JP2001097753A - Reducing agent for bleeding and method for producing centrifugally molded product using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a reducing agent for bleeding capable of exhibiting stable reducing power for the bleeding, and to provide a method for producing a centrifugally molded product using the reducing agent for bleeding. SOLUTION: (1) This reducing agent for bleeding consists essentially of a sodium type bentonite in <=5.0 SiO2/Al2O3 weight ratio of chemical components. (2) The method for producing the centrifugally molded product comprises adding the reducing agent for bleeding consisting essentially of the sodium type bentonite in <=5.0 SiO2/Al2O3 weight ratio of the chemical components in an amount of 1-12 kg/m3 to a mortar or a concrete.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slag reducing agent and a method for producing a centrifugally molded product using the same, and more specifically, a concrete pile, a steel pipe / concrete composite pile, produced by centrifugally molding mortar or concrete.
A slag reducing agent for reducing or preventing the generation of slag of centrifugal force molded products such as poles, fume pipes and steel pipe linings, and a method of manufacturing centrifugal force molded products using the same.

[0002]

2. Description of the Related Art Conventionally, in a concrete product manufactured by centrifugal force molding, a large amount of slag is squeezed out by centrifugal force. This slag has a solid content of 20 to 40 in addition to water.
Since it is includes strongly alkaline by weight% of the cement and fine sand, can not be on the pollution control be discarded outside the factory directly, for example, a high cement concentration pile, Noro pole or the like, the container of 1 to 2 m ³ Into the final disposal site. In the fume tube with low cement concentration, after solid matter is precipitated and filtered, it is finally treated as a flake by applying a dehydrator, and the remaining alkaline water is neutralized and drained to sewage. For some reasons, solids are difficult to dispose of as industrial waste, as is the case with piles, and the burden of treating alkaline water is also a burden.

For this reason, there is a strong demand in the concrete product industry to reduce or prevent slag. Therefore, the present inventors have proposed a slag reducing agent containing bentonite as a main component (JP-A-3-247543). Bentonite is a fine particle in which primary particles are formed of sheet-like crystals of several microns (montmorillonite crystals arranged in a book shape). The effect of this bentonite to reduce the generation of slag when a centrifugal force of about 30 times the gravitational acceleration is applied is not sufficiently elucidated, but the cement paste immediately after mixing with the bentonite is mixed with liquid nitrogen. When frozen and observed with a scanning electron microscope, the edges of the bentonite sheet-shaped crystals contact each other on the cement particles, forming a continuous hexagonal chamber. It can easily be inferred that the movement of water caused by the water is suppressed.

[0004] When the amount of bentonite is fixed,
In order to reduce the generation of slag by resisting centrifugal force, it is necessary to confine a large amount of water, and for that purpose, sodium-type bentonite having a larger swelling degree than calcium-type is advantageous, and sodium-type bentonite is advantageous. Among them, it can be easily inferred that those having a large swelling degree are preferable.

[0005]

However, the present inventors have studied the slag reduction effect of various sodium-type bentonite and found that even if the swelling degree is large, the swelling degree is inferior or the swelling degree is small. It was also found that there were many types having a high slag reduction effect, and it was found that there was a problem that the slag reduction force fluctuated only by controlling the degree of swelling and it was difficult to reduce the slag stably.

Accordingly, the present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that by using bentonite having a specific chemical component and its content ratio, a stable slag reduction power can be exhibited. Thus, the present invention has been completed.

[0007]

That is, the present invention provides:
(1) A slag-reducing agent containing sodium-type bentonite as a main component having a weight ratio of SiO ₂ / Al ₂ O ₃ of 5.0 or less, and (2) a mortar or concrete.
A noro reduction agent containing sodium-type bentonite as a main component and having a chemical component SiO ₂ / Al ₂ O ₃ weight ratio of 5.0 or less,
This is a method for producing a centrifugally molded product, characterized by adding １２12 kg / m ³ .

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

[0009] The present invention relates to the chemical component Si in bentonite.
It is a slag reducing agent containing sodium-type bentonite as a main component and having an O ₂ / Al ₂ O ₃ weight ratio of 5.0 or less. The sodium-type bentonite of the present invention is bentonite in which alkali metals such as sodium and potassium ions are adsorbed between layers of sheet-like crystals of montmorillonite, and bentonite which incorporates alkaline earth metals such as calcium and magnesium ions. It has a larger swelling property than that of.

The weight ratio of SiO ₂ / Al ₂ O _{3 in} the bentonite of the present invention is 5.0 or less, and when the weight ratio of SiO ₂ / Al ₂ O ₃ exceeds 5.0, the degree of swelling is large. Also, the slag reduction force is reduced, preferably 4.5 or less, more preferably 4.2 or less. Further, the lower the ratio, the greater the slag reduction power. However, the lower limit is about 3.0 for naturally occurring bentonite, and this ratio can be reduced by artificially purifying montmorillonite, but it is expensive.

Although the relationship between the weight ratio of SiO ₂ / Al ₂ O ₃ and the slag reduction power is not always clear, the association mode of montmorillonite when bentonite is made into a suspension with water is as follows. There is a mode in which crystal pieces are randomly dispersed, and a mode in which a plurality of thin crystal pieces are randomly dispersed while overlapping. In addition, there are a mode in which one thin crystal piece forms a square or hexagonal room (space), and a mode in which a plurality of thin crystal pieces are overlapped to form a square or hexagonal room. Furthermore, when forming a quadrangular or hexagonal room, there are various modes such as a mode in which an edge is in contact with an edge, a mode in which an edge is in contact with a surface, and a mode in which one side of a rectangular or hexagonal room is open.

Considering the slag reduction force due to the centrifugal force, it is considered that there is no space in the randomly dispersed mode, so that there is no ability to fix water, and the slag reduction force is presumed to be small. Also, in a mode in which one side of a square or hexagonal room is open, it is presumed that water is easy to move.

From the above, the relationship between the weight ratio of SiO ₂ / Al ₂ O ₃ and the slag reduction power is not surmised, but in the presence of calcium ions, such as mortar and concrete, SiO ₂ / Al ₂ O ₃ can be used. meeting mode montmorillonite crystals is changed by the weight ratio of _{2 / Al 2 O 3, SiO} 2 / Al 2 O 3
The smaller the weight ratio of, the easier it is to form a continuous square or hexagonal room consisting of thin crystal pieces one by one, or
It is considered that an association mode in which a plurality of thin crystal pieces are overlapped to form a continuous square or hexagonal room or the like is easily formed.

In the present invention, a slag-reducing agent (hereinafter, simply referred to as a slag-reducing agent) containing sodium-type bentonite as a main component and having a weight ratio of SiO ₂ / Al ₂ O ₃ of 5.0 or less is converted into 1 m ³ of mortar or concrete. Add 1-12 kg and knead. If the weight is less than 1 kg, the weight ratio of SiO ₂ / Al ₂ O ₃ is 3.0.
Even if it is as small as possible, the practical slag reduction effect is small, and when added over 12 kg, the unit water amount increases greatly, and when adding a high-performance water reducing agent so as to reduce the unit water amount and not decrease the strength, Since the amount of addition increases, the viscosity peculiar to the high-performance water reducing agent easily appears in the mortar or concrete, and on the contrary, the amount of slag generation increases, which is not preferable. Preferably it is 1.5 to 10 kg, more preferably 2 to 8 kg.

When the mortar or concrete to which the slag reducing agent of the present invention is added is kneaded, the unit water amount tends to increase. If the amount of increase is large, the strength is reduced. The type of water reducing agent is not particularly limited, but a polyalkyl allyl sulfonate-based or melamine resin sulfonate-based high-performance water reducing agent increases the water reduction rate as the amount of addition increases, and, This is preferable because there is no setting delay or air entrainment.

Commercially available polyalkylallyl sulfonate-based high performance water reducing agents include Grace Chemicals' trade name "FT-500" series, Kao Corporation's trade name "Mighty" series, Nippon Paper Industries Co., Ltd. ) Sanflow PS
Series, “Cell Flow 110P” of Daiichi Kogyo Seiyaku Co., Ltd.
And the like. Commercially available high performance water reducing agents based on melamine resin sulfonate include “Molmaster” (trade name of Showa Denko KK) and “FT-3” (trade name of Grace Chemicals)
S "and the like.

The amount of the water reducing agent added is usually such that the larger the amount of the noro reducing agent added, the smaller the unit water amount so that the strength is not greatly reduced with respect to the original formulation (plain formulation without adding the noro reducing agent). To increase. In addition, the method of adding the water reducing agent (the simultaneous addition method of dissolving in the whole amount of mixing water, adding the cement, fine aggregate, coarse aggregate and mixing water to the mixer and then adding the water reducing agent stock solution later The water reduction rate varies greatly depending on the type of post-addition).
Although it cannot be specified uniformly, when the addition amount of the noro reduction agent is large, and in the simultaneous addition method, even if it is large in terms of solid content, 2.0 weight per portland cement (mixed cement is based on the whole mixed cement) %. Even when the amount of the slag reducing agent added is small and the post-addition method has a high water reduction rate, 0.36% by weight of cement is required in terms of solid content. In the simultaneous addition method, not only does the water reduction rate not increase even if it is added in excess of 2.0% by weight, but even if the amount of the slag reducing agent is large, the mortar or concrete comes out with the viscosity peculiar to the high-performance water reducing agent. It is not preferable because slag easily occurs. Further, even in the case of the post-addition method, 0.36
If it is less than% by weight, not only is the amount of unit water increased so much that the strength is greatly reduced, but also the amount of slag generated is undesirably increased.

The method for adding the slag reducing agent of the present invention includes:
When kneading the mortar or concrete, use a part or all amount of the kneading agent in a powder state or kneading water, and add it as a suspension slurry, and use the entire amount of kneading water and water reducing agent, Although it may be added as a suspension slurry, it is preferable to add a part of the mixing water as a suspension slurry, store it in a storage tank, and then measure and add the required amount for each mixing from there. .

The kind of the mixer for kneading the mortar or concrete to which the slag reducing agent of the present invention is added may be any of commonly used pan-type, twin-shaft, planetary-type forced kneading mixers and the like. There is no particular limitation.

The type of cement used in the present invention is not particularly limited as long as it is a Portland cement type, but from the viewpoint of reducing slag, fly ash cement, early-strength cement, silica cement, ordinary cement, and blast furnace slag cement in this order. Preferred, especially fly ash cement.

The method for centrifugal force molding of mortar or concrete to which the slag reducing agent is added according to the present invention reduces generation of slag, has good clogging and tightness at both ends of the centrifugally formed body, and has vibration and impact during transportation. As long as it does not fall off, it is not particularly limited, but usually, the rotation is sequentially increased in each of the initial speed, low speed, medium speed, and high speed, and the initial speed is a multiple of the gravitational acceleration (G) of 3 G or less, and 4 ~ 12G, medium speed 15 ~
The general molding conditions are 20 G and 25-35 G at high speed.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments.

Example 1 Degree of swelling and chemical components (Ig.loss,
For bentonite with different SiO ₂ , Al ₂ O ₃ ), mix concrete with different types of cement, put it in a centrifugal forming mold, perform centrifugal forming, and measure the amount of slag generated. The mold was tilted, and the discharged slag was taken in a measuring cylinder and its capacity was measured.) After molding, steam curing was carried out. After demolding the next day, autoclave curing was carried out and the compressive strength (n = 2) was measured. Table 1 shows the chemical components of bentonite, Table 2 shows the basic composition of concrete, and Tables 3 and 4 show the measurement results.

For mixing concrete, the aggregate and cement are put into a planetary forced kneading mixer and kneaded for 20 seconds, and then water containing a water reducing agent is added (simultaneous addition method) and kneaded for 30 seconds. Then, a slurry of 10 parts by weight of water (a part of kneading water) was added to 1 part by weight of bentonite, and 30 liters of concrete was added to 60 parts by weight of 60 parts.
Kneaded for seconds. The slight fluctuation of the slump depending on the type of bentonite was adjusted by finely adjusting the amount of the water reducing agent.

In the centrifugal force forming, the mixed concrete is mixed for 2 centimeters.
17.5 centrifugal force forming mold of 0cmφ × 30cmL × 5cmT
After loading the kg, cover the holes at both ends of the form with rubber stoppers, then set the low speed to 2G for 3 minutes, medium speed I to 10G for 2 minutes, and medium speed II to 20 minutes.
G was performed for 2 minutes, and high speed was performed at 30 G for 3 minutes.

The steam curing method is as follows: after the centrifugal molding, after curing in a room at 20 ° C. for 4 hours, the temperature is raised to 75 ° C. in 3 hours;
After holding for 4 hours as it was, the steam valve was stopped, and allowed to cool naturally in the steam curing tank until the next day, and the mold was removed the next day. In the autoclave curing, the demolded specimen is put in an autoclave, the temperature is raised from 20 ° C. to 180 ° C. (10 atm) in 3 hours, kept as it is for 3 hours, lowered to atmospheric pressure over 6 hours, and taken out, and the room is taken as it is. And left to cool.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

[0030]

[Table 4]

From Tables 3 and 4, there is a correlation between the weight ratio of SiO ₂ / Al ₂ O ₃ , a chemical component of bentonite, and the reduction of slag.
In particular, when the weight ratio of SiO ₂ / Al ₂ O ₃ of bentonite is 5.0 or less, the amount of slag generated can be suppressed to about 1/2 which is practically effective. The weight ratio of SiO ₂ / Al ₂ O ₃ is 4.5
Hereinafter, when the value is 4.2 or less, the amount of slag generation can be more remarkably suppressed. The bentonite SiO ₂ / Al
_When the weight ratio of ₂ O ₃ exceeds 5.0, it is shown that the effect of reducing the amount of slag generation is small although the degree of swelling is as large as about 23.

The slag reduction effect differs depending on the type of cement, and the amount of generated blast furnace slag cement, ordinary cement, silica cement, high-strength cement, and fly ash cement tend to decrease in order.

Regarding the compressive strength, the difference in the amount of slag generated when no bentonite is added (the higher the amount of slag generated, the lower the water cement ratio of the specimen itself) contributes to the strength. It is considered that the reason why the slag is not squeezed is that when the slag is squeezed out, the slag flows out around the coarse aggregate, so that the larger the amount of the slag generated, the more the void is formed around the coarse aggregate.

Example 2 Using the same materials and concrete basic mix as in Example 1,
For the formulation No. a-2, the amount of bentonite H was changed, the amount of the water reducing agent was adjusted so that the slump was constant, and the unit water amount was finely adjusted to such an extent that the strength was not greatly reduced. The same test was performed. Table 5 shows the results.

[0035]

[Table 5]

From Table 5, it can be seen that when the amount of bentonite is increased, the amount of the water reducing agent is adjusted (to a smaller amount) to significantly reduce the slag from 1.0 kg / m ³ . In addition, when the unit water amount and the total amount of the water reducing agent are fixed, 1.
5 to 10 kg / m ³ is preferable, and more preferably 2 to 8 kg / m ³
Is shown. 12 kg of bentonite
be many and / m ^3, the concrete tends to Noro generation amount in the viscosity exits the greater the observed, and also increases the viscosity when water reducing agent amount is more than 2.0 wt% (solids), rapid In addition, the amount of slag generated increases.

In this embodiment, the original concrete (plain concrete without added bentonite) is used.
It is also shown that the unit water amount increases somewhat but the addition amount of the water reducing agent tends to be more stable when the amount of the water reducing agent is slightly reduced than when the water-cement ratio is adjusted.

Example 3 Concrete was mixed with the basic composition of the concrete shown in Table 6 by changing the amount of bentonite and the amount of the water reducing agent as a post-addition method, and the same test as in Example 1 was carried out. Table 7 shows the results of measuring the amount of generation and the compressive strength. The bentonite used was J, and the water reducing agent amount and the unit water amount when the slump was adjusted to the design range are also shown in Table 7.

Concrete mixing method of post-addition concrete is as follows. Cement, fine aggregate and coarse aggregate are put into a mixer, rotated for 20 seconds, and then mixed water is added.
After kneading for 2 seconds, the stock solution of the water reducing agent was added and kneaded for 20 seconds, and then a slurry in which 10 parts by weight of water (a part of the kneading water was used) was added to 1 part by weight of bentonite was added to form a mixture of 90 parts. Kneaded for seconds.

[0040]

[Table 6]

[0041]

[Table 7]

From Table 7, it can be seen that in the post-addition method of the water reducing agent,
Also, the simultaneous addition of Example 2
It has the same tendency as the method. Also, bentonite
1kg / m ^ThreeThe lower limit of water reducing agent is 0.36% by weight.
It is shown that there is a
Large amount of addition, not only large decrease in strength, but also slag generation
Has also been shown to increase rapidly.

[0043]

The centrifugal force of mortar or concrete can be reduced by using a slag-reducing agent containing sodium type bentonite as a main component having a weight ratio of SiO ₂ / Al ₂ O ₃ of 5.0 or less. Stable slag reduction power can be exhibited during molding.

Claims (2)

[Claims] 1. The method according to claim 1, wherein the weight ratio of the chemical components to SiO ₂ / Al ₂ O ₃ is 5.0.
Slag reducing agent containing the following sodium-type bentonite as a main component: 2. For mortar or concrete,
Chemical component SiO_Two/ Al _TwoO_ThreeNato whose weight ratio is 5.0 or less
A noro reduction agent mainly composed of lumium bentonite,
~ 12kg / m^ThreeCentrifugal force molded product characterized by adding
Manufacturing method