JPS5869760A - Concrete composition for underwater construction - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a concrete composition for underwater construction. More particularly, the present invention relates to underwater concrete compositions having a high degree of resistance to separation.

Underwater concrete construction refers to construction work in which concrete mixed on land is poured into water, but concrete is not mixed during pouring and comes into dynamic contact with water (movement of concrete underwater, exposure of concrete to running water, etc.) ), the concrete easily separates, and the poured concrete has a non-uniform composition and is of poor quality, and the separated cement paste portions diffuse into the water, polluting the water significantly. Therefore, when performing concrete underwater construction, special equipment and construction methods have conventionally been used to avoid dynamic contact between concrete and water. It was considered to be a difficult construction technique that required special consideration during construction work.

The object of the present invention is to provide a practical concrete for underwater construction that has a high degree of separation resistance that does not cause separation even when it comes into dynamic contact with water during construction. It is.

The concrete composition for underwater construction of the present invention includes 1. water-soluble polymeric substance in concrete. This is a concrete ab
When dissolved in mixed water, the viscosity of the aqueous solution (hereinafter referred to as mixed water viscosity) is 2,000 to 100,0 at 20°C.
00 centivoice (hereinafter referred to as CpS), and an antifoaming agent is added in an amount such that the amount of air entrained in the concrete is 10% or less. It is.

The water-soluble polymeric substance used in the present invention is a substance that dissolves in water and imparts crystalline viscosity at a low concentration, and includes a substance called a thickener, such as hydroxyethyl cellulose. , hydroxyalkyl cellulose such as hydroxypropyl cellulose, methyl cellulose, high molecular weight polyethylene oxide (molecular weight from tens of thousands to several million), polyvinyl alcohol, and the like. Further, the above-mentioned mixing water viscosity is the viscosity of an aqueous solution at a concentration when a unit amount of a water-soluble polymer substance added in concrete hydraulic mixing is dissolved in a unit amount of water.

According to the present invention, the water-soluble polymeric substance is added to give concrete a high degree of resistance to separation. Although the types differ, and even if they are the same type, they differ depending on the molecular weight, degree of substitution, etc., and the level varies depending on the mix of concrete. As a result of various investigations, we found that the amount of water-soluble polymer material added was determined by mixing water with a viscosity of 2 at 20°C.
,000 to ioo, ooocps was found to be necessary. This requirement is one of the features of the present invention.・This viscosity value is 2,00 D.
When using an additive amount that gives a smaller b value than cps, the effect of imparting separation resistance is insufficient;
Even if an additive amount exceeding 000 cp6 is used, the effect of imparting separation resistance reaches its upper limit, and unfavorable side effects such as a decrease in workability and an increase in concrete cost become noticeable.

Within the above range of addition amounts, the greater the viscosity of the mixing water, the greater the effect of imparting separation resistance.
A more preferable addition amount range is 0 to 50,000.

In the past, there have been examples in which certain types of water-soluble polymeric substances (for example, methylcellulose) have been used for purposes such as improving the pumpability of concrete, suppressing breathing, and improving finishability. The amount (referring to the amount added expressed in weight% based on the cement in the concrete) is about 0.01 to 0.1%, and this is based on the viscosity of water mixed at 20 ° C in the present invention. If displayed, the maximum is 200-300 CF21 usually 100 cps
It can be seen that the amount of water-soluble polymer material added in the present invention far exceeds the amount conventionally known for use in concrete IJ-containers. Only by adding such a large amount can a sufficient degree of resistance be imparted to a concrete composition for underwater construction.

Furthermore, in the present invention, the antifoaming agent is added in an amount such that the amount of air entrained in the concrete is 10% or less; Examples of antifoaming agents include tributyl phosphate, nonionic antifoaming agents, and silicone antifoaming agents. The amount added should be sufficient to adjust the amount of air entrainment to an appropriate level, and this depends on the amount of air entrainment to be reduced, the type of water-soluble polymer substance used in combination, the mix of concrete, The amount used varies depending on the type, brand, etc. of the foaming agent, but is generally about 0.01 to 0.5%.

By adding the antifoaming agent as described above, the amount of air entrained when using the concrete composition for underwater construction of the present invention can be adjusted to an appropriate level for practical underwater construction concrete IJ-.

As described above, the present invention provides a high degree of separation resistance and a practically appropriate level of air entrainment by using a water-soluble polymer substance and an antifoaming agent in combination in specific addition ranges.・Since the concrete composition for underwater construction of the present invention has extremely high separation resistance, it is possible to directly pour concrete into water, which has conventionally been impossible. Underwater construction can be carried out without causing separation, as in the case where the concrete is allowed to fall freely to the pouring site and poured. In addition, even when placing underwater concrete through transport pipes from above the water surface to the pouring site, special consideration must be given to the use of special mechanisms to strictly avoid dynamic contact with water. Since there is no need to carry out the above work, the construction is significantly simplified compared to the conventional technology. Furthermore, since separation does not occur even if exposed to running water after pouring, it is possible to omit incidental work such as running water cut-off construction prior to pouring, which was previously required, which greatly contributes to simplifying the construction and reducing construction costs. Furthermore, by using the concrete composition for underwater construction of the present invention, it is possible to prevent the occurrence of water pollution caused by the diffusion of cement paste in concrete into water, which could not be avoided in the past.

The water-soluble polymeric substance and antifoaming agent used in the present invention are:
One type selected from the group of compounds belonging to these may be used, or two or more types may be used in combination. Preferred water-soluble polymer substances are hydroxyalkyl cellulose, methyl cellulose, and high molecular weight polyethylene oxide, and a combination of hydroxyethyl cellulose and methyl cellulose is preferred.・Water bath polymer substances and antifoaming agents are used in concrete. At the time of kneading, they may be added separately, or they may be added in the form of a blended admixture. Further, these may be added in the form of a powder or an aqueous solution.・In addition, when designing the mix of the concrete composition for underwater construction of the present invention, it is preferable to respect various regulations regarding concrete for underwater construction.7 The present invention also has high separation resistance and high self-leveling. The purpose of the present invention is to provide a concrete composition for underwater construction that has both properties and properties.

In general, concrete should be laid down and compacted at regular intervals after being poured. If compaction is not performed, the quality of the concrete after hardening will be inferior to the design standard, and the quality will vary greatly. Confidence in the quality of the concrete is greatly impaired, and concrete pour joints also become defective. Underwater concrete construction also requires leveling and compaction, but because the concrete is cast underwater, leveling and compaction work is not required unlike when concrete is cast on land. These tasks are extremely difficult and are generally omitted. For this reason, the reliability of the quality of underwater concrete has been low, and this has been one of the problems with underwater concrete.

In order to reduce the need for leveling work as much as possible, and to minimize the decrease in reliability of concrete products and the deterioration of pour joints due to omission of compaction, the fluidity of concrete to be constructed underwater should be increased. It is preferable. However, in conventional underwater concrete, increasing fluidity increases separability, and it has not been possible to achieve both local fluidity and separation resistance at a satisfactory level within a practical blending range.

The concrete IJ-concrete composition for underwater construction, which is prepared by adding specific amounts of a water-soluble polymeric substance and an antifoaming agent, provided by the present invention has extremely high separation resistance as described above, so a concrete water reducing agent is added. Even if its fluidity is increased, it exhibits satisfactory separation resistance and can achieve both high fluidity and separation resistance. Therefore, the present invention further provides a concrete composition for underwater construction that has both high fluidity and high separation resistance. These admixtures have the ability to significantly increase performance, and include those known as cement dispersants, concrete fluidizers, concrete plasticizers, etc. Examples include lignin sulfonated salts and modified products thereof, formalin condensates of naphthalene sulfonic acid or its derivatives, formalin condensates of creosote oil sulfonates, formalin condensates of the same or different aromatic sulfonic acids, and sulfonated formalin condensate of melamine,
These include oxycarboxylic acid salts, polyols, polyoxyethylene alkyl ethers, condensates of unsaturated dicarboxylic acids and diene compounds, formalin condensates I of ligninsulfonic acid and naphthalenesulfonic acids, and the like.

The usage number of these concrete water reducing agents varies depending on the type of agent, the target level of fluidity after addition, the mix of concrete, etc. Furthermore, depending on the type of agent, undesirable side effects such as abnormal delay in setting may occur. The appropriate level is determined by taking this into account.

For example, in the case of oxycarboxylate, about 0.03 to 0.
1%, about 0.2-2.0% in the case of a formalin condensate of naphthalene sulfonic acid or its derivatives or a formalin condensate of sulfonated melamine, and about 0.1-0.6 in the case of lignin sulfonate. The standard is to add it in an amount of %. These concrete water reducing agents may be used alone or in combination of two or more.

By appropriately selecting the type and amount of concrete water reducer to be added, it is possible to obtain concrete with a level of fluidity that is in the self-leveling range, which is a level of fluidity that has not previously been recognized. What is self-leveling property here?
It is important that the heaped concrete has a high degree of fluidity so that it flows and spreads on its own and finally forms a nearly flat surface, and that the aggregate and the cement burst part do not separate at this time.

Preferred examples of combinations of water-soluble polymeric substances and concrete water reducing agents that have both high separation resistance and self-leveling properties include hydroxyalkyl cellulose, methyl cellulose, and molecular weight polyethylene oxide.
Water viscosity (20°C) for mixing ridges or mixtures of two or more types
Addition amount of 2,000 to 100,000 cps and 0.5 to 1.5 of formalin condensate of naphthalene sulfonic acid or its derivatives, formalin condensate of sulfonated melamine
% usage amount or 0.6-0.
It is a combination with a usage amount of 5%.・More preferably, a mixture of one or more of hydroquine alkylcellulose, methylcellulose, and high molecular weight polyethylene oxide (particularly a mixture of hydroxyethylcellulose and methylcellulose) has a water viscosity. (20C) 5,000
~50,000 cps addition 1 and a combination of 0.7-1.2% usage of formalin condensate of sulfonated melamine and 0.4-05% usage of O-golignin sulfonate. .

Note that some concrete water reducers have some air-entraining properties, but when using such concrete water reducers, the amount of antifoaming agent should be adjusted so that the amount of air entrainment in the concrete is at an appropriate level of 10% or less. Adjusting the additive f・The concrete composition for underwater construction of the present invention, which has been given a high degree of fluidity to the extent that it exhibits self-leveling properties by adding a concrete water reducing agent, does not need to be compacted after being placed in water. However, the reliability of the concrete quality does not deteriorate much, and the pouring joints do not deteriorate too much. In addition, the effective casting area per unit of the transport pipe (the area where a substantially flat casting surface can be obtained without leveling) is significantly increased, so the casting work is simplified.

The concrete water reducing agent may be added at the same time as the water-soluble polymeric substance and the antifoaming agent, or may be added after the former two have been added, if necessary. The concrete composition for underwater construction of the present invention, which has increased fluidity by adding a concrete water reducer, has a small drop in slump, so it can be kneaded and mixed at a concrete manufacturing factory located far from the construction site and transported. It is also possible to use it in a manner in which it is used as a liquid.

Table 2 shows test results for various combinations of water bathing polymeric substances and antifoaming agents, and Table 6 shows test results for increasing fluidity by adding a concrete water reducer to these combinations.

The materials, test methods, etc. used in this example are as follows.

(1) Water-bathable polymer material (abbreviated as WLP) (a) Methyl cellulose (abbreviated as MC) hi-Metrose 9'08
H-15000, 2% aqueous solution 20℃ viscosity 10,500c
ps, Shin-Etsu Chemical Product (b) and Droxyethyl Cellulose (HEc abbreviation) Natr0801250 HHR
% 1% aqueous solution 20°C viscosity 2,670 Cp8% Herculene product (c) Shima molecular weight polyethylene oxide (abbreviated as PEO) Alcox -1301% aqueous solution 20°C viscosity 1,26
0 cps, Kaisei Chemical ■Product) Polyacrylamide (abbreviated as FAA) Orufrock AP-11% aqueous solution at 20°C Viscosity 1.2! IQ cp
s, organo■ Back product (2) Finishing foam agent (a) Nonionic antifoaming agent (abbreviated as SN) SN deformer 14 HP, 5ANNOPCO product @) Tributyl phosphate (abbreviated as TBP) reagent (3 ) Concrete water reducer (abbreviated as WRA) (a)
Formalin condensate of sulfonated melamine (abbreviated as S'MF) Melment, Showa Denko ■Product (b) Formalin condensate of naphthalene sulfone family (N
(abbreviated as SF) Mighty, Kao Soap ■Products (c) Calcium lignin sulfonate (abbreviated as LNG) A cement dispersant-grade product manufactured from sulfite pulp waste liquid (b) Sodium gluconate (abbreviated as GL) Reagent (4) Separation resistance test method: 9 tubes were placed in a transparent acrylic resin cylinder with a diameter of 19 mm and a height of 1 m.
Fill water up to the height of the tank and place about 8 tons of concrete in it.
The cement was poured in 6 times using a no-doscop and allowed to fall into the water, and the state of the cement flowing out during the dropping was observed, and the turbidity (ppm) of the water was measured after the feeding was completed. Determine resistance. The judgment result is indicated by the following symbol.

◎: Excellent, ○: Good, X: Poor (5) Judgment of self-leveling property The concrete dropped in the separation resistance test was allowed to stand until the flow stopped (5 minutes), and the leveling property was observed using only its own weight. In addition, when performing the slump test, the flow condition of the concrete after lifting the slump cone and the average value of the spread diameter of the concrete when the flow stops were also determined (referred to as flow). It helped. The judgment results are shown in the following a-pi numbers.

◎; Agitation Q: Good (6) Measurement of compressive strength Specimens of 10F x 20tM+ were prepared for both the concrete that had been mixed and the concrete that had been dropped into water in the upper J self-separation resistance test, and the compressive strength was measured. was measured.

(C) Concrete mix The basic mix of concrete is shown in Table 1. - Materials used: Cement: Fūwaku Portland Cement (Onoda) Fine aggregate: Oi Yosan FM=2.71 Specific gravity -2.61 Coarse aggregate: Ome Crushed stone MS=20 order FM=6.90 specific gravity=2.
68 Table 1 The test results are shown in Table 2.6.0 From the above table, regardless of the type of water-soluble polymer substance, 20
If the amount added makes the water viscosity less than 2,00 Q cps, the separation resistance will be poor, and if the self-leveling property is good, the compressive strength ratio between normal and water will be small ( In other words, it can be seen that even without compaction, the decrease in strength is small.

The amount of air entrained when using an antifoaming agent is, for example, 1.7.5% in the case of &5 and 15.4% in the case of A5.
It was very large. In addition, the viscosity of a 2% aqueous solution of MC (2
0℃) is 19,000 cps and 2.850 cps
A test was also conducted in combination with antifoaming agent SN, but
Similarly, the separation resistance was good in the range where the viscosity of the mixing water was 2ρ00 cps or more.

If FAA is used in conjunction with a concrete water reducing agent to increase fluidity, the separation resistance will disappear, so care must be taken.

Claims (1)

[Claims] 1) Conc IJ-) K water-soluble polymer substance, when dissolved in concrete mixing water, 20
It is added in such an amount that it exhibits a viscosity of 2,000 to 10,000 centibodies at ℃, and an antifoaming agent is added in such an amount that the amount of air entrained in the concrete is 10% or less. A concrete composition for underwater construction, characterized by
,000 to 100,000 centivoice, an antifoaming agent is added in an amount such that the amount of air entrained in the concrete is 10% or less, and a concrete water reducing agent is added. A concrete composition for underwater construction, characterized by comprising the following: