JPH0961421A - Evaluation of healthiness of concrete and repairing of deteriorated concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply and accurately measure the deterioration depth of concrete corroded by a sulfuric acid component by utilizing the color reaction of a reagent as a sulfuric acid ion judging method. SOLUTION: At first, a fragile part crumbling into decay is removed by the sulfuric acid component. Next, concrete from which a core is removed is measured on the spot. The presence of sulfuric ions is judged by utilizing the color reaction of a reagent. For example, when a 0.2% aq. sol.. of chloroforfonazo III is sprayed and a 2% barium chloride aq. soln. is sprayed, the impregnation part of sulfuric ions shows a green color and a not- impregnated part shows a redish-purple color when an 0.2% aq. soln. of dimethylsulfonazo III is sprayed and a 2% aq. soln. of barrium chloride soln. is sprayed, the impregnated part of sulfuric ions shows a redish-purple color and the non-impregnated part shows a bluish-green color.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a soundness evaluation method for concrete corroded by a sulfuric acid component and a method for repairing deteriorated concrete.

[0002]

2. Description of the Related Art For example, it is clear that the deterioration of concrete members used for sewer pipes in sewerage facilities is often attributed to sulfuric acid produced by the action of microorganisms in hydrogen sulfide generated from sewage and sludge. Has become. In order to repair such a concrete member, the weakened portion is completely removed, the neutralized portion is removed, and then the concrete member is covered with a corrosion-preventing material. In this case, a neutralization test with phenolphthalein is usually used to determine the neutralization part.

If the concrete member is severely deteriorated, neutralization is progressing to a few mm further from the surface after the weakened portion is removed, but if the deterioration is slight, the weakened portion should be removed. For example, the results of the neutralization test show alkalinity and are considered sound. As described above, in the present situation, neutralization is used as one index for determining deterioration of concrete.

However, in the neutralization test, the sulfate ion, which is a causative substance of deterioration, permeates even in a portion which is considered to be healthy and is considered to be healthy, and may cause deterioration in the future. The sexualization test alone is not sufficient. Therefore, when repairing deteriorated concrete, it is necessary to accurately grasp the range in which sulfate ions have permeated as an index of deterioration and remove all permeated parts.

On the other hand, as a method for measuring the penetration depth of sulfate ions derived from sulfates such as sodium sulfate, ammonium sulfate and aluminum sulfate, cores are taken from deteriorated concrete to prepare samples at predetermined depths. ,
A method is known in which a sulfate ion contained in a sample is dissolved in water by a dissolution test and the concentration thereof is quantified. However, this method cannot measure the sulfate ion concentration in-situ, and there is a problem in application in the field. It is also known that the chemical mechanism of concrete deterioration by sulfate is different from the mechanism by acid (“Durability series of concrete structures-chemical corrosion”,
2.2.4 Degradation by sulfate, pp. 32-35, 198
Published by Gihodo Publishing Co., Ltd. in December 2006.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a concrete soundness evaluation method capable of easily and accurately measuring the deterioration depth of concrete eroded by a sulfuric acid component. It is intended to provide a useful repair method.

[0007]

The soundness evaluation method for concrete according to the present invention is a method for measuring the depth of deterioration of concrete eroded by a sulfuric acid component, in which the weakened portion of the concrete is removed and The depth of deterioration is measured by the presence or absence of sulfate ions present in the. The presence or absence of the sulfate ion is preferably measured by a color reaction of a reagent.

The method for repairing deteriorated concrete according to the present invention is characterized in that after the deterioration depth of the concrete is measured by the soundness evaluation method for concrete, the deteriorated concrete is removed and repaired. .

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In measuring the depth of deterioration of concrete eroded by a sulfuric acid component in which hydrogen sulfide, sulfurous acid gas or the like has changed, the present invention first removes the weakened portion of the concrete. The weakened portion is a portion where concrete is broken down due to the sulfuric acid component, and the depth thereof varies depending on the degree of deterioration.

Next, the presence or absence of sulfate ions that have penetrated into the concrete is measured. In the present invention, it is desirable to carry out the measurement on the spot without taking the cored concrete back to the test room. Examples of such a method for determining the presence or absence of sulfate ion include a method utilizing a color reaction of a reagent, and in particular, the following method using a reagent can be exemplified.

A 0.2% aqueous solution of chlorophosphonazo III [2,7-bis (4-chloro-2-phosphonophenylazo) chromotropic acid disodium] was sprayed on, followed by a 2% aqueous solution of barium chloride. When sprayed, the portion where the sulfate ions penetrate is green, and the portion where it does not penetrate is magenta.

Dimethylsulfonazo III [3,6-bis ((2-sulfo-4-methylphenyl) azo) -4,5
-Dihydroxy-2,7-naphthalenedisulfonic acid disodium salt] was sprayed with a 0.2% aqueous solution of barium chloride, and then a 2% aqueous solution of barium chloride was sprayed. The part has a blue-green color.

Dinitrosulfonazo III [3,6-bis ((4-nitro-2-sulfophenyl) azo) -4,5
-Dihydroxy-2,7-naphthalenedisulfonic acid tetrasodium] was sprayed with a 0.2% aqueous solution of barium chloride, and then a 2% aqueous solution of barium chloride was sprayed, the permeation part of sulfate ion was blue-purple and did not permeate. The part is blue.

Sulfonazo III [4,5-dihydroxy-3,6bis ((o-sulfophenyl) azo) -2,7
When a 0.2% aqueous solution of naphthalenedisulfonic acid] is sprayed, and then a 2% aqueous solution of barium chloride is sprayed, the part where the sulfate ion penetrates exhibits a reddish purple color and the part that does not penetrate exhibits a blue color.

When a solution of 0.2 mol / liter barium chloride solution and potassium permanganate solution mixed at 3: 1 was sprayed and washed with distilled water for about 1 minute, the permeation part of sulfate ion became red and permeated. The part that has not been shown has a purple color.

If the depth of deterioration of the concrete can be measured by the above method, the deteriorated portion is removed and the concrete is repaired or reinforced. The repair or reinforcement can be performed by using commonly used construction methods and materials. For example, in the case of repair, surface protection, cross-section repair, surface protection, cross-section repair, using resin-based, cement-based, FRP-based repair materials, etc. A construction method such as injection can be adopted.

[0017]

[Examples] In order to confirm the color reaction by a detection reagent of sulfate ion and to confirm its effectiveness, a concrete test body was immersed in a sulfuric acid solution, and the immersion test specimen was used to determine the presence or absence of sulfate ion. The penetration depth was measured.

[Example 1] Test method : Standard Portland cement specimens A and B having a size of 10 x 10 x 40 cm were prepared. The W / C of the specimen A was 55% and the W / C of the specimen B was 100%. And The specimens A and B were immersed in a 5% sulfuric acid solution at a constant temperature of 20 ° C. for 4 weeks.

Test Items and Analytical Method After 4 weeks, each test body was taken out, and the following test was performed on the test body after removing the weakened portion on the surface.

(1) Neutralization test A test piece was cut into pieces, and phenolphthalein 1 was added to the cut surface.
% Solution was sprayed and neutralization was judged.

(2) Color reaction test with a reagent A test piece was cut and sprayed with a solution in which a 0.2 mol / liter barium chloride solution and a potassium permanganate solution were mixed at a ratio of 3: 1. The color reaction was confirmed and the color depth was measured.

(3) Quantitative Analysis of Sulfate Ion by Elution Test After extracting cores (φ20 mm) from the same split pieces used in the above color reaction test, and cutting the cores at regular intervals with a diamond cutter. Further, it was pulverized in an agate mortar. The obtained powder sample was mixed with distilled water, and the sulfate ion concentration in the eluate was quantified using an ion chromatograph.

Test Results In the result of the neutralization test (1), the surfaces of the test bodies A and B from which the weakened portions were removed exhibited a reddish purple color and were alkaline.

FIG. 1 and FIG. 2 show the results of the analysis of sulfate ion in the above-mentioned dissolution test (3) in the test bodies A and B, respectively. Represents the depth from the plane, and the vertical axis represents the sulfate ion concentration.

Further, in FIGS. 1 and 2, the color change point due to the color reaction (2) using the above-mentioned reagent is shown by a broken line. A region on the left side of the broken line (in FIG. 1, a range from the surface to 4 to 6 mm, in FIG. 2, a range from the surface to 2 to 4 mm) is
This is the portion where the test body was colored red due to the permeation of sulfate ions.

From the above-mentioned test results, it was confirmed that the permeation of sulfate ions was carried out from a portion considered healthy in the neutralization test with phenolphthalein to the inside by about several mm.
Further, the penetration depth of the sulfate ions that have entered from the outside and the color development depth due to the color reaction are almost the same, which shows that the method for determining the sulfate ions by the reagent is effective.

[Example 2] Test method Samples A and B prepared in Example 1 were added to a 2% 5% sulfuric acid solution.
Immersion was carried out at a constant temperature of 0 ° C. for 8 months.

Test Items and Analytical Method After 8 months, each test body was taken out, and the test body after removing the weakened portion on the surface was subjected to a neutralization test and a color reaction test with a reagent as in Example 1. I went.

Test Results As a result of comparing the neutralization depth by phenolphthalein and the coloring depth by the reagent, both of the samples A and B, the latter had a value larger by an average of 2 to 3 mm than the former. That is, it can be seen that it is difficult to judge the deterioration due to the permeation of sulfate ions in the neutralization test which has been conventionally used as a standard for evaluating the deterioration degree of concrete.

[Comparative Example] Using the same reagent as the reagent judged to be deteriorated by the sulfuric acid component, a color test was carried out on the deteriorated concrete by the sulfuric acid salt to compare the difference between the two.

Test Method Ordinary Portland Cement Specimen C of φ10 × 20 cm
(W / C: 55%) was prepared, and this sample C was immersed in a 5% and 10% sodium sulfate aqueous solution at a constant temperature of 20 ° C. for 12 months.

Test Items and Analytical Method Immersion Specimen C was taken out every 3 months and the following tests were conducted. (1) A color reaction test was conducted in the same manner as in Example 1 using the above reagents and. (2) In the same manner as in Example 1, the sulfate ion was quantitatively analyzed by the dissolution test. (3) In addition, the appearance was visually observed and the surface was observed with an electron microscope.

Test Results Regarding the color reaction, regardless of the dipping period, no matter what reagent was used, the boundary of color development was not clear, such as deterioration due to the sulfuric acid component. For this reason, the depth of permeation of sulfate ions could not be measured by this test.

In visual observation and observation with an electron microscope,
Within a range of several mm from the surface, decolorization and lack of denseness were observed, but weakening as in the case of immersion in sulfuric acid was not observed. The analysis result of the sulfate ion by the dissolution test was about 5 to 10 mm from the surface with the 5% sodium sulfate aqueous solution and about 10 to 15 mm from the surface with the 10% aqueous solution at the 12th month of immersion.

From the above test results, in the case of deterioration of concrete due to sodium sulfate, the depth of penetration of sulfate ions (the depth of penetration after removal of the weakened portion in the case of sulfuric acid immersion is greater than that in the case of sulfuric acid immersion). ) Is deep, the determination of sulfate ion by the color reagent is uncertain and not effective.

[0036]

According to the method of the present invention, the depth of deterioration of concrete can be accurately measured by determining the presence or absence of sulfate ions in the concrete eroded by the sulfuric acid component. Further, by utilizing the color reaction by spraying the reagent, the sulfate ion concentration in the concrete can be measured on site, which is a very simple concrete soundness evaluation method suitable for the site.

Therefore, in the method of the present invention, in addition to sewer pipes, basins and other sewer incidental equipment, sulfuric acid is used as a direct or indirect cause of sulfuric acid in septic tanks, building pits, drainage facilities such as chemical plants, storage tanks for chemicals and the like. This is a particularly useful repairing method against the deterioration of the concrete member. It is also effective for repairing deteriorated concrete members due to acid rain containing sulfuric acid components.

[Brief description of drawings]

FIG. 1 shows the results of quantitative analysis of sulfate ions in the dissolution test of test sample A in Example 1.

FIG. 2 shows the results of quantitative analysis of sulfate ions in the dissolution test of test sample B in Example 1.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shizuro Sasaki 1043-1, Shimoyama, Onigakushi, Tsukuba, Ibaraki Prefecture Inside Kumagai Technical Research Institute (72) Takahiro Matsumura Onigagaku, Tsukuba, Ibaraki 1043-1, Shimoyama, Kumagai Gumi Research Laboratory, Ltd. (72) Inventor, Ryohei Ishida, Onigakubo, Tsukuba, Ibaraki Prefecture 1043-1, Shimoyama, Kumagai Gumi Research Laboratory

Claims (3)

[Claims] 1. When measuring the deterioration depth of concrete eroded by a sulfuric acid component, after removing the weakened part of the concrete, measuring the deterioration depth by the presence or absence of sulfate ions existing in the concrete. A method for evaluating the soundness of concrete, characterized by. 2. The soundness evaluation method for concrete according to claim 1, wherein the presence or absence of the sulfate ion is measured by a color reaction of a reagent. 3. Repair of deteriorated concrete, characterized in that the deteriorated concrete is removed and repaired after the deterioration depth of the concrete is measured by the concrete soundness evaluation method according to claim 1 or 2. Method.