Solid waste-based high-strength phase change light aggregate, preparation method and application thereof

Abstract

This invention belongs to the field of building materials technology, specifically relating to a solid waste-based high-strength phase change lightweight aggregate, its preparation method, and its application. The solid waste-based high-strength phase change lightweight aggregate provided by this invention comprises the following raw materials in parts by weight: 26-32 parts cement, 4-6 parts steel slag powder, 32-36 parts ice chips, 14-16 parts dry ice, 12-16 parts brick slag powder, 2.7-3.6 parts paraffin emulsion, and 0.3-0.4 parts organosilicon water-repellent agent. This invention uses construction solid waste brick slag loaded with paraffin emulsion to prepare phase change microparticles, and uses cement and steel slag powder to react under ice chips and dry ice conditions to form high-strength lightweight aggregate. Simultaneously, ice chips and dry ice are used for room-temperature pore formation and to improve curing efficiency. The resulting solid waste-based high-strength phase change lightweight aggregate achieves an organic combination of phase change products and pure lightweight aggregate, exhibiting high strength, good stability, and low manufacturing cost. It is a new type of solid waste-based energy-saving building material with higher quality and more convenient application.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a solid waste-based high-strength phase change lightweight aggregate, its preparation method, and its application. Background Technology

[0002] With the vigorous promotion of passive buildings and other technologies, the demand for new phase change building materials is becoming increasingly urgent. The key technologies for phase change building materials lie in suitable phase change temperatures, reliable carriers, and effective encapsulation techniques. One of the main constraints on the application of phase change materials in the construction field is cost. The molding technology of phase change microcapsules is too expensive; although the building materials prepared using this technology have excellent performance, their high cost prevents their widespread use in ordinary industrial and civil buildings.

[0003] Currently, phase change building materials mainly utilize the porous nature of building materials as carriers for phase change materials. Most research findings involve using one or more natural materials or industrial solid waste to prepare ceramsite through high-temperature calcination, directly using the finished ceramsite as a carrier for the phase change material. However, this still requires surface encapsulation using specific materials and processes to prepare the phase change building material. The product preparation process is complex and costly, preventing large-scale industrial application.

[0004] Furthermore, there is currently limited research on high-strength phase change lightweight aggregates, especially those made from construction waste. Most studies focus on phase change products or simple lightweight aggregate preparation, and the preparation and application technologies are relatively rudimentary, resulting in problems such as high cost, low strength, poor stability, and significant application limitations. Summary of the Invention

[0005] The purpose of this invention is to provide a solid waste-based high-strength phase change lightweight aggregate, its preparation method, and its application. The solid waste-based high-strength phase change lightweight aggregate provided by this invention organically combines phase change products and pure lightweight aggregate, and has the characteristics of high strength and good stability. At the same time, it has low manufacturing cost and a wide range of applications.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a solid waste-based high-strength phase change lightweight aggregate, comprising the following raw materials in parts by weight:

[0008] The ingredients are: 26-32 parts cement, 4-6 parts steel slag powder, 32-36 parts ice chips, 14-16 parts dry ice, 12-16 parts brick slag powder, 2.7-3.6 parts paraffin emulsion, and 0.3-0.4 parts organosilicon water-repellent agent.

[0009] Preferably, the specific surface area of ​​the steel slag powder is >400m². 2 / kg; the specific surface area of ​​the brick slag powder is 200-240m². 2 / kg.

[0010] Preferably, the ice chips have a particle size of 1–3 mm; the dry ice has a particle size of <3 mm; the paraffin emulsion has a particle size range of 50–200 nm; and the paraffin in the paraffin emulsion has a phase transition temperature range of 18–22 °C.

[0011] Preferably, the organosilicon water-repellent agent is a solid powder with a solid content ≥99%; the cement includes 42.5 grade ordinary Portland cement.

[0012] Preferably, the solid waste-based high-strength phase change lightweight aggregate has a density grade of 700-800 and a compressive strength >6.0MPa.

[0013] This invention provides a method for preparing solid waste-based high-strength phase change lightweight aggregate as described in the above technical solution, comprising the following steps:

[0014] Paraffin emulsion and brick slag powder are mixed to obtain a first mixture; the first mixture is subjected to vacuum adsorption to obtain phase change brick slag microparticles.

[0015] Ice chips, dry ice, and organosilicon hydrophobic agent are mixed in an environment of ≤-5℃ to obtain material A;

[0016] The phase change brick slag particles, cement, and steel slag powder are mixed to obtain a second mixture; the second mixture and material A are mixed in an environment of ≤-5℃ to obtain material B;

[0017] Under room temperature conditions, material B is loaded into a mold, and then pressed and cured in a dry heat. After demolding, block I is obtained.

[0018] The block material I is subjected to autoclaving to obtain block material II;

[0019] The block material II is crushed, screened, and left to stand in sequence to obtain the solid waste-based high-strength phase change lightweight aggregate.

[0020] Preferably, the vacuum adsorption is carried out in a vacuum dryer, and the temperature of the vacuum adsorption is 35±2℃, and the vacuum degree is >-0.1MPa.

[0021] Preferably, the pressing pressure is 8-10 MPa;

[0022] The dry heat curing is carried out in a microwave curing kiln. The holding temperature of the dry heat curing is 50-55℃, the holding time is 2-3h, and the heating rate from room temperature to the holding temperature of the dry heat curing is 5-8℃ / min.

[0023] The autoclaving is carried out in an autoclave at a temperature of 140–150°C, a pressure of 0.3–0.5 MPa, and a time of 8–12 hours.

[0024] Preferably, the crushing includes sequential first-stage crushing and second-stage crushing, wherein the first-stage crushing is performed using a jaw crusher and the second-stage crushing is performed using a hammer crusher.

[0025] The sieving process yields first-graded particles and second-graded particles, wherein the particle size of the first-graded particles is 5-20 mm and the particle size of the second-graded particles is 2-4 mm.

[0026] The settling process is carried out outdoors. When the outdoor ambient temperature is ≤15℃, the settling time is 10 to 14 days. When the outdoor ambient temperature is >15℃, the settling time is 7 to 10 days.

[0027] This invention provides the application of the solid waste-based high-strength phase change lightweight aggregate described in the above technical solution or the solid waste-based high-strength phase change lightweight aggregate prepared by the preparation method described in the above technical solution as a building material, wherein the building material includes lightweight aggregate concrete of C40 grade and above, building blocks or building wall panels.

[0028] This invention provides a solid waste-based high-strength phase change lightweight aggregate, comprising the following raw materials in parts by weight: 26-32 parts cement, 4-6 parts steel slag powder, 32-36 parts ice chips, 14-16 parts dry ice, 12-16 parts brick slag powder, 2.7-3.6 parts paraffin emulsion, and 0.3-0.4 parts organosilicon water-repellent agent. Compared with the prior art, the solid waste-based high-strength phase change lightweight aggregate provided by this invention has the following beneficial technical effects:

[0029] This invention uses paraffin emulsion as the phase change material and brick slag with micron-sized pores as the carrier for the phase change material. This yields phase change brick slag microparticles. After the micron-sized pores in these microparticles adsorb paraffin, their stability within the brick slag carrier after paraffin solidification is significantly superior to that of traditional macroporous adsorption carriers such as ceramsite. Furthermore, after the paraffin melts upon heating, it is less likely to flow out of the brick slag pores due to capillary action. Therefore, this invention reduces the encapsulation process required for existing phase change microcapsule products. Moreover, the phase change brick slag microparticles exhibit better dispersion in solid waste-based high-strength phase change lightweight aggregates, improving the homogeneity and isotropic thermal properties of the solid waste-based high-strength phase change lightweight aggregates. Thus, the structural stability and thermal properties of the solid waste-based high-strength phase change lightweight aggregates provided by this invention are significantly superior to those of traditional ceramsite-adsorbed phase change materials.

[0030] This invention utilizes ice chips and dry ice as raw materials to prepare high-strength phase change lightweight aggregates based on solid waste under liquid-free or liquid-lean conditions. This effectively avoids the problem of solid particle agglomeration under low water-to-powder ratio conditions, improves mixing efficiency, and reduces stirring time and energy consumption. By fixing ice chips and dry ice within the material's structure during the initial curing stage, they simultaneously liquefy and vaporize, gradually providing moisture and carbon dioxide for the hydration hardening (cement) and carbonation hardening (steel slag powder) of both cement and steel slag powder. Simultaneously, the dry ice continuously converts into gaseous carbon dioxide within the compact space, effectively reacting with expansive substances such as calcium oxide in the steel slag powder. This compensates for the early hydration shrinkage of cement while eliminating the harm caused by poor volume stability of steel slag powder in the later stages, providing a broader technical approach for the resource utilization and high-value-added processing of steel slag. Meanwhile, since both ice chips and dry ice particles are mixed under solid conditions, they are uniformly distributed in the raw materials. During the pressing, molding, and curing process into lightweight aggregate, the ice chips liquefy and the dry ice particles vaporize, transforming their original space into uniformly distributed pores. In other words, this invention allows for the artificial structural design of high-strength phase change lightweight aggregate based on solid waste by controlling the particle size, gradation, and dosage of ice chips and dry ice particles, thereby regulating their internal porosity, pore size, and number of pores. Furthermore, this invention uses both ice chips and dry ice as raw materials, eliminating the need for high-temperature calcination during the preparation process to obtain high-strength lightweight aggregate materials. This method is simpler, lower in cost, and offers significant economic, environmental, and social benefits compared to existing methods for preparing lightweight aggregates from ceramsite products.

[0031] In summary, this invention uses construction solid waste brick slag loaded with paraffin emulsion to prepare phase change microparticles, and uses cement and steel slag powder to react under ice chips and dry ice conditions to form high-strength lightweight aggregate. At the same time, ice chips and dry ice are used for room temperature pore formation and to improve curing efficiency. The resulting solid waste-based high-strength phase change lightweight aggregate achieves an organic combination of phase change products and pure lightweight aggregate, with the characteristics of high strength, good stability, and low manufacturing cost. It is a new type of solid waste-based energy-saving building material with higher quality and more convenient application, which can effectively solve the technical problems of efficient and high-value-added disposal of construction solid waste and improved production flexibility of building energy-saving products. Attached Figure Description

[0032] Figure 1 This is a physical image of the solid waste-based high-strength phase change lightweight aggregate prepared in Example 1 of the present invention. Detailed Implementation

[0033] This invention provides a solid waste-based high-strength phase change lightweight aggregate, comprising the following raw materials in parts by weight:

[0034] The ingredients are: 26-32 parts cement, 4-6 parts steel slag powder, 32-36 parts ice chips, 14-16 parts dry ice, 12-16 parts brick slag powder, 2.7-3.6 parts paraffin emulsion, and 0.3-0.4 parts organosilicon water-repellent agent.

[0035] In this invention, unless otherwise specified, all raw materials / components used in the preparation are commercially available products well known to those skilled in the art.

[0036] By weight, the solid waste-based high-strength phase change lightweight aggregate provided by this invention comprises 26-32 parts of cement, which in the embodiments may be 30 parts, 32 parts, or 26 parts. In this invention, the cement is preferably ordinary Portland cement, and in the embodiments specifically, it is 42.5 grade ordinary Portland cement.

[0037] Based on the mass fraction of the cement, the solid waste-based high-strength phase change lightweight aggregate provided by this invention comprises 4 to 6 parts of steel slag powder, which can be 5, 4, or 6 parts in the embodiments. In this invention, the specific surface area of ​​the steel slag powder is preferably >400 m². 2 / kg. The present invention preferably uses materials with a specific surface area greater than 400m². 2 The steel slag powder at a particle size of / kg complements the particle size distribution of cement, improving the density of the cementitious structure, including cement paste and steel slag hydration products, thereby enhancing the structural strength of lightweight aggregate. Simultaneously, the steel slag powder at this particle size exhibits high reaction efficiency with carbon dioxide, ensuring that carbonation in the early stages of hydration eliminates the potential for instability issues later in the cementitious process. Furthermore, the expansion generated during early carbonation compensates for the shrinkage caused by cement hydration, reducing the formation of micro-cracks within the cementitious structure and effectively improving structural strength.

[0038] Based on the mass fraction of cement, the solid waste-based high-strength phase change lightweight aggregate provided by this invention includes 32-36 parts of ice chips, which may be 33 or 32 parts in the embodiments. In this invention, the particle size of the ice chips is preferably 1-3 mm. Using ice chips with a particle size of 1-3 mm facilitates dispersion during mixing in the preparation process and avoids agglomeration problems under low water-to-powder ratio conditions. After pressing, the ice chips exist as macroscopically uniformly distributed solid particles within the material. Furthermore, during curing, the ice melts into water, providing the moisture required for the hydration of cement and steel slag powder. The volume occupied by the ice chips within the material after pressing, as the moisture is gradually consumed, forms pores of equal volume, reducing the material's bulk density. The bulk density of the material can be controlled by changing the amount of ice chips used. Simultaneously, this invention can achieve artificial intervention in the internal pore size and distribution of the solid waste-based high-strength phase change lightweight aggregate based on material design by changing the ice chip particle size and particle gradation, forming a material structure with optimal strength under the same bulk density conditions.

[0039] Based on the mass fraction of cement, the solid waste-based high-strength phase change lightweight aggregate provided by this invention includes 14-16 parts of dry ice, which can be 15, 14, or 16 parts in the embodiments. In this invention, the particle size of the dry ice is preferably <3mm. Dry ice with a particle size of less than 3mm is easily dispersed during solid mixing. After pressing, it is also macroscopically and uniformly distributed as solid particles within the material. After tight pressing, the gasification rate of the dry ice slows down due to the interference between the internal gas pressure and the solid phase. Furthermore, because of the dense material structure, the generated carbon dioxide gas migrates slowly outward and remains inside the material for a long time, thus maintaining a high carbon dioxide concentration inside the material for a considerable period. This ensures the carbonation hardening efficiency of cement and steel slag powder, thereby improving the strength of the lightweight aggregate, and also eliminates the potential instability of steel slag powder in the later stages. Meanwhile, after dry ice is vaporized and consumed, the space it originally occupied becomes pores, which reduces the bulk density of lightweight aggregates. Furthermore, the porosity and pore characteristics within lightweight aggregates can be controlled by altering the particle size and dosage of dry ice. Simultaneously, the vaporization of dry ice absorbs heat, thus reducing the melting rate of the ice chips. This facilitates the slow release of liquid water and maintains high humidity within the material over a longer period, which is beneficial for the hydration process of cement and steel slag powder.

[0040] Based on the mass fraction of the cement, the solid waste-based high-strength phase change lightweight aggregate provided by this invention comprises 12-16 parts of brick slag powder, which may be 14 or 16 parts in the embodiments. In this invention, the brick slag powder has micron-level pores. The specific surface area of ​​the brick slag powder is preferably 200-240 m². 2 / kg. The preferred surface area for this invention is 200–240 m². 2 / kg of brick slag powder contains a large number of micron-sized pores inside its particles, which can serve as a carrier for phase change materials and achieve stable loading of phase change materials such as paraffin.

[0041] Based on the mass fraction of the cement, the solid waste-based high-strength phase change lightweight aggregate provided by this invention includes 2.7 to 3.6 parts of paraffin emulsion, which can be 2.7 or 3.6 parts in the embodiments. In this invention, the particle size of the paraffin emulsion is preferably in the nanometer range, and the particle size range of the paraffin emulsion is preferably 50 to 200 nm. The phase change temperature range of the paraffin in the paraffin emulsion is preferably 18 to 22°C, which is 20°C in the embodiments. In this invention, the paraffin particles in the nanometer-sized paraffin emulsion can penetrate into and be carried within the pores of the brick slag powder under vacuum conditions, forming phase change brick slag microparticles (i.e., phase change materials with a supported structure). The phase change temperature range of the paraffin in the paraffin emulsion is preferably 18 to 22°C, which can achieve heat flow regulation within the comfortable indoor temperature range, effectively improving the indoor thermal environment. The carrier brick powder in phase change brick slag particles has micron-sized pores, which can effectively adsorb nano-sized paraffin wax and firmly adhere the solidified paraffin wax to the pores. The paraffin wax that has been heated and melted can also be prevented from flowing out of the pores by capillary siphon, thus forming a stable carrier composite under solidification-melting cycle conditions.

[0042] In this invention, the brick slag powder has micron-sized pores, and the paraffin emulsion preferably has a nanometer-sized particle size. The micron-sized pores of the brick slag powder can effectively adsorb and load nano-sized paraffin, and the paraffin exhibits high stability within these pores after solidification. Furthermore, after melting at elevated temperatures, the paraffin is not easily leached out of the micron-sized pores due to capillary action. Therefore, this invention can reduce the encapsulation process required for existing phase change microcapsule products.

[0043] Based on the mass fraction of the cement, the solid waste-based high-strength phase change lightweight aggregate provided by this invention includes 0.3 to 0.4 parts of organosilicon water-repellent agent, which can be 0.3 or 0.4 parts in the embodiments. In this invention, the organosilicon water-repellent agent is a solid powder with a solid content ≥99%. This invention selects an organosilicon water-repellent agent in solid powder form with a solid content ≥99%, which can ensure effective dispersibility in the material under low dosage conditions, and can control the water absorption of the lightweight aggregate, reducing the water absorption rate of the solid waste-based high-strength phase change lightweight aggregate by 15% to 25%, avoiding the impact of self-absorption of water on production during use, reducing the traditional pre-saturation process of ceramsite, and simplifying the application process.

[0044] In this invention, the density grade of the solid waste-based high-strength phase change lightweight aggregate is 700-800, and the compressive strength is >6.0MPa.

[0045] This invention provides a method for preparing solid waste-based high-strength phase change lightweight aggregate as described in the above technical solution, comprising the following steps:

[0046] Paraffin emulsion and brick slag powder are mixed to obtain a first mixture; the first mixture is subjected to vacuum adsorption to obtain phase change brick slag microparticles.

[0047] Ice chips, dry ice, and organosilicon hydrophobic agent are mixed in an environment of ≤-5℃ to obtain material A;

[0048] The phase change brick slag particles, cement, and steel slag powder are mixed to obtain a second mixture; the second mixture and material A are mixed in an environment of ≤-5℃ to obtain material B;

[0049] Under room temperature conditions, material B is loaded into a mold, and then pressed and cured in a dry heat. After demolding, block I is obtained.

[0050] The block material I is subjected to autoclaving to obtain block material II;

[0051] The block material II is crushed, screened, and left to stand in sequence to obtain the solid waste-based high-strength phase change lightweight aggregate.

[0052] This invention mixes paraffin emulsion and brick slag powder to obtain a first mixture; the first mixture is then subjected to vacuum adsorption to obtain phase change brick slag microparticles. In this invention, the mixing of the paraffin emulsion and brick slag powder is preferably carried out by incorporating brick slag powder into the paraffin emulsion before mixing, preferably under stirring conditions, with a mixing speed of 100–150 rpm and a mixing time of 1–3 min. In this invention, the vacuum adsorption is preferably carried out in a vacuum dryer, with a vacuum adsorption temperature of 35 ± 2 °C, a vacuum degree of > -0.1 MPa, and a vacuum adsorption time of 5–10 min. After vacuum adsorption, this invention preferably allows the vacuum adsorbed product to cool naturally to room temperature or <20 °C.

[0053] This invention involves mixing ice chips, dry ice, and an organosilicon water-repellent agent in an environment ≤-5°C to obtain material A. This invention does not specify the particular method for mixing the ice chips, dry ice, and organosilicon water-repellent agent.

[0054] After obtaining the phase change brick slag microparticles, the present invention mixes the phase change brick slag microparticles, cement, and steel slag powder to obtain a second mixture. The present invention does not have specific requirements regarding the specific implementation method of mixing the phase change brick slag microparticles, cement, and steel slag powder.

[0055] After obtaining the second mixture and material A, the present invention mixes the second mixture and material A in an environment ≤-5°C to obtain material B. In this invention, there are no special requirements regarding the specific implementation method of mixing the second mixture and material A.

[0056] After obtaining material B, under room temperature conditions, material B is placed into a mold and subjected to pressing and dry heat curing in sequence. After demolding, block I is obtained. In this invention, the pressing pressure is preferably 8-10 MPa. This invention preferably uses a pressing pressure of 8-10 MPa to physically improve the material density, increase the physical interlocking effect between particles, and reduce macroscopic defects, thereby obtaining a superior internal structure and higher strength after cement hydration. In this invention, the dry heat curing is preferably carried out in a microwave curing kiln, the holding temperature is preferably 50-55°C, the holding time is preferably 2-3 hours, and the heating rate from room temperature to the holding temperature is preferably 5-8°C / min. In this invention, before demolding, the dry heat-cured product is preferably cooled to room temperature after exiting the kiln.

[0057] In this invention, the dry heat curing is preferably carried out in a microwave curing kiln. The dry heat curing primarily relies on the water from the melting of ice chips inside the compacted material and the carbon dioxide from the vaporization of dry ice to participate in the hydration, carbonization, and hardening of the cementitious material, forming initial strength. The heating reaction process of dry heat curing ensures that the alkaline substances generated during the early hydration of cement react almost completely with the calcium oxide in the steel slag powder. This further enhances the structural strength of the internal pore walls of the material. Simultaneously, dry heat curing creates a unidirectional moisture migration tendency within the material, avoiding the bidirectional moisture migration caused by wet heat curing, thereby reducing the number of microcracks caused by seepage channels.

[0058] After obtaining block I, the present invention subjectes block I to autoclaving to obtain block II. In this invention, the autoclaving is carried out in an autoclave at a temperature of 140–150°C, a pressure of 0.3–0.5 MPa, and a time of 8–12 hours. After autoclaving, the product is preferably depressurized and cooled to room temperature, then left at room temperature for 3–5 days to obtain block II.

[0059] In this invention, the resulting block I after demolding is further subjected to autoclaving. During this stage, the internal humidity of the material tends to be constant. However, due to the uneven humidity caused by the previous dry heat curing stage, the internal hydration level is high, while the external hydration level is relatively low. Autoclaving improves the hydration level of the material, especially the external cementing material, further enhancing the structural strength of the material. After depressurization during autoclaving, placing the material at room temperature for 3-5 days can eliminate residual stress caused by temperature and expansion during the initial curing process.

[0060] After obtaining block material II, the present invention sequentially crushes, screens, and settles the block material II to obtain the solid waste-based high-strength phase change lightweight aggregate. In this invention, the crushing preferably includes sequential first-stage crushing and second-stage crushing. The first-stage crushing is preferably performed using a jaw crusher, and the second-stage crushing is preferably performed using a hammer crusher. Using a jaw crusher for the first-stage crushing and a hammer crusher for the second-stage crushing allows for better particle shape modification, making the particles tend towards regular polyhedra. In this invention, the screening preferably yields first-graded particles and second-graded particles. The particle size of the first-graded particles is preferably 5–20 mm, and the particle size of the second-graded particles is preferably 2–4 mm. In this invention, the settling is preferably carried out outdoors, specifically in an outdoor stockpile. When the outdoor ambient temperature for settling is preferably ≤15℃, the settling time is preferably 10–14 days. When the outdoor ambient temperature for settling is preferably >15℃, the settling time is preferably 7–10 days. During the settling process, the present invention utilizes the post-hydration of the cementing substances in the material to self-repair the micro-cracks in the particles caused by crushing, ultimately obtaining a high-strength phase change lightweight aggregate with a density grade of 700-800 and a compressive strength >6.0MPa.

[0061] This invention provides the application of the solid waste-based high-strength phase change lightweight aggregate described in the above technical solution or the solid waste-based high-strength phase change lightweight aggregate prepared by the preparation method described in the above technical solution as a building material, wherein the building material includes lightweight aggregate concrete of C40 grade and above, building blocks or building wall panels.

[0062] In this invention, the building blocks are specifically prefabricated blocks; the building wall panels are specifically prefabricated building wall panels.

[0063] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0064] The raw material types and parameters used in the following examples and comparative examples include:

[0065] 42.5 grade ordinary Portland cement: 28-day compressive strength is 44.3 MPa, purchased from Liaoning Shanshui Cement Co., Ltd.

[0066] Brick slag powder: It is produced by crushing and screening construction waste bricks generated from the demolition of old houses in the old city of Shenyang, Liaoning Province, and is purchased from Shenyang Zhongcheng Urban Mineral Resources Development Group Co., Ltd.

[0067] Steel slag powder: purchased from Liaoning Benxi Iron and Steel Group Co., Ltd.;

[0068] Paraffin emulsions: phase transition temperature 20℃, all purchased from Nanjing Tianshi New Materials Technology Co., Ltd.;

[0069] Organosilicon water-repellent agent: purchased from Shanghai Kaiyuan Chemical Co., Ltd.

[0070] Dry ice: homemade;

[0071] Ice chips: homemade.

[0072] Example 1

[0073] The solid waste-based high-strength phase change lightweight aggregate provided in this embodiment includes the following raw materials by mass: 30 parts of 42.5 grade ordinary silicate cement, 5 parts of steel slag powder, 33 parts of ice chips, 15 parts of dry ice, 14 parts of brick slag powder, 2.7 parts of paraffin emulsion, and 0.3 parts of organosilicon water-repellent agent.

[0074] The solid waste-based high-strength phase change lightweight aggregate provided in this embodiment is prepared using the following method:

[0075] S1. After adding brick slag powder to the paraffin emulsion, stir at 100 rpm / min for 3 min, then place it in a vacuum dryer with a vacuum degree > -0.1 MPa and perform vacuum adsorption at 35±2℃ for 10 min. After taking it out, let it cool naturally to room temperature of 20℃ to obtain phase change brick slag microparticles for later use.

[0076] S2. Mix ice chips, dry ice, and organosilicon water-repellent agent evenly in an environment of -5℃ to obtain material A;

[0077] S3. After mixing the phase change brick slag particles, 42.5 grade ordinary Portland cement, and steel slag powder evenly, transfer the mixture to an environment of -5℃ and then add the material A obtained in step S2 and mix evenly to obtain material B.

[0078] S4. Under room temperature conditions, the mixture B obtained in step S3 is loaded into a mold and pressed at 10MPa. Then it is transferred to a microwave curing kiln and heated from room temperature to 55℃ at a heating rate of 5℃ / min. After holding the temperature for 2 hours, it is removed from the kiln, cooled to room temperature, and demolded to obtain block I.

[0079] S5. Transfer the block material I obtained in S4 into an autoclave and autoclave it at 150℃ and 0.5MPa for 12 hours. After depressurization, cool it to room temperature and place it for 3 days to obtain block material II.

[0080] S6. The block material II obtained in S5 is crushed in two stages by a jaw crusher and a hammer crusher, and then screened into particles with two gradations: 5-20mm and 2-4mm. The particles are then transferred to an outdoor stockpile and left to stand for 10 days at an average outdoor temperature of 13℃. This process yields a solid waste-based high-strength phase change lightweight aggregate with a density grade of 700 and a compressive strength of 6.5MPa.

[0081] Example 2

[0082] The solid waste-based high-strength phase change lightweight aggregate provided in this embodiment includes the following raw materials by weight: 32 parts of 42.5 grade ordinary silicate cement, 4 parts of steel slag powder, 32 parts of ice chips, 14 parts of dry ice, 14 parts of brick slag powder, 3.6 parts of paraffin emulsion, and 0.4 parts of organosilicon water-repellent agent.

[0083] The solid waste-based high-strength phase change lightweight aggregate provided in this embodiment differs from that in Example 1 in the following ways: In step S2, the ambient temperature for mixing ice chips, dry ice, and organosilicon water-repellent agent is -10℃; in step S3, phase change brick slag particles, 42.5 grade ordinary silicate cement, and steel slag powder are mixed and then transferred to an environment of -10℃ to mix with material A; in step S4, the microwave curing kiln has a heating rate of 6℃ / min and is kept at a constant temperature for 3 hours; in step S5, the autoclaving time is 8 hours, and after depressurization, it is placed in a room temperature environment for 5 days; in step S6, the average outdoor ambient temperature is 18℃, and it is left to stand for 7 days.

[0084] Example 3

[0085] The solid waste-based high-strength phase change lightweight aggregate provided in this embodiment includes the following raw materials by weight: 26 parts of 42.5 grade ordinary silicate cement, 6 parts of steel slag powder, 32 parts of ice chips, 16 parts of dry ice, 16 parts of brick slag powder, 3.6 parts of paraffin emulsion, and 0.4 parts of organosilicon water-repellent agent.

[0086] The solid waste-based high-strength phase change lightweight aggregate provided in this embodiment differs from that in Example 1 in that: in step S4, the microwave curing kiln heating rate is 8℃ / min, and the temperature is kept constant for 3 hours; in step S5, after depressurization, it is placed in a room temperature environment for 4 days; and in step S6, the average outdoor temperature is 18℃, and it is left to stand for 10 days.

[0087] Example 4

[0088] The solid waste-based high-strength phase change lightweight aggregate provided in this embodiment uses the same raw materials as in Example 1, by weight. The difference between the preparation method and that in Example 1 is that: in step S4, the microwave curing kiln heating rate is 7℃ / min, and the temperature is maintained for 2.5 hours; in step S5, the autoclaving is carried out for 8 hours; and in step S6, the average outdoor ambient temperature is 19℃, and the mixture is left to stand for 9 days.

[0089] Example 5

[0090] The solid waste-based high-strength phase change lightweight aggregate provided in this embodiment uses the same raw materials as in Example 1, by weight. The difference in preparation method compared to Example 1 is that in step S5, the material is autoclaved for 9 hours, then depressurized and cooled to room temperature for 5 days.

[0091] Comparative Example 1

[0092] The solid waste-based high-strength phase change lightweight aggregate provided in this comparative example uses essentially the same raw materials as in Example 1, except that steel slag powder is replaced with fly ash (Grade II), purchased from Shenyang Zhenghuan Fly Ash Co., Ltd., in the raw materials used in Comparative Example 1. The types and proportions of other raw materials remain unchanged. The preparation method of the solid waste-based high-strength phase change lightweight aggregate provided in this comparative example is essentially the same as in Example 1, except that steel slag powder in step S3 of Example 1 is replaced with fly ash.

[0093] Comparative Example 2

[0094] The solid waste-based high-strength phase change lightweight aggregate provided in this comparative example is prepared using essentially the same raw materials as in Example 1, except that the raw materials used in Comparative Example 2 do not contain organosilicon hydrophobic agents, the mass fraction of brick slag powder is increased by 0.3 parts, and the types and mass fractions of other raw materials remain unchanged. The preparation method of the solid waste-based high-strength phase change lightweight aggregate provided in this comparative example is essentially the same as in Example 1, except that the organosilicon hydrophobic agent is omitted from the raw materials mixed in step S2 of Example 1.

[0095] Comparative Example 3

[0096] The solid waste-based high-strength phase change lightweight aggregate provided in this comparative example uses essentially the same raw materials as in Example 1, except that ice chips are replaced with a 0°C ice-water mixture in the raw materials used in Comparative Example 3, while the types and quantities of other raw materials remain unchanged. The preparation method of the solid waste-based high-strength phase change lightweight aggregate provided in this comparative example is essentially the same as in Example 1, except that ice chips in step S2 of Example 1 are replaced with a 0°C ice-water mixture.

[0097] Application examples

[0098] Performance evaluation of solid waste-based high-strength phase change lightweight aggregates in the above embodiments and comparative examples:

[0099] The high-strength phase change lightweight aggregates prepared in Examples 1-5 and Comparative Examples 1-3 were tested for bulk density, thermal conductivity, compressive strength, water absorption, and heat transfer coefficient.

[0100] 1. The bulk density, compressive strength and water absorption of solid waste-based high-strength phase change lightweight aggregates shall be determined in accordance with the requirements of GB / T17431.2-2010 "Lightweight aggregates and their test methods Part 2: Lightweight aggregates test methods";

[0101] 2. The thermal conductivity of solid waste-based high-strength phase change lightweight aggregate shall be tested in accordance with the requirements of GB / T 10294-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Insulation Materials - Protective Hot Plate Method".

[0102] 3. The heat transfer coefficient of solid waste-based high-strength phase change lightweight aggregate shall be tested in accordance with the requirements of GB / T 13475-2008 "Determination, Calibration and Protective Heat Box Method for Adiabatic Steady-State Heat Transfer Properties";

[0103] The test results of its bulk density, thermal conductivity, cylinder compressive strength, water absorption rate and heat transfer coefficient are shown in Table 1.

[0104] Table 1. Test results of the high-strength phase change lightweight aggregates prepared in Examples 1-5 and Comparative Examples 1-3.

[0105]

[0106]

[0107] Based on the test results in Table 1, and comparing Examples 1-3, it can be seen that changing the amounts of 42.5 grade ordinary Portland cement, steel slag powder, ice chips, dry ice, brick slag powder, paraffin emulsion, and organosilicon water-repellent agent significantly affects the bulk density, thermal conductivity, cylinder compressive strength, water absorption, and heat transfer coefficient of the solid waste-based high-strength phase change lightweight aggregate. Comparing Examples 1, 4, and 5, it can be seen that changing the curing regime during preparation affects the bulk density, thermal conductivity, cylinder compressive strength, water absorption, and heat transfer coefficient of the high-strength phase change lightweight aggregate.

[0108] By comparing Example 1 and Comparative Examples 1-3, it can be determined that using fly ash instead of steel slag powder will have a significant adverse effect on the bulk density, thermal conductivity, compressive strength, water absorption, and heat transfer coefficient of solid waste-based high-strength phase change lightweight aggregate. The absence of an organosilicon water-repellent agent will also significantly affect the water absorption rate of solid waste-based high-strength phase change lightweight aggregate. Using a 0°C ice-water mixture will lead to a deterioration in the bulk density, thermal conductivity, compressive strength, water absorption, and heat transfer coefficient of the high-strength phase change lightweight aggregate.

[0109] This demonstrates that steel slag powder, ice chips, dry ice, and organosilicon water-repellent agents are irreplaceable in the solid waste-based high-strength phase change lightweight aggregate raw materials of this invention. Steel slag powder enhances the pore wall strength and microstructure stability of the high-strength phase change lightweight aggregate during carbonization, thus positively impacting indicators such as bulk density, cylinder compressive strength, and heat transfer coefficient. Ice chips can create designable pores and improve continuous hydration conditions, maintaining the vapor pressure inside the material under dry heat curing conditions, providing continuous hydration reaction for cement and other cementitious materials, which is beneficial to the strength improvement of the solid waste-based high-strength phase change lightweight aggregate. Dry ice, in addition to participating in designable pore creation, also participates in the carbonization and hardening of cementitious materials, improving hardening efficiency and eliminating the potential for later-stage stability issues with steel slag powder, thus improving the strength development of the solid waste-based high-strength phase change lightweight aggregate. Organosilicon water-repellent agents can still ensure effective dispersion even at low dosages, controlling the water absorption of the lightweight aggregate and reducing its water absorption rate.

[0110] This invention incorporates phase change materials into solid waste-based high-strength phase change lightweight aggregates. When these aggregates are used to prepare phase change building materials such as phase change concrete, cementitious materials such as cement bond the aggregates within the structure and seal any remaining open pores, thereby sealing the phase change materials within the solid waste-based high-strength phase change lightweight aggregates.

[0111] As can be seen from the above embodiments, the present invention uses construction solid waste brick slag loaded with paraffin emulsion to prepare phase change microparticles, and uses cement and steel slag powder to react under ice chips and dry ice conditions to form high-strength lightweight aggregate. At the same time, ice chips and dry ice are used for room temperature pore formation and to improve curing efficiency. The resulting solid waste-based high-strength phase change lightweight aggregate achieves an organic combination of phase change products and pure lightweight aggregate, with the characteristics of high strength, good stability and low manufacturing cost. It is a new type of solid waste-based energy-saving building material with higher quality and more convenient application, which can effectively solve the technical problems of efficient and high-value-added disposal of construction solid waste and improved production flexibility of building energy-saving products.

[0112] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A solid waste-based high-strength phase change lightweight aggregate, characterized by: The preparation raw materials include the following parts by weight: The ingredients are: 26-32 parts cement, 4-6 parts steel slag powder, 32-36 parts ice chips, 14-16 parts dry ice, 12-16 parts brick slag powder, 2.7-3.6 parts paraffin emulsion, and 0.3-0.4 parts organosilicon water-repellent agent.

2. The solid waste based high strength phase change light aggregate according to claim 1, characterized by: The specific surface area of the steel slag powder is > 400 m 2 / kg; and the specific surface area of the brick slag powder is 200-240 m 2 / kg.

3. The solid waste based high strength phase change light weight aggregate as claimed in claim 1 wherein: The ice chips have a particle size of 1–3 mm; the dry ice has a particle size of <3 mm; the paraffin emulsion has a particle size range of 50–200 nm; and the paraffin in the paraffin emulsion has a phase transition temperature range of 18–22 °C.

4. The solid waste based high strength phase change light weight aggregate as claimed in claim 1 wherein: The organosilicon water-repellent agent is a solid powder with a solid content ≥99%; the cement includes 42.5 grade ordinary Portland cement.

5. The solid waste based high strength phase change light weight aggregate as claimed in claim 1 wherein: The solid waste-based high-strength phase change lightweight aggregate has a density grade of 700-800 and a compressive strength of >6.0MPa.

6. The preparation method of solid waste-based high-strength phase change lightweight aggregate according to any one of claims 1-5, characterized in that: Includes the following steps: Paraffin emulsion and brick slag powder are mixed to obtain a first mixture; the first mixture is subjected to vacuum adsorption to obtain phase change brick slag microparticles. Ice chips, dry ice, and organosilicon hydrophobic agent are mixed in an environment of ≤-5℃ to obtain material A; The phase change brick slag particles, cement, and steel slag powder are mixed to obtain a second mixture; the second mixture and material A are mixed in an environment of ≤-5℃ to obtain material B; Under room temperature conditions, material B is loaded into a mold, and then pressed and cured in a dry heat. After demolding, block I is obtained. The block material I is subjected to autoclaving to obtain block material II; The block material II is crushed, screened, and left to stand in sequence to obtain the solid waste-based high-strength phase change lightweight aggregate.

7. The method of claim 6, wherein: The vacuum adsorption is carried out in a vacuum dryer at a temperature of 35±2℃ and a vacuum degree of >-0.1MPa.

8. The method of claim 6, wherein: The pressing pressure is 8-10 MPa; The dry heat curing is carried out in a microwave curing kiln. The holding temperature of the dry heat curing is 50-55℃, the holding time is 2-3h, and the heating rate from room temperature to the holding temperature of the dry heat curing is 5-8℃ / min. The autoclaving is carried out in an autoclave at a temperature of 140–150°C, a pressure of 0.3–0.5 MPa, and a time of 8–12 hours.

9. The preparation method according to claim 6, characterized in that, The crushing process includes sequential first-stage crushing and second-stage crushing, wherein the first-stage crushing is performed using a jaw crusher and the second-stage crushing is performed using a hammer crusher. The sieving process yields first-graded particles and second-graded particles, wherein the particle size of the first-graded particles is 5-20 mm and the particle size of the second-graded particles is 2-4 mm. The settling process is carried out outdoors. When the outdoor ambient temperature is ≤15℃, the settling time is 10 to 14 days. When the outdoor ambient temperature is >15℃, the settling time is 7 to 10 days.

10. The application of the solid waste-based high-strength phase change lightweight aggregate according to any one of claims 1 to 5 or the solid waste-based high-strength phase change lightweight aggregate prepared by the preparation method according to any one of claims 6 to 9 as a building material, wherein the building material includes lightweight aggregate concrete, building blocks or building wall panels of grade C40 and above.

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