JP4115802B2 - Cement admixture and cement composition - Google Patents

Description

【００４０】
実験例２
γ-Ｃ_２Ｓと表２に示す種類の水和熱抑制剤を９：１で混合してなるセメント混和材を作製し、セメント９４部に対し、該セメント混和材６部を使用したこと以外は、実験例１と同様に試験した。結果を表２に示す。
【００４１】
＜使用材料＞
水和熱抑制剤ア：市販品、グルコン酸ナトリウム
水和熱抑制剤イ：市販品、D-グルコノ-1,5-ラクトン
水和熱抑制剤ウ：市販品、ソルビトール
水和熱抑制剤エ：市販品、尿素
水和熱抑制剤オ：市販品、ケイフッ化ナトリウム
水和熱抑制剤カ：市販品、酸化亜鉛
水和熱抑制剤キ：市販デキストリン、冷水可溶分０％
水和熱抑制剤ク：市販デキストリン、冷水可溶分１０％
水和熱抑制剤ケ：市販デキストリン、冷水可溶分３０％
水和熱抑制剤コ：市販デキストリン、冷水可溶分５０％
水和熱抑制剤サ：市販デキストリン、冷水可溶分８０％
【００４２】
【表２】

【００４３】
実験例３
表３に示す量のγ-Ｃ_２Ｓと水和熱抑制剤ケからなるセメント混和材を６部、セメント９４部を混合して100部としたこと以外は、実験例１と同様に試験した。結果を表３に示す。
【００４４】
【表３】

【００４５】
実験例４
表４に示すブレーン比表面積値のγ-Ｃ_２Ｓ粉末を作製し、γ-Ｃ_２Ｓと水和熱抑制剤ケとを９：１で混合してセメント混和材とし、セメントとセメント混和材からなるセメント組成物100部中、セメント混和材を６部使用したこと以外は実験例１と同様に試験した。結果を表４に示す。
【００４６】
【表４】

【００４７】
【発明の効果】
本発明のセメント混和材及びセメント組成物は、単位セメント量の多い配合とした材料設計においても、水和発熱量を著しく低減できるために熱ひび割れ発生を抑制することができ、かつ中性化抑制効果を有するという特徴を有する。本発明のセメント混和材及びセメント組成物は、土木・建築分野におけるコンクリート構造物、特に中性化を受けやすい環境に設置されるコンクリート構造物及びマスコンに適する。[0001]
BACKGROUND OF THE INVENTION
The present invention mainly relates to a cement admixture and a cement composition used in the civil engineering and construction industries.
[0002]
In the present invention, the blending ratio, part, and% are shown on a mass basis unless otherwise specified. The concrete referred to in the present invention is a general term for cement paste, mortar, and concrete.
[0003]
[Prior art and its problems]
Concrete is an excellent material capable of constructing a large structure at low cost, and in recent years, it has been increasingly required to have high durability due to diversification of the environment in which concrete is used.
[0004]
However, when a high-strength material is designed, the amount of unit cement to be used inevitably increases, and the flow retention may decrease accordingly. Thermal cracking may occur due to an increase in the sum of heat.
[0005]
As described above, as a result of material design aiming at high strength, it has become a problem that thermal cracking is induced and durability is lowered, and a cement admixture that suppresses heat of hydration has been developed ( JP 57-261, JP Kokoku 5-79619 and JP see JP Laid-open flat 6-298560).
[0006]
In addition to the thermal cracking of concrete, neutralization is a phenomenon that degrades concrete structures and reduces strength. In the civil engineering and construction industries, cement admixtures that have a particularly high neutralization-inhibiting effect are used. It has been sought.
[0007]
Neutralization is a phenomenon in which calcium hydroxide reacts with carbon dioxide in the atmosphere and is carbonated, and concrete deteriorates from the surface. It is said that concrete with a lower calcium hydroxide content is more susceptible to neutralization.
[0008]
The problem with the neutralization of concrete is that the neutralization erodes the concrete and destroys the passive state of the reinforcing bars, and rust occurs in the reinforcing bars in the concrete. Stress is generated and cracks are generated. Further, when the reinforcing bar directly contacts with the outside air or moisture through the crack, rust progresses, the adhesion between the reinforcing bar and the concrete is rapidly lost, and there is a case where the concrete piece is peeled off.
[0009]
The biggest problem here is that the strength of the concrete is emphasized, and the structure using concrete with high strength blending is prone to thermal cracking, and further, the composite deterioration such that the neutralization of the concrete proceeds from the location where the thermal cracking has occurred. In order to increase the total durability of concrete, it is important to suppress both neutralization and thermal cracking.
[0010]
Therefore, today, the development of a material having a low hydration heat generation effect and an effect of suppressing neutralization has been awaited even in material design in which strength is emphasized and the amount of unit cement is large.
[0011]
Therefore, as a result of various investigations, the present inventors have an effect of suppressing neutralization even in material design using a specific cement admixture and a cement composition so that the amount of unit cement is large. The present invention has been completed with the knowledge that the generation of heat cracks can be suppressed because the amount of heat generated by hydration can be significantly reduced.
[0012]
[Means for Solving the Problems]
That is, the present invention contains γ-2CaO · SiO ₂ having a Blaine specific surface area value of 2,000 cm ² / g or more and a hydration heat inhibitor, and the content of γ-2CaO · SiO ₂ is 50% or more. A cement admixture, wherein the hydration heat inhibitor is dextrin, and is a cement composition comprising cement and the cement admixture.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
[0014]
Γ-2CaO · SiO ₂ (hereinafter referred to as γ-C ₂ S) used in the present invention is known as a low-temperature phase of a forsterite (Mg ₂ SiO ₄ ) type structure among the compounds represented by 2CaO · SiO _2. It is a high-temperature phase and is different from α-CaO · SiO ₂ and β-CaO · SiO ₂ having a K ₂ SO ₄ type structure. These are both 2CaO · SiO ₂ and have the same chemical composition, but their crystal structures are different. 2CaO · SiO ₂ present in the cement clinker is β-CaO · SiO ₂ . Although α-CaO · SiO ₂ and β-CaO · SiO ₂ having a K ₂ SO ₄ type structure have hydraulic properties, they do not exhibit neutralization-inhibiting effects like γ-C ₂ S of the present invention.
[0015]
Γ-C ₂ S of the present invention is obtained by mixing a CaO raw material such as limestone and a SiO ₂ raw material such as silica sand at a molar ratio of about 2: 1 and heat-treating. The heat treatment temperature is not particularly limited, but is usually about 1,200 to 1,800 ° C. The cooling method is not particularly limited. Although rapid cooling is not preferable, special slow cooling is not necessary, and natural cooling is sufficient.
[0016]
The presence of impurities in γ-C ₂ S obtained by the above method is not particularly limited, and β-type 2CaO · SiO ₂ (β-C ₂ S), tricalcium silicate 3CaO · SiO ₂ (C ₃ S), lanquinite 3CaO.2SiO ₂ (C ₃ S ₂ ), wollastonite CaO.SiO ₂ (CS), and other calcium silicates may be mixed.
[0017]
In addition to synthetic products γ-C _{2 S} as described above, may be used various slag such as materials containing γ-C _{2 S.} Specific examples thereof include air furnace reduction period slag collector, stainless slag and molten iron pretreatment slag, and the like.
[0018]
However, these electric furnace reduction period slag, stainless steel slag, even molten iron pretreatment slag, not to obtain the effect of the present invention for those that do not contain γ-C _{2 S.}
[0019]
SiO ₂ as a component of these slags, CaO, Al ₂ O _3, and MgO and the like as the major chemical component, _{other, TiO 2, MnO, Na 2} O, S, P 2 O 5, and Fe ₂ O ₃ Etc.
[0020]
In addition, these slags contain tricalcium silicate 3CaO · SiO ₂ (C ₃ S), lanquinite 3CaO · 2SiO ₂ (C ₃ S ₂ ), wollastonite CaO · SiO ₂ as components other than γ-C ₂ S. (CS) calcium such silicates, calcium ferrite such as 2CaO · Fe ₂ O _3, calcium aluminate such as 12CaO · 7Al ₂ O _3, of gehlenite _{2CaO · Al 2 O 3 · SiO} 2 and Akerumanaito 2CaO · MgO · 2SiO ₂ The main component is so-called melilite, which is a mixed crystal, melvinite 3CaO · MgO · 2SiO ₂ , calcium magnesium silicates such as monticite CaO · MgO · SiO ₂ , anorthite CaO · Al ₂ O ₃ · 2SiO ₂ , leucite (K ₂ O, Na ₂ O) · Al ₂ O ₃ · SiO ₂ , spinel MgO · Al ₂ O ₃ , magnetite Fe ₃ O ₄ , and sulfides such as calcium sulfide CaS and iron sulfide FeS may be included.
[0021]
gamma-C ₂ is the particle size of _S is not particularly limited, Blaine specific surface area value is preferably at least 3,000 cm ² / g, more preferably ^{3,500cm 2 / g~8,000cm 2 / g,} 4,000cm 2 / g~7,000cm ² / g is most preferred. If the Blaine specific surface area value is less than 3,000 cm ² / g, the neutralization suppressing effect is not sufficient, and the material separation resistance cannot be obtained. Furthermore, if it exceeds 8,000 cm ² / g, excessive grinding power is required, which may be uneconomical. As materials containing γ-C _{2 S,} electric furnace reduction period slag, stainless slag, and the like molten iron pretreatment slag, have a similar particle size also to use a substance containing the γ-C _{2 S} preferred .
[0022]
The hydration heat inhibitor of the present invention is a general term for those which suppress heat of hydration by mixing with cement, and can be broadly classified into inorganic and organic substances.
[0023]
Specific examples of inorganic hydration heat inhibitors include fluorosilicates such as magnesium fluorosilicate and sodium fluorosilicate, cryolite, and calcium fluoroaluminate, phosphoric acid, phosphate, oxidation Zinc, lead oxide, boric acid, etc. can be used.
[0024]
Moreover, as a specific example of organic matter,
(1) Polysaccharides such as dextrin, hemicellulose, inulin, alginic acid, xylan, and dextran
(2) High molecular organic acids such as lignin sulfonic acid, humic acid, and tannic acid and their salts
(3) Citric acid, malic acid, tartaric acid, arabonic acid, glucoheptonic acid, oxycarboxylic acids such as gluconic acid and their salts
(4) Keto acids such as 2-ketocarboxylic acid and urea and their salts
(5) Aminocarboxylic acid such as glutamic acid and its salt
(6) Polyalcohols
(7) Simple sugars such as glucose, fructose, gluconolactone, galactose, saccharose, xylose, xylitol, abitose, lipidose, and isomerized sugar
(8) Sugars such as oligosaccharides of 2 to 3 sugars
(9) Sugar alcohols such as sorbitol are included.
[0025]
In this invention, it is possible to use 1 type, or 2 or more types of these hydration heat inhibitors in the range which does not inhibit the objective of this invention.
[0026]
In addition, when the form of the hydration heat inhibitor is liquid, by encapsulating a substance that gradually dissolves with water or a substance that gradually dissolves with increasing temperature, such as an oblate, Furthermore, the effect can be enhanced.
[0027]
Of these, dextrin is also commonly referred to as modified starch, which is a hydrolyzed starch. Maldextrin, British gum, pregelatinized starch, or these dextrins are dissolved in water and the residue is dried to be soluble in cold water. A powder from which most of the minute has been removed. A substance obtained by chemically modifying the dextrin with carboxylic acid esterification, carbonic acid esterification, etherification or the like can also be used.
[0028]
Here, the cold water soluble content of dextrin means the amount of dextrin dissolved in distilled water at a temperature of 21 ° C. Specifically, 10 g of dextrin is put in a 200 ml flask and the temperature at 21 ° C. Add 150 ml of distilled water, hold at a temperature of 21 ± 1 ° C. for 1 hour, filter, and evaporate the filtrate to dryness. It is.
[0029]
In the present invention, when dextrin is used as the hydration heat inhibitor, it is preferable that the cold water soluble content at 21 ° C. is 80% or less, and the cold water soluble content is in the range of 10 to 50%. Is more preferable. When the cold water soluble content exceeds 80%, there is a case where sufficient effect of suppressing heat of hydration cannot be obtained.
[0030]
The blending ratio of γ-C ₂ S and the hydration heat inhibitor in the cement admixture of the present invention is not particularly limited, but usually 50 parts or more of γ-C ₂ S in 100 parts of cement admixture. Is preferable, 50 to 98 parts is more preferable, and 70 to 95 parts is most preferable. When γ-C ₂ S is less than 50 parts, a sufficient neutralization suppressing effect may not be obtained, and when it exceeds 98 parts, a sufficient hydration heat suppressing effect may not be obtained. The hydration heat inhibitor is preferably 2 to 50 parts, more preferably 5 to 30 parts. If it is less than 2 parts, a sufficient effect of suppressing the heat of hydration may not be obtained, and if it exceeds 50 parts, curing failure may occur.
[0031]
Although the usage-amount of the cement admixture of this invention is not specifically limited, Usually, 2-15 parts are preferable in 100 parts of cement compositions which consist of a cement and a cement admixture, and 4-9 parts are more preferable. If the amount is less than 2 parts, the effects of the present invention may not be sufficiently obtained. If the amount exceeds 15 parts, strength development may be deteriorated.
[0032]
The cement used in the present invention is not particularly limited, but it is preferable to use a cement containing Portland cement. For example, various Portland cements such as normal, early strength, ultra-early strength, low heat, or moderate heat, and blast furnaces for these Portland cements are used. Examples include various mixed cements obtained by mixing granulated slag, fly ash, or silica, or limestone filler cement obtained by mixing limestone powder with Portland cement.
[0033]
In the present invention, aggregates such as sand and gravel, water reducing agent, AE water reducing agent, high performance water reducing agent, high performance AE water reducing agent, antifoaming agent, thickener, rust preventive agent, antifreezing agent, expansion material, shrinkage reduction 1 type or 2 types or more of agents, polymer emulsions, setting modifiers, cement hardeners, clay minerals such as bentonite or zeolite, and ion exchangers such as hydrotalcite, etc. It is possible to use in the range which does not inhibit.
[0034]
In the present invention, the mixing method of each material is not particularly limited, and the respective materials may be mixed at the time of construction, or a part or all of them may be mixed in advance. Any existing apparatus can be used as the mixing apparatus, and for example, a tilting cylinder mixer, an omni mixer, a Henschel mixer, a V-type mixer, a Nauter mixer, and the like can be used.
[0035]
[Experimental example]
Hereinafter, description will be made based on experimental examples of the present invention.
[0036]
Experimental example 1
A cement admixture was prepared by mixing γ-C ₂ S pulverized to a Blaine specific surface area value of 4,000 cm ² / g and a hydration heat inhibitor at a ratio of 9: 1. Further, cement was added to the cement admixture in the amount shown in Table 1 to obtain 100 parts of a cement composition. Further, using the cement composition, a mortar having a water / cement composition ratio = 50% and a cement composition / sand ratio = 1/3 was prepared, the maximum temperature of the mortar center, the compressive strength at the age of 28 days, The sexual depth was measured. The results are shown in Table 1.
[0037]
<Materials used>
γ-C ₂ S: A raw material obtained by mixing and grinding 2 mol of calcium carbonate as a reagent and 1 mol of silicon dioxide was baked at 1,500 ° C. for 3 hours in an electric furnace, then taken out of the furnace and cooled to synthesize. Further, it was pulverized to prepare a Blaine specific surface area value of 4,000 cm ² / g.
Hydration heat inhibitor ke: Commercial dextrin, 30% cold water soluble content
Cement: Commercial ordinary Portland cement Water: Tap water sand: ISO679 compliant, Standard sand
<Measurement method>
Maximum temperature in the center of the mortar: Put the mortar into a cylindrical polystyrene foam container with a depth of 30 cm, an inner diameter of 13 cm, and a thickness of 10 cm and cure the maximum temperature at the center of the mortar when cured in a constant temperature room at 20 ° C. Measured automatically in pairs and compared calorific value due to hydration.
Compressive strength: 4 × 4 × 16 cm specimens were prepared, and the strength at 28 days of age was measured according to JIS A 1108, casting temperature 20 ° C.
Neutralization depth: 4 x 4 x 16 cm specimens are prepared and cured in water at 20 ° C until the age of 28 days, and then promoted in an environment of 30 ° C, relative humidity 60% and carbon dioxide concentration 10% It became sex. Six months later, the specimen was cut into pieces, a phenolphthalein solution was applied to the cross section, the neutralization depth was measured, and the neutralization inhibitory effect was evaluated.
[0039]
[Table 1]

[0040]
Experimental example 2
A cement admixture prepared by mixing γ-C ₂ S and a hydration heat inhibitor of the type shown in Table 2 at 9: 1 was used, except that 6 parts of the cement admixture was used for 94 parts of cement. Were tested in the same manner as in Experimental Example 1. The results are shown in Table 2.
[0041]
<Materials used>
Hydration heat inhibitor A: Commercial product, sodium gluconate hydration heat inhibitor A: Commercial product, D-glucono-1,5-lactone hydration heat inhibitor C: Commercial product, sorbitol hydration heat inhibitor D: Commercially available product, urea hydration heat inhibitor o: Commercially available product, sodium silicofluoride hydrated heat inhibitor mosquito: Commercially available product, zinc oxide hydrated heat inhibitory agent: Commercially available dextrin, cold water soluble content 0%
Hydration heat inhibitor: Commercial dextrin, 10% cold water soluble
Hydration heat inhibitor ke: Commercial dextrin, 30% cold water soluble content
Hydration heat inhibitor Co: Commercial dextrin, cold water soluble content 50%
Hydration heat inhibitor: Commercial dextrin, cold water soluble content 80%
[0042]
[Table 2]

[0043]
Experimental example 3
Tested in the same manner as in Experimental Example 1 except that 6 parts of a cement admixture composed of γ-C ₂ S and hydration heat inhibitor K in the amount shown in Table 3 and 94 parts of cement were mixed to make 100 parts. . The results are shown in Table 3.
[0044]
[Table 3]

[0045]
Experimental Example 4
Γ-C ₂ S powder having a specific surface area of Blane shown in Table 4 was prepared, and γ-C ₂ S and a hydration heat inhibitor were mixed at 9: 1 to obtain a cement admixture. Cement and cement admixture The test was conducted in the same manner as in Experimental Example 1 except that 6 parts of cement admixture was used in 100 parts of the cement composition. The results are shown in Table 4.
[0046]
[Table 4]

[0047]
【The invention's effect】
The cement admixture and cement composition of the present invention can suppress the occurrence of thermal cracking and can suppress neutralization even in material design with a large amount of unit cement, because the hydration heat value can be significantly reduced. It has the feature of having an effect. The cement admixture and the cement composition of the present invention are suitable for a concrete structure in the field of civil engineering and construction, particularly a concrete structure and a mascon installed in an environment susceptible to neutralization.

Claims (3)

And also contains a Blaine specific surface area 2,000 cm ² / g or more γ-2CaO · SiO ₂ and hydration heat inhibitor, a cement content of γ-2CaO · SiO ₂ is equal to or not less than 50% Admixture.   The cement admixture according to claim 1, wherein the heat of hydration inhibitor is dextrin.   A cement composition comprising cement and the cement admixture according to claim 1 or 2.