KR101662434B1 - Light-weight aerated concrete mix method using the special composition with emhancement of crack control and flexural performance - Google Patents

Abstract

A lightweight foamed concrete composition using an admixture and fiber of an optimum composition for improving crack control and flexural strength generated in the process of manufacturing a lightweight foamed concrete, and a method of manufacturing a lightweight foamed concrete using the same. The present invention relates to a lightweight foamed concrete composition comprising a binder consisting of 40 to 80% by weight of cement and 20 to 60% by weight of an admixture; Reinforcing fiber for improving crack control and flexural strength of the foamed concrete, wherein the reinforcing fiber is 0.3 to 1.2 kg per 1 m 3 of the binder; 20 to 40% of water based on the weight of the binder as the mixing water; And 50 to 70% of bubbles based on volume after curing of the foamed concrete, and a method of manufacturing a lightweight foamed concrete using the same.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightweight foamed concrete composition having improved crack control and flexural performance, and a method of manufacturing lightweight foamed concrete using the same. BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

The present invention relates to a lightweight foamed concrete composition and a method of manufacturing a lightweight foamed concrete using the same. More particularly, the present invention relates to a lightweight foamed concrete which is used for insulation and lightweight purposes, To the production of foamed concrete.

The present invention is derived from the research carried out as part of the 'Land Transport Technology Promotion Research Project' supported by the Ministry of Land, Transport and Maritime Affairs.

[Project number: 14CTAP-C078666-01, Title: Development of terra-con artificial soil aggregate having a specific gravity of 0.3 or less and having its own plant growth environment]

A cellular concrete (foamed concrete or aerated concrete) without aggregate is a cement paste which is formed by mixing a large amount of air bubbles generated by the physical surfactant action of foaming agent to form bubbles in the concrete, It is a concrete in which many pores are formed. This lightweight foamed concrete is a material with low thermal conductivity, which is excellent in heat insulation performance and can be expected to have an energy saving effect by improving the thermal efficiency of the building, and it is advantageous in construction that it can be pressed into a space having a complicated shape, Partition walls of buildings, and slab insulation finishing materials.

However, lightweight foamed concrete is easy to brittle and brittle compared to ordinary concrete. Therefore, when used for plate members such as wall and slab finishing materials without additional reinforcement, it is likely that cracks will develop and break down easily. Lightweight foamed concrete is generally made of paste, bubbles and water, so its fluidity and moisture content are very high. As a result, lightweight foamed concrete can cause many shrinkage and shrinkage cracks during drying and curing after mixing, deterioration of heat insulation performance due to cracks generated and decrease in moisture resistance (moisture penetration, condensation and fungal ) May be caused. Especially, when the compressive strength of foamed concrete is increased to control cracks, the amount of cement used increases and cracks due to hydration heat can be serious.

In order to solve these problems, fiber reinforced foamed concrete with fiber addition or crack control of bubble by adding various admixtures in addition to cement has been studied. However, in these techniques, there are problems such as low compressive strength due to the use of an admixture and fiber aggregation upon addition of fibers. Therefore, it is necessary to define a proper range of fiber selection and its content in the production of foamed concrete with improved crack control and flexural strength of lightweight foamed concrete.

[Prior Art]

- Korean Registered Patent No. 0802002 (Jan. 31, 2008)

- Korean Unexamined Patent Publication No. 1995-0024997 (September 15, 1995)

Accordingly, the present invention proposes a lightweight foamed concrete composition using an admixture and fibers of an optimum composition for improving crack control and flexural strength generated in the process of manufacturing lightweight foamed concrete, and a method of manufacturing a lightweight foamed concrete using the same.

As a means for solving the above technical problems, the present invention provides a lightweight foamed concrete composition comprising: a binder consisting of 40 to 80% by weight of cement and 20 to 60% by weight of an admixture; Reinforcing fiber for improving crack control and flexural strength of the foamed concrete, wherein the reinforcing fiber is 0.3 to 1.2 kg per 1 m 3 of the binder; 20 to 40% of water based on the weight of the binder as the mixing water; And 50 to 70% of bubbles based on volume after curing of the foamed concrete.

Also, the above-mentioned admixture is composed of 10 to 50% by weight of blast furnace slag and 10 to 30% by weight of fly ash with respect to 100% by weight of the binder.

And the reinforcing fiber is polyvinyl alcohol or polyamide.

Also, the foamed concrete has a compressive strength of 1 MPa or more and a flexural strength of 0.1 MPa or more after curing.

In order to solve the above-mentioned problem, the present invention provides a method of producing a composite material comprising (a) a binder consisting of 40 to 80% by weight of cement, 10 to 50% by weight of blast furnace slag and 10 to 30% by weight of fly ash, Mixing polyvinyl alcohol or polyamide as a reinforcing fiber of the reinforcing fiber, (b) adding 20 to 40% of water to the dried composite to a weight of the binder and preparing a paste by primary wet bombardment; (c) adding a bubble group generated by using a bubble generator to the paste and generating a bubble slurry by secondary wet beam; And (d) curing the foamed slurry by pouring the foamed slurry into a mold to produce a lightweight foamed concrete.

According to the present invention, it is possible to control the crack generated by hydration heat in the production of foamed concrete by suppressing the heat of hydration by using blast furnace slag or fly ash as a proper admixture, It is possible to provide a lightweight foamed concrete composition which is very easy to control cracking and dramatically improves the bending performance and can be used for walls and the like without further reinforcement.

Also, in the production of lightweight foamed concrete using the lightweight foamed concrete composition of the above composition, an optimal blending method and a manufacturing method of foamed concrete employing the linear foamed method are proposed, and lightweight foamed concrete with improved crack control and flexural strength can be easily manufactured .

Hereinafter, preferred embodiments of the present invention will be described in detail. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. Throughout the specification, when an element is referred to as "including " an element, it means that it can include other elements, not excluding other elements, unless specifically stated otherwise.

The inventors of the present invention have found that when a lightweight foamed concrete is manufactured by adding various admixtures to control the cracking of bubbles or adding fibers to fiber reinforced foamed concrete, problems such as low compressive strength due to the use of admixture, As a result of intensive investigations, it has been found that when the foamed concrete is fabricated through the selection of the optimum combination of reinforcing fibers with the proper binder composition and the use of the linear bubble method in the production of lightweight foamed concrete, crack control and bending strength And the present invention has been achieved.

Accordingly, the present invention provides a lightweight foamed concrete composition comprising: a binder consisting of 40 to 80% by weight of cement and 20 to 60% by weight of an admixture; Reinforcing fiber for improving crack control and flexural strength of the foamed concrete, wherein the reinforcing fiber is 0.3 to 1.2 kg per 1 m 3 of the binder; 20 to 40% of water based on the weight of the binder as the mixing water; And 50 to 70% of bubbles on the basis of volume after curing of the foamed concrete, and a method of manufacturing a lightweight foamed concrete using the same.

As a binder in the present invention, industrial by-products are used as an admixture together with cement for reducing hydration heat. Various industrial by-products can be used. However, blast furnace slag is suitable considering the availability, crack control and bending performance improvement, and fly ash can be used together with blast furnace slag for more effective reduction of heat of hydration. Meanwhile, the cement material is not particularly limited, and for example, ordinary portland cement (OPC) may be used.

The admixture may be contained in an amount of 20 to 60 wt%, preferably 30 to 50 wt%, based on the total weight of the binder, and the other binder component is made of cement. In this case, when the fly ash is used together with the blast furnace slag alone, it is preferable that blast furnace slag is 10 to 50 wt% and fly ash is 10 to 30 wt%, blast furnace slag 30 to 50 wt% and fly ash 10 By weight to 20% by weight. If the content of the binder is less than 20% by weight, the hydrothermal reduction performance may not be satisfactory. If the content of the binder exceeds 60% by weight, the strength formation by the cement may be slowed down and sufficient time may be required to form sufficient strength. If the content of the fly ash is less than 10% by weight, it may be difficult to improve the hydrolytic reduction performance. If the content of the fly ash is more than 30% by weight, the bending performance may be somewhat lowered.

In the present invention, polyvinyl alcohol (PVA) or polyamide (PA) is used as a reinforcing fiber for crack control and flexural performance improvement in lightweight foamed concrete production process with reduction of heat of hydration through the admixture of proper composition. Is used.

In the case of polyvinyl alcohol or polyamide, the problem of aggregation of fibers can be completely solved, crack control of foamed concrete is easy, and bending strength can be remarkably improved as compared with the case of using other kinds of fibers. At this time, polyvinyl alcohol and polyamide may be used singly or in combination, but it is most preferable to use polyamide alone to further improve the bending strength against the same content.

The content of the polyvinyl alcohol or polyamide is important in terms of maintaining the optimum bubble content of the foamed concrete after curing and controlling the crack in the production process of the foamed concrete, particularly in terms of maximizing the bending performance without lowering the compressive strength. That is, when the content of polyvinyl alcohol or polyamide is 0.3 to 1.2 kg per 1 m 3 of the binder, the above-mentioned object can be sufficiently achieved, and most preferably 0.6 to 1.2 kg per 1 m 3 of the binder .

Water may be used as the blending water in the process of producing the lightweight foamed concrete according to the present invention. However, when a binder having a composition including a specific admixture is used, 20-40% of water is used based on the weight of the binder, Preferably, 25 to 35% can be used.

In the present invention, the bubbles are added to reduce the weight of the concrete. The amount of bubbles to be injected is 50 to 70% by volume after curing of the foamed concrete in order to manufacture the foamed concrete without cracking control, Level, and it is preferable to maintain the level at 55 to 65%. Such bubbles may be preformed bubbles using a foaming agent, and details thereof will be described later.

Meanwhile, in the lightweight foamed concrete composition according to the present invention, a high-performance water reducing agent generally used for improving the compressive strength and improving the fluidity can be used in a range of maximum 2%, preferably 1% maximum, based on the weight of the binder.

The lightweight foamed concrete composition containing the above-mentioned binder, specific reinforcing fiber, water and air bubbles composed of cement and specific admixture has a compressive strength of more than 1 MPa and a flexural strength of more than 1 MPa after curing, Of not less than 0.1 MPa, preferably not less than 4 MPa, and a flexural strength of not less than 0.3 MPa, more preferably not less than 4.3 MPa and a flexural strength of not less than 0.4 MPa, still more preferably not less than 4.6 MPa, The excellent performance of 0.5 MPa or more can be realized.

The production of the lightweight foamed concrete according to the present invention is carried out by the pre-bubble method. In the line bubble method, a paste is formed by firstly mixing a binder and a compounding water, and a bubble group generated through a bubble generator is put into a paste, followed by secondary mixing to complete a foamed concrete slurry.

Accordingly, the lightweight foamed concrete according to the present invention comprises (a) a binder composed of 40 to 80 wt% of cement, 10 to 50 wt% of blast furnace slag and 10 to 30 wt% of fly ash, and 0.3 to 1.2 kg Mixing polyvinyl alcohol or polyamide as a reinforcing fiber and dry-blending the mixture; (b) adding 20 to 40% of water to the dried composite to a weight of the binder and preparing a paste by primary wet bombardment; (c) adding a bubble group generated by using a bubble generator to the paste and generating a bubble slurry by secondary wet beam; And (d) curing the foamed slurry by placing it in a mold.

That is, the method of adding the preformed bubbles as in the present invention is generally referred to as a pre-bubble mixing method. The bubble fraction or the foaming agent is added to the raw material mixture in advance, It is preferable to employ a pre-bubble mixing method in order to control the uniform dispersion of the reinforcing fibers. In the pre-bubble mixing method, any method known in the art can be applied to a method of previously forming bubbles by using a foaming agent and a method of injecting the produced bubbles into concrete.

The foaming agent used herein may be an animal, vegetable or mineral foaming agent which is easily available, and may be diluted to a range of 2.5 to 5 wt%. The diluted bubble liquid can be used by foaming at about 1,000 to 1,500% at a pressure of about 6 bar through a bubble generator.

The curing method can be carried out through curing or wet curing, and can be carried out under conditions such as high temperature, high temperature / wetting, high temperature / high pressure and the like, if necessary.

Hereinafter, the present invention will be described in more detail with reference to examples.

Example  One

(Unitary disposal amount 500 kg / m 3) consisting of 70 wt% of ordinary Portland cement having a specific gravity of 3.14 to 3.15 and 30 wt% of blast furnace slag, 0.3 wt% of polyvinyl alcohol and 0.3 wt% of a high performance water reducing agent Followed by dry blending, 30% water was added to the weight of the binder, and the first wet blending was carried out to prepare a paste. A bubble slurry was formed by introducing a bubble group generated by using a bubble generator in a paste and a secondary wet beam, and the resulting bubble slurry was placed in a mold and cured for 7 days to prepare a lightweight foamed concrete.

Example 2

Lightweight foamed concrete was prepared in the same manner as in Example 1, except that 0.6 kg of polyvinyl alcohol per 1 m 3 of the binder was mixed in Example 1.

Example 3

Lightweight foamed concrete was prepared in the same manner as in Example 1 except that 0.9 kg of polyvinyl alcohol per 1 m 3 of the binder was mixed in Example 1.

Example 4

Lightweight foamed concrete was prepared in the same manner as in Example 1, except that 1.2 kg of polyvinyl alcohol per 1 m 3 of the binder was mixed in Example 1.

Example 5

Lightweight foamed concrete was prepared in the same manner as in Example 1 except that 0.6 kg per 1 m 3 of the binder was mixed with polyamide instead of polyvinyl alcohol in Example 1.

Example 6

Same as Example 1, except that a binder consisting of 50 wt% of ordinary Portland cement, 30 wt% of blast furnace slag and 20 wt% of fly ash was used in Example 1, and 0.9 kg of polyvinyl alcohol was mixed per 1 m 3 of binder Lightweight foamed concrete.

Comparative Example

Lightweight foamed concrete was prepared in the same manner as in Example 1 except that polyvinyl alcohol was not mixed in Example 1.

Experimental Example

The bubble ratio, compressive strength (ASTM C 39) and flexural strength (ASTM C 78) of lightweight foamed concrete prepared according to the above Examples and Comparative Examples were measured and the results are shown in Table 1 below.

Referring to Table 1, the foamed concrete manufactured by using a lightweight foamed concrete composition using a cement and a specific admixture, a specific reinforcing fiber, water, and a certain amount of foam in accordance with the present invention, It can be seen that excellent performance with a compression strength of 4 MPa or more and a flexural strength of 0.3 MPa or more can be realized without any problem in crack control. In addition, when polyamide was used instead of polyvinyl alcohol as the reinforcing fiber, it was confirmed that the bending performance with respect to the same content was further improved. On the other hand, when the blast furnace slag and the fly ash are used as the admixture in a certain amount, it can be understood that the decrease of the compressive strength and the bending strength does not occur largely while the hydration heat reduction is implemented more effectively.

On the other hand, when the reinforcing fibers were not mixed with each other, the compressive strength was not lowered, but the flexural strength was remarkably decreased.

The preferred embodiments of the present invention have been described in detail with reference to the drawings. 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 present invention as defined by the appended claims.

Accordingly, the scope of the present invention is defined by the appended claims rather than the foregoing detailed description, and all changes or modifications derived from the meaning, range, and equivalence of the claims are included in the scope of the present invention Should be interpreted.

Claims (5)

delete delete delete delete (a) a binder composed of 40 to 80% by weight of cement, 10 to 50% by weight of blast furnace slag and 10 to 30% by weight of fly ash, and polyamide as a reinforcing fiber of 0.6 to 1.2 kg per 1 m 3 of the binder, ;
(b) adding 20 to 40% of water to the dried composite to a weight of the binder and preparing a paste by primary wet bombardment;
(c) adding a bubble group generated by using a bubble generator to the paste and generating a bubble slurry by secondary wet beam; And
(d) curing the foamed slurry by placing it in a mold;
Wherein the foamed concrete has a compressive strength of at least 4 MPa and a flexural strength of at least 0.5 MPa after curing.