JP6846744B2 - Precast cement panel for residual formwork and its manufacturing method - Google Patents

Description

The present invention relates to a precast cement panel for a residual formwork and a method for manufacturing the same.

By using the remaining formwork instead of the conventional metal or wooden formwork, concrete can be cast inside the formwork to form a building, and after the cast concrete has solidified. It is a building material that becomes the surface part of the building as it is without being removed. This residual formwork is usually formed using a precast panel member made of a cement-based hardened body. This is because the precast panel can enjoy the preferable features of high quality stability including improvement of on-site construction efficiency and aesthetics of the panel surface (see Patent Documents 1 and 2).

The remaining formwork is required to have sufficient strength to withstand the impact at the time of placing concrete, as in the case of general formwork. In addition to this, long-term durability is also required on the assumption that it will remain in the building even after the concrete is placed. As an attempt to meet such demands for strength and durability, a concrete residual formwork having improved strength by adding reinforcing fibers has also been developed (see Patent Document 3).

However, in the formwork described in Patent Document 3, it is necessary to use expensive alkali-resistant glass fiber as a reinforcing fiber in order to avoid deterioration of the glass fiber in the basically alkaline hardened concrete. The mold described in Patent Document 3 can ensure long-term durability by using this alkali-resistant glass fiber, but the alkali-resistant glass fiber is expensive and the material cost increases. This has hindered the widespread use of this type of formwork.

On the other hand, with respect to CO ₂ emissions is large concrete products in general in the production process or the like, due to environmental considerations, it has been strongly demanded in recent years to reduce the total emissions of CO _2. As an attempt to solve this problem, _{the development of CO 2} absorbing precast concrete is also in progress (see Patent Document 4).

Here, if this CO _{2 absorbing precast concrete can be used as a residual formwork, the total CO 2} emissions will increase due to the transition to a concrete residual formwork instead of the conventional metal or wooden formwork. It is possible to expand its spread while avoiding. _{However, the CO 2} absorbing precast concrete described in Patent Document 4 is at present, for example, even in comparison with the conventional formwork described in Patent Document 3, and the cost is equal to or higher than that. Although it is a precast member with extremely excellent environmental protection, it has been a factor in its widespread use as a formwork.

Japanese Unexamined Patent Publication No. 6-5522 Japanese Unexamined Patent Publication No. 9-217366 Japanese Unexamined Patent Publication No. 2006-118236 Japanese Unexamined Patent Publication No. 2011-168436

An object of the present invention is to provide a residual formwork which is excellent in strength and durability and can avoid an increase in total _{CO 2 emissions.}

_{Since the CO 2} absorbing precast concrete disclosed in Patent Document 4 has the alkali content in the hardened cement neutralized by carbonation curing, the present inventors are inexpensive E glass fibers as reinforcing fibers. First of all, we focused on the fact that even if we use, we can maintain the strength and durability comparable to the case of using expensive alkali-resistant glass fiber. Furthermore, _{they have found that by adding an appropriate amount of sepiolite to the conventional composition for CO 2} absorbing precast concrete, it is possible to produce by so-called immediate demolding, thereby for formwork. We have succeeded in dramatically increasing the productivity of precast panels. Through these research and development processes, the present inventors have achieved the present invention, that is, they are excellent in strength and durability, and further, _{while being able to suppress total CO 2} emissions, they are much cheaper than conventional products. We have completed a precast cement panel for the remaining formwork that can be manufactured in. Specifically, the present invention provides the following.

(1) A precast cement panel for residual formwork in which one surface is the finished surface of the building and the other surface is the concrete placement side. Cement material, aggregate, glass fiber, and sepiolite. The cement composition is composed of a hardened cement obtained by curing and carbonizing the cement composition containing, and the cement material contains Portland cement and γ-C2S, and the ratio of γ-C2S in the cement material. However, the precast cement panel for the residual formwork is 5% by mass or more and 50% by mass or less, and the content of the sepiolite in the hardened cement is 0.5% by mass or more and 2% by mass or less.

According to the invention of (1), it is possible to obtain a precast cement panel for a residual formwork which _{is excellent in strength and durability and can also suppress the total amount of CO 2 emissions.} Further, since the strength of this precast cement panel is improved by carbonizing γ-C2S, it is not necessary to use expensive alkali-resistant glass fiber as the glass fiber. Then, it is made of a cement composition that can be immediately demolded by adding an appropriate amount of sepiolite. From the above, the precast cement panel for the residual formwork according to the invention of (1) can be mass-produced at a lower cost than the conventional one and under high productivity dramatically improved as compared with the conventional one. ..

(2) The precast cement panel according to (1), wherein the pH of the hardened cement is 10.0 or less and the glass fiber is E glass fiber.

In the invention of (2), the pH of a general hardened concrete product is about 12 to 13, while the hardened cement product in the invention of (1) is weakly alkaline with a pH of 10.0 or less. And said. In the hardened cement body whose pH has been lowered to this extent, deterioration of the glass fiber can be reliably avoided even when inexpensive E glass fiber is used. As a result, the economic efficiency and quality stability of the precast cement panel (1) can be further improved.

(3) A method for manufacturing a precast cement panel for a residual mold, in which one surface is the finished surface of the building and the other surface is the concrete casting side. A pre-molding step of performing pre-molding by immediate demolding, which promptly demolds after placing and compacting the cement, and a carbonation curing step of carbonizing and curing the semi-hardened body of the ready-mixed cement after the pre-molding step. The raw cement contains water, cement material, aggregate, glass fiber, and sepiolite, and the ratio (W / P) of water to cement material is 25% or more and 50% or less. The cement material contains Portorand cement and γ-C2S, and the ratio of γ-C2S in the cement material is 5% by mass or more and 50% by mass or less, and the content of the sepiolite in water. However, the production method is 3% by mass or more and 10% by mass or less.

According to the invention of (3), it is possible to obtain a precast cement panel for a residual formwork which _{is excellent in strength and durability and can also suppress the total amount of CO 2 emissions.} Further, the method for producing this precast cement panel is a method of performing carbonation curing mainly for the purpose of improving the strength by carbonizing γ-C2S, and the pH of the cured product during curing is higher than that of general concrete. It is not always necessary to use expensive alkali-resistant glass fiber as the glass fiber because it falls to a low range. In addition, this production method can also be molded by immediate demolding by adding an appropriate amount of sepiolite. Based on the above, the method for manufacturing a precast cement panel for a residual formwork according to the invention (3) can be mass-produced at a lower cost than before and under high productivity that is dramatically improved than before. It is a possible manufacturing method.

According to the present invention, it is possible to provide a residual formwork having excellent strength and durability, and further, a _{residual formwork capable of avoiding an increase in total CO 2 emissions.}

<Residual formwork>
The residual formwork is a formwork for placing concrete, and is a formwork that constitutes the surface portion of the building as it is without being removed even after the cast concrete has solidified. For example, the formwork disclosed in FIGS. 1 to 8 of Patent Document 1 can be mentioned as a specific example of the form of the residual formwork. (Note that this formwork is also referred to as a waste formwork as another general name.) By connecting a plurality of precast cement panels for the remaining formwork of the present invention with, for example, steel materials. , A residual formwork of the desired shape and size can be formed.

The remaining formwork has a structure that allows concrete to be cast inside the formwork for placing concrete, and has sufficient strength to withstand vibration during casting. Is required. This point is the same as that required for a general concrete casting formwork.

However, since the remaining formwork is a building material that remains as a part of the building, unlike a general formwork, long-term durability equivalent to the durability required for the building is required. The remaining formwork is also required to have the same aesthetics as the surface of the building in which it is used, on at least one surface. In these respects, the residual formwork must meet different requirements than general concrete casting formwork.

_{Further, the residual formwork according to the present invention has a function as a CO 2} absorbing concrete having excellent environmental conservation in addition to the basic function as a residual formwork provided in the conventional general residual formwork. There is a further feature in that.

The application location of the residual formwork of the present invention having such various functions is not particularly different from the conventional application range, and is not particularly limited. For example, it can be appropriately used as a formwork, a top plate lower surface formwork, a partition formwork, a buried formwork for underdraining, a structure repair formwork, a side wall formwork, various large formwork and the like.

<Precast cement panel for residual formwork>
The precast cement panel of the present invention (hereinafter, also simply referred to as "precast cement panel") is a panel-shaped building material made of a carbonic acid-cured cement cured product. This hardened cement product shall be produced using a cement composition (raw cement) containing water, a cement material containing at least Portland cement and γ-C2S, an aggregate, glass fiber, and an appropriate amount of sepiolite. Can be done.

The precast cement panel made of the above cement composition is a so-called hardened cement body that can be molded by immediate demolding. As a result, the precast cement panel of the present invention is dramatically improved in productivity as compared with the conventional precast panel for residual formwork.

Further, it is assumed that the pH of the precast cement panel is lower than that of a general hardened concrete body because the alkali content in the hardened cement body is neutralized during carbonation curing. Specifically, the pH of this hardened cement product is preferably 10 or less. As a result, the deterioration of the glass fiber can be suppressed more remarkably, and the deterioration of the precast cement panel with time can be suppressed more remarkably. In the present specification, the pH of the hardened cement product indicates a value measured using a "desktop pH water quality analyzer (manufactured by HORIBA, Ltd.)".

As the cement material to be blended in the cement composition used for producing the precast cement panel of the present invention (hereinafter, also simply referred to as “cement composition”), a cement material containing at least Portland cement and γ-C2S is used. Of these, γ-C2S is a substance involved in the carbonation reaction in carbonation curing, and consumes (absorbs) _{CO 2 supplied from the curing atmosphere to produce calcium carbonate CaCO 3} , which is necessary as a hardened cement product. Takes strength. On the other hand, Portland cement immediately starts the hydration reaction after being placed in the mold and functions as a binder, and can be immediately demolded together with the effect of improving the viscosity of sepiolite. Is provided with a strength level sufficient to maintain the shape of the predetermined precast concrete when it is subjected to carbonation curing. A part of Portland cement can be replaced with blast furnace slag. As a result, CO ₂ emissions at the cement manufacturing stage can be reduced.

In the cement composition, the ratio of γ-C2S in the cement material may be 5% by mass or more and 50% by mass or less, preferably 25% by mass or more. If this ratio is less than 5% by mass, the _{amount of CO 2} absorbed in the carbonation curing is reduced, and the effect of reducing the amount of _{CO 2 emitted as a concrete product is not exhibited.} On the other hand, when the above ratio exceeds 50% by mass, even if the water-cement ratio is adjusted within the range described later, the contribution of Portland cement to hardening is insufficient, and it is difficult to obtain strength that can be immediately demolded.

In addition to ordinary Portland cement, there are various types of Portland cement such as early-strength, ultra-fast-strength, moderate heat, and low heat. In the cement composition, one or more of these various Portland cements can be blended. Among these, it is preferable to use one or two types of ordinary Portland cement and low-heat Portland cement.

The glass fiber used in the cement composition is not particularly limited, and conventionally known glass fibers such as E glass fiber and AR glass fiber can be appropriately selected. However, in the precast cement panel of the present invention, the alkali content in the hardened cement is neutralized by carbonation curing and the pH is lower than that of a general hardened concrete, so that long-term durability is conventionally required. Instead of AR glass fiber, which has been widely used in formwork and has excellent alkali resistance, it is possible to select relatively inexpensive E-glass, which can significantly reduce the manufacturing cost of the remaining formwork. Can be done.

The fiber diameter of the glass fiber used in the cement composition is not particularly limited. For example, it is preferably 10 μm or more and 20 μm or less, and more preferably 13 μm or more and 18 μm or less. As a result, various strengths of the precast cement panel are further improved, and in particular, the bending strength tends to be remarkably improved. Further, the fiber length of the glass fiber is not particularly limited, and is preferably 3 mm or more and 35 mm or less, and more preferably 5 mm or more and 30 mm or less. As a result, various strengths of the precast cement panel are further improved, and in particular, the bending strength tends to be remarkably improved. In addition, the glass fiber may be partially broken due to kneading, filling in a mold, or the like, and the fiber length may be shortened. Therefore, the above-mentioned suitable fiber length indicates the maximum fiber length of the glass fiber in the cement cured product or the fiber length of the glass fiber blended in the cement composition.

The content of glass fiber in the cement composition can be appropriately adjusted according to the individual required characteristics of the precast cement panel. The content of the glass fiber is, for example, preferably 0.5% by volume or more and 5.0% by volume or less, and 0.7% by volume or more and 3.0% by volume or less based on the total volume of the precast cement panel. Is more preferable. Increasing the content of glass fiber within the above range further improves various strengths of the precast cement panel, and in particular, the bending strength tends to be remarkably improved, and increasing the content of glass fiber immediately improves the strength. Demoldability tends to improve. By keeping the content of the glass fiber within the above range, it is possible to enjoy the effects of reducing the material cost, improving the manufacturability in the case of cast molding, reducing the labor required for fiber input, and suppressing the reduction of the compressive strength.

These glass fibers are dispersed in the hardened cement body, which makes the precast cement panel have excellent strength. In addition, since the alkali content in the hardened cement of the precast cement panel is neutralized by carbonation curing, the strength deterioration due to the corrosion of the glass fiber is sufficiently suppressed, and good durability is maintained for a long period of time. Can be maintained. Therefore, the precast cement panel can be extremely preferably used for residual formwork applications in which both initial strength and long-term reliability are required.

The cement composition may further contain other admixtures. As the other admixture, a known admixture may be used without particular limitation. The amount of the admixture is not particularly limited, and can be appropriately adjusted according to the application of the precast cement panel, the required characteristics, and the like. Examples of the admixture include coal ash, fly ash, limestone fine powder and the like.

Here, in the cement composition, the water powder ratio (W / P), which is the blending ratio of water and the powder containing the cement material and other admixture, may be 25% or more and 50% or less, and is 30. It is preferably about%. If the water powder ratio (W / P) is less than 25%, kneading becomes difficult, and further, compaction becomes insufficient. In addition, it becomes difficult to offset the amount _{of CO 2 emitted in the cement manufacturing process by the amount of CO 2} absorbed in the carbonation curing due to the increase in the amount of unit cement. On the other hand, if the water powder ratio (W / P) exceeds 50%, it becomes difficult to obtain the viscosity required for immediate demolding. The cement material in the present specification refers to a powder component containing at least the above-mentioned Portland cement and γ-C2S, and further containing a blast furnace slag and other powdery binder as needed. .. Glass fiber and sepiolite shall not be included in this. In addition, in this specification, the powder (P) of a cement composition means a combination of the above-mentioned cement material (C) and powder (lime ash, etc.) used as an admixture. The amount of the powder (P) means the total amount of these, and the water powder ratio (W / P) is the amount of the powder (P) in the cement composition (raw cement). It refers to the ratio of the amount of water (W).

As the cement composition according to the present invention, for example, a known fine aggregate may be used without particular limitation. By blending a fine aggregate, the precast cement panel can be suitably used as a mortar material. The type and blending amount of the fine aggregate may be appropriately adjusted according to the application of the precast cement panel, the required characteristics, and the like.

The fine aggregate is an aggregate defined by JIS A 5308, JIS A 5005, JIS A 5002 and JIS A 5011, and examples of the fine aggregate include crushed sand, sand, river sand, sea sand, lime crushed sand, and recycled sand. Examples include aggregates, lightweight aggregates, heavy aggregates and the like. When the fine aggregate is blended, the blending amount is preferably 50 parts by mass or more and 400 parts by mass or less with respect to 100 parts by mass of the cement material, for example.

The cement composition according to the present invention may contain various admixtures, if necessary, like a general cement composition. Examples of the admixture include a water reducing agent, an AE water reducing agent, a high-performance water reducing agent, a high-performance AE water reducing agent, an AE agent, a fluidizing agent and the like. The blending amount of the admixture is preferably 0.001 part by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the cement component, for example.

The cement composition is, for example, filled in a mold, cured into a predetermined shape, and then carbonated and cured. The cement composition does not need to be completely cured prior to carbonation curing, as long as it is self-supporting (to the extent that it can maintain its predetermined shape even when removed from the mold). The glass fiber may be mixed with the cement composition before being filled in the mold, or may be mixed with the cement composition after being filled in the mold and before being cured.

<Manufacturing method of precast cement panel>
The precast cement panel of the present invention has a pre-molding process in which a ready-made cement obtained by kneading the above-mentioned cement composition is hardened (semi-hardened) in a mold and pre-molded by immediate demolding, and this hardened product is used. It is preferably produced by the production method of the present invention comprising a carbonation curing step of carbonation curing. The precast cement panel produced by this production method contains glass fiber and has excellent strength. Further, since the alkali content derived from the cement component is neutralized by carbonation curing, the strength deterioration due to the corrosion of the glass fiber is sufficiently suppressed, and a precast cement panel having excellent long-term reliability can be obtained. And since the pre-molding is performed by immediate demolding, the precast cement panel can be manufactured under high productivity which is dramatically improved as compared with the conventional case. Hereinafter, each step will be described in detail.

[Preliminary molding process]
Fresh cement, which is made by kneading the cement composition described in detail in the material composition above, is poured into a precast concrete formwork having a predetermined shape. This kneading is preferably carried out at a low to medium speed (for example, 100 to 200 rpm) so as to reduce the breakage of the glass fiber.

After placing, the raw cement in the above mold is compacted using a vibrator or the like, and the surface shape is adjusted as needed, and immediately after that, within 3 minutes at the longest, the state of the semi-cured body. Immediately demold with. The concrete solidified body (semi-cured body) thus obtained is subjected to the carbonation curing step curing which is the next step.

In this preformation step, it is not necessary to completely harden the ready-made cement, for example, it may be hardened to the extent that it can stand on its own while maintaining its shape within the required accuracy range. As described above, the raw cement made of the cement composition of the present invention contains an appropriate amount of sepiolite, so that the accuracy of shape retention in the case of immediate demolding as described above is increased to a necessary and sufficient level. Has been done. The necessary and sufficient accuracy of shape retention at the time of immediate demolding may be within each range required for each site or application, but in general, it is immediately that the product size is within ± 2 mm. This is a preferable range required as a quality control standard for cement molded products by demolding. According to the manufacturing method of the present invention, it is possible to sufficiently clear such a standard.

[Carbonated curing process]
After the pre-molding step, a step of carbonating and curing the semi-cured product of raw cement is performed. This carbonation curing can be carried out, for example, by exposing the semi-cured product to a carbon dioxide-containing gas. The content ratio of carbon dioxide in the carbon dioxide-containing gas is, for example, preferably 1% or more, and more preferably 10% or more. As a result, carbonation curing is rapidly carried out, and deterioration of the glass fiber in the cement composition due to the alkali content can be suppressed. Combustion exhaust gas emitted from factories and facilities can be used as a source of _{CO 2} used for carbonation curing. The combustion exhaust gas may be sent directly into the carbonation curing chamber, or may be mixed with other gases before being sent.

The temperature at the time of carbonation curing is not particularly limited, but is preferably 15 ° C. or higher, and more preferably 50 ° C. or higher. Further, the temperature at the time of carbonation curing is preferably 70 ° C. or lower, for example.

The curing period of carbonation curing may be appropriately set according to the shape of the object to be cured, the curing conditions, and the like. For example, the curing period may be about 1 to 28 days. In the carbonation curing step, the curing reaction of the uncured component may proceed at the same time. As described above, since it is assumed that the curing is not completed in the premolding step by immediate demolding, the uncured components may be sufficiently cured during the carbonation curing step. ..

The precast cement panel of the present invention that can be obtained by the above manufacturing method may be used as it is for applications such as residual molds, and may be molded, processed, etc. as necessary before being used for specific applications. May be good. The precast cement panel of the present invention can be used very preferably for the residual formwork, but it can also be used for other purposes. Specific examples of diversion of the precast cement panel of the present invention to other uses include fish reef blocks, floor protection blocks, building material panels, cable troughs, U-shaped side grooves, GC lids, utility poles, and the like. ..

Hereinafter, the precast cement panel for the residual formwork of the present invention will be described in detail with reference to examples. The present invention is not limited to the examples shown below.

In order to confirm the particular effect of the present invention, first, using each of the materials described below, each raw cement used for molding the precast cement panel specimens of each Example and Comparative Example is shown in Table 1 below. It was prepared using each material shown in. Table 2 shows the composition of each raw cement. However, among the materials used below, the admixture (Sp) was added in a proportion of 0.35% by mass in the blending ratio with respect to the powder (P) in all the ready-made cements.

Table 3 shows "ratio of water (W) to cement material (C) (W / C) (%)" and "water (W)" in the ready-made cement used for molding the specimens of each Example and Comparative Example. ) And powder (P) (W / P) (%) ”and“ Sepiolite (Sep) content in water (W) (Sep / W) (%) ”are shown, respectively.

Table 4 shows the content of sepiolite in each cured product obtained by curing the raw cement of each Example and Comparative Example. The content of sepiolite in the cured product is measured as follows. After demolding, each precast cement panel specimen of the semi-cured product obtained by immediate demolding is subjected to carbonation curing under the conditions described below. For each specimen at the stage where curing was completed, 0.5 part of magnesium oxide was added to 4.5 parts of the cured product, and the mixture was sufficiently mixed in a Menou mortar, and then powder X-ray diffraction measurement was performed. It is a numerical value obtained by analyzing the measurement result with the quantitative software "SIROQUANT" manufactured by Siteronics and measuring the content of sepiolite in each cured product.

[Shape retention accuracy test during immediate demolding]
(Test method)
For the raw cement of each example and comparative example, the inner glue was driven into a mold of 100 mm × 40 mm × 400 mm, compacted with a rammer for 5 seconds, and then the side mold was immediately demolded (immediate demolding). A semi-cured specimen was obtained. For the specimens of each Example and Comparative Example, the inner dimension of the mold and the difference between the length, width, and height of the specimen (hereinafter referred to as "deviation width") were measured. The evaluation criteria in this test are as follows, and the evaluation results are shown in Table 3 as "shape retention accuracy".
(Evaluation criteria)
◯: The length, width, and height deviation width of the specimen are all 2 mm or less.
Δ: The maximum value of the deviation width exceeds 2 mm and is 4 mm or less.
X: The maximum value of the deviation width exceeds 4 mm.

[Bending strength test (initial)]
(Test method)
Each specimen in the semi-cured state of each of the Examples and Comparative Examples obtained by the above immediate demolding was carbonated and cured up to 14 days in age at _{50 ° C., 40% RH, and 50% CO 2 environment.} , Curing was completed, and a precast cement panel specimen was obtained. Each specimen thus obtained was subjected to a test with trisection loading according to JSCE G 552, and the bending strength of each specimen was measured. The evaluation criteria in this test are as follows, and the evaluation results are shown in Table 3 as "bending strength (initial)".
(Evaluation criteria)
◯: Bending strength is 4 N / mm ² or more.
Δ: Bending strength is 3 N / mm ² or more and less than 4 N / mm ^2.
X: Bending strength is less than ^{3 N / mm 2.}

[Durability test]
(Test method)
The precast cement panel specimen used in the above-mentioned "bending strength test (initial)" was subjected to a deterioration acceleration test by immersing it in warm water at 70 ° C., and the bending strength was measured after 30 days of acceleration. The bending strength test was carried out by the same method as the above-mentioned "bending strength test (initial)". In addition, each specimen was pulled up from warm water at 70 ° C. for a predetermined number of promotion days (immersion period), slowly cooled to room temperature, and then subjected to each test. The evaluation criteria in this test are as follows, and the evaluation results are shown in Table 3 as "durability (after accelerated test)".
(Evaluation criteria)
◯: The bending strength after the deterioration acceleration test is 95% or more of the initial strength.
Δ: The bending strength after the deterioration acceleration test is 85% or more and less than 95% of the initial strength.
X: The bending strength after the deterioration acceleration test is less than 85% of the initial strength.

[CO ₂ emission control performance test]
(Test method)
For the precast panel that has been cured, the CO2 fixation amount was determined by inorganic carbon analysis, and it is a numerical value obtained by subtracting it from the CO2 emission amount during material production. The evaluation criteria in this test are as follows, and the evaluation results are shown in Table 3 as _{"CO 2 absorption".}
(Evaluation criteria)
◯: CO ₂ emissions are negative.
Δ: CO ₂ emission is 0 kg / m ³ or more and less than 10 kg / m ^3.
X: CO ₂ emission is 10 kg / m ³ or more.

From the above results, the precast cement panel for the residual formwork according to the present invention can be produced under high productivity by immediate demolding, and is excellent in strength and durability, and further, CO. It can be seen that the remaining formwork can avoid the increase in the total emission amount of _2.

Claims (3)

A precast cement panel for residual formwork, one side being the finished surface of the building and the other side being the concrete placement side.
It is composed of a hardened cement obtained by curing and carbonating a cement composition containing a cement material, an aggregate, a glass fiber, and sepiolite.
The cement material contains Portland cement and γ-C2S, and the proportion of γ-C2S in the cement material is 5% by mass or more and 50% by mass or less.
A precast cement panel for a residual formwork in which the content of the sepiolite in the hardened cement is 0.5% by mass or more and 2% by mass or less. The pH of the hardened cement is 10 or less,
The precast cement panel according to claim 1, wherein the glass fiber is E glass fiber. A method for manufacturing precast cement panels for residual formwork, where one surface is the finished surface of the building and the other surface is the concrete placement side.
Precast cement panel A pre-molding process in which pre-molding is performed by immediate demolding, which quickly demolds after placing and compacting the raw cement into the mold for molding.
A carbonation curing step of carbonating and curing the semi-cured body of the raw cement after the pre-molding step is provided.
The raw cement contains water, cement material, aggregate, glass fiber, and sepiolite, and has a water powder ratio (W / P) of 25% or more and 50% or less.
The cement material contains Portland cement and γ-C2S, and the proportion of γ-C2S in the cement material is 5% by mass or more and 50% by mass or less.
A production method in which the content of sepiolite in water is 3% by mass or more and 10% by mass or less.