JP3199456B2 - Cement admixture and cement composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002] The concrete in the present invention is a general term for cement paste, mortar and concrete.

[0003]

2. Description of the Related Art Recently, early deterioration of concrete structures which have been considered to be durable semipermanently has become a social problem. The causes of concrete deterioration are known to be salt damage, carbonation, alkali-aggregate reaction, and the like.

[0004] Conventionally, the use of these deterrent materials against the deterioration of concrete has been proposed (JP-A-53-3423, JP-A-1-103970, JP-A-3-224635, and Concrete Engineering). Next Paper 13-1 1991 745-75
0). However, although these deterrent materials can be individually countermeasures for salt damage, carbonation, and alkali-aggregate reaction of concrete, they do not suppress composite deterioration, but cement that suppresses composite deterioration is strongly required. ing.

[0005] The present inventor has proposed that salt damage of concrete,
As a result of various studies to solve the problems of the conventional technology, such as preventing carbonation and alkali-aggregate reaction, and at the same time minimizing the occurrence of these deteriorations, a specific cement admixture was obtained. By using
The present invention has been completed based on knowledge that can solve the above problems.

[0006]

That is, the present invention relates to Mg, Z
n, Cu, and a cement admixture comprising one or more selected from hydroxides of divalent metals of Fe and hydroxyapatite, comprising cement and the cement admixture It is a cement composition.

Hereinafter, the present invention will be described in detail.

[0008] The hydroxide according to the present invention is Mg, Zn, Cu,
And one or more selected from hydroxides of divalent metals of Fe and Fe. Specifically, Mg (OH) ₂ , Zn (OH) ₂ , Cu
(OH) ₂ , and represented by Fe (OH) ₂ , magnesium hydroxide,
Zinc hydroxide, copper hydroxide, and iron hydroxide, of which
It is preferable to use Mg (OH) ₂ from the viewpoints of economy and suppression effect.

In the production of a hydroxide or the use of a substance containing a large amount of the hydroxide, the presence of impurities of other components is not particularly limited. Quality, any of which can be used, but the use of amorphous is preferred.

The particle size of the hydroxide is preferably from 0.1 to 100 μm. If it is less than 0.1 μm, the amount of kneading water increases, which may adversely affect physical properties such as strength, and if it exceeds 100 μm, the surface area of the hydroxide may decrease, and the effect of suppressing the effect may become insufficient.

The amount of the hydroxide used is preferably 0.5 to 30 parts by weight, more preferably 1 to 10 parts by weight, based on 100 parts by weight of cement. If the amount is less than 0.5 part by weight, the effect of suppressing the effect is not sufficient. If the amount exceeds 30 parts by weight, abnormal expansion may occur.

As the cement, various portland cements such as ordinary / early high strength / ultra-early high strength / medium heat / sulfate resistance, various kinds of cement obtained by mixing blast furnace slag, fly ash or silica with these portland cements, and , Alumina cement and the like.

The hydroxyapatite according to the present invention is a kind of calcium phosphate, and is _{composed of} Ca _{(0.5m + 1.5n)} (O
It is a complex compound represented as _{H) m (PO 4) n} . Generally, well-known hydroxyapatite has m = 2, n
Is represented by Ca ₁₀ (OH) ₂ (PO ₄ ) ₆ of ₆ .

Here, when hydroxyapatite is produced or when a substance containing a large amount thereof is used, the presence of impurities of other components is not particularly limited. Although any of amorphous and amorphous can be used, the use of crystalline is preferred.

Hydroxyapatite can be used in any form of powder or slurry.

When hydroxyapatite is used as a powder, the particle size is preferably from 0.1 to 100 μm. If it is less than 0.1 μm, the amount of kneading water increases, which may adversely affect physical properties such as strength. If it exceeds 100 μm, the surface area of hydroxyapatite decreases, and the inhibitory effect may become insufficient. When hydroxyapatite is used in the form of a slurry, the average particle size is 0.
1-0.5μ is preferred.

The solid content of the slurry is preferably 0.5 to 40% by weight, more preferably 10 to 20% by weight. If the amount is less than 0.5% by weight, the water / cement ratio becomes insufficient due to the balance with the water / cement ratio, and the suppression effect may not be sufficiently obtained. If it exceeds 40% by weight, the dispersion in the kneading water may be poor.

The amount of hydroxyapatite used is preferably 0.1 to 30 parts by weight based on 100 parts by weight of cement.
-15 parts by weight is more preferable, and 2-5 parts by weight is most preferable. If the amount is less than 0.1 part by weight, the effect of suppressing the effect is not sufficient, and if the amount exceeds 30 parts by weight, the amount of kneading water increases, which may cause a problem in long-term durability.

The cement admixture of the present invention contains a hydroxide and hydroxyapatite.

In the present invention, the use amount of the cement admixture is strongly affected by the materials used and the compatibility of each, and is not particularly limited. The total amount of apatite is preferably 0.5 to 35 parts by weight, more preferably 1 to 10 parts by weight. The ratio of hydroxide to hydroxyapatite is not particularly limited.

Further, in the present invention, a cement rapid hardening material or a cement expanding material, an aggregate such as silica sand, natural sand and gravel, and a fibrous substance such as glass fiber, carbon fiber and steel fiber are used. In addition, high-molecular polymer emulsions and latex, AE agents, water reducing agents, AE water reducing agents, superplasticizers, rust inhibitors, non-separable admixtures such as methylcellulose in water, thickeners, water retention agents, and sodium silicate waterproofing. One or more of an agent, a foaming agent, a foaming agent, an antifreezing agent, and an alkaline substance such as calcium hydroxide can be used in combination as long as the object of the present invention is not substantially inhibited.

The hydroxide according to the present invention reacts with chloride ions and carbonate ions in the concrete to form insoluble basic chlorides and basic carbonates, and to form a denser structure, thereby reducing the carbonate. Since the penetration of gas and chlorine ions is remarkably prevented, salt damage and carbonation of concrete can be suppressed.

That is, the reaction of the hydroxide to take in the chloride ion and the carbonate ion is considered as follows. Carbonation reaction _{2Mg (OH) 2 + CO 2} + 2H 2 O → MgCO 3 · Mg (OH) 2 · 3H 2 O 4Zn (OH) 2 + CO 2 → ZnCO 3 · 3Zn (OH) 2 · H 2 O 2Cu (OH) ₂ + CO ₂ → CuCO ₃・ Cu (OH) ₂ + H ₂ O 2Fe (OH) ₂ + CO ₂ → FeCO ₃・ Fe (OH) ₂ + H ₂ O Chlorination reaction 2Mg (OH) ₂ + 2NaCl → MgCl ₂・ Mg (OH _{) 2 + 2NaOH 2Zn (OH)} 2 + 2NaCl → ZnCl 2 · Zn (OH) 2 + 2NaOH 2Cu (OH) 2 + 2NaCl → CuCl 2 · Cu (OH) 2 + 2NaOH 4Fe (OH) 2 + 2NaCl → FeCl 2 · 3Fe (OH) 2 + 2NaOH

The hydroxyapatite according to the present invention comprises:
Chlorine ion, carbonate ion and alkali metal ion in concrete can be easily collected by ion exchange reaction.
And an alkali-aggregate reaction can be suppressed. That is, chloride ions and carbonate ions in concrete are ion-exchanged with hydroxide ions in hydroxyapatite, and alkali metal ions are ion-exchanged with calcium ions in hydroxyapatite. Moreover, since two or more of these ion exchange reactions can occur simultaneously, hydroxyapatite suppresses deterioration of concrete from multiple aspects.

[0025]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1 100 parts by weight of cement, 225 parts by weight of sand, and 50 parts by weight of water
A mortar bar was prepared using hydroxide and hydroxyapatite having the composition shown in Table 1, and the expansion coefficient was measured.
Inhibition of the alkali silica reaction was evaluated according to the alkali silica reactivity test method (mortar bar method) specified in Table 8 of Appendix 5308. The results are also shown in Table 1.

<Materials Used> Cement: Ordinary Portland cement manufactured by Denki Kagaku Kogyo Co., Ltd. Sand: A mixture of crushed opal silica silica as a reactive aggregate and Himekawa river sand with a Gmax of 5 mm in a weight ratio of 8:92. ,
Surface dry state Hydroxide A: Magnesium hydroxide, manufactured by Mizusawa Chemical Industry Co., Ltd. Hydroxide B: zinc hydroxide, reagent grade 1 manufactured by Kishida Chemical Co., Ltd. Hydroxide C: copper hydroxide, Wako Pure Chemical Industries Reagent 1st grade hydroxyapatite manufactured by Nippon Kagaku Kogyo Co., Ltd. “Supatite” (trade name), average particle size 0.1 to 0.5μ

[0028]

[Table 1]

Example 2 A mixture of 100 parts by weight of cement, 10 parts by weight of aggregate, and 44 parts by weight of water, and a mortar were mixed with a hydroxide and a hydroxyapatite having the composition shown in Table 2 to obtain a diameter of 10 cm and a height of 20 cm. Was prepared. The specimen was pre-cured for 28 days at a temperature of 20 ° C and a humidity of 60%,
Curing was performed for 3 months in an environmental test room at a temperature of 60 ° C., a humidity of 60% and a carbon dioxide concentration of 5%. Thereafter, the specimen was sliced, phenolphthalein was applied, and the depth up to the discolored portion was measured to determine the depth of penetration of carbon dioxide gas from the surface of the specimen. Calipers were used for the measurement, and the measurement was made at four places per circumference, and the average value was defined as the penetration depth of carbon dioxide gas. In addition, the specimens prepared in the same manner were preliminarily cured in water at a temperature of 20 ° C. for 7 days, and immersed in a 5% saline solution at a temperature of 20 ° C. for 3 months. Cut the specimen into slices and apply 1N silver nitrate aqueous solution, then 10%
The potassium chromate solution was sprayed to measure the depth to the place where the discoloration occurred, and the depth from the surface of the test specimen was determined to include chloride ions. The results are also shown in Table 2.

<Materials Used> Aggregate: Sankilite YO4 (trade name), a lightweight aggregate manufactured by Sanki Kogyo Co., Ltd., main component: SiO ₂ silver nitrate: Reagent 1st grade potassium chromate manufactured by Wako Pure Chemical Industries, Ltd .: Sum Reagent 1st grade manufactured by Kojun Pharmaceutical Co., Ltd. Others are the same as in Example 1.

[0031]

[Table 2]

[0032]

When the cement admixture of the present invention is used, it reacts with chloride ions and carbonate ions in concrete to form an insoluble and dense salt, thereby suppressing intrusion of chlorine ions and carbonate ions from the outside. I do. Further, it functions as an amphoteric ion exchanger, and efficiently and efficiently suppresses deterioration phenomena such as salt damage, carbonation, and alkali-aggregate reaction of concrete. It produces effects such as:

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C04B 22/00-28/36

Claims (2)

(57) [Claims] 1. A cement admixture comprising one or more selected from hydroxides of divalent metals of Mg, Zn, Cu and Fe, and hydroxyapatite. 2. A cement composition comprising a cement and the cement admixture according to claim 1.