JPH0735049B2 - Concrete pipe manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a concrete pipe by using a fresh concrete by a centrifugal molding method, which is excellent in chemical resistance, particularly acid resistance.

[0002]

2. Description of the Related Art Conventionally, as a method for improving the chemical resistance, particularly acid resistance, of a concrete pipe, a method of forming a concrete pipe and then impregnating a dried concrete pipe with a resin A method of lining vinyl chloride on the inner surface of a dry concrete tube. After forming a concrete tube, a method of applying asphalt, tar, synthetic resin paint, etc. to the inner surface of a dried concrete tube. Resin concrete using thermosetting resin. The method of lining the concrete cement mortar with epoxy resin emulsion on the inner surface of the hardened and dried concrete tube after forming the concrete tube. The concrete outer shell layer containing expansive cement is subjected to resin mortar lining to make the concrete tube. Method (JP-A-51-978 No. 9), and the like are known.

[0003]

However, the method (1) is not suitable for large-sized members because the manufacturing process is complicated, and a satisfactory acid-resistant coating cannot be obtained with the amount of impregnation applied. The method of (1) has a complicated process, the strength of the film formed is weak, and the adhesiveness to the concrete pipe is insufficient, so that there is a problem that the entire pipe is destroyed when a specific portion is broken. The coating obtained by the method of 1) has a thin coating film and has insufficient adhesive strength and coating film strength, which makes it difficult to put into practical use.
The method (1) is economically disadvantageous even though it has excellent acid resistance because it uses a large amount of expensive resin, and is not practical.
Even if the acid resistance is improved, this method requires two additional steps: a step of forming a concrete pipe, hardening and drying it, and a process of cleaning the inner surface of the pipe, treating it with a primer, and lining a polymer cement mortar, which is economical. Not only is it disadvantageous, but there is a risk of peeling due to the existence of the interface between the concrete layer and the polymer cement mortar. Even if the other method is excellent in effect, this method is complicated because the number of manufacturing steps is increased, and the economic disadvantage is unavoidable.

[0004]

As a result of intensive studies to solve the above problems, the present inventors have found that in the process of manufacturing a conventional concrete pipe by a centrifugal molding method, the uncured concrete layer on the inner surface of the concrete pipe is uncured. And an aqueous polymer dispersion and a hydraulic inorganic powder (hereinafter, a mixture of the both or a non-hydraulic inorganic powder is a polymer cement mortar. It has been found that a concrete pipe having excellent acid resistance can be obtained by curing, and that the productivity is high and the method is economically excellent, and the method of the present invention was developed. That is, the present invention puts ready-mixed concrete into a rotary mold, and in the step of producing a concrete pipe by a centrifugal molding method, forms an uncured concrete pipe, in which an aqueous polymer dispersion liquid and a hydraulic inorganic powder are added. Injecting, the concrete of the inner surface layer of the concrete pipe and the aqueous polymer dispersion liquid and hydraulic inorganic powder are mixed by external force in order to integrate them, the surface is adjusted, and after that curing curing is performed. The present invention relates to a characteristic concrete pipe manufacturing method.

The present invention is a method for producing a concrete pipe in which green concrete is put into a rotary mold and is molded by a centrifugal molding method. In the present invention, while the concrete pipe is rotating at a high speed, it is made by introducing polymer cement mortar into the concrete pipe inner surface layer,
The inner surface layer of the concrete pipe is not yet hardened, so that it is hardened after the cement layer of the inner surface layer of the concrete pipe and the polymer cement mortar are mixed by an external force with the polymer cement mortar introduced after the concrete pipe is formed, for example, by a stirring rod. In addition, there is no boundary between the concrete surface layer of the pipe and the polymer cement mortar layer, and unlike simple coating and adhesion to form a strong layer by integrating, there is no delamination due to being integrated .

Generally, at the final stage of forming a concrete pipe, an operation of smoothing the inner surface of the pipe with a leveling rod is performed. In the present invention, an amount of polymer cement sufficient to form a protective layer at this stage of operation is used. While the mortar is charged, the inner surface layer of the concrete pipe is scraped off by an external force, for example, a stirring rod, and mixed and integrated with the polymer cement mortar. Subsequently, the operation of smoothing with a conventional leveling rod is performed. Examples of the external force used in the present invention include a method using a stirring rod. In this case, an uncured concrete pipe surface which is rotating at a high speed is equipped with an acute-angled iron claw-like object at the tip portion required for shaving to a depth of about 2 to 3 mm. The number of the nails may be 2 to 3, but in order to improve the efficiency, it is preferable that the number of the nails is 5 to 20. With this, the inner surface of the concrete pipe is scraped, and a layer integrated with the polymer cement mortar is formed. Of course, any means can be used in the present invention as long as it has the same effect by mixing the thin cement layer on the inner surface of the cement pipe and the polymer cement mortar.

The hydraulic inorganic powder is added to aid the precipitation of the polymer and subsequent film formation by hydration hardening with water in the aqueous polymer dispersion, and to increase the physical strength of the coating film. Therefore, if there is a large amount of water in the polymer cement mortar, a large amount of hydraulic inorganic powder will be used, so the water that has exuded to the inner surface of the concrete pipe at the final stage of formation will be separated before the polymer cement mortar is added, It is preferable to discharge.

In terms of the relationship between the amount of the aqueous polymer dispersion, the hydraulic inorganic powder, and the non-hydraulic inorganic powder (hereinafter, both components are referred to as the inorganic powder) added as needed, the inorganic powder is used. Should be less than or equal to the amount at which the polymer forms the continuous phase. If the polymer does not form a continuous phase, the cement and hydraulic inorganic powder will be attacked by the acid component, and the concrete pipe itself will be attacked by the acid, so the effect of adding the polymer will disappear. is there. The approximate ratio of the aqueous polymer dispersion and the inorganic powder is 300 parts by weight or less of the inorganic powder with respect to 100 parts by weight of the polymer in the aqueous polymer dispersion (including 0-50 for the non-hydraulic inorganic powder). However, it goes without saying that it also depends on the composition of the inorganic powder and the relative miscibility of the aqueous polymer dispersion. The non-hydraulic inorganic powder is added for crushing the powder as cement and for increasing the amount. The aqueous polymer dispersion used in the present invention is not particularly limited as long as it has good miscibility with the inorganic powder, can form a film under the manufacturing conditions of the concrete pipe, and has excellent acid resistance.

Further, when the resin composition is hard and the emulsion is difficult to form into a film at the curing temperature of the cement mortar,
Further, when it is desired to lower the MFT, it is also a preferable embodiment to add a polymer plasticizer or a solvent as a film-forming agent to enhance the film-forming property.

Since the cement slurry contains calcium ions and sodium ions in a high concentration, it is preferably a nonionic aqueous polymer dispersion, but it may be cationic or anionic and nonionic. It is well known that the stability is improved by the addition of a surface active agent or a protective colloid, and these can be used as a matter of course.

The MFT (minimum film forming temperature) of the aqueous polymer dispersion must be below the temperature for steam curing. MFT forms a continuous film when a polymer dispersion is dried at a temperature higher than the temperature at which the polymer softens and deforms. The critical temperature for forming this continuous film is MFT.
(Minimum Film-Forming tem
perature). 60 for concrete pipes
Since steam curing is performed at ˜70 ° C., MFT must be 60 to 70 ° C. or lower. Otherwise, the polymer will not form a film, and thus a continuous film will not be formed as a matrix of the polymer cement mortar. In terms of the amount of polymer cement mortar used, it is theoretically considered that the thicker the coating layer, the higher the effect. However, in reality, it is sufficient that the fluid flowing in the concrete pipe has chemical resistance and a protective effect against acid components, and it is usually 2 mm or more, preferably 3 mm or more as a mixture layer with concrete.
A thickness of mm or more is sufficient.

Any type of polymer may be used as long as it has good acid resistance. Examples include SBR latex and NBR
Examples include latex, vinyl chloride-based or vinylidene chloride-based emulsion, polyacrylic acid ester-based emulsion, styrene emulsion, styrene-acrylic acid ester copolymer emulsion, epoxy resin-based emulsion, urethane resin-based emulsion, etc. Not something.

[0013]

According to the method for producing a concrete pipe according to the present invention, after the concrete pipe is molded, the aqueous polymer dispersion, the hydraulic inorganic powder and, if necessary, the non-hydraulic inorganic powder are mixed before the hardening of the concrete proceeds. After pouring it in, scraping off the concrete pipe inner surface layer with a stirring rod, the polymer cement mortar is mixed and hardened, so if you observe the cross section near the concrete pipe inner surface layer after completion, the concrete layer and polymer cement layer It can be seen that the concrete layer does not consist of two layers but changes continuously from the concrete layer to the polymer cement mortar layer. As a result, a polymer cement mortar layer in which a polymer having a good acid resistance is a continuous phase is formed on the surface, so that the acid resistance is dramatically improved. Moreover, since it has an integrated structure in which the concrete phase continuously changes to the polymer-cement mortar layer, delamination does not occur and the mechanical properties are extremely excellent.

When a concrete pipe is manufactured by spraying an aqueous polymer dispersion liquid on the surface of the concrete pipe before hardening, allowing the concrete pipe to penetrate into the concrete, and then curing / curing the concrete pipe, when the concrete pipe is manufactured, the aqueous polymer dispersion liquid is dispersed in the concrete layer. Since the liquid penetrates and is integrated, delamination does not occur,
It seems that there are delicate requirements for the conditions under which the polymer dispersion penetrates well into the cement layer, and if the polymer dispersion is added at a relatively early stage of concrete pipe molding, it will be diluted by the water separated from the cement, and it will take a long time to cure. In short, productivity seems to be low, and the cement layer becomes hard after the separated water is separated, resulting in insufficient penetration of the polymer dispersion.

On the other hand, in the production method of the present invention, the thin concrete layer on the inner surface of the uncured cement pipe is scraped off by an external force and forcedly mixed with the injected polymer cement mortar so that the polymer cement mortar penetrates. Has the advantage that it can be completely mixed, and even if the cement layer hardens, both can be mixed.

Further, in order to forcefully mix by an external force,
Even after the separated water has been separated, even if there is little excess water, a hydraulic inorganic powder for absorbing the water, and in some cases a non-hydraulic inorganic powder is added at the same time as the polymer dispersion liquid, so that it hardens. Since the time is short and the water usage ratio is small, the strength of the concrete pipe obtained is naturally high.

[0017]

(Examples) Next, the present invention will be specifically described with reference to Examples. A screw-shaped rebar is arranged in a cylindrical rotating mold frame having an outer diameter of 38 cm and a length of 200 cm. Separately, 1000 parts by weight of Portland cement, 1600 parts by weight of No. 7 sand,
Coarse aggregate (No. 6 fine stone) 1700 parts by weight, water 340 parts by weight,
A high-performance water reducing agent Mighty 150 (manufactured by Kao Corporation) was mixed with 10 parts by weight of a fresh concrete mixture. While rotating the mold and supplying fresh concrete from the fresh concrete supply port, the mold frame is initially 150 to 300 rpm,
Finally, the rotation was increased to 500 rpm to form a concrete pipe. Next, the rotation was slowed down to about 50 rpm, the water exuded on the inner surface of the tube was removed, and the rotation was increased again to 350 rpm. Polysol TC-2 is added to this uncured concrete pipe.
MFT by adding a film forming agent (dibutyl phthalate) to 00 (Showa Highpolymer Co., Ltd. styrene-based aqueous polymer dispersion)
Was 40 ° C. 4 kg of the aqueous dispersion was added, and subsequently 4 kg of inorganic powder obtained by mixing Portland cement and No. 7 silica sand in a ratio of 1: 0.5 was added. At the beginning, polymer cement mortar was added while shaving the concrete inner surface layer with a stirring rod with iron claws. Next, the surface was smoothed with a surface smoothing rod. Subsequently, the temperature of the centrifugally molded concrete pipe was raised to 65 ° C over 1 hour at room temperature, and the temperature was raised to 65 ° C.
It was kept warm for 4 hours and steam curing was continued. Then, it was cooled to room temperature and then air-dried in the atmosphere to obtain a product. The concrete pipe thus produced had an inner diameter of 34.0 cm, a length of 200 cm, and a wall thickness of 4.0 cm. When this concrete pipe was cut in the direction perpendicular to the length direction and observed,
The polymer cement mortar layer reached 5 to 6 mm, the concrete layer and the polymer cement layer were integrated, and the interface was in an unclear state.

(Comparative Example 1) In the method for producing a concrete pipe by the centrifugal method, except that the inner surface layer of the concrete pipe was not ground with a stirring rod having an iron claw, and the polymer inner surface mortar was simply coated with polymer cement mortar. Produced a concrete pipe in the same manner as in the example. The concrete pipe thus made has an inner diameter of 34.1 cm and a length of 2
It was 00 cm and the wall thickness was 3.9 cm. When this concrete pipe was cut in the direction perpendicular to the length direction and observed, the polymer cement mortar layer had a thickness of 2 to 3 mm, and its interface was clear. This is because effluent of cement, sand, mud contained in crushed stone, etc. come out to the surface with water leaching from the concrete layer to form a fragile layer, and this fragile layer was added after the concrete pipe was formed. This indicates that it was because it was not mixed with the polymer cement mortar and remained as it was between the concrete and the polymer cement mortar layer. For this reason, the polymer-cement mortar layer was strong, but some could be peeled off with a slight force, making it impossible to put into practical use. In addition, the measurement values were omitted because there were large variations in measurement and stable data could not be obtained.

(Comparative Example 2) In the method for producing a concrete pipe by the centrifugal method, the inner surface layer of the concrete pipe was not coated with the polymer cement mortar consisting of the aqueous polymer dispersion and the inorganic powder, and the mixing operation was performed with a stirring rod. A concrete pipe was prepared in the same manner as in the example except that it was not used. The concrete pipe thus produced had an inner diameter of 34.4 cm, a length of 200 cm, and a wall thickness of 3.6 cm. The concrete pipes prepared in Examples and Comparative Example 2 were filled with an acidic chemical liquid, and the weight loss rate of the pipes when circulating for 1 month at 20 ° C. was measured to examine the degree of erosion.

[0020] As described above, the erosion of the concrete pipe produced by the present invention by the acidic water was extremely slight as compared with the erosion of the blank.

[0021]

According to the present invention, water-based polymer cement mortar is added at the time of manufacturing a concrete pipe, and in terms of equipment, in addition to a conventional leveling rod, a mixing means by an external force, for example, a stirrer bar with a claw is attached. However, the manufacturing time is shorter than that of polymer untreated concrete pipes, or the molds can be demolded in almost the same time. It is a method that is extremely excellent and has extremely high productivity. In addition, the manufactured concrete pipe is a hydraulic powder to remove exudate water and reduce excess water,
Since non-hydraulic powder is added as needed, not only the water usage ratio is small, but also the penetration of polymer cement mortar into the concrete layer is sufficient, there is no exfoliation of polymer cement mortar, and the one with high strength is used. can get. In addition, since the inner surface is covered with a polymer layer that is much smoother than that of concrete, the flow of fluid is improved, and since it is smooth, sedimentation of sediment is reduced. In particular, the inner surface layer of concrete pipes, which are inherently vulnerable to acidic components, is protected by a permeation layer of a polymer with excellent acid resistance. It is economically extremely advantageous because the service life can be greatly extended when it is used for a water pipe or the like.

Claims (5)

[Claims] 1. An uncured concrete pipe is formed in a step of producing a concrete pipe by a centrifugal molding method in which fresh concrete is put into a rotary mold, and an aqueous polymer dispersion liquid and a hydraulic inorganic powder are added thereto. Injecting, the concrete of the inner surface layer of the concrete pipe and the aqueous polymer dispersion liquid and hydraulic inorganic powder are mixed by external force in order to integrate them, the surface is adjusted, and after that curing curing is performed. A method for producing a characteristic concrete pipe. 2. The step of producing a concrete pipe by a centrifugal method, wherein an uncured concrete pipe is formed and exuded water is separated, and then an aqueous polymer dispersion liquid and a water-curable inorganic powder are added thereto. 1. A method for manufacturing a concrete pipe. 3. An aqueous polymer dispersion is an SBR latex, an NBR latex, a vinyl chloride emulsion, a vinylidene chloride emulsion, a polyacrylic acid ester emulsion, a styrene emulsion, a styrene-acrylic acid ester copolymer emulsion, an epoxy resin type. The method for producing a concrete pipe according to claim 1, wherein the concrete pipe is an emulsion or a urethane resin emulsion. 4. The method for producing a concrete pipe according to claim 1, wherein the hydraulic inorganic powder is ordinary Portland cement, ordinary white cement, sulfate resistant Portland cement, blast furnace cement, early-strength Portland cement or gypsum. 5. A non-hydraulic inorganic powder such as acid-resistant ceramic powder, fly ash, silica sand, river sand, land sand, sea sand, slag, etc., when an aqueous polymer dispersion and a hydraulic inorganic powder are added. The method for producing a concrete pipe according to claim 1, wherein