Low-temperature mortar composition and mortar cured body

Abstract

To provide a low-temperature mortar composition that allows formation of a mortar cured body exhibiting superior early compressive strength even in a low-temperature environment without the need for large-scale installation work.SOLUTION: A low-temperature mortar composition comprising: a hydraulic composition that contains a hydraulic component composed of amorphous calcium aluminate and gypsum, as well as fine aggregate, a water-reducing agent, and a setting modifier; and water. The content of the hydraulic component is more than 50 mass% based on the total amount of the hydraulic composition.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a mortar composition for low temperature use and a hardened mortar. Specifically, the present disclosure relates to a low-temperature mortar composition and hardened mortar used in various construction projects in the fields of civil engineering and construction, which exhibit excellent strength development at low temperatures such as below freezing. [Background technology]

[0002] The reactivity of mortar compositions used in various civil engineering and construction projects changes dramatically depending on the ambient temperature. In particular, in low-temperature environments such as below freezing, the water necessary for the reaction freezes, making it difficult to obtain a hardened mortar that exhibits sufficient compressive strength. Meanwhile, the concrete floors of refrigerated and frozen warehouses often crack and peel due to the movement of forklifts. From the perspective of maintaining the freshness of stored products and preventing condensation on equipment, it is desirable to repair the concrete as soon as possible while maintaining a low-temperature environment.

[0003] In view of the above circumstances, for example, Patent Document 1 discloses a repair method for the floor of a freezer in which a filling cement-based material is heated and cured, and Patent Document 2 discloses a low-temperature hydraulic composition comprising calcium aluminate powder, hydroxycarboxylic acids, and inorganic salts. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 04-182562 [Patent Document 2] Japanese Patent Application Publication No. 01-215749 Summary of the Invention [Problem to be solved by the invention]

[0005] However, Patent Document 1 has a problem in that large-scale equipment construction work is required in advance to heat and cure the freezer floor. Furthermore, with the hydraulic composition of Patent Document 2, it is difficult to achieve a compressive strength sufficient to allow forklift passage within a few hours of the day of construction, which poses the problem of prolonging the construction period.

[0006] The present disclosure has been made in consideration of the above circumstances, and aims to provide a mortar composition for low temperature use that does not require large-scale facility construction and that can quickly produce a hardened mortar having excellent compressive strength even in a low-temperature environment. Another object of the present disclosure is to provide a hardened mortar obtained by hardening the mortar composition. [Means for solving the problem]

[0007] As a result of intensive research to solve the above problems, the inventors have found that the ratio of the hydraulic components consisting of amorphous calcium aluminate and gypsum in the hydraulic composition is important for solving the problems, and have developed the mortar composition of the present disclosure.

[0008] The outline of this disclosure is as follows. [1] A low-temperature mortar composition comprising a hydraulic component consisting of amorphous calcium aluminate and gypsum, a hydraulic composition containing fine aggregate, a water-reducing agent, and a setting modifier, and water, A mortar composition for low temperature use, wherein the content of the hydraulic component is more than 50 mass% based on the total amount of the hydraulic composition. [2] The mortar composition for low temperature use according to [1], wherein the vitrification rate of the amorphous calcium aluminate is 80% or more. [3] A hardened mortar obtained by hardening the low-temperature mortar composition according to [1] or [2]. [Effects of the Invention]

[0009] According to the present disclosure, there is provided a mortar composition for low temperature use that can quickly produce a hardened mortar having excellent compressive strength even in a low-temperature environment without requiring large-scale facility construction. The mortar composition for low temperature use maintains fluidity and softness suitable for work during construction, and hardens quickly after construction (after work is completed) to quickly develop compressive strength. The present disclosure also provides a hardened mortar obtained by hardening the mortar composition. DETAILED DESCRIPTION OF THE INVENTION

[0010] Preferred embodiments of the present disclosure will be described in detail below, although the present disclosure is not limited to the following embodiments.

[0011] <Low temperature mortar composition> The low-temperature mortar composition includes a hydraulic composition and water. The hydraulic composition includes a hydraulic component consisting of amorphous calcium aluminate and gypsum, as well as fine aggregate, a water-reducing agent, and a set adjuster. A hydraulic composition containing a hydraulic component, fine aggregate, a water-reducing agent and a setting adjuster can be referred to as a low-temperature hydraulic composition.

[0012] (hydraulic component) The content of the hydraulic component in the hydraulic composition is more than 50% by mass. When the content is more than 50% by mass, the fluidity and softness of the composition suitable for work are maintained during application, compared to when the content is 50% by mass or less, and the composition hardens quickly after application, quickly developing compressive strength. From this perspective, the content may be 55% by mass or more, or 60% by mass or more. On the other hand, the upper limit of the content is not particularly limited and may be 100% by mass, but can be 98%, 97%, or 95% by mass from the viewpoint of suppressing reaction heat generated during curing.

[0013] (Hydraulic component: amorphous calcium aluminate) Commercially available amorphous calcium aluminate can be used. These products are prepared by mixing the mineral composition in a specified ratio, melting it at high temperatures in an electric furnace, and then rapidly cooling it to form a glass. The main component of all commercial products is amorphous dodecacalcium heptaaluminate (amorphous 12CaO 7Al2O3 (amorphous C12A7), amorphous mayenite).

[0014] In order to ensure an appropriate working time for the hydration reaction to proceed favorably at low temperatures, the amorphous calcium aluminate preferably has a CaO / Al2O3 molar ratio of more than 0.7, more preferably in the range of 0.8 to 2.8, and even more preferably in the range of 1.0 to 2.5.

[0015] The vitrification rate of amorphous calcium aluminate is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more, from the viewpoint of compressive strength development at low temperatures. The upper limit of the vitrification rate is not particularly limited, but can be set to 99% from the viewpoint of production efficiency.

[0016] The vitrification rate (%) of amorphous calcium aluminate is calculated by fitting the crystalline portion (peak) and amorphous portion (halo) of the X-ray diffraction pattern of an amorphous calcium aluminate sample obtained by powder X-ray diffraction, and then applying the integrated intensity to the following equation: Powder X-ray diffraction measurements were performed using a D2 PHASER 2nd Gen powder X-ray diffractometer (Bruker Japan) under the following conditions: tube voltage 35 kV, tube current 110 mA, measurement range 2θ = 5 to 70°, step width 0.02°, counting time 2 s, divergence slit 1°, and receiving slit 0.15 mm. Vitrification rate (%) = 100 - (100 × Ic / (Ic + Is)) (Ic: Crystalline scattering integrated intensity, Is: Amorphous scattering integrated intensity)

[0017] The content of amorphous calcium aluminate in the hydraulic component may be 35 to 99 mass %, 40 to 97 mass %, or 45 to 95 mass %, from the viewpoint of improving early strength development at low temperatures.

[0018] (Hydraulic component: gypsum) Examples of gypsum include anhydrous gypsum, hemihydrate gypsum, and dihydrate gypsum, and one or more of these may be used regardless of the type. When the hydraulic component contains gypsum, the hydration reaction proceeds favorably, resulting in appropriate workability, early strength development, and excellent dimensional stability.

[0019] The gypsum content in the hydraulic component may be the balance of the amorphous calcium aluminate content.

[0020] (fine aggregate) Examples of fine aggregate include sands such as silica sand, river sand, land sand, sea sand, and crushed sand, and one or more kinds of these may be used regardless of their type.

[0021] The content of the fine aggregate is preferably 0.01 to 99 parts by mass, more preferably 0.03 to 97 parts by mass, and even more preferably 1 to 95 parts by mass, relative to 100 parts by mass of the hydraulic component. By setting the content of the fine aggregate within the above range, it is easy to further improve the strength while maintaining workability.

[0022] (water reducing agent) Examples of water-reducing agents include polycarboxylic acid-based water-reducing agents, naphthalene sulfonic acid-based water-reducing agents, melamine sulfonic acid-based water-reducing agents, lignin sulfonic acid-based water-reducing agents, amino sulfonic acid-based water-reducing agents, and polystyrene sulfonic acid-based water-reducing agents, which have both water-reducing effects and suitable fluidity. Among these, polycarboxylic acid-based water-reducing agents are preferably used. One or more types of water-reducing agents can be used.

[0023] The content of the water-reducing agent is preferably 0.001 to 2.00 parts by mass, more preferably 0.05 to 1.50 parts by mass, and even more preferably 0.10 to 1.20 parts by mass, relative to 100 parts by mass of the hydraulic component. By setting the content of the water-reducing agent within the above range, it is easy to impart suitable workability to the mortar.

[0024] (setting regulator) As the setting regulator, known setting retarders and / or setting accelerators can be used. Examples of setting retarders include organic acids such as hydroxycarboxylic acids, sugars such as glucose, maltose, and dextrin, sodium bicarbonate, and sodium phosphate. Examples of hydroxycarboxylic acids include hydroxycarboxylic acids and their salts. Specific examples of hydroxycarboxylic acids include aliphatic hydroxyacids such as citric acid, gluconic acid, tartaric acid, glycolic acid, lactic acid, hydroacrylic acid, α-hydroxybutyric acid, glyceric acid, tartronic acid, and malic acid, and aromatic hydroxyacids such as salicylic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid, gallic acid, mandelic acid, and tropic acid. Examples of salts of hydroxycarboxylic acids include alkali metal salts (specifically, sodium salts, potassium salts, and the like) and alkaline earth metal salts (specifically, calcium salts, barium salts, magnesium salts, and the like). Among these, sodium salts are preferred, and sodium citrate is more preferred. Setting retarders can be used singly or in combination.

[0025] The content of the setting retarder is preferably 0.001 to 6.0 parts by mass, more preferably 0.002 to 5.5 parts by mass, even more preferably 0.003 to 5.0 parts by mass, and extremely preferably 0.005 to 4.5 parts by mass, relative to 100 parts by mass of the hydraulic component. By keeping the content of the setting retarder within the above range, it is easy to ensure a suitable pot life.

[0026] Examples of the setting accelerator include lithium salts such as lithium carbonate, which have a setting accelerator effect, sulfates such as potassium sulfate and aluminum sulfate, and calcium salts such as calcium formate, calcium hydroxide (slaked lime), and calcium chloride. One or more setting accelerators can be used.

[0027] The content of the setting accelerator is preferably 0.001 to 13.5 parts by mass, more preferably 0.03 to 13.0 parts by mass, even more preferably 0.05 to 12.5 parts by mass, and extremely preferably 0.10 to 12.0 parts by mass, relative to 100 parts by mass of the hydraulic component. By setting the content of the setting accelerator within the above range, it is easy to ensure a suitable pot life and early development of compressive strength.

[0028] (Other ingredients) The hydraulic composition may contain, as other components, one or more of blast furnace slag, metakaolin, limestone, fly ash, silica fume, expansion agents, shrinkage reducing agents, resin powders, synthetic resin fibers, thickeners, antifoaming agents, etc.

[0029] The content of the other components can be adjusted as appropriate within a range that does not substantially impair the desired functions of the low-temperature mortar composition. For example, the content of the other components can be 5 parts by mass or less per 100 parts by mass of the hydraulic component.

[0030] The content of the hydraulic component, fine aggregate, water-reducing agent and setting regulator can be 95% by mass or more, or 97% by mass or more, or 100% by mass (when the hydraulic composition is essentially composed of these components) based on the total amount of the hydraulic composition. The content of the other components can be the remainder of the content of these components.

[0031] (water) The water content in the low-temperature mortar composition is preferably 12 to 40 parts by mass, more preferably 15 to 37 parts by mass, and even more preferably 17 to 35 parts by mass, relative to 100 parts by mass of the hydraulic composition. By setting the water content within the above range, appropriate fluidity and softness are obtained, and workability is improved.

[0032] The low-temperature mortar composition can be prepared, for example, by weighing and mixing the various components that make up the hydraulic composition, and then adding water (which may be warm water) and kneading the mixture.

[0033] The temperature of the prepared low-temperature mortar composition (the temperature immediately after mixing) is preferably 15° C. or higher, more preferably 18° C. or higher, from the viewpoint of preventing freezing at the interface with the concrete structure immediately after construction. The upper limit of the temperature is not particularly limited, but can be set to 35° C. from the viewpoint of suppressing long-term strength reduction due to rapid progress of hydration reaction.

[0034] The low-temperature mortar composition is useful as an inorganic filler for civil engineering and construction applications in low-temperature environments. For example, it can be used as a flooring material, joint material, or filler for refrigerated and frozen warehouses (classes C3 to F4), or for repair and reinforcement work on civil engineering and construction structures in extremely cold regions. The low-temperature mortar composition can also be called a mortar composition for extremely low temperatures or a mortar composition for freezing environments. The low temperature environment may be, for example, 10° C. or lower, −20° C. or lower, or −30° C. or lower, or may be −60° C. or higher. The low temperature environment may also be referred to as a cryogenic environment.

[0035] The flow value (initial fluidity) of the low-temperature mortar composition is preferably 180 mm or more. The flow value is a value measured in accordance with the test method of JASS 15M-103 "Quality Standards for Self-Leveling Materials by the Architectural Institute of Japan."

[0036] The pot life of the mortar composition for low temperature use is preferably 1 minute or more. The pot life is measured by filling the mortar composition for low temperature use into a cylindrical polypropylene formwork having a diameter of 50 mm and a height of 100 mm, and then measuring the central temperature of the mortar composition every minute with a K-type thermocouple, and measuring the time until the central temperature rises by 2°C from the temperature of the mortar composition before filling (after mixing).

[0037] Examples of methods for applying the low-temperature mortar composition to predetermined parts of a concrete structure include plastering (trowel application), spraying, and formwork (pouring and filling).

[0038] For example, in a construction method such as plastering (troweling) in which a low-temperature mortar composition having a relatively low fluidity can be used, the low-temperature mortar composition does not need to contain a water-reducing agent or a setting adjuster. In other words, in this case, a low-temperature mortar composition can be used which contains a hydraulic composition containing a hydraulic component consisting of amorphous calcium aluminate and gypsum, and fine aggregate, and water, and in which the content of the hydraulic component is more than 50 mass% based on the total amount of the hydraulic composition.

[0039] <Hardened mortar> The hardened mortar is obtained by hardening the above-mentioned mortar composition for low temperature use. That is, the hardened mortar contains a hardened product of the above-mentioned mortar composition for low temperature use. The low-temperature mortar composition is poured into the area to be repaired or reinforced, or applied with a roller, trowel, brush, etc., and cured for 1 to 3 hours in the above-mentioned low-temperature environment (for example, an environment of -60 to 10°C), thereby forming a hardened mortar containing the hardened product of the low-temperature mortar composition.

[0040] (Compressive strength at -25°C for 3 hours) The compressive strength of the hardened mortar at -25°C for 3 hours is 24N / mm 2 It is preferable that the resistance is 30N / mm or more. 2The compressive strength of the hardened mortar is measured as follows. First, the mortar composition for low temperature use is filled into a cylindrical formwork made of polypropylene, 50 mm in diameter and 100 mm in height, cooled to -25°C, and the top surface is smoothed and immediately cured in a freezer at -25°C for 3 hours. Thereafter, the hardened mortar is removed from the formwork and immediately measured for compressive strength (N / mm) in accordance with JIS A-1108. 2 ) is measured. [Example]

[0041] The present disclosure will be described in more detail with reference to the following examples, but the present disclosure is not limited to these examples.

[0042] (Preparation of mortar composition and production of hardened mortar) The components were mixed in the proportions shown in Table 1 and allowed to stand at 10°C for 12 hours or more to obtain a hydraulic composition. Water was added to the obtained hydraulic composition (powder) so that the water-powder ratio was 18-22% by mass (135-165g water / 750g powder, temperature 30°C), and the mixture was kneaded using a chemical stirrer to prepare a mortar composition. The temperature of the prepared mortar composition immediately after kneading was 20±1°C. The prepared mortar composition was filled into a cylindrical polypropylene formwork measuring 50 mm in diameter and 100 mm in height that had been cooled to -25°C, the top surface was smoothed, and the formwork was immediately cured in a freezer at -25°C for 3 hours, yielding a hardened mortar.

[0043] In Table 1, the materials are as follows: Amorphous C12A7: Amorphous calcium aluminate (main component: amorphous 12CaO·7Al2O3, CaO / Al2O3 molar ratio: 1.7, vitrification rate: 99%) Crystalline C12A7: Crystalline calcium aluminate (main component: crystalline 12CaO 7Al2O3) Crystalline CA: Crystalline calcium aluminate (main component: crystalline CaO·Al2O3) Gypsum: Anhydrite (natural anhydrite CaSO4) Setting agent: Sodium citrate: NaH2(C3H5O(COO)3) :Sodium tartrate:C4H4Na2O6·2H2O :Sodium bicarbonate:NaHCO3 :Slaked lime:Ca(OH)2 :Lithium carbonate:LiCO3 Water reducing agent: Polycarboxylic acid water reducing agent Fine aggregate: silica sand with a particle size of 2 mm or less

[0044] (Evaluation: Compressive strength at -25°C for 3 hours) The hardened mortar obtained in each example was demolded and immediately measured for compressive strength (N / mm 2 The results are shown in Table 1. 2 If the above compressive strength is obtained, it can be evaluated that the compressive strength was able to be developed early even in a low-temperature environment.

[0045] (Evaluation: Flow value (initial liquidity)) The flow value of the mortar composition prepared in each example was measured in accordance with the test method of JASS 15M-103 "Quality Standards for Self-Leveling Materials, Architectural Institute of Japan." The results are shown in Table 1.

[0046] (Evaluation: pot life) The pot life of the mortar composition prepared in each example was measured as follows. The mortar composition was filled into a polypropylene cylindrical formwork with a diameter of 50 mm and a height of 100 mm that had been cooled to -25°C, and then immediately placed in a -25°C freezer. The central temperature of the mortar composition was measured every minute using a K-type thermocouple, and the time until the central temperature rose by 2°C above the temperature of the mortar composition before filling (after mixing was completed) was measured.

[0047] [Table 1]

Claims

1. A mortar composition for low temperature use comprising: a hydraulic composition including a hydraulic component consisting of amorphous calcium aluminate and gypsum, as well as fine aggregate, a water-reducing agent, and a setting modifier; and water, A mortar composition for low temperature use, wherein the content of the hydraulic component is more than 50 mass% based on the total amount of the hydraulic composition.

2. 2. The mortar composition for low temperature use according to claim 1, wherein the vitrification rate of the amorphous calcium aluminate is 80% or more.

3. A hardened mortar obtained by hardening the mortar composition for low temperature use according to claim 1 or 2.

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