Steel slag-construction waste-based composite material for building 3D printing and preparation method and application thereof

Abstract

This invention relates to a composite material for 3D printing in construction, its preparation method, and its application. By weight, the composite material comprises 35-55 parts of gel material, 30-45 parts of recycled aggregate, and 0.2-1 parts of reinforcing material. The gel material includes mineralized steel slag powder, construction waste powder, cement, and silica fume, wherein the particle size of the mineralized steel slag powder and construction waste powder is less than or equal to 0.075 mm. The recycled aggregate includes mineralized steel slag sand and construction waste sand, wherein the particle size of the mineralized steel slag sand is larger than that of the mineralized steel slag powder, and the particle size of the construction waste sand is larger than that of the construction waste powder. The mineralized steel slag powder and mineralized steel slag sand are obtained by mineralizing and curing steel slag, followed by grinding and crushing. The composite material of this invention significantly increases the utilization rate of construction waste and steel slag, reduces usage costs, and minimizes environmental impact. Simultaneously, the composite material of this invention has controllable setting time, superior printability and constructability, realizing the preparation of low-carbon, high-performance 3D printing materials for construction, and possessing certain economic and social value.

Description

Technical Field

[0001] This invention belongs to the field of building 3D printing materials technology, specifically relating to a steel slag-construction waste based composite material for building 3D printing, its preparation method and application. Background Technology

[0002] As a component of intelligent manufacturing processes, 3D printing in construction boasts advantages such as moldlessness, rapid construction, and lightweight design, making it an increasingly popular research area in the building materials field in recent years. With the rapid development of printing technology, the requirements for printing accuracy and stability are also increasing. As a rising star, 3D printing in construction places increasingly higher demands on the mechanical and performance properties of printing materials. With the national standardization and regulation of energy conservation and emission reduction, there is an urgent need to develop a solid waste-based 3D printing material that simultaneously meets the requirements of green and low-carbon construction while maintaining high workability.

[0003] As a typical industrial solid waste, steel slag has a comprehensive utilization rate of less than 30% in Jiangsu, Zhejiang and other regions, and even lower in some areas. At present, steel slag is mainly used in roadbeds, cement calcination and other fields, and some is used in non-structural concrete components such as bricks and blocks.

[0004] Currently, some patents also utilize steel slag in 3D printing materials for construction. For example, Chinese patent CN115466090A discloses a cement-based 3D printing material utilizing solid waste, its preparation method, and its application. This material comprises the following components in parts by weight: 60-110 parts cement-based composite material, 80-150 parts fine aggregate, 25-50 parts industrial solid waste, 0.2-0.5 parts water-reducing agent, 0.5-3 parts thickener, 0.1-1.5 parts thixotropic agent, 0.1-1.5 parts fiber-reinforcing material, and 13-27 parts water. The solid waste includes one or more of steel slag, blast furnace slag, and fly ash. While this method can achieve high strength, it requires a large amount of fine aggregate, its flowability needs improvement, and the utilization rate of steel slag is extremely low. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a steel slag-construction waste-based composite material. This composite material not only completely replaces natural sand or manufactured sand with recycled aggregates, but also replaces part of the gel material with recycled aggregates, which significantly reduces the cost of the composite material. At the same time, the composite material has good printability and constructability, and is suitable for 3D printing of buildings.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A composite material for 3D printing of buildings, comprising, by weight, 35-55 parts of gel material, 30-45 parts of recycled aggregate, and 0.2-1 parts of reinforcing material;

[0008] Wherein: the gel material includes mineralized steel slag powder, construction waste powder, cement and silica fume, and the particle size of the mineralized steel slag powder and construction waste powder is less than or equal to 0.075 mm;

[0009] The recycled aggregate includes mineralized steel slag sand and construction waste sand, wherein the particle size of the mineralized steel slag sand is larger than that of the mineralized steel slag powder, and the particle size of the construction waste sand is larger than that of the construction waste powder.

[0010] The mineralized steel slag powder and mineralized steel slag sand are obtained by grinding and crushing steel slag after it has been mineralized and cured.

[0011] The construction waste used in this invention is mainly waste concrete and / or waste bricks, which are first crushed and collected by a crushing production line, and then screened for later use.

[0012] This invention, based on the theory of close packing, improves the bulk density of screened recycled aggregates. The mineralized steel slag aggregate exhibits higher sphericity, as does the construction waste aggregate. The resulting mixed recycled aggregate enhances the printability of the printing material. Based on the theory of excess slurry, the proportion of cementitious material in the mix is ​​higher than in typical construction mortar. After sufficient cementitious material fills the aggregate pores, the excess mineralized steel slag powder and construction waste powder can synergistically interact in an alkaline environment, regulating the rheological properties of the printing material and improving its mechanical properties.

[0013] Advantageously, the particle size of the construction waste powder is 0.006 to 60 micrometers, and the particle size of the mineralized steel slag powder is 0.01 to 75 micrometers.

[0014] By leveraging the difference in particle size between construction waste powder and mineralized steel slag powder, the yield stress of the printing material is synergistically adjusted after mixing, thereby improving the construction performance of the system. Some of the auxiliary cementitious materials in the mixture do not participate in the hydration reaction; their particle-filling effect improves the porosity distribution of the system, reduces the number of harmful pores, and enhances the mechanical and long-term performance of the printing material. Simultaneously, construction waste powder and mineralized steel slag powder are rich in aluminosilicate mineral phases, exhibiting strong complementarity in physical, chemical, and mineralogical properties. They also possess a certain degree of activity in the later stages of hydration, further enhancing the long-term performance of the printing material.

[0015] Advantageously, the particle size D90 of the construction waste powder is 5-25 micrometers, and the particle size D90 of the mineralized steel slag powder is 15-40 micrometers. Further, the particle size D90 of the construction waste powder is 10-20 micrometers, and the particle size D90 of the mineralized steel slag powder is 20-30 micrometers.

[0016] This invention addresses the drawbacks of steel slag aggregate, such as poor grindability and stability, by developing a mineralization technology to treat steel slag. The treated steel slag is then crushed to prepare mineralized steel slag powder and mineralized steel slag sand aggregate. This improves the stability of the steel slag aggregate while also refining the particle size distribution of the steel slag powder. Research on the impact of reduced activity of the mineralized steel slag powder on the mechanical properties of the printing material shows that the activity decreases by only 2%, and the printing performance of the printed material is significantly improved after mineralization. The anisotropic mechanical properties of the printed specimens are also closely related to the printing performance. Compared with the original steel slag, mineralized steel slag as a printing material improves the anisotropic mechanical properties. In summary, using construction waste powder and mineralized steel slag powder as auxiliary cementitious materials can meet the various requirements of cementitious materials in 3D building printing systems. The mixed recycled aggregate prepared by mixing construction waste sand and mineralized steel slag sand, after screening, can also meet the various requirements of aggregates in 3D building printing systems.

[0017] This invention improves the suspension capacity of particles, increases the viscosity of the system by using a thickener, and improves the compatibility of reinforcing materials by utilizing material structure reconstruction. In order to improve the uniformity of system distribution, the irregularity of the mixed recycled aggregate after optimization is reduced, and the agglomeration phenomenon between aggregates is reduced.

[0018] This invention is based on the principles of cementitious materials and geopolymer preparation technology. It utilizes two types of bulk solid waste, steel slag and construction waste, to prepare composite steel slag-construction waste-based materials for 3D printing of buildings. This can significantly reduce the cost of 3D printing materials and provide a new path and idea for the comprehensive utilization of bulk solid waste.

[0019] In some embodiments, the mass ratio of the mineralized steel slag sand to the construction waste sand is 1.5 to 3:1.

[0020] In some specific embodiments, the mineralized steel slag sand is a combination of mineralized steel slag sand with a particle size of 0.15-0.3 mm and mineralized steel slag sand with a particle size of 0.3-0.6 mm in a mass ratio of 1:1.1-2; the construction waste sand is a combination of construction waste sand with a particle size of 0.15-0.3 mm and construction waste sand with a particle size of 0.3-0.6 mm in a mass ratio of 1:1.1-2.

[0021] In some specific embodiments, the recycled aggregate comprises, by weight, 24-28 parts of mineralized steel slag sand of 0.15-0.3 mm, 35-42 parts of mineralized steel slag sand of 0.3-0.6 mm, 10-12 parts of construction waste sand of 0.15-0.3 mm, and 15-18 parts of construction waste sand of 0.3-0.6 mm.

[0022] In some embodiments, the total amount of the mineralized steel slag powder and construction waste powder accounts for 60-70% of the total mass of the gel material.

[0023] In some specific embodiments, the mass ratio of the mineralized steel slag powder to the construction waste powder is 1:0.8 to 1.2.

[0024] In some embodiments, the gel material comprises, by weight, 28-32 parts mineralized steel slag powder, 28-32 parts construction waste powder, 30-33 parts cement, and 2-3 parts silica fume.

[0025] In some embodiments, the reinforcing material includes a water-reducing agent, a thickener, and fibers. Further, the reinforcing material is a combination of water-reducing agent, thickener, and fibers in a mass ratio of 35–40:20–22:30–35.

[0026] The water-reducing agent is not specifically specified, and may be a commercially available powder, with sulfonated melamine as the main component; the thickener is not specifically specified, and may be a combination of polyacrylamide and cellulose ether in a mass ratio of 3:5 to 10; the fiber is PVA fiber.

[0027] When the composite material is used, it also contains water, and the amount of water is 10 to 20 parts.

[0028] In some specific embodiments, the mineralization maintenance method includes the following steps:

[0029] (1) Pre-curing the steel slag, with the ambient temperature controlled at 10-25℃ and the relative humidity at 55-80%;

[0030] (2) The steel slag after pre-curing is subjected to first-stage curing and second-stage curing in sequence. The curing conditions for the first stage are: curing temperature of 15-25℃, humidity of 65-75%RH, CO2 concentration of 10-30%, pressure of 35-45kPa, and curing time of 1-3h. The curing conditions for the second stage are: curing temperature of 45-55℃, humidity of 90-98%RH, CO2 concentration of 35-45%, pressure of 0.05-0.15MPa, and curing time of 1-3h.

[0031] In some specific embodiments, the composite material comprises 38-48 parts of gel material, 33-42 parts of recycled aggregate, 0.5-1 parts of reinforcing material, and 10-15 parts of water.

[0032] Furthermore, the composite material comprises 40-45 parts of gel material, 35-40 parts of recycled aggregate, 0.6-0.8 parts of reinforcing material, and 10-15 parts of water.

[0033] The second technical solution adopted by this invention is: a method for preparing the composite material for 3D printing of buildings as described above, comprising the following steps:

[0034] Step S1: Mix the gel material and recycled aggregate to obtain a mixed dry material;

[0035] Step S2: Mix the reinforcing material and water to obtain a mixture, and then add 60-70% of the mixture to the dry material and stir evenly to obtain a premix.

[0036] Step S3: Add the remaining mixture to the premix and stir evenly to obtain the composite material mixture.

[0037] The preparation method of this invention helps to homogenize the system and improve printing continuity.

[0038] The third technical solution adopted in this invention is a 3D printed building structure, which is prepared by 3D printing using the composite material for 3D printing of buildings described above or the composite material for 3D printing of buildings prepared by the above preparation method.

[0039] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0040] The composite material of this invention uses mineralized steel slag powder and construction waste powder as auxiliary gelling materials to replace part of the gelling material. Simultaneously, it uses mineralized steel slag sand and construction waste sand as aggregates to completely replace manufactured sand and other aggregates. Through optimized formulation, the utilization rate of construction waste and steel slag is greatly increased, reducing usage costs and environmental impact. This also solves the problem of excessive gelling material usage and environmental unfriendliness in 3D printing processes. Furthermore, the composite material of this invention has controllable setting time, superior printability and constructability, realizing the preparation of low-carbon, high-performance building 3D printing materials, and possessing significant economic and social value. Attached Figure Description

[0041] Figure 1 This is a particle size distribution curve of the construction waste powder and mineralized steel slag powder used in Example 1.

[0042] Figure 2 This is a schematic diagram of the structure of the printed specimen after cutting.

[0043] Figure 3 This is a schematic diagram of the deformation rate test. Detailed Implementation

[0044] As described in the background section, there are currently many problems with using steel slag in building 3D printing materials.

[0045] If steel slag is used as a cementitious material, its extremely poor grindability will lead to excessively high energy consumption; if used as an aggregate, it will have problems such as poor stability. However, the chemical composition of steel slag is similar to that of cement, possessing potential activity. Extending the setting time of cement mortar and increasing its fluidity can reduce the porosity of cementitious materials and improve pore distribution, but due to insufficient early hydration, early strength is affected. The inventors of this application have discovered that mineralizing steel slag can reduce its wear resistance and improve its stability. The prepared mineralized steel slag, when applied to 3D printing materials for buildings, can open up a new low-carbon pathway for the utilization of industrial solid waste and provide new materials for 3D printing of buildings.

[0046] Construction waste has a complex composition, making it difficult to utilize at a high quality. It is mostly used as roadbed filling material, and its utilization rate in my country is low, with the technology for utilizing waste concrete being even more immature. Due to the inherent characteristics of waste concrete, the recycled aggregate produced after crushing has many shortcomings, such as high porosity, high water absorption, and low strength. This limits its utilization potential and primarily results in its use in water-stabilized subbase or base courses for low-grade roads, resulting in low added value.

[0047] The main concept of this application is to synergistically apply mineralized steel slag and construction waste to composite materials for 3D printing of buildings. Mineralized steel slag and construction waste completely replace aggregates such as natural sand or manufactured sand, while also replacing some gel materials. The optimized particle size of the mineralized steel slag and construction waste significantly increases the utilization rate of construction waste and steel slag, reduces usage costs, minimizes environmental impact, and solves the problem of excessive gel material usage and environmental unfriendliness in 3D printing processes. Simultaneously, the setting time of the 3D printed composite material is adjusted to compensate for insufficient material strength caused by excessively high levels of single-component solid waste with low activity, while also mitigating the drawback of insufficient controllable printing time for highly active cementitious materials. Furthermore, the use of mineralized steel slag in 3D printed composite materials ensures both aggregate strength and powder activity while better meeting the printing performance requirements of 3D printing material systems. Ultimately, the 3D printed composite material exhibits good uniformity, ensuring printability and constructability, and providing a reference for the high-value and high-quantity resource utilization of steel slag and construction waste.

[0048] A further concept of this application is to optimize the stirring method for preparing composite materials in order to increase the uniformity of the system and ensure printing continuity.

[0049] The technical solutions of the present invention will be described in detail below with reference to specific embodiments, so that those skilled in the art can better understand and implement the technical solutions of the present invention, but the present invention is not limited to the scope of the examples described.

[0050] In the following examples, the cement used is PO 52.5 ordinary Portland cement; the water-reducing agent is a commercially available powder, the main component of which is sulfonated melamine; the thickener is a mixture of polyacrylamide and cellulose ether in a mass ratio of 3:7.

[0051] Example 1

[0052] The steel slag-construction waste-based composite material for building 3D printing provided in this embodiment is composed of the following parts by weight:

[0053] 40 portions of gel material;

[0054] 35 parts recycled aggregate;

[0055] 0.6 parts of reinforcing material;

[0056] 13 parts water.

[0057] The gel material is composed of the following components by weight: 28 parts mineralized steel slag powder, 28 parts construction waste powder, 30 parts cement, and 2 parts silica fume. The particle size of the mineralized steel slag powder and construction waste powder is less than 0.075 mm. In this example, the particle size distribution curves of the selected mineralized steel slag powder and construction waste powder are shown below. Figure 1 As shown.

[0058] The recycled aggregate consists of the following components by weight: 24 parts of mineralized steel slag sand (0.15–0.3 mm), 35 parts of mineralized steel slag sand (0.3–0.6 mm), 10 parts of construction waste sand (0.15–0.3 mm), and 15 parts of construction waste sand (0.3–0.6 mm).

[0059] Mineralized steel slag powder is obtained by grinding and crushing steel slag after mineralization and curing, and then passing it through a 0.075mm sieve. Mineralized steel slag sand is obtained by grinding and crushing steel slag after mineralization and curing, and then passing it through 0.15mm, 0.3mm and 0.6mm sieves.

[0060] The mineralization curing method is as follows: (1) First, pre-curing is carried out, with the ambient temperature controlled at 15-20℃ and the relative humidity at 60%-75%; (2) The mineralization curing is divided into two stages. The first stage curing temperature is 20℃, the humidity is 70%RH, the CO2 concentration is 20%, the pressure is 40kPa, and the curing time is 2h; the second stage curing temperature is 50℃, the humidity is 95%RH, the CO2 concentration is 40%, the pressure is 0.1MPa, and the curing time is 2h.

[0061] The reinforcing material consists of the following components by weight: 35 parts water-reducing agent, 20 parts thickener, and 30 parts PVA fiber.

[0062] The steel slag-construction waste-based composite material for 3D printing of buildings was prepared by the following method:

[0063] Step S1: Slowly dry mix the weighed cementitious materials and recycled aggregates in a mortar mixer for 60 seconds, and manually mix the reinforcing materials with water to form a mixture.

[0064] Step S2: Continue to stir slowly for 60 seconds. During this period, slowly add 65% of the total volume of the mixture into the mortar mixer. After adding the material, stir quickly for 30 seconds.

[0065] Step S3: Stir slowly for another 30 seconds. During this period, slowly add all the remaining mixture into the mortar mixer. After the addition is complete, continue to stir rapidly for 60 seconds to obtain a steel slag-construction waste-based composite material for 3D printing of buildings.

[0066] Example 2

[0067] The steel slag-construction waste-based composite material for building 3D printing provided in this embodiment is composed of the following parts by weight:

[0068] 42 parts of cementitious material;

[0069] 36 portions of recycled aggregate;

[0070] 0.7 parts of reinforcing material;

[0071] 13 parts water;

[0072] The gel material is composed of the following components by weight: 29 parts mineralized steel slag powder, 30 parts construction waste powder, 31 parts cement and 2 parts silica fume, with the mineralized steel slag powder and construction waste powder having a particle size of less than 0.075 mm.

[0073] The recycled aggregate consists of the following components by weight: 25 parts of mineralized steel slag sand (0.15–0.3 mm), 37 parts of mineralized steel slag sand (0.3–0.6 mm), 11 parts of construction waste sand (0.15–0.3 mm), and 16 parts of construction waste sand (0.3–0.6 mm). The screening of mineralized steel slag powder, mineralized steel slag sand, construction waste powder, and construction waste sand is the same as in Example 1.

[0074] The reinforcing material consists of the following components by weight: 36 parts water-reducing agent, 20 parts thickener, and 31 parts PVA fiber.

[0075] The preparation of the composite material is the same as in Example 1.

[0076] Example 3

[0077] The steel slag-construction waste-based composite material for building 3D printing provided in this embodiment is composed of the following parts by weight:

[0078] 42 parts of cementitious material;

[0079] 38 parts of recycled aggregate;

[0080] 0.6 parts of reinforcing material;

[0081] 14 parts water;

[0082] The gel material is composed of the following components by weight: 30 parts mineralized steel slag powder, 30 parts construction waste powder, 32 parts cement and 3 parts silica fume, with the mineralized steel slag powder and construction waste powder having a particle size of less than 0.075 mm.

[0083] The recycled aggregate consists of the following components by weight: 26 parts of mineralized steel slag sand (0.15–0.3 mm), 38 parts of mineralized steel slag sand (0.3–0.6 mm), 11 parts of construction waste sand (0.15–0.3 mm), and 16 parts of construction waste sand (0.3–0.6 mm). The screening of mineralized steel slag powder, mineralized steel slag sand, construction waste powder, and construction waste sand is the same as in Example 1.

[0084] The reinforcing material consists of the following components by weight: 37 parts water-reducing agent, 21 parts thickener, and 32 parts PVA fiber.

[0085] The preparation of the composite material is the same as in Example 1.

[0086] Example 4

[0087] The steel slag-construction waste-based composite material for building 3D printing provided in this embodiment is composed of the following parts by weight:

[0088] 43 parts of cementitious material

[0089] 38 parts of mixed recycled aggregate

[0090] 0.8 parts of reinforcing material

[0091] 14 parts water

[0092] The gel material is composed of the following components by weight: 30 parts mineralized steel slag powder, 30 parts construction waste powder, 30 parts cement, and 3 parts silica fume. The particle size of the mineralized steel slag powder and construction waste powder is less than 0.075 mm.

[0093] The recycled aggregate consists of the following components by weight: 26 parts of mineralized steel slag sand (0.15–0.3 mm), 38 parts of mineralized steel slag sand (0.3–0.6 mm), 11 parts of construction waste sand (0.15–0.3 mm), and 16 parts of construction waste sand (0.3–0.6 mm). The screening of mineralized steel slag powder, mineralized steel slag sand, construction waste powder, and construction waste sand is the same as in Example 1.

[0094] The reinforcing material consists of the following components by weight: 37 parts water-reducing agent, 21 parts thickener, and 32 parts PVA fiber.

[0095] The preparation of the composite material is the same as in Example 1.

[0096] Example 5

[0097] The steel slag-construction waste-based composite material for building 3D printing provided in this embodiment is composed of the following parts by weight:

[0098] 43 parts of cementitious material;

[0099] 38 parts of recycled aggregate;

[0100] 0.7 parts of reinforcing material;

[0101] 13 parts water;

[0102] The gel material is composed of the following components by weight: 31 parts mineralized steel slag powder, 30 parts construction waste powder, 30 parts cement, and 2 parts silica fume. The particle size of the mineralized steel slag powder and construction waste powder is less than 0.075 mm.

[0103] The recycled aggregate consists of the following components by weight: 26 parts of mineralized steel slag sand (0.15–0.3 mm), 39 parts of mineralized steel slag sand (0.3–0.6 mm), 11 parts of construction waste sand (0.15–0.3 mm), and 16 parts of construction waste sand (0.3–0.6 mm). The screening of mineralized steel slag powder, mineralized steel slag sand, construction waste powder, and construction waste sand is the same as in Example 1.

[0104] The reinforcing material consists of the following components by weight: 36 parts water-reducing agent, 21 parts thickener, and 33 parts PVA fiber.

[0105] The preparation of the composite material is the same as in Example 1.

[0106] Example 6

[0107] The steel slag-construction waste-based composite material for building 3D printing provided in this embodiment is composed of the following parts by weight:

[0108] 44 parts of cementitious material;

[0109] 39 portions of recycled aggregate;

[0110] 0.7 parts of reinforcing material;

[0111] 13 parts water;

[0112] The gel material is composed of the following components by weight: 31 parts mineralized steel slag powder, 32 parts construction waste powder, 32 parts cement, and 2 parts silica fume. The particle size of the mineralized steel slag powder and construction waste powder is less than 0.075 mm.

[0113] The recycled aggregate consists of the following components by weight: 25 parts of mineralized steel slag sand (0.15–0.3 mm), 37 parts of mineralized steel slag sand (0.3–0.6 mm), 12 parts of construction waste sand (0.15–0.3 mm), and 17 parts of construction waste sand (0.3–0.6 mm). The screening of mineralized steel slag powder, mineralized steel slag sand, construction waste powder, and construction waste sand is the same as in Example 1.

[0114] The reinforcing material consists of the following components by weight: 37 parts water-reducing agent, 21 parts thickener, and 34 parts PVA fiber.

[0115] The preparation of the composite material is the same as in Example 1.

[0116] Example 7

[0117] The steel slag-construction waste-based composite material for building 3D printing provided in this embodiment is composed of the following parts by weight:

[0118] 44 parts of cementitious material;

[0119] 40 parts of recycled aggregate;

[0120] 0.7 parts of reinforcing material;

[0121] 14 parts water;

[0122] The gel material is composed of the following components by weight: 31 parts mineralized steel slag powder, 31 parts construction waste powder, 33 parts cement, and 3 parts silica fume. The particle size of the mineralized steel slag powder and construction waste powder is less than 0.075 mm.

[0123] The recycled aggregate consists of the following components by weight: 27 parts of mineralized steel slag sand (0.15–0.3 mm), 40 parts of mineralized steel slag sand (0.3–0.6 mm), 11 parts of construction waste sand (0.15–0.3 mm), and 16 parts of construction waste sand (0.3–0.6 mm). The screening of mineralized steel slag powder, mineralized steel slag sand, construction waste powder, and construction waste sand is the same as in Example 1.

[0124] The reinforcing material consists of the following components by weight: 39 parts water-reducing agent, 22 parts thickener, and 35 parts PVA fiber.

[0125] The preparation of the composite material is the same as in Example 1.

[0126] Example 8

[0127] The steel slag-construction waste-based composite material for building 3D printing provided in this embodiment is composed of the following parts by weight:

[0128] 45 parts of cementitious material;

[0129] 40 parts of recycled aggregate;

[0130] 0.8 parts of reinforcing material;

[0131] 14 parts water;

[0132] The gel material consists of the following components by weight: 32 parts mineralized steel slag powder, 32 parts construction waste powder, 33 parts cement, and 3 parts silica fume. The particle size of the mineralized steel slag powder and construction waste powder is less than 0.075 mm. The recycled aggregate consists of the following components by weight: 28 parts mineralized steel slag sand (0.15–0.3 mm), 42 parts mineralized steel slag sand (0.3–0.6 mm), 12 parts construction waste sand (0.15–0.3 mm), and 18 parts construction waste sand (0.3–0.6 mm). The screening of the mineralized steel slag powder, mineralized steel slag sand, construction waste powder, and construction waste sand is the same as in Example 1.

[0133] The reinforcing material consists of the following components by weight: 40 parts water-reducing agent, 22 parts thickener, and 35 parts PVA fiber.

[0134] The preparation of the composite material is the same as in Example 1.

[0135] Comparative Example 1

[0136] The composite material for building 3D printing provided in this comparative example differs from that in Example 8 in that the mineralization process is omitted, i.e., steel slag powder and steel slag sand are used directly.

[0137] Comparative Example 2

[0138] The composite material for building 3D printing provided in this comparative example differs from that in Example 8 in that the mixture is added to the mortar mixer all at once during the preparation of the composite material.

[0139] Comparative Examples 3-4

[0140] The composite materials for building 3D printing provided in Comparative Examples 3-4 differ from those in Example 8 in that the ratio of construction waste sand and mineralized steel slag sand is adjusted, as detailed in Table 1.

[0141] Comparative Example 5

[0142] The composite material for building 3D printing provided in this comparative example differs from that in Example 8 in that 64 parts of mineralized steel slag powder are used in the gel material instead of 32 parts of mineralized steel slag powder and 32 parts of construction waste powder.

[0143] Comparative Example 6

[0144] The composite material for building 3D printing provided in this comparative example differs from that in Example 8 in that 64 parts of construction waste powder are used in the gel material instead of 32 parts of mineralized steel slag powder and 32 parts of construction waste powder.

[0145] Table 1 shows the formulations of recycled aggregate in the composite materials of Comparative Examples 3-4.

[0146]

[0147] Performance testing

[0148] The composite materials used for building 3D printing in Examples 1-8 and Comparative Examples 1-6 were tested for building 3D printing performance, and the results are shown in Table 2.

[0149] 1. For mechanical property testing, the printed specimens are cut to 40×40×160mm and then tested according to the Cement Mortar Strength Test Method (ISO Method) for flexural strength in the Y and Z directions, and compressive strength in the X, Y, and Z directions. A schematic diagram of the cut printed specimen is shown below. Figure 2 .

[0150] 2. Printing performance was evaluated using a printing deformation rate system. The test method involved using a 20mm diameter circular nozzle, a printing speed of 6400mm / min, and printing 10 layers. The evaluation method was as follows: Figure 3 As shown, the standard height (HS) for printing is 100mm. Measure the maximum length (L), minimum length (l), height (H), maximum width (W), and minimum width (w) of the specimen, and calculate the deformation rate using the following formula:

[0151]

[0152] 3. The setting time and fluidity shall be in accordance with JGJ / T 70-2009 "Standard for Test Methods of Basic Performance of Building Mortar" and GB / T 2419-2005 "Method for Determination of Flowability of Cement Mortar".

[0153] Table 2 shows the performance test results of the composite materials in Examples 1-8 and Comparative Examples 1-6.

[0154]

[0155] As shown in Table 2, the setting time of the composite material in the representative embodiment of the present invention can be controlled within 30 to 110 minutes. Under the material compatibility specified in this system, the structure can be constructed quickly, and while having excellent fluidity, the printing performance and construction performance of the material are improved, and the mechanical properties of the material are guaranteed.

[0156] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

[0157] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

Claims

1. A composite material for architectural 3D printing, characterized in that: By weight, the composite material comprises 35-55 parts of gel material, 30-45 parts of recycled aggregate, and 0.2-1 parts of reinforcing material; Wherein: by weight, the gel material comprises 28-32 parts of mineralized steel slag powder, 28-32 parts of construction waste powder, 30-33 parts of cement, and 2-3 parts of silica fume; By weight, the recycled aggregate comprises 24-28 parts of mineralized steel slag sand (0.15-0.3mm), 35-42 parts of mineralized steel slag sand (0.3-0.6mm), 10-12 parts of construction waste sand (0.15-0.3mm), and 15-18 parts of construction waste sand (0.3-0.6mm). The particle size of the mineralized steel slag sand is larger than that of the mineralized steel slag powder, and the particle size of the construction waste sand is larger than that of the construction waste powder. The mineralized steel slag powder and mineralized steel slag sand are obtained by grinding and crushing steel slag after it has been mineralized and cured.

2. The composite material for architectural 3D printing according to claim 1, characterized in that: The reinforcing material includes water-reducing agents, thickeners, and fibers; and / or, The composite material also contains water, and the amount of water is 10 to 20 parts.

3. The composite material for architectural 3D printing according to claim 2, characterized in that: The reinforcing material is a combination of water-reducing agent, thickener, and fiber in a mass ratio of 35~40:20~22:30~35; and / or, The fiber is PVA fiber.

4. The composite material for architectural 3D printing according to any one of claims 1 to 3, characterized in that: The composite material comprises 38-48 parts of gel material, 33-42 parts of recycled aggregate, 0.5-1 parts of reinforcing material, and 10-15 parts of water.

5. The composite material for architectural 3D printing according to claim 1, characterized in that, The particle size of the construction waste powder is 0.006 to 60 micrometers, and the particle size of the mineralized steel slag powder is 0.01 to 75 micrometers.

6. The composite material for architectural 3D printing according to claim 1, characterized in that, The method for mineralization maintenance includes the following steps: (1) Pre-curing the steel slag, with the ambient temperature controlled at 10~25℃ and the relative humidity at 55~80%; (2) The steel slag after pre-curing is subjected to first-stage curing and second-stage curing in sequence. The curing conditions for the first stage are: curing temperature of 15~25℃, humidity of 65~75%RH, CO2 concentration of 10~30%, and pressure of 35~45kPa. The curing conditions for the second stage are: curing temperature of 45~55℃, humidity of 90~98%RH, CO2 concentration of 35~45%, and pressure of 0.05~0.15MPa.

7. A method for preparing a composite material for architectural 3D printing according to any one of claims 1 to 6, characterized in that, The preparation method includes the following steps: Step S1: Mix the gel material and recycled aggregate to obtain a mixed dry material; Step S2: Mix the reinforcing material and water to obtain a mixture, and then add 60-70% of the mixture to the dry material and stir evenly to obtain a premix. Step S3: Add the remaining mixture to the premix and stir evenly to obtain the composite material mixture.

8. A 3D printed building structure, characterized in that: The composite material for building 3D printing prepared by any one of claims 1 to 6 or the preparation method of claim 7 is prepared and then 3D printed.

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