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 and dispersibility. [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, bentonite, 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 inorganic fine powder content is 6 to 50 parts by mass per 100 parts by mass of cement, 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] Cement-based composite materials containing reinforcing fibers are known as cement-based materials for reinforcing highway floor slabs. As such a cement-based composite material, for example, a mortar composition containing cement, high-strength fibers, a rapid hardening material, a retarder, fine aggregate, and a water reducing agent has been developed. The mortar composition used for such applications is required to have strength and durability sufficient to suppress cracking, exhibit appropriate fluidity during construction, and be excellent in short-time strength development in order to shorten the closure period of repair work. In Patent Document 1, an attempt is 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

Summary of the Invention

Problems to be Solved by the Invention

[0004] Highways have gradients, and for example, the Road Structure Ordinance allows a maximum gradient of 10%. Therefore, the mortar composition used in the deck top thickening construction method is required to suppress the occurrence of sagging due to flow when constructed on a deck with a 10% gradient. This is because when sagging becomes large, construction and finishing become difficult, and measures during construction require labor. On the other hand, such a mortar composition is required to be excellent in dispersibility because it contains high-strength fibers, and from the viewpoint of shortening the construction period for road repair, the mortar composition is also required to be excellent in workability.

[0005] This invention provides a mortar composition that suppresses sagging due to gradients and exhibits excellent workability and dispersibility. Furthermore, it provides a method for using such a mortar composition, enabling the formation of a highly reliable hardened material 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 offers excellent reliability. [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, bentonite, 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 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-to-binder ratio of 22-29% by mass. This water-to-binder ratio is relatively high for repair applications, resulting in excellent workability and fiber dispersibility. However, a higher water-to-binder ratio increases viscosity, making sagging more likely due to slopes. However, in the above mortar composition, the bentonite absorbs the water contained in the mortar composition with a high water-to-binder ratio and swells, filling the gaps in the mortar composition and its hardened product, improving self-supporting properties, and suppressing sagging due to slopes. Furthermore, the inclusion of silica fume is thought to improve workability through the bearing effect of fine particles, and also impart thixotropy, which suppresses sagging due to slopes. Due to these effects, the above cement composition is thought to suppress sagging due to slopes and have excellent workability and dispersibility.

[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 and dispersibility. Using such a mortar composition makes construction easier and increases the strength after construction, resulting in a superior reinforcing effect. Therefore, it is possible to form a hardened material with 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 includes a hardened mortar composition that suppresses sagging due to slope and has excellent workability and dispersibility. 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 and dispersibility. 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 can form a highly reliable hardened material even in situations requiring short construction periods, such as highway deck repair. Moreover, by incorporating a hardened material 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, 650 to 1100 kg / m³. 3 , or 700-900 kg / m 3 It may be as follows: When the total amount of binder contained in the mortar composition is 100 parts by mass, the cement content may be 70 parts by mass or more, 80 parts by mass or more, or 85 parts by mass or more, from the viewpoint of sufficiently increasing the strength development of the mortar composition. When the total amount of binder contained in the mortar composition is 100 parts by mass, the cement content may be 92 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, fused 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. Use of such silica fume can further improve workability due to the bearing effect of fine particles. Further, the compressive strength of a cured mortar can be sufficiently increased while maintaining high fluidity of the mortar composition. Unless otherwise specified, the average particle diameter as used herein refers to the particle diameter at which the cumulative passing fraction is 50% by volume in a particle diameter-cumulative passing fraction % curve obtained using a laser diffraction / scattering type 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 preferably 8 parts by mass or more and less than 20 parts by mass, more preferably 10 parts by mass or more and less than 18 parts by mass. When silica fume is contained in such a mass ratio, appropriate thixotropy is imparted to the mortar composition. This makes it possible to achieve both workability and suppression of sagging due to gradient at a higher level. 1 m of mortar composition 3 the unit amount of silica fume per unit is, for example, 40 to 250 kg / m 3 , 60 to 200 kg / m 3 , or 80 to 150 kg / m 3 may be used.

[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 (polyparaphenylene benzobisoxazole) fibers. Examples of the metal fibers include steel fibers, stainless steel fibers, amorphous alloy fibers, and the like. The tensile strength of the high-tensile fibers is, for example, 100 to 10000 N / mm 2 , 500 to 5000 N / 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 fiber may be, for example, 0.05 to 1.20 mm. The fiber length of the high-tensile fiber may be, for example, 3 to 60 mm. The content of the high-tensile fiber 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 per 100 parts by mass of cement is 6 to 50 parts by mass. 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 of cement is preferably 7 to 40 parts by mass, more preferably 8 to 35 parts by mass, and even more preferably 9 to 30 parts by mass.

[0026] The Blaine specific surface area of ​​inorganic fine powder is, for example, 3500 to 5500 cm². 2 / g, 4000~5000cm 2 / g, or 4200-4800cm 2The 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, 40-400 kg / m³. 3 , 50-300 kg / m 3 , or 60-250 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. 3 900-1180 kg / m 3 , or 950-1150 kg / m 3 This may be the case. The fine aggregate may be prepared by mixing multiple fine aggregates with different particle sizes.

[0028] Bentonite absorbs water and swells in the mortar composition, thereby filling gaps in the mortar composition and hardened material, increasing its self-supporting properties, and suppressing sagging due to gradients. Although bentonite is known as a type of thickener, this sagging suppression effect cannot be obtained with polymer-based, cellulose-based, and acrylic-based thickeners, which have different thickening mechanisms than bentonite. This is thought to be because polymer-based, cellulose-based, and acrylic-based thickeners thicken by the entanglement of polymers or the formation of a gel-like structure, and therefore cannot sufficiently fill gaps in the mortar composition and hardened material, thus failing to suppress sagging due to gradients.

[0029] The particle size of the bentonite may be 150 μm or less, 100 μm or less, or 90 μm or less. The moisture content of the bentonite may be 20% by mass or less, or 15% by mass or less.

[0030] The bentonite content is as follows: 1 m³ of mortar composition 3 Preferably, 1.0 to 10.0 kg / m 3 , more preferably 2.0 to 8.0 kg / m 3 More preferably 3.0 to 7.0 kg / m 3 This allows for maintaining a sufficiently high level of workability while further suppressing the occurrence of sagging due to the slope. Mortar composition 1m in this specification 3 The bentonite content is the content divided by the outside. From a similar viewpoint, the bentonite content relative to the total powder material contained in the mortar composition is preferably 0.1 to 2.0% by mass, more preferably 0.2 to 1.5% by mass, and even more preferably 0.3 to 1.0% by mass.

[0031] 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.

[0032] 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 / m3 That's fine.

[0033] 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.

[0034] 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.

[0035] Mortar compositions may contain defoaming agents. The inclusion of defoaming agents can improve workability. Examples of defoaming agents include special nonionic surfactants, polyalkylene derivatives, hydrophobic silica, and polyether-based surfactants. (1 m of mortar composition) 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.

[0036] The mortar composition may contain at least one selected from a rapid hardening agent, a retarder, a shrinkage reducing agent, glass fibers, organic fibers, synthetic resin powder, polymer emulsion, and polymer dispersion. Of these, the rapid hardening agent corresponds to a binder.

[0037] 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 34 N / mm 2 More preferably 35 N / mm 2 That 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.

[0038] 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 That concludes the explanation. This allows for the formation of a hardened material with excellent durability.

[0039] 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 50 N / mm². 2 It may be less than 150 N / mm². From a similar perspective, the compressive strength of the material at 28 days of age mentioned above is 150 N / mm². 2 It can be less than [amount].

[0040] 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 and dispersibility. 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%. In this specification, workability 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. In this specification, dispersibility is evaluated visually by the dispersibility of the high-tensile fibers contained in the mortar composition.

[0041] 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.

[0042] 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. This method of use uses a mortar composition that suppresses sagging due to gradients and has excellent workability and dispersibility. Using such a mortar composition makes construction easier and increases the strength after construction, resulting in an excellent reinforcement effect. Therefore, a highly reliable hardened material and structure can be obtained even in situations where a short construction period is required, such as the repair of highway deck slabs.

[0043] 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.

[0044] The above-described structure features a hardened mortar composition that suppresses sagging due to gradients and offers excellent workability and dispersibility. Such a structure can be constructed in a short timeframe and is highly reliable.

[0045] Although embodiments of the present invention have been described above, the present invention is not limited in any way to the embodiments described above.

[0046] 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, bentonite, 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 amount of the inorganic fine powder per 100 parts by mass of the cement is 6 to 50 parts by mass. A mortar composition having a water-binder ratio of 22-29% by mass. [2] The mortar composition according to claim 1, wherein the amount of silica fume relative to 100 parts by mass of the cement and the silica fume is 8 parts by mass or more and less than 20 parts by mass. [3] The bentonite content is as follows: 3 For comparison, 1.0~10.0 kg / m 3 The mortar composition described in [1] or [2]. [4] The mortar composition according to any one of [1] to [3], 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. [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]

[0047] 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.

[0048] [Preparation of mortar composition] The following raw materials were prepared to prepare the mortar compositions for each example and comparative example.

[0049] (1) Cement (C) Two types of cement, a and b, were prepared. Cement a is sulfate-resistant Portland cement, and cement b is ordinary Portland cement. The chemical components of cements a and b were 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 ​​cements a and b was measured in accordance with JIS R 5201:1997 "Methods for Physical Testing of Cement." The results are shown in Table 1.

[0050] [Table 1]

[0051] (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.

[0052] (3) Fine aggregate (S) The following two types of fine aggregate were prepared. Silica sand N30: ​​Produced in Tochigi Prefecture, particle size 2.5 mm or less, absolute dry density 2.62 g / cm³ 3 Silica sand N50: Produced in Tochigi Prefecture, particle size 1.2 mm or less, absolute dry density 2.62 g / cm³ 3

[0053] (4) Inorganic fine powder (LP) Inorganic fine powder: Limestone fine powder (density: 2.71 g / cm³) 3 Brain specific surface area: 4570 cm² 2 I prepared / g).

[0054] (5) Water-reducing agent (SP) We prepared the following two types of water-reducing agents. L: Polycarboxylic acid-based high-performance water-reducing agent (solid content concentration: 25% by mass) LS: High-performance AE water-reducing agent (manufactured by Sika Japan Co., Ltd., product name "Viscocrete SP8HVM", polycarboxylic acid ether type)

[0055] (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.

[0056] [Table 2]

[0057] (7) Expansion agent (EX) As an expansive material, we prepared an ettringite-lime composite expansive material manufactured by Denka Co., Ltd.

[0058] (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) 3 Fiber diameter: 0.16 mm, Fiber length: 13 mm, Aspect ratio: 81.25, Tensile strength: 2200 N / mm 2 I prepared ).

[0059] (9) Thickener (Z) We prepared the following three types of thickeners. Zb: Bentonite (Chemical composition: Al2O3·4SiO2·H2, manufactured by PVK Minerals & Chemicals Pvt. Ltd, product name "PVK BOND") 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).

[0060] (Examples 1-14, Comparative Examples 1-10) 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, only for Comparative Examples 10 and 14) for 30 seconds. Water (W) and high-performance water-reducing agent were then added and mixed for 5 minutes (defoaming agent was added only for Example 14 and Comparative Example 10). Subsequently, steel fibers and a thickener (Z) were added and mixed for 2 minutes to obtain the mortar compositions for each example and comparative example. Note that no thickener was added in Comparative Examples 4 and 10. Table 3 shows the "unit amount (kg / m)". 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 3This table shows the amount of additive added to the external ratio. A "-" in Table 3 indicates that it is not included.

[0061] [Table 3]

[0062] Table 4 shows the types of cement (C), water-reducing agent (SP), and thickener (Z). Table 4 also summarizes the water-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), all calculated based on the formulations shown in Table 3. All "%" in Table 4 represent "mass%".

[0063] [Table 4]

[0064] [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.

[0065] (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.

[0066] (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. A: There is almost no swelling due to sagging (swell height: 1 mm or less). 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).

[0067] (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.

[0068] [Table 5]

[0069] In Table 5, "-" indicates that an evaluation was not performed. As shown in Table 5, all of Examples 1 to 14 received an "A" rating for workability, fiber dispersibility, and gradient sagging. In contrast, Comparative Examples 1 to 10 had a rating of "B" or lower for at least one of the workability, fiber dispersibility, and gradient sagging. For example, Comparative Examples 5 to 7, which used ordinary Portland cement, received a "B" or "C" rating for gradient sagging.

[0070] Comparative Examples 4 and 10, which did not use a thickening agent, both received a "C" rating for gradient sagging. Comparative Example 8, which contained modified cellulose ether as a thickening agent, also received a "C" rating for workability despite containing only 0.02% by mass of modified cellulose ether relative to the total powder material. Comparative Example 9, which contained unmodified cellulose ether as a thickening agent, also received a "B" rating for workability. It was clear that increasing the amount of thickening agent further would worsen the workability ratings, and therefore, the amount of thickening agent could not be increased. The compressive strength of the examples at 1 day (sealed curing) and 28 days (standard curing) tended to be moderately high. [Explanation of Symbols]

[0071] 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, bentonite, 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 amount of the inorganic fine powder per 100 parts by mass of the cement is 6 to 50 parts by mass. 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 silica fume relative to 100 parts by mass of the cement and the silica fume is 8 parts by mass or more and less than 20 parts by mass.

3. The bentonite content is as follows: 1 m of mortar composition ３ For comparison, 1.0 to 10.0 kg / m ３ The mortar composition according to claim 1 or 2.

4. 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.

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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