3d-printed low-carbon concrete containing modified recycled aggregates and micro-fines reinforcing agents

Abstract

The application discloses a kind of 3D printing low-carbon concrete containing modified recycled aggregate and micro powder reinforcing agent, comprising the following steps: (1) after placing recycled concrete coarse aggregate in sodium or potassium water glass, ultrasonic treatment is carried out.Then the coarse aggregate is separated and carbonized, after completion, the obtained coarse aggregate is heated to obtain pretreated recycled aggregate.(2) after placing the pretreated recycled aggregate in saturated lime water, heat and keep warm treatment is carried out, and modified recycled aggregate is obtained after completion.(3) waste cement slurry powder, γ-C2S powder and water are formed into wet material, then carbonization treatment is carried out, then heating treatment is carried out, the obtained solid is ground to obtain modified recycled micro powder reinforcing agent.(4) cement, modified recycled aggregate, fine aggregate, micro powder reinforcing agent, water reducing agent and water are uniformly mixed, and 3D printing low-carbon concrete is obtained.The process of the application not only improves the mechanical strength and fluidity of 3D printing concrete prepared from recycled concrete aggregate, but also consumes carbon dioxide and reduces carbon emissions.

Description

Technical Field

[0001] This invention relates to the field of 3D printing material preparation technology, specifically to a 3D printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent. Background Technology

[0002] Concrete is an irreplaceable basic building material. 3D printed concrete is a new construction technology that combines 3D printing technology with traditional concrete materials. It uses a printer controlled by computer software to rapidly print complex structures layer by layer from concrete. Traditional 3D printed concrete mainly uses cement as a binder, but cement production is not only energy-intensive but also emits large amounts of carbon dioxide.

[0003] Recycled concrete aggregate is obtained from waste concrete blocks through processes such as crushing, washing, and grading. Reusing it in concrete production helps reduce the raw materials required for new concrete, thereby lowering carbon emissions. However, the high porosity of recycled concrete aggregate leads to increased water absorption and reduced strength compared to natural aggregate, resulting in insufficient flowability and strength in the prepared 3D printed concrete, affecting its construction and structural strength. Furthermore, the production of cement-based slurry at commercial concrete plants generates a large amount of waste slurry from cleaning mixing tanks and other equipment. The sediment in this waste is mainly silicate cement-based material, which, having undergone hydration, lacks cementitious properties and cannot be recycled as cement. The treatment and utilization of these wastes has become one of the challenges faced by commercial concrete plants. Summary of the Invention

[0004] This invention provides a 3D-printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent. This not only improves the mechanical strength and flowability of the 3D-printed concrete prepared from recycled aggregate, but also consumes carbon dioxide, reducing carbon emissions. Specifically, the technical solution of this invention is as follows.

[0005] A 3D-printed low-carbon concrete containing modified recycled aggregate and micronized powder reinforcing agent comprises the following raw materials: 300-360 parts by weight of cementitious material, 620-750 parts by weight of modified recycled aggregate, 400-480 parts by weight of fine aggregate, 50-70 parts by weight of modified recycled micronized powder reinforcing agent, 4.5-7.2 parts by weight of water-reducing agent, and water, with a water-cement ratio of 0.35-0.45. The modified recycled aggregate and modified recycled micronized powder reinforcing agent are prepared using the following method:

[0006] (1) The recycled concrete coarse aggregate is placed in sodium or potassium silicate and then subjected to ultrasonic treatment. The coarse aggregate is then separated and placed in a sealed container with a carbon dioxide atmosphere for carbonization treatment. After completion, the obtained coarse aggregate is heated to obtain pretreated recycled aggregate.

[0007] (2) The pretreated recycled aggregate is placed in saturated lime water and then heated and kept warm. After the treatment is completed, the solid matter is separated to obtain the modified recycled aggregate.

[0008] (3) After sedimentation of silicate cement-based waste slurry, the precipitate is separated, dried and ground into powder. The powder, γ-C2S powder and water are mixed evenly to form a wet material. The wet material is then placed in a sealed container with a carbon dioxide atmosphere for carbonization treatment. After completion, it is heated and the resulting solid is ground to obtain the modified recycled micro powder reinforcing agent.

[0009] Furthermore, the water-reducing agent includes any one of polycarboxylate water-reducing agents, lignin sulfonate water-reducing agents, naphthalene-based water-reducing agents, aliphatic water-reducing agents, etc.

[0010] Further, the particle size of the fine aggregate is 0.5~1mm. Optionally, the fine aggregate includes at least one of river sand, manufactured sand, etc.

[0011] Further, in step (1), the amount of recycled concrete coarse aggregate added to the sodium or potassium silicate is 25~70 g / L. Optionally, the mass fraction of the sodium or potassium silicate is not less than 20%.

[0012] Further, in step (1), the ultrasonic treatment time is 30-40 minutes. Optionally, the particle size of the recycled concrete coarse aggregate is 10-20 mm.

[0013] Further, in step (1), the carbonization treatment temperature is 40~60℃ and the time is 1~1.5h. Optionally, the pressure in the sealed container is 0.2~0.35MPa.

[0014] Further, in step (1), the temperature of the heat treatment is 180~250℃, and the coarse aggregate is heated at this temperature until the weight of the coarse aggregate is constant.

[0015] Furthermore, in step (2), the amount of pretreated recycled aggregate added to the saturated lime water is 20~40g / L.

[0016] Furthermore, in step (2), the heating temperature is 50~80℃ and the time is 4~7h.

[0017] Further, in step (3), the ratio of the powder, γ-C2S powder, and water is 1~1.15 parts by weight: 0.18~0.25 parts by weight: 0.3~0.4 parts by weight. Optionally, the fineness of the powder and γ-C2S powder is not less than 200 mesh.

[0018] Further, in step (3), the carbonization treatment time is 30~50 min. Optionally, the pressure in the sealed container is 0.2~0.35 MPa.

[0019] Further, in step (3), the heat treatment temperature is 80~100℃ and the time is 1~2h. Optionally, the fineness of the modified recycled micro powder reinforcing agent is 300~600 mesh.

[0020] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0021] Recycled concrete coarse aggregate contains numerous pores and cracks, leading to deterioration in the flowability and mechanical strength of 3D printed concrete prepared from it. To address this, this invention first utilizes the pores of the recycled concrete coarse aggregate to absorb sodium or potassium silicate, followed by carbonation treatment in a carbon dioxide atmosphere, resulting in the formation of carbonate and silicate precipitates. This not only achieves carbon dioxide solidification, helping to offset carbon emissions generated during the production of the cementitious material, but also, after heat treatment, the silicate precipitates decompose into nano-silica particles that fill the pores and cracks of the recycled concrete coarse aggregate, reducing porosity. Further treatment of the recycled concrete coarse aggregate in saturated lime water further enhances its porosity. On one hand, the nano-silica particles react with calcium hydroxide in the saturated lime water to form hydrated calcium silicate cement, further filling, bonding, and repairing the pores and cracks within the coarse aggregate. On the other hand, the reaction of the carbonates with calcium hydroxide in the saturated lime water to form nano-calcium carbonate particles that fill the pores and cracks within the coarse aggregate also reduces porosity. The 3D-printed concrete prepared from the modified recycled aggregate obtained by the above method not only has good fluidity and mechanical strength, but also the hydrated calcium silicate and nano-calcium carbonate on the surface of the coarse aggregate have an inducing hydration effect. These act as nucleation sites for the hydration of cementitious materials, promoting the hydration reaction, forming more cementitious components, and improving the mechanical strength of the concrete. Furthermore, this invention uses waste slurry generated from the production of cement-based slurry at commercial concrete plants to prepare a modified recycled micro-powder reinforcing agent, not only realizing the utilization of this solid waste but also enhancing the mechanical strength of the prepared 3D-printed concrete. This invention mixes the waste slurry with γ-C2S powder and then performs carbonation treatment. Utilizing the low hydration activity of γ-C2S but its rapid reaction with carbon dioxide, not only is the γ-C2S converted into calcium carbonate and nano-silica, but the calcium hydroxide in the waste slurry is also converted into calcium carbonate, simultaneously achieving carbon dioxide consumption and solidification. After the modified recycled micro-powder reinforcing agent is incorporated into the concrete, the nano-silica undergoes a secondary hydration reaction with calcium hydroxide, a hydration product of cement, to form calcium silicate hydrate cementitious components, thereby improving the strength of the concrete structure. Simultaneously, the calcium carbonate also helps fill the pores in the concrete matrix, increasing density and further enhancing the strength of the concrete structure. Attached Figure Description

[0022] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings, wherein:

[0023] Figure 1 The image below shows the effect of 3D printing the low-carbon concrete prepared in Example 1.

[0024] Figure 2 The rheological test diagram is for the 3D-printed low-carbon concrete prepared in Example 1 below. Detailed Implementation

[0025] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. The present invention will now be further described with reference to specific embodiments.

[0026] Example 1

[0027] The preparation of 3D-printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent includes the following steps:

[0028] (1) Continuously graded recycled concrete coarse aggregate with a particle size between 10 and 20 mm was added to 30% sodium silicate solution at a ratio of 40 g / L, and then ultrasonically vibrated for 35 min. After completion, the coarse aggregate was filtered out and placed in a high-pressure reactor. After sealing, carbon dioxide gas was introduced and the pressure was set to 0.3 MPa. Then, it was heated to 50°C and held for 1 h for carbonation treatment. After completion, the obtained coarse aggregate was heated at 220°C until the weight was constant to obtain pretreated recycled aggregate.

[0029] (2) Add the pretreated recycled aggregate to saturated lime water at a ratio of 30 g / L, then heat it in a water bath to 60°C and keep it at that temperature for 5.5 h. After the solids are filtered out, the aggregate is dried to obtain the modified recycled aggregate for later use.

[0030] (3) After sedimentation of silicate cement-based waste slurry, the precipitate is separated, dried, ground, and sieved. The resulting powder (200 mesh), γ-C2S powder (200 mesh), and water are mixed in a ratio of 1.0 parts by weight: 0.2 parts by weight: 0.35 parts by weight and stirred evenly to form a wet material. The wet material is then placed in a high-pressure reactor, sealed, and carbonized with carbon dioxide gas for 40 minutes at a pressure of 0.3 MPa. After completion, the product is removed and heated at 85°C for 2 hours. The resulting solid is then ground and sieved through a 500-mesh sieve to obtain the modified recycled micro-powder reinforcing agent, which is ready for use.

[0031] (4) Take the following components: 330 parts by weight of 42.5 ordinary silicate cement, 670 parts by weight of the modified recycled aggregate described in this embodiment, 440 parts by weight of fine river sand with a continuous gradation between 0.5 and 1 mm particle size, 60 parts by weight of the modified recycled micro powder reinforcing agent of this embodiment, 6.5 parts by weight of polycarboxylate superplasticizer, and 132 parts by weight of water. Mix the above components and stir for 3 minutes to obtain 3D printed low-carbon concrete.

[0032] After printing the 3D-printed low-carbon concrete described in this embodiment (as shown in the example) Figure 1 (As shown) After natural curing for 28 days, specimens were cut and their compressive strength was tested according to the "Standard for Test Methods of Physical and Mechanical Properties of Concrete" (GB / T 50081-2019). Additionally, creep-recovery tests were performed on the 3D-printed low-carbon concrete using a HAAKE Mars 40 rotational rheometer (e.g., Figure 2 As shown in the figure, the rheological properties of concrete materials were measured. The results showed that the compressive strength was 52.39 MPa and the recovery rate was 83.7%.

[0033] Example 2

[0034] The preparation of 3D-printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent includes the following steps:

[0035] (1) Continuously graded recycled concrete coarse aggregate with a particle size between 10 and 20 mm was added to 20% potassium silicate by mass at a ratio of 25 g / L, and then ultrasonically vibrated for 30 min. After completion, the coarse aggregate was filtered out and placed in a high-pressure reactor. After sealing, carbon dioxide gas was introduced and the pressure was set to 0.35 MPa. Then, it was heated to 40°C and held for 1.5 h for carbonization treatment. After completion, the obtained coarse aggregate was heated at 180°C until the weight was constant to obtain pretreated recycled aggregate.

[0036] (2) Add the pretreated recycled aggregate to saturated lime water at a ratio of 20 g / L, then heat it in a water bath to 50°C and keep it warm for 7 hours. After the solid matter is filtered out, it is dried to obtain the modified recycled aggregate for later use.

[0037] (3) After sedimentation of silicate cement-based waste slurry, the precipitate is separated, dried, ground, and sieved. The resulting powder (300 mesh), γ-C2S powder (300 mesh), and water are mixed in a ratio of 1.15 parts by weight: 0.25 parts by weight: 0.4 parts by weight and stirred evenly to form a wet material. The wet material is then placed in a high-pressure reactor, sealed, and carbonized with carbon dioxide gas for 50 minutes at a pressure of 0.2 MPa. After completion, the product is removed and heated at 100°C for 1 hour. The resulting solid is then ground and sieved through a 600-mesh sieve to obtain the modified recycled micro-powder reinforcing agent, which is ready for use.

[0038] (4) Take the following components: 360 parts by weight of 42.5 ordinary Portland cement, 750 parts by weight of the modified recycled aggregate described in this embodiment, 480 parts by weight of fine river sand with a continuous gradation between 0.5 and 1 mm particle size, 70 parts by weight of the modified recycled micro powder reinforcing agent described in this embodiment, 7.2 parts by weight of naphthalene-based water-reducing agent, and 162 parts by weight of water. Mix the above components and stir for 3 minutes to obtain 3D printed low-carbon concrete.

[0039] The compressive strength and creep-recovery tests were performed on the 3D-printed low-carbon concrete prepared in this example using the same method as in Example 1. The results showed that the compressive strength was 51.83 MPa and the recovery deformation rate was 85.4%.

[0040] Example 3

[0041] The preparation of 3D-printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent includes the following steps:

[0042] (1) Continuously graded recycled concrete coarse aggregate with a particle size between 10 and 20 mm was added to 35% sodium silicate solution at a ratio of 70 g / L, and then ultrasonically vibrated for 40 min. After completion, the coarse aggregate was filtered out and placed in a high-pressure reactor. After sealing, carbon dioxide gas was introduced and the pressure was set to 0.2 MPa. Then, it was heated to 60°C and held for 1.5 h for carbonization treatment. After completion, the obtained coarse aggregate was heated at 250°C until the weight was constant to obtain pretreated recycled aggregate.

[0043] (2) Add the pretreated recycled aggregate to saturated lime water at a ratio of 40 g / L, then heat it in a water bath to 80°C and keep it warm for 4 hours. After the solid matter is filtered out, it is dried to obtain the modified recycled aggregate for later use.

[0044] (3) After sedimentation of silicate cement-based waste slurry, the precipitate is separated, dried, ground, and sieved. The resulting powder (200 mesh), γ-C2S powder (200 mesh), and water are mixed in a ratio of 1.1 parts by weight: 0.18 parts by weight: 0.3 parts by weight and stirred evenly to form a wet material. The wet material is then placed in a high-pressure reactor, sealed, and carbonized with carbon dioxide gas for 30 minutes at a pressure of 0.35 MPa. After completion, the product is removed and heated at 80°C for 1.5 hours. The resulting solid is then ground and sieved through a 300-mesh sieve to obtain the modified recycled micro-powder reinforcing agent, which is ready for use.

[0045] (4) Take the following components: 300 parts by weight of 42.5 ordinary Portland cement, 620 parts by weight of the modified recycled aggregate described in this embodiment, 400 parts by weight of fine river sand with a continuous gradation between 0.5 and 1 mm particle size, 50 parts by weight of the modified recycled micro powder reinforcing agent described in this embodiment, 4.5 parts by weight of sodium lignosulfonate water-reducing agent, and 105 parts by weight of water. Mix the above components and stir for 3 minutes to obtain 3D printed low-carbon concrete.

[0046] The compressive strength and creep-recovery tests were performed on the 3D-printed low-carbon concrete prepared in this example using the same method as in Example 1. The results showed that the compressive strength was 54.12 MPa and the recovery deformation rate was 81.6%.

[0047] Example 4

[0048] The preparation of 3D-printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent includes the following steps:

[0049] (1) Add recycled concrete coarse aggregate with a continuous gradation between 10 and 20 mm to clean water at a ratio of 40 g / L, and then treat it with ultrasonic vibration for 35 min. After completion, filter out the coarse aggregate, place it in a high-pressure reactor, seal it, fill it with carbon dioxide gas, set the pressure to 0.3 MPa, and then heat it to 50 °C and keep it at that temperature for 1 h for carbonation treatment. After completion, heat the obtained coarse aggregate at 220 °C until the weight is constant to obtain pretreated recycled aggregate.

[0050] (2) Add the pretreated recycled aggregate to saturated lime water at a ratio of 30 g / L, then heat it in a water bath to 60°C and keep it at that temperature for 5.5 h. After the solids are filtered out, the aggregate is dried to obtain the modified recycled aggregate for later use.

[0051] (3) Take the following components: 330 parts by weight of 42.5 ordinary silicate cement, 670 parts by weight of the modified recycled aggregate described in this embodiment, 440 parts by weight of fine river sand with a continuous gradation between 0.5 and 1 mm particle size, 60 parts by weight of the modified recycled micro powder reinforcing agent prepared in Example 1, 6.5 parts by weight of polycarboxylate superplasticizer, and 132 parts by weight of water. Mix the above components and stir for 3 minutes to obtain 3D printed low-carbon concrete.

[0052] The compressive strength and creep-recovery tests were performed on the 3D-printed low-carbon concrete prepared in this example using the same method as in Example 1. The results showed that the compressive strength was 45.27 MPa and the recovery deformation rate was 72.5%.

[0053] Example 5

[0054] The preparation of 3D-printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent includes the following steps:

[0055] (1) Continuously graded recycled concrete coarse aggregate with a particle size between 10 and 20 mm was added to 35% sodium silicate solution at a ratio of 70 g / L, and then ultrasonically vibrated for 40 min. After completion, the coarse aggregate was filtered out and placed in a high-pressure reactor. After sealing, carbon dioxide gas was introduced and the pressure was set to 0.2 MPa. Then, it was heated to 60°C and held for 1.5 h for carbonization treatment. After completion, the obtained coarse aggregate was heated at 250°C until the weight was constant to obtain pretreated recycled aggregate.

[0056] (1) Continuously graded recycled concrete coarse aggregate with a particle size between 10 and 20 mm was added to 35% sodium silicate solution at a ratio of 70 g / L, and then ultrasonically vibrated for 40 min. After completion, the coarse aggregate was filtered out and placed in a high-pressure reactor. After sealing, it was heated to 60°C and kept at that temperature for 1.5 h. After completion, the obtained coarse aggregate was heated at 250°C until its weight was constant to obtain pretreated recycled aggregate.

[0057] (2) Add the pretreated recycled aggregate to saturated lime water at a ratio of 40 g / L, then heat it in a water bath to 80°C and keep it warm for 4 hours. After the solid matter is filtered out, it is dried to obtain the modified recycled aggregate for later use.

[0058] (3) Take the following components: 300 parts by weight of 42.5 ordinary silicate cement, 620 parts by weight of the modified recycled aggregate described in this embodiment, 400 parts by weight of fine river sand with a continuous gradation between 0.5 and 1 mm particle size, 50 parts by weight of the modified recycled micro powder reinforcing agent described in Example 3, 4.5 parts by weight of sodium lignosulfonate water-reducing agent, and 105 parts by weight of water. Mix the above components and stir for 3 minutes to obtain 3D printed low-carbon concrete.

[0059] The compressive strength and creep-recovery tests were performed on the 3D-printed low-carbon concrete prepared in this example using the same method as in Example 1. The results showed that the compressive strength was 49.04 MPa and the recovery deformation rate was 77.1%.

[0060] Example 6

[0061] The preparation of 3D-printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent includes the following steps:

[0062] (1) Continuously graded recycled concrete coarse aggregate with a particle size between 10 and 20 mm was added to 20% potassium silicate solution at a ratio of 25 g / L, and then ultrasonically vibrated for 30 min. After completion, the coarse aggregate was filtered out, placed in a high-pressure reactor, sealed, and filled with carbon dioxide gas at a pressure of 0.35 MPa. Then it was heated to 40°C and held for 1.5 h for carbonation treatment to obtain pretreated recycled aggregate.

[0063] (2) Add the pretreated recycled aggregate to saturated lime water at a ratio of 20 g / L, then heat it in a water bath to 50°C and keep it warm for 7 hours. After the solid matter is filtered out, it is dried to obtain the modified recycled aggregate for later use.

[0064] (3) Take the following components: 360 parts by weight of 42.5 ordinary silicate cement, 750 parts by weight of the modified recycled aggregate described in this embodiment, 480 parts by weight of fine river sand with a continuous gradation between 0.5 and 1 mm particle size, 70 parts by weight of the modified recycled micro powder reinforcing agent described in Example 2, 7.2 parts by weight of naphthalene-based water-reducing agent, and 162 parts by weight of water. Mix the above components and stir for 3 minutes to obtain 3D printed low-carbon concrete.

[0065] The compressive strength and creep-recovery tests were performed on the 3D-printed low-carbon concrete prepared in this example using the same method as in Example 1. The results showed that the compressive strength was 46.71 MPa and the recovery deformation rate was 79.3%.

[0066] Example 7

[0067] The preparation of 3D-printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent includes the following steps:

[0068] (1) After sedimentation of silicate cement-based waste slurry, the precipitate is separated, dried, ground and sieved to obtain micro powder with a fineness of 200 mesh, which is then used for later use.

[0069] (2) Take the following components: 330 parts by weight of 42.5 ordinary Portland cement, 670 parts by weight of the modified recycled aggregate of Example 1 above, 440 parts by weight of fine river sand with a continuous gradation between 0.5 and 1 mm particle size, 60 parts by weight of the micro powder of this example, 6.5 parts by weight of polycarboxylate superplasticizer, and 132 parts by weight of water. Mix the above components and stir for 3 minutes to obtain 3D printed low-carbon concrete.

[0070] The compressive strength and creep-recovery tests were performed on the 3D-printed low-carbon concrete prepared in this example using the same method as in Example 1. The results showed that the compressive strength was 50.16 MPa and the recovery deformation rate was 82.9%.

[0071] Example 8

[0072] The preparation of 3D-printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent includes the following steps:

[0073] (1) After sedimentation of silicate cement-based waste slurry, the precipitate is separated, dried, ground, and sieved. The resulting powder (300 mesh) is mixed with water in a ratio of 1.15 parts by weight to 0.4 parts by weight and stirred evenly to form a wet material. The wet material is then placed in a high-pressure reactor, sealed, and carbonized with carbon dioxide gas for 50 minutes at a pressure of 0.2 MPa. After completion, the product is removed and heated at 100°C for 1 hour. The resulting solid is then ground and sieved through a 600-mesh sieve to obtain a modified recycled micro-powder reinforcing agent for later use.

[0074] (2) Take the following components: 360 parts by weight of 42.5 ordinary silicate cement, 750 parts by weight of the modified recycled aggregate of Example 2, 480 parts by weight of fine river sand with a continuous gradation between 0.5 and 1 mm particle size, 70 parts by weight of the modified recycled micro powder reinforcing agent of this example, 7.2 parts by weight of naphthalene-based water-reducing agent, and 162 parts by weight of water. Mix the above components and stir for 3 minutes to obtain 3D printed low-carbon concrete.

[0075] The compressive strength and creep-recovery tests were performed on the 3D-printed low-carbon concrete prepared in this example using the same method as in Example 1. The results showed that the compressive strength was 48.43 MPa and the recovery deformation rate was 85.1%.

[0076] Example 9

[0077] The preparation of 3D-printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent includes the following steps:

[0078] (1) After sedimentation of silicate cement-based waste slurry, the precipitate is separated, dried, ground and sieved. The obtained powder (fineness 200 mesh), γ-C2S powder (fineness 200 mesh) and water are mixed in a ratio of 1.1 parts by weight: 0.18 parts by weight: 0.3 parts by weight and stirred evenly to form a wet material. The wet material is heated at 80°C for 1.5 hours. The obtained solid is ground and sieved through a 300-mesh sieve to obtain the modified recycled micro powder reinforcing agent for later use.

[0079] (2) Take the following components: 300 parts by weight of 42.5 ordinary Portland cement, 620 parts by weight of the modified recycled aggregate described in Example 3, 400 parts by weight of fine river sand with a continuous gradation between 0.5 and 1 mm particle size, 50 parts by weight of the modified recycled micro powder reinforcing agent described in this example, 4.5 parts by weight of sodium lignosulfonate water-reducing agent, and 105 parts by weight of water. Mix the above components and stir for 3 minutes to obtain 3D printed low-carbon concrete.

[0080] The compressive strength and creep-recovery tests were performed on the 3D-printed low-carbon concrete prepared in this example using the same method as in Example 1. The results showed that the compressive strength was 49.56 MPa and the recovery deformation rate was 80.8%.

[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A 3D-printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent, characterized in that, The composition includes: 300-360 parts by weight of cementitious material, 620-750 parts by weight of modified recycled aggregate, 400-480 parts by weight of fine aggregate, 50-70 parts by weight of modified recycled micro-powder reinforcing agent, 4.5-7.2 parts by weight of water-reducing agent, and clean water, with a water-cement ratio of 0.35-0.45; wherein: The modified recycled aggregate and modified recycled micro powder reinforcing agent are prepared by the following method: (1) Place the recycled concrete coarse aggregate in sodium or potassium water glass and then perform ultrasonic treatment; then separate the coarse aggregate and place it in a sealed container with carbon dioxide atmosphere for carbonization treatment. After completion, heat the obtained coarse aggregate to obtain pretreated recycled aggregate. (2) The pretreated recycled aggregate is placed in saturated lime water and then heated and kept warm. After the treatment is completed, the solids are separated to obtain the modified recycled aggregate. The amount of pretreated recycled aggregate added to the saturated lime water is 20~40g / L. (3) After sedimentation of silicate cement-based waste slurry, the precipitate is separated, dried and ground into powder. The powder, γ-C2S powder and water are mixed evenly in the proportion of 1~1.15 parts by weight: 0.18~0.25 parts by weight: 0.3~0.4 parts by weight to form a wet material. The wet material is then placed in a sealed container with a carbon dioxide atmosphere for carbonization treatment. After completion, it is heated. The obtained solid is ground to obtain the modified recycled micro powder reinforcing agent.

2. The 3D-printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent according to claim 1, characterized in that, In step (1), the amount of recycled concrete coarse aggregate added to the sodium or potassium water glass is 25~70g / L.

3. The 3D-printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent according to claim 1, characterized in that, In step (1), the mass fraction of the sodium or potassium silicate is not less than 20%.

4. The 3D-printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent according to claim 1, characterized in that, In step (1), the ultrasonic treatment time is 30~40 min.

5. The 3D-printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent according to claim 1, characterized in that, In step (1), the particle size of the recycled concrete coarse aggregate is 10~20mm.

6. The 3D-printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent according to claim 1, characterized in that, In step (1), the carbonization treatment is carried out at a temperature of 40~60℃ for 1~1.5h.

7. The 3D-printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent according to claim 1, characterized in that, In step (1), the pressure in the sealed container is 0.2~0.35MPa.

8. The 3D-printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent according to claim 1, characterized in that, In step (1), the temperature of the heat treatment is 180~250℃, and the coarse aggregate is heated at this temperature until the weight of the coarse aggregate is constant.

9. The 3D-printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent according to claim 1, characterized in that, In step (2), the heating temperature is 50~80℃ and the time is 4~7h.

10. The 3D-printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent according to claim 1, characterized in that, In step (3), the fineness of the powder and γ-C2S powder is not less than 200 mesh.

11. The 3D-printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent according to claim 1, characterized in that, In step (3), the carbonization process takes 30 to 50 minutes.

12. The 3D-printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent according to claim 1, characterized in that, In step (3), the pressure in the sealed container is 0.2~0.35MPa.

13. The 3D-printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent according to claim 1, characterized in that, In step (3), the temperature of the heat treatment is 80~100℃ and the time is 1~2h.

14. The 3D-printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent according to claim 1, characterized in that, In step (3), the modified recycled micro powder reinforcing agent has a fineness of 300~600 mesh.

15. The 3D-printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent according to any one of claims 1-14, characterized in that, The water-reducing agent includes any one of polycarboxylate water-reducing agents, lignin sulfonate water-reducing agents, naphthalene-based water-reducing agents, and aliphatic water-reducing agents.

16. The 3D-printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent according to any one of claims 1-14, characterized in that, The fine aggregate has a particle size of 0.5~1mm.

17. The 3D-printed low-carbon concrete containing modified recycled aggregate and micronized reinforcing agent according to any one of claims 1-14, characterized in that, The fine aggregate includes at least one of river sand and manufactured sand.

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