KR20110109286A - Autoclaved lightweight concrete using base materials for high strength concrete and its preparing method - Google Patents

Abstract

The present invention relates to a composition for lightweight foamed concrete, and to a lightweight foamed concrete using the same, by applying the composition of ultra-high strength concrete to autoclave curing lightweight foamed concrete, while maintaining the lightness, sound insulation, heat insulation, and the like as it is. 10 to 20 parts by weight of calcined lime, 0.5 to 2 parts by weight of foaming agent, and 100 parts by weight of a mixed raw material mixed with 60 parts by weight, silica fume 10 to 30 parts by weight and 20 to 55 parts by weight of silica having an average particle size of 1 to 40 μm. Admixture is made by mixing 0.2 to 0.8 parts by weight.

Description

Autoclaved lightweight concrete using base materials for high strength concrete and its preparing method}

The present invention relates to a lightweight foamed concrete and a method for manufacturing the same, which can be used in various architectural and civil structures and concrete secondary products, while improving the compressive strength while maintaining light weight, sound insulation, and thermal insulation.

Recently, as part of high quality concrete, research on high strength has been actively conducted to improve low strength, that is, specific strength, compared to weight, which is the biggest disadvantage of concrete. In the United States, 60MPa high-strength concrete was constructed in 1975 at 262m Water Tower Palace, and 120MPa high-strength concrete was installed in Two Union Square, a 58-story Seattle in 1988-89. In Korea, since the need for high-strength concrete was greatly recognized in Korea, full-scale research began in the late 80s. Recently, researches for practical use and characterization have been actively conducted, especially in construction-related research institutes and university laboratories. Due to limitations and lack of confidence in quality, the application to actual structures is extremely rare. At this time, attention is focused on "Super Ductal," a highly flexible concrete, jointly researched and developed by world-class companies Lafarge, Bouygues and Rhodia in the building materials, construction and chemical industries. The duct is a fiber-cement matrix construction material with ultra high strength, high ductility, high durability and beauty, which can be used without additional reinforcing materials such as steel. In 1993, Bouygue, a world-renowned building company, applied for a patent on reactive powder concrete and began a five-year study between Bouygue-Lafarge-Rhodia in October 1994. As a result, a patent was filed for Ductal FM in which metal fiber was added in November 1997, and Ductal FO in which organic fiber was added in April 1998. In other words, Deoktal is a product related to ultra-high strength cement and concrete of La Paz, France, and can be named as ultra-high strength fiber reinforced concrete in general academic terms.

The physical properties of ultra high strength fiber reinforced concrete have high compressive strength, flexural strength and ductility. The compressive strength is 160 ~ 230 N / mm ² , which is about 8 times higher than general concrete (21 ~ 28 N / mm ² ). . In addition, bending strength is also at least about 10 times the 40 ~ 50 N / mm2 class in plain concrete ^{(3.5 ~ 5.6 N / mm 2} ). Therefore, ultra-high strength fiber-reinforced concrete without reinforcing bars, 1) the structure made of ducts replaces reinforcing bars with ultra high-strength fibers; Rebar and member thickness reduction (ultra high and long bridge glass) has the advantage.

On the other hand, lightweight foamed concrete, which is generally used in construction and construction of civil engineering structures, is a kind of lightweight concrete that has much higher hygroscopicity and dry shrinkage than ordinary concrete. It uses animal or vegetable foaming agent and mixes portland cement with water. In the slurrying state, the foaming agent passes through the foaming machine and mixed with the foamed foam liquid to prepare proper physical properties. Conventional lightweight foam concrete has a compressive strength of 6-60 kgf / cm 2, specific gravity of 0.5-1.8 based on the 28-day strength, depending on the input amount of the material. The lightweight foamed concrete is divided into two types: curing at room temperature and atmospheric pressure and autoclave curing.

Lightweight foamed concrete cured at room temperature and atmospheric pressure is mixed with cement solution and foamed liquid passed through foaming machine and cured at room temperature and atmospheric pressure.It is usually 0.4 to 0.6 with a specific gravity of 8 to 12kgf / ㎠ and has high absorbency and cracks during drying. Due to this disadvantage, it is mainly used for filling the tunnel, filling the abandoned mine, and filling the floor of an apartment, and is rarely used for other purposes.

Lightweight foamed concrete cured with autoclave is made of sand and quicklime, which contain a lot of silica, as a main raw material, and is mixed with a blowing agent (alumina powder) and stabilizer in a slurry, put into a mold, foamed and expanded, and then taken out when it solidifies into a cake shape. The shape is cut out and cured at 10 atm for about 180 ° C in the autoclave. It is usually called ALC (autoclaved lightweight concrete), and its specific gravity is about 0.5 to 0.8, its compressive strength is about 40 to 60 kgf / ㎠, and it has the advantages of low volumetric deformation, less cracking, and excellent thermal insulation when absorbed and dried. Because of the low level, there was a limit to use in various architectural and civil structures and concrete secondary products.

The present invention is to provide a composition for lightweight foamed concrete and a lightweight foamed concrete using the composition of the ultra-high-strength concrete, the compressive strength is greatly improved while maintaining light weight, sound insulation, heat insulation and the like by applying the composition of the autoclave curing lightweight foamed concrete.

High-strength lightweight foamed concrete composition of the present invention is based on 100 to 100 parts by weight of the mixed raw material mixed with 30 to 60 parts by weight of cement, 10 to 30 parts by weight of silica fume and 20 to 55 parts by weight of silica having an average particle size of 1 to 40 μm. It consists of 20 weight part, 0.5-2 weight part of foaming agents, and 0.2-0.8 weight part of admixtures.

In the high strength lightweight foamed concrete composition of the present invention, the admixture is characterized in that the polycarboxylic acid-based admixture.

In the high-strength lightweight foamed concrete composition of the present invention, the foaming agent is characterized in that the aluminum powder.

In addition, the high-strength lightweight foamed concrete manufacturing method of the present invention is a slurry prepared by mixing while adding water to the high-strength lightweight foamed concrete composition to have a viscosity of 1200 ~ 2500 centipoise, and heat the slurry at 160 ~ 220 ℃ for 4 to 10 hours It comprises the step of synthesizing.

In addition, the high-strength lightweight foam concrete of the present invention is produced by the above method, the specific gravity is 0.7 to 1.0, characterized in that the compressive strength is 100 kgf / cm ² or more.

Lightweight foamed concrete of the present invention can be used in a variety of construction and civil engineering structures and concrete secondary products, the compressive strength is greatly improved while maintaining the lightness, sound insulation, insulation and the like.

1 is a graph showing the particle size distribution of the starting material of Preparation Example A of the present invention.
2 is a photograph of a specimen of Preparation Example A without adding slaked lime.
3 is a photograph of Preparation Example B-1 showing that cracking occurred due to high content of polycarboxylic acid-based admixture but the addition of slaked lime.
4 is X-ray diffraction analysis results of Preparation Examples B and B-1 in which only the particle size of cement powder differs.
5 is X-ray diffraction analysis results of Preparation Examples E and B having different silica contents.
6 is a microstructure photograph using a photograph of Preparation Example E and a scanning electron microscope.

High-strength lightweight foamed concrete composition of the present invention is based on 100 to 100 parts by weight of the mixed raw material mixed with 30 to 60 parts by weight of cement, 10 to 30 parts by weight of silica fume and 20 to 55 parts by weight of silica having an average particle size of 1 to 40 μm. It consists of 20 weight part, 0.5-2 weight part of foaming agents, and 0.2-0.8 weight part of admixtures.

In the present invention, in consideration of the practical use of high-strength lightweight foam concrete, general ordinary portland cement is used. Other cements include medium heat, crude steel, crude steel, and slag mixed cements, which have particularly good strength when using double crude steel portland cement. In the present invention, milled cement having an average particle size of 1 to 50 µm, more preferably 2 to 20 µm, is used.

Silica fume used in the manufacture of high-strength concrete is used as a substitute for cement and to enhance strength and durability. Silica fume is a condensation trapped SiO2 ultrafine particles volatilized as by-products produced during the production of metal silicon and silicon steel at about 2000 ° C., and has very high activity as ultrafine particles having an average particle diameter of 1 μm or less. In addition, since the silica fume is an ultra fine particle having a blain value of about 200,000 cm 2 / g, adding 2 to 40% by weight of the silica fume has an effect of preventing the increase in strength and whitening. In the high-strength lightweight foamed concrete composition of the present invention, the silica fume preferably contains 10 to 30 parts by weight based on 100 parts by weight of the mixed material consisting of cement, silica fume, and silica. Below the lower limit, it is difficult to express sufficient strength, and when the upper limit is exceeded, a gel-like substance is formed by rapid reaction with slaked lime, making it difficult to form a uniform slurry.

In the high-strength lightweight foamed concrete composition of the present invention, the silica has an average particle size of 1 to 40 μm, and preferably 20 to 55 parts by weight based on 100 parts by weight of the mixed material consisting of cement, silica fume, and silica. If the particle size of the silica is less than the lower limit, it takes a long time to form a slurry, and if it exceeds the upper limit, it is difficult to express sufficient strength. When the content of silica is less than the lower limit, cement hydrate is formed, and when the content exceeds the upper limit, the silica that fails to react is greatly increased.

In the high-strength lightweight foamed concrete composition of the present invention, it is preferable to add 10 to 20 parts by weight of slaked lime to 100 parts by weight of a mixed raw material consisting of cement, silica fume and silica because it is difficult to generate sufficient bubbles by reacting with the foaming agent only with cement. Do.

As a foaming agent that generates bubbles by reacting with the slaked lime, conventional foaming agents such as aluminum powder, aluminum paste, and zinc powder may be used, but aluminum powder and paste are preferable in terms of rapid foaming. The content of the foaming agent is preferably added 0.5 to 2 parts by weight based on 100 parts by weight of the mixed material consisting of cement, silica fume and silica.

In the high-strength lightweight foamed concrete composition of the present invention, the admixture may be polycarboxylic acid, lignin sulfonic acid, glucoic acid, naphthalene sulfonic acid formalin condensate, melamine sulfonic acid formalin condensate, and the like. Preference is given to using polycarboxylic acid admixtures for the production of lightweight foamed concrete. The admixture of the present invention is preferably used 0.2 to 0.8 parts by weight based on 100 parts by weight of the mixed material consisting of cement, silica fume and silica. If the admixture is less than the lower limit, the strength is not sufficiently expressed, there is a problem that the fluidity of the slurry is low, and if the upper limit is exceeded, there is a problem of cracking in the cured lightweight foamed concrete.

In the present invention, a slurry is prepared by mixing the composition comprising the cement, silica fume, silica, hydrated lime, foaming agent and admixture while adding water so as to have a viscosity of 1200 to 2500 centipoise, preferably 1600 to 2000 centipoise. It can be prepared by hydrothermal synthesis reaction in an autoclave at 160 ~ 220 ℃ for 4 to 10 hours. Preferably, the slurry prepared before the hydrothermal synthesis can be aged for 3 to 12 hours at 20 ~ 80 ℃.

High-strength lightweight foam concrete produced by the method of the present invention has a specific gravity of 0.7 to 1.0, 28 days curing compressive strength of 100 kgf / cm ² or more, more preferably 0.7 ~ 0.9, 28 days curing compressive strength 110 ~ 140 kgf / cm ² .

Hereinafter, the present invention will be described in more detail with reference to examples and preparation examples. The following preparation examples are merely illustrative for the purpose of illustrating the present invention, thereby not limiting the scope of the technical idea of the present invention.

Reference Example

Ultra high strength fiber reinforced concrete is composed of mixed powder (Premix), reinforcing fibers (organic fibers, inorganic fibers, etc.), chemical admixtures, and the like. At this time, the blended powder is composed of portland cement, silica fume, silica and silica as an intermediate particle.

division Composition (wt%) Portland Cement (Low Heat) 33-45 Silica fume 7-22 Intermediate Particles (Pulverized Quartz) 10-24 Fine aggregate 28-42

In the present invention, the applicability of the autoclave curing lightweight foamed concrete was examined by applying the compounding powder used in the ultra high strength concrete.

Manufacturing example

Cement was ground to an average particle size of 8 μm, low heat Portland cement finely ground to 15 μm, silica was an average particle size of about 20 μm and about 1 mm, and silica fume was used as a starting material.

Table 2 shows the mixing ratios of quicklime and slaked lime to help the starting materials and the expansion of the starting materials.

division cement
(8 μm) cement
(15㎛) Silica fume burr
(20 μm) burr
(1mm) Slaked lime quicklime A 1650 - 630 720 - - - A-1 - 1650 630 720 - - - B 1650 - 630 720 - 450 - B-1 - 1650 630 720 - 450 - C 1200 - 600 1200 - - - C-1 - 1200 600 1200 - - D 1050 - 450 1500 - - - D-1 - 1050 450 1500 - - - E 1050 - 450 1500 - 450 - E-1 - 1050 450 1500 - 450 - E-2 1050 450 1500 - - 450 E-3 1050 450 - 1500 450 - F 1050 - 750 1200 - - - G 1050 - 750 1200 - 450 - H 1350 - 450 1200 - - - I 1350 - 450 1200 - 450 - J 900 - 450 1650 - - - J-1 - 900 450 1650 - 450 -

1 part by weight of aluminum powder was used as a foaming agent with respect to 100 parts by weight of the mixed powder mixed with cement, silica fume and silica, and a polycarboxylic acid-based admixture (ECONEX Coona-L, Econex Co., Ltd.) was prepared to reduce the amount of mixing. A, A-1, B, B-1, C, C-1, D and D-1, 1 part by weight of a polycarboxylic acid admixture with respect to 100 parts by weight of the mixed powder of cement, silica fume and silica, E, E -1, F and G used 0.6 weight part of polycarboxylic-acid admixtures, and H and I used 0.2 weight part of 0.2 polycarboxylic-acid admixtures.

First, the particle size distribution of the starting material of Preparation Example 1 is shown in FIG.

After mixing the mixed powder of the starting material and limestone to make a slurry by adding water to the viscosity of the slurry to 1800 ± 100 centipoise. The slurry was aged at 50 ° C. for 6 hours, and then maintained at 180 ° C. in autoclave conditions for 6 hours to prepare a specimen.

A, A-1, C, C-1, D, D-1, F, H, and J in which the lime is not added in the preparation example of Table 2 are necessary for the foaming of lightweight foam concrete with calcium hydroxide produced from cement. It was not produced as rapidly as it had a weak expansion. 2 is a photograph of the cross section (left) and the whole (right) of the specimen without addition of slaked lime, which shows that the expansion is significantly weaker than in Preparation Example E (FIG. 6).

The foaming mechanism when using aluminum powder can be represented by the following reaction formula.

Scheme 1

2Al + 3Ca (OH) ₂ + 6H ₂ O → 3CaO + Al ₂ O ₃ + 6H ₂ O + 3H ₂

Aluminum and slaked lime (Ca (OH) ₂ ) is reacted to generate hydrogen gas, a problem arises that the expansion is not properly performed if not enough slaked lime is supplied.

In Preparation Examples A, A-1, B, B-1, C, C-1, D and D-1, 1 part by weight of a polycarboxylic acid admixture was added to 100 parts by weight of a mixed powder of cement, silica fume and silica. As a result, the viscosity of the admixture itself and the passage of time after kneading caused a problem of cracking in the final product due to an increase in the viscosity of the slurry. This is because some of the hydrogen gas generated in the hydrothermal synthesis process must escape from the slurry, but the viscosity does not escape due to the high viscosity and the phenomenon of merging of the gas inside the slurry occurs. Figure 3 is a photograph of Preparation Example B-1 showing that the expansion was made to the level similar to the general ALC by the addition of hydrated lime, but due to the high content of admixture, the left side is the entire specimen, the right side is the crack It is enlarged.

In addition, the hydrate formation of the specimens using the finely divided cement having an average particle size of 15 μm and the cement ground with an average particle size of 8 μm, respectively, showed that tobermorite, a hydrothermal synthesis product, was produced in both conditions. there was. The results of X-ray diffraction analysis of Preparation Examples B and B-1, which showed different compounding ratios but differed only in the particle size of cement powder, were almost as shown in FIG. 4.

In addition, when the mixing ratio of cement, silica fume and silica was changed, all of the tobermorite was observed. Among them, preparation E having a high silica content was observed to have a higher intensity of quartz peak than B having a low content (FIG. 5).

In addition, tobermorite crystals were also confirmed in the microstructure observation results using the scanning electron microscope of Preparation Example E, which was confirmed again that the hydrate produced during the hydrothermal synthesis reaction (Fig. 6).

The compressive strength and specific gravity of specimens with expansion equal to those of general ALC were measured and the results are shown in Table 3.

division Compressive strength
(kgf / cm ² ) importance General ALC 40 to 60 0.5 to 0.8 B 125 0.84 B-1 105 0.92 E 100 0.81 E-1 110 0.86 E-2 80 0.80 E-3 130 1.3

Lightweight foamed concrete prepared in the present invention has a specific gravity is somewhat higher than the general ALC, but the compressive strength is improved by about 2 to 3 times the compressive strength showed more than 100 kgf / cm ² . However, in the case of Preparation Example E-2 in which the silica grain size was not pulverized to 1 to 40 μm, the expression of compressive strength was not sufficient, and in Preparation Example E-3 in which the quicklime was used without the use of calcined lime, it was compressed. The strength was high, but the expansion was not enough, so the specific gravity was too high to be suitable for light weight.

Claims (5)

10 to 20 parts by weight of calcined lime, 0.5 to 2 parts by weight of foaming agent, based on 100 parts by weight of a mixed raw material mixed with 30 to 60 parts by weight of cement, 10 to 30 parts by weight of silica fume and 20 to 55 parts by weight of silica with an average particle size of 1 to 40 μm. High strength lightweight foamed concrete composition comprising 0.2 parts to 0.8 parts by weight of admixtures and admixtures.
The high strength lightweight foamed concrete composition of claim 1, wherein the admixture is a polycarboxylic acid admixture.
The high-strength lightweight foam concrete composition according to claim 1, wherein the foaming agent is aluminum powder.
Claim 1 to 3 to prepare a slurry for mixing the high-strength lightweight foamed concrete composition of any one of claims 1 to 3 while adding water so that the viscosity is 1200 to 2500 centipoise, the slurry is hydrothermally heated at 160 ~ 220 ℃ for 4 to 10 hours Method for producing a high-strength lightweight foamed concrete comprising the step of synthesizing.
The high-strength lightweight foamed concrete prepared by the method of claim 4, having a specific gravity of 0.7 to 1.1 and a compressive strength of 100 kgf / cm ² or more.

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