JP7296839B2 - Cement manufacturing method - Google Patents

Description

The present invention relates to a method for producing cement.

Concrete may be left over after being mixed and used at a construction site. In this case, the surplus concrete is disposed of after hardening, or for the purpose of reusing the aggregate, water is added to the above concrete and the aggregate is separated to form ready-mixed concrete sludge. Become.
As a technique for reusing ready-mixed concrete sludge, Patent Document 1 discloses a water hardening method obtained by kneading concrete sludge fine powder, ordinary Portland cement, aggregate, and an admixture added as necessary. The fine powder of concrete sludge, which is a hardening material, is prepared by adding water to residual concrete or returned concrete to form a slurry, and removing gravel, sand, and fine sand from the slurry to obtain sludge water. Manufactured by a recovery step comprising a separation step, a dehydration step of dehydrating the sludge water to obtain a dehydrated cake, and a crushing and drying step of crushing and drying the dehydrated cake, A water-curable hardening product is described in which sludge fine powder is mixed so as to satisfy the following two formulas.
DSP≦-0.02×S+230 (1 formula)
10≦DSP≦70 (2 formulas)
(However, DSP: the ratio of the concrete sludge fine powder to the binder consisting of the concrete sludge fine powder and the ordinary Portland cement (unit: %), S: the specific surface area of the concrete sludge fine powder (unit: cm ² /g))

JP 2016-204194 A

In recent years, the effective use of ready-mixed concrete sludge has been promoted, but there are still cases where it is discarded, and further effective use of ready-mixed concrete sludge is required.
SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing cement using ready-mixed concrete sludge as a part of cement raw materials, and a method for treating ready-mixed concrete, without disposing of ready-mixed concrete sludge.

As a result of intensive studies to solve the above problems, the inventors of the present invention have found that fresh concrete sludge is dewatered at a temperature of 200 to 1,350 ° C in either the front of the rotary kiln or the cooler. According to the method for manufacturing cement, which includes the steps of: adding a treated material to obtain a raw material for cement consisting of the dehydrated material and cement clinker; and pulverizing and mixing the raw material for cement and gypsum to obtain cement. They found that the object can be achieved, and completed the present invention.
That is, the present invention provides the following [1] to [6].
[1] A method of manufacturing cement using a cement manufacturing apparatus including a rotary kiln and a cooler, wherein the temperature is 200 to 1,350 ° C. in either the front of the rotary kiln or the cooler. a cement raw material manufacturing step for obtaining a cement raw material comprising a dehydrated product of ready-mixed concrete sludge and a cement clinker obtained by firing the cement clinker raw material in the rotary kiln by charging the dehydrated raw concrete sludge to a certain position; A method for producing cement, comprising a pulverizing step of pulverizing and mixing cement raw materials and gypsum to obtain cement.

[2] The method for producing cement according to [1] above, wherein properties of the dehydrated material are determined, and a position for charging the dehydrated material is determined according to the properties.
[3] The above properties are the water content, the content of unhydrated matter, the content of fine aggregate, the content of Ca(OH) ₂ , the content of CaCO ₃ , and CaO of the dehydrated product. The method for producing cement according to the above [1] or [2], wherein the cement is at least one selected from the mass ratio of SiO ₂ (CaO/SiO ₂ ).
[4] The method for producing cement according to any one of [1] to [3], wherein the dehydrated material is introduced at a temperature of 200°C or higher and lower than 400°C.
[5] The method for producing cement according to any one of [1] to [4], wherein the dehydrated product has a median diameter of 250 μm to 100 mm.
[6] A method of treating ready-mixed concrete sludge using a cement manufacturing apparatus including a rotary kiln and a cooler, wherein the temperature is 200 to 1,350 at a position in front of the rotary kiln or in the cooler. ° C. to obtain a cement raw material composed of the dehydrated raw concrete sludge and a cement clinker obtained by firing the cement clinker raw material in the rotary kiln, thereby producing ready-mixed concrete sludge. A method for treating ready-mixed concrete sludge, characterized by including a cement raw material manufacturing step of treating

According to the method for producing cement of the present invention, cement can be produced by using ready-mixed concrete sludge as a part of the raw material for cement. The method can effectively utilize ready-mixed concrete sludge.
Moreover, according to the method for treating fresh concrete sludge of the present invention, by using the fresh concrete sludge as a part of the raw material for cement, the raw concrete sludge can be treated without being disposed of.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing an example of a cement manufacturing apparatus for carrying out the cement manufacturing method of the present invention;

The method for producing cement of the present invention is a method for producing cement using a cement production apparatus including a rotary kiln and a cooler, wherein the temperature is 200 to 1 at any position in front of the rotary kiln or in the cooler. , Dehydrated raw concrete sludge (hereinafter also referred to as "dehydrated product") is put into a position at 350 ° C, and the dehydrated product and cement clinker raw material are fired in a rotary kiln. It includes a cement raw material manufacturing process for obtaining a cement raw material composed of clinker and a pulverizing process for obtaining cement by pulverizing and mixing the cement raw material and gypsum.
Each step will be described in detail below with reference to FIG.
The cement manufacturing apparatus 7 including the rotary kiln 1 and the cooler 3 used in the present invention is not particularly limited, and may be one commonly used in cement manufacturing plants. Further, as the cooler 3, an air quenching cooler is preferable because it is easy to put the dehydrated material into a desired position in the cooler.

[Cement raw material manufacturing process]
In this process, the dehydrated fresh concrete sludge is put into a position in front of the kiln 4 or in the cooler 3 of the rotary kiln 1 and the temperature is 200 to 1,350 ° C., and the dewatered. This is a step of obtaining a cement raw material composed of a treated material and a cement clinker obtained by firing the cement clinker raw material in the rotary kiln 1 .
Examples of ready-mixed concrete sludge include (i) aggregates (coarse aggregates and fine aggregates) contained in the slurry after water is added to concrete left over from construction sites, etc., to form a slurry; (ii) Those containing fine powder components such as cement obtained by separating coarse particles such as (ii) from residues containing concrete generated when agitator trucks are washed, etc., separated from coarse particles such as aggregates and those containing fine powder components such as cement.
As a method for separating coarse particles such as aggregates, for example, a method of separating coarse aggregates and fine aggregates from slurry and residue using a plurality of vibrating sieves with different mesh sizes. is mentioned. The separated coarse aggregate and fine aggregate are reused as aggregate.

The dehydrated product of fresh concrete sludge used in the present invention is obtained by subjecting fresh concrete sludge containing a large amount of water (for example, water content exceeding 80% by mass) to sedimentation treatment, sun drying, filter press, or the like. It is a dehydrated cake (dehydrated cake).
The dehydration means is not particularly limited, but includes, for example, a filter press and the like.
The water content of the dehydrated product is preferably 50% by mass or less, more preferably 45% by mass or less, still more preferably 40% by mass or less, and particularly preferably 35% by mass or less. If the content is 50% by mass or less, the unhydrated matter contained in the dehydrated product reacts while the dehydrated product is transported to the cement factory where the cement manufacturing apparatus 7 is installed. The amount of hydrate can be made smaller, and the strength development of cement can be further improved.

The content of unhydrated matter in the dehydrated product is preferably 10% by mass or more, more preferably 15% by mass or more, and particularly preferably 20% by mass or more. If the content is 10% by mass or more, the strength development of the cement can be further improved.
The content of unhydrated matter in the dehydrated product can be determined, for example, by using the Rietveld method using X-ray diffraction to determine belite (2CaO.SiO ₂ ), alite (3CaO.SiO ₂ ), aluminum in the dehydrated product. Obtained by measuring the content (% by mass) of the nate phase (3CaO.Al ₂ O ₃ ) and the ferrite phase (4CaO.Al ₂ O ₃ .Fe ₂ O ₃ ) and calculating the total of each content can be done.
The content of fine aggregate in the dehydrated product is to increase the amount of fine aggregate recovered in the coarse particle separation step described above to promote the reuse of fine aggregate, and From the viewpoint of removing fine aggregates as much as possible so as not to reduce the strength development of cement manufactured using the dehydrated material as one of the raw materials, it is preferably 20% by mass or less, more preferably 18% by mass or less, and further It is preferably 15% by mass or less, particularly preferably 12% by mass or less.

The content of Ca(OH) ₂ in the dehydrated product is preferably 15% by mass or less, more preferably 10% by mass or less, and particularly preferably 8% by mass or less. If the content is 15% by mass or less, the adverse effects of Ca(OH) ₂ on the setting time and fluidity of cement (specifically, the shortening of the setting time and the decrease in fluidity) can be further reduced. can be done. In addition, when the content exceeds 15% by mass, Ca(OH) ₂ changes to quicklime (CaO) depending on the position where the dehydrated material is introduced, so the amount of quicklime in the obtained cement raw material increases. In some cases, the adverse effects of quicklime on the setting time and fluidity of cement (specifically, a significant shortening of the setting time and the accompanying decrease in fluidity) may become greater.

The content of CaCO ₃ in the dehydrated product is preferably 20% by mass or less, more preferably 15% by mass or less, and particularly preferably 12% by mass or less. If the content exceeds 20% by mass, CaCO ₃ changes to quicklime (CaO) depending on the position where the dehydrated product is introduced, so the amount of quicklime contained in the obtained cement raw material increases, and cement coagulates. The adverse effects of quicklime on time and fluidity (specifically, a significant shortening of setting time and a concomitant decrease in fluidity) may be greater.
The mass ratio of CaO to SiO ₂ (CaO/SiO ₂ ) in the dehydrated product is preferably 1.5 or more, more preferably 2.0 or more, and particularly preferably 2.2 or more. When the mass ratio is 1.5 or more, the strength development of cement is further improved. Further, if the mass ratio is less than 1.5, depending on the position at which the dehydrated material is added, non-hydraulic minerals may be produced, resulting in a decrease in strength development of the cement.
In addition, from the viewpoint of further improving the strength development of cement, the dehydrated product is preferably used (thrown in) within 7 days (more preferably within 4 days) after being obtained by the dehydration treatment. .

The position at which the dehydrated material is charged is either the kiln front 4 of the rotary kiln 1 or the cooler 3, and the temperature is 200 to 1,350°C.
When the dehydrated material is added at a position where the temperature is lower than 200° C. (for example, near the end point of the cooler 3), the strength development and fluidity of the cement are lowered.
When the dehydrated material is put in at a position where the temperature exceeds 1,350 ° C (for example, the kiln bottom side of the rotary kiln 1 rather than the kiln front 4 part of the rotary kiln 1), the cement The energy cost for clinker production increases, stable firing becomes difficult, the quality of the resulting cement clinker becomes uneven, and dust may be generated in the kiln or calciner.

The position at which the dehydrated material is charged is such that the quicklime or slaked lime contained in the dehydrated material is reacted to generate β-C ₂ S (2CaO.SiO ₂ ) or the like, and the quicklime and From the viewpoint of reducing the amount of slaked lime and further improving the strength development of cement, the position where the temperature exceeds 800° C. and is 1,350° C. or less is preferable.
The position of the above temperature range (over 800° C. and 1,350° C. or less) in the cement manufacturing apparatus 7 varies depending on the type of cement clinker raw material, the set temperature of the rotary kiln 1, etc. 800° C.) to Kiln Front 4 (about 1,350° C.).
In addition, heat that has not been used in the past can be used, and the temperature of the secondary air and the tertiary air is lowered, so there is no need to increase the energy required to produce cement clinker. From the point of view, the position where the temperature is 200 to 800° C. is preferable. The location of the above temperature range (200 to 800° C.) in the cement manufacturing apparatus 7 is normally inside the cooler 3 . Among the positions within the above temperature range, positions where the temperature is 200° C. or more and less than 400° C. are more preferable from the viewpoint of further improving the strength development property and fluidity of the cement.

Moreover, the quality of the cement obtained varies depending on the properties of the dehydrated material and the temperature at the position where the dehydrated material is introduced.
For this reason, from the viewpoint of obtaining cement excellent in strength development and fluidity, it is preferable to grasp the properties of the dehydrated material in advance and appropriately determine the position at which the dehydrated material is introduced according to the properties. .
Examples of the properties include the water content, the content of unhydrated matter, the content of fine aggregate, the content of Ca(OH) ₂ , the content of CaCO ₃ , and Mass ratio (CaO/ _SiO2 ) of CaO and _SiO2 etc. are mentioned. These may be used individually by 1 type, and may be used in combination of 2 or more type.

In addition, after dividing the inside of the cooler 3 from the kiln front 4 of the rotary kiln 1 into the following positions (1) to (3) according to the temperature, Depending on the situation, it may be determined which one of the positions (1) to (3) should be used.
(1) Locations where the temperature is above 800°C and 1,350°C or less (2) Locations where the temperature is between 400°C and 800°C (3) Locations where the temperature is between 200°C and below 400°C

Specific examples of determining the position for introducing the dehydrated material according to the properties of the dehydrated material include the following cases.
When the water content of the dehydrated product is small (for example, when the water content is 50% by mass or less), the quality of the cement is little affected regardless of the position of the dehydrated product. It can be determined that positions (positions (1) to (3)) may be thrown.
On the other hand, when the moisture content of the dehydrated product is high (for example, when the moisture content exceeds 50% by mass), the adverse effect of kiln disturbance on cement quality is reduced, and the generation of dust due to heating is reduced. , to the lower temperature position (eg position (3)).
Further, when the content of unhydrated matter in the dehydrated product is large (for example, when the content exceeds 20% by mass), any position (position (1) to (3)) can be determined as good. On the other hand, when the content of unhydrated matter in the dehydrated product is small (for example, when the content is 20% by mass or less), from the viewpoint of further improving the strength development of cement, a higher temperature position ( For example, it can be determined that the fuel is introduced at position (1), preferably at 1,000 to 1,350°C.

When the content of Ca(OH) ₂ in the dehydrated product is small (for example, when the content is 15% by mass or less), it can be added to any position (positions (1) to (3)). can be determined as good.
On the other hand, when the content of Ca(OH) ₂ in the dehydrated product is large (for example, when the content exceeds 15% by mass), the Ca(OH) ₂ contained in the dehydrated product is replaced with quicklime (CaO). and then react with quicklime to generate β-C ₂ S (2CaO.SiO ₂ ) and the like, and improve the strength development of cement. For example, it can be determined that the fuel is introduced at position (1), preferably at 1,000 to 1,350°C.
When the content of CaCO ₃ in the dehydrated product is small (for example, when the content is 20% by mass or less), it is determined that any position (positions (1) to (3)) may be added. be able to.
On the other hand, when the content of CaCO ₃ in the dehydrated product is large (for example, when the content exceeds 20% by mass), CaCO ₃ contained in the dehydrated product is changed to quicklime (CaO), and then , By reacting quicklime, β-C ₂ S (2CaO SiO ₂ ) and the like are generated, and from the viewpoint that the strength development of cement can be improved, a position with a higher temperature (for example, (1) position, preferably between 1,000 and 1,350° C.).

When the mass ratio of CaO to SiO ₂ (CaO/SiO ₂ ) in the dehydrated product is small (for example, when the mass ratio is less than 1.5), non-hydraulic minerals produced by reaction at high temperature From the standpoint of less formation, it can be determined to inject at a lower temperature position (eg, position (3)).
On the other hand, when the mass ratio of CaO to SiO ₂ in the dehydrated product (CaO/SiO ₂ ) is large (for example, when the mass ratio is 1.5 or more), any position ((1) to (3) position), but by reacting quicklime (CaO), β-C ₂ S (2CaO SiO ₂ ) etc. are generated and the strength development of cement can be improved. It can be determined that it is preferable to charge at a higher temperature position (for example, the position (1), preferably the position of 1,000 to 1,350° C.).
When the mass ratio of CaO to SiO ₂ (CaO/SiO ₂ ) is small, limestone or the like is added to the dehydrated product to increase the mass ratio of CaO to SiO ₂ (CaO/SiO ₂ ) (for example, the mass ratio of 1 .5 or higher). When limestone is added, CaCO ₃ contained in the dehydrated product is changed to quicklime (CaO), and then by reacting quicklime (CaO), β-C ₂ S (2CaO SiO ₂ ) etc. From the viewpoint of being able to generate and improve the strength development of cement, the dehydrated product is placed at a higher temperature position (for example, the position of (1), preferably the position of 1,000 to 1,350 ° C.). Throwing in is preferred.

In the cement manufacturing apparatus 7, the cement clinker raw material passes through the preheater 2, is charged from the kiln bottom of the rotary kiln 1, and is fired while moving to the outlet side of the rotary kiln 1 to become the cement clinker 6. - 特許庁The cement clinker 6 is cooled after being discharged from the outlet of the rotary kiln 1 to the cooler 3 .
The dehydrated product is fed from the above-described position into a cement clinker produced by firing a cement clinker raw material at either position in front of the kiln 4 of the rotary kiln 1 or in the cooler 3 in the cement manufacturing apparatus 7, and exits the cooler 3. After being conveyed to, it is recovered as a cement raw material consisting of the dehydrated material and cement clinker, and is used in the next crushing process.
The cement clinker raw material is not particularly limited, and includes CaO raw materials such as limestone, quicklime, and slaked lime, SiO ₂ raw materials such as silica stone and clay, and Fe ₂ O ₃ raw materials such as iron slag and iron cake. , a raw material generally used for the production of cement clinker may be used.
In addition, when the mass ratio of CaO to SiO ₂ in the dehydrated product (CaO/SiO ₂ ) is small, or when the amount of the dehydrated product added is large, when the strength development of cement is expected to decrease, The composition of the raw material for cement clinker that is put into the bottom of the kiln may be appropriately adjusted so as to obtain a cement clinker with excellent strength development.

As a method of introducing the dehydrated product into the front of the kiln 4, for example, a dedicated nozzle is installed, and using the nozzle, the cement clinker temperature is 1,350 ° C. or less from this side of the outlet of the rotary kiln 1. A method of blowing in using an air flow can be mentioned.
As a method of putting the dehydrated material into the cooler 3 , there is a method of dropping the dehydrated material from the upper part of the cooler 3 to a desired temperature position within the cooler 3 .

The median diameter (D50) of the dehydrated product varies depending on the temperature at the position where the dehydrated product is introduced, but is preferably 250 μm to 100 mm, more preferably 500 μm to 50 mm, still more preferably 750 μm to 20 mm, particularly preferably 2 to 2 mm. 10 mm. If the diameter is 250 μm or more, the dehydrated material is less likely to scatter when the dehydrated material is introduced. If the diameter is 100 mm or less, the dehydrated material can be sufficiently heated, and the strength development of cement can be further improved. In particular, when the temperature is 200° C. or more and less than 400° C., the median diameter of the dehydrated product is preferably 50 mm or less.
The input amount of the dehydrated material is the amount of the dehydrated material (dried under conditions of 105° C.) from which water has been removed in the cement raw material (the cement raw material discharged from the cooler 3) obtained after the cement raw material manufacturing process. The content is preferably 1 to 10% by mass, more preferably 2 to 8% by mass, and particularly preferably 4 to 6% by mass. If the content is 1% by mass or more, a larger amount of ready-mixed concrete sludge can be treated as part of the raw material for cement. If the content is 10% by mass or less, the strength development of the cement can be further improved.

[Pulverization process]
This step is a step of pulverizing and mixing the cement raw material and gypsum obtained in the cement raw material manufacturing step to obtain cement.
Means for pulverizing and mixing cement raw materials and gypsum are not particularly limited, and examples thereof include pulverizers such as ball mills and rod mills used in general cement factories.
The amount of gypsum is preferably 1.5 to 5.0 parts by mass, more preferably 2.0 to 4.0 parts by mass in terms of SO ₃ with respect to 100 parts by mass of cement raw material. If the amount is within the above numerical range, the strength development and fluidity of the cement can be further improved.

Gypsum is not particularly limited, and examples thereof include natural dihydrate gypsum, flue gas desulfurization gypsum, phosphate gypsum, titanium gypsum, hydrofluoric gypsum, refined gypsum, hemihydrate gypsum, and anhydrous gypsum. These may be used individually by 1 type, and may be used in combination of 2 or more type.
The Blaine specific surface area of gypsum is preferably 2,000 to 5,000 cm ² /g, more preferably 3,000 to 4,000 cm ² /g. If the Blaine specific surface area is within the above numerical range, the strength development of the cement composition can be further improved, and the heat of hydration of the cement can be further reduced.

The Blaine specific surface area of the obtained cement is preferably 3,000 to 5,000 cm ² /g, more preferably 3,500 to 4,500 cm, from the viewpoint of strength development, workability, and cost required for production. ² /g.

EXAMPLES The present invention will be specifically described below by way of examples, but the present invention is not limited to these examples.
[Production of dehydrated product of ready-mixed concrete sludge and understanding of properties of the dehydrated product]
After dehydrating the ready-mixed concrete sludge, it is dried under conditions of 105°C for 24 hours and then coarsely crushed to dehydrate ready-mixed concrete sludge having a maximum particle size of 20 mm and a median diameter (D50) of 3 mm. A processed product (dehydrated cake) was obtained.
The chemical composition of the dehydrated product is measured using a fluorescent X-ray analyzer (manufactured by Rigaku, trade name “ZSX Primus II”) in accordance with “JIS R 5204:2019 (method for fluorescent X-ray analysis of cement)”. bottom. Table 1 shows the results.
In the examples, fresh concrete sludge was dehydrated and then dried, and was used as the dehydrated product. Therefore, when cement is actually produced using a rotary kiln, drying after dehydration treatment may not be performed.

The dehydrated product was dried at 105° C. for 24 hours, and the moisture content of the dehydrated product was measured using the following formula from the weight before drying and the weight after drying.
Moisture content (mass%) = {(mass of dehydrated product before drying - mass of dehydrated product after drying) / mass of dehydrated product before drying} x 100
Also, the content of fine aggregate in the dehydrated material was calculated by the following procedure.
First, the chemical composition (each content of CaO and SiO ₂ ) of cement (used in ready-mixed concrete from which ready-mixed concrete sludge was obtained) was determined according to "JIS R 5204: 2019 (Fluorescent X-ray analysis method for cement )” was measured using a fluorescent X-ray spectrometer (manufactured by Rigaku, trade name “ZSX Primus II”). In addition, the chemical composition (each content of CaO and _SiO2 ) of the fine aggregate contained in the dehydrated product (which was used in the ready-mixed concrete from which the ready-mixed concrete sludge was obtained) was measured by the FP method (fundamental parameter method). was measured using the above fluorescent X-ray spectrometer in accordance with the above.
Next, after calculating the ratio A and the ratio B using the following formulas (1) to (2), the average value of the ratio A and the ratio B is calculated, and the average value is the fine aggregate in the dehydrated material content (unit: mass %).
Ratio A = (Content of CaO in dehydrated material - Content of CaO in cement) / (Content of CaO in fine aggregate - Content of CaO in cement x 100 (1)
Ratio B = (content of SiO ₂ in dehydrated product - content of SiO ₂ in cement) / (content of SiO ₂ in fine aggregate - content of SiO ₂ in cement) x 100 ( 2)
The ratio A was 10, the ratio B was 9, and the calculated content of fine aggregate in the dehydrated material was 9.5% by mass.

Also, the contents of Ca(OH) ₂ and CaCO ₃ in the dehydrated product were each measured by thermogravimetric differential thermal analysis (TG-DTA). Table 2 shows the results.
Furthermore, the mineral composition of the dehydrated product was analyzed using an X-ray diffractometer (manufactured by Bruker Japan, trade name “D8 ADVANCE”) and analysis software “DIFFRAC plus TOPAS (Ver3.0)” manufactured by Bruker Japan. and analyzed by the Riedveld method. Specifically, the theoretical profiles of C ₃ S, C ₂ S, C ₃ A, C ₄ AF, calcite, calcium hydroxide, coal, albite, and anorthite minerals were obtained from the results of powder X-ray diffraction. The content of each crystalline phase was determined by fitting to the measured profile obtained. When the content of unhydrated matter in the dehydrated product was calculated from the content of each crystalline phase obtained, it was 26.1% by mass (C ₃ S: 8.1% by mass, C ₂ S: 11% by mass). .0% by mass, C ₃ A: 1.4% by mass, C4AF: 5.6% by mass).

[Example 1]
95 g of ordinary Portland cement clinker and 5 g of the dehydrated raw concrete sludge (obtained in the production of the dehydrated raw concrete sludge described above) were mixed to obtain a mixture, and then the mixture was added to 1,350 g. It was put into an electric furnace A heated to ℃, the heating of the electric furnace A was stopped, and it was slowly cooled for 8 minutes. After the slow cooling, the mixture was taken out and put into an electric furnace B heated to 750° C., the heating of the electric furnace B was stopped, and the mixture was slowly cooled for 5 minutes. Then, after slow cooling, the mixture was taken out, put into an electric furnace C heated to 400°C, stopped heating in the electric furnace C, and slowly cooled to 150°C.
After slow cooling, the mixture and gypsum in an amount such that the amount of gypsum in the cement is 2.0% by mass in terms of SO ₃ are processed using a disc mill to give a Blaine specific surface area of 4,000 ± 100 cm ² /g. Cement was obtained by pulverizing to
Using the obtained cement, the compressive strength and flow value of the mortar were measured at ages 3 days, 7 days and 28 days in accordance with "JIS R 5201:2015 (physical test methods for cement)".
The reason why electric furnaces A to C having different heating temperatures were used was to simulate a rotary kiln and a cooler.

[Example 2]
95 g of ordinary Portland cement clinker was put into an electric furnace A heated to 1,350° C., the heating of the electric furnace A was stopped, and the mixture was slowly cooled for 8 minutes. After slow cooling, the ordinary Portland cement clinker was taken out, and 5 g of the ordinary Portland cement clinker and the dehydrated raw concrete sludge (obtained in the production of the dehydrated raw concrete sludge described above) were mixed to form a mixture. After obtaining, the mixture was put into an electric furnace B heated to 750° C., the heating of the electric furnace B was stopped, and slowly cooled for 5 minutes. Then, after slow cooling, the mixture was taken out, put into an electric furnace C heated to 400°C, stopped heating in the electric furnace C, and slowly cooled to 150°C.
After slow cooling, the mixture and gypsum in an amount such that the amount of gypsum in the cement is 2.0% by mass in terms of SO ₃ are processed using a disc mill to give a Blaine specific surface area of 4,000 ± 100 cm ² /g. Cement was obtained by pulverizing to
Using the obtained cement, the compressive strength and flow value of the mortar at the material ages of 3 days, 7 days and 28 days were measured in the same manner as in Example 1.

[Example 3]
95 g of ordinary Portland cement clinker was put into an electric furnace A heated to 1,350° C., the heating of the electric furnace A was stopped, and the mixture was slowly cooled for 8 minutes. After slow cooling, the ordinary Portland cement clinker was taken out and put into an electric furnace B heated to 750° C., the heating of the electric furnace B was stopped, and it was slowly cooled for 5 minutes. Next, after slow cooling, ordinary Portland cement clinker was taken out, and ordinary Portland cement clinker and 5 g of the dehydrated raw concrete sludge (obtained in the production of the dehydrated raw concrete sludge described above) were mixed. After obtaining the mixture, the mixture was taken out, put into an electric furnace C heated to 380°C, stopped heating in the electric furnace C, and slowly cooled to 150°C.
After slow cooling, the mixture and gypsum in an amount such that the amount of gypsum in the cement is 2.0% by mass in terms of SO ₃ are processed using a disc mill to give a Blaine specific surface area of 4,000 ± 100 cm ² /g. Cement was obtained by pulverizing to
Using the obtained cement, the compressive strength and flow value of the mortar at the material ages of 3 days, 7 days and 28 days were measured in the same manner as in Example 1.

[Comparative Example 1]
After mixing 95 g of ordinary Portland cement clinker and 5 g of the above dehydrated ready-mixed concrete sludge (obtained in the production of the above-mentioned dehydrated ready-mixed concrete sludge), the amount of gypsum in the mixture and cement is SO Gypsum in an amount of 2.0% by mass in terms of ₃ was pulverized using a disc mill until the Blaine specific surface area reached 4,000±100 cm ² /g to obtain cement.
Using the obtained cement, the compressive strength and flow value of the mortar at the material ages of 3 days, 7 days and 28 days were measured in the same manner as in Example 1.
[Reference example 1]
Compressive strength and flow of mortar at 3 days, 7 days, and 28 days of material age using what was pulverized with a disk mill to a Blaine specific surface area of 4,000 ± 100 cm ² /g of ordinary Portland cement commercial product Values were determined analogously to Example 1.
Each result is shown in Table 3.

From Table 3, the compressive strength of the mortars of Examples 1 to 3 (3 days: 27.2 to 29.1 N/mm ² , 7 days: 43.3 to 44.9 N/mm ² , 28 days: 59.5 ~ 61.6 N/mm ² ) is the compressive strength of the mortar of Comparative Example 1 (3 days: 26.7 N/mm ² , 7 days: 43.8 N/mm ² , 28 days: 59.5 N/mm ² ) It can be seen that it is equal to or greater than
It can be seen that the flow values of Examples 1-3 (187-198 mm) are greater than the flow value of Comparative Example 1 (185 mm).

Comparing Examples 1 to 3, the compressive strength of Example 1 (the dehydrated product was charged at 1,350 ° C.) is the highest (however, regarding the compressive strength at the age of 28 days, Example 3 is the largest), the compressive strength of Example 3 (the dehydrated product is charged at 400 ° C.) is the second highest, and the compressive strength of Example 2 (the dehydrated product is charged at 750 ° C.) is was the third largest.
In addition, when comparing Examples 1 to 3, the flow value of Example 3 (with the dehydrated product added at 400 ° C.) is the largest, and the flow value of Example 2 (with the dehydrated product added at 750 ° C.) The value was the second largest, and the flow value of Example 1 (the dehydrated material was charged at 1,350°C) was the third largest.

1 rotary kiln 2 preheater 3 cooler 4 kiln front 5 main burner 6 cement clinker 7 cement production equipment

Claims (3)

A method of producing cement using a cement production apparatus comprising a rotary kiln and a cooler, comprising:
A dehydrated product of fresh concrete sludge is introduced into the cooler at a temperature of 200 ° C. or more and less than 400° C. , and the dehydrated product and cement clinker raw material are fired in the rotary kiln. a cement raw material manufacturing process for obtaining a cement raw material consisting of cement clinker;
A method for producing cement, comprising a pulverizing step for obtaining cement by pulverizing and mixing the raw material for cement and gypsum. 2. The method for producing cement according to claim 1 , wherein the dehydrated product has a median diameter of 250 μm to 100 mm. The water content of the dehydrated product is 50% by mass or less, and the content of unhydrated matter in the dehydrated product exceeds 20% by mass, and the content of fine aggregate is 20% by mass. and Ca(OH) ₂ content is 15% by mass or less, and CaCO ₃ The method for producing cement according to claim 1 or 2, wherein the content of is 20% by mass or less.

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