JP3209581B2 - How to add thickener to concrete - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of uniformly adding a thickener to concrete.

[0002]

2. Description of the Related Art In recent years, examples of construction of underwater non-separable concrete and compaction-free concrete (superfluid concrete) have been increasing. To knead these concretes, various admixtures are mixed according to the purpose of the concrete, but it is necessary to add a thickener.

[0003] Conventional methods for adding a thickener include a method of adding a thickener in a powder state and a method of adding the thickener once in the form of a viscous liquid once dissolved in water.

[0004]

When added in powder form, the thickener does not mix well with the concrete mix, and may become lumpy (camel-like), which increases the mixing time in the mixer. In some cases, it was necessary and even if it was lengthened, it could not be completely and uniformly dispersed.

[0005] For this reason, a thickener is generally dissolved in an appropriate amount of water and added as a viscous liquid.
In compaction-free concrete and the like, since the amount of the thickener to be added is relatively small, the thickener does not mix well with the entire mix.

[0006] Unless the thickener is mixed well, the separation resistance of the concrete is reduced, and the concrete having the intended properties cannot be obtained.

[0007]

Means for Solving the Problems According to the present invention, when kneading concrete mixed with a thickener, the viscosity is increased.
A unit pack consisting of powdered welan gum and a powdered premix of powdered dispersant in a water-soluble film bag using powdered welan gum as a dispersant is required in the concrete mix during mixing. The present invention provides a method for adding a thickener to concrete, characterized in that the concrete is charged several times.

[0008]

[Effect] A unit of a powder in which a powdery thickener and a powdery dispersant are previously mixed and mixed is packed in a bag made of a water-soluble film, and the unit pack is mixed in a mixer while mixing concrete. When the unit pack is charged, the unit pack is taken into the kneading mix and stirred under flow, and the water-soluble film dissolves or breaks and the powder flows out into the flowing mass.

[0009] At that time, the powder that flows out always contains a dispersant near the thickener, and is dispersed and diffused in contact with the mixed water in the flowing mix. For this reason, they can be evenly distributed without being left behind. The water-soluble film eventually loses its solid form and dissolves in the mix.

When the unit pack is charged, the unit pack may be charged in a cement storage bin in advance, and the unit pack may be accompanied when the cement is charged into the mixer.

As the thickener, in addition to commonly used thickeners such as methylcellulose and hydroxyethylcellulose, welan gum (a microbial fermented polysaccharide produced by a strain of Alcaligenes ATTC 31961) can be used. As the dispersant, β-naphthalenesulfonic acid formalin condensate, ligninsulfonate, melaminesulfonate, carboxylate and the like can be used.

The ratio between the thickener and the dispersant is appropriately selected according to the type of the thickener and the dispersant used, but the ratio of the thickener / dispersant is preferably in the range of 1/1 to 1/5. ing. When welan gum is used as a thickener and calcium β-naphthalenesulfonate or sodium β-naphthalenesulfonate is used as a dispersant, the ratio is preferably about 1/3. As the water-soluble film for enclosing the mixed powder, polyvinyl alcohol is preferable.

As the unit pack, various weight units are used according to the mixer capacity and the mixing amount. For example, 10
A variety of unit weights ranging from 0 g to 1000 g are prepared. In practice, it is convenient to use the required number of units having the same unit weight. It is better to do batchwise batching than batch loading. The unit pack can be easily put into the mixer by hand. It is more convenient to use a device that can be continuously charged at regular time intervals.

FIGS. 1 and 2 show an example of an apparatus for feeding a predetermined number of unit packs according to the present invention into a mixer or a cement storage bin. Several arms 2 are mounted radially from a central axis 3 on the upper surface of a fixed disk 1 placed horizontally. The central shaft 3 is provided with power for rotating around the axis. Therefore, when the central shaft 3 rotates, each arm 2 rotates around the central axis.

An opening 4 is provided at a predetermined position of the fixed disk 1, and a unit pack 5 carried by the arm 2 is dropped on the chute 6 from the opening 4. On the other hand, the required number of unit packs 5 are stacked in a shaft 7 provided at the same radius as the opening 4, and since the lowermost edge of the shaft 7 and the disk 1 have a predetermined gap, When the arm 2 passes through the gap, the unit packs are picked up one by one and transferred to the opening 4. The arm 2 is provided with a pack lock 8 so that the unit pack 5 can be transported reliably.

The chute 6 is connected to a mixer or a cement storage bin (not shown), and a required number of unit packs 5 are supplied at predetermined intervals by rotating the arm 2.

[0017]

EXAMPLE A concrete mixing test shown in Table 1 was conducted for two cases in which the method of adding a thickener was changed, and a mixing test was conducted.

[0018]

[Table 1]

The test involved mixing 50 liters of concrete for 90 seconds using a 100 liter forced twin-screw mixer. The kneading time is determined to be equivalent to the kneading time of the actual mixer of 45 to 60 seconds.

As the thickening agent, welan gum manufactured by Kelco (microbial fermentation polysaccharide produced by the strain of Alcaligenes ATTC 31961) was used.

Case 1: The thickener powder was mixed with cement and stone powder in advance, and the ingredients shown in Table 1 were added at once and mixed. Case 2: A unit pack in which 100 g of a mixed powder obtained by premixing a thickener powder and a dispersant powder (β-naphthalene sulfonate) at a weight ratio of 1: 3 in a water-soluble film (polyvinyl alcohol) is kneaded. The concrete material being mixed was charged from above. In both cases 1 and 2, the amount of the thickener added was the same as shown in Table 1 at 0.004 kg.

The slump flow value (measured value of the spread width by the slump test) of the obtained concrete was 75 cm in both cases 1 and 2 and there was no difference. However, in case 1, there was a phenomenon in which the coarse aggregate separated downward and the mortar separated upward, and a phenomenon in which water rose to the upper part in a short time.
In Case 1, such a phenomenon was completely absent, and good concrete with high viscosity was obtained.

From the above, it was found that the thickener was not uniformly dispersed in the case 1
It is clear that the distribution was even.

[0024]

As described above, according to the present invention, a thickener can be evenly dispersed in concrete, and it is intended for use in underwater non-separable concrete or compaction-free concrete using a thickener. Properties can be satisfactorily exhibited. In particular, even when the amount of the thickener used is small, the fact that it can be dispersed evenly has a great effect on the production of superfluid concrete.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of a unit pack charging device according to the present invention.

FIG. 2 is a schematic sectional view of the apparatus of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed disk 2 Arm 3 Rotating central axis 4 Opening 5 Unit pack 6 Unit pack introduction chute 7 Shaft for unit pack accommodation

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Goro Sakai 2-9-1-1, Tobita-Sen, Chofu-shi, Tokyo Kashima Construction Research Institute (72) Inventor Masayoshi Minami No. 1 Kitahama Higashi, Chuo-ku, Osaka-shi, Osaka No. 29 Sansei Co., Ltd. (72) Inventor Masato Yoshizaki 1-29 Kitahama Higashi, Chuo-ku, Osaka City, Osaka Prefecture No. 29 Sankei Co., Ltd. Document JP-A-2-161015 (JP, A) JP-A-59-192523 (JP, A) JP-A-3-272808 (JP, A) JP-A-60-171259 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B28C 7/06 C04B 24/00

Claims (2)

(57) [Claims] 1. A powdered welan gum is used as a thickener when kneading concrete mixed with a thickener.
The required number of unit packs in which a powder of premixed powdered welan gum and a powdered dispersant are loaded into a bag made of a water-soluble film are put into a concrete mix and mixed. How to add thickener to concrete. 2. The method according to claim 1, wherein the dispersant is a formalin condensate of β-naphthalenesulfonic acid.