JP2012188319A - γ BELITE-CONTAINING FOAM MORTAR MIXTURE - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foam mortar exhibiting excellent carbon dioxide-absorbing capability in the natural environment (atmospheric environment) and not having problems such as pH rise and soil contamination due to the solution of cement components.SOLUTION: In mortar mixture constituted by mixing water, powder, air bubbles, admixture, Vp:Vso is 2:8 to 6:4 wherein total of a volume unit quantity (L/m) of the water and a volume unit quantity (L/m) of the powder is Vp, a volume unit quantity (L/m) of the air bubbles is Vso, the mortar mixture contains cement and γ belite as powder components, and the ratio of the γ belite in the powder is 20 to 70 pts.mass.

Description

  The present invention relates to a kneaded material for obtaining a bubble mortar exhibiting excellent carbon dioxide absorption ability in a natural environment (atmospheric environment).

  Cement-based materials typified by mortar and concrete are materials that absorb carbon dioxide when the cement matrix after curing reacts with carbon dioxide and carbonizes (neutralizes). However, it has been conventionally considered insignificant to actively use common cement-based materials as carbon dioxide absorbers from the viewpoint of preventing global warming. This is because the cement-based material reacts with carbon dioxide only in the vicinity of the surface, and usually the amount of carbon dioxide emitted when producing cement used in the cement-based material exceeds the absorbed amount.

  On the other hand, in the case of bubble mortar, the amount of carbon dioxide absorbed becomes considerably large in consideration of the surface of voids existing inside. Bubble mortar has already been applied to lightweight embankments as part of soil-based materials. However, the conventional bubble mortar can absorb a large amount of carbon dioxide when accelerated carbonation curing is performed in an environment where the carbon dioxide concentration is increased, but carbonation proceeds in a natural atmospheric environment. Slowly, it was not very effective for use as a carbon dioxide absorber.

  In addition, when a large amount of foam mortar is used for the use of soil-based materials, there is a concern about the influence on living organisms due to pH increase and soil contamination due to elution of cement components. For this reason, the application range of the bubble mortar as a soil type material was limited.

JP 2003-212617 A JP 2006-182583 A

  It is an object of the present invention to provide a foam mortar that exhibits excellent carbon dioxide absorption ability in a natural environment (atmospheric environment), and has few problems of pH increase and soil contamination due to elution of cement components. To do.

The above-mentioned purpose is a mortar kneaded material in which water, powder, bubbles and admixture are blended, and the sum of the volume unit amount of water (L / m ³ ) and the volume unit amount of powder (L / m ³ ) When Vp and the volume unit amount (L / m ³ ) of bubbles are expressed as Vso, Vp: Vso is 2: 8 to 6: 4, and cement and γ belite are contained as powder components and occupy the powder. This is achieved by a foam mortar kneaded product having a γ belite ratio of 20 to 70% by mass. In particular, the compression strength of the cured body at the age of 28 days is 0.5 to 5.0 (N / mm ² ), the air permeability coefficient is 1.0 × 10 ⁻¹ (cm / s) or more, and the specific gravity is 0.4. It is more preferable that the kneaded product is blended and adjusted so as to be -0.7.

  According to the present invention, it is possible to provide a bubble mortar that exhibits excellent carbon dioxide absorption ability in a natural environment (atmospheric environment). This bubble mortar absorbs carbon dioxide by utilizing the carbonation reaction of γ belite, and the reaction product is formed on the surface of the internal void, thereby suppressing the elution of cement components alkali and heavy metals. . Therefore, it has less influence on the living environment of living organisms than conventional bubble mortar, and is highly safe against soil contamination. Therefore, it can be widely applied as a soil-based material such as lightweight embankment, and thereby can greatly contribute to the reduction of carbon dioxide in the atmosphere.

  Further, since the cured foamed mortar obtained by the present invention is a porous material, it is also useful as a heat insulating material. Furthermore, since it has open cells, it can be used as an exhaust gas filter for heavy machinery and automobiles. It is also possible to produce a product by forcible carbonation treatment, and the elution prevention performance of the cement component is exhibited even in various uses that are not exposed to the atmospheric environment. Moreover, the amount of carbon dioxide emission can be reduced by using exhaust gas discharged from a factory or power plant for forced carbonation treatment.

The graph which shows the compressive strength about the foam mortar test piece (case No. 1, 2, 3) of the γC2S substitution rate which gave the air curing and the accelerated carbonation curing. The graph which shows the relationship between (gamma) C2S substitution rate and compressive strength about the bubble mortar specimen (case No. 1, 4, 5, 6) using OPC. The graph which shows the relationship between (gamma) C2S substitution rate and the carbon dioxide absorption by accelerated carbonation curing about the bubble mortar specimen (case No. 1, 4, 5, 6) using OPC. The graph which shows the time-dependent change of the weight about the foam mortar test piece set | placed by the atmospheric environment. The graph which shows the weight increase amount on the basis of the test piece weight of the 1st week about the bubble mortar test piece set | placed by the atmospheric environment. The graph which shows the relationship between (gamma) C2S substitution rate and the weight increase amount in the 25th week from the start of indoor storage about the foam mortar specimen (case No. 1, 4, 5, 6) using OPC.

Among admixtures added to cement-based materials, it is known that γ belite (γ-2CaO · SiO ₂ ) reacts with carbon dioxide and has a function of densifying the cement matrix. Its action is remarkably exhibited by performing accelerated carbonation curing, and it is possible to increase the strength of cementitious materials (Patent Document 1), and to improve Ca elution resistance, salt damage resistance, scaling resistance, and freeze-thaw resistance. It can be improved (Patent Document 2).

  On the other hand, in the case of bubble mortar, according to the investigation by the inventors, when a part of the cement is replaced with γ belite, the carbon dioxide absorption amount by accelerated carbonation curing tends to decrease. There are many unexplained reasons for that, but the reaction product of γ belite and carbon dioxide narrows the internal voids of the bubble mortar due to the rapid carbonation of γ belite in an accelerated carbonation environment, This is probably because the supply of carbon dioxide into the cured mortar is obstructed relatively early. Therefore, in order to improve the carbon dioxide absorption performance of the bubble mortar, it was predicted that the blending of γ belite was not effective.

However, as a result of further studies, in the atmospheric environment at room temperature rather than in an accelerated carbonation environment, the amount of carbon dioxide absorbed increased in the foam mortar containing γ belite compared to the one not containing γ belite. It became clear to do. In the case of a mild carbonation reaction in an atmospheric environment, carbon dioxide can reach the inside of the void over a long period of time without causing rapid void narrowing due to the reaction product caused by γ belite. Carbonation of cement itself and carbonation of γ belite are considered to continue for a long time.
The present invention has been completed based on such findings.

  The foamed mortar kneaded product of the present invention is a mixture of water, powder, foam and admixture. Although an aggregate can use a well-known thing according to a use, it can also be set as the bubble mortar which does not use an aggregate.

As a powder component, at least cement and γ belite are mixed. Depending on the required strength level, a portion of the cement may be replaced with a powder such as calcium carbonate.
The proportion of γ belite in the powder is 20 to 70% by mass. If it is less than 20% by mass, the effect of improving the carbon dioxide absorption capacity in the atmospheric environment by γ belite will not be sufficiently exhibited. On the other hand, if the proportion of γ belite exceeds 70% by mass, the carbon dioxide absorption capacity is rather lowered, which is not effective. The proportion of γ belite in the powder is more preferably 40 to 60% by mass.
As the cement, portland cement, fly ash cement, blast furnace cement B type and the like are suitable targets.

It is desirable to apply a preform generated by a foaming apparatus using a known foaming agent (surfactant). A known bubble mortar manufacturing technique can be used for the method of generating bubbles and the kind of foaming agent. However, in the present invention, the amount of bubbles is set to the following range.
When the sum of the volume unit amount of water (L / m ³ ) and the volume unit amount of powder (L / m ³ ) is Vp, and the volume unit amount of bubbles (L / m ³ ) is Vso, Vp: Vso is The range is 2: 8 to 6: 4.
If the amount of bubbles is less than the above, it may be difficult to form open cells in the mortar cured body, and in this case, the void wall surface that does not come into contact with outside carbon dioxide increases, which is not preferable. On the other hand, when the amount of bubbles is larger than the above, the strength of the mortar cured body is significantly reduced.

  As the admixture, an AE water reducing agent, a high performance water reducing agent or a high performance AE water reducing agent is used.

In the mortar kneaded material satisfying the above formulation, in particular, the compression strength of the cured body at the age of 28 days of the mortar kneaded material is 0.5 to 5.0 (N / mm ² ), and the air permeability coefficient is 1.0 ×. What is blended and adjusted so that the specific gravity is 0.4 to 0.7 is 10 ^-1 (cm / s) or more is a more preferable target. If the air permeability coefficient increases, the compressive strength and specific gravity decrease, so the upper limit of the air permeability coefficient is necessarily restricted by the lower limit of the compressive strength or the lower limit of the specific gravity. Therefore, the upper limit of the air permeability coefficient is not particularly required, but can be suitably used in various applications, for example, within a range of 1.0 (cm / s) or less. The compressive strength can be adjusted mainly by the water powder ratio and the unit aggregate amount, the air permeability coefficient can be adjusted mainly by the volume unit amount Vso of the bubble and the kind / addition amount of the admixture, and the specific gravity is mainly the unit aggregate amount and the volume unit of the bubble. It can be adjusted by the amount Vso.

[Experimental example of accelerated carbonation curing]
A foam mortar having the composition shown in Table 1 was prepared. The powder used is as follows.
・ OPC: Ordinary Portland cement ・ FAC: Fly ash cement ・ BB: Blast furnace cement type B ・ γ: γ Belite (γC ₂ S)
W / P in Table 1 means the water powder ratio. In the following, “γC2S substitution rate” means “ratio of γ belite in the powder”.

A foam mortar kneaded material was prepared as follows.
Pre-mix water, powder and high-performance water reducing agent to make a paste. At this time, the paste is sufficiently mixed so as not to be fooled, and then the stirring of the paste is continued intermittently or continuously so as not to cause bleeding. Separately, a foaming device is used to generate mousse-like air bubbles (preform), which is added to the paste in a predetermined amount, and immediately kneaded to be finished.

After placing the obtained foamed mortar kneaded material, 20 ° C. wet air curing (humidity of 80% or more) was performed for 10 days to demold, and the obtained foamed foamed mortar was subjected to accelerated carbonation curing. The accelerated carbonation curing was performed at a temperature of 60 ° C., a humidity of 50%, and a CO ₂ concentration of 20% for 7 days or 28 days. Moreover, in order to compare compressive strength, it replaced with said accelerated carbonation curing and the sample used for the air curing (the said wet air curing conditions) was also produced.
Each mortar cured body was confirmed to have an air permeability coefficient of 1.0 × 10 ⁻¹ (cm / s) or more and a specific gravity of 0.4 to 0.7 at the age of 28 days. .

  FIG. 1 shows the compressive strength of a foam mortar specimen (case No. 1, 2, 3) subjected to air curing and accelerated carbonation curing and having a γC2S substitution rate of 50%. For each cement type, data for 7 days air curing, 7 days accelerated carbonation curing, 28 days air curing, and 28 days accelerated carbonation curing are shown in order from the left. When accelerated carbonation curing was performed, the strength increased due to carbonation of γ-belite, but when the accelerated carbonation curing period became longer, the strength increasing effect tended to decrease. In terms of the type of cement, OPC and BB are relatively preferable from the viewpoint of strength development.

  FIG. 2 shows the relationship between the γC2S substitution rate and the compressive strength for the bubble mortar specimens (cases Nos. 1, 4, 5, and 6) using OPC. When the blending ratio of γ belite increases, the compressive strength tends to decrease. However, when accelerated carbonation curing is performed, the decrease in strength relative to those without γ belite is reduced. With the γC2S substitution rate of 30%, the accelerated carbonation curing yielded the same strength level as that without γ belite.

  FIG. 3 shows the relationship between the γC2S substitution rate and the amount of carbon dioxide absorbed by accelerated carbonation curing for the foam mortar specimens (cases No. 1, 4, 5, and 6) using OPC. The plot marked with ■ is the accelerated carbonation curing for 7 days, and the plot marked with ● is the accelerated carbonation curing for 28 days. The vertical axis represents the amount of carbon dioxide absorbed per apparent unit volume (including internal voids) of the foam mortar specimen. In the accelerated carbonation environment, carbon dioxide absorption is reduced in the foam mortar containing a large amount of γ belite. In addition to the carbon dioxide absorption performance in the atmospheric environment described later, in the case where the carbon dioxide absorption performance in the accelerated carbonation environment is also emphasized, the γC2S substitution rate is preferably in the range of 20 to 30%.

[Experimental example by exposure to atmospheric environment]
The foamed mortar kneaded material having the composition shown in Table 1 was prepared and placed in the manner described above, and then subjected to 20 ° C. wet air curing (humidity of 80% or more) for 10 days for demolding. The obtained foamed mortar hardened body was placed in a room temperature and atmospheric environment and stored up to 49 weeks in a state exposed to the atmosphere.

  FIG. 4 shows the change over time in the weight of the foam mortar specimen placed in the atmospheric environment. The horizontal axis is a √ week scale of age based on the start of indoor storage. That is, √weeks 1, 2, 3, 4, 5, 6 and 7 are the 1st week, 4th week, 9th week, 16th week, 25th week, 36th week and 49th week from the start of indoor storage, respectively. It means the time of eye. Weight loss was observed in the first week for all blended foam mortar specimens. This is a phenomenon due to the amount of water loss accompanying drying exceeding the amount of carbon dioxide absorbed. Thereafter, the specimen weight starts to increase. In the case of a general cementitious material, unless the carbonation treatment is forcibly performed, the weight usually continues to decrease at 49 weeks after demolding. The phenomenon that bubble mortar during exposure to the air environment rapidly increases in weight is considered to be very rare for cementitious materials.

  FIG. 5 shows the weight increase based on the weight of the first week specimen for the foam mortar specimen placed in the atmospheric environment. The vertical axis shows the weight increase amount of the bubble mortar specimen converted into the weight increase amount per unit area of the apparent surface exposed to the atmosphere of the specimen (surface not considering the surface area of the internal void). . This increase in weight corresponds to a value obtained by subtracting the mass of water vaporized by drying from the mass of absorbed carbon dioxide, and it can be considered that carbon dioxide in an amount exceeding this weight increase was absorbed.

  FIG. 6 shows the relationship between the γC2S substitution rate and the weight increase amount at the 25th and 49th weeks from the start of indoor storage for the foam mortar specimens (cases No. 1, 4, 5, and 6) using OPC. It became clear that the amount of carbon dioxide absorbed by the foamed mortar hardened body in the ambient air environment increased by adding γ belite. In particular, it is effective to set the γC2S substitution rate to 30 to 70%, and it is more preferable to set the γC2S substitution rate to 40 to 60% for applications that are used in a natural environment such as lightweight embankment.

Claims (2)

A mortar kneaded material containing water, powder, bubbles and admixture, and the sum of volume unit amount of water (L / m ³ ) and volume unit amount of powder (L / m ³ ) is Vp, When the volume unit amount (L / m ³ ) is expressed as Vso, Vp: Vso is 2: 8 to 6: 4, and cement and γ belite are contained as powder components. A foam mortar kneaded product having a ratio of 20 to 70% by mass. The compression strength of the cured body at the age of 28 days is 0.5 to 5.0 (N / mm ² ), the air permeability coefficient is 1.0 × 10 ⁻¹ (cm / s) or more, and the specific gravity is 0.4 to 0. The foamed mortar kneaded product according to claim 1, which is blended and adjusted to have a ratio of 0.7.

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