JPS61104804A - Manufacture of concrete - 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] [Field of Industrial Application] The present invention relates to a method for centrifugal molding of mortar or concrete, and more specifically, a method for centrifugal molding of concrete secondary products such as holes, balls, and humid pipes. This relates to a centrifugal forming method that prevents the generation of slag, which is an industrial waste generated during forming, and improves the physical properties of concrete.
[Conventional technology and problems] Conventionally, secondary concrete products such as concrete piles, balls, and humid pipes are produced by pouring unhardened concrete into a formwork and then rotating the formwork at high speed. The resulting centrifugal force is used to densely fill concrete with concrete to produce hollow cylindrical products. Centrifugal compaction uses its centrifugal action to squeeze out water in concrete and agglomerate fine particles such as cement particles.

As a result, the unhardened concrete loses its fluidity and a hollow cylindrical product is manufactured. However, along with the water that is pumped out, light particles in the concrete and cement paste are also pumped out. This suspension is generally an industrial waste called slag, and its disposal costs a lot of money.

A known method for preventing the generation of slag, which is industrial waste, is to add a flocculant to concrete (Japanese Patent Publication No. 55-20525). However, this method also has the problem that the workability of concrete that does not harden decreases, making it extremely difficult to handle the concrete. A method of adding a coagulation accelerator during centrifugal molding is also known (Japanese Patent Application Laid-Open No. 1611-1989).
Publication No. 08). However, this method involves the risk of adding a setting accelerator into the rotating body, and the setting accelerator is added to forms such as piles and poles whose length is more than 10 meters. It is extremely difficult to do so, and it has not yet been put to practical use.

[Means for solving problems]

Therefore, as a result of intensive research to solve the above drawbacks, the present inventors have succeeded in preventing the generation of slag during centrifugal force forming by an easy method that does not increase the risk or process, and further improve the physical properties of concrete. We have discovered an improved centrifugal force forming method.

The present invention provides a method for producing concrete, which is characterized in that a setting accelerator is added to concrete during centrifugal forming, from the end of mixing to the start of centrifugal compaction. More specifically, the present invention is characterized in that a cement setting accelerator is quantitatively added to the concrete at the same time that unhardened concrete is charged into a centrifugal molding form using a pump or a packet. This is a centrifugal molding method.

The concrete used in the present invention preferably contains a β-naphthalene sulfonic acid formaldehyde condensate and has a water-cement ratio of 40% or less. More preferably, the content of β-naphthalene sulfonic acid formalin round metal is 0.0.
Water-cement ratio is 35% with 5-0.5 weight percent
These are as follows. In order to prevent the generation of slag, it is important to keep the water-cement ratio to a low value of 40% or less.

The setting accelerators used in the present invention include aluminum sulfate, polyaluminum chloride, aluminium-branched soda, ferric sulfate, ferrous sulfate, ferric chloride, zinc chloride, sodium carbonate, aluminum hydroxide, and activated silicic acid. , sodium alginate, CMO-Na, water-soluble aniline resin hydrochloride, polythiourea acetate, polyethyleneimine, polyvinylbenzyltrimethylammonium chloride, starch, water-soluble urea resin, gelatin, sodium polyacrylate, maleic acid copolymer salt , polyacrylamide partial hydrolyzate salt.

Examples include one or more selected from polyvinylpyridine hydrochloride, vinylpyridine/copolymer salt, polyacrylamide, polyoxyethylene, polyoxypropylene, and silicate, and may be added in liquid, powder, or atomized form. Ru. The amount added is 0.0001 to the prepared concrete.
~1 weight percent is preferred. This setting accelerator has the ability to physically aggregate or chemically coagulate fine particles in concrete, which are the main component of slag, and is effective in preventing the generation of slag. In particular, a setting accelerator made of polyacrylamide or a copolymer thereof and a silicate has an extremely remarkable effect of preventing slag formation due to the synergistic effect of physical aggregation and chemical coagulation. The blending ratio is 95:5~
5 to 95 is desirable. This setting accelerator may be added as a mixture of two components or may be added separately.
Examples include copolymers with meth)acrylic acid, copolymers with acrylamide and dimethylaminoethyl methacrylate, and copolymers with acrylamide and dimethylaminoethyl methacrylate methyl chloride.

In the present invention, as mentioned above, the method of adding the setting accelerator is characteristic and extremely important. If a setting accelerator is added to concrete at the time of crosstalk, the workability of the concrete will decrease, making the concrete extremely difficult to handle.

Further, in some cases, the pump may be blocked or centrifugal compaction may be difficult, which is extremely inconvenient. On the other hand, in the method of adding a setting accelerator during centrifugal molding, it is an extremely dangerous process to add the setting accelerator into one rotating body, and the length of the star frame is long enough, such as in piles and balls. It is virtually impossible to uniformly add setting accelerator over a length of several meters.

Furthermore, during centrifugal compaction or after centrifugal compaction, the rotation is temporarily stopped and a setting accelerator is added.

One possible method is to rotate the formwork again to prevent slag. Although this method is extremely desirable in terms of preventing slag, it is an extremely complicated process in which rotation is temporarily interrupted, a setting accelerator is added, and then rotation is restarted, which greatly reduces productivity. It has its drawbacks.

In contrast, in the method of the present invention, when concrete is charged into a centrifugal forming form using a concrete pump or packet, a setting accelerator is added at the tip of the cylinder at a rate corresponding to the concrete feeding speed. There is no reduction in the workability of concrete, and there is no increase in the number of steps due to the addition of a setting accelerator.

Furthermore, surprisingly, adding a setting accelerator immediately before centrifugal forming promotes dehydration, resulting in a low water-cement ratio in the concrete after centrifugal forming, and therefore a low hardened product. The strength becomes extremely large. Furthermore, the dehydrated water generated in the present invention is clear and completely free of slag components, making it possible to significantly reduce the cost required for slag treatment.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in detail with reference to Examples, but the present invention is not limited to these Examples.

1. Concrete materials and blended cement: Onohi Cement Specific gravity: 3.16 Fine aggregate: Kinoyo Ubukawa sand Specific gravity: 2.56 Coarse aggregate: Crushed stone from Takarazuka Specific gravity: 2.60 β-naphthalene sulfonic acid formalin condensate: Kao Mighty 150, manufactured by Soap Co., Ltd. Blend 2 Set accelerator polyacrylamide: AP-, manufactured by Diafloc Co., Ltd.
Sodium silicate 0.3% aqueous solution of 410 Sodium silicate No. 5 No. 3 manufactured by Nippon Ichitatsu Co., Ltd. Centrifugal force molding Fill a centrifugal molding frame (200φx goo) with 16 to 4 concrete and rotate at low speed C3G/4 minutes) , medium speed rotation (12G/2 minutes), and high speed rotation (55076 minutes).

4. Addition method of setting accelerator To the concrete, 1 weight percent of 0.3% aqueous solution of polyacrylamide, sodium silicate, and a 1:1 blend of 0.3% aqueous solution of polyacrylamide and sodium silicate were added.

The following three methods were used for addition.

Method A: Added when concrete is mixed.

Method: Spray into the mold using a spray gun equipped with an air compressor during centrifugal molding at medium speed.

Method C (method of the present invention): Concrete is poured into the formwork using a bucket, and at the same time, it is sprinkled onto the concrete surface using a metering pump.

5. Measurement of results Collect the slag generated after centrifugal molding, separate it into water (dehydrated amount) and solid content (slag amount) by suction filtration, and measure the weight of each to determine the dehydration effect and slag. The effect of preventing generation was measured by centrifugation; concrete specimen #:l: demolded after steam curing, and the compressive strength of the material after 1 day of age was measured. The experimental results are shown in Table 1.

According to the actual results in Table 1, in Method A, in which a setting accelerator is added at the time of mixing concrete, the slump value of the mixed concrete decreases and the workability decreases. Method B, in which a setting accelerator is added during centrifugal molding, has the disadvantage that the amount of water removed is small and the compressive strength is therefore reduced.

Although the effect of reducing slag can be expected, the amount of water removed is the same as additive-free concrete, and no increase in strength is observed.

On the other hand, in method C of the present invention, in which a setting accelerator is sprayed in parallel with concrete preparation, the effect of reducing slag is remarkable, the dewatering property is also good, and an increase in compressive strength is observed.

Claims (1)

[Scope of Claims] 1. A method for producing concrete, which comprises adding a setting accelerator to concrete between the end of mixing and the start of centrifugal compaction during centrifugal forming of concrete. 2. The concrete contains β-naphthalene sulfonic acid formaldehyde condensate and the water-cement ratio is 40% or less, and the method of adding the setting accelerator is not to charge the concrete into a centrifugal molding form using a pump or a packet. 2. The method according to claim 1, wherein a setting accelerator is added in parallel in the form of a liquid, powder or spray. 3 The setting accelerator is aluminum sulfate, polyaluminum chloride, sodium aluminate, ferric sulfate, ferrous sulfate,
Ferric chloride, zinc chloride, sodium carbonate, aluminum hydroxide, activated silicic acid, sodium alginate, CMC-
Na, water-soluble aniline resin hydrochloride, polythiourea acetate, polyethyleneimine, polyvinylbenzyltrimethylammonium chloride, starch, water-soluble urea resin,
Selected from gelatin, sodium polyacrylate, maleic acid copolymer salt, polyacrylamide partial hydrolyzate salt, polyvinylpyridine hydrochloride, vinylpyridine copolymer salt, polyacrylamide, polyoxyethylene, polyoxypropylene and silicate The method for producing concrete according to claim 1 or 2, characterized in that one or more types of concrete are used. 4. The method for producing concrete according to claim 3, wherein the setting accelerator comprises polyacrylamide or a copolymer thereof and a silicate.