CN108590187B - Method for toughening 3D printed concrete structure by using high-ductility cement-based material - Google Patents
Method for toughening 3D printed concrete structure by using high-ductility cement-based material Download PDFInfo
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Abstract
The invention relates to a method for toughening a 3D printed concrete structure by using a high-ductility cement-based material, which comprises the following steps: designing a three-dimensional digital model of a composite structure: firstly, designing or modeling a composite beam structure through three-dimensional modeling software or a three-dimensional scanner to obtain geometric structure information of a three-dimensional model of the composite beam structure to be printed; then dividing the three-dimensional model into two parts according to the geometric form and stress condition of the composite beam structure to be printed, wherein one part is a common concrete layer for printing common concrete, and the other part is a high-ductility cement-based material reinforcing layer for printing high-ductility cement-based material, and the high-ductility cement-based material reinforcing layer and the common concrete layer form a three-dimensional digital model of the composite structure; STL file generation and restoration; layering and slicing the three-dimensional model; planning and designing a printing path; 3D printing of the composite structure; and (5) curing the concrete structure. The method has the advantages of simple process, high construction speed, low labor cost and high automation degree.
Description
Technical Field
The invention belongs to the field of building structure engineering, and particularly relates to a method for toughening a 3D printed concrete structure by using a high-ductility cement-based material.
Background
The 3D printing concrete technology has the advantages of free design, flexibility in construction, high construction speed, low labor cost, high automation degree, small environmental pollution and the like, and has been widely paid attention to and remarkably developed in the civil construction field in recent years. Examples of 3D printed bridges, 3D printed houses, etc. are often reported, which to a large extent confirm the feasibility of applying 3D printing techniques to the civil construction field. The preparation of 3D printed cementitious materials is critical to facilitate the application of this technology in engineering practice. However, cement concrete is notable for low ultimate elongation and significant brittle failure. Moreover, since the process of 3D printing concrete is by continuously extruding concrete material and stacking layer by layer to finally construct a shape. Therefore, the traditional reinforcement cage and the like are difficult to implant into concrete in the printing process on one hand, and the reinforcement cage is difficult to adapt to the flexible variability of the 3D printing structure on the other hand. It is therefore of great importance to find a method of reinforcing the 'reinforcing bar-like' of 3D printed concrete structures.
The fiber reinforced high-ductility cement-based material is prepared by adding fibers through micromechanics design, so that the cement-based material shows strain hardening characteristics and has higher ultimate tensile strain and elongation. Reasonably blending the fiber material can effectively improve the brittleness characteristics of the concrete material, so that the concrete material has higher ductility and ductility characteristics. Therefore, the common concrete material is reinforced by using the high-ductility cement-based material capable of being printed in 3D, and the composite structure of the similar reinforced concrete is manufactured, so that the bearing capacity of the 3D printed concrete structure can be effectively improved, and the engineering practical application of the composite structure is promoted.
In terms of the reinforcing method of the 'reinforcing bar-like' effect of the concrete structure, chinese patent with the patent number ZL200510046304.2 discloses a fiber woven mesh reinforced self-compacting concrete method; chinese patent application No. 201210532856.4 discloses a method for reinforcing prestressed concrete hollow slab by sticking carbon fiber cloth. However, the carbon fiber cloth, the fiber woven mesh and the like mentioned in the above patent cannot be effectively adapted to the extrusion process, the layer-by-layer construction process and the like of the concrete material in the 3D printing, and the 3D printing structure often has personalized, flexible and complex structural shapes, and the woven mesh and the like cannot be applied. Up to now, no method for reinforcing and toughening 3D printed concrete structures by using high-ductility concrete has been disclosed.
Disclosure of Invention
In order to adapt to the flexibility and high automation degree of the concrete 3D printing process, the invention provides a method for toughening a 3D printing concrete structure by using a high-ductility cement-based material, which has the advantages of simple process, high construction speed, low labor cost and high automation degree.
The technical scheme of the invention is to provide a method for toughening a 3D printed concrete structure by using a high-ductility cement-based material, which comprises the following steps:
s1, designing a three-dimensional digital model of a composite structure: firstly, designing or modeling a composite beam structure through three-dimensional modeling software or a three-dimensional scanner to obtain geometric structure information of a three-dimensional model of the composite beam structure to be printed; then dividing the three-dimensional model into two parts according to the geometric form and stress condition of the composite beam structure to be printed, wherein one part is a common concrete layer for printing common concrete, and the other part is a high-ductility cement-based material reinforcing layer for printing high-ductility cement-based material, and the high-ductility cement-based material reinforcing layer and the common concrete layer form a three-dimensional digital model of the composite structure;
s2, STL file generation and restoration: exporting the high-ductility cement-based material reinforcing layer and the common concrete layer respectively in dwg format files, then respectively reading the dwg format files into STL file editing software, repairing the STL format files, and exporting the STL format files after the repairing;
s3, layering and slicing the three-dimensional model: reading the repaired STL format file into slicing software, setting the slicing thickness, and slicing the repaired STL format file;
s4, planning and designing a printing path: planning a path for the slice, designing a corresponding printing path in path planning software according to the geometric structure of the three-dimensional digital model of the composite structure in the step S1, and then deriving a G file containing the slice and path information;
s5, 3D printing of the composite structure: the G file saved in the step S4 is imported into a program control system of a 3D printer, a common 3D printable concrete material and a 3D printable high-ductility cement-based material are respectively conveyed into a material storage system of the 3D printer through corresponding conveying equipment, then the 3D printer is started, and the moving speed and the material extrusion speed of a printing spray head in the corresponding 3D printer are set according to the flowability of the used concrete material; after the setting is completed, the printing spray heads respectively extrude the high-ductility cement-based material and the common concrete material continuously layer by layer to be finally formed under the drive of the program control system according to the path information contained in the G file;
s6, curing the concrete structure: after the model structure is printed, standard curing, water curing or high-temperature steam curing and the like can be carried out according to specifications, and the concrete structure toughened by the cement-based material with high ductility is obtained.
The concrete structure is prepared by the method for toughening the 3D printed concrete structure by using the high-ductility cement-based material.
Compared with the prior art, the invention has the beneficial effects that:
the high-ductility cement-based material is used for toughening 3D printing plain concrete based on a 3D printing technology, so that the strength and ductility of a 3D printing plain concrete structure can be improved, and the experimental result shows that the ultimate bending deflection of the high-ductility cement-based material reinforced 3D printing concrete composite structure can be increased by 120-330% when the high-ductility cement-based material is applied to the bottom tension area of a beam structure. The invention has simple reinforcement process, low cost and high construction speed, and can be suitable for the flexible activation of the 3D printed concrete structure and improve the automation degree.
Description of the drawings:
FIG. 1 is a schematic flow chart of a method of toughening a 3D printed concrete structure with a high-ductility cement-based material according to the present invention;
FIG. 2 is a schematic force diagram of a 3D printed high ductility concrete and plain concrete composite structural beam of example 1;
FIG. 3 is a path planning design of the composite beam of example 1;
FIG. 4 is a graph of four-point bending stress versus mid-span deflection for the concrete composite structural beams of the examples and comparative examples;
fig. 5 is a schematic diagram of a path planning design of the combined column.
FIG. 6 is a schematic cross-sectional view of a rectangular composite beam;
FIG. 7 is a schematic cross-sectional view of a composite column having a shape of a circle;
FIG. 8 is a schematic cross-sectional view of a corrugated composite board;
FIG. 9 is a schematic cross-sectional view of an I-shaped composite beam;
FIG. 10 is a schematic cross-sectional view of a T-shaped composite beam;
FIG. 11 is a schematic top view of a bi-directional reinforcement composite board;
FIG. 12 is a schematic top view of a unidirectional reinforcing composite board;
in the figure, 1 is a common concrete material, and 2 is a high-ductility cement-based material.
The specific embodiment is as follows:
the present invention is further explained below with reference to examples and drawings, but is not to be construed as limiting the scope of the present application.
The invention relates to a method for toughening a 3D printed concrete structure by using a high-ductility cement-based material, which comprises the following steps:
s1, designing a three-dimensional digital model of a composite structure: firstly, designing or modeling a composite beam structure through three-dimensional modeling software or a three-dimensional scanner to obtain geometric structure information of a three-dimensional model of the composite beam structure to be printed; then dividing the three-dimensional model into two parts according to the geometric form and stress condition of the composite beam structure to be printed, wherein one part is a common concrete layer for printing common concrete, and the other part is a high-ductility cement-based material reinforcing layer for printing high-ductility cement-based material, and the high-ductility cement-based material reinforcing layer and the common concrete layer form a three-dimensional digital model of the composite structure; the spatial positions of the high-ductility cement-based material reinforcing layer and the common concrete layer are required to be comprehensively designed according to the form, the use condition and the like of the composite beam structure to be printed;
s2, STL file generation and restoration: exporting the high-ductility cement-based material reinforcing layer and the common concrete layer respectively in dwg format files, then respectively reading the dwg format files into STL file editing software, repairing the STL format files, and exporting the STL format files after the repairing;
s3, layering and slicing the three-dimensional model: reading the repaired STL format file into slicing software, setting the slicing thickness, and slicing the repaired STL format file;
s4, planning and designing a printing path: planning a path for the slice, designing a corresponding printing path in path planning software according to the geometric structure of the three-dimensional digital model of the composite structure in the step S1, and then deriving a G file containing the slice and path information;
s5, 3D printing of the composite structure: the G file saved in the step S4 is imported into a program control system of a 3D printer, the common 3D printable concrete material and the 3D printable high-ductility cement-based material are respectively conveyed into a material storage system of the 3D printer through corresponding conveying equipment, then the 3D printer is started, the moving speed of a printing spray head in the corresponding 3D printer, namely the printing speed, is set according to the flowability of the used concrete material, and the rotating speed of a driving motor assembled by the printing spray head, namely the material extrusion speed and the like; after the setting is completed, the printing spray heads respectively extrude the high-ductility cement-based material and the common concrete material continuously layer by layer to be finally formed under the drive of the program control system according to the path information contained in the G file;
s6, curing the concrete structure: after the model structure is printed, standard curing, water curing or high-temperature steam curing and the like can be carried out according to specifications, and the concrete structure toughened by the cement-based material with high ductility is obtained.
The invention is further characterized in that the high-ductility cement-based material comprises the following components in parts by weight:
0.8 to 1.2 portions of quick hardening ordinary Portland cement;
0.96-1.44 parts of F-level fly ash;
0.64-0.96 part of quartz sand, wherein the particle size range of the quartz sand is 0.075-0.15mm;
0.29 to 0.43 portion of water;
0.005-0.01 part of water reducer;
0.0017 to 0.0018 parts of PVA fiber;
0.0043-0.0078 parts of basalt fiber.
The preparation method of the high-ductility cement-based material comprises the following steps:
pouring 0.8-1.2 parts of quick hardening Portland cement, 0.96-1.44 parts of F-level fly ash and 0.64-0.96 parts of quartz sand into a stirrer according to parts by weight, and stirring for 2-3 minutes; then pouring 2/3 of the mixture of 0.29-0.43 part of water and 0.005-0.01 part of water reducer into a stirrer for stirring for 5-6 minutes; then pouring the rest 1/3 of the mixture of water and the water reducing agent into a stirrer to stir for 2-3 minutes; and sequentially placing PVA fibers and basalt fibers into a stirrer for stirring, thus obtaining the concrete.
When the high-ductility cement-based material is pumped or mechanically conveyed into a printing nozzle of a 3D printer, printing is performedThe outlet cross section of the printing nozzle is set to be 64-110 mm 2 The extrusion speed is set to be 0.35-0.50m 3 And/h, setting the horizontal printing speed to 280-310m/h.
The invention also protects the concrete structure which is prepared by the method and contains the high-ductility cement-based material for toughening, and the structure can be a beam structure, a plate structure, a column structure and the like.
The concrete structure comprises a plain concrete layer made of a 3D printable plain concrete material 1 and a high-ductility cement-based material reinforcement layer made of a 3D printable high-ductility cement-based material 2, the high-ductility cement-based material having a yield deflection of greater than 1mm.
The concrete structure is a rectangular composite beam (see fig. 6), a square composite column (see fig. 7), a sandwich plate, a corrugated composite plate (see fig. 8), an i-shaped composite beam (see fig. 9), a T-shaped composite beam (see fig. 10), a unidirectional reinforcing composite plate (see fig. 12), a bidirectional reinforcing composite plate (see fig. 11) or the like.
The common concrete material is a concrete material which is obtained by mixing and stirring fine sand, water, a water reducing agent, cement, silica fume and other cementing materials and can be printed in a 3D mode. The high-ductility cement-based material refers to a 3D printable concrete material with yield deflection, namely, the difference between limit deflection and peak deflection, of more than 1mm.
The method of the present invention will be further explained below taking a high-ductility cement-based material toughened 3D printed concrete beam as an example.
Example 1:
the composite beam structure is prepared by a method of toughening a 3D printed concrete structure by using a high-ductility cement-based material, the composite beam structure to be printed in the embodiment is a cuboid beam structure with the size of 150 multiplied by 700mm,
preparing a common concrete material 1: 52.5 parts of quick hardening ordinary Portland cement, 0.9 part of F-grade fly ash, 1.18 parts of quartz sand and 0.75 part of quartz sand are poured into an 80L planetary stirrer to be stirred for 2 minutes; then pouring 2/3 of the mixture of 0.32 part of water and 0.006 part of water reducer into a stirrer for stirring for 5 minutes; then pouring the mixture of the rest 1/3 water and the water reducing agent into a stirrer to stir for 2 minutes to obtain 3D printing concrete;
preparation of high-ductility cement-based material 2: 52.5 parts of quick hardening ordinary Portland cement, 0.9 part of F-grade fly ash, 1.18 parts of quartz sand and 0.75 part of quartz sand are poured into an 80L planetary stirrer to be stirred for 2 minutes; then pouring 2/3 of the mixture of 0.32 part of water and 0.006 part of water reducer into a stirrer for stirring for 5 minutes; then pouring the rest 1/3 of the mixture of water and the water reducing agent into a stirrer to stir for 2 minutes; and sequentially placing 0.0017 parts of polyvinyl alcohol (PVA) fiber and 0.0045 parts of basalt fiber into a stirrer for stirring, thus obtaining the high-ductility concrete. The PVA fiber has the length of 12mm, the diameter of 39 mu m, the tensile strength of 1600MPa and the elastic modulus of 41GPa; the length of basalt fiber is 12mm, the diameter is 18 mu m, the tensile strength is 4400MPa, and the elastic modulus is 89GPa;
the method comprises the following specific steps:
s1, three-dimensional modeling is carried out on a composite beam structure through AutoCAD software, namely, firstly, a cuboid with the size of 150 multiplied by 700mm is drawn, then, the composite beam structure is divided into two parts according to the geometric form and stress condition of the composite beam structure to be printed, one part is a common concrete layer used for printing common concrete, the other part is a high-ductility cement-based material reinforcing layer used for printing high-ductility cement-based materials, and the high-ductility cement-based material reinforcing layer and the common concrete layer form a three-dimensional digital model of the composite structure; in this embodiment, the high-ductility cement-based material is applied to the bottom tension region of the beam structure, the common concrete is applied to the upper load bearing compression region of the beam structure, namely, the lower part is a high-ductility cement-based material reinforcing layer with the size of 45×150×700mm, the upper part is a plain concrete (i.e., common concrete) layer with the size of 105×150×700mm, wherein the high-ductility cement-based material reinforcing layer occupies 30% (45 mm/150 mm) of the overall structure;
s2, STL file generation and restoration: and (3) respectively exporting the high-ductility cement-based material reinforcing layer obtained in the step (S1) and the common concrete layer in dwg format files in AutoCAD software, importing the files into Solidworks software or magic software, repairing the files in Solidworks software, and exporting the STL-1 format file corresponding to the high-ductility cement-based material reinforcing layer and the other STL-2 format file corresponding to the common concrete layer.
S3, reading the STL-1 and STL-2 format files derived in the step S2 into slicing software slice3r, and slicing at equal layer heights, wherein the slice layer thickness is uniformly set to be 8mm. Therefore, the high-ductility cement-based material reinforcing layers are 6 layers in total, the height is 48mm, the height is 3mm higher than the design size, the plain concrete part is 13 layers, the height is 104mm, the height is 1mm lower than the design size, and the slice modeling accuracy is 99%.
S4, planning a path of the slice, wherein a straight-line Z-shaped path planning method is adopted in software slice3r, and the straight line is kept parallel to the length direction; the printer nozzle is set to be 12mm, the running speed of the printer is 35mm/s, and the stepping value of a stepping motor for material extrusion is set to be 2500; and finally, generating G-1 and G-2 files corresponding to the STL-1 and STL-2 format files in the slice3 r. The G-1 and G-2 files are G files, i.e. parameters including planned paths of the printing process, etc., as shown in FIG. 3.
S5, conveying the 3D printable high-ductility cement-based material to a material storage system of a 3D printer through conveying equipment, loading the G-1 file into printing control software repeater-Host, setting the printing space size in the printing control software repeater-Host to be 45 multiplied by 150 multiplied by 700mm, connecting the printer, clicking for printing, and finishing printing of the high-ductility cement-based material reinforcing layer. And (3) conveying the 3D printable common concrete material to a material storage system of a 3D printer through conveying equipment, loading the G-2 file into a printing control software repeater-Host, setting the printing space size in the software repeater-Host to be 105 multiplied by 150 multiplied by 700mm, connecting the printer, and performing clicking operation to print to finish the printing of the concrete. The print initiation layer of the 3D printable plain concrete material is started on top of the top layer of the high-ductility cement-based material.
S6, curing the concrete structure: and after the model structure is printed, curing for 24 hours at room temperature, then transferring the model structure to a standard curing room, controlling the temperature to be 20+/-2 ℃, controlling the relative humidity to be 95+/-5%, and curing for 28 days to obtain the concrete structure toughened by the high-ductility cement-based material.
The mechanical property test of the materials used in the implementation is carried out by referring to the standard of the common concrete mechanical property test method (GB/T50081-2002). The tensile strength of the common concrete material capable of being printed in a 3D mode is 2.61MPa, the compressive strength is 31.57MPa, the bending strength is 5.42MPa, and the ultimate tensile strain is 0.0118%. The tensile strength of the 3D printable high-ductility cement-based material is 4.35MPa, the compressive strength is 38.1MPa, the bending strength is 8.51MPa, and the ultimate tensile strain is 0.0225%.
The four-point bending mechanical property test is carried out on the concrete composite structure beam (the concrete structure toughened by the high-ductility cement-based material) obtained by the embodiment by referring to the standard of a common concrete mechanical property test method (GB/T50081-2002), the loading scheme is as shown in figure 2, the loading force is applied to the upper surface of the common concrete material 1, the bending span distance of the bottom end is 600mm, the load of two concentrated forces is simultaneously applied to the top at 50N/s, the distance between the two loading points C, D and the adjacent supporting point A, B at the bottom is 200mm, and the distance between the two loading points C, D for concentrated loads is 200mm. The bending stress and mid-span deflection curves obtained by the experimental process are drawn in fig. 4, and fig. 4 strongly illustrates that the toughened composite beam has the characteristic of high ductility by toughening plain concrete by adopting the method described in the embodiment. Test results: the peak load is 32.2kN, the cracking deflection is 0.577mm, the peak deflection is 0.715mm, the ultimate deflection is 1.953mm, and the yield deformation (the ultimate deflection is different from the cracking deflection) is 1.376mm. The toughening effect of the high-ductility cement-based material reinforcing layer in this embodiment is calculated to be equivalent to that of a reinforcing steel bar with a diameter of 8.8 mm.
Example 2:
in this example, the manufacturing process and material parameters were the same as those in example 1 except that the thickness of the high-ductility cement-based material layer was changed to 60mm and the plain concrete layer was changed to 90mm, which corresponds to 40% of the reinforcing layer of the fiber cement-based material. The four-point bending mechanical property test is carried out on the concrete beam of the embodiment by referring to the standard of the common concrete mechanical property test method (GB/T50081-2002), and the loading scheme is shown in figure 2. The bending stress and mid-span deflection curves obtained by the experimental process test are drawn in fig. 4, and the curves strongly illustrate that the toughened composite beam has the characteristic of high ductility by adopting the method to toughen plain concrete in the embodiment. Test results: the peak load is 39.0kN, the cracking deflection is 0.642mm, the peak deflection is 1.655mm, the limit deflection is 2.267mm, and the yield deformation (difference between the limit deflection and the cracking deflection) is 1.625mm. After adjusting the high-ductility cement-based material reinforcement thickness from 30% to 40%, the peak load increased by 21.5%, the ultimate deflection increased by 16.1%, and the yield deformation increased by 18.1%. The toughening effect of the high-ductility cement-based material reinforcing layer in this embodiment is calculated to be equivalent to that of a reinforcing steel bar having a diameter of 9.7 mm.
Example 3:
in this example, except that the thickness of the high-ductility cement-based material layer was changed to 75mm, and the thickness of the plain concrete layer was changed to 75mm, the other manufacturing processes, material parameters, and the like were the same as those in example 1, which corresponds to 50% of the reinforcing layer of the fiber cement-based material. The four-point bending mechanical property test is carried out on the concrete beam of the embodiment by referring to the standard of the common concrete mechanical property test method (GB/T50081-2002). The bending stress and mid-span deflection curves obtained by the experimental process test are drawn in fig. 4, and the curves strongly illustrate that the toughened composite beam has the characteristic of high ductility by adopting the method to toughen plain concrete in the embodiment. Test results: the peak load is 49.6kN, the cracking deflection is 1.699mm, the peak deflection is 3.079mm, the limit deflection is 3.807mm, and the yield deformation (the limit deflection is less than the cracking deflection) is 2.108mm. After adjusting the high-ductility cement-based material reinforcement thickness from 30% to 50%, the peak load increased by 54.4%, the ultimate deflection increased by 43.2%, and the yield deformation increased by 53.2%. The toughening effect of the high-ductility cement-based material reinforcing layer in this embodiment is calculated to be equivalent to that of one reinforcing bar having a diameter of 11.0mm or 2 reinforcing bars having a diameter of 7.8 mm.
In comparative examples 1 to 3, it is understood that the toughening effect is more remarkable as the proportion of the high-ductility cement-based material reinforcing layer is larger, but the cost of the high-ductility cement-based material is significantly higher than that of the common concrete material, and the cost of the material is increased by gradually increasing the replacement proportion, so that the proper proportion is selected in practical use.
The beam structure is taken as a carrier in the implementation, and the method for printing the concrete structure can be used for toughening the concrete structure and replacing the reinforcing steel bars.
Comparative example 1
In this comparative example, the procedure and material parameters were the same as in example 1 except that the high-ductility cement-based material layer thickness was changed to 0 and the plain concrete layer thickness was changed to 150mm, which corresponds to the 3D printed plain concrete without toughening with high-ductility cement-based material. The four-point bending mechanical property test of the concrete beam of this example was performed with reference to the standard of the ordinary concrete mechanical property test method (GB/T50081-2002), and the test results are plotted in FIG. 4. The curve shows that the characteristics of high brittleness and low strain rate of the plain concrete structure are proved. Test results: the peak load is 16.5kN, the cracking deflection is 0.176mm, the peak deflection is 0.176mm, the limit deflection is 0.176mm, and the yield deformation (the difference between the limit deflection and the cracking deflection) is 0.
Comparative example 2
In the comparative example, except that the mixing amount of basalt fiber is changed to 0, other manufacturing processes, material parameters and the like are the same as those of the embodiment 1, namely, cement-based materials with relatively poor ductility are adopted to toughen 3D printing plain concrete. The four-point bending mechanical property test of the concrete beam of this example was performed with reference to the standard of the ordinary concrete mechanical property test method (GB/T50081-2002), and the test results are plotted in FIG. 4. The curves demonstrate that PVA fiber reinforced plain concrete has a certain reinforcing and toughening effect, but has a poor toughening effect compared with examples 1 to 3. Test results: the peak load is 30.2kN, the cracking deflection is 0.775mm, the peak deflection is 0.758mm, the limit deflection is 0.872mm, and the yield deformation (difference between the limit deflection and the cracking deflection) is 0.097mm.
Example 4
This example prepares a composite beam structure of a composite column in a loop type (see figure 7) by toughening a 3D printed concrete structure with a high-ductility cement-based material,
s1, three-dimensional modeling is carried out on a composite beam structure through AutoCAD software, namely, firstly, a cuboid with the size of 180 multiplied by 840mm is drawn, then, the composite beam structure is divided into two parts according to the geometric form and stress condition of the composite beam structure to be printed, one part is a common concrete layer used for printing common concrete, the other part is a high-ductility cement-based material reinforcing layer used for printing high-ductility cement-based materials, and the high-ductility cement-based material reinforcing layer and the common concrete layer form a three-dimensional digital model of the composite structure; in the embodiment, the high-ductility cement-based material is applied to a hollow loop formed by the upper surface, the lower surface, the left surface and the right surface of the beam structure, the external dimension of the loop is 180×180mm, the internal dimension is 140×140mm, the length is 840mm, the common concrete is applied to the middle area of the beam structure, the three-dimensional dimension is 140×140×840mm, and the high-ductility cement-based material reinforcing layer accounts for 35% of the whole structure;
s2, STL file generation and restoration: and (3) respectively exporting the high-ductility cement-based material reinforcing layer obtained in the step (S1) and the common concrete layer in dwg format files in AutoCAD software, importing the files into Solidworks software or magic software, repairing the files in Solidworks software, and exporting the STL-1 format file corresponding to the high-ductility cement-based material reinforcing layer and the other STL-2 format file corresponding to the common concrete layer.
S3, reading the STL-1 and STL-2 format files derived in the step S2 into slicing software slice3r, and slicing the rectangular column at equal layer heights along the height direction, wherein the slice layer thickness is uniformly set to be 8mm. Therefore, the whole column structure was cut into 23 pieces, 184mm in total, 4mm higher than the design size, and the slice modeling accuracy was 97.8%.
S4, planning a path of the slice, wherein a linear back-shaped path planning method is adopted in software slice3r, namely a mode of gradually moving towards the center along the outer boundary shape of the structure; the printer nozzle is set to be 12mm, the running speed of the printer is 35mm/s, and the stepping value of a stepping motor for material extrusion is set to be 2500; and finally, generating G-1 and G-2 files corresponding to the STL-1 and STL-2 format files in the slice3 r. The G-1 and G-2 files are G files, namely parameters such as planned paths including the printing process, and slicing and path planning are shown in FIG. 6.
S5, conveying the 3D printable high-ductility cement-based material to a material storage system of a 3D printer through conveying equipment, loading the G-1 file and the G-2 file into printing control software repeater-Host, connecting the printer, clicking to run for printing, and when each slice is layered, printing an outer high-ductility cement-based material reinforcing layer according to the path information of the G-1 file, and then finishing the common concrete material in the inner area according to the path information of the G-2 file. After one slice is printed layer by layer, the subsequent slices are printed according to the same method, and the subsequent slices are stacked layer by layer, so that the construction of the whole structure is completed.
S6, curing the concrete structure: and after the model structure is printed, curing for 24 hours at room temperature, then transferring the model structure to a standard curing room, controlling the temperature to be 20+/-2 ℃, controlling the relative humidity to be 95+/-5%, and curing for 28 days to obtain the concrete structure toughened by the high-ductility cement-based material.
The components not explicitly described in this embodiment can be implemented by using the prior art. The illustrated embodiment of the invention is but one application of the method described for toughening 3D printed concrete structures with high-ductility cement-based materials. In addition, as shown in fig. 6-12, the method of the present invention is equally applicable to rectangular composite beams, rectangular composite columns, sandwich panels, corrugated composite panels, i-shaped composite beams, T-shaped composite beams, unidirectional reinforcing composite panels, bi-directional reinforcing composite panels. It should be noted that modifications and adaptations to the present invention may occur to one skilled in the art without departing from the principles of the present invention and are intended to be comprehended within the scope of the present invention.
The preparation of the two concrete material composite beams of each of the examples and comparative examples described in the present invention was carried out by printing in two times by a 3D concrete printer of a single head. If a 3D concrete printer with double spray heads is designed, the combined structure of the double materials can be manufactured at one time.
The invention is applicable to the prior art where it is not described.
Claims (3)
1. A method of toughening a 3D printed concrete structure with a high-ductility cement-based material, the method comprising the steps of:
s1, designing a three-dimensional digital model of a composite structure: firstly, designing or modeling a composite beam structure through three-dimensional modeling software or a three-dimensional scanner to obtain geometric structure information of a three-dimensional model of the composite beam structure to be printed; then dividing the three-dimensional model into two parts according to the geometric form and stress condition of the composite beam structure to be printed, wherein one part is a common concrete layer for printing common concrete, and the other part is a high-ductility cement-based material reinforcing layer for printing high-ductility cement-based material, and the high-ductility cement-based material reinforcing layer and the common concrete layer form a three-dimensional digital model of the composite structure;
s2, STL file generation and restoration: exporting the high-ductility cement-based material reinforcing layer and the common concrete layer respectively in dwg format files, then respectively reading the dwg format files into STL file editing software, repairing the STL format files, and exporting the STL format files after the repairing;
s3, layering and slicing the three-dimensional model: reading the repaired STL format file into slicing software, setting the slicing thickness, and slicing the repaired STL format file;
s4, planning and designing a printing path: planning a path for the slice, designing a corresponding printing path in path planning software according to the geometric structure of the three-dimensional digital model of the composite structure in the step S1, and then deriving a G file containing the slice and path information;
s5, 3D printing of the composite structure: the G file saved in the step S4 is imported into a program control system of a 3D printer, a common 3D printable concrete material and a 3D printable high-ductility cement-based material are respectively conveyed into a material storage system of the 3D printer through corresponding conveying equipment, then the 3D printer is started, and the moving speed and the material extrusion speed of a printing spray head in the corresponding 3D printer are set according to the flowability of the used concrete material; after the setting is completed, the printing spray heads respectively extrude the high-ductility cement-based material and the common concrete material continuously layer by layer to be finally formed under the drive of the program control system according to the path information contained in the G file;
s6, curing the concrete structure: after the model structure is printed, standard curing, water curing or high-temperature steam curing is carried out according to the specifications, so that the concrete structure toughened by the cement-based material with high ductility is obtained;
the high-ductility cement-based material comprises the following components in parts by weight:
0.8 to 1.2 portions of quick hardening ordinary Portland cement;
0.96-1.44 parts of F-level fly ash;
0.64-0.96 part of quartz sand, wherein the particle size range of the quartz sand is 0.075-0.15mm;
0.29 to 0.43 portion of water;
0.005-0.01 part of water reducer;
0.0017 to 0.0018 parts of PVA fiber;
0.0043-0.0078 parts of basalt fiber.
2. A concrete structure, characterized in that the structure is produced by the method for toughening a 3D printed concrete structure with a high-ductility cement-based material according to claim 1.
3. The concrete structure of claim 2, wherein the concrete structure is a rectangular composite beam, a unidirectional reinforcing composite slab, a sandwich slab, an i-shaped composite beam, a T-shaped composite beam, a bidirectional reinforcing composite slab, a corrugated composite slab.
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| CN109610841A (en) * | 2019-01-21 | 2019-04-12 | 齐鲁工业大学 | A kind of cement 3D printing apparatus control method, system and printing device |
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| CN114083639B (en) * | 2022-01-20 | 2022-04-29 | 中交第一公路勘察设计研究院有限公司 | Plane path fitting method and system for concrete 3D printing |
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