JP7251505B2 - Fast-hardening cement additive, method for producing the same, and fast-hardening cement composition using the additive - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fast-hardening cement additive, a method for producing the same, and a fast-hardening cement composition using the additive. The present invention relates to a C12A7-based fast-hardening cement additive that has a predetermined fluidity and is excellent in workability, a method for producing the same, and a fast-hardening cement composition using the additive.

In recent years, in the construction of tunnels and underground spaces, a spraying construction method is widely used in which a cement mixture such as mortar or concrete is sprayed onto a wall surface or exposed surface to form a lining to prevent the wall surface or exposed surface from collapsing.
In this concrete spraying method, not only in summer but also in winter, concrete, etc. is prepared and the minimum usable time (handling time) required when handling it is secured, and spraying on walls and exposed surfaces After that, the concrete or the like must be cured immediately.
Also, in water stoppage work and emergency work, it is necessary to ensure the pot life of mortar and concrete, and to harden them immediately.

Recently, in the production of cement clinker, the reuse of industrial waste as a raw material for cement clinker has increased, and MgO is often contained in industrial waste.
When such MgO is contained in cement, it reacts with hydration activity to form Mg(OH) ₂ and has volume expandability.
Therefore, the hardened cement will collapse, and it is desired to suppress the volume expansibility due to such MgO.

As the calcium aluminate containing MgO, for example, Japanese Patent Application Laid-Open No. 6-321608 (Patent Document 1) discloses a cement composition containing magnesia spinel or calcium aluminate obtained by forming a solid solution of magnesia spinel and magnesia. things are disclosed.

In addition, in Japanese Patent Application Laid-Open No. 8-198649 (Patent Document 2), a CaO raw material, an Al ₂ O ₃ raw material, and a MgO raw material are blended and heat-treated, and the product contains magnesia spinels and is produced Calcium aluminates are disclosed in which the chemical components in the product are 15-30 wt% CaO, 60-75 wt% Al ₂ O ₃ , and 3-15 wt% MgO.

Further, Japanese Patent Application Laid-Open No. 2007-8785 (Patent Document 3) discloses a method for producing a cement clinker containing 2% by mass or more of MgO, wherein barium is added to the raw material of Portland cement and the cement clinker is fired. is disclosed, wherein the barium is represented by the following formula in terms of BaO;
BaO amount (% by mass) = A × [MgO amount in cement clinker - 2.0]
A≤3.8
where A is (the formula weight of BaO)/(the formula weight of MgO),
Disclosed is a method of manufacturing cement clinker, including under .

These conventional cement clinker and the like increase f-MgO (periclase) solid solution in C3S and C2S to reduce f-MgO.
However, there is a limit to the amount of solid solution of f-MgO in minerals, and depending on the content of MgO contained in industrial wastes, it is not possible to sufficiently suppress the disintegration of the resulting hardened cement.
In particular, in calcium aluminate-based cement compositions, the solid solution of MgO in minerals affects not only C3S and C2S but also the hydration activity of calcium aluminate-based compounds, and early strength development is improved. The problem was that it was undesirable from the point of view.

JP-A-6-321608 JP-A-8-198649 JP-A-2007-8785

An object of the present invention is to solve the above problems, suppress the volume expansion of contained MgO, and add it to any cement, so that the obtained cement composition has good fluidity in a low-temperature environment. To provide a C12A7-based fast-hardening cement additive having excellent hydration activity, which can be ensured and easily imparted with excellent fast-hardening performance, and a method for producing the same.
In particular, the cement composition obtained by adding it to any cement on site, etc., has excellent initial strength development at low temperatures of about 5 ° C, and secures fluidity such as easy pumping. An object of the present invention is to provide a C12A7-based fast-hardening cement additive and a method for producing the same.

Another object of the present invention is to provide a cement composition containing the fast-hardening cement additive of the present invention, which can ensure good fluidity in a low-temperature environment and has early strength development. To provide a fast-hardening cement composition excellent in

The present inventors have found that part of the contained MgO has a spinel structure, and f-MgO (periclase) and spinel (MgO.Al ₂ O ₃ ) are contained in a specific range, thereby achieving the above-mentioned The inventors have found that the problem can be solved and have completed the present invention.
That is, the fast-hardening cement additive of the present invention is an additive containing a C12A7-based mineral phase as a main mineral, and contains f-MgO and spinel (MgO.Al ₂ O ₃ ) in the manual additive. , the molar ratio of f-MgO to the total number of moles of f-MgO and spinel (MgO.Al ₂ O ₃ ) (MgO / (MgO + spinel) (molar ratio)) is 0.30 to 0.95 It is an additive for fast-hardening cement.
Preferably, in the fast-hardening cement additive of the present invention, the CaO/Al ₂ O ₃ (molar ratio) in the additive containing the C12A7-based mineral phase as the main mineral is 1.3 to 2.0, The fast-hardening cement additive is characterized in that the total amount of CaO and Al ₂ O ₃ is 80% by mass or more.

In the method for producing a fast-hardening cement additive of the present invention, the molar ratio of CaO and Al ₂ O ₃ contained in a cement clinker raw material containing MgO is set to 1.3 to 2.0, and CaO and Al ₂ O ₃ are mixed. and the total amount of 80% by mass or more is fired, and the molar ratio of f-MgO to the total number of moles of f-MgO and spinel (MgO.Al ₂ O ₃ ) (MgO / (MgO + spinel) (molar ratio )) is 0.30 to 0.95.

The fast-hardening cement composition of the present invention is a fast-hardening cement composition characterized by containing the fast-hardening cement additive of the present invention, Portland cement and gypsum.

The fast-hardening cement additive of the present invention is an additive whose main mineral is a C12A7-based mineral phase for mixing with any cement. It is possible to improve the hydration activity of the obtained mortar and the like, thereby rapidly obtaining the desired excellent rapid hardening performance, and ensuring excellent workability with predetermined fluidity.
Therefore, it is possible to effectively apply the fast-hardening cement additive at work sites, etc. in rapid-hardening applications. Therefore, it becomes easy to design to obtain the desired rapid hardening property, and in particular, the initial strength is excellent at a low temperature of 5°C or less.
In addition, mortar or the like using the fast-hardening cement additive of the present invention can have fluidity that improves pumpability, for example.

The method for producing the fast-hardening cement additive of the present invention does not substantially require the formation of a certain amount of melt phase, and the above-described fast-hardening cement additive of the present invention can be easily produced. It can be manufactured economically using existing equipment without the need for special equipment and facilities.
In addition, the fast-hardening cement composition of the present invention can improve the hydration activity of mortar and the like obtained even in a low-temperature environment by adding the fast-hardening cement additive of the present invention to Portland cement. It is possible to obtain a fast-hardening cement composition that can quickly obtain a desired fast-hardening performance and has a predetermined fluidity to ensure excellent workability.

1 is a graph showing the relationship between CaO/Al ₂ O ₃ (molar ratio) and f-MgO/(f-MgO+spinel) (molar ratio) contained in a cement additive containing a C12A7-based mineral phase as a main mineral. . 4 is a graph showing the relationship between f-MgO/(f-MgO+spinel) (molar ratio) contained in a cement additive containing a C12A7-based mineral phase as a main mineral and the 3-hour strength of mortar at 5.degree. Graph showing the relationship between f-MgO/(f-MgO + spinel) (molar ratio) contained in a cement additive containing a C12A7-based mineral phase as the main mineral and the mortar setting time (hour: minute) at 5 ° C. be.

The present invention will be described by the following forms, but is not limited thereto.
The fast-hardening cement additive of the present invention is an additive whose main mineral is a C12A7-based mineral phase, and contains f-MgO and spinel (MgO.Al ₂ O ₃ ) in the additive, and f- Additives for fast-hardening cement in which the molar ratio of f-MgO to the total number of moles of MgO and spinel (MgO.Al ₂ O ₃ ) (MgO/(MgO + spinel) (molar ratio)) is 0.30 to 0.95 It is wood.
Preferably, in the fast-hardening cement additive of the present invention, the CaO/Al ₂ O ₃ (molar ratio) in the additive containing the C12A7-based mineral phase as the main mineral is 1.3 to 2.0, The total amount of CaO and Al ₂ O ₃ is 80% by mass or more.

The fast-hardening cement additive of the present invention can be added to any commercially available Portland cement, and the hydration activity of the resulting mortar or the like can be expressed at an early stage. Also, the early strength development property can be excellent, and the fluidity can be secured.

The fast-hardening cement additive of the present invention is a material containing calcium aluminate phase CaO and Al ₂ O ₃ as main chemical components, and its mineral composition is mainly composed of C12A7 mineral phase. Yes, preferably 70% by mass, more preferably 80% by mass or more of the C12A7 mineral phase.
When the content of the C12A7-based mineral phase is less than 70% by mass, sufficient rapid hardening cannot be obtained, the initial strength is lowered, and the above effects of the present invention cannot be obtained.
Here, the C12A7-based mineral phase includes C12A7 and C11A7·CaX ₂ (where X is a halogen such as F, Cl, Br), or a mixed phase thereof.
Further, it is desirable that the fast-hardening cement additive of the present invention does not substantially contain erwin. "Substantially free" means that it does not interfere with the case where it is produced by SO ₃ , which is an impurity contained in the raw material, and does not mean that it is intentionally produced and contained.

The content of the C12A7-based mineral phase in such a suitable C12A7-based calcium aluminate material is measured using, for example, the X-ray diffraction/Rietveld method (device: X'Pert MPD manufactured by PANalytical, analysis software: HighScorePlus). can do.
Tube voltage: 45 kV Tube current: 40 mA

In addition, since the main mineral of the fast-hardening cement additive of the present invention is C12A7-based, it is desirable that C2S is not more than 7% by mass at the most, and that C2S is not substantially contained. When C2S exceeds 7% by mass, the content of the C12A7-based mineral phase decreases, so that sufficient rapid hardening cannot be obtained, and the initial strength may decrease.

It is desirable that the rapid-hardening additive for cement of the present invention, which contains such a C12A7-based mineral phase as a main component and contains substantially no C3A, also contains substantially no C2AS or C3A.
The term "substantially free" means that these mineral phases are not prevented from being produced by impurities contained in the raw material, and are not intentionally produced and contained. It is desirable that the total content of C2S and C3A is at most 3% by mass and less.
This is because the content of the C12A7 mineral phase, which is the calcium aluminate phase, is not reduced from the above range.
The quick-hardening additive for cement of the present invention is prepared by firing at 1250 to 1400° C., preferably 1300 to 1360° C., and C2AS, C3A, and C ₃ S are hardly generated, and substantially is not included. Moreover, since the amount of Fe ₂ O ₃ in the quick-hardening additive of the present invention is small, C4AF is hardly produced and is not substantially contained.
Here, "substantially not contained" means that these mineral phases are impurities contained in the raw material, which are Si, Ca-rich, or Al-rich raw materials. It means that it is not actively generated and contained.

Further, the fast-hardening cement additive of the present invention contains f-MgO and spinel (MgO.Al ₂ O ₃ ).
In the present invention, a part of f--MgO is made to be MgO--Al ₂ O ₃ spinel mineral which is a stable mineral.
By making f-MgO into a spinel (MgO.Al ₂ O ₃ ) structure, conventionally, f-MgO contained with cement hydration chemically changes to Mg(OH) ₂ to cause volume expansion and cement hardening. You can suppress what was causing your body to collapse.
Conventionally, f-MgO was contained in solid solution, but in the present invention, it contributes to the formation of spinel, and spinel is not contained in solid solution in the present invention.

Specifically, the relationship between the contents of f-MgO and spinel (MgO.Al ₂ O ₃ ) contained in the fast-hardening cement additive of the present invention is 0 as MgO / (MgO + spinel) (molar ratio). 0.30 to 0.95, preferably 0.50 to 0.85, more preferably 0.75 to 0.85.
As a result, the effects of the present invention can be obtained, and especially in a low-temperature environment, the setting time can be secured and the initial strength development is excellent.

Also preferably, the CaO/Al ₂ O ₃ (molar ratio) contained in the fast-hardening cement additive of the present invention is 1.3 to 2.0, more preferably 1.5 to 1.86, still more preferably is 1.70 to 1.86, and the total amount of CaO and Al ₂ O ₃ is 80% by mass or more, more preferably 85% by mass or more, and still more preferably 90% by mass or more.
By doing so, it is possible to effectively set the relationship between the contents of f-MgO and spinel (MgO.Al ₂ O ₃ ) contained in the above range, and to maximize the content of the C12A7 mineral phase. It is possible to increase the 3-hour strength expression more effectively.

The fast-hardening cement additive of the present invention includes calcium raw materials such as quicklime, slaked lime and limestone; aluminum raw materials such as aluminum hydroxide, alumina, bauxite and banded shale; magnesium raw materials such as dolomite; Fluorine raw materials such as the above are mixed and pulverized, or pulverized and mixed, and the powder mixture is molded to obtain a molded body, which is fired using a heating furnace such as an electric furnace, and cooled. A fast-hardening cement additive is prepared.
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. The Ti and Fe contained in the resulting quick-hardening additive for cement may be contained as impurities in the above raw materials, and should not be intentionally contained.

As a specific example, the quick-hardening additive for cement of the present invention has a CaO/Al ₂ O ₃ (molar ratio) in the raw material of 1.3 to 2.0, preferably 1.5 to 1.86, More preferably, the total amount of CaO and Al ₂ O ₃ in the raw material is 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass, so that it is 1.70 to 1.86. It can be produced by blending the raw materials as described above, pulverizing and mixing the raw materials, and firing the molded body obtained by molding the mixed powder. It can be produced by sufficiently firing at a temperature of 1300 to 1360° C. for, for example, 0.5 to 3 hours, and then cooling at a cooling rate of, for example, 40° C./min or less, preferably 5 to 30° C./min.
When preparing a suitable C12A7-based calcium aluminate material, the raw materials are blended so as to contain 70% by mass or more of the C12A7-based mineral.
The quick-hardening additive for cement of the present invention thus obtained can effectively exhibit the effects of the present invention. By adjusting it within the range, it becomes excellent in rapid hardening property, especially 3-hour strength at a low temperature of 5°C.

The fast-hardening cement additive of the present invention is pulverized into a fast-hardening cement additive powder, and the powder is blended with an arbitrary cement such as ordinary Portland cement together with a sulfate or the like to form a fast-hardening cement composition. The quick-hardening cement additive of the present invention that can be used is preferably pulverized to have a Blaine specific surface area of ⁴⁵⁰⁰ cm ² /g or more. This is because hardness may not be obtained.
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.

Any commercially available cement can be applied as the cement to which the fast-hardening cement additive of the present invention is blended. At least one selected from hot Portland cement, low heat Portland cement, sulfate-resistant Portland cement, fly ash cement, blast furnace cement, silica cement, and the like can be used.

Examples of sulfates include mirabilite (sodium sulfate), alkali metal sulfates such as potassium sulfate, alkaline earth metal sulfates such as magnesium sulfate and gypsum (calcium sulfate), and aluminum sulfate. Because of its properties, it is preferable to use gypsum, or to use gypsum and Glauber's salt in combination.
Examples of gypsum include anhydrous gypsum, hemihydrate gypsum, dihydrate gypsum, and mixtures thereof.
In addition, slaked lime can be cited as another material that can be blended as necessary.

A fast-hardening cement composition can be obtained by mixing the fast-hardening cement additive of the present invention, the cement, the sulfate, and the following additive blended as necessary.
The method of mixing the fast-hardening cement composition of the present invention with water, etc. is not particularly limited.
In addition, there are also setting modifiers (ligninsulfonic acid, oxycarboxylic acid, various organic acids such as sugars, or alkali metal salts and alkaline earth metal salts of organic acids) and water reducing agents (alkylallylsulfonic acid, naphthalenesulfonic acid, etc.). melamine sulfonic acid-based, polycarboxylic acid-based, AE water reducing agent, high performance water reducing agent, and high performance AE water reducing agent), 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.

In addition, the method of mixing with water and aggregate when preparing cement paste, mortar, concrete, etc. using the quick-hardening cement composition of the present invention is not particularly limited, and the composition is mixed in a predetermined ratio. Mixing may then be performed using a conventional mixing device.

As described above, the additive for fast-hardening cement of the present invention, when added to any cement, ensures workability due to fluidity even in low-temperature work, and has good 3-hour strength development. However, the desired rapid hardening property can be obtained on site, and the initial strength development design can be very easily manipulated.

The present invention will be explained based on the following examples, comparative examples and test examples.
(Examples 1 to 5, Comparative Examples 1 to 3)
1) Preparation of additive _for cement containing _{C12A7 -} based mineral phase as main mineral By mixing reagents O ₃ , Fe ₂ O ₃ , MgO, TiO ₂ and CaF ₂ and mixing and pulverizing the mixture, raw materials for cement additives containing C12A7 mineral phases as main minerals were prepared.
Here, Fe ₂ O ₃ and TiO ₂ are used in actual production of the fast-hardening cement additive of the present invention using calcium raw materials such as quicklime, slaked lime and limestone, aluminum hydroxide, alumina and bauxite. When using raw materials such as aluminum raw materials such as banded shale, magnesium raw materials such as dolomite, and fluorine raw materials such as fluorite that are blended as necessary, Fe ₂ O ₃ and TiO ₂ may be included as impurities as a result. Therefore, it is used assuming such a case.

Each of the above cement quick-hardening additive raw materials is pulverized and pressure-molded, each molded body is fired in an electric furnace at 1300 ° C. for 30 minutes, and then cooled at a cooling rate of 10 ° C./min to obtain C12A7. Additives for cement were prepared which consisted mainly of the sintered mineral phase.

2) Measurement of SiO ₂ , Al ₂ O ₃ , CaO, TiO _{2 ,} MgO, Fe ₂ O ₃ , F component content Analyzed according to JIS R 5204 using an analyzer (manufactured by PANalytical; Axios) to identify SiO ₂ , Al ₂ O ₃ , CaO, TiO _{2 ,} MgO, Fe ₂ O ₃ , F component, etc. was measured.
Also, the CaO/Al ₂ O ₃ (molar ratio) was calculated from the measured contents of CaO and Al ₂ O ₃ .
The results are shown in Table 2.

3) Mineral Analysis of Cement Additives Having C12A7-based Mineral Phases as Main Minerals The obtained cement additives having C12A7-based mineral phases as main minerals were subjected to X-ray diffraction/Rietveld method (apparatus: Panalytical X'Pert MPD manufactured by Co., Ltd., analysis software: HighScorePlus) was used to measure the contents of C12A7 series, C3A, C2S, f-MgO and spinel minerals.
Tube voltage: 45kV
Tube current: 40mA
Table 2 shows the results.

From the contents of f-MgO and spinel (MgO.Al ₂ O ₃ ) measured above, the molecular weight of f-MgO is 40.3, and the molecular weight of spinel (MgO.Al ₂ O ₃ ) is 142.3. The number of moles of each f-MgO and spinel (MgO.Al ₂ O ₃ ) used was calculated, and the values of MgO/(MgO+spinel) (molar ratio) are shown in Table 2.

FIG. 1 shows the relationship between CaO/Al ₂ O ₃ (molar ratio) and MgO/(MgO+spinel) (molar ratio) in each additive for cement prepared.

4) Preparation of Cement Composition Next, each cement additive containing the C12A7-based mineral phase as a main mineral was pulverized to a Blaine specific surface area of about 5200 cm ² /g to obtain each cement additive powder.
To high-early-strength cement (HC: manufactured by Sumitomo Osaka Cement Co., Ltd.), cement additive powder containing each C12A7-based mineral phase as the main mineral, anhydrous gypsum (manufactured by Sumitomo Osaka Cement Co., Ltd.) and Na ₂ SO ₄ (salt) : Reagent) were blended at the blending ratio shown in Table 3 below to prepare each cement composition.
The amount of high-early-strength cement was adjusted so that the amount of crystals of the C12A7-based mineral phase in the cement composition was the same (20% by mass).

5) Preparation of mortar Each cement composition above, fine aggregate (sand (silica sand)), setting modifier (reagent; citric acid, manufactured by Wako Pure Chemical Industries, Ltd.), water and admixture (Kao Corporation) (trade name: Mighty 150) was blended and uniformly kneaded as shown in Table 4 below so that the water/cement composition amount ratio was 0.34 and the sand/cement composition amount ratio was 1.2. and obtained each mortar.

6) Strength measurement and flow value measurement For each mortar obtained above, the strength (initial strength) at 5°C for 3 hours, the flow value and the setting time were measured according to JIS R 5201. However, as the ending time in the setting time, a conical needle with a diameter of 1 inch and a height of 2 inches was used, and the time when the penetration depth reached 1.5 mm was defined as the setting (ending) time.
The results are also shown in Table 2 above.

The relationship between MgO / (MgO + spinel) (molar ratio) in each cement additive and mortar strength is shown in FIG. ) and the setting time (hours:minutes) is shown in FIG.

From Table 2, FIGS. 2 and 3 above, Examples 1 to 5 show that the value of MgO/(MgO+spinel) (molar ratio) contained in the cement additive containing the C12A7-based mineral phase as the main mineral is 0.00. Examples 1 to 5, which range from 3 to 0.9, are compared to Comparative Examples 1 to 3, in which the value of MgO/(MgO + spinel) (molar ratio) is outside the range of 0.3 to 0.9. , By adding the above cement additives to cement, the mortar obtained has excellent early strength development at 5 ° C for 3 hours, and has a sufficient flow value, even at low temperatures. It can be seen that it has high rapid hardening property, excellent initial strength development, sufficient fluidity, and can secure a sufficient working time.

By adding the fast-hardening cement additive of the present invention to any cement, it becomes easy to design the desired fast-hardening property even at low temperatures. Spraying work on walls, etc., urgent repair work on roads, etc., and work that requires a rapid development of strength after the pot life has passed while securing a predetermined handling time as a soil improvement material. It can be usefully applied to the site.

Claims (4)

An additive containing a C12A7-based mineral phase as a main mineral, containing f-MgO and spinel (MgO.Al ₂ O ₃ ) in the additive, f-MgO and spinel (MgO.Al ₂ O ₃ ) A fast-hardening cement additive, characterized in that the molar ratio of f-MgO to the total number of moles of f-MgO (MgO/(MgO + spinel) (molar ratio)) is 0.30 to 0.95. 2. The fast-hardening cement additive according to claim 1, wherein the CaO/Al ₂ O ₃ (molar ratio) in the additive containing the C12A7-based mineral phase as a main mineral is 1.3 to 2.0, and CaO and An additive for fast-hardening cement, characterized by having a total amount of 80% by mass or more with Al ₂ O ₃ . The molar ratio of CaO and Al ₂ O ₃ contained in the cement clinker raw material containing MgO is set to 1.3 to 2.0, and the raw material is fired so that the total amount of CaO and Al ₂ O ₃ is 80% by mass or more. and the molar ratio of f-MgO to the total number of moles of f-MgO and spinel (MgO.Al ₂ O ₃ ) (MgO / (MgO + spinel) (molar ratio)) is 0.30 to 0.95. A method for producing an additive for fast-hardening cement, comprising producing the additive. A fast-hardening cement composition comprising the fast-hardening cement additive according to claim 1 or 2, Portland cement and gypsum.

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