JPS6159258B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a centrifugally reinforced concrete molded body, and more specifically, centrifugally reinforced concrete molding, which comprises centrifugally molding concrete to which molded anhydrite and monosaccharides and/or disaccharides have been added, followed by steam curing. It is related to the method of manufacturing the body. In the present invention, concrete means Portland cement paste, mortar, or concrete, and centrifugal reinforced concrete moldings refer to reinforced concrete products manufactured using centrifugal force such as piles, poles, and humid pipes. do. Conventionally, concrete made by adding molded anhydrite or a high-strength material containing molded anhydrite, or concrete made by further adding a high-performance water reducing agent to this concrete, is centrifugally formed and then steam-cured. It is known that a high-strength centrifugal reinforced concrete molded body having a demolding strength of about 800 Kgf/cm ² can be obtained. However, the concrete used in this manufacturing method has a significantly large slump loss, so
Due to poor workability in centrifugal force forming, such as elongation and drainage of concrete, even if concrete is placed in a formwork and centrifugally formed, the concrete does not pack well into the formwork and "stains" occur. , a phenomenon called "jyanka" may occur, or a weak layer may be formed at a depth of about 1 cm from the inner surface of the obtained reinforced concrete molding, where water cannot drain through. As a result, the strength of the material decreased and the characteristics of the high-strength material could not be fully demonstrated. As a means to eliminate these defects, it is possible to use concrete immediately after mixing, so that the slump loss of the concrete is not a problem, or to prevent slump from the beginning in anticipation of slump loss during use. One possibility is to mix large concrete. However, the former method is impossible due to the current manufacturing process, and the latter method conversely causes breathing of the material, which in turn increases the reduction in strength. The present inventors proposed a method different from these, that is, adding a small amount of monosaccharide and/or
The present inventors have also discovered that the slump loss of concrete can be significantly reduced by adding disaccharides, leading them to propose the present invention. That is, the present invention provides concrete made by adding molded anhydrite or inorganic powder mainly composed of molded anhydrite, or concrete made by further adding a high-performance water reducing agent to this concrete, after centrifugal molding, and then steam-forming. A method for producing a centrifugal reinforced concrete molded body, characterized in that during curing and manufacturing the molded body, 0.001 to 0.3% by weight of one or more monosaccharides or disaccharides is added to the Portland cement content of the concrete. be. In the present invention, the molded anhydrite used is, for example, as shown in Japanese Patent Application Laid-Open No. 53-49021, 100 g of a 0.05% by weight aqueous solution of Na ₂ HPO ₄ at a temperature of 20°C and 1 g of molded anhydrite are mixed together. When the aqueous solution is in contact with the SO ₄ ion concentration from 0.03 to
Type anhydrite with a concentration of 0.12% by weight, preferably 0.05 to 0.10% by weight is convenient. Specifically, typed anhydrite obtained by calcining dihydrate gypsum or gypsum by-product during the production of hydrofluoric acid is mixed with Blaine 3000. ~ ^10000cm2 /g
Anhydrous gypsum, which has been crushed to a certain degree, is used. Mold anhydrite may be used alone, or it may be mixed or co-fired with other inorganic substances, and the main component is moulded anhydrite, which contains about 50% by weight or more of moulded anhydrite. It may also be an inorganic powder. Other inorganic substances include silica flour, silicate clay, silicate opal, fly ash, siliceous fine powder such as clay, quicklime and/or 3CaO.
Examples include powders of 3Al ₂ O ₃ and CaSO ₄ minerals. A commercially available inorganic powder whose main component is molded anhydrite is Denka Kagaku Kogyo Co., Ltd. under the trade name "Denka".
CSA", Nippon Cement Co., Ltd.'s product name "Asano Gypcal" and other cement expansion agents; Denki Kagaku Kogyo Co., Ltd.'s product name "Denka Σ1000" and Nippon Cement Co., Ltd.'s product name "Asano Super Mix" and other high-strength cements. Examples include admixtures. When using a material containing free CaO, such as the former cement expansion material, in order to improve the development of high strength, add water to make a slurry rather than adding it as a powder. It is preferable to convert it into (OH) ₂ before adding it. The amount of molded anhydrite or inorganic powder mainly composed of molded anhydrite (hereinafter referred to as typed anhydrite) is 3 to 30% of the Portland cement content in concrete (hereinafter simply referred to as cement content).
In particular, when aiming for high strength, CaSO ₄ is preferably 3 to 10% by weight based on the cement content, and when aiming for even higher strength and expansion, CaSO ₄ is added to cement. 10-20 against
Weight percent is preferred. Further, the concrete according to the present invention may contain a high-performance water reducing agent (hereinafter simply referred to as a water reducing agent). As a specific example of a water reducing agent, the main component is a salt of a formalin condensate of naphthalene sulfonic acid. For example, Kao Soap Co., Ltd.'s product names "Mighty 100" and "Mighty 150", Takemoto Yushi Co., Ltd.'s product name "Pole Huain", Sanyo Kokusaku Pulp Co., Ltd.'s product name "Sunflow PS", "San Flow PSP100'', those whose main component is a water-soluble polymer condensed with trimethylolmelamine monosulfonate, such as Showa Denko Co., Ltd.'s product name ``Melment F-10'', and highly condensed triazine compounds. The main ingredient is
For example, the product name "NL-4000" manufactured by Pozoris Bussan Co., Ltd. can be mentioned. The amount of water reducing agent used is usually about 3% by weight or less based on the cement content in concrete. The main feature of the present invention is that one or more monosaccharides or disaccharides are added in a minute amount of 0.001 to 0.3% by weight to the cement content of such concrete, thereby improving the excellent high strength development properties of conventional concrete. The object of the present invention is to significantly reduce the decrease in slump loss without impairing the slump loss. Specific examples of monosaccharides include arabinose, xylose, ribose, glucose, mannose, galactose, and fructose, and specific examples of disaccharides include maltose, cellobiose, trehalose, gentiobiose, and isobiose. Examples include maltose, lactose and sucrose, and one or more of these are added in an amount of 0.001 to 0.3% by weight based on the cement content in concrete. These saccharides have the effect of suppressing the slump loss of concrete, and in particular, in centrifugal force forming, they improve the elongation and drainage of concrete, and ensure sufficient compaction of concrete, thereby preventing phenomena such as "janka". doesn't happen. In addition, in terms of strength, not only centrifugal force forming but also vibration compaction forming does not have an adverse effect. If the amount of sugar added is less than 0.001% by weight, the effect of suppressing slump loss will be small, and if it exceeds 0.3% by weight, strength development will deteriorate. In the present invention, the most preferable saccharide is a disaccharide, and the most preferable addition amount is 0.005 to 0.005 to the cement content in concrete.
It is 0.1% by weight. The timing of adding sugars is not particularly limited, but it is preferably at the time of mixing concrete. In the present invention, the concrete prepared in this manner is centrifugally formed by a conventional method, and then steam-cured after sufficient pre-curing if necessary. Preferably, the heating is carried out at a temperature of 100°C for 2 hours or more. As explained above, the present invention involves centrifugally molding concrete containing molded anhydrite and minute amounts of monosaccharides and/or disaccharides, or concrete containing a water reducing agent, and then According to the present invention, even if concrete is used for about 30 minutes after being mixed, it is equivalent to molded concrete immediately after being mixed. The effect is that a high-strength reinforced concrete product that does not cause "jumpiness" etc. can be obtained. The present invention will be further explained below with reference to Examples. Example 1 Ordinary Portland cement as cement,
Tests were conducted using the high-strength cement admixture ``Denka Σ1000'' as a molded anhydrite and ``Mighty 150'' as a water reducing agent, with the concrete formulation shown in Table 1 varying the type and amount of sugar added. The specimens are a centrifugal force molded specimen (specimen) with a diameter of 20 cm x height 30 cm x thickness and a 10 cm diameter x height
A 20 cm vibratory compaction specimen (test specimen) was used; the former was molded 30 minutes after kneading, and the latter was molded immediately after kneading, taking into consideration the working time of the actual manufacturing process. Concrete slump and steam curing (65℃)
Table 3 shows the average value of the three samples measured for the 24-hour demolding compressive strength after 4 hours. Table 2 shows the chemical composition of the commercially available high-strength cement admixture "Denka Σ1000" used as molded anhydrite. Note that the amounts of sugars added shown in Table 3 are expressed as % by weight relative to the cement content.

【table】

【table】

[Table] In addition, when concrete without added sugars was centrifugally formed immediately after mixing and steam-cured, the compressive strength was 820 Kgf/cm ² . Example 2 The amount of cane sugar added was 0.05% by weight based on the cement, the product name "NL-4000" and the product name "Melment F-10" were used as water reducing agents, and the fineness was 4500 cm ² /g.
Using anhydrous gypsum alone, mix concrete with the composition shown in Table 4 to form a 300mm diameter x 60mm thick concrete.
A single pile with a length of 1 m, 10 main reinforcements of 13 mmφ, and an effective prestress of 160 Kgf/cm ² was formed by centrifugal force. The centrifugal force moldability at that time, the 24-hour demolding compressive strength after steam curing, and the compressive strength of the centrifugally molded specimen were measured in the same manner as in Example 1. These conditions and results are shown in Table 5. The steam curing conditions were held at 75℃ for 4 hours,
After that, it was allowed to cool naturally. Furthermore, the measured compressive strength values in Table 5 indicate the average value of two samples. In addition, the same materials as in Example 1 were used except for the water reducing agent and molded anhydrite.

【table】

[Table] Example 3 Concrete with the formulation shown in Table 7 using the registered trademark "Mighty 150" as a water reducing agent, the product name "Asano Super Mikkus" or the product name "Asano Dipcal" as a molded anhydrite, and sucrose as a sugar. using, outer diameter 1276 mm x pipe length 2430 mm x pipe thickness 88 mm, longitudinal reinforcing bar ratio 0.14%, spiral direction reinforcing bar ratio 0.25%.
A centrifugal force molded specimen measuring 20 cm in diameter, 30 cm in length, and 4 cm in thickness was molded. These were demolded after 24 hours of steam curing (temperature 70°C x 4 hours), and were tested after being cured with water for 7 days. The chemical components of type anhydrite are shown in Table 6, and the test results are shown in Table 8.

【table】

[Table] When adding slurry, type anhydrite was dispersed in a portion of the kneading water to convert at least a portion of f-CaO into Ca(OH) ₂ before use.

[Table] This improvement in concrete strength is remarkable in centrifugal force forming, but it is also effective in vibration compaction forming, and is effective for manufacturing vibration compacted concrete products such as PC sleepers, sheet piles, box culverts, and bridges. be.

Claims (1)

[Claims] 1 Concrete made by adding type anhydrite or inorganic powder mainly composed of type anhydrite, or concrete made by adding a high-performance water reducing agent to this concrete, is centrifugally molded and then steam-cured to produce a molded body. 0.001 to 0.001 to the Portland cement content of the concrete.
A method for producing a centrifugal reinforced concrete molded body, characterized by adding 0.3% by weight of one or more monosaccharides or disaccharides.