JPH05319885A - Method for improving resistance of concrete to freezing damage - Google Patents

Abstract

PURPOSE:To improve the resistance of concrete to freezing damage by adding an AE agent consisting of a modified rosin oxide surfactant to the unsolidified concrete contg. water-soluble cellulose ether. CONSTITUTION:About 290-450kg of normal Portland cement and about 180+ or -5kg of water are contained per m<3> of concrete composition, and the composition further contains about 0.01-0.6wt.%, based on the cement binder, of a water-soluble cellulose ether and 0.5-6.0wt.% of a high-performance water reducing agent. An AE agent consisting of a modified rosin oxide surfactant is added by 0.0001-0.05wt.%, based on the cement binder. The viscosity of a 1% aq. soln. of the cellulose ether is controlled to 100-10,000cP (centipoise). Consequently, the air content of the concrete is kept at 3-6%, and excellent freezing damage resistance is imparted to the concrete.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving frost resistance of concrete using water-soluble cellulose ether as a separation reducing material.

[0002]

2. Description of the Related Art Concrete using a separation reducing material is applied in various fields. Cellulose-based and acrylic-based materials are well known as separation reducing materials, and both are water-soluble polymers.

One of the concretes using such a separation reducing material is concrete having high fluidity as proposed in Japanese Patent Laid-Open No. 337049/1993. This is a combination of ordinary Portland cement, blast furnace slag, fly ash, and expansive material, as well as separation reduction material and high performance (A
E) By adding an appropriate amount of a water reducing agent, high fluidity is exhibited without causing material separation.

The concrete of this system is characterized in that it is excellent in fluidity and filling so that vibration compaction such as a vibrator is unnecessary, and is expected to contribute to improvement of workability and quality of buildings. The development research is actively progressing.

[0005]

In order to secure frost damage resistance of concrete, the amount of air in the concrete is 4 to 6
% Is desirable, but in high-fluidity concrete using a cellulosic separation-reducing material, it is generally easy to enclose large numbers of fragile bubbles with large diameters. The apparent amount of air immediately after kneading is as large as 6 to 9%, but it is lost rapidly with the passage of time, and the remaining bubbles also have a large diameter, so they do not contribute much to frost damage resistance.

Therefore, until now, a defoaming agent was put in before kneading, and a conventional AE agent was added to carry ordinary air. However, it was very difficult to control the addition amount of the defoaming agent and the AE agent in consideration of temperature and compatibility with other materials.

The present invention is intended to solve such problems and improve the frost damage resistance of concrete when water-soluble cellulose ether is used as a separation reducing material.

[0008]

Means for Solving the Problems The inventors of the present invention have found that the frost damage resistance of concrete using water-soluble cellulose ether as a separation reducing agent is a modified rosin acid compound-based surfactant (this It has been found that the improvement can be achieved by adding an AE agent consisting of (abbreviated as compound). In particular, in high-fluidity concrete containing a water-soluble cellulose ether as a separation reducing agent and a high-performance water-reducing agent, addition of a rosin acid compound has excellent frost damage resistance while maintaining an air content of 3 to 6%. Was found to show. The preferable addition amount of the AE agent composed of a rosin acid compound to such a high-fluidity concrete is in the range of 0.0001 to 0.05% by weight with respect to the cement binder.

[0009]

[Function] The AE agent, which is one of the concrete admixtures,
Many of them are known, but in concrete using water-soluble cellulose ether as a separation reducing agent, especially in flowable concrete combined with a high-performance water-reducing agent, among the many AE agents, a rosin acid compound-based AE agent Serves to significantly improve the frost damage resistance of the concrete.

Among the same AE agents, natural resin acid-based agents and surfactant-based agents tend to slightly improve the frost damage resistance of concrete when added so that the air content in the concrete is 3 to 6%. Although it is observed, it does not show a remarkable improving effect unlike the AE agent of the rosin acid compound type.

The concrete targeted by the present invention is a concrete using water-soluble cellulose ether as a separation reducing material. In particular, by mixing this separation reducing material with a high performance water reducing agent, high fluidity and high filling can be achieved. It is useful for improving the frost damage resistance of concrete that exhibits good properties.

The concrete composition having such a high fluidity and a high filling property is used as a normal Portland cement 290 to ⁴ per 1 m ^{3 of} concrete, as shown in the examples below.
AE containing 50 kg and 180 ± 5 kg of water, 0.01 to 0.6% by weight of water-soluble cellulose ether to the cement binder, 0.5 to 6.0% by weight of superplasticizer to the cement binder, and rosin acid compound The agent is blended in an amount of 0.0001 to 0.05% by weight based on the cement binder. Also,
AE water reducing agent or water reducing agent may be added to the composition in an amount of 0.1 to 2.0% by weight based on the cement binder, and fly ash may be added in an amount of 15 to 60% by weight based on the cement. ..

Immediately after mixing, this concrete had a slump value of 26.5 cm or more and a slump flow value of 61 cm.
It exhibits the above-mentioned high fluidity and high filling property, and the slump value and slump flow value do not change over time, and the air amount does not change over time. Then, in the freeze-thaw test based on JIS A 6204, a rosin acid compound-based AE agent was added to the freeze-thaw cycle 30 after curing in standard water for 2 weeks.
The relative dynamic elastic modulus (durability index) at 0 times is maintained at 80% or more.

The action of each compounding material for the high-fluidity and high-filling concrete composition will be described below individually. a) Separation-reducing material Water-soluble cellulose ether as a separation-reducing material improves the action of not separating concrete and the filling property even when the slump value is 26 to 28 cm and the spread of concrete in the slump test is as large as 500 to 800 mm. Provide the action of In the concrete of the present invention, these effects are obtained by adding water-soluble cellulose ether to the cement binder in an amount of 0.01 to
0.6% by weight range (0.1 to ³ m3 of concrete
0.7 kg).

The water-soluble cellulose ether to be used has a viscosity in the range of 100 to 10,000 cP, preferably 500 to 5,000 cP as a 1% aqueous solution viscosity measured using a B type rotational viscometer.
belongs to. If the viscosity is 100 cP or less, the viscosity required to suppress aggregate sedimentation cannot be obtained, and the effect of the present invention cannot be sufficiently exhibited. Even with such a low viscosity, the viscosity necessary to suppress the sedimentation of aggregate can be obtained by increasing the addition amount, but the frost damage resistance decreases when the addition amount is increased. Therefore, from the viewpoint of improving frost damage resistance, the viscosity of 1% aqueous solution
The range of 100 to 10,000 cP, preferably the range of 500 to 5,000 cP, should be used in the range of 0.01 to 0.6% by weight based on the cement binder.

B) High-performance water reducing agent The high-performance water reducing agent can reduce the increment of the unit water amount by increasing the spread of slump or concrete. For this reason, an appropriate amount of the high-performance water reducing agent is added. Secure the required consistency and workability. In addition, the addition of a high-performance water reducing agent suppresses an increase in the unit amount of water, thereby reducing the drying shrinkage amount of concrete and improving the durability. Such an effect can be achieved with cement binders when, for example, highly condensed triazine compounds are used.
It is obtained by blending 5 to 6.0% by weight.

As the high-performance water reducing agent, a highly condensed triazine compound, a formalin condensate of melamine sulfonate, a polycarboxylate derivative, a modified lignin sulfonate, etc. can be used, but the concrete composition of the present invention can be used. Particularly preferred among these are highly condensed triazine compounds and melamine sulfonate compounds.

C) Regarding AE water reducing agent or water reducing agent Although the AE water reducing agent or water reducing agent has an action of improving the consistency of concrete, in the present invention, by combining it with a water-soluble cellulose ether and a high-performance water reducing agent. , The effect of keeping the high fluidity of fresh concrete for a long time and the effect of stabilizing the air volume are exhibited. Particularly preferable as the AE water-reducing agent used in the present invention is a lignin sulfonic acid compound system or a lignin fulphonic acid polyol composite system, which is used for the cement binder.
The effect is exhibited by adding 0.1 to 2.0% by weight.

D) AE agent The AE agent is added so that the amount of air in the concrete is 3 to 6%. The freeze-thaw resistance of the concrete composition using a water-soluble cellulose ether can be significantly improved by a rosin acid compound-based AE agent,
This point is a feature of the present invention. In this case, 0.0001 to 0.05% by weight of the rosin acid compound-based AE agent is mixed with the cement binder. As the AE agent, a natural resin acid type or an alkylbenzene sulfonic acid type, which is used in ordinary concrete, can be used, but the rosin resistance does not show the remarkable effect of the rosin acid compound type.

E) Fly ash Fly ash has the effects of suppressing alkali-aggregate reaction, improving concrete consistency, reducing the amount of drying shrinkage, and improving durability. To obtain this effect, it is sufficient to add 15 to 60% of fly ash to the unit amount of cement.

Typical test results conducted by the present inventor will be given below as examples.

[0022]

【Example】

(1) Materials used in the test Cement (OPC): Ordinary Portland cement, specific gravity 3.16 Coarse aggregate (G): Crushed stone (maximum size 20 mm from Izu) Fine aggregate (S): Land sand (from Kashima) (S ₁ Called): Crushed sand (Tochigi) (Called S ₂ ) Admixture: Fly ash (FA), Specific gravity 2.24

Types of admixture Separation reducing agent: Water-soluble cellulose ether (called WSP) Shin-Etsu Chemical Co., Ltd. High-performance water-reducing agent: Highly condensed triazine compound Nisso Master Builders (AE) Water-reducing agent: Lignin sulfone Acid compound (including polyol compound), AE agent manufactured by Nisso Master Builders: rosin acid compound (referred to as Agent A) Nisso Master Builders manufactured: alkylallyl sulfonic acid compound-based anionic surfactant (B Made by Nisso Master Builders Co., Ltd.

(2) Mixing of concrete Table 1 shows the mixing standard of concrete.

(3) Mixing of concrete According to the mixing standard of Table 1, the water cement ratio (W /
C) and fine aggregate (s / a) fresh concrete was made. When kneading (G + S + C + WS
P) in advance and after 15 to 20 seconds, (0.9 × water + (A
E) Water reducing agent + AE agent) was added, and after 15 to 20 seconds
(0.1 x water + high performance water reducing agent) was added and mixed for 2 minutes.

(4) Evaluation test A slump test of the obtained fresh concrete was performed according to JIS.
Immediately after mixing according to A 1101, measurements were taken at intervals of 60 minutes up to 120 minutes, and at the same time, the spread of concrete (slump flow value) was also measured and the changes over time were investigated. The values immediately after kneading are shown in Table 2, and the values after aging are shown in Table 3.

The slump flow test was conducted in accordance with the underwater non-separable concrete manual (Appendix 1, Underwater non-separable concrete test, slump flow test).
That is, according to JIS A 1101 concrete slump test method, the spread distance on the iron plate 3 after 5 minutes when the slump cone 2 loaded with the test concrete 1 was lifted as shown in FIG. 1 was measured.

According to JIS A 1128, immediately after kneading
The air content was measured at intervals of 60 minutes up to 120 minutes, and the values immediately after kneading are shown in Table 2 and changes over time in Table 3. Furthermore, JIS A
A breathing test was conducted according to 1123, and the breathing amount is shown in Table 2. .. In addition, the degree of material separation such as aggregate was visually determined, and those where no separation was observed were evaluated as ◯, and those where separation was recognized were evaluated as x, and are shown in the column of aggregate precipitation in Table 2.

Further, the filling property of concrete was evaluated by the rebar permeability. As shown in Fig. 2, this was fitted with a rebar mesh 4 (reinforcing bar D-16) with openings of 50 mm at the bottom 318.
30 liters of concrete was packed in a container 5 mm × 318 mm × height 400 mm, and the discharge amount passing through the reinforcing bar net 4 was measured.
The reinforcing bar transmittance was calculated by the following formula. The values are shown in Table 2. Reinforcing bar permeability (%) = (emission amount / fill amount) x 100 Fill amount = initial sample weight

(6) Test results

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

The following can be seen from the results of Tables 2 and 3.

All the fresh concretes of Examples 1 to 5 had a slump value of 26.5 cm or more and a slump flow value of 6
It has more than 10 mm and shows superfluidity.

In Examples 1 to 3, the unit cement amount was changed, but the more unit cement, the higher the slump flow value and the reinforcing bar permeability, and the better the fluidity and the filling property.

Further, in Examples 1 to 3 and 5, the water reducing agent was added, whereas in Example 4, the water reducing agent was not added. As a result, as seen in Table 3, in Example 4, the slump value, the slump flow value, and the air amount decreased with time, whereas in Examples 1 to 3 and 5,
Even after a lapse of time, the degree of decrease is extremely small or hardly changes. That is, the water reducing agent serves to prevent slump loss and prevent a decrease in the amount of air in the concrete composition of the present invention.

Example 5 is an example in which fly ash is used. Cement 300 kg / m ³ and fly ash 60 kg
/ is obtained using the binder of the total 360 kg / m ³ of m ^3.
The use of fly ash, as is clear from a comparison with Example 2 using the same 360 kg / m ³ cement,
It can be seen that the slump value, slump flow value, air amount, and rebar permeability are all improved, exhibiting good fluidity and filling properties, and improving the consistency. The action of this fly ash is more apparent when compared with Example 1 in which the cement is 300 kg / m ³ .

Comparative Examples 1 and 2 are examples in which water-soluble cellulose ether was not added. From the results in Table 2, it can be seen that in the slump flow equivalent to general fluidized concrete as in Comparative Example 1, the rebar permeability is low and the filling property is poor. Further, it is possible to increase the slump flow by adding a large amount of a high-performance water reducing agent as in Comparative Example 2, but this is not suitable for practical use because of the large amount of aggregate separation. Comparative Example 1,
Both 2 have a lot of breathing.

Comparative Example 3 has the same composition as in Example 2 except that the amount of the high-performance water reducing agent added was lowered, but as shown in the results of Table 2, the reinforcing bar permeability was 0%, Poor fluidity and filling.

(7) Freezing / Thawing Resistance Evaluation Test The concrete in Table 1 was subjected to a freeze / thaw test based on JIS A 6204. That is, a freeze-thaw test was started after the concrete was cured in standard water for 2 weeks. In the test, 300 cycles of freezing and thawing were performed, and the durability index based on the relative dynamic elastic modulus was evaluated. Further, the compressive strength of 7 days old and the compressive strength of 28 days old were also measured. The results are shown in Table 4.

[0042]

[Table 4]

As can be seen from the results of Table 4, the concretes of Examples 1 to 5 using the rosin acid compound (A agent) as the AE agent have a high durability index of 80 or more (nearly 90 or more). Very good frost resistance.

On the other hand, Comparative Example 4 uses an alkylallyl sulfonic acid compound type anionic surfactant (B agent) as the AE agent. The durability index is lower and the frost damage resistance is inferior when compared with those using (A agent). Further, as can be seen from the results in Table 3, the slump value and the slump flow of the comparative example 4 are good, but the decrease in the air amount over time is large. On the other hand, Comparative Example 5 is an example in which no AE agent is used,
In this case, the durability index becomes extremely low and the frost damage resistance is poor.

That is, in Comparative Examples 4 and 5, the addition amounts of the separation reducing material and the high-performance water reducing agent (further, the water reducing agent) were the same as in Example 2 as shown in the formulation table of Table 1. As can be seen in 3, the slump value and slump plow value immediately after kneading also show sufficient values. However, even such high-fluidity concrete has a problem of low freeze-thaw resistance and poor durability. This problem is almost completely solved in the first to fifth embodiments.

Thus, the concrete using the rosin acid compound (A agent) as the AE agent has significantly improved frost damage resistance, and the concrete is compared with general fluidized concrete as in Comparative Example 1, for example. It is clear that the slump flow value and the reinforcing bar permeability are both high, no sedimentation of aggregates and other materials is observed, and breathing is extremely low, indicating that the concrete is a highly highly filled concrete.

Therefore, the durability is not deteriorated even in the cold zone or the environment where the temperature difference is large, and the filling can be performed with good filling property.

[0048]

As described above, according to the present invention, the frost damage resistance of concrete can be remarkably enhanced, and the effect is particularly excellent in concrete using water-soluble cellulose ether as a separation reducing material. Therefore, the freezing damage resistance of the high-fluidity and high-filling concrete using water-soluble cellulose ether and high-performance water-reducing agent in the in-situ casting is improved, and the filling of the concrete in winter or in cold regions is improved. Since it is possible to make high-quality concrete structures with good durability and durability, it is possible to make a great contribution to this field.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a test method for obtaining a slump flow value.

FIG. 2 is a perspective view showing a test tool for obtaining a reinforcing bar permeability for evaluation of filling property.

[Explanation of symbols]

 1 Concrete that does not solidify yet 2 Slump cone 3 Iron plate 4 Reinforcing bar net 5 Concrete loading container

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C04B 24:38 D 2102-4G 24:30 D 2102-4G 24:18 B 2102-4G 24:04 2102-4G 24:16 2102-4G 24:34) 2102-4G

Claims (7)

[Claims] 1. An AE agent comprising a modified rosin acid compound-based surfactant (referred to as a rosin acid compound) for improving the frost damage resistance of concrete that has not solidified yet using water-soluble cellulose ether as a separation reducing agent. A method comprising adding to the concrete. 2. The method according to claim 1, wherein the AE agent comprising a rosin acid compound is added in the range of 0.0001 to 0.05% by weight with respect to the cement binder. 3. The method according to claim 1, wherein the water-soluble cellulose ether used has a viscosity of a 1% aqueous solution of 100 to 10,000 cP (centipoise). 4. The method according to claim 1, 2 or 3, wherein the concrete which does not harden yet contains 0.5 to 6.0% by weight of a high-performance water-reducing agent with respect to the cement binder. 5. The concrete which is not yet set is AE
Water reducer or water reducer for cement binder 0.1-2.0
5. The composition is blended in a weight percentage of 1, 2, 3 or 4.
The method described in. 6. The concrete which has not yet set is JIS
In the freeze-thaw test based on A 6204, the relative dynamic elastic modulus (durability index) at 300 freeze-thaw cycles after curing in standard water for 2 weeks is 80% or more, and air is maintained for 2 hours immediately after mixing. A method according to claim 1, 2, 3, 4 or 5, wherein the amount is maintained in the range of 3-6%. 7. The concrete which does not harden yet has high slump value: 26.5 cm or more and slump flow value: 61 cm or more and shows high fluidity and high filling property immediately after mixing. The method described in.