JP6579977B2 - Cement composition - Google Patents

Description

  The present invention relates to a cement composition having good initial strength and strength enhancement that can be suitably used as a cement for concrete or mortar, a solidifying material in a ground improvement material, or the like.

  Conventionally, various mixed cements such as blast furnace cement and fly ash cement have been developed and used depending on purposes. In addition, various cement compositions have been developed in which cement admixtures such as blast furnace slag fine powder, fly ash, and limestone fine powder are mixed with base cement such as ordinary Portland cement in order to obtain strength development and fluidity according to the purpose. Has been used.

In particular, in recent years, from the viewpoint of reducing environmental impacts such as CO ₂ reduction in the cement and concrete fields and processing and reuse of industrial by-products, effective mixing as resources for industrial by-products such as blast furnace slag fine powder and fly ash The study of cement and cement compositions has attracted attention.

  However, in the above mixed cement and cement composition using ordinary Portland cement or a cement exhibiting the same strength development as the base cement, mixing may be sufficient depending on the type of admixture such as blast furnace slag fine powder and fly ash. There was a problem that the initial strength could not be obtained.

  Therefore, although active silica powders such as silica fume and strength enhancers such as potassium carbonate have been solved, strength development is improved, but other performance such as coagulation, fluidity, and drying shrinkage, New problems may arise in terms of cost and the like, and this is not always an effective solution.

  Fast-strength Portland cement is known as a cement with good strength development, but since it lacks practicality in terms of price, supply, etc. compared to ordinary Portland cement, mixed cement and cement composition using this as base cement It is not used much.

  In recent years, studies have been made focusing on the mineral composition of the cement clinker, returning to the cement clinker constituting the base cement.

For example, Patent Document 1 discloses water containing gypsum and 5% by mass of limestone per total composition in a high C ₃ S and low C ₂ S cement clinker having a C ₃ S amount of 60% or more calculated by the Borg formula. A hard composition is described. And it is described by mix | blending limestone that it shows favorable strength expression compared with the case where it does not mix | blend.

Further, in Patent Document 2, the mineral composition of cement clinker is calculated by the Borg formula, C ₃ S> 70%, C ₂ S <5%, and the amount of free lime in the cement clinker is 0.5 to 7.5. A highly active cement clinker having a weight% and a highly active cement obtained by adding gypsum to the highly active cement clinker so as to be 1.5 to 4.0% by weight in terms of SO ₃ are described.

Patent Document 3 discloses a highly active cement clinker having a mineral composition calculated by the Borg formula of C ₃ S> 70% and C ₂ S <5% and a free lime content of 0.5 to 7.5% by weight. One or more of high-activity cement obtained by adding gypsum to 1.5 to 4.0% by weight in terms of SO ₃ , blast furnace slag, anhydrous gypsum, fine limestone powder, and pozzolanic material A neutralization-suppressing type early strong cement composition comprising 3 to 40% by weight of an inorganic admixture is described.

JP 2014-97918 A Japanese Patent No. 5747407 Japanese Patent No. 5818579

The hydraulic composition described in Patent Document 1 is based on a high C ₃ S and low C ₂ S cement clinker having a C ₃ S amount of 60% or more, and the strength is further increased by adding limestone. Although the strength is ensured, the initial strength at the age of 3 days is not high compared to ordinary Portland cement, and it cannot be said that the strength at the age of 28 days is sufficiently secured. The strength at the age of 3 days or 7 days was increased due to the hydration reaction between the interstitial phase and limestone, but the strength at the age of 28 days cannot be said to increase.

Moreover, although the cement using the highly active cement clinker described in Patent Document 2 and Patent Document 3 can secure the initial strength at a material age of 3 days, the amount of C ₂ S in the clinker is significantly less than 1%. Since the amount of free lime is as high as 5% by weight or more, the increase in strength after the age of 7 days is not sufficient, and it cannot be said that the strength at the age of 28 days is sufficiently high.

  Moreover, the cement composition described in Patent Document 3 may not be able to sufficiently secure the strength of 28 days of age depending on the admixture with a slow pozzolanic reaction at the age of 28 days.

  Furthermore, the highly active cement clinker described in Patent Document 2 and Patent Document 3 has a large amount of free lime of 5% by weight or more, and thus there is a risk that stable production may be difficult depending on the firing method.

  The present invention has been made in view of the above-described problems, and provides a cement (cement composition) that has good initial strength development and strength enhancement and can sufficiently secure strength at the age of 28 days. With the goal.

The present invention is a related invention of the high activity cement described in Patent Document 2 and the like, and the present inventor uses the mineral composition in the cement clinker in the high activity cement clinker described in Patent Document 2 and Patent Document 3 ( In particular, by controlling the amount of C ₃ S, the amount of C ₂ S, and their proportions) and the amount of free lime, a stable production is possible and a cement with good initial strength development and strength enhancement can be obtained. It was found that if a specific amount of fine limestone powder was added to the cement to obtain a cement composition comprising the cement and fine limestone powder, the strength could be further improved and the object of the present invention could be achieved, thereby completing the present invention.

The invention according to claim 1 of the present application states that “the amount of C ₃ S determined by the Borg formula is 60 to 71%, the amount of C ₂ S is 1% or more, and the total amount of C ₃ S and C ₂ S is 70 to 80%. %, And a C ₃ S / C ₂ S ratio is at least 5 or more, and gypsum is added to an alite-rich clinker having a free lime content of 1.0 to 4.0% by weight. The cement composition is characterized in that 2 to 10% by weight of fine limestone powder is added to the cement.

  The cement composition of the present invention comprises cement and fine limestone powder. Cement is made by adding gypsum to clinker with high alite content. The gypsum is not particularly limited as long as it is conventionally used for producing cement, such as dihydrate gypsum and anhydrous gypsum.

The addition amount of gypsum is preferably 1.5 to 4.0% by weight in terms of SO ₃ with respect to the high lite content clinker. If it is less than 1.5% by weight, fresh properties such as fluidity and coagulation in the initial stage of hydration are deteriorated, and workability may be hindered. On the other hand, if it exceeds 4.0% by weight, it may be difficult to obtain the strength enhancement effect at the age of 28 days.

The fineness of the cement is not particularly limited, but it is preferably 3500 to 5500 (cm ² / g) in terms of brain value. Needless to say, the higher the degree of fineness, the better the strength development. However, if the degree of fineness is too high, the increase in strength until the age of 28 days is small, and if the degree of fineness is too low, the strength is sufficient from the initial age. Disappear. In order to achieve the object of the present invention economically, the brane value is preferably set to about 3500 to 4500 (cm ² / g).

Alite-rich clinker has a C ₃ S amount of 60 to 71%, a C ₂ S amount of 1% or more and a total amount of C ₃ S and C ₂ S of 70 to 80% determined by the Borg formula. _It has a specific clinker mineral composition such that the ₃ S / C ₂ S amount ratio is at least 5 or more. Thus, by achieving a balance between the amount of C ₃ S and the amount of C ₂ S in the clinker, a stable clinker can be produced, and a cement with good initial strength development and strength enhancement can be obtained.

The amount of C ₃ S in the clinker is 60 to 71%. If the amount of C ₃ S is less than 60%, it becomes difficult to obtain a cement having good fresh properties at the initial stage of hydration and good initial strength development and strength enhancement. In some cases, sufficient strength at 28 days of age is ensured. It becomes difficult to do.

On the other hand, if it exceeds 71% by weight, the amount of C ₂ S and the amount of interstitial phase (aluminate phase) are relatively small, and there is a risk that stable clinker production may be difficult depending on the firing method.

The amount of C ₂ S in the clinker is 1% or more. If the amount of C ₂ S is less than 1%, the amount of the interstitial phase (aluminate phase) becomes excessive, and the fresh properties and strength enhancement properties may deteriorate. Further, the strength enhancement property may be reduced, and the strength at the age of 28 days may be reduced.

The total amount of C ₃ S and C ₂ S in the clinker is 70 to 80%. If it is less than 70%, the amount of the interstitial phase (aluminate phase) becomes relatively large, so that the fresh properties may be deteriorated or the strength enhancement property may be poor, and the strength at the age of 28 days may be sufficiently secured. .

  On the other hand, if it exceeds 80%, the amount of the interstitial phase (aluminate phase) becomes relatively small, and depending on the baking method, it becomes difficult to produce a stable clinker or a sufficient initial strength cannot be obtained.

The C ₃ S / C ₂ S amount ratio in the clinker is important in terms of strength, strength enhancement, and the like, and in the present invention, the C ₃ S / C ₂ S amount ratio is at least 5 or more. If it is less than 5, the amount of C ₂ S is relatively increased, resulting in insufficient strength development.

An object of the present invention is to provide an initial strength development property and strength enhancement property and to sufficiently ensure strength at a material age of 28 days. Specifically, when the mortar age 3 day strength in the compressive strength test according to JIS R 5201 is 35 to 40 N / mm ² , the material age 28 day strength ratio is 1.50. As described above, when the material age 3 day strength exceeds 40 N / mm ² , the material quality 28 day strength ratio with respect to the material age 3 day strength is set to 1.35 or more, which is used as a criterion for quality determination.

  Therefore, “sufficient initial strength” in the present specification satisfies the above-mentioned numerical value at a material age of 3 days, and “sufficiently secures strength at a material age of 28 days” means a material for a material age of 3 days. The above numerical value in the intensity ratio at the age of 28 days is satisfied.

The amount of free lime in the clinker is important from the viewpoints of stable production of the clinker, ensuring initial strength, a stimulating agent for enhancing the hydration activity of C ₃ S, and the like, and must be tightly controlled. If it is 1.0-4.0 weight%, each performance in the said viewpoint will be acquired, and achievement of the objective of the said this invention will become easy.

  As described above, the cement composition of the present invention is obtained by adding 2 to 10% by weight of limestone fine powder to the above cement and mixing them. By adding limestone fine powder within this range, strength can be enhanced and stable initial hydration properties can be achieved. If it is less than 2% by weight, a sufficient addition effect cannot be obtained. On the other hand, if it exceeds 10% by weight, the amount of addition increases and the strength enhancement property deteriorates. From the viewpoint of active use of limestone, effective addition amount of limestone fine powder, etc., it is preferably 2.5 to 7.5% by weight.

  In general, the effect on the strength of the limestone fine powder is such that the strength increases at the age of 3 days or 7 days of age, and the effect of increasing the strength of the limestone fine powder is small at the age of 28 days. In the present invention, it has been found that the strength can be increased at the age of 28 days by adding a specific amount of fine limestone powder even with cement using the specific clinker as described above.

The limestone fine powder is not particularly limited as long as it is conventionally used as a cement composition, a cement admixture, or a constituent material of concrete. The fineness of the fine limestone powder is preferably 2000 to 10000 (cm ² / g) in terms of Blaine value. By making it in this range, the effect of the present invention is more exhibited.

  The cement composition of the present invention can sufficiently achieve the object of the present invention even if it consists of only two raw materials, the cement and the limestone fine powder. Third components such as blast furnace slag and fly ash can be included.

The invention according to claim 2 of the present application is as follows: “In the lite with high alite content, the C ₂ S amount obtained by the Borg formula has a clinker mineral composition of 1 to 15%. Cement composition ".

As described above, C ₂ S requires a certain amount in the clinker from the viewpoint of fresh properties, strength enhancement, stable clinker production, etc., but it is not preferable to exceed 15%. If it exceeds 15%, the amount of C ₃ S and / or the amount of interstitial phase (aluminate phase) is relatively reduced, so that the initial to intermediate strength development becomes worse and the object of the present invention cannot be achieved. There is a case.

  A more preferred amount is 4 to 10%. Within this range, clinker can be produced economically and stably, and the strength development can also achieve the object of the present invention.

The invention according to claim 3 of the present application is “the clinker mineral composition having a C ₃ S / C ₂ S amount ratio of 5 to 55 in the high alite content clinker, according to claim 1 or 2”. Cement composition ".

As described above, the C ₃ S / C ₂ S amount ratio (the balance between the C ₃ S amount and the C ₂ S amount) is important in achieving the object of the present invention, and it is necessary to make it at least 5 or more. 5 to 55 is preferable, and 7 to 20 is more preferable. If the balance between the amount of C ₃ S and the amount of C ₂ S is good, the clinker can be manufactured easily, the target strength can be ensured at the age of 3 days and 28 days, and further, long-term strength can be expected.

The invention according to claim 4 of the present application states that, in the clinker containing a high amount of alite, the C ₃ A amount determined by the Borg formula is 8 to 12%, the C ₄ AF amount is 7 to 10%, and C ₃ A and C ₄ 4. The clinker mineral composition according to claim 1, wherein the total amount of AF is 18 to 19% and the C ₃ A / C ₄ AF amount ratio is 0.9 to 1.5. The cement composition to be described.

As described above, the amount of C ₃ S and the amount of C ₂ S are important in the present invention, but the amount of C ₃ A in the clinker is effective in securing the initial strength and effectively extracting the effect of adding the limestone fine powder. It is preferable to control the amount of C ₄ AF.

In the high alite content clinker, the amount of C ₃ A is preferably 8 to 12%. If the amount of C ₃ A is less than 8%, the initial strength may be difficult to ensure easily depending on the use environment of the cement composition of the present invention, such as low temperature and water temperature of the kneaded water. On the other hand, if it exceeds 12%, depending on the use environment of the cement composition of the present invention, such as the air temperature or the temperature of the kneaded water, the fresh properties may be deteriorated and workability may be hindered.

In the high alite content clinker, the amount of C ₄ AF is preferably 7 to 10%. If the amount of C ₄ AF is less than 7%, the interstitial phase may be reduced and clinker production may be difficult. In addition, when it exceeds 10%, the amount of C ₃ A is relatively reduced, and the initial strength is difficult to ensure depending on the use environment of the cement composition of the present invention, such as the temperature and the temperature of the kneaded water being low. There is.

Further, the total amount of the C ₃ A and the C ₄ AF is preferably 18 to 19%. If in this range, with alite (C 3 _S) becomes easier clinker production even at high content, the effect of adding the powder the limestone fine powder with respect to the cement is effective.

Furthermore, in the lite having a high alite content, the C ₃ A / C ₄ AF amount ratio is preferably 0.9 to 1.5. By setting the balance between the amount of C ₃ A and the amount of C ₄ AF within this range, stable clinker production can be performed while ensuring a predetermined amount of C ₃ A.

  The invention according to claim 5 of the present application is “the cement composition according to any one of claims 1 to 4, wherein the cement composition includes only two raw materials of the cement and the fine limestone powder”. A cement composition characterized by comprising the following:

  As described above, the cement composition of the present invention can contain a third component as needed as long as it does not inhibit the strength development. However, the present invention includes two types of the cement and the limestone fine powder. It is characterized in that the object of the present invention can be achieved with only one raw material (constituent material).

  Therefore, since a plurality of inorganic admixtures can be omitted as in the cement composition of Patent Document 3, the production becomes simple and the cost is superior. Moreover, in this invention of this application, since there are few raw materials (constituent material) of a cement composition, compared with the cement composition using a several inorganic admixture, what has a uniform performance is easy to be obtained.

  Moreover, if it is used as an alternative to a commonly used cement such as ordinary cement, it is not necessary to add the third component to the cement composition, and it can be used in the same manner as conventional ordinary cement. Therefore, this cement composition of the present invention is highly versatile as an alternative to ordinary cement used in various fields such as civil engineering, construction, and ground improvement.

  The cement composition of the present invention has good initial strength development and strength enhancement, and can sufficiently secure strength at a material age of 28 days. In addition, since the high alite content clinker to be used can be stably produced, the hydration performance is uniform and stable.

  Hereinafter, the cement composition of the present invention will be described in more detail.

[Cement composition]
The cement composition of the present invention basically consists of only two constituent materials, cement and limestone fine powder using a high lite clinker. Since this cement composition has better initial strength and higher strength at the age of 28 days than conventional ordinary cement, it can be widely used as a substitute cement for ordinary cement in fields such as civil engineering / architecture and ground improvement. It is highly versatile. The cement composition may be manufactured by mixing or mixing and grinding the following cement and the following limestone fine powder by a conventional method.

  If necessary, a third component such as blast furnace slag powder or fly ash may be added as long as strength development is not significantly impaired. Further, since the strength development is better than ordinary cement, the cement composition of the present invention can be used as an alternative cement to ordinary cement which is a base cement of conventional mixed cement such as blast furnace cement and fly ash cement. Below, each structural material of the cement composition of this invention is demonstrated.

[Constituent material of cement composition]
A. Cement The cement used in the present invention is obtained by adding a predetermined amount of the following gypsum to the following high alite content clinker and mixing and grinding. The cement manufacturing apparatus and manufacturing method may be the same as those in the past.

Also, for example, the cement of the present invention may be produced by mixing and / or separating and pulverizing an alite-rich clinker having a C ₂ S content of less than 1% and a free lime content of more than 4% by weight. it can.

The fineness of the cement is not particularly limited, but it is preferably 3500 to 5500 (cm ² / g) in terms of brain value. More preferably, it is 3700-4500 (cm < ² > / g).

[Alite-rich clinker]
(1) Clinker Mineral Composition The alite-rich clinker used in the present invention has a C ₃ S amount of 60 to 71% and a C ₂ S amount of 1% or more (preferably 1 to 15%, more preferably determined by the Borg formula). 4 to 10%) and the total amount of C ₃ S and C ₂ S is 70 to 80%, and the C ₃ S / C ₂ S amount ratio is at least 5 or more (preferably 5 to 55, more preferably 7 to 20) Clinker mineral composition.

Such a mineral composition is as described above. Except for C ₃ S and C ₂ S, it consists of a porous phase mainly composed of calcium aluminate, and the porous phase contains minerals such as C ₃ A and C ₄ AF.

_{C 3} A and _C 4 AF in the gap membrane phase, the total amount of _{C 3} A content is 8% to 12% and _C 4 AF weight 7% -10% and _{C 3} A and _C 4 AF obtained by Borg formula It is preferable to have a clinker mineral composition of 18 to 19% and a C ₃ A / C ₄ AF amount ratio of 0.9 to 1.5. Such a mineral composition is preferred as described above.

  The Borg formula used in the present invention is a formula conventionally used to calculate the main mineral composition in the cement clinker, and the proportion of each mineral is calculated from the analysis result of the chemical composition of the cement clinker. Since the obtained ratio is a calculated value based on the analysis result of the chemical composition, it does not match 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 the initial age to the long-term age, and the more it is, the higher the strength and the early strength. The larger the amount of production, the more difficult it is to fire, for example, high temperature firing and sufficient firing time are required.

C ₂ S does not contribute much to the strength development at the initial age, but contributes to the strength development at the medium to long-term age because hydration is continued for a long time. Therefore, it is necessary to some extent to increase strength. It is also indispensable for stable clinker firing. Furthermore, the more this, the better the chemical resistance and drying shrinkage.

C ₃ A has a high hydration activity and greatly contributes to the development of strength at the initial age. However, if the amount is too large, the fresh properties such as rapid hardening become worse and the strength enhancement property also worsens.
C ₄ AF has no outstanding characteristics as hydration performance, but contributes to easy firing and stable firing as a porous phase in clinker firing.

In addition to the above C ₃ S, C ₂ S, C ₃ A, and C ₄ AF, there are other aluminate minerals, aluminosilicate minerals, amorphous interstitial phases, etc. in the clinker depending on the production conditions. To do.

(2) Free lime It is important to control the amount of free lime from the viewpoint of stable production of clinker, stimulant for enhancing the hydration activity of C ₃ S, and the like. Also, if there is free lime, the calorific value at the initial stage of hydration increases and the kneading temperature increases, so the initial strength increases. However, if the amount is too large, there is a possibility of causing expansion, a decrease in fluidity, popping out, weathering of the clinker, and the like.

  In the present invention, the amount of free lime in the clinker is 1.0 to 4.0% by weight. If it is in this range, it becomes easy to obtain only the above-mentioned positive effect due to the inclusion of free lime in the clinker.

(3) Clinker production The production of a high lite clinker used in the present invention may be carried out in accordance with, for example, the method for producing highly active cement clinker described in Patent Document 2 and Patent Document 3.

  That is, HM (hydraulic modulus), AI (activity coefficient) so that raw materials such as limestone, clay, silica stone, and iron raw materials that have been conventionally used as clinker main raw materials have a predetermined mineral composition and free lime content. , SM (silicic acid ratio), IM (iron ratio), LSD (lime saturation), etc. based on the blending design obtained by using a material mill and blending silo, and the resulting blended raw material is cement Clinker is obtained by baking in a baking kiln. The firing temperature is preferably 1250 to 1600 ° C. Clinker cooling, coarse crushing, etc. after firing are the same as in the past.

[plaster]
The gypsum is not particularly limited as long as it is conventionally used for cement production, such as anhydrous gypsum and dihydrate gypsum.

The addition amount of gypsum is preferably 1.5 to 4.0% by weight in terms of SO ₃ with respect to the high alite content clinker. If it is less than 1.5% by weight, fresh properties such as fluidity and coagulation in the initial stage of hydration are deteriorated, and workability may be hindered. On the other hand, if it exceeds 4.0% by weight, the strength from the material age 28 days may not be improved.

B. Limestone fine powder The limestone fine powder is added to the cement in a predetermined amount in order to ensure fluidity, increase strength in the age of 3 to 28 days, suppress shrinkage, and the like. The amount of fine limestone powder added to the cement is 2 to 10% by weight, preferably 2.5 to 7.5% by weight. The amount is set as described above.

The limestone fine powder is not particularly limited as long as it is conventionally used as a cement composition, a cement admixture, or a constituent material of concrete. The fineness of the fine limestone powder is preferably 2000 to 10000 (cm ² / g) in terms of Blaine value.

  Next, the strength performance confirmation test of the cement composition of the present invention will be described.

≪Strength performance confirmation test; Examples≫
<Materials used>
(1) Cement ・ Prototype cements shown in Table 1 (Gypsum is drained dihydrate gypsum manufactured by Showa Denko KK, and 2.5% is uniformly added to the clinker in terms of SO ₃ )
(2) Limestone fine powder ・ Limestone fine powder (manufactured by Chichibu Pacific Co., Ltd .; brain value 4770 cm ² / g)
(3) Blast furnace slag fine powder ・ Blast furnace slag fine powder (manufactured by D Shii Co., Ltd .; brain value 4350 cm ² / g)

<Base cement and cement composition>
Table 1 shows the clinker composition and fineness of the base cement, and Table 2 shows the composition of the cement composition using the base cement. As described above, the base cement and the cement composition were manufactured according to the conventional method. The clinker contains a small amount of free lime, alkali sulfate, etc. in addition to the described minerals. Further, the base cement E in Table 1 corresponds to ordinary Portland cement.

<Strength performance confirmation test>
Mortar specimens were prepared in accordance with JIS R 5201 “Cement physical test method”, and a compressive strength test was conducted according to the compressive strength test method described in the JIS standard at each test material age. The test material age was 3, 7, and 28 days. The compressive strength test results are shown in Table 3.

Here, when the material age 3 day strength is 35 to 40 (N / mm ² ), the material age 28 day strength ratio is 1.50 or more and the material age 3 day strength is 40 (N / mm ² ). / Mm ² ), the cement composition using the base cement having a strength ratio of 1.35 or more and a strength of 28 days of age to the strength of 3 days of age and the same strength as that of the base cement. Is judged to be good when it is high.

  Formula No. using base cement A In Nos. 1 to 7, blending Nos. Using fine blast furnace slag powder. In 2, the strength was small as compared with base cement A alone (formulation No. 1). Further, even if there is a certain amount of blast furnace slag fine powder added, the amount of fine limestone powder added is 1% by weight and the blending No. In 3, the effect of strength enhancement was small. In addition, the amount of addition of fine limestone powder was 15% by weight and the blending No. In No. 7, the strength was lower than that of base cement A alone (formulation No. 1).

In contrast to the above, the addition amount of limestone fine powder is 2 to 10% by weight within the range of the present invention. 4 to 6, the initial strength at the age of 3 days exceeded 35 (N / mm ² ) and the strength at the age of 28 days was higher than that of the base cement A alone (compound No. 1), and the age of 28 days The strength was sufficiently secured while satisfying the strength ratio.

  Formula No. using base cement B Also in 9-10, by adding limestone fine powder within the scope of the present invention, the initial strength development and strength enhancement are good, and the strength at the age of 28 days is secured while satisfying the strength ratio of the age of 28 days. What we can do is obtained.

  In addition, no. 12, no. The invention of No. 14 of the present invention had a satisfactory result satisfying the above judgment criteria as compared with the base cement C only (Compound No. 11) and the base cement D only (Compound No. 13).

  The composition No. using the base cement E in which the composition of the base cement deviates from the scope of the present invention. In the case of 15-17, the addition effect was not obtained despite the addition of limestone fine powder in the addition amount range of the present invention, and the initial strength expression at the age of 3 days was not sufficient.

Claims (5)

The C ₃ S amount determined by the Borg formula is 60 to 71%, the C ₂ S amount is 1% or more, the total amount of C ₃ S and C ₂ S is 70 to 80%, and the C ₃ S / C ₂ S amount A cement having a clinker mineral composition with a ratio of at least 5 and a free lime content of 1.0 to 4.0% by weight and containing a high amount of alite, and adding gypsum to a cement containing 2 parts of limestone. Cement composition characterized by adding 10 wt% to 10 wt%. _2. The cement composition according to claim 1, wherein the high lite clinker has a clinker mineral composition having a C ₂ S content of 1 to 15% determined by a Borg formula. In the alite-rich clinker, C 3 _{S /} C 2 _S content ratio cement composition according to claim 1 or 2, characterized in that it has a clinker mineral composition of 5 to 55. In the alite high content clinker, the C ₃ A amount determined by the Borg formula is 8 to 12%, the C ₄ AF amount is 7 to 10%, and the total amount of C ₃ A and C ₄ AF is 18 to 19%, _{C 3} a _/ C 4 cement compositions AF amount ratio described in claim 1, characterized in that it comprises a clinker mineral composition of 0.9 to 1.5.   It is a cement composition as described in any one of the said Claims 1-4, Comprising: This cement composition consists only of two raw materials of the said cement and the said limestone fine powder, The cement composition characterized by the above-mentioned.