A 3D printing concrete mixing proportion acquisition and low carbonization printing method

Abstract

The application discloses a 3D printing concrete mixing proportion acquisition and low-carbon printing method, and relates to the field of 3D printing concrete mixing proportion acquisition and low-carbon printing method. The 3D printing concrete mixing proportion acquisition method comprises the following steps: step one, determining the mechanical property target value of 3D printing concrete; step two, selecting the composite cementitious material mixing proportion corresponding to the 3D printing concrete with the maximum construction value; step three, obtaining the secondary selected mixing proportion of 3D printing concrete based on the initial selected mixing proportion obtained in step two; step four, obtaining the final selected mixing proportion of 3D printing concrete based on the secondary selected mixing proportion obtained in step three; and step five, testing whether the mechanical property of the final selected mixing proportion of 3D printing concrete obtained in step four meets the design requirement. The application adopts the principle of printing performance priority for mixing proportion design, and is used for the mixing proportion design of 3D printing concrete with complex composite cementitious material components.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of building 3D printing, and particularly relates to a 3D printing concrete mix proportion acquisition and low-carbon printing method. BACKGROUND

[0002] In view of the construction method of 3D printing concrete for building entities by extruding printing strips, the mechanical properties of 3D printing concrete are different in different directions, that is, there is mechanical anisotropy, and the requirements for mechanical properties are different at different parts of the printed entity. According to the mechanical anisotropy characteristics of the material, different printing path directions are used at different stress parts, so that the requirements for the material can be reduced on the basis of not reducing the overall performance of the entity. Similarly, different printing materials are used at different parts of the printed entity, which can also reduce the consumption of high-performance printing materials, thereby achieving the purpose of reducing carbon.

[0003] In view of the change of the construction method, the requirements for the performance of 3D printing concrete are different from those of traditional concrete. In addition to meeting the requirements for the conventional working performance, mechanical properties and durability, the most basic requirement for 3D printing concrete is to meet the printing performance. Generally, the printing performance of 3D printing concrete includes the requirements for pumpability, extrudability, buildability and open time, and the conventional concrete performance detection method cannot fully express the printing performance of 3D printing concrete. At present, the buildability of the material is usually detected by the height of the test body after being pulled out of the mold, thixotropy and direct printing on the machine. However, when the fluidity of the concrete is quite different, the height of the test body is basically meaningless. Since the fluidity of the concrete is difficult to be completely the same, it is also difficult to carry out meaningful comparison and selection between different materials. The use of thixotropy to evaluate the buildability of concrete is relatively accurate, but the rheological parameter detection instrument is relatively expensive, and the detection and data processing process is also relatively complex, which is not suitable for material testing before each printing. As the most important printing performance of 3D printing concrete, buildability needs a simple and quantifiable detection method.

[0004] In addition, the conventional concrete mix proportion design method does not consider the printing performance, so the conventional concrete mix proportion design method is no longer applicable to 3D printing concrete. Various recycled components and tailings waste have been used as concrete raw materials. Among these low-carbon materials, the powdery material is the most difficult to dispose. Using it as a cement substitute for 3D printing concrete with low strength requirement is one of the feasible ways. However, the addition of these powder materials undoubtedly makes the composition of 3D printing concrete composite cementitious material more complex, further increasing the difficulty of mix proportion design.

[0005] Thickeners, redispersible latex powders and thixotropic lubricants, etc. which have regulating effects on rheological properties of concrete can be used to improve the printing performance of concrete, but the addition of such admixtures generally leads to a significant decrease in the strength of concrete, and the amount of such admixtures needs to be strictly controlled. SUMMARY

[0006] In view of the problems in the prior art, the present application provides a 3D printing concrete mix proportion obtaining method, the present application designs the mix proportion according to the principle of prioritizing printing performance, plans the printing path according to the mechanical distribution characteristics of the printing object, and selects the printing material, and provides a 3D printing concrete constructability detection method for mix proportion optimization, and the present application can prepare 3D printing concrete with superior printing performance.

[0007] To achieve the above object, the present application adopts the following technical scheme:

[0008] In a first aspect of the present application, a 3D printing concrete mix proportion obtaining method is provided, comprising the following steps:

[0009] Step one, determining the target value of the mechanical properties of 3D printing concrete, and selecting the water-binder ratio, bone glue ratio and fiber content of 3D printing concrete with higher mechanical properties than the target value;

[0010] Step two, selecting the composite cementitious material mixing ratio corresponding to the 3D printing concrete with the maximum construct value, so as to obtain the preliminary selected mix proportion of the 3D printing concrete;

[0011] Step three, based on the preliminary selected mix proportion obtained in step two, adding a thickening agent to improve the extrudability of the concrete, adjusting the fluidity to 175mm-190mm by adding a water reducing agent, and printing on the machine until the material has good extrudability, so as to obtain the secondary selected mix proportion of the 3D printing concrete;

[0012] Step four, based on the secondary selected mix proportion obtained in step three, adding a redispersible latex powder to improve the extrudability of the material, adjusting the fluidity to 175mm-190mm by adjusting the amount of water reducing agent, and printing on the machine until the material has good constructability, so as to obtain the final selected mix proportion of the 3D printing concrete;

[0013] Step five, testing whether the mechanical properties of the 3D printing concrete with the final selected mix proportion obtained in step four meet the design requirements, if yes, the final selected mix proportion of the 3D printing concrete is the target mix proportion; if not, returning to step one.

[0014] As a preferred technical solution, in the step one, the bone glue ratio is the ratio of fine aggregate to cementitious material, the value range is 1-1.5, the water-binder ratio is the ratio of water to cementitious material, the value range is 0.25-0.45, the cementitious material includes cement and all other admixtures, the water-binder ratio of high-performance printing material is 0.25-0.35, and the water-binder ratio of low-performance printing material is 0.35-0.45.

[0015] As a preferred technical solution, in the step two, the construction value acquisition method of the 3D printing concrete includes the following steps:

[0016] S1, preparing the 3D printing concrete mixture according to the mixing ratio;

[0017] S2, testing the micro-slump of the 3D printing concrete mixture;

[0018] S3, testing the fluidity and consistency of the 3D printing concrete mixture;

[0019] S4, calculating the construction value of the 3D printing concrete mixture according to the micro-slump, fluidity and consistency, B=FS+CS, wherein, F is the fluidity, C is the consistency, S is the micro-slump, and B is the construction value.

[0020] S5, using the construction value to characterize the constructability of the 3D printing concrete, the greater the construction value, the better the constructability.

[0021] As a preferred technical solution, in the step S1, the fluidity of the 3D printing concrete mixture is 170-200 mm, and the consistency is not less than 50 mm.

[0022] As a preferred technical solution, in the step S2, the micro-slump of the 3D printing concrete mixture is detected using the test tools in GB / T 2419-2005 "Cement mortar fluidity determination method", and the measurement method is the vertical distance between the top center point of the test body and the top surface of the truncated cone after the truncated cone is pulled out.

[0023] As a preferred technical solution, in the step S3, the fluidity of the 3D printing concrete mixture is detected according to the standard GB / T 2419-2005 "Cement mortar fluidity determination method", and the consistency is detected according to the standard JGJ / T 70-2009 "Building mortar basic performance test method standard".

[0024] As a preferred technical solution, in the step S2 and step S3, after the micro-slump detection of the 3D printing concrete mixture is completed, the flow table is started to directly detect the fluidity of the 3D printing concrete mixture.

[0025] As a preferred technical scheme, in the step two, the composite cementitious material is selected from one or more of cement, silica fume, slag powder, fly ash, recycled micro-powder and tailing powder, and in the process of testing the construction value, the fluidity of the mixture is adjusted to 170-200mm by using water reducing agent.

[0026] As a preferred technical scheme, in the step two, the construction of the composite cementitious material can be preferably selected by any test method capable of obtaining the optimal solution, and the orthogonal test method is suggested.

[0027] As a preferred technical scheme, in the step three, the thickening agent is hydroxypropyl methyl cellulose ether.

[0028] As a preferred technical scheme, in the step four, the redispersible latex powder is vinyl acetate-ethylene copolymer powder.

[0029] The second aspect of the present application provides a 3D printing concrete low-carbon printing method, which adopts the 3D printing concrete target mixing ratio obtained by the above method, and has the following steps.

[0030] The first step is to input a printing model.

[0031] The second step is to calculate a printing model mechanical property distribution map.

[0032] The third step is to set a printing path according to the printing model mechanical property distribution map and the mechanical anisotropy of the 3D printing concrete.

[0033] The fourth step is to divide the printing entity into key parts and ordinary parts according to the printing model mechanical property distribution map and the mechanical property requirements.

[0034] The fifth step is to install the printing path set in the third step, and the key parts are printed by using high-performance printing materials, and the ordinary parts are printed by using low-performance printing materials.

[0035] As a preferred technical scheme, in the fifth step, the high-performance printing material is 3D printing concrete with high mechanical property and durability performance indexes, and the low-performance printing material is 3D printing concrete with mechanical property and durability performance obviously lower than that of the high-performance material.

[0036] Compared with the prior art, the present application has the following technical effects:

[0037] (1) The present application can reasonably utilize the mechanical anisotropy of 3D printing concrete, detect and evaluate the construction of 3D printing concrete by a quantitative method, and is simple in operation and calculation, and suitable for pre-printing inspection by using existing detection equipment and standards.

[0038] (2) The present application adopts the principle of printing performance priority for mix proportion design, without new equipment and complex calculation, and is suitable for the mix proportion design of 3D printing concrete with complex composition of composite cementitious material.

[0039] (3) The construction value, flow slump ratio and thick slump ratio proposed in the present application can quantitatively evaluate the constructability of 3D printing concrete, and can be used for comparison and material selection between different 3D printing concretes, and is a detection method which can be independent of printing equipment. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0041] Figure 1 It is a 3D printing concrete micro-slump detection schematic diagram of the present application.

[0042] Figure 2 It is a 3D printing concrete mix proportion acquisition flow chart of the present application.

[0043] Figure 3 It is a 3D printing concrete printing cylinder comparison diagram of the present application.

[0044] Figure 4 It is a comparison diagram of the influence law of recycled micro-powder on the constructability of 3D printing concrete of the present application.

[0045] Figure 5 It is a comparison diagram of the influence law of admixture on the constructability of 3D printing concrete of the present application.

[0046] Figure 6 It is a 3D printing concrete printing on machine schematic diagram of the present application.

[0047] Figure 7 It is a 3D printing concrete low-carbon printing method flow chart of the present application.

[0048] Among them, the specific explanation of the reference signs is as follows: test body 1, truncated cone round die 2, jump table 3, flat plate 4, ruler 5. DETAILED DESCRIPTION

[0049] In the description of the present application, it should be understood that the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0050] Embodiment 1

[0051] The present embodiment provides a 3D printing concrete construction value detection method for evaluating the construction of 3D printing concrete mixture, comprising the following steps:

[0052] S1, each raw material is weighed according to the mixing ratio to prepare 3D printing concrete mixture;

[0053] S2, the 3D printing concrete mixture prepared in step S1 is placed in the truncated cone circular mold 2 according to the standard GB / T 2419-2005 "Cement mortar flow test method", the truncated cone circular mold 2 is pulled out, the truncated cone circular mold 2 is placed on one side of the test body 1, the flat plate 4 is placed on the upper surface of the truncated cone circular mold 2, and the flat plate 4 extends over the test body 1, and the distance between the lower surface of the flat plate 4 and the center of the top surface of the test body 1 is measured with a ruler 5, which is accurate to 1mm, that is, the micro-slump of the 3D printing concrete mixture.

[0054] S3, start the jump table 3, and detect the flow of the 3D printing concrete mixture according to the standard GB / T 2419-2005 "Cement mortar flow test method";

[0055] S4, detect the consistency of the 3D printing concrete mixture according to the standard JGJ / T 70-2009 "Building mortar basic performance test method standard";

[0056] Step S5, calculate the construction value of the 3D printing concrete according to the following formula:

[0057]

[0058]

[0059] B=FS+CS

[0060] In the formula, B is the construction value, dimensionless, accurate to 0.1; FS is the flow-slump ratio, dimensionless, accurate to 0.01; CS is the consistency-slump ratio, dimensionless, accurate to 0.01; F is the flow, mm; C is the consistency, mm; S is the micro-slump, mm.

[0061] Step six, the greater the build value of the 3D printing concrete mixture, the better the build performance, and when the build value is not less than 5, the printing performance is good.

[0062] Embodiment 2

[0063] The embodiment provides a case of using a build value to study the influence law of the recycled micro-powder mixing amount on the build performance of 3D printing concrete.

[0064] Table 1 3D printing concrete test mix proportion

[0065]

[0066] The 3D printing concrete test mix proportion is shown in Table 1, a 20mm circular printing nozzle is used to print a cylinder, the cylinder diameter is 200mm, the layer height is 10mm, the printing speed is 1680mm / min, and the flow slump ratio, the thick slump ratio, the build value and the printing height are used to evaluate the build performance of the material. The test results are shown in Table 2, and the photos of the printed cylinders are shown in Figure 3 The influence law of the recycled micro-powder on the build performance of the 3D printing concrete is shown in Figure 4 .

[0067] Table 2 3D printing concrete test results

[0068] Mix ratio Mini slump (mm) Slump (mm) Consistency (mm) Slump mini ratio Slump consistency ratio Build value Print height (layers) RP0 23 175 67 3.26 2.91 6.17 33 RP20 28 177 72 2.75 2.57 5.32 13 RP40 25 177 68 3.08 2.72 5.80 19 RP60 22 176 67 3.45 3.05 6.50 39

[0069] It can be easily seen from Figure 4 that the flow slump ratio, the thick slump ratio and the build value and the printing height change with the recycled micro-powder mixing amount in a completely consistent manner, and all show that the build performance of the material first decreases and then increases with the increase of the recycled micro-powder mixing amount, which shows that the method for evaluating the build performance of the 3D printing concrete by using the flow slump ratio, the thick slump ratio or the build value is high in accuracy.

[0070] Embodiment 3

[0071] The embodiment provides a 3D printing concrete mix proportion acquisition method, a 3D printing concrete mix proportion containing a plurality of admixtures is designed, and the 28d compressive strength is required to be not less than 40MPa.

[0072] Step one, according to the strength requirement, the water-binder ratio 0.31, the bone glue ratio 1.3 and the polypropylene fiber mixing amount 0.61% are selected according to the previous experience, the fiber is mixed according to the volume ratio, and the mix proportion S1 is obtained, as shown in Table 3.

[0073] Table 3

[0074]

[0075] Step two, according to the production needs to select silica fume, slag powder, stone powder and fly ash four admixtures, each admixture and additive are added according to the proportion of composite cementitious material, composite cementitious material includes cement, stone powder, silica fume, slag powder and fly ash, according to the water-binder ratio, bone glue ratio and fiber content in S1, the orthogonal test design method is used to obtain the optimal test mix proportion of composite cementitious material, see table 4, and the test results are shown in table 5.

[0076] Table 4 optimal test mix proportion of composite cementitious material

[0077]

[0078] Table 5 optimal test results of mix proportion

[0079]

[0080]

[0081] The orthogonal test results are analyzed, and the influence law of each admixture on the buildability of 3D printing concrete is obtained, see Figure 4 , according to the influence law of each admixture on the flow slump ratio, thick slump ratio and build value of 3D printing concrete, the mixing ratio of cementitious material is obtained under the optimal solution of buildability, cement: stone powder: silica fume: slag powder: fly ash = 45%: 5%: 0%: 20%: 30%, and the mix proportion S2 is obtained, see Figure 5 , S2 mix proportion does not have extrusion performance, and the printing photo is shown in Figure 6 .

[0082] Step three, 0.1% thickening agent is added in mix proportion S2 to improve the extrusion performance of concrete, and the material flow degree is adjusted to 175mm-190mm by polycarboxylic acid water reducing agent, and the printing is carried out on the machine, it is found that the material extrusion performance is good, and the thickening agent content is not increased, and the mix proportion S3 is obtained, see Figure 5 , S3 has good extrusion performance, but the buildability is poor, and the printing photo is shown in Figure 6 .

[0083] Step four, 0.2% redispersible latex powder is added in mix proportion S3 to further improve the buildability of the material, and the flow degree is adjusted to 175mm-190mm by water reducing agent, and the printing is carried out on the machine, it is found that the material buildability is good, but the surface state is poor, and the redispersible latex powder content is further increased to 0.6%, the surface state of the printing strip is improved, and the mix proportion S4 is obtained, see Figure 5 , S4 has good buildability and extrusion performance, and at least 47 layers of continuous printing can be carried out, and a 470mm high cylinder is printed, and the printing photo is shown in Figure 6 .

[0084] Step five, pouring 70.7mm cubic test specimen test mix proportion S3 compressive strength is 41.6MPa, meet the design requirements, mix proportion S4 is the target mix proportion.

[0085] Example 4

[0086] The embodiment provides a 3D printing concrete low-carbon printing method, which comprises the following steps as shown in the figure: Figure 7

[0087] Step one, input the printing model;

[0088] Step two, calculate the stress distribution diagram of the printing model;

[0089] Step three, set the printing path according to the mechanical property distribution diagram of the printing model and the mechanical anisotropy of 3D printing concrete;

[0090] Step four, according to the mechanical property distribution diagram of the printing model, the printing entity is divided into key parts and ordinary parts according to the mechanical property requirements;

[0091] Step five, according to the printing path set in step three, the key parts are printed by using high-performance printing materials, and the ordinary parts are printed by using low-performance printing materials.

[0092] Although the above embodiment has been specifically described, it should be understood by those skilled in the art that modifications or improvements can be made based on the disclosure of the present application without departing from the spirit and scope of the present application, and these modifications and improvements are within the spirit and scope of the present application.​

Claims

1. A method for obtaining a mix proportion of 3D printing concrete, characterized in that, The method comprises the following steps: Step one, determining the target value of the mechanical properties of 3D printing concrete, selecting the water-binder ratio, bone glue ratio and fiber content of 3D printing concrete with mechanical properties higher than the target value; Step two, selecting the composite cementitious material mixing ratio corresponding to the 3D printing concrete with the maximum construction value, thereby obtaining the initial mixing ratio of the 3D printing concrete; Step three, based on the initial mixing ratio obtained in step two, adding a thickening agent to improve the extrudability of the concrete, adjusting the fluidity by adding a water reducing agent, and printing on the machine until the material has good extrudability, thereby obtaining the secondary mixing ratio of the 3D printing concrete; Step four, based on the secondary mixing ratio obtained in step three, adding a redispersible latex powder to improve the extrudability of the material, adjusting the fluidity by adjusting the amount of water reducing agent, and printing on the machine until the material has good buildability, thereby obtaining the final mixing ratio of the 3D printing concrete; Step five, testing whether the final mixing ratio of the 3D printing concrete obtained in step four meets the design requirements in terms of mechanical properties, if it does, the final mixing ratio of the 3D printing concrete is the target mixing ratio; if it does not, return to step one.

2. The method of claim 1, wherein the 3D printing concrete mixture ratio is obtained by, In step one, the bone glue ratio is the ratio of fine aggregate to cementitious material, with a value range of 1-1.5, and the water-binder ratio is the ratio of water to cementitious material, with a value range of 0.25-0.

45.

3. The method of claim 1, wherein the 3D printing concrete mixture ratio is obtained by, In step two, the method for obtaining the construction value of 3D printing concrete comprises the following steps: S1, preparing 3D printing concrete mixture according to the mixing ratio; S2, testing the micro-slump of the 3D printing concrete mixture; S3, testing the fluidity and consistency of the 3D printing concrete mixture; S4. Calculate the build value of the 3D-printed concrete mixture from the microslump, the fluidity, and the consistency, wherein, , F is the fluidity, C is the consistency, S is the microslump, and B is the build value. S5, using the construction value to represent the buildability of the 3D printing concrete, the larger the construction value, the better the buildability.

4. The method of claim 3, wherein the 3D printing concrete mixture ratio is obtained by, In step S1, the fluidity of the 3D printing concrete mixture is 170-200 mm, and the consistency is not less than 50 mm. 5.The method of claim 1, wherein, In step two, during the testing of the construction value, the fluidity of the mixture is adjusted to 170-200 mm by adding a water reducing agent. 6.The method of claim 1, wherein, In step three, the thickening agent is hydroxypropyl methylcellulose ether. 7.The method of claim 1, wherein, In step four, the redispersible latex powder is a vinyl acetate-ethylene copolymer powder.

8. A low-carbon printing method of 3D printed concrete, using the 3D printed concrete target mix proportion obtained by the method of any one of claims 1-7, characterized in that, The method comprises the following steps: First step, inputting the printing model; Second step, calculating the mechanical property distribution map of the printing model; Third step, setting the printing path according to the mechanical property distribution map of the printing model and the mechanical anisotropy of the 3D printing concrete; Fourth step, dividing the printing entity into key parts and ordinary parts according to the mechanical property distribution map of the printing model; Fifth step, installing the printing path set in the third step, using high-performance printing materials to print the key parts, and using low-performance printing materials to print the ordinary parts.

9. A 3D printing concrete low-carbonization printing method according to claim 8, characterized in that, In the fifth step, the high-performance printing material is 3D printing concrete with high mechanical properties and durability, and the low-performance printing material is 3D printing concrete with significantly lower mechanical properties and durability than the high-performance material.

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