JP2975422B2 - Cement admixture and cement composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a cement admixture, particularly to a cement admixture and a cement composition used for preventing and repairing deterioration of a cement structure.

(Prior Art) In recent years, the deterioration of cement structures has become a social problem, and there is an urgent need to establish countermeasures and repair methods.

The main causes of deterioration of cement structures are: (1) Iron rust in cement structures due to the neutralization of hardened cement.

(2) Cracking due to drying shrinkage.

(3) Deterioration due to chemical action of cement.

(4) Damage due to freeze-thaw action.

(5) Rust of iron in cement structure due to salt content or intrusion salt.

(6) Deterioration due to alkali-aggregate reaction.

(7) Damage due to repeated or sustained loading.

And so on.

(Problems to be Solved by the Invention) The inventors of the present invention particularly aimed at suppressing the neutralization of hardened cement and shortening the period of repair work (by improving the strength development) among the above-mentioned problems. After various studies,
The present inventors have found that a specific composition is effective and completed the present invention.

(Means for Solving the Problems) That is, the present invention provides a calcium aluminosilicate glass,
A cement admixture comprising an inorganic sulfate and a reactive siliceous substance as main components, and a cement composition comprising the cement admixture and cement as main components. Hereinafter, the present invention will be described in detail.

Calcium aluminosilicate glass according to the present invention (hereinafter referred to as
That CAS glass) is a composition region, CaO: 60 to 30 wt% Al ₂ O _3: 20~60 〃 SiO _2: 5 to 25 〃, more preferably CaO: fifty-five to thirty wt% Al ₂ O _3: 30-60 〃 SiO _2: 10 to 20 〃. If CaO is less than 30% by weight or Al ₂ O ₃ exceeds 60% by weight, rapid hardening is inferior. Conversely, if CaO exceeds 60% by weight or Al ₂ O ₃ is less than 20% by weight, coagulation occurs. Even if a large amount of the adjusting agent is added, it instantaneously forms, which is not preferable from the viewpoint of workability. When the content of SiO ₂ is less than 5% by weight, a long-term elongation of strength cannot be expected, and when it exceeds 25% by weight, the initial strength is low. In addition, MgO, Fe
Naturally contains impurities such as ₂ O ₃ , TiO ₂ , K ₂ O, Na ₂ O, etc.
In addition, since these impurities extend the vitrified region of the CaO-Al ₂ O ₃ -SiO ₂ system, the presence of less than 10% by weight is preferable, and rapid hardening, workability, elongation of long-term strength, etc. No problem. It is preferable to add alkali nitrate (NaNO ₃ , KNO _3, etc.), calcium fluoride (CaF ₂ ), borax, or the like, which is a general glass flux, from the viewpoint of lowering the melting point of the glass.

The glass referred to here is usually one in the glass field, that is, "a glass transition point". In addition, it is not necessary that all be glass, and there is no problem if the vitrification ratio is 50% by weight or more. It is more preferably at least 70% by weight, further preferably at least 80% by weight. If it is less than 50% by weight, there is a problem in terms of early strength.

In addition, the measuring method of the vitrification rate, the glass of the present invention,
After heating at 1000 ° C. for 2 hours (h), the mixture was gradually cooled at a cooling rate of 5 ° C./min (m), and the area S ₀ of the main peak of the crystalline mineral was determined by the powder X-ray diffraction method. The vitrification ratio χ was determined from the main peak area S of the crystal.

The above CAS glass is completely different from the composition of granulated blast furnace slag produced as a by-product in metallurgy or metal smelting, and the present invention is not derived from the composition of granulated blast furnace slag. Incidentally average chemical composition of the granulated blast furnace slag is, CaO: 40 to 43 wt%, MgO: 5 to 8 wt%, Al ₂ O _3: 1
3-15 wt%, and SiO _2: 31 to 35 percent by weight.

Furthermore, the CAS glass of the present invention is not derived from alumina cement. That is, the amount of SiO ₂ in ordinary alumina cement is less than 5% by weight [Junichi Kasai, Concrete Engineering, Vol. 22, No. 8, p. 67 (1984)], and the vitrification rate must exceed 25%. None [1964, London City Academic Press Inc., Limited, by HFWTaylor, The Chemistry of Cement, Volume 2, Volume 1
6 pages].

As a raw material of the CAS glass according to the present invention, quick lime (CaO), slaked lime [Ca (OH) ₂ ], limestone (CaCO ₃ ), or the like can be used as a CaO raw material, and as an Al ₂ O ₃ raw material,
Alumina, bauxite, diaspore, feldspar, clay and the like can be used, and silica sand, white clay, diatomaceous earth and the like can be used as the SiO ₂ raw material. Alternatively, it can be achieved by supplementing a relatively inexpensive blast furnace slag with a CaO-based raw material and an Al ₂ O ₃ -based raw material.

More CaO raw material, Al ₂ O ₃ feedstocks, after blended with SiO ₂ feedstocks at a predetermined ratio, direct current melting furnace or melt using a high frequency furnace, resulting pressurized air or the melt It is manufactured by a method of blowing off with water or a method of pouring into water. Alternatively, CAS glass can be produced by melting in a rotary kiln and quenching.

The finer the fineness of the CAS glass is, the better the reactivity is. The specific surface area of the brane is preferably 3,000 cm ² / g or more.

The inorganic sulfate according to the present invention refers to an alkali metal or alkaline earth metal sulfate, for example, anhydrous, hemihydrate,
In addition, calcium sulfate dihydrate is mentioned as a preferable one, and among them, a hardly soluble or insoluble one such as type II anhydrous gypsum is mentioned as a particularly preferable one. The fineness of the inorganic sulfate is usually preferably 3,000 cm ² / g or more.

The amount of inorganic sulfate used is based on 100 parts by weight of CAS glass.
It is 50 to 500 parts by weight, preferably 100 to 300 parts by weight. 50
If the amount is less than part by weight, rapid hardening is insufficiently expressed, and if it exceeds 500 parts by weight, dimensional stability of the cement composition may be deteriorated.

Examples of the reactive siliceous substance according to the present invention include activated silica, opal silica, silica fume, colloidal silica, diatomaceous earth, aerosil, silica gel, and glassy sodium 1,2,3,4 sodium silicate, and crystalline silica. There are sodium silicate-based substances such as sodium metasilicate, sodium orthosilicate, and sodium pyrosilicate, and one or more of these can be used. Of which
The composition of the sodium silicate-based material has a molar ratio of Na ₂ O / SiO
₂ = 0.1 to 5.0 is preferred, and those in the range of 0.2 to 1.1 are more preferred, and they can be used in powder or solution form.

The particle size of the reactive siliceous substance is not particularly limited, but is usually preferably 5 μm or less.

The amount of the reactive siliceous substance to be used is 20 to 300 parts by weight, preferably 50 to 200 parts by weight, based on 100 parts by weight of CAS glass. If the amount is other than the above, a favorable effect in terms of neutralization cannot be obtained.

The cement admixture of the present invention can be used in admixture with various portland cements such as ordinary / early high strength / ultra-early high strength / moderate heat and various mixed cements in which silica, blast furnace slag and fly ash are mixed.

The use amount of the cement admixture is preferably 10 to 50 parts by weight based on 100 parts by weight of cement. If the amount is less than 10 parts by weight, strength developability is small, that is, it is not preferable from the viewpoint of shortening the construction period.

Various additives other than those described above can be used in combination with the cement admixture and the cement composition of the present invention. For example, setting modifiers, aggregates such as silica sand, natural sand and gravel, fibrous materials such as glass fibers, carbon fibers and steel fibers, polymer emulsions (latex), colorants (pigments), AE agents, Water reducing agent, AE water reducing agent, superplasticizer, rust inhibitor, inseparable admixture in water such as methylcellulose, thickener, water retention agent, waterproofing agent such as calcium chloride, sodium silicate, foaming agent, foaming agent, One or more of calcium-containing compounds such as calcium hydroxide and antifreezes can be used together in an amount that does not substantially inhibit the object of the present invention.

Specific examples of the setting modifier include chlorides such as calcium chloride, ferric chloride and aluminum chloride, aluminates such as sodium aluminate and potassium aluminate, carbonates such as sodium carbonate and potassium carbonate, and sodium hydroxide. , Hydroxides such as calcium hydroxide, zinc fluorosilicate,
There are inorganic salts such as silicofluorides such as magnesium silicofluoride and sodium silicofluoride, and also organic acid compounds such as citric acid, gluconic acid, tartaric acid, and calcium salts, sodium salts and potassium salts thereof, which are added alone. Or two or more of them may be used in combination.

The amount of the setting modifier used is usually about 0.1 to 20 parts by weight based on 100 parts by weight of CAS glass.

As a mixing device used for producing each composition of the present invention, any existing stirring device can be used, for example, a tilting mixer, an omni mixer (Chiyoda Giken Kogyo Co., Ltd.), a V-type mixer, a Henschel mixer A Nauta mixer or the like can be used. In addition, the mixing may be performed by mixing the respective materials at the time of construction or by mixing a part or all of them in advance.

The actual method of applying the cement composition of the present invention may be in accordance with a conventional method of applying mortar or concrete, and does not require any special equipment, construction method and the like.

(Examples) Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1 Commercially available special grade reagents, CaCO ₃ , Al ₂ O ₃ , and SiO ₂ were mixed,
300 g was placed in a carbon crucible, heated and melted in a high-frequency furnace at about 2,000 ° C, then quenched in water and cooled as shown in Table 1.
~ N of 14 glasses were synthesized. Incidentally, as shown in the remarks column, A, B, H, J , K, N because not in CaO-Al ₂ O ₃ -SiO ₂ based glass of the region of 1% by weight of CaF ₂ in the outer split
It was vitrified by adding, adding, and quenching after melting. L, M, and N are comparative examples other than the present invention. these
Each of the CAS glasses was pulverized to a plain specific surface area of 4,000 cm ² / g. The analysis results are shown in Table 1.

Next, a mixture having the composition shown in Table 2 was prepared, and the compressive strength and the neutralization depth were measured (W / C was 60%).

(Materials used) Cement: Andes Cement Ordinary Portland cement Inorganic sulfate: Type II anhydrous gypsum, Blaine specific surface area 5,900cm ² /
g Reactive siliceous substances a: Silica fume, a by-product of ferrosilicon production b: Sodium silicate (reagent) c: Sodium metasilicate (reagent) d: Opal silica stone e: Silica gel (reagent) Aggregate: No. 8 silica sand (Measurement method) Compressive strength: Conforms to JIS R5201. However, the curing condition is temperature 20
℃, humidity 65% RH.

Neutralization test: Housing and Urban Development Corporation In accordance with the test method of “Premix polymer cement mortar for initial repair,” the thickness of the kneaded material is set on a mortar base plate of 10 × 10 × 10cm, according to the test method of “Premix polymer cement mortar for initial repair”. After applying for 5 mm, the specimen was cured under standard conditions for 14 days, and kept on a shelf in an accelerated neutralization test room at a temperature of 30 ° C., a humidity of 60% RH and a CO ₂ concentration of 5% for 30 days.
Neutralization was determined by the color reaction of a 1% solution of phenolphthalein. The neutralization depth was measured at six locations per specimen, and the average value of a total of 18 locations of three specimens was determined.

(Effects of the Invention) According to the present invention, a cement composition having good strength expression and less susceptible to neutralization can be obtained.

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C04B 22/14 C04B 22/14 B 28/02 28/02 // C04B 103: 14 111: 22 (58) Fields surveyed (Int.Cl. ⁶ , DB name) C04B 22/08 C04B 22/14 C04B 22/06 C04B 14/04 C04B 14/06 C04B 28/02

Claims (2)

(57) [Claims] 1. A cement admixture comprising calcium aluminosilicate glass, an inorganic sulfate and a reactive siliceous substance as main components. 2. A cement composition comprising the cement admixture according to claim 1 and cement as a main component.