A 3D printed coarse aggregate concrete material and its preparation method and application

Abstract

The present invention discloses a 3D printing coarse aggregate concrete material and a preparation method and application thereof, belonging to the technical field of 3D printing concrete materials. The coarse aggregate concrete material of the present invention comprises the following components: a cementitious material, fine aggregate, coarse aggregate, a pumping agent, water and a microcapsule slow-release setting agent, wherein a C component microcapsule slow-release setting agent with a slow-release characteristic is innovatively used to enable the concrete structure to have a good bearing capacity, thereby achieving continuous and rapid molding of 3D printing concrete materials, improving the continuous printing ability and construction efficiency of 3D printing concrete materials, and eliminating the need for manual feeding into the funnel, which greatly reduces the labor level of 3D printing concrete materials. The present invention solves the technical problem that the existing 3D printing concrete materials have insufficient continuous printing ability due to slow coagulation speed.

Description

Technical Field

[0001] The present invention belongs to the technical field of 3D printing concrete materials, and specifically relates to a 3D printing coarse aggregate concrete material and a preparation method and application thereof. Background Art

[0002] In recent years, concrete 3D printing technology has been developed and applied in fields such as civil engineering and construction, and a series of 3D printed concrete products have been launched. In concrete 3D printing technology, the concrete material needs to have a certain fluidity so that it can smoothly pass through the pipeline during pumping and be evenly deposited at the print head. Insufficient fluidity can cause pumping difficulties and even block the pipeline. During the pumping process, the consistency of the concrete should remain stable to avoid stratification, water seepage and other phenomena to ensure the printing quality. The setting time of the concrete needs to be moderate to adapt to the layer-by-layer deposition process of 3D printing. Too fast setting time will result in poor bonding between the printed layers, and too slow setting time will affect the printing efficiency. Concrete should be able to develop strength quickly after printing to meet the requirements of structural safety. At the same time, the development of strength should match the printing speed to avoid structural damage caused by insufficient strength.

[0003] The current concrete 3D printing prepares the final printing material by mixing the raw materials and admixtures in advance, and then manually loading the materials into the printing funnel, and printing and forming by spiral extrusion. It is mainly used in small art printing and indoor experiments. This type of concrete material often has insufficient fluidity and slow coagulation rate, and cannot be transported by pumping, so it is difficult to meet the requirements of 3D printing for continuous and uniform deposition of materials, which will cause problems such as material breakage and blockage during the printing process, affecting the continuity and efficiency of printing. In addition, this type of concrete material requires manual loading and spiral extrusion printing, which has problems such as complex operation and high labor intensity, limiting the construction efficiency and application scope of 3D printing technology. In the application process, this 3D printing technology has problems such as small aggregate particle size, high material cost, high labor intensity, low degree of automation, discontinuous pumping printing, and low construction efficiency.

[0004] Chinese patent CN117486555 A discloses a two-component 3D printing concrete containing coarse aggregate and a preparation method and device thereof. The two-component 3D printing concrete containing coarse aggregate is prepared by mixing component A consisting of cement, admixtures, coarse aggregate and fine aggregate with component B consisting of thickener, setting regulator and thixotropic agent. However, the setting speed is slow, resulting in weak bearing capacity of concrete, which leads to insufficient continuous printing capacity of 3D printing concrete. Summary of the invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a 3D printed coarse aggregate concrete material and a preparation method and application thereof, which solves the technical problem that the existing 3D printed concrete material has insufficient continuous printing capacity due to its slow setting speed.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention provides a 3D printing coarse aggregate concrete material, which comprises, by weight: 35-50 parts of cementitious material, 20-35 parts of fine aggregate, 10-30 parts of coarse aggregate, 0.01-0.2 parts of pumping agent, 10-20 parts of water, 1-10 parts of flow regulator and 3-8 parts of microcapsule slow-release setting regulator.

[0007] Furthermore, the cementitious material includes ordinary Portland cement and fly ash.

[0008] Furthermore, ordinary Portland cement is one of P.O42.5, P.O42.5R or P.O52.5 cement.

[0009] Furthermore, the specific surface area of ​​fly ash is 400-700m 2 / kg, with a particle size range of 0.2-60 microns.

[0010] Furthermore, the fine aggregate particle size range is river sand of 0.18-4.75 mm and the fineness modulus is 1.5-3.0.

[0011] Furthermore, the coarse aggregate is basalt or limestone, with a particle size range of 5.0 mm-10 mm, conforming to continuous grading.

[0012] Furthermore, the pumping agent is a compound of a water reducer and a retarder in a dosage ratio of (15-25ml):1g, wherein the water reducer is a high-performance polycarboxylic acid liquid with a solid content of ≥15% and a water reduction rate of greater than 20%; the retarder is one or more of sodium gluconate, sodium tripolyphosphate or sodium polyphosphate.

[0013] Furthermore, the flow regulator is a high molecular flow regulator aqueous solution with a concentration of 3-12 g / L, which is prepared from one or more of xanthan gum, vinyl gum, hydroxypropyl methylcellulose ether or polyacrylamide. The flow regulator can significantly change the slump and rheological properties of concrete, so that the coarse aggregate concrete material meets the performance requirements of entering the print head area.

[0014] Furthermore, the microcapsule sustained-release coagulant is prepared by mixing an aluminum sulfate solution with a concentration of 20-100 g / L, a sodium aluminate solution with a concentration of 10-50 g / L, and gelatin and gum arabic powders in a mass ratio of (20-50): (10-30).

[0015] The present invention also provides a method for preparing the above-mentioned 3D printed coarse aggregate concrete material, comprising the following steps: 1) First-stage continuous pumping concrete: Add cementitious materials, fine aggregates and coarse aggregates into the mixing device in proportion and mix them evenly. Then add pumping agent and water into the mixer to make a mixture. Add water and control the water consumption to 240-280k / m 3 , so that the slump of concrete is controlled within 180mm-220mm, which can not only ensure the pumpability of concrete and allow the concrete to enter the print head, but also quickly reduce the slump of concrete after mixing with the subsequent flow regulating agent, so that it meets the printability requirements; wherein, the mixing device adopts a mixer; 2) Secondary mixing and extruding concrete: The above mixture is transported to the print head by a conveying device, and a flow regulator and a microcapsule slow-release coagulant are added at the print head inlet. The mixing and extruding spiral in the print head mixes the mixture with the flow regulator and the microcapsule slow-release coagulant to obtain a 3D printed coarse aggregate concrete material, which is extruded from the print head outlet to complete the printing work. The slump of the second mixing and extruding concrete is controlled within 80mm-120mm. By controlling the slump within the range of 80mm-120mm, it can be ensured that the concrete has appropriate fluidity and extrudability at the print head outlet, thereby meeting the requirements of printing accuracy.

[0016] Furthermore, the conveying device adopts a concrete pump.

[0017] Furthermore, the preparation method of the microcapsule sustained-release coagulant comprises the following steps: S1: preparing an aluminum sulfate solution with a concentration of 20-100 g / L and a sodium aluminate solution with a concentration of 10-50 g / L; S2: Add gelatin, gum arabic powder and water in a ratio of (20-50 g): (10-30 g): 1 L into a beaker, mix, and heat in a water bath until completely dissolved to prepare a mixed solution; S3: The mixed solution prepared in S2 is mixed with the aluminum sulfate solution and sodium aluminate solution prepared in S1 in a volume ratio of 1:2, and dispersed in an ultrasonic disperser. After 5 minutes, the mixture is taken out and allowed to settle to terminate the reaction, and the emulsion is spray-dried to obtain the microcapsule sustained-release coagulant.

[0018] Furthermore, in S1, the preparation method of the aluminum sulfate solution and the sodium aluminate solution includes: adding aluminum sulfate and sodium aluminate to a beaker containing an appropriate amount of deionized water, respectively, and slowly stirring to dissolve them, to obtain an aluminum sulfate solution with a concentration of 20-100 g / L and a sodium aluminate solution with a concentration of 10-50 g / L.

[0019] The present invention also provides application of the above coarse aggregate concrete material in 3D printing technology.

[0020] Under the action of the primary continuous pumping pressure of the concrete pump and the secondary mixing and extrusion pressure of the print head, the pumping and printing of concrete can be carried out continuously.

[0021] Compared with the prior art, the present invention has the following beneficial effects: The present invention proposes a 3D printing coarse aggregate concrete material, including a cementitious material, a fine aggregate, a coarse aggregate, a pumping agent, water, a flow regulator and a microcapsule slow-release coagulant, wherein the pumping agent has good fluidity, improves the pumpability of the concrete material, enables the concrete material to be quickly pumped to the inlet of the print head, and does not need to be manually loaded into the funnel, greatly reducing the labor of the 3D printing coarse aggregate concrete material, the flow regulator can rapidly reduce the fluidity of the concrete to ensure that it can flow smoothly and fill the printing path, meet the requirements of printing deposition accuracy, and improve the construction efficiency of the 3D printing coarse aggregate concrete material, and the microcapsule slow-release coagulant can quickly coagulate the concrete after it is squeezed out of the printing funnel, and before the next layer of concrete material is deposited, the concrete reaches the final setting state, so that the coarse aggregate concrete material structure has good bearing capacity, thereby achieving continuous and rapid molding of the 3D printing concrete material, and effectively improving the continuous printing ability of the 3D printing concrete material. The present invention solves the technical problem that the existing 3D printing concrete material has insufficient continuous printing ability due to the slow coagulation speed.

[0022] The present invention provides a preparation method of a 3D printed concrete material. The 3D printed concrete material realizes a two-stage operation in the 3D printing process, namely, the first-stage continuous stirring and pumping in step 1) and the second-stage continuous stirring and extrusion molding in step 2) through the concrete material mix ratio design and the combination and graded use of different functional admixtures. From the perspective of concrete mix ratio design, 3D printed concrete needs to have good extrudability. First of all, in order to meet the requirement that the concrete has good pumpability during the pumping process, a pumping agent is compounded to obtain a mixture with good fluidity and good collapse retention, and experiments show that the collapse retention time can reach 30-120 minutes, which is conducive to the pumping of concrete and avoids the problems of pipe blockage and pipe burst caused by the high viscosity of conventional 3D printed concrete. Secondly, at the entrance of the print head, the flow regulator and microcapsule slow-release coagulant are introduced. The introduction of the flow regulator quickly reduces the fluidity of the concrete, so that the concrete does not deform after extrusion and has good extrudability; the addition of the microcapsule slow-release coagulant enables the concrete to quickly solidify after extrusion and has good bearing capacity. It can continuously withstand the load of new concrete printing strips without deformation, thereby ensuring the integrity of the printed concrete structure. Among them, the microcapsule slow-release coagulant is innovatively used. The slow release characteristic of the coagulant enables it to not be released within 5-10 seconds at the entrance of the print head. At this time, the concrete can still be shaped, and the concrete can be extruded from the exit of the print head. When the concrete is extruded, the microcapsule slow-release coagulant is released. At this time, the concrete quickly solidifies and reaches the final setting state before the next layer of concrete material is deposited, so that the concrete structure has good bearing capacity, thereby achieving continuous and rapid molding of 3D printed concrete materials and improving the continuous printing ability of 3D printed concrete materials.

[0023] The application of the 3D printing concrete material of the present invention is specifically: using the 3D printing concrete material as a rapid prototyping concrete material, which has the characteristics of high construction efficiency and low labor intensity. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0025] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0026] The present invention is described in further detail below in conjunction with embodiments: The preparation method of the present invention uses cementitious material, coarse aggregate, fine aggregate, water and pumping agent as raw materials, and prepares a concrete mixture through stirring. The cementitious material in the concrete mixture is mixed with water to prepare cement slurry. The coarse aggregate and fine aggregate in the concrete mixture are completely wrapped by the cement slurry, and the cement slurry has a large surplus. The surplus cement slurry has thixotropy, so it is extruded at the printing head to meet the design requirements of extrudability. The volume ratio of cement slurry to concrete mixture is usually controlled at (1.1-1.3):1.

[0027] Example 1 This embodiment 1 provides a 3D printing concrete material, and the raw materials of the 3D printing concrete material include: 38 parts of P.O42.5, 6 parts of fly ash, 25 parts of fine aggregate, 16 parts of coarse aggregate, 0.12 parts of pumping agent, 13 parts of water, 5 parts of hydroxypropyl methylcellulose ether liquid flow regulator, and 8 parts of microcapsule sustained-release setting regulator.

[0028] The preparation method is: 1) Preparation of microcapsule sustained-release coagulant: Aluminum sulfate and sodium aluminate are added to a beaker containing an appropriate amount of deionized water, respectively, and slowly stirred to dissolve, to prepare an aluminum sulfate solution with a concentration of 20 g / L and a sodium aluminate solution with a concentration of 10 g / L; 20 g of gelatin and 10 g of gum arabic powder are weighed and put into a beaker, and 1 L of water is added and heated in a water bath until completely dissolved; the above-mentioned dissolved mixed solution is mixed with the prepared aluminum sulfate solution and sodium aluminate solution in a volume ratio of 1:2, and dispersed in an ultrasonic disperser, and after 5 minutes, the mixture is taken out and allowed to settle to terminate the reaction, and the emulsion is spray-dried to obtain the microcapsule sustained-release coagulant; 2) Take 38 parts of P.O42.5 and 6 parts of fly ash (surface area 400m 2 / kg, particle size range of 0.2 microns), 25 parts of fine aggregate (river sand with a particle size range of 0.18mm and a fineness modulus of 1.5) and 16 parts of coarse aggregate (basalt with a particle size range of 5.0mm) were poured into the mixer and stirred for 1 minute. Then 0.12 parts of pumping agent and 13 parts of water were added, and the water consumption was controlled to 240k / m 3 , so that the slump value of the first-stage concrete pumping reaches 190mm; the pumping agent is composed of 16ml of high-performance polycarboxylic acid liquid and 1g of sodium gluconate, the solid content of the high-performance polycarboxylic acid liquid is 16%, and the water reduction rate is 21%; 3) Use a concrete pump to deliver the mixture in step 2) to the print head, and add 5 parts of 3g / L hydroxypropyl methylcellulose ether liquid flow regulator at the print head position, and detect the slump of the concrete material extruded at the end of the print head. The slump meets the slump of the secondary extrusion molding concrete, which reaches 120mm; then add 8 parts of microcapsule slow-release setting regulator at the print head, mix and stir to obtain 3D printed coarse aggregate concrete material, and extrude it from the print head outlet to complete the printing work. The final setting time of the extruded concrete at the end of the print head is 8.5min. When all three indicators meet the technical indicator requirements, it indicates that the concrete material is qualified.

[0029] Comparative Example 1 The difference between the material preparation steps shown in this comparative example 1 and the example 1 is that an accelerating setting agent is used to participate in the preparation of the concrete material. The setting time and rheological properties of the 3D printing concrete material prepared by the microcapsule slow-release setting agent in example 1 and the concrete material prepared by the conventional concrete accelerating setting agent in comparative example 1 are compared to obtain the following Tables 1 and 2. As can be seen from Table 1, after the microcapsule slow-release setting agent is added to the concrete material prepared in this example 1, the setting time is significantly adjusted, and the fluidity can be maintained for a longer time; as can be seen from Table 2, when the static yield stress of the concrete prepared by the present invention is 4000-6000Pa under the rheometer, the concrete can maintain a slump of 80-120mm, and the static yield stress retention time in this state can be maintained for 10-30s. During this time, the mixing and extrusion of the concrete at the print head can be achieved. After the concrete is extruded, within 10 minutes before the next layer of printing and stacking, the concrete can reach a hardened state, thereby achieving the bearing capacity of the concrete structure. After conventional concrete accelerator is added to the concrete mixture, its static yield stress is maintained for only 0-10s. It can be seen that the concrete mixture is difficult to maintain fluidity and tends to lose its plasticity quickly, which limits its application in construction scenarios that require maintaining fluidity for a longer period of time. Table 1 Effect of setting time of concrete obtained in Example 1 and Comparative Example 1

[0030] Table 2 Changes in rheological properties of concrete obtained in Example 1 and Comparative Example 1

[0031] Example 2 This embodiment 2 provides a 3D printing concrete material and the raw materials of the 3D printing concrete material, which include, by mass: 35 parts of P.O42.5, 8 parts of fly ash, 28 parts of fine aggregate, 15 parts of coarse aggregate, 0.14 parts of pumping agent, 14 parts of water, 4 parts of xanthan gum liquid flow regulator and 7 parts of microcapsule sustained-release setting regulator.

[0032] The preparation method is: 1) Preparation of microcapsule sustained-release coagulant: adding aluminum sulfate and sodium aluminate to a beaker containing an appropriate amount of deionized water, respectively, and slowly stirring to dissolve them, to prepare an aluminum sulfate solution with a concentration of 25 g / L and a sodium aluminate solution with a concentration of 15 g / L; weighing 25 g of gelatin and 15 g of gum arabic powder and putting them into a beaker, adding 1 L of water and heating them in a water bath until they are completely dissolved; mixing the above-mentioned dissolved mixed solution with the prepared aluminum sulfate solution and sodium aluminate solution in a volume ratio of 1:2, dispersing them under an ultrasonic disperser, taking them out after 5 minutes and placing them to settle to terminate the reaction, and spray drying the emulsion to obtain the microcapsule sustained-release coagulant; 2) Take 38 parts of P.O42.5 and 8 parts of fly ash (surface area of ​​450m 2 / kg, particle size range of 5 microns), 28 parts of fine aggregate (river sand with a particle size range of 1.28mm and a fineness modulus of 1.6) and 15 parts of coarse aggregate (basalt with a particle size range of 6.0mm) were poured into the mixer and stirred for 1 minute. Then 0.14 parts of pumping agent and 14 parts of water were added to control the water consumption to 245k / m 3 , so that the slump value of the first-stage concrete pumping reaches 200mm; the pumping agent is composed of 17ml of high-performance polycarboxylic acid liquid and 1g of sodium tripolyphosphate, the solid content of the high-performance polycarboxylic acid liquid is 20%, and the water reduction rate is 25%; 3) Use a concrete pump to deliver the mixture in step 2) to the print head, and add 4 portions of xanthan gum liquid flow regulator with a concentration of 4g / L at the print head position. Detect the slump of the concrete material extruded at the end of the print head. The slump meets the slump of the secondary extrusion molding concrete, which reaches 90mm. Then add 7 portions of microcapsule slow-release setting regulator at the print head, mix and stir to obtain 3D printed coarse aggregate concrete material, and extrude it from the print head outlet to complete the printing work. The final setting time of the extruded concrete at the end of the print head is 6.4min. When all three indicators meet the technical indicator requirements, it indicates that the concrete material is qualified.

[0033] Example 3 This embodiment 3 provides a 3D printing concrete material. The raw materials of the 3D printing concrete material, measured by mass, include: 33 parts of P.O42.5, 9 parts of fly ash, 22.5 parts of fine aggregate, 22.5 parts of coarse aggregate, 0.18 parts of pumping agent, 13 parts of water, 5 parts of polyacrylamide liquid flow regulator and 8 parts of microcapsule sustained-release setting regulator.

[0034] The preparation method is: 1) Preparation of microcapsule sustained-release coagulant: adding aluminum sulfate and sodium aluminate to a beaker containing an appropriate amount of deionized water, respectively, and slowly stirring to dissolve them, to prepare an aluminum sulfate solution with a concentration of 30 g / L and a sodium aluminate solution with a concentration of 20 g / L; weighing 25 g of gelatin and 20 g of gum arabic powder and putting them into a beaker, adding 1 L of water and heating in a water bath until they are completely dissolved; mixing the above-mentioned dissolved mixed solution with the prepared aluminum sulfate solution and sodium aluminate solution in a volume ratio of 1:2, dispersing them under an ultrasonic disperser, taking them out after 5 minutes and placing them to settle to terminate the reaction, and spray drying the emulsion to obtain the microcapsule sustained-release coagulant; 2) Take 33 parts of P.O42.5 and 9 parts of fly ash (surface area of ​​500m 2 / kg, particle size range of 10 microns), 22.5 parts of fine aggregate (river sand with a particle size range of 2.33mm and a fineness modulus of 2.0) and 22.5 parts of coarse aggregate (basalt with a particle size range of 6.5mm) are poured into the mixer and stirred for 1 minute. Then 0.18 parts of pumping agent and 13 parts of water are added to control the water consumption to 250k / m 3 , so that the slump value of the first-stage concrete pumping reaches 180mm; the pumping agent is composed of 19ml of high-performance polycarboxylic acid liquid and 1g of sodium polyphosphate, the solid content of the high-performance polycarboxylic acid liquid is 30%, and the water reduction rate is 32%; 3) Use a concrete pump to deliver the mixture in step 2) to the print head, and add 5 parts of 5g / L polyacrylamide liquid flow regulator at the print head position, and detect the slump of the concrete material extruded at the end of the print head. The slump meets the slump of the secondary extrusion molding concrete and reaches 100mm; then add 8 parts of microcapsule slow-release setting regulator at the print head, mix and stir to obtain 3D printed coarse aggregate concrete material, and extrude it from the print head outlet to complete the printing work. The final setting time of the extruded concrete at the end of the print head is 7.3min. When all three indicators meet the technical indicator requirements, it indicates that the concrete material is qualified.

[0035] Example 4 This embodiment 4 provides a 3D printing concrete material. The raw materials of the 3D printing concrete material, measured by mass, include: 34 parts of P.O42.5R, 7 parts of fly ash, 31 parts of fine aggregate, 16 parts of coarse aggregate, 0.15 parts of pumping agent, 12 parts of water, 4 parts of Wenlun glue liquid flow regulator and 6 parts of microcapsule slow-release setting regulator.

[0036] The preparation method is: 1) Preparation of microcapsule sustained-release coagulant: Aluminum sulfate and sodium aluminate are added to a beaker containing an appropriate amount of deionized water, respectively, and slowly stirred to dissolve, to obtain an aluminum sulfate solution with a concentration of 30 g / L and a sodium aluminate solution with a concentration of 30 g / L; 30 g of gelatin and 25 g of gum arabic powder are weighed and put into a beaker, and 1 L of water is added and heated in a water bath until completely dissolved; the above-mentioned dissolved mixed solution is mixed with the prepared aluminum sulfate solution and sodium aluminate solution in a volume ratio of 1:2, and dispersed under an ultrasonic disperser. After 5 minutes, the mixture is taken out and allowed to settle to terminate the reaction, and the emulsion is spray-dried to obtain the microcapsule sustained-release coagulant; 2) Take 34 parts of P.O42.5R and 7 parts of fly ash (surface area of ​​550m 2 / kg, particle size range of 22 microns), 31 parts of fine aggregate (river sand with a particle size range of 3.16mm and a fineness modulus of 2.5) and 16 parts of coarse aggregate (basalt with a particle size range of 7mm) were poured into the mixer and stirred for 2 minutes. Then 0.15 parts of pumping agent and 12 parts of water were added to control the water consumption to 255k / m 3 , so that the slump value of the first-stage concrete pumping reaches 210mm; the pumping agent is composed of 20ml of high-performance polycarboxylic acid liquid and 1g of sodium gluconate, the solid content of the high-performance polycarboxylic acid liquid is 43%, and the water reduction rate is 47%; 3) Use a concrete pump to deliver the mixture in step 2) to the print head, and add 4 portions of 6g / L Wenlunjiao liquid flow regulator at the print head position, and detect the slump of the concrete material extruded at the end of the print head. The slump meets the slump of secondary extrusion molding concrete, which reaches 80mm; then add 6 portions of microcapsule slow-release coagulation regulator at the print head, mix and stir to obtain 3D printed coarse aggregate concrete material, and extrude it from the print head outlet to complete the printing work. The final setting time of the extruded concrete at the end of the print head is 6.8min. When all three indicators meet the technical indicator requirements, it indicates that the concrete material is qualified.

[0037] Example 5 This embodiment 5 provides a 3D printing concrete material. The raw materials of the 3D printing concrete material, measured by mass, include: 35 parts of P.O42.5R, 9 parts of fly ash, 23 parts of fine aggregate, 20.5 parts of coarse aggregate, 0.2 parts of pumping agent, 12.5 parts of water, 6 parts of hydroxypropyl methylcellulose ether flow regulator, and 8 parts of microcapsule sustained-release setting regulator.

[0038] The preparation method is: 1) Preparation of microcapsule sustained-release coagulant: Aluminum sulfate and sodium aluminate are added to a beaker containing an appropriate amount of deionized water, respectively, and slowly stirred to dissolve, to obtain an aluminum sulfate solution with a concentration of 40 g / L and a sodium aluminate solution with a concentration of 35 g / L; 35 g of gelatin and 26 g of gum arabic powder are weighed and put into a beaker, and 1 L of water is added and heated in a water bath until completely dissolved; the above-mentioned dissolved mixed solution is mixed with the prepared aluminum sulfate solution and sodium aluminate solution in a volume ratio of 1:2, and dispersed under an ultrasonic disperser. After 5 minutes, the mixture is taken out and allowed to settle to terminate the reaction, and the emulsion is spray-dried to obtain the microcapsule sustained-release coagulant; 2) Take 35 parts of P.O42.5R and 9 parts of fly ash (surface area of ​​600m 2 / kg, particle size range of 40 microns), 9 parts of fine aggregate (river sand with a particle size range of 4.75mm and a fineness modulus of 3.0) and 20.5 parts of coarse aggregate (basalt with a particle size range of 8mm) were poured into the mixer and stirred for 2 minutes. Then 0.2 parts of pumping agent and 12.5 parts of water were added to control the water consumption to 260k / m 3 , so that the slump value of the first-stage concrete pumping reaches 200mm; the pumping agent is composed of 21ml of high-performance polycarboxylic acid liquid and 1g of sodium gluconate, the solid content of the high-performance polycarboxylic acid liquid is 43%, and the water reduction rate is 47%; 3) Use a concrete pump to deliver the mixture in step 2) to the print head, and add 6 parts of hydroxypropyl methylcellulose ether flow regulator with a concentration of 8g / L at the print head position, and detect the slump of the concrete material extruded at the end of the print head. The slump meets the slump of the secondary extrusion molding concrete, which reaches 95mm; then add 8 parts of microcapsule slow-release setting regulator at the print head, mix and stir to obtain 3D printed coarse aggregate concrete material, and extrude it from the print head outlet to complete the printing work. The final setting time of the extruded concrete at the end of the print head is 7.3min. When all three indicators meet the technical indicator requirements, it indicates that the concrete material is qualified.

[0039] Example 6 This embodiment 6 provides a 3D printing concrete material. The raw materials of the 3D printing concrete material, measured by mass, include: 38 parts of P.O42.5R, 4 parts of fly ash, 30 parts of fine aggregate, 15 parts of coarse aggregate, 0.18 parts of pumping agent, 13 parts of water, 4.5 parts of polyacrylamide liquid flow regulator and 6 parts of microcapsule slow-release setting regulator.

[0040] The preparation method is: 1) Preparation of microcapsule sustained-release coagulant: Aluminum sulfate and sodium aluminate are added to a beaker containing an appropriate amount of deionized water, respectively, and slowly stirred to dissolve, to obtain an aluminum sulfate solution with a concentration of 60 g / L and a sodium aluminate solution with a concentration of 45 g / L; 50 g of gelatin and 30 g of gum arabic powder are weighed and put into a beaker, and 1 L of water is added and heated in a water bath until completely dissolved; the above-mentioned dissolved mixed solution is mixed with the prepared aluminum sulfate solution and sodium aluminate solution in a volume ratio of 1:2, and dispersed under an ultrasonic disperser. After 5 minutes, the mixture is taken out and allowed to settle to terminate the reaction, and the emulsion is spray-dried to obtain the microcapsule sustained-release coagulant; 2) Take 38 parts of P.O42.5R and 4 parts of fly ash (surface area of ​​700m 2 / kg, particle size range of 60 microns), 30 parts of fine aggregate (river sand with a particle size range of 4.75mm and a fineness modulus of 3.0) and 15 parts of coarse aggregate (basalt with a particle size range of 10mm) were poured into the mixer and stirred for 2 minutes. Then 0.18 parts of pumping agent and 13 parts of water were added to control the water consumption to 265k / m 3 , so that the slump value of the first-stage concrete pumping reaches 180mm; the pumping agent is composed of 22ml of high-performance polycarboxylic acid liquid and 1g of sodium gluconate, the solid content of the high-performance polycarboxylic acid liquid is 43%, and the water reduction rate is 47%; 3) Use a concrete pump to transport the mixture in step 2) to the print head, and add 4.5 parts of 12g / L polyacrylamide liquid flow regulator at the print head position, and detect the slump of the concrete material extruded at the end of the print head. The slump meets the slump of the secondary extrusion molding concrete and reaches 100mm; then add 6 parts of microcapsule slow-release setting regulator at the print head, mix and stir to obtain 3D printed coarse aggregate concrete material, and extrude it from the print head outlet to complete the printing work. The final setting time of the extruded concrete at the end of the print head is 6.3min. When all three indicators meet the technical indicator requirements, it indicates that the concrete material is qualified.

[0041] Example 7 This embodiment 7 provides a 3D printing concrete material. The raw materials of the 3D printing concrete material, measured by mass, include: 33 parts of P.O52.5, 9 parts of fly ash, 26 parts of fine aggregate, 20 parts of coarse aggregate, 0.19 parts of pumping agent, 12 parts of water, 5 parts of hydroxypropyl methylcellulose ether liquid flow regulator and 7 parts of microcapsule sustained-release setting regulator.

[0042] The preparation method is: 1) Preparation of microcapsule sustained-release coagulant: Aluminum sulfate and sodium aluminate are added to a beaker containing an appropriate amount of deionized water, respectively, and slowly stirred to dissolve, to prepare an aluminum sulfate solution with a concentration of 100 g / L and a sodium aluminate solution with a concentration of 50 g / L; 50 g of gelatin and 30 g of gum arabic powder are weighed and put into a beaker, and 1 L of water is added and heated in a water bath until completely dissolved; the above-mentioned dissolved mixed solution is mixed with the prepared aluminum sulfate solution and sodium aluminate solution in a volume ratio of 1:2, and dispersed under an ultrasonic disperser. After 5 minutes, the mixture is taken out and allowed to settle to terminate the reaction, and the emulsion is spray-dried to obtain the microcapsule sustained-release coagulant; 2) Take 33 parts of P.O52.5 and 9 parts of fly ash (surface area of ​​700m 2 / kg, particle size range of 60 microns), 26 parts of fine aggregate (river sand with a particle size range of 4.75mm and a fineness modulus of 3.0) and 20 parts of coarse aggregate (limestone with a particle size range of 10mm) were poured into the mixer and stirred for 3 minutes. Then 0.19 parts of pumping agent and 12 parts of water were added to control the water consumption to 270k / m 3 , so that the slump value of the first-stage concrete pumping reaches 190mm; the pumping agent is composed of 23ml of high-performance polycarboxylic acid liquid and 1g of sodium gluconate, the solid content of the high-performance polycarboxylic acid liquid is 43%, and the water reduction rate is 47%; 3) Use a concrete pump to transport the mixture in step 2) to the print head, and add 5 parts of 12g / L hydroxypropyl methylcellulose ether liquid flow regulator at the print head position, and detect the slump of the concrete material extruded at the end of the print head. The slump meets the slump of secondary extrusion molding concrete, which reaches 80mm; then add 7 parts of microcapsule slow-release setting regulator at the print head, mix and stir to obtain 3D printed coarse aggregate concrete material, and extrude it from the print head outlet to complete the printing work. The final setting time of the extruded concrete at the end of the print head is 7.5min. When all three indicators meet the technical indicator requirements, it indicates that the concrete material is qualified.

[0043] Example 8 This embodiment 8 provides a 3D printing concrete material. The raw materials of the 3D printing concrete material, measured by mass, include: 35 parts of P.O52.5, 3 parts of fly ash, 30 parts of fine aggregate, 20 parts of coarse aggregate, 0.15 parts of pumping agent, 12 parts of water, 4.3 parts of xanthan gum liquid flow regulator and 6 parts of microcapsule slow-release setting regulator.

[0044] The preparation method is: 1) Preparation of microcapsule sustained-release coagulant: Aluminum sulfate and sodium aluminate are added to a beaker containing an appropriate amount of deionized water, respectively, and slowly stirred to dissolve, to prepare an aluminum sulfate solution with a concentration of 100 g / L and a sodium aluminate solution with a concentration of 50 g / L; 50 g of gelatin and 30 g of gum arabic powder are weighed and put into a beaker, and 1 L of water is added and heated in a water bath until completely dissolved; the above-mentioned dissolved mixed solution is mixed with the prepared aluminum sulfate solution and sodium aluminate solution in a volume ratio of 1:2, and dispersed under an ultrasonic disperser. After 5 minutes, the mixture is taken out and allowed to settle to terminate the reaction, and the emulsion is spray-dried to obtain the microcapsule sustained-release coagulant; 2) First, take 35 parts of P.O52.5 and 3 parts of fly ash (surface area of ​​700m 2 / kg, particle size range of 60 microns), 30 parts of fine aggregate (river sand with a particle size range of 4.75mm and a fineness modulus of 3.0) and 20 parts of coarse aggregate (limestone with a particle size range of 10mm) are poured into the mixer and stirred for 3 minutes. Then 0.15 parts of pumping agent and 12 parts of water are added to control the water consumption to 275k / m 3 , so that the slump value of the first-stage concrete pumping reaches 200mm; the pumping agent is composed of 25ml of high-performance polycarboxylic acid liquid and 1g of sodium gluconate, the solid content of the high-performance polycarboxylic acid liquid is 43%, and the water reduction rate is 47%; 3) Use a concrete pump to deliver the mixture in step 2) to the print head, and add 4.3 parts of xanthan gum liquid flow regulator with a concentration of 12g / L at the print head position. Detect the slump of the concrete material extruded at the end of the print head. The slump meets the slump of the secondary extrusion molding concrete of 100mm; then add 6 parts of microcapsule slow-release setting regulator at the print head, mix and stir to obtain 3D printed coarse aggregate concrete material, and extrude it from the print head outlet to complete the printing work. The final setting time of the extruded concrete at the end of the print head is 6.5min. When all three indicators meet the technical indicator requirements, it indicates that the concrete material is qualified.

[0045] Example 9 This embodiment 9 provides a 3D printing concrete material. The raw materials of the 3D printing concrete material, measured by mass, include: 40 parts of P.O52.5, 2 parts of fly ash, 30.5 parts of fine aggregate, 15 parts of coarse aggregate, 0.25 parts of pumping agent, 12.5 parts of water, 5 parts of polyacrylamide liquid flow regulator and 6 parts of microcapsule sustained-release setting regulator.

[0046] The preparation method is: 1) Preparation of microcapsule sustained-release coagulant: Aluminum sulfate and sodium aluminate are added to a beaker containing an appropriate amount of deionized water, respectively, and slowly stirred to dissolve, to prepare an aluminum sulfate solution with a concentration of 100 g / L and a sodium aluminate solution with a concentration of 50 g / L; 50 g of gelatin and 30 g of gum arabic powder are weighed and put into a beaker, and 1 L of water is added and heated in a water bath until completely dissolved; the above-mentioned dissolved mixed solution is mixed with the prepared aluminum sulfate solution and sodium aluminate solution in a volume ratio of 1:2, and dispersed under an ultrasonic disperser. After 5 minutes, the mixture is taken out and allowed to settle to terminate the reaction, and the emulsion is spray-dried to obtain the microcapsule sustained-release coagulant; 2) Take 40 parts of P.O52.5 and 2 parts of fly ash (surface area of ​​700m 2 / kg, particle size range of 60 microns), 30.5 parts of fine aggregate (river sand with a particle size range of 4.75mm and a fineness modulus of 3.0) and 15 parts of coarse aggregate (limestone with a particle size range of 10mm) were poured into the mixer and stirred for 3 minutes. Then 0.25 parts of pumping agent and 12.5 parts of water were added, and the water consumption was controlled to 280k / m 3 , so that the slump value of the first-stage concrete pumping reaches 220mm; the pumping agent is composed of 15ml of high-performance polycarboxylic acid liquid and 1g of sodium gluconate, the solid content of the high-performance polycarboxylic acid liquid is 43%, and the water reduction rate is 47%; 3) Use a concrete pump to deliver the mixture in step 2) to the print head, and add 5 parts of 12g / L polyacrylamide liquid flow regulator at the print head position, and detect the slump of the concrete material extruded at the end of the print head. The slump meets the slump of the secondary extrusion molding concrete, which reaches 110mm; then add 6 parts of microcapsule slow-release setting regulator at the print head, mix and stir to obtain 3D printed coarse aggregate concrete material, and extrude it from the print head outlet to complete the printing work. The final setting time of the extruded concrete at the end of the print head is 6.9min. When all three indicators meet the technical indicator requirements, it indicates that the concrete material is qualified.

[0047] The 3D printing concrete materials prepared in the above Examples 1-9 were subjected to first-level continuous pumping slump, second-level continuous extrusion molding slump, bearing capacity performance testing and compressive strength testing. Among them, (1) the slump testing method refers to GB / T50080-2016 "Standard for Test Methods of Ordinary Concrete Mixture Performance"; (2) the compressive strength testing method refers to GB / T50107-2010 "Standard for Testing and Evaluation of Concrete Strength", and the results are shown in Table 3: Table 3 Performance of 3D printing concrete materials

[0048] According to Table 3, the performance of the 3D printing concrete material prepared by the present invention can meet the construction technical requirements of continuous pumping and rapid prototyping; the 3D printing concrete material described in the present invention adopts a two-stage construction process, namely, first-stage continuous pumping and second-stage continuous extrusion molding. (1) The high fluidity and collapse-preserving type of the concrete mixture favorably support the first-stage continuous pumping; (2) After the concrete mixture enters the print head, the viscosity of the high-fluidity concrete material increases rapidly under the sequential action of the flow regulator and the microcapsule slow-release coagulant, ensuring that the concrete printed strip can maintain its shape after extrusion molding; then the coagulant takes effect, and the setting time of the concrete printed strip is rapidly shortened, the initial setting time does not exceed 5 minutes, and the final setting time does not exceed 9 minutes, which can bear the cumulative load brought by the subsequent accumulated printed strips, thereby ensuring a higher construction efficiency.

[0049] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A 3D printed coarse aggregate concrete material, characterized in that: Calculated by mass, it includes: 35-50 parts of cementitious materials, 20-35 parts of fine aggregate, 10-30 parts of coarse aggregate, 0.01-0.2 parts of pumping agent, 10-20 parts of water, 1-10 parts of flow regulator and 3-8 parts of microcapsule slow-release setting agent.

2. A 3D printing coarse aggregate concrete material according to claim 1, characterized in that: The cementitious material comprises ordinary Portland cement and fly ash, and the mass ratio of the two is (33-40): (2-9).

3. A 3D printing coarse aggregate concrete material according to claim 1, characterized in that: The fine aggregate includes river sand with a particle size ranging from 0.18 mm to 4.75 mm and a fineness modulus of 1.5 to 3.

0.

4. A 3D printing coarse aggregate concrete material according to claim 1, characterized in that: The coarse aggregate includes basalt or limestone, and the particle size ranges from 5.0 mm to 10 mm.

5. A 3D printing coarse aggregate concrete material according to claim 1, characterized in that: The pumping agent includes a water reducer and a retarder in a dosage ratio of (15-25 ml): 1 g; the water reducer is a high-performance polycarboxylic acid liquid with a solid content of ≥15% and a water reduction rate of greater than 20%; the retarder is one or more of sodium gluconate, sodium tripolyphosphate or sodium polyphosphate.

6. A 3D printing coarse aggregate concrete material according to claim 1, characterized in that: The flow regulator is a high molecular flow regulator aqueous solution with a concentration of 3-12 g / L, which is prepared from one or more of xanthan gum, vinblastine gum, hydroxypropyl methylcellulose ether or polyacrylamide.

7. A 3D printing coarse aggregate concrete material according to claim 1, characterized in that: The microcapsule sustained-release coagulant is prepared by mixing an aluminum sulfate solution with a concentration of 20-100 g / L, a sodium aluminate solution with a concentration of 10-50 g / L, and gelatin and gum arabic powders in a mass ratio of (20-50): (10-30).

8. A method for preparing a 3D printed coarse aggregate concrete material according to any one of claims 1 to 7, characterized in that: The following steps are involved: 1) The cementitious material, fine aggregate and coarse aggregate are mixed in proportion, and then a pumping agent and water are added to prepare a mixture; 2) The mixture is transported to the print head, and a flow regulator and a microcapsule slow-release coagulant are added at the print head inlet for mixing and stirring to obtain a 3D printed coarse aggregate concrete material, which is finally extruded at the print head outlet.

9. The method for preparing a 3D printed coarse aggregate concrete material according to claim 8, characterized in that: In step 2), the preparation method of the microcapsule sustained-release coagulant comprises the following steps: S1: preparing an aluminum sulfate solution with a concentration of 20-100 g / L and a sodium aluminate solution with a concentration of 10-50 g / L; S2: Mix gelatin and gum arabic powder and water in a ratio of (20-50 g): (10-30 g): 1 L, and heat in a water bath to prepare a mixed solution; S3: the mixed solution obtained in S2 is mixed with the aluminum sulfate solution and the sodium aluminate solution obtained in S1 in a volume ratio of 1:2, and an emulsion is obtained after ultrasonic dispersion, and the emulsion is spray-dried to obtain the microcapsule sustained-release coagulant.

10. Application of a 3D printing coarse aggregate concrete material as claimed in any one of claims 1 to 7 in 3D printing technology.

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