KR101606840B1 - Concrete composition for reinforcing structure and manufacturing method of thereof - Google Patents

Abstract

Disclosed in the present invention are a concrete composition for reinforcing a structure mixed with 9.0-20.0 vol% of steel fibers, having water-binder ratio of 0.30-0.50, and formed in a slurry form, wherein the binder includes 30-70 wt% of cement, and 30-70 wt% of fine blast furnace powder; and a manufacturing method thereof. The composition reduces vibration and impact delivered to a structure by increasing resistance against explosion load, high pressure load, high impact load, and earthquake load; secures long term and short term stability of the structure by improving sensitivity, toughness, and durability; and reduces manufacturing expense.

Description

TECHNICAL FIELD [0001] The present invention relates to a concrete composition for reinforcing a structure and a method for manufacturing the concrete composition.

The present invention relates to a civil engineering field, and more particularly, to a concrete composition for reinforcing a structure and a method of manufacturing the same.

Recently, the social demands for securing safety against accidents and terrorism of major national facilities such as defense facilities, large-scale industrial facilities, and complexes are increasing rapidly.

However, in Korea, defense and explosion-related research is mostly carried out in the defense industry.

On the other hand, due to the expansion of industrial facilities and the upgrading of plant production capacity, the expected amount of damages is increasing exponentially.

Especially, Korea, which is the only divided nation, is exposed to the highest risk of terrorism, collision and explosion.

Also, as the population density of large cities increases, large-scale shocks or explosions cause not only great national losses, but also large economic and social costs required for recovery and serious social disruption.

1 is a graph compiling the number of explosion incidents per year.

Although explosion accidents and damage are increasing every year, research and development of materials that constitute efficient protection and explosion-proof systems of national important facilities are currently inadequate in Korea, and protection and explosion-proof structural members And there is no developed technology for evaluating the performance of structures.

In addition, in Korea, the market related to collision, impact protection, and explosion-proof safety is mainly used for protection of important national facilities such as a collision barrier of a car collision, a marine bridge collision prevention ball, a chemical plant such as an oil and gas plant, And the related market is not activated.

In addition to the new structures, there is a need to provide separate countermeasures in order to provide protection and explosion-proof functions in the case of infrastructure and buildings in use.

In other words, there is a need for developing and applying high performance reinforcing materials for providing protection and explosion protection and strengthening of existing structures.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to improve resistance to explosive load, high-pressure load, The present invention also provides a concrete composition for reinforcing a structure and a method of manufacturing the same.

In order to solve the above-mentioned problems, the present invention provides a method for producing a steel sheet, which comprises mixing 9.0 to 20% by volume of a steel fiber with a water-binder ratio of 0.30 to 0.50, And 30 to 70% by weight of fine blast furnace slag powder, and is formed in the form of a slurry.

Based on 100 parts by weight of the binder, 30 to 50 parts by weight of water; And 45 to 55 parts by weight of the aggregate.

The binder usually comprises 40 to 60% by weight of Portland cement; And 40 to 60% by weight of the fine blast furnace slag powder.

The blast furnace slag fine powder preferably has a powderity of 8000 to 9000 cm ² / g.

The binder preferably further comprises 0.4 to 0.6 parts by weight of a fluidizing agent based on 100 parts by weight of the binder.

The binder preferably further comprises 0.04 to 0.06 part by weight of a thickener based on 100 parts by weight of the binder.

The binder may further include 0.05 to 0.15 parts by weight of a defoaming agent based on 100 parts by weight of the binder.

The present invention relates to a method of manufacturing a concrete composition for reinforcing a structure, comprising the steps of: mixing the binder; Pre-arranging the steel fiber inside the mold; And filling the mixed binder into the mold. The present invention also provides a method of manufacturing a concrete composition.

The present invention increases resistance to explosive load, high-pressure load, high-load-load and seismic load, dissipates vibration and shock transmitted to a structure, and improves strength, toughness and durability to secure long- And which is economical in construction cost, and a method for producing the same.

1 is a graph showing the number of explosion accidents per year as a background art of the present invention.
2 shows an experimental example for verifying the effect of the present invention,
FIG. 2 is a graph showing the powdery degree of slag fine powder and the activity index by age. FIG.
3 is a graph showing the results of analysis of slag fine powder.
4 is a graph showing the activity index of the slag fine powder.
FIG. 5 is a graph showing the strengths of the slag fine powder replacement ratio.
6 is a graph showing the compressive strength ratios (ages of 7 days) for each kind of admixture and slag replacement ratio.
7 is a graph showing the compressive strength ratios (ages of 28 days) of the type of admixture and the slag replacement ratio.
8 is a graph showing the compressive strength ratios (age at 56 days) of the type of admixture and the slag replacement ratio.
9 is a graph showing the compressive strength ratios (age of 91 days) of the type of admixture and the slag replacement ratio.
10 is a graph showing a dropping time (W / B 50%) for each binder type.
FIG. 11 is a graph showing the dropping time (W / B 40%) for each binder type.
12 is a graph showing the dropping time (W / B 30%) for each binder type.
13 is a graph showing the fluidity of the slurry.
14 is a graph showing the compressive strength of the slurry.
15 is a graph showing the types of binders and the water drop time of each water-binder.
FIG. 16 is a graph showing the results of length change test (W / B 50%) for each type of binder. FIG.
FIG. 17 is a graph showing a result of length change test (W / B 40%) for each binder type. FIG.
18 is a graph showing a result of a length change test (W / B 30%) for each type of binder.
19 is a graph showing the results of chlorine ion penetration resistance test.
FIG. 20 is a graph showing the results of the test for freeze-thaw resistance.
21 is a load-deflection curve graph;
22 is a graph showing the results of bending strength measurement.
23 is a graph showing the results of the flexural tensile toughness test.
24 is a graph showing a compressive stress-strain curve.
25 is a graph showing the results of compression strength measurement.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings and the accompanying drawings.

The concrete composition for reinforcing a structure proposed in the present invention is mixed with 9.0-20 volume% of a steel fiber; the water-binder ratio is 0.30-0.50; the binder is 30-70 weight% of cement; And 30 to 70% by weight of fine blast furnace slag powder, and is formed in the form of a slurry.

That is, the concrete composition of the present invention is used as a high performance fiber reinforced cement composite (HPFRCC) mixed with a steel fiber.

Particularly, the conventional fiber reinforced cement composite material is characterized in that silica fume is used, while in the present invention, blast furnace slag fine powder is used instead of silica fume.

Here, the blast furnace slag fine powder has a powderity of 8000 to 9000 cm ² / g, and thus the strength can be further improved as the blast furnace slag manufacturing technology is applied.

Advantages of the concrete composition are as follows.

First, the strength, toughness and durability of fiber reinforced composites incorporating steel fiber can be improved to ensure the stability of the structure.

In particular, it has the advantage of maximizing its function as a protection and explosion-proof material of a structure.

Second, the concrete composition of the present invention is formed with a structure in which a binder in a slurry form is filled after a steel fiber is pre-disposed.

As a result, the filling performance of the slurry is improved and fluidity can be secured.

Third, there is an advantage in that it is economical because blast furnace blast furnace slag is mixed as a substitute material of expensive silica fume.

Fourth, conventional fiber-reinforced composite materials generally contain about 5% by volume of a steel fiber incorporated therein, and are mixed in the latter half of the manufacturing process, whereas the concrete composition of the present invention can incorporate about 9.5 to 10% by volume of a steel fiber, (Pre-Placed) in the process.

Therefore, the concrete composition of the present invention has an advantage that strength and toughness can be further improved because the incorporation rate of the steel fiber is high.

In such a concrete composition, the binder may contain, based on 100 parts by weight of the binder, 30 to 50 parts by weight of water; And 45 to 55 parts by weight of the aggregate.

In addition, the binder usually contains 40 to 60% by weight of Portland cement; And 40 to 60% by weight of fine blast furnace slag powder.

Further, the binder may further comprise 0.4 to 0.6 parts by weight of a fluidizing agent based on 100 parts by weight of the binder.

The binder may further contain 0.04 to 0.06 part by weight of a thickener based on 100 parts by weight of the binder.

As the thickener is mixed, the viscosity is imparted and the strength is further improved.

The binder may further contain 0.05 to 0.15 parts by weight of a defoaming agent based on 100 parts by weight of the binder.

As the antifoaming agent is incorporated, the air bubbles of the concrete composition are removed, thereby improving the workability and securing the quality.

A method for manufacturing a concrete composition for reinforcing a structure of the present invention is as follows.

A manufacturing step of mixing the binder is carried out.

A step of pre-placing the steel fiber inside the mold is performed.

A step of filling the mixed binder into the mold is performed.

That is, conventionally, the steel fiber is mixed in the latter half of the manufacturing process, while the manufacturing method proposed in the present invention differs in that the steel fiber is pre-disposed and then filled with a binder in the form of a slurry.

As a result, concrete having high mixing ratio of steel fiber and excellent workability, high quality and durability can be obtained.

Hereinafter, experimental examples for explaining the effects of the present invention will be described.

Table 1 shows the quality standards and composition of the fine blast furnace slag powder.

Table 2 shows the mixing design conditions of the binder in the form of slurry. Table 2 shows the weight ratio of binder to binder. Table 3 shows the unit weight.

In Tables 2 and 3, SG85-3-5, SG85-5-5, and SG85-7-5 satisfy the mixing conditions of the concrete composition presented in the present invention.

The activity index according to the powderiness of the blast furnace slag powder was evaluated for the test specimens produced according to the specifications and mixing conditions shown in Tables 1, 2 and 3.

As shown in Table 1, the strength development of the blast furnace slag fine powder was expressed by the activity index.

The activity index is expressed as a percentage of the strength of the ordinary portland cement in terms of the mortar strength according to the 'KS LISO 679 Cement Strength Test Method' of a binder in which the replacement ratio of the slag fine powder is 50%

FIG. 2 shows an example of the activity index of the blast furnace slag powder having a different powder degree. As the powder degree increases, the activity index increases, and it can be confirmed that the strength is particularly excellent in the early age.

FIG. 3 is a graph showing the material and the powdery graph, and Table 4 is a table showing the values in FIG. 3. As shown in FIG.

FIG. 4 is a graph showing the activity of the blast furnace slag fine powder, and FIG. 5 is a graph showing the strength of the blast furnace slag fine powder with respect to the ordinary Portland cement.

Next, an experiment was conducted to measure the powderiness of the blast furnace slag and the compressive strength ratio (by age) according to the replacement ratio.

Table 5 shows the compressive strengths and compressive strength ratios of the binders.

6 to 9 are graphs showing the strength of each test level at 7 days, 28 days, 56 days and 91 days of age, respectively, as a percentage of ordinary portland cement. The 3 day strength of the mortar substituted with blast furnace slag fine powder is shown in FIG. , But it was lower than that of ordinary portland cement and SF10 at all levels, and the strength was further decreased with increasing substitution rate.

In particular, the strength of the specimen SG45 tended to decrease with increasing substitution rate at all ages. At 30% and 50% substitution rate, the strength was higher than ordinary portland cement after 28 days, And also showed a low value in the day.

Unlike SG45, SG70 and SG85 exhibited the highest intensities at 50% substitution after 7 days of age and higher than those of SF10 at 30% and 50%, respectively.

FIG. 10 is a graph showing the dropping time (W / B 50%) by binder type. As shown in FIG. 10, the activity of silica fume was about 107% at 7 days old age, 108% and 118%, respectively.

FIG. 11 shows the dropping time (W / B 40%) for each type of binder, and FIG. 12 shows the dropping time (W / B 30%) for each binder type. As shown in FIGS. 11 and 12, Even when the substitution ratio was 30%, the intensity was equal to or higher than that of SF10.

In SG85, the substitution ratio of 30% and 70% was higher than that of SF10.

In SG 91 and SG 85, the strength was higher than SF 10 regardless of the substitution rate.

Additional experiments were conducted to evaluate the binder formulation design and properties of the concrete compositions of the present invention.

Table 6 shows binder blend design conditions.

FIG. 13 is a graph showing the binder fluidity of a test specimen designed according to the mixing conditions shown in Table 6, and FIG. 14 is a graph showing the compressive strength of the binder.

Next, the falling time of each binder was measured.

Table 7 shows the water-binder ratio and the dropping time for each type of binder, and this is shown graphically in FIG. 10 to FIG.

As a result of the test, SF10 shows the same or higher dipping time than ordinary portland cement.

This is because, when silica fume is used, the amount of the fluidizing agent is doubled and the mixing ratio is adjusted so as not to use 50% or more of the thickener in comparison with the ordinary portland cement in consideration of a decrease in fluidity and an increase in viscosity.

Under the condition that the amount of fluidizing agent and thickener used is the same, the descending time of SF10 is about 3 ~ 4 times longer than that of Portland cement.

SG45, which has a low powdered blast furnace slag powder, showed the same level as portland cement but it increased with increasing rate of substitution.

In the case of SG70 and SG85 using blast furnace slag fine powder, the dropping time was significantly reduced compared to the other levels, especially the lowest value in SG70.

The dropping time of SG85 was increased at the water - binder ratio of 50%, but it increased at 40% and 30% of water - binder as in SG45.

In the above, the powder composition of the blast furnace slag was also tested for the composition and effect of the binder. Next, an experiment was conducted to analyze the durability of the charging slurry.

As mentioned above, the level of slurry for the durability evaluation is 3 levels of water-binder ratio of 50%, 40% and 30%, the level of ordinary portland cement used alone, the level of silica fume replaced by 10% And 50% replacement of slag powder.

Table 8 shows the slurry mixing conditions by unit weight, and Table 9 shows the slurry mixing conditions in terms of the weight ratio to the binder.

For durability analysis, first of all,

The results of the measurement of the dropping time of the water-binder according to the type of the binder are shown in Table 10 and FIG.

At the water-binder ratio of 50%, the flowability of the formulation using SG was about twice as good as that of the ordinary Portland cement formulation. However, as the water-binder ratio was lower, the width decreased to 40% %, The flowability of ordinary Portland cement formulation was rather good.

On the other hand, in the case of the SF formulation using twice the fluidizing agent compared to the other formulation, the fluidity was lowered by about 35% to 40% compared with the ordinary Portland cement formulation at the water-binder ratio of 50% % Showed a flow characteristic which is about 50% lower than that of OPC blend.

When the same binder is used, it can be seen that the best flowability is obtained when the water-binder ratio is 40%, that is, when the fine aggregate ratio to the binder is 0.5, when the water-binder ratio is changed.

For durability analysis, length change test was performed.

The results of measurement of the water-binder ratio change up to 8 weeks of age are shown in Figs. 16 to 18.

At the water-binder ratio of 40%, the rate of change of the length of the SF composition was noticeable from the beginning, and at the water-binder ratio of 50% and 30%, the variation of the length of the SG composition was relatively high at the beginning However, it shows a tendency to decrease compared to other formulations starting from 3 weeks of age.

It can be seen that the Portland cement formulations and SF formulations usually show the same length change by age.

Next, a chlorine ion penetration resistance test was conducted.

In general concrete specimens, 60Volt power is supplied to the measuring circuit. However, in case of slurry mixture without coarse aggregate, the amount of water passing through the specimen is very large.

Table 11, Table 12, and FIG. 19 show the results of the chloride ion penetration resistance test. In the case of the ordinary Portland cement formulation, the amount of passing charge at all levels, regardless of the water-binder ratio, .

On the other hand, the SF and SG combination had a high water content and a low water permeability, and the lower the water - binder ratio, the better the water resistance.

Based on the above test results, the Portland cement formulation showed very low penetration resistance and the other formulation had good results.

Next, accelerated carbonation experiments were carried out.

The carbonation test specimens were subjected to accelerated carbonation test at the temperature of 20 ± 2 ℃, relative humidity of 60 ± 5% and carbon dioxide concentration of 5 ± 0.2% after 28 days of water curing. At 4 weeks after the initiation of the promotion, phenolphthalein 1% The depth of carbonation was measured.

The results of the accelerated carbonation test using the specimen after 4 weeks showed that the effect of water binder ratio was larger than that of using powders as shown in Table 13 and the carbonation depth was 1 mm even under the condition of 50%

Therefore, the effect of accelerated carbonation on the durability was not significant.

In addition, experiments were conducted to measure the resistance to freezing and thawing.

20 is a graph showing the result of measurement of the freeze-thaw resistance.

Next, an experiment was conducted to analyze the characteristics of the concrete composition formed by mixing blast furnace slag with silica fume.

For the above experiment, two types of high-strength slurry were used and the mixing conditions of the slurry used in Table 14 were shown.

The two types of slurries used in the above experiment have the same water-binder ratio of 0.4. In the case of SG30, 30% of cement is replaced with blast furnace slag. SF10 is a mixture of 10% of cement with silica fume to be.

In both blends, the cement used was one kind of ordinary Portland cement of the same S company. In case of blast furnace slag, powder of 8500 cm2 / g was used for the powder supplied by S, and the powder of silica fume was 200000 cm2 / g Were used.

As a fine aggregate for the slurry composition, silica sand (maximum particle diameter 0.2mm) was used. In order to ensure the workability and quality of the slurry, a small amount of powdery high-performance water reducing agent, thickener and defoamer were added.

First, the bending tensile strength test of a mixture containing blast furnace slag powder substituted with silica fume was performed.

Fig. 21 shows that both of the tests with two load-deflection curves showed that the deflection reference point jig attached to the upper part of the center of the test specimen dropped out after the load peak during the 8-day test at the time of the test, showing only meaningful deflections after the maximum load.

Based on the results of FIG. 21, the maximum load and the bending strength of each test specimen are shown in Table 15, and the average of the bending strengths for each combination is shown in the graph of FIG.

As can be seen from FIG. 22, in the bending strengths, the SG30 blend was slightly higher than the SF 10 blend in both the ages of 8 and 14 days.

The flexural strengths of SF10 and SG30 were 32.7 MPa and 33.8 MPa, respectively. The flexural strengths of SF10 and SG30 were 34.7 MPa and 37.47 MPa, respectively.

The flexural strengths of SF10 and SG30 were 48.19MPa and 48.39MPa, respectively.

Next, the flexural tensile toughness test of the concrete composition containing the blast furnace slag fine powder was performed in place of the silica fume.

The flexural toughness index I5 of ASTM C1018 was calculated based on the load-deflection curve and the initial crack deflection of FIG. 21, and is shown in Table 16.

The flexural toughness index I5 is obtained by dividing the area up to 3.0 times the initial crack deflection of the area under the load-deflection curve by the area up to the initial crack deflection. The difference between the SF10 blend and the SG30 blend toughness index I5 is insignificant.

In addition, the tendency to increase or decrease in age did not seem obvious.

Next, the uniaxial compressive strength test of the concrete mixture was carried out.

24 is a compressive stress-strain curve of the combination of SF10 and SG30 calculated using the load-strain relationship curve.

The maximum load deviations of the same age specimens of each formulation are somewhat different, but the overall tendency of the stress - strain curves was comparable.

Based on the results shown in Fig. 24, the compressive strengths of the respective test specimens were obtained and are shown in Table 17.

The compression strength average for each formulation is the same as the graph shown in Fig.

In the uniaxial compressive strength, SG30 blend showed higher strength than that of SF10 blend at 8 days and 14 days of age. Compressive strengths of SF10 and SG30 were 82.15MPa and 83.6MPa, respectively.

Compressive strengths of SF10 and SG30 were 14.2 MPa, 92.91, and 106.21MPa and 99.14, respectively.

Next, the unconfined compression toughness test of the concrete composition containing the blast furnace slag fine powder replacing silica fume was performed.

The compression toughness index was calculated based on the compressive stress-strain curve of FIG. 24, and is shown in Table 18.

The compressive toughness index can be obtained by the JSCE-SF5 method of the Japan Society of Civil Engineering, but the JSCE-SF5 takes into account only the strain up to the strain of 0.75% of the stress-strain curve.

As shown in FIG. 24, since the strain of 0.75% (0.0075 mm / mm) belongs to the linear elastic section, the compression toughness index based on JSCE-SF5 is not applicable to the HPFRCC material. And the lower area of the test piece was defined as a value obtained up to a strain of 10%.

The compressive toughness index according to each blend and age is shown. There is no significant difference between compressive toughness index of SF10 blend and SG30 blend, and compressive toughness increases with age.

As a result, it was confirmed through the verification test that the concrete composition of the present invention can secure strength and durability by mixing the blast furnace slag fine powder with the high melting point blast furnace, .

Further, it can be confirmed that not only the compressive strength but also the compressive toughness, the flexural strength and the flexural toughness are excellent by mixing the blast furnace slag fine powder replacing silica fume.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. It is to be understood that both the technical idea and the technical spirit of the invention are included in the scope of the present invention.

Claims (8)

9.0 to 20% by volume of a steel fiber is mixed,
Water-binder ratio of 0.30 to 0.50,
The binder
30 to 70% by weight of cement;
And 30 to 70% by weight of a blast furnace slag powder having a powder viscosity of 8000 to 9000 cm < ² > / g,
Based on 100 parts by weight of the binder,
30 to 50 parts by weight of water;
45 to 55 parts by weight of aggregate;
0.4 to 0.6 parts by weight of a fluidizing agent,
A method for producing a concrete composition for reinforcing a structure formed in a slurry form,
Preparing a mixture by mixing the binder;
Pre-arranging the steel fiber inside the mold;
Filling the mixed binder into the mold;
By weight based on the total weight of the concrete composition. delete The method according to claim 1,
The binder
Usually 40 to 60% by weight of Portland cement;
40 to 60% by weight of the blast furnace slag powder;
By weight based on the total weight of the concrete composition. delete delete The method according to claim 1,
The binder
Based on 100 parts by weight of the binder,
0.04 to 0.06 parts by weight of a thickener;
The method of claim 1, The method according to claim 1,
The binder
Based on 100 parts by weight of the binder,
0.05 to 0.15 parts by weight of a defoaming agent;
The method of claim 1, delete

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