Solid waste-based 3D printing material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of industrial solid waste resource utilization, and particularly relates to a solid waste based 3D printing material and a preparation method and application thereof. The solid waste-based 3D printing material comprises the following components: ordinary Portland cement, sulphoaluminate cement, circulating fluidized bed fly ash, circulating fluidized bed slag, ground blast furnace slag, sandstone and water. According to the solid waste-based 3D material, cement is partially replaced by circulating fluidized bed fly ash and slag, waste is turned into wealth, and the utilization rate of industrial solid waste is increased. The solid waste-based 3D printing material disclosed by the invention has very good flowability, does not have a blocking phenomenon in a printing process, can quickly stand without collapsing or flowing on a concrete building layer after printing, also has certain supporting strength, and can support printing of the next layer, so that the continuity of concrete 3D printing is ensured, and the 3D printing efficiency is improved. The method can be widely applied to the field of 3D printing buildings.

Description

Technical Field

[0001] The present invention belongs to the technical field of industrial solid waste resource utilization, and particularly relates to a solid waste-based 3D printing material, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, with the development of science and technology, all industries are developing towards the direction of intelligence and informatization, and additive manufacturing technology has become the choice of many industries. Cement-based additive manufacturing technology, also known as 3D printing concrete technology, "3D stereoscopic printing technology" or "rapid prototyping technology", is a three-dimensional object printing technology developed on the basis of 3D printing technology, which is based on a digital model and uses cementitious materials such as concrete that can be bonded to stack layers by layers through a printing bar. Compared with traditional architecture, the advantages of 3D printing architecture are as follows: fast speed, no need to use formwork, which can greatly save costs; no need for a large number of construction workers, which greatly improves production efficiency; it has the characteristics of green, low-carbon and environmental protection.

[0003] 3D printing technology is different from traditional construction methods. For freshly mixed concrete slurry, to meet the requirements of 3D printing, specific performance requirements must be met. First is extrudability. In 3D printing concrete technology, the concrete slurry is extruded through the nozzle at the front end of the extrusion device for printing, so the particle size in the formulated slurry is determined by the size of the nozzle orifice and must not be blocked during the printing process to ensure the smooth extrusion of the slurry. Secondly, the printing material should have good cohesiveness. Good cohesiveness can ensure that the printing material will not be interrupted due to the properties of the slurry itself during the extrusion process through the nozzle, strengthen the bond between printing layers, and weaken the negative impact of the printing layer. Finally are mechanical properties and durability. 3D printing requires the printing material to have good strength, stiffness, good crack resistance and plasticity. Currently, the main 3D printing materials are concrete materials. Although they have good compressive capacity, their tensile and shear properties are poor, and the materials are prone to brittle failure under the action of force. Adding fibers to the printing material and reinforcing the printed structure can well improve the mechanical properties of the printing material. Durability is also a key performance of 3D printing concrete. For example, temperature, external force, chemical action, etc. will all affect durability, thus affecting the safety and service life of 3D printing building structures. Currently, additives are often added to concrete or other cementitious materials with good performance are used to improve its performance to meet the durability requirements of the printing material.

[0004] Circulating fluidized bed fly ash and slag are by-products of circulating fluidized bed combustion. With the large-scale application of clean combustion technology for circulating fluidized bed boilers, the treatment of the discharged circulating fluidized bed ash and slag has become an urgent problem to be solved. According to statistics, the annual discharge of circulating fluidized bed ash and slag in China is nearly 120 million tons, but the utilization rate is less than 15%. The main treatment method is landfill, and a large amount of stacking seriously threatens the ecological environment. It is urgent to solve the problems of treatment and utilization of circulating fluidized bed ash and slag. Circulating fluidized bed ash and slag not only have pozzolanic effect and hydraulicity, but also have great potential for preparing cementitious materials. Using it to prepare 3D printing materials can greatly utilize it and reduce its environmental pollution. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to overcome the above-mentioned deficiencies existing in the prior art, and provide a solid waste-based 3D printing material, its preparation method and application. The solid waste-based 3D printing material provided by the present invention has good fluidity, can stand quickly after printing without collapsing or flowing, and at the same time has a certain supporting strength to support the printing of its subsequent layers. In addition, the solid waste-based 3D printing concrete provided by the present invention has excellent mechanical properties, and uses industrial solid waste, which can save costs and protect the environment.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] In the first aspect, the present invention provides a solid waste-based 3D printing material, which includes the following components: cementitious material, industrial solid waste, mineral admixture, sand and gravel, and water.

[0008] In an optional embodiment, the cementitious material is ordinary Portland cement and calcium sulfoaluminate cement. Due to the characteristics of long hydration time and slow setting time of ordinary Portland cement, it cannot meet the requirements of 3D printing. Calcium sulfoaluminate cement has the characteristics of early strength, rapid hardening and high strength. Its main mineral component is anhydrous calcium sulfoaluminate, and its hydration speed is fast, which can quickly react with gypsum to generate ettringite and alumina gel, thereby shortening the setting time of the composite system. Incorporating calcium sulfoaluminate cement as a setting regulator into the composite material can make the composite material have good printing performance.

[0009] In an optional embodiment, the industrial solid waste is circulating fluidized bed fly ash and circulating fluidized bed slag. A large amount of anhydrite and unreacted active calcium oxide are contained in circulating fluidized bed fly ash and circulating fluidized bed slag, which can react with the calcined clay component therein to generate calcium silicate hydrate and ettringite, supporting the early strength of the material. Therefore, circulating fluidized bed ash and slag not only have pozzolanic activity and hydraulicity, but also have great potential for preparing cementitious materials. At the same time, in the present invention, circulating fluidized bed ash and slag are used to replace ordinary Portland cement, turning waste into treasure and greatly reducing the cost of the 3D printing material of the present invention.

[0010] In an alternative embodiment, the mineral admixture is ground granulated blast furnace slag. Ground granulated blast furnace slag is a solid waste generated during the process of smelting pig iron. Its main chemical components are similar to those of cement clinker, containing hydration active components such as dicalcium silicate and having high hydration activity. Incorporating ground granulated blast furnace slag, a mineral admixture, into the 3D printing material can achieve good filling effect and pozzolanic effect, effectively improve the workability of the 3D printing material, enhance its mechanical properties, and also play a role in saving resources and protecting the environment.

[0011] In an alternative embodiment, the sand and gravel is river sand.

[0012] In an alternative embodiment, the weight percentages of each component are as follows: 4.7% - 12.6% ordinary Portland cement, 6.3% - 12.5% sulfoaluminate cement, 6.3% - 8.4% circulating fluidized bed fly ash, 7.9% - 12.5% circulating fluidized bed slag, 1.5% - 2% ground granulated blast furnace slag, 42% - 53% sand and gravel, and 14.1% - 16.6% water.

[0013] In an alternative embodiment, the specific surface area of the ordinary Portland cement is 300 - 400 m 2 / kg, the specific surface area of the circulating fluidized bed fly ash is 400 - 500 m 2 / kg, and the specific surface area of the ground granulated blast furnace slag is 400 - 500 m 2 / kg.

[0014] In an alternative embodiment, the CaO content in the circulating fluidized bed fly ash and the circulating fluidized bed slag does not exceed 22%, and the SO3 content does not exceed 12%.

[0015] In an alternative embodiment, D10 of the circulating fluidized bed slag is 1 - 3 μm, D50 is 20 - 30 μm, and D90 is 58 - 62 μm.

[0016] In an alternative embodiment, the fineness modulus of the river sand is 2.5 - 2.8, and the mud content is 2% - 4%.

[0017] In a second aspect, the present invention provides a preparation method of the solid waste-based 3D printing material described in the first aspect, including the following steps:

[0018] Step 1: Mix the cementitious material, industrial solid waste, and mineral admixture evenly to obtain mixture A;

[0019] Step 2: Add water to mixture A to obtain mixture B;

[0020] Step 3: Add sand and gravel to mixture B to obtain the solid waste-based 3D printing material.

[0021] In a third aspect, the present invention provides an application of the solid waste-based 3D printing material described in the first aspect, which is used in the field of 3D printing construction.

[0022] In an optional embodiment, the parameters of the 3D printing are as follows: the printing speed is 50 - 125 mm / s, the vertical lifting speed is 8 - 12 mm / s, the nozzle height is 15 mm, and the single-layer printing cycle is 5 - 10 min.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] In the present invention, the action mechanism of the solid waste-based 3D printing material system includes: ① The hydration of cement, where C3S and C2S in portland cement react with water to form C-S-H gel (hydrated calcium silicate) and calcium hydroxide (CH), providing early strength. Among them, CH raises the pH of the system, providing necessary conditions for the activation of the activity of slag powder and circulating fluidized bed ash. ② The alkali activation reaction of slag powder: The CaO-SiO2-Al2O3 vitreous body in slag dissociates in an alkaline environment, releasing Ca 2+ , [SiO4] 4- and [AlO4] 5- plasma ions, undergoing secondary hydration. The active SiO2 reacts with CH to form additional C-S-H gel, enhancing the later strength; Al 3+ participates in the formation of AFt (ettringite) or AFm (monosulfate calcium sulfoaluminate), optimizing the microstructure. ③ The pozzolanic reaction of circulating fluidized bed ash: The amorphous SiO2 and Al2O3 in circulating fluidized bed ash gradually dissolve under alkaline conditions. The dissolved SiO2 reacts with CH to form C-S-H gel, and Al2O3 participates in the formation of aluminate phase, thereby providing the strength of the system.

[0025] In the present invention, the coordination effect among the solid waste-based 3D printing material systems is as follows: Cement provides early strength and an alkaline environment; slag powder continues to hydrate in the middle and late stages, further increasing the strength of the system; the pozzolanic reaction of circulating fluidized bed ash further fills the pores, enhancing the durability of the system.

[0026] The solid waste-based 3D printing material provided by the present invention has good printability. During the printing process, the slurry can be smoothly extruded from the nozzle without nozzle blockage and print bar breakage. The printing material has good constructability. After printing, the concrete building layer can quickly stand without collapsing or flowing, and also has a certain supporting strength to support the printing of the next layer, thus ensuring the continuity of concrete 3D printing.

[0027] The preparation method of the solid waste-based 3D printing material of the present invention has the following advantages: low energy consumption and material consumption, no need to add chemical aids such as water reducers and accelerators, which is conducive to cost reduction; high utilization rate of industrial solid waste, effectively reducing CO2 emissions, which is conducive to environmental protection; simple technological process, easy to realize industrial production, which is conducive to rapid popularization and application; can realize the high-value utilization of solid waste, contributing to the recycling and sustainable development of resources; having good environmental benefits and broad market prospects, and being a new technology with potential in future development. Therefore, this method is an innovative technology with broad application prospects and significant social and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is the preparation flow chart of the solid waste-based 3D printing material in the present invention.

[0029] Figure 2 It is the printing test piece diagram of Examples 1-6 in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure content of the present invention more thorough and comprehensive.

[0031] In the embodiments of the present invention, the cementitious material is composed of 42.5-grade ordinary Portland cement and 42.5-grade sulfoaluminate cement.

[0032] In the embodiments of the present invention, the specific surface area of the ordinary Portland cement is 300-400 m 2 / kg, the specific surface area of the circulating fluidized bed fly ash is 400-500 m 2 / kg, and the specific surface area of the ground granulated blast furnace slag is 400-500 m 2 / kg.

[0033] In the embodiments of the present invention, the CaO content in the circulating fluidized bed fly ash and the circulating fluidized bed slag does not exceed 22%, and the SO3 content does not exceed 12%.

[0034] In the embodiments of the present invention, the D50 of the circulating fluidized bed fly ash is 17.88 μm, the D50 of the ordinary Portland cement is 15.61 μm, and the D50 of the ground granulated blast furnace slag powder is 14.26 μm. In order to make the powder have good particle gradation and improve the strength and stability of the material, the circulating fluidized bed slag is ground for 30 minutes, and its D50 is 25.87 μm.

[0035] In the embodiments of the present invention, the sand and gravel is river sand. Preferably, river sand with a particle size less than 4.75 mm is used as the fine aggregate of the 3D printing material. According to GB / T 14684-2022 "Sand for construction", its fineness modulus is 2.54 and the mud content is 2.4%, belonging to medium sand in Zone 2.

[0036] Example 1

[0037] The solid waste-based 3D printing material is prepared from the following components by weight: 1.5 kg of ordinary Portland cement, 1 kg of sulphoaluminate cement, 1 kg of circulating fluidized bed fly ash, 1.25 kg of circulating fluidized bed slag, 0.25 kg of ground granulated blast-furnace slag powder, 8.3 kg of well-graded river sand and 2.3 kg of water.

[0038] Preparation method of the solid waste-based 3D printing material: Add the formulated amounts of ordinary Portland cement, sulphoaluminate cement, circulating fluidized bed fly ash, circulating fluidized bed slag and ground granulated blast-furnace slag powder into a stirrer for premixing to obtain a mixed material A. Then add the formulated amount of water into the stirrer and stir for a certain time to obtain a mixed material B. Add the formulated amount of river sand into the mixed material B and continue to stir evenly to obtain the solid waste-based 3D printing material. Pump the prepared solid waste-based 3D printing material into a concrete 3D printer through a pump and start the concrete 3D printing. Set the 3D printing parameters: the printing speed is 50 - 125 mm / s, the vertical lifting speed is 8 - 12 mm / s, the nozzle height is 15 mm, and the single-layer printing cycle is 5 - 10 min.

[0039] Example 2

[0040] The solid waste-based 3D printing material is prepared from the following components by weight: 1.8 kg of ordinary Portland cement, 1.2 kg of sulphoaluminate cement, 1.2 kg of circulating fluidized bed fly ash, 1.5 kg of circulating fluidized bed slag, 0.3 kg of ground granulated blast-furnace slag powder, 7.5 kg of well-graded river sand and 2.52 kg of water.

[0041] The preparation method of the solid waste-based 3D printing material is the same as that of Example 1.

[0042] Example 3

[0043] The solid waste-based 3D printing material is prepared from the following components by weight: 2.1 kg of ordinary Portland cement, 1.4 kg of sulphoaluminate cement, 1.4 kg of circulating fluidized bed fly ash, 1.75 kg of circulating fluidized bed slag, 0.35 kg of ground granulated blast-furnace slag powder, 7 kg of well-graded river sand and 2.66 kg of water.

[0044] The preparation method of the solid waste-based 3D printing material is the same as that of Example 1.

[0045] Example 4

[0046] The solid waste-based 3D printing material is prepared from the following components by weight: 0.75 kg of ordinary Portland cement, 1.5 kg of sulfoaluminate cement, 1 kg of circulating fluidized bed fly ash, 1.5 kg of circulating fluidized bed slag, 0.25 kg of ground granulated blast furnace slag powder, 8.3 kg of well-graded river sand, and 2.4 kg of water.

[0047] The preparation method of the solid waste-based 3D printing material is the same as that of Example 1.

[0048] Example 5

[0049] The solid waste-based 3D printing material is prepared from the following components by weight: 0.9 kg of ordinary Portland cement, 1.8 kg of sulfoaluminate cement, 1.2 kg of circulating fluidized bed fly ash, 1.8 kg of circulating fluidized bed slag, 0.3 kg of ground granulated blast furnace slag powder, 7.5 kg of well-graded river sand, and 2.64 kg of water.

[0050] The preparation method of the solid waste-based 3D printing material is the same as that of Example 1.

[0051] Example 6

[0052] The solid waste-based 3D printing material is prepared from the following components by weight: 1.05 kg of ordinary Portland cement, 2.1 kg of sulfoaluminate cement, 1.4 kg of circulating fluidized bed fly ash, 2.1 kg of circulating fluidized bed slag, 0.35 kg of ground granulated blast furnace slag powder, 7 kg of well-graded river sand, and 2.8 kg of water.

[0053] The preparation method of the solid waste-based 3D printing material is the same as that of Example 1.

[0054] Performance test:

[0055] 1. Fluidity

[0056] Fluidity, as an important parameter of 3D printing materials, is directly related to the extrudability of the materials. If the fluidity is too large, the material cannot be stacked; conversely, it will cause blockage of the 3D printing conveying pipeline. Therefore, 3D printing concrete requires appropriate fluidity. The operation is carried out for measurement with reference to GB / T 2419-2005 "Test Method for Fluidity of Cement Mortar".

[0057] 2. Extrudability

[0058] Extrudability is the ability to ensure that the printable concrete does not tear or interrupt when extruded at the printing nozzle. The test method is as follows: control the extrusion speed of the printing nozzle screw to be 1 r / s, and extrude a concrete layer with a length of 300 mm. When the extruded concrete layer is significantly torn or interrupted, the extrudability test ends.

[0059] 3. Buildability

[0060] 3D printing materials should not only be able to be extruded, but also possess the ability to print continuously. Buildability is a characterization of the continuous printing ability of 3D printed concrete to support its own weight. The test method is as follows: Design a printed specimen with dimensions of 400mm×200mm×100mm in length, width and height. After printing, measure its maximum width Wmax, minimum width Wmin, maximum length Lmax, minimum length Lmin and vertical height H, and reflect its buildability through the structural deformation rate.

[0061] 4. Ultimate open time

[0062] The open time is the time period during which the fresh mixture exhibits acceptable extrudability. The test method is as follows: Control the extrusion speed of the printing nozzle screw to be 1 r / s, extrude a concrete layer with a length of 300 mm, and the time interval between each extrusion is 10 min. Determine the open time when the extruded concrete layer is significantly torn or interrupted.

[0063] 5. Mechanical properties

[0064] Due to the layer-by-layer construction process of 3D printing, gaps will appear between concrete layers, resulting in different stress magnitudes in different directions of the printed building. The existence of interlayer gaps is the reason for the anisotropy of 3D printed concrete. The test method is as follows: Three-way flexural strength: Cut the printed specimen according to the size of 40mm×40mm×160mm; Three-way compressive strength: Cut the printed specimen according to the size of 40mm×40mm×40mm. Operate and measure with reference to GB / T 17671-2021 "Test Method for the Strength of Cement Mortar".

[0065] Table 1 shows the performance comparison of waste-based 3D printing materials in Examples 1-6

[0066]

[0067] It can be seen from Table 1 that the fluidity of the waste-based 3D printing materials prepared in Examples 1-6 of the present invention is between 210 and 230 mm, the printability and buildability are excellent, the open time is greater than or equal to 30 min, and the structural deformation rate is less than 6%. The waste utilization rate of the waste-based 3D printing materials prepared by the present invention is 50% - 60%, and it has good printability, buildability and good mechanical properties.

[0068] The above are only examples for better explaining the present invention, and are not intended to limit it. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention shall fall within the scope covered by the present invention.

Claims

1. A solid waste-based 3D printing material, characterized in that It includes the following components: cementitious materials, industrial solid wastes, mineral admixtures, sand and gravel, and water.

2. The solid waste-based 3D printing material according to claim 1, characterized in that, The cementitious materials are ordinary Portland cement and sulphoaluminate cement, the industrial solid wastes are circulating fluidized bed fly ash and circulating fluidized bed slag, the mineral admixture is ground granulated blast furnace slag, and the sand and gravel are river sand.

3. The solid waste-based 3D printing material according to claim 2, wherein, The weight percentages of each component are as follows: 4.7% - 12.6% ordinary Portland cement, 6.3% - 12.5% sulphoaluminate cement, 6.3% - 8.4% circulating fluidized bed fly ash, 7.9% - 12.5% circulating fluidized bed slag, 1.5% - 2% ground granulated blast furnace slag, 42% - 53% sand and gravel, and 14.1% - 16.6% water.

4. The solid waste-based 3D printing material according to claim 2, wherein The specific surface area of the ordinary Portland cement is 300 - 400 m 2 / kg, the specific surface area of the circulating fluidized bed fly ash is 400 - 500 m 2 / kg, and the specific surface area of the ground granulated blast furnace slag is 400 - 500 m 2 / kg.

5. The solid waste-based 3D printing material according to claim 2, wherein, The CaO content in the circulating fluidized bed fly ash and circulating fluidized bed slag does not exceed 22%, and the SO3 content does not exceed 12%.

6. The solid waste-based 3D printing material according to claim 2, wherein The D10 of the circulating fluidized bed slag is 1 - 3μm, the D50 is 20 - 30μm, and the D90 is 58 - 62μm.

7. The solid waste-based 3D printing material according to claim 2, wherein, The fineness modulus of the river sand is 2.5 - 2.8, and the mud content is 2% - 4%.

8. The preparation method of the solid waste-based 3D printing material according to any one of claims 1 to 7, characterized in that, It includes the following steps: Step 1: Mix the cementitious materials, industrial solid wastes, and mineral admixtures evenly to obtain mixture A; Step 2: Add water to mixture A to obtain mixture B; Step 3: Add sand and gravel to mixture B to obtain the solid waste-based 3D printing material.

9. Use of the solid waste-based 3D printing material according to any one of claims 1 to 7, characterized in that, It is used in the field of 3D printing for construction.

10. The application of the solid waste-based 3D printing material according to claim 9, characterized in that, The parameters of the 3D printing are as follows: the printing speed is 50 - 125mm / s, the vertical lifting speed is 8 - 12mm / s, the nozzle height is 15mm, and the single-layer printing cycle is 5 - 10min.

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