When ultrasonic waves act on the liquid, a large number of tiny bubbles will continue to be produced inside the liquid. When the bubbles are generated in the liquid from the high pressure area to the low pressure area, the bubbles will burst, and the burst of each bubble will produce nearly a thousand atmospheres. Shock wave, namely "cavitation phenomenon", the shock wave generated by cavitation can impact and peel off the attachments on the surface of the object. At present, ultrasonic cleaning has been widely used in machinery, medical and other industries, but it has not seen application in the field of road engineering material testing. Therefore, the inventor considered placing the asphalt mixture sample in an ultrasonic water tank, and using the "cavitation" of the ultrasonic wave on the liquid. When the bubble bursts, the water penetrates into the space of the asphalt mixture sample and further impacts the asphalt cement The bonding surface with the aggregate promotes the peeling of the asphalt from the surface of the aggregate, causing the loosening and shedding of the asphalt mixture to simulate the destruction process of the asphalt pavement under the actual hydrodynamic pressure. The ultimate manifestation of water damage on asphalt pavement is the looseness and shedding of asphalt mixture particles on the pavement, the formation of pits and other diseases, and this process is accelerated by ultrasonic cleaning technology.
The invention provides an asphalt mixture water stability test device and an evaluation method which can simulate the driving load and dynamic water effects. This method simulates the aging of the asphalt mixture during the construction and use of the pavement, and also takes into account the peeling effect of the internal hydrodynamic pressure of the asphalt mixture on the asphalt film of the aggregate particles under the wheel load. The test evaluation method is closer to the actual use of the pavement. Condition and destruction process.
The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative, and in no way serves as any limitation to the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.
Such asfigure 1 The long-term water stability evaluation test device of the asphalt mixture shown is an environmental tank 10, a water tank 20, an ultrasonic transducer 30, a sample loading assembly 40 and a screen 50;
The environmental tank 10 is a semi-closed container with an opening at one end. The water tank 20 is fixed in the environmental tank 10, and the water tank 20 is used to simulate the immersion environment of the test piece; preferably, the water tank 20 is welded by steel plates, and the water tank 20 is a closed container with an upper opening. , The use of steel plate welding can improve the reliability of the water tank 20 and increase the service life of the water tank 20. The bottom of the water tank 20 is also provided with a drain port to facilitate the replacement of the water in the experimental environment and ensure that the water environment is consistent during each test.
The ultrasonic transducer 30 is fixed on the water tank 20, and the hydrodynamic pressure is simulated by ultrasonic cavitation; the ultrasonic transducer uses the cavitation phenomenon when the ultrasonic is applied to the liquid to make water penetrate into the gap of the asphalt mixture specimen and further impact the asphalt The bonding surface of the cement and the aggregate promotes the asphalt to peel off from the surface of the aggregate, thereby simulating the internal destruction process of the asphalt mixture specimen under the action of hydrodynamic pressure. In the embodiment of the present invention, the working frequency of the ultrasonic transducer 30 is 40-60kHz, the power is 90-100W, and the range of action is 35-40cm. When an ultrasonic transducer 30 cannot fully cover the water tank 20, multiple One.
The sample loading component 40 is set in the water tank 20 to fix the asphalt mixture sample and apply load; it should be pointed out that the power driving device of the sample loading component 40 is a UTM testing machine, and the load parameters can be set in the laboratory , To simulate different vehicle loads.
The screen 50 is arranged in the water tank 20 and is arranged in the direction where the asphalt mixture sample is peeled and dropped to collect the peeled aggregate of the asphalt mixture sample. The function of the screen 50 is to collect loose and flaked aggregate particles in the asphalt mixture sample to facilitate later data collection. Preferably, the screen 50 is arranged in two upper and lower layers, and the aperture of the upper layer is larger than the aperture of the lower layer, which improves the collection effect of the screen 50 and improves the accuracy of the final data.
As a preference of the above embodiment, such asfigure 2 As shown, the test piece loading assembly 40 includes a test piece bearing platform 41, a test piece pressing plate 42 and a loading pressure rod 43. The asphalt mixture sample is fixed on the bearing platform 41, and the test piece pressing plate 42 is fixed on the top of the asphalt mixture sample. The loading pressure rod 43 is arranged above the test piece pressing plate 42 for applying a load to the test piece pressing plate 42. During the specific installation, the center lines of the loading pressure rod 43, the test piece pressing plate 42, the asphalt mixture specimen and the bearing platform 41 are set on the same straight line, and in the embodiment of the present invention, the asphalt mixture specimen is set as a cylinder The shape of the body facilitates the installation and fixation of the test piece. During the specific installation, the other end of the loading pressure rod 43 is connected with the UTM testing machine to set different load parameters.
Further, please continue to referfigure 2 An anchor 411 is provided on the test piece bearing platform 41, and the anchor 411 is connected with the asphalt mixture test piece. Through the fixing of the anchor 411, the reliability of fixing the asphalt mixture specimen is improved, and the test effect of the specimen is improved.
As the preferred embodiment of the above, please continue to refer tofigure 1 A shock-absorbing seat 12 is provided at the bottom of the water tank 20, which is fixed to the environmental tank 10 through the shock-absorbing seat 12. The function of the damping seat 12 is to reduce the interaction between the water tank 20 and the environmental tank 10 and improve the reliability of the fixing of the water tank 20. The shock-absorbing seat 12 may be made of elastic material to reduce the influence of the UTM testing machine and the ultrasonic transducer 30 on the environmental box 10.
As the preferred embodiment of the above, please continue to refer tofigure 1 A heating pipe 61 and a temperature controller 62 are also provided in the water tank 20, and the heating pipe 61 is connected with the temperature controller 62 to adjust the water temperature in the water tank 20. In the embodiment of the present invention, the heating tube 61 is arranged in a circular shape and is arranged around the inside of the water tank 20. This arrangement has more uniform heating and better heat preservation effect. The thermostat 62 is an existing technology, and it controls the on and off of the heating pipe 61 in real time by measuring and feedback of the water temperature, so as to keep the water temperature constant. The specific principle and connection relationship are not repeated here.
The following parts of the present invention describe in detail the method for evaluating the long-term water stability of asphalt mixtures, such asimage 3As shown, including the following steps:
S11: Prepare the asphalt mixture specimen according to the design requirements, and record the mass m1 and m4 of the asphalt mixture specimen; it should be pointed out that the mass m1 of the asphalt mixture specimen can be weighed after the specimen is made The quality of the asphalt mass m4 can be calculated by the mixture ratio. Among them, the specific production process of the asphalt mixture test piece is: mix the asphalt mixture according to the design gradation and the amount of asphalt, spread the mixed asphalt mixture evenly on the enamel tray, and loosely spread about 21-22kg/m3, Put the mixture into an oven at 135℃±3℃ and heat it for 4h±5min under forced ventilation. During the addition, the asphalt mixture is stirred every hour; the asphalt mixture in the oven is heated to 160℃, using rotary pressure The actual instrument is formed into a cylinder with a diameter of 150±0.1mm, a height of 95±3mm, and a porosity of 7±1%. Place the test piece together with the test mold at room temperature to cool for not less than 16 hours, and then demold; Place the sample in a 85℃±3℃ oven with forced ventilation and heat for 5d (120h±0.5h). Do not touch or move the sample before heating at a constant temperature until it cools; close the oven after 5d, open the oven door, and cool down for no less than 16h To room temperature. The purpose of the above operations is to age the asphalt mixture specimens. The purpose of aging is to simulate the entire process of asphalt mixture mixing and paving from the construction site to the service life.
S12: Fix the test piece of asphalt mixture in the water tank and pour water into the water tank; during installation, ensure that the loading pressure rod 43 is in the same straight line with the center of the test piece, and the water surface needs to exceed the pressure plate 42 of the test piece during water injection. Above. During the test, a piece of polytetrafluoroethylene film was placed on each end of the mixture sample to prevent the asphalt mixture sample from sticking to the test piece pressing plate 42 and the bearing platform 41.
S13: Load the asphalt mixture specimen through the loading rod 43, and turn on the ultrasonic transducer at the same time to carry out the ultrasonic cleaning test of the asphalt mixture specimen under the force condition; specifically, turn on the UTM testing machine, set the load parameters, and use the bias Sinusoidal loading mode, loading frequency 20Hz, load 25kPa; turn on the ultrasonic transducer 30, set the frequency to 50kHz; start the UTM testing machine to load, carry out the ultrasonic cleaning test of asphalt mixture under stress conditions, the test time is 2.5h.
S14: After the test is completed, take out the asphalt mixture sample and the stripped aggregate collected on the screen, and weigh the mass m2 of the sample and the mass m3 of the stripped aggregate after drying; the specific steps are: after the test is completed, the testing machine is unloaded, Turn off the ultrasonic transducer, take out test piece 4, dry it with a wrung out wet towel, and dry it indoors or blow it to a constant weight with a hair dryer. Weigh the mass of the test piece and record it as m2; clean all the stripped aggregates on the screen , After taking it out, dry it in the same way or blow it with a hair dryer to a constant weight, recorded as m3;
S15: Calculate the residual rate MR and the asphalt film loss rate AR of the asphalt mixture specimen,
Where MR=m2/m1, AR=m1-m2-m3/m4. It should be pointed out here that the greater the residual rate MR of the specimen, the smaller the asphalt film loss rate AR, which indicates the better the water stability of the asphalt mixture.
In addition, in order to improve the accuracy of the test results, for the same kind of test piece, at least three valid tests should be repeated. When the difference between a certain data in a set of measured values and the average value is greater than k times the standard deviation, the measured value should be discarded, and the average of the remaining measured values shall be used as the test result; when the number of tests n is 3, 4, 5 , 6, the k values are 1.15, 1.46, 1.67, 1.82 respectively.
As a preference of the above embodiment, after preparing the asphalt mixture sample, put the asphalt mixture sample into the water tank and keep it in a vacuum box with a vacuum of 97.3~98.7kPa for 15 minutes, and then open the vacuum box valve to restore normal pressure. Place the test piece in water for 15h; after taking out the test piece, put it into a plastic bag, add 10-15ml of water, tie the bag tightly and put it in the refrigerator to freeze, set the temperature to -18℃±2℃, and store for 16h.
As a preference of the above-mentioned embodiment, before the ultrasonic cleaning test of the asphalt mixture specimen under the stressed condition, the thermostat is turned on to maintain the water temperature in the water tank to 60°C. Through the setting of water temperature, it can cooperate with load and hydrodynamic pressure to make the simulation environment more realistic.
Those skilled in the industry should understand that the present invention is not limited by the foregoing embodiments. The foregoing embodiments and descriptions only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have Various changes and improvements, these changes and improvements all fall within the scope of the claimed invention. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.