JP2002226243A - Expansive admixture and cement composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an expansive admixture exhibiting excellent expanding performance without generating pop-out after placing concrete, and a cement composition. SOLUTION: The expansive admixture comprises an expansive material as the principal component which is obtained by thermally treating a mixture comprising CaO raw material, CaSO4 raw material and one or more kinds selected from Al2O3 raw material, Fe2O3 raw material and SiO2 raw material, wherein the expansive material comprises free lime, anhydrous gypsum and one or more kinds selected from calcium aluminoferrite, calcium ferrite, hauyne and calcium silicate, where the free lime is contained by 35 to 60%, and characterized in that the content of calcium hydroxide is 1 to 15 pts. to 100 pts. of the expansive admixture. The cement composition comprises the expansive admixture and cement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an expanding material and a cement composition mainly used in the field of civil engineering and construction, which do not cause pop-out or partial abnormal expansion of concrete after construction. The concrete in the present invention is a general term for cement paste, mortar and concrete.

[0002]

2. Description of the Related Art It is important to reduce the cracking and improve the bending strength of cement and concrete from the viewpoint of reliability, durability and aesthetics of concrete structures. Progress is desired. Conventionally, as an expanding material that gives expandability to cement / concrete, for example, a free lime-auyne-anhydrous gypsum-based expanding material (Japanese Patent Publication No. 42-21840).
And a free lime-calcium silicate-anhydrite gypsum-based expanding material (Japanese Patent Publication No. 53-31170).

[0003]

However, when a conventional expanding material is added to mortar or concrete by a raw plant or a mixer at the site, if the dispersion of the expanding material is insufficient at the time of mixing, the concrete called pop-out cannot be obtained. In some cases, a cone-shaped peeling phenomenon may occur under the surface layer due to expansion and destruction, and there is a problem that not only the performance of concrete is reduced but also the peeled portion may fall. In addition, recently, the transition from the conventional specification-based design system to a performance-based design system has been considered, and a clear performance rule has been established for the durability of concrete, which was somewhat neglected until now. It is considered that the effect of the crack on the durability is quantified. Therefore, reducing cracks is an important issue, but in order to widely use expandable materials that are effective in reducing cracks, it is essential to use expandable materials that are less used, have less economic burden, and have excellent expansion characteristics. is there. The present inventors have conducted various studies in order to solve these problems, and as a result, have found that the use of a specific inflating material can solve the above problems, thereby completing the present invention. .

[0004]

That is, the present invention provides a C
aO raw material, CaSO ₄ raw material, Al ₂ O ₃ raw material, Fe ₂ O
₃ is an expanding substance obtained by heat-treating one or two or more selected from raw materials and SiO ₂ raw materials, and free lime;
An expanding material 1 containing an expanding material having an amount of free lime of 35 to 60% and containing an anhydrous gypsum and one or two or more selected from calcium aluminoferrite, calcium ferrite, eauin and calcium silicate.
An expanding material characterized in that the amount of calcium hydroxide is 1 to 15 parts in 00 parts, and is a cement composition containing cement and the expanding material. In addition, the part and% which show the mixing ratio used by this invention are a mass unit.

[0005]

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

[0006] The expanding substance in the present invention comprises free lime,
It contains anhydrous gypsum and one or more kinds selected from calcium aluminoferrite, calcium ferrite, eauin and calcium silicate (hereinafter referred to as hydraulic compound). Is preferably from 35 to 60 parts, more preferably from 40 to 55 parts. Further, the hydraulic compound is preferably 10 to 40 parts, more preferably 15 to 30 parts. Further, the amount of anhydrous gypsum is preferably 10 to 40 parts, more preferably 20 to 35 parts. The proportions of calcium aluminoferrite, calcium ferrite, auin and calcium silicate in the hydraulic compound are not particularly limited.

[0007] The expanding material of the present invention contains impurities.
Specific _{examples, MgO, TiO 2, P 2} O 5, Na 2
O, K ₂ O, chlorine, fluorine and the like can be mentioned, but they do not cause any particular problem as long as the object of the present invention is not substantially inhibited.

The hydraulic compound of the present invention will be described below. The calcium alumino ferrite of the present invention is C
aO—Al ₂ O ₃ —Fe ₂ O ₃ -based compound is a general term and is not particularly limited.
Is C, Al ₂ O ₃ is A, and Fe ₂ O ₃ is F, C ₄ AF
And compounds represented by C ₆ A ₂ F and the like. Usually, C
It is considered to exist as ₄ AF, and in the present invention, calcium aluminoferrite is hereinafter referred to as C ₄ AF. The calcium ferrite of the present invention is a general term for CaO—Fe ₂ O ₃ -based compounds, and is not particularly limited. Generally, when CaO is C and Fe ₂ O ₃ is F, C compounds such as ₂ F and CF are well known. In the present invention, it is preferable to use C ₂ F because the expansion characteristics are improved. In the present invention, calcium ferrite is hereinafter referred to as C ₂ F. The auin of the present invention is 3C
shows the compound represented by _{aO · 3Al 2 O 3 · CaSO} 4. The calcium silicate of the present invention refers to Ca
O—SiO ₂ -based compounds are generic terms and are not particularly limited, but generally, CaO is C, SiO ₂
When S is S, compounds such as C ₃ S and C ₂ S are known.

In producing the expansion material of the present invention, a CaO raw material, a CaSO ₄ raw material, and one or more selected from Al ₂ O ₃ raw material, Fe ₂ O ₃ raw material and SiO ₂ raw material are heat-treated. Then, a swelling substance composed of free lime, a hydraulic compound and anhydrous gypsum is synthesized and crushed and used. If the free lime, the hydraulic compound, and the anhydrous gypsum are separately synthesized, and those obtained by pulverizing and mixing these are not used, the effect of the present invention cannot be obtained. CaO raw material,
CaSO ₄ raw material, Al ₂ O ₃ raw material, Fe ₂ O ₃ raw material and S
Heat-treating one or two or more selected from iO ₂ raw materials to synthesize an expanding material composed of free lime, a hydraulic compound and anhydrous gypsum, and confirm whether or not it is produced by grinding the expanded material. As a method, for example, coarse particles in the expanding material, specifically, particles larger than 100 μm are observed by a microscope or the like to perform composition analysis, and free lime, a hydraulic compound, and anhydrous gypsum are mixed in the particles. Can be easily determined by confirming that the

[0010] The fineness of the expanding material is 1 in terms of Blaine specific surface area.
It is preferably from 500 to 7000 cm ² / g,
Those having 0 to 4000 cm ² / g are more preferred. If the particle size of the expanding material is less than 1500 cm ² / g, the long-term durability of the concrete structure may be deteriorated, and 7000 c
If it exceeds m ² / g, sufficient expansion characteristics may not be obtained.

The heat treatment temperature for producing the expanding material of the present invention is preferably in the range of 1100 to 1600 ° C.
The range of 1200 to 1500C is more preferable. 1100
If the temperature is lower than ℃, the expansion properties of the obtained expanding material are not sufficient,
If the temperature exceeds 1600 ° C., anhydrous gypsum may decompose.

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; and examples of the Fe ₂ O ₃ raw material include copper calami and iron powder and commercially available iron oxide. Examples of the SiO ₂ raw material include silica stone and clay, and examples of the CaSO ₄ raw material include dihydrate gypsum, hemihydrate gypsum and anhydrous gypsum.

In the present invention, what is most important for preventing pop-out is the amount of calcium hydroxide contained in the expandable material. It may become a lump, partially abnormally expand after construction, and cracks and pop-outs may occur. The amount of calcium hydroxide can be adjusted by expanding material 10
In 0 parts, 1 to 15 parts is preferable, 1.5 to 10 parts is more preferable, and 2 to 5 parts is further preferable. If it is less than 1 part, the effect of preventing pop-out is poor, and if it exceeds 15 parts, the amount of expansion decreases, which is not preferable.

The method for adjusting the amount of calcium hydroxide in the expanding material of the present invention is not particularly limited, but water and / or water is added so that a predetermined amount can be obtained at the time of and / or after the pulverization of the expanding substance. Examples thereof include a method of adding and mixing calcium hydroxide, and a method of leaving it for a long time to absorb moisture in the air. The amount of water used when adding water varies depending on the type of crusher and the like. Further, at the time of pulverization, diethylene glycol or trialkanolamines can be used in combination as a pulverization aid. The content of calcium hydroxide in the expanding material is determined by DSC, TG-DTA, IR, and FT-I.
It can be quantified by R, X-ray diffraction, chemical analysis and the like.

The amount of the expanding material of the present invention is not particularly limited, but is preferably 3 to 12 parts of the expanding material in 100 parts of the cement composition comprising cement and the expanding material, and more preferably 4 to 4 parts.
8 parts is more preferred. If the amount of the expanding material of the present invention is out of this range, the effect of the present invention, that is, excellent expansion characteristics may not be obtained. If less than 3 parts, excellent expansion characteristics may not be obtained, and if more than 12 parts are used,
There is a case where the strength expression is reduced.

The cement composition of the present invention is defined by JIS R
Various Portland cements specified in 5210, J
IS R 5211, JIS R 5212 and JIS
Among various mixed cements specified in R5213, blast furnace cements manufactured with an admixture ratio of the admixtures higher than those specified in JIS, fly ash cements, silica cements, filler cements mixed with limestone powder, and alumina cements And one or more of the above and the expanding material of the present invention. The cement composition of the present invention can be used not only as a cement paste as it is, but also as a mortar or concrete by mixing with an aggregate.

[0017] In the present invention, in addition to aggregates such as sand and gravel, cement, expansion agent, setting accelerator, setting retarder, dextrin, water reducing agent, AE water reducing agent, high performance AE water reducing agent, AE agent,
One or more of a thickener, a cement hardened material, a rust inhibitor, a polymer emulsion, clay minerals such as bentonite and montmorillonite, and inorganic phosphates do not substantially inhibit the object of the present invention. It is possible to use together within the range.

As a mixing device used for producing concrete, mortar and the like using the expanding material of the present invention, any existing stirring device can be used. For example, a tilting mixer, an omni mixer, a V-type mixer, Henschel mixers and Nauta mixers are available. In the mixing, the respective materials may be mixed at the time of construction, or some or all of them may be mixed in advance. The mixing order is not particularly limited.

[0019]

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

EXAMPLE 1 CaO raw material, CaSO ₄ raw material, Al ₂ O ₃ raw material, Fe ₂
One or more selected from the O ₃ raw material and the SiO ₂ raw material are blended and heat-treated at 1400 ° C. using an electric furnace to obtain various compositions of A to T shown in Table 1 (for each component). (Proportion of 100 parts in total).

A predetermined amount of water is added to the expanded material and pulverized by a ball mill, and the Blaine specific surface area is 3500 ± 200.
An expanding material having an amount of calcium hydroxide of 3 parts per 100 parts of the expanding material was prepared at cm ² / g. 6 parts of an expanding material is used for 100 parts of a cement composition composed of cement and an expanding material, a unit cement composition amount is 310 kg / m ³ , a water / cement composition ratio = 55%, s / a = 44%, and water reduction. Concrete was prepared by adding 1% of the agent to the cement, and the length change rate of 7 days of age and the pop-out test were performed. In addition, a commercially available expandable material was tested at the same amount of the expandable material used. Table 2 shows the results.

<Material used> Cement: Commercial ordinary Portland cement CaO raw material: Reagent primary calcium carbonate Al ₂ O ₃ raw material: Reagent primary alumina Fe ₂ O ₃ raw material: Reagent primary ferric oxide SiO ₂ raw material: Reagent primary silicon oxide CaSO ₄ Raw material: Reagent grade 1 water gypsum Sand: Himekawa, Niigata prefecture, specific gravity 2.62, FM value 2.86 Gravel: Himekawa, Niigata prefecture, specific gravity 2.64 Water: tap water Water reducing agent: polycarboxylic acid, commercial product Expansive material: Calcium sulfoaluminate-based expansive material, commercially available Expansive material: Lime-based expansive material, commercially available product

<Measurement method> Length change rate: Measured in accordance with JIS A 6202 B Pop-out test: Concrete is prepared in advance using a material other than the expanding material, and the concrete is placed in a tilting mixer and rotated 12 times / While the mixer was agitated at the speed of 1 minute, the expanding material was added later, and after 10 minutes, discharged, discharged into a mold having a length of 1 m, a width of 50 cm and a height of 10 cm, and observed a pop-out phenomenon.

[0024]

[Table 1]

[0025]

[Table 2]

As is evident from Table 2, any of the concretes using the expansive material of the present invention show excellent expansive properties and no pop-out is observed.

Example 2 The procedure of Example 1 was repeated, except that the amount of the calcium hydroxide expander shown in Table 3 was used in 100 parts of the expander D shown in Table 1. The results are also shown in Table 3.

[0028]

[Table 3]

As is clear from Table 3, the concrete of the present invention mixed with an expander having an amount of calcium hydroxide of 1 to 15 parts has no pop-out and shows excellent expansion characteristics.

Example 3 In 100 parts of a cement composition comprising cement and an expanding material,
Example 1 except that the amount of expanding material shown in Table 4 was used.
The same was done. The results are also shown in Table 4.

[0031]

[Table 4]

As is evident from Table 4, as the amount of the expanding material of the present invention increases, the concrete exhibits excellent expansion characteristics.

[0033]

By using the expanding material of the present invention and the cement composition containing the same, the concrete exhibits no pop-out after construction and exhibits excellent expansion characteristics.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroyuki Ohashi 2209 Aomi, Aomi-cho, Nishikubiki-gun, Niigata Inside the Aomi Plant of Denki Kagaku Kogyo Co., Ltd. Chemical industry Co., Ltd. Aomi factory F term (reference) 4G012 MB00 PB03

Claims (2)

[Claims] 1. A CaO raw material, a CaSO ₄ raw material, and an Al ₂ raw material.
O ₃ raw material, selected from Fe ₂ O ₃ raw material and a SiO ₂ raw material 1
An expanding substance obtained by heat-treating a seed or two or more kinds, comprising free lime, anhydrous gypsum, and one or more kinds selected from calcium aluminoferrite, calcium ferrite, auyne and calcium silicate. The amount of calcium hydroxide is 1 to 100 parts in an expanding material mainly containing an expanding substance having a free lime amount of 35 to 60%.
An inflatable material comprising 15 parts. 2. A cement composition comprising a cement and the expanding material according to claim 1.