Method for determining the quality of steel fibers for concrete, and method for mixing steel fiber-reinforced concrete.
By immersing steel fiber bundles in dilute acids to assess dispersion, the method addresses the issue of insufficient steel fiber dispersion in concrete, ensuring high-quality dispersion and improved mechanical properties.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2021-12-09
- Publication Date
- 2026-03-19
AI Technical Summary
Existing methods for dispersing steel fibers in concrete are inadequate, leading to reduced mechanical properties due to insufficient dispersion, which is traditionally assessed through visual inspection and lacks a reliable quality control method.
A method involving immersing steel fiber bundles in dilute acids like hydrochloric, tartaric, or acetic acid to determine dispersion by checking the state of individual fibers, with specific concentration and pH ranges, followed by shaking and visual inspection.
Enables quick and simple determination of steel fiber dispersibility, ensuring high-quality dispersion in concrete, thereby improving mechanical properties.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to a method for determining the quality of steel fibers for concrete and a method for preparing steel fiber reinforced concrete.
Background Art
[0002] In order to improve the brittle fracture of concrete, steel fiber reinforced concrete containing 20 kg / m 3 ~80 kg / m 3 of steel fibers (with a diameter of 0.62 mm to 0.75 mm and a length of about 30 mm to 60 mm as single fibers) is known.
[0003] Generally, as steel fibers, in order to facilitate handling and suppress the generation of fiber balls in which the steel fibers become lumps, a plurality of (for example, 36) steel single fibers (steel monofilaments) are joined with a water-soluble adhesive and bundled (steel fiber bundle) is used (see, for example, Patent Document 1). When this steel fiber bundle and concrete are mixed by mixing with a mixer or stirring with an agitator truck, the adhesive melts and the impact by aggregates or the like is applied, so that the steel single fibers are dispersed from the steel fiber bundle and the steel single fibers are dispersed in the concrete.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0005] The adhesive that joins the steel fibers together may dissolve and then solidify again when wet or absorb moisture. When the adhesive solidifies again in this way, its adhesive strength becomes stronger. With the adhesive strength strengthened, even if the steel fiber bundle and concrete are mixed as described above, it becomes difficult to disperse the steel fibers from the bundle and then disperse them into the concrete. It is known that steel fiber-reinforced concrete with insufficient dispersion of steel fibers has reduced mechanical properties in terms of strength and toughness.
[0006] It would be beneficial to ensure the quality of steel fiber-reinforced concrete if the dispersion of individual steel fibers into the concrete could be confirmed before manufacturing, that is, while the steel fibers are still in bundle form. However, conventionally, the only method for confirming the dispersion of individual steel fibers has been to visually inspect the bundle of steel fibers.
[0007] Traditionally, there has been no method for determining the dispersibility of steel single fibers.
[0008] The present invention has been made in view of the above circumstances, and aims to provide a method for determining the quality of steel fibers for concrete, which can determine the dispersion of steel monofibers in concrete in a simple and short time, and a method for mixing steel fiber-reinforced concrete using the method for determining the quality of steel fibers for concrete. [Means for solving the problem]
[0009] The present invention has the following aspects. [1] A method for determining the quality of steel fibers for concrete, comprising immersing a bundle of steel fibers in dilute acid, shaking the dilute acid and the bundle of steel fibers, and then confirming the dispersion state of the single steel fibers constituting the bundle of steel fibers, The dilute acid is dilute hydrochloric acid, tartaric acid, or acetic acid. The aforementioned Dilute hydrochloric acid or the aforementioned tartaric acid The time for immersing the steel fiber bundle in the solution is 3 minutes or more. 5 Less than a minute the law of nature , The immersion time for the steel fiber bundle in the acetic acid is 5 minutes. A method for determining the quality of steel fibers used in concrete. [2] The above Dilute hydrochloric acid The concentration is 1% by mass or more. 5 Mass% or less The concentration of tartaric acid is 10% by mass, and the concentration of acetic acid is 10% by mass. The method for determining the quality of steel fibers for concrete, as described in [1]. [3] The above Dilute hydrochloric acid The pH is -0.16 or higher. 0.49 below The pH of the tartaric acid is 1.29, and the pH of the acetic acid is 2.02. The method for determining the quality of steel fibers for concrete, as described in [1] or [2]. [4] A method for mixing steel fiber reinforced concrete, comprising mixing cement, water, coarse aggregate, fine aggregate, chemical admixture, and steel fiber bundles, A method for mixing steel fiber-reinforced concrete, wherein the steel fiber bundles used are from lots that have passed the quality determination method for concrete steel fibers described in any of [1] to [3]. [Effects of the Invention]
[0010] According to the present invention, it is possible to provide a method for determining the quality of steel fibers for concrete, which can determine the dispersion of steel single fibers in concrete in a simple and short time, and a method for mixing steel fiber-reinforced concrete using the method for determining the quality of steel fibers for concrete. [Brief explanation of the drawing]
[0011] [Figure 1] This photograph shows a bundle of zinc-plated steel fibers immersed in 1% by mass dilute hydrochloric acid. [Figure 2] This photograph shows the dispersion state of normal zinc-plated steel fiber bundles after immersion in 1% by mass dilute hydrochloric acid. [Figure 3] This photograph shows the dispersion state of simulated degraded zinc-plated steel fiber bundles after immersion in 1% by mass dilute hydrochloric acid. [Figure 4] This photograph shows the dispersion state of normal zinc-plated steel fiber bundles after immersion in 3% by mass dilute hydrochloric acid. [Figure 5] This photograph shows the dispersion state of simulated degraded zinc-plated steel fiber bundles after immersion in 3% by mass dilute hydrochloric acid. [Figure 6]It is a photograph showing the dispersion state of a normal product of zinc-plated steel fiber bundles after immersion in 5 mass% dilute hydrochloric acid. [Figure 7] It is a photograph showing the dispersion state of a pseudo-deteriorated product of zinc-plated steel fiber bundles after immersion in 5 mass% dilute hydrochloric acid. [Figure 8] It is a photograph showing the state of a normal product of zinc-plated steel fiber bundles immersed in a 5 mass% (1.35 mol / L) aqueous sodium hydroxide solution. [Figure 9] It is a photograph showing the dispersion state of a normal product of zinc-plated steel fiber bundles after immersion in 3 mass% dilute sulfuric acid. [Figure 10] It is a photograph showing the dispersion state of a pseudo-deteriorated product of zinc-plated steel fiber bundles after immersion in 3 mass% dilute sulfuric acid. [Figure 11] It is a photograph showing the dispersion state of a normal product of zinc-plated steel fiber bundles after immersion in 10 mass% tartaric acid. [Figure 12] It is a photograph showing the dispersion state of a pseudo-deteriorated product of zinc-plated steel fiber bundles after immersion in 10 mass% tartaric acid. [Figure 13] It is a photograph showing the dispersion state of a normal product of zinc-plated steel fiber bundles after immersion in 10 mass% acetic acid. [Figure 14] It is a photograph showing the dispersion state of a pseudo-deteriorated product of zinc-plated steel fiber bundles after immersion in 10 mass% acetic acid. [Embodiments for Carrying Out the Invention]
[0012] Hereinafter, a method for determining the quality of steel fibers for concrete according to an embodiment of the present invention, and a method for preparing steel fiber reinforced concrete using the method for determining the quality of steel fibers for concrete will be described. Note that this embodiment is specifically described to better understand the gist of the invention, and does not limit the present invention unless otherwise specified.
[0013] [Method for Determining the Quality of Steel Fibers for Concrete] The method for determining the quality of steel fibers for concrete in this embodiment involves immersing a bundle of steel fibers in dilute acid, shaking the bundle of steel fibers with the dilute acid, and then checking the dispersion state of the steel single fibers constituting the bundle of steel fibers.
[0014] The concrete steel fiber quality determination method of this embodiment determines the dispersibility of steel single fibers in concrete by checking the dispersion state of the steel single fibers constituting the steel fiber bundle.
[0015] Examples of steel fiber bundles include those made by joining multiple single steel fibers (approximately 0.62 mm to 0.75 mm in diameter and 30 mm to 60 mm in length) with a water-soluble adhesive. In this steel fiber bundle, multiple single steel fibers are arranged parallel to each other in the planar direction, forming a rectangular bundle when viewed from above. The number of single steel fibers constituting a steel fiber bundle is usually a maximum of 36. The length of the steel fiber bundle is, for example, 30 mm to 60 mm. The width of the steel fiber bundle is, for example, 23 mm to 29 mm. The steel fiber bundle may also be a galvanized steel fiber bundle, which is a bundle of single steel fibers that have been coated with zinc.
[0016] Examples of dilute acids include dilute hydrochloric acid, dilute sulfuric acid, tartaric acid, and acetic acid. Among these, dilute hydrochloric acid is preferred from the viewpoint of being able to disperse the steel fiber bundles into individual steel single fibers at a low concentration.
[0017] For containers to hold the steel fiber bundles and dilute acid, for example, lidded sample vials, beakers, flasks, etc., can be used. Since hydrogen gas is generated when the steel fiber bundles are immersed in dilute acid, it is preferable to use lidded reagent bottles as containers. The containers may be made of glass or plastic such as polyethylene.
[0018] An arbitrary amount of dilute acid is injected into the container. The arbitrary amount is not particularly limited, but it is preferable that the mass be 20 times or more the mass of the steel fiber bundle. When dealing with a steel fiber bundle that is 30 mm to 60 mm in length, 23 mm to 29 mm in width, and has 36 single steel fibers, the volume of dilute acid is usually about 50 mL to 100 mL.
[0019] The concentration of the dilute acid is preferably 1% by mass or more and 15% by mass or less. If the dilute acid is dilute hydrochloric acid or dilute sulfuric acid, its concentration is more preferably 1% by mass or more and 5% by mass or less. If the dilute acid is tartaric acid or acetic acid, its concentration is more preferably 10% by mass or more and 15% by mass or less. If the concentration of the dilute acid is above the lower limit above, the steel fiber bundles can be dispersed into individual steel single fibers. If the concentration of the dilute acid is below the upper limit above, there is a possibility that even deteriorated steel fiber bundles can be dispersed into individual steel single fibers.
[0020] The pH of the dilute acid is preferably between -0.16 and 2.02. If the dilute acid is dilute hydrochloric acid or dilute sulfuric acid, the pH is preferably between -0.16 and 0.49. If the dilute acid is tartaric acid or acetic acid, the pH is preferably between 1.29 and 2.02. If the pH of the dilute acid is above the lower limit, the steel fiber bundles can be dispersed into individual steel fibers. If the pH of the dilute acid is below the upper limit, there is a possibility that even deteriorated steel fiber bundles can be dispersed into individual steel fibers.
[0021] The immersion time of the steel fiber bundles in dilute acid (hereinafter referred to as "immersion time") is adjusted according to the pH of the dilute acid. The appropriate immersion time for determining the dispersibility of the steel fiber bundles differs depending on the pH of the dilute acid. The appropriate immersion time for determining the dispersibility of the steel fiber bundles is the time during which the steel fiber bundles can be distinguished between normal products and defective products (including pseudo-degraded products, as described later) by immersing them in dilute acid. A normal product is one in which, when the steel fiber bundle is mixed with concrete, the individual steel fibers can be dispersed from the steel fiber bundle and dispersed into the concrete. In contrast, a defective product is one in which, when the steel fiber bundle is mixed with concrete, the individual steel fibers cannot be dispersed from the steel fiber bundle and dispersed into the concrete. The immersion time is preferably 3 minutes or more and 5 minutes or less, and more preferably 4 minutes or more and 5 minutes or less. If the immersion time is above the lower limit, the steel fiber bundles can be dispersed into individual steel single fibers. If the immersion time is below the upper limit, there is a possibility that even deteriorated steel fiber bundles can be dispersed into individual steel single fibers. If the pH of the dilute acid is 0.1 or less, the immersion time is preferably 3 minutes. If the pH of the dilute acid is greater than 0.1 and 2.0 or less, the immersion time is preferably 3 minutes or more and 5 minutes or less, and more preferably 4 minutes or more and 5 minutes or less.
[0022] After immersing the steel fiber bundles in dilute acid for a predetermined time, the dilute acid and steel fiber bundles are shaken. Specifically, the container holding the steel fiber bundles and dilute acid is shaken.
[0023] The time for shaking the dilute acid and the steel fiber bundle (hereinafter referred to as "shaking time") is preferably 5 seconds or more and 60 seconds or less, and more preferably 10 seconds or more and 30 seconds or less. When the shaking time is within the above range, the steel fiber bundle can be dispersed into individual steel single fibers. If the shaking time exceeds the above upper limit, it becomes difficult to disperse the steel fiber bundle into individual steel single fibers.
[0024] There are no particular limitations on the method for shaking the dilute acid and the steel fiber bundle, but examples include shaking a container containing the steel fiber bundle and dilute acid using a shaker, shaking the steel fiber bundle and dilute acid contained in a container using an ultrasonic cleaner, and shaking the container containing the steel fiber bundle and dilute acid by hand.
[0025] Furthermore, when steel fiber bundles are immersed in dilute acid, hydrogen gas originating from the dilute acid is generated. When the generation of this hydrogen gas ceases, it indicates that the immersion time has been sufficient.
[0026] After the shaking of the dilute acid and steel fiber bundle is complete, it is preferable to remove the steel single fibers from the dilute acid and wash off any dilute acid adhering to them with water. Washing off the dilute acid with water makes it easier to check the dispersion state of the steel single fibers. For the water source, purified water, deionized water, or tap water can be used.
[0027] The method for washing steel monofilaments with water is not particularly limited, but examples include rinsing the steel monofilaments with running water, spraying water onto the steel monofilaments, and agitating the steel monofilaments in water.
[0028] After the shaking of the dilute acid and steel fiber bundles is completed, or after the washing of the steel fibers with water is completed, the dispersion state of the steel fibers is visually checked. If the steel fiber bundles are completely dispersed in each individual steel fiber, the steel fibers can be dispersed in the concrete when the steel fiber bundles are mixed or combined with concrete. In other words, the steel fibers have excellent dispersibility, and the steel fiber bundle composed of those steel fibers can be judged as a good product. On the other hand, if the steel fiber bundles are not completely dispersed in each individual steel fiber, the steel fibers cannot be dispersed in the concrete when the steel fibers are mixed or combined with concrete. In other words, the steel fibers have poor dispersibility, and the steel fiber bundle composed of those steel fibers can be judged as a defective product.
[0029] It is preferable to perform quality assessment of steel fiber bundles for each lot. A lot of steel fiber bundles is, for example, one bag containing 20 kg of steel fiber bundles. Three steel fiber bundles are randomly selected from this bag, and the above quality assessment is performed on these bundles. If even one defective product is found during the quality assessment, the entire lot is judged to be defective, and that lot is not used in the manufacture of steel fiber reinforced concrete.
[0030] According to the concrete steel fiber quality determination method of this embodiment, the steel fiber bundle is immersed in dilute acid, the dilute acid and the steel fiber bundle are shaken, and then the dilute acid is washed off with water to confirm the dispersion state of the steel single fibers constituting the steel fiber bundle. Therefore, the dispersibility of steel single fibers in concrete can be determined simply and quickly.
[0031] [Mixing method for steel fiber reinforced concrete] The concrete mixing method of this embodiment is a method for mixing steel fiber-reinforced concrete, which involves mixing cement, water, coarse aggregate, fine aggregate, chemical admixture, and steel fiber bundles, wherein the steel fiber bundles used are from lots that have passed the quality determination method for concrete steel fibers of the above embodiment.
[0032] In the concrete mixing method for steel fiber reinforced concrete of this embodiment, first, all materials other than the additives (cement, water, coarse aggregate, fine aggregate, and chemical admixtures) are put into a mixer and mixed to prepare the base concrete. Next, the base concrete is discharged into a truck agitator vehicle, and the additives are added to the base concrete and mixed. Then, steel fiber bundles from lots that have passed the quality determination method for concrete steel fibers of the above embodiment are added to the base concrete to which the additives have been added, and after the addition is complete, a predetermined mixing is performed with high-speed stirring (for example, 15 rpm). By adjusting the high-speed stirring time, the dispersion rate of the steel fiber bundles is brought within the desired range.
[0033] As for the cement, moderate-heat Portland cement and low-heat Portland cement are preferred due to their low heat of hydration.
[0034] Examples of coarse aggregates include crushed hard sandstone, crushed andesite, and crushed rhyolite.
[0035] Examples of fine aggregates include crushed sand, mountain sand, and land sand.
[0036] The chemical admixture includes at least one of a high-performance water-reducing agent and a high-performance AE water-reducing agent (hereinafter collectively referred to as "high-performance (AE) water-reducing agent") and a thickening agent. The chemical admixture may, if necessary, contain other chemical admixtures, provided that they do not impair the effects of the present invention. High-performance (AE) water-reducing agents are used to improve the workability of the steel fiber-reinforced concrete in this embodiment. The definitions of high-performance water-reducing agents and high-performance AE water-reducing agents are in accordance with JIS A 6204. Examples of high-performance water-reducing agents include those whose main component is a polycarboxylic acid ether, and those whose main component is a polycarboxylate copolymer. Examples of high-performance AE water-reducing agents include those whose main component is polycarboxylic acid-based.
[0037] Although the present invention has been described above with reference to embodiments, the present invention is not limited to the above embodiments. The configurations and combinations thereof in the above embodiments are examples, and additions, omissions, substitutions, and other modifications are possible without departing from the spirit of the present invention. [Examples]
[0038] 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.
[0039] [Experimental Example 1] For the steel fiber bundle, galvanized steel fiber bundles (normal products) were prepared. As the galvanized steel fiber bundle, 36 individual galvanized steel fibers (hereinafter referred to as "galvanized steel single fibers"; diameter: 0.61 mm, length: 30 mm) were joined together with adhesive, and the 36 galvanized steel single fibers were arranged parallel to each other, forming a rectangular bundle with a length of 30 mm and a width of 23 mm in plan view. As the dilute acid, a 1% by mass dilute hydrochloric acid (pH 0.49) was used, which was obtained by diluting 36% by mass hydrochloric acid with pure water. The pH of the dilute acid was measured using a glass electrode type hydrogen ion concentration indicator (HORIBA, model: D-71). 25 mL of dilute hydrochloric acid was poured into a 30 mL glass sample vial. As shown in Figure 1, 2.5 (2.54) g of zinc-plated steel fiber bundles were immersed in dilute hydrochloric acid in a sample vial, and the vial was then capped. When the zinc-plated steel fiber bundles were immersed in dilute hydrochloric acid, bubbles (hydrogen gas) were generated. After immersing the steel fiber bundle in dilute hydrochloric acid for 1 minute, the dilute hydrochloric acid and steel fiber bundle in the sample vial were shaken. Next, the zinc-plated steel fiber bundles were removed from the dilute acid, and the dilute acid adhering to the zinc-plated steel fiber bundles was washed off with running water. Next, the dispersion state of the galvanized steel fiber bundles was visually inspected. A "○" indicated that the dispersion state of the galvanized steel fiber bundles could be determined, a "×" indicated that the dispersion state could not be determined, and a "△" indicated that it may not be possible to clearly determine the dispersion state of the galvanized steel fiber bundles depending on the degree of deterioration of the galvanized steel fiber bundles. The results are shown in Table 1 and Figure 2.
[0040] [Experimental Example 2] The dispersion state of the zinc-plated steel fiber bundles (normal product) was confirmed in the same manner as in Experimental Example 1, except that the immersion time was set to 3 minutes. The results are shown in Table 1 and Figure 2.
[0041] [Experimental Example 3] The dispersion state of the zinc-plated steel fiber bundles (normal product) was confirmed in the same manner as in Experimental Example 1, except that the immersion time was set to 5 minutes. The results are shown in Table 1 and Figure 2.
[0042] [Experimental Example 4] As a simulated example of deteriorated steel fiber bundles, the above-mentioned galvanized steel fiber bundles were immersed in water and then dried. This simulated deteriorated product was intended to simulate the state in which the adhesive of the galvanized steel fiber bundle dissolves due to moisture, etc., and then re-solidifies. The dispersion state of the zinc-plated steel fiber bundle (simulated degradation product) was confirmed in the same manner as in Experimental Example 1, except that the above-mentioned simulated degradation product was used. The results are shown in Table 1 and Figure 3.
[0043] [Experimental Example 5] Aside from using the simulated degraded material described above, the dispersion state of the zinc-plated steel fiber bundle (simulated degraded material) was confirmed in the same manner as in Experimental Example 2. The results are shown in Table 1 and Figure 3.
[0044] [Experimental Example 6] Aside from using the simulated degraded material described above, the dispersion state of the zinc-plated steel fiber bundle (simulated degraded material) was confirmed in the same manner as in Experimental Example 3. The results are shown in Table 1 and Figure 3.
[0045] [Table 1]
[0046] The results shown in Table 1 and Figure 2 confirm that when normal zinc-plated steel fiber bundles were immersed in 1% by mass dilute hydrochloric acid, the steel fiber bundles did not disperse into individual steel fibers after immersion for 1 minute, but after immersion for 3 to 5 minutes, the steel fiber bundles were completely dispersed into individual steel fibers. On the other hand, the results shown in Table 1 and Figure 3 confirm that when a simulated degraded sample of zinc-plated steel fiber bundles was immersed in 1% by mass dilute hydrochloric acid, the steel fiber bundles did not disperse into individual steel single fibers when the immersion time was between 1 and 5 minutes. Furthermore, when steel fiber reinforced concrete is manufactured using a simulated deteriorated product, the dispersion rate of steel single fibers in the steel fiber reinforced concrete (test results by wash analysis) is 39.9% by mass, resulting in a decrease in the bending strength and bending toughness of the steel fiber reinforced concrete.
[0047] [Experimental Example 7] The dispersion state of zinc-plated steel fiber bundles (normal products) was confirmed in the same manner as in Experimental Example 1, except that the dilute hydrochloric acid concentration was set to 3% by mass (pH 0.05). The results are shown in Table 2 and Figure 4.
[0048] [Experimental Example 8] The dispersion state of zinc-plated steel fiber bundles (normal products) was confirmed in the same manner as in Experimental Example 2, except that the dilute hydrochloric acid concentration was set to 3% by mass. The results are shown in Table 2 and Figure 4.
[0049] [Experimental Example 9] The dispersion state of zinc-plated steel fiber bundles (normal products) was confirmed in the same manner as in Experimental Example 3, except that the dilute hydrochloric acid concentration was set to 3% by mass. The results are shown in Table 12 and Figure 4.
[0050] [Experimental Example 10] The dispersion state of the zinc-plated steel fiber bundle (simulated degraded product) was confirmed in the same manner as in Experimental Example 4, except that the dilute hydrochloric acid concentration was set to 3% by mass. The results are shown in Table 2 and Figure 5.
[0051] [Experimental Example 11] The dispersion state of the zinc-plated steel fiber bundle (simulated degraded product) was confirmed in the same manner as in Experimental Example 5, except that the dilute hydrochloric acid concentration was set to 3% by mass. The results are shown in Table 2 and Figure 5.
[0052] [Experimental Example 12] The dispersion state of the zinc-plated steel fiber bundle (simulated degraded product) was confirmed in the same manner as in Experimental Example 6, except that the dilute hydrochloric acid concentration was set to 3% by mass. The results are shown in Table 2 and Figure 5.
[0053] [Table 2]
[0054] The results shown in Table 2 and Figure 4 confirm that when normal zinc-plated steel fiber bundles were immersed in 3% by mass dilute hydrochloric acid, the fiber bundles did not disperse into individual steel fibers after immersion for 1 minute, but after immersion for 3 to 5 minutes, the fiber bundles were completely dispersed into individual steel fibers. On the other hand, the results shown in Table 2 and Figure 5 indicate that when a simulated degraded sample of zinc-plated steel fiber bundles was immersed in 3% by mass dilute hydrochloric acid, the steel fiber bundles did not disperse into individual steel fibers when the immersion time was 1 to 3 minutes, but when the immersion time was 5 minutes, the steel fiber bundles were almost completely dispersed into individual steel fibers.
[0055] [Experimental Example 13] The dispersion state of zinc-plated steel fiber bundles (normal products) was confirmed in the same manner as in Experimental Example 1, except that the dilute hydrochloric acid concentration was set to 5% by mass (pH -0.16). The results are shown in Table 3 and Figure 6.
[0056] [Experimental Example 14] The dispersion state of zinc-plated steel fiber bundles (normal products) was confirmed in the same manner as in Experimental Example 2, except that the dilute hydrochloric acid concentration was set to 5% by mass. The results are shown in Table 3 and Figure 6.
[0057] [Experimental Example 15] The dispersion state of zinc-plated steel fiber bundles (normal products) was confirmed in the same manner as in Experimental Example 3, except that the dilute hydrochloric acid concentration was set to 5% by mass. The results are shown in Table 3 and Figure 6.
[0058] [Experimental Example 16] The dispersion state of the zinc-plated steel fiber bundle (simulated degraded product) was confirmed in the same manner as in Experimental Example 4, except that the dilute hydrochloric acid concentration was set to 5% by mass. The results are shown in Table 3 and Figure 7.
[0059] [Experimental Example 17] The dispersion state of the zinc-plated steel fiber bundle (simulated degraded product) was confirmed in the same manner as in Experimental Example 5, except that the dilute hydrochloric acid concentration was set to 5% by mass. The results are shown in Table 3 and Figure 7.
[0060] [Experimental Example 18] The dispersion state of the zinc-plated steel fiber bundle (simulated degraded product) was confirmed in the same manner as in Experimental Example 6, except that the dilute hydrochloric acid concentration was set to 5% by mass. The results are shown in Table 3 and Figure 7.
[0061] [Table 3]
[0062] The results shown in Table 3 and Figure 6 indicate that when normal zinc-plated steel fiber bundles were immersed in 5% by mass dilute hydrochloric acid, the fiber bundles did not disperse into individual steel fibers after immersion for 1 minute, but after immersion for 3 to 5 minutes, the fiber bundles were completely dispersed into individual steel fibers. On the other hand, the results shown in Table 3 and Figure 7 confirm that when a simulated degraded galvanized steel fiber bundle was immersed in 5% by mass dilute hydrochloric acid, the steel fiber bundle did not disperse into individual steel fibers when the immersion time was 1 to 3 minutes, but when the immersion time was 5 minutes, the steel fiber bundle was almost completely dispersed into individual steel fibers.
[0063] [Experimental Example 19] The dispersion state of zinc-plated steel fiber bundles (normal products) was confirmed in the same manner as in Experimental Example 1, except that a 5% by mass (1.35 mol / L) sodium hydroxide aqueous solution was used instead of dilute hydrochloric acid, and the immersion time of the zinc-plated steel fiber bundles in the sodium hydroxide aqueous solution was set to 24 hours (1440 minutes). As a result, as shown in Figure 8, no bubbles were generated when the zinc-plated steel fiber bundles were immersed in an aqueous sodium hydroxide solution. In other words, the adhesive of the zinc-plated steel fiber bundles did not dissolve in the aqueous sodium hydroxide solution. Consequently, the steel fiber bundles were not dispersed into individual steel fibers.
[0064] [Experimental Example 20] The dispersion state of zinc-plated steel fiber bundles (normal products) was confirmed in the same manner as in Experimental Example 1, except that ethanol was used instead of dilute hydrochloric acid, and the immersion time of the zinc-plated steel fiber bundles in ethanol was set to 24 hours (1440 minutes). As a result, no bubbles were generated when the zinc-plated steel fiber bundles were immersed in ethanol. In other words, the adhesive of the zinc-plated steel fiber bundles did not dissolve in the ethanol. Consequently, the steel fiber bundles did not disperse into individual steel fibers.
[0065] [Experimental Example 21] The dispersion state of zinc-plated steel fiber bundles (normal products) was confirmed in the same manner as in Experimental Example 1, except that acetone was used instead of dilute hydrochloric acid, and the immersion time of the zinc-plated steel fiber bundles in acetone was set to 24 hours (1440 minutes). As a result, no bubbles were generated when the zinc-plated steel fiber bundles were immersed in acetone. In other words, the adhesive of the zinc-plated steel fiber bundles did not dissolve in the acetone. Consequently, the steel fiber bundles did not disperse into individual steel fibers.
[0066] [Experimental Example 22] The dispersion state of zinc-plated steel fiber bundles (normal products) was confirmed in the same manner as in Experimental Example 1, except that methanol was used instead of dilute hydrochloric acid, and the immersion time of the zinc-plated steel fiber bundles in methanol was set to 24 hours (1440 minutes). As a result, no bubbles were generated when the zinc-plated steel fiber bundles were immersed in methanol. In other words, the adhesive of the zinc-plated steel fiber bundles did not dissolve in methanol. Consequently, the steel fiber bundles were not dispersed into individual steel fibers.
[0067] [Experimental Example 23] The dispersion state of zinc-plated steel fiber bundles (normal products) was confirmed in the same manner as in Experimental Example 1, except that 3% by mass of dilute sulfuric acid (pH 0.20) was used instead of dilute hydrochloric acid. The results are shown in Table 4 and Figure 9.
[0068] [Experimental Example 24] The dispersion state of zinc-plated steel fiber bundles (normal products) was confirmed in the same manner as in Experimental Example 2, except that 3% by mass of dilute sulfuric acid was used instead of dilute hydrochloric acid. The results are shown in Table 4 and Figure 9.
[0069] [Experimental Example 25] The dispersion state of zinc-plated steel fiber bundles (normal products) was confirmed in the same manner as in Experimental Example 3, except that 3% by mass of dilute sulfuric acid was used instead of dilute hydrochloric acid. The results are shown in Table 4 and Figure 9.
[0070] [Experimental Example 26] The dispersion state of the zinc-plated steel fiber bundles (simulated degraded product) was confirmed in the same manner as in Experimental Example 4, except that 3% by mass of dilute sulfuric acid was used instead of dilute hydrochloric acid. The results are shown in Table 4 and Figure 10.
[0071] [Experimental Example 27] The dispersion state of the zinc-plated steel fiber bundle (simulated degraded product) was confirmed in the same manner as in Experimental Example 5, except that 3% by mass of dilute sulfuric acid was used instead of dilute hydrochloric acid. The results are shown in Table 4 and Figure 10.
[0072] [Experimental Example 28] The dispersion state of the zinc-plated steel fiber bundles (simulated degraded product) was confirmed in the same manner as in Experimental Example 6, except that 3% by mass of dilute sulfuric acid was used instead of dilute hydrochloric acid. The results are shown in Table 4 and Figure 10.
[0073] [Table 4]
[0074] The results shown in Table 4 and Figure 9 confirm that when normal zinc-plated steel fiber bundles were immersed in 3% by mass dilute sulfuric acid, the steel fiber bundles did not disperse into individual steel fibers after immersion for 1 minute, but after immersion for 3 to 5 minutes, the steel fiber bundles were completely dispersed into individual steel fibers. On the other hand, the results shown in Table 4 and Figure 10 confirm that when a simulated deteriorated galvanized steel fiber bundle was immersed in 3% by mass dilute sulfuric acid, the steel fiber bundle did not disperse into individual steel fibers when the immersion time was between 1 and 5 minutes.
[0075] [Experimental Example 29] The dispersion state of zinc-plated steel fiber bundles (normal products) was confirmed in the same manner as in Experimental Example 1, except that 10% by mass of tartaric acid (pH 1.29) was used instead of dilute hydrochloric acid. The results are shown in Table 5 and Figure 11.
[0076] [Experimental Example 30] The dispersion state of zinc-plated steel fiber bundles (normal products) was confirmed in the same manner as in Experimental Example 2, except that 10% by mass of tartaric acid was used instead of dilute hydrochloric acid. The results are shown in Table 5 and Figure 11.
[0077] [Experimental Example 31] The dispersion state of zinc-plated steel fiber bundles (normal products) was confirmed in the same manner as in Experimental Example 3, except that 10% by mass of tartaric acid was used instead of dilute hydrochloric acid. The results are shown in Table 5 and Figure 11.
[0078] [Experimental Example 32] The dispersion state of the zinc-plated steel fiber bundle (simulated degraded product) was confirmed in the same manner as in Experimental Example 4, except that 10% by mass of tartaric acid was used instead of dilute hydrochloric acid. The results are shown in Table 5 and Figure 12.
[0079] [Experimental Example 33] The dispersion state of the zinc-plated steel fiber bundle (simulated degraded product) was confirmed in the same manner as in Experimental Example 5, except that 10% by mass of tartaric acid was used instead of dilute hydrochloric acid. The results are shown in Table 5 and Figure 12.
[0080] [Experimental Example 34] The dispersion state of the zinc-plated steel fiber bundles (simulated degraded product) was confirmed in the same manner as in Experimental Example 6, except that 10% tartaric acid was used instead of dilute hydrochloric acid. The results are shown in Table 5 and Figure 12.
[0081] [Table 5]
[0082] The results shown in Table 5 and Figure 11 confirm that when normal zinc-plated steel fiber bundles were immersed in 10% by mass tartaric acid, the steel fiber bundles did not disperse into individual steel fibers after immersion for 1 minute, but after immersion for 3 to 5 minutes, the steel fiber bundles were completely dispersed into individual steel fibers. On the other hand, the results shown in Table 5 and Figure 12 confirm that when a simulated degraded zinc-plated steel fiber bundle was immersed in 10% by mass tartaric acid, the steel fiber bundle did not disperse into individual steel fibers when the immersion time was between 1 and 5 minutes.
[0083] [Experimental Example 35] The dispersion state of zinc-plated steel fiber bundles (normal products) was confirmed in the same manner as in Experimental Example 1, except that 10% by mass of acetic acid (pH 2.02) was used instead of dilute hydrochloric acid. The results are shown in Table 6 and Figure 13.
[0084] [Experimental Example 36] The dispersion state of zinc-plated steel fiber bundles (normal products) was confirmed in the same manner as in Experimental Example 2, except that acetic acid with a concentration of 10% by mass was used instead of dilute hydrochloric acid. The results are shown in Table 6 and Figure 13.
[0085] [Experimental Example 37] The dispersion state of zinc-plated steel fiber bundles (normal products) was confirmed in the same manner as in Experimental Example 3, except that acetic acid with a concentration of 10% by mass was used instead of dilute hydrochloric acid. The results are shown in Table 6 and Figure 13.
[0086] [Experimental Example 38] The dispersion state of the zinc-plated steel fiber bundle (simulated degraded product) was confirmed in the same manner as in Experimental Example 4, except that acetic acid with a concentration of 10% by mass was used instead of dilute hydrochloric acid. The results are shown in Table 6 and Figure 14.
[0087] [Experimental Example 39] The dispersion state of the zinc-plated steel fiber bundles (simulated degraded product) was confirmed in the same manner as in Experimental Example 5, except that acetic acid with a concentration of 10% by mass was used instead of dilute hydrochloric acid. The results are shown in Table 6 and Figure 14.
[0088] [Experimental Example 40] The dispersion state of the zinc-plated steel fiber bundle (simulated degraded product) was confirmed in the same manner as in Experimental Example 6, except that acetic acid with a concentration of 10% by mass was used instead of dilute hydrochloric acid. The results are shown in Table 6 and Figure 14.
[0089] [Table 6]
[0090] The results shown in Table 6 and Figure 13 indicate that when normal zinc-plated steel fiber bundles were immersed in 10% by mass acetic acid, the steel fiber bundles did not disperse into individual steel fibers when immersion time was 1 to 3 minutes, but when immersion time was 5 minutes, the steel fiber bundles were completely dispersed into individual steel fibers. On the other hand, the results shown in Table 6 and Figure 14 confirm that when a simulated degraded sample of zinc-plated steel fiber bundles was immersed in 10% by mass acetic acid, the steel fiber bundles did not disperse into individual steel single fibers when the immersion time was between 1 and 5 minutes.
[0091] Table 7 shows the concentrations and pH of the dilute acids used in the experimental examples.
[0092] [Table 7]
[0093] Tables 1 through 7 are combined and shown in Table 8.
[0094] [Table 8]
[0095] As shown in Table 8, when the pH of the dilute acid is 0.1 or less, the dispersion state of the steel fiber bundles can be determined with an immersion time of 3 minutes. Furthermore, when the pH of the dilute acid is greater than 0.1 and 2.0 or less, the dispersion state of the steel fiber bundles can be determined with an immersion time of 3 minutes or more and 5 minutes or less.
Claims
1. A method for determining the quality of steel fibers for concrete, comprising immersing a bundle of steel fibers in a dilute acid, shaking the bundle of steel fibers with the dilute acid, and then confirming the dispersion state of the individual steel fibers constituting the bundle of steel fibers, The dilute acid is dilute hydrochloric acid, tartaric acid, or acetic acid. The immersion time of the steel fiber bundle in the dilute hydrochloric acid or tartaric acid is 3 minutes or more and 5 minutes or less. A method for determining the quality of steel fibers for concrete, wherein the immersion time of the steel fiber bundle in the acetic acid is 5 minutes.
2. The method for determining the quality of steel fibers for concrete according to claim 1, wherein the concentration of the dilute hydrochloric acid is 1% by mass or more and 5% by mass or less, the concentration of the tartaric acid is 10% by mass, and the concentration of the acetic acid is 10% by mass.
3. The method for determining the quality of steel fibers for concrete according to claim 1 or 2, wherein the pH of the dilute hydrochloric acid is -0.16 or more and 0.49 or less, the pH of the tartaric acid is 1.29, and the pH of the acetic acid is 2.
02.
4. A method for mixing steel fiber reinforced concrete, comprising mixing cement, water, coarse aggregate, fine aggregate, chemical admixture, and steel fiber bundles, A method for mixing steel fiber-reinforced concrete, wherein the steel fiber bundles used are from lots that have passed the quality determination method for concrete steel fibers described in any one of claims 1 to 3.
Citation Information
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