3D printing low-carbon concrete mortar, preparation method and application

Abstract

The application discloses 3D printing low-carbon environment-friendly concrete mortar, a preparation method and application, and each raw material comprises, in weight parts, Portland cement 40-80 parts, aluminate cement 40-80 parts, solid waste cementitious material 100-200 parts, fine aggregate 140-300 parts, water-retaining agent 0.1-0.5 parts, interface activator 0.1-0.4 parts, complexing agent 0.4-0.8 parts, aluminum oxide powder 10-15 parts, efficient water reducing agent 0.5-1.0, surface film forming agent 0.2-3.0 parts, functional composite penetrating agent 0.7-6.0 parts and water 200 parts-880 parts. The application solves the problem that the interlayer structural strength performance of the existing 3D printing mortar is generally poor, thereby leading to poor waterproof and thermal insulation performance.

Description

TECHNICAL FIELD

[0001] The present application relates to 3D printing building mortar technology, in particular to a kind of 3D printing low-carbon concrete mortar. BACKGROUND

[0002] This technology uses digital manufacturing technology, combined with the concept of low-carbon economy, can guarantee production efficiency, and follow the environmental protection concept, promote sustainable development. 3D printing low-carbon concrete mortar can be customized according to different needs, with the advantages of high efficiency, accuracy and customization. Compared with traditional concrete, 3D printing low-carbon concrete mortar can also greatly reduce the energy consumption and carbon emissions required for construction projects, while showing its superior weathering resistance and durability.

[0003] In addition to medical facilities, it can also be applied to commercial complexes, residential buildings, public facilities and other fields, bringing qualitative leap and economic benefits to the construction industry.

[0004] After searching CN116535156A, a kind of nano modified 3D printing high-strength concrete capable of improving pumpability and its preparation method, it is disclosed that the porous structure of fly ash modified by fulvic acid can impart good thixotropy and water retention after being added to concrete. On the other hand, fulvic acid can react with metal oxides in fly ash to improve the reactivity of fly ash. After adding nano clay, it has good interfacial adhesion performance with the concrete matrix, reducing the possibility of fiber pulling out under stress.

[0005] CN115974499A A kind of 3D printing mortar material, it is disclosed that the high molecular ether structure characteristics of cellulose ether can ensure the formation of a thin film between cellulose ether and hydrated cement particles, prevent water from seeping out, improve the water retention and workability of the mortar material, and further improve the interlayer adhesion of the 3D printing product of the mortar material. The interlayer structure strength is generally improved in a water-retaining manner, the interlayer structure strength is generally, easy to appear interlayer crack, poor thermal insulation and waterproof performance, greatly restricts the wide promotion of 3D printing concrete. SUMMARY

[0006] The technical problem to be solved by the present application is how to solve the problem of poor waterproof and thermal insulation performance caused by the general interlayer structure strength performance of the existing 3D printing mortar.

[0007] In order to solve the above technical problems, the inventors have summarized the technical solutions of the present application through practice, which are as follows:

[0008] A kind of 3D printing low-carbon concrete mortar, each raw material includes:

[0009] Silicate cement 40-80 parts, aluminate cement 40-80 parts, solid waste cementitious material 100-200 parts, fine aggregate 140-300 parts, water retaining agent 0.1-0.5 parts, interface activator 0.1-0.4 parts, complexing agent 0.4-0.8 parts, aluminum oxide powder 10-15 parts, high efficiency water reducing agent 0.5-1.0, surface film forming agent 0.2-3.0 parts, functional composite penetrating agent 0.7-6.0 parts, and water 200 parts-880 parts.

[0010] Further preferably, the solid waste cementitious material includes one or more of fly ash, zeolite powder, steel slag, and slag mixed in any ratio, with a specific surface area of 400-1000 m2 / kg and a 45 μm square hole residue of 1.5% or less.

[0011] Further preferably, the functional composite penetrating agent includes a dihydrate oxalic acid-melamine-sodium acetate composite penetrating agent.

[0012] Further preferably, the dihydrate oxalic acid-melamine-sodium acetate composite penetrating agent is prepared by the following steps: dissolving 2-4 g of dihydrate oxalic acid in 100 mL of distilled water, adding 100 mL of dimethyl sulfoxide to 1-2 g of melamine at room temperature, stirring to dissolve completely, slowly adding the dihydrate oxalic acid to the melamine solution under stirring, with a molar ratio of melamine to oxalic acid of 2:3, continuing to stir while ultrasonically oscillating for 1 h, washing 3-5 times with pure water, and drying at 60-70°C for 6-8 h to obtain an intermediate, mixing a certain amount of the intermediate with water, stirring and heating to 70-85°C, slowly adding a certain amount of a sodium chloroacetate solution, with a molar ratio of the intermediate to sodium chloroacetate of 1:6, maintaining the temperature at 70-85°C for a certain period of time, cooling, and filtering to remove insoluble matter to obtain the dihydrate oxalic acid-melamine-sodium acetate composite penetrating agent.

[0013] Further preferably, the high efficiency water reducing agent is one or more of a naphthalene series water reducing agent, a sodium lignosulfonate water reducing agent, and a polycarboxylic acid water reducing agent mixed in any ratio.

[0014] Further preferably, the concrete mortar further includes 0.2-0.8 parts of nano-silicon dioxide.

[0015] Further preferably, the complexing agent is one or more of sodium ethylenediaminetetraacetate, triethanolamine, sodium ethylenediaminetetra(methylene phosphonate), and polyhydroxyacrylic acid mixed in any ratio.

[0016] Further preferably, the interface activator is one or more of Na2SiO3, K2SiO3, NaOH, and KOH mixed in any ratio.

[0017] Further preferably, the portland cement is one or more of P.O32.5 cement and P.O42.5 cement mixed in any ratio.

[0018] A 3D printing low-carbon concrete mortar preparation method, the preparation steps are as follows:

[0019] S1: 40-80 parts of portland cement, 40-80 parts of aluminate cement, 100-200 parts of solid waste cementitious material, 140-300 parts of fine aggregate, 0.1-0.5 parts of water retaining agent, 0.4-0.8 parts of complexing agent, 10-15 parts of aluminum oxide powder, 0.5-1.0 parts of high-efficiency water reducing agent, 0.2-3.0 parts of surface film forming agent, and 0.7-6.0 parts of functional composite penetrating agent are stirred in a blender at 250 rpm / min for 8 minutes to obtain a solid powdery mixture;

[0020] S2: 0.1-0.4 parts of interface activator is dissolved in part of water and stirred at 100 rpm / min for 5 minutes to obtain an interface activator solution;

[0021] S3: the interface activator solution and the remaining part of water containing 0.7-6.0 parts of functional composite penetrating agent are added to the solid powdery mixture, and stirred at 380 rpm / min for 8 minutes to obtain a 3D printing low-carbon concrete mortar.

[0022] A 3D printing low-carbon concrete mortar, which is directly applied to a prefabricated component for 3D printing building, and the mortar is poured into an automatic stirring and spraying integrated device for spraying construction.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] 1. The metal ions in the cement and waste residue cementitious material are complexed and enriched by the complexing agent to form metal ion complexes, which combine with the hydration product calcium hydroxide and the interface activator to form a cementitious component mainly composed of calcium silicate hydrate, calcium aluminate hydrate and calcium silicate-aluminate hydrate, thereby repairing the micro-pores of the prepared concrete and the pores formed by printing, and giving the material excellent early strength and cohesiveness.

[0025] 2. Utilizing zeolite in structure, which is made by infinite extension of one-dimensional (as in medium-3 SiO2Al2O3Na2O2H2O), two-dimensional (for example in sheet zeolite: 7SiO2.Al2O3.CaO.6H2O) or more common three-dimensional (for example in chabazite: 4SiO2.Al2O3.CaO6H2) network of (Si, Al)O4 tetrahedron, these compositions are the main building blocks connected by metal cations. The above network is characterized by the presence of large monovalent or divalent ions such as Na+, K+, Ca2+or Mg2+, which distort the structure of (Si, Al)O4 tetrahedron and cause the distribution of large interconnected void space in the framework, which is conducive to the void filling of the gel material, while the composite structure of the strip microporous self-assembly is achieved by the combination of water and oxalic acid-sodium acetate-melamine complex penetrant during preparation, which can ensure the existence of the interlayer relationship with the strip microporous self-assembly as the main interlayer anchoring force during 3D printing, and the strip self-assembly will be automatically tensioned in the interlayer strip structure after the gel material penetrates the void space and undergoes hydration reaction, thereby improving the interlayer anchoring strength, and improving the waterproof, thermal insulation and air tightness through the interlayer bonding strength.

[0026] 3. Additional introduction of nano-silica with complex composite penetrant, on the one hand, provides attachment points for the flocculent C-S-H generated by the reaction, which is directly attached to the surface and continuously develops outward to form the cement stone framework, thereby forming strength, and the process of forming crystal nucleus of C-S-H itself is omitted, thereby accelerating the development of strength and greatly improving the compressive strength performance of foam concrete, on the other hand, consuming calcium hydroxide crystals promotes the hydration of cement, and the generated C-S-H gel fills the pores of the cement slurry, improves the microstructure of the interlayer concrete, and the nano-silica itself also fills the internal pores of the concrete, which provides stable framework support in the concrete slurry through the above two aspects, and the micro-porous structure of nano-silica can enter the interlayer deposited concrete voids and form a cement stone framework in the voids, thereby tensioning and anchoring the interlayer deposited strip composite penetrant. Due to the microporous structure on the strip structure, the hydration product can penetrate the micropore to further improve the anchoring effect.

[0027] 4. The metal ion complex can release the complexing agent simultaneously while reacting with calcium hydroxide in cement and interface activator to form cementitious components, which can be used continuously and can repair the internal pore structure and flow channel of the concrete through the cycle of complexing agent→metal ion complex (metal ion complexation)→complexing agent (metal ion release, cementitious material formation, and repeated use of complexing agent), thereby giving the material excellent late strength and weather resistance. DETAILED DESCRIPTION

[0028] Example 1

[0029] Silicate cement 40 parts (P.O 42.5 cement), aluminate cement 70 parts, solid waste cementitious material 150 parts (steel slag 50 parts, fly ash 50 parts, zeolite powder 50 parts), fine aggregate 300 parts (recycled machine-made sand), water retaining agent 0.3 parts (hydroxymethylpropyl cellulose ether 0.2 parts, hydroxymethylpropyl starch ether 0.1 parts), interface activator 0.4 parts (sodium silicate 0.3 parts, sodium hydroxide 0.1 parts), complexing agent 0.6 parts (ethylenediaminetetramethylene phosphonic acid sodium 0.4 parts, polyhydroxyacrylic acid 0.2 parts), high efficiency water reducing agent 0.6 parts (naphthalene series water reducing agent 0.3 parts, polycarboxylic acid water reducing agent 0.3 parts), surface film forming agent 2.8 parts (solid content 40%, methyl methacrylate-methyl methacrylate octafluoropentyl ester copolymer, methyl methacrylate content 8.0%, methyl methacrylate octafluoropentyl ester content 92.0%), functional composite penetrant 1.5 parts, nano-silicon dioxide 0.5 parts, water 550 parts.

[0030] The functional composite penetrant includes a dihydrate oxalic acid-melamine-sodium acetate composite penetrant, and the dihydrate oxalic acid-melamine-sodium acetate composite penetrant is prepared by the following steps: 2-4 g of dihydrate oxalic acid is dissolved in 100 mL of distilled water, 1-2 g of melamine is added with 100 mL of dimethyl sulfoxide at room temperature, and the melamine is completely dissolved by stirring; the dihydrate oxalic acid is slowly added to the melamine solution under stirring, and the molar ratio of melamine to oxalic acid is 2:3; after 1 h of ultrasonic oscillation under continuous stirring, the intermediate is washed with pure water for 3-5 times, and dried at 60-70 °C for 6-8 h to obtain an intermediate; a certain amount of intermediate is mixed with water, and stirred to be heated to 70-85 °C; a certain amount of sodium chloroacetate solution is slowly added dropwise, and the molar ratio of the intermediate to sodium chloroacetate is 1:6; the reaction is performed at 70-85 °C for a certain period of time; after cooling, the insoluble substances are removed by filtration to obtain the dihydrate oxalic acid-melamine-sodium acetate composite penetrant.

[0031] The above material is prepared by the following steps:

[0032] S1: Silicate cement 40 parts (P.O 42.5 cement), aluminate cement 70 parts, solid waste cementitious material 150 parts (steel slag 50 parts, fly ash 50 parts, zeolite powder 50 parts), fine aggregate 300 parts (recycled machine-made sand), water retaining agent 0.3 parts (hydroxymethyl propyl cellulose ether 0.2 parts, hydroxymethyl propyl starch ether 0.1 parts), complexing agent 0.6 parts (ethylenediamine tetramethylene phosphonic acid sodium 0.4 parts, polyhydroxy acrylic acid 0.2 parts), high efficiency water reducing agent 0.6 parts (naphthalene series water reducing agent 0.3 parts, polycarboxylic acid water reducing agent 0.3 parts), surface film forming agent 2.8 parts (solid content 40%, methyl methacrylate-methyl methacrylate octafluoropentyl ester copolymer, methyl methacrylate content 8.0%, methyl methacrylate octafluoropentyl ester content 92.0%), nano-silicon dioxide 0.5 parts are stirred in a blender at 250 rpm / min for 8 minutes to obtain a solid powdery mixture;

[0033] S2: Interface activator 0.4 parts (sodium silicate 0.3 parts, sodium hydroxide 0.1 parts) is dissolved in 350 parts of water, stirred at 100 rpm / min for 5 minutes to obtain an interface activator solution;

[0034] S3: The interface activator solution and 200 parts of water containing functional composite penetrant 1.5 parts are added to the solid powdery mixture, stirred at 380 rpm / min for 8 minutes to obtain a 3D printing low-carbon concrete mortar.

[0035] Example 2

[0036] Silicate cement 60 parts (P.O 42.5 cement), aluminate cement 40 parts, solid waste cementitious material 180 parts (steel slag 70 parts, fly ash 60 parts, zeolite powder 50 parts), fine aggregate 270 parts (recycled machine-made sand), water retaining agent 0.3 parts (hydroxymethyl propyl cellulose ether 0.2 parts, hydroxymethyl propyl starch ether 0.1 parts), interface activator 0.4 parts (sodium silicate 0.3 parts, sodium hydroxide 0.1 parts), complexing agent 0.6 parts (ethylenediamine tetramethylene phosphonic acid sodium 0.4 parts, polyhydroxy acrylic acid 0.2 parts), high efficiency water reducing agent 0.6 parts (naphthalene series water reducing agent 0.3 parts, polycarboxylic acid water reducing agent 0.3 parts), surface film forming agent 2.8 parts (solid content 40%, methyl methacrylate-methyl methacrylate octafluoropentyl ester copolymer, methyl methacrylate content 8.0%, methyl methacrylate octafluoropentyl ester content 92.0%), functional composite penetrant 1.8 parts, nano-silicon dioxide 0.8 parts, water 600 parts.

[0037] The functional composite penetrant includes oxalic acid dihydrate-melamine-sodium acetate composite penetrant, and the preparation steps of the oxalic acid dihydrate-melamine-sodium acetate composite penetrant are as follows: 2-4 g of oxalic acid dihydrate is dissolved in 100 mL of distilled water, 1-2 g of melamine is added with 100 mL of dimethyl sulfoxide at room temperature, and the melamine is completely dissolved by stirring; the oxalic acid dihydrate is slowly added to the melamine solution under stirring, the molar ratio of melamine to oxalic acid is 2:3, and then the stirring is continued while ultrasonic oscillation is performed for 1 h; the product is washed with pure water for 3-5 times, and then dried at 60-70 °C for 6-8 h to obtain an intermediate; a certain amount of the intermediate is mixed with water, and then stirred and heated to 70-85 °C; a certain amount of sodium chloroacetate solution is slowly added dropwise, the molar ratio of the intermediate to sodium chloroacetate is 1:6, and the reaction is performed at 70-85 °C for a certain period of time; after cooling, the insoluble substances are removed by filtration, and the oxalic acid dihydrate-melamine-sodium acetate composite penetrant is prepared.

[0038] The above material is prepared by the following steps:

[0039] S1: 60 parts of Portland cement (P.O 42.5 cement), 40 parts of aluminate cement, 180 parts of solid waste cementitious material (70 parts of steel slag, 60 parts of fly ash, and 50 parts of zeolite powder), 270 parts of fine aggregate (recycled machine-made sand), 0.3 parts of water retaining agent (0.2 parts of hydroxymethylpropyl cellulose ether and 0.1 parts of hydroxymethylpropyl starch ether), 0.6 parts of complexing agent (0.4 parts of ethylenediamine tetramethylene phosphonate sodium and 0.2 parts of polyhydroxyacrylic acid), 0.6 parts of high-efficiency water reducing agent (0.3 parts of naphthalene-based water reducing agent and 0.3 parts of polycarboxylic acid water reducing agent), 2.8 parts of surface film-forming agent (solid content 40%, methacrylic acid-methyl methacrylic acid octafluoropentyl ester copolymer, methacrylic acid content 8.0%, and methyl methacrylic acid octafluoropentyl ester content 92.0%), and 0.8 parts of nano-silicon dioxide are stirred in a blender at 250 rpm / minute for 8 minutes to obtain a solid powder mixture;

[0040] S2: 0.4 parts of interfacial activator (0.3 parts of sodium silicate and 0.1 parts of sodium hydroxide) is dissolved in 350 parts of water to obtain an interfacial activator solution by stirring at 100 rpm / minute for 5 minutes;

[0041] S3: the interfacial activator solution and 250 parts of water containing 1.8 parts of the functional composite penetrant are added to the solid powder mixture to obtain a 3D printing low-carbon concrete mortar by stirring at 380 rpm / minute for 8 minutes.

[0042] Example 3

[0043] Silicate cement 50 parts (P.O 42.5 cement), aluminate cement 50 parts, solid waste cementitious material 200 parts (steel slag 80 parts, fly ash 80 parts, zeolite powder 60 parts), fine aggregate 180 parts (recycled manufactured sand), water retaining agent 0.3 parts (hydroxymethyl propyl cellulose ether 0.2 parts, hydroxymethyl propyl starch ether 0.1 parts), interface activator 0.4 parts (sodium silicate 0.3 parts, sodium hydroxide 0.1 parts), complexing agent 0.6 parts (ethylenediamine tetramethylene phosphonic acid sodium 0.4 parts, polyhydroxy acrylic acid 0.2 parts), high efficiency water reducing agent 0.6 parts (naphthalene series water reducing agent 0.3 parts, polycarboxylic acid water reducing agent 0.3 parts), surface film forming agent 2.8 parts (solid content 40%, methyl methacrylate-octofluoropentyl methacrylate copolymer, methyl methacrylate content 8.0%, octofluoropentyl methacrylate content 92.0%), functional composite penetrant 3.0 parts, nano silicon dioxide 0.5 parts, water 650 parts.

[0044] The functional composite penetrant includes a dihydrate oxalic acid-melamine-sodium acetate composite penetrant, and the dihydrate oxalic acid-melamine-sodium acetate composite penetrant is prepared by the following steps: 2-4 g of dihydrate oxalic acid is dissolved in 100 mL of distilled water, 1-2 g of melamine is added with 100 mL of dimethyl sulfoxide at room temperature, and the melamine is completely dissolved by stirring; the dihydrate oxalic acid is slowly added to the melamine solution under stirring, and the molar ratio of melamine to oxalic acid is 2:3; after 1 h of continuous stirring and ultrasonic oscillation, the mixture is washed with pure water for 3-5 times, and is dried at 60-70 °C for 6-8 h to obtain an intermediate; a certain amount of the intermediate is mixed with water, and is stirred to be heated to 70-85 °C; a certain amount of sodium chloroacetate solution is slowly added dropwise, and the molar ratio of the intermediate to sodium chloroacetate is 1:6; the mixture is kept at 70-85 °C for a certain time; after cooling, the insoluble substances are removed by filtration to obtain the dihydrate oxalic acid-melamine-sodium acetate composite penetrant.

[0045] S1: silicate cement 50 parts (P.O 42.5 cement), aluminate cement 50 parts, solid waste cementitious material 200 parts (steel slag 80 parts, fly ash 80 parts, zeolite powder 60 parts), fine aggregate 180 parts (recycled manufactured sand), water retaining agent 0.3 parts (hydroxymethyl propyl cellulose ether 0.2 parts, hydroxymethyl propyl starch ether 0.1 parts), complexing agent 0.6 parts (ethylenediamine tetramethylene phosphonic acid sodium 0.4 parts, polyhydroxy acrylic acid 0.2 parts), high efficiency water reducing agent 0.6 parts (naphthalene series water reducing agent 0.3 parts, polycarboxylic acid water reducing agent 0.3 parts), surface film forming agent 2.8 parts (solid content 40%, methyl methacrylate-octofluoropentyl methacrylate copolymer, methyl methacrylate content 8.0%, octofluoropentyl methacrylate content 92.0%), nano silicon dioxide 0.5 parts are stirred in a blender at 250 rpm / min for 8 min to obtain a solid powder mixture;

[0046] S2: 0.4 parts of interface activator (0.3 parts of sodium silicate, 0.1 parts of sodium hydroxide) was dissolved in 350 parts of water to obtain an interface activator solution by stirring at 100 rpm / min for 5 minutes;

[0047] S3: The interface activator solution and 3.0 parts of functional composite penetrant-containing 300 parts of water were added to the solid powder mixture to obtain a 3D-printed low-carbon concrete mortar by stirring at 380 rpm / min for 8 minutes.

[0048] Test

[0049] The setting time, fluidity, flexural strength, compressive strength and other parameters of the 3D-printed low-carbon concrete mortar obtained in Examples 1-3 were tested, as follows:

[0050] Test piece preparation: The test piece size was 40*40*160mm, and the specific manufacturing method referred to GB / T17671-2020 "Cement mortar strength test method (ISO method)". The test piece was cured under the condition of temperature 20±2℃ and relative humidity 95% to the test age.

[0051] Setting test piece: Refer to the provisions in GB / T50080-2016 "Standard for test methods of performance of ordinary concrete mixture".

[0052] Fluidity: Refer to the provisions in GB / T50448-2015 "Technical specification for application of cement-based grouting materials".

[0053] Flexural strength and compressive strength: Refer to the provisions in GB / T GB / T17671-2000 "Cement mortar strength test method (ISO method)".

[0054] Test results: The results of setting time, fluidity, flexural strength, compressive strength, toughness measurement, and interlayer bonding strength are shown in Table 1.

[0055] Table 1: Performance test results

[0056] Test Example 1 Example 2 Example 3 Initial setting / min 21 23 19 Final setting / min 49 50 46 Fluidity / min 173 168 177 1 day compressive strength / MPa 53.45 56.13 52.51 1 day flexural strength / MPa 13.24 14.12 14.30 3 day compressive strength / MPa 69.75 70.31 72.42 3 day flexural strength / MPa 17.97 19.72 20.43 28 day compressive strength / MPa 147.73 148.86 137.94 28 day flexural strength / MPa 37.86 39.75 39.46 Interlaminar bond strength / MPa 9.31 8.79 9.67

[0057] An application of a 3D-printed low-carbon concrete mortar, the mortar is directly applied to a prefabricated component for 3D-printed buildings, and the mortar is poured into an automatic stirring and spraying integrated device for spraying construction.

[0058] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application are equivalent replacement methods, and are all included in the protection scope of the present application.

Claims

1. A 3D printed low-carbon concrete mortar, characterized in that, The raw materials include, by weight: 40-80 parts of Portland cement, 40-80 parts of aluminate cement, 100-200 parts of solid waste cementitious material, 140-300 parts of fine aggregate, 0.1-0.5 parts of water retaining agent, 0.1-0.4 parts of interface activator, 0.4-0.8 parts of complexing agent, 10-15 parts of aluminum oxide powder, 0.5-1.0 parts of high-efficiency water reducing agent, 0.2-3.0 parts of surface film forming agent, 0.7-6.0 parts of functional composite penetrating agent, and 200-880 parts of water; The functional composite penetrating agent comprises oxalic acid dihydrate-melamine-sodium acetate composite penetrating agent. The preparation steps of the oxalic acid dihydrate-melamine-sodium acetate composite penetrating agent are as follows: 2-4 g of oxalic acid dihydrate is dissolved in 100 mL of distilled water, 1-2 g of melamine is added with 100 mL of dimethyl sulfoxide at room temperature, and the mixture is stirred to completely dissolve; the oxalic acid dihydrate is slowly added to the melamine solution under stirring, and the molar ratio of melamine to oxalic acid is 2:3; the stirring is continued while ultrasonic oscillation is performed for 1 h; the mixture is washed with pure water for 3-5 times; and the mixture is dried at 60-70 °C for 6-8 h to obtain an intermediate; a certain amount of the intermediate is mixed with water, and the mixture is stirred and heated to 70-85 °C; a certain amount of sodium chloroacetate solution is slowly added dropwise, and the molar ratio of the intermediate to sodium chloroacetate is 1:6; the mixture is kept at 70-85 °C for a certain period of time; after cooling, the insoluble substances are removed by filtration to obtain the oxalic acid dihydrate-melamine-sodium acetate composite penetrating agent.

2. The 3D-printed low-carbon concrete mortar according to claim 1, characterized in that, The solid waste cementitious material includes one or more of fly ash, zeolite powder, steel slag and slag mixed in any ratio, specific surface area 400-1000 m 2 / kg, 45 μm square hole sieve residue 1.5% or less.

3. The 3D-printed low-carbon concrete mortar according to claim 1, characterized in that, The high-efficiency water reducing agent is one or more of naphthalene-based water reducing agent, sodium lignosulfonate water reducing agent, and polycarboxylic acid water reducing agent mixed in any ratio.

4. The 3D-printed low-carbon concrete mortar according to claim 3, characterized in that, The concrete mortar further comprises 0.2-0.8 parts of nano-silicon dioxide.

5. The 3D-printed low-carbon concrete mortar according to claim 1, characterized in that, The complexing agent is one or more of sodium ethylenediaminetetraacetate, triethanolamine, sodium ethylenediaminetetra(methylene phosphonate), and polyhydroxyacrylic acid mixed in any ratio.

6. The 3D-printed low-carbon concrete mortar according to claim 1, characterized in that, The interface activator is one or more of Na2SiO3, K2SiO3, NaOH, and KOH mixed in any ratio, and the Portland cement is one or more of P.O 32.5 cement and P.O 42.5 cement mixed in any ratio.

7. A method for preparing a 3D-printed low-carbon concrete mortar according to claim 1, characterized in that, The preparation steps are as follows: S1: 40-80 parts of Portland cement, 40-80 parts of aluminate cement, 100-200 parts of solid waste cementitious material, 140-300 parts of fine aggregate, 0.1-0.5 parts of water retaining agent, 0.4-0.8 parts of complexing agent, 10-15 parts of aluminum oxide powder, 0.5-1.0 parts of high-efficiency water reducing agent, 0.2-3.0 parts of surface film forming agent, and 0.7-6.0 parts of functional composite penetrating agent are stirred in a blender at 250 rpm for 8 minutes to obtain a solid powder mixture; S2: 0.1-0.4 parts of interface activator is dissolved in a part of water and stirred at 100 rpm for 5 minutes to obtain an interface activator solution; S3: the interface activator solution and the remaining part of water containing 0.7-6.0 parts of functional composite penetrating agent are added to the solid powder mixture, and the mixture is stirred at 380 rpm for 8 minutes to obtain the 3D printing low-carbon concrete mortar.

8. Use of the 3D-printed low-carbon concrete mortar according to any one of claims 1 to 6, characterized in that, The mortar is directly applied to a prefabricated component for 3D printing building, and the mortar is sprayed in an automatic stirring and spraying integrated equipment for spraying construction.