KR20040057212A - A Method of Neutralizing Surface of Concrete - Google Patents

Abstract

PURPOSE: Provided is a method for neutralizing the surface and the inside of concrete effectively in a short time by curing concrete in the air and then in CO2 atmosphere. The neutralized concrete is used for concrete structures of oceanic habitats. CONSTITUTION: The surface and the inside of concrete are neutralized by curing concrete within 5days and then curing the cured, not completely hardened, concrete in CO2 atmosphere for 6-24hrs, wherein the concentration of CO2 is less than 5%. The resultant concrete is neutralized to the depth of 6mm and the pH of liquid eluted from the surface of concrete is 8.5 or less.

Description

A Method of Neutralizing Surface of Concrete

The present invention relates to a method of neutralizing the surface of concrete using carbon dioxide, and more particularly to a method of neutralizing the concrete surface with carbon dioxide at a specific curing time.

Concrete is composed of three materials, water, cement and aggregate, in which a paste formed by mixing water and cement becomes a rigid structure while bonding between aggregate and aggregate. At this time, the main component of the cement is CaO, and generally takes up more than 60% of the cement. Therefore, in the case of concrete having cement as a binder, calcium components can be eluted for a considerable period of time, which causes alkaline elution water. That is, alkaline effluent will continue to be produced until the concrete is neutralized.

When the concrete structure is installed in seawater, alkaline elution water is generated in the concrete structure. In addition, very local but strongly alkaline thin films are formed on the surface of the structure, making them inadequate for marine life for a period of time.

In order to use the concrete structure in the biological habitat environment, such as sofa bed, artificial reefs, and seaweeds, the pH of the surface is preferably weakly alkaline or neutral, especially for animals inhabiting by attaching to seaweeds or facilities. Therefore, there is a need for a method of neutralizing the surface of concrete.

Conventional methods for preventing the formation of alkaline effluent water around the surface of concrete structures include immersing sludge solids in seawater for a considerable time in Japanese Patent Laid-Open No. 6-106195, immersing them in acidic solutions such as sulfuric acid solution, or reacting with carbon dioxide gas. And the like are disclosed.

It is therefore an object of the present invention to provide a method for effectively neutralizing a concrete surface.

Another object of the present invention is to provide a method for effectively neutralizing in a short time from the concrete surface to a certain depth.

According to the invention,

When curing concrete, a method of curing concrete for less than 5 days and then curing for 6-24 hours in a carbon dioxide atmosphere is provided to neutralize the concrete surface.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

Concrete is neutralized by treatment with carbon dioxide. That is, in the hardened concrete, calcium hydroxide, which is a hydration product of cement, is eluted out of glass and exhibits alkalinity. Calcium hydroxide in the concrete surface reacts with carbon dioxide and the like to become calcium carbonate, thus neutralizing the concrete concrete surface.

However, during concrete manufacturing, if the concrete is completely cured for about 30 days and then treated with carbon dioxide, the cement is completely solidified and the pores in the concrete become smaller and the penetration of carbon dioxide through the pores becomes difficult. Thus, carbon dioxide does not penetrate into the concrete and does not neutralize to a sufficient depth from the concrete surface.

Therefore, in the present invention, during curing during the manufacturing process of the concrete to be neutralized to a sufficient depth from the surface and the surface of the concrete, after curing for a period within 5 days, by curing in a carbon dioxide atmosphere to be neutralized to a certain depth from the concrete surface. .

In a carbon dioxide atmosphere, it cure for about 6-24 hours. Curing in less than 6 hours in a carbon dioxide atmosphere is not sufficiently neutralized, even if more than 24 hours, the effect of increasing the neutralization is weak.

Carbon dioxide is preferably cured in a carbon dioxide atmosphere whose concentration is 5% by weight or more. The greater the concentration of carbon dioxide, the shorter the neutralization time, but if the concentration is less than 5% by weight does not exhibit sufficient neutralization effect.

Before curing in a carbon dioxide atmosphere, it is usually cured for a period of less than 5 days. After curing for more than 5 days, when treated with carbon dioxide, the solidification of the cement proceeds considerably, even if curing in a carbon dioxide atmosphere, the depth of neutralization is reduced.

The shorter the normal curing period before curing in the carbon dioxide atmosphere, the deeper the neutralization depth during the neutralization treatment, but curing for less than about 5 days, and curing in the carbon dioxide atmosphere, corresponding to a depth of about 6mm from the concrete surface. The pH of the effluent from the neutralized concrete surface is less than or equal to 8.5, which is neutral to the part, which meets the ocean water quality standard pH.

After curing in a carbon dioxide atmosphere, general curing is performed until sufficient strength is achieved again.

The concrete neutralized by the method of the present invention is particularly suitable for use when the concrete is applied in water, and may be used in the biological habitat environment composition such as sofa bed, artificial reefs, seaweeds and seaweeds.

Hereinafter, the present invention will be described in detail through examples.

Example

Example 1

To prepare a specimen by combining the components shown in Table 1 to the content described.

As a coarse aggregate, aggregates of 5-25 mm in particle size were used, and Jugjin standard yarn was used as fine aggregate. As a specimen, a 10 × 20 cm cylindrical specimen was prepared and used.

The curing method is to cure the specimens at 23 ^o C and 65% RH for 1, 2, 3, 4, 5, 6, 7, 28 days, and then at 40 ^o C, 65% RH, and CO ₂ concentration 5 Cured and neutralized for 24 hours in% environment. After that, the remaining period was cured at 23 ^° C. and 65% RH so that the total curing period was 28 days.

Neutralization depth measurement was determined by discoloration by spraying the phenolphthalein solution after the cleavage and the results are shown in Table 2 below.

TABLE 1

Concrete mix (based on 1m ³ )

Water / cement ratio (%) Water (Kg) Cement amount (Kg) Fine Aggregate (Kg) Coarse aggregate (Kg) 56 195 348 715 1018

TABLE 2

Neutralization Depth by Curing Age

Curing days (days) Neutralization Depth (mm) 123456728 88876432

As shown in Table 2, when the curing days before carbon dioxide treatment exceeded 5 days, the depth to be neutralized under the same conditions was not sufficient.

Example 2

As in Example 1, the specimens cured for each initial curing period were neutralized under carbon dioxide under the same conditions as in Example 1, and then each specimen was charged into seawater (pH = 8.2). After 24 hours, the pH of seawater was measured and shown in Table 3 below. The ratio of seawater and concrete specimens used was seawater volume (liters): specimen weight (Kg) = 10: 1.

TABLE 3

Curing days (days) Neutralization Depth (mm) PH of eluted seawater 123456728 88876432 8.68.78.78.98.99.29.69.6

As can be seen in Table 3, in the case of the specimen that the curing days before the carbon dioxide treatment is more than 5 days, the pH of the elution water showed an alkalinity of 9 or more, from which neutralization was not sufficient.

When neutralizing the concrete surface by the method of the present invention is effectively neutralized in a short time to the interior of the concrete, the pH of the neutralized concrete leaching water satisfies the marine water quality standards.

Claims (2)

In the case of concrete curing, the concrete surface is cured for less than 5 days, and then neutralized for 6-24 hours in a carbon dioxide atmosphere. The method of claim 1 wherein the concrete surface is neutralized to a depth of 6 mm from the concrete surface.