JP6462405B2 - Method for predicting activity index of fly ash and method for producing fly ash mixed cement - Google Patents

Description

  The present invention relates to a method for predicting an activity index of fly ash, a fly ash for cement admixture or concrete admixture selected by the method, and a method for producing fly ash mixed cement using the fly ash.

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

By the way, according to the coal ash national fact-finding report of the Japan Coal Energy Center, the amount of generated coal ash in 2012 was 12.65 million tons (the breakdown of the generated amount was 9.50 million tons in the electric business, general industry It is 3.6 million tons.) Moreover, in Japan, where the power source must largely depend on thermal power generation, the situation where a large amount of coal ash is generated is expected to continue for a while.
Of this coal ash, the amount effectively used as cement admixture and concrete admixture (fly ash) is about 200,000 tons, which is only 1.6% of the total amount of coal 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.

  Under these circumstances, 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. However, 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 until this test result is obtained. 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)

The research described in Non-Patent Document 3 relates to the effect of suppressing alkali silica reaction (ASR) by fly ash. As a research tool, fly ash is characterized by particle analysis using backscattered electron diffraction, an energy dispersive X-ray spectrometer, and the like, and the fly ash particles are classified into five types of particle constituent phases. Among the five types of particles, the amorphous particles made of Al ₂ O ₃ —SiO ₂ are the total surface area SiO ₂ amount of the particles and ASTM C 1260 “Standard Test Method for Potential Alkali Reactivity of Aggregates ( It is said that there is a negative correlation with the 14-day expansion specified in “Mortar-Bar Method”.
Since the inhibitory effect of fly ash on ASR and the pozzolanic reactivity of fly ash are considered to be closely related, the above study shows that the characteristics of specific fly ash particles classified by the particle constituent phase are indicators of pozzolanic reactivity there is a possibility.

The research described in Non-Patent Document 4 relates to the dissolution behavior of fly ash particles in a high pH solution when cement is hydrated. And the dissolution characteristics of fly ash up to the age of 28 days differ depending on the chemical composition of the amorphous phase, and Al ₂ O ₃ —SiO ₂ amorphous particles having a high CaO content are the highest in pozzolanic reactivity, Al ₂ O ₃ —SiO ₂ amorphous particles with low CaO content follow, followed by Al ₂ O ₃ —SiO ₂ amorphous particles with medium CaO content reported the lowest pozzolanic reactivity doing.

  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.

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 Industry, N04008 (2004) Taku Otsuka et al., “Mineral composition of fly ash and pozzolanic reactivity”, Cement and concrete papers, No. 63, pp. 16-21 (2009) Haruka Takahashi et al., "FA Characterization Using SEM-EDS / EBSD and Particle Analysis", Taiheiyo Cement Research Report, 162, pp. 3-14 (2012) K.L.Aughenbaugh et al., “An examination of the reactivity of fly ash in cementitious pore solutions”, Materials and Structures, Vol.46, pp.869-880 (2013)

JP 2012-47587 A

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

Therefore, as a result of intensive studies on the prediction method, the present inventor obtained (1) particles composed of mullite and an amorphous phase, and (2) Al, obtained by classifying fly ash particles based on the particle constituent phase. About two types of fly ash particles of particles composed only of ₂ O ₃ —SiO ₂ system amorphous phase, the volume ratio in the total fly ash and the particles before and after the hydration test of fly ash in an alkaline aqueous solution The present inventors have found that the activity index of fly ash can be predicted based on the geometrical metric values.
That is, the present invention is a fly ash activity index predicting method having the following configuration.

[1] Fly ash in an alkaline aqueous solution using fly ash particles whose particle constituent phase is composed of mullite and an amorphous phase and fly ash particles composed of only an Al ₂ O ₃ —SiO ₂ -based amorphous phase Hydration reaction test (hereinafter referred to as “alkali hydration reaction test”) was performed, and the prediction formula derived based on the geometric metric values of fly ash particles measured before and after the alkali hydration reaction test was used. A method for predicting the activity index of fly ash, which calculates a predicted value of the activity index of fly ash.
[2] The fly ash activity index prediction method according to [1], wherein the geometric metric value of the fly ash particles is a volume ratio and a particle size distribution of a circle-equivalent diameter.
[3] The alkali hydration reaction test is the test according to the above [1] or [2], wherein the fly ash is immersed in a 0.5 M aqueous sodium hydroxide solution and cured in an environment of 70 ° C. to 90 ° C. Fly ash activity index prediction method.
[4] Using a prediction formula for the fly ash activity index obtained by performing the following steps (A) to (G), the predicted value of the fly ash activity index is calculated and predicted. The fly ash activity index prediction method according to any one of [1] to [3].
(A) Acquisition step of reflected electron image (hereinafter referred to as “BSE image”) and backscattered electron diffraction pattern (hereinafter referred to as “EBSD pattern”) of fly ash particles (B) Specific step of fly ash particles (C) Mullite (A) Step of measuring geometrical metric values of fly ash particles consisting of only amorphous and amorphous phases, and fly ash particles consisting only of Al ₂ O ₃ —SiO ₂ based amorphous phase (D) consisting of mullite and amorphous phase Step of performing alkali hydration reaction test using fly ash particles and fly ash particles comprising only an Al ₂ O ₃ —SiO ₂ -based amorphous phase (E) Fly ash after completion of alkali hydration reaction test Particle identification step (F) After the completion of the alkali hydration reaction test, fly ash particles comprising the identified mullite and amorphous phase, And Al ₂ O ₃ -SiO ₂ system geometric metric of the fly ash particles consisting of an amorphous phase only measuring step (G) the step of deriving the prediction formula for deriving the prediction expression based on the geometric metric [ 5 ] Cement and fly ash for cement mixture selected based on the fly ash activity index predicted using the fly ash activity index prediction method according to any one of [1] to [4] A method for producing fly ash mixed cement.

  The fly ash activity index predicting method of the present invention can accurately predict the fly ash activity index in a short time. The fly ash for cement admixture or concrete admixture of the present invention has high pozzolanic reactivity. Furthermore, the method for producing fly ash mixed cement of the present invention can produce a fly ash mixed cement having excellent strength development.

It is a graph which shows the correlation with the predicted value of the activity index calculated | required in the below-mentioned Example 1, and the measured value of an activity index, (a) is a graph in material age 28 days, (b) is material age 91. It is a graph in a day. It is a graph which shows the correlation with the API value calculated | required in the comparative example 1 of the postscript, and the measured value of an activity index | exponent, Comprising: (a) is a graph in material age 28 days, (b) is a graph in material age 91 days. is there.

As described above, the present invention uses a fly ash particle whose particle constituent phase is composed of mullite and an amorphous phase and a fly ash particle composed only of an Al ₂ O ₃ —SiO ₂ based amorphous phase, The fly ash activity was calculated by calculating a predicted value of the activity index of fly ash using a geometric metric of fly ash particles measured before and after the alkali hydration test. It is a method of predicting an index.
In the present invention, preferably, (A) a BSE image and EBSD pattern acquisition process of fly ash particles, (B) a fly ash particle identification process, and (C) a geometric metric measurement process for fly ash particles. , (D) Step of performing alkali hydration test, (E) Step of specifying fly ash particles after completion of alkali hydration test, (F) Geometry of fly ash particles after completion of alkali hydration test The fly ash activity index is calculated using a prediction formula obtained by performing a measurement step of a static metric value, and (G) a prediction formula derivation step of deriving a prediction formula based on the geometric metric value. It is a method of prediction.
Hereinafter, the present invention will be specifically described for each step.

(A) BSE image and EBSD pattern acquisition step of fly ash particles The step includes (A-1) a preparation process of a sample in which fly ash and a resin before alkali hydration test are mixed and cured, and (A -2) It consists of the acquisition process of the BSE image and EBSD pattern which acquires the BSE image and EBSD pattern of fly ash particle | grains using a scanning electron microscope. The scanning electron microscope preferably includes a field emission electron gun that can be used to make a microprobe and has high energy resolution.
Next, the BSE image and the EBSD pattern will be described.
(I) BSE image The BSE image is represented by gray level shading, and reflects the average value of the atomic numbers of atoms present in the region where the reflected electrons are generated. The larger the average value, the brighter the BSE image, that is, the gray level becomes lighter. Accordingly, the greater the gray level difference between fly ash particles, the greater the difference in chemical composition of the particles. As will be described later, the BSE image is further binarized and then used for specifying fly ash particles.
(Ii) EBSD pattern An EBSD pattern is generated when an electron beam is incident on fly ash particles. A region where the EBSD pattern exists is determined as a crystalline phase, and a region where the pattern does not exist is determined as an amorphous phase. .

(B) Fly ash particle identification step In this BSE image, the BSE image is binarized based on the gray level of the BSE image in order to separate the fly ash particles from the resin and extract the fly ash particles. Is a step of extracting (identifying) and identifying. Specifically, the step creates a histogram based on the gray level of the BSE image, determines a threshold value for extracting fly ash particles from the histogram, and binarizes the BSE image using the threshold value. Process to identify fly ash particles. For example, when the BSE measurement conditions are an irradiation current of 300 pA and an acceleration voltage of 15 keV, a region having a gray level value of 100 or more as a threshold can be specified as fly ash particles.

(C) Step of measuring geometric metric value of fly ash particles The step includes fly ash particles composed of mullite and an amorphous phase, and fly ash particles composed only of an Al ₂ O ₃ —SiO ₂ based amorphous phase. It is the process of measuring the geometrical metric value of.
The fly ash particles consisting of mullite and amorphous phase, and Al ₂ O ₃ -SiO ₂ -based process to identify the fly ash particles consisting of an amorphous phase alone, the following (C-1) ~ ( C-4).

(C-1) Determination process of crystal phase and amorphous phase of particle constituent phase in fly ash particle This process is based on the acquired EBSD pattern, and the particle constituent phase in the identified fly ash particle is a crystal Whether the phase is an amorphous phase or not is determined, and what is determined as a crystalline phase is a process of further identifying a crystalline phase (specifying a particle constituent phase) based on an EBSD pattern.

(C-2) Chemical composition threshold value determination process for classifying fly ash particles into particle constituent phases The process involves determining the chemical composition of fly ash particles used to classify fly ash particles into five types of particle constituent phases. It is a process of measuring. The five types of particle constituent phases are hematite (Fe ₂ O ₃ ) or magnetite (Magnetite, Fe ₃ O ₄ ) and an amorphous phase, α-quartz (Low-Quartz, SiO ₂ ). a phase as a main phase, mullite _{(mullite, 2SiO 2 · 3Al 2} O 3) and phase of an amorphous _phase, Al ₂ O 3 -SiO ₂ based amorphous phase alone of phase, and _Al 2 _{O 3} It is a phase composed only of a —SiO ₂ —CaO-based amorphous phase.
The crystalline phase is classified based on the identification result of the previous item (C-1), and the amorphous phase is classified based on the analytical value of the chemical composition by energy dispersive X-ray spectroscopy (hereinafter referred to as “EDS”). The chemical composition of several tens of representative particles is measured using EDS, and the chemical composition threshold value used for classifying each fly ash particle into the particle constituent phase based only on the chemical composition is determined.

(C-3) Classification process of fly ash particles This process is a process of classifying all fly ash particles whose chemical composition is measured using EDS based on the determined chemical composition threshold value for each particle constituent phase. is there. The number of fly ash particles (parameter) used for classification is preferably 5000 or more per fly ash sample.

(C-4) Measuring process of geometric measurement value of fly ash particles
(C-3) Among the particle constituent phases classified in the process, fly ash particles composed of mullite and an amorphous phase, and fly ash particles composed only of an Al ₂ O ₃ —SiO ₂ based amorphous phase are identified. Measure the geometrical metric of the particles.
Examples of the geometric metric value of the fly ash particles include a volume ratio and a particle size distribution of a circle-equivalent diameter (50% particle size (D50) and the like). The particle size distribution of the volume ratio and the equivalent circle diameter can be measured using commercially available particle analysis software.

(D) Implementation Step of Alkaline Hydration Reaction Test This step can be performed, for example, according to the following procedures (1) to (5).
(1) 20 g of fly ash and 100 g of a 0.5 M aqueous sodium hydroxide solution (pH 13.7) are placed in a polypropylene lidded container and stirred at room temperature for 1 hour using a stirrer.
(2) The container is transferred into a thermostat and hydrated in the alkaline aqueous solution at 80 ± 5 ° C. for 3 days.
(3) After completion of the reaction, the reaction solution is cooled to room temperature and suction filtered to separate fly ash.
(4) The separated fly ash is washed with acetone and then immersed in acetone to completely stop the hydration reaction.
(5) After suction filtration to separate fly ash and acetone, the fly ash is dried at room temperature for 12 hours.

(E) Step of specifying fly ash particles after completion of alkali hydration test, (F) Geometry of fly ash particles after completion of alkali hydration test Each process of the measurement process
(i) The subject is fly ash particles after completion of the alkali hydration test,
(ii) The image analysis of the geometric metric value is performed only for the particle size distribution of the equivalent circle diameter, and
(iii) Since the chemical composition of the fly ash particles after the alkali hydration test is changed due to the hydration reaction, other than the three items for identifying the particle constituent phase using the chemical composition at the center of the particles Are carried out in the same manner as in the steps (B), (C-3) and (C-4), respectively.

When the volume ratio and the equivalent circle diameter particle size distribution are used as the geometric measurement value, for example, D50, which is an index indicating the particle size distribution, is obtained for each of the particle constituent phases. Substituting into the formula, C value is obtained.
C = 1 − ((D50 before alkali hydration test) / (D50 after alkali hydration test)) ³ (3)
The number of fly ash particles used for measurement is preferably 1000 or more, more preferably 2000 or more, and still more preferably 5000 or more.

(G) Step of deriving a prediction formula for deriving a prediction formula based on the geometric metric value This step uses, for example, an actual measurement value of fly ash activity index as an objective variable, and mullite and amorphous as explanatory variables Using the volume ratio and C value of fly ash particles composed of a solid phase and the volume ratio and C value of fly ash particles composed of an Al ₂ O ₃ —SiO ₂ system amorphous phase, multiple regression analysis was performed, and fly ash was analyzed. To obtain a formula for predicting the activity index.

The fly ash for cement admixture or concrete admixture of the present invention is a fly ash selected based on the activity index predicted using the fly ash activity index prediction method of the present invention. As the reference value of the activity index used as the selection criterion, the activity index defined in JIS A 6201 can be used. For example, when the rule of fly ash type II is adopted as the selection criterion, the standard value of the activity index is 80% or more at the age of 28 days and 90% or more at the age of 91 days.
Moreover, the manufacturing method of the fly ash mixed cement of the present invention is a method of manufacturing a fly ash mixed cement by mixing the cement and the fly ash for a cement mixed material of the present invention. The cement to be mixed is not particularly limited, and may be one or more selected from the group consisting of ordinary Portland cement, early-strength Portland cement, moderately hot Portland cement, low heat Portland cement, blast furnace cement, silica cement, and ecocement. Examples of the mixing device include a ball mill, a Henschel mixer, and a Nauter mixer.

Hereinafter, although the Example of this invention is divided and demonstrated to the said (A)-(G) process, this invention is not limited to this Example.
1. Fly ash used The following four types of fly ash (taken from three lines of two power plants) were used. Table 1 shows the chemical composition and basicity of the fly ash (FA), and Table 2 shows the fineness (brane specific surface area) of the fly ash.

[Example 1]
(A) Process This process includes (A-1) a sample preparation process before the alkali hydration reaction test, and (A-2) a BSE image and EBSD pattern acquisition process.
(A-1) Process A sample was prepared according to the method described in Non-Patent Document 3. Specifically, fly ash and low-viscosity epoxy resin were kneaded at a mass ratio of 1: 1 and cut into a size of about 5 × 5 × 2 mm after the resin was cured. This cut piece was polished using a cross section polisher (manufactured by JEOL Ltd., SM-09020, argon ion beam) under the conditions of an acceleration voltage of 6 keV and a polishing time of 10 hours, and finally carbon was deposited in a thickness of about 5 nm. did.

(A-2) Process A BSE image and an EBSD pattern of fly ash particles were obtained using the prepared sample and a scanning electron microscope equipped with a BSE detector and an EBSD detector.
The equipment used and the analysis conditions are as follows.
[Scanning electron microscope]
Model number: JSM-7001F (field emission type), manufactured by JEOL Ltd.
[BSE detector]
Model number: SM-54060RBEI, manufactured by JEOL Ltd. However, the measurement conditions of BSE were an acceleration voltage of 15 keV, an irradiation current of 300 pA, and a magnification of 1000 times.
[EBSD detector]
Model number: HKL Channel 15, manufactured by Oxford Instruments Inc. However, the measurement condition of EBSD was an acceleration voltage of 3 keV, and the magnification was selected according to the observation object.

Step (B) This step is a step of binarizing the BSE image based on the threshold value provided for extracting the fly ash particles and identifying the fly ash particles in the BSE image based on the binarized image. is there. Specifically, a particle image having a gray level value of 100 or more was specified as fly ash particles under the measurement conditions of the BSE image.

(C) Step The step includes (C-1) a determination process of the crystal phase and the amorphous phase of the particle constituent phase in the fly ash particles, and (C-2) for classifying the fly ash particles into the particle constituent phases. It includes a process of determining a chemical composition threshold, (C-3) a classification process of fly ash particles, and (C-4) a process of measuring geometric metrics of fly ash particles.

(C-1) Process Based on the acquired EBSD pattern, it is determined whether the particle constituent phase in the identified fly ash particle is a crystalline phase or an amorphous phase. Based on the above, identification of the crystal phase (specification of the particle constituent phase) was performed.

(C-2) Process In order to determine the threshold value of the chemical composition value for classifying fly ash particles into the five kinds of particle constituent phases using the chemical composition value, the crystal phase is the identification result in the process (C-1). In addition, the amorphous phase was classified based on the chemical composition value by EDS.
Based on the results thus obtained, the chemical composition values of the fly ash particles classified into each particle constituent phase were measured using EDS for 20 particles for each classification. In addition, the total number of the particle | grain constituent phase whose particle number is less than 20 was measured.
And based on the obtained chemical composition value, the chemical composition threshold value of the particle | grain constituent phase was determined for every fly ash ad. The determined chemical composition threshold is shown in Table 3. The equipment used and the analysis conditions are as follows.
[EDS detector]
Model number: INCA energy, manufactured by Oxford Instruments Inc. However, the measurement conditions of EDS were an acceleration voltage of 15 keV, an irradiation current of 300 pA, a working distance of 10 mm, and an analysis time of 100 sec / measurement point.

(C-3) Process Based on the chemical composition threshold of the particle constituent phase described in Table 3, the particle constituent phase was classified for each of 5000 fly ash particles for each fly ash ad.

(C-4) Process Among the classified particle constituent phases, fly ash particles composed of mullite and an amorphous phase, and fly ash particles composed only of an Al ₂ O ₃ —SiO ₂ based amorphous phase The volume ratio (equivalent to the area ratio) and the particle size distribution of equivalent circle diameter (50% particle size: D50) were measured using the following commercially available particle analysis software.
[Particle analysis software]
Part number: INCA Feature, manufactured by Oxford Instruments

Furthermore, the C value was obtained by substituting the D50 into the equation (3). Table 4 shows the volume ratio, and Table 5 shows the D50 and C values. However, in Tables 4 and 5, the data of particles composed of five types of particle constituent phases are also shown for reference.
The number of fly ash particles used for measurement was 5000 for each sample of fly ash ad.

(D) Process The process was implemented in the following procedures.
(1) 20 g of fly ash and 100 g of a 0.5 M aqueous sodium hydroxide solution were placed in a polypropylene lidded container and stirred at room temperature for 1 hour using a stirrer.
(2) The container was moved into a thermostatic bath and hydrated at 80 ± 5 ° C. for 3 days (72 hours).
(3) After completion of the hydration reaction, the reaction solution was cooled to room temperature and subjected to suction filtration to separate fly ash.
(4) After the separated fly ash was washed with acetone, it was further immersed in acetone to completely stop the hydration reaction.
(5) After separating the fly ash by suction filtration, the fly ash was dried at room temperature for 12 hours.

The next steps, (E) to (F),
(i) The subject is fly ash particles after completion of the alkali hydration test,
(ii) The image analysis of the geometric metric value was performed only for the particle size distribution of the equivalent circle diameter, and
(iii) Step (B), (C-3) and (C) described above, respectively, except that the particle constituent phase was identified using the chemical composition at the center of the fly ash particles after completion of the alkali hydration test. C-4) It implemented similarly to the process. Table 5 shows D50 of the obtained fly ash particles after the alkali hydration test.

As shown in Table 5, the particle constituent phases of the fly ash particles are i) hematite (Fe ₂ O ₃ ) or magnetite (Fe ₃ O), as in Non-Patent Document 2, regardless of the alkali hydration test. ₄₎ a phase amorphous coexist, ii) alpha-quartz (phase SiO ₂₎ is the main phase, iii) mullite _{(2SiO 2 · 3Al 2 O 3} ) and phase amorphous coexist, iv) Al _The phase could be classified into five types: a phase composed solely of ₂ O ₃ —SiO ₂ -based amorphous material, and v) a phase composed solely of Al ₂ O ₃ —SiO ₂ —CaO-based amorphous material.

(G) Process Using the activity index of fly ash 28 days and 91 days of age in Table 2 as the objective variable, the volume ratio of fly ash particles composed of mullite and an amorphous phase as the explanatory variable (Table 4) Values) and C values (values in Table 5), and volume fractions of fly ash particles consisting only of the Al ₂ O ₃ —SiO ₂ system amorphous phase (values in Table 4) and C values (values in Table 5) Multiple regression analysis was performed using the following formulas (4) and (5). However, the coefficient of determination (R ² ) was 0.985 in equation (4) and 0.972 in equation (5). Further, FIG. 1 shows the correlation between the predicted value of the activity index calculated using the prediction formula and the actual measured value of the activity index.
Activity index at 28 days of age = 0.091 × (volume ratio of fly ash particles composed of mullite and amorphous phase × C value) + 0.108 × (Al ₂ O ₃ —SiO ₂ based amorphous phase (Volume ratio of fly ash particles × C value) +76.163 (4)
Activity index at 91 days of age = 0.187 × (volume ratio of fly ash particles composed of mullite and amorphous phase × C value) + 0.210 × (Al ₂ O ₃ —SiO ₂ based amorphous phase (Volume ratio of fly ash particles composed of particles x C value) +83.832 (5)

[Comparative Example 1]
For comparison, the pozzolanic reactivity of fly ash a to d was evaluated by the following procedure using the API method described in Non-Patent Document 1.
(1) As a sample for evaluation, 1.5 g of fly ash, 1.5 g of ordinary Portland cement and 50 mL of pure water, and 1.5 g of ordinary Portland cement and 50 mL of pure water as reference samples, respectively, are made of polypropylene. And stirred for 1 hour at room temperature using a stirrer. Ordinary Portland cement is made by Taiheiyo Cement.
(2) Next, the above-mentioned container was transferred into a thermostat and reacted at 80 ° C. for 18 hours.
(3) After the lapse of the time, the reaction solution was cooled to room temperature and filtered through a polyethylene membrane filter having a pore size of 0.2 μm, and the filtrate was collected.
(4) Further, Ca ²⁺ ions in the filtrate were quantified using an ICP emission spectrometer.
(5) The API value was calculated using the formula (1).
The calculated API values are shown in Table 6. FIG. 2 shows the correlation between the API value and the actually measured activity index value.

  As shown in FIG. 2, the determination coefficient of Comparative Example 1 is 0.162 for material age 28 days and 0.192 for material age 91 days, whereas the determination coefficient of Example 1 is as described above. Age 28 days is 0.985 and material age 91 days is 0.972. Therefore, the fly ash activity index predicting method of the present invention can accurately predict the fly ash activity index in a short time.

Claims (5)

Hydration of fly ash in an aqueous alkali solution using fly ash particles whose particle constituent phase is composed of mullite and an amorphous phase and fly ash particles composed of only an Al ₂ O ₃ —SiO ₂ based amorphous phase A fly ash is calculated by performing a reaction test and calculating a predicted value of an activity index of fly ash using a prediction formula derived based on a geometric metric value of fly ash particles measured before and after the hydration reaction test. Activity index prediction method.   The fly ash activity index prediction method according to claim 1, wherein a geometric metric value of the fly ash particles is a volume ratio and a particle size distribution of equivalent circle diameter.   The activity index prediction of fly ash according to claim 1 or 2, wherein the hydration test is a test in which fly ash is immersed in a 0.5M aqueous sodium hydroxide solution and cured in an environment of 70 ° C to 90 ° C. Method. The predicted value of the activity index of fly ash obtained using the prediction formula of the activity index of fly ash obtained through the following steps (A) to (G) is calculated and predicted. 4. The fly ash activity index prediction method according to any one of 3 above.
(A) Acquisition step of reflected electron image and backscattered electron diffraction pattern of fly ash particle (B) Specification step of fly ash particle (C) Fly ash particle composed of mullite and amorphous phase, and Al ₂ O ₃ —SiO ₂ Step of measuring geometric metric value of fly ash particles consisting of only _two amorphous phases (D) Fly ash particles consisting of mullite and amorphous phases, and only Al ₂ O ₃ —SiO ₂ amorphous phase Step (E) for performing hydration test of fly ash in alkaline aqueous solution using fly ash particles comprising: (E) Step for specifying fly ash particles after completion of hydration test (F) after completion, the identified mullite and fly ash particles of amorphous phase, and Al ₂ O ₃ hula consisting -SiO ₂ based amorphous phase only Prediction equation of deriving step of deriving a predictive equation based on the measuring step (G) the geometric metric geometric metric of ash particles The cement is mixed with fly ash for a cement mixture selected based on the fly ash activity index predicted using the fly ash activity index prediction method according to any one of claims 1 to 4. A method for producing fly ash mixed cement.

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