JP2024008193A - Cement composition and method for producing cement molded body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cement composition capable of obtaining a cement molded body with relatively high snow-melting efficiency, and to provide a method for producing the cement molded body.

SOLUTION: A cement composition according to the present invention comprises cement, graphite, and water. A method for producing a cement molded body according to the present invention also includes: an addition step of adding 1 mass% or more and 40 mass% or less of water to an addition amount of the graphite to obtain a graphite water containing material; a kneading step of kneading the water-added graphite, the cement, and the water to obtain an unhardened mixture; and a vibrating step of applying vibrations to the unhardened mixture.

SELECTED DRAWING: None

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a cement composition and a method for producing a cement molded body.

Spraying snow melting agents and antifreeze agents has been widely known as a measure to prevent snow accumulation and snow melt from freezing. However, for example, when a snow melting agent or an antifreeze agent is sprayed on a road surface, it may be washed away by vehicles passing by, and the expected snow melting effect may not be obtained. Furthermore, since spraying snow melting agents and antifreeze agents is not a permanent measure, there is also an issue in terms of sustainability of the snow melting effect. Therefore, in snowy and cold regions, snow melting systems, snow melting blocks, and the like are widely used as a measure to prevent snow accumulation and melted snow from freezing.

For example, Patent Document 1 discloses a concrete flat plate that has a built-in heat pipe or electric heater wire and can be used as a snow melting block. The concrete slab contains cement, inorganic particles having a predetermined specific surface area, a water reducing agent, and water, and has high thermal conductivity. Therefore, even if the concrete slab is constructed thickly and the distance from the heat source to the surface (road surface) is large, it is possible to suppress the delay in the rise of the surface temperature, and also to suppress the energy consumption of heat pipes, etc. be able to.

JP2004-284913A

In recent years, there has been a need to further reduce energy consumption from economic and environmental protection perspectives. Therefore, as in Patent Document 1, methods are being considered to suppress energy consumption by increasing thermal conductivity and improving snow melting efficiency, and a method that further improves snow melting efficiency is desired.

The present invention has been made in view of the current situation, and an object of the present invention is to provide a cement composition and a method for producing a cement molded body that can obtain a cement molded body with relatively excellent snow melting efficiency. shall be.

The cement composition according to the present invention includes cement, graphite, and water.

By containing cement, graphite, and water, the cement composition can provide a cement molded body with relatively excellent snow melting efficiency. More specifically, by containing the graphite, the cement composition can increase the thermal conductivity of the cement molded body. As a result, the snow melting efficiency of the cement molded body can be improved.

In the cement composition according to the present invention, the graphite may include flaky graphite.

With such a configuration, the cement composition can provide a cement molded body with even more excellent snow melting efficiency. More specifically, since flaky graphite has a flat shape and a flat surface, it is easier to orient than graphite having other shapes. Thermal conductivity increases when the flaky graphite is oriented and the plane directions are aligned. Therefore, it is possible to obtain a cement molded body with even more excellent snow melting efficiency.

In the cement composition according to the present invention, the aspect ratio (longest diameter/thickness) of the flaky graphite may be 10 or more and 200 or less.

With such a configuration, the cement composition can provide a cement molded body with even more excellent snow melting efficiency.

In the cement composition according to the present invention, the graphite content may be 11% by mass or more and 40% by mass or less based on the entire cement composition.

With such a configuration, the cement composition can provide a cement molded body with even more excellent snow melting efficiency.

In the cement composition according to the present invention, the graphite may have an average particle size of 30 μm or more and 700 μm or less.

With such a configuration, the cement composition can provide a cement molded body with even more excellent snow melting efficiency. Moreover, when manufacturing the cement molded body, the materials can be easily kneaded.

The method for producing a cement molded body according to the present invention includes the steps of: adding water to graphite in an amount of 1% by mass or more and 40% by mass or less based on the added amount of graphite to obtain a graphite water-containing material; The method includes a kneading step of kneading the graphite water-containing material obtained in step 1, cement, and water to obtain an unhardened kneaded material, and a vibration step of applying vibration to the unhardened kneaded material.

By including the above-mentioned addition step, the above-mentioned kneading step, and the above-mentioned vibration step, the method for producing a cement formed object can obtain a cement formed object with relatively excellent snow melting efficiency. More specifically, by including the vibration step, the plane directions of the flaky graphite can be aligned so that they are parallel to the concrete placement surface. As a result, the snow melting efficiency of the cement molded body can be improved.

Moreover, the method for manufacturing the cement molded body can improve the workability of manufacturing the cement molded body with such a configuration. More specifically, by including the addition step, it is possible to prevent graphite from scattering and deteriorating the working environment when measuring graphite or kneading graphite with other materials such as cement. . Furthermore, by including the above-mentioned addition step, graphite and other materials become compatible with each other, so it is possible to add graphite in the amount necessary to obtain a cement molded body with relatively excellent snow melting efficiency.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the cement composition and cement molded object which can obtain a cement molded object with comparatively excellent snow melting efficiency can be provided.

<Cement composition>
The cement composition according to this embodiment will be described below.

The cement composition according to this embodiment includes cement, graphite, and water.

Examples of cement include ordinary Portland cement, early strength Portland cement, ultra early strength Portland cement, moderate heat Portland cement, low heat Portland cement, sulfate-resistant Portland cement, white Portland cement, etc. as specified in JIS R 5210. , ultra-fast hardening cement, alumina cement, etc. Furthermore, various mixed cements in which fly ash, blast furnace slag, etc. are mixed with the Portland cement can also be used. Among these, it is preferable to use early-strength Portland cement as the cement. In addition, one type of cement may be used alone, or two or more types may be used in combination.

From the viewpoint of increasing strength development, the content of the cement is preferably 10% by mass or more and 70% by mass or less, more preferably 50% by mass or more and 65% by mass or less, based on the entire cement composition. . In addition, when two or more types of cement are included, the content is the total content of cement.

Examples of graphite include natural graphite and artificial graphite. Among these, it is preferable to use natural graphite from the viewpoint of ensuring snow melting efficiency and improving thermal conductivity. Examples of the shape of graphite include scale-like, lump-like, earth-like, and spherical shapes. Among these, the shape of graphite is preferably scaly from the viewpoint of improving orientation. Note that scaly means a flat shape like fish scales. Regarding the production areas of natural graphite, scaly graphite is mainly produced in China, Brazil, etc., and massive graphite is mainly produced in China, Sri Lanka, etc.

The graphite preferably includes flaky graphite from the viewpoint of improving snow melting efficiency. The aspect ratio of the flaky graphite is preferably 10 or more and 200 or less, more preferably 12 or more and 115 or less. The aspect ratio of flaky graphite is expressed as the ratio between the longest diameter of the flaky graphite particles and the thickness of the flaky graphite particles (longest diameter/thickness). The aspect ratio can be measured by observing the scale-like graphite particles under magnification using a scanning electron microscope or the like.

The average particle size (median diameter) of the graphite is preferably 30 μm or more and 700 μm or less, more preferably 100 μm or more and 500 μm or less, from the viewpoint of improving snow melting efficiency and facilitating material kneading. It is particularly preferable that the thickness is 200 μm or more and 300 μm or less. Note that the average particle size can be measured by, for example, a laser diffraction scattering method.

From the viewpoint of ensuring snow melting efficiency and improving thermal conductivity, the content of graphite is preferably 11% by mass or more and 40% by mass or less, and 15% by mass or more and 30% by mass, based on the entire cement composition. It is more preferably the following, and more preferably 15% by mass or more and 25% by mass or less. In addition, when two or more types of cement are included, the content is the total content of cement.

Water is not particularly limited, and for example, tap water, industrial water, recovered water, underground water, river water, rainwater, etc. can be used.

From the viewpoint of ensuring fluidity, the water content is preferably 4% by mass or more and 30% by mass or less, more preferably 19% by mass or more and 25% by mass or less, based on the entire cement composition. , it is particularly preferable that the amount is 19% by mass or more and 22% by mass or less.

The water-cement ratio (W/C) between the water and the cement is preferably 25% or more and 60% or less, more preferably 25% or more and 50% or less, from the viewpoint of increasing strength development, and more preferably 25% or more and 50% or less, and 30% or more. % or more and 40% or less is particularly preferable.

The cement composition according to this embodiment may contain a water reducing agent from the viewpoint of ensuring fluidity. Water reducing agents are not particularly limited, and include, for example, "water reducing agents", "high performance water reducing agents", "AE water reducing agents", and "high performance AE water reducing agents" that comply with the provisions of JIS A 6204:2011. etc. can be used. Specifically, polycarboxylic acid-based water reducing agents, naphthalene-based water reducing agents, aminosulfonic acid-based water reducing agents, melamine-based water reducing agents, etc. that meet the regulations of JIS A 6204:2011 can be used. Note that the water reducing agent may be used alone or in combination of two or more.

From the viewpoint of ensuring fluidity, the content of the water reducing agent is preferably 4.0% by mass or less, and 0.5% by mass or more and 3.5% by mass or less, based on the entire cement composition. is more preferable, and particularly preferably 1.5% by mass or more and 3.5% by mass or less. In addition, when two or more types of water reducing agents are included, the content is the total content of the water reducing agents.

The cement composition according to the present embodiment may contain organic fibers from the viewpoint of preventing drying shrinkage cracks. Examples of organic fibers include vinylon fibers, aramid fibers, polyacetal fibers, and polyethylene fibers. In addition, one type of organic fiber may be used alone or two or more types may be used in combination.

From the viewpoint of preventing drying shrinkage cracks, the content of the organic fiber is preferably 0.7% by mass or less, and 0.2% by mass or more and 0.5% by mass or less, based on the entire cement composition. It is more preferable that there be. In addition, when two or more types of organic fibers are included, the content is the total content of the organic fibers.

The cement composition according to this embodiment may contain other admixtures other than the water reducing agent. Other admixtures include, for example, AE agents, fluidizers, thickeners, rust preventive agents, separation reducing agents, setting retarders (e.g. tartaric acid, etc.), setting accelerators (e.g. aluminum sulfate, etc.), Examples include binders, shrinkage reducers, foaming agents, foaming agents, waterproofing agents, antifoaming agents, and the like. In addition, one type of other admixtures may be used alone, or two or more types may be used in combination.

The cement composition according to this embodiment may contain an admixture. Examples of admixtures include silica fume, fly ash, pulverized blast furnace slag, cement kiln dust, blast furnace fume, pulverized converter slag, anhydrite, gypsum hemihydrate, gypsum dihydrate, expansive agents, pulverized limestone, and pulverized quicklime. Powder, inorganic fine powder such as dolomite fine powder, sodium bentonite, calcium bentonite, attapulgite, sepiolite, activated clay, acid clay, allophane, imogolite, shirasu (volcanic ash), shirasu balloon, kaolinite, metakaolin (calcined clay), Examples include inorganic fillers such as synthetic zeolite, artificial zeolite, artificial zeolite, mordenite, and clinoptilolite. In addition, one type of admixture may be used alone, or two or more types may be used in combination.

The cement composition according to this embodiment may contain fine aggregate. Examples of fine aggregates include naturally derived sands such as mountain sand, river sand, land sand, sea sand, crushed sand, and crushed limestone sand specified in JIS A 5308 Annex A ready-mixed concrete aggregates, blast furnace slag, and electric sand. Examples include sand derived from slag such as furnace oxidation slag and ferronickel slag. In addition, these fine aggregates may be used alone or in combination of two or more types.

The cement composition according to the present embodiment contains cement, graphite, and water, so that a cement molded body with relatively excellent snow melting efficiency can be obtained. More specifically, by including graphite in the cement composition, the thermal conductivity of the cement molded body can be increased. As a result, the snow melting efficiency of the cement molded body can be improved.

In the cement composition according to the present embodiment, since the graphite includes flaky graphite, it is possible to obtain a cement molded body with even more excellent snow melting efficiency. More specifically, since flaky graphite has a flat shape and a flat surface, it is easier to orient than graphite having other shapes. Thermal conductivity increases when the flaky graphite is oriented and the plane directions are aligned. Therefore, it is possible to obtain a cement molded body with even more excellent snow melting efficiency.

In the cement composition according to the present embodiment, since the aspect ratio (longest diameter/thickness) of the flaky graphite is 10 or more and 200 or less, it is possible to obtain a cement molded body with even more excellent snow melting efficiency. .

The cement composition according to the present embodiment has a graphite content of 11% by mass or more and 40% by mass or less based on the entire cement composition, thereby producing a cement molded body with even more excellent snow melting efficiency. Obtainable.

In the cement composition according to the present embodiment, since the average particle size of the graphite is 30 μm or more and 700 μm or less, a cement molded body with even more excellent snow melting efficiency can be obtained. Moreover, when manufacturing the cement molded body, the materials can be easily kneaded.

<Method for producing cement molded body>
Hereinafter, a method for manufacturing a cement molded body according to the present embodiment will be described.

The method for manufacturing a cement molded body according to the present embodiment includes an addition step, a kneading step, and a vibration step.

In the addition step, water is added to graphite in an amount of 1% by mass or more and 40% by mass or less, preferably 3% by mass or more and 40% by mass or less, and more preferably , 5% by mass or more and 35% by mass or less of water is added to obtain a graphite water-containing material. More specifically, a water-containing graphite material can be obtained by adding water to graphite and then kneading it in a mixer or the like. The mixer is not particularly limited, and for example, a conventionally known mixer such as a kneader can be used.

In the kneading step, the graphite water-containing material obtained in the addition step, cement, water, and other necessary components are kneaded to obtain an unhardened kneaded product. The kneading method is not particularly limited, and for example, kneading can be performed by a conventionally known method using a conventionally known mixer or the like. The amount of water added in the kneading step can be the value obtained by subtracting the amount of water added to graphite in the addition step from the content of water contained in the cement composition.

In the vibration step, vibration is applied to the uncured kneaded material. For example, after the uncured kneaded material is placed in a mold, vibration can be applied using a vibrator. The effect of vibration is proportional to acceleration, and a vibrator with a higher frequency is more effective for compaction, so the vibrator can be selected depending on the size of the cement molded body. Examples of the vibrator include a rod vibrator, a table vibrator, a mold vibrator, and the like. For example, when using a rod-shaped vibrator (frequency 200 to 280Hz), the insertion interval of the rod-shaped vibrator should be 50 cm or less, and from the viewpoint of filling the formwork and graphite orientation, the number of rod-shaped vibrators per insertion point should be Vibration can be applied under the condition that the vibration time is 5 seconds or more and 300 seconds or less.

The cement molded body produced in this way can be suitably used for, for example, the surface of roads and sidewalks, the floors, walls, and ceilings of architectural structures.

The method for manufacturing a cement molded body according to the present embodiment includes the addition step, the kneading step, and the vibration step, thereby making it possible to obtain a cement molded product with excellent snow melting efficiency. More specifically, by including the vibration step, the plane directions of the flaky graphite can be aligned so that they are parallel to the concrete placement surface. As a result, the snow melting efficiency of the cement molded body can be improved.

Further, the method for manufacturing a cement molded body according to the present embodiment includes the addition step, the kneading step, and the vibration step, thereby improving the workability of manufacturing the cement molded body. can. More specifically, by including the addition step, it is possible to prevent graphite from scattering and deteriorating the working environment when measuring graphite or kneading graphite with other materials such as cement. . Furthermore, by including the above-mentioned addition step, graphite and other materials become compatible with each other, so it is possible to add graphite in the amount necessary to obtain a cement molded body with relatively excellent snow melting efficiency.

The present invention includes the following aspects.
[1] A cement composition containing cement, graphite, and water.
[2] The cement composition according to [1], wherein the graphite includes flaky graphite.
[3] The cement composition according to [2], wherein the aspect ratio (longest diameter/thickness) of the flaky graphite is 10 or more and 200 or less.
[4] The cement composition according to any one of [1] to [3], wherein the graphite content is 11% by mass or more and 40% by mass or less, based on the entire cement composition.
[5] The cement composition according to any one of [1] to [4], wherein the graphite has an average particle size of 30 μm or more and 700 μm or less.
[6] Adding water to graphite in an amount of 1% by mass or more and 40% by mass or less based on the amount of graphite added to obtain a graphite water-containing material;
a kneading step of kneading the graphite water-containing material obtained in the addition step, cement, and water to obtain an unhardened kneaded product;
A method for producing a cement molded body, comprising a vibration step of applying vibration to the uncured kneaded material.
[7] The method for producing a cement molded body according to [6], wherein the graphite includes scaly graphite.
[8] The method for producing a cement molded body according to [7], wherein the aspect ratio (longest diameter/thickness) of the flaky graphite is 10 or more and 200 or less.
[9] Production of the cement molded body according to any one of [6] to [8], wherein the content of the graphite is 11% by mass or more and 40% by mass or less with respect to the entire cement molded body. Method.
[10] The method for producing a cement molded body according to any one of [6] to [9], wherein the graphite has an average particle size of 30 μm or more and 700 μm or less.

Examples of the present invention will be described below, but the present invention is not limited to the following examples.

Uncured kneaded products of each Example and each Comparative Example were prepared using the formulations shown in Table 1. More specifically, for the uncured kneaded products of each Example and Comparative Examples 2 and 3, water was first added to graphite to produce a graphite water-containing material (addition step). Subsequently, cement, water, and a water reducing agent were added to the kneading pot and stirred for 60 seconds, and then graphite water-containing material, organic fibers, and fine aggregate as needed were added to the kneading pot, and the mixture was stirred for another 60 seconds. Stirred (kneading process). After stopping the mixer once and scraping off the uncured kneaded material adhering to the edge, bottom, and paddle of the kneading pot, stirring was continued for an additional 60 seconds. A hardened kneaded product was prepared. Moreover, the uncured kneaded material of Comparative Example 1 was produced by a method according to JIS R 5201. Note that graphite (Grap) in Table 1 is a converted value of the dry weight of graphite water-containing material, excluding water contained therein. The amount of water input in the kneading step was the amount obtained by subtracting the water contained in the graphite water-containing material from the total amount of water (W).

Details of each component shown in Table 1 are shown below.
Cement (C): Early strength Portland cement, manufactured by Sumitomo Osaka Cement Co., Ltd. Graphite (Grap): FB-100 (scaly graphite), 50% cumulative diameter in volume-based particle size distribution is 80 μm, graphite (Grap) manufactured by Nippon Graphite Industries Co., Ltd. : F#2-R (scaly graphite), 50% cumulative diameter in volume-based particle size distribution is 260 μm, manufactured by Nippon Graphite Industries, Ltd. Water (W): Tap water Water reducer (SP) (high performance AE water reducer): SP8SV (polycarboxylic acid type), manufactured by Pozolis Solutions Organic fiber (Fiber): RMS702 (vinylon fiber), fiber length 6 mm, manufactured by Kuraray Co., Ltd. Fine aggregate (S): Standard sand for cement strength testing

The aspect ratio of the graphite is determined by measuring the length of the longest line segment connecting any two points on the basal plane of the particle using a scanning electron microscope (SEM) (S-3400N, manufactured by Hitachi High-Technology). An imaginary line segment that connects the length (longest diameter) and both ends of the edge surface in the longitudinal direction of the particle, and that is the position of 1/2 of the longest imaginary line segment among the imaginary line segments in the direction along the basal surface ( The thickness (thickness) in the direction orthogonal to the longest virtual line segment was measured at the middle point), and the ratio of the longest diameter to the thickness (longest diameter/thickness) was determined as the aspect ratio. Note that the longest diameter and thickness were measured for different particles. The longest diameter was measured for particles with a basal surface exposed, and the thickness was measured for particles with an edge surface exposed.

More specifically, first, graphite was sieved to +30M (+500 μm), +50M (+300 μm), +60M (+250 μm), +83M (+180 μm), +100M (+150 μm), +140M (+106 μm), +200M (+75 μm), and , -200M (-75 μm) particle size range. In each sieved particle size range, a plurality of particles with a basal surface to measure the longest diameter and a plurality of particles with an edge surface to measure the thickness were selected, and the scanning electron The longest diameter or thickness of the selected particles was measured using a microscope. The average values of the measured longest diameter and thickness were calculated, respectively, and the aspect ratio was determined. In addition, the number of particles whose longest diameter and thickness are measured is 100 in total, and the number of particles measured in each particle size range above (i.e., the allocation of the total 100 particles to be measured) is based on sieved graphite. It was determined according to the distribution of each particle size range.

The longest diameter and thickness of graphite (F#2-R) were measured by the above method, and the average value of the longest diameter and thickness and the aspect ratio were determined. The average value of the longest diameter was 406.67 μm, the average value of the thickness was 12.22 μm, and the aspect ratio was 33.3.

The longest diameter and thickness of graphite (FB-100) were measured by the above method, and the average value of the longest diameter and thickness and the aspect ratio were determined. The average value of the longest diameter was 166.65 μm, the average value of the thickness was 4.19 μm, and the aspect ratio was 39.8.

The average particle size of the graphite was determined by a laser diffraction scattering method. Specifically, graphite particles were placed in an aqueous solvent containing a dispersant, subjected to ultrasonic vibration for 180 seconds, and then measured according to JIS-8511 using a Microtrac particle size distribution analyzer (MICROTRAC3300EXII, manufactured by Nikkiso Co., Ltd.). The average particle size (median diameter) was determined using a method according to the standards.

[Compressive strength]
The uncured kneaded materials of each Example and each Comparative Example were molded by a molding method according to JIS R 5201 to prepare specimens. For each of the prepared specimens, the compressive strength at ages of 1 day, 3 days, 7 days, and 14 days was measured in accordance with JIS R 5201. The measured values of compressive strength are shown in Table 2.

[Bending strength]
The uncured kneaded materials of each Example and each Comparative Example were molded by a method according to JIS R 5201 to produce test specimens. For each of the prepared specimens, the bending strength at ages of 1 day, 2 days, 3 days, 7 days, and 14 days was measured by a method according to JIS R 5201. The measured values of bending strength are shown in Table 2.

[Snow melting efficiency]
(Preparation of specimen)
Test specimens were prepared using the uncured kneaded materials of each Example and each Comparative Example. More specifically, first, a mold for forming a mortar specimen conforming to JIS R 5201 was assembled (inner dimensions 160 mm x 176 mm x 40 mm), and in order to make a hole for water drainage, an iron mold was placed at a predetermined position in the mold. A rod (3 mm in diameter) was inserted. Next, after pouring the uncured kneaded material of Comparative Example 1 into the mold, it was sufficiently heated using a table vibrator (55.5 Hz) (manufactured by Maruto Seisakusho Co., Ltd.) until no air bubbles were formed (about 3 minutes). vibrated (vibration process). Thereafter, it was sealed and removed from the mold after one day of age to obtain a mortar molded product. Subsequently, the prepared mortar molded body was cut into four equal parts with a cutter to obtain four specimens. The cut surface and the cast upper surface of each specimen were polished to predetermined dimensions (70 mm x 70 mm x 25 mm) to obtain four specimens of Comparative Example 1. In addition, since nine specimens were used in the snow melting test described later, the above procedure was repeated to produce a total of nine specimens. For Comparative Examples 2 and 3, the snow melting test was not conducted because the compressive strength at 14 days of age was less than 25 N/mm ² . Therefore, no specimen was prepared.

For the specimens of each example, four test specimen base materials were first prepared using an uncured kneaded material having the same composition as that of Comparative Example 1 and by the same method as that of Comparative Example 1. In addition, the dimensions of the four base materials were polished to 70 mm x 70 mm x 20 mm in order to cast the uncured kneaded material of each example on the upper surface of the base materials. Next, the four base materials were returned to the mold, and the uncured kneaded material of each example was placed on the upper surface of the base materials. Subsequently, mortar molded bodies were formed in the same manner as in Comparative Example 1 to obtain four specimens. Thereafter, in the same manner as in Comparative Example 1, the cut surface and the pouring upper surface of each specimen were polished to predetermined dimensions (70 mm x 70 mm x 25 mm) to obtain four specimens of each example. . Further, in the same manner as Comparative Example 1, the above procedure was repeated to produce a total of nine specimens in each Example.

(Snow melting test)
A snow melting test was conducted using the specimens of each Example and Comparative Example 1. More specifically, first, a desk (70 cm from the floor to the top of the top plate) was installed in a large constant temperature bath (TBE-3EW6PZT, manufactured by Espec) with set atmospheric temperatures of 5°C, 0°C, and -5°C. Three specimens were arranged in one direction on top of each other at intervals of 10 mm. Next, a far-infrared heater was installed at a distance of 300 ± 10 mm from the top surface of the specimen, and the position was adjusted so that the center of the far-infrared heater coincided with the center of the central specimen lined up in one direction. did.

Subsequently, an ice block (24 mm x 24 mm x 24 mm) was placed on each specimen and heated by a far-infrared heater, and the time until the ice block melted was measured. Since the far-infrared heater used had been operated for 30 minutes or more in advance, the measurement was started when the placing of the ice block and the arrangement of the far-infrared heater and the specimen were completed. Each specimen was left standing in a small constant temperature bath (manufactured by ESPEC) with a set temperature of 0° C. for 24 hours or more. In addition, a rubber band was placed on top of each specimen to surround the ice block in order to prevent the ice block from slipping. Further, the placing of the ice block and the arrangement of the far-infrared heater and the specimen took about 1 minute.

The situation until the ice block melted was photographed with a video camera and an infrared thermography camera, and the end point of the measurement (that is, the time required for the ice block to melt) was determined from the recorded video. More specifically, the end point of the measurement was determined based on the melting of the ice blocks until they were completely invisible to the naked eye and the temperature distribution based on the infrared thermography image.

The snow melting test was evaluated based on the snow melting efficiency shown by the following formula (1). Snow melting efficiency indicates the amount of ice cubes melted per second, and the larger the value, the easier it is for the ice cubes to melt.
Snow melting efficiency (mg/sec) = Mass of ice block (g) / Time required for melting (sec) x 1000 (1)
The snow melting test was evaluated using the average value of the snow melting efficiency calculated for each of the three test specimens. The average values of the snow melting efficiency are shown in Table 2.

[Thermal conductivity]
Using the uncured kneaded materials of each Example and each Comparative Example, specimens (300 mm x 300 mm x 100 mm) were prepared by a method according to JIS A 1132, and the thermal conductivity at the age of 28 days was measured. Thermal conductivity was measured by a steady method based on JIS A 1412-2, in which a steady heat flow was applied to one end of the specimen at 60°C and the other end at 20°C, passing through the temperature gradient. Calculated from heat flux. The measured values of thermal conductivity are shown in Table 2.

As can be seen from the results in Table 2, the cement molded bodies formed from the cement compositions of each example that satisfy all the constituent requirements of the present invention are different from the cement molded bodies formed from the cement composition of Comparative Example 1 that does not contain graphite. An improvement in snow melting efficiency was observed at almost all test temperatures compared to the conventional method.

Further, the cement molded body formed from the cement composition of each example that satisfies all the constituent requirements of the present invention has a compressive strength of 15 N/mm 2 or more at the age of 1 day, and a compressive strength of 15 N/mm ² or more at the age of 7 days. Since it has a compressive strength of 25 N/mm ² or more, sufficient compressive strength can be obtained. Furthermore, the cement molded bodies formed from the cement compositions of each example that satisfy all the constituent requirements of the present invention have superior bending strength compared to the cement molded bodies formed from the cement compositions of each comparative example. Can be done.

Claims (6)

A cement composition including cement, graphite, and water. The cement composition according to claim 1, wherein the graphite includes flaky graphite. The cement composition according to claim 2, wherein the aspect ratio (longest diameter/thickness) of the flaky graphite is 10 or more and 200 or less. The cement composition according to any one of claims 1 to 3, wherein the graphite content is 11% by mass or more and 40% by mass or less based on the entire cement composition. The cement composition according to any one of claims 1 to 3, wherein the graphite has an average particle size of 30 μm or more and 700 μm or less. an addition step of adding water to graphite in an amount of 1% by mass or more and 40% by mass or less based on the amount of graphite added to obtain a graphite water-containing material;
a kneading step of kneading the graphite water-containing material obtained in the addition step, cement, and water to obtain an unhardened kneaded product;
A method for producing a cement molded body, comprising a vibration step of applying vibration to the uncured kneaded material.