KR20220097663A - Manufacturing Method of Calcium Silicated Base Cement Clinker And Calcium Silicated Base Cement Clinker Hardening Body - Google Patents

Abstract

The present invention provides a calcium silicate-based cement clinker and a method for manufacturing a hardening body using the same, in which the hardening body can be used as an eco-friendly building material such as blocks, ALC, high early strength cement, etc. by manufacturing the calcium silicate-based cement clinker having a property of absorbing and hardening carbon dioxide using middle and high quality domestic raw materials, performing primary curing (wet curing) and then secondary curing (carbonization curing) at room temperature so as to maintain the shape of a product such that a hardening body having compressive strength equal to or better than that of KS standard type 1 cement can be manufactured. In addition, the method for manufacturing the calcium silicate-based cement clinker hardening body according to the present invention can be used as a base technology for developing eco-friendly building materials with various physical properties by enabling a physical property design in accordance with the concentration of carbon dioxide.

Description

Calcium-silicate cement clinker and method of manufacturing a hardening body using the same

The present invention relates to calcium-silicate cement clinker and a method for preparing a hardened body using the same.

More than 60% of the greenhouse effect is caused by carbon dioxide, and each industry group is focused on finding ways to reduce carbon dioxide. In particular, in the case of the cement industry, there is a lot of pressure on carbon dioxide emission regulation within the industry as it is a production process that inevitably generates an excess of carbon dioxide during the manufacturing process. Accordingly, methods such as improvement/repair of production facilities, use of fuel/raw material substitutes, and cement manufacturing using inorganic admixtures are being sought, but until now, methods that can dramatically reduce carbon dioxide emissions in the manufacturing process itself are limited to pilot studies. have.

Calcium silicated base cement (hereinafter referred to as CSC) clinker is a low-carbon cement-based clinker composed of major mineral phases such as CS, C ₃ S ₂ , C ₂ S and unreacted SiO ₂ . It exhibits the ability to absorb and harden. CSC has a manufacturing firing temperature of around 1200℃, which is about 200℃ lower than general cement firing conditions, so it can reduce energy generated in the fuel part, and the main mineral phase composition ratio is (Ca:Si = 1:1 or 3:2). Because of its composition, the amount of CO ₂ generated from the raw material is also lower than that of cement. In addition, since it absorbs and hardens CO ₂ , it can reduce about 30% of CO ₂ compared to cement during the curing process, so it is possible to reduce CO ₂ by up to 70% compared to cement in the entire process, including manufacturing and application.

The theoretical major mineral phases of CSC are CS (CaO·SiO ₂ , pseudowollastonite) and C ₃ S ₂ (3CaO·2SiO ₂ , Rankinite). Depending on the raw material mixture and plasticity characteristics, cement mineral phases such as C ₂ S and C ₃ S are contained. and unreacted SiO ₂ may remain. At this time, the mineral phase reacting with CO ₂ is CS and C ₃ S ₂ , and can exhibit compressive strength characteristics of up to 70 MPa or more through the reaction formulas shown in Chemical Formulas 1 and 2 below.

The mineral phase that contributes to the carbonation reaction is decomposed into CaCO ₃ and SiO ₂ through the carbonation reaction into CS and C ₃ S ₂ and contributes to the improvement of the physical properties of the hardened body through crystal growth. It is possible to design physical properties with a compressive strength of up to 70 MPa or more depending on the degree of carbonation, and it is an eco-friendly/high-performance construction material that can reduce CO ₂ by up to 70% compared to the cement manufacturing process when considering the amount of CO ₂ absorbed by the carbonation reaction from the manufacturing process. . In advanced countries such as Europe, the United States, and China, a number of studies are already underway to determine the utility and applicability of CSC as an eco-friendly construction material. Only a small number of research cases are confirmed, and there are no research cases related to CSC clinker and self-curing properties.

The patents and references mentioned in this specification are hereby incorporated by reference to the same extent as if each publication was individually and expressly specified by reference.

US registered patent US 10173927 B2 US registered patent US 10196311 B2 US Patent Publication US 2017/0253530 A1 US Patent Publication US 2018/0186696 A1

An object of the present invention is to provide a method for producing a calcium silicated base cement clinker by mixing and calcining domestic high-grade limestone and silica fume.

Another object of the present invention is to prepare a first hardened body by adding water to the prepared calcium-silicate cement clinker to prepare a paste, mold the paste, and then perform primary curing. An object of the present invention is to provide a method for producing a calcium-silicate cement clinker hardened body having a compressive strength equal to or superior to that of a KS standard type 1 cement hardening body as a method of performing secondary curing.

Other objects and technical features of the present invention are more specifically set forth by the following detailed description of the invention, claims and drawings.

The present invention comprises: a first step of pulverizing domestic high-grade limestone and silica fume to have a particle diameter of 5 to 70 μm to produce a fine limestone powder and a fine silica fume powder; a second step of mixing the limestone fine powder and the silica fume fine powder in a molar ratio of 1:1 to prepare a limestone-silica fume mixed powder; a third step of calcining the limestone-silica fume mixed powder at 1150 to 1350° C. to prepare a calcium silicated base cement clinker; a fourth step of preparing a calcium-silicate cement clinker paste by mixing 35 to 45 parts by weight of water based on 100 parts by weight of the calcium-silicate cement clinker; A fifth step of preparing a calcium-silicate cement clinker first hardened body by putting the calcium-silicate cement clinker paste in a mold and first curing it for 44 to 52 hours at a temperature of 15 to 25° C. and a relative humidity of 65 to 75%; And Calcium-silicate cement clinker by removing the mold of the first hardening body of the calcium-silicate cement clinker and curing it for 124 to 172 hours in an atmosphere of 15 to 25% of carbon dioxide, a temperature of 15 to 25°C, and a relative humidity of 65 to 75%. A sixth step of producing a second hardened body; using domestic limestone and silica fume, characterized in that it includes a calcium-silicate cement clinker hardening body manufacturing method.

The main mineral phase of the domestic high-grade limestone is CaCO ₃ , SiO ₂ , CaMg(CO ₃ ) ₂ It is characterized in that the calcium-silicate cement clinker is the main mineral phase of CS 72.2 to 74.3 wt%, C ₃ S ₂ 17.1 to 18.9 % by weight, C ₂ S 4.8 to 5.3% by weight, and unreacted SiO ₂ 3.2 to 3.6% by weight.

The calcium-silicate cement clinker first hardened body is characterized in that water is dried and hardened without a separate chemical reaction, and the calcium-silicate cement clinker second hardened body contains CaCO ₃ and amorphous SiO ₂ resulting from carbonation reaction. characterized.

The calcium-silicate cement clinker secondary hardening body is characterized in that CaCO ₃ is formed from the age of 10 hours of secondary curing, and the compressive strength at the age of 150 to 180 hours is 50 to 60 MPa.

The calcium-silicate cement clinker of the present invention and the method for producing a hardening body using the same are produced by using high-grade domestic raw materials of calcium-silicate cement clinker, which absorbs carbon dioxide and hardens, and only by carbonation curing at room temperature without heating at high temperature. It has the advantage of being able to manufacture a hardened body with performance equal to or superior to that of KS standard type 1 cement. In addition, the calcium-silicate cement clinker manufacturing method of the present invention is judged to be capable of designing physical properties according to the concentration of carbon dioxide, so it is possible to produce eco-friendly building materials such as blocks, ALCs, panels, and crude steel type cement and develop new eco-friendly building materials with various properties. It is judged that it can be utilized as a base technology.

1 shows the XRD analysis results of limestone and silica fume, which are raw materials of the present invention.
2 shows the particle size distribution of the raw material of the present invention.
Figure 3 shows the calcium-silicate cement clinker prepared through the calcination of the present invention. Panel (a) shows the results of XRD analysis, and panel (b) shows calcium-silicate cement clinker prepared by calcining at 1300°C.
Figure 4 shows the results of analyzing the properties of the calcium-silicate cement clinker prepared using the calcination of the present invention. Panel (a) shows the results of XRD analysis, and panel (b) shows the particle size distribution.
5 shows the XRD analysis results of the calcium-silicate cement clinker hardened body according to the curing conditions of the present invention. Panel (a) shows the mineral phase analysis results of the CSC hardened body prepared under normal wet curing conditions (20° C., 70% humidity) without CO ₂ supply, and panel (b) shows the wet curing conditions of the panel (a). The mineral phase analysis results of the CSC hardened body prepared under the curing condition in which ₅ % CO ₂ was supplied to It shows the mineral phase analysis result of the CSC hardened body, and panel (d) shows the mineral phase analysis result of the CSC hardened body manufactured under the curing condition in which 20% CO ₂ was supplied to the wet curing condition of the panel (a).
6 shows the results of Differential Scanning Calorimetry (DSC) according to the carbonation reaction conditions of the CSC cured body of the present invention. Panel (a) shows the thermal analysis results of the CSC cured body prepared under normal wet curing conditions (20° C., 70% humidity) without CO ₂ supply, and panel (b) shows the wet curing conditions of the panel (a). The thermal analysis result of the CSC cured body prepared under the curing condition in which ₅ % CO ₂ was supplied to The thermal analysis result of the CSC cured product is shown, and panel (d) shows the thermal analysis result of the CSC cured product prepared under the curing condition in which 20% CO ₂ was supplied to the wet curing condition of the panel (a).
7 shows the results of scanning electron microscopy analysis according to the age of the cured CSC clinker cured under the conditions of 20% CO ₂ of the present invention. Panel (a) shows the results at the age of 10 hours, panel (b) shows the results at the age of 48 hours, and panel (c) shows the results at the age of 96 hours.
8 shows the results of measuring the compressive strength of the CSC cured body of the present invention at the age of 7 days according to the change in the concentration of CO ₂ .

The present invention relates to a first step of producing a fine limestone powder and a fine silica fume powder by pulverizing domestic high-grade limestone and silica fume to have a particle size of 5 to 70 μm; a second step of mixing the limestone fine powder and the silica fume fine powder in a molar ratio of 1:1 to prepare a limestone-silica fume mixed powder; a third step of calcining the limestone-silica fume mixed powder at 1150 to 1350° C. to prepare a calcium silicated base cement clinker; a fourth step of preparing a calcium-silicate cement clinker paste by mixing 35 to 45 parts by weight of water based on 100 parts by weight of the calcium-silicate cement clinker; A fifth step of preparing a calcium-silicate cement clinker first hardened body by putting the calcium-silicate cement clinker paste in a mold and first curing it for 44 to 52 hours at a temperature of 15 to 25°C and a relative humidity of 65 to 75%: And The calcium-silicate cement clinker is removed by removing the mold of the first hardening body of the calcium-silicate cement clinker, and secondary curing for 124 to 172 hours in an atmosphere of 15 to 25% carbon dioxide, a temperature of 15 to 25°C, and a relative humidity of 65 to 75%. A sixth step of producing a second hardened body; using domestic limestone and silica fume, characterized in that it includes a calcium-silicate cement clinker hardening body manufacturing method.

The domestic high-grade limestone fine powder and silica fume fine powder preferably have a similar particle size, and the particle size has a particle size of 5 to 70 μm, preferably 5 to 20, and more preferably a particle size of 10 μm. have If the particle diameter is less than 5㎛, the particles are too small and easily agglomerate, so the efficiency of the reaction to form the main mineral phase may be reduced. There is a risk that it will be required or that the compressive strength may be lowered.

The main mineral phase of the domestic high-grade limestone of the present invention is CaCO ₃ , SiO ₂ , and CaMg(CO ₃ ) ₂ It is characterized in that it is CS, C ₃ S ₂ , C ₂ S and unreacted SiO through reaction with silica fume. ₂ , calcium-silicate cement clinker having a major mineral phase is prepared. To this end, the fine limestone powder and the fine silica fume powder are prepared as limestone-silica fume mixed powder mixed in a molar ratio of 1:1, and the mixed powder is calcined at 1150 to 1350° C. to make calcium silicated base cement clinker. is manufactured with

According to an embodiment of the present invention, calcium-silicate cement clinker of the present invention is a major mineral phase of CS 72.2 to 74.3 wt%, C ₃ S ₂ 17.1 to 18.9 wt%, C ₂ S 4.8 to 5.3 wt% and unreacted SiO ₂ 3.2 to 3.6% by weight, preferably CS 73.6% by weight, C ₃ S ₂ 18% by weight, C ₂ S 5.0% by weight, and unreacted SiO ₂ 3.4% by weight.

The calcium silicate cement clinker of the present invention may further be calcined at 900° C. for 1 hour before the calcination. Preferably, the calcination is performed under the conditions of a temperature increase temperature of 10 °C/min, a calcination temperature of 900 °C, and a calcination time of 1 hour, followed by a temperature rise temperature of 10 °C/min, a calcination temperature of 1150 to 1350 °C, and a calcination time of 2 hours. Firing is carried out with More preferably, the pre-firing is performed under the conditions of a heating temperature of 10°C/min, a firing temperature of 900°C, and a firing time of 1 hour, followed by firing under the conditions of a heating temperature of 10°C/min, a firing temperature of 1250°C, and a firing time of 2 hours. do.

According to an embodiment of the present invention, the calcium-silicate cement clinker produced by calcining may exist in a lump state, and the calcium-silicate cement clinker in a lump state may be pulverized to an average particle diameter of about 10 μm for the production of a paste. .

The calcium-silicate cement clinker prepared by the calcination is prepared in the form of a paste by adding water. The paste is prepared by adding 35 to 45 parts by weight of water based on 100 parts by weight of the calcium-silicate cement clinker. When the water is added in an amount of less than 35 parts by weight, workability is low, and when it is added in more than 45 parts by weight, it may take a lot of time to remove moisture during curing. Preferably, the calcium-silicate cement clinker paste is prepared by adding 40 parts by weight of water to 100 parts by weight of calcium-silicate cement clinker.

The calcium-silicate cement clinker paste is put into a mold and first cured for 44 to 52 hours at a temperature of 15 to 25° C. and a relative humidity of 65 to 75% to prepare a first hardened calcium silicate cement clinker.

The calcium-silicate cement clinker does not undergo hardening properties through hydration. Therefore, during the first curing, only the water in the paste is evaporated and removed, but the mineral phase formed by the hydration reaction of general cement is not formed. Therefore, the primary curing corresponds to a process in which water in the paste is evaporated and the paste is dried to a level that maintains its shape even when the mold is removed, unlike the general curing process.

The first curing is preferably performed for 48 hours at a temperature of 20°C and a relative humidity of 70%. The primary curing is a wet curing method, and if it is out of the temperature range and humidity range, it may take more curing time, and the appearance of the first cured body may be deformed due to drying shrinkage, and there is a risk that cracks may be formed on the surface.

The secondary curing of the present invention is carbonation curing using carbon dioxide gas. The carbonation curing is based on the basic principle that carbon dioxide penetrates into the paste and reacts to form a mineral phase. The paste has a disadvantage in that the shape is not maintained during the curing process unless the paste is put into a molding to maintain a desired shape when manufacturing a precast product such as a block or panel. However, when the mold (molding) is positioned outside the paste, the surface area through which carbon dioxide can smoothly penetrate is reduced, so there is a problem in that the efficiency of carbonation curing is rapidly reduced. In the present invention, the first curing is performed by a wet curing method in a carbon dioxide-free atmosphere until the calcium-silicate cement clinker paste can maintain the desired shape, and the molding is removed to ensure a sufficient surface area of the paste through which carbon dioxide can smoothly penetrate. It is characterized in that the carbonation curing (secondary curing) is performed.

The present invention removes the mold of the calcium-silicate cement clinker first hardened body and performs secondary curing for 124 to 172 hours in an atmosphere of 15 to 25% carbon dioxide, a temperature of 15 to 25 ° C., and a relative humidity of 65 to 75%. A second hardened body of silicate cement clinker is prepared. Preferably, secondary curing is performed for 148 hours in an atmosphere of 20% carbon dioxide, a temperature of 20°C, and a relative humidity of 70% to prepare a second hardened calcium-silicate cement clinker. The calcium-silicate cement clinker second hardened body prepared by the above method contains CaCO ₃ and amorphous SiO ₂ as a result of the carbonation reaction, and has a compressive strength of 50 to 60 MPa at an age of 150 to 180 hours. Preferably, the compressive strength is 56 MPa, and it is characterized in that it has a higher compressive strength than the 28-day compressive strength of KS standard type 1 cement.

When the carbon dioxide content is less than 15%, a calcium-silicate cement clinker second hardened body having a compressive strength of less than 50 KPa may be prepared. When the carbon dioxide content exceeds 25%, it is determined that the compressive strength of the calcium-silicate cement clinker second hardened body will further increase. However, in the above carbon dioxide range, since it already has a compressive strength higher than the 28-day compressive strength of KS standard type 1 cement, curing carbon dioxide exceeding 25% is unnecessary in terms of economic feasibility.

If the temperature is less than 15 ℃, the rate of the chemical reaction for carbonation curing is lowered, and curing time may be longer. When the temperature exceeds 25 ℃, the rate of the chemical reaction increases and there is an effect of reducing the curing time, but considering the cost for raising the temperature and the use of fossil fuels for this, no heating is required It is considered desirable to carry out curing in

The present invention will be described in detail through the following examples.

Example

1. Experimental method

1) Raw material properties of CSC clinker

According to the results of previous studies, the main mineral phase of CSC clinker is CS, C ₃ S ₂ , C ₂ S, C ₃ S and unreacted SiO ₂ It is investigated that it can be prepared by mixing Ca and Si sources in an appropriate molar ratio. do. In the present invention, CSC clinker was prepared by using limestone and silica fume as Ca and Si sources, and the mineral phase of the raw material was analyzed for this (see FIG. 1 ).

As a result of mineral phase analysis, the main mineral phases of limestone were CaCO ₃ , SiO ₂ , and CaMg(CO ₃ ) ₂ , and it was found that they were high-grade limestone. In the case of silica fume, it was confirmed that amorphous SiO ₂ was the main mineral phase. At the time of supply and demand, limestone was pulverized to a particle size similar to that of silica fume (a particle size of about 50 μm) for homogeneous mixing between raw materials in a bulk state of 20-30 mm size (see FIG. 2). The pulverized limestone was mixed with silica fume in an appropriate molar ratio (1:1) to prepare a raw material (mixed powder) for manufacturing CSC clinker.

2) Preparation of CSC clinker

In order to derive optimal calcination conditions for CSC clinker production, the prepared mixed powder was calcined at various temperatures. The calcination temperature was set from the temperature at which the decarboxylation reaction of limestone starts at 900 °C to the temperature at which the synthesis of CS and C ₃ S ₂ theoretically ends at 1300 °C, and the calcination time was set at 2 hours. Prior to the full-scale firing experiment, preliminary firing was performed under the conditions of a temperature increase rate of 10°C/min, a firing temperature of 900°C, and a firing time of 1 h to facilitate the mineral phase synthesis. Table 1 below shows the firing conditions of the present invention.

raw materials Limestone (Ca source), Silica fume (Si source) De-carbonation 10℃/min, 900℃, 1h
(heating rate, temperature, time, holding time) Heating rate 10℃/min Temperature (900, 1000, 1100, 1200, 1250, 1300)℃ holding time 2h

3) CSC clinker curing experiment and physical property evaluation

In order to elucidate the curing mechanism of CSC clinker, which can only exhibit physical properties under a carbon dioxide atmosphere, water was added to the prepared CSC clinker to prepare a paste, and then general wet curing and carbonation curing were performed. In addition, the change in properties of the CSC cured body according to the curing atmosphere was observed, and the property expression performance was investigated in the ambient temperature/normal pressure atmosphere.

Table 2 below shows the test conditions for the CSC hardened body of the present invention and the cement (OPC) hardened body as a comparative example. Cement and CSC clinker were prepared to have an average particle diameter of around 10㎛, and all experimental samples were prepared in the form of paste. part).

Test samples for instrument analysis such as XRD, TG/DSC, SEM and Porosimeter were spread out in a reagent dish with a width of about 100 mm and a height of about 10 mm, cured for a certain period of time, and then pre-treated for instrument analysis by each age. In the case of the test sample for measuring the compressive strength, (width × length × height) was sampled by molding in a cement mortar specimen manufacturing mold having a size of (40 × 40 × 160) mm. Compressive strength was measured at 7 days of age, and the test was conducted at a load rate of 144KN/min in accordance with KS L ISO 679.

In particular, after the paste was molded, it was dried and cured to the extent that demolding was possible (first curing, 1 ^st curing), and then curing (accelerated carbonation) was carried out in earnest. At this time, the drying and curing time was It was carried out based on 48 hours.

Sample CSC, OPC
※ all samples are produced paste water ratio 40% 1st ^Curing condition Temperature 20℃, Relative humidity 70% Accelerated
carbonation condition Temperature 20℃, Relative humidity 70%,
CO ₂ concentration 0, 5, 10, 20% Curing time (carbonation) (5, 10, 24, 48, 72, 96)h Instrument analysis item XRD, DSC, Porosimeter, SEM Mechanical properties Compressive strength

2. Experimental results

1) Optimum calcination temperature for CSC clinker production

Among the major mineral phases of CSC clinker, CS and C ₃ S ₂ , which are directly related to the carbonation reaction, are mineral phases synthesized at a calcination temperature of about 1200~1250℃, and are about 200~250℃ lower than the calcination temperature for general cement clinker production. As a result, the utility as a low-energy/low-carbon cementitious clinker can be increased, but there have been no research cases related to the manufacture and use of CSC clinker in Korea so far, and it was necessary to confirm the ease of manufacture and applicability through basic research. Accordingly, in the present invention, the amounts of CS and C ₃ S ₂ synthesized according to the firing temperature were investigated to confirm the ease of manufacture of CSC using domestic raw materials (see panel (a) of FIG. 3 ).

As a result of the mineral phase analysis, it was found that there was a difference in the major mineral phases based on the calcination temperature of 1200℃, which is the time of formation of the CS and C ₃ S ₂ mineral phases. Under the firing condition of 1100℃ or less, SiO ₂ peak near 21° and CaO peak around 38° were simultaneously detected, and it was confirmed that the raw material was not consumed in full for CS and C ₃ S ₂ phase synthesis. I think it was because it was low. CS and C ₃ S ₂ peaks were detected from 1200° C., and as the firing temperature increased, the amount of CS and C ₃ S ₂ production tended to increase, and it was found that the production amount was maximum at 1300° C. However, as the phenomenon caused by under-drying was confirmed on the sample surface fired at 1300°C (see panel (b) of FIG. 3), the optimum firing temperature for CSC production was established at 1250°C, and domestic raw materials under conditions similar to those of the prior art. It was confirmed that CSC production and synthesis using

2) Characteristics of CSC clinker produced through calcination

4 shows the results of analyzing the mineral phase by pulverizing CSC clinker prepared through the calcination of the present invention. The CSC clinker was pulverized to about 10 μm to exhibit a particle size range similar to that of OPC.

The major mineral phases of CSC clinker are CS, C ₃ S ₂ , SiO ₂ and C ₂ S, which exhibited the same properties as the theoretical major mineral phases _of CSC _. %, C ₂ S 4.8 to 5.3 wt% and unreacted SiO ₂ 3.2 to 3.6 wt%. Among the components of CSC, CS and C ₃ S ₂ are substances that react with carbonation with CO ₂ and act as major factors for strength expression _{. 2} was around 18%, and it was judged that there was no problem in contributing to the enhancement of CSC durability. In the case of C ₂ S produced in a trace amount of about 5% on average, it is a compound that can improve strength by hydration reaction, but given that the amount produced is relatively small and the reaction continues until after 28 days of age, it has a direct effect on the strength characteristics of CSC. was judged not to be reached. In the case of SiO ₂ , it was confirmed that about 3.3% was present as an unreacted material.

When referring to the prior art, it is confirmed that it is difficult to consume the entire amount of the compound, and when considering the curing mechanism in which CaCO ₃ and SiO ₂ are produced by the carbonation reaction of CS and C ₃ S ₂ , the presence of unreacted SiO ₂ is CSC itself. It is judged not to have a significant effect on the characteristics.

3) Optimum curing conditions for manufacturing CSC hardened body

In the case of the prior art, after sampling through molding or compression, carbonation curing was performed immediately to prepare a cured body. In contrast, in the present invention, after the CSC paste is sampled through molding or compression, the drying and curing process (primary curing) is performed to the extent that demolding is possible for 48 hours in an atmosphere of a temperature of 20 ° C. and a humidity of 70%, followed by CO ₂ 5 to 20 %, carbonation curing (secondary curing) was carried out for 5 to 96 hours in an atmosphere of 20 ℃ temperature and 70% humidity to prepare a CSC cured body.

5 shows the mineral phase analysis results of the CSC hardened body according to the curing conditions of the present invention. As a result of the analysis, it was confirmed that the CaCO ₃ peak size near 30° increased as the CO ₂ concentration increased. The above result is judged because the carbonation reaction contribution of C ₃ S ₂ and CS increased as the CO ₂ concentration increased, and it is also judged to be related to the CaCO ₃ generation timing according to the CO ₂ concentration. However, it was not possible to distinguish the carbonation reaction contribution according to the change in C ₃ S ₂ and CS peak size only from the mineral phase analysis result, and the amorphous SiO ₂ , one of the carbonation reaction result products, It could not be clearly ascertained whether it was created or not.

Unlike the mineral phase analysis results (panels (b), (c) and (d) of FIG. 5) of the CSC cured product prepared by carbonation curing, the CSC cured product cured under normal wet curing conditions without CO ₂ (FIG. 5) In panel (a)), no change in mineral phase according to age was observed, and no product by carbonation was identified. Therefore, it is judged that carbonation curing is essential for the expression of physical properties of the CSC cured body of the present invention.

4) Characterization of CSC cured body

(1) Thermal analysis result of CSC hardened body

Differential Scanning Calorimetry (DSC) was performed to quantitatively evaluate the carbonation reaction product of the CSC cured body (see FIG. 6 ). As a result of thermal analysis, it was confirmed that the CaCO ₃ peak size near 800° C. increased as the CO ₂ concentration increased and the age increased. In addition, it was possible to predict the correlation between the CO ₂ concentration and the carbonation reaction rate, because the higher the CO ₂ concentration, the faster the CaCO ₃ generation time. When carbonation curing was performed (panels (b), (c) and (d) of FIG. 6 ), it was expected that there would be a difference in the final amount of CaCO ₃ , a reaction product, depending on the concentration of CO ₂ . However, as a result of the experiment, it was confirmed that the final amount of CaCO ₃ did not differ significantly depending on the concentration of CO ₂ . In general, the carbonation reaction starts from the sample surface and is densified by mineral phase crystal growth from the CO ₂ interface. However, after the reaction has progressed to some extent, since the crystal structure is already densified and CO ₂ does not flow smoothly into the sample, it is difficult to confirm the immediate reaction result.

As a result of this study, it was possible to macroscopically confirm the degree and rate of carbonation reaction according to the change in CO ₂ concentration at the beginning of curing (24h), when the reaction is relatively in progress _. It is judged that the amount of total reaction products has not increased any more because the reaction does not occur because it does not occur.

Additionally, the hyperbolic peak around 100~200°C is considered to be due to 2H ₄ SiO ₄ generated as an intermediate compound in the process of producing SiO ₂ , which is one of the carbonation reaction products of CS and C ₃ S ₂ .

(2) Scanning electron microscope analysis result of CSC cured body

A scanning electron microscope analysis was performed to confirm the results of CaCO ₃ crystal growth of the CSC cured body. 7 shows the results of scanning electron microscopy (SEM) analysis according to the age of the CSC cured body cured at a concentration of CO ₂ of 20% of the present invention.

According to the thermal analysis result of the CSC cured body, in the case of the CSC cured product cured at a CO ₂ concentration of 20%, the carbonation reaction proceeded somewhat faster than the samples cured under other conditions, and CaCO ₃ production was confirmed even at the initial stage of curing for 10 hours. do. Similarly, in the SEM analysis result of the CSC hardened body, CaCO ₃ crystallinity is confirmed at 10 hours of age. In detail, it was confirmed that the crystallinity was somewhat decreased at the beginning of the age, but as the age increased, the crystallinity became clear and the hardening body structure became dense. The above results are macroscopically showing that the durability of the CSC cured body is enhanced by carbonation.

(3) Measurement result of compressive strength of CSC hardened body

8 shows the results of measuring the compressive strength of the CSC cured body of the present invention at the age of 7 days according to the change in the concentration of CO ₂ . As a result of the experiment, it was confirmed that the compressive strengths of 28 MPa, 37 MPa and 56 MPa were exhibited at the CO ₂ concentration of 5%, 10% and 20%, respectively, and it was confirmed that the compressive strength increased as the CO ₂ concentration increased.

In the case of Class 1 cement (usually Portland cement) conforming to the KS standard, the compressive strength at 7 days of age is 22.5 MPa and the compressive strength at 28 days of age is 42.5 MPa. In the case of the CSC hardened body subjected to carbonation curing of the present invention, it was confirmed to be superior to the compressive strength of type 1 cement at 7 days of age according to KS at 7 days of age regardless of the curing conditions (CO ₂ concentration), and particularly, it was cured at 20% of CO ₂ In the case of a CSC hardened body, the strength characteristics were significantly higher than the compressive strength at 28 days of age of type 1 cement according to KS. For reference, the sample cured in a normal wet condition with a CO ₂ concentration of 0% had a compressive strength of 1 MPa or less at 7 days of age, so it was difficult to measure the compressive strength.

The present invention is manufactured by performing primary curing at a level capable of demolding in a general wet state without CO ₂ after molding CSC paste, and then performing secondary curing in carbonation curing conditions of 20% CO ₂ . As a result of carbonation (CO ₂ ) curing under CO ₂ 20% conditions immediately after molding the CSC paste without the first curing process, demoulding was not possible in 12 hours of curing, and the compressive strength was also 1.2 MPa, so it was confirmed that curing did not proceed at all. became In addition, demolding was possible only after 12 hours of carbonation curing after molding the CSC paste, and the compressive strength after 72 hours of carbonation curing was only 34.5 MPa.

In summary, in the case of the present invention, since the carbonation curing (secondary curing) is performed after primary curing in a wet atmosphere before carbonation curing and demolding, the contact area with CO ₂ is large, so that effective inflow of CO ₂ is possible, whereas the primary If carbonation curing is performed immediately without a curing process, effective CO ₂ inflow is not possible, so the effect of increasing the compressive strength due to carbonation is judged to be limited.

The above result means that the effect of improving strength due to carbonation is insignificant if carbonation curing is performed directly on the paste in a state without demolding. Therefore, as in the present invention, it is determined that the carbonation curing after drying the paste through the primary curing process and demolding is a way to improve the strength of the CSC cured body and reduce the maintenance cost of the carbonation curing.

It is considered that carbonation curing is essential for the CSC curing body of the present invention to express physical properties, and it is judged that the physical properties design according to the curing conditions is possible. In addition, it is thought that it will be easy to expand the range of applications such as block, ALC, panel, and crude steel type cement as it is possible to secure physical properties equivalent to or higher than that of type 1 cement in accordance with KS.

3. Conclusion

In the present invention, verification of CSC manufacturing characteristics using domestic raw materials and evaluation of in-house properties were investigated, and the following conclusions were drawn.

1) Domestically available limestone and silica fume were mixed and used as raw materials for the manufacture of CSC clinker. As a result of investigating the manufacturing characteristics of CSC clinker according to the calcination temperature, CS and C ₃ S, which are major CSC minerals, at a calcination temperature of 1200℃ or higher. ₂ generation is possible. Considering the maximum production amount of major mineral phases and appropriate test conditions, it is judged that the optimum firing conditions for CSC production are a firing temperature of 1250℃ and a holding time of 2 hours.

2) The main mineral phases of CSC prepared at a calcination temperature of 1250°C and a holding time of 2 hours were CS, C ₃ S ₂ , C ₂ S and unreacted SiO ₂ , which were similar to the theoretical major mineral phases of CSC. Through this, it was found that it was easy to manufacture domestic CSC using domestic raw materials.

3) As a result of observing the physical properties of CSC according to the concentration of CO ₂ in the curing atmosphere using CSC manufactured using domestic raw materials, when curing in a general wet curing atmosphere with a CO ₂ concentration of 0%, reaction products according to age change was hardly confirmed, and it could be seen that there was almost no actual physical property expression with a compressive strength of 1 MPa as of 7 days of age.

4) As a result of analysis of mineral phase according to CO ₂ concentration, it was confirmed that the higher the CO ₂ concentration, the larger the CaCO ₃ peak size was formed as a carbonation reaction product. However, it was difficult to clearly determine whether amorphous SiO ₂ was formed.

5) As a result of thermal analysis, in the case of samples cured at a CO ₂ concentration of 5% and 10%, the peak of CaCO ₃ production by carbonation reaction was confirmed from 24 hours of age, and in the case of samples cured at a CO ₂ concentration of 20%, the age It was possible to confirm whether CaCO ₃ was formed from 10 hours. Judging from this, it seems that the higher the CO ₂ concentration, the faster the carbonation reaction is promoted and the faster the physical properties are expressed. However, there was no significant difference in the final CaCO ₃ production rate regardless of the curing conditions.

6) As a result of thermal analysis, it was possible to predict that amorphous SiO ₂ was being generated as a peak was detected by the intermediate compound 2H ₄ SiO ₄ for the production of amorphous SiO ₂ near 100~200℃, and it could be inferred that the carbonation reaction was continuing. could

7) As a result of CSC's 7-day compressive strength measurement, the compressive strengths of samples cured at 5%, 10% and 20% CO ₂ concentrations were 28 MPa, 37 MPa and 56 MPa, respectively. It was found that the compressive strength at the age of 7 days was equal to or higher than that of the grade cement, and the sample cured at 20% CO ₂ concentration showed a higher result than that of the type 1 cement according to KS at the age of 28 days and showed excellent early strength characteristics. could

8) CSC is an essential material for carbonation reaction, and it is judged that it is possible to design the physical properties according to the curing atmosphere CO ₂ concentration, and it is judged that the application range can be expected to expand as an eco-friendly construction material such as block, ALC, panel, and crude steel type cement.

Specific examples described herein are meant to represent preferred embodiments or examples of the present invention, and the scope of the present invention is not limited thereby. It will be apparent to those skilled in the art that modifications and other uses of the present invention do not depart from the scope of the invention as set forth in the claims herein.

Claims (7)

A first step of pulverizing domestic high-grade limestone and silica fume to have a particle size of 5 to 70 μm to produce a fine limestone powder and a fine silica fume powder;
a second step of mixing the limestone fine powder and the silica fume fine powder in a molar ratio of 1:1 to prepare a limestone-silica fume mixed powder;
a third step of calcining the limestone-silica fume mixed powder at 1150 to 1350° C. to prepare a calcium silicated base cement clinker;
a fourth step of preparing a calcium-silicate cement clinker paste by mixing 35 to 45 parts by weight of water based on 100 parts by weight of the calcium-silicate cement clinker;
A fifth step of preparing a calcium-silicate cement clinker first hardened body by putting the calcium-silicate cement clinker paste in a mold and first curing it for 44 to 52 hours at a temperature of 15 to 25° C. and a relative humidity of 65 to 75%; And
Calcium-silicate cement clinker by removing the mold of the first hardening body of the calcium-silicate cement clinker and curing it for 124 to 172 hours in an atmosphere of 15 to 25% of carbon dioxide, a temperature of 15 to 25°C, and a relative humidity of 65 to 75%. A method for producing a hardened calcium silicate cement clinker using domestic limestone and silica fume, comprising: a sixth step of preparing a second hardened body.
The method of claim 1, wherein the major mineral phases of the domestic high-grade limestone are CaCO ₃ , SiO ₂ , and CaMg(CO ₃ ) ₂ .
The method according to claim 1, wherein the calcium-silicate cement clinker is 72.2 to 74.3% by weight of CS, 17.1 to 18.9% by weight of C ₃ S ₂ , 4.8 to 5.3% by weight of C ₂ S and 3.2 to 3.6% by weight of unreacted SiO ₂ as the main mineral phase. % Calcium using domestic limestone and silica fume, characterized in that it comprises a method for producing a hardened silica silicate cement clinker.
[2] The method of claim 1, wherein the calcium-silicate cement clinker first hardened body is dried and hardened with water.
The method of claim 1, wherein the calcium-silicate cement clinker secondary hardened body contains CaCO ₃ and amorphous SiO ₂ resulting from the carbonation reaction. .
According to claim 1, wherein the calcium-silicate cement clinker secondary hardening body is calcium-silicate cement clinker production method, characterized in that from the age of 10 hours of secondary curing CaCO ₃ is formed.
The method of claim 1, wherein the calcium-silicate cement clinker secondary hardening body has a compressive strength of 50 to 60 MPa at an age of 150 to 180 hours of secondary curing.

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