JP2002068807A - Cement admixture and cement composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cement admixture which imparts superior expanding performance, prevents pop-out phenomenon and enhances water proofness even when the amount of the admixture blended is small and to provide a cement composition containing the admixture. SOLUTION: The cement admixture contains an expansive material which is a substance obtained by heat-treating raw materials of CaO, MgO, SiO2 and CaSO4 and contains free lime, free magnesia, calcium silicate and anhydrous gypsum as principal constituent compounds and a siliceous fine powder and/or fine limestone powder. The expansive material has 30-65% free lime content and 1-30% free magnesia content. The cement composition contains cement and the cement admixture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cement admixture and a cement composition mainly used in the fields of civil engineering and construction.

[0002]

2. Description of the Related Art Cement is an excellent material which is inexpensive and capable of forming large concrete structures into arbitrary shapes. In addition, by using various cement admixtures together with cement, it is possible to improve the strength and durability of the structure. Many cement admixtures have been proposed so far, but from the viewpoints of reliability, durability, aesthetics, etc. of concrete structures, further technological development of a cement admixture imparting expandability is desired. . Concrete
As a cement admixture that gives expandability to
For example, there are a free lime-auyne-anhydrous gypsum-based expanding material (Japanese Patent Publication No. 4221840) and a free lime-calcium silicate-anhydrous gypsum-based expanding material (Japanese Patent Publication No. 5331170).

[0003]

However, when the cement admixture is opened and put into the mixer of the raw conplant,
If the cement admixture is not sufficiently kneaded, the cement admixture may not be uniformly dispersed in the concrete but may be agglomerated, which may cause a so-called pop-out phenomenon in which the cured concrete locally expands abnormally. As a method of preventing the pop-out phenomenon, an inactive inorganic powder or the like is mixed in advance with the expanding material, and even if the cement admixture is not sufficiently kneaded, the expanding material components do not aggregate and form a lump. However, it is conceivable that a certain degree of dispersion can be expected.However, since the expansion component is diluted by mixing the inert inorganic powder, the amount of the cement admixture is required to satisfy the required performance. The problem arises that must be increased. Further, there is a need for a cement admixture that imparts waterproofness to concrete. In the present invention, concrete is a general term for cement paste, mortar and concrete. Therefore, the present inventors have conducted various studies in view of such a situation, and as a result, a cement admixture that can solve the above-mentioned problem by blending a specific expanding material and a siliceous fine powder and / or a limestone fine powder has been found. The inventor has obtained the knowledge that it can be obtained, and has completed the present invention.

[0004]

That is, the present invention provides CaO
Raw material, MgO raw material, SiO ₂ raw material and CaSO ₄ raw material, obtained by heat treatment, free lime, free magnesia, calcium silicate and anhydrous gypsum as a major constituent compound, a silica fine powder, And / or a cement admixture containing limestone fine powder,
The cement admixture, characterized in that the expandable material has a free lime content of 30 to 65% and a free magnesia content of 1 to 30%, the cement comprising the cement and the cement admixture. A composition.

[0005]

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

The expansive material of the present invention is a substance obtained by heat-treating a CaO raw material, a MgO raw material, a SiO ₂ raw material and a CaSO ₄ raw material, and comprises free lime, free magnesia, calcium silicate and anhydrous gypsum as main constituent compounds. It is assumed that. The composition ratio is not particularly limited, but free lime is 30 parts in 100 parts of the expanding material.
It is preferably from 65 to 65 parts, more preferably from 40 to 55 parts. The amount of free magnesia is preferably 1 to 10 parts, more preferably 2 to 7 parts. If the free magnesia is less than 1 part, excellent expansion performance may not be obtained, and if it exceeds 10 parts, long-term dimensional stability may be deteriorated. The calcium silicate is preferably used in an amount of 5 to 44 parts, more preferably 10 to 40 parts. Further, the amount of anhydrous gypsum is preferably 5 to 35 parts, and
0 to 30 parts is more preferable. If the composition ratio of each compound in the cement admixture is not in the above range, excellent expansion performance may not be obtained. The parts and% used in the present invention represent mass units.

[0007] The calcium silicate contained in the expanding material of the present invention is a general term for CaO-SiO ₂ compounds, and is not particularly limited, but may be C ₃ S or C ₂
S is well known. Usually, it can be considered that it exists as C ₃ S. Hereinafter, in the present invention, calcium silicate is abbreviated as C ₃ S.

In producing the expanding material used in the cement admixture of the present invention, a CaO raw material, a MgO raw material, a SiO ₂ raw material and a CaSO ₄ raw material are heat-treated to obtain free lime, free magnesia, C ₃ S and anhydrous gypsum. Clinker consisting of
Is synthesized and produced. Free lime, free magnesia, C ₃
The effect of the present invention cannot be obtained by synthesizing S and anhydrous gypsum separately and mixing them. CaO raw material, Mg
O raw material, SiO ₂ raw material and CaSO ₄ raw material
Whether clinker composed of free lime, free magnesia, C ₃ S and anhydrous gypsum was synthesized, for example, by microscopic observation of coarse particles of 100 μm or more in the pulverized material (SEM-
EDX) or the like to confirm that free lime, free magnesia, C ₃ S and anhydrous gypsum are mixed in the particles.

The heat treatment method for the production of the present invention is not particularly limited, but it is preferable to perform firing in a temperature range of 1100 to 1600 ° C. using an electric furnace, a kiln or the like, and 1200 to 1500 ° C. C. is more preferred. If the temperature is lower than 1100 ° C., the obtained cement admixture has insufficient expansion performance, and if it exceeds 1600 ° C., anhydrous gypsum may be decomposed.

Limestone and slaked lime are examples of CaO raw materials.
As a raw material of MgO, commercially available magnesium oxide
, Magnesium hydroxide and dolomite, etc.
SiO _TwoRaw materials include commercially available silicon dioxide and silica stone.
CaSO_FourRaw materials include dihydrate gypsum and hemihydrate
Gypsum and anhydrous gypsum are exemplified. These raw materials
There are various impurities inside, and specific examples are T
iO_Two, P_TwoO_Five, Na_TwoO, K_TwoO, fluorine, chlorine, etc.
To the extent that the object of the present invention is not substantially impaired.
It does not matter.

The particle size of the expanding material of the present invention is not particularly limited.
6000 cm ² / g is preferable, 2500 to 4000 c
m ² / g is more preferred. If it is less than 1500 cm ² / g,
6000 cm ² / g
If it exceeds, excellent expansion performance may not be obtained.

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

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

The fine siliceous powder used in the present invention and / or
Alternatively, the particle size of the limestone fine powder is not particularly limited, but is usually preferably 3000 cm ² / g or more in terms of the specific surface area of the limestone. If it is less than 3000 cm ² / g, a sufficient pop-out suppressing effect may not be obtained.

[0015] The expandable material of the present invention, a fine silica powder and / or
Alternatively, the mixing ratio of the limestone fine powder is not particularly limited, but usually, in 100 parts of the cement admixture, the expansion material is preferably 50 to 95 parts, more preferably 60 to 90 parts. If the amount of the intumescent material is less than 50 parts, sufficient inflation performance may not be obtained, and if it exceeds 95 parts, 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
It is preferably from 50 to 50 parts, more preferably from 10 to 40 parts. 5
If the amount is less than 50 parts, a sufficient effect of suppressing the pop-out phenomenon and the effect of improving waterproofness may not be obtained. If the amount exceeds 50 parts, sufficient expansion performance may not be obtained.

The amount of the cement admixture of the present invention is not particularly limited, but is usually 5 to 15 parts, preferably 7 to 13 parts, per 100 parts of the cement composition comprising the cement and the cement admixture. Is more preferred. If the amount is less than 5 parts, the effect of the present invention may not be sufficiently obtained. If the amount is more than 15 parts, the amount of expansion may be too large and the strength expression may be deteriorated.

As the cement of the present invention, there are various portland cements such as ordinary cement, high-strength, ultra-high-strength, low heat and moderate heat, various cements obtained by mixing blast furnace slag, fly ash and silica with these cements, and limestone powder. Filler cement, alumina cement, etc., and one or more of these can be used.

The cement admixture and the cement composition of the present invention may further contain a water reducing agent, a high performance water reducing agent,
AE water reducer, high-performance AE water reducer, fluidizer, defoamer, thickener, rust inhibitor, anti-freezing agent, shrinkage reducer, polymer emulsion and setting regulator, cement hardening material, cement expanding material Minerals, such as bentonite and zeolite, anion exchangers such as hydrotalcite, etc. or 2
More than one species can be used without substantially inhibiting the purpose of the present invention.

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 some or all of them may be mixed in advance. . As the mixing device, any existing device can be used, and examples thereof include a tilting mixer, an omni mixer, a Henschel mixer, a V-type mixer, and a Nauta mixer.

[0020]

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

Example 1 A raw material of CaO, a raw material of MgO, a raw material of SiO _{2 and a} raw material of CaSO ₄ were blended and mixed and pulverized.
For 2 hours to produce expanders having various compound compositions shown in Table 1, and a specific surface area of the branes of 3500 ± 200 cm.
² / g. 75 parts of these expanding materials and 25 parts of limestone fine powder were mixed to obtain a cement admixture, and 100 parts of a cement composition composed of cement and a cement admixture were mixed with 10 parts of a cement admixture to obtain a unit cement composition. Physical quantity 300 kg / m ³ , water / cement composition ratio = 62
%, S / a = 45% concrete was prepared, and the length change rate was measured and a pop-out test was performed. The results are also shown in Table 1. The produced expanding material is converted to a powder X-ray diffractometer (XR).
D), free lime, free magnesia, C ₃ S
And anhydrous gypsum were confirmed to be the main constituent compounds. The chemical composition was determined by chemical analysis, and the compound composition was determined by calculation based on the chemical analysis values. The expansive material O (Experiment No. 1-14) was composed of free lime, free magnesia,
It was prepared by separately synthesizing C ₃ S and anhydrous gypsum and then mixing them.

<Materials Used> Cement: Commercial ordinary Portland cement Limestone fine powder: Limestone from Aomi mine, Niigata prefecture, crushed to a specific surface area of 5,000 cm ² / g. Water: Tap water sand: Niigata Prefecture Himekawa production, specific gravity 2.62 gravel: Niigata Prefecture Himekawa production, specific gravity 2.64 CaO raw materials: first-class reagent calcium carbonate MgO raw materials: first-class reagent magnesium oxide SiO ₂ raw materials: first-class reagent dioxide Silicon CaSO ₄ raw material: first grade anhydrous gypsum reagent Free lime: CaO raw material synthesized by firing at 1350 ° C. for 3 hours. Free magnesia: synthesized by firing MgO raw material at 1350 ° C for 3 hours. C ₃ S: 3 mol of CaO raw material and 1 mol of SiO ₂ raw material are mixed and fired at 1600 ° C. for 3 hours to synthesize. Anhydrite: calcined CaSO ₄ raw material at 1350 ° C. for 3 hours for synthesis.

<Measurement method> Chemical analysis: Measured according to JIS R 5202. Length change rate: Measured according to JIS A 6202 B. Pop-out test: Concrete is prepared in advance without adding a cement admixture, and it is cooled in a tilting mixer.
The cement admixture is added after agitating the mixer at a rate of 12 revolutions / minute, and after 10 minutes, the mixture is discharged and punched into a mold 1 m long, 50 cm wide and 10 cm high. And confirmed the pop-out phenomenon. The ambient temperature is 20
° C.

[0024]

[Table 1]

From Table 1, it can be seen that the cement admixture and the cement composition of the present invention impart excellent expansion performance to concrete and prevent the pop-out phenomenon.

Example 2 An expanding material having a composition shown in Table 2 was produced by blending a CaO raw material, a MgO raw material, a SiO ₂ raw material and a CaSO ₄ raw material, which are industrial raw materials, and performing a heat treatment at 1400 ° C. using a rotary kiln. Except for this, the procedure was the same as in Example 1.
Table 3 shows the compound composition calculated from the chemical composition, and Table 4 shows the measurement results. For comparison, a similar experiment was performed on two types of commercially available expanding materials.

<Materials> CaO raw material: Limestone from Aomi mine, Niigata Prefecture MgO raw material: Dolomite from China SiO ₂ raw material: Silica CaSO ₄ raw material: Natural anhydrous gypsum from Thailand Expanding material A: Commercial calcium sulfoaluminate expanding material Expanding material B: Commercial lime-based expanding material

[0028]

[Table 2]

[0029]

[Table 3]

[0030]

[Table 4]

From Table 4, it can be seen that the cement admixture and the cement composition of the present invention impart excellent expansion properties to concrete and prevent the pop-out phenomenon.

Example 3 The same procedure as in Example 2 was carried out except that the expanding material 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 5. Was. Note that a waterproof test was also performed. The results are also shown in Table 5.

<Materials used> Silica fine powder: Commercial blast furnace slag is used with a brain specific surface
5000cm product^Two/ G. Silica fine powder: Commercial silica fume, Brain ratio
Surface area 200000cm ^Two/ G. Silica fine powder: Commercial fly ash with a Brain ratio
5000cm surface area^Two/ G. Siliceous fine powder: Commercial diatomaceous earth with a specific surface of Brain
5000cm product^Two/ G. Siliceous fine powder: Siliceous fine powder and siliceous fine powder
Equivalent mixture of Brine specific surface area 102500cm^Two
/ G. Silica fine powder: Silica fine powder and limestone fine powder
Equivalent mixture, Brain specific surface area 102500cm^Two/
g.

<Measurement Method> Waterproof test: φ15 × 30 cm, center hole diameter 2.0c
A m-shaped hollow specimen was prepared, demolded at a material age of 1 day, water-cured for 6 days up to a material age of 7 days, and then subjected to a water permeability test. The test method was an output method. A water pressure of 10 kg / cm ² was applied from the outside of the test body for 48 hours, the amount of water coming out of the center hole was measured, and the water permeation of concrete not containing the cement admixture was taken as 100. Was expressed as a water permeability.

[0035]

[Table 5]

From Table 5, it can be seen that the cement admixture and the cement composition of the present invention impart excellent expansion performance to concrete, prevent the pop-out phenomenon, and enhance the waterproofness.

Example 4 A cement admixture prepared by mixing 75 parts of the expanding material of the present invention of Example 2 and 25 parts of siliceous fine powder was used, and the mixture of the cement admixture in 100 parts of the cement composition was used. The procedure was as in Example 2, except that the amounts were changed as shown in Table 6. The results are also shown in Table 6.

[0038]

[Table 6]

From Table 6, it can be seen that the cement admixture of the present invention provides an excellent expansion performance in which the rate of change in concrete length increases as the amount of the cement admixture increases, and also prevents the pop-out phenomenon and the waterproofness. It can be seen that it increases.

[0040]

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

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C04B 22:08 C04B 22:08 A 22:10 22:10 22:14) 22:14) B 103: 60 103: 60 111: 27 111: 27 (72) Inventor Mitsuo Takahashi 2209 Aomi, Aomi-cho, Nishikubiki-gun, Niigata Pref. PC13

Claims (3)

[Claims] An expanding material obtained by heat-treating a CaO raw material, a MgO raw material, a SiO ₂ raw material and a CaSO ₄ raw material, wherein the expanding material mainly comprises free lime, free magnesia, calcium silicate and anhydrous gypsum. ,
A cement admixture containing siliceous fine powder and / or limestone fine powder. 2. The expansive material has a free lime content of 30 to 65.
% And a free magnesia content of 1 to 10%. 3. A cement composition comprising a cement and the cement admixture according to claim 1 or 2.