JP7590940B2 - Method and device for estimating time to strength development of concrete - Google Patents

Description

The present invention relates to a method and device for estimating the time it takes for concrete to develop a specified compressive strength, and in particular to a method and device for estimating the strength development time using the propagation speed of ultrasonic waves propagating through concrete.

Conventionally, in a cast-in-place support system using a shield (SENS; Shield ECL NATM System), a tunnel is excavated while maintaining the stability of the tunnel face by the shield method, and then a primary lining is applied by a cast-in-place lining method, after which a secondary lining concrete is poured to complete the tunnel (see, for example, non-patent document 1).
In SENS, the primary lining is constructed with cast-in-place concrete poured in parallel with the shield tunneling, so the concrete used for the primary lining (hereafter referred to as SENS concrete) must have a fluidity that allows reliable pumping, a freshness retention that takes into account the process from mixing to pouring, and strength development to obtain a reaction force during shield tunneling. Specifically, fluidity and freshness retention are determined by a slump flow test (JIS A 1150), and strength development is determined by a compressive strength test (JIS
A 1108).

Masaaki Hasegawa, Mamoru Noguchi, Tatsuya Tamai: Development of SENS (cast-in-place concrete system using shield) concrete - Hokkaido Shinkansen, Tsugaru Yomota Tunnel, Concrete Engineering, pp. 106-109, 2011.1

Incidentally, concrete for SENS is required to have a compressive strength of 15 N/mm2 or ^more at 24 hours and 30 N/mm2 ^{or more} at 28 days, in order to absorb the reaction force of the shield machine from the concrete.
However, the compressive strength test (JIS A 1108) involves clamping a cylindrical specimen in a special machine, applying a compressive force from above, and measuring the strength until the specimen breaks. This not only takes time to measure, but also requires multiple tests to accurately determine the time to develop strength.

The present invention was made in consideration of the problems of the past, and aims to provide a method and device for easily and efficiently estimating the strength development of SENS concrete.

The present invention is a method for estimating the time until concrete develops a predetermined compressive strength, comprising the steps of pouring concrete into a formwork, measuring the ultrasonic propagation velocity of the concrete poured into the formwork, and estimating a strength development time, which is the time until the concrete develops a predetermined compressive strength, from actual data, which is data on the change in the measured ultrasonic propagation velocity over time, and a relational equation that expresses the relationship between the compressive strength of the concrete and the ultrasonic propagation velocity that has been obtained in advance. The present invention is characterized in that, when the time from the time of pouring water to the time at which the rate of change of the ultrasonic propagation velocity becomes discontinuous is defined as the rise time of the ultrasonic propagation velocity, and data calculated from data on the change in the ultrasonic propagation velocity over time after the rise time of concrete of a plurality of blends is defined as standard data, the relational equation is obtained from the relationship between the elapsed time measured from the rise time of the ultrasonic propagation velocity of concrete of a plurality of blends and the compressive strength at the elapsed time, and the relationship between the elapsed time and the ultrasonic propagation velocity in the standard data.
This makes it possible to easily and efficiently estimate the strength development time of concrete without conducting compressive strength tests multiple times (since it is only necessary to conduct a compressive strength test at 24 hours, which is a test item for the required performance of concrete).
As described above, the rise time is the time from the time water is poured to the time when the ultrasonic propagation velocity rises sharply. Note that "rising sharply" means that, for example, if the ultrasonic propagation velocity is measured at one-minute intervals, the difference (speed difference) between the ultrasonic propagation velocity at the rise time and the ultrasonic propagation velocity one minute later is the largest.
In the time domain before the rising time, the ultrasonic propagation velocity is not observed or is very small (50 to 100 m/s or less), and the rate of change of the ultrasonic propagation velocity is also very small compared to the rate of change at the rising time. Also, in the time domain after the rising time, the rate of change is considerably smaller than the rate of change at the rising time.
That is, at the rise time, the rate of change of the ultrasonic propagation velocity can be considered to be discontinuous.
In addition, in the step of determining in advance the compressive strength of the concrete at an age of 24 hours and estimating the strength development time, the actual data is corrected using the standard ultrasonic propagation velocity, which is the ultrasonic propagation velocity corresponding to the compressive strength at an age of 24 hours in the relational equation, and the actual ultrasonic propagation velocity, which is the ultrasonic propagation velocity in the actual data 24 hours after water injection, and an ultrasonic propagation velocity for estimation, which is the ultrasonic propagation velocity corresponding to the predetermined compressive strength, is obtained from the relational equation. After that, the time corresponding to the ultrasonic propagation velocity for estimation in the corrected actual data is obtained, and this obtained time is estimated to be the strength development time of the concrete, so that the strength development time of the concrete can be accurately estimated.

In addition, a device for estimating the time from when water is poured into cement until the concrete develops a predetermined compressive strength is composed of a formwork for storing the concrete, an ultrasonic measuring device that is installed in the formwork so that the tip of the transmitting probe and the tip of the receiving probe are positioned a predetermined distance apart within the formwork and that measures the propagation speed of ultrasonic waves propagating through the concrete, actual data detection means for detecting actual data which is data of the measured change in ultrasonic propagation speed over time, storage means for storing standard data which is data calculated from data of time changes after the rise time of the ultrasonic propagation speed of concrete of a plurality of blends, a relationship between the elapsed time measured from the rise time of the ultrasonic propagation speed of concrete of a plurality of blends and the compressive strength at the elapsed time, and a relational equation showing the relationship between the compressive strength of the concrete and the ultrasonic propagation speed obtained using the relationship between the elapsed time and the ultrasonic propagation speed in the standard data, and a strength development time estimation means for estimating the strength development time, which is the time until the concrete develops a predetermined compressive strength, using the actual data and the relational equation, so that a device that can accurately estimate the strength development time of concrete can be obtained.
The rise time of the ultrasonic propagation velocity is as described above.

FIG. 1 is a diagram showing an estimation device for concrete strength development time according to an embodiment of the present invention. 1 is a diagram showing the time change in the propagation velocity of ultrasonic waves and the rising points. FIG. FIG. 13 is a diagram showing the change over time in ultrasonic propagation velocity of a sample for creating standard data. FIG. 13 is a diagram showing a method for creating standard data. FIG. 1 is a graph showing the relationship between ultrasonic propagation speed and compressive strength. 1A to 1C are diagrams illustrating a method for calculating an actual ultrasonic propagation velocity and a method for creating correction data. FIG. 1 is a diagram showing a method for estimating the strength development time of concrete. 1 is a flowchart showing a method for estimating the strength development time of concrete.

FIG. 1 shows an apparatus for estimating the strength development time of concrete according to this embodiment (hereinafter referred to as the estimation apparatus 10), and the estimation apparatus 10 comprises a formwork 11, an ultrasonic measuring device 12, an actual data detection means 13, a memory means 14, and a strength development time estimation means 15.
Each of the means from the actual data detection means 13 to the intensity onset time estimation means 15 is constituted by, for example, computer software and a memory such as a RAM.
The formwork 11 is a flat container with an open top, and has a cylindrical side wall 11a, a disk-shaped bottom plate 11b, and a storage space 11c which is a hollow space formed by the side wall 11a and the bottom plate 11b. The side wall 11a is formed with probe insertion holes 11p and 11q for storing a transmitting probe 12p and a receiving probe 12q, which will be described later, and concrete 1 is poured in a mixed state into the storage space 11c.
In this example, assuming that the height of the formwork 11 is H and its radius is R, and that the depth of the storage space 11c is h and its radius is r, then h = 2H/3 and r = R/2, and the storage space 11c is formed so that the central axis of the cylinder constituting the side wall 11a coincides with the central axis of the column constituting the storage space 11c. In this example, the probe insertion holes 11p and 11q are formed at a depth of h/2 from the upper surface of the side wall 11a (the surface opposite to the bottom plate 11b), facing each other, and extending in the radial direction of the cylinder.
The ultrasonic measuring device 12 comprises a transmitting unit 12a equipped with a transmitting probe 12p, a receiving unit 12b equipped with a receiving probe 12q, and a propagation velocity measuring unit 12c, and measures the propagation velocity of ultrasonic waves at one-minute intervals starting immediately after the concrete 1 is poured, for 24 hours after the water is poured.
The transmitting probe 12p and the receiving probe 12q are attached to the probe insertion holes 11p, 11q such that the tip of the transmitting probe 12p and the tip of the receiving probe 12q are exposed in the storage space 11c and face each other at a predetermined distance.
The propagation velocity measuring unit 12c compares the phase of the ultrasonic waves transmitted from the transmitting unit 12a with the phase of the ultrasonic waves received by the receiving unit 12b to measure the propagation velocity of the ultrasonic waves propagating through the concrete 1. The measured propagation velocity is sent to the actual data detecting means 13.

The actual data detection means 13 detects data on the change over time in the propagation velocity v of ultrasonic waves propagating through the concrete 1 measured by the propagation velocity measurement unit 12c.
2(a) is a diagram showing an example of the change in ultrasonic propagation velocity over time, where the horizontal axis is the elapsed time t [min] from the time water is poured into the cement, and the vertical axis is the ultrasonic propagation velocity v [m/s]. In this example, the pouring of water into the cement and mixing are performed outside the formwork 11, and then the mixed concrete 1 is stored in the storage space 11c of the formwork 11, and the propagation velocity of the ultrasonic waves propagating through this stored concrete 1 is measured using an ultrasonic measuring device 12.
Hereinafter, the measured data of the change in the propagation velocity of the ultrasonic waves over time will be referred to as actual data.
Immediately after pouring water, the concrete 1 has not yet started hardening, so the ultrasonic waves irradiated from the transmitting probe 12p are scattered within the concrete 1 and do not reach the receiving probe 12q. In other words, the ultrasonic waves are not observed by the receiving probe 12q until the setting and hardening of the concrete 1 has progressed to a certain extent.
After that, a point where the ultrasonic propagation velocity rises suddenly (ultrasonic wave rise time in the figure) was observed. The point where the ultrasonic propagation velocity rises suddenly can be, as in sample k1 in Figure 2(b), a case where the ultrasonic propagation velocity rises suddenly from v=0, or a case where the ultrasonic propagation velocity rises at a certain slope from v=0 and then rises suddenly, as in samples k2 to k4 and k6. Also, as in sample k5, a case where the ultrasonic propagation velocity rises slightly from v=0, then rises gradually, and then rises suddenly. In this case, the point where the ultrasonic propagation velocity rises later is regarded as the point where the ultrasonic propagation velocity rises suddenly.
The time when this sudden rise is observed is called the rise time, and the time elapsed from the time water is poured to the time when it rises is hereinafter called the rise time.
The rate of change of the ultrasonic propagation velocity at the rising time is extremely large compared to the rate of change in the time domain before the rising time and the rate of change in the time domain after the rising time. In other words, at the rising time, the rate of change of the ultrasonic propagation velocity becomes discontinuous.
To find the rise time, it is sufficient to measure the propagation velocity v of the ultrasonic wave until it reaches approximately 500 [m/s], as shown in the figure.
Although the rise time and the manner in which the ultrasonic propagation velocity rises differ depending on the concrete mix, there is no correlation between the rise time and the manner in which the ultrasonic propagation velocity rises.

また、配合材料は以下の通りである。
（１）セメント（Ｃ）：早強ポルトランドセメント（太平洋セメント（株）製、密度 3.14g/cm³）
（２）水（Ｗ）：水道水
（３）細骨材（Ｓ）；洗砂（歌棄産、表乾密度
2.60g/cm³）
（４）粗骨材（Ｇ）：砕石1505（峩朗産、表乾密度 2.68g/cm³）
（５）界面活性剤系増粘剤（Vt）：ビスコトップ400S（花王（株）製）
（６）ポリカルボン酸系高性能減水剤(SN1）：高性能減水剤SN1（花王（株）製）
（７）シリコーン系消泡剤（花王（株）製） The memory means 14 stores standard data 14a obtained by standardizing the data on the time change of ultrasonic propagation velocity, and a relational equation (hereinafter referred to as relational equation 14b) that represents the relationship between the compressive strength of concrete and the ultrasonic propagation velocity.
The standard data 14a is calculated using data on the time change after the rise time of the ultrasonic propagation velocity for concrete of a plurality of mix proportions.
The data of the time change after the rise time is the data of the time change after the rise time tx of the ultrasonic propagation velocity among the actual data of Fig. 2(a), and the origin of the time axis is set to t = tx, as shown in Fig. 2(c). Note that the elapsed time T from the rise time tx is T = t - tx, where t is the elapsed time from the time of water injection.
In this example, the standard data 14a was obtained from the data of the change in ultrasonic propagation velocity over time of the eight samples of the blend A and the data of the change in ultrasonic propagation velocity over time of the seven samples of the blend B. The blending conditions of the blends A and B are shown in Table 1 below.

The compounding materials are as follows:
(1) Cement (C): High-early-strength Portland cement (manufactured by Taiheiyo Cement Corporation, density 3.14 g/cm ³ )
(2) Water (W): Tap water (3) Fine aggregate (S): Washed sand (Utsukashi product, surface dry density
2.60g/ ^cm3 )
(4) Coarse aggregate (G): Crushed stone 1505 (produced in Garo, surface dry density 2.68 g/cm ³ )
(5) Surfactant-based thickener (Vt): Viscotop 400S (Kao Corporation)
(6) Polycarboxylic acid-based high-performance water reducing agent (SN1): High-performance water reducing agent SN1 (manufactured by Kao Corporation)
(7) Silicone-based defoamer (Kao Corporation)

3(a) is a diagram showing data on the change in ultrasonic propagation velocity over time for two samples of blend A and five samples of blend B, obtained using the above-mentioned mold 11 and ultrasonic measuring device 12. The horizontal axis is the elapsed time t (min) from water pouring, and the vertical axis is the ultrasonic propagation velocity v (m/s). The water pouring times are different for samples A11 and A12, samples B11 and B12, samples B21 and B22, and sample B31.
FIG. 3(b) shows data on the change in ultrasonic propagation velocity over time for six samples of blend A and two samples of blend B. The water injection times are different for samples B41, B41, samples A21, A22, samples A31, A32, and A41, A42.
Figure 4(a) shows the data of the sample of blend A and the sample of blend B, organized from the ultrasonic rise time, where the horizontal axis is the elapsed time T (min) from the ultrasonic rise time and the vertical axis is the ultrasonic propagation velocity v (m/s). An is the average value of samples An1 and An2, and Bn is the average value of samples Bn1 and Bn2 (n = 1 to 4, except B3 = B31).
Fig. 4(b) is a graph showing the standard data 14a, which is created by plotting the average values of the eight graphs shown in Fig. 4(a). The horizontal axis of the graph of the standard data 14a is the elapsed time T (min) from the ultrasonic rise time, and the vertical axis is the ultrasonic propagation velocity v (m/s). Note that Fig. 4(b) shows only the range of ultrasonic propagation velocity v used when estimating the intensity onset time, where v ≥ 3600 (m/s).

Relational formula 14b was determined by the following procedure.
First, through experiments, the concrete compressive strength fc (N/ ^mm2 ) at the elapsed time T (min) from the ultrasonic rise time is measured and plotted for multiple mixes at specified time intervals to determine the relationship between the elapsed time T (min) from the ultrasonic rise time and the concrete compressive strength fc (N/ ^mm2 ), as shown in Figure 5 (a).
Next, by replacing the time T (min) elapsed from the ultrasonic rise time in Fig. 5(a) with ultrasonic propagation velocity v (m/s) using graph 14a of the standard data shown in Fig. 4(b), the data in Fig. 5(a) is converted into data as shown in Fig. 5(b) in which the horizontal axis (x-axis) is concrete compressive strength fc (N/ ^mm2 ) and the vertical axis (y-axis) is ultrasonic propagation velocity v (m/s). After that, from the graph plotting the relationship between this concrete compressive strength fc (N/ ^mm2 ) and ultrasonic propagation velocity v (m/s), a relational expression 14b between concrete compressive strength fc (N/ ^mm2 ) and ultrasonic propagation velocity v (m/s) is obtained.
Relational expression 14b can be expressed by the following formula (1), where the compressive strength of concrete fc (N/mm ² ) is x and the ultrasonic propagation velocity v (m/s) is y.
y=509.66・ln(x)+2719.9...(1)
The correlation coefficient between equation 14b and the data was R ² =0.9189.

As shown in FIG. 1, the intensity onset time estimation means 15 includes an actual ultrasonic velocity calculation unit 15a, a standard ultrasonic velocity calculation unit 15b, a data correction unit 15c, and an intensity onset time estimation unit 15d.
As shown in Fig. 6(a), the actual ultrasonic propagation velocity calculation unit 15a calculates the ultrasonic propagation velocity 24 hours (1440 min) after water injection from the actual data detected by the actual data detection means 13, and sets this as the actual ultrasonic propagation velocity vk. From the figure, vk = 4073 m/s is obtained.
As shown in Fig. 5B, the standard ultrasonic velocity calculation unit 15b calculates the ultrasonic velocity corresponding to the compressive strength at 24 hours in the relational expression 14b, and sets this as the standard ultrasonic velocity vm. In this example, since the compressive strength at 24 hours is fc = 20 N/ ^mm2 , the standard ultrasonic velocity is vm = 4221 m/s.
As shown in FIG. 6B, the data correction unit 15c corrects the actual data shown in FIG. 2A using the actual ultrasonic propagation velocity vk calculated by the actual ultrasonic propagation velocity calculation unit 15a and the standard ultrasonic propagation velocity vm calculated by the standard ultrasonic propagation velocity calculation unit 15b.
The corrected ultrasonic propagation velocity v′, which is the ultrasonic propagation velocity after correction, is calculated from the following formula (2).
v'=(vm/vk)・v=1.0363・v……(2)
6B shows a graph of the corrected data, which is the actual data that has been corrected. Note that the dashed line in the figure shows the graph of the actual data before correction.
As shown in FIG. 7(a), the strength development time estimation unit 15d calculates the ultrasonic propagation velocity for estimation v, which is the ultrasonic propagation velocity corresponding to a predetermined compressive strength, from the relational expression 14b, and then, as shown in FIG. 7(b), calculates the elapsed time corresponding to the ultrasonic propagation velocity for estimation v in the corrected data, and estimates the calculated elapsed time to be the strength development time, which is the time measured from the time water is poured until the concrete develops a predetermined compressive strength.
Here, the predetermined compressive strength is 15 N/ ^mm2 , so the ultrasonic propagation velocity for estimation obtained from Fig. 7(a) is v = 4100 m/s. Therefore, the elapsed time (the time elapsed from the time of water injection) corresponding to the ultrasonic propagation velocity for estimation v = 4100 m/s in the corrected data of Fig. 7(b) is 1237 min (20.6 hr).
In other words, the time required for the concrete 1 to reach the specified compressive strength of 15 N/ ^mm2 is estimated to be 20.6 hours.

Next, a method for estimating the strength development time of concrete using the estimation device 10 of the present invention will be described with reference to the flowchart of FIG.
First, after mixing the concrete, the concrete 1 is poured into the formwork 11, and the propagation speed of ultrasonic waves propagating through the concrete 1 is measured using the ultrasonic measuring device 12 (step S10). Actual data, which is data on the change over time in the propagation speed of ultrasonic waves in the concrete 1, is detected (step S11), as shown in FIG. 2(a).
The mix for Concrete 1 was prepared by changing the amount of SN1, a high-performance water reducing agent, from C×2% to C×1.5% in the mix for Concrete A described above.
Next, the actual ultrasonic propagation velocity vk, which is the ultrasonic propagation velocity of the actual data after 24 hours has elapsed, is calculated (step S12), and the standard ultrasonic propagation velocity vm, which is the ultrasonic propagation velocity corresponding to the 24-hour compressive strength of the concrete 1 in relational expression 14b, is calculated (step S13).
Next, the actual data is corrected using the measured ultrasonic propagation velocity vk calculated in steps S12 and S13 and the standard ultrasonic propagation velocity vm, to obtain corrected data as shown in FIG. 6B (step S14).
Then, as shown in Fig. 7(a), the ultrasonic propagation velocity corresponding to a predetermined compressive strength (here, fc = 15 N/ ^mm2 ) is obtained from relational expression 14b, and this obtained ultrasonic propagation velocity is set as the ultrasonic propagation velocity for estimation vc (step S15). Finally, as shown in Fig. 7(b), the elapsed time corresponding to the ultrasonic propagation velocity for estimation vc in the corrected data is obtained, and this obtained time is estimated as the time until the concrete 1 develops a predetermined compressive strength, i.e., the strength development time (step S16).

The present invention has been described above using an embodiment, but the technical scope of the present invention is not limited to the scope described in the above embodiment. It is clear to those skilled in the art that various modifications and improvements can be made to the above embodiment. It is clear from the claims that forms with such modifications or improvements can also be included in the technical scope of the present invention.

For example, in the above embodiment, the compressive strength fc of the concrete 1 was measured after 24 hours had elapsed, but the measurement of the compressive strength fc is not limited to 24 hours after pouring water, and the elapsed time for measuring the compressive strength fc may be any time from pouring water until the concrete 1 has a certain level of compressive strength fc (for example, 800 min or more).
In the above embodiment, the water-cement ratio (W/C) and the fine aggregate ratio (s/a) of the concrete used in the experiment are almost constant. However, the present invention is not limited to this, and can be applied as long as the water-cement ratio (W/C) and the fine aggregate ratio (s/a) of the concrete used as the SENS concrete are within the range.
Furthermore, well-known thickeners and high-performance water reducing agents may also be used.

1 Concrete, 10 Concrete strength development time estimation device (estimation device),
11 formwork, 11a side wall, 11b bottom plate, 11c storage space,
11p, 11q probe insertion hole,
12 ultrasonic measuring device, 12a transmitting unit, 12b receiving unit, 12c propagation velocity measuring unit,
12p transmit probe, 12q receive probe,
13 actual data detection means, 14 storage means, 14a standard data, 14b relational expression,
15 Intensity development time estimation means, 15a Actual ultrasonic propagation velocity calculation unit,
15b standard ultrasonic propagation velocity calculation unit, 15c data correction unit,
15d Intensity onset time estimation unit.

Claims (3)

A method for estimating the time until concrete develops a predetermined compressive strength, comprising:
pouring concrete into the formwork;
Measuring the ultrasonic propagation velocity of concrete poured into the formwork;
and estimating a strength development time, which is a time until the concrete develops a predetermined compressive strength, from actual data, which is data on the change over time of the measured ultrasonic propagation velocity, and a previously obtained relational expression expressing a relationship between the compressive strength of the concrete and the ultrasonic propagation velocity,
The time from the time when water is poured to the time when the rate of change of the ultrasonic propagation velocity becomes discontinuous is defined as the rise time of the ultrasonic propagation velocity,
When the data calculated from the data of the time change of the ultrasonic propagation velocity of concrete of a plurality of mixes after the rise time is used as the standard data,
A method for estimating strength development time of concrete, characterized in that the relational equation is obtained from a relationship between the elapsed time and the compressive strength at the elapsed time measured from the rise time of the ultrasonic propagation velocity of concrete of a plurality of blend proportions, and a relationship between the elapsed time and the ultrasonic propagation velocity in the standard data. The compressive strength of the concrete at 24 hours of age is obtained in advance,
In the step of estimating the strength onset time,
The method for estimating the strength development time of concrete according to claim 1, characterized in that the actual data is corrected using a standard ultrasonic propagation velocity, which is the ultrasonic propagation velocity corresponding to the compressive strength at an age of 24 hours in the relational equation, and an actual ultrasonic propagation velocity, which is the ultrasonic propagation velocity 24 hours after water injection in the actual data, and an ultrasonic propagation velocity for estimation, which is the ultrasonic propagation velocity corresponding to the specified compressive strength, is obtained from the relational equation, and then a time corresponding to the ultrasonic propagation velocity for estimation in the corrected actual data is obtained, and the obtained time is estimated to be the strength development time of the concrete. A device for estimating the time until concrete develops a predetermined compressive strength,
A formwork for containing the concrete;
an ultrasonic measuring device that is installed in the formwork so that a tip of a transmitting probe and a tip of a receiving probe are positioned at a predetermined distance from each other within the formwork and that measures the propagation speed of ultrasonic waves propagating through the concrete;
an actual data detection means for detecting actual data which is data on the change over time of the measured ultrasonic propagation velocity;
A storage means for storing standard data calculated from data on time changes after the rise time of ultrasonic propagation velocity of concretes of a plurality of compounding ratios, a relationship between the elapsed time measured from the rise time of ultrasonic propagation velocity of concretes of a plurality of compounding ratios and the compressive strength at the elapsed time, and a relational equation showing the relationship between the compressive strength of the concrete and ultrasonic propagation velocity obtained using the relationship between the elapsed time and ultrasonic propagation velocity in the standard data;
A strength development time estimation means for estimating a strength development time, which is a time required for the concrete to develop a predetermined compressive strength, using the actual data and the relational expression;
Equipped with
The rise time of the ultrasonic propagation velocity is the elapsed time from the time water is poured to the time when the rate of change of the ultrasonic propagation velocity becomes discontinuous.

Images