KR100658965B1 - Cement admixture and cement composition using thereof - Google Patents

Abstract

The present invention relates to a cement admixture obtained by mixing metakaolin and dihydrate gypsum and a cement composition using the same.

Cement admixture of the present invention is a homogeneous mixture of 30% to 60% by weight of dihydrate gypsum in metakaolin, cement composition is added 5% to 25% by weight of the admixture to cement and 0.5% to 3.0% by weight Is to use a water reducer.

Cement Admixtures, Cement Compositions, Dihydrate Gypsum, Metakaolin

Description

Cement admixture and cement composition using same

The present invention relates to a cement admixture added to cement and to a cement composition using the same for improving properties of cement products in the manufacture of cement mortar or concrete.

It is known from Japanese Patent Laid-Open No. 3-265549 by substituting 5% to 30% by weight of cement with meta kaolin to promote the pozzolan reaction to form a high strength cement mortar and concrete composition. Meanwhile, Korean Laid-Open Patent Publication No. 2000-0037750 discloses that 5 to 20 wt% of cement is substituted with metakaolin to obtain the same result as Japanese Patent No. Hei 3-265549.

Fly ash and blast furnace slag also promote pozzolanic reaction to obtain a high strength cement composition. However, the pozzolanic reaction caused by fly ash and blast furnace slag relatively contributes to the increase of long-term strength of cement concrete, but the short-term strength decreases considerably, so it is difficult to work effectively due to the delayed demolding time at the construction site or concrete secondary product plant. There was this.

In order to solve this problem and increase the short-term strength of the cement concrete, there is a method of adding an inorganic curing accelerator such as CaCl ₂ or mixing a cement admixture for fast curing.

However, when mixed with an inorganic admixture such as CaCl ₂ , rust occurs in the reinforcing bars, and short-term strength increases but long-term strength decreases. On the other hand, fast admixtures are expensive and have difficulty in controlling the setting time and adversely affecting the expression of long-term strength.

It is an object of the present invention to increase the short-term strength of concrete while increasing its long-term strength, and to improve the chemical resistance of concrete, to prevent permeability, and to prevent the alkali aggregate reaction. To provide a composition.

The present inventors add 5% to 25% by weight of the cement admixture to the cement and the admixture of the admixture in the homogeneous mixture of 30% to 60% by weight of dihydrate gypsum in the metakaolin and 0.5% to 3.0% by weight of a water reducing agent The present invention was completed by confirming that the cement composition was able to increase the short-term strength and long-term strength of concrete, and to obtain effects such as improvement of chemical resistance and prevention of permeability.

Hereinafter, the structure of the present invention will be described in detail with reference to Examples.

The composition of the present invention is 30% to 60% by weight, preferably 40% to 60% by weight of dihydrate gypsum (CaSo ₄ 2H ₂ O) in the amount of metakaolin, which is a mixed material that promotes the pozzolanic reaction to increase long-term strength. It is to provide a cement admixture added 50% by weight.

As long as it can be used in the cement industry, such as flue gas desulfurization gypsum, phosphate gypsum and natural gypsum, it can be used as a raw material of dihydrate gypsum. It is preferable to mix and grind metakaolin and dihydrate gypsum, but if dihydrate gypsum is a fine powder in a dry state, it is also possible to mix and adjust metakaolin and dihydrate gypsum by a mixer.

Thus, it is characterized in that 5% by weight to 25% by weight, preferably 10% by weight to 20% by weight, of the metakaolin-dihydrate gypsum admixture adjusted by mixing or grinding is added to the cement as a reference amount.

Naphthalene-based and melamine-based sensitizers are suitable among the naphthalene-based, melamine-based and polycarboxylic acid-based systems.

Polycarboxylic acid-based admixtures require the use of a defoaming agent that suppresses the generation of bubbles in order to increase the short-term strength because the bubbles increase in cement mortar or concrete rubbing, and technology development for this is necessary.
If only metakaolin is added to the cement, the long-term strength of the cement mortar or concrete will be significantly increased compared to the formulation using only cement. However, the daily strength is hardly increased compared to the formulation using only cement. The three-day and seven-day strengths increase in strength, but are small.

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On the other hand, the admixture of the present invention significantly increases the strength of 1 day and 3 days, and at the same time increases the strength of 7 days and 28 days as compared with the combination using only cement. That is, the short-term strength is greatly improved while maintaining the long-term strength characteristic of metakaolin.

In this way, it is possible to significantly increase the short-term to long-term strength of cement mortar and concrete by adding a mixed material of metakaolin and dihydrate gypsum. If metahydrate is added without metakaolin, short-term strength increases but long-term strength decreases.

In addition, by adding dihydrate gypsum to metakaolin, there is an economical advantage that the manufacturing cost is reduced compared to using metakaolin alone, and it also has the effect of preventing good deterioration in fluidity of cement mortar or concrete over time to maintain good workability. In other words, it was found that the admixture mixed with dihydrate gypsum and metakaolin significantly increased the short-term strength of cement mortar and concrete, and at the same time, the long-term strength maintained the effect of metakaolin to secure high strength and prevent the deterioration of fluidity at the same time. .

The cause is not clear, but is estimated as follows.

In short, it is thought that the mixture of cement and metakaolin causes the fluidity deterioration by the rapid hydration of C ₃ A (calcium aluminate compound) in cement in the presence of soluble aluminum (Al ions) generated from metakaolin.

However, in the present invention, it is estimated that by adding an appropriate amount of gypsum (particularly hydrated gypsum) to the mixture of cement and metakaolin, the C ₃ A reaction is suppressed to prevent a decrease in fluidity.

On the other hand, by adding hydrated gypsum, soluble aluminum (Al ions) from C ₃ A and metakaolin in cement is thought to help produce ettlingite or a similar compound by reacting with hydrated gypsum.

The increase in the short-term strength of cement mortar and concrete by the addition of dihydrate gypsum is believed to increase the timing of the formation of ethringite due to the addition of dihydrate gypsum at the time of cement hardening, thereby densifying the structure and increasing the short-term strength.

On the other hand, in the medium and long term strength, the pozzolanic reaction between metakaolin and cement is accelerated as it is, and the medium and long term strength is considered to increase without being disturbed by the addition of gypsum.

In this way, the admixture mixed with hydrated gypsum and metakaolin can contribute to remarkable increase in short-term strength and mid-long-term strength of cement mortar and concrete.

Next, examples of the cement mortar test and the concrete test according to the present invention will be described.

Basically, the cement mortar test was conducted in various ways, and the concrete test confirmed the effect of admixtures under the optimum conditions.

(Example)

 Table 1. Ingredients of Raw Material Metakaolin (Products of Aceaceratek Co., Ltd.) Unit: Weight%

SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ TiO ₂ CaO MgO K ₂ O, Na ₂ O Etc 46.5 35.5 2.3 0.1 1.0 0.2 0.7 13.7

                    Average particle size: 7.5 µm, BET value: 28 m2 / g

Mortar Test

 1) Material used

      end. Cement Plain Portland Cement

      I. Sand Korea KS Standard Yarn

      All. Water-Resistant Naphthalene M-150, Melamine NEXO-slip

      la. Metakaolin Co., Ltd.

      hemp. Gypsum flue gas desulfurization gypsum

 2) Test method

      end. Strength test

            Based on JIS mortar test in Japan

            Powder (cement + metakaolin + hydrated gypsum) / sand = 1/1

            Water / Powder (Cement + Metakaolin + Dihydrate Gypsum) = 30% by weight

            Size of specimen (test sample) = 40 mm × 40 mm × 160 mm

            Underwater curing temperature = 20 ℃ ± 1 ℃

      I. Flow Test (Slump Loss)

            According to Japanese JIS

            Powder (cement + metakaolin + hydrated gypsum) / sand = 1 / 1.5

            Water / Powder (Cement + Metakaolin + Dihydrate Gypsum) = 50% by weight

           Measure change over time after adjusting with water reducing agent so that fluidity is 20cm ± 1cm

 3) Test result

      end. Mortar Strength Test

Table 2. Mortar strength test result using naphthalene type water reducing agent

Cement standard Metakaolin addition amount (to cement weight%) Amount of gypsum added (to cement weight%) Reducing agent addition amount (large powder weight%) Daily compressive strength (kg / ㎠) 3 days compressive strength (kg / ㎠) 7 days compressive strength (kg / ㎠) 28 days compressive strength (kg / ㎠) 100 0 0.0 1.94 297 640 772 880 100 10 0.0 2.13 289 680 861 1,043 100 10 2.0 2.15 301 710 880 1,015 100 10 3.0 2.20 350 730 893 996 100 10 4.0 2.33 436 760 954 1,052 100 10 5.0 2.33 420 742 920 1,030 100 10 7.0 2.35 386 710 942 1,010 100 10 10.0 2.40 392 720 910 885 100 0 4.0 1.69 410 695 888 872 100 5 4.0 2.05 360 672 890 927 100 15 4.0 2.72 354 723 925 1,024 100 25 4.0 3.20 292 756 911 1,072

 Table 3. Result of mortar strength test using melamine-based water reducing agent

Cement standard Metakaolin addition amount (to cement weight%) Amount of gypsum added (to cement weight%) Amount of reducing agent (large weight%) Daily compressive strength (kg / ㎠) 3 days compressive strength (kg / ㎠) 7 days compressive strength (kg / ㎠) 28 days compressive strength (kg / ㎠) 100 0 0.0 1.63 300 580 880 982 100 10 0.0 2.12 295 620 925 1,180 100 10 2.0 2.30 310 642 920 1,146 100 10 3.0 2.56 380 725 910 1,120 100 10 4.0 2.29 416 780 936 1,192 100 10 5.0 2.31 425 768 915 1,158 100 10 7.0 2.32 396 710 890 1,052 100 10 10.0 2.35 350 646 858 960 100 0 4.0 1.69 405 633 840 875 100 5 4.0 2.01 380 652 880 1,050 100 15 4.0 2.54 368 770 925 1,165 100 25 4.0 3.12 345 755 932 1,176

<Concrete Strength Test>

 1) Material used

      end. Cement Plain Portland Cement

      I. Rough aggregate limestone specific gravity 2.58

      All. Sand Sand Gravity 2.65

      la. Water-Resistant Naphthalene M-150, Melamine NEXO-slip

      hemp. Metakaolin Co., Ltd.

      bar. Gypsum flue gas desulfurization gypsum

 Table 4. Concrete mixing table (when using naphthalene water-based reducing agent)

Compounding level W / P (wt%) Unit weight (kg / ㎡) AE water reducer + AE adjuster cement MK Isu plaster water Coarse aggregate sand ①B.B 55 300 0 0 164 1,025 784 0.10 + 0,002 ②B 55 270 30 0 164 1,025 784 0.43 + 0.002 ③ 55 258 30 12 164 1,025 784 0.54 + 0,002

 * W / P (% by weight) represents the weight ratio of water / powder, MK represents metakaolin, and AE regulator represents a bubble regulator.

Table 5. Concrete mixing table (when using melamine type water reducing agent)

Compounding level W / P (wt%) Unit weight (kg / ㎡) AE water reducer + AE adjuster cement MK Isu plaster water Coarse aggregate sand ④B.B 55 300 0 0 164 1,025 784 0.10 + 0.002 ⑤B 55 270 30 0 164 1,025 784 0.37 + 0.002 ⑥ 55 258 30 12 164 1,025 784 0.55 + 0.002

 * W / P (% by weight) represents the weight ratio of water / powder, MK represents metakaolin, and AE regulator represents a bubble regulator.

2) Properties of Flesh Concrete

Table 6. Properties of Fresh Concrete (When Using Naphthalene Water-Resistant)

Compounding level W / P (wt%) S / A (wt%) Cement (kg / ㎡) MK (kg / ㎡) Isu plaster (kg / ㎡) Slump (cm) Air volume (% by volume) Temperature (℃) ①B.B 55 43 300 0 0 12.4 5.1 20.6 ②B 55 43 270 30 0 11.2 5.3 21.0 ③ 55 43 258 30 12 12.8 5.3 20.9

※ W / P (% by weight) represents the weight ratio of water / powder, S / A (% by weight) represents the weight ratio of sand / crude aggregate, and MK represents metakaolin.

Table 7. Properties of fresh concrete (when using melamine type water reducing agent)

Compounding level W / P (wt%) S / A (wt%) Cement (kg / ㎡) MK (kg / ㎡) Isu plaster (kg / ㎡) Slump (cm) Air volume (% by volume) Temperature (℃) ④B.B 55 43 300 0 0 11.5 5.8 20.8 ⑤B 55 43 270 30 0 12.6 5.6 21.2 ⑥ 55 43 258 30 12 12.0 5.5 20.4

※ W / P (% by weight) represents the weight ratio of water / powder, S / A (% by weight) represents the weight ratio of sand / crude aggregate, and MK represents metakaolin.

3) Properties of Hardened Concrete

Table 8. Properties of Hardened Concrete

Compounding level W / P (wt%) S / A (wt%) Cement (kg / ㎡) MK (KG / ㎡) Isu plaster (kg / ㎡) Compressive strength (kg / ㎠) 1 day 3 days 7 days 28 days ①B.B 55 43 300 0 0 115 212 297 385 ②B 55 43 270 30 0 110 230 330 470 ③ 55 43 258 30 12 192 282 350 466 ④B.B 55 43 300 0 0 120 207 301 392 ⑤B 55 43 270 30 0 122 240 323 455 ⑥ 55 43 258 30 12 204 291 362 460

※ W / P (% by weight) represents the weight ratio of water / powder, S / A (% by weight) represents the weight ratio of sand / crude aggregate, and MK represents metakaolin.

<Slump-Loss Test>

Slump-Loss test was evaluated by the mortar flow change over time using a sample of mortar strength test instead of concrete slumping test.

The Slump-Loss test was carried out in comparison with the formulation using pure cement without adding the admixture with respect to the formulation using "metakaline + dihydrate gypsum" as admixture.

 Table 9. Slump-Loss Data-Sheet

sample Cement (g) MF (g) Water (g) Admixture Water reducing agent Difference in Flow Value from Start (mm) Kinds Stand powder weight% Kinds Stand powder weight% Flow (mm) 15 minutes later (mm) 30 minutes later (mm) After 60 minutes (mm) 90 minutes later (mm) Judgment One 650 0 325 BB 0 - 0.00 206 10 23 24 30 Standard 2 585 65 325 B 0 M150 0.43 200 15 25 26 38 ×× 3 585 65 325 B 0 M150 0.43 196 13 18 24 35 △ 4 585 65 325 gypsum 2.0 M150 0.46 197 15 23 30 34 △ 5 585 65 325 gypsum 4.0 M150 0.54 194 14 18 24 30 ○ 6 585 65 325 B 0 Mela 0.37 199 7 18 30 31 ○ 7 585 65 325 gypsum 2.0 Mela 0.49 197 11 14 27 32 ○ △ 8 585 65 325 gypsum 4,0 Mela 0.55 191 8 14 23 31 ○ 9 585 65 325 B 0 M2000 0.31 204 6 18 26 35 × 10 585 65 325 gypsum 2.0 M2000 0.35 199 13 16 23 34 △ 11 585 65 325 gypsum 4.0 M2000 0.46 200 10 17 25 30 ○

※ From the above table

        BB: No Admixture

        B: Use only metakaolin as admixture

       Gypsum: Metakaolin and Isu plaster are used as admixtures

 ※ In the category of the above table

        M-150, M2000: Naphthalene type water reducing agent, Mela: Melamine type water reducing agent

 ※ In the above table

          ○: Good

          ○ △: slightly good

          △: normal

          X: slightly worse

          XX: bad

Description of Example

Next, the effect thereof will be described sequentially based on the embodiment.

Table 2 shows the results of the mortar test using the naphthalene-based water reducing agent (M-150). The test was carried out while the hydrated gypsum was changed from 0 wt% to 10 wt% with respect to the cement reference amount 100 and metakaolin from 0 wt% to 25 wt% with respect to the cement reference amount 100. As a result, 10% by weight of metakaolin and 3% by weight to 7% by weight of dihydrate gypsum were added to the cement reference amount of 100%. The strength increased compared to the formulation. The blending level of 0% by weight of metakaolin and 4% by weight of dihydrate gypsum in the cement standard 100 also increased the short-term strength but not the 7-day strength and the 28-day strength.

Table 3 shows the results of the mortar test using melamine-based sensitizers (NEXO-slip). Overall, the strength is higher than that of using Na-phthalene-based M-150, but the result tends to be as shown in Table 2, with the addition of 10% by weight of metakaolin and 3% by weight to 7% by weight of dihydrate gypsum with respect to the cement reference 100. The increase in short-term intensity was remarkable, while the long-term intensity also increased. The combination without metakaolin was low in long term strength. When the addition rate of dihydrate gypsum is small, the effect is also small and it is unpreferable. In addition, if too much is added, the setting time becomes long and the long-term strength does not increase.

The concrete test was conducted at the level deemed optimal by judging from the mortar test results.

Also in the results of Table 6, Table 7, and 8, the effect was confirmed by addition of metakaolin and dihydrate gypsum.

Table 9 shows the results of the fluidity change.

It was tested using "metakaolin + Isu plaster" as a mixed material. As a result, in the combination of cement and metakaolin, the decrease in fluidity was large, but the decrease in fluidity was alleviated by adding dihydrate gypsum.

According to the present invention described above, the admixture of the present invention increases the long-term strength while significantly increasing the short-term strength of cement mortar and concrete, while improving the chemical resistance of cement mortar and concrete, preventing permeability, preventing whitening, alkali aggregate It has the effect which can improve the physical property of hardened | cured material widely, such as prevention of reaction.

Claims (5)

delete Cement admixture, The cement admixture obtained by adding 30 to 60% by weight of dihydrate gypsum to metakaolin. delete The cement composition comprising 5 to 25% by weight of cement admixture added to the metakaolin by adding 30 to 60% by weight of dihydrate gypsum to cement, and 0.5 to 3.0% by weight of a water reducing agent. The cement composition according to claim 4, wherein the water reducing agent uses any one of naphthalene-based, melamine-based and polycarboxylic acid-based.