JPH07206505A - Concrete composition resistant to separation in water - Google Patents

Abstract

PURPOSE:To improve the separation resistance of components of a concrete composition by compounding a water-soluble cellulose ether, hollow microspheres and a defoamant. CONSTITUTION:This concrete composition resistant to separation in water can be produced by weighing respective specific amounts of cement, aggregate and water, weighing about 0.1-5wt.% (based on water) of one or more kinds of nonionic cellulose ester having a 1% aqueous solution viscosity of 1,000-50,000cP such as hydroxyethylcellulose and hydroxypropylmethylcellulose, about 0.1-5.0wt.% (based on the cement) of hollow microspheres of a polymer such as PS having a diameter of about <=200mum, especially <=507mum, about 0.02-0.5 pts.wt. (based on 1.0 pt.wt. of the water-soluble cellulose ether) of a defoamant such as tributyl phosphate and about 1-5wt.% (based on the cement) of a high-performance water-reducing agent composed of an isoprene compound, etc., and kneading these weighed components with a pan-type mixer, etc.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an underwater non-separable concrete composition having both high fluidity and resistance to material separation in water.

[0002]

2. Description of the Prior Art When pouring concrete mixed in advance into water, the concrete comes into contact with water and separates,
The cast concrete may be uneven.
In order to prevent such a phenomenon and ensure a predetermined mechanical property and watertightness, water-soluble cellulose ether is added.

The water-soluble cellulose ether is excellent not only in resistance to material separation but also in fluidity. In addition to hydroxypropylmethylcellulose and hydroxyethylcellulose, hydroxyethylmethylcellulose and the like are the main components of the inseparable admixture in water. Widely used as.

Here, in general, concrete containing a water-soluble cellulose ether such as hydroxypropylmethyl cellulose is difficult to remove air bubbles entrapped in the concrete due to the interfacial activity of the hydroxyl group of cellulose and various substituents that react with it. Become.

If a large amount of air bubbles are mixed, the air amount deviates from the standard and the compressive strength is lowered. Therefore, an antifoaming agent such as tributyl phosphate is used together to control the air amount. ing.

[0006]

However, the air bubbles mixed by the water-soluble cellulose ether are relatively large,
And it is non-uniform. Further, since the amount of air is controlled by the defoaming agent, unlike the AE agent which is an air entraining agent, the bubble diameter is generally relatively large and it is not effective in freezing resistance. Therefore, even if an antifoaming agent is used, it is difficult to secure good quality air bubbles, and it is generally said that concrete using water-soluble cellulose ether is inferior in frost damage resistance (underwater non-separable concrete Symposium on Freezing Resistance and Underwater Non-separable Concrete, 161-166, August 1990; Basic Research on Freezing Resistance of Underwater Non-separable Concrete, same as above, 167-174, August 1990 ).

Therefore, the underwater non-separable concrete is actually limited in construction in cold regions where there is a risk of freezing in winter, construction in tidal zones, etc. Concrete design and construction guidelines (draft), Japan Society of Civil Engineers, May 1991).

An object of the present invention is to provide a concrete composition which is excellent in freezing damage resistance while ensuring material separation resistance and fluidity in water by adding a water-soluble cellulose ether. .

[0009]

In view of the above situation, the inventors of the present invention have ensured material separation resistance and fluidity by adding a water-soluble cellulose ether, and further, have air equivalent to ordinary concrete. As a result of diligent study on a concrete composition capable of obtaining frost damage resistance in an amount, concrete having a controlled amount of air by an antifoaming agent, combined with polymer type hollow microspheres, has various frost damage resistance I have found that I can get concrete.

That is, in order to achieve the above object, the present invention is characterized in that a hollow microsphere and an antifoaming agent are blended in an underwater non-separable concrete composition containing a water-soluble cellulose ether.

The water-soluble cellulose ether used in the present invention is used for imparting tackiness to concrete to prevent material separation such as aggregates, and is a nonionic cellulose ether such as hydroxyethyl cellulose (HE).
C) and hydroxyalkyl celluloses such as hydroxypropyl cellulose (HPC) may be mentioned.
In addition, hydroxyethyl methylcellulose (HEM
C), hydroxypropyl methylcellulose (HPM
C), hydroxyethyl ethyl cellulose (HEEC)
Mention may be made of hydroxyalkylalkylcelluloses such as Among such nonionic water-soluble cellulose ethers, HPMC and HEC are particularly preferable because they have excellent fluidity. In addition, you may use these water-soluble cellulose ethers individually by 1 type or in combination of 2 or more types.

The viscosity of the water-soluble cellulose ether is not particularly limited, but the viscosity of a 1% aqueous solution measured with a B type viscometer is 1,000 to 50,000.
If it is 0 cP, the object of the present invention can be sufficiently achieved.

The amount of the water-soluble cellulose ether added varies depending on the type, molecular weight, degree of substitution, unit cement amount, setting environment, etc., but generally 0.1 to 5% by weight based on the mixing water. Preferably, by adding 0.5 to 2% by weight, a concrete having excellent resistance to material separation in water can be obtained.

The polymer-based hollow microspheres used in the present invention are made of a polymer spherical elastic membrane and have a diameter of 200.
It is desirable that the thickness is less than or equal to μm, preferably less than or equal to 50 μm. If the particle size is large, there is the disadvantage that the compressive strength will decrease even with the same amount added.

Although the material is not limited, polystyrene, polyvinylidene chloride, polymethylmethacrylate, acrylic resin and the like can be used.

The amount of addition varies depending on the required freeze-thaw resistance, concrete material / mixture, amount of water-soluble cellulose ether added, amount of defoaming agent, etc. It is preferably about 5.0% by weight.

The defoaming agent used in the present invention is to reduce the amount of air in concrete which increases due to the use of water-soluble cellulose ether and suppress the decrease in compressive strength, and is used as a defoaming agent for cement or gypsum. The existing one can be used. For example, Pluronic type defoaming agent [Pluronic L61 (manufactured by Asahi Denka Kogyo)], tributyl phosphate (reagent), silicone type defoaming agent [KN
73 (manufactured by Shin-Etsu Chemical Co., Ltd.)], acetylene glycol derivatives and the like are used.

The amount of the defoaming agent used varies depending on its type, but is preferably 0.02 to 0.5 part by weight with respect to 1.0 part by weight of the water-soluble cellulose ether.

In the present invention, the intended purpose is achieved by adding the hollow microspheres instead of the AE water reducing agent. However, a water reducing agent may be added in order to further improve characteristics such as fluidity and self-leveling property.

The water reducing agent used in the present invention includes a high performance water reducing agent, an AE water reducing agent, and the like in addition to an ordinary water reducing agent. Among these, the high performance water reducing agent is preferable. As the high-performance water reducing agent, a highly condensed triazine compound, a formalin condensate of melamine sulfonate, a polycarboxylic acid salt derivative, a modified lignin sulfonate compound, an amino sulfonic acid polymer compound, a naphthalene sulfonate Formalin condensates, isoprene compounds, etc.
Among these, highly condensed triazine compounds, formalin condensates of melamine sulfonates, polycarboxylic acid salt derivatives, modified lignin sulfonate compounds and isoprene compounds are preferable. These water reducing agents are generally 1 to 5% by weight, preferably 1 to 3% by weight, based on the cement binder.
Used by weight percent.

The cement binder of the present invention includes, in addition to ordinary Portland cement, fast-strength Portland cement, moderate heat Portland cement, white Portland cement, super fast-strength Portland cement, blast furnace cement, silica cement, fly ash cement, and blast furnace. In addition to inorganic powders such as slag and fly ash, stone powder, silica fume and other substances that have a posolane reaction are also included.
It is used in one kind or a combination of two or more kinds selected from these.

Representative examples of the water-separable concrete mixture composition according to the present invention are as follows. Cement binder 300-500 kg / m ³ Aggregate 1650-1900 kg / m ³ Water 150-240 kg / m ³ Water-soluble cellulose ether 1.0-4.0 kg / m ³ Hollow microspheres 0.2-10.0 kg / m ³ Defoaming agent 0.05 to 0.4 kg / m ³ Water reducing agent ^{3 to} 15 L / m ³

The composition of the present invention can be produced according to a conventional method. For example, in a raw cement plant or on-site, cement binder, aggregate, water-reducing agent and water are mixed with water-soluble cellulose ether, hollow microspheres and silica. It is produced by adding a foaming agent and stirring and mixing. The hollow microspheres and defoamers can be used either by premixing with the water-soluble cellulose ether or by direct addition to concrete.

[0024]

EXAMPLES Hereinafter, specific embodiments of the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited thereto. (Examples 1 to 5 and Comparative Examples 1 to 4) Materials and test methods used in each example are as follows. 1. Water-soluble cellulose ether: Hydroxypropylmethyl cellulose (1% viscosity 4,500 cP, H in the table)
(Abbreviated as PMC) 2. Hollow microspheres: ADDIMENT [Hollow Microsp
heres, abbreviated as HMS in the table, trade name, Heidelberger Cement (manufactured by HEIDELBERGER ZEMENT)) 3. Defoaming agent: tributyl phosphate (first-grade reagent) 4. Fine aggregate: Sea sand from Tarumae City, Tomakomai City, (Water absorption 1.17
%, Specific gravity 2.60, F.I. M. 2.67) 5. Coarse aggregate: crushed stone from Miharu, Otaru (water absorption 1.17%,
Specific gravity 2.68) 6. Cement: Ordinary Portland cement (specific gravity: 3.
16) 7. High-performance water reducing agent: Reobuild UC-150 (manufactured by Pozzolis & Co., abbreviated as UC-150 in the table) 8. Air entraining agent: No. 775 S (Pozoris product, abbreviated as AE agent in the table) 9. Formulation Example underwater nondisjunction concrete: water cement ratio 45.0% fine aggregate ratio 45.4% cement 389kg / m ³ fine aggregate 809kg / m ³ Coarse aggregate 976kg / m ³ water 175 kg / m ³ water-soluble cellulose ether 1.75 kg / m ³ hollow microspheres 3.89kg / m ³ defoamer 0.09 kg / m ³ superplasticizer 9.0 L / m ³ 10. Kneading: Using a pan mixer, the total kneading time was 3 minutes and 30 seconds. 11. Concrete test, test method: 1) Slump flow test (concrete slump flow test method (draft), JSCE) 2) Air volume (JIS A 1128) 3) Compressive strength test (JIS A 1108) 4) Freeze-thaw test (Freezing and thawing test method for concrete, JSCE)

Examples 1 to 5 are water-separable concretes having different water-cement ratios, and hollow microspheres are added to all of them, so that the compressive strength is not adversely affected and a high durability index is obtained. It can be seen that the frost damage resistance is excellent. Examples 2 to 4 are examples in which the addition amount of the hollow microspheres was changed, and it can be seen that frost damage resistance is excellent when 0.5% or more is added to cement.

In comparison with this, Comparative Examples 1 to 4 are cases where no hollow fine particles were added. Comparative Example 1 is a case where the air entraining agent is not used, and there is no adverse effect on the compressive strength, but the frost damage resistance is extremely poor. Comparative Example 2 is a case where no antifoaming agent is added,
Due to the air entrainment of the water-soluble cellulose ether, the amount of air is significantly increased and the compressive strength is reduced. Comparative Example 3
Is a case where an air entraining agent is added to improve frost resistance and the amount of air is increased, but frost resistance is improved,
Since there is a large amount of air, there is the disadvantage that the compressive strength is poor.

The above results are shown in Table 1.

[0028]

[Table 1]

[0029]

Industrial Applicability As described above, by using a water-soluble cellulose ether, an antifoaming agent and hollow fine particles as essential components, a concrete composition having excellent frost damage resistance while ensuring material separation resistance and fluidity. Can be obtained.

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Claims (1)

[Claims] 1. An in-water non-separable concrete composition comprising a water-soluble cellulose ether and hollow microspheres and an antifoaming agent.