Alkali-silica reaction-inhibiting material, method for producing alkali-silica reaction-inhibiting material, and method for inhibiting alkali-silica reaction

Abstract

To provide an alkali-silica reaction-inhibiting material capable of being produced in a short time without using an expensive lithium-based material and having excellent alkali-silica reaction-inhibiting effect, a method for producing the alkali-silica reaction-inhibiting material, and a method for inhibiting an alkali-silica reaction.SOLUTION: This invention relates to: an alkali-silica reaction-inhibiting material in which at least a part of alkali ions of natural zeolite are ion-exchanged to hydrogen ions by acid treatment; and a method for producing the alkali-silica reaction inhibiting material, comprising ion-exchanging the alkali ions to hydrogen ions by the acid treatment of the natural zeolite.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an alkali-silica reaction-inhibiting material used to inhibit alkali-silica reaction (ASR) in concrete or mortar, a method for producing the alkali-silica reaction-inhibiting material, and a method for inhibiting alkali-silica reaction. [Background technology]

[0002] Alkali-silica reaction (ASR) is a chemical reaction between the silica components in the aggregate of concrete or mortar and an alkaline solution. This reaction causes localized volume expansion in the concrete or mortar structure, resulting in cracking and deterioration of the structure. To inhibit the alkali-silica reaction that causes this cracking, alkali-silica reaction inhibitors have traditionally been used.

[0003] Examples of alkali-silica reaction inhibitors include lithium nitrite solution or lithium-containing lithium-type zeolite, which are injected into concrete structures to inhibit the alkali-silica reaction and prevent cracking. Patent Document 1 discloses a method for producing lithium-type zeolite by adding an aqueous solution of lithium hydroxide to metakaolin, which is obtained by calcining and activating kaolinite, a natural clay mineral, and allowing the reaction to occur at a low temperature of 20°C to 50°C.

[0004] Furthermore, Patent Document 2 discloses a method for producing an alkali-silica reaction-inhibiting material that does not require the use of expensive lithium-based materials, and includes a first step of obtaining an alkali ion-type hardened body through a polymerization reaction caused by mixing an alkaline agent with an amorphous material containing silica and alumina, and a second step of powdering the alkali ion-type hardened body and then acid-treating the powdered alkali ion-type hardened body to exchange the alkali ions for hydrogen ions. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5594710 [Patent Document 2] Patent No. 5739296 Summary of the Invention [Problem to be solved by the invention]

[0006] However, conventional methods using lithium nitrite solution as an alkali-silica reaction inhibitor are prone to soil and groundwater contamination by nitrite, which is undesirable as it causes environmental problems. On the other hand, conventional methods using lithium-type zeolite have the problem of being costly and impractical because lithium-based materials are expensive. The production of lithium-type zeolite described in Patent Document 1 requires a long reaction time (e.g., 168 hours) in a low-temperature environment where temperature control is relatively difficult.

[0007] Furthermore, in the method for producing an alkali-silica reaction-inhibiting material described in Patent Document 2, after the alkali ion-type hardened body is produced, it is necessary to pulverize it before the acid treatment, which increases the production cost.

[0008] The present invention has been made in consideration of the above problems, and aims to provide an alkali-silica reaction-inhibiting material, a method for producing an alkali-silica reaction-inhibiting material, and a method for inhibiting an alkali-silica reaction, which do not require the use of expensive lithium-based materials, can be produced in a short time, and have an excellent effect of inhibiting the alkali-silica reaction. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention employs the following configuration. [1] An alkali-silica reaction inhibitor material having the crystalline structure of natural zeolite, An alkali-silica reaction-inhibiting material in which at least a portion of the alkali ions in natural zeolite have been ion-exchanged with hydrogen ions through acid treatment. [2] The alkali-silica reaction-inhibiting material according to [1], wherein the crystalline structure comprises a mordenite crystalline structure. [3] A method for producing the alkali-silica reaction-inhibiting material according to [1], comprising: treating natural zeolite with an acid to exchange alkali ions for hydrogen ions. [4] The method for producing an alkali-silica reaction-inhibiting material according to [3], wherein the natural zeolite includes mordenite. [5] A method for inhibiting alkali-silica reaction using the alkali-silica reaction-inhibiting material according to [1] or [2], A method for inhibiting alkali-silica reaction, comprising applying a cement paste containing the alkali-silica reaction-inhibiting material to a repair site of a concrete or mortar structure. [Effects of the Invention]

[0010] The present invention can provide an alkali-silica reaction-inhibiting material, a method for producing an alkali-silica reaction-inhibiting material, and a method for inhibiting an alkali-silica reaction, which can be produced in a short time without using expensive lithium-based materials and have an excellent effect of inhibiting the alkali-silica reaction. [Brief explanation of the drawings]

[0011] [Figure 1] X-ray diffraction charts of the natural zeolite used in Experimental Example 1 and the acid-treated natural zeolite obtained in Experimental Example 1 [Figure 2] X-ray diffraction charts of the natural zeolite used in Experimental Example 1 and the acid-treated natural zeolite obtained in Experimental Example 1 [Figure 3] X-ray diffraction chart of natural zeolite used in Experimental Example 2 [Figure 4] X-ray diffraction chart of acid-treated natural zeolite obtained in Experimental Example 2 [Figure 5] Scanning electron microscope image of natural zeolite used in Experimental Example 2 [Figure 6] Scanning electron microscope photograph of acid-treated natural zeolite obtained in Experimental Example 2 [Figure 7]A perspective view of mortar specimen 1 used in the ASR suppression test in Experimental Example 3 [Figure 8] Graph showing the results of the expansion rate of the ASR inhibition test in Experimental Example 3 [Figure 9] Graph showing the results of the mass change rate in the ASR inhibition test of Experimental Example 3 DETAILED DESCRIPTION OF THE INVENTION

[0012] [Alkali-silica reaction inhibitor] The alkali-silica reaction-inhibiting material of this embodiment is an alkali-silica reaction-inhibiting material having the crystalline structure of natural zeolite, in which at least a portion of the alkali ions of the natural zeolite have been ion-exchanged with hydrogen ions by acid treatment.

[0013] Natural zeolite is a natural mineral formed when volcanic ash produced by volcanic activity is transformed under high pressure in the presence of water. It contains sodium and potassium elements within its porous crystalline structure of Si-O-Al-O-Si, in which silicon and aluminum are bonded via oxygen.

[0014] The ratio of the equivalent alkali amount to the silicon oxide equivalent mass (SiO2) of natural zeolite is in the range of 0.040 to 0.051. Here, the ratio of the equivalent alkali amount to the silicon oxide equivalent mass (SiO2) is calculated by fluorescent X-ray quantitative analysis to calculate the silicon oxide equivalent mass (SiO2), sodium oxide equivalent mass (Na2O), and potassium oxide equivalent mass (KO) and then obtained from the following formula. (Na2O+0.658K2O) / SiO2 In contrast, the ratio of the equivalent alkali amount to the silicon oxide equivalent mass (SiO2) of the alkali-silica reaction-inhibiting material of this embodiment [(Na2O+0.658K2O) / SiO2] is preferably in the range of 0.007 to 0.035, more preferably in the range of 0.007 to 0.031, and even more preferably in the range of 0.015 to 0.030. When the equivalent alkali amount is equal to or less than the upper limit, the alkali-silica reaction is inhibited effectively, and when the equivalent alkali amount is equal to or more than the lower limit, the crystal structure of the natural zeolite is easily maintained.

[0015] When the alkali-silica reaction-inhibiting material of this embodiment is applied to a concrete or mortar structure to be repaired, it is believed that alkali ions in the concrete or mortar are exchanged for hydrogen ions in the alkali-silica reaction-inhibiting material of this embodiment, thereby inhibiting the alkali-silica reaction. By inhibiting the alkali-silica reaction, it is possible to inhibit the expansion of the concrete or mortar structure and prevent cracks caused by the expansion.

[0016] The alkali-silica reaction-inhibiting material of this embodiment has the crystal structure of natural zeolite. Examples of the crystal structure of natural zeolite include mordenite and clinoptilolite. The crystal structure preferably includes the crystal structure of mordenite.

[0017] [Method of manufacturing alkali-silica reaction inhibitor] The method for producing the alkali-silica reaction-inhibiting material of this embodiment includes treating natural zeolite with an acid to exchange alkali ions for hydrogen ions.

[0018] Acid treatment is carried out by placing natural zeolite in an acid of a specified concentration, stirring for a specified time, filtering, and washing the filtrate. The acid used for acid treatment can be any of nitric acid, sulfuric acid, or hydrochloric acid. When sulfuric acid is used, residual sulfate ions can produce sulfide and sulfate substances, while when hydrochloric acid is used, residual chloride ions can produce chlorides, which can have a negative effect on concrete or mortar. Therefore, when using sulfuric or hydrochloric acid for acid treatment, it is important to thoroughly wash the material after the treatment.

[0019] By treating natural zeolite with acid, the alkali ions in the natural zeolite are exchanged with the hydrogen ions in the acid. Ion exchange can be easily performed by acid treatment, in which the natural zeolite is placed in acid and stirred.

[0020] In the method for producing an alkali-silica reaction-inhibiting material of this embodiment, the natural zeolite preferably includes mordenite. Many synthetic zeolites lose their crystalline structure and become amorphous when treated with acid. Natural zeolites including mordenite are available at low cost.

[0021] It is preferable that the natural mordenite is powdered and then treated with acid in the powder state. The 50% cumulative frequency diameter of the powdered natural mordenite, as determined by a laser diffraction / scattering method, is preferably 2 μm or more and 200 μm or less, more preferably 4 μm or more and 100 μm or less, and even more preferably 8 μm or more and 50 μm or less. When the 50% cumulative frequency diameter is equal to or more than the lower limit, the crystalline structure of the natural zeolite is easily maintained, and when the 50% cumulative frequency diameter is equal to or less than the upper limit, ion exchange with hydrogen ions can be performed by a short-term acid treatment.

[0022] The method for producing an alkali-silica reaction-inhibiting material according to the present embodiment does not require the use of expensive lithium-based materials, allowing for inexpensive production of the alkali-silica reaction-inhibiting material. Furthermore, because no lithium nitrite solution is used, soil and groundwater contamination by nitrite does not occur, which is a cause of environmental problems. Furthermore, the acid treatment for ion exchange can be completed in a short time of less than one hour, allowing for rapid production.

[0023] [Method for inhibiting alkali-silica reaction] The method for inhibiting alkali-silica reaction of this embodiment is a method for inhibiting alkali-silica reaction using the alkali-silica reaction-inhibiting material of the above embodiment, in which a cement paste containing the alkali-silica reaction-inhibiting material is applied to a repair location of a concrete or mortar structure.

[0024] For example, when a concrete or mortar structure has a crack with a width of 0.3 mm to 1.0 mm, the cement paste containing the alkali-silica reaction-inhibiting material of the above embodiment is injected. For example, when a concrete or mortar structure has a crack with a width exceeding 1.0 mm, the concrete or mortar structure is cut into a U- or V-shape along the crack, and the cement paste containing the alkali-silica reaction-inhibiting material of the above embodiment is filled into the U- or V-shaped cut. [Example]

[0025] The present invention will be specifically explained below by way of experimental examples, but the present invention is not limited to these examples.

[0026] [Experimental Example 1] Natural zeolite (mordenite, manufactured by Daifuku Kogyo Co., Ltd., particle size: less than 2 mm) was acid-treated with 1 to 9 M (mol / L) sulfuric acid, in a solid-liquid ratio of 1 g:50 g, at 60 to 70°C, and stirred for 10 minutes, then washed with water and dried (single acid treatment). A sample was also prepared by acid-treating it twice under the same conditions, washing with water, and drying. Table 1 shows the chemical composition (mass%) of untreated natural zeolite and the obtained acid-treated natural zeolite, determined by fluorescent X-ray quantitative analysis (Rigaku Corporation, ZSX Primus II, measured elements: Na to U), with elements with atomic numbers Na to U calculated as 100% oxide. Note that the total does not equal 100% because trace elements are excluded.

[0027] The ratio of the equivalent alkali amount to the silicon oxide equivalent mass (SiO2) of the natural zeolite used in Experimental Example 1 [(Na2O+0.658K2O) / SiO2] was 0.050.

[0028] In contrast, the ratio of the equivalent alkali amount to the silicon oxide equivalent mass (SiO2) of the alkali-silica reaction-inhibiting material (acid-treated natural zeolite) of Experimental Example 1 [(Na2O+0.658K2O) / SiO2] was reduced to the range of 0.023 to 0.031.

[0029] Although the amount of sodium and potassium components decreased after acid treatment, a certain amount remained even when the sulfuric acid was used at a high concentration. It was also confirmed that the amount of sulfur components increased when the number of treatments with high-concentration sulfuric acid was increased.

[0030] [Table 1]

[0031] FIG. 1 shows an X-ray diffraction chart of untreated natural zeolite and X-ray diffraction charts of acid-treated natural zeolite that was subjected to a single acid treatment with 1M, 3M, and 9M sulfuric acid. FIG. 2 shows an X-ray diffraction chart of untreated natural zeolite and an X-ray diffraction chart of acid-treated natural zeolite that had been treated twice with 1M, 3M, and 9M sulfuric acid. The X-ray diffraction patterns of all samples were identified as mordenite, clinoptilolite, and feldspar. The acid treatment did not significantly change the X-ray diffraction profiles, confirming that the so-called zeolite framework structure remained.

[0032] [Experimental Example 2] Natural zeolite (mordenite manufactured by Daifuku Kogyo Co., Ltd., 50% cumulative frequency diameter: 17.14 μm) was acid-treated with 9 M (mol / L) sulfuric acid, a solid-liquid ratio of 1 g:10 g, and stirred at 60°C for 60 minutes, washed with water, and dried. The 50% cumulative frequency diameter of natural zeolite was measured using a laser diffraction / scattering particle size distribution analyzer Partica LA-950V2 manufactured by Horiba, Ltd.

[0033] Table 2 shows the chemical compositions (mass %) of the untreated natural zeolite and the obtained acid-treated natural zeolite determined by fluorescent X-ray quantitative analysis.

[0034] The ratio of the equivalent alkali amount to the silicon oxide converted mass (SiO2) of the natural zeolite used in Experimental Example 2 [(Na2O+0.658K2O) / SiO2] was 0.044.

[0035] In contrast, the ratio of the equivalent alkali amount to the silicon oxide equivalent mass (SiO2) of the alkali-silica reaction-inhibiting material (acid-treated natural zeolite) of Experimental Example 2 [(Na2O+0.658K2O) / SiO2] was reduced to 0.016.

[0036] The acid treatment reduced the amounts of Na and K components and slightly increased the amount of S components, but because it was a single treatment, it was confirmed that the increase was not extreme. In Experimental Example 2, natural zeolite with a small particle size was acid treated, so the amounts of Na and K components after the single 3M acid treatment in Table 2 were lower than the values ​​after the single 3M acid treatment in Table 1.

[0037] [Table 2]

[0038] FIG. 3 is an X-ray diffraction chart of the natural zeolite used in Experimental Example 2. FIG. 4 is an X-ray diffraction chart of the acid-treated natural zeolite of Experimental Example 2, which was subjected to a single acid treatment with 3 M (mol / L) sulfuric acid. In Table 2, the chemical composition after the first 3M acid treatment showed a slight decrease in the amount of Al component, indicating that Al had been leached out by the acid treatment. However, there was no significant change in the X-ray diffraction profile, confirming that the zeolite framework structure was maintained.

[0039] FIG. 5 is a scanning electron microscope (SEM) photograph of the untreated natural zeolite used in Experimental Example 2. FIG. 6 is a scanning electron microscope (SEM) photograph of the acid-treated natural zeolite of Experimental Example 2, which was subjected to a single acid treatment with 3 M (mol / L) sulfuric acid. The acid treatment resulted in finer particles, and some aggregates were observed.

[0040] [Experimental Example 3] (ASR suppression test) The inhibitory effect of the acid-treated natural zeolite obtained in Experimental Example 2 on alkali-silica reaction (ASR) was investigated.

[0041] Figure 7 shows the mortar specimen 1 used in Experimental Example 3. Using reactive aggregate in which cristobalite is the main reactive mineral, and adjusting the alkali content (Na2O) to 1.6%, a rectangular block of mortar measuring 4 x 4 x 16 cm was prepared, and through holes 2 with a diameter of 6 mm were formed in 36 places (12 places in each row). Next, 40 parts by mass of the acid-treated natural zeolite obtained in Experimental Example 2 was added to 60 parts by mass of ultrafine particle cement, and water was added to make a mass ratio of W / P = 0.68 to prepare a cement paste. This cement paste was injected into all of the through holes 2, and the expansion rate and mass change rate over time up to 260 days after 24 hours had elapsed were measured using the following equations, with the number of days elapsed being 0.

[0042] Expansion rate = (length of mortar specimen at each elapsed day - length of mortar specimen at 0 days elapsed) / (length of mortar specimen at 0 days elapsed) x 100 Mass change rate = (mass of mortar specimen at each elapsed day - mass of mortar specimen at 0 days elapsed) / (mass of mortar specimen at 0 days elapsed) x 100

[0043] The measurement results of the expansion coefficient are shown as "H mordenite" in Figure 8. The measurement results of the mass change rate are shown as "H mordenite" in Figure 9.

[0044] For comparison, lithium-type EDI zeolite was prepared by adding a lithium hydroxide solution to metakaolin, which was activated by calcining kaolinite, a natural clay mineral, and reacting at 30°C for 24 hours. Forty parts by mass of the resulting lithium-type EDI zeolite was added to 60 parts by mass of ultrafine cement, and water was added to make a cement paste with a W / P ratio of 0.68. This cement paste was then poured into all through-holes 2, and the expansion rate and mass change rate over time were measured. The expansion rate measurement results are shown in Figure 8 as "Li-EDI." The mass change rate measurement results are shown in Figure 9 as "Li-EDI."

[0045] "No additives" in Figure 3 indicates that water was added to the ultrafine cement to make a mass ratio of W / P = 0.68 to form a cement paste, which was then poured into all of the through holes 2, and the expansion rate and mass change rate over time were measured. The measurement results for the expansion rate are shown in Figure 8 as "No additives." The measurement results for the mass change rate are shown in Figure 9 as "No additives."

[0046] The alkali-silica reaction-inhibiting material of the present invention has the crystalline structure of natural zeolite, and at least a portion of the alkali ions in natural zeolite have been ion-exchanged with hydrogen ions through acid treatment. When lithium-type EDI zeolite was added to ultrafine particle cement, both the expansion rate and mass change rate were smaller than when no lithium-type EDI zeolite was added, demonstrating a high inhibitory effect on alkali-silica reaction (ASR). The alkali-silica reaction-inhibiting material of this embodiment has at least a portion of the alkali ions in natural zeolite ion-exchanged with hydrogen ions through acid treatment, and also has the crystalline structure of natural zeolite, so the porous crystalline structure of Si-O-Al-O-Si is maintained, which is thought to be why it has such a great effect in inhibiting the alkali-silica reaction. [Industrial Applicability]

[0047] INDUSTRIAL APPLICABILITY The present invention can be used as an alkali-silica reaction-inhibiting material for inhibiting alkali-silica reaction in concrete or mortar. [Explanation of symbols]

[0048] 1...Mortar specimen 2...Through hole

Claims

1. An alkali-silica reaction-inhibiting material having a crystalline structure of natural zeolite, At least a portion of the alkali ions in the natural zeolite are ion-exchanged with hydrogen ions by acid treatment; An alkali-silica reaction-inhibiting material having a ratio of equivalent alkali amount to silicon oxide (SiO 2 ) in the range of 0.007 to 0.

031.

2. 2. The alkali-silica reaction-inhibiting material according to claim 1, wherein the crystalline structure comprises the crystalline structure of mordenite.

3. 2. The method for producing an alkali-silica reaction-inhibiting material according to claim 1, further comprising: treating natural zeolite with an acid to exchange alkali ions for hydrogen ions.

4. The method for producing an alkali-silica reaction-inhibiting material according to claim 3 , wherein the natural zeolite comprises mordenite.

5. A method for inhibiting alkali-silica reaction using the alkali-silica reaction-inhibiting material according to claim 1 or 2, comprising: A method for inhibiting alkali-silica reaction, comprising applying a cement paste containing the alkali-silica reaction-inhibiting material to a repair site of a concrete or mortar structure.

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