KR101111635B1 - Low alkali concrete composition with tannin and block unit comprising the same - Google Patents

Abstract

PURPOSE: A low-alkaline concrete composition using tannin and a block including thereof are provided to enhance compressive strength without eluting strong alkaline substances by including dihydrate gypsum and silica fume. CONSTITUTION: A low-alkaline concrete composition using tannin comprises 10-30 parts by weight of normal Portland cement, 20-40 parts by weight of slag powder, 20-40 parts by weight of fly ash, 5-15 parts by weight of limestone powder, 5-10 parts by weight of quicklime, 1-5 parts by weight of sodium sulfate, 0.5-2.0 parts by weight of tannin, 15-25 parts by weight of dihydrate gypsum, and 3-10 parts by weight of silica fume. A pH of 56-day concrete composition using tannin is 9.6-10.25. A block including the concrete composition using tannin is environmentally-friendly and has an excellent strength.

Description

Low alkali concrete composition with tannin and block unit comprising the same}

The present invention relates to environmentally friendly cement for blocks, to an environmentally friendly cement for low alkali concrete.

Recently, due to the occurrence of abnormal climate such as abnormal temperature, drought, and flood caused by greenhouse gases, discussions on environmental issues are actively conducted around the world, and global warming is attributed to the large use of fossil fuels after the Industrial Revolution. He also argued that it would be necessary to reduce CO2 emissions by 50% compared to 2000 in order to curb temperature rises before the Industrial Revolution before 1750 to 2.0 ℃ ~ 2.4 ℃. As a countermeasure, countries have announced reductions in carbon dioxide, a representative greenhouse gas, and Korea has also reduced its greenhouse gas reduction target by 30% compared to the Business AS Usual (BAU) by 2020 (or 4% compared to 2005). Reduction).

  Domestic CO2 emissions are expected to reach 5.9 million tons in 2010 and 710 million tons in 2020. About 10% of these emissions come from the cement industry, and about 800kg-CO2 / ton tons of carbon dioxide is produced when producing one ton of cement. However, there is a method to reduce the production amount to suppress the carbon dioxide generated in the cement industry, but this is difficult in reality, so the solution to reduce the absolute amount of cement is to come up as a countermeasure, which is a mixture produced by mixing industrial by-products blast furnace slag and fly ash with cement. It is used as cement and has developed non-cement based inorganic powder based on this industrial by-product and applied it to construction materials. However, the non-cement type inorganic powder has the problem that strength falls.

In addition, the cement has a strong alkalinity, the strong alkali of the cement serves to prevent the corrosion of the reinforcement to maintain a strong reinforced concrete structure. However, carbon dioxide in the atmosphere reacts with calcium hydroxide in the cement, which is converted into calcium carbonate, which leads to neutralization of the cement, which causes severe cracking in the structure due to corrosion and expansion of the steel. Alkali in the cement is an important property, but when a block made of cement is used in the waterfront space, the strong alkali component of pH 11 ~ 13 in the cement will be eluted, which will have a significant adverse effect on the ecological environment. Reinforced concrete products facing the waterfront using cement are mainly used in the form of secondary products. Representative products include reinforced concrete plume and bench plume, rafting block and masonry retaining wall block. Because it is produced in the form of environmental problems, such as strong alkali component eluted has been greatly shown.

Accordingly, the problem to be solved by the present invention is to solve the above problems, to provide a low alkali concrete composition using tannin excellent in compressive strength and can reduce the emission of carbon dioxide without eluting a strong alkali component.

In order to achieve the above object, the low alkali concrete composition using tannin of the present invention is usually 10 to 30 parts by weight of Portland cement, 20 to 40 parts by weight of slag powder, 20 to 40 parts by weight of fly ash, 5 to 15 parts by weight of limestone powder , 5 to 10 parts by weight of quicklime, 1 to 5 parts by weight of sodium sulfate, 0.5 to 2 parts by weight of tannin, 15 to 25 parts by weight of gypsum gypsum and 3 to 10 parts by weight of silica fume.

The low alkali concrete composition using tannin of the present invention has a relatively low pH, including tannin, and has excellent compressive strength by preventing coagulation delay and lowering of initial strength, which are side effects of using tannin, using dihydrate gypsum and silica fume. . In addition, the tannins of the low alkali concrete composition using the tannins of the present invention can prevent rebar oxidation. In addition, the low alkali concrete composition using the tannin of the present invention has a carbon dioxide saving effect.

Hereinafter, the present invention will be described in detail. Prior to this, terms or words used in the specification and claims should not be construed as having a conventional or dictionary meaning, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the configurations described in the embodiments described herein are only one of the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention, and various equivalents may be substituted for them at the time of the present application. It should be understood that there may be variations.

Low alkali concrete composition using tannin of the present invention is usually 10 to 30 parts by weight of Portland cement, 20 to 40 parts by weight of slag powder, 20 to 40 parts by weight of fly ash, 5 to 15 parts by weight of limestone fine powder, 5 to 10 parts by weight of quicklime 1 to 5 parts by weight of sodium sulfate, 0.5 to 2 parts by weight of tannin, 15 to 25 parts by weight of hydrated gypsum and 3 to 10 parts by weight of silica fume. In addition, according to the present invention, the pH of the 56-day-old age of the low-alkali concrete composition using the tannin is 9.6 to 10.25 depending on the content of tannin.

The main components of ordinary Portland cement are lime, silica, alumina, iron oxide, etc., and the raw materials containing them are sufficiently mixed in an appropriate ratio, and a portion of the cement is added to the clinker, which is melted and calcined, to give a suitable amount of powder. It is made with. When cement is kneaded with water, it hardens like a stone because the cement component reacts with water to form a new structure. Portland cement contains tricalcium silicate (3CaO? SiO ₂ ) and dicalcium silicate (2CaO? SiO ₂ ) as the main components. When water is added, the following chemical changes occur.

3CaO? SiO ₂ + (n + 2) H ₂ O → CaO? SiO ₂ ? NH ₂ O + 2Ca (OH) ₂

2CaO? SiO ₂ + (n + 1) H ₂ O → CaO? SiO ₂ ? NH ₂ O + Ca (OH) ₂

That is, unstable calcium silicate is decomposed into two crystalline stable substances. The combination and crystallization of these tissues is said to give strength to the cement. In addition, calcium hydroxide (Ca (OH) ₂ ) produced by the above reaction again absorbs carbon dioxide in the air to become hard calcium carbonate (CaCO ₃ ), which also increases the hardness of cement. This common Portland cement is widely used to combine aggregates for building buildings, and has been used as one of the most important building materials for a long time. However, the ordinary portland cement needs to maintain strong alkalinity to prevent corrosion of reinforcing steel used, but when used in contact with the waterfront space, it elutes the strong alkaline component of pH 11-13 and has a great adverse effect on the ecological environment. Will be affected.

Tannin is widely distributed in many plants, and aqueous solution is a generic name of compound with strong astringent and astringent taste. It is a complex polymer material (molecular weight 600 ~ 2000) in which various polyphenols are polymerized. It is originally colorless, but is easily oxidized by the action of polyphenol oxidase to give brown color. The low alkali concrete composition using tannin of the present invention contains tannins to adjust the pH to 10.15 or less to prevent strong alkali components, and when tannins are added, the hydroxyl group of tannins is a calcium silicate hydrate which is produced by the hydration of cement. By combining with the calcium salt, the carbonation reaction between the carbon dioxide gas and calcium silicate hydrate in the outside air is blocked, and the hydroxyl group is bonded to the carbonated calcium carbonate to effectively prevent corrosion of the steel. However, it is thought that the hydrolyzable tannins may deteriorate the hydration reaction by surrounding the cement particles, which may lead to a decrease in the initial strength of the cement. Accordingly, the low alkali concrete composition using tannin of the present invention is excellent in compressive strength by preventing coagulation delay and initial strength degradation, which are side effects of using tannin, using dihydrate gypsum and silica fume using dihydrate gypsum and silica fume.

It is preferable to use 0.5 to 2 parts by weight of such tannins. When the amount of tannins used is less than 0.5 parts by weight, the content of tannin is too small, so that the effect of pH adjustment is insignificant. It is because intensity | strength falls too much.

Gypsum is a very soft sulphate mineral mainly composed of calcium sulfate (CaSO ₄ ). Especially, gypsum is CaSO ₄ -2H ₂ O, which has a great influence on the initial hydration and condensation of cement. When less than 15 parts by weight of these gypsum is used, the effect of improving the condensation rate is insignificant, and when it is used in excess of 25 parts by weight, the strength may be negatively affected.

The silica fume is a microsilica particle that is collected by collecting and filtering the gas generated in the production process of silicon iron and silicon metal, and thus the silica fume may be filled between cement particles because of its high powder density and large amount of silica, thereby obtaining a very dense hardened structure. It can bring about an improvement in strength. If the silica fume is used in less than 3 parts by weight, the effect of improving the strength is insignificant, and when used in excess of 10 parts by weight may cause a problem that the curing rate is reduced.

Slag is Ca ^{2 +} a dissolution when in contact with water as latent hydraulic reaction does not occur by controlling the air ions eluted from the infiltration of water and particles to form a glass film on the surface of the particles of indefinite shape. However, the addition of a small amount of alkali stimulant (CaO, NaSO ₃ ) adsorbs OH ^- on the slag fine powder to break the amorphous glass film and elutes reactive materials such as SiO ₂ , AL ₂ O ₃ , CaO and MgO to cause curing reaction. The ions of Ca, Mg, Al, etc. contained in the network are easily cleaved by the alkaline stimulant of the combination of the three-dimensional network structure of -O-Si-O-Al-O- which constitutes the glassy material of the slag powder. Because they can be easily eluted, each ion produces and hardens calcium silicate hydrate or calcium aluminate hydrate.

  Slag fine powder chemical reaction

The slag powder has the advantages of not only reducing the amount of cement used but also suppressing a temperature increase due to a hydration reaction and increasing long-term strength. The secondary reaction between the slag fine powder and the cement hydrate makes the pore structure more dense and the watertightness increases greatly, thereby increasing the resistance to penetration of various harmful substances including chlorides. Therefore, concrete including slag is used in particular in terms of durability. However, since the slag fine powder is generally low initial strength expression, it is preferable to use 20 to 40 parts by weight of such fine slag powder.

The fly ash cement can be used as a concrete admixture by substituting a part of cement as fine coal ash from Busan thermal power plant, and the fly ash is conceived as artificial pozzolanic instead of natural volcanic ash. It is an unresolved bullet of glassy fine particles with The use of fly ash is to be noted that the effect of fly ash is especially important to improve the strength and watertightness. Wet curing is important and care must be taken for curing temperature. In addition, since the initial strength is low and the curing is slowed, care should be taken to prevent freezing after pouring. The fly ash is preferably used 20 to 40 parts by weight.

The components that cause the pozzolanic reaction in fly ash components are known as soluble silica (SiO₂) and alumina (Al₂O₃). When fly ash is mixed with cement, Ca (OH) ₂ generated by the hydration of cement reacts with silica or aluminum oxide eluted from fly ash to form calcium silicate hydrate (CSH) or calcium aluminate hydrate (CAH). Produce and solidify over a long period of time to develop strength.

The chemical composition of fly ash is known to have a great influence on the properties of hardened concrete, such as the strength and chemical resistance of concrete, and depends greatly on the type of coal, combustion conditions and efficiency of site pollution prevention equipment. The crystalline composition of fly ash is quartz, quartzite, magnetite, hematite, hematite and anhydrous calcium sulfate. The main component of glass ash is 75 ~ 85%. 7 ~ 12%, 3Al₂O₃? 2SiO₂ contains 7 ~ 15%, a small amount of magnetite, hematite, metal iron, unburned carbon, etc., and 2 ~ 3% (by weight percentage) of fly ash is a water-soluble component. The liquidity of the fly ash solution is generally alkaline and contains calcium and sulfate ions and also contains magnesium, sodium, carry and silicate ions.

The major components of fly ash are silica (SiO₂), alumina (Al₂O₃) and ferric oxide (Fe₂O₃). These three components make up 80 ~ 90% of the total. Soluble SiO2 in fly ash is slowly combined with calcium hydroxide produced during cement hydration at room temperature to produce insoluble stable calcium silicate, which improves the compressive strength of concrete in the long term. Accordingly, many countries' standards, such as KS, specify the minimum content of SiO₂ or the minimum content of SiO₂ + A O₃ + Fe₂O₃. Magnesium oxide contained in fly ash reacts in concrete to form magnesium hydroxide, which causes expansion of concrete. Therefore, in order to prevent this, the maximum content of KS L 5405 is limited to 5% or less. In the case of fly ash from domestic bituminous coal, magnesium oxide content is less than 3%. Sulfuric anhydride (SO₃) exists mainly in the form of calcium sulfonate, which causes the crack and strength deterioration of concrete due to volume expansion, so the maximum content of SO₃ is regulated to 3% in KS L 5405 and 5% in ASTM C618. We regulate with. However, in the case of domestic imported bituminous coal, the content of sulfuric anhydride (SO₃) is within 2%. Activated alkali (Na₂O) present in fly ash causes alkali-aggregate reaction with reactive silicon (Si) in the aggregate, which causes expansion of concrete, so that KS L 5405 contains up to 1.5% of alkali (Na₂O) content. We regulate with.

Many of the glass phases present in fly ash are highly related to pozzolanic activity, and these glass phase particles react with Ca (OH) 2, which is produced during cement hydration, to produce hydrates. The glass phase in fly ash is determined according to the chemical composition of the ash and the combustion temperature of the lime, and the melting point of the ash is 1,250 ~ 1,500 ℃ for SiO₂-Al₂O₃ and 1,100 ~ 1,250 ℃ for CaO-SiO₂-Al₂O₃. Fly ashes as admixtures are encouraged to be rich in glass phase, and fly ashes produced at low temperatures are not suitable as admixtures. The ratio of the glass phase in the fly ash is mainly calculated from the quantitative value of each crystal phase by X-ray diffraction, but is usually assumed to be 60% or more. Fly ash having a large particle size is generally suitable as a mixed material because of its low cooling rate, and a fly ash having a small particle size is rich in a glass phase.

Pozzolan is a miscible material comprising silicate in a finely divided state without hydraulicity, and can be divided into natural pozzolan and artificial pozzolan. Natural pozzolans include volcanic ash, diatomaceous earth, silicate clay, and the like. Artificial pozzolans include fly ash, slag, calcined clay, shale, etc. These pozzolanes react with calcium hydroxide produced during the hydration of cement to form insoluble compounds.

If the fly ash is packed in a vessel and heated to a high temperature of about 950 ° C in the furnace, the amount of unburned carbon (C, CO) or sulfur (S) excluding chemically bonded water is reduced. What is expressed as a percentage of raw materials is called ignition loss. The loss of ignition is greatly influenced by the content of unburned carbon, so the loss of ignition and unburned carbon are used almost equally, and fly ash generally contains about 2 ~ 10% unburned carbon, and its content is usually 5% Although regulated below, even within this range, admixtures with organic admixtures interfere with the function of concrete admixtures. When the blower between the coal pulverizer and the boiler combustion chamber is operated at a slow speed, the air supply speed is reduced, which lowers the combustion efficiency of coal and produces fly ash with a high content of unburned carbon. The fly ash is relatively porous and amorphous carbon It has the same properties as Particularly, in AE concrete, since the adsorption property of AE agent is much greater, special measures and management for maintaining required air volume are required. When the unburned carbon content is less than 3%, there is no significant effect, but when it is over 4.5%, the effect is great, and when it is more than 6%, it is very severe. Unburned carbon is usually black, and the higher the content, the more the cement color becomes gray, the darker the appearance of concrete, and the lower the effect of admixture, low ignition loss fly ash is required. In addition, the content of unburned carbon, together with the vanadium (V₂) component affects the setting time of concrete. When the content of unburned carbon increases, both the initial and final times of the concrete become slower, but there is no significant change in the time from initial to final termination. It is about 1-2 hours. The pH value of fly ash is in the range of 8 to 13, and the pH when used as concrete admixtures affects concrete neutralization. Since the pH value of cement is around 12, the fly ash pH value should be similar to or larger than cement.

The limestone fine powder refers to the fine particles collected by using an electrostatic precipitator to the gas generated by heating the upper part of the preheater before the fly dust and the crushed raw material of the original grinding process during the cement manufacturing process into the kiln. Can be prevented from deteriorating. Such limestone fine powder is preferably used 5 to 15 parts by weight.

The calcium oxide is also called quicklime, and the chemical formula is CaO, and the pure is 2570 DEG C. When left in the air, it absorbs moisture and carbon dioxide, decomposes it into calcium hydroxide (calcite) and calcium carbonate, and serves to strengthen the hardness of concrete. Such quicklime is preferably used 5 to 10 parts by weight.

The sodium sulfate is used as a curing accelerator, it is preferable to use 1 to 5 parts by weight of such sodium sulfate.

In general, Portland cement is about 800 kg of carbon dioxide produced to produce 1 ton, which is contrary to the recent trend to reduce the amount of carbon dioxide for greenhouse gas reduction. However, low-alkali concrete compositions using tannins of the present invention are used in small amounts in place of ordinary portland cement, thereby reducing carbon dioxide.

Using low-alkali concrete composition using tannin of the present invention, reinforced concrete plume and bench plume, raft block, masonry retaining wall block, etc. can be manufactured, and these products are environmentally friendly and do not emit strong alkali, and also have high strength. Do.

Hereinafter, the present invention will be described in detail with reference to Examples. However, embodiments according to the present invention can be modified in many different forms, the scope of the invention should not be construed as limited to the embodiments described below. Embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

Example

Example 1 Cement Composition Containing 1 part by weight of tannin, hydrated gypsum and silica fume

20 parts by weight of ordinary portland cement, 30 parts by weight of slag powder, 30 parts by weight of fly ash, 10 parts by weight of limestone powder, 7 parts by weight of quicklime, 3 parts by weight of sodium sulfate, 1 part by weight of tannin, 20 parts by weight of gypsum and 5 parts of silica fume The cement composition was prepared by mixing uniformly.

A weight ratio of the prepared cement composition and standard yarn was prepared to be 1: 3, and water was added to have a content of 50% by weight to uniformly mix with a mortar mixer to prepare mortar.

Using the mortar prepared as described above to prepare a specimen of footnote of 40mm × 40mm × 160mm.

Example 2 Cement Composition Containing 1.5 Parts by Weight of Tannin, Dihydrate Gypsum and Silica Fume

20 parts by weight of ordinary Portland cement, 30 parts by weight of slag powder, 30 parts by weight of fly ash, 10 parts by weight of limestone powder, 7 parts by weight of quicklime, 3 parts by weight of sodium sulfate, 1.5 parts by weight of tannin, 20 parts by weight of gypsum and 5 parts of silica fume The cement composition was prepared by mixing uniformly.

A weight ratio of the prepared cement composition and the standard yarn was prepared to be 1: 3, and water was added to have a content of 50% by weight to uniformly mix with a mortar mixer to prepare mortar.

Using the mortar prepared as described above to prepare a specimen of footnote of 40mm × 40mm × 160mm.

Comparative Example 1. Common Portland Cement

Ordinary Portland cement was prepared such that the weight ratio of standard yarn was 1: 3, water was added so that the content was 50 wt%, and uniformly mixed with a mortar mixer to prepare mortar.

Using the mortar prepared as described above to prepare a specimen of footnote of 40mm × 40mm × 160mm.

Comparative Example 2. A cement composition comprising 1 part by weight of tannins

The cement composition was prepared by uniformly mixing 20 parts by weight of ordinary Portland cement, 30 parts by weight of slag powder, 30 parts by weight of fly ash, 10 parts by weight of limestone powder, 7 parts by weight of quicklime, 3 parts by weight of sodium sulfate, and 1 part by weight of tannin.

A weight ratio of the prepared cement composition and the standard yarn was prepared to be 1: 3, and water was added to have a content of 50% by weight to uniformly mix with a mortar mixer to prepare mortar.

Using the mortar prepared as described above to prepare a specimen of footnote of 40mm × 40mm × 160mm.

Comparative Example 3. A cement composition comprising 1.5 parts by weight of tannins

The cement composition was prepared by uniformly mixing 20 parts by weight of ordinary Portland cement, 30 parts by weight of slag powder, 30 parts by weight of fly ash, 10 parts by weight of limestone powder, 7 parts by weight of quicklime, 3 parts by weight of sodium sulfate, and 1.5 parts by weight of tannin.

A weight ratio of the prepared cement composition and the standard yarn was prepared to be 1: 3, and water was added to have a content of 50% by weight to uniformly mix with a mortar mixer to prepare mortar.

Using the mortar prepared as described above to prepare a specimen of footnote of 40mm × 40mm × 160mm.

Test Example 1 Measurement of Compressive Strength

The specimens prepared in Examples 1-2 and Comparative Examples 1-3 were shown in Table 1 by measuring the compressive strength every 3 days, 7 days, 14 days, 28 days and 56 days.

Compressive strength of specimen (unit: MPa) 3 days 7 days 14 days 28 days 56 days Example 1 7.1 9.1 14.3 15.0 18.2 Example 2 6.0 8.7 11.2 12.1 15.2 Comparative Example 1 10.6 15.7 19.9 20.5 24.4 Comparative Example 2 9.2 10.8 15.4 16.1 19.3 Comparative Example 3 8.2 10.3 12.6 13.2 16.6

Test Example 2 Measurement of pH

The specimens prepared in Examples 1-2 and Comparative Examples 1-3 were shown in Table 2 by measuring the pH every 1 day, 3 days, 7 days, 14 days, 28 days and 56 days.

pH measurement 1 day 3 days 7 days 14 days 28 days 56 days Example 1 12.62 12.20 12.18 11.60 11.42 10.13 Example 2 12.51 12.21 12.15 11.77 11.52 9.91 Comparative Example 1 12.90 12.6 12.14 11.82 11.80 11.41 Comparative Example 2 12.39 12.13 12.03 11.86 11.51 10.22 Comparative Example 3 12.46 12.18 12.02 11.93 11.79  10.34

Test Example 3 Measurement of Carbon Dioxide Emission

The carbon dioxide emissions of the compositions of Example 1 and Comparative Example 1 were calculated and shown in Table 3 below.

CO2 emissions CO2 emissions (CO2 kg / ton) Comparative Example 1 746 Example 1 262

The present invention has been described with reference to the preferred embodiment as described above, but is not limited to the above embodiment, it should be interpreted by the appended claims. It will be apparent to those skilled in the art that various changes and modifications may be made without departing from the scope of the present invention as defined by the appended claims and their equivalents.

Claims (3)

10 to 30 parts by weight of ordinary Portland cement, 20 to 40 parts by weight of slag fine powder, 20 to 40 parts by weight of fly ash, 5 to 15 parts by weight of limestone fine powder, 5 to 10 parts by weight of quicklime, 1 to 5 parts by weight of sodium sulfate, 0.5 to tannins Concrete composition using tannins including 2.0 parts by weight, 15 to 25 parts by weight of gypsum and 3 to 10 parts by weight of silica fume. The method of claim 1,
56 days of age of the concrete composition using the tannins concrete composition using tannins, characterized in that 9.6 ~ 10.25. Block comprising a concrete composition using the tannins of claim 1 or claim 2.