CN114132047A

CN114132047A - Printing and reinforcing method for 3D printed concrete member

Info

Publication number: CN114132047A
Application number: CN202111255058.7A
Authority: CN
Inventors: 周鑫; 王伟光; 林镜星; 谢志炜; 桑成磊; 梁汝锡; 廖磊; 郑皓云
Original assignee: Guangzhou Power Supply Bureau of Guangdong Power Grid Co Ltd
Current assignee: Guangzhou Power Supply Bureau of Guangdong Power Grid Co Ltd
Priority date: 2021-10-27
Filing date: 2021-10-27
Publication date: 2022-03-04

Abstract

The invention relates to a printing and reinforcing method for a 3D printed concrete member, which comprises the following steps: (1) and (3) determining the mixing ratio: preparing concrete suitable for a 3D printing structure, fully mixing, testing related printing performance, and meeting various performance requirements, or else, adjusting or re-preparing until the requirements are met; (2) determining relevant parameters of a component, equipment and reinforcement according to design requirements; (3) and (3) laying rib grids after printing the single-layer concrete, repeatedly printing the concrete layer and laying the rib grids until a complete assembled rib cage is formed, and finally covering the concrete to form a complete member. According to the method, the influence of 3D printing anisotropy on the 3D printed concrete structure is reduced by using a staggered joint printing method, and meanwhile, the tensile longitudinal ribs, the erection ribs and the hooping integrated reinforcing ribs are configured, so that an assembled rib cage is formed, and the stress performance of the 3D printed concrete structure is improved.

Description

Printing and reinforcing method for 3D printed concrete member

Technical Field

The invention belongs to the technical field of 3D printing beam component reinforcement, and particularly relates to a method for 3D printing of a concrete component and reinforcement.

Background

The 3D concrete printing technology is a novel construction technology for tightly combining concrete structure construction with a digital model, and the working principle of 3D concrete printing is to extrude building materials through a printer extrusion head according to a printing path generated based on the digital model and stack the extruded concrete to form a three-dimensional structure. Applying the 3D printing concept to concrete structures has many advantages not found in traditional construction processes: flexible structure, high construction speed, higher refinement degree, less manual demands, environment friendliness and the like.

But the 3D printed concrete structure also has a problem that the conventional concrete structure construction process does not exist. The traditional cast-in-place method can use a complete reinforcement cage to be matched with the poured concrete to work together, the concrete mainly bears the pressure, and when the concrete quits working, the reinforcement can also continue to play a role, so that the bearing capacity of the reinforced concrete structure is greatly improved; in addition, as the steel bar is made of ductile material, the steel bar is obviously deformed during yielding, so that the ductility of the reinforced concrete structure is improved, and the use is convenient. However, since the 3D printed concrete cannot be provided with a steel reinforcement cage, in order to improve the stress performance of the 3D printed concrete structure, there are methods of adding fibers, presetting steel cables, improving the printer process, laying reinforcement in layers and the like, and most of the methods cannot play a comprehensive reinforcing role as that of the conventional steel reinforcement cage.

Disclosure of Invention

Based on the above problems, the invention aims to provide a printing and reinforcement method for a 3D printed concrete member, which utilizes a staggered joint printing method to reduce the influence of 3D printing anisotropy on a 3D printed concrete structure, and simultaneously configures a reinforcement with integrated tension longitudinal ribs, erection ribs and stirrups to form an assembled reinforcement cage, thereby improving the stress performance of the 3D printed concrete structure.

In order to achieve the purpose, the invention provides the following technical scheme: a printing and reinforcing method for 3D printing of a concrete member comprises the following steps:

the method comprises the following steps: and (3) determining the mixing ratio: preparing concrete suitable for a 3D printing structure, fully mixing, testing related printing performance, and meeting various performance requirements, or else, adjusting or re-preparing until the requirements are met;

step two: determining relevant parameters of the component, equipment and reinforcing bars according to design requirements;

relevant parameters of the component include length, width, load and the like; relevant parameters of the equipment comprise the size of an extrusion head, the extrusion amount, the extrusion speed and the like; the relevant parameters of the reinforcement comprise the type of the reinforcement, the quantity of the reinforcement, the diameter of the reinforcement, the distance between stirrups, the bending position of the longitudinal reinforcement and the like;

step three: and (3) laying rib grids after printing the single-layer concrete, repeatedly printing the concrete layer and laying the rib grids until a complete assembled rib cage is formed, and finally covering the concrete to form a complete member.

Further, the strength grade of the concrete designed in the first step is not less than C20 and not more than C50;

furthermore, the 3D printing concrete prepared in the first step is preferably portland cement or ordinary portland cement, and the requirements of the current national standard 'general portland cement' GB175 are met. When adopting other kinds of cement, the performance index of the cement is in accordance with the regulations of the current relevant standards of China;

furthermore, the coarse aggregate is preferably crushed stone or pebble with reasonable gradation, good particle shape and firm texture, the maximum nominal particle size is less than or equal to 10mm, and the maximum nominal particle size is the minimum value of the maximum nominal particle size and the maximum nominal particle size which is adjusted according to the outlet diameter R of the extrusion head of the actual printing equipment and the diameter R of the rib material. The reason is to prevent the influence of the damage and the insertion of the rib material when wet-cutting: when the particle size is too large, the coarse aggregate can slide in concrete to cause mechanical damage, and in addition, the insertion of the reinforcement material can cause deviation when the stirrup limb is inserted due to the coarse aggregate with too large particle size;

preferably, the particle size of the coarse aggregate is 5-10 mm;

furthermore, the mud content of the coarse aggregate is less than or equal to 1 percent;

furthermore, the fine aggregate is preferably medium sand in a grading II area. Including but not limited to river sand, sea sand, machine sand, and reclaimed sand;

furthermore, the mixing proportion is not required to be unified when the 3D printing concrete is prepared in the first step, and the prepared concrete only needs to meet the related performance requirements;

further, the concrete performance test in the first step requires that a trial-and-error work should be performed before formal printing, and segregation and bleeding phenomena should not occur when concrete is stirred;

further, the performance in step one requires the extrudability of the concrete: continuous and uniform printing, no blockage and no obvious tension crack can be observed;

further, the performance in said step one requires the constructability of the concrete: the form is kept stable and does not collapse during printing;

furthermore, the slump of the concrete is required to be between 100 and 160 in the performance requirement in the step one, and the reason that the process of tiling longitudinal bars and inserting stirrup limbs is adopted, the concrete needs high fluidity, the influence of the bars is reduced, and the defects caused when the bars are placed can be filled;

further, the performance in the first step requires that the setting time of the concrete should meet the requirement of printable time;

further, the relevant parameters of the components in the second step are determined after the printing device is adjusted in size;

further, the equipment in the second step is only a common concrete printer;

further, the parameters of the equipment in the second step comprise that the size of the concrete extrusion head is determined according to the size of the printed component;

further, the equipment parameters in the second step further include the extrusion amount of the concrete, the concrete extrusion amount is determined according to the size of the component, and the printing is required to be uninterrupted while the height of each layer is reached;

further, the integrated rib grid in the second step is shown in fig. 1, and relevant parameters of the reinforcing bar include a bending position D of the longitudinal bar, an anchoring distance D of the bent bar and the like;

further, the bending angle theta of the longitudinal ribs of the integrated rib grid in the second step is determined according to the size of the member, and when the height h of the member is less than 800mm, the theta is 45 degrees; when the height h of the component is more than or equal to 800mm, theta is 60 degrees;

the hook angle and the length of the longitudinal bar are consistent with the concrete structure design standard;

furthermore, the stirrup layout in the second step is as shown in fig. 2, the length S of the stirrup limb is determined according to the height of each layer of concrete, the length of the stirrup limb exceeding the next layer of longitudinal bar after the stirrup limb is inserted is the thickness of one layer of concrete, and two adjacent layers of concrete are connected at the same time, but it needs to be pointed out that the stirrup of the initial layer does not extend out of the stirrup limb, and only the longitudinal bar is connected with the erection bar;

further, the reinforcing material used in the second step includes, but is not limited to, reinforcing steel bars, composite bars, and the like;

further, the concrete printing in the third step requires staggered joint printing, and as shown in fig. 3, the concrete cannot be printed in a mode of changing the printing direction, so that the joint is ensured to be perpendicular to the load direction as much as possible, and a component force parallel to the joint direction is prevented from occurring during loading;

further, the printing path of step three includes, but is not limited to, the printing path of fig. 4;

further, the number of printing layers in the third step needs to be determined according to the actual size, as shown in fig. 3, the uppermost layer is the printing size, and gradually increases from layer to layer, and the materials can be recycled after wet cutting is completed;

preferably, the position of wet cutting is slightly larger than the size of the component, the redundant and uneven part is subjected to dry cutting after hardening, and the initial mechanical damage to the component can be prevented by rough wet cutting, dry cutting after hardening and dry cutting;

furthermore, the rib grid is required to be laid in the third step, the longitudinal ribs are prevented from being placed in the concrete joints as much as possible, and the condition that the concrete and the rib materials are not bonded sufficiently is prevented;

furthermore, when the rib grids are laid in the third step, the stirrup limbs are required to be inserted downwards below the next layer of longitudinal ribs, so that the lap joint of the rib grids of two adjacent layers and the connection of concrete are ensured;

further, in the third step, the steps of printing concrete and paving the rib grids are repeated until a complete assembled rib cage is formed, the last layer of printed concrete is covered, and after maintenance is completed, the printing component is rotated by 90 degrees and then put into normal use, as shown in fig. 5.

Compared with the prior art, the invention has the beneficial effects that:

the staggered joint printing method can effectively reduce the defect accumulation among the bars to cause larger defects, and is beneficial to reducing the influence of the anisotropy of 3D printed concrete

The tensioned longitudinal ribs and the erected ribs can bear bending moment together, the connection between the tensioned longitudinal ribs and the erected ribs can resist shearing force, meanwhile, bent ribs can be arranged to resist shearing force together, and the bent ribs can be arranged at the corners of concrete similarly as a plurality of sections of rib materials are connected into a whole;

the tensile longitudinal ribs and the vertical ribs are connected into a whole, so that the integrity and the relative position of the rib cage can be ensured, and the reinforcing bar effect of the 3D printed concrete can be more fully exerted; meanwhile, the rib cage can ensure that the two side ribs have enough bearing capacity, and the erection ribs can play a role of negative ribs to prevent damage caused by uncertain load.

Drawings

FIG. 1 is a schematic view of a rib grid of the present invention; wherein D is the anchoring length of the bent-up rib, D is more than or equal to 10r, and D is the bent-up position of the bent-up rib; theta is the bending angle of the bent rib; alpha is the angle of the steel bar hook; and a is the distance between the stirrups.

Fig. 2 is a simplified schematic diagram of the stirrup of the present invention, with S indicating the length of the stirrup limb.

FIG. 3 is a left side view of a schematic of the present invention for offset printing.

FIG. 4 is a schematic diagram of a print path according to the present invention.

Fig. 5 is a schematic view of the printing member rotated 90 ° and then put into normal use.

Fig. 6 is a schematic view of a printing path of embodiment 1.

FIG. 7 is a partial schematic view of staggered joint printing and reinforcement in example 1.

Fig. 8 is a schematic view of a printing path of embodiment 2.

FIG. 9 is a partial schematic view of staggered joint printing and reinforcement in example 2.

FIG. 10 is a schematic view of a printing path of embodiment 4.

FIG. 11 is a partial schematic view of a general printing and reinforcing bar of example 4.

Detailed Description

The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.

Example 1

Concrete was prepared according to the mix proportion in table 1:

TABLE 1 compounding ratio #1

Description of the drawings: wherein the dosage of the cellulose ether, the sodium gluconate and the polycarboxylate superplasticizer is calculated by taking the dosage of the cement as a reference.

Preparing concrete according to the mixing proportion and stirring, wherein the concrete is not required to be separated and exuded when being stirred, and the slump is measured to be 120mm after the concrete is fully stirred; during printing, the concrete is continuously and uniformly observed, has no blockage or obvious tension crack, and the form is kept stable and does not collapse;

the member is a beam member, the size is 240 multiplied by 600 multiplied by 2000, the size of the extruded single-layer concrete is 30mm multiplied by 100mm, and 8 layers are printed;

the reinforcing bars are arranged according to the bar grid shown in fig. 1, the relevant parameters alpha is 45 degrees, theta is 45 degrees, the tension area is provided with 4 HRBs 400 with the diameter of 16mm, and the compression area is symmetrically reinforced, namely As is 803.84mm²The stirrups are four layers of HPB300 with the diameter of 8mm, the distance between the stirrups is 200mm, the length of a stirrup limb is 65mm, and the stirrups are respectively inserted into the printed concrete on the 1 st, 3 rd, 5 th and 7 th layers (the first layer does not need the stirrup limb and does not need to be inserted);

the printing paths select parallel printing and staggered printing, as shown in FIGS. 6 and 7

The printing member-related information is shown in table 2:

table 2 example #1 related parameters

Example 2

Concrete was formulated according to the mix ratio #2 of table 3:

TABLE 3 mix ratio #2

the reinforcing bars are arranged according to the bar grid shown in fig. 1, the relevant parameters alpha is 45 degrees, theta is 45 degrees, the tension area is provided with 4 HRBs 400 with the diameter of 16mm, and the compression area is symmetrically reinforced, namely As is 803.84mm²The stirrups are 2 layers of the stirrups which are selected from HPB300 with the diameter of 8mm, the distance between the stirrups is 250mm, the length of the stirrup limbs is 185mm, and the stirrups are double-limb hoops and are respectively inserted into the printed 1 st and 7 th layers of concrete (the first layer does not have the stirrup limbs and does not need to be inserted);

the printing path selects continuous printing and staggered printing, as shown in FIGS. 8 and 9

The printing member-related information is shown in table 4:

table 4 example #2 related parameters

The bending resistance bearing capacity is not obviously reduced, the shearing resistance bearing capacity is obviously reduced, mainly the hoop ratio is reduced, but all the rib grids can be provided with bent reinforcing steel bars, so the shearing resistance bearing capacity can still be normally used.

Example 3 comparative example

Concrete was formulated as per mix ratio #3 of table 5:

TABLE 5 mix ratio #2

Preparing concrete according to the mixing proportion and stirring, wherein segregation and bleeding phenomena occur during stirring of the concrete, and after the concrete is fully stirred, the slump is measured to be 180 mm; during printing, the concrete is observed to be continuous and non-blocking, but is not uniform, and when the upper layer concrete is printed, the lower layer concrete is easy to deform, collapse and cannot be printed, so that the printing performance requirements indicated by the invention are required for preparing the concrete.

Example 4 comparative example

Concrete was prepared according to the mix ratio of table 6:

TABLE 6 mix ratio #3

the reinforcing bars are arranged according to the bar grid shown in fig. 1, the related parameters alpha are 45 degrees, theta is 45 degrees, the tension area is provided with 4 HRBs 400 with the diameter of 16mm, the compression area is symmetrically reinforced, namely As is equal toAs’＝803.84mm²The stirrups are four layers of four-limb hoops which are HPB300 with the diameter of 8mm, the distance between the stirrups is 200mm, the length of each stirrup limb is 65mm, and the stirrups are respectively inserted into the printed concrete on the 1 st, 3 rd, 5 th and 7 th layers (the first layer does not have the stirrup limbs and does not need to be inserted);

the printing path selects parallel printing and does not print wrong seams, as shown in figures 10 and 11

The printing member-related information is shown in table 7:

table 7 example 4 relevant parameters

Because no staggered joint printing is carried out, the bending resistance bearing capacity and the shearing resistance bearing capacity are obviously reduced, the bearing capacity of the 3D printed concrete member can be improved by the staggered joint printing, and the stress performance of the 3D printed concrete member can be improved to a certain extent by the staggered joint printing method.

Claims

1. A3D printing concrete member printing and reinforcing method is characterized in that:

the method comprises the following steps: preparing concrete suitable for a 3D printing structure, and fully mixing;

step two: determining relevant parameters of a component, equipment and reinforcement according to design requirements;

relevant parameters of the component include length, width, and load; relevant parameters of the equipment comprise extrusion head size, extrusion amount and extrusion speed; the relevant parameters of the reinforcement comprise the type of the reinforcement, the quantity of the reinforcement, the diameter of the reinforcement, the distance between stirrups and the bending position of the longitudinal reinforcement;

2. The method of claim 1, wherein the composition of the concrete in the first step comprises: mixing water, cement, coarse aggregate, fine aggregate, fly ash, silica fume, cellulose ether, sodium gluconate and a polycarboxylic acid water reducing agent;

the concrete is not separated and weeped when being stirred in the first step, and after being fully stirred, the slump is 100-160 mm; when the printing is carried out, the concrete is continuous and uniform, has no blockage or obvious tension crack, and the form is kept stable and does not collapse; the setting time of the concrete should meet the requirement of printable time;

the strength grade of the concrete designed in the first step is not less than C20 and not more than C50.

3. The method according to claim 2, wherein the 3D printing concrete prepared in the first step is portland cement or ordinary portland cement, and the method is in accordance with the regulations of the current national standard "universal portland cement" GB 175.

4. The method according to claim 2, wherein in the first step, the coarse aggregate of the concrete is broken stone or pebble with reasonable gradation, good grain shape and firm texture, and the particle size of the coarse aggregate is 5-10 mm; the maximum nominal grain size is less than or equal to 10mm, and is adjusted according to the outlet diameter R of the extrusion head of the actual printing equipment and the diameter R of the rib material, wherein the maximum nominal grain size is the minimum value of the maximum nominal grain size, the maximum nominal grain size and the rib material; the mud content of the coarse aggregate is less than or equal to 1 percent;

the fine aggregate is medium sand in grading II area, including river sand, sea sand, machine-made sand and regenerated sand.

5. The method according to claim 1, wherein the relevant parameters of the members in the second step are determined according to the size of the printing equipment;

the size of the concrete extrusion head in the second step is determined according to the size of the printed component;

and in the second step, the extrusion amount of the concrete is determined according to the size of the member, and the printing is required to be uninterrupted while the height of each layer is reached.

6. The method according to claim 1, wherein the integral rib grid in the second step is shown in fig. 1;

determining the bending angle theta of the longitudinal ribs of the integrated rib grids in the second step according to the size of the member, wherein when the height h of the member is less than 800mm, the theta is 45 degrees;

when the height h of the component is more than or equal to 800mm, theta is 60 degrees; the hook angle and the length of the longitudinal bar are consistent with the design standard of concrete structures.

7. The method according to claim 1, wherein the arrangement of the stirrups in the second step is as shown in fig. 2, the length S of the stirrup limb is determined according to the height of each layer of concrete, and the specific length is that after the stirrup limb is inserted, the length of the longitudinal bar beyond the next layer is the thickness of one layer of concrete; but the stirrup of the initial layer does not extend out of the stirrup limb, and only the longitudinal bar is connected with the erection bar;

the reinforcement used in the second step comprises a steel bar and a composite bar.

8. The method according to claim 1, wherein the concrete printed in the third step is printed by staggered seam printing, and the concrete is printed in a way that the printing direction is changed as shown in fig. 3, so that the seam is ensured to be vertical to the loading direction;

preferably, the print path of step three comprises the print path of fig. 4.

9. The method according to claim 1, wherein the number of printing layers in the third step is determined according to the target size of the component and the common size of the printing device, as shown in fig. 3, the uppermost layer is the printing size, and the number increases from layer to layer; wet cutting after printing is finished;

preferably, the location of the wet cut is slightly larger than the component size.

10. The method of claim 1, wherein when the reinforcement grids are laid in the third step, the stirrup limbs are inserted downwards below the longitudinal bars of the next layer, so that the overlapping of the reinforcement grids of the two adjacent layers and the connection of concrete are ensured.