JP3105521B2 - Cement admixture and cement composition - Google Patents

Description

The present invention relates to a mortar or concrete cement admixture mainly used in the field of civil engineering and a cement composition using the same.

[Conventional technology and its problems]

In recent years, instead of the conventional underwater concrete method using ordinary concrete, construction using new concrete in which the concrete itself has resistance to material separation against water washing action has been increasing. This type of concrete is called special underwater concrete, and is defined as "concrete with resistance to underwater separation by adding a special underwater concrete admixture"("Special underwater concrete manual (design, Construction),
Coastal Development Technology Research Center, Fishing Port Fishing Village Construction Technology Research Institute, Sankaido, 1986, 12).

Also, the admixture for special underwater concrete is defined as "an admixture that suppresses the separation of cement and aggregate in water by adding viscosity to concrete poured into water to give the concrete viscosity." The use of natural or synthetic polymers such as methylcellulose or polyvinyl alcohol (JP-A-57-123850); the use of polyacrylamide (JP-A-59-54656); The use of a series monomer (JP-A-61-111951) has been proposed.

However, the current special underwater concrete has a problem that its hardening speed is equal to or slower than that of conventional concrete, and it is impossible to apply it to emergency construction.

In view of the present situation, the present inventors have conducted various studies on a cement admixture that imparts rapid hardening and resistance to material separation in water and an appropriate working time, and as a result, a specific cement admixture imparts the above performance. The inventor has obtained the knowledge and completed the present invention.

[Means for solving the problem]

That is, the present invention relates to xCaO.yAl ₂ O ₃ .zCaF ₂ (where x / y / z
/ = 1 / 0.65 to 1.5 / 0.01 to 0.32 molar ratio) calcium fluoroaluminate, inorganic sulfate, setting regulator,
And a cement admixture containing a cellulose substance as a main component, and a cement and a cement composition containing the cement admixture as a main component.

 Hereinafter, the present invention will be described in detail.

The calcium fluoroaluminate according to the present invention, xC
_{aO · yAl 2 O 3 · zCaF} 2 ( where, x / y / z / = 1 / 0.65~1.5 / 0.01
モ ル 0.32 molar ratio).

Calcium fluoroaluminate is a calcareous raw material, an alumina raw material, and a raw material mainly composed of fluoride. If the molar ratio of CaO, Al ₂ O ₃ and CaF _{2 in} the calcined product is 1 for CaO, Al ₂ O ₃ is from 0.65 to 1.5, were mixed in proportions such that CaF ₂ is from 0.01 to 0.32, for example, obtained by sintering at 1,000 ° C. or higher. Practically, it is further crushed or classified to a suitable fineness, for example, Blaine 1,000 to
It is preferably 8,000 cm ² / g.

The molar ratio of CaO, Al ₂ O ₃ and CaF ₂ is in the above range.
If the ratio is out of the range, an appropriate working time cannot be obtained.

The firing conditions such as the firing temperature and the firing time, and the firing device are not particularly limited, and for example, an electric furnace or a rotary kiln can be used.

There is also no particular limitation on the method of cooling the fired product, and for example, rapid cooling with water, high-pressure air, or the like, or slow cooling by standing can be performed.

The form of the obtained fired product is not particularly limited, and may be crystalline or amorphous, or a coexistent material thereof, for example, a mixed crystal. Further, the presence of other components and impurities mixed in the production process is not particularly limited.
In particular, in industrial processes, SiO ₂ ,
Fe ₂ O ₃ , TiO ₂ , MgO and SO ₃ are expected to be mixed as other components, but the mixing amount of these and other unavoidable impurities is less than 20% by weight, and the cement admixture of the present invention There is no loss in properties.

The inorganic sulfate according to the present invention refers to a sulfate of an alkali metal or an alkaline earth metal, and anhydrous, semi-hydrated and dihydrated calcium sulfate are preferably used. Insoluble ones are particularly preferred.

The particle size of the inorganic sulfate, Blaine 2,000~10,000cm ² / g are preferred, 3,000~8,000cm ² / g is more preferable.

The amount of the inorganic sulfate is preferably 50 to 300 parts by weight, based on 100 parts by weight of calcium fluoroaluminate, and 100 parts by weight.
~ 200 parts by weight is more preferred. Outside the above range, rapid hardening may be insufficient or long-term stability of the underwater concrete composition may be impaired.

Examples of the setting regulator according to the present invention include organic acids and salts thereof such as citric acid, tartaric acid, gluconic acid, succinic acid and maleic acid; alkali carbonates such as sodium carbonate and potassium carbonate; phosphoric acids and salts thereof; Examples thereof include acids, alkali borates, silicofluorides, starch, sugars, alcohols and the like, and mixtures thereof, and among them, the use of organic acids is preferred. In particular, a combination of an alkali carbonate and an organic acid is most preferable.

The amount of the setting regulator used is preferably about 1 to 30 parts by weight based on 100 parts by weight of calcium fluoroaluminate from the viewpoint of obtaining an appropriate working time. The appropriate working time at the construction site is usually about 20 to 240 minutes.

The cellulose substance according to the present invention is a cellulose ether obtained by introducing various substituents into cellulose which is a fiber component of wood or cotton, and specifically, methyl cellulose (M
C), hydroxyethylcellulose (HEC), hydroxyethylmethylcellulose (HEMC) and hydroxypropylmethylcellulose (HPMC) are known.

The cellulose substance preferably has a degree of polymerization of 200 or more. If the degree of polymerization is less than 200, the thickening effect (viscosity imparting effect) may be insufficient. Cellulose materials are readily available as commercial products.

The amount of the cellulose substance used is preferably 2 to 30 parts by weight based on 100 parts by weight of calcium fluoroaluminate.
Outside this range, the underwater separation resistance or workability of the underwater concrete composition may be impaired.

The cement according to the present invention includes various commonly used portland cements such as ordinary / early high strength / super early strength, and various mixed cements obtained by mixing blast furnace slag, fly ash or silica, or expanded into portland cement. Expansion cement, special cement such as alumina cement, and the like.

In the present invention, the use amount of the cement admixture is preferably 5 to 30 parts by weight with respect to 100 parts by weight of cement, and if it is outside this range, the object of the present invention may not be achieved.

The aggregate used in the present invention is not particularly limited, and ordinary aggregates such as silica sand, natural sand, and gravel can be used.

In the present invention, other various additives can be used in combination.

Examples of the various additives herein include, for example, fibers such as glass fiber, carbon fiber and steel fiber, polymer emulsion, coloring agent, AE agent, water reducing agent, AE water reducing agent, fluidizing agent,
Rust inhibitors, water retention agents, waterproofing agents such as calcium chloride and sodium silicate, foaming agents, foaming agents, calcium salts such as calcium hydroxide and antifreeze agents, etc., one or more of them, It is possible to use together in an amount that does not substantially inhibit the object of the present invention.

The mixing device of the cement admixture of the present invention is not particularly limited, and for example, existing mixing devices such as a tilting mixer, an omni mixer (manufactured by Chiyoda Giken Kogyo Co., Ltd.), a V-type mixer, a Henschel mixer, and a Nauter mixer can be used. Any agitator can be used.

The method of mixing the respective materials is not particularly limited, and the respective materials may be mixed at the time of construction, or some or all of them may be mixed in advance.

In the present invention, it is further possible to adjust underwater concrete by mixing water with cement and a cement admixture, but the amount of water is not particularly limited, and is adjusted according to the conventional adjustment of concrete. It is possible to decide.

The mixing device used when producing underwater concrete is not particularly limited, either, and the mixing device described above can be used.

In addition, as the method of applying the underwater concrete of the present invention, a conventional method of applying the underwater concrete, for example, a tremy method, a concrete pump method, a bottom-opening container method, or the like can be used.

〔Example〕

Hereinafter, the present invention will be described more specifically with reference to examples.

Example 1 A commercially available calcium carbonate as a calcareous material, a commercially available alumina as an alumina material and calcium fluoride of a reagent grade as a fluoride were mixed, and fired at 1,700 ° C. for 2 hours in a platinum crucible using an electric furnace. Then, it was put into water and quenched to obtain a calcined product of calcium fluoroaluminate. The obtained fired product was pulverized to 88 μ or less. Table 1 shows the results of analysis of the fired product.

Next, using the fired material in Table 1, concrete having the composition shown in Table 2 was prepared, and the working time and compressive strength were measured.
An underwater drop test was performed. The materials used and test methods are as follows. The results are shown in Table 3.

(Materials used) Cement: ordinary Portland cement manufactured by Andes Cement Inorganic sulfate: type II anhydrous gypsum, brane 5,900 cm ² / g Setting regulator: sodium gluconate, reagent Cellulose substance: manufactured by Denki Kagaku, trade name “Dencastabi Light ”, main component methylcellulose Fine aggregate: river sand from Himekawa, Niigata prefecture, specific gravity 2.6, FM2.62 Coarse aggregate: crushed stone from Himekawa, Niigata prefecture, Gmax 20m / m, specific gravity 2.
6, FM 6.7 AE water reducing agent: Denka Grace Co., Ltd., trade name "Darlex WRDA" (Test method) Working time (HT): Time when hardened and fluidity disappeared.

That is, after mixing all the ingredients with a mixer, put them in a 500 cc beaker and allow them to stand still.

Compressive strength: Put a cylindrical form with a diameter of 100mm and a height of 200mm in a container. Add neutral water such as drinking water and mix well, and add water at 20 ± 1 ℃, water depth to 50cm. Hold so that

At the top of the formwork, a cylindrical 10mm with a diameter of 100mm and a height of 300mm
Set the mesh wire mesh upright and set so that the upper end of the wire mesh is in contact with the water surface. The kneaded underwater concrete is gently dropped from the water surface through a wire mesh and filled into a mold. The amount of underwater concrete charged per formwork is about 2, and the same amount is poured in 15 times.
The time required for charging should be 30 seconds or more and 1 minute or less per formwork. Adjust so that the water depth does not change before and after charging. After the underwater concrete has been charged, the form is allowed to stand in water for 15 minutes, and then taken out. Side 2 of the formwork to promote the replacement of water in the form with concrete
Tap lightly with a mallet 2-3 times in each direction. After confirming that water does not flow from the boundary between the inner wall of the formwork and the concrete, the top is leveled.

Follow JIS A 1132 "How to make test specimens for concrete strength test", perform curing, capping and demolding thereafter.

The specimen thus prepared was subjected to standard curing in water at 20 ± 3 ° C, and the compressive strength was measured according to JIS A 1108 “Test method for compressive strength of concrete”.

The number of specimens is three for each batch, and two batches total 6
Find the average value of books.

Underwater drop test; 800cc of water is placed in a 1,000cc beaker with an outer diameter of 110mm and a height of 150mm. Divide 500g of underwater concrete into 10 equal parts and gently drop it from the water surface. The fall is completed between 10 and 20 seconds. After that, leave the beaker still for 3 minutes and gently dispense 600 cc of water in the beaker with a dropper so that concrete does not mix. Using the collected water, the suspended substance and pH were measured. The pH was measured three times, and the average value was taken as the pH value. The measurement of suspended solids was performed according to JIS K 0102 “Factory drainage test method”.

Example 2 The same procedure as in Example 1 was carried out except that the amount of the cement admixture in Table 2 was changed using the formulation of Experiment Nos. 1-6 in Table 3. The results are shown in Table 4.

[Effects of the Invention] As described above, the cement admixture of the present invention is particularly useful for underwater concrete applications.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-49-69761 (JP, A) JP-A-59-131547 (JP, A) JP-A-60-65755 (JP, A) JP-A-58-58 115051 (JP, A) JP-B 57-10059 (JP, B2) JP-B 62-34704 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) C04B 22/14 C04B 28 / 04

Claims (2)

(57) [Claims] 1. A _{xCaO · yAl 2 O 3 · zCaF} 2 ( where, x / y / z / = 1 /
(A molar ratio of 0.65 to 1.5 / 0.01 to 0.32), a cement admixture containing calcium fluoroaluminate, an inorganic sulfate, a setting regulator, and a cellulose substance as main components. 2. A cement composition comprising a cement and the cement admixture according to claim 1 as a main component.