JP7136296B2 - Cement composition and its manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a cement composition and a method for producing the same, and more particularly to a cement composition capable of exhibiting sufficient initial strength even at low temperatures and suppressing the occurrence of initial shrinkage cracks, and a method for producing the same.

Cracks that occur in the initial stage of concrete construction are called initial cracks, and there are several types of initial cracks.
For example, a subsidence crack is a crack that occurs due to the difference in the amount of subsidence caused by the bleeding of the concrete, which causes the surface of the concrete to subside. Subsidence cracks can be reduced by suppressing bleeding.

Among the initial cracks, shrinkage cracks caused by restricting shrinkage are particularly problematic.
The causes of shrinkage cracks include autogenous shrinkage of the concrete itself, drying shrinkage, and temperature shrinkage caused by the accumulation of heat of hydration inside the concrete structure and subsequent heat dissipation.
Such shrinkage cracks, for example, have a problem in that self-shrinkage increases as the strength is increased, making it difficult to suppress cracks.

Drying shrinkage is related to curing conditions such as humidity and wind, but it can be prevented by measures such as sprinkling a curing agent on the surface of the structure after construction.
Temperature shrinkage is shrinkage that occurs when the temperature inside the structure, which has risen due to the heat of hydration of cement, drops.
Autogenous shrinkage is a combination of chemical shrinkage, which is the phase volume change caused by the hydration reaction of cement, and capillary void change, and it always occurs when cement reacts and hardens. In particular, autogenous shrinkage of materials such as rapid-hardening materials that rapidly harden due to hydration of cement is large, and cracks are likely to occur.

Conventionally, as a cement having rapid hardening property, there is a rapid hardening cement such as jet cement. _Clinkers used in these cements include jet cement clinker, Erwin _- based clinker containing _C4A3SO3 as a main component, and alumina cement clinker containing CA as a main component.
There is also a method of obtaining amorphous C ₁₂ A ₇ by melting a clinker mainly composed of C ₁₂ A ₇ , which is a quick-hardening component, and then quenching it.

In particular, the conventional jet cement clinker is a clinker containing a calcium silicate phase as a main component and about 20 to 30% by mass of C ₁₁ A ₇ ·CaF ₂ as a fast-hardening component, such as C ₁₁ A ₇ CaF ₂ and C ₄ AF. It is formed by generating a melt phase such as. Therefore, if the content of C ₁₂ A ₇ , which is a quick-hardening component, is above the above range, the melt phase becomes too large and the clinker melts, making production in an actual facility extremely difficult.

Erwin-based clinker contains 70% by mass or more of Erwin (C ₄ A ₃ SO ₃ ), which has rapid hardening properties, and is therefore used as a clinker for fast-hardening cement. There is a problem that it is inferior to the rapid hardening property.
Furthermore, alumina cement clinker containing CA as a main component is inferior in rapid hardening property to clinker containing C ₁₂ A ₇ as a main component.

On the other hand, as a cement composition, it has hitherto been practiced to mix calcium aluminate and gypsum with Portland cement in order to impart rapid hardening properties.
However, cement compositions containing calcium aluminate and gypsum quick-hardening components are difficult to obtain sufficient quick-hardening properties at low temperatures.

Therefore, in Japanese Patent Application Laid-Open No. 2014-201462 (Patent Document 1), a chemical composition of 35 to 50% by mass of CaO, 35 to 50% by mass of Al ₂ O ₃ and 7 to 18% by mass of SiO ₂ has an amorphous degree of 70. % or more of ultra-rapid hardening clinker pulverized, Blaine specific surface area 4000 to 9000 cm ² /g, content of particles exceeding 30 μm is 5% by mass or less, and content of particles less than 1.0 μm is 5% by mass. A cement composition containing 25 to 200 parts by mass of gypsum with respect to 100 parts by mass of pulverized ultra-fast-hardening clinker of 100 parts by mass or less is disclosed in Japanese Patent Application Laid-Open No. 2014-196245 (Patent Document 2), cement, water, nitrous acid Contains calcium, polycarboxylic acid-based water reducing agent and melamine-based water reducing agent, and 2 to 5 parts by weight of calcium nitrite, 0.1 to 2.5 parts by weight of polycarboxylic acid-based water reducing agent, and melamine per 100 parts by weight of cement A cement composition is disclosed comprising from 0.1 to 2.5 parts by weight of a system water reducing agent.

However, in a low-temperature environment, it is difficult to promote the hydration reaction to sufficiently obtain the desired rapid hardening property, such as 3-hour strength, and to ensure sufficient fluidity of cement. This is because the conditions for generating the melt phase and the conditions for maximizing the hydration activity of the solid solution state of the quick-hardening component do not necessarily match. there were.
Furthermore, in a low-temperature environment, it has been difficult to effectively suppress the occurrence of initial shrinkage cracks due to autogenous shrinkage while promoting the hydration reaction.

JP 2014-201462 A JP 2014-196245 A

An object of the present invention is to provide a cement admixture that exhibits sufficient strength even in a low-temperature environment, exhibits excellent hydration activity and good rapid hardening performance, and can suppress the occurrence of initial shrinkage cracks due to autogenous shrinkage. An object of the present invention is to provide a composition and its production method, and a cement composition and its production method.

In particular, even at a low temperature such as 5°C, an admixture composition for cement, a method for producing the same, and a cement composition and a method for producing the same, which can suppress initial shrinkage cracking due to autogenous shrinkage of mortar-concrete structures. is to provide

The cement admixture composition comprises a cement quick _- setting additive containing a _C12A7 mineral phase, gypsum, an alkali sulfate compound, a calcium salt and lithium carbonate, and contains 36 _{C12A7 minerals} . ~55% by mass, 0.3 to 1.7% by mass of alkali sulfate compound (in terms of sodium sulfate), 0.01 to 1.3% by mass of lithium carbonate (in terms of lithium), and calcium salt (in terms of calcium hydroxide) 1 to 14% by mass, the mass ratio of gypsum (converted to anhydrite)/C ₁₂ A ₇ mineral phase content is 0.5 to 1.2, and the C ₁₂ A ₇ system measured by X-ray diffraction The cement admixture is characterized in that the mineral phase has a crystallite diameter of 150 to 500 nm and a lattice constant of 11.940 to 11.975 Å.

The admixture for cement is an admixture for cement, wherein the C ₁₂ A ₇ mineral phase is a mixed phase of C ₁₁ A ₇ CaX ₂ (X is a halogen) and C ₁₂ A ₇ . be.

The admixture composition for cement further comprises _C3A / _C12A7 mineral phase _≤7 (%), _TiO2 / _C12A7 mineral phase _≤1.4 (%) _, and _Fe2O3 /C ₁₂ A ₇ mineral phase ≤ 2.0 (%), an admixture for cement.

A cement composition according to claim ₁ , comprising a cement quick _- hardening additive containing a _C12A7 mineral phase, gypsum, an alkali sulfate compound, a calcium salt, lithium carbonate, and cement, wherein C12 Contains 8 to 32 % by mass of A7 minerals, _0.7 to 0.9 % by mass of alkali sulfate compounds (in terms of sodium sulfate), and has a content of lithium carbonate (in terms of lithium)/C _{12 A7} mineral phase content The ratio is 0.001 to 0.006 , the mass ratio of the content of calcium salt (calcium hydroxide)/C ₁₂ A ₇ mineral phase is 0.07 to 0.18 , gypsum (calculated as anhydrous gypsum)/C ₁₂ The mass ratio of the content of the A7 mineral phase is 0.71 to 1.31 , the crystallite diameter of the _C12A7 mineral phase measured by X _- ray diffraction is 150 to 500 nm, and the lattice constant is _11.940 . ˜11.975 Å.

The cement composition according to claim 2 is the cement composition, wherein the C ₁₂ A ₇ mineral phase is a mixed phase of C ₁₁ A ₇ CaX ₂ (X is a halogen) and C ₁₂ A ₇ . It is a cement composition.

In the method for producing the admixture for cement, the crystallite diameter of the C ₁₂ A ₇ mineral phase measured by X-ray diffraction is 150 to 500 nm and the lattice constant is 11.940 to 11.975 Å. Material, gypsum, alkali sulfate compound, lithium carbonate, and calcium salt, 36 to 55% by mass of C ₁₂ A ₇ mineral, and 0.3 to 1.7 mass of alkali sulfate compound (converted to sodium sulfate) %, 0.01 to 1.3% by mass of lithium carbonate (calculated as lithium), 1 to 14% by mass of calcium salt (calculated as calcium hydroxide), and gypsum (calculated as anhydrous gypsum) / C ₁₂ A ₇ mineral phase A method for producing an admixture composition for cement, characterized by mixing so that the mass ratio of the content of is 0.5 to 1.2.

In the method for producing the admixture composition for cement, the quick-hardening additive for cement is formed by pulverizing and mixing the raw materials, molding, firing at 1250 to 1400 ° C., and cooling at a cooling rate of 40 ° C./min or less. , the crystallite diameter of the C ₁₂ A ₇ -based mineral phase measured by X-ray diffraction is 150 to 500 nm, and the lattice constant of the C ₁₂ A ₇ -based mineral phase is 11.940 to 11.975 Å. , a method for producing an admixture composition for cement.

In the method for producing a cement composition according to claim 3, the C ₁₂ A ₇ mineral phase has a crystallite diameter of 150 to 500 nm and a lattice constant of 11.940 to 11.975 Å as measured by X-ray diffraction. Hard additive, gypsum, alkali sulfate compound, lithium carbonate, calcium salt, cement, 8 to 32 % by mass of C ₁₂ A ₇ mineral, alkali sulfate compound (converted to sodium sulfate) of 0.7 Contains ~0.9 % by mass, lithium carbonate (calculated as lithium)/C ₁₂ A ₇ mineral phase content mass ratio is 0.001 to 0.006 , calcium salt (calculated as calcium hydroxide)/C ₁₂ A ₇ The mass ratio of the content of the mineral phase is 0.07 to 0.18 , and the mass ratio of the content of gypsum (converted to anhydrite)/C ₁₂ A ₇ mineral phase is 0.71 to 1.31 . A method for producing a cement composition, characterized by blending.

The method for producing a cement composition according to claim 4 is characterized in that, in the method for producing a cement composition, the quick-hardening additive for cement is obtained by pulverizing a raw material, molding the pulverized raw material, and firing at 1250 to 1400 ° C. , by cooling the fired compact at a cooling rate of 40° C./min or less, the C ₁₂ A ₇ mineral phase having a crystallite diameter of 150 to 500 nm as measured by X _- ray diffraction _. Lattice constant of 11.940 ~ 11.975 Å, characterized in that a method for producing a cement composition.

The admixture for cement can be blended with any cement, whereby cement mortar or concrete using the admixture for cement exhibits sufficient strength in a low-temperature environment and sufficiently prevents initial shrinkage cracking. can be suppressed.

In addition, the cement composition of the present invention enables cement mortar and concrete using the cement composition to have sufficient strength in a low-temperature environment and to sufficiently suppress initial shrinkage cracking.

Furthermore, in addition to the above effects, it has a predetermined fluidity and can ensure a certain usable life, and it is possible to ensure excellent workability such as pumpability.

Moreover, the method for producing the admixture for cement and the method for producing the cement composition can effectively prepare the admixture for cement and the cement composition.

In particular, by blending a cement admixture composition containing a specific cement quick-hardening additive with any cement and water, or by blending a cement composition containing a specific cement quick-hardening additive with water. This makes it possible to easily obtain cement mortar/concrete on site.

In addition, a specific admixture composition for cement can be easily added in an arbitrary amount according to the desired initial strength, with arbitrary cement, accelerators, admixtures, etc. to be blended as necessary, and water while adjusting on site. By doing, or by adding a specific cement composition in any amount according to the desired initial strength, adjusting it on site with an accelerator, an admixture, etc., and water to be blended as necessary. In particular, it is possible to produce cement mortar concrete on-site, which has excellent initial strength development at low temperatures such as 5 ° C and can suppress initial shrinkage cracks. It becomes possible.

FIG. 4 is a diagram schematically showing a formwork for conducting a crack test;

The present invention will be described by the following forms, but is not limited thereto.
(Admixture composition for cement)
The cement admixture composition comprises a cement quick _- setting additive containing a _C12A7 mineral phase, gypsum, an alkali sulfate compound, a calcium salt and lithium carbonate, and contains 36 _{C12A7 minerals} . ~55% by mass, 0.3 to 1.7% by mass of alkali sulfate compound (in terms of sodium sulfate), 0.01 to 1.3% by mass of lithium carbonate (in terms of lithium), and calcium salt (in terms of calcium hydroxide) 1 to 14% by mass, the mass ratio of gypsum (converted to anhydrite)/C ₁₂ A ₇ mineral phase content is 0.5 to 1.2, and the C ₁₂ A ₇ system measured by X-ray diffraction The cement admixture comprises a mineral phase having a crystallite diameter of 150 to 500 nm and a lattice constant of 11.940 to 11.975 Å.

Preferably, in the cement admixture composition, the C ₁₂ A ₇ mineral phase is a mixed phase of C ₁₁ A ₇ CaX ₂ (halogen) and C ₁₂ A ₇ .

By having the above structure, the admixture composition for cement can exhibit excellent initial strength even at a low temperature of about 5 ° C., can suppress the occurrence of initial shrinkage cracks, and can also ensure fluidity. .

As described above, the C ₁₂ A ₇ mineral phase, which is the calcium aluminate phase, contained in the admixture composition for cement is contained in an amount of 36 to 55% by mass, preferably 40 to 52% by mass.
Such a C ₁₂ A ₇ mineral phase is derived from a quick-hardening additive for cement, which is added and blended when preparing the admixture composition for cement.
By containing the C ₁₂ A ₇ mineral phase, preferably in the above content, sufficient rapid hardening and excellent initial strength can be obtained even at low temperatures, and the desired effects of the present invention can be obtained. It becomes possible.

The admixture for cement does not contain erwin.
In addition, the content of the C ₁₂ A ₇ mineral phase, which is the calcium aluminate phase, in the obtained admixture composition for cement is measured by measuring the content of the C ₁₂ A ₇ mineral phase, which is the calcium aluminate phase. If possible, any known measuring method can be applied, for example, the following X-ray diffraction/Rietveld method can be used.

The C ₁₂ A ₇ mineral in the admixture composition for cement has a crystallite diameter of 150 to 500 nm, preferably 150 to 300 nm, of the C ₁₂ A ₇ mineral phase measured by X-ray diffraction.
When the crystallite size of the C ₁₂ A ₇ -based mineral phase is in such a range, it is possible to obtain excellent initial strength development even at low temperatures and good fluidity that can secure a pot life.
The crystallite size is, for example, a value measured by powder X-ray diffraction, and is a value measured using an X-ray diffraction/Rietveld method (device: D4 Endeavor manufactured by Bruker, analysis software: Topas).
Tube voltage: 45 kV Tube current: 40 mA

Furthermore, the C ₁₂ A ₇ mineral in the admixture composition for cement has a lattice constant of 11.940 to 11.975 Å for the C ₁₂ A ₇ mineral phase measured by X-ray diffraction.
By setting the lattice constant within such a range, it is possible to secure a predetermined fluidity and to have excellent rapid hardening properties, thereby achieving the effects of the present invention.
The lattice constant is, for example, a value measured by powder X-ray diffraction, and a value measured using an X-ray diffraction/Rietveld method (device: X'Pert MPD manufactured by PANalytical, analysis software: HighScorePlus). is.
Tube voltage: 45 kV Tube current: 40 mA

Examples of the gypsum (calcium sulfate) contained in the admixture composition for cement include anhydrous gypsum, hemihydrate gypsum, dihydrate gypsum, and mixtures thereof.
Such gypsum is contained in the admixture composition for cement such that the mass ratio of the gypsum/C ₁₂ A ₇ mineral phase content is 0.5 to 1.2, preferably 0.7 to 1.1. included in However, the gypsum content is an amount calculated as a total amount converted to CaSO ₄ (anhydrous gypsum).
In addition, the measurement of the gypsum content in the obtained admixture composition for cement can be applied by any known measurement method as long as the content of gypsum (converted to anhydrous gypsum) can be measured. It can be measured by the line diffraction/Rietveld method.

Examples of the alkali sulfate compounds contained in the admixture for cement include alkali metal sulfates such as mirabilite (sodium sulfate) and potassium sulfate.
Any known measuring method can be applied to the content of such an alkali sulfate compound as long as the content of the alkali sulfate compound can be measured. , the total amount converted to Na ₂ SO ₄ is desirably 0.3 to 1.7% by mass, preferably 0.5 to 1.5% by mass in the admixture composition for cement. .

Furthermore, as the calcium salt contained in the admixture for cement, for example, a salt that is not sparingly soluble in water such as slaked lime and quicklime can be used, but calcium hydroxide is preferable, and the calcium salt is converted into calcium hydroxide. 1 to 14% by mass, preferably 2 to 12% by mass.
In addition, the content of calcium salt (in terms of calcium hydroxide) in the obtained admixture composition for cement can be applied by any known measuring method as long as the content of calcium salt (in terms of calcium hydroxide) can be measured. can be measured, for example, by the X-ray diffraction/Rietveld method described above.

Furthermore, it is desirable that the admix composition for cement contains 0.01 to 1.3% by mass, preferably 0.01 to 1.0% by mass, of lithium carbonate (calculated as lithium).
Further, the content of lithium carbonate (in terms of lithium) in the obtained admixture composition for cement can be applied by any known measuring method as long as the content of lithium carbonate (in terms of lithium) can be measured. , can be measured using ICP emission spectroscopy.

By containing gypsum, an alkali sulfate compound, a calcium salt, and lithium carbonate together with the following quick-hardening additive for cement in the admixture for cement within the above range, the above effects of the present invention are effectively exhibited. becomes possible.

Preferably, the fluorine (F) contained in the admixture composition for cement is derived from the rapid-hardening additive for cement contained, and its content is the content of the fluorine/C ₁₂ A ₇ mineral phase is contained in a content such that the mass ratio of is 0.006 to 0.04, more preferably 0.01 to 0.035.
When the amount of F contained is in such a range, it is possible to have a more excellent initial strength development property, to ensure a sufficient pot life, and to further effectively exhibit the effects of the present invention. .

In addition, the admixture composition for cement preferably satisfies the following formula, so that even at a low temperature, for example, 5 ° C., it is possible to make it more excellent in 3-hour strength development, so it is desirable.
X=-0.93(F/Q)-Qa+11.98≧0
In the above formula, F is the fluorine content (% by mass) in the admixture for cement, Qa is the lattice constant (Å) of the C ₁₂ A ₇ mineral phase in the admixture for cement, and Q is the admixture for cement. It represents the content (mass %) of the C ₁₂ A ₇ mineral phase in the composition.

In addition, it is preferable that the admixture composition for cement does not substantially contain C ₃ A, and it is preferable that at most C ₃ A/C ₁₂ A ₇ minerals≦0.07. .
This is because when C ₃ A increases, the content of the C ₁₂ A ₇ -based mineral phase decreases, and sufficient initial strength may not be obtained. The C ₃ A in the admixture composition for cement is derived from the quick-hardening additive for cement contained.

Furthermore, it is desirable that the admixture composition for cement does not substantially contain _Ti , _Fe , _{C 2} S and C ₂ AS. It is desirable that Fe ₂ O ₃ /C ₁₂ A ₇ ≤ 2.0 (mass% ratio of content). TiO ₂ and Fe ₂ O ₃ in the admixture composition for cement are derived from the quick-hardening additives for cement contained therein. Rapid hardening at low temperatures, for example, early strength development at 5°C or less (3 hours after construction, etc.) is excellent.

By making the admixture composition for cement to have the above structure, the cement mortar/concrete obtained by adding it to any cement or the like available on the market has excellent initial strength development even at low temperatures, and initial shrinkage cracking does not occur. can be suppressed and liquidity can be secured.

(Cement composition)
The cement composition of the present invention comprises a cement quick-hardening additive containing a C ₁₂ A ₇ mineral phase, gypsum, an alkali sulfate compound, a calcium salt, lithium carbonate and cement, and C ₁₂ A ₇ containing 8 to 32 % by mass of minerals, 0.7 to 0.9 % by mass of alkali sulfate compounds (in terms of sodium sulfate), and a mass ratio of lithium carbonate (in terms of lithium)/C ₁₂ A ₇ -based mineral phase content 0.001 to 0.006 , mass ratio of content of calcium salt (calcium hydroxide)/C ₁₂ A ₇ mineral phase is 0.07 to 0.18 , gypsum (converted to anhydrous gypsum)/C ₁₂ A ₇ The mass ratio of the content of the C 12 A 7-based mineral phase is 0.71 to 1.31 , and the crystallite diameter of the C ₁₂ A ₇ -based mineral phase measured by X-ray diffraction is 150 to 500 nm and the lattice constant is 11.940 to 11. .975 Å, a cement composition.

Preferably, in the above cement composition, the C ₁₂ A ₇ mineral phase is a mixed phase of C ₁₁ A ₇ CaX ₂ (X is halogen) and C ₁₂ A ₇ .

The cement composition of the present invention has the above-described structure, so that it can exhibit excellent initial strength even at a low temperature of about 5° C., can suppress the occurrence of initial shrinkage cracks, and can ensure fluidity. Become.

As described above, the C ₁₂ A ₇ mineral phase, which is the calcium aluminate phase, contained in the cement composition of the present invention is 5 to 40% by mass, preferably 5 to 36% by mass, more than The content is preferably 10 to 30% by mass , particularly 8 to 32% by mass .
Such a C ₁₂ A ₇ -based mineral phase is derived from a quick-hardening additive for cement, which is added when preparing a cement composition.
By containing the C ₁₂ A ₇ mineral phase, preferably in the above content, sufficient rapid hardening and excellent initial strength can be obtained even at low temperatures, and the desired effects of the present invention can be obtained. It becomes possible.
The cement composition of the present invention does not contain erwin.
In addition, measurement of the content of the C ₁₂ A ₇ mineral phase, which is the calcium aluminate phase, in the obtained cement composition can be performed if the content of the C ₁₂ A ₇ mineral phase, which is the calcium aluminate phase, can be measured. Any known measurement method can be applied, and as described above, for example, the following X-ray diffraction/Rietveld method can be used for measurement.

The C ₁₂ A ₇ mineral in the cement composition of the present invention is derived from the cement quick-hardening additive contained in the cement composition, and the C ₁₂ A ₇ mineral phase measured by X-ray diffraction is The crystallite size is 150-500 nm, preferably 150-300 nm.
When the crystallite size of the C ₁₂ A ₇ -based mineral phase is in such a range, it is possible to obtain excellent initial strength development even at low temperatures and good fluidity that can secure a pot life.
The crystallite size is, for example, a value measured by powder X-ray diffraction, and is a value measured using an X-ray diffraction/Rietveld method (device: D4 Endeavor manufactured by Bruker, analysis software: Topas).
Tube voltage: 45 kV Tube current: 40 mA

Further, the C ₁₂ A ₇ mineral in the cement composition of the present invention has a lattice constant of 11.940 to 11.975 Å for the C ₁₂ A ₇ mineral phase measured by X-ray diffraction.
By setting the lattice constant within such a range, it is possible to secure a predetermined fluidity and to have excellent rapid hardening properties, thereby achieving the effects of the present invention.
The lattice constant is, for example, a value measured by powder X-ray diffraction, and a value measured using an X-ray diffraction/Rietveld method (device: X'Pert MPD manufactured by PANalytical, analysis software: HighScorePlus). is.
Tube voltage: 45 kV Tube current: 40 mA

Examples of the gypsum (calcium sulfate) contained in the cement composition of the present invention include anhydrous gypsum, hemihydrate gypsum, dihydrate gypsum, and mixtures thereof, similarly to the gypsum contained in the admixture composition for cement. .
Such gypsum has a mass ratio of gypsum/C ₁₂ A ₇ mineral phase content in the cement composition of 0.6 to 1.4, preferably 0.8 to 1.3 , particularly 0.71 to 1.0. 31 is included. However, the gypsum content is an amount calculated as a total amount converted to CaSO ₄ (anhydrous gypsum).
In addition, the measurement of the gypsum content in the obtained cement composition can be performed by any known measuring method as long as the content of gypsum (converted to anhydrous gypsum) can be measured. / can be measured by the Rietveld method.

Further, as the alkali sulfate compound contained in the cement composition of the present invention, similar to the alkali sulfate compound contained in the admixture composition for cement, for example, alkali metal sulfates such as mirabilite (sodium sulfate) and potassium sulfate are used. can be exemplified.
Any known measuring method can be applied to the content of such an alkali sulfate compound as long as the content of the alkali sulfate compound can be measured. _0.5 to 1.0% by mass, preferably _0.6 to 1.0% by mass , particularly 0.7 to 0.9 %, in the cement composition It is desirable to contain in mass % .

Furthermore, as the calcium salt contained in the cement composition of the present invention, a salt that is not sparingly soluble in water, such as slaked lime and quicklime, can be used in the same manner as the calcium salt contained in the admixture composition for cement. , preferably calcium hydroxide.
Such a calcium salt has a mass ratio of calcium salt/C ₁₂ A ₇ mineral phase content in the cement composition of 0.03 to 0.4, preferably 0.05 to 0.35 , particularly 0.07 to 0.07. It is included at a content of 0.18 . However, the calcium salt content is an amount calculated as a total amount in terms of calcium hydroxide.
Any known measuring method can be applied to the content of calcium salt (calculated as calcium hydroxide) in the obtained cement composition as long as the content of calcium salt (calculated as calcium hydroxide) can be measured. For example, it can be measured by the X-ray diffraction/Rietveld method described above.

In addition, the lithium carbonate contained in the cement composition of the present invention has a mass ratio of lithium carbonate (in terms of lithium)/content of C ₁₂ A ₇ mineral phase in the cement composition of 0.0005 to 0.03, preferably is contained in a content of 0.0005 to 0.025 , especially 0.001 to 0.006 .
The content of lithium carbonate (in terms of lithium) in the obtained cement composition can be measured by any known measuring method as long as the content of lithium carbonate (in terms of lithium) can be measured, for example, ICP emission spectroscopy. It can be measured using an analytical method.

By containing gypsum, an alkali sulfate compound, a calcium salt, and lithium carbonate in the cement composition within the above ranges, the above effects of the present invention can be effectively exhibited.

As the cement contained in the cement composition of the present invention, any commercially available cement can be applied. At least one selected from Portland cement, sulfate-resistant Portland cement, fly ash cement, blast furnace cement, silica cement, etc. can be exemplified.

Preferably, the fluorine (F) contained in the cement composition of the present invention is mainly derived from a cement quick-hardening additive, and its content is equal to the content of the fluorine/C ₁₂ A ₇ mineral phase is contained in a content such that the mass ratio of is 0.008 to 0.04, more preferably 0.015 to 0.035.
For example, the fluorine content in Portland cement, which is a raw material, is at most 0.05% by mass, compared to the fluorine content (0.5 to 3.0% by mass) contained in the cement quick-hardening additive. Since the amount is extremely low, most of the fluorine contained in the resulting cement composition is that of the cement quick-hardening additive.
When the amount of F contained is in such a range, it is possible to have a more excellent initial strength development property, to ensure a sufficient pot life, and to further effectively exhibit the effects of the present invention. .

In addition, the cement composition of the present invention preferably has the following formula: C ₁₂ A ₇ mineral phase lattice constant (Å) ≤ [(0.05-fluorine content (mass%))]/C ₁₂ It is particularly desirable to have a relationship that satisfies the content (% by mass) of the _A7 mineral phase + 11.98, and by having such a relationship, it has excellent initial strength development even at low temperatures, such as 5 ° C., It becomes possible to secure the pot life.

Furthermore, it is desirable that the cement composition of the present invention does not substantially contain Ti, and the content (% by mass) of the C ₁₂ A ₇ mineral phase ≥ 83 x (TiO ₂ content (% by mass) -0.3) is desirable.

If necessary, the cement composition of the present invention may contain, for example, a setting modifier (eg, various organic acids such as ligninsulfonic acids, oxycarboxylic acids, sugars, etc., or alkalis of organic acids), as long as it does not impair the above effects. metal salts and alkalinity metal salts) and water reducing agents (alkylallylsulfonic acid-based, naphthalenesulfonic acid-based, melamine sulfonic acid-based, polycarboxylic acid-based, AE water reducing agents, high performance water reducing agents, and high performance AE water reducing agents are also included. ) and other admixtures can be added.

By configuring the cement composition of the present invention as described above, the cement mortar-concrete composition and mortar-concrete using the cement composition of the present invention have excellent initial strength development even at low temperatures, and are free from initial shrinkage cracks. It is possible to suppress the occurrence and to ensure fluidity.

(Preparation of admixture composition for cement)
In the method of producing the admixture for cement, the cement quick-hardening additive, gypsum, an alkali sulfate compound, a calcium salt and lithium carbonate are mixed to prepare the above specific composition.
The production method is not particularly limited, but specifically, a specific quick-hardening additive for cement, gypsum, an alkali sulfate compound, a calcium salt and lithium carbonate, and 36 to 55 masses of a C ₁₂ A ₇ mineral. 0.3 to 1.7% by mass of alkali sulfate compounds (in terms of sodium sulfate), 0.01 to 1.3% by mass of lithium carbonate (in terms of lithium), and 1 to 14% by mass of calcium salts (in terms of calcium hydroxide). The mixed composition for cement is prepared by uniformly mixing so that the mass ratio of gypsum (converted to anhydrous gypsum)/C ₁₂ A ₇ mineral phase content is 0.5 to 1.2. .

Rapid-hardening additives for cement to be blended in the admixture composition for cement include calcium raw materials such as quicklime and limestone, aluminum raw materials such as aluminum hydroxide, alumina, bauxite and banded shale, fluorine raw materials such as fluorite, and if necessary Magnesium raw materials such as dolomite blended in the above are mixed and pulverized, or pulverized and mixed, the powder mixture is molded to obtain a molded body, and this is fired using a heating furnace such as an electric furnace. and cooled to prepare a quick-hardening additive for cement.
It should be noted that raw materials for Ti and Fe (for example, red iron oxide, etc.) contained in the resulting quick-hardening additive for cement are not actively blended. Ti and Fe contained in the cement quick-hardening additive to be blended may be included as impurities in the above-described blending raw materials, and are not intentionally included.

In addition, the cement quick-hardening additive blended in the production of the admixture composition for cement has a crystallite size of the C ₁₂ A ₇ mineral phase measured by X-ray diffraction of 150 to 500 nm, preferably 150 to 300 nm, It is a quick-hardening additive with a lattice constant of 11.940-11.975 Å.
By including a quick-hardening composition for cement having a C ₁₂ A ₇ mineral phase crystallite size and lattice constant in the above range in the cement admixture composition, hydration activity is promoted, while water in a low-temperature environment It is possible to reduce shrinkage due to reactivity, and obtain excellent initial strength development even at low temperatures and good fluidity that can ensure a usable life.
The crystallite size and lattice constant are values measured by the same measurement method as above.

Particularly preferably, the rapid-hardening additive for cement contains 70% by mass or more of the C ₁₂ A ₇ mineral phase, and substantially does not contain C ₃ A, Ti, and Fe, even if they are contained as impurities in the raw material. C ₃ A is 5.0% by mass or less, Ti is 1.0% by mass or less in terms of TiO ₂ , Fe is 1.5% by mass or less in terms of Fe ₂ O ₃ , and F is 0.5 to 3 A rapid hardening additive containing 0.0% by mass is desirable.
When C ₃ A exceeds 5.0% by mass, the content of the C ₁₂ A ₇ -based mineral phase decreases, so that sufficient rapid hardening cannot be obtained by addition on site, and initial strength decreases. There is

The rapid-hardening additive for cement containing such a C ₁₂ A ₇ -based mineral phase as a main component and containing a certain amount or less of C ₃ A further does not substantially contain C ₂ S or C ₂ AS. desirable.
“Substantially not included” means that it does not prevent the formation of these mineral phases from SiO ₂ , which is an impurity contained in the raw material, and does not mean that they are actively generated and included. The total content of C ₂ S and C ₂ AS is desirably at most 10% by mass and less.
This is because the content of the C ₁₂ A ₇ mineral phase, which is the calcium aluminate phase, is not reduced from the above range.

In addition, as described below, such a quick-hardening additive for cement is prepared by firing at 1250 to 1400° C., preferably at 1300 to 1360° C., so that C ₃ S is hardly generated and substantially not included in the target. In addition, since the content of Fe ₂ O ₃ in the cement quick-hardening additive is 1.5% by mass or less, C ₄ AF is hardly produced and is not substantially contained.

In addition, it is desirable that the quick-hardening additive for cement does not actively contain Ti, and does not substantially contain Ti.
"Substantially free" means that Ti does not interfere with the formation of impurities contained in the raw material, and does not mean that it is intentionally included.
For example, the Ti content is set to 1.0% by mass or less, preferably 0.5% by mass or less in terms of _TiO2 oxide.
That is, since the rapid-hardening additive for cement does not require the formation of a certain amount of melt phase, it is not necessary to positively include Ti, which is related to the formation of the melt phase.
By substantially not containing TiO ₂ and making the content at most equal to or less than the above content, rapid hardening at low temperature, for example, early strength development at 5° C. or less (3 hours after construction, etc.) will be excellent.
If Ti exceeds 1.0% by mass in terms of TiO ₂ , C ₃ A is generated in excess of 5.0% by mass, and the effects of the present invention cannot be obtained.

Moreover, it is desirable that the cement hardening additive does not actively contain Fe, and that it does not substantially contain Fe.
The term "substantially free" means that Fe does not interfere with the generation of impurities contained in the raw material, and does not intentionally contain Fe.
For example, the Fe content is set to 1.5% by mass or less, preferably 1.0% by mass or less in terms of Fe ₂ O ₃ oxide.
That is, since the rapid-hardening additive for cement does not require the formation of a certain amount of melt phase, it is not necessary to positively contain Fe, which is related to the formation of the melt phase.
If the content of Fe ₂ O ₃ exceeds the above content, the lattice constant of the C ₁₂ A ₇ -based mineral phase increases, and rapid hardening at low temperatures, such as initial strength development at 5 ° C. or less (3 hours after construction etc.) is inferior, and the smaller the number, the better.

Further, it is desirable that the above-mentioned quick-hardening additive for cement further contains 0.5 to 3.0% by mass, preferably 1.0 to 2.5% by mass of F.
By setting the content of F contained in the quick-hardening additive for cement within the above range, the C ₁₂ A ₇ -based mineral phase is stably generated, and the lattice constant of the C ₁₂ A ₇ -based mineral phase is within the appropriate range. The hydration activity can be enhanced, and the cement composition obtained by post-adding the cement quick-hardening additive to cement can more effectively exhibit the above effects of the present invention.

The quick-hardening additive for cement is obtained by pulverizing and mixing the raw materials to be mixed, molding the mixed powder, and heating the molded product at a temperature of, for example, 1250 to 1400°C, preferably 1300 to 1360°C. It can be produced by firing for 5 to 3 hours and then cooling at a cooling rate of 40° C./min or less, preferably 5 to 40° C./min. In addition, the raw materials are blended so as to achieve the above content ratio.
The quick-hardening additive for cement obtained in this way does not require the formation of a certain amount of melt phase, so that the hydration activity of the C ₁₂ A ₇ -based solid solution can be fully expressed. As such, Ti, Fe, etc. are substantially not contained, and the contents thereof are adjusted to be at most the above contents, and are post-added to cement to improve rapid hardening, especially at low temperatures such as 5 ° C. It becomes excellent in initial strength of.

_In this way, the molded body obtained by molding the raw material mixed powder is fired and cooled at a cooling rate of 40 ° C./min or less, preferably ₅ to 40 ° C./min. A quick-hardening additive for cement can be produced in which the crystallite size of the mineral phase is 150-500 nm, preferably 150-300 nm, and the lattice constant of the C ₁₂ A ₇ -based mineral phase is 11.940-11.975 Å. .

As the crystallite size differs, the hydration activity, that is, the degree of rapid hardening, differs. By adjusting the speed, it is possible to obtain a rapid-hardening additive for cement with a crystallite size in the range of 150 to 500 nm. Further, by making the preferable range of 150 to 300 nm, the rapid hardening property becomes more excellent.
When the crystallite diameter of the C ₁₂ A ₇ mineral phase is within such a range, the cement mortar and concrete obtained by adding the admixture composition for cement containing such a quick-hardening additive etc. to cement etc. will have an appropriate fluidity. It is possible to maintain the properties and obtain good initial strength development at low temperatures.

In particular, the rapid-hardening additive for cement is preferably pulverized to have a Blaine specific surface area of 4,500 cm ² /g or more, because if it is less than 4,500 cm ² /g, good rapid-hardening may not be obtained. is.
Also, Blaine's specific surface area is desirably 5,000 to 7,000 cm ² /g because too large Blaine specific surface area adversely affects fluidity, requires a long time for pulverization, lowers productivity, and increases cost.
Moreover, when pulverizing, a pulverizing aid (diethylene glycol, triethanolamine, etc.) may be added.

The admixture composition for cement is prepared by pulverizing the quick-hardening additive for cement, further adding gypsum, an alkali sulfate compound, a calcium salt and lithium carbonate, and adding 36 to 55% by mass of a C ₁₂ A ₇ mineral and sulfuric acid. 0.3 to 1.7% by mass of alkaline compound, 0.01 to 1.3% by mass of lithium carbonate, 1 to 14% by mass of calcium salt, and the mass ratio of gypsum/C ₁₂ A ₇ mineral phase content There is no particular limitation on the mixing method, and any mixing method can be used as long as the ingredients can be uniformly blended so that the value of is 0.5 to 1.2.

The above-mentioned gypsum content is an amount calculated as a total amount converted to CaSO ₄ (anhydrous gypsum), and the content of the alkali sulfate compound is calculated according to JCAS I-04, including the amount of Na and K. All of the measured amounts are the total amounts converted into Na ₂ SO ₄ equivalents, the lithium carbonate amounts are the lithium equivalent amounts, and the calcium salts are all calcium hydroxide equivalent total amounts.

Specifically, the admixture composition for cement can be prepared by adding and mixing a rapid-hardening additive for cement to a mixture obtained by previously mixing gypsum, an alkali sulfate compound, a calcium salt, and lithium carbonate. Even if the alkali sulfate compound, calcium salt, lithium carbonate and the cement hardening additive are mixed at the same time, any method can be used as long as they can be uniformly mixed.

(Preparation of cement composition)
The method for producing the cement composition of the present invention comprises mixing the cement quick-hardening additive, the gypsum, the alkali sulfate compound, the calcium salt, the lithium carbonate, and the cement to obtain the specific composition. Prepared by blending in
Its production method is not particularly limited, but specifically, for example, the above-mentioned specific quick-hardening additive for cement, gypsum, an alkali sulfate compound, lithium carbonate, a calcium salt, and cement are mixed with C ₁₂ A ₇ containing 8 to 32 % by mass of minerals, 0.7 to 0.9 % by mass of alkali sulfate compounds (in terms of sodium sulfate) , and a mass ratio of lithium carbonate (in terms of lithium)/C ₁₂ A ₇ -based mineral phase content 0.001 to 0.006 , mass ratio of content of calcium salt (calcium hydroxide)/C ₁₂ A ₇ mineral phase is 0.07 to 0.18 , gypsum (converted to anhydrous gypsum)/C ₁₂ A ₇ Any mixing method can be used to prepare the cement composition of the present invention as long as the mass ratio of the content of the mineral phase is 0.71 to 1.31 and can be uniformly mixed.
The specific rapid-hardening additive for cement that constitutes the cement composition of the present invention can be the same as the rapid-hardening additive for cement that constitutes the admixture composition for cement.

Furthermore, if necessary, the cement composition of the present invention may contain, for example, water reducing agents (alkylallylsulfonic acid-based, naphthalenesulfonic acid-based, melamine sulfonic acid-based, polycarboxylic acid-based, AE water reducing agents, high performance water reducing agents, , including a high-performance AE water reducing agent) can be blended with a liquid or powder admixture.

Specifically, the cement composition can be prepared by adding cement to a mixture obtained by previously blending gypsum, an alkali sulfate compound, a calcium salt, lithium carbonate, and a rapid-hardening additive for cement. Even if the compound, calcium salt, lithium carbonate, cement hardening additive and cement are mixed at the same time, any method can be used as long as they can be uniformly mixed.
The admixtures, etc., which are added as necessary, may be added at the same time as the cement, etc., if they can be uniformly mixed, or added in succession, or may be added when kneading with water when preparing the mortar, etc. However, the addition method is not particularly limited.

(Preparation of cement mortar and concrete)
Cement mortar-concrete can be prepared by blending the admixture composition for cement, any cement, and water, or by blending the cement composition of the present invention and water.

Furthermore, if necessary, for example, within a range that does not impair the above effects, accelerators (chlorides, sulfates, carbonates, nitrites, rhodanates, inorganic oxides, inorganic hydroxides, aluminate salt, etc.), water reducing agents (including alkylallylsulfonic acid-based, naphthalenesulfonic acid-based, melamine sulfonic acid-based, polycarboxylic acid-based, AE water reducing agents, high performance water reducing agents, and high performance AE water reducing agents), etc., liquid or powder Admixtures, fine aggregates (river sand, sea sand, mountain sand, crushed sand and mixtures thereof), coarse aggregates (river gravel, sea gravel, crushed stone and mixtures thereof) and the like can be added.

The method of mixing with water when preparing cement paste, mortar, concrete, etc. is not particularly limited.

Specifically, even if cement mortar/concrete is prepared by simultaneously blending a cement admixture composition, an arbitrary cement, and water, a mixture of a cement admixture composition and cement may be mixed with water. may be mixed to prepare cement mortar/concrete, or any method may be used as long as it can be uniformly mixed.

Moreover, even if the cement composition of the present invention and water are blended together to prepare cement mortar/concrete, or if the cement composition and water are blended to prepare cement mortar/concrete, the result will be uniform. Any method may be used as long as it can be mixed into

In addition, accelerators, admixtures, aggregates, etc., which are added as necessary, can be added simultaneously with cement, etc., if they can be mixed uniformly, or added sequentially, or mixed with water when preparing mortar, etc. It is not particularly limited whether it is added at the time of addition or by any addition method.

The cement mortar/concrete obtained in this way ensures workability such as fluidity even in low-temperature work, and even at low temperatures of about 5°C, it has excellent initial strength development and is resistant to initial shrinkage cracks. It is possible to suppress the occurrence, and it is also possible to secure the fluidity and secure the workability.

The present invention will be explained based on the following examples, comparative examples and test examples.
1) Preparation of quick-hardening additive for cement CaCO ₃ , SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , MgO, TiO ₂ , CaF ₂ so that the target chemical composition of the quick-hardening additive for cement is as shown in Table 1. Each reagent was blended, mixed and pulverized to prepare a raw material for each cement additive.

Here, SiO ₂ , Fe ₂ O ₃ , and TiO ₂ are used as calcium raw materials such as quicklime, slaked lime, and limestone, aluminum hydroxide, When aluminum raw materials such as alumina, bauxite and banded shale, fluorine raw materials such as fluorite, and optionally mixed magnesium raw materials such as dolomite are used, SiO ₂ , Fe ₂ O ₃ and TiO ₂ are included as impurities. It is used assuming such a case because there are cases where it is included (it is not intended to be included actively).

Each of the above cement quick-hardening additive raw materials was pressure-molded, each molded body was fired in an electric furnace at 1300 ° C. for 30 minutes, and then cooled at each cooling rate shown in Table 2. A quick-hardening additive for cement was obtained.

2) Measurement of content of TiO ₂ , Fe ₂ O ₃ , F component, etc. Each of the obtained quick-hardening additives for cement was measured according to JIS R 5204 using a fluorescent X-ray spectrometer (manufactured by Panalytical; Axios). and measured the content ratios of TiO _{2 ,} Fe ₂ O _{3 ,} F components, and the like.
These results are shown in Table 2.

3) Mineral analysis of quick-hardening additives for cement (C ₁₂ A ₇ series and C ₃ A)
Using the X-ray diffraction / Rietveld method (equipment: X'Pert MPD manufactured by PANalytical, analysis software: HighScorePlus), the resulting quick-hardening additives for cement were analyzed for C ₁₂ A ₇ series and C ₃ A minerals. The content and the crystal lattice constant of the C ₁₂ A ₇ mineral phase were measured. Tube voltage: 45 kV Tube current: 40 mA
Table 2 shows the results. Here, the lattice constant of the crystal of the C ₁₂ A ₇ system mineral phase was measured using the crystal structure of C ₁₁ A ₇ CaF ₂ .

In addition, the crystallite diameter of the crystal of the C ₁₂ A ₇ -based mineral phase is determined by the X-ray diffraction/Rietveld method using the C ₁₁ A ₇ CaF ₂ crystal structure (apparatus: D4 Endeavor manufactured by Bruker, analysis software: Topas). Measured by Tube voltage: 45 kV Tube current: 40 mA
Table 2 shows the results.

4) Preparation of admixture composition for cement (Examples 1 to 10, Comparative Examples 1 to 11)
Then, each of the above cement quick-hardening additives was pulverized to a Blaine specific surface area of about 5200±200 cm ² /g to obtain each cement quick-hardening additive powder.
The resulting cement additive powder, anhydrous gypsum (trade name: Nonclave, manufactured by Sumitomo Osaka Cement Co., Ltd.), Na ₂ SO ₄ (mirabilite, reagent), slaked lime (calcium hydroxide: reagent), and lithium carbonate (Reagent) was blended at the blending ratios shown in Tables 3 to 5 below to prepare each admixture composition for cement.
In addition, in Tables 3 to 5, the values of lithium carbonate are converted to lithium.

5) Measurement of the mineral content (C ₁₂ A ₇ system) in the admixture composition for cement and the lattice constant and crystallite diameter of the crystal of the C ₁₂ A ₇ system mineral phase The same method as the method described in 3) above , the content of the C ₁₂ A ₇ mineral phase (Q), the lattice constant of the crystal of the C ₁₂ A ₇ mineral phase, and the crystallite diameter in each admixture for cement were measured.
These results are shown in Tables 3-5.
The C ₁₂ A ₇ mineral phase in the admixture composition for cement is derived from the above-mentioned quick-hardening additive for cement.

6) Anhydrous gypsum/C ₁₂ A ₇ mineral phase (mass ratio) in cement admixture
From the C ₁₂ A ₇ mineral phase content in each admixture for cement measured in 5) above and the amount of anhydrite in each admixture for cement shown in Tables 3 to 5, each cement The anhydrite/C ₁₂ A ₇ mineral phase (mass ratio) in the admixture composition was calculated.
The results are shown in Tables 3-5.

7) C ₃ A/C ₁₂ A ₇ mineral phase (%), TiO ₂ /C ₁₂ A ₇ mineral phase (%), Fe ₂ O ₃ /C ₁₂ A ₇ mineral phase (%) in cement admixture composition
The amounts of C ₃ A, TiO ₂ , and Fe ₂ O ₃ in Table 2, the amounts of the cement quick-hardening additives in the cement admixtures in Tables 3 to 5, and the cement admixture compositions in Tables 3 to 5 From the content (% by mass) of the C ₁₂ A ₇ mineral phase in the material, C ₃ A / C ₁₂ A ₇ mineral phase (%), TiO ₂ /C ₁₂ A ₇ mineral phase (%), Fe ₂ O ₃ /C ₁₂ A ₇ mineral phase (%) was calculated. All of them have _C3A / _C12A7 mineral phase _{≦ 7} (%), _TiO2 / _C12A7 mineral phase≦1.4(%), and _Fe2O3 / _{C12A7 mineral} phase≦ ₂ 0 (%) was satisfied. The C ₁₂ A ₇ mineral phase, C ₃ A mineral phase, TiO _{2 and} Fe ₂ O ₃ in the admixture composition for cement are derived from the quick-hardening additive for cement.

8) Preparation of cement mortar High-early-strength Portland cement (PC: manufactured by Sumitomo Osaka Cement Co., Ltd.), the obtained mixed composition for cement (Examples 1 to 10, Comparative Examples 1 to 11), and an accelerator (water Lithium oxide and sodium carbonate), water, etc. were blended at the blending ratios shown in Table 6 to prepare each cement mortar.

9) Preparation of cement composition (Examples 11-23, Comparative Examples 12-22)
The quick-hardening additive for cement was pulverized to a Blaine specific surface area of about 5200±200 cm ² /g to obtain a powder of each quick-hardening additive for cement.
The resulting cement additive powder, anhydride gypsum (trade name: Nonclave, manufactured by Sumitomo Osaka Cement Co., Ltd.), Glauber's salt (Na ₂ SO ₄ , reagent), slaked lime (calcium hydroxide: reagent), lithium carbonate (reagent) and high-early-strength Portland cement (PC: manufactured by Sumitomo Osaka Cement Co., Ltd.) were blended to prepare cement compositions having the content ratios shown in Tables 7 to 10 below.
In addition, in Tables 7 to 10, the values of lithium carbonate are converted to lithium.

10) Analysis of mineral content in cement composition (C ₁₂ A ₇ system) and measurement of crystal lattice constant and crystallite diameter of the C ₁₂ A ₇ system mineral phase Method similar to the method described in 3) above , the content of the C ₁₂ A ₇ mineral phase (Q) in each cement composition, the lattice constant of the crystal of the C ₁₂ A ₇ mineral phase, and the crystallite diameter were measured.
These results are shown in Tables 7-10.
The C ₁₂ A ₇ -based mineral phase in the cement composition is derived from the above-mentioned quick-hardening additive for cement.

11) Measurement of gypsum content and calcium salt content in cement composition By the same method as the XRD/Rietveld method described in 3) above, the content of gypsum and calcium salts in each cement composition was measured. measured respectively. However, gypsum dihydrate and gypsum hemihydrate were converted into anhydrous gypsum to calculate the amount of CaSO ₄ (the amount of gypsum), and calcium salts were calculated by converting them into calcium hydroxide.
The results are shown in Tables 7-10.

12) Measurement of Content of Alkali Sulfate Compounds in Cement Composition was measured, and the total amount converted to Na ₂ SO ₄ as Na ₂ SO ₄ and K ₂ SO ₄ was taken as the alkali sulfate compound content.

13) Slaked lime (calcium hydroxide) / C ₁₂ A ₇ mineral phase (mass ratio of content), anhydrous gypsum / C ₁₂ A ₇ mineral phase (mass ratio of content), lithium carbonate / C ₁₂ A ₇ system Mineral phase (mass ratio of content)
From the values shown in Tables 7 to 10, the content of C ₁₂ A ₇ mineral phase, the content of slaked lime, the content of gypsum (converted to anhydrous gypsum), and the content of lithium carbonate (converted to lithium) in each cement composition, Slaked lime (calcium hydroxide)/C ₁₂ A ₇ mineral phase (mass ratio: %), gypsum (converted to anhydrous gypsum)/C ₁₂ A ₇ mineral phase (mass ratio), lithium carbonate (converted to lithium)/C ₁₂ A The ₇ -series mineral phase (mass ratio: %) was calculated.
The results are shown in Tables 7-10.

14) Preparation of mortar The cement compositions of Examples 1 to 20 and Comparative Examples 1 to 22, fine aggregate (silica sand), water, accelerator and admixture (Mighty 150: manufactured by Kao Corporation) were prepared according to Table 11 below. and uniformly kneaded to obtain each mortar.

15) Preparation of mortar The cement compositions of Examples 21 to 23 and the control example, fine aggregate (silica sand), water, accelerator and admixture (Mighty 150: manufactured by Kao Corporation) were blended as shown in Table 12 below. and uniformly kneaded to obtain each mortar. The cement composition as a control example is high-early-strength Portland cement (PC: manufactured by Sumitomo Osaka Cement Co., Ltd.) itself.

16) Strength measurement and flow value measurement For each mortar of Examples 1 to 23, Comparative Examples 1 to 22 and Control Example obtained above, the strength at 5 ° C. for 3 hours and the flow value at 5 ° C. were measured according to JIS R 5201.
The results are also shown in Tables 3-5 and Tables 7-10 above.

17) Cracking Test The mortars of Examples 1 to 23, Comparative Examples 1 to 22 and Control Example obtained above were subjected to a cracking test at 5°C as follows.
A mortar specimen was prepared according to JSCE-F506 (Manufacturing of cylindrical specimen for compressive strength test of mortar or cement paste). However, as shown in Fig. 1, the formwork used was a formwork for a cylindrical specimen (φ5 x 10 cm) with a hole drilled in the upper part and bolts inserted and fixed.
For evaluation of cracks, the length of cracks generated on the upper surface of the test piece (upper surface of the bolt) after 3 hours of kneading was measured in units of 5 mm (rounded up), and the state of 5 mm or less was accepted.
These results are shown in Tables 3-5 and Tables 7-10.

The admixture composition for cement and the cement composition of the present invention exhibit sufficient strength even in a low-temperature environment, exhibit excellent hydration activity and good rapid hardening performance, and suppress the occurrence of initial shrinkage cracks due to autogenous shrinkage. It can be applied to various construction works, civil engineering works, road works, and building structures.

Claims (4)

A quick-hardening additive for cement containing a C ₁₂ A ₇ mineral phase, gypsum, an alkali sulfate compound, a calcium salt, lithium carbonate and cement, containing 8 to 32 % by mass of a C ₁₂ A ₇ mineral , containing 0.7 to 0.9 % by mass of an alkali sulfate compound (in terms of sodium sulfate), and having a mass ratio of lithium carbonate (in terms of lithium)/C ₁₂ A ₇ mineral phase content of 0.001 to 0.006 , Mass ratio of calcium salt (in terms of calcium hydroxide)/content of C ₁₂ A ₇ mineral phase is 0.07 to 0.18 , gypsum (in terms of anhydrous gypsum)/mass of content of C ₁₂ A ₇ mineral phase The ratio is 0.71 to 1.31 , the crystallite diameter of the C ₁₂ A ₇ mineral phase measured by X-ray diffraction is 150 to 500 nm, and the lattice constant is 11.940 to 11.975 Å. a cement composition. 2. The cement composition according to claim ₁ , wherein said _C12A7 mineral phase is a _mixed phase of _{C11A7CaX2 (} X is _halogen ) and _C12A7 . A quick-hardening additive for cement having a C ₁₂ A ₇ -based mineral phase with a crystallite diameter of 150 to 500 nm and a lattice constant of 11.940 to 11.975 Å as measured by X-ray diffraction, gypsum, an alkali sulfate compound, Lithium carbonate, calcium salt, and cement, containing 8 to 32 % by mass of C ₁₂ A ₇ mineral, 0.7 to 0.9 % by mass of alkali sulfate compound (converted to sodium sulfate), lithium carbonate (converted to lithium) )/C ₁₂ A ₇ mineral phase content mass ratio of 0.001 to 0.006 , calcium salt (in terms of calcium hydroxide)/C ₁₂ A ₇ mineral phase content mass ratio of 0.07 Manufacture of a cement composition characterized by blending so that the mass ratio of gypsum (converted to anhydrous gypsum)/C ₁₂ A ₇ mineral phase content is 0.71 to 1.31 . Method. In the method for producing a cement composition according to claim 3, the quick-hardening additive for cement is obtained by pulverizing the raw material, molding the powdered raw material, firing at 1250 to 1400 ° C., and cooling the fired compact. By cooling at a rate of 40° C./min or less, the crystallite diameter of the C ₁₂ A ₇ mineral phase measured by X-ray diffraction is 150 to 500 nm, and the lattice constant of the C ₁₂ A ₇ mineral phase is 11.940 to 11. A method for producing a cement composition characterized in that it is produced as 0.975 Å.

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