Granules, cement-based admixture, method for producing granules, and method for producing cement-based admixture

Abstract

The present invention provides granules capable of imparting self-repairing performance to a concrete structure or the periphery thereof and maintaining the self-repairing performance over a long period of time. Granules according to the present invention each contain a thermoplastic resin and an ion-releasing compound capable of releasing carbonate ions or hydrogen carbonate ions, wherein the thermoplastic resin contains a polyolefin resin, the ion-releasing compound contains a water-soluble carbonate compound or a water-soluble hydrogen carbonate compound, and in the volume-based particle size distribution of the granules, the particle diameter D90 is 5 mm or less.

Description

Granules, cement-based admixtures, method for producing granules, and method for producing cement-based admixtures

[0001] The present invention relates to granules, use thereof, and a method for producing the same. The present invention also relates to a cement-based admixture using the above granules and a method for producing the same.

[0002] Underground structures such as tunnels, subways, underground shopping arcades, and underground passages have been increasing along with the development of underground spaces. When constructing an underground structure, shrinkage of concrete or other factors may cause a cavity to form between the underground structure and the ground behind it. In addition, cavities may form between the underground structure and the ground behind it due to external stress such as earthquakes or ground subsidence accompanying the decrease in groundwater.

[0003] If such a cavity is left untreated for a long period of time, the ground (natural ground) may collapse or the underground structure may tilt, which may make it impossible to ensure safety inside the underground structure. Therefore, a construction method of filling the cavity by injecting a filler into the cavity between the underground structure and the ground behind it is widely practiced (for example, Patent Documents 1 and 2).

[0004] In addition, the following Patent Document 3 (publication date: March 18, 2025) discloses a powder or granular material used for self-healing repair of concrete structures and their surroundings over a long period of time. This powder or granular material is obtained by mixing an ion-releasing compound capable of releasing cations or anions with a curable resin or a polyethylene terephthalate resin, and then molding the mixture. The ion-releasing compound includes sodium carbonate or sodium hydrogen carbonate. Patent Document 3 also discloses a cement-based admixture containing the above powder or granular material, cement, and water.

[0005] Japanese Unexamined Patent Publication No. 04-001366, Japanese Unexamined Patent Publication No. 2019-044417, Japanese Unexamined Patent Publication No. 2025-037851

[0006] The filler material injected into the above-mentioned cavities may gradually deteriorate due to contact with groundwater, causing cracks to form. Furthermore, the gradual deterioration of the filler material may create microscopic voids between the filler material and the ground or underground structure. If cracks or microscopic voids occur in or around the filler material, further reinforcement may be necessary.

[0007] To fill cracks and microscopic voids that occur in and around the filler material, it is conceivable to impart self-healing properties to the filler material. For example, to impart self-healing properties to the filler material, it is conceivable to include an ion-releasing compound capable of generating poorly water-soluble salts in the filler material, as described in Patent Document 3 for granular materials and cement-based mixtures. When a filler material containing the above ion-releasing compound is used, if the filler material comes into contact with water such as groundwater, ions will leach out from the ion-releasing compound, generating poorly water-soluble salts. Furthermore, the leached ions will diffuse into the water such as groundwater and move into the microscopic voids, so poorly water-soluble salts will also be formed in these microscopic voids. Therefore, even if cracks and microscopic voids occur in and around the filler material, they can be self-healed (self-healing properties).

[0008] However, simply adding ion-releasing compounds to conventional fillers makes it difficult to achieve long-term self-healing performance.

[0009] Furthermore, in the granular materials and cement-based mixtures described in Patent Document 3, a curable resin or polyethylene terephthalate resin is used along with the ion-releasing compound. When a curable resin is used, extrusion molding, which is excellent for continuous production, cannot be used during the production of the granular materials, resulting in low productivity. Also, when polyethylene terephthalate resin is used, hydrolysis of the polyethylene terephthalate resin may progress due to the ion-releasing compound. For this reason, it is difficult to achieve long-term continuous production during the production of the granular materials, the self-healing performance of the resulting granular materials may decrease, or it may be difficult to maintain the self-healing performance of the resulting granular materials over a long period of time.

[0010] The object of the present invention is to provide granular material that can impart self-healing properties to concrete structures or their surroundings, and that can maintain these self-healing properties over a long period of time, as well as its use and a method for manufacturing the same. The present invention also aims to provide a cement-based mixture using the above-mentioned granular material and a method for manufacturing the same.

[0011] This specification discloses the following granules, uses of the granules, cement-based admixtures, methods for manufacturing the granules, and methods for manufacturing cement-based admixtures.

[0012] Item 1. Granules comprising a thermoplastic resin and an ion-releasing compound capable of releasing carbonate ions or bicarbonate ions, wherein the thermoplastic resin comprises a polyolefin resin, and the ion-releasing compound comprises a water-soluble carbonate compound or a water-soluble bicarbonate compound, and the particle size distribution on a volume basis of the granules has a particle size D90 of 5 mm or less.

[0013] Item 2. The granular material according to Item 1, wherein the thermoplastic resin comprises polystyrene, polyethylene, or polypropylene.

[0014] Item 3. The granular material according to item 1 or 2, wherein the thermoplastic resin comprises a crystalline thermoplastic resin.

[0015] Item 4. A granular material according to any one of items 1 to 3, wherein the particle size distribution based on the volume of the granular material is such that the particle size D50 is 80 μm or less.

[0016] Item 5. The granular material according to Item 4, wherein the particle size distribution based on the volume of the granular material is such that the particle size D50 is 30 μm or less.

[0017] Item 6. The granular material according to any one of items 1 to 5, wherein the melting point of the thermoplastic resin is 200°C or less.

[0018] Item 7. The granular material according to any one of items 1 to 6, wherein the ion-releasing compound comprises sodium carbonate or sodium bicarbonate.

[0019] Item 8. Granules according to any one of items 1 to 7, which are extruded or injection molded articles.

[0020] Item 9. Granules according to any one of items 1 to 8, which are used to obtain a cement-based mixture by mixing with cement and water.

[0021] Item 10. Use of granules described in any one of items 1 to 9 in cement-based mixtures containing cement and water.

[0022] Item 11. A cement-based mixture comprising cement, water, and granular material as described in any one of items 1 to 9.

[0023] Item 12. A method for producing granules according to any one of items 1 to 9, comprising the steps of: heating and mixing a thermoplastic resin containing a polyolefin resin with an ion-releasing compound containing a water-soluble carbonate compound or a water-soluble bicarbonate compound that can release carbonate ions or bicarbonate ions, then solidifying the mixture to obtain a resin molded body; and crushing the obtained resin molded body to obtain granules.

[0024] Item 13. The method for producing granules according to Item 12, wherein in the step of obtaining the resin molded body, the resin molded body is obtained by extrusion molding or injection molding, wherein the resin molded body is an extruded body or an injection molded body.

[0025] Item 14. A method for producing a cement-based mixed material, comprising the steps of mixing cement and water, and mixing the mixture of cement and water with granules described in any one of items 1 to 9.

[0026] The granular material according to the present invention comprises a thermoplastic resin and an ion-releasing compound capable of releasing carbonate ions or bicarbonate ions. In the granular material according to the present invention, the thermoplastic resin comprises a polyolefin resin, and the ion-releasing compound comprises a water-soluble carbonate compound or a water-soluble bicarbonate compound. In the volume-based particle size distribution of the granular material according to the present invention, the particle size D90 is 5 mm or less. Because the granular material according to the present invention has the above configuration, it can impart self-healing properties to concrete structures or their surroundings, and can maintain these self-healing properties over a long period of time.

[0027] Figure 1 is a schematic cross-sectional view showing granules according to the first embodiment of the present invention. Figure 2 is a schematic cross-sectional view showing granules according to the second embodiment of the present invention. Figure 3 is a schematic diagram illustrating a method for manufacturing a structure using granules according to one embodiment of the present invention.

[0028] The present invention will be described in detail below.

[0029] (Granules) The granules according to the present invention comprise a thermoplastic resin and an ion-releasing compound capable of releasing carbonate ions or bicarbonate ions. In the granules according to the present invention, the thermoplastic resin comprises a polyolefin resin, and the ion-releasing compound comprises a water-soluble carbonate compound or a water-soluble bicarbonate compound. In the volume-based particle size distribution of the granules according to the present invention, the particle size D90 is 5 mm or less.

[0030] The granular material according to the present invention has the above-described configuration, which allows for the imparting of self-healing properties to concrete structures or their surroundings, and enables the maintenance of these self-healing properties over a long period of time.

[0031] Furthermore, when curable resins are used, extrusion molding, which offers excellent continuous production capabilities, cannot be employed during the manufacturing of powders and granules, resulting in low productivity. In addition, when polyethylene terephthalate resin is used, hydrolysis of the polyethylene terephthalate resin may progress due to ion-releasing compounds. As a result, continuous production over long periods is difficult during the manufacturing of powders and granules, the self-healing performance of the resulting powders and granules decreases, and it becomes difficult to maintain the self-healing performance of the resulting powders and granules over a long period.

[0032] In contrast, the granules according to the present invention have the above-mentioned structure, and in particular, polyolefin resin is used, so that the self-healing performance can be enhanced, and moreover, continuous productivity can be increased during the manufacturing of the granules. The excellent self-healing performance and excellent continuous productivity of the granules are also effects of the present invention.

[0033] Therefore, the granular material according to the present invention is preferably used as a filler material for concrete structures (use of the granular material as a filler for concrete structures). The granular material according to the present invention is preferably used in combination with cement (use of the granular material in cement-based mixed materials containing cement), and more preferably used in combination with cement and water (use of the granular material in cement-based mixed materials containing cement and water). The granular material according to the present invention is preferably used in combination with cement to obtain a cement-based mixed material, and more preferably used in combination with cement and water to obtain a cement-based mixed material.

[0034] The granular material according to the present invention contains the above-mentioned ion-releasing compound. When the above-mentioned granular material comes into contact with water such as groundwater in and around a concrete structure, ions are released from the ion-releasing compound, and salts (for example, poorly water-soluble salts) are generated. Furthermore, the released ions diffuse into the water such as groundwater and move into fine voids, so poorly water-soluble salts are also formed in these fine voids. For example, if the above-mentioned ion-releasing compound is sodium bicarbonate or sodium carbonate, sodium ions are replaced by calcium ions in the cement, and calcium carbonate precipitates and accumulates in the hardened material of the ground improvement material and in cracks and fine voids that occur in and around it. The accumulated calcium carbonate then fills in the cracks and fine voids. Therefore, even if cracks or fine voids occur in and around a concrete structure, they are self-healed (self-healing performance).

[0035] In the particle size distribution based on volume of the granular material according to the present invention, the particle size D90 is 5 mm or less.

[0036] Because the size of the granules according to the present invention (especially the size of granules with large particle sizes) is relatively small, and because a specific thermoplastic resin is used as the material constituting the granules, the effect of eluting the ion-releasing compound from the granules and the effect of releasing ions from the ion-releasing compound persist for a long period of time. Therefore, the self-healing performance is maintained over a long period of time. Furthermore, the effect of excellent continuous productivity of the granules is realized.

[0037] Therefore, by using the granular material according to the present invention, the repair effect can be maintained over a long period of time, and for example, the infiltration of groundwater into concrete structures can be effectively suppressed.

[0038] Furthermore, since the size of the granules according to the present invention is relatively small, these granules moderately slow down the hydration reaction of cement.

[0039] For larger particle sizes, smaller sizes are preferable. In the particle size distribution based on volume, it is preferable that particle size D91 is 5 mm or less, more preferably that particle size D92 is 5 mm or less, even more preferably that particle size D93 is 5 mm or less, particularly preferably that particle size D94 is 5 mm or less, and most preferably that particle size D95 is 5 mm or less. In these cases, the particle can be injected into smaller gaps, and the self-healing performance can be maintained for an even longer period. In addition, the fluidity of the resulting cement-based mixture is improved, allowing the cement-based mixture to be injected into even finer gaps, and the self-healing performance can be maintained for an even longer period.

[0040] The particle size D90 is preferably 2.5 mm or less, more preferably 1.2 mm or less, even more preferably 0.6 mm or less, still more preferably 0.3 mm or less, particularly preferably 0.15 mm or less, and most preferably 0.075 mm or less. When the particle size D90 is below the upper limit, the self-healing performance can be maintained for an even longer period of time. The particle size D90 may be 2 μm or more, or 8 μm or more. The range of the particle size D90 can be appropriately selected and set from the lower limit and upper limit.

[0041] The shape of the granules is not particularly limited. The granules may be spherical, substantially spherical, cylindrical, columnar, rectangular, or any other shape.

[0042] From the viewpoint of exerting the effects of the present invention more effectively, in the above granules, it is preferable that the ion-releasing compound is present inside or on the outer surface of the granules. From the viewpoint of exerting the effects of the present invention more effectively, in the above granules, it is preferable that the ion-releasing compound is present at least inside the granules. In the above granules, the ion-releasing compound may be present both inside the granules and on the outer surface of the granules.

[0043] The ion-releasing compound present inside the granules is preferably present in a dispersed state inside the granules. In this case, since ions are gradually released from the ion-releasing compound present inside the granules, the self-healing performance can be maintained over a longer period of time.

[0044] In the volume-based particle size distribution of the granules, the particle diameter D50 is preferably 300 µm or less, more preferably 100 µm or less, still more preferably 80 µm or less, further preferably 50 µm or less, still further preferably 30 µm or less, particularly preferably 25 µm or less, even more particularly preferably 20 µm or less, and most preferably 15 µm or less. When the particle diameter D50 is not more than the above upper limit, the cement-based mixture can be injected into even finer gaps, and the self-healing performance can be maintained over a longer period of time. The particle diameter D50 may be 1 µm or more, or may be 4 µm or more. The range of the particle diameter D50 can be appropriately selected and set from the above lower limit value and the above upper limit value.

[0045] Said particle diameter D50 and particle diameter D90 of the granules are particle diameters measured on a volume basis, and are the value of the particle diameter (D50) at which the cumulative distribution value reaches 50% and the value of the particle diameter (D90) at which the cumulative distribution value reaches 90%. Said particle diameter D50 and particle diameter D90 can be measured by a laser diffraction / scattering method or the like. That is, said particle diameter D50 and particle diameter D90 are, in the volume-based particle size distribution of said granules, the diameter value corresponding to 50% and the diameter value corresponding to 90% when accumulated from the side of smaller particle diameters. As a measuring apparatus, a laser diffraction particle size distribution analyzer is suitably used. Commercially available products of said laser diffraction particle size distribution analyzer include "AEROTRAC" manufactured by MicrotracBEL, etc. The details are the same for the above particle diameters D91 to D95.

[0046] The density of said granules is preferably larger than the density of water. The density of said granules at 25°C is preferably 1.0 g / cm ３ 3, more preferably 1.2 g / cm ３ 3 or more. When said density is not less than (or exceeds) the above lower limit, the miscibility with cement can be further improved. The density of said granules at 25°C may be 3.0 g / cm ３ 3 or less, and may also be 2.5 g / cm ３ 3 or less. The range of the density of said granules at 25°C can be set by appropriately selecting the above lower limit value and the above upper limit value.

[0047] Hereinafter, the present invention will be specifically described with reference to the drawings. In the following drawings, for convenience of illustration, the size of each component may differ from the actual size.

[0048] FIG. 1 is a cross-sectional view schematically showing granules according to a first embodiment of the present invention.

[0049] The granule 1 shown in FIG. 1 contains a thermoplastic resin 2 and an ion-releasing compound 3. The granule 1 has a rectangular parallelepiped shape. The ion-releasing compound 3 is present inside the granule 1. The ion-releasing compound 3 is present in a dispersed state inside the granule 1. The thermoplastic resin 2 preferably contains a crystalline thermoplastic resin.

[0050] Figure 2 is a schematic cross-sectional view showing granules according to a second embodiment of the present invention.

[0051] The granules 1A shown in Figure 2 contain a thermoplastic resin 2 and an ion-releasing compound 3. The granules 1A are spherical. The ion-releasing compound 3 is present inside the granules 1A. The ion-releasing compound 3 is dispersed inside the granules 1A. Preferably, the thermoplastic resin 2 contains a crystalline thermoplastic resin.

[0052] In the granules 1 and 1A shown in Figures 1 and 2, the ion-releasing compound 3 is located inside the granules 1 and 1A. However, the ion-releasing compound may be located inside or on the outer surface of the granules, or it may be located on the outer surface of the granules.

[0053] The details of each component used in the granular material according to the present invention will be explained below.

[0054] <Thermoplastic Resin> The above granules contain a thermoplastic resin. The above thermoplastic resin is preferably a material for coating an ion-releasing compound. Only one type of thermoplastic resin may be used, or two or more types may be used in combination.

[0055] The above thermoplastic resin includes a polyolefin resin. The above polyolefin resin may be used alone, or two or more may be used in combination.

[0056] Examples of the polyolefin resins mentioned above include polyethylene, polypropylene, polystyrene, polybutene, polyisobutylene, polybutadiene, ethylene-vinyl acetate copolymer, and ethylene-α-olefin copolymer.

[0057] From the viewpoint of exhibiting the effects of the present invention more effectively, it is preferable that the thermoplastic resin includes a crystalline thermoplastic resin.

[0058] From the viewpoint of exhibiting the effects of the present invention more effectively, the thermoplastic resin more preferably contains polystyrene, polyethylene, or polypropylene. In this case, the thermoplastic resin may contain polystyrene, polyethylene, or polypropylene. The thermoplastic resin may contain polystyrene and polyethylene, polystyrene and polypropylene, or polyethylene and polypropylene. The thermoplastic resin may contain polystyrene, polyethylene, and polypropylene. From the viewpoint of exhibiting the effects of the present invention more effectively, the thermoplastic resin more preferably contains polyethylene or polypropylene.

[0059] The melting point of the thermoplastic resin is preferably 270°C or lower, more preferably 200°C or lower, and even more preferably 180°C or lower. If the melting point is below the upper limit, the decomposition of the ion-releasing compound during heating and mixing can be further suppressed. The melting point of the thermoplastic resin may be 100°C or higher, or 120°C or higher. The range of the melting point of the thermoplastic resin can be appropriately selected and set from the lower limit and upper limit.

[0060] In 100% by mass of the above granules, the content of the above thermoplastic resin is preferably 5% by mass or more, more preferably 10% by mass or more, preferably 90% by mass or less, and more preferably 80% by mass or less. When the content of the above thermoplastic resin is above the lower limit and below the upper limit, the content of the ion-releasing compound in the above granules can be set to a suitable range, and the effects of the present invention can be exhibited even more effectively.

[0061] In 100% by mass of the above granules, the content of the above crystalline thermoplastic resin is preferably 5% by mass or more, more preferably 10% by mass or more, preferably 90% by mass or less, and more preferably 80% by mass or less. When the content of the above crystalline thermoplastic resin is above the lower limit and below the upper limit, the content of the ion-releasing compound in the above granules can be set to a suitable range, and the effects of the present invention can be exhibited even more effectively.

[0062] In 100% by mass of the above granules, the content of the above polyolefin resin is preferably 5% by mass or more, more preferably 10% by mass or more, preferably 90% by mass or less, and more preferably 80% by mass or less. When the content of the above polyolefin resin is above the lower limit and below the upper limit, the content of the ion-releasing compound in the above granules can be set to a suitable range, and the effects of the present invention can be exhibited even more effectively.

[0063] In 100% by mass of the above granules, the total content of the thermoplastic resin and the ion-releasing compound is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 97.5% by mass or more, particularly preferably 99% by mass or more, and most preferably 100% by mass. When the total content is above the lower limit, the effects of the present invention can be exhibited even more effectively. In addition, the total content of the thermoplastic resin and the ion-releasing compound in 100% by mass of the above granules may be 100% by mass or less, less than 100% by mass, 99% by mass or less, or 98% by mass or less. The range of the total content of the thermoplastic resin and the ion-releasing compound in 100% by mass of the above granules can be appropriately selected and set from the lower limit and upper limit.

[0064] In 100% by mass of the above granules, the total content of the above crystalline thermoplastic resin and the above ion-releasing compound is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 97.5% by mass or more, particularly preferably 99% by mass or more, and most preferably 100% by mass. When the above total content is above the lower limit, the effects of the present invention can be exhibited even more effectively. In addition, the total content of the above crystalline thermoplastic resin and the above ion-releasing compound in 100% by mass of the above granules may be 100% by mass or less, less than 100% by mass, 99% by mass or less, or 98% by mass or less. The range of the total content of the above crystalline thermoplastic resin and the above ion-releasing compound in 100% by mass of the above granules can be appropriately selected and set from the above lower limit and upper limit.

[0065] In 100% by mass of the above granules, the total content of the polyolefin resin and the ion-releasing compound is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 97.5% by mass or more, particularly preferably 99% by mass or more, and most preferably 100% by mass. When the total content is above the lower limit, the effects of the present invention can be exhibited even more effectively. In addition, the total content of the polyolefin resin and the ion-releasing compound in 100% by mass of the above granules may be 100% by mass or less, less than 100% by mass, 99% by mass or less, or 98% by mass or less. The range of the total content of the polyolefin resin and the ion-releasing compound in 100% by mass of the above granules can be appropriately selected and set from the lower limit and upper limit.

[0066] <Ion-releasing compound> The above granules contain an ion-releasing compound capable of releasing carbonate ions or bicarbonate ions. The above ion-releasing compound may be used alone, or two or more may be used in combination.

[0067] The above-mentioned ion-releasing compound is a compound capable of releasing carbonate ions or bicarbonate ions. The above-mentioned ion-releasing compound may be a compound capable of releasing carbonate ions, a compound capable of releasing bicarbonate ions, a compound capable of releasing both carbonate ions and bicarbonate ions, or a mixture of a compound capable of releasing carbonate ions and a compound capable of releasing bicarbonate ions. The above-mentioned ion-releasing compound may be in particulate form.

[0068] It is preferable that the above-mentioned ion-releasing compound is capable of producing poorly water-soluble salts. In this case, the effects of the present invention can be exhibited even more effectively.

[0069] The term "spaciously water-soluble salt" refers to a salt in which, when 1 g of the sparingly water-soluble salt (product) is placed in 100 g of water and held at 20°C for 10 minutes, the mass of the sparingly water-soluble salt that dissolves in water is 0.1 g or less.

[0070] The above-mentioned ion-releasing compound is preferably a compound capable of producing a poorly water-soluble salt upon contact with moisture. If the above-mentioned ion-releasing compound is a compound capable of releasing cations, it is preferable that the cations released from the above-mentioned ion-releasing compound react chemically with anions dissolved in moisture, etc., to produce a poorly water-soluble salt. It is preferable that carbonate ions or bicarbonate ions released from the above-mentioned ion-releasing compound react chemically with cations dissolved in moisture, etc., to produce a poorly water-soluble salt.

[0071] Examples of poorly water-soluble salts include calcium carbonate, magnesium carbonate, and barium carbonate.

[0072] The poorly water-soluble salt is preferably calcium carbonate. That is, it is preferable that the above-mentioned ion-releasing compound is capable of producing calcium carbonate as the poorly water-soluble salt.

[0073] Examples of the ion-releasing compounds mentioned above include lithium carbonate, sodium carbonate, potassium carbonate, ammonium bicarbonate, calcium bicarbonate, potassium bicarbonate, and sodium bicarbonate.

[0074] The above ion-releasing compound preferably contains lithium carbonate, sodium carbonate, potassium carbonate, ammonium bicarbonate, calcium bicarbonate, potassium bicarbonate, or sodium bicarbonate, and more preferably contains sodium bicarbonate or sodium carbonate. In this case, the effects of the present invention can be exhibited even more effectively.

[0075] The ion-releasing compound may be spherical, or it may have a shape other than spherical, or it may be flattened. It is preferable that the ion-releasing compound be spherical.

[0076] In the volume-based particle size distribution of the above ion-releasing compound, the particle size D50 of the above ion-releasing compound is preferably less than 300 μm, more preferably less than 100 μm, more preferably less than 80 μm, more preferably less than 50 μm, even more preferably less than 30 μm, even more preferably 29 μm or less, even more preferably 28 μm or less, particularly preferably less than 25 μm, particularly more preferably less than 20 μm, and most preferably less than 15 μm. When the particle size D50 of the above ion-releasing compound is less than or equal to the above upper limit, the effects of the present invention can be exhibited more effectively. When the particle size D50 of the above ion-releasing compound is less than or equal to the above upper limit, the dispersibility in the granules can be improved, and the above ion-releasing compound can be well coated with the thermoplastic resin, and the sustained release in the granules can be improved. In the volume-based particle size distribution of the above ion-releasing compound, the particle size D50 of the above ion-releasing compound may be 0.5 μm or more, or 3 μm or more. The particle size D50 of the above-mentioned ion-releasing compound can be appropriately selected and set from the above-mentioned lower limit and upper limit.

[0077] The particle size D50 of the above-mentioned ion-releasing compound is the particle size measured on a volume basis, and is the value of the particle size (D50) at which the cumulative distribution value reaches 50%. The particle size D50 can be measured by laser diffraction / scattering methods, etc. That is, the particle size D50 is the diameter value corresponding to 50% when cumulatively calculated from the smallest particle size in the volume-based particle size distribution of the above-mentioned ion-releasing compound. A laser diffraction particle size distribution analyzer is preferably used as the measuring device. A commercially available example of such a laser diffraction particle size distribution analyzer is the "AEROTRAC" manufactured by MicrotracBEL.

[0078] In the above-mentioned granules, it is preferable that part or all of the surface of the ion-releasing compound is coated with the thermoplastic resin. More preferably, in the above-mentioned granules, part or all of the surface of the ion-releasing compound is coated with the crystalline thermoplastic resin. In these cases, the timing and amount of cations or anions released from the ion-releasing compound can be controlled even more effectively.

[0079] Preferably, the ion-releasing compound coated with the above-mentioned thermoplastic resin is capable of releasing carbonate ions or bicarbonate ions when moisture comes into contact with the granules and the moisture diffuses into the interior of the thermoplastic resin. The ion-releasing compound coated with the above-mentioned thermoplastic resin may also be capable of releasing carbonate ions or bicarbonate ions from the voids in the thermoplastic resin. The ion-releasing compound coated with the above-mentioned thermoplastic resin may also be capable of diffusing into the interior of the thermoplastic resin and releasing carbonate ions or bicarbonate ions. In these cases, the timing and amount of carbonate ions or bicarbonate ions released from the ion-releasing compound can be controlled even more effectively.

[0080] When part or all of the surface of the ion-releasing compound is coated with the thermoplastic resin, the thickness of the thermoplastic resin (thickness of the coating layer made of the thermoplastic resin) is not particularly limited. From the viewpoint of better controlling the timing and amount of carbonate ions or bicarbonate ions released from the ion-releasing compound, the thickness of the thermoplastic resin is preferably 0.5 μm or more, more preferably 1 μm or more, more preferably 100 μm or less, and more preferably 50 μm or less. When a crystalline thermoplastic resin is used, the thickness of the thermoplastic resin is the thickness of the crystalline thermoplastic resin.

[0081] In 100% by mass of the above granules, the content of the above ion-releasing compound is preferably 5% by mass or more, more preferably 20% by mass or more, preferably 95% by mass or less, and more preferably 85% by mass or less. When the content of the above ion-releasing compound is above the lower limit and below the upper limit, the effects of the present invention can be exhibited even more effectively.

[0082] It is particularly preferable that the content of the ion-releasing compound in the granules is 50 parts by mass or more and 200 parts by mass or less, relative to 100 parts by mass of the thermoplastic resin in the granules. In this case, the effects of the present invention can be exhibited even more effectively.

[0083] It is particularly preferable that the content of the ion-releasing compound in the granules is 50 parts by mass or more and 200 parts by mass or less, relative to 100 parts by mass of the crystalline thermoplastic resin in the granules. In this case, the effects of the present invention can be exhibited even more effectively.

[0084] <Other Components> The granules may contain other components different from both the thermoplastic resin and the ion-releasing compound. Examples of these other components include surface modifiers, thixotropic agents, and antioxidants. Only one of these other components may be used, or two or more may be used in combination.

[0085] <Further Details of the Granules> The above granules are preferably extruded or injection-molded articles, and more preferably extruded articles. Since polyolefin resin is used for the above granules, the granules can be manufactured well by extrusion molding or injection molding during production, thereby increasing continuous productivity. Extruded or injection-molded articles can be manufactured at low cost.

[0086] (Method for producing granules) The method for producing granules according to the present invention is a method for producing granules as described in the "(Granules)" section above. The method for producing granules according to the present invention comprises a step (molding step) of mixing a thermoplastic resin containing a polyolefin resin and an ion-releasing compound capable of releasing carbonate ions or bicarbonate ions containing a water-soluble carbonate compound or a water-soluble bicarbonate compound while heating, and then solidifying the mixture to obtain a resin molded body. The method for producing granules according to the present invention further comprises a step (crushing step) of crushing the obtained resin molded body to obtain granules.

[0087] From the viewpoint of more effectively demonstrating the effects of the present invention, in the method for producing granules according to the present invention, the thermoplastic resin containing the polyolefin resin is preferably a crystalline thermoplastic resin containing the polyolefin resin.

[0088] The molding process described above includes a mixing step of heating and mixing the thermoplastic resin and the ion-releasing compound to obtain a mixture, and a solidification step of solidifying the obtained mixture.

[0089] In the mixing step described above, it is preferable to stir the mixture at a temperature above the melting point of the thermoplastic resin. It is preferable that the molten thermoplastic resin and the ion-releasing compound are mixed together.

[0090] Mixing methods include extrusion mixing, kneader mixing, roll mixing, internal mixer mixing, and Banbury mixer mixing. Extrusion mixing is preferred because it offers excellent continuous productivity and allows for the inexpensive production of granules.

[0091] In the solidification process described above, for example, the temperature of the mixture is lowered to below the melting point of the thermoplastic resin, thereby solidifying the mixture. This yields a resin molded article.

[0092] Methods for cooling the above mixture to lower its temperature include leaving it in the air, cooling it in water, and cooling it using a cooling device.

[0093] Furthermore, in the process of obtaining the above-mentioned resin molded article, it is preferable to obtain the resin molded article, which is an extruded or injection-molded article, by extrusion molding or injection molding, and it is more preferable to obtain the resin molded article, which is an extruded or injection-molded article, by extrusion molding. In the above-mentioned method for producing granules, since polyolefin resin is used, the granules can be produced well by extrusion molding or injection molding during the production of the granules, and continuous productivity can be increased. Extruded or injection-molded articles can be produced at low cost, and extruded articles can be produced at even lower cost.

[0094] In the above grinding process, it is preferable to grind the granules until the desired particle size is achieved. When the resin molded body, which is an extruded or injection-molded body, is ground in the above grinding process, the resulting powder is the ground extruded body or the ground injection-molded body. The ground material obtained by grinding an extruded or injection-molded body is also referred to as an extruded or injection-molded body.

[0095] Methods for grinding the above-mentioned resin molded body include dry grinding, wet grinding, low-temperature grinding, dry grinding, heat grinding, and cryogenic grinding.

[0096] (Cement-based mixture) The cement-based mixture comprises cement and the granular material described above. This cement-based mixture can be obtained by mixing the cement and the granular material.

[0097] The cement-based mixture according to the present invention comprises cement, water, and the granular material described above. This cement-based mixture is fluid. This cement-based mixture can be obtained by mixing the cement, water, and granular material.

[0098] Examples of the cements mentioned above include Portland cement, blast furnace cement, silica cement, and fly ash cement. The blast furnace cement may contain blast furnace slag.

[0099] The viscosity of the above cement-based mixture at 25°C is preferably 3 mPa·s or higher, and preferably 200 mPa·s or lower. When the viscosity is above the lower limit and below the upper limit, the fluidity of the cement-based mixture can be appropriately increased.

[0100] The viscosity of the above cement-based mixture is measured in accordance with JIS Z 8803:2011, "Method for Measuring the Viscosity of Liquids".

[0101] In 100% by mass of the above cement-based mixture, the cement content is preferably 10% by mass or more, more preferably 15% by mass or more, preferably 70% by mass or less, and more preferably 60% by mass or less.

[0102] In 100% by mass of the above cement-based mixture, the water content is preferably 20% by mass or more, more preferably 25% by mass or more, preferably 90% by mass or less, and more preferably 80% by mass or less.

[0103] In 100% by mass of the above cement-based mixture, the content of the above granular material is preferably 1% by mass or more, more preferably 3% by mass or more, preferably 50% by mass or less, and more preferably 40% by mass or less. When the content of the above granular material is above the lower limit and below the upper limit, the effects of the present invention can be exhibited even more effectively. Furthermore, when the content of the above granular material is above the lower limit and below the upper limit, the inhibition of the cement hydration reaction can be further suppressed.

[0104] The amount of granular material in the cement-based mixture is preferably 30 parts by mass or more, and preferably 500 parts by mass or less, relative to 100 parts by mass of cement. When the amount of granular material is above the lower limit, the effects of the present invention can be exhibited more effectively. When the amount of granular material is below the upper limit, the strength of the solidified cement-based mixture can be further increased.

[0105] The amount of water in the cement-based mixture is preferably 50 parts by mass or more, and preferably 100,000 parts by mass or less, relative to 100 parts by mass of the total amount of cement and granules in the cement-based mixture. If the amount of water is above the lower limit, the fluidity of the cement-based mixture can be moderately increased. If the amount of water is below the upper limit, the cement-based mixture can be solidified well.

[0106] The above cement-based mixture may, if necessary, contain other components besides the three types of cement, water, and granular material. Examples of these other components include sand, fine aggregate, and coarse aggregate. Only one of these other components may be used, or two or more may be used in combination.

[0107] (Method for manufacturing cement-based mixed material, and uses of cement-based mixed material) The method for manufacturing cement-based mixed material comprises a step of mixing cement with the above-mentioned granular material. In this case, the method may further comprise a step of mixing the mixture of cement and the above-mentioned granular material with water.

[0108] The method for producing a cement-based mixed material according to the present invention comprises a step of mixing cement and water (first mixing step) and a step of mixing the mixture of cement and water with granular material (second mixing step). In other examples of the method for producing a cement-based mixed material, the mixing order of the cement, granular material and water can be changed as appropriate.

[0109] Examples of mixing methods in the first and second mixing steps described above include grout mixer mixing, cement milk mixer mixing, and hand mixer mixing. It is preferable that the cement, water, and granules are mixed such that the content of these components satisfies the preferred range described above.

[0110] (Method for improving ground or concrete, and structure and method for manufacturing the structure) Ground or concrete can be improved using the above-mentioned granular material or cement-based mixture. The method for improving ground or concrete described herein is a method for improving ground or concrete using the above-mentioned granular material or cement-based mixture. In order to improve the ground or concrete, the above-mentioned granular material or cement-based mixture is injected into the ground or concrete.

[0111] Furthermore, a structure can be obtained using the granular material or the cement-based mixture. The structure preferably comprises a filler object having a filler portion and a filler material filled into the filler portion. The filler material is preferably formed from the granular material or the cement-based mixture.

[0112] The method for manufacturing a structure described herein comprises a filling step of filling the portion of the object to be filled with the granular material or the cement-based mixture. The method for manufacturing the structure may also comprise a solidification step of solidifying the cement-based mixture.

[0113] The above method for manufacturing the structure yields a structure comprising a filler material filled into the portion to be filled. The filler material is the granular material or the cement-based mixture.

[0114] In the above structure, the areas filled with the granular material or cement-based mixture and their surroundings are densified by the granular material or cement-based mixture, thus maintaining a stable state over a long period of time.

[0115] The material to be filled preferably includes ground or concrete. The part to be filled preferably is a cavity in the ground or concrete.

[0116] The method for filling the above-mentioned area to be filled with the granular material or cement-based mixture is not particularly limited. Examples of methods for filling the above-mentioned area to be filled with the granular material or cement-based mixture include forming an injection port in the structure that penetrates from the front to the back of the structure, and injecting the granular material or cement-based mixture into the area to be filled through the injection port. The amount of granular material or cement-based mixture injected can be appropriately changed depending on the size of the area to be filled (the area to be filled). The area to be filled is preferably a cavity. The area to be filled may also be a cavity between the underground structure and the ground. The granular material or cement-based mixture is preferably filled by a backfilling method.

[0117] The pressure used when filling (injecting) the above-mentioned granules or cement-based mixture can be appropriately changed depending on the size of the area to be filled (the part to be filled). The above-mentioned granules or cement-based mixture may be filled (injected) at high pressure or at low pressure. When filling at high pressure, the pressure is preferably 0.5 MPa or more and 24 MPa or less. When filling at low pressure, the pressure is preferably 0.01 MPa or more and less than 0.5 MPa. From the viewpoint of improving the injectability of the above-mentioned granules or cement-based mixture into the fine details of the part to be filled, the pressure used when injecting the above-mentioned granules or cement-based mixture is preferably 0.1 MPa or more and 4 MPa or less.

[0118] Figure 3 is a schematic diagram illustrating a method for manufacturing a structure using granules according to one embodiment of the present invention.

[0119] Structure 100 is an underground structure. A cavity 103 to be filled exists between structure 100 and the ground 102.

[0120] The supply device 5 for the granular material or cement-based mixture comprises an injection gun 51 and a tank 52. The tank 52 is filled with the granular material or cement-based mixture.

[0121] First, a hole is drilled at a predetermined angle from the front to the back of the structure 100 to form an injection port 101. Next, the injection plug 6 and the injection gun 51 are connected. Then, using a compressor, the granular material or cement-based mixture is filled (injected) into the area to be filled (cavity) 103 through the injection port 101 (filling process). Before the above filling process, an injection plate may be installed on the front side of the structure so as to cover the area around the injection plug in order to prevent the granular material or cement-based mixture from flowing out from the front of the structure.

[0122] Next, when using a cement-based mixture containing the granular material, the cement-based mixture may be solidified (solidification step). In this way, a structure can be obtained. The structure comprises the granular material or the cement-based mixture as a filler material filled into the area to be filled.

[0123] When filling with the above-mentioned cement-based mixture, the type of cement-based mixture may differ between the initial and later filling stages. For example, in the initial filling stage, a cement-based mixture that does not contain the above-mentioned particles (conventional cement-based mixture) may be used, and in the later filling stage, a cement-based mixture that contains the above-mentioned particles (cement-based mixture according to the present invention) may be used. By using a cement-based mixture that does not contain the above-mentioned particles (conventional cement-based mixture) in the initial filling stage, the cement-based mixture can be spread throughout the space or voids.

[0124] The above-mentioned cement-based mixture can be used in tunnels (concrete structures). The ground can be reinforced by forming multiple holes at predetermined intervals in the circumferential direction on the inner surface of the tunnel, and inserting rock bolts and the cement-based mixture into each of the multiple holes. The rock bolts may also be provided at predetermined intervals along the axis of the tunnel.

[0125] The above-mentioned cement-based mixture can be used as a filler to fill the void between the rock bolt and the ground. When the cement-based mixture filled into the holes formed in the ground solidifies, it can integrate the rock bolt and the ground. This improves the strength of the ground.

[0126] The above cement-based mixture can be used as a material for the lining concrete that covers the inner surface of a tunnel.

[0127] The above cement-based mixture can be used in ground where multiple boreholes have been drilled near the planned tunnel excavation site before tunnel excavation. Multiple boreholes are formed around the planned tunnel excavation site, along the tunnel. The cement-based mixture can then be filled into these boreholes.

[0128] The above-mentioned cement-based mixture can be used as a filler material to fill boreholes. Cracks may exist in the ground surrounding the borehole. Therefore, by injecting the above-mentioned cement-based mixture into the space under pressure, the cement-based mixture penetrates from the borehole into the cracks. As the cement-based mixture that has penetrated into the cracks solidifies, the cracks are sealed. This can improve the watertightness of the ground.

[0129] The above-mentioned cement-based mixture can be used as a filler material to fill boreholes, and can also be used as a waterproofing material to stop groundwater from seeping into the area surrounding the boreholes. In this example, the cement-based mixture is filled into the boreholes under pressure. This causes the cement-based mixture to penetrate into cracks and voids in the ground surrounding the boreholes. As the cement-based mixture inside the boreholes and the cement-based mixture that has penetrated into the cracks and voids in the ground solidifies, the strength of the cracks and voids in the ground surrounding the boreholes can be improved, and a sealing zone that suppresses groundwater infiltration can be formed around the boreholes. This ensures the strength of the ground surrounding the tunnel and suppresses the intrusion of groundwater into the tunnel during tunnel excavation.

[0130] The above cement-based mixture can be used in boreholes formed vertically in the ground. The cement-based mixture can be injected into the space within the borehole that is partitioned by expandable and contractible packers.

[0131] Cement-based mixtures that have hardened due to the hardening of cement components may develop cracks over time due to factors such as the infiltration of groundwater and other water into the mixture, earthquakes, and the expansion and contraction of the cement-based mixture. In addition, the cement-based mixture may melt, creating a gap between the cement-based mixture and the ground.

[0132] Normally, when a cement-based mixture cracks or melts, the strength of the ground and the mixture itself decreases. However, because the cement-based mixture contains granular material, carbonate ions or bicarbonate ions leach from the granular material, forming carbonates. Specifically, the carbonate ions or bicarbonate ions contained in the granular material combine with calcium ions in the cement contained in the ground and the cement-based mixture, causing calcium carbonate to precipitate and accumulate in the gaps between the cement-based mixture and the ground, and in the cracks within the cement-based mixture. This accumulation of calcium carbonate in the cracks of the cement-based mixture and the gaps between the cement-based mixture and the ground fills these areas. In other words, by using a cement-based mixture that contains granular material, the cement-based mixture and its surroundings become denser than they were at the beginning of construction.

[0133] In this way, because the cement-based mixture contains granular material, even if cracks occur in the cement-based mixture or gaps form between the cement-based mixture and the ground, the cement-based mixture will self-heal and repair itself over a long period of time. As a result, the ground improvement effect is maintained over a long period of time, and the infiltration of groundwater into concrete structures (tunnels, etc.) can be suppressed.

[0134] Furthermore, the uses of the above-mentioned cement-based mixture are not limited to those described above. For example, the cement-based mixture can be used as a material for sprayed concrete applied to support structures and the inner walls of tunnels. In addition, the cement-based mixture can be used to fill (backfill) tunnels.

[0135] Furthermore, although the above-mentioned applications mainly describe the use in the ground, the cement-based mixture can also be used in gaps in bedrock, as well as in gaps between bedrock and concrete structures built on bedrock.

[0136] The granular material and cement-based mixture described above can be used whether the area to be filled is dry or wet. Furthermore, the granular material and cement-based mixture can be used even if water is leaking from the area to be filled. For this reason, the granular material and cement-based mixture can be used to maintain structures for various purposes and can be repaired quickly. The present invention contributes to the preventive maintenance of structures. In particular, the present invention contributes to the preventive maintenance of existing underground structures.

[0137] Examples of the above-mentioned structures include underground structures. Examples of the above-mentioned underground structures include underground concrete structures, underground tunnels, underwater tunnels, and mountain tunnels. The above-mentioned granular material and cement-based mixture are suitably used in cavities between underground structures and the ground behind them. Furthermore, the above-mentioned granular material and cement-based mixture are suitably used in cavities created beneath the floor of a structure due to ground subsidence. In addition, the above-mentioned granular material and cement-based mixture are suitably used in cavities in unused tunnels and water and sewage pipes, as well as in lightweight embankments behind bridge abutments.

[0138] The present invention will be described in more detail below with reference to examples. The present invention is not limited to the following examples.

[0139] [First Experimental Example] As the first experimental example, the experiments of Example A and Example B below were conducted.

[0140] (Example A) A mixed material was obtained by mixing 100 parts by mass of polyethylene resin (LDPE Petrocene #360, manufactured by Tosoh Corporation) and 100 parts by mass of sodium carbonate. The obtained mixed material was mixed using a twin-screw compounding extruder (TEX30, manufactured by Japan Steel Works Co., Ltd.) while heating the mixed material to a temperature of 190°C, then molded and cryopreserved to obtain granules. The obtained granules were subjected to a sieving test to obtain granules.

[0141] Using MicrotracBEL's "AEROTRAC," the volume-based particle size distribution of the obtained particles was measured, and the particle size D90 was 5 mm or less, and the particle size D50 was 30 μm or less.

[0142] (Example B) A mixed material was obtained by mixing 100 parts by mass of polypropylene resin (Prime PolyPro E111G, manufactured by Prime Polymer Co., Ltd.) and 100 parts by mass of sodium carbonate. The obtained mixed material was mixed while being heated in a twin-screw compounding extruder (TEX30, manufactured by Japan Steel Works, Ltd.) under conditions that the temperature of the mixed material was 210°C, molded, and then cryopreserved to obtain granules. The obtained granules were subjected to a sieving test to obtain granules.

[0143] Using MicrotracBEL's "AEROTRAC," the volume-based particle size distribution of the obtained particles was measured, and the particle size D90 was 5 mm or less, and the particle size D50 was 30 μm or less.

[0144] By using the cement-based mixture containing the granules obtained in Examples A and B, even if cracks or fine voids occur in concrete structures and their surroundings, these cracks and fine voids can be self-healed and repaired.

[0145] [Second Experimental Example] As a second experimental example, the experiments described in Examples 1 to 4 and Comparative Examples 1 to 2 below were conducted.

[0146] (Example 1) Pellet preparation: Polystyrene resin (INEOS "Styrolution PS 158K GR2", melting point: approximately 220°C) was dried in an oven at 120°C for 6 hours. 100 parts by mass of the dried polystyrene resin and 150 parts by mass of sodium carbonate were melt-mixed using a twin-screw compounding extruder (Japan Steel Works "TEX30") while heating under conditions that the temperature of the mixed material reached 250°C, and extruded into strands to obtain pellets (granules). The size of the obtained pellets was approximately 3 mm in diameter and 3.5 mm in maximum length.

[0147] (Example 2) Preparation of granules: The pellets obtained in Example 1 were crushed using a turbo mill manufactured by Freund Turbo to obtain pulverized material. The obtained pulverized material was subjected to a sieving test to obtain granules.

[0148] Using MicrotracBEL's "AEROTRAC," the volume-based particle size distribution of the obtained particles was measured. The particle size D90 was 49 μm, and the particle size D50 was 21 μm.

[0149] (Example 3) Pellet preparation: 100 parts by mass of polypropylene resin (Prime PolyPro E111G, manufactured by Prime Polymer Co., Ltd., melting point: approximately 160°C) and 150 parts by mass of sodium carbonate were melted and mixed using a twin-screw compounding extruder (TEX30, manufactured by Japan Steel Works Co., Ltd.) while heating under conditions that the temperature of the mixed material was 210°C, and the mixture was extruded in a strand shape to obtain pellets (granules). The size of the obtained pellets was approximately 3 mm in diameter and 3.5 mm in maximum length.

[0150] (Example 4) Preparation of granules: The pellets obtained in Example 3 were crushed using a Freund Turbo turbo mill to obtain pulverized material. The obtained pulverized material was subjected to a sieving test to obtain granules.

[0151] Using MicrotracBEL's "AEROTRAC," the volume-based particle size distribution of the obtained particles was measured. The particle size D90 was 153 μm, and the particle size D50 was 74 μm.

[0152] (Comparative Example 1) Pellet Preparation: Polyethylene terephthalate resin (RAMAPET N1, manufactured by Indorama Ventures, melting point: approximately 255°C) was dried in an oven at 120°C for 6 hours. 100 parts by mass of the dried polyethylene terephthalate resin and 100 parts by mass of sodium carbonate were melted and mixed using a twin-screw compounding extruder (TEX30, manufactured by Japan Steel Works) while heating under conditions that the temperature of the mixed material reached 255°C, and then extruded into strands to obtain pellets (granules). 30 minutes after the start of extrusion, decomposition gas was generated due to the decomposition of the polyethylene terephthalate resin, making it difficult to continue extrusion. The size of the pellets obtained in the first 30 minutes was approximately 3 mm in diameter and 3.5 mm in maximum length.

[0153] (Comparative Example 2) Preparation of granules: The pellets obtained in Comparative Example 1 were crushed using a turbo mill manufactured by Freund Turbo to obtain pulverized material. The obtained pulverized material was subjected to a sieving test to obtain granules.

[0154] Using MicrotracBEL's "AEROTRAC," the particle size distribution of the obtained granules was measured based on volume. The particle size D90 was 30 μm, and the particle size D50 was 14 μm.

[0155] (Evaluation) (1) Continuous productivity For each composition of the second experimental example, the continuous formability was evaluated when extruded at a temperature above the melting point using a twin-screw compounding extruder (TEX30, manufactured by Japan Steel Works, Ltd.). The continuous productivity of the granules was determined according to the following criteria.

[0156] [Criteria for determining continuous productivity of granular materials] ○: Continuous molding is possible for more than one hour ×: Continuous molding is not possible for more than one hour

[0157] (2) Self-healing performance Preparation of test specimens for evaluating self-healing performance: 30 g or 60 g of the obtained granules (amount of granules mixed in the table) and 160 g of Tohoku Silica Sand No. 8 (manufactured by Tohoku Silica Sand Co., Ltd.) (amount of silica sand mixed in the table) were uniformly mixed, and the resulting mixture was filled into an acrylic cylinder with a diameter of 46 mm and a length of 50 mm to the top (filling amount in the table) to obtain a test specimen.

[0158] Evaluation of self-healing performance: Measurements were taken of the obtained test specimens using a digital soil permeability meter (DIK-4056, manufactured by Daiki Rika Kogyo Co., Ltd.), and the initial saturated hydraulic conductivity was determined using the following formula (1).

[0159]

[0160] K: Saturated hydraulic conductivity of the test specimen a: Cross-sectional area of ​​the variable water level scale tube A: Length of the test specimen H1: Length from the upper line of the scale tube to the bottom of the acrylic tube H2: Length from the lower line of the scale tube to the bottom of the acrylic tube t: Time required for the water level inside the scale tube to descend from the upper line to the lower line

[0161] After measuring the initial saturated hydraulic conductivity, the inside of the acrylic cylinder was replaced with a 30% calcium chloride aqueous solution to prevent water evaporation from the top and bottom of the cylinder, and the cylinder was left standing for one week in a constant temperature environment of 23°C. After standing, the saturated hydraulic conductivity was measured after one week using a digital soil hydraulic conductivity meter. The rate of decrease in the saturated hydraulic conductivity after one week from the initial saturated hydraulic conductivity was also calculated.

[0162] In this measurement, the 30% calcium chloride aqueous solution simulates the calcium ions released from cement when granular material is mixed with cement. The carbonate ions and calcium ions released from the granular material form calcium carbonate, a poorly water-soluble salt, in the gaps of Tohoku Silica Sand No. 8, and this self-repair of the gaps is observed as a decrease in the hydraulic conductivity.

[0163] The composition of the granular material, the composition of the test specimens used to evaluate the self-healing performance, and the evaluation results are shown in Tables 1 to 3 below.

[0164]

[0165]

[0166]

[0167] By using the cement-based mixture containing the granules obtained in Examples 1 to 4, even if cracks or fine voids occur in concrete structures and their surroundings, these cracks and fine voids can be self-healed and repaired.

[0168] 1, 1A... Granules 2... Thermoplastic resin 3... Ion-releasing compound 5... Supply device 6... Injection plug 10, 10A... Particles 51... Injection gun 52... Tank 100... Structure 101... Injection port 102... Ground 103... Area to be filled (cavity)

Claims

1. A granular material comprising a thermoplastic resin and an ion-releasing compound capable of releasing carbonate ions or bicarbonate ions, wherein the thermoplastic resin comprises a polyolefin resin, and the ion-releasing compound comprises a water-soluble carbonate compound or a water-soluble bicarbonate compound, and the particle size distribution based on the volume of the granular material has a particle size D90 of 5 mm or less.

2. The granular material according to claim 1, wherein the thermoplastic resin comprises polystyrene, polyethylene, or polypropylene.

3. The granular material according to claim 1, wherein the thermoplastic resin includes a crystalline thermoplastic resin.

4. The granular material according to any one of claims 1 to 3, wherein the particle size distribution based on the volume of the granular material is such that the particle size D50 is 80 μm or less.

5. The granular material according to claim 4, wherein the particle size distribution based on the volume of the granular material is such that the particle size D50 is 30 μm or less.

6. The granular material according to any one of claims 1 to 3, wherein the melting point of the thermoplastic resin is 200°C or less.

7. The granular material according to any one of claims 1 to 3, wherein the ion-releasing compound comprises sodium carbonate or sodium bicarbonate.

8. The granular material according to any one of claims 1 to 3, which is an extruded or injection-molded article.

9. Granules according to any one of claims 1 to 3, which are mixed with cement and water to obtain a cement-based mixture.

10. Use of the granular material according to any one of claims 1 to 3 in a cement-based mixture containing cement and water.

11. A cement-based mixture comprising cement, water, and the granular material described in any one of claims 1 to 3.

12. A method for producing granules according to any one of claims 1 to 3, comprising the steps of: mixing a thermoplastic resin containing a polyolefin resin and an ion-releasing compound containing a water-soluble carbonate compound or a water-soluble bicarbonate compound that can release carbonate ions or bicarbonate ions while heating, then solidifying the mixture to obtain a resin molded body; and crushing the obtained resin molded body to obtain granules.

13. The method for producing granules according to claim 12, wherein in the step of obtaining the resin molded body, the resin molded body is obtained by extrusion molding or injection molding, wherein the resin molded body is an extruded body or an injection molded body.

14. A method for producing a cement-based mixed material, comprising the steps of: mixing cement and water; and mixing the mixture of cement and water with granular material according to any one of claims 1 to 3.

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