Method for enhancing interlayer impermeability of 3D printing concrete

Abstract

The invention discloses a method for enhancing interlayer impermeability of 3D printing concrete, and belongs to the technical field of building materials. A hydrophobic interface agent is smeared in the area between any two layers of the 3D printing concrete; the hydrophobic interface agent is prepared from, by mass, 65%-70% of ordinary Portland cement, 5%-8% of silane water-based emulsion, 25%-28% of water and 2%-5% of hydroxypropyl methyl cellulose, and coating of the hydrophobic interface agent between 3D printing concrete is achieved through an integrated printing system. By means of the method, the problems that in the prior art, the anti-permeability performance of the 3D printing concrete interlayer area is poor, and water easily enters the structure through the interlayer weak face are solved, and the effect of enhancing the anti-permeability performance is achieved by smearing the hydrophobic interface agent on the interlayer area.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a method for enhancing the interlayer impermeability of 3D printed concrete. Background Technology

[0002] 3D-printed concrete technology, as an important development direction of building industrialization, has attracted much attention due to its advantages such as digitalization, automation, and saving on formwork. However, the inherent process characteristics of this technology, which involves layer-by-layer stacking, create weak interfaces in the microstructure between concrete layers. These interlayer regions, due to their inherent porosity and microcracks, constitute rapid channels for corrosive media to penetrate into the concrete. For example, the penetration of corrosive media such as sulfate ions can trigger expansion products, leading to concrete cracking and spalling; while the penetration of chloride ions can damage the passivation film on the surface of steel bars, initiating and accelerating steel corrosion, ultimately weakening the structural load-bearing capacity and durability from the inside. It is these durability bottlenecks caused by permeability that severely restrict the reliability and application scope of 3D-printed concrete technology, causing it to be mostly limited to small buildings or non-load-bearing components with low load requirements and mild environmental conditions, making it difficult to achieve large-scale application in major engineering fields with extremely high durability requirements, such as bridges, tunnels, and marine engineering.

[0003] To overcome the challenge of insufficient interlayer performance, current industry research has primarily focused on improving the mechanical bond strength between layers. This is mainly achieved by spraying or treating the interlayer with materials such as special mortars and modified sand. These methods can indeed effectively enhance the interlayer bonding force between printed strips and reduce macroscopic cracks and structural defects caused by insufficient bonding. However, these technical solutions have a fundamental limitation: they mainly improve the mechanical properties of the interface but fail to effectively block the transport paths of moisture and corrosive ions dissolved within it. After reinforcement treatment, the interlayer region may be physically stronger, but its microstructure remains loose, making it still a preferred pathway for moisture. Therefore, the problem of weak interlayer impermeability has remained unresolved, becoming a key technical bottleneck hindering the improvement of the long-term durability and widespread application of 3D printed concrete. Summary of the Invention

[0004] The purpose of this invention is to provide a method for enhancing the interlayer impermeability of 3D printed concrete. This invention achieves the effect of enhancing impermeability by applying a hydrophobic interface agent to the interlayer area, thereby solving the problem in the background art where the interlayer area of ​​3D printed concrete has weak impermeability and water can easily enter the interior of the structure through the weak interlayer surface.

[0005] To achieve the above objectives, the present invention provides a method for enhancing the interlayer impermeability of 3D printed concrete, which is achieved by applying a hydrophobic interface agent to the interlayer region between any two layers of 3D printed concrete. The hydrophobic interface agent is prepared from the following components by mass percentage: 65%–70% ordinary silicate cement, 5%–8% silane aqueous emulsion, 25%–28% water, and 2%–5% hydroxypropyl methylcellulose.

[0006] Preferably, the coating thickness of the hydrophobic interface agent is 1 mm.

[0007] Preferably, the silane aqueous emulsion uses polymethylhydrosiloxane as the main active ingredient, employs anionic and nonionic composite emulsifiers, and uses an emulsification system composed of anionic and nonionic emulsifiers for emulsification. The anionic emulsifier is sodium dodecylbenzenesulfonate, and the nonionic composite emulsifier is polyoxyethylene (20) sorbitan monostearate. The ratio of anionic emulsifier to nonionic emulsifier is 1:1.5. The emulsion is a white aqueous emulsion produced by a high-shear emulsification process.

[0008] Preferably, the method for preparing the hydrophobic interface agent includes the following steps: (1) Hydroxypropyl methylcellulose is pre-dissolved in water to form a homogeneous gel; (2) The adhesive obtained in step (1), the silane aqueous emulsion, the remaining water and ordinary silicate cement are put into a mixing device and mechanically mixed to obtain a cement paste with uniform color and no visible agglomerates, which is the hydrophobic interface agent.

[0009] Preferably, the method is implemented through an integrated printing system, which includes a 3D printer host, a concrete extrusion device, a hydrophobic interface agent spraying device, and a control system. The concrete extrusion device includes a concrete conveying mechanism and a concrete printing nozzle; The hydrophobic interface agent spraying device includes a storage tank, a peristaltic pump, and an interface agent nozzle. The storage tank is used to hold the hydrophobic interface agent and is equipped with a mechanical stirrer inside. The peristaltic pump is connected to the storage tank and the interface agent nozzle through a pipeline. The interface agent nozzle is configured to uniformly spray the interface agent onto the concrete surface. The interface agent nozzle is fixedly located behind the concrete printing nozzle so that the surface of the concrete strip can be immediately sprayed with the hydrophobic interface agent after it is extruded. The control system is connected to the peristaltic pump via a signal and is equipped with a control valve to control the opening and closing sequence of the interface agent spraying.

[0010] Preferably, starting the integrated printing system includes the following steps: S1: Printing parameter optimization steps, determining stable basic printing parameters through step-by-step testing; S2: Prepare a hydrophobic interface agent and load it into the storage tank, and start the mechanical stirrer; S3: Synchronous printing and spraying steps: Start the 3D printing host to print the concrete component, and at the same time control the hydrophobic interface agent spraying device through the control system. After each layer of concrete strip is extruded, the hydrophobic interface agent is sprayed on its surface.

[0011] Preferably, the printing parameter optimization step in step S1 further includes: S1.1: Single strip printing test: By printing a single concrete strip, observe the extrusion situation and adjust the printing parameters until a strip with a normal shape is obtained, thereby determining the initial printing speed, extrusion rate, layer height and row width; S1.2: Single-layer printing test: Print a complete single layer using the parameters determined in S1.1, identify and correct printing defects such as material buildup at corners, defects at the start and end points, and unevenness of arcs, in order to verify and optimize the feasibility of the printing model and the range of printing parameters.

[0012] Preferably, in S1.2, when material accumulation occurs at corners, adjustments are made by enabling corner deceleration function in the model slicing software and / or enabling extrusion rate compensation function in the printer; when printing defects occur at the start and end points, the problem is solved by adjusting the extrusion base amount at the start and end of printing; when the printed model arc is not smooth, the problem is solved by changing the model slicing accuracy and / or reducing the printing speed of the printed arc area.

[0013] Preferably, a circular nozzle with an inner diameter of 20 mm was used for the printing process. The single-layer height was 12 mm, the extruder rotated at a speed of 1.5 r / s, and the nozzle movement speed was set to 50 mm / s.

[0014] Therefore, the present invention employs the above-mentioned method for enhancing the interlayer impermeability of 3D printed concrete, and the specific beneficial effects are as follows: 1. This method constructs a continuous hydrophobic interface layer in the interlayer region of 3D printed concrete, which cuts off the rapid migration channels of moisture and corrosive ions, effectively delaying the corrosion of internal steel bars and the expansion and cracking of external concrete, thus giving 3D printed concrete components long-term durability.

[0015] 2. This method establishes an integrated system that ensures that each layer of fresh concrete is covered with an interface agent in a timely and uniform manner, avoiding omissions or unevenness that may be caused by manual intervention. This ensures the consistency and reliability of the interface performance between all layers, and guarantees the continuity and high efficiency of 3D printing construction.

[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0017] Figure 1This is a schematic diagram of the integrated printing system structure; Figure 2 This is a schematic diagram illustrating the principle of capillary water absorption. Figure 3 The water absorption curves of the integrated concrete samples prepared in Examples 1-2 and Comparative Example 1 are shown. Figure 4 The water absorption curves are for the integrated concrete samples prepared in Examples 3-4 and Comparative Example 2. Detailed Implementation

[0018] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0019] The present invention will be further described below through specific embodiments. However, it should be understood that these embodiments are only for more detailed description and should not be construed as limiting the present invention in any way, that is, not intended to limit the scope of protection of the present invention.

[0020] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0021] Example 1 This embodiment provides a method for enhancing the interlayer impermeability of 3D printed concrete, the steps of which are as follows: S1. Printing parameter optimization steps First, using Figure 1 The integrated printing system shown underwent step-by-step testing to determine stable and reliable basic printing parameters. A benchmark concrete material was used for this process. S1.1 Single-strip printing test: Use a nozzle of fixed diameter, set the initial layer height to 12mm, the line width to 20mm, and the printing speed to a fixed 50mm / s. Perform continuous printing and observe the extrusion pattern of the concrete strips. If insufficient extrusion (broken strips) or excessive extrusion (material accumulation, collapse) occurs, fine-tune the extrusion rate of the delivery pump and the printing speed accordingly until a continuous printed strip with neat edges, uniform cross-section, and no defects is obtained.

[0022] S1.2 Single-layer printing test: Using the optimized parameters in S1.1, print a complete single-layer model containing right angles, arcs, and closed start and end points. Observe the printing effect: If material accumulation occurs at the corners, enable the "corner deceleration" function in the slicing software and set the deceleration ratio to 30%, while enabling extrusion rate compensation; if there are defects at the junction of the start and end points, correct them by adjusting the extrusion ratio of the first and last circles of the printer; if the arc segment exhibits an unsmooth polygonal phenomenon, resolve it by increasing the model slicing accuracy to 0.1mm and appropriately reducing the printing speed in that area to 45mm / s.

[0023] S2. Preparation and loading steps of hydrophobic interface agent Using polymethylhydrosiloxane as the main active ingredient, a compound emulsification system composed of sodium dodecylbenzenesulfonate and polyoxyethylene (20) sorbitan monostearate in a ratio of 1:1.5 was used to emulsify the white silane aqueous emulsion through a high-shear emulsification process.

[0024] Weigh out 65% ordinary Portland cement, 5% silane aqueous emulsion, 25% water, and 5% hydroxypropyl methylcellulose (HPMC) by weight percentage. First, pre-dissolve HCMC in 1% of the total water volume in room temperature deionized water and mechanically stir for 3 minutes to form a uniform and transparent adhesive solution. Then, add this adhesive solution, silane aqueous emulsion, the remaining water, and all cement into a planetary mixer and stir at 140 rpm for 4 minutes until a hydrophobic interface agent slurry with uniform color, fine texture, and no agglomerated particles is formed. After preparation, immediately inject the interface agent into the storage tank of the spraying device and start the built-in mechanical agitator in the tank, continuously stirring at a low speed of 80 rpm to prevent slurry sedimentation and segregation, and ensure consistent delivery concentration.

[0025] S3. Synchronous Printing and Spraying Steps The optimized printing parameters are imported into the 3D printer's main control system. The mixed concrete is loaded into the delivery pump, and the nozzle of the hydrophobic interface agent spraying device is securely attached approximately 15mm behind the concrete printing nozzle. The printing program is started; the delivery pump forces the concrete through the pipe into the nozzle and extrudes it, forming a concrete printing strip. Almost simultaneously, the control system commands the peristaltic pump to open the control valve. The hydrophobic interface agent, propelled by the peristaltic pump, is evenly atomized and sprayed onto the surface of the newly formed, yet-to-set concrete strip through a shower-type nozzle. This process is repeated synchronously with each layer of printing, ensuring that each interlayer interface is completely covered by the hydrophobic interface agent.

[0026] Example 2 This embodiment provides a method for enhancing the interlayer impermeability of 3D printed concrete. The steps are as shown in Embodiment 1, except that in step S2, the mass percentage of the silane aqueous emulsion is reduced by 2%, while the mass percentage of water is increased by 28%.

[0027] Example 3 This embodiment provides a method to enhance the interlayer impermeability of 3D printed concrete. The steps are as shown in Embodiment 1, except that in step S3, there is a 10-minute interval between printing each layer of concrete strip.

[0028] Example 4 This embodiment provides a method to enhance the interlayer impermeability of 3D printed concrete. The steps are as shown in Embodiment 2, except that in step S3, there is a 10-minute interval between printing each layer of concrete strip.

[0029] Comparative Example 1 This comparative example provides a method for enhancing the interlayer impermeability of 3D printed concrete. The steps are as shown in Example 1, except that the interface agent does not contain silane aqueous emulsion and the water mass percentage is 30%.

[0030] Comparative Example 2 This comparative example provides a method to enhance the interlayer impermeability of 3D printed concrete, with the steps shown in Comparative Example 1, except that in step S3, there is a 10-minute interval between printing each layer of concrete strip.

[0031] Capillary water absorption is an important indicator for characterizing moisture transport in hardened cementitious materials. It reflects the relationship between the resistance of capillaries to water intrusion and the change over time when the cementitious material comes into contact with water. A schematic diagram of a capillary water absorption experiment is shown below. Figure 1 As shown, the structure design of immersing the bottom of the hardened cement-based specimen in water and sealing the side surface with epoxy resin ensures that water is only absorbed in the vertical direction, and the interlayer weak surface is used to simulate the high permeability area of ​​the internal defects of the material; the experiment is based on the principle of capillary action to observe the migration process of water in the pores in order to quantify the material's resistance to water transport.

[0032] Examples 1-2, Comparative Example 1, Examples 3-4, and Comparative Example 2 were used as groups to discuss the effect of silane emulsion ratio on capillary water absorption experiments. The results are as follows: Figure 3-4 As shown, the water absorption was reduced by 26.59% and 40.45% for silane emulsion ratios of 2% and 5%, respectively, and the presence of a printing time interval would further enhance this effect.

[0033] Therefore, the present invention adopts the above-mentioned method to enhance the interlayer impermeability of 3D printed concrete, which solves the problem of weak impermeability in the interlayer region of 3D printed concrete in the prior art, and the easy entry of water into the interior of the structure through the weak interlayer surface. By applying a hydrophobic interface agent to the interlayer region, the effect of enhancing impermeability is achieved.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for enhancing the interlayer impermeability of 3D printed concrete, characterized in that: Apply a hydrophobic interface agent to the interlayer area between any two layers of 3D printed concrete; The hydrophobic interface agent is prepared from the following components by mass percentage: 65%–70% ordinary silicate cement, 5%–8% silane aqueous emulsion, 25%–28% water, and 2%–5% hydroxypropyl methylcellulose.

2. The method for enhancing the interlayer impermeability of 3D printed concrete according to claim 1, characterized in that: The coating thickness of the hydrophobic interface agent is 1 mm.

3. The method for enhancing the interlayer impermeability of 3D printed concrete according to claim 1, characterized in that: The silane aqueous emulsion uses polymethylhydrosiloxane as the main active ingredient and is emulsified using an emulsification system composed of anionic and nonionic emulsifiers. The anionic emulsifier is sodium dodecylbenzenesulfonate and the nonionic composite emulsifier is polyoxyethylene (20) sorbitan monostearate. The ratio of anionic emulsifier to nonionic emulsifier is 1:1.

5.

4. The method for enhancing the interlayer impermeability of 3D printed concrete according to claim 1, characterized in that: The preparation method of the hydrophobic interface agent includes the following steps: (1) Hydroxypropyl methylcellulose is pre-dissolved in water to form a homogeneous gel; (2) The adhesive obtained in step (1), the silane aqueous emulsion, the remaining water and ordinary silicate cement are put into a mixing device and mechanically mixed to obtain a cement paste with uniform color and no visible agglomerates, which is the hydrophobic interface agent.

5. A method for enhancing the interlayer impermeability of 3D printed concrete according to claim 1, characterized in that: The method is implemented through an integrated printing system, which includes a 3D printer host, a concrete extrusion device, a hydrophobic interface agent spraying device, and a control system. The concrete extrusion device includes a concrete conveying mechanism and a concrete printing nozzle; The hydrophobic interface agent spraying device includes a storage tank, a peristaltic pump, and an interface agent nozzle. The storage tank is used to hold the hydrophobic interface agent and is equipped with a mechanical stirrer inside. The peristaltic pump is connected to the storage tank and the interface agent nozzle through a pipeline. The interface agent nozzle is configured to uniformly spray the interface agent onto the concrete surface. The interface agent nozzle is fixedly located behind the concrete printing nozzle, and after the concrete strip is extruded, its surface is immediately sprayed with the hydrophobic interface agent. The control system is connected to the peristaltic pump via a signal and is equipped with a control valve to control the opening and closing sequence of the interface agent spraying.

6. A method for enhancing the interlayer impermeability of 3D printed concrete according to claim 5, characterized in that: The startup of the integrated printing system includes the following steps: S1: Printing parameter optimization steps, determining stable basic printing parameters through step-by-step testing; S2: Prepare a hydrophobic interface agent and load it into the storage tank, and start the mechanical stirrer; S3: Synchronous printing and spraying steps: Start the 3D printing host to print the concrete component, and at the same time control the hydrophobic interface agent spraying device through the control system. After each layer of concrete strip is extruded, the hydrophobic interface agent is sprayed on its surface.

7. A method for enhancing the interlayer impermeability of 3D printed concrete according to claim 6, characterized in that: The print parameter optimization step in step S1 further includes: S1.1: Single strip printing test: By printing a single concrete strip, observe the extrusion situation and adjust the printing parameters until a strip with a normal shape is obtained, thereby determining the initial printing speed, extrusion rate, layer height and row width; S1.2: Single-layer printing test: Print a complete single layer using the parameters determined in S1.1, identify and correct printing defects such as material buildup at corners, defects at the start and end points, and unevenness of arcs, in order to verify and optimize the feasibility of the printing model and the range of printing parameters.

8. A method for enhancing the interlayer impermeability of 3D printed concrete according to claim 7, characterized in that: In S1.2, when material accumulation occurs at corners, adjustments are made by enabling the corner deceleration function in the model slicing software and / or enabling the extrusion rate compensation function in the printer; when printing defects occur at the start and end points, the problem is solved by adjusting the extrusion base amount at the start and end of printing; when the printed model arc is not smooth, the problem is solved by changing the model slicing accuracy and / or reducing the printing speed of the printed arc area.

9. A method for enhancing the interlayer impermeability of 3D printed concrete according to claim 7, characterized in that: The printing process used a circular nozzle with an inner diameter of 20 mm for the experiment; the single layer height was 12 cm; the extruder rotated at a speed of 1.5 r / s; and the nozzle movement speed was set to 50 mm / s.

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