JP6636351B2 - Underwater non-separable concrete composition and cured product thereof - Google Patents

Description

  The present invention relates to a water-inseparable concrete composition and a cured product thereof.

  Generally, when constructing a bridge (pier) or breakwater on a coast, ocean, port or river, concrete is directly poured into water in civil engineering construction work. However, at that time, the strength of the concrete structure may be reduced by washing away the cement component with water. For this purpose, a non-separable underwater concrete composition in which a thickener such as a methylcellulose type, an acrylic type or a gum type is mixed with concrete is used for construction.

  As such a water-inseparable concrete composition, Patent Literature 1 proposes a water-inseparable concrete composition containing a thickener containing cellulose ether, dutan gum, polyacrylamide and bentonite. Patent Literature 2 proposes a cement composition for grouting in water containing an expanding material, a thickener, and a water reducing agent for use in water. This cited reference 2 discloses, as an example of the thickener, a cellulose-based, ethylene oxide-based, acrylic-based, or polyvinyl alcohol-based thickener.

  As the thickener used in the water-immiscible admixture used for the water-immiscible concrete, a cellulose-based, acrylic, or gum-based thickener is typical. By using these water-immiscible admixtures, material separation preventing effect and self-leveling effect are exhibited, cement particles do not separate and disperse even in water, and self-filling property is obtained, so workability can be secured. . Among these thickeners, gum-based thickeners are characterized in that the addition of an admixture has a small effect on the fluidity of concrete, so that self-filling concrete can be easily manufactured.

  However, when a galactomannan-based thickener, which is known as a gum-based thickener, is applied to water-inseparable concrete, the water-insoluble property tends to be insufficient. Difficult to be satisfied. As a conventionally used galactomannan-based thickener, guar gum is generally used. However, guar gum has hardly been reported as an in-water non-separable concrete for the above reasons (Patent Document 3). ).

JP 2014-37329 A JP-A-07-138055 JP-A-06-135750

  Under such a background, the present invention provides a novel underwater non-separable concrete composition which can simultaneously satisfy both fluidity and underwater inseparability while using a galactomannan-based thickener. is there.

  The present invention also provides a hardened non-separable concrete composition obtained by curing the above-mentioned non-separable concrete composition.

  According to one aspect of the present invention, a water-inseparable concrete composition comprising cement and a thickener comprising galactomannan, wherein the galactomannan has a mannose / galactose ratio of more than 4 Is provided.

  According to another aspect of the present invention, there is provided a hardened non-separable concrete material, which is obtained by hardening the underwater non-separable concrete composition.

  According to another aspect of the present invention, for a non-separable water-insoluble concrete composition, comprising galactomannan and an antifoaming component, wherein the galactomannan has a mannose / galactose ratio of more than 4. An additive is provided.

  The underwater non-separable concrete composition according to the present invention can satisfy both fluidity and underwater non-separability at the same time. Therefore, the underwater-non-separable concrete composition according to the present invention has sufficient fluidity and can be easily filled in a mold formed in water, and the filled composition is separated and dispersed in water. Therefore, a desired cured product can be obtained without depending on the underwater environment. In addition, the cured body of the non-separable concrete obtained by curing the underwater non-separable concrete composition according to the present invention has a small influence of the underwater environment at the time of formation. It can be suitably used when constructing bridges (piers), breakwaters, etc. on coasts, oceans, ports or rivers.

  In the present specification, “water-inseparable concrete” refers to underwater concrete in which a material separation resistance in water is increased by mixing a thickener or the like. In addition, in this specification, the "water-inseparable concrete composition" (hereinafter may be simply referred to as "composition") means a composition of water-inseparable concrete before curing, while "water-inseparable concrete composition" The “non-separable concrete hardened body” (hereinafter sometimes simply referred to as “hardened body”) means a hardened non-separable concrete composition in water.

  The contents of the present invention will be described in detail below.

<Underwater inseparable concrete composition>
The non-separable concrete composition in water according to the present invention contains cement, a thickener composed of galactomannan, and other components as required. Hereinafter, each component will be described below. In this specification, “unit amount (kg / m ³ )” means the amount of each raw material used when producing 1 m ³ of concrete.

[cement]
Various cements can be used as the cement used in the present invention, and for example, Portland cement and mixed cement can be used. Such Portland cements include, for example, various Portland cements such as ordinary, fast, super fast, low heat and moderate heat. Examples of the mixed cement include various mixed cements in which fly ash, blast furnace slag, silica fume, limestone fine powder, and the like are mixed. Examples of the cement other than the above include ordinary cement type eco-cement having no quick-setting property. Any one of these cements can be selected and used, but two or more cements may be used in combination.

The amount of cement in the composition according to the present invention can be appropriately set depending on the type of cement used and the unit water amount, but is preferably from 300 to 550 kg / m ³ in unit amount.

[Thickener]
The composition according to the invention comprises a thickener consisting of galactomannan. Galactomannan is a polysaccharide composed of a unit in which galactose is bonded as a side chain to a linear main chain composed of mannose. It can be obtained as a natural product from endosperm of legume seeds. Galactomannan is collected from various plants, and the ratio between mannose and galactose changes depending on the type of plant. For example, a natural polysaccharide obtained from guar seed is called guar gum, and the ratio of main chain mannose to side chain galactose in guar gum is 2: 1. Other commonly known galactomannans include tara gum with a mannose to galactose ratio of 3: 1 and locust bean gum with a 4: 1 ratio.

  The galactomannan used in the present invention has a ratio of mannose to galactose, that is, a mannose / galactose ratio of more than 4. Among such galactomannans, those having a mannose / galactose ratio of 5 are preferred. Examples of such galactomannans include cassia gum, which is a natural product containing a polysaccharide as a main component and obtained by crushing the seeds of Ebisugusamodoki. Cassia gum is the most preferable because it is easily available and has excellent handling properties. In the present invention, the galactomannan needs to have a mannose / galactose ratio of more than 4, but may be a mixture of two or more galactomannans. That is, even if a mixture of one having a high mannose / galactose ratio and one having a low mannose / galactose ratio is used, it is sufficient if the mannose / galactose ratio in the entire galactomannan is more than 4. Galactomannan does not need to be a natural product, but may be a purified or modified natural product or a synthetic product. In the present invention, the galactomannan needs to have a mannose / galactose ratio of more than 4, but it is preferably 4.8 or more, more preferably 5 or more. In the present invention, these ratios mean the ratio of the constituent units, that is, the molar ratio.

The amount of thickener consisting of galactomannan in unit dose is preferably from 2.5~5.0kg / ^{m 3,} more preferably 3.5~4.5kg / ^{m 3.} By setting the compounding amount of the thickener to 2.5 kg / m ³ or more, it is possible to sufficiently impart non-separation in water to concrete, and by setting the compounding amount to 5.0 kg / m ³ or less, coagulation is significantly increased. Delay can be prevented.

  The composition according to the invention may contain a thickener other than galactomannan. Such a thickener is not particularly limited as long as it is generally used for concrete, but one that does not impair the effects of the present invention is desired. Examples of such thickeners include cellulose-based thickeners, acrylic-based thickeners, and gum-based thickeners other than galactomannan. Examples of the cellulosic thickener include carboxymethyl cellulose, alkyl cellulose, hydroxyalkyl cellulose, and hydroxyalkylalkyl cellulose. Examples of the acrylic thickener include carboxyvinyl polymers. Examples of the gum thickener include xanthan gum and gellan gum.

[Other components]
The in-water inseparable concrete composition according to the present invention can contain the following components as required.

(Defoaming agent)
The composition in the present invention preferably further contains an antifoaming component, that is, an antifoaming agent. As the defoaming agent used in the present invention, a defoaming agent for cement generally used in the production of mortar and concrete can be used as it is. Specific examples of such antifoaming agents include mineral, ester, amine, amide, polyether, and silicon antifoaming agents.

  The addition amount of the defoaming agent is preferably 0.05 to 1.0% by mass, more preferably 0.1 to 1.0% by mass, based on the total mass of the thickener.

  The method of adding the defoaming agent to the composition is not particularly limited, and for example, there is a method of adding and kneading together with other compounding materials in a concrete plant, or a method of adding and kneading last at a concrete construction site. Alternatively, a thickener and an antifoaming agent may be mixed in advance.

(Dispersant)
Preferably, the composition according to the invention further comprises a dispersant. As the dispersant used in the present invention, a dispersant for cement generally used in the production of mortar or concrete can be used as it is. Examples of such a dispersant include a water reducing agent, an AE water reducing agent, a high performance water reducing agent, a high performance AE water reducing agent, and a fluidizing agent. Specific examples include dispersants such as melaminesulfonic acid-based dispersants, polycarboxylic acid-based dispersants, and naphthalenesulfonic acid-based dispersants. Among these, a polycarboxylic acid-based dispersant is particularly preferred.

  The amount of the dispersant added is preferably 1.0 to 3.5% by mass, more preferably 1.5 to 3.0% by mass, based on the total mass of the cement powder.

  The method of adding the dispersant to the composition is not particularly limited, and for example, there is a method in which the dispersant is added and kneaded together with other compounding materials in a concrete plant, or a method in which the dispersant is added last and kneaded in a concrete construction site.

(aggregate)
Preferably, the composition according to the invention further comprises a bone agent. The aggregate used in the present invention is not particularly limited, and any of fine aggregate and coarse aggregate used in the production of ordinary concrete can be used. Such fine and coarse aggregates include, for example, river sand, sea sand, mountain sand, crushed sand, artificial fine aggregate, slag fine aggregate, recycled fine aggregate, silica sand, river gravel, land gravel, crushed stone, artificial coarse Aggregate, slag coarse aggregate, recycled coarse aggregate and the like can be mentioned.

The blending amount of the aggregate is 1,500 to 2,000 kg / m ³ in unit amount, and further, 1,600 to 1,800 kg / m ³ is the balance of suppressing heat generation and drying shrinkage and ensuring workability. It is preferred in terms of.

  The ratio (s / a) of the volume of the fine aggregate to the volume of the total aggregate is usually 35 to 50%, and preferably 40 to 45% from the viewpoint of ensuring workability.

(water)
The composition according to the invention is kneaded with water. The blending amount of water (unit water amount) is preferably 150 to 250 kg / m ³ from the viewpoint of increasing material separation resistance. It is preferable to use a concrete mixer for kneading.

  The mass ratio (W / C) of water (W) and cement (C) is usually 40 to 65%, and is preferably 45 to 60% from the viewpoint of reducing hydration heat generation and securing compressive strength. .

(Other admixtures)
Further, the composition according to the present invention may contain other components (admixtures (materials)) that can be used, for example, in mortar and concrete as long as the effects of the present invention are not substantially impaired. Specific examples of such a component include a shrinkage reducing agent, an expanding material, a water retention agent, a rust inhibitor, an air entraining agent, a waterproof material, a water repellent, a whitening inhibitor, a setting regulator, a curing accelerator (material ), Pigments, fibers, silica fume, slag, fly ash and the like.

<Underwater non-separable hardened concrete>
The hardened concrete that is inseparable in water according to the present invention can be obtained by curing the above composition. Curing can be performed by any method. For example, the composition may be kneaded, and the kneaded product may be poured into a mold or the like and then cured to cure. The cured product according to the present invention can be cured either in water or in the air.

<Additive for non-separable concrete composition in water>
The additive for a water-insoluble separable concrete composition according to the present invention contains the galactomannan and an antifoaming component. Such an additive can produce an in-water inseparable concrete composition only by mixing it with ordinary cement, and by changing the mixing ratio of the additive to cement, the physical properties of the concrete composition can be improved. It is convenient because it can be adjusted. Such an additive may contain, in addition to the galactomannan and the defoaming component, the components exemplified as the admixture.

  Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the examples.

<Preparation of underwater non-separable concrete composition>
The method for producing a water-inseparable concrete composition according to the present invention will be described.
First, the materials used are shown below.
Water (W): Tap water
Cement (C): ordinary Portland cement
Fine aggregate (S): Mountain sand from Shizuoka Prefecture
Coarse aggregate (G): Crushed stone from Ibaraki Prefecture
Thickener (V): (1) Cassia gum (mannose / galactose ratio = 5)
(2) Gua gum (mannose / galactose ratio = 2)
(3) Tara gum (mannose / galactose ratio = 3)
(4) Locust bean gum (mannose / galactose ratio = 4)
Antifoaming agent (F): Polyether dispersant (D): Polycarboxylic acid dispersant

環境温度２０℃にて、コンクリートミキサを用いて各材料を上記のコンクリート配合で練り混ぜて水中不分離性コンクリート組成物を製造した。また、増粘剤の種類と配合量、ならびに消泡剤および分散剤との配合比を変更して、実施例２〜７および比較例１〜３の組成物も調製した。各組成物の配合比は表２に示す。なお、これらの組成物における目標スランプフローは５００±３０ｍｍ、目標空気量は４．０％以下である。

Table 1 shows the concrete composition in Example 1.

At an environmental temperature of 20 ° C., each material was kneaded with the above-mentioned concrete mixture using a concrete mixer to produce a water-inseparable concrete composition. The compositions of Examples 2 to 7 and Comparative Examples 1 to 3 were also prepared by changing the type and amount of the thickener and the mixing ratio of the defoamer and the dispersant. The composition ratio of each composition is shown in Table 2. The target slump flow of these compositions is 500 ± 30 mm, and the target air amount is 4.0% or less.

<Measurement of slump flow>
The slump flow of the composition was measured in accordance with JIS A 1150 “Slump flow test method for concrete”. At the time of the measurement, a slump cone made of a metal specified in JIS A 1101 was used, and a flat plate made of steel was used.

<Measurement of air volume>
The air content of the composition was measured in accordance with JIS A 1128 "Test method by pressure of air content of fresh concrete-air chamber pressure method".

<Measurement of suspended solid amount>
The amount of the suspended substance when the composition is put into water is determined in accordance with JSCE-D 104-2013 “Quality standard for non-separable admixture for water for concrete (draft)” which is a standard set by the Japan Society of Civil Engineers. It was measured. The measurement method is briefly described below.

  First, 500 g of a sample of the composition was weighed into a charging container having a predetermined shape, and was charged into 800 ml of distilled water in ten portions. After placing all the samples in water, they were allowed to stand for 3 minutes, and about 600 ml of the supernatant was gently collected. The collected water was mixed uniformly, and a part thereof was accurately measured and taken as test water. The test water was filtered, the residue (also referred to as a residue) was dried, and the weight was measured. The suspended substance amount (mg / l) was calculated by dividing the residue weight (mg) by the test water amount (l).

<Measurement of strength ratio in water and air>
The water-in-air strength ratio of the cured product of the composition was measured in accordance with JSCE-D 104-2013 “Specification of water-inseparable admixture for concrete quality standard (draft)” which is a standard set by the Japan Society of Civil Engineers. At this time, the preparation of the test piece in the air was performed in accordance with JIS A 1132 “8. How to prepare a test piece for concrete strength test”, and the test piece in the water was prepared in accordance with JSCE-F 504 “Inseparable in water. How to Make Cylinder Specimen for Concrete Compressive Strength Test ". The compressive strength of each of the obtained specimens was measured in accordance with JIS A 1108 “3. Test method for compressive strength of concrete”. The outline of these procedures is shown below.

(Preparation of specimen in air)
A sample obtained by mixing the raw materials having the mixing ratios shown in Table 2 and kneading them using a mixer was poured into a filling portion of a mold (inner diameter 100 mm, height 200 mm). The concrete was left for 24 hours until the concrete hardened sufficiently, and then the mold was removed to obtain a concrete specimen. Thereafter, the test specimen was cured in water at 20 ° C. and cured until the age of 28 days, and then used in the compressive strength test.

(Preparation of specimens in water)
Tap water was filled to fill the water tank, and the mold was placed in the water tank such that the opening of the mold faced upward. The same mold as that used for the preparation of the test piece in the air was used. The raw materials having the compounding ratios shown in Table 2 were mixed and kneaded using a mixer, and the sample was divided into about 10 times and gently charged into the mold. The mold filled with the sample was gently taken out of the water, allowed to stand in the air for 15 minutes, and then moved to a curing place and cured for 24 hours. Thereafter, the specimen was removed from the mold, immediately started to be cured in water at 20 ° C., and after being cured until the age of 28 days, it was used for the compressive strength test.

(Compression strength test)
A compressive strength test was performed on each specimen obtained in air and water. The compressive strength of each of the obtained specimens was calculated, and the underwater / air strength ratio was obtained. The water-in-air strength ratio is the percentage obtained by dividing the compressive strength of a specimen obtained in water by the compressive strength of a specimen obtained in air.

The results obtained in the above test are as shown in Table 3.

  As is clear from the results, it is found that the amount of suspended substances is smaller in the examples using galactomannan (cassia gum) having a mannose / galactose ratio exceeding 4 as a thickener as compared with the comparative example. When the amount of the suspended substance is 50 mg / l or less, it can be said that there is sufficient inseparability in water, but all the compositions according to the present invention exceed this level. Further, it can be seen that the slump flow of each of the examples using cassia gum as a thickener is close to the target value and has sufficient fluidity. That is, by using Cassia gum as a thickener, a composition satisfying both inseparability in water and fluidity can be obtained. Furthermore, the compositions of these examples have a small difference between the in-air strength and the underwater strength, and also achieve an excellent underwater-air strength ratio.

  In addition, as compared with Example 3 using the composition containing no antifoaming agent, Example 1 or 2 using the composition containing the antifoaming agent has a small amount of air and excellent slump flow. Aerial strength and underwater strength are also high. Therefore, it can be seen that the composition containing the antifoaming agent shows more preferable performance.

Claims (6)

An in-water-inseparable concrete composition comprising cement and a thickener comprising galactomannan, wherein the galactomannan is cassia gum having a mannose / galactose ratio of 4.8 or more . The content of the thickener is a 2.5~5.0kg / ^{m 3} in unit dose composition of claim 1. The composition according to claim 1 or 2 , further comprising an antifoaming agent. The composition according to claim 3 , wherein the content of the antifoaming agent is 0.05 to 1.0% by mass based on the total mass of the thickener. A hardened non-separable concrete underwater product obtained by curing the non-separable underwater concrete composition according to any one of claims 1 to 4 . And a galactomannan and defoaming component, the Garakutoman'na down, characterized in that the mannose / galactose ratio is 4.8 or more cassia gum, water nondisjunction concrete composition additives.