CN114988787B - A preparation method of cement-based toughened material based on 3D coaxial printing - Google Patents

Abstract

The invention relates to the technical field of advanced preparation of building materials, in particular to a method for preparing cement-based toughened materials based on 3D coaxial printing, including raw material preparation and processing, printing slurry preparation, coaxial printing platform construction, toughening Printing and maintenance hydration of cement-based materials; by integrating the toughening mechanism of micro-interface polymers, the precise construction of multi-scale bionic structures and the regulation of toughening properties have been realized. A new type of cement-based engineering material with high strength and high toughness has been prepared, which solves the bottleneck problem of mutual exclusion of strength and toughness of cement-based materials. Therefore, the risk ability of the structure to resist disasters is improved, the long-term cooperative work of reinforced concrete is guaranteed, and the low energy consumption and green development of the civil engineering field are promoted.

Description

A preparation method of cement-based toughened material based on 3D coaxial printing

technical field

The invention relates to the technical field of advanced preparation of building materials, in particular to a preparation method of a cement-based strengthening and toughening material based on 3D coaxial printing.

Background technique

Traditional cement-based materials have disadvantages such as low tensile strength, insufficient toughness, and difficulty in controlling the crack width after cracking. Therefore, traditional cement-based materials are prone to unpredictable brittle failure behaviors under the impact of earthquakes and explosions. And there is a potential risk of triggering the failure of building structural components or overall collapse and damage, which brings huge challenges to the safety of people's lives and property and the city's ability to resist disasters. The main reason for brittle failure is the highly disordered internal microstructure and the large number of defects such as weak interfaces and microcracks.

Architectural 3D printed cement-based materials also have the above-mentioned insufficient toughness problems, which are caused by insufficient interlayer bond strength, poor microstructure order, and a large number of weak interfaces, microcracks and other defects in printed cement-based materials. The application of 3D printing of cement-based materials has been limited to a certain extent, hindering its further development.

Therefore, for cement-based materials, it is necessary to develop a high-strength, high-toughness 3D printing preparation method to solve the key scientific problems of weak interfaces between layers, disordered structure and brittle quality in current engineering materials.

Contents of the invention

In order to solve the problems raised in the above-mentioned background technology, the present invention provides a method for preparing cement-based strengthening and toughening materials based on 3D coaxial printing to realize simultaneous enhancement of the strength and toughness of cement-based materials.

To achieve the above object, the present invention provides the following technical solutions:

A method for preparing a cement-based toughening material based on 3D coaxial printing, characterized in that it comprises the following steps:

Step 1, raw material preparation and processing

The raw materials used in the inner shaft are ordinary portland cement, retarder, water reducing agent and plasticizer, and the inner shaft raw material is refined by ball milling, and the inner shaft raw material is prepared into ultra-fine particles with a particle size distribution in the range of 200nm to 10μm. Powder raw material; the raw material used for the outer shaft is an elastic plasticized material and a fiber material, and the elastic plasticized material is an aqueous solution mixed with polyvinyl alcohol, water-based epoxy resin, polyvinylpyrrolidone and polyethylene glycol;

Step 2, printing paste preparation

The inner shaft slurry is prepared in proportion to the ultra-fine powder raw materials that have been refined by ball milling, and then stirred evenly by a high-speed shear mixer at a speed of 3000-5000r/min;

Outer shaft reinforcement slurry: add the fiber material to the aqueous solution of the elastic plasticized material, and stir evenly;

Step 3, coaxial printing platform construction

Using servo motors and high-precision transmission screws, combined with auxiliary components such as space limiters and lifting tables, a three-axis mechanical platform with fast transmission and high-precision positioning functions in the three-axis directions of X, Y, and Z spaces is built. The positioning accuracy is 1-10μm; micro-digital control syringe pump and high-precision pressure controller are used for slurry propulsion and pressure feedback and control; manufacturing coaxial printing nozzles;

Step 4. Printing of strengthened and toughened cement-based materials

Use computer software (CAD, 3DMax, Solidworks, etc.) for structural design, import the processed STL model slice data into the computer numerical control end, the computer transmits the digital signal to the communication board, and connects the control computer (G-Code drive) through the control communication board software), and send ink supply communication commands and printing drive commands simultaneously; based on micro-digital control syringe pumps and high-precision pressure controllers, after the coaxial ink supply communication commands are issued, open the gas electromagnetic control valves of different channels to form internal and external pipelines Printable pressurized slurry, and then the slurry is extruded on demand, quantitatively and uniformly through the coaxial printing needle, and finally forms a rigid-soft two-phase interlaced "brick-mud" layered cement through layer-by-layer deposition base structure;

Step five, maintain hydration

The printed cement-based material is cured under standard conditions, and finally forms a cement-based material with high strength and high toughness.

Further, in step one, the retarder is phosphate and alcohols; the water reducer is polycarboxylate and lignosulfonate; the plasticizer is polyvinyl alcohol and fatty acid ester.

Further, in step one, the fiber material is glass fiber and carbon fiber.

Further, in step 2, the ratio of the superfine powder raw materials is 50-70wt% of ordinary portland cement, 1-3wt% of setting retarder, 0.5-2wt% of water reducing agent, and 2-5wt% of plasticizer , Water 30-40wt%.

Further, in step 2, the content of the fiber material is 2-5wt%.

Further, in step 3, the coaxial printing nozzle includes an inner nozzle sleeve 1 and an outer nozzle sleeve 2, the inner nozzle sleeve 1 is sleeved inside the outer nozzle sleeve 2, and the inner The layer nozzle sleeve 1 and the outer layer nozzle sleeve 2 are connected by screws 3, and an air pressure sealing ring 4 is installed between the outer wall of the inner layer nozzle sleeve 1 and the inner wall of the outer layer nozzle sleeve 2; The rear end of the layer nozzle sleeve 1 is the inner pipe inlet 101, the front end of the inner layer nozzle sleeve 1 is the inner pipe outlet 103, and the inside of the inner layer nozzle sleeve 1 is the inner layer storage chamber 102; the rear end of the outer nozzle sleeve 2 is the connection end 201, the inner nozzle sleeve 1 is set inside the connection end 201, and the front end of the outer nozzle sleeve 2 is the outlet of the outer pipe 202, the inside of the outer layer nozzle sleeve 2 is an outer layer storage chamber 203, and the outer wall of the outer layer nozzle sleeve 2 is provided with two outer tube feed ports 204 communicating with the outer layer storage chamber 203 .

Further, the air pressure sealing ring 4 is a fluororubber mechanical sealing ring.

Further, in step five, the standard curing conditions are: humidity>95%, temperature 20±2°C.

Compared with prior art, the beneficial effect of the present invention is:

The invention provides a preparation method of cement-based toughening material based on 3D coaxial printing, which realizes the precise construction of multi-scale bionic structures and the regulation of toughening performance by integrating the toughening mechanism of micro-interface polymers. A new type of cement-based engineering material with high strength and high toughness has been prepared, which solves the bottleneck problem of mutual exclusion of strength and toughness of cement-based materials. Therefore, the risk ability of the structure to resist disasters is improved, the long-term cooperative work of steel and concrete is guaranteed, and the low energy consumption and green development in the field of civil engineering are promoted.

The coaxial printing nozzle in the present invention has exquisite structure, uniform and stable material extrusion, convenient use and easy construction of structural units. During the printing process, cement-based paste and polymer paste with good cohesiveness are overlapped to form a complex layered structure. , greatly improving the strength and toughness of cement-based materials, reducing the microscopic cracks and weak interfaces between layers of 3D printed concrete materials, realizing the strengthening and toughening of cement-based materials, and improving the ability of building structures to resist disaster risks and ensuring the reinforcement-concrete Long-term collaborative work and the promotion of low energy consumption and green development in the field of civil engineering are of great significance.

Description of drawings

The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the description, together with the embodiments of the present invention, are used to explain the present invention, and do not constitute a limitation to the present invention. In the attached picture:

Fig. 1 is the structural representation of coaxial printing nozzle in the present invention;

Fig. 2 is a sectional view of the coaxial printing nozzle in the present invention;

Fig. 3 is the cement-based strengthening and toughening material prepared by the preparation method of the present invention;

Fig. 4 is a cube compression test diagram of the cement-based toughened material prepared in the present invention.

As shown in the figure: inner layer nozzle sleeve 1, outer layer nozzle sleeve 2, screw 3, air pressure sealing ring 4, inner pipe inlet 101, inner layer storage chamber 102, inner pipe outlet 103, connection end 201, an outer tube material outlet 202, an outer material storage chamber 203, and an outer tube material inlet 204.

Detailed ways

In order to make the object, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

Example 1

A method for preparing a cement-based toughened material based on 3D coaxial printing, characterized in that it comprises the following steps:

Step 1, raw material preparation and processing

The raw materials used in the inner shaft are ordinary portland cement, retarder, water reducing agent and plasticizer, and the inner shaft raw material is refined by ball milling, and the inner shaft raw material is prepared into ultra-fine particles with a particle size distribution in the range of 200nm to 10μm. Powder raw material; the raw material used for the outer shaft is an elastic plasticized material and a fiber material, and the elastic plasticized material is an aqueous solution mixed with polyvinyl alcohol, water-based epoxy resin, polyvinylpyrrolidone and polyethylene glycol;

Step 2, printing paste preparation

The inner shaft slurry is prepared in proportion to the ultra-fine powder raw materials that have been refined by ball milling, and then stirred evenly by a high-speed shear mixer at a speed of 3000-5000r/min;

Outer shaft reinforcement slurry: add the fiber material to the aqueous solution of the elastic plasticized material, and stir evenly;

Step 3, coaxial printing platform construction

Using servo motors and high-precision transmission screws, combined with auxiliary components such as space limiters and lifting tables, a three-axis mechanical platform with fast transmission and high-precision positioning functions in the three-axis directions of X, Y, and Z spaces is built. The positioning accuracy is 1-10μm; micro-digital control syringe pump and high-precision pressure controller are used for slurry propulsion and pressure feedback and control; manufacturing coaxial printing nozzles;

Step 4. Printing of strengthened and toughened cement-based materials

Use computer software (CAD, 3DMax, Solidworks, etc.) for structural design, import the processed STL model slice data into the computer numerical control end, the computer transmits the digital signal to the communication board, and connects the control computer (G-Code drive) through the control communication board software), and send ink supply communication commands and printing drive commands simultaneously; based on micro-digital control syringe pumps and high-precision pressure controllers, after the coaxial ink supply communication commands are issued, open the gas electromagnetic control valves of different channels to form internal and external pipelines Printable pressurized slurry, and then the slurry is extruded on demand, quantitatively and uniformly through the coaxial printing needle, and finally forms a rigid-soft two-phase interlaced "brick-mud" layered cement through layer-by-layer deposition base structure;

Step five, maintain hydration

As shown in Figure 3, the printed cement-based material is cured under standard conditions, and finally a cement-based material with high strength and high toughness is formed.

Further, in step one, the retarder is phosphate and alcohols; the water reducer is polycarboxylate and lignosulfonate; the plasticizer is polyvinyl alcohol and fatty acid ester.

Further, in step one, the fiber material is glass fiber and carbon fiber.

Further, in step 2, the ratio of the superfine powder raw materials is 50-70wt% of ordinary portland cement, 1-3wt% of setting retarder, 0.5-2wt% of water reducing agent, and 2-5wt% of plasticizer , Water 30-40wt%.

Further, in step 2, the content of the fiber material is 2-5wt%.

Further, in step three, as shown in Figure 1 and Figure 2, the coaxial printing nozzle includes an inner layer nozzle sleeve 1 and an outer layer nozzle sleeve 2, and the inner layer nozzle sleeve 1 is sleeved on the outer layer Inside the nozzle sleeve 2, the inner layer nozzle sleeve 1 and the outer layer nozzle sleeve 2 are connected by screws 3, and the outer wall of the inner layer nozzle sleeve 1 and the inner wall of the outer layer nozzle sleeve 2 are installed There is an air pressure sealing ring 4; the rear end of the inner nozzle sleeve 1 is the inner pipe inlet 101, the front end of the inner nozzle sleeve 1 is the inner pipe outlet 103, and the inner nozzle sleeve The inside of 1 is the inner layer storage chamber 102; the rear end of the outer layer nozzle sleeve 2 is the connection end 201, and the inner layer nozzle sleeve 1 is set inside the connection end 201, and the outer layer nozzle sleeve The front end of 2 is the outer pipe discharge port 202, the inside of the outer layer nozzle sleeve 2 is the outer layer storage chamber 203, and the outer wall of the outer layer nozzle sleeve 2 is provided with two outer layer storage chambers. 203 communicates with the outer pipe feed port 204.

Further, the air pressure sealing ring 4 is a fluororubber mechanical sealing ring.

Further, in step five, the standard curing conditions are: humidity>95%, temperature 20±2°C.

Example 2

Test its strength and toughness by compressing cubes on a macro scale.

Ordinary Portland cement (P·O42.5) was used as the inner layer of the compression sample, and the outer layer was printed and maintained with epoxy resin as the bonding layer. A universal testing machine was used to conduct a compression test on a cubic compression sample with a size of 3×3×3cm ³ . As shown in Figure 4, it can be seen that the compressive strength is greater than 40MPa, and the failure strain is about 2.4%, which is obvious. Higher than traditional cement material strength and toughness.

In describing the present invention, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", The orientation or positional relationship indicated by "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than Nothing indicating or implying that a referenced device or element must have a particular orientation, be constructed, and operate in a particular orientation should therefore not be construed as limiting the invention. In addition, in the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention. Inside.

Claims (8)

1. A preparation method of a cement-based strengthening and toughening material based on 3D coaxial printing molding is characterized by comprising the following steps:

step one, raw material preparation and treatment

The raw materials used for the inner shaft are ordinary portland cement, a retarder, a water reducing agent and a plasticizer, the raw materials for the inner shaft are subjected to ball milling and refining treatment, and the raw materials for the inner shaft are prepared into superfine powder raw materials with the particle size distribution ranging from 200nm to 10 mu m; the raw materials used by the outer shaft are an elastic plasticizing material and a fiber material, wherein the elastic plasticizing material is an aqueous solution formed by mixing polyvinyl alcohol, water-based epoxy resin, polyvinylpyrrolidone and polyethylene glycol;

step two, preparing printing paste

Inner shaft slurry, namely preparing superfine powder raw materials subjected to ball milling and refining in proportion, and then uniformly stirring at the rotating speed of 3000-5000r/min by using a high-speed shearing stirrer;

outer shaft reinforced slurry: adding the fiber material into the aqueous solution of the elastic plasticizing material, and uniformly stirring;

step three, constructing a coaxial printing platform

A servo motor and a high-precision transmission screw rod are adopted, and a space limiter and an auxiliary component of a lifting platform are combined to build a three-axis mechanical platform with the functions of X, Y, Z space three-axis direction quick transmission and high-precision positioning, wherein the positioning precision is 1-10 mu m; adopting a micro digital control injection pump and a high-precision pressure controller to carry out slurry propulsion and pressure feedback and control; manufacturing a coaxial printing nozzle;

fourthly, printing the toughened cement-based material

Adopting computer software to carry out structural design, leading the processed STL model slice data into a computer numerical control end, transmitting a digital signal to a communication board by a computer, and synchronously sending an ink supply communication instruction and a printing driving instruction by controlling the connection of the communication board and a control computer; based on a micro digital control injection pump and a high-precision pressure controller, after a coaxial ink supply communication instruction is sent out, gas electromagnetic control valves of different channels are opened, printable slurry with pressure is formed in an inner pipeline and an outer pipeline, then the slurry is extruded out uniformly in a quantitative mode through a coaxial printing needle head according to needs, and finally a rigid-flexible two-phase staggered and overlapped 'brick-mud' layered cement-based structure is formed in a layer-by-layer deposition mode;

step five, curing and hydrating

And maintaining the printed and molded cement-based material under standard conditions to finally form the cement-based material with high strength and high toughness.

2. The preparation method of the cement-based strengthening and toughening material based on 3D coaxial printing molding according to claim 1, characterized in that: in the first step, the retarder is phosphate and alcohol; the water reducing agent is polycarboxylic acid and lignosulfonate; the plasticizer is polyvinyl alcohol and fatty acid ester.

3. The preparation method of the cement-based strengthening and toughening material based on 3D coaxial printing molding according to claim 1, characterized in that: in the first step, the fiber material is glass fiber and carbon fiber.

4. The preparation method of the cement-based strengthening and toughening material based on 3D coaxial printing molding according to claim 1, characterized in that: in the second step, the proportion of the superfine powder raw materials is 50-70wt% of ordinary portland cement, 1-3wt% of retarder, 0.5-2wt% of water reducing agent, 2-5wt% of plasticizer and 30-40wt% of water.

5. The preparation method of the cement-based strengthening and toughening material based on 3D coaxial printing molding according to claim 1, characterized in that: in step two, the content of the fiber material is 2-5wt%.

6. The preparation method of the cement-based strengthening and toughening material based on 3D coaxial printing molding according to claim 1, characterized in that: in the third step, the coaxial printing nozzle comprises an inner-layer nozzle sleeve (1) and an outer-layer nozzle sleeve (2), the inner-layer nozzle sleeve (1) is sleeved inside the outer-layer nozzle sleeve (2), the inner-layer nozzle sleeve (1) is connected with the outer-layer nozzle sleeve (2) through a screw (3), and an air pressure sealing ring (4) is arranged between the outer wall of the inner-layer nozzle sleeve (1) and the inner wall of the outer-layer nozzle sleeve (2); the rear end of the inner-layer nozzle sleeve (1) is provided with an inner tube feeding hole (101), the front end of the inner-layer nozzle sleeve (1) is provided with an inner tube discharging hole (103), and the inner part of the inner-layer nozzle sleeve (1) is provided with an inner-layer storage cavity (102); the rear end of outer shower nozzle sleeve (2) is link (201), link (201) endotheca is equipped with inlayer shower nozzle sleeve (1), the front end of outer shower nozzle sleeve (2) is outer tube discharge gate (202), the inside of outer shower nozzle sleeve (2) is outer storage cavity (203), seted up on the outer wall of outer shower nozzle sleeve (2) two and outer storage cavity (203) communicating outer tube feed inlet (204).

7. The preparation method of the cement-based strengthening and toughening material based on 3D coaxial printing molding according to claim 6, characterized in that: the air pressure sealing ring (4) is a fluororubber mechanical sealing ring.

8. The preparation method of the cement-based strengthening and toughening material based on 3D coaxial printing molding according to claim 1, characterized in that: in step five, the standard curing conditions are as follows: the humidity is more than 95 percent, and the temperature is 20 +/-2 ℃.

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