JPH0451504B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a method for manufacturing a hume tube with high external pressure strength. Conventionally, Huum pipes are classified into Class 1 pipes, Class 2 pipes (JIS-A5303), and Class 3 pipes (designated by the Huum Pipe Association, substandard products) based on the magnitude of external pressure strength. For class 2 or higher grade humid pipes, the bending strength of concrete is usually increased by introducing chemical prestressing using expanded cement or chemical pressing to increase the external pressure strength, but this is not advantageous because of the problem of expansion cracks. There is a limit to the strength that can be achieved. Therefore, at present, it is impossible to manufacture type 3 pipes with stable quality, and it is not possible to completely prevent expansion cracks in type 2 pipes. The external pressure strength of a humid pipe increases as the bending strength of concrete increases, so it is possible to reduce the water/cement ratio by adding a large amount of a high-performance water reducer, or to add a high-strength mixture containing gypsum as the main component. It is also possible to add materials to increase the strength. However, the compressive strength is 800~1000Kgf/
Even if the bending strength is increased to ^cm2 , the bending strength does not increase that much, at most 70 to 90℃f/ ^cm2 , and concrete added with a high-performance water reducer has a high viscosity and a large slump loss, so the centrifugal force It has the disadvantage of poor moldability. For example, due to poor drainage, a layer of water forms between the concrete layer and the mortar layer that separates on the inner surface of the concrete layer. Because it is so-called jittery, or has poor tightness and stickiness, the inner surface will sag or ripple when the centrifugal force stops. Furthermore, the slump loss becomes extremely rapid depending on the temperature of the concrete and the mixing state, making it impossible to fill the pipe with sufficient concrete to the ends and making it impossible to finish the inner surface with a smooth finish. For this reason, even if a bending strength of around 70 to 90 Kgf/cm ² is obtained with the vibration-packed test piece, the bending strength of the centrifugally formed tube itself decreases, making it impossible to manufacture Huyum tubes of type 2 or higher. However, in order to manufacture type 2 or type 3 pipes, the bending strength of the centrifugally formed pipes must be 80 kg each.
It is necessary to constantly express f/cm ² or more or 100 Kgf/cm ² or more. On the other hand, conventional steam curing methods for hume pipes are stipulated in JISA-5303 as a maximum of 65℃, but in the case of Class 2 or Class 3 pipes using expanded cement,
If the expansion reaction is not completely carried out during steam curing, expansion failure will occur later, so in reality, curing is carried out at a high temperature of around 75℃, and apart from expansion cracks, cracks due to temperature stress are a problem. The present invention provides a method for manufacturing a hume tube with high external pressure strength, which solves the above-mentioned conventional drawbacks and problems. That is, in the present invention, citric acid,
One or more types selected from tartaric acid, malic acid, and their salts (hereinafter referred to as oxycarboxylic acids, etc.) from 0.01 to
Hume tube with high external pressure strength, characterized by adding 0.5% by weight, or at most 15% by weight of gypsum (calculated as CaSO ₄ ), and after centrifugal force molding, heat retention or steam curing at a temperature of 60°C or less. This is a manufacturing method. The present invention will be explained in detail below. The high-performance water reducing agent used in the present invention is a water reducing agent that exhibits high dispersion power with little side effects such as over-delayed setting or air entrainment even when added in a relatively large amount. Products classified as triazine derivative high condensates are commercially available, and representative examples of each are Kao Soap Co., Ltd.'s product name "Mighty 150" and Showa Denko Co., Ltd.'s product name "Melment F-10". It is. These superplasticizers are
In order to obtain external pressure strength equal to or higher than that of Class 2 pipes, approximately 0.4 to 2.0% by weight of solids is added to the cement content in concrete with a unit cement amount of 400 to 500 kg/ ^m3 , and water and cement are added. Adjustments are made so that the ratio is 40% or less. Oxycarboxylic acids used in the present invention include citric acid, tartaric acid, malic acid, and sodium, potassium, lithium, calcium,
Magnesium, strontium, zinc, copper, lead,
One or more salts selected from salts such as ferric iron are used. The effects of its addition include improved centrifugal formability and a synergistic increase in bending strength when used in combination with plaster. Oxycarboxylic acid, etc. is 0.01 to 0.01 to the cement content in concrete.
If 0.5% by weight is added, and if it is less than 0.01% by weight, the improvement effect on centrifugal formability and bending strength will be small.
Moreover, if it exceeds 0.5% by weight, the development of bending strength will deteriorate. The preferred amount added is 0.1 to 0.3% by weight. Plasters include molded and molded anhydrite, dihydrate gypsum,
Commercially available high-strength admixtures containing various types of gypsum hemihydrate as well as molded anhydrite as a main component, such as Denka Kagaku Kogyo Co., Ltd.'s product name "Denka 1000", Nippon Cement
Product name: Asano Super Mix Co., Ltd., Showa Kogyo Co., Ltd.
Co., Ltd.'s product name "Daimics" may be used.Furthermore, as shown in Japanese Patent Application Laid-Open No. 123596/1983, various types of compounds of one or more metals or non-metals belonging to Groups 1 to 3 of the periodic table are used. It may be a special anhydrite (type anhydrite) obtained by adding gypsum or a compound whose main component is gypsum or a material that becomes anhydrite when fired and firing. Gypsum is at most CaSO ₄ equivalent.
Added to 15% by weight of cement. If the amount added is larger than this, the effect of increasing bending strength is small or not at all. Normally, gypsum hemihydrate and type anhydrite have a fast dissolution rate, and when added to cement in large quantities, they exhibit a remarkable rapid setting effect. No results will be shown. In addition, the effect of increasing bending strength due to the form and fineness of gypsum is almost the same on the 14th, which is the deadline for shipping Huyum pipes. In the present invention, the relationship between the amount of gypsum added and the curing temperature has the greatest effect on the increase in bending strength.
That is, during thermal curing at 35°C or lower, the bending strength peaks at around 5% by weight, at around 45°C it reaches around 8% by weight, and at around 60°C it reaches around 12% by weight. The absolute value of the bending strength is in the following order: 5% by weight below 35℃ > 8% by weight at about 45℃ > 12% by weight at about 60℃.At temperatures above 60℃, the compressive strength becomes even higher, but the bending strength The absolute value decreases rapidly and 2
It becomes impossible to manufacture a hume tube with external pressure strength greater than that of a seed tube. Since oxycarboxylic acids have a strong setting retarding effect, a curing temperature of 15°C or higher is required in order to demold the pipe the next day at the latest after making the pipe, but it is also possible to improve the demolding strength by increasing the demolding strength. In order to advance the timing and increase the bending strength, aluminum sulfate or alum may be added in an amount of at most 3% by weight based on the cement. As described above, the present invention uses oxycarboxylic acid, etc. and gypsum in combination with concrete to which a high-performance water reducing agent has been added, and after centrifugal force molding, heat insulating or steam curing at a temperature of 60° C. or less is used to manufacture humid pipes. It is something. Normally, greater compressive strength and corresponding bending strength can be obtained by adding a large amount of gypsum and raising the curing temperature, but in the present invention, the curing temperature is lowered and the curing temperature is increased. The feature is that high bending strength is achieved by reducing the amount of addition. Since the concrete used in the present invention has excellent centrifugal force formability and exhibits high bending strength without exhibiting expansion, it is possible to manufacture humid pipes with high external pressure strength. Furthermore, the present invention can be applied to box culverts that require bending strength for vibration forming, and although condensation hardening is delayed, the curing temperature does not need to be high, so physical thermal expansion is reduced. It is possible to manufacture thinner and thinner products. The present invention will be explained below with reference to Examples. Example 1 To the concrete mixture shown in Table 1, type anhydrous gypsum (powderity 3800 cm ² /g) generated by hydrofluoric acid was added in place of sand and added in an amount of 5% by weight based on the cement, and the type and addition of oxycarboxylic acid, etc. Tests were conducted with different amounts. The centrifugal force specimen has an outer diameter of 20 cm, a length of 30 cm, and a thickness of 4
After centrifugal molding, the temperature was raised for 2 hours, held at 35℃ for 6 hours, and then allowed to cool naturally.
The next day, after demolding, the mold was cured with water for 14 days, the external pressure load was measured, and the bending strength was calculated. Formability due to centrifugal force was determined by measuring the depth of the soft mortar separation layer on the inner surface and visually observing the presence or absence of sag, undulation, and floating stones. For reference, 10×
A 10 x 40 cm vibratory packed specimen was taken, and its bending strength was measured 14 days after curing in the same manner. These results are shown in Table 2. Experiment Nos. 1 and 8 are comparative examples, and the others are examples of the present invention.

[Table] The high-performance water reducing agent used was Kao Soap Co., Ltd.'s product name "Mighty 150," which is based on polyalkylaryl sulfonate, and oxycarboxylic acids were added to the cement by dissolving it in water. . Chemical analysis showed that SO ₃ in ordinary Portland cement was 1.8%, and the concrete was mixed and molded in a thermostatic chamber at 20°C ± 1°C. Centrifugal force molding is performed at low speed (5.6G) for 2 minutes, medium speed (17G) for 2 minutes,
High speed (35G) 4 minutes.

【table】

[Table] Example 2 Nominal diameter using concrete of Experiment Nos. 1, 2, 5, and 7 (each experiment No. is 22 to 25)
A 1000 mm real pipe was prepared using the same curing method as in Example 1, and an external pressure test was conducted when the material was 14 days old. The wall thickness of the tube is
The reinforcing steel ratio for straight bars was 0.26% for the A-type pipe with a length of 82 mm and 2430 mm, and the double spiral bars were 1.49%. On the other hand, using a centrifugal force specimen having the same dimensions as in Example 1, the bending strength and compressive strength under external pressure load were determined. These results are shown in Table 3. Experiment No. 22 is a comparative example, and the others are examples.

[Table] Example 3 The same tests as in Example 1 were conducted on centrifugal force specimens by changing the type and amount of gypsum added in the concrete formulation shown in Table 1, and changing the curing conditions after molding. . In addition, 0.15% by weight of citric acid was uniformly blended with the cement as oxycarboxylic acid. The results are shown in Table 4. Experiment No. 26, 43,
44 and 45 are comparative examples, and the others are examples of the present invention.

【table】

[Table] Example 4 In place of molded anhydrite in the concrete formulation in Table 1, a commercially available high-strength admixture containing molded anhydrite as the main component, manufactured by Nippon Cement Co., Ltd. under the trade name "Asano Super Mix", was used. (SO ₃ content 33.4%) was used,
The amount added was changed and sand was added.
In addition, a high-performance water reducing agent is manufactured by Showa Denko Co., Ltd. under the trade name "Meltont F-", which is a high condensate based triazine derivative.
10'' was added to the cement at an amount of 1% by weight (powder) so that the water/cement ratio and slump were the same. As for oxycarboxylic acids, tartaric acid was kept constant at 0.15% by weight based on the cement, and in some experiments, aluminum sulfate and alum (both first grade reagents) were added. Using these concretes, a real pipe production test similar to that in Example 2 was conducted. The results are shown in Table 5. In addition, centrifugal force moldability was good in all cases. Experiment No. 46 is a comparative example, and the others are examples of the present invention.

[Table] As shown in the examples above, the bending strength of the centrifugal force specimen (test piece) is 80Kgf/cm ² or more without separation, and the second type pipe is 100Kg.
It has become possible to manufacture three types of Huyum tubes with f/cm ² or more. Additionally, if the curing temperature is lower, a hume pipe with higher external pressure strength can be obtained by using a small amount of gypsum, and furthermore, by adding aluminum sulfate or alum, the bending and compressive strength can be improved. Ta.

Claims (1)

[Claims] 1 One or more selected from citric acid, tartaric acid, malic acid, and their salts is added by 0.01 to 0.5 to the cement content in concrete to which a high-performance water reducer has been added.
% by weight and at most 15% by weight of gypsum (calculated as CaSO ₄ ), and after centrifugal force molding, heat insulation or steam curing is performed at a temperature of 60°C or less. Method.