KR20180078803A - Cement board - Google Patents

Abstract

Disclosed is a cement board. The cement board of the present invention manufactures a mixture by mixing 35-55 wt% of cement, 10-20 wt% of silica, 20-35 wt% of bottom ash, 2-5 wt% of silica fume, 1-6 wt% of anhydrite, 0.1-1.5 wt% of water-repellent agent, 0.1-1 wt% of water-reducing agent, 0.01-1 wt% of viscosity agent, and 0.02-1.2 wt% of superplasticizer, and manufactures the mixture by compression-molding the same.

Description

CEMENT BOARD

The present invention relates to a cement board, and more particularly, to a cement board capable of securing water resistance and durability while reducing the strength drop when using bottom ash as an aggregate.

Generally, coal-fired power plants produce electricity by burning coal. As coal is burned, fly ash is generated. Fly ash is divided into fly ash and bottom ash depending on the collection location.

The fly ash is contained in the combustion gas in the boiler of the power plant and is collected in the electrostatic precipitator. Fly ash is a fine powder. Bottom ash is a powder that falls on the floor due to its own weight attached to the furnace wall, superheater, reheater, etc. The size of the bottom ash is about 1-2.5 mm. Bottom ash accounts for approximately 10-20% of the coal ash generated during the development process.

However, conventionally, since the recycling rate of bottom ash is low, most of the bottom ash is buried in a landfill or the like. Therefore, recycling and treatment of bottom ash are required.

BACKGROUND ART [0002] The background art of the present invention is disclosed in Korean Patent Laid-Open Publication No. 2016-0108881 (published on Sep. 21, 201, entitled "Luminescent Ecological Block").

It is an object of the present invention to provide a cement board capable of securing waterproofness and durability while reducing strength deterioration when using bottom ash as an aggregate.

The cement board according to the present invention comprises: cement 35-55 wt%, silica 10-20 wt%, bottom ash 20-35 wt%, silica fume 2-5 wt%, anhydrous gypsum 1-6 wt%, water repellent 0.1-1.5 wt By weight of a water reducing agent, 0.1 to 1% by weight of a water reducing agent, 0.01 to 1% by weight of a thickening agent and 0.02 to 1.2% by weight of a fluidizing agent to prepare a mixture.

The water-repellent agent may be a metal salt and an oleate compound.

The thickening agent may be a methylcellulose compound.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to manufacture a cement board which can ensure durability and waterproof property by using bottom ash. Therefore, since the bottom ash can be recycled without being discarded, environmental pollution and waste of resources can be prevented.

Hereinafter, an embodiment of the cement board according to the present invention will be described. In describing the cement board, the terms described below are defined in consideration of the functions of the present invention, which may vary depending on the intention or custom of the user, the operator. Therefore, definitions of these terms should be made based on the contents throughout this specification.

The cement board according to an embodiment of the present invention may include cement 35-55 wt%, silica 10-20 wt%, bottom ash 20-35 wt%, silica fume 2-5 wt%, anhydrous gypsum 1-6 wt%, water repellent 0.1 -1.5 wt%, a water reducing agent 0.1-1 wt%, a thickening agent 0.01-1 wt%, and a fluidizing agent 0.02-1.2 wt% are mixed to prepare a mixture, and the mixture is compression molded.

The cement board is prepared by stirring the mixture with water, followed by compression molding and curing. The bottom ash has a particle size distribution similar to sand due to its physical properties. Since bottom ash is used in the production of the cement board, a property improving agent is added to improve the characteristics of the cement board. Examples of the property improving agent include silica fume, anhydrous gypsum, water repellent agent, water reducing agent, thickening agent, and high range water reducing agent. have.

Portland cement is used as the cement, and the composition ratio is preferably 35-55 wt%. The content of cement can be appropriately adjusted to increase the durability and compressive strength of the cement board. The compressive strength of cement board increases in proportion to the content of cement. In general, the content of cement in concrete mortar is 15-25 wt%, but in the present invention, the content of cement is increased to 35-55 wt% to increase the compressive strength.

It is preferable that the bottom ash is selected and dried at a particle size of 1 mm or less. When the particle size of the bottom ash exceeds 1 mm, the feed filler effect as a fine aggregate, reactivity and workability are lowered.

The silica fume may be the silicon by-product of the ultrafine particles generated during the production of silicon. Silica fume is about 1/25 of cement particles. Silica fume is a substance that causes a pozzolan reaction in the presence of an alkali. In the presence of water and alkali, the hydration of cement, calcium hydrate (CH), reacts with calcium hydroxide to form calcium silicate hydrate. Silica fume reacts with the calcium hydroxide produced in hydration reaction when combined with cement, thereby increasing the ratio of hydrate that acts as cement. Silica fume not only increases the compressive strength of cement board but also increases stability, water tightness and chemical resistance.

Anhydrous gypsum is added to reduce cracking of the cement board. Anhydrous gypsum causes an expansion reaction with water to induce surface stabilization and durability enhancement after production of the cement board. It is preferable that the anhydrous gypsum is confined within the range of 1-6 wt%, since excessive introduction of the gypsum into the mixture accelerates cracking due to the expansion and after manufacture of the cement board.

The water repellent improves the waterproof performance of the cement board. As water repellent agents, metal salts and oleate compounds are suggested. The water repellent improves the compressive strength and improves the dispersibility. The water repellent agent is preferably added in an amount of 0.1 to 1.5% by weight. When the water repellent agent is used in an amount of less than 0.1 wt%, the waterproof property is poor. When the water repellent agent is used in an amount exceeding 1.5 wt%, the viscosity of the cement board is remarkably decreased due to the viscosity transient.

The water reducing agent is added only about 0.1-1% of the weight of the cement, but it increases durability and strength, and it helps to save cement. It is preferable that 0.1-1 wt% of the water reducing agent is added. When the water reducing agent is added in an amount of less than 0.1% by weight, the water reducing performance is deteriorated. When the water reducing agent is added in an amount exceeding 1% by weight, the raw material cost is increased and the durability is decreased. A melamine water reducing agent is used as the water reducing agent. The melanin-based water reducing agent improves the compressive strength and dispersibility by reducing the unit water.

Thickener improves adhesion between materials as viscosity increases. As a thickener, methyl cellulose is suggested. The thickener is preferably added in an amount of 0.01 to 1% by weight.

The fluidizing agent temporarily disperses the cement particles at a repulsive interval between the negatively charged particles adsorbed on the cement particles to temporarily improve the fluidity of the cement paste. As the fluidizing agent, a polycarbonate-based powder fluidizer or the like may be used. The fluidizing agent is preferably added in an amount of 0.02 to 1.2% by weight.

The above-mentioned composition of the cement mortar is not a method of mixing cement, aggregate and waterproofing agent with water at the working site but is a product which is preliminarily mixed with the cement, silica sand, bottom ash and characteristics improving agent in a dry state. May be mixed and used.

Hereinafter, a test example for producing a cement board using the above mixture will be described.

First, the case where only silica sand is used as an aggregate without adding bottom ashes to the mixture will be described.

45 wt% of cement, 49 wt% of silica sand, 2 wt% of silica fume, 3.38 wt% of anhydrous gypsum, 0.4 wt% of water repellent agent, 0.15 wt% of water reducing agent, 0.04 wt% of thickener and 0.03 wt% of fluidizing agent are mixed.

Water is mixed into the mixture mortar described above. At this time, water is added and mixed so that the water / mortar ratio is 0.22, and then the test is conducted on the compressive strength, permeability and flow according to the test method of cement liquid type waterproofing material (KS F 4925-2001).

, 7일째 28

, 28일째 36

로 나타났고, 투수비는 0.65, 플로우는 21.8cm로 나타났다. As a result of the test according to this test method, the compressive strength was 20

, Day 7 28

, Day 28

, The pitch ratio was 0.65, and the flow was 21.8cm.

, 투수비 0.7 이하의 규정치를 충분히 만족한다.For the above test, the compressive strength specified in the test method for cement liquid type waterproofing material 26

, And the specified value of the permeability ratio of 0.7 or less is sufficiently satisfied.

Next, a case in which bottom ashes are added to the mixture to use silica sand and bottom ashes as aggregates will be described.

A mixture of 45 wt% of cement, 17 wt% of silica, 33 wt% of bottom ash, 2 wt% of silica fume, 3.38 wt% of anhydrous gypsum, 0.4 wt% of water repellent agent, 0.15 wt% of water reducing agent, 0.04 wt% of thickener, .

Water is mixed into the mixture mortar described above. At this time, water is added and mixed so that the water / mortar ratio is 0.29, and then the compression strength, permeability and flow test are performed according to the test method of the cement liquid type waterproofing material (KS F 4925-2001).

, 7일째 33.2

, 28일째 41.6

로 나타났고, 투수비는 0.49, 플로우는 22.4cm로 나타났다.As a result of the test according to this test method, the compressive strength was 24

, Day 7 33.2

, Day 28 on day 41.6

, The permeability ratio was 0.49, and the flow was 22.4cm.

In the above test, the compressive strength, flow and waterproof performance are increased in the case of using a mixture of silica sand and bottom ash at a ratio of about 1: 2 as an aggregate.

Next, the case where the bottom ash is used as the aggregate in the mixture and the sandpaper is not used will be described.

A mixture of 45 wt% of cement, 49 wt% of bottom ash, 2 wt% of silica fume, 3.38 wt% of anhydrous gypsum, 0.4 wt% of a water repellent agent, 0.15 wt% of a water reducing agent, 0.04 wt% of a thickener and 0.03 wt% of a fluidizing agent.

Water is mixed into the mixture mortar described above. At this time, water is added and mixed so that the water / mortar ratio is 0.35, and then the test is conducted on the compressive strength, permeability and flow according to the test method of cement liquid type waterproofing material (KS F 4925-2001).

, 7일째

, 28일째 26.7

로 나타났고, 투수비는 0.68, 플로우는 17.8cm로 나타났다.According to this test method, the compressive strength was 15.2

, Day 7

, Day 26 on day 28

, The permeability ratio was 0.68, and the flow was 17.8cm.

In the test described above, the compressive strength, flow, and waterproof performance are drastically lowered in the case of using as a bottom ash aggregate.

In addition to the above test examples, the test was carried out while varying various conditions such as the mixing ratio of the mortar composition and the water / mortar ratio. As a result, the mixing ratio of the composition capable of securing water resistance and durability can be derived while minimizing the strength drop.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. I will understand.

Accordingly, the true scope of protection of the present invention should be defined by the claims.

Claims (3)

A water-repellent agent 0.1-1.5 wt.%, A water reducing agent 0.1-1 wt.%, A water-repellent agent 0.1-3 wt.%, 0.01 to 1% by weight of a thickener, 0.02 to 1.2% by weight of a fluidizing agent to prepare a mixture, and the mixture is compression molded.
The method according to claim 1,
Wherein the water repellent agent is a metal salt and an oleate compound.
The method according to claim 1,
Wherein the thickening agent is a methylcellulose compound.