JPH0516331B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for mixing concrete.

(Prior art) Generally, in concrete plants, etc., concrete is manufactured using cement, coarse aggregate, fine aggregate,
The method used is to put water, etc. into a mixer and mix it for a certain period of time.

Among the aggregates used in concrete production, the surface water content of fine aggregate in particular varies greatly depending on where it is collected, weather, and storage conditions, resulting in variations in the quality of concrete after mixing.
Therefore, it is important for concrete quality control to accurately and quickly determine the surface water content of fine aggregate and to modify the mix according to changes in the surface water content.

Currently, the surface water amount of fine aggregate is determined by sampling a part of the fine aggregate before feeding it into a mixer, and measuring the surface water according to JIS standards.
Values are determined in accordance with A-1111. That is, the ninth
As shown in the figure, fine aggregate is carried from a stockyard 1 to a storage bin 3 by a belt conveyor 2, and in the process of being sent to a weighing bin 4, a part of the fine aggregate is sampled and a surface water amount measuring section 5 The amount of surface water is measured in accordance with 1111, the result is given to the mix correction section 6 to correct the mix in the weighing bottle 4, and fine aggregate is charged from the weigh bottle 4 to the mixer 7.

The mixing time of concrete is also an important point in concrete quality control.

Conventionally, the procedure for determining the concrete mixing time is as follows.

(a) Determine the kneading capacity of one batch.

(b) Select three kneading times and test a certain slump formulation three times.

(c) For each, find the difference in unit volume mass of mortar and difference in amount of coarse aggregate.

(d) Find the standard deviation of the test values for each kneading time.

(e) Draw a 95% confidence limit line, find the kneading time at the intersection with the standard value, and choose the longer time.

(Problems to be Solved by the Invention) However, this method of determining the surface water content of fine aggregate has the following problems.

(a ₁ ) 10
It takes several minutes, and when kneading is performed continuously, it is difficult to measure the amount of surface water in all batches.

(a ₂ ) Because sampling is performed when feeding into the weighing bin 4, the surface water content of the fine aggregate used for mix correction differs from the actual value.

(a ₃ ) Because the amount of sampling is small, variations in the amount of surface water occur due to differences in sampling locations.

(a ₄ ) In order to feed back changes in surface water content to the formulation, it is necessary to have personnel available for constant sampling and measurement.

On the other hand, the method of determining the kneading time as described above has the following problems.

( _b1 ) Since it is determined according to the amount of kneading and the slump value, the number of measurements becomes enormous, it is impossible to perform it for all combinations, and the test itself becomes complicated.

(b ₂ ) The mixing time determined by this method does not take into account changes in material quality (aggregate surface water amount, etc.), so in actual mixing, if the surface water amount changes, the quality will be stable. do not.

(b ₃ ) Since the uniformity of concrete materials is evaluated only by the difference in unit volume mass of mortar and the difference in unit coarse aggregate amount, the actual required quality of concrete (slump, air content, breathing, etc.)
is not guaranteed.

An object of the present invention is to provide a concrete mixing method that can ensure stable quality and improve mixing efficiency.

(Means for solving the problem) The concrete mixing method according to the present invention includes:
When concrete materials such as cement, coarse aggregate, and fine aggregate are put into a mixer and mixed by rotating the mixer, the power consumption of the mixer is measured from the start of adding mixing water, and water is added. Calculate the integrated power value until the measured power value reaches the preset reference power value during the process, and apply the obtained integrated power value to the previously stored integrated power value and target data of fine aggregate surface water percentage. The surface water content is estimated based on the estimated surface water content, the corrected amount of water is calculated based on the estimated surface water content, and the corrected water is added. An appropriate kneading energy value for the estimated surface water content is determined, the mixer is rotated until the appropriate kneading energy value is reached, and when the kneading energy value of the mixer reaches the appropriate kneading energy value, the mixer is rotated. The kneading process is characterized by stopping the rotation and finishing the kneading process.

(Function) When concrete materials are mixed, small lumps of fine aggregate and cement are formed due to the surface tension of the surface water contained in the aggregate. As the amount of surface water increases, the number of nodules increases and the resistance that affects the rotation of the mixer increases. This resistance is expressed as a power load and integrated, the value when the integrated power value reaches the reference power value is determined, the surface water rate is estimated based on this integrated power value, and this estimated surface water rate is Since the appropriate mixing energy is determined based on the mixing energy, the amount of water added is corrected based on each value, and the mixing time is determined, it becomes possible to obtain concrete of stable quality and improve mixing efficiency. be able to.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings. The present inventor noticed that the resistance during kneading (in other words, mixer power consumption) is related to the amount of surface water of fine aggregate, and created a configuration as shown in Figure 1 to determine the amount of surface water during kneading and the mixer. We investigated the relationship with power consumption. In the figure, 8U, 8V, 8W are power supply lines that feed power from the three-phase power supply to the motor 7A of the mixer 7;
9 is a power converter that calculates the power load value of mixer 7 using the two-wattmeter method; 10 is a three-phase power supply line 8U, 8V, 8
A voltage converter that provides voltage input from W to the power converter 8, and 11 an X-Y display that displays the output of the power converter 9.
A recorder 12 is an analog/digital (A/D) converter that converts the output of the power converter 9 into a digital signal.
D) It is a board.

According to experiments, the rate of water addition was slow (2Kg/sec).
As a result, the change in mixer power consumption when adding water was as shown in Figure 2, and it was found that the difference depending on the surface water percentage was significant.

Furthermore, when the relationship between the change in the water-cement ratio (W/C) during water addition and the mixer power consumption was investigated when the water addition rate was slowed down, a relationship as shown in FIG. 3 was obtained. From this relationship, it was found that when the power decreases, the water-cement ratio when a certain power value is reached is constant regardless of the surface water percentage.
From this, when the amount of surface water differs, there will be a difference in the electrical energy consumed until a certain amount of water is reached.

Therefore, when we determined the relationship between the cumulative power value from the time of adding water until reaching the reference power value and the surface water percentage, we obtained the results shown in FIG. 4. As is clear from the figure, a good correlation is obtained for any of the three set reference power values. This relationship can be applied even when the water addition rate is different, and its effectiveness was confirmed in experiments when the water addition rate was in the range of 1 to 4 kg/sec.

Furthermore, when the water addition rate is set arbitrarily, it has been confirmed that the relationship between the product (TR・Vw) of the integrated power value TR multiplied by the water addition rate Vw and the surface water rate is always constant, as shown in Figure 5. Ta.

The above experiments revealed that the surface water content can be estimated at any hydration rate.

Next, we also investigated concrete quality control using appropriate mixing energy.

The quality of mixed concrete varies depending on mixing time, mixer blade rotation speed, surface water content of fine aggregate, etc. Due to these factors, fluctuations in concrete quality can be determined by the amount of work done by the mixer 7 during mixing (hereinafter referred to as mixing energy).
As shown in Figure 6 A, B, and C, mixing energy and concrete quality (i.e., slump, air volume, and breathing rate)
It was found that the relationship between water and water can be expressed by a single curve with the surface water content of fine aggregate as a parameter.

Therefore, in order to maintain a constant quality of concrete, it is sufficient to determine the appropriate mixing energy according to the surface water content. For example, when a permissible value for breeling is set, the relationship between surface water content and appropriate kneading energy is as shown in FIG. By setting the breathing rate as necessary, the kneading energy corresponding to the surface water content can be determined. Also, as shown in Figure 6 A and B, the fluctuations in slump and changes in air volume become large when the kneading energy is 1.0wh/or less.
In order to keep these stable, control values are
If it is set to 1.0wh/or more, the quality of concrete will be further improved.

Based on these results, in this example of the present invention, kneading was carried out as follows.

(A) Weigh each concrete material according to the specified mix.

(B) Pour each concrete material into the mixer. At this time, the speed of adding water for kneading (water addition speed) is reduced to a constant speed by operating a valve or the like. The kneading water may be added at the same time as other ingredients or after dry kneading.

(C) Measure and record mixer power consumption from the start of water addition.

(D) Calculate the cumulative power value until the measured power value reaches a preset reference power value during water addition.

(E) Using a computer, etc., estimate the surface water percentage by applying the obtained integrated power value to the relational data between the integrated power value and fine aggregate surface water percentage, which is stored in advance as back data (see Figure 4). , see Figure 5).

(F) Calculate the corrected water addition amount based on the estimated surface water percentage,
Continuously add correction water after adding water.

(G) In parallel with the work in (F) above, determine the appropriate kneading energy according to the required quality based on the estimated surface water content (see Figure 7).

Note that processes (C) to (G) are performed in real time.

(H) Determine whether the kneading energy for the batch has reached the appropriate kneading energy.
When this is reached, the mixing is terminated and the concrete is discharged from the mixer 7.

A flowchart of the kneading method of this embodiment as described above is shown in FIG.

(Effects of the Invention) As explained above, in the present invention, the mixer integrated power value is measured, the surface water rate is estimated based on this, and the appropriate kneading energy is determined based on this estimated surface water rate. Since the amount of water added is corrected based on the value of and the kneading time is determined, the following effects can be obtained.

(a) Aggregate surface water management (a-1) Even when kneading is performed continuously, the amount of surface water can be measured in a short time.
It is possible to capture variations in surface water content between batches.

(a-2) Since the surface water amount of the total amount of kneading is determined, there is no variation depending on the sampling location.

(a-3) Measurement is possible even if the hydration rate is arbitrarily selected.

(a-4) It can be performed as part of the operator's kneading work, and there is no need to deploy personnel for surface water measurement.

(a-5) By simply adding a simple device to control the water addition rate (such as a cylinder valve with stroke adjustment), a power detection device, and a personal computer (commercially available), etc. Since it can manage water, it can be systemized at a much lower cost than other systems (sand controllers, moisture meters, etc.).

(b) Quality of concrete (b-1) Since this method determines the appropriate mixing energy according to the amount of surface water in the fine aggregate, there is no change in quality due to changes in the amount of surface water.
We can supply stable concrete.

(b-2) Since the range of variations in slump, air volume, etc. can be interpreted as changes in kneading energy, quality control becomes easier.

(b-3) Since tolerance values such as breathing can be set arbitrarily, concrete can be manufactured with consideration to workability (surface finish, etc.).

(b-4) Since the kneading energy can be treated as a constant index value even if the kneading amount and mixer capacity change, stable quality can be obtained with any kneading amount.

(c) Improving mixing efficiency (c-1) Instead of mixing for a fixed period of time as in the past, the mixing energy is determined to suit each batch, eliminating wasted mixing time and improving the efficiency of concrete mixing. Manufacturing efficiency improves.

(d) Systemization (d-1) Instead of relying on the operator's visual inspection and intuition as in the past, quality control can be performed automatically as a system, eliminating the need for skilled operators and reducing the number of operators. This can be handled by deploying personnel.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an example of a mixer power measuring device according to the method of the present invention, Fig. 2 is a characteristic diagram showing the relationship between kneading time and mixer power consumption when the water addition rate is slowed down, and Fig. 3 is a characteristic diagram showing the relationship between water-cement ratio during water addition and mixer power consumption,
Figure 4 is a characteristic diagram showing the relationship between the integrated power value and fine aggregate surface water content when adding water, and Figure 5 is a characteristic diagram showing the relationship between the product of the integrated power value and the water addition rate and the fine aggregate surface water content. Figures 6A, B, and C are characteristic diagrams showing the relationship between mixing energy and various properties of concrete, Figure 7 is a characteristic diagram showing the relationship between fine aggregate surface water content and appropriate mixing energy, and Figure 8 9 is a flowchart showing an example of the steps of the method of the present invention, and FIG. 9 is a block diagram showing the conventional steps. 7...Mixer, 9...Power converter.

Claims (1)

[Claims] 1. When concrete materials such as cement, coarse aggregate, and fine aggregate are put into a mixer and mixed by rotating the mixer, the power consumption of the mixer is measured from the start of adding mixing water, Calculate the integrated power value until the measured power value reaches the preset reference power value during water addition, and use the obtained integrated power value as the target data of the integrated power value and fine aggregate surface water percentage stored in advance. Estimate the surface water percentage by applying the application, calculate the corrected water addition amount based on the estimated surface water percentage obtained, add correction water, and calculate from the characteristic curve of surface water percentage and appropriate kneading energy for the required quality. An appropriate kneading energy value for the estimated surface water content is determined, the mixer is rotated until the appropriate kneading energy value is reached, and when the kneading energy value of the mixer reaches the appropriate kneading energy value, the mixer is rotated. A concrete mixing method characterized in that mixing is ended by stopping the rotation of the concrete.