JP7828786B2 - High-strength mortar repair material - Google Patents

Description

This invention relates to a high-strength mortar repair material.

Concrete and mortar harden with binders such as cement to form hardened materials with desired properties. Hydraulic compositions used to form such hardened materials are required to have various properties depending on their application. For example, Patent Document 1 proposes a technique for repairing existing concrete structures by incorporating reinforcing fibers. The cross-linking effect of these reinforcing fibers prevents cracking and forms high-density, high-strength concrete.

Japanese Patent Publication No. 2017-133344

When repairing existing structures, workers may perform on-site work using trowels and other tools. Repair areas may be located at high elevations or in narrow gaps. Therefore, mortar repair materials used for these repairs must possess not only excellent strength after hardening, but also superior workability for trowel application and other processes. Accordingly, this invention provides a high-strength mortar repair material that offers excellent workability for plastering finishes and superior hardening properties.

The present invention relates to a high-strength mortar repair material comprising cement, silica fume, a water-reducing agent, an antifoaming agent, inorganic fine powder, and fine aggregate, wherein the cement contains 40.0 to 75.0% by mass of _C3S , and _C3 The present invention provides a high-strength mortar repair material that contains more than 0% by mass and less than 2.7% by mass of A, and has a 45 μm sieve residue of less than 25.0% by mass, and the inorganic fine powder and fine aggregate together contain 10.0% by mass or more and less than 40.0% by mass of particles with a particle size of 0.15 mm or less, and 5.0% by mass or more and 30.0% by mass of particles with a particle size of 0.075 mm or less, and the inorganic fine powder is one or more fine powders selected from the group consisting of limestone fine powder, silica powder and crushed stone powder, and contains 3 to 30 parts by mass of silica fume and 0.1 to 6.0 parts by mass of water-reducing agent per 100 parts by mass of the total amount of cement and silica fume, and contains 300 to 1200 kg/ ^m³ of fine aggregate and 50 to 600 kg/ ^m³ of inorganic fine powder based on 1 ^m³ of high-strength mortar repair material.

Such high-strength mortar repair materials contain each component in a predetermined proportion along with a specified cement. The inorganic fine powder and fine aggregate, combined, have a predetermined particle size. This high-strength mortar repair material forms a slurry with a high yield value, achieving high levels of all properties: good trowel release and spreadability during application, crack resistance during application, and resistance to sagging after application. Therefore, it facilitates plastering work and offers excellent workability. Furthermore, it achieves sufficiently high compressive strength after hardening, resulting in superior hardening properties.

The above-mentioned high-strength mortar repair material preferably further contains a thickening agent. While the flow value of the high-strength mortar repair material increases when it contains a water-reducing agent, the thickening agent imparts thixotropy to the high-strength mortar repair material when it is made into a slurry, further improving its trowel spreadability, sagging resistance, and crack resistance during plastering.

The above-mentioned thickening agent preferably includes a bentonite-based thickening agent or a polymer-based thickening agent. This allows the viscosity of the high-strength mortar repair material when it is made into a slurry to be within an appropriate range, further improving the trowel spreadability, sagging resistance, and crack resistance during plastering.

The above-mentioned high-strength mortar repair material preferably contains 0.01 to 2.0 parts by mass of a thickening agent per 100 parts by mass of cement and silica fume. This further improves the trowel spreadability, sagging resistance, and crack resistance during plastering.

The above-mentioned high-strength mortar repair material preferably further contains fibers, and these fibers preferably include at least one of inorganic fibers and organic fibers. This further improves the curing properties of the high-strength mortar repair material. Specifically, it reduces the occurrence of cracks in the cured material and effectively suppresses spalling.

If the above fibers include inorganic fibers, it is preferable that the inorganic fibers include at least one selected from the group consisting of steel fibers, stainless steel fibers, amorphous alloy fibers, glass fibers, carbon fibers, and basalt fibers. If the above fibers include organic fibers, it is preferable that the organic fibers include at least one selected from the group consisting of vinylon fibers, aramid fibers, nylon fibers, PE fibers, PP fibers, PVA fibers, and PBO fibers. This further improves the curing properties of the high-strength mortar repair material.

The fiber content is preferably 0.1 to 3% by volume relative to the total amount of non-fiber components. This further improves the curing properties of the high-strength mortar repair material.

The above-mentioned high-strength mortar repair material preferably contains 10 to 25 parts by mass of water per 100 parts by mass of cement and silica fume. Such a slurry-like high-strength mortar repair material offers excellent workability for plastering finishes.

The above-mentioned high-strength mortar repair material is preferably used for repairing structures with a compressive strength design standard of 150 N/ ^mm² or higher. Because this high-strength mortar repair material has excellent curing properties, it can form a cured material with sufficiently high compressive strength. For example, if conventional low-strength mortar repair material is used as a repair material for high-strength structures with a compressive strength design standard of 150 N/ ^mm² or higher, the resulting structural load-bearing capacity will be insufficient. Therefore, as described above, the above-mentioned high-strength mortar repair material can be suitably used as a repair material for high-strength structures with a compressive strength design standard of 150 N/ ^mm² or higher.

This material provides a high-strength mortar repair material with excellent workability and hardening properties for plastering finishes.

This is a photograph showing the appearance of the test specimen after a 26-week acceleration period, used in the evaluation of resistance to carbonation. This graph shows the distribution of chloride ion concentration along the depth direction from the surface of the mortar. (A) is a graph showing the relationship between the number of freeze-thaw cycles and the mass loss rate, and (B) is a graph showing the relationship between the number of freeze-thaw cycles and the relative dynamic elastic modulus.

The following describes one embodiment of the present invention. However, the following embodiments are illustrative for illustrating the present invention and are not intended to limit the present invention to the following.

A high-strength mortar repair material according to one embodiment comprises cement, silica fume, a water-reducing agent, an antifoaming agent, inorganic fine powder, and fine aggregate. The high-strength mortar repair material may be in powder form, or it may be in a slurry form by adding water. A slurry-type high-strength mortar repair material may be prepared by mixing water with a powdered high-strength mortar repair material.

The mineral composition of the cement contains 40.0 to 75.0% by mass of _C3S and more than 0% but less than 2.7% by mass of _C3A . The mineral composition of the cement preferably contains 45.0 to 73.0% by mass of _C3S , more preferably 48.0 to 70.0% by mass, and even more preferably 50.0 to 68.0% by mass. The mineral composition of the cement preferably contains more than 0% but less than 2.3% by mass of _C3A , more preferably more than 0% but less than 2.1% by mass, and even more preferably more than 0% but less than 1.9% by mass. When the _C3S content is less than 40.0% by mass, the compressive strength tends to decrease, and when it exceeds 75.0% by mass, the firing of the cement itself tends to become difficult. Also, when the _C3A content is 2.7% by mass or more, the fluidity tends to decrease. The lower limit of the _C3A content is not particularly limited and may be, for example, 0.1% by mass.

The mineral composition of the cement preferably contains 9.5 to 40.0% by mass of _C2S , more preferably 10.0 to 35.0% by mass, and even more preferably 12.0 to 30.0% by mass. The mineral composition of the cement preferably contains 9.0 to 18.0% by mass of _C4AF , more preferably 10.0 to 15.0% by mass, and even more preferably 11.0 to 15.0% by mass. Within this range of mineral composition of the cement, it is possible to achieve a sufficiently high level of both fluidity and compressive strength after hardening in the high-strength mortar repair material.

The particle size of the cement is such that the residue after sieving through a 45 μm sieve is less than 25.0% by mass, preferably less than 20.0% by mass, more preferably less than 18.0% by mass, and even more preferably less than 15.0% by mass. The lower limit of the residue after sieving through a 45 μm sieve is 0.0% by mass, preferably 1.0% by mass, and more preferably 4.0% by mass. If the particle size of the cement is within this range, a hardened material with sufficiently high compressive strength can be formed. Furthermore, this slurry-like high-strength mortar repair material containing cement has appropriate viscosity. Therefore, sufficient dispersibility can be ensured even when fibers are added.

The Blaine specific surface area of cement is preferably 2,500 to 4,800 ^cm² /g, more preferably 2,800 to 4,000 ^cm² /g, even more preferably 3,000 to 3,600 ^cm² /g, and particularly preferably 3,100 to 3,500 ^cm² /g. If the Blaine specific surface area of cement is too low, the strength of the hardened high-strength mortar repair material tends to decrease. If the Blaine specific surface area of cement is too high, the fluidity at low water-cement ratios tends to decrease.

The above-mentioned cement can be manufactured by adjusting the blending of raw materials such as limestone, silica, slag, coal ash, construction waste soil, and blast furnace dust according to the target mineral composition, firing them in a kiln, and then adding gypsum to the resulting clinker and grinding it to a predetermined particle size. A general NSP kiln or SP kiln can be used for firing, and a general ball mill or similar grinder can be used for grinding. Furthermore, two or more types of cement can be used as needed.

Silica fume is a by-product obtained by collecting dust from exhaust gas generated during the production of metallic silicon, ferrosilicon, electrofused zirconia, etc., and its main component is amorphous _SiO₂ that dissolves in alkaline solutions. The average particle size of silica fume is preferably 0.05 to 2.0 μm, more preferably 0.10 to 1.5 μm, and even more preferably 0.18 to 0.28 μm. By using such silica fume, it is possible to improve the mixability of high-strength mortar repair materials while further increasing the compressive strength of the cured product.

The high-strength mortar repair material contains 3 to 30 parts by mass of silica fume, preferably 10 to 25 parts by mass, and more preferably 15 to 20 parts by mass, per 100 parts by mass of the total amount of cement and silica fume. This formulation allows for good mixability of the high-strength mortar repair material while achieving sufficiently high compressive strength after hardening.

Examples of water-reducing agents include polycarboxylic acid-based, lignin-based, naphthalene sulfonic acid-based, and aminosulfonic acid-based water-reducing agents, high-performance water-reducing agents, and high-performance AE water-reducing agents. From the viewpoint of ensuring fluidity at low water-cement ratios, it is preferable that the water-reducing agent includes at least one selected from the group consisting of polycarboxylic acid-based water-reducing agents, high-performance water-reducing agents, and high-performance AE water-reducing agents, and more preferably a polycarboxylic acid-based high-performance water-reducing agent.

The high-strength mortar repair material contains 0.1 to 6.0 parts by mass, preferably 0.2 to 4.0 parts by mass, and more preferably 0.3 to 3.0 parts by mass, of a water-reducing agent per 100 parts by mass of the total amount of cement and silica fume.

Examples of defoaming agents include special nonionic surfactants, polyalkylene derivatives, hydrophobic silica, and polyether-based surfactants. For high-strength mortar repair material, the amount of defoaming agent is preferably 0.01 to 2.0 parts by mass, more preferably 0.02 to 1.5 parts by mass, and even more preferably 0.03 to 1.0 parts by mass, per 100 parts by mass of the total amount of cement and silica fume.

The inorganic fine powder includes at least one selected from the group consisting of limestone fine powder, silica powder, and crushed stone powder. The inorganic fine powder is a fine powder obtained by grinding or classifying limestone fine powder, silica powder, and/or crushed stone powder, etc., until the Blaine specific surface area is 2500 ^cm² /g or more, and is blended for the purpose of adjusting the fine particle content. When such inorganic fine powder and the fine aggregate described later have a predetermined particle size, the viscosity and yield value of the high-strength mortar repair material are within an appropriate range, improving the suitability for plastering finishes such as trowel spreadability, trowel releaseability, sagging resistance, and crack resistance. The Blaine specific surface area of the inorganic fine powder is preferably 3000 to 5500 ^cm² /g, more preferably 3500 to 5000 ^cm² /g, and even more preferably 4000 to 4500 ^cm² /g.

The high-strength mortar repair material contains 50 to 600 kg/ ^m³ of inorganic fine powder per 1 ^m³ of high-strength mortar repair material, preferably 100 to 500 kg/ ^m³ , more preferably 150 to 400 kg/ ^m³ , and even more preferably 200 to 300 kg/ ^m³ . This allows for an even higher level of balance between workability for plastering finishes and hardening properties.

The inorganic fine powder preferably contains 85.0% to 100.0% by mass of particles with a particle size of 0.15 mm or less, more preferably 90.0% to 100.0% by mass, and even more preferably 95.0% to 100.0% by mass. The inorganic fine powder preferably contains 80.0% to 100.0% by mass of particles with a particle size of 0.075 mm or less, more preferably 85.0% to 100.0% by mass, and even more preferably 90.0% to 100.0% by mass.

Examples of fine aggregates include river sand, land sand, sea sand, crushed sand, silica sand (crushed silica sand), limestone aggregate, blast furnace slag fine aggregate, ferronickel slag fine aggregate, copper slag fine aggregate, and electric furnace oxidized slag fine aggregate. The particle size of the fine aggregate is such that it passes completely through a 10 mm sieve and passes through a 5 mm sieve at least 85% by mass.

The high-strength mortar repair material contains 300 to 1200 kg/ ^m³ of fine aggregate per 1 ^m³ of high-strength mortar repair material, preferably 400 to 1000 kg/ ^m³ , more preferably 500 to 900 kg/ ^m³ , and even more preferably 600 to 800 kg/ ^m³ . This makes it possible to achieve an even higher level of balance between workability for plastering finishes and hardening properties.

It is preferable to use a combination of multiple fine aggregates with different particle sizes. For example, when using a first fine aggregate and a second fine aggregate with different particle sizes, the particle size of the first fine aggregate is preferably 0.2 to 1.0, more preferably 0.4 to 0.8, and the particle size of the second fine aggregate is preferably 1.5 to 3.0, more preferably 2.0 to 2.8. By using multiple fine aggregates with different particle sizes in this way, it is possible to achieve a higher level of both workability and hardening properties in plastering finishes. The particle size ratio is the value obtained by dividing the sum of the mass percentages of aggregate remaining in each of 10 types of sieves with mesh openings ranging from 80 mm to 0.15 mm by 100.

The inorganic fine powder and fine aggregate together contain 10.0% to less than 40.0% by mass, preferably 20.0% to 37.0% by mass, and more preferably 25.0% to 35.0% by mass, of particles with a particle size of 0.15 mm or less. Furthermore, the inorganic fine powder and fine aggregate together contain 5.0% to 30.0% by mass, preferably 10.0% to 27.0% by mass, and more preferably 20.0% to 25.0% by mass, of particles with a particle size of 0.075 mm or less. By having the combined particle size of the inorganic fine powder and fine aggregate within the above range, a highly uniform slurry can be prepared in a short time. In this way, the slurrying time can be shortened. Furthermore, when the high-strength mortar repair material is made into a slurry, its viscosity and yield value are kept within an appropriate range, improving its suitability for plastering finishes, including trowel application, trowel release, sagging resistance, and crack resistance.

The combined particle size of inorganic fine powder and fine aggregate can be measured by actually preparing a mixture of inorganic fine powder and fine aggregate and using a sieve, or it can be calculated from the individual particle sizes of the inorganic fine powder and fine aggregate and their mixing ratio. Note that preparing a mixture of inorganic fine powder and fine aggregate is not essential when manufacturing high-strength mortar repair material; inorganic fine powder and fine aggregate can be mixed together with other raw materials.

In this specification, the content of particles with a particle size of 0.15 mm or less is determined as the mass ratio below the sieve when sieving using a sieve with a mesh opening of 0.15 mm. The content of particles with a particle size of 0.075 mm or less is determined as the mass ratio below the sieve when sieving using a sieve with a mesh opening of 0.075 mm.

High-strength mortar repair material may contain any optional components. Examples of optional components include thickeners, fibers, synthetic resin powders, and setting retarders.

Examples of thickening agents include bentonite-based, cellulose-based, acrylic-based, and polymer-based agents. Of these, it is preferable to include a bentonite-based or polymer-based thickening agent, and more preferably a bentonite-based thickening agent. This ensures that the viscosity of the high-strength mortar repair material when it is made into a slurry is within an appropriate range, further improving the trowel spreadability, sagging resistance, and crack resistance during plastering. Furthermore, it shortens the slurrying time, improving workability.

The high-strength mortar repair material preferably contains 0.01 to 2.0 parts by mass, more preferably 0.03 to 1.5 parts by mass, and even more preferably 0.05 to 1.0 parts by mass, of a total of 100 parts by mass of cement and silica fume, a thickening agent. By including the thickening agent within this range, the viscosity of the high-strength mortar repair material when it is made into a slurry can be maintained within a more favorable range.

As the expanding agent, metal powder, calcium sulfoaluminate (CSA-based), and lime-based agents mainly composed of CaO can be used. Examples of calcium sulfoaluminate-based expanding agents include hauyne, with expanding agents that produce erintgeite being particularly preferred. Examples of lime-based expanding agents include quicklime, quicklime-gypsum mixtures, and calcined dolomite, with quicklime and/or quicklime-gypsum mixtures being preferred. These expanding agents can be used individually or in combination of two or more.

The amount of expansive agent per 1 ^m³ of high-strength mortar repair material is preferably 5 to 40 kg, more preferably 10 to 35 kg, even more preferably 15 to 35 kg, and particularly preferably 20 to 35 kg. A low amount does not contribute to the expansiveness, and a high amount causes excessive expansion, which is undesirable.

The fibers may include at least one of inorganic fibers and organic fibers. The inorganic fibers preferably include at least one selected from the group consisting of steel fibers, stainless steel fibers, amorphous alloy fibers, glass fibers, carbon fibers, and basalt fibers. The organic fibers preferably include at least one selected from the group consisting of vinylon fibers, aramid fibers, nylon fibers, PE fibers, PP fibers, PVA fibers, and PBO fibers. Including such fibers further improves the curing properties of the high-strength mortar repair material. Examples of curing properties include compressive strength and splitting tensile strength. Therefore, the occurrence of cracks in the cured material and the resulting spalling can be sufficiently suppressed. The fiber content in the high-strength mortar repair material is preferably 0.1 to 3% by volume, more preferably 0.1 to 2% by volume, even more preferably 0.1 to 1% by volume, and even more preferably 0.2 to 0.5% by volume, relative to the total components of the high-strength mortar repair material other than the fibers. This further improves the curing properties of the high-strength mortar repair material.

The high-strength mortar repair material preferably contains 10 to 25 parts by mass of water, more preferably 12 to 20 parts by mass, and even more preferably 13 to 18 parts by mass, per 100 parts by mass of the total amount of cement and silica fume. The unit water content per 1 ^m³ of the high-strength mortar repair material is preferably 150 to 250 kg/ ^m³ , more preferably 160 to 240 kg/ ^m³ , and even more preferably 180 to 220 kg/ ^m³ . Such a slurry-like high-strength mortar repair material has excellent workability for plastering finishes.

The fluidity of the slurry-type high-strength mortar repair material is preferably 120 to 140 mm per 15-putt flow. This allows for sufficiently smooth plastering. The hardened product of the high-strength mortar repair material has sufficiently high compressive strength. For this reason, it can be suitably used as a repair material for structures, for example, where the design standard for compressive strength is 150 N/ ^mm² or higher. The compressive strength of the hardened product of the high-strength mortar repair material (age: 28 days) is preferably 150 N/ ^mm² or higher, more preferably 160 N/ ^mm² or higher, and even more preferably 165 N/ ^mm² or higher. Such a high-strength mortar repair material can be even more suitably used as a repair material for the above-mentioned structures. This compressive strength is a value measured by the method described in the examples.

The manufacturing method for the repair mortar is not particularly limited. For example, some or all of the raw materials other than water may be mixed in advance, then water may be added and mixed in a mixer to form a slurry. After that, some or the remaining raw materials other than water may be mixed in. In this way, the raw materials other than water may be added to the slurry in multiple stages. When incorporating fibers, after preparing the slurry, the fibers are added to the mixer and mixed further. The mixer used for each mixing stage is not particularly limited; mortar mixers, twin-shaft forced mixers, pan mixers, grout mixers, and hand mixers can be used. As such, it is easy to mix even at low water-cement ratios, so various mixers can be used. For example, since a hand mixer can be used, it is easy to prepare on-site and provides excellent workability for plastering finishes.

High-strength mortar repair materials are useful as mortar repair materials for plastering finishes, for example, because they are suitable for plastering finishes. Such high-strength mortar repair materials can be suitably used, for example, for small-scale repair applications and for repairing structures with a compressive strength design standard of 150 N/ ^mm² or higher.

Although one embodiment of the present invention has been described above, the present invention is not limited in any way to the above embodiment.

The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[Preparation of mortar repair material 1]
The following raw materials (1) to (10) were prepared.
(1) Cement (C)
Portland cement was prepared by mixing raw materials such as limestone, silica, slag, coal ash, construction waste soil, and copper ash, firing them in a kiln, and then adding gypsum and grinding the mixture. The chemical composition of the prepared Portland cement was measured according to JIS R 5202:2010 "Methods for Chemical Analysis of Cement," and the mineral composition was calculated using the Bogue formula shown below. The mineral composition is shown in Table 1.

C ₃ S = (4.07 x CaO) - (7.60 x SiO ₂ ) - (6.72 x Al ₂ O ₃ ) - (1.43 x Fe ₂ O ₃ ) - (2.85 x SO ₃ )
C ₂ S=(2.87×SiO ₂ )−(0.754×C ₃ S)
C ₃ A=(2.65×Al ₂ O ₃ )−(1.69×Fe ₂ O ₃ )
_C4AF =3.04 _{× Fe2O3}

The residue of Portland cement was measured using a 45 μm sieve according to the Japan Cement Association standard test method JCAS K-02, "Test Method for Fineness of Cement Using a 45 μm Sieve," and the Blaine specific surface area was measured according to JIS R 5201-1997, "Physical Test Methods for Cement." The results are shown in Table 1.

(2) Silica fume (SF) Average particle size: 0.24 μm
The average particle size of silica fume was determined by the following procedure. The particle size distribution of silica fume was measured using a laser diffraction/scattering particle size distribution analyzer (Horiba, Ltd., product name "LA-950V2"). From this measurement result, a particle size-passage integrated % curve was calculated, and the particle size at which the passage integrated 50% by volume was determined from the particle size-passage integrated % curve was found. This particle size was taken as the average particle size. An aqueous solution of sodium hexametaphosphate (sodium hexametaphosphate concentration: 0.2 mass%) was used as the sample dispersion medium. Before measuring the particle size distribution, the sample was dispersed for 10 minutes using a homogenizer with an output of 600W. The calculation of the particle size distribution followed the Mie scattering theory. The particle refractive index was set to 1.45-0.00i, and the solvent refractive index to 1.333. Table 2 shows the passage integrated (volume %) for each particle size.

(3) Inorganic fine powder: Limestone fine powder, density 2.71 g/ ^cm³ , Blaine specific surface area 4280 ^cm² /g
(4) Fine aggregate Silica sand A: crushed silica sand, absolute dry density 2.56 g/cm ³ , coarse grain ratio 0.57
Silica sand B: crushed silica sand, absolute dry density 2.56 g/cm ³ , coarse particle ratio 2.33

The particle size of the above-mentioned inorganic fine powder and fine aggregate was measured according to JIS A 1102-2006 "Sieving Test Method for Aggregates." The results are shown in Table 3.

(5) Antifoaming agent: Special nonionic surfactant (6) Water-reducing agent: High-performance polycarboxylic acid-based water-reducing agent (powder type)
(7) Thickener Thickener A: Bentonite-based thickener Thickener B: Polymer-based thickener (8) Expanding agent: Calcium sulfoaluminate/lime composite, conforms to JIS A 6202:2017 "Expanding agent for concrete" (9) Fiber Fiber A: Steel fiber, fiber diameter: 220 μm, fiber length: 6 mm
Fiber B: Vinylon fiber, fiber diameter: 26 μm, fiber length: 6 mm
(10) Mixing water (W): Tap water

<How to mix>
A CB-34 high-power mortar mixer manufactured by Maruto Seisakusho Co., Ltd. was used to mix each of the raw materials. First, all the raw materials except the mixing water were placed in a plastic bag and mixed by hand, incorporating air. The hand-mixed mixture was then placed in a mixing container and dry-mixed at low speed for 30 seconds. After that, the mixer was stopped and all of the mixing water was added. After adding the mixing water, mixing was started at low speed, and this point was defined as the start time for measuring the slurry formation time. The time taken to visually determine when the mixture changed from a powdery state to a slurry state was defined as the slurry formation time.

After slurrying, the mixture was kneaded at low speed for one minute, then the mixer was stopped. A spatula was used to scrape off any mortar lumps and powder adhering to the mixing container and paddle. Afterward, the mixture was kneaded again at low speed for one minute to complete the mixing process. The mixing volume was 1.3 L of mortar repair material (mortar composition) including water. The mortar repair materials for each example and comparative example were prepared in this manner.

The mixing ratios and amounts of raw materials in each example and comparative example are shown in Tables 4 and 5. In Table 4, "W/(C+SF)" indicates parts by mass of mixing water relative to 100 parts by mass of the total amount of cement and silica fume, and "SF/(C+SF)" indicates parts by mass of silica fume relative to 100 parts by mass of the total amount of cement and silica fume. In addition, "parts by mass" for inorganic fine powder, fine aggregate, defoamer, water-reducing agent, and thickener in Tables 4 and 5 indicates parts by mass relative to the total amount of cement and silica fume. Furthermore, "kg/ ^m³ " for inorganic fine powder and fine aggregate in Table 4, and for expansive agent in Table 5, indicates the mixing amount based on 1 ^m³ of high-strength mortar repair material, and "Fiber A" and "Fiber B" in Table 5 indicate the percentage (volume %) added to the total amount of raw materials other than fibers.

From the particle sizes (Table 3) and blending ratios (Table 4) of the inorganic fine powder and fine aggregate used in each example and comparative example, the mass ratios of particles with a particle size of 0.15 mm or less and the mass ratios of particles with a particle size of 0.075 mm or less were calculated when the inorganic fine powder and fine aggregate were mixed. In other words, these values represent the combined particle sizes of the inorganic fine powder and fine aggregate. The results are shown in Table 6.

[Assessment of suitability for plaster finishes]
The suitability of the mortar repair materials prepared in each example and comparative example for plastering was evaluated from the viewpoints of trowel release, trowel spreadability, sagging resistance, and crack resistance, according to the following criteria. The evaluation results are shown in Table 7.

<Ease of releasing the curling iron>
The ease of application of mortar repair material to the repair area using a trowel, and then removing the trowel from the applied mortar repair material, was ranked from 1 to 3 according to the following evaluation criteria. Of the following evaluation criteria, "1" represents the worst trowel release, and "3" represents the best trowel release.
1. When removing the trowel from the mortar repair material, the mortar repair material sticks to the trowel and adheres to it.
2. When removing the trowel from the mortar repair material, some of the material may stick to the trowel, but it will peel off if you remove it slowly.
3. The trowel easily separates from the mortar repair material.

<Curling iron spreadability>
The ease of application of mortar repair material to the repair area using a trowel was ranked from 1 to 3 according to the following evaluation criteria. Of the following evaluation criteria, "1" represents the worst trowel spreadability, and "3" represents the best trowel spreadability.
1. When applying the mortar repair material, the trowel is heavy, causing the mortar repair material to break up and making it impossible to spread it evenly.
2. When applying the mortar repair material, some force is required, but the mortar repair material does not crack and can be spread over a wide area.
3. When applying mortar repair material, it can be spread over a wide area with almost no effort.

<Sagging resistance>
The presence or absence of sagging when mortar repair material is applied to the repair area with a trowel and left to stand was ranked from 1 to 3 according to the following evaluation criteria. Of the following evaluation criteria, "1" is the worst resistance to sagging, and "3" is the best resistance to sagging.
1. When mortar repair material is left to stand, it will sag.
2. Mortar repair material does not sag when left standing, but sagging occurs when slight vibration is applied.
3. The mortar repair material does not sag even when subjected to slight vibration.

<Crack resistance>
The surface of the mortar repair material applied to the repair area was finished by sliding a trowel over it several times. The crack formation on the finished surface was ranked from 1 to 3 according to the following evaluation criteria. Of the following evaluation criteria, "1" represents the worst crack resistance, and "3" represents the best crack resistance.
1. Numerous fine cracks appear on the surface of the repaired area.
2. Fine cracks may appear on the surface of the repaired area.
3. No microscopic cracks appear on the surface of the repaired area.

The average values of the above evaluation results were calculated and shown in Table 7 with two significant figures.

[Evaluation of freshness]
The fresh properties of the mortar repair materials prepared in each example and comparative example were evaluated using the following procedure. The evaluation results are shown in Table 8.

<Slurry Formation Time>
This is the slurry formation time described in the "mixing method" above.

<Mortar 15-strand flow>
The mortar flow rate of 15 applications was measured in accordance with JIS R 5201:1997 "Physical Testing Methods for Cement," under conditions without dropping. If the mortar flow rate of 15 applications is between 120 and 140 mm, it can be said that it is a mortar repair material that is easy to apply with plastering finishes.

[Evaluation of hardening properties]
The curing properties of the mortar repair materials prepared in each example and comparative example were evaluated using the following procedure. The evaluation results are shown in Table 8.

<Compressive strength>
A cylindrical specimen measuring 5 cm (diameter) x 10 cm (height) was prepared in accordance with JIS A 1132:2020 "Method for preparing specimens for concrete strength testing". The specimen was cured to the standard age (28 days). The compressive strength was measured in accordance with JIS A 1108:2018 "Test method for compressive strength of concrete".

<Tensile strength of splitting>
Cylindrical specimens were prepared using the same procedure as for measuring compressive strength. The splitting tensile strength was measured in accordance with JIS A 1113:2006 "Test method for splitting tensile strength of concrete".

The "Overall Evaluation" in Table 8 was determined by considering the evaluation results for suitability of the plaster finish, fresh properties, and hardened properties, and was evaluated according to the following criteria.
◎: When the suitability evaluation for plaster finish is 2.5 or higher, the slurrying time is less than 1 minute 30 seconds, and the compressive strength is 160 N/ ^mm² or higher. ○: When the suitability evaluation for plaster finish is 1.5 or higher but less than 2.5, the slurrying time is 1 minute 30 seconds or longer, and the compressive strength is 160 N/mm² or ^higher . △: When the suitability evaluation for plaster finish is less than 1.5, the slurrying time is 1 minute 30 seconds or longer, and the compressive strength is 160 N/ ^mm² or higher. ×: When the suitability evaluation for plaster finish is less than 1.5, the slurrying time is 1 minute 30 seconds or longer, and the compressive strength is less than 160 N/ ^mm².

The overall evaluation of each example was ◎ or ○, confirming that the suitability for plastering finishes, fresh properties, and hardening properties were all excellent.

[Durability]
The cured mortar repair material of Example 5 was used to evaluate its resistance to neutralization, chloride ion penetration, and freeze-thaw cycles using the following procedure.

<Evaluation of resistance to carbonation>
Rectangular specimens (40 mm × 40 mm × 160 mm) were prepared, and the carbonation depth was measured in accordance with JIS A 1153:2012 "Test Method for Accelerated Carbonation of Concrete". The sample size was 3. As shown in Table 9, all specimens had a carbonation depth of 0.0 mm at each stage of the acceleration period from 2 to 26 weeks. From these results, it was confirmed that the hardened mortar repair material of Example 5 has excellent resistance to carbonation. Figure 1 is a photograph showing the appearance of the specimen after 26 weeks of acceleration.

<Evaluation of resistance to chloride ion osmosis>
Rectangular specimens (40 mm × 40 mm × 160 mm) were prepared, and the penetration of chloride ions into the specimens, which were immersed in a 10% by mass sodium chloride aqueous solution for 6 months in accordance with JSCE-G572-2010 "Draft Test Method for Apparent Diffusion Coefficient of Chloride Ions in Concrete by Immersion," was analyzed and evaluated using EPMA. For the EPMA measurement, a test piece cut from the immersed specimen was divided into 520 × 520 points within a 40 mm × 40 mm area, and surface analysis was performed. The chloride ion concentration distribution along the depth direction from the mortar surface obtained from the measurement was examined. The results are shown in Figure 2.

In accordance with JSCE-G572-2010, the apparent diffusion coefficient of chloride ions was calculated from the measurement results in Figure 2 using the least squares method. The surface chloride ion concentration used was the value obtained by converting the concentration of a 10% sodium chloride aqueous solution to a unit volume (64.9 kg/ ^m³ ). As a result, the chloride ion penetration depth during 6 months of immersion was 2 mm or less, and the apparent diffusion coefficient of chloride ions was 0.0055 ^cm² /year. These values are significantly smaller than those of general concrete. From these results, it was confirmed that the hardened mortar repair material of Example 5 has sufficiently excellent resistance to chloride ion penetration.

<Evaluation of freeze-thaw resistance>
Rectangular specimens (100 mm x 100 mm x 400 mm) were prepared, and the mass loss rate and relative dynamic elastic modulus were measured in accordance with JIS A 1148:2010 "Test method for freeze-thaw cycles of concrete (Method A)". The results are shown in Figure 3 and Table 7. As shown in Table 10, in Example 5, even after more than 1000 freeze-thaw cycles, there was almost no mass loss, and the relative dynamic elastic modulus did not decrease. From these results, it was confirmed that the hardened mortar repair material of Example 5 has excellent freeze-thaw resistance.

<Preparation of mortar repair material 2>
Mortar repair materials for Examples 7 and 8 were prepared using a hand mixer instead of a mortar mixer. The raw materials, mixing ratios, and amounts of each raw material used in Examples 7 and 8 were the same as those in Examples 5 and 6. As the hand mixer, a UM15V mixer manufactured by Koki Holdings Japan Co., Ltd. and sold under the HiKOKI brand was used, and the screw used was HiKOKI model number: 981706 screw (A1) (standard accessory for UM15, outer diameter: 115 mm).

All ingredients except the mixing water were placed in a plastic bag, air was incorporated, and the mixture was hand-mixed to prepare the mixture. For mixing, first, all of the mixing water and half of the hand-mixed ingredients were placed in an 18L steel pail and mixed for 1 minute until it transformed from a powder to a slurry. Then, one-quarter of the hand-mixed ingredients were added and mixed for 2 minutes until it became a slurry again. Finally, the remaining hand-mixed ingredients were added and mixed for 5 minutes until it became a slurry once more, completing the mixing process. In this manner, the mortar repair materials of Examples 7 and 8 were prepared.

The mortar repair materials prepared in this manner for Examples 7 and 8 were evaluated for their suitability for plastering finishes, their fresh properties, and their hardening properties. The evaluation methods were as described above. The results are shown in Table 11.

Even when a hand mixer was used instead of a mortar mixer, it was confirmed that the suitability for plastering finishes, fresh properties, and hardening properties were all evaluated favorably.

This material provides a high-strength mortar repair material that facilitates plastering work and exhibits excellent hardening properties.

Claims (9)

A high-strength mortar repair material comprising cement, silica fume, water-reducing agent, defoaming agent, inorganic fine powder, fine aggregate , and expansive agent ,
The cement contains 40.0 to 75.0% by mass of _C3S and more than 0% by mass and less than 2.7% by mass of _C3A , and the residue on a 45 μm sieve is less than 25.0% by mass.
The inorganic fine powder and the fine aggregate together contain 10.0% by mass or more and less than 40.0% by mass of particles with a particle size of 0.15 mm or less, and 5.0% by mass or more and 30.0% by mass or less of particles with a particle size of 0.075 mm or less.
The inorganic fine powder contains limestone fine powder,
The total amount of the cement and the silica fume is 100 parts by mass, and the mixture contains 3 to 30 parts by mass of the silica fume and 0.1 to 6.0 parts by mass of the water-reducing agent.
A high-strength mortar repair material comprising 300 to 1200 kg/ ^m³ of the fine aggregate and 50 to 600 kg/ ^m³ of the inorganic fine powder, based on 1 ^m³ of the aforementioned high-strength mortar repair material. The high-strength mortar repair material according to claim 1, further comprising a thickening agent. The high-strength mortar repair material according to claim 2, wherein the thickening agent comprises a bentonite-based thickening agent or a polymer-based thickening agent. The high-strength mortar repair material according to claim 2 or 3, comprising 0.01 to 2.0 parts by mass of the thickening agent per 100 parts by mass of the total amount of the cement and the silica fume. It contains even more fibers,
The high-strength mortar repair material according to any one of claims 1 to 4, wherein the fibers include at least one of inorganic fibers and organic fibers. If the aforementioned fibers include the aforementioned inorganic fibers, the inorganic fibers include at least one selected from the group consisting of steel fibers, stainless steel fibers, amorphous alloy fibers, glass fibers, carbon fibers, and basalt fibers.
The high-strength mortar repair material according to claim 5, wherein if the fibers include the organic fibers, the organic fibers include at least one selected from the group consisting of vinylon fibers, aramid fibers, nylon fibers, PE fibers, PP fibers, PVA fibers, and PBO fibers. The high-strength mortar repair material according to claim 5 or 6, wherein the fiber content is 0.1 to 3% by volume relative to the total amount of components other than the fiber. A high-strength mortar repair material according to any one of claims 1 to 7, comprising 10 to 25 parts by mass of water per 100 parts by mass of the total amount of cement and silica fume. The high-strength mortar repair material is used for repairing structures with a compressive strength design standard of 150 N/ ^mm² or more, as described in any one of claims 1 to 8.