KR20200103407A - Engineered Cementitious Composite using Cellulose Nanocrystal and Manufacturing method thereof - Google Patents

Abstract

The present invention relates to a fiber-reinforced high toughness cement composite composition using cellulose nanocrystals and a method for manufacturing the same, and more specifically, to a fiber-reinforced high toughness cement composite composition having improved compressive strength and bending strength by mixing cellulose nanocrystals and steel fibers in an optimal mixing ratio, and a method for manufacturing the same. The fiber-reinforced high toughness cement composite composition using cellulose nanocrystals comprises, based on 100 parts by weight of cement; 30-50 parts by weight of water; 30-50 parts by weight of sand; and 15-40 parts by weight of fly ash. Also, the fiber-reinforced high toughness cement composite composition using cellulose nanocrystals further comprises, based on 100 parts by volume of the cement: 0.1 to 3 parts by volume of water-reducing agent; 0.1 to 2 parts by volume of steel fiber; and 0.1 to 2 parts by volume of cellulose nanocrystals (CNC).

Description

TECHNICAL FIELD [Engineered Cementitious Composite using Cellulose Nanocrystal and Manufacturing method thereof]

The present invention relates to a fiber-reinforced high-toughness cement composite composition using cellulose nanocrystals and a method for manufacturing the same, and more particularly, to a fiber-reinforced high toughness that improves compressive strength and flexural strength by mixing cellulose nanocrystals and steel fibers at an optimal blending ratio. It relates to a cement composite composition and a method of manufacturing the same.

Cement mortar, one of the most widely used materials in modern building structures, is economical, is relatively easy to obtain, and is easy to shape, has the advantages of easy compression strength, excellent durability, and stable construction of structures. Because it has it, it is widely used as a building and civil engineering material.

However, cement mortar has weak deficiencies in bending and tensile strength, adhesion, and chemical resistance, and to improve the above problems, the strength and durability of cement mortar are improved by adding organic and inorganic fillers to the cement mortar. The research to be done is ongoing.

In this regard, Korean Patent Registration No. 10-1743042 discloses excellent strength and fluidity by mixing a cement-based binder, a water-soluble polymer and an inorganic reinforcing material in order to repair deteriorated parts, cracks and damaged parts of a structure by mixing a water-soluble polymer and an inorganic reinforcing material. It proposes a lightweight and eco-friendly polymer cement cross-section recovery mortar composition having elasticity, adhesiveness, waterproofness, and airtightness.

On the other hand, according to the trend of reducing carbon emissions and the use of eco-friendly and natural materials that are mandated worldwide, interest in bio-friendly materials replacing petroleum-based polymer admixtures as building materials is increasing.

Recently, nanocellulose, a polymeric nanomaterial obtained from woody biomass, is attracting attention as a high-performance, eco-friendly, next-generation new material in which nanotechnology (NT) and biotechnology (BT) are fused.

Nano cellulose refers to nano-micrometer-sized rod-shaped particles or fibers in which cellulose chains form a bundle and are tightly bound. In general, nanocellulose has a tensile modulus similar to that of steel or Kevlar (100-160 GPa), has a small density (0.8-1.5 g/cm3), and has a large specific surface area. Have.

Nanocellulose can be largely divided into cellulose nanofibril (CNF) and cellulose nanocrystal (CNC) according to the method of extraction from biomass.

Cellulose nanofibril (CNF) is a fiber with a diameter (width) of 5 to 100 nm and a length of several to tens of μm and is manufactured through mechanical treatment, whereas cellulose nanocrystal (CNC) Silver is a rod-shaped crystal with a diameter (width) of 5 to 30 nm and a length of 100 to 700 nm, obtained through chemical treatment.

Cellulose nanocrystals are a promising material as a nanoscale reinforcing material for cement in that they have high elastic modulus and high strength functionalization properties, and have a lower safety risk compared to other construction materials in the extraction process environment and are sustainable. There are such advantages.

As a patent document using conventional cellulose nanocrystals for building materials, Korean Patent No. 10-1683090 proposes a cement binder composition to which crystalline cellulose is added as a reinforcing material.

However, since cellulose materials have high hydrophilicity, aggregation may occur when reacting with moisture, and cellulose nanocrystals (CNCs) having a nano size are more likely to cause aggregation. Can be, and should be mixed in an optimal blending ratio.

The inventors of the present invention improve dispersibility through pretreatment of cellulose nanocrystals as part of a study for the application of cellulose nanocrystals to building materials, and at the same time, additionally, engineered cementitious composites (ECC) using steel fibers and flax fibers. Through the structural performance evaluation of, the optimal formulation was suggested, and physical properties were improved, in particular, the improvement of compressive strength was confirmed, leading to the present invention.

Domestic Registration Patent No. 10-1743042 (Lightweight and eco-friendly polymer cement cross section restoration mortar composition) Domestic Registration Patent No. 10-1683090 (Organic-inorganic fusion self-healing admixture composition with acicular crystal structure and cement binder composition containing the same)

An object of the present invention for solving the above problems is to provide a fiber-reinforced high-toughness cement composite composition and a method for producing the same, in which cellulose nanocrystals and steel fibers are mixed in an optimal blending ratio to improve compressive strength and flexural strength.

Fiber-reinforced high toughness cement composite composition using cellulose nanocrystals of the present invention for solving the above problems is based on 100 parts by weight of cement, 30 to 50 parts by weight of water; 30 to 50 parts by weight of sand; and 15 to 40 fly ash And 0.1 to 3 parts by volume of a water reducing agent; 0.1 to 2 parts by volume of steel fibers; and 0.1 to 2 parts by volume of cellulose nanocrystal (CNC) based on 100 parts by volume of the cement.

The cellulose nanocrystal (CNC) is characterized in that the dispersion treatment is carried out using any one of magnetic stirring, ultrasonic dispersion, high pressure dispersion, and a combination thereof by being added to water.

In order to solve the above problems, the method for preparing a fiber-reinforced high-toughness cement composite composition using cellulose nanocrystals of the present invention comprises adding and dispersing 0.1 to 2 parts by volume of cellulose nanocrystals (CNC) to 100 parts by volume of cement. Cellulose nanocrystal (CNC) dispersion step (S100); and cement; and, based on 100 parts by weight of cement, 30 to 50 parts by weight of water in which cellulose nanocrystal is dispersed, 15 to 40 parts by weight of fly ash, and 100 parts by weight of the cement On the other hand, it includes a mixing step (S200) of mixing 0.1 to 3 parts by volume of a water reducing agent and 0.1 to 2 parts by volume of steel fibers.

The cellulose nanocrystal (CNC) dispersion step (S100) is characterized in that dispersion treatment is performed using any one of magnetic stirring, ultrasonic dispersion, high pressure dispersion, and combinations thereof by injecting cellulose nanocrystal (CNC) into water. do.

As described above, according to the fiber-reinforced high-toughness cement composite composition using cellulose nanocrystals according to the present invention and a method for producing the same, there is an effect of improving compressive strength and flexural strength by mixing cellulose nanocrystals and steel fibers at an optimal mixing ratio. .

1 is a picture comparing CNCs before and after dispersion treatment, (A) CNCs powder before dispersion treatment, (B) is a TEM photo of CNCs powder before dispersion treatment, (C) is a suspension after high pressure dispersion and (D ) Is an enlarged TEM photograph of the suspension.
Figure 2 shows the diameter change of the CNCs according to Example 1, (A) is 1 day, (B) is 3 days, and (C) is the diameter change after 7 days.
3 is data showing zeta potential measurement results of CNCs according to Example 1. FIG.
Figure 4 shows the diameter change of the CNCs according to Example 2, (A) is 1 day, (B) is 3 days, and (C) is the diameter change after 7 days.
5 is data showing zeta potential measurement results of CNCs according to Example 2.
6 shows the diameter change of CNCs according to Example 3, where (A) is 1 day, (B) is 3 days, and (C) is 7 days later.
7 is data showing zeta potential measurement results of CNCs according to Example 3.
8 shows the results of a physical property test of a cement paste conducted based on Table 14, where (A) is an average compressive strength, (B) is an average flexural strength, and (C) is an average tensile strength.
9 shows the results of the compressive strength test of the fiber-reinforced high-toughness cement composite (ECC) conducted based on Table 15, where (A) is a fiber-reinforced ECC, (B) is a flax fiber-reinforced ECC, (C) Is the ECC reinforced with steel fibers.
10 shows the results of the flexural strength test of the fiber-reinforced high-toughness cement composite (ECC) conducted based on Table 15, where (A) is a fiber-reinforced ECC, (B) is a flax fiber-reinforced ECC, and (C) is ECC reinforced with steel fibers.
11 is a SEM (20K) photograph for confirming the dispersibility of CNCs in cement in cement.
12 is a SEM (5K) photograph of the ECC test body reinforced with flax fibers.

Specific features and advantages of the present invention will be described in detail below with reference to the accompanying drawings. Prior to this, when it is determined that a detailed description of functions and configurations related to the present invention may unnecessarily obscure the subject matter of the present invention, a detailed description will be omitted.

The present invention relates to a fiber-reinforced high-toughness cement composite composition using cellulose nanocrystals and a method for manufacturing the same, and more particularly, to a fiber-reinforced high toughness that improves compressive strength and flexural strength by mixing cellulose nanocrystals and steel fibers at an optimal blending ratio. It relates to a cement composite composition and a method of manufacturing the same.

The fiber-reinforced high toughness cement composite composition using cellulose nanocrystals of the present invention is based on 100 parts by weight of cement, 30 to 50 parts by weight of water, 30 to 50 parts by weight of sand, 15 to 40 parts by weight of fly ash, and 100 parts by weight of the cement For this, 0.1 to 3 parts by volume of a water reducing agent, 0.1 to 2 parts by volume of steel fibers, and 0.1 to 2 parts by volume of a cellulose nanocrystal (CNC) are included.

As for the cement, one type of ordinary Portland cement can be used, and more specifically, specific gravity 3.0 to 3.2 g/cm 3, powder degree 3000 to 4000 ㎠/g, initial setting time 200 to 300 minutes, final setting time 300 to 600 minutes, Normally Portland cement, which has a stability of 0.1 to 0.5%, can be used.

As for the sand, it is preferable to use sand having a size that passes through 90% or more of the standard 0.08mm mesh, and the SiO ₂ content is preferably from 98% to 99.99%.

Fly ash is effective in improving fluidity due to the ball bearing effect due to the spherical shape, and one having a specific surface area of 2000 to 5000 ㎠/g and a density of 1.5 to 3 g/cm3 can be used, but limited to this. Is not.

Steel fibers may have a strength of 500 to 4000 MPa, a density of 5 to 10 g/cm 3, a diameter of 0.1 to 1 mm, and a length of 10 to 100 mm, but are not limited thereto.

A water reducing agent (Superplasticizer) is used to increase the fluidity of the cement composition, and the water reducing agent is preferably selected from one of lignin-based, naphthalene-based, melamine-based, and polycarboxylic acid-based.

Cellulose nanocrystal (CNC) is manufactured through chemical treatment of cellulose-based fibers.

Cellulose-based fibers can be obtained from terminal hair fibers, bast fibers, leaf vein fibers, and fruit fibers, and specific examples include cotton and kapok as terminal hair fibers, and flax, germ, hemp, jute as bast fibers It may, and may include manila hemp and sisal hemp as leaf vein fibers, and may include palm fibers as fruit fibers, but are not limited thereto.

In order to obtain cellulose nanocrystals from the cellulose fibers, pretreatment is performed using an alkali solution and a buffer solution.

The cellulose fiber is composed of cellulose and non-cellulose components such as pectin, hemicellulose, lignin, wax, and fat, and pretreatment with an alkaline solution promotes swelling and hydrolysis reactions, resulting in cellulose nanoparticles having excellent crystallinity within a shorter time. You will be able to produce crystals.

The alkali solution may include sodium hydroxide and potassium hydroxide, but is not limited thereto.

At this time, the concentration of the sodium hydroxide solution may be 1 to 5% (w/v), the concentration of the potassium hydroxide solution may be used having a concentration of 3 to 7% (w/v), and at a reaction temperature of 60 to 85 °C for 30 minutes to Alkaline treatment is performed for 5 hours.

The alkali-treated cellulosic fibers may be further subjected to bleaching treatment in a buffer solution of sodium chlorite and acetic acid having a pH of 4 to 6.

Cellulose-based fibers pretreated with an alkali solution and a buffer solution undergo a hydrolysis step to decompose amorphous regions contained in the cellulosic fibers and form cellulose nanocrystals.

At this time, the hydrolysis method includes a method of using an acid solution, and the acid solution may be a strong acid such as hydrochloric acid, sulfuric acid, phosphoric acid, hydrobromic acid, nitric acid, and more preferably, a sulfuric acid solution.

This is because nanocrystals made of sulfuric acid solution do not aggregate with each other and have excellent dispersibility compared to nanocrystals made of other strong acids.When sulfuric acid is added to the cellulose fiber, some of the hydroxyl groups on the surface of the cellulose nanocrystals become esterified with sulfuric acid. ) was the sulfate ester group (-SO ₃ negatively charged ^- are changed to), to the surface of the cellulose nanocrystals formed a negative electrostatic layer of the particles repel each other, each able to exist in a stable state well dispersed in the solvent do.

At this time, the concentration of the acid solution is preferably 20 to 70% (w/v), and the reaction is performed at 30 to 60°C for 6 hours to 18 hours. If the concentration, temperature, and time range are less than the above range, the amorphous region cannot be removed and agglomeration phenomenon occurs between the fibers.When mixing the cement composite composition, sufficient strength cannot be given. Since decomposition is involved, the length and diameter of the cellulose nanocrystals are too small, and the dispersibility is deteriorated, it is preferable not to deviate from the above concentration, temperature, and time range.

Thereafter, it undergoes a washing process to remove the residual acid solution, and is then powdered and manufactured through processes such as drying and spray drying.

In addition, there is also a method of specifically hydrolyzing an amorphous region of cellulose using a cellulase, wherein the cellulase may be selected from any one of endoglucanases, exoglucanases, cellobiohydrolases, and combinations thereof.

Cellulose nanocrystal (CNC) has a specific surface area of 100 to 1000 m 2 /g, an average particle diameter of 1 to 100 μm, a crystal density of 0.5 to 5 g/cm 3, a weight moisture content of 3 to 8%, an average crystal diameter of 2 to 5 nm, and an average length of crystals 20 to 150 nm, pH 6 to 7, bulk density 0.5 to 1.5 g/cm 3, crystal fraction (XRD measurement) 0.6 to 1.0, ionic strength 230 to 270 mmol/kg, zeta potential ±30 to ±60 mV. , The dispersibility and property improvement effect is excellent under the above characteristic conditions.

The cellulose nanocrystal (CNC) may be dispersed in water using any one of magnetic stirring, ultrasonic dispersion, high pressure dispersion, and combinations thereof, and then introduced in the form of a dispersion.

As a result, the cellulose nanocrystals are uniformly dispersed in the cement and sand particles, and aggregation can be prevented, thereby maximizing the strength enhancing effect.

Preferably, after first removing the agglomeration through magnetic stirring, the second dispersion may be performed using either high pressure dispersion or ultrasonic dispersion, and the zeta potential is dispersed to have a zeta potential of ±30 to ±60mV.

The magnetic stirring is carried out for 5 to 30 minutes at a rotational speed of 1,000 to 2,000 rpm per minute using a magnetic stirrer after 0.1 to 30 parts by weight of cellulose nanocrystals (CNCs) are mixed with respect to 1,000 parts by weight of distilled water.

At this time, the container in which the distilled water and cellulose nanocrystals (CNCs) will be accommodated is a container that is 10 to 30% larger than the volume of distilled water, so that the reactants (distilled water and CNCs) are not leaked out or lost to the outside of the container due to the fast rotation speed during stirring. This is desirable.

In addition, the size of the magnetic bar is not limited, but it is preferable to use a magnetic force of 1,000 to 10,000 Gauss.

The high-pressure dispersion is performed using a high-pressure disperser, and dispersion treatment is performed 1 to 5 times at a pressure of 3,000 to 30,000 psi.

The ultrasonic dispersion is performed for 5 to 30 minutes under an intensity of 30,000 to 50,000 J.

More preferably, it is also possible to further prevent agglomeration by hydrophobic treatment during the dispersion process of the cellulose nanocrystals.

As the hydrophobic treatment agent for cellulose nanocrystals, any one of a fluorine-based surfactant, a silicone-based surfactant, a silane coupling agent, and a combination thereof may be used.

The silane coupling agent is a vinyl silane coupling agent, an alkoxysilane coupling agent, an aminosilane coupling agent, an epoxy silane coupling agent, a methacryloxysilane coupling agent, an acryloxysilane coupling agent, a ureide silane coupling agent, and a mercaptosilane coupling agent. And any one of a group selected from a combination thereof may be used.

The hydrophobic treatment agent is mixed with the acid-treated cellulose nanocrystal extract in the spray drying process for obtaining the cellulose nanocrystals described above and spray-dried to be treated with a hydrophobic coating, or dispersed in water during the dispersion process of the cellulose nanocrystals to be treated. I can.

More preferably, it may be carried out before performing high-pressure dispersion or ultrasonic dispersion after magnetic stirring, and hydrophobic treatment may be performed by mixing 0.05 to 3 parts by weight of the hydrophobic treatment agent with respect to 100 parts by weight of water.

Hereinafter, a method of manufacturing a fiber-reinforced high toughness cement composite composition using cellulose nanocrystals according to the present invention will be described.

The manufacturing method of the fiber-reinforced high-toughness cement composite composition using cellulose nanocrystals according to the present invention is a method for manufacturing the fiber-reinforced high-toughness cement composite composition using the above-described cellulose nanocrystals, and in the case described above in describing the manufacturing method If so, the explanation will be omitted.

The manufacturing method of the fiber-reinforced high-toughness cement composite composition using cellulose nanocrystals according to the present invention is a cellulose nanocrystal (CNC) in which 0.1 to 2 parts by volume are added and dispersed with respect to 100 parts by volume of cement in water. ) Dispersion step (S100) and cement; and, based on 100 parts by weight of cement, 30 to 50 parts by weight of water in which cellulose nanocrystals are dispersed, 15 to 40 parts by weight of fly ash, based on 100 parts by weight of the cement, 0.1 to 3 water reducing agents It includes a mixing step (S200) of mixing the volume part and 0.1 to 2 volume parts of steel fibers.

The manufacturing method of the fiber-reinforced high-toughness cement composite composition using cellulose nanocrystals according to the present invention according to the present invention comprises a manufacturing step of preparing a cellulose nanocrystal for preparing a cellulose nanocrystal before the cellulose nanocrystal (CNC) dispersion step (S100). Can include.

In the cellulose nanocrystal manufacturing step, the cellulose nanocrystal may be obtained by the method for manufacturing the cellulose nanocrystal described above, and a detailed description thereof will be omitted as described above.

Cellulose nanocrystal (CNC) has a specific surface area of 100 to 1000 m 2 /g, an average particle diameter of 1 to 100 μm, a crystal density of 0.5 to 5 g/cm 3, a weight moisture content of 3 to 8%, an average crystal diameter of 2 to 5 nm, and an average length of crystals 20 to 150 nm, pH 6 to 7, bulk density 0.5 to 1.5 g/cm 3, crystal fraction (XRD measurement) 0.6 to 1.0, ionic strength 230 to 270 mmol/kg, zeta potential ±30 to ±60 mV. , The dispersibility and property improvement effect is excellent under the above characteristic conditions.

In the cellulose nanocrystal (CNC) dispersing step (S100), a dispersion is formed by dispersing the cellulose nanocrystal (CNC) in water, and the dispersion method includes any one of ultrasonic dispersion, magnetic stirring, high pressure dispersion, and combinations thereof. It is done using

As a result, the cellulose nanocrystals are uniformly dispersed in the cement and sand particles, and aggregation can be prevented, thereby maximizing the strength enhancing effect.

Preferably, after first removing the agglomeration through magnetic stirring, the second dispersion may be performed using either high pressure dispersion or ultrasonic dispersion, and the zeta potential is dispersed to have a zeta potential of ±30 to ±60mV.

The magnetic stirring is carried out for 5 to 30 minutes at a rotational speed of 1,000 to 2,000 rpm per minute using a magnetic stirrer after 0.1 to 30 parts by weight of cellulose nanocrystals (CNCs) are mixed with respect to 1,000 parts by weight of distilled water.

At this time, the container in which the distilled water and cellulose nanocrystals (CNCs) will be accommodated is a container that is 10 to 30% larger than the volume of distilled water, so that the reactants (distilled water and CNCs) are not leaked out or lost to the outside of the container due to the fast rotation speed during stirring. This is desirable.

In addition, the size of the magnetic bar is not limited, but it is preferable to use a magnetic force of 1,000 to 10,000 Gauss.

The high-pressure dispersion is performed using a high-pressure disperser, and dispersion treatment is performed 1 to 5 times at a pressure of 3,000 to 30,000 psi.

The ultrasonic dispersion is performed for 5 to 30 minutes under an intensity of 30,000 to 50,000 J.

More preferably, it is also possible to further prevent agglomeration by hydrophobic treatment during the dispersion process of the cellulose nanocrystals.

As the hydrophobic treatment agent for cellulose nanocrystals, any one of a fluorine-based surfactant, a silicone-based surfactant, a silane coupling agent, and a combination thereof may be used.

The silane coupling agent is a vinyl silane coupling agent, an alkoxysilane coupling agent, an aminosilane coupling agent, an epoxy silane coupling agent, a methacryloxysilane coupling agent, an acryloxysilane coupling agent, a ureide silane coupling agent, and a mercaptosilane coupling agent. And any one of a group selected from a combination thereof may be used.

The hydrophobic treatment agent is mixed with the acid-treated cellulose nanocrystal extract in the spray drying process for obtaining the cellulose nanocrystals described above and spray-dried to be treated with a hydrophobic coating, or dispersed in water during the dispersion process of the cellulose nanocrystals to be treated. I can.

More preferably, it may be carried out before performing high-pressure dispersion or ultrasonic dispersion after magnetic stirring, and hydrophobic treatment may be performed by mixing 0.05 to 3 parts by weight of the hydrophobic treatment agent with respect to 100 parts by weight of water.

In the mixing step (S200), based on 100 parts by weight of cement and cement, 30 to 50 parts by weight of water in which cellulose nanocrystals are dispersed, 15 to 40 parts by weight of fly ash, and 0.1 to 3 parts of water reducing agent per 100 parts by weight of the cement The skin and 0.1 to 2 parts of the steel fiber are mixed.

Hereinafter, the present invention will be described in detail with reference to a preferred embodiment. However, the following examples are intended to specifically illustrate the present invention, and are not limited thereto.

1. Preparation of ingredients

The cement used is one type, usually Portland cement, and its properties are shown in Table 1 below.

The sand used was KCL standard yarn (SiO2 content of 98% or more), and the mass fraction according to the particle diameter of the sand is shown in Table 2 below.

2. Preparation of cellulose nanocrystal dispersion

A cellulose nanocrystal (CNC) purchased from Canadian company C was prepared.

Table 3 below shows the physical properties of the cellulose nanocrystal (CNC) used in the present invention. (A) of FIG. 1 shows a TEM photograph (×500) of CNCs powder, and (B) is a CNCs powder.

Parameter product form appearance
(color) crystallite density specific surface area Particle diameter
(crystallite) particle
length
(crystallite) pH specification Powder White 1.5g / cm ³ 400m ² / g 2.3∼4.5 nm (by AFM) 44-108 nm
(by AFM) 6-7

Magnetic stirring

A 3-position/integral plate was used as a magnetic stirrer, and 400 ml of distilled water was filled in a 500 ml beaker, and cellulose nanocrystals (CNCs) were added. Since the addition of a large amount of cellulose nanocrystals (CNCs) can cause gelation, 1 g of CNCs was added to maintain the colloidal state without affecting the rotation of the magnetic bar. Magnetic stirring was performed for a rotational speed of 1500rpm per minute and a dispersion time of 10 minutes using a 23mm magnetic bar.

High pressure dispersion

The cellulose nanocrystal suspension dispersed through a magnetic stirrer was dispersed under high pressure using a high-pressure disperser with varying dispersion pressures (5,000, 15,000, 23,000 psi) and number of dispersions (1 to 3 pass).

Fig. 1 (C) shows a suspension of CNCs subjected to a high pressure dispersion process, and (D) shows a TEM photograph magnified × 40,000, and it can be seen that the CNCs are well dispersed in distilled water after the dispersion treatment.

In order to evaluate dispersibility and dispersion retention, changes in the average diameter and average diameter size were checked after 1, 3, and 7 days after the high-pressure dispersion was performed, and zeta potential analysis was performed.

The Zeta Potential is used as an important measure to evaluate the stability of Colloidal Dispersion because it represents the degree of repulsion between adjacent particles charged in the dispersion. When the negative (-) or positive (+) Zeta Potential value is high, aggregation between particles does not occur and dispersion stability is good, and when the value is low, the attraction between particles acts more and it is easy to coagulation or flocculation.

In general, when the zeta potential value is 0 to ± 30 mV, it is judged to have unstable dispersion, and when the zeta potential value is between ± 30 mV and ± 60 mV (when the absolute value is 30 to 60 mV), the dispersion is stable. It can be judged as.

Example 1 is to perform high-pressure dispersion under 5,000 psi, Example 2 is to perform high-pressure dispersion under 15,000 psi, and Example 3 is to perform high-pressure dispersion under 23,000 psi.

In order to confirm the change in the average diameter according to the number of dispersions, Examples 1 to 3 were all carried out 1 to 3 times, and the diameter values were measured after the 1st, 2nd, and 3rd runs of the number of dispersions.

Figure 2 shows the diameter change of the CNCs according to Example 1, (A) shows the diameter change after 1 day, (B) 3 days, and (C) 7 days.

Table 4 below is the average diameter value measured after 1 day of CNCs according to Example 1, Table 5 is the average diameter value measured after 3 days of CNCs according to Example 1, and Table 6 is the average diameter value of CNCs according to Example 1. It shows the average diameter value measured after 7 days.

Variance 1pass 2pass 3pass Average diameter (nm) 91.5454 82.2061 79.9046

Variance 1pass 2pass 3pass Average diameter (nm) 92.1298 82.8799 80.7117

Variance 1pass 2pass 3pass Average diameter (nm) 89.8048 81.8922 80.4522

As a result, as the number of dispersion increases, the average diameter tends to decrease, and the change in diameter from 1 to 7 days after high-pressure dispersion is insignificant, so that aggregation does not occur, and dispersion stability is excellent.

3 shows data showing the zeta potential measurement result of CNCs according to Example 1. As a result of the zeta potential analysis, it was confirmed that the zeta potential value was -50.25 mV at a dispersion pressure of 5,000 psi, indicating excellent dispersibility.

Figure 4 shows the diameter change of the CNCs according to Example 2, (A) shows the diameter change after 1 day, (B) 3 days, and (C) 7 days.

Table 7 below shows the average diameter values measured after 1 day of CNCs according to Example 2, Table 8 is the average diameter values measured after 3 days of CNCs according to Example 2, and Table 9 shows the CNCs according to Example 2. It shows the average diameter value measured after 7 days.

Variance 1pass 2pass 3pass Average diameter (nm) 83.1936 79.6807 76.6127

Variance 1pass 2pass 3pass Average diameter (nm) 84.2621 78.5334 77.2400

Variance 1pass 2pass 3pass Average diameter (nm) 81.2812 75.2890 74.7776

As in Example 1, in Example 2, as the number of dispersions increased, the average diameter decreased, and it was confirmed that there was no large change in diameter from 1 to 7 days after high-pressure dispersion.

5 shows data showing the zeta potential measurement result of CNCs according to Example 2, as a result of the zeta potential analysis, the zeta potential value was measured as -47.81 mV at a dispersion pressure of 15,000 psi, confirming that the dispersion property was excellent.

6 shows the diameter change of CNCs according to Example 3, where (A) shows the change in diameter after 1 day, (B) 3 days, and (C) 7 days.

Table 10 below is the average diameter value measured after 1 day of CNCs according to Example 3, Table 11 is the average diameter value measured after 3 days of CNCs according to Example 3, and Table 12 is the average diameter value of CNCs according to Example 3. It shows the average diameter value measured after 7 days.

Variance 1pass 2pass 3pass Average diameter (nm) 72.3224 64.5370 63.7265

Variance 1pass 2pass 3pass Average diameter (nm) 71.3466 63.9299 62.6828

Variance 1pass 2pass 3pass Average diameter (nm) 70.3422 64.7147 63.2365

As the number of dispersion increased, the average diameter tended to decrease, but it was found that the change in the average diameter size of the second and third dispersions was insignificant. Through this, as the overall pressure increased and the number of dispersion increased, Although the average diameter tends to decrease, it is desirable to perform the number of dispersions 1 to 5 times in consideration of the required average diameter and dispersion efficiency, as the higher the high pressure dispersion pressure, the smaller the average diameter decreases from the second round. Was judged.

7 shows data showing the zeta potential measurement result of CNCs according to Example 3, and as a result of the zeta potential analysis, the zeta potential value was measured as -46.69 mV at a dispersion pressure of 23,000 psi, confirming that the dispersion property was excellent.

As described above, it was observed that the cellulose nanocrystal with improved dispersibility according to the present invention had a small change in the size of the average diameter, and that the state was maintained for a long time. In the case of the zeta potential analysis value, the absolute value was 30 or more. It was confirmed that the dispersibility and dispersion stability were high.

In order to check the dispersion according to the dispersion method and the dispersion pressure, CNCs (Comparative Example 1) that performed only magnetic stirring (1500rpm, magnetic bar 23mm, 10 minutes), CNCs that performed only high-pressure dispersion (15,000psi, one time) ( Comparative Example 2), CNCs performing ultrasonic dispersion (20 kHz, output 750 W, 10 minutes) (Comparative Example 3), untreated CNCs (Comparative Example 4), magnetic stirring (1500 rpm, magnetic bar 23 mm, 10 minutes) + high pressure dispersion The average diameter and zeta potential measurements were confirmed after 1, 3, and 7 days of CNCs (Comparative Example 5) performed (2500psi, once).

Table 13 below shows the average diameter and zeta potential measured values of Comparative Examples 1 to 5.

Average diameter (nm) Zeta potential (mV) 1 day 3 days 7 days Comparative Example 1 103.5874 106.7469 108.4268 -26.45 Comparative Example 2 98.4568 99.5486 100.0054 -36.59 Comparative Example 3 87.5642 88.5565 89.2156 -41.66 Comparative Example 4 124.6859 129.3321 131.3575 -16.34 Comparative Example 5 92.6554 95.2622 96.5644 -28.39

As a result, it was confirmed that the diameter of the untreated CNCs was the highest and the absolute value of the zeta potential was also as low as 16, indicating that the dispersion characteristics were poor.This is due to the occurrence of aggregation between particles due to the hydrophilicity of CNCs. Was judged. In addition, dispersibility was superior when magnetic stirring and high-pressure dispersion were performed together rather than magnetic stirring or high-pressure dispersion alone. Even if magnetic stirring and high-pressure dispersion were performed together, it is difficult to obtain satisfactory dispersion when the high-pressure dispersion pressure is low. Could be confirmed.

In addition, it was confirmed that the dispersibility was the best when the CNCs were first magnetically stirred and dispersed at high pressure in the second.

3. Preparation of cement composition

During cement hardening, the hydration product forms a shell around the unhydrated cement particles, slowing the diffusion of water into the shell. This phenomenon affects the hydration in the cement core and consequently affects the strength. The CNC in the cement acts as a water path to the unhydrated cement core, thus affecting the strength enhancement. Therefore, in this experiment, the strength characteristics of cement paste according to the CNC mixing rate were analyzed, and based on the results, a fiber reinforced ECC type using mortar added with fine aggregate and additional steel fiber and flax fiber to examine the change in strength according to the increase in the mixing rate. The mechanical properties of the cement composite were analyzed.

Cement paste and ECC formulations using aqueous solutions according to the CNC mixing ratio are shown in Tables 14 and 15, respectively. In the case of cement paste, strength tests were conducted according to the amount of mixing 0.1, 0.2, and 0.4 (vol.%) compared to cement, and in the case of ECC, to more clearly evaluate the strength characteristics according to the amount of CNC increase based on the results of the previous cement paste basic test. Cement composites with mixing ratios of 0.4, 0.8, and 1.2 (vol.%) were prepared. In addition, the fiber was reinforced according to the CNC mixing ratio to compare the strength characteristics according to the CNC mixing ratio and the fiber presence.

In addition, as the amount of CNC mixed increases, the water absorption power due to the hydrophilic property increases, so the fluidity decreases during cement mixing. In order to maintain a constant flow value accordingly, the amount of water reducing agent was increased as shown in Table 15.

The flax fiber used in the experiment had a tensile strength of 1500 MPa (density 1.5g/cm3), and the steel fiber was 2750 MPa (density 7.75g/cm3).

In the case of the compressive strength test, it was carried out according to KS L ISO 679, and the 28-day average compressive strength according to the amount of CNC mixing and fibers were compared after being manufactured in a mortar mold (50mm×50mm×50mm).In the case of bending strength, the beam according to KS F 2408 A mold (40mm×40mm×160mm) experiment was conducted, and after it was manufactured in a dog-bone (25.4mm×25.4mm×76.2mm) mold, the experiment was conducted according to KS F 5104. In addition, SEM (Scanning Electrochemical Microscope) analysis was performed to confirm the shape of the CNC in the cement according to the strength characteristics analysis.

4. Experimental results and discussion

4.1 Cement paste strength test result

8 shows the results of the physical property test of the cement paste conducted based on Table 14, where (A) shows the average compressive strength, (B) shows the average flexural strength, and (C) shows the average tensile strength.

The 28-day average compressive strength of the cement paste was 47 MPa in plain, and the strength increased rapidly as the CNC aqueous solution was added. From CNC 0.1 (vol.%) or higher, the increase in strength was insignificant, and at 0.4 (vol.%), the result was improved by about 40% compared to Plain. In the case of the average flexural strength, it was confirmed that the strength increase range was large in the test specimen added with the CNC aqueous solution, as in the compressive strength. In the case of flexural strength, as the amount of CNC mixed increased, the strength increased, and at 0.4 (vol.%), the result was about 8 times higher than that of plain. The results of the average tensile strength test showed a similar pattern to the flexural strength. As the CNC aqueous solution was added, the strength increased rapidly, and the result was slightly increased from 0.1 to 0.2 (vol.%) of CNC, and then increased 5 times compared to Plain at 0.4 (vol.%). This strength test result is judged to be due to the increase in C-S-H gel generation as the addition of CNC affects the hydration in the cement core.

4.2 Fiber reinforced high toughness cement composite (ECC) strength test result

9 shows the results of the compressive strength test of the fiber-reinforced high-toughness cement composite (ECC) conducted based on Table 15, where (A) is a fiber-reinforced ECC, (B) is a flax fiber-reinforced ECC, (C) Shows the ECC reinforced with steel fibers.

As a result of confirming the compressive strength characteristics of CNC-reinforced cement composites that were not reinforced with ECC fiber mixed with CNC, the strength was improved as CNC was added. At 0.4 and 0.8 (vol.%), the maximum increased about 40% compared to plain, and at 1.2 (vol.%), the strength decreased. It was judged that when a large amount of CNCs were mixed, agglomeration phenomenon occurred in the cement, thereby interfering with hydration.

As a result of checking the compressive strength characteristics according to the CNC mixing ratio reinforced with flax fiber, the highest strength was shown at 0.8 (vol.%) even in the test specimen reinforced with flax fiber. However, even if CNC was added when reinforcing flax fiber, there was a tendency that the strength increase width was not large. This is believed to be a factor due to the generation of voids due to fibers in the cement.

As a result of confirming the compressive strength characteristics of the CNC-mixed cement composite reinforced with steel fiber, the strength change was insufficient except for the 0.8 (vol.%) test specimen, which showed an increase rate of about 15% compared to plain, in the test specimen containing steel fiber.

10 shows the results of the flexural strength test of the fiber-reinforced high-toughness cement composite (ECC) conducted based on Table 15, where (A) is a fiber-reinforced ECC, (B) is a flax fiber-reinforced ECC, and (C) is It shows the ECC reinforced with steel fibers.

As a result of confirming the flexural strength characteristics according to the mixing ratio of the CNC without fiber mixing, the pattern was similar to that of the plain test sample at 0.4 and 1.2 (vol.%), and increased about 2.5 times compared to the plain at 0.8 (vol.%). Showed.

In the test sample containing flax fiber, the change in flexural strength was insufficient compared to the plain test sample. However, when steel fibers were mixed, a slight increase was observed at 0.4 and 1.2 (vol.%), and approximately doubled at 0.8 (vol.%).

4.3 SEM analysis result

11 is an SEM (20K) for confirming the dispersibility of CNCs in the cement in cement, and it was confirmed that the CNCs particles in the shape of a rod were distributed in the cement, which serves to help hydration into the cement core. Is judged.

12 shows the results of SEM (5K) analysis of the ECC test specimen reinforced with flax fibers, and it was determined that the addition of flax fibers causes a void phenomenon to be a factor of strength reduction.

5. Conclusion

In this study, a cement paste according to the mixing rate of CNC was tested, and the ECC was produced according to the increase of the mixing rate, and the strength characteristics were compared.

As follows.

1) In the cement paste mixed with CNC, the effect of improving the strength by the increase of the mixing ratio was shown. In the test sample mixed with 0.4 (vol.%), the compressive strength improved by about 40% compared to the plain, and the bending and tensile strength were 5-8 compared to the plain. It showed a double improvement result.

2) As a result of comparison of the ECC strength test according to the increase of the CNC mixing ratio, the test specimen reinforced with flax fiber showed a tendency that the change in strength was insufficient compared to plain. It was judged that the loss occurred due to the absorption of the CNC aqueous solution due to the characteristics of the pores around the fibers and the high water absorption rate of natural fibers, which hindered the hydration function. However, in the specimen reinforced with steel fibers, the strength generally increased. Among them, bending

In the case of the strength test, the result was approximately doubled at 0.8 (vol.%), and in the overall failure pattern, it was found that the ductile effect was seen in the specimen containing CNC compared to the brittle fracture in the plain.

3) When comparing the strength development in cement according to the amount of CNC mixing, it was judged that the proper mixing ratio was 0.8 (vol.%), and when mixing more than that, the strength showed a tendency to decrease. This is believed to be due to the phenomenon of clumping without being dispersed in the cement when a large amount of CNC is mixed.

As described above, the present invention has been described based on preferred embodiments with reference to the accompanying drawings, but those of ordinary skill in the technical field to which the present invention pertains within the scope not departing from the technical spirit and scope described in the claims of the present invention. In various modifications or variations of the present invention can be implemented. Accordingly, the scope of the invention should be construed by the claims set forth to include examples of such many variations.

Claims (4)

Based on 100 parts by weight of cement, 30 to 50 parts by weight of water; 30 to 50 parts by weight of sand; and 15 to 40 parts by weight of fly ash; and
With respect to 100 parts by volume of the cement, 0.1 to 3 parts by volume of a water reducing agent; 0.1 to 2 parts by volume of steel fibers; and 0.1 to 2 parts by volume of cellulose nanocrystal (CNC)
Fiber reinforced high toughness cement composite composition using cellulose nano crystals.
The method of claim 1,
The cellulose nanocrystal (CNC) is
It is characterized in that the dispersion treatment is carried out using any one of magnetic stirring, ultrasonic dispersion, high pressure dispersion, and combinations thereof by putting it in water.
Fiber reinforced high toughness cement composite composition using cellulose nano crystals.
Cellulose nanocrystal (CNC) dispersion step (S100) of injecting and dispersing 0.1 to 2 parts by volume of cellulose nanocrystal (CNC) in water with respect to 100 parts by volume of cement; And
Cement; With respect to 100 parts by weight of cement, 30 to 50 parts by weight of water in which cellulose nanocrystals are dispersed, 15 to 40 parts by weight of fly ash, based on 100 parts by volume of the cement, 0.1 to 3 parts by volume of water reducing agent, 0.1 to 2 parts by weight of steel fibers Characterized in that it comprises a mixing step (S200) of mixing the volume part
Method for producing a fiber-reinforced high toughness cement composite composition using cellulose nanocrystals.
The method of claim 3,
The cellulose nanocrystal (CNC) dispersion step (S100)
Characterized in that the dispersion treatment is performed using any one of magnetic stirring, ultrasonic dispersion, high pressure dispersion, and combinations thereof by injecting cellulose nanocrystal (CNC) into water.
Method for producing a fiber-reinforced high toughness cement composite composition using cellulose nanocrystals.

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