A 3D printed clay-based magnesium recycled aggregate concrete and a manufacturing method thereof

Abstract

The present invention discloses a clay-based magnesium recycled aggregate concrete for 3D printing and a manufacturing method thereof, wherein the 3D printing clay-based magnesium recycled aggregate concrete comprises the following raw materials by weight: 68 to 95 parts of 3D printing mortar, 5 to 32 parts of clay-based magnesium recycled aggregate for 3D printing; the 3D printing clay-based magnesium recycled aggregate comprises the following raw materials by weight: 63.9 to 80.8 parts of clay base material, 19.2 to 36.1 parts of magnesium cementitious material. The present invention adopts clay-based magnesium recycled aggregate for 3D printing, the clay base material used is cheap and easy to obtain, and the extrusion molding technology is used to efficiently utilize the municipal sludge slurry waste, which not only realizes the low-cost large-scale production of coarse aggregate for 3D printing, but also effectively improves the resource utilization rate and added value of recycled aggregate, and reduces the cost of 3D printing engineering construction materials.

Description

Technical Field

[0001] The present invention belongs to the field of building 3D printing materials, and in particular relates to a 3D printed clay-based magnesium recycled aggregate concrete and a manufacturing method thereof. Background Art

[0002] At present, the research on construction waste mainly focuses on waste concrete. Although waste concrete occupies a large proportion of buildings, it still has certain mechanical strength after being crushed and recycled after being discarded. It has certain advantages in recycling as recycled aggregate, and the research and practical application in this regard are relatively mature. Due to the weak interface transition zone in recycled aggregate concrete (the interface between recycled aggregate, new cement hydration matrix, and old cement hydration matrix), the damage to aggregate during the crushing production of recycled aggregate, and the high water absorption and porosity of recycled aggregate, the compressive strength of recycled aggregate concrete is 12-30% lower than that of natural aggregate concrete, and the splitting tensile strength is 10-24% lower. However, there are few studies on how to recycle the engineering waste soil in the construction process, especially the engineering output soil. The engineering output soil has natural characteristics such as dispersed particles, poor mechanical properties and high water absorption. Therefore, direct landfill treatment of engineering output soil is prone to secondary disasters, and landfill treatment does not achieve the resource recycling of engineering output soil. How to utilize existing technical conditions to solidify engineering output soil and apply it in engineering construction to achieve efficient on-site resource utilization of engineering output soil is an engineering problem that urgently needs to be solved in research at home and abroad.

[0003] In addition, although 3D printing construction technology has been successfully used in actual engineering construction and is gradually becoming a smart construction technology in the future, the material cost of 3D printing concrete is relatively high due to the high content of cementitious materials and low amount of coarse aggregate in the printing materials of concrete currently used, which restricts the large-scale engineering application of 3D printing construction technology. Therefore, it is urgent to conduct breakthrough research on economical and applicable 3D printing inorganic solidified high-strength coarse aggregates to accelerate the realization of economical and applicable 3D printing concrete bulk building materials that can replace existing traditional concrete, thereby providing economical and stable raw materials for smart construction technology. Summary of the invention

[0004] The purpose of the present invention is to propose a 3D printed clay-based magnesium recycled aggregate concrete and a manufacturing method thereof in view of the current lack of low-cost coarse aggregate that can be mass-produced and is suitable for 3D printed mortar.

[0005] The present invention provides a 3D printing clay-based magnesium recycled aggregate concrete, wherein the 3D printing clay-based magnesium recycled aggregate concrete comprises the following raw materials in parts by weight: 68 to 95 parts of 3D printing mortar, 5 to 32 parts of clay-based magnesium recycled aggregate for 3D printing;

[0006] The 3D printing mortar includes the following materials by weight: 37.9-40.8 parts of sand, 37.9-40.8 parts of curing agent, 2.2-3.5 parts of additives, 0.41-0.51 parts of chopped fibers, and 15.8-20.2 parts of water, wherein the sand particle size is less than 1.18 mm;

[0007] The curing agent is a magnesium gelling material;

[0008] The additive is one of fast-hardening sulphoaluminate cement and fast-hardening ferroaluminate cement.

[0009] Furthermore, the chopped fibers are one of polyvinyl alcohol fibers, polyvinyl alcohol nitrile fibers, polypropylene fibers, glass fibers, basalt fibers, and carbon fibers, and the length of the chopped fibers is 3 mm or 6 mm.

[0010] Furthermore, the clay-based magnesium recycled aggregate for 3D printing includes the following raw materials in parts by weight: 63.9 to 80.8 parts of clay-based material and 19.2 to 36.1 parts of magnesium cementitious material.

[0011] Furthermore, the clay base material is municipal sludge, which is powder particles obtained by crushing the sludge cleaned from rivers or pipelines after natural drying or sun drying, with a moisture content of 7% to 10% and a particle size less than 2.36 mm.

[0012] Furthermore, the water is groundwater or surface water.

[0013] Further, the magnesium gelling material is magnesium oxychloride gelling material or magnesium oxysulfide gelling material;

[0014] The magnesium oxysulfide gelling material comprises the following raw materials in parts by weight: 86 to 98 parts of light-burned magnesium oxide, 42 to 91 parts of magnesium sulfate heptahydrate, and 0 to 14 parts of dead-burned magnesium oxide;

[0015] The magnesium oxychloride gelling material comprises the following raw materials in parts by weight: 65 to 96 parts of light-burned magnesium oxide, 135 to 148 parts of magnesium chloride hexahydrate, and 0 to 35 parts of dead-burned magnesium oxide;

[0016] The active magnesium oxide content in the light-burned magnesium oxide is 77%, and the magnesium chloride hexahydrate content is 43%.

[0017] Another object of the present invention is to provide a method for manufacturing 3D printed clay-based magnesia recycled aggregate concrete, the manufacturing method comprising the following steps:

[0018] S1. Setting the required weight of the clay-based magnesium recycled aggregate raw material for 3D printing through the control system of the clay-based magnesium recycled aggregate production equipment for 3D printing;

[0019] S2. Weigh the raw materials of clay-based magnesium recycled aggregate for 3D printing according to the designed ratio, weigh the clay-based material in two portions, the mass percentages of the first portion and the second portion are 70% and 30% respectively, add the weighed cementitious material to the first portion of the clay material and stir, then add the second portion of the clay-based material and add the weighed water and stir;

[0020] S3, adding the stirred mixture to the clay-based magnesium recycled aggregate extrusion molding equipment for 3D printing, and extruding the clay-based magnesium recycled aggregate for 3D printing;

[0021] S4. Perform indoor curing, water immersion curing or carbonization curing on clay-based magnesium recycled aggregate for 3D printing;

[0022] S5. According to the mix ratio design of 3D printing clay-based magnesium recycled aggregate concrete, weigh the calculated 3D printing mortar and clay-based magnesium recycled aggregate for 3D printing, stir the 3D printing mortar first, then add the clay-based magnesium recycled aggregate for 3D printing, stir and pump it into the hopper of the 3D printing equipment for 3D printing.

[0023] Furthermore, the particle sizes of the clay-based magnesium recycled aggregate for 3D printing are 10 mm, 20 mm and 30 mm.

[0024] Furthermore, the clay-based magnesium recycled aggregate for 3D printing has a 28d cylinder compressive strength greater than 2MPa, a crushing index less than 30%, and a 1h water absorption rate less than 20%.

[0025] Furthermore, the carbonization curing conditions of the clay-based magnesium recycled aggregate for 3D printing are: temperature 3-48° C., relative humidity 36-62%, and pressure 0-2.8 MPa.

[0026] The 3D printing clay-based magnesium recycled aggregate concrete of the present invention adopts clay-based magnesium recycled aggregate for 3D printing. The clay-based material used is cheap and easily available, and the extrusion molding technology efficiently utilizes slurry waste with a high water content as a resource, which not only realizes low-cost large-scale production of coarse aggregate for 3D printing, but also effectively improves the resource utilization rate and added value of recycled aggregate, and reduces the cost of 3D printing engineering construction materials; the produced clay-based magnesium recycled aggregate for 3D printing can also be recycled and reused after being discarded, further reducing the engineering application cost of coarse aggregate for 3D printing, and at the same time effectively solves the technical problem of efficient and high-value-added resource utilization of municipal sludge waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of an ellipsoidal clay-based magnesium recycled aggregate for 3D printing. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described 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, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0029] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0030] Example 1

[0031] The 3D printed clay-based magnesium recycled aggregate concrete in this embodiment includes the following raw materials in parts by weight: 85 parts of 3D printed mortar and 15 parts of clay-based magnesium recycled aggregate. The 3D printed mortar includes the following materials in parts by weight: 40.8 parts of sand, 40.8 parts of curing agent, 2.2 parts of additives, 0.41 parts of chopped fibers, and 15.8 parts of water. The sand particle size is less than 1.18 mm. The curing agent is a magnesium oxysulfide cementitious material. The magnesium oxysulfide cementitious material contains 98 parts of light-burned magnesium oxide and 42 parts of magnesium sulfate heptahydrate. The active magnesium oxide content in the light-burned magnesium oxide is 77%, the additive is fast-hardening ferroaluminate cement, the chopped fibers are 3 mm polyvinyl alcohol fibers, and the particle size of the clay-based magnesium recycled aggregate is 10 mm.

[0032] The clay-based magnesium recycled aggregate for 3D printing includes the following raw materials in parts by weight: 68.6 parts of municipal sludge with a moisture content of 7% and 31.4 parts of magnesium oxysulfide gelling material, wherein the municipal sludge is powder particles obtained by crushing the sludge cleared from the river or pipeline after natural drying or sun drying, and the particle size is less than 2.36 mm, and the magnesium oxysulfide gelling material contains 98 parts of light-burned magnesium oxide and 42 parts of magnesium sulfate heptahydrate. The raw materials of clay-based magnesium recycled aggregate for 3D printing are weighed according to the designed ratio. The clay-based material is weighed in two portions, and the mass percentages of the first and second portions are 70% and 30% respectively. The weighed cementitious material is added to the first portion of the clay material and stirred. Then the second portion of the clay-based material is added and the weighed admixture and water are added and stirred. The stirred mixture is added to the clay-based magnesium recycled aggregate extrusion molding equipment for 3D printing to extrude the clay-based magnesium recycled aggregate for 3D printing. The clay-based magnesium recycled aggregate for 3D printing is cured indoors. The aggregate produced by the extrusion molding equipment is as follows: Figure 1As shown, the cylinder compressive strength of the clay-based magnesium recycled aggregate for 3D printing after indoor curing for 28 days is 3.8MPa, the crushing index is 15%, and the water absorption rate is 16% in 1h; the cylinder compressive strength of the clay-based magnesium recycled aggregate for 3D printing after carbonization curing for 28 days is 4.5MPa, the crushing index is 14%, and the water absorption rate is 15% in 1h. The carbonization curing conditions of the clay-based magnesium recycled aggregate for 3D printing are: temperature 25°C, relative humidity 50%, and pressure 1.6MPa.

[0033] Example 2

[0034] In this embodiment, 3D printed clay-based magnesium recycled aggregate concrete comprises the following raw materials in parts by weight: 88 parts of 3D printed mortar, 12 parts of clay-based magnesium recycled aggregate, and the 3D printed mortar comprises the following materials in parts by weight: 40.8 parts of sand, 40.8 parts of curing agent, 2.2 parts of additives, 0.41 parts of chopped fibers, and 15.8 parts of water. The sand particle size is less than 1.18 mm, and the curing agent is a magnesium oxysulfide gelling material. The magnesium oxysulfide gelling material contains 86 parts of light-burned magnesium oxide, 66 parts of magnesium sulfate heptahydrate, and 7 parts of dead-burned magnesium oxide. The active magnesium oxide content in the light-burned magnesium oxide is 77%, and the additive is fast-hardening ferroaluminate cement. The chopped fibers are 3 mm polyvinyl alcohol nitrile fibers, and the particle size of the clay-based magnesium recycled aggregate is 20 mm.

[0035] The clay-based magnesium recycled aggregate for 3D printing includes the following raw materials in parts by weight: 72.3 parts of municipal sludge with a moisture content of 8% and 27.7 parts of magnesium oxysulfide gelling material, wherein the municipal sludge is powder particles obtained by crushing the sludge cleared from the river or pipeline after natural drying or sun drying, and the particle size is less than 2.36 mm, and the magnesium oxysulfide gelling material includes 86 parts of light-burned magnesium oxide, 66 parts of magnesium sulfate heptahydrate, and 7 parts of heavy-burned magnesium oxide. The raw materials of clay-based magnesium recycled aggregate for 3D printing are weighed according to the designed ratio. The clay-based material is weighed in two portions, and the mass percentages of the first and second portions are 70% and 30% respectively. The weighed cementitious material is added to the first portion of the clay material and stirred. Then the second portion of the clay-based material is added and the weighed admixture and water are added and stirred. The stirred mixture is added to the clay-based magnesium recycled aggregate extrusion molding equipment for 3D printing to extrude the clay-based magnesium recycled aggregate for 3D printing. The clay-based magnesium recycled aggregate for 3D printing is cured indoors. The aggregate produced by the extrusion molding equipment is as follows: Figure 1As shown, the cylinder compressive strength of the clay-based magnesium recycled aggregate for 3D printing after indoor curing for 28 days is 4.6MPa, the crushing index is 14%, and the water absorption rate is 13% in 1h; the cylinder compressive strength of the clay-based magnesium recycled aggregate for 3D printing after carbonization curing for 28 days is 5.7MPa, the crushing index is 11%, and the water absorption rate is 10% in 1h. The carbonization curing conditions of the clay-based magnesium recycled aggregate for 3D printing are: temperature 22°C, relative humidity 56%, and pressure 2.5MPa.

[0036] Example 3

[0037] The 3D printed clay-based magnesium recycled aggregate concrete in this embodiment includes the following raw materials in parts by weight: 90 parts of 3D printed mortar and 10 parts of clay-based magnesium recycled aggregate. The 3D printed mortar includes the following materials in parts by weight: 40.8 parts of sand, 40.8 parts of curing agent, 2.2 parts of additives, 0.41 parts of chopped fibers, and 15.8 parts of water. The sand particle size is less than 1.18 mm. The curing agent is a magnesium oxysulfide gelling material. The magnesium oxysulfide gelling material contains 92 parts of light-burned magnesium oxide, 91 parts of magnesium sulfate heptahydrate, and 14 parts of dead-burned magnesium oxide. The light-burned magnesium oxide has an active magnesium oxide content of 77%, the additive is fast-hardening ferroaluminate cement, the chopped fibers are 6 mm polypropylene fibers, and the clay-based magnesium recycled aggregate has a particle size of 20 mm.

[0038] The clay-based magnesium recycled aggregate for 3D printing includes the following raw materials in parts by weight: 76.4 parts of municipal sludge with a moisture content of 9% and 23.6 parts of magnesium oxysulfide gelling material, wherein the municipal sludge is powder particles obtained by crushing the sludge cleared from the river or pipeline after natural drying or sun drying, and the particle size is less than 2.36 mm, and the magnesium oxysulfide gelling material includes 92 parts of light-burned magnesium oxide, 91 parts of magnesium sulfate heptahydrate, and 14 parts of dead-burned magnesium oxide. The raw materials of clay-based magnesium recycled aggregate for 3D printing are weighed according to the designed ratio. The clay-based material is weighed in two portions, and the mass percentages of the first and second portions are 70% and 30% respectively. The weighed cementitious material is added to the first portion of the clay material and stirred. Then the second portion of the clay-based material is added and the weighed admixture and water are added and stirred. The stirred mixture is added to the clay-based magnesium recycled aggregate extrusion molding equipment for 3D printing to extrude the clay-based magnesium recycled aggregate for 3D printing. The clay-based magnesium recycled aggregate for 3D printing is cured indoors. The aggregate produced by the extrusion molding equipment is as follows: Figure 1As shown, the cylinder compressive strength of the clay-based magnesium recycled aggregate for 3D printing after indoor curing for 28 days is 6.7MPa, the crushing index is 12%, and the water absorption rate is 10% in 1h; the cylinder compressive strength of the clay-based magnesium recycled aggregate for 3D printing after carbonization curing for 28 days is 7.6MPa, the crushing index is 10%, and the water absorption rate is 9% in 1h. The carbonization curing conditions of the clay-based magnesium recycled aggregate for 3D printing are: temperature 28°C, relative humidity 60%, and pressure 2.6MPa.

[0039] Example 4

[0040] The 3D printed clay-based magnesium recycled aggregate concrete in this embodiment includes the following raw materials in parts by weight: 70 parts of 3D printed mortar and 30 parts of clay-based magnesium recycled aggregate. The 3D printed mortar includes the following materials in parts by weight: 40.8 parts of sand, 40.8 parts of curing agent, 2.2 parts of additives, 0.41 parts of chopped fibers, and 15.8 parts of water. The sand particle size is less than 1.18 mm. The curing agent is a magnesium oxychloride gelling material. The magnesium oxychloride gelling material contains 91 parts of light-burned magnesium oxide and 135 parts of magnesium chloride hexahydrate. The light-burned magnesium oxide contains 77% active magnesium oxide, and the magnesium chloride hexahydrate content is 43%. The additive is fast-hardening sulphoaluminate cement, the chopped fibers are 3 mm glass fibers, and the clay-based magnesium recycled aggregate has a particle size of 10 mm.

[0041] The clay-based magnesium recycled aggregate for 3D printing includes the following raw materials in parts by weight: 63.9 parts of municipal sludge with a moisture content of 10% and 36.1 parts of magnesium oxychloride gelling material, wherein the municipal sludge is powder particles obtained by crushing the sludge cleared from the river or pipeline after natural drying or sun drying, and the particle size is less than 2.36 mm, and the magnesium oxychloride gelling material contains 91 parts of light-burned magnesium oxide and 135 parts of magnesium chloride hexahydrate. The raw materials of clay-based magnesium recycled aggregate for 3D printing are weighed according to the designed ratio. The clay-based material is weighed in two portions, and the mass percentages of the first and second portions are 70% and 30% respectively. The weighed cementitious material is added to the first portion of the clay material and stirred. Then the second portion of the clay-based material is added and the weighed admixture and water are added and stirred. The stirred mixture is added to the clay-based magnesium recycled aggregate extrusion molding equipment for 3D printing to extrude the clay-based magnesium recycled aggregate for 3D printing. The clay-based magnesium recycled aggregate for 3D printing is cured indoors. The aggregate produced by the extrusion molding equipment is as follows: Figure 1As shown, the cylinder compressive strength of the clay-based magnesium recycled aggregate for 3D printing after indoor curing for 28 days is 7.9 MPa, the crushing index is 19.8%, and the water absorption rate is 12% in 1 hour; the cylinder compressive strength of the clay-based magnesium recycled aggregate for 3D printing after carbonization curing for 28 days is 8.5 MPa, the crushing index is 14%, and the water absorption rate is 9% in 1 hour. The carbonization curing conditions of the clay-based magnesium recycled aggregate for 3D printing are: temperature 26°C, relative humidity 49%, and pressure 1.4 MPa.

[0042] Example 5

[0043] The 3D printed clay-based magnesium recycled aggregate concrete in this embodiment includes the following raw materials in parts by weight: 68 parts of 3D printed mortar and 32 parts of clay-based magnesium recycled aggregate. The 3D printed mortar includes the following materials in parts by weight: 37.9 parts of sand, 37.9 parts of curing agent, 3.5 parts of additives, 0.51 parts of chopped fibers, and 20.2 parts of water. The sand particle size is less than 1.18 mm. The curing agent is a magnesium oxychloride gelling material. The magnesium oxychloride gelling material contains 65 parts of light-burned magnesium oxide, 142 parts of magnesium chloride hexahydrate, and 17.5 parts of dead-burned magnesium oxide. The light-burned magnesium oxide has an active magnesium oxide content of 77%, and the magnesium chloride hexahydrate has a content of 43%. The additive is fast-hardening sulphoaluminate cement, the chopped fibers are 3 mm basalt fibers, and the clay-based magnesium recycled aggregate has a particle size of 10 mm.

[0044] The clay-based magnesium recycled aggregate for 3D printing includes the following raw materials in parts by weight: 67.7 parts of municipal sludge with a moisture content of 7%, 32.3 parts of magnesium oxychloride gelling material, and 8 parts of tap water. The municipal sludge is powder particles obtained by crushing the sludge cleared from the river or pipeline after natural drying or sun drying, and the particle size is less than 2.36 mm. The magnesium oxychloride gelling material contains 65 parts of light-burned magnesium oxide, 142 parts of magnesium chloride hexahydrate, and 17.5 parts of dead-burned magnesium oxide. The raw materials of clay-based magnesium recycled aggregate for 3D printing are weighed according to the designed ratio. The clay-based material is weighed in two portions, and the mass percentages of the first and second portions are 70% and 30% respectively. The weighed cementitious material is added to the first portion of the clay material and stirred. Then the second portion of the clay-based material is added and the weighed admixture and water are added and stirred. The stirred mixture is added to the clay-based magnesium recycled aggregate extrusion molding equipment for 3D printing to extrude the clay-based magnesium recycled aggregate for 3D printing. The clay-based magnesium recycled aggregate for 3D printing is cured indoors. The aggregate produced by the extrusion molding equipment is as follows: Figure 1As shown, the cylinder compressive strength of the clay-based magnesium recycled aggregate for 3D printing after indoor curing for 28 days is 5.3MPa, the crushing index is 20.6%, and the water absorption rate is 16% in 1h; the cylinder compressive strength of the clay-based magnesium recycled aggregate for 3D printing after carbonization curing for 28 days is 6.8MPa, the crushing index is 18%, and the water absorption rate is 12% in 1h. The carbonization curing conditions of the clay-based magnesium recycled aggregate for 3D printing are: temperature 3°C, relative humidity 36%, and pressure 0MPa.

[0045] Example 6

[0046] The 3D printed clay-based magnesium recycled aggregate concrete in this embodiment includes the following raw materials in parts by weight: 95 parts of 3D printed mortar and 5 parts of clay-based magnesium recycled aggregate. The 3D printed mortar includes the following materials in parts by weight: 40.8 parts of sand, 40.8 parts of curing agent, 2.2 parts of additives, 0.41 parts of chopped fibers, and 15.8 parts of water. The sand particle size is less than 1.18 mm. The curing agent is a magnesium oxychloride gelling material. The magnesium oxychloride gelling material contains 96 parts of light-burned magnesium oxide, 148 parts of magnesium chloride hexahydrate, and 35 parts of dead-burned magnesium oxide. The light-burned magnesium oxide has an active magnesium oxide content of 77%, and the magnesium chloride hexahydrate has a content of 43%. The additive is fast-hardening sulphoaluminate cement, the chopped fibers are 6 mm carbon fibers, and the clay-based magnesium recycled aggregate has a particle size of 30 mm.

[0047] The clay-based magnesium recycled aggregate for 3D printing includes the following raw materials in parts by weight: 80.8 parts of municipal sludge with a moisture content of 8%, 19.2 parts of magnesium oxychloride gelling material, and 11 parts of tap water. The municipal sludge is powder particles obtained by crushing the sludge cleared from the river or pipeline after natural drying or sun drying, and the particle size is less than 2.36 mm. The magnesium oxychloride gelling material contains 96 parts of light-burned magnesium oxide, 148 parts of magnesium chloride hexahydrate, and 35 parts of heavily-burned magnesium oxide. The raw materials of clay-based magnesium recycled aggregate for 3D printing are weighed according to the designed ratio. The clay-based material is weighed in two portions, and the mass percentages of the first and second portions are 70% and 30% respectively. The weighed cementitious material is added to the first portion of the clay material and stirred. Then the second portion of the clay-based material is added and the weighed admixture and water are added and stirred. The stirred mixture is added to the clay-based magnesium recycled aggregate extrusion molding equipment for 3D printing to extrude the clay-based magnesium recycled aggregate for 3D printing. The clay-based magnesium recycled aggregate for 3D printing is cured indoors. The aggregate produced by the extrusion molding equipment is as follows: Figure 1As shown, the cylinder compressive strength of the clay-based magnesium recycled aggregate for 3D printing after indoor curing for 28 days is 6.2MPa, the crushing index is 19.6%, and the water absorption rate is 15% in 1h; the cylinder compressive strength of the clay-based magnesium recycled aggregate for 3D printing after carbonization curing for 28 days is 7.5MPa, the crushing index is 17%, and the water absorption rate is 11% in 1h. The carbonization curing conditions of the clay-based magnesium recycled aggregate for 3D printing are: temperature 48°C, relative humidity 62%, and pressure 2.8MPa.

[0048] By utilizing circular arcs, the clay-based magnesium recycled aggregate for 3D printing is designed into an arch shape, which effectively takes advantage of the arch structure's high compressive strength. At the same time, it is produced using extrusion molding equipment, which has the advantages of fast molding, low manufacturing cost, and no waste of raw materials during the molding process. It also gives full play to the high compressive strength of the magnesium cementitious material used, making the clay-based magnesium recycled aggregate for 3D printing stronger.

[0049] The clay-based magnesium recycled aggregate concrete for 3D printing effectively reduces the cost of 3D printing inkjet materials by adopting clay-based magnesium recycled aggregate for 3D printing, and at the same time fully transforms municipal sludge solid waste into recycled aggregate that can meet engineering needs, thereby realizing efficient resource utilization of municipal sludge.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that after reading the specification of this application, the technicians can still modify or replace the specific implementation mode of the present invention with equivalents, but these modifications or changes do not deviate from the scope of protection of the pending claims of the present application.

Claims

1. A 3D printed clay-based magnesium recycled aggregate concrete, characterized in that: The 3D printing clay-based magnesium recycled aggregate concrete comprises the following raw materials in parts by weight: 68-95 parts of 3D printing mortar, 5-32 parts of clay-based magnesium recycled aggregate for 3D printing; The 3D printing mortar includes the following materials by weight: 37.9-40.8 parts of sand, 37.9-40.8 parts of curing agent, 2.2-3.5 parts of additives, 0.41-0.51 parts of chopped fibers, and 15.8-20.2 parts of water, wherein the sand particle size is less than 1.18 mm; The curing agent is a magnesium gelling material; The additive is one of fast-hardening sulphoaluminate cement and fast-hardening ferroaluminate cement; The clay-based magnesium recycled aggregate for 3D printing comprises the following raw materials in parts by weight: 63.9 to 80.8 parts of clay-based material and 19.2 to 36.1 parts of magnesium gelling material; The clay base material is municipal sludge, which is powder particles obtained by crushing the sludge cleaned from rivers or pipelines after natural drying or sun drying, with a moisture content of 7% to 10% and a particle size of less than 2.36 mm; The magnesium gelling material is magnesium oxychloride gelling material or magnesium oxysulfide gelling material; The magnesium oxysulfide gelling material comprises the following raw materials in parts by weight: 86-98 parts of light-burned magnesium oxide, 42-91 parts of magnesium sulfate heptahydrate, and 0-14 parts of dead-burned magnesium oxide; The magnesium oxychloride gelling material comprises the following raw materials in parts by weight: 65-96 parts of light-burned magnesium oxide, 135-148 parts of magnesium chloride hexahydrate, and 0-35 parts of dead-burned magnesium oxide; The active magnesium oxide content in the light-burned magnesium oxide is 77%, and the magnesium chloride hexahydrate content is 43%; The method for manufacturing the 3D printed clay-based magnesium recycled aggregate comprises the following steps: S1. Setting the required weight of the clay-based magnesium recycled aggregate raw material for 3D printing through the control system of the clay-based magnesium recycled aggregate production equipment for 3D printing; S2. Weigh the raw materials of clay-based magnesium recycled aggregate for 3D printing according to the designed ratio, weigh the clay-based material in two portions, the mass percentages of the first portion and the second portion are 70% and 30% respectively, add the weighed cementitious material to the first portion of the clay-based material and stir, then add the second portion of the clay-based material and add the weighed water and stir; S3, adding the stirred mixture to the clay-based magnesium recycled aggregate extrusion molding equipment for 3D printing, and extruding the clay-based magnesium recycled aggregate for 3D printing; S4. Carry out indoor curing, water immersion curing or carbonization curing on clay-based magnesium recycled aggregate for 3D printing.

2. A 3D printed clay-based magnesia recycled aggregate concrete according to claim 1, characterized in that: The chopped fibers are one of polyvinyl alcohol fibers, polyvinyl alcohol nitrile fibers, polypropylene fibers, glass fibers, basalt fibers, and carbon fibers, and the length of the chopped fibers is 3 mm or 6 mm.

3. A method for manufacturing 3D printed clay-based magnesia recycled aggregate concrete according to any one of claims 1-2, characterized in that: The manufacturing method comprises the following steps: S1. Setting the required weight of the clay-based magnesium recycled aggregate raw material for 3D printing through the control system of the clay-based magnesium recycled aggregate production equipment for 3D printing; S2. Weigh the raw materials of clay-based magnesium recycled aggregate for 3D printing according to the designed ratio, weigh the clay-based material in two portions, the mass percentages of the first portion and the second portion are 70% and 30% respectively, add the weighed gelling material to the first portion of the clay-based material and stir, then add the second portion of the clay-based material and add the weighed water and stir; S3, adding the stirred mixture to the clay-based magnesium recycled aggregate extrusion molding equipment for 3D printing, and extruding the clay-based magnesium recycled aggregate for 3D printing; S4. Perform indoor curing, water immersion curing or carbonization curing on clay-based magnesium recycled aggregate for 3D printing; S5. According to the mix ratio design of 3D printing clay-based magnesium recycled aggregate concrete, weigh the calculated 3D printing mortar and clay-based magnesium recycled aggregate for 3D printing, stir the 3D printing mortar first, then add the clay-based magnesium recycled aggregate for 3D printing, stir and pump it into the hopper of the 3D printing equipment for 3D printing.

4. A method for manufacturing 3D printed clay-based magnesia recycled aggregate concrete according to claim 3, characterized in that: The particle sizes of the clay-based magnesium recycled aggregate for 3D printing are 10 mm, 20 mm and 30 mm.

5. A method for manufacturing 3D printed clay-based magnesia recycled aggregate concrete according to claim 3, characterized in that: The clay-based magnesium recycled aggregate for 3D printing has a 28d cylinder compressive strength greater than 2MPa, a crushing index less than 30%, and a 1h water absorption rate less than 20%.

6. A method for manufacturing 3D printed clay-based magnesia recycled aggregate concrete according to claim 3, characterized in that: The carbonization curing conditions of the clay-based magnesium recycled aggregate for 3D printing are: temperature 3~48°C, relative humidity 36~62%, and pressure 0~2.8MPa.

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