JP2012229132A - Cement admixture and cement composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cement admixture and a cement composition that give a good expansion strain without pop-out even when addition of a shrinkage reducing agent is suppressed.SOLUTION: There are provided a cement admixture (1) that includes free lime, a hydraulic compound, anhydrous gypsum, and an expanding agent having 40 mass% or more of a residue on 45 μm sieve and 30 mass% or less of a residue on 90 μm sieve; a cement admixture (2) that is the cement admixture (1) further including the shrinkage reducing agent; a cement admixture (3) that is the cement admixture (2) including 80-95 pts.mass of the expanding agent and 5-20 pts.mass of the shrinkage reducing agent; a cement admixture (4) that is the cement admixture (2) or (3) of which the shrinkage reducing agent contains an alkylene oxide/propylene oxide copolymer and a polyoxypropylene monoalkyl ether; and a cement composition (5) including cement and cement admixtures (1) to (4).

Description

  The present invention relates to a concrete expansion material used in the field of civil engineering and construction, and a method for producing the same.

A concrete expansion material having excellent expansion characteristics with a small addition amount has been proposed (see Patent Document 1). In addition, cement admixtures that have both expansion performance and shrinkage reduction performance by adding a shrinkage reduction agent to these expansion materials and combining the expansion material and the shrinkage reduction agent have been proposed (see Patent Documents 2 and 3).
Furthermore, the technique of preventing pop-out and ensuring the expansion rate by adjusting the particle size of the expansion material is disclosed (see Patent Documents 4 and 5). However, in these documents, particle size adjustment was performed at 200 to 300 μm, 90 μm, 5 to 20 μm, 150 μm, and the like.

Japanese Patent No. 4244261 JP 2000-264694 A JP 2003-12352 A JP 2007-131484 A JP 2008-201592 A

The present invention has been found that by adjusting a specific expansion material with a specific particle size, pop-out can be further prevented and expansion strain can be increased.
In addition, although a material obtained by slurrying an expansion material with a shrinkage reducing agent is excellent in terms of performance, the shrinkage reducing agent has a high cost. Therefore, a material in which the blending ratio of the shrinkage reducing agent is suppressed as much as possible has been demanded. However, when the amount of the shrinkage reducing agent added is suppressed, there are problems such that the expansion material aggregates to cause a pop-out phenomenon, and the effect of increasing the expansion strain is reduced.
The present invention has been found that the use of a specific expansion material solves the above-described problem even if a shrinkage reducing agent is not blended or the amount of shrinkage reducing agent added is suppressed as compared with the prior art.

  That is, the present invention includes (1) an expanded material containing free lime, a hydraulic compound, and anhydrous gypsum and having a 45 μm sieve residue of 40% by mass or more and a 90 μm sieve residue of 30% by mass or less. Cement admixture, (2) Cement admixture of (1) further comprising a shrinkage reducing agent, (3) 80 to 95 parts by mass of expansion material, and 5 to 20 parts by mass of shrinkage reducing agent (2 ) Cement admixture, (4) the shrinkage reducing agent contains an alkylene oxide / propylene oxide copolymer and a polyoxypropylene monoalkyl ether (2) or (3) the cement admixture, (5) cement and ( A cement composition comprising the cement admixtures of 1) to (4).

  The cement admixture of the present invention can suppress the aggregation of the expansion material even if the shrinkage reducing agent is not blended or the blending ratio of the shrinkage reducing agent is less than that of the conventional one, has no pop-out, and satisfies the same or larger expansion strain than the conventional one. A cement admixture is provided.

The parts and% used in the present invention are based on mass unless otherwise specified.
The concrete referred to in the present invention is a generic term for cement paste, cement mortar, and cement concrete.

The expansion material used in the present invention is a free lime, hydraulic compound, anhydrous obtained by heat-mixing CaO raw material, Al ₂ O ₃ raw material, Fe ₂ O ₃ raw material, SiO ₂ raw material, and CaSO ₄ raw material as appropriate. It is obtained by pulverizing a clinker containing gypsum to a predetermined particle size.
The free lime referred to in the present invention is usually called f-CaO.
Table In the hydraulic compound referred to in the present invention, Auin represented by _{3CaO · 3Al 2 O 3 · CaSO} 4, 3CaO · SiO 2 (C 3 S for short) and 2CaO · _{SiO 2 (C} 2 S for short) Calcium silicate, 4CaO.Al ₂ O ₃ .Fe ₂ O ₃ (abbreviated as C ₄ AF), 6CaO.2Al ₂ O ₃ .Fe ₂ O ₃ (abbreviated as C ₆ A ₂ F), 6CaO.Al ₂ O Calcium aluminoferrite represented by ₃ · Fe ₂ O ₃ (abbreviated as C ₆ AF), calcium ferrite such as 2CaO · Fe ₂ O ₃ (abbreviated as C ₂ F), and one or two of these Preferably it contains more than one species.
The anhydrous gypsum referred to in the present invention is expressed as CaSO ₄ .

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 calami and commercially available iron oxide, and examples of the SiO ₂ raw material include silica stone. However, examples of the CaSO ₄ raw material include dihydrate gypsum, hemihydrate gypsum, and anhydrous gypsum. These raw materials may contain impurities, but this is not a problem as long as the effects of the present invention are not impaired. Examples of impurities include MgO, TiO ₂ , ZrO ₂ , MnO, P ₂ O ₅ , Na ₂ O, K ₂ O, Li ₂ O, sulfur, fluorine, and chlorine.

  Although the heat processing method of the clinker used for the expansion material used by this invention is not specifically limited, It is preferable to bake at the temperature of 1100-1600 degreeC using an electric furnace, a kiln, etc., and 1200-1500 degreeC is. More preferred. If it is less than 1100 ° C., the expansion performance is not sufficient, and if it exceeds 1600 ° C., anhydrous gypsum may decompose.

  It is preferable that the ratio of each mineral contained in the clinker used for the expansion material used by this invention is the following ranges. The content of free lime is preferably 30 to 70 parts, more preferably 40 to 60 parts, in 100 parts of clinker. As for content of a hydraulic compound, 10-40 parts are preferable in 100 parts of clinker, and 20-30 parts are more preferable. The content of anhydrous gypsum is preferably 10 to 40 parts and more preferably 20 to 30 parts in 100 parts of clinker. Outside the above range, the amount of expansion may decrease, or conversely, it may become extremely large and the compression strength may decrease.

  The mineral content can be confirmed by a conventional analysis method. For example, the pulverized sample can be applied to a powder X-ray diffractometer to confirm the produced mineral and analyze the data by the Rietveld method to quantify the mineral. Further, based on the identification result of chemical components and powder X-ray diffraction, the amount of minerals can also be obtained by calculation.

The fineness of the expandable material used in the present invention is particularly important. The 45 μm sieve residue is preferably 40% or more and the 90 μm sieve residue is preferably 30% or less, and the 45 μm sieve residue is 80% or more and 90 μm sieve. More preferably, the balance is less than 20%. In the above range, the amount of expansion may be small, or pop-out may easily occur.
The method for adjusting the fineness is not particularly limited, and an airflow classification method, a sieve classification method, and the like are applicable.

  The kind of shrinkage reducing agent used in the present invention is not particularly limited, and alkylene oxide / propylene oxide copolymer, polyoxypropylene monoalkyl ether, glycol ether / amino alcohol derivative, and alkylene oxide adduct of lower alcohol. In particular, the combined use of an alkylene oxide / propylene oxide copolymer and a polyoxypropylene monoalkyl ether is preferable from the viewpoint of expansion performance.

  When a shrinkage reducing agent is used in combination with the expansion material in the present invention, the ratio of the shrinkage reduction agent is 20 parts or less, preferably 3 to 20 parts, and preferably 5 to 15 parts, in a total of 100 parts of the expansion material and the shrinkage reduction agent More preferred. If it exceeds 20 parts, the expansion strain may be reduced.

  The amount of the cement admixture of the present invention is not particularly limited because it varies depending on the blending of concrete, but usually 3 to 10 parts are preferable in 100 parts of a cement composition composed of cement and a cement admixture, 5-8 parts is more preferable. If it is less than 3 parts, sufficient expansion performance may not be obtained, and if it exceeds 10 parts, it may overexpand and may cause expansion cracks in the concrete.

  As the cement used in the cement composition of the present invention, various portland cements such as normal, early strength, super early strength, low heat, and moderate heat, various mixed cements obtained by mixing these cements with blast furnace slag, fly ash, silica, And filler cement mixed with limestone powder.

  In the present invention, sand, gravel, water reducing agent, high performance water reducing agent, AE water reducing agent, high performance AE water reducing agent, fluidizing agent, antifoaming agent, thickener, rust preventive agent, antifreeze agent, polymer emulsion, and Examples of setting modifiers include cement hardeners, clay minerals such as bentonite, ion exchangers such as zeolite, siliceous fine powder, calcium carbonate, calcium hydroxide, gypsum, calcium silicate, etc. And fibrous materials such as vinylon fiber, acrylic fiber, and carbon fiber.

  Examples will be described in detail below.

"Experiment 1"
CaO raw material so that it becomes 50 parts of free lime, 10 parts of Auin, 5 parts of calcium aluminoferrite (4CaO.Al ₂ O ₃ .Fe ₂ O ₃ ), 5 parts of calcium silicate (2CaO.SiO ₂ ), and 30 parts of anhydrous gypsum. Then, Al ₂ O ₃ raw material, Fe ₂ O ₃ raw material, SiO ₂ raw material, and CaSO ₄ raw material were prepared and heat-treated at 1350 ° C. to synthesize an expansion material clinker. The intumescent clinker was pulverized using a ball mill and adjusted to a particle size as shown in Table 1 using a sieve. As the sieve, a metal mesh sieve having a mesh size of 300 μm, 90 μm, and 45 μm as defined in JIS Z8801-1 was used.
As shown in Table 1, a cement admixture composed of an expansion material and a cement admixture composed of 85 parts of the expansion material and 15 parts of the shrinkage reducing agent were prepared.
Among 100 parts of cement composition consisting of cement and cement admixture, 7 parts of cement admixture were used, water / cement composition ratio = 50%, cement composition / sand ratio = 1/3 mortar at 20 ° C. The length change rate (expansion strain) was measured. A pop-out test was also conducted. The same evaluation was performed on a commercially available expansion material. The results are shown in Table 1.

(Materials used)
CaO raw material: limestone Al ₂ O ₃ raw material: bauxite Fe ₂ O ₃ raw material: iron oxide SiO ₂ raw material: silica CaSO ₄ raw material: dihydrate gypsum sand: JIS standard sand water: tap water cement: ordinary Portland cement, reduction of shrinkage on commercial products Agent A: Mixture shrinkage reducing agent of 50 parts of a copolymer of alkylene oxide and propylene oxide and 50 parts of polyoxypropylene monoalkyl ether B: Copolymer of alkylene oxide and propylene oxide Here, a copolymer of alkylene oxide and propylene oxide The average structural formula of the polymer can be represented by HO— (C ₃ H ₆ O _11.3 / C ₂ H ₄ O _3.7 ) —H. The average structural formula of polyoxypropylene monoalkyl ether can be represented by C ₄ H ₉ O— (C ₂ H ₄ O) ₂ — (C ₃ H ₆ O) ₂ —H.
Shrinkage reducing agent C: Polyglycol ether compound commercially available expansion material (1): Ettlingite-lime composite expansion material Commercial expansion material (2): Lime-based expansion material

(Test method)
Mineral composition: Obtained by calculation based on the chemical composition and the identification result of powder X-ray diffraction.
Length change rate: JIS A 6202 Appendix 1 The expansion strain up to 7 days of age was measured according to the expansibility test method using mortar of expansive material.
Pop-out test: Kneaded mortar is molded into a flat plate of 20 x 20 x 5 cm to smooth the surface. After curing for 6 months in a room at 20 ° C and 60%, the surface of the mortar is observed for the presence or absence of pop-out. confirmed.

"Experimental example 2"
The particle size of the expansion material was 45% sieving residue 100%, 90 μm sieving residue 30%, the shrinkage reducing agent was fixed to A, and the mixing ratio of the expansion material and the shrinkage reducing agent was changed as shown in Table 2. Except for this, the same procedure as in Experimental Example 1 was performed. The results are shown in Table 2.

"Experiment 3"
The procedure was the same as in Experimental Example 2 except that the amount of cement admixture added was changed as shown in Table 3. The results are shown in Table 3.

  With the cement admixture and the cement composition of the present invention, even if the blending ratio of the expensive shrinkage reducing agent is suppressed, pop-out does not occur and good expansion strain can be obtained.

Claims (5)

A cement admixture containing free lime, a hydraulic compound, and anhydrous gypsum, and an expansion material having a 45 μm sieve residue of 40% by mass or more and a 90 μm sieve residue of 30% by mass or less. The cement admixture according to claim 1, further comprising a shrinkage reducing agent. The cement admixture according to claim 2, wherein the expansion material is 80 to 95 parts by mass and the shrinkage reducing agent is 5 to 20 parts by mass. 4. The cement admixture according to claim 2, wherein the shrinkage reducing agent contains an alkylene oxide / propylene oxide copolymer and a polyoxypropylene monoalkyl ether. A cement composition comprising cement and the cement admixture according to any one of claims 1 to 4.