JP2005308679A - Salinity concentration measuring method, unit water amount measuring method, and measuring instrument therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately find a salinity concentration of a measuring sample without requiring times and labors, even when the salinity concentration is not predicted in advance even roughly, and to easily measure the salinity concentration and a unit water amount in ready-mixed concrete. <P>SOLUTION: In this salinity concentration measuring method by coulometric titration capable of detecting the presence of a current flow of a potential or more set as an end point potential in an end point detecting electrode pair 11, and capable of switching a constant current level between Ag rods 10a, 10b in a plurality of stages, an electronic controller 2 monitors the potential between the paired end point detecting electrodes 11 after starting the titration by the starting constant current, and switches sequentially the constant current to a current level fit to the salinity concentration of the sample, in every time when the it reaches a preset constant current switching reference value. The unit water amount is measured using the fact that the salinity concentration is diluted when a known salinity concentration of standard water is mixed with the sample, using the salinity concentration measuring method. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a salinity concentration measuring method, a unit water amount measuring method, and an apparatus for measuring the same, and more particularly to a method and apparatus for measuring a salinity concentration and unit water amount of raw concrete using coulometric titration.

In quality control of ready-mixed concrete, the salinity concentration and unit water volume are inspection items required to ensure the reliability of the strength and durability of the concrete structure. The necessity of this has come to be noticed, for example, because it is obliged to be carried out in the construction where 100 m ³ or more is laid per day starting from the problem.

  A titration method called Mohr's method using silver nitrate aqueous solution is widely known for measuring the salinity concentration of ready-mixed concrete, and by applying this principle, a titration vessel containing an acid reagent and a sample is connected to a power source. A further method for determining the salinity from the time until all the chlorine ions are consumed by immersing a negative Ag bar and combining the silver ions eluted by electrolysis with the chlorine ions of the sample, in particular coulometric titration. A measurement method using coulometric titration using is widely implemented.

  This utilizes the fact that a proportional relationship is established between the time required until the end of titration and the concentration of salt contained in the standard solution or sample in coulometric titration performed with a constant stable current. Further, in recent years, an automatic salinity measuring apparatus that automatically calculates a salinity concentration by detecting that a predetermined amount of current or more flows in the acid reagent due to consumption of the chlorine ions is also used. Became.

  On the other hand, in the measurement of the unit water amount of ready-mixed concrete, there is a method of calculating by evaporating the water contained in ready-mixed concrete by heating or depressurizing and comparing the weight before and after that, as disclosed in JP-A-8-338838 and JP-A-11 -83846. Japanese Laid-Open Patent Publication No. 2000-304708 describes a microwave transmission method utilizing the fact that moisture easily absorbs microwaves, and Japanese Laid-Open Patent Publication No. 2004-77454 discloses a standard by measuring capacitance and impedance. A method for measuring unit water volume by comparing with the value is described.

  Furthermore, JP-A-62-106368 and JP-A-2001-116748 describe a measuring method for obtaining a unit water amount by applying the above-described salinity concentration measuring method. In these samples, a reference solution containing a specific concentration of specific ions such as chlorine ions is added to the sample, and the unit water amount in the sample is calculated from the concentration change caused by the specific ions being diluted with the water in the sample. .

  And, in the measurement method applying such a salinity concentration measurement method to the unit water amount measurement, the device used for the unit water amount measurement has a complicated configuration and is expensive and takes a long time for the measurement. Since the measurement is completed in a relatively short time using a relatively compact and inexpensive general-purpose salinity measurement device, each measurement device must be brought to a large number of concrete placement sites in a wide area, and in a short time on the spot. There is a merit that the unit water quantity can be measured. And according to the measuring apparatus, since the unit water amount can be measured and the salinity concentration can be known at the same time, it is possible to greatly reduce the labor of the inspection in the quality control of the ready-mixed concrete.

  By the way, in coulometric titration, the amount of constant current that flows during titration and the time required to complete the titration are inversely proportional, so if the salt concentration is high, the titration time can be shortened by increasing the amount of current that flows. When the concentration is low, the reverse relationship is established. Therefore, a salinity measuring device is generally provided with a changeover switch for manually switching the current level in 3 to 4 steps according to the salinity of the sample.

However, salinity measurement of ready-mixed concrete is different from salinity measurement in other fields, and samples taken from ready-mixed concrete have a relatively high salinity level of 0.50%, and are moderate to 0.10%. In general, there are samples with a wide range of salinity concentrations up to a relatively low salinity concentration of 0.05% or less, and the salinity concentration of the sample is usually unknown and cannot be predicted before the measurement. Therefore, for example, when the salinity concentration is as low as 0.03%, if it is measured at 40 mA which is a current level for high concentration, the end point is reached immediately after the start of measurement, and an accurate numerical value cannot be measured. On the other hand, when the salt concentration is as high as 0.50%, if it is measured at 5 mA, which is a current level for low concentration, the measurement takes too much time, and there is a problem that the convenience at the site is lacking.
JP-A-8-338838 Japanese Patent Laid-Open No. 11-83846 JP 2000-304708 A JP 2004-77454 A JP-A 62-106368 JP 2001-116748 A

  The present invention is to solve the problems in the measurement of the salinity concentration using the coulometric titration as described above and the measurement of the unit water amount of the ready-mixed concrete, and the salinity concentration of the sample to be measured cannot be predicted. However, it is an object of the present invention to enable the salinity concentration measurement or the unit water amount measurement to be easily performed so that the salinity concentration can be accurately obtained without requiring time and labor.

  In view of this, the present invention detects when the current equal to or higher than the potential set in advance as the end point potential flows to the end point detection electrode pair, detects this as the end point current by the end point detection circuit, and uses two Ag bars for electrolysis. In the salinity measurement method using coulometric titration, in which the constant current level is switched to multiple levels according to the salinity of the sample, the electronic controller ends after the coulometric titration is started with the constant current for starting at the predetermined current level. When the potential of the detection electrode pair is monitored and it is detected that this has reached a preset constant current switching reference value, the constant current is switched to another current level suitable for the salt concentration of the sample.

  This allows the controller to adjust the constant current level of the sample to a current level that matches the salinity concentration when the monitor potential reaches a predetermined current switching reference even if the salinity concentration of the sample cannot be predicted. It is easy to avoid the fact that the coulometric titration is completed in a very short time due to the constant current level being too high, making accurate measurement difficult, or the measurement time is prolonged due to the low current level being too low. be able to.

Further, in the above-described salinity concentration measurement method, at the start of coulometric titration, the potential of the end point detection electrode pair is detected and stored as the start point potential,
Formula: (end point potential−start point potential) × Z% + start point potential (where Z is a constant from 0 to 100)
If the controller determines the constant current switching reference value, the constant current switching reference value can be easily determined by setting a predetermined constant between the start point potential and the end point potential. By setting the constant current switching reference based on the reference value in a plurality of stages, it becomes easy to ensure high measurement accuracy while responding to various conditions.

  Furthermore, when the starting point potential is higher than a predetermined reference potential, coulometric titration is started at the lowest constant current, and when the starting potential is lower than the predetermined reference potential, coulometric titration is started at the highest constant current. If started, it becomes easy to appropriately control the measurement time while ensuring measurement accuracy in coulometric titration. And, if this reference potential level is set to around 50 mV, a constant current at the start of titration should be suitable in the measurement of salinity of fresh concrete having a salinity of 0.01 to 0.50%. Becomes even easier.

  Furthermore, the constant Z in the formula for calculating the constant current switching reference value when the constant current is switched from the uppermost stage to the next lower stage is set to 25 to 35, and the constant current stage is set to the lowest stage. If the constant Z in the formula for calculating the constant current switching reference value when switching from the upper stage to the lowest stage is set to 65 to 80, the time to completion of titration and the measurement accuracy can be made appropriate. .

  In addition, a plurality of stages at a constant current level are divided into four stages, ie, a level 1 around 5 mA, a level 2 around 20 mA, a level 3 around 25 mA, and a level 4 around 40 mA. If it is almost less than 0.03%, level 2 is about 0.03% or more and less than 0.10%, level 3 is about 0.10% or more and less than 0.50%, and level 4 is about 0.50% or more, In particular, it is a constant current level setting suitable for measuring the salinity concentration of ready-mixed concrete.

  In addition, in the above-described salinity concentration measurement method in which the constant current level is set in four stages, the constant Z in the constant current switching reference value calculation formula when switching from level 4 to level 3 is set to about 30, If the constant Z when switching to 2 is set to around 50 and the constant Z when switching from level 2 to 1 is set to around 75, the constant current near the end point is controlled in trace amounts in the measurement of the salinity of fresh concrete. The measurement accuracy can be improved.

  If the numerical value count at the time of salinity measurement in the above-mentioned salinity concentration measurement method is switched to the count time of the least displayed digit corresponding to the current level every time the constant current level is switched, the constant current level changes. Even so, the salinity concentration can be obtained accurately.

  In addition, if the salinity measurement of the ready-mixed concrete is performed using the above-described salinity concentration measuring method, the measurement becomes extremely easy and accurate. As a measuring method, a standard solution with a predetermined salt concentration is added to and mixed with a certain volume of ready-mixed concrete sample, and the filtrate before and after mixing is collected and the salt concentration is measured. The added standard solution is contained in ready-mixed concrete. If the unit water volume is calculated based on the concentration change caused by dilution with water, the unit water volume can be obtained accurately in a short time without using a large and expensive device. The unit water volume can be easily measured on the spot.

  Further, the titration container holding a predetermined acid reagent and sample, two Ag bars for electrolysis connected to a power source, an end point detection circuit having an end point detection electrode pair, and a constant current level are switched in a plurality of stages. A switching means, a display means for displaying a measurement result, an electronic controller having a calculation / control device and a storage device and storing a program for executing the procedure in the measurement method described above, and controlled by this controller. Thus, if the measuring device for the salinity concentration or unit water amount of the ready-mixed concrete for carrying out the above-described measuring method is used, the above-described effects can be easily realized while minimizing the labor of the operator.

  Furthermore, if the controller calculates the salinity concentration or unit water amount of the sample and displays it on the display means using a predetermined calculation formula after measuring the sample, the labor of the measurer can be further reduced. It is possible to avoid the occurrence of calculation errors, and in addition to this, it is possible to input composition data such as aggregate and mixed air amount data, and if the controller performs compound correction and air amount correction, further measurement The accuracy can be accurate.

  According to the present invention, even if the salinity of a sample to be measured cannot be predicted, the salinity can be measured accurately without requiring time and labor. Unit water volume can be easily measured.

  A measuring apparatus for carrying out a method for measuring a salinity concentration of ready-mixed concrete according to a first embodiment of the present invention will be described below with reference to the drawings. The measuring apparatus 1 of the present embodiment shown in the layout diagram of FIG. 1 is a salinity concentration measuring apparatus suitable for measurement of ready-mixed concrete, and an end point detection composed of plus and minus Ag bars 10a and 10b and electrodes 11a and 11b. The electrode pair 11 and the stirring blade 9a of the stirrer 9 are arranged so as to be inserted from above into a cup-shaped titration container 10 containing an acid buffer solution and a fresh concrete sample.

  The electronic controller 2 includes an arithmetic / control device and a storage device, as well as an operation panel 21, which is an operation unit, a measurement time count manual adjuster 22, a current level manual switch 23, and an end point detection circuit 7 which is a detection unit. A microcomputer connected to the constant current generator 8, the stirrer 9, the printer 6, and the display 5, which are operating parts, via predetermined connection means, and a salinity concentration measuring method and unit water amount measurement described later in the ROM A program for executing the method is stored.

That is, the current taken in by the main power supply circuit 4 is converted to a constant current by the constant current generator 8 and passed through the Ag rods 10a and 10b to generate Ag ⁺ by electrolysis, which is combined with Cl ⁻ in the sample to form AgCl. It is adapted to cause to become reactive, ending at the end point potential E _{end the} from the potential of the reaction in the end-point detection electrode pair 11 is utilized to coulometric titration start not to rise above a predetermined potential (the end point potential E _{end the)} The same as a general-purpose measuring apparatus for performing a salinity concentration measuring method by coulometric titration in which the electronic controller 2 detects the time until detection by the detection circuit 7 and obtains the salinity concentration in the sample based on this time. However, this embodiment is characterized by the control of the controller 2 in the measurement method.

  Details of the method for measuring the salinity concentration of the ready-mixed concrete sample of the present embodiment will be described below. Unlike the salinity measurement in other fields, the salinity measurement of ready-mixed concrete samples has a large range from 0.03% to 0.5% in salinity. Although it is necessary to switch by the manual switch 23, it is normal that even the approximate concentration is unknown before the measurement.

  For example, the present inventor has found from his own experience that when the salinity is less than 0.03%, the current level is about 5 mA, and when the salinity is 0.03% or more and less than 0.10%, about 20 mA, 0.10% or more and 0. When it is less than 50%, it is considered that coulometric titration at about 25 mA and 0.50% or more at 40 mA makes it easy to obtain accurate measurement results while keeping the titration time within an appropriate range. Therefore, in the present embodiment, the current level manual switching unit 23 can be used for adjustment in four steps of levels 1 to 4 of the same current level, and in addition, the electronic controller 2 can be adjusted appropriately. Control to automatically switch to a constant current level is performed.

Prior to measuring the salinity of the sample, measure the concentration of a standard solution (saline) with a known concentration, and perform manual or automatic fine adjustment of the numerical count for each current level to be performed. Since it is the same as the apparatus, detailed description thereof is omitted, but in this embodiment, only stirring is performed for several seconds (for example, 5 seconds) at the start of measurement, and the end point is reached in the final stage for several milliseconds (for example, 5 milliseconds). The controller 2 monitors the potential of the detection electrode pair 11 a predetermined number of times (for example, 5 times), calculates the average value, and stores it as the starting point potential E ₀ .

When the starting point potential E ₀ is higher than the reference potential 50 mV, the titration is started at a constant current of 5 mA from level 1 from the beginning, and when it is less than 50 mV, the titration is started at 40 mA at level 4. Yes. The setting of the starting constant current may be switched by the operator with the current level manual switch 23 or the controller 2 may be switched automatically.

The potential of the end point detection electrode pair 11 is determined in advance in a plurality of stages: (E _end −E ₀ ) × Z% + E ₀ (where Z is a constant of 0 to 100)
Is reached, the electronic controller 2 switches the level of the constant current.

  In addition, the constant Z is set to 30 when switching from level 4 to 3, 50 when switching from level 3 to 2, and 75 when switching from level 2 to 1, so as to suit the measurement of salinity in ready-mixed concrete. Yes. In this embodiment, from the viewpoint of saving the constant current level as the titration end point is approached, the relationship between the above-described salinity concentration and the constant current level adapted thereto is shifted by one step, and the target concentration is set at level 3. The constant Z is set in the range of 0.03% to 0.1%, and the target concentration is about 0.03% at level 2, and is determined in consideration of measurement accuracy and measurement time (Table 1). reference).

  On the other hand, the basis for determining 50 mV as the reference potential will be described below. Table 2 shows the average value obtained by repeatedly measuring the salinity concentration and the reference potential at the start of titration, and the salinity concentration is 0.02%. The potential at the beginning of the titration of the sample to be titrated at the lowest level 1 below is over 50 mV, and all the samples with salinity to be measured at levels 2 to 4 above this should be less than 50 mV. I understand.

For example, when the salinity concentration is 0.05%, E ₀ = 42 mV, and E _end = 80 mV, the constant current level is switched at the time when the end point detection circuit 7 detects the following potentials. That is, constant current switching reference value from level 4 to 3; (80−42) × 0.3 + 42 = 53.4 mV, constant current switching reference value from level 3 to 2; (80−42) × 0.5 + 42 = 61.0 mV, constant current switching reference value from level 4 to 3; (80−42) × 0.75 + 42 = 70.5 mV.

  On the other hand, when the salt concentration is 0.02% and the titration is started at level 4 without setting the starting current with the constant current switching reference value of 50 mV, the constant current level is switched to the following potential. It is the time of detection. That is, constant current switching reference value from level 4 to 3; (80−65) × 0.3 + 65 = 69.5 mV, constant current switching reference value from level 3 to 2; (80−65) × 0.5 + 65 = 72.5 mV, constant current switching reference value from level 4 to 3; (80−65) × 0.75 + 65 = 76.3 mV.

  Even in this case, the potential is clearly determined theoretically, but these are extremely close to the end point potential of 80 mV, so when the measurement is started when the salinity concentration is low in this way, the level is instantaneously switched from level 4 to level 1. Will end up. Therefore, the present inventor confirmed that the concentration at which the influence on reproducibility and measurement accuracy starts to appear in a low-concentration sample is 0.02% based on a large number of experimental results, and 50 mV as one reference potential at the start of titration. When the branch point is determined, automatic control is performed in which the titration current is sequentially switched according to the calculation formula starting from level 4 if the branch point is lower, and coulometric titration is performed only in level 1 if it is higher. .

  Hereinafter, the operation of the electronic controller 2 after the start of titration will be described. Referring to the flowchart of FIG. 2, for example, when the starting point potential is less than 50 mV (A1), the titration start command (B1) of the electronic controller 2 starts titration at 40 mA of level 4 (C1). The formula controller 2 continuously monitors the potential data from the end point detection circuit 11 for a predetermined number of times (for example, 5 times) from the end point detection circuit 7 for several m seconds (for example, 5 m seconds) after the start of titration (A2). (B2) The coulometric titration is continued while calculating the average potential E, and when the following conditions are reached, the constant current level is sequentially switched as follows.

That is, when the constant current switching reference value: (E _end −E ₀ ) × 0.3 + E ₀ is reached (A3), the switching command (B3) switches the constant current from level 4 to level 3 (C2). Switching reference value: When (E _end -E ₀ ) × 0.5 + E ₀ is reached (A 4), the switching command (B 4) switches from level 3 to level 2 (C 3). Further, when the constant current switching reference value: (E _end −E ₀ ) × 0.75 + E ₀ is reached (A5), the level is switched from level 2 to level 1 by the switching command (B5) (C4).

The numerical value count at the time of salinity measurement is automatically switched to the minimum display digit count time corresponding to the current level whenever the constant current level is switched. That is, the electronic controller 2 has the formula: [current value of constant current level 1 × numerical count time of constant current level 1] = f ₂ × [current value of constant current level 2 × numerical count time of constant current level 2] = f ₃ × [current value of constant current level 3 × numerical count time of constant current level 3] = f ₄ × [current value of constant current level 4 × numerical count time of constant current level 4] (however, f ₂ , f ₃ and f ₄ are controlled so that the relationship of the experimental value factor) for linearity correction can be maintained.

As for the control at the end point, one of the following two methods is adopted so that the manufacturer can set a control method that matches the target sample. That is, after the constant current of the lowest current level 1 is finally reached, coulometric titration is performed until the _end point potential E _end is exceeded without performing the predetermined number of times of the potential sampling and the calculation of the average potential E in the predetermined time. And monitoring the transition until the _end point potential E _end is exceeded by performing the above-described potential sampling and average potential E calculation one after another even after the constant current of the lowest current level 1 is finally reached. There are two ways to continue coulometric titration. In this embodiment, after reaching level 1, the potential sampling and the calculation of the average potential E are not performed (B6). When the _end point potential E _end is exceeded (A6), a coulometric titration end command is issued (B7). Then, the constant current is stopped (C5) to complete the coulometric titration.

The electronic controller 2 obtains the salinity concentration by specifying the time from the start of titration to the end of titration and comparing it with the salinity concentration Cstd of the standard solution and the time Tstd until the end of the titration. That is, in coulometric titration performed with a constant stable current, a proportional relationship is established between the time T required until the end of titration and the salt concentration Cstd of the standard solution or the salt concentration Csam of the sample. The salinity Csam of the unknown sample is
Formula: Csam = (Cstd × Tsam) / Tstd (%)
The controller 2 performs calculation based on this calculation formula (B8), and automatically displays the result on the display 5 (B9).

  As described above, even if the salinity concentration of the ready-mixed concrete is rough or not known according to this embodiment, the electronic controller monitors the potential at the end point detection electrode pair and reaches the constant current switching reference value provided in a plurality of stages. Since the constant current level is switched each time, it can be controlled to a constant current level that matches the salinity of the sample in a relatively short time, and appropriate measurement time and measurement accuracy can be ensured. And this salt concentration measurement can be normally implemented about 10 times with the same acid buffer solution.

  The description of the salinity concentration measuring method and the salinity concentration measuring apparatus in the present embodiment has been described for the case where the sample is ready-mixed concrete, but is not limited thereto, and may be a mortar. It can also be applied to samples with relatively high salinity, or samples with relatively low salinity such as in the beverage field, and various constants and control methods at the end point can be selected and changed appropriately in the measurement method program. This makes it possible to deal with many fields.

  Next, although the measuring apparatus used for the unit water quantity measurement of the ready-mixed concrete which is 2nd embodiment of this invention is demonstrated, the apparatus used for a measurement can utilize the above-mentioned measuring apparatus 1 as it is. In this case, the unit water content is measured by adding and mixing a standard solution (saline solution) of known concentration to a certain volume of ready-mixed concrete sample, collecting the filtrate before and after that, and measuring the salinity concentration. This is a measurement method based on the so-called salinity difference method using the principle that the liquid is diluted with moisture in the ready-mixed concrete, and this method itself is well known.

  In the present embodiment, the unit water amount in the sample is calculated by performing a predetermined calculation from the respective salt concentrations before and after mixing the standard solution obtained by the above-described salt concentration measurement method. The electronic controller 2 in which a unit water quantity measurement program for executing this is stored automatically calculates and displays the result on the display 23.

That is, the electronic controller 2 has the following formula: unit water amount (W1) = f (Cstd−Cmix) / (Cmix−Csam) (where Cstd is the salt concentration (%) of the standard solution to be mixed, and Cmix is Salinity concentration (%) in the extract, Csam is the salt concentration (%) of bleeding water before adding the standard solution, and f is the addition amount of the standard solution (kg / m ³ ))
The calculation is performed using the following formula.

In order to correct the air volume,
Formula: Correction unit water amount (W2) = (1000−A1 × 10) ÷ (1000−A2 × 10) (where A1 is the target air amount (%) and A2 is the actually measured air amount (%))
Calculate using the following formula. Furthermore, for correction of adsorbed water such as aggregates,
Formula: Correction unit water amount (W3) = W2 + 0.017C− (S × Sq−0.18) +15.9) −G × Gq × (35.5 ÷ (Gq + 0.07) +9.90)) / 10000 (however, , C is the unit cement amount (kg / m ³ ), S and G are the fine aggregate amount and coarse aggregate amount (kg / m ³ ), and Sq and Gq are the water absorption rate of the fine and coarse aggregate (%).
Calculate using the following formula.

  When performing calculations using these calculation formulas, the electronic controller 2 automatically performs calculations by inputting each numerical value in advance using the operation panel 21. Since the influence of contaminants such as aggregate and air mixed in the concrete is automatically corrected, the measurement result becomes even more accurate.

  Below, an example of the procedure of the unit water quantity measurement of the ready-mixed concrete by this Embodiment is demonstrated. It is assumed that the above-described preliminary operation in the salinity concentration measurement has already been performed, and that there are already no numerical values and numerical values for unit water amount correction already input.

  Transfer 1.5 liters of ready-mixed concrete 40 to the measuring container 30a with a hand scoop (see FIG. 3 (A)), and poke it once with a cue stick / 10 times (8 times with a diameter of 10 cm). Strike with a rubber hammer to remove large bubbles and finish the surface flat with a straight edge. Two samples of the same sample are made in advance.

  Then, a connecting tool 30b is attached to the upper surface side of the weighing container 30a of one sample (see FIG. 3B), and a stirring cylinder 30c is further connected thereto, so that the concentration is a standard solution that has been weighed in advance. Then, 240 ml of the saline solution 50 is poured into the cylinder stirring cylinder 30c, and the lid 30d is closed to form the mixing container 30 (see FIG. 3C). This is mixed in a state where the container is tilted so that the ready-mixed concrete 40 and the saline solution 50 are mixed, and the mixture is shaken vigorously for about 20 seconds while being turned upside down in a state where the fluidity is generated.

  Next, the mixing container 30 is placed on a rotary mixing device and kept in a fluid state until the total time is 2 minutes. During this mixing, the bleeding water (pore water) collected by inserting a conical filter paper or the like into the upper surface of the other sample collected at the same time is weighed with a 0.2 ml pipetter and discharged into the titration vessel 10 to start the measuring device 1. Press the switch to start salinity measurement. This measurement is carried out about 3 times, but if the measured value varies greatly, the measurement is added once.

  After the mixing time reaches 2 minutes, the mixing container 30 is picked up from the rotary mixing apparatus and shaken vigorously with both hands for about 10 seconds. After mixing, place the lid 30d down, remove the measuring container, and squeeze the upper sample. Pour into a vessel and pressurize to squeeze out about 1 ml of pore water. This is collected with a 0.2 ml pipettor and discharged in the titration container 10 shown in FIG. 1, and the start switch is pressed to measure the salt concentration.

  When this measurement is performed about three times and the variation in the measured value is large, adding the measurement once is the same as the measurement of the standard solution. When the measured value is displayed on the display 5, the unit water amount calculation switch is pressed to cause the electronic controller 2 to perform the above calculation, and the unit water amount (%) contained in the sample is calculated and displayed on the display 5. .

  As described above, the unit water amount measurement in the present embodiment is such that the electronic controller automatically adjusts the low current level even if the salinity of the sample is rough or unpredictable. However, an accurate measurement result can be obtained in a short time (about 15 minutes). In addition, the measuring device used is a general-purpose salinity concentration measuring device that stores a program for executing the measuring method of the present invention in a controller, and the measuring device itself is compact and inexpensive. Therefore, by incorporating or connecting a battery, it is possible to bring the concrete to the concrete placement site for each measurement and easily carry out the measurement at the site. Moreover, since it has an automatic calculation function, it is not necessary to prepare a separate computer for calculation, and an accurate measurement result without any calculation error can be easily obtained even if it is not an expert.

The layout which shows 1st embodiment of this invention. The flowchart which shows the operation | movement of the electronic controller of FIG. (A) is a front view of the weighing container in the second embodiment of the present invention, (B) is a front view showing a state in which the connector is attached to the weighing container of (A), and (C) is a view of (B). The front view which shows the state which mounted | wore the connection tool with the stirring cylinder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Measuring apparatus, 2 Electronic controller, 5 Display, 7 End point detection circuit, 8 Constant current generator, 9 Stirrer, 10 Titration container, 10a, 10b Ag bar, 11 End point detection electrode pair, 21 Operation panel, 22 Measurement time count Manual adjuster, 23 Current level manual selector

Claims (12)

When a current equal to or higher than the potential set in advance as the end point potential flows to the end point detection electrode pair, this is detected by the end point detection circuit as the end point current, and the constant current level between the two Ag rods for electrolysis is detected. In the salt concentration measurement method using coulometric titration that switches to multiple stages according to the salt concentration of
After starting titration with a starting constant current at a predetermined current level, the electronic controller monitors the potential of the end point detection electrode pair and detects that the monitoring potential has reached a preset constant current switching reference value. The constant current is to be switched to another current level that matches the salinity of the sample,
The salinity concentration measuring method characterized by this. In the salinity concentration measurement method according to claim 1, while detecting and storing the potential of the end point detection electrode pair as a start point potential at the start of coulometric titration,
Formula: (end point potential−start point potential) × Z% + start point potential (where Z is a constant from 0 to 100)
Wherein the controller determines the constant current switching reference value.   When the starting point potential is higher than a predetermined reference potential, the constant current is started at the lowest level, and when it is lower than the predetermined reference potential, the constant current is set at the highest level. The salt concentration measuring method according to claim 1 or 2, wherein   4. The salt concentration measuring method according to claim 3, wherein the reference potential is set to about 50 mV.   The constant Z in the formula for calculating the constant current switching reference value when switching the constant current from the uppermost stage to the next lower stage is set to 25 to 35, and the constant current stage is moved up to the lowermost stage. The salt concentration measuring method according to claim 1, 2, 3, or 4, wherein the constant Z in the calculation formula when switching from the stage to the lowest stage is 65 to 80.   The plurality of steps at the constant current level are four steps, ie, a level 1 of around 5 mA, a level 2 of around 20 mA, a level 3 of around 25 mA, and a level 4 of around 40 mA. Almost less than 0.03%, Level 2 is almost 0.03% or more and less than 0.10%, Level 3 is almost 0.10% or more and less than 0.50%, Level 4 is almost 0.50% or more The method for measuring a salt concentration according to claim 1, 2, 3, 4 or 5.   7. The salinity concentration measuring method according to claim 6, wherein the constant Z in the constant current switching reference value calculation formula is about 30 when switching from level 4 to level 3, about 50 when switching from level 3 to level 2, and level 2 A salinity concentration measuring method, characterized in that it is about 75 when switching from 1 to level 1.   The numerical value count at the time of measuring the salinity concentration is switched to the count time of the least displayed digit corresponding to the constant current level after switching every time the constant current level is switched. The salinity measurement method according to 5, 6 or 7.   A salinity concentration measuring method according to claim 1, wherein the salinity concentration measuring method according to claim 1 is performed for the salinity concentration measurement of ready-mixed concrete. A method for measuring the unit water content of ready-mixed concrete using the method for measuring the salinity concentration of ready-mixed concrete according to claim 9,
Add and mix salt solution of a certain concentration to a certain volume of ready-mixed concrete, collect the filtrate before and after mixing, determine the salt concentration by the above-mentioned salt concentration measurement method, and the added salt solution is included in ready-mixed concrete A method for measuring the unit water volume of ready-mixed concrete, which calculates the unit water volume using a formula that utilizes dilution with water.   Titration container for holding a predetermined acid reagent and sample, two Ag rods for electrolysis connected to a power source, an end point detection circuit having the end point detection electrode pair, and switching for switching the constant current level in a plurality of stages Means, a display means for displaying a measurement result, an electronic controller that includes a calculation / control device and a storage device and operates according to a program for executing the procedure in the above-described measurement method, and is controlled by the controller. Item 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10. The measuring device characterized in that the measuring method is performed. In the measuring apparatus according to claim 11, the composition correction data and the air amount correction data can be input, and the controller performs the composition correction and the air amount correction when calculating the measurement value. Characteristic measuring device.

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