KR101736595B1 - Composition of slag cement with high strength and lower shrinkage - Google Patents

Abstract

The present invention generally provides a slag cement composition comprising Portland cement, water chain slag, steel making slag and gypsum, wherein the water chain slag content is usually greater than or equal to the Portland cement content, and the slag cement composition has a high water- It is eco-friendly because it reduces the amount of carbon dioxide generated, and it has an excellent strength and low shrinkage rate and low occurrence of cracks even though the mixing ratio of water-chain slag is high.

Description

Technical Field [0001] The present invention relates to a slag cement composition for high strength and low shrinkage,

The present invention relates to a slag cement composition, and more particularly, to a slag cement composition excellent in strength and shrinkage crack reduction effect.

Recently, the cement industry is studying cement manufacturing technology that does not use portland cement in order to reduce the amount of carbon dioxide generated. The above cement is a cement which uses water-chain slag as the main raw material and improves the activity of water-chain slag by using sodium hydroxide (NaOH), sodium carbonate (Na ₂ CO ₃ ), water glass or the like as an alkali stimulant. However, the above-mentioned alkali stimulants are highly toxic and expensive, and since cement is a non-standard product at present, it has not been commercialized as a commercialization technology.

Slag cement manufacturers are attempting to manufacture blended cement with improved mixing ratio of slag cement in slag cement in order to reduce the amount of carbon dioxide. Generally, slag cement containing water- have. Also, in the case of slag cement mixed with a large amount of water-containing slag having a high degree of powderyness compared to ordinary portland cement, the capillary tension largely acts due to the pore water between the hydration bodies, resulting in a large shrinkage.

Therefore, in order to reduce shrinkage of concrete using slag cement, it is tried to reduce the shrinkage of concrete by mixing CSA type expansion material or liquid shrinkage reducing agent. Examples of the inorganic expansion agent include CSA-based compounds, C ₃ A and calcium oxide (CaO). Particularly, CSA and C ₃ A expander react with gypsum to form expandable etchringite crystal phase To compensate for the shrinkage of the concrete. The calcium oxide has a volume expansion of about 2.2 times as calcium hydroxide (Ca (OH) ₂ ) is generated in the hydration reaction with water as shown in the following formula 3 to compensate the shrinkage of the concrete.

_{3CaO3Al 2 O 3 CaSO 4 + 6CaO} + 8CaSO 4 + 96H 2 O → 3 (3CaOAl 2 O 3 3CaSO 4 32H 2 O) - (1)

3CaOAl ₂ O ₃ + 3CaSO ₄ + 32H ₂ O 3CaOAl ₂ O ₃ 3CaSO ₄ 32H ₂ O (2)

CaO + H ₂ O → Ca (OH) ₂ --------------------------------------------- (3)

However, when the expanding agent is used alone, the expansion performance is weak or the hydration reaction rate is too fast to contribute to swelling, and it is difficult to remove the hydration rate by mainly performing the function as an alkali stimulant. In the case of the electrochemical industry in Japan, CaO-CSA-CaSO ₄ compound is made and used as an expansion agent, but it is not widely used in the market due to its high price.

On the other hand, in the process of deoxidation with aluminum in order to remove oxygen in the refined tungsten product, a large amount of steel making slag having a high content of CaO-Al ₂ O ₃ compound is generated in the integrated steelworks. However, these steel slabs are used as lobsters and embankment materials without any special purpose. Therefore, it is necessary to make steel slag as a high-value-added resource by taking advantage of the characteristics of CaO-Al ₂ O ₃ .

Disclosed is a slag cement composition, which is excellent in strength and low in shrinkage percentage and is less susceptible to cracking even though it is a slag cement having improved water mixing ratio.

According to an embodiment of the present invention, there is provided a slag cement composition comprising ordinary Portland cement, water chain slag, steel making slag and gypsum, the content of the water chain slag being usually not less than the content of Portland cement.

The steelmaking slag and gypsum may have a content of 3 to 15% by weight.

The water-chain slag may have a powder degree of 4000 to 8000 cm < ² > / g.

The steelmaking slag may be at least one selected from the group consisting of desulfurization slag, ladle slag, STS converter slag, and STS performance slag.

The steelmaking slag may have a powder degree of 4000 to 8000 cm < ² > / g.

The content of the gypsum may be 50 to 80% by weight with respect to the content of the steelmaking slag and gypsum.

The gypsum may be at least one selected from the group consisting of anhydrous gypsum and anhydrite.

The content of the gypsum anhydrite may be 50% by weight or more based on the total gypsum content.

The slag cement composition of the present invention is environmentally friendly because it reduces the amount of carbon dioxide generated due to the mixing ratio of high water-chain slag, and has an excellent strength and low shrinkage due to low shrinkage even though the mixing ratio of water-chain slag is high.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below.

According to one embodiment of the present invention, it is possible to provide a slag cement composition comprising ordinary Portland cement, water-chain slag, steel making slag and gypsum, and the content of the water-chain slag is usually not less than the content of Portland cement.

In order to reduce the amount of carbon dioxide generated during the production of cement, slag cement in which a large amount of water-chain slag is mixed instead of Portland cement is provided. However, slag cement mixed with a large amount of water- There is a problem that the expression is delayed and cracks due to shrinkage occur.

Conventionally, in order to solve such a problem, an expansion material such as a CSA-based compound, C ₃ A and CaO has been used. However, when the expander is used alone, its expansion performance is weak or the hydration reaction rate is too fast, The CaO-CSA-CaSO ₄ -based compound is used as an expanding material because it is expensive, so that it is not commonly used in the market.

Although the mixing ratio of water-chain slag is higher than that of ordinary portland cement, slag cement can be provided with low cost, low strength, and low shrinkage due to the use of steelmaking slag and gypsum as an expansion material. .

Since the content of the water-chain slag is higher than the content of the ordinary Portland cement, the amount of carbon dioxide generated during the production of the cement is small and thus it can be eco-friendly. On the other hand, the slag materials are fineness is 4000 to 8000 cm ² / g is preferable, and the fineness of the slag materials 4000cm ² / g is less than if the slow and have low strength-activity of the slag materials 8000cm ² / g greater than The activity of the water-milled slag is good, but it is not preferable because it takes a lot of energy cost in manufacturing.

The present invention can include a steelmaking slag and a gypsum as an expanding agent. In particular, a steelmaking slag is generated in a process of deoxidizing aluminum in order to remove oxygen in a refined tungsten steel product, CaO, Al ₂ O _3, etc.) and a large amount of crystal phase.

The type of the steelmaking slag is not limited, but is preferably at least one selected from the group consisting of, for example, desulfurization slag, ladle slag, STS converter slag, and STS performance slag. Lt; / RTI >

Category (% by weight) CaO Al ₂ O ₃ SiO ₂ MgO MnO Fe ₂ O ₃ Major Crystalline Phase Desulfurization slag 51.1 5.8 15.8 3.1 0.3 7.2 Ca (OH) ₂ , CaCO ₃ , C ₂ S Ladle slag 39.0 18.1 13.6 5.3 2.1 17.8 C ₁₂ A ₇ , C ₂ S, FeO STS converter slag 53.4 8.2 23.5 8.2 1.2 0.3 C ₁₂ A ₇ , C ₂ S STS-playing slag 48.9 33.0 2.3 9.0 3.7 0.8 C ₃ A, C ₁₂ A ₇

The desulfurization slag is slag mixed with quicklime to remove the sulfur component contained in the molten iron in the blast furnace, and the ladle slag is subjected to secondary refining with an aluminum deoxidation material to remove oxygen components from the refinery after the oxygen- Is a slag generated in the process. Also, the STS converter slag is a slag generated in the process of manufacturing the STS tumbler using the blast furnace charcoal, and the STS-treated slag is the slag generated in the second refining process of the STS tumbler using the blast furnace charcoal.

Since the desulfurized slag is differentiated as hydrated lime components are hydrated in the process of cooling the molten desulfurized slag with water, it contains many fine particles and contains a large amount of calcium hydroxide (Ca (OH) ₂ ) and C ₂ S crystal phase. The calcium hydroxide acts as an alkali stimulant of water-chain slag when mixed with the slag cement, thereby improving the strength of the slag cement. In addition, the C ₂ S crystalline phase not only contributes to the improvement of the strength of the slag cement but also causes the expansion reaction to be slowly developed, which can be useful for controlling the expansion property of the expander at the same time as the strength development.

On the other hand, the ladle slag and the STS converter slag have many C ₁₂ A ₇ and C ₂ S crystal phases, and the STS performance slag contains many C ₃ A and C ₁₂ A ₇ crystal phases. The C ₁₂ A ₇ and C ₃ A crystal phases can be hydrated by hydration with calcium hydroxide or gypsum as shown in the following formulas 4 to 6, thereby forming an etringyzite crystal phase.

C ₁₂ A _{7 + 3Ca (OH) 2 + 5CaSO} 4 + 57H ₂ O → 5 (3C ₃ ACaSO ₄ 12H ₂ O) - (4)

3C ₃ ACaSO ₄ 12H ₂ O + 2CaSO ₄ + 20H ₂ O? C _{3 A 3} CaSO ₄ 32H ₂ O (5)

_{C 3 A + 3CaSO 4 2H 2} O + 26H 2 O → C 3 A3CaSO 4 32H 2 O -------------------------- (6)

In addition, since the C ₁₂ A ₇ and C ₃ A crystal phases are hydrated sufficiently, the calcium hydroxide component contained in the concrete reaction water can be easily dissolved. Since the calcium hydroxide serves also to stimulate alkaline water-containing slag contained in the slag cement, the C ₁₂ A ₇ and C ₃ A crystalline phases not only compensate for the shrinkage but also promote the hydration reaction of the slag cement to improve the strength of the concrete .

The content of the steel making slag and the gypsum is preferably 3 to 15% by weight, more preferably 5 to 10% by weight. If the content of the steel making slag and the gypsum is less than 3% by weight, the effect of shrinkage reduction and strength improvement by the steelmaking slag and gypsum can not be expected. On the other hand, if it exceeds 15% by weight, the shrinkage reduction is effective but the strength is lowered. Especially, when the mixing ratio of the gypsum is excessively high, it is used for promoting the hydration reaction of the water- There is a concern that the creation of delayed ettringite formation (DEF) may cause over expansion problems.

It is preferable that the steel making slag has a powder degree of 4000 to 8000 cm ² / g, and when the steel making rate of the steel making slag is less than 4000 cm ² / g, the reactivity is low and hydration reaction and shrinkage reduction effect are not exhibited. If it is more than 8000 cm ² / g, the energy cost is excessively consumed in manufacturing the steel slag fine powder, which leads to a reduction in economic efficiency and a difficulty in controlling the hydration reaction and shrinkage rate because of too high reactivity

The content of the gypsum is preferably 50 to 80% by weight with respect to the content of the steelmaking slag and gypsum. If the content of the gypsum is less than 50% by weight, the effect of shrinkage reduction and strength improvement due to steelmaking slag and gypsum can not be expected. Particularly, in the case of steel making slag having a high Al ₂ O ₃ content, CaO-Al ₂ O ₃ -H ₂ O A hydrate may be formed and the strength may be lowered due to the pores formed by the removal of water during the crystal phase transition of these hydrates. If the content of the gypsum exceeds 80% by weight, the component to produce etringite is insufficient, and the effect of shrinkage reduction as well as strength improvement is poor.

The gypsum is preferably at least one selected from the group consisting of anhydrous gypsum and anhydrite. In particular, the content of the anhydrous gypsum is preferably 50% by weight or more, more preferably 50 to 75% by weight based on the total gypsum content. If the content of the gypsum anhydride is less than 50% by weight, the reaction with the gypsum and the steel slag is weak, so that the ettringite can not be produced well, and the strength improvement and shrinkage reduction effect are weakened.

Hereinafter, the present invention will be described more specifically by way of specific examples. The following examples are provided to aid understanding of the present invention, and the scope of the present invention is not limited thereto.

Example

The compositions and contents of the ordinary Portland cement, water-chain slag and gypsum used in this test are shown in Table 2 below. On the other hand, the steelmaking slag used was desulfurized slag, ladle slag, STS converter slag, and STS performance slag having the composition and contents shown in Table 1 above.

Category (% by weight) CaO SiO ₂ MgO Al ₂ O ₃ Fe ₂ O ₃ SO ₃ Usually Portland Cement 62.6 16.6 2.78 4.34 3.00 5.44 Milled slag 44.1 35.7 3.87 12.5 0.42 1.5 Anhydrous plaster 45.9 0.26 0.78 0.10 0.07 46.2 Lee Soo Seok 44.0 1.96 0.81 1.25 0.41 43.8

The compressive strength test and the paste shrinkage test were conducted after mixing Portland cement, water-chain slag (Blaine 4300 cm ² / g), steel slag (Blaine 4300 cm ² / g) and gypsum in the amounts shown in Table 3 below. The above compressive strength test was carried out in accordance with the strength test method of cement of KS L ISO 679. The paste shrinkage test was performed by mixing a mixture of 25.4 x 25.4 x 254 mm molds with a water: cement ratio of 1: 0.37 and molding. The mold was cured at 20 ± 2 ° C for 1 day after demolding. The shrinkage rate was evaluated by measuring the change in length with time.

The results of the compressive strength test and the paste shrinkage test are shown in Table 3 below.

division Combination ratio (% by weight) Measurement result Usually Portland Cement Milled slag Desulfurization
Slag Ladle
Slag STS
converter
Slag STS
play
Slag myriad
gypsum complete
gypsum Shrinkage rate
(Mu m / m) Compressive strength (MPa) 28th 3 days Comparative Example 1 55 45 -700 25.7 Comparative Example 2 40 60 -800 22.7 Comparative Example 3 100 -830 26.7 Comparative Example 4 40 59 0.25 0.25 0.5 -750 22.0 Comparative Example 5 40 59 0.25 0.25 0.5 -760 22.2 Comparative Example 6 40 40 5.0 5.0 10.0 -180 17.0 Comparative Example 7 40 55 2.0 2.0 1.0 -750 18.0 Comparative Example 8 40 55 5.0 -700 20.0 Comparative Example 9 40 55 1.25 1.25 2.5 -750 19.7 Example 1 40 57 0.75 0.75 1.5 -400 25.8 Example 2 40 57 0.75 0.75 1.5 -380 26.0 Example 3 40 50 2.5 2.5 5.0 -300 27.5 Example 4 40 50 2.5 2.5 5.0 -330 25.9 Example 5 40 55 1.25 1.25 1.25 1.25 -350 26.0 Example 6 35 50 1.5 1.5 6 6 -380 25.8 Example 7 35 50 1.5 1.5 9 3 -330 26.0

The content of the water-chain slag in Examples 1 to 7 is usually higher than the content of Portland cement, the content of steel making slag and gypsum is 3 to 15 wt%, the content of gypsum is 50 to 80 And the content of anhydrous gypsum was 50 wt% or more with respect to the total amount of gypsum, and the shrinkage rate was very low, i.e., -300 to -400 (탆 m / m), and the strength was extremely high, 25.8 to 27.5 MPa .

Comparative Examples 1 to 3 did not include steelmaking slag and gypsum, and Comparative Example 3, in which the content of water-chain slag was the highest, was confirmed to have high shrinkage and low strength. In Comparative Examples 1 and 3, it was confirmed that the shrinkage ratio was very high in strength. In Comparative Example 5, the content of steelmaking slag and gypsum was 1% by weight, in Comparative Example 7, the content of gypsum was 20% by weight based on the steelmaking slag and the total amount of gypsum, Comparative Example 8 contained no steelmaking slag, In Comparative Example 9, since no anhydrous gypsum was contained, it was confirmed that the shrinkage ratio was high and the strength was reduced. On the other hand, in Comparative Example 6, it was confirmed that the content of steelmaking slag and gypsum was 20% by weight and the shrinkage rate was low but the strength was low.

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 exemplary embodiments, but, on the contrary, It will be obvious to those of ordinary skill in the art.

Claims (8)

Usually Portland cement, water chain slag, steel making slag and gypsum,
The content of the water-chain slag is usually more than the content of the Portland cement,
The steelmaking slag is at least one selected from the group consisting of desulfurization slag, ladle slag, STS converter slag, and STS performance slag,
The steel making slag and the gypsum have a total content of the two components of 3 to 15% by weight,
Wherein the content of the gypsum is 50 to 80% by weight based on the total content of the steelmaking slag and the gypsum.
delete The method according to claim 1,
Wherein the water-chain slag has a powder degree of 4000 to 8000 cm < ² > / g.
delete The method according to claim 1,
Wherein the steel making slag has a powder degree of 4000 to 8000 cm ² / g.
delete The method of claim 1, wherein
Wherein the gypsum is at least one selected from the group consisting of anhydrous gypsum and anisotrope.
8. The method of claim 7,
Wherein the content of the anhydrous gypsum is 50 wt% or more with respect to the total gypsum content.