JPH0618397A - Method and apparatus for testing flowability of fresh concrete - Google Patents

Abstract

PURPOSE:To measure the properties of various kinds of concrete which have been diversified in fluid states as and their workability in actual situations. CONSTITUTION:A coarse sieve 4 is placed below a discharge port 3 of a fresh concrete projector 3. The weight of fresh concrete remaining on the sieve 4 is measured continuously while the concrete is passed downward through the sieve 4, and flowability is measured based on the measured value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a test method and apparatus for examining workability and separation resistance of fresh concrete before hardening.

[0002]

2. Description of the Related Art Conventionally, as a measure for knowing the workability of fresh concrete, concrete is put in a cylinder placed on a flat plate, the cylinder is lifted and the internal concrete is diffused and flowed in all directions on the flat plate. A slump test is used in which the slump value is the difference between the maximum height when the flow is stopped and the height inside the cylinder.

However, this slump test is effective as a traditional test method for ordinary concrete having conventional and very general properties, but in this method, the slump test is carried out when the concrete stops flowing on a flat plate. As a measure to know the workability of concrete with various properties recently diversified and specialized, such as high strength concrete with high viscosity, it is not possible to grasp the property from the start to the stop of flow. There is a problem that it is not possible to respond, and there is no result as a measure to know the workability of the actual concrete placed in the formwork where the reinforcing bar is reinforced, and there is a problem that it does not correspond to the feeling according to the actual situation there were.

[0004]

The present invention solves the problem that in the slump test, only one result is obtained when the flow of concrete is in a stopped state, which does not correspond to the feeling according to the actual situation of placing concrete. Especially.

[0005]

[Means for Solving the Problems] A coarse sieve is installed below a fresh concrete throwing device, fresh concrete is thrown on the sieve, and the fresh concrete remaining on the sieve is permeated downward from the sieve. We propose a method and an apparatus for testing the fluidity of fresh concrete, in which one or both of the weight and the weight that has passed through the sieve are continuously measured over time, and the fluidity is measured based on these both measured values. It is a thing.

[0006]

[Action] Fresh concrete permeates through the sieve in the same condition as the reinforcing bars in the formwork to be actually placed, so by continuously measuring the weight per unit time, the flow of various diversifying concretes You can learn the nature of the situation and the workability according to the actual situation.

[0007]

1 and 2 show a measuring apparatus according to the present invention, in which a concrete injector 2 is installed on an upper part of a main body frame 1, and a concrete mold is actually provided below an outlet 3 with an opening / closing lid. A coarse sieve 4 is installed on the assumption of the condition of reinforcing bars when placing concrete in the frame, and a concrete receiver 5 is installed further below the sieve 4.

The concrete thrower 2, the sieve 4 and the concrete receiver 5 are respectively connected to a static strain gauge or the like, and an electronic weighing scale or the like is used to measure the weight continuously with time 6.
The weight of the fresh concrete, which is supported by 7, 8 and is respectively loaded or loaded, is continuously measured over time,
The measured value can be obtained as an electric signal or its converted value.

When measuring with the above measuring device,
After a certain amount of fresh concrete is put into the concrete thrower 2, the discharge port 3 is opened and the fresh concrete in the inside is put on the sieve 4, and sequentially passed through the sieve 4 to be deposited down on the concrete receiver 5.

At the same time as the concrete is put into the sieve 4, the weight Wa of the concrete remaining on the sieve 4 and the weight ΔWb of the concrete per unit time flowing down on the concrete receiver 5 by the weight scales 7 and 8 are changed with time. Measure continuously. In this case, only one of the weight scales 7 and 8 may be used for measurement, and Wa and ΔWb of the other weight may be calculated based on the measured values.

Based on the measured values of Wa and ΔWb, the fluidity of concrete can be examined as follows.

That is, assuming that concrete now flows as a Bingham body (fluid that does not flow until a certain force is applied), and it is assumed that only shearing force acts between the concrete and the mesh of the sieve 4, The stress τ that causes concrete to flow can be expressed by Equation 1 below.

[0013]

[Equation 1]

Here, η is the plastic viscosity, γ is the strain rate of concrete, and τy is the force (yield value) until the flow starts.

When the acting force and the displacement of the concrete per unit time are calculated based on such an assumption, it can be expressed by the following equation (2).

[0016]

[Equation 2]

Here, ΔWb is the weight of concrete that permeates the sieve 4 per unit time, A is the permeation area of concrete on the sieve 4, and ζ is the unit volume weight of concrete.

In Equation 2, η / ζ means the viscosity I of concrete, and τy · A means the force (deformation yield value) Ty at which the concrete on the sieve 4 starts to permeate, and these viscosity I and The force Ty can be considered as a factor representing the workability of concrete.

“Comparative Experimental Example”

The results of the slump test and the test by the apparatus of the present invention by using the samples having different compositions for the super high strength concrete (denoted as super concrete) and the ordinary concrete (denoted as ordinary concrete) are shown in Table 1. Shown in.

[0021]

[Table 1]

The results of Table 1 are set as the deformation yield value Ty on the X axis,
FIG. 3 is a graph showing the viscosity I on the Y axis.
In FIG. 3, □ indicates ultra-high strength concrete and Δ indicates ordinary concrete, and the numbers below each point are slump values.

It can be seen from FIG. 3 that the viscosity I and the deformation yield value Ty are remarkably different between the ultra-high-strength concrete and the ordinary concrete, even if the slump values are about the same, and the fluidity properties of the two are different.

For example, in ultra-high strength concrete, the larger the slump value (generally softer), the higher the viscosity and the smaller the deformation yield value, and in the ordinary concrete, the slump value changes. It was found that the viscosity did not change much and the deformation yield value was larger than that of ultra high strength concrete even at the same slump value.

Next, as a sample having the same slump value as shown in Table 1, the supercon UC-24 (slump value 23.8) was added to the normal control sample.
In OC-24 (slump value 23.2), the weight ΔWb of concrete that permeates through the sieve 4 per unit time is taken as the X axis,
4 and 5 show changes in ΔWb in the range of 0 kg / sec to 10 kg / sec with the weight Wa of the concrete remaining on the sieve 4 as the Y axis.

From FIGS. 4 and 5, for example, ΔWb is 6 kg.
Looking at the Wa of both parties at the time of / sec, it is Wa in the super computer UC-24.
＝ 20Kg, while Fu-Con OC-24 has Wa = 1
It is 0 kg, and it can be seen that after all, ordinary concrete has a higher viscosity and a smaller deformation yield value Ty than super-strength concrete.

Looking at the change over time in the weight Wa of the concrete remaining on the sieve 4, the ordinary concrete decreases sharply at the same time when the addition is started, whereas in the super high strength concrete, it is relatively gentle after the start. The tendency was to decrease.

[0028]

As described above, according to the present invention, the weight remaining on the sieve and the permeation weight per unit time are passed through in order to pass through the sieve in the same condition as the reinforcing bars in the mold for actually placing fresh concrete. By measuring continuously, various flow properties of various concretes with different qualities can be investigated from various angles, and the workability according to the actual situation can be known, and the measurement results are very easy to understand. It is possible to obtain the data close to the feeling of as a continuous numerical value.

[Brief description of drawings]

FIG. 1 is a side view of a test apparatus according to the present invention.

FIG. 2 is a plan view of the test apparatus of the present invention.

FIG. 3 is a diagram showing one result obtained by the method of the present invention.

FIG. 4 is a diagram showing another result obtained by the method of the present invention.

FIG. 5 is a diagram showing still another result obtained by the method of the present invention.

[Explanation of symbols]

 1 Main frame 2 Concrete thrower 3 Discharge port 4 Sieve 5 Concrete receiver 6 Electronic weighing scale 7 Electronic weighing scale 8 Electronic weighing scale

Claims (4)

[Claims] 1. The fresh concrete is put on a coarse sieve, and either one of the weight of the fresh concrete remaining on the sieve while permeating downward from the sieve and the weight per unit time passing through the sieve, or A fluidity test method for fresh concrete, characterized in that both are continuously measured over time, and fluidity is examined based on the weight values. 2. A fresh concrete throwing device, a coarse sieve installed below the fresh concrete throwing device, and a weight scale for continuously measuring the weight of the fresh concrete put on the sieve over time. A characteristic fluidity tester for fresh concrete. 3. The weight of the fresh concrete throwing device, the coarse sieve installed below it, the receiver installed below it, and the weight of the fresh concrete that has passed through the screen and flowed down onto the receiver. A fluidity test device for fresh concrete, comprising a weight scale that continuously measures with time. 4. A fresh concrete throwing device, a coarse sieve installed below it, a receiver placed below it, the weight of the fresh concrete put into the sieve and the flow down onto the receiver. A fluidity test device for fresh concrete, comprising a weight scale for continuously measuring the weight of the fresh concrete with time.