JP6675033B1 - Cement admixture and hydraulic composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic composition in which storage stability does not easily deteriorate even when preliminarily blended with an alkaline admixture in a hydraulic composition, and a cured product having ultrafast curing and high strength can be obtained. A cement admixture capable of SOLUTION: (1) The aluminum sulfate is amorphous. (2) The solid obtained by solid-state 27Al-NMR of aluminum sulfate has a peak at a chemical shift of -0.20 to -20.00 ppm. The half width of the peak is 10.00 to 35.00 ppm, (3) the pH of the aluminum sulfate is 1 to 6, (4) 70% by mass or less of particles having a particle size of 100 μm or more, and It is a cement admixture containing aluminum sulfate that satisfies the condition that particles having a particle size of 10 μm or less are less than 30% by mass. [Selection diagram] None

Description

  The present invention relates to a cement admixture and a hydraulic composition used in the field of civil engineering, the field of construction, and the like.

  In recent years, hydraulic compositions have been required to have a wide variety of performances in the fields of civil engineering and construction. Above all, simplification of construction is a very important factor in considering worker safety. Here, the simplification of construction refers to, for example, comprehensive rationalization such as improvement of construction speed, materialization of materials, and improvement of handleability. In order to achieve the simplification of the construction, for example, the key is to improve the curing speed of the hydraulic composition, to perform premixing, etc. In fact, the so-called ultra-rapid hardening, which is quick to set and has high strength development. Various hydraulic compositions having the following have been proposed (for example, Patent Documents 1 to 3). Also, recently, with further improvement of simplification of construction and adaptation to new applications, the performance required of hydraulic compositions has been increasing more and more.

JP-A-3-12350 JP-A-1-230455 JP-A-11-139859

The hydraulic composition contains a cement admixture for the purpose of improving various properties such as curing speed. Conventionally, an alkaline admixture has been used as a cement admixture, but from the viewpoint of safety, it is desired to use an acidic admixture.
However, since a hydraulic substance such as cement is strongly alkaline, it is difficult to combine it with an acidic cement admixture, and there is a problem that a hydraulic composition having desired characteristics cannot be obtained. In fact, if a conventional acidic cement admixture suitable for improving the curing speed and premixing is added to the hydraulic composition, the storage stability of the hydraulic composition, the strength of the cured product, etc. will be reduced.

  The present invention has been made in order to solve the above problems, storage stability is not easily reduced even if it is previously blended with an alkaline admixture in a hydraulic composition, and has ultra-fast curing and An object of the present invention is to provide a cement admixture capable of providing a hydraulic composition capable of obtaining a cured product having high strength.

The present inventors have conducted intensive studies in order to solve the above-described problems, and as a result, despite the fact that a cement admixture containing aluminum sulfate having specific properties is acidic, the above-mentioned problems can be solved. And completed the present invention.
That is, the present invention is as follows.

[1] A cement admixture containing aluminum sulfate satisfying the following (1) to (4).
(1) The aluminum sulfate is amorphous.
(2) In the spectrum obtained by the solid ²⁷ Al-NMR of the aluminum sulfate, the spectrum has a peak at a chemical shift of −0.20 to −20.00 ppm, and a half width of the peak is 10.00 to 35.00 ppm. .
(3) The pH of the aluminum sulfate is 1 to 6.
(4) 70% by mass or less of particles having a particle size of 100 μm or more and less than 30% by mass of particles having a particle size of 10 μm or less.
[2] The cement admixture according to [1], wherein an alkaline admixture having a pH of 8 or more is mixed.
[3] The cement admixture according to [2], wherein the alkaline admixture contains an alkali metal carbonate.
[4] The cement admixture according to [2] or [3], wherein the alkaline admixture contains an alkaline earth metal hydroxide.
[5] A hydraulic composition comprising the cement admixture according to any one of [1] to [4] and a hydraulic substance.

  ADVANTAGE OF THE INVENTION According to this invention, even if it mix | blends with a hydraulic composition in advance with an alkaline admixture, the storage stability is hard to fall, and the hydraulic composition which has a super rapid-hardening property and can obtain the hardened body of high intensity | strength Can be provided.

Hereinafter, embodiments of the present invention will be described in detail. The parts and percentages used in this specification are based on mass unless otherwise specified.
[Cement admixture]
The cement admixture of the present invention contains aluminum sulfate satisfying the following (1) to (4).
(1) Aluminum sulfate is amorphous.
When aluminum sulfate is not amorphous, it is difficult to premix with a hydraulic substance having strong alkalinity such as cement, and even if premixing is possible, the storage stability of the hydraulic composition is reduced.
Here, whether or not aluminum sulfate is amorphous can be determined by X-ray diffraction analysis. Specifically, if the X-ray diffraction spectrum of aluminum sulfate is broad, it can be determined that the aluminum sulfate is amorphous. For aluminum sulfate, a clear peak can be confirmed in the range of 2θ = 20 to 30 °, but those without a peak were amorphous.

(2) In a spectrum obtained by solid-state ²⁷ Al-NMR of aluminum sulfate, the chemical shift has a peak at -0.20 to -20.00 ppm, and the half width of the peak is 10.00 to 35.00 ppm. .
When the peak chemical shift is larger than -0.20 ppm, it is difficult to premix with the hydraulic substance, and even if the premix can be formed, the storage stability of the hydraulic composition may decrease. On the other hand, when the peak chemical shift is smaller than -20.00 ppm, a synergistic effect with an alkaline admixture having a pH of 8 or more may not be obtained.
The chemical shift of the peak is preferably from -1.00 to -16.00 ppm, more preferably from -2 to -15 ppm.

  If the half width of the peak is outside the above range, the curing speed of the hydraulic composition may not be sufficiently obtained. The half width of the peak is preferably 10 to 35 ppm, more preferably 25 to 32 ppm.

Here, the solid ²⁷ Al-NMR measurement of aluminum sulfate can be performed using a commercially available measuring device, for example, a superconducting nuclear magnetic resonance device “ECX-400” manufactured by JEOL Ltd. under the following conditions. .
Observed nucleus: ²⁷ Al
Sample tube rotation speed: 10 KHz
Measurement temperature: room temperature Pulse width: 3.3 μsec (90 ° pulse)
Waiting time: 5 seconds External standard: Aluminum nitrate

  In order to obtain aluminum sulfate satisfying the requirements (1) and (2), for example, the heating temperature when heating a mixture composed of various raw materials may be adjusted.

(3) The pH of the aluminum sulfate is 1 to 6.
If the pH of the aluminum sulfate is out of the above range, the curing speed of the hydraulic composition will decrease. The pH is preferably from 2 to 5, and more preferably from 2 to 4. Further, in order to adjust the pH of aluminum sulfate to 1 to 6, the above heating temperature may be adjusted.
In the present specification, the pH can be measured by adding 10 g to 100 ml of water at 20 ± 2 ° C. using a pH meter and stirring at 500 rpm.

(4) In aluminum sulfate, 70% or less of particles having a particle size of 100 μm or more and less than 30% of particles having a particle size of 10 μm or less.
When the particles having a particle diameter of 100 μm or more exceed 70%, the curing speed of the hydraulic substance cannot be sufficiently obtained, and when the particles having a particle diameter of 10 μm or less are 30% or more, an alkaline admixture having a pH of 8 or more is exhibited. By coexisting with, storage deterioration becomes remarkable.
The particles having a particle diameter of 100 μm or more are preferably 50% or less, more preferably 30% or less. Further, particles having a particle size of 10 μm or less are preferably at least 40%, more preferably at least 50%. The particle size can be adjusted by, for example, a sieve.
It should be noted that, with the admixture using aluminum sulfate in the range of (4), a sufficient curing speed cannot be obtained from a low temperature to a high temperature, and the curing speed is expected to increase particularly at a high temperature. It is considered that the curing rate can be controlled by the coexistence of an alkaline substance having a pH of 8 or more, so that it can be used in a wide temperature range from a low temperature (10 ° C.) to a high temperature (30 ° C.). is there.

Aluminum sulfate satisfying the above-mentioned (1) to (4) is obtained by mixing raw materials such as an Al ₂ O ₃ source and an SO ₃ source using an Al ₂ O ₃ source and an SO ₃ source to form a mixture. A method of heat treatment, a method of directly reacting an Al ₂ O ₃ source with an SO ₃ source, a method of introducing an Al ₂ O ₃ source and an SO ₃ source into a solvent such as pure water, mixing them, and then performing a chemical reaction. Can be used. In these methods, by controlling the production conditions, aluminum sulfate satisfying the above (1) to (3) can be obtained.

The source of Al ₂ O ₃ is not particularly limited, but aluminum sulfate, aluminate, other inorganic aluminum compounds, organic aluminum compounds, and aluminum complexes can be used.

The aluminum sulfate is not particularly limited, and examples thereof include ammonium alum, aluminum hydroxysulfate, and aluminum sulfate.
The aluminate is not particularly limited, and examples thereof include lithium aluminate, sodium aluminate, potassium aluminate, calcium aluminate, and magnesium aluminate.
Examples of other inorganic aluminum compounds include, but are not limited to, bauxite, aluminum oxide, aluminum hydroxide, aluminum chloride, aluminum phosphate, aluminum nitrate, aluminum fluoride, polyaluminum chloride, aluminum carbonate hydroxide, synthetic hydrotal Site and aluminum metasilicate.

The organic aluminum compound is not particularly limited, but examples include aluminum stearate, aluminum oxalate, aluminum isopropoxide, and aluminum formate.
Although it does not specifically limit as an aluminum complex, For example, tris (8-hydroxyquinolinato) aluminum etc. are mentioned.
As the Al ₂ O ₃ source, a single species may be used, but two or more species may be used in combination. Also, among the various Al ₂ O ₃ sources described above, aluminum sulfate is preferred from the viewpoint of high solubility in water, low production cost and excellent coagulability, but aluminum hydroxide is also preferred.

The SO ₃ source is not particularly limited, but includes sulfur, sulfuric acid, sulfate, sulfite, sulfite, thiosulfate, thiosulfate, and organic sulfur compounds in addition to elemental sulfur such as sulfur and sulfur. Can be used.
Although it does not specifically limit as a sulfide, For example, magnesium sulfide, calcium sulfide, iron sulfide, phosphorus pentasulfide, etc. are mentioned.
Examples of the sulfate include, but are not particularly limited to, aniline sulfate, aluminum sulfate, ammonium sulfate, magnesium sulfate, manganese sulfate, barium sulfate, calcium sulfate, sodium alum, potassium alum, ammonium alum, and hydroxylamine sulfate.

Although it does not specifically limit as a sulfite, For example, ammonium hydrogen sulfite, calcium sulfite, etc. are mentioned.
Although it does not specifically limit as a thiosulfate, For example, ammonium thiosulfate, barium thiosulfate, etc. are mentioned.
The organic sulfur compound is not particularly limited, and examples thereof include resins such as sulfonic acid derivatives, salts of sulfonic acid derivatives, mercaptans, thiophenes, thiophene derivatives, polysulfone, polyethersulfone, and polyphenylene sulfide.
A single SO ₃ source can be used, but two or more SO ₃ sources may be used in combination. In addition, among the various SO ₃ sources described above, sulfuric acid or sulfate is preferable, and sulfuric acid or ammonium alum is most preferable, in view of high solubility in water, low production cost, and excellent coagulability.

  Here, the obtained aluminum sulfate is preferably pulverized by, for example, a known mill or the like, and sieved or the like to satisfy the requirement of (4).

  The cement admixture according to the present invention is preferably mixed with an alkaline admixture having a pH of 8 or more. Examples of the alkaline admixture include alkali metal aluminates, alkaline earth metal aluminates, alkaline earth metal carbonates, alkali metal hydroxides, alkali metal carbonates, alkaline earth metal hydroxides, and the like. In particular, it is preferable to contain an alkali metal carbonate and an alkaline earth metal hydroxide.

  Alkali metal carbonates can provide the cement with additional setting and rapid hardening properties. Examples of the alkali metal carbonate include sodium carbonate, sodium hydrogencarbonate, calcium carbonate, potassium carbonate, lithium carbonate, lithium hydrogencarbonate, beryllium carbonate, magnesium carbonate, and the like. Among them, sodium carbonate, sodium hydrogencarbonate, calcium carbonate, carbonate Potassium is preferred. The content of the alkali metal carbonate in the alkaline admixture is preferably at least 50%, more preferably at least 80%.

  Alkaline earth metal hydroxides can provide cement with further setting, rapid hardening and long term strength development. Examples of the alkaline earth metal hydroxide include calcium hydroxide, magnesium hydroxide, sodium hydroxide, potassium hydroxide, lithium hydroxide, beryllium hydroxide and the like. Among them, calcium hydroxide, magnesium hydroxide, hydroxide Sodium and potassium hydroxide are preferred. The content of the alkaline earth metal hydroxide in the alkaline admixture is preferably at least 50%, more preferably at least 80%.

  The alkaline admixture used in the cement admixture according to the present invention preferably contains a combination of an alkali metal carbonate and an alkaline earth metal hydroxide. By this combination, remarkable setting of the cement, rapid hardening, and imparting strength development can be achieved. The combination of the alkali metal carbonate and the alkaline earth metal hydroxide in the alkaline admixture is preferably at least 50%, more preferably at least 80%. In addition, the mass ratio of the alkali metal carbonate and the alkaline earth metal hydroxide in the combination is preferably 30/70 to 70/30 in terms of alkali metal carbonate / alkaline earth metal hydroxide. , 40/60 to 60/40.

  The cement admixture and the alkaline admixture according to the present invention are preferably mixed when added to a hydraulic substance.However, the cement admixture according to the present invention has excellent storage stability against alkali. It is preferred to mix 2-3 weeks before addition.

[Hydraulic composition]
The hydraulic composition according to the present invention preferably includes the cement admixture according to the present invention and a hydraulic substance, and further includes the above-described alkaline admixture.
The cement admixture according to the present invention can be used together with various hydraulic substances to prepare a hydraulic composition. In particular, the cement admixture according to the present invention can be used together with an alkaline hydraulic substance even though it is acidic. In general, when an acidic cement admixture is used together with an alkaline hydraulic substance to prepare a hydraulic composition, storage stability tends to decrease, but the cement admixture according to the present invention is an alkaline hydraulic substance. Even when used together with a hydraulic composition, storage stability does not easily decrease. Therefore, the hydraulic composition prepared using the cement admixture according to the present invention can be stored for a long period of time without performing any special storage method, construction method or handling method. Further, the hydraulic composition has an ultra-rapid curing property and can form a cured product having high strength. Therefore, by using this hydraulic composition, the construction can be simplified.

The hydraulic substance used in the hydraulic composition is not particularly limited, but includes, for example, various portland cements such as ordinary, fast, medium heat, low heat, and white; manufactured from municipal garbage incineration ash and sewage sludge incineration ash. Eco-cement; blast furnace slag, silica fume, limestone, fly ash, mixed cement containing gypsum and the like.
The pH of the hydraulic substance is not particularly limited, but is preferably more than 7, more preferably 8 or more, and further preferably 10 or more.

  The hydraulic composition may contain known additives that can be generally blended within a range that does not impair the effects of the present invention. Examples of the additive include, but are not particularly limited to, a rust inhibitor, a colorant, a polymer, a fiber, a fluidizing agent, a neutralization inhibitor, a waterproofing agent, a thickener, a waterproofing agent, a retarder, an early strengthener, and an accelerator , Water reducing agent, high performance (AE) water reducing agent, foaming agent, foaming agent, AE agent, drying shrinkage reducing agent, quick setting agent, swelling agent, cold resistance promoter, efflorescence inhibitor, alkali aggregate reaction inhibitor, Black unevenness reducing agents, environmental purification admixtures, and the like. These additives can be used alone or in combination of two or more.

  The amount of the cement admixture according to the present invention in the hydraulic composition is preferably 1 to 30% by mass, and more preferably 2 to 20% by mass. When the above-described alkaline admixture is contained, the alkaline admixture is preferably 2 to 30 parts, more preferably 2 to 20 parts, per 100 parts of the cement admixture according to the present invention.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless departing from the gist thereof.

<Preparation of aluminum sulfates A to E>
The following substances were used as raw materials.
Al ₂ O ₃ source: aluminum hydroxide, reagent, purity 99%
SO ₃ source: sulfuric acid, reagent, purity 99%
Solvent: pure water

Aluminum sulfates A to E were prepared by mixing an Al ₂ O ₃ source, an SO ₃ source, and a solvent at a molar ratio of 2: 3: 10, and heating and reacting the mixture to each temperature shown in Table 1. . Thereafter, the mixture was pulverized using a ball mill, and pulverized by a sieve so that 30% of the particles had a particle size of 100 μm or more and 20% of the particles had a particle size of 10 μm or less.
The aluminum sulfate prepared as described above was evaluated for X-ray diffraction, solid ²⁷ Al-NMR, and pH.

  X-ray diffraction was measured using Multi-Flex manufactured by Rigaku Corporation. The measurement was performed at a tube voltage-tube current of 40 KV-40 mA under the condition of 2θ = 5 ° to 60 °, 5 ° / min. The analysis software used was PDXL. In the evaluation of X-ray diffraction, if the X-ray diffraction spectrum was broad, it was determined to be amorphous, and the others were determined to be crystalline. Table 1 shows the results.

The solid ²⁷ Al-NMR was performed under the above conditions using a superconducting nuclear magnetic resonance apparatus (ECX-400) manufactured by JEOL Ltd., and the chemical shift and half width of the peak were measured. Table 1 shows the results.

  The pH was measured by using the pH meter (D-53S) manufactured by HORIBA for the aluminum sulfate adjusted by the above method, according to the method described above. Table 1 shows the results.

Next, 100 parts of the aluminum sulfate of the type shown in Table 1 prepared above were mixed with 20 parts of an alkaline admixture A shown in Table 2 to prepare a cement admixture. After storing at 60 ° C. and a humidity of 60%, a hydraulic composition comprising 100 parts of ordinary Portland cement (pH 14, industrial product) and 10 parts of a cement admixture was obtained.
Thereafter, 40 parts by mass of water (tap water) was further added to and mixed with this hydraulic composition, and a setting test was performed.
The setting test was performed in accordance with JIS R5201 “Physical test method for cement”. The setting test measured the starting time of setting.
Table 2 shows the results of each of the above evaluations.

Alkaline admixture a: sodium carbonate, reagent, pH 11
Alkaline admixture A: sodium bicarbonate, reagent, pH 8.3
Alkaline admixture c: calcium carbonate, reagent, pH 10
Alkaline admixture d: potassium carbonate, reagent, pH 12
Alkaline admixture e: calcium hydroxide, reagent, pH 10
Alkaline admixture: magnesium hydroxide, reagent, pH 10.5
Alkaline admixture: sodium hydroxide, reagent, pH 14
Alkaline admixture: potassium hydroxide, reagent, pH 13

  As shown in Table 2, the use of aluminum sulfate A changed the setting time with storage days. This is thought to be due to storage deterioration of the compound and the admixture. However, in the case of aluminum sulfates B to E, no storage deterioration was observed, and it was confirmed that aluminum sulfates B to D were particularly likely to provide a promoting effect.

Next, 100 parts of aluminum sulfate C or the proportion of particles having a particle size of 100 μm or more with aluminum sulfate C adjusted to be as shown in Table 3 were mixed with 20 parts of an alkaline admixture of the type shown in Table 3 and mixed. To prepare a cement admixture, stored at a temperature of 20 ° C. and a humidity of 60% as shown in Table 3, and then a hydraulic composition comprising 100 parts of ordinary Portland cement (pH 14, industrial product) and 10 parts of the cement admixture I got something. Thereafter, 40 parts by mass of water (tap water) was further blended and mixed with the hydraulic composition, and a setting test and a measurement of compressive strength were performed.
The setting test and the measurement of the compressive strength were performed according to JIS R5201 “Physical test method for cement”. The setting test measured the starting time of setting.
Table 3 shows the results of the above evaluations.

  As shown in Table 3, it was confirmed that when the proportion of aluminum sulfate particles having a particle diameter of 100 μm or more was 71% or 99%, the onset time of coagulation was delayed. When the proportion of aluminum sulfate particles having a particle diameter of 100 μm or more was 70% or less, the coagulability and strength were all good.

Next, 100 parts of aluminum sulfate C, or the proportion of particles having a particle diameter of 10 μm or less in aluminum sulfate C adjusted to be as shown in Table 4, and 20 parts of an alkaline admixture of the type shown in Table 4 were blended. A cement admixture was prepared by mixing and stored at the days, temperature 20 ° C., and humidity 60% shown in Table 4, and then hydraulically composed of 100 parts of ordinary Portland cement (pH 14, industrial product) and 10 parts of the cement admixture. A composition was obtained. Thereafter, 40 parts by mass of water (tap water) was further blended and mixed with the hydraulic composition, and a setting test and a measurement of compressive strength were performed.
The setting test and the measurement of the compressive strength were performed according to JIS R5201 “Physical test method for cement”. The setting test measured the starting time of setting.
Table 4 shows the results of the above evaluations.

  As shown in Table 4, storage degradation was confirmed when the proportion of particles having a particle size of 10 μm or less in aluminum sulfate C was 30% or more, and storage degradation was not particularly confirmed when the proportion was less than 30%. .

Next, 100 parts of aluminum sulfate of the type shown in Table 5 and 20 parts of various alkaline admixtures were blended and mixed to prepare a cement admixture. After storage, a hydraulic composition comprising 100 parts of ordinary Portland cement (pH 14, industrial product) and 10 parts of a cement admixture was obtained.
Thereafter, 40 parts by mass of water (tap water) was further added to and mixed with this hydraulic composition, and a strength test was performed. The strength test was performed in accordance with JIS R5201 “Physical test method for cement”. In the strength test, the strength was measured 28 days after water was added to the hydraulic composition.
Table 5 shows the results of each of the above evaluations.

  As shown in Table 5, although the 28-day-old strength changes with the number of storage days for each type of admixture, the strength of the combination of aluminum sulfate A and various alkaline admixtures decreased with the number of storage days. On the other hand, it was confirmed that the combination of aluminum sulfate C and various kinds of alkaline admixtures had good storage stability, and the strength did not decrease regardless of the number of storage days.

Next, 100 parts of aluminum sulfate of the type shown in Table 6 prepared above and 20 parts of various alkaline admixtures were blended and mixed to prepare a cement admixture. After storing at 60% humidity, a hydraulic composition comprising 100 parts of ordinary Portland cement (pH 14, industrial product) and 10 parts of a cement admixture was obtained. When the alkaline admixtures A and O were mixed (Experiment Nos. 30 and 31), their ratio (A: O) was 50:50.
Thereafter, 40 parts by mass of water (tap water) was further added to and mixed with this hydraulic composition, and a strength test was performed. The strength test was performed in accordance with JIS R5201 “Physical test method for cement”. In the strength test, the strength was measured 28 days after water was added to the hydraulic composition.
Table 6 shows the results of the above evaluations.

  As shown in Table 6, although the strength of aluminum sulfate A was reduced due to the number of storage days even when the admixture type was A or A, the strength was further improved when aluminum sulfate C was combined with A or O. It was confirmed.

Next, in Experiment Nos. 3, No. For 6 to 17, 100 parts of ordinary Portland cement (pH 14, industrial product), except that the temperature (test temperature) for obtaining the hydraulic composition was changed from 20 ° C. to 10 ° C. or 30 ° C., a cement admixture A hydraulic composition consisting of 10 parts was obtained.
Thereafter, 40 parts by mass of water (tap water) was further added to and mixed with this hydraulic composition, and a setting test was performed.
The setting test was performed in accordance with JIS R5201 “Physical test method for cement”. The setting test measured the starting time of setting.
Table 7 shows the results of the above evaluations.

  As shown in Table 7, the admixture using aluminum sulfate within the scope of the present invention can be used in a wide temperature range from a low temperature (10 ° C.) to a high temperature (30 ° C.). It is possible.

  As can be seen from the above results, according to the present invention, the storage stability is not easily reduced even if the hydraulic composition is previously blended with the hydraulic composition, and the hydraulic composition has ultra-fast curing and high strength of the cured product. Provideable cement admixtures can be provided. Further, according to the present invention, it is possible to provide a hydraulic composition having storage stability that is not easily reduced, has ultra-rapid curing properties, and has high strength of a cured product.

  INDUSTRIAL APPLICATION This invention can be suitably applied especially to the cement admixture used in the civil engineering field, the construction field, etc.

Claims (4)

Following (1) to look containing aluminum sulfate satisfying (4), cement admixture alkaline admixture are mixed pH of 8 or more.
(1) The aluminum sulfate is amorphous.
(2) In the spectrum obtained by the solid ²⁷ Al-NMR of the aluminum sulfate, the spectrum has a peak at a chemical shift of −0.20 to −20.00 ppm, and a half width of the peak is 10.00 to 35.00 ppm. .
(3) The pH of the aluminum sulfate is 1 to 6.
(4) 70% by mass or less of particles having a particle size of 100 μm or more and less than 30% by mass of particles having a particle size of 10 μm or less. The cement admixture according to claim 1, wherein the alkaline admixture comprises an alkali metal carbonate. The cement admixture according to claim 1 or 2 , wherein the alkaline admixture comprises an alkaline earth metal hydroxide. A hydraulic composition comprising the cement admixture according to any one of claims 1 to 3 and a hydraulic substance.