阅读说明：本技术 一种新拌混凝土凝固时间检测方法和装置 (Method and device for detecting setting time of fresh concrete ) 是由 龙士国 唐好文 于 2020-12-31 设计创作，主要内容包括：本发明公开了一种新拌混凝土凝固时间检测方法,步骤为在待测容器一侧激发应力波,将换能器采集的新拌混凝土的时域信息进行降噪、归一化处理,截取局部声波时域图；求局部声波时域图的频域图,并对频域图的各分波包的声波数据求积分面积C；再通过C求钢筋导波凝固时间参数i的峰值点,该峰值点即为新拌混凝土的初凝时间。本发明所采用的方法,可以方便简单的得出混凝土的凝固情况。相比于传统的使用的笨重的混凝土贯入仪测试贯入度的方法,其大大减少了试验的前置流程,减少了检测时的人为因素的干扰,并且装置结构简单,便于推广,适合在施工现场使用。(The invention discloses a method for detecting the setting time of fresh concrete, which comprises the steps of exciting a stress wave at one side of a container to be detected, carrying out noise reduction and normalization processing on time domain information of the fresh concrete collected by a transducer, and intercepting a local sound wave time domain diagram; solving a frequency domain diagram of the local sound wave time domain diagram, and solving an integral area C of sound wave data of each wave division packet of the frequency domain diagram; and solving a peak point of the steel bar guided wave solidification time parameter i through the C, wherein the peak point is the initial setting time of the fresh concrete. The method adopted by the invention can conveniently and simply obtain the concrete solidification condition. Compared with the traditional method for testing the penetration degree by using the heavy concrete penetrometer, the method has the advantages that the test preposed flow is greatly reduced, the interference of human factors during detection is reduced, the device is simple in structure and convenient to popularize, and the method is suitable for being used on a construction site.)

1. The method for detecting the setting time of the fresh concrete is characterized by comprising the following steps of:

step a) exciting a stress wave at one side of a container to be tested, carrying out noise reduction and normalization processing on time domain information of fresh concrete collected by a transducer, and intercepting a local sound wave time domain diagram;

step b) solving a frequency domain diagram of the local sound wave time domain diagram obtained in the step a), and solving an integral area C of sound wave data of each wave division packet of the frequency domain diagram;

step c) substituting the integral area obtained in step b) into a formulaSolving a peak point of the steel bar guided wave solidification time parameter i, wherein the peak point is the initial setting time of the fresh concrete;

wherein, C1-C3 are the integral areas of the first, second and third wavelet packets in the frequency domain diagram.

2. The utility model provides a fresh concrete setting time detection device, its characterized in that, including rectangle container (4), "people" type wood die-pin (3), U type groove (2) and reinforcing bar (1), one "people" type wood die-pin (3) are installed respectively to the both sides of rectangle container (4) opening part, the opening part of rectangle container (4) is withstood to the bottom depressed part of "people" type wood die-pin (3), U type groove (2) are placed to the top level of "people" type wood die-pin (3), during the detection, rectangle container (4) are arranged in to reinforcing bar (1), the both ends of reinforcing bar (1) contact with U type groove (2) of installing at rectangle container (4) both ends respectively.

3. The fresh concrete setting time detection device of claim 2, wherein the spiral part of the reinforcing steel bar is arranged in the cavity of the rectangular container (4), and the head and tail bent parts are arranged outside the rectangular container (4) and are respectively contacted with the U-shaped groove (2).

4. The apparatus for detecting the setting time of fresh concrete according to claim 2, wherein the apparatus is made of non-metallic material except for the steel bars.

5. The fresh concrete setting time detection device of claim 2, wherein the middle of the steel bar (1) is processed in a spiral mode, the steel bar (1) is bent to be 90 degrees in an end-to-end mode, and the end-to-end position of the steel bar (1) is respectively in contact with the U-shaped grooves (2) on two sides of the rectangular container (4).

6. The fresh concrete setting time detection device of claim 2, wherein the "herringbone" wooden support rod (3) comprises a first support rod (31) and a second support rod (32), an included angle between the first support rod (31) and the second support rod (32) is 110 degrees, the herringbone is formed, the top of the first support rod (31) is connected with the U-shaped groove (2), the bottom of the first support rod (31) is connected with the rectangular container (4), the top of the second support rod (32) is connected with the middle upper part of the first support rod (31), and the bottom of the second support rod (32) is connected with the bending part of the reinforcing steel bar (1).

7. The setting time detection device of fresh concrete according to claim 2, characterized in that the lower end of the human-shaped wood support rod (3) is respectively connected with the side wall and the opening of the upper edge of the rectangular container (4), the upper end of the human-shaped wood support rod is connected with the U-shaped groove (2), and the angles between the rectangular container (4) and the human-shaped wood support rod (3) are respectively 15 degrees and 54 degrees; specifically, the angle between the side wall of the rectangular container (4) and the first support rod (31) is 15 degrees, and the angle between the side wall of the rectangular container (4) and the second support rod (32) is 54 degrees.

8. The fresh concrete setting time detection device of claim 2, characterized in that a receiving transducer and an exciting transducer are respectively arranged in the U-shaped groove (2), and the transducers are compressed by certain compressibility of rubber.

9. The fresh concrete setting time detection apparatus according to claim 2, wherein the step of detecting the initial setting time of fresh concrete by the detection apparatus is:

step a') clamping the bent part of the steel bar (1) on a man-shaped wood support rod (3);

step b') horizontally placing a transmitting transducer/a receiving transducer in the U-shaped groove (2), ensuring that a transmitting point and a receiving point of the transducer are in close contact with the cross section of the steel bar (1), and ensuring that the pressure is constant; coupling agent is added between the U-shaped groove (2) and the transducer;

step c') injecting fresh concrete into the rectangular container (4) while ensuring the close contact of the transducer with the steel bar (1);

and d') exciting stress waves by using a transmitting transducer, setting attenuation parameters in an ultrasonic detector, and recording the time domain signals of the sound waves after the wave forms are stabilized.

Technical Field

The invention relates to a method for detecting concrete setting time, in particular to a method and a device for detecting the setting time of fresh concrete, and belongs to the field of sound wave detection.

Background

Setting time is a sign of the progress of concrete hydration reaction, and during the setting process, slurry itself undergoes a series of physical and chemical changes. The setting time is divided into an initial setting time and a final setting time. The initial setting time is the time required from the mixing of cement and water until the cement paste begins to lose plasticity. The final set time is the time from when the cement mixes with water until the cement paste loses plasticity completely and begins to develop strength. The setting time of the cement has important significance in construction, the initial setting time is not too short, and the final setting time is not too long.

At present, the penetration resistance method is the current standard test method of the setting time in China, the current standard is 'standard test method of the performance of common concrete mixture' (GB/T50080-. During the test, mortar is screened out from concrete through a test screen, and the setting time is measured from the time when water is added into the concrete. And determining the test time of the measuring probe according to the performance of the concrete mixture, testing once every 0.5h, and shortening the test interval time when the initial setting and the final setting are approached. During testing, the mortar sample cylinder is placed on a penetration resistance instrument, and the maximum penetration resistance value is recorded. Each mortar cylinder is tested for 1-2 points each time, and the penetration test of each sample is not less than 6 times until the penetration resistance value of unit area is more than 28MPa (final setting is achieved). The subsequent coagulation time is determined by linear regression according to equation (1):

lnt＝a+blnf_PR (1)

wherein t is the testing time (min) corresponding to the unit area penetration resistance, and a and b are linear regression coefficients.

The coagulation time can also be determined by a drawing and fitting method, and a relation curve between the penetration resistance in unit area and the test time is drawn by taking the penetration resistance in unit area as a vertical coordinate and taking the test time as a horizontal coordinate; drawing two straight lines parallel to the abscissa at 3.5MPa and 28MPa respectively, wherein the abscissa of the intersection point of the straight lines and the curve is the initial setting time and the final setting time respectively.

The penetration resistance method is complicated and has many disadvantages, such as: the setting and hardening process of the slurry cannot be continuously tested, the test result is related to the skill of an operator, and the setting time of the test piece is difficult to accurately judge due to the large difference of parallel test results. In addition, when the setting time of the concrete is tested, the mortar in the concrete needs to be screened out, which is difficult for the concrete with low fluidity.

In research, people try to establish a new method for testing the coagulation time from different aspects, such as hydration heat, nuclear magnetic resonance, resistivity, ultrasonic waves and the like. The ultrasonic detection method has the most research, has close relation with basic cement microstructure parameters such as hydration degree, and can monitor the coagulation process of samples such as mortar, concrete and the like nondestructively and continuously. Shruti Sharma et al monitor the setting of fresh concrete by the propagation of ultrasonic waves through the rebar and test results show that as the concrete sets, more wave energy escapes into the surrounding concrete, causing signal attenuation with a trend toward attenuation and setting time. The measuring result is not accurate, and the concrete solidification time needs to be conveniently detected on a construction site to judge whether the initial solidification time is reached.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide a method for detecting the setting time of fresh concrete, which can conveniently detect the setting time of the concrete on a construction site, judge whether the setting time reaches the initial setting time or not and save a large amount of time cost and labor cost.

In order to realize the purpose, the invention provides a brand-new method for detecting the setting time of fresh concrete, which comprises the following steps:

step a) exciting a stress wave at one side of a container to be tested, carrying out noise reduction and normalization processing on time domain information of fresh concrete collected by a transducer, and intercepting a local sound wave time domain diagram;

step b) solving a frequency domain diagram of the local sound wave time domain diagram obtained in the step a), and solving an integral area C of sound wave data of each wave division packet of the frequency domain diagram;

step c) substituting the integral area obtained in step b) into a formulaSolving a peak point of the steel bar guided wave solidification time parameter i, wherein the peak point is the initial setting time of the fresh concrete;

wherein, C1-C3 are the integral areas of the first, second and third wavelet packets in the frequency domain diagram.

The invention provides a device for detecting the setting time of fresh concrete, which comprises a rectangular container, a 'man' -shaped wood support rod, a U-shaped groove and a steel bar, wherein the two sides of the opening of the rectangular container are respectively provided with the 'man' -shaped wood support rod, the bottom of the 'man' -shaped wood support rod is sunken to prop against the opening of the rectangular container, the top of the 'man' -shaped wood support rod is horizontally provided with the U-shaped groove, the steel bar is arranged in the rectangular container during detection, and the two ends of the steel bar are respectively contacted with the U-shaped grooves arranged at the two ends of the rectangular container.

The spiral position of the reinforcing steel bar is arranged in the containing cavity of the rectangular container, and the head and tail bent positions are arranged outside the rectangular container and are respectively contacted with the U-shaped groove.

In order to ensure the detection accuracy of the sound wave data, the detection device is made of non-metal materials except the steel bars.

Longer reinforcing bar can be put into in the space of minimum in order to make things convenient for, guarantee that longer reinforcing bar buries long, consequently with the middle part helicization of reinforcing bar handle to bend into 90 with the reinforcing bar head and the tail, the head and the tail department of reinforcing bar contacts with the U type groove of rectangle container both sides respectively.

The 'people' type wood bracket rod comprises a first bracket rod and a second bracket rod, an included angle between the first bracket rod and the second bracket rod is 110 degrees to form a 'people' shape, the top of the first bracket rod is connected with a U-shaped groove, the bottom of the first bracket rod is connected with a rectangular container, the top of the second bracket rod is connected with the middle upper part of the first bracket rod, and the bottom of the second bracket rod is connected with the bending part of a reinforcing steel bar.

The lower end of the inverted V-shaped wood support rod is connected with the side wall and the opening of the upper edge of the rectangular container respectively, the upper end of the inverted V-shaped wood support rod is connected with the U-shaped groove, and the angles between the rectangular container and the inverted V-shaped wood support rod are 15 degrees and 54 degrees respectively; specifically, the angle between the side wall of the rectangular container and the first support rod is 15 degrees, and the angle between the side wall of the rectangular container and the second support rod is 54 degrees.

When the two U-shaped grooves are used for detection, a receiving transducer and an exciting transducer are respectively placed in the U-shaped grooves, and the transducers are tightly pressed by utilizing certain compressibility of rubber.

The reinforcing steel bars are plain round reinforcing steel bars.

The total length of the plain round steel bar is 1000 mm.

The nominal diameter of the plain round steel bar is 6 mm.

The step of detecting the initial setting time of the fresh concrete by the detection device is as follows:

step a ') clamping the bending part of the steel bar on a ' man ' -shaped wood support rod;

step b') horizontally placing a transmitting transducer/a receiving transducer in the U-shaped groove, ensuring that a transmitting point and a receiving point of the transducer are in close contact with the cross section of the steel bar and ensuring the pressure to be constant; coupling agent is added between the U-shaped groove and the transducer;

step c') injecting fresh concrete into the rectangular container, and simultaneously ensuring that the transducer is tightly contacted with the steel bar;

and d') exciting stress waves by using a transmitting transducer, setting attenuation parameters in an ultrasonic detector, and recording the time domain signals of the sound waves after the wave forms are stabilized.

Compared with the prior art, the invention has the beneficial effects that: the method does not need a complex penetration resistance value detection device and detection method, only needs to fill the rectangular container with fresh concrete, and then continuously measures the solidification condition of the fresh concrete through a fixed transducer and only needs to connect the sound wave detector to a computer (sound wave data is continuously input to the computer for data processing, and the computer directly obtains initial setting time); the original test detection method needs to filter out the mortar through a screen, but the test method does not need the complicated step and directly detects the mortar in the fresh concrete; because the original fresh concrete is detected, the in-situ measurement of the fresh concrete is basically realized; the method realizes the theoretical breakthrough of the method for detecting the fresh concrete by using the ultrasonic wave in the early stage and provides a foresight for the intelligent detection of the fresh concrete in the future.

Drawings

FIG. 1a is a front view of a fresh concrete setting time detection apparatus;

FIG. 1b is a side view of a fresh concrete setting time detection apparatus;

FIG. 1c is a top view of the apparatus for measuring the setting time of fresh concrete;

FIG. 2 is a schematic view of a steel bar of the fresh concrete setting time detection device;

FIG. 3 is a schematic view of a "man" -shaped wooden support rod of the fresh concrete setting time detection device;

FIG. 4a is a front view of a section of a fresh concrete setting time detection apparatus;

FIG. 4b is a sectional top view of the experimental apparatus for setting time of fresh concrete;

FIG. 4c is a cross-sectional side view of the fresh concrete setting time experimental apparatus;

FIG. 5 is a sound wave time domain diagram of fresh concrete with a water-cement ratio of 0.51 in 0-270 minutes;

FIG. 6 is a partial time domain diagram of the first four wave packets of FIG. 3 being truncated;

FIG. 7 is a graph of the packet local spectrum of a first set of data for fresh concrete at a water-to-cement ratio of 0.51;

FIG. 8 is a plot of the integration points of the wave packet spectrum of fresh concrete at a water-cement ratio of 0.51;

FIG. 9 is a graph of i-t relationship for fresh concrete at 0.51 water-to-cement ratio;

FIG. 10 is a graph of i-t relationship for fresh concrete at 0.31 water-cement ratio;

FIG. 11 is a schematic graph showing the initial setting time of fresh concrete using the penetration resistance method to detect the water-cement ratio of 0.51 and 0.31, respectively;

wherein, 1, reinforcing steel bars; 2. a U-shaped groove; 3. a 'human' type wood support rod; 31. a first support rod; 32. a second support rod; 4. a rectangular container.

Detailed Description

The present invention will be described more fully with reference to the following examples and comparative examples.

As shown in fig. 1 to 9, a novel method and a kit for detecting the setting time of fresh concrete according to this embodiment are provided. The structure of the device for detecting the setting time of fresh concrete provided by the invention is shown in figure 1, and mainly comprises a rectangular container 4 made of wood, a pair of 'herringbone' wooden support rods 3, a pair of rectangular U-shaped grooves 2 made of rubber, and smooth round steel bars 1 with the total length of 1000mm and the nominal diameter of 6 mm; wherein, one "people" type wood bracket pole 3 is installed respectively to the both sides of 4 openings of rectangle container, and the opening part of rectangle container 4 is withstood to the bottom depressed part of this "people" type wood bracket pole 3, "U type groove 2 has been placed to the top level of" people "type wood bracket pole 3, longer reinforcing bar can be put into in the space of minimum in order to make things convenient for, guarantee that longer reinforcing bar buries long, consequently with the middle part spiral processing of reinforcing bar 1, and buckle into 90 with the reinforcing bar end to end, the end to end department of reinforcing bar 1 contacts with the U type groove 2 of rectangle container both sides respectively.

The 'people' shaped wood support rod 3 comprises a first support rod 31 and a second support rod 32, an included angle between the first support rod 31 and the second support rod 32 is 110 degrees to form a 'people' shape, the top of the first support rod 31 is connected with a U-shaped groove 2, the bottom of the first support rod 31 is connected with a rectangular container 4, the top of the second support rod 32 is connected with the middle upper part of the first support rod 31, and the bottom of the second support rod 32 is connected with a bending part of the steel bar 1.

The 'man' shaped wooden support rod 3 can be respectively connected with the rectangular container 4 and the U-shaped groove 2 through 520 glue, the angle between the side surface of the rectangular container 4 and the first support rod 31 is 15 degrees, and the angle between the side surface of the rectangular container 4 and the second support rod 32 is 54 degrees.

During detection, the spiral part of the reinforcing steel bar 1 is arranged in the cavity of the rectangular container, and the head and tail bent parts are arranged outside the rectangular container 4 and are respectively contacted with the U-shaped groove 2.

The method for detecting the initial setting time of the fresh concrete by the device comprises the following steps:

step 1) clamping the bent part of the steel bar 1 on a man-shaped wood support rod 3;

step 2) horizontally placing a transmitting transducer/a receiving transducer in the U-shaped groove, ensuring that a transmitting point and a receiving point of the transducers are in close contact with the cross section of the steel bar, and ensuring the pressure to be constant; coupling agent is added between the U-shaped groove and the transducer;

step 3) injecting fresh concrete into the rectangular container 4, and simultaneously ensuring that the transducer is tightly contacted with the reinforcing steel bar;

step 4) using a transmitting transducer with the excitation frequency of 100khz, setting the attenuation parameter to be 20 in an ultrasonic detector, recording the attenuation parameter as a final sound wave time domain signal after the waveform is stabilized, and repeatedly detecting for three times each time to obtain an average value;

step 5) carrying out noise reduction and normalization processing on the time domain information obtained in the step 4), and intercepting a local sound wave time domain diagram;

step 6) solving a frequency domain diagram of the local sound wave time domain diagram obtained in the step 5), and solving an integral area of each sound wave data of the frequency domain diagram;

step 7) through steel bar guided wave solidification time parametersSubstituting the integral area obtained in the step 6) into the formula to obtain a peak point of i, wherein the peak point is the initial setting time of the fresh concrete.

In this embodiment, select the multi-functional sound wave parameter tester of TH204 type to carry out data acquisition, the transducer chooses for use piezoelectric transducer to stimulate/receive the sound wave to test 6mm plain round steel bar screw-spinning, the fresh concrete that the water cement ratio is 0.31 as the example, specifically do:

(1) setting the time for filling the concrete into the wooden box as 0 minute, and exciting stress waves by a transmitting transducer and receiving time domain information of sound wave signals by the receiving transducer at 0min, 15min, 30min, 45min, 60min, 90min, 120min, 150min, 210min and 270min respectively;

(2) denoising and normalizing the time domain information obtained in the step (1), wherein the time domain information is the sound wave time domain graph change trend of fresh concrete with a water-cement ratio of 0.51 in 0-270 minutes as shown in FIG. 5;

(3) by observing fig. 5, it can be found that, as the concrete solidifies, the wave velocity of the guided wave of the steel bar is basically unchanged, but the number and the size of the wave packets have a relatively obvious change trend with time, the normalized visual size of the first wave packet does not change much, but as the concrete solidifies, the guided wave of the steel bar begins to diffuse gradually into the concrete, so that the areas of the second, third and fourth wave packets gradually decrease and even disappear finally, and therefore, the first four wave packets of the acoustic signals of 0min, 15min and 30min in fig. 5 are separately intercepted to form a new acoustic time domain diagram, as shown in fig. 6 (here, 45min, 60min, 90min, 120min, 150min, 210min and 270min have been omitted, and the data processing is the same);

(4) the sound wave signal of fig. 6 is subjected to fourier transform to obtain a frequency domain diagram, and fig. 7 is a frequency domain diagram of the first four sub-wave packets of the fresh concrete sound wave signal with the water-cement ratio of 0.51 obtained at 0min, and it can be found that each wave packet represents a complete content, which is particularly shown in that the fluctuation trend of each wave packet is consistent;

(5) using Origin software by integrating formulaThe data corresponding to the four wavelet packets in fig. 7 are respectively integrated, and the processing of the sound wave signals at other times is the same as the above operation steps (steps 4 to 5), which are not described herein again, and the obtained results are shown in table 1 and fig. 8:

TABLE 1

Elapsed time	First wave packet	Second wave packet	Third wave packet	Fourth wave packet
					0min	0.51497	0.31778	0.20955	0.15052
15min	0.37642	0.23315	0.17714	0.13042
					30min	0.39141	0.22	0.14317	0.10642
45min	0.38445	0.21717	0.13711	0.08394
					60min	0.38473	0.21023	0.11737	0.07491
90min	0.35174	0.14062	0.06541	0.04325
					120min	0.39195	0.13777	0.06896	0.06498
150min	0.36227	0.06377	0.04533	0.06029
					210min	0.62453	0.35828	0.34292	0.43752
270min	0.64639	0.34918	0.33765	0.4274

(6) Observing table 1, it can be seen that the integrated area C1 of the first wave packet is in a relatively stable state, the areas of the second, third and fourth wave packets have a tendency to decrease significantly, and the data each vary greatly at 150min and remain substantially stable in the following, so that the fourth wave packet which disappears too early to be followed by a noise component is not considered here. Defining the integral area of the first wave division packet frequency domain diagram as C1, respectively naming the integral areas of the second and third wave division packet frequency domain diagrams as C2 and C3 in the same way, and defining parameter steel bar guided wave solidification time parameterThe results corresponding to each time are plotted in an i-t relationship, as shown in FIG. 9. The area of the fourth packet is not considered here, because the fourth packet actually represents an abnormal situation of data. Fig. 8 shows that the area of the fourth wave packet is abnormally and suddenly increased at a time point, and in the actual situation, the energy diffused by the steel bar guided wave is gradually increased along with the solidification process, so that the fourth wave packet can only be smaller and smaller. The analysis reason is that the acoustic wave energy is diffused more and more due to solidification, the received acoustic wave signals are fewer and less, and the noise occupation proportion is gradually increased, so that after the data is normalized, the noise affects the final spectrogram, and finally the unconventional change is caused. The fourth wave packet can also serve as a secondary to the i parameter.

As can be seen from FIG. 9, when the concrete was added to the vessel up to 150min, the value of i reached the peak point; the steps 1-6 are repeated to process the fresh concrete with the water-cement ratio of 0.31, the data processing result is shown in figure 10, the same change rule can be found, and the peak value point of i is earlier than the fresh concrete with the water-cement ratio of 0.51; therefore, the peak point of i can be predicted as the initial setting time point.

The initial setting time of the fresh concrete used in the test was measured by the penetration resistance method under the same environment, and the obtained data is shown in fig. 11. From fig. 11, it can be seen that the time spent on fresh concrete with a water-cement ratio of 0.31 is about 120 minutes, and the time spent on fresh concrete with a water-cement ratio of 0.51 is about 150 minutes when the penetration resistance is 3.5MPa, which substantially coincides with the i peak conclusion defined previously, which proves the feasibility of the method provided by the present invention.

Finally, it must be said here that: the above embodiments are only used for further detailed description of the technical solutions of the present invention, and should not be understood as limiting the scope of the present invention, and the insubstantial modifications and adaptations made by those skilled in the art according to the above descriptions of the present invention are within the scope of the present invention.