KR101568765B1 - Concrete composite for preventing drying shrinkage and crack - Google Patents

Abstract

A concrete composition capable of preventing cracking due to drying shrinkage by adding trehalose so as to suppress moisture evaporation on the surface during the initial curing process is disclosed.
The concrete composition according to the present invention is characterized in that trehalose is added to cement, sand and water to prevent drying shrinkage in the initial curing process.

Description

Technical Field [0001] The present invention relates to a concrete composition for preventing shrinkage and cracking,

The present invention relates to a concrete composition, and more particularly, to a concrete composition capable of preventing cracking due to drying shrinkage by adding trehalose so as to suppress moisture evaporation on the surface during an initial curing process .

In the concrete frame construction, if the concrete quality is met by the quality after the concrete is laid, etc., the form will be dismantled and the subsequent process will proceed. Generally, the concrete used in the construction site requires a strength level of about 21 ~ 35 MPa (210 ~ 350㎏f / ㎠).

However, the existing concrete cracks due to the drying shrinkage during the initial curing process. Especially, when the high strength concrete or mass concrete having high cement content is cast, the drying shrinkage and cracking due to high hydration heat are accelerated. Thus, when low-temperature cement or mixed cement is used, the early strength is lowered, and when the summer or mass concrete is placed at a high temperature, the hydration heat is high, resulting in drying shrinkage and cracking.

In order to prevent such drying shrinkage and cracking, attempts have been made to use low heat cement and mixed cement. However, this is based on the principle of reducing the cement ratio and reducing the hydration reaction. Since special cement is used instead of general cement, There is a problem that the unit price rises.

A related prior art is Korean Patent Laid-Open Publication No. 10-2005-0031605 (published Apr. 26, 2005), which discloses a composition for accelerating type of admixture and an early strength expressing concrete composition containing the same.

It is an object of the present invention to provide a concrete composition for preventing shrinkage and cracking which can prevent the occurrence of cracks caused by drying shrinkage during initial curing by suppressing moisture evaporation.

To achieve the above object, the concrete composition according to the present invention is characterized in that trehalose is added to cement, sand and water to prevent drying shrinkage during the initial curing process.

At this time, the concrete composition is composed of a binder including 30 to 40% by weight of cement and 60 to 70% by weight of sand, and water added in an amount of 10 to 20 parts by weight and 0.1 to 0.6 part by weight based on 100 parts by weight of the binder And trehalose.

The cement may be selected from the group consisting of 25-30% by weight of Portland cement, 35-45% by weight of silica, 15-25% by weight of calcium carbonate, 0.05-0.10% by weight of defoamer, 0.1-5% by weight of shrinkage reducing agent, 0.1 to 0.3% by weight of methyl cellulose and 0.1 to 0.2% by weight of methyl ethyl cellulose.

At this time, the antifoaming agent may include a single compound or a mixture of two or more selected from the group consisting of a silicone type, an alcohol type, and an ethylene oxide propylene (EOPO) type, and a shrinkage reducing agent based on a heavy glycol series may be used as the shrinkage reducing agent .

In particular, trehalose is more preferably added in an amount of 0.15 to 0.30 parts by weight based on 100 parts by weight of the binder.

The trehalose has a molecular structure represented by the following formula (1).

[Chemical Formula 1]

The concrete shrinkage and shrinkage prevention concrete cement according to the present invention can prevent the drying shrinkage due to hydration heat during the initial curing process by adding trehalose which suppresses moisture evaporation of the concrete surface even if high-strength concrete or mass concrete having a large cement content is placed. The occurrence of cracks can be prevented in advance.

Fig. 1 is a graph showing changes in water content by curing time for Examples 1 and 2 and Comparative Example 1. Fig.
2 is a graph showing changes in compressive strength for each of the curing times for Examples 1 and 2 and Comparative Example 1. Fig.
3 is a graph showing changes in length of curing time for Examples 1 and 2 and Comparative Example 1. Fig.

In order to fully understand the present invention, operational advantages of the present invention, and objects achieved by the practice of the present invention, reference should be made to the accompanying drawings and the accompanying drawings which illustrate preferred embodiments of the present invention.

Hereinafter, the present invention will be described in detail with reference to the preferred embodiments of the present invention with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in order to avoid unnecessary obscuration of the present invention.

Concrete composition for drying shrinkage and crack prevention

The concrete composition for drying shrinkage and crack prevention according to an embodiment of the present invention is characterized in that trehalose is added to cement, sand and water to prevent drying shrinkage during the initial curing process. Also, the concrete composition according to an embodiment of the present invention may further include gravel.

Particularly, the concrete composition for drying shrinkage and crack prevention according to the embodiment of the present invention is composed of a binder containing 30 to 40% by weight of cement and 60 to 70% by weight of sand, 10 to 20 parts by weight of 100 parts by weight of the binder, Added water and 0.1 to 0.6 parts by weight of trehalose.

The cement may be selected from the group consisting of 25-30% by weight of Portland cement, 35-45% by weight of silica, 15-25% by weight of calcium carbonate, 0.05-0.10% by weight of defoamer, 0.1-5% by weight of shrinkage reducing agent, 0.1 to 0.3% by weight of methyl cellulose and 0.1 to 0.2% by weight of methyl ethyl cellulose.

Here, the antifoaming agent may include a single or a mixture of two or more selected from the group consisting of a silicone type, an alcohol type, and an ethylene oxide propylene (EOPO) type, and a shrinkage reducing agent is preferably a heavy glycol type shrinkage reducing agent Do.

In particular, trehalose is more preferably added in an amount of 0.15 to 0.30 parts by weight based on 100 parts by weight of the binder.

cement

The Portland cement can be produced by grinding a mixture of calcareous raw material and clayy raw material in an appropriate ratio and then firing the mixture until a part thereof is melted and finely pulverizing the obtained clinker by adding a little gypsum as a coagulation controlling agent. Such Portland cement can be made of lime (CaO), silica (SiO ₂ ), alumina (Al ₂ O ₃ ), iron oxide (Fe ₂ O ₃ ), and the like.

The Portland cement is preferably added at a content ratio of 25-30% by weight of the total weight of the cement. If the content of Portland cement is less than 25% by weight, it may be difficult to secure sufficient rigidity. On the contrary, when the content of the Portland cement is more than 30% by weight, it is not economical because there is a high possibility of raising the manufacturing cost without further adding effect.

In this case, instead of Portland cement, crude steel cement, high strength cement, and mass cement, which generate a large amount of hydration heat during the initial curing process, may be applied, which is attributed to addition of trehalose having a moisture evaporation inhibiting function to be described later.

Silica sand is added for the purpose of improving the surface roughness of the mortar after application. It is preferable to use such a sandpaper having an average diameter of about 0.01 to 0.3 mm. When the average diameter of the silica sand is less than 0.01 mm, the effect of increasing the surface roughness to the time and cost required for obtaining the fine particles may be insignificant, which is not economical. On the other hand, when the average diameter of silica sand is more than 0.3 mm, not only is it difficult to exhibit the surface roughness improving effect properly, but also the crack resistance sharply decreases.

The silica sand is preferably added at a content ratio of 35 to 45% by weight of the total weight of the cement according to the present invention. When the content of silica sand is less than 35% by weight, it may be difficult to exhibit the surface roughness improving effect properly. On the other hand, when the content of silica sand is more than 45% by weight, there is a great possibility of raising the manufacturing cost without further adding effect.

Calcium carbonate (CaCO ₃ ) is not soluble in water and precipitates in an aqueous solution, so it is used as a fine powder filler.

The calcium carbonate is preferably added at a content ratio of 15 to 25% by weight based on the total weight of the cement according to the present invention. When the content of calcium carbonate is less than 15% by weight, it may be difficult to properly exhibit the particle size dispersion efficiency. On the other hand, if the content of calcium carbonate exceeds 25% by weight, there is a great possibility that the increase of the cost is caused only by no further effect of addition.

The antifoaming agent is added for the purpose of preventing the formation of bubbles and removing the generated bubbles. As the antifoaming agent, it is preferable to use a single or a mixture of two or more selected from the group consisting of a silicone type, an alcohol type, and an ethylene oxide propylene (EOPO) type.

The antifoaming agent is preferably added at a content ratio of 0.05 to 0.10% by weight of the total weight of the cement. If the content of the antifoaming agent is less than 0.05% by weight, the addition amount of the antifoaming agent is insignificant, so that it may be difficult to exhibit the bubble formation inhibiting and removing effect properly. On the other hand, if the content of the defoaming agent exceeds 0.10% by weight, the defoaming agent can be a factor for raising the manufacturing cost without further increase in the effect, which is not economical.

The shrinkage reducing agent is added for the purpose of reducing the shrinkage, and as the shrinkage reducing agent, a heavy-glycol shrinkage reducing agent may be used.

In the present invention, the shrinkage reducing agent is preferably added in a content ratio of 0.1 to 5% by weight based on the total weight of the cement. If the content of the shrinkage reducing agent is less than 0.1% by weight, it may be difficult to exhibit the effect of addition properly. On the other hand, if the content of the shrinkage reducing agent exceeds 5% by weight, it may be a factor for raising the manufacturing cost without further increase in the effect, which is not economical.

Methylcellulose is one of the alkylcelluloses, which increases the viscosity under alkaline conditions and has the role of adhesion and moisturizing. However, when methyl cellulose is used alone, there is a problem that the workability is lowered as the content of methyl cellulose is increased. Therefore, methyl ethyl cellulose, which is an auxiliary additive to be described later, is mixed together It is desirable to improve adhesion and long-term durability while preventing excessive deterioration of the workability.

Therefore, methylcellulose is preferably added at a content ratio of 0.1 to 0.3% by weight of the total weight of the cement. If the content of methylcellulose is less than 0.1% by weight, it may be difficult to exhibit the above effects properly. On the contrary, when the content of methylcellulose exceeds 0.3% by weight, the tackiness is excessively tacky and the workability is deteriorated.

Methyl ethyl cellulose is added for the purpose of preventing an excessive drop in the workability due to an increase in the amount of methyl cellulose.

It is preferable that methyl ethyl cellulose is added at a content ratio of 0.1 to 0.2% by weight based on the total weight of the cement. If the content of methyl ethyl cellulose is less than 0.1% by weight, it may be difficult to exhibit the effect of preventing the drop in workability. On the contrary, when the content of methyl ethyl cellulose is more than 0.2% by weight, there is a high possibility of raising the production cost compared to the effect of addition, which is not economical. Further, a phenomenon of tagging due to a drop in viscosity may occur.

Trehalose

Trehalose is a non-reducing, natural disaccharide made from starch as the raw material and manufactured with the latest fermentation technology. Trehalose is a carbohydrate widely found in nature such as plants and microorganisms. In particular, trehalose has a property of absorbing moisture and thus has a protective action against drying and freezing.

In the present invention, trehalose is preferably added in an amount of 0.1 to 0.6 parts by weight, more preferably 0.15 to 0.30 parts by weight, based on 100 parts by weight of a binding material containing 30 to 40% by weight of cement and 60 to 70% We can present wealth. When the amount of trehalose added is less than 0.1 part by weight, the content thereof is insignificant, so that it may be difficult to exhibit the above effect properly. On the contrary, when the addition amount of trehalose is more than 0.6 part by weight, it acts as a factor for raising the manufacturing cost without increasing the effect, which is not economical.

At this time, the existing concrete causes drying shrinkage and crack due to water loss in the curing process. Especially, in the case of crude steel cement, high strength cement, and mass cement, a lot of hydration heat is generated, and an increase in hydration heat accelerates the occurrence of cracks.

On the other hand, in the present invention, trehalose is used as an admixture of concrete to improve the quality by suppressing drying shrinkage and cracking which are disadvantages of conventional concrete.

The trehalose has a molecular structure represented by the following formula (1).

[Chemical Formula 1]

The concrete cement for drying shrinkage and crack prevention according to the embodiment of the present invention can be obtained by adding trehalose which suppresses water evaporation on the concrete surface even when high-strength concrete or mass concrete having a large cement content is laid, It is possible to prevent the occurrence of drying and shrinkage due to the occurrence of cracks and to prevent the occurrence of cracks in advance.

Example

Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

The contents not described here are sufficiently technically inferior to those skilled in the art, and a description thereof will be omitted.

1. Sample preparation

Samples according to Examples 1 to 7 and Comparative Example 1 having the compositions shown in Table 1 were prepared.

The samples according to Examples 1 to 7 and Comparative Example 1 were mixed in a motorized mixer for 10 minutes, dried at 65 占 폚 for 48 hours, and then dried at 3 cm (width) * 3 cm (length) And cut into 3 cm (thickness) to obtain a sample.

As the cement, Portland cement: 28 wt%, silica sand: 45 wt%, calcium carbonate: 23.75 wt%, defoamer: 0.05 wt%, shrinkage reducing agent: 3 wt%, methyl cellulose: 0.1 wt % And methyl ethyl cellulose: 0.1% by weight were used.

Remarks Binders ( wt %) H ₂ O Trehalose cement sand Comparative Example  One 35 65 16 - Example  One 35 65 16 0.15 Example  2 35 65 16 0.30 Example  3 35 65 16 0.20 Example  4 30 70 16 0.35 Example  5 30 70 16 0.40 Example  6 40 60 16 0.45 Example  7 40 60 16 0.50

2. Property evaluation

Table 2 shows the results of measurement of moisture contents by curing time for Examples 1 to 7 and Comparative Example 1, and FIG. 1 is a graph showing changes in moisture content for each of Examples 1 to 2 and Comparative Example 1 according to curing time.

Remarks Moisture Content (g) 24 hours 30 hours 4 days Comparative Example  One 5.8 5.1 3.8 Example  One 6.3 5.9 3.9 Example  2 8.4 8.0 5.0 Example  3 8.5 8.0 5.0 Example  4 8.6 8.1 5.1 Example  5 8.6 8.2 5.2 Example  6 8.7 8.2 5.3 Example  7 8.8 8.3 5.3

Referring to Table 2 and FIG. 1, it can be seen that after 24 hours of curing, the moisture contents of Examples 1 to 2 (b, c) and Examples 3 to 7 are larger than those of Comparative Example 1 (a) have. At this time, it can be seen that the more the amount of trehalose added, the more moisture content appears.

In particular, it can be seen that the water content reduction rate becomes abrupt after 2 days of curing, which is attributed to accelerated cement hydration reaction.

In the case of Example 1 (b), the water content was similar to that of Comparative Example 1 (a) after 4 days of curing. In the case of Example 2 (c), however, after 5 days of curing, ), The water content was consistently high at about 1.5 g.

Table 3 shows the results of measuring the compressive strengths for the curing time for Examples 1 to 7 and Comparative Example 1, and Fig. 2 is a graph showing the changes in compressive strength for the curing time according to Examples 1 to 2 and Comparative Example 1.

Remarks Compressive strength ( MPa ) 1 day 3 days 4 days 7 days Comparative Example  One 20 33 36 41 Example  One 11 31 38 44 Example  2 8 28 37 39 Example  3 8 27 39 42 Example  4 8 29 37 41 Example  5 7 26 38 40 Example  6 7 27 39 41 Example  7 7 26 37 42

Referring to Table 3 and FIG. 2, compressive strength was measured to be 50% or less as compared with Comparative Example 1 (a) in Examples 1 to 2 (b, c) and Examples 3 to 7 after 1 day of curing. Particularly, in all of Examples 1 to 2 (b, c) and Examples 3 to 7 after 3 days of curing, the compressive strength relative to Comparative Example 1 was measured to be 90% or more.

In other words, it was found that the initial strength was lower as the amount of trehalose was increased, but the compressive strengths were similar after 4 days of curing. This indicates that the total amount of cement hydration is similar to that of cement hydration.

Further, after 7 days of curing, the compressive strength of Examples 1 to 2 (b, c) and Examples 3 to 7 was measured to be higher than that of Comparative Example 1 (a) .

Table 4 shows the results of measuring the change in length by curing time for Examples 1 to 7 and Comparative Example 1, and FIG. 3 is a graph showing changes in length for curing time for Examples 1 to 2 and Comparative Example 1.

Remarks Length change (%) 4 days 6 days 8 days 10 days Comparative Example  One 0.00 -0.04 -0.06 -0.07 Example  One 0.00 -0.05 -0.09 -0.12 Example  2 0.00 -0.03 -0.06 -0.08 Example  3 0.00 -0.05 -0.07 -0.11 Example  4 0.00 -0.04 -0.09 -0.12 Example  5 0.00 -0.03 -0.08 -0.12 Example  6 0.00 -0.04 -0.09 -0.10 Example  7 0.00 -0.05 -0.08 -0.11

Referring to Table 4 and FIG. 3, all of the samples were swollen after 3 days of curing, and the rate of change was lower in Examples 1 to 2 (b, c) and Examples 3 to 7 than Comparative Example 1 (a).

After 4 days of curing, both shrinkage was observed on the previous day. The rate of change was smaller than those of Comparative Examples 1 (a) in Examples 1 to 2 (b, c) and Examples 3 to 7.

In addition, the shrinkage was observed after 5 days of curing, and the rate of change was less in the case of Example 2 (c) than in Comparative Example 1 (a), but was similar to that of Comparative Example 1 (a) .

In addition, all of the shrinkage occurred after 6 days of curing, and the rate of change was similar to that of Comparative Example 1 (a) in all of Examples 1 to 2 (b, c). That is, the rate of change in Example 2 (c) was lower than that in Example 1 (b), and the rate of change similar to that of Comparative Example 1 (a) was shown from 7 days after curing.

As can be seen from the above experimental results, it can be seen that the rate of change in length due to the content of trehalose does not show a linear trend.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, will be. Accordingly, the true scope of the present invention should be determined by the following claims

Claims (7)

Trehalose is added to cement, sand and water,
A binder containing 30 to 40% by weight of the cement and 60 to 70% by weight of sand,
Water added in an amount of 10 to 20 parts by weight with respect to 100 parts by weight of the binder, and trehalose added in an amount of 0.1 to 0.6 part by weight,
The cement,
A shrinkage reducing agent in an amount of 0.1 to 5% by weight, a methylcellulose (methyl (meth) acrylate, a methylcellulose 0.1 to 0.3% by weight of cellulose, and 0.1 to 0.2% by weight of methyl ethyl cellulose,
Wherein the silica sand has an average diameter of 0.01 to 0.3 mm.
delete delete The method according to claim 1,
The anti-
Based, alcohol-based, and ethylene oxide propylene (EOPO) -based ones, or a mixture of two or more thereof.
The method according to claim 1,
The shrinkage-
Wherein the shrinkage reducing agent is a heavy-glycol shrinkage reducing agent.
delete The method according to claim 1,
The trehalose,
1. A concrete composition for preventing shrinkage and cracking of dry matter, which has a molecular structure represented by the following formula (1).

[Chemical Formula 1]

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