KR20200021266A - Binder composition comprising fly ash and high-strength binder prepared therefrom - Google Patents

Abstract

The present invention relates to a binder composition including fly ash and a high strength binder prepared therefrom. According to the present invention, a specific content of formate is mixed with a binder obtained by mixing fly ash which is an industrial by-product and quicklime (CaO) to form a C-S-H bond, AFm phase, and katoite and calcite crystals in a binder after curing, and to increase a ratio thereof at the same time, thereby reducing pores and enhancing the initial strength and the long-term strength over time. The binder of the present invention may exhibit the strength the same as or higher than that of a cement-based binder, thereby being used as a binder substituted for the conventional cement-based binder.

Description

Binder composition comprising a fly ash and a high-strength binder prepared therefrom BINDER COMPOSITION COMPRISING FLY ASH AND HIGH-STRENGTH BINDER PREPARED THEREFROM

The present invention relates to a binder composition comprising a fly ash and a high strength binder prepared therefrom. Specifically, the present invention relates to a technology for obtaining an environmentally friendly and cost-competitive binder that can replace an existing cement-based binder using a composition mixed with formate of fly ash, which is an industrial by-product.

Portland cement is a structural material widely used in the construction of various social overhead capital such as roads, bridges, tunnels, harbors, houses, buildings. Such cement is manufactured through a high temperature firing process using limestone as a main raw material, and in this process, about 0.7 to 1.0 ton of carbon dioxide gas is discharged per ton of cement produced.

Accordingly, research on replacing cement by recycling industrial by-products is being conducted in an environmental aspect (see Korean Laid-Open Patent Publication No. 2002-0070527).

Recycling industrial by-products to replace cement can reduce the carbon dioxide emissions from cement production, which can have a positive impact on the global environment. Research into recycling fly ash, a major industrial by-product of thermal power plants, has been ongoing since the early 20th century. In Korea, fly ash is mainly used as a mixed material of mortar and concrete, but since most of them use low-calcium fly ash with low activity, the total consumption of fly ash is lower than that of developed countries. In addition, only binders manufactured by mixing some industrial by-products such as fly ash with cement are known (Japanese Patent No. 5688069), and cement-based substitutes which do not use cement at all are not known or in terms of strength. Most of them show poor physical properties.

Korean Unexamined Patent Publication No. 2002-0070527 Japanese Patent No. 5688069

Accordingly, the present invention provides an environmentally friendly binder composition having a level of strength equivalent to or superior to that of cement-based binders, but also to provide a binder composition that can be manufactured more economically in terms of cost.

In order to achieve the above object, the present invention provides a binder composition comprising 100 parts by weight of fly ash, 5 to 40 parts by weight of quicklime (CaO) and 1 to 20 parts by weight of formate.

In order to achieve the above another object, the present invention comprises the steps of (1) preparing a binder composition by mixing 100 parts by weight of fly ash, 5 to 40 parts by weight of quicklime (CaO) and 1 to 20 parts by weight of formate; And (2) it provides a method for producing a binder, comprising the step of curing by mixing water to the composition.

In order to achieve the above another object, the present invention provides a binder obtained by curing the binder composition.

The present invention is to mix the formate to a specific content in a binder of a mixture of fly ash and quicklime (CaO), which is an industrial by-product, after the curing, the katoite crystal in the binder, CSH bond, AFm phase, and calcite By increasing the proportion of these while forming crystals, it is possible to reduce the voids and to increase the initial strength and the long-term strength over time. Thus prepared binder of the present invention may exhibit the same or more strength than the cement-based binder, it can be used as a binder that can replace the conventional cement-based binder.

In addition, since the present invention is mainly composed of fly ash, which is an industrial by-product, it produces less carbon dioxide in the manufacturing process and is environmentally friendly, and it is possible to economically manufacture a desired binder by simply mixing materials without a large manufacturing facility.

Therefore, the binder composition of the present invention and the binder prepared therefrom can be usefully applied to all fields in which cement-based binders can be used, such as construction, tile bonding, joint construction, and the like.

1 is a graph showing the compressive strength according to the curing period of the binder samples (Evaluation Example 1).
2 is an XRD diffraction graph according to the curing period of the binder samples (Evaluation Example 2).
3 is a thermogravimetric analysis of binder samples of age 28 days (Evaluation Example 3).
4 is a graph of ²⁷ Al nuclear magnetic resonance spectroscopy of the binder samples of age 28 days (Evaluation 4).
5 to 7 are graphs showing the pore sizes of the binder samples of age 3 and 28 by mercury intrusion (evaluation example 5).

The present invention is not limited to the contents disclosed below, but may be modified in various forms as long as the gist of the present invention is not changed.

"Including" in the present specification means that it may further include other components unless otherwise specified. In addition, all numbers and expressions indicating the amounts of ingredients, reaction conditions, and the like described herein are to be understood as being modified in all instances by the term "about" unless otherwise specified.

The present invention provides a binder composition comprising 100 parts by weight of fly ash, 5 to 40 parts by weight of quicklime (CaO) and 1 to 20 parts by weight of formate.

Each of the raw material components may be mixed in a dry state. For example, the composition may be a mixture of the powder of each of the fly ash, quicklime and formate.

Hereinafter, each component will be described in detail.

Fly ash (Fly ash; FA )

Fly ash refers to particulate ash collected by a dust collector of a pulverized coal combustion boiler among coal ashes generated from a coal-fired power plant.

Fly ash is used for the purpose of improving the properties of cement, and is mainly mixed with cement as admixture.

In the present invention, the fly ash may be included as a main component and mixed with other components described below to form a binder having a strength equal to or greater than that of cement.

Fly Ash is SiO ₂ , Al ₂ O ₃ It is a glassy substance containing as a main component, and has a particle shape close to spherical shape.

Specifically, the fly ash may have an average particle diameter of 0.5 to 500 ㎛, 1 to 500 ㎛, 0.5 to 300 ㎛, 0.5 to 280 ㎛, or 0.5 to 235 ㎛, SiO ₂ , Al ₂ O ₃ , Fe ₂ 45 to 70 weight percent, 15 to 30 weight percent, 5 to 15 weight percent, 1 to 10 weight percent of O ₃ , CaO, K ₂ O, MgO, Na ₂ O, TiO ₂ , SO ₃ and P ₂ O ₅ , respectively. , 0.1 to 3 wt%, 0.1 to 3 wt%, 0.1 to 3 wt%, 0.1 to 2 wt%, 0.1 to 2 wt% and 0.1 to 2 wt%.

quicklime( CaO )

Quicklime is an activator that induces the pozzolanic response of the fly ash.

The pozzolanic reaction refers to a reaction in which substances which cannot react with water alone and harden, for example, fly ash, diatomaceous earth, volcanic ash, cement, and the like react with lime in water to cure.

Since the fly ash alone cannot react with and harden with water, it was generally used by activating a strong alkali activator such as NaOH. However, alkali activators have high pH and high price, which causes problems in commercialization.

The present invention can induce pozzolanic reactions by lime-activating fly ashes using quicklime which is cheaper than these alkali activators and has a lower pH. Furthermore, the composition including the quicklime may have properties similar to those of cement by having the same C-S-H bond as cement in the binder after curing.

The quicklime content may be 5 to 40 parts by weight, or 10 to 35 parts by weight based on 100 parts by weight of the fly ash. Within this range, the pozzolanic reaction of the fly ash can be induced at an appropriate rate.

Formate

Formate is generally used as a coagulant, corrosion inhibitor, and cryoprotectant of cement, but in the present invention, it is added to lime-activated fly ash to form CSH bond, alumina-iron oxide-sulphate (AFm phase) crystal, katoite) crystals and calcite crystals can be formed.

C-S-H bond (calcium-silicate-hydrate bond) is the main bond structure present in cement, and AFm phase includes alumina-iron oxide-sulphate as a phase or structure formed in the hydrated binder.

Katoite crystals refer to cube minerals including aluminum, calcium, hydrogen, oxygen, and silicon. Calcite crystals are white or transparent minerals made of calcium carbonate.

Binders containing such bonds and crystals can promote C-S-H bond formation and reduce the porosity and pore size in the cured body, which can significantly improve the strength of the binder.

According to the present invention, the formate may be at least one selected from the group consisting of Ca (HCOO) ₂ , NaHCOO, and KHCOO, and specifically, Ca (HCOO) ₂ , NaHCOO, or KHCOO. In this case, the formate may be 99% pure.

The content of the formate may be 1 to 20 parts by weight, or 1 to 15 parts by weight based on 100 parts by weight of the fly ash. Within this range, it is possible to form CSH bonds, alumina-iron oxide-sulphate (AFm phase) crystals, katowite (katoite) crystals, and calcite crystals in the binder when the binder is formed, thereby improving compressive strength. .

The composition as described above may include a CSH peak, an alumina-iron oxide-sulphate (AFm phase) peak, a katotoite peak, and a calcite peak after X-ray diffraction (XRD) spectrum measurement after curing. . In this case, the CSH peak is a peak due to the CSH bond, the AFm phase peak is a peak due to the presence of alumina-iron oxide-sulphate crystals, the cathotic peak is a peak due to the presence of the cathoid crystals, calcite Peaks each mean a peak resulting from the presence of calcite crystals.

In this case, curing is an environmental treatment applied to the binder to maintain or promote curing of the binder, and specifically, refers to a high temperature wet curing for curing the binder composition under wet environment conditions.

The composition may include a reduced amount of aluminum (Al) after curing compared to before curing. Specifically, since the aluminum is the main component of the fly ash, the fly ash is lime activated by quicklime, and then reacted and cured with formate in water to form the CSH bond, alumina-iron oxide-sulphate (AFm phase) crystal, and katoi. It is reduced by forming a katoite crystal.

High strength Of binder  Manufacturing method

The present invention is to prepare a binder composition by mixing (1) 100 parts by weight of fly ash, 5 to 40 parts by weight of quicklime (CaO) and 1 to 20 parts by weight of formate; And (2) it provides a method for producing a binder, comprising the step of curing by mixing water to the composition.

Age is the number of days since the start of curing by mixing water with the composition.

Step (1) prepares a composition comprising fly ash, quicklime and formate.

The composition may mix these respective raw ingredients in a dry state.

The mixing ratio of the components included in the composition may be 5 to 40 parts by weight, or 10 to 35 parts by weight, based on 100 parts by weight of the fly ash, and formate is 1 to 20 parts by weight, or 1 to 15 parts by weight. It may be wealth.

In step (2), the composition is cured by mixing water. Specifically, in step (2), water may be mixed in an amount of 20 to 50 parts by weight, or 20 to 40 parts by weight based on 100 parts by weight of the composition. When in the said range, it is more advantageous to exhibit high compressive strength after composition curing.

The curing may be carried out for a period of 1 to 50 days, 3 to 40 days, 7 to 30 days, 15 to 30 days, or 25 to 30 days. Within the curing period, the composition can exhibit a higher compressive strength.

 The curing of step (2) may be high temperature wet curing. For example, curing of step (2) can be carried out at a temperature of 40 to 80 ℃ or 50 to 75 ℃ and a relative humidity (RH) of 80% or more, 80 to 95%, or 90 to 99%. .

More specifically, the curing of step (2) may be carried out for 3 to 28 days of mixing with water at 60 ℃ and 95% relative humidity conditions. The compressive strength may be measured according to the standards of KS L 5105, for example. For example, the compressive strength is 8 to 25 MPa at 3 days of age, 10 to 45 MPa at 7 days of age, or 10 to 42 MPa, or at least 10 MPa, at least 13 MPa, 10 to 55 MPa at 28 days of age, or 13 to 51 MPa.

By this method, the present invention can provide a binder obtained by curing the binder composition after curing.

Binder

According to the present invention, the binder may have a plurality of voids. Specifically, the binder may have pores having a size of 50 nm or less, 20 nm or less, 20 to 40 nm, 10 nm to 20 nm, or 10 nm or less in the structure.

The pores in the binder may be divided into capillary pores and air voids (greater than capillary pores). In general, the smaller the proportion of the pores, the better in terms of strength, and the higher the proportion of the capillary pores than the proportion of the air pores.

Including capillary pores with a size of 50 nm or less may have a desirable effect on long-term behaviors such as creep (a phenomenon in which binder deformation increases when a constant load is maintained for a long time) and shrinkage, while larger than 50 nm Including capillary pores can negatively affect strength.

The binder according to the present invention is not only fine in the average size of the capillary pores, but also has a low ratio of capillary pores and air pores compared to conventional cement-based binders, and thus is more effective in improving strength.

 Further, the binder may have a porosity of 50% or less, 40-50%, 30-40%, or 20-30%. When in the above range, the initial strength and the long term strength of the binder can be improved better.

The binder may have a compressive strength of at least 10 MPa, at least 13 MPa, at least 10 MPa, at least 55 MPa, or at least 13 MPa at 25 days or more, or 28 days of age after the start of curing.

As described above, the present invention is to mix the formate to a specific content in a binder of fly ash and quicklime (CaO), which is an industrial by-product, after curing, the catoite crystals in the binder, CSH bond, AFm phase, And by forming calcite crystals and increasing their ratios, it is possible to reduce voids and to increase initial strength and long-term strength over time. Thus prepared binder of the present invention may exhibit the same or more strength than the cement-based binder, it can be used as a binder that can replace the conventional cement-based binder.

In addition, since the present invention is mainly composed of fly ash, which is an industrial by-product, it produces less carbon dioxide in the manufacturing process and is environmentally friendly, and it is possible to economically manufacture a desired binder by simply mixing materials without a large manufacturing facility.

Therefore, the binder composition of the present invention and the binder prepared therefrom can be usefully applied to all fields in which cement-based binders can be used, such as construction, tile bonding, joint construction, and the like.

The above content is described in more detail by the following examples. However, the following examples are only for illustrating the present invention, and the scope of the examples is not limited thereto.

[ Example ]

Example  One: Fly ash  Containing Binder  Preparation of the composition

A binder composition was prepared by mixing 85 parts by weight of fly ash (FA) (Hadong Thermal Power Plant), 15 parts by weight of quicklime (CaO), and 1 part by weight of calcium formate (Ca (HCOO) ₂ ) as formate.

Example  2 to 15: Fly ash  Containing Binder  Preparation of the composition

A binder composition was prepared in the same manner as in Example 1, except that the content (parts by weight) and / or type of the formate described in Table 1 below were used.

FA CaO Formate Ca (HCOO) ₂ NaHCOO KHCOO Control 85 15 - - - Example 1 85 15 One - - Example 2 85 15 2 - - Example 3 85 15 3 - - Example 4 85 15 4 - - Example 5 85 15 5 - - Example 6 85 15 - One - Example 7 85 15 - 2 - Example 8 85 15 - 3 - Example 9 85 15 - 4 - Example 10 85 15 - 5 - Example 11 85 15 - - One Example 12 85 15 - - 2 Example 13 85 15 - - 3 Example 14 85 15 - - 4 Example 15 85 15 - - 5

[ Evaluation example ]

Evaluation Example 1: Compressive Strength

A paste was prepared by mixing 30 parts by weight of water with respect to 100 parts by weight of the composition of Examples 1 to 15. The paste was placed in a 50 mm cube-shaped mold and cured up to 28 days at 60 ° C. and 95% relative humidity to obtain a binder.

The compressive strength of the obtained binder was measured according to the Portland Cement Physical Performance Standard (KS L 5105), and the results are shown in FIG. 1.

Looking at Figure 1, in the case of Examples 1 to 5 added calcium formate, it can be seen that the compressive strength sharply increased at 3 days (initial) age, and confirmed that the compressive strength reached 45 MPa at 28 days of age Can be. In addition, even when sodium formate and potassium formate are added (Examples 6 to 15), it can be seen that the compressive strength is higher than that of the control group without the formate. From this, it can be seen that formate is effective for improving the strength of the binder.

Evaluation Example 2 X-Ray Diffraction (XRD) Analysis

For the compositions of Examples 3, 8 and 13, a binder was prepared in the same manner as in Evaluation Example 1. The binder was cured for 1 day, 3 days and 28 days of age, respectively, and ground and measured by an X-ray diffractometer (D / MAX 2500V / PC, Rigaku Co., Ltd.). The results are shown in FIG.

Referring to FIG. 2, the graph of the control group shows that the CSH peak, the katotoite peak, the calcite peak, and the calcium hydroxide (Ca (OH) ₂ ) peak appear with the crystals present in the fly ash.

On the other hand, the binder prepared from Example 3 containing calcium formate increased the hump of the CSH peak (smooth peak portion emerging from the peak) instead of the sharp decrease in the calcium hydroxide peak, and the AFm phase decreased over time. I could confirm that. Similarly, Examples 8 and 13, including sodium formate and potassium formate, showed similar graphs. From this, it can be seen that the binder prepared from the binder composition including the formate is effective in improving the strength of the binder by increasing the ratio of AFm phase, C-S-H bond, and katowite crystal in the structure.

Evaluation example  3: Heat weight  analysis( Thermo Gravimetric / Derivative Thermo Gravimetric  Analysis; TG / DTG)

For the compositions of Examples 3, 8 and 13, a binder was prepared in the same manner as in Evaluation Example 1. The binder was cured for 28 days and then crushed and analyzed by thermogravimetric analyzer (SDT Q600, TA Instruments). The results are shown in FIG.

Referring to Figure 3, the DTG peak of the C-S-H and AFm phase can be seen in the vicinity of 100 ℃, DTG peak of the calcite can be seen around 600 to 700 ℃.

On the other hand, in the case of the control group, the peak of the calcium hydroxide was observed, it can be confirmed that it remains unreacted, while in the case of Example 3 (including calcium formate), all of the calcium hydroxide is consumed, the peak is not observed and at the same time CSH and katoi Increased peaks in the bonds indicate the formation of CSH and catheters in the binder.

In addition, it can be seen that the binders obtained from the compositions of Examples 3, 8, and 13 are significantly reduced in total weight loss based on the 28-day age. This means that the amount of reactants decreases as C-S-H and catoite crystals form in the binder and their proportions increase. Therefore, it can be seen that the binder containing calcium formate is effective in enhancing the strength of the binder by promoting the formation of C-S-H and the catote.

Evaluation example 4: ²⁷ Al  Nuclear magnetic resonance spectroscopy ( ²⁷ Al  Magic Angle Spinning Nuclear Magnetic Resonance; ²⁷ Al MAS NMR)

For the compositions of Examples 3, 8 and 13, a binder was prepared in the same manner as in Evaluation Example 1. The binder was cured for 28 days and then crushed and analyzed by a ²⁷ Al nuclear magnetic resonance spectrometer (400 MHz (C) Solid State Nuclear Magnetic Resonance Spectrometer, Bruker). The results are shown in FIG.

In this case, since fly ash is the main source of Al, all spectra of FIG. 4 are normalized to have the same area as the fly ash. For reference, the fly ash has a peak of tetrahedral coordination centered at 50 ppm, a broad asymmetric pentahedral coordination peak near 50 ppm, and a hexahedral coordination peak near 0 ppm.

Referring to FIG. 4, it can be seen that the peak in the 50 ppm center (a tetrahedral coordination) decreases sharply, indicating that Al in the fly ash is decreased, which is expected to be reduced by dissolution due to the activator (CaO).

On the other hand, since the peak of tetrahedral coordination appeared in the vicinity of 60 to 70 ppm, it can be seen that Al is substituted with a C-S-H bond and / or a catote is formed. In addition, strong hexahedral coordination peaks appeared near 10 ppm, indicating that the AFm phase was formed in the binder.

Evaluation example  5: Binder  Measure porosity Mercury intrusion Mercury Intrusion Porosimetry ; MIP)

For the compositions of Examples 3, 8 and 13, a binder was prepared in the same manner as in Evaluation Example 1. At this time, the binder was prepared in a cube shape of one side 5mm.

After curing the binder for 3 days and 28 days, using a porosity meter (Autopore IV 9500, Micrometrics), by mercury intrusion The porosity and average pore size in the binder were measured. The results are shown in FIGS. 5 to 7.

Referring to FIGS. 5 to 7, the capillary pores having various sizes of about 50 nm were distributed in the control group, whereas in Example 3 (including calcium formate), the pores of 50 nm or less were distributed. It can be seen that the strength is improved.

On the other hand, as the curing time elapses, it can be seen that both the pore volume and the average size of the pores decrease.

Comparing the porosity and the pore size at the same 28-day age, the decrease in porosity while the decrease in pore size is very large, it can be seen that the reduction in pore size is effective to increase the strength.

Claims (13)

A binder composition comprising 100 parts by weight of fly ash, 5 to 40 parts by weight of quicklime (CaO) and 1 to 20 parts by weight of formate. The method of claim 1,
The binder composition is at least one member selected from the group consisting of Ca (HCOO) ₂ , NaHCOO, and KHCOO. The method of claim 1,
The quicklime is a binder composition, which is an activator for inducing a pozzolanic reaction of fly ash. The method of claim 1,
The fly ash has an average particle diameter of 1 to 500 μm,
SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , CaO, K ₂ O, MgO, Na ₂ O, TiO ₂ , SO ₃ and P ₂ O ₅ , respectively, 45 to 70 wt%, 15 to 30 wt%, 5 In amounts of from 15% by weight, 1 to 10% by weight, 0.1 to 3% by weight, 0.1 to 3% by weight, 0.1 to 3% by weight, 0.1 to 2% by weight, 0.1 to 2% by weight and 0.1 to 2% by weight. Binder composition. The method of claim 1,
The binder composition, after curing, comprises a CSH peak, an alumina-iron oxide-sulphate (AFm phase) peak, a katotoite peak, and a calcite peak upon X-ray diffraction (XRD) spectrum measurement. The method of claim 1,
Binder composition, wherein the composition comprises a reduced amount of aluminum (Al) after curing compared to before curing. (1) preparing a binder composition by mixing 100 parts by weight of fly ash, 5 to 40 parts by weight of quicklime (CaO) and 1 to 20 parts by weight of formate; And
(2) mixing and curing water in the composition, a method for producing a binder. The method of claim 7, wherein
In the step (2), the water is mixed in an amount of 20 to 50 parts by weight based on 100 parts by weight of the composition, a method for producing a binder. In claim 7,
Curing of the step (2) is carried out at a temperature of 40 to 80 ℃ and relative humidity (RH) of 80% or more, the manufacturing method of the binder. A binder obtained by curing the binder composition of claim 1. The method of claim 10,
The binder has a plurality of pores, the pores having a size of 20 nm or less. The method of claim 10,
The binder having a porosity of 50% or less. The method of claim 10,
The binder has a compressive strength of at least 13 MPa when the binder is at least 25 days after the start of curing.

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