JP2010228923A - Cement clinker, method for producing the same and cement composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide cement clinker where the elution of water-soluble Cr (VI) is sufficiently suppressed and wastes are effectively utilized, a method for producing the same and a cement composition. <P>SOLUTION: The cement clinker is characterized by having 47-58 mass% C<SB>3</SB>S in terms of Bogue equation, 11-13 mass% C<SB>3</SB>A, 6-9 mass% C<SB>4</SB>AF and a total content of Cr of 10-60 mg/kg. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a cement clinker manufactured using waste as part of a raw material and a method for manufacturing the cement clinker. Moreover, this invention relates to the cement composition manufactured using the said cement clinker.

  Conventionally, cement clinker is manufactured by firing main raw materials such as limestone, clay, silica stone, and iron raw materials in a kiln at a high temperature. In the production of clinker, not only these main raw materials but also various wastes are effectively used as raw materials. On the other hand, depending on the selection of raw materials, Cr may be brought into the clinker and Cr may exist in the form of harmful Cr (VI) in the clinker obtained by high-temperature firing. A part of Cr (VI) is water-soluble, and when a cement composition containing this is used, Cr (VI) may be eluted from the mortar hardened body or the concrete hardened body. Water-soluble Cr (VI) is combined with a minor component such as alkali contained in the clinker. If the amount of the small component contained in the waste material increases, water-soluble Cr (VI) increases.

  The following is known as a method for reducing water-soluble Cr (VI) in cement. The first is a method by adding an elution reducing material. Patent Document 1 describes a method of obtaining a hydraulic substance by adding a reducing substance of Cr (VI) and an immobilized substance of lead during kneading of raw materials. Claim 2 of this document describes that ferrous salt, blast furnace slag, sulfur, thiosulfate or iron powder is used as a reducing substance, and a chelating agent, an insolubilizing agent or an adsorbent is used as an immobilizing substance. Has been.

  Second, it is a method of processing or sorting the raw materials in advance. Patent Document 2 discloses that iron-based waste materials are pulverized and classified to remove heavy particles by removing particles having a particle size of 10 μm or less from the pulverized and classified product, and the remaining iron-based waste exceeding 10 μm. A method for reusing raw material particles as cement raw material is described. Patent Document 3 discloses a method of estimating the elution amount of Cr (VI) from coal ash by measuring the content of CaO in the coal ash, and selecting coal ash with less elution amount of Cr (VI). Is described.

  Third, there is a method for controlling the firing atmosphere. Patent Document 4 describes a method in which a cement clinker containing Cr (VI) is heated at 650 to 1100 ° C. in a reducing atmosphere. Patent Document 5 describes a method of supplying a solid combustible material having a predetermined particle size to a region where the temperature of the cement clinker introduced into the clinker cooler is 850 ° C to 1000 ° C.

JP 2001-191322 A JP 2008-80299 A JP 2001-281235 A JP 2004-18339 A JP 2002-211961 A

  However, the method of using the elution reducing material and the method of pre-processing or sorting the raw materials increase the manufacturing cost of the cement. In addition, the method of controlling the firing atmosphere may affect the color of the cement.

  By the way, in order to reduce water-soluble Cr (VI) contained in the cement composition, it is effective to use a cement clinker with a small amount of total Cr. Iron sources used in the production of cement clinker (for example, iron concentrate, copper shells, etc.) have a larger amount of Cr than other raw materials, so reducing the amount of iron source reduces the total amount of Cr in the clinker. It is considered possible.

  However, a method for producing a cement clinker using a raw material with a small amount of Cr has not been studied so far. In particular, when producing cement clinker by reducing the amount of iron source used, what kind of mineral composition should be considered has not been studied. In addition, simply reducing the amount of waste containing a large amount of Cr, represented by iron sources, reduces the amount of waste used, leading to an increase in cement manufacturing costs. Therefore, when manufacturing cement clinker, instead of reducing the amount of waste containing a large amount of Cr, it is required to increase the amount of other waste used to prevent a significant reduction in the amount of waste used.

  The present invention has been made in view of the above circumstances, can sufficiently suppress the elution of water-soluble Cr (VI), can effectively use waste, and can further suppress a decrease in cement strength. An object of the present invention is to provide a cement clinker and a method for producing the same. Another object of the present invention is to provide a cement composition produced using the cement clinker as a raw material.

In the present invention, the C ₃ S amount is 47 to 58% by mass, the C ₃ A amount is 11 to 13% by mass, the C ₄ AF amount is 6 to 9% by mass, and the total Cr amount is 10 to 60 mg in terms of Borg conversion. A cement clinker is provided. Here, C ₃ S is alite (3CaO · SiO ₂ ), C ₄ AF is a ferrite phase (4CaO · Al ₂ O ₃ · Fe ₂ O ₃ ), and C ₃ A is an aluminate phase (3CaO · Al ₂ O ₃ ) is shown respectively.

  Further, the present invention is a cement composition comprising the cement clinker and gypsum, wherein the cement clinker content based on the total mass of the cement composition is 95 to 97% by mass and the gypsum content A cement composition is provided in which the amount is 3 to 5% by mass.

Furthermore, this invention provides the manufacturing method of the said cement clinker. That is, the manufacturing method uses 1000 to 1200 kg of limestone, 160 to 360 kg of coal ash, 10 to 50 kg of construction generated soil, and 10 to 40 kg of blast furnace dust on a dry basis per ton of cement clinker to obtain a mixture. A first step and a second step of firing the mixture to obtain a cement clinker. In the second step, the C ₃ S amount is 47 to 58 mass% and the C ₃ A amount is 11 to 13 mass in terms of Borg conversion. % And C ₄ AF amount of 6 to 9% by mass and a total amount of Cr of 10 to 60 mg / kg of cement clinker is obtained in the first step of limestone, coal ash, construction generated soil and blast furnace dust The blending amount is adjusted.

The cement clinker of the present invention has a composition with a small amount of C ₄ AF and a large amount of C ₃ A compared with a conventional cement clinker. In other words, the cement clinker of the present invention can be manufactured by reducing the amount of waste containing a large amount of Cr (particularly iron source) and increasing the amount of coal ash generated at a thermal power plant or the like. is there.

  In the cement clinker of the present invention, the amount of waste containing a large amount of Cr is reduced, so that the total Cr amount is as low as 10 to 60 mg / kg, and the elution of water-soluble Cr (VI) is sufficiently suppressed. It is possible. In addition, instead of reducing the amount of waste containing a large amount of Cr, the amount of coal ash used can be increased, and waste can be used effectively. As a result, an increase in cement manufacturing costs can be sufficiently suppressed.

  According to the present invention, elution of water-soluble Cr (VI) can be sufficiently suppressed, waste can be effectively used, and further, a reduction in cement strength can be suppressed.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

(Cement clinker)
Cement clinker according to the present embodiment, _{C 3} S content in Borg type conversion mineral composition 47-58 wt%, _{C 3} A weight 11 to 13 _mass%, a _C 4 AF weight 6-9 wt% The total Cr amount is 10 to 60 mg / kg · clinker.

The amount of C ₃ S of the cement clinker is 47 to 58% by mass, preferably 48 to 57% by mass, more preferably 49 to 56% by mass, and still more preferably 50 to 55% by mass. If the amount of C ₃ S is less than 47% by mass, the initial strength development is lowered, which is not preferable. When the amount of C ₃ S exceeds 58% by mass, the calorific value due to heat of hydration increases, which is not preferable.

The amount of C ₃ A in the cement clinker is 11 to 13% by mass, preferably 11.5 to 12.5% by mass. In order to reduce the C ₃ A amount of the clinker to less than 11%, it is not preferable because the amount of waste used must be significantly reduced, and the cost of cement production increases. If the amount of C ₃ A exceeds 13%, the amount of heat generated by heat of hydration increases, which is not preferable.

The amount of C ₄ AF of the cement clinker is 6.0 to 9.0% by mass, preferably 6.5 to 8.5% by mass, and more preferably 7.0 to 8.0% by mass. In order to reduce the amount of C ₄ AF of the clinker to less than 6.0% by mass, it is not preferable because the amount of waste used must be greatly reduced, and the cement manufacturing cost increases. When the amount of C ₄ AF exceeds 9.0% by mass, the effect of reducing the total Cr amount becomes small, and the effect of reducing water-soluble Cr (VI) becomes insufficient.

The C ₂ S amount of the cement clinker may be substantially equal to the amount obtained by excluding the total of the above C ₃ S amount, C ₃ A amount, and C ₄ AF amount from the total mass of the clinker. The total amount of C ₃ S amount, C ₂ S amount, C ₃ A amount and C ₄ AF amount of the cement clinker is preferably 94% by mass or more based on the total mass of the clinker, and is 95% by mass or more. More preferably. If the total amount is less than 94% by mass, the amount of clinker in the cement is reduced, and the strength of the cement may be insufficient. C ₂ S represents belite (2CaO · SiO ₂ ).

  The total Cr amount of the cement clinker is 10 to 60 mg / kg · clinker, preferably 20 to 50 mg / kg · clinker, more preferably 25 to 45 mg / kg · clinker. In order to reduce the Cr content of the clinker to less than 10 mg / kg · clinker, the amount of waste used must be significantly reduced, and the cement manufacturing cost increases, which is not preferable. When the amount of Cr exceeds 60 mg / kg · clinker, the effect of reducing water-soluble Cr (VI) becomes insufficient.

  The amount of f.CaO in the cement clinker is preferably 0.5 to 2.0% by mass, more preferably 0.6 to 1.5% by mass, still more preferably 0.65 to 1.3% by mass, and much more. Preferably it is 0.70-1.2 mass%. f. If the amount of CaO is within the above range, sufficient strength of the cement can be obtained. Note that f.CaO indicates free lime in the cement clinker.

  The water-soluble alkali amount of the cement clinker is preferably 0.05 to 0.4% by mass, more preferably 0.1 to 0.35% by mass, and still more preferably 0.15 to 0.30% by mass. If the amount of water-soluble alkali is within the above range, it will not lead to a decrease in the physical properties of cement such as strength and fluidity. The “water-soluble alkali amount” referred to here means a value measured by JCAS I-04: 2004 “Analyzing method of water-soluble components of cement”.

  The cement clinker according to the present embodiment can be manufactured on a dry basis per ton of the cement clinker using the following amounts of limestone, coal ash, construction generated soil, and blast furnace dust. By setting the amount of each raw material used within the following range, it is possible to stably produce a cement clinker capable of sufficiently suppressing elution of water-soluble Cr (VI) and suppressing a decrease in cement strength.

  The amount of limestone used is preferably 1000 to 1200 kg, more preferably 1020 to 1180 kg, still more preferably 1050 to 1150 kg, and even more preferably 1080 to 1130 kg per ton of cement clinker.

  The amount of coal ash used is preferably 160 to 360 kg, more preferably 190 to 330 kg, still more preferably 210 to 310 kg, even more preferably 220 to 300 kg, and even more preferably 220 on a dry basis per ton of cement clinker. ~ 280 kg.

  The amount of construction generated soil is preferably 10 to 50 kg, more preferably 15 to 40 kg, still more preferably 20 to 35 kg, and even more preferably 22 to 30 kg on a dry basis per ton of cement clinker.

  The amount of blast furnace dust used is preferably 10 to 40 kg, more preferably 15 to 35 kg, still more preferably 20 to 30 kg, and still more preferably 22 to 28 kg on a dry basis per ton of cement clinker.

The cement clinker is manufactured by the following method. That is, the cement clinker manufacturing method includes a first step of obtaining a mixture using a predetermined amount of limestone, coal ash, construction generated soil, and blast furnace dust, and a second step of firing the mixture to obtain the above-described cement clinker. In the second step, the C ₃ S amount is 47 to 58% by mass, the C ₃ A amount is 11 to 13% by mass, the C ₄ AF amount is 6 to 9% by mass, and the total Cr amount in the second step. In the first step, the blending amount of limestone, coal ash, construction generated soil, and blast furnace dust is adjusted so that a cement clinker having an amount of 10 to 60 mg / kg can be obtained.

The feature of the cement clinker according to the present embodiment is that the amount of coal ash used during production is larger than that of a normal Portland cement clinker. As above-mentioned, the suitable usage-amount of coal ash is the range of 160-360 kg. If the amount used is less than 160 kg, the Al ₂ O ₃ source will be insufficient, and it will be difficult to obtain the target mineral composition, while if it exceeds 360 kg, it will be difficult to prepare the raw materials. The coal ash is typically fly ash, bottom ash or the like generated from a coal-fired power plant or the like, but is not limited thereto.

The amount of Al ₂ O _{3 in the} cement clinker is preferably 5.3 to 6.9% by mass, more preferably 5.6 to 6.6% by mass, and still more preferably 5.7 to 6.5% by mass. When the amount of Al ₂ O ₃ in the cement clinker is less than 5.3% by mass, the amount of waste used is reduced and the cement manufacturing cost is likely to increase. On the other hand, when it exceeds 6.9% by mass, it is difficult to prepare the raw material. Cheap.

The amount of Fe ₂ O _{3 in the} cement clinker is preferably 1.9 to 3.0% by mass, more preferably 2.0 to 2.9% by mass, and still more preferably 2.1 to 2.8% by mass. When the amount of Fe ₂ O ₃ in the cement clinker is less than 1.9% by mass, the amount of waste used is reduced and the cement manufacturing cost is likely to increase. On the other hand, when the amount exceeds 3.0% by mass, the total amount of Cr is reduced. The effect is reduced, and the effect of reducing water-soluble Cr (VI) is insufficient.

(Cement composition)
The cement composition according to the present embodiment contains the cement clinker and gypsum, the cement clinker content based on the total mass of the cement composition is 95 to 97% by mass, and the gypsum content Is 3 to 5% by mass. If the gypsum content is less than 3% by mass, the cement composition will condense in a short time, while if it exceeds 5% by mass, the production cost will increase and the long-term strength will decrease.

When producing a cement composition by mixing cement clinker and gypsum, the amount of gypsum added is adjusted so that the SO ₃ amount based on the total mass of the cement composition is 1.0 to 4.0% by mass. It is preferable to do. By setting the amount of SO _{3 in the} cement composition to 1.0% by mass or more, a cement composition having moderate fluidity can be obtained as compared with the case of less than 1.0% by mass. On the other hand, when the amount of SO _{3 in the} cement composition is 4.0% by mass or less, the strength of the cement can be sufficiently increased as compared with a case where the amount is more than 4.0% by mass. From the viewpoint of the fluidity of the cement composition and the strength of the cement, the amount of SO _{3 in the} cement composition is more preferably 1.5 to 3.5% by mass, still more preferably 1.5 to 3.5% by mass. It is.

The cement composition according to the present embodiment can be produced by mixing and grinding the mixture of the cement clinker and gypsum. A general mill such as a tube mill, a vibration mill, or a vertical mill can be used for mixing and grinding the mixture. The brane specific surface area of the cement composition is preferably 2800 to 3500 cm ² / g, more preferably 2900 to 3400 cm ² / g, still more preferably 2850 to 3350 cm ² / g. If the Blaine specific surface area is within the above range, the cement composition can exhibit sufficient initial strength and long-term strength.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, this invention is not limited to these Examples.

[1. Clinker ingredients and ingredients]
Among the raw materials shown in Table 1 as raw materials for the cement clinker according to Example 1, limestone, silica stone, slag, coal ash, construction generated soil, blast furnace dust, calcium sulfate dihydrate (reagent), sodium carbonate (reagent) and Potassium carbonate (reagent) was used. As raw materials for the cement clinker according to Comparative Example 1, in addition to the raw materials for the cement clinker of Example 1, copper curl and deiron slag were further used. The raw material preparation of these cement clinker was performed according to the raw material basic unit (dry basis, unit: kg / t-clinker) shown in Table 2.

[2. Production of cement clinker and test method thereof]
The mixture of the raw materials was baked in an electric furnace at 1500 ° C. for 30 minutes to produce cement clinkers according to Example 1 and Comparative Example 1, respectively. The main chemical composition of the obtained clinker is shown in Table 3. The chemical composition of the clinker was measured according to JIS R5202: 1999 “Chemical analysis method of Portland cement”. f. The amount of CaO was measured according to JCAS I-01: 1997 “Method for Quantifying Free Calcium Oxide” of the Cement Association Standard Test Method. Table 3 shows the total Cr amount and water-soluble Cr (VI) amount in the clinker. The amount of Cr in the clinker was measured in accordance with JCAS I-52 “Analytical Method for Analyzing Trace Components of Cement by ICP Emission Spectroscopy and Electric Heating Atomic Absorption Spectroscopy” of the Cement Association Standard Test Method. The amount of water-soluble Cr (VI) was measured according to JCAS I-51-1981 “Method for quantifying trace components in cement and cement raw materials” of the Cement Association standard test method.

Table 4 shows various ratios and mineral compositions of the clinker according to Example 1 and Comparative Example 1. In addition, various ratios and mineral compositions of clinker were calculated using the following equations.

The total Cr amount and water-soluble Cr (VI) amount in the clinker of Example 1 were reduced as compared with the clinker of Comparative Example 1. This is probably because the total Cr amount was reduced because the amount of C ₄ AF in Example 1 was reduced, and thus the amount of water-soluble Cr (VI) was reduced.

[3. Cement preparation and test method]
Each of the clinkers according to Example 1 and Comparative Example 1 was put into a ball mill and pulverized so that the specific surface area of the brane was 3200 ± 50 cm ² / g. Two-water gypsum (reagent) and half-water gypsum (reagent) were added to the clinker grind so that the amount of SO _{3 in the} cement composition was 2.0 mass%. A cement composition was prepared by mixing with a rocking mixer. The gypsum was added with a predetermined amount of two-water gypsum and half-water gypsum so that the gypsum hemihydrate ratio (the amount of gypsum in the total gypsum amount) was 70%. The specific surface area of the brane was measured using a brane air permeation apparatus in accordance with JIS R5201 “Cement physical test method”. The results are shown in Table 5.

[4. Mortar compressive strength test]
The mortar compressive strength was measured according to JIS R5201: 1997 “Cement physical test method”. Table 5 shows the mortar compressive strength. It was found that the compressive strength comparable to that of Comparative Example 1 can be maintained even with the mineral composition (Example 1) with a reduced amount of C ₃ S. Thus, it can be considered that the reason why the strength was maintained is that the amount of C ₃ A was increased.

Claims (7)

The amount of C ₃ S is 47 to 58% by mass, the amount of C ₃ A is 11 to 13% by mass, the amount of C ₄ AF is 6 to 9% by mass, and the total amount of Cr is 10 to 60 mg / kg in terms of Borg conversion. Cement clinker characterized by that.   f. The cement clinker according to claim 1, wherein the CaO amount is 0.5 to 2.0 mass%. The cement clinker according to claim 1 or 2, wherein the amount of Al ₂ O ₃ is 5.3 to 6.9% by mass and the amount of Fe ₂ O ₃ is 1.9 to 3.0% by mass.   Any one of Claims 1-3 obtained by using 1000-1200 kg of limestone, 160-360 kg of coal ash, 10-50 kg of construction generated soil, and 10-40 kg of blast furnace dust on a dry basis per ton of cement clinker. The cement clinker according to claim 1. A cement composition comprising the cement clinker according to any one of claims 1 to 4 and gypsum,
A cement composition, wherein the cement clinker content is 95 to 97% by mass and the gypsum content is 3 to 5% by mass based on the total mass of the cement composition. The cement composition according to claim 5, wherein the specific surface area of the brain is 2800-3500 cm ² / g. A first step of obtaining a mixture using 1000 to 1200 kg of limestone, 160 to 360 kg of coal ash, 10 to 50 kg of construction generated soil, and 10 to 40 kg of blast furnace dust on a dry basis per ton of cement clinker;
A second step of firing the mixture to obtain a cement clinker;
With
In the second step, the C ₃ S amount is 47 to 58% by mass, the C ₃ A amount is 11 to 13% by mass, the C ₄ AF amount is 6 to 9% by mass, and the total Cr amount is 10 to 10% in terms of Borg conversion. The manufacturing method of the cement clinker characterized by adjusting the compounding quantity of a limestone, coal ash, construction generated soil, and blast furnace dust in the said 1st process so that the cement clinker which is 60 mg / kg may be obtained.