JP2022055425A - Manufacturing method of concrete member with neutralization inhibition effect - Google Patents

Abstract

To propose a manufacturing method of a concrete member with a neutralization inhibition effect, which can easily manufacture the concrete member capable of easily densifying a concrete surface without requiring special equipment or skill.SOLUTION: The method includes preparation step S1 of applying a neutralization inhibitor to an inner surface of a formwork 2 or attaching a face material 3 containing the neutralization inhibitor to the inner surface of the formwork 2, casting step S2 for casting concrete 1 in the formwork 2, and removal step S3 for removing the formwork 2 or the face material 3 from a concrete surface. The removal step S3 is performed after strength of the concrete 1 is developed to the extent that the surface of the concrete 1 in contact with the formwork 2 or the face material 3 is not peeled off by removal of the formwork 2 or the face material 3.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for manufacturing a concrete member having a neutralization suppressing effect.

If carbon dioxide invades the concrete from the outside and the alkalinity of the cement, which is the main component of the concrete, is impaired, the passivation film of the steel material in the concrete such as reinforcing bars may be lost and the corrosion resistance may decrease. This is because calcium hydroxide, which has worked to maintain an appropriate alkaline environment in concrete, reacts with carbon dioxide in the air to produce calcium carbonate, and the concrete loses its alkaline state and becomes acidic. There are roughly two methods for suppressing the neutralization of concrete, one is to mix concrete and the other is to provide a shielding layer on the concrete surface.
The former measures are mainly taken by reducing the water-cement ratio. On the other hand, the latter countermeasure is carried out by surface coating with a resin-based coating film. For example, in Patent Document 1, a synthetic resin aqueous dispersion, a water-soluble resin, and a swellable clay mineral are immediately placed on the surface after concrete is placed. A method for surface treatment of concrete to which an organic-inorganic composite coating film curing agent mainly composed of the above is applied is disclosed.

Japanese Unexamined Patent Publication No. 2008-194900

Countermeasures by blending concrete need to cover all concrete to be cast, which tends to increase costs. In addition, since the composition is corrected in the direction of increasing the unit cement amount, the risk of cracking due to temperature stress increases in mass concrete, such as an increase in calorific value, which may lead to the promotion of neutralization.
On the other hand, measures for providing a shielding layer on the concrete surface, including the concrete surface treatment method described in Patent Document 1, need to be implemented as a separate step after the formwork is removed. For example, it is necessary to consider the process such as providing a certain drying period for adjusting the base.
From this point of view, the present invention is to manufacture a concrete member having a neutralization suppressing effect, which can easily manufacture a concrete member capable of densifying the concrete surface without requiring special equipment or skill. The challenge is to propose a method.

In order to solve the above problems, the method for producing concrete having the neutralization suppressing effect of the present invention coats the neutralization inhibitor on the inner surface of the formwork or contains the neutralization inhibitor on the inner surface of the formwork. The removal step comprises a preparatory step for attaching the face material, a placing step for placing concrete in the formwork, and a removal step for removing the formwork or the face material from the concrete surface. It is characterized in that the concrete is strengthened to such an extent that the surface of the concrete in contact with the formwork or the face material is not peeled off by removing the formwork or the face material. As the neutralization inhibitor, an admixture containing any one of oxycarboxylic acid, polyol complex, alkylaminosulfonic acid and ligninsulfonic acid as a main component may be used. Further, it is desirable to use a non-woven fabric or a woven fabric as the face material. The neutralization inhibitor referred to here refers to a concrete admixture having a condensation delaying effect.
According to the method for manufacturing a concrete member having such a neutralization inhibitory effect, the portion in contact with the neutralization inhibitor is denser than the other portions, so that the concrete surface is provided with the neutralization inhibitory effect. A surface layer is formed. Therefore, by removing the formwork coated with the neutralization inhibitor or the face material containing the neutralization inhibitor from the concrete surface, a separate process for suppressing the neutralization is not required, and a skilled technique can be used. The concrete surface can be densified without the need for special equipment.

According to the method for manufacturing a concrete member having a neutralization suppressing effect of the present invention, a separate process for suppressing neutralization is not required, and the concrete surface is easily densified without requiring special equipment or skill. It becomes possible to suppress neutralization.

It is a flowchart of the concrete member manufacturing method which concerns on embodiment of this invention. It is sectional drawing which shows typically the manufacturing method of the concrete member. It is a graph which shows the neutralization inhibitory effect of the neutralization inhibitor which concerns on this embodiment. It is a graph which shows the neutralization suppressing effect by the concrete member manufacturing method which concerns on this embodiment.

In this embodiment, for example, a method for manufacturing a concrete member for manufacturing a secondary concrete product such as a box culvert or a precast retaining wall will be described. In the present embodiment, the surface of the concrete member is densified for the purpose of suppressing the neutralization of concrete. The location where the concrete member is installed is not limited.
As shown in FIG. 1, the method for manufacturing a concrete member according to the present embodiment includes a preparation step S1, a casting step S2, and a removal step S3.

As shown in FIG. 2, in the preparation step S1, the face material 3 containing the neutralization inhibitor is attached to the inner surface (the surface in contact with the concrete 1) of the weir of the formwork 2. In this embodiment, an admixture containing oxycarboxylic acid as a main component is used as the neutralization inhibitor. The face material 3 of the present embodiment is made of a non-woven fabric impregnated with a neutralization inhibitor. The material constituting the neutralization inhibitor is not limited, and may be, for example, an admixture containing a polyol complex, an alkylaminosulfonic acid, or a ligninsulfonic acid as a main component. The neutralization inhibitor referred to here refers to a concrete admixture having a condensation delaying effect.
The material constituting the face material 3 (base material of the face material 3) is not limited to the non-woven fabric, and may be, for example, a woven fabric. Further, the face material 3 does not necessarily have to be impregnated with a neutralization inhibitor in a base material such as a non-woven fabric, and the base material to which a neutralization inhibitor is added or the surface of the base material is neutralized. It may be one to which an inhibitor is attached. The face material 3 may be fixed (attached) to the formwork 2 (damp) via a jig, or may be attached using an adhesive or the like. When the face material 3 is not used, the neutralization inhibitor may be applied directly to the mold 2.

Further, as shown in FIG. 2, in the casting step S2, the concrete 1 is driven into the formwork 2. The composition of the concrete 1 is not limited, and may be appropriately determined. The excess water of the concrete 1 poured into the formwork 2 is absorbed by the face material 3. By removing the excess water on the surface of the concrete 1, no gap is formed between the surface of the concrete 1 and the formwork 2 (face material 3), and the concrete 1 adheres to the face material 3. Therefore, the surface of the concrete 1 becomes homogeneous.

In the removal step S3, the face material 3 is removed from the surface of the concrete 1. In the present embodiment, the face material 3 is removed together with the formwork 2 being removed. The face material 3 does not necessarily have to be removed at the same time as the mold 2 is removed, and may be left behind when the mold 2 is removed and removed after a predetermined period of time has elapsed. That is, the timing of demolding the formwork 2 and removing the face material 3 may be staggered depending on the hardening condition of the concrete 1.
The removal step S3 is performed after the strength of the concrete 1 is developed to the extent that the surface of the concrete 1 does not peel off. That is, after the cement paste or a part of the mortar is cured together with the face material 3 (formwork 2 when the face material 3 is not used) until the strength of the concrete 1 is developed to the extent that the cement paste or a part of the mortar does not peel off from the surface of the concrete 1. Material 3 (formwork 2) is removed.

As described above, according to the method for manufacturing a concrete member having a neutralization suppressing effect of the present embodiment, the paste on the surface of the concrete 1 is condensed by the neutralization suppressing agent (concrete admixture having a setting delay effect). Due to the delay, the concrete structure is densified during the hardening process. Therefore, it is possible to form a concrete member on the surface of the concrete 1 in which carbon dioxide or other carbon dioxide gas in the air is difficult to permeate. As a result, it is possible to improve the durability of the concrete structure, which is concerned about the progress of corrosion deterioration of steel materials such as reinforcing bars due to neutralization.
It is only necessary to remove the face material 3 (formwork 2 when the face material 3 is not used), which requires another process such as applying a resin to the surface of the concrete 1 afterwards, as well as skillful techniques and special equipment. You can easily work without any problems.
Further, since the work in the preparation step S1 can be performed relatively easily and in a short time, the work is easy even in a large area.

Hereinafter, the test results carried out for confirming the effect of the method for manufacturing a concrete member having the neutralization suppressing effect of the above-described embodiment will be described.

<Test 1>
In this test, in order to understand the presence or absence of the neutralization inhibitor and the difference in the effects of several types of neutralization inhibitors, mortar was used for convenience, and the neutralization inhibitor was kneaded as an admixture and added to water. used. The cross-sectional dimensions of the specimen were 100 × 100 mm. The composition of the mortar is shown in Table 1.
In order to confirm the neutralization inhibitory effect of the neutralization inhibitor, a list of a total of 5 test cases, one without the neutralization inhibitor and the other with the addition of four types of neutralization inhibitor, is shown. It is shown in Table 2. In this test, the neutralization depth was measured every 1,4,8,13,26,52 weeks, which is the neutralization promotion period. The results are shown in FIG.

From FIG. 3, the neutralization is suppressed in any of the neutralization inhibitors, and the neutralization inhibitory effect is 30 to 50% as compared with the untreated case in which the neutralization inhibitor is not used. It turned out to be. It was also found that the degree of inhibition differs depending on the type of neutralization inhibitor, and the inhibitory effect of R1 and R2 is relatively high. All of the neutralization inhibitors used in this test have the effect of delaying the condensation of mortar and concrete, and by allowing them to condense over time, the structure of the concrete surface is densified, and it is a neutralization promoting factor. It is considered that the main factor is that the infiltration of certain carbon dioxide was suppressed.

<Test 2>
This test was carried out on concrete, and a specimen having a cross section of 100 × 100 mm was used as in Test 1. The composition of concrete is shown in Table 3. In Test 1, the neutralization inhibitor was used as an admixture by adding it to the kneading water, so that the neutralization inhibitor acted on the entire specimen. In this test, the concrete produced according to the embodiment of the present invention was produced. For the purpose of confirming the effect of the method, a comparison was made between the case where the neutralization inhibitor was not applied from one side of the mold and the case where the neutralization inhibitor was allowed to act. Specifically, when the neutralization inhibitor does not act on the formwork surface, it is provided as a normal concrete surface (hereinafter referred to as "formwork surface") in which the formwork is removed and for reference. There are two cases of the surface in which the specimen is cut and the aggregate is exposed on the surface (hereinafter referred to as "cut surface"), and when the neutralization inhibitor is applied, it is the same as "when not allowed". A test was conducted to measure the neutralization depth in a total of three cases, one case of the concrete surface (hereinafter referred to as "treated surface"). A list of test cases is shown in Table 4. The "treated surface" is treated with water to clean the concrete surface of about 1 to 2 mm that could not be completely cured immediately after demolding. In this test, as in Test 1, the neutralization depth was measured every 1,4,8,13,26,52 weeks, which is the neutralization promotion period. The results are shown in FIG.

From FIG. 4, the neutralization inhibitory effect can be confirmed even in the specimen prepared by applying the neutralization inhibitor from only one surface of the formwork by the same concrete manufacturing method as in the present embodiment. It was found that the neutralization depth was suppressed to about 30 to 40% as compared with the untreated "formwork surface" and "cut surface" on which the neutralization inhibitor did not act.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and each of the above-mentioned components can be appropriately changed without departing from the spirit of the present invention.
Although the case where the concrete member manufactured by the method for manufacturing the concrete member having the effect of suppressing neutralization is a secondary concrete product has been described, the concrete member may be a concrete member constructed by on-site construction or the like. It is not limited to secondary products. Further, the base material of the face material 3 is not limited to the non-woven fabric or the woven fabric, and for example, a paper sheet material, a textile sheet, or the like may be used.

1 Concrete 2 Formwork 3 Face material S1 Preparation process S2 Casting process S3 Removal process

Claims (3)

A preparatory step of applying a neutralization inhibitor to the inner surface of the mold or attaching a surface material containing the neutralization inhibitor to the inner surface of the mold.
The casting process of placing concrete in the formwork and
A removal step of removing the formwork or the face material from the concrete surface is provided.
The removal step is performed after the strength of the concrete is developed to the extent that the surface of the concrete in contact with the formwork or the face material is not peeled off by the removal of the formwork or the face material.
A method for manufacturing concrete having a neutralization suppressing effect. The neutrality according to claim 1, wherein the neutralization inhibitor is an admixture containing any one of an oxycarboxylic acid, a polyol complex, an alkylaminosulfonic acid, and a ligninsulfonic acid as a main component. A method for manufacturing a concrete member having an effect of suppressing conversion. The method for producing a concrete member having a neutralization suppressing effect according to claim 1 or 2, wherein the face material is made of a non-woven fabric or a woven fabric.

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