JP3001664B2 - Concrete composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concrete composition having high-speed fluidity for shortening a casting time and labor.

[0002]

2. Description of the Related Art The performance of concrete as a structural material is different from steel or rebar, etc., and depends on the quality of construction. Generally, concrete is put into a mold using a pump, a bucket or the like after kneading, and compaction is performed using a vibrator or the like so as to uniformly fill a predetermined portion.

Under special construction conditions in water or the like where compaction cannot be performed, the addition of a thickener or the like enhances the separation resistance of concrete and ensures homogeneity, and at the same time, the concrete itself has a self-leveling property. A technique for adding and filling is given. However, such a conventional concrete composition has the following technical problems.

[0004]

That is, in the above-mentioned concrete, workability such as casting efficiency and compaction workability is low, which hinders rationalization and labor saving of concrete work. In particular, ultra-high strength concrete
As the process proceeds , concrete mixing with a low water cement ratio is being used, but in this case, there is also a problem that an increase in viscosity lowers workability.

The inventors of the present invention have studied various concrete compositions that satisfy both the deformation potential and the deformation speed, which are factors for evaluating the ease of placing concrete. It has been found that the object can be achieved by appropriately combining the fine powders.

The present invention has been made on the basis of the above findings, and it is an object of the present invention to provide a concrete composition which can flow at a high speed and improve workability even at a low cement ratio.

[0007]

In order to achieve the above object, the present invention provides a concrete composition comprising a unit hydraulic binder having a volume of 120 to 140 liters / m ³ , the balance being water and aggregate, The binder has a specific surface area of 250.
0-4500 cm ² / g Portland cement 20-
50%, blast furnace slag fine powder having a specific surface area of 2500 to 10000 cm ² / g 50 to 80%, specific surface area of 2,500 to 2,500
It is characterized by comprising a combination of fly ash of 10,000 cm ² / g in a range of 0 to 30%.

The fly ash in the concrete composition has a specific surface area of 2,500 to 8,000 based on the total amount thereof.
substituting limestone powder 0-30% and / or silica fume 1-10% cm ² / g may be blended. The said concrete composition, a thickening agent per 1 m ³ may be added 0.1～1.0Kg.

[0009] described in detail below reasons for limitation of the above next various materials and the amount thereof.

First, as a method of evaluating the fluidity of the concrete composition, the concrete composition can be evaluated by dividing it into factors of a deformation potential and a deformation speed. Among them, the deformation potential indicates the yield value of the concrete composition and is represented by a slump or a slump flow value. The flow velocity is mainly related to the viscosity of the concrete composition, and can be evaluated by the below-mentioned flow test method developed by the present inventors.

When the unit water amount, unit binder volume, fine aggregate ratio, and slump flow value are kept constant, any of the blast-furnace slag powder and fly ash powder mixed with Portland cement alone, which is found in ordinary concrete, cannot be used. Also, the falling speed is increased, and the maximum value is 2-2.5 times the speed.

When a part of fly ash is replaced with limestone powder, the flow rate is slightly reduced to about 30%, which is the total amount thereof, but hardly changes, and the limestone powder also has a viscosity reducing effect. Furthermore, when the fly ash is replaced with silica fume, the flow rate further increases to a mixing rate of 10%, and especially when the mixing rate is 5%, the flow rate of ordinary concrete is reduced.
It has also been found to exhibit twice the liquidity.

When the unit water amount, the unit coarse aggregate volume, and the slump flow are kept constant, the flow rate of the unit binder volume is 120 to 140 liters / liter, which is within the range of the present invention.
This speed is the fastest at about m ³ , and the flow speed becomes slower when the upper limit and the lower limit of the range are exceeded. Therefore, this range is the most preferable. In particular, when the mixing ratio is lower than the lower limit, the tendency of aggregate separation becomes remarkable, and the above range is preferable in order to improve separation resistance.

In the present invention, a thickener comprising a water-soluble polymer or the like can be added for the purpose of reducing separation in underwater concrete and self-leveling, but 0.1 kg / m ^{3 of the} concrete composition is used. / M ³ or less has no thickening effect, and if added over 1 kg / m ³ , the fluidity, which is the object of the present invention, is impaired.
It is limited to the above range.

Further, in the present invention, it is needless to say that a necessary amount of the admixture can be added, and the overall composition ratio is set in consideration of the influence on the composition due to the fine aggregate ratio, unit water amount, and the like. You.

[0016]

[Action] In the concrete composition having the above constitution,
The deformation rate is improved by the optimal blending of various fine powders constituting the unit hydraulic binder with the same slump flow. This is achieved by mixing the above-mentioned various fine powder materials with different particle shapes and particle sizes at the optimum ratio to adjust the overall particle size distribution, and furthermore, by making the composition considering the unit water volume, unit binder volume, fine aggregate ratio, etc. , Deformation potential and deformation speed can be increased.

[0017]

Next, embodiments of the present invention will be described. However, it is not limited only to the following embodiments. (1) Materials Used First, the names of the materials used in the present invention and the characteristics such as specific gravity and specific surface area are as shown in FIG. As shown in the figure, five types of materials were selected. As the admixture, a high-performance AE water reducing agent having good cement dispersibility and little change with time was used. In the following description, description will be made using the abbreviations shown in the drawings. (2) Mixing and kneading method As shown in FIG. 2, mixing under various mixing conditions was carried out according to the study factors. The slump flow value is considered to be 60
The measurement was performed at a constant value of ± 3 cm to specify (a) the type of fine powder and the compounding ratio thereof and (b) the unit binder volume as described above. The kneading was performed in a batch of 80 liters using a 100 liter biaxial forced kneading mixer. The kneading time was 1 minute for the kneading with the fine powder material and the aggregate, and 2 minutes for the main kneading with the admixture and water. (3) Test method The flow rate test method is as follows. A 10-liter sample is placed in the funnel-shaped container 1 shown in FIG. 3, and the straight pipe section 1a is taken from the total flow time after opening the lower straight pipe section 1a. Was calculated and expressed as the Q funnel flow time (seconds).
The test results are the average of three tests. Although this test method has not been adopted as a standard such as JIS, the reproducibility is sufficient and the test method is sufficiently reliable. The container 1 used for the test
Are the dimensions shown in FIG. (4) Test results (a) Relationship between mixing rate and average flow rate when Fa and Sg fine powder is mixed into Np (unit water volume, unit binder volume, fine aggregate ratio, slump flow: constant) As shown in the figure, the flow speed is higher than that of Np alone having the same slump flow. It is the falling speed. (B) Np 20%, Sg 50%, Fa in (a)
Relationship between the mixing rate and the average flow rate in the composition in which Fa was partially replaced with stone powder or Sf in the 30% mixture: As shown in FIG. 5, the mixing rate was 10% when the powder was replaced with stone powder.
Even if it replaces up to about (1/3 is replaced), the flowing speed hardly changes, and even if it replaces the whole amount (30%), the flowing speed is slightly slowed down and there is little adverse effect due to the difference in grain shape, and the viscosity due to stone powder It has been confirmed that the reduction effect is also large. In addition, it was confirmed that when the substitution was performed with Sf, the downflow speed was increased up to the mixing rate of 10%, and the downflow speed was maximized at 5%. (C) Relationship between unit binder volume and flow velocity (unit water volume,
(Unit coarse aggregate volume, constant slump flow): As shown in FIG. 6, the maximum average flow velocity is obtained when the unit binder volume is about 120 to 140 l / m ³ , and becomes slow when it is 160 or more or 110 l / m ³ or less. There was found. Especially 1
It has been found that below 20 causes fine aggregate separation during flow down. (5) Conclusion From the above results, the flow velocity in the case of an appropriate unit binder volume of the composition is, for example, Fa (including stone powder) by 4
By mixing 0%, Np alone is doubled and Fa is also increased.
Mixing a mixture of 30% (including stone flour) and 50% Sg is about 2.5 times faster than Np alone. In addition, Fa
By replacing with Sf of%, the speed can be increased up to three times.

In the above embodiment, the example of adding the thickener is omitted, but it is also possible to add the thickener in accordance with the use such as underwater concrete.

[0019]

As explained in detail in the above examples, in the concrete composition according to the present invention, the flow rate is optimized by the optimal blending of various fine powders constituting the unit hydraulic binder with the same slump flow. This improves the time required for the installation work using a tremy tube or a pump, and can reduce or omit the compaction work, which is suitable for achieving rationalization and labor saving of concrete work.

[Brief description of the drawings]

FIG. 1 is a table showing characteristics of materials used in the present invention.

FIG. 2 is a table showing the composition of the present invention.

FIG. 3 is an explanatory view showing an instrument used for a fluidity test.

FIG. 4 is a graph showing a relationship between a mixing ratio of fine powder and an average flow velocity.

FIG. 5 is a graph showing the relationship between the mixing ratio of fine powder and the average flow velocity.

FIG. 6 is a graph showing a relationship between a unit binder volume and a flowing speed.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigeru Aoki 4-640, Shimoseito, Kiyose-shi, Tokyo Obayashi Technical Research Institute (72) Inventor Shigeyuki Togawa 4-640, Shimoseito, Kiyose-shi, Tokyo In Obayashi Technical Research Institute (56) References JP-A-63-129052 (JP, A) JP-B-63-10110 (JP, B2)

Claims (3)

(57) [Claims] 1. A unit hydraulic binder having a volume of 120 to 1
40 liters / m ³ , the remainder being water and aggregates, the binder comprising 20-50% of Portland cement having a specific surface area of 2500-4500 cm ² / g, and a specific surface area of 2500
Blast furnace slag fine powder of 50 to 80 cm ² / g
%, A specific composition comprising a combination of fly ash having a specific surface area of 2500 to 10000 cm ² / g in a range of 0 to 30%. 2. A specific surface area of 2,500 to 8,000 cm based on the total amount of fly ash in the concrete composition.
The concrete composition according to claim 1, wherein 0 to 30% of ² / g of limestone powder and / or 1 to 10% of silica fume are replaced. 3. The concrete composition according to claim 1, wherein 0.1 to 1.0 kg of a thickener is added to 1 m ³ of the concrete composition.