JP2001260111A - Method for manufacturing concrete secondary product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently manufacturing a concrete secondary product which is excellent in an initial strength and a strength for a long period of time by using a form repeatedly. SOLUTION: A method for manufacturing the concrete secondary product is provided wherein kneaded concrete is filled into a preheated form, and after start of curing of the concrete, the form is removed quickly as a bottom plate of the form is left as it is.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a secondary concrete product used in the fields of civil engineering and construction. The concrete in the present invention is a general term for mortar and concrete.

[0002]

2. Description of the Related Art Conventionally, a method for producing a concrete secondary product is as follows. A slump of about 3 to 10 cm is applied to a form while vibrating a concrete, and after 15 to 20 hours, steam is added to the form at 15 to 20 ° C./hr. The temperature rises at the speed of
After holding at about 5 ° C. for about 3 to 5 hours, the mold is released when the strength becomes 15 to 25 N / mm ² , depending on the size and shape of the product. Therefore, the time required from the time of kneading to the time of demolding takes 5 to 8 hours.

[0003] The reason for adjusting the slump of concrete to about 3 to 10 cm when manufacturing a secondary concrete product is to take into consideration the fact that vibration compaction is easily performed. If the slump is too large, the vibration of the concrete causes material separation, bleeding, or setting delay.

The reason why the rate of temperature rise is controlled in the range of 15 to 20 ° C./hr is that if the temperature is rapidly increased, concrete will crack due to thermal expansion, and the durability of concrete will be significantly reduced. Regarding the maximum temperature, if the temperature is too high, the demolding strength increases, but the long-term strength increase is small, and the design strength cannot be obtained at a general shipping material age.

[0005]

However, in the method of manufacturing secondary concrete products, it is necessary to manufacture a large number of products in a short period of time in order to diversify varieties and to meet the construction period while precasting concrete is progressing. Has been requested. In order to cope with this, a large number of expensive molds must be prepared, which causes an increase in product cost. Furthermore, since steam curing is performed, transportation from the molding place to the steam curing room, a large space for installing a pit for steam curing a large number of products at once, and a fuel cost for generating steam are a large cost burden. Has become.

[0006] In order to solve these problems, it has been attempted to increase the production efficiency by using cement having high hydraulicity or adding a hardening accelerator represented by chloride, nitrate, nitrite and the like to concrete. Have been. However,
The effects of these curing accelerators are insufficient and it is difficult to significantly reduce the pre-installation time. Therefore, it has been attempted to increase the strength in a short time by combining the heat curing and the addition of a curing accelerator, but conversely, there is a problem that the increase in the long-term strength cannot be obtained.

Attempts have also been made to remove the mold early by using a hardened material (agent). However, since the concrete hardening time varies greatly due to temperature changes in the four seasons, the working time such as hardening of the concrete in the mixer is required. In fact, it has not been put to practical use because of difficulties in controlling the temperature.

Furthermore, in order to simultaneously realize the development of short-term strength and the enhancement of long-term strength on the premise of steam curing, an additive for forming ettringite combining gypsum and aluminum sulfate or alumite and sodium nitrite is used. (Japanese Patent Application Laid-Open No. 4-160042), however, has not yet achieved a sufficient effect.

In view of these circumstances, the present inventors have conducted intensive studies to solve the above-mentioned problems. As a result, the concrete was demolded after the hardening of the concrete was started, the demolded mold was used efficiently, and the initial strength was reduced. It has been found that the above problems can be solved by efficiently producing a concrete secondary product having excellent long-term strength, and the present invention has been completed.

[0010]

That is, according to the present invention, a preheated formwork is filled with kneaded concrete,
This is a method for producing a secondary concrete product, wherein the concrete is quickly released after the concrete starts to harden, while leaving the mold bottom plate.

In the present invention, the concrete preferably has a compressive strength of 1 N / mm ² or more at the time of demolding. It is also preferred that the concrete is quick-setting. Also,
It is preferable that the mold is previously heated to 40 to 85 ° C.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The method for producing a secondary concrete product of the present invention uses a mold that can be assembled and separated, and fills the preheated mold with the kneaded concrete, and the concrete starts to harden and separates from the mold. After being able to do so, it is characterized in that it is quickly removed with the mold bottom plate left.

[0013] The mold used in the present invention is composed of independent members, and is constituted by combining those members. Therefore, the mold can be removed by separating these members.

The formwork leaving the formwork bottom plate used in the present invention is a conventional formwork in which the formwork bottom plate is attached in accordance with the shape of concrete, for example, in combination with an inner formwork or an outer formwork. , These molds are removed at one time, and are attached to the concrete with hanging brackets and transported by heavy machinery.
In the present invention, in addition to the inner mold and the outer mold, a mold combined with an independent mold bottom plate (processed into a flat plate for easy transportation) is used to remove the inner mold and the outer mold. After the molding, the product is left on the bottom plate of the mold, and the mold bottom plate is transported under a load.

Further, in the conventional mold, the bottom plate may be attached to the outer mold or the inner mold, or the bottom plate may be independent of the outer mold or the inner mold. (1) Although the shape of the bottom plate of the conventional mold is adjusted to the product shape, the bottom plate of the present invention is a flat plate, and (2) the bottom plate of the conventional mold is Although no consideration is given to proof stress because the product is not transported, a difference is that the present invention uses a product that sufficiently withstands the weight of the product.

The cement used in the concrete of the present invention is not particularly limited. For example, a setting retarder is added to ordinary Portland cement, quick-setting cement or rapid-setting cement to extend the setting time. Things. Among them, it is preferable to use quick-setting cement or quick-setting cement for immediate demolding.

Fast-setting cement or quick-setting cement
Is not particularly limited, for example, hydration reaction
Ettringai with Portland cement hydrate
To = C _ThreeA ・ CaSO_Four・ 32H_TwoO (C = CaO, A =
Al_TwoO_ThreeAbbreviated as cement) and hardened material
Cement or the like can be used. Setting retarders are:
Although not particularly limited, for example, oxycarbo
Acid-based retarders can be used.

The water reducing agent used in the present invention is not particularly limited, and is generally called a water reducing agent, an AE water reducing agent, a high performance water reducing agent, or a high performance AE water reducing agent.
Formalin condensate of naphthalene sulfonate, formalin condensate of methyl naphthalene sulfonate, formalin condensate of anthracene sulfonate and polyalkylallyl sulfonate of co-condensate of these and lignin, and melamine For example, a formalin condensate of a sulfonate, a polycarboxylic acid and the like can be mentioned.

[0019] The temperature of the concrete immediately after mixing is preferably 10 to 50 ° C, more preferably 20 to 30 ° C. When the temperature of the concrete is less than 10 ° C., the curing time is too long, and the short-time strength development is not preferable because it is small. When it exceeds 50 ° C., the curing time is too fast,
It is not preferable because the time required for filling the concrete formwork cannot be obtained. Although it is possible to delay by adding a setting retarder, it is uneconomical due to the large amount of addition, and changing the addition amount each time due to a change in concrete temperature causes troubles on site. Therefore, it is important to control the temperature of the concrete, for example, to heat and keep warm in the severe winter season, and to produce concrete with a constant concrete mix and a stable working time throughout the year.

In the present invention, the temperature of the pre-heated formwork is preferably 40 to 85 ° C, more preferably 50 to 85 ° C.
75 ° C. If the temperature exceeds 85 ° C., not only is the concrete thermally expanded, but also a crack is generated in the concrete product due to a rapid temperature change after demolding, and the long-term strength increase is not preferable. 40 ℃
If it is less than 30 minutes, cracks due to insufficient strength and short-time strength are small, and demolding within 30 minutes may be difficult, which is not preferable. In the present invention, the concrete filled in the mold starts to set from the concrete in contact with the preheated form, and the whole hardens.

The method of heating the formwork used in the present invention is not particularly limited, and any method such as steam, electric heater, hot water, electromagnetic wave and the like can be used.

The compressive strength of the concrete according to the present invention at the time of demolding is such that the filled concrete does not change its shape and does not adhere to the side form when the filled concrete is left as it is. 1 N / mm ² or more. In a conventional demolding method that does not leave a mold bottom plate, 15 to 2
A strength of 5 N / mm ² or more is required, and in the present invention, the mold bottom can be left as it is, so that the mold can be removed with low strength.
Further, the method for producing a secondary concrete product of the present invention can be applied regardless of the size or shape of the product.

[0023]

Hereinafter, the present invention will be described in detail with reference to Examples.
It is not limited to these. The materials and test methods used in the examples are summarized below.

<Materials used> (1) Concrete material Cement: Rapid-setting cement (Denka Super Cement manufactured by Denki Kagaku Kogyo Co., Ltd.) Fine aggregate: River sand from Himekawa, Niigata Coarse aggregate: Crushed stone from Himekawa, Niigata Water reducing agent: Grace Chemicals "Super 200",
Polycarboxylic acid-based setting retarder: Setter (oxycarboxylic acid-based) manufactured by Denki Kagaku Kogyo Co., Ltd.

<Test Method> (1) Compressive strength: Measured in accordance with JIS A 1108. (2) Curing time: A thermocouple was embedded in concrete and judged from a rise in temperature.

Example 1 Using the concrete composition shown in Table 1, the temperature of the concrete material was adjusted and kneaded so that the concrete temperature became 20 ° C., and as shown in Table 2, a mold for compressive strength measurement (inner diameter) For a case in which a cylinder having a height of 100 mm and a height of 200 mm) is not heated (20 ° C.) and a case where it is heated to a predetermined temperature (50 to 70 ° C.), the mold is filled and then removed from the mold 30 minutes later, and the strength is immediately increased. Was measured. The mold is a combination of a mold bottom plate and a cylindrical mold that can be divided into two in the vertical direction.

The 28-day strength test specimen was removed from the mold one day old, and after 28-day indoor curing, the compressive strength was measured. Table 2 shows the above results.

[0028]

[Table 1]

[0029]

[Table 2]

(Note) The setting time indicates the time when the concrete sets and the strength starts to increase.

From Table 2, it can be seen that in the comparative examples (Experiment Nos. 1 and 2) in which the mold temperature was 20 ° C. without heating the mold in advance, the curing time was long and the initial strength was small. Although it is impossible to remove the mold in a short time, the mold is heated in advance in the embodiment of the present invention (Experiment Nos. 4 and 5), and the mold bottom plate is left as it is. 30 minutes after the filling, a compressive strength of 1 N / mm ² or more is exhibited, and it can be seen that immediate demolding is possible and high initial strength and long-term strength.

Example 2 The inner shape was 1000 mm in inner width, 1000 mm in inner height, and 20 in length.
A box culvert having a thickness of 00 mm and a thickness of 130 mm was manufactured using the concrete shown in Table 1 at a concrete temperature of 2 mm.
After filling the mold under the conditions of 0 ° C and the mold temperature of 70 ° C, 30
After one minute, it was removed from the mold.

The box culvert, which is an actual concrete product, can be immediately demolded within 30 minutes by leaving the mold bottom plate at the time of demolding.

[0034]

As described above, according to the present invention, a preheated mold is filled with kneaded concrete by using a mold that can be removed from the mold while leaving the mold bottom plate. By leaving the mold bottom plate as it is at the time of molding, the mold can be quickly removed after the concrete starts to be cured, and a concrete secondary product having excellent initial strength and long-term strength can be efficiently produced.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yu Murase 1-22-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Haneda Hume Kanko Co., Ltd. (72) Inventor Nobuhiro Ito 1-22-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo No. Haneda Hume Kanko Co., Ltd. (72) Inventor Yuji Nanbu 1-22-2 Nishi Shinjuku, Shinjuku-ku, Tokyo Haneda Hume Kanko Co., Ltd. (72) Shintaro Tsubakimori 1-22-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo No. Haneda Hume Kanko Co., Ltd. (72) Inventor Tetsuya Ando 1-4-1, Yurakucho, Chiyoda-ku, Tokyo Denki Kagaku Kogyo Co., Ltd. Chemical Industry Co., Ltd.

Claims (4)

[Claims] 1. A concrete secondary product characterized in that a preheated formwork is filled with kneaded concrete, and after the concrete starts to harden, the mold is quickly removed while leaving the formwork bottom plate. Production method. 2. The concrete has a compressive strength of 1N at the time of demolding.
The method for producing a concrete secondary product according to claim 1, wherein the ratio is not less than / mm ² . 3. The method for producing a secondary concrete product according to claim 1, wherein the concrete is quick-setting. 4. The method for producing a secondary concrete product according to claim 1, wherein the mold is heated to 40 to 85 ° C. in advance.