Method of detecting amine compounds in hardened cement body

Abstract

To provide an amine compound detection method which enables easy grasping of the presence or absence of and the amount of an amine compound contained in a hardened cement body.SOLUTION: An amine compound detection method is provided, comprising: a first step of pulverizing a hardened cement body to obtain cement powder; a second step of mixing the cement powder with an acidic reagent and coloring regent to obtain a mixture containing the cement powder, acidic reagent, and coloring reagent; and a third step of checking the coloring state of the mixture.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for detecting an amine compound in a hardened cement paste. [Background technology]

[0002] As a technology for removing carbon dioxide (hereinafter also referred to as "CO2") from the atmosphere to prevent global warming, a technology has been proposed in which an amine-based impregnating agent is allowed to penetrate the surface of hardened cement bodies such as concrete structures, and the amine-based impregnating agent promotes fixation of CO2 in the hardened cement bodies. Regarding the amine-based impregnating agent that has penetrated the surface of the hardened cement body, it is necessary to measure the concentration distribution of the amine-based impregnating agent in the depth direction of the hardened cement body in order to determine the timing for applying additional coats of the amine-based impregnating agent and to maximize the amount of fixed CO2.

[0003] Amine compounds are used in concrete as rebar rust inhibitors (e.g., see Non-Patent Document 1 and Patent Document 1), setting accelerators (e.g., see Non-Patent Document 2), strength enhancers (e.g., see Non-Patent Document 3), etc. However, there are very few examples of measuring the concentration of amine compounds in hardened cement paste. As techniques for measuring the concentration of amine compounds in hardened cement paste, precise measurement methods and simple measurement methods have been developed and deployed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-179919 A [Non-patent literature]

[0005] [Non-Patent Document 1] Hirotake Endo, Zenji Kubo, and Akinori Shimada, "Effect of surface impregnation materials on frost and salt damage prevention of existing concrete in cold regions," Monthly Report of the Civil Engineering Research Institute for Cold Regions, No. 752, pp. 2-10 (2016). [Non-Patent Document 2] Etsuro Sakai, “Chemical Admixtures”, Concrete Engineering, Vol. 51, No. 1, pp. 40-44 (2013). [Non-Patent Document 3] Miho Miyagawa, Keisuke Iwaki, Daiki Shin, Tomoyuki Koyama, “Effect of Amine-Based Strength Enhancer on Early Strength of Fly Ash Mixtures,” Journal of Structural Engineering, Architectural Institute of Japan, Vol. 82, No. 736, pp. 783-789 (2017). Summary of the Invention [Problem to be solved by the invention]

[0006] Nuclear magnetic resonance (NMR) and high-performance liquid chromatography (HPLC), which are used to precisely measure amine compounds, are unsuitable for on-site measurements because they require complicated pretreatment of the target samples and expensive, large-scale analytical equipment.

[0007] In addition, kits for amino acids and stimulants are commercially available as instruments for performing color testing, which is a simple method for measuring amine compounds. Such kits are suitable for on-site measurements because a color reaction occurs when a sample containing an amine compound is mixed with multiple reagents (heated if necessary). However, commercially available color reagents cannot be directly applied to samples such as hardened cement, which are strongly basic and contain a large amount of impurity ion components.

[0008] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a method for detecting an amine compound, which can easily grasp the presence or absence of an amine compound in a hardened cement body and the amount of the amine compound contained therein. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention has the following aspects. [1] A first step of pulverizing a hardened cement body to obtain cement powder; A second step of mixing the cement powder, the acidic reagent, and the color reagent to obtain a mixture containing the cement powder, the acidic reagent, and the color reagent; and a third step of confirming the color state of the mixture. [2] The method for detecting an amine compound according to [1], wherein in the second step, after mixing the cement powder and the acidic reagent, the color reagent is further mixed therein. [3] The method for detecting an amine compound according to [1] or [2], wherein the average particle size of the cement powder is 80 μm or more and 150 μm or less. [4] The method for detecting an amine compound according to any one of [1] to [3], wherein the acidic reagent is at least one selected from the group consisting of nitric acid, sulfuric acid, hydrochloric acid, acetic acid and phosphoric acid. [5] The method for detecting an amine compound according to any one of [1] to [4], wherein the amount of the acidic reagent added is 0.1 to 10 times the mass of the mixture of the cement powder and water. [6] The method for detecting an amine compound according to any one of [1] to [5], wherein the color reagent is at least one selected from a ninhydrin reagent, a Dragendorff reagent, a Marquis reagent, a Simon reagent, and a Scott test. [7] The method for detecting an amine compound according to any one of [1] to [6], wherein the amount of the color reagent added is 0.1 to 10 times the mass of the mixture of the cement powder and water. [8] The method for detecting an amine compound according to [7], wherein the amount of the color reagent added is 0.2 to 5 times the mass of the mixture of the cement powder and water. Effect of the Invention

[0010] According to the present invention, it is possible to easily grasp the presence or absence of an amine compound in a hardened cement body and the amount of the amine compound contained therein. [Brief description of the drawings]

[0011] [Figure 1]1 is a photograph showing the results of a color test performed in an experimental example on the basis of the content of an amine compound in a cement powder. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] An embodiment of a method for detecting an amine compound according to the present invention will be described. It should be noted that the present embodiment is specifically described to allow a better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

[0013] [Detection method for amine compounds] The method for detecting an amine compound according to the present embodiment is a method for detecting the presence or absence of an amine compound in a hardened cement paste. The method for detecting an amine compound of this embodiment includes a first step of pulverizing a hardened cement body to obtain cement powder, a second step of mixing the cement powder, an acidic reagent, and a color reagent to obtain a mixture containing the cement powder, the acidic reagent, and the color reagent, and a third step of confirming the color state of the mixture.

[0014] "First step" In the first step, the hardened cement body is pulverized to produce cement powder.

[0015] (hardened cement) In the detection method for an amine compound of the present embodiment, the hardened cement product is a hardened cement product for carbon dioxide fixation in which a carbon dioxide absorbent is supported in the hardened cement product. The hardened cement product for carbon dioxide fixation is used for fixation of carbon dioxide. In this specification, the term "supported" refers to the carbon dioxide absorbent being attached to at least one of the inside and the surface of the hardened cement body. In this specification, the hardened cement body functions as a so-called carrier.

[0016] The hardened cement product is a hardened product of a cement-containing composition that contains cement and water. In this specification, the term "cured product" refers to a product that has cured to the extent that it does not deform when pressed with a finger. Examples of the cement-containing composition include concrete (ready mixed concrete), mortar (paste mortar), and cement milk (cement paste). In this specification, concrete refers to a mixture of cement, fine aggregate (sand), and coarse aggregate (gravel (crushed stone)), mixed with water. In this specification, mortar refers to a mixture of cement and fine aggregate (sand) kneaded with water. In this specification, cement milk refers to cement mixed with water only. In this specification, cement refers to a powder that is made primarily from limestone, clay, silica, iron oxide raw materials, etc., and hardens through a chemical reaction with water. In this specification, fine aggregate refers to sand with a diameter of 5 mm or less. In this specification, coarse aggregate refers to gravel (crushed stone) having a diameter of more than 5 mm, and the diameter of the coarse aggregate is preferably 25 mm or less.

[0017] The mixing ratio of cement, fine aggregate, and coarse aggregate in concrete can be appropriately determined depending on the strength required for the concrete. The mixing ratio of cement, fine aggregate, and coarse aggregate is preferably, for example, 1 part cement, 2 to 3 parts fine aggregate, and 4 to 6 parts coarse aggregate by mass ratio.

[0018] The mixing ratio of cement to fine aggregate in the mortar can be appropriately determined depending on the strength required for the mortar. The mixing ratio of cement to fine aggregate is preferably, for example, 1 part cement to 2 to 4 parts fine aggregate by mass ratio.

[0019] The hardened cement body is not particularly limited, but since it is used in a high proportion in existing structures, concrete is preferable, and reinforced concrete is more preferable.

[0020] (Carbon dioxide absorbent) The carbon dioxide absorbent is supported in the hardened cement paste and absorbs carbon dioxide in the atmosphere. Therefore, carbon dioxide in the atmosphere is absorbed into the hardened cement body, and the carbon dioxide concentration in the atmosphere is reduced. In other words, carbon dioxide in the atmosphere can be fixed in the hardened cement body. The carbon dioxide absorbent may be a solid or a liquid at room temperature and pressure. In this specification, "normal temperature" refers to the standard temperature of the atmosphere, for example, 15 to 25° C. "Normal pressure" refers to the standard pressure of the atmosphere, for example, 1 atmosphere (1013 hPa).

[0021] The carbon dioxide absorbent may be, for example, an alkaline compound. Here, the term "alkaline compound" refers to a compound that has a pH of greater than 7 when dissolved in water. The alkaline compound may be an inorganic compound, an organic compound, or a mixture thereof. Examples of inorganic alkaline compounds include calcium hydroxide, magnesium hydroxide, sodium silicate, potassium silicate, lithium silicate, lithium nitrite, and calcium nitrite. Examples of the organic alkaline compound include arginine, lysine, urea, sodium acetate, potassium acetate, and amine compounds. The carbon dioxide absorbent may be used alone or in combination of two or more kinds. Furthermore, the carbon dioxide absorbent is not limited to an alkaline compound, and may be any compound capable of fixing carbon dioxide in the hardened cement body.

[0022] Examples of the amine compounds include aliphatic amines and aromatic amines. As the amine compound, an aliphatic amine is preferred since it is easily soluble in water. Examples of the aliphatic amine include alkylamines and alkanolamines. Examples of alkylamines include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, propylamine, and butylamine. Examples of alkanolamines include monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), monoisopropanolamine (MIPA), diisopropanolamine (DIPA), triisopropanolamine (TIPA), N-methylethanolamine (MMEA), and N-methyldiethanolamine (MDEA).

[0023] The amine compound may be any of a primary amine, a secondary amine, a tertiary amine, and a quaternary ammonium salt, and may have a cyclic structure. In addition to the above, examples of amine compounds include dicyclohexylamine (DCHA), dimethylcyclohexylamine (DMCHA), polyetheramine (PEA), diglycolamine (DGA), 2-amino-2-methyl-1-propanol (AMP90), n-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), pyrrolidine, piperidine, piperazine, morpholine, and the like. These amine compounds may be used alone or in combination of two or more.

[0024] Alkaline compounds have the effect of inhibiting corrosion of steel materials such as carbon steel. Therefore, when the hardened cement body is reinforced concrete, alkaline compounds can inhibit corrosion of the reinforcing bars in the reinforced concrete. It is generally known that when reinforced concrete absorbs carbon dioxide, neutralization progresses and there is a risk of corrosion of the reinforcing bars due to a decrease in pH. By impregnating the hardened cement body with an alkaline compound, the risk can be reduced. From the above viewpoints, alkaline compounds are preferred as carbon dioxide absorbents.

[0025] The content of the carbon dioxide absorbent in the hardened cement body (amount of carbon dioxide absorbent supported by the hardened cement body) is preferably 5 to 20 parts by mass per 100 parts by mass of the hardened cement body serving as a carrier. When the amount of carbon dioxide absorbent supported by the hardened cement body is equal to or more than the above lower limit, the amount of carbon dioxide that can be fixed can be increased. When the amount of carbon dioxide absorbent supported by the hardened cement body is equal to or less than the above upper limit, the amount of carbon dioxide absorbent attached to the hardened cement body can be maintained. The amount of carbon dioxide absorbent supported in the hardened cement body can be adjusted by the type of hardened cement body, the type of carbon dioxide absorbent, the content of the carbon dioxide absorbent in the carbon dioxide absorbing liquid (concentration of the carbon dioxide absorbent in the carbon dioxide absorbing liquid), the amount of the carbon dioxide absorbing liquid, or a combination of these.

[0026] In the first step, the method for pulverizing the hardened cement body to obtain cement powder is not particularly limited, but may be, for example, a method in which small pieces are taken from the hardened cement body and the pieces are pulverized in a mortar or the like.

[0027] The average particle size of the cement powder is preferably 1 μm or more and 250 μm or less, more preferably 10 μm or more and 200 μm or less, and even more preferably 80 μm or more and 150 μm or less. If the average particle size of the cement powder is equal to or more than the lower limit, the operation of crushing the cement hardened body can be efficiently performed. If the average particle size of the cement powder is equal to or less than the upper limit, the reaction between the carbon dioxide absorbent and the color reagent contained in the cement powder proceeds uniformly.

[0028] The average particle size of the cement powder can be measured by a particle size distribution measuring device (for example, MT3300II manufactured by Microtrac Corporation).

[0029] "Second step" In the second step, the cement powder, the acidic reagent, and the color reagent are mixed to obtain a mixture containing the cement powder, the acidic reagent, and the color reagent. In the second step, after the cement powder and the acidic reagent are mixed, it is preferable to further mix the color reagent.

[0030] (acidic reagent) The acidic reagent blocks the hydroxide ions contained in the cement powder, thereby suppressing inhibition of the reaction (color reaction) between the carbon dioxide absorbent (amine compound) contained in the cement powder and the color reagent. Suitable examples of the acidic reagent include nitric acid, sulfuric acid, hydrochloric acid, acetic acid, phosphoric acid, etc. The acidic reagent may be used alone or in combination of two or more kinds.

[0031] The amount of the acidic reagent to be added is not particularly limited and is appropriately adjusted depending on the type of carbon dioxide absorbent contained in the cement powder. The amount of the acidic reagent to be added is, for example, preferably 0.1 to 10 times the mass of the mixture of cement powder and water (cement paste), more preferably 0.2 to 5 times, and even more preferably 0.5 to 2 times. If the amount of the acidic reagent to be added is equal to or more than the lower limit, the carbon dioxide absorbent can be sufficiently extracted from the cement powder, and the reaction between the carbon dioxide absorbent contained in the cement powder and the color reagent proceeds sufficiently. If the amount of the acidic reagent to be added is equal to or less than the upper limit, the carbon dioxide absorbent is not diluted or dissolved by the acidic reagent, and the color state of the mixture can be easily confirmed.

[0032] The water-cement ratio (W / C) of the mixture of cement powder and water (cement paste) is not particularly limited, and is adjusted appropriately depending on the type of carbon dioxide absorbent contained in the cement powder, etc.

[0033] As a method for extracting the carbon dioxide absorbent from the cement powder, a method in which ultrasonic waves are applied to warm water in which the cement powder is immersed to extract the carbon dioxide absorbent in the warm water, or a method in which the carbon dioxide absorbent contained in the cement powder is dissolved (extracted) in an organic solvent by the Soxhlet extraction method may be used.

[0034] (Color reagent) The color reagent is used in a color reaction of the carbon dioxide absorbent contained in the cement powder. As the color reagent, a ninhydrin reagent, a Dragendorff reagent, a Marquis reagent, a Simon reagent, a Scott test, or the like is preferably used. Ninhydrin reagent is primarily used as a color reagent for primary and secondary amines. The Dragendorff reagent is primarily used as a color reagent for tertiary and quaternary amines. Marquis' reagent is primarily used as a color reagent for aromatic amines. Simon's reagent is primarily used as a color reagent for primary and secondary amines. The Scott test is primarily used as a color reagent for tertiary amines, including cocaine. The color reagent may be used alone or in combination of two or more kinds.

[0035] The amount of the color reagent added is not particularly limited and is adjusted appropriately depending on the type of carbon dioxide absorbent contained in the cement powder. The amount of the color reagent added is, for example, preferably 0.1 to 10 times the mass of the mixture of cement powder and water (cement paste), more preferably 0.2 to 5 times, and even more preferably 0.5 to 2 times. If the amount of the color reagent added is equal to or more than the lower limit, the reaction between the carbon dioxide absorbent contained in the cement powder and the color reagent proceeds sufficiently. If the amount of the color reagent added is equal to or less than the upper limit, the carbon dioxide absorbent is not diluted or dissolved by the color reagent, and the color state of the mixture can be easily confirmed.

[0036] When a ninhydrin reagent is used as the color reagent, the acidic reagent is preferably nitric acid, sulfuric acid, hydrochloric acid, acetic acid, or phosphoric acid, and more preferably acetic acid. When the Dragendorff reagent is used as the color reagent, the acidic reagent is preferably nitric acid, sulfuric acid, hydrochloric acid, acetic acid, or phosphoric acid, and more preferably hydrochloric acid or acetic acid. When a Marquis reagent is used as the color reagent, the acidic reagent is preferably nitric acid, sulfuric acid, hydrochloric acid, acetic acid, or phosphoric acid, and more preferably sulfuric acid. When Simon's reagent is used as the color reagent, the acidic reagent is preferably nitric acid, sulfuric acid, hydrochloric acid, acetic acid, or phosphoric acid, and more preferably acetic acid or phosphoric acid. When the Scott test is used as the color reagent, the acidic reagent is preferably nitric acid, sulfuric acid, hydrochloric acid, acetic acid, or phosphoric acid, and more preferably hydrochloric acid.

[0037] The mixing ratio of the acidic reagent to the color reagent (acidic reagent / color reagent) is preferably 0.1 to 10 times by mass, more preferably 0.2 to 5 times by mass, and even more preferably 0.5 to 2 times by mass. If the mixing ratio of the acidic reagent to the color reagent is equal to or greater than the lower limit, the reaction between the carbon dioxide absorbent and the color reagent contained in the cement powder proceeds sufficiently. If the mixing ratio of the acidic reagent to the color reagent is equal to or less than the upper limit, the carbon dioxide absorbent is not diluted or dissolved by the acidic reagent, and the color state of the mixture can be easily confirmed.

[0038] "The third step" In the third step, the color state of the mixture is confirmed.

[0039] Methods for confirming the colored state of the mixture include, for example, a visual confirmation method and a method for measuring absorbance using an absorptiometer (for example, GL SPECTIS 5.0 Touch manufactured by GL Optic).

[0040] In the color reaction of an amine compound, color occurs due to a chemical reaction or a complex formation reaction between a color reagent and the amine compound. Therefore, the chemical reaction and the complex formation reaction are inhibited by cations (e.g., calcium ions, magnesium ions, sodium ions) and anions (e.g., chloride ions, hydroxide ions) contained in the hardened cement body. In the detection method of an amine compound of this embodiment, focusing particularly on the fact that the color reaction is inhibited by the hydroxide ions contained in the hardened cement body, the color reaction of the amine compound in the hardened cement body can be realized by mixing a color reagent and an appropriate acidic reagent with the cement powder. In addition, since a precipitate (e.g., a black precipitate) is generated in the chemical reaction or the complex formation reaction between the color reagent and the amine compound, the color state can be confirmed visually.

[0041] According to the method for detecting an amine compound of the present embodiment, a cement powder obtained by pulverizing a hardened cement body is mixed with an acidic reagent and a color reagent to prepare a mixture, and the color state of the mixture is confirmed, thereby making it possible to easily grasp on-site whether or not the hardened cement body contains an amine compound and the amount of the amine compound contained therein.

[0042] According to the method for detecting an amine compound of the present embodiment, by using an appropriate acidic reagent in addition to a color reagent, it is possible to detect an amine compound (carbon dioxide absorbent) contained in a hardened cement body that is strongly basic and contains a large amount of impurity ion components.

[0043] According to the method for detecting an amine compound of the present embodiment, it is possible to create a color sample showing the content of the amine compound in a hardened cement body by correlating the content of the amine compound with the color state of a mixture containing cement powder, an acidic reagent, and a color reagent. EXAMPLES

[0044] The present invention will be described in more detail below with reference to experimental examples, but the present invention is not limited to the following experimental examples.

[0045] [Experimental Example] The tertiary amine N-methyldiethanolamine (MDEA) was used as the amine compound, the Dragendorff reagent was used as the color reagent, and concentrated hydrochloric acid (12N) was used as the acidic reagent. Cement paste containing an amine compound was ground in a mortar and mixed with a color reagent and an acidic reagent on a coloring dish, and the coloring state was judged based on the presence or absence of black precipitate. In judging the coloring state, if no black precipitate was observed, it was rated as "-", if black precipitate was observed, it was rated as "+", and if a large amount of black precipitate was observed, it was rated as "++". The results are shown in Tables 1 and 2 and Figure 1.

[0046] [Table 1]

[0047] [Table 2]

[0048] The results of the coloring test using the color reagent and the acidic reagent are shown in Table 1. In this test, black precipitates were formed only when 100 μL each of the color reagent and the acidic reagent was added. The results of the color test according to the content of the amine compound in the cement powder are shown in Table 2 and Figure 1. In Figure 1, Experimental Example 9, Experimental Example 10, Experimental Example 11, and Experimental Example 12 are shown from the left. In this study, black precipitate was confirmed only when the mixing water contained 1 volume % and 5 volume % of the amine compound, and the amount was larger at 5 volume % compared to 1 volume %.

Claims

1. A first step of pulverizing the hardened cement body to obtain cement powder; A second step of mixing the cement powder, the acidic reagent, and the color reagent to obtain a mixture containing the cement powder, the acidic reagent, and the color reagent; and a third step of confirming the color state of the mixture.

2. 2. The method for detecting an amine compound according to claim 1, wherein in the second step, after mixing the cement powder with the acidic reagent, the color reagent is further mixed therewith.

3. 2. The method for detecting an amine compound according to claim 1, wherein the cement powder has an average particle size of 80 μm or more and 150 μm or less.

4. 2. The method for detecting an amine compound according to claim 1, wherein the acidic reagent is at least one selected from the group consisting of nitric acid, sulfuric acid, hydrochloric acid, acetic acid and phosphoric acid.

5. 2. The method for detecting an amine compound according to claim 1, wherein the amount of the acidic reagent added is 0.1 to 10 times the mass of the mixture of the cement powder and water.

6. 2. The method for detecting an amine compound according to claim 1, wherein the color reagent is at least one selected from the group consisting of a ninhydrin reagent, a Dragendorff reagent, a Marquis reagent, a Simon reagent, and a Scott test.

7. 2. The method for detecting an amine compound according to claim 1, wherein the amount of the color reagent added is 0.1 to 10 times the mass of the mixture of the cement powder and water.

8. 8. The method for detecting an amine compound according to claim 7, wherein the amount of the color reagent added is 0.2 to 5 times the mass of the mixture of the cement powder and water.

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