JP7390885B2 - Cement composition for modeling - Google Patents

Description

The present invention relates to a cement composition for modeling.

BACKGROUND ART In recent years, additive manufacturing devices that can mold delicate shapes by continuously extruding molding materials such as resin onto a loading table (pedestal), solidifying and layering them one after another have become popular.
Recently, methods have been proposed for forming objects using hydraulic materials such as cement and gypsum, in addition to resins, and additive manufacturing equipment. For example, Patent Document 1 describes (A) mixing a cement composition for modeling and water as an additive manufacturing method that can manufacture modeling objects with delicate and diverse designs using a cementitious mixture and an additive manufacturing device. An additive manufacturing method is described that includes at least a kneading step for kneading to obtain a cementitious kneaded product, and (B) an extrusion step for extruding and hardening the cementitious kneaded product to obtain a shaped object. has been done.

On the other hand, Patent Document 2 describes a method for producing a cementitious hardened body using a cement composition containing urea for the purpose of preventing cracks due to restraint of embedded metal fittings, ^etc. g fine powder, fine aggregate, water reducing agent, water, and a mixture containing a shrinkage reducing agent and/or urea are molded, first cured, demolded, and then further secondarily cured. A method for producing a hardened cementitious material, characterized in that the amount of shrinkage reducing agent and/or urea is 0.5 to 3.0 parts by mass per 100 parts by mass of cement. Are listed.

Japanese Patent Application Publication No. 2018-122539 Japanese Patent Application Publication No. 2008-230955

An object of the present invention is to provide a composition for manufacturing a model, which is obtained by mixing a cement composition for model and water, to have appropriate fluidity immediately after preparation (mixing), and to maintain the fluidity for a long period of time (e.g. , 2 hours), and when modeling using a nozzle or the like in additive manufacturing technology, the shape of the composition for producing a shaped object immediately after modeling does not collapse, and the shaped object Since the manufacturing composition has excellent quick hardening properties, even if the above-mentioned composition for manufacturing a modeled object is laminated, the shape of the modeled object (especially the lower part of the stacked object) does not collapse, and furthermore, the dimensional stability is maintained. It is an object of the present invention to provide a cement composition for modeling that allows obtaining a shaped object (hardened body) with excellent properties.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above-mentioned objects can be achieved with a modeling cement composition containing specific amounts of Portland cement, super-fast hardening cement, fibers, and a setting retarder. They discovered what they could do and completed the present invention.
That is, the present invention provides the following [1] to [4].
[1] A modeling cement composition containing Portland cement, super-fast-hardening cement, fiber, and a setting retardant, wherein the proportion of the super-fast-hardening cement in the total of 100% by mass of the Portland cement and the super-fast-hardening cement is 20%. to 80% by mass, the amount of the fibers is 0.3 to 4.8 parts by mass, and the amount of the setting retarder is 0.3 to 4.8 parts by mass, based on a total of 100 parts by mass of the Portland cement and the ultra-fast hardening cement. A cement composition for modeling, characterized in that it contains 1 to 5 parts by mass.
[2] The molding material according to [1] above, which contains a setting accelerator and has an amount of 5 parts by mass or less based on a total of 100 parts by mass of the Portland cement and the ultra-fast hardening cement. cement composition.
[3] The modeling cement composition according to [1] or [2] above, which contains fine aggregate.
[4] A method for producing a shaped object using the cement composition for modeling according to any one of [1] to [3] above, comprising each material constituting the cement composition for modeling, and water. A method for manufacturing a shaped object, the method comprising the steps of: preparing a composition for producing a shaped article; and producing the shaped article by additive manufacturing technology using the composition for producing a shaped article.

According to the cement composition for modeling of the present invention, the composition for producing a modeled object obtained by mixing the cement composition for modeling and water has appropriate fluidity immediately after preparation (mixing), and It is possible to maintain the sex for a long time (for example, 2 hours).
In addition, when modeling using a nozzle or the like in additive manufacturing technology, since the composition for manufacturing a shaped object has appropriate fluidity (that is, does not have excessive fluidity), the above-mentioned shape immediately after modeling The shape of the composition for manufacturing objects does not collapse, and the composition for manufacturing objects has excellent quick hardening properties. It is possible to obtain a shaped article (hardened body) in which the lower part of the shaped article does not collapse and has excellent dimensional stability.

The modeling cement composition of the present invention is a modeling cement composition containing Portland cement, super-fast-hardening cement, fiber, and a setting retarder, wherein the super-fast-hardening cement contains 100% by mass of the total of Portland cement and super-fast-hardening cement. The proportion of fibers is 0.3 to 4.8 parts by mass, and the amount of setting retarder is 0.3 to 4.8 parts by mass, based on a total of 100 parts by mass of Portland cement and super fast-hardening cement. The amount is 1 to 5 parts by mass.
Examples of Portland cement include various Portland cements such as white Portland cement, ordinary Portland cement, early strength Portland cement, moderate heat Portland cement, and low heat Portland cement. These may be used alone or in combination of two or more.
Among these, white Portland cement is preferred because it can be colored freely and has an excellent design.

Examples of super-fast hardening cements include C ₁₂ A ₇ (12CaO・7Al ₂ O ₃ ), C ₃ A (3CaO・Al ₂ O ₃ ), and C ₁₁ A ₇・CaF ₂ (11CaO・7Al ₂ O ₃・CaF ₂ ), NC ₈ A ₃ (Na ₂ O・8CaO・3Al ₂ O ₃ ), Auin (3CaO・3Al ₂ O ₃・CaSO ₄ ), CA (CaO・Al ₂ O ₃ ), CA ₂ (CaO・2Al ₂ O Examples include cement containing 15% by mass or more of one or more minerals selected from ₃ ).
Among these, cement containing 15% by mass or more of Auin (3CaO.3Al ₂ O ₃ .CaSO ₄ ) is preferred from the viewpoint of excellent quick hardening properties and easy control of pot life using a setting retarder.
A commercially available cement containing 15 to 35% by mass of Auin (3CaO.3Al _{2 O} 3.CaSO ₄ ) includes the trade name "Super Jet Cement" manufactured by Taiheiyo Cement Co., Ltd.

The proportion of the super fast hardening cement in the total of 100% by mass of the Portland cement and the super fast hardening cement is 20 to 80 mass%, preferably 25 to 75 mass%, more preferably 28 to 72 mass%. If the above ratio is less than 20% by mass, the fluidity immediately after preparation will be excessive. If the above ratio exceeds 80% by mass, the dimensional stability of the shaped object will decrease.

The modeling cement composition of the present invention may contain cement other than Portland cement and ultra-fast hardening cement within a range that does not impede the object of the present invention.
Examples of other cements include mixed cements such as blast furnace cement and fly ash cement, and ecocement.
The content of other cements in the modeling cement composition is preferably 10% by mass or less, more preferably 5% by mass or less, particularly preferably 3% by mass or less.

Examples of fibers include glass fibers, metal fibers, organic fibers, carbon fibers, and the like. These may be used alone or in combination of two or more. Among these, glass fiber is preferred from the viewpoint of economy and compatibility with cement.
The shape and dimensions of the fibers are preferably such that the length is 0.1 mm or more and the length/diameter ratio is 20 or more, more preferably the length is 0.1 to 30 mm and the length/diameter ratio is 20 or more. 20 to 1,000, more preferably a length of 1 to 10 mm, and a length/diameter ratio of 50 to 500, and even more preferably a length of 2 to 5 mm, and a length/diameter ratio of 50 to 500. is 100-400.
If the fiber length is 0.1 mm or more, the effect of improving strength (for example, bending strength and breaking strength) will be greater. If the length is 30 mm or less, fiber balls are less likely to form during kneading.
In addition, if the fiber length/diameter ratio is 20 or more, the number of fibers in the same amount (same volume) will increase, and the effect of improving strength (for example, bending strength and breaking strength) will be greater. . Further, when the ratio is 1,000 or less, the strength of the fiber itself is sufficient and it becomes difficult to break when subjected to tension.

The amount of fibers is 0.3 to 4.8 parts by mass, preferably 0.4 to 4.6 parts by mass, based on 100 parts by mass of the total of Portland cement and ultra-fast hardening cement (hereinafter also referred to as "total cement"). More preferably, it is 0.5 to 4.4 parts by mass. If the amount is less than 0.3 parts by mass, the bending strength and fracture energy of the shaped object will decrease. If the amount exceeds 4.8 parts by mass, fluidity immediately after kneading will decrease. Furthermore, in order to ensure workability during kneading, the unit amount of water is increased, which may lead to a decrease in the strength of the constructed product.

Examples of glass fibers include alkali-resistant glass fibers. Alkali-resistant glass fiber is suitable from the viewpoint of affinity with cement and economic efficiency.
Examples of alkali-resistant glass fibers include those containing 14% by mass or more of zirconium oxide (ZrO ₂ ).
The shape and dimensions of the glass fibers are preferably such that the length is 2 mm or more and the length/diameter ratio is 20 or more, more preferably the length is 2 to 30 mm and the length/diameter ratio is 20. ~200. If the length of the glass fiber is 2 mm or more, the effect of improving bending strength will be greater. If the length is 30 mm or less, fiber balls are less likely to form during kneading.
Furthermore, if the length/diameter ratio of glass fibers is 20 or more, the number of glass fibers in the same amount (same volume) increases, and the effect of improving bending strength becomes greater. Moreover, when the ratio is 200 or less, the strength of the glass fiber itself is sufficient, and it becomes more difficult to break when subjected to tension.

Examples of metal fibers include steel fibers and amorphous fibers. Among these, steel fibers are preferred because they have high strength and are excellent in terms of cost and availability.
The dimensions, length/diameter ratio and loadings of the metal fibers are similar to those of the glass fibers.

Examples of organic fibers include one or more selected from the group consisting of vinylon fibers, polypropylene fibers, polyethylene fibers, aramid fibers, and carbon fibers. Among these, vinylon fibers and polypropylene fibers are preferred because they have high strength, are low in cost, and are easily available.
The shape and dimensions of the organic fibers are preferably such that the length is 2 mm or more and the length/diameter ratio is 20 or more, and more preferably the length is 2 to 30 mm and the length/diameter ratio is 20 or more. ~500. If the length of the organic fiber is 2 mm or more, the effect of improving the breaking strength will be greater. If the length is 30 mm or less, fiber balls are less likely to form during kneading.
Further, if the length/diameter ratio of the organic fibers is 20 or more, the number of organic fibers in the same amount (same volume) increases, and the effect of improving the breaking strength becomes greater. Moreover, when the ratio is 500 or less, the strength of the organic fiber itself is sufficient, and it becomes more difficult to break when subjected to tension.

Furthermore, examples of carbon fibers include PAN-based carbon fibers and pitch-based carbon fibers. Further, the dimensions, aspect ratio and blending amount of carbon fibers are the same as those of organic fibers.

Examples of setting retarders include citric acid and its salts, heptonic acid and its salts, succinic acid and its salts, tartaric acid and its salts, gluconic acid and its salts, malic acid and its salts, and the like. These may be used alone or in combination of two or more.
Among these, citric acid is preferred from the viewpoint of being able to maintain the fluidity of the composition for producing a shaped object for a longer period of time.
The amount of setting retarder relative to 100 parts by mass of cement is 0.1 to 5 parts by mass, preferably 0.5 to 3 parts by mass, more preferably 0.8 to 2 parts by mass, particularly preferably 1.0 to 1 part by mass. .8 parts by mass. If the amount is less than 0.1 part by mass, the fluidity of the composition for producing a shaped object cannot be maintained for a long time (for example, 2 hours), and the pot life becomes short. If the amount exceeds 5 parts by mass, it will take too long for the composition for producing a shaped object to finish coagulating.

The modeling cement composition of the present invention may also contain a setting accelerator.
Examples of setting accelerators include sodium sulfate, sodium thiosulfate, calcium lactate, sodium carbonate, potassium sulfate, aluminum sulfate, ferrous sulfate, ferric sulfate, magnesium nitrate, calcium nitrate, potassium nitrite, sodium carbonate, etc. Can be mentioned. These may be used alone or in combination of two or more.
Among these, sodium sulfate is preferred from the viewpoint of ease of acquisition.
The amount of setting accelerator relative to 100 parts by mass of cement is preferably 5 parts by mass or less, more preferably 0.1 to 4 parts by mass, even more preferably 0.5 to 3 parts by mass, particularly preferably 0.8 to 2 parts by mass. .5 parts by mass. When the cement composition for modeling contains a setting accelerator in an amount of 5 parts by mass or less, it is possible to shorten the time until setting of the composition for manufacturing a model starts, and improve workability. .

The modeling cement composition of the present invention preferably contains fine aggregate from the viewpoint of lowering the calorific value.
Examples of fine aggregates include limestone powder, river sand, mountain sand, land sand, sea sand, crushed sand, silica sand, slag fine aggregate, lightweight fine aggregate, and the like. These may be used alone or in combination of two or more.
Among these, it is preferable to use limestone powder because it can be colored freely and has an excellent design.
The amount of fine aggregate relative to 100 parts by mass of cement is preferably 100 to 700 parts by mass, more preferably 120 to 500 parts by mass, particularly preferably 150 to 400 parts by mass.

The modeling cement composition of the present invention may contain other materials as necessary. Other materials that may be included as necessary include coarse aggregate, various admixtures such as AE agents, water reducers, AE water reducers, high performance water reducers, and high performance AE water reducers, fly ash, silica fume, Examples include various admixtures such as pulverized blast furnace slag powder.
In the present invention, the cement composition for modeling does not include water for preparing paste, mortar, or concrete.

An example of a method for producing a modeled object using the above-described cement composition for modeling includes a step of mixing each material constituting the cement composition for modeling and water to prepare a composition for producing a modeled object; Further, there may be mentioned a method for producing a shaped article, which includes a step of producing a shaped article by an additive manufacturing technique using the composition for producing a shaped article.
The water is not particularly limited, and tap water, sludge water, etc. can be used.
The mass ratio of water to the cement composition for modeling (water/cement composition for modeling) is preferably 0.10 to 0.60, more preferably 0.11 to 0.40, particularly preferably 0.12 to 0. It is .30. If the ratio is 0.10 or more, fluidity necessary for producing a shaped article by additive manufacturing technology can be ensured. If the ratio is 0.60 or less, the strength of the shaped object can be further improved.

The means for mixing each material is not particularly limited, and a mixer commonly used for mixing mortar and concrete can be used.
Specifically, a vertical mixer, a horizontal mixer, a Nauta mixer, a tilting mixer, a forced mixer, a biaxial mixer, etc. may be mentioned. Examples of the vertical mixer include "Hobart Mixer" manufactured by Hobart, "Henschel Mixer" manufactured by Henschel, and the like. Examples of the horizontal mixer include "Ledige Mixer" manufactured by Ledige Co., Ltd.
An example of a method for producing a shaped object using an additive manufacturing technique includes a method in which a composition for producing a shaped article is extruded from a nozzle or the like and deposited. A commercially available additive manufacturing device (3D printer) can be used as a means for creating the shaped object.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples.
[Materials used]
(1) Portland cement; white Portland cement, manufactured by Taiheiyo Cement Co., Ltd. (2) Super fast-hardening cement; content of Auin (3CaO・3Al ₂ O ₃・CaSO ₄ ); 15 to 35% by mass, manufactured by Taiheiyo Cement Co., Ltd., product name "Super Jet Cement"
(3) Fiber: alkali-resistant glass fiber, length: 3 mm, diameter: 13.5 μm, length/diameter: 222, manufactured by Nippon Electric Glass Co., Ltd. (4) Fine aggregate: limestone sand, maximum particle size 0.3 mm
(5) Water reducing agent; powdered polycarboxylic acid water reducing agent, manufactured by Taiheiyo Materials Co., Ltd., product name: NF-200
(6) Set accelerator; sodium sulfate, reagent (7) Set retarder; citric acid, reagent (8) Water; tap water

[Examples 1 to 5, Comparative Examples 1 to 2]
The above-mentioned materials in the amounts shown in Table 1 were put into a Hobart mixer and mixed for 2 minutes to prepare a composition for manufacturing a shaped object.
The mortar flow value, completion time, and length change rate were obtained for the obtained composition for producing a shaped object according to the following method. The results are shown in Table 1.

[Mortar flow value]
The mortar flow value (0 stroke) of the composition for manufacturing a modeled object (mortar made by mixing a cement composition for modelling and water) immediately after preparation is described in "JIS R 5201:2015 (Physical test method for cement)" The measurement was carried out without performing 15 falling movements according to the method of . If the mortar flow value (0 strokes) is less than 120 mm, the fluidity immediately after preparation is considered to be appropriate, and it is evaluated as "〇", and if the mortar flow value (0 strokes) is 120 mm or more, it is evaluated as "x". evaluated.
Immediately after preparation, stirring was performed at low speed for 10 seconds every 30 minutes, and after 120 minutes, the mortar flow value (15 strokes) of the composition for manufacturing a shaped object was determined according to "JIS R 5201:2015 (Cement The measurement was performed by performing a falling motion 15 times in accordance with the physical test method (Physical Test Method). If the mortar flow value (15 strokes) is 120 mm or more, it is possible to maintain the fluidity of the composition for manufacturing a shaped object for a long time and has a long pot life, and is evaluated as "〇". Those with a flow value (15 strokes) of less than 120 mm were evaluated as "x".

[Ending time]
In accordance with the method described in "JIS A 1147:2007 (Concrete setting time test method)", the completion time of setting of the composition for modeling production was measured. Those whose finishing time was less than 4 hours were evaluated as "Good" as having excellent quick hardening properties, and those whose finishing time was 4 hours or more were evaluated as "x".
[Length change rate]
Measure the length change rate of the composition for modeling according to the method described in "JIS A 1129-3:2010 (Length change measurement method for mortar and concrete - Part 3: Dial gauge method)" did. The rate of change in length is determined by measuring the base length of the specimen demolded 24 hours after molding, storing the specimen in water at 20°C, and measuring the length of the specimen at 28 days old. were measured and calculated using these measured values.
Items with the above rate of change in length less than 1,000 x 10 ^-6 are evaluated as "〇" as having excellent dimensional stability, and items with the rate of change in length above 1,000 x 10 ^-6 or more are evaluated as having excellent dimensional stability. was evaluated as "x".

From Table 1, it can be seen that the mortar flow value (0 stroke) immediately after preparation was 105 to 117 mm for the composition for manufacturing a model using the cement composition for model of the present invention (Examples 1 to 5), and the mortar flow value (0 stroke) immediately after preparation was 105 to 117 mm. Since the mortar flow (15 strokes) after the elapse of time is 141 to 169 mm, the compositions for manufacturing shaped objects of Examples 1 to 5 have appropriate fluidity immediately after preparation, and the fluidity is 2. I know I can keep up with the time.
In addition, since the completion time of the composition for manufacturing a model (Examples 1 to 5) using the cement composition for model of the present invention is 2 hours and 25 minutes to 3 hours and 20 minutes, Examples 1 to 5 It can be seen that the composition for producing a shaped object has excellent quick hardening properties.
Furthermore, since the length change rate of the compositions for producing shaped objects (Examples 1 to 5) using the cement composition for modeling of the present invention is 705 to 891×10 ^-6 , Examples 1 to 5 It can be seen that the composition for producing a shaped object has excellent dimensional stability.

In addition, since the mortar flow (0 stroke) immediately after preparation of Comparative Example 1 in which the amount of fibers was 0.1 part by mass based on 100 parts by mass of cement in total was 134 mm, the composition for manufacturing a modeled object of Comparative Example 1 was , it can be seen that it does not have adequate fluidity immediately after preparation.
In addition, the mortar flow (15 strokes) after 120 minutes of preparation in Comparative Example 2, in which the amount of fibers was 5.0 parts by mass based on 100 parts by mass of cement, had no fluidity and could not be measured. It can be seen that the composition for manufacturing a shaped object of Comparative Example 2 cannot maintain appropriate fluidity for 2 hours.

Claims (4)

A modeling cement composition comprising portland cement, ultra-fast hardening cement, fibers , a setting retarder , and a setting accelerator, the composition comprising:
The ultra-rapid hardening cement is a cement containing Auin (3CaO・3Al ₂ O ₃ ・CaSO ₄ ) in a proportion of 15% by mass or more,
The setting accelerator is sodium sulfate,
The proportion of the super-fast-hardening cement in the total of 100 mass% of the Portland cement and the super-fast-hardening cement is 20 to 80% by mass,
The amount of the fiber is 0.5 to 4.4 parts by mass, and the amount of the setting retarder is 0.5 to 1.8 parts by mass with respect to a total of 100 parts by mass of the Portland cement and the ultra-fast hardening cement. A cement composition for modeling , characterized in that the amount of the setting accelerator is 0.8 to 2.5 parts by mass . The cement composition for modeling according to claim 1 , comprising fine aggregate. A composition for manufacturing a shaped object comprising the cement composition for modeling according to claim 2 and a mortar that is a mixture of water,
Manufacture of molded objects whose mortar flow value (0 stroke) measured without performing 15 falling motions is less than 120 mm in accordance with the method described in "JIS R 5201:2015 (Physical test method for cement)" Composition for use. A method for manufacturing a shaped object using the composition for manufacturing a shaped object according to claim 3 ,
A method for producing a shaped object, comprising the step of producing the shaped article by an additive manufacturing technique using the composition for producing a shaped article.