JPH08245254A - Low-strength and high-packability concrete composition - Google Patents

Abstract

PURPOSE: To obtain a concrete compsn. having excellent fluidity and packability, low strength and excellent executability by specifying the water cement ratio, thickener contact and high-performance water-reducing agent of the concrete compsn. CONSTITUTION: Cement, such as normal Portland cement and high-early-strength Portland cement, and aggregate, such as natural aggregate, artificial aggregate and by-product aggregate, all of which are the aggregate having the max. grain size of about 20mm, of 70 to 83wt.% of the total weight of the compsn., are compounded in such a manner that the ratio of the cement attains 100 to 150% and the compressive strength of the resulted concrete attains 50 to 120kgf/cm<2> . Thickeners, such as cellulose thickeners including hydroxyethyl cellulose, etc., acrylic thickeners or polyvinyl alcohol thickeners, are compounded thereto at 0.25 to 0.75 pts.wt. per 100 pts.wt. cement-component and a high-performance water-reducing agent, such as polyglycol ester, is compounded thereto at 1.0 to 2.0 pts.wt. per 100 pts.wt. cement and the mixture is uniformly stirred and compounded in such a manner that the slump flow value attains 45 to 65cm.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a concrete composition having a low strength and a high filling property, which has a low strength, is excellent in fluidity and filling property and can be used as a concrete material for an underground continuous wall, a retaining wall, etc. Regarding things.

[0002]

2. Description of the Related Art Conventionally, when constructing a concrete continuous wall, it was common to install a form such as a rocking pipe or a partition plate in the joint, but due to the recent progress of excavating machines, the form is installed. The cutting joint construction method etc. which constructs a continuous wall without it are implemented. In this construction method,
Since no time is required to install the formwork, the construction period can be shortened accordingly. That is, it is a method of constructing a leading element at a constant interval without providing a formwork, and then constructing a trailing element in the gap between the leading elements, wherein when the trailing element is constructed, It is a method of constructing while cutting a part. The time required for this cutting depends on the concrete strength of the preceding element and the like, and the concrete strength is an important factor for shortening the construction time.

[0003]

However, in the conventional art, the fact that the strength of concrete is made to be low has not been studied so far. The reason why this concrete strength is not studied so much is that, generally, when the water-cement ratio is increased to reduce the strength of concrete, bleeding increases, material separation is large, and poor concrete with reduced workability results. It is also considered that the higher the strength, the better. Therefore, it has been conventionally considered difficult to develop concrete having low strength and little variation in quality. Moreover, in the conventional concrete structure,
Not only those that are required to have the same strength as the present, but sufficient waterproofness such as earth retaining walls,
In the case where only the rigidity that suppresses the soil retaining deformation is required, the current concrete strength is a cause of a decrease in construction capacity and an increase in cost.

Therefore, the object of the present invention is to provide excellent fluidity and filling properties and low strength, and to exhibit excellent workability for construction of underground continuous walls, retaining walls, etc.
It is to provide a highly-fillable concrete composition.

[0005]

According to the present invention, in a concrete composition containing cement, aggregate, water, a thickener and a superplasticizer, the water-cement ratio (W / C) is 100%.
The above is characterized in that the content of the thickener is 0.25 to 0.75 parts by weight with respect to 100 parts by weight of cement, and the content of the high-performance water reducing agent is an amount that provides a slump flow value of 45 to 65 cm. A low-strength, high-filling concrete composition is provided.

The present invention will be described in more detail below. The composition of the present invention has cement, aggregate, water, a thickener and a high-performance water reducing agent as active ingredients, and in particular, a water-cement ratio and a content ratio of the thickener and the high-performance water reducing agent to a specific amount. By doing so, for example, the concrete obtained is 100 kgf / c
Even if the strength is as low as m ² , it exhibits excellent filling property and fluidity. This composition can be used as concrete in the construction of underground continuous walls, earth retaining walls, and the like.

As the cement, ordinary Portland cement, early-strength Portland cement, blast furnace cement or the like can be used.

The aggregate is not particularly limited as long as it is one that is usually used in concrete, and natural aggregate,
Both artificial aggregates and by-product aggregates can be used.
The maximum particle size is preferably about 20 mm. The blending ratio of the aggregate is not particularly limited and is usually 70 to 83% by weight, and particularly preferably 75 to 82% by weight based on the total amount of the composition.

The water has a water-cement ratio of 100% or more,
It is preferable that the content is 100 to 150% so that the resulting concrete has a compressive strength of 50 to 120.
It is preferably about kgf / cm ² . When the water-cement ratio is less than 100%, the concrete strength obtained is high, and when it is used, for example, in a cutting joint construction method, cutting becomes difficult and the construction time is extended.

The thickener, together with a high-performance water-reducing agent which will be described later, prevents the separation of each material of the composition obtained even when the water-cement ratio is increased and the deterioration of workability, thereby reducing the variation in concrete quality. A component to be added, for example, a cellulosic thickener such as hydroxyethyl cellulose, hydroxymethyl cellulose, cellulose ether; an acrylic thickener; an acrylamide thickener such as polyacrylamide; a polyvinyl alcohol thickener such as polyethylene oxide. Can be mentioned. The mixing ratio of the thickener is 0.25 to 0.75 parts by weight, preferably 0.5 to 100 parts by weight with respect to 100 parts by weight of the cement component.
It is 1.5 parts by weight. If less than 0.25 parts by weight,
If the desired effect is not obtained, and if it exceeds 0.75 parts by weight, the viscosity is increased, the desired fluidity is not obtained, and the desired slump flow value is not obtained even by blending the high-performance water reducing agent described later.

The high-performance water-reducing agent is a component having the same effect as the above-mentioned thickener, especially a component imparting fluidity. It includes. Specifically, polyglycol ester,
Naphthalene sulfonic acid formalin high condensate, sulfonated melamine formalin condensate, polystyrene sulfonate, hydroxypolyacrylate, copolymer of unsaturated dicarboxylic acid and olefin, isobutylene-styrene maleic acid copolymer, isobutylene-acrylic acid Ester-maleic acid-based copolymer, isobutylene-styrene-
Examples thereof include acrylic acid ester-maleic copolymers, aromatic aminosulfonic acid-based polymer compounds, and the like.
The high-performance water-reducing agent can be appropriately mixed so that the concrete has a slump flow value of 45 to 65 cm, preferably 50 to 60 cm. When the slump flow value is less than 45 cm, the fluidity is insufficient, and when it exceeds 65 cm, the fluidity is sufficient, but other components such as aggregates are separated and a uniform composition is obtained. Can not. The blending ratio of this high-performance water reducing agent may be such that it has the above-mentioned slump flow value, and can be appropriately selected according to other compositions. For example, 1.0 to 2. It can be blended in the range of 0 parts by weight. The slump flow value is a value measured in accordance with the standards of the Japan Society of Civil Engineers (concrete slump flow test method).

In addition to the above-mentioned essential components, the composition of the present invention contains various admixtures such as an AE agent and an AE water-reducing agent within the range where the water cement ratio, the slump flow value and the like are secured. You can also At this time, when the high performance AE water reducing agent is adopted as the high performance water reducing agent,
It has already been blended. It is desirable to adjust the air content in the composition of the present invention to 3 to 5% by this AE agent, because the fluidity of the composition and the separability of the material can be easily adjusted.

To prepare the composition of the present invention, a thickener is added to cement, aggregate, and water at a raw plant or on site, and a high-performance water-reducing material is further added to uniformly stir and mix. It can be prepared by the method described above. The prepared composition can be used in a manner similar to the usual use in applications where the concrete strength meets the low strength of the present invention.
Compressive strength after curing for 28 days is preferably 70 to 130 k
The strength of gf / cm ² , particularly preferably 100 kgf / cm ² , is sufficient. By using it as concrete used for the construction method of cutting joints such as underground continuous walls and earth retaining walls, the construction time can be shortened. .

[0014]

The low-strength, high-filling concrete composition of the present invention contains a thickener and a high-performance water reducing agent in a predetermined amount to adjust the slump flow value to a predetermined range, and has a water-cement ratio of 100. %, It is possible to obtain a low-strength concrete exhibiting excellent fluidity and filling properties, compaction strength after 28-day curing of about 70 to 130 kgf / cm ² without requiring compaction. Therefore, when constructing an underground continuous wall, an earth retaining wall, etc., it is possible to shorten the construction time and surely fill every corner.

[0015]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples below, but the present invention is not limited thereto.

[0016]

Example 1 195 parts by weight of ordinary Portland cement,
Water 195 parts by weight, river sand (coarse grain ratio 2.89) 895 parts by weight, river gravel (maximum particle size 20 mm) 937 parts by weight and AE
0.78 parts by weight of a water-reducing agent is mixed, and 1.0 part by weight of cellulose ether as a thickener, 3.90 parts by weight of a melamine-based high-performance water-reducing agent, and 20 parts by weight of water are uniformly mixed by stirring. A concrete composition was prepared. The water-cement ratio (W / C) of the obtained composition was 110%, and the amount of air was 3.0.
± 1.5%, the slump flow value measured by the JSCE standard (concrete slump flow test method) is 5
It was 6.3 cm.

Next, the following tests were carried out on the obtained composition. The results are shown in Table 1. Breathing rate: Measured by the JIS A 1123 concrete breathing test method. Fillability; using the L-type box fillability test apparatus shown in FIG. 1, after filling the box (A) with the concrete composition through the opening 1, the slide plate 2 is slid upward to fill the box (A). The amount of the concrete composition moved to the box (B) through the obstacles 3 having a diameter of 13 mm (obstacle distance 50 mm) was measured. Compressive strength: Measured by the JIS A 1108 concrete compressive strength test method.

[0018]

[Comparative Example 1] Same as Example 1 except that the blending amount of the superplasticizer was changed to 0.5 parts by weight relative to 100 parts by weight of cement (0.98 parts by weight relative to 195 parts by weight of cement). A composition was prepared. The water-cement ratio (W / C) of the obtained composition was 110%, the air content was 3.0 ± 1.5%, the fine aggregate ratio (s / a) was 50%, and the slump flow value was 35.
It was 5 cm. Then, the same test as in Example 1 was performed on the obtained composition. The results are shown in Table 1.

[0019]

[Comparative Example 2] Normal Portland cement 239 parts by weight,
Water 195 parts by weight, river sand (coarse grain ratio 2.89) 877 parts by weight, river gravel (maximum particle size 20 mm) 918 parts by weight and AE
0.96 parts by weight of a water reducing agent is mixed, and further 1.0 part by weight of cellulose ether as a thickening agent, 4.80 parts by weight of a high-performance water reducing agent of melamine type, and 20 parts by weight of water are uniformly stirred and mixed. A concrete composition was prepared. The water-cement ratio (W / C) of the obtained composition was 90%, and the air content was 3.0 ±.
The fine aggregate ratio (s / a) was 1.5%, and the slump flow value was 54.5 cm. Then, the same test as in Example 1 was performed on the obtained composition. The results are shown in Table 1. From Table 1, it can be seen that in Comparative Example 2, the concrete compressive strength after curing for 28 days becomes too high.

[0020]

[Table 1]

[Brief description of drawings]

FIG. 1 is a schematic view of a filling tester used in Examples.

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Claims (1)

[Claims] 1. A concrete composition containing cement, aggregate, water, a thickener and a high-performance water reducing agent, wherein the water-cement ratio (W / C) is 100% or more, and the content of the thickener is 100% by weight of the cement. A low-strength, high-filling concrete composition, characterized in that the content of the high-performance water reducing agent is 0.25 to 0.75 parts by weight, and the slump flow value is 45 to 65 cm.