JP2004136452A - Concrete manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture concrete excellent in workability while suppressing the use amount of an admixture. <P>SOLUTION: This concrete manufacturing method includes a first process (process B) for kneading a cement slurry containing a binding material and water and a second process (process C) for charging aggregate in the cement slurry kneaded in the first process to knead the same with the slurry. In the first process, a shearing mixer 20 for relatively rotating shearing blades 26 and 28 superposed one upon another so as to leave a gap between the shearing blades 26 and 28 is used to knead the cement slurry introduced into the gap between the shearing blades 26 and 28. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing concrete, and more particularly to a method for producing concrete suitable for producing concrete having high fluidity and excellent workability.
[0002]
[Prior art]
BACKGROUND ART Conventionally, the production of concrete has been carried out by sequentially charging a coarse aggregate, an admixture, cement, water, and an admixture into a concrete mixer and stirring. Among them, the admixture is used for dispersing cement particles in order to enhance workability such as fluidity of concrete. In particular, in recent years, chemical admixtures for dispersing cement particles by electrostatic repulsion due to charging of cement particles have become widespread. For example, AE agents, AE water reducing agents, high-performance AE water reducing agents, and the like have been used.
[0003]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2000-37721
[Patent Document 2]
JP-A-6-144908
[Problems to be solved by the invention]
By the way, in the case of producing high-strength concrete or high-fluidity concrete, or in the case where fly ash, blast furnace slag fine powder, and fine particles generated when producing recycled aggregate are frequently used, the conventional concrete production Compared with the case, the amount of the binder, which is a mixture of the cement and the admixture, increases. Experience has shown that when the amount of binder used increases, the amount of admixture required per unit amount of concrete also increases and the viscosity increases. This leads to an increase in the unit production cost of the concrete, and also causes inconvenience such as not being able to obtain stable properties of fresh concrete depending on the properties of the binder (particularly, the property of adsorbing the admixture).
[0006]
The present invention has been made in view of the above points, and an object of the present invention is to make it possible to produce concrete with excellent workability while suppressing the amount of an admixture used.
[0007]
[Means for Solving the Problems]
The inventor of the present application states that as the amount of the binder increases, the amount of the admixture required per unit amount of concrete increases because the fine particles constituting the binder aggregate with each other and are agitated during the production of concrete. Was not sufficiently dispersed. The grounds are that, for example, when ultrasonic waves are applied to the grout material injected into the joints for the purpose of waterproofing the rock, the permeability of the grout material tends to be greatly improved. This is because the aggregated particles in the inside are considered to be dispersed by the ultrasonic vibration.
[0008]
When a large amount of the binder is used, even if the admixture is used, the aggregated fine particles cannot be sufficiently dispersed, so that the effect of the admixture decreases as the amount of the binder increases. As a result, the fluidity of the produced concrete decreases, the viscosity increases, the workability deteriorates, or a large amount of an admixture is required to obtain the desired workability, and the concrete production unit cost is reduced. Will increase.
[0009]
Therefore, in the present invention, in the first step, fine particles contained in the binder are sufficiently dispersed by shearing and kneading the cement slurry containing the binder, water, and the admixture with a shear mixer. At this time, since the aggregate has not been mixed yet, the aggregate is not broken by the shear mixer. Thereafter, in a second step, the cement slurry is put into the aggregate and further stirred. This makes it possible to produce concrete with excellent workability in which fine particles are dispersed, without using a large amount of admixture.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a diagram schematically showing a flow of steps in a concrete manufacturing method according to one embodiment of the present invention.
[0011]
As shown in FIG. 1, first, in step A, water, a binder (admixture with cement), and an admixture are charged into a kneading tank 10 such as a slurry kneading mixer and kneaded. Next, in step B, the cement slurry containing the kneaded water, the binder, and the admixture is charged into the high-speed shear mixer 20 and further kneaded.
[0012]
FIG. 2 is an enlarged front view showing the high-speed shear mixer 20. As shown in FIG. 2, the high-speed shear mixer 20 includes a vertical drum 22. A rotating shaft 24 extending in the vertical direction is provided at the center of the drum 22. A number of shear blades 26 are provided around the rotary shaft 24. A number of shear blades 28 are also provided on the inner peripheral surface of the drum 22 at a height that does not interfere with the shear blades 26. The shear blade 26 on the rotating shaft 24 side and the shear blade 28 on the drum 22 side are arranged so as to vertically overlap with a small gap therebetween. A rotating blade 30 is provided at the uppermost stage of the rotating shaft 24 so as to be inclined, so that the cement slurry supplied from above is sent below the drum 22.
[0013]
When the rotating shaft 24 rotates, the shear blade 26 also rotates. For this reason, the cement slurry that has been fed from above by the rotating blades 30 and entered the gap between the shearing blades 26 and 28 is sheared by the shearing blades 26 and 28, whereby the aggregated fine particles in the cement slurry are dispersed. . The shear blades 26 and 28 are rotated in a state where all the shear blades 26 and 28 and the rotary blade 30 are completely immersed in the cement slurry so that air is not entrained by the rotational stirring. An opening is provided on the lower bottom surface of the drum 22, and the cement slurry that has reached the lowermost portion of the drum 22 passes through the opening and moves the outside of the drum 22 upward as indicated by an arrow in FIG. And is again fed into the drum 22 by the rotating blades 30.
[0014]
3 and 4 show another configuration example of the high-speed shear mixer 20. FIG. Here, an example of a four-shaft type high-speed shear mixer is shown, FIG. 3 is a front view, and FIG. 4 is a plan view. As shown in FIGS. 3 and 4, four rotating shafts 104 are provided inside the kneading container 102. Each rotary shaft 104 is provided with a number of shear blades 106. A number of shear blades 108 are also provided on the inner wall surface of the kneading vessel 102. The shear blades 106 of each rotary shaft 104 are provided so as to overlap with the shear blades 106 of the adjacent rotary shaft 104 and the shear blade 108 of the kneading vessel 102 with a small gap therebetween. Then, when each rotating shaft 104 is rotationally driven in the opposite direction to the adjacent rotating shaft 104, the cement slurry that has entered the gap between the shear blades 106 and 108 is sheared, whereby fine particles in the cement slurry are removed. Distributed.
[0015]
As described above, after the cement slurry is kneaded while being sheared by the high-speed shear mixer 20, in the step C, the cement slurry is charged into the stirring mixer 40 together with the coarse aggregate and the fine aggregate and further kneaded, whereby the concrete Is completed.
[0016]
According to the concrete manufacturing method of the present embodiment described above, the cement slurry in which the binder, the water, and the admixture are mixed is kneaded with the high-speed shear mixer 20, so that the fine particles contained in the binder are dispersed from the aggregated state. Can be done. For this reason, even if the admixture is not used excessively, the fluidity of the produced concrete is increased, and thereby the workability is improved. That is, according to the present embodiment, it is possible to produce concrete with excellent workability while reducing the amount of the admixture used and reducing costs. In addition, since the reactivity is enhanced by dispersing the fine particles of cement, it is also possible to improve the manifestation of concrete strength.
[0017]
In addition, even when a binder having high adsorbability of the admixture or a binder whose quality is not stable is used, the fine particles can be sufficiently dispersed, so that the effect of the stable admixture can be expected. Also in this respect, the use amount of the admixture can be reduced.
[0018]
Further, in this embodiment, a vertical shear mixer is used as the high-speed shear mixer 20, and the kneading of the cement slurry by the shear blade is performed in a state where the shear blade is completely immersed in the cement slurry. It is possible to prevent air from being caught in the concrete accompanying the stirring of the slurry.
[0019]
Further, after the binder, water and the admixture are stirred by the high-speed shear mixer 20 to disperse the fine particles, the high-speed shear mixer 20 stirs the aggregate together with the aggregate. It can be prevented from being destroyed.
[0020]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the concrete which was excellent in workability can be manufactured, suppressing the use amount of an admixture.
FIG. 1 is a view schematically showing a flow of steps in a method for producing concrete according to one embodiment of the present invention.
FIG. 2 is an enlarged front view showing a high-speed shear mixer used in the embodiment.
FIG. 3 is a front view showing another configuration example of the high-speed shear mixer.
FIG. 4 is a plan view of the high-speed shear mixer of FIG. 3;
[Explanation of symbols]
Reference Signs List 10 Kneading tank 20 High-speed shear mixer 22 Drum 24, 104 Rotary shaft 26, 28, 106, 108 Shear blade 40 Stirring mixer

Claims (1)

A first step of kneading a cement slurry containing a binder, water, and an admixture, and a second step of charging and kneading the cement slurry kneaded in the first step into aggregate. In the first step, the cement slurry introduced into the gap is sheared by using a shear mixer that moves blades provided substantially parallel to each other with a gap therebetween while maintaining the gap. A method for producing concrete, characterized by kneading by mixing.

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