JP5818579B2 - Neutralization suppression type early strong cement composition - Google Patents

Description

The present invention is a neutralization-suppressing type early-strength cement composition based on a highly active cement having a mineral composition calculated by the Borg formula in a clinker of C ₃ S> 70% and C ₂ S <5%. Even if it is similar to mixed cement, it has the same strength development and neutralization control performance as ordinary Portland cement, and it is used in concrete and mortar used in low temperature environments such as cold districts or environments where neutralization is likely to proceed. The present invention relates to a neutralization-suppressing type early-strength cement composition suitable as a cement.

  In recent years, reduction of carbon dioxide emissions has been demanded as one of the measures to prevent global warming, and the cement industry has been working on such reduction. However, as one of the reduction measures, blast furnace slag, fly ash, etc. Attention has been focused on the use of mixed cements and cement compositions containing these inorganic admixtures.

  If these mixed cements and cement compositions are utilized, not only the reduction of carbon dioxide generated from the fuel accompanying cement firing but also the generation of carbon dioxide due to the decarboxylation of limestone as the main raw material can be reduced. In general, mixed cements and cement compositions containing inorganic admixtures such as blast furnace slag and fly ash are less heat-resistant, salt-insulating, sulfate-resistant, and alkali-aggregate reaction suppression compared to Portland cement. Because it is excellent, there is an increasing need for performance.

  However, there are some drawbacks. One of them is that the mixed cement and cement composition have less alkali content (mainly calcium content) than Portland cement and can be easily neutralized. Neutralization suppression has been studied in the past. For example, in Patent Document 1, steel slag, blast furnace slag fine powder and fly ash are selected from the group of Portland cement, blast furnace cement, fly ash cement and slaked lime. The cement composition which suppresses corrosion of a reinforcing bar also in the environment which consists of 1 type or 2 types or more made and is easy to neutralize is disclosed.

Patent Document 2 contains (A) one or more powders selected from blast furnace slag powder, fly ash, and silica fume, and (B) ₂ CaO · SiO ₂ and 2CaO · Al ₂ O ₃ · SiO _2. · respect SiO ₂ 100 parts by weight of a _{2CaO · Al 2 O 3 · SiO} 2 + 4CaO · Al 2 O 3 · Fe 2 O 3 is 10 to 100 parts by weight, the content of 3CaO · Al ₂ O ₃ A cement composition having good neutralization characteristics is disclosed, including a pulverized product of 20 parts by mass or less, (C) gypsum, and (D) a Portland cement clinker pulverized product.

  Another drawback of the above mixed cement and cement composition is that the strength developability in short-term ages is small, and it is not good at low temperatures such as in winter.

Improvements in strength development at low temperatures have also been studied. For example, Patent Document 3 discloses that the content of 3CaO · SiO ₂ is 60% by weight or more and the brain value is 100 parts by weight of cement of 3500 to 7000 cm ² / g. On the other hand, 100 parts by weight of anhydrous gypsum, 20 to 150 parts by weight of aluminum sulfate in terms of anhydride, 5 to 15 parts by weight of alkali metal aluminate, and 20 to 30 parts of nitrate and / or nitrite of alkali metal or alkaline earth metal A cement composition containing 2 to 10 parts by weight of a cement admixture containing 150 parts by weight is disclosed.

Further, Patent Document 4 discloses an attempt to solve both the neutralization and the strength development under the low temperature environment. Here, the brane specific surface area is 6000 to 10000 cm ² / g and the vitrification rate is 70% or more of CaO 40 to 55 mass%, Al ₂ O ₃ 25 to 40 mass%, SiO ₂ 10 to 25 mass%, and Li ₂ O 1 100 parts by mass of 10% by mass of CaO—Al ₂ O ₃ —SiO ₂ —Li ₂ O-based glass and 5 to 300 parts by mass of γ-2CaO · SiO ₂ having a Blaine specific surface area of 2000 to 8000 cm ² / g There is disclosed a hydraulic cement composition that is excellent in strength development, sulfate resistance and neutralization resistance in a low temperature environment.

JP 2007-210850 A JP 2008-105902 A Japanese Patent No. 3549579 Japanese Patent No. 4457786

  As shown in Patent Document 1 and Patent Document 2, some cement compositions that have been neutralized are known, but since the cement used is conventional Portland cement and mixed cement, short-term strength is obtained. It cannot be said that the expression is good, and the short-term strength in a low-temperature environment may not be sufficiently secured.

  Further, as shown in Patent Document 3, a cement composition that improves strength development at low temperatures is also known, but it is not a mixed cement considering neutralization suppression, but various kinds of curing accelerators and the like. Since the additive is used together, it becomes expensive.

  Patent Document 4 discloses a hydraulic cement composition excellent in strength development and neutralization resistance in a low-temperature environment. However, since it is a hydraulic composition having a special chemical composition, it is difficult to manufacture and is versatile. Lack.

On the other hand, prior to the present invention, the inventors of the present application developed a “highly active cement” having high C ₃ S, free lime, and extremely low C ₂ S. (See Japanese Patent Application No. 2011-35810) This cement has higher hydration activity than early-strength Portland cement, and is a cement that does not fall under the conventional standards in which industrial waste can be used as a cement firing raw material.

  In view of the above problems, the present invention is intended to effectively use the above-mentioned "highly active cement", and even if it is similar to a mixed cement, it has the same strength development and neutralization suppression performance as ordinary Portland cement, An object of the present invention is to provide a neutralization-suppressing type early-strength cement composition suitable as a concrete or mortar cement used in a low-temperature environment such as a cold region or an environment where neutralization is likely to proceed.

According to the present invention, when the mineral composition calculated by the Borg formula is C ₃ S> 70% and C ₂ S <5%, S. D. Is obtained by adding gypsum to 1.5 to 4.0% by weight in terms of SO ₃ to a highly active cement clinker having a free lime content of more than 1 and 0.5 to 7.5% by weight. A neutralization-suppressing type early-strength cement composition characterized by comprising 3% to 40% by weight of an inorganic admixture composed of at least one of blast furnace slag, anhydrous gypsum, limestone fine powder, and pozzolanic material. is there.

  Highly active cement clinker has high hydration activity, and the peak value of the hydration exotherm rate in the cement calorimeter of the cement clinker is larger than that of the cement by the clinker equivalent to the early strong cement clinker, and water. A clinker whose sum of calorific value is higher than that of cement by a clinker equivalent to an early strong cement clinker

This highly active cement clinker has a mineral composition calculated by the Borg formula, C ₃ S> 70%, C ₂ S <5%, preferably C ₂ S <3%.

When C ₃ S is 70% or less, it becomes difficult to obtain a highly active cement having a hydration activity equivalent to or higher than that of a conventional early strong cement. Moreover, there is a possibility that neutralization suppression may be insufficient depending on environmental conditions.

When the C ₂ S content is 5% or more, the interstitial phase composed of calcium aluminate minerals or amorphous materials is reduced, so that it becomes difficult to fire a highly active cement clinker or a cement firing material for industrial waste containing a large amount of aluminum. It becomes difficult to use as.

In addition, with conventional early strong cement, cement clinker L.P. S. D. The cement fired raw material is prepared so that (lime saturation) is 1 or less. In the highly active cement clinker of the present invention, L. S. D. > 1. L. S. D. By blending the cement firing raw material so that> 1, it becomes easy to obtain a highly active cement clinker with C ₃ S> 70% and C ₂ S <5%.

  As described above, in the highly active cement clinker of the present invention, L. S. D. Since> 1, the cement clinker will contain free lime, but the amount is limited to 0.5-7.5 wt%.

  If it is less than 0.5% by weight, the position and length of the high-temperature firing or firing zone may change, and the brick inside the kiln may be damaged. If it exceeds 7.5% by weight, excessive swelling may occur due to hydration of free lime in the cement clinker.

The high activity cement is obtained by adding gypsum to the high activity cement clinker so as to be 1.5 to 4.0% by weight in terms of SO ₃ . If the amount is less than 1.5% by weight, C ₃ A in the cement clinker may quickly set to produce a concrete product, which may not ensure sufficient work time. If it exceeds 4.0% by weight, delayed expansion may occur due to unreacted gypsum after the cement has hardened.

  Since this highly active cement is based on the above highly active cement clinker, it has a hydration activity higher than that of early strong Portland cement. In addition, since it is not constrained by conventional cement standards, it is difficult to use in applications where the cement standards are emphasized and must be Portland cement or the like.

  In addition, since calcium content is higher than silica content and free lime is included, calcium hydroxide is easily generated and effective for neutralization suppression.

  The neutralization-suppressing type early strong cement composition of the present invention comprises an inorganic admixture 3 comprising 60 to 97% by weight of the above highly active cement and one or more of blast furnace slag, anhydrous gypsum, limestone fine powder, and pozzolanic material. 40% by weight.

  By using the above highly active cement and increasing the blending ratio of this highly active cement, it is possible to develop short-term strength, especially short-term at low temperatures, without using chemical additives consisting of various inorganic salts and organic polymers. A cement composition having excellent strength development and neutralization suppressing ability is obtained.

  The inorganic admixture used in the present invention consists of one or more of blast furnace slag, anhydrous gypsum, limestone fine powder, and pozzolanic material.

  The blast furnace slag is not particularly limited as long as it is conventionally used for blast furnace cement, cement admixture or cement composition. Blast furnace slag may be used alone or in combination with other inorganic admixtures. Blast furnace slag contributes to securing fluidity, extending long-term strength, suppressing heat of hydration, and salt barrier properties.

  Anhydrous gypsum is not particularly limited as long as it is conventionally used in cement admixtures and cement compositions. Anhydrous gypsum contributes to securing fluidity, short-term strength elongation, and suppression of shrinkage. Anhydrous gypsum is preferably used in combination with other inorganic admixtures.

  The limestone fine powder is not particularly limited as long as it is conventionally used in cement admixtures and cement compositions. Limestone fine powder contributes to securing fluidity, short-term strength elongation, and suppression of shrinkage. Limestone fine powder is also preferably used in combination with other inorganic admixtures.

  Examples of the pozzolanic substance include those conventionally used as cement admixtures such as silica fume, metakaolin, activated silica powder, diatomaceous earth, rice husk ash, activated clay, fly ash fine powder, fly ash coarse powder and the like. A pozzolanic substance contributes to strength development, securing fluidity, and suppressing heat of hydration. The pozzolanic substance may be used alone or in combination with other inorganic admixtures.

  In the neutralization-suppressing type early strong cement composition of the present invention, the content of the highly active cement is 60 to 97% by weight.

  If it is less than 60% by weight (inorganic admixture is 40% by weight or more), sufficient strength may not be obtained in a low temperature environment, or neutralization may not be suppressed in an environment where neutralization tends to proceed. If it exceeds 97% by weight (inorganic admixture is 3% by weight or less), the effect of mixing the above-mentioned inorganic admixture cannot be obtained sufficiently, and the effects of conventional mixed cement (for example, low heat, salt barrier property, resistance to resistance) It is difficult to obtain sulfate-like properties, and it is difficult to say that it is equivalent to mixed cement.

  In the neutralization-suppressing early strong cement composition of the present invention, there are a plurality of preferred forms of the inorganic admixture, and any of these may be used. If each constituent material is within the following ranges in each of the following systems, not only strength improvement and neutralization suppression, but also the performance of conventional mixed cement (for example, low heat, salt insulation, sulfate resistance, etc.) ) Is also easily obtained.

<Blast furnace slag-limestone fine powder based inorganic admixture>
One preferred form is a blast furnace slag-limestone fine powder system. This system may be used when it is desired to suppress shrinkage or heat generation or to reduce costs. Effective utilization of blast furnace slag, an industrial by-product, is also possible. In this system, the inorganic admixture is composed of blast furnace slag and fine limestone powder. In the neutralization-suppressing early strength cement composition, the content of the blast furnace slag is 2 to 39% by weight, and the content of the fine limestone powder. Is 1 to 10% by weight.

  The reason why the content of blast furnace slag is 2 to 39% by weight is that if it is less than 2% by weight, the effect of addition cannot be sufficiently obtained, and if it exceeds 39% by weight, the expression of short-term strength may deteriorate. is there.

  In addition, the content of fine limestone powder is 1 to 10% by weight when the effect of addition is not sufficiently obtained if it is less than 1% by weight or the elongation of long-term strength becomes insufficient if it exceeds 10% by weight. Because there is.

<Blast furnace slag-Limestone fine powder-Anhydrous gypsum inorganic admixture>
Another preferred form is the blast furnace slag-limestone fine powder-anhydrite system. This system is obtained by adding anhydrous gypsum to the above blast furnace slag-limestone fine powder system. Since the production of ettringite increases by adding anhydrous gypsum, the initial strength development in a low temperature environment can be further enhanced.

  This system is preferably used when it is desired to suppress shrinkage, to obtain chemical resistance such as sulfate, or to produce an immediate release product. In this system, the inorganic admixture is composed of blast furnace slag, limestone fine powder and anhydrous gypsum, and the neutralization-suppressing type early strong cement composition has a blast furnace slag content of 1 to 38% by weight, and the limestone fine powder. Is 1 to 10% by weight, and the anhydrous gypsum content is 1 to 5% by weight.

The reason for setting the blast furnace slag content to 1 to 38% by weight is the same as described above. The reason why the content of the limestone fine powder is 1 to 10% by weight is the same as the above reason. The reason why the content of anhydrous gypsum is 1 to 5% by weight is that if it is less than 1% by weight, the effect of addition may not be sufficiently obtained, and if it exceeds 5% by weight, delayed expansion may occur. It is. The reason why the preferred content range of the blast furnace slag is slightly different from the above system is that anhydrous gypsum was further added.

<Blast furnace slag-pozzolanic material-limestone fine powder-anhydrous gypsum-based inorganic admixture>
Another preferred form is the blast furnace slag-pozzolanic material-limestone fine powder-anhydrite system. This system is obtained by adding a pozzolanic material to the above blast furnace slag-limestone fine powder-anhydrous gypsum system.

  This system is preferably used when it is desired to suppress heat of hydration, to obtain a highly durable product, or to produce a heat-cured product. By adding the pozzolanic substance, calcium silicate hydrate (C—S—H) is easily generated by the pozzolanic reaction, so that durability against deterioration factors such as neutralization reaction of calcium hydroxide in sulfuric acid immersion is also improved.

  The pozzolanic substance is not limited as long as it has a high pozzolanic activity, but fly ash is preferred. Since fly ash is an industrial by-product, it can be used effectively in the same way as blast furnace slag, and fluidity is also improved.

  Therefore, in this system, the inorganic admixture is composed of blast furnace slag, pozzolanic material, fine limestone powder and anhydrous gypsum, and the blast furnace slag content is 1 to 38% by weight in the neutralization-suppressing early strong cement composition. The content of fly ash as the pozzolanic material is 1 to 38% by weight, the content of the limestone fine powder is 0.5 to 5% by weight, and the content of the anhydrous gypsum is 0.5 to 5% by weight. . The reason for setting the blast furnace slag content to 1 to 38% by weight is the same as described above.

  The reason why the content of the limestone fine powder is 0.5 to 5% by weight is the same as the above reason. The reason why the content of anhydrous gypsum is 0.5 to 5% by weight is the same as the above reason. The reason why the fly ash content is 1 to 38% by weight is that if it is less than 1% by weight, the effect of addition cannot be sufficiently obtained, and if it exceeds 38% by weight, the expression of short-term strength may deteriorate. is there.

  The reason why the range of the preferred content of anhydrous gypsum and fine limestone powder slightly deviates from the above system is that pozzolanic material was further added to achieve consistency.

<Pozzolanic Inorganic Admixture>
Another preferred form is a pozzolanic material system. This system is the simplest system consisting of a simple pozzolanic substance. This system is preferably used when it is desired to obtain a high-strength product at low cost while suppressing heat of hydration.

  By adding the pozzolanic substance, calcium silicate hydrate (C—S—H) is easily generated by the pozzolanic reaction, so that the medium to long-term strength is excellent. In addition, since the cement is the highly active cement, a short-term strength can be sufficiently secured and a neutralization suppressing performance is also obtained. The pozzolanic substance is not limited as long as it has a high pozzolanic activity, but silica fume having an extremely high pozzolanic activity is preferred when used as a simple substance.

  Therefore, in this system, the inorganic admixture is made of a pozzolanic material, and the content of silica fume, which is the pozzolanic material, is 3 to 15% by weight in the neutralization-suppressing type early strong cement composition. The content of silica fume is 3 to 15% by weight. If the content is less than 3% by weight, the effect of addition may not be sufficiently obtained. If it exceeds 15% by weight, it becomes difficult to ensure workability and the cost is increased. Because.

<Blast furnace slag-pozzolanic material based inorganic admixture>
Another preferred form is the blast furnace slag-pozzolanic material system. This system is obtained by adding blast furnace slag to the pozzolanic material system. This system is preferably used when it is desired to obtain high strength at low cost while effectively utilizing blast furnace slag. When silica fume is used as the pozzolanic material, the addition of blast furnace slag can improve fluidity and long-term strength elongation and reduce costs.

  Therefore, in this system, the inorganic admixture is composed of blast furnace slag and a pozzolanic material. In the neutralization-suppressing type early strong cement composition, the content of the blast furnace slag is 1 to 38% by weight, and the silica fume is the pozzolanic material. The content of is 2 to 15% by weight. The reason for setting the blast furnace slag content to 1 to 38% by weight is the same as described above.

  The reason why the content of silica fume is 2 to 15% by weight is the same reason as above. The reason why the range of the preferred content of silica fume is slightly shifted from that of the above system is that the blast furnace slag is further added to achieve consistency.

<Blast furnace slag-pozzolanic material-anhydrous gypsum inorganic admixture>
Another preferred form is the blast furnace slag-pozzolanic material-anhydrite system. This system is obtained by adding anhydrous gypsum to the above blast furnace slag-pozzolanic material system. This system may be used when it is desired to obtain a high-strength heat-cured product or a high-strength quick release product.

  Since the production of ettringite increases by adding anhydrous gypsum, the initial strength development in a low temperature environment can be further enhanced. Therefore, in this system, the inorganic admixture is composed of blast furnace slag, pozzolanic material, and anhydrous gypsum, and the neutralization-suppressing early strength cement composition has a blast furnace slag content of 1 to 37 wt%, and the pozzolanic material. The silica fume content is 1 to 15% by weight, and the anhydrous gypsum content is 1 to 9% by weight.

  The reason for setting the content of blast furnace slag to 1 to 37% by weight is the same reason as described above. The reason why the content of silica fume is 1 to 15% by weight is the same reason as above. The reason why the content of anhydrous gypsum is 1 to 9% by weight is that if it is less than 1% by weight, the effect of addition may not be sufficiently obtained, and if it exceeds 9% by weight, there is a possibility that delayed expansion may occur. The reason why the preferred content ranges of the blast furnace slag and silica fume slightly deviate from the above-mentioned system is that the anhydrous gypsum was further added to achieve consistency.

<Inorganic admixtures other than those listed above>
From the viewpoint of supply of each material, economic aspect, etc., inorganic admixtures other than those mentioned above can also be used. For example, blast furnace slag-anhydrous gypsum system, pozzolanic substance-anhydrite system, and the like. Also in these systems, the preferable range of the content of each material is about the same as the above range.

The high activity cement clinker in highly active cement above the present invention, as described above, but mineral composition is C _{2 S} <5% in the calculated value by the Borg type, calculated values by Borg expression of the C _{2 S} Is preferably less than 0% (negative value). Since the clinker mineral composition according to the Borg formula is a calculated value, the calculated value may be negative depending on conditions.

Actually, since the content does not become negative, a slight peak may be confirmed by analysis by X-ray diffraction. In the present invention, the calculated value of the C ₂ S according to the Borg formula is less than 0% (minus value), which indicates that C ₂ S is not included in the calculation. The negative value is, for example, about −4% to −14%.

It is also preferable that the sulfuric acid content in the highly active cement clinker is less than 1% by weight in terms of SO ₃ . By making it less than 1% by weight, generation of SO _X (sulfur oxide) in the exhaust gas during clinker firing is suppressed.

(1) According to the neutralization-suppressing type early strong cement composition of the present invention, the mineral composition calculated by the Borg formula is C ₃ S> 70% and C ₂ S <5%. S. D. Is newly developed by adding 1.5 to 4.0% by weight of gypsum in terms of SO ₃ to a highly active cement clinker having a free lime content of more than 1 and 0.5 to 7.5% by weight. Effective use of “active cement” can be achieved. Moreover, since this highly active cement is a cement that does not meet the standards, industrial waste can be used as a cement firing raw material, and it can also serve as industrial waste treatment.

(2) The neutralization-suppressing early strong cement composition of the present invention is based on a highly active cement, so it has excellent strength development in a low-temperature environment and also has a neutralization-inhibiting effect, and is equivalent to a mixed cement. Nevertheless, it has strength development and neutralization suppression performance equal to or better than ordinary Portland cement. In addition, depending on the blending composition form of the neutralization-suppressing type early-strength cement composition, the conventional mixed cement can also have performances such as salt barrier property and sulfate resistance. It is suitable as an alternative cement for the mixed cement that has been used and a mixed cement that has been used in an environment where neutralization is likely to proceed.

(3) The neutralization-suppressing type early-strength cement composition of the present invention comprises a combination of highly active cement and an inorganic admixture (blast furnace slag, fine limestone powder, anhydrous gypsum, pozzolanic substance), depending on the purpose and application. The system and blending ratio of inorganic admixture and the blending ratio of highly active cement and inorganic admixture can be freely designed, so mixed cement has been used not only in low-temperature environments and environments that require neutralization resistance. It can be used widely in the field of civil engineering and architecture, soil / ground, and waste disposal.

  Hereinafter, the neutralization suppression type early strong cement composition of the present invention will be described in more detail.

  As described above, the neutralization-suppressing type early-strength cement composition of the present invention is composed of the “highly active cement” and the inorganic admixture (blast furnace slag, anhydrous gypsum, limestone fine powder, pozzolanic substance) previously developed by the present inventors. Or more). First, each of these materials will be described.

[Constituent materials]
A. Highly active cement The highly active cement used in the present invention was previously developed by the present inventors prior to the present invention, and is obtained by adding gypsum to the previously developed highly active cement clinker. Both short-term strength development and medium to long-term development are good and effective for neutralization suppression.

[Highly active cement clinker]
(1) Mineral composition The highly active cement clinker used in the present invention has a mineral composition calculated by the Borg formula, C ₃ S> 70%, C ₂ S <5%, and the remainder mainly composed of calcium aluminate. It is a gap phase.

  The Borg formula is a formula that is conventionally used to calculate the main mineral composition in cement clinker, and the proportion of each mineral is calculated from the chemical composition analysis results. Since the obtained ratio is a calculated value based on the analysis result of the chemical composition to the last, it does not coincide with the actual ratio in the cement clinker. In addition,% is the mass%.

[Borg type]
C ₃ S (%) = (4.07 × CaO%) − (7.60 × SiO ₂ %) − (6.7 × Al ₂ O ₃ %) − (1.43 × Fe ₂ O ₃ %) − (2.85 x SO ₃ %)
C ₂ S (%) = (2.8 × SiO ₂ %) − (0.754 × C ₃ S%)
C ₃ A (%) = (2.65 × Al ₂ O ₃ %) − (1.69 × Fe ₂ O ₃ %)
C ₄ AF (%) = 3.04 × Fe ₂ O ₃ %

C ₃ S is a mineral that mainly develops cement strength from a short term to a long term, and the greater the amount, the higher the strength and the faster the strength. C ₂ S does not contribute much to the strength development in the short-term material age, but it contributes to the strength development in the long-term material age because it continues to hydrate for a long time. The growth of is good. Moreover, it will be excellent in chemical resistance and drying shrinkage.

C ₃ A has a high hydration activity and greatly contributes to the development of strength under short-term ages. However, if there are many of these, it will become hard and it will become a thing with a bad elongation of intensity | strength by long-term material age. Moreover, the heat of hydration is high and the chemical resistance and drying shrinkage are poor.

C ₄ AF has no outstanding characteristics as hydration performance, but contributes to easy firing as a gap phase in clinker firing.

The reason why C ₃ S> 70% in the present invention is to obtain a cement having an extremely high initial hydration activity, and when C ₃ S is 70% or less, it has a hydration activity equivalent to or higher than that of conventional early strong cement. It becomes difficult to obtain highly active cement. Although an upper limit is not specifically limited, 85% or less is preferable.

If it exceeds 85%, the amount of free lime may increase remarkably, and the quality stability of the cement clinker cannot be maintained. Moreover, the reason why calcium aluminate minerals such as C ₃ A having higher hydration activity are not frequently used is due to consideration of long-term strength development, workability, durability, and the like.

On the other hand, C ₂ S <5% in the present invention is to obtain a cement having a very high initial hydration activity without greatly changing the clinker firing conditions as compared with the conventional case, and C ₂ S is 5% or more. In addition, since the interstitial phase composed of calcium aluminate-based minerals and amorphous substances is reduced, it becomes difficult to fire the cement clinker, and the amount of C ₃ S is relatively reduced, which makes it difficult to achieve the object of the present invention.

Although the lower limit is not particularly limited, it is a value calculated by the Borg equation, and the C ₂ S amount is determined by the relationship between the SiO ₂ amount and the C ₃ S amount as shown in the above equation. Therefore, the SiO ₂ amount is small and the C ₃ S amount is small. If there are many, the calculated value may be less than 0 (minus value). In the present invention, including less than 0, it is preferably less than 0 in order to stably obtain a large amount of C ₃ S.

The highly active cement clinker used in the present invention is composed of a gap phase mainly composed of a calcium aluminate system except for the above C ₃ S and C ₂ S. The interstitial phase contains minerals such as C ₃ A and C ₄ AF. C ₃ A is preferably 4 to 9% as calculated by the above-mentioned Borg equation. _{Moreover, C} 4 AF are preferably contained 8-16%. Within this range, a cement clinker having C ₃ S> 70% and C ₂ S <5% can be stably fired. The rest is an amorphous interstitial phase.

(2) sulfuric acid content in the highly active cement clinker used in the sulfuric acid content present invention is less than 1 wt% converted to SO ₃ is preferred. If it is 1% by weight or more, SO _X (sulfur oxide) may be generated in the exhaust gas, or a solidified product may be generated inside the preheater, which is not preferable.

(3) Free lime In the high activity cement clinker used in the present invention, in order to increase the hydration activity of C ₃ S, free lime is included in the clinker to increase the calorific value and increase the kneading temperature. Is preferable. The amount is 0.5 to 7.5% by weight. If it is less than 0.5% by weight, a sufficient effect cannot be obtained. Exceeding 7.5% by weight is not preferable because it causes expansion or a decrease in fluidity.

Next, the manufacturing method of the said highly active cement clinker is demonstrated.
(4) Production method The production of the high activity cement clinker is not particularly different from the production of the conventional early-strength Portland cement clinker, and a predetermined cement firing raw material is C ₃ S> 70%, C ₂ S <5%. The amount of free lime is 0.5 to 7.5% by weight, and the mixture is prepared so that a cement clinker with a sulfuric acid content of less than 1% by weight in terms of SO ₃ is obtained. To do.

i) Cement clinker firing raw materials The limestone, clay, silica stone, and iron raw materials that have been used as the main raw materials for clinker can be used in the same way as before. In addition to this, it is preferable to use calcium-rich industrial waste, which is not so much reused and contains a calcium content of 20% by weight or more in terms of CaO.

  Wastes containing 20% by weight or more of calcium content in terms of CaO include desulfurization slag by hot metal pretreatment, desulfurization slag from which iron has been removed by magnetic separation, converter slag from which iron has been removed by reduction treatment, and ceramic siding Examples include waste building materials such as waste materials, and ready-mixed sludge.

  Desulfurization slag by hot metal pretreatment is slag from which sulfur content in pig iron is removed, and the main components are calcium and iron. Desulfurized slag containing a large amount of calcium that has been iron-removed by selection with a magnet can also be used. The hot metal preliminary treatment is a step of removing silicon, phosphorus and sulfur in a pre-process of converter refining in order to increase the purity of steel.

  The converter slag from which iron has been removed by reduction treatment is, for example, LD slag described in the following document. This LD slag can also be used.

  S. Kubodera, T. Koyama, R. Ando and R. Kondo, An Approach to the full utilization of LD Slag, Transactions of The Iron and Steel Institute of Japan, 419-427 (1979)

  Ceramic siding materials are cement materials and fiber materials that are molded and cured and hardened as the main raw materials. There are wood fiber reinforced cement boards, fiber reinforced cement boards, fiber reinforced calcium boards, etc. It is used as.

  With the recent repairs and dismantling of houses, waste materials are increasing and their treatment is under consideration. Since the cementitious portion of the waste material has a calcium-rich cement composition, it can be used as a raw material for producing a highly active cement clinker.

  The ready-mixed sludge is a sludge that has lost its fluidity by concentrating the concrete, return concrete, and return waste water from the mixer, hopper, agitator vehicle, etc. in the ready-mixed concrete plant, or drying the sludge. Is.

  These industrial wastes can be used as a partial replacement for limestone and clay. The amount added to the cement clinker firing raw material is preferably 400 kg or less per 1 ton of cement clinker, although it depends on the chemical components of limestone and clay. When 400 kg or more is added per 1 ton of cement clinker, impurities may increase, and it may be difficult to perform clinker firing or adversely affect the quality of the obtained cement clinker. If industrial waste is used as a partial substitute for limestone, it leads to a reduction in carbon dioxide emission, which is preferable from the viewpoint of reducing environmental impact.

ii) Raw material preparation The mixture is designed so that clinker of the desired chemical composition and mineral composition can be obtained after firing. Based on this, the above-mentioned cement clinker fired raw materials are weighed and mixed and ground in the raw material mill and blended in a blending silo. .

The above blending design is the same as in the conventional case. M.M. (Hydraulic modulus), A.I. I. (Activity coefficient), S.P. M.M. (Silicic acid ratio), I.V. M.M. (Iron rate), L. S. D. The ratio coefficient (modulus) of (lime saturation) is used. Typically, crucially involved the amount of _{C 3} S H. M.M. And S. relating to ease of firing. M.M. However, in the present invention, L. S. D. Emphasis on (lime saturation).

  L. S. D. (Lime saturation) is an index that sets the amount of calcium oxide that can be combined with silicon dioxide, aluminum oxide, and iron oxide to 1.0, and is expressed by the following equation.

L. S. D. = 100CaO / (2.80 × SiO ₂ % + 1.18 × Al ₂ O ₃ % + 0.65Fe ₂ O ₃ %)

  L. S. D. Is 1 or less, free lime can be reduced to 0% by taking sufficient time. S. D. In the case of> 1, free lime always remains even if the firing temperature is increased or the firing time is increased. The normal cement clinker is 0.92 to 0.96, and the early strong Portland cement clinker is 0.94 to 1.00.

In the high activity cement clinker of the present invention, L. S. D. > 1. L. S. D. A cement clinker having a high calcium content of C ₃ S> 70% and C ₂ S <5% can be fired by preparing a cement firing raw material so that free lime remains and> 1. The presence of free lime increases the initial heat of hydration, so C ₃ S can be activated and acts as a stimulant when mixed with blast furnace slag.

  The upper limit is not particularly limited, but is preferably about 1.16 or less because the clinker is not stable because the amount of free lime is too large.

  H. M (hydraulic modulus), A.I. I. (Activity coefficient), S.P. M.M. (Silicic acid ratio), I.V. M.M. When the ratio coefficient (modulus) of (iron ratio) is used, When M (hydraulic modulus) is 2.2 to 2.3, S.M. M.M. (Silicic acid ratio) is 1.7 to 2.4 and I.V. M.M. (Iron rate) is 1.0 to 2.1. When M (hydraulic modulus) is less than 2.1 to 2.2, S.I. M.M. (Silicic acid ratio) is 1.5 to 2.0 and I.I. M.M. The (iron ratio) is preferably 0.9 to 1.4.

iii) Clinker firing The highly active cement clinker used in the present invention can be obtained by firing the cement firing raw material prepared in the above-described raw material preparation in the same manner as conventional early-strength Portland cement clinker firing using a cement firing kiln. If it is a small amount of firing, electric furnace firing may be used.

The firing temperature is preferably 1250 to 1600 ° C. It is less than 1250 ° C. is not possible generation itself of _{C 3} S. In addition, when the temperature exceeds 1600 ° C., the refractory inside the rotary kiln is dissolved, which may be used for cement clinker firing. Clinker cooling, coarse crushing, etc. after firing are the same as in the past.

[Highly active cement]
The highly active cement used in the present invention is obtained by adding gypsum to the above highly active cement clinker so as to be 1.5 to 4.0% by weight in terms of SO ₃ and mixing and grinding with a finishing mill or the like together with a grinding aid. . The process and equipment are the same as the finishing process in conventional cement production. Gypsum and grinding aids are the same as those used in conventional cement production.

The amount of gypsum to be added is 1.5 to 4.0% by weight in terms of SO ₃ . If it is less than 1.5% by weight, sufficient work time may not be ensured when C ₃ A in the cement clinker is rapidly set to produce a concrete product or the like. If it exceeds 4.0% by weight, delayed expansion may occur due to unreacted gypsum after the cement has hardened. The fineness is not particularly limited, but is preferably 3000 cm ² / g or more in terms of brain value.

  Conventional high-strength Portland cement has a high degree of fineness and it is difficult to use high-performance water reducing agents. To obtain the desired fluidity, the water ratio must be increased or the amount of high-performance water reducing agent must be increased slightly. The high-activity cement used in the present invention has higher hydration activity than conventional early-strength Portland cement, so it is not necessary to increase the degree of fineness as conventional early-strength Portland cement. In this case, free lime etc. is quickly hydrated to form a hydrate layer on the particle surface, so that the predetermined fluidity can be achieved without increasing the water ratio or increasing the amount of the high-performance water reducing agent more than necessary. can get.

B. Inorganic admixture
(a) Blast Furnace Slag Blast furnace slag is a by-product generated when making pig iron in a blast furnace at a steelworks. It is taken out from the blast furnace together with pig iron in a molten state of about 1500 ° C, and then water-cooled and solidified in a sandy amorphous form. It is a pulverized body that has latent hydraulic properties that cause a hydration reaction with an alkali stimulant. The quality is not particularly limited as long as it is used for blast furnace cement and cement admixture and has a brane value of 1500 cm ² / g or more, but it conforms to JIS A 6206: 1997 “Blast furnace slag fine powder for concrete”. Those that do are preferred. Blast furnace slag contributes to securing fluidity, suppressing heat of hydration, increasing long-term strength, and salt-insulating properties.

(b) Limestone fine powder The limestone fine powder can be used without any problem as long as it is made of calcium carbonate and the purity is usually available. Any material conventionally used in cement, cement composition, or cement admixture is preferable from the viewpoint of supply and economy. The limestone fine powder is produced by pulverizing limestone and classifying as necessary, but the specific surface area of the brain is preferably 2000 to 10,000 cm ² / g. If it is less than 2000 cm ² / g, the effect of adding limestone fine powder cannot be obtained. When it exceeds 1000 cm ² / g, depending on the content, the fluidity is deteriorated and the cost is increased. Limestone fine powder contributes to securing fluidity, increasing short-term strength, and suppressing shrinkage.

(c) Anhydrous gypsum Anhydrous gypsum includes natural anhydrous gypsum, hydrofluoric acid anhydrous gypsum, natural 2-hydrate gypsum, by-product 2-hydrate gypsum, or anhydrous gypsum produced by firing dihydrate gypsum recovered from waste gypsum board. However, any gypsum containing 90% or more of anhydrous gypsum can be used. Further, the powder of the anhydrous gypsum is not particularly limited, 3000~8000cm ² / g, with Blaine value is preferably 4000~6000cm ² / g. Anhydrite mainly contributes to the improvement of short-term strength, but also works to secure fluidity and suppress shrinkage.

(d) Pozzolanic substance A pozzolanic substance is SiO ₂ or Al ₂ O ₃ having a reaction characteristic (pozzolanic reaction characteristic) that reacts with Ca (OH) ₂ or Ca ions in the presence of water to form a new hydrate. An inorganic substance rich in, including silica fume, metakaolin, activated silica powder, diatomaceous earth, rice husk ash, activated clay, fly ash fine powder, fly ash coarse powder, and the like. (Although the blast furnace slag cannot be regarded as a kind of pozzolanic material, the pozzolanic material referred to in the present invention does not include blast furnace slag.)

  Among them, silica fume, a by-product contained in exhaust gas when refining metallic silicon and ferrosilicon with an arc electric furnace, etc. has high pozzolanic reaction characteristics and can effectively use the by-product. Although many have been used as chemical materials, it is preferable to use silica fume as a pozzolanic material in the present invention.

  Silica fume is not particularly limited in quality as long as it is conventionally used for cement admixtures, but is preferably compliant with JIS A 6207: 2000 “silica fume for concrete”. A pozzolanic substance contributes to strength development, and improves durability and suppresses heat of hydration.

Next, a blending example of the neutralization-suppressing type early strong cement composition of the present invention using each of the above materials will be described.
[Composition example]
The neutralization-suppressing type early-strength cement composition of the present invention is obtained by mixing the high-activity cement with an inorganic admixture composed of one or more of the blast furnace slag, the limestone fine powder, the anhydrous gypsum, and the pozzolanic substance. Become.

  This neutralization-suppressing type early strong cement composition must contain at least 60% by weight of highly active cement and 3% by weight of inorganic admixture. If the high-activity cement is less than 60% by weight, it is difficult to obtain the strength improvement and neutralization suppression that are aimed by the present invention. That is, it is not possible to obtain a mixed cement equivalent in strength development and neutralization suppressing performance equivalent to that of ordinary Portland cement.

  In addition, when the inorganic admixture is less than 3% by weight, it is difficult to obtain the effects of the above-mentioned materials constituting the inorganic admixture, and not only the strength improvement and neutralization suppression, but also the performance of the conventional mixed cement has. Performance (e.g., low heat, salt barrier, sulfate resistance, etc.) is difficult to obtain, and it is difficult to say that it is similar to mixed cement.

  As described above, the pozzolanic material may be used alone or in combination with blast furnace slag, limestone fine powder or anhydrous gypsum, but blast furnace slag, limestone fine powder, anhydrous gypsum is at least one of the other two. It is preferable to use in combination.

  This is because, as described above, the pozzolanic material greatly contributes to the expression of short to long-term strength, so it is easy to achieve the object of the present invention even if it is simple, but blast furnace slag, fine limestone powder, and anhydrous gypsum have at least short to long-term strength expression. This is because although it contributes in part, a simple effect cannot be obtained.

  The neutralization-suppressing type early-strength cement composition of the present invention only needs to satisfy the above-mentioned conditions, and the inorganic admixtures are of various systems in consideration of material supply, waste material utilization, cost, and the like. be able to.

  Preferred systems include (a) blast furnace slag-limestone fine powder system, (b) blast furnace slag-limestone fine powder-anhydrite system, (c) blast furnace slag-limestone fine powder-anhydrite-pozzolanic material system, It is a pozzolanic material system, (e) a blast furnace slag-pozzolanic material system, and (f) a blast furnace slag-pozzolanic material-anhydrite system.

  If these systems are used, not only can the strength be improved and the neutralization suppression can be improved, but also the effects of the conventional mixed cement can be easily maintained. The proper use of each neutralization-suppressing type early strong cement composition using the inorganic admixtures (a) to (f) is as described above.

[Inorganic admixture]
(I) Blast Furnace Slag-Limestone Fine Powder System A suitable blend in the blast furnace slag-limestone fine powder system is that the neutralization-suppressing type early strong cement composition has a blast furnace slag content of 2 to 39% by weight, the limestone The content of fine powder is 1 to 10% by weight. The formulation is as described above.

(B) Blast furnace slag-limestone fine powder-anhydrous gypsum system The preferred composition in the blast furnace slag-limestone fine powder-anhydrous gypsum system is such that the content of the blast furnace slag is 1 to 3 in the neutralization-suppressing type early strong cement composition. 38% by weight, the content of the limestone fine powder is 1 to 10% by weight, and the content of the anhydrous gypsum is 1 to 5% by weight. The formulation is as described above.

(C) Blast furnace slag-limestone fine powder-anhydrous gypsum-pozzolanic substance system Suitable materials and blends in the blast furnace slag-limestone fine powder-anhydrous gypsum-pozzolanic substance system are the neutralization-suppressing type early strong cement composition, The content of blast furnace slag is 1 to 38% by weight, the content of fly ash as the pozzolanic material is 1 to 38% by weight, the content of the limestone fine powder is 0.5 to 5% by weight, the content of the anhydrous gypsum The amount is 0.5-5% by weight. The combination with such materials is as described above.

(D) Pozzolanic substance system A suitable material and blending in the pozzolanic substance system is that the content of silica fume, which is the pozzolanic substance, is 3 to 15% by weight in the neutralization-suppressing early strength cement composition. The combination with such materials is as described above.

(E) Blast Furnace Slag-Pozzolanic Material System Suitable materials and blends in the blast furnace slag-pozzolanic material system include a neutralization-suppressing fast-strength cement composition with a blast furnace slag content of 1 to 38% by weight, and the pozzolanic material. The content of silica fume as a substance is 2 to 15% by weight. The combination with such materials is as described above.

(F) Blast furnace slag-pozzolanic material-anhydrous gypsum system Suitable materials and blends in the blast furnace slag-pozzolanic material-anhydrous gypsum system are those in which the content of the blast furnace slag is 1 to 3 in the neutralization-suppressing early strength cement composition. 37% by weight, the content of silica fume as the pozzolanic material is 1 to 15% by weight, and the content of the anhydrous gypsum is 1 to 9% by weight. The combination with such materials is as described above.

Next, the manufacturing method of the neutralization suppression type early strong cement composition of this invention is demonstrated.
[Manufacture of neutralization-suppressed early-strength cement composition]
For the production of the neutralization-suppressing early strong cement composition of the present invention, a conventional mixing facility for producing a mixed cement may be used as appropriate. Moreover, you may manufacture a highly active cement and an inorganic type admixture by separate measurement at the time of concrete manufacture in a ready-mixed concrete factory.

Next, the performance confirmation test of the neutralization-suppressing type early strong cement composition of the present invention will be described.
[Performance confirmation test of neutralization-suppressing early strong cement composition]
The object of the present invention is to provide a neutralization-suppressing type early-strength cement composition that is excellent in strength development, particularly short-term strength development in a low-temperature environment, and has a neutralization-inhibiting effect as described above. .

  Therefore, an accelerated neutralization test and a compressive strength test at 10 ° C. and 20 ° C. were performed.

<Materials used>
(1) cement
1) Highly active cement By calcining a cement fired raw material prepared from industrial raw materials such as limestone and clay so as to have predetermined components at 1450 ° C., C ₃ S is 72% and C ₂ S is 1%. S. D. Is a high activity cement clinker having a free lime content of 2.5% by weight, to which is added 3.0% by weight of dihydrate gypsum in terms of SO ₃ to obtain a trial high activity cement. It was. Manufacturing was done using the actual equipment of the cement factory from the raw material process to the finishing process.
2) Ordinary Portland cement (manufactured by Taiheiyo Cement, for comparison)

(2) Inorganic admixture
1) Ground granulated blast furnace slag (Derai's Seramento; Brain value 4470cm ² / g)
2) Limestone fine powder (manufactured by Chichibu Pacific Corp .; brain value 10240cm ² / g)
3) Anhydrous gypsum (manufactured by D.S.I .; brain value 3840 cm ² / g)
4) Pozzolanic material ・ Fly ash (manufactured by Power Supply Development Co.)
・ Silica fume (from Egypt)
5) Sand ・ Standard sand according to JIS R 5201 “Physical testing of cement”

<Formulation of cement composition>
Table 1 shows the respective compositions of the neutralization-suppressing early-strength cement composition of the present invention and the cement composition in the comparative example.

上記各セメント組成物は、所定配合の各構成材料をＶ型混合機で混合して得た。

Each of the above cement compositions was obtained by mixing each constituent material having a predetermined composition with a V-type mixer.

<Mortar preparation and mixing>
The mortar was prepared and kneaded in accordance with the mortar preparation and kneading method described in JIS R 5201 “Physical testing method for cement”. In addition, the cement composition was prepared by regarding the whole as cement.

<Accelerated neutralization test>
The mortar produced by the above method was subjected to accelerated neutralization according to JIS A 1153 “Testing method for accelerated neutralization of concrete”, and the accelerated neutralization depth was measured. The measurement age was 1 week, 4 weeks, and 8 weeks.

<Compressive strength test>
Using a 4 × 4 × 16 cm mortar specimen made of the mortar prepared by the above method, the test was performed according to the compressive strength test method described in JIS R 5201 “Cement physical test method”. However, the test material ages were 3, 7, and 28 days. Moreover, the curing to the test material age was performed at two curing temperatures of 10 ° C and 20 ° C.

  In addition, in short-term ages (3 days, 7 days), in order to see the effect of curing temperature on strength development, the ratio of strength at 10 ° C and strength at 20 ° C [strength ratio = (at 10 ° C Compression strength at 20 ° C.) × 100 ”.

<Result>
The results of the accelerated neutralization test are shown in Table 2. Table 3 shows the results of the compressive strength test.

  As can be seen from Table 2 above, the Examples have a smaller accelerated neutralization depth than Comparative Examples other than Comparative Example No. 2 that cannot be said to be equivalent to mixed cement. In particular, the accelerated neutralization depth is small as compared with Comparative Example No. 3 which is a mixed cement equivalent to blast furnace cement and Comparative Example No. 4 which is plain Portland cement.

  Therefore, the neutralization-suppressing type early strong cement composition of the present invention has a neutralization-inhibiting performance higher than that of conventional mixed cements despite being similar to conventional mixed cements, and is equivalent to or better than ordinary Portland cements. It can be said that it has neutralization suppression performance.

  As can be seen from Table 3 above, the Examples generally have better strength development than the Comparative Examples. Compared with Comparative Example No. 3 which is a mixed cement equivalent to blast furnace cement and Comparative Example No. 4 which is a plain Portland cement, the difference in short-term strength is particularly large on the 3rd day of the age. The strength ratio is preferably 75% or more, but all the examples are as high as 75% or more.

  In addition, except for the type of cement, it can be seen from the comparison of each of No.9 and No.10, No.15 and No.16, No.23 and No.24, and No.28 and No.29. As described above, the strength development is better when the high activity cement is used, and the short-term strength under a low temperature environment such as 10 ° C. is greatly improved.

  The neutralization-suppressing early-strength cement composition of the present invention has better strength development than the conventional mixed cement, although it is similar to the conventional mixed cement, and the short-term strength is improved particularly in a low-temperature environment. It can be said that it has the same or better strength than ordinary Portland cement.

Claims (7)

The mineral composition calculated by the Borg formula is C ₃ S> 70% and C ₂ S <5%. S. D. Is obtained by adding gypsum to 1.5 to 4.0% by weight in terms of SO ₃ to a highly active cement clinker having a free lime content of more than 1 and 0.5 to 7.5% by weight. A neutralization-suppressing type early-strength cement composition comprising: 3% by weight of an inorganic admixture composed of at least one of blast furnace slag, anhydrous gypsum, limestone fine powder, and pozzolanic material.   The inorganic admixture is composed of blast furnace slag and fine limestone powder. In the neutralization-suppressing type early strong cement composition, the content of the blast furnace slag is 2 to 39% by weight, and the content of the limestone fine powder is 1 to The neutralization-suppressing type early strong cement composition according to claim 1, wherein the composition is 10% by weight.   The inorganic admixture is composed of blast furnace slag, limestone fine powder and anhydrous gypsum, and in the neutralization-suppressing type early strong cement composition, the content of the blast furnace slag is 1 to 38% by weight, and the content of the limestone fine powder. The neutralization-suppressing type early-strength cement composition according to claim 1, wherein the content of the gypsum is 1 to 10% by weight and the content of the anhydrous gypsum is 1 to 5% by weight.   The inorganic admixture is composed of blast furnace slag, pozzolanic material, limestone fine powder and anhydrous gypsum, and the neutralization-suppressing early strength cement composition has a blast furnace slag content of 1 to 38% by weight, the pozzolanic material. The content of a certain fly ash is 1 to 38% by weight, the content of the limestone fine powder is 0.5 to 5% by weight, and the content of the anhydrous gypsum is 0.5 to 5% by weight. The neutralization-suppressing type early strong cement composition according to claim 1.   The said inorganic admixture consists of a pozzolanic substance, and content of the silica fume which is the said pozzolanic substance is 3 to 15 weight% in the said neutralization suppression type early strong cement composition. Neutralization suppression type early strong cement composition.   The inorganic admixture is composed of blast furnace slag and a pozzolanic material. In the neutralization-suppressing type early strong cement composition, the content of the blast furnace slag is 1 to 38% by weight, and the content of silica fume that is the pozzolanic material is 2. The neutralization-suppressing type early strong cement composition according to claim 1, wherein the composition is -15% by weight.   The inorganic admixture is composed of blast furnace slag, pozzolanic material, and anhydrous gypsum. In the neutralization-suppressing type early-strength cement composition, the content of the blast furnace slag is 1 to 37% by weight, and the content of silica fume, which is the pozzolanic material. The neutralization-suppressing type early strong cement composition according to claim 1, wherein the amount is 1 to 15% by weight and the content of the anhydrous gypsum is 1 to 9% by weight.