KR101345198B1 - Low alkali concrete composition with green tea and block unit comprising the same - Google Patents

Abstract

The present invention relates to a low-alkali concrete composition using green tea, and more particularly, to 10 to 30 parts by weight of ordinary portland cement, 20 to 40 parts by weight of slag powder, 20 to 40 parts by weight of fly ash, and 5 to 15 pieces of limestone powder. For the low alkali concrete composition using green tea, including parts by weight, 5 to 10 parts by weight of quicklime, 1 to 5 parts by weight of sodium sulfate, 25 to 40 parts by weight of green tea solution, 15 to 25 parts by weight of hydrated gypsum and 3 to 10 parts by weight of silica fume. will be. The low-alkali concrete composition using the green tea of the present invention has a relatively low pH, including green tea solution, and compressive strength by preventing the coagulation delay and initial strength deterioration, which are side effects of using green tea solution, using dihydrate gypsum and silica fume. Is excellent. In addition, the green tea solution of the low-alkali concrete composition using the green tea of the present invention can form a coating on the surface of the rebar to prevent oxidation. In addition, the low alkali concrete composition using the green tea of the present invention has a carbon dioxide saving effect.

Description

LOW ALKALI CONCRETE COMPOSITION WITH GREEN TEA 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 CO2 emissions would need to be reduced by 50% compared to 2000 in order to curb temperature rises before the Industrial Revolution before 1750 to 2.0 ℃ to 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-CO ² / ton tons of carbon dioxide are 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, raft block, and masonry retaining wall block. Since it is produced in the form, environmental problems such as the strong alkali component is eluted has appeared large.

Accordingly, the problem to be solved by the present invention is to solve the above problems, to provide a low-alkali concrete composition using green tea that is 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 the green tea 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, 25 to 40 parts by weight of green tea solution, 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 green tea of the present invention has a relatively low pH, including green tea solution, and uses compressive strength and silica fume to prevent the coagulation delay and lowering of initial strength resulting from the use of green tea solution. great. In addition, the green tea solution of the low-alkali concrete composition using the green tea of the present invention can form a coating on the surface of the rebar to prevent oxidation. And, low alkali concrete composition using the green tea 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 constitutions described in the embodiments described herein are merely the most preferred embodiments of the present invention, and are not intended to represent all of the technical ideas of the present invention. Therefore, various equivalents which can be substituted at the time of application It should be understood that variations can be made.

Low alkali concrete composition using green tea of the present invention is usually 10 to 30 parts by weight of 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, 25 to 40 parts by weight of green tea solution, 15 to 25 parts by weight of hydrated gypsum and 3 to 10 parts by weight of silica fume. In addition, the concentration of the green tea solution is preferably 200 ~ 300 ppm. In addition, according to the present invention, the pH of the 56-day-old age of low-alkali concrete composition using the green tea according to the content of the green tea solution is 9.8 ~ 10.3.

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 melted or calcined, and then a suitable amount of powder is applied to the 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.

The low-alkali concrete composition using the green tea of the present invention contains a green tea solution to prevent the strong alkali by adjusting the pH to 10.3 or less, and at the same time, when using reinforcing bar to form a film of green tea component on the surface of the reinforcing steel to oxidize the steel Can be prevented. However, it is thought that the sugar component contained in the green tea slows the hydration reaction by surrounding the cement particles. In particular, when the green tea powder is used, the green tea powder surrounds the cement particles, which significantly delays the hydration reaction. The negative effect of green tea can lead to a decrease in the initial strength of the cement.

Therefore, the low-alkali concrete composition using green tea of the present invention is excellent in compressive strength by preventing the coagulation delay and initial strength decrease, which are side effects of using green tea solution, using Isu Gypsum and silica fume. In addition, the present invention can be used to reduce the delay of the hydration reaction using the green tea solution effectively extracted green tea powder without using the green tea powder.

The green tea solution of the present invention refers to a solution in which green tea is poured into water, and the type of water is not particularly limited, but distilled water is preferably used. The temperature of the water to brew the green tea is not particularly limited, and water at a temperature of about 80 ° C. in which the active ingredient is best extracted is preferably used, but water at room temperature may be used.

Green tea solution of the present invention is preferably used 25 to 40 parts by weight, when the amount of the green tea solution is less than 25 parts by weight of the active ingredient of green tea is too small, so the effect of pH adjustment is insignificant, 40 parts by weight This is because the initial strength is excessively lowered when used excessively. In addition, the concentration of the green tea solution of the present invention is expressed in mg of the green tea component brewed in green tea on the basis of 1 l of water, and the concentration of such green tea solution is preferably 200 to 300 ppm. This is because when the concentration of the green tea solution is less than 200 ppm, the content of the active ingredient of green tea is too small, so the effect of pH adjustment is insignificant, and when the concentration exceeds 300 ppm, there is a problem that the initial strength is excessively lowered. There is a problem that effective extraction of ingredients is difficult.

Gypsum is a very soft sulphate mineral mainly composed of calcium sulfate (CaSO ₄ ). Especially, gypsum is CaSO ₄ · 2H ₂ O and 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 the fly ash component are known as soluble silica (SiO ₂ ) and alumina (Al ₂ O ₃ ). 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 component of fly ash is quartz, quartzite, magnetite, hematite, hematite and anhydrous calcium sulphate. The main constituent is 75 ~ 85% of glassy crystalline SiO ₂ Is 7 ~ 12%, 3Al ₂ O ₃ · 2SiO ₂ is 7 ~ 15%, and other small amount of magnetite, hematite, metal iron, unburned carbon are present, and 2 ~ 3% of fly ash (% by weight) is water-soluble. Ingredient. 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 main components of fly ash are silica (SiO ₂ ), alumina (Al ₂ O ₃ ) and ferric oxide (Fe₂O ₃ ). These three components make up 80 ~ 90% of the total. Soluble SiO ₂ in fly ash combines with calcium hydroxide, which is produced during cement hydration, at room temperature to produce insoluble stable calcium silicate, increasing the compressive strength of concrete in the long term. Accordingly, or are defined as a minimum value for the content of SiO ₂ in the standard of many countries, such as KS, and defining the minimum content of _{SiO 2 + Al 2 O 3 +} Fe 2 O 3. 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 (SO ₃ ) 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 SO 3 is regulated to 3% in KS L 5405 and 5 in ASTM C618. Regulated in%. However, in the case of domestic imported bituminous coal, the content of sulfuric anhydride (SO ₃ ) is within 2%. Active alkali (Na ₂ O) present in the fly ash is a reactive silicon (Si) component and the alkali in the aggregate-content of the alkali (Na ₂ O), this causes the aggregate reaction resulting expansion can cause the concrete cracks KS L 5405 Is regulated up to 1.5%.

Many of the glass phases present in fly ash are closely related to pozzolanic activity, and these glass phase particles react with Ca (OH) ₂ , which occurs during cement hydration, to produce hydrates. Fly ash is a glass phase is determined according to the chemical composition and the burning temperature of the lime in the ash content, the melting point of the ash content in the system SiO ₂ -Al ₂ O ₃ 1,250 ~ 1,500 ℃ a-SiO ₂ -Al ₂ O in the CaO-based ₃ ~ 1100 in 1,250 ° C. 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, the chemical formula is CaO, and the pure is 2570? 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, the low-alkali concrete composition using green tea of the present invention has a small amount of carbon dioxide because it replaces the ordinary portland cement.

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

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the above-described embodiments. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art.

Example

Example  One. Green Tea Solution  25 Weight portion , Gypsum plaster, Silica fume  Cement composition comprising

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, 25 parts by weight of green tea solution, 20 parts by weight of gypsum and 5 parts of silica fume The parts were uniformly mixed to prepare a cement composition. In particular, the green tea solution is green tea in water at 90 ℃ until the concentration is 300ppm It used the thing which boiled.

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. Green Tea Solution  40 Weight portion , Gypsum plaster, Silica fume  Cement composition comprising

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, 40 parts by weight of green tea solution, 20 parts by weight of gypsum and 5 parts of silica fume The parts were uniformly mixed to prepare a cement composition. In particular, the green tea solution is green tea in water at 90 ℃ until the concentration is 300ppm It used the thing which boiled.

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  One. 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. Green Tea Solution  25 Weight  Cement composition comprising

A 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 25 parts by weight of green tea solution. In particular, the green tea solution is green tea in water at 90 ℃ until the concentration is 300ppm It used the thing which boiled.

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. Green Tea Solution  40 Weight  Cement composition comprising

A 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 40 parts by weight of green tea solution. In particular, the green tea solution is green tea in water at 90 ℃ until the concentration is 300ppm It used the thing which boiled.

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 28th 56 days Example 1 10.7 16.1 20.3 21.5 26.1 Example 2 10.6 15.5 19.4 21.1 24.8 Comparative Example 1 10.6 15.7 19.9 20.5 24.4 Comparative Example 2 10.2 14.7 18.1 19.2 23.5 Comparative Example 3 10.0 14.3 18.0 19.5 23.6

Test Example  2. pH Measurement of

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 28th 56 days Example 1 11.60 11.50 11.84 11.00 10.52 10.22 Example 2 11.52 11.21 10.44 10.21 10.13 9.82 Comparative Example 1 12.90 12.60 12.44 12.22 12.15 12.11 Comparative Example 2 12.86 12.56 11.97 11.90 11.47 10.91 Comparative Example 3 12.04 12.00 11.56 11.21 11.03 10.79

Test Example  3. Measurement of CO2 Emissions

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

Claims (4)

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, green tea solution 25 Concrete composition using green tea containing ~ 40 parts by weight, 15 to 25 parts by weight of gypsum and 3 to 10 parts by weight of silica fume. delete The method of claim 1,
56 days of age of the concrete composition using the green tea concrete composition using green tea, characterized in that 9.82 ~ 10.22. Block comprising a concrete composition using the green tea of claim 1.