WO2013022197A2 - Mortar or concrete composition using coal ash, and usage thereof - Google Patents

Abstract

Provided is a mortar composition in which water is mixed with solids that comprise: 7.5 weight parts of coal ash; 1.5 to 3.0 weight parts of cement; 1.0 to 2.0 weight parts of calcined gypsum; 1.0 to 2.0 weight parts of quicklime (CaO); 0.01 to 2.0 weight parts of a retardant; and 0.01 to 0.5 weight parts of a viscosity increasing agent, to thereby prepare a mortar having high compressive strength without using sand.

Description

Mortar or concrete composition using coal ash and use thereof

FIELD OF THE INVENTION The present invention relates to mortars or concrete compositions and uses thereof, and more particularly to mortars or concrete compositions using coal ash and uses thereof.

Generally, mortar is mixed with ash and cement with sand, and is hardened when the water is removed. It is mainly used for laying bricks or stones. Cement mortar includes portland cement mortar and natural cement mortar, which contains 3 parts by weight of sand and 1 part by weight of cement, and a suitable amount of water, and 2 parts by weight of natural cement mortar. Parts by weight of cement are mixed. In the case of these cement mortars, a large amount of cement is consumed, the amount of sand used as aggregate increases the construction cost, and there is a problem in that the compressive strength of these mortars is not so high.

Meanwhile, coal ash is a non-combustible component remaining after coal combustion in a thermal power plant, and is classified into coal ash or fly ash and floor ash or bottom ash. The main components are silicon dioxide (SiO ₂ ) and aluminum oxide. (Al ₂ O ₃ ), iron oxide (Fe ₂ O ₃ ), calcium oxide (CaO), magnesium oxide (MgO), sodium oxide (Na ₂ O), potassium oxide (K ₂ O), titanium dioxide (TiO ₂ ), etc. to be. These coal ashes are representative industrial wastes, and their use is not appropriate, and almost all of them are buried, causing serious environmental pollution problems.

Thus, attempts are being made to recycle the coal ash, and such techniques include agitated by adding an appropriate amount of water to 60% by weight of powdered coal ash, 23% by weight of a curing agent, and 17% by weight of sand, and then molded by a brick molding machine. Korean Unexamined Patent Publication No. 2002-0065190 for bricks, 30-80 parts by weight of waste slugs, 10-40 parts by weight of waste foundry sand, 5-20 parts by weight of coal ash, 15-20 parts by weight of cement and 20 parts by weight of water are prepared. Republic of Korea Patent No. 237557 for mortar composition, the production of coal ash brick comprising the step of kneading Portland cement, diatomaceous earth and magnesia cement to coal ash as a coagulant and curing at a pressure of 1 kg / cm ² with a steam of 65 ℃ Republic of Korea Patent Publication No. 86-001754 call, calcium oxide (CaO) and cement, potassium fluoride (KF), sulfuric acid, calcium oxide (CaSO _4), sodium sulfate (Na ₂ SO ₄₎ relates to a method, a mixture of calcium chloride (CaCl ₂₎ And the like crane compositions 1 to 4.5% and from 40 to 90% coal ash and cement Republic of Korea Patent Laid-Open Publication relates to a method for manufacturing blocks of a chair the coal ash is prepared by mixing 20 to 23% of the number 1999-0011079.

However, these conventional methods of manufacturing mortar or brick using coal ash are limited in the amount of coal used and do not completely exclude the use of sand or reduce the amount of cement used. There was a drawback in the complexity of the manufacturing process, such as having to undergo a curing process of temperature or high temperature.

The present invention is to solve a number of problems including the above problems, completely excluding the use of aggregates such as sand and sand substitutes of coal ash, as well as curing at room temperature as in the general mortar manufacturing process, such as brick It is an object of the present invention to provide a mortar or concrete composition and a use thereof which are superior in compressive strength to a molded cement mortar molded body. However, these problems are exemplary, and the scope of the present invention is not limited thereby.

According to an aspect of the present invention, 7.5 parts by weight of coal ash, 1.5 to 3.0 parts by weight of cement, 1.0 to 2.0 parts by weight of calcined gypsum, 1.0 to 2.0 parts by weight of quicklime (CaO), 0.01 to 2.0 parts by weight of retardant and 0.01 to 0.5 parts by weight of thickener. There is provided a mortar composition in which water is blended into a solid containing parts.

In the mortar composition, the coal ash may be fly ash, bottom ash or a mixture thereof.

In the mortar composition, the cement may be Portland cement, blast furnace slag cement or Portland pozzolane cement.

In the mortar composition, the retarder is used for the purpose of inhibiting the rapid hardening of the mortar, a cement / concrete sensitizer, a hydration delay for cement, inorganic acids, alcohols, amino acids, proteins or sugars, or their It may be a mixture, wherein the protein may be gelatin and the amino acid may be proline or glutamic acid.

In the mortar composition, the thickener may be a cellulose thickener, a polyacrylamide-based water-soluble polymer, polyvinyl alcohol or polyvinylacetate as an additive added to improve the viscosity and cohesive action of the mortar or concrete. As the thickener, methyl cellulose, methyl cellulose acetate or ethyl cellulose may be used.

In addition, in the mortar composition according to an embodiment of the present invention, the solid content is at least one concrete selected from the group consisting of a crack reducing agent, an antibacterial agent, a durability improving agent, a water reducing agent, a fastener, an expansion material, a foam material, and a admixture. Additives may further be included.

In the mortar composition, water may be added in an appropriate amount within the range having the proper fluidity of the mortar composition may be added to 100 to 300% by weight relative to the cement content.

According to another aspect of the present invention, there is provided a concrete composition comprising 1 part by weight of the mortar composition and 0.5 to 3 parts by weight of aggregate.

In the concrete composition, the aggregate may be fine aggregate, coarse aggregate, waste foundry sand, construction waste, blast furnace slug, porcelain piece or mixed aggregate thereof.

According to another aspect of the invention, the building material molding step of molding the mortar composition; And it provides a method for producing an artificial building material containing coal ash comprising a curing step of curing the molded building material at room temperature.

In the method of manufacturing the artificial building material, the building material may be artificial sand, artificial gravel or brick.

According to another aspect of the invention, there is provided a coal ash-containing artificial building material produced by the above production method.

According to one embodiment of the present invention made as described above, it is possible to produce a mortar having a high compressive strength after curing without using any aggregate, and to produce a concrete with high compressive strength while reducing cement consumption. In addition, when manufacturing the building material with a mortar composition according to an embodiment of the present invention, the fire resistance and sound insulation is very excellent compared to conventional cement bricks. Of course, the scope of the present invention is not limited by these effects.

According to an aspect of the present invention, 7.5 parts by weight of coal ash, 1.5 to 3.0 parts by weight of cement, 1.0 to 2.0 parts by weight of calcined gypsum, 1.0 to 2.0 parts by weight of quicklime (CaO), 0.01 to 2.0 parts by weight of retardant and 0.01 to 0.5 parts by weight of thickener. There is provided a mortar composition in which water is blended into a solid containing parts.

In the mortar composition, the coal ash may be fly ash, bottom ash or a mixture thereof.

When ash is burned in coal, coal ash is first generated from the combustion exhaust gas, which falls under the boiler part and generates lump ash which is quenched with water. This is called bottom ash or clinker ash, and then economizer. Ash falling from the heat recovery device of the air feeder portion is generated, which is called a cinder ash. However, most coal ash is collected in the electrostatic precipitator of the last process, which is called fly ash or fly ash. The three types of coal ash account for 10% to 15%, bottom ash to 3% to 7%, and fly ash to 80% to 90%. The size of the coal ash particles is 0.1 to 10 mm in the bottom ash, 0.1 to 1 mm in the Sinder Ash and the fly ash is about 1 to 100 ㎛. Chemical composition and physical properties of fly ash and bottom ash, which occupy most of the coal ash, are shown in Table 1 below.

Table 1 Chemical Composition and Physical Properties of Coal Ash

	Chemical composition (%)					Physical properties
	CaO	SiO 2	Al 2 O 3	MgO	Fe 2 O 3	Density (g / cm 3 )	Particle size distribution (㎛)	Bulk density (g / cm 3 )
Fly ash	1.2	66.1	23.3	0.8	4.2	2.13	1-100	0.75
Flooring	1.9	45.5	27.8	0.9	5.7	1.98	100-10000	0.85

Since the coal ash has similar properties to those of the cement, its utilization as a cement substitute is being sought. However, the specific composition ratio of constituents is different from cement, so it is not possible to replace 100% of cement, and there is no method of replacing coal ash such as fine aggregate such as sand or coarse aggregate such as gravel. .

In the mortar composition, the cement may be portland cement, blast furnace slag cement, or portland pozzolan cement.

In the case of the most commonly used portland cement of the cement chemical composition and physical properties are shown in Table 2 below.

TABLE 2 Chemical Composition and Physical Properties of Portland Cement

Chemical composition (%)						Physical properties
CaO	SiO 2	Al 2 O 3	MgO	Fe 2 O 3	SO 3	Density (g / cm 3 )	Particle size distribution (㎛)	Bulk density (g / cm 3 )
64.9	22.0	5.3	1.3	3.0	1.9	3.15	20-30	1.5

In the mortar composition, the calcined gypsum is a common name for calcium sulfate hemihydrate, and the chemical formula is CaSO ₄ H ₂ O. Also known as baked gypsum, hemihydrate gypsum or calcined gypsum, it is a powder produced by heating gypsum (CaSO _{4 ·} 2H ₂ O) to 120 to 130 ° C and removing 3/4 of the crystal water. In the case of calcined plaster powder, the specific gravity is 1.7 g / cm ³ , and the powder specific gravity is 1.0 g / cm ³ . Although gypsum is the oldest cement material, it has only been used in modern times as a building interior material such as gypsum board.

In the mortar composition, the quicklime is an oxide of calcium, and is generally produced when carbon dioxide (CaCO ₃ ) is heated in a state in which air is blocked, and carbon dioxide (CO ₂ ) is lost.

CaCO ₃ (S) → CaO (S) + CO ₂ (G) (heat in vacuum)

Quicklime has a melting point of 2,572 ℃, a boiling point of 2,850 ℃, specific gravity of 3.3 g / cm ³ , and a powder specific gravity of 1.0 g / cm ^3. When left in the air, it absorbs water and carbonic acid gas, Calcium carbonate (limestone). Because of the high melting point, quicklime is used to coat the furnace walls of crucibles and crucibles, as a desulfurization and dephosphorizing agent in steelmaking, and in the neutralization of acidified land in agriculture, and as a subsidiary material in the manufacturing of light foam concrete. It is used extremely limitedly, such as injecting.

The present inventors, based on coal ash, when mixing a certain weight ratio of cement, calcined gypsum, quicklime powder, retardant and thickener, and then add a suitable amount of water to prepare mortar, to supplement the physical properties of the coal ash lacking calcium oxide, etc. It is possible to produce high-quality mortar at low cost without using and using additional energy, and also to produce concrete having excellent properties even when manufacturing reinforced concrete by mixing coarse aggregate without using sand in the mortar. The present invention was completed by confirming. In particular, when manufacturing a building material, such as a brick using a mortar composition according to an embodiment of the present invention, compared to the compressive strength that meets the KS standard and the thermal conductivity is only 1/3 and compared with the general cement brick building interior materials Very suitable for use as

Mortar composition of the present invention is when mixing the coal ash and cement when the mortar is prepared by adding calcined gypsum and quicklime with additives other than coal ash and cement to produce the ettringite to increase the initial strength of the molding, The increase in tobermorite leads to an increase in late intensity.

When calcined gypsum is added to cement, C3A (3CaO.Al ₂ O ₃ ) in the cement component reacts with calcined gypsum to produce ettringite, and the process of producing ettringite is shown in the following scheme.

_{3CaO · Al 2 O 3 + 3CaSO} 4 · H 2 O + xH 2 O → 3CaO · Al 2 O 3 · 3CaSO 4 · 31H 2 O

  Cement + Plaster + Water → Ettringite

Tobermorite production process is shown in the following scheme.

CaOSi0 ₂ H ₂ O (II) → Ca ₅ Si ₆ O ₁₆ (OH) ₂ 4H ₂ O

    C-S-H (II) → Tobermorite

However, in the above process, a problem occurs in which a rapid freezing phenomenon occurs depending on the ratio of coal ash, cement and calcined gypsum.

In the present invention, to solve this problem, the inventors arbitrarily adjusted the setting speed during the time useful for the operation by adding an appropriate amount of retarder.

The retarder is used for the purpose of suppressing the rapid hardening of the mortar, and may be a cement / concrete sensitizer, a hydrating retardant for cement, an inorganic acid, an alcohol, or a sugar.

In the present invention, a retarder used in specific embodiments is gelatin, and glutamic acid (glutaminate or glutamic acid) or proline contained in gelatin is reacted in an alkaline aqueous solution to cause hydrolysis of a carboxyl group (COOH). At this time, the carboxy anion (COO ⁻ ) formed by the separation of the protons (H ⁺ ) in the carboxyl group surrounds the crystal surface of Ca ^{2+ in} the coal ash-cement-calcined gypsum, and condensation is delayed. The hydrolysis reaction by glutamic acid or proline is as follows.

1) glutamic acid

2) proline

As can be seen from the above formula, by adding an appropriate amount of the retarder in the alkaline solution, it is possible to appropriately adjust the setting speed of the molded product.

However, plaster alone alone has low water content, which lowers the workability of plastering, and it is impossible to adjust the curing time of plaster without adhesive. Homogeneous blending of trace amounts of thickeners in plaster may enhance moisture content, improve plaster workability, and delay the hardening of gypsum.

The thickener is an additive added to improve the viscosity and cohesion of mortar or concrete. Cellulose thickener, polyacryl amide water-soluble polymer, polyvinyl alcohol or polyvinyl acetate acetate) and methylcellulose, methylcellulose acetate, or ethylcellulose may be used as the cellulose thickener.

In addition, the solid content may further include one or more concrete additives selected from the group consisting of crack reducing agents, antibacterial agents, durability improvers, water reducers, rapideners, expansion agents, foaming agents, and admixtures.

In the mortar composition, water may be added in an appropriate amount within the range having the proper fluidity of the mortar composition may be added to 100 to 300% by weight relative to the cement content.

The present inventors have continuously tried to manufacture bricks by a combination of coal ash, cement and calcined gypsum using coal ash instead of sand, but failed to produce bricks of required physical properties. Thus, by adding quicklime (CaO) to coal ash, cement and calcined gypsum and adding the above-described retarder and thickener to the mortar to prepare mortar, the present invention was completed by successfully producing a brick having desirable physical properties.

The above results indicate that in the case of coal ash, the content of silica (SiO ₂ ) or alumina (Al ₂ O ₃ ) used in the production of ettringite or tobermorite is very high, but the content of calcium oxide (CaO) is low, It is understood that the reaction did not proceed smoothly despite the addition of cement with a relatively high content of calcium oxide.

According to another aspect of the present invention, there is provided a concrete composition comprising 1 part by weight of the mortar composition and 0.5 to 3 parts by weight of aggregate.

In the concrete composition, the aggregate may be fine aggregate, coarse aggregate, waste foundry sand, construction waste, blast furnace slug, porcelain piece or mixed aggregate thereof, and it is also possible to use only coarse aggregate without fine aggregate.

According to another aspect of the invention, the building material molding step of molding the mortar composition; And it provides a method for producing an artificial building material containing coal ash comprising a curing step of curing the molded building material at room temperature.

In the method of manufacturing the artificial building material, the building material may be artificial sand, artificial gravel or brick.

In the manufacturing method of the artificial building material, in the process of curing the mortar composition in the case of artificial sand, the particles can be molded by using a sieve of the appropriate size, in the case of the artificial gravel or brick mortar composition in the form of gravel or brick form, respectively After pouring to cure can be prepared by separating the dried gravel or brick from the mold.

According to another aspect of the invention, there is provided a coal ash-containing artificial building material produced by the above production method.

Hereinafter, the present invention will be described in more detail through Examples and Experimental Examples. However, the present invention is not limited to the examples and experimental examples disclosed below, but may be embodied in various different forms. The following examples and experimental examples are provided to make the disclosure of the present invention complete and the general knowledge. It is provided to fully inform those who have the scope of the invention.

EXAMPLE

Preparation of mortar:

7.5 kg of coal ash, 1.5 kg of cement, 1 kg of calcined gypsum and 1 kg of coke pulverized to 10 mm or less are mixed with 1 kg of gelatin as a retardant and 100 g of methyl cellulose as a thickener, and then 2.7 L of water is added for proper fluidity. A mortar having was prepared. The water can be adjusted according to the moisture content of each component.

Manufacture of bricks:

The prepared mortar was poured into a rectangular brick mold, and then cured at room temperature for 7 days.

Manufacture of panels:

The prepared mortar was molded into a panel having a thickness of 90 mm (90 × 333 × 500 mm) and cured at room temperature for 7 days.

Experimental Example

Experimental Example 1: Measurement of compressive strength, water absorption and thermal conductivity:

The compressive strength, water absorption and thermal conductivity of the bricks manufactured above were measured by requesting the Korea Institute of Construction and Environmental Testing of Daejeon, and the results are shown in Table 3 below.

TABLE 3 Physical properties of coal ash bricks

Test Items	Test result	Test Methods
Water absorption	27.3%	KS L 8520 2007
Compressive strength	86.7 kgf / cm 2	KS L 8520 2007
Thermal conductivity	0.269 kcal / mh ℃	KS L 9016

As a result, the compressive strength exceeded 80 kgf / cm ² , which is the KS criterion for the combustion material brick. However, according to the KS L 8520 2007 standard, the compressive strength is measured while the cured brick is immersed in water for 2 hours and absorbed. Therefore, the compressive strength is expected to increase when measured without absorbing. The volcanic ash brick according to an embodiment of the present invention is cured for 7 days, and when the above-described tobermorite formation reaction is progressed through long-term curing, the compressive strength is expected to further increase.

Absorption rate was 27.3%, 82% higher than the standard absorption rate of the cement brick 15% or less, but this is excessive moisture in summer when the brick made of a mortar composition according to an embodiment of the present invention as a building interior material It can be advantageous in that it can control the humidity of the room by exhaling moisture in winter. Optionally, when the coal ash brick according to an embodiment of the present invention is coated with a waterproofing agent, it may be used as a building exterior material.

Experimental Example 2: Sound Insulation Test

The coal ash panel manufactured according to the above embodiment was subjected to a reverberation chamber having a measurement environment of a sound source chamber volume of 77.7 m ³ , a sound receiving chamber volume of 218 m ³ , an opening area of 5.88 m ^2, and a sound source 1/3 octave band noise according to ISO 140. The sound insulation test was carried out six times to obtain an average value. The results are shown in Table 4.

Table 4 Sound insulation effect of coal ash panel

Frequency (Hz)	Transmission loss (dB)
125	36.0
160	35.3
200	39.8
250	37.6
315	37.0
400	34.6
500	36.8
630	39.8
800	42.9
1.0 k	46.3
1.25 k	48.6
1.6 k	49.6
2.0 k	51.0
2.5 k	53.5
3.15 k	55.5
4.0 k	55.0

* STC: 43 (dB)

The results are comparable to the sound insulation of the ALC block 200 mm + 10 mm double-sided remittal (//www.alc.or.kr/sta-03.htm, see Korea Light Foam Concrete Association homepage), When manufacturing the interior plate with a mortar according to an embodiment, it is possible to achieve an excellent sound insulation effect while configuring a thinner wall.

 Although the present invention has been described with reference to the above-described examples and experimental examples, these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (10)

1. Water is blended into solids comprising 7.5 parts by weight of coal ash, 1.5 to 3.0 parts by weight of cement, 1.0 to 2.0 parts by weight of calcined gypsum, 1.0 to 2.0 parts by weight of quicklime (CaO), 0.01 to 2.0 parts by weight of retardant and 0.01 to 0.5 parts by weight of thickener. Mortar composition.
2. The method of claim 1,

   The coal ash is fly ash, bottom ash or a mixture thereof, mortar composition.
3. The method of claim 1,

   Wherein the cement is Portland cement, blast furnace slag cement or Portland pozzolane cement.
4. The method of claim 1,

   The retarder is a mortar composition for a cement / concrete water reducing agent, a cement hydration delay agent, an inorganic acid, an alcohol, an amino acid, a protein or a sugar, or a mixture thereof.
5. The method of claim 1,

   The thickener is a mortar composition, a cellulose thickener, a polyacrylamide-based water-soluble polymer, polyvinyl alcohol or polyvinylacetate.
6. Concrete composition comprising 1 part by weight of the mortar composition of any one of claims 1 to 5 and 0.5 to 3 parts by weight of aggregate.
7. The method of claim 6,

   The aggregate is fine aggregate, coarse aggregate, waste foundry sand, building waste, blast furnace slug, porcelain piece or mixed aggregate thereof, concrete composition.
8. A molding step of molding the mortar composition of any one of claims 1 to 5; And

   A method for producing an artificial building material containing coal ash comprising a curing step of curing the molded body at room temperature.
9. The method of claim 8,

   The artificial building material is artificial sand, artificial gravel or brick, manufacturing method.
10. Artificial building materials containing coal ash produced by the manufacturing method of claim 8.