JP6240400B2 - Method for producing substance having hardened cement - Google Patents

Description

  The present invention relates to a method for producing a substance having a cemented body. In particular, the present invention provides a cured cement having at least one characteristic of i) high density; ii) high calcium carbonate content; iii) low porosity; and iv) low water absorption. The present invention relates to a method for producing a substance having a hardened cement body.

  Many of Japan's concrete structures are approaching the renewal period, and if they are demolished, it is predicted that a huge amount of waste concrete exceeding 40 million tons will be generated annually. Therefore, when rebuilding a concrete structure in the renewal period, a large amount of waste concrete processing method becomes a big problem.

  In addition, recycling of waste concrete is required due to the problem of depletion of natural resources. Regarding recycled coarse aggregate, recycling to obtain high-quality recycled coarse aggregate has been established and put into practical use by techniques such as grinding treatment and heat scumming treatment. On the other hand, with regard to recycled fine aggregate, even if the same method as recycled coarse aggregate is used, the separation of aggregate and cement paste has not succeeded due to its small particle size, and recycling is not possible. However, there is a problem that only low-quality recycled fine aggregate can be obtained even if it is made into a material.

  Furthermore, repairing of deteriorated concrete structures has also been made. Currently, the restoration is carried out by methods such as removing concrete that has deteriorated on the surface of the structure, or applying a resin film that prevents the intrusion of deteriorated substances on the surface of the structure. There is a problem that.

  Non-Patent Document 1 attempts to improve the properties of recycled aggregate in a short time using a carbonation acceleration chamber (see Non-Patent Document 1). However, the accelerating tank is a special device, and it is difficult to use it at a site where recycling is performed, for example, at a location where a concrete structure is broken. Further, since the accelerating tank consumes a lot of energy, an energy saving method is required.

Yoichiro Kunieda: Research on low-quality recycled aggregate modification technology by forced carbonation, Master's thesis, University of Tokyo, February 2010.

There is a need for a method for obtaining a high-quality material having a hardened cement, for example, a high-quality recycled fine aggregate, in a short time, at low cost and with energy saving.
In addition, there is a need for a method for repairing deterioration of a concrete structure in a short time, at low cost and energy saving without rebuilding the concrete structure.

Therefore, an object of the present invention is to provide a method capable of improving the quality of a substance having a hardened cement body in a short time, at low cost and with energy saving.
Moreover, the objective of this invention is providing the method of repairing deterioration of a concrete structure in a short time, low cost, and energy saving in addition to the said objective or in addition to the said objective.
Furthermore, an object of the present invention is to provide a high-quality material having a hardened cement body, such as a high-quality recycled fine aggregate.
It is another object of the present invention to provide a material having a repaired hardened cement body, such as a repaired concrete structure.

The inventors have found the following invention.
<1> A method for producing a substance having a cement hardened body, wherein the substance has at least one of the following characteristics i) to iv):
1) Carbon dioxide bubbles having a diameter of 1 mm or less in water, preferably 100 μm or less, more preferably 1 μm or less, are 0.05% or more, specifically 0.05 to 0.12%, preferably 0.08% or more. , Specifically, a step of preparing carbonated bubble water having 0.08 to 0.12%, more preferably 0.10% or more, specifically 0.10 to 0.12%; and 2) carbonated bubble water A first carbonic acid bubble water introduction step for introducing the water into the substance having a hardened cement body;
To obtain a substance having at least one of the following characteristics i) to iv).

i) A density higher than that of the material having a hardened cement body before applying this method, specifically 1.02 times or more, preferably 1.05 times the density of the material having a hardened cement body before applying this method. More preferably, the density is 1.08 times or more.
ii) Calcium carbonate content higher than that of the material having a hardened cement body before applying this method, specifically, more than twice, preferably 3 times the calcium carbonate amount of the material having a hardened cement material before applying this method. As mentioned above, specifically, the amount of calcium carbonate is 2 to 10 times, preferably 3 to 10 times.
iii) Porosity lower than that of the material having a cemented body before applying this method, specifically 0.9 times or less of the porosity of the material having a cemented material before applying this method, preferably 0.8. Porosity less than 85 times. In the present specification, the “porosity” after applying this method means a value measured within 28 days after this method.
iv) A water absorption lower than that of the substance having a cemented body before application of the present method, specifically 0.8 times or less of the substance having a cemented body before application of the present method, preferably 0.8. Water absorption of 7 times or less, more preferably 0.6 times or less.

<2> Before step 2) of <1> above,
0) A first calcium hydroxide introduction step for introducing a calcium hydroxide aqueous solution, preferably a calcium hydroxide aqueous solution having a concentration of 0.15% or more, more preferably a saturated calcium hydroxide aqueous solution, into a substance having a cemented body. ;
It is good to have further.

<3> After step 2) of <1> or <2> above,
3) First, a calcium hydroxide aqueous solution, preferably a calcium hydroxide aqueous solution having a concentration of 0.15% or more, more preferably a saturated calcium hydroxide aqueous solution is introduced into the substance having a hardened cement obtained in step 2). 2) calcium hydroxide introduction step; and 4) a second carbonated bubble water introduction step of introducing the carbonated bubble water prepared in step 1) into the substance having a cemented body obtained in step 3);
It is good to have further.

<4> In the above <3>, after the step (2n-2)),
(2n-1)) A calcium hydroxide aqueous solution, preferably a calcium hydroxide aqueous solution having a concentration of 0.15% or more, more preferably a saturated hydroxylated hydroxide, is added to the cement-containing substance obtained in the step (2n-2)). N-th calcium hydroxide introduction step of introducing an aqueous calcium solution; and (2n)) Carbonate bubble water prepared in step 1) is introduced into the substance having a hardened cement obtained in step (2n-1)) Nth carbonated bubble water introduction step;
It is preferable to further include a combination of step (2n-1)) and step (2n)) (where n is an integer of 3 or more, meaning the number of repetitions of the combination).

  <5> In any one of the above items <1> to <4>, step 0), step 2) to 4), step (2n-1)) and step (2n)) (n is an integer of 3 or more) After at least one step, it is preferable to further include a step of coating at least a part of the surface of the substance having the cemented body obtained in the one step.

<6> In any one of the above items <1> to <5>, the substance having a cement hardened body may be selected from the group consisting of recycled aggregate, finished mortar, concrete product, and concrete structure.
<7> A substance having a hardened cement body having at least one of the above characteristics i) to iv) obtained by any one of the above methods <1> to <5>.

According to the present invention, it is possible to provide a method capable of improving the quality of a substance having a cemented cement body in a short time, at low cost and with energy saving.
In addition to the above effects or in addition to the above effects, the present invention can provide a method for repairing deterioration of a concrete structure in a short time, at low cost and with energy saving.
Furthermore, according to the present invention, it is possible to provide a high-quality substance having a hardened cement body, such as a high-quality recycled fine aggregate.
In addition, according to the present invention, it is possible to provide a material having a repaired cement cured body, for example, a repaired concrete structure.

It is a figure which shows the time-dependent change of the mass of the samples X1-1 to X1-4 of Example 1. It is a figure which shows the time-dependent change of the density of the samples X1-1 to X1-4 of Example 1. It is a figure which shows the time-dependent change of the absorptivity of the sample X1-1 to X1-4 of Example 1. It is a figure which shows the time-dependent change of the porosity of the samples X1-1 to X1-4 of Example 1. It is a figure which shows the time-dependent change of the amount of calcium carbonate and the amount of calcium hydroxide of Samples X1-1 to X1-4 in Example 1. It is a figure which shows the time-dependent change of the amount of CSH (g / g fraction) (left) and the amount of silica gel (g / g fraction) (right) of samples Y1-11 to Y1-14 in Example 2. The figure which shows the time-dependent change of Ca / Si amount (g / g fraction) (left) and Ca (OH) ₂ amount (g / g fraction) (right) of samples Y1-11 to Y1-14 in Example 2. is there. It is a figure which shows a time-dependent change of the decreasing degree of the porosity of the samples Y1-11 to Y1-14 of Example 2. FIG. It is the figure which plotted the density before and behind modification | reformation of the samples Z1-Z4 of Example 3. FIG. It is the figure which graphed the water absorption rate before and behind modification | reformation of the samples Z1-Z4 of Example 3. FIG.

Hereinafter, the invention described in the present application will be described in detail.
The present application discloses a method for producing a substance having a hardened cement body, wherein the substance has at least one of the following characteristics i) to iv).

Property i): density higher than that of a substance having a hardened cement body (hereinafter sometimes simply referred to as “substance”) before applying the method of the present invention, specifically, before applying the method of the present invention The density is 1.02 times or more, preferably 1.05 times or more, more preferably 1.08 times or more the density of the substance.
Property ii): Calcium carbonate amount higher than that of the material before the method of the present invention, specifically, 2 times or more, preferably 3 times or more of the calcium carbonate amount of the material before the method of the present invention. 2-10 times, preferably 3-10 times the amount of calcium carbonate.
Characteristic iii): lower porosity than the material before applying the method of the present invention, specifically 0.9 times or less, preferably 0.85 times or less the porosity of the material before applying the method of the present invention Porosity. In the present specification, the “porosity” after applying this method means a value measured within 28 days after this method.
Characteristic iv): lower water absorption than the material before the method of the present invention, specifically 0.8 times or less, preferably 0.7 times or less, more preferably the water absorption rate of the material before the method. Is a water absorption of 0.6 times or less.

The properties of the substance obtained should have any one of the above i) to iv), preferably any two, more preferably any three, most preferably all.
In the method of the present invention, the substance having a hardened cement body is preferably selected from the group consisting of recycled aggregate, finished mortar, concrete product, and concrete structure. More specifically, examples of the recycled aggregate include recycled coarse aggregate and recycled fine aggregate. Examples of the finishing mortar include cement-based finishing materials, cement-based joint materials, and cement-based floor finishing materials. As concrete products, in addition to concrete floor boards, cement-based boards defined in JIS A 5430, JIS A 5414, and JIS A 5404 can be cited. Examples of the concrete structure include a structural precast concrete member.

The method of the present invention comprises:
1) Carbon dioxide bubbles having a diameter of 1 mm or less in water, preferably 100 μm or less, more preferably 1 μm or less, are 0.05% or more, specifically 0.05 to 0.12%, preferably 0.08% or more. , Specifically, a step of preparing carbonated bubble water having 0.08 to 0.12%, more preferably 0.10% or more, specifically 0.10 to 0.12%; and 2) carbonated bubble water A first carbonic acid bubble water introduction step for introducing the water into the substance having a hardened cement body;
Have

Step 1) is a step of preparing carbonated bubble water.
Carbonated bubble water can be obtained by introducing carbon dioxide (CO ₂ gas) into water.
The diameter of the carbonic acid bubbles in the carbonic acid bubble water is 1 mm or less, preferably 100 μm or less, more preferably 1 μm or less. The smaller the diameter, the better because it can be introduced into the pores of the substance having a cemented body. Further, the smaller the diameter, the higher the carbon dioxide gas concentration in the water, which is preferable. Furthermore, since the reaction efficiency in the hole of the substance which has a cement hardening body increases, it is so preferable that it is a small diameter.

The amount of carbonic acid bubbles is 0.05% or more, specifically 0.05 to 0.12%, preferably 0.08% or more, specifically 0.08 to 0.12%, more preferably 0. .10% or more, specifically 0.10 to 0.12%. Here, “%” represents the volume of carbon dioxide gas in%, where the total volume of carbonated bubble water is 100%. The amount of bubbles can be obtained by measuring the volume change of the solution by eliminating carbonated bubble water by ultrasonic irradiation.
In order to prepare the carbonated bubble water, it is preferable to use a machine such as a pore type, a pressure dissolution type, an ultrasonic type, a swirling liquid flow type, and a gas-liquid mixed shear type.

Step 2) is a step of introducing the carbonic acid bubble water obtained in the above step 1) into a substance having a cement hardened body.
In step 2), carbonic acid bubble water, particularly CO ₂ enters the substance having the cement hardened body, and the CO ₂ reacts with the calcium hydroxide present in the substance having the cement hardened body, particularly in the cement hardened body, As described in the following formula A and / or the following formula B, formation of calcium carbonate is promoted.
Calcium carbonate is formed in a substance having a hardened cement body, particularly in a hardened cement body, thereby improving the properties of the material having a hardened cement body, particularly a hardened cement body (high density, low porosity, low water absorption) Rate).

Ca (OH) ₂ + CO ₂ → CaCO ₃ + H ₂ O Formula A
CaO + CO ₂ → CaCO ₃ formula B

In step 2), various methods can be adopted depending on the size, porosity, etc. of the substance having a cement hardened body to be used.
For example, when the substance having a cement hardened body is a regenerated fine aggregate having a small particle diameter such as sand, a technique of immersing the sand in carbonated bubble water can be employed. In addition, when immersing, it is good to employ | adopt appropriate immersion time depending on the magnitude | size of the substance which has cement hardening bodies, such as a particle size. When immersed for a long time, it becomes a factor that works in the direction of deteriorating the cement hardened body due to the effect of acid of carbonic acid bubble water. Therefore, the immersion time is preferably set to an appropriate time depending on the substance having the cemented body to be used. For example, in the case of a regenerated fine aggregate having a particle size of 5 mm or less, after quickly introducing carbonic acid bubble water to the saturated water absorption rate of the aggregate, in order to reduce the surface area in contact with air, for example, in order to reduce the surface area in contact with air, It is better to pile up or store in a resin film or sealed container for curing.

On the other hand, when the substance having a hardened cement body is an inanimate object such as a concrete structure, for example, a technique of applying carbonated bubble water to the exposed surface of the concrete structure can be used. A conventionally known method can be used as a method for coating.
In the present specification, the method of introducing the step 2) has been described above for the recycled fine aggregate having a small particle size and the concrete structure having a large size. However, those skilled in the art can introduce various methods depending on the size. Techniques can be used.

Before performing step 2), the method of the present invention
0) A first calcium hydroxide introduction step for introducing a calcium hydroxide aqueous solution, preferably a calcium hydroxide aqueous solution having a concentration of 0.15% or more, more preferably a saturated calcium hydroxide aqueous solution, into a substance having a cemented body. ;
It is good to have further.

Step 0) is a step of introducing calcium hydroxide.
As shown in the above formula A, the CO ₂ introduced in step 2) reacts with the calcium hydroxide present in the substance having a hardened cement, particularly in the hardened cement, thereby promoting the formation of calcium carbonate and increasing the density. In addition, low porosity and low water absorption can be achieved. However, when calcium hydroxide is not present or poorly present in the material having the hardened cement to be used, particularly in the hardened cement to be used, the amount of formation is small even if the above formula A does not occur or occurs. Therefore, it is preferable to provide step 0) and introduce calcium hydroxide into the substance having a cemented body.

The calcium hydroxide aqueous solution to be introduced has a concentration of 0.15% or more, preferably saturated.
The method of introduction depends on the size of the substance having the hardened cement to be used, as described in the step 2). However, as a method relatively independent of the size, an aqueous calcium hydroxide solution is used for the hardened cementitious material. It is a technique of sprinkling water on the substances it has. For example, when the substance having a hardened cement to be used is relatively small, it is possible to adopt a technique in which a calcium hydroxide aqueous solution is showered from above while the substance is transported by a belt conveyor.

In the case where the particle size of the substance having a hardened cement body to be used is small, the introduction method is not particularly limited. In this case, unlike the step 2), the immersion time is not particularly limited, but it is preferable to immerse for the time until the saturated water absorption rate of the substance having a cemented body is reached. Moreover, it is good to use the method of providing a drying process after immersion, and the process of further dipping, and also repeating these processes.
In addition, when the substance having a hardened cement body to be used is an animal such as a concrete structure, an aqueous calcium hydroxide solution is preferably applied to the exposed surface of the concrete structure. A conventionally well-known method can be used for the coating method. Also in the application, a method of repeating drying and application may be used thereafter.

The method of the present invention comprises after step 2)
3) First, a calcium hydroxide aqueous solution, preferably a calcium hydroxide aqueous solution having a concentration of 0.15% or more, more preferably a saturated calcium hydroxide aqueous solution is introduced into the substance having a hardened cement obtained in step 2). 2) calcium hydroxide introduction step; and 4) a second carbonated bubble water introduction step of introducing the carbonated bubble water prepared in step 1) into the substance having a cemented body obtained in step 3);
It is good to have further.

Step 3) is a step of introducing calcium hydroxide into the substance having a hardened cement obtained in step 2).
Step 3) is the same as step 0) in the case where calcium hydroxide is not present or poorly present in the material having a hardened cement, particularly in the hardened cement used, obtained by step 2). This is a step of introducing calcium oxide. Moreover, as represented by the above-mentioned formula B in step 2), it is also a step of replenishing the Ca source that has become scarce by reacting from CaO to CaCO ₃ .
The aqueous calcium hydroxide solution used in step 3) can be the same as that used in step 0) and can be the same as or different from that used in step 0).
Further, examples of the introduction method in step 3) include those used in step 0), and the same method as that method or a different method may be used.

Step 4) is a step of introducing carbonic acid bubble water into the substance having a hardened cement obtained in step 3).
In step 4), as in step 2), formation of calcium carbonate is promoted in the substance having a hardened cement, particularly in the hardened cement. By adopting step 4) together with step 3), the amount of calcium carbonate in the substance having a hardened cement, particularly in the hardened cement, is increased, and high density, low porosity and low water absorption are achieved. .
Carbonic acid bubble water used in step 4) can be the same as in step 2), and may be the same as or different from step 2).
Further, examples of the introduction method in step 4) include those used in step 2), and the same method as the method may be used, or a different method may be used.

The combination of step 3) and step 4) may be repeated further.
That is, after the step (2n-2))
(2n-1)) A calcium hydroxide aqueous solution, preferably a calcium hydroxide aqueous solution having a concentration of 0.15% or more, more preferably a saturated hydroxylated hydroxide, is added to the cement-containing substance obtained in the step (2n-2)). N-th calcium hydroxide introduction step of introducing an aqueous calcium solution; and (2n)) Carbonate bubble water prepared in step 1) is introduced into the substance having a hardened cement obtained in step (2n-1)) Nth carbonated bubble water introduction step;
And a combination of step (2n-1)) and step (2n)) (n is an integer of 3 or more, meaning the number of repetitions of the combination).
Here, the step (2n-1)) can be performed in the same manner as the step 3).
Step (2n)) can be performed in the same manner as in step 4).

The method of the present invention comprises the step 0), the steps 2) to 4), and the step (2n-1)) and the step (2n)) (n is an integer of 3 or more) after the one You may further have the process of coat | covering at least one part of the surface of the substance which has a cement hardening body obtained at the process.
In addition, not only after “one step”, a covering step may be provided after a plurality of steps, for example, a covering step may be provided after all steps.
By providing the coating step, the reaction represented by Formula A and / or Formula B and / or introduction of calcium hydroxide can be efficiently performed.

In the coating step, various coating materials and various coating methods can be used depending on the size of the substance having a cemented body to be used.
For example, when the material having a hardened cement body is a regenerated fine aggregate such as sand, it is preferable to use the technique of putting the sand together in a container and sealing the container as the covering technique.
Further, for example, if the size of the substance having a hardened cement body can be handled, the substance having the hardened cement body can be covered with a coating material such as a resin film.
Furthermore, for example, when the substance having a cement hardened body is a non-animal such as a concrete structure, as a covering material, a member covering the exposed surface of the concrete structure, for example, various resin sheets such as a resin sheet for concrete curing, or A nonwoven fabric or the like is preferably used. Further, examples of the covering method include a method of attaching the above member using an adhesive or the like, a method of winding the above member around the entire structure, and the like, but are not limited thereto.

The present invention can provide a substance having a hardened cement body, particularly a substance having at least one of the above characteristics i) to iv) obtained by the above method.
EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to a present Example.

<Preparation of carbonic acid nanobubble water A-1>
By using a two-phase flow micronano bubble generator manufactured by Skillkit, the flow rate of carbon dioxide gas is controlled to 0.1 liter / second, and carbon dioxide gas is introduced into 30 L of water, resulting in a bubble diameter of 100 μm to 10 nm. Carbonic acid nanobubble water A-1 having a pH of 6 to 4 and an amount of bubbles of 0.05 to 0.10% (volume%) was obtained.

<Sample X>
Water / cement ratio (hereinafter simply abbreviated as “W / C”) = 55% Cement cured body 40 mm × 40 mm × 160 mm was cured in water for 120 days, then cut to 5 mm thickness (40 mm × 40 mm × 5 mm), an ambient temperature of 20 ° C. and a relative humidity of 60%, and cured for 2 days.
Before performing the following immersion treatment, Sample X was characterized by mass, density, absorption rate, TG-DTA (thermogravimetry-differential thermal analysis), porosity, SEM, and the like. Further, the amount of calcium hydroxide and the amount of calcium carbonate were also measured by TG-DTA.

<Immersion in carbonated nanobubble water A-1 and subsequent treatment>
<< Treatment 1 (Underwater) >>
A water tank containing the carbonated nanobubble water A-1 was prepared, and the sample X was immersed in the carbonated nanobubble water A-1 for a predetermined period of time to obtain a sample X1-1.
<< Process 2 (Stirring in water) >>
In the process 1, it carried out similarly to the process 1 except having stirred carbonic acid nano bubble water A-1 during immersion, and obtained the sample X1-2.

<< Process 3 (Atmosphere) >>
In the treatment 1, after setting the immersion time to 1 hour, the sample was left in an atmosphere of 20 ° C. and a relative humidity of 70% for a predetermined period to obtain a sample X1-3.
<< Process 4 (Sealing) >>
In the treatment 3, after the immersion, the exposed surface of the sample was sealed with a wrap (manufactured by Kureha Chemical Co., Ltd.), and was subjected to the same treatment as the treatment 3 except that it was cured for a predetermined period of time to obtain a sample X1-4.

After each predetermined period of treatments 1-4, the characteristics of the respective samples X1-1 to X1-4 were measured for their mass, density, absorption rate, and porosity. The characteristic before processing is assumed to be 100%, and the change is shown in FIGS.
Moreover, about the sample X1-1 to X1-4 after a predetermined period, the amount of calcium hydroxide and the amount of calcium carbonate were measured, and the result is shown in FIG. 5 as “g / g fraction”.
1 to 5, “underwater” indicates process 1, “underwater stirring” indicates process 2, “atmosphere” indicates process 3, and “sealing” indicates process 4.

FIG. 1 is a diagram showing a change with time of mass of samples X1-1 to X1-4. The horizontal axis indicates a predetermined period in days, and the vertical axis indicates mass change in%.
The left side of FIG. 1 shows the results of “atmosphere” (processing 3) and “sealing” (processing 4), “air” (processing 3) is indicated by ○, and “sealing” (processing 4) is indicated by ●.
Further, the right side of FIG. 1 shows the results of “underwater” (treatment 1) and “underwater agitation” (treatment 2), “underwater” (treatment 1) is indicated by ○, and “underwater agitation” (treatment 2) is indicated by ●. It shows with.
From FIG. 1, particularly from the right side of FIG. 1, it can be seen that in “underwater” (treatment 1) and “underwater agitation” (treatment 2), the mass decreases with time. On the other hand, it can be seen from FIG. 1, particularly from the left side of FIG. 1, that “atmosphere” (processing 3) and “sealing” (processing 4) increase in mass as time passes. Also, it can be seen that the change in both the left and right diagrams in FIG. 1 is becoming constant with the period.

FIG. 2 is a diagram showing the change over time in the density of samples X1-1 to X1-4. The horizontal axis indicates the predetermined period in days, and the vertical axis indicates the density change in%.
The left side of FIG. 2 shows the results of “atmosphere” (processing 3) and “sealing” (processing 4), “atmosphere” (processing 3) is indicated by ○, and “sealing” (processing 4) is indicated by ●.
Also, the right side of FIG. 2 shows the results of “underwater” (treatment 1) and “underwater agitation” (treatment 2), “underwater” (treatment 1) is indicated by ○, and “underwater agitation” (treatment 2) is indicated by ●. It shows with.
From FIG. 2, as in FIG. 1, in “underwater” (treatment 1) and “underwater agitation” (treatment 2), the density decreases with the passage of time, while “atmosphere” (treatment 3) and “ In “sealing” (process 4), it can be seen that the density increases as time passes. Moreover, it turns out that the change of FIG. 2 is becoming a constant state with a period.

FIG. 3 is a diagram showing the change over time in the absorptance of samples X1-1 to X1-4. The horizontal axis indicates the predetermined period in days, and the vertical axis indicates the change in absorption rate in%.
3, as in FIGS. 1 and 2, the left side shows the results of “atmosphere” (processing 3) and “sealing” (processing 4), and the right side shows “underwater” (processing 1) and “underwater”. The result of “stirring” (treatment 2) is shown.
From FIG. 3, in “underwater” (treatment 1) and “underwater agitation” (treatment 2), the absorption rate increased with time, while “atmosphere” (treatment 3) and “sealing” (treatment 4). ) Shows that the absorption rate decreases with the passage of time. Moreover, it turns out that the change of FIG. 3 is becoming a constant state with a period.

FIG. 4 is a diagram showing the change over time in the porosity of Samples X1-1 to X1-4. The horizontal axis shows the predetermined period in days, and the vertical axis shows the change in porosity in%.
4, as in FIGS. 1 to 3, the left side shows the results of “atmosphere” (processing 3) and “sealing” (processing 4), and the right side shows “underwater” (processing 1) and “underwater”. The result of “stirring” (treatment 2) is shown.
From FIG. 4, in “underwater” (treatment 1) and “underwater agitation” (treatment 2), the porosity increases as time passes, while “atmosphere” (treatment 3) and “sealing” (treatment 4). ) Shows that the porosity decreases with the passage of time. It can also be seen that the change in FIG. 4 is becoming constant with the period.

FIG. 5 shows the amount of calcium hydroxide (expressed as “CH” or “Ca (OH) 2” in the figure) and the amount of calcium carbonate (“CC” in the figure) for each of Samples X1-1 to X1-4. Or “CaCO 3”).
In FIG. 5, sample X1-3 (atmosphere) in the upper left, sample X1-4 (sealed) in the upper right, sample X1-1 (in water) in the lower left, and sample X1-4 (in water stirring) in the lower right. Show.

It can be seen that the upper part of FIG. 5, that is, the sample X1-3 (atmosphere) and the sample X1-4 (sealing), as time passes, the amount of calcium carbonate increases and the amount of calcium hydroxide decreases. This is considered to be due to the reaction of the above formula A in which CO ₂ of the carbonic acid nanobubble water A-1 reacts with calcium hydroxide.
Moreover, when it considers with FIGS. 1-4, when the reaction of the said Formula A advances, it is thought that the mass and the density are increasing by the increase in calcium hydroxide. Moreover, it is thought that the porosity and the absorptance are reducing because the increased calcium hydroxide fills the voids in the sample.
Therefore, it has been confirmed that the quality of the hardened cement can be improved by appropriately treating the hardened cement with the carbonic acid nanobubble water A-1, that is, by performing the treatment 3 or the treatment 4.

<Sample Y>
Water / cement ratio (hereinafter simply abbreviated as “W / C”) = 55% Cement cured body 40 mm × 40 mm × 160 mm was cured in water for 1 year and then cut into 5 mm thickness (40 mm × 40 mm × 5 mm). The obtained cut sample was immersed in acetone to stop the hydration reaction, and then left in a vacuum environment at 20 ° C. for one week to be vacuum-dried. Thereafter, the obtained substance was neutralized by being left in a chamber at 20 ° C., a relative humidity of 60%, and a CO ₂ concentration of 5% for 2 months.
Sample Y has C—S—H amount (g / g fraction), silica gel amount (g / g fraction), Ca / Si amount (g / g fraction), calcium hydroxide amount (g / g fraction), and voids. The rate was measured. Each measurement method is described below.

<< Methods for measuring various characteristics >>
<Silica gel amount>
The amount of silica gel was obtained by extracting the insoluble residue obtained by dissolving the sample with a salicylic acid-methanol solution.
<Calcium hydroxide amount>
The amount of calcium hydroxide was measured by TG-DTA as described above.
<Porosity>
The porosity was measured by the MIP method (mercury intrusion method) (measuring device: Autopore III 9400 manufactured by Shimadzu Corporation).
<CSH amount>
The amount of C—S—H was measured as follows.
(1) Si after subtracting the amount of Si obtained from the silica gel of the insoluble residue from the total amount of Si in the sample obtained by atomic absorption,
(2) The total amount of water in the sample obtained from TG-DTA, the amount of water obtained by subtracting the amount of adsorbed water on silica gel of the insoluble residue and the amount of bound water in monosulfate,
(3) Other than CSH obtained from the amount of calcium hydroxide, calcium carbonate, and monosulfate obtained by thermal analysis such as TG-DTA and DSC with respect to the total amount of Ca in the sample obtained by EDTA titration. Ca content,
Calculations were made by adding (1) to (3) and further correcting the amount of alumina normally dissolved in CSH.

<Immersion in saturated aqueous calcium hydroxide and subsequent treatment>
Apart from sample Y, a saturated aqueous solution of calcium hydroxide (20 ° C.) was prepared. Sample Y was immersed in this solution for 1 hour.
<Process 11 (R20)>
The sample Y after immersion was taken up and cured for a predetermined period of time at 20 ° C. and a relative humidity of 70% to obtain a sample Y1-11 (R20).
<Process 12 (S20)>
The sample Y after immersion was taken up, the exposed surface of the sample Y was sealed with a wrap (manufactured by Kureha Chemical Co., Ltd.), and cured for a predetermined period of time at 20 ° C. and a relative humidity of 70% to obtain a sample Y1-12 ( S20).

<Process 13 (S40)>
The sample Y after immersion was taken up, the exposed surface of the sample Y was sealed with a wrap (manufactured by Kureha Chemical Co., Ltd.), and cured for a predetermined period of time at 40 ° C. and a relative humidity of 70% to obtain a sample Y1-13 ( S40).
<Process 14 (I40)>
Sample Y1-14 was obtained by immersing sample Y after immersion in a saturated calcium hydroxide solution as it was for a predetermined period (I40).

Each C—S—H amount (g / g fraction), silica gel amount (g / g fraction), and Ca / Si amount of each of samples Y1-11 to Y1-14 after treatments 11 to 14 The amount (g / g fraction), the amount of calcium hydroxide (g / g fraction), and the porosity were measured. The change with time is shown in FIGS.
In FIGS. 6 to 8, ◯ indicates the result of the sample Y1-11 by the process 11 (R20), ● indicates the result of the sample Y1-12 by the process 12 (S20), and ■ indicates the sample Y1-13 by the process 13 (S40). As a result, x indicates the result of the sample Y1-14 by the process 14 (I40).

FIG. 6 shows changes over time in the C—S—H amount (g / g fraction) (left side of FIG. 6) and the silica gel amount (g / g fraction) (right side of FIG. 6) of Samples Y1-111 to Y1-14. FIG. The horizontal axis indicates the predetermined period in days, and the vertical axis indicates the amount of each.
From the left side of FIG. 6, it can be seen that the C—S—H amount gradually increases with time. Moreover, it can be seen from the right side of FIG. 6 that the amount of silica gel gradually decreases with time. Furthermore, each of them seems to be moving toward a certain state as time passes. Further, it can be seen that in the processing 13 (S40) and the processing 14 (I40), the degree of increase in the C—S—H amount and the degree of decrease in the amount of silica gel are severe.
Since silica gel decreased and C—S—H increased, it was found that C—S—H was repaired from the silica gel by introducing calcium hydroxide.

FIG. 7 shows the time course of the Ca / Si amount (g / g fraction) (left side of FIG. 7) and the Ca (OH) ₂ amount (g / g fraction) (right side of FIG. 7) of samples Y1-11 to Y1-14. It is a figure which shows a change. The horizontal axis indicates the predetermined period in days, and the vertical axis indicates the amount of each.
From the left side of FIG. 7, it can be seen that the Ca / Si amount gradually increases with time. Further, it can be seen from the right side of FIG. 7 that the amount of Ca (OH) ₂ gradually increases with time. Furthermore, each of them seems to be moving toward a certain state as time passes. Moreover, in the process 13 (S40) and the process 14 (I40), it turns out that the degree of increase of Ca / Si amount and Ca (OH) ₂ amount is intense.
FIG. 7 also shows that C—S—H is repaired from the silica gel by introducing calcium hydroxide.

FIG. 8 is a diagram showing the change over time of the degree of decrease in the porosity of samples Y1-11 to Y1-14. The horizontal axis indicates the predetermined period in days, and the vertical axis indicates the degree of decrease in the porosity.
From FIG. 8, in the process 13 (S40) and the process 14 (I40), the degree of change in the porosity is more intense than the other two (process 11 (R20) and process 12 (S20)), and the porosity is high. It can be seen that it is decreasing rapidly. 6 to 8 show that by introducing calcium hydroxide, C—S—H is repaired from the silica gel, and voids are filled with the repaired C—S—H.

<Sample Z>
<< Sample Z1 >>
W / C = 55%, 1 m × 1 m × 1 m of slump 18 cm, concrete for building structure was produced and then cured in the atmosphere for 3 months. After that, the obtained concrete is crushed, and after grinding with a crushed stone rod mill for 30 minutes, it is made into a range of 5 mm to 150 μm by sieving, and immediately after that, it is stored in a sealed container and is not deteriorated. Was designated as Sample Z1.
<< Sample Z2 >>
Sample Z2 was obtained by the same method as Sample Z1, except that W / C = 45% was used instead of W / C = 55% in Sample Z1.

<< Sample Z3 >>
Sample Z3 was obtained by the same method as Sample Z1, except that W / C = 65% was used instead of W / C = 55% in Sample Z1.
<< Sample Z4 >>
In sample Z1, sample Z4 was obtained by the same method as in sample Z1, without any surging treatment.
Samples Z1 to Z4 were measured for mass, volume, density, and absorptance before the following immersion treatment or the like.

<Primary modification-Immersion in carbonated nanobubble water and subsequent treatment->
Samples Z1 to Z4 were immersed in carbonic acid nanobubble water A-1 prepared in Example 1 for 1 day. After immersion, the exposed surface of the sample was sealed with a wrap (manufactured by Kureha Chemical Co., Ltd.) and cured at 20 ° C. and a relative humidity of 70% for 1 day. About each obtained sample, mass, a volume, a density, and an absorptance were measured.

<Secondary reforming>
<< Introduction of calcium hydroxide aqueous solution >>
The sample obtained above was immersed in a saturated calcium hydroxide aqueous solution (20 ° C.) for 1 hour. Thereafter, the sample was taken up, and the exposed surface of the sample was sealed with a wrap (manufactured by Kureha Chemical Co., Ltd.) and cured at 20 ° C. and a relative humidity of 70% for 1 day.
<< Secondary Modification-Immersion in Carbon Nanobubble Water and Subsequent Treatment->>
The sample obtained above was again immersed in the carbonated nanobubble water A-1 prepared in Example 1 for 1 day. After immersion, the exposed surface of the sample was sealed with a wrap (manufactured by Kureha Chemical Co., Ltd.) and cured at 20 ° C. and a relative humidity of 70% for 1 day. About each obtained sample, mass, a volume, a density, and an absorptance were measured.

Regarding Z1 to Z4, characteristics such as density immediately after being obtained, characteristics after primary reforming, and characteristics after secondary reforming are shown in FIG. 9 and FIG.
9 and 10, the horizontal axis indicates the sample, “45” indicates Z2, “55” indicates Z1, “65” indicates Z3, and “Non55” indicates Z4. “General” indicates characteristics immediately after the samples Z1 to Z4 are obtained, “primary reforming” indicates characteristics after primary reforming, and “secondary reforming” indicates characteristics after secondary reforming.

FIG. 9 is a graph of the density before the modification, the density due to the primary modification, and the density due to the secondary modification of the samples Z1 to Z4. A vertical axis | shaft shows a density (g / cm < ² >).
From FIG. 9, it can be seen that the density of each sample is increased by the modification. Since calcium carbonate has a higher density than calcium hydroxide, this increase in density is thought to be due to the formation of calcium carbonate. In short, the amount of calcium carbonate in the sample increased due to the modification, and the density increased.

FIG. 10 is a graph of the water absorption before the modification, the water absorption by the primary reforming, and the water absorption by the secondary reforming of the samples Z1 to Z4. The vertical axis represents the water absorption rate (%).
From FIG. 10, it can be seen that the water absorption rate is reduced by modifying each sample. It can be seen that the quality of the recycled coarse aggregate is improved by the modification.
From FIG. 9 and FIG. 10, it can be seen that the modification increases the amount of calcium carbonate in the recycled coarse aggregate, increases the density, and decreases the water absorption rate. It can be seen that the quality of the recycled coarse aggregate can be improved by repeating the modification once, twice, and three times.

Claims (7)

A method for producing a substance having a hardened cement body, wherein the substance has at least one of the following characteristics i) to iv ):
1) a step of preparing carbonic acid bubble water having 0.05% or more of carbon dioxide bubbles having a diameter of 1 mm or less in water; and 2) a first carbonic acid bubble that introduces the carbonic acid bubble water into a substance having a cemented body. Water introduction step;
To obtain a substance having at least one of the following characteristics i) to iv ):
i) a higher density than the material having a hardened cement body before applying the method,
ii) a higher amount of calcium carbonate than the substance having a hardened cement before applying the method,
iii) a porosity lower than that of the material having a hardened cement body before applying the method,
iv) A water absorption lower than that of the substance having a hardened cement body before the above method is applied. Before step 2),
0) a first calcium hydroxide introduction step of introducing an aqueous calcium hydroxide solution into a substance having a cemented body;
The method of claim 1 further comprising: After step 2),
3) a second calcium hydroxide introduction step for introducing a calcium hydroxide aqueous solution into the substance having the cement hardened body obtained in the step 2); and 4) the cement hardened body obtained in the step 3). A second carbonated bubble water introduction step for introducing the carbonated bubble water prepared in the step 1) into the substance;
The method according to claim 1 or 2, further comprising: After step (2n-2))
(2n-1)) an n-th calcium hydroxide introduction step for introducing a calcium hydroxide aqueous solution into the cement-containing substance obtained by the step (2n-2)); and (2n)) the step (2n-1) )) The n-th carbonic acid bubble water introducing step of introducing the carbonic acid bubble water prepared in the step 1) to the substance having a hardened cement body obtained by the above));
The method according to claim 3, further comprising a combination of step (2n-1)) and step (2n)), wherein n is an integer of 3 or more, meaning the number of repetitions of the combination.   The cement obtained in the one step after at least one step of the steps 0), steps 2) to 4), and steps (2n-1)) and steps (2n)) (n is an integer of 3 or more). The method of any one of Claims 1-4 which further has the process of coat | covering at least one part of the surface of the substance which has a hardening body.   The method according to claim 1, wherein the substance having a hardened cement body is selected from the group consisting of recycled aggregate, finished mortar, concrete product, and concrete structure. The method according to claim 1, wherein the carbonic acid bubble water has 0.05% or more of carbon dioxide bubbles having a diameter of 100 μm or less in the water .

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