JP2017142140A - Fly ash activity index prediction method, and method for producing fly ash mixed cement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for accurately predicting an activity index that is one of indices showing pozzolanic reactivity of fly ash in a short period of time.SOLUTION: The fly ash activity index prediction method includes calculating a prediction value of an activity index of fly ash using a Blaine specific surface area of the fly ash, a SOcontent in the fly ash, a content of mullite in the fly ash and a content of an amorphous phase in the fly ash to predict the activity index. Further, the method for producing fly ash mixed cement includes determining a mixing ratio of one kind of fly ash or two or more kinds of fly ash having different activity indices to a substrate cement according to the activity index determined using the fly ash activity index prediction method, and mixing the fly ash and the base material cement according to the mixing ratio to produce fly ash mixed cement.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for predicting an activity index of fly ash and a method for producing fly ash mixed cement using the method.

  In the fly ash mixed cement in which a part of the cement is replaced with fly ash, Si and Al eluted from the fly ash are incorporated into the cement hydrate in the vicinity of the fly ash particles, and the low Ca type CS— An H (calcium silicate hydrate) phase is produced. This generation reaction is called a pozzolanic reaction, and the C—S—H phase has an effect of enhancing the durability of the concrete, for example, suppressing the alkali silica reaction (ASR).

By the way, according to the fly ash nationwide survey report of the coal energy center of Japan, the amount of fly ash generated in 2013 was 12.89 million tons (the breakdown is 9.93 million tons in the electric business, 29.6 million tons.) Moreover, in Japan, where the power source must largely depend on thermal power generation, a situation where a large amount of fly ash is generated is expected to continue for a while.
Of this fly ash, the amount effectively used as cement admixture or concrete admixture is about 180,000 tons, which is only 1.4% of the total amount of fly ash generated. In this way, one of the reasons for the low utilization rate of fly ash in the field of actively utilizing fly ash's pozzolanic reactivity is the type of coal and combustion process that strongly affect the chemical composition and powder characteristics of fly ash. This is because the quality of the fly ash generated and supplied is not stable because the factors such as these differ for each line of the coal-fired power plant.

  From this situation, when fly ash is used as a cement mixture or the like, it is necessary to check whether the fly ash satisfies the required quality for each lot. Normally, the pozzolanic reactivity of fly ash is evaluated using the activity index test method specified in JIS A 6201 “Fly Ash for Concrete”, but it takes 28 days or 91 to obtain this test result. Since a long period of time is required, it was difficult to say that it was a practical quality evaluation test method. Therefore, there has been a need for an efficient method for early determination of fly ash pozzolanic reactivity.

Under such circumstances, several methods for determining the pozzolanic reactivity of fly ash have been proposed.
For example, in the study described in Non-Patent Document 1, the correlation coefficient (R) between the API value of the following formula (1) obtained by reacting at a temperature of 80 ° C. for 12 to 24 hours and the activity index is 0. Since it is as high as .78 to 0.93, it is said that the pozzolanic reactivity of fly ash can be evaluated using the API value.
API (%) = ((Ca (C) −Ca (F + C)) / Ca (C)) × 100 (1)
Here, Ca (C) represents the Ca ²⁺ concentration in the liquid phase (reference sample) in which the cement sample alone is hydrated, and Ca (F + C) is the liquid phase in which the mixture of fly ash and cement is hydrated (for evaluation) Represents the Ca ²⁺ concentration in the sample.

The research described in Non-Patent Document 2 relates to the relationship between the mineral composition of fly ash and the pozzolanic reactivity. In fly ash, which has almost the same degree of fineness as the glass phase related to pozzolanic reactivity, the M value of the following formula (2) considering the modified oxide in the glass phase is an index for evaluating pozzolanic reactivity. It is going to be.
M = (CaO + MgO + R ₂ O) / SiO ₂ (2)

  Furthermore, the method for predicting the activity index of concrete fly ash described in Patent Document 1 measures the electrical resistance value within 7 days of age of the cured fly ash obtained by the pozzolanic reaction of fly ash, and obtains it in advance. This is a method for predicting the activity index of fly ash based on the correlation between the activity index and the electrical resistance value. However, the prediction method is not practical because the test method is special and it takes about 7 days at the longest to obtain the prediction result.

  Incidentally, in recent years, a new method has been developed that quantitatively analyzes constituent phases in a plurality of mixed phases using powder X-ray diffraction. For example, the PONKCS (Partial Or No Known Crystal Structure) method is a data analysis method capable of quantitatively analyzing constituent phases of a plurality of mixed phases including an amorphous phase such as fly ash without using an internal standard substance. . Further, Non-Patent Document 3 reports that if this is further developed and the PONKCS method and the Rietveld analysis method are combined, quantitative analysis of constituent phases in a plurality of mixed phases can be performed in a short time. Furthermore, Non-Patent Document 4 reports that the method based on this combination is also useful for quantitative analysis of the amount of blast furnace slag in blast furnace cement.

Takeshi Yamamoto et al., “Study on pozzolanic reaction of fly ash-elucidation of pozzolanic reaction mechanism and optimization of accelerated chemical test method (API method)-”, Central Research Institute of Electric Power, N04008 (2004) Taku Otsuka et al., “Mineral composition of fly ash and pozzolanic reactivity”, Cement and concrete papers, No. 63, pp. 16-21 (2009) N.V.Y.Scarlett et al .; Quantification of phases with partial or no known crystal structures, Powder Diffraction, Vol. 21, No. 4, pp. 278-284 (2006) BRUKER website; QPA with Partial or No Known Crystal Structures (PONKCS), BRUKER Advanced XRD Workshop (2011)

JP 2012-47587 A

  Therefore, an object of the present invention is to provide a method capable of accurately predicting the activity index of fly ash in a short time.

Therefore, as a result of intensive studies on the method for predicting the activity index of fly ash, the present inventor has rapidly and quantitatively evaluated the activity index of fly ash by using the following formulas (3) and (4). We found what we could do and completed the present invention.
That is, the present invention is a method for predicting the activity index of fly ash having the following configuration.

[1] Fly ash brain specific surface area (cm ² / g), SO ₃ content (mass%) in fly ash, mullite content (mass%) in fly ash, and amorphous in fly ash A fly ash activity index prediction method that calculates and predicts a predicted value of fly ash activity index using the mass phase content (% by mass).
[2] The fly ash activity index prediction method according to [1], wherein the predicted value of the fly ash activity index is calculated and predicted using the following formulas (3) and (4): .
28-day age activity index = 12.95
+0.005 x (Brain specific surface area of fly ash)
+ 4.51 × (SO ₃ content in fly ash)
+ 0.60 × (Mullite content in fly ash)
+ 0.57 × (content ratio of amorphous phase in fly ash) (3)
91-day age activity index = 1.88
+ 0.008x (Brain specific surface area of fly ash)
+ 13.53 × (SO ₃ content in fly ash)
+ 0.78x (content of mullite in fly ash)
+ 0.70 × (content ratio of amorphous phase in fly ash) (4)
However, the unit of the variable in the above formula is that the specific surface area of branes is cm ² / g, the content of SO ₃ , the content of mullite, and the content of amorphous phase is mass%.
[3] The fly ash activity according to [1] or [2], wherein the content of the amorphous phase of the fly ash is determined using a powder X-ray diffraction-Riet belt analysis method combined with a PONKCS method. Degree index prediction method.
[4] One type of fly ash or two types having different activity indexes based on the activity index calculated using the fly ash activity index prediction method according to any one of [1] to [3] A method for producing fly ash mixed cement, wherein the fly ash is mixed with base cement, and fly ash and base cement are mixed according to the mixing ratio to produce fly ash mixed cement.
Here, the mixing ratio is a fly ash content (mass%) when the total amount of one kind of fly ash or two or more kinds of fly ash having different activity indexes and the base cement is 100. ).

  The fly ash activity index predicting method of the present invention can accurately predict the fly ash activity index in a short time. Moreover, the manufacturing method of the fly ash mixed cement of this invention using this activity index prediction method has an on-line analysis system provided with the powder X-ray diffractometer, the fluorescent X-ray analyzer, and the Blaine specific surface area automatic measuring device. If used at the cement manufacturing site, quality control personnel in the manufacturing process of fly ash mixed cement can be minimized.

It is a figure which shows the correlation of the predicted value of fly ash activity index | exponent, and a measured value, (a) shows the correlation in 28-day material age, (b) shows the correlation in 91-day material age.

As described above, the fly ash activity index predicting method of the present invention uses the fly ash specific surface area, SO ₃ content, amorphous phase content, and mullite content to determine the activity of fly ash. This is a method of predicting by calculating the predicted value of the degree index.
Hereinafter, the present invention will be specifically described by dividing it into a fly ash activity index prediction method and a fly ash mixed cement production method.

1. Activity index prediction method of fly ash (1) Measurement of fly ash and its specific surface area of fly ash The fly ash which is the object of the evaluation of the present invention is not particularly limited, and is a coal-fired power plant, an oil refinery, and other chemical plants. It is the fine powder collected by the dust collector from the combustion gas generated when pulverized coal is burned by the above method.
The measurement of the specific surface area of fly ash is usually performed in accordance with JIS A 6201 “Fly Ash for Concrete”.

(2) Determination of SO ₃ content of fly ash The fly ash is preferably dried in advance. Although the drying method of fly ash is not specifically limited, For example, according to JIS A6201 "Fly ash for concrete", the method of heating at 105 degreeC until fly ash becomes constant weight is mentioned.
The method for quantifying the amount of SO _{3 in} fly ash is not particularly limited, but since it can be quantified in a short time, it is preferably carried out by fluorescent X-ray analysis (calibration curve method or fundamental parameter method).
Note that the SO ₃ of fly ash is estimated to be derived from the SO _X component in the combustion gas aggregated on the surface of the fly ash when it is collected by the dust collector. In addition, the mechanism of action by which the SO ₃ component of fly ash increases the pozzolanic reactivity of fly ash is considered to be the same as the mechanism of action of gypsum, which is a stimulant of pozzolanic activity. However, since the same pozzolanic reactivity can be obtained with a small amount of SO _{3 in} comparison with gypsum added from the outside, it is expected that the SO ₃ component is effectively present on the surface of the fly ash particles.

(3) Quantification of mullite and amorphous phase in fly ash The method for quantifying the mineral composition (content) of mullite in fly ash is not particularly limited, but can be quantified in a short time. Performed by powder X-ray diffraction-Riet belt analysis method described in A. By this quantitative method, the mullite content in fly ash and the amorphous phase content in the prediction formula are obtained.
Reference A: Kiyoichi Hoshino et al. “Application of X-ray diffraction / Rietbelt method in the determination of minerals of cement containing amorphous admixtures”, Cement and Concrete Papers, No. 59, pp. 14-21 (2005)
Examples of the powder X-ray diffractometer include D8 ADVANCE (manufactured by Bruker AXS), and examples of the analysis software include DIFFRAC ^plus TOPAS (Ver. 3) (manufactured by Bruker AXS). Can be mentioned.

（iii）前記（ii）で求めたＺ_ｍ×Ｍ_ｍは、フライアッシュにほぼ固有の値であって、フライアッシュの銘柄間の相違は、非晶質相の定量精度に影響しないため、一度求めたＺ_ｍ×Ｍ_ｍは銘柄の異なるフライアッシュにも使用できるから、前記（ii）で求めたＺ_ｍ×Ｍ_ｍを、前記（５）式に代入して、非晶質相の含有率が未知であるフライアッシュのＷ_ｍの計算に使用する。
なお、フライアッシュ中のα-石英やムライト等の非晶質相以外の鉱物は、公知の結晶構造データを用いることにより前記（５）式中のＺ、Ｍ、およびＶの各定数を算出できる。
リートベルト解析−ＰＯＮＫＣＳ法による解析は、市販のＸ線回折解析ソフトウェアを用いることができ、例えば、前記ＤＩＦＦＲＡＣ^ｐｌｕｓＴＯＰＡＳ（Ｖｅｒ．３）（ブルカー・エイエックスエス社製）が挙げられる。 Furthermore, in order to improve the quantitative accuracy of the content ratio of the amorphous phase, it is more preferable to use a method in which the Rietveld analysis is combined with the PONKCS method (hereinafter referred to as “Rietveld analysis—PONKCS method”).
The quantification of the amorphous phase using the Rietveld analysis-PONKCS method is specifically performed according to the following procedures (i) to (iii).
(I) A powder X-ray diffraction of fly ash is measured, a virtual crystal structure model showing the same X-ray diffraction profile as the obtained halo pattern is calculated, and a unit cell volume V _m of the virtual crystal is obtained.
(Ii) Prepare fly ash with a known amorphous phase content determined in advance using an internal standard method, external standard, dummy peak method or the like, and obtain an X-ray diffraction pattern of the fly ash . Then, from the V _m obtained in the above (i) and the content of the amorphous phase, the amorphous phase constant Z _m × M _m in the quantitative equation of the Rietveld analysis method represented by the following formula (5) Ask for. The fly ash used in (ii) is preferably the same as the fly ash obtained by determining the unit cell volume V _m in (i), but the difference in the halo pattern of the X-ray diffraction profile between the brands of fly ash is ignored. Since it is as small as possible, it is possible to use a fly ash different from the fly ash used in (i).

(Iii) Z _m × M _m obtained in the above (ii) is a value inherent to fly ash, and the difference between brands of fly ash does not affect the quantitative accuracy of the amorphous phase. Since the obtained Z _m × M _m can be used for fly ash with different brands, the Z _m × M _m obtained in the above (ii) is substituted into the equation (5) to obtain the content of the amorphous phase. Is used to calculate W _m of fly ash for which is unknown.
For minerals other than the amorphous phase such as α-quartz and mullite in fly ash, the constants Z, M, and V in the formula (5) can be calculated by using known crystal structure data. .
For the analysis by Rietveld analysis-PONKCS method, commercially available X-ray diffraction analysis software can be used, and examples thereof include DIFFRAC ^plus TOPAS (Ver. 3) (manufactured by Bruker AXS).

(4) Derivation of activity index prediction formula The activity index prediction formula used in the present invention (formulas (3) and (4)) is based on the activity index shown in Table 1 below as an objective variable. It is a multiple regression equation obtained by multiple regression analysis using the Blaine specific surface area, SO ₃ content, amorphous phase content, and mullite content as explanatory variables. In addition, since the same multiple regression equation is obtained also for fly ash (group) other than the fly ash of Table 1, the fluctuation | variation of the constant and coefficient in the multiple regression equation by the difference in fly ash (group) is small. .

2. Manufacturing method of fly ash mixed cement The manufacturing method of the fly ash mixed cement of this invention was calculated | required using the activity index prediction method of the fly ash in any one of said [1]-[3] as above-mentioned. Based on the activity index, the mixing ratio of one type of fly ash or two or more types of fly ash having different activity indexes to the base cement is determined, and the fly ash and the base cement are mixed according to the mixing ratio. The method for producing fly ash mixed cement includes the following methods (a) and (b).
That is, based on the predicted value of the fly ash activity index determined using the fly ash activity index prediction method,
(A) When the mixing ratio of fly ash in the fly ash mixed cement is fixed, a plurality of fly ash having different activity index prediction values are used to satisfy the strength expression required for the fly ash mixed cement. After setting the mixing ratio of each fly ash so as to be a fly ash having an index, the manufacturing method of mixing each fly ash and the base cement according to the mixing ratio and the mixing ratio,
(B) When the mixing ratio of fly ash in the fly ash mixed cement is arbitrary, after setting the mixing ratio of fly ash so as to satisfy the strength development of the fly ash mixed cement, the mixing ratio and the mixing ratio are determined. This is a manufacturing method in which fly ash and base cement are mixed.
Here, when the mixing ratio of the fly ash of the fly ash mixed cement (a) is fixed, if there is a fly ash having an activity index that satisfies the strength development of the fly ash mixed cement, by one type It is sufficient to mix the one type of fly ash with the base cement.
The base cement used in the method for producing the fly ash mixed cement of the present invention is not particularly limited, and is usually Portland cement, early-strength Portland cement, ultra-early-strength Portland cement, moderately hot Portland cement, low heat Portland cement, sulfuric acid resistant 1 or more types chosen from salt Portland cement, eco-cement, and blast furnace cement are mentioned.

Hereinafter, the two production methods of fly ash mixed cement will be described more specifically.
(A) When the fly ash mixing ratio in the fly ash mixing cement is fixed For the purpose of ensuring the suppression effect of the alkali silica reaction, the mixing ratio of the fly ash in the fly ash mixing cement is already fixed (set ), For example, a fly ash mixed cement is produced according to the procedures described in the following (i) to (iv).
(I) Fly ash received at the manufacturing site of fly ash mixed cement is stored in separate storage facilities for each appropriate category such as the receiving lot, and using the fly ash activity index prediction method, For each storage facility, determine the predicted value of the fly ash activity index.
(Ii) Next, the fly ash activity index target is set so as to satisfy the strength development required for the fly ash mixed cement under the fly ash mixing rate fixed (set) to the fly ash mixed cement. The value is set based on the actual value.
(Iii) The mixing ratio of each fly ash is set for each storage facility obtained in (i) so as to satisfy the target value of the activity index of fly ash set in (ii). Specifically, for example, the predicted value of the activity index of each fly ash for each storage facility obtained in (i) above is a weighted average value based on the mixing ratio of each fly ash, in (ii) above. What is necessary is just to satisfy the target value of the activity index of the set fly ash.
(Iv) Next, fly ash and base cement are mixed to obtain fly ash mixed cement. In this step, according to the mixing ratio of each fly ash set in (iii) above, the fly ash extracted from each storage facility is mixed to prepare a fly ash mixture, and then the mixture and the base cement are mixed. Alternatively, the base cement and a plurality of fly ash may be mixed at the same time. In addition, including the case of (b) described later, the apparatus used for mixing fly ash with each other or fly ash and base cement is an apparatus usually used for manufacturing mixed cement in a cement factory, that is, a continuous type or a batch type. In addition, various mixing devices such as a container rotating type, a container fixing type, and a particle motion type can be used.

(B) When the mixing rate of fly ash in the fly ash mixing cement is arbitrary When the variation of the mixing rate of fly ash in the fly ash mixing cement is acceptable, such as when the performance specification type quality standard is applied mutatis mutandis. According to the procedure described in the following (v) to (viii), a fly ash mixed cement is produced. In the case of (b), it is possible to use a mixture of a plurality of fly ash as in the case of (a), but for the sake of clarity, one type of fly ash is used. This will be described below.
(V) The predicted value of the activity index of fly ash is obtained in the same manner as in (i) above.
(Vi) Next, a fly ash mixed cement (hereinafter referred to as “reference fly ash mixed cement”) that satisfies the actual strength development required for the fly ash mixed cement is selected and the activity of the fly ash used in the cement is selected. The degree index (P _A ) and the fly ash mixing ratio (F _A ) are confirmed and set as the target value of the fly ash mixed cement to be manufactured.
(Vii) The fly ash mixing ratio (F _B ) of the fly ash mixed cement to be manufactured is calculated using the following formula (6). In the following formula (6), it is assumed that the strength development of the base cement in the reference fly ash mixed cement and the fly ash mixed cement to be manufactured is the same.
F _B = (P _A −100) / (P _B −100) × F _A (6)
However, the in (6), the mixing ratio of the fly ash of the fly ash mixed cement F _B is the manufacture (mass%), P _A is the measured value of the activity index of the fly ash used in the reference fly ash mixed cement (%), P _B represents a predicted value (%) of fly ash of the fly ash mixed cement to be manufactured, and F _A represents an actually measured value (mass%) of the mixing ratio of the fly ash of the reference fly ash mixed cement. Further, 100 in the formula (6) is a value related to the strength development of the base cement and corresponds to the activity index of fly ash, and is set to 100 for convenience.
(Viii) The base cement and the fly ash are mixed in accordance with the fly ash mixing ratio (F _B ) obtained in (vii).

EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.
1. Physicochemical property values of fly ash (1) Measurement of fly ash brain specific surface area and activity index The fly ash used was 14 brands of fly ash A to N collected from different thermal power plants, JIS A 6201 It corresponds to fly ash type II to type IV described in “Fly ash for concrete”. And the brane specific surface area and activity index of this fly ash were measured based on the said JIS. The results are shown in Table 1.

(2) Determination of SO ₃ content of fly ash In accordance with the above JIS, fly ash A to N was heated to a constant weight at 105 ° C. to remove moisture, and then the fly ash (hereinafter “dry” The content of SO _{3 in} “fly ash”) was quantified using a fluorescent X-ray analysis method (calibration curve method). The results are shown in Table 1.

(3) Determination of fly ash mullite and amorphous phase content The mineral composition of the dry fly ash was determined using a powder X-ray diffraction-Riet belt analysis method combined with the PONKCS method. The X-ray diffractometer used was D8 ADVANCE (manufactured by Bruker AXS), and the analysis software was DIFFRAC ^plus TOPAS (Ver. 3) (manufactured by Bruker AXS). The results are shown in Table 1.

2. Properties of cement Table 2 shows the Blaine specific surface area and chemical composition of ordinary Portland cement (manufactured by Taiheiyo Cement), and Table 3 shows the mineral composition.
The Blaine specific surface area conforms to JIS R 5201 “Cement physical test method”, LOI (ignition loss) conforms to JIS R 5202 “Cement chemical analysis method”, and the chemical composition conforms to JIS R 5204. The measurement was performed in accordance with “Method for X-ray fluorescence analysis of cement”. Further, the mineral composition was determined using the powder X-ray diffraction-Riet belt analysis method described in Document A. The X-ray diffractometer used was D8 ADVANCE (manufactured by Bruker AXS), and the analysis software was DIFFRAC ^plus TOPAS (Ver. 3) (manufactured by Bruker AXS).

3. Derivation of prediction formula The activity index prediction formula (formulas (3) and (4) above) uses the activity index shown in Table 1 as the objective variable, and uses the brain specific surface area, SO ₃ content, amorphous Using the content rate of the mass phase and the content rate of mullite as explanatory variables, it was determined by performing multiple regression analysis.

4). Prediction of activity index of fly ash (1) Evaluation of prediction accuracy of activity index obtained by the method of predicting activity index of fly ash according to the present invention The specific surface area of fly ash shown in Table 1, SO in fly ash The predicted value of the activity index of fly ash was calculated by substituting the content rate of _3, the content rate of mullite, and the content rate of the amorphous phase into the formulas (3) and (4). The results are shown in Table 4. FIG. 1 shows the correlation between the actually measured fly ash activity index shown in Table 1 and the predicted value shown in Table 4.

As shown in FIG. 1, the correlation between the actual measurement value of the fly ash activity index and the predicted value obtained by the prediction method of the present invention is as follows. The coefficient of determination of age is 0.89, both of which are high. Therefore, the method for predicting the activity index of fly ash according to the present invention, which requires only 1 hour of calculation time, is more useful than the conventional test that required several months to complete the test. Can be used. Then, in a cement factory equipped with an X-ray diffractometer or the like, a fly ash mixed cement having a target strength development property can be easily manufactured using the fly ash activity index prediction method of the present invention. .

Claims (4)

The specific surface area of fly ash (cm ² / g), the content of SO _{3 in} the fly ash (% by mass), the content of mullite in the fly ash (% by mass), and the amorphous phase in the fly ash A fly ash activity index prediction method that calculates and predicts a predicted value of fly ash activity index using content (mass%). The fly ash activity index prediction method according to claim 1, wherein the predicted value of the fly ash activity index is calculated and predicted using the following formulas (3) and (4).
28-day age activity index = 12.95
+0.005 x (Brain specific surface area of fly ash)
+ 4.51 × (SO ₃ content in fly ash)
+ 0.60 × (Mullite content in fly ash)
+ 0.57 × (content ratio of amorphous phase in fly ash) (3)
91-day age activity index = 1.88
+ 0.008x (Brain specific surface area of fly ash)
+ 13.53 × (SO ₃ content in fly ash)
+ 0.78x (content of mullite in fly ash)
+ 0.70 × (content ratio of amorphous phase in fly ash) (4)
However, the unit of the variable in the above formula is that the specific surface area of branes is cm ² / g, the content of SO ₃ , the content of mullite, and the content of amorphous phase is mass%.   The fly ash activity index prediction method according to claim 1 or 2, wherein the amount of amorphous phase of the fly ash is determined using a powder X-ray diffraction-Riet belt analysis method combined with a PONKCS method. One type of fly ash or two or more types of fly ash having different activity indexes based on the activity index determined using the fly ash activity index prediction method according to any one of claims 1 to 3. The fly ash mixed cement is manufactured by determining the mixing ratio of the base cement and mixing the fly ash and the base cement according to the mixing ratio to manufacture the fly ash mixed cement.

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