JP4152268B2 - Method for measuring salinity in hardened concrete and mortar - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for simply measuring the amount of salt contained in hardened concrete or hardened mortar.
[0002]
[Prior art]
In order to grasp the deterioration state of hardened concrete or hardened mortar, the salt content of the concrete or mortar is measured. As a method for measuring the amount of salt in hardened concrete, Japan Concrete Institute Standard JCI-SC4 “Analytical Method for Chloride Contained in Hardened Concrete” has been used. Although this analysis method can obtain salinity with very high accuracy, it takes time and skill to measure, and it uses a strong acid such as nitric acid to extract chloride from concrete, and requires operations such as heating and boiling. There are many work restrictions from the safety aspect. In addition, it is necessary to use the silver chromate-absorptiometric method or silver nitrate titration method to measure the amount of extracted chloride, which may require the use of expensive measuring equipment and complicated measurement operations. It is not a simple and easy method.
[0003]
For this reason, a method that can more easily measure the amount of salt in hardened concrete and hardened mortar has been studied, and as a method that can be applied relatively easily in the field, an acidic solution containing chloride extracted from concrete with an organic acid, There has been reported a method for measuring the salt concentration of a solution in which an organic acid sodium is generated by neutralization with anhydrous sodium carbonate. (For example, refer nonpatent literature 1). It is also known to measure the salinity concentration of a solution in which sodium organic acid is produced, particularly by a method using a detection agent that can be easily and rapidly measured using the principle of the Mole method. (For example, refer to Patent Document 1). However, anhydrous sodium carbonate used as a neutralizing agent in these methods has a relatively high hygroscopicity and is not necessarily suitable for long-term storage at the site or the like. In addition, generally available anhydrous sodium carbonate contains about 0.05% by weight of chloride in the production process, so if the amount used during neutralization increases, the concentration of chloride in the extract increases, and the actual hardened concrete There was a tendency for values higher than the amount of chloride in them to be measured.
[0004]
[Non-Patent Document 1]
Development of simple salinity measurement technology, “Development report on durability improvement technology of concrete <Part 1>”, Ministry of Construction, November 1988, p. 109-114
[Patent Document 1]
Japanese Patent Laid-Open No. 62-91860
[Problems to be solved by the invention]
The present invention is a method for measuring salinity in hardened concrete and hardened mortar that can be measured at the site of deterioration diagnosis of concrete and mortar structures, and has very few work restrictions and loads, and can be measured very easily and with high accuracy. Provided is a salinity measuring method capable of
[0006]
[Means for Solving the Problems]
As a result of repeated investigations for solving the above problems, the present inventors generally used a neutralizing agent used after treating a hardened concrete or mortar with an organic acid, and the mixing of chlorides in the raw material and the manufacturing process generally occurred. In addition, calcium carbonate and calcium hydroxide with relatively low hygroscopicity are used to prevent chloride contamination from outside the system, and the low-solubility organic acid calcium precipitated during neutralization is filtered. The present invention has been completed because it has become a method that facilitates the measurement of the salinity and can measure the salinity quickly and easily with high accuracy.
[0007]
That is, this invention is a salt content measuring method in the hardened concrete mortar represented by following (1)-(4). (1) After adding anhydrous organic acid to hardened concrete and mortar to extract chlorides, neutralize by adding calcium carbonate or calcium hydroxide neutralizer, and the solution in which organic acid calcium is precipitated by neutralization A method for measuring salinity in hardened concrete mortar, which comprises filtering and measuring the chlorine concentration of the filtrate. (2) The method for measuring salinity in hardened concrete / mortar according to (1) above, wherein the calcium carbonate-based or calcium hydroxide-based neutralizing agent is natural stone grains mainly composed of calcium carbonate or calcium hydroxide. (3) The method for measuring salinity in hardened concrete mortar as described in (1) or (2) above, wherein the chloride concentration of the filtrate is measured by the Mohr method. (4) Any of (1) to (3) above, wherein the steps from addition of anhydrous organic acid to hardened concrete / mortar to organic acid calcium precipitation by neutralization are performed in a sealed container having a gas discharge port. Method for measuring salinity in hardened concrete mortar.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The cured concrete and cured mortar to be measured by the salt content measuring method of the present invention are not particularly limited. As a measurement sample, a small piece or powder is collected from a desired portion of the target concrete or mortar cured product by an arbitrary method such as drilling or cutting. The amount of concrete mortar collected for the measurement according to the present invention may be as small as 2 to 10 g per measurement. In addition, when the collected material is a small piece, it is desirable to pulverize and collect the powder as much as possible when a sample having a size exceeding about 0.5 mm is included.
[0009]
The collected concrete mortar is put in deionized water, and chloride is extracted by adding 20 to 100 parts by weight of an organic acid anhydride to 100 parts by weight of the concrete mortar. The deionized water may be water that does not contain chlorine ions. For example, distilled water, ion exchange water, purified water, and the like can be used. About 200 parts by weight or more of deionized water is recommended. In addition, it is desirable to perform stirring when extracting chloride.
[0010]
The anhydrous organic acid used for the chloride extraction may be any anhydrous organic acid as long as it does not release chlorine ions in water. For example, acetic acid, citric acid, tartaric acid, maleic acid, malic acid, sulfamic acid and other anhydrides. Is mentioned. Preferably, powdered organic acid anhydride is used. If the amount of the organic acid anhydride used is less than 20 parts by weight, the extraction of the chloride becomes insufficient, which is not preferable. If the amount exceeds 100 parts by weight, a large amount of neutralizing agent is required and the neutralization reaction becomes intense, which is preferable. Absent. The chloride extraction time in the hardened concrete mortar with anhydrous organic acid is preferably 3 to 10 minutes. An extraction time of less than 3 minutes is not preferable because the extraction becomes insufficient, and even if the extraction time exceeds 10 minutes, the extraction of chloride does not increase any more.
[0011]
The liquid from which chloride is extracted by addition of anhydrous organic acid is neutralized by adding a calcium carbonate or calcium hydroxide neutralizer. The neutralization time is preferably about 10 to 20 minutes. The calcium carbonate neutralizer may be calcium carbonate powder, and the calcium hydroxide neutralizer may be calcium hydroxide powder. However, when the average particle size is about 45 μm or less, the powder reacts violently when neutralizing the extract. However, since it may overflow from the reaction vessel, natural stone grains mainly composed of calcium carbonate or calcium hydroxide are preferably used. The natural stone grains mainly composed of calcium carbonate are not particularly limited as long as they do not contain chloride, and for example, calcite, cryolite, limestone and the like can be used. Moreover, the natural stone grain which has calcium hydroxide as a main component will not be specifically limited if it does not contain a chloride, For example, slaked lime etc. can be used. The natural stone grains generally have a lower reaction activity than calcium carbonate and calcium hydroxide powders, and even those having an average particle size somewhat smaller than 45 μm, for example, about 30 μm can be used without any problem. On the other hand, when the average particle size exceeds about 200 μm, the reaction activity becomes poor, and it may take 1 hour or more to complete the neutralization reaction, which is not preferable.
[0012]
Since organic acid calcium precipitates in the liquid after neutralization, it is removed by filtration, and the chlorine-containing concentration of the obtained filtrate is measured. The chlorine content concentration in the filtrate can be measured by any measurement method including, for example, conventional measurement methods, but preferably a measurement method based on the Mole method is recommended because of its rapidity and accuracy. The In the present invention, the operations from the dissolution of the concrete / mortar sample to the measurement of chloride in the filtrate can all be performed at around room temperature (about 5 to 35 ° C.), and the treatment such as heating is not particularly required.
[0013]
Moreover, this invention performs the process from the addition of an anhydrous organic acid to the said concrete mortar extract to organic acid calcium precipitation by neutralization in a sealed container. It is desirable that the state of the contents of the container can be always easily visually confirmed from the outside. Specifically, it is desirable that a part or all of the container is colorless and transparent or lightly colored and translucent. The container material is not limited as long as it can withstand the chemical used, and for example, a hard resin or glass can be used. The container is a container that can be sealed with a stopper or a lid so that the contents do not leak out when vibration or the like is applied. Further, it is desirable that the container has a small hole for discharging the gas produced by the reaction out of the container. The small hole has a diameter of about 1 to 10 mm, preferably one at the top of the container body or one at the sealing lid or stopper. In order to make the small hole sealable, it is preferable to have a structure in which a stopper or a lid can be attached to the small hole. However, the small hole may be closed and sealed with a finger or an impermeable tape. An opening structure without a lid attached may be used. The shape and size of such a container are not particularly limited. For example, a container having an outer shape of a cylinder or a prismatic column and an internal volume of about 40 to 500 ml is recommended from the viewpoint of portability. The reaction such as extraction / neutralization in the container is preferable because the reaction time tends to be shortened if vibration or the like is appropriately added. Moreover, after organic acid calcium precipitation, after removing all the contents from a container and performing the said filtration, the chlorine concentration in a filtrate is measured.
[0014]
【Example】
Hereinafter, the present invention will be described in detail by way of examples.
[0015]
[Materials used]
The following materials A to D were selected.
A: Distilled water (“Distilled water for fluorescence analysis” manufactured by Kanto Chemical Co., Inc.)
B1: Tartaric acid (Reagent manufactured by Kanto Chemical Co., Inc.)
B2: Citric acid (Reagent manufactured by Kanto Chemical Co., Inc.)
C1: Cryolite with an average particle size of about 100 μm (manufactured by Hitachi Seisui Co., Ltd.)
C2: Calcium carbonate (Reagent manufactured by Kanto Chemical Co., Inc.)
C3: Calcium hydroxide (Reagent manufactured by Kanto Chemical Co., Inc.)
D: Anhydrous sodium carbonate (reagent manufactured by Kanto Chemical Co., Inc.)
[0016]
[Example 1]
The hardened concrete body was punched using a hammer drill, and concrete powder (average particle diameter of about 120 μm) was collected.
[0017]
Distilled water (A) has a small hole with a diameter of 2 mm on the side surface at a height of 227 mm from the bottom, and a polypropylene cylindrical container with an inner diameter of 28 mm and an inner height of 230 mm that can be screwed with a sealing plug at the top. 20.0 g), and 5.0 g of the collected concrete powder and 2.0 g of tartaric acid (B1) as the organic acid were added. Next, the container was sealed with a stopper, the small hole was closed with a finger, the container was shaken for about 10 seconds, the finger with the small hole closed was loosened for 2 to 3 seconds, and the gas generated in the container was released to the outside. After repeating the vibration and gas release of this container five times, the stopper was opened with the small holes opened, and 2.0 g of cold water stone (C1) as a neutralizing agent was placed in the container and left for about 1 minute. After standing, it was sealed with a stopper, the small hole was closed with a finger, the container was shaken for about 10 seconds, the finger with the small hole closed was loosened for 2 to 3 seconds, and the gas generated in the container was released outside the container. After repeating this container vibration and gas release five times, the small holes were opened and left for about 10 minutes. After standing, the entire contents of the container were taken out and filtered. The filtrate after filtration was measured for chlorine concentration with a commercially available chloride concentration detecting agent (trade name “Cantab”, manufactured by Taiheiyo Materials Co., Ltd.) using the Mole method. As a result, the chlorine content was 0.068% by weight.
[0018]
[Example 2]
The same sample of the hardened concrete body as in Example 1 is used as the measurement object, and all the same as Example 1 except that 2.0 g of citric acid (B2) is used instead of 2.0 g of tartaric acid (B1) as the organic acid. The chlorine content concentration in the hardened concrete was measured by this method. As a result, the chlorine content was 0.067% by weight.
[0019]
[Example 3]
Example 1 is the same as Example 1 except that 3.0 g of calcium carbonate (C2) is used in place of 3.0 g of cold water stone (C1) as a neutralizing agent. The chlorine content concentration in the hardened concrete was measured by the same method. As a result, the chlorine content was 0.067% by weight.
[0020]
[Example 4]
Example 1 is the same except that 3.0 g of calcium hydroxide (C3) is used instead of 3.0 g of cold water stone (C1) as a neutralizing agent. In the same manner as above, the chlorine content in the hardened concrete was measured. As a result, the chlorine content was 0.066% by weight.
[0021]
[Comparative Example 1]
Example 1 is the same as in Example 1 except that 3.0 g of sodium carbonate (D) is used in place of 3.0 g of cold water stone (C1) as a neutralizing agent. The chlorine content concentration in the hardened concrete was measured by the same method. As a result, the chlorine content was 0.098% by weight.
[0022]
[Comparative Example 2]
Concrete was obtained in the same manner as in Example 1 except that the same hardened concrete sample as in Example 1 was used for measurement, the liquid after neutralization was not filtered at all, and the contents of the container were directly used for chloride concentration measurement. The chlorine content concentration in the cured product was measured. As a result, the chlorine content was 0.025% by weight.
[0023]
[Comparative Example 3]
Using the same hardened concrete specimen as in Example 1 as the measurement object, the specimen was treated by a method in accordance with Japan Concrete Institute Standard JCI-SC4 “Analytical Method for Chloride Contained in Hardened Concrete”, and silver nitrate The total chlorine content was measured by titration. As a result, the chlorine content was 0.068% by weight.
[0024]
From the above results, if the method for measuring salinity in hardened concrete mortar according to the present invention is used, the value of total chlorine content measured by a method based on JCI-SC4 with the highest accuracy and reliability (Comparative Example 3). ) And a chlorine-containing concentration value almost inferior to each other, and it can be seen that highly accurate and reliable measurement results (Examples 1 to 4) were obtained.
[0025]
【The invention's effect】
The method for measuring the salinity in the hardened concrete mortar of the present invention can be measured very easily and with considerably high accuracy in a relatively short time even when performed by an unskilled person. In particular, if a sealed container suitable for the analysis according to the present invention is used, since it is excellent in portability, it can be easily brought into a work site and the like, and it is necessary to perform complicated operations using various analytical instruments. As a result, the measurement work efficiency increases.

Claims (4)

After adding anhydrous organic acid to hardened concrete and mortar and extracting chloride, neutralize by adding calcium carbonate or calcium hydroxide neutralizer, filter the liquid from which organic acid calcium is precipitated by neutralization, A method for measuring salinity in hardened concrete mortar, characterized by measuring a chlorine concentration in a filtrate. 2. The method for measuring salinity in hardened concrete mortar according to claim 1, wherein the calcium carbonate-based or calcium hydroxide-based neutralizing agent is natural stone grains mainly composed of calcium carbonate or calcium hydroxide. 3. The method for measuring the salinity in hardened concrete mortar according to claim 1, wherein the chloride concentration of the filtrate is measured by the Mole method. The process from addition of anhydrous organic acid to hardened concrete mortar to organic acid calcium precipitation by neutralization is carried out in a sealed container having a gas discharge port. Method for measuring salinity in mortar.