JPH042535B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention aims to eliminate various drawbacks that occur when centrifugal force forming aid and centrifugal force forming method using the same, specifically, centrifugal force forming of concrete to which a high performance water reducing agent has been added. Regarding centrifugal force molding method. Conventionally, concrete with a relatively large amount of high-performance water reducer added and a low water-to-cement ratio was centrifugally formed to produce concrete piles, steel pipe composite piles, propulsion fume pipes, CP type 1 pipes, and CP2 pipes that require high strength. Manufactures seed tubes (huyum tubes), etc. However, concrete with a low water-to-cement ratio that has been added with a high-performance water reducer has high viscosity and a significantly large slump loss, resulting in poor elongation and water drainage during centrifugal force forming, resulting in jitters or 1 cm below the inner surface. Water may not be able to drain through to a certain depth and a weak layer may be formed, resulting in a decrease in strength. For example, the production of concrete piles, which are typical centrifugally formed products that use a lot of high-performance water reducing agents, involves mixing the concrete, pouring it into formwork, assembling the formwork, introducing prestress, and centrifugal forming. This process takes 10 to 20 minutes, and if there are any problems, it may take up to 30 minutes. When observing the inner surface of the pile after centrifugal force forming, the internal state of each pile is different. That is, the inner surface becomes hard and the watery slag separates. The thick paste-like slag separates, and a soft paste layer about 1 cm thick that you can insert your finger into is formed on its inner surface. The slag does not separate, but a 1cm thick layer of paste is formed on the inside that is soft enough to put your finger in, and it ripples or sag.
Jiyanka generates it. These phenomena occur and greatly affect the quality of the pile, especially its strength. Currently, as a solution to these problems, the method of increasing the slump during concrete mixing to a greater extent than necessary in anticipation of slump loss is commonly practiced (especially in the case of pumping), but usually, the slump during centrifugal forming is This often results in increased material separation. Furthermore, even if material separation could be prevented by applying rotation, the inner surface would sag after centrifugal force forming due to poor compaction and high viscosity of concrete, which would limit the amount of high performance water reducing agent used in the manufacture of humid pipes. has been added. Furthermore, recently, with the aim of further increasing the strength of centrifugal force-formed bodies, ettringite-forming systems have been developed that are used in combination with gypsum, gypsum and alum, aluminum sulfate, etc., in concrete to which high-performance water reducing agents have been added. High-strength admixtures or cement expansion agents are mixed in, but when concrete mixed with these is centrifugally molded, material separation occurs, and a larger amount must be mixed in than when centrifugal molding is not performed. There is a drawback. As a result of various studies to solve these drawbacks, the inventor of the present invention found that by using specific oxycarboxylic acids to prevent slump drop and reduce viscosity,
The present invention was completed based on the knowledge that the slump value and viscosity state, which greatly affect the state of the inner surface after centrifugal force molding, can be adjusted and the above-mentioned drawbacks can be overcome. That is, the present invention provides a high performance water reducing agent, citric acid,
It is a centrifugal forming aid whose main component is one or more oxycarboxylic acids selected from the group consisting of tartaric acid, malic acid, or their salts, and is added to 100 parts by weight of cement for concrete containing a high performance water reducer. On the other hand, this is a centrifugal force molding method in which 0.005 to 0.5 parts by weight of the oxycarboxylic acids are used in combination and centrifugal force molding is performed. The present invention will be explained in more detail below. The high-performance water reducing agent referred to in the present invention is broadly classified into polyalkylaryl sulfonate type and high condensate type of triazine derivative based on the chemical structural formula of its main component. Commercially available products include Kao Soap Co., Ltd.'s "Mighty 100" and "Mighty 150,"
“Mighty HS”, Takemoto Yushi Co., Ltd. “Pole Huain”
510N'', Sanyo Kokusaku Pulp Co., Ltd.'s ``Sunflow PS'', Pozolis Bussan Co., Ltd.'s ``NL-1400'' and ``NL-4000'', Showa Denko Co., Ltd.'s ``Melment'', etc.
It is a cement dispersant that exhibits high dispersion power with little side effects such as excessive setting delay or air entrainment even when added in a relatively large amount. Usually, these are active ingredients and are added to cement in an amount of about 0.3 to 2% by weight. The oxycarboxylic acids referred to in the present invention are one or more selected from the group consisting of citric acid, tartaric acid, malic acid, or salts thereof. Salts of oxycarboxylic acids include sodium, potassium, lithium, zinc, lead, ferric iron, copper, strontium, citric acid, tartaric acid and malic acid.
Examples include magnesium and calcium. Among these, citric acid, tartaric acid and their sodium and potassium salts are preferred, as they have good performance, are economical, and are non-toxic. Most preferred are citric acid and its sodium and potassium salts. The reason why the amount of oxycarboxylic acids added was limited to 0.005 to 0.5% by weight based on the cement content of concrete is that 0.005
If it is less than % by weight, the effect of preventing slump loss and reducing viscosity is small, so the initial purpose cannot be improved. Furthermore, if the amount exceeds 0.5% by weight, a decrease in strength is observed even if steam curing is performed. The preferred range is 0.01-0.2% by weight. In addition, in order to promote the above-mentioned action of oxycarboxylic acids,
It is preferred to add at most 1.0% by weight of sodium, potassium and lithium carbonates and bicarbonates to the cement. As the cement for preparing concrete, any cement such as ordinary, early-strength, ultra-early-strength, white Portland cement, fly-a-thonyu cement, blast-furnace cement, etc. can be used. As explained above, the present invention enables centrifugal force forming of concrete to which a high performance water reducing agent has been added.
A reduced amount of oxycarboxylic acids is added. According to the present invention, the slump of concrete can be reduced or prevented, and the viscosity can be made small, so water drainage during centrifugal force molding is improved, and there is no jitter or material separation, compared to conventional various types in which a high-performance water reducing agent is added. This has the effect of eliminating the drawbacks of molding, and making it possible to produce high-strength molded bodies. The present invention also exhibits particularly good effects on centrifugal force forming of fiber concrete mixed with steel fibers or glass fibers, and when used in combination with commercially available high-strength admixtures, plasters, cement expansion agents, etc. High strength and ultra-high bending strength can be obtained, making it possible to manufacture pipes without reinforcing bars, poles, propulsion pipes, and humid pipes with high external pressure strength. Hereinafter, the present invention will be explained in more detail with reference to examples. Example 1 A test was conducted by changing the type and amount of oxycarboxylic acids added to the concrete formulation shown in Table 1. The centrifugal force specimen has a diameter (outer diameter) of 20 cm and a length of 30 cm.
cm, 4 cm thick, and centrifugal force forming was performed at an outside temperature of 12 degrees Celsius after concrete was mixed.
After 4 hours of pre-curing, steam curing (75℃)
x 4 hours), and the demolding strength was measured 24 hours after cooling naturally. In addition, the water-cement ratio of the specimen was calculated from the slump measurements immediately after kneading and 30 minutes later, and the amount of water dehydrated by centrifugal force, and the state of compaction by centrifugal force was also observed. The results are shown in Table 2.

[Table] The high-performance water reducing agent is polyalkylaryl sulfonate-based product name "Mighty 150" manufactured by Kao Soap Co., Ltd.
was used, and changes in slump due to the addition of oxycarboxylic acids were made by finely adjusting the unit water amount. Oxycarboxylic acids were added to the cement in portions and dissolved in mixing water, and the amount of concrete charged into the formwork was kept constant at 15 kg.

【table】

[Table] Example 2 In Experiment No. 3, a test similar to Example 1 was conducted in the case where an alkali metal carbonate was further added to the cement weight. The results are shown in Table 3.

[Table] (Note) The observation results of the centrifugal compaction state were all good.
Example 3 In the concrete formulation shown in Table 1, 1.2% by weight of a high-performance water reducing agent was added to the cement instead of ``Melment F-10'' manufactured by Showa Denko Co., Ltd., which is a high condensate based triazine derivative. Water-cement ratio 31%,
The concrete mix with a slump of 10±2cm was redesigned. Various amounts of sodium citrate were added to this concrete, and the maximum value of the lateral spread of the concrete at the time of slump measurement was measured in order to determine the degree of viscosity of the concrete. The results are shown in Table 4. Highly viscous concrete has the ability to roll under its own weight, and its lateral spread is larger than its slump value.

【table】

[Table] Yes.
Example 4 Add various types of gypsum or "Asano Super Mix" (trade name of Nippon Cement Co., Ltd.) whose main ingredient is gypsum as a high-strength admixture to the concrete mixture of Example 3.
10% by weight of cement, and cement expansion agent "Onoda Expan" (trade name of Onoda Cement Co., Ltd.)
Added 10% by weight of steel fibers (0.3 mm in diameter,
30 mm in length) was mixed by replacing 3% of the cement volume with sand. A test similar to that in Example 1 was conducted using this concrete. The result is the fifth
Shown in the table.

[Table] In Experiment No. 40, a comparative example, centrifugal force molding appeared to be good, but there was a soft paste part separated to a depth of about 1 cm from the inner surface, and a tendency for separation was observed. On the other hand, in the case of the example of the present invention, there is no separation and the strength is extremely high. This is considered to be due to improved water drainage due to a decrease in concrete viscosity, rather than the effect of preventing slump loss. Experiment No. 39, a comparative example, is
The measured strength is extremely low due to poor elongation of the concrete, inconsistent wall thickness, and jitters at the edges. Corresponding experiments Nos. 43 and 44 of the present invention show that distant forming is good and that the properties of high-strength admixtures, cement expansion materials, and steel fibers can be brought out more rationally.

Claims (1)

[Claims] 1. A centrifugal force forming aid whose main components are a high performance water reducing agent and one or more oxycarboxylic acids selected from the group consisting of citric acid, tartaric acid, malic acid, or their salts. . 2. Concrete cement containing high performance water reducer
Characterized by centrifugal force molding using 0.005 to 0.5 parts by weight of one or more oxycarboxylic acids selected from the group consisting of citric acid, tartaric acid, malic acid, or their salts per 100 parts by weight. Centrifugal force molding method.