JP4315400B2 - Method and device for measuring unit water volume of fresh concrete - Google Patents

Description

The present invention relates to a method for measuring the amount of unit water of fresh concrete and its measuring device, more specifically, sieving fresh concrete to obtain a mortar sample, drying the mortar sample by high-frequency heating, and based on the amount of evaporated water at that time, about the unit water content measuring method and measuring apparatus for fresh concrete to measure the unit water.

A wide variety of methods for measuring the unit water amount of fresh concrete (fresh concrete), such as that described in Patent Document 1, are known. Among them, the unit water quantity measurement method (hereinafter referred to as a microwave oven method) that employs a high-frequency heater is prevalent due to its versatility and the clarification of the principle.
There are various procedures and calculation methods in the microwave oven method. The basics are outlined below.

(1) First, wet screening is performed by sieving fresh concrete using a screen having a mesh size of 5 mm, and a mortar sample is collected. In the microwave method, the amount of the mortar sample used at one time (one batch) is generally less than 1 kg (usually about 400 g). In addition, the weight of fresh concrete 1 m ³ is around 2300 kg, of which the weight of mortar is around 1300 kg. Therefore, the amount of evaporated water of the mortar sample calculated from the weight contrast of the mortar sample before and after high-frequency heating is multiplied by several thousand when measuring the unit water amount of fresh concrete.
As a result, if the sample to be heated does not accurately represent the concrete component, a huge error occurs in the measurement result of the unit water amount. If the sample is not mortar but fresh concrete, the unit water amount of the fresh concrete varies greatly depending on whether or not there is one coarse aggregate in the concrete sample (fresh concrete sample). In that respect, if the sample is fresh mortar (raw mortar) that does not contain coarse aggregate, the error is reduced. From this point, the mortar sample is adopted in the microwave oven method.

(2) Next, a predetermined amount of the mortar sample after the wet screening is heated by a high-frequency heater to evaporate water in the mortar sample. A high-frequency heater having a high output of 1600 W is widely used.
(3) Then, weigh the heated mortar sample to determine the amount of evaporated water. At this time, as the cement hydration reaction proceeds, the amount of water evaporated from the mortar sample also changes. Therefore, based on the following formula, correction calculation is performed corresponding to the change, and the unit water amount of 1 m ³ of fresh concrete is obtained.

W = (amount of evaporating water) × {(amount of mortar on the design blend) / (sample before drying)} + X ₁ −X ₂ + X ₃ + X ₄
W: Unit water volume of fresh concrete (kg / m ³ )
X ₁ : Correction amount of cement bound water (kg / m ³ )
X ₂ : Correction amount of moisture absorption of fine aggregate (kg / m ³ )
X ₃ : Correction amount of solid content of the admixture (kg / m ³ )
X _4: oversize aggregate, the correction due to excessive particle (kg / m ³⁾

In addition, in the microwave oven method, the heating time by a high-frequency heater is used as a discrimination criterion, the heating time is variable for heating treatment until the mortar sample is completely evaporated at any heating time, and the heating time is 4 minutes, 5 minutes, for example. There is a method of dividing the heating time fixed type. For example, the National Federation of Ready-mixed Concrete Industry Association Standardized ZKT-210 “Rapid estimation test method for fresh concrete (high-frequency heating method)”, which standardizes the microwave oven method, belongs to the heating time variation type. According to the fixed heating time type, in most cases, the water in the mortar sample is not completely evaporated. Therefore, after high frequency heating, for example, the cement water content is changed to correct the unit water amount of fresh concrete.
JP 2002-355811 A

By the way, the biggest error factor in measuring the unit water volume of fresh concrete by the heating time fluctuation type microwave method is that the mortar sample after wet screening does not represent the components of fresh concrete. is there.
Even if the moisture in the mortar sample after high-frequency heating is accurately measured, a small amount of mortar sample is converted to 1 m ³ of fresh concrete to calculate the unit water volume, so the mortar sample accurately represents the components of fresh concrete. If not, the reliability of the measured unit water volume is poor.
Therefore, in order to eliminate this problem as much as possible, in the actual unit water quantity measurement test, the vibration sampler is used to screen the concrete sample more vigorously and for a longer time so that the mortar completely separates from the coarse aggregate. Things have been done. However, even if the sieving time is lengthened, the paste adhered to the surface of the coarse aggregate cannot be completely removed, and natural evaporation is induced. The result of was not obtained.

In addition, for example, according to the above-described ZKT-210 heating time variation type microwave oven method, since the mortar sample is continuously heated until it reaches a constant weight, the device (microwave oven) is burdened and the device is easily damaged. . Moreover, it took 10 minutes or more to complete the measurement, and there was a problem in the speed of measurement. In addition, since the mortar sample is heated to 200 ° C. or higher, a heat-resistant dish having problems in durability and price has to be adopted as a heating container in which the mortar sample is put. If a disposable paper dish is used, it is carbonized when heated.
In the unit water quantity measurement test, a high-frequency heater having a high output of 1600 W is designated. As a result, equipment costs have also increased.

Even in the case of the microwave oven method with a fixed heating time, there are the following problems.
(1) The heating time was fixed at, for example, 4 minutes or 5 minutes. Therefore, non-evaporated water that could not be evaporated remains in the mortar sample after frequency heating. With respect to this point, conventionally, there is known a method in which non-evaporated water is considered as cement-bound water and is corrected by the cement-bound water rate. This correction reduces the measurement time by about 5 minutes. Also, paper plates can be used.
(2) Cement binding water ratio varies depending on the type of cement and water cement ratio. Thus, a preliminary test (paste test) must be performed for each cement used. In addition, it cannot be determined whether the cement-bound water ratio obtained in the paste experiment matches the cement-bound water ratio of the paste in the actual fresh concrete.
(3) Even if the cement-bound water ratio is obtained in advance, the measurement results of the cement-bound water obtained vary greatly.

This invention can measure the unit water amount of fresh concrete quickly and with high accuracy, regardless of the material and preparation of fresh concrete, even in the microwave oven method with a fixed heating time. It is an object of the present invention to provide a fresh concrete unit water amount measuring method and apparatus capable of using a disposable paper plate as a heating container for high-frequency heating, as well as being highly representative of mortar samples for components.

In the wet screening method of collecting mortar samples by sieving fresh concrete with a screen having a mesh size of 5 mm, the sieving operation of the fresh concrete is performed by sieving the mortar sample with respect to the total amount of mortar in the fresh concrete. The wet screening method for fresh concrete is applied until a mortar sample of 20 to 40% by weight per batch is collected at a mortar collection rate indicating the ratio of the weight of the mortar .

When sieving fresh concrete with a screen, the sieving operation per batch is performed until a mortar sample having a mortar collection rate of 20 to 40% by weight is obtained. Thereby, sieving is finished before the mortar and coarse aggregate, and the mortar and water are separated. As a result, compared to the conventional method in which the mortar sample is vigorously sieved for a long time (60 to 150 seconds), the moisture in the obtained mortar sample is highly accurate and close to the blended value. Moreover, it can be applied not only to a unit water amount measurement test using a microwave oven method, a capacitance method, etc., but also to a setting test of fresh concrete.

The components of fresh concrete mainly consist of cement, coarse aggregate having a particle size of 5 mm or more, fine aggregate having a particle size of less than 5 mm, and water.
The components of mortar are mainly composed of cement, fine aggregate and water. That is, including mortar samples, mortar here is fresh mortar (raw mortar) having fluidity.
The sieving operation of fresh concrete can be performed by a vibration sieving machine. Further, although it takes a long time, it may be sieved manually. The sieving time by the vibration sieve is 2 to 30 seconds, preferably 2 to 15 seconds per batch.
The mortar collection rate refers to the ratio of the mortar amount screened out to the total mortar amount in fresh concrete. For example, a mortar collection rate of 100% means that all mortar in fresh concrete has been sieved off.
If sieving work per batch of fresh concrete is less than 20% by weight, the amount of mortar to be screened out is too small, and it takes a long time to obtain a predetermined amount of mortar, and many of them have a high density. Separation such as sieving may occur. Moreover, when it exceeds 40 weight%, a coarse aggregate and a paste will remain on a sieve and the paste in the extract | collected mortar will decrease compared with a compounding value. If it is 20-40 weight%, it is less than +/- 3% with respect to a compounding value as a measurement result of a unit water amount. A preferable amount of sieving work per batch of fresh concrete is 25 to 35% by weight in terms of mortar collection rate. If it is this range, the more suitable effect of +/- 1.5% with respect to a compounding value will be acquired as a measurement result of unit water quantity.

Sieve fresh concrete through a screen having a mesh size of 5 mm, a vibrating sieve that collects a mortar sample from the fresh concrete, a measuring instrument that is arranged below the screen and measures the collected mortar sample, and the previously registered It is possible to use a wet concrete wet screening apparatus provided with a sampling rate calculating means for obtaining a mortar sampling rate which is a ratio of the weight of the mortar sample sieved to the total amount of mortar in the fresh concrete .

When sieving fresh concrete with a screen of a vibration sieving machine, the sieving operation per batch is performed until a mortar sample having a mortar collection rate of 20 to 40% by weight is obtained. At this time, the mortar sample sieved off the screen is weighed over time by a measuring instrument. Further, the mortar collection rate is obtained from the measured value and the total amount of mortar in fresh concrete registered in advance in the collection rate calculation means. Thereby, sieving is finished before the mortar and coarse aggregate, and the mortar and water are separated.
The water content in the obtained mortar sample is close to the blended value as compared with that obtained by the conventional method, and there is no difference in the fine aggregate particle size in the mortar sample. As a result, a mortar sample having high representativeness of fresh concrete can be obtained.
As the measuring device, for example, a balance, a load cell, or the like can be adopted.

The invention according to claim 1 is a mortar sampling rate indicating the ratio of the weight of the mortar sample sieved to the total amount of mortar in the fresh concrete by a screen having a mesh size of 5 mm. Wet screening step of sieving until 20 to 40% by weight of mortar sample is collected per batch, first weighing step for weighing mortar sample after wet screening, and predetermined amount of mortar sample after wet screening Is inserted into a high-frequency heater, high-frequency heating is performed for a preset time, a part of the moisture in the mortar sample is evaporated, and a second measurement for weighing the mortar sample after high-frequency heating From the difference between the weight of the mortar sample before and after the high-frequency heating process, And a vaporization water measuring step for obtaining the originating water for measurement of the evaporation amount of water, based on the following equation to calculate the water mortar ratio of mortar before heating, the fresh concrete to obtain the unit water content of fresh concrete 1 m ³ It is a unit water quantity measurement method.
Water mortar ratio = a × (evaporated water rate) ² + b × (evaporated water rate) + c
However, the water mortar ratio is water / mortar amount, the evaporating water rate is evaporating water amount / mortar amount, and a, b, and c are coefficients specific to the high-frequency heater.

According to the invention described in claim 1, during wet screening, fresh concrete is sieved until a mortar sample of 20 to 40% by weight is collected at a mortar collection rate per batch. Thereafter, the obtained mortar sample is heated at high frequency for a preset time (fixed heating time type) to evaporate a part of moisture in the mortar sample. Next, the amount of evaporated water from the mortar sample is determined from the difference in the weight of the mortar sample before and after the high-frequency heating. Then, a correction calculation (water mortar ratio = a × (evaporated water rate) ² + b × (evaporated water rate) + c) using the correlation between the water mortar ratio and the evaporated water rate is performed on the measured amount of evaporated water. applied, determine the total amount of water in the mortar in the fresh concrete 1m ^3. Thereafter, the water absorption correction of the aggregate and the correction of the admixture are performed to determine the unit water amount.

According to a lot of experimental data, when heated in a microwave for a certain period of time (eg 1500 W, 4 minutes), the amount of water in the substance to be heated and the amount of moisture evaporated from the substance by heating, regardless of the composition ratio of the material And found that there is a very high correlation. By utilizing this correlation, the amount of water in the substance can be estimated from the amount of water evaporated.
Mortar = C + S + W (C: cement, S: fine dry aggregate, W: water)
Water mortar ratio = W / (C + S + W)
Evaporation water rate = evaporation water amount / mortar Water mortar ratio = a × (evaporation water rate) ² + b × (evaporation water rate) + c

Therefore, the water mortar ratio can be obtained by measuring the amount of evaporated water. Since the amount of mortar is known, the water content in the mortar, and consequently the water content in the fresh concrete, is determined from this water mortar ratio. Therefore, the magnitude of the high-frequency output of the high-frequency heater is arbitrary. However, it takes a long time at low output.
Thereby, even if it is a microwave oven method of fixed heating time type, the unit water quantity of fresh concrete can be measured rapidly and with high precision irrespective of the material and preparation of fresh concrete. Moreover, the representativeness of the mortar sample for the fresh concrete component is high, and a disposable paper plate can be used as a heating container for high-frequency heating.

The type of cement is not limited. For example, ordinary Portland cement (N), early-strength Portland cement (H), blast furnace cement type B (BB), moderately hot Portland cement (M), low heat Portland cement (L), and the like can be used.
The water mortar ratio of the mortar sample is not limited.
The time for high-frequency heating of the mortar sample is not limited. For example, 4 minutes and 5 minutes.
The amount of water in the mortar sample evaporated by high frequency heating is not limited as long as it is a part of the water in the mortar sample.

The invention according to claim 2 is a heating box into which a heating container containing a mortar sample obtained by wet screening of fresh concrete is inserted, and the heating box is provided in the heating box, and the mortar sample is set in advance. A unit water amount measuring apparatus for fresh concrete comprising a high-frequency heater having high-frequency heating means having high-frequency heating for evaporating a part of the water in the mortar sample by high-frequency heating for a period of time, provided in the heating box, From the weighing means for measuring the weight of the mortar sample and the difference in the weight of the mortar sample before and after high-frequency heating based on the weighing data from the weighing means, the amount of evaporated water from the mortar sample by high-frequency heating is obtained. Based on the following equation, the water mortar ratio of the mortar before heating is calculated based on the following equation for the measured amount of evaporated water and the amount of evaporated water. Tsu is the unit water amount measuring device of fresh concrete and a correction calculation means for calculating the unit quantity of water Gerhard concrete 1 m ^3.
Water mortar ratio = a × (evaporated water rate) ² + b × (evaporated water rate) + c
However, the water mortar ratio is water / mortar amount, the evaporating water rate is evaporating water amount / mortar amount, and a, b, and c are coefficients specific to the high-frequency heater.

According to the invention described in claim 2, for example, during wet screening, fresh concrete is sieved in advance until a mortar sample of 20 to 40% by weight is collected at a mortar collection rate per batch. Thereafter, a heating container containing a predetermined amount of the obtained mortar sample is inserted into a heating box, and then the mortar sample is subjected to high frequency heating by high frequency heating means. Then, the difference in the weight of the mortar sample before and after the high frequency heating is measured by the measuring means, and the amount of evaporated water from the mortar sample is obtained by the evaporated water amount measuring means based on the difference in the weight. Next, a correction calculation using the correlation between the water mortar ratio and the evaporation water rate by the correction calculation means (water mortar ratio = a × (evaporation water rate) ² + b × (evaporation water rate)) + C) to obtain the unit water volume of 1 m ³ of fresh concrete.
As a result, even with a microwave oven method with a fixed heating time, the unit water volume of fresh concrete can be measured quickly and with high accuracy regardless of the material and preparation of fresh concrete. The mortar sample is highly representative and a disposable paper plate can be used as a heating container for high-frequency heating.

The material, shape, and size of the heating container are not limited. For example, the same bakeware as before may be employed. Moreover, you may employ | adopt a disposable paper plate.
The material of the heating box is not limited as long as high-frequency heating is possible. The shape and size of the heating box are not limited.
The kind of high frequency heating means is not limited. For example, 100V, 200V, etc. can be adopted as the power source.
The high-frequency heating means may be a turntable type or a fixed table type.
The kind of measuring means is not limited. For example, an electronic balance or the like can be employed.

In the method for measuring the unit water amount of fresh concrete according to claim 1, since fresh concrete is sieved until 20 to 40% by weight of a mortar sample is collected at a mortar collection rate per batch during wet screening. High accuracy and high representativeness of mortar samples for fresh concrete components .

According to the unit water amount measuring device of fresh concrete according to the unit water amount measuring method and a second aspect of the fresh concrete of claim 1, the correlation with respect to the measurement value of the evaporation water quantity, water mortar ratio and evaporating water ratio Correction calculation (water mortar ratio = a × (evaporation water rate) ² + b × (evaporation water rate) + c) is performed and the unit water amount of 1 m ³ of fresh concrete is obtained. However, regardless of the material and blending of the fresh concrete, the unit water volume of the fresh concrete can be measured quickly and with high accuracy (for example, an error of about 1%), and the mortar sample for the fresh concrete components can be measured. It is highly representative, and a disposable paper plate can be used as a heating container for high-frequency heating.

  Embodiments of the present invention will be described below with reference to the drawings.

In the method for measuring the unit water amount of fresh concrete according to Example 1 of the present invention, as shown in FIGS. 1 and 2, the unit water amounts of three high-frequency heaters (commercial microwave ovens) A, B, C and fresh concrete are shown. A measuring device (1500 W) D was used.
Hereinafter, the unit water amount measuring device D will be described in detail. The unit water amount measuring device D is installed in the heating box 11 into which the heating container 20 into which a predetermined amount (400 ± 10 g) of a mortar sample obtained by wet screening of fresh concrete is inserted, and the heating box 11, The high-frequency heater 30 </ b> D having high-frequency heating means 12 that heats the mortar sample for a preset time and evaporates a part of moisture in the mortar sample is provided.

The high-frequency heater 30D is installed in the heating box 11 and measures the weight of the mortar sample, and the difference in the weight of the mortar sample before and after the high-frequency heating based on the weighing data from the weighing means 13. , and evaporated water amount measuring means 14 for determining the evaporation amount of water from the mortar samples by high-frequency heating, with respect to the measurement value of the evaporation water, based on the following equation, applying the correction calculation of the evaporation amount of water, the unit water content of fresh concrete 1 m ³ And a correction calculation means 15 to be obtained. Among these, the evaporating water amount measurement means 14 and the correction calculation means 15 are incorporated in the control unit as an electric circuit.

The heating box 11 is a rectangular parallelepiped box, and an opening / closing door 11b that closes the heating chamber 11a, a display unit 11c of a liquid crystal display, and an operation unit 11d are disposed on the front surface. In the heating chamber 11a, a turntable 11e on which the heating container 20 containing a mortar sample is placed is provided.
By turning on the operation unit 11d, the turntable 11e rotates, and a high frequency is irradiated from the high frequency heating means 12 into the heating chamber 11a for a certain period of time to heat the mortar sample in the heating container 20.

The high-frequency heater A is manufactured by Hitachi, Ltd. and has an output of 1500W. The high frequency heater B is manufactured by Mitsubishi Electric Corporation and has an output of 1500 W. The high frequency heater C is manufactured by Hitachi, Ltd. and has an output of 750 W.
The three high-frequency heaters A to C have substantially the same structure except that the manufacturer and output are different.

Hereinafter, a wet screening method for fresh concrete and a method for measuring the unit water amount will be described using each of the devices A to D.
First, the relational expression of the water mortar ratio of each apparatus AD and an evaporating water rate is calculated | required by a mortar test.
That is, five types of commercially available cement (ordinary Portland cement (N), early-strength Portland cement (H), blast furnace cement B type (BB), moderately hot Portland cement (M), low heat Portland cement (L)) Two kinds of fine aggregates, mountain sand and crushed sand, are used. A predetermined amount of water was added to these and kneaded to prepare a mortar having a water cement ratio of 10 to 80%.
Thereafter, high-frequency heating is performed for 4 minutes in the case of the high-frequency heaters of the devices A, B, and D having an output of 1500 W, and high-frequency heating is performed for 8 minutes in the case of the device C having an output of 750 W. The rate was determined. Next, the cement type and the fine aggregate type were changed, and the same operation was repeated to obtain a relational expression (Table 1) between the water mortar ratio and the evaporation water rate of each of the devices A to D. An example of the relationship between the water mortar ratio and the evaporation water rate is shown in FIG. FIG. 3 shows a case where the high frequency heater A is used.

Next, the fresh concrete shown in Table 2 and Table 3 was wet screened using the fresh concrete wet screening apparatus shown in FIG.
As shown in FIG. 4, the wet screening device 40 is disposed below the screen 41, a vibrating screen 43 with a vibrator 42 that screens fresh concrete using a screen 41 and collects a mortar sample from the fresh concrete. The weight of the mortar sample that has been sieved out with respect to the total amount of mortar in the fresh concrete registered in the memory, and the measuring device 45 that has a weighing tray 44 and measures the collected mortar sample A collection rate calculation means (electric circuit) 46 for obtaining a mortar collection rate and a control unit 47 provided with the collection rate calculation means 46 are provided.

  Fresh concrete is dropped on the screen 41, the vibrator 42 is operated, and the fresh concrete is sieved by the vibration sieve 43. The mortar sample in the fresh concrete passes through the mesh (5 mm) of the screen 41 and falls on the weighing tray 44 and is collected. The obtained mortar sample is weighed by the measuring device 45. Thereafter, in the case of Example 1, in the sampling rate calculation means 46 of the control unit 47, the mortar sampling that is the ratio of the weight of the mortar sample that has been sieved to the total amount of mortar in fresh concrete registered in advance. The rate is calculated. When the mortar collection rate reaches a predetermined value, the vibration sieve 43 is stopped. In the case of the conventional method, the vibration sieve 43 is stopped when a predetermined sieving time has elapsed.

  Specifically, during wet screening, sieving is performed for 60 to 150 seconds in the case of the conventional method, and in the case of Example 1, a mortar sample having a mortar collection rate of 25 to 35% by weight is collected (2 to 15). (Second). Thereafter, a mortar sample obtained by changing the wet screening time or the mortar collection rate was heated by the high-frequency heater A for 4 minutes, and the evaporation water rate was determined. Each result was plotted in FIG. 3 to evaluate the representativeness of the mortar. The result of the wet screening by the conventional method is shown in FIG. Moreover, the result of the wet screening by Example 1 is shown in FIG. FIG. 7 shows the fine aggregate particle size in the mortar sample after wet screening for each of the fresh concretes (1), (3), and (5) in Table 3.

As a result of the above, according to the wet screening method of Example 1, the moisture in the obtained mortar sample is close to the blended value compared to the conventional method, and there is no difference in the fine aggregate particle size in the mortar sample, There was no change in the composition ratio of the material in the mortar, and there was no material separation. Here, FIG. 8 shows the relationship between the mortar collection rate and the unit water amount measurement error.
As apparent from FIG. 8, when the mortar collection rate was 20 to 40% by weight, the unit water amount measurement error was as small as ± 3%. Furthermore, the working time of wet screening for obtaining a predetermined amount of a mortar sample using the vibration sieve 40 was shortened to 10 to 30 times that of the conventional method, and the speed was high.

Next, a method for measuring the unit water amount of fresh concrete will be described.
For each fresh concrete in Table 3, the unit amount of water was measured. At this time, the high frequency heater A was used. As comparative examples, the unit water amount was also measured for the conventional microwave method (method using ZKT-210 and cement-bound water ratio), air meter method, and capacitance method.
Among these, the specific unit water amount measuring method of Example 1 first performs wet screening on fresh concrete and collects a mortar sample (wet screening step). Next, the mortar sample after the wet screening is inserted into the high-frequency heater A, and the weight of the mortar sample is weighed by the weighing means 13 (first weighing step). Thereafter, high-frequency heating is performed for a preset time to evaporate a part of the moisture in the mortar sample (high-frequency heating step). Next, the weight of the mortar sample after high frequency heating is weighed by the weighing means 13 (second weighing step). And the amount of evaporating water from the mortar sample by high frequency heating is calculated | required from the difference in the weight of the mortar sample before and behind high frequency heating (evaporated water amount measurement process). Then, with respect to the measurement value of the evaporation water, based on the relational expression Table 1, subjected to a correction calculation of the evaporation amount of water by the correction calculating unit 15 corrects aggregate water content, the admixture solids, fresh concrete 1 m ³ Obtain the unit water volume. The results are shown in Table 4. Table 5 shows the unit water amount measurement error. Furthermore, Table 6 shows the unit water amount measurement time.

As a result of the above, according to the method for measuring the unit water amount of fresh concrete according to Example 1, compared to other conventional methods, even in the microwave oven method with a fixed heating time, it is concerned with the material and preparation of fresh concrete. In addition, the unit water volume of fresh concrete can be measured quickly and with high accuracy (with an error of about 1%), and the representativeness of the mortar sample with respect to the components of fresh concrete is high, and it is disposable as a heating container 20 for high-frequency heating. It was also found that paper plates can be used.
In addition, in the unit water amount measuring device D, it was possible to output the unit water amount measurement result of the fresh concrete with one switch by inputting the material properties of the fresh concrete and its blending beforehand.

These measurement results are digitally displayed on the display unit 11c of the unit water volume measuring device D, and can also be displayed on a personal computer screen by inputting data to the personal computer via a cable or a memory card. Can do.
In addition, the calibration of the coefficient in the relational expression between the water mortar ratio and the evaporating water ratio is calibrated and automatically overwritten if the measurement is repeated using a material with a known water mortar ratio in a calibration mode (not shown). You may set so that.

It is a perspective view of the unit water quantity measuring device of fresh concrete concerning Example 1 of this invention. It is a block diagram of the unit water quantity measuring apparatus of fresh concrete which concerns on Example 1 of this invention. It is a graph which shows the relationship between the water mortar ratio for every cement kind in the wet screening method of the fresh concrete which concerns on Example 1 of this invention, and an evaporative water rate. It is a perspective view which shows the wet screening apparatus of the fresh concrete which concerns on Example 1 of this invention. It is a graph which shows the relationship between the water mortar ratio and the evaporation water rate in the wet screening method of the fresh concrete which concerns on the conventional method. It is a graph which shows the relationship between the water mortar ratio and the evaporating water rate in the wet screening method of the fresh concrete which concerns on this invention. It is a graph which shows the relationship of the fine aggregate particle size in the mortar sample after the wet screening which concerns on this invention. It is a graph which shows the relationship between the mortar collection rate in the wet screening which concerns on this invention, and a unit water quantity measurement error.

11 Heating box,
12 High-frequency heating means,
13 Weighing means,
14 means for measuring the amount of evaporated water,
15 correction calculation means,
20 Heating container
40 Wet screening equipment for fresh concrete,
41 screens,
43 Vibrating sieve,
45 Weighing machine,
46 Sampling rate calculation means,
A to C, 30D high frequency heater,
D Unit for measuring water volume of fresh concrete.

Claims (2)

The fresh concrete was screened with a mesh size of 5 mm, and the mortar collection rate indicating the ratio of the weight of the sieved mortar sample to the total amount of mortar in the fresh concrete was 20 to 40% by weight per batch. A wet screening process of sieving until a mortar sample is collected;
  A first weighing step for weighing a mortar sample after wet screening;
  A predetermined amount of the mortar sample after wet screening is inserted into a high-frequency heater, high-frequency heating is performed for a preset time, and a high-frequency heating step of evaporating a part of the moisture in the mortar sample;
  A second weighing step for weighing the mortar sample after high-frequency heating;
  From the difference in the weight of the mortar sample before and after high-frequency heating, it is equipped with an evaporating water amount measuring step for obtaining the amount of evaporating water from the mortar sample by high-frequency heating,
  Based on the following equation, the water mortar ratio of the mortar before heating is calculated based on the measured value of the amount of evaporated water. ³ A method for measuring the unit water volume of fresh concrete to determine the unit water volume.
  Water mortar ratio = a x (evaporated water rate) ² + B × (evaporated water ratio) + c
  However, the water mortar ratio is water / mortar amount, the evaporating water rate is evaporating water amount / mortar amount, and a, b, and c are coefficients specific to the high-frequency heater. A heating box into which a heating container containing a mortar sample obtained by wet screening of fresh concrete is inserted;
  A unit of fresh concrete provided with a high-frequency heater provided in the heating box and having high-frequency heating means for high-frequency heating the mortar sample for a preset time and evaporating a part of water in the mortar sample A water measuring device,
  A weighing means installed in the heating box and weighing the mortar sample;
  From the difference in weight of the mortar sample before and after high-frequency heating based on the measurement data from the measurement means, evaporative water amount measuring means for obtaining the amount of evaporated water from the mortar sample by high-frequency heating;
  Based on the following equation, the water mortar ratio of the mortar before heating is calculated based on the measured value of the amount of evaporated water. ³ A device for measuring the unit water amount of fresh concrete, comprising correction calculation means for obtaining the unit water amount.
  Water mortar ratio = a x (evaporated water rate) ² + B × (evaporated water ratio) + c
  However, the water mortar ratio is water / mortar amount, the evaporating water rate is evaporating water amount / mortar amount, and a, b, and c are coefficients specific to the high-frequency heater.

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