JPH0797246A - Cement admixture and cement composition - Google Patents

Abstract

PURPOSE:To improve the swelling characteristics of mixed cement by compounding a specific swelling material and amorphous calcium aluminate. CONSTITUTION:90-50 pts.wt. of CaO raw material and 10-50 pts.wt. of CaSO4 raw material are mixed in such a manner as to make the total 100 pts.wt. and then the mixture is subjected to a heat treatment at 1100-1600 deg.C to obtain a swelling material having a Blaine value of 1500-8000cm<2>/g. A cement admixture is obtained by compounding 100 pts.wt. of the swelling material with 10-100 pts.wt. of an amorphous calcium aluminate containing 35-45wt.% of CaO. A cement composition is obtained by compounding 100 pts.wt. of cement with 3-15 pts.wt. of the above mentioned cement admixture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a cement admixture and a cement composition used in the civil engineering / construction industry.

[0002]

2. Description of the Related Art Cement is an indispensable material because it is inexpensive and allows the construction of large-scale structures. However, cement has the drawback of shrinking, and many cement expanders have been proposed for the purpose of preventing this shrinkage.

The cement expansive material is a lime-containing cement expansive agent which produces ettringite or Ca (OH) ₂ which is an expansive hydrate, a metal powder type cement expansive agent such as iron powder or aluminum powder, and a magnesia type cement. Expansive materials are roughly classified into three types, and in Japan, lime-based cement expansive materials are the mainstream because they are inexpensive.

Conventionally, CaO has been used as a lime-based cement expansive material.
Sources and SiO ₂ sources are heat treated to produce free lime (f-CaO) and f-CaO-C ₃ S based cement expansives containing 3CaO ・ SiO ₂ (C ₃ S) which is the cement mineral as the main components. (Japanese Patent Publication No. 53-13650). However, when this cement expansive material is used in a mixed cement in which a pozzolanic substance is mixed, there is a problem that not only the expansion amount decreases but also the expansion developing property slows down and the dimensional stability and strength developing property decrease. It was

On the other hand, calcium aluminate is used alone or in combination with gypsum as a cement rapid hardening material (Japanese Patent Publication No. 54-17771).

As a result of various efforts to solve the above problems, the present inventor has completed the present invention by finding that the above problems can be solved by using a specific cement admixture. It was

[0007]

[Means for Solving the Problems] That is, according to the present invention, CaO produced by heat-treating a mixture containing a CaO raw material and a CaSO ₄ raw material is produced.
And CaSO ₄ as an active ingredient consisting of minerals, and the component ratio in the mineral, CaSO ₄ is 10 to 50 parts by weight of CaO and CaSO ₄ total 100 parts by weight, and amorphous A cement admixture prepared by mixing calcium aluminate, and a cement composition containing cement and the cement admixture.

The present invention will be described in more detail below.

The expansive substance of the cement admixture according to the present invention is obtained by mixing a CaO raw material and a CaSO ₄ raw material and heat-treating, and the CaSO ₄ in the product is 10 to 10 parts by weight in total of 100 parts by weight of CaO and CaSO _4. 50
Parts by weight.

The raw material for the expansion material is
It can be arbitrarily selected, but is not particularly limited, for example, as CaO raw material, CaCO ₃ quality such as limestone and slaked lime and Ca (OH) ₂ quality, and also as CaSO ₄ raw material, anhydrous Gypsum, semi-water gypsum, dihydrate gypsum, etc. are mentioned. SiO ₂ , Fe ₂ O ₃ , CaF ₂ , M existing in the raw material
Impurities such as gO and TiO ₂ are not particularly limited as long as they do not substantially impair the object of the present invention.

CaO raw material and CaSO of the expanding material of the present invention_FourRaw materials and
The compounding ratio of CaO and CaSO of the expanding substance_FourOf
CaSO in 100 parts by weight_FourTo be 10 to 50 parts by weight
It is preferable to add 20 to 40 parts by weight.
More preferably. CaSO _FourIs less than 10 parts by weight,
For example, it shows expansive expansion by the first day of age,
The hardened cement using quality will not crack or
Expression may decrease, and CaSO_FourExceeds 50 parts by weight
If the amount is large, the expandability tends to decrease.

In the present invention, the desulfurization temperature of gypsum varies greatly depending on the blending ratio of raw materials and the content of impurities. Therefore, the firing temperature at the time of firing the raw materials is not particularly limited, but it is usually 1,100 to About 1,600 ° C is preferable.

The method of mixing the raw materials is not particularly limited, and an ordinary method can be used.

The heat treatment method for producing the expansive substance of the present invention is not particularly limited, and may be, for example, a rotary type.
Any method such as firing with a kiln or melting with an electric furnace is possible.

The degree of fineness of the expansive substance of the present invention depends on the purpose and application for which it is used and is not particularly limited.
It is preferably 1,500 to 8,000 cm ² / g. If it is less than 1,500 cm ² / g, strength development may decrease, and 8,000 cm ² / g
If it exceeds, the expandability may not be sufficiently exhibited.

The amorphous calcium aluminate according to the present invention is obtained by melting a mixture of a CaO raw material and an Al ₂ O ₃ raw material and quenching the resulting clinker.

The melting temperature of the raw material is not particularly limited because it varies depending on impurities, but it is usually 1,500.
-1,700 ° C is preferable.

The content of CaO in the amorphous calcium aluminate is preferably 35 to 45% by weight, more preferably 38 to 42% by weight. If it is less than 35% by weight, the expandability may be insufficient, and if it exceeds 45% by weight, the fluidity of the cement kneaded product using amorphous calcium aluminate may be impaired and the workability may be impaired. There is. The fineness of amorphous calcium aluminate depends on the purpose of use,
The Blaine value is usually 1, but not limited to
500 to 6,000 cm ² / g is preferable. If it is less than 1,500 cm ² / g, sufficient expandability may not be obtained, and if it exceeds 6,000 cm ² / g, workability may deteriorate.

The amount of the amorphous calcium aluminate compounded is preferably 10 to 100 parts by weight, more preferably 20 to 50 parts by weight, based on 100 parts by weight of the expansive substance. If it is less than 10 parts by weight, the cement hardened product using it tends to crack, and if it exceeds 100 parts by weight, the expandability tends to be insufficient.

The cement admixture of the present invention is prepared by blending 10 to 50 parts by weight of CaSO _{4 with} 100% by weight of CaO and an amorphous calcium aluminate. It gives effective swelling property to the cement.By using the swelling substance and amorphous calcium aluminum in combination, free CaO in the composition is consumed by the pozzolanic substance in the mixed cement and swelling. It suppresses the decrease of the amount and prevents the delay of the strength onset time, and the coexistence of amorphous calcium alumine effectively produces ettringite. In addition, by adjusting the mixing ratio of CaO raw material and CaSO ₄ raw material and the mixing ratio of expansive substance and amorphous calcium aluminum, the expansion amount and expansion timing of the cement admixture is adjusted according to the type of cement used. It is possible.

The fineness of the cement admixture of the present invention depends on the purpose and application of use and is not particularly limited, but usually,
The brain value is preferably 1,500 to 8,000 cm ² / g. 1,500 cm ² /
If it is less than g, the strength developability may be reduced to 8,000.
If it exceeds cm ² / g, the expandability may not be exhibited sufficiently. The amount of the cement admixture of the present invention to be used varies depending on the purpose for which it is used, but is usually preferably 3 to 15 parts by weight, more preferably 5 to 10 parts by weight, relative to 100 parts by weight of cement. If it is less than 3 parts by weight, the expandability is not sufficient, and if it exceeds 12 parts by weight, abnormal expansion may occur.

Here, as the cement, various portland cements such as normal, early strength, super early strength, and moderate heat, various mixed cements obtained by mixing these portland cements with pozzolanic materials such as blast furnace slag and fly ash, and Alumina cement or the like can be used. In particular,
The characteristic is remarkable in the mixed cement.

The amount of water used in the present invention may be the amount used in ordinary mortar or concrete, and is not particularly limited.

Although the reason for improving the expansiveness of the cement admixture of the present invention with respect to the mixed cement is not clear, the hydration reaction of the expansive substance by allowing the expansive substance of the present invention and the amorphous calcium aluminate to coexist. It is presumed that the amorphous calcium aluminate supplements the calcium ion consumed by the pozzolanic substance in the mixed cement while preventing the timing lag from the hydration reaction of the matrix cement.

In the present invention, in addition to cement admixtures, aggregates such as sand and gravel, set retarders, water reducing agents, high performance water reducing agents,
AE agent, AE water reducing agent, high performance AE water reducing agent, cement rapid hardening material, rust preventive agent, antifreezing agent, polymer emulsion, clay minerals such as bentonite and montmorillonite, zeolite, hydrotalcite, and ions such as hydrocalumite Exchangers, inorganic sulfates such as aluminum sulfate and sodium sulfate, inorganic phosphates, and one or more selected from the group consisting of boric acid, etc. within a range that does not substantially inhibit the object of the present invention. It is possible to use together.

The cement admixture of the present invention is used by adjusting the mixing ratio of the CaO raw material and CaSO ₄ raw material, which are raw materials for the expanding substance, and the mixing ratio of the expanding substance and the amorphous calcium aluminate. It is possible to adjust the expansion properties according to the cement used and the purpose of use.

The method for mixing and kneading the cement admixture or cement composition of the present invention is not particularly limited, and a usual method is sufficient. As a mixing device for the cement admixture of the present invention and cement or the like, an existing stirring device can be used. For example, a tilt cylinder mixer, omni mixer, V
Type mixers, Henschel mixers, Nauta mixers and the like can be used. Further, the mixing may be carried out by mixing the respective materials at the time of construction, or by mixing a part or all of them in advance.

The method for curing a hardened cement product using the cement admixture of the present invention is not particularly limited, and any of the commonly used methods such as ordinary temperature / normal pressure curing, steam curing, high temperature / high pressure curing, and pressure curing may be used. The method of can also be used.

[0029]

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

Example 1 CaO and CaSO ₄ in the product were adjusted so as to have the ratios shown in Table 1.
The O raw material and the CaSO ₄ raw material were mixed and fired at 1,200 ° C. for 2 hours in an electric furnace to obtain clinker of various expansive substances having different CaSO ₄ contents. The weight ratio of CaO and CaSO ₄ of the expanding material was obtained from the chemical analysis value. CaSO ₄ is converted from the SO ₃ value of chemical analysis, and CaO is the value obtained by subtracting CaO in CaSO ₄ from total CaO. This clinker has a Blaine value of 3,000
The swelling material was adjusted by crushing to ± 200 cm ² / g.
Further, using CaO raw material and Al ₂ O ₃ raw material, using an electric furnace, they were melted at 1,650 ° C. and rapidly cooled to synthesize an amorphous calcium aluminate clinker. The obtained amorphous calcium aluminate clinker was pulverized to prepare amorphous calcium aluminate (A-CA). 50 parts by weight of A-CA was added to 100 parts by weight of the adjusted expansive substance to prepare a cement admixture, and 7 parts by weight of the cement admixture was added to 100 parts by weight of cement, and the water / cement ratio was 60%. The cement / sand ratio was 1/2, the curing was carried out in air at 20 ° C. and the humidity was 80%, and the expansion rate of the mortar was measured. The results are also shown in Table 1.

<Materials used> CaO raw material: Limestone from Aomi mine of Denki Kagaku Kogyo CaSO ₄ raw material: Hydrofluoric acid generation by-product anhydrous gypsum Al ₂ O ₃ raw material: Commercial bauxite A-CAi: CaO content 40% by weight, brain Value 3,740 cm ² /
g Cement: Ordinary Portland cement manufactured by Denki Kagaku Co., Ltd. Sand: Standard sand produced by Toyoura Commercial product A: Expansion material under the Onoda Cement company "Expan"
Blaine value 3,100 cm ² / g Commercial product B: Expansion material manufactured by Denki Kagaku Kogyo Co., Ltd. “CAS # 20”, Blaine value 2,950 cm ² / g Water: Tap water

<Test method> Expansion amount: According to JIS A 6202 (method B).

[0033]

[Table 1]

Example 2 A cement admixture was prepared by changing the type and amount of A-CA as shown in Table 2 by using an expansive substance having a CaSO ₄ content of 30 parts by weight in a total of 100 parts by weight of CaO and CaSO _4. The same procedure as in Example 1 was carried out except that The results are shown in Table 2.

<Materials used> A-CA B: CaO content 35% by weight, Blaine value 3,150 cm ² /
g A-CA C: CaO content 45% by weight, Blaine value 3,090 cm ² /
g

[0036]

[Table 2]

Example 3 A cement admixture was prepared by using an expansive substance having a CaSO ₄ content of 50 parts by weight in a total of 100 parts by weight of CaO and CaSO ₄ , and cement was prepared as shown in Table 3 with respect to 100 parts by weight of cement. Example 1 was repeated except that the amount of admixture was changed. The results are shown in Table 3.
Also described in.

[0038]

[Table 3]

Example 4 Example 4 was repeated except that blast furnace cement type B was used as the cement. The results are shown in Table 4.

<Materials to be used> Cement: Class B blast furnace cement manufactured by Ube Industries

[0041]

[Table 4]

Example 5 Example 5 was repeated except that blast furnace cement type B was used as the cement. The results are shown in Table 5.

[0043]

[Table 5]

Example 6 Example 6 was repeated except that blast furnace cement type B was used as the cement. The results are shown in Table 6.

[0045]

[Table 6]

[0046]

As is apparent from the examples, the cement admixture and cement composition of the present invention exhibit good expansiveness with respect to mixed cement.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C04B 22:14 E 22:06) Z 103: 60 (72) Inventor Yoshihisa Matsunaga Aomi, Nishikubiki-gun, Niigata Prefecture 2209, Aomi, Aomachi

Claims (2)

[Claims] 1. A mineral containing CaO and CaSO ₄ as an active ingredient, which is produced by heat-treating a mixture containing a CaO raw material and a CaSO ₄ raw material, and the proportion of the components in the mineral is CaSO ₄ is CaO. And Ca
10 to 50 parts by weight of a total of 100 parts by weight of SO ₄ , an expanding substance,
A cement admixture prepared by blending with amorphous calcium aluminate. 2. A cement composition comprising cement and the cement admixture according to claim 1.