KR20200124498A - SBR Latex Modified Polymer Cement Mixtures for 3D Concrete Printing and Its Manufacturing Method - Google Patents

Abstract

The present invention relates to an SBR latex-modified polymer cement mixture for 3D concrete printing, in which SBR latex, a water-soluble polymer compound, is properly mixed with cement to improve fluidity, extrudability, lamination and open time, so as to facilitate printing and enhance the compressive strength, flexural strength, modulus of elasticity, drying shrinkage, etc., thereby securing the safety and durability of a printed structure. Accordingly, the present invention not only facilitates construction by obtaining properties such as suitable fluidity, extrudability, lamination, and open time before hardening, but also improves properties such as compressive strength, flexural strength, modulus of elasticity, drying shrinkage, etc., after hardening, thereby securing stability and durability of a printed structure.

Description

SBR Latex Modified Polymer Cement Mixtures for 3D Concrete Printing and Its Manufacturing Method {SBR Latex Modified Polymer Cement Mixtures for 3D Concrete Printing and Its Manufacturing Method}

The present invention relates to a polymer cement mixture, and more particularly, to a SBR (Styrene Butadiene Rubber) latex-modified polymer cement mixture for 3D concrete printing and a method of manufacturing the same.

In recent years, rapid prototyping technology, particularly 3D printing technology, has been successfully used in various fields. In particular, it is widely used in the manufacturing field, medical field, and food field. In these fields, 3D printing technology has developed rapidly, but in the construction industry, the pace of development is very slow.

In particular, concrete, which plays an important role in the construction industry, is the most widely used among construction materials, but formwork is essential to construct such concrete. Formwork is expensive for materials, manpower, construction period, and equipment, and there are negative aspects in terms of environment.

So, as a new technology that combines new knowledge from digital technology and material technology, research on construction methods applying 3D printing technology that can construct free-form construction without using a formwork has been conducted worldwide since 1997. it started.

This technology requires large equipment using a gantry or a robotic arm, and a large amount of printing materials are required. So, because it is small and precise, it is different from 3D printing technology in other industrial fields, so its name is also called 3D Concrete Printing (3DCP) method.

3DCP is an additive manufacturing technology in which cement composite materials are stacked and constructed. Looking at the 3DCP system in more detail, printing methods include extrusion-based technology and powder-based technology, and most of the technologies currently being developed are extrusion. 3DCP is a method that does not require a formwork by operating by computer control and sequentially stacking according to a predetermined process to accurately form and cure a predetermined size.

3DCP technology is also an environmentally friendly technology that offers virtually unlimited possibilities for realizing geometric complexity compared to traditional construction technology. And this technology has advantages such as saving cost and time, minimizing environmental pollution and reducing accidents at construction sites. Above all, 3DCP technology is a technology that represents'no-form construction' and is expected to be the future technology of the construction industry because it enables rapid construction.

3DCP technology consists of concrete printing equipment, 3D modeling software, and materials for printing, and is automatically operated by a computer. However, the characteristics of these elements can be seen as independent, and the major fields consist of machinery, IT, and materials.

In particular, in recent years, research on the development of printing materials suitable for the characteristics of structures to be constructed has been actively and competitively conducted.

However, the technology for materials for 3DCP currently being used is still at a rudimentary level. Because of this, not only is there a lot of difficulties in lamination because the predetermined non-hardening properties are not secured, but also the formability is very poor, and quality control is difficult because the properties are not secured after predetermined hardening, and the stability or durability of the constructed structure is not secured. Is being exposed.

KR 10-1620075 B1

The present invention is to solve the above-described conventional problems, and an object of the present invention is to improve fluidity, extrudability, lamination and open time by appropriately blending SBR latex, which is a water-soluble high molecular compound in cement, to facilitate printing, It is to provide a SBR latex-modified polymer cement mixture for 3D concrete printing that can secure safety and durability of printed structures by improving compressive strength, flexural strength, modulus of elasticity, and drying shrinkage, and a manufacturing method thereof.

In order to achieve the object of the present invention as described above, the SBR latex-modified polymer cement mixture for 3D concrete printing according to the present invention includes 1 to 5% by weight of SBR (Styrene Butadiene Rubber) latex and 23 to 25% by weight of Portland cement, and water. 7 to 12% by weight, 50 to 54% by weight of fine aggregate, 5 to 8% by weight of fly ash, 2 to 4% by weight of silica fume, 0.23 to 0.26% by weight of water reducing agent and 0.009 to 0.015% by weight of viscosity modifier It is characterized by including %.

In the SBR latex-modified polymer cement mixture for 3D concrete printing according to the present invention, the SBR latex is in the form of an emulsion and has a total solid content of 47-50%.

In the SBR latex-modified polymer cement mixture for 3D concrete printing according to the present invention, the fine aggregate is a prismatic particle with a particle size of 0.05 to 5 mm in diameter, a specific gravity of 1.5 to 1.6, and a moisture content of 0.1% or less with a purity of 90% or more It is characterized by being.

In the SBR latex-modified polymer cement mixture for 3D concrete printing according to the present invention, the fly ash is two types of fly ash specified in KS L 5405 (fly ash) and has a moisture content of 1.0% or less.

In the SBR latex-modified polymer cement mixture for 3D concrete printing according to the present invention, the silica fume has a silicon dioxide (SiO ₂ ) content of 90% or more, a moisture content of 1.0% or less, and a specific surface area of 155000 to 159000 cm2/g. do.

In the SBR latex-modified polymer cement mixture for 3D concrete printing according to the present invention, the water reducing agent is characterized in that the water reducing agent is a polycarbonate type water reducing agent.

In the SBR latex-modified polymer cement mixture for 3D concrete printing according to the present invention, the viscosity modifier is characterized in that it is an organic modified clay.

In order to achieve the object of the present invention as described above, the SBR latex-modified polymer cement mixture manufacturing method for 3D concrete printing according to the present invention includes 1 to 5% by weight of SBR latex, 23 to 25% by weight of Portland cement, and 7 to 12 of water. Modified SBR latex for 3D concrete printing containing weight %, fine aggregate 50 to 54 weight %, fly ash 5 to 8 weight %, silica fume 2 to 4 weight %, water reducing agent 0.23 to 0.26 weight %, and viscosity modifier 0.009 to 0.015 weight% A first step of weighing each of the above materials with a weighing scale having 1/100 accuracy in order to prepare a polymer cement mixture; A second process of mixing fine aggregate, fly ash, and silica fume among the materials measured in the first process with a forced mixer; A third step of adding a water reducing agent and a viscosity modifier to water among the materials measured in the first step and mixing them with a table mixer; A fourth step of putting SBR latex among the materials measured in the first step into the mixture made in the third step and mixing with a table mixer; And a fifth process of injecting the mixture made in the fourth process into the mixture made by hot mixing in the second process and mixing it with a forced mixer to complete the production of the SBR latex-modified polymer cement mixture for 3D concrete printing. It characterized in that it is made.

In the method for producing a SBR latex-modified polymer cement mixture for 3D concrete printing according to the present invention, in the third step, a water reducing agent and a viscosity modifier are added to water at 20 to 30° C. and mixed for 5 to 10 minutes.

In the method for manufacturing the SBR latex-modified polymer cement mixture for 3D concrete printing according to the present invention, in the fourth step, SBR latex among the materials measured in the first step is added to the mixture prepared in the third step and for 5 to 10 minutes. It is characterized by mixing.

In the method for manufacturing the SBR latex-modified polymer cement mixture for 3D concrete printing according to the present invention, in the fifth process, the mixture made in the fourth process is added to the mixture made by hot mixing in the second process, and then 5-10 minutes It characterized in that the production of the SBR latex-modified polymer cement mixture for 3D concrete printing is completed by mixing.

The present invention not only facilitates construction by obtaining properties before hardening, particularly suitable fluidity, extrudability, lamination, and open time, but also improves properties after hardening, especially compressive strength, flexural strength, elastic modulus, drying shrinkage, etc. Stability and durability can be secured.

1 is an example showing the nozzle shape and operation form of the 3DCP equipment used in the fluidity and lamination test of the mixture of the present invention.
2 to 5 are examples showing the state of the printing test according to the flow rate.
Figure 6 is an embodiment showing a surface defect of the filament when the flow rate is low.
Figure 7 is an example showing a one-layer extrusion test state of the present invention mixture by 3DCP equipment.
8 is an example showing the state of the 10-layer lamination test of the mixture of the present invention.
Figure 9 is a graph showing the flow rate change of the mixture of the present invention according to the SBR latex content.
10 is a graph showing the expression pattern of compressive strength by age of the inventive mixture according to the SBR latex content.
Figure 11 is a graph showing the appearance of the flexural strength of the mixture according to the age of the present invention according to the SBR latex content.
12 is a graph showing the relationship between the compressive stress-strain of the inventive mixture according to the SBR latex content.
13 is a graph showing the change in the amount of drying shrinkage by age of the inventive mixture according to the SBR latex content.
14 is an example showing a change in the structure of the mixture of the present invention modified with a normal cement mixture and SBR latex.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

The SBR latex-modified polymer cement mixture for 3D concrete printing according to the present invention described below and a method of manufacturing the same are not limited to the following examples, and are generally applicable to the technical field without departing from the gist of the technology claimed in the claims. Anyone who has the knowledge of this has the technical spirit to the extent that anyone can change and implement it.

SBR latex-modified polymer cement mixture for 3D concrete printing according to a preferred embodiment of the present invention is SBR (Styrene Butadiene Rubber) latex 1-5% by weight, Portland cement 23-25% by weight, water 7-12% by weight, fine aggregate 50- 54 wt%, fly ash 5-8 wt%, silica fume 2-4 wt%, water reducing agent 0.23-0.26 wt%, and viscosity modifier 0.009-0.015 wt%.

The SBR latex is in the form of an emulsion and preferably has a total solid content of 47 to 50%, and has an effect of improving compression, warpage, tensile strength, waterproofness, adhesion, and chemical resistance by forming a polymer film.

The Portland cement is suitable for KS L 5201 (Portland Cement) and ASTM C 150 (Standard Specification for Portland Cement), and it is preferable to use one type of ordinary Portland cement.

As for the water, it is preferable to use tap water for drinking as the mixing water.

The fine aggregate is a prismatic particle, and a particle size of 0.05 to 5 mm (preferably 0.08 mm), a specific gravity of 1.5 to 1.6 (preferably 1.57), a water content of 0.1% or less, and a purity of 90% or more silica sand is preferred. .

The fly ash is two types of fly ash specified in KS L 5405 (fly ash), and preferably has a moisture content of 1.0% or less, and has effects such as improving the fluidity and watertightness of concrete, and inhibiting initial heat of hydration.

The silica fume is preferably a silicon dioxide (SiO ₂ ) content of 90% or more, a moisture content of 1.0% or less, a specific surface area of 155000 to 159000 ㎠/g (preferably 157000 ㎠/g), and calcium hydroxide <Ca(OH) ₂ Pozzolanic reaction with )> has the characteristics of forming a CSH gel with excellent high strength, high durability, material separation resistance, and water tightness.

The water reducing agent is preferably a polycarbonate type water reducing agent, which is a high-performance water reducing agent that has superior dispersion effect than general water reducing agents, and is used for the purpose of improving workability.

The viscosity modifier is organic modified clay, and is used for the purpose of improving initial adhesion, reducing material separation and securing fluidity.

The SBR latex-modified polymer cement mixture for 3D concrete printing according to the present invention constituted as described above is prepared as follows.

First, 1 to 5% by weight of SBR latex and 23 to 25% by weight of Portland cement, 7 to 12% by weight of water, 50 to 54% by weight of fine aggregate, 5 to 8% by weight of fly ash, 2 to 4% by weight of silica fume, 0.23 water reducing agent To prepare a SBR latex-modified polymer cement mixture for 3D concrete printing containing -0.26% by weight and 0.009 to 0.015% by weight of a viscosity modifier, each of the above materials is weighed with a 1/100-accuracy weighing scale (1st step). .

In the first step, the reason for using a weighing scale with 1/100 accuracy is that the water reducing agent and the viscosity modifier are trace amounts, so a weighing scale with high precision is required, and other materials must be accurately weighed for thorough quality control. .

Subsequently, the fine aggregate, fly ash, and silica fume among the materials measured in the first step are mixed with a forced mixer (second step).

Then, a water reducing agent and a viscosity modifier are added to water among the materials measured in the first step and mixed (third step). At this time, it is most preferable to put a water reducing agent and a viscosity modifier in water at 20 to 30° C. and mix with a table mixer for 5 to 10 minutes.

In the third process, if the water is less than 20°C, the dissolution rate of the water reducing agent and the viscosity modifier is slow, and if the water is 30°C or more, too fast curing reaction may occur in the fifth step below. In addition, when mixing for less than 5 minutes, the water reducing agent and the viscosity modifier may be mixed unevenly, and when mixing for 10 minutes or more, separation of the material may occur, and excessive mixing time decreases productivity.

Accordingly, in a preferred embodiment of the present invention, the temperature of water in the third process is limited to 20 to 30° C. and the mixing time is limited to 5 to 10 minutes.

Subsequently, SBR latex among the materials measured in the first step is added to the mixture prepared in the third step and mixed (step 4). At this time, it is most preferable to put the SBR latex into the mixture made in the third step and mix it with a table mixer for 5 to 10 minutes.

In the fourth process, when the mixture is mixed for less than 5 minutes, the mixture of the third process and the SBR latex may be mixed unevenly, and when the mixture is mixed for more than 10 minutes, separation of the material may occur, and excessive mixing time decreases productivity.

Therefore, in a preferred embodiment of the present invention, the mixing time in the fourth process is limited to 5 to 10 minutes.

Finally, the mixture made in the fourth process is added to the mixture made by hot mixing in the second process and then mixed to complete the production of the SBR latex-modified polymer cement mixture for 3D concrete printing (step 5). At this time, it is most preferable to add the mixture made in the fourth process to the mixture made by hot mixing in the second process and then mix it with a forced mixer for 5 to 10 minutes.

In the fifth process, when mixing for less than 5 minutes, the mixture of the second process and the mixture of the fourth process may be mixed unevenly, and when mixing for more than 10 minutes, separation of the material may occur, and excessive mixing time decreases productivity. Let it.

Therefore, in a preferred embodiment of the present invention, the mixing time in the fifth process is limited to 5 to 10 minutes.

It is preferable to perform the first to fifth processes sequentially, and in particular, if in the second process, a trace amount of the water reducing agent and the viscosity modifier used in the third process are first added to the forced mixer, and then later When mixed with water, the water reducing agent and the viscosity modifier are mixed with other materials in a non-uniform state that is not sufficiently mixed with water, so the performance of the SBR latex-modified polymer cement mixture for 3D concrete printing according to the present invention cannot be obtained.

The SBR latex-modified polymer cement mixture for 3D concrete printing according to the present invention prepared as described above is used for automated construction by the 3D concrete printing (3DCP) method described above.

For example, the SBR latex-modified polymer cement mixture for 3D concrete printing according to the present invention is injected into a bucket and transferred to a pump, then compressed into a filament form through a nozzle, stacked in a predetermined structure shape, and then cured. Automated construction by 3DCP work is completed.

Hereinafter, a process determined by deriving an appropriate mixing ratio of the SBR latex-modified polymer cement mixture (hereinafter, the present invention mixture) for 3D concrete printing according to the present invention in the construction work by the 3D printing equipment equipped with the 3D modeling software. It will be described in detail.

In order to derive and determine an appropriate blending ratio of the mixture of the present invention, the blending ratio (% by weight) of SBR latex was varied as shown in Table 1 below.

The SBR latex was used with a total solid content of 50%, and the Portland cement was used as a type of normal Portland cement, and tap water was used as the water.

The fine aggregates were prismatic particles, and a particle size of 0.08mm in diameter, a specific gravity of 1.57, and a water content of 0.1% or less with a purity of 90% or more of silica sand were used.

The silica fume was used having a silicon dioxide (SiO ₂ ) content of 90% or more, a moisture content of 1.0% or less, and a specific surface area of 157000 cm2/g.

Flowmix 3000S was used as the water reducing agent as a polycarbonate type water reducing agent, which is a high-performance water reducing agent that has better dispersion effect than general water reducing agents.

THICKENT W was used as an organic modified clay as the viscosity modifier.

(1) Derivation of an appropriate flow rate

The mixture of the present invention should be smoothly moved from the bucket to the nozzle through the pump, and the filament extruded through the nozzle should satisfy the basic requirement that lamination should be stable, and this requirement is a flow rate. It is desirable to measure and use it as a reference.

The nozzle shape and operation form of the 3DCP equipment used for the fluidity and lamination test of the mixture of the present invention are shown in FIG. 1. For reference, FIG. 1 shows an example in which filaments extruded to a length of 50 cm are stacked with 3DCP equipment having a nozzle size of 5.7 cm in width and 1.4 cm in length.

The flow rate that has the smoothest fluidity and lamination by repeated tests is found by the test according to ASTM C1437-15 (Standard Test Method for Flow of Hydraulic Cement Mortar).

2 is a photograph showing a flow rate of 60% when the SBR latex content of the mixture of the present invention is 3.65% by weight.

3 is a photograph showing a flow rate of 65% when the SBR latex content of the mixture of the present invention is 3.65% by weight.

4 is a photograph showing a flow rate of 70% when the SBR latex content of the inventive mixture is 3.65% by weight.

3 is a photograph showing a flow rate of 75% when the SBR latex content of the inventive mixture is 3.65% by weight.

As a result of the test, in the case of a flow rate of 55%, the inventive mixture was not extruded, in the case of a flow rate of 60%, 11.5 cm (see Fig. 2), in a case of a flow rate of 65%, 11.3 cm (see Fig. 3), and a flow rate of 70% In the case of 12.5 cm (see Fig. 4), it was laminated, and in the case of a flow rate of 75%, the inventive mixture was extruded, but it was not measurable (see Fig. 5).

(2) Derivation of the proper mixing ratio

The above-described test results are divided and the flow rate having smooth fluidity and lamination property is set to 70%, and is used as a criterion for determining the proper mixing ratio of the mixture of the present invention.

The appropriate mixing ratio of the mixture of the present invention according to the change in the content of the SBR latex was derived as shown in Table 1 below, and the unit of the mixing ratio of each material shown in Table 1 is% by weight.

SBR latex Portland cement water Fine aggregate Fly ash Silica fume Water reducer Viscosity
Modulator 0.00 24.80 11.16 53.15 7.09 3.54 0.25 0.01 1.23 24.65 10.48 52.82 7.04 3.52 0.25 0.01 2.45 24.50 9.80 52.50 7.00 3.50 0.24 0.01 3.65 24.35 9.13 52.18 6.96 3.48 0.24 0.01 4.84 24.20 8.47 51.86 6.91 3.46 0.24 0.01

In the following, in the construction work by the 3D printing equipment equipped with the 3D modeling software, the properties before hardening of the mixture of the present invention will be described in detail.

(1) flowability

The flowability indicates the excellence in moving to the nozzle after the agitated mixture of the present invention was introduced into the bucket of the pump, and was tested according to ASTM C1437-15 (Standard Test Method for Flow of Hydraulic Cement Mortar).

As a result of the test, the optimum flow rate was 70%, which was also used as a criterion for determining the mixing ratio suggested above. If the flow rate is less than 60%, the ground fluidity is rapidly deteriorated, resulting in a defect on the surface of the filament as shown in FIG.

(2) extrudability

The starting and ending times of extrusion, and the total length of the extruded filament were measured to calculate the extruded length in 1 minute.

That is, the length of one layer was 50 cm and the number of layers was 10 to evaluate the extrudability of the mixture of the present invention according to the SBR latex content, and the appearance of the extrusion test is shown in FIG. 7. The reason why the number of stacking is 10 layers is that the width of the filaments is narrow and the stacking method is structurally unstable and straight, so a stable height that does not fall is selected.

As a result of the test, as shown in Table 2 below, the extrudability of the SBR content of 0% by weight is 41.7cm/min, in the case of 1.23% by weight, 41.7cm/min, in the case of 2.45% by weight, 41.7cm/min, and 3.65% by weight. In the case of 50.0cm/min, and in the case of 4.84% by weight, it was 62.5cm/min. It can be seen that the higher the content of SBR latex, the better. This tendency facilitates the relative movement of cement and hydration particles due to the ball bearing action of particles dispersed in the SBR latex.

SBR latex content
(weight%) Length
(cm) Printing time
(min) Extrudability
(cm/min) 0 500 12 41.7 1.23 12 41.7 2.45 12 41.7 3.65 10 50.0 4.84 8 62.5

(3) buildability

The above-described fluidity and extrudability have a close relationship with the lamination property. In order to evaluate the stackability, when stacking into 10 layers with a length of 50 cm as shown in FIG. 8, the height immediately after stacking and the height after stacking 30 minutes were measured to investigate the difference.

As a result of the test, the height immediately after lamination was less than 1 mm for the SBR latex content of 0% by weight, 1.23% by weight and 2.45% by weight, 5 mm for 3.65% by weight, and 20 mm for 4.84% by weight. The height after 30 minutes of lamination decreased within 1 mm for the SBR latex content of 0 wt%, 1.23 wt%, and 2.45 wt%, 4 mm for 3.65 wt%, and 3 mm for 4.84 wt%. Therefore, it is preferable to add 1.23 to 3.65% by weight of SBR latex in terms of lamination properties.

(4) open time

Open time is the time to maintain fluidity, and in the case of the 3DCP method, it is an important index to determine the workable time and is obtained by flow rate test. The flow rate was tested according to ASTM C1437-15 (Standard Test Method for Flow of Hydraulic Cement Mortar).

The flow rate change according to the content of the SBR latex was measured, and the reference flow rate was set to 70%, and the time until the value reached 55% of the flow rate at which extrusion was impossible was set as the open time.

As a result of the test, SBR latex content of 0% by weight was 46 minutes, 1,23% by weight was 110 minutes, 2.45% by weight was 122 minutes, 3.65% by weight was 131 minutes, and 4.84% by weight was 140 minutes. It was longer as the content of latex increased, and this result is as shown in FIG. 9. In FIG. 9, (1) represents the starting point, and (2) represents the boundary line at a flow rate of 55% at which extrusion is not performed.

In the following, in the construction work by the 3D printing equipment equipped with the 3D modeling software, the properties after hardening of the mixture of the present invention will be described in detail.

(1) compressive strength

The compressive strength test was conducted by ASTM C349-14 (Standard Test Method for Compressive Strength of Hydraulic-cement Mortars), and the expression pattern of compressive strength by age according to the SBR latex content is as shown in FIG.

The compressive strength at 28 days of age according to the SBR latex content and the relative compressive strength calculated based on the SBR latex content of 0% by weight are shown in Table 3 below.

SBR latex content (% by weight) 0 1.23 2.45 3.65 4.84 Compressive strength (MPa) 43.5 50.4 54.3 60.5 63.2 Relative compressive strength (%) 100 116 125 139 145

The compressive strength of 28 days of age was 43.5~63.2 MPa, which increased as the content of SBR latex increased, but the increase slowed when the content of SBR latex exceeded 3.65% by weight, and the relative compressive strength for 0% by weight of SBR latex was also small.

In terms of compressive strength, it shows that the amount of SBR latex added is 2.45 to 3.65% by weight.

(2) flexural strength

The flexural strength test was performed according to ASTM C348-14 (Standard Test of Method for Flexural Strength of Hydraulic-Cement Mortars), and the appearance of flexural strength for each age according to the SBR latex content is as shown in FIG.

The 28-day flexural strength according to the SBR latex content and the relative flexural strength calculated based on the SBR latex content of 0% by weight are shown in Table 4 below.

SBR latex content (% by weight) 0 1.23 2.45 3.65 4.84 Flexural strength (MPa) 12.7 13.6 14.5 16.7 17.9 Relative flexural strength (%) 100 107 114 130 140

The flexural strength at 28 days of age was 12.7 to 17.9 MPa, which increased as the content of SBR latex increased, but the relative flexural strength to 0% by weight of SBR latex increased consistently.

(3) modulus of elasticity

The compressive stress-strain relationship diagram of the inventive mixture is as shown in FIG. 12, and the elastic modulus calculated from this relationship is shown in Table 5 below.

SBR latex content (% by weight) Compressive strength (MPa)

)(MPa)Modulus of elasticity (

)(MPa) 0 50.9 2.16 1.23 54.3 2.29 2.45 58.0 2.31 3.65 60.4 2.44 4.84 63.5 2.53

The modulus of elasticity is the secant modulus of elasticity obtained from the slope at 1/3 of the compressive strength, and is 2.16×10 ⁴ MPa for 0% by weight of SBR latex, 2.29×10 ⁴ MPa for 1.23% by weight, In the case of 2.45% by weight, 2.31×10 ⁴ MPa, in the case of 3.65% by weight 2.44×10 ⁴ MPa, and in the case of 4.84% by weight, 2.53×10 ⁴ MPa, the modulus of elasticity increases as the SBR latex content increases.

(4) drying shrinkage

As shown in FIG. 13, the results of the dry shrinkage test at 28 days of age are 3.31×10 ^{-4 for} 0% by weight of SBR latex content, 2.82×10 ^{-4 for} 1.23% by weight of SBR latex content, 2.45% by weight of SBR latex content. In the case of 2.25×10 ^-4 , the SBR latex content of 3.65 wt% is 1.84×10 ^-4 , and the SBR latex content of 4.84 wt% is 1.44×10 ^-4 , which decreases as the SBR latex content increases.

This decrease in drying shrinkage is due to the fact that the formation of a polymer film due to SBR latex modification acts as microfibers that limit the shrinkage phenomenon in the matrix, and blocks the pores to inhibit water evaporation.

(5) Changes in organizational structure

14 is a photograph of the structure of a cement mixture and an SBR-modified cement mixture by a high-resolution scanning electron microscope (Hitachi S-4800 model) in order to grasp the basis of the performance improvement by SBR latex.

In the case of the normal cement mixture shown in FIG. 14(a), only the shape of calcium hydroxide <Ca(OH) ₂ > and ettringite crystal was observed, but modified with the SBR latex shown in FIG. 14(b) In the case of the mixture of the present invention, the shape of the polymer (SBR latex) particle was also observed along with calcium hydroxide and ethringite crystals. The polymer itself or the surfactant contained in the SBR latex acts like a water reducing agent, increasing the slump value and reducing the amount of water used, and the polymer is a cured inventive mixture, that is, a SBR latex modified polymer for 3D concrete printing. By forming a film inside the cement mixture, it has the effect of improving compression and flexural strength, modulus of elasticity, and drying shrinkage.

Claims (11)

SBR (Styrene Butadiene Rubber) latex 1-5% by weight and Portland cement 23-25% by weight, water 7-12% by weight, fine aggregate 50-54% by weight, fly ash 5-8% by weight, silica fume ( Silica fume) SBR latex-modified polymer cement mixture for 3D concrete printing, characterized in that it comprises 2-4% by weight, a water reducing agent 0.23-0.26% by weight, and a viscosity modifier 0.009-0.015% by weight. The SBR latex-modified polymer cement mixture for 3D concrete printing according to claim 1, wherein the SBR latex is in the form of an emulsion and has a total solid content of 47-50%. The SBR latex for 3D concrete printing according to claim 1, wherein the fine aggregate is a prismatic particle, the particle size is 0.05 to 5 mm in diameter, the specific gravity is 1.5 to 1.6, and the water content is less than 0.1% and a purity of 90% or more siliceous sand. Modified polymer cement mixture. The SBR latex-modified polymer cement mixture for 3D concrete printing according to claim 1, wherein the fly ash is two types of fly ash specified in KS L 5405 (fly ash) and has a moisture content of 1.0% or less. The SBR latex-modified polymer cement mixture for 3D concrete printing according to claim 1, wherein the silica fume has a silicon dioxide (SiO ₂ ) content of 90% or more, a moisture content of 1.0% or less, and a specific surface area of 155000 to 159000 cm2/g. . The SBR latex-modified polymer cement mixture for 3D concrete printing according to claim 1, wherein the water reducing agent is a polycarbonate type water reducing agent. The SBR latex-modified polymer cement mixture for 3D concrete printing according to claim 1, wherein the viscosity modifier is organic modified clay. 1 to 5% by weight of SBR latex and 23 to 25% by weight of Portland cement, 7 to 12% by weight of water, 50 to 54% by weight of fine aggregate, 5 to 8% by weight of fly ash, 2 to 4% by weight of silica fume, 0.23 to 0.26 of water reducing agent In order to prepare a SBR latex-modified polymer cement mixture for 3D concrete printing containing 0.009 to 0.015 wt% of a viscosity modifier and a weight%, a first step of weighing each of the above materials with a weighing scale with 1/100 accuracy;
A second process of mixing fine aggregate, fly ash, and silica fume among the materials measured in the first process with a forced mixer;
A third step of adding a water reducing agent and a viscosity modifier to water among the materials measured in the first step and mixing them with a table mixer;
A fourth step of putting SBR latex among the materials measured in the first step into the mixture made in the third step and mixing with a table mixer; And
A fifth process of injecting the mixture made in the fourth process into the mixture made by hot mixing in the second process and mixing with a forced mixer to complete the production of the SBR latex-modified polymer cement mixture for 3D concrete printing;
SBR latex-modified polymer cement mixture manufacturing method for 3D concrete printing, characterized in that consisting of. The method of claim 8, wherein in the third step, a water reducing agent and a viscosity modifier are added to water at 20 to 30° C. and mixed with a table mixer for 5 to 10 minutes. The 3D concrete printing method according to claim 8, wherein in the fourth step, SBR latex among the materials measured in the first step is added to the mixture made in the third step and mixed with a table mixer for 5 to 10 minutes. SBR latex modified polymer cement mixture manufacturing method. The SBR latex for 3D concrete printing according to claim 8, wherein in the fifth step, the mixture made in the fourth step is added to the mixture made by hot mixing in the second step, and then mixed with a forced mixer for 5 to 10 minutes. SBR latex modified polymer cement mixture manufacturing method for 3D concrete printing, characterized in that to complete the production of the modified polymer cement mixture.

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