JPH08109053A - Cement additive for slip foam method of construction - Google Patents

Abstract

PURPOSE: To obtain a cement additive capable of being added in a freshly mixed concrete plant, having fluidity required for production, transportation and execution, capable of producing concrete having excellent vibration fluidity free from occurrence of swelling caused by empty weight, by blending a reducing agent with a natural polysaccharide or a water-soluble acrylic polymer. CONSTITUTION: This cement additive is obtained by blending 90-99.9wt.% of a water-reducing agent with 0.1-10wt.% of a natural polysaccharide and/or a water-soluble acrylic polymer. A lignin sulfonate and sodium polyacrylate are especially preferable as the water-reducing agent. Sodium polyacrylate, polyacrylamide and a partial hydrolyzate of polyacrylamide are especially preferable as the water-soluble polymer. The amount of the cement additive used is properly determined corresponding to a cement composition used, for example, is 0.1-5.0wt.% calculated as a solid content based on the weight of cement contained in the cement composition.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a cement additive for significantly improving the production, transportation, construction and finish of a cement composition used in a slip foam method. More specifically, the cement additive for slip-form construction method of the present invention can be added at a ready-mixed concrete factory when used, has fluidity necessary for production, transportation and construction (vibration filling), and has a mold After slipping the frame, the cement composition has a thixotropic property with no generation of scintillation and a good finished state.

[0002]

[Background Art] Slip form method (hereinafter abbreviated as SF method) is a concrete structure with a same cross section that is made by using a self-propelled construction machine equipped with a compaction device and a shaping device. This is a method of constructing a concrete structure continuously by compacting and shaping the concrete shape while moving the formwork, which makes it possible to construct a concrete structure in a short time with a small number of people. It is an excellent construction method. In recent years, construction of road related facilities such as median strips of roads, circular waterways, gutters, windings, and standing walls, and other structures for civil engineering has been performed by this SF construction method. S
The concrete used in the F method maintains the fluidity necessary for manufacturing, transportation, and construction, and the placed concrete is self-supporting (so that it does not move due to its own weight) so that the formwork can be quickly slipped after vibration molding. Is not generated), that is, it is required to have deformation resistance.

Conventionally, as concrete used in the SF method, hard concrete having a slump of 2 to 5 cm is used in order to prevent the occurrence of flapping due to its own weight. Such hard-mixed concrete has extremely poor fluidity required for production, transportation, and construction, so when shipping concrete manufactured in a ready-mixed concrete plant, the concrete is clogged in a hopper or the like, or the concrete is used as an agitator vehicle. It has various problems such as being unable to load it, not being able to discharge concrete from the agitator vehicle when it arrives at the construction site, and being very time-consuming even if loading or discharging is possible. Therefore, under the present circumstances, a dump truck is often used for transporting concrete, and there is a problem that the quality of concrete is impaired in hot weather or rainy weather.

Manufacture, transportation and construction of soft concrete or lignin sulfonate, polycarboxylate, naphthalene sulfonate formalin condensate, melamine sulfonate formalin condensate, etc. The concrete to which the necessary fluidity is added is not suitable as the concrete for the SF construction method because the occurrence of flapping due to its own weight.

On the other hand, a method of adding a water-absorbing polymer material to green concrete that has been transported to a construction site (Japanese Patent Laid-Open No. Hei 6)
No. 23735), or a method of imparting deformation resistance by a method of adding carboxymethyl cellulose (see Japanese Patent Application Laid-Open No. 5-154829), etc., but these methods control the amount of air. However, it is difficult to use concrete immediately to add and knead it at the construction site, it is difficult to keep the quality of concrete constant, and it takes time and labor. Have a

Therefore, it can be added in the ready-mixed concrete plant,
There has been a strong demand for the development of a cement additive for the SF construction method, which has the fluidity necessary for production, transportation and construction, and also enables the production of concrete that has excellent vibration fluidity and does not cause entrainment due to its own weight. .

[0007]

DISCLOSURE OF THE INVENTION As a result of intensive studies to solve various problems in the prior art as described above, the present inventors have found that a water reducing agent and a natural polysaccharide and / or a water-soluble acrylic polymer are used. By using a cement additive compounded in a specific ratio, it can be added at a ready-mixed concrete plant,
It enables the production of concrete that has the fluidity necessary for transportation and construction, excellent vibration fluidity, and free from entrapment due to its own weight. Furthermore, workability and durability are achieved without entraining excess air. We have succeeded in providing an improved cement additive for SF method.

That is, the present invention relates to a water reducing agent, 90 to 9
To provide a cement additive for a slip-form construction method, which contains 9.9% by weight of natural polysaccharides and / or water-soluble acrylic polymer, in an amount of 0.1 to 10% by weight. is there.

In the cement additive for the SF method of the present invention, the water-reducing agent exceeds 99.9% by weight in the mixing ratio of the water-reducing agent and the natural polysaccharide and / or the water-soluble acrylic polymer. If the water-soluble acrylic polymer is less than 0.1% by weight, fluidity required for production, transportation, and construction can be obtained, but entrapment due to its own weight cannot be prevented. Further, the water-reducing agent is less than 90% by weight, and the natural polysaccharide and / or the water-soluble acrylic polymer is 10% by weight.
When the content is more than 10% by weight, cohesiveness is exhibited, and entrainment due to its own weight is prevented, but desired fluidity cannot be obtained.

As the water reducing agent in the present invention, lignin sulfonate and sugar alcohol are particularly preferable, but naphthalene sulfonate formalin condensate,
Examples thereof include melamine sulfonate formalin condensate and polycarboxylate. As the natural polysaccharide in the present invention, xanthan gum, locust bean gum, sodium alginate and λ-carrageenan are particularly preferable, and karaya gum, guar gum, pectin and β- are preferable.
1,3-glucan, β-1,4-glucan and the like can also be exemplified.

As the water-soluble acrylic polymer in the present invention, sodium polyacrylate, polyacrylamide,
Partial polyacrylamide hydrolysates are particularly preferred, but polyacrylic acid, copolymers of acrylamide and sodium acrylate, copolymers of acrylamide and sodium acrylate and acrylamide, and copolymers of 2,2 dimethylethanesulfonic acid sodium. , Polyvinyl alcohol, polyethyleneimine, polydiallylamine, copolymers of aminoalkyl (meth) acrylate and acrylamide,
Polyvinyl imidazoline etc. can also be illustrated.

The cement additive for the SF construction method of the present invention may contain other additives, if desired, depending on the variety of purposes. Examples of other additives include an air amount adjusting agent, a drying shrinkage reducing agent, an accelerator, a retarder, a defoaming agent, a rust preventive, a quick-setting agent, and a thickener.

The amount of the cement additive for the SF construction method of the present invention to be used is appropriately determined according to the cement composition to be used, but basically, the fluidity required for the production, transportation and construction of the cement composition is basically determined. And, sufficient to impart the desired vibration fluidity and the effect of preventing entrainment due to its own weight, the cement composition may be an amount showing thixotropy, for example, usually contained in the cement composition. It is appropriate to add the cement additive of the present invention in an amount of 0.1 to 5.0% by weight in terms of solid content, based on the weight of cement, but the amount is not limited to this range.

The cement additive for the SF method of the present invention is S
The concrete for the F method can of course be used very effectively for the production of cement compositions that require particularly thixotropy in commonly used cement paste, mortar, grout, concrete and the like.

Specific examples of the case where the cement additive for SF method of the present invention is used in mortar and concrete are shown below, but the present invention is not limited to these embodiments.

[0016]

【Example】

1) Mixing and Preparation of Mortar and Concrete 1-1) Mortar As for mortar, the evaluation test was conducted with the mixing shown in Table 1.
In this mortar, each material was weighed so that the kneading amount was 2.5 liters, all the materials were put into an ASTM mortar mixer, and then kneading for 120 seconds for adjustment. However, the composition of mortar shown in Table 1 is based on the composition of concrete having a slump value of 8.0 ± 1.0 cm, based on the water-cement ratio, unit water content, unit cement content, unit fine aggregate. The amount and sand cement ratio are set. The slump value, flow value, and air amount of the mortar are 1.4 to 8.5 cm, 104 to 131 mm,
It was within the range of 4.5 ± 0.5% by volume.

[0017]

[Table 1]

1-2) Concrete Concrete was subjected to an evaluation test with the composition shown in Table 2. This concrete was prepared by weighing the materials so that the mixing amount was 80 liters, adding all the materials to a 100-liter pan-type forced mixer, and then mixing for 90 seconds. The slump value and the air content of the concrete were 2.5 to 8.5 cm and 2.0 to 4.6% by volume, respectively.

[0019]

[Table 2]

1-3) Materials used Fine aggregate: Oi River water-based land sand (specific gravity = 2.60, coarse grain ratio =
2.76) Coarse aggregate: Hard sandstone crushed from Ome (specific gravity = 2.65, maximum particle size = 20 mm) Cement: Normal Portland cement (specific gravity = 3.1)
6. Equal amounts of Onoda, Sumitomo and Mitsubishi cement were mixed) Water reducing agent: Sugar alcohol (Solvit D-7 manufactured by Towa Kasei)
A mixture of 0 and PO-20 manufactured by the same company at a weight ratio of 9: 1. Hereinafter, abbreviated as SAL), lignin sulfonate (hereinafter abbreviated as LSA) Natural polysaccharides: xanthan gum (hereinafter abbreviated as XG), locust bean gum (hereinafter abbreviated as LBG), and alginic acid. Soda (hereinafter abbreviated as ALA), λ-carrageenan (hereinafter abbreviated as CGN) Water-soluble acrylic polymer: sodium polyacrylate (average molecular weight 220,000, hereinafter abbreviated as PA-1). ), Sodium polyacrylate (average molecular weight: 50,000)
0, hereinafter abbreviated as PA-2. ), Polyacrylamide (average molecular weight 1,000,000, hereinafter abbreviated as PAA), polyacrylamide partial hydrolyzate (average molecular weight 1,000,000, hereinafter abbreviated as HPAA).

Table 3 shows the types of water-reducing agents, natural polysaccharides and water-soluble acrylic polymers as cement additives used in Examples and Comparative Examples, and their mixing ratios.

[0022]

[Table 3]

2) Test method for mortar and concrete 2-1) Mortar In order to evaluate the fluidity of mortar kneaded with the composition shown in Table 1, slump value and flow value were measured and vibration was also measured. The fluidity and the deformation resistance were evaluated, and the thixotropy of the mortar was evaluated from these characteristics of the vibration fluidity and the deformation resistance. The results of these tests are shown in Table 4. a) Flowability: The slump value and flow value were measured using a slump cone (made of iron having an inner diameter of 50 mm at the upper end, an inner diameter of the lower end of 150 mm, and a height of 150 mm) used in the slump test method for polymer cement mortar. -Slump value: According to JIS A 1173. -Flow value: The spread of the flow of mortar was measured. b) Vibratory flowability: After the slump cone is filled with mortar, the slump cone is pulled up, and vibration (frequency of 2,700 / min) is applied to the mortar using a bar-shaped vibrator to reach a mortar flow value of 300 mm. Was measured. c) Deformation resistance (effect of preventing entrapment due to its own weight): φ10
The amount of vertical and horizontal deformation of the mortar generated when the mortar was vibration-molded into a × 20 mold and immediately removed from the mold was measured. d) Thixotropy: Evaluated from the vibration fluidity and deformation resistance of the mortar. A (good): A state in which both vibration fluidity and deformation resistance are good. B (Poor): A state in which either vibration fluidity or deformation resistance is poor.

2-2) Concrete Testing Method The air amount was measured to evaluate the slump value and the air entrainment property in order to evaluate the fluidity of the concrete mixed with the composition shown in Table 2. Further, the vibration fluidity and the deformation resistance were evaluated, and the thixotropy of the concrete was evaluated from both the characteristics of the vibration fluidity and the deformation resistance. Furthermore, while measuring the compressive strength of 28 days old,
The appearance of the surface of the hardened concrete was visually observed and evaluated. The results are shown in Table 5.

A) Fluidity: According to JIS A 1101. b) Air entrainment: According to JIS A 1128. c) Vibration fluidity: After filling the slump cone with concrete, pulling up the slump cone and applying vibration to the concrete using a bar-shaped vibrator (frequency of 10,000).
0 / min), and the time required for the concrete flow value to reach 600 mm was measured. d) Deformation resistance: The amount of vertical deformation and the amount of horizontal deformation of the concrete, which were generated when the φ20 × 40 mold was filled with concrete and then immediately removed from the mold, were measured. e) Thixotropy: Evaluated from the vibration fluidity and deformation resistance of concrete. A (good): A state in which both vibration fluidity and deformation resistance are good. B (Poor): A state in which either vibration fluidity or deformation resistance is poor. f) Compressive strength: JIS A 1118, JIS A 1
132. g) Visual observation: The appearance of the surface of the hardened concrete was evaluated by visual observation. A (good): There is no void and the surface is smooth. B (ordinary): Slight voids are observed, but there is no problem in appearance. C (bad): A state where the exposed voids and gravel are conspicuous and there is a problem in appearance.

3) Test Results 3-1) Mortar Table 4 shows the test results using mortar. Experiment No. in Table 4 1 to 13 are examples, and Experiment No. 14-16
Is a comparative example in which only the water reducing agent is added to the mortar,
o. Nos. 17 and 18 are comparative examples in which only natural polysaccharides or water-soluble acrylic polymers were added to the mortar, and Experiment No. 19
Nos. 21 to 21 show the results of tests carried out using comparative examples in which the mixing ratio of the water reducing agent and the natural polysaccharide or the water-soluble acrylic polymer deviates from the above range.

[0027]

[Table 4]

As can be seen from the results shown in Table 4, the following effects are confirmed when the cement additive for SF construction method of the present invention is used in mortar. a) Fluidity Experiment No. Experiment Nos. 1 to 13 (Examples) were used. 14-1
As is clear from comparison with No. 6 (Comparative Example), equivalent fluidity is exhibited. On the other hand, in Experiment No. Nos. 17 and 18 (comparative examples) have poor fluidity. b) Oscillating fluidity Experiment No. under the same fluidity conditions. 1 to 13 (Example)
And Experiment No. 14 to 16 (comparative examples) showed good oscillatory fluidity. On the other hand, in Experiment No. 17-21
(Comparative Example) has poor vibration fluidity.

C) Deformation resistance Experiment No. The deformation amounts in the horizontal direction (X) and the vertical direction (Y) of Experiment Nos. 1 to 13 (Examples) were substantially the same in Experiment No. 14 to 16 (Comparative Example), which was small and showed excellent deformation resistance. Experiment No.
The deformation amounts of 1 to 13 (Example) are those of Experiment No. 1 having poor fluidity and vibration fluidity. 17 to 21 (comparative example). d) Evaluation of thixotropy Experiment No. 1 to 13 (Examples) showed good thixotropy. On the other hand, in Experiment No. Nos. 14 to 16 (Comparative Examples) show excellent oscillating fluidity, but poor deformation resistance and poor thixotropy. Experiment No.
Nos. 17 to 21 (Comparative Examples) show excellent deformation resistance, but the vibration fluidity is poor and the thixotropy is inferior.

3-2) Concrete Table 5 shows Experiment No. No. 22, 23 (Example), and Experiment No. in which only the water reducing agent was added to the concrete. No. 24 (Comparative Example), Experiment No. in which only natural polysaccharides or water-soluble acrylic polymers were added to concrete. The test results of 25 and 26 (comparative examples) are shown.

[0031]

[Table 5]

Experiment No. 5 in Table 5 22 and 23, when the cement additive for SF construction method of the present invention is used in concrete, the following effects are confirmed. a) Fluidity Experiment No. Nos. 22 and 23 (Examples) are experimental Nos. 24
It shows the same excellent fluidity as (Comparative Example). On the other hand, in Experiment No. 25 and 26 (Comparative Examples) are all inferior in fluidity. b) Air entrainment experiment No. Nos. 22 and 23 (Examples) are experimental Nos. 24
It shows the same degree of air entrainment as (Comparative Example), and no excessive air entrainment is observed. c) Compressive strength Experiment No. The compressive strengths of Nos. 22 and 23 (Examples) were measured in Experiment N
o. 24 to 26 (comparative example), a large value is shown and improved. d) Visual observation Experiment No. 22 (Example) and Experiment No. It was recognized that the aesthetic appearance of the skin surface of No. 24 (Comparative Example) was extremely excellent. Experiment No. On the skin surface of No. 23 (Example), slight voids were observed, but there was no problem in appearance. On the other hand, in Experiment No. 25 and 26 (comparative examples) showed extremely poor results.

E) Oscillating fluidity Experiment No. 22, 23 (Example) and Experiment No. 24
(Comparative example) shows excellent oscillatory fluidity. On the other hand, in Experiment No. Nos. 25 and 26 (Comparative Examples) exhibited poor vibration fluidity. f) Deformation resistance Experiment No. Nos. 22 and 23 (Examples) are experimental Nos. 24
Compared with (Comparative Example), it is significantly smaller, and the experimental No. 25,
No. 26 (Comparative Example) or a little larger than that of Comparative Example No. 26, indicating excellent deformation resistance. g) Evaluation of thixotropy Experiment No. 22 and 23 (Examples) showed good thixotropy. On the other hand, in Experiment No. No. 24 (Comparative Example) showed excellent vibration flowability, but poor deformation resistance and poor thixotropy. Experiment No. Two
Nos. 5,26 (Comparative Examples) show excellent deformation resistance, but the vibration fluidity is poor and the thixotropy is inferior.

[0034]

The SF method cement additive of the present invention is
A thixotropic cement that can be added at a ready-mixed concrete plant, retains the fluidity necessary for the production, transportation and construction of the cement composition used in the SF construction method, and that does not cause excellent vibration fluidity and entrainment due to its own weight. It enables the production of the composition and further improves workability and durability without entraining excess air.

Claims (4)

[Claims] 1. A water-reducing agent, 90 to 99.9% by weight, a natural polysaccharide and / or a water-soluble acrylic polymer, 0.1 to 1
A cement additive for a slip-form construction method, characterized by containing 0% by weight. 2. The cement additive for slip-form construction method according to claim 1, wherein the water reducing agent contains a lignin sulfonate and / or a sugar alcohol. 3. The slip foam method according to claim 1 or 2, wherein the natural polysaccharide is one or more selected from xanthan gum, locust bean gum, sodium alginate, and λ-carrageenan. Cement additive. 4. The water-soluble acrylic polymer is one or more selected from sodium polyacrylate, polyacrylamide, and a partial polyacrylamide hydrolyzate. The cement additive for the slip-form construction method according to any one of claims.