KR101343454B1 - Hydration heat dissipation concrete composition using CNT - Google Patents

Abstract

The present invention relates to hydration heat-dissipating concrete that reduces the temperature cracking by heat dissipating cement hydration heat and improving the tensile strength of the concrete using the properties of the CNT.
The present invention is "concrete composition comprising a binder, fine aggregate, coarse aggregate and compounding water, the compounding water is composed of 80 to 97 parts by weight of general water and 3 to 20 parts by weight of CNT dispersion, the CNT dispersion is a solvent 96-98 It is composed of 2 parts by weight to 4 parts by weight of CNT powder, and the amount of CNTs is 0.12 to 0.4 parts by weight based on 100 parts by weight of the blended water.

Description

Hydration heat dissipation concrete composition using CNT

The present invention relates to a hydration heat-dissipating concrete composition that reduces the temperature cracking by heat dissipating cement hydration heat using the properties of CNTs and improving the tensile strength of concrete.

Due to the development of the construction industry, the size of concrete structures is getting bigger and higher, resulting in the increase of hydration heat of cement, which is increasing the frequency of cracking of concrete structures. In concrete, the heat of hydration of cement accumulates during hardening, thereby increasing the internal temperature of concrete. At this time, a stress is generated by the temperature difference between the surface of the concrete member and the inside or by the restraint of shrinkage deformation when the temperature of the entire member decreases, and when the stress exceeds the tensile strength of the concrete, cracking occurs. Thus, the heat of sign language can cause structural problems. Problems caused by hydration heat have a great impact on the safety of the structure, which leads to very dangerous situations where the safety of the structure cannot be guaranteed.

[Reference Figure 1]-Crack Generation by Hydration Heat

In order to solve this problem, methods such as pipe cooling, precooling, low heat generation cement, three-component concrete, and super-delaying agent have been introduced. However, pipe cooling and precooling have various problems such as process problems, site management problems, and production problems, and there is a limit in reducing the heat of hydration even when using low heat cement or three-component concrete. Even if this is accompanied by a process problem that must delay the mold demoulding time.

[Reference Figure 2]-Heat of hydration according to material type

Therefore, it is time to develop functional concrete that combines both existing engineering and material parts, and if such technology is developed, not only can it reduce the heat of hydration, but also it is not necessary to extend the period of form retention. It can shorten the construction cost and reduce the construction cost, and it will be able to play a very important role in the large foundation mat construction because the durability of the structure is strengthened by reducing the temperature crack.

[Graph 1] below shows the generated stress and allowable stress distribution of general concrete. As mentioned in [Technological Background of the Invention], the stress is generated in the concrete member due to the temperature difference between the surface and the interior of the concrete member or the restraint of shrinkage deformation when the temperature of the member drops. This stress is the tensile strength of the concrete. If it exceeds, cracking occurs. This is called temperature cracking.

[Graph 1]-Allowable stress and generated stress of general concrete

The present invention aims to reduce the temperature cracking of the concrete as described above.

The present invention is "concrete composition comprising a binder, fine aggregate, coarse aggregate and compounding water, the compounding water is composed of 80 to 97 parts by weight of general water and 3 to 20 parts by weight of CNT dispersion, the CNT dispersion is a solvent 96-98 It is composed of 2 parts by weight to 4 parts by weight of CNT powder, and the amount of CNTs is 0.12 to 0.4 parts by weight based on 100 parts by weight of the blended water.

In another aspect, the present invention provides the "hydration heat radiating mass concrete composition containing CNTs, characterized in that the surface of the CNT is coated with magnesium oxide (MgO).

In addition, the present invention provides the "hydration heat radiation mass concrete composition containing CNTs, characterized in that 0.25 to 0.5 parts by weight of carbon fiber having a length of 6 to 12 mm is added to 100 parts by weight of the binder.

Carbon Nano Tube (CNT) is a new material in which hexagonal elements consisting of six carbons are connected to each other to form a tubular shape, and the diameter of the tube is several tens to tens of nanometers (nm), which is called carbon nanotubes.

[Reference Figure 3]-Shape of Carbon Nanotubes

Carbon nanotubes (CNTs) are known to have the best thermal conductivity among existing materials. In the case of single-walled carbon nanotubes (SWCNT), the thermal conductivity is 6,000 W / mK, which is three times that of diamond and 15 times that of silver, which is the most thermally conductive metal. Therefore, extensive research is being conducted to use the excellent thermal conductivity of carbon nanotubes in industry. In the case of heat-dissipating paint using carbon nanotubes, it is possible to improve the cooling performance by up to 20% or more simply by coating on metal surfaces such as aluminum and copper, which are substrates, and CNT-metal composites and CNT-ceramic composites incorporating carbon nanotubes It is recognized as a basic material for developing a new concept of material having excellent mechanical properties as well as thermal properties. In addition, the tensile strength of carbon nanotubes is 20 times better than that of high strength alloys.

The characteristics of the carbon nanotubes as described above are summarized in the following [Table 1].

The tensile strength 20 times better than high strength alloy Heat transfer 3 times of diamond Allowable current density 1,000 times of metal Electrical conductivity 70 times better than conventional computer silicon chips at room temperature (25% better than semiconductor materials) Mechanical properties 100 times the strength and wear resistance of steel, ultralight, excellent elasticity and resilience Chemical property Excellent structural stability (minimization of quantum mechanical interference at high temperatures) Other characteristics High gas adsorption and charge storage capacity per unit mass, affinity with biological tissues and hydrogen detection ability

The present invention is to improve the early strength expression performance while controlling the temperature cracking of the concrete by applying the characteristics of the carbon nanotubes as described above.

When CNT is incorporated into concrete, the tensile strength of the concrete increases. In addition, the heat conductivity of the concrete is increased, thereby rapidly transferring heat generated from the center to the surface, thereby lowering the center temperature. That is, when CNT is mixed in concrete, as shown in [Graph 2], the allowable stress is increased and the generated stress is reduced, thereby reducing the temperature crack due to the heat of hydration.

[Graph 2]-Allowable and generated stress of CNT mixed concrete

"Hydration heat dissipating concrete composition containing CNTs" according to the present invention improves the tensile strength of the concrete and quickly dissipates the heat of hydration to the outside, thereby increasing the allowable stress and lowering the generated stress by reducing the temperature cracking compared to general concrete without mixing the CNTs. Let's go. On the other hand, as the amount of CNT incorporation increases, the fluidity decreases, but by controlling the amount of CNT dispersion in which the general water is substituted with the CNT dispersion and the CNT content of the CNT dispersion itself, it is possible to maintain fluidity in an appropriate range for construction.

The present invention is "concrete composition comprising a binder, fine aggregate, coarse aggregate and compounding water, the compounding water is composed of 80 to 97 parts by weight of general water and 3 to 20 parts by weight of CNT dispersion, the CNT dispersion is a solvent 96-98 It is composed of 2 parts by weight to 4 parts by weight of CNT powder, and the amount of CNTs is 0.12 to 0.4 parts by weight based on 100 parts by weight of the blended water.

The present invention has a great feature in that a part of the general concrete composition blended water is replaced with a CNT dispersion. Therefore, any binder, fine aggregate, coarse aggregate and general water other than the CNT dispersion may be applied as long as it can express a function as concrete. In addition, it is possible to mix the admixture for enhancing the performance required, such as the fluidity of the concrete, the construction year.

The binder is a common portland cement (OPC) mainly composed of lime, silica, alumina, etc., as well as inorganic binder hardeners such as fly ash, bottom ash, blast furnace slag, furnace oxide slag and loess. When the low thermal cement is used as the binder applied to the present invention, the heat of hydration may be lowered together with the heat dissipation effect by the CNT.

The fine aggregate is aggregate that passes 85% or more of a 5mm sieve as fine aggregate such as sand. The coarse aggregate refers to aggregates that remain at least 85% in the 5 mm sieve as natural gravel or artificial crushed stone, and in construction, those having a diameter of 25 mm or less are used. However, the size and size of the fine aggregate and coarse aggregate may be somewhat adjusted according to the use of concrete.

The blended water in the present invention is composed of 80 to 97 parts by weight of general water and 3 to 20 parts by weight of CNT dispersion. The general water collectively refers to tap water, river water, ground water, etc., which do not include oil, acid, alkali, salts, organic matters, and the like. The CNT dispersion refers to a solution in which CNT powder is uniformly dispersed in a solvent, and was developed for coating CNT on a substrate. CNTs are entangled with each other because they are composed of linear lines, and thus, when they are directly administered to the concrete composition, the CNTs are not evenly dispersed in the concrete composition by entanglement between the CNTs. Therefore, in the present invention, by applying the CNT dispersion developed for coating as part of the blending water, the CNT is evenly dispersed in the concrete composition, and any of the conventionally developed CNT dispersions may be applied. However, by applying the CNT dispersion, consisting of 96 to 98 parts by weight of solvent and 2 to 4 parts by weight of CNT powder, when the amount of CNT becomes 0.12 to 0.4 parts by weight based on 100 parts by weight of the blended water, in terms of heat dissipation and fluidity of cement hydration desirable. The solvent may be mixed with one or more selected from the group consisting of alcohols, amides, pyrrolidones, hydroxyesters, organic halides, nitro compounds and nitrile compounds, based on water. Various dispersants may be added. The CNT powder is obtained by cutting CNTs by physical or chemical methods. The CNT powder is visually observed as a powder, but from a microscopic point of view, it is also a linear structure.

Hereinafter, the significance of the mixing ratio (3 to 20 parts by weight) of the CNT dispersion in the blended water and the effects of the present invention will be described in detail through specific test examples and test results.

Table 2 below shows the binder (usually Portland cement and fly ash) 457㎏ / ㎥, coarse aggregate 908㎏ / ㎥, fine aggregate 799㎏ / ㎥, water binder ratio (mixture water (general water and CNT dispersion)) / Weight of the binder × 100) is 35, the aggregate aggregate (weight of the aggregate / weight of the total aggregate × 100) is compounded to 47, and the concrete composition of the concrete composition in which 0.8 parts by weight of AD reducing agent added to 100 parts by weight of the total concrete composition It is a combination table. In this embodiment, "Plain" is a mixture of 160kg / ㎥ of ordinary water only without mixing the CNT dispersion, CNT mixed concrete I to III is to replace 2, 4, 6% by weight of CNT dispersion with CNT dispersion, respectively . The CNT dispersion liquid at this time is comprised of 98 weight part of solvents, and 2 weight part of CNT powders.

division W / B S / a Unit material amount (kg / m3) AD
(%)
W OPC F / A CNT
(2wt%) S G Plain

35


47
160.0

343


114
-

799


908


0.8
CNT mixed concrete Ⅰ
Test Example 1 156.8 3.2 CNT mixed concrete Ⅱ
Test Example 2 153.6 6.4 CNT mixed concrete Ⅲ
Test Example 3 150.4 9.6

W / B: Water Binder S / a: Fine Aggregate Rate

W: Regular OPC: Common Portland Cement

F / A: fly ash CNT: CNT dispersion (contains 2wt% of CNT)

S: fine aggregate G: coarse aggregate

Therefore, the mixing water of CNT mixed concrete I (hereinafter, Test Example 1) is a mixture of 156.8 kg / m3 of general water and 3.2 kg / m3 of CNT dispersion liquid, and the content of CNT is 64 g / m3, which is 0.04 parts by weight. That's the amount.

CNT mixed concrete II (hereinafter, Test Example 2) is a mixture of 153.6 kg / m 3 of general water and 6.4 kg / m 3 of CNT dispersion, and the content of CNT is 128 g / m 3, which corresponds to 0.08 parts by weight of the blended water.

CNT mixed concrete III (hereinafter Test Example 3) is a mixture of 150.4 kg / m 3 of general water and 9.6 kg / m 3 of CNT dispersion, and the content of CNT is 192 g / m 3, corresponding to 0.12 parts by weight of the blended water.

Items to be tested through the above test examples are summarized in [Table 3] below. That is, the slump of slump, slump flow and air volume, compressive strength of hardened concrete, splitting tensile strength, simple thermal insulation temperature rise test, and thermal conductivity were tested.

division Substitution rate (wt%) Test Items Remarks Plain 0 slump
Slump flow
Air volume
Compressive strength
Split Tensile Strength
Simple Insulation Temperature Rise Test
Thermal conductivity measurement Substitution rate is the ratio (weight ratio) which replaced the water (mixture water) mix | blended with concrete with CNT dispersion liquid. CNT mixed concrete Ⅰ
Test Example 1 2 CNT mixed concrete Ⅱ
Test Example 2 4 CNT mixed concrete Ⅲ
Test Example 3 6

Hereinafter, the test results derived from the various test items described above will be described.

1. Flow Characteristics

For stiff concrete, flow characteristics can be tested by slump measurement, slump flow measurement and air volume measurement. The flow characteristic measurement results for each test example are summarized in [Table 4] below.

division Slump (mm) Slump flow (mm) Air volume (vol%) Concrete temperature (℃) Plain 235 400 × 400 2.0 22.5 Test Example 1 220 330 × 335 1.4 22.6 Test Example 2 220 360 × 350 1.5 22.6 Test Example 3 210 330 × 330 1.6 22.4

Slump and slump flow measurements were made according to KS F 2402 and air volume measurements were made according to KS F 2421.

[Graph 3]-Slump and air volume test result

As a result of the test, as shown in [Graph 3], the slump values of all the experimental examples were found to be within 210 ± 25mm. The amount of air dropped to 1.4% by volume in Test Example 1, but gradually increased in Test Examples 2 and 3. The slump flow values were lower than those of Test Examples 1 to 3 that did not contain CNTs (Plain, hereinafter referred to as 'reference concrete'), but it was found that there was no significant difference between Test Examples 1 to 3.

Overall, the fluidity change according to CNT incorporation can be easily observed in the slump value, and the slump decreases as the amount of CNT incorporation increases. Since the appropriate slump value according to KS F 4009 is 210 ± 25mm, both the reference concrete and Test Examples 1 to 3 above satisfy the appropriate slump range. However, under the same conditions as the above-mentioned concrete, the slump test was carried out while increasing the amount by which the general water in the blended water was replaced with the CNT dispersion by 1 part by weight in the same condition, as shown in [Graph 4]. If the slump at 20 parts by weight of the blended water is 185 mm, and the slump until this time is in the range of 210 ± 25 mm and exceeds the above range, problems such as poor construction due to fluidity decrease may be caused.

[Graph 4] Trend of Slump Change According to Application Rate of CNT Dispersion Substitution

Since the above-mentioned slump change is caused by the amount of CNT in the concrete, the ratio of replacing the general water with the CNT dispersion in the blended water based on the amount of CNT is converted into CNT in the range of 0.12-0.4 parts by weight relative to 100 parts by weight of the blended water. When mixed, it can be said that the proper fluidity of the concrete is maintained.

2. Strength characteristics

The compressive strength and splitting tensile strength of the concrete (split tensile strength) were carried out on the 3rd, 7th and 28th days, respectively, as summarized in [Table 5] below.

division
Compressive strength (MPa) Split Tensile Strength (MPa) 3 days 7 days 28th 3 days 7 days 28th Plain 29.8 45.8 58.7 2.50 2.86 3.9 Test Example 1 32.0 45.8 60.2 2.55 3.19 4.0 Test Example 2 31.6 46.3 59.8 2.75 2.94 4.2 Test Example 3 31.8 47.9 60.3 2.74 3.54 4.2

Compressive strength measurement results of concrete are shown in [Graph 5] below. The compressive strength of concrete showed a tendency to increase from the reference concrete to Test Examples 1 to 3, that is, the amount of CNT incorporation increased. The compressive strength at 3 days of age was the highest in Test Example 1, but there was no significant difference from Test 3, and in Test Example 3, the compressive strength was increased by more than 6.7% compared to the reference concrete. However, since the compressive strength of concrete is not a critical factor in order to reduce the desired temperature crack, the present invention explains the significance of the compressive strength test in terms of confirming that there is no adverse effect on the compressive strength according to the mixing of CNTs. can do.

[Graph 5]-Compressive strength measurement result

Tensile strength measurement results of concrete are shown in [Graph 6] below. It was found that the tensile strength of concrete tended to increase from the reference concrete to Test Examples 1 to 3, that is, the amount of CNT incorporation increased. Tensile strength at 3 days of age was the highest in Test Example 2, but there is no significant difference from Test 3, and Test 3 also showed that the tensile strength at 3 days of age was 9.6% higher than the reference concrete. In the case of continuous increase in the amount of CNT incorporation, the three-day tensile strength converges to 10% improvement compared to the reference concrete, and the 28-day tensile strength converges to an 8% improvement. Therefore, there is no great advantage in excessively mixing the CNTs to improve the tensile strength of the concrete, it is preferable to make the CNT 0.12 ~ 0.4 parts by weight compared to 100 parts by weight of the blended water in consideration of the fluidity of the solidified concrete.

[Graph 6]-Tensile strength measurement result

3. Thermal properties

The present invention relates to hydrated heat-dissipating concrete incorporating CNTs, and it is important to watch for changes in thermal properties of concrete according to the amount of CNT incorporation. The thermal properties of the concrete were tested by the simple thermal insulation temperature rise test and the thermal conductivity measurement.

In the simple thermal insulation temperature rising test, as shown in [Reference 4] below, a box-shaped container having a thermal insulation performance (width, length, and height is 220 mm (220 × 220 × 220), respectively) is filled with concrete, and the upper part is It was to indirectly check the heat dissipation performance of concrete mixed with CNTs by measuring the temperature difference between the center and the surface in the open state.

[Reference Figure 4]-Simple Insulation Temperature Rise Test Vessel

The results of the simple thermal insulation temperature rising test in which the central temperature and the surface temperature of the test body were measured in the same manner as described above are summarized in [Table 6] below.

division time
(h: m) Temperature (℃) Central temperature reaching time When the maximum temperature is reached Worst point Temperature difference between the center and the surface center
Temperature Surface part
Temperature center
Temperature Surface part
Temperature Temperature
Reach Worst point Plain 15:30 32.6 29.4 32.6 28.8 3.2 3.8 Test Example 1 16:20 32.6 29.3 32.6 29.3 3.3 3.3 Test Example 2 15:30 32.6 29.5 32.6 29.3 3.1 3.3 Test Example 3 15:20 31.6 28.8 31.6 28.5 2.8 3.1

In the above [Table 6], the "highest time point" refers to the point at which the cement hydration heat reaches the highest temperature at the center and the surface of the test specimen, and the "lowest point" refers to the temperature difference between the center and the surface of the test specimen. The big point is to call. At the peak temperature and at the worst temperature, the central temperature and the surface temperature of the test specimens cannot be significantly improved compared to the reference concrete. However, in Test Example 3, the temperature at the center was 1 ° C. and the surface temperature was 0.6 ° C. at the time of reaching the highest temperature compared to the reference concrete. At the worst time, the temperature at the center was 1 ° C. and the surface temperature was 0.3 ° C. This can be said to be a significant improvement compared to the reference concrete, considering that the specimen size is 220 × 220 × 220 (mm). In addition, the temperature difference between the center and the surface is 2.8 ° C at the time of reaching the highest temperature and 3.1 ° C at the worst, which is an improvement of 12.5% and 18.4%, respectively, compared to the temperature difference between the central part and the surface of the reference concrete. Cracks occur when the stress caused by the shrinkage strain restraint caused by the temperature difference between the center and the surface of the member of the concrete and the shrinkage strain restraint when the temperature rises due to the heat of hydration exceeds the tensile strength of the concrete. Therefore, Test Example 3, in which the temperature rise due to the heat of hydration is lowered and the temperature difference between the central part and the surface part is decreased, can be judged to be effective in reducing the occurrence of cracks.

Time-specific temperature change patterns for the reference concrete and Test Examples 1 to 3 are shown in [Graph 7] to [Graph 10] below.

[Graph 7]-Test result of simple thermal insulation temperature rise (Plain)

[Graph 8]-Test result of simple insulation temperature rise (CNT 2%)

[Graph 9]-Test result of simple insulation temperature rise (CNT 4%)

[Graph 10]-Test result of simple thermal insulation temperature rise (CNT 6%)

The thermal conductivity test utilized QTM-500 which measures the thermal conductivity by the abnormal heat wire method. Thermal conductivity measurement results are summarized in [Table 7] below.

division Thermal conductivity (W / mK) Plain 2.1148 Test Example 1 2.0875 Test Example 2 2.2112 Test Example 3 2.5200

Thermal conductivity is increased from the reference concrete to Test Examples 1 to 3, Test Example 3 was increased by about 19% compared to the reference concrete.

As a result of the thermal properties of the concrete test results showed a significant effect on the temperature cracking reduction in the CNT content of Test Example 3 (0.12 parts by weight of CNTs compared to 100 parts by weight of mixed water). When the CNT content is continuously increased, the thermal properties of the concrete are improved, but considering the fluidity and economics, the CNT is preferably 0.12 to 0.4 parts by weight based on 100 parts by weight of the blended water.

4. Drying shrinkage length change

In order to verify that the test example 3 has the effect of reducing the temperature cracks, a dry test for the reference concrete and the test example 3 was further performed. The change in the generated stress over time is shown in [Graph 11] below.

[Graph 11]-Measurement result of dry shrinkage length change

As a result of measuring dry shrinkage length change, Test Example 3 was found to not only reduce the amount of dry shrinkage but also cause delayed expansion as indicated by the dotted lines in [Graph 11] at the point of reaching the maximum temperature of the concrete center. The delayed expansion performance is also considered to have an effect on the improvement of tensile strength, and the crack reduction effect by dry shrinkage is excellent.

On the other hand, CNTs have a low density, so as the curing of the concrete composition proceeds, some of them rise toward the surface, and the crack resistance performance of the mass concrete may be lowered compared to the amount of CNT incorporation. Accordingly, the present invention provides the "hydration heat dissipation mass concrete composition incorporating CNT, wherein the surface of the CNT is coated with magnesium oxide (MgO)." Accordingly, the problem of CNTs rising to the surface is improved, and the crack resistance performance of the mass concrete is further improved through the incorporation of magnesium oxide having a delayed expansion property.

Tables 8 to 10 below compare concrete properties before and after coating magnesium oxide on the surface of CNTs. Test Example 4 is the same as in Test Example 3, but was applied by coating the contained CNT with magnesium oxide.

division Slump (mm) Slump flow (mm) Air volume (vol%) Concrete temperature (℃) Test Example 3 210 330 × 330 1.6 22.4 Test Example 4 215 335 × 330 1.6 22.2

As shown in the above [Table 8], the change in the fluidity of the hardened concrete does not appear significantly depending on whether MgO is coated on the CNT, but when MgO is coated, it is confirmed that the fluidity of the equivalent level is higher than that of the case where the MgO is coated.

division time
(h: m) Temperature (℃) Central temperature reaching time When the maximum temperature is reached Worst point Center and surface
Temperature difference center
Temperature Surface part
Temperature center
Temperature Surface part
Temperature Temperature
Reach Worst point Test Example 3 15:20 31.6 28.8 31.6 28.5 2.8 3.1 Test Example 4 15:20 31.4 28.9 31.4 28.6 2.5 2.8

[Table 9] summarizes the results of the simple thermal insulation temperature rise test by measuring the central temperature and the surface temperature of the test specimens 3 and 4.

In Test Example 4, the temperature of the center portion decreased by 0.2 ° C, the surface temperature increased by 0.1 ° C, and the temperature of the center part decreased by 0.2 ° C, and the surface temperature increased by 0.1 ° C at the time of reaching the highest temperature compared to Test Example 3. It was. As a result, the temperature difference between the center and the surface is narrowed to 2.5 ° C at the time of reaching the highest temperature and 2.8 ° C at the worst, so that the effect of reducing the temperature cracking of the concrete will be greatly improved by coating MgO on the CNT.

division
Compressive strength (MPa) Split Tensile Strength (MPa) 3 days 7 days 28th 3 days 7 days 28th Test Example 3 31.8 47.9 60.3 2.74 3.54 4.2 Test Example 4 33.2 49.3 63.2 2.63 3.65 4.52

Table 10 above summarizes the results of compressive and split tensile strength measurements of Test Samples 3 and 4. The MgO coating on the CNTs improved overall compressive and split tensile strengths. This is judged to be the result of the CNT mechanical performance of the CNT by increasing the density of the CNT by applying MgO coating on the CNT, and the filling of micropores in the concrete due to the expansion performance of the coated MgO also affects the compressive strength improvement. It is judged to be crazy.

On the other hand, the present invention provides a "hydration heat dissipation mass concrete composition containing CNTs, characterized in that 0.25 to 0.5 parts by weight of carbon fiber having a length of 6 to 12 mm is added to 100 parts by weight of the binder. The carbon fiber is introduced as a medium for maximizing the performance of the CNT.

[Table 11] below is a concrete compounding table having different lengths and contents of added carbon fibers. Comparative Example 1 is an example of a concrete composition containing CNT is 0.12 parts by weight relative to 100 parts by weight of the blended water, Comparative Example 2 is an example in which the carbon fiber of 6mm length was added to Comparative Example 1 by varying the content, Comparative Example 3 Is an example in which the carbon fiber having a length of 12mm was added to the Comparative Example 1 by varying the content. [Table 12] summarizes the results of measuring the fluidity of the hard concrete by comparative examples, [Table 13] summarizes the results of measuring the thermal conductivity of the hardened concrete by comparative examples.

division Carbon fiber
Addition rate (wt%)
Of binder Unit material amount (kg / m3) W OPC Carbon fiber CNT S CNT Concrete (Comparative Example 1) -


225


450 -


27


1350
CNT + Carbon Fiber (6) Concrete
(Comparative Example 2) 0.25 1.125 0.5 2.25 1.0 4.5 2.0 9.0
CNT + Carbon Fiber (12) Concrete
(Comparative Example 3) 0.25 1.125 0.5 2.5 1.0 4.5 2.0 9.0

division Slump (mm) 1 time Episode 2 Average Comparative Example 1 215.0 221.0 218.0
Comparative Example 2 0.25 209.0 207.0 208.0 0.5 193.0 189.0 191.0 1.0 197.0 192.0 194.5 2.0 173.0 174.0 173.5
Comparative Example 3 0.25 200.0 196.0 198.0 0.5 186.0 187.0 186.5 1.0 146.0 147.0 146.5 2.0 111.0 109.0 110.0

As shown in [Table 12], the fluidity of the unconsolidated concrete was found to decrease with increasing carbon fiber incorporation regardless of the length of the carbon fiber. However, since the appropriate slump value according to KS F 4009 is 210 ± 25mm, in Comparative Example 2 in which the length of the added carbon fiber is 6mm, the carbon fiber addition rate satisfies the above optimum value in the range of 0.25 to 1.0wt% of the binder. In Comparative Example 3 having a fiber length of 12 mm, the carbon fiber addition rate was found to satisfy the above titer value in the range of 0.25 to 0.5 wt% relative to the binder.

division Thermal conductivity (W / mK) Comparative Example 1 1.6488
Comparative Example 2 0.25 1.6802 0.5 1.7005 1.0 1.6077 2.0 1.5946
Comparative Example 3 0.25 1.6983 0.5 1.6786 1.0 1.6075 2.0 1.4794

In both Comparative Examples 2 and 3, the thermal conductivity was higher than that of Comparative Example 1 when the carbon fiber addition rate was in the range of 0.25 to 0.5 wt% relative to the binder.

Summarizing the results shown in [Table 12] and [Table 13] above, the thermal conductivity is satisfactory while satisfying the fluidity in the appropriate range when 0.25 to 0.5 parts by weight of carbon fiber having a length of 6 to 12 mm is added to 100 parts by weight of the binder. Is improved.

Claims (3)

delete As a concrete composition comprising a binder, fine aggregate, coarse aggregate and blending water,
The blended water is composed of 80 to 97 parts by weight of general water and 3 to 20 parts by weight of CNT dispersion liquid,
The CNT dispersion is composed of 96 to 98 parts by weight of solvent and 2 to 4 parts by weight of CNT powder,
The amount of CNT is 0.12 to 0.4 parts by weight based on 100 parts by weight of the blended water,
The surface of the CNT is magnesium oxide (MgO) is coated with the hydration heat radiation mass concrete composition incorporating CNT, characterized in that the coating.
3. The method of claim 2,
Hydrated heat-dissipating mass concrete composition containing CNTs having a carbon fiber of 6 to 12 mm in length and 0.25 to 0.5 parts by weight based on 100 parts by weight of the binder.