JP7323256B2 - Bonding material with freshness and mechanical properties suitable for extrusion 3D printing - Google Patents

Description

Cementitious materials for 3D printing

Forming workpieces using 3D printing techniques or additive manufacturing processes is currently prevalent in various industries, especially in the medical, aeronautical, and automotive industries. The processes or materials used for molding are diversified to accommodate various applications. Most of the molding processes are based on a similar principle, ie the workpiece is completed layer by layer with a bonding material. The workpiece is designed and shaped using a computer aided program that controls the motion. One widely adopted molding method using 3D printing is extrusion 3D printing, also known as Fuse Deposition Modeling (FDM). This is an economical and widely used printing method compared to other methods. The principle of this extrusion printing method is that the flowable material used for extrusion is forced to flow through a nozzle, and the nozzle moves along the shape of the design path of each layer until the workpiece is completed. . Extrusion 3D printing methods are compatible with a variety of materials such as plastics, ceramics and metals.

Nevertheless, plastics, ceramics or metals must be heated to high temperatures until they become flowable like the bonding material. After being extruded from the nozzle, the material becomes solid. High energy is required to mold these materials. The construction industry requires economical and environmentally durable materials. As mentioned above, forming workpieces by 3D printing methods using these materials requires high costs, and the materials have low environmental durability. Therefore, 3D printing molding in the construction industry is instead using environmentally durable and low cost materials. Cementitious materials are well suited for such industrial uses because cement is a versatile bonding material that is widely accepted for its excellent environmental durability. Cementitious materials used in extrusion 3D printing are mixed with water and other liquid materials to form a cement paste or mortar. Although the cementitious materials used to shape workpieces using 3D printing methods have been continually improved, there are still problems associated with their application in various aspects, such as the following.

- Leakage from the nozzle when not in use or under external forces (external forces are air pressure, vibration, screw feeding, etc.). This leads to wasted material, increased waste volume, and increased operational complexity.

- Poor extrudability as seen in fluidity when external force is applied. - In order to obtain a material with high compressive strength, it is necessary to design a high density material, which requires a high force to flow the material, resulting in poor extrudability. This results in material clogging the nozzles and lack of extrusion force.

- Working time too short - The design of cementitious materials for 3D printing requires proper molding of each layer. Therefore, there is a need to develop materials that solidify rapidly. Rapid solidification further reduces working time, but causes material to clog in mixers and/or material transport pipelines during extrusion. This results in printing discontinuities, poor handling and interruptions in concrete placement, and reduced mechanical properties of the workpiece. Cementitious materials that provide longer working times and accommodate the length of material delivery pipelines allow for more manageable and efficient operations.

Exemplary applications of cementitious materials for extrusion 3D printing to obtain high quality printing are as follows.

- WO 2017221058 "Online Control of Rheology of Building Material for 3D Printing" published in 2017 discloses a method for forming cement mortar using an extrusion 3D printing method. . The purpose of this invention is to develop an ultra-high performance concrete construction material having fluidity suitable for the above molding method by using hydraulic binders, aggregates, auxiliary cementitious materials and mineral and chemical additives. When mixed with a certain weight ratio of water to binder to obtain a fresh mortar with adequate fluidity, the yield stress of fresh concrete was found to be in the range of 600-4,000 pascals. . This test is intended to test the dynamic properties, ie the stress of the cementitious material in motion, not enough to stabilize the cement or mortar exiting the nozzle. Therefore, the present invention added a quicklime cement additive or a calcium sulfoaluminate cement to enhance the static yield stress properties, i.e. the material properties at rest, which in this case are properties of the paste or mortar extruded from the nozzle. The purpose is to develop cementitious materials. If the static yield stress is high, the resulting cement paste or mortar will be very stable. Therefore, the resulting printed workpiece has significantly reduced errors and is easier to use.

- Patent Document 2, Chinese Patent Application Publication No. 104891891 of Tongji University entitled "3D Printing Cement-based Material and Preparation Method thereof", relates to a cement-based bonding material for 3D printing and its preparation method. is. Materials used in the present invention include cement, additives, fine aggregates, water reducing agents, hydration accelerators, thickeners, AE agents (air entrainers), fibers, initial compressive strength accelerators, copolymers, water repellent and dry powdered ettringite expansion in a ratio of 100 parts cement to cement expansion-producing admixture in an amount of 0.01-5.00% by weight or 0.0033-1.6600% by weight of the dry mortar powder. or calcium oxide. Hydration enhancers serve to promote solidification of the material. When mixed with water, the accelerator can be used as concrete and mortar to form workpieces. Accelerators used in US Pat. No. 5,400,005 are chemical admixtures associated with sodium and calcium groups that do not significantly stabilize the material or increase the dynamic yield stress during the early stages of the reaction. Therefore, cement paste or mortar cannot be extruded from the nozzle.

- Patent Document 3, Indian Patent Application No. IN201914026163 entitled "A Binding Material Suitable for Three-Dimensional Printing" aims to provide a cementitious binding material extruded from a nozzle with adequate stability. The workpiece obtained by the 3D printing method is therefore less error-prone, more improved and easier to handle. The binding materials used consist of cement, fine aggregate, powdered limestone, expansion-producing admixtures, retardants, consistency admixtures, and rheology modifiers. However, this invention still does not solve the problem of nozzle leakage. The material tends to leak from the nozzle and is difficult to handle.

- Patent Document 4, that is, Chinese Patent Application Publication No. 110317027 entitled "A Kind of Lower Shrinkage 3D Printing Mortar and Preparation Method thereof" filed in 2019, describes a mortar using low shrinkage 3D printing Formulation development is described. The formulation contains Portland cement, aluminum sulphate cement, fine mineral powder, crushed sand, basalt and polymer fibers, magnesia sulfoaluminate or oxygen swelling agents, water reducing agents, hydration accelerators, early compressive strength accelerators and antifoaming agents. in different ratios. In such formulations, it was found that the shrinkage of mortars molded using 3D printing methods could be significantly reduced, as moisture evaporation from fresh mortar was reduced by the addition of fibers. Also, the expansion of the swelling agent could obviously improve the tensile strength properties of the set mortar, reducing mortar shrinkage and long-term cracking. However, this invention does not address the problem of mortar freshness properties related to nozzle leakage.

It can be seen that none of the prior art inventions prevent leakage of cementitious material while the material is not in use or while the material exits the nozzle when no external force is applied. Also, those inventions do not allow control of extrudability and, in addition, do not allow for long working times. In other words, a cementitious material is a flowable material that creates problems with the material flowing out when printing is not taking place. In addition, cementitious materials need to have high compressive strength for use in a variety of construction works, particularly load-bearing structures such as load-bearing walls. Therefore the material must be designed to have a high density. Higher densities usually cause problems in extruding the material from the nozzle. Therefore, the material developed should have a high air content so that it can be easily extruded through the nozzle. Finally, we have to solve this problem to get longer working time. If the working time is too short, the material will start to solidify inside the printer or in the material transport pipeline, which is the main cause of discontinuous molding. Therefore, the present invention aims to develop a bonding material suitable for extrusion 3D printing in order to solve the problems encountered in the cement-based 3D printing molding process and increase the effectiveness of the process.

WO2017221058 Chinese Patent Application Publication No. 104891891 Indian patent application number IN201914026163 Chinese Patent Application Publication No. 110317027

The objective of the present invention is to develop a cementitious bonding material suitable for extrusion 3D printing, where the mortar material extruded from the nozzle by the 3D printer has the following freshness and mechanical properties:
- Prevention of flow when no external force is applied - Longer working time - Ability to be extruded through nozzle - High compressive strength

By using a binding material comprising cementitious binder, fine aggregate, retarder, thickener, surfactant and rheology modifier, the above four properties of fresh mortar and hardened mortar The properties make the workpieces resulting from 3D printing molding more efficient and robust, suitable for use in load-bearing structures, and also more suitable for other applications.

The present invention includes the following aspects.
<1> A binding material having fresh properties and mechanical properties suitable for extrusion 3D printing,
20-50% by weight of the dry binder material of binder;
50-80% by weight of the dry bond material fine aggregate;
0.010 to 1.000% by weight of the dry bond material of a retarder;
0.001 to 0.500% by weight of the dry binding material of a thickening agent;
0.001 to 1.000% by weight of the dry bond material of a surfactant;
0.010 to 1.000% by weight of the dry bond material of a rheology modifier;
The water retention according to ASTM C1506 standard is 85% to 100%, the air content according to ASTM C185 standard is greater than 9%, and the weight ratio of the thickener to the surfactant is 0.5 to is 2.0;
Bonding material with freshness and mechanical properties suitable for extrusion 3D printing.
<2> The binder is at least one selected from Portland cement, mixed cement, and alumina cement, and the cement has an average Blaine fineness of 2,700 to 5,600 cm ³ /g. A binding material having fresh properties and mechanical properties suitable for extrusion 3D printing according to 1>.
<3> The binder contains 0.1% to 5.0% alumina cement or sulfoaluminate cement, and the cement has an average Blaine fineness of 2,700 to 5,600 cm ³ /g. A binding material having fresh properties and mechanical properties suitable for extrusion 3D printing according to 1> or <2>.
<4> The fine aggregate is selected from naturally occurring or crushed and separated limestone, powdered limestone, fine sand, waste, and unused cement material, preferably powdered limestone, <1 A binding material having fresh properties and mechanical properties suitable for extrusion 3D printing according to any one of > to <3>.
<5> The fine aggregate has an average Blaine fineness of 7,000 to 13,000 cm ³ /g, fresh suitable for extrusion molding 3D printing according to any one of <1> to <4> Bonding material with properties and mechanical properties.
<6> The fine aggregate has less than 10% of particles with an average size of more than 600 microns, and the fine aggregate has a coarse particle size of 2.3 to 5.5, <1> to <5> A binding material having freshness and mechanical properties suitable for extrusion 3D printing according to any one of claims 1 to 3.
<7> The extrusion according to any one of <1> to <6>, wherein the retarder is water-soluble dry powder particles, or a liquid solution substantially composed of sugars or sugar-based solutions. Bonding material with freshness and mechanical properties suitable for molded 3D printing.
<8> The retarder contains gluconate, sucrose, or sodium fluorosilicate as a component, fresh suitable for extrusion molding 3D printing according to any one of <1> to <7> Bonding material with properties and mechanical properties.
<9> The thickener according to any one of <1> to <8>, wherein the thickener is water-soluble dry powder particles substantially composed of natural and modified cellulose and natural and modified starch. Bonding material with freshness and mechanical properties suitable for extrusion 3D printing.
<10> Any of <1> to <9>, wherein the surfactant is water-soluble dry powder particles or a liquid solution substantially composed of an alkyl sulfate, an alkyl sulfonate, or an anionic agent. A binding material having freshness and mechanical properties suitable for extrusion 3D printing according to claim 1.
<11> Any one of <1> to <10>, wherein the surfactant is an anionic surfactant having a reactive anionic substance in an amount exceeding 95.0% by dry weight of the surfactant. A binding material having fresh properties and mechanical properties suitable for extrusion 3D printing according to 1.
<12> The rheology modifier is a water-soluble dry powder particle or liquid solution substantially composed of a carboxylate, F-type or G-type water reducer according to ASTM 494/494M standards, <1 > ~ <11> A binding material having fresh properties and mechanical properties suitable for extrusion 3D printing.
<13> comprising any of natural fibers, synthetic fibers, metallic fibers, or combinations thereof as components, wherein the amount of each fiber type is 0-2% by weight of the dry bond material; <1> A binding material having fresh properties and mechanical properties suitable for extrusion 3D printing according to any one of <12>.

A bonding material with freshness and mechanical properties suitable for extrusion 3D printing according to the present invention is
- 20 to 50% by weight of the dry binder material, and
- 50-80% by weight of the dry bonded material fine aggregate;
- 0.010 to 1.000% by weight of the dry binding material of a retarder;
- 0.001 to 0.500% by weight of the dry binding material of a thickener;
- 0.001 to 1.000% by weight of the dry binding material of a surfactant;
- from 0.010 to 1.000% by weight of the dry bond material of a rheology modifier;
including.

By "weight of dry binder" is meant the weight of the binder and the binder portion which is fine aggregate. On a dry basis, the binding material may include auxiliary cementitious materials such as fly ash, bottom ash, rice husk ash, volcanic ash, calcined kaolin, granulated stone, blast furnace slag, aluminum blast furnace slag, or fumed silica. Often these are also considered dry bonding materials. The amount used in the present invention is 20-50% of the total weight of the dry binding material. To prepare the bonding material according to the invention, the dry bonding material is mixed with fresh cement conditioning agents, which are retardants, thickeners, surfactants and rheology modifiers. Mineral and chemical additives or expansion-producing admixtures widely used in the cement industry may also be added to modify other properties. This binding material is mixed with water at a rate of 9-16% by weight of the dry binding material to form a mortar suitable for extrusion 3D printing.

Suitable binders for 3D printing molding are binders comprising mixtures of Portland cement and alumina cement, sulfoaluminate cements and/or solutions of said cements. The amount of alumina cement, sulfoaluminate cement and/or solution of said cement ranges from 0.1 to 5.0% of the total weight of the binder. Alumina cements or sulfoaluminate cements contain an alumina phase component in the range of 30-98% by weight and have an average Blaine fineness in the range of 2,700-5,600 cm ³ /g.

The fine aggregate may be selected from naturally occurring or crushed and separated limestone, powdered limestone, fine sand, waste and virgin cementitious materials, most preferably having an average particle size of 600 microns. Limestone in an amount of ultra-fine aggregate less than 10% with a coarse grain size of 2.3-5.5. The resulting mortar has good fluidity for 3D printing and does not clog nozzles. Also, the mortar surface is smooth and does not become rough or crack. Compressive strength and long-term durability are thus improved, especially in terms of drying shrinkage of the cementitious material. The amount used in the present invention is 50-80% of the total weight of the dry binding material.

For the powdered limestone fine aggregate used in the present invention, a binding material suitable for 3D printing is substantially composed of more than 90% calcium carbonate and has an average blaine of 7,000-13,000 cm ³ /g. It has fineness. Using an average Blaine fineness of about 11,000 cm ³ /g provides adequate flowability and good formability to the cementitious material, optimizes dynamic yield stress properties, and promotes nucleation reactions. promotes the hydration reaction of cement in the initial stage to form portlandite. Calcium ions dissolved from powdered limestone in the strongly basic state of the cement paste can form hydration reactions at the interfacial transition zone, so very fine powdered limestone can be mixed with powdered limestone lumps or other fine aggregates and cement. can help improve the interfacial transition zone between

Fresh cement conditioning agents used in the 3D printing suitable bond material of the present invention are retardants, thickeners, surfactants and rheology modifiers, as well as mineral and chemical or swelling additives. , which, when mixed in the proper proportions, provide fresh property properties, especially those required for 3D printing. These properties are workpiece shaping, dynamic and static flowability, improved working time for various 3D printers, enhanced compressive strength, and improved mechanical properties.

Retardants are water soluble dry powder particles or liquid solutions composed primarily of sugars such as gluconate, sucrose, or sodium fluorosilicate. For example, sodium gluconate can help extend the working time of fresh mortar, depending on the amount added. The amounts used in the present invention are 0.010-1.000% of the total weight of the dry bonding material.

Rheology modifiers are water-soluble, such as polycarboxylates, consisting essentially of carboxylates, F-type or G-type water reducers according to the ASTM 494/494M standard (Standard Specification for Chemical Admixtures for Concrete). dry powder particles or a liquid solution. Thus, the amount of water required for mixing is reduced, resulting in improved mechanical properties (eg compressive strength) of the set mortar, depending on the amount added. The amounts used in the present invention are 0.010-1.000% of the total weight of the dry bonding material.

Thickeners are water-soluble dry powder particles, primarily natural or modified cellulose or natural or modified starch. For example, depending on the amount added, methyl cellulose plays a role in adjusting the fresh mortar consistency to be suitable for extrusion molding using a 3D printer and increasing the water retention and air content contained in the fresh mortar. The amounts used in the present invention are 0.001-0.500% of the total weight of the dry bond material.

The surfactant is an anionic agent such as an alkyl sulfate, an alkyl sulfonate such as sodium lauryl sulfate, or a sulfonic or carboxylic acid having a reactive anionic substance in an amount greater than 95.0% by dry weight of the surfactant. It is a water-soluble dry powder particle or liquid solution consisting mainly of When mixed with water to obtain a 1.0% concentration solution, the surfactant has a pH value of 7.5-10.5. Surfactants play a role in reducing the surface tension of fresh mortar, depending on the amount added. The amounts used in the present invention are 0.001-1.000% of the total weight of the dry bonding material.

The use of thickeners in combination with surfactants can improve the non-flowing properties of binding materials suitable for 3D printing when no force is applied. The combined use of thickeners and surfactants intensifies the positive influence on the properties of the fresh mortar. A preferred weight ratio of thickener to surfactant is 0.5 to 2.0. The non-fluidity when no external force is applied is determined from the flow diameter difference at zero stroke according to the ASTM C1437 standard (standard test method for fluidity of hydraulic cement mortar) and the ASTM C230/C230M standard (hydraulic cement can be measured using a flow table conforming to the standard specification of flow table for use in the test).

In turn, the long working time properties of bonding materials suitable for 3D printing increase the working time of the material and reduce the risk of material clogging inside the material transport pipelines or nozzles of the 3D printer. This property can be improved by using retardants in combination with surfactants. The above properties are determined according to the ASTM C1437 standard (standard test method for fluidity of hydraulic cement mortar) and ASTM C1506 standard (standard for water retention of hydraulic cementitious mortar and plaster). test method) can be measured from the water retention of the mortar material.

Another important property for forming a 3D workpiece with a bonding material suitable for 3D printing is the extrudability of the mortar. This performance is considered a dynamic property because forces are applied from outside the 3D printer during extrusion. The forces in question are pneumatic pressure, vibration, and screw feeding. This property depends on the density of the fresh mortar or the air content in the fresh mortar. As the density decreases or the air content increases, the mortar becomes lighter in weight and easier to extrude through the nozzle. However, increasing air content directly affects compressive strength. Therefore, it is necessary to adjust the amount of binder and rheology modifier. Properties relating to the ability of a mortar to be extruded through a nozzle can be determined from the air content of the fresh mortar according to the ASTM C185 standard (Standard Test Method for Air Content of Hydraulic Cement Mortars).

Another important mechanical property of materials used in construction is the ability of the workpiece to withstand compression with varying curing times. This property of mortars obtained from binding materials suitable for 3D printing should be effective enough for use in the construction and building sector. The required compressive strength must be high for both early and late setting times, i.e., the compressive strength at 1-3 days of age must be sufficient for the workpiece to continue and effectively perform construction. must be high enough to allow repositioning of Compressive strength at 28 days of age signifies long-term use of construction structures and long-term durability of workpieces in various conditions. The compressive strength test according to the present invention is performed by forming and cutting an extruded mortar material to meet the ASTM C109/C109M standard (Standard Test Method for Compressive Strength of Hydraulic Cement Mortar) (2-inch or 50 mm cube-shaped test specimens). This can be done by obtaining a smooth surface and size of the material shown in (Use). The standardized workpiece is then cured under conditions according to the ASTM C511 standard (Standard Specification for Mixing Chambers, Wetting Cabinets, Wetting Chambers, and Water Tanks Used in Testing Hydraulic Cement and Concrete). Test conditions depend on the cure time of the workpiece being tested.

<Test Results of Exemplary Bonding Materials According to the Present Invention>
We provide seven exemplary formulations of bonding materials with freshness and mechanical properties suitable for extrusion 3D printing. A fresh mortar obtained by mixing a binding material with water works well in a 3D printer. It is composed of binders, fine aggregates, rheology modifiers, hydration retardants, thickeners and surfactants in different proportions by weight of dry mortar according to Table 1.

Table 1 shows the composition of dry mortar with different proportions. Formulation 1 is the composition of the mortar formulation as a test control. For Formulations 1, 6, 7, no surfactant and different proportions of thickening agent were added ranging from 0.010 to 0.070% by weight of the dry mortar.

Formulation 4 is the composition of dry mortar without thickening agent and with surfactant added at a rate of 0.030% by weight of dry mortar.

Formulations 2, 3, 5 are compositions of dry mortar with different additions of thickener and surfactant.

According to the test results of the fresh property properties of the 3D printing mortar shown in Table 2, the mortar was mixed with different ratios of water within the range of 10.5 to 14.5% by weight of the dry mortar, and the When obtaining a fresh mortar with a similar fluidity within the appropriate range of 57.0%, the mortar of Formulation 1 without surfactant and with added thickener at a rate of 0.010% by weight of dry mortar: It was found that the weight ratio of thickener to surfactant was inadequate. The flow diameter difference without force is 16.0%, ie the formulation is fluid at rest and not suitable for use in a 3D printer. The air content is as low as 3.32% and the flow diameter difference should be less than 4.0% to be suitable for 3D printers. It was therefore difficult to push out the mortar. Suitable air content of fresh mortar should be in the range of 9.00-15.00%. The fluidity decreased rapidly and stopped flowing in 90 minutes, indicating a short working time. Suitable 90 minute fluidity of fresh mortar should be in the range of 35.0-45.0%. Due to poor fluidity, Formulation 1 was not suitable for its intended use despite its high water retention of 100%. In this case, the appropriate water retention was in the appropriate range of 85.0% to 100.0%. The above formulation was advantageous in terms of high compressive strength, which was 94.3 MPa at 28 days as shown in Table 3. Adequate high compressive strength should not be less than 60.0 MPa for load-bearing structures.

The mortar of Formulation 2, with thickener and surfactant added in proportions of 0.030% and 0.030% by weight of the dry mortar, respectively, had a thickener to surfactant weight ratio of 1.000. The flow diameter difference was 0.0% when no force was applied. This indicates that the mortar formulation does not move at rest, thus solving the problem of fresh mortar leaking out of the nozzles. The air content was 9.78%, high enough for extrusion and providing a light mortar. Extrusion through the nozzle was thus facilitated. Liquidity did not decline significantly. Since the water retention was 92.9%, the 90-minute fluidity was 44%, indicating a long working time. Also, the above formulation provided a high 28-day compressive strength of 65.1 MPa. Such mortar formulations with compressive strengths above 60.0 MPa are sufficient for use in the construction and building sector. Adding both thickeners and surfactants directly impacted the key properties required for mortar extrusion using the 3D extrusion method.

The mortar of Formulation 3 with thickener and surfactant added in proportions of 0.039 % and 0.039 % by weight of the dry mortar, respectively, had a thickener to surfactant weight ratio of 1.000. there were. The percentage of cementitious binder was increased from 31.892% to 45.073%. According to Table 2, the formulation was found to provide an acceptable water retention of 92.3%. A high air content of 12.63% gave a light mortar that was easy to extrude. Liquidity did not decline significantly. The 90 minute fluidity was 36%, indicating a long enough working time to use. The above formulation also exhibited a higher compressive strength at 28 days of cure, 14% greater than the formulation 2 mortar due to the higher binder content.

The formulation 4 mortar with no thickener and added surfactant at a rate of 0.0030% by weight of the dry mortar had a weight ratio of thickener to surfactant of 0.000. The formulation is intended to compare the mortar properties with no thickening agent added to the mortar. The test results showed a 7.1% higher water retention and an approximately 43% higher air content relative to Formulation 2 when no thickening agent was added to the mortar. Therefore, the mortar extrudability was significantly improved. Both formulations had a flowability of 44% after standing for 90 minutes. Compressive strength was about 21% higher. However, the formulation remains problematic when extrusion is performed using a 3D printer, as the mortar remains fluid in the static state (4% difference in flow diameter when no force is applied). Therefore, it can be summarized that the addition of surfactant alone is not suitable for 3D printing extrusion molding.

The mortar of Formulation 5 with the addition of thickener and surfactant in proportions of 0.039% and 0.050% by weight of the dry mortar, respectively, had a thickener to surfactant weight ratio of 0.7800. there were. The mortar of this formulation is suitable because it did not flow at rest due to the addition of both thickener and surfactant. Fresh mortar was also easy to extrude (air content was 14.03%). Working time was long due to high water retention (both formulations had 44% fluidity when left to stand for 90 minutes). The compressive strength of the workpiece cured for 28 days was as high as 60.9 MPa. The formulations are therefore suitable for extrusion 3D printing.

The formulation 6 mortar with thickener added at a ratio of 0.030% by weight of the dry mortar without surfactant had an inappropriate weight ratio of thickener to surfactant. Test results indicated that the mortar of the formulation still flowed at rest and was not suitable for its intended use. In addition, the water retention was low, and therefore it was difficult to extrude the mortar. The fluidity was not sufficient after the mortar was allowed to stand for 90 minutes. However, this formulation had moderate compressive strength.

The formulation 7 mortar with thickener added at a ratio of 0.070% by weight of the dry mortar without surfactant had an inappropriate weight ratio of thickener to surfactant. Test results of the formulation showed that there was a serious problem with static fluidity. It was difficult to push out the fresh mortar. The working time was short and the compressive strength was low. It can be seen that if a surfactant is not used in combination with a thickener, problems arise in fresh or dry use, or both.

The most suitable mortar formulations for the present invention are formulations 2, 3 and 5 due to the synergistic effect of surfactant and thickener. A suitable thickener to surfactant weight ratio of 0.5 to 2.0 provides the following advantages for workpieces molded using 3D printing methods. (1) Significant fluidity at rest, (2) Longer working time of fresh mortar, (3) Ease of extrusion from nozzles, (4) Early repositioning, load-bearing structures and final stage of building applications. Sufficient compressive strength.

<Best mode of the present invention>
The best mode of the invention is as described in the detailed description of the invention.

Claims (8)

A bonding material with freshness and mechanical properties suitable for extrusion 3D printing, comprising:
said binding material comprises a dry binding material and a fresh cement conditioning agent;
the dry binding material comprises a binding material and fine aggregate;
the fresh cement conditioning agent comprises a retardant, a thickener, a surfactant, and a rheology modifier;
said binder is present in an amount of 20 to 50% by weight of said dry binder;
said fine aggregate is present in an amount of 50 to 80% by weight of said dry bond material;
The retardant is present in an amount of 0.010 to 1.000% by weight of the dry bond material, wherein the retardant consists essentially of water-soluble dry powder particles or sugars or sugar-based solutions. is a liquid solution,
a water-soluble liquid wherein said thickening agent is present in an amount of 0.001 to 0.500% by weight of said dry binding material, said thickening agent consisting essentially of natural and modified cellulose and natural and modified starch; are dry powder particles of
water-soluble, wherein said surfactant is present in an amount of 0.001 to 1.000% by weight of said dry bond material, said surfactant consisting essentially of an alkyl sulfate or an alkyl sulfonate; is a dry powder particle or liquid solution of
The rheology modifier is present in an amount of 0.010 to 1.000% by weight of the dry bond material, and the rheology modifier is a carboxylate, F-type, or G-type according to ASTM 494/494M standards. Water soluble dry powder particles or a liquid solution substantially composed of a water reducing agent,
The water retention according to ASTM C1506 standard is 85% to 100%, the air content according to ASTM C185 standard is greater than 9%, and the weight ratio of the thickener to the surfactant is 0.5 to is 1.0 ;
Bonding material with freshness and mechanical properties suitable for extrusion 3D printing. 2. The method according to claim 1, wherein the binder is at least one selected from Portland cement, mixed cement, and alumina cement, and the cement has a Blaine specific surface area of 2,700 to 5,600 cm ² /g. Bonding material with freshness and mechanical properties suitable for extrusion 3D printing. 2. The method according to claim 1, wherein the binder comprises 0.1% to 5.0% alumina cement or sulfoaluminate cement, and the cement has a Blaine specific surface area of 2,700 to 5,600 cm ² /g. Bonding material with freshness and mechanical properties suitable for extrusion 3D printing. The fine aggregate is selected from naturally occurring or crushed and separated limestone, powdered limestone, fine sand, waste, and virgin cementitious materials. Binder material with freshness and mechanical properties suitable for extrusion 3D printing according to paragraph 1. The fine aggregate has a fresh property and mechanical properties suitable for extrusion 3D printing according to any one of claims 1 to 4, having a Blaine specific surface area of 7,000 to 13,000 cm ² /g. Bonding material with properties. 6. The fine aggregate has less than 10% particles with an average size greater than 600 microns, and the coarse particle size of the fine aggregate is between 2.3 and 5.5. A bonding material having freshness and mechanical properties suitable for extrusion 3D printing according to claim 1. Fresh property and machine suitable for extrusion 3D printing according to any one of claims 1 to 6, wherein the retardant comprises gluconate, sucrose, or sodium fluorosilicate as ingredients. bonding material with mechanical properties. Claims 1-claims comprising any of natural fibers, synthetic fibers, metallic fibers or combinations thereof as constituents, wherein the amount of said respective fiber type is between 0 and 2% by weight of said dry bond material. 8. Bonding material with freshness and mechanical properties suitable for extrusion 3D printing according to any one of clause 7 .