Lightweight aggregate foaming cement mortar, preparation method thereof and application of lightweight aggregate foaming cement mortar in 3D printing

Abstract

The invention provides lightweight aggregate foamed cement mortar as well as a preparation method and application thereof in 3D printing, and belongs to the technical field of building materials. The lightweight aggregate foamed cement mortar suitable for 3D printing is prepared from the following components in parts by weight: 40 to 50 parts of cement, 10 to 16 parts of fly ash, 2 to 4.5 parts of silica fume, 25 to 27 parts of water, 49 to 52 parts of lightweight aggregate, 1.5 to 1.7 parts of fiber, 0.2 to 0.5 part of a water reducing agent, 2 to 2.5 parts of an accelerator, 0.075 to 0.15 part of cellulose ether and 0.058 to 0.072 part of a composite foaming agent. According to the lightweight aggregate foaming cement mortar for 3D printing, the volume weight of a 3D printing material is remarkably reduced, the extrusion performance of a 3D printing cement-based material is improved, and a printing component has the characteristic of low self weight. According to the preparation method, the mortar is mixed more uniformly, and the performance is more stable.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a lightweight aggregate foamed cement mortar, its preparation method, and its application in 3D printing. Background Technology

[0002] 3D printing of buildings is a rapid construction technology first proposed by American scholar Joseph in 1997. This technology is based on a material deposition method, which involves pre-creating a three-dimensional model of the building's outline, slicing the outline into layers, and converting it into a layered pattern. Subsequently, printing paths are planned based on the sliced ​​outline data, and these paths are input into the program.

[0003] Compared to ordinary mortar, lightweight aggregate mortar has a higher specific strength and can significantly reduce the self-weight of components. In addition, it has excellent seismic performance because the porous structure of lightweight aggregate allows it to absorb a large amount of shock wave energy under seismic loads. In terms of durability, the porous structure of lightweight aggregate mortar gives it excellent properties such as high frost resistance, high permeability, high fire resistance, and no alkali-aggregate reaction. Foamed mortar, as a commonly used thermal insulation material in the construction industry, has received much attention since its inception due to its advantages such as self-leveling, low thermal conductivity, low raw material requirements, and low density. Currently, it is widely used in areas such as exterior wall and roof insulation in residential buildings, and tunnel and pipe filling in underground engineering.

[0004] Compared to traditional molding processes, 3D-printed concrete offers advantages such as eliminating the need for formwork support, convenient construction, high design freedom, reduced labor, reduced production waste, and improved construction environment. It can reduce the negative environmental impact of the construction industry and decrease carbon dioxide emissions, thus possessing significant development and application prospects. However, 3D printing technology also places higher demands on building materials; during the concrete 3D printing process, material blockage, interruption, deformation, tearing, and even collapse are prone to occur.

[0005] If lightweight aggregate mortar and foamed mortar can be combined and applied to 3D printing mortar, it can solve, to some extent, the problems of heavy 3D printed components, high construction costs, and excessively high production capacity during the printing process. It can also compensate for the shortcomings of 3D printing technology, such as the large amount of adhesive materials required and its insufficient carbon footprint. Summary of the Invention

[0006] The purpose of this invention is to provide a lightweight aggregate foamed cement mortar, its preparation method, and its application in 3D printing, so as to solve the above-mentioned technical problems.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] This invention provides a lightweight aggregate foamed cement mortar, which is composed of components comprising the following parts by weight:

[0009] 40-50 parts cement, 10-16 parts fly ash, 2-4.5 parts silica fume, 25-27 parts water, 49-52 parts lightweight aggregate, 1.5-1.7 parts fiber, 0.2-0.5 parts water-reducing agent, 2-2.5 parts quick-setting agent, 0.075-0.15 parts cellulose ether, and 0.058-0.072 parts composite foaming agent.

[0010] Furthermore, the lightweight aggregate is crushed aerated concrete block; the particle size of the lightweight aggregate is 0.075mm to 2.36mm; and the moisture content of the lightweight aggregate is the saturated surface dry moisture content.

[0011] Furthermore, the SiO2 content in the silica fume is ≥85%.

[0012] Furthermore, the fiber comprises one or more of polyvinyl alcohol fiber, polypropylene fiber, polyethylene fiber, and basalt fiber; the fiber has a length of 6 to 12 mm and an aspect ratio of 100 to 500.

[0013] Furthermore, the fly ash is Class II fly ash, the cement is 42.5R ordinary Portland cement, the water-reducing agent is polycarboxylate high-efficiency water-reducing agent, the accelerator is alkali-free liquid accelerator, and the cellulose ether is hydroxypropyl methylcellulose.

[0014] Furthermore, the composite foaming agent comprises: 4.7-5.1% animal protein, 0.75-0.80% sodium dodecyl sulfate, 0.75-0.80% sodium α-alkenyl sulfonate, and 93-95% water.

[0015] This invention also provides a method for preparing lightweight aggregate foamed cement mortar, comprising the following steps:

[0016] A1: According to the proportions, weigh out cement, fly ash, silica fume, fiber and cellulose ether and mix them to obtain dry-mixed mortar material M1;

[0017] A2: According to the proportion, weigh the lightweight aggregate and water and mix them to make the lightweight aggregate reach a saturated surface-dry state to obtain pre-wetted lightweight aggregate M2;

[0018] A3: According to the proportions, weigh out the water-reducing agent, quick-setting agent and water and mix them to obtain solution M3;

[0019] A4: Add the solution M3 to the dry-mixed mortar M1 and mix to obtain the initial slurry M4;

[0020] A5: Add pre-wetted lightweight aggregate M2 to the initial slurry M4 and mix to obtain lightweight aggregate mortar M5;

[0021] A6: According to the proportion, the composite foaming agent is added to the lightweight aggregate mortar M5 through physical foaming method, and the foam is obtained by stirring and mixing.

[0022] Furthermore, in step A1, the mixing time is 120–240 s;

[0023] In step A2, the mixing time is 120–240 s;

[0024] In step A3, the mixing time is 60–120 seconds;

[0025] In step A4, the mixing time is 120–240 s;

[0026] In step A5, the mixing time is 120–240 s;

[0027] In step A6, the mixing time is 180–300 s.

[0028] The present invention also provides an application of lightweight aggregate foamed cement mortar in 3D printing, comprising the following steps: feeding the lightweight aggregate foamed cement mortar into the printing hopper of the 3D printer, extruding it through the printing nozzle, forming a component, and then hardening it.

[0029] Furthermore, the nozzle of the 3D printer has an outlet diameter of ≥5mm; the single continuous printing height of the 3D printed component is ≤900mm; and the horizontal printing speed of the 3D printed layer is 20~50mm / s.

[0030] The beneficial effects of this invention are:

[0031] (1) The present invention provides a lightweight aggregate foamed cement mortar, its preparation method and its application in 3D printing. The material preparation uses crushed aerated block sand instead of ordinary sand. Lightweight sand can effectively reduce the bulk density of mortar, which is beneficial to improve the self-weight of 3D printing materials and at the same time improve the buildability of 3D printing materials. It can solve the problem of high self-weight and high transportation cost of 3D printed components.

[0032] (2) The present invention provides a lightweight aggregate foamed cement mortar, its preparation method and its application in 3D printing. The preparation process of foamed mortar is adopted in the preparation of the material. On the one hand, the high fluidity of foamed mortar is utilized to ensure that the 3D printing material has good extrudability. On the other hand, it can further effectively reduce the density of 3D printed cement-based materials and reduce the cost of 3D printing materials. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the printing path for the extrudability test of lightweight aggregate foamed cement mortar according to the present invention;

[0034] Figure 2 This is a schematic diagram of the printing path for the support test of lightweight aggregate foamed cement mortar according to the present invention. Detailed Implementation

[0035] This invention provides a lightweight aggregate foamed cement mortar, which is composed of components comprising the following parts by weight:

[0036] 40-50 parts cement, 10-16 parts fly ash, 2-4.5 parts silica fume, 25-27 parts water, 49-52 parts lightweight aggregate, 1.5-1.7 parts fiber, 0.2-0.5 parts water-reducing agent, 2-2.5 parts quick-setting agent, 0.075-0.15 parts cellulose ether, and 0.058-0.072 parts composite foaming agent.

[0037] In this invention, the cement content, by weight, is preferably 42-48 parts, more preferably 44-46 parts. The cement is 42.5R ordinary Portland cement, and the ordinary Portland cement has a specific surface area >320 m². 2 / kg, 28-day compressive strength ≥48.0MPa, 28-day flexural strength >8MPa.

[0038] In this invention, the content of fly ash is preferably 11-15 parts by weight, more preferably 12-14 parts. The fly ash is Class II fly ash.

[0039] In this invention, the content of silica fume is preferably 2.5 to 4 parts by weight, more preferably 3 to 3.5 parts. The SiO2 content in the silica fume is ≥85%.

[0040] In this invention, the water content is preferably 25.5 to 26.5 parts by weight, and more preferably 26 parts by weight.

[0041] In this invention, the content of the lightweight aggregate is preferably 50-51 parts by weight, more preferably 50.5 parts, and the lightweight aggregate is crushed aerated concrete block; the particle size of the lightweight aggregate is 0.075mm-2.36mm; and the moisture content of the lightweight aggregate is saturated surface dry moisture content.

[0042] In this invention, the fiber content is preferably 1.6 parts by weight, and the fiber comprises one or more of polyvinyl alcohol fiber, polypropylene fiber, polyethylene fiber and basalt fiber, preferably polyvinyl alcohol fiber; the length of the fiber is 6 to 12 mm, preferably 8 to 10 mm; the aspect ratio of the fiber is 100 to 500, preferably 200 to 400.

[0043] In this invention, the content of the water-reducing agent is preferably 0.3 to 0.4 parts by weight, and the water-reducing agent is a polycarboxylate high-efficiency water-reducing agent, which is a conventionally used polycarboxylate water-reducing agent that can be purchased from the market.

[0044] In this invention, the content of the quick-setting agent is preferably 2.1 to 2.4 parts by weight, more preferably 2.2 to 2.3 parts, and the quick-setting agent is an alkali-free liquid quick-setting agent.

[0045] In this invention, the content of the cellulose ether is preferably 0.08 to 0.12 parts by weight, more preferably 0.09 to 0.11 parts, the cellulose ether is hydroxypropyl methylcellulose, and the viscosity of the cellulose ether is 100,000 to 200,000.

[0046] In this invention, the content of the composite foaming agent is preferably 0.062 to 0.070 parts by weight, more preferably 0.065 parts. The composite foaming agent comprises: 4.7 to 5.1% animal protein, 0.75 to 0.80% sodium dodecyl sulfate, 0.75 to 0.80% sodium α-olefin sulfonate, and 93 to 95% water.

[0047] In this invention, the animal protein is an animal protein foaming agent. The animal protein foaming agent is a brownish-black liquid with a pH of 6.8 and a density of 1.09 g / cm³. 3 It can be purchased from the market; the sodium dodecyl sulfate is a white needle-like solid; the sodium α-alkenyl sulfonate is a white powder.

[0048] This invention also provides a method for preparing lightweight aggregate foamed cement mortar, comprising the following steps:

[0049] A1: According to the proportions, weigh out cement, fly ash, silica fume, fiber and cellulose ether and mix them to obtain dry-mixed mortar material M1;

[0050] A2: According to the proportion, weigh the lightweight aggregate and water and mix them to make the lightweight aggregate reach a saturated surface-dry state to obtain pre-wetted lightweight aggregate M2;

[0051] A3: According to the proportions, weigh out the water-reducing agent, quick-setting agent and water and mix them to obtain solution M3;

[0052] A4: Add the solution M3 to the dry-mixed mortar M1 and mix to obtain the initial slurry M4;

[0053] A5: Add pre-wetted lightweight aggregate M2 to the initial slurry M4 and mix to obtain lightweight aggregate mortar M5;

[0054] A6: According to the proportion, the composite foaming agent is added to the lightweight aggregate mortar M5 through physical foaming method, and the foam is obtained by stirring and mixing.

[0055] In this invention, the mixing time in step A1 is 120-240 s, preferably 120-200 s;

[0056] In step A2, the mixing time is 120-240 s, preferably 200-240 s;

[0057] In step A3, the mixing time is 60-120 seconds, preferably 100-120 seconds;

[0058] In step A4, the mixing time is 120–240 s, preferably 180–200 s;

[0059] In step A5, the mixing time is 120–240 s, preferably 150–200 s;

[0060] In step A6, the mixing time is 180–300 s, preferably 200–240 s.

[0061] In this invention, the preparation of the lightweight aggregate foamed cement mortar is carried out in a mixer, which is an SJ-15 type mortar mixer.

[0062] The present invention also provides an application of lightweight aggregate foamed cement mortar in 3D printing, comprising the following steps: feeding the lightweight aggregate foamed cement mortar into the printing hopper of the 3D printer, extruding it through the printing nozzle, forming a component, and then hardening it.

[0063] In this invention, the nozzle of the 3D printer has an outlet diameter of ≥5mm, preferably 5-30mm; the single continuous printing height of the 3D printed component is ≤900mm; and the horizontal printing speed of the 3D printed layer is 20-50mm / s.

[0064] In this invention, the printing nozzle extrusion is performed using a screw rotary extrusion method, and the printing nozzle operates according to a set program under the control of a computer system. The thickness of the 3D printed layer is 5–20 mm.

[0065] In this invention, the components are to be cured for a period of not less than 7 days.

[0066] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0067] The 3D printers used in the following embodiments have a nozzle exit diameter of 20 mm. The thickness of the 3D printed layer is 9 mm. The horizontal printing speed is 20 mm / s.

[0068] Extrudability and buildability tests were conducted on 3D printing materials. Extrusion uniformity corresponds to the extrudability of the material, and cumulative deformation rate corresponds to the buildability of the material. The specific test methods are as follows:

[0069] Extrusion uniformity: The slurry is extruded according to... Figure 1 After actual printing, the width of each vertical printing strip was measured at three different locations using a ruler, and its width variation coefficient was calculated. The average of the three strip width variation coefficients was used to characterize the extrusion uniformity of the material. The smaller the variation coefficient, the better the extrusion uniformity and extrudability, and vice versa. The calculation formulas are shown in Equations 1 and 2.

[0070]

[0071] In the formula C k —Coefficient of variation of vertical strip width;

[0072] S—Standard deviation of vertical strip width (mm);

[0073] —The average width of the vertical strips (mm);

[0074] x i —Vertical strip width (mm);

[0075] n—the number of vertical stripes;

[0076] —The average coefficient of variation of the vertical strip width.

[0077] Cumulative deformation rate:

[0078] The prepared 3D printing slurry is processed as follows: Figure 2 The printing path shown is used for stacked printing. When the number of printing layers is ≥20, the maximum actual height of the printed wall is measured with a ruler and its cumulative deformation rate is calculated, as shown in Equation 3. The smaller the cumulative deformation rate, the stronger the resistance of the paste to deformation and the better the support. In addition, when the number of printing layers is <20, the paste is considered to have no support and the cumulative deformation rate is not calculated.

[0079]

[0080] In the formula, Δh represents the cumulative deformation rate (%) of the printed wall height;

[0081] H – Theoretical printing wall height (i.e. printer nozzle height) (mm);

[0082] H'——Actual printed wall height (mm).

[0083] Example 1

[0084] A lightweight aggregate foamed mortar suitable for 3D printing is composed of the following components in parts by weight: 40 parts cement, 16 parts fly ash, 2 parts silica fume, 25 parts water, 52 parts lightweight aggregate, 1.7 parts PP fiber, 0.2 parts water-reducing agent, 2.5 parts quick-setting agent, 0.15 parts cellulose ether, and 0.058 parts composite foaming agent; the length of the PP fiber is 6 mm.

[0085] Its preparation method includes the following steps:

[0086] According to the proportions, weigh out ordinary silicate cement, fly ash, silica fume, PP fiber and cellulose ether, and mix them to obtain dry-mixed mortar material M1;

[0087] According to the proportion, weigh the lightweight aggregate and pre-wetting water, stir and mix them until the lightweight aggregate reaches a saturated surface-dry state to obtain pre-wetted lightweight aggregate M2.

[0088] According to the formula, weigh out the water-reducing agent, quick-setting agent and water, stir and mix them evenly to obtain solution M3;

[0089] A4. Add the solution M3 to the dry-mixed mortar M1 and stir evenly to obtain the initial slurry M4.

[0090] A5 adds pre-wetted lightweight aggregate M2 to initial slurry M4 and mixes it evenly to obtain lightweight aggregate mortar M5;

[0091] According to the formula, weigh out 5.0% animal protein, 0.75% sodium dodecyl sulfate, 0.75% sodium α-olefin sulfonate and 93.8% water, stir and mix evenly to obtain composite foaming agent M6;

[0092] A7 adds the composite foaming agent M6 to the lightweight aggregate mortar M5 through a physical foaming method, and mixes it evenly to obtain lightweight aggregate foamed cement mortar suitable for 3D printing.

[0093] Example 2

[0094] A lightweight aggregate foamed mortar suitable for 3D printing is composed of the following components in parts by weight: 50 parts cement, 10 parts fly ash, 3 parts silica fume, 27 parts water, 49 parts lightweight aggregate, 1.5 parts PP fiber, 0.5 parts water-reducing agent, 2 parts quick-setting agent, 0.075 parts cellulose ether, and 0.072 parts composite foaming agent; the length of the PP fiber is 7 mm.

[0095] Its preparation method includes the following steps:

[0096] According to the proportions, weigh out ordinary silicate cement, fly ash, silica fume, PP fiber and cellulose ether, and mix them to obtain dry-mixed mortar material M1;

[0097] According to the proportion, weigh the lightweight aggregate and pre-wetting water, stir and mix them until the lightweight aggregate reaches a saturated surface-dry state to obtain pre-wetted lightweight aggregate M2.

[0098] According to the formula, weigh out the water-reducing agent, quick-setting agent, thickener and water, stir and mix them evenly to obtain solution M3;

[0099] A4. Add the solution M3 to the dry-mixed mortar M1 and stir evenly to obtain the initial slurry M4.

[0100] A5 adds pre-wetted lightweight aggregate M2 to initial slurry M4 and mixes it evenly to obtain lightweight aggregate mortar M5;

[0101] According to the formula, weigh out 5.0% animal protein, 0.75% sodium dodecyl sulfate, 0.75% sodium α-olefin sulfonate and 93.8% water, stir and mix evenly to obtain composite foaming agent M6;

[0102] A7 adds the composite foaming agent M6 to the lightweight aggregate mortar M5 through a physical foaming method, and mixes it evenly to obtain lightweight aggregate foamed cement mortar suitable for 3D printing.

[0103] Comparative Example 1

[0104] A lightweight aggregate mortar suitable for 3D printing differs from Example 2 in that only the 3D printing lightweight aggregate mortar is prepared without foaming.

[0105] Comparative Example 2

[0106] A foamed mortar suitable for 3D printing, which differs from Example 2 in that only the 3D printing foamed mortar is prepared without adding lightweight aggregate to the mortar.

[0107] Comparative Example 3

[0108] A lightweight aggregate mortar suitable for 3D printing differs from Example 2 in that it uses sodium fatty alcohol polyoxyethylene ether sulfate, a conventional foaming agent, instead of a composite foaming agent.

[0109] Comparative Example 4

[0110] A lightweight aggregate mortar suitable for 3D printing differs from Example 2 in that the composite foaming agent consists of 5% animal protein foaming agent and 95% water.

[0111] Comparative Example 5

[0112] A type of concrete for 3D printing, comprising the following components:

[0113] 300 parts cement, 160 parts water, 1200 parts sand, 2.75 parts water-reducing agent, 25 parts quick-setting agent, and 1 part foaming agent; wherein the cement is Onoda PⅡ52.5 cement, the water-reducing agent is PCA-(Ⅰ) type carboxylic acid water-reducing agent, the quick-setting agent is SBT-N(Ⅱ) type liquid quick-setting agent, and the foaming agent is sodium dodecyl sulfate.

[0114] preparation:

[0115] (1) Put cement and sand into a mixing pot and mix thoroughly;

[0116] (2) Add the mixture of water, quick-setting agent, foaming agent and water-reducing agent slowly into the mixing pot while stirring. Stir continuously at low speed for 2 minutes, then manually separate the material stuck to the mixing pot and continue stirring at high speed for 2 minutes to obtain concrete for 3D printing.

[0117] Comparative Example 6

[0118] A type of 3D-printed foamed concrete comprising the following components:

[0119] The composition includes 32.4 parts ordinary silicate cement, 15.43 parts fly ash, 34.29 parts quartz sand, 12.86 parts water, 3.6 parts setting regulator, 0.15 parts water-reducing agent, 0.26 parts viscosity modifier, 0.26 parts shrinkage reducer, 0.51 parts expansion agent, and 0.24 parts fiber.

[0120] The ordinary Portland cement is P·II 52.5 ordinary Portland cement with an apparent density of 3150 kg / m³. 3 Specific surface area is 360m² 2 The fly ash used has a density of 2600 kg / m³, a particle size range of 0.62-420 μm, and an average particle size of 16.6 μm. The fly ash used is Grade I fly ash. 3 Specific surface area is 420m² 2 The particle size ranges from 0.58 to 157 μm, with an average particle size of 7 μm. The quartz sand used is 70-120 mesh dried quartz sand with an apparent density of 2650 kg / m³. 3 The cement has a mud content of 0.1 wt% and a moisture content of 0.1 wt%. The setting regulator used is a fast-setting, fast-hardening, low-alkalinity 52.5 sulfoaluminate cement, with an initial setting time of 5 minutes and a final setting time of 12 minutes. The water-reducing agent used is a polycarboxylate high-efficiency water-reducing agent mother liquor with a solid content of 50% and a water reduction rate of not less than 35%. The viscosity modifier used is hydroxypropyl methylcellulose ether with a moisture content of less than 5.0 wt%, a pH value of 4-8, and a viscosity of 100,000 mPa·s. The shrinkage reducing agent used is an inorganic medium, ethylene glycol, high-efficiency shrinkage reducing agent with an active substance content of 65 wt%, an ash content of 32 wt%, and a bulk density of 450 kg / m³. 3The expansive agent used is an electrochemical high-performance concrete ettringite-lime composite expansive agent. The fiber used is polyethylene fiber, with a length of 3-6 mm, a diameter of 10-25 μm, a tensile strength ≥500 MPa, and an elastic modulus of 0.8-1.5 GPa.

[0121] The nano-foaming agent used is NFA330, a composite nano-foaming agent produced by Zhenjiang Yifa New Material Technology Co., Ltd. This foaming agent is a white powder, mainly composed of a foaming agent, a viscosity modifier, and a nanoparticle foam stabilizer. The foaming agent is a type of surfactant, composed of a surfactant with a hydrophilic carboxyl group, a surfactant with a long-chain hydrophobic hydroxyl group, a monohydric rosin soap, and a surfactant with a sulfonic acid group. The viscosity modifier is a mixture of polyacrylamide, methylcellulose, polyvinyl alcohol, polyethylene oxide, and polyacrylic acid. The foam stabilizer is nano-titanium oxide. The addition ratio of the foaming agent, viscosity modifier, and foam stabilizer is: 15 wt% foaming agent, 75 wt% viscosity modifier, and 10 wt% foam stabilizer.

[0122] preparation:

[0123] First, ordinary silicate cement, fly ash, quartz sand, setting regulator, shrinkage reducer, expansion agent, and fiber are added to a mixer and stirred evenly for 4 minutes to obtain a dry powder material. Then, a mixed solution prepared by thoroughly mixing water-reducing agent and viscosity modifier in water is added to the mixer and stirred together with the dry powder material for approximately 4 minutes. After stirring, a slurry is obtained. A foaming agent solution is prepared by mixing nano-foaming agent powder with water at a weight ratio of 1:303. During stirring, the nano-foaming agent powder is slowly poured in while stirring, and the water temperature should be controlled at 30℃. After the mixed foaming solution is allowed to stand for 30 minutes, it is then processed into foam clusters using a foaming machine, with a foam density of 35 kg / m³. 3 Then it can be used. Quickly mix the prepared slurry with the foam group at a volume ratio of 1.50:1, stir for 4 minutes, and mix evenly to obtain 3D printed foam concrete.

[0124] The mortar samples prepared in Examples 1-2 and Comparative Examples 1-6 were subjected to extrudability and constructability tests, and the specific test results are shown in Table 1.

[0125] Table 1 Test Results

[0126]

[0127]

[0128] As can be seen from the above embodiments, the present invention provides a lightweight aggregate foamed cement mortar, its preparation method, and its application in 3D printing. Table 1 shows that both the examples and the comparative examples exhibit good extrudability and buildability. From the extrudability test results, the extrusion uniformity of Examples 1-2 is between that of Comparative Examples 1-2, but the overall difference is not significant, all falling between 2.38% and 2.86%. Simultaneously, the cumulative deformation rate of Examples 1-2 is also between that of Comparative Examples 1-2. Adding lightweight aggregate to the foamed cement mortar significantly improves the buildability of 3D printed cement-based materials. Furthermore, the dry density of Examples 1-2 is significantly better than that of Comparative Examples 1-2. In addition, observations of Comparative Examples 3-4 show that the use of a composite foaming agent can effectively improve the buildability of 3D printed foamed cement-based materials without causing excessive slurry fluidity that prevents stacking. It is evident that Examples 1 and 2, after incorporating lightweight aggregate and foam, still maintain relatively good extrudability and constructability, while also possessing lower self-weight, effectively reducing the self-weight of the components while meeting the requirements of 3D printing construction. Comparative Examples 5 and 6 both used existing technologies to prepare 3D-printed concrete. The experimental results above show that neither the concrete materials of Comparative Examples 5 nor 6 can simultaneously achieve improvements in material lightweighting and 3D printing performance.

[0129] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A lightweight aggregate foamed cement mortar, characterized in that, Consists of components comprising the following weight parts: Cement 40-50 parts, fly ash 10-16 parts, silica ash 2-4.5 parts, water 25-27 parts, lightweight aggregate 49-52 parts, fiber 1.5-1.7 parts, water reducing agent 0.2-0.5 parts, accelerator 2-2.5 parts, cellulose ether 0.075-0.15 parts, composite foaming agent 0.058-0.072 parts; The lightweight aggregate is broken aerated block; the particle size of the lightweight aggregate is 0.075mm-2.36mm; the moisture content of the lightweight aggregate is saturated surface dry moisture content; The composite foaming agent comprises: 4.7-5.1% animal protein, 0.75-0.80% sodium lauryl sulfate, 0.75-0.80% sodium alpha-alkenyl sulfonate, 93-95% water.

2. The lightweight aggregate autoclaved aerated cement mortar according to claim 1, characterized in that, The content of SiO2 in the silica ash is ≥85%.

3. A lightweight aggregate aerated cement mortar according to claim 1 or 2, c h a r a c t e r i s e d in that The fiber comprises one or more of polyvinyl alcohol fiber, polypropylene fiber, polyethylene fiber and basalt fiber; the length of the fiber is 6-12mm, and the aspect ratio of the fiber is 100-500.

4. A lightweight aerated cement mortar according to claim 3, characterised in that, The fly ash is grade II fly ash, the cement is ordinary portland cement of 42.5R, the water reducing agent is polycarboxylic acid superplasticizer, the accelerator is alkali-free liquid accelerator, and the cellulose ether is hydroxypropyl methyl cellulose.

5. The method for producing a lightweight aggregate foamed cement mortar according to any one of claims 1 to 4, characterized in that, Comprising the following steps: A1: according to the proportion, take cement, fly ash, silica ash, fiber and cellulose ether, mix to get dry mixed mortar M1; A2: according to the proportion, take lightweight aggregate and water, mix to make the lightweight aggregate reach the state of saturated surface dry to get pre-wetted lightweight aggregate M2; A3: according to the proportion, take water reducing agent, accelerator and water, mix to get solution M3; A4: add the solution M3 to the dry mixed mortar M1, mix to get initial slurry M4; A5: add the pre-wetted lightweight aggregate M2 to the initial slurry M4, mix to get lightweight aggregate mortar M5; A6: according to the proportion, add the composite foaming agent to the lightweight aggregate mortar M5 by physical foaming method, mix after stirring to get lightweight aggregate foamed cement mortar.

6. The preparation method of the lightweight aggregate foamed cement mortar according to claim 5, characterized in that, In step A1, the mixing time is 120-240s; In step A2, the mixing time is 120-240s; In step A3, the mixing time is 60-120s; In step A4, the mixing time is 120-240s; In step A5, the mixing time is 120-240s; In step A6, the mixing time is 180-300s.

7. Use of the lightweight aggregate foamed cement mortar according to any one of claims 1 to 4 in 3D printing, characterized in that, Comprising the following steps: after the lightweight aggregate foamed cement mortar is sent into the printing material bin of the 3D printer, it is extruded through the printing nozzle to form a component which is then hardened.

8. Use of the lightweight aggregate aerated cement mortar according to claim 7 in 3D printing, characterized in that, The outlet diameter of the printing nozzle of the 3D printer is ≥5mm; the single continuous printing height of the 3D printed component is ≤900mm, and the horizontal printing speed of the 3D printing layer is 20-50mm / s.

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