Mortar composition and method of use thereof, and structure

Abstract

To provide a mortar composition that suppresses sagging due to gradients and exhibits excellent workability, dispersibility, and strength development. [Solution] A mortar composition for a floor slab top surface thickening method is provided, comprising cement, silica fume, high-tensile fibers, water-reducing agent, inorganic fine powder, fine aggregate, and water, wherein the mineral composition of the cement is such that the C3S content is 25.0 to 75.0% by mass and the C3A content is less than 4.0% by mass, the silica fume content is 19 to 28 parts by mass per 100 parts by mass of the total of cement and silica fume, and the water-binder ratio is 22 to 29% by mass.

Description

[Technical Field]

[0001] The present invention relates to a mortar composition, a method of using the same, and a structure. [Background Art]

[0002] A cement-based composite material containing reinforcing fibers is known as a cement-based material for reinforcing highway slabs. As such a cement-based composite material, for example, a mortar composition containing cement, high-tensile-strength fibers, a rapid-hardening material, a retarder, fine aggregate, and a water reducing agent has been developed. A mortar composition used for such applications is required to have strength and durability sufficient to suppress cracking, and in order to shorten the closure period for repair work, it is required to exhibit appropriate fluidity during construction while being excellent in short-time strength development. In Patent Document 1, an attempt has been made to provide a mortar composition excellent in fluidity in a low-temperature environment and short-time strength development by adjusting the unit amounts and content ratios of the rapid-hardening material, the retarder, and the water reducing agent contained in the mortar composition. [Prior Art Literature] [Patent Literature]

[0003] [Patent Document 1] Japanese Unexamined Patent Publication No. 2023-30817 [Summary of the Invention] [Problems to be Solved by the Invention]

[0004] Highways have gradients; for example, the Road Structure Ordinance allows gradients of up to 10%. Therefore, the mortar composition used in the deck slab thickening method needs to suppress the occurrence of sagging due to flow when applied to a deck slab with a 10% gradient. This is because if sagging becomes significant, application and finishing become difficult, and countermeasures during application become time-consuming. On the other hand, such mortar compositions are required to have excellent dispersibility due to the incorporation of high-tensile fibers, and also to have excellent workability and strength development from the perspective of shortening the construction period for road repairs.

[0005] This invention provides a mortar composition that suppresses sagging due to gradients and exhibits excellent workability, dispersibility, and strength development. Furthermore, it provides a method for using such a mortar composition, enabling the formation of a hardened material with sufficient compressive strength and high reliability, even in situations requiring short construction periods, such as highway deck repair. Additionally, by incorporating a hardened material of such a mortar composition, the invention provides a structure that can be constructed in a short period and is highly reliable. [Means for solving the problem]

[0006] One aspect of the present invention provides a mortar composition for a floor slab top surface thickening method, comprising cement, silica fume, high-tensile fibers, water-reducing agent, inorganic fine powder, fine aggregate, and water, wherein the mineral composition of the cement is such that the C3S content is 25.0 to 75.0% by mass and the C3A content is less than 4.0% by mass, the silica fume content is 19 to 28 parts by mass per 100 parts by mass of the total of the cement and the silica fume, the inorganic fine powder content is 6 to 50 parts by mass per 100 parts by mass of the cement, and the water-binder ratio is 22 to 29% by mass.

[0007] The above mortar composition contains cement, silica fume, high-tensile fibers, water-reducing agent, inorganic fine powder, bentonite, and fine aggregate, with a water-binder ratio of 22-29% by mass. This water-binder ratio is relatively high for repair applications, resulting in excellent workability and fiber dispersibility. However, a higher water-binder ratio tends to increase viscosity and make sagging due to slopes more likely. However, the inventors have found that by including a sufficient amount of silica fume in the mortar composition, even with a high water-binder ratio, sufficient strength development can be maintained while improving self-support and suppressing sagging due to slopes. The reason for this is thought to be that the inclusion of silica fume improves workability due to the bearing effect of the fine particles, and further imparts thixotropy, which suppresses sagging due to slopes. Due to these factors, the above cement composition is thought to suppress sagging due to slopes and have excellent workability, dispersibility, and strength development.

[0008] One aspect of the present invention provides a method for using a mortar composition, comprising the steps of: pouring the mortar composition onto a deck slab; and providing an asphalt layer on top of the hardened mortar composition. This method of using a mortar composition utilizes a mortar composition that suppresses sagging due to gradients and exhibits excellent workability, dispersibility, and strength development. Using such a mortar composition makes construction easier and increases the strength after construction, resulting in an excellent reinforcing effect. Therefore, it is possible to form a hardened material with sufficient compressive strength and excellent reliability, even in situations where a short construction period is required, such as the repair of highway deck slabs.

[0009] One aspect of the present invention provides a structure comprising a floor slab and a hardened mortar composition cast on the floor slab. This structure features a hardened mortar composition that suppresses sagging due to gradients and exhibits excellent workability, dispersibility, and strength development. Such a structure can be constructed in a short period of time and is highly reliable. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a mortar composition that suppresses sagging due to gradients by imparting thixotropy, while also exhibiting excellent workability, dispersibility, and strength development. Furthermore, using such a mortar composition facilitates construction work and increases post-construction strength, resulting in excellent reinforcement effects. Therefore, it is possible to provide a method for using a mortar composition that has sufficient compressive strength and can form a highly reliable hardened product even in situations requiring short construction periods, such as highway deck repair. Moreover, by incorporating a hardened product of such a mortar composition, it is possible to provide a structure that can be constructed in a short period and is highly reliable. [Brief explanation of the drawing]

[0011] [Figure 1] This is the 1H-NMR spectrum of the defoaming agent used in the example. [Figure 2] This photograph shows an example of a rise caused by slope sagging, used in the evaluation of slope sagging. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described below. However, the following embodiments are illustrative for explaining the present invention and are not intended to limit the present invention to the following. Positional relationships such as up, down, left, and right in the drawings are based on positional relationships based on the orientation of the reference numerals shown in the drawings. Numerical ranges illustrated by "a~b" are numerical ranges that include a and b, with a lower limit being a and b being the upper limit. This embodiment also includes cases where the upper or lower limit of each numerical range is replaced with the numerical value of any embodiment. When multiple materials are illustrated, one of them may be used alone, or multiple materials may be used in combination.

[0013] A mortar composition according to one embodiment is a mortar composition for a deck slab top surface thickening method, comprising cement, silica fume, high-tensile fibers, water-reducing agent, inorganic fine powder, bentonite, and fine aggregate. In the deck slab top surface thickening method, for example, the deck slab can be thickened and its load-bearing capacity improved by pouring the mortar composition onto the existing concrete deck slab surface of highways and bridges and integrating it. The mortar composition of this embodiment has thixotropy, which suppresses sagging due to gradients, and also has excellent workability and dispersibility, making it particularly suitable for reinforcing deck slabs on highways with gradients.

[0014] Cement and silica fume function as binders. In this specification, a binder is a hydraulic binder that hardens upon reaction with water. The cement preferably includes sulfate-resistant cement. This effectively suppresses sagging due to gradients. The mineral composition of the cement has a C3S content of 25.0 to 75.0% by mass and a C3A content of less than 4.0% by mass. This effectively suppresses sagging when the gradient increases (e.g., a 10% gradient). From a similar viewpoint, the C3S content is preferably 40.0 to 73.0% by mass, more preferably 48.0 to 70.0% by mass, and even more preferably 50.0 to 68.0% by mass. From a similar viewpoint, the C3A content is preferably less than 2.7% by mass, more preferably less than 2.3% by mass, and even more preferably less than 1.5% by mass. The lower limit of the C3A content is not particularly limited and may be, for example, 0.1% by mass.

[0015] The C2S content is preferably 9.5 to 40.0% by mass, more preferably 10.0 to 35.0% by mass, and even more preferably 12.0 to 30.0% by mass. The C4AF content is preferably 9.0 to 18.0% by mass, more preferably 10.0 to 16.0% by mass, and even more preferably 11.0 to 15.0% by mass. Having such a mineral composition allows for sufficient suppression of sagging when the gradient becomes large.

[0016] The mineral composition described above is calculated using the Bogue formula shown below. Each chemical component of the cement used in the Bogue formula can be measured in accordance with JIS R 5202:2010 "Methods for Chemical Analysis of Cement".

[0017] C3S content=(4.07×CaO)-(7.60×SiO2)-(6.72×Al2O3)-(1.43×Fe2O3)-(2.85×SO3) C2S content=(2.87×SiO2)-(0.754×C3S) C3A content=(2.65×Al2O3)-(1.69×Fe2O3) C4AF content=3.04×Fe2O3

[0018] The 45 μm sieve residue of cement may be, for example, less than 25.0% by mass, less than 20.0% by mass, less than 18.0% by mass, or less than 16.0% by mass. The 45 μm sieve residue may be 0% by mass or 1.0% by mass or more. If the particle size of the cement is within the above range, a hardened product with even higher compressive strength can be obtained. The 45 μm sieve residue of cement can be measured in accordance with the Japan Cement Association standard test method JCAS K-02 "Method for testing the fineness of cement using a 45 μm mesh sieve".

[0019] The specific surface area of ​​cement is preferably 2500 to 4800 cm². 2 / g, more preferably 2800-4000cm 2 / g, more preferably 2900-3600 cm 2 The value is / g, and is particularly preferably 3000-3500 cm². 2 The value is / g. If the Blaine specific surface area of ​​cement is too small, the strength of the mortar composition tends to decrease, and if it is too large, the fluidity tends to decrease. The Blaine specific surface area of ​​cement can be measured in accordance with JIS R 5201:1997 "Physical Testing Methods for Cement".

[0020] Mortar composition 1 m 3 The unit amount of cement per unit is, for example, 600-950 kg / m³. 3, 650~900kg / m 3 , or 680~850kg / m 3 . When the total amount of the binder contained in the mortar composition is taken as 100 parts by mass, the content of cement may be 60 parts by mass or more, 65 parts by mass or more, or 70 parts by mass or more from the viewpoint of sufficiently enhancing the strength development property of the mortar composition. When the total amount of the binder contained in the mortar composition is taken as 100 parts by mass, the content of cement may be 81 parts by mass or less.

[0021] Silica fume is a by-product obtained by collecting dust from exhaust gas generated during the production of metallic silicon, ferrosilicon, electrofused zirconia, or the like. Silica fume contains, as a main component, amorphous SiO₂ that dissolves in an alkaline solution. The average particle diameter of silica fume is preferably 0.05 to 2.0 μm, more preferably 0.10 to 1.5 μm, and still more preferably 0.18 to 0.28 μm. By using such silica fume, workability can be further improved by the bearing effect of fine particles. Further, the compressive strength of the hardened mortar can be sufficiently increased while maintaining high fluidity of the mortar composition. Unless otherwise specified, the average particle diameter referred to in the present specification means the particle diameter at which the cumulative passing amount reaches 50% by volume in a particle diameter-cumulative passing percentage curve obtained using a laser diffraction / scattering particle size distribution analyzer.

[0022] The content of silica fume relative to a total of 100 parts by mass of cement and silica fume is 19 to 28 parts by mass. From the viewpoint of satisfying all properties including workability, dispersibility, suppression of sag when the gradient is increased, and strength development at a higher level, the content of silica fume relative to a total of 100 parts by mass of cement and silica fume is preferably 20 to 27 parts by mass, more preferably 21 to 26 parts by mass. 1m of the mortar composition 3 The unit amount of silica fume per unit is, for example, 130~260kg / m 3 , 150~250kg / m 3 , or 170~240kg / m 3 .

[0023] High-tensile fibers include at least one fiber selected from the group consisting of metal fibers, carbon fibers, aramid fibers, PP (polypropylene) fibers, PVA (polyvinyl alcohol) fibers, PE (polyethylene) fibers, glass fibers, nylon fibers, and PBO (poly-p-phenylene-benzobiz-oxazole) fibers. Examples of metal fibers include steel fibers, stainless steel fibers, and amorphous alloy fibers. The tensile strength of high-tensile fibers is, for example, 100 to 10,000 N / mm². 2 , 500~5000N / mm 2 , 2000~3000 N / mm 2 , or 2000~2500 N / mm 2 The aspect ratio (fiber length / fiber diameter) of the high-tensile fibers may be, for example, 40-250, 50-200, or 60-170. By including such high-tensile fibers, the toughness and tensile strength of the hardened mortar can be sufficiently increased.

[0024] The fiber diameter of the high-tensile fibers may be, for example, 0.05 to 1.20 mm. The fiber length of the high-tensile fibers may be, for example, 3 to 60 mm. The content of the high-tensile fibers is 1 m of mortar composition. 3 For example, 30-400 kg / m 3 , 50-300 kg / m 3 , 100-200 kg / m 3 , or 120-180 kg / m 3 This may be the case. Mortar composition 1 m in this specification 3 The high-tensile fiber content is the content of the outer layer.

[0025] Examples of inorganic fine powders include limestone fine powder, silica fine powder, and crushed stone fine powder. The inorganic fine powder may be fine powder obtained by crushing and / or classifying limestone powder, silica powder, crushed stone powder, etc. The inorganic fine powder may have the function of supplementing the fine particles of the fine aggregate. The inorganic fine powder content is preferably 5 to 30 parts by mass per 100 parts by mass of cement. This makes it possible to suppress shrinkage during hardening while maintaining sufficiently high dispersibility of high-tensile fibers and strength development of the mortar composition. From a similar viewpoint, the inorganic fine powder content per 100 parts by mass is more preferably 7 to 25 parts by mass, even more preferably 8 to 20 parts by mass, and particularly preferably 9 to 15 parts by mass.

[0026] The Blaine specific surface area of ​​inorganic fine powders is, for example, 3500 to 5500 cm². 2 / g, 4000~5000cm 2 / g, or 4200-4800cm 2 The density may be / g. This allows the fluidity of the mortar composition to be sufficiently high. The density of the inorganic fine powder is 2.4~2.9 g / cm³. 3 , or 2.6~2.8 g / cm³ 3 This may be the case. This further improves the dispersibility of inorganic fine powder in the mortar composition. Mortar composition 1 m 3 The unit amount of inorganic fine powder per unit is, for example, 30-300 kg / m³. 3 , 40-200 kg / m 3 , or 50-150 kg / m 3 That's fine.

[0027] Examples of fine aggregates include river sand, land sand, sea sand, crushed sand, 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, measured in accordance with JIS A 1102:2014, is preferably 5.0 mm or less, more preferably 3.0 mm or less, even more preferably 2.0 mm or less, and particularly preferably 1.5 mm or less. Mortar composition 1 m 3 The unit amount of fine aggregate per unit is, for example, 800-1200 kg / m³. 3900-1150 kg / m 3 , or 950-1100 kg / m 3 This may be the case. The fine aggregate may be prepared by mixing multiple fine aggregates with different particle sizes.

[0028] The water-reducing agent has the effect of improving the fluidity and dispersibility of the mortar composition. Examples of water-reducing agents include high-performance water-reducing agents and high-performance AE water-reducing agents. High-performance water-reducing agents and high-performance AE water-reducing agents can be polycarboxylic acid-based or polycarboxylic acid ether-based. In this embodiment, given the water-binder ratio, the effect of the water-reducing agent on improving fluidity does not need to be very strong, so the water-reducing agent may include a high-performance AE water-reducing agent.

[0029] The water-reducing agent content relative to the total powder material in the mortar composition is preferably 0.2 to 1.5% by mass, more preferably 0.3 to 1.2% by mass, and even more preferably 0.4 to 1.0% by mass. This makes it easier to achieve a sufficiently high level of both fluidity, workability, and strength development in the mortar composition. From a similar viewpoint, 1 m of mortar composition 3 The unit amount of water-reducing agent per unit is, for example, 2-30 kg / m³. 3 , 3-20 kg / m 3 , or 4-10 kg / m 3 That's fine.

[0030] The mortar composition contains water. The water-to-binder ratio (W / B) of the mortar composition is 22-29% by mass, preferably 23-28% by mass, and more preferably 24-27% by mass. This satisfies the requirements for workability, dispersibility, and suppression of sagging due to gradients, while also allowing for sufficiently high compressive strength of the hardened material. Mortar composition 1 m 3 The unit water volume per unit is, for example, 170-280 kg / m³. 3 , 190~260 kg / m 3 , or 210-250 kg / m 3 That's fine.

[0031] The mortar composition may contain an expansive agent. Expansive agents are commercially available, and for example, ettringite-lime composites or lime-based agents can be used. (1 m of mortar composition) 3 The unit amount of expansion material per unit is, for example, 1 to 50 kg / m³. 3 , 5-40 kg / m 3 , or 10-30 kg / m 3 That's fine.

[0032] The mortar composition preferably contains an antifoaming agent. In the mortar composition of this embodiment, which contains a considerable amount of silica fume, the inclusion of an antifoaming agent can further suppress the occurrence of sagging due to the slope. Examples of antifoaming agents include special nonionic surfactants, polyalkylene derivatives, hydrophobic silica, and polyether-based surfactants. Mortar composition 1 m 3 The unit amount of defoaming agent per unit is, for example, 0.1 to 20 kg / m³. 3 , 0.5~10kg / m 3 , or 1-5 kg / m 3 That's fine.

[0033] The mortar composition may contain at least one selected from a rapid-setting agent, a retarder, a shrinkage-reducing agent, a thickener, glass fibers, organic fibers, synthetic resin powder, polymer emulsion, and polymer dispersion. Of these, the rapid-setting agent corresponds to a binder.

[0034] The initial strength development of a mortar composition can be evaluated, for example, by its compressive strength at 1 day of age. A mortar composition specimen prepared in accordance with JIS A 1132:2020 "Method for preparing test specimens for concrete strength testing" was sealed and cured at 20°C, and its compressive strength at 1 day of age was preferably 30 N / mm². 2 More preferably 35 N / mm 2 More preferably 40 N / mm 2That concludes the explanation. With a mortar composition that exhibits excellent initial strength development, the next step can be started soon after the pouring step of pouring the mortar composition onto the floor slab. The next step may be started within, for example, 48 hours, preferably within 24 hours, after the pouring step is completed. The next step may be a step of providing an intermediate layer (for example, a waterproof layer), which may be a step of directly providing an asphalt layer on top of the hardened mortar composition, or a step of providing an asphalt layer on top of an intermediate layer such as a waterproof layer.

[0035] The long-term strength development of a mortar composition can be evaluated, for example, by its compressive strength at 28 days of age. A mortar composition specimen prepared in accordance with JIS A 1132:2020 "Method for preparing test specimens for concrete strength testing" is preferably 110 N / mm² when cured under standard conditions at 20°C. 2 More preferably, 120 N / mm 2 More preferably 130 N / mm 2 That concludes the explanation. This allows for the formation of a hardened material with excellent durability.

[0036] If the strength development of the mortar composition is too high, workability and / or excellent dispersibility may decrease. From this perspective, the compressive strength at 1 day of age mentioned above is 60 N / mm². 2 Less than 50 N / mm 2 It may be less than 160 N / mm². From a similar perspective, the compressive strength of the material at 28 days of age mentioned above is 160 N / mm². 2 Less than 150 N / mm² 2 It can be less than [amount].

[0037] The mortar composition of this embodiment can sufficiently suppress sagging caused by a slope when applied to a deck slab with a slope of 10% or less. For example, even when applied to a deck slab that includes a section with a slope of more than 5% or 6% or more, the occurrence of sagging can be sufficiently suppressed. The mortar composition of this embodiment also has excellent workability, dispersibility, and strength development. For this reason, the mortar composition of this embodiment can be suitably used, for example, when applying a deck slab top surface thickening method to roads (expressways) or bridges. For example, it is particularly suitable as a mortar composition for a deck slab top surface thickening method for deck slabs that include a section with a slope of more than 5% and less than or equal to 10%. Workability as used herein refers to the ease of application when spreading the mortar with a trowel to a thickness of, for example, about 2 cm, and is evaluated from the viewpoint of trowel release and trowel feed. Dispersibility as used herein is evaluated visually by the dispersibility of the high-tensile fibers contained in the mortar composition.

[0038] The mortar composition may be prepared by simultaneously blending and mixing all the raw materials, or by pre-mixing only some of the raw materials and then simultaneously or sequentially blending and mixing the remaining raw materials. For example, the raw materials other than water may be blended and mixed, water may be added to the powdered mixture, and the mixture may be kneaded in a mixer to prepare the mortar composition. A mortar mixer, forced mixer, pan mixer, grout mixer, etc., can be used for mixing. The above-described manufacturing method is an example, and the mortar may be manufactured by a method other than those described above.

[0039] A method of using a mortar composition according to one embodiment comprises the steps of pouring the mortar composition onto a deck slab and providing an asphalt layer on top of the hardened mortar composition. The mortar composition can be the mortar composition of the above embodiment. According to this method of use, the hardened mortar composition can reinforce the existing deck slab and improve the overall durability of the deck slab. An intermediate layer may be provided between the steps of pouring the mortar composition onto the deck slab and providing the asphalt layer. An example of an intermediate layer is a waterproof layer. In this method of use, a mortar composition is used that suppresses sagging due to gradients and has excellent workability, dispersibility, and strength development. Using such a mortar composition makes the work during construction easier and increases the strength after construction, resulting in an excellent reinforcement effect. Therefore, it is possible to obtain a hardened material and structure that has sufficient compressive strength and is highly reliable even in situations where a short construction period is required, such as the repair of highway deck slabs.

[0040] A structure according to one embodiment comprises a floor slab and a hardened mortar composition poured onto the floor slab. The mortar composition can be the mortar composition of the above embodiment. An asphalt layer may be provided on the hardened mortar composition, and an intermediate layer may be provided between the hardened mortar and the asphalt layer. The intermediate layer may be a waterproof layer or another layer.

[0041] The above-mentioned structure features a hardened mortar composition that suppresses sagging due to gradients and exhibits excellent workability, dispersibility, and strength development. Such a structure can be constructed in a short period of time and offers excellent reliability.

[0042] Although embodiments of the present invention have been described above, the present invention is not limited in any way to the embodiments described above.

[0043] As described above, the present invention includes at least the following [1] to [8] embodiments. [1] A mortar composition for a method of thickening the upper surface of a deck slab, It contains cement, silica fume, high-tensile fibers, water-reducing agent, inorganic fine powder, fine aggregate, and water. The mineral composition of the cement is such that the C3S content is 25.0 to 75.0% by mass, and the C3A content is less than 4.0% by mass. The silica fume content is 19 to 28 parts by mass relative to 100 parts by mass of the total of the cement and the silica fume. A mortar composition having a water-binder ratio of 22-29% by mass. [2] The mortar composition according to [1], wherein the content of the inorganic fine powder is 5 to 30 parts by mass per 100 parts by mass of cement. [3] The mortar composition according to [1] or [2], wherein the content of the water-reducing agent relative to the total amount of powder material contained in the mortar composition is 0.3 to 1.5% by mass. [4] A mortar composition according to any one of [1] to [3], further comprising an antifoaming agent. [5] A specimen prepared in accordance with JIS A 1132:2020 "Method for preparing test specimens for concrete strength testing" was sealed and cured at a temperature of 20°C, and its compressive strength at 1 day was 30 N / mm². 2 The above is a mortar composition as described in any one of [1] to [4]. [6] A specimen prepared in accordance with JIS A 1132:2020 "Method for preparing test specimens for concrete strength testing" was cured under standard conditions at a temperature of 20°C, and its compressive strength at 28 days was 110 N / mm². 2 The above is a mortar composition as described in any one of [1] to [5]. [7] A method for using a mortar composition, comprising the steps of: pouring the mortar composition described in any one of [1] to [6] above onto a floor slab; and providing an asphalt layer on top of the hardened mortar composition. [8] A structure comprising a floor slab and a hardened product of any one of the mortar compositions described in [1] to [7] cast on the floor slab. [Examples]

[0044] 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.

[0045] [Preparation of mortar composition] The following raw materials were prepared to prepare the mortar compositions for each example and comparative example.

[0046] (1) Cement (C) Portland cement resistant to sulfates was prepared as the cement. The chemical composition of this cement was measured in accordance with JIS R 5202:2010 "Methods for Chemical Analysis of Cement," and the mineral composition was calculated using the Bogue formula described above. The Blaine specific surface area of ​​this cement was measured in accordance with JIS R 5201:1997 "Methods for Physical Testing of Cement." The results are shown in Table 1.

[0047] [Table 1]

[0048] (2) Silica fume (SF) Silica fume was prepared. The average particle size of this silica fume was 0.24 μm. This average particle size was determined by the following procedure. First, the particle size distribution of this silica fume was measured using a laser diffraction / scattering particle size distribution analyzer (Horiba, Ltd., product name "LA-950V2"). Based on the measurement results, a particle size-passage integrated % curve was calculated, and the particle size at which the passage integrated % was 50 volume% was determined from the particle size-passage integrated % curve. This particle size was taken as the average particle size.

[0049] (3) Fine aggregate (S) The following fine aggregates were prepared. Silica sand N50: Produced in Tochigi Prefecture, particle size 1.2 mm or less, absolute dry density 2.62 g / cm³ 3

[0050] (4) Inorganic fine powder (LP) Inorganic fine powder: Limestone fine powder (density: 2.71 g / cm³) 3Brain specific surface area: 4570 cm² 2 I prepared / g).

[0051] (5) Water-reducing agent (SP) The following water-reducing agents were prepared. LS: High-performance AE water-reducing agent (manufactured by Sika Japan Co., Ltd., product name "Viscocrete SP8HVM", polycarboxylic acid ether type)

[0052] (6) Antifoaming agent (T) A special nonionic surfactant was prepared as an antifoaming agent. Figure 1 shows the results of dissolving this antifoaming agent in deuterated methanol and measuring it using an NMR analyzer (BRUKER, product name "AVANCE"). 1 This is the 1H-NMR spectrum. The molar ratios of the structural units of the antifoaming agent, namely polyoxypropylene (hereinafter abbreviated as "POP"), polyoxyethylene (hereinafter abbreviated as "POE"), and alkyl chain, were calculated based on the integrated signal value originating from the methyl group in POP. Of these, the molar ratio of POE to POP was calculated by subtracting the integrated signal value originating from hydrocarbon groups other than the methyl group in POP from the integrated signal value originating from hydrocarbon groups other than the methyl group in POP and the integrated signal value originating from hydrocarbon groups in POE, which appear around 3.5 ppm. The molar ratios of the structural units of POP, POE, and alkyl chain in the antifoaming agent are shown in Table 2.

[0053] [Table 2]

[0054] (7) Expansion agent (EX) As an expansive material, we prepared an ettringite-lime composite expansive material manufactured by Denka Co., Ltd.

[0055] (8) High-tensile fibers (steel fibers) As a high-tensile fiber, steel fiber (manufactured by Tokyo Rope Milling Co., Ltd., product name "CW9416", density: 7.87 g / cm³) 3Fiber diameter: 0.16 mm, Fiber length: 13 mm, Aspect ratio: 81.25, Tensile strength: 2200 N / mm 2 I prepared ).

[0056] (9) Thickener (Z) We prepared the following two types of thickeners. Zc1: Modified cellulose ether (Adeka Corporation, product name "ADK-C8381") Zc2: Unmodified cellulose ether (Adeka Corporation, product name "ADK-HK4M") (10) Mixing water (W) Tap water was prepared as the mixing water (W).

[0057] (Examples 1-3, Comparative Examples 1-6) Mortar compositions were prepared by mixing the above-mentioned raw materials in the unit amounts shown in Table 3 under conditions of 20°C. Mixing was performed using a Hobart mixer, dry-mixing cement (C), silica fume (SF), fine aggregate (S), inorganic fine powder (LP), expansive agent (EX), water-reducing agent (SP), and defoaming agent (T) for 30 seconds. Water (W) and high-performance water-reducing agent were then added and mixed for 5 minutes (defoaming agent was added only in Example 2 and Comparative Example 4). Subsequently, steel fibers, and in Comparative Examples 5 and 6, a thickening agent (Z), were added and mixed for 2 minutes to obtain the mortar compositions for each example and comparative example. Table 3 shows the "unit amount (kg / m³)". 3 )" is a mortar composition 1m 3 This indicates the mass per unit (unit amount). Table 3 shows the "Addition amount (kg / m³)". 3 )" is a mortar composition 1m 3 This table shows the amount of additive added to the external ratio. A "-" in Table 3 indicates that it is not included.

[0058] [Table 3]

[0059] Table 4 summarizes the water-to-binder ratio (W / B), the mass ratio of silica fume (SF) to binder (B) (i.e., the sum of cement (C) and silica fume (SF)) (SF substitution rate), the mass ratio of inorganic fine powder (LP) to cement (C) (LP ratio), the mass ratio of water-reducing agent (SP) to the total powder material (sum of cement (C), silica fume (SF), inorganic fine powder (LP), and expansive agent (EX)) (SP addition rate), and the mass ratio of thickener (Z) to the total powder material (Z addition rate), calculated based on the formulations shown in Table 3. The type of thickener (Z) is also shown in Table 4. All "%" in Table 4 represents "mass%".

[0060] [Table 4]

[0061] [Evaluation of mortar compositions] (1) Workability The workability of the mortar composition immediately after mixing was evaluated using the following criteria when spreading it with a trowel. The evaluation results are shown in Table 5. A: It could be easily applied to a thickness of 2 cm with a trowel, and the trowel release and feed were good. B: It was possible to apply the material to a thickness of 2 cm using a trowel, but the trowel release and trowel feeding were inferior to A. C: It was difficult to apply the trowel to a thickness of 2 cm.

[0062] (2) Dispersibility of fibers The mortar composition was visually observed immediately after mixing, and the dispersibility of steel fibers was evaluated according to the following criteria. The evaluation results are shown in Table 5. A: The steel fibers are uniformly dispersed in the mortar composition. B: The mortar composition contains partial chunks of steel fibers. C: It has even more chunks of steel fiber than B.

[0063] (3) Evaluation of gradient sag The mortar composition, immediately after mixing, was placed in a mold (length: 25 cm, width: 17 cm, depth: 4 cm) and compacted with a vibrator, filling the mold to the brim with the mortar composition. The presence or absence of sagging of the mortar composition and the height of the resulting mound were evaluated according to the following criteria when the mold filled with the mortar composition was tilted to a 10% slope (angle of inclination relative to the horizontal plane: approximately 6°). The height of the mound is the height of the mortar composition 20 relative to the height of the mold 10, measured on the side 25 (right side of the photograph) that was lower when the mold 10 was tilted, as shown in the photograph in Figure 2. The evaluation results are shown in Table 5. AA: There is absolutely no swelling due to sagging (swell height: 0mm). A: There is almost no swelling due to sagging (swell height: greater than 0mm and less than 1mm). B: There is a bulge due to sagging (bulge height: greater than 1mm and less than or equal to 2mm). C: There is a bulge due to sagging (bulge height: 2mm or more).

[0064] (4) Strength test Cylindrical specimens measuring 5 cm (diameter) x 10 cm (height) were prepared in accordance with JIS A 1132:2020 "Method for preparing specimens for concrete strength testing". These cylindrical specimens were sealed and cured for 1 day at a temperature of 20°C, and then their compressive strength was measured in accordance with JIS A 1108:2006 "Test method for compressive strength of concrete". Furthermore, cylindrical specimens prepared using the above procedure were subjected to standard curing for 28 days at a temperature of 20°C, and then their compressive strength was measured in accordance with JIS A 1108:2006 "Test method for compressive strength of concrete". The results of these measurements are shown in Table 5.

[0065] [Table 5]

[0066] In Table 5, "-" indicates that an evaluation was not performed. As shown in Table 5, all of Examples 1-3 received an "A" or higher rating for workability, fiber dispersibility, and gradient sagging. Furthermore, it was confirmed that Examples 1-3 exhibited superior strength development compared to Comparative Examples 1-6. Comparative Examples 1, 3-6 received a "B" or lower rating for at least one of the following: workability, fiber dispersibility, and gradient sagging. Comparative Example 2 also exhibited inferior strength development.

[0067] In Comparative Examples 5 and 6, where a thickening agent was added to the mortar composition of Comparative Example 4, sagging due to gradient tended to be suppressed, but workability deteriorated and compressive strength was low. From these results, it was confirmed that adding a cellulose-based thickening agent does not improve the properties. [Explanation of Symbols]

[0068] 10...Formwork, 20...Mortar composition.

Claims

1. A mortar composition for thickening the top surface of a deck slab, It contains cement, silica fume, high-tensile fibers, water-reducing agent, inorganic fine powder, fine aggregate, and water. The mineral composition of the cement is C ３ S content is 25.0 to 75.0% by mass, and C ３ The A content is less than 4.0% by mass, The silica fume content is 19 to 28 parts by mass relative to 100 parts by mass of the total of the cement and the silica fume. A mortar composition having a water-binder ratio of 22 to 29% by mass.

2. The mortar composition according to claim 1, wherein the amount of inorganic fine powder per 100 parts by mass of cement is 5 to 30 parts by mass.

3. The mortar composition according to claim 1 or 2, wherein the content of the water-reducing agent relative to the total powder material contained in the mortar composition is 0.3 to 1.5% by mass.

4. The mortar composition according to claim 1 or 2, further comprising an antifoaming agent.

5. A specimen prepared in accordance with JIS A 1132:2020 "Method for preparing test specimens for concrete strength testing" exhibited a compressive strength of 30 N / mm² at 1 day of age after being sealed and cured at a temperature of 20°C. ２ The mortar composition according to claim 1 or 2, as described above.

6. A specimen prepared in accordance with JIS A 1132:2020 "Method for preparing test specimens for concrete strength testing" exhibited a compressive strength of 110 N / mm² at 28 days of age after standard curing at a temperature of 20°C. ２ The mortar composition according to claim 1 or 2, as described above.

7. A method for using a mortar composition, comprising the steps of: pouring the mortar composition described in claim 1 or 2 onto a floor slab; and providing an asphalt layer on top of the hardened mortar composition.

8. A structure comprising a floor slab and a hardened mortar composition according to claim 1 or 2 cast on the floor slab.

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