JPH0576884B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for controlling the slump value of concrete by adjusting the amount of water in a ready-mixed concrete factory. The invention also relates to a method for rapid control.

[Conventional technology]

In a stationary cement concrete batcher plant, a so-called ready-mixed concrete factory,
We manufacture concrete with various mixes according to customer requirements. The mix differs depending on the specifics of the intended concrete work and is determined primarily by workability during concrete placement and the strength of the concrete required by the structure.

The slump value, which governs the strength and workability of concrete, is determined by the mixing ratio of cement, water, fine aggregate, coarse aggregate, etc. Among these, the amount of water has a particularly large effect, and the amount of water in concrete The amount is expressed as the magnitude of the slump value. Therefore, it is possible to control the amount of moisture by controlling the slump value.

Among concrete materials, the moisture content of aggregate tends to fluctuate, and even if the blending amount and material quality of other materials are adequately controlled, the slump value will vary due to fluctuations in the moisture content of aggregate, especially fine aggregate. changes.

Although it is possible to measure the moisture content of the aggregate supplied to the kneading machine in advance, it is difficult to collect representative samples, the reliability of the measured values is low, and it takes a long time to measure. Fluctuations in the moisture content of aggregates are often not adequately captured. Continuous aggregate moisture measurement devices are available, but these are still unreliable.

In addition, measuring the slump value of concrete requires skill and takes time, so in reality it is not always measured, and the control of the slump value by adjusting the moisture content in a ready-mixed concrete factory is performed by the operator. This is done based on visual inspection and intuition. However, methods that rely on visual inspection and intuition cannot avoid fluctuations due to the physical condition of the operator, and are prone to errors due to individual differences due to changes in operators.
It was not necessarily suitable as a means of controlling the slump value, which has a large effect on the strength and workability of concrete.

The slump value is an index indicating the workability, that is, fluidity, of concrete, and is known to have a negative correlation with the load power of a mixer when mixing concrete. Therefore, as a method to solve the above problem, a method has been considered that utilizes this correlation and controls the slump value of concrete by adjusting the amount of water using the load power of the mixer as a parameter. 57−39914, Tokukai Sho
59-17930, JP-A-60-6412, JP-A-61-217215
Related technologies are disclosed in, etc.

[Problem that the invention seeks to solve]

The conventional method of controlling the slump value by detecting the concrete mixing load power of the concrete mixer and adjusting the moisture content of the concrete based on this detects the concrete mixing load power. Since the load power is measured at the time of the test and the amount of water is adjusted based on the measured value, a time delay is unavoidable.

Recently, due to advances in technology, the performance of mixers has improved and the time required to mix concrete has been significantly shortened. Therefore, in order to achieve its effect,
It is necessary to eliminate as much as possible the conventional time delay caused by controlling the slump value.

An object of the present invention is to provide a method for controlling the moisture content of fresh concrete that solves these problems.

[Means for solving problems]

In order to solve the above problems, in the present invention, instead of correcting the amount of water when mixing has been sufficiently performed, the amount of water is corrected intermittently during the mixing process from the early stage of concrete mixing, and for a short time. The purpose is to finish the kneading at this point.

That is, in the method of the present invention, (1) First, as a preliminary step, a standard mix is determined in advance for each slump value, (i) concrete of this standard mix is kneaded, and the load power of the mixer during mixing is determined over time. Understand the change pattern and memorize it.

(ii) Mix and mix concrete with a predetermined amount of water reduced from the standard mix using several different amounts of water, and memorize changes over time in the concrete mixing load power at that time.

(iii) Compare the kneading load power while mixing concrete with the above standard mix and the kneading load power while kneading concrete with a reduced amount of water, and check the difference between the two kneading load powers and the kneading power at each time after the start of mixing. Calculate the relationship with the difference in water volume and store it in memory.

(2) By inputting shipping concrete specification instructions, derive a standard mix of concrete that should obtain a target slump value, and instruct the material supply device to create a mix with a certain percentage of water content reduced from the derived standard mix.

(3) Feed the materials to the kneading machine according to the specified mixture (including water content). After the supply of materials is finished, kneading is started. At this time, it is also possible to start kneading immediately or halfway after the material is supplied.

(4) Detect the concrete kneading load power for each elapsed time from the start of mixing, compare it with the load power during concrete mixing of the standard mix, and calculate the change.

(5) Convert the calculated concrete mixing load power deviation into water volume. A predetermined proportion of this water amount is instructed to the material supply device as a correction water amount.

(6) Detect the actual kneading load power, continue to compare it with the kneading load power of the concrete of the standard mix, repeat the correction of the make-up water amount in several stages, and bring the deviation of the kneading load power to zero, Make the slump value match the shipping target value.

[Effect]

The present invention makes the slump value of concrete match the target value through the above-described procedure.

According to this procedure, the mixing is completed faster than the conventional method of detecting the concrete mixing load power once the mixing is completed and correcting the water amount based on this, and the actual mixing load power is intermittently added to the standard mixture. The amount of water can be corrected while comparing and comparing it with the concrete mixing load power of the concrete, making it possible to make highly accurate corrections.

The standard mix is a mix determined for each step of the slump value, and can be represented by the mix corresponding to the concrete shipped the most among a group of concretes with the same slump value.

The materials used to create the standard mix are coarse aggregate and fine aggregate that have been pre-moistened.

As for the increments of the slump value, it is easy to apply an integer value within the range of the slump value of concrete manufactured in a ready-mixed concrete factory and represented by an integer value of 1 cm.

The range of the slump value is 5 cm to 22 cm, and it is sufficient to calculate it in 1 cm increments.The allowable range for each slump value is about 0.3 cm, and it is also possible to measure the same composition several times and calculate the average value.

A negative correlation exists between the slump value and the concrete mixing load power. This relationship holds approximately even if the water-cement ratio differs, except for special formulations.

Concrete mixing load power can be expressed as a power value or current value that represents the load on the mixer, or it can also be expressed as a value obtained by subtracting the power or current value at no load from the total power or total current value. can.

The corrected water amount can be calculated using the following general formula.

ΔH=Ha−Hb/Wb−Wa(Wc−Wa)F However, ΔH: Corrected water volume Ha: Water volume of standard mixture Hb: Water volume when reduced from the standard mixture Wa: Load power while kneading the standard mixture Wb: Standard Load power when the amount is reduced from the mixture Wc: Load power when shipping concrete is mixed F: Correction ratio.

In the method of the present invention, it is necessary to respond to changes in the condition of the kneader blades and the adhesion condition of concrete. Regarding this point, it is possible to measure the change over time in the concrete mixing load power at each increment of the slump value according to the change, and use that value to correct the change over time in the mixer load power when mixing concrete of the standard mix. preferable.

For example, it is possible to measure three representative levels of slump values: high, medium, and low, and perform correction accordingly.

Adjustment of increase/decrease in the amount of correction water is performed by changing the opening time of the electromagnetic valve.

When correction make-up water is supplied, the deviation between the actual mixing load power of the mixer and the mixing load power during concrete mixing of the standard mix will become smaller, but since there will be a time delay, Mix concrete with a certain proportion of water content compared to concrete, and make simulation corrections to understand the time delay.

The above operation is repeated several times to match the kneading load power to the kneading load power during kneading concrete of the standard mix, thereby making the amount of water in the concrete match the target amount of water.

It is necessary to match the measurement start time when measuring the kneading load power of the standard mix with the time when controlling the actual concrete slump value, but the selection of the correction start time depends on the concrete mix. It is possible to start correction from any time.

According to the present invention, it is possible to estimate the moisture content of the aggregate from the total corrected water amount, and the next time and subsequent formulations can be corrected based on this estimated moisture content.

The technical means of the present invention will be explained in more detail with reference to FIG. FIG. 1 shows the change in kneading load power over time.

In FIG. 1, the vertical axis is the kneading load power, and the horizontal axis is the time from the start of kneading.

The concrete kneading load power increases at the start of kneading, decreases as kneading progresses, and when a sufficient kneading state is achieved, it reaches a certain value and does not change thereafter.

In FIG. 1, curve a shows the change over time in the kneading load power during mixing of concrete with a standard mix. Curve b shows the estimated change in concrete mixing load power over time assuming that mixing was performed without correcting the water amount. Curve c shows the change over time in the kneading load power when the water amount was corrected in three stages for shipped concrete.

Next, changes in curve c will be explained. Curve c initially coincides with curve b, and gradually approaches curve a by correcting the amount of water. At the start of mixing, measurement of the concrete mixing load power starts (point A). The electric power for 2 seconds (point A to point B), 10 to 12 seconds after the start of kneading, is averaged and compared with the change in load power over time (curve a) of a standard mixture at the same measurement level. The deviation in the comparison result is converted into water content, and a certain percentage of the water content (for example, 70%) is instructed to the water supply device as the corrected water content.

In the figure, 12 to 14 seconds (points B to C) is the waiting time required for verification of measurement results, calculations, and instructions for correction.

At the start of correction (point C), the solenoid valve of the water supply device is opened, and the water amount addition correction is performed for 2 seconds from 14 to 16 seconds (point C to point D). Due to the correction, the load power value decreases to 16
Although the correction ends after a second (point D), the concrete mixing load power continues to decrease.

The period of 16 to 18 seconds (point D to point E) is the delay time for power reduction due to the addition of water. During this time, the power decrease ends, and the curve c becomes parallel to the curve a (point E to point F). This completes the first stage of correction.

In the same procedure, in the second stage (points F to J), perform a correction corresponding to, for example, 20% of the corrected water volume, and in the third stage (points J to N), perform a correction corresponding to, for example, 10% of the corrected water volume. Approximate curve c to curve a. after that,
Kneading is continued until there is no change in the kneading load power, and then the kneading is completed.

〔Example〕

The present invention will be explained in detail below with reference to Examples.

A block diagram of an apparatus in which the present invention can be preferably carried out is shown in FIG.

The kneader 1 is attached with a water supply device 4 and a supply device 5 for cement, fine aggregate, coarse aggregate, etc., from which raw materials are supplied. The kneading machine 1 is driven by a drive motor 2, and the power of the drive motor 2 is actually measured by a power value measuring device 3. This measured value is input to the microcomputer 6.

The microcomputer 6 is attached with a storage device 7 for basic formulations and a storage device 8 for pre-stage measured values.
The storage devices 7 and 8 can also be built into the microcomputer 6. The microcomputer 6 is given the moisture content of fine aggregate and coarse aggregate, and is also input with shipping instructions according to the concrete order specifications.

Next, the operation of the method for controlling the slump value of fresh concrete according to the present invention will be explained step by step with reference to FIG. The method of the present invention consists of two stages: a preliminary stage and an operational stage.

The preliminary steps of the present invention are carried out by the following steps (a) to (f).

Preliminary step (a) At the factory, a provisional standard mix of concrete is determined for each step of the slump value within the range of slump values that are shipped in relatively large quantities.

(b) Test mix concrete using this provisional standard mix, and based on the results, adjust the moisture content and determine the standard mix.

(c) Store in a memory device the changes over time in the mixing load power while mixing concrete with the standard mix. In the embodiment, the information was stored in a storage device built into a microcomputer.

(d) Mix concrete with a water content reduced by a certain percentage from the standard mix, and store the kneading load power in the memory device. In the embodiment, the information was stored in a storage device built into a microcomputer. This formulation was performed for multiple formulations.

(e) Compare the temporal changes in the kneading load power memorized in (c) and (d) above, find the difference in the kneading load power for each elapsed time from the start of kneading, and calculate the difference in the kneading load power and the amount of water required for correction. Derive the relationship between

(f) Store the relationship in (e) above in the storage device as a formula for calculating the amount of water required for correction. In the embodiment, the information was stored in a storage device built into a microcomputer.

The previous steps are completed by following steps (a) to (f) above, and then (g) below describes the steps for the operation step during operation.
~(r) steps will be explained.

Operation step (g) In accordance with the shipping instructions, a temporary mix of concrete to be mixed is extracted from a pre-stored microcomputer file.

For example, the type of concrete, including the cement brand, slump value, nominal strength, etc., is input based on shipping instructions. Based on this shipping instruction, the microcomputer selects the cement to be mixed from a list of concrete types stored in advance.
A mixture of water, sand and crushed stone is called. An example is shown below.

Slump value: 15cm Water-cement ratio: 55% Mixture: Cement ^: 318Kg/m ^3Water : 176Kg/m ^3Sand : 740Kg/m ^3Gravel : 1072Kg/m 3Difference in water amount for slump value 10cm: 27/m ^3Water amount for 10 Slump value difference: 3.7cm 7% value of water amount: 12.3/m ³ 2% value of sand (converted to water amount): 14.8/m ³ (h) Calculate a mixture by subtracting a certain percentage of water from this mixture.

From the above called combination, the predetermined proportion,
For example, a formulation in which the amount of water added is reduced by 2 to 5% is calculated.

(j) Instruct the material supply device to calculate the amount of water.

(k) Supply materials in accordance with instructions.

The operation time of the cement, fine aggregate, and coarse aggregate supply devices and the opening time of the solenoid valve of the water supply device are determined and operated.

(l) Start kneading When kneading starts, measurement of the kneading load power of the kneader drive motor starts. The measured concrete mixing load power is input to the microcomputer 6 and processed as a signal with a time constant of 2 seconds (a value averaged every 2 seconds).

(m) From the start of mixing, compare the concrete mixing load power for each elapsed time with the mixing load power of the corresponding slump value in (c) above, and calculate the deviation of the mixing load power.

The average value of the above-mentioned processed signal is compared and verified with the change over time of the mixing load power of the concrete of the standard mix, which has been inputted in the same manner in advance.

(n) Calculate the amount of water required for correction from the deviation of the kneading load power during a predetermined time period.

The start of correction depends on the mix of concrete.
Correction can be started at any time.

(p) Instruct the water supply device to supply the amount of water required for correction multiplied by a certain percentage.

The deviation of the kneading load power after a certain time after the start of mixing, which is found as a result of comparison and verification of the concrete kneading load power, is calculated as the difference in water volume, and this water volume is multiplied by a predetermined coefficient to determine the water volume for the first correction. Instruct the supply device to add the amount of water. A second correction water amount is further calculated based on the result of comparison and verification of the concrete kneading load power after a certain period of time after the end of the correction, and this corrected water amount is replenished to the concrete.

(q) Perform the operations (n) and (p) above a predetermined number of times to converge the deviation of the concrete mixing load power to zero,
Make the slump value match the target value.

The amount of water added is corrected in several steps. The correction ratio is changed at each stage to accurately match the load power to the reference. For example, the first stage is 70%, the second stage is 20%.
%, and the third stage is 10%, and it is preferable to converge to the target value. Further, the rate of change of the correction ratio for each slump value can change the correction ratio depending on the magnitude of the slump value.

(r) Kneading ends when there is no change in the load power.

〔Effect of the invention〕

According to the method of the present invention, concrete having a desired slump can be mixed and manufactured with high precision without causing a delay in the mixing time of fresh concrete.

[Brief explanation of the drawing]

FIG. 1 is a graph showing changes in kneading load power over time, FIG. 2 is a block diagram of an apparatus to which the method of the present invention is applied, and FIG. 3 is a flowchart illustrating the content of the present invention. 1... Kneading machine, 2... Motor, 3... Power measuring device, 4... Water supply device, 5... Supply device for cement etc., 6... Microcomputer, 7, 8...
…Storage device.

Claims (1)

[Claims] 1. When mixing ready-mixed concrete, the changes over time in the mixing load power of concrete with a standard mix and concrete with water content reduced from the standard mix are memorized in advance for each slump value, and the water content is adjusted from the standard mix to obtain the target slump value. Start mixing with a reduced mix, compare the change in concrete mixing load power over time with the change in concrete kneading load power over time for the standard mix, find the deviation for each elapsed time, and calculate the amount of make-up water corresponding to the deviation. A method for controlling the moisture content of fresh concrete, which comprises: supplying a corrected amount of water, then actually measuring the concrete mixing load power, and correcting the amount of replenishing water based on the measured value while converging the deviation to zero.