KR102321772B1 - Strength-strengthening method of concrete-structures with blast furnace flag powder - Google Patents

Abstract

The present invention discloses a method for strengthening the strength of a concrete structure containing fine powder of blast furnace slag.
The method for strengthening the strength of a concrete structure containing fine powder of blast furnace slag according to the present invention is characterized in that an alkali solution is applied to the concrete structure. There is an effect of recovering the compressive strength through the construction method.

Description

Strength-strengthening method of concrete-structures containing blast furnace slag fine powder {Strength-strengthening method of concrete-structures with blast furnace flag powder}

The present invention relates to a method for strengthening the strength of a concrete structure containing fine powder of blast furnace slag, and more particularly, a fine powder of blast furnace slag for recovering compressive strength through a simple construction method of a concrete structure having less than a predetermined strength by replacing a large amount of blast furnace slag. It relates to a method for strengthening the strength of a concrete structure, including

Conventionally, blast furnace slag cement is manufactured by mixing cement or clinker and slag fine powder. When manufacturing blast furnace slag cement, as a limestone raw material, clay materials containing silica, alumina, iron oxide and lime, etc. are mixed in an appropriate ratio, It is produced by cooling and grinding clinker obtained by calcining in a cement kiln furnace to about 1450°C.

In the production of cement or clinker used for this, since about 0.85 tons of carbon dioxide is generated in the production of 1 ton of cement raw material by the calcination process, it is environmentally desirable to reduce the amount of cement used, which is accompanied by a _{large amount of CO 2 generation problem.} .

Therefore, among the slag generated in the blast furnace process, the blast furnace water ash slag cooled by high-pressure watering is pulverized and used as a slag fine powder admixture and slag cement. and blast furnace slag cement is stipulated in KS L 5210.

Conventional domestic blast furnace slag cement is manufactured at 60wt% of cement or clinker and 40wt% of fine slag powder. When the content of the fine slag powder is increased, the fine powder of blast furnace slag is not hydrated early, so there is a problem that the initial and long-term strength decrease compared to the existing blast furnace slag cement and the air length becomes longer. have.

Therefore, if the initial strength and long-term strength of the existing blast furnace slag cement can be maintained while increasing the content of fine powder in blast furnace slag, it is possible to reduce the cost of producers and consumers and ultimately reduce the amount _{of CO 2 generated in the cement industry.} There is a demand for technology development to increase usage.

In consideration of this problem, Korean Patent Laid-Open No. 2001-0038096 discloses a blast furnace slag cement composition using blast furnace slag as a material, and specifically, 45 to 55 wt% of Portland clinker, 40 to 55 wt% of blast furnace slag, and anhydrous Each of gypsum and dihydrate gypsum contains 2-3% by weight, 03-1% by weight of slaked lime, 1-5% by weight of limestone, and 2-5% by weight of fly ash.

However, in recent years, domestic ready-mixed concrete companies are increasingly using large amounts of mineral admixtures such as blast furnace slag fine powder (BS or less) for the purpose of environmental protection and cost reduction.

However, there are cases where a large amount of mineral admixture is replaced by an unintentional mistake, and the design standard strength is significantly lower than the design age. will occur

Therefore, the technical problem to be solved by the invention of the ball is to provide a method of strengthening the strength of a concrete structure containing an excess of fine powder of blast furnace slag in which a large amount of fine powder of blast furnace slag is substituted to restore compressive strength of a concrete structure of less than a predetermined strength through a simple construction method. will be.

In order to solve the above technical problem, in the method for strengthening the strength of a concrete structure containing fine powder of blast furnace slag, the present invention provides a method for treating a concrete structure, characterized in that an alkali solution is applied to the concrete structure.

According to an embodiment of the present invention, the blast furnace slag may have a fineness of 4,000 to 10,000 cm 2 /g.

According to another embodiment of the present invention, the alkali solution may contain metal hydroxide.

According to another embodiment of the present invention, the metal ion of the alkali solution may be sodium, magnesium, potassium or calcium ions.

According to another embodiment of the present invention, the curing temperature after the application may be 15 to 70 ℃.

According to another embodiment of the present invention, the application may be performed by dividing it into a plurality of times.

According to another embodiment of the present invention, the interval between the plurality of application may be that the next application is made before the coating film is dried.

According to the method of strengthening the strength of a concrete structure containing an excess of blast furnace slag according to the present invention, there is an effect of recovering the compressive strength of a concrete structure having less than a predetermined strength by replacing a large amount of the blast furnace slag through a simple construction method.

1 is a graph showing the compressive strength according to a change in the binder composition ratio of a concrete structure according to an embodiment of the present invention;
Figure 2 is a graph showing the compressive strength and strength expression rate by curing temperature after applying a sodium hydroxide solution to the surface of another embodiment (BS 90% by weight) of the present invention,
3 is a graph showing the compressive strength and strength expression rate by curing temperature after applying calcium hydroxide to another embodiment of the present invention (BS 90% by weight);
4 is a photograph of a dried sample after immersion in water of a mortar according to another embodiment of the present invention (BS 90% by weight). The sodium hydroxide solution and the calcium hydroxide solution are divided into 20 ℃ and 65 ℃ in units of 30 minutes, respectively. it has been shown

Hereinafter, the present invention will be described in detail.

It should be noted that the technical terms used in the present invention are used only to describe specific embodiments, and are not intended to limit the present invention, and the technical terms used in the present invention are not specifically defined in other meanings in the present invention. Unless, it should be interpreted in a meaning generally understood by those of ordinary skill in the art to which the present invention pertains, and should not be interpreted in an excessively comprehensive meaning or in an excessively reduced meaning.

In addition, when the technical term used in the present invention is an erroneous technical term that does not accurately express the spirit of the present invention, it should be understood by being replaced with a technical term that can be correctly understood by those skilled in the art.

In addition, the general terms used in the present invention should be interpreted as defined in advance or according to the context before and after, and should not be interpreted in an excessively reduced meaning.

In addition, the singular expression used in the present invention includes a plural expression unless the context clearly indicates otherwise, and in the present invention, terms such as "consisting of" or "comprising" refer to several elements described in the invention, Or, it should not be construed as necessarily including all of several steps, and it should be construed that some components or some steps may not be included, or additional components or steps may be further included.

1 is a graph showing the compressive strength according to a change in the binder composition ratio of a concrete structure according to an embodiment of the present invention, and FIG. 2 is a sodium hydroxide solution applied to the surface in another embodiment (BS 90 wt%) of the present invention. It is a graph showing the compressive strength and strength expression rate by curing temperature after, Figure 3 is a graph showing the compressive strength and strength expression rate by curing temperature after applying calcium hydroxide to another embodiment (BS 90% by weight) of the present invention, Figure 4 is a photograph of a dried sample after immersion of the mortar in water according to another embodiment of the present invention (BS 90% by weight), and the sodium hydroxide solution and the calcium hydroxide solution are divided into 20 ° C and 65 ° C in 30-minute units, respectively. , refer to this.

The method for treating a concrete structure according to the present invention is a method for treating a concrete structure containing blast furnace slag, characterized in that an alkali solution is applied to the concrete structure.

The concrete structure including the blast furnace slag may further include a binder, fine aggregate, coarse aggregate, and mixing water in addition to the blast furnace slag powder.

Here, the blast furnace slag is preferably used in a fine powder state, and the fineness may be 4,000 to 10,000 cm2/g, and if it is less than 4,000 cm2/g, KS F 2563 blast furnace slag fine powder type 3 standards or less , and has low reactivity, which is unfavorable to strength development. Conversely, if it exceeds 10,000 cm2/g, it is more than KS F 2563 blast furnace slag fine powder type 1 standard, and penetration of alkali solution is difficult, so there may be difficulty in recovery of the structure.

In addition, the concentration of the alkali solution may be 3 to 20 mol (mol). If the concentration of the alkali solution is less than 3 mol, there is a problem because the concentration of the alkali solution is low and the strength strengthening effect is decreased. Conversely, if it exceeds 20 mol, the viscosity of the alkali solution This is not preferable because the effect of penetrating into the structure is lowered and the effect of reinforcing the strength is lowered.

Of course, water can be used as the solvent, but a weak electrolyte or a non-electrolyte solvent can be used to improve the penetration rate into the concrete structure.

In addition, the alkali solution may contain metal hydroxide, whereby the concrete structure is hardened by expressing latent hydraulic properties on the surface or inside, and a desired compressive strength can be secured.

It is characterized in that the metal ions of the alkali solution are sodium, magnesium, potassium or calcium ions. These ions react with the hydroxyl group of the solution entering the structure together with calcium, silicon, and aluminum contained in the unreacted blast furnace slag to hydrate The production of the product can be made effective more quickly.

In addition, as the solvent of the alkaline solution, acetonitrile, acetic acid, hydrofluoric acid, nitrous acid, methanol, ethanol or urea may be used. These solvents are solvents with weak or no electrolytic properties and have excellent permeability to the concrete structure than water, so that the time is faster. It has an advantageous aspect to develop latent hydraulic properties by guiding metal ions or hydroxyl groups.

On the other hand, the application temperature of the alkali solution may be 15 to 70 ° C. Depending on the temperature, the movement rate of ions in the alkali solution or the hydration reaction rate of the blast furnace slag is affected. If it is less than 15 ° C, the alkali solution and It can be beneficial to water penetration, but a lot of energy can be thrown to maintaining a low temperature. Conversely, if it exceeds 70℃, it is not only energy inefficient, but also the degree of penetration of a solution or water is lower than at a low temperature, which is disadvantageous for strength expression. .

In addition, it is preferable to perform the application by dividing it into a plurality of times. When the solution penetrates into the concrete structure and dries on the application surface forming the coating film, the capillary movement, which is the driving force for penetrating the solution, may be disturbed, and Rather than applying an amount, it is preferable to divide the coating into multiple times to maintain an undried state.

<Example>

The preparation of the concrete structure according to the present invention is B:S (W/B) 1:3 (50% by weight) as a formulation, and the BS substitution rate for OPC (usually Portland cement) is 0% by weight of BS, 60% by weight , prepared at 90% by weight, and as a coating treatment method, sodium hydroxide solution and calcium hydroxide solution were prepared for 90% BS, and repeated several times to prevent drying for 3 hours. In the case of sodium hydroxide, there is no viscosity Since it is in a liquid state, it has to be applied every 30 minutes to become a non-dry state, and in the case of calcium hydroxide, since it is in a viscous state, it was able to maintain a non-dry state by applying it several times. After application of sodium hydroxide and calcium hydroxide, the curing temperature was carried out at 2 levels of 20 and 65°C. As an experiment, the compressive strength of the hardened mortar was measured at 3, 7, and 28 days of age, and the concrete structure was immersed in water and then dried. By periodically measuring 10 minutes, recovery of concrete and strengthening of strength were visually confirmed.

experimental factor experimental level combination
matters B:S(W/B) One · 1:3 (50%) BS substitution rate for OPC (wt%) 3 · BS 0 · BS 60 · BS 90 Experiment
variable burglar
recovery method ¹⁾ 2 · NaOH (12 mol) Ca(OH) ₂ (6 mol) treatment method One · apply curing temperature
(℃) 2 · 20 ²⁾ 65 ³⁾ Experiment
matters hardening mortar 2 Compressive strength (3, 7, 28 days) Drying after immersion in water

1) Apply the strength recovery method only in the formulation of BS 60

2) Applies to all levels

3) Applied only to the application of NaOH, Ca(OH) ₂

Referring to FIG. 1, this shows the compressive strength according to the change in the composition ratio of the binder, and it can be seen that the compressive strength increased as the age increased, but the compressive strength decreased as the replacement rate of BS increased.

In addition, Figure 2 shows the compressive strength and strength expression rate by curing temperature after applying a sodium hydroxide solution to 90% BS on the surface. At 65℃ was higher than at 20℃, but at 28 days of age, at the curing temperature of 65℃, 48.8% was exhibited at 16.1MPa, whereas at 20℃, it was 21.7MPa, showing compressive strength and strength development rate of 65.8%. However, this indicates that maintaining the temperature at 20°C rather than 65°C is helpful in securing compressive strength in case of coating with sodium hydroxide.

In addition, Figure 3 shows the compressive strength and strength expression rate by curing temperature after applying calcium hydroxide to 90% by weight of BS. As the age of age elapsed, the overall compressive strength increased, but in the case of 7 days, the temperature was 65 than 20 °C. It was found that higher compressive strength was exhibited at ℃, and at 28 days of age, when the curing temperature was 65℃, it was 16.1MPa and 48.8%, whereas at 20℃, it was 20.8MPa, about 63%. It seems that keeping the temperature at 20°C rather than 65°C contributed to the permeability and strength development.

However, 7 days and 28 days of age, and temperatures of 20°C and 65°C both showed a lower trend than sodium hydroxide.

In addition, Figure 4 is a photograph showing the sodium hydroxide solution and the calcium hydroxide solution divided into 20 ℃ and 65 ℃, respectively, each 30 minutes after immersing the mortar having a BS substitution rate of 90% for OPC in water, and sodium hydroxide over time. It can be seen that the applied calcium hydroxide showed a difference in the brightness of the color with the difference in the degree of solvent evaporation between the reacted and non-reacted parts from 30 minutes.

That is, through this, the boundary line appears clearly when 60 minutes have elapsed, and it can be seen that the penetration depth is deeper at 20°C than at 65°C.

Claims (7)

In the method of strengthening the strength of a concrete structure containing blast furnace slag,
Applying an alkali solution to the concrete structure,
The alkali solution contains metal hydroxide,
The solvent of the alkaline solution is acetonitrile, acetic acid, hydrofluoric acid, nitrous acid, methanol, ethanol or urea,
The concentration of the alkali solution is 3 to 20 mol (mol), characterized in that the strength strengthening method of the concrete structure containing the blast furnace slag fine powder.
The method of claim 1,
The method for strengthening the strength of a concrete structure comprising fine powder of blast furnace slag, characterized in that the blast furnace slag has a fineness of 4,000 to 10,000 cm2/g.
delete The method of claim 1,
The method for strengthening the strength of a concrete structure comprising a fine powder of blast furnace slag, characterized in that the metal ion of the alkali solution is sodium, magnesium, potassium or calcium ion.
The method of claim 1,
The method for strengthening the strength of a concrete structure comprising a fine powder of blast furnace slag, characterized in that the application temperature of the alkali solution is 15 to 70 ℃.
6. The method of claim 5,
The method for strengthening the strength of a concrete structure comprising a blast furnace slag fine powder, characterized in that the application is divided into a plurality of times.
7. The method of claim 6,
The interval of the multiple application is a method for strengthening the strength of a concrete structure including a blast furnace slag fine powder, characterized in that the following application is made before the coating film is dried.

Images