JP2001048615A - Cement admixture and cement composition using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce cement with expansivity and sufficient strength even when cured in an unrestrained state by adding a specified amount of a powdery material which is capable of reacting with cement and/or a cement hydrate and has an average particle size of a specified value or lower, to an expansive material. SOLUTION: This cement admixture consisting of an expansive material and a powdery material having a >=20 μm average particle size, contains the powdery material in a 10-2,000 pts.wt. ratio of it to 100 pts.wt. of the expansive material, wherein the expansive material is capable of exhibiting expansivity by forming crystals through its hydration and, more specifically, examples that can be used as the expansive material, are calcium sulfoaluminate based compounds represented by 3CaO.3Al2O3.CaSO4, an aluminum compound and gypsum, and quick lime; as the powdery material, a powdery material capable of reacting with calcium silicate hydrate, slaked lime, or the like, each of which is a constituent of cement or a cement hydrate in a cement hydration process, such as pozzolanic material (fumed silica, fly ash, or the like) or fine-powdery latent hydraulic blast-furnace slag, is used; and also preferably, modified starch is further added to the admixture so that a heat-of-hydration inhibitory effect is brought about.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a cement admixture mainly used in the field of civil engineering and construction, particularly to an expandable cement admixture and a cement composition using the same.

[0002]

2. Description of the Related Art Cement is an indispensable material for forming civil and architectural structures, and it can be said that there is no material capable of forming a large structure at a lower cost than cement. However, there is a problem that a hardened body using cement has cracks. There are several causes for this crack. One is caused by drying shrinkage, and many cement expanders have been proposed for the purpose of compensating for the drying shrinkage.

[0003] The second cause is temperature cracking due to heat of hydration. Conventionally, as a method of reducing the temperature crack, the use of a cement with a low calorific value of hydration, that is, a cement with a low calorific value, has been attracting attention, and a method of using a cement expanding agent and a hydration heat inhibitor in combination has also been proposed. I have. As the low heat cement, Portland cement which has a large amount of blast furnace slag having latent hydraulic properties and fly ash of a pozzolanic substance, a low heat Portland cement with a high content of belite in the cement, etc. are used. It has been known that since the initial heat value of hydration can be significantly reduced, it is particularly effective for suppressing the temperature cracking of mass concrete.

However, since cracks that occur in actual structures are a combination of cracks due to drying shrinkage and temperature cracks, low heat-generating cement and concrete expanding materials are used to comprehensively suppress cracks. May be. The expansion material, 3CaO · 3Al ₂ O ₃ ·
It is known to contain a calcium sulfoaluminate-based compound represented by CaSO ₄ , a calcined lime, a gypsum and other expandable substances. As a hydration heat inhibitor, a method of adding dextrin having a soluble content in cold water (a ratio soluble in distilled water at 21 ° C.) of 10 to 65% by weight (Japanese Patent Publication No. 57-262).
No.) and gelatinization start temperature of 30-60 ° C and 50 ° C
A method of adding a modified starch having a 20% aqueous solution viscosity of 20 to 5000 centipoise (Japanese Patent Application Laid-Open No. 6-305799) is known.

[0005]

However, in the case of an actual structure, except for a special case such as casting in a steel pipe, it is rarely cured in a completely restrained state.
A cement composition using the above-mentioned expanding material for concrete has a higher strength when cured in a restrained state than that in which no expanding material is used, but has a lower strength when cured in an unrestrained state. This is significant when low heat Portland cement is combined with a cement expander.

[0006] Accordingly, an object of the present invention is to provide a cement admixture which gives a cement sufficient expandability and sufficient strength even in curing in an unrestrained state, and a cement composition using the same.

[0007]

In order to solve the above-mentioned problems, the present inventor has made various studies. As a result, an expansible substance and a powder which reacts with the expansible substance with a certain amount of cement and / or cement hydrate are used. It has been found that the use of a combination of the above can provide a cement admixture having excellent expansion performance and capable of imparting high strength to cement even in curing in an unrestrained state, and completed the present invention.

That is, the present invention provides a cement admixture containing 10 to 2000 parts by weight of a powder having an average particle diameter of 20 μm or less, which reacts with cement and / or cement hydrate, based on 100 parts by weight of the expansive substance. Things. The present invention also provides a cement composition containing the cement admixture in an amount of 0.5 to 300 parts by weight based on 100 parts by weight of cement.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION
Has the property of expanding by forming crystals by hydration.
What is necessary is just to show, specifically, 3CaO.3Al
_TwoO_Three・ CaSO_FourCalcium Sulfo Aluminum
Nate compounds, aluminum compounds and gypsum, raw stone
Ash, magnesia, gypsum, etc., one or two types
These are used in combination. Especially included in cement minerals
Quicklime, 3CaO.3Al _TwoO_Three・ CaSO_Four,Nothing
One or more components of water gypsum
Are preferred.

[0010] The powder which reacts with cement and / or cement hydrate refers to a reaction with one or more of calcium silicate hydrate, slaked lime, etc. which are cement or cement hydrate during the hydration of cement. Any powder may be used, and specific examples thereof include pozzolanic substances such as silica fume and fly ash, and blast furnace slag fine powder having latent hydraulic properties.

The powder that reacts with the cement and / or cement hydrate used in the present invention must have an average particle size of 20 μm or less. If the average particle size exceeds 20 μm, the long-term strength will be insufficient. Become.

The amount of the powder that reacts with cement and / or cement hydrate in the cement admixture of the present invention is 10 to 2,000 parts by weight based on 100 parts by weight of the expansive substance. A more preferable amount varies depending on the form to be used.
The amount is 200 parts by weight, and the preferred amount when used as a cement composition is 15 to 1500 parts by weight. 10
If the amount is less than parts by weight, the long-term strength is insufficient, and
If it is larger than the weight part, the initial strength cannot be secured.

[0013] It is more preferable to add a modified starch to the cement admixture of the present invention since an effect of suppressing heat of hydration can be obtained. As the modified starch used in the present invention, potato, sweet potato, corn, tapioca, wheat, and other raw starch are acid-decomposed, oxidized, esterified, etherified, cross-linked, and grafted by copolymerization of a synthetic polymer. For example, those chemically changed are preferable. Among them, those having a water-soluble content of 5% by weight or more at 30 ° C. are preferred. Further, etherified starch into which an alkylammonium salt is introduced is preferable.

[0014] The amount of the modified starch is preferably 0.1 to 1 with respect to 100 parts by weight of the expansible substance in the cement admixture.
00 parts by weight, more preferably 2 to 30 parts by weight. If it is less than 0.1 part by weight, the effect of suppressing hydration heat is insufficient, and if it is more than 100 parts by weight, the initial strength cannot be secured.

The amount of the cement admixture used in the cement composition is 0.5 to 300 parts by weight per 100 parts by weight of cement.
Parts by weight, preferably 2 to 100 parts by weight.
If the amount is less than 0.5 part by weight, the expansion is insufficient, and
If the amount is more than the weight part, the initial strength cannot be secured.

The cement referred to in the present invention includes ordinary Portland cement, Portland cement having high strength, Portland cement having moderate heat, Portland cement having low heat, etc., various mixed cements obtained by mixing blast furnace slag, fly ash, etc. with these Portland cements; In addition, cement containing calcium silicate can be used. Particularly, low heat Portland cement is preferable. The cement composition of the present invention may contain, if necessary, one or more admixtures (materials) such as a hardening accelerator, a retarder, a water reducing agent and a thickener, and one or more aggregates. it can.

[0017]

By using the cement admixture of the present invention, low heat Portland cement can be used.
Good expansion properties and an effect of suppressing heat of hydration can be obtained without reducing strength.

[0018]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

Example 1 As shown in Table 1, an expanding material composed of a fine powder of a mineral substance was blended as a powder that reacts with an expanding substance and cement hydrate.
Each unit amount is 290 kg / m ³ for binder and 815 kg / m for fine aggregate
^3. Concrete was kneaded with coarse aggregate of 1037 kg / m ³ and water of 160 kg / m ³ by replacing the compounded expanding material with cement. A compressive strength test and a length change test were performed using the kneaded concrete. As a result, as shown in the table, it is found that when the expandable substance and a certain amount of the mineral substance fine powder are used in combination, excellent expandable properties and strength can be obtained.

<Materials used> Cement: Low-heat Portland cement manufactured by Taiheiyo Cement Co. Fine aggregate: Ogasa inland sand Coarse aggregate: Iwase crushed stone Water: Tap water Expansive substance: Main constituents Quicklime contained in cement minerals Gypsum (20 kg / m ³ ) Mineral fine powder: Fly ash Average particle size 10.6 μm

<Test Method> Compressive strength test: In accordance with JIS A 1108 “Method for testing compressive strength of concrete”. Length change test: JIS A 6202 “Expanding material for concrete” Reference 1 “Test method for restraining expansion and shrinkage of expanded concrete” (Method A).

[0022]

[Table 1]

Example 2 The level No. of Example 1 was used. The same test as in Example 1 was performed, except that the type and the average particle size of the mineral substance fine powder blended in 1-3 were changed. As a result, as shown in the table, it is found that the use of the fine mineral powder having an average particle diameter of 20 μm or less achieves both excellent expandability and strength.

[0024]

[Table 2]

Example 3 As shown in Table 3, an intumescent material consisting of a fine mineral powder and a modified starch was blended as an intumescent substance and a substance which reacts with cement hydrate. Water / (cement + expansion material) = 0.6, sand /
A mortar adjusted to a kneading temperature of about 20 ° C., in which (cement + expanding material) = 2, expansive material / (cement + expanding material) = 0.1, is made of styrene foam having an inner dimension of 150 × 150 × 200 (mm). The temperature in the center of the mortar when placed in a container and cured in a constant temperature room at 20 ° C. was automatically measured with a thermocouple. A compression strength test was also performed. As a result, as shown in Table 3, it can be seen that when a modified starch is added in addition to the expansive substance and the mineral substance fine powder, not only strength but also an effect of suppressing heat of hydration can be obtained.

<Materials used> Cement: Low heat Portland cement manufactured by Taiheiyo Cement Co., Ltd. Sand: Silica sand from Toyoura Water: Tap water Expansible substance: Main constituents Quicklime, gypsum mineral powder included in cement mineral Fine fly ash: Average grain size Chemically modified starch: cationized starch, dextrin

[0027]

[Table 3]

Claims (3)

[Claims] A powder having an average particle size of not more than 20 μm, which reacts with cement and / or cement hydrate, is added to the expansive substance 10.
A cement admixture containing 10 to 2000 parts by weight with respect to 0 parts by weight. 2. The modified starch (C) is further expanded with an intumescent substance 10.
The cement admixture according to claim 1, which is contained in an amount of 0.1 to 100 parts by weight based on 0 parts by weight. 3. A cement composition comprising 0.5 to 300 parts by weight of the cement admixture according to claim 1 or 2 based on 100 parts by weight of cement.