WO2020250359A1

WO2020250359A1 - Highly chemically resistant concrete structure and production method

Info

Publication number: WO2020250359A1
Application number: PCT/JP2019/023365
Authority: WO
Inventors: 昌紀塩見; 清武大森
Original assignee: ゼニス羽田株式会社
Priority date: 2019-06-12
Filing date: 2019-06-12
Publication date: 2020-12-17
Also published as: JP6654273B1; JPWO2020250359A1

Abstract

[Problem] To provide a highly chemically resistant concrete structure having excellent productivity as well as low production cost, and a production method. [Solution] A concrete layer 11 and an inner surface protective layer 12, comprising a concrete layer 11 molded by supplying concrete to the form of a centrifugal molding machine and an inner surface protective layer 12 molded by supplying a mixed material, including at least a binder B having the property of being cured by a sludge component discharged to the inner surface of the concrete layer 11 and a fine aggregate C, to the inner surface of the concrete layer 11 and laminating, are centrifugally molded simultaneously to create an integrated construction having continuity.

Description

Highly chemically resistant concrete structure and manufacturing method

The present invention relates to a highly chemically resistant concrete structure and a manufacturing method having excellent chemical resistance such as acid resistance and salt damage resistance, which can be applied to concrete structures such as hume pipes and manholes.

As for the sewerage pipelines that support Japan's sewerage infrastructure, the number of pipelines that have been built for 50 years, which is considered to be the standard service life, is rapidly increasing, and in the future, appropriate stock management such as extending the life will be required. It has been demanded.
The sewerage pipeline reconstruction project with such a background focuses on the rehabilitation and replacement of deteriorated concrete pipes.

In general, there are various forms of damage to concrete pipes such as sagging due to uneven subsidence, foreign matter contamination such as tree roots, and cracks, but concrete corrosion due to the action of acid from hydrogen sulfide generation to sulfuric acid is a particularly serious form of damage. is there.
If the cross section of the concrete pipe is greatly damaged due to acid corrosion, it is necessary to replace it with a new concrete pipe immediately. If left unattended, external factors such as load and vibration will trigger the road to collapse. There is a danger of doing.

It is desirable that the concrete pipe to be replaced is an acid-resistant pipe that is resistant to corrosion by acid.
Known acid-resistant pipes include resin lining pipes in which the surface of concrete pipes is coated with resins such as epoxy resin, urethane resin, and acrylic resin, and resin concrete pipes using unsaturated polyester resin as a substitute for cement ( Patent Documents 1 to 3).

Further, as a low-priced acid-resistant pipe, a concrete pipe in which 70% or more of the cement content in the cement concrete compound is replaced with blast furnace slag fine powder has been proposed (Patent Document 4).

Japanese Unexamined Patent Publication No. 52-13020 Japanese Unexamined Patent Publication No. 63-264676 JP-A-2002-248637 Japanese Patent No. 5878258

The conventional acid-resistant pipe and its manufacturing technology have the following points to be improved.
<1> The resin lining pipe is based on a concrete pipe manufactured by a centrifugal molding machine.
When the concrete pipe is centrifuged, sludge components are discharged to the inner surface of the concrete pipe.
Since this sludge component is strongly alkaline and has a small amount of cement component, it is difficult to reuse it as a concrete product, and it takes a lot of labor and cost to process the sludge component, and an effective treatment method for the sludge component is in the industry. It has been an issue for many years.
<2> In addition, in order to manufacture a resin lining pipe, a lot of work such as centrifugation, curing, and demolding of the concrete pipe, primer treatment on the surface of the hardened concrete pipe, resin coating, etc. is required. Therefore, the concrete pipe must be continuously rotated for a long time until the coating resin poured into the concrete pipe is completely cured.
Therefore, the productivity of the resin lining pipe is extremely poor, and the manufacturing cost is very high.
<3> In a resin lining pipe in which the surface of the concrete pipe is coated with a resin, a boundary is formed between the concrete pipe and the coated resin, and the coating resin is liable to cause interfacial peeling.
<4> Resin concrete pipes use unsaturated polyester resin, which is more than 10 times more expensive than cement, so the manufacturing cost is very high. In addition, unsaturated polyester resin polymerizes and bonds when centrifugally molded. The formwork needs to be kept rotating until the resin concrete hardens, and the productivity of the resin concrete pipe is very poor.
For this reason, there are very few records of using resin concrete pipes.
<5> A concrete pipe in which 70% or more of the cement content is replaced with blast furnace slag fine powder in order to improve acid resistance is difficult to centrifuge because the viscosity of the concrete becomes high.
<6> For concrete pipes with increased replacement amount of blast furnace slag fine powder and fly ash instead of cement to improve acid resistance, large quantities of blast furnace slag and fly ash, which are by-products of steelmaking and thermal power generation, are available. There are many difficult developing regions and countries, and if manufactured in such regions and countries, product costs will rise.
<7> Generally, concrete using a large amount of blast furnace slag fine powder has a low initial strength, so it takes a long time to demold and deteriorates productivity.

The present invention has been made in view of the above points, and an object of the present invention is to provide a highly chemically resistant concrete structure and a manufacturing method, which are excellent in productivity and can be manufactured at a low cost. ..

The present invention is a highly chemically resistant concrete structure produced by centrifugation, which is latent hydraulic or pozzolan hardened by a concrete layer containing a cement-based binder A and a sludge component discharged to the inner surface of the concrete layer. It contains at least a reactive binder B and a fine aggregate C, and comprises an inner surface protective layer laminated on the inner surface of the concrete layer and centrifugally formed at the same time as the concrete layer.
In another embodiment of the present invention, the binder B is a latent hydraulic or pozzolan-reactive binder, for example, one or more selected from blast furnace slag fine powder, fly ash, silica fume, volcanic ash, silicic acid clay, and diatomaceous earth group. Is.
In another embodiment of the present invention, the fine aggregate C of the inner surface protective layer supplied to the inner surface of the concrete layer is any one or a plurality of slag-based fine aggregates, silica sand, and natural fine aggregates.
In another embodiment of the present invention, the inner surface protective layer comprises a buffer layer formed as a continuous structure on the inner surface side of the concrete layer and a chemical resistance layer formed as a continuous structure on the inner surface side of the buffer layer. The resistance layer has a relationship in which the amount of sludge mixed from the concrete layer is smaller than that of the buffer layer.
In another embodiment of the present invention, the chemical resistance layer is composed of at least a mixture of binder B, fine aggregate C and sludge water.
The present invention is a method for manufacturing a highly chemically resistant concrete structure manufactured by a centrifugal molding machine, in which concrete is supplied into a formwork of the centrifugal molding machine, the concrete layer is centrifugally molded and compacted, and the concrete layer is compacted. A mixed material containing at least a latent hydraulic or pozzolan-reactive binder B and fine aggregate C, which is hardened by the sludge component discharged to the inner surface of the concrete layer at the time of compaction, is supplied to the inner surface of the concrete layer to provide concrete. The layer and the inner surface protective layer are simultaneously centrifugally molded to be integrally molded.
In another embodiment of the present invention, a dry mixed material containing the binder B and the fine aggregate C is supplied to the inner surface of the concrete layer being centrifuged, or the binder B and the fine aggregate C are kneaded. A paste-like mixed material containing water is supplied.
In another embodiment of the present invention, the binder B of the inner surface protective layer is a latent hydraulic or pozzolan-reactive binder, and is selected from, for example, blast furnace slag fine powder, fly ash, silica fume, volcanic ash, silicic acid clay, and diatomaceous earth group. It is more than one kind that was done.
In another embodiment of the present invention, the fine aggregate C of the inner surface protective layer is one or more selected from the slag-based fine aggregate, silica sand, and natural fine aggregate group.

The present invention has at least one of the following effects.
<1> Since the cement-based binder A is used as the binder of the concrete layer which occupies most of the frame of the concrete structure, the concrete layer can be easily manufactured and the binder B having high chemical resistance is used. Since the inner surface protective layer is formed at the same time as the concrete layer, a highly chemically resistant concrete structure can be manufactured in a short period of time at low cost.
Furthermore, since it can be manufactured using a known centrifugal molding machine, no special additional equipment is required.
<2> In the present invention, the pipe making process can be completed and the final curing process can be started in about several tens of minutes to 2 hours while simultaneously molding the concrete layer and the inner surface protective layer.
Therefore, the resin does not adhere until after the concrete pipe is manufactured and the inner surface is dried by steam curing, so the resin lining pipe requires a minimum of two days to manufacture, and the material reacts with the polymerization during centrifugation and is chemically hardened. Compared with conventional manufacturing techniques such as resin concrete pipes whose rotation cannot be stopped without it, the time and labor required to manufacture a highly chemically resistant concrete structure can be significantly reduced, and productivity can be greatly improved. ..
<3> Since the binder B having high chemical resistance is used only for the inner protective layer that requires protection of the concrete structure, the amount of the binder B used is kept low and the chemical resistance of the inner protective layer is effective. Can be enhanced to.
<4> Since the concrete layer occupies most of the pipe thickness, the strength development time is fast, and it does not require a long time to demold.
<5> The mixed material of the inner surface protective layer does not contain the cement-based binder A, and when the inner surface protective layer is cured by utilizing sludge water, the inner surface protective layer is contained by the binder B such as blast furnace slag or fly ash. Since the calcium hydroxide is consumed, the calcium component of the finally formed inner protective layer is significantly reduced.
Therefore, the chemical resistance of the inner protective layer is significantly higher than that of the conventional one.
<6> By simultaneously molding the concrete layer and the inner surface protection layer, the concrete layer and the inner surface protection layer can be integrated, and the entire cross section of the concrete structure becomes a continuous structure without a clear boundary.
Therefore, even if an impact is applied, the phenomenon that the inner surface protective layer is peeled off from the concrete layer is less likely to occur, and the good chemical resistance of the concrete structure can be maintained for a long period of time.
<7> Even if a part of the chemical resistance layer of the inner protective layer is damaged, the buffer layer continues to function as the protective layer of the concrete layer, so that the guarantee period of the chemical resistance of the inner protective layer becomes extremely long. ..
<8> When the mixed material of the inner surface protective layer is supplied in a dry state, the sludge or sludge water discharged from the concrete layer can be used to cure the inner surface protective layer, so that sludge or sludge water that had to be discarded until now can be cured. The final recovery amount and disposal amount can be reduced.
<9> Even in developing regions and countries where it is difficult to procure binder B such as blast furnace slag fine powder and fly ash, high-quality, highly chemically resistant concrete structures can be economically manufactured.
Even in regions and countries where it is difficult to obtain the mixed material of the inner protective layer, the mixed material of the inner protective layer can be easily packaged and transported in the easily available region and country.
<10> Blast furnace slag and fly ash are by-products of steelmaking, thermal power generation, etc., and the amount of CO ₂ generated when manufacturing binder B with high chemical resistance is zero, which contributes to the reduction of environmental load. can do.

Enlarged sectional view of the surface layer of a concrete pipe, which is a highly chemically resistant concrete structure. Model diagram of centrifugal molding machine Cross-sectional view of a concrete pipe when forming a concrete layer with a part omitted Cross-sectional view of the concrete pipe when forming the inner protective layer with a part omitted Enlarged sectional view of concrete pipe after hardening Explanatory drawing of change in tube thickness of each specimen of Example 1 and Comparative Example 1 in the acid resistance test

The present invention will be described below with reference to the drawings.
The "chemical resistance" used in the present invention means acid resistance, salt damage resistance, corrosion resistance, chemical resistance and the like.

<1> Highly Chemically Resistant Concrete Structure In this example, a form in which the highly chemically resistant concrete structure is a concrete pipe 10 such as a hume pipe or a manhole manufactured by centrifugal molding will be described.

FIG. 1 shows an enlarged cross-sectional view of the inner surface side of the concrete pipe 10.
The concrete pipe 10 is composed of a concrete layer 11 made of concrete formed into a cylindrical shape and an inner surface protective layer 12 formed into a tubular shape on the inner surface of the concrete layer 11.

<2> Concrete layer The concrete layer 11 is a cylindrical tube obtained by centrifuging concrete obtained by adding and kneading cement-based binder A, an admixture such as an expansion material, fine aggregate, and coarse aggregate.
The cement-based binder A is not particularly limited, and for example, ordinary Portland cement, early-strength Portland cement, ultra-early-strength Portland cement, moderate heat Portland cement, low heat Portland cement, sulfuric acid-resistant Portland cement and the like can be applied.
The composition of the concrete layer 11 is known and is not a special formulation.

<3> Inner surface protective layer The inner surface protective layer 12 is a hard layer that prevents sulfuric acid and the like from penetrating into the concrete layer 11.
The inner protective layer 12 is composed of at least a latent hydraulic or pozzolan-reactive binder B and a fine aggregate C.
These mixed materials are supplied to the inner surface of the concrete layer 11 in a dry state containing no water or a paste state containing kneading water to simultaneously form the concrete layer 11 and the inner surface protective layer 12.
The inner surface protective layer 12 is composed of a buffer layer 14 formed as a continuous structure with the concrete layer 11 on the inner surface side of the concrete layer 11, and a chemical resistance layer 15 formed as a continuous structure on the inner surface side of the buffer layer 14.

<3.1> Reason for forming the inner surface protective layer The reason why the inner surface of the concrete layer 11 is covered with the inner surface protective layer 12 is that when the concrete layer 11 comes into contact with sulfuric acid, for example, a large amount of calcium hydroxide is contained in the concrete layer 11. This is to prevent the progress of corrosion that peels off when coarse and fragile dihydrate gypsum is produced by the violent reaction of sulfuric acid.

<3.2> Layer thickness of inner surface protective layer The inner surface protective layer 12 has an appropriate layer thickness at which sulfuric acid does not penetrate into the concrete layer 11.
The layer thickness of the inner surface protective layer 12 varies depending on the pipe diameter, but when the layer thickness is about 3 to 50 mm, it takes a long time for sulfuric acid to permeate into the concrete layer 11, and the chemical resistance of the concrete pipe 10 and two The anti-peeling effect of the water gypsum film can be guaranteed for a long period of time.
It is desirable that the minimum layer thickness of the inner surface protective layer 12 is selected in consideration of the layer thickness capable of suppressing the pop-out phenomenon.

<3.3> Binder B
As the binder of the inner surface protective layer 12, a binder B having a property of combining with the sludge component (cement mortar component) of the concrete layer 11 and hardening is used. The mixed material of the inner surface protective layer 12 before supply does not contain a cement-based binder.
The sludge component is a slurry containing cement-based binder A, fine aggregate, water, etc., and means sludge containing a large amount of solid components or sludge water containing a large amount of water components with extremely few solid components.
The binder B means a latent hydraulic binder or a pozzolan-reactive binder having silica or alumina that is not cured only by mixing with water but is cured by alkaline stimulation.

As the latent hydraulic binder B, for example, one or more of blast furnace slag fine powder, blast furnace granulated slag, blast furnace slow cooling slag, steelmaking slag and the like can be used.
In particular, the blast furnace slag fine powder defined in JIS A 6206 "Blast furnace slag fine powder for concrete" has a latent hydraulic property that densifies the structure of the inner surface protective layer 12 to improve sulfuric acid resistance and salt damage resistance.

As the pozzolan-reactive binder B, for example, one or more of fly ash, silica fume, etc. can be used, and soluble silicon dioxide (SiO ₂ ) is produced during hydration of cement calcium hydroxide (Ca (OH)). Combines with ₂ ) to turn into insoluble hydrate.
In addition, volcanic ash, silicic acid white clay, or the like can be used as the binder B.

<3.4> Fine aggregate C
As the fine aggregate C for the inner surface protective layer, for example, slag fine aggregate, silica sand, natural fine aggregate and the like can be used.
Since the inner surface protective layer 12 has a lower calcium content than the concrete layer 11, the chemical resistance is improved. If a slag fine aggregate is used as the fine aggregate C, the chemical resistance of the inner surface protective layer 12 is further improved.

<3.5> Blending ratio of binder B and fine aggregate C The blending ratio of binder B and fine aggregate C is about 1: 2 as a guide.
The blending ratio of the binder B and the fine aggregate C is not limited to this range, and is appropriately selected in consideration of the usage of the concrete pipe 10 and the usage environment.

<3.6> Reason why the inner surface protective layer does not have a homogeneous structure The inner surface protective layer 12 does not have a homogeneous structure mainly composed of the binder B and the fine aggregate C which are hardened by combining with the sludge component. The reason why the structure is not homogeneous is that the sludge component of the concrete layer 11 is mixed with the inner surface protective layer 12 under the influence of the rotational centrifugal force, and the amount of the sludge mixed is different depending on the site.
Therefore, the closer the inner surface protective layer 12 is to the inner surface of the concrete layer 11, the larger the amount of sludge mixed in, and the farther away from the inner surface of the concrete layer 11 is, the smaller the amount of sludge mixed in.

<3.7> Buffer layer Explaining with reference to FIG. 1, the buffer layer 14 laminated on the inner surface of the concrete layer 11 is mainly a mixed material of a binder B and a fine aggregate C which is hardened by combining with a sludge component. It is an intermediate protective layer formed between the concrete layer 11 and the chemical resistance layer 15.
A part of the sludge component of the concrete layer 11 is mixed and compounded in the cushioning layer 14 during the molding of the inner surface protective layer 12. The amount of sludge mixed is gradually reduced from the outer surface to the inner surface of the buffer layer 14.
The buffer layer 14 supports chemical resistance when the chemical resistance layer 15 is damaged.

<3.8> Chemical resistance layer The chemical resistance layer 15 laminated on the inner surface of the buffer layer 14 is a protective layer mainly composed of a mixed material of a binder B and a fine aggregate C, and is formed during molding of the inner surface protective layer 12. Combines with sludge water.
The chemical resistance layer 15 has a relationship in which the amount of sludge mixed is smaller than that of the buffer layer 14.
The chemical resistance layer 15 contains almost no sludge due to centrifugal molding, and contains almost 100% of the binder B and the fine aggregate C.

[Production method]
Next, a method of manufacturing the concrete pipe 10 will be described.

<1> Molding of Concrete Layer The molding process of the concrete layer 11 will be described with reference to FIGS. 2 to 5.

<1.1> Reinforcing bar cage setting Explaining with reference to FIG. 2, the reinforcing bar cage knitted in a tubular shape is set inside to assemble the formwork 20. The formwork 20 is composed of an outer frame 21 and a donut-shaped wife formwork 22, and there is no inner formwork.

<1.2> Supply of concrete Next, while supplying concrete containing the cement-based binder A kneaded with a mixer or the like through a supply device 23 such as a conveyor into the assembled formwork 20, the formwork 20 is placed on the centrifugal molding machine. To rotate. The composition of concrete is known.

<1.3> Rotation of formwork At the initial stage of molding, the formwork 20 is rotated at a low speed (2 to 3 G) to diffuse the concrete throughout, and then the rotation speed is increased to a medium speed (10 to 15 G) to make the concrete. The concrete is compacted to some extent, and finally the concrete is compacted densely by high-speed rotation (about 30 G) to form the cylindrical concrete layer 11.

<1.4> Layer thickness of concrete layer FIG. 3 shows a cross section of the formwork 20 and the concrete layer 11 at the time of centrifugal molding.
In the molding process of the concrete layer 11, the amount of concrete charged is less than the predetermined pipe thickness, and the pipe thickness of the concrete layer 11 is reduced in anticipation of the layer thickness of the inner surface protective layer 12 to be molded in the next step. deep.
The estimated thickness of the inner surface protective layer 12 may be set to about 3 to 50 mm depending on the diameter of the concrete pipe 10, but it is appropriately selected in consideration of the usage conditions, usage environment, etc. of the concrete pipe 10.
For integration with the inner surface protection layer 12, it is desirable to leave the inner surface of the concrete layer 11 as a rough surface without finishing it completely smooth.

<2> Molding of Inner Surface Protective Layer The molding process of the inner surface protective layer 12 will be described with reference to FIG.

<2.1> Example of mixed material for inner surface protective layer As the mixed material of the inner surface protective layer 12, for example, the following combinations can be applied.
・ Blast furnace slag fine powder, etc. binder B,
・ Slag fine aggregate C,
・ Fly ash,
・ Silica fume,
-A lime-gypsum composite (expansion material) containing 1 to 15% by mass of aluminum oxide as a chemical component.

<2.2> Supply form of mixed material These mixed materials may be supplied to the inner surface of the concrete layer 11 in a dry state without containing water, or may be supplied in a paste state previously kneaded with kneaded water. ..

<2.2.1> When supplying in a dry state When the concrete layer 11 is centrifuged, sludge components containing water, cement components, aggregate fine particles, etc. are discharged to the inner surface of the concrete layer 11 by centrifugation. To.
Next, when the mixed material of the inner surface protective layer 12 is supplied to the inner surface of the concrete layer 11 in a dry state, the sludge component is mixed with the mixed material in the process of passing through the mixed material by centrifugal force, and the inner surface protective layer 12 becomes a paste. become.
When the mixed material of the inner surface protective layer 12 is supplied in a dry state, the amount of sludge component consumed increases when the inner surface protective layer 12 is made into a paste, so that the final amount of sludge component recovered is further reduced.

<2.2.2> When supplied in a paste state An appropriate amount of kneading water may be added to the mixed material of the inner surface protective layer 12 and kneaded in advance, and then supplied in a paste state.
When supplied in a paste state, cement particles, aggregate fine particles, etc. are screened and it becomes difficult to pass through the inner surface protective layer 12 as compared with the dry state, so that the sludge of the inner surface protective layer 12 is reduced, but the sludge component. Considering the amount of water recovered, the kneading water should be the minimum amount of water that can secure the fluidity that can supply the mixed material.

<2.3> Rotation of mold When the inner surface protection layer 12 is centrifugally molded, it is tightened by centrifugal force while gradually increasing the rotation speeds such as low speed rotation, medium speed rotation, and high speed rotation as in the case of molding the concrete layer 11. The inner surface protective layer 12 having a dense structure is formed on the inner surface of the concrete layer 11 by hardening.
Also in the molding process of the inner surface protective layer 12, sludge water containing almost no cement component permeated through the inner surface of the inner surface protective layer 12 is discharged as the inner surface protective layer 12 rotates at high speed.
When the inner surface is smoothed while removing excess sludge water using a bar or spatula, the rotation of the mold 20 is stopped.

<2.4> Composition of inner surface protective layer The inner surface protective layer 12 is not a homogeneous structure as a whole, and a portion adjacent to the inner surface of the concrete layer 11 is formed as a buffer layer 14 in which a large amount of sludge is mixed, and the inner surface of the concrete layer 11 is formed. It is formed as a chemical resistance layer 15 in which the amount of sludge mixed is small as the portion is separated from the concrete resistance layer 15 (FIG. 1).

<3> Curing reaction The concrete pipe 10 undergoes a curing reaction in the concrete layer 11 and the inner surface protective layer 12 in parallel with compaction, and the strength gradually increases.

In the concrete layer 11, the cement-based binder A reacts with the kneading water and hardening proceeds.
In the inner surface protective layer 12, the latent hydraulic or pozzolan-reactive binder B combines with sludge or sludge water 13 to proceed with hardening.

<4> Curing and demolding The mold 20 is removed from the centrifugal molding machine, and the concrete pipe 10 is moved to a predetermined curing place with the concrete pipe 10 in the mold 20.
As the curing means, for example, steam curing can be used. Demolding can be accelerated by steam curing.
The steam curing temperature of the concrete pipe 10 is selected as appropriate so as not to adversely affect the physical properties of the concrete pipe 10.
The curing method is not limited to steam curing, and natural curing may be performed.

When the concrete pipe 10 reaches a predetermined demolding strength, the concrete pipe 10 is taken out from the mold 20 and a series of operations is completed.

<5> Characteristics of Concrete Pipe The main characteristics of the concrete pipe 10 will be described with reference to FIG.

<5.1> Integration of Concrete Layer and Inner Surface Protective Layer Since the concrete pipe 10 of the present invention is not a manufacturing method in which the inner surface protective layer 12 is joined to the inner surface of the concrete layer 11 hardened in advance, a cold joint is used. Does not occur.

In the concrete pipe 10 of the present invention, since the concrete layer 11 and the inner surface protective layer 12 are simultaneously molded before hardening, the inner surface of the concrete layer 11 and the inner surface protective layer 12 become more familiar, and the concrete layer 11 and the inner surface protective layer 12 become more familiar. The boundary between the two and the buffer layer 14 and the chemical resistance layer 15 forming the inner surface protective layer 12 is mixed and integrated into a continuous structure.
That is, the cross section of the concrete pipe 10 does not have a clear boundary surface as seen in the cross section of the conventional resin lining pipe.
In particular, since the inner surface protective layer 12 is laminated in a rough surface state in which fine irregularities exist without finishing the inner surface of the concrete layer 11 smoothly, the adhesiveness (integration) between the concrete layer 11 and the inner surface protective layer 12 is remarkably improved. Get better.

Since the cross-sectional structure of the concrete pipe 10 has an integrated continuous structure in this way, even if the inner surface of the concrete pipe 10 receives an impact, the peeling phenomenon of the inner surface protective layer 12 is unlikely to occur.

<5.2> Chemical resistance action of inner surface protective layer The inner surface protective layer 12 is a protective layer containing a latent hydraulic or pozzolan-reactive binder B as a main component, and is said to be the most sensitive to acid among cement hydrates. The content of calcium hydroxide (Ca (OH) ₂ ) to be produced is significantly reduced.
For example, when the binder B is a latent hydraulic binder typified by blast furnace slag fine powder, the inner surface protective layer 12 is required to be stimulated by an alkali with sludge or sludge water 13 to cure the binder B. When the slag is cured, the calcium hydroxide contained in the sludge component is further consumed, the calcium component of the inner surface protective layer 12 is further reduced, and the chemical resistance is improved.
For example, when the binder B is pozzolan-reactive, the calcium hydroxide contained in the sludge component is combined with silicon dioxide and consumed in the curing of the binder B, so that the calcium component of the inner protective layer 12 is consumed. It decreases and the chemical resistance improves.

When sulfuric acid or the like comes into contact with the inner surface protective layer 12, it permeates due to a capillary phenomenon, but since calcium hydroxide is almost absent, a violent reaction does not occur, and sulfuric acid and CS-contained in the inner surface protective layer 12 do not occur. The calcium content of H and CAH reacts with each other, and a dihydrate gypsum layer is laminated near the surface of the inner surface protective layer 12 over time.
Since this dihydrate gypsum has a dense structure and has acid resistance, the inner surface protective layer 12 on which the dense dihydrate gypsum layer is laminated even if the inner surface of the concrete pipe 10 is continuously exposed to sulfuric acid is formed. It is possible to suppress the infiltration of sulfuric acid and effectively prevent the sulfuric acid from reaching the concrete layer 11.

Even if sulfuric acid permeates and reaches the buffer layer 14 on the deep side of the chemical resistance layer 15 due to aging on a scale of several decades, the calcium component of the buffer layer 14 is much smaller than that of the concrete layer 11, so it takes a short time. Corrosion does not proceed, and corrosion due to sulfuric acid can be continuously suppressed as the thickness of the dihydrate gypsum layer increases.
As described above, the presence of the buffer layer 14 not only serves as a quasi-chemical resistance layer against capillary penetration, but also easily corrodes the concrete layer 11 even if the chemical resistance layer 15 is lost due to an external impact. It also serves as a fail-safe that does not exert any effect.
Since the dihydrate gypsum layer can be formed over the entire cross section of the inner surface protective layer 12, it takes an extremely long time for sulfuric acid to reach the concrete layer 11, and chemical resistance is compared with that of conventional ordinary concrete. The sexual guarantee period is dramatically extended.

It is assumed that the dihydrate gypsum layer is automatically formed when it comes into contact with acid in a common environment, but the concrete pipe 10 is preliminarily treated with sulfuric acid before shipping in a factory with a well-established manufacturing environment. It may be formed on the inner surface.

Hereinafter, examples of the present invention will be described in detail.

<1> Materials used The following materials were used for the concrete layer 11. (Numbers are density)

The following materials were used for the internal protective layer 12. (Numbers are density)

<2> Specimen A specimen of concrete pipe 10 was manufactured by using the above materials and using the formulations shown in Table 1 (Example 1, Comparative Example 1).

The mixed material for the inner surface protective layer in Example 1 was kneaded at a ratio of blast furnace slag fine powder: blast furnace slag fine aggregate to 1: 2 and a water cement ratio of 40%.

<3> Acid resistance test A pipe body with an inner diameter of 300 mm, a pipe thickness of 30 mm, and a length of 300 mm was prepared by blending the concrete of Example 1 and Comparative Example 1, and a section of approximately 100 mm × 150 mm was cut out from the pipe body, except for the inner surface. Was coated with an epoxy resin to prepare a specimen.
Each of the specimens of Example 1 and Comparative Example 1 was immersed in a 5% sulfuric acid solution, and the increase or decrease in the tube thickness was measured. The test results are shown in Table 2, and FIG. 6 shows each actual specimen.

In the specimen of Example 1 of the present invention, the tube thickness (mass) was increased due to the precipitation and formation of dihydrate gypsum, but it was not dissolved in sulfuric acid.
On the other hand, in the specimen of Comparative Example 1, it was confirmed that the tube thickness (mass) was significantly reduced by dissolving in sulfuric acid from the surface.

10 ... Concrete pipe (highly chemically resistant concrete structure)
11 ... Concrete layer 12 ... Inner surface protective layer 13 ... Sludge or sludge water (sludge component)
14 ... Buffer layer 15 ... Chemical resistance layer 20 ... Formwork 21 ... Outer frame 22 ... Wife formwork 23 ... Supply device

Claims

A highly chemically resistant concrete structure manufactured by centrifugal molding.
A concrete layer containing cement-based binder A and
It contains at least a latent hydraulic or pozzolan-reactive binder B and fine aggregate C that are hardened by sludge components discharged to the inner surface of the concrete layer, and is laminated on the inner surface of the concrete layer and centrifuged at the same time as the concrete layer. It is characterized by being composed of an inner protective layer.
Highly chemically resistant concrete structure.
The highly chemically resistant concrete structure according to claim 1, wherein the binder B is at least one selected from the blast furnace slag fine powder, fly ash, silica fume, volcanic ash, silicate clay, and diatomaceous earth group. ..
The first aspect of the present invention is characterized in that the fine aggregate C of the inner surface protective layer supplied to the inner surface of the concrete layer is any one or a plurality of slag-based fine aggregates, silica sand, and natural fine aggregates. The high chemical resistance concrete structure described.
The inner surface protective layer is composed of a buffer layer formed as a continuous structure on the inner surface side of the concrete layer and a chemical resistance layer formed as a continuous structure on the inner surface side of the buffer layer, and the chemical resistance layer is compared with the buffer layer. The highly chemically resistant concrete structure according to any one of claims 1 to 3, wherein the amount of sludge mixed from the concrete layer is small.
The highly chemically resistant concrete structure according to claim 4, wherein the chemical resistance layer is composed of at least a binder B, a fine aggregate C, and a kneaded product of sludge water.
A method for manufacturing a highly chemically resistant concrete structure manufactured by a centrifugal molding machine.
Supply concrete into the formwork of the centrifugal molding machine, centrifuge the concrete layer, and compact it.
A mixed material containing at least a latent hydraulic or pozzolan-reactive binder B and fine aggregate C, which is hardened by a sludge component discharged to the inner surface of the concrete layer when the concrete layer is compacted, is supplied to the inner surface of the concrete layer. The concrete layer and the inner surface protective layer are simultaneously centrifugally molded and integrally molded.
A method for manufacturing a highly chemically resistant concrete structure.
The production of the highly chemically resistant concrete structure according to claim 6, wherein a dry mixed material containing the binder B and the fine aggregate C is supplied to the inner surface of the concrete layer during centrifugal molding. Method.
The highly chemically resistant concrete structure according to claim 6, wherein a paste-like mixed material containing a binder B, a fine aggregate C, and kneading water is supplied to the inner surface of the concrete layer during centrifugal molding. How to make a body.
The invention according to any one of claims 6 to 8, wherein the binder B is at least one selected from the blast furnace slag fine powder, fly ash, silica fume, volcanic ash, silicic acid clay, and diatomaceous earth group. A method for manufacturing a highly chemically resistant concrete structure.
The invention according to any one of claims 6 to 8, wherein the fine aggregate C of the inner surface protective layer is at least one selected from the slag-based fine aggregate, silica sand, and natural fine aggregate group. A method for manufacturing a highly chemically resistant concrete structure.