KR20120069324A - Method for manufacturing an autoclave lightweight concrete and autoclave lightweight concrete - Google Patents

Abstract

PURPOSE: A manufacturing method of lightweight aerated concrete and lightweight cellular concrete is provided to adding excellent physical property to final products by adjusting fineness of silica stone. CONSTITUTION: A manufacturing method of lightweight cellular concrete comprises the following steps: pulverizing silica in a vibrating mill for predetermined time; manufacturing slurry by adding water to silicate powder, quick lime, and a mixture of cement; forming a molding product by mixing 0.05-1 parts by weight of aluminum powder to the slurry as a foaming agent based on the 100.0 parts by weight of the mixture; and processing hydrothermal reaction on the molding product by maturing at 45-55 deg. Celsius and relative humidity of 45-55% for 4-6 hours.

Description

Method for manufacturing an autoclave lightweight concrete and autoclave lightweight concrete

The present invention relates to a method for manufacturing lightweight foamed concrete, and to lightweight foamed concrete. More specifically, the physical properties of the final hydrothermally synthesized product by finely powdering silica, which is the main component of lightweight foamed concrete, and adjusting the powder degree of silica The present invention relates to a method for manufacturing lightweight foamed concrete, which has a substantial change, and to have excellent properties such as compressive strength and flexural strength of the final product, and lightweight foamed concrete produced accordingly.

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 reinforcement 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, ductal is a product related to ultra-high strength cement and concrete of La Paz, France, and may be referred to 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 / mm2, which is about 8 times higher than that of general concrete (21 ~ 28 N / mm2). In addition, the flexural strength is 40 ~ 50 N / mm2, which is about 10 times higher than that of general concrete (3.5 ~ 5.6 N / mm2). 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 660 kgf / ㎠, specific gravity of 0.5 ~ 1.8 about 28 days of strength, depending on the amount of material input. The lightweight foam concrete is divided into two types: curing at normal temperature and pressure and autoclave curing.

Lightweight foamed concrete cured at room temperature and atmospheric pressure is cured at room temperature by mixing the foam liquid passed through the foaming machine with cement dough, and it is cured at normal temperature and normal pressure.It is usually 0.4 ~ 0.6, compressive strength 8 ~ 12kgf / ㎠, which has high absorbency and cracks when drying. Due to the drawbacks, it is mainly used for filling the tunnel, filling the abandoned mine, and filling the floor of the apartment, and it 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 the main raw materials, and when the slurry is mixed with foaming agent (alumina powder) and stabilizer, it is put into the formwork and foamed to expand into a cake shape. Cut off and cure in autoclave at about 180 ℃, 10 atm. It is usually called ALC (autoclaved lightweight concrete), and its specific gravity is about 0.5 ~ 0.8, its compressive strength is about 40 ~ 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 control the particle size of the silica to improve the properties of lightweight foam concrete while maintaining light weight, sound insulation, heat insulation, etc. while maintaining the properties such as compressive strength, flexural strength significantly improved lightweight foam concrete and the resulting lightweight foam concrete Providing is a challenge.

Method for producing a lightweight foam concrete of the present invention to solve the above problems is the step of pulverizing for a predetermined time by adding silica to a vibration mill; Preparing a slurry by adding water to a mixture of the pulverized silica powder, quicklime and cement to have a predetermined viscosity; Mixing the aluminum powder with a foaming agent to 0.05 to 0.1 parts by weight based on 100 parts by weight of the mixture to form a molded body in the slurry; It characterized in that it comprises the step of hydrothermally synthesized while the molded body is aged for 4 to 6 hours at a temperature of 45 ~ 55 ℃, relative humidity 45 ~ 55% conditions in a thermo-hygrostat.

Here, the grinding of the silica is characterized in that the grinding time 20 to 40 minutes, the average particle size of 90㎛, the residual fraction is 1.0 to 5.0%.

Here, the slurry is characterized in that it is mixed to include 55 to 60% by weight of silica, 12 to 15% by weight of quicklime and 30 to 35% by weight of cement, 40 to 50% by weight of water.

In addition, the present invention provides a lightweight foam concrete produced by the above-described manufacturing method.

Lightweight foamed concrete prepared according to the method for manufacturing light-weight foamed concrete provided by the present invention has the effect of greatly improving the physical properties such as compressive strength, flexural strength, etc., while maintaining light weight, sound insulation, heat insulation, etc. by controlling the particle size of silica. Have

1 is a graph showing a change in the powder degree of silica with grinding time.
2 and 3 show the results of measuring compressive strength and flexural strength according to the grinding time of silica.
4 is a scanning electron micrograph for observing the microstructure according to the grinding time of silica.
FIG. 5 is a scanning electron micrograph of silicas in ALC hydrothermally synthesized in an initial pulverized state.
Figure 6 shows the XRD pattern according to the grinding time of the silica.

Hereinafter, the present invention will be described in more detail.

Method for producing lightweight foamed concrete according to the present invention comprises the steps of pulverizing for a predetermined time by putting the silica into a vibration mill; Preparing a slurry by adding water to a mixture of the pulverized silica powder, quicklime and cement to have a predetermined viscosity; Mixing the aluminum powder with a foaming agent to 0.05 to 0.1 parts by weight based on 100 parts by weight of the mixture to form a molded body in the slurry; The molded body is subjected to hydrothermal synthesis while aging for 4 to 6 hours at 45-55 ° C. and 45-55% relative humidity in a thermo-hygrostat.

Here, the grinding of the silica is preferably pulverizing such that the grinding time is 20 to 40 minutes, the average particle size is 90㎛, the residual fraction is 1.0 to 5.0%.

Here, the slurry is preferably mixed to include 55 to 60% by weight of silica, 12 to 15% by weight of quicklime, 30 to 35% by weight of cement, and 40 to 50% by weight of water.

According to the present invention, there is provided a lightweight foam concrete prepared according to the manufacturing method disclosed above.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. However, the present invention is not limited to the following examples.

[Example]

As the chemical composition, silica, quicklime and cement shown in Table 1 were used. The SiO ₂ content of silica, one of the main raw materials of ALC, was 88.0%, and the CaO content of quicklime was 67.6%. The raw materials of this experiment were obtained and used raw materials currently used by domestic ALC manufacturers.

To determine the particle size of the starting material, that is, the reactivity according to the specific surface area of the silica, it was pulverized using a vibration mill (WTBM-01, Unbisa, Korea). In order to measure the basic physical properties according to the size of the silica and to derive the optimum blending technology for ALC manufacturing, 3 kg each of the silica was put in the sample container and ground at intervals of 5 minutes from 5 minutes to 30 minutes. In order to confirm the powder level of the crushed silica, 90 µm sieve residue experiment was conducted according to KS L 5117-2010 standard, and the Blaine powder test according to KS L 5106-2009 was also conducted.

The starting materials, pulverized silica, quicklime and cement were designed and blended as shown in Table 2, and the CaO / SiO ₂ ratio, which had a great influence on the strength of the product, was fixed at 0.5, which is currently being applied by the manufacturer. The mixed water was blended with 45% of the powder. At this time, aluminum powder was added 0.08% of the starting material as a blowing agent. Then, the manufactured molded product was placed in a constant temperature and humidity chamber (CC600, Woojin Precision, Korea) of 50 ° C and 50% relative humidity, and aged for 5 hours. At this time, as the hydrothermal synthesis progresses, volume expansion occurs, and the aluminum powder added as the blowing agent forms pores. The molded product thus prepared was charged into an autoclave, heated to 180 ° C. for 1 hour, and then hydrothermal synthesis was performed at 180 ° C. for 7 hours.

   After completion of hydrothermal synthesis in the autoclave, the specimens were cut into 160 × 40 × 40 mm for flexural strength and 40 × 40 × 40 mm for compressive strength to measure specific gravity and compressive strength. The cut molded body was dried at 100 ° C. until a constant weight was obtained. The microstructure and crystal phase were also examined using a scanning electron microscope (SM-300, Topcon, Japan) and an X-ray diffractometer (D5005D, Siemens, Germany).

Materials SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ CaO K ₂ O Na ₂ O SO ₃ Quartzite 88.0 5.11 2.09 0.36 0.76 0.08 - Lime 1.54 0.42 0.41 67.60 0.10 0.12 0.10 OPC 20.45 5.47 3.03 62.22 0.34 0.80 2.38

Starting Materials Quartzite
burr Lime
quicklime OPC
cement Water Mixing Ratio (wt%) 56.4 12.4 31.2 45

[Results and Discussions According to the Example]

<Change of Powder Content of Silica According to Grinding Time>

1 shows the results of grinding using a vibrating mill to observe the change in the powder degree according to the grinding time of silica, that is, 90 μm sieve residue. The percentage of silica obtained initially was 38%, followed by 16% for 10-minute grinding (1,548 cm2 / g based on Blaine powder), 4.9% (3,233 cm2 / g) for 20-minute grinding, and 1.3% (30-minute grinding). 5,491 cm 2 / g). This is also in line with the general trend that the residues decrease with grinding time. The difference between the residual fractions of the unpolished silica and the 30 minutes ground silica was 36.7%. As the grinding time increased, the decrease of the residual fraction decreased. Also, from 25 minutes, the 90 μm sieve fraction did not tend to decrease significantly.

<Abstract weight>

Specific gravity according to the grinding time of the silica was measured by the volume specific gravity including the open pores, and the specific dry weight after the 100 ℃ dosage is shown in Table 3. Drying specific gravity according to the grinding time ranged from 0.55 g / cm 3 to a maximum of 0.61 g / cm 3, but there was no significant difference. The lowest specific gravity value was obtained in ALC using silica as the initial acquisition state. Thereafter, with the increase of the grinding time, a small increase in the specific gravity of the prepared ALC was accompanied. It was determined that as the grinding time increases, the particle size of the silica decreases, the specific surface area increases, the reactivity with the CaO raw material increases, and the curing time of the molded body is shortened, thereby reducing the pore merging in the molded body.

Grinding time
(min) 0 5 10 15 20 25 30 Specific Gravity 0.55 0.59 0.58 0.59 0.60 0.58 0.61

Compression and Flexural Strength

Compressive strength tester using the compressive strength test results are shown in Figure 2 according to the grinding time of the silica. As the grinding time increased, the strength value also increased. The compressive strength was 2.2MPa when pulverized silica was used and 5.4MPa after 30 minutes grinding, resulting in about 250% improvement in compressive strength. This may be due to the increase in specific surface area and the responsiveness according to the reduction of silica residue. In addition, the increase in the value of compressive strength showed a tendency to decrease the secondary function as the increase of the grinding time, and similar to the 90㎛ residue level, it was also confirmed that the strength enhancement range is not large after 25 minutes of grinding time.

Similar to compressive strength, flexural strength increased with increasing grinding time. When unpolished silica was used, the lowest value was 0.9 MPa. After 25 minutes of grinding, the flexural strength was 3.2MPa, which was the highest.

The increase in strength with increasing grinding time also showed the tendency of the secondary function to be smaller than that of compressive strength. In addition, when grinding for 25 minutes, the strength was slightly higher than that for 30 minutes, but also the grinding time exceeded 25 minutes, and there was no significant difference in the specific surface area of the silica particles, even if the specific surface area of the silica particles was widened. This is because it does not participate in the% response. The correlation between the compressive / bending strength and the silica powder of the ALC material obtained above is shown in FIG. 3. These correlations were analyzed using the Origin 6.0 program. As shown in FIG. 3, the correlation coefficient between the compressive strength and the 90 μm residue was −0.97 and the correlation coefficient between the bending strength and −0.99, and the 90 μm residue was closely related to the strength.

<Microstructure>

 Scanning electron microscope was used to observe the microstructure according to the grinding time of the silica, and the photograph is shown in FIG. 4. When the first obtained silica was used, the hydrothermally synthesized tobermorite crystal was produced in a poor state, but as the grinding time increased, the crystal shape changed to a hexagonal tobermorite crystal. Could. In particular, it was confirmed that the tobermorite crystals were completely formed under 20 minutes of grinding time, and the same crystals as 20 minutes were observed even after 20 minutes. That is, tobermorite crystal formation was improved with increasing grinding time, but no further crystal change was observed below a certain residue level. In addition, the silicas in ALC hydrothermally synthesized in the initial milling state are shown in Fig. It was present as unreacted particles as in 5. In order to improve hydrothermal reaction, appropriate micronization of silica particles is essential. In this study, 90μm residue level of silica could be selected around 2.5%.

Crystal Structure Analysis

Figure 6 shows the XRD pattern according to the grinding time of the silica. The formation of tobermorite and the presence of other crystal phases were investigated by analyzing the XRD pattern of ALC as the starting material from the pulverized silica from 0 to 25 minutes at regular intervals. As a result of comparing the degree of Tobermorite formation by XRD measurement, it was found that the same Tobermorite and quartz peak were formed in all specimens, and other crystal phases could not be observed. In addition, as the grinding time increases, the XRD strength also increases. Table 4 compares the intensities of the quartz peak occurring at about 26.5 degrees and the Tobermorite peak occurring at about 29.5 degrees. As shown in Table 4, it was confirmed that both the tobermorite peak and the quartz peak increased as the grinding time increased. The increase in the intensity of the tobermorite peak is due to the enhancement of hydrothermal reaction with the fine powder of silica. In addition, the increase of the quartz peak was presumed to be due to the increase in the volume due to the fine silica powder and the volume of the fine silica powder in the part not participating in the hydrothermal synthesis reaction.

Claims (4)

Pulverizing the silica for a predetermined time by putting it in a vibrating mill;
Preparing a slurry by adding water to a mixture of the pulverized silica powder, quicklime and cement to have a predetermined viscosity;
Mixing the aluminum powder with a foaming agent to 0.05 to 0.1 parts by weight based on 100 parts by weight of the mixture to form a molded body in the slurry;
Method for producing a lightweight foam concrete, characterized in that it comprises the step of hydrothermal synthesis while aging the molded body 4 ~ 6 hours at 45 ~ 55 ℃, relative humidity 45 ~ 55% conditions in a constant temperature and humidity.
The method of claim 1,
The grinding of the silica is a pulverization time 20 to 40 minutes, the average particle size of 90㎛, the remaining fraction is 1.0 to 5.0% of the manufacturing method of light weight foam concrete, characterized in that the grinding.
The method of claim 1,
Said slurry is 55 to 60% by weight of silica, 12 to 15% by weight of quicklime and 30 to 35% by weight of cement, 40 to 50% by weight of water, characterized in that the mixing method for producing a lightweight foamed concrete.
Claims 1 to 3, according to any one of the manufacturing method of the substrate, the compressive strength lightweight foam concrete.

Images