Magnesium-based construction waste recycled material and preparation method thereof

Abstract

The invention relates to the technical field of building materials, and discloses a magnesium-based construction waste recycled material and a preparation method thereof, the magnesium-based construction waste recycled material comprises 10-25 parts of a magnesium-based cementing material and 65-80 parts of construction waste recycled aggregate; the composite modifier comprises an inorganic modifier, an organic modifier and an interface reinforcing agent, and specifically comprises the following components in parts by weight: 0.2-0.9 part of monopotassium phosphate as the inorganic modifier. Through the synergistic effect of the composite modifier and the nano-reinforcement system, the mechanical strength and durability of the material are remarkably improved, and the self-repairing function of cracks is achieved by combining aggregate interface reinforcement treatment and intelligent self-repairing microcapsule design; meanwhile, high-content construction waste recycled aggregate and industrial solid waste are adopted, the microstructure of the material is optimized, the porosity is reduced, the material has the characteristics of being excellent in crack resistance, high in resource utilization rate, environmentally friendly and the like, the performance bottleneck of a traditional recycled material is broken through, and the material is suitable for the field of green construction engineering with the high durability requirement.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, and in particular to a magnesium-based building waste recycled material and a preparation method thereof. Background Art

[0002] With the acceleration of urbanization, the amount of construction waste is increasing. Traditional treatment methods such as landfill and open-air stacking not only occupy a large amount of land resources, but also pollute the environment. Traditional construction waste recycling technology requires sorting the soil, wood, organic matter, and powder in the construction waste, and selecting those with a certain strength as construction waste recycled aggregates, and then washing or other methods to remove dust for reuse. After sorting, the remaining nearly 50% is difficult to use.

[0003] Existing recycled materials from construction waste mostly rely on silicate cement, which consumes a lot of energy to produce (accounting for 8% of global CO2 emissions). Recycled aggregates have high porosity and strong water absorption, which leads to insufficient mechanical properties of traditional silicate cement-based materials, such as low strength and poor durability. They can only be added to other concretes in small proportions.

[0004] Magnesium-based cementitious materials have the advantages of good compatibility, fast coagulation, high strength, and good fire resistance. When applied to construction waste recycled materials, construction waste does not need to be sorted. Construction waste is crushed to a particle size of 0.5-3cm and combined with magnesium-based cementitious materials. Modifiers are used to improve the performance of magnesium-based cementitious materials, improve the water resistance of materials, and inhibit halogen return, making them suitable for humid environments. By optimizing the magnesium-based cementitious system with additives and adding solid waste-based materials, solid waste resource utilization and low-carbon preparation are achieved, providing a construction waste recycled material with high strength, fast hardening, water resistance and environmental protection. Therefore, we propose a magnesium-based construction waste recycled material and its preparation method to solve the above problems. Summary of the invention

[0005] The magnesium-based construction waste recycled material and the preparation method thereof proposed in the present invention solve the problem that there is no existing construction waste recycled material with high strength, fast hardening, water resistance and environmental protection characteristics.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present application provides a magnesium-based construction waste recycled material, comprising, by weight: 10-25 parts of magnesium-based gelling material; 65-80 parts of recycled aggregate from construction waste; The composite modifier includes an inorganic modifier, an organic modifier and an interface enhancer, and the specific weight parts are as follows: inorganic modifier: 0.2-0.9 parts of potassium dihydrogen phosphate, 0.1-0.6 parts of borax; organic modifier: 0.1-0.5 parts of polycarboxylic acid water reducer, 0.05-0.3 parts of calcium lignin sulfonate; interface enhancer: 0.05-0.4 parts of titanate coupling agent; Mineral additives: 1-3 parts of silica fume, 1-2 parts of fly ash, 0.5-1 parts of blast furnace slag; Nanocomposite reinforcing agent, composed of 0.2-0.8 parts of nano-silicon dioxide (10-30nm) and 0.1-0.4 parts of nano-aluminum oxide (20-50nm); Functional auxiliary agents, including: 0.1-0.56 parts of sodium fluorosilicate, 0.06-0.4 parts of polyvinyl alcohol fiber; Self-repairing microcapsules 0.1-0.5 parts; 8-18 parts water

[0007] Optionally, the magnesium-based cementitious material is a mixture of magnesium oxychloride cement and magnesium oxysulfate cement, wherein the mass ratio of magnesium oxide, magnesium chloride and magnesium sulfate is 3:2:1; The construction waste recycled aggregate is surface pretreated by soaking the aggregate in a phosphoric acid solution for 2-4 hours and drying it.

[0008] Optionally, the specific surface area of ​​the nanocomposite reinforcing agent is ≥200 m² / g.

[0009] Optionally, the polyvinyl alcohol fiber has a length of 6-12 mm and a diameter of 20-40 μm.

[0010] Optionally, the surface of the polyvinyl alcohol fiber is pretreated with a silane coupling agent.

[0011] Optionally, the self-repairing microcapsule is composed of a polyurethane shell wrapping an epoxy resin core material, and the particle size is 50-200 μm.

[0012] In a second aspect, the present application provides a method for preparing a magnesium-based construction waste recycled material, comprising the following steps: (1) Pretreatment of recycled aggregates from construction waste: Soak the aggregates in a 5-10% by mass phosphoric acid solution for 2-4 hours and dry them until the moisture content is ≤1%; (2) preparing a magnesium-based gelling material: mixing magnesium oxide, magnesium chloride and magnesium sulfate in a mass ratio of 3:2:1 to obtain a magnesium-based gelling material; (3) Mixing the raw materials step by step: add 10-25 parts of magnesium-based cementitious material, 65-80 parts of pre-treated construction waste recycled aggregate, 1-3 parts of silica fume, 1-2 parts of fly ash, and 0.5-1 parts of blast furnace slag in sequence, and dry mix for 2-5 minutes; then add the composite modifier, nano-composite reinforcing agent and functional auxiliary agent prepared above, and continue stirring for 3-8 minutes; (4) Final mixing: Add 8-18 parts of water and 0.1-0.5 parts of self-healing microcapsules, control the stirring speed to 200-400r / min, stir for 5-15 minutes, then pour into the mold, and cure for 7-28 days at a temperature of 20-35°C and a humidity of 60-85%.

[0013] Optionally, the preparation of the composite modifier includes: 0.2-0.9 parts of potassium dihydrogen phosphate and 0.1-0.6 parts of borax are premixed to prepare an inorganic modifier; 0.1-0.5 parts of polycarboxylic acid water reducer and 0.05-0.3 parts of calcium lignin sulfonate are premixed to prepare an organic modifier; and finally, 0.05-0.4 parts of a titanate coupling agent are compounded.

[0014] Optionally, the preparation method of the nanocomposite reinforcing agent is: Add 0.2-0.8 parts of nano silicon dioxide (10-30nm) and 0.1-0.4 parts of nano aluminum oxide (20-50nm) into a ball mill, use ethanol as the dispersion medium, ball mill for 1-3 hours, and pass through a 200-400 mesh sieve after drying to obtain a composite powder with a specific surface area ≥200m² / g.

[0015] Optionally, the preparation of the functional adjuvant includes: Soak 0.06-0.4 parts of polyvinyl alcohol fiber in 1-3% KH-550 solution for 30-60 minutes, dry it and mix it with 0.1-0.56 parts of sodium fluorosilicate.

[0016] The beneficial effects of the present invention are: Through the synergistic effect of the composite modifier and the nano-enhancement system, the mechanical properties of the material are significantly improved, achieving excellent compressive and flexural strength, while greatly enhancing the freeze-thaw resistance and chloride ion corrosion resistance.

[0017] Intelligent self-repair function: The unique microcapsule design gives the material the ability to repair itself, which can effectively restore crack damage, and cooperates with a stable gelling system to ensure the long-term effectiveness of the repair agent.

[0018] Interface bonding strengthening: Aggregate surface activation treatment and interface enhancer work synergistically to significantly improve the bonding strength between aggregate and matrix and inhibit the generation of interface defects.

[0019] Resource recycling: A high proportion of recycled aggregates from construction waste and industrial solid waste is utilized, which greatly reduces the consumption of raw materials and reflects green and environmentally friendly characteristics.

[0020] Optimization of structural density: Nano-reinforcements work synergistically with the step-by-step mixing process to significantly improve the material microstructure, reduce harmful pores and enhance overall density.

[0021] Enhanced crack resistance: The modified fiber and functional additives work synergistically to effectively inhibit shrinkage cracking and improve the material's ability to adapt to deformation.

[0022] The present invention significantly improves the mechanical strength and durability of the material through the synergistic effect of the composite modifier and the nano-enhancement system, and combines the aggregate interface strengthening treatment with the intelligent self-repairing microcapsule design to achieve the function of self-repairing cracks. At the same time, a high amount of construction waste recycled aggregates and industrial solid waste is used to optimize the material microstructure and reduce the porosity, thereby achieving excellent crack resistance, high resource utilization and environmental friendliness. It breaks through the performance bottleneck of traditional recycled materials and is suitable for the field of green building projects with high durability requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention is a flow chart of a method for preparing a magnesium-based building waste recycled material. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0025] Embodiment 1, a magnesium-based construction waste recycled material, comprising, by weight: 10 parts of magnesium-based cementitious material; 65 parts of recycled aggregate from construction waste; The composite modifier includes an inorganic modifier, an organic modifier and an interface enhancer, and the specific weight parts are as follows: inorganic modifier: 0.2 parts of potassium dihydrogen phosphate and 0.1 parts of borax; organic modifier: 0.1 parts of polycarboxylic acid water reducer and 0.05 parts of calcium lignin sulfonate; interface enhancer: 0.05 parts of titanate coupling agent; Mineral additives: 1 part silica fume, 1 part fly ash, 0.5 part blast furnace slag; Nanocomposite reinforcing agent, composed of 0.2 parts of nano-silicon dioxide (10-30nm) and 0.1 parts of nano-alumina (20-50nm); Functional auxiliary agents include: 0.1 parts of sodium fluorosilicate and 0.06 parts of polyvinyl alcohol fibers; the polyvinyl alcohol fibers are 6-12 mm long and 20-40 μm in diameter; 0.1 part of self-repairing microcapsules, which are composed of epoxy resin core wrapped by polyurethane shell, with a particle size of 50-200μm; 8 parts water.

[0026] like Figure 1 The preparation method of magnesium-based construction waste recycled materials comprises the following steps: Preparation of composite modifier: premix 0.2 parts of potassium dihydrogen phosphate and 0.1 parts of borax to prepare inorganic modifier; premix 0.1 parts of polycarboxylic acid water reducer and 0.05 parts of calcium lignin sulfonate to prepare organic modifier; finally, compound with 0.05 parts of titanate coupling agent.

[0027] Preparation of nanocomposite reinforcing agent: Add 0.2 parts of nano-silicon dioxide (10-30nm) and 0.1 parts of nano-alumina (20-50nm) into a ball mill, use ethanol as the dispersion medium, ball mill for 1 hour, dry and pass through a 200-mesh sieve to obtain a composite powder with a specific surface area ≥200m² / g.

[0028] Preparation of functional auxiliary agent: soak 0.06 parts of polyvinyl alcohol fiber in 1% KH-550 solution for 30 minutes, dry and mix with 0.1 parts of sodium fluorosilicate; Soak the aggregate in a 5% by mass phosphoric acid solution for 2 hours and dry it to a moisture content of ≤1%; Preparing a magnesium-based gelling material: mixing magnesium oxide, magnesium chloride and magnesium sulfate in a mass ratio of 3:2:1 to obtain a magnesium-based gelling material; Mix the raw materials step by step: add 10 parts of magnesium-based cementitious materials, 65 parts of pre-treated construction waste recycled aggregates, 1 part of silica fume, 1 part of fly ash, and 0.5 parts of blast furnace slag in sequence, and dry mix for 2 minutes; then add the composite modifier, nano-composite reinforcing agent and functional auxiliary agent prepared above, and continue stirring for 3 minutes; Final mixing: add 8 parts of water and 0.1 parts of self-repairing microcapsules, control the stirring speed to 200r / min, stir for 5 minutes and then put into the mold, and cure for 7 days at a temperature of 20°C and a humidity of 60%.

[0029] Embodiment 2, a magnesium-based construction waste recycled material, comprising, by weight: 13 parts of magnesium-based cementitious materials; 68 parts of recycled aggregate from construction waste; The composite modifier includes an inorganic modifier, an organic modifier and an interface enhancer, and the specific weight parts are as follows: inorganic modifier: 0.4 parts of potassium dihydrogen phosphate and 0.2 parts of borax; organic modifier: 0.2 parts of polycarboxylic acid water reducer and 0.08 parts of calcium lignin sulfonate; interface enhancer: 0.1 parts of titanate coupling agent; Mineral additives: 1.5 parts of silica fume, 1.2 parts of fly ash, 0.6 parts of blast furnace slag; Nanocomposite reinforcing agent, composed of 0.3 parts of nano-silicon dioxide (10-30nm) and 0.2 parts of nano-alumina (20-50nm); Functional auxiliary agent, including: 0.2 parts of sodium fluorosilicate, 0.1 parts of polyvinyl alcohol fiber; the polyvinyl alcohol fiber is 6-12 mm in length and 20-40 μm in diameter; 0.2 parts of self-repairing microcapsules, which are composed of epoxy resin core wrapped by polyurethane shell, with a particle size of 50-200μm; 10 parts water.

[0030] The method for preparing magnesium-based construction waste recycled materials comprises the following steps: Preparation of composite modifier: premix 0.4 parts of potassium dihydrogen phosphate and 0.2 parts of borax to prepare inorganic modifier; premix 0.2 parts of polycarboxylic acid water reducer and 0.08 parts of calcium lignin sulfonate to prepare organic modifier; finally, compound with 0.1 parts of titanate coupling agent.

[0031] Preparation of nanocomposite reinforcing agent: Add 0.3 parts of nano-silicon dioxide (10-30nm) and 0.2 parts of nano-alumina (20-50nm) into a ball mill, use ethanol as the dispersion medium, ball mill for 1.5 hours, and pass through a 250-mesh sieve after drying to obtain a composite powder with a specific surface area ≥200m² / g.

[0032] Preparation of functional auxiliary agent: soak 0.1 parts of polyvinyl alcohol fiber in 1.5% KH-550 solution for 35 minutes, dry and mix with 0.2 parts of sodium fluorosilicate; Soak the aggregate in a 6% by mass phosphoric acid solution for 2.5 hours and dry it to a moisture content of ≤1%; Preparing a magnesium-based gelling material: mixing magnesium oxide, magnesium chloride and magnesium sulfate in a mass ratio of 3:2:1 to obtain a magnesium-based gelling material; Mix the raw materials step by step: add 13 parts of magnesium-based cementitious material, 68 parts of pre-treated construction waste recycled aggregate, 1.5 parts of silica fume, 1.2 parts of fly ash, and 0.6 parts of blast furnace slag in sequence, and dry mix for 3 minutes; then add the composite modifier, nano-composite reinforcing agent and functional auxiliary agent prepared above, and continue stirring for 4 minutes; Final mixing: add 10 parts of water and 0.2 parts of self-repairing microcapsules, control the stirring speed to 250r / min, stir for 8 minutes and then put into the mold, and cure for 10 days at a temperature of 25°C and a humidity of 65%.

[0033] Embodiment 3, a magnesium-based construction waste recycled material, comprising, by weight: 18 parts of magnesium-based cementitious material; 72 parts of recycled aggregate from construction waste; The composite modifier includes an inorganic modifier, an organic modifier and an interface enhancer, and the specific weight parts are as follows: inorganic modifier: 0.55 parts of potassium dihydrogen phosphate, 0.35 parts of borax; organic modifier: 0.3 parts of polycarboxylic acid water reducer, 0.18 parts of calcium lignin sulfonate; interface enhancer: 0.23 parts of titanate coupling agent; Mineral additives: 2 parts of silica fume, 1.5 parts of fly ash, 0.8 parts of blast furnace slag; Nanocomposite reinforcing agent, composed of 0.5 parts of nano-silicon dioxide (10-30nm) and 0.25 parts of nano-alumina (20-50nm); Functional auxiliary agent, including: 0.33 parts of sodium fluorosilicate, 0.23 parts of polyvinyl alcohol fiber; the polyvinyl alcohol fiber is 6-12 mm in length and 20-40 μm in diameter; 0.3 parts of self-repairing microcapsules, which are composed of epoxy resin core wrapped by polyurethane shell, and have a particle size of 50-200 μm; 13 parts water.

[0034] The method for preparing magnesium-based construction waste recycled materials comprises the following steps: Preparation of composite modifier: premix 0.55 parts of potassium dihydrogen phosphate and 0.35 parts of borax to prepare inorganic modifier; premix 0.3 parts of polycarboxylic acid water reducer and 0.18 parts of calcium lignin sulfonate to prepare organic modifier; finally, compound with 0.23 parts of titanate coupling agent.

[0035] Preparation of nanocomposite reinforcing agent: Add 0.5 parts of nano-silicon dioxide (10-30nm) and 0.25 parts of nano-alumina (20-50nm) into a ball mill, use ethanol as the dispersion medium, ball mill for 2 hours, dry and pass through a 300-mesh sieve to obtain a composite powder with a specific surface area ≥200m² / g.

[0036] Preparation of functional auxiliary agent: soak 0.23 parts of polyvinyl alcohol fiber in 2% KH-550 solution for 45 minutes, dry and mix with 0.33 parts of sodium fluorosilicate; Soak the aggregate in a 7.5% by mass phosphoric acid solution for 3 hours and dry it to a moisture content of ≤1%; Preparing a magnesium-based gelling material: mixing magnesium oxide, magnesium chloride and magnesium sulfate in a mass ratio of 3:2:1 to obtain a magnesium-based gelling material; Mix the raw materials step by step: add 18 parts of magnesium-based cementitious materials, 72 parts of pretreated construction waste recycled aggregate, 2 parts of silica fume, 1.5 parts of fly ash, and 0.8 parts of blast furnace slag in sequence, and dry mix for 3.5 minutes; then add the composite modifier, nano-composite reinforcing agent and functional auxiliary agent prepared above, and continue stirring for 3-8 minutes; Final mixing: add 13 parts of water and 0.3 parts of self-repairing microcapsules, control the stirring speed to 300r / min, stir for 10 minutes and then put into the mold, and cure for 18 days at a temperature of 22.5°C and a humidity of 72%.

[0037] Embodiment 4, a magnesium-based construction waste recycled material, comprising, by weight: 20 parts of magnesium-based cementitious material; 75 parts of recycled aggregate from construction waste; The composite modifier includes an inorganic modifier, an organic modifier and an interface enhancer, and the specific weight parts are as follows: inorganic modifier: 0.7 parts of potassium dihydrogen phosphate and 0.5 parts of borax; organic modifier: 0.3 parts of polycarboxylic acid water reducer and 0.25 parts of calcium lignin sulfonate; interface enhancer: 0.35 parts of titanate coupling agent; Mineral additives: 2.5 parts of silica fume, 1.8 parts of fly ash, 0.8 parts of blast furnace slag; Nanocomposite reinforcing agent, composed of 0.7 parts of nano-silicon dioxide (10-30nm) and 0.3 parts of nano-alumina (20-50nm); Functional auxiliary agent, including: 0.50 parts of sodium fluorosilicate, 0.35 parts of polyvinyl alcohol fiber; the polyvinyl alcohol fiber is 6-12 mm in length and 20-40 μm in diameter; 0.4 parts of self-repairing microcapsules, which are composed of epoxy resin core wrapped by polyurethane shell, and have a particle size of 50-200 μm; 16 parts water.

[0038] The method for preparing magnesium-based construction waste recycled materials comprises the following steps: Preparation of composite modifier: premix 0.7 parts of potassium dihydrogen phosphate and 0.5 parts of borax to prepare inorganic modifier; premix 0.3 parts of polycarboxylic acid water reducer and 0.25 parts of calcium lignin sulfonate to prepare organic modifier; finally, compound with 0.35 parts of titanate coupling agent.

[0039] Preparation of nanocomposite reinforcing agent: Add 0.7 parts of nano-silicon dioxide (10-30nm) and 0.3 parts of nano-alumina (20-50nm) into a ball mill, use ethanol as the dispersion medium, ball mill for 2.5 hours, and pass through a 350-mesh sieve after drying to obtain a composite powder with a specific surface area ≥200m² / g.

[0040] Preparation of functional auxiliary agent: soak 0.35 parts of polyvinyl alcohol fiber in 2.5% KH-550 solution for 50 minutes, dry and mix with 0.50 parts of sodium fluorosilicate; Soak the aggregate in a 9% by mass phosphoric acid solution for 3.5 hours and dry it to a moisture content of ≤1%; Preparing a magnesium-based gelling material: mixing magnesium oxide, magnesium chloride and magnesium sulfate in a mass ratio of 3:2:1 to obtain a magnesium-based gelling material; Mix the raw materials step by step: add 20 parts of magnesium-based cementitious material, 75 parts of pre-treated construction waste recycled aggregate, 2.5 parts of silica fume, 1.8 parts of fly ash, and 0.8 parts of blast furnace slag in sequence, and dry mix for 4.5 minutes; then add the composite modifier, nano-composite reinforcing agent and functional auxiliary agent prepared above, and continue stirring for 7 minutes; Final mixing: add 16 parts of water and 0.4 parts of self-repairing microcapsules, control the stirring speed to 350r / min, stir for 12 minutes and then put into the mold, and cure for 22 days at a temperature of 30°C and a humidity of 80%.

[0041] Embodiment 5, a magnesium-based construction waste recycled material, comprising, by weight: 25 parts of magnesium-based cementitious material; 80 parts of recycled aggregate from construction waste; The composite modifier includes an inorganic modifier, an organic modifier and an interface enhancer, and the specific weight parts are as follows: inorganic modifier: 0.9 parts of potassium dihydrogen phosphate and 0.6 parts of borax; organic modifier: 0.5 parts of polycarboxylic acid water reducer and 0.3 parts of calcium lignin sulfonate; interface enhancer: 0.4 parts of titanate coupling agent; Mineral additives: 3 parts of silica fume, 2 parts of fly ash, 1 part of blast furnace slag; Nanocomposite reinforcing agent, composed of 0.8 parts of nano-silicon dioxide (10-30nm) and 0.4 parts of nano-alumina (20-50nm); Functional auxiliary agent, including: 0.56 parts of sodium fluorosilicate, 0.4 parts of polyvinyl alcohol fiber; the polyvinyl alcohol fiber is 6-12 mm in length and 20-40 μm in diameter; 0.5 parts of self-repairing microcapsules, which are composed of epoxy resin core wrapped by polyurethane shell, with a particle size of 200 μm; 18 parts water.

[0042] The method for preparing magnesium-based construction waste recycled materials comprises the following steps: Preparation of composite modifier: premix 0.9 parts of potassium dihydrogen phosphate and 0.6 parts of borax to prepare inorganic modifier; premix 0.5 parts of polycarboxylic acid water reducer and 0.3 parts of calcium lignin sulfonate to prepare organic modifier; finally, compound with 0.4 parts of titanate coupling agent.

[0043] Preparation of nanocomposite reinforcing agent: Add 0.8 parts of nano-silicon dioxide (10-30nm) and 0.4 parts of nano-alumina (20-50nm) into a ball mill, use ethanol as the dispersion medium, ball mill for 3 hours, dry and pass through a 400-mesh sieve to obtain a composite powder with a specific surface area ≥200m² / g.

[0044] Preparation of functional auxiliary agent: 0.4 parts of polyvinyl alcohol fiber was soaked in 3% KH-550 solution for 60 minutes, and then dried and mixed with 0.56 parts of sodium fluorosilicate; Soak the aggregate in a 10% by mass phosphoric acid solution for 4 hours and dry it to a moisture content of ≤1%; Preparing a magnesium-based gelling material: mixing magnesium oxide, magnesium chloride and magnesium sulfate in a mass ratio of 3:2:1 to obtain a magnesium-based gelling material; Mix the raw materials step by step: add 25 parts of magnesium-based cementitious materials, 80 parts of pre-treated construction waste recycled aggregates, 3 parts of silica fume, 2 parts of fly ash, and 1 part of blast furnace slag in sequence, and dry mix for 5 minutes; then add the composite modifier, nano-composite reinforcing agent and functional auxiliary agent prepared above, and continue stirring for 8 minutes; Final mixing: add 18 parts of water and 0.5 parts of self-repairing microcapsules, control the stirring speed to 400r / min, stir for 15 minutes and then put into the mold, and cure for 28 days at a temperature of 35°C and a humidity of 85%.

[0045] Comparative Example 1 The difference between this comparative example and Example 1 is that the interface enhancer (titanate coupling agent) in the composite modifier is removed, and only the inorganic modifier and the organic modifier are retained. The other components are the same as those in Example 1.

[0046] Comparative Example 2 The difference between this comparative example and Example 2 is that the nano-composite reinforcing agent is changed to single nano-silicon dioxide (0.3 parts) and the nano-alumina component is removed. The other components are the same as those in Example 2.

[0047] Comparative Example 3 The difference between this comparative example and Example 3 is that no self-repairing microcapsules are added, the amount of water is increased by 0.2 parts to maintain the total liquid volume, and the other components are the same as those in Example 3.

[0048] Comparative Example 4 The difference between this comparative example and Example 4 is that the recycled aggregate from construction waste is not pretreated with phosphoric acid solution, and the aggregate with original moisture content (about 5%) is directly used. The rest of the preparation process is the same as that of Example 4.

[0049] Comparative Example 5 The difference between this comparative example and Example 5 is that the magnesium-based gelling material only uses magnesium oxide + magnesium chloride (mass ratio 3:2) to remove the magnesium sulfate component, and the remaining components are the same as those in Example 5.

[0050] In order to verify the technical effect of the present invention, the magnesium-based construction waste recycled materials prepared in Examples 1-5 and Comparative Examples 1-5 were tested.

[0051] Validation Experimental Design Test items and standards: 1. Mechanical properties (GB / T50081-2019): 7 / 28 days compressive strength, 28 days flexural strength; 2. Durability (GB / T50082-2009): strength loss rate after 50 freeze-thaw cycles, chloride ion permeability coefficient (Coulomb method); 3. Self-repair performance: strength recovery rate after 0.3mm pre-crack 30 days, SEM observation of crack healing; 4. Microstructure: porosity measured by mercury intrusion method, hydration product analysis by XRD; 5. Interface characteristics: aggregate-matrix interface microhardness, aggregate peeling strength test.

[0052] The test results are shown in the following table: Table 1 Test data of Examples 1-5 and Comparative Examples 1-5

[0053] In Table 1, the only removal of self-healing microcapsules: Only comparative example 3 explicitly removed the self-healing microcapsules (replaced with an equal amount of water), so its recovery rate (12.5%) reflects the natural healing ability without a repair system (such as carbonization healing of cement-based materials). Other comparative examples retain microcapsules: Although the remaining comparative examples (1 / 2 / 4 / 5) retain microcapsules, the microcapsules cannot work properly due to the lack of their key synergistic components.

[0054] The present invention significantly improves the comprehensive performance of construction waste recycled materials through the synergistic optimization of technical features. The interface enhancer (titanate coupling agent) in the composite modifier increases the aggregate-matrix interface hardness by 35%-45%. The comparison between Example 1 and Comparative Example 1 shows that the 28-day compressive strength is increased from 38.7MPa to 52.3MPa, and the freeze-thaw loss rate is reduced by 124%, verifying the key role of interface modification. The nano-Al2O3 / SiO2 compound optimizes the pore structure through the synergistic filling effect. The chloride ion permeability coefficient of Example 2 is reduced by 72% compared with that of Comparative Example 2 of single nano-SiO2, and the proportion of harmless pores below 100nm is increased by 62%. The self-healing microcapsule system achieves intelligent repair under the support of a complete technology chain. The crack recovery rate of Example 3 reaches 82.4%, far exceeding the 12.5% ​​of Comparative Example 3 without capsules; while Comparative Example 5, in which the gelling system lacks magnesium sulfate, causes the microcapsules to fail prematurely due to pH imbalance, and the repair rate is less than 5%, highlighting the necessity of the ternary gelling system (MgO-MgCl2-MgSO4) to maintain the stability of the repair agent. In addition, 5%-10% phosphoric acid pretreatment increases the aggregate peeling strength by 68%. Compared with the untreated Comparative Example 4, the freeze-thaw loss rate of Example 4 is reduced by 280%, and the porosity is optimized from 20.3% to 9.7%. Through the four mechanisms of interface strengthening, structural densification, self-repair synergy and stable hydration, the various technical features enable the embodiments to form significant advantages in mechanical strength, durability and intelligent repair. The compressive strength (52.3-68.9MPa) and flexural strength (6.8-8.7MPa) comprehensively surpass the control examples, and the chloride ion permeability coefficient (720-1280 coulombs) is 42%-72% lower than that of the control examples, fully demonstrating the synergistic effect of component optimization and process innovation.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A magnesium-based construction waste recycled material, characterized in that: By weight, it includes: 10-25 parts of magnesium-based gelling material; 65-80 parts of recycled aggregate from construction waste; The composite modifier includes an inorganic modifier, an organic modifier and an interface enhancer, and the specific weight parts are as follows: inorganic modifier: 0.2-0.9 parts of potassium dihydrogen phosphate, 0.1-0.6 parts of borax; organic modifier: 0.1-0.5 parts of polycarboxylic acid water reducer, 0.05-0.3 parts of calcium lignin sulfonate; interface enhancer: 0.05-0.4 parts of titanate coupling agent; Mineral additives: 1-3 parts of silica fume, 1-2 parts of fly ash, 0.5-1 parts of blast furnace slag; Nanocomposite reinforcing agent, which is compounded by 0.2-0.8 parts of nano silicon dioxide and 0.1-0.4 parts of nano aluminum oxide; Functional auxiliary agents, including: 0.1-0.56 parts of sodium fluorosilicate, 0.06-0.4 parts of polyvinyl alcohol fiber; Self-repairing microcapsules 0.1-0.5 parts; 8-18 parts water 2. A magnesium-based construction waste recycled material according to claim 1, characterized in that: The magnesium-based cementitious material is a mixture of magnesium oxychloride cement and magnesium oxysulfate cement, wherein the mass ratio of magnesium oxide, magnesium chloride and magnesium sulfate is 3:2:1; The construction waste recycled aggregate is surface pretreated by soaking the aggregate in a phosphoric acid solution for 2-4 hours and drying it.

3. The magnesium-based construction waste recycled material according to claim 1, characterized in that: The specific surface area of ​​the nanocomposite reinforcing agent is ≥200 m² / g.

4. The magnesium-based construction waste recycled material according to claim 1, characterized in that: The polyvinyl alcohol fiber has a length of 6-12 mm and a diameter of 20-40 μm.

5. The magnesium-based construction waste recycled material according to claim 4, characterized in that: The surface of the polyvinyl alcohol fiber is pretreated with a silane coupling agent.

6. The magnesium-based construction waste recycled material according to claim 1, characterized in that: The self-repairing microcapsule is composed of a polyurethane shell wrapping an epoxy resin core material, and the particle size is 50-200 μm.

7. A method for preparing magnesium-based construction waste recycled materials according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) Pretreatment of recycled aggregates from construction waste: Soak the aggregates in a 5-10% by mass phosphoric acid solution for 2-4 hours and dry them until the moisture content is ≤1%; (2) preparing a magnesium-based gelling material: mixing magnesium oxide, magnesium chloride and magnesium sulfate in a mass ratio of 3:2:1 to obtain a magnesium-based gelling material; (3) Mixing the raw materials step by step: add 10-25 parts of magnesium-based cementitious material, 65-80 parts of pre-treated construction waste recycled aggregate, 1-3 parts of silica fume, 1-2 parts of fly ash, and 0.5-1 parts of blast furnace slag in sequence, and dry mix for 2-5 minutes; then add the composite modifier, nano-composite reinforcing agent and functional auxiliary agent prepared above, and continue stirring for 3-8 minutes; (4) Final mixing: Add 8-18 parts of water and 0.1-0.5 parts of self-healing microcapsules, control the stirring speed to 200-400r / min, stir for 5-15 minutes, then pour into the mold, and cure for 7-28 days at a temperature of 20-35°C and a humidity of 60-85%.

8. The method for preparing magnesium-based construction waste recycled materials according to claim 7, characterized in that: The preparation of the composite modifier includes: 0.2-0.9 parts of potassium dihydrogen phosphate and 0.1-0.6 parts of borax are premixed to prepare an inorganic modifier; 0.1-0.5 parts of polycarboxylic acid water reducer and 0.05-0.3 parts of calcium lignin sulfonate are premixed to prepare an organic modifier; and finally, 0.05-0.4 parts of a titanate coupling agent are compounded.

9. The method for preparing magnesium-based construction waste recycled materials according to claim 7, characterized in that: The preparation method of the nanocomposite reinforcing agent is: Add 0.2-0.8 parts of nano silicon dioxide and 0.1-0.4 parts of nano aluminum oxide into a ball mill, use ethanol as a dispersion medium, ball mill for 1-3 hours, and pass through a 200-400 mesh sieve after drying to obtain a composite powder with a specific surface area ≥200m² / g.

10. The method for preparing magnesium-based construction waste recycled materials according to claim 7, characterized in that: The preparation of the functional adjuvant comprises: Soak 0.06-0.4 parts of polyvinyl alcohol fiber in 1-3% KH-550 solution for 30-60 minutes, dry it and mix it with 0.1-0.56 parts of sodium fluorosilicate.

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