying oven and maintain it at 0.05 MPa vacuum and 70°C for 2 hours for vacuum impregnation.

[0082] Step S3: After impregnation, the mixture is transferred to a vacuum oven and dried at 85°C and 0.05MPa vacuum for 20 hours. After cooling, it is crushed and sieved to obtain phase change temperature-regulating steel slag filler.

[0083] A phase change temperature-regulating mineral filler comprises the following raw materials in parts by weight: 12 parts metakaolin, 3 parts ethylene glycol stearate diester (second phase change material), and 4 parts hexagonal boron nitride. Its preparation method is as follows:

[0084] Step S1: Dry the metakaolin in an oven at 160°C for 6 hours to remove moisture and activate the pores.

[0085] Step S2: Weigh the raw materials according to the following ratio: 12 parts metakaolin, 3 parts ethylene glycol stearate (second phase change material), and 4 parts hexagonal boron nitride. Place the three materials in a beaker, heat in a 70°C water bath and stir until the ethylene glycol stearate is completely melted. Then transfer the beaker to a vacuum drying oven and maintain it at 0.05 MPa vacuum and 70°C for 2 hours for vacuum impregnation.

[0086] Step S3: After impregnation, the mixture is transferred to a vacuum oven and dried at 85°C and 0.05MPa vacuum for 20 hours. After cooling, it is crushed and sieved to obtain phase change temperature-regulating mineral filler.

[0087] The steel slag cement stone phase change material of this embodiment includes a cement matrix, the aforementioned phase change temperature-regulating steel slag filler, and the aforementioned phase change temperature-regulating mineral filler. The specific proportions and preparation methods are as follows:

[0088] (1) Weigh each component according to the following mass percentages: cement matrix raw materials: sand 21.7%, cement 23%, mixing water 12%, quick-setting agent 0.3%, stabilizer 1.8%, water-reducing agent 1.2%; functional fillers: the above-prepared phase change temperature regulating steel slag filler 25% and phase change temperature regulating mineral filler 15%.

[0089] (2) Add sand, stabilizer, water-reducing agent and cement into the paste mixer in proportion, dry mix for 90 seconds, then add mixing water and continue mixing for 90 seconds to form a uniform paste. Then add phase change temperature regulating steel slag filler and phase change temperature regulating mineral filler to the paste in sequence, mix at low speed for 40 seconds, and finally add quick-setting agent and switch to high speed mixing for 50 seconds.

[0090] (3) The mixed slurry is injected into the precast mold. The mold cavity is designed as an irregular polyhedron, which is intended to form a cement stone precast unit with multiple edges and irregular shape after demolding. After vibration and compaction, the mold is placed in a standard curing box (temperature 20±1℃, relative humidity ≥95%) for 24 hours before demolding. Then, standard curing is continued for 28 days to obtain the steel slag cement stone phase change material unit specimen of this embodiment.

[0091] Example 4:

[0092] A phase change temperature-regulating steel slag filler comprises the following raw materials in parts by weight: 12 parts steel slag powder, 4.5 parts PEG2000 (first phase change material), and 3 parts graphene powder. Its preparation method is as follows:

[0093] Step S1: Place 1 kg of steel slag in a high-energy ball mill, add 0.5 wt% triethanolamine as a grinding aid, and ball mill until the particle size D50 is approximately 20 μm. Then, perform sieving and magnetic separation to remove light impurities and residual iron. Next, mix the above steel slag powder with 5 wt% sodium aluminosilicate powder, and perform dry alkaline activation to obtain activated steel slag powder for later use.

[0094] Step S2: Weigh the raw materials according to the ratio of 12 parts activated steel slag powder, 4.5 parts PEG2000 (first phase change material), and 3 parts graphene powder. Place the three materials in a beaker, heat in a 70°C water bath and stir until the PEG2000 is completely melted. Then transfer the beaker to a vacuum drying oven and maintain it at 0.05MPa vacuum and 70°C for 2 hours for vacuum impregnation.

[0095] Step S3: After impregnation, the mixture is transferred to a vacuum oven and dried at 85°C and 0.05MPa vacuum for 20 hours. After cooling, it is crushed and sieved to obtain phase change temperature-regulating steel slag filler.

[0096] A phase change temperature-regulating mineral filler comprises the following raw materials in parts by weight: 10 parts metakaolin, 4.5 parts PEG6000 (second phase change material), and 3 parts hexagonal boron nitride. Its preparation method is as follows:

[0097] Step S1: Dry the metakaolin in an oven at 160°C for 6 hours to remove moisture and activate the pores.

[0098] Step S2: Prepare a coupling agent solution using γ-aminopropyltriethoxysilane (silane coupling agent KH-550): Add KH-550 to a mixed solvent of ethanol / deionized water (volume ratio 95 / 5) to make the concentration of KH-550 1.0 wt% of the solution mass, and stir for 30 min to pre-hydrolyze it; then add the metakaolin dried in step S1 to the above coupling agent solution, and stir and react at 50°C for 2 h to form a stable binding layer of silane coupling agent on the surface of metakaolin; after the reaction is completed, filter and wash with ethanol to remove unreacted coupling agent, and finally dry at 110°C for 2 h to obtain silane-modified metakaolin for later use.

[0099] Step S3: Weigh the raw materials according to the ratio of 10 parts silane-modified metakaolin, 4.5 parts PEG6000 (second phase change material), and 3 parts hexagonal boron nitride. Place the three materials in a beaker, heat in a 70°C water bath and stir until the PEG6000 is completely melted. Then transfer the beaker to a vacuum drying oven and maintain it at 0.05 MPa vacuum and 70°C for 2 hours for vacuum impregnation.

[0100] Step S4: After impregnation, the mixture is transferred to a vacuum oven and dried at 85°C and 0.05MPa vacuum for 20 hours. After cooling, it is crushed and sieved to obtain phase change temperature-regulating mineral filler.

[0101] The steel slag cement stone phase change material of this embodiment includes a cement matrix, the aforementioned phase change temperature-regulating steel slag filler, and the aforementioned phase change temperature-regulating mineral filler. The specific proportions and preparation methods are as follows:

[0102] (1) Weigh each component according to the following mass percentages: cement matrix raw materials: sand 20.7%, cement 25.7%, mixing water 14%, quick-setting agent 0.6%, stabilizer 1.5%, water-reducing agent 1.5%; functional fillers: the phase change temperature regulating steel slag filler prepared above 18%, and the phase change temperature regulating mineral filler 18%.

[0103] (2) Add sand, stabilizer, water-reducing agent and cement into the paste mixer in proportion, dry mix for 90 seconds, then add mixing water and continue mixing for 90 seconds to form a uniform paste. Then add phase change temperature regulating steel slag filler and phase change temperature regulating mineral filler to the paste in sequence, mix at low speed for 40 seconds, and finally add quick-setting agent and switch to high speed mixing for 50 seconds.

[0104] (3) The mixed slurry is injected into the precast mold. The mold cavity is designed as an irregular polyhedron, which is intended to form a cement stone precast unit with multiple edges and irregular shape after demolding. After vibration and compaction, the mold is placed in a standard curing box (temperature 20±1℃, relative humidity ≥95%) for 24 hours before demolding. Then, standard curing is continued for 28 days to obtain the steel slag cement stone phase change material unit specimen of this embodiment.

[0105] Example 5:

[0106] A phase change temperature-regulating steel slag filler comprises the following raw materials in parts by weight: 12 parts steel slag powder, 4.5 parts PEG2000 (first phase change material), and 3 parts graphene powder. Its preparation method is as follows:

[0107] Step S1: Place 1 kg of steel slag in a high-energy ball mill, add 0.5 wt% triethanolamine as a grinding aid, and ball mill until the particle size D50 is approximately 20 μm. Then, perform sieving and magnetic separation to remove light impurities and residual iron. Next, mix the above steel slag powder with 5 wt% sodium aluminosilicate powder, and perform dry alkaline activation to obtain activated steel slag powder for later use.

[0108] Step S2: Weigh the raw materials according to the ratio of 12 parts activated steel slag powder, 4.5 parts PEG2000 (first phase change material), and 3 parts graphene powder. Place the three materials in a beaker, heat in a 70°C water bath and stir until the PEG2000 is completely melted. Then transfer the beaker to a vacuum drying oven and maintain it at 0.05MPa vacuum and 70°C for 2 hours for vacuum impregnation.

[0109] Step S3: After impregnation, the mixture is transferred to a vacuum oven and dried at 85°C and 0.05MPa vacuum for 20 hours. After cooling, it is crushed and sieved to obtain phase change temperature-regulating steel slag filler.

[0110] A phase change temperature-regulating mineral filler comprises the following raw materials in parts by weight: 10 parts metakaolin, 4.5 parts PEG6000 (second phase change material), and 3 parts hexagonal boron nitride. Its preparation method is as follows:

[0111] Step S1: Dry the metakaolin in an oven at 160°C for 6 hours to remove moisture and activate the pores.

[0112] Step S2: Prepare a coupling agent solution using γ-aminopropyltriethoxysilane (silane coupling agent KH-550): Add KH-550 to a mixed solvent of ethanol / deionized water (volume ratio 95 / 5) to make the concentration of KH-550 1.0 wt% of the solution mass, and stir for 30 min to pre-hydrolyze it; then add the metakaolin dried in step S1 to the above coupling agent solution, and stir and react at 50°C for 2 h to form a stable binding layer of silane coupling agent on the surface of metakaolin; after the reaction is completed, filter and wash with ethanol to remove unreacted coupling agent, and finally dry at 110°C for 2 h to obtain silane-modified metakaolin for later use.

[0113] Step S3: Weigh the raw materials according to the ratio of 10 parts silane-modified metakaolin, 4.5 parts PEG6000 (second phase change material), and 3 parts hexagonal boron nitride. Place the three materials in a beaker, heat in a 70°C water bath and stir until the PEG6000 is completely melted. Then transfer the beaker to a vacuum drying oven and maintain it at 0.05 MPa vacuum and 70°C for 2 hours for vacuum impregnation.

[0114] Step S4: After impregnation, the mixture is transferred to a vacuum oven and dried at 85°C and 0.05MPa vacuum for 20 hours. After cooling, it is crushed and sieved to obtain phase change temperature-regulating mineral filler.

[0115] The steel slag cement stone phase change material of this embodiment includes a cement matrix, the aforementioned phase change temperature-regulating steel slag filler, and the aforementioned phase change temperature-regulating mineral filler. The specific proportions and preparation methods are as follows:

[0116] (1) Weigh each component according to the following mass percentages: cement matrix raw materials: sand 20.7%, cement 25.7%, mixing water 14%, quick-setting agent 0.6%, stabilizer 1.5%, water-reducing agent 1.5%; functional fillers: the phase change temperature regulating steel slag filler prepared above 18%, and the phase change temperature regulating mineral filler 18%.

[0117] (2) Add sand, stabilizer, water-reducing agent and cement into the paste mixer in proportion, dry mix for 90 seconds, then add mixing water (deduct the amount of pre-dispersion water), and continue mixing for 90 seconds to form a uniform paste.

[0118] (2-1) Take 20% of the total mixing water and use it for the pre-dispersion of the two types of fillers respectively: add phase change temperature regulating mineral filler to 10% of the mixing water and add the corresponding proportion of water reducing agent and stabilizer, and use high-speed shear stirring for 30 seconds to obtain phase change temperature regulating mineral filler pre-dispersion slurry; add phase change temperature regulating steel slag filler to 10% of the mixing water and use high-speed shear stirring for 30 seconds to obtain phase change temperature regulating steel slag filler pre-dispersion slurry.

[0119] (2-2) First, add the phase change temperature-regulating mineral filler pre-dispersed slurry to the slurry and stir at low speed for 30 seconds; then add the phase change temperature-regulating steel slag filler pre-dispersed slurry and stir at low speed for 30 seconds, followed by stirring at medium speed for 20 seconds to further homogenize; finally, add the quick-setting agent and switch to high speed stirring for 50 seconds.

[0120] (3) The mixed slurry is injected into the precast mold. The mold cavity is designed as an irregular polyhedron, which is intended to form a cement stone precast unit with multiple edges and irregular shape after demolding. After vibration and compaction, the mold is placed in a standard curing box (temperature 20±1℃, relative humidity ≥95%) for 24 hours before demolding. Then, standard curing is continued for 28 days to obtain the steel slag cement stone phase change material unit specimen of this embodiment.

[0121] Example 6:

[0122] A phase change temperature-regulating steel slag filler comprises the following raw materials in parts by weight: 12 parts steel slag powder, 4.5 parts PEG2000 (first phase change material), and 3 parts graphene powder. Its preparation method is as follows:

[0123] Step S1: Place 1 kg of steel slag in a high-energy ball mill, add 0.5 wt% triethanolamine as a grinding aid, and ball mill until the particle size D50 is approximately 20 μm. Then, perform sieving and magnetic separation to remove light impurities and residual iron. Next, mix the above steel slag powder with 5 wt% sodium aluminosilicate powder, and perform dry alkaline activation to obtain activated steel slag powder for later use.

[0124] Step S2: Weigh the raw materials according to the ratio of 12 parts activated steel slag powder, 4.5 parts PEG2000 (first phase change material), and 3 parts graphene powder. Place the three materials in a beaker, heat in a 70°C water bath and stir until the PEG2000 is completely melted. Then transfer the beaker to a vacuum drying oven and maintain it at 0.05MPa vacuum and 70°C for 2 hours for vacuum impregnation.

[0125] Step S3: After impregnation, the mixture is transferred to a vacuum oven and dried at 85°C and 0.05MPa vacuum for 20 hours. After cooling, it is crushed and sieved to obtain phase change temperature-regulating steel slag filler.

[0126] A phase change temperature-regulating mineral filler comprises the following raw materials in parts by weight: 10 parts metakaolin, 4.5 parts PEG6000 (second phase change material), and 3 parts hexagonal boron nitride. Its preparation method is as follows:

[0127] Step S1: Dry the metakaolin in an oven at 160°C for 6 hours to remove moisture and activate the pores.

[0128] Step S2: Prepare a coupling agent solution using γ-aminopropyltriethoxysilane (silane coupling agent KH-550): Add KH-550 to a mixed solvent of ethanol / deionized water (volume ratio 95 / 5) to make the concentration of KH-550 1.0 wt% of the solution mass, and stir for 30 min to pre-hydrolyze it; then add the metakaolin dried in step S1 to the above coupling agent solution, and stir and react at 50°C for 2 h to form a stable binding layer of silane coupling agent on the surface of metakaolin; after the reaction is completed, filter and wash with ethanol to remove unreacted coupling agent, and finally dry at 110°C for 2 h to obtain silane-modified metakaolin for later use.

[0129] Step S3: Weigh the raw materials according to the ratio of 10 parts silane-modified metakaolin, 4.5 parts PEG6000 (second phase change material), and 3 parts hexagonal boron nitride. Place the three materials in a beaker, heat in a 70°C water bath and stir until the PEG6000 is completely melted. Then transfer the beaker to a vacuum drying oven and maintain it at 0.05 MPa vacuum and 70°C for 2 hours for vacuum impregnation.

[0130] Step S4: After impregnation, the mixture is transferred to a vacuum oven and dried at 85°C and 0.05MPa vacuum for 20 hours. After cooling, it is crushed and sieved to obtain phase change temperature-regulating mineral filler.

[0131] The steel slag cement stone phase change material of this embodiment includes a cement matrix, the aforementioned phase change temperature-regulating steel slag filler, and the aforementioned phase change temperature-regulating mineral filler. The specific proportions and preparation methods are as follows:

[0132] (1) Weigh each component according to the following mass percentages: cement matrix raw materials: sand 20.7%, cement 25.7%, mixing water 14%, quick-setting agent 0.6%, stabilizer 1.5%, water-reducing agent 1.5%; functional fillers: the phase change temperature regulating steel slag filler prepared above 18%, and the phase change temperature regulating mineral filler 18%.

[0133] (2) Add sand, stabilizer, water-reducing agent and cement into the paste mixer in proportion, dry mix for 90 seconds, then add mixing water (deduct the amount of pre-dispersion water), and continue mixing for 90 seconds to form a uniform paste.

[0134] (2-1) Take 20% of the total mixing water and use it for the pre-dispersion of the two types of fillers respectively: add phase change temperature regulating mineral filler to 10% of the mixing water and add the corresponding proportion of water reducing agent and stabilizer, and use high-speed shear stirring for 30 seconds to obtain phase change temperature regulating mineral filler pre-dispersion slurry; add phase change temperature regulating steel slag filler to 10% of the mixing water and use high-speed shear stirring for 30 seconds to obtain phase change temperature regulating steel slag filler pre-dispersion slurry.

[0135] (2-2) First, add the phase change temperature-regulating mineral filler pre-dispersed slurry to the slurry and stir at low speed for 30 seconds; then add the phase change temperature-regulating steel slag filler pre-dispersed slurry and stir at low speed for 30 seconds, followed by stirring at medium speed for 20 seconds to further homogenize; finally, add the quick-setting agent and switch to high speed stirring for 50 seconds.

[0136] (3) After the slurry is mixed, it is poured into the mold and vibrated to compact it. Before the slurry sets, the mold is placed in a magnetic field device and a constant magnetic field with a strength of 0.15T is applied for 180 seconds. After the magnetic field is applied, the mold is placed in a standard curing chamber (temperature 20±1℃, relative humidity ≥95%) for 24 hours and then demolded. The mold is then cured in a standard manner for 28 days to obtain the steel slag cement stone phase change material unit specimen of this embodiment.

[0137] Comparative Example 1:

[0138] This comparative example does not use phase change temperature-regulating steel slag filler or phase change temperature-regulating mineral filler; instead, it directly adds an equal amount of phase change material to the cement matrix. The preparation method includes the following steps:

[0139] (1) Weigh each component according to the following mass percentages: cement matrix raw materials: sand 47.92%, cement 25.7%, mixing water 14%, quick-setting agent 0.6%, stabilizer 1.5%, water-reducing agent 1.5%; phase change materials: PEG2000: 4.15%, PEG6000: 4.63%.

[0140] (2) Add sand, stabilizer, water-reducing agent and cement into the paste mixer in proportion, dry mix for 90 seconds, then add mixing water and continue mixing for 90 seconds to form a uniform paste. Then add phase change material PEG2000 and phase change material PEG6000 to the paste in sequence, mix at low speed for 40 seconds, and finally add quick-setting agent and switch to high speed mixing for 50 seconds.

[0141] (3) The mixed slurry is injected into the precast mold. The mold cavity is designed as an irregular polyhedron, which is intended to form a cement stone precast unit with multiple edges and irregular shape after demolding. After vibration and compaction, the mold is placed in a standard curing box (temperature 20±1℃, relative humidity ≥95%) for 24 hours before demolding. Then, standard curing is continued for 28 days to obtain the steel slag cement stone phase change material unit specimen of this comparative example.

[0142] Comparative Example 2:

[0143] The phase change temperature-regulating steel slag filler and its preparation method in this comparative example are the same as in Example 1.

[0144] A phase change temperature-regulating mineral filler comprises the following raw materials in parts by weight: 10 parts metakaolin, 4.5 parts PEG2000, and 3 parts hexagonal boron nitride; its preparation method is as follows:

[0145] Step S1: Dry the metakaolin in an oven at 160°C for 6 hours to remove moisture and activate the pores.

[0146] Step S2: Weigh the raw materials according to the ratio of 10 parts metakaolin, 4.5 parts PEG2000 (first phase change material), and 3 parts hexagonal boron nitride. Place the three materials in a beaker, heat in a 70°C water bath and stir until the PEG2000 is completely melted. Then transfer the beaker to a vacuum drying oven and maintain it at 0.05 MPa vacuum and 70°C for 2 hours for vacuum impregnation.

[0147] Step S3: After impregnation, the mixture is transferred to a vacuum oven and dried at 85°C and 0.05MPa vacuum for 20 hours. After cooling, it is crushed and sieved to obtain phase change temperature-regulating mineral filler.

[0148] The steel slag cement stone phase change material of this comparative example includes a cement matrix, the aforementioned phase change temperature-regulating steel slag filler, and the aforementioned phase change temperature-regulating mineral filler. Its proportions and preparation method are as follows:

[0149] (1) Weigh each component according to the following mass percentages: cement matrix raw materials: sand 20.7%, cement 25.7%, mixing water 14%, quick-setting agent 0.6%, stabilizer 1.5%, water-reducing agent 1.5%; functional fillers: the phase change temperature regulating steel slag filler prepared above 18%, and the phase change temperature regulating mineral filler 18%.

[0150] (2) Add sand, stabilizer, water-reducing agent and cement into the paste mixer in proportion, dry mix for 90 seconds, then add mixing water and continue mixing for 90 seconds to form a uniform paste. Then add phase change temperature regulating steel slag filler and phase change temperature regulating mineral filler to the paste in sequence, mix at low speed for 40 seconds, and finally add quick-setting agent and switch to high speed mixing for 50 seconds.

[0151] (3) The mixed slurry is injected into the precast mold. The mold cavity is designed as an irregular polyhedron, which is intended to form a cement stone precast unit with multiple edges and irregular shape after demolding. After vibration and compaction, the mold is placed in a standard curing box (temperature 20±1℃, relative humidity ≥95%) for 24 hours before demolding. Then, standard curing is continued for 28 days to obtain the steel slag cement stone phase change material unit specimen of this comparative example.

[0152] Comparative Example 3:

[0153] A phase change temperature-regulating steel slag filler comprises the following raw materials in parts by weight: 15 parts steel slag powder and 4.5 parts PEG2000 (first phase change material). Its preparation method is as follows:

[0154] Step S1: Place 1 kg of steel slag in a high-energy ball mill, add 0.5 wt% triethanolamine as a grinding aid, and ball mill until the particle size D50 is approximately 20 μm. Then, perform sieving and magnetic separation to remove light impurities and residual iron. Next, mix the above steel slag powder with 5 wt% sodium aluminosilicate powder, and perform dry alkaline activation to obtain activated steel slag powder for later use.

[0155] Step S2: Weigh the raw materials according to the ratio of 15 parts activated steel slag powder and 4.5 parts PEG2000 (first phase change material). Place both in a beaker, heat in a 70°C water bath and stir until the PEG2000 is completely melted. Then transfer the beaker to a vacuum drying oven and maintain it at 0.05MPa vacuum and 70°C for 2 hours for vacuum impregnation.

[0156] Step S3: After impregnation, the mixture is transferred to a vacuum oven and dried at 85°C and 0.05MPa vacuum for 20 hours. After cooling, it is crushed and sieved to obtain phase change temperature-regulating steel slag filler.

[0157] The phase change temperature-regulating mineral filler and its preparation method in this comparative example are the same as in Example 1.

[0158] The steel slag cement stone phase change material of this comparative example includes a cement matrix, the aforementioned phase change temperature-regulating steel slag filler, and the aforementioned phase change temperature-regulating mineral filler. Its proportions and preparation method are as follows:

[0159] (1) Weigh each component according to the following mass percentages: cement matrix raw materials: sand 20.7%, cement 25.7%, mixing water 14%, quick-setting agent 0.6%, stabilizer 1.5%, water-reducing agent 1.5%; functional fillers: the phase change temperature regulating steel slag filler prepared above 18%, and the phase change temperature regulating mineral filler 18%.

[0160] (2) Add sand, stabilizer, water-reducing agent and cement into the paste mixer in proportion, dry mix for 90 seconds, then add mixing water and continue mixing for 90 seconds to form a uniform paste. Then add phase change temperature regulating steel slag filler and phase change temperature regulating mineral filler to the paste in sequence, mix at low speed for 40 seconds, and finally add quick-setting agent and switch to high speed mixing for 50 seconds.

[0161] (3) The mixed slurry is injected into the precast mold. The mold cavity is designed as an irregular polyhedron, which is intended to form a cement stone precast unit with multiple edges and irregular shape after demolding. After vibration and compaction, the mold is placed in a standard curing box (temperature 20±1℃, relative humidity ≥95%) for 24 hours before demolding. Then, standard curing is continued for 28 days to obtain the steel slag cement stone phase change material unit specimen of this comparative example.

[0162] Comparative Example 4:

[0163] A phase change temperature-regulating steel slag filler (using mineral powder) comprises the following raw materials in parts by weight: 12 parts S95 grade mineral powder, 4.5 parts PEG2000 (first phase change material), and 3 parts graphene powder. Its preparation method is as follows:

[0164] Step S1: Weigh the raw materials according to the ratio of 12 parts S95 grade mineral powder, 4.5 parts PEG2000 (first phase change material), and 3 parts graphene powder. Place the three materials in a beaker, heat in a 70°C water bath and stir until the PEG2000 is completely melted. Then transfer the beaker to a vacuum drying oven and maintain it at 0.05 MPa vacuum and 70°C for 2 hours for vacuum impregnation.

[0165] Step S2: After impregnation, the mixture is transferred to a vacuum oven and dried at 85°C and 0.05MPa vacuum for 20 hours. After cooling, it is crushed and sieved to obtain phase change temperature-regulating steel slag filler (made of mineral powder).

[0166] The phase change temperature-regulating mineral filler and its preparation method in this comparative example are the same as in Example 1.

[0167] The steel slag cement stone phase change material of this comparative example includes a cement matrix, the aforementioned phase change temperature-regulating steel slag filler, and the aforementioned phase change temperature-regulating mineral filler. Its proportions and preparation method are as follows:

[0168] (1) Weigh each component according to the following mass percentages: cement matrix raw materials: sand 20.7%, cement 25.7%, mixing water 14%, quick-setting agent 0.6%, stabilizer 1.5%, water-reducing agent 1.5%; functional filler: the phase change temperature regulating steel slag filler (with mineral powder) prepared above 18%, phase change temperature regulating mineral filler 18%.

[0169] (2) Add sand, stabilizer, water-reducing agent and cement into the paste mixer in proportion, dry mix for 90 seconds, then add mixing water and continue mixing for 90 seconds to form a uniform paste. Then add phase change temperature regulating steel slag filler and phase change temperature regulating mineral filler to the paste in sequence, mix at low speed for 40 seconds, and finally add quick-setting agent and switch to high speed mixing for 50 seconds.

[0170] (3) The mixed slurry is injected into the precast mold. The mold cavity is designed as an irregular polyhedron, which is intended to form a cement stone precast unit with multiple edges and irregular shape after demolding. After vibration and compaction, the mold is placed in a standard curing box (temperature 20±1℃, relative humidity ≥95%) for 24 hours before demolding. Then, standard curing is continued for 28 days to obtain the steel slag cement stone phase change material unit specimen of this comparative example.

[0171] The specimens from the above embodiments and comparative examples were subjected to the following tests:

[0172] Single-particle compressive strength test: Several intact steel slag cement stone phase change material unit specimens were randomly selected. Using a pressure testing machine, a high-strength pad was placed above and below each unit specimen, and a load was applied at a rate of 1.0 mm / min until the unit specimen failed. The maximum pressure was recorded, and the single-particle compressive strength was calculated based on the approximate projected area of ​​the unit bearing the pressure, and the average value was taken.

[0173] Interlocking body compressive strength test: Prefabricated units are filled into a Φ150mm×H150mm steel mold in a tightly packed manner as in actual application to form an interlocking body. A compression testing machine is used to conduct a compressive test on the entire interlocking body, and its overall compressive strength is calculated.

[0174] Thermal conductivity test: The steel slag cement stone phase change material specimen was cut into smooth flat specimens with a thickness of 0.3 mm and a diameter of 25 mm, and the thermal conductivity was measured using a hot wire thermal conductivity meter.

[0175] Phase change latent heat test: Differential scanning calorimetry was used to test the prepared prefabricated unit specimen powder samples.

[0176] Leakage rate test: A prefabricated unit of a certain mass (m0) is placed in a 60℃ oven for 24 hours. After removal, any liquid that may have seeped from the surface is wiped off, and the weight (m1) is measured. Leakage rate = (m0-m1) / m0 × 100%.

[0177] Los Angeles abrasion test: The abrasion test (Los Angeles method) shall be conducted in accordance with the requirements of JTG3432-2024 "Specifications for Testing Aggregates in Highway Engineering".

[0178] Thermal cycling stability test: After the prefabricated unit is repeatedly cycled 100 times within the phase change temperature range, its latent heat of phase change is tested again, and the latent heat retention rate is calculated.

[0179] Cross-sectional uniformity test (coefficient of variation, CV): Representative cross-sections were obtained by cutting steel slag cement stone phase change material unit specimens and imaging the cross-sections (CT or polished microscopy). The cross-sections were divided into n equal-area grids (e.g., 10×10), and the area proportion of phase change temperature-regulating steel slag filler in each grid was statistically analyzed. And calculate its mean. And standard deviation s, define the coefficient of variation of steel slag packing distribution. Similarly, the area ratio of phase change temperature-regulating mineral fillers was statistically analyzed and calculated. A smaller CV indicates a more uniform distribution.

[0180] Thermal response rate test: The unit specimen is placed on a constant temperature hot table or under constant heat flow conditions for heating, and the time required for the specimen surface temperature to rise from 40℃ to 60℃ is recorded as _____. To characterize the thermal response rate of the material, The smaller the value, the faster the thermal response.

[0181] The specific test data can be found in Tables 1 and 2.

[0182] Table 1: Performance test results of each embodiment and comparative example

[0183]

[0184] Table 2: Examples of Distribution Uniformity and Thermal Response Rate Results in Examples 4-6

[0185]

[0186] As shown in Table 1, the steel slag cement stone phase change materials prepared in Examples 1-6 are significantly superior to those in Comparative Examples 1-4 in terms of overall performance. Regarding encapsulation and durability, the leakage rates of Examples 1-6 are all at low levels, far lower than that of Comparative Example 1, indicating that the vacuum impregnation encapsulation technology based on steel slag and metakaolin can effectively suppress leakage of the phase change material, thereby ensuring thermal cycling stability and wear resistance. In Example 4, after high-temperature drying of metakaolin, surface modification with a silane coupling agent was further applied to improve the wetting and interfacial bonding of the second phase change material, reducing the leakage rate to 0.5 wt% and increasing the thermal cycling stability to 97.0%. Based on this, Example 5 further improved the distribution uniformity and structural compactness of the two types of fillers through "pre-dispersion + sequential multi-step mixing", further reducing the leakage rate to 0.4 wt% and increasing the thermal cycling stability to 97.4%. In Example 6, after superimposed magnetic field-assisted distribution control, the leakage rate was the lowest (0.3 wt%) and the thermal cycling stability was the highest (97.8%), demonstrating the synergistic benefit of "interfacial modification + distribution configuration optimization".

[0187] In terms of thermal performance, Examples 1-6 all maintain a high latent heat of phase change and achieve a high thermal conductivity by relying on the synergistic thermal conduction network constructed by graphene and hexagonal boron nitride, thus possessing both thermal storage and temperature regulation capabilities and thermal response capabilities. In particular, Examples 4-6 maintain a latent heat of phase change of approximately 59.0 J / g while achieving a thermal conductivity as high as 2.81 W / (m·K), indicating that without weakening the thermal storage capacity, the heat transfer pathway can be further optimized and the thermal response improved through interface modification and distribution control.

[0188] In terms of mechanical and structural properties, Examples 1-6, thanks to the secondary encapsulation of cement stone, the reinforcement effect of fillers, and the multi-faceted prefabricated interlocking structure, all exhibited high single-particle compressive strength and interlocking compressive strength. Examples 4-6 reached 48.6 / 19.6 MPa, 48.9 / 19.9 MPa, and 49.2 / 20.2 MPa, respectively, indicating that silane coupling agent modification and subsequent dispersion and magnetic field distribution control helped to further improve the overall structural load-bearing capacity and stability. In contrast, Comparative Example 1 suffered from severe leakage due to the lack of encapsulation, resulting in a significant decrease in overall performance; Comparative Example 2, while having acceptable basic performance, struggled to achieve graded temperature control; Comparative Example 3 suffered from deteriorated thermal conductivity and mechanical properties due to the absence of graphene; and Comparative Example 4 demonstrated that pretreated steel slag was superior to ordinary mineral powder in terms of strength, durability, and thermal conductivity.

[0189] As shown in Table 2, based on the silane-modified system (Example 4), Example 5, which introduces "pre-dispersion slurry preparation + sequential multi-step mixing," can significantly reduce the distribution variation coefficient of both types of fillers. , (both decreased), thermal response time The reduction from 390s to 335s indicates a more uniform packing distribution and a more stable interpenetrating structure, which is beneficial for rapid heat transfer and release. Furthermore, after superimposing magnetic field-assisted distribution control in Example 6, Further reduction and Further shortened to 295s; at the same time, The concentration of mineral fillers also decreased. This indicates that the magnetic field primarily improves the uniformity of mineral filler distribution by promoting microscale rearrangement of magnetically responsive steel slag fillers, inhibiting local enrichment and sedimentation segregation, and optimizing the spatial synergistic distribution of the two types of fillers in the slurry, ultimately forming a higher-quality double-network interpenetrating structure.

Claims

1. A steel slag cement stone phase change material, characterized in that, The components include the following parts by weight: 50-65 parts cementitious matrix; 15-25 parts of phase change temperature regulating steel slag filler; 15-25 parts of phase change temperature-regulating mineral filler; The phase change temperature-regulating steel slag filler comprises the following components in parts by weight: 10-15 parts steel slag powder, 3-6 parts first phase change material, and 2-4 parts graphene powder. The phase change temperature-regulating mineral filler comprises the following components in parts by weight: 8-12 parts metakaolin, 3-6 parts second phase change material, and 2-4 parts hexagonal boron nitride; The solid-liquid phase transition temperature ranges of the first phase change material and the second phase change material do not overlap or are at least partially offset from each other; The cement matrix comprises the following raw materials in parts by weight: 10-30 parts sand, 23-27 parts cement, 11-17 parts mixing water, 0.2-1.0 parts quick-setting agent, 1-2 parts stabilizer, and 1-2 parts water-reducing agent; The first phase change material includes one or more of polyethylene glycol 2000, myristic acid, n-hexadecyl alcohol and caprylic acid, and its phase change temperature is 40-50℃, and its latent heat of phase change is ≥150J / g; the second phase change material includes one or more of polyethylene glycol 4000, polyethylene glycol 6000, stearic acid and ethylene glycol stearate, and its phase change temperature is 50-60℃, and its latent heat of phase change is ≥150J / g.

2. The steel slag cement stone phase change material according to claim 1, characterized in that, The cement includes one or more silicate cements, and its strength grade is not less than 42.5, and the specific surface area of ​​the cement is not less than 300 m² / kg; the sand includes one or more quartz sands or manufactured sands; the quick-setting agent includes one or more of chlorate, silicate and alkali-free liquid quick-setting agents; the stabilizer includes hydroxypropyl methylcellulose or its derivatives.

3. The steel slag cement stone phase change material according to claim 1, characterized in that, The graphene powder has 1-10 layers, an average sheet diameter of 0.5-10 μm, and a specific surface area of ​​50-1000 m² / g; the hexagonal boron nitride has a particle size and packing morphology adapted to the pores of metakaolin.

4. A method for preparing a steel slag cement stone phase change material according to any one of claims 1-3, characterized in that, Includes the following steps: (1) Steel slag is pretreated to obtain steel slag powder; the steel slag powder is activated by alkali, and then mixed with the first phase change material and graphene powder by vacuum impregnation to prepare a phase change temperature-regulating steel slag filler precursor. Finally, the phase change temperature-regulating steel slag filler precursor is dried to obtain phase change temperature-regulating steel slag filler. (2) A phase change temperature-regulating mineral filler precursor was prepared by mixing metakaolin, second phase change material and hexagonal boron nitride using a vacuum impregnation method. Finally, the phase change temperature-regulating mineral filler precursor was dried to obtain the phase change temperature-regulating mineral filler. (3) Mix the cement matrix, phase change temperature regulating steel slag filler and phase change temperature regulating mineral filler, pour into a mold, and cure to obtain steel slag cement stone phase change material.

5. The preparation method according to claim 4, characterized in that, The pretreatment of steel slag includes the following steps: The steel slag is finely pulverized using a high-energy ball mill, and then the particle size distribution is optimized using sieving and magnetic separation to obtain steel slag powder with a particle size D50 of 5-50 μm. Heavy and light impurities are then separated. An organic alcohol amine grinding aid is added during ball milling. The organic alcohol amine includes one or more of monoethanolamine, diethanolamine, triethanolamine, isopropanolamine, diisopropanolamine, and triisopropanolamine. The amount of the grinding aid added is 0.1-2.0 wt% of the steel slag mass. An activator for alkaline activation of the steel slag powder includes one or more of potassium aluminosilicate, sodium aluminosilicate, and aluminum hydroxide. The amount of the activator is 1-10 wt% of the steel slag powder mass. The activation treatment is carried out at 20-90℃ for 0.5-6 hours.

6. The preparation method according to claim 4, characterized in that, Alkali-activated steel slag powder, along with a first phase change material and graphene powder, were vacuum impregnated and stirred in a water bath at 60-80℃, allowing the phase change material to penetrate the pores of the steel slag powder and fully disperse with the graphene powder. The phase change temperature-regulating steel slag filler precursor was dried in a vacuum oven at a vacuum degree of 0.02-0.08 MPa and a temperature of 80-90℃ for 18-24 hours. Metakaolin, a second phase change material, and hexagonal boron nitride were vacuum impregnated and stirred in a water bath at 60-80℃ to obtain a phase change temperature-regulating mineral filler precursor, which was then dried in a vacuum oven at a vacuum degree of 0.02-0.08 MPa and a temperature of 80-90℃ for 18-24 hours.

7. The preparation method according to claim 4, characterized in that, First, the metakaolin was dried in a high-temperature oven at a temperature of ≥150℃, and then the surface of the metakaolin was modified using a silane coupling agent.

8. The preparation method according to claim 4, characterized in that, Before adding the phase change temperature regulating steel slag filler and the phase change temperature regulating mineral filler to the cement matrix, the phase change temperature regulating steel slag filler and the phase change temperature regulating mineral filler are pre-dispersed with a portion of mixing water to form a slurry, and then added to the cement matrix in steps.

9. The preparation method according to claim 4, characterized in that, After pouring into the mold and before the slurry initially sets, apply a magnetic field of 0.01-0.30T to the slurry inside the mold for 30-300 seconds.

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