Method for evaluating homogeneity of fresh concrete

Abstract

To provide a method for evaluating homogeneity of fresh concrete with high accuracy by revealing an effect of concrete compounding on impedance.SOLUTION: A correlation diagram is previously obtained, with one axis taken as impedance (Ω), and the other axis taken as a paste volume (L / m3) defined as a sum of a volume of water per 1 m3 of concrete and a volume of cement. In the correlation diagram, a paste volume target value and an allowance range thereof are set on the basis of a compounding plan, and an impedance target value and an allowance range thereof corresponding to the paste volume target value and the allowance range thereof are set on the basis of a correlation expression. Impedance of the concrete is measured upon force-feeding or placing of the concrete. A shift of an aggregate mixture proportion is estimated from a difference from target impedance.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for assessing the homogeneity of fresh concrete by impedance measurements. [Background technology]

[0002] As shown in the following Non-Patent Document 1, a sheet-type sensor that uses AC impedance measurement for filling management during concrete pouring has been developed and applied to the top end of mountain tunnel lining concrete. This sheet-type sensor sets a threshold value by utilizing the fact that the impedance of concrete, bleeding water, and air shows different values ​​in stages, and distinguishes between them, ensuring sufficient accuracy in concrete filling management.

[0003] However, the impedance of concrete changes depending on the mix. Possible causes include the materials used, the time elapsed since the cement came into contact with water, the temperature, and the mix. In the following Non-Patent Document 2, the electrical resistance of unhardened concrete is measured using a DC four-electrode method, and the effects of cement type, the time elapsed since the cement came into contact with water, and other factors are investigated. As a result, the electrical resistance reaches its minimum value about two hours after contact with water, and it is considered to be affected by the amount of hydration products, such as sodium hydroxide.

[0004] In addition, in the following Non-Patent Document 3, the resistivity of hardened mortar is measured by using an AC voltage with reference to the four-electrode method, and the effect of temperature is investigated. As a result, it is revealed that the resistivity tends to decrease as the temperature increases. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Tsutomu Yamada and 2 others, "Study on detection of filling and compaction vibration using electrical properties and vibration propagation characteristics of fresh concrete", Proceedings of the Japan Concrete Institute, p935-p940, Vol.42, No.1, 2020 [Non-Patent Document 2] Takehiro Misaka and 2 others, "Effect of Hydration of Fresh Concrete on Electrical Resistance", Proceedings of the Japan Concrete Institute, p505-p510, Vol.39, No.1, 2017 [Non-Patent Document 3] Toshinori Omoto et al., "Electrochemical Study on Electrical Resistance Properties of Mortar", Proceedings of the Japan Concrete Institute, p907-p912, Vol. 27, No. 1, 2005 Summary of the Invention [Problem to be solved by the invention]

[0006] AC impedance measurement is being used to control the filling of concrete when it is poured. It is known that impedance changes when the concrete mix is ​​different, but the reason for this has not been clarified.

[0007] Therefore, a main object of the present invention is to provide a method for evaluating the homogeneity of fresh concrete with high accuracy by clarifying the effect of concrete mix proportions on impedance. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention relates to a method for evaluating the homogeneity of fresh concrete, comprising: In advance, one axis is set to impedance (Ω) and the other axis is set to 1m of concrete. 3 The paste volume (L / m) is defined as the sum of the volume of water and the volume of cement per 3 ) Effective paste volume obtained by subtracting the volume of the paste film (thickness α) adsorbed on the aggregate surface from the total volume A correlation diagram will be obtained. , distribution Based on the combined plan, a paste volume target value is set, In the correlation diagram setting an impedance target value corresponding to the paste volume target value based on the correlation; The present invention provides a method for evaluating the homogeneity of fresh concrete, which is characterized by measuring the impedance of concrete when it is pumped or poured, and estimating the deviation of the aggregate mixing ratio from the difference between the measured impedance and a target impedance.

[0009] In the invention described in claim 1, when evaluating the homogeneity (mixture ratio of aggregate) of fresh concrete, one axis is set to impedance (Ω) and the other axis is set to 1 m of concrete. 3 The paste volume (L / m) is defined as the sum of the volume of water and the volume of cement per 3 ) Effective paste volume obtained by subtracting the volume of the paste film (thickness α) adsorbed on the aggregate surface from the total volume A correlation diagram will be obtained. , distribution Based on the combined plan, a paste volume target value is set, In the correlation diagram Based on the correlation, an impedance target value corresponding to the paste volume target value is set. As a result of intensive research by the inventors of the present invention, the impedance (Ω) of fresh concrete is 3 The paste volume (L / m) is defined as the sum of the volume of water and the volume of cement per 3 This is based on the finding that there is a strong correlation between

[0010] On the paste volume axis, a paste volume that is smaller than the target paste volume value means that there is a relatively more coarse aggregate, and a paste volume that is larger than the target paste volume value means that there is a relatively more fine aggregate.

[0011] Therefore, by measuring the impedance of the concrete when it is pumped or poured, it is possible to estimate the deviation of the aggregate mixture ratio, i.e., which side the aggregate mixture ratio (ratio of coarse aggregate to fine aggregate) is biased, from the difference between the impedance of the concrete and the target impedance.

[0012] Also, The above claims 1The described invention aims to further improve the accuracy. As shown in the experimental example described later, it is assumed that the paste film adsorbed on the aggregate surface is not involved in ion induction, so by subtracting the volume of this paste film from the paste volume, it is possible to further improve the correlation with impedance (Ω).

[0013] According to a second aspect of the present invention, there is provided a method for evaluating the homogeneity of fresh concrete according to the first aspect, in which allowable ranges are set for the target paste volume value and the target impedance value, taking into account variations in the aggregate mixing ratio.

[0014] The invention described in claim 2 sets allowable ranges for the paste volume target value and the impedance target value, respectively, taking into consideration variations in the aggregate mixing ratio. In actual quality control of concrete (aggregate mixing ratio control), control is performed so as to approach the target impedance value, but since a control error (tolerance) is necessary, it is desirable to set the allowable range in advance and control and manage the impedance so that it falls within the allowable range.

[0015] Claim 3 As the present invention, the impedance is measured using an alternating current with a frequency of 1 kHz to 1 MHz. 、2 The method for evaluating the homogeneity of fresh concrete according to any one of the above is provided.

[0016] The above claims 3 In the described invention, an alternating current is used for measuring impedance, and its frequency is set to 1 kHz to 1 MHz.

[0017] Claim 4 As the present invention, the electrodes for measuring impedance during pumping of concrete are installed in the concrete pumping pipe according to claims 1 to 5. 3 The method for evaluating the homogeneity of fresh concrete according to any one of the above is provided.

[0018] The above claims 4The described invention specifies the manner in which electrodes are installed in impedance measurement during concrete pumping. In this case, impedance can be measured in real time by installing a pair of electrodes on the inner surface of the concrete pumping pipe.

[0019] Claim 5 As the present invention related to the above, the electrodes for measuring impedance during concrete pouring are arranged on the formwork, on the vibrator, or on a dedicated rod, as described in claims 1 to 5. 3 The method for evaluating the homogeneity of fresh concrete according to any one of the above is provided.

[0020] The above claims 5 The described invention specifies the manner of installation of electrodes for impedance measurement during concrete pouring. In this case, electrodes are installed on the inner surfaces of the opposing forms, a pair of electrodes is installed for the vibrator and impedance is measured in parallel with vibration, or a pair of electrodes is installed on a separate dedicated rod to measure impedance. Effect of the Invention

[0021] As described above in detail, according to the present invention, by clarifying the influence of concrete mix proportions on impedance, it is possible to provide a highly accurate method for evaluating the homogeneity of fresh concrete. [Brief description of the drawings]

[0022] [Figure 1] This is an example of a correlation diagram in which one axis represents impedance (Ω) and the other axis represents paste volume (L / m3), which is defined as the sum of the volume of water and the volume of cement per 1 m3 of concrete. [Diagram 2] FIG. 11 is a vertical cross-sectional view showing an example of a procedure for measuring impedance during pumping of concrete. [Diagram 3] 1A to 1C show an example of a procedure for measuring impedance when pouring concrete. [Figure 4]The experimental setup is shown in (A) plan view and (B) side view. [Diagram 5] 1 is a graph showing the relationship between frequency and impedance. [Figure 6] 1 is a graph showing the relationship between frequency and phase angle. [Figure 7] 1 is a graph showing the relationship between water-cement ratio and impedance. [Figure 8] 1 is a graph (part 1) showing the relationship between paste volume and impedance. [Figure 9] 13 is a second graph showing the relationship between paste volume and impedance. [Figure 10] 1 is a graph showing the relationship between fine aggregate ratio and impedance. [Figure 11] 1 is a graph showing the relationship between aggregate surface area and impedance. [Figure 12] 1 is a graph showing the relationship between paste volume and impedance. [Figure 13] FIG. 2 is a conceptual diagram of an effective paste volume. [Figure 14] 1 is a graph showing the relationship between effective paste volume and impedance. [Figure 15] 1 is a graph showing a method for evaluating the homogeneity of fresh concrete using a correlation diagram between effective paste volume and impedance. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0024] The present invention is a method for evaluating the homogeneity (aggregate mixing ratio) of fresh concrete in order to ensure the quality of the concrete when pouring it.

[0025] In the past, when pouring concrete, there were cases where the coarse aggregate separated due to lateral flow, or where the flow was hindered by reinforcing bars, causing the concrete to become brittle (junka). To deal with this, methods such as applying a vibrator according to well-defined rules or installing a wall vibrator have been used, but the occurrence of brittle (junka) on the concrete surface has not been completely eliminated.

[0026] In this invention, the concrete itself is mixed properly with the proper amounts of water, cement, coarse aggregate, and fine aggregate according to the initial mix plan (mix design), but the concrete does not have a uniform consistency. This is thought to be due to the unevenness of the mix ratio of coarse aggregate and fine aggregate in each location, and the invention was developed based on the recognition that in order to ensure the uniformity of concrete (aggregate mix ratio), it is necessary to grasp the aggregate mix ratio in real time when the concrete is poured. Specifically, the deviation in the aggregate mix ratio is estimated in real time by the following procedure.

[0027] In advance, one axis is set to impedance (Ω) and the other axis is set to 1m of concrete. 3 The paste volume (L / m) is defined as the sum of the volume of water and the volume of cement per 3 ) to obtain a correlation diagram , distribution Based on the combined plan, a paste volume target value is set, In the correlation diagram setting an impedance target value corresponding to the paste volume target value based on the correlation; The impedance of the concrete is measured when the concrete is pumped or poured, and the deviation of the aggregate mixing ratio is estimated from the difference between the impedance and the target impedance.

[0028] That is, in the present invention, prior to pouring concrete, an indoor experiment is carried out, for example, with the vertical axis representing impedance (Ω) and the horizontal axis representing the impedance per 1 m of concrete. 3 The paste volume (L / m) is defined as the sum of the volume of water and the volume of cement per 3In this correlation diagram, both the vertical and horizontal axes are logarithmic.

[0029] The "paste volume" is a factor that the present inventors have focused on. When concrete is composed of water, cement, coarse aggregate, and fine aggregate, it is believed that the volume of the cement paste excluding the coarse aggregate and fine aggregate is largely related to the induction of ions, and therefore the volume involved in the induction of ions is calculated based on the volume of 1 m of concrete. 3 The "paste volume" is defined as the sum of the volume of water and the volume of cement per unit area.

[0030] The paste volume (L / m 3 ) can be calculated by the following formula (1).

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[0031] Paste volume (L / m 3 )=170(kg / m 3 ) / 1000(kg / m 3 )+293(kg / m 3 ) / 3160(kg / m 3 ) =0.170(m 3 / m 3 )+0.093(m 3 / m 3 )=0.263(m 3 / m 3 )=263(L / m 3 ) As shown in the examples below, the relationship between impedance (Ω) and paste volume (L / m 3 ) in the correlation diagram, the coefficient of determination (R 2 )=0.933, which indicates a high correlation. , distribution Based on the combined plan, a paste volume target value is set, In the correlation diagramBased on the correlation, a target impedance value corresponding to the target paste volume value is set. At this time, it is preferable to set an allowable range for each of the target paste volume value and the target impedance value, taking into consideration the variation in the aggregate mixing ratio.

[0032] Figure 1 shows the relationship between impedance (Ω) and paste volume (L / m 3 ) is shown, and to explain in detail based on this, the amounts of water, cement, coarse aggregate, and fine aggregate are clear based on the mix plan. Therefore, the paste volume can be calculated and the target paste volume value is clear. In addition, taking into consideration the variation in the aggregate mixing ratio, the target paste volume value is set as the median and a predetermined allowable range is set in the ± direction. It is desirable to set this allowable range based on experience and experiments. In general, it is desirable to set the target paste volume value as the median within a range of ±25% of the target paste volume value, preferably within a range of ±20%. As will be described later, on the paste volume axis, a decrease in paste volume compared to the target paste volume value means that there is relatively more coarse aggregate, and an increase in paste volume compared to the target paste volume value means that there is relatively more fine aggregate.

[0033] Impedance (Ω) and paste volume (L / m 3 Since the correlation equation with the target paste volume and the allowable range thereof is known, the target impedance value and the allowable range thereof corresponding to the target paste volume and the allowable range thereof are automatically set.

[0034] Thereafter, by measuring the impedance of the concrete while it is being pumped or poured, it becomes possible to estimate the deviation in the aggregate mixture ratio, i.e., which side the aggregate mixture ratio (ratio of coarse aggregate to fine aggregate) is biased, from the difference between the impedance of the concrete and the target impedance.

[0035] The impedance is measured with an alternating current, and the frequency can be set to 1 kHz to 1 MHz. In this case, when an alternating current is used, the impedance of the material changes depending on the measurement frequency. Therefore, by measuring the impedance and phase angle while changing the frequency and organizing the relationship between frequency and phase angle, it was found that the impedance changes relatively large at frequencies below 1 kHz, but changes are small on the higher frequency side, and the phase angle is 0° in the vicinity of 10 to 100 kHz. Therefore, it is desirable to measure the impedance at a frequency of 10 kHz to 100 kHz.

[0036] To measure impedance while concrete is being pumped, a pair of electrodes 2A, 2B are installed facing each other on the inner surface of pumping pipe 1 which pumps concrete C, as shown in Fig. 2. As for the electrodes for impedance measurement while concrete is being poured, as shown in Fig. 3(A), electrodes 2A, 2B are installed on the inner surfaces of opposing forms 3A, 3B, respectively, or as shown in Fig. 3(B), a vibrator 4 is modified to install paired electrodes 2A, 2B on vibrating part 4A and impedance is measured in parallel with vibration, or as shown in Fig. 3(C), a pair of electrodes 2A, 2B are installed on a separate dedicated rod 5, so that impedance can be measured.

[0037] By the way, impedance (Ω) and paste volume (L / m 3 In the correlation diagram with impedance (Ω), in order to further improve accuracy, the paste volume axis in the correlation diagram can be replaced with the effective paste volume obtained by subtracting the volume of the paste film (thickness α) adsorbed on the aggregate surface from the paste volume. Since the paste film adsorbed on the aggregate surface is assumed not to be involved in ion induction, by subtracting the volume of this paste film from the paste volume, it becomes possible to further improve the correlation with impedance (Ω), and to improve accuracy. EXAMPLES

[0038] The inventors of the present invention conducted experiments to clarify the effect of concrete mix on impedance.

[0039] 1. Experimental Overview 1.1 Materials and composition The cement used was ordinary Portland cement (density 3.16 g / cm 3 ), and fine aggregate is mountain sand (surface dry density 2.56 g / cm 3 ), and the coarse aggregate is crushed stone (surface dry density 2.64g / cm 3 These materials were stored in a thermostatic chamber at 20°C and kept at a constant temperature. Tap water adjusted to 20°C was used.

[0040] Table 1 below shows the mix ratio, and Table 2 below shows the volume composition ratio. For paste, the P series was set, with the water-cement ratio varying from 20 to 100,000%. For mortar, three mixes were set: the M1 series (water-cement ratio 40-70%) with a constant paste volume, the M2 series (fine aggregate cement mass ratio 2-3, water-cement ratio 50%) with variable paste volume, and the M3 series (fine aggregate cement mass ratio 1-5, water-cement ratio 55%). For special mixes in which coarse aggregate is mixed into the paste, the PG1 series (coarse aggregate cement mass ratio 1-3, water-cement ratio 40%) and PG2 series (coarse aggregate cement mass ratio 1-3, water-cement ratio 55%) with variable paste volume were set. For concrete, three mixes were set: the C1 series (water-cement ratio 58%) with variable paste volume, the C2 series (water-cement ratio 55%) with a constant paste volume, and the C3 series with underwater concrete mix.

[0041] [Table 1]

[0042] [Table 2]

[0043] 1.2 Experimental Method An outline of the experiment is shown in Figure 4. A plastic container (145mm wide x 215mm long, 160mm tall) was placed on an insulating rubber sheet, and one rod-shaped electrode (SUS304, φ3.0mm) was placed vertically in the center of each short side of the container. The depth of each sample was standardized to 100mm. Each composition was mixed and placed in the container, after which it was appropriately struck with a mallet and allowed to stand, and 15 minutes after contact with water, an AC voltage was applied between both electrodes using an LCR meter (HIOKI, IM3536) to measure the impedance.

[0044] 2. Experimental Results 2.1 Influence of measurement frequency The impedance of a material changes depending on the measurement frequency. In a research example of resistivity measurement using the AC impedance method, it is important to measure at a frequency with as small a phase difference as possible, because the impedance and phase difference increase as the frequency decreases due to polarization occurring between the electrolyte solution and the electrodes, and the smaller the phase difference, the closer the value is to the theoretical value. Therefore, in this experiment, the impedance and phase angle were measured for all samples while changing the frequency in the range of 5Hz to 1MHz. The measurement signal level was 5Vrms.

[0045] As examples of impedance and phase angle measurements, the results of impedance and phase angle measurements for one mix each of the P series, M2 series, and C2 series with water-cement ratios of 50-55% are shown in Figures 5 and 6, respectively. The impedance changes relatively greatly at frequencies below 1 kHz, but changes are small at higher frequencies. The phase angle is 0° in the 10 kHz to 100 kHz range. Therefore, the following experimental results will be organized using the impedance at a frequency of 10 kHz.

[0046] 2.2 Effect of water-cement ratio To investigate the effect of the water-cement ratio on impedance, the impedance of the P and M1 series was compared with the water-cement ratio as a variable. The paste volume was constant for each series. Figure 7 shows the relationship between the water-cement ratio and impedance. The impedance of the P series was constant at water-cement ratios of less than 100%, which was thought to indicate that the concentration of ions dissolved from the cement was constant.

[0047] The impedance was also constant in the M1 series. As with the P series, if the paste volume is constant even when aggregate is mixed into the paste, the impedance does not change even if the water-cement ratio changes. As a result, it was thought that the water-cement ratio and unit water volume have a weak correlation with the impedance.

[0048] 2.3 Effect of paste volume To investigate the effect of paste volume on impedance, the impedance of the M2, M3, PG1, and PG2 series was compared, with paste volume as a variable (i.e., aggregate volume as a variable). Figure 8 shows the relationship between paste volume and impedance. A negative correlation was obtained in all series, with impedance decreasing as the paste volume increased. It is presumed that when the paste volume is small, the volume of electrically insulating aggregate is relatively large, and many aggregate particles are densely distributed, inhibiting ion migration, but when the paste volume is large, ion migration becomes easier. In other words, it was thought that the impedance changes due to differences in the ease of ion migration occurring depending on the distribution status of the electrically insulating aggregate.

[0049] Furthermore, when comparing the M2 and M3 series, which contain fine aggregate, with the PG1 and PG2 series, which contain coarse aggregate, the impedance of the M2 and M3 series was greater, even though the paste volume was the same (i.e., the aggregate volume was also the same). In other words, it is not the aggregate volume, but the difference between fine and coarse aggregate that affects the impedance. It was thought that in concrete, which contains both fine and coarse aggregate, the fine aggregate ratio affects the impedance.

[0050] 2.4 Effect of fine aggregate ratio In order to investigate the effect of fine aggregate ratio on impedance, the impedance of C1 and C2 series with fine aggregate ratio as a variable was compared. C1 series is a mixture with changing paste volume, and C2 series is a mixture with constant paste volume.

[0051] The relationship between paste volume and impedance is shown in Figure 9. In the C1 series, the impedance decreased as the paste volume increased, showing a similar trend to the M2 and M3 series. In the C2 series, the impedance change was relatively small at 52 Ω, but the impedance increased as the fine aggregate ratio increased.

[0052] Figure 10 shows the relationship between fine aggregate ratio and impedance. An inverse positive and negative correlation is seen between the C1 and C2 series. Compared to the change in the C2 series, which is affected only by the fine aggregate ratio, the change in the C1 series, which includes the effects of both paste volume and fine aggregate ratio, is approximately 10 times larger. From these facts, it can be considered that the paste volume and fine aggregate ratio affect impedance in ways that cancel each other out, but that the effect of the fine aggregate ratio is smaller than that of the paste volume.

[0053] 2.5 Effect of aggregate surface area Finally, we consider the factors that affect the fine aggregate ratio in impedance. In Figure 8, because the impedance of the M2 and M3 series is greater than that of the PG1 and PG2 series even though the aggregate volume is the same, we focused on the specific surface area as a difference between fine and coarse aggregate. As the amount of fine aggregate with a large specific surface area increases, the total aggregate surface area per unit volume (hereinafter referred to as aggregate surface area) increases. Figure 11 shows the relationship between aggregate surface area and impedance. The aggregate surface area was found by calculating the specific surface area of ​​each from the particle size distribution of the fine and coarse aggregate, multiplying them by the unit volume, and adding them up. However, this is close to the relationship between fine aggregate ratio and impedance, and no new knowledge could be obtained.

[0054] 2.6 Correlation with impedance (1) Paste volume From the experiments conducted up to this point, it was found that there is a strong correlation between impedance and paste volume, so the relationship between paste volume and impedance was rearranged for all the mixes in Table 1 in which aggregate was mixed, as shown in Figure 12, which is a logarithmic graph on both axes.

[0055] As is clear from the figure, the relationship between impedance and paste volume is determined by the coefficient of determination (R 2 )=0.933, which shows a high correlation.

[0056] (2) Effective paste volume Furthermore, we hypothesized that the paste film (thickness α) adsorbed on the aggregate surface is not involved in ion migration, as shown in Figure 13. As the fine aggregate ratio increases, the aggregate surface area also increases, and the volume of adsorbed paste not involved in ion migration also increases, so the paste volume effective for ion migration (hereinafter referred to as effective paste volume) decreases, and impedance tends to decrease. In other words, we thought that the effective paste volume, which is the paste volume minus the volume of the paste film (thickness α) adsorbed on the aggregate surface, is more effective. The effective paste volume (Veff) can be calculated using the following formula (2).

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[0057] Figure 14 shows the relationship between the effective paste volume and impedance (double logarithmic). When calculating the effective paste volume (Veff), α (constant) in formula (2) was set to 0.003. When the horizontal axis is the effective paste volume, the coefficient of determination (R 2 ) increased from 0.933 to 0.975, demonstrating that impedance prediction can be performed with higher accuracy.

[0058] 3. Method for evaluating homogeneity Figure 15 shows an image of the method for evaluating the homogeneity of concrete using the relationship between the effective paste volume and impedance mentioned above.

[0059] First, the paste volume and aggregate surface area are calculated based on the planned mix (mix design) and aggregate particle size distribution to determine the effective paste volume (e.g., C1-3). Next, the separation of aggregate during concrete pumping or pouring is assumed, the allowable limits are set (e.g., C1-1 and C1-5), and the effective paste volume is determined. In addition, the impedance of each is calculated using the function (correlation equation) in Figure 15. When pouring concrete, the impedance of the concrete is constantly measured while the concrete is being pumped or poured, and the deviation from the planned aggregate mixture ratio (degree of material separation) is estimated in real time from the difference with the impedance predicted in advance (target impedance value).

[0060] In other words, if the measured impedance is higher than the target impedance (biased toward C1-1), it can be determined that there is more coarse aggregate present than in the planned mix (C1-3), as is clear from the mix table in Table 1, and if the impedance is lower than the target impedance (biased toward C1-5), it can be determined that there is more fine aggregate present than in the planned mix (C1-3), as is clear from the mix table in Table 1.The difference from the target impedance value makes it possible to estimate the deviation from the planned aggregate mixture ratio (the degree of material separation).

[0061] Based on the homogeneity evaluation method of the present invention, it is possible to provide a high-quality concrete structure by improving the construction method to maintain homogeneity before it reaches the limit of the allowable range. It is also possible to measure the impedance during pumping or pouring and record it as initial quality data for maintenance management.

[0062] 4. Summary In this experiment, impedance was measured for various mixes of paste, mortar, a special mix in which coarse aggregate was mixed into paste, and concrete, and the following findings were obtained. (1) Within the range of water-cement ratios used in concrete, the impedance of the paste is not affected by the water-cement ratio or unit water content. (2) The impedance of mortar and concrete is most affected by the change in paste volume caused by the addition of aggregate. (3) The impedance of concrete is affected by the fine aggregate ratio. However, the degree of influence is smaller than the change in paste volume. The fine aggregate ratio affects the impedance due to the paste film adsorbed on the aggregate surface. (4) The impedance can be accurately predicted using the effective paste volume, which is the paste volume minus the volume of the paste film adsorbed on the aggregate surface.

[0063] [Other examples] (1) In the above example, impedance (Ω) and paste volume (L / m 3 ) the vertical axis is impedance (Ω) and the horizontal axis is paste volume (L / m 3 ), while the vertical axis represents the paste volume (L / m 3 ) and the horizontal axis can be impedance (Ω). [Explanation of symbols]

[0064] 1... Pressure pipe, 2A·2B... Electrode, 3A·3B... Formwork, 4... Vibrator, 5... Special rod

Claims

1. A method for evaluating the homogeneity of fresh concrete, comprising the steps of: In advance, one axis is set to impedance (Ω) and the other axis is set to 1 m of concrete. 3 The paste volume (L / m) is defined as the sum of the volume of water and the volume of cement per 3 a correlation diagram is obtained by subtracting the volume of the paste film (thickness α) adsorbed on the aggregate surface from the effective paste volume, and a paste volume target value is set based on a blending plan, and an impedance target value corresponding to the paste volume target value is set based on the correlation in the correlation diagram, A method for evaluating the homogeneity of fresh concrete, comprising measuring the impedance of the concrete when it is pumped or poured, and estimating the deviation in the aggregate mixing ratio from the difference between the impedance and a target impedance.

2. 2. The method for evaluating homogeneity of fresh concrete according to claim 1, wherein allowable ranges are set for the target paste volume value and the target impedance value, taking into consideration variations in the aggregate mixing ratio.

3. 3. The method for evaluating homogeneity of fresh concrete according to claim 1, wherein the impedance is measured using an alternating current having a frequency of 1 kHz to 1 MHz.

4. 4. The method for evaluating homogeneity of fresh concrete according to claim 1, wherein the electrodes for measuring impedance during pumping of concrete are installed in a concrete pumping pipe.

5. 4. The method for evaluating homogeneity of fresh concrete according to claim 1, wherein electrodes for measuring impedance during pouring of concrete are arranged on a formwork, on a vibrator, or on a dedicated rod.

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