JP6400426B2 - Underwater inseparable concrete composition and cured body thereof - Google Patents

Description

  The present invention relates to an underwater inseparable concrete composition and a cured body thereof.

  Normally, when constructing bridges (piers), breakwaters, etc. on the coast, ocean, harbor or river, concrete is directly placed in the water during civil engineering construction. However, at that time, the cement component is washed away with water, which may cause water pollution of rivers and the like, and decrease in strength of the concrete structure. Therefore, the construction uses a non-separable concrete composition in water in which a thickener such as methylcellulose, acrylic and gum is mixed with concrete.

  As such an underwater inseparable concrete composition, Patent Document 1 proposes an underwater inseparable concrete composition containing a thickener containing cellulose ether, detan gum, polyacrylamide and bentonite. Patent Document 2 proposes a cement composition for an underwater grout, which is intended to be used in water and contains an expanding material, a thickener, and a water reducing agent.

JP 2014-37329 A Japanese Patent Application Laid-Open No. 07-138055

As described above, the underwater inseparable concrete composition has been widely used in the industry so far, but a general underwater inseparable concrete composition has a large unit water amount (about 220 kg / m ³ ). It is common to use thickeners mixed with cellulose-based 2.4-2.6 kg / m ³ or acrylic-based about 3.3-3.5 kg / m ³ . However, these thickeners are expensive, and the current underwater non-separable concrete composition, which uses a large amount of thickener, costs about 3 to 4 times as much as ordinary ready-mixed concrete (green concrete). There is a problem that it becomes high. Therefore, an underwater non-separable concrete composition that is economical and highly practical is desired.

  Furthermore, since the underwater non-separable concrete composition has a large amount of unit water, it has a property that the resulting cured body has a large amount of shrinkage when dried. For this reason, underwater inseparable concrete hardened bodies should be used in places where the influence of drying shrinkage is large, such as the tidal zone at the bridge pier (where the sea is at sea level at high tide, but where it is dried at low tide) Is difficult. Therefore, when using an underwater inseparable concrete hardened body for the pier, it is necessary to place an underwater inseparable concrete composition before the tidal zone, and to place a different type of concrete composition from above. There was a problem that cost and labor were increased.

  In response to such problems, the present inventors have recently obtained a high water inseparability even when the content of the thickener is reduced by using an expansion material having a specific surface area (brane value) of a certain level or more. In addition, they have obtained knowledge that shrinkage during drying after curing can be suppressed. The present invention has been made based on such knowledge.

  Therefore, the present invention provides an underwater inseparable concrete composition that exhibits high underwater inseparability with a smaller amount of thickener than conventional underwater inseparable concrete compositions and has reduced drying shrinkage after curing. It is to provide.

  Moreover, this invention provides the underwater non-separable concrete hardening body by which drying shrinkage reduced by hardening the said underwater inseparable concrete composition was reduced.

According to one aspect of the invention,
Cement,
An expansion material;
An underwater inseparable concrete composition comprising a thickener,
The expansion material has a Blaine specific surface area of 4,000 cm ² / g to 7,000 cm ² / g , the blending amount of the expansion material is 12 to 28 kg / m ³ in a unit amount, and the viscosity increase The compounding amount of the agent is 0.8 to 3.0 kg / m ^{3 in} unit amount.
An underwater non-separable concrete composition is provided.

  Moreover, according to the other aspect of this invention, the underwater inseparable concrete hardening body obtained by hardening | curing the said underwater inseparable concrete composition is provided.

  According to the present invention, an underwater inseparable concrete composition that exhibits high underwater inseparability with a smaller amount of thickener than a conventional underwater inseparable concrete composition and has reduced drying shrinkage after curing. Can be obtained.

  In the present specification, “underwater inseparable concrete” refers to underwater concrete in which material separation resistance in water is increased by mixing a thickener or the like. Further, in this specification, “high inseparability in water” is in accordance with JSCE-D 104-2013 “Quality Standard for Underwater Inseparability for Concrete (Draft)”, which is a standard established by the Japan Society of Civil Engineers. The amount of suspended solids is 50 mg / L or less, and the strength ratio in the air at the age of 28 days after curing is 80% or more. If the amount of suspended solids is 50 mg / L or less, the separation of concrete in water can be effectively suppressed, and if the underwater strength ratio is 80% or more, strength development in water can be maintained. it can. In this specification, “underwater inseparable concrete composition” means a composition of underwater inseparable concrete before curing, while “underwater inseparable concrete cured body” means underwater inseparable concrete composition. The hardened concrete composition is meant.

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

<Unseparable concrete composition in water>
The underwater inseparable concrete composition according to the present invention includes an expansion material having a specific surface area (brane value) of a certain level or more, and thus has a higher viscosity and less underwater inseparability than a conventional underwater inseparable concrete composition. Indicates. Therefore, cost can be held down rather than the conventional underwater non-separable concrete composition. Furthermore, since the composition has reduced drying shrinkage after curing, it can also be used for tidal zones in bridge piers. Accordingly, the entire pier can be formed using the underwater inseparable concrete composition according to the present invention, which eliminates the need to switch the type of concrete in the middle of the pier, thereby greatly reducing costs and labor. it can. The drying shrinkage after curing can be measured according to JIS A 1129 “Method for measuring change in length of mortar and concrete”, and the rate of change in length after curing at the age of 6 months is 800 × 10 ^−. It is preferable that it is ⁶ or less from a viewpoint of preventing the crack by shrinkage | contraction.

The underwater inseparable concrete composition according to the present invention includes cement, an expansion material, and a thickener. Each component will be described below. In the present 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. For example, Portland cement or mixed cement can be used. Examples of such Portland cement include various Portland cements such as normal, early strength, ultra early strength, low heat and moderate heat. Examples of the mixed cement include various mixed cements mixed with fly ash, blast furnace slag, silica fume, limestone fine powder, and the like. Moreover, as cement other than the above, the normal cement type eco-cement etc. which do not have quick hardening are mentioned. Any one of these cements can be selected and used, but two or more cements may be used in combination.

Although the compounding quantity of the cement in the underwater non-separable concrete composition by this invention can be suitably set with the kind of cement to be used, and unit water quantity, it is preferable that it is 300-550 kg / m < ³ > by unit quantity.

[Expandable material]
Expansion material used in the present invention, the particle size is expanding material of 4,000cm ² / g~7,000cm ² / g in Blaine specific surface area. On the other hand, the conventionally used expansion material has a particle size of about 2,500 to 3,500 cm ² / g. If the particle size is too high, the expandability tends to be difficult to obtain, so far, an expander having a Blaine specific surface area of 4,000 cm ² / g or more has generally not been used. However, the present inventors have found that by expanding material the appropriate quantity formulation Blaine specific surface area of 4,000cm ² / g~7,000cm ² / g, less thickening than conventional water nondisjunction concrete composition It has been found that an underwater inseparable concrete composition can be obtained which shows high inseparability in water by the amount of the agent and has reduced drying shrinkage after curing. The expandable material used in the present invention preferably has a grain size of 4,500 to 6,000 cm ² / g in terms of the specific surface area of branes. The specific surface area of the brain is determined by the change time of the solution head by using the brain air permeation device specified in JIS R 5201 (cement physical test method) to determine the speed of air passing through the cell filled with cement. It is calculated by comparing with a standard sample.

The amount of expanding material are 12~28kg / ^{m 3} in a unit volume, and preferably from 15 to 25 kg / ^{m 3.} When the blending amount is set to 12 kg / m ³ or more, the effect of reducing drying shrinkage is increased, and when the blending amount is set to 28 kg / m ³ or less, the excessive expansion is suppressed and the compressive strength is reduced. Can be prevented.

  As the type of the expansion material used in the present invention, various expansion materials can be used as long as the particle size is within the above range. Specifically, a lime-based expansion material and a calcium sulfoaluminate-based expansion material are used. can do. Among these, lime-based expansion materials are particularly preferable from the viewpoint of reaction rate.

  The lime-based expansion material is composed of an expansive calcined product containing free quick lime (CaO) and gypsum. The expansive calcined product containing free calcined calcination is calcined with calcined raw materials such as calcium carbonate, slaked lime and quick lime, siliceous raw material, alumina raw material, iron oxide raw material and gypsum raw material in an electric furnace or rotary kiln. Can be obtained. The obtained expandable fired product is pulverized and classified by a ball mill or the like to adjust the particle size. As for the gypsum, the powdered powder may be mixed with the pulverized product of the expandable fired product and the mixer, or the gypsum and the expanded fired product may be mixed and pulverized. Various types of gypsum can be used, but anhydrous gypsum is preferable, and type II anhydrous gypsum is more preferable.

[Thickener]
The thickening agent used in the present invention is not particularly limited as long as it is usually used in concrete, but it imparts thickening to the concrete, and the material separation resistance when thrown into water. It is desirable to have an excellent quality. Examples of such thickeners include cellulose thickeners, gum thickeners, and acrylic thickeners. Examples of the cellulose thickener include carboxymethyl cellulose, alkyl cellulose, hydroxyalkyl cellulose, and hydroxyalkylalkyl cellulose. Examples of the acrylic thickener include carboxyvinyl polymer. Examples of gum thickeners include locust bean gum, xanthan gum and gellan gum. Of these, cellulose thickeners are particularly preferred.

The blending amount of the thickener is preferably 0.8 to 3.8 kg / m ³ as a unit amount. By setting the blending amount of the thickener to 0.8 kg / m ³ or more, it is possible to sufficiently impart water inseparability to the concrete, and by setting it to 3.8 kg / m ³ or less, the setting is greatly reduced. Can be prevented from being delayed. A more preferable blending amount of the thickener is 1.4 to 2.2 kg / m ³ .

[Other components]
The underwater non-separable concrete composition according to the present invention can contain the following components as required.

(Dispersant)
The underwater inseparable concrete composition according to the present invention preferably further includes a dispersant. The dispersant used in the present invention is a dispersant for cement that is generally used in the production of mortar and concrete. 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 melamine sulfonic acid dispersants, polycarboxylic acid dispersants, and naphthalene sulfonic acid dispersants. Of these, polycarboxylic acid-based dispersants are particularly preferable.

  The addition amount of the dispersant is preferably 1.0 to 3.5% by mass with respect to the total weight of the powder such as cement and expansion material, and from the viewpoint of securing required fluidity and initial strength, 1.5% is preferable. -3.0 mass% is more preferable.

  As a method for adding a dispersant, 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 at the end of a concrete construction site. is not.

(aggregate)
The aggregate used in the present invention is not particularly limited, and any of fine aggregates and coarse aggregates used in ordinary concrete production can be used. Examples of such fine aggregate and coarse aggregate include river sand, sea sand, mountain sand, crushed sand, artificial fine aggregate, slag fine aggregate, recycled fine aggregate, quartz sand, river gravel, land gravel, crushed stone, artificial coarse Examples include aggregates, coarse slag aggregates, and recycled coarse aggregates.

The blending amount of the aggregate is 1500 to 2000 kg / m ^{3 as} a unit amount, and 1600 to 1800 kg / m ³ is preferable from the viewpoint of balance between suppression of heat generation and drying shrinkage and ensuring workability.

  Further, 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 underwater inseparable concrete composition according to the present invention is kneaded with water. The blending amount of water (unit water amount) is preferably 150 to 250 kg / m ³ , because it increases material separation resistance and suppresses drying shrinkage. It is preferable to use a concrete mixer for kneading.

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

(Any admixture)
Furthermore, the underwater inseparable concrete composition according to the present invention may contain other components (admixtures (materials)) that can be used for mortar and concrete, for example, within a range that does not substantially lose the effects of the present invention. good. As such components, specifically, shrinkage reducing agents, water retention agents, rust prevention agents, air entraining agents, antifoaming agents, foaming agents, waterproofing materials, water repellents, whitening prevention agents, anti-caking agents, Examples thereof include curing accelerators (materials), pigments, fibers, silica fume, slag, fly ash and the like.

<Uncured hardened concrete in water>
The underwater inseparable concrete cured body according to the present invention can be obtained by curing the underwater inseparable concrete composition. Curing can be carried out by any method. For example, the underwater inseparable concrete composition may be kneaded, and the kneaded product may be poured into a mold or the like and then cured. The underwater separable concrete cured body according to the present invention can be cured either in water or in the air, and the strength ratio of the underwater air in the air is JSCE-D 104-2013 “Concrete Water” which is a standard defined by the Japan Society of Civil Engineers. When measured according to the “medium non-separable admixture quality standard (draft)”, it shows a high value of 80% or more. Therefore, the underwater inseparable concrete cured body according to the present invention has a small difference in strength when cured in water and in the air, and constructs bridges (piers), breakwaters, etc. on the coast, ocean, harbor or river. In this case, it can be suitably used. Furthermore, since the drying shrinkage is reduced as compared with the conventional hardened water-unseparable concrete body, there is an advantage that it can be used for a tidal zone in a bridge pier.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited by an Example.

<Preparation of expansion material>
A mixture of quartzite, bangshale shale, iron oxide, anhydrous gypsum and industrial quicklime was fired at 1400 ° C. using an electric furnace and pulverized to produce an expansive fired product containing 50% by mass of free quicklime. . Main minerals other than the free quick lime contained in the expansive calcined product are trilime silicate (3CaO.SiO ₂ ) and anhydrous gypsum (CaSO ₄ ). The produced expandable fired product was pulverized by a ball mill to obtain three types of pulverized expandable fired products having different Blaine specific surface areas. By mixing 80 parts by mass of these expansive calcined products and 20 parts by mass of type II anhydrous gypsum (Brain specific surface area of 7,000 cm ² / g), lime-based expansive materials (No. 1 to 3) were produced. The Blaine specific surface area of each of the produced expansion materials is as follows.
・ Expandable material 1: 5,080 cm ² / g
・ Expandable material 2: 4,110 cm ² / g
・ Expandable material 3: 3,540 cm ² / g

<Preparation of underwater inseparable concrete composition>
Subsequently, the manufacturing method of the underwater non-separable concrete composition by this invention is demonstrated. First, the materials used for production are summarized in the table below.

The above materials were used and kneaded with a concrete mixer at an environmental temperature of 20 ° C. to produce an underwater inseparable concrete composition. Table 2 shows the composition of each water-inseparable concrete composition produced. In addition, the compounding quantity of the dispersing agent was represented by% with respect to the weight of the amount of powders (P: cement + expansion material). That is, the blending amount (%) of the dispersant is a value obtained by the following formula.
Dispersant content (%) = {dispersant (g) / [cement (g) + expansion material (g)]} × 100

  Various characteristics of the underwater inseparable concrete composition described in Table 2 and its cured body were evaluated. Details will be described below.

<Measurement of suspended solids>
The amount of suspended solids when an underwater inseparable concrete composition is put into water is determined by JSCE-D 104-2013 “Quality Standard for Underwater Inseparable Admixture for Concrete (Draft)” ”In accordance with the measurement. The measurement method is briefly shown below.

  First, 500 g of a sample of an inseparable concrete composition in water was weighed out into a predetermined shaped charging container and charged into 800 mL of distilled water in 10 batches. All the samples were put into water and allowed to stand for 3 minutes, and about 600 mL of the supernatant was gently collected. The collected water was uniformly mixed, and a part of the water was accurately measured to obtain test water. The test water was filtered, the residue (also referred to as filtrate) was dried, and the weight was measured. The amount of suspended solids (mg / L) was calculated by dividing the weight of the residue (mg) by the amount of test water (L).

<Measurement of underwater strength ratio>
The strength ratio of underwater inseparable concrete composition in the air is in accordance with JSCE-D 104-2013 “Underwater inseparable admixture quality standard for concrete (draft)”, which is a standard established by the Japan Society of Civil Engineers. And measured. At that time, preparation of the specimen in the air is performed in accordance with JIS A 1132 “8. How to make specimen for concrete strength test”, and specimen preparation in water is JSCE-F 504 “Unseparable in water. This was carried out in accordance with “How to make a cylindrical specimen for compressive strength test of concrete”. The compressive strength of each obtained specimen was measured according to JIS A 1108 “3. Compressive strength test method for concrete”. The outline of these procedures is shown below.

(Preparation of specimen in the air)
A sample in which the raw materials having the blending ratios shown in Table 2 were mixed and kneaded 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 was fully cured, and then the mold was removed to obtain a concrete specimen. Thereafter, the specimen was cured in water at 20 ° C. and cured until the age of 28 days, and then used for the compressive strength test.

(Production of specimens in water)
Tap water was filled into the tank, and the mold was placed in the tank so that the opening of the mold faced upward. The same mold as that used for producing the specimen in the air was used. A sample in which the raw materials having the blending ratios shown in Table 2 were mixed and kneaded using a mixer was divided into about 10 times and gently put into the mold. The mold filled with the sample was gently taken out of the water and allowed to stand in the atmosphere for 15 minutes, and then moved to a curing place and cured for 2 days. Thereafter, the specimen was removed from the mold, immediately started curing at 20 ° C., and was cured until the age of 28 days before being used for the compressive strength test.

式中、f_ｃは圧縮強度（Ｎ／ｍｍ^２）を示し、Pは試験で得られた最大荷重（Ｎ）を示し、ｄは測定した供試体の直径（ｍｍ）を示す。 (Compressive strength test)
For each specimen obtained in air and water, a compressive strength test was performed as follows. First, the diameter and height of the specimen used for measurement were measured accurately. Thereafter, the surface of the specimen was cleaned, placed in the center of the pressure plate, and a load was applied at a uniform speed so as not to give an impact to the specimen. The speed at which the load was applied was adjusted so that the increase in the degree of compressive stress was 0.6 ± 0.4 N / mm ² per second. After the specimen started to suddenly deform, the load speed adjustment was stopped, the load was continuously applied until the specimen broke, and the maximum load indicated until the specimen was broken was recorded. Based on the data obtained by the test, the compressive strength of the specimen was calculated using the following equation.

In the formula, f _c represents the compressive strength (N / mm ² ), P represents the maximum load (N) obtained in the test, and d represents the diameter (mm) of the measured specimen.

  The compressive strength of each specimen obtained in the air and water was calculated according to the above procedure, and the water-to-air strength ratio was determined. The underwater strength ratio is expressed as a percentage by dividing the compressive strength of the specimen obtained in water by the compressive strength of the specimen obtained in the air.

<Measurement of the rate of change in length of 6 months of age>
The 6-month length change rate of the cured product obtained by curing the underwater inseparable concrete composition was measured in accordance with JIS A 1129 “Method for measuring mortar and concrete length change”. A specimen having a size of 100 mm × 100 mm × 400 mm was used for the test. A gauge plug was attached to the specimen, and the change in length was measured after storage for 6 months in an environment of a temperature of 20 ° C. and a relative humidity of 60%. The length change rate is preferably as the numerical value is smaller.

Table 3 shows the results obtained in the above test.

ブレーン比表面積が低い膨張材（膨張材３）を用いた比較例２では、懸濁物質量が６７ｍｇ/ｌと大きく（すなわち、水中不分離性に劣る）、さらに水中気中強度比の値が７７％と低いことが分かった。一方、ブレーン比表面積が４，０００ｃｍ^２/ｇ以上の膨張材（膨張材１および２）を用いた実施例１および４では、懸濁物質量が５０ｍｇ/ｌ以下と小さく（すなわち、水中不分離性に優れる）、水中気中強度比の値が大きく、かつ材齢６カ月における長さ変化率も低減された、バランスの良い水中不分離性コンクリートが得られることが分かった。 <Comparison due to difference in Blaine specific surface area of expanded material>
Based on the above results for Examples 1 and 4 and Comparative Example 2, the influence on various properties due to the difference in the Blaine specific surface area of the expansion material was evaluated (Table 4).

In Comparative Example 2 using an expandable material (expanded material 3) having a low Blaine specific surface area, the amount of suspended solids is as large as 67 mg / l (that is, inferior inseparability in water), and the value of the strength ratio in the air It was found to be as low as 77%. On the other hand, in Examples 1 and 4 using the expansion material (expansion materials 1 and 2) having a Blaine specific surface area of 4,000 cm ² / g or more, the suspended solid amount was as small as 50 mg / l or less (that is, non-separated in water). It was found that a well-balanced underwater non-separable concrete having a high value of the strength ratio in water and in the air and having a reduced rate of change in length at the age of 6 months can be obtained.

膨張材の単位量が１０ｋｇ／ｍ^３と少ない比較例３では、懸濁物質量、水中気中強度、長さ変化率のいずれの特性も良くないことが分かった。また、膨張材の単位量を３０ｋｇ／ｍ^３に増加させた比較例４では、材齢２８日の気中及び水中における圧縮強度が大きく低下しており好ましくない。一方、実施例１、２および３では、全ての特性において良好な結果が得られた。 <Comparison due to difference in unit amount of expansion material>
Based on the above results for Examples 1, 2 and 3, and Comparative Examples 3 and 4, the effect on the various properties due to the difference in the unit amount of the expansion material was evaluated (Table 5).

It was found that in Comparative Example 3 where the unit amount of the expansion material was as small as 10 kg / m ³ , none of the characteristics of the suspended solid amount, the strength in the air and the length change rate were good. Further, in Comparative Example 4 in which the unit amount of the expanded material was increased to 30 kg / m ³ , the compressive strength in the air and water at 28 days of age was greatly reduced, which is not preferable. On the other hand, in Examples 1, 2 and 3, good results were obtained in all characteristics.

増粘剤の種類によって好適な単位量は異なるが、０．８〜３．０ｋｇ／ｍ^３で良好な水中不分離性コンクリート組成物が得られることが分かった。 <Comparison by the type of thickener and difference in unit amount>
Based on the above results for Examples 7 and 8 and Comparative Examples 5 and 6, the effect on the various properties due to the difference in the type and unit amount of the thickener was evaluated (Table 6).

Although the suitable unit amount differs depending on the type of the thickener, it was found that a good in-water non-separable concrete composition can be obtained at 0.8 to 3.0 kg / m ³ .

Claims (5)

Cement,
Lime-based expansion material,
An inseparable concrete composition in water containing a cellulosic thickener,
Blaine specific surface area of the lime expansion material is 4,000cm ² / g~7,000cm ² / g,
The amount of the lime-based expansion material is 12 to 28 kg / m ³ in unit quantity ,
The blending amount of the cellulosic thickener is 0.8 to 3.0 kg / m ³ in unit amount , and
An inseparable concrete composition in water, characterized in that the amount of suspended solids evaluated according to JSCE-D 104 is 50 mg / l or less .   The underwater non-separable concrete composition according to claim 1, further comprising a dispersant. The underwater non-separable concrete composition according to claim 1 or 2, wherein a blending amount of the cellulosic thickener is 1.4 to 2.2 kg / m ³ in a unit amount . The strength ratio in water and air at the age of 28 days after curing is 80% or more, and the rate of change in length at the age of 6 months is 800 × 10 ⁻⁶ or less. The underwater non-separable concrete composition according to any one of 3 above.   The underwater inseparable concrete hardening body obtained by hardening the underwater inseparable concrete composition as described in any one of Claims 1-4.