JPS6163558A - Manufacture of centrifugally molded steel composite concretemember using high strength admixing material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides extremely high bending resistance and bending rigidity with only atmospheric pressure steam curing, and furthermore, separation occurs during centrifugal force molding to create a homogeneous product. The present invention relates to a method of manufacturing an m-tube composite concrete member that can prevent the properties from being impaired.

[Conventional technology] Conventionally, steel pipe composite concrete members, which have been put into practical use for various purposes, have a steel pipe as an outer shell, and high-strength concrete of a predetermined thickness is placed inside the shell by centrifugal compaction to cause receding. Most of the products are manufactured by curing with high temperature and high pressure in an autoclave after curing with pressure steam. However, if high-temperature, high-pressure tea curing is performed using an autoclave device, manufacturing costs will increase.

Moreover, not only for this type of product but also for concrete products in general, it is ideal that homogeneously mixed concrete be molded while remaining homogeneous. In other words, it is desirable that the composition ratios of cement, water, fine aggregate, etc. that make up the concrete remain constant no matter what part of the concrete product, but separation is a phenomenon that impairs this homogeneity, and is particularly During centrifugal force molding, a characteristic phenomenon called "toro" occurs. Conventionally, when this type of composite concrete member is formed by centrifugal force, it is easy to cause separation and melting, which causes undesirable elution of cement and admixtures into the melting, resulting in the strength of the hardened concrete. This resulted in uneven distribution and inconsistencies that impeded the beauty and durability of the product. At the same time, the reality is that the disposal of the separated product, Toro, was a considerable burden in terms of both labor and cost.

[Problems to be Solved by the Invention] The present invention has been made with attention to the above-mentioned circumstances, and when manufacturing this type of composite concrete member by centrifugal force molding, high temperature and high pressure steam curing using an autoclave device is required. In other words, it is possible to obtain a product with high bending resistance and bending rigidity comparable to conventional normal pressure curing and high temperature and high pressure steam curing with only normal pressure steam curing. The generation of melt during molding and the elution of undesirable cement and admixtures into the melt can be prevented as much as possible, thereby guaranteeing the quality such as the homogeneity of the W4 pipe composite concrete member, and at the same time reducing the hassle of disposal etc. It was also an attempt to overcome the problem of processing fatty tuna.

[Means for Solving the Problems] In order to achieve the above objects, the present invention has a plain specific surface area of 800 for Portland cement dishes.
0~8QOOcm'/g, particle size of 2 colors or less is 15~
5 to 20 mass % of the cement admixture J made of special anhydrite described in Japanese Patent Publication No. 57-22907, which is 40 mass %, 5 to 15 mass % of the cement expansion agent, and 0.5 mass % of the water reducing agent. The concrete is characterized by pouring concrete containing 5 to 2.0% by mass into a W4 pipe, centrifugally molding it, and then curing it with atmospheric pressure steam.

The present invention will be described in detail below. First, in order to develop the necessary strength etc. only by normal pressure steam curing.

As mentioned above, for the concrete to be placed inside the steel pipe, use a mixture of Portland cement, a cement admixture made of special anhydrite, a cement expanding agent, and a water reducing agent mixed uniformly in predetermined amounts. do.

Here, a cement admixture made of special anhydrite (
Hereinafter, simply referred to as high-strength admixture) means
As described in No. 2907, magnesium sulfate,
The main ingredients are gypsum or anhydrite obtained by firing one or more compounds selected from the group consisting of borax, zinc oxide, ammonium phosphate, zirconium nitrate, chromium oxide, hydrofluoric acid, calcium fluoride, and iron oxide. It is obtained by adding it to a natural or synthetic product and firing it at 400 to 1000°C. In other words, if conocrete made by blending an appropriate amount of this high-strength admixture with Portland cement is cured in normal pressure steam at any temperature below t o ``c, it will have a remarkable initial and long-term strength without high-temperature and high-pressure steam curing. It has been found that this high-strength admixture is used in an amount of 5 to 20% by mass, preferably 8 to 12% by mass based on the amount of cement, from the viewpoint of strength development.

Further, the cement expansion agent is effective in developing strength through a synergistic effect with the high-strength admixture, and various commercially available products with a proven track record can be used. Specifically, calcium sulfoaluminate-based cement expanding materials (for example, Nippon Cement Co., Ltd.'s product name "Asanojipcal", Denki Kagaku Kogyo Co., Ltd.'s product name "Denka C5AJ"), lime-based cement expanding materials (for example, Onoda Cement Co., Ltd.'s product name "Denka C5AJ"), Product name: “Onoda Expan”
) etc. are excellent. The amount of cement expansion material used is
Synergistic effect with high-strength admixture From the relationship between expansion amount and bending/compressive strength, it is appropriate to use 5 to 15% by mass of cement. In other words, if it is less than 5% by mass, it is difficult to expect an effect on adhesive strength, while if it is more than 15% by mass, the amount of expansion will be excessive, and the physical properties such as compressive strength will be greatly reduced, making it impossible to expect performance as high-strength concrete. It's for a reason.

In addition, water reducing agents are used to reduce the unit water content of concrete.
In particular, it is necessary to add so-called superplasticizers. The amount of water reducing agent added is 0.5 to cement.
~2.0 mass % is appropriate. That is, 0.5% by mass
This is because if it is less than that, the unit amount of water required to obtain a predetermined slump will increase significantly, and material separation will occur, making it impossible to reach the required performance in terms of strength etc. despite the addition of high-strength admixtures. In addition, if it exceeds 2.0% by mass, the manufactured concrete will become extremely viscous, making work such as pouring difficult, and at the same time causing material separation, resulting in the inability to obtain the required performance. It is. Note that the amount of water reducing agent added is more preferably 0.8 to 1.8% by mass.

Also, specifically as a commercial product.

For example, the product name "Mighty 150" manufactured by Kao Sekitoge Co., Ltd. is an excellent example.

Next, in the present invention, in order to prevent the occurrence of melting during centrifugal force molding and further suppress the elution of cement and admixtures into melting, the high-strength admixture has a specific particle size distribution. I try to do that. To explain this, high-strength admixtures added to cement require a certain level of specific surface area in order to maintain reactivity, but on the other hand, excessive specific surface area promotes separation during centrifugal molding. Encourage the occurrence of Toro. Therefore, the present inventor has developed a high-strength admixture that can minimize the generation of melting while maintaining appropriate reactivity, has a small amount of solid content in the melt, and can obtain the required high concrete strength. As a result of intensive research on the conditions that should be met, we found that the plain specific surface area of the high-strength admixture is 6000 to 8000 cm''/
It has been found that the necessary and sufficient condition is to simultaneously satisfy two conditions: the particle size is in the range of g, and the grain If, 2 p- or less, is in the range of 15 to 40 ν%. It was. In other words, by using a material having such a specific particle size distribution, problems such as the occurrence of inconvenient melting during centrifugal force molding can be avoided.

ttP3. In order to maintain reactivity with cement, this high-strength admixture preferably has a target specific gravity of 2.95, which is as close as possible to that of cement, to prevent separation of the two.

The uninvented manufacturing method is to apply high-strength admixtures, cement expansion agents, and water-reducing agents with specific particle size distributions to Portland cement. What is made by combining
Concrete obtained by mixing with the necessary aggregate and water is poured into steel pipes in the same manner as before, centrifugally formed, and then only subjected to atmospheric pressure steam curing to produce a product.

[Function J] According to the production and application method of the present invention, a high-strength admixture as described above is used as an admixture for Portland cement,
Moreover, since this concrete is mixed with the necessary cement expansion agent and water reducing agent in predetermined amounts and poured into the steel pipe, it is possible to cast the concrete into the steel pipe using only normal pressure steam curing after centrifugal force forming. It is possible to obtain concrete with performance comparable to that of pressure steam-cured and high-temperature, high-pressure M-air cured concrete. At the same time, the high strength admixture is
Since particles having a specific particle size distribution as described above are used, there is less formation of sludge during centrifugal force molding, and the elution of solid content into the sludge is also reduced.

[Example] Hereinafter, the manufacturing method of the present invention will be specifically explained with reference to Examples.

<Example 1> First, in order to confirm the separation prevention effect during centrifugal force forming of poured concrete by the method of the present invention, high strength admixtures with various particle size distributions were examined for The quantity and demolding strength were investigated. The results are shown in Table 82.

However, the test was conducted using the high strength admixture as the first
Make concrete with the mixture shown in the table, and
)・Constant! It is cast into a Ti pipe and molded by centrifugal force. Further, the atmospheric pressure brown curing conditions after molding were as follows: 4 hours at 20° C., heating rate of 20° C., and 3 hours at a maximum temperature of 70° C., followed by cooling in the curing tank.

Table 1 Cement: Ordinary Portland cement (specific gravity 3.18) Coarse aggregate: crushed stone (specific gravity 2.70) Aggregate material: sea sand (specific gravity 2.54) High performance water reducer: Mighty 150 (manufactured by Kao Soap Co., Ltd.) Margins below> Table 2 From the perspective of strength, a strong correlation with plane specific surface area is recognized, and as plane specific surface area increases, strength also increases. Since a strength of about 700 Kgf/C11' is normally required, a desirable plane specific surface area value is 600 Qctx'/g or more.

Next, looking at the amount of fatty tuna generated, when the amount of particles with a particle size of 2 pots or less exceeds 40% by mass, the amount of fatty tuna and the proportion of solid content in the fatty tuna rapidly increases. Since it is desirable to have fewer textures, the upper limit for particles with one particle size and two colors or less was set at 40% by mass.

Note that the upper limit of the plain specific surface area value and the lower limit of the particle size of 2 rivers or less were determined depending on the manufacturing characteristics. In other words, the plane specific surface area value is 8000 cm
'/g or more, it is difficult to reduce the amount to 15% by mass or less for particles with a particle size of 2 or more, and it is difficult to reduce the amount to less than 15% by mass for particles with a particle size of 2 or less.
If it is 0% by mass or less, the plane ratio table fl'ij ! A
is determined based on the fact that it is approximately 8000 cm2/g or less.

Next, the above-mentioned high-strength admixture (plain specific surface area near 410
cm/g, particle size of 2 square meters or less; Examples using 33% of purchase amount) are listed in the table below. Table 3 shows the mix of concrete, and Table 4 shows the amount and properties of torsion during centrifugal force forming, as well as the concrete compressive strength. Incidentally, the conditions for curing the moss are the same as those described above.

<Example 2> As shown in Table 5, concrete was produced with various formulations in which the amount of cement expansion agent was varied.

Each piece of concrete has a diameter of 200 mm and a length of 300 mm.
, cast in a 4.5 mm thick steel pipe and centrifugally formed 6
The steam curing conditions after molding were as follows: 20'04 hours in advance, a temperature increase rate of 20'0/hr, and a maximum temperature of 70°C for 3 hours, after which it was left to cool in the curing tank.

From then on, the temperature is 20°C until the specified material order! , air curing was performed at RH 60%.

Table 6 shows the measurements of slump and compressive strength. However, the compressive strength test was conducted on a concrete test piece taken out from the steel pipe on the 7th day of age.

Table 5 Note that in Table 1, the cement expansion materials No. 2 to 6 are "Atoge Nojipkal J," No. 7 "Denka C5AJ.

No. 8 is "Onoda Expan", and the cement is ordinary Portland cement h (Hishin 3.16), the coarse aggregate is crushed stone (specific gravity 2.70), and the fine aggregate is sea sand (specific gravity 2.54).
), the high-strength admixture is the Osaka Cement>+w trade name "Non-Crepe" (plain specific surface area: 7410 cm, particle size 2 and the following: 33 quality 7J-%, ratio 2.9
5).

Table 6 (Example 3) As shown in Table 7, the temperature of the cement expanding material is constant,
Concrete was produced with various formulations in which the amount of high-strength admixture was changed, and composite steel pipe concrete members were produced in the same manner as in Example 2 using each concrete.

The manufacturing conditions and air curing conditions for the specimen were the same as in Example 2.

Table 8 shows the measurements of slump, compressive strength and bond strength.

In addition, regarding the cement expansion materials in Table 7, Nos. 9 to 14 are the above-mentioned "Asani Jipcal J", Nos. 15 to 16 are the above-mentioned "Denka C5AJ", and the high-strength admixture is the above-mentioned "Non-Crepe". Table 8 (Example 4) Conc 1 note was manufactured using the No. 4 formulation shown in Table 5,
This was cast into a steel pipe (STK41), subjected to centrifugal force forming, and then subjected to atmospheric pressure steam curing to produce a steel pipe composite nozzle.

The test results for this steel pipe composite pile are shown in Table 9. In addition, the compressive strength test t± was carried out on concrete test pieces taken out from the steel pipes at 7 days old as in Example 2. It is something that

Table 9 [Effect of the invention]

Claims (1)

[Claims] Gypsum or anhydrous gypsum obtained by baking one or more compounds selected from the group consisting of magnesium sulfate, borax, zinc oxide, ammonium phosphate, zirconium nitrate, chromium oxide, hydrofluoric acid, calcium fluoride, and iron oxide. 400 to 10
Obtained by firing at 00℃, its plain specific surface area is 6000-8000cm^2/g, and the particle size is 2μ
A high-strength admixture containing a special anhydrite containing 15-40% by mass of the following is 5-20% by mass based on the amount of Portland cement, and a cement expansion agent is also 5-15% by mass.
A high-strength admixture characterized by pouring concrete containing 0.5 to 2.0 mass% of water reducing agent into a steel pipe, centrifugally forming it, and then curing it with atmospheric pressure steam. A method for manufacturing a centrifugally formed steel pipe composite concrete member using