KR20180000375A - A Alkali-activated and Aerated building material using blast furnace slag and its preparation method - Google Patents

Abstract

The present invention relates to an autoclaved lightweight building material. To this end, alkali-activated blast furnace slag cement is used as an alternative to Portland cement which consumes a huge amount of energy in the production, emits green-house gases, and causes environmental pollution. In addition, the alkali-activated blast furnace slag cement is an inorganic insulation material functioning as autoclaved lightweight concrete, maintains specific strength, and increases energy-saving effects.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkali activated lightweight foamed building material using a blast furnace slag,

The present invention uses a slag cement with an alkaline active blast as a substitute for Portland cement which consumes a large amount of energy in the manufacturing process and emits not only greenhouse gas but also environmental pollution and has a certain strength to act as lightweight foamed concrete as an inorganic insulator Lightweight air bubble building material which can maintain energy saving while maintaining high efficiency.

In recent years, the government has been making various efforts to cope with climate change globally. In this regard, the government also announced the 'Guidelines for the designation and management of greenhouse gas energy management companies' in 2010 to reduce greenhouse gas emissions. . This is not only manufactured at the high temperature (1,450) state of cement clinker manufacturing, but also produces 0.7-1.0 tons of carbon dioxide gas to produce one ton of cement, which is 7% of the world's carbon dioxide emissions.

With the economic development, the cement industry continues to grow in size, and the amount of carbon dioxide emitted from the production of cement is increasing every year. Portland Cement Clinker is currently attracting much attention as an alternative to portland cement because of the large amount of carbon dioxide emitted by humans on the planet.

On the other hand, since the energy crisis and environmental problems have arisen, the global warming prevention meeting agreed in Kyoto, Japan in 1997 obliges the developed countries to reduce their greenhouse gas emissions by 5.2% Therefore, regulation of greenhouse gas emission is considered to be the most difficult issue in the cement industry, and it is becoming urgent to manufacture concrete with high strength by using cement with low carbon dioxide emission in the future.

In addition, insulation materials such as sandwich panels, which can be applied in various forms, have been widely used for energy saving of buildings, reduction of construction period, and so on. In the form of sandwich panels, there are organic and inorganic insulation materials. Organic insulation materials have the advantages of low cost, but they can cause life damage due to toxic gas in case of fire. Lightweight foamed concrete among inorganic insulation materials, Lightweight, and so on, so that much research has been conducted to solve the drawbacks of the organic system by applying it to the sandwich panel. Lightweight foamed concrete is produced by generating a large amount of voids in cement mortar using bubble formers, which is a good insulation material with excellent heat insulation, fire resistance and light weight.

Korean Patent Registration No. 1303195 Korean Patent Application No. 2015-0094637

The present invention has been made to solve the above problems and it is an object of the present invention to use alkali active blast furnace slag cement in place of portland cement which consumes a large amount of energy during production and emits greenhouse gas as well as environmental pollution, It is an object of the present invention to provide an alkali active lightweight foamed building material having a certain strength to replace lightweight foamed concrete as an inorganic thermal insulator and having a high energy saving effect during the manufacturing process.

The alkali active lightweight foam building material according to the present invention is prepared from less than 3 molar and less than 5 molar alkali activator, bubbling agent and residual blast furnace slag.

The blast furnace slag preferably has a specific surface area of 4.000 to 6,000 cm ² / g and a specific gravity of 2.5 to 3.0. The larger the specific surface area, the better the reactivity. However, it is unreasonable in terms of economy to increase the powderity too much for this purpose.

The alkali activator is preferably used in an amount of more than 3 moles and less than 5 moles. When the amount of the alkali activator is less than 3 moles, sufficient compressive strength can not be ensured. When the amount of the alkali activator is more than 5 moles, It is not preferable because it increases or decreases.

The alkali activator is preferably added in an amount of 0.3 to 0.5% by weight based on the weight of the blast furnace slag. When the alkali activating agent is less than 0.3 wt%, the alkali activation is insufficient, and when the alkali activating agent is added in an amount exceeding 0.5 wt%, the structure is undesirable and uneven hydrate is formed.

As the alkali activating agent, sodium hydroxide, potassium hydroxide and an auxiliary agent can be used, and other alkali activators can be used within a range that is obvious to a person skilled in the art.

The bubbling agent is preferably added in an amount of 0.05 to 0.10% by weight. When the bubbling agent is added in an amount of less than 0.05% by weight, sufficient porosity can not be secured. When the bubbling agent is added in an amount exceeding 0.10% by weight, it is somewhat difficult to ensure uniform porosity, It is not preferable because the compressive strength may be significantly lowered due to the large voids and the like.

As the bubbling agent, it is preferable to use an aluminum powder, but it is preferable that the bubble forming agent is as small as possible and a powder of 3um to 8um is suitable. Smaller 1um powder is good for forming fine porosity but is disadvantageous in terms of economy. Hydrogen peroxide (H 2 O 2) may be used as the bubbling agent, but other bubbling agents may be used within the scope that is obvious to a person skilled in the art.

The alkali active lightweight foam building material has a compressive strength of more than 13 N / mm < ² > and a porosity of more than 55%. It is impossible to use it as a building material if the compressive strength, etc. is below the standard.

A method for producing an alkali active lightweight foamed building material according to the present invention is as follows.

(a) mixing an alkali activating agent and water to produce an alkali activating solution of more than 3 mole but less than 5 moles;

(b) mixing less than 3 molar and less than 5 molar alkali activating solution and a bubble former with blast furnace slag; And

(c) shaping the mixture into a mold and curing the mixture.

As described above, according to the present invention, a lightweight foamed material can be easily manufactured by using only blast furnace slag and a foaming agent, and firing the mixture into a simple alkali activity at room temperature without a high temperature and high pressure steam curing process.

Fig. 1 is a graph showing changes in compressive strength depending on the concentration of sodium hydroxide.
Fig. 2 shows the compressive strength measured according to sodium hydroxide 4M and activator / slag = 0.4 / 1.0.
Fig. 3 is a graph showing the specific gravity of alkali-active lightweight foamed building materials added with foaming agent.
4 is a graph showing changes in compressive strength according to the amount of foaming agent added.
5 is an SEM photograph of an alkali active lightweight foamed building material according to the present invention.
6A and 6B are XRD analysis photographs before and after the alkali activation reaction.

Hereinafter, preferred embodiments of the present invention will be described. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below.

The blast furnace slag used in the present invention is blast furnace slag (hereinafter referred to as blast furnace slag) which is generated as an industrial by-product in the steelmaking process of Gwangyang steel mill. The blast furnace slag used in the present invention preferably has a specific surface area of 4,000 to 6,000 cm ² / g and a specific surface area of 4,234 cm ² / g and a specific gravity of 2.91 in the following examples. The chemical composition of the blast furnace slag is shown in Table 1 below. As a result of the chemical analysis of blast furnace slag, it was found that the slag containing 43.9% of CaO and 32.8% of SiO ₂ as main components, containing 14.9% of Al ₂ O ₃ and 5.0% of MgO and having high vitrification rate and low crystallinity, System.

Comparison of composition of blast furnace slag and Portland cement division OPC Cement Blast furnace slag (Sg) Mix ratio design






SiO ₂ 21.9 32.8 CaO 64.2 43.9 Al ₂ O ₃ 5.0 14.9 Fe ₂ O ₃ 3.7 0.4 MgO 2.0 5.0 SO ₃ 1.8 1.2 K ₂ O 0.9 0.6 Na ₂ O 0.0 0.0

As an alkali activator for alkali activation reaction of the blast furnace slag of the present invention, industrial sodium hydroxide (purity: 98 wt%) was dissolved in water to prepare a 2M to 5M NaOH solution, and then an optimum blast furnace slag mixing ratio and NaOH content .

In order to prepare specimens of the alkali active lightweight foamed building material of the present invention, the activating solution and the blast furnace slag prepared above were kneaded at a low speed using a Hobart mixer and mixed. The specimens used for making specimens were rectangular molds with a width of 50 mm, a length of 50 mm and a height of 50 mm. The mold was filled with a sample of silicone grease by thin layer of silicone grease. The mold was filled 25 times each time. The top layer was chopped and then the concrete surface was capped with trowel (KS F 2403). After filling the mold with the specimen, it was tightened. As the compressive strength was influenced by the sealing strength, one person was sealed. After capping, it was activated in air at room temperature for 1 day. Then, demolding was performed, and specimen was prepared by curing curing method at room temperature until the measurement of compressive strength.

The alkali activator concentration was varied from 2 to 5 M and the alkali activator / blast furnace slag composition ratio was changed from 0.3 to 0.5 / 1.0 weight ratio as shown in the following table for proper compression strength development in the production of alkali active lightweight foam building materials. Respectively. The specimens were cured at room temperature for 1-28 days.

NaOH 2M 3M 4M 5M ratio Alkali activator / blast furnace slag (wt% ratio)
0.3 1.0 0.3 1.0

0.3 1.0 0.3 1.0 0.4 0.4 0.4 0.4 0.5 0.5 0.5 0.5

The compressive strength of the alkali active lightweight foam building material was measured according to KS F 2405. The uniaxial compressive strength test equipment is a universal material testing machine (UTM) of STM-5 model manufactured by United Calibrafun Co. The load can be measured up to 100ton and the displacement can be measured up to 0.01mm. Three specimens were prepared for each measurement and the compressive strength was measured at a rate of about 0.2 N / mm ² (2.04 kgf / cm ² ) per second using a 100 ton unconfined compression tester. Compressive strength was calculated by averaging excluding data with a breaking strength of ± 5% or more.

As can be seen in FIG. 1, the compressive strength of the specimens prepared by curing at room temperature for 1 to 28 days was found to increase gradually with increasing sodium hydroxide concentration. Compressive strength at 4M concentration increased over time The compressive strength tends to increase with increasing the amount of alkali activator. The optimum amount of alkali activator was 3 ~ 5M. This result is interpreted as a result of increasing the concentration of sodium hydroxide compared to a relatively constant amount of water as the amount of activator added increases, thereby promoting the alkali activation reaction of the sample, . The compressive strength of the specimens prepared by increasing the concentration of sodium hydroxide to 5M or more decreased and the compressive strength of the specimens increased irregularly with time. This showed that the alkali activity of sodium hydroxide and blast furnace slag , The optimum concentration of sodium hydroxide solution was 3 ~ 5M in terms of compressive strength. In general, when excess NaOH is added to the alkali activated reaction of blast furnace slag, it causes undesirable structure and uneven hydrate in the specimen. Therefore, it is considered that there is no significant increase in strength when NaOH is added over a certain amount.

The compressive strength of cementitious materials is the most important evaluation item. The slag used for the production of alkali active lightweight foamed construction material was 100% blast furnace slag. The specimens were prepared by using blend ratio of alkali activator and blast furnace slag with various concentrations. As a result, It was found that the activator / slag = 0.3-0.5 / 1.0 is the most appropriate mixing condition for the intensity activation for the alkali activation reaction (FIGS. 1 and 2).

Meanwhile, FIG. 3 shows the results of measurement of the specific gravity of the alkali active lightweight foamed building material according to the addition amount of aluminum foaming agent. It was found that the specific gravity when the foaming agent was not added was 1.9, whereas when the amount of foaming agent was increased to 0.05 wt%, 0.1 wt% and 0.15 wt%, it decreased to 1.33, 1.29 and 1.15, respectively.

Therefore, in order to determine the content of a suitable foaming agent, an experiment was conducted on the change of compressive strength according to the amount of foaming agent added. As can be seen from the results in FIG. 4, the content of the foaming agent satisfying the KS standard 13 N / mm ² against the compressive strength of the alkali active lightweight foamed building material was found to be 0.05 to 0.10%.

The water absorption and porosity of the alkali-activated lightweight foamed building materials were measured to be 21.1% and 55.5%, respectively, after the specimens were prepared with the concentration of NaOH, the alkali activator, of 4M and the foaming agent content of 0.1% I could. It is considered that the reason why the absorption rate is 21.1% is caused by the void caused by the bubble formed by the foaming agent.

Further, FIG. 5 is an SEM image of the surface of the alkali active lightweight foamed building material obtained through the alkali activation reaction. As a result of alkali activation of the blast furnace slag with a specific surface area of 3,000 cm2 / g or more from the SEM image, the fine powder particle is hardly detected and shows a new dense surface. This means that under high pH caused by the NaOH solution used as an alkaline activator, the blast-shaped blast-furnace slag was dissolved via chemical reaction and recombined. Through this process, CaO, SiO2 and Al2O3 contained in the blast furnace slag react with cement-like pozzolanic reaction to form ettringite, which is converted to a dense structure, and the compressive strength is exhibited.

Finally, FIG. 6A is the XRD result for the alkali active reactant, and FIG. 6B is the XRD analysis of the slag before the reaction analyzed for comparison. From the figure, it can be seen that the XRD results of the original slag show a relatively simple pattern, but the results obtained after the reaction show more complex and various peak shapes. Here, the various peaks were found to be formed by dissolving the powdery slag at high pH through alkali activation reaction and then solidifying through chemical bonding and reaction of ions. The form of dissolved ions from the slag powder at high pH, which is formed according to the conditions of the mixture of NaOH solution and activator, is SiO2, which is the largest proportion of the chemical constituents in the slag, and chemical species such as CaO and Al2O3 . It is believed that these ions grow in the ionic state as the reaction with the exothermic reaction progresses, and through the pozzolanic reaction, some hydroxide formation and evaporation process removes the moisture, and a new type of dry and hard crystal grows.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be obvious to those of ordinary skill in the art.

Claims (9)

Alkali-active lightweight foam building materials made from compositions of less than 3 moles and less than 5 moles of alkali activators, bubblers, and remainder blast furnace slag
2. The alkali-active lightweight foamed building material according to claim 1, wherein the blast furnace slag has a specific surface area of 4.000 to 6,000 cm < 2 > / g and a specific gravity of 2.5 to 3.0.
The alkali activated lightweight foamed building material according to claim 1, wherein the alkali activator is contained in an amount of 0.3 to 0.5% by weight
The alkali activated lightweight foamed building material according to claim 1, wherein the alkali activator is at least one selected from sodium hydroxide, potassium hydroxide and water glass
An alkali activated lightweight foamed building material according to claim 1, characterized in that it comprises 0.05 to 0.10% by weight of the bubble former
The bubble generator as claimed in claim 1, wherein the bubbling agent is aluminum or hydrogen peroxide.
7. The alkali-active lightweight foamed building material according to claim 6, wherein the aluminum is 3um to 8um powder
The alkali activated lightweight foamed building material according to claim 1, wherein the alkali active lightweight foamed building material has a compression strength of more than 13 N / mm < 2 > and a porosity of more than 55%
(a) mixing an alkali activating agent and water to produce an alkali activating solution of more than 3 mole but less than 5 moles;
(b) mixing less than 3 molar and less than 5 molar alkali activating solution and a bubble former with blast furnace slag; And
(c) molding the mixture in a mold and curing the mixture to form a lightweight foamed structure.

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