JP5816731B2 - Method for producing high-strength concrete - Google Patents

Description

  The present invention relates to a method for producing high-strength concrete.

  High-strength concrete is obtained by increasing the compressive strength by reducing the weight ratio of water to the binder (water binder ratio) and densifying the concrete structure after hardening.

High strength concrete before hardening is required to have high fluidity in order to fill the formwork densely. However, if the fluidity is excessively increased, the aggregate and the cement paste are separated.
Therefore, conventionally, it is intended to produce high-quality high-strength concrete by appropriately adjusting the amount of water-reducing agent (high-performance water-reducing agent, AE water-reducing agent, high-performance AE water-reducing agent, etc. in JIS A 6204). .

  High-strength concrete having a low water binder ratio generally tends to increase self-shrinkage when cured. High self-contraction causes cracking, so high-strength concrete has been developed to reduce self-contraction.

For example, in Patent Document 1, in the blending of high-strength concrete having a design standard strength exceeding 100 N / mm ² , the amount of water reducing agent added is less than 2% by weight with respect to the binder, and 30% by volume or less of the coarse aggregate. A high-strength concrete is disclosed that is replaced with artificial lightweight aggregate and added with an expansion material of 30 kg or less per 1 m ^{3 of} concrete.

Patent Document 2 discloses high-strength concrete in which an expansion material and a setting retarder are mixed in a blend of high-strength concrete having a design standard strength exceeding 60 N / mm ² .

JP 2005-022931 A JP 2006-282435 A

  However, since the artificial lightweight aggregate is inferior in terms of strength characteristics as compared with the coarse aggregate made of gravel or the like, the invention described in Patent Document 1 is not suitable for further increasing the strength of concrete. there were.

  In addition, as in the high-strength concrete described in Patent Document 2, when using a low heat Portland cement and a setting retarder, the initial curing tends to be delayed, and the construction problems such as the demolding of the formwork are delayed. was there.

  The present invention has been made to solve such problems, and has high fluidity and material separation resistance at the time of casting, and can be removed from the mold in about one day, and is high after curing. It is an object of the present invention to provide a method for producing self-shrinkage reduction type high-strength concrete that exhibits strength.

In order to solve the above-described problems, the present invention provides a binder containing at least cement, silica fume, and an expansion material, water added so that the weight ratio to the binder is 10 to 15%, and fine aggregate And a coarse aggregate made of gravel or crushed stone, and a water-reducing agent added so that the weight ratio to the binder is 2 to 4%, which is a method for producing high-strength concrete, Preparing a mixing ratio setting binding material in which the expansion material in the material is replaced with a replacement binding material obtained by removing the expansion material from the binding material, the mixing ratio setting binding material, the water, the fine aggregate, and the The mixing ratio of the binder, the water, the fine aggregate, and the water reducing agent is set so that the zero flow value of the mortar that is a mixture with the water reducing agent is 250 to 350 mm. The replacement binder is obtained by removing the expansion material from the binder.
Also, the expanding material is desirably added in a range of 1 m ³ per 20~40kg for the entire concrete.

  According to such a method for producing high-strength concrete, it is extremely high in strength due to the sufficiently dispersed binder, and exhibits high fluidity when placed. Moreover, the expansion | swelling material can acquire the suppression effect of material separation of concrete, and can acquire the shrinkage reduction effect.

  According to the method for producing high-strength concrete of the present invention, it is possible to provide high-strength concrete that has high fluidity and material separation resistance at the time of casting and exhibits high strength after curing.

Hereinafter, preferred embodiments of the present invention will be described.
The high-strength concrete according to the present embodiment is composed of a mixture including at least a binder, water, fine aggregate, coarse aggregate, and a water reducing agent.

The binder includes at least cement, silica fume, and an expansion material. Further, an admixture such as blast furnace slag fine powder may be included within a range that does not adversely affect the compressive strength and fluidity.
As the binder, a premixed product previously mixed in a predetermined composition may be used, or may be mixed during concrete production.

  Although the kind of cement is not limited, moderately hot portland cement is used in this embodiment.

The expansive material suppresses the shrinkage of concrete by generating crystals of ettringite and calcium hydroxide by a hydration reaction to expand the concrete.
In this embodiment, 30 kg per 1 m ³ is added to the whole concrete.

If the addition amount of the expansion material is small, it is not possible to secure the material separation resistance of the concrete whose dispersibility is enhanced by the addition of a large amount of water reducing agent, so it is desirable to add 20 kg or more per 1 m ³ . On the other hand, since the excessive use expansive concrete expanding material which has not been reacted in the curing initial there is a risk of developing later abnormal swelling, it is desirable to less concrete 1 m ³ per 40 kg.
In addition, although the material which comprises an expansion | swelling material is not limited, a lime type expansion | swelling material is used in this embodiment.

Water is added so that the weight ratio to the binder is 10 to 15%. In the high-strength concrete of this embodiment, a large amount of a water reducing agent is added to increase the dispersibility of cement. Thereby, high compressive strength can be obtained even with a relatively high water binder ratio. In consideration of workability and manufacturing cost, the water binder ratio is desirably as high as possible within a range where the target compressive strength can be realized, and less than 10% is not desirable. In this embodiment, for the purpose of producing high-strength concrete having a compressive strength of 200 N / mm ² by applying heat curing for about two days using a normal heat curing facility such as a precast factory, the water binder ratio Is in the range of 10 to 15%.

  As the fine aggregate, crushed sand is used in the present embodiment, but the material constituting the fine aggregate is not limited. For example, natural aggregate such as river sand and mountain sand, blast furnace slag fine aggregate, etc. can be adopted. It is.

  Gravel or crushed stone is used for coarse aggregate.

The water reducing agent enhances the dispersibility of the binder, and is added so that the weight ratio with respect to the binder is 2 to 4%. If the weight ratio of the water reducing agent to the binder is less than 2%, the dispersibility of the binder in the concrete cannot be ensured sufficiently, and the compressive strength of 200 N / mm ² may not be ensured. On the other hand, if the weight ratio of the water reducing agent to the binder exceeds 4%, the setting may be excessively delayed or the separation resistance may be excessively reduced.
Although the kind of water reducing agent is not limited, in this embodiment, a polycarboxylic acid-based high performance water reducing agent is used.

The combination of the binder, water, fine aggregate, and water reducing agent consists of a mortar that is a mixture of water, fine aggregate, and water reducing agent. It is determined by finding a composition that gives a zero-stroke flow value of 250 to 350 mm.
High-strength concrete is determined by adding expansion material and coarse aggregate while maintaining the blending ratio of the mortar (binding material, water, fine aggregate, and water reducing agent). Realizing high-strength concrete with higher compressive strength even with the same water binder ratio by ensuring high fluidity and dispersibility of the binder with a zero mortar flow value of 250 mm or more, more desirably 300 mm or more Is possible. However, if the fluidity is increased excessively, it will be difficult to secure separation resistance, so that the expansion material in the binder is replaced with a material obtained by removing the expansion material from the binder, water, fine aggregate, and water reducing agent. It is desirable that the zero flow rate value of the mortar as a mixture does not exceed 350 mm.

  As described above, according to the high-strength concrete of the present embodiment, by adding a large amount of water reducing agent, the dispersibility of the binder is increased, and at the same time, an expansion material having an effect of reducing the slump flow of the concrete at the time of placing is selected. Therefore, since it is used as a part of the binder, the compressive strength, proper fluidity and separation resistance of high-strength concrete can be raised to a high level.

That is, in the initial stage of kneading, the dispersibility of the binder is increased by adding a large amount of water reducing agent, thereby contributing to the improvement of the compressive strength of the concrete.
After the binder is sufficiently dispersed, the fluidity of the concrete decreases due to the effect of the expansion material, making it difficult to separate the materials. Even after the fluidity is lowered, the slump flow is maintained at 550 to 750 mm, so that the mold can be filled firmly. This is because it is a few minutes after the start of kneading that the expanding material used starts to exert the effect of reducing the slump flow.

  According to the method for producing high-strength concrete according to the present embodiment, the addition of a large amount of water reducing agent indicates that the fluidity becomes excessively high due to the addition of a large amount of water reducing agent, or that the fluidity decreases by adding an expansion material. By using both and the expansive material, it is possible to cancel each other and achieve an appropriate fluidity.

  In addition, the combined use of a water reducing agent and an expanding material slows down the initial strength development of concrete due to the addition of a large amount of water reducing agent. It is possible to prevent the occurrence of a decrease and realize an appropriate initial strength expression property.

  Moreover, it becomes possible to reduce the self-shrinkage of high-strength concrete and to suppress the occurrence of cracks by using the expansion material.

Moreover, since the dispersibility of the binder is increased by adding a large amount of the water reducing agent, the compressive strength of the high-strength concrete can be increased.
Moreover, since gravel or crushed stone is used as the coarse aggregate, it is possible to realize high-strength concrete having a compressive strength of 200 N / mm ² or more.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and it goes without saying that the above-described constituent elements can be appropriately changed without departing from the spirit of the present invention.

  Hereinafter, experimental results carried out to confirm the effectiveness of the high-strength concrete according to the present invention will be shown.

First, it experimented about the influence of the addition amount of a water reducing agent regarding the compressive strength of mortar.
In this experiment, the zero hit flow value and the compression strength after curing were measured and compared for three types of mortars with different types or addition amounts of water reducing agents.

  Table 1 shows the materials used for the mortar used in this experiment, and Table 2 shows the composition of the mortar.

In this experiment, as shown in Table 2, a mortar 1 in which a polycarboxylic acid-based high-performance water reducing agent (water reducing agent A) having a higher dispersion performance than a commercially available product is used at a weight ratio of 2% with respect to the binder, generally Mortar 2 using 3% by weight of a commercially available polycarboxylic acid-based high-performance water reducing agent (water-reducing agent b) to the binder, and the same polycarboxylic acid-based high-performance water reducing agent as mortar 2 for the binder. Experiments were conducted on mortar 3 used at a weight ratio of 2%.
In addition, the kind and mixing | blending of the binder, water, fine aggregate, and antifoamer which are contained in the mortars 1-3 were made the same.

Table 3 shows the zero hit flow value and compressive strength of mortars 1 to 3.
In addition, the zero hit flow value was tested based on JASS 5T-701-2005 “Quality standards for high-strength concrete cement (draft)”. The compressive strength is the compressive strength of a φ50 × 100 mm specimen that was sealed at 90 ° C. for 48 hours after being sealed at 20 ° C. per day.

As shown in Table 3, the compression strength of the mortar 1 having the highest zero hit flow value was the highest, and the compression strength of the mortar 3 having the lowest zero hit flow value was the lowest.
Therefore, the higher the zero flow value, the higher the compressive strength, and the improvement in fluidity and dispersibility of the binder due to the addition of a large amount of water reducing agent will lead to an improvement in the compressive strength of high-strength concrete (mortar). Was confirmed.

Further, the mortar 1 and the mortar 2 have compressive strengths of 231 N / mm ² and 217 N / mm ² , respectively, and are close to the Young's modulus of the mortar like the andesite-based coarse aggregate shown in Reference 1, that is, By using a coarse aggregate that is relatively small and high in strength as the Young's modulus of the coarse aggregate, a decrease in strength due to mixing of the coarse aggregate can be reduced to about 5%. It can be evaluated that 200 N / mm ² or more can be secured as the compressive strength of the added high-strength concrete. Therefore, when evaluating the dispersibility of the binder based on the fluidity of the mortar, the mixture ratio setting binder obtained by replacing the expansion material in the binder with the replacement binder, water, and fine bone What is necessary is just to mix | blend so that the zero strike flow value of the mortar which is a mixture of a material and a water reducing agent may be set to 250-350 mm. The replacement binder is obtained by removing the expansion material from the binder. In order to obtain a mortar having such a high fluidity using a commercially available water reducing agent, it is necessary to add 2 to 4% of the water reducing agent in a weight ratio to the binder.
(Reference 1: Satoshi Watanabe, Shusuke Kuroiwa, Hiroshi Jinnai, Satoshi Namiki: Research on physical properties of coarse aggregates affecting the compressive strength of high-strength concrete, Architectural Institute of Japan, No. 588, pp. 21- 27, 2005.2)

Next, the result of investigating the influence of the use of expansion material on the fluidity of concrete will be shown.
In this demonstration experiment, the slump flow value of the high-strength concrete to which the expansion material was added was measured, and the fluidity was confirmed.

  Table 4 shows the materials used for the high-strength concrete A used in this demonstration experiment. Table 5 shows the composition of the high-strength concrete A according to this demonstration experiment. In this demonstration experiment, as Comparative Example B, the slump flow was measured and compared for high-strength concrete having the same blending conditions as high-strength concrete A except that no expansion material was used as part of the binder. .

  Table 6 shows the test results.

The mortar of the composition obtained by removing coarse aggregate from Comparative Example B has a zero striking flow value of 316 mm, a compression strength of a φ50 × 100 mm specimen cured at 90 ° C. for 48 hours after sealing at 20 ° C. for 1 day, and 228 N / mm ² . Yes, and had the same performance as mortar 1 in Table 3. Moreover, as shown in Table 6, the high-strength concrete of Comparative Example B has a high compressive strength of 200 N / mm ² or more in a φ100 × 200 mm specimen that was sealed at 90 ° C. for 48 hours after sealing at 20 ° C. for one day. It was. However, in Comparative Example B, the slump flow was 820 mm, the mortar exuded to the outer periphery of the sample after the slump flow test, and it was determined that the separation resistance was insufficient. Therefore, it was demonstrated that the separation resistance is reduced by adding a large amount of water reducing agent.

  On the other hand, as shown in Table 6, the high-strength concrete A according to the present example showed a slump flow of 750 mm or less, and no mortar exudation was observed in the outer periphery of the sample after the test. Therefore, it was confirmed that the use of the expansion material has sufficient separation resistance. In addition, although the high strength concrete A which concerns on a present Example shown in Table 6 and the high strength concrete B of the comparative example B are substantially the same intensity | strength, this arises because a test piece is small and it is unstrained. ing. When it is placed on an actual structure, if the slump flow is large as in Comparative Example B, problems such as cracks due to self-shrinkage tend to occur at sites where there is little aggregate caused by material separation.

  From the above results, it was proved that the separation resistance decreased by adding a large amount of water reducing agent can be improved by using the expansion material in combination.

Further, the high-strength concrete A exhibited 200 N / mm ² in compressive strength of a φ100 × 200 mm specimen that was sealed and cured at 90 ° C. for 48 hours after being sealed at 20 ° C. per day, and it was demonstrated that sufficient compressive strength was exhibited.

Claims (2)

A binder comprising at least cement, silica fume and an expansion material;
Water added so that the weight ratio to the binder is 10 to 15%;
Fine aggregate,
Coarse aggregate made of gravel or crushed stone,
A water-reducing agent added so that the weight ratio to the binder is 2 to 4%, and a method for producing high-strength concrete,
A mixing ratio setting binding material is prepared by replacing the expansion material in the binding material with a replacement binding material obtained by removing the expansion material from the binding material, the mixing ratio setting binding material, the water, and the fine aggregate. The mixing ratio of the binder, the water, the fine aggregate, and the water reducing agent is set so that the zero flow rate value of the mortar that is a mixture of the water reducing agent and the water reducing agent is 250 to 350 mm. The manufacturing method of high-strength concrete. The method for producing high-strength concrete according to claim 1, wherein the expansion material is added within a range of 20 to 40 kg per 1 m ^{3 with} respect to the whole concrete.