cementitious composition

Abstract

To provide a fiber-reinforced cementitious composition that, in a fresh state (uncured state), has flowability suitable for placing work by cast-in-place, and which, after curing, has high compressive strength and small autogenous shrinkage, and hardly generates a shape change caused by flow-down even when placement is performed at a construction site with a slope.SOLUTION: Provided is a cementitious composition that contains powder containing cement, a fine aggregate, water, a cement dispersant and fiber, in which a paste-fine aggregate void ratio is 1.30 to 3.00, and a water-powder ratio is 10 to 30%. Provided is a cementitious composition that contains powder containing cement, a fine aggregate, water, a cement dispersant, fiber and a shrinkage reducing agent, in which a paste-fine aggregate void ratio is 3.00 to 5.00, a water-powder ratio is 10 to 30%, and an aspect ratio of the fiber is 25 to 150.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to cementitious compositions. [Background technology]

[0002] Conventionally, cementitious compositions such as mortar containing fibers (hereinafter also referred to as "fiber-reinforced cementitious compositions") are known. For example, Patent Document 1 describes a low-shrinkage, ultra-high-strength fiber-reinforced cement composition characterized by containing cement, silica fume, gasified coal fly ash, gypsum, a specific expansive agent, a specific shrinkage reducing agent, and metal fibers, each in a specific amount. Furthermore, it is known that fiber-reinforced cement compositions can be cast in place. For example, Patent Document 2 describes a cement composition having specific physical properties, comprising cement, pozzolanic fine powder, fine aggregate with a particle size of 2 mm or less, a cement dispersant (e.g., a polycarboxylic acid-based high-performance water-reducing agent), a hardening accelerator, reinforcing fibers (e.g., steel fibers), and water. This cement composition offers good workability when poured on-site and is suitable for applications such as paving that allow for early reopening of traffic. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2009-84095 [Patent Document 2] Japanese Patent Publication No. 2018-168037 [Overview of the project] [Problems that the invention aims to solve]

[0004] The fiber-reinforced cementum composition should ideally have moderate fluidity when fresh (uncured), and after curing, high compressive strength and low autologous shrinkage. In order to obtain a composition having such excellent physical properties, it is conceivable to optimize the material composition by increasing the water-to-powder ratio (mass ratio of water / (powder containing cement)) to improve fluidity, or by using a cement dispersant (e.g., a high-performance water-reducing agent) to improve the physical properties (compressive strength and autogenous shrinkage rate) after hardening while suppressing an excessive increase in the amount of water. However, when a fiber-reinforced cementitious composition is placed on-site at a construction site having a gradient, there may be a slight flow-down in the composition, and the shape of the hardened body made of the composition may be slightly different from the designed shape. An object of the present invention is to provide a fiber-reinforced cementitious composition that has fluidity suitable for on-site placement work during the fresh (unhardened) state, has high compressive strength and a small autogenous shrinkage rate after hardening, and exhibits almost no change in shape due to flow-down even when placed at a construction site having a gradient. [Means for Solving the Problems]

[0005] As a result of intensive studies to solve the above problems, the present inventor has found that a cementitious composition containing a powder containing cement, fine aggregate, water, a cement dispersant, and fibers, having a paste-fine aggregate void ratio (which may be denoted as "Kp" in this specification) within a specific range and a water-to-powder ratio of 10 to 30%, can achieve the above object, and thus completed the present invention. The present invention provides the following [1] to

[10] .

[0006] [1] A cementitious composition containing a powder containing cement, fine aggregate, water, a cement dispersant, and fibers, characterized in that the paste-fine aggregate void ratio (Kp) is 1.30 to 3.00 and the water-to-powder ratio is 10 to 30%. [2] The cementitious composition according to [1] above, wherein the powder contains a pozzolanic fine powder having a BET specific surface area of 5 to 25 m 2 / g. [3] The cementitious composition is the cementitious composition described in [1] or [2] above, wherein the flow value when 15 dropping motions are not performed in the flow value measurement method described in "JIS R 5201:2015 Physical Testing Methods for Cement" is within the range of 90 to 180 mm. [4] The cementitious composition described in any one of [1] to [3] above, wherein the final setting time according to the method for measuring the physical properties of mortar described in "JIS A 1147:2007 Test Method for Setting Time of Concrete" is within 8 hours. [5] The cementitious composition described in any one of [1] to [4] above, wherein the cementitious composition contains either or both of an inorganic powder (excluding cement) having a Blaine specific surface area of 3,500 to 10,000 cm 2 / g and an expansive agent. [6] The cementitious composition described in any one of [1] to [5] above, wherein the cementitious composition contains a shrinkage reducing agent. [7] The cementitious composition described in any one of [1] to [6] above, wherein the coarse aggregate ratio of the fine aggregate is 1.0 to 2.4. [8] A cementitious composition containing a powder containing cement, a fine aggregate, water, a cement dispersant, a fiber, and a shrinkage reducing agent, wherein the paste fine aggregate void ratio is 3.00 to 5.00, the water-powder ratio is 10 to 30%, and the aspect ratio of the fiber is 25 to 150. [9] The cementitious composition described in [8] above, wherein the amount of the fine aggregate with respect to 100 parts by mass of the powder containing cement is 15 to 50 parts by mass.

[10] A method for producing the cementitious composition described in any one of [1] to [9] above, the method including a material composition determination step of determining the amounts of the powder, the water, and the fine aggregate so that the value of the paste fine aggregate void ratio is within a specific range and the water-powder ratio is 10 to 30%.

[0007] The cementitious composition of the present invention, when fresh (unhardened), has fluidity suitable for on-site placement work, and after hardening, it has high compressive strength and a small self-shrinkage rate, and even when placed in a construction area with a slope, there is almost no change in shape due to flow. The cementitious composition of the present invention is used for applications such as repairing sloped floor slabs. [Modes for carrying out the invention]

[0008] [A. First Embodiment of the Cementaceous Composition of the Present Invention] The cementitious composition of the present invention (hereinafter sometimes abbreviated as "composition") is a composition comprising a cement-containing powder, fine aggregate, water, a cement dispersant, and fibers, wherein the paste-fine aggregate void ratio is 1.30 to 3.00 and the water-powder ratio is 10 to 30%. Examples of cement are not limited to these, but include various types of Portland cement such as ordinary Portland cement, rapid-hardening Portland cement, moderate-heat Portland cement, and low-heat Portland cement, as well as blended cements such as blast furnace cement, silica cement, and fly ash cement, and eco-cements.

[0009] Examples of non-cemental powders in a cement-containing powder include those with a BET specific surface area of ​​5-25 m². 2 Pozzolanic fine powder (hereinafter sometimes abbreviated as "pozzolanic fine powder") in gram amounts, or Blaine specific surface area of ​​3,500 to 10,000 cm² 2 Examples include inorganic powders in a quantity of / g (hereinafter sometimes abbreviated as "inorganic powders"). Examples of pozzolanic fine powders include silica fume, silica dust, fly ash, slag powder, volcanic ash, silica sol, and precipitated silica. In particular, silica fume and silica dust have a BET specific surface area of ​​5 to 25 m². 2 Since it is / g and does not require grinding, it is preferably used in the present invention.

[0010] The BET specific surface area of the pozzolanic fine powder is 5 to 25 m 2 / g, preferably 7 to 20 m 2 / g, more preferably 8 to 16 m 2 / g. When the value is 5 m 2 / g or more, the filling property of the pozzolanic fine powder in the composition is improved, and the compressive strength etc. of the hardened body of the composition increase. When the value is 25 m 2 / g or less, the amount of water for obtaining the desired fluidity decreases, and the compressive strength etc. after the composition is hardened increase. The amount of the pozzolanic fine powder is preferably 3 to 45 parts by mass, more preferably 5 to 40 parts by mass, still more preferably 8 to 35 parts by mass, still more preferably 10 to 33 parts by mass, particularly preferably 12 to 30 parts by mass, relative to 100 parts by mass of the cement. When the amount is 3 parts by mass or more, the fluidity, compressive strength etc. of the composition can be further improved. When the amount is 45 parts by mass or less, the fluidity of the composition can be further improved.

[0011] Examples of the inorganic powder having a Blaine specific surface area of 3,500 to 10,000 cm 2 / g include quartz powder, limestone powder, alumina powder etc. The Blaine specific surface area of the inorganic powder is 3,500 to 10,000 cm 2 / g, preferably 5,000 to 9,500 cm 2 / g, 6,500 to 8,500 cm 2 / g. When the value is 3,500 cm 2 / g or more, the difference in the Blaine specific surface area from the cement becomes large, and the fluidity of the composition can be further improved. When the value is 10,000 cm 2 / g or less, the labor of grinding can be further reduced, and the fluidity of the composition can be further improved. The amount of inorganic powder is preferably 20 to 55 parts by mass, more preferably 25 to 50 parts by mass, and particularly preferably 30 to 45 parts by mass, per 100 parts by mass of cement. If the amount is 20 parts by mass or more, the fluidity of the composition can be further improved due to the particle size of the inorganic powder. If the amount is 55 parts by mass or less, it is not necessary to excessively increase the amount of water to obtain the desired fluidity, and thus a decrease in compressive strength and other properties can be avoided.

[0012] An expanding agent may be incorporated as part of the powder used in this invention. Examples of expansive materials include lime-based expansive materials. The amount of expansive agent is equal to the unit volume (1 m³) of the composition. 3 The amount is preferably 1 to 100 kg, more preferably 5 to 80 kg, even more preferably 10 to 60 kg, and particularly preferably 20 to 50 kg. If the amount is 1 kg or more, the amount of shrinkage of the cured body of the composition can be further reduced. If the amount is 100 kg or less, a decrease in durability due to abnormal expansion can be avoided.

[0013] Examples of fine aggregates include silica sand, river sand, land sand, sea sand, and crushed sand. The particle size distribution of the fine aggregate is preferably such that 80% or more by mass of particles having a particle size of 2.0 mm or less is included, more preferably such that 80% or more by mass of particles having a particle size of 1.5 mm or less is included, even more preferably such that 80% or more by mass of particles having a particle size of 1.0 mm or less is included, and particularly preferably such that 80% or more by mass (preferably 90% or more by mass) of particles having a particle size of 0.15 to 0.6 mm is included. By reducing the proportion of particles with a particle size greater than 1.5 mm, the fluidity of the composition and the compressive strength after hardening can be improved. By reducing the proportion of particles with a particle size of 0.15 mm or less (especially less than 75 μm), the fluidity of the composition can be improved.

[0014] The actual aggregate content is preferably 54% or more, more preferably 57% or more. A value of 54% or more can further improve the fluidity of the composition. There is no particular upper limit to the actual volume ratio of fine aggregate, but it is usually 65%. The amount of fine aggregate is preferably 230 parts by mass or less, more preferably 30 to 210 parts by mass, even more preferably 50 to 200 parts by mass, and particularly preferably 60 to 180 parts by mass, per 100 parts by mass of the cement-containing powder. When the amount is 230 parts by mass or less, the bending strength of the composition becomes greater.

[0015] In this invention, coarse aggregate can be added in addition to fine aggregate. Examples of coarse aggregates include river gravel, land gravel, and crushed stone. The amount of coarse aggregate is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, and particularly preferably 80 parts by mass or less, per 100 parts by mass of the cement-containing powder. When the amount is 120 parts by mass or less, the compressive strength of the composition can be further increased.

[0016] The amount of water should be such that the water-to-powder ratio is 10-30%. The water-to-powder ratio is 10-30%, preferably 11-25%, more preferably 12-21%, even more preferably 13-19%, and particularly preferably 14-17%. If the ratio is less than 10%, the fluidity of the composition decreases. If the ratio exceeds 30%, the compressive strength of the composition decreases. The water-to-powder ratio is calculated using the following formula. Water-to-powder ratio (%) = [Mass of water] × 100 ÷ [Mass of powder containing cement]

[0017] Examples of cement dispersants include lignin-based, naphthalene sulfonic acid-based, melamine-based, and polycarboxylic acid-based water-reducing agents, as well as high-performance water-reducing agents or high-performance water-reducing agents. Among these, high-performance water-reducing agents are preferred due to their significant water-reducing effect. In particular, polycarboxylic acid-based high-performance water-reducing agents are more preferred in terms of improving the fluidity and compressive strength of the composition. The amount of cement dispersant is preferably 0.5 to 3.0 parts by mass, more preferably 0.7 to 2.5 parts by mass, and particularly preferably 0.9 to 2.1 parts by mass, per 100 parts by mass of the cement-containing powder. If the amount is 0.5 parts by mass or more, the water-reducing effect is enhanced. If the amount is 2.5 parts by mass or less, the strength development is further improved.

[0018] In the present invention, a shrinkage reducing agent can be used. Examples of shrinkage-reducing agents include lower alcohol-based (e.g., alkylene oxide adducts of lower alcohols) and higher alcohol-based (e.g., alkylene oxide adducts of higher alcohols). The amount of shrinkage reducing agent is the amount per unit volume (1 m) of the composition. 3 The amount is preferably 1 to 30 kg, more preferably 3 to 25 kg, and particularly preferably 5 to 20 kg. If the amount is 1 kg or more, the amount of shrinkage of the cured body of the composition can be further reduced. If the amount is 30 kg or less, the increase in cost due to excessive inclusion of shrinkage reducing agent can be suppressed. In the present invention, a curing accelerator can be used. Examples of hardening accelerators include nitrite-based, thiocyanate-based, sulfate-based, thiosulfate-based, chloride-based, and alumina-based hardening accelerators, as well as triethanolamine, calcium formate, calcium acetate, and calcium silicate hydrate. In particular, nitrite-based curing accelerators are preferred in the present invention because they can accelerate the initial setting time without reducing the fluidity of the composition.

[0019] Examples of fibers include metal fibers, organic fibers, and carbon fibers. Examples of metal fibers include steel fibers. Examples of organic fibers include vinylon fibers, polypropylene fibers, aramid fibers, high-strength aramid fibers, high-strength polyethylene fibers, high-strength polyarylate fibers, basalt fibers, and PBO fibers. From the viewpoint of preventing material separation of fibers in the composition and improving the fluidity and tensile strength of the composition, the dimensions of the fibers are preferably such that the diameter is 0.05 to 0.5 mm and the length is 5 to 30 mm, more preferably the diameter is 0.1 to 0.4 mm and the length is 8 to 25 mm, and particularly preferably the diameter is 0.1 to 0.3 mm and the length is 12 to 20 mm. The amount of fiber in the composition is preferably 0.5 to 4 volume%, more preferably 1 to 3 volume%, and particularly preferably 1.5 to 2.5 volume%. If the amount is 0.5 volume% or more, the effects of incorporating the fiber (such as increased bending strength) can be further enhanced. If the amount exceeds 4 volume%, the fluidity of the composition decreases.

[0020] The void ratio (Kp) of the paste fine aggregate of the composition of the present invention is 1.30 to 3.00, preferably 1.30 to 2.80, more preferably 1.30 to 2.60, even more preferably 1.30 to 2.30, even more preferably 1.35 to 2.20, and particularly preferably 1.38 to 2.10. If this value is less than 1.30, the compressive strength of the composition will be low. If this value exceeds 3.00, when the composition is cast onto an inclined surface with a gradient, the accuracy of the shape of the hardened composition relative to the design dimensions will be low.

[0021] The paste-to-aggregate void ratio (Kp) refers to the volume ratio of paste to the voids between aggregate particles (paste / voids between aggregate particles). Specifically, the void ratio (Kp) of the paste fine aggregate is expressed by the following formula. Kp = [Volume of paste per unit volume of composition (L / m³)] 3 )÷[Volume of voids between fine aggregate particles per unit volume of composition (L / m 3 )] In the above formula, the volume of paste per unit volume of the composition (L / m³) 3 ) can be calculated using the following formula. [Volume of paste per unit volume of composition (L / m³)] 3 )]={[Unit water volume (kg / m³)] 3 )]÷[Density of water (g / cm³) 3)]}+{[Unit powder amount (kg / m 3 )]÷[Density of powder (g / cm³) 3 )]} Here, the unit water content and unit powder content are values ​​set in the formulation design. The density of water is a value that can be obtained from a commonly used "temperature and density conversion table". The density of the powder is determined experimentally using a method compliant with "JIS R 5201" (Physical Testing Methods for Cement) or a dry density measuring instrument using gas.

[0022] Furthermore, in the above formula, [the volume of voids between fine aggregate particles per unit volume of the composition (L / m³)] 3 )] can be calculated using the following formula. [Volume of voids between fine aggregate particles per unit volume of composition (L / m³)] 3 )] = [Volume of fine aggregate including voids between particles (L / m³) 3 )]-[Unit volume of fine aggregate (L / m³) 3 )] Here, in the formula, [the volume of fine aggregate including the voids between particles (L / m³)] 3 )], and [Unit fine aggregate volume (L / m³ 3 Each of these can be calculated using the following formulas. [Volume of fine aggregate including voids between particles (L / m³)] 3 )] = [Unit volume of fine aggregate (L / m³) 3 )]÷{[Actual volume ratio of fine aggregate (%)]÷100} [Unit volume of fine aggregate (L / m³)] 3 )]=[Unit amount of fine aggregate (kg / m 3 )]÷[[Density of fine aggregate (g / cm³) 3 )] Here, the unit amount of fine aggregate is a value set in the mix design. The density of the fine aggregate is determined experimentally using a method compliant with "JIS A 1109" (Test method for density and water absorption rate of fine aggregate).

[0023] The composition of the present invention has the following physical properties. (a) Physical properties before hardening (fresh state) (a-1) 0 strokes flow In the method for measuring the flow value described in "JIS R 5201:2015 Physical Test Methods for Cement," the flow value when 15 drop motions are not performed (hereinafter also referred to as "0-strike flow") is preferably 90 to 170 mm, more preferably 90 to 150 mm, even more preferably 90 to 130 mm, and particularly preferably 100 to 120 mm. If this value is 90 mm or more, the fluidity of the composition will be better, and the workability of the composition during placement will be better. If this value is 130 mm or less, the accuracy of the shape of the hardened composition relative to the design dimensions will be higher when the composition is placed on an inclined surface with a gradient. Furthermore, while it is preferable to measure the zero-impact flow 90 seconds after removing the flow cone, since the increase in the zero-impact flow usually stops within 90 seconds even if the zero-impact flow is very large, if the zero-impact flow is within the range of 90 to 170 mm, the zero-impact flow value does not change immediately after removing the flow cone, even if 90 seconds have not elapsed, so the value before 90 seconds may be used as the measured value of the zero-impact flow.

[0024] (a-2) 15 strokes flow The flow value measured in accordance with the flow value measurement method described in "JIS R 5201:2015 Physical Test Methods for Cement" (unlike the "0-strike flow" described above, this method involves 15 drop motions and is therefore also referred to as the "15-strike flow" in this specification) is preferably 120 to 200 mm, more preferably 120 to 185 mm, even more preferably 120 to 175 mm, more preferably 125 to 170 mm, and particularly preferably 130 to 165 mm. If this value is 120 mm or more, the fluidity of the composition will be better, and the workability of the composition when it is cast will be better. If this value is 200 mm or less, the accuracy of the shape of the hardened composition when it is cast onto an inclined surface with a gradient will be higher.

[0025] (b) Physical properties after curing (b-1) Compressive strength The compressive strength measured in accordance with the Japan Society of Civil Engineers standard "JSCE-G 505-2010" (Draft Test Method for Compressive Strength of Mortar or Cement Paste Using Cylindrical Specimens) is preferably 90 N / mm² as the value at 28 days of age. 2 More preferably, 110 N / mm 2 The above, particularly preferably 130 N / mm 2 That's all. (b-2) Congealing time The setting times measured in accordance with "JIS A1147:2019" (Test method for concrete setting time) are as follows: The start time is preferably 2 hours or more, more preferably 2 hours and 10 minutes or more, and particularly preferably 2 hours and 20 minutes or more. A start time of 2 hours or more ensures sufficient pot life for the composition. The completion time is preferably 8 hours or less, more preferably 7 hours and 45 minutes or less, and particularly preferably 7 hours and 30 minutes or less. If the completion time is 8 hours or less, for example, when the composition is used as a pavement repair material, traffic can be reopened sooner. The setting time should be measured without incorporating fibers.

[0026] (b-3) Dimensional difference when a slope is applied After placing the composition inside the formwork (internal dimensions: length 40cm x width 10cm x height 10cm), one end in the longitudinal direction was lifted to create a slope of 11% (11cm in height per 100cm in length). Hereafter, the lifted end of the formwork will be referred to as the "upper side," and the end of the formwork on the opposite side will be referred to as the "lower side." After one day of curing, the hardened body of the composition was demolded, and the height dimensions of both ends in the longitudinal direction of the hardened body were measured. The difference between the obtained dimensions and the inner dimensions of the formwork (height 10 cm) was calculated. Specifically, the following two values ​​were calculated. [Dimensional difference at the lower end of the hardened body] = [Height dimension of the lower end of the demolded hardened body] - [100 mm (height dimension within the mold)] [Dimensional difference at the upper end of the hardened body] = [Height dimension of the upper end of the demolded hardened body] - [100 mm (height dimension within the inner dimensions of the formwork)]

[0027] (b-4) Amount of contraction In accordance with the "Autologous Shrinkage Test Method for High-Flow Concrete" of the Japan Concrete Institute (JCI) Superfluid Concrete Research Committee, the composition was placed inside a formwork (internal dimensions: length 160cm x width 40cm x height 40cm), and the amount of autologous shrinkage of the test specimen was measured by installing an embedded strain gauge in the center of the composition (test specimen). The test specimens were demolded at 1 day of age and cured in a sealed state at a constant temperature (20°C). The amount of autologous shrinkage of the cured composition (test specimens) was measured at 182 days of age.

[0028] Next, a method for producing the composition of the present invention will be described. The method for producing the composition of the present invention includes a material composition determination step in which the amounts of powder (cement and other powders), water, and fine aggregate are determined such that the paste fine aggregate void ratio is 1.30 to 3.00 and the water-to-powder ratio is 10 to 30%. The method for producing the composition of the present invention may include, in addition to the material composition determination step, a composition preparation step of kneading each of the materials constituting the composition to obtain the composition. One example of a mixing method is to put a portion of the materials (e.g., cement, other powders, and fine aggregate) into a mixer and mix (dry mix), then add a portion of the remaining materials (e.g., water and cement dispersant) and mix, and finally add the remaining portion of the materials (e.g., fibers) into the mixer and mix.

[0029] [B. Second Embodiment of the Cementaceous Composition of the Present Invention] The cementitious composition of the present invention is a cementitious composition comprising a cement-containing powder, fine aggregate, water, a cement dispersant, fibers, and a shrinkage reducing agent, wherein the paste fine aggregate void ratio (Kp) is 3.00 to 5.00, the water-to-powder ratio is 10 to 30%, and the aspect ratio of the fibers is 25 to 150. The cementitious composition is the same as the cementitious composition of the first embodiment described above, except that the numerical range of the paste fine aggregate void ratio (Kp) is different.

[0030] In the first embodiment described above, a cementitious composition satisfying conditions such as a paste fine aggregate void ratio of 1.30 to 3.00 and a water-to-powder ratio of 10 to 30% can be used to obtain fluidity suitable for placement work without material segregation when fresh (unhardened), and after hardening, it is possible to obtain high compressive strength and low shrinkage, as well as effects such as almost no change in shape due to flow even when placed in construction sites with slopes. However, when filling a narrow space with cementitious composition (mortar) or when producing mortar molded products with a small thickness, improving fluidity may be more important than improving dimensional accuracy in construction areas with slopes. Furthermore, in cases where the thickness of the member cannot be increased, or when applied to roads with heavy traffic of large vehicles, it is desirable to further improve the tensile strength. From this perspective, there is a need for cementitious compositions with a reduced amount of fine aggregate. In this case, however, reducing the amount of fine aggregate presents the problem of increased shrinkage of the hardened mortar. Therefore, in the second embodiment of the present invention, in addition to the excellent physical properties obtained in the first embodiment, a cementitious composition having the above-described structure is provided that can reduce the amount of shrinkage during hardening despite the small amount of fine aggregate.

[0031] In the present invention (second embodiment), the void ratio (Kp) of the paste fine aggregate is 3.00 to 5.00. If the ratio is less than 3.00, the fluidity decreases. If the ratio exceeds 5.00, when the composition is cast onto an inclined surface with a gradient, the accuracy of the cured composition's shape relative to the design dimensions decreases. The water-to-powder ratio is 10-30%, preferably 11-20%, and particularly preferably 12-15%. If the ratio is less than 10%, fluidity decreases. If the ratio exceeds 30%, compressive strength and other properties decrease. The aspect ratio of the fibers is between 25 and 150. If the ratio is less than 25, the tensile strength and other properties will decrease. If the ratio exceeds 150, the fluidity will decrease. The amount of fine aggregate is preferably 15 to 50 parts by mass, more preferably 18 to 46 parts by mass, and particularly preferably 21 to 44 parts by mass, per 100 parts by mass of the cement-containing powder.

[0032] In the second embodiment, in addition to the excellent physical properties such as zero flow described in the first embodiment, there is the advantage of high tensile strength of the cured product. Tensile strength can be measured in accordance with the Japan Concrete Institute standard "JCI-S-002-2003" (Test method for load-displacement curves of fiber-reinforced concrete using notched beams). The tensile strength is preferably 7.5 N / mm 2 More preferably 8.0 N / mm 2 More preferably 8.5 N / mm 2 More preferably 9.0 N / mm 2 More preferably 9.5 N / mm 2 The above, and especially preferably 10.0 N / mm², 2 That's all.

[0033] The compositions of the present invention (first and second embodiments) can be used, for example, as materials for repairing floor slabs. The composition of the present invention is used by pouring it onto the area of ​​the deck slab that needs repair. In this case, even if the upper surface of the deck slab is sloped, the composition will not flow down on the sloped surface, and the repair can be carried out. [Examples]

[0034] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. [Materials used] (1) Cement: Moderate-heat Portland cement (Blaine specific surface area: 3,180 cm²) 2 / g) (2) Pozzolanic fine powder: Silica fume (BET specific surface area: 11m²) 2 / g) (3) Inorganic powder: Quartz powder (Blaine specific surface area: 7,500 cm²) 2 / g) (4) Expansion agent: Lime-based expansion agent (5) Aggregate A: Silica sand (containing granular material with a particle size of 0.15 to 0.6 mm in proportion to 95% by mass or more; actual volume ratio: 59%; coarse particle ratio: 1.9) (6) Aggregate B: Silica sand (containing granular material with a particle size of 0.15 to 0.6 mm in proportion to 95% by mass or more; actual volume ratio: 60%; coarse particle ratio: 1.3) (7) Fibers (First embodiment; Examples 1-13, Comparative Examples 1-9): Steel fibers (Diameter: 0.2 mm, Length: 15 mm) (8) Fibers (Second embodiment; Examples 14-19, Comparative Examples 10-14): Steel fibers (Diameter: 0.20 mm, Length: 3-34 mm) (9) Cement dispersant: Polycarboxylic acid-based high-performance water-reducing agent (liquid; solid content: 27.4% by mass) (10) Shrinkage reducing agent: Lower alcohol-based shrinkage reducing agent (11) Water: Tap water

[0035] [Experimental example relating to the first embodiment of the cementitious composition of the present invention] [Example 1] Cementaceous compositions were prepared using the materials shown in Table 1. Specifically, cement, other powders, and fine aggregate were placed in a pan-type mixer (capacity: 55 liters), dry-mixed for 30 seconds, then water and cement dispersant were added and mixed for 7 minutes. Finally, fibers (and shrinkage reducing agents in Example 6 described later) were added to the mixer and mixed for a further 2 minutes to obtain the composition (volume: 20 liters). The obtained compositions were subjected to the tests shown in Table 2. Details of each test are as described above.

[0036] [Examples 2-13, Comparative Examples 1-9] The experiment was conducted in the same manner as in Example 1, except that the materials shown in Table 1 were used. The results are shown in Table 2. In Table 1, "Kp" represents the void ratio of the paste fine aggregate. "Water-to-powder ratio (%)" is based on mass. "Fine powder" refers to pozzolanic fine powder. "Inorganic powder" refers to quartz powder. "Dispersant" refers to a cement dispersant. "Parts" refers to "parts by mass". "Fibers (%)" is the volume-based proportion (internal allocation) of the composition. Here, "internal percentage" refers to the amount of fiber relative to 100% of the total volume of materials in a composition that includes fiber, rather than the amount of fiber relative to 100% of the total volume of materials in a composition that excludes fiber (volume percentage).

[0037] [Table 1]

[0038] [Table 2]

[0039] Table 2 shows that in Examples 1 to 13, excellent results were obtained in terms of flow value (fluidity), setting time (pot life and early road opening), compressive strength (strength of the repaired portion of the pavement), dimensional difference when a gradient is applied (applicability to pavements with gradients), and shrinkage amount. In Example 5, the water-to-powder ratio was low at 10%, resulting in a longer mixing time compared to the other examples. On the other hand, Comparative Examples 2, 5-9 were inferior to Examples 1-13, at least in the respect of having a large dimensional difference when a gradient was applied. In Comparative Example 3, while the dimensional difference when a gradient was applied was as good as in the example, it was inferior in that its compressive strength was very low.

[0040] [Experimental example relating to a second embodiment of the cementitious composition of the present invention] [Examples 14-19, Comparative Examples 10-14] Cementaceous compositions (Examples 14-19, Comparative Examples 10-14) were prepared in the same manner as in Example 1, except that the materials shown in Table 3 were used, and the physical properties shown in Table 4 were measured. The results are shown in Table 4.

[0041] [Table 3]

[0042] [Table 4]

[0043] As shown in Tables 3 to 4, Examples 14 to 19 exhibited moderate fluidity (0-strand flow, 15-strand flow), high tensile strength, high dimensional accuracy when a gradient was applied, and low shrinkage. On the other hand, in Comparative Example 10, the Kp (paste fine aggregate void ratio) is below the range specified in the present invention (3.00 to 5.00), resulting in poor fluidity (flow value) and large shrinkage. In Comparative Example 11, the Kp is above the range specified in the present invention (3.00 to 5.00), resulting in very low dimensional accuracy when a gradient is applied. In Comparative Example 12, the tensile strength is low because the aspect ratio of the fibers is below the range specified in the present invention (25 to 150). In Comparative Example 13, the fluidity (flow value) is poor because the aspect ratio of the fibers is above the range specified in the present invention (25 to 150). In Comparative Example 14, the amount of shrinkage is very large because no shrinkage-reducing agent is included.

Claims

1. A cementitious composition comprising a cement-containing powder, fine aggregate, water, a cement dispersant, and fibers, The above powder contains, per 100 parts by mass of the above cement, 3 to 45 parts by mass of pozzolanic fine powder having a BET specific surface area of ​​5 to 25 m² / g. The void ratio of the paste aggregate is 1.30 to 3.

00. The water-to-powder ratio is 10-30%. The amount of the fine aggregate is 60 to 230 parts by mass per 100 parts by mass of the powder containing the cement. The above cement dispersant is a high-performance water-reducing agent, and the amount of the above cement dispersant is 0.5 to 3.0 parts by mass per 100 parts by mass of the powder containing the above cement. The above-mentioned fibers have a diameter of 0.05 to 0.5 mm and a length of 5 to 30 mm, and the amount of the above-mentioned fibers is 0.5 to 4% by volume in the above-mentioned cementitious composition. The above cementitious composition is characterized in that, in the flow value measurement method described in "JIS R 5201:2015 Physical Test Methods for Cement," the flow value when 15 drop motions are not performed is within the range of 108 to 130 mm.

2. The cementitious composition according to claim 1, wherein the settling time, as determined by the method for measuring the physical properties of mortar described in "JIS A 1147:2007 Method for testing the setting time of concrete," is 8 hours or less.

3. The above cementitious composition has a Blaine specific surface area of ​​3,500 to 10,000 cm². ２ A cementitious composition according to claim 1 or 2, comprising one or both of the following: inorganic powder (excluding cement and expansive agents) in a quantity of / g and an expansive agent.

4. The cementitious composition according to any one of claims 1 to 3, wherein the cementitious composition comprises a shrinkage reducing agent.

5. The cementitious composition according to any one of claims 1 to 4, wherein the coarseness ratio of the fine aggregate is 1.0 to 2.

4.

6. A cementitious composition comprising a cement-containing powder, fine aggregate, water, a cement dispersant, fibers, and a shrinkage reducing agent, The above powder contains, per 100 parts by mass of the above cement, 3 to 45 parts by mass of pozzolanic fine powder having a BET specific surface area of ​​5 to 25 m² / g. The void ratio of the paste fine aggregate is 3.00 to 5.

00. The water-to-powder ratio is 10-20%. The amount of the above-mentioned fine aggregate is 15 to 50 parts by mass per 100 parts by mass of the above-mentioned powder containing cement. The above cement dispersant is a high-performance water-reducing agent, and the amount of the above cement dispersant is 0.5 to 3.0 parts by mass per 100 parts by mass of the powder containing the above cement. The above-mentioned fibers have a diameter of 0.05 to 0.5 mm, a length of 5 to 30 mm, and an aspect ratio of 25 to 150, and the amount of the above-mentioned fibers is 0.5 to 4% by volume in the above-mentioned cementitious composition. The amount of the above shrinkage reducing agent is 5 to 20 kg per unit volume (1 m³) of the above cementitious composition. The above cementitious composition is characterized in that, in the flow value measurement method described in "JIS R 5201:2015 Physical Test Methods for Cement," the flow value when 15 drop motions are not performed is within the range of 112 to 130 mm.

7. A method for producing a cementitious composition according to any one of claims 1 to 6, A material composition determination step in which the amounts of the powder, water, and fine aggregate are determined such that the void ratio of the paste fine aggregate is within a specific range and the water-to-powder ratio is within a specific range. A method for producing a cementitious composition containing the above.

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