Method for regulating and controlling rheological property of 3D printing concrete

Abstract

The invention relates to a method for regulating and controlling the rheological property of 3D printing concrete. The method comprises the following steps: S1, preparing concrete printing slurry; the concrete printing slurry is prepared from the following components in parts by weight: 75 to 100 parts of cement clinker, 75 to 125 parts of aggregate, 0 to 25 parts of mineral admixture, 0 to 1 part of concrete admixture and 25 to 40 parts of water, s2, the concrete printing slurry is input into a pressurized carbonization stirrer, and CO2 is introduced after sealing; and S3, when the air pressure of CO2 is 0.05-0.5 MPa, pressurizing, carbonizing and stirring to obtain the concrete material with high constructability. Compared with the prior art, the concrete slurry is pressurized, carbonized and stirred before 3D printing of the concrete slurry, so that the concrete material can be effectively promoted to be converted from high working performance to high constructability, and the contradiction of the concrete material in rheological properties during transportation, pumping and printing is solved. Meanwhile, part of industrial waste gas with the high CO2 content can be consumed, and carbon emission of 3D printing buildings can be further reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of 3D printing concrete, and in particular relates to a method for regulating the rheological properties of 3D printing concrete. Background Art

[0002] 3D printing concrete is an emerging intelligent construction technology for the future, which has the advantages of no need for templates, high construction efficiency, and rich shapes. However, 3D printing requires concrete to have good fluidity to ensure that it can flow smoothly in the pumping pipeline (pumpability) and meet the requirements of continuous and stable extrusion (printability); at the same time, the mortar fluidity should not be too high, otherwise it will affect the number of continuous printable layers and reduce the constructability of 3D printing. How to solve the contradiction between pumpability, printability and constructability has always been one of the hot spots and difficulties in the field of 3D printing concrete technology.

[0003] The main solution currently adopted by the academic and industry circles to solve the contradiction between pumpability, printability and constructability is to find a balance point to simultaneously meet the rheological properties required by pumpability, printability and constructability, and design the mix ratio of printing materials based on this balance point. However, this method limits the scope of application of the mix ratio of printing materials and increases the amount of cement in the printing materials, thereby increasing the carbon footprint of this technology.

[0004] In recent years, a concept of "on-demand solidification" 3D printing concrete technology has been proposed. The characteristic of this technology is that it can more accurately control the rheological properties of concrete and adjust the rheological properties of the printed material as needed when printing. The high-fluidity concrete material is pumped to the print head, and then an accelerator is injected near the nozzle and combined with the concrete to accelerate the solidification and improve the rheological properties of the concrete so that it can have a certain strength after extrusion. However, this technology has the disadvantages of reducing the later mechanical properties and durability of concrete, increasing material costs, and uneven mixing.

[0005] In addition, another method similar to "solidification on demand" - carbonization mixing, was also proposed not long ago. It uses CO2 as a coagulant to accelerate the hardening and coagulation of concrete materials, thereby improving constructability. However, this method still has defects such as low efficiency, long mixing time, large amount of CO2 escape, and the accelerating effect needs to be further improved.

[0006] Therefore, the contradiction between the pumpability and constructability of 3D printed concrete remains to be resolved, and a new method for regulating the rheological properties of 3D printed concrete is urgently needed. Summary of the invention

[0007] The purpose of the present invention is to provide a method for regulating the rheological properties of 3D printed concrete in order to overcome the defects of the prior art and solve the contradiction between the pumpability and constructability of 3D printed concrete.

[0008] The purpose of the present invention can be achieved by the following technical solutions:

[0009] The present invention provides a method for regulating the rheological properties of 3D printed concrete, comprising the following steps:

[0010] S1: Preparation of concrete printing slurry;

[0011] The concrete printing slurry comprises the following components in parts by weight:

[0012]

[0013] S2: The concrete printing slurry is input into the pressurized carbonization mixer, and CO2 is introduced after sealing;

[0014] S3: When the CO2 gas pressure is 0.05-0.5MPa (with atmospheric pressure as the zero point), pressurized carbonization and mixing are carried out to obtain a concrete material with high constructability.

[0015] Furthermore, in step S1, the cement clinker includes one or more of Portland cement and clinker, aluminate cement and clinker, and sulphoaluminate cement and clinker.

[0016] Furthermore, in step S1, the mineral admixture includes one or more of fly ash, silica ash, mineral powder, glass powder, steel slag, recycled powder, and limestone powder. The mineral admixture can react with CO2 to generate carbonate, accelerate coagulation, and improve the strength of the extruded material.

[0017] Furthermore, in step S1, the aggregate includes one or more of river sand, machine-made sand, and regenerated sand.

[0018] Furthermore, in step S1, the concrete admixture includes one or more of a water reducing agent, a retarder, a thickener, and an accelerator.

[0019] Furthermore, the water reducer includes polycarboxylic acid type water reducer, lignin sulfonate type water reducer, naphthalene type water reducer, melamine type water reducer, etc.; the retarder includes phosphate type water reducer, borax, sucrose, etc.; the thickener includes hydroxypropyl methylcellulose ether, sodium polyacrylate, etc.; the early strength agent includes chloride early strength agent, sulfate early strength agent, sodium aluminate, etc.

[0020] Furthermore, in step S1, the water is selected from tap water or purified water.

[0021] Furthermore, in step S2, the CO2 gas flow rate introduced per kg of the concrete printing slurry is 3-5 L / min.

[0022] Furthermore, in step S2, the CO2 is selected from industrial-grade CO2 with a concentration ≥ 99% or industrial waste gas with a concentration ≥ 30%.

[0023] Further, in step S2, the pressurized carbonization agitator includes: a device body; a stirring paddle arranged in the device body, the stirring paddle is connected to a motor that can drive it to rotate; a concrete feed port arranged at the top of the device body, for inputting concrete printing slurry; a concrete discharge port arranged at the bottom of the device body, for discharging highly buildable concrete materials; a CO2 feed port arranged on the device body for introducing CO2, the CO2 feed port is provided with a flow meter and an air valve; a barometer arranged on the device body, for monitoring the air pressure conditions in the device body.

[0024] Furthermore, the pressurized carbonization agitator is an agitator with good air tightness, and can manually or automatically control the introduction of CO2 and the feeding and discharging of concrete materials.

[0025] Furthermore, in step S3, the carbonization time is 20-240s.

[0026] Furthermore, in step S3, the stirring speed is 100-300 rpm.

[0027] Furthermore, in step S3, the target workability of the carbonization stirring is 150-180 mm.

[0028] (1) The present invention performs pressurized carbonization and stirring treatment on the concrete slurry before 3D printing the concrete slurry, which can effectively promote the transformation of the concrete material from having high working performance to having high constructability, and solves the contradiction in the rheological properties of the concrete material during transportation, pumping and printing.

[0029] (2) The present invention combines pressurization and carbonization mixing, which effectively improves the speed and effect of carbonization mixing, and can improve the rheological properties and constructability of concrete materials to a greater extent in a shorter time while maintaining a high compressive strength. It is expected that the prepared 3D printing concrete material can be used in 3D printing buildings.

[0030] (3) The concrete rheological properties control method of the present invention can reduce the fluidity of the concrete material after carbonization and mixing, accelerate the hardening speed, and enhance the early strength in a relatively short period of time, thereby efficiently and quickly improving the constructability of 3D printed concrete.

[0031] (4) The pressurized carbonization agitator of the present application has good air tightness, and the CO2 pressure in the device can be monitored by a barometer, which is beneficial to reduce the escape of CO2, improve the efficiency and speed of the carbonization reaction, and give full play to the carbonization effect of CO2.

[0032] (5) The CO2 used in the present invention may be industrial waste gas from factory production. By absorbing these industrial waste gases with high CO2 content, the present invention can further reduce the carbon emissions of 3D printed buildings. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic structural diagram of the pressurized carbonization agitator of the present invention.

[0034] Description of the markings in the figure:

[0035] 1-device body, 2-mixing paddle, 3-motor, 4-concrete feed port, 5-concrete discharge port, 6-CO2 feed port, 7-flow meter, 8-air valve, 9-air pressure gauge. DETAILED DESCRIPTION

[0036] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0037] In the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention; the terms "first", "second", and "third" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance; in addition, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0038] In addition, unless otherwise specified, the reagents, methods, instruments and equipment used in the present invention are conventional reagents, methods, instruments and equipment in the art. Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0039] The pressurized carbonization agitator in the following embodiments is an agitator with good airtightness, which can manually or automatically control the introduction of CO2 and the feeding and discharging of concrete materials, and specifically includes: a device body 1; a stirring paddle 2 arranged in the device body 1, and the stirring paddle 2 is connected to a motor 3 that can drive it to rotate; a concrete feed port 4 arranged at the top of the device body 1, for inputting concrete printing slurry; a concrete discharge port 5 arranged at the bottom of the device body 1, for discharging highly buildable concrete materials; a CO2 feed port 6 arranged on the device body 1 for introducing CO2, and the CO2 feed port 6 is provided with a flow meter 7 and an air valve 8; a barometer 9 arranged on the device body 1, for monitoring the air pressure conditions in the device body 1.

[0040] The concrete printing slurry ratios in the following examples and comparative examples are specifically shown in Table 1.

[0041] Embodiment 1:

[0042] This embodiment provides a method for controlling the rheological properties of 3D printed concrete. A 3D concrete printing material is prepared according to the mix ratio in Table 1 and CO2 is introduced for pressurized carbonization and stirring. The specific preparation method and parameters are as follows:

[0043] S1: First, dry-mix the silicate cement and river sand thoroughly, then add tap water and mix evenly to obtain concrete printing slurry.

[0044] S2: Concrete slurry with good working performance is transported to the pressurized carbonization agitator, and all valves are closed, and then CO2 is continuously introduced until the pressure in the pressurized carbonization agitator reaches 0.1 MPa. The CO2 flow rate is determined according to the amount of concrete material used, and in this embodiment it is 3L / min / kg; the CO2 concentration is 99% or above.

[0045] S3: Then start the stirring device to perform pressurized carbonization stirring, the carbonization stirring machine speed is 240rpm, and stirring is performed for 20s. After the stirring is completed, a concrete material with good constructability can be obtained, which can be used for 3D printing.

[0046] Embodiment 2:

[0047] The present embodiment provides a method for regulating the rheological properties of 3D printed concrete. The 3D concrete printing material is prepared according to the mix ratio in Table 1 and CO2 is introduced for pressurized carbonization. The difference from Example 1 is that the pressurized carbonization in this embodiment is stirred for 60 seconds and the CO2 pressure is 0.1 MPa.

[0048] Embodiment 3:

[0049] The present embodiment provides a method for regulating the rheological properties of 3D printed concrete. The 3D concrete printing material is prepared according to the mix ratio in Table 1 and CO2 is introduced for pressurized carbonization. The difference from Example 1 is that the pressurized carbonization in this embodiment is stirred for 60 seconds and the CO2 pressure is 0.05 MPa.

[0050] Embodiment 4:

[0051] The present embodiment provides a method for regulating the rheological properties of 3D printed concrete. The 3D concrete printing material is prepared according to the mix ratio in Table 1 and CO2 is introduced for pressurized carbonization. The difference from Example 1 is that the pressurized carbonization in this embodiment is stirred for 60 seconds and the CO2 pressure is 0.15 MPa.

[0052] Comparative Example 1:

[0053] In this comparative example, 3D concrete printing materials were prepared according to the mix ratio in Table 1. The difference from Example 1 is that in this comparative example, CO2 was not introduced for pressurized carbonization and stirring.

[0054] Comparative Example 2:

[0055] This comparative example provides a method for regulating the rheological properties of 3D printed concrete. A 3D concrete printing material is prepared according to the mix ratio in Table 1 and CO2 is introduced for pressurized carbonization. The difference from Example 1 is that the pressurized carbonization in this comparative example is stirred for 20 seconds, and the CO2 pressure is 0 MPa (i.e., atmospheric pressure is maintained).

[0056] Comparative Example 3:

[0057] This comparative example provides a method for regulating the rheological properties of 3D printed concrete. A 3D concrete printing material is prepared according to the mix ratio in Table 1 and CO2 is introduced for pressurized carbonization. The difference from Example 1 is that the pressurized carbonization in this comparative example is stirred for 60s, and the CO2 pressure is 0MPa (i.e., atmospheric pressure is maintained).

[0058] Table 1 Concrete mix ratio and carbonization mixing parameter settings of the embodiment and the comparative example

[0059]

[0060] The present invention carries out the following tests on the above-mentioned embodiments and comparative examples:

[0061] (1) Pumpability: According to the national standard "Method for Determination of Fluidity of Cement Mortar" (GB / T2419-2005), the fluidity (pumpability) is measured using a cement mortar fluidity tester (jump table). The average diameter of the mortar after 25 vertical vibrations is the fluidity;

[0062] (2) Constructability: According to the industry standard "Standard for Test Methods for Basic Properties of Building Mortar" (JGJ / T70-2009), the penetration resistance (constructability) of the mortar is measured using an electronic penetration resistance meter with a probe diameter of 5 mm. The maximum penetration resistance when the probe is pressed down after 2 hours is measured.

[0063] (3) Compressive strength test: According to the industry standard “Standard for Test Methods for Basic Properties of Building Mortar” (JGJ / T70-2009), a test block size of 50×50×50 mm was selected, and an electronic servo press with a range of 600 kN was used to test the 7-day and 28-day compressive strength of the mortar. The loading rate was set to 2.4 kN / s.

[0064] The concrete material performance indicators of the above comparative examples and embodiments are shown in Table 2:

[0065] Table 2 Concrete material performance indicators

[0066]

[0067]

[0068] As can be seen from the above table, compared with no carbonization stirring and normal pressure carbonization stirring, the pressurized carbonization stirring of the concrete slurry by the control method of the present invention can significantly reduce the working performance (i.e., pumpability) of the concrete slurry, and significantly improve the buildability of the concrete material. After 2 hours, the penetration resistance (i.e., buildability) is increased from 0.16MPa to about 0.9MPa. It can be seen that compared with normal pressure carbonization stirring, the method of pressurized control of the present invention can better take into account the high working performance and high buildability of 3D printed concrete.

[0069] In addition, compared with the conventional concrete material in Comparative Example 1 which is not carbonized and pressurized, the pressurized control method of the present invention can still improve the 7-day and 28-day compressive strength of the concrete material. Therefore, in general, the control method provided by the present application can more effectively and quickly control the rheological properties of the concrete material as needed, solve the contradiction between high workability and high constructability, and maintain good compressive strength.

[0070] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for regulating the rheological properties of 3D printed concrete, characterized in that: The following steps are involved: S1: Preparation of concrete printing slurry; The concrete printing slurry comprises the following components in parts by weight: S2: The concrete printing slurry is input into the pressurized carbonization mixer, and CO2 is introduced after sealing; S3: When the CO2 pressure is 0.05-0.5MPa, pressurized carbonization and mixing are carried out to obtain a concrete material with high constructability.

2. A method for controlling rheological properties of 3D printed concrete according to claim 1, characterized in that: In step S1, the cement clinker includes one or more of silicate cement and clinker, aluminate cement and clinker, and sulphoaluminate cement and clinker.

3. A method for controlling rheological properties of 3D printed concrete according to claim 1, characterized in that: In step S1, the mineral admixture includes one or more of fly ash, silica ash, mineral powder, glass powder, steel slag, recycled powder, and limestone powder.

4. A method for controlling rheological properties of 3D printed concrete according to claim 1, characterized in that: In step S1, the aggregate includes one or more of river sand, machine-made sand, and regenerated sand.

5. A method for controlling rheological properties of 3D printed concrete according to claim 1, characterized in that: In step S1, the concrete admixture includes one or more of a water reducing agent, a retarder, a thickener, and an accelerator.

6. A method for controlling rheological properties of 3D printed concrete according to claim 1, characterized in that: In step S2, the CO2 is selected from industrial-grade CO2 with a concentration of ≥99% or industrial waste gas with a concentration of ≥30%.

7. A method for controlling rheological properties of 3D printed concrete according to claim 1, characterized in that: In step S2, the pressurized carbonization agitator comprises: Device body (1); A stirring paddle (2) is arranged in the device body (1), and the stirring paddle (2) is connected to a motor (3) capable of driving the stirring paddle (2) to rotate; A concrete feed port (4) provided at the top of the device body (1) for inputting concrete printing slurry; A concrete discharge port (5) provided at the bottom of the device body (1) is used to discharge concrete material with high buildability; A CO2 feed port (6) is provided on the device body (1) for introducing CO2, and a flow meter (7) and a gas valve (8) are provided on the CO2 feed port (6); The barometer (9) provided on the device body (1) is used to monitor the air pressure condition in the device body (1).

8. A method for controlling rheological properties of 3D printed concrete according to claim 1, characterized in that: In step S3, the time of pressurized carbonization stirring is 20-240s.

9. A method for controlling rheological properties of 3D printed concrete according to claim 1, characterized in that: In step S3, the stirring speed is 100-300 rpm.

10. A method for controlling rheological properties of 3D printed concrete according to claim 1, characterized in that: In step S3, the target workability of the pressurized carbonization stirring is 150-180 mm.

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