KR102130653B1 - Binder composition comprising fly ash and nitrate, and high-strength binder prepared therefrom - Google Patents

Abstract

The present invention relates to a binder composition comprising a fly ash and a high strength binder prepared therefrom. Specifically, the present invention is to form a CSH bond, AFm phase, and calcite crystals in the binder after curing by mixing nitrate with a specific content in a binder that mixes industrial by-products fly ash and quicklime (CaO). At the same time, by increasing their proportions, it is possible to reduce voids and improve the initial strength and long-term strength over time. Since the binder of the present invention prepared in this way can exhibit the same or higher strength than the cement-based binder, it can be used as a binder that can replace the conventional cement-based binder.

Description

Fly ash-containing binder composition added with nitrate and high strength binder prepared therefrom {BINDER COMPOSITION COMPRISING FLY ASH AND NITRATE, 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 eco-friendly and cost-effective binder that can replace the existing cement-based binder by using a composition in which an industrial by-product fly ash is mixed with nitrate.

Portland cement is a structural material widely used in the construction of various social overhead capitals such as roads, bridges, tunnels, ports, houses, and buildings. The cement is produced through a high-temperature calcination process using limestone and the like as a main raw material. In this process, about 0.7 to 1.0 ton of carbon dioxide gas is emitted per ton of cement produced.

Accordingly, research into replacing cement by recycling industrial by-products from an environmental point of view continues (see Korean Patent Publication No. 2002-0070527).

Recycling industrial by-products to replace cement can reduce carbon dioxide emissions from cement manufacturing, which can have a positive impact on the global environment. Since the early 20th century, research into recycling fly ash, a major industrial by-product of thermal power plants, has been ongoing. In Korea, fly ash is mainly used as a material for mixing mortar and concrete, but most use low-calcium fly ash with low activity, so the total consumption of fly ash is lower than that of developed countries.

Recently, cement-free binders that do not use cement have been known (Korean Patent No. 10-0943096), but few binders based on eco-friendly materials such as fly ash have been known, or properties are less than cement in terms of strength. It was mostly showing.

Korean Patent Publication No. 2002-0070527 Korean Registered Patent No. 10-0943096

Accordingly, the present invention is to provide an eco-friendly binder composition having a strength equal to or superior to that of a cement-based binder, but to provide a binder composition that can be more economically produced in terms of cost.

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 nitrate.

In order to achieve the other object, the present invention (1) fly ash 100 parts by weight, 5 to 40 parts by weight of quicklime (CaO) and 1 to 20 parts by weight of nitrate to prepare a binder composition; And (2) mixing and curing the water in the composition.

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

The present invention, by mixing nitrate at a specific content in a binder mixed with fly ash and quicklime (CaO), an industrial byproduct, forms CSH bonds, AFm phases, and calcite crystals in the binder after curing. By increasing the ratio, it is possible to reduce voids and improve initial strength and long-term strength over time. Since the binder of the present invention prepared in this way can exhibit the same or higher 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 based on fly ash, which is an industrial by-product, it is eco-friendly due to less carbon dioxide generation in the manufacturing process, 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 such as construction, tile adhesion, joint construction, etc. can be used.

1 is a graph showing the compressive strength according to the curing period (age) of the binder samples (Evaluation Example 1).
2 is a graph of XRD diffraction analysis according to the curing period of the binder samples (evaluation example 2).
3 to 5 are thermogravimetric graphs of binder samples based on ages 3, 28 and 91 (Evaluation Example 3).
6 is a ²⁷ Al nuclear magnetic resonance spectroscopy analysis graph of the binder samples at the age of 91 days (evaluation example 4).
7 to 9 are graphs obtained by measuring the pore size of the binder samples based on age 3, 28, and 91 by mercury intrusion (evaluation example 5).

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

“Including” in the present specification means that other components may be further included unless otherwise specified. In addition, it should be understood that all numbers and expressions indicative of the amount of ingredients, reaction conditions, and the like described in this specification are modified in all cases with 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 nitrate.

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

Hereinafter, each component will be described in detail.

Fly ash (Fly ash;FA )

Fly ash is a particulate ash that is collected by a dust collector of a pulverized coal combustion boiler among coal ash generated from a coal-fired thermal power plant or the like.

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

In the present invention, it is possible to form a binder having a strength equal to or higher than that of cement by including such a fly ash as a main component and mixing with other components described below.

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

Specifically, the fly ash may have an average particle diameter of 0.5 to 500 μm, 1 to 500 μm, 0.5 to 300 μm, 0.5 to 280 μm, or 0.5 to 235 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% by weight, 15 to 30% by weight, 5 to 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.

quicklime( CaO )

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

The pozzolanic reaction refers to a reaction in which substances that cannot be hardened by reacting with water alone, such as fly ash, diatomaceous earth, volcanic ash, cement, etc., react with lime in water to harden.

Since the fly ash does not react and harden with water alone, it is common to use it by activating it using a strong alkali activator such as NaOH. However, the alkali activator has a problem in commercialization due to its high pH and high price.

The present invention can induce a pozzolanic reaction by activating fly ash using lime, which is cheaper than the alkali activator and has a low pH. Furthermore, the composition containing the quicklime may have properties similar to cement by curing and having the same C-S-H bond as cement in the bonding material.

The content of the quicklime 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. When within the above range, the pozzolanic reaction of fly ash can be induced at an appropriate rate.

nitrate

Nitrates are commonly used as cement condensation accelerators, corrosion inhibitors, and cryoprotectants, but in the present invention, they are added to the lime-activated fly ash to bind CSH in the binder, crystal of alumina-iron oxide-sulfate (AFm phase), and calcite ) Can form crystals.

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

In the composition according to the present invention, the AFm phase may be in a nitrate-AFm phase.

Calcite crystals are white or transparent minerals made of calcium carbonate.

The bonding material containing such bonds and crystals can promote C-S-H bond formation and reduce porosity and void size in the cured body, thereby significantly improving the strength of the bonding material.

According to the present invention, the nitrate may be at least one selected from the group consisting of Ca(NO ₃ ) ₂ and NaNO ₃ , and specifically Ca(NO ₃ ) ₂ or NaNO ₃ .

The content of the nitrate 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. When within the above range, C-S-H bonds in the binder, alumina-iron oxide-AF (AFm phase) crystals, and calcite crystals can be formed when the binder is formed, so that the compressive strength can be further improved.

The composition as described above, after curing, may include a C-S-H peak, an alumina-iron oxide-sulfate (AFm phase) peak, and a calcite peak in X-ray diffraction (XRD) spectrum measurement. At this time, the C-S-H peak refers to a peak resulting from the C-S-H bond, the AFm phase peak refers to a peak resulting from the presence of alumina-iron oxide-sulfate crystals, and the calcite peak refers to a peak resulting from the presence of calcite crystals, respectively.

At this time, curing is an environmental treatment applied to the binder to maintain or promote curing of the binder, specifically, refers to a high-temperature wet curing that hardens the binder composition under environmental conditions wet at high temperatures.

The composition may include aluminum (Al) in a reduced amount after curing compared to before curing. Specifically, since the aluminum is a main component of fly ash, fly ash is activated by lime, and then reacted and cured with nitrate in water to reduce the formation of the CSH bond and alumina-iron oxide-sulfate (AFm phase) crystals. Is done.

High strength Binder Manufacturing method

The present invention (1) fly ash 100 parts by weight, 5 to 40 parts by weight of quicklime (CaO) and 1 to 20 parts by weight of nitrate to prepare a binder composition; And (2) mixing and curing the water in the composition.

Age refers to the number of days elapsed since the start of curing by mixing water with the composition.

In step (1), a composition comprising fly ash, quicklime and nitrate is prepared.

The composition can mix each of these raw ingredients in a dry state.

The mixing ratio of the components included in the composition, based on 100 parts by weight of the fly ash, may be 5 to 40 parts by weight of quicklime, or 10 to 35 parts by weight, nitrate 1 to 20 parts by weight, or 1 to 15 parts by weight Can.

In step (2), water is mixed with the composition to cure. Specifically, in the 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 within the above range, it is more advantageous to exert a high compressive strength after curing the composition.

The curing may be performed 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 may exhibit higher compressive strength.

The curing in step (2) may be high temperature wet curing. For example, the curing in step (2) may be performed at a temperature of 40 to 80°C or 50 to 75°C and a relative humidity (RH) of 80% or more, 80 to 95%, or 90 to 99%. .

More specifically, the curing of step (2) can be carried out for a period of 3 to 28 days after mixing with water at 60° C. and 95% relative humidity. The compressive strength may be, for example, measured in accordance with KS L 5105. For example, the compressive strength is 3 to 30 MPa at 3 days age, 10 to 40 MPa at 7 days age, 13 to 45 MPa at 28 days age, or 15 to 70 MPa at 91 days age, or 20 to 60 MPa Can be

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 number of voids. Specifically, the binder may have pores having a size of 50 nm or less, 20 nm or less, 20 to 30 nm, or 10 to 15 nm 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 voids, the more preferable in terms of strength, and the higher the proportion of capillary voids than the proportion of air voids, the better.

When the capillary pores having a size of 50 nm or less are included, they may have a favorable effect on long-term behavior such as creep (a phenomenon in which the deformation of the binder increases when a constant load is maintained for a long time) and shrinkage. The inclusion of large capillary voids can negatively affect strength.

The binder according to the present invention is more effective in improving strength because the average size of the capillary pores is not only a fine level, but the ratio of capillary pores and air pores is lower than that of the conventional cement-based binder.

Furthermore, the bonding material may have a porosity of 50% or less, 30 to 40%, or 40 to 45%. When within the above range, the initial strength and long-term strength of the bonding material may be improved better.

The bonding material may have a compressive strength of 15 MPa or more, 15 to 70 MPa, or 15 to 65 MPa at the time of regeneration for 80 days or more after the start of curing, or at 91 days of regeneration.

As described above, the present invention is to form a CSH bond, AFm phase, and calcite crystals in a binder after curing by mixing nitrate with a specific content in a binder mixed with fly ash and quicklime (CaO), an industrial by-product. At the same time, by increasing their ratio, it is possible to reduce the voids and improve the initial strength and long-term strength over time. Since the binder of the present invention prepared in this way can exhibit the same or higher 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 based on fly ash, which is an industrial by-product, it is eco-friendly due to less carbon dioxide generation in the manufacturing process, 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 such as construction, tile adhesion, joint construction, etc. can be used.

The above contents will be 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 to these.

[ Example ]

Example One: Fly ash Containing Binder Preparation of the composition

A fly ash (FA) (Hadong Thermal Power Plant) 85 parts by weight, 15 parts by weight of quicklime (CaO) and 5 parts by weight of calcium nitrate (Ca(NO ₃ ) ₂ ) as nitrate were mixed to prepare a binder composition.

Example 2: Fly ash Containing Binder Preparation of the composition

A binder composition was prepared in the same manner as in Example 1, except that sodium nitrate (NaNO ₃ ) was used instead of calcium nitrate as the nitrate.

FA CaO nitrate Ca(NO ₃ ) ₂ NaNO ₃ Control 85 15 - - Example 1 85 15 5 - Example 2 85 15 - 5

[ Evaluation example ]

Evaluation example 1: Compressive strength

Pastes were prepared by mixing 30 parts by weight of water with respect to 100 parts by weight of the compositions of Examples 1 and 2 above. The paste was placed in a cube-shaped mold having 50 mm on one side, and was cured up to 91 days of aging at 60°C and maintaining a relative humidity of 95%, thereby obtaining a binder.

The compressive strength of the obtained binder was measured according to the Portland Cement Physical Performance Standards (KS L 5105), and the results are shown in Table 2 and FIG. 1 below.

MPa Compressive strength (standard deviation) 3 days old age 7 days old age 28 days old age 91 days old age Control 6.61 (0.54) 9.08 (0.83) 11.72 (0.99) 14.69 (1.34) Example 1 29.03 (1.74) 38.24 (4.07) 45.52 (3.12) 59.37 (2.91) Example 2 3.78 (0.97) 14.91 (0.46) 15.91 (1.33) 20.32 (0.53)

Referring to FIG. 1, in the case of Example 1 (including calcium nitrate), the initial strength was significantly increased, and not only showed a compressive strength more than 4 times higher than that of the control group at the age of 3 days, particularly over time, especially at the age of 91 days Showed a remarkably excellent compressive strength. Furthermore, it can be confirmed that even in Example 2 (including sodium nitrate), it exhibits a significantly superior compressive strength when compared to the control group. From this, it can be seen that nitrate is effective for improving the strength of the binder.

Evaluation example 2: X-Ray Diffraction; XRD ) analysis

For the compositions of Examples 1 and 2, a binder was prepared in the same manner as in Evaluation Example 1. The binder was cured after curing for 3, 7, 28, and 91 days of age, respectively, and then measured by an X-ray diffraction analyzer (D/MAX 2500V/PC, Rigaku). The results are shown in FIG. 2.

Referring to FIG. 2, it can be seen that a graph of the control group showed a CSH peak, a katoite peak, a calcite peak, and a calcium hydroxide (Ca(OH) ₂ ) peak together with crystals present in the fly ash.

Katoite refers to an isotropic hexagonal cube mineral containing aluminum, calcium, hydrogen, oxygen and silicon.

On the other hand, it can be seen that the binders prepared from Examples 1 and 2 containing nitrate showed the C-S-H peak, AFm phase peak, and calcite peak as the main ones, and were effective in improving the binder strength.

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

For the compositions of Examples 1 and 2, a binder was prepared in the same manner as in Evaluation Example 1. The binder was cured after curing for 3, 28 and 91 days, and then analyzed by a thermogravimetric analyzer (SDT Q600, TA Instruments Co., Ltd.). The results are shown in FIGS. 3 to 5.

Looking at Figures 3 to 5, it can be seen that the binder formed from the compositions of Examples 1 and 2 exhibits a remarkable mass loss around 270°C. On the other hand, it can be seen that the binders formed from the compositions of Examples 1 and 2 have a greater weight loss over time than the control group. This means that the C-S-H and nitrate-AFm phases in the binder are formed, and the amount of reactants decreases as their ratio increases. Therefore, it can be seen that the binder containing nitrate promotes C-S-H and nitrate-AFm phase formation in the binder and is effective in enhancing the strength of the binder.

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 1 and 2, a binder was prepared in the same manner as in Evaluation Example 1. The binder was cured after curing for 91 days and analyzed by a ²⁷ Al nuclear magnetic resonance spectrometer (400 MHz(C) Solid State Nuclear Magnetic Resonance Spectrometer, Bruker Co.). The results are shown in FIG. 6.

At this time, since fly ash is the main source of Al, all the spectra in FIG. 6 are standardized to have the same area as fly ash. For reference, the fly ash has a peak of a tetrahedral configuration centered at 50 ppm, a broad asymmetrical pentahedral configuration peak around 50 ppm, and a peak of a hexahedral configuration around 0 ppm.

Referring to FIG. 6, it can be seen that Al in the fly ash was decreased as the peak (tetrahedral coordination) centered on 50 ppm was rapidly decreased, which is expected to be reduced by dissolution due to the activator (CaO).

On the other hand, as the peak of the tetrahedral coordination shifted around 70 ppm, it can be seen that Al shifted by C-S-H bond substitution and/or AFm phase formation. In addition, it can be seen that the AFm phase in the binder was formed because the hexahedral coordination peak was strong at around 10 ppm.

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

For the compositions of Examples 1 and 2, a binder was prepared in the same manner as in Evaluation Example 1. At this time, the binding material was manufactured in a cube shape with one side of 5 mm.

After curing the binder for 3, 28, and 91 days, the binder was measured using a porosity meter (Autopore IV 9500, Micrometrics, Inc.) by mercury intrusion. The porosity and average pore size in the binder were measured. The results are shown in FIGS. 7 to 9.

Looking at Figures 7 to 9, the control group is 0.02 to 0.5 μm, the pores are sporadically distributed, while Examples 1 and 2 can be confirmed that the size of the pores is smaller than or equal to the control group, and has a uniform size. In particular, in the case of Example 1, the initial age (3 days old age) showed a very small size of pores of 20 nm or less, and even looking up to 91 days of age, it can be seen that all have pore sizes of 50 nm or less.

From this, it can be seen that the binder according to the present invention acts more effectively to increase initial strength by having a smaller pore size and porosity from the initial age.

Claims (13)

100 parts by weight of fly ash, 5 to 40 parts by weight of quicklime (CaO) and 1 to 20 parts by weight of nitrate,
The quicklime is an activator for inducing a pozzolanic reaction of fly ash, a binder composition. According to claim 1,
The nitrate is one or more selected from the group consisting of Ca (NO ₃ ) ₂ and NaNO ₃ , binder composition. delete According to claim 1,
The fly ash has an average particle diameter of 1 to 500 ㎛,
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 45 to 70 wt%, 15 to 30 wt%, 5 To 15 to 15%, 1 to 10%, 0.1 to 3%, 0.1 to 3%, 0.1 to 3%, 0.1 to 2%, 0.1 to 2% and 0.1 to 2% by weight The binder composition. According to claim 1,
After curing, the composition comprises a CSH peak, X-ray diffraction (XRD) spectrum measurement, alumina-iron oxide-sulfate (AFm phase) peak, and calcite peak. According to claim 1,
The composition comprises a reduced amount of aluminum (Al) after curing compared to before curing, the binder composition. (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 nitrate; And
(2) mixing the composition with water and curing,
In the step (1), the quicklime is an activator for inducing a pozzolanic reaction of the fly ash, a method of manufacturing a binder. The method of claim 7,
In the step (2), mixing the water in an amount of 20 to 50 parts by weight based on 100 parts by weight of the composition, the method of manufacturing a binder. The method of claim 7,
The curing of the step (2) is carried out at a temperature of 40 to 80 ℃ and a relative humidity (RH) of 80% or more, the method of manufacturing a binder. A binder obtained by curing the binder composition of claim 1. The method of claim 10,
The binder has a plurality of pores, and the pores have a size of 20 nm or less. The method of claim 10,
The binder has a porosity of 50% or less. The method of claim 10,
When the binder is 80 days or more after curing starts, the binder has a compressive strength of 15 MPa or more.

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