JPH02145468A - Underwater concrete composition - Google Patents

Abstract

PURPOSE:To improve various properties of concrete and inhibit separation and diffusion of the additives into water by adding specific amounts of an emulsion of PVA-containing ethylene-vinyl acetateunsaturated carboxylic acid copolymer and a PVA gelling agent. CONSTITUTION:The subject underwater concrete composition is composed of 100 pts.wt. of cement, 0.5 to 20 pts.wt., based on the solid components, of an emulsion of a PVA-containing ethylene-PVAc-unsaturated carboxylic acid copolymer, and less than 0.005 pt.wt. of a PVA gelling agent. In this composition, the emulsion improves the strength and various properties such as deformation properties of the concrete, and simultaneously gives cohesion to the concrete, since a part of the surface layer of the emulsion particles dissolves in an alkaline atmosphere. The separation and dispersion of the concrete cannot inhibit with the cohesion, and the combination of the gelling agent can attain the inhibition.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an underwater concrete composition for underwater pouring.

(Conventional technology) Conventionally, when concrete is placed underwater in port construction, coastal construction, etc., separation of cement and aggregate occurs, making it impossible to obtain a hardened material with the desired strength. Problems such as pollution caused by the spread of

In order to solve these problems, the use of natural or synthetic polymers such as methylcellulose or L-polyvinyl alcohol as concrete admixtures (1986-123850
(Japanese Patent Application Laid-Open No. 1982-5), Use of Polyacrylamide
4656), use of specific acrylic monomers (
% KOKAI No. 61-111951) and the like have been proposed.

(Problem to be solved by the invention @) The above-mentioned concrete admixture is added to concrete as a viscosity imparting agent. That is, it is mixed into concrete in order to maintain the cohesive force necessary to prevent the various materials of the concrete from separating and dispersing due to water intrusion when the concrete falls into water.

However, concrete containing the above-mentioned concrete admixture has problems such as delayed setting, lower initial strength, and lower cross-talk properties than concrete that does not contain the above-mentioned concrete admixture.
There were issues such as the negative effects of concrete admixtures on the physical properties of concrete.

On the other hand, it is known that polymer emulsion added to mortar or concrete improves various properties such as strength, deformation characteristics, drying shrinkage, adhesion, and chemical resistance. However, it was not possible to suppress the separation and dispersion of each concrete material in water (for example, "cement").
Admixtures for concrete” Gijutsu Shoin. 861.5.15
issue).

As a result of various studies to solve the above problems, the present inventors have found that a specific polymer emulsion that improves the various properties of concrete has the ability as a cohesive agent for concrete as described above, and that concrete separates in water. The present invention was completed based on the knowledge that this property does not exist.

(Means for Solving the Problems) That is, the present invention provides an amount of ethylene-vinyl acetate-unsaturated carboxylic acid co-emulsion containing polyvinyl alcohol in an amount of 0.5 to 0.5 to 100 parts by weight in terms of solid content, based on 100 parts by weight of cement.
20 Kenhobe, polyvinyl alcohol gelling agent 0.0
This is an underwater concrete composition containing 0.05 parts by weight or more.

The present invention will be explained in detail below.

The ethylene-vinyl acetate-unsaturated carboxylic acid copolymer emulsion (hereinafter referred to as woodwork→lusion) containing polyvinyl alcohol (hereinafter referred to as PVA) according to the present invention is:
When used in concrete, it forms polymer concrete and improves various physical properties of concrete such as strength and deformation characteristics.At the same time, it is dicarboxylated with unsaturated carboxylic acid, one of its components, so it can be used in an alkaline atmosphere. Part of the surface layer of the emulsion particles dissolves (alkali thickening phenomenon), giving concrete cohesive force. However, the cohesive force provided by the emulsion alone is insufficient because it cannot suppress the separation and dispersion of concrete in water. However, since this emulsion contains PVA'4 as an emulsifier, it gels almost instantaneously by adding a PvA gelling agent (hereinafter referred to as gelling agent) and imparts cohesive force to concrete.

Therefore, by using the present emulsion in combination with a gelling agent, a stable concrete composition without separation of materials can be obtained even in water.

The ethylene content in this emulsion is between 10 and 40 parts by weight. If the weight is less than 10 weight, the alkali resistance of the present emulsion will be insufficient, and if the weight exceeds 40 weight, the emulsion state will become unstable, and there is a risk that it will be a problem in actual use.

Examples of the unsaturated carboxylic acid according to the present invention (hereinafter referred to as the present carboxylic acid) include acrylic acid, methacrylic acid, itaconic acid, and crotonic acid, but acrylic acid is generally used. The content of this carboxylic acid in this emulsion is 0
．． It is preferably 1 to 7% by weight.

If it is less than 0.1%, the cohesive force of the concrete will be insufficient and it will separate and disperse in water. On the other hand, if it exceeds 7 1' by weight, the carboxylic acid is water-soluble and may interfere with emulsion polymerization, which is not preferable.

The vinyl acetate (hereinafter referred to as vinyl acetate) content according to the present invention is:
It is necessarily determined by the amounts of ethylene and the carboxylic acid mentioned above.

This emulsion may also contain a copolymerizable additive, if necessary.

Copolymerizable monomers include cyanated vinyl monomers such as acrylonitrile and methacrylate, acrylic acid ester monomers such as methyl acrylate, ether acrylate-butyl acrylate, hexyl acrylate, cyclohexyl acrylate, octyl acrylate, hydroxyethyl acrylate, and glycidyl acrylate. Ether methacrylate・
Methacrylic acid ester monomers such as butyl methacrylate, hydroxyethyl methacrylate, glycidyl methacrylate, vinyl ether monomers such as methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether, phenyl vinyl ether, amide monomers such as acrylamide and methacrylamide, maleimide,
Maleimide monomers such as N-methelmaleimide, N-ethylmaleimide, N-propylmaleimide-N-7enylmaleimide, φN-toluylmaleimide, halogenated olefin monomers such as vinyl chloride and vinylidene chloride, and divinylbenzene and ethylene glycol dimethacrylate.・1゜6-Bunalene gelicold dimethacrylate ・1゜4-Bunalene glycol dimethacrylate ・Propylene glycol dimethacrylate ・Polyethylene glycol dimethacrylate ・Polypropylene glycol dimethacrylate ・Ethylene dalicold diacrylate ・Polyethylene glycol diacrylate ・Cyanuric Polyfunctional vinyl monomers such as triallyl acid, triallyl isocyanurate, trimethylolpropane trimethacrylate, allyl acrylate, allyl methacrylate, vinyl acrylate, and vinyl acrylate.
It's up to the person in charge.

There are no particular limitations on the method for producing the emulsion of the present invention. A known emulsion polymerization method can be used. Although there are no particular limitations on the polymerization conditions, the polymerization temperature is generally 20 to so'c, and examples of the catalyst include persulfates such as potassium persulfate, hydrogen peroxide, and various organic peroxides. In the case of a redox initiation system, a reducing substance such as formaldehyde sodium sulfoxylate may be used in combination.

The emulsifier used in emulsion polymerization contains P as a protective colloid.
Use VA. For emulsion polymerization, a saponification degree of 85 mo/1 or higher and a polymerization degree of 300 to 2.000 opvA are suitable.
The amount used is 3 to 8 parts by weight of the total monomer.

Nonionic surfactants such as polyoxyenaene condensates and polyoxyethylene polyoxypropylene block copolymers, and anionic surfactants such as alkylbenzene sulfonates and lauryl sulfate salts can also be used in combination. It is possible. When a surfactant is used in combination, the amount used is preferably 50 weight lees of the total amount of emulsifier. 5o
If the weight exceeds 100 kg, the cohesive force of the concrete may be insufficient.

The solid content of this emulsion is not particularly limited, but is 40 to 6
Fivefold i=1 is preferable from an industrial standpoint.

The present emulsion of the present invention may have a known pH value, if necessary.
N [It is also possible to use additives such as buffers, antifoaming agents, and preservatives.

The amount of the emulsion of the present invention to be used is 0.5 to 20 parts by weight based on 100 parts of cement in terms of solid content. If it is less than 0.5 parts by weight, the cohesive force of the concrete will be insufficient and it will separate and disperse in water. On the other hand, if it exceeds 20 parts by weight,
The strength of concrete tends to decrease.

Examples of the gelling agent of the present invention include boron compounds and compounds containing sulfate groups, which may be used alone or in combination.

Examples of boron compounds include boric acid, potassium tetraborate, ammonium hydrogen tetraborate, and sodium tetraborate (borax). Any boron compound may be used, but borax is most effective. It is a gelling agent.

Compounds containing sulfate groups are not particularly limited as long as they are soluble in water, and examples include sodium sulfate, potassium sulfate, ammonium sulfate, ferrous sulfate, copper sulfate, zinc sulfate, aluminum sulfate, potassium alum, and Although sulfuric acid and the like can be used, sodium sulfate and ammonium sulfate are particularly preferred.

The amount of the gelling agent of the present invention used is 0.005 parts by weight or more per 100 parts by weight of cement.

If it is less than 0.005 parts by weight, the cohesive force of the concrete will be insufficient and it will separate and disperse in water. Preferably 0.005 to 3.
The amount is about 0 parts by weight, and even if more than that is used, there is no significant improvement in the cohesive force of concrete, which is not only economically disadvantageous, but also requires the use of other concrete admixtures such as AE agents and water reducers. It may have an adverse effect in some cases.

In the underwater concrete composition of the present invention, the present emulsion may be directly mixed with fresh concrete, or may be diluted in water in advance and mixed with fresh concrete. It's 1.
The gelling agent is preferably dissolved in a small amount of water and mixed immediately before pouring. This is because the concrete does not lose its fluidity and becomes viscous as the gelling agent is mixed.

It should be noted that there is no problem in using the mixing line of the present emulsion and gelling agent, and a normal concrete mixing line. The underwater concrete composition of the present invention may be mixed with other concrete admixtures depending on the purpose of construction, such as an AE agent, a water reducing agent, or an AE agent.
It is possible to use a water reducing agent, a fluidizing agent, a shrinkage control agent, a setting/hardening time control agent, a rust preventive agent, a waterproofing agent, a foaming agent, an antifreeze agent, and the like.

1. It is possible to use it in combination with water-soluble polymers such as methylcellulose or PVA, which have traditionally been used as thickeners in underwater concrete, but the amount used should be kept to a minimum depending on the purpose of use and concrete composition. This is desirable.

(Example) The present invention will be explained below with reference to Examples. In addition, "Excellent" indicates the weight person.

Example 1 Contents & The following raw materials were charged into a 101 stainless steel autoclave equipped with an electromagnetic stirrer.

Pure water 3,000g vinegar
B 3.0 0 0 9
Acrylic acid 140 g PVA 155 & Sodium acetate 12 g The internal temperature was raised to 70° C. 1 and ethylene was introduced at a pressure of 75 ICg/crIL2.

0.6 g of ammonium persulfate was added as a catalyst to initiate polymerization. The internal temperature was kept constant by adjusting the jacket temperature. After 10 hours, it was cooled and the contents were taken out. Contents: solid content 52.5% by weight, 30°C with BM type rotational viscosity needle
, with a viscosity of 2+500 cps measured at 30 rpm,
The polymer composition had a vinyl acetate content of 80 parts by weight, an ethylene content of 16 parts by weight, and an acrylic acid content of 4 parts by weight.

Using the concrete composition shown in Table 1, the mixture was mixed as shown in Table 2, and an underwater drop test and a compressive strength test were conducted. The concrete was mixed using an experimental concrete mixer by changing the EVC emulsions and monomer loading ratios of Test/I66.7.16 and 17.

The test method was as follows.

(1) Underwater drop test The concrete mixture was allowed to fall freely in water using a guide pipe into a cylindrical form (diameter 10 cIn 1 height 20 cln) submerged in water 1 screen deep, and the presence or absence of separation of each component of the material was determined. Judgment was made visually.

"B-17J acetic acid) IJum; reagent grade ammonium persulfate: reagent grade borax: reagent grade Na9804: sodium sulfate, reagent grade coating -1 (2) Compressive strength Cylindrical formwork with a diameter of 10 cm and a height of 20 cFn Pour concrete mixture into
The compressive strength was measured on the 7th and 28th days of age.

Materials used> Ethylene: Commercially available vinegar Vinyl: Vinyl acetate, Denki Kagaku Kogyo AA
Niacrylic acid, Mitsubishi Yukai PVA:
Manufactured by Denki Kagaku Kogyo Co., Ltd., trade/product name (effects of the invention) As described above, the present invention provides a concrete composition that is stable even in water and suitable for underwater pouring due to the alkaline thickening action of the linear carboxylated emulsion and the gelling action of the gelling agent. can get things.

Claims (1)

[Claims] (1) For 100 parts by weight of cement, 0.5 to 20 parts by weight of an ethylene-vinyl acetate-unsaturated carboxylic acid copolymer emulsion containing polyvinyl alcohol in terms of solid content, and 0.005 parts by weight of a polyvinyl alcohol gelling agent. An underwater concrete composition containing at least part by weight.