JP7259502B2 - Concrete hardening body construction method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for constructing a hardened concrete body having a protective layer formed on the surface thereof.

Effluent standards stipulated by law are applied to water discharged into public water areas from facilities such as factories and business establishments. For this reason, in general, appropriate water treatment is performed by installing wastewater treatment equipment or the like in the facility so that the water immediately before being discharged meets the wastewater standards.

The water to which such wastewater standards are applied includes not only wastewater generated by business activities within the facility, but also rainwater, snowmelt water, spring water, etc. discharged from the facility. Therefore, for example, in a closed mine, since the ground is strongly acidic, strongly acidic spring water and rainwater continue to be discharged. In many cases, wastewater treatment facilities are required to treat spring water.

Therefore, in order to reduce the burden on wastewater treatment facilities, measures to suppress rainwater permeating into the mine by covering the surface of the mine with a waterproof sheet after the mine is closed are being studied. Specifically, a seepage control sheet is laid on the slope of the mine, and concrete that doubles as a drainage channel is placed from the top surface of the seepage control sheet on the steps of the slope. It is intended to be covered with As a result, rainwater flows down the impermeable sheet without permeating into the mine and is then discharged via the drainage channel, making it possible to reduce the amount of strongly acidic spring water discharged.

However, even if the cement component remaining on the surface of the holding concrete which also serves as a drainage channel is thoroughly washed with high-pressure washing water after construction, the alkaline component is leached from the surface when it comes into contact with water. For this reason, when rainwater flows down onto the holding concrete through the impermeable sheet, the longer the contact time, the higher the pH. can occur.

If such a situation occurs, it will be necessary to construct a neutralization treatment facility to neutralize rainwater with a high pH, and a great deal of cost and labor will be required for its construction and operation. . In addition, not only does the neutralization process take a long time, but in recent years, it is expected that rainwater will exceed the processing capacity of the neutralization equipment due to the effects of typhoons and heavy rains. It is also necessary to secure a reservoir for storage.

Under such circumstances, Patent Document 1, for example, discloses a method of neutralizing the surface of concrete and the walls of voids. Regardless of whether the concrete is wet or dry, after the surface of the cast concrete is sprayed with carbon dioxide gas and a waterproofing agent to cover the surface with a coating material, carbon dioxide gas is blown in between the coating material and the concrete for a considerable period of time. It is left to stand and forms an emulsion on the concrete surface.

JP-A-11-255568

According to the method of Patent Document 1, since the concrete surface can be evenly covered with the emulsion, it is possible to prevent leaching of alkali from the concrete surface. However, it is known that the emulsion tends to peel off when placed in a harsh environment, and it is not always suitable to form it for a concrete structure that is constantly exposed to wind and rain and rainwater flows down. do not have.

Further, in the case of pouring a holding concrete which also serves as a drainage channel on the upper surface of the impermeable sheet, it is difficult to coat the contact surface of the holding concrete with the impermeable sheet with an emulsion.

The present invention has been made in view of such problems, and its main purpose is to enable the formation of a protective layer on the surface of hardened concrete for suppressing the leaching of various components including alkaline components. Another object of the present invention is to provide a method for constructing a hardened concrete body.

In order to achieve such an object, the method for constructing a hardened concrete body of the present invention includes, after placing concrete, contacting the concrete before hardening with a neutralizing solution in which a neutralizing agent is dissolved, and wet-curing the concrete. In the method for constructing a hardened concrete body for hardening the concrete, the neutralizing agent is a composite agent containing water-soluble phosphoric acid, and at the planned concrete placing position before placing the concrete, It is characterized by laying a porous sheet material impregnated with the neutralizing solution .

According to the method for constructing a hardened concrete body of the present invention, the concrete is wet-cured for a predetermined time in a state in which a neutralizing solution containing a complex agent containing water-soluble phosphoric acid as a neutralizing agent is brought into contact with the concrete. The hydroxide ions leached from the concrete react with the phosphate ions in the neutralizing solution and are neutralized, neutralizing the concrete surface. Calcium hydroxide leached out of concrete reacts with phosphate ions in the neutralization solution to synthesize hydroxyapatite on the surface of the hardened concrete.

In this way, the surface of the hardened concrete is neutralized, and hydroxyapatite acts as a protective layer of the hardened concrete to suppress the leaching of alkaline components. It is possible to control the phenomenon of (exhibiting alkalinity).

In addition, by forming a protective layer on the surface of the hardened concrete, even if fine cracks or the like occur in the vicinity of the surface, rainwater can be prevented from penetrating through the cracks. This makes it possible to suppress the progress of neutralization of the hardened concrete due to permeation of rainwater.

Furthermore, hydroxyapatite, which functions as a protective layer, is a substance that is stably fixed on the surface of the hardened concrete, so even when the hardened concrete is constructed in a harsh environment such as being exposed to wind and rain, It is possible to reliably suppress the phenomenon of alkali components leaching out from the hardened concrete over a long period of time without peeling off.

In the method for constructing a hardened concrete body of the present invention, after concrete is placed, the concrete before hardening is brought into contact with a neutralizing solution in which a neutralizing agent is dissolved, and the concrete is moist-cured to harden the concrete. A method for constructing a hardened concrete body, wherein the neutralizing agent is a composite agent containing water-soluble phosphoric acid, and the neutralizing agent is retained at a position where the concrete is to be placed before the concrete is placed. It is characterized by laying a porous sheet material.

Further, in the method for constructing a hardened concrete body of the present invention, after concrete is placed, the concrete before hardening is brought into contact with a neutralizing solution in which a neutralizing agent is dissolved, and the concrete is wet-cured to remove the concrete. A method for constructing a hardened concrete body to be hardened, wherein the neutralizing agent is a composite agent containing water-soluble phosphoric acid, and the position where concrete is to be placed is impregnated with the neutralizing solution before the concrete is placed. and laying a porous sheet material holding the neutralizing agent.

Furthermore, in the method for constructing a hardened concrete body of the present invention, an extra length is secured in the porous sheet, and the surface of the concrete that is not in contact with the porous sheet is removed before wet curing. It is characterized by covering the long part.

According to the method for constructing a hardened concrete body of the present invention, it is possible to form hydroxyapatite functioning as a protective layer on the entire outer peripheral surface of the hardened concrete body.

In addition, when a porous sheet material containing a neutralizing agent made of a complex agent containing water-soluble phosphoric acid is used, even if the porous sheet is laid on a slope, the neutralizing agent can be absorbed into the porous sheet. It is possible to form a homogeneous protective layer on the entire outer peripheral surface of the hardened concrete body because it is easy to stay in and can suppress the outflow.

The method for constructing a hardened concrete body of the present invention is characterized in that the scheduled concrete placement position is the upper surface of the impermeable sheet at the stepped portion of the slope covered with the impermeable sheet.

According to the method for constructing a hardened concrete body of the present invention, it is possible to construct a holding concrete in which a protective layer is formed on the entire outer peripheral surface of the impermeable sheet. As a result, it becomes possible to suppress not only the rainwater flowing down on the pressing concrete via the impermeable sheet, but also the increase in pH of the rainwater entering between the impermeable sheet and the pressing concrete.

Therefore, when impervious sheets and holding concrete are applied to strongly acidic ground such as closed mines, they can be installed on the premises of facilities that do not generate wastewater from business activities to treat rainwater and spring water. It is possible to reduce the scale of the neutralization treatment facility, the wastewater treatment facility, or the reservoir for storing rainwater and spring water before treatment, or eliminate the need for it.

The method for constructing a hardened concrete body of the present invention is characterized in that the porous sheet has one surface in contact with the concrete and the other surface in contact with a swelling material.

According to the method for constructing a hardened concrete body of the present invention, a waterproof layer made of a swelling material can be formed on the outer periphery of the hardened concrete body having a protective layer formed on the surface thereof. In addition, the protective layer can suppress leaching of not only alkaline components but also calcium components, which are known to deteriorate bentonite to the extent that it impairs swelling performance. becomes possible.

As a result, for example, when hardened cement mixed with radioactive waste is covered with a water-shielding material and buried in the ground, bentonite powder or sheet-shaped bentonite water-shielding material can be used as a swelling material for the water-shielding material. To prevent groundwater from coming into contact with hardened cement and flowing out as water containing radioactive substances stably over a long period of time without using a special swelling material without using a sheet. becomes possible.

The method for constructing a hardened concrete body of the present invention is characterized by using a curing sheet during wet curing.

According to the method for constructing a hardened concrete body of the present invention, the curing sheet has the effect of preventing drying during wet curing and also the effect of keeping the concrete heat-retained, which has generated heat of hydration due to the hydration reaction. Therefore, at the temperature of the heat of hydration, the calcium hydroxide eluted from the concrete can be reacted with the phosphate ions in the neutralization solution, and hydroxyapatite with a good crystal state and stable quality can be formed on the surface of the concrete. It is possible to form

According to the present invention, since hydroxyapatite can be formed on the surface of the hardened concrete, the hydroxyapatite serves as a protective layer for the hardened concrete and prevents various components such as alkali and calcium components generated from the hardened concrete after construction. Leaching can be suppressed over a long period of time.

It is a figure which shows the construction method of the concrete hardening body in embodiment of this invention. It is a figure which shows the holding concrete built on the slope in embodiment of this invention. It is a figure which shows the other example of the construction method of the concrete hardened body in embodiment of this invention (the 1). It is a figure which shows the other example of the construction method of the concrete hardened body in embodiment of this invention (2). It is a figure which shows the example in the case of burying the concrete hardened body in embodiment of this invention in the ground. FIG. 5 is a diagram showing another example of burying the hardened concrete body in the ground according to the embodiment of the present invention; FIG. 4 is a diagram showing an example of holding a neutralizing chemical in a porous sheet according to an embodiment of the present invention;

The method for constructing a hardened concrete body of the present invention is a method for constructing a hardened concrete body having hydroxyapatite formed on the surface thereof as a protective layer. The details of the method for constructing a hardened concrete body will be described below with reference to FIGS. 1 to 7. FIG.

<First Embodiment>
As shown in FIG. 1( a ), hydroxyapatite that functions as a protective layer 2 is formed on the surface of the hardened concrete 1 . Hydroxyapatite is a substance that is stably fixed to the surface of concrete, and does not peel off even when the hardened concrete 1 is constructed under a severe environment such as being exposed to wind and rain. It is possible to reliably suppress the phenomenon of leaching of alkaline components over a long period of time.

In the construction method of the hardened concrete body 1 having such a protective layer 2, first, as shown in FIG. Next, as shown in FIG. 1(c), a neutralizing solution 53 in which a neutralizing agent 51 is dissolved in a solvent 52 is sprayed on the exposed surface of the concrete 4 before hardening.

The neutralizing agent 51 may be any compound agent containing water-soluble phosphoric acid. For example, lime superphosphate, which is widely traded in the market as a general fertilizer that is an agricultural material, can be used. Water such as tap water can be used as the solvent 52 .

Thereafter, as shown in FIG. 1(d), the surface of the concrete 4 is covered with a curing sheet 6, and wet curing is performed for a predetermined time. The curing sheet 6 is used for the purpose of preventing a phenomenon in which moisture escapes from the surface of the concrete 4 after placement. Any one may be adopted as long as it is adopted.

During the curing period described above, among the alkali components 41 eluted from the concrete 4, the hydroxide ions react with the phosphate ions in the neutralizing solution 53 and are neutralized, so that the surface of the hardened concrete 1 after hardening is neutralized. sexualized. Among the alkali components 41 leached from the concrete 4, calcium hydroxide is synthesized by reacting with the phosphate ions in the neutralizing solution 53 during wet curing, and functions as a protective layer 2 on the surface of the hardened concrete 1. Hydroxyapatite is formed.

A method for forming hydroxyapatite as a protective layer of the hardened concrete 1 is a so-called wet method, in which calcium ions and phosphate ions are reacted in a neutral or alkaline aqueous solution. Considering that it is necessary to retain sufficient moisture during the reaction period in the wet method, the optimal curing method for the concrete 4 is wet curing, and the moisture retention period should be at least 24 hours.

By the above procedure, the surface of the hardened concrete 1 is neutralized, and the protective layer 2 of hydroxyapatite is formed as shown in FIG. components can be suppressed. As a result, it is possible to control the phenomenon in which even if water contacts the surface of the hardened concrete 1, the water will have a high pH (exhibit alkalinity).

Moreover, even if fine cracks or the like occur in the vicinity of the surface of the hardened concrete 1 after hardening, the protective layer 2 can prevent rainwater from penetrating into the cracks. As a result, the calcium hydroxide in the hardened concrete 1 is leached out by rainwater that permeates through the cracks, reacts with carbon dioxide gas in the air to form calcium carbonate, and the neutralization of the hardened concrete 1 progresses. can be suppressed.

The concentration of the neutralizing solution 53 and the period during which the water is retained during curing may be appropriately adjusted according to the composition of the concrete 4, the weather, the thickness of the protective layer 2 to be formed, and the like.

Calcium hydroxide and phosphate ions may be reacted at room temperature, but it is known that hydroxyapatite, which has a better crystalline state and is more stable, is formed when the reaction is carried out at a temperature higher than room temperature. there is Therefore, if the curing sheet 6 is made of a material with high heat retention performance as well as moisture retention performance, the heat of hydration generated by the hydration reaction will be kept warm, and the concrete will be leached out from the concrete at a temperature of about 60°C. Calcium hydroxide and phosphate ions in the neutralization solution can be reacted to form high-quality hydroxyapatite.

<Second Embodiment>
Next, as an example, the case of constructing the pressing concrete 11 on the slope stepped portion 31 on which the impermeable sheet 7 is laid as shown in FIG. A method for forming the cured body 1 will be described. The holding concrete 11 in the present embodiment is used for fixing the impermeable sheet 7 covering the entire slope of the ground showing strong acidity such as a closed mine. It is built in the part 31 and also has a function as a drainage channel.

In the construction method of the holding concrete 11 having the protective layer 2 formed on the entire outer peripheral surface, first, as a pretreatment, as shown in FIG. A trench 32 is formed, and a waterproof sheet 7 is laid along the shape of the trench 32.例文帳に追加

Next, a porous sheet material 8 is laid from the upper surface of the impermeable sheet 7 along the shape of the trench 32 , and a neutralizing solution 53 obtained by dissolving a neutralizing agent 51 in a solvent 52 is applied to the porous sheet material 8 . to scatter. After the porous sheet material 8 is sufficiently impregnated with the neutralizing solution 53, concrete 4 is placed on the porous sheet material 8 as shown in FIG. 3(b).

Before the concrete 4 hardens, the same neutralizing solution 53 that impregnated the porous sheet material 8 is sprinkled on the surface where the concrete 4 is exposed. Thereafter, as shown in FIG. 4(a), the surface of the concrete 4 is covered with a curing sheet 6, and wet curing is performed for a predetermined time.

The neutralizing agent 51 and the curing sheet 6 used in the second embodiment are both the same as in the first embodiment. As the porous sheet material 8 laid before placing the concrete 4, any sheet material such as a non-woven fabric may be adopted as long as it is a porous sheet material capable of retaining the water of the neutralizing solution 53.

In this way, the concrete 4 whose upper surface is covered with the curing sheet 6 and whose side and bottom surfaces are covered with the porous sheet material 8 impregnated with the neutralizing solution 53 is put in a state as if it were cured in water. becomes. As a result, the holding concrete 11 constructed by hardening the concrete 4 is neutralized not only on the upper surface covered with the curing sheet 6 but also on the side surfaces and the bottom surface covered with the porous sheet material 8. At the same time, hydroxyapatite that functions as the protective layer 2 is formed.

As a result, when it rains as shown in FIG. 4(b), the rainwater that flows down on the impermeable sheet 7 without permeating the natural ground only passes through the upper surface of the holding concrete 11 that also functions as a drainage channel. In addition, even if it enters between the impervious sheet 7 and the pressing concrete 11, it will not raise the pH (become alkaline) during drainage.

For this reason, neutralization treatment is not required when draining rainwater that has flowed down on the impervious sheet 7 and the pressing concrete 11 . Therefore, it is necessary to construct a neutralization facility to neutralize rainwater and a reservoir to store rainwater before neutralization, which will be installed on the premises of a facility such as a closed mine that does not generate wastewater from business activities. It is possible to reduce the scale or make it unnecessary.

If the impermeable sheet 7 covers the entire slope surface, rainwater will not permeate into the strongly acidic ground. Therefore, if the entire mine after closing is covered with the impervious sheet 7 and the holding concrete 11 having the protective layer 2 formed on the entire outer peripheral surface, the scale of the wastewater treatment facility for treating the strongly acidic seepage will also be reduced. It is possible to reduce or eliminate the need.

<Third Embodiment>
In the second embodiment, the concrete hardened body 1 constructed by using the porous sheet material 8 explained by taking the holding concrete 12 as an example is suitable for underground structures and underground buried objects placed in the ground. It is also possible to adopt A case where the hardened concrete 1 is a waste-containing concrete 12 in which waste and cement are mixed will be described below in detail.

In the construction method of the waste-containing concrete 12 shown in FIG. 5(a), first, as shown in FIG. A bentonite impermeable sheet 9 is laid on the bentonite impermeable sheet 9 , and a porous sheet material 8 is laid on the upper surface of the bentonite impermeable sheet 9 . At this time, both the bentonite impermeable sheet 9 and the porous sheet material 8 are formed in sizes that allow sufficient extra lengths 91 and 81 to be secured even if they are laid in the underground hole 33 .

Next, as shown in FIG. 5C, a neutralizing solution 53 obtained by dissolving a neutralizing agent 51 in a solvent 52 is sprayed on the porous sheet material 8, and the neutralizing solution 53 is applied to the porous sheet material 8. sufficiently impregnated with After that, as shown in FIG. 5(d), concrete 4 is placed on the porous sheet material 8, and before the concrete 4 hardens, the upper surface of the concrete 4, which is not in contact with the porous sheet material 8, is removed. It is covered with the extra length 81 of the porous sheet material 8 and further covered with the extra length 91 of the bentonite waterproof sheet 9 .

Then, the underground hole 33 is backfilled with the backfilling soil 331 while the wet curing of the concrete 4 is performed for a predetermined time. As a result, as shown in FIG. 5( a ), the waste-containing concrete 12 has a protective layer 2 formed on the entire surface, and a water-impermeable layer formed by a bentonite water-impervious sheet 9 via a porous sheet 8 on the outer periphery. is formed.

The bentonite waterproof sheet 9 is formed by processing bentonite, which is generally known as a swelling material, into a sheet shape. Also, the neutralizing agent 51 is the same as in the first and second embodiments. Further, the porous sheet material 8 laid before placing the concrete 4 may be any sheet material such as non-woven fabric as long as it is a porous sheet material capable of retaining the neutralizing solution 53 as in the second embodiment. material may be used.

By the way, it is known that the protective layer formed on the surface of hardened concrete can suppress the leaching of not only alkaline components but also calcium components. In addition, bentonite, which is widely used as a water-blocking material, is known to be a stable swelling material that does not deteriorate to the extent that swelling performance is impaired in an environment where calcium ions are not present.

In other words, by forming the protective layer 2 on the surface of the waste-containing concrete 12, it is possible to suppress the leaching of the calcium component. A bentonite waterproof sheet 9 obtained by processing bentonite, which is generally and widely used as a swelling material, can be used without any preparation.

Therefore, for example, when the waste-containing concrete 12 is a mixture of radioactive waste and cement and is buried in the ground, the bentonite impermeable sheet 9 stabilizes the waste-containing concrete for a long period of time so that groundwater can be discharged into the waste-containing concrete. It is possible to prevent a phenomenon in which water containing radioactive substances comes into contact with 12 and flows out.

The impermeable layer formed on the outer peripheral surface of the waste-containing concrete 12 via the porous sheet 8 is not limited to the bentonite impermeable sheet 9. As shown in FIG. It is also possible to adopt and form.

In this case, the mold 10 is placed inside the underground hole 33 and the gap between the mold 10 and the underground hole 33 is filled with the bentonite powder 92 . In addition, when filling back the underground hole 33 while wet curing the concrete 4 for a predetermined time, bentonite is added to a predetermined height above the extra length 81 of the porous sheet material 8 covering the upper surface of the concrete 4 . After the powder 92 is filled, the upper surface thereof may be backfilled with backfilling soil 331 .

Moreover, in FIG. 6, the extra length portion 81 of the porous sheet material 8 is configured to be detachable instead of being folded, and the cut extra length portion 81 is placed on the upper surface of the concrete 4 where the porous sheet material 8 is not in contact. Placed and coated. In this manner, the excess length portion 81 may be secured by any method. The same applies to the extra length portion 91 of the bentonite waterproof sheet 9 .

The film forming method of the present invention is not limited to the above embodiments, and various modifications are possible without departing from the scope of the present invention.

For example, in the second embodiment and the third embodiment, after laying the porous sheet material 8, the neutralizing solution 53 in which the neutralizing agent 51 is dissolved in the solvent 52 is sprayed to obtain the porous sheet. Material 8 was impregnated with neutralizing solution 53 . However, the porous sheet material 8 pre-impregnated with the neutralizing solution 53 may be prepared and laid in the trench 32 or the underground hole 33 .

In addition, instead of impregnating the porous sheet material 8 with the neutralizing solution 53, as shown in FIG. The drug 51 may be retained on the porous sheet material 8 . Alternatively, the neutralizing agent 51 in powder form may be further dispersed on the porous sheet material 8 impregnated with the neutralizing solution 53 .

In this way, for example, even if the laying position of the porous sheet material 8 is on a slope, the neutralizing agent 51 remains in the porous sheet material 8 without flowing. Then, the neutralizing agent 51 dissolves in the water liberated from the concrete 4 and reacts with calcium hydroxide among the alkali components 41 eluted from the concrete 4 before hardening in this aqueous solution. Thereby, it becomes possible to form a uniform protective layer 2 on the entire outer peripheral surface of the pressing concrete 11 .

In the third embodiment, the waste-containing concrete 12 is covered with the bentonite impermeable sheet 9 or the impermeable layer composed of the bentonite powder 92, but any swelling material capable of forming the impermeable layer may be used. It is also possible to adopt

1 concrete hardened body 11 holding concrete (concrete hardened body)
12 Waste Concrete (Hardened Concrete)
2 Protective layer 3 Concrete casting position 31 Slope step 32 Trench 33 Underground hole 331 Backfilling soil 4 Concrete 41 Alkaline component 51 Neutralizing agent 52 Solvent 53 Neutralizing solution 6 Curing sheet 7 Impervious sheet 8 Porous sheet material 81 Extra length 9 Bentonite waterproof sheet (swellable material)
91 Extra length 92 Bentonite powder (swellable material)
10 Formwork

Claims (7)

After placing the concrete
contacting the concrete before hardening with a neutralizing solution in which a neutralizing agent is dissolved to wet cure the concrete;
A method for constructing a hardened concrete body for hardening the concrete,
The neutralizing agent is a complex agent containing water-soluble phosphoric acid , and
A method for constructing a hardened concrete body, characterized by laying a porous sheet material impregnated with the neutralizing solution at a position where the concrete is to be placed before the concrete is placed. After placing the concrete
contacting the concrete before hardening with a neutralizing solution in which a neutralizing agent is dissolved to wet cure the concrete;
A method for constructing a hardened concrete body for hardening the concrete,
The neutralizing agent is a complex agent containing water-soluble phosphoric acid , and
A method for constructing a hardened concrete body , which comprises laying a porous sheet material holding the neutralizing agent at a position where the concrete is to be placed before the concrete is placed. After placing the concrete
contacting the concrete before hardening with a neutralizing solution in which a neutralizing agent is dissolved to wet cure the concrete;
A method for constructing a hardened concrete body for hardening the concrete,
The neutralizing agent is a complex agent containing water-soluble phosphoric acid , and
Construction of a hardened concrete body characterized by laying a porous sheet material impregnated with the neutralizing solution and holding the neutralizing agent at a planned concrete casting position before the concrete is cast. Method. In the method for constructing a hardened concrete body according to any one of claims 1 to 3 ,
An extra length is secured in the porous sheet,
A method for constructing a hardened concrete body, wherein a surface of the concrete that is not in contact with the porous sheet is covered with the surplus portion before wet curing. In the method for constructing a hardened concrete body according to any one of claims 1 to 4,
A method for constructing a hardened concrete body, wherein the scheduled concrete placement position is an upper surface of the impermeable sheet in a stepped portion of a slope covered with the impermeable sheet. In the method for constructing a hardened concrete body according to claim 4,
A method for constructing a hardened concrete body, wherein the porous sheet has one surface in contact with the concrete and the other surface in contact with a swelling material. In the method for constructing a hardened concrete body according to any one of claims 1 to 3,
A method for constructing a hardened concrete body, characterized by using a curing sheet during wet curing.

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