CN113433221A - Cement concrete pavement joint sawing time prediction device and method - Google Patents
Cement concrete pavement joint sawing time prediction device and method Download PDFInfo
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- E01C23/0906—Devices or arrangements for working the finished surface; Devices for repairing or reconditioning the surface of damaged paving; Recycling in place or on the road for forming cuts, grooves, or recesses, e.g. for making joints or channels for markings, for cutting-out sections to be removed; for cleaning, treating, or filling cuts, grooves, recesses, or fissures; for trimming paving edges for forming, opening-out, cleaning, drying or heating cuts, grooves, recesses or, excluding forming, cracks, e.g. cleaning by sand-blasting or air-jet ; for trimming paving edges
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Abstract
The invention provides a cement concrete pavement joint sawing time prediction device, which comprises a box body, wherein a concrete charging barrel is fixed in the box body, a telescopic piece is fixed at the position above the box body, which is opposite to the concrete charging barrel, the telescopic end of the telescopic piece is fixed with a plate body matched with the inner diameter of the concrete charging barrel, an ultrasonic transmitting device is fixed on the plate body, and an ultrasonic receiving device for receiving an ultrasonic pulse signal is fixed on the lower surface of the concrete charging barrel; a distance measuring device for measuring the distance between the upper surface in the box body and the plate body is fixed at the position in the box body, which is opposite to the plate body; a temperature sensor for measuring the internal temperature of the concrete is fixed on the outer side wall of the concrete charging barrel; the invention predicts the optimal joint sawing time range of the road slab by the action of the ultrasonic wave and the temperature, can accurately test the time of the cement concrete pavement reaching the initial setting state, and can accurately predict the time range of the joint of the cement concrete pavement starting to be sawn by utilizing the initial setting time.
Description
Technical Field
The invention belongs to the technical field of road engineering, and particularly relates to a device and a method for predicting sawing time of a cement concrete pavement joint.
Background
The cement concrete pavement is widely applied to highway construction in China and plays an important role in pavement structure in China. However, when the concrete pavement is constructed, in order to reduce the damage of the temperature and the cyclic load stress to the concrete pavement, the pavement needs to be subjected to seam sawing treatment, so that the stress is concentrated and released at the seams, and the structural integrity of the concrete pavement is further protected. However, the joints of the concrete pavement need to be sawed at the proper time, when the sawing is performed too early, the concrete is loosened and peeled off, and when the sawing time is too late, the concrete pavement is cracked randomly, and the structure of the concrete pavement is damaged. At present, the specification of China does not clearly stipulate the joint sawing time of the concrete pavement, but in the field construction process, the concrete pavement sawing time is often determined according to experience, and two common methods are adopted, namely scratching the surface of a flat plate by using a knife or standing on a concrete slab to observe the depth of a footprint. Another approach is to try to cut and observe the extent of the scatter. However, these prediction methods are often subjective and often result in the sawing time not being at the optimum time, causing random crack failure or loosening and spalling of the concrete pavement slab.
Disclosure of Invention
The invention aims to provide a device and a method for predicting the sawing time of a joint of a cement concrete pavement, which can predict the optimal sawing time of the joint of a pavement slab by utilizing the action of ultrasonic waves and temperature, accurately test the time of the cement concrete pavement reaching an initial set state and accurately predict the sawing time of the cement concrete pavement after being unsealed by utilizing the initial set time.
The technical scheme of the invention is as follows:
a cement concrete pavement joint sawing time prediction device comprising:
a box body;
the concrete charging barrel is fixed inside the box body;
the fixed end of the telescopic piece is fixed above the box body at a position opposite to the opening of the concrete charging barrel, and the telescopic end of the telescopic piece longitudinally stretches downwards;
the plate body is fixed at the end part of the telescopic end of the telescopic piece, is matched with the inner diameter of the concrete charging barrel and is used for synchronously compacting a test piece in the concrete charging barrel downwards along with the telescopic end of the telescopic piece;
the ultrasonic transmitting device is fixed on the plate body;
the ultrasonic receiving device is fixed on the lower surface of the concrete charging barrel, is opposite to the ultrasonic transmitting device and is used for receiving ultrasonic pulse signals transmitted by the ultrasonic transmitting device;
the distance measuring device is fixed on the position, opposite to the plate body, of the upper surface in the box body and is used for measuring the distance between the upper surface in the box body and the plate body;
and the temperature sensor is fixed on the outer side wall of the concrete charging barrel and used for measuring the internal temperature of the concrete.
The lateral wall of above-mentioned concrete feed cylinder is equipped with a plurality of pits, all is equipped with a temperature sensor who is used for measuring the inside temperature of concrete in every pit.
The above prediction apparatus further comprises a control system, the control system comprising:
a data receiving module connected with the ultrasonic transmitting device and used for recording the time A of the ultrasonic transmitting device transmitting the ultrasonic pulse signalti(ii) a Time B connected with the ultrasonic receiving device and used for receiving ultrasonic pulse signalsti(ii) a The distance measuring device is connected with the box body and used for recording the distance value L between the top surface in the box body and the plate body measured by the distance measuring deviceiRecording the default value of the internal height of the box body as L0(ii) a A temperature value Q connected with the temperature sensor and used for recording the temperature measured by the temperature sensori；
The data processing module receives the data recorded by the data receiving module through the data transmission module and calculates the data according to a wave speed calculation formula delta V ═ L0-Li)/(STi+1-STi) Carrying out treatment;
the central processing unit is used for coordinating the work of the data receiving module, the data transmission module and the data processing module;
and the power supply module is connected with the central processing unit and used for supplying power to the ultrasonic transmitting device, the ultrasonic receiving device and the distance measuring device.
The telescopic end of the telescopic piece is fixedly connected with the upper end of the round rod, and the lower end of the round rod is fixedly connected with the center of the plate body; the round rod is of a hollow shell structure, and the ultrasonic transmitting device is contained in the hollow shell.
The lower surface of the concrete charging barrel is fixed with a bottom plate which is fixed at the bottom of the box body, and the lower surface of the bottom plate is fixed with the ultrasonic receiving device; the bottom of the box body is provided with a groove for accommodating the ultrasonic receiving device.
The central processing unit, the data receiving module, the data transmission module and the data processing module of the control system are all arranged on a circuit board, the circuit board is fixed inside an outer shell, the outer shell is fixed on the upper surface of the box body, and a display device, a control button and a setting button are arranged on the front surface of the outer shell; the display device, the control button and the setting button are all connected with the central processing unit.
The ultrasonic transmitting device, the ultrasonic receiving device and the distance measuring device are connected with a data transmission module positioned in the outer shell through cables.
The box body is internally positioned at one side of the concrete charging barrel and is fixedly provided with a bayonet, and a glass rod for calibrating the device is clamped on the bayonet.
A method for predicting sawing time of a cement concrete pavement joint comprises the following steps:
1) detecting the propagation time T of the ultrasonic pulse signal in the interior of the freshly mixed concrete test piece;
2) calculating the propagation speed V of the ultrasonic wave in the test piece according to the propagation time T and the height H of the test piece; at each interval of time i, the propagation velocity of the ultrasonic wave in the test piece is calculated again to obtain the propagation velocity Vi+1；
3) Deriving the change of the propagation speed V along with time, recording the time as the initial setting time t1 of the concrete when the value of the derivative at a certain time exceeds a set value, and calculating the predicted sawing starting time t2 by a calculation formula;
4) detecting the temperature Q of the concrete sample, and detecting the temperature of the sample again at intervals of i to obtain the temperature Qi+1；
5) Integrating the temperature Q along with the change of time, recording the time as the initial setting time t3 of the concrete when the value of the integral at a certain time exceeds a set value, and calculating the predicted sawing starting time t4 by a calculation formula;
6) and (min (t2, t4) and max (t2, t4)) are calculated to be the time range of the concrete pavement to start sawing.
The method for predicting the sawing time of the cement concrete pavement joint specifically comprises the following steps:
1) transmitting ultrasonic waves by using an ultrasonic transmitting device to penetrate through a fresh concrete test piece and recording the moment A at the momentti；
2) Receiving the ultrasonic signal attenuated by the test piece by using an ultrasonic receiving device, and recording the time B at the momentti；
3) Calculating the propagation time T of the pulse signal in the concrete sample as Bti-Ati；
4) Measuring the height H of the test piece by using a distance measuring device, and calculating the propagation speed V of the ultrasonic wave in the test piece; at each interval of time i, the propagation velocity of the ultrasonic wave in the test piece is calculated again to obtain the propagation velocity Vi+1；
5) Deriving the change of the propagation speed V along with time, recording the time as the initial setting time t1 of the concrete when the value of the derivative at a certain time exceeds a set value, and calculating the predicted sawing starting time t2 by a calculation formula;
6) detecting the temperature Q of the concrete sample, and detecting the temperature of the sample again at intervals of i to obtain the temperature Qi+1；
7) Integrating the temperature Q along with the change of time, recording the time as the initial setting time t3 of the concrete when the value of the integral at a certain time exceeds a set value, and calculating the predicted sawing starting time t4 by a calculation formula;
8) and (min (t2, t4) and max (t2, t4)) are calculated to be the time range of the concrete pavement to start sawing.
The invention has the beneficial effects that:
1. according to the device and the method for predicting the sawing time of the cement concrete pavement joint, the optimal joint sawing time of a pavement slab is predicted by utilizing the action of ultrasonic waves and temperature, the time of the cement concrete pavement reaching an initial set state can be accurately tested, and the sawing time of the cement concrete pavement deblocking start can be accurately predicted by utilizing the initial set time. In the actual construction process, when the pavement reaches the initial setting state, the joint sawing is known to be started, so that the work arrangement can be made in advance, and the delay of the construction period is avoided.
2. According to the device and the method for predicting the sawing time of the joint of the cement concrete pavement, provided by the invention, the ultrasonic wave and the hydration mechanism of a concrete material are effectively combined in an intelligent mode, the change of the ultrasonic wave speed and the change of the hydration heat temperature are monitored in real time, and the optimal sawing time of the joint of the concrete is finally predicted by an optimization algorithm and automatic correction of two modes. The device and the method can effectively reduce random cracking at the joint of the concrete pavement slab, improve the durability of the concrete pavement and prolong the service life of the concrete pavement slab.
3. The invention provides a device and a method for predicting the sawing time of a cement concrete pavement joint, which are used for predicting the optimal sawing time of the joint of a pavement slab by utilizing the action of temperature and ultrasonic waves. In order to predict the optimal joint sawing time, the hydration degree of cement concrete needs to be judged, and the hydration and setting process of the cement concrete is the process of the hydration reaction of the cement particle materials, and in the hydration reaction process, solid phase is generated and liquid phase is reduced, and heat is emitted. The invention determines the initial setting time of the cement concrete by using the principle that the propagation speeds of ultrasonic waves in a solid phase and a liquid phase are different and the heat released by hydration reaction is detected through an ultrasonic transmitting device, an ultrasonic receiving device and a temperature detecting device, thereby predicting the optimal joint sawing time by using the relationship between the initial setting time and the joint sawing time.
4. The device and the method for predicting the sawing time of the cement concrete pavement joint can calculate the optimal time range of starting sawing of the concrete pavement. The construction worker can start the sawing work of the road surface at any time within the range. Meanwhile, through mutual verification of the two optimal seam sawing times, errors possibly occurring in the single maximum seam sawing time can be judged and corrected.
5. In the prior art, the sawing time of a concrete pavement is determined through the temperature change in the hydration process of cement concrete, however, the method can only inform when the sawing time of the concrete is reached, can not directly give the sawing starting time of the concrete when the concrete is initially set, can only determine but not predict in the early stage, and has insufficient operability in the actual construction process. Meanwhile, in the prior art, the temperature is measured only by using hydration heat, the method is single, and large errors are easy to generate. The method disclosed by the invention has the advantages that the measured data under the two conditions of the temperature field and the wave velocity field are predicted, so that the accuracy of the prediction of the optimal concrete joint sawing time is greatly improved, and the method has very accurate guiding significance for actual construction.
Drawings
Fig. 1 is a schematic view of the overall structure of the present invention.
FIG. 2 is a schematic structural diagram of the cartridge and the upper and lower fixing and testing modules inside the box of the present invention.
FIG. 3 is a schematic structural diagram of the circuit board inside the upper portion of the case according to the present invention.
Fig. 4 is a control schematic block diagram of the present invention.
FIG. 5 is a graph comparing predicted sawing and empirical sawing using the method of the present invention.
FIG. 6 is comparative data obtained after testing using the method of this patent.
Description of reference numerals:
1. an outer housing; 2. a box body; 3. a box door; 4. a handle; 5. a display device; 6. a control button; 7. setting a button; 8. a telescoping member; 9. a plate body; 10. a temperature sensor; 11. a concrete charging barrel; 12. a base plate; 13. an ultrasonic wave emitting device; 14. an ultrasonic receiving device; 15. a data receiving module; 16. a data transmission module; 17. a data processing module; 18. a power supply module; 19. a universal wheel; 20. a distance measuring device; 21. a bayonet; 22. a glass rod; 23. a power plug; 24. and a power interface.
Detailed Description
An embodiment of the present invention will be described in detail with reference to fig. 1 and 4, but it should be understood that the scope of the present invention is not limited by the embodiment.
Example 1:
as shown in fig. 1, an embodiment of the present invention provides a cement concrete pavement joint sawing time prediction device, which includes a box body 2, a concrete charging barrel 11 is fixed inside the box body 2, a telescopic member 8 is fixed above the box body 2 and opposite to an opening of the concrete charging barrel 11, the telescopic member 8 is preferably an electric push rod, a telescopic end of the telescopic member 8 longitudinally extends downward, a plate body 9 is fixed at an end of the telescopic member 8, the plate body 9 is adapted to an inner diameter of the concrete charging barrel 11, and the telescopic member 8 extends downward to drive the plate body 9 to downwardly compact a test piece inside the concrete charging barrel 11; an ultrasonic transmitting device 13 is fixed on the plate body 9, an ultrasonic receiving device 14 opposite to the ultrasonic transmitting device 13 is fixed on the lower surface of the concrete charging barrel 11, and the ultrasonic receiving device 14 is used for receiving ultrasonic pulse signals transmitted by the ultrasonic transmitting device 13; a distance measuring device 20 for measuring the distance between the upper surface inside the box body 2 and the plate body 9 is fixed at the position, opposite to the plate body 9, of the upper surface inside the box body 2, and the distance measuring device 20 is a laser distance measuring device; the outer side wall of the concrete charging barrel 11 is fixed with a temperature sensor 10 for measuring the internal temperature of concrete.
Further, a plurality of pits are arranged on the outer side wall of the concrete charging barrel 11, and a temperature sensor 10 for measuring the internal temperature of concrete is arranged in each pit; according to the invention, the temperature in the concrete charging barrel 11 is measured by using the plurality of temperature sensors 10, so that the accuracy of the measured data can be ensured.
The outer side wall of the concrete charging barrel 11 is provided with a pit, the pit is a hole which is not communicated with the inner wall, the wall thickness corresponding to the pit position on the concrete charging barrel 11 is thin enough, and the wall thickness at the pit position is thin enough, so that the temperature sensor 10 positioned in the pit can monitor the temperature change in the concrete charging barrel 11 at any time.
Furthermore, the prediction device further comprises a control system, and the control system comprises a data receiving module 15, a data transmission module 16, a data processing module 17, and a central processing unitAnd a power supply module 18; the data receiving module 15 is connected with the ultrasonic transmitting device 13 and is used for recording the time A of the ultrasonic transmitting device 13 transmitting the ultrasonic pulse signalti(ii) a Time B of receiving ultrasonic pulse signal connected to the ultrasonic wave receiving device 14ti(ii) a Is connected with the distance measuring device 20 and is used for recording the distance value L between the top surface in the box body 2 and the plate body 9 measured by the distance measuring device 20iRecording the default value of the internal height of the box body 2 as L0(ii) a Is connected with the temperature sensor 10 and is used for recording the temperature value Q measured by the temperature sensor 10i(ii) a The data processing module 17 receives the data recorded by the data receiving module 15 through the data transmission module 16, and calculates the data according to the wave velocity calculation formula Δ V ═ L0-Li/STi+1-STiCarrying out treatment; the central processing unit is used for coordinating the work of the data receiving module 15, the data transmission module 16 and the data processing module 17; the power module 18 is connected to the central processing unit 15 and configured to supply power to the ultrasonic wave emitting device 13, the ultrasonic wave receiving device 14, and the distance measuring device 20, the power module 18 is further connected to a power plug 23, and the power plug 23 is electrically connected to an external device and configured to charge the power module 18.
Furthermore, a central processing unit, a data receiving module 15, a data transmission module 16 and a data processing module 17 of the control system are all arranged on a circuit board, the circuit board is fixed inside the outer shell 1, the outer shell 1 is fixed on the upper surface of the box body 2, a handle 4 is fixed at the top end of the outer shell 1, a universal wheel structure 19 is fixed at the bottom of the box body 2, and a display device 5, a control button 6 and a setting button 7 are arranged on the front surface of the outer shell 1; the display device 5, the control button 6 and the setting button 7 are all connected with the central processing unit.
Further, the ultrasonic wave emitting device 13, the ultrasonic wave receiving device 14 and the distance measuring device 20 are all connected with a data transmission module 16 located inside the outer shell 1 through cables.
The invention provides a cement concrete pavement joint sawing time prediction device, which predicts the optimal joint sawing time of a pavement slab by using the action of temperature and ultrasonic waves. In order to predict the optimal joint sawing time, the hydration degree of cement concrete needs to be judged, the hydration and setting process of the cement concrete is substantially the progress of the hydration reaction of cement particle materials, and in the hydration reaction process, solid phase is generated, liquid phase is reduced and heat is emitted. In the actual construction process, when the pavement reaches the initial setting state, the joint sawing is known to be started, so that the work arrangement can be made in advance, and the delay of the construction period is avoided.
Example 2:
in this embodiment, based on embodiment 1, the telescopic end of the telescopic member 8 is fixedly connected with the upper end of the round bar, and the lower end of the round bar is fixedly connected with the center of the plate body 9; the round bar is of a hollow shell structure, the ultrasonic emission device 13 is contained in the hollow shell, the ultrasonic emission device 13 is provided with a cable, and the cable penetrates through the hollow round bar 8 and is connected to the data transmission module 16 through an opening in the bottom of the upper box body 1.
Further, a bottom plate 12 is fixed on the lower surface of the concrete charging barrel 11, the bottom plate 12 is fixed on the bottom of the box body 2, and the ultrasonic receiving device 14 is fixed on the lower surface of the bottom plate 12; the bottom of the box body 2 is provided with a groove for accommodating the ultrasonic receiving device 14, and the ultrasonic receiving device 14 is provided with a cable which passes through the box body 2, enters the outer shell 1 and is connected with a data transmission module 16 positioned inside the outer shell 1.
The concrete charging barrel 11 is a hollow cylindrical structure with a bottom, the inner diameter of the concrete charging barrel 11 is the same as that of the plate body 9, the outer diameter of the bottom of the concrete charging barrel 11 is the same as that of the bottom plate 12 fixed at the lower part of the concrete charging barrel 11, and the bottom of the concrete charging barrel 11 is provided with a power supply interface 24.
Example 3:
in this embodiment, based on embodiment 1, a bayonet 21 is fixed at one side of the concrete charging barrel 11 inside the box body 2, and a glass rod 22 for calibrating the device is clamped on the bayonet 21.
In the invention, a glass rod 22 is clamped in the box body, and the glass rod 22 is used for calibrating the device for predicting the sawing time of the joint of the cement concrete pavement.
Example 4:
the embodiment provides a method for predicting the sawing time of a cement concrete pavement joint, which specifically comprises the following steps:
1) transmitting ultrasonic waves by using an ultrasonic transmitting device to penetrate through a fresh concrete test piece and recording the moment A at the momentti；
2) Receiving the ultrasonic signal attenuated by the test piece by using an ultrasonic receiving device, and recording the time B at the momentti；
3) Calculating the propagation time T of the pulse signal in the concrete sample as Bti-Ati；
4) Measuring the height H of the test piece by using a distance measuring device, and calculating the propagation speed V of the ultrasonic wave in the test piece; at each interval of time i, the propagation velocity of the ultrasonic wave in the test piece is calculated again to obtain the propagation velocity Vi+1i；
5) Deriving the change of the propagation speed V along with time, recording the time as the initial setting time t1 of the concrete when the value of the derivative at a certain time exceeds a set value, and calculating the predicted sawing starting time t2 by a calculation formula;
6) detecting the temperature Q of the concrete sample, and detecting the temperature of the sample again at intervals of i to obtain the temperature Qi+1；
7) Integrating the temperature Q along with the change of time, recording the time as the initial setting time t3 of the concrete when the value of the integral at a certain time exceeds a set value, and calculating the predicted sawing starting time t4 by a calculation formula;
8) and (min (t2, t4) and max (t2 and t4)) are calculated to be the optimal time range for the concrete pavement to start sawing.
The working principle is as follows:
the concrete steps for predicting the sawing time of the cement concrete pavement joint by using the prediction device are as follows:
1) pressing a power key in the control button 6 to turn on the power of the device, taking the glass rod 22 with known length and internal sound wave propagation speed down from the buckle 21, vertically placing the glass rod into the concrete charging barrel 11, and placing the concrete charging barrel 11 on the bottom plate 12 in the box body 2;
2) the calibration button of the setting button 7 is pressed to perform wave velocity measurement and calibration of the apparatus. A descending key in the button 6 is pressed, so that the telescopic piece 8 pushes the hollow round rod 8 to drive the disc 9 to move downwards, the disc enters the concrete charging barrel 11, contacts the glass rod 22 in the concrete charging barrel 11, and the box door 3 is closed;
3a) pressing the start button of the setting button 7 causes the ultrasonic wave transmitter 13 to transmit an ultrasonic pulse signal once, and the data receiver 15 records the time ST at that timeiThen, the ultrasonic receiving device 14 receives the signal and records the reception time STi+1；
At the same time, the distance measuring device 20 is activated and the distance L between the device and the disc 9 is measurediThe internal height of the lower box 2 is a default value L0；
The data enters a data processing module 17 through a data transmission module 16, and the measurement wave velocity is V ═ L0-Li)/(STi+1-STi) Correcting the device;
4a) after the correction is finished, the lifting key in the control keys 6 is pressed, so that the telescopic piece 8 with the hollow round rod 8 and the disc 9 synchronously moves upwards to leave the concrete charging barrel 11, and the glass rod 22 is taken out and put back into the buckle 21.
5a) Taking out the concrete charging barrel 11 from the box body, filling fresh concrete of the same batch as that of the concrete pavement into the concrete charging barrel 11, and placing the concrete charging barrel 11 filled with the concrete on a bottom plate 12 in the box body 2;
6a) pressing down a descending key in the control button 6 to enable the telescopic piece 8 to drive the hollow round rod 8 and the disc 9 to synchronously move downwards, enter the concrete charging barrel 11 and contact with concrete in the concrete charging barrel 11, and closing the box door 3;
7a) pressing the measurement key of the set keys 7 switches to the measurement mode, and pressing the start key start program of the keys 7 tests. The distance measuring device 20 is put into operation and the distance L between the device and the disc 9 is measured1The internal height of the lower box 2 is a default value L0；
The ultrasonic transmitter 13 generates an ultrasonic pulse of a fixed frequency, and records the time A at that timetiThe pulse signal is received by the ultrasonic receiver 14 after being attenuated by the concrete in the concrete cylinder 11, and the time B at this time is recordedti. The propagation time of the pulse signal in the concrete interior can be measured as Bti-Ati. The internal concrete height H ═ L of the concrete cylinder 11 obtained before the combination0-L1It can be known that Vi＝(L0-L1)/(Bti-Ati)。
After a time interval of 20-30S every U, the ultrasonic transmitter 13 again generates a pulse signal, and V is measuredi+1＝(L0-L1)/(Bti+1-Ati+1). After that, record Δ V ═ Vi+1-Vi，KiΔ V/U, when KiWhen the time exceeds a certain set value delta K0, the time is recorded as concrete initial setting time t1, and the predicted value t2 of the sawing start time is calculated according to the calculation formula t2 of 1.24 multiplied by t1+ 273.
In the step, an ultrasonic test is carried out, the sound velocity is obtained through conversion of the time of the ultrasonic wave passing through the concrete, then derivation is carried out on the sound velocity, and when the value of the derivative at a certain moment exceeds a set value, namely the slope change exceeds the set value, the moment at the moment is recorded as the initial setting time t1 of the concrete. Then, the data processing module 17 calculates the predicted value t2 of the sawing start time according to the formula t2 being 1.24 × t1+ 273.
8a) The temperature sensor 10 records the internal temperature Qi of the concrete once every 1S, draws a curve of the temperature along with the change of time, and integrates the change of the temperature Q along with the change of time to obtain real-time integralValue WiWhen the value of the integral at a certain time exceeds the set value, the time at this time is recorded as the initial concrete setting time t3, and the data processing module 17 calculates the predicted value t4 of the sawing start time according to the calculation formula t4 being 1.24 × t3+ 273.
In the step, the temperature inside the concrete is detected in real time through a temperature sensor, a curve of the temperature Q along with time is drawn, the change of the temperature Q along with time is integrated to obtain the maturity W, and when the value of the maturity W at a certain moment exceeds a set value, the moment is the initial setting time t3 of the concrete. Then, the predicted value t4 of the start sawing time is calculated by the formula t4 being 1.24 × t3+ 273.
9a) The data processing module 17 calculates (min (t2, t4), max (t2, t4)) as the optimal time range for the concrete road surface to start sawing.
The calculated (min (t2, t4) and max (t2, t4)) are the optimal time range for the concrete pavement to start sawing. The construction worker can start the sawing work of the road surface at any time within the range. Meanwhile, through mutual verification of the two optimal seam sawing times, errors possibly occurring in the single maximum seam sawing time can be judged and corrected.
When the ultrasonic wave device is used, the temperature change of the concrete caused by heat release in the setting and hardening process is measured through the temperature detection device, and the wave speed change of the concrete in the setting and hardening process can be measured through the ultrasonic wave device. According to the method, the measured data under the two conditions of the temperature field and the wave velocity field are predicted, so that the accuracy of predicting the optimal concrete joint sawing time is greatly improved, and a valuable guiding significance is provided for the construction process. Compared with the method for determining the sawing time of the concrete pavement in the prior patent, the method can give the sawing time of the pavement when the concrete reaches the initial setting time, and can make full early-stage preparation for sawing the pavement.
Compared with the method for predicting the hydration heat by only aiming at the single factor in the prior patent, the device effectively combines the hydration mechanisms of the ultrasonic waves and the concrete material in an intelligent mode, monitors the change of the ultrasonic wave speed and the change of the hydration heat temperature in real time, and finally realizes the prediction of the optimal joint sawing time of the concrete through an optimization algorithm and automatic correction of the two modes. The device and the method can effectively reduce random cracking at the joint of the concrete pavement slab, improve the durability of the concrete pavement and prolong the service life of the concrete pavement slab.
Test verification:
the freshly mixed cement concrete can continuously release heat in the process of setting and hardening, the heat release amount is different along with the time, the processes of heat release and setting and hardening of the concrete are carried out simultaneously, so that the hardening state of the concrete can be represented by measuring the heat release amount, the initial setting time can be determined, and the optimal joint sawing time of the concrete pavement slab can be further determined. Meanwhile, the principle of ultrasonic velocity measurement is that the transmission speed of ultrasonic waves in different media such as solid and liquid is different, and the propagation speed of the ultrasonic waves in fluid is slower than that in solid. The freshly mixed cement concrete can be regarded as fluid, and as the concrete is solidified and hardened, the concrete material is changed from a fluid state to a solid state, and the propagation speed of ultrasonic waves in the concrete is increased. The hardening state of the concrete can be characterized by the ultrasonic velocity.
If the heat release amount, i.e. the temperature change, of the concrete or the speed of the ultrasonic wave inside the concrete is detected separately to predict the optimal seam sawing time of the concrete pavement slab, the accuracy of the detection result is easily not required due to the influence of independent variables. The two methods are adopted to predict the optimal joint sawing time in parallel, so that the precision of the pavement slab joint sawing prediction can be effectively improved, and the concrete pavement slab can reach the optimal use state after being sawed. As shown in fig. 5, the left graph shows the effect of sawing the concrete panel by an empirical method in construction, and the right graph shows the effect of sawing at the optimal time after prediction by the method. The right picture shows that the joint sawed at the optimal time is flat, and compared with the empirical method, the sawed joint has the advantages that no cracks are generated on the two sides of the sawed joint, and the state is good. The comparative data obtained after the tests carried out with the method of this patent are shown in FIG. 6. The results obtained by the hydration heat test and the ultrasonic test of the concrete have good correlation and can be verified mutually.
In summary, the present invention provides a device and a method for predicting the sawing time of joints on a cement concrete pavement, which can predict the optimal sawing time of joints on a pavement slab by using the temperature and the ultrasonic wave, accurately test the time of the cement concrete pavement reaching the initial set state, and accurately predict the sawing time range of the cement concrete pavement after being unsealed by using the initial set time.
The above disclosure is only for a few specific embodiments of the present invention, however, the present invention is not limited to the above embodiments, and any variations that can be made by those skilled in the art are intended to fall within the scope of the present invention.
Claims (10)
1. A cement concrete pavement joint sawing time prediction device comprising:
a box body (2);
a concrete charging barrel (11) fixed inside the box body (2);
the fixed end of the telescopic piece (8) is fixed at the position above the box body (2) and opposite to the opening of the concrete charging barrel (11), and the telescopic end of the telescopic piece (8) longitudinally stretches downwards;
the plate body (9) is fixed at the end part of the telescopic end of the telescopic piece (8), is matched with the inner diameter of the concrete charging barrel (11), and is used for synchronously compacting a test piece in the concrete charging barrel (11) downwards along with the telescopic end of the telescopic piece (8);
the ultrasonic transmitting device (13) is fixed on the plate body (9);
the ultrasonic receiving device (14) is fixed on the lower surface of the concrete charging barrel (11) and is opposite to the ultrasonic transmitting device (13) and used for receiving the ultrasonic pulse signal transmitted by the ultrasonic transmitting device (13);
the distance measuring device (20) is fixed at the position, opposite to the plate body (9), of the upper surface in the box body (2) and used for measuring the distance between the upper surface in the box body (2) and the plate body (9);
and the temperature sensor (10) is fixed on the outer side wall of the concrete charging barrel (11) and is used for measuring the internal temperature of the concrete.
2. The sawing time prediction device for cement concrete pavement joints according to claim 1, wherein the outer side wall of the concrete charging barrel (11) is provided with a plurality of pits, and each pit is provided with a temperature sensor (10) for measuring the internal temperature of the concrete.
3. The cement concrete pavement joint sawing time prediction device of claim 2, further comprising a control system, the control system comprising:
a data receiving module (15) connected with the ultrasonic transmitting device (13) and used for recording the time A of the ultrasonic pulse signal transmitted by the ultrasonic transmitting device (13)ti(ii) a A time B connected to the ultrasonic wave receiving device (14) for receiving the ultrasonic pulse signalti(ii) a Is connected with the distance measuring device (20) and is used for recording the distance value L between the top surface inside the box body (2) and the plate body (9) measured by the distance measuring device (20)iThe default value of the internal height of the recording box body (2) is L0(ii) a Is connected with the temperature sensor (10) and is used for recording the temperature value Q measured by the temperature sensor (10)i；
The data processing module (17) receives the data recorded by the data receiving module (15) through the data transmission module (16) and processes the data according to a calculation formula;
the central processing unit is used for coordinating the work of the data receiving module (15), the data transmission module (16) and the data processing module (17);
and the power supply module (18) is connected with the central processing unit (15) and is used for supplying power to the ultrasonic transmitting device (13), the ultrasonic receiving device (14) and the distance measuring device (20).
4. The sawing time prediction device for cement concrete pavement joints according to claim 1, wherein the telescopic end of the telescopic member (8) is fixedly connected with the upper end of a round rod, and the lower end of the round rod is fixedly connected with the center of the plate body (9); the round rod is of a hollow shell structure, and the ultrasonic transmitting device (13) is contained in the hollow shell.
5. The sawing time prediction device for cement concrete pavement joints according to claim 1, wherein a bottom plate (12) is fixed to the lower surface of the concrete charging barrel (11), the bottom plate (12) is fixed to the bottom of the box body (2), and the ultrasonic wave receiving device (14) is fixed to the lower surface of the bottom plate (12); the bottom of the box body (2) is provided with a groove for accommodating the ultrasonic receiving device (14).
6. The cement concrete pavement joint sawing time prediction device according to claim 3, wherein the CPU, the data receiving module (15), the data transmission module (16) and the data processing module (17) of the control system are all arranged on a circuit board, the circuit board is fixed inside the outer shell (1), the outer shell (1) is fixed on the upper surface of the box body (2), and the front surface of the outer shell (1) is provided with the display device (5), the control button (6) and the setting button (7); the display device (5), the control button (6) and the setting button (7) are all connected with the central processing unit.
7. The cement concrete pavement joint sawing time prediction device according to claim 6, characterized in that the ultrasonic wave transmitting device (13), the ultrasonic wave receiving device (14) and the distance measuring device (20) are all connected with a data transmission module (16) inside the outer shell (1) through cables.
8. The sawing time prediction device for cement concrete pavement joints according to claim 1, characterized in that a bayonet (21) is fixed inside the box body (2) at one side of the concrete charging barrel (11), and a glass rod (22) for calibrating the device is clamped on the bayonet (21).
9. A method for predicting sawing time of a cement concrete pavement joint is characterized by comprising the following steps:
1) detecting the propagation time T of the ultrasonic pulse signal in the interior of the freshly mixed concrete test piece;
2) calculating the propagation speed V of the ultrasonic wave in the test piece according to the propagation time T and the height H of the test piece; at each interval of time i, the propagation velocity of the ultrasonic wave in the test piece is calculated again to obtain the propagation velocity Vi+1；
3) Deriving the change of the propagation speed V along with time, recording the time as the initial setting time t1 of the concrete when the value of the derivative at a certain time exceeds a set value, and calculating the predicted sawing starting time t2 by a calculation formula;
4) detecting the temperature Q of the concrete sample, and detecting the temperature of the sample again at intervals of i to obtain the temperature Qi+1；
5) Integrating the temperature Q along with the change of time, recording the time as the initial setting time t3 of the concrete when the value of the integral at a certain time exceeds a set value, and calculating the predicted sawing starting time t4 by a calculation formula;
6) and (min (t2, t4) and max (t2, t4)) are calculated to be the time range of the concrete pavement to start sawing.
10. The method for predicting the sawing time of the joint of the cement concrete pavement as claimed in claim 9, which comprises the following steps:
1) transmitting ultrasonic waves by using an ultrasonic transmitting device to penetrate through a fresh concrete test piece and recording the moment A at the momentti；
2) Receiving the ultrasonic signal attenuated by the test piece by using an ultrasonic receiving device, and recording the time B at the momentti；
3) Calculating the propagation time T of the pulse signal in the concrete sample as Bti-Ati；
4) Measuring the height H of the test piece by using a distance measuring device, and calculating the propagation speed V of the ultrasonic wave in the test piece; at each interval of time i, the propagation velocity of the ultrasonic wave in the test piece is calculated again to obtain the propagation velocity Vi+1；
5) Deriving the change of the propagation speed V along with time, recording the time as the initial setting time t1 of the concrete when the value of the derivative at a certain time exceeds a set value, and calculating the predicted sawing starting time t2 by a calculation formula;
6) detecting the temperature Q of the concrete sample, and detecting the temperature of the sample again at intervals of i to obtain the temperature Qi+1；
7) Integrating the temperature Q along with the change of time, recording the time as the initial setting time t3 of the concrete when the value of the integral at a certain time exceeds a set value, and calculating the predicted sawing starting time t4 by a calculation formula;
8) and (min (t2, t4) and max (t2, t4)) are calculated to be the time range of the concrete pavement to start sawing.
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