Building waste environment-friendly water stabilizing material as well as preparation method and application thereof

Abstract

The invention discloses a building waste environment-friendly water stabilizing material and a preparation method and application thereof, and belongs to the technical field of recycled concretes.A microcapsule structure with n-docosyl serving as a core layer, silicon dioxide serving as an interlayer and chitosan serving as a shell layer is loaded on the surface of phase-change gravel, free calcium ions are directionally adsorbed, and the environment-friendly water stabilizing material is prepared; after alkali steaming, calcium hydroxide precipitates are formed and attached to the surface of a chitosan shell layer, the strength of the phase change microcapsule is improved, and then pores of the phase change broken stone are filled with calcium alginate gel, so that the phase change microcapsule can stably play a role; n-docosane can absorb a large amount of heat to be melted from a solid state to a liquid state and prevent the temperature from further rapid rising, free calcium ions distributed on the surface of the phase change gravel can provide calcium ions for gel formation in the gel formation process, the crosslinking degree with sodium alginate is further increased, the strength and the stabilizing effect of the calcium alginate gel are improved, and the stability of the calcium alginate gel is improved. The structural bearing capacity of the concrete is maintained.

Description

Technical Field

[0001] The present invention belongs to the technical field of recycled concrete, and specifically relates to an environmentally friendly water-stabilized material made from construction waste, a preparation method thereof, and an application thereof. Background Art

[0002] my country's construction industry is facing two problems: on the one hand, in order to meet the huge demand for sand and gravel aggregates, a large amount of quarrying has caused damage to the ecological environment; on the other hand, my country's construction field wins a large number of reconstruction, demolition and other projects every year, which produces a large amount of waste concrete, and most of these waste concretes are landfilled or piled up as construction waste, which not only occupies a large amount of land, but also easily causes environmental pollution. To solve the above problems, one of the current methods is to crush the waste concrete blocks and use them as phase change gravel to replace the natural coarse aggregate in concrete, and use them in my country's urban and rural buildings. This is not only conducive to saving natural resources, but also can solve the growing construction waste crisis, and has good environmental and economic benefits.

[0003] Cement-stabilized crushed stone uses graded crushed stone as the aggregate. A certain amount of cementitious material and sufficient mortar volume are used to fill the gaps between the aggregates. The material is spread and compacted according to the principle of interlocking. Its compaction is close to its density, and its strength is primarily due to the interlocking and interlocking of the crushed stone. Because the unconfined compressive strength of the cement-stabilized layer can reach 1.5-4.0 MPa after 7 days, which is higher than other roadbed materials, and the cement-stabilized layer does not become muddy in rain, its surface is solid, making it an ideal base material for high-grade pavement. Due to its excellent performance, the preparation of various cement-stabilized layer materials has become a hot research topic both domestically and internationally.

[0004] Chinese patent publication number CN109516736B discloses a temperature-shrinkage actively controlled cement-stabilized gravel and its preparation method. Diatomaceous earth is added to liquid n-tetradecane to obtain a composite phase-change material, which is then mixed with silicate cement to obtain phase-change gravel with a self-temperature-regulating function. When the road surface exchanges heat with the external environment, the self-temperature-regulating cement-stabilized gravel can maintain a constant temperature or delay temperature changes. However, in this solution, n-tetradecane is loaded on the surface of the diatomaceous earth, relying on the porosity and surface roughness of the diatomaceous earth to physically adsorb n-tetradecane. During use, the phase-change material is easily lost, making it impossible to stably maintain the self-temperature-regulating function of the road surface. Summary of the Invention

[0005] The purpose of the present invention is to provide an environmentally friendly water-stabilizing material made from construction waste, a preparation method and application thereof, by loading a microcapsule structure with n-docosane as a core layer, silicon dioxide as an interlayer and chitosan as a shell layer on the surface of phase-change crushed stone, directionally adsorbing free calcium ions, and forming calcium hydroxide precipitates after alkali evaporation and adhering to the surface of the chitosan shell layer, thereby improving the strength of the phase-change microcapsules, reducing the loss of the phase-change microcapsules, and enabling the phase-change microcapsules to stably exert their self-temperature regulating effect, thereby avoiding affecting the service life of the road.

[0006] The purpose of the present invention can be achieved through the following technical solutions: A method for preparing environmentally friendly water-stabilized material from construction waste comprises the following steps: Step 1: Generate silica phase change microcapsules with n-docosane as the core layer and silica as the shell layer by in situ polymerization, and obtain chitosan-coated silica phase change microcapsules after chitosan coating and modification.

[0007] Step 2: Sodium alginate, ordinary Portland cement and chitosan-coated silica phase change microcapsules are mixed, and then stirred and mixed with calcium chloride solution, hardened to obtain a cement mixed material, and then cured with ammonia steam and crushed to obtain phase change gravel.

[0008] Step 3: Crush the construction waste to obtain 8-10 mm construction waste gravel; wet-mix the SBR latex, phase change gravel, construction waste gravel and water in a mass ratio of 0.5:60:50:5 for 1-2 minutes to obtain an environmentally friendly water-stabilized material of construction waste.

[0009] SBR latex, phase change gravel, construction waste gravel and water are wet-mixed at a mass ratio of 0.5:60:50:5 for 1-2 minutes to obtain an environmentally friendly water-stabilized material made from construction waste.

[0010] Furthermore, the usage ratio of construction waste, deionized water, phosphogypsum, Portland cement clinker and phase change gravel is 1-2 kg: 15-20 L: 0.8-1 kg: 0.5-0.7 kg: 6-7 kg.

[0011] Furthermore, chitosan-coated silica phase change microcapsules are prepared by the following steps: Silica phase change microcapsules, acetic acid solution and 80-90L sodium acetate solution are added to a reactor and stirred at 50-55°C and 500-600r / min for 20-30min. Then, sodium dodecylbenzenesulfonate with a concentration of 0.025mol / L is added and stirring is continued for 1-2h. Then, chitosan solution with a mass fraction of 2-3% is added and stirred and reacted for 4-5h. Then, 800-820mL of glutaraldehyde as a cross-linking agent is added and the reaction is continued for 4-5h. The solvent is removed by rotary evaporation to obtain chitosan-coated silica phase change microcapsules.

[0012] Furthermore, the usage ratio of the silica phase change microcapsules, acetic acid solution, sodium acetate solution, sodium dodecylbenzenesulfonate, chitosan solution and glutaraldehyde is 2.4-3 kg: 80-90 L: 80-90 L: 2-2.2 L: 1.2-1.4 L: 1800-820 mL.

[0013] Furthermore, the silica phase change microcapsules are prepared by the following steps: Add n-docosane and formamide to a reactor, stir at 50-55°C and 500-600 r / min for 30-40 minutes, add hexadecyltrimethylammonium bromide and stir for 5-6 hours, then add tetraethyl silicate and continue stirring for 4-5 hours, then add dropwise a 2.0M hydrochloric acid solution and stir for 5-6 hours, keep warm and let stand for 24-26 hours, separate the liquids, wash, and vacuum dry at 60-80°C for 1-2 hours to obtain silica phase change microcapsules.

[0014] Furthermore, the usage ratio of n-docosane, formamide, hexadecyltrimethylammonium bromide, tetraethyl silicate and hydrochloric acid solution is 2-3 kg: 30-35 L: 400-500 g: 2-3 L: 3-3.2 L.

[0015] Furthermore, the phase change gravel is prepared by the following steps: Ordinary Portland cement, sodium alginate powder and chitosan-coated silica phase change microcapsules are stirred and mixed, and then 3-4wt% calcium chloride solution is added. After stirring and mixing, the mixture is poured into a mold for hardening. The obtained cement mixture is cured with ammonia steam and crushed to obtain 5-8mm phase change gravel.

[0016] Furthermore, the usage ratio of ordinary Portland cement, sodium alginate powder, chitosan-coated silica phase change microcapsules and calcium chloride solution is 100-120 kg: 1-2 kg: 2-3 kg: 5-6 L.

[0017] Furthermore, the specific method of ammonia steam curing is: Ammonia water with a mass fraction of 25-30% is added to the high-pressure reaction tank, and a support mesh is set above the ammonia water in the high-pressure reaction tank. The cement mixture is placed on the support mesh. Then the sealing cover of the reaction tank is closed, and the high-pressure reaction tank is heated to 55-60°C in a water bath and kept warm for 3-4 hours to steam-cure the cement mixture using alkaline water vapor obtained by heating the ammonia water.

[0018] Furthermore, the usage ratio of ammonia water and phase change gravel is 80-90L:8-9kg.

[0019] The present invention also provides an application of environmentally friendly water-stabilized material made from construction waste in road materials.

[0020] Beneficial effects of the present invention: 1. The modified permeable recycled concrete prepared by this invention incorporates chitosan-coated silica phase-change microcapsules. When the ambient temperature or concrete hydration causes the internal temperature of the material to rise to the melting point of n-docosane, the n-docosane absorbs a large amount of heat and melts from a solid state to a liquid state, preventing further rapid temperature rise. This helps reduce thermal expansion and, consequently, cracks during pavement application. Compared to direct adsorption of diatomaceous earth, chitosan-coated silica phase-change microcapsules are less susceptible to phase-change material loss, resulting in superior durability and helping to extend the service life of pavement materials.

[0021] 2. The chitosan-coated silica phase change microcapsules of the present invention have a microcapsule structure with n-docosane as the core layer, silica as the interlayer, and chitosan as the outer layer. The chitosan surface carries a large number of carboxyl groups, which can selectively adsorb free calcium ions and free calcium ions on the surface of the phase change gravel. It can also directionally adsorb free calcium ions, forming calcium hydroxide precipitates attached to the surface of the chitosan shell after ammonia evaporation, which helps to further improve the encapsulation effect of the phase change material.

[0022] 3. The carboxyl groups on the surface of sodium alginate cross-link with the calcium ions in calcium chloride to form calcium alginate gel. By regulating the calcium ions, the initial setting time of cement is delayed, making construction easier. The gel system can also act as a buffer, reducing the wear of the chitosan-coated silica phase change microcapsules during the stirring process.

[0023] 4. The present invention utilizes alkaline water vapor formed by ammonia and water vapor generated by high-pressure alkali steam under heating conditions to steam-cure the cement mixture. The ammonia reacts with the calcium chloride solution therein to convert free calcium ions into calcium hydroxide precipitates that fill the microcracks and pores of the phase-change gravel, thereby increasing the interfacial bonding strength between the chitosan-coated silica phase-change microcapsules and the cement matrix of the phase-change gravel. This reduces the generation of cracks at the interface during the subsequent crushing process and helps avoid the loss of the phase-change microcapsules. DETAILED DESCRIPTION

[0024] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0025] Example 1: A method for preparing environmentally friendly water-stabilized material from construction waste, comprising the following steps: S1: Add 2 kg of n-docosane and 30 L of formamide to a reactor and stir at 50°C and 500 r / min for 30 min. After the n-docosane is completely dissolved, add 400 g of hexadecyltrimethylammonium bromide and continue stirring for 5 h. Then add 2 L of tetraethyl silicate and continue stirring for 4 h. Add 3 L of 2.0 M hydrochloric acid solution dropwise at a rate of 8 mL / min and continue stirring for 5 h. Keep warm and let stand for 24 h. Separate the liquid, wash, and vacuum dry at 60°C for 1 h to obtain silica phase change microcapsules.

[0026] The phase change properties of n-docosane can provide temperature stability assistance for cement-based materials and indirectly reduce damage by buffering thermal stress during freeze-thaw processes. Silica has been proven to be an ideal shell material, providing a tight seal and effective anti-permeation for the n-docosane core material. Silica phase change microcapsules were prepared by in situ polymerization using hydrochloric acid as a catalyst.

[0027] S2: Add 2.4 kg of silica phase change microcapsules, 80 L of acetic acid solution and 80 L of sodium acetate solution into the reactor, stir at 50 ° C and 500 r / min for 20 min, then add 2 L of sodium dodecylbenzene sulfonate with a concentration of 0.025 mol / L, continue stirring for 1 hour, then add 1.20 L of chitosan solution with a mass fraction of 2%, stir and react for 4 hours, then add 800 mL of glutaraldehyde as a cross-linking agent, continue to react for 4 hours, and remove the solvent by rotary evaporation to obtain chitosan-coated silica phase change microcapsules.

[0028] S3: Stir and mix 100 kg of ordinary Portland cement, 1 kg of sodium alginate powder and 2 kg of chitosan-coated silica phase change microcapsules, then add 5 L of 3% calcium chloride solution, stir and mix, and pour into a mold to harden. The hardened cement mixture is cured with ammonia steam and crushed to obtain 5-8 mm phase change gravel.

[0029] The carboxyl groups on the surface of sodium alginate cross-link with the calcium ions in calcium chloride to form calcium alginate gel. By regulating the calcium ions, the initial setting time of the cement is delayed, making construction easier. The gel system can also act as a buffer, reducing the wear of the chitosan-coated silica phase change microcapsules during the stirring process.

[0030] Among them, the specific method of ammonia steam curing is: 80 L of 25% ammonia water was added to a high-pressure reactor, and a support mesh was set above the ammonia water in the high-pressure reactor. 8 kg of cement mixture was placed on the support mesh. The sealing cover of the reactor was then closed, and the high-pressure reactor was heated to 55° C. in a water bath and kept warm for 3 hours to steam-cure the cement mixture using alkaline water vapor obtained from the heated ammonia water.

[0031] The cement mixture is steam-cured using alkaline water vapor formed by ammonia and water vapor produced by high-pressure alkali steam under heating conditions. The ammonia reacts with the calcium chloride solution therein to convert free calcium ions into calcium hydroxide precipitates.

[0032] S4: Crushing construction waste to obtain 8 mm construction waste gravel; wet-mixing SBR latex, phase change gravel, construction waste gravel and water in a mass ratio of 0.5:60:50:5 for 1 minute to obtain an environmentally friendly water-stabilized material made of construction waste.

[0033] Example 2: A method for preparing environmentally friendly water-stabilized material from construction waste, comprising the following steps: S1: Add 2.5 kg of n-docosane and 32.5 L of formamide to a reactor, stir at 52.5 ° C and 550 r / min for 35 minutes, and after the n-docosane is completely dissolved, add 450 g of hexadecyltrimethylammonium bromide, continue stirring for 5.5 hours, then add 2.5 L of tetraethyl silicate, continue stirring for 4.5 hours, add 3.1 L of 2.0 M hydrochloric acid solution dropwise at a rate of 8.5 mL / min, continue stirring for 5.5 hours, keep warm and stand for 25 hours, separate the liquid, wash, and vacuum dry at 70 ° C for 1.5 hours to obtain silica phase change microcapsules.

[0034] S2: Add 2.7 kg of silica phase change microcapsules, 85 L of acetic acid solution and 85 L of sodium acetate solution into the reactor, stir at 52.5 ° C and 550 r / min for 25 minutes, then add 2.1 L of sodium dodecylbenzene sulfonate with a concentration of 0.025 mol / L, continue stirring for 1.5 hours, then add 1.3 L of chitosan solution with a mass fraction of 2.5%, stir and react for 4.5 hours, then add 810 mL of glutaraldehyde as a cross-linking agent, continue to react for 4.5 hours, and remove the solvent by rotary evaporation to obtain chitosan-coated silica phase change microcapsules.

[0035] S3: 110 kg of ordinary Portland cement, 1.5 kg of sodium alginate powder and 2.5 kg of chitosan-coated silica phase change microcapsules were stirred and mixed, and then 5.5 L of 3.5% calcium chloride solution was added. After stirring and mixing, the mixture was poured into a mold and hardened to obtain a cement mixture. The mixture was cured with ammonia steam and crushed to obtain 5-8 mm phase change gravel.

[0036] Among them, the specific method of ammonia steam curing is: 85 L of 27.5% ammonia water was added to a high-pressure reactor, and a support mesh was set above the ammonia water in the high-pressure reactor. 8.5 kg of cement mixture was placed on the support mesh. The sealing cover of the reactor was then closed, and the high-pressure reactor was heated in a water bath to 57.5° C. and kept warm for 3.5 hours to steam-cure the cement mixture using alkaline water vapor obtained from the heated ammonia water.

[0037] S4: Crushing construction waste to obtain 9 mm construction waste gravel; wet-mixing SBR latex, phase change gravel, construction waste gravel and water at a mass ratio of 0.5:60:50:5 for 1.5 minutes to obtain an environmentally friendly water-stabilized material made of construction waste.

[0038] Example 3: A method for preparing environmentally friendly water-stabilized material from construction waste, comprising the following steps: S1: Add 3 kg of n-docosane and 35 L of formamide into a reactor and stir at 55°C and 600 r / min for 40 min. After the n-docosane is completely dissolved, add 500 g of hexadecyltrimethylammonium bromide and continue stirring for 6 h. Then add 3 L of tetraethyl silicate and continue stirring for 5 h. Add 3.2 L of 2.0 M hydrochloric acid solution dropwise at a rate of 9 mL / min and continue stirring for 6 h. Keep warm and let stand for 26 h. Separate the liquid, wash, and vacuum dry at 80°C for 2 h to obtain silica phase change microcapsules.

[0039] S2: Add 3 kg of silica phase change microcapsules, 90 L of acetic acid solution and 90 L of sodium acetate solution into the reactor, stir at 55 ° C and 600 r / min for 30 minutes, then add 2.2 L of sodium dodecylbenzene sulfonate with a concentration of 0.025 mol / L, continue stirring for 2 hours, then add 1.4 L of chitosan solution with a mass fraction of 3%, stir and react for 5 hours, then add 820 mL of glutaraldehyde as a cross-linking agent, continue to react for 5 hours, and remove the solvent by rotary evaporation to obtain chitosan-coated silica phase change microcapsules.

[0040] S3: 120 kg of ordinary Portland cement, 2 kg of sodium alginate powder and 3 kg of chitosan-coated silica phase change microcapsules were stirred and mixed, and then 6 L of 4% calcium chloride solution was added. After stirring and mixing, the mixture was poured into a mold and hardened to obtain a cement mixture. The mixture was cured with ammonia steam and crushed to obtain 5-8 mm phase change gravel.

[0041] Among them, the specific method of ammonia steam curing is: 90 L of 30% by mass ammonia water was added to a high-pressure reactor, and a support mesh was set above the ammonia water in the high-pressure reactor. 9 kg of cement mixture was placed on the support mesh. The sealing cover of the reactor was then closed, and the high-pressure reactor was heated to 60° C. in a water bath and kept warm for 4 hours to steam-cure the cement mixture using alkaline water vapor obtained from the heated ammonia water.

[0042] S4: Crushing construction waste to obtain 10 mm construction waste gravel; wet-mixing SBR latex, phase change gravel, construction waste gravel and water at a mass ratio of 0.5:60:50:5 for 2 minutes to obtain an environmentally friendly water-stabilized material made of construction waste.

[0043] Comparative Example 1: Referring to the Chinese patent announcement with publication number CN109516736B, a temperature shrinkage actively controlled cement-stabilized gravel and its preparation method are disclosed. The preparation process described in paragraph 35 of the specification is based on Example 3 of the present invention. In step S1, after completely dissolving n-docosane, hexadecyltrimethylammonium bromide is added and stirring is continued. Then, silica powder is added and stirring is continued to obtain a silica phase change material, which replaces the silica phase change microcapsules in the original solution. The remaining steps remain unchanged to obtain an environmentally friendly water-stabilizing material for construction waste. Comparative Example 2: Based on Example 3, the silica phase change microcapsules in step S2 are replaced with n-docosane in step S1, so that chitosan-coated phase change microcapsules with n-docosane as the core layer and chitosan as the shell layer are obtained. These chitosan-coated silica phase change microcapsules are replaced in subsequent steps. The remaining steps remain unchanged to obtain an environmentally friendly water-stabilizing material for construction waste.

[0044] Comparative Example 3: Based on Example 3, the chitosan-coated silica phase-change microcapsules in step S3 are replaced with the silica phase-change microcapsules in step S1, and the other steps remain unchanged to obtain an environmentally friendly water-stabilized material made from construction waste.

[0045] Comparative Example 4: Based on Example 3, the sodium alginate in the gel dispersion in step S3 was discarded, and the other steps remained unchanged to obtain an environmentally friendly water-stabilized material made from construction waste.

[0046] The modified permeable recycled concrete obtained from Examples 1 to 3 and Comparative Examples 1 to 3 was cast in a mold (100mm×100mm×100mm) and demolded after 24 hours. The concrete specimens were then transferred to a curing room for standard curing for 28 days before testing. The compressive strength of each concrete specimen was tested in accordance with the "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" (GB / T50081-2016); the environmentally friendly water-stabilized material from construction waste was formed into cylindrical specimens (Ф150×h100mm) by vibration molding, and the temperature shrinkage coefficient in the range of 20-30°C was determined by the strain gauge method specified in the "Test Procedure for Stabilized Materials of Inorganic Binders for Highway Engineering" (JTGE51-2009); the carbonization experimental environment was set as follows: the carbon dioxide concentration in the carbonization box was 20%, the humidity was controlled at 70%, and the temperature was controlled at 20°C. The arithmetic mean of the carbonization depth of the concrete specimens was used as the carbonization measurement value. After the specimens reach the corresponding carbonization age, a splitting test is performed on the concrete specimens using a pressure testing machine. The residue on the fracture surface of the concrete specimens is then removed to make the specimen surface clean and tidy. A 1% phenolphthalein alcohol solution (the alcohol solution contains 20% deionized water) is then sprayed on the fracture surface of the specimens. After about 30 seconds, the carbonization depth of the concrete specimens at different measuring points is measured with a vernier caliper according to the marked measuring points, and the average carbonization depth of each measuring point is calculated. The smaller the carbonization depth, the higher the concrete density, the denser the pore structure, the stronger the CO2 penetration resistance, and the better the carbonization resistance. The UV aging test is carried out in a UV aging box with an ultraviolet intensity of 210W / m 2 , the aging temperature is 60℃, the aging time is 6 days, and the results are shown in Table 1: Table 1 Performance test table of modified permeable recycled concrete , As can be seen from Table 1, the modified permeable recycled concrete obtained in Examples 1 to 3 has significantly better compressive strength than the comparative example, and the temperature shrinkage coefficient and carbonization depth are significantly lower than the comparative example, indicating that the modified permeable recycled concrete prepared by the present invention has good compressive strength, good durability, is not easily affected by temperature changes, has high density and dense pore structure.

[0047] In Comparative Example 1, n-docosane is dissolved and then silica powder is added. The n-docosane is adsorbed on the silica surface by physical adsorption. During the mixing and crushing of the concrete, the phase change material is easily lost by physical adsorption alone, and its function cannot be maintained. Compared with direct adsorption of diatomaceous earth, the phase change material is not easily lost by chitosan-coated silica phase change microcapsules, so the durability is good, which helps to increase the service life of the pavement material.

[0048] In Comparative Example 2, the silica phase change microcapsules are replaced with n-docosane. Silica as an interlayer can significantly increase the overall strength of the phase change microcapsules, avoiding the rupture of the microcapsules due to the irregular shape and edges of the phase change gravel when mixed with the phase change gravel. The sealing property of silica can protect the n-docosane in the core layer from flowing out even when it reaches the melting point.

[0049] In Comparative Example 3, the chitosan-coated silica phase change microcapsules were replaced with silica phase change microcapsules. The chitosan coating can, on the one hand, improve the bonding strength between the silica phase change microcapsules and the phase change gravel, and on the other hand, can directionally adsorb the free calcium ions in the calcium chloride solution and the phase change gravel, so that when the microcapsules are steam-cured in alkaline water vapor, a layer of calcium hydroxide precipitate can be formed outside the chitosan coating layer, further improving the strength of the microcapsules.

[0050] In Comparative Example 4, sodium alginate was omitted from the gel dispersion, and the carboxyl groups on the surface of sodium alginate were cross-linked with the calcium ions in calcium chloride to form calcium alginate gel. By regulating the calcium ions, the initial setting time of the cement was delayed, facilitating construction. The gel system also played a buffering role, reducing the wear of the chitosan-coated silica phase change microcapsules during the stirring process.

[0051] While the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing environmentally friendly water-stabilized materials from construction waste, characterized in that: The steps include: Step 1: generating silica phase change microcapsules with n-docosane as the core layer and silica as the shell layer by in situ polymerization, and then coating and modifying them with chitosan to obtain chitosan-coated silica phase change microcapsules; Step 2: Sodium alginate, ordinary Portland cement and chitosan-coated silica phase change microcapsules are mixed, and then stirred and mixed with calcium chloride solution, hardened to obtain a cement mixture, and then cured with ammonia steam and crushed to obtain phase change gravel; Step 3: Crush the construction waste to obtain 8-10 mm construction waste gravel; wet-mix the SBR latex, phase change gravel, construction waste gravel and water in a mass ratio of 0.5:60:50:5 for 1-2 minutes to obtain an environmentally friendly water-stabilized material of construction waste.

2. The method for preparing an environmentally friendly water-stabilized material from construction waste according to claim 1, characterized in that: The usage ratio of the construction waste, deionized water, phosphogypsum, Portland cement clinker and phase change gravel is 1-2 kg: 15-20 L: 0.8-1 kg: 0.5-0.7 kg: 6-7 kg.

3. The method for preparing an environmentally friendly water-stabilized material from construction waste according to claim 1, characterized in that: The chitosan-coated silica phase change microcapsules are prepared by the following steps: Add silica phase change microcapsules, acetic acid solution and 80-90L sodium acetate solution into a reactor, stir at 50-55°C and 500-600r / min for 20-30min, then add sodium dodecylbenzenesulfonate with a concentration of 0.025mol / L, continue stirring for 1-2h, then add 2-3wt% chitosan solution, stir and react for 4-5h, then add 800-820mL glutaraldehyde, continue to react for 4-5h, and remove the solvent by rotary evaporation to obtain chitosan-coated silica phase change microcapsules.

4. The method for preparing an environmentally friendly water-stabilized material from construction waste according to claim 3, characterized in that: The usage ratio of the silicon dioxide phase change microcapsules, acetic acid solution, sodium acetate solution, sodium dodecylbenzenesulfonate, chitosan solution and glutaraldehyde is 2.4-3 kg: 80-90 L: 80-90 L: 2-2.2 L: 1.2-1.4 L: 1800-820 mL.

5. The method for preparing environmentally friendly water-stabilized material from construction waste according to claim 3, characterized in that: The silica phase change microcapsules are prepared by the following steps: Add n-docosane and formamide to a reactor, stir at 50-55°C and 500-600 r / min for 30-40 min, add hexadecyltrimethylammonium bromide and stir for 5-6 h, then add tetraethyl silicate and continue stirring for 4-5 h, then add dropwise a 2.0 M hydrochloric acid solution and stir for 5-6 h, keep warm and let stand for 24-26 h, separate the liquid, wash, and vacuum dry at 60-80°C for 1-2 h to obtain silica phase change microcapsules.

6. The method for preparing environmentally friendly water-stabilized material from construction waste according to claim 5, characterized in that: The usage ratio of n-docosane, formamide, hexadecyltrimethylammonium bromide, tetraethyl silicate and hydrochloric acid solution is 2-3 kg: 30-35 L: 400-500 g: 2-3 L: 3-3.2 L.

7. The method for preparing environmentally friendly water-stabilized material from construction waste according to claim 1, characterized in that: The phase change gravel is prepared by the following steps: Ordinary Portland cement, sodium alginate powder and chitosan-coated silica phase change microcapsules are stirred and mixed, and then 3-4 wt% calcium chloride solution is added. After stirring and mixing, the mixture is poured into a mold to harden. The obtained cement mixture is cured with ammonia steam and crushed to obtain 5-8 mm phase change gravel; The usage ratio of the ordinary Portland cement, sodium alginate powder, chitosan-coated silicon dioxide phase-change microcapsules and calcium chloride solution is 100-120 kg: 1-2 kg: 2-3 kg: 5-6 L.

8. The method for preparing environmentally friendly water-stabilized material from construction waste according to claim 1, characterized in that: The specific method of the ammonia steam curing is: Adding 25-30% ammonia water by mass into a high-pressure reaction tank, setting a support mesh plate above the ammonia water in the high-pressure reaction tank, placing the cement mixture on the support mesh plate, then closing the sealing cover of the reaction tank, heating the high-pressure reaction tank in a water bath to 55-60°C, and keeping the temperature for 3-4 hours, so that the cement mixture is steam-cured by the alkaline water vapor obtained by heating the ammonia water; The usage ratio of the ammonia water and the phase change gravel is 80-90L:8-9kg.

9. An environmentally friendly water-stabilized material made from construction waste, characterized in that: Prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the environmentally friendly water-stabilized material made from construction waste according to claim 9 in road materials.