JP2001122650A - Cement admixture and cement composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cement admixture capable of providing a cement composition containing the admixture with excellent expansion performance even when a small amount of the admixture is blended in the composition, preventing any pop-out phenomenon from being caused and improving waterproofness of the concrete and also to provide the cement composition. SOLUTION: This cement admixture comprises an expansive material containing, as its main constituent compounds, free lime, calcium aluminoferrite and anhydrous gypsum, and also a fine silica powder and/or a fine limestone powder. The cement composition comprises cement and the cement admixture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a cement admixture and a cement composition mainly used in the civil engineering and construction industries.

[0002]

2. Description of the Related Art Cement is an excellent material which is inexpensive and can be used to form a large concrete structure into an arbitrary shape. Furthermore, by using a cement admixture together, it is possible to improve the strength and durability of the structure. Many cement admixtures have been proposed so far, but the most used one is a cement admixture that imparts expandability to concrete. Here, concrete is
A generic term for cement, mortar and concrete.

As a cement admixture for imparting expandability to a concrete structure, for example, CaO—Al ₂ O ₃ —S
Known are those containing an O ₃ -based compound as an active ingredient (JP-B-42-21840, JP-B-42-19473, JP-B-53-1).
No. 6007).

[0004]

However, since these cement admixtures are opened in a ready-mixed plant and mixed with concrete, the cement admixtures may be shipped without being sufficiently kneaded in some cases. Sometimes. In such a case, the cement admixture is often in a lump without being uniformly dispersed in the concrete, and in the hardened concrete, the lump cement admixture locally causes abnormal expansion, There is a problem that a so-called pop-out phenomenon occurs in which the surface of the cured body macroscopically swells, peels, and falls.

As a method for preventing the pop-out phenomenon, an inactive inorganic powder or the like is mixed in advance with the expanding material,
Even if the cement admixture is not sufficiently kneaded, a method is conceivable in which the expanded components do not agglomerate into a lump and a certain degree of dispersion can be expected, but by mixing inactive inorganic powder. In addition, there is a problem that the expansion component is diluted and the amount of the cement admixture for imparting the required performance increases.

[0006] In recent years, the performance required of a cement admixture that imparts expandability has been increasing more and more. That is, the reality is that the development of a cement admixture that can impart excellent expansion performance even with a small amount of compounding has been awaited. Therefore,
Although it is intended to prevent the pop-out phenomenon, a method in which the amount of the cement admixture is increased is not useful, and it is necessary to find a method that can prevent the pop-out phenomenon without increasing the amount.

On the other hand, a cement admixture for imparting waterproofness to concrete is also required. Thus, the present inventors
In view of such a situation, as a result of various studies to solve the above problem, a cement admixture which can solve the above problem by mixing a specific expanding substance with a siliceous fine powder and / or a limestone fine powder is obtained. Gained the knowledge that
The present invention has been completed.

[0008]

That is, the present invention comprises an expanding substance mainly composed of free lime, calcium aluminoferrite and anhydrous gypsum, and a fine silica powder and / or a fine limestone powder. And a cement composition containing cement and the cement admixture.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

The swelling substance of the present invention comprises free lime, calcium aluminoferrite and anhydrous gypsum as main constituent compounds, and the ratio thereof is not particularly limited, but the free lime is preferably 30 to 60%, and 40 to 60%. ~ 5
0% is more preferable. The content of calcium alumino ferrite is preferably 10 to 40%, more preferably 15 to 30%. The amount of anhydrous gypsum is preferably 10 to 40%, preferably 20 to 3%.
5% is more preferred. If the proportion of each compound in the expanding substance is out of the above range, excellent expansion characteristics may not be obtained in some cases. Here,% indicates weight percentage.

The calcium alumino ferrite of the present invention is a general term for CaO—Al ₂ O ₃ —Fe ₂ O ₃ compounds, and is not particularly limited.
When CaO is C, Al ₂ O ₃ is A, and Fe ₂ O ₃ is F, C
Compounds such as ₄ AF and C ₆ A ₂ F are well known. Typically, it believed to be present as C ₄ AF, in the present invention, a calcium alumino ferrite hereinafter referred C ₄ AF.

When producing the cement admixture of the present invention, C
aO raw material, Al ₂ O ₃ raw material, Fe ₂ O ₃ raw material and CaSO ₄
The raw material is heat-treated to synthesize a clinker composed of free lime, C ₄ AF and anhydrous gypsum, and then pulverized to produce the clinker. Free lime, C ₄ AF and anhydrous gypsum are separately synthesized, and a mixture of these does not provide the effects of the present invention. The CaO raw material, the Al ₂ O ₃ raw material, the Fe ₂ O ₃ raw material and the CaSO ₄ raw material are heat-treated to obtain free lime, C ₄ AF.
Whether or not clinker composed of anhydrous gypsum was synthesized, for example, microscopic observation of coarse particles of 100 μm or more in the pulverized material, free lime, C ₄ AF and anhydrous gypsum are mixed in the particles. Can be determined by checking.

The heat treatment temperature for producing the cement admixture of the present invention is preferably in the range of 1100 to 1600 ° C, more preferably in the range of 1200 to 1500 ° C. 1
If the temperature is lower than 100 ° C., the obtained cement admixture has insufficient expansion performance. If the temperature exceeds 1600 ° C., anhydrous gypsum may be decomposed.

Examples of the CaO raw material include limestone and slaked lime. Examples of the Al ₂ O ₃ raw material include bauxite and aluminum residual ash. Examples of the Fe ₂ O ₃ raw material include copper karami, iron powder and commercially available iron oxide. Iron oxide and the like are mentioned, and as the CaSO ₄ raw material, dihydrate gypsum, hemihydrate gypsum and anhydrous gypsum are exemplified. Various impurities are present in these raw materials, and specific examples thereof include SiO ₂ , MgO, and Ti.
_{O 2, P 2 O 5,} Na 2 O, K 2 O , and the like, although no particular problem in the range that does not substantially impair the object of the present invention, among these, in particular, SiO ₂ is silica 0 at the rate.
It is preferably in the range of less than 5. If the silicate ratio is 0.5 or more, excellent expansion performance may not be obtained. The silicic acid ratio in the present invention means the amount of SiO ₂ in the cement admixture,
It is calculated from the following formula based on the l ₂ O ₃ amount and the Fe ₂ O ₃ amount. Silicic acid ratio = SiO ₂ / (Al ₂ O ₃ + Fe ₂ O ₃ )

The amount of SiO ₂ in the cement admixture is
It is preferably at most 5.0%, more preferably at most 3.0%. Specifically, if it exceeds 5.0%, excellent expansion performance may not be obtained.

The particle size of the expandable substance of the present invention is not particularly limited, but is usually 1500 in terms of Blaine specific surface area.
6000 cm ² / g is preferable, and 2500 to 4000
cm ² / g is more preferred. 1500cm is less than ² / g, may strength development is deteriorated, 6000 cm ²
/ G, excellent expansion performance may not be obtained.

Although the silica fine powder of the present invention is not particularly limited, it is a general term for silica fume, blast furnace slag, fly ash, diatomaceous earth, silica dust such as fused silica, and the like. The siliceous fine powder has an effect of improving the waterproofness of concrete in addition to the effect of suppressing the pop-out phenomenon.

Although the limestone fine powder of the present invention is not particularly limited, it is a general term for ore mainly composed of naturally occurring calcium carbonate. The limestone fine powder does not have the effect of improving the waterproofness unlike the silica-based fine powder, but has a sufficient effect of suppressing the pop-out phenomenon, and has the advantage that it can be obtained at low cost in some areas.

The siliceous fine powder and / or limestone of the present invention
The particle size of the fine powder is not particularly limited.
Normally, the specific surface area of the brane is 3000-9000cm^Two/ G
Is preferably 3500-6000 cm^Two/ G is more preferred
New 3000cm^Two/ G is insufficient pop-out
In some cases, the effect of suppressing the phenomenon of
m ^Two/ G cannot be expected to further increase the effect.
The financial burden also increases.

An expanding substance in the cement admixture of the present invention;
The mixing ratio of the siliceous fine powder and / or limestone fine powder is
Although not particularly limited, usually, the expanding material is preferably 50 to 95 parts by weight, more preferably 60 to 90 parts by weight, per 100 parts by weight of the cement admixture. 50 swelling substances
If the amount is less than parts by weight, sufficient expansion performance may not be obtained, and if it exceeds 95 parts by weight, a sufficient effect of suppressing a pop-out phenomenon and an effect of improving waterproofness may not be obtained. Silica fine powder and / or limestone fine powder is 5 to 5
0 parts by weight is preferable, and 10 to 40 parts by weight is more preferable. If the amount is less than 5 parts by weight, a sufficient effect of suppressing a pop-out phenomenon and an effect of improving waterproofness may not be obtained.
If it exceeds 50 parts by weight, sufficient expansion performance may not be obtained.

[0021] The particle size of the cement admixture of the present invention is not particularly limited.
500-6000 cm ² / g is preferable, and 3000-5
000 cm ² / g is more preferred. 2500cm is less than ² / g, there is a case where the effect of suppressing sufficient pop-out phenomenon is not obtained, there may not be obtained with excellent expansion performance and greater than 6000 cm ² / g.

The amount of the cement admixture of the present invention is not particularly limited, but is usually 3 to 1 in 100 parts by weight of the cement composition comprising cement and the cement admixture.
2 parts by weight is preferable, and 5 to 9 parts by weight is more preferable. Three
If the amount is less than 10 parts by weight, the effect of the present invention may not be sufficiently obtained. If the amount is more than 12 parts by weight, the strength development may be deteriorated.

The cement according to the present invention is JIS R 5210
Various Portland cements specified in JIS R 5211,
JIS R 5212, various mixed cement specified in JIS R 5213, blast furnace cement produced by mixing admixtures in the range specified in JIS or more, fly ash cement and silica cement, filler cement mixed with limestone powder,
And alumina cement and the like, and one or more of these can be used.

The cement of the present invention and the cement composition containing the cement admixture can be used as a cement mortar or cement concrete by mixing with an aggregate such as sand or gravel, in addition to using the cement composition as it is as a cement paste. used. In the present invention, further, a water reducing agent, an AE water reducing agent, a high-performance water reducing agent, a high-performance AE water reducing agent, an antifoaming agent, a thickener, a rust inhibitor, an antifreezing agent, a shrinkage reducing agent, a polymer emulsion, a setting regulator One or two or more of cement hardened materials, clay minerals such as bentonite and zeolite, and ion exchangers such as hydrotalcite can be used in a range that does not substantially impair the object of the present invention. It is possible.

In the present invention, the method of mixing the respective materials is not particularly limited, and the respective materials may be mixed at the time of construction or may be partially or entirely mixed in advance. As the mixing device, any existing device can be used, and for example, a tilting cylinder mixer, an omni mixer, a Henschel mixer, a V-type mixer, a Nauta mixer and the like can be used.

[0026]

The present invention will be described below in detail with reference to examples.

Example 1 CaO raw material, Al ₂ O ₃ raw material, Fe ₂ O ₃ raw material and CaSO
_{The four} raw materials are blended, mixed and pulverized, and then heat-treated at 1350 ° C. for 2 hours to produce expanded materials having various compositions shown in Table 1,
It was pulverized to a Blaine specific surface area of 3500 ± 200 cm ² / g. 75 parts by weight of these intumescent substances and 25 parts by weight of limestone fine powder are mixed to form a cement admixture, and 7 parts by weight of the cement admixture are mixed in 100 parts by weight of a cement composition composed of cement and cement admixture. Cement composition amount: 300 kg / m ³ , water / cement composition ratio = 62%,
Concrete having an s / a of 45% was prepared, and the expansion coefficient was measured and a pop-out test was performed. In addition, in order to confirm the storage stability of the cement admixture, the cement admixture was put in a paper bag, closed with a sewing machine and closed for one month in a test room at a temperature of 20 ° C. and a relative humidity of 80%. The expansion rate on day 7 was measured. Table 2 shows the test results. The expanding substance was identified by powder X-ray diffraction (XRD) and free lime, C
₄ It was confirmed that AF and anhydrous gypsum were the main constituent compounds. The chemical composition was determined by chemical analysis, and the compound composition was calculated from the result of chemical analysis.

<Materials Used> Cement: Commercial ordinary Portland cement Limestone fine powder: Limestone obtained by milling limestone from the Aomi mine in Niigata Prefecture to a Blaine specific surface area of 5,000 cm ² / g. Water: tap water Sand: from Himekawa, Niigata, specific gravity 2.62 Gravel: from Himekawa, Niigata, specific gravity 2.64 CaO raw material: reagent grade calcium carbonate Al ₂ O ₃ raw material: reagent grade aluminum oxide Fe ₂ O ₃ raw material: reagent Primary iron oxide CaSO ₄ Raw material: Special grade anhydrous gypsum reagent <Measurement method> Chemical analysis: Measured according to JIS R 5202. Compound composition: Free lime content was measured according to JIS R 5202, and other compounds were determined by calculation.
That is, the C ₄ AF amount is calculated from the Fe ₂ O ₃ amount, and then the S ₄ AF amount is calculated.
The amount of anhydrous gypsum was calculated from the amount of O ₃ . Expansion coefficient: Measured according to JIS A 6202 B. Pop-out test: Concrete was prepared in advance without adding a cement admixture, this concrete was put into a tilting mixer, and the cement admixture was added later while agitating the mixer at a speed of 12 revolutions / minute. After a minute, it was discharged and poured into a mold having a length of 1 m, a width of 50 cm and a height of 10 cm, and a pop-out phenomenon was observed.

[0029]

[Table 1]

[0030]

[Table 2]

From Table 2, it can be seen that the cement admixture of the present invention has excellent expansion performance and storage stability, and also prevents the pop-out phenomenon.

Example 2 A mixture of CaO raw material, Al ₂ O ₃ raw material, Fe ₂ O ₃ raw material and CaSO ₄ raw material, which are industrial raw materials, was heat-treated at 1400 ° C. using a rotary kiln, as shown in Table 3. The same procedure was performed as in Example 1 except that an intumescent substance having a composition was produced. Table 4 shows the compound composition calculated from the chemical composition, and Table 5 shows the measurement results of the expansion coefficient. For comparison, a similar experiment was performed with two types of commercially available cement admixtures. <Materials> CaO raw material: Limestone from Aomi mine, Niigata Prefecture Al ₂ O ₃ raw material: Chinese bauxite Fe ₂ O ₃ raw material: Industrial iron oxide CaSO ₄ raw material: Natural anhydrous gypsum from Thailand Expansive material A: Commercial calcium sulfoaluminate Expanding Material Expanding Material B: Commercial quicklime expanding material

[0033]

[Table 3]

[0034]

[Table 4]

[0035]

[Table 5]

From Table 5, it can be seen that the cement admixture of the present invention has excellent expansion performance and prevents the pop-out phenomenon.

Example 3 The same procedure as in Example 2 was carried out except that the expanding substance of the present invention of Example 2 was used and a cement admixture was prepared by changing the type and amount of the siliceous fine powder shown in Table 6. Was. The waterproof test was also performed. The results are shown in Table 6.

<Materials used> Silica fine powder: Commercial blast furnace slag was converted to a Blaine specific surface
5000cm product^Two/ G. Silica fine powder: Commercial silica fume, Blaine ratio
Surface area 200000cm ^Two/ G. Siliceous fine powder: Commercial fly ash with Blaine ratio
5000cm surface area^Two/ G. Silica fine powder: Commercial diatomaceous earth has a Blaine specific surface
5000cm product^Two/ G. Siliceous fine powder: Siliceous fine powder and siliceous fine powder
Mixture of the same weight of
^Two/ G. Silica fine powder: Silica fine powder and limestone fine powder
Equal weight mixture, Blaine specific surface area 102500cm^Two/
g. <Measurement method> Waterproof test: φ15 × 30cm, center hole diameter 2.0c
After making a hollow specimen of m, demolding at the age of 1 day, 7 days old
After curing for 6 days in water, conduct water permeability test
Was. The test was conducted using the output method.
10kg / cm^TwoFor 48 hours and ooze from the center hole
Measure the amount of water in the concrete
The relative value when the amount of water permeation of the sheet is 100
expressed.

[0039]

[Table 6]

From Table 6, it can be seen that the cement admixture of the present invention has excellent expansion performance, prevents pop-out phenomenon, and has high waterproofness.

Example 4 A cement admixture comprising 75 parts by weight of the intumescent substance of the present invention of Example 2 and 25 parts by weight of siliceous fine powder was used, and the amount of the cement admixture in 100 parts by weight of the cement composition was used. Was carried out in the same manner as in Example 2 except that was changed as shown in Table 7. The results are shown in Table 7.

[0042]

[Table 7]

From Table 7, it can be seen that the concrete containing the cement admixture of the present invention has an increased coefficient of expansion as the compounding amount increases, thereby preventing the pop-out phenomenon and increasing the waterproofness.

[0044]

The cement admixture of the present invention can provide excellent expansion performance, prevent the pop-out phenomenon, and improve the waterproofness, even if the amount is small.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C04B 28/02 C04B 28/02 (72) Inventor Toshiyuki Tamaki 2209 Aomi, Aomi-cho, Nishikubiki-gun, Niigata Prefecture Electrochemistry 4G012 MB23 MB24 MB26 PA28 PB03

Claims (2)

[Claims] 1. A cement admixture containing an expanding substance mainly composed of free lime, calcium aluminoferrite and anhydrous gypsum, and a siliceous fine powder and / or limestone fine powder. 2. A cement composition comprising a cement and the cement admixture according to claim 1.