Ultra-fast hardening cement mortar

Abstract

To provide an ultra-fast setting cement mortar useful as a repair material for cement structures, the mortar having: a low fluctuation of setting time due to temperature environment; a low change in properties such as setting time even after long-term storage in a solid state; a low length change rate; and a high freeze-thaw resistance of the hardened material.SOLUTION: An ultra-fast setting cement mortar comprises cement, a fast setting admixture, a fine aggregate, silica fume, oxycarboxylic acid, an inorganic carbonate, alum, a synthetic polymer-based thickening and water retention agent, and water. A content of the inorganic carbonate is in a range of 1.0 pts.mass or more and 2.0 pts.mass or less per 1.0 pts.mass of the oxycarboxylic acid, and a content of the alum is in a range of 0.4 pt.mass or more and 9.0 pts.mass or less per 100 pts.mass of the total of a fast-curing admixture and cement.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an ultra-rapid hardening cement mortar. [Background technology]

[0002] Repair materials (hereinafter also referred to as repair materials) are filled into the recesses of deteriorated concrete. Mortar is used as the repair material, which is prepared by adding water to a mortar composition (solid content) whose main components are cement and fine aggregate, and mixing the mixture.

[0003] Mortars used as repair materials are generally ultra-fast-setting cement mortars containing admixtures such as fast-setting admixtures and set retarders. Fast-setting admixtures accelerate the setting rate of mortar, while set retarders slow the setting rate of repair materials. The setting rate of repair materials can be adjusted by using fast-setting admixtures and set retarders. Known fast-setting admixtures include compositions containing calcium aluminate and anhydrous gypsum (Patent Documents 1 to 3). Known set retarders include a combination of inorganic carbonate, hydroxycarboxylic acid, sodium aluminate, and sodium sulfate (Patent Document 1), and a combination of inorganic carbonate, hydroxycarboxylic acid, and alum (Patent Document 2). The addition of silica fume to mortar to reduce the rate of length change during setting has also been investigated, as has the addition of synthetic polymer-based thickening water-retaining agents to mortar to reduce the static elastic modulus of the hardened mortar (Patent Document 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6183571 [Patent Document 2] Japanese Patent Publication No. 2021-160989 [Patent Document 3] Patent No. 6653077 Summary of the Invention [Problem to be solved by the invention]

[0005] Adding admixtures such as silica fume or synthetic polymer-based thickening water-retaining agents is effective for improving the long-term strength development and freeze-thaw resistance of repair materials. However, the temperature environment for filling deteriorated concrete with repair materials differs significantly between summer and winter. If the properties of the repair material change depending on the temperature environment, the work may become complicated. Therefore, it is preferable for repair materials to maintain stable properties over a wide temperature range. However, because each admixture has different properties relative to temperature, adding a large number of admixtures to a repair material may result in significant variations in properties due to environmental temperature. Furthermore, repair materials are usually prepared at the concrete pavement repair site. For this reason, repair materials are stored in a solid state (mortar composition). Therefore, repair materials are required to be resistant to changes in properties such as setting time even when stored in a solid state.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide an ultra-fast hardening cement mortar which is useful as a repair material, in which the setting time does not vary much depending on the temperature environment, and in which properties such as setting time do not change easily even when stored in a solid state for a long period of time, the rate of length change is low, and the hardened product has high resistance to freezing and thawing. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides an ultra-rapid-setting cement mortar comprising a mortar composition and water, wherein the mortar composition comprises cement, a rapid-setting admixture, a fine aggregate, silica fume, an oxycarboxylic acid, an inorganic carbonate, alum, and a synthetic polymer-based thickening water-retaining agent; the rapid-setting admixture comprises calcium aluminate and anhydrous gypsum, and the calcium aluminate has a CaO to Al2O3 molar ratio of 1.5 to 2.0 and a vitrification rate of 80% or more; the anhydrous gypsum content is 45 to 56 parts by mass per 100 parts by mass of the total amount of the calcium aluminate and the anhydrous gypsum; the cement content is 100 to 1900 parts by mass per 100 parts by mass of the rapid-setting admixture; and the fine aggregate content is 100 parts by mass per 100 parts by mass of the total amount of the rapid-setting admixture and the cement. the silica fume content is in the range of 2 parts by mass to 8 parts by mass per 100 parts by mass of the total amount of the rapid-hardening admixture and the cement; the hydroxycarboxylic acid content is in the range of 0.1 parts by mass to 5 parts by mass per 100 parts by mass of the total amount of the rapid-hardening admixture and the cement; the inorganic carbonate content is in the range of 1.0 parts by mass to 2.0 parts by mass per 1.0 part by mass of the hydroxycarboxylic acid; the alum content is in the range of 0.4 parts by mass to 9.0 parts by mass per 100 parts by mass of the total amount of the rapid-hardening admixture and the cement; the synthetic polymer thickening water-retaining agent content is in the range of 0.05 parts by mass to 0.4 parts by mass per 100 parts by mass of the total amount of the rapid-hardening admixture and the cement; and the water content is in the range of 10 parts by mass to 20 parts by mass per 100 parts by mass of the mortar composition.

[0008] The ultra-rapid-setting cement mortar of the present invention, configured as described above, contains silica fume within the above range, thereby reducing the rate of length change, and contains a synthetic polymer-based thickening water-retaining agent within the above range, thereby increasing the freeze-thaw resistance of the set product. Furthermore, the hydroxycarboxylic acid and inorganic carbonate contents within the above ranges reduce fluctuations in setting time due to temperature. Furthermore, even when stored in a solid state for a long period of time, properties such as setting time are unlikely to change. Furthermore, the alum content within the above ranges ensures that properties such as setting time are unlikely to change even when stored in a solid state for a long period of time.

[0009] Here, the ultra rapid hardening cement mortar of the present invention may be configured such that the molar ratio of the total SO3 content to the total Al2O3 content in the mortar composition is in the range of 1.0 or more and 2.0 or less. In this case, since the molar ratio of the total SO3 content to the total Al2O3 content is within the above range, the strength development is particularly high at low temperatures (5°C).

[0010] The ultra-rapid-hardening cement mortar of the present invention may further contain sodium silicate, and the content of the sodium silicate may be in the range of 0.1 parts by mass or more and 5.0 parts by mass or less per 100 parts by mass of the total amount of the rapid-hardening admixture and the cement. In this case, since sodium silicate is contained in the above ratio, the initial strength of the hardened product of the ultra rapid hardening cement mortar is increased, which makes it easier to shorten the repair work period.

[0011] In the ultra rapid hardening cement mortar of the present invention, the inorganic carbonate may be sodium carbonate. In this case, sodium carbonate has a high setting adjustment effect, so it is possible to adjust the setting time of the ultra-fast hardening cement mortar by using a small amount, and it is also possible to further reduce the variation in setting time due to the temperature environment.

[0012] In the ultra rapid hardening cement mortar of the present invention, the hydroxycarboxylic acid may be tartaric acid. In this case, since tartaric acid has a high setting adjustment effect, it is possible to adjust the setting time of the ultra-fast hardening cement mortar by using a small amount, and it is also possible to further reduce the variation in setting time due to the temperature environment.

[0013] In addition, in the ultra-fast hardening cement mortar of the present invention, the length change rate is ±250 × 10 -6 The configuration may be within the range of In this case, since the rate of change in length is within the above range, defects are less likely to occur in the repaired concrete pavement.

[0014] The ultra rapid hardening cement mortar of the present invention may have a mini-slump flow value in the range of 150 mm or more and 210 mm or less. In this case, there is no separation of the material and workability is good.

[0015] The ultra rapid hardening cement mortar of the present invention may be configured so that the initial setting time is 30 minutes or more and the final setting time is 75 minutes or less at an ambient temperature of 20°C. If the initial setting time at an ambient temperature of 20°C is 30 minutes or more, there is sufficient time between preparing the ultra-rapid-setting cement mortar and filling the defects in the concrete pavement. Also, if the final setting time at an ambient temperature of 20°C is 75 minutes or less, the time between filling the defects with the ultra-rapid-setting cement mortar and hardening can be shortened, which helps to shorten the repair work period.

[0016] The ultra rapid hardening cement mortar of the present invention may be configured so that the relative dynamic modulus of elasticity after 300 cycles of freeze-thaw testing is 80% or more. In this case, the hardened product of this ultra-rapid setting cement mortar is less likely to develop defects due to freezing and thawing, and therefore this ultra-rapid setting cement mortar can be advantageously used to repair concrete pavements in cold regions.

[0017] Furthermore, the ultra-fast hardening cement mortar of the present invention has a compressive strength of 28 N / mm2 at 4 hours measured according to a method in accordance with JIS A 1108:2018 (Test method for compressive strength of concrete). 2 The static modulus of elasticity at 28 days measured in accordance with JIS A 1149:2017 (Testing method for static modulus of elasticity of concrete) is 31.5 kN / mm 2 The following configuration may be adopted. In this case, since the compressive strength and static modulus of elasticity satisfy the above conditions, the hardened product of this ultra rapid hardening cement mortar has high durability against impact, and therefore concrete pavement repaired with this ultra rapid hardening cement mortar is less likely to develop defects over the long term. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide an ultra-rapid hardening cement mortar which has a small variation in setting time due to temperature environment, and which is resistant to changes in properties such as setting time even when stored in a solid state for a long period of time, has a low rate of length change, and has a low static elastic modulus of the hardened product, making it useful as a repair material for cement structures. DETAILED DESCRIPTION OF THE INVENTION

[0019] An embodiment of the present invention will be described below. Ultra-rapid hardening cement mortar is an aqueous composition used as a repair material for repairing defects such as chips and cracks in concrete structures by filling the defect and hardening it. Examples of concrete structures for which the repair material is used include bridges, buildings, etc.

[0020] The ultra-rapid-setting cement mortar of this embodiment is an aqueous composition prepared by kneading cement, a rapid-setting admixture, fine aggregate, silica fume, an oxycarboxylic acid, an inorganic carbonate, alum, a synthetic polymer-based thickening water-retaining agent, and water. The ultra-rapid-setting cement mortar of this embodiment may further contain sodium silicate, a re-emulsified powdered polymer, a water-reducing agent, an antifoaming agent, and short fibers.

[0021] (Fast hardening admixture) The fast-setting admixture includes calcium aluminate and anhydrite. Calcium aluminate is generally 12CaO·7Al2O3, 11CaO·7A l2 It is a compound having a composition of O3·CaF2 and CaO·Al2O3. The calcium aluminate used in this embodiment has a molar ratio of CaO to Al2O3 of 1.50 or more to 2.0 or less. If the CaO content to Al2O3 is outside this range, it may be difficult to obtain the effects of improving the early strength of the ultra-rapid-hardening cement mortar and preventing the occurrence of white spots.

[0022] Furthermore, calcium aluminate is required to have a vitrification rate of 80% or more. If the vitrification rate is too low, it may be difficult to obtain the effect of improving the early strength of ultra-rapid-hardening cement mortar. The vitrification rate is preferably in the range of 80% to 99%, and more preferably in the range of 90% to 99%. The vitrification rate (%) of the calcium aluminate was calculated by fitting the crystalline peaks and amorphous haloes from the X-ray diffraction pattern of the calcium aluminate sample measured by X-ray diffraction, and then applying the integrated intensities to the following equation: Vitrification rate (%) = 100 - (100 × Ic / (Ic + Is)) Ic: Crystalline scattering integrated intensity Is: Amorphous scattering integrated intensity

[0023] Calcium aluminate has a Blaine specific surface area of ​​3000 cm 2 / g or more 5500cm 2 When the Blaine specific surface area of ​​calcium aluminate is within the above range, the hardening rate of the ultra fast hardening cement mortar can be increased, and the effect of improving the early strength can be improved.

[0024] The content of anhydrous gypsum is within the range of 45 to 56 parts by mass per 100 parts by mass of the total amount of calcium aluminate and anhydrous gypsum. By including calcium aluminate and anhydrous gypsum in the above ratio, the hardening speed of the ultra-fast-hardening cement mortar can be increased, and the effect of improving the early strength can be improved.

[0025] The molar ratio of the SO3 content to the Al2O3 content of the rapid-hardening admixture (SO3 / Al2O3 molar ratio) is preferably within the range of 1.5 to 2.4. When the SO3 / Al2O3 molar ratio is within this range, strength development is particularly high at low temperatures. The SO3 / Al2O3 molar ratio can be measured, for example, as follows: First, the SO3 and Al2O3 contents in a sample are measured according to a method in accordance with JIS R 5204:2019 (Method for X-ray fluorescence analysis of cement). The obtained SO3 content (unit: mass%) is designated as X, and the Al2O3 content (unit: mass%) is designated as Y, and these are substituted into the following formula to calculate the SO3 / Al2O3 molar ratio. Molar ratio of SO3 / Al2O3 = (X / 80.06) / (Y / 101.96)

[0026] (cement) As the cement, various cements that are used as raw materials for ultra-rapid hardening cement mortars, such as ordinary Portland cement, high-early-strength Portland cement, moderate-heat Portland cement, low-heat Portland cement, blast-furnace cement, etc., can be used. The cement is preferably ordinary Portland cement. The cement content is in the range of 100 to 1900 parts by mass per 100 parts by mass of the rapid-hardening admixture. By having the cement content in this range, the compressive strength at 4 hours measured in accordance with the method in accordance with JIS A1108:2018 is 28 N / mm 2 It is possible to obtain the above-mentioned ultra-fast hardening cement mortar hardened product.

[0027] (fine aggregate) There are no particular limitations on the fine aggregate, and any known fine aggregate used as a fine aggregate for ultra-rapid hardening cement mortar can be used. Examples of fine aggregate that can be used include mountain sand, river sand, land sand, crushed sand, sea sand, and silica sand No. 3 to No. 8. The aggregate content is in the range of 50 to 300 parts by mass per 100 parts by mass of the total amount of the rapid-hardening admixture and cement. By keeping the fine aggregate content within this range, the shape of the hardened ultra-rapid-hardening cement mortar is stable.

[0028] (Silica fume) Silica fume has a pozzolanic effect, which improves the long-term strength development of ultra-fast hardening cement mortar containing silica fume, and the hardened material becomes denser, with a smaller total pore volume, a reduced rate of length change, and the progression of carbonation and the diffusion of chloride ions is inhibited. The silica fume content is within the range of 2 to 8 parts by mass per 100 parts by mass of the total amount of the rapid-hardening admixture and cement. By keeping the silica fume content within this range, the long-term strength development of the hardened product of the ultra-rapid-hardening cement mortar is improved.

[0029] (hydroxycarboxylic acid) The hydroxycarboxylic acid acts as a setting regulator. Examples of the hydroxycarboxylic acid include tartaric acid, citric acid, malic acid, gluconic acid, and maleic acid. These hydroxycarboxylic acids may be used alone or in combination of two or more. The hydroxycarboxylic acid may be a salt. The salt is preferably a metal salt such as a sodium salt, a calcium salt, or an aluminum salt. The content of the hydroxycarboxylic acid is in the range of 0.1 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the total amount of the rapid-hardening admixture and cement.

[0030] (inorganic carbonates) The inorganic carbonate acts as a setting modifier. The inorganic carbonate is preferably an alkali metal carbonate or bicarbonate. Examples of inorganic carbonates include sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, lithium carbonate, and ammonium carbonate. These inorganic carbonates may be used alone or in combination of two or more. The content of the inorganic carbonate is in the range of 1.0 to 2.0 parts by mass per 1.0 part by mass of the hydroxycarboxylic acid. When the content of the inorganic carbonate is equal to or greater than the content of the hydroxycarboxylic acid, the variation in the setting time of the ultra-rapid-hardening cement mortar due to the temperature environment is reduced.

[0031] The hydroxycarboxylic acid and the inorganic carbonate are preferably contained in the ultra rapid hardening cement mortar as a premixed mixture (setting retarder), which further reduces the variation in the setting time of the ultra rapid hardening cement mortar depending on the temperature environment.

[0032] (Alum) Alum contains aluminum and, like sodium aluminate, a set modifier, acts as an aluminum auxiliary to adjust the setting time and early strength of ultra-rapid-setting cement mortar. Alum also inhibits the formation of white spots on the surface of hardened ultra-rapid-setting cement mortar. Furthermore, alum has higher chemical stability than sodium aluminate. Therefore, even if ultra-rapid-setting cement mortar is stored in a solid state for a long period of time, its properties, such as setting time, are less likely to change. Sodium alum (NaAl(SO4)2·12H2O) and potassium alum (AlK(SO4)2·12H2O) are preferred, with potassium alum being particularly preferred. The average particle size of the alum is preferably between 1 μm and 100 μm. The content of alum is in the range of 0.4 parts by mass or more and 9.0 parts by mass or less per 100 parts by mass of the total amount of the rapid-hardening admixture and cement.

[0033] By keeping the contents of hydroxycarboxylic acid, inorganic carbonate, and alum within the above ranges, it is possible to adjust the initial setting time of the ultra-fast hardening cement mortar to 30 minutes or more and the final setting time to 75 minutes or less at an ambient temperature of 20°C.

[0034] (Synthetic polymer thickener and water-retaining agent) Synthetic polymer-based thickening and water-retaining agents have the ability to generate tiny air bubbles when they come into contact with water. As a result, the hardened product of ultra-fast-hardening cement mortar containing synthetic polymer-based thickening and water-retaining agents has excellent freeze-thaw resistance because pseudo-entrained air is introduced into the hardened product. As a result, the hardened product maintains a high relative dynamic modulus of elasticity even after repeated freeze-thaw cycles. The content of the synthetic polymer-based thickening water-retaining agent is within the range of 0.05 to 0.4 parts by mass per 100 parts by mass of the total amount of the rapid-hardening admixture and the cement. By having the content of the synthetic polymer-based thickening water-retaining agent within this range, the freeze-thaw resistance of the hardened product of the ultra-rapid-hardening cement mortar is improved, and it is possible to make the relative dynamic modulus of elasticity 80% or more after 300 cycles of freeze-thaw testing.

[0035] (sodium silicate) Sodium silicate functions as an alkalinity adjuster and has the effect of increasing the early strength of the hardened product of ultra-fast hardening cement mortar. Examples of sodium silicate that can be used include sodium metasilicate (Na2SiO3), sodium orthosilicate (Na4SiO4), sodium disilicate (Na2Si2O5), and sodium tetrasilicate (Na2Si4O9). Sodium silicate may be anhydrous or a hydrate (e.g., Na2SiO3·9H2O). The content of sodium silicate can be, for example, within the range of 0.1 to 5.0 parts by mass per 100 parts by mass of the total amount of the rapid-hardening admixture and cement. By keeping the content of sodium silicate within this range, the occurrence of white spots that precipitate on the surface of the hardened ultra-rapid-hardening cement mortar can be suppressed.

[0036] (Re-emulsified powder polymer) The re-emulsified powdered polymer has the effect of making water less likely to penetrate into defects in concrete structures using ultra-rapid-setting cement mortar. The re-emulsified powdered polymer also has the effect of improving the adhesive strength of the ultra-rapid-setting cement mortar to defects in concrete structures. Therefore, ultra-rapid-setting cement mortar containing the re-emulsified powdered polymer has excellent freeze-thaw resistance after immersion in water, and improved adhesive strength to defects. Furthermore, the re-emulsified powdered polymer also has the effect of reducing the length change rate of the ultra-rapid-setting cement mortar. Examples of re-emulsified powdered polymers include vinyl acetate / Veova / acrylic ester copolymer resins, vinyl acetate copolymer resins, vinyl acetate / ethylene copolymers, vinyl acetate / acrylic copolymer resins, and acrylic resins. These re-emulsified powdered polymers may be used alone or in combination of two or more. The content of the re-emulsified powdery polymer can be, for example, within the range of 0.1 to 10.0 parts by mass per 100 parts by mass of the total amount of the rapid-hardening admixture and cement. By having the content of the re-emulsified powdery polymer within this range, the freeze-thaw resistance after 300 cycles in a freeze-thaw test is further improved.

[0037] (water reducing agent) Water-reducing agents have the effect of increasing the dispersibility of cement and admixtures in ultra-rapid-setting cement mortar, improving the fluidity of the ultra-rapid-setting cement mortar, and reducing its viscosity. Examples of water-reducing agents that can be used include water-reducing agents, high-performance water-reducing agents, air-entraining water-reducing agents, and high-performance air-entraining water-reducing agents. Examples of water-reducing agents that can be used include known materials used as water-reducing agents in repair materials, such as lignin sulfonates, oxyorganic acid salts, β-naphthalene sulfonates, polycarboxylates, melamine resin sulfonates, and creosote oil sulfonic acid condensate salts. The content of the water-reducing agent can be, for example, in the range of 0.005 parts by mass or more and 1.0 parts by mass or less per 100 parts by mass of the total amount of the fast-hardening admixture and cement, and it is preferable to set it in the range of 0.010 parts by mass or more and 0.040 parts by mass or less.

[0038] (Antifoaming agent) The antifoaming agent has the effect of suppressing the generation of coarse bubbles in the ultra-rapid hardening cement mortar and improving its fluidity. As the antifoaming agent, for example, known materials used as antifoaming agents for repair materials, such as ethers, fatty acid esters, fatty acid amides, higher alcohols, highly polymerized glycols, silicones, etc., can be used. The content of the antifoaming agent can be, for example, within the range of 0.01 part by mass to 1.0 part by mass per 100 parts by mass of the total amount of the rapid-hardening admixture and cement.

[0039] (short fibers) The short fibers act as a reinforcing material for the cured product of the ultra-rapid hardening cement mortar. By adding short fibers, the crack resistance of the cured product of the ultra-rapid hardening cement mortar is improved, and durability against fatigue is excellent. As the short fibers, organic short fibers and carbon short fibers can be used. Examples of organic short fibers include PVA short fibers (polyvinyl alcohol short fibers), nylon short fibers, aramid short fibers, polypropylene short fibers, and rayon short fibers. These short fibers may be used alone or in combination of two or more. The fiber length of the short fibers is preferably within the range of 1 mm to 10 mm. The content of short fibers can be, for example, within the range of 0.01 part by mass or more and 1.0 part by mass or less per 100 parts by mass of the total amount of the rapid-hardening admixture and cement.

[0040] (water) There are no particular limitations on the water, and ordinary water used in ultra rapid hardening cement mortar can be used. The content of water is in the range of 10 to 20 parts by mass per 100 parts by mass of the mortar composition (solid content). The mortar composition is the components of the ultra rapid hardening cement mortar other than water.

[0041] (Total SO3 / Total Al2O3 molar ratio) The ultra-rapid-setting cement mortar of this embodiment preferably has a molar ratio of the total SO3 content to the total Al2O3 content (total SO3 / total Al2O3 molar ratio) in the range of 1.0 to 2.0. Total Al2O3 is the Al2O3 content in the mortar composition that is the raw material for the ultra-rapid-setting cement mortar. Total SO3 is the same as the SO3 content in the mortar composition that is the raw material for the ultra-rapid-setting cement mortar. The total SO3 and total Al2O3 contents can be obtained by measuring the Al2O3 and SO3 contents in the solid content recovered from the ultra-rapid-setting cement mortar. The Al2O3 and SO3 contents in the solid content can be measured according to a method in accordance with JIS R 5204:2019 (Method for X-ray fluorescence analysis of cement).

[0042] (length change rate) The ultra-fast hardening cement mortar of this embodiment has a length change rate of ±250×10 -6 The length change rate is a value measured in accordance with NEXCO Test Methods (Part 4, Structural Test Methods), Test Method 439, "Test Method for Repair Materials for Section Repair on Deck Surfaces."

[0043] (Mini-slump flow value) The repair material of this embodiment preferably has a mini-slump flow value in the range of 150 mm to 210 mm. The mini-slump flow value is a value measured in accordance with JIS A 1171:2000 (polymer cement mortar test method) using a cone with an upper inner diameter of 50 mm, a lower inner diameter of 100 mm, and a height of 150 mm.

[0044] (initial setting time, final setting time) The ultra-rapid-hardening cement mortar of this embodiment preferably has an initial setting time of 30 minutes or more and a final setting time of 75 minutes or less at an ambient temperature of 20° C. Furthermore, it is more preferable that the initial setting time is 30 minutes or more and the final setting time is 75 minutes or less at ambient temperatures of 5° C. and 35° C. In addition, the initial condensation time (T 20) vs. the rate of change of the initial condensation time (T5) at an ambient temperature of 5°C ((T5-T 20 ) / T 20 ×100) is preferably within ±40%, more preferably within ±20%. 20 ) at an ambient temperature of 35°C vs. the initial condensation time (T 35 ) change rate ((T 35 -T 20 ) / T 20 × 100) is preferably within ±40%, more preferably within ±20%. The initial setting time and final setting time of the ultra-rapid hardening cement mortar are values ​​measured in accordance with JIS R 5201:2015 (Physical testing methods for cement).

[0045] (freeze-thaw resistance) The ultra-rapid hardening cement mortar of this embodiment preferably has a relative dynamic modulus of elasticity of 80% or more after 300 cycles of freeze-thaw testing. The freeze-thaw resistance is the relative dynamic modulus of elasticity measured after 300 freeze-thaw cycles in accordance with JIS A 1148:2010 (freeze-thaw test method for concrete).

[0046] (Compressive strength, static modulus of elasticity) The ultra-fast hardening cement mortar of this embodiment has a compressive strength of 28 N / mm at 4 hours. 2 The static modulus of elasticity at 28 days is 31.5 kN / mm 2 The compressive strength is a value measured in accordance with JIS A 1108:2018 (Method for compressive testing of concrete). The static modulus of elasticity is a value measured in accordance with JIS A 1149:2017 (Method for testing static modulus of elasticity of concrete).

[0047] (Manufacturing method) The ultra-rapid-setting cement mortar of this embodiment can be produced by mixing a mortar composition prepared by mixing the above-mentioned materials with water and kneading the mixture. As a mixing device for producing the mortar composition, a conventional powder mixing device such as a rocking mixer, a V-type mixer, a vertical mixer, a universal mixer, or a Plossar mixer can be used. Furthermore, as a kneading device for producing the ultra-rapid-setting cement mortar, a conventional solid-liquid mixing device such as a mortar mixer or a hand mixer can be used.

[0048] The ultra-rapid-hardening cement mortar of this embodiment, configured as described above, contains silica fume within the above range, thereby reducing the rate of length change, and contains a synthetic polymer-based thickening water-retaining agent within the above range, thereby increasing freeze-thaw resistance. Furthermore, the hydroxycarboxylic acid and inorganic carbonate contents within the above ranges reduce fluctuations in setting time due to temperature. Furthermore, even when stored in a solid state for a long period of time, properties such as setting time are unlikely to change. Furthermore, the alum content within the above ranges ensures that properties such as setting time are unlikely to change even when stored in a solid state for a long period of time.

[0049] In addition, in the ultra rapid hardening cement mortar of this embodiment, when the molar ratio of the total SO3 content to the total Al2O3 content is within the range of 0.8 to 1.6, the strength development at ages of 2 hours and 4 hours is high.

[0050] Furthermore, when the ultra rapid hardening cement mortar of this embodiment further contains sodium silicate in the above-mentioned proportion, the initial strength of the hardened product of the ultra rapid hardening cement mortar is increased, which makes it easier to shorten the period of repair work for concrete pavement.

[0051] Furthermore, in the ultra rapid hardening cement mortar of this embodiment, when the inorganic carbonate is sodium carbonate, sodium carbonate has a high setting adjustment effect, so that it is possible to adjust the setting time of the ultra rapid hardening cement mortar by using a small amount of sodium carbonate, and also to further reduce the variation in setting time due to the temperature environment.

[0052] Furthermore, in the ultra rapid hardening cement mortar of this embodiment, when the hydroxycarboxylic acid is tartaric acid, tartaric acid has a high setting adjustment effect, so that it is possible to adjust the setting time of the ultra rapid hardening cement mortar by using a small amount of tartar, and it is also possible to further reduce the variation in setting time due to the temperature environment.

[0053] Furthermore, in the ultra-fast hardening cement mortar of this embodiment, if the length change rate is within the above range, the change in shape after filling into the defective part of the concrete structure is small, so defects are less likely to occur in the concrete pavement after repair.

[0054] In the ultra rapid hardening cement mortar of this embodiment, when the mini-slump flow value is within the above range, material separation is less likely to occur, and workability is improved.

[0055] Furthermore, when the ultra-rapid-setting cement mortar of this embodiment has an initial setting time of 30 minutes or more at an ambient temperature of 20°C, a sufficient time can be ensured from the preparation of the ultra-rapid-setting cement mortar to filling defects in concrete pavement. Furthermore, when the final setting time at an ambient temperature of 20°C is 75 minutes or less, the time from filling defects with the ultra-rapid-setting cement mortar to hardening can be shortened, which makes it easier to shorten the repair work period.

[0056] Furthermore, when the relative dynamic modulus of elasticity of the ultra-rapid setting cement mortar of this embodiment after 300 cycles of freeze-thaw testing is within the above range, the hardened product of the repair material is less likely to develop defects due to freeze-thawing. Therefore, this ultra-rapid setting cement mortar can be advantageously used for repairing concrete structures in cold regions.

[0057] Furthermore, when the compressive strength at 4 hours measured in accordance with JIS A 1108:2018 and the static elastic modulus at 28 days measured in accordance with JIS A 1149:2017 of the ultra-rapid-setting cement mortar of this embodiment are within the above-mentioned ranges, the hardened product of the repair material has excellent durability against impact. Therefore, concrete structures repaired with this ultra-rapid-setting cement mortar are less likely to develop defects over the long term.

[0058] Although the ultra rapid hardening cement mortar according to the present invention has been described above as an embodiment thereof, the present invention is not limited thereto and can be modified as appropriate within the scope of the technical concept of the invention. For example, the ultra rapid hardening cement mortar according to the present invention may contain an expansive agent, ground granulated blast furnace slag, calcium carbonate, etc. [Example]

[0059] The effects of the present invention will be explained in more detail with reference to examples. The types, names, manufacturers and symbols of the materials used in this example are shown in Table 1 below. The composition of the setting regulator used in this example is shown in Table 2 below.

[0060] [Table 1]

[0061] [Table 2]

[0062] 100 parts by mass of calcium aluminate clinker shown in Table 3 below, 1.0 part by mass of sodium carbonate (Na), and 0.5 part by mass of tartaric acid (Ta) were mixed, and the resulting mixture was pulverized to prepare calcium aluminate pulverized products shown in Table 4 below.

[0063] [Table 3]

[0064] [Table 4]

[0065] [Example 1 of the present invention] A rapid-setting admixture was prepared by adding 45 parts by weight of ground calcium aluminate (CA) and 55 parts by weight of anhydrous gypsum (CS) to a V-type mixer and mixing for 10 minutes. Mortar compositions with the compositions shown in Table 5 were prepared using this rapid-setting admixture. The values ​​in parentheses in Table 5 are based on 100 parts by weight of the combined rapid-setting admixture and ordinary Portland cement (N). Table 6 shows the molar ratio of SO3 to Al2O3 in the rapid-setting admixture (SO3 / Al2O3 molar ratio), the total tartaric acid content when the combined rapid-setting admixture and ordinary Portland cement (N) in the mortar composition is 100 parts by weight, the total sodium carbonate content per 1.0 part by weight of the total tartaric acid content, and the molar ratio of total SO3 to total Al2O3 in the mortar composition (total SO3 / total Al2O3 molar ratio).

[0066] The mortar composition was mixed with water in an amount of 15 parts by mass per 100 parts by mass of the mortar composition (solid content), and the mixture was kneaded to prepare a mortar. The content of the synthetic polymer-based thickening water-retaining agent in the resulting mortar is shown in Table 6.

[0067] [Comparative Example 1] A mortar composition was prepared in the same manner as in Invention Example 1, except that sodium aluminate (Al) was used in place of the sodium metasilicate (MS) and potassium alum mixture (BK) in the mortar composition in the amount shown in Table 5. Then, water was added to the obtained mortar composition and mixed to prepare a mortar in the same manner as Invention Example 1. Table 6 shows the SO3 / Al2O3 molar ratio of the rapid-hardening admixture, the total amount of tartaric acid in the mortar composition, the total amount of sodium carbonate per 1.0 part by mass of the total amount of tartaric acid, the total SO3 / total Al2O3 molar ratio, and the content of the synthetic polymer-based thickening water-retaining agent in the mortar.

[0068] Comparative Example 2 A rapid-setting admixture was obtained by adding 40 parts by mass of ground calcium aluminate (CA) and 60 parts by mass of anhydrous gypsum (CS) to a V-type mixer and mixing for 10 minutes. A mortar composition was prepared in the same manner as in Example 1 of the present invention. Water was then added to the resulting mortar composition and mixed to prepare a mortar in the same manner as in Example 1 of the present invention. Table 6 shows the SO3 / Al2O3 molar ratio of the rapid-setting admixture, the total amount of tartaric acid in the mortar composition, the total amount of sodium carbonate per 1.0 part by mass of the total amount of tartaric acid, the total SO3 / total Al2O3 molar ratio, and the content of the synthetic polymer-based thickening water-retaining agent in the mortar.

[0069] Comparative Example 3 A rapid-setting admixture was obtained by adding 60 parts by mass of ground calcium aluminate (CA) and 40 parts by mass of anhydrous gypsum (CS) to a V-type mixer and mixing for 10 minutes. A mortar composition was prepared in the same manner as in Example 1 of the present invention. Water was then added to the resulting mortar composition and mixed to prepare a mortar in the same manner as in Example 1 of the present invention. Table 6 shows the SO3 / Al2O3 molar ratio of the rapid-setting admixture, the total amount of tartaric acid in the mortar composition, the total amount of sodium carbonate per 1.0 part by mass of the total amount of tartaric acid, the total SO3 / total Al2O3 molar ratio, and the content of the synthetic polymer-based thickening water-retaining agent in the mortar.

[0070] [Table 5]

[0071] [Table 6]

[0072] [evaluation] The resulting mortars were measured for their physical properties, including mini-slump flow, setting time (initial setting time, final setting time), compressive strength, presence or absence of white spots, static modulus of elasticity, length change, and freeze-thaw resistance, using the methods described below. Measurements of mini-slump flow, setting time (initial setting time, final setting time), compressive strength, and presence or absence of white spots were performed at ambient temperatures of 5°C, 20°C, and 35°C. The results of the measurements of mini-slump flow, setting time (initial setting time, final setting time), compressive strength, and presence or absence of white spots are shown in Table 7, and the results of the measurements of static modulus of elasticity, length change, and freeze-thaw resistance are shown in Table 8. Note that Comparative Examples 2 and 3 had lower compressive strengths at 2 and 4 hours than Inventive Example 1 and Comparative Example 1, and therefore were not evaluated for static modulus of elasticity, length change, or freeze-thaw resistance. Table 8 lists the standard values ​​for each characteristic.

[0073] In order to confirm the storage stability of the mortar compositions, the mortar compositions obtained in Inventive Example 1 and Comparative Example 1 were subjected to the following tests. The mortar composition was packed in a plastic bag, pinholes (hole diameter: 0.5 mm) were opened in four corners of the bag, and the bag was left to stand in a room at a temperature of 30°C and a humidity of 80%RH. Mortars were prepared in the same manner as above using the mortar compositions after 3 and 6 months of storage, and the mini-slump flow, setting time (initial setting time, final setting time), compressive strength, and the presence or absence of white spots were measured at an ambient temperature of 20°C. The results are shown in Table 9, along with the results for mortars prepared using the mortar compositions immediately after production.

[0074] (Mini Slump Flow) Measurement is performed using a method in accordance with JIS A 1171:2000 (Testing method for polymer cement mortar).

[0075] (setting time) Measurements are taken using a setting test device that complies with JIS R 5201:2015 (Physical Testing Methods for Cement). The initial setting time and final setting time are measured using a standard starting needle. The initial setting is when the tip of the standard starting needle stops 1 mm from the top surface of the bottom plate. The initial setting time is the time from the start of mixing the mortar to the start of setting. Final setting is when the last standard starting needle drops after the tip of the standard starting needle no longer penetrates the mortar three times in a row. The final setting time is the time from the start of mixing to the end of setting. Measurements and indications of the setting time of the mortar composition are in 1-minute increments.

[0076] (Compressive strength) Measurements are made in accordance with JIS A 1108:2018. The specimens are prepared as follows: Mortar is poured into a φ10 x 20 cm formwork. The 2-hour and 4-hour test specimens are tested immediately after demolding. The 28-day test specimens are demolded after one day, and the resulting hardened material is cured in water for up to 28 days.

[0077] (presence or absence of vitiligo) Observe the formwork surface of the 28-day-old specimens prepared for compressive strength measurements to check for the presence of white spots. If 1 / 5 or more of the formwork surface is white, it is considered to have white spots.

[0078] (Static elastic modulus) The static modulus of elasticity of a 28-day-old specimen is measured according to a method conforming to JIS A 1149:2017 (Testing method for static modulus of elasticity of concrete).

[0079] (length change rate) In accordance with NEXCO test method (Part 4, structural test method), test method 439 "Test method for repair materials for cross-section repair on the upper surface of deck slabs", the material is cured in air (humidity 60±10%), demolded at 110 minutes of age, the base length is measured at 2 hours of age, and the length at 6 hours, 1, 3, 7 and 28 days of age is measured. The length change rate (×10 -6 ) is X=(L m -L0) / L0, L mis the length (mm) of the specimen at the age of m (hours, days), and L0 is the base length (length (mm) of the specimen at the age of 2 hours. The specimen is 100 x 100 x 400 mm.

[0080] (Freeze-thaw resistance: relative dynamic modulus of elasticity after 300 cycles) The specimen is subjected to 300 freeze-thaw cycles in accordance with JIS A 1148:2010 (freeze-thaw test method for concrete). After that, the relative dynamic modulus of elasticity is measured.

[0081] [Table 7]

[0082] [Table 8]

[0083] [Table 9]

[0084] The results in Table 7 show that the mortar of Example 1, which contained sodium metasilicate (MS) and a potassium alum mixture (BK) and had a total SO3 / Al2O3 molar ratio of 2.01 for the rapid-setting admixture and 1.67 for the mortar composition, and the mortar of Comparative Example 1, which contained sodium aluminate (Al), had comparable mini-slump flow, setting time, compressive strength, and the presence or absence of white spots at ambient temperatures of 5°C, 20°C, and 35°C. In contrast, Comparative Example 2, which had a total SO3 / Al2O3 molar ratio of 1.10 for the rapid-setting admixture and 0.97 for the mortar composition, and Comparative Example 3, which had a total SO3 / Al2O3 molar ratio of 2.47 for the rapid-setting admixture and 2.06 for the mortar composition, had low 2-hour and 4-hour strengths at 20°C. Furthermore, the results in Table 8 show that the mortar of Example 1 of the present invention and the mortar of Comparative Example 1 satisfy the standard values ​​for static elastic modulus, rate of length change, and freeze-thaw resistance, and are equivalent.

[0085] The results in Table 9 show that in Inventive Example 1, there were no differences in the mini-slump flow, setting time, compressive strength, or presence or absence of white spots between the mortars prepared using the mortar composition immediately after production, after 3 months of storage, and after 6 months of storage. Therefore, it can be seen that the mortar of Inventive Example 1 is less susceptible to deterioration in its mortar composition state (solid state) and is stable over a long period of time. In contrast, in Comparative Example 1, compared to the mortars prepared using the mortar composition immediately after production and after 3 months of storage, the mortar prepared using the mortar composition after 6 months of storage had a lower mini-slump flow, a longer setting time, lower compressive strength, and the occurrence of white spots. Therefore, it can be seen that the mortar of Comparative Example 1 is more susceptible to deterioration in its mortar composition state (solid state).

[0086] [Invention Examples 2 to 4, Comparative Examples 4 to 5] Mortar compositions were prepared in the same manner as in Example 1 of the present invention, except that Sets 2 to 6 shown in Table 10 were used as the set adjuster, and water was added to the resulting mortar compositions and mixed to prepare mortars. Table 10 shows the total amount of tartaric acid in the mortar compositions and the total amount of sodium carbonate per 1.0 part by mass of the total amount of tartaric acid.

[0087] [Table 10]

[0088] [evaluation] The mini-slump flow, setting time (initial setting time, final setting time), and compressive strength of the resulting mortar were measured using the methods described above. Each property was measured at ambient temperatures of 5°C, 20°C, and 35°C. The rate of change in the initial setting times measured at ambient temperatures of 5°C and 35°C relative to the initial setting time at an ambient temperature of 20°C was calculated. The results are shown in Table 11, along with the results of Example 1 of the present invention.

[0089] [Table 11]

[0090] The results in Table 11 show that in Examples 1 to 4 of the present invention, in which the content of sodium carbonate per 1.0 part by mass of tartaric acid is within the range of the present invention, the initial setting times at an ambient temperature of 5°C and 35°C relative to an ambient temperature of 20°C are within a range of ±40%, indicating a small temperature dependency of the setting time. In contrast, in Comparative Examples 4 and 5, in which the content of sodium carbonate per 1.0 part by mass of tartaric acid is outside the range of the present invention, the rate of change in the initial setting times at an ambient temperature of 5°C and 35°C relative to an ambient temperature of 20°C fluctuated by more than 40%, indicating a large temperature dependency of the setting time.

Claims

1. An ultra-fast hardening cement mortar comprising a mortar composition and water, The mortar composition comprises cement, a rapid-hardening admixture, a fine aggregate, silica fume, an oxycarboxylic acid, an inorganic carbonate, alum, and a synthetic polymer-based thickening water-retaining agent, wherein the oxycarboxylic acid in the mortar composition is tartaric acid, and the inorganic carbonate in the mortar composition is sodium carbonate, The rapid-hardening admixture contains calcium aluminate, anhydrous gypsum, tartaric acid, and sodium carbonate, and the calcium aluminate contains Al ２ O ３ the content of CaO relative to the total amount of the calcium aluminate and the anhydrous gypsum is in the range of 1.5 to 2.0 in terms of molar ratio, the vitrification rate is 80% or more, and the content of the anhydrous gypsum is in the range of 45 to 56 parts by mass relative to 100 parts by mass of the total amount of the calcium aluminate and the anhydrous gypsum, The content of the cement is in the range of 100 parts by mass or more and 1900 parts by mass or less relative to 100 parts by mass of the rapid-hardening admixture, The content of the fine aggregate is in the range of 50 parts by mass or more and 300 parts by mass or less per 100 parts by mass of the total amount of the rapid-hardening admixture and the cement, The content of the silica fume is in the range of 2 parts by mass or more and 8 parts by mass or less per 100 parts by mass of the total amount of the rapid-hardening admixture and the cement, a total content of the oxycarboxylic acid in the mortar composition and the tartaric acid in the rapid-hardening admixture is in the range of 0.1 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the total amount of the rapid-hardening admixture and the cement, a total content of the inorganic carbonate in the mortar composition and the sodium carbonate in the rapid-hardening admixture is in the range of 1.0 parts by mass or more and 2.0 parts by mass or less, relative to 1.0 part by mass of the total content of the oxycarboxylic acid in the mortar composition and the tartaric acid in the rapid-hardening admixture; The content of the alum is in the range of 0.4 parts by mass or more and 9.0 parts by mass or less per 100 parts by mass of the total amount of the rapid-hardening admixture and the cement, The content of the synthetic polymer-based thickening water-retaining agent is in the range of 0.05 parts by mass or more and 0.4 parts by mass or less per 100 parts by mass of the total amount of the rapid-hardening admixture and the cement, The content of the water is in the range of 10 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the mortar composition, An ultra-rapid-hardening cement mortar, wherein the molar ratio of the total SO 3 content to the total Al 2 O 3 content in the mortar composition is in the range of 1.0 or more and 2.0 or less.

2. 2. The ultra-rapid-hardening cement mortar according to claim 1, further comprising sodium silicate, wherein the content of said sodium silicate is in the range of 0.1 parts by mass or more and 5.0 parts by mass or less per 100 parts by mass of the total amount of said rapid-hardening admixture and said cement.

3. Length change rate is ±250 x 10 －６ 3. The ultra rapid hardening cement mortar according to claim 1 or 2, wherein the hardness is within the range of 1000:1 or 1000:

2.

4. An ultra-fast hardening cement mortar described in any one of claims 1 to 3, whose mini-slump flow values ​​at 5°C, 20°C, and 35°C are all within the range of 150 mm or more and 210 mm or less.

5. 5. The ultra-rapid hardening cement mortar according to claim 1, wherein the initial setting time is 30 minutes or more and the final setting time is 75 minutes or less at an ambient temperature of 20°C.

6. 6. The ultra-rapid hardening cement mortar according to claim 1, which has a relative dynamic modulus of elasticity of 80% or more after 300 cycles of freeze-thaw testing.

7. The compressive strength at 4 hours measured in accordance with JIS A 1108:2018 (Concrete compressive strength test method) is 28 N / mm ２ or more, and the static elastic modulus at 28 days measured according to a method conforming to JIS A 1149:2017 (test method for static elastic modulus of concrete) is 31.5 kN / mm ２ The ultra-rapid hardening cement mortar according to any one of claims 1 to 6, wherein:

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